autoconf2.64-2.64/ 0000755 0002024 0002024 00000000000 11233220606 013152 5 ustar arthur arthur autoconf2.64-2.64/configure.ac 0000644 0002024 0002024 00000015272 11232574542 015461 0 ustar arthur arthur # -*- Autoconf -*-
# Process this file with autoconf to produce a configure script.
# Copyright (C) 1992, 1993, 1994, 1995, 1999, 2000, 2001, 2002, 2003,
# 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see .
# We need AC_CONFIG_TESTDIR, AC_PROG_SED, AC_PROG_GREP.
AC_PREREQ([2.60])
AC_INIT([GNU Autoconf],
m4_esyscmd([build-aux/git-version-gen .tarball-version]),
[bug-autoconf@gnu.org])
AC_CONFIG_SRCDIR([ChangeLog])
AC_CONFIG_AUX_DIR([build-aux])
AM_INIT_AUTOMAKE([1.10 dist-bzip2 readme-alpha no-texinfo.tex std-options])
# We use `/bin/sh -n script' to check that there are no syntax errors
# in the scripts. Although incredible, there are /bin/sh that go into
# endless loops with `-n', e.g., SunOS's:
#
# $ uname -a
# SunOS ondine 4.1.3 2 sun4m unknown
# $ cat endless.sh
# while false
# do
# :
# done
# exit 0
# $ time sh endless.sh
# sh endless.sh 0,02s user 0,03s system 78% cpu 0,064 total
# $ time sh -nx endless.sh
# ^Csh -nx endless.sh 3,67s user 0,03s system 63% cpu 5,868 total
#
# Also, some implementations of /bin/sh (e.g., Solaris 8) are soooo slow
# that they are unusable on large scripts like our testsuite.
# So before using `/bin/sh -n' to check our scripts, we first check
# that `/bin/sh -n' is known to not have these problems.
AC_CACHE_CHECK([whether /bin/sh -n is known to work], [ac_cv_sh_n_works],
[if (
unset BASH_VERSION ZSH_VERSION
/bin/sh -c '
test -n "${BASH_VERSION+set}" || # Bash
test -n "${KSH_VERSION+set}" || # pdksh
test -n "${ZSH_VERSION+set}" || # zsh
test -n "${.sh.version}" # ksh93; put this last since its syntax is dodgy
'
) 2>/dev/null
then ac_cv_sh_n_works=yes
else ac_cv_sh_n_works=no
fi
])
AC_SUBST([ac_cv_sh_n_works])
AC_MSG_CHECKING([for characters that cannot appear in file names])
AC_CACHE_VAL([ac_cv_unsupported_fs_chars],
[ac_cv_unsupported_fs_chars=
for c in '\\' \" '<' '>' '*' '?' '|'
do
touch "conftest.t${c}t" 2>/dev/null
test -f "conftest.t${c}t" && rm -f "conftest.t${c}t" && continue
# $c cannot be used in a file name.
ac_cv_unsupported_fs_chars=$ac_cv_unsupported_fs_chars$c
done
])
if test -n "$ac_cv_unsupported_fs_chars"; then
AC_MSG_RESULT([$ac_cv_unsupported_fs_chars])
else
AC_MSG_RESULT([none])
fi
AC_SUBST([ac_cv_unsupported_fs_chars])
AC_CACHE_CHECK([whether directories can have trailing spaces],
[ac_cv_dir_trailing_space],
[rm -rf 'conftest.d ' && mkdir 'conftest.d ' && touch 'conftest.d /tfile' 2>/dev/null
stat=$?
rm -rf 'conftest.d '
case $stat$? in #(
00) ac_cv_dir_trailing_space=yes ;; #(
*) ac_cv_dir_trailing_space=no ;;
esac
])
AC_SUBST([ac_cv_dir_trailing_space])
# Initialize the test suite.
AC_CONFIG_TESTDIR([tests])
AC_CONFIG_FILES([tests/Makefile tests/atlocal])
AC_PATH_PROG([EXPR], [expr])
## ---- ##
## M4. ##
## ---- ##
# We use an absolute name for GNU m4 so even if users have another m4 first in
# their path, the installer can configure with a path that has GNU m4
# on it and get that path embedded in the installed autoconf and
# autoheader scripts.
AC_PROG_GNU_M4
## ----------- ##
## Man pages. ##
## ----------- ##
AC_CONFIG_FILES([man/Makefile])
AM_MISSING_PROG([HELP2MAN], [help2man])
## ------ ##
## Perl. ##
## ------ ##
# We use an absolute name for perl so the #! line in autoscan will work.
AC_PATH_PROG([PERL], [perl], [no])
AC_SUBST([PERL])dnl
if test "$PERL" = no; then
AC_MSG_ERROR([perl is not found])
fi
$PERL -e 'require 5.005_03;' || {
AC_MSG_ERROR([Perl 5.005_03 or better is required])
}
## ------- ##
## Emacs. ##
## ------- ##
AC_CONFIG_FILES([lib/emacs/Makefile])
TEST_EMACS=$EMACS
test x"$TEST_EMACS" = xt && TEST_EMACS=
AC_CHECK_PROGS([TEST_EMACS], [emacs xemacs], [no])
# autoconf-mode.el and autotest-mode.el do not work with older version of
# Emacs (i.e. 18.x.x). During byte-compilation, Emacs complains:
# "Variable (broken nil) seen on pass 2 of byte compiler but not pass 1"
# We detect this problem here.
AS_IF([test "$TEST_EMACS" != no],
[AC_CACHE_CHECK([whether $TEST_EMACS is sufficiently recent],
[ac_cv_prog_emacs_ok],
[# Note: The quoted "EOF" is intentional. It protects the ` in the text.
cat >conftest.el << "EOF"
(defvar broken)
(defun broken-mode () (setq broken-defaults `(broken nil)))
EOF
AS_IF([AC_RUN_LOG(
[$TEST_EMACS -batch -q -f batch-byte-compile conftest.el 1>&2])],
[ac_cv_prog_emacs_ok=yes], [ac_cv_prog_emacs_ok=no])
rm -f conftest.el conftest.elc])
AS_IF([test $ac_cv_prog_emacs_ok = no], [TEST_EMACS=no])])
AC_SUBST([EMACS], [$TEST_EMACS])
AM_PATH_LISPDIR
## ------------ ##
## Grep & sed. ##
## ------------ ##
AC_PROG_GREP
AC_PROG_EGREP
AC_PROG_SED
## ----- ##
## Make. ##
## ----- ##
AC_PROG_MAKE_CASE_SENSITIVE
## ------------ ##
## Conclusion. ##
## ------------ ##
dnl Allow maintainer rules under GNU make even in VPATH builds. This does
dnl not work in autoconf 2.61 or earlier, but we don't want to require
dnl unreleased autoconf during bootstrap, hence the version test.
dnl TODO remove the version check once we depend on autoconf 2.62.
dnl Meanwhile, we must use a shell variable so that we bypass automake's
dnl attempts to remove the sole copy of GNUmakefile in a non-VPATH build
dnl during 'make distclean'.
dnl TODO avoid the shell variable once automake is fixed.
GNUmakefile=GNUmakefile
m4_if(m4_version_compare([2.61a.100],
m4_defn([m4_PACKAGE_VERSION])), [1], [],
[AC_CONFIG_LINKS([$GNUmakefile:$GNUmakefile], [],
[GNUmakefile=$GNUmakefile])])
AC_CONFIG_FILES([Makefile doc/Makefile
lib/Makefile lib/Autom4te/Makefile lib/autoscan/Makefile
lib/m4sugar/Makefile
lib/autoconf/Makefile lib/autotest/Makefile
bin/Makefile])
AC_OUTPUT
# Report the state of this version of Autoconf if this is a beta.
m4_bmatch(m4_defn([AC_PACKAGE_VERSION]), [[-a-z]],
[ cat <.
Below you will find information on the status of this version of Autoconf.
EOF
sed -n '/^\* Status/,$p' $srcdir/BUGS
echo
])dnl
autoconf2.64-2.64/Makefile.am 0000644 0002024 0002024 00000006120 11173335201 015206 0 ustar arthur arthur # Make Autoconf.
# Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2006, 2007, 2008,
# 2009 Free Software Foundation, Inc.
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License
# along with this program. If not, see .
# bin/ must be run first, as it builds executables needed for tests.
# autom4te uses autotest.m4f to generate `testsuite', so build tests last.
# Rules in man/ use scripts from both bin/ and tests/, so *it* goes last.
SUBDIRS = bin . lib doc tests man
ACLOCAL_AMFLAGS = -I m4
EXTRA_DIST = ChangeLog.0 ChangeLog.1 ChangeLog.2 \
BUGS COPYINGv3 \
GNUmakefile maint.mk cfg.mk \
build-aux/gendocs.sh \
build-aux/git-version-gen \
build-aux/announce-gen build-aux/gnupload \
.prev-version .version
## --------- ##
## INSTALL. ##
## --------- ##
AM_MAKEINFOFLAGS = --no-headers --no-validate --no-split
if MAKE_CASE_SENSITIVE
pkgdata_DATA = $(srcdir)/INSTALL
MAINTAINERCLEANFILES = $(srcdir)/INSTALL
$(srcdir)/INSTALL: $(top_srcdir)/doc/install.texi
$(MAKEINFO) $(AM_MAKEINFOFLAGS) $(MAKEINFOFLAGS) --plaintext -o $@ \
$(top_srcdir)/doc/install.texi
endif
# Version string management. There are two files to be aware of:
# .tarball-version - present only in a distribution tarball, and not in
# a checked-out repository. Created with contents that were learned at
# the last time autoconf was run, and used by git-version-gen. Must not
# be present in either $(srcdir) or $(builddir) for git-version-gen to
# give accurate answers during normal development with a checked out tree,
# but must be present in a tarball when there is no version control system.
# Therefore, it cannot be used in any dependencies. GNUmakefile has
# hooks to force a reconfigure at distribution time to get the value
# correct, without penalizing normal development with extra reconfigures.
# .version - present in a checked-out repository and in a distribution
# tarball. At least as current as the most recent .tarball-version
# creation. Usable in dependencies, particularly for files that don't
# want to depend on config.h but do want to track version changes.
BUILT_SOURCES = $(top_srcdir)/.version
$(top_srcdir)/.version:
echo $(VERSION) > $@-t && mv $@-t $@
# Arrange so that .tarball-version appears only in distribution tarballs,
# never in a checked-out repository.
dist-hook:
echo $(VERSION) > $(distdir)/.tarball-version
# Arrange to remove the symlink to GNUmakefile in VPATH builds.
# TODO remove this once automake vs. AC_CONFIG_LINKS issue is fixed.
distclean-local:
if test x"$(VPATH)" != x ; then rm -f GNUmakefile ; fi
autoconf2.64-2.64/maint.mk 0000644 0002024 0002024 00000047453 11173335023 014633 0 ustar arthur arthur # -*-Makefile-*-
# This Makefile fragment tries to be general-purpose enough to be
# used by at least coreutils, idutils, CPPI, Bison, and Autoconf.
## Copyright (C) 2001-2009 Free Software Foundation, Inc.
##
## This program is free software: you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program. If not, see .
# This is reported not to work with make-3.79.1
# ME := $(word $(words $(MAKEFILE_LIST)),$(MAKEFILE_LIST))
ME := maint.mk
# Do not save the original name or timestamp in the .tar.gz file.
# Use --rsyncable if available.
gzip_rsyncable := \
$(shell gzip --help 2>/dev/null|grep rsyncable >/dev/null && echo --rsyncable)
GZIP_ENV = '--no-name --best $(gzip_rsyncable)'
GIT = git
VC = $(GIT)
VC-tag = git tag -s -m '$(VERSION)'
VC_LIST = $(srcdir)/build-aux/vc-list-files -C $(srcdir)
VC_LIST_EXCEPT = \
$(VC_LIST) | if test -f $(srcdir)/.x-$@; then \
grep -vEf $(srcdir)/.x-$@; \
else \
grep -v ChangeLog; \
fi
ifeq ($(origin prev_version_file), undefined)
prev_version_file = $(srcdir)/.prev-version
endif
PREV_VERSION := $(shell cat $(prev_version_file))
VERSION_REGEXP = $(subst .,\.,$(VERSION))
this-vc-tag = v$(VERSION)
this-vc-tag-regexp = v$(VERSION_REGEXP)
my_distdir = $(PACKAGE)-$(VERSION)
# Old releases are stored here.
# Used for diffs.
release_archive_dir ?= ../release
# Prevent programs like 'sort' from considering distinct strings to be equal.
# Doing it here saves us from having to set LC_ALL elsewhere in this file.
export LC_ALL = C
## --------------- ##
## Sanity checks. ##
## --------------- ##
# Collect the names of rules starting with `sc_'.
syntax-check-rules := $(shell sed -n 's/^\(sc_[a-zA-Z0-9_-]*\):.*/\1/p' \
$(srcdir)/$(ME))
.PHONY: $(syntax-check-rules)
local-checks-available = \
po-check copyright-check writable-files m4-check author_mark_check \
changelog-check patch-check strftime-check $(syntax-check-rules) \
makefile_path_separator_check \
makefile-check check-AUTHORS
.PHONY: $(local-checks-available)
local-check := $(filter-out $(local-checks-to-skip), $(local-checks-available))
syntax-check: $(local-check)
# @shopt -s nullglob; \
# grep -nE '# *include <(limits|std(def|arg|bool))\.h>' \
# $$(find -type f -name '*.[chly]') /dev/null && \
# { echo '$(ME): found conditional include' 1>&2; \
# exit 1; } || :
# grep -nE '^# *include <(string|stdlib)\.h>' \
# $(srcdir)/{lib,src}/*.[chly] /dev/null && \
# { echo '$(ME): FIXME' 1>&2; \
# exit 1; } || :
# FIXME: don't allow `#include .strings\.h' anywhere
sc_cast_of_argument_to_free:
@shopt -s nullglob; \
grep -nE '\&2; \
exit 1; } || :
sc_cast_of_x_alloc_return_value:
@shopt -s nullglob; \
grep -nE --exclude=$(srcdir)/lib/regex.c \
'\*\) *x(m|c|re)alloc\>' \
$(srcdir)/{lib,src}/*.[chly] /dev/null && \
{ echo '$(ME): don'\''t cast x*alloc return value' 1>&2; \
exit 1; } || :
sc_cast_of_alloca_return_value:
@shopt -s nullglob; \
grep -nE '\*\) *alloca\>' \
$(srcdir)/src/*.[chly] /dev/null && \
{ echo '$(ME): don'\''t cast alloca return value' 1>&2; \
exit 1; } || :
sc_space_tab:
@grep -n '[ ] ' $$($(VC_LIST_EXCEPT)) && \
{ echo '$(ME): found SPACE-TAB sequence; remove the SPACE' \
1>&2; exit 1; } || :
# Don't use *scanf or the old ato* functions in `real' code.
# They provide no error checking mechanism.
# Instead, use strto* functions.
sc_prohibit_atoi_atof:
@grep -nE '\<([fs]?scanf|ato([filq]|ll))\>' $$($(VC_LIST_EXCEPT)) && \
{ echo '$(ME): do not use *scan''f, ato''f, ato''i, ato''l, ato''ll, ato''q, or ss''canf' \
1>&2; exit 1; } || :
# Using EXIT_SUCCESS as the first argument to error is misleading,
# since when that parameter is 0, error does not exit. Use `0' instead.
sc_error_exit_success:
@grep -nF 'error (EXIT_SUCCESS,' \
$$(find -type f -name '*.[chly]') /dev/null && \
{ echo '$(ME): found error (EXIT_SUCCESS' 1>&2; \
exit 1; } || :
sc_file_system:
@grep -ni 'file''system' $$($(VC_LIST_EXCEPT)) \
| grep -v 'File''system Hierarchy Standard' && \
{ echo '$(ME): found use of "file''system";' \
'rewrite to use "file system"' 1>&2; \
exit 1; } || :
sc_no_have_config_h:
@grep -n '^# *if.*HAVE''_CONFIG_H' $$($(VC_LIST_EXCEPT)) && \
{ echo '$(ME): found use of HAVE''_CONFIG_H; remove' \
1>&2; exit 1; } || :
# Nearly all .c files must include .
sc_require_config_h:
@if $(VC_LIST_EXCEPT) | grep '\.c$$' > /dev/null; then \
grep -L '^# *include ' \
$$($(VC_LIST_EXCEPT) | grep '\.c$$') \
| grep . && \
{ echo '$(ME): the above files do not include ' \
1>&2; exit 1; } || :; \
else :; \
fi
# To use this "command" macro, you must first define two shell variables:
# h: the header, enclosed in <> or ""
# re: a regular expression that matches IFF something provided by $h is used.
define _header_without_use
h_esc=`echo "$$h"|sed 's/\./\\./'`; \
if $(VC_LIST_EXCEPT) | grep '\.c$$' > /dev/null; then \
files=$$(grep -l '^# *include '"$$h_esc" \
$$($(VC_LIST_EXCEPT) | grep '\.c$$')) && \
grep -LE "$$re" $$files | grep . && \
{ echo "$(ME): the above files include $$h but don't use it" \
1>&2; exit 1; } || :; \
else :; \
fi
endef
# Prohibit the inclusion of assert.h without an actual use of assert.
sc_prohibit_assert_without_use:
@h='' re='\' \
$$($(VC_LIST_EXCEPT)) && \
{ echo '$(ME): do not use HAVE''_FCNTL_H or O''_NDELAY' \
1>&2; exit 1; } || :
# FIXME: warn about definitions of EXIT_FAILURE, EXIT_SUCCESS, STREQ
# Each nonempty line must start with a year number, or a TAB.
sc_changelog:
@grep -n '^[^12 ]' $$(find $(srcdir) -maxdepth 2 -name ChangeLog) && \
{ echo '$(ME): found unexpected prefix in a ChangeLog' 1>&2; \
exit 1; } || :
# Ensure that dd's definition of LONGEST_SYMBOL stays in sync
# with the strings from the two affected variables.
dd_c = $(srcdir)/src/dd.c
sc_dd_max_sym_length:
ifneq ($(wildcard $(dd_c)),)
@len=$$( (sed -n '/conversions\[\] =$$/,/^};/p' $(dd_c);\
sed -n '/flags\[\] =$$/,/^};/p' $(dd_c) ) \
|sed -n '/"/s/^[^"]*"\([^"]*\)".*/\1/p' \
| wc --max-line-length); \
max=$$(sed -n '/^#define LONGEST_SYMBOL /s///p' $(dd_c) \
|tr -d '"' | wc --max-line-length); \
if test "$$len" = "$$max"; then :; else \
echo 'dd.c: LONGEST_SYMBOL is not longest' 1>&2; \
exit 1; \
fi
endif
# Many m4 macros names once began with `jm_'.
# On 2004-04-13, they were all changed to start with gl_ instead.
# Make sure that none are inadvertently reintroduced.
sc_prohibit_jm_in_m4:
@grep -nE 'jm_[A-Z]' \
$$($(VC_LIST) m4 |grep '\.m4$$') && \
{ echo '$(ME): do not use jm_ in m4 macro names' \
1>&2; exit 1; } || :
sc_root_tests:
@t1=sc-root.expected; t2=sc-root.actual; \
grep -nl '^PRIV_CHECK_ARG=require-root' \
$$($(VC_LIST) tests) |sed s/tests/./ |sort > $$t1; \
sed -n 's, cd \([^ ]*\) .*MAKE..check TESTS=\(.*\),./\1/\2,p' \
$(srcdir)/tests/Makefile.am |sort > $$t2; \
diff -u $$t1 $$t2 || diff=1; \
rm -f $$t1 $$t2; \
test "$$diff" \
&& { echo 'tests/Makefile.am: missing check-root action'>&2; \
exit 1; } || :
# Files in src/ should not include directly any of
# the headers already included via system.h.
sc_system_h_headers:
@if test -f $(srcdir)/src/system.h; then \
pat=$$( \
sed -n '/^# *include /s///p' $(srcdir)/src/system.h /dev/null \
| grep -Ev 'sys/(param|file)\.h' \
| sed 's/ .*//;;s/^["<]/^# *include [<"]/;s/\.h[">]$$/\\.h[">]/' \
) && \
grep -nE -f "$pat" \
$$($(VC_LIST) src | \
grep -Ev '((copy|system)\.h|parse-gram\.c)$$') \
&& { echo '$(ME): the above are already included via system.h'\
1>&2; exit 1; } || :; \
fi
sc_sun_os_names:
@grep -nEi \
'solaris[^[:alnum:]]*2\.(7|8|9|[1-9][0-9])|sunos[^[:alnum:]][6-9]' \
$$($(VC_LIST_EXCEPT)) && \
{ echo '$(ME): found misuse of Sun OS version numbers' 1>&2; \
exit 1; } || :
sc_the_the:
@grep -ni '\' $$($(VC_LIST_EXCEPT)) && \
{ echo '$(ME): found use of "the ''the";' 1>&2; \
exit 1; } || :
sc_tight_scope:
test ! -d src || $(MAKE) -C src $@
sc_trailing_blank:
@grep -n '[ ]$$' $$($(VC_LIST_EXCEPT)) && \
{ echo '$(ME): found trailing blank(s)' \
1>&2; exit 1; } || :
# Match lines like the following, but where there is only one space
# between the options and the description:
# -D, --all-repeated[=delimit-method] print all duplicate lines\n
longopt_re = --[a-z][0-9A-Za-z-]*(\[?=[0-9A-Za-z-]*\]?)?
sc_two_space_separator_in_usage:
@grep -nE '^ *(-[A-Za-z],)? $(longopt_re) [^ ].*\\$$' \
$$($(VC_LIST_EXCEPT)) && \
{ echo "$(ME): help2man requires at least two spaces between"; \
echo "$(ME): an option and its description"; \
1>&2; exit 1; } || :
# Look for diagnostics that aren't marked for translation.
# This won't find any for which error's format string is on a separate line.
sc_unmarked_diagnostics:
@grep -nE \
'\&2; \
exit 1; } || :
# Avoid useless parentheses like those in this example:
# #if defined (SYMBOL) || defined (SYM2)
sc_useless_cpp_parens:
@grep -n '^# *if .*defined *(' $$($(VC_LIST_EXCEPT)) && \
{ echo '$(ME): found useless parentheses in cpp directive' \
1>&2; exit 1; } || :
# Ensure that the c99-to-c89 patch applies cleanly.
patch-check:
if test -f src/c99-to-c89.diff; then \
rm -rf src-c89 $@.1 $@.2 && \
cp -a src src-c89 && \
(cd src-c89; patch -V never --fuzz=0) < src/c99-to-c89.diff \
> $@.1 2>&1 && \
{ grep -v '^patching file ' $@.1 > $@.2 || :; } && \
test -s $@.2 && \
rm -rf src-c89 $@.1 $@.2; \
fi
# Ensure that date's --help output stays in sync with the info
# documentation for GNU strftime. The only exception is %N,
# which date accepts but GNU strftime does not.
extract_char = sed 's/^[^%][^%]*%\(.\).*/\1/'
strftime-check:
if test -f $(srcdir)/src/date.c; then \
grep '^ %. ' $(srcdir)/src/date.c | sort \
| $(extract_char) > $@-src; \
{ echo N; \
info libc date calendar format | grep '^ `%.'\' \
| $(extract_char); } | sort > $@-info; \
diff -u $@-src $@-info || exit 1; \
rm -f $@-src $@-info; \
fi
check-AUTHORS:
test ! -d src || $(MAKE) -C src $@
# Ensure that we use only the standard $(VAR) notation,
# not @...@ in Makefile.am, now that we can rely on automake
# to emit a definition for each substituted variable.
makefile-check:
grep -nE '@[A-Z_0-9]+@' `find $(srcdir) -name Makefile.am` \
&& { echo '$(ME): use $$(...), not @...@' 1>&2; exit 1; } || :
news-date-check: NEWS
today=`date +%Y-%m-%d`; \
if head NEWS | grep '^\*.* $(VERSION_REGEXP) ('$$today')' \
>/dev/null; then \
:; \
else \
echo "version or today's date is not in NEWS" 1>&2; \
exit 1; \
fi
changelog-check:
if head ChangeLog | grep 'Version $(VERSION_REGEXP)\.$$' \
>/dev/null; then \
:; \
else \
echo "$(VERSION) not in ChangeLog" 1>&2; \
exit 1; \
fi
m4-check:
@shopt -s nullglob; \
grep 'AC_DEFUN([^[]' m4/*.m4 /dev/null \
&& { echo '$(ME): quote the first arg to AC_DEFUN' 1>&2; \
exit 1; } || :
# Verify that all source files using _() are listed in po/POTFILES.in.
# FIXME: don't hard-code file names below; use a more general mechanism.
po-check:
if test -f po/POTFILES.in; then \
grep -E -v '^(#|$$)' po/POTFILES.in \
| grep -v '^src/false\.c$$' | sort > $@-1; \
files=; \
for file in $$($(VC_LIST_EXCEPT)) lib/*.[ch]; do \
case $$file in \
djgpp/* | man/*) continue;; \
*/c99-to-c89.diff) continue;; \
esac; \
case $$file in \
*.[ch]) \
base=`expr " $$file" : ' \(.*\)\..'`; \
{ test -f $$base.l || test -f $$base.y; } && continue;; \
esac; \
files="$$files $$file"; \
done; \
grep -E -l '\b(N?_|gettext *)\([^)"]*("|$$)' $$files \
| sort -u > $@-2; \
diff -u $@-1 $@-2 || exit 1; \
rm -f $@-1 $@-2; \
fi
# In a definition of #define AUTHORS "... and ..." where the RHS contains
# the English word `and', the string must be marked with `N_ (...)' so that
# gettext recognizes it as a string requiring translation.
author_mark_check:
@shopt -s nullglob; \
grep -n '^# *define AUTHORS "[^"]* and ' src/*.c /dev/null \
| grep -v ' N_ (' && \
{ echo '$(ME): enclose the above strings in N_ (...)' 1>&2; \
exit 1; } || :
# Sometimes it is useful to change the PATH environment variable
# in Makefiles. When doing so, it's better not to use the Unix-centric
# path separator of `:', but rather the automake-provided `@PATH_SEPARATOR@'.
# It'd be better to use `find -print0 ...|xargs -0 ...', but less portable,
# and there probably aren't many projects with so many Makefile.am files
# that we'd have to worry about limits on command line length.
msg = '$(ME): Do not use `:'\'' above; use @PATH_SEPARATOR@ instead'
makefile_path_separator_check:
@grep -n 'PATH=.*:' `find $(srcdir) -name Makefile.am` \
&& { echo $(msg) 1>&2; exit 1; } || :
# Check that `make alpha' will not fail at the end of the process.
writable-files:
if test -d $(release_archive_dir); then :; else \
mkdir $(release_archive_dir); \
fi
for file in $(distdir).tar.gz $(xd-delta) \
$(release_archive_dir)/$(distdir).tar.gz \
$(release_archive_dir)/$(xd-delta); do \
test -e $$file || continue; \
test -w $$file \
|| { echo ERROR: $$file is not writable; fail=1; }; \
done; \
test "$$fail" && exit 1 || :
v_etc_file = lib/version-etc.c
# Make sure that the copyright date in $(v_etc_file) is up to date.
copyright-check:
@if test -f $(v_etc_file); then \
grep 'enum { COPYRIGHT_YEAR = '$$(date +%Y)' };' $(v_etc_file) \
>/dev/null \
|| { echo 'out of date copyright in $(v_etc_file); update it' 1>&2; \
exit 1; }; \
fi
vc-diff-check:
(CDPATH=; cd $(srcdir) && $(VC) diff) > vc-diffs || :
if test -s vc-diffs; then \
cat vc-diffs; \
echo "Some files are locally modified:" 1>&2; \
exit 1; \
else \
rm vc-diffs; \
fi
cvs-check: vc-diff-check
maintainer-distcheck:
$(MAKE) distcheck
$(MAKE) -C tests $(AM_MAKEFLAGS) maintainer-check
$(MAKE) my-distcheck
# Don't make a distribution if checks fail.
# Also, make sure the NEWS file is up-to-date.
vc-dist: $(local-check) cvs-check maintainer-distcheck
$(MAKE) dist
# Use this to make sure we don't run these programs when building
# from a virgin tgz file, below.
null_AM_MAKEFLAGS = \
ACLOCAL=false \
AUTOCONF=false \
AUTOMAKE=false \
AUTOHEADER=false \
MAKEINFO=false
# Detect format-string/arg-list mismatches that would normally be obscured
# by the use of _(). The --disable-nls effectively defines away that macro,
# and building with CFLAGS='-Wformat -Werror' causes any format warning to be
# treated as a failure. Also, check for shadowing problems with -Wshadow,
# and for pointer arithmetic problems with -Wpointer-arith.
# These CFLAGS are pretty strict. If you build this target, you probably
# have to have a recent version of gcc and glibc headers.
TMPDIR ?= /tmp
t=$(TMPDIR)/$(PACKAGE)/test
my-distcheck: $(local-check) $(release_archive_dir)/$(prev-tgz)
-rm -rf $(t)
mkdir -p $(t)
GZIP=$(GZIP_ENV) $(AMTAR) -C $(t) -zxf $(distdir).tar.gz
cd $(t)/$(distdir) \
&& ./configure --disable-nls \
&& $(MAKE) CFLAGS='-Werror -Wall -Wformat -Wshadow -Wpointer-arith' \
AM_MAKEFLAGS='$(null_AM_MAKEFLAGS)' \
&& $(MAKE) dvi \
&& $(MAKE) check \
&& $(MAKE) distclean
(cd $(t) && mv $(distdir) $(distdir).old \
&& $(AMTAR) -zxf - ) < $(distdir).tar.gz
diff -ur $(t)/$(distdir).old $(t)/$(distdir)
-rm -rf $(t)
@echo "========================"; \
echo "$(distdir).tar.gz is ready for distribution"; \
echo "========================"
prev-tgz = $(PACKAGE)-$(PREV_VERSION).tar.gz
rel-files = $(DIST_ARCHIVES)
announcement: NEWS ChangeLog $(rel-files)
@$(announce_gen) \
--release-type=$(RELEASE_TYPE) \
--package=$(PACKAGE) \
--prev=$(PREV_VERSION) \
--curr=$(VERSION) \
--gpg-key-id=$(gpg_key_ID) \
--news=$(srcdir)/NEWS \
--bootstrap-tools=automake \
$(addprefix --url-dir=, $(url_dir_list))
## ---------------- ##
## Updating files. ##
## ---------------- ##
ftp-gnu = ftp://ftp.gnu.org/gnu
www-gnu = http://www.gnu.org
# Use mv, if you don't have/want move-if-change.
move_if_change ?= move-if-change
emit_upload_commands:
@echo =====================================
@echo =====================================
@echo "$(srcdir)/build-aux/gnupload $(GNUPLOADFLAGS) \\"
@echo " --to $(gnu_rel_host):$(PACKAGE) \\"
@echo " $(rel-files)"
@echo '# send the /tmp/announcement e-mail'
@echo =====================================
@echo =====================================
.PHONY: alpha beta major
alpha beta major: news-date-check changelog-check $(local-check)
test $@ = major \
&& { echo $(VERSION) | grep -E '^[0-9]+(\.[0-9]+)+$$' \
|| { echo "invalid version string: $(VERSION)" 1>&2; exit 1;};}\
|| :
$(MAKE) vc-dist
$(MAKE) $(xd-delta)
$(MAKE) -s announcement RELEASE_TYPE=$@ > /tmp/announce-$(my_distdir)
ln $(rel-files) $(release_archive_dir)
chmod a-w $(rel-files)
$(MAKE) -s emit_upload_commands RELEASE_TYPE=$@
echo $(VERSION) > $(prev_version_file)
$(VC) commit -m \
'$(prev_version_file): Record previous version: $(VERSION).' \
$(prev_version_file)
autoconf2.64-2.64/ChangeLog.0 0000644 0002024 0002024 00000031217 11204770547 015102 0 ustar arthur arthur Mon Jul 20 01:08:01 1992 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acspecific.m4 (AC_ALLOCA): Don't try -lucb -- it's too often broken.
Sat Jul 18 13:40:46 1992 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acspecific.m4 (AC_MAJOR_HEADER): Add missing "$".
* acspecific.m4 (AC_ALLOCA): Put -lc before -lucb.
Fri Jul 17 00:00:07 1992 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* autoconf.sh: Print the lines of the input file where
unresolved macros occur. From Francois Pinard.
* acspecific.m4 (AC_PROG_INSTALL), acgeneral.m4
(AC_PROGRAM_CHECK): Use test -f instead of -s.
* autoconf.sh: grep for undefined macros in output.
Tue Jul 14 01:19:26 1992 David J. MacKenzie (djm@apple-gunkies.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PROGRAM_CHECK): Search PATH manually to
avoid "command not found" messages on /dev/tty. Remove "args
for check" argument.
(AC_INIT): Don't define checkfor; no longer needed.
* acspecific.m4 (AC_PROG_CC, AC_PROG_RANLIB, AC_PROG_YACC,
AC_PROG_LEX): Don't pass "args for check" argument.
* acgeneral.m4 (AC_PROGRAMS_CHECK): New macro.
* acspecific.m4 (AC_PROG_AWK): Use it. Check for mawk, gawk,
nawk, and awk.
(AC_PROG_YACC): Check for byacc if bison isn't found.
* acspecific.m4 (AC_PROG_CC): Renamed from AC_PROG_GCC.
(AC_PROG_YACC): Renamed from AC_PROG_BISON.
(AC_PROG_AWK): Renamed from AC_PROG_GAWK.
(AC_PROG_LEX): Renamed from AC_PROG_FLEX.
* acgeneral.m4 (AC_TEST_PROGRAM): Redirect stderr to /dev/null
both inside and outside the subshell to try to prevent core
dumped messages. Who knows, it might even help.
Thu Jul 9 21:37:45 1992 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_GETLOADAVG): Check for DGUX before SVR4.
Fri Jul 3 01:01:50 1992 David J. MacKenzie (djm@wookumz.gnu.ai.mit.edu)
* acspecific.m4 (AC_REMOTE_TAPE): Renamed from AC_MTIO.
Define HAVE_SYS_MTIO_H instead of NO_MTIO.
(AC_LONG_FILE_NAMES): Renamed from AC_LONG_FILENAMES.
(AC_RSH): Define HAVE_NETDB_H instead of USE_REXEC.
Above mostly from Richard Stallman.
* acgeneral.m4 (AC_MISSING_FUNCS): Macro removed.
* acspecific.m4 (AC_VPRINTF, AC_WAIT3, AC_UTIME_NULL,
AC_TIMEZONE, AC_ST_BLOCKS, AC_ST_BLKSIZE): Change from
FOO_MISSING to HAVE_FOO.
(AC_WAIT3): Renamed from AC_WAIT3_RUSAGE.
(AC_TIMEZONE): Require AC_STRUCT_TM.
(AC_STRUCT_TM): Provide itself.
* acgeneral.m4 (AC_OUTPUT): Add --recheck option to config.status.
* acspecific.m4 (AC_ST_RDEV, AC_CONST): New macros.
* acgeneral.m4 (AC_DEFINE): Don't consider an empty value arg to
be an omitted arg.
Thu Jul 2 16:05:05 1992 David J. MacKenzie (djm@wookumz.gnu.ai.mit.edu)
* acspecific.m4 (AC_GETLOADAVG): New macro.
* autoconf.sh: Only reject an arg that's not a known option if it
is an option.
Tue Jun 30 16:08:04 1992 David J. MacKenzie (djm@wookumz.gnu.ai.mit.edu)
* acgeneral.m4 (AC_INIT, AC_OUTPUT): Eliminate vpsub.
Thu Jun 25 12:42:10 1992 David J. MacKenzie (djm@apple-gunkies.gnu.ai.mit.edu)
* autoconf.sh: Add --version option.
* acgeneral.m4: Support it.
Wed Jun 24 14:04:13 1992 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acspecific.m4 (AC_TIMEZONE): Do the checks unconditionally,
not only if strftime.o is in LIBOBJS.
* acspecific.m4 (AC_DIR_HEADER): Don't assume sys/dir.h exists.
* acgeneral.m4 (AC_PROGRAM_CHECK): Don't include the program
name in the value-if-found. From Rich Murphey.
* acspecific.m4 (AC_PROG_{GCC,RANLIB,GAWK,BISON,FLEX}): Change
callers.
* acgeneral.m4 (AC_OUTPUT): Mention the args given to
configure in a comment in config.status.
Fri Jun 19 13:18:12 1992 David J. MacKenzie (djm@wookumz.gnu.ai.mit.edu)
* acgeneral.m4 (AC_FUNC_CHECK): Use the third arg when it's
non-null, not when it's null. From Ian Lance Taylor.
Thu Jun 18 12:10:27 1992 David J. MacKenzie (djm@wookumz.gnu.ai.mit.edu)
* acgeneral.m4 (AC_BEFORE): Print message in next-error format.
From Franc,ois Pinard.
* acgeneral.m4 (AC_PROGRAM_CHECK): If args-for-use is empty,
don't put a space after the program name.
* acspecific.m4 (AC_DECLARE_YYTEXT): Move AC_REQUIREs from
AC_PROG_FLEX to here, where they belong.
* acspecific.m4 (AC_MEMORY_H): Look for memchr instead of memcpy.
From Karl Berry.
Wed Jun 17 09:56:59 1992 David J. MacKenzie (djm@wookumz.gnu.ai.mit.edu)
* acgeneral.m4 (AC_BEFORE): New macro.
* acspecific.m4 (AC_PROG_GCC, AC_DIR_HEADER, AC_AIX,
AC_MINIX, AC_ISC_POSIX): Use it.
Tue Jun 16 14:46:29 1992 David J. MacKenzie (djm@wookumz.gnu.ai.mit.edu)
* autoconf.sh: Remove incomplete output file if interrupted.
* acgeneral.m4 (AC_INIT): Avoid running an extra subshell for pwd.
From Franc,ois Pinard.
Mon Jun 15 21:27:49 1992 David J. MacKenzie (djm@wookumz.gnu.ai.mit.edu)
* acgeneral.m4 (AC_TEST_PROGRAM): Take another arg for
cross-compiling.
* acspecific.m4 (AC_CROSS_CHECK): New program.
* acgeneral.m4 (AC_REQUIRE, AC_PROVIDE): New macros.
(AC_HEADER_EGREP, AC_PROGRAM_EGREP, AC_TEST_CPP): Use them.
* acspecific.m4 (AC_PROG_GCC, AC_GCC_TRADITIONAL, AC_PROG_CPP,
AC_PROG_FLEX, AC_INLINE): Ditto.
Sat Jun 13 17:54:24 1992 David J. MacKenzie (djm@wookumz.gnu.ai.mit.edu)
* acspecific.m4 (AC_MEMORY_H): echo what it's doing.
Thu Jun 11 14:18:35 1992 David J. MacKenzie (djm@wookumz.gnu.ai.mit.edu)
* acspecific.m4 (AC_MINUS_C_MINUS_O, AC_INLINE,
AC_SETVBUF_REVERSED): New macros.
(AC_ALLOCA): Define HAVE_ALLOCA_H if appropriate.
* acgeneral.m4 (AC_INIT): Do pwd in the srcdir, not current dir.
Scan through "$@" (implicitly) instead of $*.
(AC_HEADER_EGREP, AC_PROGRAM_EGREP, AC_COMPILE_CHECK,
AC_TEST_PROGRAM, AC_TEST_CPP): Supply a `:' if `true' argument
is empty.
* acgeneral.m4, acspecific.m4: Omit `:' in callers.
Wed Jun 10 12:03:11 1992 David J. MacKenzie (djm@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_HEADER_EGREP, AC_PROGRAM_EGREP, AC_HEADER_CHECK,
AC_COMPILE_CHECK, AC_TEST_PROGRAM, AC_TEST_CPP, AC_FUNC_CHECK):
Make the last argument (program to run if test fails) optional.
(AC_HAVE_FUNCS, AC_HAVE_HEADERS): Don't pass optional last args.
* acspecific.m4 (most macros): Likewise.
Mon Jun 8 16:27:10 1992 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acspecific.m4 (AC_VFORK): Get rid of backquotes.
* acgeneral.m4 (AC_OUTPUT): Exit with 0 status when
--no-create was given.
Only write to the AC_CONFIG_NAME file if it doesn't exist or is
different from what we'd write. From Ian Lance Taylor.
Thu Jun 4 14:46:22 1992 David J. MacKenzie (djm@geech.gnu.ai.mit.edu)
* acspecific.m4 (AC_UNISTD_H, AC_UID_T, AC_SIZE_T, AC_PID_T,
AC_ST_BLKSIZE, AC_STRUCT_TM): Quote the whole macro body.
* acgeneral.m4 (AC_OUTPUT): Look for config header.in in
top_srcdir, not srcdir. From Garrett Wollman.
* acgeneral.m4 (AC_OUTPUT): Don't add make .NOEXPORT rule to
output files.
* acgeneral.m4, acspecific.m4: Rename AC_PROG_CHECK to
AC_PROGRAM_CHECK, AC_PROG_EGREP to AC_PROGRAM_EGREP,
AC_TEST_PROG to AC_TEST_PROGRAM.
Wed Jun 3 14:00:07 1992 David J. MacKenzie (djm@wookumz.gnu.ai.mit.edu)
* acgeneral.m4 (AC_INIT, AC_OUTPUT): Add --no-create option.
* acgeneral.m4 (AC_COMPILE_CHECK): Check the C compiler exit
status instead of trying to run the test program.
* acspecific.m4 (AC_RESTARTABLE_SYSCALLS): Use AC_TEST_PROG
instead of doing it by hand.
* acspecific.m4 (AC_PROG_GCC, AC_AIX, AC_XENIX_DIR,
AC_SCO_INTL, AC_DYNIX_SEQ): Use AC_PROG_EGREP instead of
AC_TEST_PROG.
* acgeneral.m4 (AC_TEST_PROG): Renamed from AC_TEST_PROGRAM.
* acgeneral.m4 (AC_INIT): Don't relativize `.'.
(AC_OUTPUT): Substitute the subdirectory path, not the top
path, for srcdir, unless the top path is `.'.
* acgeneral.m4 (AC_OUTPUT): Special-case substituting DEFS.
From Ian Lance Taylor.
* acspecific.m4 (AC_GCC_TRADITIONAL): Use CPP instead of
compiling a test program.
* acgeneral.m4 (AC_TEST_CPP): Pass DEFS to CPP.
(AC_HEADER_EGREP): Don't echo anything.
(AC_PROG_EGREP): New macro.
Tue Jun 2 14:07:27 1992 David J. MacKenzie (djm@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_CONFIG_HEADER): Renamed from AC_HEADER_FILE.
Rename AC_HEADER_NAME TO AC_CONFIG_NAME.
(AC_SUBST): Add the arg variable to a diversion for config.status.
(AC_OUTPUT): Write the code to create output files into config.status,
then run that. Always use `awk'; checking for nawk in a subshell
doesn't seem to work on 4.3BSD.
* acgeneral.m4 (AC_HEADER_EGREP): Pass DEFS to CPP.
* acspecific.m4 (AC_SIZE_T): Define size_t as int, not long.
From Ian Lance Taylor.
* acspecific.m4 (AC_STDC_HEADERS): Also check for stdarg.h.
From Garrett Wollman.
Wed May 20 00:34:03 1992 David J. MacKenzie (djm@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT): Use nawk if available.
* acgeneral.m4 (AC_INIT): Make srcdir=`.' absolute.
* acspecific.m4 (AC_DIR_HEADER): Include sys/types.h before
dir header in closedir test.
* acgeneral.m4, acspecific.m4: AC_LIBTHING_CHECK renamed to
AC_COMPILE_CHECK.
* acspecific.m4 (AC_AIX, AC_XENIX_DIR, AC_SCO_INTL, AC_DYNIX_SEQ):
Use the C preprocessor instead of just looking for files.
Mon May 18 20:51:50 1992 David J. MacKenzie (djm@wookumz.gnu.ai.mit.edu)
* acspecific.m4 (WORDS_BIGENDIAN): Fix exit expression.
(AC_DECLARE_YYTEXT): Eval $CPP.
(AC_DIR_HEADER): Compile the test program; don't just
preprocess it. Above all from Karl Berry.
Fri May 15 00:57:01 1992 David J. MacKenzie (djm@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_AIX): Don't define _BSD, to avoid getting
union wait.
* acgeneral.m4 (AC_HEADER_EGREP): New macro, replacing AC_IDENT*.
* acspecific.m4 (AC_MEMORY_H, AC_RETSIGTYPE, AC_{UID,SIZE,PID}_T):
Use it.
* acgeneral.m4 (AC_TEST_CPP): New macro.
(AC_IDENT_{PRESENT,MISSING}): Macros deleted.
(AC_HEADER_CHECK): Use AC_TEST_CPP, replaces AC_HEADER_{PRESENT,
MISSING}.
(AC_LIBTHING_CHECK): Replace AC_LIBTHING_{PRESENT,MISSING}.
(AC_FUNC_CHECK): Replace AC_FUNC_PRESENT.
(AC_INIT): Don't set INCLUDEDIR.
* acspecific.m4 (AC_DIR_HEADER): Use AC_TEST_CPP.
* All other macros: Don't refer to INCLUDEDIR; use
AC_HEADER_CHECK instead.
* acspecific.m4 (AC_PROG_CPP): Don't evaluate $CC until called.
Try $CC -E before /lib/cpp.
Thu May 14 23:15:02 1992 David J. MacKenzie (djm@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT): Remove each file before creating it.
Sat May 9 14:52:57 1992 David J. MacKenzie (djm@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_WAIT3_RUSAGE): New macro.
* acgeneral.m4 (AC_INIT, AC_OUTPUT): Use AC_SUBST instead of a
special mechanism to substitute for srcdir.
* acgeneral.m4 (AC_OUTPUT): Substitute for exec_prefix if it
was given, even if not substituting for prefix.
* acgeneral.m4 (AC_INIT, AC_OUTPUT): Remove @VPATH@
substitution; use @srcdir@ instead.
Sun May 3 01:21:47 1992 David J. MacKenzie (djm@geech.gnu.ai.mit.edu)
* acgeneral.m4 (AC_NOTICE): New macro taken from AC_INIT, to avoid
m4 coredump. From Karl Berry.
* acgeneral.m4 (AC_OUTPUT): Look for header-file.in in $srcdir,
not current dir.
* acgeneral.m4 (AC_IDENT_{MISSING,PRESENT}): Make them agree
with the documentation -- the third arg is a shell command,
not an identifier to define.
* acspecific.m4 (AC_DIR_HEADER): Change the caller.
Mon Apr 27 09:15:15 1992 David J. MacKenzie (djm@churchy.gnu.ai.mit.edu)
* acspecific.m4: Use AC_TEST_PROGRAM wherever $compile was
being used directly.
* acgeneral.m4 (AC_HAVE_HEADERS, AC_HAVE_FUNCS,
AC_FUNC_PRESENT, AC_TEST_PROGRAM): New macros from Ian Lance Taylor.
* acspecific.m4 (AC_PROG_INSTALL): Screen out /usr/sbin/install.
(AC_CHAR_UNSIGNED): Don't define __CHAR_UNSIGNED__ if it's
predefined.
Fri Apr 24 10:08:21 1992 David J. MacKenzie (djm@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT): Make the arg a list of files instead of
directories.
* acspecific.m4 (AC_ALLOCA): Check whether the alternate libraries
actually contain alloca. From Ian Lance Taylor.
* acspecific.m4 (AC_PROG_CPP): New macro.
* acgeneral.m4 (AC_OUTPUT): Allow newly defined values to be more
than one word for AC_HEADER_FILE. From Karl Berry.
* acgeneral.m4 (AC_OUTPUT): Don't substitute DEFS if AC_HEADER_FILE.
(AC_LIBTHING{PRESENT,MISSING}): Run conftest in subshell.
From Ian Lance Taylor.
-----
Copyright (C) 1992 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation, either version 3 of the
License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see
.
autoconf2.64-2.64/THANKS 0000644 0002024 0002024 00000044570 11227003710 014075 0 ustar arthur arthur GNU Autoconf THANKS file
GNU Autoconf was originally written by David J. MacKenzie. It would
not be what it is today without the invaluable help of these people,
who have reported problems, suggested improvements, or submitted
actual code. Please help us keep this list complete and free from
errors. Also see the AUTHORS file for the list of people with
contributions significant enough to warrant copyright assignment.
Aaron Crane aaronc@pobox.com
Aaron M. Ucko amu@alum.mit.edu
Aaron W. LaFramboise aaronenvelope277@aaronwl.com
Adam J. Richter adam@yggdrasil.com
Aharon Robbins arnold@gnu.org
Akim Demaille akim@freefriends.org
Akinori Musha knu@iDaemons.org
Alain Knaff Alain.Knaff@imag.fr
Albert Chin-A-Young china@thewrittenword.com
Alec Wolman wolman@cs.washington.edu
Alex Unleashed unledev@gmail.com
Alexander Kurz alexander.kurz@qsc.de
Alexander Mai ?
Alexandre Duret-Lutz duret_g@epita.fr
Alexandre Julliard ?
Alexandre Oliva oliva@lsd.ic.unicamp.br
Alfred G. de Wijn dwijn@iluvatar.eu.org
Allan Caffee allan.caffee@gmail.com
Andreas Buening andreas.buening@nexgo.de
Andreas Jaeger aj@suse.de
Andreas Schott schott@rzg.mpg.de
Andreas Schwab schwab@issan.informatik.uni-dortmund.de
Andreas Waechter andreasw@watson.ibm.com
Andrej Borsenkow borsenkow.msk@sni.de
Andrew Belov ?
Andrew Church achurch@achurch.org
Andrey Simonenko simon@comsys.ntu-kpi.kiev.ua
Andris Pavenis andris.pavenis@iki.fi
Anthony N. Frasso afrasso@yahoo.com
Art Haas ahaas@neosoft.com
Arto C. Nirkko ?
Artur Frysiak wiget@pld.org.pl
Assar Westerlund assar@sics.se
Axel Thimm Axel.Thimm@physik.fu-berlin.de
Ben Elliston bje@redhat.com
Ben Pfaff pfaffben@debian.org
Bill Moseley moseley@hank.org
Bill Northcott w.northcott@unsw.edu.au
Bill Sommerfeld sommerfeld@apollo.hp.com
BJ Terry bjterry@gmail.com
Bob Friesenhahn bfriesen@simple.dallas.tx.us
Bob Proulx bob@proulx.com
Bob Rossi bob_rossi@cox.net
Bob Wilson bwilson@tensilica.com
Brad Walker me@bradmwalker.com
Braden McDaniel braden@endoframe.com
Bram Moolenaar bram@vim.org
Brian Gough bjg@network-theory.co.uk
Bruce Dugan bld0401@gmail.com
Bruce Korb bkorb@gnu.org
Bruce Lilly ?
Bruno Haible haible@ilog.fr
Björn Lindqvist bjourne@gmail.com
Carl Edman cedman@princeton.edu
Carlos Velasco carlosev@newipnet.com
Chad R. Larson chad@anasazi.com
Charles 'Buck' Krasic krasic@cs.ubc.ca
Chikama Masaki masaki.chikama@gmail.com
Chris P. Ross cross@uu.net
Chris Pickett chris.pickett@mail.mcgill.ca
Chris Provenzano proven@cygnus.com
Chris Torek torek@bsdi.com
Christian Cornelssen ccorn@cs.tu-berlin.de
Christian Krackowizer ckrackowiz@std.schuler-ag.com
Christian Krone krischan@sql.de
Christian Rössel christian.roessel@gmx.de
Christopher Hulbert cchgroupmail@gmail.com
Christopher Lee chrislee@ri.cmu.edu
Clinton Roy clinton.roy@gmail.com
Cort Dougan cort@cs.nmt.edu
D'Arcy A MacIsaac ?
Dalibor Topic robilad@kaffe.org
Dan Manthey dan_manthey@partech.com
Daniel Carroll dan@mesastate.edu
Daniel Jacobowitz drow@mvista.com
Daniel Reed ?
Daniele Arena daniele@ripe.net
Dave Adams adams@hpesdwa.fc.hp.com
Dave Erickson retrorandomaccess@hotmail.com
Dave Love fx@gnu.org
David Byron dbyron@hheld.com
David Carter david@carter.net
David Cournapeau david@ar.media.kyoto-u.ac.jp
David Fang fang@csl.cornell.edu
David J. MacKenzie djm@uunet.uu.net
David M. Lloyd dmlloyd@tds.net
David Morgan dmorgan@symark.com
David Relson relson@osagesoftware.com
Dennis J. Linse ?
Derek R. Price derek.price@openavenue.com
Didier Desseaux didess@infonie.fr
Didier Verna didier@xemacs.org
Dietmar P. Schindler schd@mra.man.de
Doug Evans dje@canuck.cygnus.com
Dries Kimpe ?
Edouard Bechetoille ebecheto@ens-lyon.fr
Elbert Pol elbert.pol@gmail.com
Eli Zaretskii eliz@gnu.org
Elias Pipping pipping@macports.org
Enrique Robledo Arnuncio enrique.robledo@wanadoo.es
Erez Zadok ezk@cs.columbia.edu
Eric Backus ericb@lsid.hp.com
Eric Blake ebb9@byu.net
Eric Lemings lemings@roguewave.com
Eric Mumpower nocturne@mit.edu
Eric Paire ?
Eric Sunshine sunshine@sunshineco.com
Ezra Peisach epeisach@zif.mit.edu
Fedor Sergeev ?
Felix Lee flee@cygnus.com
Franceseco Romani fromani@gmail.com
Frank Denis j@jedi.claranet.fr
François Pinard pinard@iro.umontreal.ca
Fred Kreek Fred.Kreek@kadaster.nl
Frederik Fouvry fouvry@CoLi.Uni-SB.DE
Gareth McCaughan gareth.mccaughan@pobox.com
Gary V. Vaughan gvaughan@oranda.demon.co.uk
Geir Ove Myhr myhr@stud.fim.ntnu.no
Gerrit P. Haase gp@familiehaase.de
Gideon Go gideon.go@gmail.com
Giuseppe Guerrini guisguerrini@racine.ra.it
Glenn P. Davis davis@unidata.ucar.edu
Godmar Back gback@cs.utah.edu
Gordon Matzigkeit gord@trick.fig.org
Graham Jenkins c714553@vus415.telstra.com.au
Greg A. Woods woods@weird.com
Greg Schafer gschafer@zip.com.au
Gregorio Guidi ?
Gregory Giannoni sand@narguile.org
Guido Draheim Guido.Draheim@gmx.de
Guido Flohr gufl0000@stud.uni-sb.de
Guido van Rossum ?
Guillermo Gomez gomez@mi.uni-erlangen.de
H. Merijn Brand h.m.brand@hccnet.nl
H. Peter Anvin ?
H.J. Lu hjl@gnu.org
Hallvard B Furuseth h.b.furuseth@usit.uio.no
Hans Aberg haberg@math.su.se
Hans Olsson Hans.Olsson@dna.lth.se
Hans Ulrich Niedermann hun@n-dimensional.de
Harlan Stenn stenn@whimsy.udel.edu
Henk Krus h.krus@cyclone.nl
Howard Chu hyc@highlandsun.com
Ian Lance Taylor ian@cygnus.com
Ian Macdonald iamacdo@telkomsa.net
Ian Redfern Ian.Redfern@logicacmg.com
Ilya Bobir ilya.bobir@gmail.com
Ilya Zakharevich ilya@Math.Berkeley.EDU
Ineiev ineiev@yahoo.co.uk
Iohannes m zmoelnig zmoelnig@iem.at
J C Fitzgerald v7022@wave.co.nz
Jaap Haitsma jaap@haitsma.org
James A. Lupo lupoja@feynman.ml.wpafb.af.mil
Jan Madzik jmadzik@gmail.com
Jason Molenda jsm@cygnus.com
Jeff Garzik jgarzik@pobox.com
Jeff Painter ?
Jeff Squyres jsquyres@cisco.com
Jeffrey A Law law@cygnus.com
Jeffrey J. Barteet ?
Jennis Pruett ?
Jens Petersen petersen@redhat.com
Jens Schmidt jens.schmidt35@arcor.de
Jeremy Yallop jeremy@yallop.org
Jerker Bäck jerker.back@home.se
Jim Blandy jimb@wookumz.gnu.ai.mit.edu
Jim Meyering meyering@ascend.com
Jiro Takabatake jiro@din.or.jp
Jochen Friedrich jochen@scram.de
Joel E. Denny jdenny@ces.clemson.edu
Joey Mingrone joey@mingrone.org
Johan Danielsson joda@pdc.kth.se
John Calcote john.calcote@gmail.com
John David Anglin dave@hiauly1.hia.nrc.ca
John Fortin fortinj@attglobal.net
John Interrante interran@uluru.stanford.edu
John R. Cary cary@txcorp.com
John W. Eaton jwe@bevo.che.wisc.edu
Jonathan Kamens jik@kamens.brookline.ma.us
Josef Tran josef@timetrackertechnology.com
Joseph S. Myers jsm28@cam.ac.uk
Jules Colding colding@42tools.com
Julian Onions j.onions@nexor.co.uk
Julien Danjou acid@debian.org
Julio Garvia ?
Justace Clutter ?
Jörn Rennecke amylaar@cygnus.co.uk
Karl Berry karl@cs.umb.edu
Karl Heuer kwzh@gnu.org
Karsten Hopp karsten@redhat.com
Kate Hedstrom ?
Kathryn Hargreaves kathryn@deas.harvard.edu
Kaveh R. Ghazi ghazi@caip.rutgers.edu
Keith Bostic bostic@abyssinian.sleepycat.com
Keith Marshall keith.marshall@total.com
Kelly Anderson tgcorp@attglobal.net
Ken Pizzini ken@halcyon.com
Ken Raeburn raeburn@cygnus.com
Kevin Ryde user42@zip.com.au
Klee Dienes kdienes@apple.com
Koji Arai JCA02266@nifty.ne.jp
Kristian Kvilekval kris@cs.ucsb.edu
Kurt D. Zeilenga kurt@openldap.org
Larry Jones larry.jones@sdrc.com
Larry Schmitt larry@mail.haleakalawebdesigns.com
Larry Schwimmer rosebud@cyclone.stanford.edu
Lars Hecking lhecking@nmrc.ucc.ie
Lars J. Aas larsa@sim.no
Laurence Darbe ldarby@tuffmail.com
Leo Moisio leo.moisio@gmail.com
Loulou Pouchet loulou@lrde.epita.fr
Ludovic Courtes ?
Magnus Therning therning@gforge.natlab.research.philips.com
Manu manubee@wanadoo.fr
Marc Espie Marc.Espie@liafa.jussieu.fr
Marcus Brinkmann ?
Marcus Daniels marcus@sysc.pdx.edu
Marcus Thiessel marcus@xemacs.org
Mark Cave-Ayland ?
Mark D. Baushke ?
Mark D. Roth ?
Mark Elbrecht snowball3@usa.net
Mark Kettenis kettenis@gnu.org
Markku Savela msa@msa.tte.vtt.fi
Markus Oberhumer markus.oberhumer@jk.uni-linz.ac.at
Martin Buchholz martin@xemacs.org
Martin Costabel costabel@wanadoo.fr
Martin Frydl martin@systinet.com
Martin Koeppe mkoeppe@gmx.de
Martin Mokrejs mmokrejs@natur.cuni.cz
Martin Wilck martin@tropos.de
Martyn Johnson Martyn.Johnson@cl.cam.ac.uk
Matěj Týč matej.tyc@gmail.com
Matteo Frigo ?
Matthew D. Langston langston@SLAC.Stanford.EDU
Matthew Mueller donut@azstarnet.com
Matthew Woehlke mw_triad@users.sourceforge.net
Matthias Andree matthias.andree@gmx.de
Michael Elizabeth Chastain chastain@cygnus.com
Michael Jenning ?
Michael Matz matz@kde.org
Michael Schoene mrs@mlc.de
Michael Wardle ?
Mike Frysinger vapier@gentoo.org
Mike Hopkirk hops@sco.com
Mike Stump mrs@wrs.com
Mikulas Patocka ?
Miles Bader miles@gnu.ai.mit.edu
Mo DeJong mdejong@cygnus.com
Momchil Velkov velco@fadata.bg
Monty Taylor mordred@inaugust.com
Morten Eriksen mortene@sim.no
Motoyuki Kasahara m-kasahr@sra.co.jp
Nathanael Nerode neroden@gcc.gnu.org
Nelson H. F. Beebe beebe@math.utah.edu
Nicolas Joly njoly@pasteur.fr
Nicolás Lichtmaier jnl@synapsis-sa.com.ar
Nishio Futoshi fut_nis@d3.dion.ne.jp
Noah Elliott elliott@hera.llnl.gov
Noah Friedman friedman@gnu.ai.mit.edu
Noah Misch noah@cs.caltech.edu
Norman Gray ?
Olaf Lenz olenz@fias.uni-frankfurt.de
Ole Holm Nielsen Ole.H.Nielsen@fysik.dtu.dk
Oliver Kiddle opk@zsh.org
Olly Betts olly@survex.com
Ossama Othman ossama@debian.org
Pallav Gupta pallavgupta@gmail.com
Paolo Bonzini bonzini@gnu.org
Patrick Tullmann tullmann@cs.utah.edu
Patrick Welche prlw1@newn.cam.ac.uk
Paul Berrevoets paul@swi.com
Paul D. Smith psmith@gnu.org
Paul Eggert eggert@cs.ucla.edu
Paul Gampe paulg@apnic.net
Paul Jarc prj@po.cwru.edu
Paul Martinolich martinol@datasync.com
Paul Pogonyshev ?
Paul Townsend ?
Pavel Roskin pavel_roskin@geocities.com
Per Øyvind Karlsen peroyvind@mandriva.org
Peter Breitenlohner peb@mppmu.mpg.de
Peter Eisentraut peter_e@gmx.net
Peter Hendrickson pdh@wiredyne.com
Peter O'Gorman peter@pogma.com
Peter Palfrader weasel@debian.org
Peter Simons simons@cryp.to
Peter Stephenson pws@csr.com
Philipp Thomas kthomas@gwdg.de
Philippe De Muyter ?
Pierre pierre42d@9online.fr
Pontus Skoeld pont@soua.net
Rainer Orth ro@TechFak.Uni-Bielefeld.DE
Raja R Harinath harinath@cs.umn.edu
Ralf Corsepius corsepiu@faw.uni-ulm.de
Ralf Menzel menzel@ls6.cs.uni-dortmund.de
Ralf S. Engelschall rse@engelschall.com
Ralf Wildenhues Ralf.Wildenhues@gmx.de
Reuben Thomas rrt@sc3d.org
Richard Dawe rich@phekda.freeserve.co.uk
Richard Stallman rms@gnu.org
Robert Lipe robertlipe@usa.net
Robert S. Maier rsm@math.arizona.edu
Roberto Bagnara bagnara@cs.unipr.it
Roger Leigh rleigh@whinlatter.ukfsn.org
Roland McGrath roland@gnu.org
Rolf Ebert rolf.ebert.gcc@gmx.de
Rolf Vandevaart Rolf.Vandevaart@sun.com
Romain Lenglet romain.lenglet@laposte.net
Ruediger Kuhlmann info@ruediger-kuhlmann.de
Ruslan Babayev ruslan@babayev.com
Russ Allbery rra@stanford.edu
Russ Boylan ross@biostat.ucsf.edu
Ryuji Abe raeva@t3.rim.or.jp
Sam Sexton Sam.Sexton@reuters.com
Sam Sirlin sam@kalessin.jpl.nasa.gov
Sam Varshavchik mrsam@courier-mta.com
Sander Niemeijer niemeijer@science-and-technology.nl
Scott Bambrough scottb@corelcomputer.com
Scott Stanton stanton@scriptics.com
Sebastian Freundt hroptatyr@gna.org
Sergey Poznyakoff ?
Simon Josefsson jas@extundo.com
Simon Leinen simon@lia.di.epfl.ch
Slava Sysoltsev Viatcheslav.Sysoltsev@h-d-gmbh.de
Stefan Seefeld stefan@codesourcery.com
Stefan `Sec' Zehl ?
Stepan Kasal kasal@ucw.cz
Stéphane Chazelas Stephane_Chazelas@yahoo.fr
Stephen Gildea filtered@against.spam
Stephen Rasku srasku@mail.tantalus-systems.com
Stephen P. Schaefer sschaefer@acm.org
Steve Chamberlain sac@cygnus.com
Steve Huston shuston@riverace.com
Steve Robbins steve@nyongwa.montreal.qc.ca
Steven G. Johnson stevenj@alum.mit.edu
Steven R. Loomis srl@icu-project.org
Stu Grossman grossman@cygnus.com
Sumit Pandya sumit@elitecore.com
Syd Polk spolk@cygnus.com
T.E. Dickey dickey@clark.net
Ted Bullock tbullock@canada.com
Theodore Ts'o tytso@mit.edu
Thien-Thi Nguyen ttn@gnu.org
Thomas Winder tom@vlsivie.tuwien.ac.at
Tim Freeman tim@fungible.com
Tim Mooney mooney@dogbert.cc.ndsu.NoDak.edu
Tim Rice tim@multitalents.net
Tim Van Holder tim.van.holder@pandora.be
Tom Browder tom.browder@gmail.com
Tom Epperly tepperly@llnl.gov
Tom Lane tgl@sss.pgh.pa.us
Tom Purcell Tom.Purcell@wang.com
Tom Tromey tromey@cygnus.com
Tom Yu tlyu@mit.edu
Tomohiro Suzuki ?
Tony Leneis tony@plaza.ds.adp.com
Toshio Kuratomi ?
Uwe Seimet us@orbacus.com
Vance Shipley vances@motivity.ca
Viktor Dukhovni viktor@anaheim.esm.com
Ville Karaila karaila@iki.fi
Vincent Lefèvre vincent@vinc17.org
Vincent Torri vtorri at univ-evry.fr
Vladimir Volovich vvv@vsu.ru
Volker Borchert bt@teknon.de
Wayne Chapeskie waynec@spinnaker.com
Werner Lemberg wl@gnu.org
Wilfredo Sanchez wsanchez@apple.com
William Pursell bill.pursell@gmail.com
Wolfgang Mueller Wolfgang.Mueller@cui.unige.ch
Yury Puhalsky pooh@cryptopro.ru
Zack Weinberg zack@codesourcery.com
? Seanster@Seanster.com
Many people are not named here because we lost track of them. We
thank them! Please, help us keep this list up to date.
================
Local Variables:
mode: text
coding: utf-8
End:
Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,
2008, 2009 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see .
autoconf2.64-2.64/AUTHORS 0000644 0002024 0002024 00000016210 11207476641 014237 0 ustar arthur arthur Authors of GNU Autoconf.
Autoconf was originally written by David MacKenzie, with help from
François Pinard, Karl Berry, Richard Pixley, Ian Lance Taylor, Roland
McGrath, Noah Friedman, david d zuhn, and many others.
Ben Elliston next took over the maintenance, facing a huge Autoconf
backlog that had been piling up since the departure of David. Other
maintainers have included Akim Demaille, Jim Meyering, Alexandre
Oliva, and Tom Tromey, with plenty of contributions from Lars J. Aas,
Mo DeJong, Steven G. Johnson, Matthew D. Langston, Pavel Roskin.
Today, the primary maintainers are Paul Eggert and Eric Blake, with
help from Ralf Wildenhues, Stepan Kasal, and Benoit Sigoure. Many
other people have contributed, as listed in the THANKS file.
The following contributors have warranted legal paper exchanges with
the Free Software Foundation for their contributions to GNU Autoconf.
This list results from searching for AUTOCONF in the file
/gd/gnuorg/copyright.list on the fencepost.gnu.org machine.
David J. MacKenzie djm@gnu.org 1991-07-09
James L. Avera ? 1993-10-04
Roland McGrath roland@gnu.org 1994-06-24
Noah Friedman friedman@gnu.org 1994-07-15
Francois Pinard pinard@iro.umontreal.ca 1997-02-02
Thomas E. Dickey dickey@clark.net 1998-01-11
Matthew D. Langston langston@slac.stanford.edu 1998-09-29
Mark Elbrecht snowball3@usa.net 1999-01-11
Akim Demaille akim@gnu.org 1999-02-02
Pavel Roskin pavel_roskin@geocities.com 1999-02-24
Alexandre Oliva oliva@dcc.unicamp.br 1999-03-26
Thomas Tanner tanner@ffii.org 1999-06-23
Gary V. Vaughan gary@gnu.org 2000-01-10
Joseph Samuel Myers jsm28@cam.ac.uk 2000-03-13
Lars J. Aas larsa@sim.no 2000-07-07
Morten Eriksen mortene@sim.no 2000-07-07
Martin Wilck martin@tropos.de 2000-07-12
Paul Eggert eggert@twinsun.com 2000-10-13
Alexandre Duret-Lutz duret_g@epita.fr 2001-02-12
Tim Van Holder tim.van.holder@pandora.be 2001-02-13
Christian Marquardt marq@gfz-potsdam.de 2001-02-19
Derek R. Price dprice@collab.net 2001-03-12
Markus Kuhn Markus.Kuhn@cl.cam.ac.uk 2001-07-07
Erik Lindahl erik@theophys.kth.se 2001-08-22
Hans-Peter Nilsson hp@bitrange.com 2001-10-24
Paul Wagland paul@wagland.net 2001-10-30
Paolo Bonzini bonzini@gnu.org 2001-11-08
Nishio Futoshi fut_nis@d3.dion.ne.jp 2002-01-23
Federico G. Schwindt fgsch@openbsd.org 2002-05-21
Mark D. Roth roth@feep.net 2002-05-28
Greg McGary greg@mcgary.org 2002-06-05
Charles Stephen Wilson cwilson@ece.gatech.edu 2002-07-25
Robert Bernstein rocky@panix.com 2002-08-20
Assar Westerlund assar@kth.se 2002-09-13
Scott Bambrough sbambrough@storm.ca 2002-09-24
Richard Dawe rich@phekda.freeserve.co.uk 2003-01-23
Andreas Buening andreas.buening@nexgo.de 2003-02-18
Raja R. Harinath harinath@acm.org 2003-02-25
Ilya Zakharevich ilya@Math.Berkeley.EDU 2003-03-11
Kaveh Ghazi ghazi@caip.rutgers.edu 2003-03-15
Felix Lee felix.1@canids.net 2003-03-31
Nathanael Nerode neroden@twcny.rr.com 2003-04-04
Gavin Puche user42@zip.com.au 2003-04-10
Steven Glenn Johnson stevenj@alum.mit.edu 2003-07-26
Bernardo Innocenti bernie@codewiz.org 2003-07-31
Albert Marsden Chin-A-Young china@thewrittenword.com 2003-08-02
Ralf Corsepius corsepiu@faw.uni-ulm.de 2003-09-03
Scott Remnant scott@netsplit.com 2003-10-04
Daniel Jacobowitz dan@debian.org 2003-10-17
Kevin Fleming kpfleming@backtobasicsmgmt.com 2003-11-17
John David Anglin dave.anglin@nrc-cnrc.gc.ca 2004-01-21
Eric Sunshine sunshine@sunshineco.com 2004-01-25
Ralf Wildenhues Ralf.Wildenhues@gmx.de 2004-02-12
Noah Jeffrey Misch noah@cs.caltech.edu 2004-07-05
Thorsten Glaser tg@66h.42h.de 2004-10-11
Peter O'Gorman peter@pogma.com 2004-11-14
Toshio Ernie Kuratomi toshio@tiki-lounge.com 2004-11-17
Roger Leigh rleigh@whinlatter.ukfsn.org 2004-12-09
Ian Lance Taylor ian@airs.com 2004-12-22
Daniel Manthey dan_manthey@partech.com 2005-02-14
Gregorio Guidi greg_g@gentoo.org 2005-03-03
Bruno Haible bruno@clisp.org 2005-06-12
Toby Oliver Hilary White tow21@cam.ac.uk 2005-10-18
Eric Benjamin Blake ebb9@byu.net 2006-01-18
Romain Lenglet romain.lenglet@laposte.net 2006-02-10
Markus Duft markus.duft@salomon.at 2006-08-03
Robert Schiele rschiele@gmail.com 2006-09-12
Joel Edward Denny jdenny@clemson.edu 2006-09-15
Helge Deller deller@gmx.de 2007-02-01
Benoit Sigoure tsuna@lrde.epita.fr 2007-04-20
Bob Proulx bob@proulx.com 2007-06-25
Bruce Korb bkorb@gnu.org 2008-05-06
Benjamin Pfaff blp@gnu.org 2008-09-29
========================================================================
Local Variables:
mode: text
coding: utf-8
End:
Copyright (C) 1996, 2000, 2001, 2005, 2007, 2008 Free Software
Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see .
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@$(MAKE) $(AM_MAKEFLAGS) install-exec-am install-data-am
installcheck: installcheck-recursive
install-strip:
$(MAKE) $(AM_MAKEFLAGS) INSTALL_PROGRAM="$(INSTALL_STRIP_PROGRAM)" \
install_sh_PROGRAM="$(INSTALL_STRIP_PROGRAM)" INSTALL_STRIP_FLAG=-s \
`test -z '$(STRIP)' || \
echo "INSTALL_PROGRAM_ENV=STRIPPROG='$(STRIP)'"` install
mostlyclean-generic:
clean-generic:
distclean-generic:
-test -z "$(CONFIG_CLEAN_FILES)" || rm -f $(CONFIG_CLEAN_FILES)
-test . = "$(srcdir)" || test -z "$(CONFIG_CLEAN_VPATH_FILES)" || rm -f $(CONFIG_CLEAN_VPATH_FILES)
maintainer-clean-generic:
@echo "This command is intended for maintainers to use"
@echo "it deletes files that may require special tools to rebuild."
-test -z "$(BUILT_SOURCES)" || rm -f $(BUILT_SOURCES)
-test -z "$(MAINTAINERCLEANFILES)" || rm -f $(MAINTAINERCLEANFILES)
clean: clean-recursive
clean-am: clean-generic mostlyclean-am
distclean: distclean-recursive
-rm -f $(am__CONFIG_DISTCLEAN_FILES)
-rm -f Makefile
distclean-am: clean-am distclean-generic distclean-local \
distclean-tags
dvi: dvi-recursive
dvi-am:
html: html-recursive
html-am:
info: info-recursive
info-am:
install-data-am: install-pkgdataDATA
install-dvi: install-dvi-recursive
install-dvi-am:
install-exec-am:
install-html: install-html-recursive
install-html-am:
install-info: install-info-recursive
install-info-am:
install-man:
install-pdf: install-pdf-recursive
install-pdf-am:
install-ps: install-ps-recursive
install-ps-am:
installcheck-am:
maintainer-clean: maintainer-clean-recursive
-rm -f $(am__CONFIG_DISTCLEAN_FILES)
-rm -rf $(top_srcdir)/autom4te.cache
-rm -f Makefile
maintainer-clean-am: distclean-am maintainer-clean-generic
mostlyclean: mostlyclean-recursive
mostlyclean-am: mostlyclean-generic
pdf: pdf-recursive
pdf-am:
ps: ps-recursive
ps-am:
uninstall-am: uninstall-pkgdataDATA
.MAKE: $(RECURSIVE_CLEAN_TARGETS) $(RECURSIVE_TARGETS) all check \
ctags-recursive install install-am install-strip \
tags-recursive
.PHONY: $(RECURSIVE_CLEAN_TARGETS) $(RECURSIVE_TARGETS) CTAGS GTAGS \
all all-am am--refresh check check-am clean clean-generic \
ctags ctags-recursive dist dist-all dist-bzip2 dist-gzip \
dist-hook dist-lzma dist-shar dist-tarZ dist-xz dist-zip \
distcheck distclean distclean-generic distclean-local \
distclean-tags distcleancheck distdir distuninstallcheck dvi \
dvi-am html html-am info info-am install install-am \
install-data install-data-am install-dvi install-dvi-am \
install-exec install-exec-am install-html install-html-am \
install-info install-info-am install-man install-pdf \
install-pdf-am install-pkgdataDATA install-ps install-ps-am \
install-strip installcheck installcheck-am installdirs \
installdirs-am maintainer-clean maintainer-clean-generic \
mostlyclean mostlyclean-generic pdf pdf-am ps ps-am tags \
tags-recursive uninstall uninstall-am uninstall-pkgdataDATA
@MAKE_CASE_SENSITIVE_TRUE@$(srcdir)/INSTALL: $(top_srcdir)/doc/install.texi
@MAKE_CASE_SENSITIVE_TRUE@ $(MAKEINFO) $(AM_MAKEINFOFLAGS) $(MAKEINFOFLAGS) --plaintext -o $@ \
@MAKE_CASE_SENSITIVE_TRUE@ $(top_srcdir)/doc/install.texi
$(top_srcdir)/.version:
echo $(VERSION) > $@-t && mv $@-t $@
# Arrange so that .tarball-version appears only in distribution tarballs,
# never in a checked-out repository.
dist-hook:
echo $(VERSION) > $(distdir)/.tarball-version
# Arrange to remove the symlink to GNUmakefile in VPATH builds.
# TODO remove this once automake vs. AC_CONFIG_LINKS issue is fixed.
distclean-local:
if test x"$(VPATH)" != x ; then rm -f GNUmakefile ; fi
# Tell versions [3.59,3.63) of GNU make to not export all variables.
# Otherwise a system limit (for SysV at least) may be exceeded.
.NOEXPORT:
autoconf2.64-2.64/ChangeLog.1 0000644 0002024 0002024 00000206262 11204770547 015107 0 ustar arthur arthur Thu May 12 15:55:40 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* Version 1.11.
* autoconf.texi: Document filename restriction on CPP.
Thu May 12 10:11:20 1994 David J. MacKenzie (djm@hill.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT): Treat "./Makefile" like "Makefile".
From Karl Berry.
Tue May 10 00:08:19 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT): Set prefix and exec_prefix if they
weren't set already.
Sat May 7 20:06:59 1994 Noah Friedman (friedman@kropotkin.gnu.ai.mit.edu)
* acspecific.m4 (AC_PROG_INSTALL): If using install.sh, add `-c'
to INSTALL.
Sat May 7 15:36:22 1994 David J. MacKenzie (djm@aria.eng.umd.edu)
* acgeneral.m4 (AC_OUTPUT): If configuring in the source tree,
don't end top_srcdir with "/.".
* acspecific.m4 (AC_SET_MAKE): Remove temp file.
From John Interrante .
Fri May 6 15:26:48 1994 David J. MacKenzie (djm@aria.eng.umd.edu)
* acgeneral.m4 (AC_SIZEOF_TYPE): Fatal error if test program fails.
Fri May 6 12:52:19 1994 David J. MacKenzie (djm@gamera.eng.umd.edu)
* acgeneral.m4 (AC_OUTPUT): Run "./config.status", not "config.status".
From Kevin Gallagher .
Fri May 6 00:45:29 1994 David J. MacKenzie (djm@aria.eng.umd.edu)
* acspecific.m4 (AC_WAIT3): Sleep in the parent to avoid rm
problems on fast machines. From david d zuhn.
Thu May 5 12:51:32 1994 David J. MacKenzie (djm@gamera.eng.umd.edu)
* Version 1.10.
* Makefile.in (install): Don't install INSTALL.
(installcheck, install-info): New targets.
Mon May 2 16:31:33 1994 David J. MacKenzie (djm@aria.eng.umd.edu)
* autoconf.sh, autoheader.sh: If M4 is an absolute file name that
no longer exists, use M4=m4.
Mon May 2 13:06:06 1994 David J. MacKenzie (djm@burnout.eng.umd.edu)
* acspecific.m4 (AC_HAVE_POUNDBANG): Quote # in message.
From schwab@issan.informatik.uni-dortmund.de (Andreas Schwab).
* autoconf.texi: Document config.h.bot. Fix typo in AC_HAVE_POUNDBANG.
* acspecific.m4 (AC_PROG_CXX): Look for "cxx" (DEC C++ compiler) too.
* autoheader.sh: Fix tr string for Solaris tr.
Add config.h.bot if present.
From richard@sol.kbsi.com (Richard Henderson).
Fri Apr 29 12:53:53 1994 David J. MacKenzie (djm@burnout.eng.umd.edu)
* acspecific.m4 (AC_PROG_INSTALL): Use install.sh from srcdir
or srcdir/.. or srcdir/../.. and never default to cp.
Thu Apr 28 12:01:01 1994 David J. MacKenzie (djm@burnout.eng.umd.edu)
* acconfig.h: Add HAVE_MMAP entry.
* acspecific.m4 (AC_MMAP): If NBPC is not defined, use PAGESIZE.
From "Kaveh R. Ghazi" .
* acgeneral.m4 (AC_OUTPUT_HEADER): For each file being created,
munge a copy of conftest.sed rather than the original.
From brook@trillium.botany.utexas.edu (Brook Milligan).
Tue Apr 26 00:27:21 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acgeneral.m4 (AC_LANG_C, AC_LANG_CPLUSPLUS): Remove CFLAGS and
CXXFLAGS from ac_cpp.
Thu Apr 21 19:43:20 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* Version 1.9.
* autoconf.texi: Document special AC_FIND_XTRA ordering
dependencies.
* acspecific.m4 (AC_FIND_XTRA): Reorder AC_REQUIREs.
* acspecific.m4 (AC_FIND_X): AC_REQUIRE_CPP.
* acspecific.m4 (AC_PROG_LEX): Say what we set LEXLIB to.
Wed Apr 20 13:17:05 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PARSEARGS): Allow . in hostnames. Use string
comparison on them.
(AC_HAVE_LIBRARY): namespace cleanup.
* autoconf.texi: Describe changes to AC_FIND_X, AC_FIND_XTRA, and
AC_YYTEXT_POINTER.
* acconfig.h: Replace DECLARE_YYTEXT with YYTEXT_POINTER.
* acgeneral.m4 (AC_PARSEARGS): --gas and --x set with_gas and
with_x to yes, not 1.
* acspecific.m4 (AC_YYTEXT_POINTER): New macro, replacing
AC_DECLARE_YYTEXT.
(AC_FIND_X): Assume no X if --without-x was given.
(AC_FIND_XTRA): Quotes AC_REQUIRE args. Run uname in a subshell in
case it's missing. Put -l options in X_EXTRA_LIBS. Print values
of the variables we set if verbose.
Tue Apr 19 14:14:25 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* autoconf.texi: Note GNU m4 1.0 bugs.
* acspecific.m4 (AC_FIND_X_XMKMF): Set variables correctly.
* autoconf.texi: Don't @setchapternewpage odd by default. Mention
autoheader AC_SIZEOF_TYPE symbol generation.
* acgeneral.m4 (AC_SIZEOF_TYPE): Fix typo.
* Makefile.in (install): Don't install aclocal.m4.
* autoheader.sh: Generate entries for AC_SIZEOF_TYPE
automatically.
Mon Apr 18 22:14:59 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acgeneral.m4 (AC_SIZEOF_TYPE): Remove second arg, and generate a
symbol name automatically.
* autoconf.texi: Document new AC_SIZEOF_TYPE usage.
* acspecific.m4 (AC_PROG_INSTALL): Only filter out "install"
containing "dspmsg".
(AC_FIND_X_XMKMF): Fix variable names to not conflict with grep -v.
* autoconf.texi: Various small fixes.
* INSTALL: Say configure takes "awhile".
Sat Apr 16 15:05:31 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acgeneral.m4: Call AC_LANG_C in AC_PREPARE, not AC_INIT.
Fri Apr 15 07:00:37 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* Version 1.8.
* acgeneral.m4: Rename ac_configure_args back to configure_args,
since some people have been using it.
Thu Apr 14 14:45:29 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* autoconf.texi: Note that AC_ENABLE and AC_WITH arguments
shouldn't contain blanks, for now.
Wed Apr 13 17:26:36 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acspecific.m4 (AC_SET_MAKE): Use $MAKE if defined, else "make".
* autoconf.texi: Add missing files to diagram.
* acgeneral.m4 (AC_TEST_CPP): Propogate comment about Coherent
lossage into configures.
Sat Apr 9 17:34:29 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PARSEARGS): Unknown option is a fatal error.
* acgeneral.m4: Remove ac_ prefix from some variables set by
options, for consistency and backward compatibility.
Fri Apr 8 13:24:29 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acspecific.m4 (AC_FIND_XTRA): Don't test for -lsocket on IRIX.
From Karl Berry.
* acspecific.m4 (AC_FIND_X_XMKMF, AC_FIND_X_DIRECT): Don't
override --x-includes and --x-libraries. Check openwin last due
to its bugs.
* acgeneral.m4: Add --x-includes, --x-libraries options. Document
them and --build, --host, --target.
* autoconf.texi: Mention --x-includes and --x-libraries.
* INSTALL: Mention --x-includes and --x-libraries.
Tue Apr 5 12:46:47 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* autoconf.texi: Document top_srcdir substitution.
* acspecific.m4 (AC_PROG_INSTALL): Look for install.sh in
@top_srcdir@, not $srcdir.
* acgeneral.m4 (AC_OUTPUT): AC_SUBST top_srcdir. Set it.
Mon Apr 4 20:13:08 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* autoconf.texi: Fix dependencies examples.
* Makefile.in: Update configuration dependencies.
* acgeneral.m4: Add back --no-create option. Make config.status
--recheck use it.
* autoheader.sh: Go back to doing move-if-change. (Work around in
dependencies by using stamp files.)
Thu Mar 31 11:34:50 1994 David J. MacKenzie (djm@hill.gnu.ai.mit.edu)
* Makefile.in (autoconf, autoheader, configure): Write to $@.tmp
instead of to $@ directly so that after a disk full error, the
targets to not exist. Otherwise, a subsequent make could install
a corrupt (but not executable) script. From Jim Meyering.
Thu Mar 31 08:22:29 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* autoconf.texi: Re-document --with argument.
* acgeneral.m4 (AC_PARSEARGS): --with can take an argument again.
Wed Mar 30 20:01:57 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* autoconf.texi: Document --disable- options.
* acgeneral.m4 (AC_PARSEARGS): Add --disable-FEATURE.
* INSTALL: Mention --enable- options.
Mon Mar 28 17:43:22 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PARSEARGS): Make multiple non-option args a
fatal error.
* acspecific.m4: Change all occurrences of $(MAKE_VAR) to
${MAKE_VAR}.
* autoconf.texi (Command Line): New node. Move some descriptions
here from General Feature Tests. Describe --without- options.
* acgeneral.m4 (AC_PARSEARGS): Rewrite again, using ideas from the
GNU libc configure.in. All options that take an argument set
shell variables.
(AC_COMPILE_CHECK): Add `return' in `int' function.
* INSTALL: Fix typo.
Sun Mar 27 00:44:07 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acgeneral.m4 (AC_NOTICE): Don't save original args or initialize
options here.
(AC_PARSEARGS): Do them here.
(AC_PREPARE): Save a copy of original args here, if it hasn't been
done yet.
Sat Mar 26 01:32:40 1994 David J. MacKenzie (djm@geech.gnu.ai.mit.edu)
* acgeneral.m4: Omit obsolete options from usage message.
Quote args to AC_CHECKING that contain m4 variables.
* INSTALL: Note that env can be used to set env vars.
* autoconf.texi: Document AC_SET_MAKE.
Note that vsprintf and vfprintf come with vprintf.
Note that env can be used to set env vars.
* acspecific.m4 (AC_SET_MAKE): New macro.
(AC_PROG_INSTALL): Find scoinst as a good install program.
* acgeneral.m4: Initialize variables set by options.
(AC_HAVE_HEADERS): Require cpp.
* autoconf.texi: Document AC_ENABLE and @prefix@ and @exec_prefix@
substitutions.
* acgeneral.m4: Recognize all the Cygnus configure options; warn
about other arguments. Make default value for --with "yes", not
"1". AC_SUBST for prefix and exec_prefix.
(AC_ENABLE): New macro.
Thu Mar 24 18:11:00 1994 David J. MacKenzie (djm@geech.gnu.ai.mit.edu)
* INSTALL: Describe recently added configure options.
* autoconf.texi: Style cleanups. Mention config.h.top.
* autoheader.sh: Add ${config_h}.top to the output, if it's
present.
Thu Mar 24 13:36:19 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* autoconf.sh: Remove all temp files when exiting. If m4 fails,
produce no output and exit with the m4 exit status.
* autoconf.texi: Document AC_PREREQ.
* acgeneral.m4 (AC_PREREQ): New macro, with some helper macros.
Thu Mar 24 01:20:49 1994 David J. MacKenzie (djm@geech.gnu.ai.mit.edu)
* Makefile.in (acdatadir): New variable based on datadir, giving
Autoconf lib files their own subdirectory. Use it instead of
datadir.
Wed Mar 23 22:41:54 1994 David J. MacKenzie (djm@geech.gnu.ai.mit.edu)
* autoconf.texi: Change names of nodes that describe invoking
configure and config.status to conform to coding standards.
Document --version, --help, --silent/--quiet, --verbose options to
configure and config.status.
* acgeneral.m4 (AC_PARSEARGS): Add --help and --version to
configure. Simplify getting option arguments. Complain about
impossible host arguments.
(AC_OUTPUT): Add --help and --version to config.status.
Wed Mar 23 00:16:28 1994 Roland McGrath (roland@mole.gnu.ai.mit.edu)
* acgeneral.m4 (AC_CHECKING): Do nothing if $ac_silent is set.
(AC_PARSEARGS): Grok -q/--quiet/--silent and set $ac_silent.
Tue Mar 22 18:28:30 1994 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* autoconf.texi: Document AC_SIZEOF_TYPE.
* acspecific.m4 (AC_INT_16_BITS, AC_LONG_64_BITS): Mark obsolete
with advice to use AC_SIZEOF_TYPE instead.
* acgeneral.m4 (AC_SIZEOF_TYPE): New macro.
Tue Mar 22 08:44:40 1994 David J. MacKenzie (djm@geech.gnu.ai.mit.edu)
* autoconf.texi: Describe AC_CHECKING et al.
* acspecific.m4: Use AC_CHECKING et al. where appropriate.
* acgeneral.m4 (AC_CHECKING, AC_VERBOSE, AC_ERROR, AC_WARN): New
macros. Use them where appropriate.
(AC_LANG_C, AC_LANG_CPLUSPLUS): Fix quoting of ac_cpp.
* acspecific.m4 (AC_PROG_CPP): Don't add $CFLAGS to CPP.
(AC_PROG_CXXCPP): Don't add $CXXFLAGS to CXXCPP.
* acgeneral.m4 (AC_OUTPUT): Don't remove VPATH lines containing
colons. From Jim Meyering (meyering@comco.com).
(AC_LANG_C): Add CFLAGS to ac_cpp.
(AC_LANG_CPLUSPLUS): Add CXXFLAGS to ac_cpp.
Sat Mar 19 16:38:03 1994 David J. MacKenzie (djm@geech.gnu.ai.mit.edu)
* acgeneral.m4 (AC_LANG_RESTORE): Only emit shell code to change
the current language if it actually changed.
* autoconf.texi: Add info dir entry. Describe new C++ macros and
AC_MMAP.
(Language Choice): New section.
Add another example of dependencies.
* acspecific.m4 (AC_PROG_CXX, AC_PROG_CXXCPP, AC_REQUIRE_CPP): New
macros based on work by zoo@aggregate.com (david d zuhn).
(AC_DECLARE_YYTEXT): Use AC_REQUIRE_CPP. Warn that it's broken.
(AC_STDC_HEADERS): Use AC_REQUIRE_CPP.
(AC_MMAP): New macro from Mike Haertel and Jim Avera.
* acgeneral.m4 (AC_PARSEARGS): Check for missing arguments to
options. Recognize --target. Save the original args before
modifying them.
(AC_INIT): Call AC_LANG_C.
(AC_PREPARE): Don't save the original args here (too late).
(AC_LANG_C, AC_LANG_CPLUSPLUS, AC_LANG_SAVE, AC_LANG_RESTORE):
New macros based on work by zoo@aggregate.com (david d zuhn).
(AC_HEADER_EGREP, AC_PROGRAM_EGREP, AC_COMPILE_CHECK,
AC_TEST_PROGRAM, AC_TEST_CPP): Use AC_REQUIRE_CPP and ac_ext and
ac_cpp.
* autoheader.sh: Update the file even if it is unchanged, to avoid
foiling a Makefile rule that makes it from configure.in. If you
let the rule for making config.status from configure create
config.h from config.h.in, then an unnecessary update here will
not cause unneeded recompilation. Recompilation should only
happen if config.h is updated, which won't occur if config.h.in
had the same contents, even if its timestamp changed. (Ick.)
* Makefile.in (Makefile): Don't depend on config.status, to avoid
running config.status too many times.
Fri Mar 18 00:43:21 1994 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* autoconf.texi: Document AC_FIND_XTRA.
* acgeneral.m4 (AC_OUTPUT): Remove VPATH lines if srcdir=., to
work around Sun make bug. From Karl Berry.
Rename internal use shell variables to start with "ac_".
Trap signal 2 (SIGINT), not signal 3 (SIGQUIT), which means stop
without cleaning up. From eggert@twinsun.com (Paul Eggert).
* acspecific.m4 (AC_FIND_XTRA): New macro from Karl Berry
(karl@cs.umb.edu).
(AC_FIND_X, AC_ISC_POSIX): Provide self.
(AC_DECLARE_YYTEXT): Move AC_SUBST. Don't quote value of
DECLARE_YYTEXT. From Karl Berry.
(AC_PROG_CPP): Include $CFLAGS in CPP.
Rename internal use shell variables to start with "ac_".
* autoconf.sh, autoheader.sh: Trap signal 2 (SIGINT), not signal 3
(SIGQUIT), which means stop without cleaning up. From
eggert@twinsun.com (Paul Eggert).
* autoconf.texi: Mention shell variable prefixes.
* autoconf.texi: Work around RCS substitution in AC_REVISION
example.
Wed Mar 16 19:55:17 1994 Noah Friedman (friedman@prep.ai.mit.edu)
* acgeneral.m4 (compile): Include $LDFLAGS.
Thu Mar 10 01:27:20 1994 David J. MacKenzie (djm@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PREPARE): Don't absolutize relative paths.
(AC_OUTPUT): For relative paths, prepend to $srcdir as many
"../" as the number of subdirectories deep the file being created is.
Tue Feb 15 16:02:19 1994 Noah Friedman (friedman@prep.ai.mit.edu)
* acspecific.m4 (AC_PROG_INSTALL): Reject /sbin/install.
Sun Feb 13 21:15:45 1994 Noah Friedman (friedman@prep.ai.mit.edu)
* autoconf.texi (Setting Variables, Sample configure.in): Replace
references to AC_UNISTD_H with AC_HAVE_HEADERS(unistd.h).
Thu Feb 10 21:39:43 1994 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_SYS_SIGLIST_DECLARED): New macro.
Sat Feb 5 13:35:52 1994 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_GETLOADAVG): Check for -lkvm separately after
-lutil check.
Fri Feb 4 17:17:11 1994 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT_HEADER): Move creation of conftest.sed
outside of `for' loop. We need only do this once for all the
output files.
Fri Jan 21 16:35:00 1994 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_PROG_INSTALL_INSTALL_SH): New macro for
INSTALL value to use install.sh.
(AC_PROG_INSTALL): Use it.
Thu Jan 6 16:22:25 1994 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* acgeneral.m4 (AC_DEFINE): Use AC_QUOTE_SQUOTE instead of
AC_DEFINE_QUOTE on AC_VAL. From Bruno Haible
.
* acgeneral.m4 (AC_DEFINE_UNQUOTED): pushdef/popdef
AC_QUOTE_SQUOTE instead of AC_DEFINE_QUOTE.
Wed Dec 22 03:51:53 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* acgeneral.m4 (AC_DEFINE): in verbose strings, put
AC_DEFINE_QUOTE exprs in double quotes to avoid shell wildcard
expansion.
* acgeneral.m4 (AC_PROGRAM_PATH, AC_PROGRAMS_PATH): New macros.
* autoconf.texi (General Tests): Document them.
* configure.in: Use AC_PROGRAMS_PATH to find m4, not AC_PROGRAMS_CHECK.
Put `m4' in the list of progs-to-check, since we want the absolute
pathname for that too if we can get it.
Fri Dec 17 13:44:24 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* acspecific.m4 (AC_ALLOCA): define HAVE_ALLOCA if alloca is
present in system libraries.
Tue Dec 14 14:53:55 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PREPARE): Remove $ac_clean_files in traps.
* acspecific.m4 (AC_STDC_HEADERS): Check that free appears in stdlib.h.
Fri Dec 10 06:35:25 1993 Noah Friedman (friedman@gnu.ai.mit.edu)
* acspecific.m4 (AC_PROG_INSTALL): Don't look for install in `.'.
Wed Dec 8 12:10:59 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_FIND_X_XMKMF): Redirect stderr to /dev/null in
eval'd make pipeline.
* acgeneral.m4 (AC_QUOTE_SED): Quote ! as well.
Mon Dec 6 23:41:05 1993 Noah Friedman (friedman@gnu.ai.mit.edu)
* acspecific.m4 (AC_PROG_CPP): Try 'cc -E -traditional-cpp' for NeXT.
Thu Dec 2 02:25:39 1993 Noah Friedman (friedman@gnu.ai.mit.edu)
* acgeneral.m4 (AC_PREPARE): use rm -r to remove conftest* both in
exit traps and at start of script.
Wed Dec 1 03:22:21 1993 Noah Friedman (friedman@gnu.ai.mit.edu)
* acspecific.m4 (AC_FIND_X_DIRECT): Search for includes and libs
in more places.
Sun Nov 28 21:57:31 1993 Noah Friedman (friedman@gnu.ai.mit.edu)
* acgeneral.m4 (AC_NOTICE): Replace "this program" with "this
configure script" to disambiguate between configure and the
program it is distributed with (which can have different terms).
Tue Nov 23 19:41:53 1993 Noah Friedman (friedman@gnu.ai.mit.edu)
* acspecific.m4 (AC_FIND_X_DIRECT): Use the shell variable
`x_direct_test_include' to choose the include file to search for.
Sat Nov 20 17:58:09 1993 Noah Friedman (friedman@gnu.ai.mit.edu)
* acspecific.m4 (AC_FIND_X_DIRECT): Search for R6 includes & libs
in various places. Look for /usr/athena/include & /usr/athena/lib.
Make AC_HAVE_LIBRARY check for the library specified by the shell
variable `x_direct_test_library', rather than hardcoding Xt (to
which the shell variable now defaults).
Thu Nov 18 18:17:21 1993 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT_HEADER): Use ! instead of @ as the
sed substitution separator.
* install.sh: New file.
* Makefile.in (DISTFILES): Add it.
* acspecific.m4 (AC_PROG_INSTALL): Use it as the default
instead of cp, if it's there.
Sat Nov 13 12:24:57 1993 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT): Extend that last change to also
happen for .C, .cc, and .m (objc) files.
Wed Nov 10 09:26:35 1993 Noah Friedman (friedman@gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT): When substituting .c or .h files, put
autoconf-added comments in '/* ... */'.
Mon Nov 8 16:22:48 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* acgeneral.m4 (AC_NOTICE): Put autoconf version number in configure.
Fri Nov 5 23:31:28 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* acspecific.m4 (AC_FIND_X_XMKMF): properly quote `acfindx' rule.
Fri Oct 29 21:46:57 1993 Jim Meyering (meyering@comco.com)
* acspecific.m4 (HAVE_LONG_DOUBLE): Add code to detect Stardent
Vistra lossage. From Kaveh R. Ghazi (ghazi@noc.rutgers.edu).
Tue Oct 26 15:24:33 1993 David J. MacKenzie (djm@churchy.gnu.ai.mit.edu)
* Version 1.7.
Tue Oct 19 23:49:50 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_TEST_PROGRAM): Don't remove conftest* before
running $2 or $3 or $4; just once at the end.
Mon Oct 18 01:38:00 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PREPARE): Echo a newline into confdefs.h so it
is never empty.
Fri Oct 15 18:49:20 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_CONST): Added test of trivial use for broken
Ultrix-32 V3.1 Rev 9 vcc.
Fri Oct 15 15:44:39 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OBSOLETE): New macro.
* acspecific.m4 (AC_UNISTD_H, AC_USG, AC_MEMORY_H): Call it.
* acspecific.m4 (AC_LONG_FILE_NAMES): Try to create files in
${prefix}/lib and ${exec_prefix}/lib instead of ${prefix} and
${exec_prefix}; they are more likely to be writable.
* Makefile.in (clean): Remove *.ma and *.mas, the macro index files.
Tue Oct 12 16:02:52 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_RETSIGTYPE): AC_PROVIDE self.
Mon Oct 11 19:09:20 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* Makefile.in (editsh): Obfuscate @M4@ and @datadir@ references so
configure doesn't edit them.
Sun Oct 10 14:01:35 1993 Jim Meyering (meyering@comco.com)
* autoconf.sh (--help): Exit successfully.
Sat Oct 9 08:29:15 1993 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* Version 1.6.
* acconfig.h (inline): New entry.
* acspecific.m4 (AC_DIR_HEADER_CHECK): Don't call opendir, in
case the needed libraries (e.g., -ldir on Xenix) aren't in
LIBS yet. From Jim Meyering (meyering@comco.com).
* acspecific.m4 (AC_PROG_LEX): Fix typo.
* acgeneral.m4 (AC_HEADER_EGREP, AC_PROGRAM_EGREP,
AC_COMPILE_CHECK, AC_TEST_PROGRAM, AC_TEST_CPP): Remove any
temporary files before doing the actions, in case they're
nested tests. From gray@antaire.com (Gray Watson).
* configure.in: Check for GNU m4 under several names.
* Makefile.in: Use that value.
From Franc,ois Pinard.
* acspecific.m4 (AC_STRUCT_TM): Use a member of struct tm, to
make sure the compiler complains if it's not defined.
From Bruno Haible (haible@ma2s2.mathematik.uni-karlsruhe.de).
* acspecific.m4 (AC_FIND_X_XMKMF): If libX11.a isn't in
USRLIBDIR, check in LIBDIR. Filter out any make verbose messages.
Tue Oct 05 19:21:29 1993 Jim Meyering (meyering@comco.com)
* acspecific.m4 (AC_LONG_DOUBLE): Announce that this feature is being
checked even if the test is simply whether $CC is gcc.
Tue Oct 5 14:23:28 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* autoheader.sh: Produce HAVE_LIBfoo for AC_HAVE_LIBRARY.
Sun Oct 3 15:41:36 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT): Write assignment for `extrasub'; in sed
cmds, write "$extrasub" so configure.in can set it to do sed frobs.
Take second arg and write it to config.status before `exit 0'.
* acspecific.m4 (AC_CONST): Say `checking for lack of working
const'. That is precisely accurate.
Wed Sep 22 15:47:50 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acgeneral.m4: If not using GNU m4, abort.
* acgeneral.m4 (AC_PREPARE): Lose if we're not in the srcdir,
not if we're in it. But disable the check for now.
Mon Sep 20 15:32:30 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PREPARE): Check for $srcdir being configured,
diagnose and lose.
* acgeneral.m4 (AC_QUOTE_SED): Quote @ and %.
* acgeneral.m4 (AC_OUTPUT): Say "$file is unchanged" when it is.
Sat Sep 18 14:32:04 1993 Ian Lance Taylor (ian@airs.com)
* acgeneral.m4: Substitute for CONFIG_FILES and CONFIG_HEADERS
before using them, in case they have multiple values.
Fri Sep 17 14:40:20 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acspecific.m4 (AC_WAIT3): wait3 works if ru_stime is
nonzero, too.
Thu Sep 16 15:39:53 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acspecific.m4 (AC_FIND_X_XMKMF): Code moved from AC_FIND_X.
(AC_FIND_X_DIRECT): New function, derived from code by Karl
Berry and Rob Savoye.
(AC_FIND_X): Call them.
Wed Sep 15 19:06:46 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PREPARE): Remove confdefs* on exit with trap 0.
(AC_OUTPUT): Don't bother removing it.
* acgeneral.m4: Remove --no-create option; not useful.
Mon Sep 13 21:54:46 1993 Paul Eggert (eggert@twinsun.com)
* autoheader.sh: Rename the temporary output to the real
output if their contents differ, not if their contents are identical.
This fixes bug introduced in Aug 30 change.
Mon Sep 13 16:50:30 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT): Run config.status with
CONFIG_SHELL if defined. Same for configure run from config.status.
Rename gen_files to CONFIG_FILES and gen_config to CONFIG_HEADERS.
* acgeneral.m4 (AC_PREPARE): Remove confdefs* in trap.
Fri Sep 10 00:29:20 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_LONG_FILE_NAMES): Test /var/tmp as well.
In loop, skip past nonexistent dirs.
* acspecific.m4 (AC_CONST): Say "working", not "broken". We are
checking for a working const as opposed to a broken or absent
const, not for a broken const as opposed to a working one.
Thu Sep 9 09:25:49 1993 Jim Meyering (meyering@comco.com)
* acspecific.m4, acconfig.h (AC_LONG_64_BITS): New macro.
Wed Sep 1 18:54:12 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PROGRAM_CHECK): Use && instead of test -a.
Tue Aug 31 19:21:35 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT_HEADER): Support generating multiple
.h files. From gray@antaire.com (Gray Watson).
* acspecific.m4 (AC_ALLOCA): If using alloca.o, define C_ALLOCA.
* acgeneral.m4 (compile, AC_HEADER_EGREP, AC_PROGRAM_EGREP,
AC_COMPILE_CHECK, AC_TEST_PROGRAM, AC_TEST_CPP): Remove $DEFS
from cc and cpp command lines; include "confdefs.h" in test
files.
(AC_DEFINE): Append a #define to confdefs.h.
Reduce duplicated code by introducing a temp variable, AC_VAL.
Mon Aug 30 17:36:54 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* autoheader.sh: Don't write output if it is the same as output file.
Wed Aug 25 14:14:33 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_VFORK): Check for SunOS 5.2 bug with ignoring
signal in parent before vfork. From eggert.
Fri Aug 20 10:14:42 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PARSEARGS): Support giving values to --with
options. Go back to using sed for invalid test, but without
using '*' in the regex.
Thu Aug 19 14:53:29 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acspecific.m4 (AC_LONG_FILE_NAMES): eval the args.
* acgeneral.m4 (AC_PARSEARGS): Use case instead of sed and
test to detect invalid package names. Remove =value from
--with options until we support it.
Wed Aug 11 18:52:41 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acspecific.m4 (AC_FIND_X): Don't set x_includes if it's
/usr/include or x_libraries if it's /lib or /usr/lib.
Wed Aug 11 13:00:18 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_LONG_FILE_NAMES): If we cannot write $dir, echo
a warning msg and continue the loop to skip that directory.
* acgeneral.m4 (AC_REVISION): Also eat double quotes.
Thu Aug 5 14:55:59 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acconfig.h: Add TIME_WITH_SYS_TIME.
Mon Aug 2 14:55:16 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_DECLARE_YYTEXT): \-escape "s in rhs of
AC_DEFINE_UNQUOTED.
Remove gratuitous second arg to AC_SUBST.
Sun Aug 1 19:13:08 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_GETLOADAVG): Define HAVE_GETLOADAVG if we find
one and don't use our own getloadavg.c.
* acconfig.h: Add HAVE_GETLOADAVG.
Sat Jul 31 17:28:48 1993 Karl Berry (karl@cs.umb.edu)
* acspecific.m4 (AC_PROG_INSTALL): Report results under -v.
Fri Jul 30 18:08:30 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* autoheader.sh (syms, headers, funcs, libs): Run values through
sort|uniq to remove duplicates.
Wed Jul 28 00:02:34 1993 David J. MacKenzie (djm@wookumz.gnu.ai.mit.edu)
* Makefile.in (config.status): Run config.status --recheck,
not configure.
(install): Remove refs to install-info until it's released,
because people are getting confused.
* acgeneral.m4 (AC_OUTPUT): For config.status --recheck, echo
the configure command line that we run.
* acspecific.m4 (AC_PROG_FLEX): Use AC_HAVE_LIBRARY.
Mon Jul 26 19:11:01 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_GETLOADAVG): Check that both -lutil and -lkvm
exist before choosing them in hopes they will define getloadavg.
* autoheader.sh (frob): Put $2 and $3 in the expansion of
AC_HAVE_LIBRARY, so AC_DEFINE there is noticed.
Mon Jul 26 14:21:33 1993 David J. MacKenzie (djm@wookumz.gnu.ai.mit.edu)
* acspecific.m4 (INT_16_BITS): Check the obvious way, so it
doesn't pick up machines with 64 bit longs.
Mon Jul 26 14:01:38 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_GETLOADAVG): Check for -lelf with
AC_HAVE_LIBRARY instead of checking for with AC_HEADER_CHECK.
Mon Jul 26 13:58:39 1993 David J. MacKenzie (djm@wookumz.gnu.ai.mit.edu)
* acspecific.m4 (AC_SCO_INTL, AC_IRIX_SUN, AC_DYNIX_SEQ): Use
AC_HAVE_LIBRARY.
Mon Jul 26 13:55:17 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* autoheader.sh (eval frob): Restore hairy sed use; we need it to
handle multi-line macro invocations.
Mon Jul 26 00:50:43 1993 David J. MacKenzie (djm@wookumz.gnu.ai.mit.edu)
* acspecific.m4 (AC_FIND_X): Quote the Imakefile.
Sun Jul 25 08:17:11 1993 Jim Meyering (meyering@comco.com)
* acconfig.h (CRAY_STACKSEG_END): New #undef.
Thu Jul 22 20:26:12 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* Version 1.5.
* acspecific.m4 (AC_FIND_X): Let make substitute any variables
in INCROOT and USRLIBDIR, instead of using sed.
From wojo@veritas.com (Jack Woychowski).
* acgeneral.m4 (AC_DEFINE): When printing value verbosely, use
double quotes and AC_DEFINE_QUOTE, like we do when assigning
the value, so shell variables get expanded the same way.
* acgeneral.m4 (AC_REVISION): New macro.
From wollman@uvm-gen.EMBA.UVM.EDU (Garrett Wollman).
* acgeneral.m4 (AC_DEFINE): Add newline before open brace.
Thu Jul 22 17:07:15 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_STAT_MACROS_BROKEN): New macro.
* acconfig.h (STAT_MACROS_BROKEN): New #undef.
Wed Jul 21 15:44:32 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_DECLARE_YYTEXT): Use AC_DEFINE_UNQUOTED so
shell var is replaced in rhs.
Wed Jul 21 13:31:38 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acconfig.h (size_t, mode_t, off_t): Added.
* acspecific.m4 (AC_OFF_T): New macro.
Tue Jul 20 15:39:44 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* autoheader.sh: Put header-file.in in comment at top.
* acconfig.h (NDIR): Added.
Mon Jul 19 22:10:49 1993 David J. MacKenzie (djm@churchy.gnu.ai.mit.edu)
* Makefile.in (info, dvi): New targets.
Sun Jul 18 22:36:33 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* autoheader.sh (frob): Use `#' as the first line of each definition.
(eval frob): Totally simplify sed use to just handle "^@@@.*@@@$".
Wed Jul 14 22:44:25 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acconfig.h: Restore blank lines between paragraphs.
* autoheader.sh (libs): New variable and frob to set it from
AC_HAVE_LIBRARY uses. Produce #undef HAVE_* for each $libs.
Tue Jul 13 19:03:46 1993 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acconfig.h: Sort the entries, like the comment says.
* acspecific.m4 (AC_GETLOADAVG): Only check for the AIX library
once, looking in both local and system dirs.
Consolidate SVR4 and Solaris cases.
Mon Jul 12 20:33:36 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_GETLOADAVG): If we find sys/dg_sys_info.h, do
AC_HAVE_LIBRARY on -ldgc.
Sun Jul 11 00:43:51 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acspecific.m4 (AC_GETLOADAVG): BSD library is -lutil, not
-lutils, and requires -lkvm too.
Check for local AIX library using AC_HAVE_LIBRARY, not
AC_COMPILE_CHECK.
Un-nest some conditionals. Stop checking once we've
found a way to get getloadavg.
Thu Jul 8 20:21:28 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* Makefile.in: Remove rules for making *.conf; make
Autoconf's configure script semi-normally.
Wed Jul 7 14:37:35 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* autoheader.sh (--help): Print help message to stdout and exit 0.
(--version): Exit after printing version number.
* autoconf.sh (--version): Exit after printing version number.
* acspecific.m4 (AC_LONG_DOUBLE): Make sure that long double
isn't smaller than double, as in Ultrix 4.[23] cc.
* acgeneral.m4 (AC_REPLACE_FUNCS): Include ctype.h in the test
program to get stubs.
* acspecific.m4 (AC_FIND_X): New macro.
Tue Jul 6 19:15:17 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acspecific.m4 (AC_GETLOADAVG): Try ls -L first, in case
/dev/kmem is a symlink (as on Solaris).
Wed Jun 30 22:08:22 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* acspecific.m4 (AC_MINUS_C_MINUS_O): Remove spurious `then'.
Fri Jun 25 23:16:42 1993 Paul Eggert (eggert@twinsun.com)
* acspecific.m4 (AC_CONST): Replace `p = '
with `ccp = '; the former wasn't ANSI C, and
was causing working compilers to be rejected.
Fri Jun 25 13:26:34 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* acspecific.m4 (AC_LONG_FILE_NAMES): Redirect rm's stderr to
/dev/null.
Thu Jun 24 15:58:04 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* autoconf.sh, autoheader.sh, acgeneral.m4 (AC_PREPARE): Undo
change of Jun 16 1993. Only set `LANG' and `LC_ALL' to "C" if
already set.
Sat Jun 19 00:01:51 1993 Jim Meyering (meyering@comco.com)
* acgeneral.m4: Undefine m4's `format' builtin.
* acspecific.m4 (AC_HAVE_POUNDBANG): Make conftest executable,
but not necessarily writable by group or other.
Thu Jun 17 21:10:33 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* acspecific.m4 (AC_PROG_CPP): Put double quotes around ${CC-cc},
not single quotes.
If --verbose option given, say what CPP is being set to.
Wed Jun 16 17:50:00 1993 Jim Blandy (jimb@wookumz.gnu.ai.mit.edu)
* acspecific.m4 (AC_PROG_CPP): Make sure that `cc -E` doesn't
run the program through the C compiler too. Bob Olson
says it does on the NeXT.
Wed Jun 16 16:17:05 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* autoconf.sh, autoheader.sh, acgeneral.m4 (AC_PREPARE): Always set
`LANG' and `LC_ALL' environment variables to `C'.
Fri Jun 11 14:29:31 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_MINUS_C_MINUS_O): Test that cc works at all,
and only test it for -c -o if it does.
Tue Jun 8 01:47:22 1993 Paul Eggert (eggert@twinsun.com)
* acgeneral.m4 (AC_OUTPUT): The line
DEFS="`echo \"$DEFS\" | sed 's%[&\\\]%\\\&%g'`"
doesn't work in some shells, which don't allow nesting
\"\" inside `` inside "", and which don't unescape \\\& in the
expected (?) way. Also, some versions of echo interpret
backslashes inside $DEFS. Put $DEFS into a temporary file
to avoid these portability minefields.
Mon Jun 7 20:11:50 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_GETLOADAVG): In setting KMEM_GROUP, use new sed
magic from friedman which should win with both meanings of ls -lg.
Mon Jun 7 06:48:49 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* Makefile.in (dist): Change gzipped tar file extension to `.gz'.
Use explicit --gzip option to tar to make sure tar uses the right
compression program (or else exits from failure to understand the
option).
* acgeneral.m4 (AC_OUTPUT): Don't split sed expr for exec_prefix
across two lines, since not all versions of sed understand that.
* acspecific.m4 (AC_HAVE_POUNDBANG): Complete rewrite which doesn't
depend on csh.
Tue Jun 1 03:06:28 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* Version 1.4.1 (not announced to the general public, but
a snapshot was put on the June '93 GNU CDROM).
* Makefile.in (dist): If ln fails (e.g. because of cross-device
links), mention on stdout that file is being copied.
* acgeneral.m4 (AC_PREPARE): Use `[$]*' in assignment to
configure_args to get shell positional args, rather than m4 args to
AC_PREPARE.
(AC_OUTPUT): Use `configure_args' in config.status
when invoked with --recheck, rather than $*.
Mon May 31 13:12:56 1993 Paul Eggert (eggert@twinsun.com)
* acspecific.m4 (AC_LONG_FILE_NAMES): rm $dir/conftest*,
not conftest*.
Mon May 31 04:18:18 1993 Roland McGrath (friedman@nutrimat.gnu.ai.mit.edu)
* acgeneral.m4 (AC_HAVE_LIBRARY): Quote libname in define.
Sun May 30 19:52:24 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_SETVBUF_REVERSED): Pass (char *) main to
setvbuf instead of zero.
Thu May 27 20:30:53 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PREPARE): Save $* in shell var `configure_args'.
(AC_OUTPUT): Use $configure_args in place of $*.
Wed May 26 16:19:51 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* autoconf.texi (AC_PROG_INSTALL): Doc fix.
(Automatic Remaking): Put code fragment in @example ... @end example.
Mon May 24 15:46:47 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* autoheader.sh (frob): Redefine AC_CONFIG_HEADER to set shell
variable `config_h'.
(config_h): New variable, initialize to "config.h" before frobbing.
(final output): Write ${config_h}.in.
Sat May 22 17:45:19 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* Version 1.4 released.
Thu May 20 20:25:45 1993 Jim Blandy (jimb@geech.gnu.ai.mit.edu)
* acgeneral.m4 (AC_IDENTITY): New function.
(AC_DEFINE_UNQUOTED): Use it to fix this; due to a
misunderstanding of m4, this was using its first argument as
the definition.
Thu May 20 09:21:55 1993 Jim Meyering (meyering@comco.com)
* acspecific.m4 (AC_ALLOCA) [find_stack_direction]: Return the
value from the recursive call. If it worked before, it was by luck.
From Bruno Haible .
Tue May 18 23:40:21 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* acspecific.m4 (AC_STDC_HEADERS): Require AC_PROG_CPP.
Mon May 17 18:01:09 1993 Karl Berry (karl@hal.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT): Use variables gen_files and
gen_config in the loop that generates the output (Make)files,
instead of hardwiring the filenames.
Sat May 15 17:23:19 1993 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* autoconf.sh: Accept `-' to mean read stdin as input.
* autoheader.sh: Likewise.
Fri May 14 12:41:02 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* autoheader.sh, acspecific.m4 (AC_PREPARE): If `LANG' environment
variable is set, reset its value to `C'. This is so `tr [...]'
works more portably.
Thu May 13 22:56:20 1993 Paul Eggert (eggert@twinsun.com)
* acspecific.m4 (VOID_CLOSEDIR): Test closedir instead of assuming
that it works. E.g. dynix closedir yields garbage, but has no
prototype. Presumably Xenix closedir had the same problem, so
stop special-casing it.
Wed May 12 20:25:36 1993 Jim Meyering (meyering@comco.com)
* acconfig.h: Add HAVE_LONG_DOUBLE.
Wed May 12 15:07:36 1993 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* acgeneral.m4 (AC_DEFINE_UNQUOTED): New macro.
* acgeneral.m4 (AC_FUNC_CHECK): Include ctype.h instead of stdio.h.
We want it only to define __stub_* in glibc. Using stdio.h lost
when it contained a conflicting prototype for $1; ctype.h has fewer
prototypes.
* acconfig.h: Add GETGROUPS_T.
* acspecific.m4 (AC_PROG_RANLIB): Use : instead of @: for no-op.
Some braindead make does bizarre magical things with @ in variables.
Mon May 10 14:24:27 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* acspecific.m4 (AC_HAVE_POUNDBANG): New feature.
* acgeneral.m4 (AC_OUTPUT): Add more backslashes to character class
in DEFS filter (sigh).
Sun May 9 14:04:31 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_DEFINE_QUOTE): No AC_QUOTE_SED (was innermost).
(AC_HEADER_EGREP, AC_PROGRAM_EGREP, AC_TEST_CPP): Put a \ before
$DEFS in string to be evalled.
(AC_OUTPUT): Run DEFS through a sed filter that quotes things in it
from sed (woo woo!) before writing it into config.status.
* acspecific.m4 (AC_ALLOCA): Use AC_PROGRAM_EGREP to test for [CRAY
&& !CRAY2], instead of AC_TEST_PROGRAM. No need to run a program
for this.
* acgeneral.m4 (AC_PROGRAM_CHECK): Extract the first word of $2
when looking for it in PATH, so it can be a program name with args.
Omit default assignment if $4 is empty.
Only write verbose msg if $1 was set nonempty.
* acspecific.m4 (AC_PROG_YACC): Pass 'bison -y' (quoted like that)
in list to AC_PROGRAMS_CHECK. Don't test for bison later to add -y
flag.
Sat May 8 00:23:58 1993 Jim Meyering (meyering@comco.com)
* acgeneral.m4 (AC_REPLACE_FUNCS): Add a trailing newline in
code for AC_COMPILE_CHECK. Otherwise it got spurious failures.
* acspecific.m4 (TIME_WITH_SYS_TIME): New macro.
* Makefile.in (dist): Depend on Makefile. Use gzip instead
of compress. Link files individually instead of en masse;
if a link fails, use `cp -f' on the losing file.
* acspecific.m4 (AC_ALLOCA): Define CRAY_STACKSEG_END (the
name of a function used in alloca.c) for CRAY-1, CRAY X-MP,
and CRAY Y-MP.
Fri May 7 15:56:26 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_GETLOADAVG): Check for mach/mach.h, but don't
disable nlist checks if found.
Fri May 7 04:59:25 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* acspecific.m4 (AC_PROG_INSTALL): Don't look for `install' in
/usr/ucb.
Thu May 6 20:41:35 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_FUNC_CHECK): The test program should choke on
#ifdef __stub___$1 as well.
(AC_REPLACE_FUNCS): Make the test program choke on stubs.
Wed May 5 20:43:13 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* autoconf.sh ($infile existence check): Fixed test for
nonemptiness of $print_version to not always be true.
Wed May 5 17:22:42 1993 David J. MacKenzie (djm@wookumz.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PREFIX, AC_PROGRAM_CHECK), acspecific.m4
(AC_PROG_INSTALL): If IFS wasn't set initially, give it a
normal default value. Happens on LynxOS (x86), says
Pete Klammer .
Wed May 5 13:22:52 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4: Undefine the `shift' builtin.
* acspecific.m4 (AC_PROG_YACC): Use AC_PROGRAMS_CHECK to check for
both bison and yacc, instead of two AC_PROGRAM_CHECK uses.
* autoheader.sh ($# -eq 0): Set var $tmpout to name of temp file,
send stdout there instead of config.h.in.
(just before exit): If $# -eq 0, then move $tmpout to config.h.in
if $status -eq 0, or remove $tmpout otherwise.
* acspecific.m4 (AC_STRCOLL): Rewritten to use a test program that
verifies that `strcoll' does vaguely reasonable ordering.
Tue May 4 19:59:00 1993 Jim Meyering (meyering@comco.com)
* acspecific.m4 (AC_LONG_DOUBLE): Don't explicitely echo
`checking for long double'.
Mon May 3 22:04:35 1993 Jim Meyering (meyering@comco.com)
* acspecific.m4 (AC_GETGROUPS_T): New macro.
Sat May 1 22:37:55 1993 Jim Meyering (meyering@comco.com)
* acspecific.m4 (AC_LONG_DOUBLE): New macro.
Wed Apr 28 15:52:42 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PROGRAM_CHECK): Write msg under --verbose.
Thu Apr 22 18:24:40 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_FUNC_CHECK): Remove spurious `#endif' line at end.
* acgeneral.m4 (AC_WITH): Fix reversed args to patsubst.
Test $with_FOO, not $FOO.
Wed Apr 21 18:14:19 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_QUOTE_TOKEN): New macro.
(AC_DEFINE_QUOTE): Use it.
Tue Apr 20 18:02:46 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* acspecific.m4 (AC_DECLARE_YYTEXT): Guess name of lex output file
and do AC_SUBST of `LEX_OUTPUT_ROOT'.
Add `dnl' after calling some autoconf macros.
Mon Apr 19 15:46:24 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_MINUS_C_MINUS_O): Do each compile a second time
after testing for the existence of the output. Some compilers
refuse to overwrite an existing .o file with -o, though they will
create one.
* acspecific.m4 (AC_DECLARE_YYTEXT): Changed lex input to two lines
of "%%", not just one.
Sat Apr 17 17:26:12 1993 Jim Meyering (meyering@comco.com)
* acgeneral.m4 (AC_COMPILE_CHECK): Don't print `checking for ...'
message if first argument is empty.
Sat Apr 17 01:18:41 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* acspecific.m4 (AC_PID_T): provide self.
(AC_VFORK): Require AC_PID_T.
Fri Apr 16 11:57:35 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PROGRAMS_CHECK): Take optional third arg; if
given, use it as the default value.
Thu Apr 15 16:43:45 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_REPLACE_FUNCS): Print a message under --verbose.
* acgeneral.m4 (AC_HAVE_LIBRARY): Use m4's patsubst and translit
instead of running sed and tr at runtime.
* acconfig.h: Add STACK_DIRECTION.
Wed Apr 14 17:08:47 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_ALLOCA): If we chose alloca.c, run a test
program to define STACK_DIRECTION.
Mon Apr 5 19:02:52 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_LONG_FILE_NAMES): Put test inside a for loop on
several directories: . /tmp $prefix $exec_prefix. Define
HAVE_LONG_FILE_NAMES iff long names win in all those directories.
Sun Apr 4 18:38:23 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* Makefile.in (%.info): Removed pattern rule.
(autoconf.info, standards.info): New rules.
* autoconf.sh (version_only): New variable, set nonempty for
`autoconf --version' with no input file.
(output writing): No output if $version_only is set.
Wed Mar 31 17:33:57 1993 Jim Meyering (meyering@comco.com)
* acspecific.m4 (AC_CONST): Uncomment and fix second AIX test.
Wed Mar 31 16:58:12 1993 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* acspecific.m4 (AC_CONST): Rewrite first AIX XL C 1.02.0.0 test.
Comment out bogosity in second AIX test.
Wed Mar 31 12:45:59 1993 Jim Meyering (meyering@comco.com)
* acgeneral.m4 (AC_DEFINE): Put single quotes around definition
that is echoed with --verbose. AC_DEFINE(MVDIR, "$(libdir)/mvdir")
was generating losing code.
Mon Mar 29 15:44:24 1993 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acspecific.m4 (AC_STDC_HEADERS): Add a missing pair of [quotes].
Mon Mar 29 14:54:00 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_DECLARE_YYTEXT): Change sed regexp so it won't
match other identifiers beginning with `yytext'.
Sat Mar 27 00:11:16 1993 Paul Eggert (eggert@twinsun.com)
* acspecific.m4 (AC_CONST): Detect broken AIX XL C 1.2.0.0 compiler.
Thu Mar 25 19:54:50 1993 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acspecific.m4 (AC_CONST): Remove single quotes from the C
program; they produce shell syntax errors.
* acgeneral.m4 (AC_DEFINE): Add a newline after "}" to prevent
commands following on the same line of configure.in from
generating shell syntax errors.
* acgeneral.m4 (AC_COMPILE_CHECK): Use explicit return types
to avoid warnings.
(AC_TEST_CPP): Add parens to force redirection order.
(AC_OUTPUT): Allow hostname to return bogus exit status.
From Jean-loup Gailly .
Mon Mar 22 16:53:01 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* autoconf.sh: Use $M4, not m4 explicitly.
(M4): If unset in env, initialize to @m4@.
* autoheader.sh: Likewise.
* Makefile.in (M4): Define new variable.
(autoconf.conf, %.conf): Use it.
(editsh): New variable: sed command to replace @datadir@; also
replace @M4@ with $(M4).
(autoconf, autoheader): Use $(editsh) instead of explicit sed command.
Mon Mar 22 13:08:10 1993 Jim Meyering (meyering@comco.com)
* acspecific.m4 (AC_CONST): IBM's /bin/cc under AIX-3.2 on an rs6000
rejects attempts to modify *any* member of a struct that has a
member declared like `const int *ap[2]'.
Wed Mar 17 18:08:30 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* autoconf.sh, autoheader.sh (MACRODIR): Variable renamed to
AC_MACRODIR. Don't initialize it at runtime if it is already set
in the environment.
(MACROFILES): Don't set until after options are processed.
(print_version): New temp variable.
* autoconf.sh, autoheader.sh: Rewrote argument parsing.
Added `-m', `--macrodir', `-h', `--help', and `--' options.
Updated usage string.
* autoconf.texi: Documented --macrodir option and its effects for
both scripts.
Tue Mar 16 09:10:48 1993 Jim Meyering (meyering@comco.com)
* acspecific.m4 (AC_CONST): Sun's SC1.0 ANSI compiler (acc) won't
increment a `const int *' pointer declared through a typedef.
Mon Mar 15 16:08:42 1993 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PARSEARGS): Grok `--verbose' flag; set verbose=yes.
(AC_DEFINE): Only echo "defining $1" if $verbose is set.
Sun Mar 14 18:19:21 1993 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* acspecific.m4 (AC_PROG_INSTALL): Choose `installbsd' if we find
it, in preference to `install'.
* acspecific.m4 (AC_CONST): Add a check for `const int *foo' not
allowing modification of FOO (not *FOO).
Fri Mar 12 15:27:53 1993 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT_HEADER): Remove conftest.sh before
creating it.
Thu Mar 11 12:57:53 1993 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* acgeneral.m4 (AC_DEFINE): Surround defn with { and }.
* acgeneral.m4 (AC_OUTPUT_HEADER): Split up $SEDDEFS into smaller
chunks, since some shells can't handle large here documents.
We write several commands in config.status to create conftest.sed
in pieces.
Mon Mar 8 14:40:53 1993 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* acgeneral.m4 (AC_WITH): Don't echo anything.
Use the m4 patsubst fn instead of a run-time sed invocation to
massage $1.
* acspecific.m4 (AC_DIR_HEADER_CHECK): #include
before the header we are testing.
* acgeneral.m4 (AC_DEFINE): If $2 is empty, echo "defining $1 to be
empty", rather than "defining $1 to be ".
* acspecific.m4 (AC_DIR_HEADER_CHECK): New; subr of AC_DIR_HEADER.
(AC_DIR_HEADER): Use it to test for each possible header file.
Tue Mar 2 01:06:25 1993 Noah Friedman (friedman@nutrimat.gnu.ai.mit.edu)
* autoheader.sh: Don't use /p1/,/p2/ construct with sed---it's not
portable. Handle broken AIX sed that strips \n from hold space
when it shouldn't. From Jun Hamano .
Tue Mar 02 00:08:39 1993 Jim Meyering (meyering@comco.com)
* acspecific.m4 (AC_CONST): Fix typo that caused spurious lossage
with /bin/cc from Irix-4. From Karl Berry.
Fri Feb 26 17:14:58 1993 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* acspecific.m4 (AC_CONST): Add bizarre case that loses on SCO 3.2v4.
Mon Feb 22 13:02:27 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_QUOTE_HERE, AC_QUOTE_SED): Change the quote
chars to { and } instead of nothing. Then use {} (empty quotes) to
separate the patsubst forms from the following dnl. Otherwise the
result of patsubst is pasted together with dnl and the result is
seen as a single token.
* acspecific.m4 (AC_MINUS_C_MINUS_O): Print msg saying what we are
doing before we do it.
* acgeneral.m4 (AC_PREFIX): Print out the choice made.
(AC_DEFINE): Print out the definition being done.
* acgeneral.m4 (AC_DEFINE_QUOTE): Add dnl at end of line.
* acspecific.m4 (AC_GETLOADAVG): Do changequote around listing of
/dev/kmem and sed frobbing which needs to use [ and ].
Sun Feb 21 13:57:55 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* autoheader.sh: Use brackets in tr range args.
* acspecific.m4 (AC_SETVBUF_REVERSED): Make the test fail if
setvbuf returns nonzero.
* acspecific.m4 (AC_GETLOADAVG): If we need to install setgid,
figure out what group owns /dev/kmem, and set KMEM_GROUP to that.
* acspecific.m4 (AC_MINUS_C_MINUS_O): Test plain `cc' after testing
$CC. We want to make sure both compilers grok -c -o.
Thu Feb 18 18:05:14 1993 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* acgeneral.m4 (AC_QUOTE_{DQUOTE,SQUOTE,HERE,SED}): New macros.
(AC_DEFINE_{QUOTE,SEDQUOTE}): New macros; subrs of AC_DEFINE.
(AC_DEFINE): Use them to quote $2.
Wed Feb 17 14:49:14 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_TIMEZONE): Fixed quoting in tzname check.
changequote inside quotes lost.
Mon Feb 8 14:22:11 1993 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* acconfig.h (_ALL_SOURCE): Use #ifndef; AIX compiler way too dumb.
Sun Jan 31 16:39:46 1993 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* acspecific.m4 (AC_TIMEZONE): Put newlines before `#include ...'
in $defs value.
Thu Jan 28 18:06:53 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acconfig.h (_ALL_SOURCE): Use "!defined (_ALL_SOURCE) ||
_ALL_SOURCE == 0" rather than "!_ALL_SOURCE", which bombs on the
AIX compiler.
Mon Jan 25 12:09:43 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acconfig.h (HAVE_UNION_WAIT, SYS_SIGLIST_DECLARED): New #undef's.
* acconfig.h (_ALL_SOURCE): Surround with #if !_ALL_SOURCE.
Fri Jan 22 15:08:33 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acspecific.m4 (AC_GETLOADAVG): If /usr/local/lib/libgetloadavg.a
exists, add -L/usr/local/lib to LDFLAGS.
Fri Jan 22 12:49:11 1993 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT_HEADER): Only comment out the #undef NAME
part of the line, to avoid causing errors from existing comments.
Thu Jan 21 14:50:20 1993 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* acgeneral.m4 (AC_HAVE_LIBRARY): Use $libname in "checking for"
message, not $1, to avoid "checking for -l-lfoo".
* acgeneral.m4 (AC_PREPARE): In compile defn, include $CFLAGS.
* acgeneral.m4 (AC_OUTPUT): Broke AC_CONFIG_NAME writing out into:
(AC_OUTPUT_HEADER): New macro broken out of AC_OUTPUT.
Add to conftest.sed a new sed command to turn #undef's into comments.
* acgeneral.m4 (AC_OUTPUT): Use new shell variable, $maxsedlines,
for max number of lines to feed to one sed invocation.
Lower this limit to 20; UTekV 3.2e can't cope with 40.
Tue Jan 19 13:21:02 1993 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* Version 1.3.
Fri Jan 15 16:28:18 1993 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acgeneral.m4 (AC_CONFIG_HEADER, AC_HEADER_EGREP,
AC_TEST_PROGRAM): Make DEFS always contain -D commands,
not C code.
Thu Jan 14 17:05:17 1993 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acspecific.m4 (AC_GETLOADAVG): Check for -lkvm; don't assume it.
Thu Jan 14 16:46:41 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* autoheader.sh (selecting $syms from $TEMPLATES): Use sed to
replace lines containing only blanks with empty lines.
Thu Jan 14 15:15:31 1993 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acspecific.m4 (AC_MODE_T): New macro.
* acgeneral.m4 (AC_OUTPUT): Check for grep -c returning
nothing (AIX 3.1) as well as returning 0.
Wed Jan 13 16:05:59 1993 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acgeneral.m4 (AC_FUNC_CHECK): Add missing #endif.
* acgeneral.m4 (AC_OUTPUT): Use sed, not basename.
From Francois Pinard.
Wed Jan 13 15:49:18 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT): Set exec_prefix to ${prefix}, not
$(prefix); it now works in both makefiles and shell scripts.
Wed Jan 13 15:29:04 1993 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* autoheader.sh: If input is empty, don't print all of
acconfig.h. From Francois Pinard.
* acgeneral.m4 (AC_OUTPUT): Have config.status check all of its
args for validity.
Tue Jan 12 11:11:45 1993 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT): Preserve whitespace around = in prefix
and exec_prefix assignments.
* acspecific.m4 (AC_GETLOADAVG): Values for getloadavg_missing were
reversed.
Fri Jan 8 18:45:59 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT): Make config.status not complain with
usage msg when given no args.
* acgeneral.m4 (AC_HAVE_LIBRARY): Say "checking for -lfoo", not
just "checking for foo".
* acgeneral.m4 (AC_HAVE_LIBRARY): Remove excess quoting around $2
and $3.
* acspecific.m4 (AC_GETLOADAVG): Check for getloadavg library, both
a normally installed one, and one in /usr/local/lib.
After figuring out params for getloadavg.c, figure out whether it
defined LDAV_PRIVILEGED, and if so, set NEED_SETGID to true, and
define GETLOADAVG_PRIVILEGED.
* acconfig.h: Added GETLOADAVG_PRIVILEGED.
Fri Jan 8 16:16:35 1993 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acgeneral.m4 (AC_DEFINE, AC_OUTPUT): Restore the third sed string.
* acgeneral.m4 (AC_FUNC_CHECK): Use __stub_funcname.
* autoheader.sh: Use Autoconf version number.
* acgeneral.m4 (AC_OUTPUT): Diagnose usage errors for
config.status. Use grep -c to count nonempty lines instead of
test -s.
* acspecific.m4 (AC_GETLOADAVG): Use AC_HAVE_LIBRARY.
Wed Jan 6 19:54:47 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* autoheader.sh (coverage check): Use $TEMPLATES in error msg, not
hard-wired "config.h".
Wed Jan 6 18:24:41 1993 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT): If AC_CONFIG_NAME, change
@DEFS@ to -DHAVE_CONFIG_H in Makefiles etc. Idea from Roland McGrath.
* acgeneral.m4 (AC_FUNC_CHECK): If __STUB_funcname is defined,
assume the function isn't present.
* acgeneral.m4 (AC_OUTPUT): Make no args to AC_OUTPUT work
again. From Ian Lance Taylor.
* acspecific.m4 (AC_CONST): Fix quoting problem.
* acconfig.h [const]: New addition.
Thu Dec 31 17:56:18 1992 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acgeneral.m4 (AC_HAVE_LIBRARY): New macro from Noah Friedman.
* acconfig.h: Renamed from config.h.
* autoheader.sh: Renamed from autohead.sh.
Support a local acconfig.h.
Use \\012 instead of \\n for tr for portability.
Thu Dec 31 12:30:34 1992 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* config.h: Added #undef vfork.
Tue Dec 29 14:26:43 1992 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* acgeneral.m4 (AC_COMPILE_CHECK): Use cat rather than echo to
create conftest.c, to avoid " problems.
Fri Dec 25 15:07:06 1992 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acspecific.m4 (AC_CONST): Don't define HAVE_CONST.
* acgeneral.m4 (AC_OUTPUT, AC_DEFINE): Combine the two sed
commands for #undef lines.
* acgeneral.m4 (AC_PROGRAM_EGREP, AC_TEST_PROGRAM,
AC_TEST_CPP, AC_OUTPUT), acspecific.m4 (AC_PROG_CC): Put >
before << when using both, to avoid HP-UX sh bug.
Wed Dec 23 20:47:53 1992 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PARSEARGS): Use if, not &&, for --with.
From Jan Brittenson.
Mon Dec 21 17:13:57 1992 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT): Use sed instead of head and tail.
Trap to remove the temp files.
* acgeneral.m4 (AC_OUTPUT): Quote DEFS assignment.
From Ian Lance Taylor.
Mon Dec 21 14:27:44 1992 Jim Meyering (meyering@comco.com)
* acspecific.m4 (AC_STDC_HEADERS): Make sure ctype.h macros
are ANSI. Nest tests so we don't need shell temporary variable.
Sun Dec 20 18:12:33 1992 Roland McGrath (roland@albert.gnu.ai.mit.edu)
* Makefile.in (%.h: %.in): New rule using autohead.
(all): Do autohead.
(install): Install autohead and config.h.
(autohead): New rule.
(DISTFILES): Added autohead.sh.
* autohead: New script.
Fri Dec 18 00:21:23 1992 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acgeneral.m4 (AC_HAVE_FUNCS, AC_HAVE_HEADERS): Change method
of tr quoting to keep old shells happy. From Ian Lance Taylor.
* acgeneral.m4 (AC_DEFINE): Add to SEDDEFS.
(AC_OUTPUT): Use sed instead of awk.
From Ian Lance Taylor.
Mon Dec 14 14:33:29 1992 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acspecific.m4 (AC_STDC_HEADERS): Check for string.h
declaring memchr.
* acgeneral.m4 (AC_NOTICE): Fix comment.
Fri Dec 11 17:59:23 1992 David J. MacKenzie (djm@kropotkin.gnu.ai.mit.edu)
* acspecific.m4 (AC_ALLOCA): Don't use libPW; it causes too
much trouble.
Wed Dec 9 14:04:30 1992 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* config.h: Added HAVE_SYS_WAIT, HAVE_WAITPID, SVR4, UMAX,
[ugp]id_t, UMAX4_3, DGUX.
Thu Dec 3 13:37:17 1992 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acspecific.m4 (AC_PROG_INSTALL): Ignore AFS install.
From James Clark, jjc@jclark.com.
Tue Nov 24 07:47:45 1992 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acspecific.m4 (AC_PROG_LEX, AC_DECLARE_YYTEXT, AC_VFORK, AC_WAIT3,
AC_INT_16_BITS, AC_WORDS_BIGENDIAN, AC_ARG_ARRAY): End with a newline.
* acspecific.m4 (AC_DIR_HEADER): If ndir.h exists and the other
choices don't, define NDIR.
Sat Nov 21 00:14:51 1992 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acspecific.m4 (AC_RETSIGTYPE): Instead of grepping for the signal
declaration, try redeclaring it and see if we get an error.
Always define RETSIGTYPE, not just if it's int.
From Ian Lance Taylor.
Fri Nov 20 17:06:09 1992 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acgeneral.m4 (AC_DEFINE): Only put -D option in quotes if it
actually contains blanks.
Thu Nov 19 17:18:40 1992 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PARSEARGS): Set a shell var for --with-*.
(AC_WITH): New macro.
* acspecific.m4 (AC_CONST): If const works, define HAVE_CONST.
* acspecific.m4 (AC_ALLOCA): Don't use libPW on HP-UX.
Wed Nov 18 17:36:08 1992 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* acgeneral.m4 (AC_DEFINE): When writing a -D with a value,
surround it with 's so the value can contain spaces.
Thu Nov 12 22:49:35 1992 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acspecific.m4 (AC_PROG_CC): Don't add -O to CC if GNU C.
(-O2, or nothing, might be more appropriate.)
Sun Nov 8 23:33:23 1992 david d `zoo' zuhn (zoo at cirdan.cygnus.com)
* acspecific.m4 (AC_GETLOADAVG): Check for dwarf.h for general
svr4, then elf.h for Solaris 2, which needs additional libraries.
Thu Nov 12 22:18:54 1992 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PARSEARGS): --exec_prefix -> --exec-prefix.
Tue Nov 10 16:15:10 1992 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acgeneral.m4: undef m4 `include' builtin.
* acspecific.m4 (AC_STDC_HEADERS): Don't test for limits.h
due to Ultrix conflict with float.h.
Thu Oct 29 16:16:11 1992 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* acgeneral.m4 (AC_PARSEARGS, AC_PREPARE): New macros, broken out
parts of AC_INIT.
(AC_INIT): Use them.
Thu Oct 22 20:48:12 1992 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acspecific.m4 (AC_INSTALL): Comment out arg to `:'.
AIX doesn't like it.
Wed Oct 14 12:41:02 1992 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* Version 1.2.
* acspecific.m4 (AC_INSTALL): Avoid the AIX install script.
* acspecific.m4 (AC_RESTARTABLE_SYSCALLS): Wait for child if
sys calls are not restarted, to avoid leaving the child still
running. From Ian Lance Taylor.
Tue Oct 13 15:43:56 1992 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acspecific.m4 (AC_CONST): Add more tests for brokenness.
From Jim Meyering.
* acgeneral.m4: Use % instead of ? to avoid shell variable expansion.
Fri Oct 2 06:55:05 1992 David J. MacKenzie (djm@goldman.gnu.ai.mit.edu)
* acgeneral.m4: Use ? instead of , to separate parts of sed arg.
Mon Sep 14 12:33:41 1992 David J. MacKenzie (djm@apple-gunkies.gnu.ai.mit.edu)
* acspecific.m4 (AC_STDC_HEADERS): Also check for float.h.
* acspecific.m4 (AC_TIMEZONE): Protect [] from being quotes.
Thu Sep 10 17:12:10 1992 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acgeneral.m4 (AC_OUTPUT): Include the hostname in config.status.
* acgeneral.m4 (AC_OUTPUT): Use a separate flag in the awk
script instead of checking for non-empty values, so things
like defining const as empty work. From
Steve Emmerson .
Fri Aug 28 18:51:13 1992 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acgeneral.m4 (AC_INIT): If there's no path on $0, use '.'.
Thu Aug 27 16:15:14 1992 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* config.h: New file.
* acgeneral.m4 (AC_INIT): Look for source files in the
directory containing `configure', if not given explicitly.
* acspecific.m4 (AC_TIMEZONE): Adjust tzname decl for RS6000.
* acspecific.m4 (AC_GETLOADAVG): Don't use double quotes in
the test program.
Thu Aug 27 15:26:49 1992 Roland McGrath (roland@wookumz.gnu.ai.mit.edu)
* acspecific.m4 (AC_GETLOADAVG): Don't check nlist.h if we found
one of specific things.
Mon Aug 24 16:22:45 1992 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* Version 1.1.
* acspecific.m4 (AC_TIMEZONE): Include time.h. Don't
declare tzname if it's a macro. From Jim Meyering.
Fri Aug 21 14:12:35 1992 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acspecific.m4 (AC_ALLOCA): Check whether the alloca defined by
alloca.h works when given a non-constant argument.
* acspecific.m4 (AC_GETLOADAVG): Define NLIST_STRUCT and
NLIST_NAME_UNION if appropriate.
* acgeneral.m4 (AC_OUTPUT): If no args are given, omit the loop to
produce output files.
* acgeneral.m4 (AC_TEST_PROGRAM): Add a call to exit to try to
suppress core dumped message. From Ian Lance Taylor.
* acgeneral.m4 (AC_PREFIX): Only print the message if prefix
hasn't been set. From James Clark.
* acspecific.m4 (AC_SIZE_T, AC_UID_T, AC_PID_T,
AC_RETSIGTYPE): Print a message saying what it's checking for.
(AC_SIZE_T): Define size_t to be unsigned, not int, for
ANSI-friendliness.
* acspecific.m4 (AC_GETLOADAVG): Just check for elf.h, not
dwarf.h too.
* autoconf.sh: Exit with status 1 if there are unresolved macros.
Isolate the pattern to make adding other prefixes easy.
Look for aclocal.m4 in . as well as MACRODIR.
Tue Aug 18 16:35:46 1992 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* acspecific.m4 (AC_STRCOLL): New macro.
Tue Aug 18 15:22:45 1992 Roland McGrath (roland@geech.gnu.ai.mit.edu)
* acspecific.m4 (AC_GETLOADAVG): elf.h implies SVR4.
Mon Jul 27 14:20:32 1992 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acgeneral.m4 (AC_TEST_PROGRAM): Check for cross-compiling
was missing "test -n". From Ian Lance Taylor.
Sun Jul 26 16:25:19 1992 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* acgeneral.m4 (AC_SUBST): Support multiple substitutions in a
line.
Mon Jul 20 01:08:01 1992 David J. MacKenzie (djm@nutrimat.gnu.ai.mit.edu)
* Version 1.0.
-----
Copyright (C) 1992, 1993, 1994 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation, either version 3 of the
License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see
.
autoconf2.64-2.64/NEWS 0000644 0002024 0002024 00000216157 11233215474 013674 0 ustar arthur arthur GNU Autoconf NEWS - User visible changes.
* Major changes in Autoconf 2.64 (2009-07-26) [stable]
Released by Eric Blake, based on git versions 2.63b.*.
** Autoconf now requires GNU M4 1.4.6 or later. Earlier versions of M4
have a bug in regular expression handling that interferes with some
of the speedups provided since Autoconf 2.63. GNU M4 1.4.13 or
later is recommended.
** AS_IF and AS_CASE have been taught to avoid syntax errors even when
given arguments that expand to just whitespace.
** The following documented autoconf macros are new:
AC_ERLANG_SUBST_ERTS_VER
** The autoheader tool now understands m4 macro arguments passed to
AC_DEFINE and AC_DEFINE_UNQUOTED.
** Ensure AT_CHECK can support commands that include a # given with
proper m4 quoting. For shell comments, this is a new feature; for
non-shell comments, this fixes a regression introduced in 2.63b.
Additionally, AT_CHECK correctly supplies shell escapes for
metacharacters occurring in m4 macro expansions within the expected
stdout and stderr parameters.
** The macro AT_CHECK now understands the concept of hard failure. If
a test exits with an unexpected status 99, cleanup actions for the
test are inhibited and the test is treated as a failure regardless
of AT_XFAIL_IF. It also understands the new directives
ignore-nolog, stdout-nolog, and stderr-nolog.
** The following documented autotest macros are new:
AT_CHECK_UNQUOTED AT_FAIL_IF AT_SKIP_IF
** The following documented m4sugar macros are new:
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m4_ifblank m4_ifnblank m4_rename_force
** The autoconf testsuite now exercises all Erlang macros.
* Major changes in Autoconf 2.63b (2009-03-31) [beta]
Released by Eric Blake, based on git versions 2.63.*.
** The manual is now shipped under the terms of the GNU FDL 1.3.
** AC_REQUIRE now detects the case of an outer macro which first expands
then later indirectly requires the same inner macro. Previously,
this case led to silent out-of-order expansion (bug present since
2.50); it now issues a syntax warning, and duplicates the expansion
of the inner macro to guarantee dependencies have been met. See
the manual for advice on how to refactor macros in order to avoid
the bug in earlier autoconf versions and avoid increased script
size in the current version.
** AC_DEFUN_ONCE has improved semantics. Previously, a macro declared
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expansion was still possible. Now, dependencies are guaranteed,
and subsequent invocations are a silent no-op. This makes
AC_DEFUN_ONCE an ideal macro for silencing AC_REQUIRE warnings.
** The following macros are now defined with AC_DEFUN_ONCE. This means
a subtle change in semantics; previously, an AC_DEFUN macro could
expand one of these macros multiple times or surround the macro
inside shell conditional text to bypass the effects of these
macros, but now the macro will expand exactly once, and prior to
the start of any enclosing AC_DEFUN macro:
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AC_HEADER_ASSERT AC_PROG_INSTALL AC_PROG_MKDIR_P
AC_USE_SYSTEM_EXTENSIONS
** AC_LANG_ERLANG works once again (regression introduced in 2.61a).
** AC_HEADER_ASSERT is fixed so that './configure --enable-assert' no
longer mistakenly disables assertions.
** AC_INIT now takes an optional fifth parameter that can be used to
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used in `configure --help' and is also available via AC_DEFINE.
** Autotest testsuites accept an option --jobs[=N] for parallel testing.
This feature is still in testing, and may not work on every
platform, help in improving it would be appreciated.
** Autotest testsuites do not attempt to write startup error messages
to the log file before that is opened (regression introduced in 2.63).
** Configure scripts now use shell functions. This feature leads to
smaller configure files and faster execution.
** Present But Cannot Be Compiled: Autoconf will now proceed with
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providing a fourth parameter to AC_CHECK_HEADER/AC_CHECK_HEADERS.
** Autoreconf added aclocal to the set of programs affected by the
`autoreconf -I dir' option.
** The following documented m4sugar macros are new:
m4_chomp m4_chomp_all m4_cleardivert m4_curry m4_default_quoted
m4_esyscmd_s m4_map_args m4_map_args_pair m4_map_args_sep
m4_map_args_w m4_set_map m4_set_map_sep m4_stack_foreach
m4_stack_foreach_lifo m4_stack_foreach_sep
m4_stack_foreach_sep_lifo
** The following m4sugar macros are documented now, but in some cases
with slightly different semantics than what the previous
undocumented version had:
m4_copy m4_dumpdefs m4_rename m4_version_prereq
** The m4sugar macro m4_expand has been taught to handle unterminated
comments and shell case statements. As a result, it is used
internally in more places, such as AC_DEFINE and AT_CHECK. Most
uses of AC_DEFINE and AT_CHECK should not behave any differently;
however, it may be necessary to add double-quoting around
unbalanced `(' where single-quoting used to be sufficient.
** The following documented m4sh macros are new:
AS_INIT_GENERATED AS_LINENO_PREPARE AS_ME_PREPARE AS_SET_STATUS
AS_VAR_APPEND AS_VAR_ARITH AS_VAR_COPY
** The following m4sh macros are documented now, but in some cases
with slightly different semantics than what the previous
undocumented version had:
AS_ECHO AS_ECHO_N AS_ESCAPE AS_EXIT AS_LITERAL_IF AS_UNSET
AS_VAR_IF AS_VAR_POPDEF AS_VAR_PUSHDEF AS_VAR_SET AS_VAR_SET_IF
AS_VAR_TEST_SET AS_VERSION_COMPARE
** The m4sh macros AS_IF and AS_CASE can now be used in shell lists.
The responsibility for supplying a trailing newline now belongs to
the call site, but since most users did not add dnl, this generally
results in fewer empty lines in configure.
* Major changes in Autoconf 2.63 (2008-09-09) [stable]
Released by Eric Blake, based on git versions 2.62.*.
** AC_C_BIGENDIAN does not mistakenly report "universal" for some
bigendian hosts, a regression introduced with universal binary
support in 2.62.
** AC_PATH_X now includes /lib64 and /usr/lib64 in its list of default
library directories.
** AC_USE_SYSTEM_EXTENSIONS no longer conflicts with an external
AC_DEFINE([__EXTENSIONS__]). This fixes a regression introduced in
2.62 when using macros such as AC_AIX that were made obsolete in
favor of the more portable AC_USE_SYSTEM_EXTENSIONS.
** AC_CHECK_TARGET_TOOLS is usable in the non-cross-compile case.
** Newly obsolete macros
The following macro has been marked obsolete, since current porting
targets can safely assume C89 semantics that signal handlers return
void. We have no current plans to remove the macro.
AC_TYPE_SIGNAL
** The macros m4_map and m4_map_sep now ignore any list elements
consisting of just empty quotes, and m4_map_sep now expands its
separator. This fixes a regression in 2.62 when these macros were
first documented, for the sake of clients expecting the semantics
that these macros had prior to that time. The new macros m4_mapall
and m4_mapall_sep, along with extra quoting of the separator, can
be used to get the semantics that m4_map_sep had in 2.62.
** Clients of m4_expand, such as AS_HELP_STRING and AT_SETUP, can now
handle properly quoted but otherwise unbalanced parentheses (for
some macros, this fixes a regression in 2.62).
** Two new quadrigraphs have been introduced: @{:@ for (, and @:}@ for ),
allowing the output of unbalanced parentheses in more contexts.
** The following m4sugar macros are new:
m4_cleardivert m4_joinall m4_mapall m4_mapall_sep m4_reverse
m4_set_add m4_set_add_all m4_set_contains m4_set_contents
m4_set_delete m4_set_difference m4_set_dump m4_set_empty
m4_set_foreach m4_set_intersection m4_set_list m4_set_listc
m4_set_remove m4_set_size m4_set_union
** The following m4sugar macros now accept multiple arguments, as is the
case with underlying m4:
m4_defn m4_popdef m4_undefine
** The following m4sugar macros now guarantee linear scaling; they
previously had linear scaling with m4 1.6 but quadratic scaling
when using m4 1.4.x. All macros built on top of these also gain
the scaling improvements.
m4_bmatch m4_bpatsubsts m4_case m4_cond m4_do m4_dquote_elt
m4_foreach m4_join m4_list_cmp m4_map m4_map_sep m4_max
m4_min m4_shiftn
** AT_KEYWORDS once again performs expansion on its argument, such that
AT_KEYWORDS([m4_if([$1], [], [default])]) no longer complains about
the possibly unexpanded m4_if [regression introduced in 2.62].
** Config header templates `#undef UNDEFINED /* comment */' do not lead to
nested comments any more; regression introduced in 2.62.
* Major changes in Autoconf 2.62 (2008-04-05) [stable]
Released by Eric Blake, based on git versions 2.61a.*.
** Many optimizations have been applied to make overall execution faster.
** Autotest now makes use of shell functions.
** config.status now uses awk instead of sed also for config headers.
- As a side effect, AC_DEFINE and AC_DEFINE_UNQUOTED now handle multi-line
values, i.e., backslash-newline combinations are handled correctly.
Further, for config headers, the total size of values is not limited by
the POSIX length limit of text lines any more, only each single line.
** New config variable `top_build_prefix'.
** New Autoconf macros:
AC_AUTOCONF_VERSION AC_OPENMP AC_PATH_PROGS_FEATURE_CHECK
** AC_C_BIGENDIAN now supports universal binaries a la Mac OS X.
** AC_C_RESTRICT now prefers to #define 'restrict' to a variant spelling
like '__restrict' if the variant spelling is available, as this is
more likely to work when mixing C and C++ code.
** AC_CHECK_ALIGNOF's type argument T is now documented better: it must
be a string of tokens such that "T y;" is a valid member declaration
in a struct.
** AC_CHECK_SIZEOF now accepts objects as well as types: the general rule
is that sizeof (X) works, then AC_CHECK_SIZEOF (X) should work.
** AC_CHECK_TYPE and AC_CHECK_TYPES now work on any C type-name; formerly,
they did not work for function types. In C++, they now work on any
type-id that can be the operand of sizeof; this is similar to C,
except it excludes anonymous struct and union types. Formerly,
some (but not all) C++ types involving anonymous struct and union
were accepted, though this was not documented.
** AC_CONFIG_LINKS now prefers to link against files in the build tree
if found, and it works to link against a file of the same name in
the source tree, even if both trees coincide.
** AC_INIT no longer alters $@; regression introduced in 2.60.
** AC_USE_SYSTEM_EXTENSIONS now defines _ALL_SOURCE for Interix platforms.
** AS_HELP_STRING no longer underquotes its first argument; it also handles
the case where the first argument contains single-quoted commas.
For example, "AS_HELP_STRING([-a, [--arg[=foo]]], [bar])" produces:
" -a, --arg[=foo] bar"
Additionally, the macro now takes two additional arguments,
indent-column and wrap-column; these should not normally be needed,
but can be used to fine-tune how the output text is wrapped.
** AC_PROG_INSTALL now requires an install program that can install multiple
files into a target directory.
** The command 'autoconf -' now correctly processes a file from stdin.
** 'autoreconf -m' now honors $MAKE.
** For all of the directory arguments for 'configure', such as '--prefix'
or '--bindir', trailing slashes are stripped. As an example, if
tab completion in the user's shell appends trailing slashes, the
command './configure --prefix=/usr/' will still result in an
expanded libdir value of /usr/lib, not /usr//lib.
** `configure --help=recursive' now works in read-only trees and from
unconfigured build trees.
** If precious variables differ only in whitespace, then the cache consistency
check warns instead of fails, and reuses the old value.
** AT_BANNER is now documented.
** AT_SETUP now handles macro expansions properly when calculating line
length.
** Autotest now determines $srcdir correctly.
** Testsuites built by autotest now accept a -C/--directory=DIR option
to adjust the working directory prior to creating files.
** Autoconf now requires GNU M4 1.4.5 or later. Earlier versions of M4 have
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Autoconf and Automake. GNU M4 1.4.11 or later is recommended. The
configure search for a working M4 is improved.
** For portability with the eventual M4 2.0, macros should no longer use
anything larger than $9 to refer to arguments.
** Documentation for m4sugar is improved.
- The following macros were previously available as undocumented
interfaces; the macros are now documented as stable interfaces.
__oline__ m4_assert m4_bmatch m4_bpatsubsts m4_car m4_case
m4_cdr m4_default m4_divert_once m4_divert_pop m4_divert_push
m4_divert_text m4_do m4_errprintn m4_fatal m4_flatten
m4_ifndef m4_ifset m4_ifval m4_ifvaln m4_location
m4_n m4_shiftn m4_strip m4_warn
- The following macros were previously available as undocumented
interfaces, but had bug fixes or semantic changes as part of this
release. Packages that relied on the undocumented behavior
should be analyzed to make sure they will still work with the
new documented behavior.
m4_cmp m4_list_cmp m4_join m4_map m4_map_sep m4_sign
m4_text_box m4_text_wrap m4_version_compare
- The m4_wrap macro used to have unspecified order, but now
guarantees FIFO order. m4_wrap_lifo was added to guarantee LIFO
order.
- Packages using the undocumented m4sugar macro m4_PACKAGE_VERSION
should consider using the new AC_AUTOCONF_VERSION instead.
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** The m4sugar macros m4_append and m4_append_uniq, first documented in
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of the separator resulted in a different string (for example, if it
contained quotes, a comma, or a macro name). However, it means
that programs previously using
m4_append([name], [string], [[, ]])
are now using a four-character separator instead of the intended
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Autoconf, you can insert the following snippet after AC_INIT but
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m4_pushdef([m4_append], [m4_define([$1],
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Additionally, m4_append_uniq now takes optional parameters that can
be used to take action depending on whether anything was appended,
and warns if a non-empty separator occurs within the string being
appended, since that can lead to duplicates.
** The following m4sugar macros are new:
m4_append_uniq_w m4_apply m4_combine m4_cond m4_count
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m4_min m4_newline m4_shift2 m4_shift3 m4_unquote m4_wrap_lifo
** Warnings are now generated by default when an installer invokes
'configure' with an unknown --enable-* or --with-* option.
These warnings can be disabled with the new AC_DISABLE_OPTION_CHECKING
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The following macros have been marked obsolete, as they only
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AC_AIX AC_GNU_SOURCE AC_ISC_POSIX AC_MINIX
** AC_C_LONG_DOUBLE is obsolescent.
The documentation now says that AC_C_LONG_DOUBLE is obsolescent: it
tests for problems that are so old that it is no longer of
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** AC_DIAGNOSE, AC_WARNING, and AC_FATAL are obsolescent.
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* Major changes in Autoconf 2.61a (2006-12-11)
** AC_FUNC_FSEEKO was broken in 2.61; it didn't make fseeko and ftello visible
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** AC_FUNC_SETVBUF_REVERSED is now obsolete. It is still defined for backward
compatibility but it does nothing. The macro was already
obsolescent, as the last systems to have the problem were those
based on SVR2, which became obsolete in 1987. The macro had bugs
on some modern systems and could no longer be maintained reliably
due to lack of ancient systems to test it on.
** config.status now uses awk instead of sed for most substitutions, for speed.
- As a side effect multi-line values of substituted variables no
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* Major changes in Autoconf 2.61 (2006-11-17)
** New macros AC_C_FLEXIBLE_ARRAY_MEMBER, AC_C_VARARRAYS.
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* Major changes in Autoconf 2.60b (2006-10-22)
** BIN_SH
Autoconf-generated shell scripts no longer export BIN_SH, due to
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** AC_USE_SYSTEM_EXTENSIONS now defines _TANDEM_SOURCE for NonStop platforms.
** GNU M4 1.4.7 or later is now recommended.
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New M4sugar macro, which is more secure than the POSIX M4 maketemp.
** m4_maketemp
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* Major changes in Autoconf 2.60a (2006-08-25)
** GNU M4 1.4.6 or later is now recommended.
** The check for C99 now tests for varargs macros, as documented.
It also tests that the preprocessor supports 64-bit integers.
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* Major changes in Autoconf 2.60
Released 2006-06-23, by Ralf Wildenhues.
** Autoconf no longer depends on whether m4wrap is FIFO (as Posix requires)
or LIFO (as in GNU M4 1.4.x). GNU M4 2.0 is expected to conform to Posix
here, so m4wrap/m4_wrap users should no longer depend on LIFO behavior.
** Provide a way to turn off warnings about the changed directory variables.
* Major changes in Autoconf 2.59d
Released 2006-06-05, by Ralf Wildenhues.
** GNU make now recommended for VPATH builds
INSTALL now suggests VPATH builds (e.g., "sh ../srcdir/configure")
only if you use GNU make. In practice, other 'make' implementations
have too many subtle incompatibilities in their support for VPATH.
Many packages (including Autoconf itself) are portable to other
'make' implementations, but some packages are not, and recommending
GNU make keeps the installation instructions simpler.
** Even more safety checks for the new Directory variables:
Warn about suspicious `${datarootdir}' found in config files output.
** AC_TRY_COMMAND, AC_TRY_EVAL, ac_config_guess, ac_config_sub, ac_configure
These never-documented macros and variables have been marked with
comments saying that they may be removed in a future release,
because their use can lead to unintended code being executed.
If you need functionality that only these macros or variables
currently supply, please write bug-autoconf@gnu.org.
** AC_SUBST, AC_DEFINE
Literal arguments to these are passed to m4_pattern_allow now.
** AC_PROG_CC_STDC
Passing 'ac_cv_prog_cc_stdc=no' to 'configure' now sets ac_cv_prog_cc_c99
and ac_cv_prog_cc_c89 to 'no' as well, for backward compatibility with
obsolete K&R tests in the Automake test suite.
** AC_PROG_CXX_C_O
New macro.
** AC_PROG_MKDIR_P
New macro.
** AS_MKDIR_P
Now more robust with special characters in file names, or when
multiple processes create the same directory at the same time.
** Obsolescent macros
The documentation now says that the following macros are obsolescent:
they test for problems that are so old that they are no longer of
practical importance on current systems.
AC_C_BACKSLASH_A AC_FUNC_MEMCMP AC_HEADER_DIRENT
AC_C_CONST AC_FUNC_SELECT_ARGTYPES AC_HEADER_STAT
AC_C_PROTOTYPES AC_FUNC_SETPGRP AC_HEADER_STDC
AC_C_STRINGIZE AC_FUNC_SETVBUF_REVERSED AC_HEADER_SYS_WAIT
AC_C_VOLATILE AC_FUNC_STAT AC_HEADER_TIME
AC_FUNC_CLOSEDIR_VOID AC_FUNC_STRFTIME AC_ISC_POSIX
AC_FUNC_GETPGRP AC_FUNC_UTIME_NULL AC_PROG_GCC_TRADITIONAL
AC_FUNC_LSTAT AC_FUNC_VPRINTF AC_STRUCT_TM
New programs need not use these macros. We have no current plans to
remove them.
** autoreconf
For compatibility with future Libtool 2.0, autoreconf will invoke
libtoolize with the option `--ltdl' now, if LT_CONFIG_LTDL_DIR is
used.
* Major changes in Autoconf 2.59c
Released 2006-04-12, by Ralf Wildenhues.
** The configure command now redirects standard input from /dev/null,
to help avoid problems with subsidiary commands that might mistakenly
read standard input. AS_ORIGINAL_STDIN_FD points to the original
standard input before this redirection, if you really want configure to
read from standard input.
** Directory variables adjusted to recent changes in the GNU Coding Standards.
The following directory variables are new:
datarootdir read-only architecture-independent data root [PREFIX/share]
localedir locale-specific message catalogs [DATAROOTDIR/locale]
docdir documentation root [DATAROOTDIR/doc/PACKAGE]
htmldir html documentation [DOCDIR]
dvidir dvi documentation [DOCDIR]
pdfdir pdf documentation [DOCDIR]
psdir ps documentation [DOCDIR]
The following variables have new default values:
datadir read-only architecture-independent data [DATAROOTDIR]
infodir info documentation [DATAROOTDIR/info]
mandir man documentation [DATAROOTDIR/man]
This means that if you use any of `@datadir@', `@infodir@', or
`@mandir@' in a file, you will have to ensure `${datarootdir}' is
defined in this file. As a temporary measure, if any of those are
found but no mention of `datarootdir', the substitutions will be
replaced with values that do not contain `${datarootdir}', and a
warning will be issued.
** @top_builddir@ is now a dir name: it is always nonempty and doesn't have
a trailing slash. Similar change will be made to ac_top_builddir in a
future release; the old style value, which matches (../)*, is (and will
continue to be) available as ac_top_build_prefix.
** AC_C_TYPEOF
New macro to check for support of 'typeof' syntax a la GNU C.
** AC_CHECK_DECLS_ONCE, AC_CHECK_FUNCS_ONCE, AC_CHECK_HEADERS_ONCE
New "once-only" variants of commonly-used macros, to make 'configure'
smaller and faster in common cases.
** AC_FUNC_STRTOLD
New macro to check for strtold with C99 semantics.
** AC_HEADER_ASSERT
New macro that lets builder disable assertions at 'configure'-time.
** AC_PATH_X
Now checks for X11/Xlib.h and XrmInitialize (X proper) rather than
X11/Intrinsic.h and XtMalloc (Xt).
** AC_PRESERVE_HELP_ORDER
New macro that causes `configure' to display help strings for AC_ARG_ENABLE
and AC_ARG_WITH arguments in one region, in the order defined. The default
behavior is to group options of each classes separately.
** AC_PROG_CC, AC_PROG_CXX
No longer automatically arrange to declare the 'exit' function of C,
when a C++ compiler is used. Standard Autoconf macros no longer use
'exit', so this is no longer an issue for them. If you use C++, and
want to call 'exit', you'll have to arrange for its declaration
yourself. But we now suggest you return from 'main' instead.
** AC_PROG_CC_C89, AC_PROG_CC_C99
New macros for ISO C99 support. AC_PROG_CC_C89 and AC_PROG_CC_C99
check for ANSI C89 and ISO C99 support respectively.
** AC_PROG_CC_STDC
Has been unobsoleted, and will check if the compiler supports ISO
C99, falling back to ANSI C89 if not. ac_cv_prog_cc_stdc is
retained for backwards compatibility, assuming the value of
ac_cv_prog_cc_c99 or ac_cv_prog_cc_c89 (whichever is valid, in
that order).
** AC_STRUCT_DIRENT_D_INO, AC_STRUCT_DIRENT_D_TYPE
New macros for checking commonly-used members of struct dirent.
** AC_SUBST
The substituted value can now contain newlines.
** AC_SUBST_FILE
The substitution now occurs only when @variable@ is on a line by itself,
optionally surrounded by spaces and tabs. The whole line is replaced.
** AC_TYPE_LONG_DOUBLE, AC_TYPE_LONG_DOUBLE_WIDER
New macros to check for long double, and whether it is wider than double.
The old macro AC_C_TYPE_LONG_DOUBLE has been marked as obsolete;
applications should switch to the new macro.
** AC_TYPE_INT8_T, AC_TYPE_INT16_T, AC_TYPE_INT32_T, AC_TYPE_INT64_T,
AC_TYPE_INTMAX_T, AC_TYPE_INTPTR_T, AC_TYPE_LONG_LONG_INT, AC_TYPE_SSIZE_T,
AC_TYPE_UINT8_T, AC_TYPE_UINT16_T, AC_TYPE_UINT32_T, AC_TYPE_UINT64_T,
AC_TYPE_UINTMAX_T, AC_TYPE_UINTPTR_T, AC_TYPE_UNSIGNED_LONG_LONG_INT
New macros to check for C99 and POSIX types.
** AC_USE_SYSTEM_EXTENSIONS
New macro to enable extensions to Posix.
** AH_HEADER
New macro which is defined to the name of the first declared config header
or undefined if no config headers have been declared yet.
** AS_HELP_STRING
The macro correctly handles quadrigraphs now.
** AS_BOURNE_COMPATIBLE, AS_SHELL_SANITIZE, AS_CASE
These macros are new or published now.
** AT_COPYRIGHT
New macro for copyright notices in testsuite files.
** ALLOCA, LIBOBJS, LTLIBOBJS
Object names added to these variables are now prefixed with `${LIBOBJDIR}',
as in `${LIBOBJDIR}alloca.o'. LIBOBJDIR is meant to be defined from
`Makefile.in' in case the object files lie in a different directory.
The LIBOBJDIR feature is experimental.
** autoreconf
Supports --no-recursive now.
** New macros to support Erlang/OTP.
New macros for configuring paths to Erlang tools and libraries:
AC_ERLANG_PATH_ERLC, AC_ERLANG_NEED_ERLC, AC_ERLANG_PATH_ERL,
AC_ERLANG_NEED_ERL, AC_ERLANG_CHECK_LIB, AC_ERLANG_SUBST_ROOT_DIR,
AC_ERLANG_SUBST_LIB_DIR.
New macros for configuring installation of Erlang libraries:
AC_ERLANG_SUBST_INSTALL_LIB_DIR, AC_ERLANG_SUBST_INSTALL_LIB_SUBDIR.
** The manual now mentions Gnulib more prominently.
** New macros to support Objective C.
AC_PROG_OBJC, AC_PROG_OBJCPP.
* Major changes in Autoconf 2.59b
Released 2004-08-20, by Paul Eggert.
** AC_CHECK_ALIGNOF
New macro that computes the default alignment of a type.
** AC_CHECK_TOOL, AC_PATH_TOOL, AC_CHECK_TOOLS
When cross-compiling, these macros will give a warning if the tool
is not prefixed. In the future, unprefixed cross tools will not
be detected; please consult the info documentation for information
about the reason of this change.
** AC_CHECK_TARGET_TOOL, AC_PATH_TARGET_TOOL, AC_CHECK_TARGET_TOOLS
New macros that detect programs whose name is prefixed with the
target type, if the build type and target type are different.
** AC_REQUIRE_AUX_FILE
New trace macro that declares expected auxiliary files.
** AC_PROG_GREP
New macro that tests for a grep program that accepts as a long a line
as possible.
** AC_PROG_EGREP, AC_PROG_FGREP
These macros now require AC_PROG_GREP, and try EGREP="$GREP -E" and
FGREP="$GREP -F" respectively if possible, or else run a path search for
a program that accepts as long a line as possible.
** AC_PROG_SED
New macro that tests for a sed program that truncates as few characters
as possible.
* Major changes in Autoconf 2.59
Released 2003-11-04, by Akim Demaille
** ac_abs_builddir etc.
Absolute file names were actually relative in 2.58.
* Major changes in Autoconf 2.58
Released 2003-11-04, by Akim Demaille
** core.*
core.* files are no longer removed, as they may be valid user files.
** autoreconf and auxiliary directory
Autoreconf creates the auxiliary directory if needed. This is
especially useful for initial "bootstrapping" of fresh CVS checkouts.
** AC_CONFIG_MACRO_DIR
Use this macro to declare the directory for local M4 macros for aclocal.
** AC_LIBOBJS
No longer includes twice the same file in LIBOBJS if invoked
multiple times.
** AC_CONFIG_COMMANDS
The directory for its first argument is automatically created. For
instance, with
AC_CONFIG_COMMANDS([src/modules.hh], [...])
$top_builddir/src/ is created if needed.
** Autotest and local.at
The optional file local.at is always included in Autotest test suites.
** Warnings
The warnings are always issued, including with cached runs.
This became a significant problem since aclocal and automake can
run autoconf behind the scene.
** autoheader warnings
The warnings of autoheader can be turned off, using --warning.
For instance, -Wno-obsolete disables the complaints about acconfig.h
and other deprecated constructs.
** New macros
AC_C_RESTRICT, AC_INCLUDES_DEFAULT, AC_LANG_ASSERT, AC_LANG_WERROR,
AS_SET_CATFILE.
** AC_DECL_SYS_SIGLIST
Works again.
** AC_FUNC_MKTIME
Now checks that mktime is the inverse of localtime.
** Improve DJGPP portability
The Autoconf tools and configure behave better under DJGPP.
** Present But Cannot Be Compiled
New FAQ section dedicated to the mystic
configure: WARNING: pi.h: present but cannot be compiled
configure: WARNING: pi.h: check for missing prerequisite headers?
configure: WARNING: pi.h: proceeding with the preprocessor's result
messages.
** Concurrent executions of autom4te
autom4te now locks its internal files, which enables concurrent
executions of autom4te, likely to happen if automake, autoconf,
autoheader etc. are run simultaneously.
** Libtool
Use of Libtool 1.5 and higher is encouraged. Compatibility with
Libtool pre-1.4 is not checked.
** Autotest
Testsuites no longer rerun failed tests in verbose mode; instead,
failures are logged while the test is run.
In addition, expected failures can be marked as such.
* Major changes in Autoconf 2.57
Released 2002-12-03 by Paul Eggert.
Bug fixes for problems with AIX linker, with freestanding C compilers,
with GNU M4 limitations, and with obsolete copies of GNU documents.
The Free Documentation License has been upgraded from 1.1 to 1.2.
* Major changes in Autoconf 2.56
Released 2002-11-15 by Akim Demaille.
One packaging problem fixed (config/install-sh was not executable).
* Major changes in Autoconf 2.55
Released 2002-11-14 by Akim Demaille.
Release tips:
Have your configure.ac checked by autoscan ("autoscan").
Try the warning options ("autoreconf -fv -Wall").
** Documentation
- AC_CHECK_HEADER, AC_CHECK_HEADERS
More information on proper use.
- Writing Test Programs
This sections explains how to write good test sources to use with
AC_COMPILE_IFELSE etc. It documents AC_LANG_PROGRAM and so forth.
- AC_FOO_IFELSE vs. AC_TRY_FOO
Explains why Autoconf moves from AC_TRY_COMPILE etc. to
AC_COMPILE_IFELSE and AC_LANG_PROGRAM etc.
** autoreconf
- Is more robust to different Gettext installations.
- Produces messages (when --verbose) to be understood by Emacs'
compile mode.
- Supports -W/--warnings.
- -m/--make
Once the GNU Build System reinstalled, run `./config.status
--recheck && ./config.status && make' if possible.
** autom4te
- Supports --cache, and --no-cache.
- ~/.autom4te.cfg makes it possible to disable the caching mechanism
(autom4te.cache). See `Customizing autom4te' in the documentation.
** config.status
Supports --quiet.
** Obsolete options
Support for the obsoleted options -m, --macrodir, -l, --localdir is
dropped in favor of the safer --include/--prepend-include scheme.
** Macros
- New macros
AC_COMPILER_IFELSE, AC_FUNC_MBRTOWC, AC_HEADER_STDBOOL,
AC_LANG_CONFTEST, AC_LANG_SOURCE, AC_LANG_PROGRAM, AC_LANG_CALL,
AC_LANG_FUNC_TRY_LINK, AC_MSG_FAILURE, AC_PREPROC_IFELSE.
- Obsoleted
Obsoleted macros are kept for Autoconf backward compatibility, but
should be avoided in configure.ac. Running autoupdate is advised.
AC_DECL_SYS_SIGLIST.
- AC_DEFINE/AC_DEFINE_UNQUOTED
We have to stop using the old compatibility scheme --that tried to
avoid useless backslashes-- because Libtool 1.4.3 contains a
AC_DEFINE([error_t], [int],
[Define to a type to use for \`error_t' if it is not
otherwise available.])
We have to quote the single quotes and backslashes with \. The old
compatibility scheme saw that ` was backslashed, and therefore did
not quote the single quote... Failure. Hence, Autoconf 2.54 is not
compatible with Libtool. Autoconf 2.55 is, but in some cases might
produce more \ than wanted.
Please, note that in the future the same problem will happen with
AC_MSG_*: use `autoreconf -f -Wall'.
** Bug Fixes
- Portability of the Autoconf package to Solaris.
- Spurious warnings caused by config.status.
This bug is benign, but painful: on some systems (typically
FreeBSD), warnings such as:
config.status: creating Makefile
mv: Makefile: set owner/group (was: 1357/0): Operation not permitted
could be issued. This is fixed.
- Parallel Builds
Simultaneous executions of config.status are possible again.
- Precious variables accumulation
config.status could stack several copies of the precious variables
assignments.
** Plans for later versions
- ./configure
The compatibility hooks with the old scheme will be completely
removed. Please, advice/use `--build', `--host', and `--target'
only.
- AC_CHECK_HEADER, AC_CHECK_HEADERS
The tests will be stricter, please make sure your invocations are
valid.
- shell functions
Shell functions will gradually be introduced, probably starting with
Autotest. If you know machines which are in use that you suspect
*not* to support shell functions, please run the test suite of
Autoconf 2.55 on it, and report the results to
bug-autoconf@gnu.org.
- AC_MSG_*
Special characters in AC_MSG_* need not be quoted. Currently,
Autoconf has heuristics to decide when a string is escaped, or has
to be escaped. This scheme is fragile, and will be removed; the
only risk is uglified messages. Please, run `autoreconf -f -Wall'
to find occurrences that will be affected.
* Major changes in Autoconf 2.54
Released 2002-09-13 by Akim Demaille.
** Executables
- autoreconf no longer changes the version of the gettext/po/intl
support files. It now adds the files the correspond to the
AM_GNU_GETTEXT_VERSION declared in configure.ac.
Warning: It now relies on the 'autopoint' program, which is part
of GNU gettext 0.11.4 and newer.
Please note that you need to have a GNU gettext version that
corresponds at least to the AM_GNU_GETTEXT_VERSION declared
in configure.ac. You can upgrade to newer GNU gettext versions,
though, without needing to change configure.ac.
- The -I DIR or --include=DIR option now appends DIR to the include path
instead of prepending; this is for consistency with other GNU tools.
The new -B DIR or --prepend-include=DIR option has the old behavior.
** Macros
- AC_OUTPUT
Now handles all the gory details about LIBOBJS and LTLIBOBJS.
Please, remove lines such as
# This is necessary so that .o files in LIBOBJS are also
# built via the ANSI2KNR-filtering rules.
LIBOBJS=`echo $LIBOBJS|sed 's/\.o /\$U.o /g;s/\.o$/\$U.o/'`
and read the `AC_LIBOBJ vs LIBOBJS' section. Do not define U in
your Makefiles either.
- AC_CONFIG_LINKS now makes copies if it can't make links.
- AC_FUNC_FNMATCH now tests only for POSIX compatibility, reverting to
Autoconf 2.13 behavior. The new macro AC_FUNC_FNMATCH_GNU also
tests for GNU extensions to fnmatch, and replaces fnmatch if needed.
- AC_FUNC_SETVBUF_REVERSED no longer fails when cross-compiling.
- AC_PROG_CC_STDC is integrated into AC_PROG_CC.
- AC_PROG_F77 default search no longer includes cf77 and cfg77.
- New macros
AC_C_BACKSLASH_A, AC_CONFIG_LIBOBJ_DIR, AC_GNU_SOURCE,
AC_PROG_EGREP, AC_PROG_FGREP, AC_REPLACE_FNMATCH,
AC_FUNC_FNMATCH_GNU, AC_FUNC_REALLOC, AC_TYPE_MBSTATE_T.
- AC_FUNC_GETLOADAVG
looks for getloadavg.c in the CONFIG_LIBOBJ_DIR.
- AC_FUNC_MALLOC
Now defines HAVE_MALLOC to 0 if `malloc' does not work, and asks
for an AC_LIBOBJ replacement.
** Bug fixes
- Spurious complaints from `m4_bmatch' about invalid regular
expressions are suppressed.
- Empty top_builddirs are properly handled.
- AC_CHECK_MEMBER works correctly when the member is an aggregate.
- AC_PATH_PROG
Now colon in the optional path arguments are properly handled.
** Improved portability
- Both Autoconf the package, and the scripts it produces, should run
more reliably with Zsh. Bear in mind it is the default Bourne shell
on Darwin.
- Autoconf and the scripts it produces no longer assume the existence of
the obsolescent commands egrep and fgrep.
** Documentation
- Limitations of Make
More of them.
- GNATS
The GNATS base moved to
http://bugs.gnu.org/cgi-bin/gnatsweb.pl?database=autoconf
(It is no longer available, though.)
** Misc.
- config.log
Now contains the list of ouput variables and files (AC_SUBST,
AC_SUBST_FILES).
* Major changes in Autoconf 2.53
Released 2002-03-08 by Akim Demaille.
** Requirements
Perl 5.005_03 or later is required: autom4te is written in Perl and is
needed by autoconf. autoheader, autoreconf, ifnames, and autoscan are
rewritten in Perl.
** Documentation
- AC_INIT
Argument requirements, output variables, defined macros.
- M4sugar, M4sh, Autotest
First sketch.
- Double quoting macros
AC_TRY_CPP, AC_TRY_COMPILE, AC_TRY_LINK and AC_TRY_RUN.
- Licensing
The Autoconf manual is now distributed under the terms of the GNU FDL.
- Section `Hosts and Cross-Compilation'
Explains the rationale for the 2.5x changes in the cross-compilation
chain, and in the relationships between build, host, and target
types.
Emphasizes that `cross-compilation' == `--host is given'.
If you are working on compilers etc., be sure to read this section.
- Section `AC_LIBOBJ vs. LIBOBJS'
Explains why assigning LIBOBJS directly is now an error.
Details how to update the code.
** configure
- $LINENO
Now used instead of hard coded line numbers.
This eases the comparison of `configure's, and diminishes the
pressure over control version archives.
Automatic replacement for shells that don't support this feature.
- New output variables
@builddir@, @top_builddir@, @abs_srcdir@, @abs_top_srcdir@, @abs_builddir@,
@abs_top_builddir@.
** Emacs
Autoconf and Autotest modes are provided.
** Executables
- autom4te
New, used by the Autoconf suite to cache and speed up most processing.
- --force, -f
Supported by autom4te, autoconf and autoheader.
- --include, -I
Replaces --autoconf-dir and --localdir in autoconf, autoheader,
autoupdate, and autoreconf.
- autoreconf
No longer passes --cygnus, --foreign, --gnits, --gnu, --include-deps:
automake options are to be given via AUTOMAKE_OPTIONS.
- autoreconf
Runs gettextize and libtoolize when appropriate.
- autoreconf
--m4dir is no longer supported.
- autoreconf
Now runs only in the specified directories, defaulting to `.',
but understands AC_CONFIG_SUBDIRS for dependent directories.
Before, it used to run on all the `configure.ac' found in the
current tree.
Independent packages are properly updated.
** Bug fixes
- The top level $prefix is propagated to the AC_CONFIG_SUBDIRS configures.
- AC_TRY_RUN
Under the user pressure, $? is finally available. Probably a mistake.
- AC_F77_LIBRARY_LDFLAGS now supports the HP/UX f90 compiler.
- Precious variables accumulation
config.status could stack several copies of the precious variables
assignments.
- AC_PATH_PROG and family.
Works properly when given a literal path.
- AC_FUNC_SETPGRP
Somewhere since 2.13, the result had been reversed.
** C Macros
- AC_C_BIGENDIAN supports the cross-compiling case.
- AC_C_BIGENDIAN accepts ACTION-IF-TRUE, ACTION-IF-FALSE, and
ACTION-IF-UNKNOWN arguments. All are facultative, and the default
for ACTION-IF-TRUE is to define WORDS_BIGENDIAN like AC_C_BIGENDIAN
always did.
- AC_C_LONG_DOUBLE now succeeds only if `long double' has more range or
precision than `double'.
** Generic macros
- AC_INIT
It now defines the preprocessor symbols PACKAGE_NAME,
PACKAGE_TARNAME, PACKAGE_VERSION, PACKAGE_STRING, and
PACKAGE_BUGREPORT.
- AC_INIT
Admits a fourth optional parameter: the tar name.
- AC_CONFIG_COMMANDS, HEADERS, FILES, LINKS.
Provide the user with srcdir, ac_srcdir, ac_top_srcdir, ac_builddir,
ac_top_builddir, ac_abs_srcdir, ac_abs_top_srcdir, ac_abs_builddir,
ac_abs_top_builddir.
- AC_CONFIG_COMMANDS, HEADERS, FILES, LINKS and AC_OUTPUT.
Are much less expensive when using long lists of files.
- AC_PREFIX_PROGRAM
Works with shell variables, and non alphanumeric names.
** Library macros
- AC_FUNC_STRERROR_R now sets STRERROR_R_CHAR_P, not HAVE_WORKING_STRERROR_R,
because POSIX 1003.1-200x draft 7 says strerror_r returns int, not char *.
- AC_FUNC_STRTOD substitutes POW_LIB.
- AC_FUNC_STRNLEN
New.
* Major changes in Autoconf 2.52
Released 2001-07-18 by Akim Demaille.
** Documentation
- AC_ARG_VAR
- Quadrigraphs
This feature was present in autoconf 2.50 but was not documented.
For example, `@<:@' is translated to `[' just before output. This
is useful when writing strings that contain unbalanced quotes, or
other hard-to-quote constructs.
- m4_pattern_forbid, m4_pattern_allow
- Tips for upgrading from 2.13.
- Using autoscan to maintain a configure.ac.
** Default includes
- Now include stdint.h.
- sys/types.h and sys/stat.h are guarded.
- strings.h is included if available, and not conflicting with string.h.
** Bug fixes
- The test suite is more robust and presents less false failures.
- Invocation of GNU M4 now robust to POSIXLY_CORRECT.
- configure accepts --prefix='' again.
- AC_CHECK_LIB works properly when its first argument is not a
literal.
- HAVE_INTTYPES_H is defined only if not conflicting with sys/types.h.
- build_, host_, and target_alias are AC_SUBST as in 2.13.
- AC_ARG_VAR properly propagates precious variables inherited from the
environment to ./config.status.
- Using --program-suffix/--program-prefix is portable.
- Failures to detect the default compiler's output extension are less
likely.
- `config.status foo' works properly when `foo' depends on variables
set in an AC_CONFIG_THING INIT-CMD.
- autoheader is more robust to broken input.
- Fixed Fortran name-mangling and link tests on a number of systems,
e.g. NetBSD; see AC_F77_DUMMY_MAIN, below.
** Generic macros
- AC_CHECK_HEADER and AC_CHECK_HEADERS support a fourth argument to
specify pre-includes. In this case, the headers are compiled with
cc, not merely preprocessed by cpp. Therefore it is the _usability_
of a header which is checked for, not just its availability.
- AC_ARG_VAR refuses to run configure when precious variables have
changed.
- Versions of compilers are dumped in the logs.
- AC_CHECK_TYPE recognizes use of `foo_t' as a replacement type.
** Specific Macros
- AC_PATH_XTRA only adds -ldnet to $LIBS if it's needed to link.
- AC_FUNC_WAIT3 and AC_SYS_RESTARTABLE_SYSCALLS are obsoleted.
- AM_FUNC_ERROR_AT_LINE, AM_FUNC_FNMATCH, AM_FUNC_MKTIME,
AM_FUNC_OBSTACK, and AM_FUNC_STRTOD are now activated.
Be sure to read `Upgrading from Version 2.13' to understand why
running `autoupdate' is needed.
- AC_F77_DUMMY_MAIN, AC_F77_MAIN: new macros to detect whether
a main-like routine is required/possible when linking C/C++ with
Fortran. Users of e.g. AC_F77_WRAPPERS should be aware of these.
- AC_FUNC_GETPGRG behaves better when cross-compiling.
* Major changes in Autoconf 2.51
There was no release of Autoconf 2.51 since some packagers had used
this version number without permission to ship intermediary versions
of 2.50. The version was skipped to avoid confusion.
* Major changes in Autoconf 2.50
Released 2001-05-21 by Akim Demaille.
** Lots of bug fixes
There have been far too many to enumerate them here. Check out
ChangeLog if you really want to know more.
** Improved documentation
In particular, portability issues are better covered.
** Use of Automake
All the standard GNU Makefile targets are supported. The layout has
changed: m4/ holds the M4 extensions Autoconf needs for its
configuration, doc/ contains the documentation, and tests/ contains
the test suite.
** Man pages are provided
For autoconf, autoreconf, autoupdate, autoheader, autoscan, ifnames,
config.guess, config.sub.
** autoconf
- --trace
Provides a safe and powerful means to trace the macro uses. This
provide the parsing layer for tools which need to `study'
configure.in.
- --warnings
Specify what category of warnings should be enabled.
- When recursing into subdirectories, try for configure.gnu before
configure to adapt for packages not using autoconf on case-insensitive
file systems.
- Diagnostics
More errors are now caught (circular AC_REQUIRE dependencies,
AC_DEFINE in the action part of an AC_CACHE_CHECK, too many pops
etc.). In addition, their location and call stack are given.
** autoupdate
autoupdate is much more powerful, and is able to provide the glue code
which might be needed to move from an old macro to its newer
equivalent.
You are strongly encouraged to use it to modernize both your
`configure.in' and your .m4 extension files.
** autoheader
The internal machinery of autoheader has completely changed. As a
result, using `acconfig.h' should be considered to be obsoleted, and
you are encouraged to get rid of it using the AH macros.
** autoreconf
Extensive overhaul.
** Fortran 77 compilers
Globally, the support for Fortran 77 is considerably improved.
Support for automatically determining a Fortran 77 compiler's
name-mangling scheme. New CPP macros F77_FUNC and F77_FUNC_ are
provided to wrap C/C++ identifiers, thus making it easier and more
transparent for C/C++ to call Fortran 77 routines, and Fortran 77 to
call C/C++ routines. See the Texinfo documentation for details.
** Test suite
The test suite no longer uses DejaGNU. It should be easy to submit
test cases in this new framework.
** configure
- --help, --help=long, -hl
no longer dumps useless items.
- --help=short, -hs
lists only specific options.
- --help=recursive, -hr
displays the help of all the embedded packages.
- Remembers environment variables when reconfiguring.
The previous scheme to set envvar before running configure was
ENV=VAL ./configure
what prevented configure from remembering the environment in which
it was run, therefore --recheck was run in an inconsistent
environment. Now, one should run
./configure ENV=VAR
and then --recheck will work properly. Variables declared with
AC_ARG_VAR are also preserved.
- cross-compilation
$build defaults to `config.guess`, $host to $build, and then $target
to $host.
Cross-compilation is a global status of the package, it no longer
depends upon the current language.
Cross compilation is enabled iff the user specified `--host'.
`configure' now fails if it can't run the executables it compiles,
unless cross-compilation is enabled.
- Cache file
The cache file is disabled by default. The new options
`--config-cache', `-C' set the cache to `config.cache'.
** config.status
- faster
Much faster on most architectures.
- concurrent executions
It is safe to use `make -j' with config.status.
- human interface improved
It is possible to invoke
./config.status foobar
instead of the former form (still valid)
CONFIG_COMMANDS= CONFIG_HEADERS= CONFIG_LINKS= \
CONFIG_FILES=foobar:foo.in:bar.in \
./config.status
The same holds for configuration headers and links.
You can instantiate unknown files and headers:
./config.status --header foo.h:foo.h.in --file bar:baz
- has a useful --help
- accepts special file name "-" for stdin/stdout
** Identity Macros
- AC_COPYRIGHT
Specify additional copyright information.
- AC_INIT
Now expects the identity of the package as argument.
** General changes.
- Uniform quotation
Most macros, if not all, now strictly follow the `one quotation
level' rule. This results in a more predictable expansion.
- AC_REQUIRE
A sly bug in the AC_REQUIRE machinery, which could produce incorrect
configure scripts, was fixed by Axel Thimm.
** Setup Macros
- AC_ARG_VAR
Document and ask for the registration of an envvar.
- AC_CONFIG_SRCDIR
Specifies the file which `configure' should look for when trying to
find the source tree (used to be handled by AC_INIT).
- AC_CONFIG_COMMANDS
To add new actions to config.status. Should be used instead of
AC_OUTPUT_COMMANDS.
- AC_CONFIG_LINKS
Replaces AC_LINK_FILES.
- AC_CONFIG_HEADERS, AC_CONFIG_COMMANDS, AC_CONFIG_SUBDIRS,
AC_CONFIG_LINKS, and AC_CONFIG_FILES
They now obey sh: you should no longer use shell variables as
argument. Instead of
test "$package_foo_enabled" = yes && $my_subdirs="$my_subdirs foo"
AC_CONFIG_SUBDIRS($my_subdirs)
write
if test "$package_foo_enabled" = yes; then
AC_CONFIG_SUBDIRS(foo)
fi
- AC_HELP_STRING
To format an Autoconf macro's help string so that it looks pretty
when the user executes `configure --help'.
** Generic Test Macros
- AC_CHECK families
The interface of the AC_CHECK families of macros (decl, header,
type, member, func) is now uniform. They support the same set of
default includes.
- AC_CHECK_DECL, AC_CHECK_DECLS
To check whether a symbol is declared.
- AC_CHECK_SIZEOF, AC_C_CHAR_UNSIGNED.
No longer need a cross-compilation default.
- AC_CHECK_TYPE
The test it performs is much more robust than previously, and makes
it possible to test builtin types in addition to typedefs.
It is now schizophrenic:
- AC_CHECK_TYPE(TYPE, REPLACEMENT)
remains for backward compatibility, but its use is discouraged.
- AC_CHECK_TYPE(TYPE, IF-FOUND, IF-NOT-FOUND, INCLUDES)
behaves exactly like the other AC_CHECK macros.
- AC_CHECK_TYPES
Checks whether given types are supported by the system.
- AC_CHECK_MEMBER, AC_CHECK_MEMBERS
Check for given members in aggregates (e.g., pw_gecos in struct
passwd).
- AC_PROG_CC_STDC
Checks if the compiler supports ISO C, included when needs special
options.
- AC_PROG_CPP
Checking whether the preprocessor indicates missing includes by the
error code. stderr is checked by AC_TRY_CPP only as a fallback.
- AC_LANG
Takes a language as argument and replaces AC_LANG_C,
AC_LANG_CPLUSPLUS and AC_LANG_FORTRAN77.
- AC_LANG_PUSH, AC_LANG_POP
Are preferred to AC_LANG_SAVE, AC_LANG_RESTORE.
** Specific Macros
- AC_FUNC_CHOWN, AC_FUNC_MALLOC, AC_FUNC_STRERROR_R,
AC_FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK, AC_FUNC_STAT, AC_FUNC_LSTAT,
AC_FUNC_ERROR_AT_LINE, AC_FUNC_OBSTACK, AC_FUNC_STRTOD, AC_FUNC_FSEEKO.
New.
- AC_FUNC_GETGROUPS
Sets GETGROUPS_LIBS.
- AC_FUNC_GETLOADAVG
Defines `HAVE_STRUCT_NLIST_N_UN_N_NAME' instead of `NLIST_NAME_UNION'.
- AC_PROG_LEX
Now integrates `AC_DECL_YYTEXT' which is obsoleted.
- AC_SYS_LARGEFILE
Arrange for large-file support.
- AC_EXEEXT, AC_OBJEXT
You are no longer expected to use them: their computation is
performed by default.
** C++ compatibility
Every macro has been revisited in order to support at best CC=c++.
Major changes in Autoconf 2.14:
There was no release of GNU Autoconf 2.14.
Major changes in Autoconf 2.13:
Released 1999-05-01 by Ben Elliston.
* Support for building on Win32 systems where the only available C or
C++ compiler is the Microsoft Visual C++ command line compiler
(`cl'). Additional support for building on Win32 systems which are
using the Cygwin or Mingw32 environments.
* Support for alternative object file and executable file extensions.
On Win32, for example, these are .obj and .exe. These are discovered
using AC_OBJEXT and AC_EXEEXT, which substitute @OBJEXT@ and
@EXEEXT@ in the output, respectively.
* New macros: AC_CACHE_LOAD, AC_CACHE_SAVE, AC_FUNC_SELECT_ARGTYPES,
AC_VALIDATE_CACHED_SYSTEM_TUPLE, AC_SEARCH_LIBS, AC_TRY_LINK_FUNC,
AC_C_STRINGIZE, AC_CHECK_FILE(S), AC_PROG_F77 (and friends).
* AC_DEFINE now has an optional third argument for a description to be
placed in the config header input file (e.g. config.h.in).
* The C++ code fragment compiled for the C++ compiler test had to be
improved to include an explicit return type for main(). This was
causing failures on systems using recent versions of the EGCS C++
compiler.
* Fixed an important bug in AC_CHECK_TYPE that would cause a configure
script to report that `sometype_t' was present when only `type_t'
was defined.
* Merge of the FSF version of config.guess and config.sub to modernize
these scripts. Add support for a few new hosts in config.guess.
Incorporate latest versions of install-sh, mkinstalldirs and
texinfo.tex from the FSF.
* autoreconf is capable of running automake if necessary (and
applicable).
* Support for Fortran 77. See the Texinfo documentation for details.
* Bug fixes and workarounds for quirky bugs in vendor utilities.
Major changes in Autoconf 2.12:
Released 1996-11-26 by David J. MacKenzie
* AC_OUTPUT and AC_CONFIG_HEADER can create output files by
concatenating multiple input files separated by colons, like so:
AC_CONFIG_HEADER(config.h:conf.pre:config.h.in:conf.post)
AC_OUTPUT(Makefile:Makefile.in:Makefile.rules)
The arguments may be shell variables, to compute the lists on the fly.
* AC_LINK_FILES and AC_CONFIG_SUBDIRS may be called multiple times.
* New macro AC_OUTPUT_COMMANDS adds more commands to run in config.status.
* Bug fixes.
Major changes in Autoconf 2.11:
Released November 18th, 1996, by David J. MacKenzie
* AC_PROG_CC and AC_PROG_CXX check whether the compiler works.
They also default CFLAGS/CXXFLAGS to "-g -O2" for gcc, instead of "-g -O".
* AC_REPLACE_FUNCS defines HAVE_foo if the system has the function `foo'.
* AC_CONFIG_HEADER expands shell variables in its argument.
* New macros: AC_FUNC_FNMATCH, AC_FUNC_SETPGRP.
* The "checking..." messages and the source code for test programs that
fail are saved in config.log.
* Another workaround has been added for seds with small command length limits.
* config.sub and config.guess recognize more system types.
* Bug fixes.
Major changes in Autoconf 2.10:
Released May 7th, 1996, by Roland McGrath
* Bug fixes.
* The cache variable names used by `AC_CHECK_LIB(LIB, FUNC, ...)' has
changed: now $ac_cv_lib_LIB_FUNC, previously $ac_cv_lib_LIB.
Major changes in Autoconf 2.9:
Released March 16th, 1996, by Roland McGrath
* Bug fixes.
Major changes in Autoconf 2.8:
Released March 8th, 1996, by Roland McGrath
* Bug fixes.
Major changes in Autoconf 2.7:
Released November 22nd, 1995, by David J. MacKenzie
* Bug fixes.
Major changes in Autoconf 2.6:
Released November 20th, 1995, by David J. MacKenzie
* Bug fixes.
Major changes in Autoconf 2.5:
Released November 17th, 1995, by Roland McGrath
* New configure options --bindir, --libdir, --datadir, etc., with
corresponding output variables.
* New macro: AC_CACHE_CHECK, to make using the cache easier.
* config.log contains the command being run as well as any output from it.
* AC_CHECK_LIB can check for libraries with "." or "/" or "+" in their name.
* AC_PROG_INSTALL doesn't cache a name for install-sh, for sharing caches.
* AC_CHECK_PROG, AC_PATH_PROG, AC_CHECK_PROGS, AC_PATH_PROGS, and
AC_CHECK_TOOL can search a path other than $PATH.
* AC_CHECK_SIZEOF takes an optional size to use when cross-compiling.
Major changes in Autoconf 2.4:
Released June 14th, 1995, by David J. MacKenzie
* Fix a few bugs found by Emacs testers.
Major changes in Autoconf 2.3:
Released March 27th, 1995, by David J. MacKenzie
* Fix the cleanup trap in several ways.
* Handle C compilers that are picky about option placement.
* ifnames gets the version number from the right directory.
Major changes in Autoconf 2.2:
Released March 8th, 1995, by David J. MacKenzie
* The ifnames utility is much faster but requires a "new awk" interpreter.
* AC_CHECK_LIB and AC_HAVE_LIBRARY check and add the new
library before existing libs, not after, in case it uses them.
* New macros: AC_FUNC_GETPGRP, AC_CHECK_TOOL.
* Lots of bug fixes.
* Many additions to the TODO file :-)
Major changes in Autoconf 2.1:
Released November 4th, 1994, by David J. MacKenzie
* Fix C++ problems.
* More explanations in the manual.
* Fix a spurious failure in the testsuite.
* Clarify some warning messages.
* autoreconf by default only rebuilds configure and config.h.in files
that are older than any of their particular input files; there is a
--force option to use after installing a new version of Autoconf.
Thanks to everybody who's submitted changes and additions to Autoconf!
I've incorporated many of them, and am still considering others for
future releases -- but I didn't want to postpone this release indefinitely.
Caution: don't indiscriminately rebuild configure scripts with
Autoconf version 2. Some configure.in files need minor adjustments to
work with it; the documentation has a chapter on upgrading. A few
configure.in files, including those for GNU Emacs and the GNU C
Library, need major changes because they relied on undocumented
internals of version 1. Future releases of those packages will have
updated configure.in files.
It's best to use GNU M4 1.3 (or later) with Autoconf version 2.
Autoconf now makes heavy use of M4 diversions, which were implemented
inefficiently in GNU M4 releases before 1.3.
Major changes in Autoconf 2.0:
Released October 26th, 1994, by David J. MacKenzie
** New copyright terms:
* There are no restrictions on distribution or use of configure scripts.
** Documentation:
* Autoconf manual is reorganized to make information easier to find
and has several new indexes.
* INSTALL is reorganized and clearer and is now made from Texinfo source.
** New utilities:
* autoscan to generate a preliminary configure.in for a package by
scanning its source code for commonly used nonportable functions,
programs, and header files.
* ifnames to list the symbols used in #if and #ifdef directives in a
source tree.
* autoupdate to update a configure.in to use the version 2 macro names.
* autoreconf to recursively remake configure and configuration header
files in a source tree.
** Changed utilities:
* autoheader can take pieces of acconfig.h to replace config.h.{top,bot}.
* autoconf and autoheader can look for package-local definition files
in an alternate directory.
** New macros:
* AC_CACHE_VAL to share results of tests between configure runs.
* AC_DEFUN to define macros, automatically AC_PROVIDE them, and ensure
that macros invoked with AC_REQUIRE don't interrupt other macros.
* AC_CONFIG_AUX_DIR, AC_CANONICAL_SYSTEM, AC_CANONICAL_HOST, AC_LINK_FILES to
support deciding unguessable features based on the host and target types.
* AC_CONFIG_SUBDIRS to recursively configure a source tree.
* AC_ARG_PROGRAM to use the options --program-prefix,
--program-suffix, and --program-transform-name to change the names
of programs being installed.
* AC_PREFIX_DEFAULT to change the default installation prefix.
* AC_TRY_COMPILE to compile a test program without linking it.
* AC_CHECK_TYPE to check whether sys/types.h or stdlib.h defines a given type.
* AC_CHECK_LIB to check for a particular function and library.
* AC_MSG_CHECKING and AC_MSG_RESULT to print test results, on a single line,
whether or not the test succeeds. They obsolete AC_CHECKING and AC_VERBOSE.
* AC_SUBST_FILE to insert one file into another.
* AC_FUNC_MEMCMP to check whether memcmp is 8-bit clean.
* AC_FUNC_STRFTIME to find strftime even if it's in -lintl.
* AC_FUNC_GETMNTENT to find getmntent even if it's in -lsun or -lseq.
* AC_HEADER_SYS_WAIT to check whether sys/wait.h is POSIX.1 compatible.
** Changed macros:
* Many macros renamed systematically, but old names are accepted for
backward compatibility.
* AC_OUTPUT adds the "automatically generated" comment to
non-Makefiles where it finds @configure_input@ in an input file, to
support files with various comment syntaxes.
* AC_OUTPUT does not replace "prefix" and "exec_prefix" in generated
files when they are not enclosed in @ signs.
* AC_OUTPUT allows the optional environment variable CONFIG_STATUS to
override the file name "config.status".
* AC_OUTPUT takes an optional argument for passing variables from
configure to config.status.
* AC_OUTPUT and AC_CONFIG_HEADER allow you to override the input-file names.
* AC_OUTPUT automatically substitutes the values of CFLAGS, CXXFLAGS,
CPPFLAGS, and LDFLAGS from the environment.
* AC_PROG_CC and AC_PROG_CXX now set CFLAGS and CXXFLAGS, respectively.
* AC_PROG_INSTALL looks for install-sh or install.sh in the directory
specified by AC_CONFIG_AUXDIR, or srcdir or srcdir/.. or
srcdir/../.. by default.
* AC_DEFINE, AC_DEFINE_UNQUOTED, and AC_SUBST are more robust and smaller.
* AC_DEFINE no longer prints anything, because of the new result reporting
mechanism (AC_MSG_CHECKING and AC_MSG_RESULT).
* AC_VERBOSE pays attention to --quiet/--silent, not --verbose.
* AC_ARG_ENABLE and AC_ARG_WITH support whitespace in the arguments to
--enable- and --with- options.
* AC_CHECK_FUNCS and AC_CHECK_HEADERS take optional shell commands to
execute on success or failure.
* Checking for C functions in C++ works.
** Removed macros:
* AC_REMOTE_TAPE and AC_RSH removed; too specific to tar and cpio, and
better maintained with them.
* AC_ARG_ARRAY removed because no one was likely using it.
* AC_HAVE_POUNDBANG replaced with AC_SYS_INTERPRETER, which doesn't
take arguments, for consistency with all of the other specific checks.
** New files:
* Comes with config.sub and config.guess, and uses them optionally.
* Uses config.cache to cache test results. An alternate cache file
can be selected with the --cache-file=FILE option.
* Uses optional shell scripts $prefix/share/config.site and
$prefix/etc/config.site to perform site or system specific initializations.
* configure saves compiler output to ./config.log for debugging.
* New files autoconf.m4 and autoheader.m4 load the other Autoconf macros.
* acsite.m4 is the new name for the system-wide aclocal.m4.
* Has a DejaGnu test suite.
Major changes in Autoconf 1.11:
* AC_PROG_INSTALL calls install.sh with the -c option.
* AC_SET_MAKE cleans up after itself.
* AC_OUTPUT sets prefix and exec_prefix if they weren't set already.
* AC_OUTPUT prevents shells from looking in PATH for config.status.
Plus a few other bug fixes.
Major changes in Autoconf 1.10:
* autoheader uses config.h.bot if present, analogous to config.h.top.
* AC_PROG_INSTALL looks for install.sh in srcdir or srcdir/.. and
never uses cp.
* AC_PROG_CXX looks for cxx as a C++ compiler.
Plus several bugs fixed.
Major changes in Autoconf 1.9:
* AC_YYTEXT_POINTER replaces AC_DECLARE_YYTEXT.
* AC_SIZEOF_TYPE generates the cpp symbol name automatically,
and autoheader generates entries for those names automatically.
* AC_FIND_X gets the result from xmkmf correctly.
* AC_FIND_X assumes no X if --without-x was given.
* AC_FIND_XTRA adds libraries to the variable X_EXTRA_LIBS.
* AC_PROG_INSTALL finds OSF/1 installbsd.
Major changes in Autoconf 1.8:
** New macros:
* New macros AC_LANG_C, AC_LANG_CPLUSPLUS, AC_LANG_SAVE, AC_LANG_RESTORE,
AC_PROG_CXX, AC_PROG_CXXCPP, AC_REQUIRE_CPP
for checking both C++ and C features in one configure script.
* New macros AC_CHECKING, AC_VERBOSE, AC_WARN, AC_ERROR for printing messages.
* New macros AC_FIND_XTRA, AC_MMAP, AC_SIZEOF_TYPE, AC_PREREQ,
AC_SET_MAKE, AC_ENABLE.
** Changed macros:
* AC_FIND_X looks for X in more places.
* AC_PROG_INSTALL defaults to install.sh instead of cp, if it's in srcdir.
install.sh is distributed with Autoconf.
* AC_DECLARE_YYTEXT has been removed because it can't work, pending
a rewrite of quoting in AC_DEFINE.
* AC_OUTPUT adds its comments in C format when substituting in C files.
* AC_COMPILE_CHECK protects its ECHO-TEXT argument with double quotes.
** New or changed command line options:
* configure accepts --enable-FEATURE[=ARG] and --disable-FEATURE options.
* configure accepts --without-PACKAGE, which sets withval=no.
* configure accepts --x-includes=DIR and --x-libraries=DIR.
* Giving --with-PACKAGE no argument sets withval=yes instead of withval=1.
* configure accepts --help, --version, --silent/--quiet, --no-create options.
* configure accepts and ignores most other Cygnus configure options, and
warns about unknown options.
* config.status accepts --help, --version options.
** File names and other changes:
* Relative srcdir values are not made absolute.
* The values of @prefix@ and @exec_prefix@ and @top_srcdir@ get substituted.
* Autoconf library files are installed in ${datadir}/autoconf, not ${datadir}.
* autoheader optionally copies config.h.top to the beginning of config.h.in.
* The example Makefile dependencies for configure et al. work better.
* Namespace cleanup: all shell variables used internally by Autoconf
have names beginning with `ac_'.
More big improvements are in process for future releases, but have not
yet been (variously) finished, integrated, tested, or documented enough
to release yet.
Major changes in Autoconf 1.7:
* New macro AC_OBSOLETE.
* Bugs in Makefile.in fixed.
* AC_LONG_FILE_NAMES improved.
Major changes in Autoconf 1.6:
* New macro AC_LONG_64_BITS.
* Multiple .h files can be created.
* AC_FIND_X looks for X files directly if it doesn't find xmkmf.
* AC_ALLOCA defines C_ALLOCA if using alloca.c.
* --with-NAME can take a value, e.g., --with-targets=sun4,hp300bsd.
* Unused --no-create option to configure removed.
* autoheader doesn't change the timestamp of its output file if
the file didn't change.
* All macros that look for libraries now use AC_HAVE_LIBRARY.
* config.status checks three optional environment variables to
modify its behavior.
* The usual bug fixes.
Major changes in Autoconf 1.5:
* New macros AC_FIND_X, AC_OFF_T, AC_STAT_MACROS_BROKEN, AC_REVISION.
* autoconf and autoheader scripts have GNU standards conforming
--version and --help options (they print their message and exit).
* Many bug fixes.
Major changes in Autoconf 1.4:
* New macros AC_HAVE_POUNDBANG, AC_TIME_WITH_SYS_TIME, AC_LONG_DOUBLE,
AC_GETGROUPS_T, AC_DEFINE_UNQUOTED.
* autoconf and autoheader use the M4 environment variable to determine the
name of the M4 program to use.
* The --macrodir option to autoconf and autoheader specifies the directory
in which acspecific.m4, acgeneral.m4, etc. reside if not the default.
* autoconf and autoheader can take `-' as their file names, which means to
read stdin as input.
* Resulting configure scripts can take a --verbose option which causes them
to print the results of their tests.
* AC_DEFINE quotes its second argument in such a way that spaces, magic
shell characters, etc. will be preserved during various stages of
expansion done by the shell. If you don't want this, use
AC_DEFINE_UNQUOTED instead.
* Much textual processing done with external calls to tr and sed have been
internalized with builtin M4 `patsubst' and `translit' calls.
* AC_OUTPUT doesn't hardwire the file names it outputs. Instead, you can
set the shell variables `gen_files' and `gen_config' to the list of
file names to output.
* AC_DECLARE_YYTEXT does an AC_SUBST of `LEX_OUTPUT_ROOT', which may be
"lex.yy" or "lexyy", depending on the system.
* AC_PROGRAMS_CHECK takes an optional third arg. If given, it is used as
the default value.
* If AC_ALLOCA chooses alloca.c, it also defines STACK_DIRECTION.
* AC_CONST works much more reliably on more systems.
* Many bug fixes.
Major changes in Autoconf 1.3:
configure no longer requires awk for packages that use a config.h.
Support handling --with-PACKAGE options.
New `autoheader' script to create `config.h.in' from `configure.in'.
Ignore troublesome -lucb and -lPW when searching for alloca.
Rename --exec_prefix to --exec-prefix for GNU standards conformance.
Improve detection of STDC library.
Add AC_HAVE_LIBRARY to check for non-default libraries.
Function checking should work with future GNU libc releases.
Major changes in Autoconf 1.2:
The --srcdir option is now usually unnecessary.
Add a file containing sample comments describing CPP macros.
A comment in config.status tells which host it was configured on.
Substituted variable values can now contain commas.
Fix bugs in various feature checks.
Major changes in Autoconf 1.1:
Added AC_STRCOLL macro.
Made AC_GETLOADAVG check for more things.
AC_OUTPUT argument is now optional.
Various bug fixes.
-----
Copyright (C) 1993, 1994, 1995, 1996, 1998, 1999, 2000, 2001, 2002,
2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation,
Inc.
Copying and distribution of this file, with or without modification,
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autoconf2.64-2.64/doc/ 0000755 0002024 0002024 00000000000 11233220601 013712 5 ustar arthur arthur autoconf2.64-2.64/doc/stamp-vti 0000755 0002024 0002024 00000000133 11233217441 015571 0 ustar arthur arthur @set UPDATED 26 July 2009
@set UPDATED-MONTH July 2009
@set EDITION 2.64
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autoconf2.64-2.64/doc/Makefile.am 0000644 0002024 0002024 00000002367 11157462020 015766 0 ustar arthur arthur # Make Autoconf documentation.
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AM_MAKEINFOFLAGS = --no-split
TEXI2HTML_FLAGS = -split_chapter
TEXINFO_TEX = ../build-aux/texinfo.tex
info_TEXINFOS = autoconf.texi standards.texi
autoconf_TEXINFOS = fdl.texi install.texi
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EXTRA_DIST = gendocs_template
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# not know.
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autoconf.tmp
autoconf2.64-2.64/doc/fdl.texi 0000644 0002024 0002024 00000056015 11233202134 015362 0 ustar arthur arthur @c The GNU Free Documentation License.
@center Version 1.3, 3 November 2008
@c This file is intended to be included within another document,
@c hence no sectioning command or @node.
@display
Copyright @copyright{} 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
@uref{http://fsf.org/}
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
@end display
@enumerate 0
@item
PREAMBLE
The purpose of this License is to make a manual, textbook, or other
functional and useful document @dfn{free} in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or noncommercially.
Secondarily, this License preserves for the author and publisher a way
to get credit for their work, while not being considered responsible
for modifications made by others.
This License is a kind of ``copyleft'', which means that derivative
works of the document must themselves be free in the same sense. It
complements the GNU General Public License, which is a copyleft
license designed for free software.
We have designed this License in order to use it for manuals for free
software, because free software needs free documentation: a free
program should come with manuals providing the same freedoms that the
software does. But this License is not limited to software manuals;
it can be used for any textual work, regardless of subject matter or
whether it is published as a printed book. We recommend this License
principally for works whose purpose is instruction or reference.
@item
APPLICABILITY AND DEFINITIONS
This License applies to any manual or other work, in any medium, that
contains a notice placed by the copyright holder saying it can be
distributed under the terms of this License. Such a notice grants a
world-wide, royalty-free license, unlimited in duration, to use that
work under the conditions stated herein. The ``Document'', below,
refers to any such manual or work. Any member of the public is a
licensee, and is addressed as ``you''. You accept the license if you
copy, modify or distribute the work in a way requiring permission
under copyright law.
A ``Modified Version'' of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.
A ``Secondary Section'' is a named appendix or a front-matter section
of the Document that deals exclusively with the relationship of the
publishers or authors of the Document to the Document's overall
subject (or to related matters) and contains nothing that could fall
directly within that overall subject. (Thus, if the Document is in
part a textbook of mathematics, a Secondary Section may not explain
any mathematics.) The relationship could be a matter of historical
connection with the subject or with related matters, or of legal,
commercial, philosophical, ethical or political position regarding
them.
The ``Invariant Sections'' are certain Secondary Sections whose titles
are designated, as being those of Invariant Sections, in the notice
that says that the Document is released under this License. If a
section does not fit the above definition of Secondary then it is not
allowed to be designated as Invariant. The Document may contain zero
Invariant Sections. If the Document does not identify any Invariant
Sections then there are none.
The ``Cover Texts'' are certain short passages of text that are listed,
as Front-Cover Texts or Back-Cover Texts, in the notice that says that
the Document is released under this License. A Front-Cover Text may
be at most 5 words, and a Back-Cover Text may be at most 25 words.
A ``Transparent'' copy of the Document means a machine-readable copy,
represented in a format whose specification is available to the
general public, that is suitable for revising the document
straightforwardly with generic text editors or (for images composed of
pixels) generic paint programs or (for drawings) some widely available
drawing editor, and that is suitable for input to text formatters or
for automatic translation to a variety of formats suitable for input
to text formatters. A copy made in an otherwise Transparent file
format whose markup, or absence of markup, has been arranged to thwart
or discourage subsequent modification by readers is not Transparent.
An image format is not Transparent if used for any substantial amount
of text. A copy that is not ``Transparent'' is called ``Opaque''.
Examples of suitable formats for Transparent copies include plain
@sc{ascii} without markup, Texinfo input format, La@TeX{} input
format, @acronym{SGML} or @acronym{XML} using a publicly available
@acronym{DTD}, and standard-conforming simple @acronym{HTML},
PostScript or @acronym{PDF} designed for human modification. Examples
of transparent image formats include @acronym{PNG}, @acronym{XCF} and
@acronym{JPG}. Opaque formats include proprietary formats that can be
read and edited only by proprietary word processors, @acronym{SGML} or
@acronym{XML} for which the @acronym{DTD} and/or processing tools are
not generally available, and the machine-generated @acronym{HTML},
PostScript or @acronym{PDF} produced by some word processors for
output purposes only.
The ``Title Page'' means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the material
this License requires to appear in the title page. For works in
formats which do not have any title page as such, ``Title Page'' means
the text near the most prominent appearance of the work's title,
preceding the beginning of the body of the text.
The ``publisher'' means any person or entity that distributes copies
of the Document to the public.
A section ``Entitled XYZ'' means a named subunit of the Document whose
title either is precisely XYZ or contains XYZ in parentheses following
text that translates XYZ in another language. (Here XYZ stands for a
specific section name mentioned below, such as ``Acknowledgements'',
``Dedications'', ``Endorsements'', or ``History''.) To ``Preserve the Title''
of such a section when you modify the Document means that it remains a
section ``Entitled XYZ'' according to this definition.
The Document may include Warranty Disclaimers next to the notice which
states that this License applies to the Document. These Warranty
Disclaimers are considered to be included by reference in this
License, but only as regards disclaiming warranties: any other
implication that these Warranty Disclaimers may have is void and has
no effect on the meaning of this License.
@item
VERBATIM COPYING
You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License applies
to the Document are reproduced in all copies, and that you add no other
conditions whatsoever to those of this License. You may not use
technical measures to obstruct or control the reading or further
copying of the copies you make or distribute. However, you may accept
compensation in exchange for copies. If you distribute a large enough
number of copies you must also follow the conditions in section 3.
You may also lend copies, under the same conditions stated above, and
you may publicly display copies.
@item
COPYING IN QUANTITY
If you publish printed copies (or copies in media that commonly have
printed covers) of the Document, numbering more than 100, and the
Document's license notice requires Cover Texts, you must enclose the
copies in covers that carry, clearly and legibly, all these Cover
Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
the back cover. Both covers must also clearly and legibly identify
you as the publisher of these copies. The front cover must present
the full title with all words of the title equally prominent and
visible. You may add other material on the covers in addition.
Copying with changes limited to the covers, as long as they preserve
the title of the Document and satisfy these conditions, can be treated
as verbatim copying in other respects.
If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto adjacent
pages.
If you publish or distribute Opaque copies of the Document numbering
more than 100, you must either include a machine-readable Transparent
copy along with each Opaque copy, or state in or with each Opaque copy
a computer-network location from which the general network-using
public has access to download using public-standard network protocols
a complete Transparent copy of the Document, free of added material.
If you use the latter option, you must take reasonably prudent steps,
when you begin distribution of Opaque copies in quantity, to ensure
that this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you distribute an
Opaque copy (directly or through your agents or retailers) of that
edition to the public.
It is requested, but not required, that you contact the authors of the
Document well before redistributing any large number of copies, to give
them a chance to provide you with an updated version of the Document.
@item
MODIFICATIONS
You may copy and distribute a Modified Version of the Document under
the conditions of sections 2 and 3 above, provided that you release
the Modified Version under precisely this License, with the Modified
Version filling the role of the Document, thus licensing distribution
and modification of the Modified Version to whoever possesses a copy
of it. In addition, you must do these things in the Modified Version:
@enumerate A
@item
Use in the Title Page (and on the covers, if any) a title distinct
from that of the Document, and from those of previous versions
(which should, if there were any, be listed in the History section
of the Document). You may use the same title as a previous version
if the original publisher of that version gives permission.
@item
List on the Title Page, as authors, one or more persons or entities
responsible for authorship of the modifications in the Modified
Version, together with at least five of the principal authors of the
Document (all of its principal authors, if it has fewer than five),
unless they release you from this requirement.
@item
State on the Title page the name of the publisher of the
Modified Version, as the publisher.
@item
Preserve all the copyright notices of the Document.
@item
Add an appropriate copyright notice for your modifications
adjacent to the other copyright notices.
@item
Include, immediately after the copyright notices, a license notice
giving the public permission to use the Modified Version under the
terms of this License, in the form shown in the Addendum below.
@item
Preserve in that license notice the full lists of Invariant Sections
and required Cover Texts given in the Document's license notice.
@item
Include an unaltered copy of this License.
@item
Preserve the section Entitled ``History'', Preserve its Title, and add
to it an item stating at least the title, year, new authors, and
publisher of the Modified Version as given on the Title Page. If
there is no section Entitled ``History'' in the Document, create one
stating the title, year, authors, and publisher of the Document as
given on its Title Page, then add an item describing the Modified
Version as stated in the previous sentence.
@item
Preserve the network location, if any, given in the Document for
public access to a Transparent copy of the Document, and likewise
the network locations given in the Document for previous versions
it was based on. These may be placed in the ``History'' section.
You may omit a network location for a work that was published at
least four years before the Document itself, or if the original
publisher of the version it refers to gives permission.
@item
For any section Entitled ``Acknowledgements'' or ``Dedications'', Preserve
the Title of the section, and preserve in the section all the
substance and tone of each of the contributor acknowledgements and/or
dedications given therein.
@item
Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles. Section numbers
or the equivalent are not considered part of the section titles.
@item
Delete any section Entitled ``Endorsements''. Such a section
may not be included in the Modified Version.
@item
Do not retitle any existing section to be Entitled ``Endorsements'' or
to conflict in title with any Invariant Section.
@item
Preserve any Warranty Disclaimers.
@end enumerate
If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant. To do this, add their titles to the
list of Invariant Sections in the Modified Version's license notice.
These titles must be distinct from any other section titles.
You may add a section Entitled ``Endorsements'', provided it contains
nothing but endorsements of your Modified Version by various
parties---for example, statements of peer review or that the text has
been approved by an organization as the authoritative definition of a
standard.
You may add a passage of up to five words as a Front-Cover Text, and a
passage of up to 25 words as a Back-Cover Text, to the end of the list
of Cover Texts in the Modified Version. Only one passage of
Front-Cover Text and one of Back-Cover Text may be added by (or
through arrangements made by) any one entity. If the Document already
includes a cover text for the same cover, previously added by you or
by arrangement made by the same entity you are acting on behalf of,
you may not add another; but you may replace the old one, on explicit
permission from the previous publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this License
give permission to use their names for publicity for or to assert or
imply endorsement of any Modified Version.
@item
COMBINING DOCUMENTS
You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified
versions, provided that you include in the combination all of the
Invariant Sections of all of the original documents, unmodified, and
list them all as Invariant Sections of your combined work in its
license notice, and that you preserve all their Warranty Disclaimers.
The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy. If there are multiple Invariant Sections with the same name but
different contents, make the title of each such section unique by
adding at the end of it, in parentheses, the name of the original
author or publisher of that section if known, or else a unique number.
Make the same adjustment to the section titles in the list of
Invariant Sections in the license notice of the combined work.
In the combination, you must combine any sections Entitled ``History''
in the various original documents, forming one section Entitled
``History''; likewise combine any sections Entitled ``Acknowledgements'',
and any sections Entitled ``Dedications''. You must delete all
sections Entitled ``Endorsements.''
@item
COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other documents
released under this License, and replace the individual copies of this
License in the various documents with a single copy that is included in
the collection, provided that you follow the rules of this License for
verbatim copying of each of the documents in all other respects.
You may extract a single document from such a collection, and distribute
it individually under this License, provided you insert a copy of this
License into the extracted document, and follow this License in all
other respects regarding verbatim copying of that document.
@item
AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other separate
and independent documents or works, in or on a volume of a storage or
distribution medium, is called an ``aggregate'' if the copyright
resulting from the compilation is not used to limit the legal rights
of the compilation's users beyond what the individual works permit.
When the Document is included in an aggregate, this License does not
apply to the other works in the aggregate which are not themselves
derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half of
the entire aggregate, the Document's Cover Texts may be placed on
covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic form.
Otherwise they must appear on printed covers that bracket the whole
aggregate.
@item
TRANSLATION
Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section 4.
Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections. You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also include
the original English version of this License and the original versions
of those notices and disclaimers. In case of a disagreement between
the translation and the original version of this License or a notice
or disclaimer, the original version will prevail.
If a section in the Document is Entitled ``Acknowledgements'',
``Dedications'', or ``History'', the requirement (section 4) to Preserve
its Title (section 1) will typically require changing the actual
title.
@item
TERMINATION
You may not copy, modify, sublicense, or distribute the Document
except as expressly provided under this License. Any attempt
otherwise to copy, modify, sublicense, or distribute it is void, and
will automatically terminate your rights under this License.
However, if you cease all violation of this License, then your license
from a particular copyright holder is reinstated (a) provisionally,
unless and until the copyright holder explicitly and finally
terminates your license, and (b) permanently, if the copyright holder
fails to notify you of the violation by some reasonable means prior to
60 days after the cessation.
Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from that
copyright holder, and you cure the violation prior to 30 days after
your receipt of the notice.
Termination of your rights under this section does not terminate the
licenses of parties who have received copies or rights from you under
this License. If your rights have been terminated and not permanently
reinstated, receipt of a copy of some or all of the same material does
not give you any rights to use it.
@item
FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions
of the GNU Free Documentation License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns. See
@uref{http://www.gnu.org/copyleft/}.
Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this
License ``or any later version'' applies to it, you have the option of
following the terms and conditions either of that specified version or
of any later version that has been published (not as a draft) by the
Free Software Foundation. If the Document does not specify a version
number of this License, you may choose any version ever published (not
as a draft) by the Free Software Foundation. If the Document
specifies that a proxy can decide which future versions of this
License can be used, that proxy's public statement of acceptance of a
version permanently authorizes you to choose that version for the
Document.
@item
RELICENSING
``Massive Multiauthor Collaboration Site'' (or ``MMC Site'') means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works. A
public wiki that anybody can edit is an example of such a server. A
``Massive Multiauthor Collaboration'' (or ``MMC'') contained in the
site means any set of copyrightable works thus published on the MMC
site.
``CC-BY-SA'' means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
published by that same organization.
``Incorporate'' means to publish or republish a Document, in whole or
in part, as part of another Document.
An MMC is ``eligible for relicensing'' if it is licensed under this
License, and if all works that were first published under this License
somewhere other than this MMC, and subsequently incorporated in whole
or in part into the MMC, (1) had no cover texts or invariant sections,
and (2) were thus incorporated prior to November 1, 2008.
The operator of an MMC Site may republish an MMC contained in the site
under CC-BY-SA on the same site at any time before August 1, 2009,
provided the MMC is eligible for relicensing.
@end enumerate
@page
@heading ADDENDUM: How to use this License for your documents
To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and
license notices just after the title page:
@smallexample
@group
Copyright (C) @var{year} @var{your name}.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
@end group
@end smallexample
If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the ``with@dots{}Texts.'' line with this:
@smallexample
@group
with the Invariant Sections being @var{list their titles}, with
the Front-Cover Texts being @var{list}, and with the Back-Cover Texts
being @var{list}.
@end group
@end smallexample
If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.
If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License,
to permit their use in free software.
@c Local Variables:
@c ispell-local-pdict: "ispell-dict"
@c End:
autoconf2.64-2.64/doc/standards.info 0000644 0002024 0002024 00000663270 11233216140 016573 0 ustar arthur arthur This is standards.info, produced by makeinfo version 4.13 from
standards.texi.
INFO-DIR-SECTION GNU organization
START-INFO-DIR-ENTRY
* Standards: (standards). GNU coding standards.
END-INFO-DIR-ENTRY
The GNU coding standards, last updated June 7, 2009.
Copyright (C) 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software
Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
Texts. A copy of the license is included in the section entitled "GNU
Free Documentation License".
File: standards.info, Node: Top, Next: Preface, Prev: (dir), Up: (dir)
Version
*******
The GNU coding standards, last updated June 7, 2009.
Copyright (C) 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software
Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
Texts. A copy of the license is included in the section entitled "GNU
Free Documentation License".
* Menu:
* Preface:: About the GNU Coding Standards.
* Legal Issues:: Keeping free software free.
* Design Advice:: General program design.
* Program Behavior:: Program behavior for all programs
* Writing C:: Making the best use of C.
* Documentation:: Documenting programs.
* Managing Releases:: The release process.
* References:: Mentioning non-free software or documentation.
* GNU Free Documentation License:: Copying and sharing this manual.
* Index::
File: standards.info, Node: Preface, Next: Legal Issues, Prev: Top, Up: Top
1 About the GNU Coding Standards
********************************
The GNU Coding Standards were written by Richard Stallman and other GNU
Project volunteers. Their purpose is to make the GNU system clean,
consistent, and easy to install. This document can also be read as a
guide to writing portable, robust and reliable programs. It focuses on
programs written in C, but many of the rules and principles are useful
even if you write in another programming language. The rules often
state reasons for writing in a certain way.
This release of the GNU Coding Standards was last updated June 7,
2009.
If you did not obtain this file directly from the GNU project and
recently, please check for a newer version. You can get the GNU Coding
Standards from the GNU web server in many different formats, including
the Texinfo source, PDF, HTML, DVI, plain text, and more, at:
`http://www.gnu.org/prep/standards/'.
Corrections or suggestions for this document should be sent to
. If you make a suggestion, please include a
suggested new wording for it; our time is limited. We prefer a context
diff to the `standards.texi' or `make-stds.texi' files, but if you
don't have those files, please mail your suggestion anyway.
These standards cover the minimum of what is important when writing a
GNU package. Likely, the need for additional standards will come up.
Sometimes, you might suggest that such standards be added to this
document. If you think your standards would be generally useful, please
do suggest them.
You should also set standards for your package on many questions not
addressed or not firmly specified here. The most important point is to
be self-consistent--try to stick to the conventions you pick, and try
to document them as much as possible. That way, your program will be
more maintainable by others.
The GNU Hello program serves as an example of how to follow the GNU
coding standards for a trivial program.
`http://www.gnu.org/software/hello/hello.html'.
File: standards.info, Node: Legal Issues, Next: Design Advice, Prev: Preface, Up: Top
2 Keeping Free Software Free
****************************
This chapter discusses how you can make sure that GNU software avoids
legal difficulties, and other related issues.
* Menu:
* Reading Non-Free Code:: Referring to proprietary programs.
* Contributions:: Accepting contributions.
* Trademarks:: How we deal with trademark issues.
File: standards.info, Node: Reading Non-Free Code, Next: Contributions, Up: Legal Issues
2.1 Referring to Proprietary Programs
=====================================
Don't in any circumstances refer to Unix source code for or during your
work on GNU! (Or to any other proprietary programs.)
If you have a vague recollection of the internals of a Unix program,
this does not absolutely mean you can't write an imitation of it, but
do try to organize the imitation internally along different lines,
because this is likely to make the details of the Unix version
irrelevant and dissimilar to your results.
For example, Unix utilities were generally optimized to minimize
memory use; if you go for speed instead, your program will be very
different. You could keep the entire input file in memory and scan it
there instead of using stdio. Use a smarter algorithm discovered more
recently than the Unix program. Eliminate use of temporary files. Do
it in one pass instead of two (we did this in the assembler).
Or, on the contrary, emphasize simplicity instead of speed. For some
applications, the speed of today's computers makes simpler algorithms
adequate.
Or go for generality. For example, Unix programs often have static
tables or fixed-size strings, which make for arbitrary limits; use
dynamic allocation instead. Make sure your program handles NULs and
other funny characters in the input files. Add a programming language
for extensibility and write part of the program in that language.
Or turn some parts of the program into independently usable
libraries. Or use a simple garbage collector instead of tracking
precisely when to free memory, or use a new GNU facility such as
obstacks.
File: standards.info, Node: Contributions, Next: Trademarks, Prev: Reading Non-Free Code, Up: Legal Issues
2.2 Accepting Contributions
===========================
If the program you are working on is copyrighted by the Free Software
Foundation, then when someone else sends you a piece of code to add to
the program, we need legal papers to use it--just as we asked you to
sign papers initially. _Each_ person who makes a nontrivial
contribution to a program must sign some sort of legal papers in order
for us to have clear title to the program; the main author alone is not
enough.
So, before adding in any contributions from other people, please tell
us, so we can arrange to get the papers. Then wait until we tell you
that we have received the signed papers, before you actually use the
contribution.
This applies both before you release the program and afterward. If
you receive diffs to fix a bug, and they make significant changes, we
need legal papers for that change.
This also applies to comments and documentation files. For copyright
law, comments and code are just text. Copyright applies to all kinds of
text, so we need legal papers for all kinds.
We know it is frustrating to ask for legal papers; it's frustrating
for us as well. But if you don't wait, you are going out on a limb--for
example, what if the contributor's employer won't sign a disclaimer?
You might have to take that code out again!
You don't need papers for changes of a few lines here or there, since
they are not significant for copyright purposes. Also, you don't need
papers if all you get from the suggestion is some ideas, not actual code
which you use. For example, if someone sent you one implementation, but
you write a different implementation of the same idea, you don't need to
get papers.
The very worst thing is if you forget to tell us about the other
contributor. We could be very embarrassed in court some day as a
result.
We have more detailed advice for maintainers of programs; if you have
reached the stage of actually maintaining a program for GNU (whether
released or not), please ask us for a copy. It is also available
online for your perusal: `http://www.gnu.org/prep/maintain/'.
File: standards.info, Node: Trademarks, Prev: Contributions, Up: Legal Issues
2.3 Trademarks
==============
Please do not include any trademark acknowledgements in GNU software
packages or documentation.
Trademark acknowledgements are the statements that such-and-such is a
trademark of so-and-so. The GNU Project has no objection to the basic
idea of trademarks, but these acknowledgements feel like kowtowing, and
there is no legal requirement for them, so we don't use them.
What is legally required, as regards other people's trademarks, is to
avoid using them in ways which a reader might reasonably understand as
naming or labeling our own programs or activities. For example, since
"Objective C" is (or at least was) a trademark, we made sure to say
that we provide a "compiler for the Objective C language" rather than
an "Objective C compiler". The latter would have been meant as a
shorter way of saying the former, but it does not explicitly state the
relationship, so it could be misinterpreted as using "Objective C" as a
label for the compiler rather than for the language.
Please don't use "win" as an abbreviation for Microsoft Windows in
GNU software or documentation. In hacker terminology, calling
something a "win" is a form of praise. If you wish to praise Microsoft
Windows when speaking on your own, by all means do so, but not in GNU
software. Usually we write the name "Windows" in full, but when
brevity is very important (as in file names and sometimes symbol
names), we abbreviate it to "w". For instance, the files and functions
in Emacs that deal with Windows start with `w32'.
File: standards.info, Node: Design Advice, Next: Program Behavior, Prev: Legal Issues, Up: Top
3 General Program Design
************************
This chapter discusses some of the issues you should take into account
when designing your program.
* Menu:
* Source Language:: Which languages to use.
* Compatibility:: Compatibility with other implementations.
* Using Extensions:: Using non-standard features.
* Standard C:: Using standard C features.
* Conditional Compilation:: Compiling code only if a conditional is true.
File: standards.info, Node: Source Language, Next: Compatibility, Up: Design Advice
3.1 Which Languages to Use
==========================
When you want to use a language that gets compiled and runs at high
speed, the best language to use is C. Using another language is like
using a non-standard feature: it will cause trouble for users. Even if
GCC supports the other language, users may find it inconvenient to have
to install the compiler for that other language in order to build your
program. For example, if you write your program in C++, people will
have to install the GNU C++ compiler in order to compile your program.
C has one other advantage over C++ and other compiled languages: more
people know C, so more people will find it easy to read and modify the
program if it is written in C.
So in general it is much better to use C, rather than the comparable
alternatives.
But there are two exceptions to that conclusion:
* It is no problem to use another language to write a tool
specifically intended for use with that language. That is because
the only people who want to build the tool will be those who have
installed the other language anyway.
* If an application is of interest only to a narrow part of the
community, then the question of which language it is written in
has less effect on other people, so you may as well please
yourself.
Many programs are designed to be extensible: they include an
interpreter for a language that is higher level than C. Often much of
the program is written in that language, too. The Emacs editor
pioneered this technique.
The standard extensibility interpreter for GNU software is Guile
(`http://www.gnu.org/software/guile/'), which implements the language
Scheme (an especially clean and simple dialect of Lisp). Guile also
includes bindings for GTK+/GNOME, making it practical to write modern
GUI functionality within Guile. We don't reject programs written in
other "scripting languages" such as Perl and Python, but using Guile is
very important for the overall consistency of the GNU system.
File: standards.info, Node: Compatibility, Next: Using Extensions, Prev: Source Language, Up: Design Advice
3.2 Compatibility with Other Implementations
============================================
With occasional exceptions, utility programs and libraries for GNU
should be upward compatible with those in Berkeley Unix, and upward
compatible with Standard C if Standard C specifies their behavior, and
upward compatible with POSIX if POSIX specifies their behavior.
When these standards conflict, it is useful to offer compatibility
modes for each of them.
Standard C and POSIX prohibit many kinds of extensions. Feel free
to make the extensions anyway, and include a `--ansi', `--posix', or
`--compatible' option to turn them off. However, if the extension has
a significant chance of breaking any real programs or scripts, then it
is not really upward compatible. So you should try to redesign its
interface to make it upward compatible.
Many GNU programs suppress extensions that conflict with POSIX if the
environment variable `POSIXLY_CORRECT' is defined (even if it is
defined with a null value). Please make your program recognize this
variable if appropriate.
When a feature is used only by users (not by programs or command
files), and it is done poorly in Unix, feel free to replace it
completely with something totally different and better. (For example,
`vi' is replaced with Emacs.) But it is nice to offer a compatible
feature as well. (There is a free `vi' clone, so we offer it.)
Additional useful features are welcome regardless of whether there
is any precedent for them.
File: standards.info, Node: Using Extensions, Next: Standard C, Prev: Compatibility, Up: Design Advice
3.3 Using Non-standard Features
===============================
Many GNU facilities that already exist support a number of convenient
extensions over the comparable Unix facilities. Whether to use these
extensions in implementing your program is a difficult question.
On the one hand, using the extensions can make a cleaner program.
On the other hand, people will not be able to build the program unless
the other GNU tools are available. This might cause the program to
work on fewer kinds of machines.
With some extensions, it might be easy to provide both alternatives.
For example, you can define functions with a "keyword" `INLINE' and
define that as a macro to expand into either `inline' or nothing,
depending on the compiler.
In general, perhaps it is best not to use the extensions if you can
straightforwardly do without them, but to use the extensions if they
are a big improvement.
An exception to this rule are the large, established programs (such
as Emacs) which run on a great variety of systems. Using GNU
extensions in such programs would make many users unhappy, so we don't
do that.
Another exception is for programs that are used as part of
compilation: anything that must be compiled with other compilers in
order to bootstrap the GNU compilation facilities. If these require
the GNU compiler, then no one can compile them without having them
installed already. That would be extremely troublesome in certain
cases.
File: standards.info, Node: Standard C, Next: Conditional Compilation, Prev: Using Extensions, Up: Design Advice
3.4 Standard C and Pre-Standard C
=================================
1989 Standard C is widespread enough now that it is ok to use its
features in new programs. There is one exception: do not ever use the
"trigraph" feature of Standard C.
1999 Standard C is not widespread yet, so please do not require its
features in programs. It is ok to use its features if they are present.
However, it is easy to support pre-standard compilers in most
programs, so if you know how to do that, feel free. If a program you
are maintaining has such support, you should try to keep it working.
To support pre-standard C, instead of writing function definitions in
standard prototype form,
int
foo (int x, int y)
...
write the definition in pre-standard style like this,
int
foo (x, y)
int x, y;
...
and use a separate declaration to specify the argument prototype:
int foo (int, int);
You need such a declaration anyway, in a header file, to get the
benefit of prototypes in all the files where the function is called.
And once you have the declaration, you normally lose nothing by writing
the function definition in the pre-standard style.
This technique does not work for integer types narrower than `int'.
If you think of an argument as being of a type narrower than `int',
declare it as `int' instead.
There are a few special cases where this technique is hard to use.
For example, if a function argument needs to hold the system type
`dev_t', you run into trouble, because `dev_t' is shorter than `int' on
some machines; but you cannot use `int' instead, because `dev_t' is
wider than `int' on some machines. There is no type you can safely use
on all machines in a non-standard definition. The only way to support
non-standard C and pass such an argument is to check the width of
`dev_t' using Autoconf and choose the argument type accordingly. This
may not be worth the trouble.
In order to support pre-standard compilers that do not recognize
prototypes, you may want to use a preprocessor macro like this:
/* Declare the prototype for a general external function. */
#if defined (__STDC__) || defined (WINDOWSNT)
#define P_(proto) proto
#else
#define P_(proto) ()
#endif
File: standards.info, Node: Conditional Compilation, Prev: Standard C, Up: Design Advice
3.5 Conditional Compilation
===========================
When supporting configuration options already known when building your
program we prefer using `if (... )' over conditional compilation, as in
the former case the compiler is able to perform more extensive checking
of all possible code paths.
For example, please write
if (HAS_FOO)
...
else
...
instead of:
#ifdef HAS_FOO
...
#else
...
#endif
A modern compiler such as GCC will generate exactly the same code in
both cases, and we have been using similar techniques with good success
in several projects. Of course, the former method assumes that
`HAS_FOO' is defined as either 0 or 1.
While this is not a silver bullet solving all portability problems,
and is not always appropriate, following this policy would have saved
GCC developers many hours, or even days, per year.
In the case of function-like macros like `REVERSIBLE_CC_MODE' in GCC
which cannot be simply used in `if( ...)' statements, there is an easy
workaround. Simply introduce another macro `HAS_REVERSIBLE_CC_MODE' as
in the following example:
#ifdef REVERSIBLE_CC_MODE
#define HAS_REVERSIBLE_CC_MODE 1
#else
#define HAS_REVERSIBLE_CC_MODE 0
#endif
File: standards.info, Node: Program Behavior, Next: Writing C, Prev: Design Advice, Up: Top
4 Program Behavior for All Programs
***********************************
This chapter describes conventions for writing robust software. It
also describes general standards for error messages, the command line
interface, and how libraries should behave.
* Menu:
* Non-GNU Standards:: We consider standards such as POSIX;
we don't "obey" them.
* Semantics:: Writing robust programs.
* Libraries:: Library behavior.
* Errors:: Formatting error messages.
* User Interfaces:: Standards about interfaces generally.
* Graphical Interfaces:: Standards for graphical interfaces.
* Command-Line Interfaces:: Standards for command line interfaces.
* Option Table:: Table of long options.
* OID Allocations:: Table of OID slots for GNU.
* Memory Usage:: When and how to care about memory needs.
* File Usage:: Which files to use, and where.
File: standards.info, Node: Non-GNU Standards, Next: Semantics, Up: Program Behavior
4.1 Non-GNU Standards
=====================
The GNU Project regards standards published by other organizations as
suggestions, not orders. We consider those standards, but we do not
"obey" them. In developing a GNU program, you should implement an
outside standard's specifications when that makes the GNU system better
overall in an objective sense. When it doesn't, you shouldn't.
In most cases, following published standards is convenient for
users--it means that their programs or scripts will work more portably.
For instance, GCC implements nearly all the features of Standard C as
specified by that standard. C program developers would be unhappy if
it did not. And GNU utilities mostly follow specifications of POSIX.2;
shell script writers and users would be unhappy if our programs were
incompatible.
But we do not follow either of these specifications rigidly, and
there are specific points on which we decided not to follow them, so as
to make the GNU system better for users.
For instance, Standard C says that nearly all extensions to C are
prohibited. How silly! GCC implements many extensions, some of which
were later adopted as part of the standard. If you want these
constructs to give an error message as "required" by the standard, you
must specify `--pedantic', which was implemented only so that we can
say "GCC is a 100% implementation of the standard," not because there
is any reason to actually use it.
POSIX.2 specifies that `df' and `du' must output sizes by default in
units of 512 bytes. What users want is units of 1k, so that is what we
do by default. If you want the ridiculous behavior "required" by
POSIX, you must set the environment variable `POSIXLY_CORRECT' (which
was originally going to be named `POSIX_ME_HARDER').
GNU utilities also depart from the letter of the POSIX.2
specification when they support long-named command-line options, and
intermixing options with ordinary arguments. This minor
incompatibility with POSIX is never a problem in practice, and it is
very useful.
In particular, don't reject a new feature, or remove an old one,
merely because a standard says it is "forbidden" or "deprecated."
File: standards.info, Node: Semantics, Next: Libraries, Prev: Non-GNU Standards, Up: Program Behavior
4.2 Writing Robust Programs
===========================
Avoid arbitrary limits on the length or number of _any_ data structure,
including file names, lines, files, and symbols, by allocating all data
structures dynamically. In most Unix utilities, "long lines are
silently truncated". This is not acceptable in a GNU utility.
Utilities reading files should not drop NUL characters, or any other
nonprinting characters _including those with codes above 0177_. The
only sensible exceptions would be utilities specifically intended for
interface to certain types of terminals or printers that can't handle
those characters. Whenever possible, try to make programs work
properly with sequences of bytes that represent multibyte characters,
using encodings such as UTF-8 and others.
Check every system call for an error return, unless you know you
wish to ignore errors. Include the system error text (from `perror' or
equivalent) in _every_ error message resulting from a failing system
call, as well as the name of the file if any and the name of the
utility. Just "cannot open foo.c" or "stat failed" is not sufficient.
Check every call to `malloc' or `realloc' to see if it returned
zero. Check `realloc' even if you are making the block smaller; in a
system that rounds block sizes to a power of 2, `realloc' may get a
different block if you ask for less space.
In Unix, `realloc' can destroy the storage block if it returns zero.
GNU `realloc' does not have this bug: if it fails, the original block
is unchanged. Feel free to assume the bug is fixed. If you wish to
run your program on Unix, and wish to avoid lossage in this case, you
can use the GNU `malloc'.
You must expect `free' to alter the contents of the block that was
freed. Anything you want to fetch from the block, you must fetch before
calling `free'.
If `malloc' fails in a noninteractive program, make that a fatal
error. In an interactive program (one that reads commands from the
user), it is better to abort the command and return to the command
reader loop. This allows the user to kill other processes to free up
virtual memory, and then try the command again.
Use `getopt_long' to decode arguments, unless the argument syntax
makes this unreasonable.
When static storage is to be written in during program execution, use
explicit C code to initialize it. Reserve C initialized declarations
for data that will not be changed.
Try to avoid low-level interfaces to obscure Unix data structures
(such as file directories, utmp, or the layout of kernel memory), since
these are less likely to work compatibly. If you need to find all the
files in a directory, use `readdir' or some other high-level interface.
These are supported compatibly by GNU.
The preferred signal handling facilities are the BSD variant of
`signal', and the POSIX `sigaction' function; the alternative USG
`signal' interface is an inferior design.
Nowadays, using the POSIX signal functions may be the easiest way to
make a program portable. If you use `signal', then on GNU/Linux
systems running GNU libc version 1, you should include `bsd/signal.h'
instead of `signal.h', so as to get BSD behavior. It is up to you
whether to support systems where `signal' has only the USG behavior, or
give up on them.
In error checks that detect "impossible" conditions, just abort.
There is usually no point in printing any message. These checks
indicate the existence of bugs. Whoever wants to fix the bugs will have
to read the source code and run a debugger. So explain the problem with
comments in the source. The relevant data will be in variables, which
are easy to examine with the debugger, so there is no point moving them
elsewhere.
Do not use a count of errors as the exit status for a program.
_That does not work_, because exit status values are limited to 8 bits
(0 through 255). A single run of the program might have 256 errors; if
you try to return 256 as the exit status, the parent process will see 0
as the status, and it will appear that the program succeeded.
If you make temporary files, check the `TMPDIR' environment
variable; if that variable is defined, use the specified directory
instead of `/tmp'.
In addition, be aware that there is a possible security problem when
creating temporary files in world-writable directories. In C, you can
avoid this problem by creating temporary files in this manner:
fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0600);
or by using the `mkstemps' function from libiberty.
In bash, use `set -C' to avoid this problem.
File: standards.info, Node: Libraries, Next: Errors, Prev: Semantics, Up: Program Behavior
4.3 Library Behavior
====================
Try to make library functions reentrant. If they need to do dynamic
storage allocation, at least try to avoid any nonreentrancy aside from
that of `malloc' itself.
Here are certain name conventions for libraries, to avoid name
conflicts.
Choose a name prefix for the library, more than two characters long.
All external function and variable names should start with this prefix.
In addition, there should only be one of these in any given library
member. This usually means putting each one in a separate source file.
An exception can be made when two external symbols are always used
together, so that no reasonable program could use one without the
other; then they can both go in the same file.
External symbols that are not documented entry points for the user
should have names beginning with `_'. The `_' should be followed by
the chosen name prefix for the library, to prevent collisions with
other libraries. These can go in the same files with user entry points
if you like.
Static functions and variables can be used as you like and need not
fit any naming convention.
File: standards.info, Node: Errors, Next: User Interfaces, Prev: Libraries, Up: Program Behavior
4.4 Formatting Error Messages
=============================
Error messages from compilers should look like this:
SOURCE-FILE-NAME:LINENO: MESSAGE
If you want to mention the column number, use one of these formats:
SOURCE-FILE-NAME:LINENO:COLUMN: MESSAGE
SOURCE-FILE-NAME:LINENO.COLUMN: MESSAGE
Line numbers should start from 1 at the beginning of the file, and
column numbers should start from 1 at the beginning of the line. (Both
of these conventions are chosen for compatibility.) Calculate column
numbers assuming that space and all ASCII printing characters have
equal width, and assuming tab stops every 8 columns.
The error message can also give both the starting and ending
positions of the erroneous text. There are several formats so that you
can avoid redundant information such as a duplicate line number. Here
are the possible formats:
SOURCE-FILE-NAME:LINENO-1.COLUMN-1-LINENO-2.COLUMN-2: MESSAGE
SOURCE-FILE-NAME:LINENO-1.COLUMN-1-COLUMN-2: MESSAGE
SOURCE-FILE-NAME:LINENO-1-LINENO-2: MESSAGE
When an error is spread over several files, you can use this format:
FILE-1:LINENO-1.COLUMN-1-FILE-2:LINENO-2.COLUMN-2: MESSAGE
Error messages from other noninteractive programs should look like
this:
PROGRAM:SOURCE-FILE-NAME:LINENO: MESSAGE
when there is an appropriate source file, or like this:
PROGRAM: MESSAGE
when there is no relevant source file.
If you want to mention the column number, use this format:
PROGRAM:SOURCE-FILE-NAME:LINENO:COLUMN: MESSAGE
In an interactive program (one that is reading commands from a
terminal), it is better not to include the program name in an error
message. The place to indicate which program is running is in the
prompt or with the screen layout. (When the same program runs with
input from a source other than a terminal, it is not interactive and
would do best to print error messages using the noninteractive style.)
The string MESSAGE should not begin with a capital letter when it
follows a program name and/or file name, because that isn't the
beginning of a sentence. (The sentence conceptually starts at the
beginning of the line.) Also, it should not end with a period.
Error messages from interactive programs, and other messages such as
usage messages, should start with a capital letter. But they should not
end with a period.
File: standards.info, Node: User Interfaces, Next: Graphical Interfaces, Prev: Errors, Up: Program Behavior
4.5 Standards for Interfaces Generally
======================================
Please don't make the behavior of a utility depend on the name used to
invoke it. It is useful sometimes to make a link to a utility with a
different name, and that should not change what it does.
Instead, use a run time option or a compilation switch or both to
select among the alternate behaviors.
Likewise, please don't make the behavior of the program depend on the
type of output device it is used with. Device independence is an
important principle of the system's design; do not compromise it merely
to save someone from typing an option now and then. (Variation in error
message syntax when using a terminal is ok, because that is a side issue
that people do not depend on.)
If you think one behavior is most useful when the output is to a
terminal, and another is most useful when the output is a file or a
pipe, then it is usually best to make the default behavior the one that
is useful with output to a terminal, and have an option for the other
behavior.
Compatibility requires certain programs to depend on the type of
output device. It would be disastrous if `ls' or `sh' did not do so in
the way all users expect. In some of these cases, we supplement the
program with a preferred alternate version that does not depend on the
output device type. For example, we provide a `dir' program much like
`ls' except that its default output format is always multi-column
format.
File: standards.info, Node: Graphical Interfaces, Next: Command-Line Interfaces, Prev: User Interfaces, Up: Program Behavior
4.6 Standards for Graphical Interfaces
======================================
When you write a program that provides a graphical user interface,
please make it work with X Windows and the GTK+ toolkit unless the
functionality specifically requires some alternative (for example,
"displaying jpeg images while in console mode").
In addition, please provide a command-line interface to control the
functionality. (In many cases, the graphical user interface can be a
separate program which invokes the command-line program.) This is so
that the same jobs can be done from scripts.
Please also consider providing a CORBA interface (for use from
GNOME), a library interface (for use from C), and perhaps a
keyboard-driven console interface (for use by users from console mode).
Once you are doing the work to provide the functionality and the
graphical interface, these won't be much extra work.
File: standards.info, Node: Command-Line Interfaces, Next: Option Table, Prev: Graphical Interfaces, Up: Program Behavior
4.7 Standards for Command Line Interfaces
=========================================
It is a good idea to follow the POSIX guidelines for the command-line
options of a program. The easiest way to do this is to use `getopt' to
parse them. Note that the GNU version of `getopt' will normally permit
options anywhere among the arguments unless the special argument `--'
is used. This is not what POSIX specifies; it is a GNU extension.
Please define long-named options that are equivalent to the
single-letter Unix-style options. We hope to make GNU more user
friendly this way. This is easy to do with the GNU function
`getopt_long'.
One of the advantages of long-named options is that they can be
consistent from program to program. For example, users should be able
to expect the "verbose" option of any GNU program which has one, to be
spelled precisely `--verbose'. To achieve this uniformity, look at the
table of common long-option names when you choose the option names for
your program (*note Option Table::).
It is usually a good idea for file names given as ordinary arguments
to be input files only; any output files would be specified using
options (preferably `-o' or `--output'). Even if you allow an output
file name as an ordinary argument for compatibility, try to provide an
option as another way to specify it. This will lead to more consistency
among GNU utilities, and fewer idiosyncrasies for users to remember.
All programs should support two standard options: `--version' and
`--help'. CGI programs should accept these as command-line options,
and also if given as the `PATH_INFO'; for instance, visiting
`http://example.org/p.cgi/--help' in a browser should output the same
information as invoking `p.cgi --help' from the command line.
* Menu:
* --version:: The standard output for --version.
* --help:: The standard output for --help.
File: standards.info, Node: --version, Next: --help, Up: Command-Line Interfaces
4.7.1 `--version'
-----------------
The standard `--version' option should direct the program to print
information about its name, version, origin and legal status, all on
standard output, and then exit successfully. Other options and
arguments should be ignored once this is seen, and the program should
not perform its normal function.
The first line is meant to be easy for a program to parse; the
version number proper starts after the last space. In addition, it
contains the canonical name for this program, in this format:
GNU Emacs 19.30
The program's name should be a constant string; _don't_ compute it from
`argv[0]'. The idea is to state the standard or canonical name for the
program, not its file name. There are other ways to find out the
precise file name where a command is found in `PATH'.
If the program is a subsidiary part of a larger package, mention the
package name in parentheses, like this:
emacsserver (GNU Emacs) 19.30
If the package has a version number which is different from this
program's version number, you can mention the package version number
just before the close-parenthesis.
If you _need_ to mention the version numbers of libraries which are
distributed separately from the package which contains this program,
you can do so by printing an additional line of version info for each
library you want to mention. Use the same format for these lines as for
the first line.
Please do not mention all of the libraries that the program uses
"just for completeness"--that would produce a lot of unhelpful clutter.
Please mention library version numbers only if you find in practice that
they are very important to you in debugging.
The following line, after the version number line or lines, should
be a copyright notice. If more than one copyright notice is called
for, put each on a separate line.
Next should follow a line stating the license, preferably using one
of abbrevations below, and a brief statement that the program is free
software, and that users are free to copy and change it. Also mention
that there is no warranty, to the extent permitted by law. See
recommended wording below.
It is ok to finish the output with a list of the major authors of the
program, as a way of giving credit.
Here's an example of output that follows these rules:
GNU hello 2.3
Copyright (C) 2007 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
You should adapt this to your program, of course, filling in the
proper year, copyright holder, name of program, and the references to
distribution terms, and changing the rest of the wording as necessary.
This copyright notice only needs to mention the most recent year in
which changes were made--there's no need to list the years for previous
versions' changes. You don't have to mention the name of the program in
these notices, if that is inconvenient, since it appeared in the first
line. (The rules are different for copyright notices in source files;
*note Copyright Notices: (maintain)Copyright Notices.)
Translations of the above lines must preserve the validity of the
copyright notices (*note Internationalization::). If the translation's
character set supports it, the `(C)' should be replaced with the
copyright symbol, as follows:
(the official copyright symbol, which is the letter C in a circle);
Write the word "Copyright" exactly like that, in English. Do not
translate it into another language. International treaties recognize
the English word "Copyright"; translations into other languages do not
have legal significance.
Finally, here is the table of our suggested license abbreviations.
Any abbreviation can be followed by `vVERSION[+]', meaning that
particular version, or later versions with the `+', as shown above.
In the case of exceptions for extra permissions with the GPL, we use
`/' for a separator; the version number can follow the license
abbreviation as usual, as in the examples below.
GPL
GNU General Public License, `http://www.gnu.org/licenses/gpl.html'.
LGPL
GNU Lesser General Public License,
`http://www.gnu.org/licenses/lgpl.html'.
GPL/Guile
GNU GPL with the exception for Guile; for example, GPLv3+/Guile
means the GNU GPL version 3 or later, with the extra exception for
Guile.
GPL/Ada
GNU GPL with the exception for Ada.
Apache
The Apache Software Foundation license,
`http://www.apache.org/licenses'.
Artistic
The Artistic license used for Perl,
`http://www.perlfoundation.org/legal'.
Expat
The Expat license, `http://www.jclark.com/xml/copying.txt'.
MPL
The Mozilla Public License, `http://www.mozilla.org/MPL/'.
OBSD
The original (4-clause) BSD license, incompatible with the GNU GPL
`http://www.xfree86.org/3.3.6/COPYRIGHT2.html#6'.
PHP
The license used for PHP, `http://www.php.net/license/'.
public domain
The non-license that is being in the public domain,
`http://www.gnu.org/licenses/license-list.html#PublicDomain'.
Python
The license for Python, `http://www.python.org/2.0.1/license.html'.
RBSD
The revised (3-clause) BSD, compatible with the GNU GPL,
`http://www.xfree86.org/3.3.6/COPYRIGHT2.html#5'.
X11
The simple non-copyleft license used for most versions of the X
Window system, `http://www.xfree86.org/3.3.6/COPYRIGHT2.html#3'.
Zlib
The license for Zlib, `http://www.gzip.org/zlib/zlib_license.html'.
More information about these licenses and many more are on the GNU
licensing web pages, `http://www.gnu.org/licenses/license-list.html'.
File: standards.info, Node: --help, Prev: --version, Up: Command-Line Interfaces
4.7.2 `--help'
--------------
The standard `--help' option should output brief documentation for how
to invoke the program, on standard output, then exit successfully.
Other options and arguments should be ignored once this is seen, and
the program should not perform its normal function.
Near the end of the `--help' option's output, please place lines
giving the email address for bug reports, the package's home page
(normally , and the general page for
help using GNU programs. The format should be like this:
Report bugs to: MAILING-ADDRESS
PKG home page:
General help using GNU software:
It is ok to mention other appropriate mailing lists and web pages.
File: standards.info, Node: Option Table, Next: OID Allocations, Prev: Command-Line Interfaces, Up: Program Behavior
4.8 Table of Long Options
=========================
Here is a table of long options used by GNU programs. It is surely
incomplete, but we aim to list all the options that a new program might
want to be compatible with. If you use names not already in the table,
please send a list of them, with their
meanings, so we can update the table.
`after-date'
`-N' in `tar'.
`all'
`-a' in `du', `ls', `nm', `stty', `uname', and `unexpand'.
`all-text'
`-a' in `diff'.
`almost-all'
`-A' in `ls'.
`append'
`-a' in `etags', `tee', `time'; `-r' in `tar'.
`archive'
`-a' in `cp'.
`archive-name'
`-n' in `shar'.
`arglength'
`-l' in `m4'.
`ascii'
`-a' in `diff'.
`assign'
`-v' in `gawk'.
`assume-new'
`-W' in `make'.
`assume-old'
`-o' in `make'.
`auto-check'
`-a' in `recode'.
`auto-pager'
`-a' in `wdiff'.
`auto-reference'
`-A' in `ptx'.
`avoid-wraps'
`-n' in `wdiff'.
`background'
For server programs, run in the background.
`backward-search'
`-B' in `ctags'.
`basename'
`-f' in `shar'.
`batch'
Used in GDB.
`baud'
Used in GDB.
`before'
`-b' in `tac'.
`binary'
`-b' in `cpio' and `diff'.
`bits-per-code'
`-b' in `shar'.
`block-size'
Used in `cpio' and `tar'.
`blocks'
`-b' in `head' and `tail'.
`break-file'
`-b' in `ptx'.
`brief'
Used in various programs to make output shorter.
`bytes'
`-c' in `head', `split', and `tail'.
`c++'
`-C' in `etags'.
`catenate'
`-A' in `tar'.
`cd'
Used in various programs to specify the directory to use.
`changes'
`-c' in `chgrp' and `chown'.
`classify'
`-F' in `ls'.
`colons'
`-c' in `recode'.
`command'
`-c' in `su'; `-x' in GDB.
`compare'
`-d' in `tar'.
`compat'
Used in `gawk'.
`compress'
`-Z' in `tar' and `shar'.
`concatenate'
`-A' in `tar'.
`confirmation'
`-w' in `tar'.
`context'
Used in `diff'.
`copyleft'
`-W copyleft' in `gawk'.
`copyright'
`-C' in `ptx', `recode', and `wdiff'; `-W copyright' in `gawk'.
`core'
Used in GDB.
`count'
`-q' in `who'.
`count-links'
`-l' in `du'.
`create'
Used in `tar' and `cpio'.
`cut-mark'
`-c' in `shar'.
`cxref'
`-x' in `ctags'.
`date'
`-d' in `touch'.
`debug'
`-d' in `make' and `m4'; `-t' in Bison.
`define'
`-D' in `m4'.
`defines'
`-d' in Bison and `ctags'.
`delete'
`-D' in `tar'.
`dereference'
`-L' in `chgrp', `chown', `cpio', `du', `ls', and `tar'.
`dereference-args'
`-D' in `du'.
`device'
Specify an I/O device (special file name).
`diacritics'
`-d' in `recode'.
`dictionary-order'
`-d' in `look'.
`diff'
`-d' in `tar'.
`digits'
`-n' in `csplit'.
`directory'
Specify the directory to use, in various programs. In `ls', it
means to show directories themselves rather than their contents.
In `rm' and `ln', it means to not treat links to directories
specially.
`discard-all'
`-x' in `strip'.
`discard-locals'
`-X' in `strip'.
`dry-run'
`-n' in `make'.
`ed'
`-e' in `diff'.
`elide-empty-files'
`-z' in `csplit'.
`end-delete'
`-x' in `wdiff'.
`end-insert'
`-z' in `wdiff'.
`entire-new-file'
`-N' in `diff'.
`environment-overrides'
`-e' in `make'.
`eof'
`-e' in `xargs'.
`epoch'
Used in GDB.
`error-limit'
Used in `makeinfo'.
`error-output'
`-o' in `m4'.
`escape'
`-b' in `ls'.
`exclude-from'
`-X' in `tar'.
`exec'
Used in GDB.
`exit'
`-x' in `xargs'.
`exit-0'
`-e' in `unshar'.
`expand-tabs'
`-t' in `diff'.
`expression'
`-e' in `sed'.
`extern-only'
`-g' in `nm'.
`extract'
`-i' in `cpio'; `-x' in `tar'.
`faces'
`-f' in `finger'.
`fast'
`-f' in `su'.
`fatal-warnings'
`-E' in `m4'.
`file'
`-f' in `gawk', `info', `make', `mt', `sed', and `tar'.
`field-separator'
`-F' in `gawk'.
`file-prefix'
`-b' in Bison.
`file-type'
`-F' in `ls'.
`files-from'
`-T' in `tar'.
`fill-column'
Used in `makeinfo'.
`flag-truncation'
`-F' in `ptx'.
`fixed-output-files'
`-y' in Bison.
`follow'
`-f' in `tail'.
`footnote-style'
Used in `makeinfo'.
`force'
`-f' in `cp', `ln', `mv', and `rm'.
`force-prefix'
`-F' in `shar'.
`foreground'
For server programs, run in the foreground; in other words, don't
do anything special to run the server in the background.
`format'
Used in `ls', `time', and `ptx'.
`freeze-state'
`-F' in `m4'.
`fullname'
Used in GDB.
`gap-size'
`-g' in `ptx'.
`get'
`-x' in `tar'.
`graphic'
`-i' in `ul'.
`graphics'
`-g' in `recode'.
`group'
`-g' in `install'.
`gzip'
`-z' in `tar' and `shar'.
`hashsize'
`-H' in `m4'.
`header'
`-h' in `objdump' and `recode'
`heading'
`-H' in `who'.
`help'
Used to ask for brief usage information.
`here-delimiter'
`-d' in `shar'.
`hide-control-chars'
`-q' in `ls'.
`html'
In `makeinfo', output HTML.
`idle'
`-u' in `who'.
`ifdef'
`-D' in `diff'.
`ignore'
`-I' in `ls'; `-x' in `recode'.
`ignore-all-space'
`-w' in `diff'.
`ignore-backups'
`-B' in `ls'.
`ignore-blank-lines'
`-B' in `diff'.
`ignore-case'
`-f' in `look' and `ptx'; `-i' in `diff' and `wdiff'.
`ignore-errors'
`-i' in `make'.
`ignore-file'
`-i' in `ptx'.
`ignore-indentation'
`-I' in `etags'.
`ignore-init-file'
`-f' in Oleo.
`ignore-interrupts'
`-i' in `tee'.
`ignore-matching-lines'
`-I' in `diff'.
`ignore-space-change'
`-b' in `diff'.
`ignore-zeros'
`-i' in `tar'.
`include'
`-i' in `etags'; `-I' in `m4'.
`include-dir'
`-I' in `make'.
`incremental'
`-G' in `tar'.
`info'
`-i', `-l', and `-m' in Finger.
`init-file'
In some programs, specify the name of the file to read as the
user's init file.
`initial'
`-i' in `expand'.
`initial-tab'
`-T' in `diff'.
`inode'
`-i' in `ls'.
`interactive'
`-i' in `cp', `ln', `mv', `rm'; `-e' in `m4'; `-p' in `xargs';
`-w' in `tar'.
`intermix-type'
`-p' in `shar'.
`iso-8601'
Used in `date'
`jobs'
`-j' in `make'.
`just-print'
`-n' in `make'.
`keep-going'
`-k' in `make'.
`keep-files'
`-k' in `csplit'.
`kilobytes'
`-k' in `du' and `ls'.
`language'
`-l' in `etags'.
`less-mode'
`-l' in `wdiff'.
`level-for-gzip'
`-g' in `shar'.
`line-bytes'
`-C' in `split'.
`lines'
Used in `split', `head', and `tail'.
`link'
`-l' in `cpio'.
`lint'
`lint-old'
Used in `gawk'.
`list'
`-t' in `cpio'; `-l' in `recode'.
`list'
`-t' in `tar'.
`literal'
`-N' in `ls'.
`load-average'
`-l' in `make'.
`login'
Used in `su'.
`machine'
Used in `uname'.
`macro-name'
`-M' in `ptx'.
`mail'
`-m' in `hello' and `uname'.
`make-directories'
`-d' in `cpio'.
`makefile'
`-f' in `make'.
`mapped'
Used in GDB.
`max-args'
`-n' in `xargs'.
`max-chars'
`-n' in `xargs'.
`max-lines'
`-l' in `xargs'.
`max-load'
`-l' in `make'.
`max-procs'
`-P' in `xargs'.
`mesg'
`-T' in `who'.
`message'
`-T' in `who'.
`minimal'
`-d' in `diff'.
`mixed-uuencode'
`-M' in `shar'.
`mode'
`-m' in `install', `mkdir', and `mkfifo'.
`modification-time'
`-m' in `tar'.
`multi-volume'
`-M' in `tar'.
`name-prefix'
`-a' in Bison.
`nesting-limit'
`-L' in `m4'.
`net-headers'
`-a' in `shar'.
`new-file'
`-W' in `make'.
`no-builtin-rules'
`-r' in `make'.
`no-character-count'
`-w' in `shar'.
`no-check-existing'
`-x' in `shar'.
`no-common'
`-3' in `wdiff'.
`no-create'
`-c' in `touch'.
`no-defines'
`-D' in `etags'.
`no-deleted'
`-1' in `wdiff'.
`no-dereference'
`-d' in `cp'.
`no-inserted'
`-2' in `wdiff'.
`no-keep-going'
`-S' in `make'.
`no-lines'
`-l' in Bison.
`no-piping'
`-P' in `shar'.
`no-prof'
`-e' in `gprof'.
`no-regex'
`-R' in `etags'.
`no-sort'
`-p' in `nm'.
`no-splash'
Don't print a startup splash screen.
`no-split'
Used in `makeinfo'.
`no-static'
`-a' in `gprof'.
`no-time'
`-E' in `gprof'.
`no-timestamp'
`-m' in `shar'.
`no-validate'
Used in `makeinfo'.
`no-wait'
Used in `emacsclient'.
`no-warn'
Used in various programs to inhibit warnings.
`node'
`-n' in `info'.
`nodename'
`-n' in `uname'.
`nonmatching'
`-f' in `cpio'.
`nstuff'
`-n' in `objdump'.
`null'
`-0' in `xargs'.
`number'
`-n' in `cat'.
`number-nonblank'
`-b' in `cat'.
`numeric-sort'
`-n' in `nm'.
`numeric-uid-gid'
`-n' in `cpio' and `ls'.
`nx'
Used in GDB.
`old-archive'
`-o' in `tar'.
`old-file'
`-o' in `make'.
`one-file-system'
`-l' in `tar', `cp', and `du'.
`only-file'
`-o' in `ptx'.
`only-prof'
`-f' in `gprof'.
`only-time'
`-F' in `gprof'.
`options'
`-o' in `getopt', `fdlist', `fdmount', `fdmountd', and `fdumount'.
`output'
In various programs, specify the output file name.
`output-prefix'
`-o' in `shar'.
`override'
`-o' in `rm'.
`overwrite'
`-c' in `unshar'.
`owner'
`-o' in `install'.
`paginate'
`-l' in `diff'.
`paragraph-indent'
Used in `makeinfo'.
`parents'
`-p' in `mkdir' and `rmdir'.
`pass-all'
`-p' in `ul'.
`pass-through'
`-p' in `cpio'.
`port'
`-P' in `finger'.
`portability'
`-c' in `cpio' and `tar'.
`posix'
Used in `gawk'.
`prefix-builtins'
`-P' in `m4'.
`prefix'
`-f' in `csplit'.
`preserve'
Used in `tar' and `cp'.
`preserve-environment'
`-p' in `su'.
`preserve-modification-time'
`-m' in `cpio'.
`preserve-order'
`-s' in `tar'.
`preserve-permissions'
`-p' in `tar'.
`print'
`-l' in `diff'.
`print-chars'
`-L' in `cmp'.
`print-data-base'
`-p' in `make'.
`print-directory'
`-w' in `make'.
`print-file-name'
`-o' in `nm'.
`print-symdefs'
`-s' in `nm'.
`printer'
`-p' in `wdiff'.
`prompt'
`-p' in `ed'.
`proxy'
Specify an HTTP proxy.
`query-user'
`-X' in `shar'.
`question'
`-q' in `make'.
`quiet'
Used in many programs to inhibit the usual output. Every program
accepting `--quiet' should accept `--silent' as a synonym.
`quiet-unshar'
`-Q' in `shar'
`quote-name'
`-Q' in `ls'.
`rcs'
`-n' in `diff'.
`re-interval'
Used in `gawk'.
`read-full-blocks'
`-B' in `tar'.
`readnow'
Used in GDB.
`recon'
`-n' in `make'.
`record-number'
`-R' in `tar'.
`recursive'
Used in `chgrp', `chown', `cp', `ls', `diff', and `rm'.
`reference'
`-r' in `touch'.
`references'
`-r' in `ptx'.
`regex'
`-r' in `tac' and `etags'.
`release'
`-r' in `uname'.
`reload-state'
`-R' in `m4'.
`relocation'
`-r' in `objdump'.
`rename'
`-r' in `cpio'.
`replace'
`-i' in `xargs'.
`report-identical-files'
`-s' in `diff'.
`reset-access-time'
`-a' in `cpio'.
`reverse'
`-r' in `ls' and `nm'.
`reversed-ed'
`-f' in `diff'.
`right-side-defs'
`-R' in `ptx'.
`same-order'
`-s' in `tar'.
`same-permissions'
`-p' in `tar'.
`save'
`-g' in `stty'.
`se'
Used in GDB.
`sentence-regexp'
`-S' in `ptx'.
`separate-dirs'
`-S' in `du'.
`separator'
`-s' in `tac'.
`sequence'
Used by `recode' to chose files or pipes for sequencing passes.
`shell'
`-s' in `su'.
`show-all'
`-A' in `cat'.
`show-c-function'
`-p' in `diff'.
`show-ends'
`-E' in `cat'.
`show-function-line'
`-F' in `diff'.
`show-tabs'
`-T' in `cat'.
`silent'
Used in many programs to inhibit the usual output. Every program
accepting `--silent' should accept `--quiet' as a synonym.
`size'
`-s' in `ls'.
`socket'
Specify a file descriptor for a network server to use for its
socket, instead of opening and binding a new socket. This
provides a way to run, in a non-privileged process, a server that
normally needs a reserved port number.
`sort'
Used in `ls'.
`source'
`-W source' in `gawk'.
`sparse'
`-S' in `tar'.
`speed-large-files'
`-H' in `diff'.
`split-at'
`-E' in `unshar'.
`split-size-limit'
`-L' in `shar'.
`squeeze-blank'
`-s' in `cat'.
`start-delete'
`-w' in `wdiff'.
`start-insert'
`-y' in `wdiff'.
`starting-file'
Used in `tar' and `diff' to specify which file within a directory
to start processing with.
`statistics'
`-s' in `wdiff'.
`stdin-file-list'
`-S' in `shar'.
`stop'
`-S' in `make'.
`strict'
`-s' in `recode'.
`strip'
`-s' in `install'.
`strip-all'
`-s' in `strip'.
`strip-debug'
`-S' in `strip'.
`submitter'
`-s' in `shar'.
`suffix'
`-S' in `cp', `ln', `mv'.
`suffix-format'
`-b' in `csplit'.
`sum'
`-s' in `gprof'.
`summarize'
`-s' in `du'.
`symbolic'
`-s' in `ln'.
`symbols'
Used in GDB and `objdump'.
`synclines'
`-s' in `m4'.
`sysname'
`-s' in `uname'.
`tabs'
`-t' in `expand' and `unexpand'.
`tabsize'
`-T' in `ls'.
`terminal'
`-T' in `tput' and `ul'. `-t' in `wdiff'.
`text'
`-a' in `diff'.
`text-files'
`-T' in `shar'.
`time'
Used in `ls' and `touch'.
`timeout'
Specify how long to wait before giving up on some operation.
`to-stdout'
`-O' in `tar'.
`total'
`-c' in `du'.
`touch'
`-t' in `make', `ranlib', and `recode'.
`trace'
`-t' in `m4'.
`traditional'
`-t' in `hello'; `-W traditional' in `gawk'; `-G' in `ed', `m4',
and `ptx'.
`tty'
Used in GDB.
`typedefs'
`-t' in `ctags'.
`typedefs-and-c++'
`-T' in `ctags'.
`typeset-mode'
`-t' in `ptx'.
`uncompress'
`-z' in `tar'.
`unconditional'
`-u' in `cpio'.
`undefine'
`-U' in `m4'.
`undefined-only'
`-u' in `nm'.
`update'
`-u' in `cp', `ctags', `mv', `tar'.
`usage'
Used in `gawk'; same as `--help'.
`uuencode'
`-B' in `shar'.
`vanilla-operation'
`-V' in `shar'.
`verbose'
Print more information about progress. Many programs support this.
`verify'
`-W' in `tar'.
`version'
Print the version number.
`version-control'
`-V' in `cp', `ln', `mv'.
`vgrind'
`-v' in `ctags'.
`volume'
`-V' in `tar'.
`what-if'
`-W' in `make'.
`whole-size-limit'
`-l' in `shar'.
`width'
`-w' in `ls' and `ptx'.
`word-regexp'
`-W' in `ptx'.
`writable'
`-T' in `who'.
`zeros'
`-z' in `gprof'.
File: standards.info, Node: OID Allocations, Next: Memory Usage, Prev: Option Table, Up: Program Behavior
4.9 OID Allocations
===================
The OID (object identifier) 1.3.6.1.4.1.11591 has been assigned to the
GNU Project (thanks to Werner Koch). These are used for SNMP, LDAP,
X.509 certificates, and so on. The web site
`http://www.alvestrand.no/objectid' has a (voluntary) listing of many
OID assignments.
If you need a new slot for your GNU package, write
. Here is a list of arcs currently assigned:
1.3.6.1.4.1.11591 GNU
1.3.6.1.4.1.11591.1 GNU Radius
1.3.6.1.4.1.11591.2 GnuPG
1.3.6.1.4.1.11591.2.1 notation
1.3.6.1.4.1.11591.2.1.1 pkaAddress
1.3.6.1.4.1.11591.3 GNU Radar
1.3.6.1.4.1.11591.4 GNU GSS
1.3.6.1.4.1.11591.5 GNU Mailutils
1.3.6.1.4.1.11591.5 GNU Shishi
1.3.6.1.4.1.11591.12 digestAlgorithm
1.3.6.1.4.1.11591.12.2 TIGER/192
1.3.6.1.4.1.11591.13 encryptionAlgorithm
1.3.6.1.4.1.11591.13.2 Serpent
1.3.6.1.4.1.11591.13.2.1 Serpent-128-ECB
1.3.6.1.4.1.11591.13.2.2 Serpent-128-CBC
1.3.6.1.4.1.11591.13.2.3 Serpent-128-OFB
1.3.6.1.4.1.11591.13.2.4 Serpent-128-CFB
1.3.6.1.4.1.11591.13.2.21 Serpent-192-ECB
1.3.6.1.4.1.11591.13.2.22 Serpent-192-CBC
1.3.6.1.4.1.11591.13.2.23 Serpent-192-OFB
1.3.6.1.4.1.11591.13.2.24 Serpent-192-CFB
1.3.6.1.4.1.11591.13.2.41 Serpent-256-ECB
1.3.6.1.4.1.11591.13.2.42 Serpent-256-CBC
1.3.6.1.4.1.11591.13.2.43 Serpent-256-OFB
1.3.6.1.4.1.11591.13.2.44 Serpent-256-CFB
1.3.6.1.4.1.11591.14 CRC algorithms
1.3.6.1.4.1.11591.14.1 CRC 32
File: standards.info, Node: Memory Usage, Next: File Usage, Prev: OID Allocations, Up: Program Behavior
4.10 Memory Usage
=================
If a program typically uses just a few meg of memory, don't bother
making any effort to reduce memory usage. For example, if it is
impractical for other reasons to operate on files more than a few meg
long, it is reasonable to read entire input files into memory to
operate on them.
However, for programs such as `cat' or `tail', that can usefully
operate on very large files, it is important to avoid using a technique
that would artificially limit the size of files it can handle. If a
program works by lines and could be applied to arbitrary user-supplied
input files, it should keep only a line in memory, because this is not
very hard and users will want to be able to operate on input files that
are bigger than will fit in memory all at once.
If your program creates complicated data structures, just make them
in memory and give a fatal error if `malloc' returns zero.
File: standards.info, Node: File Usage, Prev: Memory Usage, Up: Program Behavior
4.11 File Usage
===============
Programs should be prepared to operate when `/usr' and `/etc' are
read-only file systems. Thus, if the program manages log files, lock
files, backup files, score files, or any other files which are modified
for internal purposes, these files should not be stored in `/usr' or
`/etc'.
There are two exceptions. `/etc' is used to store system
configuration information; it is reasonable for a program to modify
files in `/etc' when its job is to update the system configuration.
Also, if the user explicitly asks to modify one file in a directory, it
is reasonable for the program to store other files in the same
directory.
File: standards.info, Node: Writing C, Next: Documentation, Prev: Program Behavior, Up: Top
5 Making The Best Use of C
**************************
This chapter provides advice on how best to use the C language when
writing GNU software.
* Menu:
* Formatting:: Formatting your source code.
* Comments:: Commenting your work.
* Syntactic Conventions:: Clean use of C constructs.
* Names:: Naming variables, functions, and files.
* System Portability:: Portability among different operating systems.
* CPU Portability:: Supporting the range of CPU types.
* System Functions:: Portability and ``standard'' library functions.
* Internationalization:: Techniques for internationalization.
* Character Set:: Use ASCII by default.
* Quote Characters:: Use `...' in the C locale.
* Mmap:: How you can safely use `mmap'.
File: standards.info, Node: Formatting, Next: Comments, Up: Writing C
5.1 Formatting Your Source Code
===============================
It is important to put the open-brace that starts the body of a C
function in column one, so that they will start a defun. Several tools
look for open-braces in column one to find the beginnings of C
functions. These tools will not work on code not formatted that way.
Avoid putting open-brace, open-parenthesis or open-bracket in column
one when they are inside a function, so that they won't start a defun.
The open-brace that starts a `struct' body can go in column one if you
find it useful to treat that definition as a defun.
It is also important for function definitions to start the name of
the function in column one. This helps people to search for function
definitions, and may also help certain tools recognize them. Thus,
using Standard C syntax, the format is this:
static char *
concat (char *s1, char *s2)
{
...
}
or, if you want to use traditional C syntax, format the definition like
this:
static char *
concat (s1, s2) /* Name starts in column one here */
char *s1, *s2;
{ /* Open brace in column one here */
...
}
In Standard C, if the arguments don't fit nicely on one line, split
it like this:
int
lots_of_args (int an_integer, long a_long, short a_short,
double a_double, float a_float)
...
The rest of this section gives our recommendations for other aspects
of C formatting style, which is also the default style of the `indent'
program in version 1.2 and newer. It corresponds to the options
-nbad -bap -nbc -bbo -bl -bli2 -bls -ncdb -nce -cp1 -cs -di2
-ndj -nfc1 -nfca -hnl -i2 -ip5 -lp -pcs -psl -nsc -nsob
We don't think of these recommendations as requirements, because it
causes no problems for users if two different programs have different
formatting styles.
But whatever style you use, please use it consistently, since a
mixture of styles within one program tends to look ugly. If you are
contributing changes to an existing program, please follow the style of
that program.
For the body of the function, our recommended style looks like this:
if (x < foo (y, z))
haha = bar[4] + 5;
else
{
while (z)
{
haha += foo (z, z);
z--;
}
return ++x + bar ();
}
We find it easier to read a program when it has spaces before the
open-parentheses and after the commas. Especially after the commas.
When you split an expression into multiple lines, split it before an
operator, not after one. Here is the right way:
if (foo_this_is_long && bar > win (x, y, z)
&& remaining_condition)
Try to avoid having two operators of different precedence at the same
level of indentation. For example, don't write this:
mode = (inmode[j] == VOIDmode
|| GET_MODE_SIZE (outmode[j]) > GET_MODE_SIZE (inmode[j])
? outmode[j] : inmode[j]);
Instead, use extra parentheses so that the indentation shows the
nesting:
mode = ((inmode[j] == VOIDmode
|| (GET_MODE_SIZE (outmode[j]) > GET_MODE_SIZE (inmode[j])))
? outmode[j] : inmode[j]);
Insert extra parentheses so that Emacs will indent the code properly.
For example, the following indentation looks nice if you do it by hand,
v = rup->ru_utime.tv_sec*1000 + rup->ru_utime.tv_usec/1000
+ rup->ru_stime.tv_sec*1000 + rup->ru_stime.tv_usec/1000;
but Emacs would alter it. Adding a set of parentheses produces
something that looks equally nice, and which Emacs will preserve:
v = (rup->ru_utime.tv_sec*1000 + rup->ru_utime.tv_usec/1000
+ rup->ru_stime.tv_sec*1000 + rup->ru_stime.tv_usec/1000);
Format do-while statements like this:
do
{
a = foo (a);
}
while (a > 0);
Please use formfeed characters (control-L) to divide the program into
pages at logical places (but not within a function). It does not matter
just how long the pages are, since they do not have to fit on a printed
page. The formfeeds should appear alone on lines by themselves.
File: standards.info, Node: Comments, Next: Syntactic Conventions, Prev: Formatting, Up: Writing C
5.2 Commenting Your Work
========================
Every program should start with a comment saying briefly what it is for.
Example: `fmt - filter for simple filling of text'. This comment
should be at the top of the source file containing the `main' function
of the program.
Also, please write a brief comment at the start of each source file,
with the file name and a line or two about the overall purpose of the
file.
Please write the comments in a GNU program in English, because
English is the one language that nearly all programmers in all
countries can read. If you do not write English well, please write
comments in English as well as you can, then ask other people to help
rewrite them. If you can't write comments in English, please find
someone to work with you and translate your comments into English.
Please put a comment on each function saying what the function does,
what sorts of arguments it gets, and what the possible values of
arguments mean and are used for. It is not necessary to duplicate in
words the meaning of the C argument declarations, if a C type is being
used in its customary fashion. If there is anything nonstandard about
its use (such as an argument of type `char *' which is really the
address of the second character of a string, not the first), or any
possible values that would not work the way one would expect (such as,
that strings containing newlines are not guaranteed to work), be sure
to say so.
Also explain the significance of the return value, if there is one.
Please put two spaces after the end of a sentence in your comments,
so that the Emacs sentence commands will work. Also, please write
complete sentences and capitalize the first word. If a lower-case
identifier comes at the beginning of a sentence, don't capitalize it!
Changing the spelling makes it a different identifier. If you don't
like starting a sentence with a lower case letter, write the sentence
differently (e.g., "The identifier lower-case is ...").
The comment on a function is much clearer if you use the argument
names to speak about the argument values. The variable name itself
should be lower case, but write it in upper case when you are speaking
about the value rather than the variable itself. Thus, "the inode
number NODE_NUM" rather than "an inode".
There is usually no purpose in restating the name of the function in
the comment before it, because the reader can see that for himself.
There might be an exception when the comment is so long that the
function itself would be off the bottom of the screen.
There should be a comment on each static variable as well, like this:
/* Nonzero means truncate lines in the display;
zero means continue them. */
int truncate_lines;
Every `#endif' should have a comment, except in the case of short
conditionals (just a few lines) that are not nested. The comment should
state the condition of the conditional that is ending, _including its
sense_. `#else' should have a comment describing the condition _and
sense_ of the code that follows. For example:
#ifdef foo
...
#else /* not foo */
...
#endif /* not foo */
#ifdef foo
...
#endif /* foo */
but, by contrast, write the comments this way for a `#ifndef':
#ifndef foo
...
#else /* foo */
...
#endif /* foo */
#ifndef foo
...
#endif /* not foo */
File: standards.info, Node: Syntactic Conventions, Next: Names, Prev: Comments, Up: Writing C
5.3 Clean Use of C Constructs
=============================
Please explicitly declare the types of all objects. For example, you
should explicitly declare all arguments to functions, and you should
declare functions to return `int' rather than omitting the `int'.
Some programmers like to use the GCC `-Wall' option, and change the
code whenever it issues a warning. If you want to do this, then do.
Other programmers prefer not to use `-Wall', because it gives warnings
for valid and legitimate code which they do not want to change. If you
want to do this, then do. The compiler should be your servant, not
your master.
Declarations of external functions and functions to appear later in
the source file should all go in one place near the beginning of the
file (somewhere before the first function definition in the file), or
else should go in a header file. Don't put `extern' declarations inside
functions.
It used to be common practice to use the same local variables (with
names like `tem') over and over for different values within one
function. Instead of doing this, it is better to declare a separate
local variable for each distinct purpose, and give it a name which is
meaningful. This not only makes programs easier to understand, it also
facilitates optimization by good compilers. You can also move the
declaration of each local variable into the smallest scope that includes
all its uses. This makes the program even cleaner.
Don't use local variables or parameters that shadow global
identifiers.
Don't declare multiple variables in one declaration that spans lines.
Start a new declaration on each line, instead. For example, instead of
this:
int foo,
bar;
write either this:
int foo, bar;
or this:
int foo;
int bar;
(If they are global variables, each should have a comment preceding it
anyway.)
When you have an `if'-`else' statement nested in another `if'
statement, always put braces around the `if'-`else'. Thus, never write
like this:
if (foo)
if (bar)
win ();
else
lose ();
always like this:
if (foo)
{
if (bar)
win ();
else
lose ();
}
If you have an `if' statement nested inside of an `else' statement,
either write `else if' on one line, like this,
if (foo)
...
else if (bar)
...
with its `then'-part indented like the preceding `then'-part, or write
the nested `if' within braces like this:
if (foo)
...
else
{
if (bar)
...
}
Don't declare both a structure tag and variables or typedefs in the
same declaration. Instead, declare the structure tag separately and
then use it to declare the variables or typedefs.
Try to avoid assignments inside `if'-conditions (assignments inside
`while'-conditions are ok). For example, don't write this:
if ((foo = (char *) malloc (sizeof *foo)) == 0)
fatal ("virtual memory exhausted");
instead, write this:
foo = (char *) malloc (sizeof *foo);
if (foo == 0)
fatal ("virtual memory exhausted");
Don't make the program ugly to placate `lint'. Please don't insert
any casts to `void'. Zero without a cast is perfectly fine as a null
pointer constant, except when calling a varargs function.
File: standards.info, Node: Names, Next: System Portability, Prev: Syntactic Conventions, Up: Writing C
5.4 Naming Variables, Functions, and Files
==========================================
The names of global variables and functions in a program serve as
comments of a sort. So don't choose terse names--instead, look for
names that give useful information about the meaning of the variable or
function. In a GNU program, names should be English, like other
comments.
Local variable names can be shorter, because they are used only
within one context, where (presumably) comments explain their purpose.
Try to limit your use of abbreviations in symbol names. It is ok to
make a few abbreviations, explain what they mean, and then use them
frequently, but don't use lots of obscure abbreviations.
Please use underscores to separate words in a name, so that the Emacs
word commands can be useful within them. Stick to lower case; reserve
upper case for macros and `enum' constants, and for name-prefixes that
follow a uniform convention.
For example, you should use names like `ignore_space_change_flag';
don't use names like `iCantReadThis'.
Variables that indicate whether command-line options have been
specified should be named after the meaning of the option, not after
the option-letter. A comment should state both the exact meaning of
the option and its letter. For example,
/* Ignore changes in horizontal whitespace (-b). */
int ignore_space_change_flag;
When you want to define names with constant integer values, use
`enum' rather than `#define'. GDB knows about enumeration constants.
You might want to make sure that none of the file names would
conflict if the files were loaded onto an MS-DOS file system which
shortens the names. You can use the program `doschk' to test for this.
Some GNU programs were designed to limit themselves to file names of
14 characters or less, to avoid file name conflicts if they are read
into older System V systems. Please preserve this feature in the
existing GNU programs that have it, but there is no need to do this in
new GNU programs. `doschk' also reports file names longer than 14
characters.
File: standards.info, Node: System Portability, Next: CPU Portability, Prev: Names, Up: Writing C
5.5 Portability between System Types
====================================
In the Unix world, "portability" refers to porting to different Unix
versions. For a GNU program, this kind of portability is desirable, but
not paramount.
The primary purpose of GNU software is to run on top of the GNU
kernel, compiled with the GNU C compiler, on various types of CPU. So
the kinds of portability that are absolutely necessary are quite
limited. But it is important to support Linux-based GNU systems, since
they are the form of GNU that is popular.
Beyond that, it is good to support the other free operating systems
(*BSD), and it is nice to support other Unix-like systems if you want
to. Supporting a variety of Unix-like systems is desirable, although
not paramount. It is usually not too hard, so you may as well do it.
But you don't have to consider it an obligation, if it does turn out to
be hard.
The easiest way to achieve portability to most Unix-like systems is
to use Autoconf. It's unlikely that your program needs to know more
information about the host platform than Autoconf can provide, simply
because most of the programs that need such knowledge have already been
written.
Avoid using the format of semi-internal data bases (e.g.,
directories) when there is a higher-level alternative (`readdir').
As for systems that are not like Unix, such as MSDOS, Windows, VMS,
MVS, and older Macintosh systems, supporting them is often a lot of
work. When that is the case, it is better to spend your time adding
features that will be useful on GNU and GNU/Linux, rather than on
supporting other incompatible systems.
If you do support Windows, please do not abbreviate it as "win". In
hacker terminology, calling something a "win" is a form of praise.
You're free to praise Microsoft Windows on your own if you want, but
please don't do this in GNU packages. Instead of abbreviating
"Windows" to "win", you can write it in full or abbreviate it to "woe"
or "w". In GNU Emacs, for instance, we use `w32' in file names of
Windows-specific files, but the macro for Windows conditionals is
called `WINDOWSNT'.
It is a good idea to define the "feature test macro" `_GNU_SOURCE'
when compiling your C files. When you compile on GNU or GNU/Linux,
this will enable the declarations of GNU library extension functions,
and that will usually give you a compiler error message if you define
the same function names in some other way in your program. (You don't
have to actually _use_ these functions, if you prefer to make the
program more portable to other systems.)
But whether or not you use these GNU extensions, you should avoid
using their names for any other meanings. Doing so would make it hard
to move your code into other GNU programs.
File: standards.info, Node: CPU Portability, Next: System Functions, Prev: System Portability, Up: Writing C
5.6 Portability between CPUs
============================
Even GNU systems will differ because of differences among CPU
types--for example, difference in byte ordering and alignment
requirements. It is absolutely essential to handle these differences.
However, don't make any effort to cater to the possibility that an
`int' will be less than 32 bits. We don't support 16-bit machines in
GNU.
Similarly, don't make any effort to cater to the possibility that
`long' will be smaller than predefined types like `size_t'. For
example, the following code is ok:
printf ("size = %lu\n", (unsigned long) sizeof array);
printf ("diff = %ld\n", (long) (pointer2 - pointer1));
1989 Standard C requires this to work, and we know of only one
counterexample: 64-bit programs on Microsoft Windows. We will leave it
to those who want to port GNU programs to that environment to figure
out how to do it.
Predefined file-size types like `off_t' are an exception: they are
longer than `long' on many platforms, so code like the above won't work
with them. One way to print an `off_t' value portably is to print its
digits yourself, one by one.
Don't assume that the address of an `int' object is also the address
of its least-significant byte. This is false on big-endian machines.
Thus, don't make the following mistake:
int c;
...
while ((c = getchar ()) != EOF)
write (file_descriptor, &c, 1);
Instead, use `unsigned char' as follows. (The `unsigned' is for
portability to unusual systems where `char' is signed and where there
is integer overflow checking.)
int c;
while ((c = getchar ()) != EOF)
{
unsigned char u = c;
write (file_descriptor, &u, 1);
}
It used to be ok to not worry about the difference between pointers
and integers when passing arguments to functions. However, on most
modern 64-bit machines pointers are wider than `int'. Conversely,
integer types like `long long int' and `off_t' are wider than pointers
on most modern 32-bit machines. Hence it's often better nowadays to
use prototypes to define functions whose argument types are not trivial.
In particular, if functions accept varying argument counts or types
they should be declared using prototypes containing `...' and defined
using `stdarg.h'. For an example of this, please see the Gnulib
(http://www.gnu.org/software/gnulib/) error module, which declares and
defines the following function:
/* Print a message with `fprintf (stderr, FORMAT, ...)';
if ERRNUM is nonzero, follow it with ": " and strerror (ERRNUM).
If STATUS is nonzero, terminate the program with `exit (STATUS)'. */
void error (int status, int errnum, const char *format, ...);
A simple way to use the Gnulib error module is to obtain the two
source files `error.c' and `error.h' from the Gnulib library source
code repository at `http://git.savannah.gnu.org/gitweb/?p=gnulib.git'.
Here's a sample use:
#include "error.h"
#include
#include
char *program_name = "myprogram";
FILE *
xfopen (char const *name)
{
FILE *fp = fopen (name, "r");
if (! fp)
error (1, errno, "cannot read %s", name);
return fp;
}
Avoid casting pointers to integers if you can. Such casts greatly
reduce portability, and in most programs they are easy to avoid. In the
cases where casting pointers to integers is essential--such as, a Lisp
interpreter which stores type information as well as an address in one
word--you'll have to make explicit provisions to handle different word
sizes. You will also need to make provision for systems in which the
normal range of addresses you can get from `malloc' starts far away
from zero.
File: standards.info, Node: System Functions, Next: Internationalization, Prev: CPU Portability, Up: Writing C
5.7 Calling System Functions
============================
C implementations differ substantially. Standard C reduces but does
not eliminate the incompatibilities; meanwhile, many GNU packages still
support pre-standard compilers because this is not hard to do. This
chapter gives recommendations for how to use the more-or-less standard C
library functions to avoid unnecessary loss of portability.
* Don't use the return value of `sprintf'. It returns the number of
characters written on some systems, but not on all systems.
* Be aware that `vfprintf' is not always available.
* `main' should be declared to return type `int'. It should
terminate either by calling `exit' or by returning the integer
status code; make sure it cannot ever return an undefined value.
* Don't declare system functions explicitly.
Almost any declaration for a system function is wrong on some
system. To minimize conflicts, leave it to the system header
files to declare system functions. If the headers don't declare a
function, let it remain undeclared.
While it may seem unclean to use a function without declaring it,
in practice this works fine for most system library functions on
the systems where this really happens; thus, the disadvantage is
only theoretical. By contrast, actual declarations have
frequently caused actual conflicts.
* If you must declare a system function, don't specify the argument
types. Use an old-style declaration, not a Standard C prototype.
The more you specify about the function, the more likely a
conflict.
* In particular, don't unconditionally declare `malloc' or `realloc'.
Most GNU programs use those functions just once, in functions
conventionally named `xmalloc' and `xrealloc'. These functions
call `malloc' and `realloc', respectively, and check the results.
Because `xmalloc' and `xrealloc' are defined in your program, you
can declare them in other files without any risk of type conflict.
On most systems, `int' is the same length as a pointer; thus, the
calls to `malloc' and `realloc' work fine. For the few
exceptional systems (mostly 64-bit machines), you can use
*conditionalized* declarations of `malloc' and `realloc'--or put
these declarations in configuration files specific to those
systems.
* The string functions require special treatment. Some Unix systems
have a header file `string.h'; others have `strings.h'. Neither
file name is portable. There are two things you can do: use
Autoconf to figure out which file to include, or don't include
either file.
* If you don't include either strings file, you can't get
declarations for the string functions from the header file in the
usual way.
That causes less of a problem than you might think. The newer
standard string functions should be avoided anyway because many
systems still don't support them. The string functions you can
use are these:
strcpy strncpy strcat strncat
strlen strcmp strncmp
strchr strrchr
The copy and concatenate functions work fine without a declaration
as long as you don't use their values. Using their values without
a declaration fails on systems where the width of a pointer
differs from the width of `int', and perhaps in other cases. It
is trivial to avoid using their values, so do that.
The compare functions and `strlen' work fine without a declaration
on most systems, possibly all the ones that GNU software runs on.
You may find it necessary to declare them *conditionally* on a few
systems.
The search functions must be declared to return `char *'. Luckily,
there is no variation in the data type they return. But there is
variation in their names. Some systems give these functions the
names `index' and `rindex'; other systems use the names `strchr'
and `strrchr'. Some systems support both pairs of names, but
neither pair works on all systems.
You should pick a single pair of names and use it throughout your
program. (Nowadays, it is better to choose `strchr' and `strrchr'
for new programs, since those are the standard names.) Declare
both of those names as functions returning `char *'. On systems
which don't support those names, define them as macros in terms of
the other pair. For example, here is what to put at the beginning
of your file (or in a header) if you want to use the names
`strchr' and `strrchr' throughout:
#ifndef HAVE_STRCHR
#define strchr index
#endif
#ifndef HAVE_STRRCHR
#define strrchr rindex
#endif
char *strchr ();
char *strrchr ();
Here we assume that `HAVE_STRCHR' and `HAVE_STRRCHR' are macros
defined in systems where the corresponding functions exist. One way to
get them properly defined is to use Autoconf.
File: standards.info, Node: Internationalization, Next: Character Set, Prev: System Functions, Up: Writing C
5.8 Internationalization
========================
GNU has a library called GNU gettext that makes it easy to translate the
messages in a program into various languages. You should use this
library in every program. Use English for the messages as they appear
in the program, and let gettext provide the way to translate them into
other languages.
Using GNU gettext involves putting a call to the `gettext' macro
around each string that might need translation--like this:
printf (gettext ("Processing file `%s'..."));
This permits GNU gettext to replace the string `"Processing file
`%s'..."' with a translated version.
Once a program uses gettext, please make a point of writing calls to
`gettext' when you add new strings that call for translation.
Using GNU gettext in a package involves specifying a "text domain
name" for the package. The text domain name is used to separate the
translations for this package from the translations for other packages.
Normally, the text domain name should be the same as the name of the
package--for example, `coreutils' for the GNU core utilities.
To enable gettext to work well, avoid writing code that makes
assumptions about the structure of words or sentences. When you want
the precise text of a sentence to vary depending on the data, use two or
more alternative string constants each containing a complete sentences,
rather than inserting conditionalized words or phrases into a single
sentence framework.
Here is an example of what not to do:
printf ("%s is full", capacity > 5000000 ? "disk" : "floppy disk");
If you apply gettext to all strings, like this,
printf (gettext ("%s is full"),
capacity > 5000000 ? gettext ("disk") : gettext ("floppy disk"));
the translator will hardly know that "disk" and "floppy disk" are meant
to be substituted in the other string. Worse, in some languages (like
French) the construction will not work: the translation of the word
"full" depends on the gender of the first part of the sentence; it
happens to be not the same for "disk" as for "floppy disk".
Complete sentences can be translated without problems:
printf (capacity > 5000000 ? gettext ("disk is full")
: gettext ("floppy disk is full"));
A similar problem appears at the level of sentence structure with
this code:
printf ("# Implicit rule search has%s been done.\n",
f->tried_implicit ? "" : " not");
Adding `gettext' calls to this code cannot give correct results for all
languages, because negation in some languages requires adding words at
more than one place in the sentence. By contrast, adding `gettext'
calls does the job straightforwardly if the code starts out like this:
printf (f->tried_implicit
? "# Implicit rule search has been done.\n",
: "# Implicit rule search has not been done.\n");
Another example is this one:
printf ("%d file%s processed", nfiles,
nfiles != 1 ? "s" : "");
The problem with this example is that it assumes that plurals are made
by adding `s'. If you apply gettext to the format string, like this,
printf (gettext ("%d file%s processed"), nfiles,
nfiles != 1 ? "s" : "");
the message can use different words, but it will still be forced to use
`s' for the plural. Here is a better way, with gettext being applied to
the two strings independently:
printf ((nfiles != 1 ? gettext ("%d files processed")
: gettext ("%d file processed")),
nfiles);
But this still doesn't work for languages like Polish, which has three
plural forms: one for nfiles == 1, one for nfiles == 2, 3, 4, 22, 23,
24, ... and one for the rest. The GNU `ngettext' function solves this
problem:
printf (ngettext ("%d files processed", "%d file processed", nfiles),
nfiles);
File: standards.info, Node: Character Set, Next: Quote Characters, Prev: Internationalization, Up: Writing C
5.9 Character Set
=================
Sticking to the ASCII character set (plain text, 7-bit characters) is
preferred in GNU source code comments, text documents, and other
contexts, unless there is good reason to do something else because of
the application domain. For example, if source code deals with the
French Revolutionary calendar, it is OK if its literal strings contain
accented characters in month names like "Flore'al". Also, it is OK to
use non-ASCII characters to represent proper names of contributors in
change logs (*note Change Logs::).
If you need to use non-ASCII characters, you should normally stick
with one encoding, as one cannot in general mix encodings reliably.
File: standards.info, Node: Quote Characters, Next: Mmap, Prev: Character Set, Up: Writing C
5.10 Quote Characters
=====================
In the C locale, GNU programs should stick to plain ASCII for quotation
characters in messages to users: preferably 0x60 (``') for left quotes
and 0x27 (`'') for right quotes. It is ok, but not required, to use
locale-specific quotes in other locales.
The Gnulib (http://www.gnu.org/software/gnulib/) `quote' and
`quotearg' modules provide a reasonably straightforward way to support
locale-specific quote characters, as well as taking care of other
issues, such as quoting a filename that itself contains a quote
character. See the Gnulib documentation for usage details.
In any case, the documentation for your program should clearly
specify how it does quoting, if different than the preferred method of
``' and `''. This is especially important if the output of your
program is ever likely to be parsed by another program.
Quotation characters are a difficult area in the computing world at
this time: there are no true left or right quote characters in Latin1;
the ``' character we use was standardized there as a grave accent.
Moreover, Latin1 is still not universally usable.
Unicode contains the unambiguous quote characters required, and its
common encoding UTF-8 is upward compatible with Latin1. However,
Unicode and UTF-8 are not universally well-supported, either.
This may change over the next few years, and then we will revisit
this.
File: standards.info, Node: Mmap, Prev: Quote Characters, Up: Writing C
5.11 Mmap
=========
Don't assume that `mmap' either works on all files or fails for all
files. It may work on some files and fail on others.
The proper way to use `mmap' is to try it on the specific file for
which you want to use it--and if `mmap' doesn't work, fall back on
doing the job in another way using `read' and `write'.
The reason this precaution is needed is that the GNU kernel (the
HURD) provides a user-extensible file system, in which there can be many
different kinds of "ordinary files." Many of them support `mmap', but
some do not. It is important to make programs handle all these kinds
of files.
File: standards.info, Node: Documentation, Next: Managing Releases, Prev: Writing C, Up: Top
6 Documenting Programs
**********************
A GNU program should ideally come with full free documentation, adequate
for both reference and tutorial purposes. If the package can be
programmed or extended, the documentation should cover programming or
extending it, as well as just using it.
* Menu:
* GNU Manuals:: Writing proper manuals.
* Doc Strings and Manuals:: Compiling doc strings doesn't make a manual.
* Manual Structure Details:: Specific structure conventions.
* License for Manuals:: Writing the distribution terms for a manual.
* Manual Credits:: Giving credit to documentation contributors.
* Printed Manuals:: Mentioning the printed manual.
* NEWS File:: NEWS files supplement manuals.
* Change Logs:: Recording changes.
* Man Pages:: Man pages are secondary.
* Reading other Manuals:: How far you can go in learning
from other manuals.
File: standards.info, Node: GNU Manuals, Next: Doc Strings and Manuals, Up: Documentation
6.1 GNU Manuals
===============
The preferred document format for the GNU system is the Texinfo
formatting language. Every GNU package should (ideally) have
documentation in Texinfo both for reference and for learners. Texinfo
makes it possible to produce a good quality formatted book, using TeX,
and to generate an Info file. It is also possible to generate HTML
output from Texinfo source. See the Texinfo manual, either the
hardcopy, or the on-line version available through `info' or the Emacs
Info subsystem (`C-h i').
Nowadays some other formats such as Docbook and Sgmltexi can be
converted automatically into Texinfo. It is ok to produce the Texinfo
documentation by conversion this way, as long as it gives good results.
Make sure your manual is clear to a reader who knows nothing about
the topic and reads it straight through. This means covering basic
topics at the beginning, and advanced topics only later. This also
means defining every specialized term when it is first used.
Programmers tend to carry over the structure of the program as the
structure for its documentation. But this structure is not necessarily
good for explaining how to use the program; it may be irrelevant and
confusing for a user.
Instead, the right way to structure documentation is according to the
concepts and questions that a user will have in mind when reading it.
This principle applies at every level, from the lowest (ordering
sentences in a paragraph) to the highest (ordering of chapter topics
within the manual). Sometimes this structure of ideas matches the
structure of the implementation of the software being documented--but
often they are different. An important part of learning to write good
documentation is to learn to notice when you have unthinkingly
structured the documentation like the implementation, stop yourself,
and look for better alternatives.
For example, each program in the GNU system probably ought to be
documented in one manual; but this does not mean each program should
have its own manual. That would be following the structure of the
implementation, rather than the structure that helps the user
understand.
Instead, each manual should cover a coherent _topic_. For example,
instead of a manual for `diff' and a manual for `diff3', we have one
manual for "comparison of files" which covers both of those programs,
as well as `cmp'. By documenting these programs together, we can make
the whole subject clearer.
The manual which discusses a program should certainly document all of
the program's command-line options and all of its commands. It should
give examples of their use. But don't organize the manual as a list of
features. Instead, organize it logically, by subtopics. Address the
questions that a user will ask when thinking about the job that the
program does. Don't just tell the reader what each feature can do--say
what jobs it is good for, and show how to use it for those jobs.
Explain what is recommended usage, and what kinds of usage users should
avoid.
In general, a GNU manual should serve both as tutorial and reference.
It should be set up for convenient access to each topic through Info,
and for reading straight through (appendixes aside). A GNU manual
should give a good introduction to a beginner reading through from the
start, and should also provide all the details that hackers want. The
Bison manual is a good example of this--please take a look at it to see
what we mean.
That is not as hard as it first sounds. Arrange each chapter as a
logical breakdown of its topic, but order the sections, and write their
text, so that reading the chapter straight through makes sense. Do
likewise when structuring the book into chapters, and when structuring a
section into paragraphs. The watchword is, _at each point, address the
most fundamental and important issue raised by the preceding text._
If necessary, add extra chapters at the beginning of the manual which
are purely tutorial and cover the basics of the subject. These provide
the framework for a beginner to understand the rest of the manual. The
Bison manual provides a good example of how to do this.
To serve as a reference, a manual should have an Index that list all
the functions, variables, options, and important concepts that are part
of the program. One combined Index should do for a short manual, but
sometimes for a complex package it is better to use multiple indices.
The Texinfo manual includes advice on preparing good index entries, see
*note Making Index Entries: (texinfo)Index Entries, and see *note
Defining the Entries of an Index: (texinfo)Indexing Commands.
Don't use Unix man pages as a model for how to write GNU
documentation; most of them are terse, badly structured, and give
inadequate explanation of the underlying concepts. (There are, of
course, some exceptions.) Also, Unix man pages use a particular format
which is different from what we use in GNU manuals.
Please include an email address in the manual for where to report
bugs _in the text of the manual_.
Please do not use the term "pathname" that is used in Unix
documentation; use "file name" (two words) instead. We use the term
"path" only for search paths, which are lists of directory names.
Please do not use the term "illegal" to refer to erroneous input to
a computer program. Please use "invalid" for this, and reserve the
term "illegal" for activities prohibited by law.
Please do not write `()' after a function name just to indicate it
is a function. `foo ()' is not a function, it is a function call with
no arguments.
File: standards.info, Node: Doc Strings and Manuals, Next: Manual Structure Details, Prev: GNU Manuals, Up: Documentation
6.2 Doc Strings and Manuals
===========================
Some programming systems, such as Emacs, provide a documentation string
for each function, command or variable. You may be tempted to write a
reference manual by compiling the documentation strings and writing a
little additional text to go around them--but you must not do it. That
approach is a fundamental mistake. The text of well-written
documentation strings will be entirely wrong for a manual.
A documentation string needs to stand alone--when it appears on the
screen, there will be no other text to introduce or explain it.
Meanwhile, it can be rather informal in style.
The text describing a function or variable in a manual must not stand
alone; it appears in the context of a section or subsection. Other text
at the beginning of the section should explain some of the concepts, and
should often make some general points that apply to several functions or
variables. The previous descriptions of functions and variables in the
section will also have given information about the topic. A description
written to stand alone would repeat some of that information; this
redundancy looks bad. Meanwhile, the informality that is acceptable in
a documentation string is totally unacceptable in a manual.
The only good way to use documentation strings in writing a good
manual is to use them as a source of information for writing good text.
File: standards.info, Node: Manual Structure Details, Next: License for Manuals, Prev: Doc Strings and Manuals, Up: Documentation
6.3 Manual Structure Details
============================
The title page of the manual should state the version of the programs or
packages documented in the manual. The Top node of the manual should
also contain this information. If the manual is changing more
frequently than or independent of the program, also state a version
number for the manual in both of these places.
Each program documented in the manual should have a node named
`PROGRAM Invocation' or `Invoking PROGRAM'. This node (together with
its subnodes, if any) should describe the program's command line
arguments and how to run it (the sort of information people would look
for in a man page). Start with an `@example' containing a template for
all the options and arguments that the program uses.
Alternatively, put a menu item in some menu whose item name fits one
of the above patterns. This identifies the node which that item points
to as the node for this purpose, regardless of the node's actual name.
The `--usage' feature of the Info reader looks for such a node or
menu item in order to find the relevant text, so it is essential for
every Texinfo file to have one.
If one manual describes several programs, it should have such a node
for each program described in the manual.
File: standards.info, Node: License for Manuals, Next: Manual Credits, Prev: Manual Structure Details, Up: Documentation
6.4 License for Manuals
=======================
Please use the GNU Free Documentation License for all GNU manuals that
are more than a few pages long. Likewise for a collection of short
documents--you only need one copy of the GNU FDL for the whole
collection. For a single short document, you can use a very permissive
non-copyleft license, to avoid taking up space with a long license.
See `http://www.gnu.org/copyleft/fdl-howto.html' for more explanation
of how to employ the GFDL.
Note that it is not obligatory to include a copy of the GNU GPL or
GNU LGPL in a manual whose license is neither the GPL nor the LGPL. It
can be a good idea to include the program's license in a large manual;
in a short manual, whose size would be increased considerably by
including the program's license, it is probably better not to include
it.
File: standards.info, Node: Manual Credits, Next: Printed Manuals, Prev: License for Manuals, Up: Documentation
6.5 Manual Credits
==================
Please credit the principal human writers of the manual as the authors,
on the title page of the manual. If a company sponsored the work, thank
the company in a suitable place in the manual, but do not cite the
company as an author.
File: standards.info, Node: Printed Manuals, Next: NEWS File, Prev: Manual Credits, Up: Documentation
6.6 Printed Manuals
===================
The FSF publishes some GNU manuals in printed form. To encourage sales
of these manuals, the on-line versions of the manual should mention at
the very start that the printed manual is available and should point at
information for getting it--for instance, with a link to the page
`http://www.gnu.org/order/order.html'. This should not be included in
the printed manual, though, because there it is redundant.
It is also useful to explain in the on-line forms of the manual how
the user can print out the manual from the sources.
File: standards.info, Node: NEWS File, Next: Change Logs, Prev: Printed Manuals, Up: Documentation
6.7 The NEWS File
=================
In addition to its manual, the package should have a file named `NEWS'
which contains a list of user-visible changes worth mentioning. In
each new release, add items to the front of the file and identify the
version they pertain to. Don't discard old items; leave them in the
file after the newer items. This way, a user upgrading from any
previous version can see what is new.
If the `NEWS' file gets very long, move some of the older items into
a file named `ONEWS' and put a note at the end referring the user to
that file.
File: standards.info, Node: Change Logs, Next: Man Pages, Prev: NEWS File, Up: Documentation
6.8 Change Logs
===============
Keep a change log to describe all the changes made to program source
files. The purpose of this is so that people investigating bugs in the
future will know about the changes that might have introduced the bug.
Often a new bug can be found by looking at what was recently changed.
More importantly, change logs can help you eliminate conceptual
inconsistencies between different parts of a program, by giving you a
history of how the conflicting concepts arose and who they came from.
* Menu:
* Change Log Concepts::
* Style of Change Logs::
* Simple Changes::
* Conditional Changes::
* Indicating the Part Changed::
File: standards.info, Node: Change Log Concepts, Next: Style of Change Logs, Up: Change Logs
6.8.1 Change Log Concepts
-------------------------
You can think of the change log as a conceptual "undo list" which
explains how earlier versions were different from the current version.
People can see the current version; they don't need the change log to
tell them what is in it. What they want from a change log is a clear
explanation of how the earlier version differed.
The change log file is normally called `ChangeLog' and covers an
entire directory. Each directory can have its own change log, or a
directory can use the change log of its parent directory-it's up to you.
Another alternative is to record change log information with a
version control system such as RCS or CVS. This can be converted
automatically to a `ChangeLog' file using `rcs2log'; in Emacs, the
command `C-x v a' (`vc-update-change-log') does the job.
There's no need to describe the full purpose of the changes or how
they work together. If you think that a change calls for explanation,
you're probably right. Please do explain it--but please put the
explanation in comments in the code, where people will see it whenever
they see the code. For example, "New function" is enough for the
change log when you add a function, because there should be a comment
before the function definition to explain what it does.
In the past, we recommended not mentioning changes in non-software
files (manuals, help files, etc.) in change logs. However, we've been
advised that it is a good idea to include them, for the sake of
copyright records.
However, sometimes it is useful to write one line to describe the
overall purpose of a batch of changes.
The easiest way to add an entry to `ChangeLog' is with the Emacs
command `M-x add-change-log-entry'. An entry should have an asterisk,
the name of the changed file, and then in parentheses the name of the
changed functions, variables or whatever, followed by a colon. Then
describe the changes you made to that function or variable.
File: standards.info, Node: Style of Change Logs, Next: Simple Changes, Prev: Change Log Concepts, Up: Change Logs
6.8.2 Style of Change Logs
--------------------------
Here are some simple examples of change log entries, starting with the
header line that says who made the change and when it was installed,
followed by descriptions of specific changes. (These examples are
drawn from Emacs and GCC.)
1998-08-17 Richard Stallman
* register.el (insert-register): Return nil.
(jump-to-register): Likewise.
* sort.el (sort-subr): Return nil.
* tex-mode.el (tex-bibtex-file, tex-file, tex-region):
Restart the tex shell if process is gone or stopped.
(tex-shell-running): New function.
* expr.c (store_one_arg): Round size up for move_block_to_reg.
(expand_call): Round up when emitting USE insns.
* stmt.c (assign_parms): Round size up for move_block_from_reg.
It's important to name the changed function or variable in full.
Don't abbreviate function or variable names, and don't combine them.
Subsequent maintainers will often search for a function name to find all
the change log entries that pertain to it; if you abbreviate the name,
they won't find it when they search.
For example, some people are tempted to abbreviate groups of function
names by writing `* register.el ({insert,jump-to}-register)'; this is
not a good idea, since searching for `jump-to-register' or
`insert-register' would not find that entry.
Separate unrelated change log entries with blank lines. When two
entries represent parts of the same change, so that they work together,
then don't put blank lines between them. Then you can omit the file
name and the asterisk when successive entries are in the same file.
Break long lists of function names by closing continued lines with
`)', rather than `,', and opening the continuation with `(' as in this
example:
* keyboard.c (menu_bar_items, tool_bar_items)
(Fexecute_extended_command): Deal with `keymap' property.
When you install someone else's changes, put the contributor's name
in the change log entry rather than in the text of the entry. In other
words, write this:
2002-07-14 John Doe
* sewing.c: Make it sew.
rather than this:
2002-07-14 Usual Maintainer
* sewing.c: Make it sew. Patch by jdoe@gnu.org.
As for the date, that should be the date you applied the change.
File: standards.info, Node: Simple Changes, Next: Conditional Changes, Prev: Style of Change Logs, Up: Change Logs
6.8.3 Simple Changes
--------------------
Certain simple kinds of changes don't need much detail in the change
log.
When you change the calling sequence of a function in a simple
fashion, and you change all the callers of the function to use the new
calling sequence, there is no need to make individual entries for all
the callers that you changed. Just write in the entry for the function
being called, "All callers changed"--like this:
* keyboard.c (Fcommand_execute): New arg SPECIAL.
All callers changed.
When you change just comments or doc strings, it is enough to write
an entry for the file, without mentioning the functions. Just "Doc
fixes" is enough for the change log.
There's no technical need to make change log entries for
documentation files. This is because documentation is not susceptible
to bugs that are hard to fix. Documentation does not consist of parts
that must interact in a precisely engineered fashion. To correct an
error, you need not know the history of the erroneous passage; it is
enough to compare what the documentation says with the way the program
actually works.
However, you should keep change logs for documentation files when the
project gets copyright assignments from its contributors, so as to make
the records of authorship more accurate.
File: standards.info, Node: Conditional Changes, Next: Indicating the Part Changed, Prev: Simple Changes, Up: Change Logs
6.8.4 Conditional Changes
-------------------------
C programs often contain compile-time `#if' conditionals. Many changes
are conditional; sometimes you add a new definition which is entirely
contained in a conditional. It is very useful to indicate in the
change log the conditions for which the change applies.
Our convention for indicating conditional changes is to use square
brackets around the name of the condition.
Here is a simple example, describing a change which is conditional
but does not have a function or entity name associated with it:
* xterm.c [SOLARIS2]: Include string.h.
Here is an entry describing a new definition which is entirely
conditional. This new definition for the macro `FRAME_WINDOW_P' is
used only when `HAVE_X_WINDOWS' is defined:
* frame.h [HAVE_X_WINDOWS] (FRAME_WINDOW_P): Macro defined.
Here is an entry for a change within the function `init_display',
whose definition as a whole is unconditional, but the changes themselves
are contained in a `#ifdef HAVE_LIBNCURSES' conditional:
* dispnew.c (init_display) [HAVE_LIBNCURSES]: If X, call tgetent.
Here is an entry for a change that takes affect only when a certain
macro is _not_ defined:
(gethostname) [!HAVE_SOCKETS]: Replace with winsock version.
File: standards.info, Node: Indicating the Part Changed, Prev: Conditional Changes, Up: Change Logs
6.8.5 Indicating the Part Changed
---------------------------------
Indicate the part of a function which changed by using angle brackets
enclosing an indication of what the changed part does. Here is an entry
for a change in the part of the function `sh-while-getopts' that deals
with `sh' commands:
* progmodes/sh-script.el (sh-while-getopts) : Handle case that
user-specified option string is empty.
File: standards.info, Node: Man Pages, Next: Reading other Manuals, Prev: Change Logs, Up: Documentation
6.9 Man Pages
=============
In the GNU project, man pages are secondary. It is not necessary or
expected for every GNU program to have a man page, but some of them do.
It's your choice whether to include a man page in your program.
When you make this decision, consider that supporting a man page
requires continual effort each time the program is changed. The time
you spend on the man page is time taken away from more useful work.
For a simple program which changes little, updating the man page may
be a small job. Then there is little reason not to include a man page,
if you have one.
For a large program that changes a great deal, updating a man page
may be a substantial burden. If a user offers to donate a man page,
you may find this gift costly to accept. It may be better to refuse
the man page unless the same person agrees to take full responsibility
for maintaining it--so that you can wash your hands of it entirely. If
this volunteer later ceases to do the job, then don't feel obliged to
pick it up yourself; it may be better to withdraw the man page from the
distribution until someone else agrees to update it.
When a program changes only a little, you may feel that the
discrepancies are small enough that the man page remains useful without
updating. If so, put a prominent note near the beginning of the man
page explaining that you don't maintain it and that the Texinfo manual
is more authoritative. The note should say how to access the Texinfo
documentation.
Be sure that man pages include a copyright statement and free
license. The simple all-permissive license is appropriate for simple
man pages (*note License Notices for Other Files: (maintain)License
Notices for Other Files.).
For long man pages, with enough explanation and documentation that
they can be considered true manuals, use the GFDL (*note License for
Manuals::).
Finally, the GNU help2man program
(`http://www.gnu.org/software/help2man/') is one way to automate
generation of a man page, in this case from `--help' output. This is
sufficient in many cases.
File: standards.info, Node: Reading other Manuals, Prev: Man Pages, Up: Documentation
6.10 Reading other Manuals
==========================
There may be non-free books or documentation files that describe the
program you are documenting.
It is ok to use these documents for reference, just as the author of
a new algebra textbook can read other books on algebra. A large portion
of any non-fiction book consists of facts, in this case facts about how
a certain program works, and these facts are necessarily the same for
everyone who writes about the subject. But be careful not to copy your
outline structure, wording, tables or examples from preexisting non-free
documentation. Copying from free documentation may be ok; please check
with the FSF about the individual case.
File: standards.info, Node: Managing Releases, Next: References, Prev: Documentation, Up: Top
7 The Release Process
*********************
Making a release is more than just bundling up your source files in a
tar file and putting it up for FTP. You should set up your software so
that it can be configured to run on a variety of systems. Your Makefile
should conform to the GNU standards described below, and your directory
layout should also conform to the standards discussed below. Doing so
makes it easy to include your package into the larger framework of all
GNU software.
* Menu:
* Configuration:: How configuration of GNU packages should work.
* Makefile Conventions:: Makefile conventions.
* Releases:: Making releases
File: standards.info, Node: Configuration, Next: Makefile Conventions, Up: Managing Releases
7.1 How Configuration Should Work
=================================
Each GNU distribution should come with a shell script named
`configure'. This script is given arguments which describe the kind of
machine and system you want to compile the program for. The
`configure' script must record the configuration options so that they
affect compilation.
The description here is the specification of the interface for the
`configure' script in GNU packages. Many packages implement it using
GNU Autoconf (*note Introduction: (autoconf)Top.) and/or GNU Automake
(*note Introduction: (automake)Top.), but you do not have to use these
tools. You can implement it any way you like; for instance, by making
`configure' be a wrapper around a completely different configuration
system.
Another way for the `configure' script to operate is to make a link
from a standard name such as `config.h' to the proper configuration
file for the chosen system. If you use this technique, the
distribution should _not_ contain a file named `config.h'. This is so
that people won't be able to build the program without configuring it
first.
Another thing that `configure' can do is to edit the Makefile. If
you do this, the distribution should _not_ contain a file named
`Makefile'. Instead, it should include a file `Makefile.in' which
contains the input used for editing. Once again, this is so that people
won't be able to build the program without configuring it first.
If `configure' does write the `Makefile', then `Makefile' should
have a target named `Makefile' which causes `configure' to be rerun,
setting up the same configuration that was set up last time. The files
that `configure' reads should be listed as dependencies of `Makefile'.
All the files which are output from the `configure' script should
have comments at the beginning explaining that they were generated
automatically using `configure'. This is so that users won't think of
trying to edit them by hand.
The `configure' script should write a file named `config.status'
which describes which configuration options were specified when the
program was last configured. This file should be a shell script which,
if run, will recreate the same configuration.
The `configure' script should accept an option of the form
`--srcdir=DIRNAME' to specify the directory where sources are found (if
it is not the current directory). This makes it possible to build the
program in a separate directory, so that the actual source directory is
not modified.
If the user does not specify `--srcdir', then `configure' should
check both `.' and `..' to see if it can find the sources. If it finds
the sources in one of these places, it should use them from there.
Otherwise, it should report that it cannot find the sources, and should
exit with nonzero status.
Usually the easy way to support `--srcdir' is by editing a
definition of `VPATH' into the Makefile. Some rules may need to refer
explicitly to the specified source directory. To make this possible,
`configure' can add to the Makefile a variable named `srcdir' whose
value is precisely the specified directory.
In addition, the `configure' script should take options
corresponding to most of the standard directory variables (*note
Directory Variables::). Here is the list:
--prefix --exec-prefix --bindir --sbindir --libexecdir --sysconfdir
--sharedstatedir --localstatedir --libdir --includedir --oldincludedir
--datarootdir --datadir --infodir --localedir --mandir --docdir
--htmldir --dvidir --pdfdir --psdir
The `configure' script should also take an argument which specifies
the type of system to build the program for. This argument should look
like this:
CPU-COMPANY-SYSTEM
For example, an Athlon-based GNU/Linux system might be
`i686-pc-linux-gnu'.
The `configure' script needs to be able to decode all plausible
alternatives for how to describe a machine. Thus,
`athlon-pc-gnu/linux' would be a valid alias. There is a shell script
called `config.sub'
(http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.sub;hb=HEAD)
that you can use as a subroutine to validate system types and
canonicalize aliases.
The `configure' script should also take the option
`--build=BUILDTYPE', which should be equivalent to a plain BUILDTYPE
argument. For example, `configure --build=i686-pc-linux-gnu' is
equivalent to `configure i686-pc-linux-gnu'. When the build type is
not specified by an option or argument, the `configure' script should
normally guess it using the shell script `config.guess'
(http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.guess;hb=HEAD).
Other options are permitted to specify in more detail the software
or hardware present on the machine, to include or exclude optional parts
of the package, or to adjust the name of some tools or arguments to
them:
`--enable-FEATURE[=PARAMETER]'
Configure the package to build and install an optional user-level
facility called FEATURE. This allows users to choose which
optional features to include. Giving an optional PARAMETER of
`no' should omit FEATURE, if it is built by default.
No `--enable' option should *ever* cause one feature to replace
another. No `--enable' option should ever substitute one useful
behavior for another useful behavior. The only proper use for
`--enable' is for questions of whether to build part of the program
or exclude it.
`--with-PACKAGE'
The package PACKAGE will be installed, so configure this package
to work with PACKAGE.
Possible values of PACKAGE include `gnu-as' (or `gas'), `gnu-ld',
`gnu-libc', `gdb', `x', and `x-toolkit'.
Do not use a `--with' option to specify the file name to use to
find certain files. That is outside the scope of what `--with'
options are for.
`VARIABLE=VALUE'
Set the value of the variable VARIABLE to VALUE. This is used to
override the default values of commands or arguments in the build
process. For example, the user could issue `configure CFLAGS=-g
CXXFLAGS=-g' to build with debugging information and without the
default optimization.
Specifying variables as arguments to `configure', like this:
./configure CC=gcc
is preferable to setting them in environment variables:
CC=gcc ./configure
as it helps to recreate the same configuration later with
`config.status'.
All `configure' scripts should accept all of the "detail" options
and the variable settings, whether or not they make any difference to
the particular package at hand. In particular, they should accept any
option that starts with `--with-' or `--enable-'. This is so users
will be able to configure an entire GNU source tree at once with a
single set of options.
You will note that the categories `--with-' and `--enable-' are
narrow: they *do not* provide a place for any sort of option you might
think of. That is deliberate. We want to limit the possible
configuration options in GNU software. We do not want GNU programs to
have idiosyncratic configuration options.
Packages that perform part of the compilation process may support
cross-compilation. In such a case, the host and target machines for the
program may be different.
The `configure' script should normally treat the specified type of
system as both the host and the target, thus producing a program which
works for the same type of machine that it runs on.
To compile a program to run on a host type that differs from the
build type, use the configure option `--host=HOSTTYPE', where HOSTTYPE
uses the same syntax as BUILDTYPE. The host type normally defaults to
the build type.
To configure a cross-compiler, cross-assembler, or what have you, you
should specify a target different from the host, using the configure
option `--target=TARGETTYPE'. The syntax for TARGETTYPE is the same as
for the host type. So the command would look like this:
./configure --host=HOSTTYPE --target=TARGETTYPE
The target type normally defaults to the host type. Programs for
which cross-operation is not meaningful need not accept the `--target'
option, because configuring an entire operating system for
cross-operation is not a meaningful operation.
Some programs have ways of configuring themselves automatically. If
your program is set up to do this, your `configure' script can simply
ignore most of its arguments.
File: standards.info, Node: Makefile Conventions, Next: Releases, Prev: Configuration, Up: Managing Releases
7.2 Makefile Conventions
========================
This node describes conventions for writing the Makefiles for GNU
programs. Using Automake will help you write a Makefile that follows
these conventions. For more information on portable Makefiles, see
POSIX and *note Portable Make Programming: (autoconf)Portable Make.
* Menu:
* Makefile Basics:: General conventions for Makefiles.
* Utilities in Makefiles:: Utilities to be used in Makefiles.
* Command Variables:: Variables for specifying commands.
* DESTDIR:: Supporting staged installs.
* Directory Variables:: Variables for installation directories.
* Standard Targets:: Standard targets for users.
* Install Command Categories:: Three categories of commands in the `install'
rule: normal, pre-install and post-install.
File: standards.info, Node: Makefile Basics, Next: Utilities in Makefiles, Up: Makefile Conventions
7.2.1 General Conventions for Makefiles
---------------------------------------
Every Makefile should contain this line:
SHELL = /bin/sh
to avoid trouble on systems where the `SHELL' variable might be
inherited from the environment. (This is never a problem with GNU
`make'.)
Different `make' programs have incompatible suffix lists and
implicit rules, and this sometimes creates confusion or misbehavior. So
it is a good idea to set the suffix list explicitly using only the
suffixes you need in the particular Makefile, like this:
.SUFFIXES:
.SUFFIXES: .c .o
The first line clears out the suffix list, the second introduces all
suffixes which may be subject to implicit rules in this Makefile.
Don't assume that `.' is in the path for command execution. When
you need to run programs that are a part of your package during the
make, please make sure that it uses `./' if the program is built as
part of the make or `$(srcdir)/' if the file is an unchanging part of
the source code. Without one of these prefixes, the current search
path is used.
The distinction between `./' (the "build directory") and
`$(srcdir)/' (the "source directory") is important because users can
build in a separate directory using the `--srcdir' option to
`configure'. A rule of the form:
foo.1 : foo.man sedscript
sed -e sedscript foo.man > foo.1
will fail when the build directory is not the source directory, because
`foo.man' and `sedscript' are in the source directory.
When using GNU `make', relying on `VPATH' to find the source file
will work in the case where there is a single dependency file, since
the `make' automatic variable `$<' will represent the source file
wherever it is. (Many versions of `make' set `$<' only in implicit
rules.) A Makefile target like
foo.o : bar.c
$(CC) -I. -I$(srcdir) $(CFLAGS) -c bar.c -o foo.o
should instead be written as
foo.o : bar.c
$(CC) -I. -I$(srcdir) $(CFLAGS) -c $< -o $@
in order to allow `VPATH' to work correctly. When the target has
multiple dependencies, using an explicit `$(srcdir)' is the easiest way
to make the rule work well. For example, the target above for `foo.1'
is best written as:
foo.1 : foo.man sedscript
sed -e $(srcdir)/sedscript $(srcdir)/foo.man > $@
GNU distributions usually contain some files which are not source
files--for example, Info files, and the output from Autoconf, Automake,
Bison or Flex. Since these files normally appear in the source
directory, they should always appear in the source directory, not in the
build directory. So Makefile rules to update them should put the
updated files in the source directory.
However, if a file does not appear in the distribution, then the
Makefile should not put it in the source directory, because building a
program in ordinary circumstances should not modify the source directory
in any way.
Try to make the build and installation targets, at least (and all
their subtargets) work correctly with a parallel `make'.
File: standards.info, Node: Utilities in Makefiles, Next: Command Variables, Prev: Makefile Basics, Up: Makefile Conventions
7.2.2 Utilities in Makefiles
----------------------------
Write the Makefile commands (and any shell scripts, such as
`configure') to run under `sh' (both the traditional Bourne shell and
the POSIX shell), not `csh'. Don't use any special features of `ksh'
or `bash', or POSIX features not widely supported in traditional Bourne
`sh'.
The `configure' script and the Makefile rules for building and
installation should not use any utilities directly except these:
awk cat cmp cp diff echo egrep expr false grep install-info
ln ls mkdir mv pwd rm rmdir sed sleep sort tar test touch tr true
Compression programs such as `gzip' can be used in the `dist' rule.
Generally, stick to the widely-supported (usually POSIX-specified)
options and features of these programs. For example, don't use `mkdir
-p', convenient as it may be, because a few systems don't support it at
all and with others, it is not safe for parallel execution. For a list
of known incompatibilities, see *note Portable Shell Programming:
(autoconf)Portable Shell.
It is a good idea to avoid creating symbolic links in makefiles,
since a few file systems don't support them.
The Makefile rules for building and installation can also use
compilers and related programs, but should do so via `make' variables
so that the user can substitute alternatives. Here are some of the
programs we mean:
ar bison cc flex install ld ldconfig lex
make makeinfo ranlib texi2dvi yacc
Use the following `make' variables to run those programs:
$(AR) $(BISON) $(CC) $(FLEX) $(INSTALL) $(LD) $(LDCONFIG) $(LEX)
$(MAKE) $(MAKEINFO) $(RANLIB) $(TEXI2DVI) $(YACC)
When you use `ranlib' or `ldconfig', you should make sure nothing
bad happens if the system does not have the program in question.
Arrange to ignore an error from that command, and print a message before
the command to tell the user that failure of this command does not mean
a problem. (The Autoconf `AC_PROG_RANLIB' macro can help with this.)
If you use symbolic links, you should implement a fallback for
systems that don't have symbolic links.
Additional utilities that can be used via Make variables are:
chgrp chmod chown mknod
It is ok to use other utilities in Makefile portions (or scripts)
intended only for particular systems where you know those utilities
exist.
File: standards.info, Node: Command Variables, Next: DESTDIR, Prev: Utilities in Makefiles, Up: Makefile Conventions
7.2.3 Variables for Specifying Commands
---------------------------------------
Makefiles should provide variables for overriding certain commands,
options, and so on.
In particular, you should run most utility programs via variables.
Thus, if you use Bison, have a variable named `BISON' whose default
value is set with `BISON = bison', and refer to it with `$(BISON)'
whenever you need to use Bison.
File management utilities such as `ln', `rm', `mv', and so on, need
not be referred to through variables in this way, since users don't
need to replace them with other programs.
Each program-name variable should come with an options variable that
is used to supply options to the program. Append `FLAGS' to the
program-name variable name to get the options variable name--for
example, `BISONFLAGS'. (The names `CFLAGS' for the C compiler,
`YFLAGS' for yacc, and `LFLAGS' for lex, are exceptions to this rule,
but we keep them because they are standard.) Use `CPPFLAGS' in any
compilation command that runs the preprocessor, and use `LDFLAGS' in
any compilation command that does linking as well as in any direct use
of `ld'.
If there are C compiler options that _must_ be used for proper
compilation of certain files, do not include them in `CFLAGS'. Users
expect to be able to specify `CFLAGS' freely themselves. Instead,
arrange to pass the necessary options to the C compiler independently
of `CFLAGS', by writing them explicitly in the compilation commands or
by defining an implicit rule, like this:
CFLAGS = -g
ALL_CFLAGS = -I. $(CFLAGS)
.c.o:
$(CC) -c $(CPPFLAGS) $(ALL_CFLAGS) $<
Do include the `-g' option in `CFLAGS', because that is not
_required_ for proper compilation. You can consider it a default that
is only recommended. If the package is set up so that it is compiled
with GCC by default, then you might as well include `-O' in the default
value of `CFLAGS' as well.
Put `CFLAGS' last in the compilation command, after other variables
containing compiler options, so the user can use `CFLAGS' to override
the others.
`CFLAGS' should be used in every invocation of the C compiler, both
those which do compilation and those which do linking.
Every Makefile should define the variable `INSTALL', which is the
basic command for installing a file into the system.
Every Makefile should also define the variables `INSTALL_PROGRAM'
and `INSTALL_DATA'. (The default for `INSTALL_PROGRAM' should be
`$(INSTALL)'; the default for `INSTALL_DATA' should be `${INSTALL} -m
644'.) Then it should use those variables as the commands for actual
installation, for executables and non-executables respectively.
Minimal use of these variables is as follows:
$(INSTALL_PROGRAM) foo $(bindir)/foo
$(INSTALL_DATA) libfoo.a $(libdir)/libfoo.a
However, it is preferable to support a `DESTDIR' prefix on the
target files, as explained in the next section.
It is acceptable, but not required, to install multiple files in one
command, with the final argument being a directory, as in:
$(INSTALL_PROGRAM) foo bar baz $(bindir)
File: standards.info, Node: DESTDIR, Next: Directory Variables, Prev: Command Variables, Up: Makefile Conventions
7.2.4 `DESTDIR': support for staged installs
--------------------------------------------
`DESTDIR' is a variable prepended to each installed target file, like
this:
$(INSTALL_PROGRAM) foo $(DESTDIR)$(bindir)/foo
$(INSTALL_DATA) libfoo.a $(DESTDIR)$(libdir)/libfoo.a
The `DESTDIR' variable is specified by the user on the `make'
command line as an absolute file name. For example:
make DESTDIR=/tmp/stage install
`DESTDIR' should be supported only in the `install*' and `uninstall*'
targets, as those are the only targets where it is useful.
If your installation step would normally install
`/usr/local/bin/foo' and `/usr/local/lib/libfoo.a', then an
installation invoked as in the example above would install
`/tmp/stage/usr/local/bin/foo' and `/tmp/stage/usr/local/lib/libfoo.a'
instead.
Prepending the variable `DESTDIR' to each target in this way
provides for "staged installs", where the installed files are not
placed directly into their expected location but are instead copied
into a temporary location (`DESTDIR'). However, installed files
maintain their relative directory structure and any embedded file names
will not be modified.
You should not set the value of `DESTDIR' in your `Makefile' at all;
then the files are installed into their expected locations by default.
Also, specifying `DESTDIR' should not change the operation of the
software in any way, so its value should not be included in any file
contents.
`DESTDIR' support is commonly used in package creation. It is also
helpful to users who want to understand what a given package will
install where, and to allow users who don't normally have permissions
to install into protected areas to build and install before gaining
those permissions. Finally, it can be useful with tools such as
`stow', where code is installed in one place but made to appear to be
installed somewhere else using symbolic links or special mount
operations. So, we strongly recommend GNU packages support `DESTDIR',
though it is not an absolute requirement.
File: standards.info, Node: Directory Variables, Next: Standard Targets, Prev: DESTDIR, Up: Makefile Conventions
7.2.5 Variables for Installation Directories
--------------------------------------------
Installation directories should always be named by variables, so it is
easy to install in a nonstandard place. The standard names for these
variables and the values they should have in GNU packages are described
below. They are based on a standard file system layout; variants of it
are used in GNU/Linux and other modern operating systems.
Installers are expected to override these values when calling `make'
(e.g., `make prefix=/usr install' or `configure' (e.g., `configure
--prefix=/usr'). GNU packages should not try to guess which value
should be appropriate for these variables on the system they are being
installed onto: use the default settings specified here so that all GNU
packages behave identically, allowing the installer to achieve any
desired layout.
These first two variables set the root for the installation. All the
other installation directories should be subdirectories of one of these
two, and nothing should be directly installed into these two
directories.
`prefix'
A prefix used in constructing the default values of the variables
listed below. The default value of `prefix' should be
`/usr/local'. When building the complete GNU system, the prefix
will be empty and `/usr' will be a symbolic link to `/'. (If you
are using Autoconf, write it as `@prefix@'.)
Running `make install' with a different value of `prefix' from the
one used to build the program should _not_ recompile the program.
`exec_prefix'
A prefix used in constructing the default values of some of the
variables listed below. The default value of `exec_prefix' should
be `$(prefix)'. (If you are using Autoconf, write it as
`@exec_prefix@'.)
Generally, `$(exec_prefix)' is used for directories that contain
machine-specific files (such as executables and subroutine
libraries), while `$(prefix)' is used directly for other
directories.
Running `make install' with a different value of `exec_prefix'
from the one used to build the program should _not_ recompile the
program.
Executable programs are installed in one of the following
directories.
`bindir'
The directory for installing executable programs that users can
run. This should normally be `/usr/local/bin', but write it as
`$(exec_prefix)/bin'. (If you are using Autoconf, write it as
`@bindir@'.)
`sbindir'
The directory for installing executable programs that can be run
from the shell, but are only generally useful to system
administrators. This should normally be `/usr/local/sbin', but
write it as `$(exec_prefix)/sbin'. (If you are using Autoconf,
write it as `@sbindir@'.)
`libexecdir'
The directory for installing executable programs to be run by other
programs rather than by users. This directory should normally be
`/usr/local/libexec', but write it as `$(exec_prefix)/libexec'.
(If you are using Autoconf, write it as `@libexecdir@'.)
The definition of `libexecdir' is the same for all packages, so
you should install your data in a subdirectory thereof. Most
packages install their data under `$(libexecdir)/PACKAGE-NAME/',
possibly within additional subdirectories thereof, such as
`$(libexecdir)/PACKAGE-NAME/MACHINE/VERSION'.
Data files used by the program during its execution are divided into
categories in two ways.
* Some files are normally modified by programs; others are never
normally modified (though users may edit some of these).
* Some files are architecture-independent and can be shared by all
machines at a site; some are architecture-dependent and can be
shared only by machines of the same kind and operating system;
others may never be shared between two machines.
This makes for six different possibilities. However, we want to
discourage the use of architecture-dependent files, aside from object
files and libraries. It is much cleaner to make other data files
architecture-independent, and it is generally not hard.
Here are the variables Makefiles should use to specify directories
to put these various kinds of files in:
`datarootdir'
The root of the directory tree for read-only
architecture-independent data files. This should normally be
`/usr/local/share', but write it as `$(prefix)/share'. (If you
are using Autoconf, write it as `@datarootdir@'.) `datadir''s
default value is based on this variable; so are `infodir',
`mandir', and others.
`datadir'
The directory for installing idiosyncratic read-only
architecture-independent data files for this program. This is
usually the same place as `datarootdir', but we use the two
separate variables so that you can move these program-specific
files without altering the location for Info files, man pages, etc.
This should normally be `/usr/local/share', but write it as
`$(datarootdir)'. (If you are using Autoconf, write it as
`@datadir@'.)
The definition of `datadir' is the same for all packages, so you
should install your data in a subdirectory thereof. Most packages
install their data under `$(datadir)/PACKAGE-NAME/'.
`sysconfdir'
The directory for installing read-only data files that pertain to a
single machine-that is to say, files for configuring a host.
Mailer and network configuration files, `/etc/passwd', and so
forth belong here. All the files in this directory should be
ordinary ASCII text files. This directory should normally be
`/usr/local/etc', but write it as `$(prefix)/etc'. (If you are
using Autoconf, write it as `@sysconfdir@'.)
Do not install executables here in this directory (they probably
belong in `$(libexecdir)' or `$(sbindir)'). Also do not install
files that are modified in the normal course of their use (programs
whose purpose is to change the configuration of the system
excluded). Those probably belong in `$(localstatedir)'.
`sharedstatedir'
The directory for installing architecture-independent data files
which the programs modify while they run. This should normally be
`/usr/local/com', but write it as `$(prefix)/com'. (If you are
using Autoconf, write it as `@sharedstatedir@'.)
`localstatedir'
The directory for installing data files which the programs modify
while they run, and that pertain to one specific machine. Users
should never need to modify files in this directory to configure
the package's operation; put such configuration information in
separate files that go in `$(datadir)' or `$(sysconfdir)'.
`$(localstatedir)' should normally be `/usr/local/var', but write
it as `$(prefix)/var'. (If you are using Autoconf, write it as
`@localstatedir@'.)
These variables specify the directory for installing certain specific
types of files, if your program has them. Every GNU package should
have Info files, so every program needs `infodir', but not all need
`libdir' or `lispdir'.
`includedir'
The directory for installing header files to be included by user
programs with the C `#include' preprocessor directive. This
should normally be `/usr/local/include', but write it as
`$(prefix)/include'. (If you are using Autoconf, write it as
`@includedir@'.)
Most compilers other than GCC do not look for header files in
directory `/usr/local/include'. So installing the header files
this way is only useful with GCC. Sometimes this is not a problem
because some libraries are only really intended to work with GCC.
But some libraries are intended to work with other compilers.
They should install their header files in two places, one
specified by `includedir' and one specified by `oldincludedir'.
`oldincludedir'
The directory for installing `#include' header files for use with
compilers other than GCC. This should normally be `/usr/include'.
(If you are using Autoconf, you can write it as `@oldincludedir@'.)
The Makefile commands should check whether the value of
`oldincludedir' is empty. If it is, they should not try to use
it; they should cancel the second installation of the header files.
A package should not replace an existing header in this directory
unless the header came from the same package. Thus, if your Foo
package provides a header file `foo.h', then it should install the
header file in the `oldincludedir' directory if either (1) there
is no `foo.h' there or (2) the `foo.h' that exists came from the
Foo package.
To tell whether `foo.h' came from the Foo package, put a magic
string in the file--part of a comment--and `grep' for that string.
`docdir'
The directory for installing documentation files (other than Info)
for this package. By default, it should be
`/usr/local/share/doc/YOURPKG', but it should be written as
`$(datarootdir)/doc/YOURPKG'. (If you are using Autoconf, write
it as `@docdir@'.) The YOURPKG subdirectory, which may include a
version number, prevents collisions among files with common names,
such as `README'.
`infodir'
The directory for installing the Info files for this package. By
default, it should be `/usr/local/share/info', but it should be
written as `$(datarootdir)/info'. (If you are using Autoconf,
write it as `@infodir@'.) `infodir' is separate from `docdir' for
compatibility with existing practice.
`htmldir'
`dvidir'
`pdfdir'
`psdir'
Directories for installing documentation files in the particular
format. They should all be set to `$(docdir)' by default. (If
you are using Autoconf, write them as `@htmldir@', `@dvidir@',
etc.) Packages which supply several translations of their
documentation should install them in `$(htmldir)/'LL,
`$(pdfdir)/'LL, etc. where LL is a locale abbreviation such as
`en' or `pt_BR'.
`libdir'
The directory for object files and libraries of object code. Do
not install executables here, they probably ought to go in
`$(libexecdir)' instead. The value of `libdir' should normally be
`/usr/local/lib', but write it as `$(exec_prefix)/lib'. (If you
are using Autoconf, write it as `@libdir@'.)
`lispdir'
The directory for installing any Emacs Lisp files in this package.
By default, it should be `/usr/local/share/emacs/site-lisp', but it
should be written as `$(datarootdir)/emacs/site-lisp'.
If you are using Autoconf, write the default as `@lispdir@'. In
order to make `@lispdir@' work, you need the following lines in
your `configure.in' file:
lispdir='${datarootdir}/emacs/site-lisp'
AC_SUBST(lispdir)
`localedir'
The directory for installing locale-specific message catalogs for
this package. By default, it should be `/usr/local/share/locale',
but it should be written as `$(datarootdir)/locale'. (If you are
using Autoconf, write it as `@localedir@'.) This directory
usually has a subdirectory per locale.
Unix-style man pages are installed in one of the following:
`mandir'
The top-level directory for installing the man pages (if any) for
this package. It will normally be `/usr/local/share/man', but you
should write it as `$(datarootdir)/man'. (If you are using
Autoconf, write it as `@mandir@'.)
`man1dir'
The directory for installing section 1 man pages. Write it as
`$(mandir)/man1'.
`man2dir'
The directory for installing section 2 man pages. Write it as
`$(mandir)/man2'
`...'
*Don't make the primary documentation for any GNU software be a
man page. Write a manual in Texinfo instead. Man pages are just
for the sake of people running GNU software on Unix, which is a
secondary application only.*
`manext'
The file name extension for the installed man page. This should
contain a period followed by the appropriate digit; it should
normally be `.1'.
`man1ext'
The file name extension for installed section 1 man pages.
`man2ext'
The file name extension for installed section 2 man pages.
`...'
Use these names instead of `manext' if the package needs to
install man pages in more than one section of the manual.
And finally, you should set the following variable:
`srcdir'
The directory for the sources being compiled. The value of this
variable is normally inserted by the `configure' shell script.
(If you are using Autoconf, use `srcdir = @srcdir@'.)
For example:
# Common prefix for installation directories.
# NOTE: This directory must exist when you start the install.
prefix = /usr/local
datarootdir = $(prefix)/share
datadir = $(datarootdir)
exec_prefix = $(prefix)
# Where to put the executable for the command `gcc'.
bindir = $(exec_prefix)/bin
# Where to put the directories used by the compiler.
libexecdir = $(exec_prefix)/libexec
# Where to put the Info files.
infodir = $(datarootdir)/info
If your program installs a large number of files into one of the
standard user-specified directories, it might be useful to group them
into a subdirectory particular to that program. If you do this, you
should write the `install' rule to create these subdirectories.
Do not expect the user to include the subdirectory name in the value
of any of the variables listed above. The idea of having a uniform set
of variable names for installation directories is to enable the user to
specify the exact same values for several different GNU packages. In
order for this to be useful, all the packages must be designed so that
they will work sensibly when the user does so.
At times, not all of these variables may be implemented in the
current release of Autoconf and/or Automake; but as of Autoconf 2.60, we
believe all of them are. When any are missing, the descriptions here
serve as specifications for what Autoconf will implement. As a
programmer, you can either use a development version of Autoconf or
avoid using these variables until a stable release is made which
supports them.
File: standards.info, Node: Standard Targets, Next: Install Command Categories, Prev: Directory Variables, Up: Makefile Conventions
7.2.6 Standard Targets for Users
--------------------------------
All GNU programs should have the following targets in their Makefiles:
`all'
Compile the entire program. This should be the default target.
This target need not rebuild any documentation files; Info files
should normally be included in the distribution, and DVI (and other
documentation format) files should be made only when explicitly
asked for.
By default, the Make rules should compile and link with `-g', so
that executable programs have debugging symbols. Users who don't
mind being helpless can strip the executables later if they wish.
`install'
Compile the program and copy the executables, libraries, and so on
to the file names where they should reside for actual use. If
there is a simple test to verify that a program is properly
installed, this target should run that test.
Do not strip executables when installing them. Devil-may-care
users can use the `install-strip' target to do that.
If possible, write the `install' target rule so that it does not
modify anything in the directory where the program was built,
provided `make all' has just been done. This is convenient for
building the program under one user name and installing it under
another.
The commands should create all the directories in which files are
to be installed, if they don't already exist. This includes the
directories specified as the values of the variables `prefix' and
`exec_prefix', as well as all subdirectories that are needed. One
way to do this is by means of an `installdirs' target as described
below.
Use `-' before any command for installing a man page, so that
`make' will ignore any errors. This is in case there are systems
that don't have the Unix man page documentation system installed.
The way to install Info files is to copy them into `$(infodir)'
with `$(INSTALL_DATA)' (*note Command Variables::), and then run
the `install-info' program if it is present. `install-info' is a
program that edits the Info `dir' file to add or update the menu
entry for the given Info file; it is part of the Texinfo package.
Here is a sample rule to install an Info file:
$(DESTDIR)$(infodir)/foo.info: foo.info
$(POST_INSTALL)
# There may be a newer info file in . than in srcdir.
-if test -f foo.info; then d=.; \
else d=$(srcdir); fi; \
$(INSTALL_DATA) $$d/foo.info $(DESTDIR)$@; \
# Run install-info only if it exists.
# Use `if' instead of just prepending `-' to the
# line so we notice real errors from install-info.
# We use `$(SHELL) -c' because some shells do not
# fail gracefully when there is an unknown command.
if $(SHELL) -c 'install-info --version' \
>/dev/null 2>&1; then \
install-info --dir-file=$(DESTDIR)$(infodir)/dir \
$(DESTDIR)$(infodir)/foo.info; \
else true; fi
When writing the `install' target, you must classify all the
commands into three categories: normal ones, "pre-installation"
commands and "post-installation" commands. *Note Install Command
Categories::.
`install-html'
`install-dvi'
`install-pdf'
`install-ps'
These targets install documentation in formats other than Info;
they're intended to be called explicitly by the person installing
the package, if that format is desired. GNU prefers Info files,
so these must be installed by the `install' target.
When you have many documentation files to install, we recommend
that you avoid collisions and clutter by arranging for these
targets to install in subdirectories of the appropriate
installation directory, such as `htmldir'. As one example, if
your package has multiple manuals, and you wish to install HTML
documentation with many files (such as the "split" mode output by
`makeinfo --html'), you'll certainly want to use subdirectories,
or two nodes with the same name in different manuals will
overwrite each other.
Please make these `install-FORMAT' targets invoke the commands for
the FORMAT target, for example, by making FORMAT a dependency.
`uninstall'
Delete all the installed files--the copies that the `install' and
`install-*' targets create.
This rule should not modify the directories where compilation is
done, only the directories where files are installed.
The uninstallation commands are divided into three categories,
just like the installation commands. *Note Install Command
Categories::.
`install-strip'
Like `install', but strip the executable files while installing
them. In simple cases, this target can use the `install' target in
a simple way:
install-strip:
$(MAKE) INSTALL_PROGRAM='$(INSTALL_PROGRAM) -s' \
install
But if the package installs scripts as well as real executables,
the `install-strip' target can't just refer to the `install'
target; it has to strip the executables but not the scripts.
`install-strip' should not strip the executables in the build
directory which are being copied for installation. It should only
strip the copies that are installed.
Normally we do not recommend stripping an executable unless you
are sure the program has no bugs. However, it can be reasonable
to install a stripped executable for actual execution while saving
the unstripped executable elsewhere in case there is a bug.
`clean'
Delete all files in the current directory that are normally
created by building the program. Also delete files in other
directories if they are created by this makefile. However, don't
delete the files that record the configuration. Also preserve
files that could be made by building, but normally aren't because
the distribution comes with them. There is no need to delete
parent directories that were created with `mkdir -p', since they
could have existed anyway.
Delete `.dvi' files here if they are not part of the distribution.
`distclean'
Delete all files in the current directory (or created by this
makefile) that are created by configuring or building the program.
If you have unpacked the source and built the program without
creating any other files, `make distclean' should leave only the
files that were in the distribution. However, there is no need to
delete parent directories that were created with `mkdir -p', since
they could have existed anyway.
`mostlyclean'
Like `clean', but may refrain from deleting a few files that people
normally don't want to recompile. For example, the `mostlyclean'
target for GCC does not delete `libgcc.a', because recompiling it
is rarely necessary and takes a lot of time.
`maintainer-clean'
Delete almost everything that can be reconstructed with this
Makefile. This typically includes everything deleted by
`distclean', plus more: C source files produced by Bison, tags
tables, Info files, and so on.
The reason we say "almost everything" is that running the command
`make maintainer-clean' should not delete `configure' even if
`configure' can be remade using a rule in the Makefile. More
generally, `make maintainer-clean' should not delete anything that
needs to exist in order to run `configure' and then begin to build
the program. Also, there is no need to delete parent directories
that were created with `mkdir -p', since they could have existed
anyway. These are the only exceptions; `maintainer-clean' should
delete everything else that can be rebuilt.
The `maintainer-clean' target is intended to be used by a
maintainer of the package, not by ordinary users. You may need
special tools to reconstruct some of the files that `make
maintainer-clean' deletes. Since these files are normally
included in the distribution, we don't take care to make them easy
to reconstruct. If you find you need to unpack the full
distribution again, don't blame us.
To help make users aware of this, the commands for the special
`maintainer-clean' target should start with these two:
@echo 'This command is intended for maintainers to use; it'
@echo 'deletes files that may need special tools to rebuild.'
`TAGS'
Update a tags table for this program.
`info'
Generate any Info files needed. The best way to write the rules
is as follows:
info: foo.info
foo.info: foo.texi chap1.texi chap2.texi
$(MAKEINFO) $(srcdir)/foo.texi
You must define the variable `MAKEINFO' in the Makefile. It should
run the `makeinfo' program, which is part of the Texinfo
distribution.
Normally a GNU distribution comes with Info files, and that means
the Info files are present in the source directory. Therefore,
the Make rule for an info file should update it in the source
directory. When users build the package, ordinarily Make will not
update the Info files because they will already be up to date.
`dvi'
`html'
`pdf'
`ps'
Generate documentation files in the given format. These targets
should always exist, but any or all can be a no-op if the given
output format cannot be generated. These targets should not be
dependencies of the `all' target; the user must manually invoke
them.
Here's an example rule for generating DVI files from Texinfo:
dvi: foo.dvi
foo.dvi: foo.texi chap1.texi chap2.texi
$(TEXI2DVI) $(srcdir)/foo.texi
You must define the variable `TEXI2DVI' in the Makefile. It should
run the program `texi2dvi', which is part of the Texinfo
distribution.(1) Alternatively, write just the dependencies, and
allow GNU `make' to provide the command.
Here's another example, this one for generating HTML from Texinfo:
html: foo.html
foo.html: foo.texi chap1.texi chap2.texi
$(TEXI2HTML) $(srcdir)/foo.texi
Again, you would define the variable `TEXI2HTML' in the Makefile;
for example, it might run `makeinfo --no-split --html' (`makeinfo'
is part of the Texinfo distribution).
`dist'
Create a distribution tar file for this program. The tar file
should be set up so that the file names in the tar file start with
a subdirectory name which is the name of the package it is a
distribution for. This name can include the version number.
For example, the distribution tar file of GCC version 1.40 unpacks
into a subdirectory named `gcc-1.40'.
The easiest way to do this is to create a subdirectory
appropriately named, use `ln' or `cp' to install the proper files
in it, and then `tar' that subdirectory.
Compress the tar file with `gzip'. For example, the actual
distribution file for GCC version 1.40 is called `gcc-1.40.tar.gz'.
It is ok to support other free compression formats as well, such as
`bzip2' and `lzma'.
The `dist' target should explicitly depend on all non-source files
that are in the distribution, to make sure they are up to date in
the distribution. *Note Making Releases: Releases.
`check'
Perform self-tests (if any). The user must build the program
before running the tests, but need not install the program; you
should write the self-tests so that they work when the program is
built but not installed.
The following targets are suggested as conventional names, for
programs in which they are useful.
`installcheck'
Perform installation tests (if any). The user must build and
install the program before running the tests. You should not
assume that `$(bindir)' is in the search path.
`installdirs'
It's useful to add a target named `installdirs' to create the
directories where files are installed, and their parent
directories. There is a script called `mkinstalldirs' which is
convenient for this; you can find it in the Texinfo package. You
can use a rule like this:
# Make sure all installation directories (e.g. $(bindir))
# actually exist by making them if necessary.
installdirs: mkinstalldirs
$(srcdir)/mkinstalldirs $(bindir) $(datadir) \
$(libdir) $(infodir) \
$(mandir)
or, if you wish to support `DESTDIR',
# Make sure all installation directories (e.g. $(bindir))
# actually exist by making them if necessary.
installdirs: mkinstalldirs
$(srcdir)/mkinstalldirs \
$(DESTDIR)$(bindir) $(DESTDIR)$(datadir) \
$(DESTDIR)$(libdir) $(DESTDIR)$(infodir) \
$(DESTDIR)$(mandir)
This rule should not modify the directories where compilation is
done. It should do nothing but create installation directories.
---------- Footnotes ----------
(1) `texi2dvi' uses TeX to do the real work of formatting. TeX is
not distributed with Texinfo.
File: standards.info, Node: Install Command Categories, Prev: Standard Targets, Up: Makefile Conventions
7.2.7 Install Command Categories
--------------------------------
When writing the `install' target, you must classify all the commands
into three categories: normal ones, "pre-installation" commands and
"post-installation" commands.
Normal commands move files into their proper places, and set their
modes. They may not alter any files except the ones that come entirely
from the package they belong to.
Pre-installation and post-installation commands may alter other
files; in particular, they can edit global configuration files or data
bases.
Pre-installation commands are typically executed before the normal
commands, and post-installation commands are typically run after the
normal commands.
The most common use for a post-installation command is to run
`install-info'. This cannot be done with a normal command, since it
alters a file (the Info directory) which does not come entirely and
solely from the package being installed. It is a post-installation
command because it needs to be done after the normal command which
installs the package's Info files.
Most programs don't need any pre-installation commands, but we have
the feature just in case it is needed.
To classify the commands in the `install' rule into these three
categories, insert "category lines" among them. A category line
specifies the category for the commands that follow.
A category line consists of a tab and a reference to a special Make
variable, plus an optional comment at the end. There are three
variables you can use, one for each category; the variable name
specifies the category. Category lines are no-ops in ordinary execution
because these three Make variables are normally undefined (and you
_should not_ define them in the makefile).
Here are the three possible category lines, each with a comment that
explains what it means:
$(PRE_INSTALL) # Pre-install commands follow.
$(POST_INSTALL) # Post-install commands follow.
$(NORMAL_INSTALL) # Normal commands follow.
If you don't use a category line at the beginning of the `install'
rule, all the commands are classified as normal until the first category
line. If you don't use any category lines, all the commands are
classified as normal.
These are the category lines for `uninstall':
$(PRE_UNINSTALL) # Pre-uninstall commands follow.
$(POST_UNINSTALL) # Post-uninstall commands follow.
$(NORMAL_UNINSTALL) # Normal commands follow.
Typically, a pre-uninstall command would be used for deleting entries
from the Info directory.
If the `install' or `uninstall' target has any dependencies which
act as subroutines of installation, then you should start _each_
dependency's commands with a category line, and start the main target's
commands with a category line also. This way, you can ensure that each
command is placed in the right category regardless of which of the
dependencies actually run.
Pre-installation and post-installation commands should not run any
programs except for these:
[ basename bash cat chgrp chmod chown cmp cp dd diff echo
egrep expand expr false fgrep find getopt grep gunzip gzip
hostname install install-info kill ldconfig ln ls md5sum
mkdir mkfifo mknod mv printenv pwd rm rmdir sed sort tee
test touch true uname xargs yes
The reason for distinguishing the commands in this way is for the
sake of making binary packages. Typically a binary package contains
all the executables and other files that need to be installed, and has
its own method of installing them--so it does not need to run the normal
installation commands. But installing the binary package does need to
execute the pre-installation and post-installation commands.
Programs to build binary packages work by extracting the
pre-installation and post-installation commands. Here is one way of
extracting the pre-installation commands (the `-s' option to `make' is
needed to silence messages about entering subdirectories):
make -s -n install -o all \
PRE_INSTALL=pre-install \
POST_INSTALL=post-install \
NORMAL_INSTALL=normal-install \
| gawk -f pre-install.awk
where the file `pre-install.awk' could contain this:
$0 ~ /^(normal-install|post-install)[ \t]*$/ {on = 0}
on {print $0}
$0 ~ /^pre-install[ \t]*$/ {on = 1}
File: standards.info, Node: Releases, Prev: Makefile Conventions, Up: Managing Releases
7.3 Making Releases
===================
You should identify each release with a pair of version numbers, a
major version and a minor. We have no objection to using more than two
numbers, but it is very unlikely that you really need them.
Package the distribution of `Foo version 69.96' up in a gzipped tar
file with the name `foo-69.96.tar.gz'. It should unpack into a
subdirectory named `foo-69.96'.
Building and installing the program should never modify any of the
files contained in the distribution. This means that all the files
that form part of the program in any way must be classified into "source
files" and "non-source files". Source files are written by humans and
never changed automatically; non-source files are produced from source
files by programs under the control of the Makefile.
The distribution should contain a file named `README' which gives
the name of the package, and a general description of what it does. It
is also good to explain the purpose of each of the first-level
subdirectories in the package, if there are any. The `README' file
should either state the version number of the package, or refer to where
in the package it can be found.
The `README' file should refer to the file `INSTALL', which should
contain an explanation of the installation procedure.
The `README' file should also refer to the file which contains the
copying conditions. The GNU GPL, if used, should be in a file called
`COPYING'. If the GNU LGPL is used, it should be in a file called
`COPYING.LESSER'.
Naturally, all the source files must be in the distribution. It is
okay to include non-source files in the distribution, provided they are
up-to-date and machine-independent, so that building the distribution
normally will never modify them. We commonly include non-source files
produced by Bison, `lex', TeX, and `makeinfo'; this helps avoid
unnecessary dependencies between our distributions, so that users can
install whichever packages they want to install.
Non-source files that might actually be modified by building and
installing the program should *never* be included in the distribution.
So if you do distribute non-source files, always make sure they are up
to date when you make a new distribution.
Make sure that the directory into which the distribution unpacks (as
well as any subdirectories) are all world-writable (octal mode 777).
This is so that old versions of `tar' which preserve the ownership and
permissions of the files from the tar archive will be able to extract
all the files even if the user is unprivileged.
Make sure that all the files in the distribution are world-readable.
Don't include any symbolic links in the distribution itself. If the
tar file contains symbolic links, then people cannot even unpack it on
systems that don't support symbolic links. Also, don't use multiple
names for one file in different directories, because certain file
systems cannot handle this and that prevents unpacking the distribution.
Try to make sure that all the file names will be unique on MS-DOS. A
name on MS-DOS consists of up to 8 characters, optionally followed by a
period and up to three characters. MS-DOS will truncate extra
characters both before and after the period. Thus, `foobarhacker.c'
and `foobarhacker.o' are not ambiguous; they are truncated to
`foobarha.c' and `foobarha.o', which are distinct.
Include in your distribution a copy of the `texinfo.tex' you used to
test print any `*.texinfo' or `*.texi' files.
Likewise, if your program uses small GNU software packages like
regex, getopt, obstack, or termcap, include them in the distribution
file. Leaving them out would make the distribution file a little
smaller at the expense of possible inconvenience to a user who doesn't
know what other files to get.
File: standards.info, Node: References, Next: GNU Free Documentation License, Prev: Managing Releases, Up: Top
8 References to Non-Free Software and Documentation
***************************************************
A GNU program should not recommend, promote, or grant legitimacy to the
use of any non-free program. Proprietary software is a social and
ethical problem, and our aim is to put an end to that problem. We
can't stop some people from writing proprietary programs, or stop other
people from using them, but we can and should refuse to advertise them
to new potential customers, or to give the public the idea that their
existence is ethical.
The GNU definition of free software is found on the GNU web site at
`http://www.gnu.org/philosophy/free-sw.html', and the definition of
free documentation is found at
`http://www.gnu.org/philosophy/free-doc.html'. The terms "free" and
"non-free", used in this document, refer to those definitions.
A list of important licenses and whether they qualify as free is in
`http://www.gnu.org/licenses/license-list.html'. If it is not clear
whether a license qualifies as free, please ask the GNU Project by
writing to . We will answer, and if the license is
an important one, we will add it to the list.
When a non-free program or system is well known, you can mention it
in passing--that is harmless, since users who might want to use it
probably already know about it. For instance, it is fine to explain
how to build your package on top of some widely used non-free operating
system, or how to use it together with some widely used non-free
program.
However, you should give only the necessary information to help those
who already use the non-free program to use your program with it--don't
give, or refer to, any further information about the proprietary
program, and don't imply that the proprietary program enhances your
program, or that its existence is in any way a good thing. The goal
should be that people already using the proprietary program will get
the advice they need about how to use your free program with it, while
people who don't already use the proprietary program will not see
anything likely to lead them to take an interest in it.
If a non-free program or system is obscure in your program's domain,
your program should not mention or support it at all, since doing so
would tend to popularize the non-free program more than it popularizes
your program. (You cannot hope to find many additional users for your
program among the users of Foobar, if the existence of Foobar is not
generally known among people who might want to use your program.)
Sometimes a program is free software in itself but depends on a
non-free platform in order to run. For instance, many Java programs
depend on some non-free Java libraries. To recommend or promote such a
program is to promote the other programs it needs. This is why we are
careful about listing Java programs in the Free Software Directory: we
don't want to promote the non-free Java libraries.
We hope this particular problem with Java will be gone by and by, as
we replace the remaining non-free standard Java libraries with free
software, but the general principle will remain the same: don't
recommend, promote or legitimize programs that depend on non-free
software to run.
Some free programs strongly encourage the use of non-free software.
A typical example is `mplayer'. It is free software in itself, and the
free code can handle some kinds of files. However, `mplayer'
recommends use of non-free codecs for other kinds of files, and users
that install `mplayer' are very likely to install those codecs along
with it. To recommend `mplayer' is, in effect, to promote use of the
non-free codecs.
Thus, you should not recommend programs that strongly encourage the
use of non-free software. This is why we do not list `mplayer' in the
Free Software Directory.
A GNU package should not refer the user to any non-free documentation
for free software. Free documentation that can be included in free
operating systems is essential for completing the GNU system, or any
free operating system, so encouraging it is a priority; to recommend
use of documentation that we are not allowed to include undermines the
impetus for the community to produce documentation that we can include.
So GNU packages should never recommend non-free documentation.
By contrast, it is ok to refer to journal articles and textbooks in
the comments of a program for explanation of how it functions, even
though they are non-free. This is because we don't include such things
in the GNU system even they are free--they are outside the scope of
what a software distribution needs to include.
Referring to a web site that describes or recommends a non-free
program is promoting that program, so please do not make links (or
mention by name) web sites that contain such material. This policy is
relevant particularly for the web pages for a GNU package.
Following links from nearly any web site can lead eventually to
non-free software; this is inherent in the nature of the web. So it
makes no sense to criticize a site for having such links. As long as
the site does not itself recommend a non-free program, there is no need
to consider the question of the sites that it links to for other
reasons.
Thus, for example, you should not refer to AT&T's web site if that
recommends AT&T's non-free software packages; you should not refer to a
site that links to AT&T's site presenting it as a place to get some
non-free program, because that link recommends and legitimizes the
non-free program. However, that a site contains a link to AT&T's web
site for some other purpose (such as long-distance telephone service)
is not an objection against it.
File: standards.info, Node: GNU Free Documentation License, Next: Index, Prev: References, Up: Top
Appendix A GNU Free Documentation License
*****************************************
Version 1.3, 3 November 2008
Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
`http://fsf.org/'
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
0. PREAMBLE
The purpose of this License is to make a manual, textbook, or other
functional and useful document "free" in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or
noncommercially. Secondarily, this License preserves for the
author and publisher a way to get credit for their work, while not
being considered responsible for modifications made by others.
This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense.
It complements the GNU General Public License, which is a copyleft
license designed for free software.
We have designed this License in order to use it for manuals for
free software, because free software needs free documentation: a
free program should come with manuals providing the same freedoms
that the software does. But this License is not limited to
software manuals; it can be used for any textual work, regardless
of subject matter or whether it is published as a printed book.
We recommend this License principally for works whose purpose is
instruction or reference.
1. APPLICABILITY AND DEFINITIONS
This License applies to any manual or other work, in any medium,
that contains a notice placed by the copyright holder saying it
can be distributed under the terms of this License. Such a notice
grants a world-wide, royalty-free license, unlimited in duration,
to use that work under the conditions stated herein. The
"Document", below, refers to any such manual or work. Any member
of the public is a licensee, and is addressed as "you". You
accept the license if you copy, modify or distribute the work in a
way requiring permission under copyright law.
A "Modified Version" of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.
A "Secondary Section" is a named appendix or a front-matter section
of the Document that deals exclusively with the relationship of the
publishers or authors of the Document to the Document's overall
subject (or to related matters) and contains nothing that could
fall directly within that overall subject. (Thus, if the Document
is in part a textbook of mathematics, a Secondary Section may not
explain any mathematics.) The relationship could be a matter of
historical connection with the subject or with related matters, or
of legal, commercial, philosophical, ethical or political position
regarding them.
The "Invariant Sections" are certain Secondary Sections whose
titles are designated, as being those of Invariant Sections, in
the notice that says that the Document is released under this
License. If a section does not fit the above definition of
Secondary then it is not allowed to be designated as Invariant.
The Document may contain zero Invariant Sections. If the Document
does not identify any Invariant Sections then there are none.
The "Cover Texts" are certain short passages of text that are
listed, as Front-Cover Texts or Back-Cover Texts, in the notice
that says that the Document is released under this License. A
Front-Cover Text may be at most 5 words, and a Back-Cover Text may
be at most 25 words.
A "Transparent" copy of the Document means a machine-readable copy,
represented in a format whose specification is available to the
general public, that is suitable for revising the document
straightforwardly with generic text editors or (for images
composed of pixels) generic paint programs or (for drawings) some
widely available drawing editor, and that is suitable for input to
text formatters or for automatic translation to a variety of
formats suitable for input to text formatters. A copy made in an
otherwise Transparent file format whose markup, or absence of
markup, has been arranged to thwart or discourage subsequent
modification by readers is not Transparent. An image format is
not Transparent if used for any substantial amount of text. A
copy that is not "Transparent" is called "Opaque".
Examples of suitable formats for Transparent copies include plain
ASCII without markup, Texinfo input format, LaTeX input format,
SGML or XML using a publicly available DTD, and
standard-conforming simple HTML, PostScript or PDF designed for
human modification. Examples of transparent image formats include
PNG, XCF and JPG. Opaque formats include proprietary formats that
can be read and edited only by proprietary word processors, SGML or
XML for which the DTD and/or processing tools are not generally
available, and the machine-generated HTML, PostScript or PDF
produced by some word processors for output purposes only.
The "Title Page" means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the
material this License requires to appear in the title page. For
works in formats which do not have any title page as such, "Title
Page" means the text near the most prominent appearance of the
work's title, preceding the beginning of the body of the text.
The "publisher" means any person or entity that distributes copies
of the Document to the public.
A section "Entitled XYZ" means a named subunit of the Document
whose title either is precisely XYZ or contains XYZ in parentheses
following text that translates XYZ in another language. (Here XYZ
stands for a specific section name mentioned below, such as
"Acknowledgements", "Dedications", "Endorsements", or "History".)
To "Preserve the Title" of such a section when you modify the
Document means that it remains a section "Entitled XYZ" according
to this definition.
The Document may include Warranty Disclaimers next to the notice
which states that this License applies to the Document. These
Warranty Disclaimers are considered to be included by reference in
this License, but only as regards disclaiming warranties: any other
implication that these Warranty Disclaimers may have is void and
has no effect on the meaning of this License.
2. VERBATIM COPYING
You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License
applies to the Document are reproduced in all copies, and that you
add no other conditions whatsoever to those of this License. You
may not use technical measures to obstruct or control the reading
or further copying of the copies you make or distribute. However,
you may accept compensation in exchange for copies. If you
distribute a large enough number of copies you must also follow
the conditions in section 3.
You may also lend copies, under the same conditions stated above,
and you may publicly display copies.
3. COPYING IN QUANTITY
If you publish printed copies (or copies in media that commonly
have printed covers) of the Document, numbering more than 100, and
the Document's license notice requires Cover Texts, you must
enclose the copies in covers that carry, clearly and legibly, all
these Cover Texts: Front-Cover Texts on the front cover, and
Back-Cover Texts on the back cover. Both covers must also clearly
and legibly identify you as the publisher of these copies. The
front cover must present the full title with all words of the
title equally prominent and visible. You may add other material
on the covers in addition. Copying with changes limited to the
covers, as long as they preserve the title of the Document and
satisfy these conditions, can be treated as verbatim copying in
other respects.
If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto
adjacent pages.
If you publish or distribute Opaque copies of the Document
numbering more than 100, you must either include a
machine-readable Transparent copy along with each Opaque copy, or
state in or with each Opaque copy a computer-network location from
which the general network-using public has access to download
using public-standard network protocols a complete Transparent
copy of the Document, free of added material. If you use the
latter option, you must take reasonably prudent steps, when you
begin distribution of Opaque copies in quantity, to ensure that
this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you
distribute an Opaque copy (directly or through your agents or
retailers) of that edition to the public.
It is requested, but not required, that you contact the authors of
the Document well before redistributing any large number of
copies, to give them a chance to provide you with an updated
version of the Document.
4. MODIFICATIONS
You may copy and distribute a Modified Version of the Document
under the conditions of sections 2 and 3 above, provided that you
release the Modified Version under precisely this License, with
the Modified Version filling the role of the Document, thus
licensing distribution and modification of the Modified Version to
whoever possesses a copy of it. In addition, you must do these
things in the Modified Version:
A. Use in the Title Page (and on the covers, if any) a title
distinct from that of the Document, and from those of
previous versions (which should, if there were any, be listed
in the History section of the Document). You may use the
same title as a previous version if the original publisher of
that version gives permission.
B. List on the Title Page, as authors, one or more persons or
entities responsible for authorship of the modifications in
the Modified Version, together with at least five of the
principal authors of the Document (all of its principal
authors, if it has fewer than five), unless they release you
from this requirement.
C. State on the Title page the name of the publisher of the
Modified Version, as the publisher.
D. Preserve all the copyright notices of the Document.
E. Add an appropriate copyright notice for your modifications
adjacent to the other copyright notices.
F. Include, immediately after the copyright notices, a license
notice giving the public permission to use the Modified
Version under the terms of this License, in the form shown in
the Addendum below.
G. Preserve in that license notice the full lists of Invariant
Sections and required Cover Texts given in the Document's
license notice.
H. Include an unaltered copy of this License.
I. Preserve the section Entitled "History", Preserve its Title,
and add to it an item stating at least the title, year, new
authors, and publisher of the Modified Version as given on
the Title Page. If there is no section Entitled "History" in
the Document, create one stating the title, year, authors,
and publisher of the Document as given on its Title Page,
then add an item describing the Modified Version as stated in
the previous sentence.
J. Preserve the network location, if any, given in the Document
for public access to a Transparent copy of the Document, and
likewise the network locations given in the Document for
previous versions it was based on. These may be placed in
the "History" section. You may omit a network location for a
work that was published at least four years before the
Document itself, or if the original publisher of the version
it refers to gives permission.
K. For any section Entitled "Acknowledgements" or "Dedications",
Preserve the Title of the section, and preserve in the
section all the substance and tone of each of the contributor
acknowledgements and/or dedications given therein.
L. Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles. Section numbers
or the equivalent are not considered part of the section
titles.
M. Delete any section Entitled "Endorsements". Such a section
may not be included in the Modified Version.
N. Do not retitle any existing section to be Entitled
"Endorsements" or to conflict in title with any Invariant
Section.
O. Preserve any Warranty Disclaimers.
If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no
material copied from the Document, you may at your option
designate some or all of these sections as invariant. To do this,
add their titles to the list of Invariant Sections in the Modified
Version's license notice. These titles must be distinct from any
other section titles.
You may add a section Entitled "Endorsements", provided it contains
nothing but endorsements of your Modified Version by various
parties--for example, statements of peer review or that the text
has been approved by an organization as the authoritative
definition of a standard.
You may add a passage of up to five words as a Front-Cover Text,
and a passage of up to 25 words as a Back-Cover Text, to the end
of the list of Cover Texts in the Modified Version. Only one
passage of Front-Cover Text and one of Back-Cover Text may be
added by (or through arrangements made by) any one entity. If the
Document already includes a cover text for the same cover,
previously added by you or by arrangement made by the same entity
you are acting on behalf of, you may not add another; but you may
replace the old one, on explicit permission from the previous
publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this
License give permission to use their names for publicity for or to
assert or imply endorsement of any Modified Version.
5. COMBINING DOCUMENTS
You may combine the Document with other documents released under
this License, under the terms defined in section 4 above for
modified versions, provided that you include in the combination
all of the Invariant Sections of all of the original documents,
unmodified, and list them all as Invariant Sections of your
combined work in its license notice, and that you preserve all
their Warranty Disclaimers.
The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy. If there are multiple Invariant Sections with the same name
but different contents, make the title of each such section unique
by adding at the end of it, in parentheses, the name of the
original author or publisher of that section if known, or else a
unique number. Make the same adjustment to the section titles in
the list of Invariant Sections in the license notice of the
combined work.
In the combination, you must combine any sections Entitled
"History" in the various original documents, forming one section
Entitled "History"; likewise combine any sections Entitled
"Acknowledgements", and any sections Entitled "Dedications". You
must delete all sections Entitled "Endorsements."
6. COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other
documents released under this License, and replace the individual
copies of this License in the various documents with a single copy
that is included in the collection, provided that you follow the
rules of this License for verbatim copying of each of the
documents in all other respects.
You may extract a single document from such a collection, and
distribute it individually under this License, provided you insert
a copy of this License into the extracted document, and follow
this License in all other respects regarding verbatim copying of
that document.
7. AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other
separate and independent documents or works, in or on a volume of
a storage or distribution medium, is called an "aggregate" if the
copyright resulting from the compilation is not used to limit the
legal rights of the compilation's users beyond what the individual
works permit. When the Document is included in an aggregate, this
License does not apply to the other works in the aggregate which
are not themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half
of the entire aggregate, the Document's Cover Texts may be placed
on covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic
form. Otherwise they must appear on printed covers that bracket
the whole aggregate.
8. TRANSLATION
Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section
4. Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections. You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also
include the original English version of this License and the
original versions of those notices and disclaimers. In case of a
disagreement between the translation and the original version of
this License or a notice or disclaimer, the original version will
prevail.
If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section 4) to
Preserve its Title (section 1) will typically require changing the
actual title.
9. TERMINATION
You may not copy, modify, sublicense, or distribute the Document
except as expressly provided under this License. Any attempt
otherwise to copy, modify, sublicense, or distribute it is void,
and will automatically terminate your rights under this License.
However, if you cease all violation of this License, then your
license from a particular copyright holder is reinstated (a)
provisionally, unless and until the copyright holder explicitly
and finally terminates your license, and (b) permanently, if the
copyright holder fails to notify you of the violation by some
reasonable means prior to 60 days after the cessation.
Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from
that copyright holder, and you cure the violation prior to 30 days
after your receipt of the notice.
Termination of your rights under this section does not terminate
the licenses of parties who have received copies or rights from
you under this License. If your rights have been terminated and
not permanently reinstated, receipt of a copy of some or all of
the same material does not give you any rights to use it.
10. FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions of
the GNU Free Documentation License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns. See
`http://www.gnu.org/copyleft/'.
Each version of the License is given a distinguishing version
number. If the Document specifies that a particular numbered
version of this License "or any later version" applies to it, you
have the option of following the terms and conditions either of
that specified version or of any later version that has been
published (not as a draft) by the Free Software Foundation. If
the Document does not specify a version number of this License,
you may choose any version ever published (not as a draft) by the
Free Software Foundation. If the Document specifies that a proxy
can decide which future versions of this License can be used, that
proxy's public statement of acceptance of a version permanently
authorizes you to choose that version for the Document.
11. RELICENSING
"Massive Multiauthor Collaboration Site" (or "MMC Site") means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works. A
public wiki that anybody can edit is an example of such a server.
A "Massive Multiauthor Collaboration" (or "MMC") contained in the
site means any set of copyrightable works thus published on the MMC
site.
"CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
published by that same organization.
"Incorporate" means to publish or republish a Document, in whole or
in part, as part of another Document.
An MMC is "eligible for relicensing" if it is licensed under this
License, and if all works that were first published under this
License somewhere other than this MMC, and subsequently
incorporated in whole or in part into the MMC, (1) had no cover
texts or invariant sections, and (2) were thus incorporated prior
to November 1, 2008.
The operator of an MMC Site may republish an MMC contained in the
site under CC-BY-SA on the same site at any time before August 1,
2009, provided the MMC is eligible for relicensing.
ADDENDUM: How to use this License for your documents
====================================================
To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:
Copyright (C) YEAR YOUR NAME.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts." line with this:
with the Invariant Sections being LIST THEIR TITLES, with
the Front-Cover Texts being LIST, and with the Back-Cover Texts
being LIST.
If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.
If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License, to
permit their use in free software.
File: standards.info, Node: Index, Prev: GNU Free Documentation License, Up: Top
Index
*****
[index ]
* Menu:
* #endif, commenting: Comments. (line 60)
* --help output: --help. (line 6)
* --version output: --version. (line 6)
* -Wall compiler option: Syntactic Conventions.
(line 10)
* accepting contributions: Contributions. (line 6)
* address for bug reports: --help. (line 11)
* ANSI C standard: Standard C. (line 6)
* arbitrary limits on data: Semantics. (line 6)
* ASCII characters: Character Set. (line 6)
* autoconf: System Portability. (line 23)
* avoiding proprietary code: Reading Non-Free Code.
(line 6)
* behavior, dependent on program's name: User Interfaces. (line 6)
* binary packages: Install Command Categories.
(line 80)
* bindir: Directory Variables. (line 54)
* braces, in C source: Formatting. (line 6)
* bug reports: --help. (line 11)
* canonical name of a program: --version. (line 12)
* casting pointers to integers: CPU Portability. (line 89)
* CGI programs, standard options for: Command-Line Interfaces.
(line 31)
* change logs: Change Logs. (line 6)
* change logs, conditional changes: Conditional Changes. (line 6)
* change logs, style: Style of Change Logs.
(line 6)
* character set: Character Set. (line 6)
* command-line arguments, decoding: Semantics. (line 46)
* command-line interface: Command-Line Interfaces.
(line 6)
* commenting: Comments. (line 6)
* compatibility with C and POSIX standards: Compatibility. (line 6)
* compiler warnings: Syntactic Conventions.
(line 10)
* conditional changes, and change logs: Conditional Changes. (line 6)
* conditionals, comments for: Comments. (line 60)
* configure: Configuration. (line 6)
* control-L: Formatting. (line 118)
* conventions for makefiles: Makefile Conventions.
(line 6)
* corba: Graphical Interfaces.
(line 16)
* credits for manuals: Manual Credits. (line 6)
* data types, and portability: CPU Portability. (line 6)
* declaration for system functions: System Functions. (line 21)
* DESTDIR: DESTDIR. (line 6)
* documentation: Documentation. (line 6)
* doschk: Names. (line 38)
* downloading this manual: Preface. (line 17)
* encodings: Character Set. (line 6)
* error messages: Semantics. (line 19)
* error messages, formatting: Errors. (line 6)
* exec_prefix: Directory Variables. (line 36)
* expressions, splitting: Formatting. (line 81)
* FDL, GNU Free Documentation License: GNU Free Documentation License.
(line 6)
* file usage: File Usage. (line 6)
* file-name limitations: Names. (line 38)
* formatting error messages: Errors. (line 6)
* formatting source code: Formatting. (line 6)
* formfeed: Formatting. (line 118)
* function argument, declaring: Syntactic Conventions.
(line 6)
* function prototypes: Standard C. (line 17)
* getopt: Command-Line Interfaces.
(line 6)
* gettext: Internationalization.
(line 6)
* gnome: Graphical Interfaces.
(line 16)
* GNOME and Guile: Source Language. (line 38)
* graphical user interface: Graphical Interfaces.
(line 6)
* grave accent: Quote Characters. (line 6)
* gtk+: Graphical Interfaces.
(line 6)
* Guile: Source Language. (line 38)
* implicit int: Syntactic Conventions.
(line 6)
* impossible conditions: Semantics. (line 70)
* installations, staged: DESTDIR. (line 6)
* internationalization: Internationalization.
(line 6)
* LDAP: OID Allocations. (line 6)
* left quote: Quote Characters. (line 6)
* legal aspects: Legal Issues. (line 6)
* legal papers: Contributions. (line 6)
* libexecdir: Directory Variables. (line 67)
* libraries: Libraries. (line 6)
* library functions, and portability: System Functions. (line 6)
* license for manuals: License for Manuals. (line 6)
* lint: Syntactic Conventions.
(line 109)
* locale-specific quote characters: Quote Characters. (line 6)
* long option names: Option Table. (line 6)
* long-named options: Command-Line Interfaces.
(line 12)
* makefile, conventions for: Makefile Conventions.
(line 6)
* malloc return value: Semantics. (line 25)
* man pages: Man Pages. (line 6)
* manual structure: Manual Structure Details.
(line 6)
* memory allocation failure: Semantics. (line 25)
* memory usage: Memory Usage. (line 6)
* message text, and internationalization: Internationalization.
(line 29)
* mmap: Mmap. (line 6)
* multiple variables in a line: Syntactic Conventions.
(line 35)
* names of variables, functions, and files: Names. (line 6)
* NEWS file: NEWS File. (line 6)
* non-ASCII characters: Character Set. (line 6)
* non-POSIX systems, and portability: System Portability. (line 32)
* non-standard extensions: Using Extensions. (line 6)
* NUL characters: Semantics. (line 11)
* OID allocations for GNU: OID Allocations. (line 6)
* open brace: Formatting. (line 6)
* optional features, configure-time: Configuration. (line 100)
* options for compatibility: Compatibility. (line 14)
* options, standard command-line: Command-Line Interfaces.
(line 31)
* output device and program's behavior: User Interfaces. (line 13)
* packaging: Releases. (line 6)
* PATH_INFO, specifying standard options as: Command-Line Interfaces.
(line 31)
* portability, and data types: CPU Portability. (line 6)
* portability, and library functions: System Functions. (line 6)
* portability, between system types: System Portability. (line 6)
* POSIX compatibility: Compatibility. (line 6)
* POSIXLY_CORRECT, environment variable: Compatibility. (line 21)
* post-installation commands: Install Command Categories.
(line 6)
* pre-installation commands: Install Command Categories.
(line 6)
* prefix: Directory Variables. (line 26)
* program configuration: Configuration. (line 6)
* program design: Design Advice. (line 6)
* program name and its behavior: User Interfaces. (line 6)
* program's canonical name: --version. (line 12)
* programming languages: Source Language. (line 6)
* proprietary programs: Reading Non-Free Code.
(line 6)
* quote characters: Quote Characters. (line 6)
* README file: Releases. (line 21)
* references to non-free material: References. (line 6)
* releasing: Managing Releases. (line 6)
* sbindir: Directory Variables. (line 60)
* signal handling: Semantics. (line 59)
* SNMP: OID Allocations. (line 6)
* spaces before open-paren: Formatting. (line 75)
* staged installs: DESTDIR. (line 6)
* standard command-line options: Command-Line Interfaces.
(line 31)
* standards for makefiles: Makefile Conventions.
(line 6)
* string library functions: System Functions. (line 55)
* syntactic conventions: Syntactic Conventions.
(line 6)
* table of long options: Option Table. (line 6)
* temporary files: Semantics. (line 84)
* temporary variables: Syntactic Conventions.
(line 23)
* texinfo.tex, in a distribution: Releases. (line 70)
* TMPDIR environment variable: Semantics. (line 84)
* trademarks: Trademarks. (line 6)
* where to obtain standards.texi: Preface. (line 17)
* X.509: OID Allocations. (line 6)
Tag Table:
Node: Top805
Node: Preface2072
Node: Legal Issues4186
Node: Reading Non-Free Code4656
Node: Contributions6386
Node: Trademarks8624
Node: Design Advice10259
Node: Source Language10851
Node: Compatibility12977
Node: Using Extensions14605
Node: Standard C16181
Node: Conditional Compilation18584
Node: Program Behavior19982
Node: Non-GNU Standards21098
Node: Semantics23379
Node: Libraries28098
Node: Errors29343
Node: User Interfaces31836
Node: Graphical Interfaces33441
Node: Command-Line Interfaces34477
Node: --version36509
Node: --help42410
Node: Option Table43283
Node: OID Allocations58238
Node: Memory Usage59999
Node: File Usage61035
Node: Writing C61785
Node: Formatting62757
Node: Comments67046
Node: Syntactic Conventions70598
Node: Names74060
Node: System Portability76272
Node: CPU Portability79163
Node: System Functions83064
Node: Internationalization88261
Node: Character Set92255
Node: Quote Characters93068
Node: Mmap94588
Node: Documentation95296
Node: GNU Manuals96402
Node: Doc Strings and Manuals102140
Node: Manual Structure Details103693
Node: License for Manuals105111
Node: Manual Credits106085
Node: Printed Manuals106478
Node: NEWS File107164
Node: Change Logs107842
Node: Change Log Concepts108596
Node: Style of Change Logs110685
Node: Simple Changes113185
Node: Conditional Changes114627
Node: Indicating the Part Changed116049
Node: Man Pages116576
Node: Reading other Manuals118782
Node: Managing Releases119573
Node: Configuration120354
Node: Makefile Conventions128975
Node: Makefile Basics129974
Node: Utilities in Makefiles133148
Node: Command Variables135646
Node: DESTDIR138892
Node: Directory Variables141066
Node: Standard Targets155559
Ref: Standard Targets-Footnote-1169172
Node: Install Command Categories169272
Node: Releases173805
Node: References177735
Node: GNU Free Documentation License183582
Node: Index208749
End Tag Table
autoconf2.64-2.64/doc/standards.texi 0000644 0002024 0002024 00000426464 11233203257 016620 0 ustar arthur arthur \input texinfo @c -*-texinfo-*-
@c %**start of header
@setfilename standards.info
@settitle GNU Coding Standards
@c This date is automagically updated when you save this file:
@set lastupdate June 7, 2009
@c %**end of header
@dircategory GNU organization
@direntry
* Standards: (standards). GNU coding standards.
@end direntry
@c @setchapternewpage odd
@setchapternewpage off
@c Put everything in one index (arbitrarily chosen to be the concept index).
@syncodeindex fn cp
@syncodeindex ky cp
@syncodeindex pg cp
@syncodeindex vr cp
@c This is used by a cross ref in make-stds.texi
@set CODESTD 1
@copying
The GNU coding standards, last updated @value{lastupdate}.
Copyright @copyright{} 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software
Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
Texts. A copy of the license is included in the section entitled
``GNU Free Documentation License''.
@end copying
@titlepage
@title GNU Coding Standards
@author Richard Stallman, et al.
@author last updated @value{lastupdate}
@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage
@contents
@ifnottex
@node Top, Preface, (dir), (dir)
@top Version
@insertcopying
@end ifnottex
@menu
* Preface:: About the GNU Coding Standards.
* Legal Issues:: Keeping free software free.
* Design Advice:: General program design.
* Program Behavior:: Program behavior for all programs
* Writing C:: Making the best use of C.
* Documentation:: Documenting programs.
* Managing Releases:: The release process.
* References:: Mentioning non-free software or documentation.
* GNU Free Documentation License:: Copying and sharing this manual.
* Index::
@end menu
@node Preface
@chapter About the GNU Coding Standards
The GNU Coding Standards were written by Richard Stallman and other GNU
Project volunteers. Their purpose is to make the GNU system clean,
consistent, and easy to install. This document can also be read as a
guide to writing portable, robust and reliable programs. It focuses on
programs written in C, but many of the rules and principles are useful
even if you write in another programming language. The rules often
state reasons for writing in a certain way.
This release of the GNU Coding Standards was last updated
@value{lastupdate}.
@cindex where to obtain @code{standards.texi}
@cindex downloading this manual
If you did not obtain this file directly from the GNU project and
recently, please check for a newer version. You can get the GNU
Coding Standards from the GNU web server in many
different formats, including the Texinfo source, PDF, HTML, DVI, plain
text, and more, at: @uref{http://www.gnu.org/prep/standards/}.
Corrections or suggestions for this document should be sent to
@email{bug-standards@@gnu.org}. If you make a suggestion, please include a
suggested new wording for it; our time is limited. We prefer a context
diff to the @file{standards.texi} or @file{make-stds.texi} files, but if
you don't have those files, please mail your suggestion anyway.
These standards cover the minimum of what is important when writing a
GNU package. Likely, the need for additional standards will come up.
Sometimes, you might suggest that such standards be added to this
document. If you think your standards would be generally useful, please
do suggest them.
You should also set standards for your package on many questions not
addressed or not firmly specified here. The most important point is to
be self-consistent---try to stick to the conventions you pick, and try
to document them as much as possible. That way, your program will be
more maintainable by others.
The GNU Hello program serves as an example of how to follow the GNU
coding standards for a trivial program.
@uref{http://www.gnu.org/software/hello/hello.html}.
@node Legal Issues
@chapter Keeping Free Software Free
@cindex legal aspects
This chapter discusses how you can make sure that GNU software
avoids legal difficulties, and other related issues.
@menu
* Reading Non-Free Code:: Referring to proprietary programs.
* Contributions:: Accepting contributions.
* Trademarks:: How we deal with trademark issues.
@end menu
@node Reading Non-Free Code
@section Referring to Proprietary Programs
@cindex proprietary programs
@cindex avoiding proprietary code
Don't in any circumstances refer to Unix source code for or during
your work on GNU! (Or to any other proprietary programs.)
If you have a vague recollection of the internals of a Unix program,
this does not absolutely mean you can't write an imitation of it, but
do try to organize the imitation internally along different lines,
because this is likely to make the details of the Unix version
irrelevant and dissimilar to your results.
For example, Unix utilities were generally optimized to minimize
memory use; if you go for speed instead, your program will be very
different. You could keep the entire input file in memory and scan it
there instead of using stdio. Use a smarter algorithm discovered more
recently than the Unix program. Eliminate use of temporary files. Do
it in one pass instead of two (we did this in the assembler).
Or, on the contrary, emphasize simplicity instead of speed. For some
applications, the speed of today's computers makes simpler algorithms
adequate.
Or go for generality. For example, Unix programs often have static
tables or fixed-size strings, which make for arbitrary limits; use
dynamic allocation instead. Make sure your program handles NULs and
other funny characters in the input files. Add a programming language
for extensibility and write part of the program in that language.
Or turn some parts of the program into independently usable libraries.
Or use a simple garbage collector instead of tracking precisely when
to free memory, or use a new GNU facility such as obstacks.
@node Contributions
@section Accepting Contributions
@cindex legal papers
@cindex accepting contributions
If the program you are working on is copyrighted by the Free Software
Foundation, then when someone else sends you a piece of code to add to
the program, we need legal papers to use it---just as we asked you to
sign papers initially. @emph{Each} person who makes a nontrivial
contribution to a program must sign some sort of legal papers in order
for us to have clear title to the program; the main author alone is not
enough.
So, before adding in any contributions from other people, please tell
us, so we can arrange to get the papers. Then wait until we tell you
that we have received the signed papers, before you actually use the
contribution.
This applies both before you release the program and afterward. If
you receive diffs to fix a bug, and they make significant changes, we
need legal papers for that change.
This also applies to comments and documentation files. For copyright
law, comments and code are just text. Copyright applies to all kinds of
text, so we need legal papers for all kinds.
We know it is frustrating to ask for legal papers; it's frustrating for
us as well. But if you don't wait, you are going out on a limb---for
example, what if the contributor's employer won't sign a disclaimer?
You might have to take that code out again!
You don't need papers for changes of a few lines here or there, since
they are not significant for copyright purposes. Also, you don't need
papers if all you get from the suggestion is some ideas, not actual code
which you use. For example, if someone sent you one implementation, but
you write a different implementation of the same idea, you don't need to
get papers.
The very worst thing is if you forget to tell us about the other
contributor. We could be very embarrassed in court some day as a
result.
We have more detailed advice for maintainers of programs; if you have
reached the stage of actually maintaining a program for GNU (whether
released or not), please ask us for a copy. It is also available
online for your perusal: @uref{http://www.gnu.org/prep/maintain/}.
@node Trademarks
@section Trademarks
@cindex trademarks
Please do not include any trademark acknowledgements in GNU software
packages or documentation.
Trademark acknowledgements are the statements that such-and-such is a
trademark of so-and-so. The GNU Project has no objection to the basic
idea of trademarks, but these acknowledgements feel like kowtowing,
and there is no legal requirement for them, so we don't use them.
What is legally required, as regards other people's trademarks, is to
avoid using them in ways which a reader might reasonably understand as
naming or labeling our own programs or activities. For example, since
``Objective C'' is (or at least was) a trademark, we made sure to say
that we provide a ``compiler for the Objective C language'' rather
than an ``Objective C compiler''. The latter would have been meant as
a shorter way of saying the former, but it does not explicitly state
the relationship, so it could be misinterpreted as using ``Objective
C'' as a label for the compiler rather than for the language.
Please don't use ``win'' as an abbreviation for Microsoft Windows in
GNU software or documentation. In hacker terminology, calling
something a ``win'' is a form of praise. If you wish to praise
Microsoft Windows when speaking on your own, by all means do so, but
not in GNU software. Usually we write the name ``Windows'' in full,
but when brevity is very important (as in file names and sometimes
symbol names), we abbreviate it to ``w''. For instance, the files and
functions in Emacs that deal with Windows start with @samp{w32}.
@node Design Advice
@chapter General Program Design
@cindex program design
This chapter discusses some of the issues you should take into
account when designing your program.
@c Standard or ANSI C
@c
@c In 1989 the American National Standards Institute (ANSI) standardized
@c C as standard X3.159-1989. In December of that year the
@c International Standards Organization ISO adopted the ANSI C standard
@c making minor changes. In 1990 ANSI then re-adopted ISO standard
@c C. This version of C is known as either ANSI C or Standard C.
@c A major revision of the C Standard appeared in 1999.
@menu
* Source Language:: Which languages to use.
* Compatibility:: Compatibility with other implementations.
* Using Extensions:: Using non-standard features.
* Standard C:: Using standard C features.
* Conditional Compilation:: Compiling code only if a conditional is true.
@end menu
@node Source Language
@section Which Languages to Use
@cindex programming languages
When you want to use a language that gets compiled and runs at high
speed, the best language to use is C. Using another language is like
using a non-standard feature: it will cause trouble for users. Even if
GCC supports the other language, users may find it inconvenient to have
to install the compiler for that other language in order to build your
program. For example, if you write your program in C++, people will
have to install the GNU C++ compiler in order to compile your program.
C has one other advantage over C++ and other compiled languages: more
people know C, so more people will find it easy to read and modify the
program if it is written in C.
So in general it is much better to use C, rather than the
comparable alternatives.
But there are two exceptions to that conclusion:
@itemize @bullet
@item
It is no problem to use another language to write a tool specifically
intended for use with that language. That is because the only people
who want to build the tool will be those who have installed the other
language anyway.
@item
If an application is of interest only to a narrow part of the community,
then the question of which language it is written in has less effect on
other people, so you may as well please yourself.
@end itemize
Many programs are designed to be extensible: they include an interpreter
for a language that is higher level than C. Often much of the program
is written in that language, too. The Emacs editor pioneered this
technique.
@cindex Guile
@cindex GNOME and Guile
The standard extensibility interpreter for GNU software is Guile
(@uref{http://www.gnu.org/@/software/@/guile/}), which implements the
language Scheme (an especially clean and simple dialect of Lisp).
Guile also includes bindings for GTK+/GNOME, making it practical to
write modern GUI functionality within Guile. We don't reject programs
written in other ``scripting languages'' such as Perl and Python, but
using Guile is very important for the overall consistency of the GNU
system.
@node Compatibility
@section Compatibility with Other Implementations
@cindex compatibility with C and @sc{posix} standards
@cindex @sc{posix} compatibility
With occasional exceptions, utility programs and libraries for GNU
should be upward compatible with those in Berkeley Unix, and upward
compatible with Standard C if Standard C specifies their
behavior, and upward compatible with @sc{posix} if @sc{posix} specifies
their behavior.
When these standards conflict, it is useful to offer compatibility
modes for each of them.
@cindex options for compatibility
Standard C and @sc{posix} prohibit many kinds of extensions. Feel
free to make the extensions anyway, and include a @samp{--ansi},
@samp{--posix}, or @samp{--compatible} option to turn them off.
However, if the extension has a significant chance of breaking any real
programs or scripts, then it is not really upward compatible. So you
should try to redesign its interface to make it upward compatible.
@cindex @code{POSIXLY_CORRECT}, environment variable
Many GNU programs suppress extensions that conflict with @sc{posix} if the
environment variable @code{POSIXLY_CORRECT} is defined (even if it is
defined with a null value). Please make your program recognize this
variable if appropriate.
When a feature is used only by users (not by programs or command
files), and it is done poorly in Unix, feel free to replace it
completely with something totally different and better. (For example,
@code{vi} is replaced with Emacs.) But it is nice to offer a compatible
feature as well. (There is a free @code{vi} clone, so we offer it.)
Additional useful features are welcome regardless of whether
there is any precedent for them.
@node Using Extensions
@section Using Non-standard Features
@cindex non-standard extensions
Many GNU facilities that already exist support a number of convenient
extensions over the comparable Unix facilities. Whether to use these
extensions in implementing your program is a difficult question.
On the one hand, using the extensions can make a cleaner program.
On the other hand, people will not be able to build the program
unless the other GNU tools are available. This might cause the
program to work on fewer kinds of machines.
With some extensions, it might be easy to provide both alternatives.
For example, you can define functions with a ``keyword'' @code{INLINE}
and define that as a macro to expand into either @code{inline} or
nothing, depending on the compiler.
In general, perhaps it is best not to use the extensions if you can
straightforwardly do without them, but to use the extensions if they
are a big improvement.
An exception to this rule are the large, established programs (such as
Emacs) which run on a great variety of systems. Using GNU extensions in
such programs would make many users unhappy, so we don't do that.
Another exception is for programs that are used as part of compilation:
anything that must be compiled with other compilers in order to
bootstrap the GNU compilation facilities. If these require the GNU
compiler, then no one can compile them without having them installed
already. That would be extremely troublesome in certain cases.
@node Standard C
@section Standard C and Pre-Standard C
@cindex @sc{ansi} C standard
1989 Standard C is widespread enough now that it is ok to use its
features in new programs. There is one exception: do not ever use the
``trigraph'' feature of Standard C.
1999 Standard C is not widespread yet, so please do not require its
features in programs. It is ok to use its features if they are present.
However, it is easy to support pre-standard compilers in most programs,
so if you know how to do that, feel free. If a program you are
maintaining has such support, you should try to keep it working.
@cindex function prototypes
To support pre-standard C, instead of writing function definitions in
standard prototype form,
@example
int
foo (int x, int y)
@dots{}
@end example
@noindent
write the definition in pre-standard style like this,
@example
int
foo (x, y)
int x, y;
@dots{}
@end example
@noindent
and use a separate declaration to specify the argument prototype:
@example
int foo (int, int);
@end example
You need such a declaration anyway, in a header file, to get the benefit
of prototypes in all the files where the function is called. And once
you have the declaration, you normally lose nothing by writing the
function definition in the pre-standard style.
This technique does not work for integer types narrower than @code{int}.
If you think of an argument as being of a type narrower than @code{int},
declare it as @code{int} instead.
There are a few special cases where this technique is hard to use. For
example, if a function argument needs to hold the system type
@code{dev_t}, you run into trouble, because @code{dev_t} is shorter than
@code{int} on some machines; but you cannot use @code{int} instead,
because @code{dev_t} is wider than @code{int} on some machines. There
is no type you can safely use on all machines in a non-standard
definition. The only way to support non-standard C and pass such an
argument is to check the width of @code{dev_t} using Autoconf and choose
the argument type accordingly. This may not be worth the trouble.
In order to support pre-standard compilers that do not recognize
prototypes, you may want to use a preprocessor macro like this:
@example
/* Declare the prototype for a general external function. */
#if defined (__STDC__) || defined (WINDOWSNT)
#define P_(proto) proto
#else
#define P_(proto) ()
#endif
@end example
@node Conditional Compilation
@section Conditional Compilation
When supporting configuration options already known when building your
program we prefer using @code{if (... )} over conditional compilation,
as in the former case the compiler is able to perform more extensive
checking of all possible code paths.
For example, please write
@smallexample
if (HAS_FOO)
...
else
...
@end smallexample
@noindent
instead of:
@smallexample
#ifdef HAS_FOO
...
#else
...
#endif
@end smallexample
A modern compiler such as GCC will generate exactly the same code in
both cases, and we have been using similar techniques with good success
in several projects. Of course, the former method assumes that
@code{HAS_FOO} is defined as either 0 or 1.
While this is not a silver bullet solving all portability problems,
and is not always appropriate, following this policy would have saved
GCC developers many hours, or even days, per year.
In the case of function-like macros like @code{REVERSIBLE_CC_MODE} in
GCC which cannot be simply used in @code{if( ...)} statements, there is
an easy workaround. Simply introduce another macro
@code{HAS_REVERSIBLE_CC_MODE} as in the following example:
@smallexample
#ifdef REVERSIBLE_CC_MODE
#define HAS_REVERSIBLE_CC_MODE 1
#else
#define HAS_REVERSIBLE_CC_MODE 0
#endif
@end smallexample
@node Program Behavior
@chapter Program Behavior for All Programs
This chapter describes conventions for writing robust
software. It also describes general standards for error messages, the
command line interface, and how libraries should behave.
@menu
* Non-GNU Standards:: We consider standards such as POSIX;
we don't "obey" them.
* Semantics:: Writing robust programs.
* Libraries:: Library behavior.
* Errors:: Formatting error messages.
* User Interfaces:: Standards about interfaces generally.
* Graphical Interfaces:: Standards for graphical interfaces.
* Command-Line Interfaces:: Standards for command line interfaces.
* Option Table:: Table of long options.
* OID Allocations:: Table of OID slots for GNU.
* Memory Usage:: When and how to care about memory needs.
* File Usage:: Which files to use, and where.
@end menu
@node Non-GNU Standards
@section Non-GNU Standards
The GNU Project regards standards published by other organizations as
suggestions, not orders. We consider those standards, but we do not
``obey'' them. In developing a GNU program, you should implement
an outside standard's specifications when that makes the GNU system
better overall in an objective sense. When it doesn't, you shouldn't.
In most cases, following published standards is convenient for
users---it means that their programs or scripts will work more
portably. For instance, GCC implements nearly all the features of
Standard C as specified by that standard. C program developers would
be unhappy if it did not. And GNU utilities mostly follow
specifications of POSIX.2; shell script writers and users would be
unhappy if our programs were incompatible.
But we do not follow either of these specifications rigidly, and there
are specific points on which we decided not to follow them, so as to
make the GNU system better for users.
For instance, Standard C says that nearly all extensions to C are
prohibited. How silly! GCC implements many extensions, some of which
were later adopted as part of the standard. If you want these
constructs to give an error message as ``required'' by the standard,
you must specify @samp{--pedantic}, which was implemented only so that
we can say ``GCC is a 100% implementation of the standard,'' not
because there is any reason to actually use it.
POSIX.2 specifies that @samp{df} and @samp{du} must output sizes by
default in units of 512 bytes. What users want is units of 1k, so
that is what we do by default. If you want the ridiculous behavior
``required'' by POSIX, you must set the environment variable
@samp{POSIXLY_CORRECT} (which was originally going to be named
@samp{POSIX_ME_HARDER}).
GNU utilities also depart from the letter of the POSIX.2 specification
when they support long-named command-line options, and intermixing
options with ordinary arguments. This minor incompatibility with
POSIX is never a problem in practice, and it is very useful.
In particular, don't reject a new feature, or remove an old one,
merely because a standard says it is ``forbidden'' or ``deprecated.''
@node Semantics
@section Writing Robust Programs
@cindex arbitrary limits on data
Avoid arbitrary limits on the length or number of @emph{any} data
structure, including file names, lines, files, and symbols, by allocating
all data structures dynamically. In most Unix utilities, ``long lines
are silently truncated''. This is not acceptable in a GNU utility.
@cindex @code{NUL} characters
Utilities reading files should not drop NUL characters, or any other
nonprinting characters @emph{including those with codes above 0177}.
The only sensible exceptions would be utilities specifically intended
for interface to certain types of terminals or printers
that can't handle those characters.
Whenever possible, try to make programs work properly with
sequences of bytes that represent multibyte characters, using encodings
such as UTF-8 and others.
@cindex error messages
Check every system call for an error return, unless you know you wish to
ignore errors. Include the system error text (from @code{perror} or
equivalent) in @emph{every} error message resulting from a failing
system call, as well as the name of the file if any and the name of the
utility. Just ``cannot open foo.c'' or ``stat failed'' is not
sufficient.
@cindex @code{malloc} return value
@cindex memory allocation failure
Check every call to @code{malloc} or @code{realloc} to see if it
returned zero. Check @code{realloc} even if you are making the block
smaller; in a system that rounds block sizes to a power of 2,
@code{realloc} may get a different block if you ask for less space.
In Unix, @code{realloc} can destroy the storage block if it returns
zero. GNU @code{realloc} does not have this bug: if it fails, the
original block is unchanged. Feel free to assume the bug is fixed. If
you wish to run your program on Unix, and wish to avoid lossage in this
case, you can use the GNU @code{malloc}.
You must expect @code{free} to alter the contents of the block that was
freed. Anything you want to fetch from the block, you must fetch before
calling @code{free}.
If @code{malloc} fails in a noninteractive program, make that a fatal
error. In an interactive program (one that reads commands from the
user), it is better to abort the command and return to the command
reader loop. This allows the user to kill other processes to free up
virtual memory, and then try the command again.
@cindex command-line arguments, decoding
Use @code{getopt_long} to decode arguments, unless the argument syntax
makes this unreasonable.
When static storage is to be written in during program execution, use
explicit C code to initialize it. Reserve C initialized declarations
for data that will not be changed.
@c ADR: why?
Try to avoid low-level interfaces to obscure Unix data structures (such
as file directories, utmp, or the layout of kernel memory), since these
are less likely to work compatibly. If you need to find all the files
in a directory, use @code{readdir} or some other high-level interface.
These are supported compatibly by GNU.
@cindex signal handling
The preferred signal handling facilities are the BSD variant of
@code{signal}, and the @sc{posix} @code{sigaction} function; the
alternative USG @code{signal} interface is an inferior design.
Nowadays, using the @sc{posix} signal functions may be the easiest way
to make a program portable. If you use @code{signal}, then on GNU/Linux
systems running GNU libc version 1, you should include
@file{bsd/signal.h} instead of @file{signal.h}, so as to get BSD
behavior. It is up to you whether to support systems where
@code{signal} has only the USG behavior, or give up on them.
@cindex impossible conditions
In error checks that detect ``impossible'' conditions, just abort.
There is usually no point in printing any message. These checks
indicate the existence of bugs. Whoever wants to fix the bugs will have
to read the source code and run a debugger. So explain the problem with
comments in the source. The relevant data will be in variables, which
are easy to examine with the debugger, so there is no point moving them
elsewhere.
Do not use a count of errors as the exit status for a program.
@emph{That does not work}, because exit status values are limited to 8
bits (0 through 255). A single run of the program might have 256
errors; if you try to return 256 as the exit status, the parent process
will see 0 as the status, and it will appear that the program succeeded.
@cindex temporary files
@cindex @code{TMPDIR} environment variable
If you make temporary files, check the @code{TMPDIR} environment
variable; if that variable is defined, use the specified directory
instead of @file{/tmp}.
In addition, be aware that there is a possible security problem when
creating temporary files in world-writable directories. In C, you can
avoid this problem by creating temporary files in this manner:
@example
fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0600);
@end example
@noindent
or by using the @code{mkstemps} function from libiberty.
In bash, use @code{set -C} to avoid this problem.
@node Libraries
@section Library Behavior
@cindex libraries
Try to make library functions reentrant. If they need to do dynamic
storage allocation, at least try to avoid any nonreentrancy aside from
that of @code{malloc} itself.
Here are certain name conventions for libraries, to avoid name
conflicts.
Choose a name prefix for the library, more than two characters long.
All external function and variable names should start with this
prefix. In addition, there should only be one of these in any given
library member. This usually means putting each one in a separate
source file.
An exception can be made when two external symbols are always used
together, so that no reasonable program could use one without the
other; then they can both go in the same file.
External symbols that are not documented entry points for the user
should have names beginning with @samp{_}. The @samp{_} should be
followed by the chosen name prefix for the library, to prevent
collisions with other libraries. These can go in the same files with
user entry points if you like.
Static functions and variables can be used as you like and need not
fit any naming convention.
@node Errors
@section Formatting Error Messages
@cindex formatting error messages
@cindex error messages, formatting
Error messages from compilers should look like this:
@example
@var{source-file-name}:@var{lineno}: @var{message}
@end example
@noindent
If you want to mention the column number, use one of these formats:
@example
@var{source-file-name}:@var{lineno}:@var{column}: @var{message}
@var{source-file-name}:@var{lineno}.@var{column}: @var{message}
@end example
@noindent
Line numbers should start from 1 at the beginning of the file, and
column numbers should start from 1 at the beginning of the line. (Both
of these conventions are chosen for compatibility.) Calculate column
numbers assuming that space and all ASCII printing characters have
equal width, and assuming tab stops every 8 columns.
The error message can also give both the starting and ending positions
of the erroneous text. There are several formats so that you can
avoid redundant information such as a duplicate line number.
Here are the possible formats:
@example
@var{source-file-name}:@var{lineno-1}.@var{column-1}-@var{lineno-2}.@var{column-2}: @var{message}
@var{source-file-name}:@var{lineno-1}.@var{column-1}-@var{column-2}: @var{message}
@var{source-file-name}:@var{lineno-1}-@var{lineno-2}: @var{message}
@end example
@noindent
When an error is spread over several files, you can use this format:
@example
@var{file-1}:@var{lineno-1}.@var{column-1}-@var{file-2}:@var{lineno-2}.@var{column-2}: @var{message}
@end example
Error messages from other noninteractive programs should look like this:
@example
@var{program}:@var{source-file-name}:@var{lineno}: @var{message}
@end example
@noindent
when there is an appropriate source file, or like this:
@example
@var{program}: @var{message}
@end example
@noindent
when there is no relevant source file.
If you want to mention the column number, use this format:
@example
@var{program}:@var{source-file-name}:@var{lineno}:@var{column}: @var{message}
@end example
In an interactive program (one that is reading commands from a
terminal), it is better not to include the program name in an error
message. The place to indicate which program is running is in the
prompt or with the screen layout. (When the same program runs with
input from a source other than a terminal, it is not interactive and
would do best to print error messages using the noninteractive style.)
The string @var{message} should not begin with a capital letter when
it follows a program name and/or file name, because that isn't the
beginning of a sentence. (The sentence conceptually starts at the
beginning of the line.) Also, it should not end with a period.
Error messages from interactive programs, and other messages such as
usage messages, should start with a capital letter. But they should not
end with a period.
@node User Interfaces
@section Standards for Interfaces Generally
@cindex program name and its behavior
@cindex behavior, dependent on program's name
Please don't make the behavior of a utility depend on the name used
to invoke it. It is useful sometimes to make a link to a utility
with a different name, and that should not change what it does.
Instead, use a run time option or a compilation switch or both
to select among the alternate behaviors.
@cindex output device and program's behavior
Likewise, please don't make the behavior of the program depend on the
type of output device it is used with. Device independence is an
important principle of the system's design; do not compromise it merely
to save someone from typing an option now and then. (Variation in error
message syntax when using a terminal is ok, because that is a side issue
that people do not depend on.)
If you think one behavior is most useful when the output is to a
terminal, and another is most useful when the output is a file or a
pipe, then it is usually best to make the default behavior the one that
is useful with output to a terminal, and have an option for the other
behavior.
Compatibility requires certain programs to depend on the type of output
device. It would be disastrous if @code{ls} or @code{sh} did not do so
in the way all users expect. In some of these cases, we supplement the
program with a preferred alternate version that does not depend on the
output device type. For example, we provide a @code{dir} program much
like @code{ls} except that its default output format is always
multi-column format.
@node Graphical Interfaces
@section Standards for Graphical Interfaces
@cindex graphical user interface
@cindex gtk+
When you write a program that provides a graphical user interface,
please make it work with X Windows and the GTK+ toolkit unless the
functionality specifically requires some alternative (for example,
``displaying jpeg images while in console mode'').
In addition, please provide a command-line interface to control the
functionality. (In many cases, the graphical user interface can be a
separate program which invokes the command-line program.) This is
so that the same jobs can be done from scripts.
@cindex corba
@cindex gnome
Please also consider providing a CORBA interface (for use from GNOME), a
library interface (for use from C), and perhaps a keyboard-driven
console interface (for use by users from console mode). Once you are
doing the work to provide the functionality and the graphical interface,
these won't be much extra work.
@node Command-Line Interfaces
@section Standards for Command Line Interfaces
@cindex command-line interface
@findex getopt
It is a good idea to follow the @sc{posix} guidelines for the
command-line options of a program. The easiest way to do this is to use
@code{getopt} to parse them. Note that the GNU version of @code{getopt}
will normally permit options anywhere among the arguments unless the
special argument @samp{--} is used. This is not what @sc{posix}
specifies; it is a GNU extension.
@cindex long-named options
Please define long-named options that are equivalent to the
single-letter Unix-style options. We hope to make GNU more user
friendly this way. This is easy to do with the GNU function
@code{getopt_long}.
One of the advantages of long-named options is that they can be
consistent from program to program. For example, users should be able
to expect the ``verbose'' option of any GNU program which has one, to be
spelled precisely @samp{--verbose}. To achieve this uniformity, look at
the table of common long-option names when you choose the option names
for your program (@pxref{Option Table}).
It is usually a good idea for file names given as ordinary arguments to
be input files only; any output files would be specified using options
(preferably @samp{-o} or @samp{--output}). Even if you allow an output
file name as an ordinary argument for compatibility, try to provide an
option as another way to specify it. This will lead to more consistency
among GNU utilities, and fewer idiosyncrasies for users to remember.
@cindex standard command-line options
@cindex options, standard command-line
@cindex CGI programs, standard options for
@cindex PATH_INFO, specifying standard options as
All programs should support two standard options: @samp{--version}
and @samp{--help}. CGI programs should accept these as command-line
options, and also if given as the @env{PATH_INFO}; for instance,
visiting @url{http://example.org/p.cgi/--help} in a browser should
output the same information as invoking @samp{p.cgi --help} from the
command line.
@menu
* --version:: The standard output for --version.
* --help:: The standard output for --help.
@end menu
@node --version
@subsection @option{--version}
@cindex @samp{--version} output
The standard @code{--version} option should direct the program to
print information about its name, version, origin and legal status,
all on standard output, and then exit successfully. Other options and
arguments should be ignored once this is seen, and the program should
not perform its normal function.
@cindex canonical name of a program
@cindex program's canonical name
The first line is meant to be easy for a program to parse; the version
number proper starts after the last space. In addition, it contains
the canonical name for this program, in this format:
@example
GNU Emacs 19.30
@end example
@noindent
The program's name should be a constant string; @emph{don't} compute it
from @code{argv[0]}. The idea is to state the standard or canonical
name for the program, not its file name. There are other ways to find
out the precise file name where a command is found in @code{PATH}.
If the program is a subsidiary part of a larger package, mention the
package name in parentheses, like this:
@example
emacsserver (GNU Emacs) 19.30
@end example
@noindent
If the package has a version number which is different from this
program's version number, you can mention the package version number
just before the close-parenthesis.
If you @emph{need} to mention the version numbers of libraries which
are distributed separately from the package which contains this program,
you can do so by printing an additional line of version info for each
library you want to mention. Use the same format for these lines as for
the first line.
Please do not mention all of the libraries that the program uses ``just
for completeness''---that would produce a lot of unhelpful clutter.
Please mention library version numbers only if you find in practice that
they are very important to you in debugging.
The following line, after the version number line or lines, should be a
copyright notice. If more than one copyright notice is called for, put
each on a separate line.
Next should follow a line stating the license, preferably using one of
abbrevations below, and a brief statement that the program is free
software, and that users are free to copy and change it. Also mention
that there is no warranty, to the extent permitted by law. See
recommended wording below.
It is ok to finish the output with a list of the major authors of the
program, as a way of giving credit.
Here's an example of output that follows these rules:
@smallexample
GNU hello 2.3
Copyright (C) 2007 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
@end smallexample
You should adapt this to your program, of course, filling in the proper
year, copyright holder, name of program, and the references to
distribution terms, and changing the rest of the wording as necessary.
This copyright notice only needs to mention the most recent year in
which changes were made---there's no need to list the years for previous
versions' changes. You don't have to mention the name of the program in
these notices, if that is inconvenient, since it appeared in the first
line. (The rules are different for copyright notices in source files;
@pxref{Copyright Notices,,,maintain,Information for GNU Maintainers}.)
Translations of the above lines must preserve the validity of the
copyright notices (@pxref{Internationalization}). If the translation's
character set supports it, the @samp{(C)} should be replaced with the
copyright symbol, as follows:
@ifinfo
(the official copyright symbol, which is the letter C in a circle);
@end ifinfo
@ifnotinfo
@copyright{}
@end ifnotinfo
Write the word ``Copyright'' exactly like that, in English. Do not
translate it into another language. International treaties recognize
the English word ``Copyright''; translations into other languages do not
have legal significance.
Finally, here is the table of our suggested license abbreviations.
Any abbreviation can be followed by @samp{v@var{version}[+]}, meaning
that particular version, or later versions with the @samp{+}, as shown
above.
In the case of exceptions for extra permissions with the GPL, we use
@samp{/} for a separator; the version number can follow the license
abbreviation as usual, as in the examples below.
@table @asis
@item GPL
GNU General Public License, @url{http://www.gnu.org/@/licenses/@/gpl.html}.
@item LGPL
GNU Lesser General Public License, @url{http://www.gnu.org/@/licenses/@/lgpl.html}.
@item GPL/Guile
GNU GPL with the exception for Guile; for example, GPLv3+/Guile means
the GNU GPL version 3 or later, with the extra exception for Guile.
@item GPL/Ada
GNU GPL with the exception for Ada.
@item Apache
The Apache Software Foundation license,
@url{http://www.apache.org/@/licenses}.
@item Artistic
The Artistic license used for Perl, @url{http://www.perlfoundation.org/@/legal}.
@item Expat
The Expat license, @url{http://www.jclark.com/@/xml/@/copying.txt}.
@item MPL
The Mozilla Public License, @url{http://www.mozilla.org/@/MPL/}.
@item OBSD
The original (4-clause) BSD license, incompatible with the GNU GPL
@url{http://www.xfree86.org/@/3.3.6/@/COPYRIGHT2.html#6}.
@item PHP
The license used for PHP, @url{http://www.php.net/@/license/}.
@item public domain
The non-license that is being in the public domain,
@url{http://www.gnu.org/@/licenses/@/license-list.html#PublicDomain}.
@item Python
The license for Python, @url{http://www.python.org/@/2.0.1/@/license.html}.
@item RBSD
The revised (3-clause) BSD, compatible with the GNU GPL,
@url{http://www.xfree86.org/@/3.3.6/@/COPYRIGHT2.html#5}.
@item X11
The simple non-copyleft license used for most versions of the X Window
system, @url{http://www.xfree86.org/@/3.3.6/@/COPYRIGHT2.html#3}.
@item Zlib
The license for Zlib, @url{http://www.gzip.org/@/zlib/@/zlib_license.html}.
@end table
More information about these licenses and many more are on the GNU
licensing web pages,
@url{http://www.gnu.org/@/licenses/@/license-list.html}.
@node --help
@subsection @option{--help}
@cindex @samp{--help} output
The standard @code{--help} option should output brief documentation
for how to invoke the program, on standard output, then exit
successfully. Other options and arguments should be ignored once this
is seen, and the program should not perform its normal function.
@cindex address for bug reports
@cindex bug reports
Near the end of the @samp{--help} option's output, please place lines
giving the email address for bug reports, the package's home page
(normally @indicateurl{http://www.gnu.org/software/@var{pkg}}, and the
general page for help using GNU programs. The format should be like this:
@example
Report bugs to: @var{mailing-address}
@var{pkg} home page:
General help using GNU software:
@end example
It is ok to mention other appropriate mailing lists and web pages.
@node Option Table
@section Table of Long Options
@cindex long option names
@cindex table of long options
Here is a table of long options used by GNU programs. It is surely
incomplete, but we aim to list all the options that a new program might
want to be compatible with. If you use names not already in the table,
please send @email{bug-standards@@gnu.org} a list of them, with their
meanings, so we can update the table.
@c Please leave newlines between items in this table; it's much easier
@c to update when it isn't completely squashed together and unreadable.
@c When there is more than one short option for a long option name, put
@c a semicolon between the lists of the programs that use them, not a
@c period. --friedman
@table @samp
@item after-date
@samp{-N} in @code{tar}.
@item all
@samp{-a} in @code{du}, @code{ls}, @code{nm}, @code{stty}, @code{uname},
and @code{unexpand}.
@item all-text
@samp{-a} in @code{diff}.
@item almost-all
@samp{-A} in @code{ls}.
@item append
@samp{-a} in @code{etags}, @code{tee}, @code{time};
@samp{-r} in @code{tar}.
@item archive
@samp{-a} in @code{cp}.
@item archive-name
@samp{-n} in @code{shar}.
@item arglength
@samp{-l} in @code{m4}.
@item ascii
@samp{-a} in @code{diff}.
@item assign
@samp{-v} in @code{gawk}.
@item assume-new
@samp{-W} in @code{make}.
@item assume-old
@samp{-o} in @code{make}.
@item auto-check
@samp{-a} in @code{recode}.
@item auto-pager
@samp{-a} in @code{wdiff}.
@item auto-reference
@samp{-A} in @code{ptx}.
@item avoid-wraps
@samp{-n} in @code{wdiff}.
@item background
For server programs, run in the background.
@item backward-search
@samp{-B} in @code{ctags}.
@item basename
@samp{-f} in @code{shar}.
@item batch
Used in GDB.
@item baud
Used in GDB.
@item before
@samp{-b} in @code{tac}.
@item binary
@samp{-b} in @code{cpio} and @code{diff}.
@item bits-per-code
@samp{-b} in @code{shar}.
@item block-size
Used in @code{cpio} and @code{tar}.
@item blocks
@samp{-b} in @code{head} and @code{tail}.
@item break-file
@samp{-b} in @code{ptx}.
@item brief
Used in various programs to make output shorter.
@item bytes
@samp{-c} in @code{head}, @code{split}, and @code{tail}.
@item c@t{++}
@samp{-C} in @code{etags}.
@item catenate
@samp{-A} in @code{tar}.
@item cd
Used in various programs to specify the directory to use.
@item changes
@samp{-c} in @code{chgrp} and @code{chown}.
@item classify
@samp{-F} in @code{ls}.
@item colons
@samp{-c} in @code{recode}.
@item command
@samp{-c} in @code{su};
@samp{-x} in GDB.
@item compare
@samp{-d} in @code{tar}.
@item compat
Used in @code{gawk}.
@item compress
@samp{-Z} in @code{tar} and @code{shar}.
@item concatenate
@samp{-A} in @code{tar}.
@item confirmation
@samp{-w} in @code{tar}.
@item context
Used in @code{diff}.
@item copyleft
@samp{-W copyleft} in @code{gawk}.
@item copyright
@samp{-C} in @code{ptx}, @code{recode}, and @code{wdiff};
@samp{-W copyright} in @code{gawk}.
@item core
Used in GDB.
@item count
@samp{-q} in @code{who}.
@item count-links
@samp{-l} in @code{du}.
@item create
Used in @code{tar} and @code{cpio}.
@item cut-mark
@samp{-c} in @code{shar}.
@item cxref
@samp{-x} in @code{ctags}.
@item date
@samp{-d} in @code{touch}.
@item debug
@samp{-d} in @code{make} and @code{m4};
@samp{-t} in Bison.
@item define
@samp{-D} in @code{m4}.
@item defines
@samp{-d} in Bison and @code{ctags}.
@item delete
@samp{-D} in @code{tar}.
@item dereference
@samp{-L} in @code{chgrp}, @code{chown}, @code{cpio}, @code{du},
@code{ls}, and @code{tar}.
@item dereference-args
@samp{-D} in @code{du}.
@item device
Specify an I/O device (special file name).
@item diacritics
@samp{-d} in @code{recode}.
@item dictionary-order
@samp{-d} in @code{look}.
@item diff
@samp{-d} in @code{tar}.
@item digits
@samp{-n} in @code{csplit}.
@item directory
Specify the directory to use, in various programs. In @code{ls}, it
means to show directories themselves rather than their contents. In
@code{rm} and @code{ln}, it means to not treat links to directories
specially.
@item discard-all
@samp{-x} in @code{strip}.
@item discard-locals
@samp{-X} in @code{strip}.
@item dry-run
@samp{-n} in @code{make}.
@item ed
@samp{-e} in @code{diff}.
@item elide-empty-files
@samp{-z} in @code{csplit}.
@item end-delete
@samp{-x} in @code{wdiff}.
@item end-insert
@samp{-z} in @code{wdiff}.
@item entire-new-file
@samp{-N} in @code{diff}.
@item environment-overrides
@samp{-e} in @code{make}.
@item eof
@samp{-e} in @code{xargs}.
@item epoch
Used in GDB.
@item error-limit
Used in @code{makeinfo}.
@item error-output
@samp{-o} in @code{m4}.
@item escape
@samp{-b} in @code{ls}.
@item exclude-from
@samp{-X} in @code{tar}.
@item exec
Used in GDB.
@item exit
@samp{-x} in @code{xargs}.
@item exit-0
@samp{-e} in @code{unshar}.
@item expand-tabs
@samp{-t} in @code{diff}.
@item expression
@samp{-e} in @code{sed}.
@item extern-only
@samp{-g} in @code{nm}.
@item extract
@samp{-i} in @code{cpio};
@samp{-x} in @code{tar}.
@item faces
@samp{-f} in @code{finger}.
@item fast
@samp{-f} in @code{su}.
@item fatal-warnings
@samp{-E} in @code{m4}.
@item file
@samp{-f} in @code{gawk}, @code{info}, @code{make}, @code{mt},
@code{sed}, and @code{tar}.
@item field-separator
@samp{-F} in @code{gawk}.
@item file-prefix
@samp{-b} in Bison.
@item file-type
@samp{-F} in @code{ls}.
@item files-from
@samp{-T} in @code{tar}.
@item fill-column
Used in @code{makeinfo}.
@item flag-truncation
@samp{-F} in @code{ptx}.
@item fixed-output-files
@samp{-y} in Bison.
@item follow
@samp{-f} in @code{tail}.
@item footnote-style
Used in @code{makeinfo}.
@item force
@samp{-f} in @code{cp}, @code{ln}, @code{mv}, and @code{rm}.
@item force-prefix
@samp{-F} in @code{shar}.
@item foreground
For server programs, run in the foreground;
in other words, don't do anything special to run the server
in the background.
@item format
Used in @code{ls}, @code{time}, and @code{ptx}.
@item freeze-state
@samp{-F} in @code{m4}.
@item fullname
Used in GDB.
@item gap-size
@samp{-g} in @code{ptx}.
@item get
@samp{-x} in @code{tar}.
@item graphic
@samp{-i} in @code{ul}.
@item graphics
@samp{-g} in @code{recode}.
@item group
@samp{-g} in @code{install}.
@item gzip
@samp{-z} in @code{tar} and @code{shar}.
@item hashsize
@samp{-H} in @code{m4}.
@item header
@samp{-h} in @code{objdump} and @code{recode}
@item heading
@samp{-H} in @code{who}.
@item help
Used to ask for brief usage information.
@item here-delimiter
@samp{-d} in @code{shar}.
@item hide-control-chars
@samp{-q} in @code{ls}.
@item html
In @code{makeinfo}, output HTML.
@item idle
@samp{-u} in @code{who}.
@item ifdef
@samp{-D} in @code{diff}.
@item ignore
@samp{-I} in @code{ls};
@samp{-x} in @code{recode}.
@item ignore-all-space
@samp{-w} in @code{diff}.
@item ignore-backups
@samp{-B} in @code{ls}.
@item ignore-blank-lines
@samp{-B} in @code{diff}.
@item ignore-case
@samp{-f} in @code{look} and @code{ptx};
@samp{-i} in @code{diff} and @code{wdiff}.
@item ignore-errors
@samp{-i} in @code{make}.
@item ignore-file
@samp{-i} in @code{ptx}.
@item ignore-indentation
@samp{-I} in @code{etags}.
@item ignore-init-file
@samp{-f} in Oleo.
@item ignore-interrupts
@samp{-i} in @code{tee}.
@item ignore-matching-lines
@samp{-I} in @code{diff}.
@item ignore-space-change
@samp{-b} in @code{diff}.
@item ignore-zeros
@samp{-i} in @code{tar}.
@item include
@samp{-i} in @code{etags};
@samp{-I} in @code{m4}.
@item include-dir
@samp{-I} in @code{make}.
@item incremental
@samp{-G} in @code{tar}.
@item info
@samp{-i}, @samp{-l}, and @samp{-m} in Finger.
@item init-file
In some programs, specify the name of the file to read as the user's
init file.
@item initial
@samp{-i} in @code{expand}.
@item initial-tab
@samp{-T} in @code{diff}.
@item inode
@samp{-i} in @code{ls}.
@item interactive
@samp{-i} in @code{cp}, @code{ln}, @code{mv}, @code{rm};
@samp{-e} in @code{m4};
@samp{-p} in @code{xargs};
@samp{-w} in @code{tar}.
@item intermix-type
@samp{-p} in @code{shar}.
@item iso-8601
Used in @code{date}
@item jobs
@samp{-j} in @code{make}.
@item just-print
@samp{-n} in @code{make}.
@item keep-going
@samp{-k} in @code{make}.
@item keep-files
@samp{-k} in @code{csplit}.
@item kilobytes
@samp{-k} in @code{du} and @code{ls}.
@item language
@samp{-l} in @code{etags}.
@item less-mode
@samp{-l} in @code{wdiff}.
@item level-for-gzip
@samp{-g} in @code{shar}.
@item line-bytes
@samp{-C} in @code{split}.
@item lines
Used in @code{split}, @code{head}, and @code{tail}.
@item link
@samp{-l} in @code{cpio}.
@item lint
@itemx lint-old
Used in @code{gawk}.
@item list
@samp{-t} in @code{cpio};
@samp{-l} in @code{recode}.
@item list
@samp{-t} in @code{tar}.
@item literal
@samp{-N} in @code{ls}.
@item load-average
@samp{-l} in @code{make}.
@item login
Used in @code{su}.
@item machine
Used in @code{uname}.
@item macro-name
@samp{-M} in @code{ptx}.
@item mail
@samp{-m} in @code{hello} and @code{uname}.
@item make-directories
@samp{-d} in @code{cpio}.
@item makefile
@samp{-f} in @code{make}.
@item mapped
Used in GDB.
@item max-args
@samp{-n} in @code{xargs}.
@item max-chars
@samp{-n} in @code{xargs}.
@item max-lines
@samp{-l} in @code{xargs}.
@item max-load
@samp{-l} in @code{make}.
@item max-procs
@samp{-P} in @code{xargs}.
@item mesg
@samp{-T} in @code{who}.
@item message
@samp{-T} in @code{who}.
@item minimal
@samp{-d} in @code{diff}.
@item mixed-uuencode
@samp{-M} in @code{shar}.
@item mode
@samp{-m} in @code{install}, @code{mkdir}, and @code{mkfifo}.
@item modification-time
@samp{-m} in @code{tar}.
@item multi-volume
@samp{-M} in @code{tar}.
@item name-prefix
@samp{-a} in Bison.
@item nesting-limit
@samp{-L} in @code{m4}.
@item net-headers
@samp{-a} in @code{shar}.
@item new-file
@samp{-W} in @code{make}.
@item no-builtin-rules
@samp{-r} in @code{make}.
@item no-character-count
@samp{-w} in @code{shar}.
@item no-check-existing
@samp{-x} in @code{shar}.
@item no-common
@samp{-3} in @code{wdiff}.
@item no-create
@samp{-c} in @code{touch}.
@item no-defines
@samp{-D} in @code{etags}.
@item no-deleted
@samp{-1} in @code{wdiff}.
@item no-dereference
@samp{-d} in @code{cp}.
@item no-inserted
@samp{-2} in @code{wdiff}.
@item no-keep-going
@samp{-S} in @code{make}.
@item no-lines
@samp{-l} in Bison.
@item no-piping
@samp{-P} in @code{shar}.
@item no-prof
@samp{-e} in @code{gprof}.
@item no-regex
@samp{-R} in @code{etags}.
@item no-sort
@samp{-p} in @code{nm}.
@item no-splash
Don't print a startup splash screen.
@item no-split
Used in @code{makeinfo}.
@item no-static
@samp{-a} in @code{gprof}.
@item no-time
@samp{-E} in @code{gprof}.
@item no-timestamp
@samp{-m} in @code{shar}.
@item no-validate
Used in @code{makeinfo}.
@item no-wait
Used in @code{emacsclient}.
@item no-warn
Used in various programs to inhibit warnings.
@item node
@samp{-n} in @code{info}.
@item nodename
@samp{-n} in @code{uname}.
@item nonmatching
@samp{-f} in @code{cpio}.
@item nstuff
@samp{-n} in @code{objdump}.
@item null
@samp{-0} in @code{xargs}.
@item number
@samp{-n} in @code{cat}.
@item number-nonblank
@samp{-b} in @code{cat}.
@item numeric-sort
@samp{-n} in @code{nm}.
@item numeric-uid-gid
@samp{-n} in @code{cpio} and @code{ls}.
@item nx
Used in GDB.
@item old-archive
@samp{-o} in @code{tar}.
@item old-file
@samp{-o} in @code{make}.
@item one-file-system
@samp{-l} in @code{tar}, @code{cp}, and @code{du}.
@item only-file
@samp{-o} in @code{ptx}.
@item only-prof
@samp{-f} in @code{gprof}.
@item only-time
@samp{-F} in @code{gprof}.
@item options
@samp{-o} in @code{getopt}, @code{fdlist}, @code{fdmount},
@code{fdmountd}, and @code{fdumount}.
@item output
In various programs, specify the output file name.
@item output-prefix
@samp{-o} in @code{shar}.
@item override
@samp{-o} in @code{rm}.
@item overwrite
@samp{-c} in @code{unshar}.
@item owner
@samp{-o} in @code{install}.
@item paginate
@samp{-l} in @code{diff}.
@item paragraph-indent
Used in @code{makeinfo}.
@item parents
@samp{-p} in @code{mkdir} and @code{rmdir}.
@item pass-all
@samp{-p} in @code{ul}.
@item pass-through
@samp{-p} in @code{cpio}.
@item port
@samp{-P} in @code{finger}.
@item portability
@samp{-c} in @code{cpio} and @code{tar}.
@item posix
Used in @code{gawk}.
@item prefix-builtins
@samp{-P} in @code{m4}.
@item prefix
@samp{-f} in @code{csplit}.
@item preserve
Used in @code{tar} and @code{cp}.
@item preserve-environment
@samp{-p} in @code{su}.
@item preserve-modification-time
@samp{-m} in @code{cpio}.
@item preserve-order
@samp{-s} in @code{tar}.
@item preserve-permissions
@samp{-p} in @code{tar}.
@item print
@samp{-l} in @code{diff}.
@item print-chars
@samp{-L} in @code{cmp}.
@item print-data-base
@samp{-p} in @code{make}.
@item print-directory
@samp{-w} in @code{make}.
@item print-file-name
@samp{-o} in @code{nm}.
@item print-symdefs
@samp{-s} in @code{nm}.
@item printer
@samp{-p} in @code{wdiff}.
@item prompt
@samp{-p} in @code{ed}.
@item proxy
Specify an HTTP proxy.
@item query-user
@samp{-X} in @code{shar}.
@item question
@samp{-q} in @code{make}.
@item quiet
Used in many programs to inhibit the usual output. Every
program accepting @samp{--quiet} should accept @samp{--silent} as a
synonym.
@item quiet-unshar
@samp{-Q} in @code{shar}
@item quote-name
@samp{-Q} in @code{ls}.
@item rcs
@samp{-n} in @code{diff}.
@item re-interval
Used in @code{gawk}.
@item read-full-blocks
@samp{-B} in @code{tar}.
@item readnow
Used in GDB.
@item recon
@samp{-n} in @code{make}.
@item record-number
@samp{-R} in @code{tar}.
@item recursive
Used in @code{chgrp}, @code{chown}, @code{cp}, @code{ls}, @code{diff},
and @code{rm}.
@item reference
@samp{-r} in @code{touch}.
@item references
@samp{-r} in @code{ptx}.
@item regex
@samp{-r} in @code{tac} and @code{etags}.
@item release
@samp{-r} in @code{uname}.
@item reload-state
@samp{-R} in @code{m4}.
@item relocation
@samp{-r} in @code{objdump}.
@item rename
@samp{-r} in @code{cpio}.
@item replace
@samp{-i} in @code{xargs}.
@item report-identical-files
@samp{-s} in @code{diff}.
@item reset-access-time
@samp{-a} in @code{cpio}.
@item reverse
@samp{-r} in @code{ls} and @code{nm}.
@item reversed-ed
@samp{-f} in @code{diff}.
@item right-side-defs
@samp{-R} in @code{ptx}.
@item same-order
@samp{-s} in @code{tar}.
@item same-permissions
@samp{-p} in @code{tar}.
@item save
@samp{-g} in @code{stty}.
@item se
Used in GDB.
@item sentence-regexp
@samp{-S} in @code{ptx}.
@item separate-dirs
@samp{-S} in @code{du}.
@item separator
@samp{-s} in @code{tac}.
@item sequence
Used by @code{recode} to chose files or pipes for sequencing passes.
@item shell
@samp{-s} in @code{su}.
@item show-all
@samp{-A} in @code{cat}.
@item show-c-function
@samp{-p} in @code{diff}.
@item show-ends
@samp{-E} in @code{cat}.
@item show-function-line
@samp{-F} in @code{diff}.
@item show-tabs
@samp{-T} in @code{cat}.
@item silent
Used in many programs to inhibit the usual output.
Every program accepting
@samp{--silent} should accept @samp{--quiet} as a synonym.
@item size
@samp{-s} in @code{ls}.
@item socket
Specify a file descriptor for a network server to use for its socket,
instead of opening and binding a new socket. This provides a way to
run, in a non-privileged process, a server that normally needs a
reserved port number.
@item sort
Used in @code{ls}.
@item source
@samp{-W source} in @code{gawk}.
@item sparse
@samp{-S} in @code{tar}.
@item speed-large-files
@samp{-H} in @code{diff}.
@item split-at
@samp{-E} in @code{unshar}.
@item split-size-limit
@samp{-L} in @code{shar}.
@item squeeze-blank
@samp{-s} in @code{cat}.
@item start-delete
@samp{-w} in @code{wdiff}.
@item start-insert
@samp{-y} in @code{wdiff}.
@item starting-file
Used in @code{tar} and @code{diff} to specify which file within
a directory to start processing with.
@item statistics
@samp{-s} in @code{wdiff}.
@item stdin-file-list
@samp{-S} in @code{shar}.
@item stop
@samp{-S} in @code{make}.
@item strict
@samp{-s} in @code{recode}.
@item strip
@samp{-s} in @code{install}.
@item strip-all
@samp{-s} in @code{strip}.
@item strip-debug
@samp{-S} in @code{strip}.
@item submitter
@samp{-s} in @code{shar}.
@item suffix
@samp{-S} in @code{cp}, @code{ln}, @code{mv}.
@item suffix-format
@samp{-b} in @code{csplit}.
@item sum
@samp{-s} in @code{gprof}.
@item summarize
@samp{-s} in @code{du}.
@item symbolic
@samp{-s} in @code{ln}.
@item symbols
Used in GDB and @code{objdump}.
@item synclines
@samp{-s} in @code{m4}.
@item sysname
@samp{-s} in @code{uname}.
@item tabs
@samp{-t} in @code{expand} and @code{unexpand}.
@item tabsize
@samp{-T} in @code{ls}.
@item terminal
@samp{-T} in @code{tput} and @code{ul}.
@samp{-t} in @code{wdiff}.
@item text
@samp{-a} in @code{diff}.
@item text-files
@samp{-T} in @code{shar}.
@item time
Used in @code{ls} and @code{touch}.
@item timeout
Specify how long to wait before giving up on some operation.
@item to-stdout
@samp{-O} in @code{tar}.
@item total
@samp{-c} in @code{du}.
@item touch
@samp{-t} in @code{make}, @code{ranlib}, and @code{recode}.
@item trace
@samp{-t} in @code{m4}.
@item traditional
@samp{-t} in @code{hello};
@samp{-W traditional} in @code{gawk};
@samp{-G} in @code{ed}, @code{m4}, and @code{ptx}.
@item tty
Used in GDB.
@item typedefs
@samp{-t} in @code{ctags}.
@item typedefs-and-c++
@samp{-T} in @code{ctags}.
@item typeset-mode
@samp{-t} in @code{ptx}.
@item uncompress
@samp{-z} in @code{tar}.
@item unconditional
@samp{-u} in @code{cpio}.
@item undefine
@samp{-U} in @code{m4}.
@item undefined-only
@samp{-u} in @code{nm}.
@item update
@samp{-u} in @code{cp}, @code{ctags}, @code{mv}, @code{tar}.
@item usage
Used in @code{gawk}; same as @samp{--help}.
@item uuencode
@samp{-B} in @code{shar}.
@item vanilla-operation
@samp{-V} in @code{shar}.
@item verbose
Print more information about progress. Many programs support this.
@item verify
@samp{-W} in @code{tar}.
@item version
Print the version number.
@item version-control
@samp{-V} in @code{cp}, @code{ln}, @code{mv}.
@item vgrind
@samp{-v} in @code{ctags}.
@item volume
@samp{-V} in @code{tar}.
@item what-if
@samp{-W} in @code{make}.
@item whole-size-limit
@samp{-l} in @code{shar}.
@item width
@samp{-w} in @code{ls} and @code{ptx}.
@item word-regexp
@samp{-W} in @code{ptx}.
@item writable
@samp{-T} in @code{who}.
@item zeros
@samp{-z} in @code{gprof}.
@end table
@node OID Allocations
@section OID Allocations
@cindex OID allocations for GNU
@cindex SNMP
@cindex LDAP
@cindex X.509
The OID (object identifier) 1.3.6.1.4.1.11591 has been assigned to the
GNU Project (thanks to Werner Koch). These are used for SNMP, LDAP,
X.509 certificates, and so on. The web site
@url{http://www.alvestrand.no/objectid} has a (voluntary) listing of
many OID assignments.
If you need a new slot for your GNU package, write
@email{maintainers@@gnu.org}. Here is a list of arcs currently
assigned:
@example
@include gnu-oids.texi
@end example
@node Memory Usage
@section Memory Usage
@cindex memory usage
If a program typically uses just a few meg of memory, don't bother making any
effort to reduce memory usage. For example, if it is impractical for
other reasons to operate on files more than a few meg long, it is
reasonable to read entire input files into memory to operate on them.
However, for programs such as @code{cat} or @code{tail}, that can
usefully operate on very large files, it is important to avoid using a
technique that would artificially limit the size of files it can handle.
If a program works by lines and could be applied to arbitrary
user-supplied input files, it should keep only a line in memory, because
this is not very hard and users will want to be able to operate on input
files that are bigger than will fit in memory all at once.
If your program creates complicated data structures, just make them in
memory and give a fatal error if @code{malloc} returns zero.
@node File Usage
@section File Usage
@cindex file usage
Programs should be prepared to operate when @file{/usr} and @file{/etc}
are read-only file systems. Thus, if the program manages log files,
lock files, backup files, score files, or any other files which are
modified for internal purposes, these files should not be stored in
@file{/usr} or @file{/etc}.
There are two exceptions. @file{/etc} is used to store system
configuration information; it is reasonable for a program to modify
files in @file{/etc} when its job is to update the system configuration.
Also, if the user explicitly asks to modify one file in a directory, it
is reasonable for the program to store other files in the same
directory.
@node Writing C
@chapter Making The Best Use of C
This chapter provides advice on how best to use the C language
when writing GNU software.
@menu
* Formatting:: Formatting your source code.
* Comments:: Commenting your work.
* Syntactic Conventions:: Clean use of C constructs.
* Names:: Naming variables, functions, and files.
* System Portability:: Portability among different operating systems.
* CPU Portability:: Supporting the range of CPU types.
* System Functions:: Portability and ``standard'' library functions.
* Internationalization:: Techniques for internationalization.
* Character Set:: Use ASCII by default.
* Quote Characters:: Use `...' in the C locale.
* Mmap:: How you can safely use @code{mmap}.
@end menu
@node Formatting
@section Formatting Your Source Code
@cindex formatting source code
@cindex open brace
@cindex braces, in C source
It is important to put the open-brace that starts the body of a C
function in column one, so that they will start a defun. Several
tools look for open-braces in column one to find the beginnings of C
functions. These tools will not work on code not formatted that way.
Avoid putting open-brace, open-parenthesis or open-bracket in column
one when they are inside a function, so that they won't start a defun.
The open-brace that starts a @code{struct} body can go in column one
if you find it useful to treat that definition as a defun.
It is also important for function definitions to start the name of the
function in column one. This helps people to search for function
definitions, and may also help certain tools recognize them. Thus,
using Standard C syntax, the format is this:
@example
static char *
concat (char *s1, char *s2)
@{
@dots{}
@}
@end example
@noindent
or, if you want to use traditional C syntax, format the definition like
this:
@example
static char *
concat (s1, s2) /* Name starts in column one here */
char *s1, *s2;
@{ /* Open brace in column one here */
@dots{}
@}
@end example
In Standard C, if the arguments don't fit nicely on one line,
split it like this:
@example
int
lots_of_args (int an_integer, long a_long, short a_short,
double a_double, float a_float)
@dots{}
@end example
The rest of this section gives our recommendations for other aspects of
C formatting style, which is also the default style of the @code{indent}
program in version 1.2 and newer. It corresponds to the options
@smallexample
-nbad -bap -nbc -bbo -bl -bli2 -bls -ncdb -nce -cp1 -cs -di2
-ndj -nfc1 -nfca -hnl -i2 -ip5 -lp -pcs -psl -nsc -nsob
@end smallexample
We don't think of these recommendations as requirements, because it
causes no problems for users if two different programs have different
formatting styles.
But whatever style you use, please use it consistently, since a mixture
of styles within one program tends to look ugly. If you are
contributing changes to an existing program, please follow the style of
that program.
For the body of the function, our recommended style looks like this:
@example
if (x < foo (y, z))
haha = bar[4] + 5;
else
@{
while (z)
@{
haha += foo (z, z);
z--;
@}
return ++x + bar ();
@}
@end example
@cindex spaces before open-paren
We find it easier to read a program when it has spaces before the
open-parentheses and after the commas. Especially after the commas.
When you split an expression into multiple lines, split it
before an operator, not after one. Here is the right way:
@cindex expressions, splitting
@example
if (foo_this_is_long && bar > win (x, y, z)
&& remaining_condition)
@end example
Try to avoid having two operators of different precedence at the same
level of indentation. For example, don't write this:
@example
mode = (inmode[j] == VOIDmode
|| GET_MODE_SIZE (outmode[j]) > GET_MODE_SIZE (inmode[j])
? outmode[j] : inmode[j]);
@end example
Instead, use extra parentheses so that the indentation shows the nesting:
@example
mode = ((inmode[j] == VOIDmode
|| (GET_MODE_SIZE (outmode[j]) > GET_MODE_SIZE (inmode[j])))
? outmode[j] : inmode[j]);
@end example
Insert extra parentheses so that Emacs will indent the code properly.
For example, the following indentation looks nice if you do it by hand,
@example
v = rup->ru_utime.tv_sec*1000 + rup->ru_utime.tv_usec/1000
+ rup->ru_stime.tv_sec*1000 + rup->ru_stime.tv_usec/1000;
@end example
@noindent
but Emacs would alter it. Adding a set of parentheses produces
something that looks equally nice, and which Emacs will preserve:
@example
v = (rup->ru_utime.tv_sec*1000 + rup->ru_utime.tv_usec/1000
+ rup->ru_stime.tv_sec*1000 + rup->ru_stime.tv_usec/1000);
@end example
Format do-while statements like this:
@example
do
@{
a = foo (a);
@}
while (a > 0);
@end example
@cindex formfeed
@cindex control-L
Please use formfeed characters (control-L) to divide the program into
pages at logical places (but not within a function). It does not matter
just how long the pages are, since they do not have to fit on a printed
page. The formfeeds should appear alone on lines by themselves.
@node Comments
@section Commenting Your Work
@cindex commenting
Every program should start with a comment saying briefly what it is for.
Example: @samp{fmt - filter for simple filling of text}. This comment
should be at the top of the source file containing the @samp{main}
function of the program.
Also, please write a brief comment at the start of each source file,
with the file name and a line or two about the overall purpose of the
file.
Please write the comments in a GNU program in English, because English
is the one language that nearly all programmers in all countries can
read. If you do not write English well, please write comments in
English as well as you can, then ask other people to help rewrite them.
If you can't write comments in English, please find someone to work with
you and translate your comments into English.
Please put a comment on each function saying what the function does,
what sorts of arguments it gets, and what the possible values of
arguments mean and are used for. It is not necessary to duplicate in
words the meaning of the C argument declarations, if a C type is being
used in its customary fashion. If there is anything nonstandard about
its use (such as an argument of type @code{char *} which is really the
address of the second character of a string, not the first), or any
possible values that would not work the way one would expect (such as,
that strings containing newlines are not guaranteed to work), be sure
to say so.
Also explain the significance of the return value, if there is one.
Please put two spaces after the end of a sentence in your comments, so
that the Emacs sentence commands will work. Also, please write
complete sentences and capitalize the first word. If a lower-case
identifier comes at the beginning of a sentence, don't capitalize it!
Changing the spelling makes it a different identifier. If you don't
like starting a sentence with a lower case letter, write the sentence
differently (e.g., ``The identifier lower-case is @dots{}'').
The comment on a function is much clearer if you use the argument
names to speak about the argument values. The variable name itself
should be lower case, but write it in upper case when you are speaking
about the value rather than the variable itself. Thus, ``the inode
number NODE_NUM'' rather than ``an inode''.
There is usually no purpose in restating the name of the function in
the comment before it, because the reader can see that for himself.
There might be an exception when the comment is so long that the function
itself would be off the bottom of the screen.
There should be a comment on each static variable as well, like this:
@example
/* Nonzero means truncate lines in the display;
zero means continue them. */
int truncate_lines;
@end example
@cindex conditionals, comments for
@cindex @code{#endif}, commenting
Every @samp{#endif} should have a comment, except in the case of short
conditionals (just a few lines) that are not nested. The comment should
state the condition of the conditional that is ending, @emph{including
its sense}. @samp{#else} should have a comment describing the condition
@emph{and sense} of the code that follows. For example:
@example
@group
#ifdef foo
@dots{}
#else /* not foo */
@dots{}
#endif /* not foo */
@end group
@group
#ifdef foo
@dots{}
#endif /* foo */
@end group
@end example
@noindent
but, by contrast, write the comments this way for a @samp{#ifndef}:
@example
@group
#ifndef foo
@dots{}
#else /* foo */
@dots{}
#endif /* foo */
@end group
@group
#ifndef foo
@dots{}
#endif /* not foo */
@end group
@end example
@node Syntactic Conventions
@section Clean Use of C Constructs
@cindex syntactic conventions
@cindex implicit @code{int}
@cindex function argument, declaring
Please explicitly declare the types of all objects. For example, you
should explicitly declare all arguments to functions, and you should
declare functions to return @code{int} rather than omitting the
@code{int}.
@cindex compiler warnings
@cindex @samp{-Wall} compiler option
Some programmers like to use the GCC @samp{-Wall} option, and change the
code whenever it issues a warning. If you want to do this, then do.
Other programmers prefer not to use @samp{-Wall}, because it gives
warnings for valid and legitimate code which they do not want to change.
If you want to do this, then do. The compiler should be your servant,
not your master.
Declarations of external functions and functions to appear later in the
source file should all go in one place near the beginning of the file
(somewhere before the first function definition in the file), or else
should go in a header file. Don't put @code{extern} declarations inside
functions.
@cindex temporary variables
It used to be common practice to use the same local variables (with
names like @code{tem}) over and over for different values within one
function. Instead of doing this, it is better to declare a separate local
variable for each distinct purpose, and give it a name which is
meaningful. This not only makes programs easier to understand, it also
facilitates optimization by good compilers. You can also move the
declaration of each local variable into the smallest scope that includes
all its uses. This makes the program even cleaner.
Don't use local variables or parameters that shadow global identifiers.
@cindex multiple variables in a line
Don't declare multiple variables in one declaration that spans lines.
Start a new declaration on each line, instead. For example, instead
of this:
@example
@group
int foo,
bar;
@end group
@end example
@noindent
write either this:
@example
int foo, bar;
@end example
@noindent
or this:
@example
int foo;
int bar;
@end example
@noindent
(If they are global variables, each should have a comment preceding it
anyway.)
When you have an @code{if}-@code{else} statement nested in another
@code{if} statement, always put braces around the @code{if}-@code{else}.
Thus, never write like this:
@example
if (foo)
if (bar)
win ();
else
lose ();
@end example
@noindent
always like this:
@example
if (foo)
@{
if (bar)
win ();
else
lose ();
@}
@end example
If you have an @code{if} statement nested inside of an @code{else}
statement, either write @code{else if} on one line, like this,
@example
if (foo)
@dots{}
else if (bar)
@dots{}
@end example
@noindent
with its @code{then}-part indented like the preceding @code{then}-part,
or write the nested @code{if} within braces like this:
@example
if (foo)
@dots{}
else
@{
if (bar)
@dots{}
@}
@end example
Don't declare both a structure tag and variables or typedefs in the
same declaration. Instead, declare the structure tag separately
and then use it to declare the variables or typedefs.
Try to avoid assignments inside @code{if}-conditions (assignments
inside @code{while}-conditions are ok). For example, don't write
this:
@example
if ((foo = (char *) malloc (sizeof *foo)) == 0)
fatal ("virtual memory exhausted");
@end example
@noindent
instead, write this:
@example
foo = (char *) malloc (sizeof *foo);
if (foo == 0)
fatal ("virtual memory exhausted");
@end example
@pindex lint
Don't make the program ugly to placate @code{lint}. Please don't insert any
casts to @code{void}. Zero without a cast is perfectly fine as a null
pointer constant, except when calling a varargs function.
@node Names
@section Naming Variables, Functions, and Files
@cindex names of variables, functions, and files
The names of global variables and functions in a program serve as
comments of a sort. So don't choose terse names---instead, look for
names that give useful information about the meaning of the variable or
function. In a GNU program, names should be English, like other
comments.
Local variable names can be shorter, because they are used only within
one context, where (presumably) comments explain their purpose.
Try to limit your use of abbreviations in symbol names. It is ok to
make a few abbreviations, explain what they mean, and then use them
frequently, but don't use lots of obscure abbreviations.
Please use underscores to separate words in a name, so that the Emacs
word commands can be useful within them. Stick to lower case; reserve
upper case for macros and @code{enum} constants, and for name-prefixes
that follow a uniform convention.
For example, you should use names like @code{ignore_space_change_flag};
don't use names like @code{iCantReadThis}.
Variables that indicate whether command-line options have been
specified should be named after the meaning of the option, not after
the option-letter. A comment should state both the exact meaning of
the option and its letter. For example,
@example
@group
/* Ignore changes in horizontal whitespace (-b). */
int ignore_space_change_flag;
@end group
@end example
When you want to define names with constant integer values, use
@code{enum} rather than @samp{#define}. GDB knows about enumeration
constants.
@cindex file-name limitations
@pindex doschk
You might want to make sure that none of the file names would conflict
if the files were loaded onto an MS-DOS file system which shortens the
names. You can use the program @code{doschk} to test for this.
Some GNU programs were designed to limit themselves to file names of 14
characters or less, to avoid file name conflicts if they are read into
older System V systems. Please preserve this feature in the existing
GNU programs that have it, but there is no need to do this in new GNU
programs. @code{doschk} also reports file names longer than 14
characters.
@node System Portability
@section Portability between System Types
@cindex portability, between system types
In the Unix world, ``portability'' refers to porting to different Unix
versions. For a GNU program, this kind of portability is desirable, but
not paramount.
The primary purpose of GNU software is to run on top of the GNU kernel,
compiled with the GNU C compiler, on various types of @sc{cpu}. So the
kinds of portability that are absolutely necessary are quite limited.
But it is important to support Linux-based GNU systems, since they
are the form of GNU that is popular.
Beyond that, it is good to support the other free operating systems
(*BSD), and it is nice to support other Unix-like systems if you want
to. Supporting a variety of Unix-like systems is desirable, although
not paramount. It is usually not too hard, so you may as well do it.
But you don't have to consider it an obligation, if it does turn out to
be hard.
@pindex autoconf
The easiest way to achieve portability to most Unix-like systems is to
use Autoconf. It's unlikely that your program needs to know more
information about the host platform than Autoconf can provide, simply
because most of the programs that need such knowledge have already been
written.
Avoid using the format of semi-internal data bases (e.g., directories)
when there is a higher-level alternative (@code{readdir}).
@cindex non-@sc{posix} systems, and portability
As for systems that are not like Unix, such as MSDOS, Windows, VMS, MVS,
and older Macintosh systems, supporting them is often a lot of work.
When that is the case, it is better to spend your time adding features
that will be useful on GNU and GNU/Linux, rather than on supporting
other incompatible systems.
If you do support Windows, please do not abbreviate it as ``win''. In
hacker terminology, calling something a ``win'' is a form of praise.
You're free to praise Microsoft Windows on your own if you want, but
please don't do this in GNU packages. Instead of abbreviating
``Windows'' to ``win'', you can write it in full or abbreviate it to
``woe'' or ``w''. In GNU Emacs, for instance, we use @samp{w32} in
file names of Windows-specific files, but the macro for Windows
conditionals is called @code{WINDOWSNT}.
It is a good idea to define the ``feature test macro''
@code{_GNU_SOURCE} when compiling your C files. When you compile on GNU
or GNU/Linux, this will enable the declarations of GNU library extension
functions, and that will usually give you a compiler error message if
you define the same function names in some other way in your program.
(You don't have to actually @emph{use} these functions, if you prefer
to make the program more portable to other systems.)
But whether or not you use these GNU extensions, you should avoid
using their names for any other meanings. Doing so would make it hard
to move your code into other GNU programs.
@node CPU Portability
@section Portability between @sc{cpu}s
@cindex data types, and portability
@cindex portability, and data types
Even GNU systems will differ because of differences among @sc{cpu}
types---for example, difference in byte ordering and alignment
requirements. It is absolutely essential to handle these differences.
However, don't make any effort to cater to the possibility that an
@code{int} will be less than 32 bits. We don't support 16-bit machines
in GNU.
Similarly, don't make any effort to cater to the possibility that
@code{long} will be smaller than predefined types like @code{size_t}.
For example, the following code is ok:
@example
printf ("size = %lu\n", (unsigned long) sizeof array);
printf ("diff = %ld\n", (long) (pointer2 - pointer1));
@end example
1989 Standard C requires this to work, and we know of only one
counterexample: 64-bit programs on Microsoft Windows. We will
leave it to those who want to port GNU programs to that environment
to figure out how to do it.
Predefined file-size types like @code{off_t} are an exception: they are
longer than @code{long} on many platforms, so code like the above won't
work with them. One way to print an @code{off_t} value portably is to
print its digits yourself, one by one.
Don't assume that the address of an @code{int} object is also the
address of its least-significant byte. This is false on big-endian
machines. Thus, don't make the following mistake:
@example
int c;
@dots{}
while ((c = getchar ()) != EOF)
write (file_descriptor, &c, 1);
@end example
@noindent Instead, use @code{unsigned char} as follows. (The @code{unsigned}
is for portability to unusual systems where @code{char} is signed and
where there is integer overflow checking.)
@example
int c;
while ((c = getchar ()) != EOF)
@{
unsigned char u = c;
write (file_descriptor, &u, 1);
@}
@end example
It used to be ok to not worry about the difference between pointers
and integers when passing arguments to functions. However, on most
modern 64-bit machines pointers are wider than @code{int}.
Conversely, integer types like @code{long long int} and @code{off_t}
are wider than pointers on most modern 32-bit machines. Hence it's
often better nowadays to use prototypes to define functions whose
argument types are not trivial.
In particular, if functions accept varying argument counts or types
they should be declared using prototypes containing @samp{...} and
defined using @file{stdarg.h}. For an example of this, please see the
@uref{http://www.gnu.org/software/gnulib/, Gnulib} error module, which
declares and defines the following function:
@example
/* Print a message with `fprintf (stderr, FORMAT, ...)';
if ERRNUM is nonzero, follow it with ": " and strerror (ERRNUM).
If STATUS is nonzero, terminate the program with `exit (STATUS)'. */
void error (int status, int errnum, const char *format, ...);
@end example
A simple way to use the Gnulib error module is to obtain the two
source files @file{error.c} and @file{error.h} from the Gnulib library
source code repository at
@uref{http://git.savannah.gnu.org/@/gitweb/@/?p=gnulib.git}.
Here's a sample use:
@example
#include "error.h"
#include
#include
char *program_name = "myprogram";
FILE *
xfopen (char const *name)
@{
FILE *fp = fopen (name, "r");
if (! fp)
error (1, errno, "cannot read %s", name);
return fp;
@}
@end example
@cindex casting pointers to integers
Avoid casting pointers to integers if you can. Such casts greatly
reduce portability, and in most programs they are easy to avoid. In the
cases where casting pointers to integers is essential---such as, a Lisp
interpreter which stores type information as well as an address in one
word---you'll have to make explicit provisions to handle different word
sizes. You will also need to make provision for systems in which the
normal range of addresses you can get from @code{malloc} starts far away
from zero.
@node System Functions
@section Calling System Functions
@cindex library functions, and portability
@cindex portability, and library functions
C implementations differ substantially. Standard C reduces but does
not eliminate the incompatibilities; meanwhile, many GNU packages still
support pre-standard compilers because this is not hard to do. This
chapter gives recommendations for how to use the more-or-less standard C
library functions to avoid unnecessary loss of portability.
@itemize @bullet
@item
Don't use the return value of @code{sprintf}. It returns the number of
characters written on some systems, but not on all systems.
@item
Be aware that @code{vfprintf} is not always available.
@item
@code{main} should be declared to return type @code{int}. It should
terminate either by calling @code{exit} or by returning the integer
status code; make sure it cannot ever return an undefined value.
@cindex declaration for system functions
@item
Don't declare system functions explicitly.
Almost any declaration for a system function is wrong on some system.
To minimize conflicts, leave it to the system header files to declare
system functions. If the headers don't declare a function, let it
remain undeclared.
While it may seem unclean to use a function without declaring it, in
practice this works fine for most system library functions on the
systems where this really happens; thus, the disadvantage is only
theoretical. By contrast, actual declarations have frequently caused
actual conflicts.
@item
If you must declare a system function, don't specify the argument types.
Use an old-style declaration, not a Standard C prototype. The more you
specify about the function, the more likely a conflict.
@item
In particular, don't unconditionally declare @code{malloc} or
@code{realloc}.
Most GNU programs use those functions just once, in functions
conventionally named @code{xmalloc} and @code{xrealloc}. These
functions call @code{malloc} and @code{realloc}, respectively, and
check the results.
Because @code{xmalloc} and @code{xrealloc} are defined in your program,
you can declare them in other files without any risk of type conflict.
On most systems, @code{int} is the same length as a pointer; thus, the
calls to @code{malloc} and @code{realloc} work fine. For the few
exceptional systems (mostly 64-bit machines), you can use
@strong{conditionalized} declarations of @code{malloc} and
@code{realloc}---or put these declarations in configuration files
specific to those systems.
@cindex string library functions
@item
The string functions require special treatment. Some Unix systems have
a header file @file{string.h}; others have @file{strings.h}. Neither
file name is portable. There are two things you can do: use Autoconf to
figure out which file to include, or don't include either file.
@item
If you don't include either strings file, you can't get declarations for
the string functions from the header file in the usual way.
That causes less of a problem than you might think. The newer standard
string functions should be avoided anyway because many systems still
don't support them. The string functions you can use are these:
@example
strcpy strncpy strcat strncat
strlen strcmp strncmp
strchr strrchr
@end example
The copy and concatenate functions work fine without a declaration as
long as you don't use their values. Using their values without a
declaration fails on systems where the width of a pointer differs from
the width of @code{int}, and perhaps in other cases. It is trivial to
avoid using their values, so do that.
The compare functions and @code{strlen} work fine without a declaration
on most systems, possibly all the ones that GNU software runs on.
You may find it necessary to declare them @strong{conditionally} on a
few systems.
The search functions must be declared to return @code{char *}. Luckily,
there is no variation in the data type they return. But there is
variation in their names. Some systems give these functions the names
@code{index} and @code{rindex}; other systems use the names
@code{strchr} and @code{strrchr}. Some systems support both pairs of
names, but neither pair works on all systems.
You should pick a single pair of names and use it throughout your
program. (Nowadays, it is better to choose @code{strchr} and
@code{strrchr} for new programs, since those are the standard
names.) Declare both of those names as functions returning @code{char
*}. On systems which don't support those names, define them as macros
in terms of the other pair. For example, here is what to put at the
beginning of your file (or in a header) if you want to use the names
@code{strchr} and @code{strrchr} throughout:
@example
#ifndef HAVE_STRCHR
#define strchr index
#endif
#ifndef HAVE_STRRCHR
#define strrchr rindex
#endif
char *strchr ();
char *strrchr ();
@end example
@end itemize
Here we assume that @code{HAVE_STRCHR} and @code{HAVE_STRRCHR} are
macros defined in systems where the corresponding functions exist.
One way to get them properly defined is to use Autoconf.
@node Internationalization
@section Internationalization
@cindex internationalization
@pindex gettext
GNU has a library called GNU gettext that makes it easy to translate the
messages in a program into various languages. You should use this
library in every program. Use English for the messages as they appear
in the program, and let gettext provide the way to translate them into
other languages.
Using GNU gettext involves putting a call to the @code{gettext} macro
around each string that might need translation---like this:
@example
printf (gettext ("Processing file `%s'..."));
@end example
@noindent
This permits GNU gettext to replace the string @code{"Processing file
`%s'..."} with a translated version.
Once a program uses gettext, please make a point of writing calls to
@code{gettext} when you add new strings that call for translation.
Using GNU gettext in a package involves specifying a @dfn{text domain
name} for the package. The text domain name is used to separate the
translations for this package from the translations for other packages.
Normally, the text domain name should be the same as the name of the
package---for example, @samp{coreutils} for the GNU core utilities.
@cindex message text, and internationalization
To enable gettext to work well, avoid writing code that makes
assumptions about the structure of words or sentences. When you want
the precise text of a sentence to vary depending on the data, use two or
more alternative string constants each containing a complete sentences,
rather than inserting conditionalized words or phrases into a single
sentence framework.
Here is an example of what not to do:
@smallexample
printf ("%s is full", capacity > 5000000 ? "disk" : "floppy disk");
@end smallexample
If you apply gettext to all strings, like this,
@smallexample
printf (gettext ("%s is full"),
capacity > 5000000 ? gettext ("disk") : gettext ("floppy disk"));
@end smallexample
@noindent
the translator will hardly know that "disk" and "floppy disk" are meant to
be substituted in the other string. Worse, in some languages (like French)
the construction will not work: the translation of the word "full" depends
on the gender of the first part of the sentence; it happens to be not the
same for "disk" as for "floppy disk".
Complete sentences can be translated without problems:
@example
printf (capacity > 5000000 ? gettext ("disk is full")
: gettext ("floppy disk is full"));
@end example
A similar problem appears at the level of sentence structure with this
code:
@example
printf ("# Implicit rule search has%s been done.\n",
f->tried_implicit ? "" : " not");
@end example
@noindent
Adding @code{gettext} calls to this code cannot give correct results for
all languages, because negation in some languages requires adding words
at more than one place in the sentence. By contrast, adding
@code{gettext} calls does the job straightforwardly if the code starts
out like this:
@example
printf (f->tried_implicit
? "# Implicit rule search has been done.\n",
: "# Implicit rule search has not been done.\n");
@end example
Another example is this one:
@example
printf ("%d file%s processed", nfiles,
nfiles != 1 ? "s" : "");
@end example
@noindent
The problem with this example is that it assumes that plurals are made
by adding `s'. If you apply gettext to the format string, like this,
@example
printf (gettext ("%d file%s processed"), nfiles,
nfiles != 1 ? "s" : "");
@end example
@noindent
the message can use different words, but it will still be forced to use
`s' for the plural. Here is a better way, with gettext being applied to
the two strings independently:
@example
printf ((nfiles != 1 ? gettext ("%d files processed")
: gettext ("%d file processed")),
nfiles);
@end example
@noindent
But this still doesn't work for languages like Polish, which has three
plural forms: one for nfiles == 1, one for nfiles == 2, 3, 4, 22, 23, 24, ...
and one for the rest. The GNU @code{ngettext} function solves this problem:
@example
printf (ngettext ("%d files processed", "%d file processed", nfiles),
nfiles);
@end example
@node Character Set
@section Character Set
@cindex character set
@cindex encodings
@cindex ASCII characters
@cindex non-ASCII characters
Sticking to the ASCII character set (plain text, 7-bit characters) is
preferred in GNU source code comments, text documents, and other
contexts, unless there is good reason to do something else because of
the application domain. For example, if source code deals with the
French Revolutionary calendar, it is OK if its literal strings contain
accented characters in month names like ``Flor@'eal''. Also, it is OK
to use non-ASCII characters to represent proper names of contributors in
change logs (@pxref{Change Logs}).
If you need to use non-ASCII characters, you should normally stick with
one encoding, as one cannot in general mix encodings reliably.
@node Quote Characters
@section Quote Characters
@cindex quote characters
@cindex locale-specific quote characters
@cindex left quote
@cindex grave accent
In the C locale, GNU programs should stick to plain ASCII for quotation
characters in messages to users: preferably 0x60 (@samp{`}) for left
quotes and 0x27 (@samp{'}) for right quotes. It is ok, but not
required, to use locale-specific quotes in other locales.
The @uref{http://www.gnu.org/software/gnulib/, Gnulib} @code{quote} and
@code{quotearg} modules provide a reasonably straightforward way to
support locale-specific quote characters, as well as taking care of
other issues, such as quoting a filename that itself contains a quote
character. See the Gnulib documentation for usage details.
In any case, the documentation for your program should clearly specify
how it does quoting, if different than the preferred method of @samp{`}
and @samp{'}. This is especially important if the output of your
program is ever likely to be parsed by another program.
Quotation characters are a difficult area in the computing world at
this time: there are no true left or right quote characters in Latin1;
the @samp{`} character we use was standardized there as a grave
accent. Moreover, Latin1 is still not universally usable.
Unicode contains the unambiguous quote characters required, and its
common encoding UTF-8 is upward compatible with Latin1. However,
Unicode and UTF-8 are not universally well-supported, either.
This may change over the next few years, and then we will revisit
this.
@node Mmap
@section Mmap
@findex mmap
Don't assume that @code{mmap} either works on all files or fails
for all files. It may work on some files and fail on others.
The proper way to use @code{mmap} is to try it on the specific file for
which you want to use it---and if @code{mmap} doesn't work, fall back on
doing the job in another way using @code{read} and @code{write}.
The reason this precaution is needed is that the GNU kernel (the HURD)
provides a user-extensible file system, in which there can be many
different kinds of ``ordinary files.'' Many of them support
@code{mmap}, but some do not. It is important to make programs handle
all these kinds of files.
@node Documentation
@chapter Documenting Programs
@cindex documentation
A GNU program should ideally come with full free documentation, adequate
for both reference and tutorial purposes. If the package can be
programmed or extended, the documentation should cover programming or
extending it, as well as just using it.
@menu
* GNU Manuals:: Writing proper manuals.
* Doc Strings and Manuals:: Compiling doc strings doesn't make a manual.
* Manual Structure Details:: Specific structure conventions.
* License for Manuals:: Writing the distribution terms for a manual.
* Manual Credits:: Giving credit to documentation contributors.
* Printed Manuals:: Mentioning the printed manual.
* NEWS File:: NEWS files supplement manuals.
* Change Logs:: Recording changes.
* Man Pages:: Man pages are secondary.
* Reading other Manuals:: How far you can go in learning
from other manuals.
@end menu
@node GNU Manuals
@section GNU Manuals
The preferred document format for the GNU system is the Texinfo
formatting language. Every GNU package should (ideally) have
documentation in Texinfo both for reference and for learners. Texinfo
makes it possible to produce a good quality formatted book, using
@TeX{}, and to generate an Info file. It is also possible to generate
HTML output from Texinfo source. See the Texinfo manual, either the
hardcopy, or the on-line version available through @code{info} or the
Emacs Info subsystem (@kbd{C-h i}).
Nowadays some other formats such as Docbook and Sgmltexi can be
converted automatically into Texinfo. It is ok to produce the Texinfo
documentation by conversion this way, as long as it gives good results.
Make sure your manual is clear to a reader who knows nothing about the
topic and reads it straight through. This means covering basic topics
at the beginning, and advanced topics only later. This also means
defining every specialized term when it is first used.
Programmers tend to carry over the structure of the program as the
structure for its documentation. But this structure is not
necessarily good for explaining how to use the program; it may be
irrelevant and confusing for a user.
Instead, the right way to structure documentation is according to the
concepts and questions that a user will have in mind when reading it.
This principle applies at every level, from the lowest (ordering
sentences in a paragraph) to the highest (ordering of chapter topics
within the manual). Sometimes this structure of ideas matches the
structure of the implementation of the software being documented---but
often they are different. An important part of learning to write good
documentation is to learn to notice when you have unthinkingly
structured the documentation like the implementation, stop yourself,
and look for better alternatives.
For example, each program in the GNU system probably ought to be
documented in one manual; but this does not mean each program should
have its own manual. That would be following the structure of the
implementation, rather than the structure that helps the user
understand.
Instead, each manual should cover a coherent @emph{topic}. For example,
instead of a manual for @code{diff} and a manual for @code{diff3}, we
have one manual for ``comparison of files'' which covers both of those
programs, as well as @code{cmp}. By documenting these programs
together, we can make the whole subject clearer.
The manual which discusses a program should certainly document all of
the program's command-line options and all of its commands. It should
give examples of their use. But don't organize the manual as a list
of features. Instead, organize it logically, by subtopics. Address
the questions that a user will ask when thinking about the job that
the program does. Don't just tell the reader what each feature can
do---say what jobs it is good for, and show how to use it for those
jobs. Explain what is recommended usage, and what kinds of usage
users should avoid.
In general, a GNU manual should serve both as tutorial and reference.
It should be set up for convenient access to each topic through Info,
and for reading straight through (appendixes aside). A GNU manual
should give a good introduction to a beginner reading through from the
start, and should also provide all the details that hackers want.
The Bison manual is a good example of this---please take a look at it
to see what we mean.
That is not as hard as it first sounds. Arrange each chapter as a
logical breakdown of its topic, but order the sections, and write their
text, so that reading the chapter straight through makes sense. Do
likewise when structuring the book into chapters, and when structuring a
section into paragraphs. The watchword is, @emph{at each point, address
the most fundamental and important issue raised by the preceding text.}
If necessary, add extra chapters at the beginning of the manual which
are purely tutorial and cover the basics of the subject. These provide
the framework for a beginner to understand the rest of the manual. The
Bison manual provides a good example of how to do this.
To serve as a reference, a manual should have an Index that list all the
functions, variables, options, and important concepts that are part of
the program. One combined Index should do for a short manual, but
sometimes for a complex package it is better to use multiple indices.
The Texinfo manual includes advice on preparing good index entries, see
@ref{Index Entries, , Making Index Entries, texinfo, GNU Texinfo}, and
see @ref{Indexing Commands, , Defining the Entries of an
Index, texinfo, GNU Texinfo}.
Don't use Unix man pages as a model for how to write GNU documentation;
most of them are terse, badly structured, and give inadequate
explanation of the underlying concepts. (There are, of course, some
exceptions.) Also, Unix man pages use a particular format which is
different from what we use in GNU manuals.
Please include an email address in the manual for where to report
bugs @emph{in the text of the manual}.
Please do not use the term ``pathname'' that is used in Unix
documentation; use ``file name'' (two words) instead. We use the term
``path'' only for search paths, which are lists of directory names.
Please do not use the term ``illegal'' to refer to erroneous input to
a computer program. Please use ``invalid'' for this, and reserve the
term ``illegal'' for activities prohibited by law.
Please do not write @samp{()} after a function name just to indicate
it is a function. @code{foo ()} is not a function, it is a function
call with no arguments.
@node Doc Strings and Manuals
@section Doc Strings and Manuals
Some programming systems, such as Emacs, provide a documentation string
for each function, command or variable. You may be tempted to write a
reference manual by compiling the documentation strings and writing a
little additional text to go around them---but you must not do it. That
approach is a fundamental mistake. The text of well-written
documentation strings will be entirely wrong for a manual.
A documentation string needs to stand alone---when it appears on the
screen, there will be no other text to introduce or explain it.
Meanwhile, it can be rather informal in style.
The text describing a function or variable in a manual must not stand
alone; it appears in the context of a section or subsection. Other text
at the beginning of the section should explain some of the concepts, and
should often make some general points that apply to several functions or
variables. The previous descriptions of functions and variables in the
section will also have given information about the topic. A description
written to stand alone would repeat some of that information; this
redundancy looks bad. Meanwhile, the informality that is acceptable in
a documentation string is totally unacceptable in a manual.
The only good way to use documentation strings in writing a good manual
is to use them as a source of information for writing good text.
@node Manual Structure Details
@section Manual Structure Details
@cindex manual structure
The title page of the manual should state the version of the programs or
packages documented in the manual. The Top node of the manual should
also contain this information. If the manual is changing more
frequently than or independent of the program, also state a version
number for the manual in both of these places.
Each program documented in the manual should have a node named
@samp{@var{program} Invocation} or @samp{Invoking @var{program}}. This
node (together with its subnodes, if any) should describe the program's
command line arguments and how to run it (the sort of information people
would look for in a man page). Start with an @samp{@@example}
containing a template for all the options and arguments that the program
uses.
Alternatively, put a menu item in some menu whose item name fits one of
the above patterns. This identifies the node which that item points to
as the node for this purpose, regardless of the node's actual name.
The @samp{--usage} feature of the Info reader looks for such a node
or menu item in order to find the relevant text, so it is essential
for every Texinfo file to have one.
If one manual describes several programs, it should have such a node for
each program described in the manual.
@node License for Manuals
@section License for Manuals
@cindex license for manuals
Please use the GNU Free Documentation License for all GNU manuals that
are more than a few pages long. Likewise for a collection of short
documents---you only need one copy of the GNU FDL for the whole
collection. For a single short document, you can use a very permissive
non-copyleft license, to avoid taking up space with a long license.
See @uref{http://www.gnu.org/copyleft/fdl-howto.html} for more explanation
of how to employ the GFDL.
Note that it is not obligatory to include a copy of the GNU GPL or GNU
LGPL in a manual whose license is neither the GPL nor the LGPL. It can
be a good idea to include the program's license in a large manual; in a
short manual, whose size would be increased considerably by including
the program's license, it is probably better not to include it.
@node Manual Credits
@section Manual Credits
@cindex credits for manuals
Please credit the principal human writers of the manual as the authors,
on the title page of the manual. If a company sponsored the work, thank
the company in a suitable place in the manual, but do not cite the
company as an author.
@node Printed Manuals
@section Printed Manuals
The FSF publishes some GNU manuals in printed form. To encourage sales
of these manuals, the on-line versions of the manual should mention at
the very start that the printed manual is available and should point at
information for getting it---for instance, with a link to the page
@url{http://www.gnu.org/order/order.html}. This should not be included
in the printed manual, though, because there it is redundant.
It is also useful to explain in the on-line forms of the manual how the
user can print out the manual from the sources.
@node NEWS File
@section The NEWS File
@cindex @file{NEWS} file
In addition to its manual, the package should have a file named
@file{NEWS} which contains a list of user-visible changes worth
mentioning. In each new release, add items to the front of the file and
identify the version they pertain to. Don't discard old items; leave
them in the file after the newer items. This way, a user upgrading from
any previous version can see what is new.
If the @file{NEWS} file gets very long, move some of the older items
into a file named @file{ONEWS} and put a note at the end referring the
user to that file.
@node Change Logs
@section Change Logs
@cindex change logs
Keep a change log to describe all the changes made to program source
files. The purpose of this is so that people investigating bugs in the
future will know about the changes that might have introduced the bug.
Often a new bug can be found by looking at what was recently changed.
More importantly, change logs can help you eliminate conceptual
inconsistencies between different parts of a program, by giving you a
history of how the conflicting concepts arose and who they came from.
@menu
* Change Log Concepts::
* Style of Change Logs::
* Simple Changes::
* Conditional Changes::
* Indicating the Part Changed::
@end menu
@node Change Log Concepts
@subsection Change Log Concepts
You can think of the change log as a conceptual ``undo list'' which
explains how earlier versions were different from the current version.
People can see the current version; they don't need the change log
to tell them what is in it. What they want from a change log is a
clear explanation of how the earlier version differed.
The change log file is normally called @file{ChangeLog} and covers an
entire directory. Each directory can have its own change log, or a
directory can use the change log of its parent directory--it's up to
you.
Another alternative is to record change log information with a version
control system such as RCS or CVS. This can be converted automatically
to a @file{ChangeLog} file using @code{rcs2log}; in Emacs, the command
@kbd{C-x v a} (@code{vc-update-change-log}) does the job.
There's no need to describe the full purpose of the changes or how they
work together. If you think that a change calls for explanation, you're
probably right. Please do explain it---but please put the explanation
in comments in the code, where people will see it whenever they see the
code. For example, ``New function'' is enough for the change log when
you add a function, because there should be a comment before the
function definition to explain what it does.
In the past, we recommended not mentioning changes in non-software
files (manuals, help files, etc.) in change logs. However, we've been
advised that it is a good idea to include them, for the sake of
copyright records.
However, sometimes it is useful to write one line to describe the
overall purpose of a batch of changes.
The easiest way to add an entry to @file{ChangeLog} is with the Emacs
command @kbd{M-x add-change-log-entry}. An entry should have an
asterisk, the name of the changed file, and then in parentheses the name
of the changed functions, variables or whatever, followed by a colon.
Then describe the changes you made to that function or variable.
@node Style of Change Logs
@subsection Style of Change Logs
@cindex change logs, style
Here are some simple examples of change log entries, starting with the
header line that says who made the change and when it was installed,
followed by descriptions of specific changes. (These examples are
drawn from Emacs and GCC.)
@example
1998-08-17 Richard Stallman
* register.el (insert-register): Return nil.
(jump-to-register): Likewise.
* sort.el (sort-subr): Return nil.
* tex-mode.el (tex-bibtex-file, tex-file, tex-region):
Restart the tex shell if process is gone or stopped.
(tex-shell-running): New function.
* expr.c (store_one_arg): Round size up for move_block_to_reg.
(expand_call): Round up when emitting USE insns.
* stmt.c (assign_parms): Round size up for move_block_from_reg.
@end example
It's important to name the changed function or variable in full. Don't
abbreviate function or variable names, and don't combine them.
Subsequent maintainers will often search for a function name to find all
the change log entries that pertain to it; if you abbreviate the name,
they won't find it when they search.
For example, some people are tempted to abbreviate groups of function
names by writing @samp{* register.el (@{insert,jump-to@}-register)};
this is not a good idea, since searching for @code{jump-to-register} or
@code{insert-register} would not find that entry.
Separate unrelated change log entries with blank lines. When two
entries represent parts of the same change, so that they work together,
then don't put blank lines between them. Then you can omit the file
name and the asterisk when successive entries are in the same file.
Break long lists of function names by closing continued lines with
@samp{)}, rather than @samp{,}, and opening the continuation with
@samp{(} as in this example:
@example
* keyboard.c (menu_bar_items, tool_bar_items)
(Fexecute_extended_command): Deal with `keymap' property.
@end example
When you install someone else's changes, put the contributor's name in
the change log entry rather than in the text of the entry. In other
words, write this:
@example
2002-07-14 John Doe
* sewing.c: Make it sew.
@end example
@noindent
rather than this:
@example
2002-07-14 Usual Maintainer
* sewing.c: Make it sew. Patch by jdoe@@gnu.org.
@end example
As for the date, that should be the date you applied the change.
@node Simple Changes
@subsection Simple Changes
Certain simple kinds of changes don't need much detail in the change
log.
When you change the calling sequence of a function in a simple fashion,
and you change all the callers of the function to use the new calling
sequence, there is no need to make individual entries for all the
callers that you changed. Just write in the entry for the function
being called, ``All callers changed''---like this:
@example
* keyboard.c (Fcommand_execute): New arg SPECIAL.
All callers changed.
@end example
When you change just comments or doc strings, it is enough to write an
entry for the file, without mentioning the functions. Just ``Doc
fixes'' is enough for the change log.
There's no technical need to make change log entries for documentation
files. This is because documentation is not susceptible to bugs that
are hard to fix. Documentation does not consist of parts that must
interact in a precisely engineered fashion. To correct an error, you
need not know the history of the erroneous passage; it is enough to
compare what the documentation says with the way the program actually
works.
However, you should keep change logs for documentation files when the
project gets copyright assignments from its contributors, so as to
make the records of authorship more accurate.
@node Conditional Changes
@subsection Conditional Changes
@cindex conditional changes, and change logs
@cindex change logs, conditional changes
C programs often contain compile-time @code{#if} conditionals. Many
changes are conditional; sometimes you add a new definition which is
entirely contained in a conditional. It is very useful to indicate in
the change log the conditions for which the change applies.
Our convention for indicating conditional changes is to use square
brackets around the name of the condition.
Here is a simple example, describing a change which is conditional but
does not have a function or entity name associated with it:
@example
* xterm.c [SOLARIS2]: Include string.h.
@end example
Here is an entry describing a new definition which is entirely
conditional. This new definition for the macro @code{FRAME_WINDOW_P} is
used only when @code{HAVE_X_WINDOWS} is defined:
@example
* frame.h [HAVE_X_WINDOWS] (FRAME_WINDOW_P): Macro defined.
@end example
Here is an entry for a change within the function @code{init_display},
whose definition as a whole is unconditional, but the changes themselves
are contained in a @samp{#ifdef HAVE_LIBNCURSES} conditional:
@example
* dispnew.c (init_display) [HAVE_LIBNCURSES]: If X, call tgetent.
@end example
Here is an entry for a change that takes affect only when
a certain macro is @emph{not} defined:
@example
(gethostname) [!HAVE_SOCKETS]: Replace with winsock version.
@end example
@node Indicating the Part Changed
@subsection Indicating the Part Changed
Indicate the part of a function which changed by using angle brackets
enclosing an indication of what the changed part does. Here is an entry
for a change in the part of the function @code{sh-while-getopts} that
deals with @code{sh} commands:
@example
* progmodes/sh-script.el (sh-while-getopts) : Handle case that
user-specified option string is empty.
@end example
@node Man Pages
@section Man Pages
@cindex man pages
In the GNU project, man pages are secondary. It is not necessary or
expected for every GNU program to have a man page, but some of them do.
It's your choice whether to include a man page in your program.
When you make this decision, consider that supporting a man page
requires continual effort each time the program is changed. The time
you spend on the man page is time taken away from more useful work.
For a simple program which changes little, updating the man page may be
a small job. Then there is little reason not to include a man page, if
you have one.
For a large program that changes a great deal, updating a man page may
be a substantial burden. If a user offers to donate a man page, you may
find this gift costly to accept. It may be better to refuse the man
page unless the same person agrees to take full responsibility for
maintaining it---so that you can wash your hands of it entirely. If
this volunteer later ceases to do the job, then don't feel obliged to
pick it up yourself; it may be better to withdraw the man page from the
distribution until someone else agrees to update it.
When a program changes only a little, you may feel that the
discrepancies are small enough that the man page remains useful without
updating. If so, put a prominent note near the beginning of the man
page explaining that you don't maintain it and that the Texinfo manual
is more authoritative. The note should say how to access the Texinfo
documentation.
Be sure that man pages include a copyright statement and free license.
The simple all-permissive license is appropriate for simple man pages
(@pxref{License Notices for Other Files,,,maintain,Information for GNU
Maintainers}).
For long man pages, with enough explanation and documentation that
they can be considered true manuals, use the GFDL (@pxref{License for
Manuals}).
Finally, the GNU help2man program
(@uref{http://www.gnu.org/software/help2man/}) is one way to automate
generation of a man page, in this case from @option{--help} output.
This is sufficient in many cases.
@node Reading other Manuals
@section Reading other Manuals
There may be non-free books or documentation files that describe the
program you are documenting.
It is ok to use these documents for reference, just as the author of a
new algebra textbook can read other books on algebra. A large portion
of any non-fiction book consists of facts, in this case facts about how
a certain program works, and these facts are necessarily the same for
everyone who writes about the subject. But be careful not to copy your
outline structure, wording, tables or examples from preexisting non-free
documentation. Copying from free documentation may be ok; please check
with the FSF about the individual case.
@node Managing Releases
@chapter The Release Process
@cindex releasing
Making a release is more than just bundling up your source files in a
tar file and putting it up for FTP. You should set up your software so
that it can be configured to run on a variety of systems. Your Makefile
should conform to the GNU standards described below, and your directory
layout should also conform to the standards discussed below. Doing so
makes it easy to include your package into the larger framework of
all GNU software.
@menu
* Configuration:: How configuration of GNU packages should work.
* Makefile Conventions:: Makefile conventions.
* Releases:: Making releases
@end menu
@node Configuration
@section How Configuration Should Work
@cindex program configuration
@pindex configure
Each GNU distribution should come with a shell script named
@code{configure}. This script is given arguments which describe the
kind of machine and system you want to compile the program for.
The @code{configure} script must record the configuration options so
that they affect compilation.
The description here is the specification of the interface for the
@code{configure} script in GNU packages. Many packages implement it
using GNU Autoconf (@pxref{Top,, Introduction, autoconf, Autoconf})
and/or GNU Automake (@pxref{Top,, Introduction, automake, Automake}),
but you do not have to use these tools. You can implement it any way
you like; for instance, by making @code{configure} be a wrapper around
a completely different configuration system.
Another way for the @code{configure} script to operate is to make a
link from a standard name such as @file{config.h} to the proper
configuration file for the chosen system. If you use this technique,
the distribution should @emph{not} contain a file named
@file{config.h}. This is so that people won't be able to build the
program without configuring it first.
Another thing that @code{configure} can do is to edit the Makefile. If
you do this, the distribution should @emph{not} contain a file named
@file{Makefile}. Instead, it should include a file @file{Makefile.in} which
contains the input used for editing. Once again, this is so that people
won't be able to build the program without configuring it first.
If @code{configure} does write the @file{Makefile}, then @file{Makefile}
should have a target named @file{Makefile} which causes @code{configure}
to be rerun, setting up the same configuration that was set up last
time. The files that @code{configure} reads should be listed as
dependencies of @file{Makefile}.
All the files which are output from the @code{configure} script should
have comments at the beginning explaining that they were generated
automatically using @code{configure}. This is so that users won't think
of trying to edit them by hand.
The @code{configure} script should write a file named @file{config.status}
which describes which configuration options were specified when the
program was last configured. This file should be a shell script which,
if run, will recreate the same configuration.
The @code{configure} script should accept an option of the form
@samp{--srcdir=@var{dirname}} to specify the directory where sources are found
(if it is not the current directory). This makes it possible to build
the program in a separate directory, so that the actual source directory
is not modified.
If the user does not specify @samp{--srcdir}, then @code{configure} should
check both @file{.} and @file{..} to see if it can find the sources. If
it finds the sources in one of these places, it should use them from
there. Otherwise, it should report that it cannot find the sources, and
should exit with nonzero status.
Usually the easy way to support @samp{--srcdir} is by editing a
definition of @code{VPATH} into the Makefile. Some rules may need to
refer explicitly to the specified source directory. To make this
possible, @code{configure} can add to the Makefile a variable named
@code{srcdir} whose value is precisely the specified directory.
In addition, the @samp{configure} script should take options
corresponding to most of the standard directory variables
(@pxref{Directory Variables}). Here is the list:
@example
--prefix --exec-prefix --bindir --sbindir --libexecdir --sysconfdir
--sharedstatedir --localstatedir --libdir --includedir --oldincludedir
--datarootdir --datadir --infodir --localedir --mandir --docdir
--htmldir --dvidir --pdfdir --psdir
@end example
The @code{configure} script should also take an argument which specifies the
type of system to build the program for. This argument should look like
this:
@example
@var{cpu}-@var{company}-@var{system}
@end example
For example, an Athlon-based GNU/Linux system might be
@samp{i686-pc-linux-gnu}.
The @code{configure} script needs to be able to decode all plausible
alternatives for how to describe a machine. Thus,
@samp{athlon-pc-gnu/linux} would be a valid alias. There is a shell
script called
@uref{http://git.savannah.gnu.org/@/gitweb/@/?p=config.git;a=blob_plain;f=config.sub;hb=HEAD,
@file{config.sub}} that you can use as a subroutine to validate system
types and canonicalize aliases.
The @code{configure} script should also take the option
@option{--build=@var{buildtype}}, which should be equivalent to a
plain @var{buildtype} argument. For example, @samp{configure
--build=i686-pc-linux-gnu} is equivalent to @samp{configure
i686-pc-linux-gnu}. When the build type is not specified by an option
or argument, the @code{configure} script should normally guess it using
the shell script
@uref{http://git.savannah.gnu.org/@/gitweb/@/?p=config.git;a=blob_plain;f=config.guess;hb=HEAD,
@file{config.guess}}.
@cindex optional features, configure-time
Other options are permitted to specify in more detail the software
or hardware present on the machine, to include or exclude optional parts
of the package, or to adjust the name of some tools or arguments to them:
@table @samp
@item --enable-@var{feature}@r{[}=@var{parameter}@r{]}
Configure the package to build and install an optional user-level
facility called @var{feature}. This allows users to choose which
optional features to include. Giving an optional @var{parameter} of
@samp{no} should omit @var{feature}, if it is built by default.
No @samp{--enable} option should @strong{ever} cause one feature to
replace another. No @samp{--enable} option should ever substitute one
useful behavior for another useful behavior. The only proper use for
@samp{--enable} is for questions of whether to build part of the program
or exclude it.
@item --with-@var{package}
@c @r{[}=@var{parameter}@r{]}
The package @var{package} will be installed, so configure this package
to work with @var{package}.
@c Giving an optional @var{parameter} of
@c @samp{no} should omit @var{package}, if it is used by default.
Possible values of @var{package} include
@samp{gnu-as} (or @samp{gas}), @samp{gnu-ld}, @samp{gnu-libc},
@samp{gdb},
@samp{x},
and
@samp{x-toolkit}.
Do not use a @samp{--with} option to specify the file name to use to
find certain files. That is outside the scope of what @samp{--with}
options are for.
@item @var{variable}=@var{value}
Set the value of the variable @var{variable} to @var{value}. This is
used to override the default values of commands or arguments in the
build process. For example, the user could issue @samp{configure
CFLAGS=-g CXXFLAGS=-g} to build with debugging information and without
the default optimization.
Specifying variables as arguments to @code{configure}, like this:
@example
./configure CC=gcc
@end example
is preferable to setting them in environment variables:
@example
CC=gcc ./configure
@end example
as it helps to recreate the same configuration later with
@file{config.status}.
@end table
All @code{configure} scripts should accept all of the ``detail''
options and the variable settings, whether or not they make any
difference to the particular package at hand. In particular, they
should accept any option that starts with @samp{--with-} or
@samp{--enable-}. This is so users will be able to configure an
entire GNU source tree at once with a single set of options.
You will note that the categories @samp{--with-} and @samp{--enable-}
are narrow: they @strong{do not} provide a place for any sort of option
you might think of. That is deliberate. We want to limit the possible
configuration options in GNU software. We do not want GNU programs to
have idiosyncratic configuration options.
Packages that perform part of the compilation process may support
cross-compilation. In such a case, the host and target machines for the
program may be different.
The @code{configure} script should normally treat the specified type of
system as both the host and the target, thus producing a program which
works for the same type of machine that it runs on.
To compile a program to run on a host type that differs from the build
type, use the configure option @option{--host=@var{hosttype}}, where
@var{hosttype} uses the same syntax as @var{buildtype}. The host type
normally defaults to the build type.
To configure a cross-compiler, cross-assembler, or what have you, you
should specify a target different from the host, using the configure
option @samp{--target=@var{targettype}}. The syntax for
@var{targettype} is the same as for the host type. So the command would
look like this:
@example
./configure --host=@var{hosttype} --target=@var{targettype}
@end example
The target type normally defaults to the host type.
Programs for which cross-operation is not meaningful need not accept the
@samp{--target} option, because configuring an entire operating system for
cross-operation is not a meaningful operation.
Some programs have ways of configuring themselves automatically. If
your program is set up to do this, your @code{configure} script can simply
ignore most of its arguments.
@comment The makefile standards are in a separate file that is also
@comment included by make.texinfo. Done by roland@gnu.ai.mit.edu on 1/6/93.
@comment For this document, turn chapters into sections, etc.
@lowersections
@include make-stds.texi
@raisesections
@node Releases
@section Making Releases
@cindex packaging
You should identify each release with a pair of version numbers, a
major version and a minor. We have no objection to using more than
two numbers, but it is very unlikely that you really need them.
Package the distribution of @code{Foo version 69.96} up in a gzipped tar
file with the name @file{foo-69.96.tar.gz}. It should unpack into a
subdirectory named @file{foo-69.96}.
Building and installing the program should never modify any of the files
contained in the distribution. This means that all the files that form
part of the program in any way must be classified into @dfn{source
files} and @dfn{non-source files}. Source files are written by humans
and never changed automatically; non-source files are produced from
source files by programs under the control of the Makefile.
@cindex @file{README} file
The distribution should contain a file named @file{README} which gives
the name of the package, and a general description of what it does. It
is also good to explain the purpose of each of the first-level
subdirectories in the package, if there are any. The @file{README} file
should either state the version number of the package, or refer to where
in the package it can be found.
The @file{README} file should refer to the file @file{INSTALL}, which
should contain an explanation of the installation procedure.
The @file{README} file should also refer to the file which contains the
copying conditions. The GNU GPL, if used, should be in a file called
@file{COPYING}. If the GNU LGPL is used, it should be in a file called
@file{COPYING.LESSER}.
Naturally, all the source files must be in the distribution. It is okay
to include non-source files in the distribution, provided they are
up-to-date and machine-independent, so that building the distribution
normally will never modify them. We commonly include non-source files
produced by Bison, @code{lex}, @TeX{}, and @code{makeinfo}; this helps avoid
unnecessary dependencies between our distributions, so that users can
install whichever packages they want to install.
Non-source files that might actually be modified by building and
installing the program should @strong{never} be included in the
distribution. So if you do distribute non-source files, always make
sure they are up to date when you make a new distribution.
Make sure that the directory into which the distribution unpacks (as
well as any subdirectories) are all world-writable (octal mode 777).
This is so that old versions of @code{tar} which preserve the
ownership and permissions of the files from the tar archive will be
able to extract all the files even if the user is unprivileged.
Make sure that all the files in the distribution are world-readable.
Don't include any symbolic links in the distribution itself. If the tar
file contains symbolic links, then people cannot even unpack it on
systems that don't support symbolic links. Also, don't use multiple
names for one file in different directories, because certain file
systems cannot handle this and that prevents unpacking the
distribution.
Try to make sure that all the file names will be unique on MS-DOS. A
name on MS-DOS consists of up to 8 characters, optionally followed by a
period and up to three characters. MS-DOS will truncate extra
characters both before and after the period. Thus,
@file{foobarhacker.c} and @file{foobarhacker.o} are not ambiguous; they
are truncated to @file{foobarha.c} and @file{foobarha.o}, which are
distinct.
@cindex @file{texinfo.tex}, in a distribution
Include in your distribution a copy of the @file{texinfo.tex} you used
to test print any @file{*.texinfo} or @file{*.texi} files.
Likewise, if your program uses small GNU software packages like regex,
getopt, obstack, or termcap, include them in the distribution file.
Leaving them out would make the distribution file a little smaller at
the expense of possible inconvenience to a user who doesn't know what
other files to get.
@node References
@chapter References to Non-Free Software and Documentation
@cindex references to non-free material
A GNU program should not recommend, promote, or grant legitimacy to
the use of any non-free program. Proprietary software is a social and
ethical problem, and our aim is to put an end to that problem. We
can't stop some people from writing proprietary programs, or stop
other people from using them, but we can and should refuse to
advertise them to new potential customers, or to give the public the
idea that their existence is ethical.
The GNU definition of free software is found on the GNU web site at
@url{http://www.gnu.org/@/philosophy/@/free-sw.html}, and the definition
of free documentation is found at
@url{http://www.gnu.org/@/philosophy/@/free-doc.html}. The terms ``free''
and ``non-free'', used in this document, refer to those definitions.
A list of important licenses and whether they qualify as free is in
@url{http://www.gnu.org/@/licenses/@/license-list.html}. If it is not
clear whether a license qualifies as free, please ask the GNU Project
by writing to @email{licensing@@gnu.org}. We will answer, and if the
license is an important one, we will add it to the list.
When a non-free program or system is well known, you can mention it in
passing---that is harmless, since users who might want to use it
probably already know about it. For instance, it is fine to explain
how to build your package on top of some widely used non-free
operating system, or how to use it together with some widely used
non-free program.
However, you should give only the necessary information to help those
who already use the non-free program to use your program with
it---don't give, or refer to, any further information about the
proprietary program, and don't imply that the proprietary program
enhances your program, or that its existence is in any way a good
thing. The goal should be that people already using the proprietary
program will get the advice they need about how to use your free
program with it, while people who don't already use the proprietary
program will not see anything likely to lead them to take an interest
in it.
If a non-free program or system is obscure in your program's domain,
your program should not mention or support it at all, since doing so
would tend to popularize the non-free program more than it popularizes
your program. (You cannot hope to find many additional users for your
program among the users of Foobar, if the existence of Foobar is not
generally known among people who might want to use your program.)
Sometimes a program is free software in itself but depends on a
non-free platform in order to run. For instance, many Java programs
depend on some non-free Java libraries. To recommend or promote such
a program is to promote the other programs it needs. This is why we
are careful about listing Java programs in the Free Software
Directory: we don't want to promote the non-free Java libraries.
We hope this particular problem with Java will be gone by and by, as
we replace the remaining non-free standard Java libraries with free
software, but the general principle will remain the same: don't
recommend, promote or legitimize programs that depend on non-free
software to run.
Some free programs strongly encourage the use of non-free software. A
typical example is @command{mplayer}. It is free software in itself,
and the free code can handle some kinds of files. However,
@command{mplayer} recommends use of non-free codecs for other kinds of
files, and users that install @command{mplayer} are very likely to
install those codecs along with it. To recommend @command{mplayer}
is, in effect, to promote use of the non-free codecs.
Thus, you should not recommend programs that strongly encourage the
use of non-free software. This is why we do not list
@command{mplayer} in the Free Software Directory.
A GNU package should not refer the user to any non-free documentation
for free software. Free documentation that can be included in free
operating systems is essential for completing the GNU system, or any
free operating system, so encouraging it is a priority; to recommend
use of documentation that we are not allowed to include undermines the
impetus for the community to produce documentation that we can
include. So GNU packages should never recommend non-free
documentation.
By contrast, it is ok to refer to journal articles and textbooks in
the comments of a program for explanation of how it functions, even
though they are non-free. This is because we don't include such
things in the GNU system even they are free---they are outside the
scope of what a software distribution needs to include.
Referring to a web site that describes or recommends a non-free
program is promoting that program, so please do not make links (or
mention by name) web sites that contain such material. This policy is
relevant particularly for the web pages for a GNU package.
Following links from nearly any web site can lead eventually to
non-free software; this is inherent in the nature of the web. So it
makes no sense to criticize a site for having such links. As long as
the site does not itself recommend a non-free program, there is no
need to consider the question of the sites that it links to for other
reasons.
Thus, for example, you should not refer to AT&T's web site if that
recommends AT&T's non-free software packages; you should not refer to
a site that links to AT&T's site presenting it as a place to get some
non-free program, because that link recommends and legitimizes the
non-free program. However, that a site contains a link to AT&T's web
site for some other purpose (such as long-distance telephone service)
is not an objection against it.
@node GNU Free Documentation License
@appendix GNU Free Documentation License
@cindex FDL, GNU Free Documentation License
@include fdl.texi
@node Index
@unnumbered Index
@printindex cp
@bye
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install-info-am install-man install-pdf install-pdf-am \
install-ps install-ps-am install-strip installcheck \
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uninstall-info-am uninstall-pdf-am uninstall-ps-am
# Tell versions [3.59,3.63) of GNU make to not export all variables.
# Otherwise a system limit (for SysV at least) may be exceeded.
.NOEXPORT:
autoconf2.64-2.64/doc/autoconf.info 0000644 0002024 0002024 00003721535 11233217305 016434 0 ustar arthur arthur This is autoconf.info, produced by makeinfo version 4.13 from
autoconf.texi.
This manual (26 July 2009) is for GNU Autoconf (version 2.64), a
package for creating scripts to configure source code packages using
templates and an M4 macro package.
Copyright (C) 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000, 2001,
2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software
Foundation, Inc.
Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License,
Version 1.3 or any later version published by the Free Software
Foundation; with no Invariant Sections, with the Front-Cover texts
being "A GNU Manual," and with the Back-Cover Texts as in (a)
below. A copy of the license is included in the section entitled
"GNU Free Documentation License."
(a) The FSF's Back-Cover Text is: "You have the freedom to copy and
modify this GNU manual. Buying copies from the FSF supports it in
developing GNU and promoting software freedom."
INFO-DIR-SECTION Software development
START-INFO-DIR-ENTRY
* Autoconf: (autoconf). Create source code configuration scripts.
END-INFO-DIR-ENTRY
INFO-DIR-SECTION Individual utilities
START-INFO-DIR-ENTRY
* autoscan: (autoconf)autoscan Invocation.
Semi-automatic `configure.ac' writing
* ifnames: (autoconf)ifnames Invocation. Listing conditionals in source.
* autoconf-invocation: (autoconf)autoconf Invocation.
How to create configuration scripts
* autoreconf: (autoconf)autoreconf Invocation.
Remaking multiple `configure' scripts
* autoheader: (autoconf)autoheader Invocation.
How to create configuration templates
* autom4te: (autoconf)autom4te Invocation.
The Autoconf executables backbone
* configure: (autoconf)configure Invocation. Configuring a package.
* autoupdate: (autoconf)autoupdate Invocation.
Automatic update of `configure.ac'
* config.status: (autoconf)config.status Invocation. Recreating configurations.
* testsuite: (autoconf)testsuite Invocation. Running an Autotest test suite.
END-INFO-DIR-ENTRY
File: autoconf.info, Node: Top, Next: Introduction, Up: (dir)
Autoconf
********
This manual (26 July 2009) is for GNU Autoconf (version 2.64), a
package for creating scripts to configure source code packages using
templates and an M4 macro package.
Copyright (C) 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000, 2001,
2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software
Foundation, Inc.
Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License,
Version 1.3 or any later version published by the Free Software
Foundation; with no Invariant Sections, with the Front-Cover texts
being "A GNU Manual," and with the Back-Cover Texts as in (a)
below. A copy of the license is included in the section entitled
"GNU Free Documentation License."
(a) The FSF's Back-Cover Text is: "You have the freedom to copy and
modify this GNU manual. Buying copies from the FSF supports it in
developing GNU and promoting software freedom."
* Menu:
* Introduction:: Autoconf's purpose, strengths, and weaknesses
* The GNU Build System:: A set of tools for portable software packages
* Making configure Scripts:: How to organize and produce Autoconf scripts
* Setup:: Initialization and output
* Existing Tests:: Macros that check for particular features
* Writing Tests:: How to write new feature checks
* Results:: What to do with results from feature checks
* Programming in M4:: Layers on top of which Autoconf is written
* Programming in M4sh:: Shell portability layer
* Writing Autoconf Macros:: Adding new macros to Autoconf
* Portable Shell:: Shell script portability pitfalls
* Portable Make:: Makefile portability pitfalls
* Portable C and C++:: C and C++ portability pitfalls
* Manual Configuration:: Selecting features that can't be guessed
* Site Configuration:: Local defaults for `configure'
* Running configure Scripts:: How to use the Autoconf output
* config.status Invocation:: Recreating a configuration
* Obsolete Constructs:: Kept for backward compatibility
* Using Autotest:: Creating portable test suites
* FAQ:: Frequent Autoconf Questions, with answers
* History:: History of Autoconf
* GNU Free Documentation License:: License for copying this manual
* Indices:: Indices of symbols, concepts, etc.
--- The Detailed Node Listing ---
The GNU Build System
* Automake:: Escaping makefile hell
* Gnulib:: The GNU portability library
* Libtool:: Building libraries portably
* Pointers:: More info on the GNU build system
Making `configure' Scripts
* Writing Autoconf Input:: What to put in an Autoconf input file
* autoscan Invocation:: Semi-automatic `configure.ac' writing
* ifnames Invocation:: Listing the conditionals in source code
* autoconf Invocation:: How to create configuration scripts
* autoreconf Invocation:: Remaking multiple `configure' scripts
Writing `configure.ac'
* Shell Script Compiler:: Autoconf as solution of a problem
* Autoconf Language:: Programming in Autoconf
* Autoconf Input Layout:: Standard organization of `configure.ac'
Initialization and Output Files
* Initializing configure:: Option processing etc.
* Versioning:: Dealing with Autoconf versions
* Notices:: Copyright, version numbers in `configure'
* Input:: Where Autoconf should find files
* Output:: Outputting results from the configuration
* Configuration Actions:: Preparing the output based on results
* Configuration Files:: Creating output files
* Makefile Substitutions:: Using output variables in makefiles
* Configuration Headers:: Creating a configuration header file
* Configuration Commands:: Running arbitrary instantiation commands
* Configuration Links:: Links depending on the configuration
* Subdirectories:: Configuring independent packages together
* Default Prefix:: Changing the default installation prefix
Substitutions in Makefiles
* Preset Output Variables:: Output variables that are always set
* Installation Directory Variables:: Other preset output variables
* Changed Directory Variables:: Warnings about `datarootdir'
* Build Directories:: Supporting multiple concurrent compiles
* Automatic Remaking:: Makefile rules for configuring
Configuration Header Files
* Header Templates:: Input for the configuration headers
* autoheader Invocation:: How to create configuration templates
* Autoheader Macros:: How to specify CPP templates
Existing Tests
* Common Behavior:: Macros' standard schemes
* Alternative Programs:: Selecting between alternative programs
* Files:: Checking for the existence of files
* Libraries:: Library archives that might be missing
* Library Functions:: C library functions that might be missing
* Header Files:: Header files that might be missing
* Declarations:: Declarations that may be missing
* Structures:: Structures or members that might be missing
* Types:: Types that might be missing
* Compilers and Preprocessors:: Checking for compiling programs
* System Services:: Operating system services
* Posix Variants:: Special kludges for specific Posix variants
* Erlang Libraries:: Checking for the existence of Erlang libraries
Common Behavior
* Standard Symbols:: Symbols defined by the macros
* Default Includes:: Includes used by the generic macros
Alternative Programs
* Particular Programs:: Special handling to find certain programs
* Generic Programs:: How to find other programs
Library Functions
* Function Portability:: Pitfalls with usual functions
* Particular Functions:: Special handling to find certain functions
* Generic Functions:: How to find other functions
Header Files
* Header Portability:: Collected knowledge on common headers
* Particular Headers:: Special handling to find certain headers
* Generic Headers:: How to find other headers
Declarations
* Particular Declarations:: Macros to check for certain declarations
* Generic Declarations:: How to find other declarations
Structures
* Particular Structures:: Macros to check for certain structure members
* Generic Structures:: How to find other structure members
Types
* Particular Types:: Special handling to find certain types
* Generic Types:: How to find other types
Compilers and Preprocessors
* Specific Compiler Characteristics:: Some portability issues
* Generic Compiler Characteristics:: Language independent tests and features
* C Compiler:: Checking its characteristics
* C++ Compiler:: Likewise
* Objective C Compiler:: Likewise
* Erlang Compiler and Interpreter:: Likewise
* Fortran Compiler:: Likewise
Writing Tests
* Language Choice:: Selecting which language to use for testing
* Writing Test Programs:: Forging source files for compilers
* Running the Preprocessor:: Detecting preprocessor symbols
* Running the Compiler:: Detecting language or header features
* Running the Linker:: Detecting library features
* Runtime:: Testing for runtime features
* Systemology:: A zoology of operating systems
* Multiple Cases:: Tests for several possible values
Writing Test Programs
* Guidelines:: General rules for writing test programs
* Test Functions:: Avoiding pitfalls in test programs
* Generating Sources:: Source program boilerplate
Results of Tests
* Defining Symbols:: Defining C preprocessor symbols
* Setting Output Variables:: Replacing variables in output files
* Special Chars in Variables:: Characters to beware of in variables
* Caching Results:: Speeding up subsequent `configure' runs
* Printing Messages:: Notifying `configure' users
Caching Results
* Cache Variable Names:: Shell variables used in caches
* Cache Files:: Files `configure' uses for caching
* Cache Checkpointing:: Loading and saving the cache file
Programming in M4
* M4 Quotation:: Protecting macros from unwanted expansion
* Using autom4te:: The Autoconf executables backbone
* Programming in M4sugar:: Convenient pure M4 macros
* Debugging via autom4te:: Figuring out what M4 was doing
Programming in M4sh
* Common Shell Constructs:: Portability layer for common shell constructs
* Polymorphic Variables:: Support for indirect variable names
* Initialization Macros:: Macros to establish a sane shell environment
* File Descriptor Macros:: File descriptor macros for input and output
M4 Quotation
* Active Characters:: Characters that change the behavior of M4
* One Macro Call:: Quotation and one macro call
* Quoting and Parameters:: M4 vs. shell parameters
* Quotation and Nested Macros:: Macros calling macros
* Changequote is Evil:: Worse than INTERCAL: M4 + changequote
* Quadrigraphs:: Another way to escape special characters
* Balancing Parentheses:: Dealing with unbalanced parentheses
* Quotation Rule Of Thumb:: One parenthesis, one quote
Using `autom4te'
* autom4te Invocation:: A GNU M4 wrapper
* Customizing autom4te:: Customizing the Autoconf package
Programming in M4sugar
* Redefined M4 Macros:: M4 builtins changed in M4sugar
* Diagnostic Macros:: Diagnostic messages from M4sugar
* Diversion support:: Diversions in M4sugar
* Conditional constructs:: Conditions in M4
* Looping constructs:: Iteration in M4
* Evaluation Macros:: More quotation and evaluation control
* Text processing Macros:: String manipulation in M4
* Number processing Macros:: Arithmetic computation in M4
* Set manipulation Macros:: Set manipulation in M4
* Forbidden Patterns:: Catching unexpanded macros
Writing Autoconf Macros
* Macro Definitions:: Basic format of an Autoconf macro
* Macro Names:: What to call your new macros
* Reporting Messages:: Notifying `autoconf' users
* Dependencies Between Macros:: What to do when macros depend on other macros
* Obsoleting Macros:: Warning about old ways of doing things
* Coding Style:: Writing Autoconf macros a` la Autoconf
Dependencies Between Macros
* Prerequisite Macros:: Ensuring required information
* Suggested Ordering:: Warning about possible ordering problems
* One-Shot Macros:: Ensuring a macro is called only once
Portable Shell Programming
* Shellology:: A zoology of shells
* Here-Documents:: Quirks and tricks
* File Descriptors:: FDs and redirections
* File System Conventions:: File names
* Shell Pattern Matching:: Pattern matching
* Shell Substitutions:: Variable and command expansions
* Assignments:: Varying side effects of assignments
* Parentheses:: Parentheses in shell scripts
* Slashes:: Slashes in shell scripts
* Special Shell Variables:: Variables you should not change
* Shell Functions:: What to look out for if you use them
* Limitations of Builtins:: Portable use of not so portable /bin/sh
* Limitations of Usual Tools:: Portable use of portable tools
Portable Make Programming
* $< in Ordinary Make Rules:: $< in ordinary rules
* Failure in Make Rules:: Failing portably in rules
* Special Chars in Names:: Special Characters in Macro Names
* Backslash-Newline-Newline:: Empty last lines in macro definitions
* Backslash-Newline Comments:: Spanning comments across line boundaries
* Long Lines in Makefiles:: Line length limitations
* Macros and Submakes:: `make macro=value' and submakes
* The Make Macro MAKEFLAGS:: `$(MAKEFLAGS)' portability issues
* The Make Macro SHELL:: `$(SHELL)' portability issues
* Parallel Make:: Parallel `make' quirks
* Comments in Make Rules:: Other problems with Make comments
* obj/ and Make:: Don't name a subdirectory `obj'
* make -k Status:: Exit status of `make -k'
* VPATH and Make:: `VPATH' woes
* Single Suffix Rules:: Single suffix rules and separated dependencies
* Timestamps and Make:: Subsecond timestamp resolution
`VPATH' and Make
* Variables listed in VPATH:: `VPATH' must be literal on ancient hosts
* VPATH and Double-colon:: Problems with `::' on ancient hosts
* $< in Explicit Rules:: `$<' does not work in ordinary rules
* Automatic Rule Rewriting:: `VPATH' goes wild on Solaris
* Tru64 Directory Magic:: `mkdir' goes wild on Tru64
* Make Target Lookup:: More details about `VPATH' lookup
Portable C and C++ Programming
* Varieties of Unportability:: How to make your programs unportable
* Integer Overflow:: When integers get too large
* Preprocessor Arithmetic:: `#if' expression problems
* Null Pointers:: Properties of null pointers
* Buffer Overruns:: Subscript errors and the like
* Volatile Objects:: `volatile' and signals
* Floating Point Portability:: Portable floating-point arithmetic
* Exiting Portably:: Exiting and the exit status
Manual Configuration
* Specifying Target Triplets:: Specifying target triplets
* Canonicalizing:: Getting the canonical system type
* Using System Type:: What to do with the system type
Site Configuration
* Help Formatting:: Customizing `configure --help'
* External Software:: Working with other optional software
* Package Options:: Selecting optional features
* Pretty Help Strings:: Formatting help string
* Option Checking:: Controlling checking of `configure' options
* Site Details:: Configuring site details
* Transforming Names:: Changing program names when installing
* Site Defaults:: Giving `configure' local defaults
Transforming Program Names When Installing
* Transformation Options:: `configure' options to transform names
* Transformation Examples:: Sample uses of transforming names
* Transformation Rules:: Makefile uses of transforming names
Running `configure' Scripts
* Basic Installation:: Instructions for typical cases
* Compilers and Options:: Selecting compilers and optimization
* Multiple Architectures:: Compiling for multiple architectures at once
* Installation Names:: Installing in different directories
* Optional Features:: Selecting optional features
* Particular Systems:: Particular systems
* System Type:: Specifying the system type
* Sharing Defaults:: Setting site-wide defaults for `configure'
* Defining Variables:: Specifying the compiler etc.
* configure Invocation:: Changing how `configure' runs
Obsolete Constructs
* Obsolete config.status Use:: Obsolete convention for `config.status'
* acconfig Header:: Additional entries in `config.h.in'
* autoupdate Invocation:: Automatic update of `configure.ac'
* Obsolete Macros:: Backward compatibility macros
* Autoconf 1:: Tips for upgrading your files
* Autoconf 2.13:: Some fresher tips
Upgrading From Version 1
* Changed File Names:: Files you might rename
* Changed Makefiles:: New things to put in `Makefile.in'
* Changed Macros:: Macro calls you might replace
* Changed Results:: Changes in how to check test results
* Changed Macro Writing:: Better ways to write your own macros
Upgrading From Version 2.13
* Changed Quotation:: Broken code which used to work
* New Macros:: Interaction with foreign macros
* Hosts and Cross-Compilation:: Bugward compatibility kludges
* AC_LIBOBJ vs LIBOBJS:: LIBOBJS is a forbidden token
* AC_ACT_IFELSE vs AC_TRY_ACT:: A more generic scheme for testing sources
Generating Test Suites with Autotest
* Using an Autotest Test Suite:: Autotest and the user
* Writing Testsuites:: Autotest macros
* testsuite Invocation:: Running `testsuite' scripts
* Making testsuite Scripts:: Using autom4te to create `testsuite'
Using an Autotest Test Suite
* testsuite Scripts:: The concepts of Autotest
* Autotest Logs:: Their contents
Frequent Autoconf Questions, with answers
* Distributing:: Distributing `configure' scripts
* Why GNU M4:: Why not use the standard M4?
* Bootstrapping:: Autoconf and GNU M4 require each other?
* Why Not Imake:: Why GNU uses `configure' instead of Imake
* Defining Directories:: Passing `datadir' to program
* Autom4te Cache:: What is it? Can I remove it?
* Present But Cannot Be Compiled:: Compiler and Preprocessor Disagree
* Expanded Before Required:: Expanded Before Required
History of Autoconf
* Genesis:: Prehistory and naming of `configure'
* Exodus:: The plagues of M4 and Perl
* Leviticus:: The priestly code of portability arrives
* Numbers:: Growth and contributors
* Deuteronomy:: Approaching the promises of easy configuration
Indices
* Environment Variable Index:: Index of environment variables used
* Output Variable Index:: Index of variables set in output files
* Preprocessor Symbol Index:: Index of C preprocessor symbols defined
* Autoconf Macro Index:: Index of Autoconf macros
* M4 Macro Index:: Index of M4, M4sugar, and M4sh macros
* Autotest Macro Index:: Index of Autotest macros
* Program & Function Index:: Index of those with portability problems
* Concept Index:: General index
File: autoconf.info, Node: Introduction, Next: The GNU Build System, Prev: Top, Up: Top
1 Introduction
**************
A physicist, an engineer, and a computer scientist were discussing the
nature of God. "Surely a Physicist," said the physicist, "because
early in the Creation, God made Light; and you know, Maxwell's
equations, the dual nature of electromagnetic waves, the relativistic
consequences..." "An Engineer!," said the engineer, "because
before making Light, God split the Chaos into Land and Water; it takes a
hell of an engineer to handle that big amount of mud, and orderly
separation of solids from liquids..." The computer scientist
shouted: "And the Chaos, where do you think it was coming from, hmm?"
--Anonymous
Autoconf is a tool for producing shell scripts that automatically
configure software source code packages to adapt to many kinds of
Posix-like systems. The configuration scripts produced by Autoconf are
independent of Autoconf when they are run, so their users do not need
to have Autoconf.
The configuration scripts produced by Autoconf require no manual user
intervention when run; they do not normally even need an argument
specifying the system type. Instead, they individually test for the
presence of each feature that the software package they are for might
need. (Before each check, they print a one-line message stating what
they are checking for, so the user doesn't get too bored while waiting
for the script to finish.) As a result, they deal well with systems
that are hybrids or customized from the more common Posix variants.
There is no need to maintain files that list the features supported by
each release of each variant of Posix.
For each software package that Autoconf is used with, it creates a
configuration script from a template file that lists the system features
that the package needs or can use. After the shell code to recognize
and respond to a system feature has been written, Autoconf allows it to
be shared by many software packages that can use (or need) that feature.
If it later turns out that the shell code needs adjustment for some
reason, it needs to be changed in only one place; all of the
configuration scripts can be regenerated automatically to take advantage
of the updated code.
Those who do not understand Autoconf are condemned to reinvent it,
poorly. The primary goal of Autoconf is making the _user's_ life
easier; making the _maintainer's_ life easier is only a secondary goal.
Put another way, the primary goal is not to make the generation of
`configure' automatic for package maintainers (although patches along
that front are welcome, since package maintainers form the user base of
Autoconf); rather, the goal is to make `configure' painless, portable,
and predictable for the end user of each "autoconfiscated" package.
And to this degree, Autoconf is highly successful at its goal -- most
complaints to the Autoconf list are about difficulties in writing
Autoconf input, and not in the behavior of the resulting `configure'.
Even packages that don't use Autoconf will generally provide a
`configure' script, and the most common complaint about these
alternative home-grown scripts is that they fail to meet one or more of
the GNU Coding Standards that users have come to expect from
Autoconf-generated `configure' scripts.
The Metaconfig package is similar in purpose to Autoconf, but the
scripts it produces require manual user intervention, which is quite
inconvenient when configuring large source trees. Unlike Metaconfig
scripts, Autoconf scripts can support cross-compiling, if some care is
taken in writing them.
Autoconf does not solve all problems related to making portable
software packages--for a more complete solution, it should be used in
concert with other GNU build tools like Automake and Libtool. These
other tools take on jobs like the creation of a portable, recursive
makefile with all of the standard targets, linking of shared libraries,
and so on. *Note The GNU Build System::, for more information.
Autoconf imposes some restrictions on the names of macros used with
`#if' in C programs (*note Preprocessor Symbol Index::).
Autoconf requires GNU M4 version 1.4.6 or later in order to generate
the scripts. It uses features that some versions of M4, including GNU
M4 1.3, do not have. Autoconf works better with GNU M4 version 1.4.13
or later, though this is not required.
*Note Autoconf 1::, for information about upgrading from version 1.
*Note History::, for the story of Autoconf's development. *Note FAQ::,
for answers to some common questions about Autoconf.
See the Autoconf web page (http://www.gnu.org/software/autoconf/)
for up-to-date information, details on the mailing lists, pointers to a
list of known bugs, etc.
Mail suggestions to the Autoconf mailing list .
Past suggestions are archived
(http://lists.gnu.org/archive/html/autoconf/).
Mail bug reports to the Autoconf Bugs mailing list
. Past bug reports are archived
(http://lists.gnu.org/archive/html/bug-autoconf/).
If possible, first check that your bug is not already solved in
current development versions, and that it has not been reported yet.
Be sure to include all the needed information and a short
`configure.ac' that demonstrates the problem.
Autoconf's development tree is accessible via `git'; see the
Autoconf Summary (http://savannah.gnu.org/projects/autoconf/) for
details, or view the actual repository
(http://git.sv.gnu.org/gitweb/?p=autoconf.git). Anonymous CVS access
is also available, see `README' for more details. Patches relative to
the current `git' version can be sent for review to the Autoconf
Patches mailing list , with discussion on
prior patches archived
(http://lists.gnu.org/archive/html/autoconf-patches/); and all commits
are posted in the read-only Autoconf Commit mailing list
, which is also archived
(http://lists.gnu.org/archive/html/autoconf-commit/).
Because of its mission, the Autoconf package itself includes only a
set of often-used macros that have already demonstrated their
usefulness. Nevertheless, if you wish to share your macros, or find
existing ones, see the Autoconf Macro Archive
(http://autoconf-archive.cryp.to/), which is kindly run by Peter Simons
.
File: autoconf.info, Node: The GNU Build System, Next: Making configure Scripts, Prev: Introduction, Up: Top
2 The GNU Build System
**********************
Autoconf solves an important problem--reliable discovery of
system-specific build and runtime information--but this is only one
piece of the puzzle for the development of portable software. To this
end, the GNU project has developed a suite of integrated utilities to
finish the job Autoconf started: the GNU build system, whose most
important components are Autoconf, Automake, and Libtool. In this
chapter, we introduce you to those tools, point you to sources of more
information, and try to convince you to use the entire GNU build system
for your software.
* Menu:
* Automake:: Escaping makefile hell
* Gnulib:: The GNU portability library
* Libtool:: Building libraries portably
* Pointers:: More info on the GNU build system
File: autoconf.info, Node: Automake, Next: Gnulib, Up: The GNU Build System
2.1 Automake
============
The ubiquity of `make' means that a makefile is almost the only viable
way to distribute automatic build rules for software, but one quickly
runs into its numerous limitations. Its lack of support for automatic
dependency tracking, recursive builds in subdirectories, reliable
timestamps (e.g., for network file systems), and so on, mean that
developers must painfully (and often incorrectly) reinvent the wheel
for each project. Portability is non-trivial, thanks to the quirks of
`make' on many systems. On top of all this is the manual labor
required to implement the many standard targets that users have come to
expect (`make install', `make distclean', `make uninstall', etc.).
Since you are, of course, using Autoconf, you also have to insert
repetitive code in your `Makefile.in' to recognize `@CC@', `@CFLAGS@',
and other substitutions provided by `configure'. Into this mess steps
"Automake".
Automake allows you to specify your build needs in a `Makefile.am'
file with a vastly simpler and more powerful syntax than that of a plain
makefile, and then generates a portable `Makefile.in' for use with
Autoconf. For example, the `Makefile.am' to build and install a simple
"Hello world" program might look like:
bin_PROGRAMS = hello
hello_SOURCES = hello.c
The resulting `Makefile.in' (~400 lines) automatically supports all the
standard targets, the substitutions provided by Autoconf, automatic
dependency tracking, `VPATH' building, and so on. `make' builds the
`hello' program, and `make install' installs it in `/usr/local/bin' (or
whatever prefix was given to `configure', if not `/usr/local').
The benefits of Automake increase for larger packages (especially
ones with subdirectories), but even for small programs the added
convenience and portability can be substantial. And that's not all...
File: autoconf.info, Node: Gnulib, Next: Libtool, Prev: Automake, Up: The GNU Build System
2.2 Gnulib
==========
GNU software has a well-deserved reputation for running on many
different types of systems. While our primary goal is to write
software for the GNU system, many users and developers have been
introduced to us through the systems that they were already using.
Gnulib is a central location for common GNU code, intended to be
shared among free software packages. Its components are typically
shared at the source level, rather than being a library that gets built,
installed, and linked against. The idea is to copy files from Gnulib
into your own source tree. There is no distribution tarball; developers
should just grab source modules from the repository. The source files
are available online, under various licenses, mostly GNU GPL or GNU
LGPL.
Gnulib modules typically contain C source code along with Autoconf
macros used to configure the source code. For example, the Gnulib
`stdbool' module implements a `stdbool.h' header that nearly conforms
to C99, even on old-fashioned hosts that lack `stdbool.h'. This module
contains a source file for the replacement header, along with an
Autoconf macro that arranges to use the replacement header on
old-fashioned systems.
File: autoconf.info, Node: Libtool, Next: Pointers, Prev: Gnulib, Up: The GNU Build System
2.3 Libtool
===========
Often, one wants to build not only programs, but libraries, so that
other programs can benefit from the fruits of your labor. Ideally, one
would like to produce _shared_ (dynamically linked) libraries, which
can be used by multiple programs without duplication on disk or in
memory and can be updated independently of the linked programs.
Producing shared libraries portably, however, is the stuff of
nightmares--each system has its own incompatible tools, compiler flags,
and magic incantations. Fortunately, GNU provides a solution:
"Libtool".
Libtool handles all the requirements of building shared libraries for
you, and at this time seems to be the _only_ way to do so with any
portability. It also handles many other headaches, such as: the
interaction of Make rules with the variable suffixes of shared
libraries, linking reliably with shared libraries before they are
installed by the superuser, and supplying a consistent versioning system
(so that different versions of a library can be installed or upgraded
without breaking binary compatibility). Although Libtool, like
Autoconf, can be used without Automake, it is most simply utilized in
conjunction with Automake--there, Libtool is used automatically
whenever shared libraries are needed, and you need not know its syntax.
File: autoconf.info, Node: Pointers, Prev: Libtool, Up: The GNU Build System
2.4 Pointers
============
Developers who are used to the simplicity of `make' for small projects
on a single system might be daunted at the prospect of learning to use
Automake and Autoconf. As your software is distributed to more and
more users, however, you otherwise quickly find yourself putting lots
of effort into reinventing the services that the GNU build tools
provide, and making the same mistakes that they once made and overcame.
(Besides, since you're already learning Autoconf, Automake is a piece
of cake.)
There are a number of places that you can go to for more information
on the GNU build tools.
- Web
The project home pages for Autoconf
(http://www.gnu.org/software/autoconf/), Automake
(http://www.gnu.org/software/automake/), Gnulib
(http://www.gnu.org/software/gnulib/), and Libtool
(http://www.gnu.org/software/libtool/).
- Automake Manual
*Note Automake: (automake)Top, for more information on Automake.
- Books
The book `GNU Autoconf, Automake and Libtool'(1) describes the
complete GNU build environment. You can also find the entire book
on-line (http://sources.redhat.com/autobook/).
---------- Footnotes ----------
(1) `GNU Autoconf, Automake and Libtool', by G. V. Vaughan, B.
Elliston, T. Tromey, and I. L. Taylor. SAMS (originally New Riders),
2000, ISBN 1578701902.
File: autoconf.info, Node: Making configure Scripts, Next: Setup, Prev: The GNU Build System, Up: Top
3 Making `configure' Scripts
****************************
The configuration scripts that Autoconf produces are by convention
called `configure'. When run, `configure' creates several files,
replacing configuration parameters in them with appropriate values.
The files that `configure' creates are:
- one or more `Makefile' files, usually one in each subdirectory of
the package (*note Makefile Substitutions::);
- optionally, a C header file, the name of which is configurable,
containing `#define' directives (*note Configuration Headers::);
- a shell script called `config.status' that, when run, recreates
the files listed above (*note config.status Invocation::);
- an optional shell script normally called `config.cache' (created
when using `configure --config-cache') that saves the results of
running many of the tests (*note Cache Files::);
- a file called `config.log' containing any messages produced by
compilers, to help debugging if `configure' makes a mistake.
To create a `configure' script with Autoconf, you need to write an
Autoconf input file `configure.ac' (or `configure.in') and run
`autoconf' on it. If you write your own feature tests to supplement
those that come with Autoconf, you might also write files called
`aclocal.m4' and `acsite.m4'. If you use a C header file to contain
`#define' directives, you might also run `autoheader', and you can
distribute the generated file `config.h.in' with the package.
Here is a diagram showing how the files that can be used in
configuration are produced. Programs that are executed are suffixed by
`*'. Optional files are enclosed in square brackets (`[]').
`autoconf' and `autoheader' also read the installed Autoconf macro
files (by reading `autoconf.m4').
Files used in preparing a software package for distribution:
your source files --> [autoscan*] --> [configure.scan] --> configure.ac
configure.ac --.
| .------> autoconf* -----> configure
[aclocal.m4] --+---+
| `-----> [autoheader*] --> [config.h.in]
[acsite.m4] ---'
Makefile.in -------------------------------> Makefile.in
Files used in configuring a software package:
.-------------> [config.cache]
configure* ------------+-------------> config.log
|
[config.h.in] -. v .-> [config.h] -.
+--> config.status* -+ +--> make*
Makefile.in ---' `-> Makefile ---'
* Menu:
* Writing Autoconf Input:: What to put in an Autoconf input file
* autoscan Invocation:: Semi-automatic `configure.ac' writing
* ifnames Invocation:: Listing the conditionals in source code
* autoconf Invocation:: How to create configuration scripts
* autoreconf Invocation:: Remaking multiple `configure' scripts
File: autoconf.info, Node: Writing Autoconf Input, Next: autoscan Invocation, Up: Making configure Scripts
3.1 Writing `configure.ac'
==========================
To produce a `configure' script for a software package, create a file
called `configure.ac' that contains invocations of the Autoconf macros
that test the system features your package needs or can use. Autoconf
macros already exist to check for many features; see *note Existing
Tests::, for their descriptions. For most other features, you can use
Autoconf template macros to produce custom checks; see *note Writing
Tests::, for information about them. For especially tricky or
specialized features, `configure.ac' might need to contain some
hand-crafted shell commands; see *note Portable Shell Programming:
Portable Shell. The `autoscan' program can give you a good start in
writing `configure.ac' (*note autoscan Invocation::, for more
information).
Previous versions of Autoconf promoted the name `configure.in',
which is somewhat ambiguous (the tool needed to process this file is not
described by its extension), and introduces a slight confusion with
`config.h.in' and so on (for which `.in' means "to be processed by
`configure'"). Using `configure.ac' is now preferred.
* Menu:
* Shell Script Compiler:: Autoconf as solution of a problem
* Autoconf Language:: Programming in Autoconf
* Autoconf Input Layout:: Standard organization of `configure.ac'
File: autoconf.info, Node: Shell Script Compiler, Next: Autoconf Language, Up: Writing Autoconf Input
3.1.1 A Shell Script Compiler
-----------------------------
Just as for any other computer language, in order to properly program
`configure.ac' in Autoconf you must understand _what_ problem the
language tries to address and _how_ it does so.
The problem Autoconf addresses is that the world is a mess. After
all, you are using Autoconf in order to have your package compile
easily on all sorts of different systems, some of them being extremely
hostile. Autoconf itself bears the price for these differences:
`configure' must run on all those systems, and thus `configure' must
limit itself to their lowest common denominator of features.
Naturally, you might then think of shell scripts; who needs
`autoconf'? A set of properly written shell functions is enough to
make it easy to write `configure' scripts by hand. Sigh!
Unfortunately, even in 2008, where shells without any function support
are far and few between, there are pitfalls to avoid when making use of
them. Also, finding a Bourne shell that accepts shell functions is not
trivial, even though there is almost always one on interesting porting
targets.
So, what is really needed is some kind of compiler, `autoconf', that
takes an Autoconf program, `configure.ac', and transforms it into a
portable shell script, `configure'.
How does `autoconf' perform this task?
There are two obvious possibilities: creating a brand new language or
extending an existing one. The former option is attractive: all sorts
of optimizations could easily be implemented in the compiler and many
rigorous checks could be performed on the Autoconf program (e.g.,
rejecting any non-portable construct). Alternatively, you can extend
an existing language, such as the `sh' (Bourne shell) language.
Autoconf does the latter: it is a layer on top of `sh'. It was
therefore most convenient to implement `autoconf' as a macro expander:
a program that repeatedly performs "macro expansions" on text input,
replacing macro calls with macro bodies and producing a pure `sh'
script in the end. Instead of implementing a dedicated Autoconf macro
expander, it is natural to use an existing general-purpose macro
language, such as M4, and implement the extensions as a set of M4
macros.
File: autoconf.info, Node: Autoconf Language, Next: Autoconf Input Layout, Prev: Shell Script Compiler, Up: Writing Autoconf Input
3.1.2 The Autoconf Language
---------------------------
The Autoconf language differs from many other computer languages
because it treats actual code the same as plain text. Whereas in C,
for instance, data and instructions have different syntactic status, in
Autoconf their status is rigorously the same. Therefore, we need a
means to distinguish literal strings from text to be expanded:
quotation.
When calling macros that take arguments, there must not be any white
space between the macro name and the open parenthesis. Arguments should
be enclosed within the M4 quote characters `[' and `]', and be
separated by commas. Any leading blanks or newlines in arguments are
ignored, unless they are quoted. You should always quote an argument
that might contain a macro name, comma, parenthesis, or a leading blank
or newline. This rule applies recursively for every macro call,
including macros called from other macros.
For instance:
AC_CHECK_HEADER([stdio.h],
[AC_DEFINE([HAVE_STDIO_H], [1],
[Define to 1 if you have .])],
[AC_MSG_ERROR([Sorry, can't do anything for you])])
is quoted properly. You may safely simplify its quotation to:
AC_CHECK_HEADER([stdio.h],
[AC_DEFINE([HAVE_STDIO_H], 1,
[Define to 1 if you have .])],
[AC_MSG_ERROR([Sorry, can't do anything for you])])
because `1' cannot contain a macro call. Here, the argument of
`AC_MSG_ERROR' must be quoted; otherwise, its comma would be
interpreted as an argument separator. Also, the second and third
arguments of `AC_CHECK_HEADER' must be quoted, since they contain macro
calls. The three arguments `HAVE_STDIO_H', `stdio.h', and `Define to 1
if you have .' do not need quoting, but if you unwisely
defined a macro with a name like `Define' or `stdio' then they would
need quoting. Cautious Autoconf users would keep the quotes, but many
Autoconf users find such precautions annoying, and would rewrite the
example as follows:
AC_CHECK_HEADER(stdio.h,
[AC_DEFINE(HAVE_STDIO_H, 1,
[Define to 1 if you have .])],
[AC_MSG_ERROR([Sorry, can't do anything for you])])
This is safe, so long as you adopt good naming conventions and do not
define macros with names like `HAVE_STDIO_H', `stdio', or `h'. Though
it is also safe here to omit the quotes around `Define to 1 if you have
.' this is not recommended, as message strings are more likely
to inadvertently contain commas.
The following example is wrong and dangerous, as it is underquoted:
AC_CHECK_HEADER(stdio.h,
AC_DEFINE(HAVE_STDIO_H, 1,
Define to 1 if you have .),
AC_MSG_ERROR([Sorry, can't do anything for you]))
In other cases, you may have to use text that also resembles a macro
call. You must quote that text even when it is not passed as a macro
argument:
echo "Hard rock was here! --[AC_DC]"
which results in:
echo "Hard rock was here! --AC_DC"
When you use the same text in a macro argument, you must therefore have
an extra quotation level (since one is stripped away by the macro
substitution). In general, then, it is a good idea to _use double
quoting for all literal string arguments_:
AC_MSG_WARN([[AC_DC stinks --Iron Maiden]])
You are now able to understand one of the constructs of Autoconf that
has been continually misunderstood... The rule of thumb is that
_whenever you expect macro expansion, expect quote expansion_; i.e.,
expect one level of quotes to be lost. For instance:
AC_COMPILE_IFELSE([char b[10];], [], [AC_MSG_ERROR([you lose])])
is incorrect: here, the first argument of `AC_COMPILE_IFELSE' is `char
b[10];' and is expanded once, which results in `char b10;'. (There was
an idiom common in Autoconf's past to address this issue via the M4
`changequote' primitive, but do not use it!) Let's take a closer look:
the author meant the first argument to be understood as a literal, and
therefore it must be quoted twice:
AC_COMPILE_IFELSE([[char b[10];]], [], [AC_MSG_ERROR([you lose])])
Voila`, you actually produce `char b[10];' this time!
On the other hand, descriptions (e.g., the last parameter of
`AC_DEFINE' or `AS_HELP_STRING') are not literals--they are subject to
line breaking, for example--and should not be double quoted. Even if
these descriptions are short and are not actually broken, double
quoting them yields weird results.
Some macros take optional arguments, which this documentation
represents as [ARG] (not to be confused with the quote characters).
You may just leave them empty, or use `[]' to make the emptiness of the
argument explicit, or you may simply omit the trailing commas. The
three lines below are equivalent:
AC_CHECK_HEADERS([stdio.h], [], [], [])
AC_CHECK_HEADERS([stdio.h],,,)
AC_CHECK_HEADERS([stdio.h])
It is best to put each macro call on its own line in `configure.ac'.
Most of the macros don't add extra newlines; they rely on the newline
after the macro call to terminate the commands. This approach makes
the generated `configure' script a little easier to read by not
inserting lots of blank lines. It is generally safe to set shell
variables on the same line as a macro call, because the shell allows
assignments without intervening newlines.
You can include comments in `configure.ac' files by starting them
with the `#'. For example, it is helpful to begin `configure.ac' files
with a line like this:
# Process this file with autoconf to produce a configure script.
File: autoconf.info, Node: Autoconf Input Layout, Prev: Autoconf Language, Up: Writing Autoconf Input
3.1.3 Standard `configure.ac' Layout
------------------------------------
The order in which `configure.ac' calls the Autoconf macros is not
important, with a few exceptions. Every `configure.ac' must contain a
call to `AC_INIT' before the checks, and a call to `AC_OUTPUT' at the
end (*note Output::). Additionally, some macros rely on other macros
having been called first, because they check previously set values of
some variables to decide what to do. These macros are noted in the
individual descriptions (*note Existing Tests::), and they also warn
you when `configure' is created if they are called out of order.
To encourage consistency, here is a suggested order for calling the
Autoconf macros. Generally speaking, the things near the end of this
list are those that could depend on things earlier in it. For example,
library functions could be affected by types and libraries.
Autoconf requirements
`AC_INIT(PACKAGE, VERSION, BUG-REPORT-ADDRESS)'
information on the package
checks for programs
checks for libraries
checks for header files
checks for types
checks for structures
checks for compiler characteristics
checks for library functions
checks for system services
`AC_CONFIG_FILES([FILE...])'
`AC_OUTPUT'
File: autoconf.info, Node: autoscan Invocation, Next: ifnames Invocation, Prev: Writing Autoconf Input, Up: Making configure Scripts
3.2 Using `autoscan' to Create `configure.ac'
=============================================
The `autoscan' program can help you create and/or maintain a
`configure.ac' file for a software package. `autoscan' examines source
files in the directory tree rooted at a directory given as a command
line argument, or the current directory if none is given. It searches
the source files for common portability problems and creates a file
`configure.scan' which is a preliminary `configure.ac' for that
package, and checks a possibly existing `configure.ac' for completeness.
When using `autoscan' to create a `configure.ac', you should
manually examine `configure.scan' before renaming it to `configure.ac';
it probably needs some adjustments. Occasionally, `autoscan' outputs a
macro in the wrong order relative to another macro, so that `autoconf'
produces a warning; you need to move such macros manually. Also, if
you want the package to use a configuration header file, you must add a
call to `AC_CONFIG_HEADERS' (*note Configuration Headers::). You might
also have to change or add some `#if' directives to your program in
order to make it work with Autoconf (*note ifnames Invocation::, for
information about a program that can help with that job).
When using `autoscan' to maintain a `configure.ac', simply consider
adding its suggestions. The file `autoscan.log' contains detailed
information on why a macro is requested.
`autoscan' uses several data files (installed along with Autoconf)
to determine which macros to output when it finds particular symbols in
a package's source files. These data files all have the same format:
each line consists of a symbol, one or more blanks, and the Autoconf
macro to output if that symbol is encountered. Lines starting with `#'
are comments.
`autoscan' accepts the following options:
`--help'
`-h'
Print a summary of the command line options and exit.
`--version'
`-V'
Print the version number of Autoconf and exit.
`--verbose'
`-v'
Print the names of the files it examines and the potentially
interesting symbols it finds in them. This output can be
voluminous.
`--debug'
`-d'
Don't remove temporary files.
`--include=DIR'
`-I DIR'
Append DIR to the include path. Multiple invocations accumulate.
`--prepend-include=DIR'
`-B DIR'
Prepend DIR to the include path. Multiple invocations accumulate.
File: autoconf.info, Node: ifnames Invocation, Next: autoconf Invocation, Prev: autoscan Invocation, Up: Making configure Scripts
3.3 Using `ifnames' to List Conditionals
========================================
`ifnames' can help you write `configure.ac' for a software package. It
prints the identifiers that the package already uses in C preprocessor
conditionals. If a package has already been set up to have some
portability, `ifnames' can thus help you figure out what its
`configure' needs to check for. It may help fill in some gaps in a
`configure.ac' generated by `autoscan' (*note autoscan Invocation::).
`ifnames' scans all of the C source files named on the command line
(or the standard input, if none are given) and writes to the standard
output a sorted list of all the identifiers that appear in those files
in `#if', `#elif', `#ifdef', or `#ifndef' directives. It prints each
identifier on a line, followed by a space-separated list of the files
in which that identifier occurs.
`ifnames' accepts the following options:
`--help'
`-h'
Print a summary of the command line options and exit.
`--version'
`-V'
Print the version number of Autoconf and exit.
File: autoconf.info, Node: autoconf Invocation, Next: autoreconf Invocation, Prev: ifnames Invocation, Up: Making configure Scripts
3.4 Using `autoconf' to Create `configure'
==========================================
To create `configure' from `configure.ac', run the `autoconf' program
with no arguments. `autoconf' processes `configure.ac' with the M4
macro processor, using the Autoconf macros. If you give `autoconf' an
argument, it reads that file instead of `configure.ac' and writes the
configuration script to the standard output instead of to `configure'.
If you give `autoconf' the argument `-', it reads from the standard
input instead of `configure.ac' and writes the configuration script to
the standard output.
The Autoconf macros are defined in several files. Some of the files
are distributed with Autoconf; `autoconf' reads them first. Then it
looks for the optional file `acsite.m4' in the directory that contains
the distributed Autoconf macro files, and for the optional file
`aclocal.m4' in the current directory. Those files can contain your
site's or the package's own Autoconf macro definitions (*note Writing
Autoconf Macros::, for more information). If a macro is defined in
more than one of the files that `autoconf' reads, the last definition
it reads overrides the earlier ones.
`autoconf' accepts the following options:
`--help'
`-h'
Print a summary of the command line options and exit.
`--version'
`-V'
Print the version number of Autoconf and exit.
`--verbose'
`-v'
Report processing steps.
`--debug'
`-d'
Don't remove the temporary files.
`--force'
`-f'
Remake `configure' even if newer than its input files.
`--include=DIR'
`-I DIR'
Append DIR to the include path. Multiple invocations accumulate.
`--prepend-include=DIR'
`-B DIR'
Prepend DIR to the include path. Multiple invocations accumulate.
`--output=FILE'
`-o FILE'
Save output (script or trace) to FILE. The file `-' stands for
the standard output.
`--warnings=CATEGORY'
`-W CATEGORY'
Report the warnings related to CATEGORY (which can actually be a
comma separated list). *Note Reporting Messages::, macro
`AC_DIAGNOSE', for a comprehensive list of categories. Special
values include:
`all'
report all the warnings
`none'
report none
`error'
treats warnings as errors
`no-CATEGORY'
disable warnings falling into CATEGORY
Warnings about `syntax' are enabled by default, and the environment
variable `WARNINGS', a comma separated list of categories, is
honored as well. Passing `-W CATEGORY' actually behaves as if you
had passed `--warnings syntax,$WARNINGS,CATEGORY'. To disable the
defaults and `WARNINGS', and then enable warnings about obsolete
constructs, use `-W none,obsolete'.
Because `autoconf' uses `autom4te' behind the scenes, it displays
a back trace for errors, but not for warnings; if you want them,
just pass `-W error'. *Note autom4te Invocation::, for some
examples.
`--trace=MACRO[:FORMAT]'
`-t MACRO[:FORMAT]'
Do not create the `configure' script, but list the calls to MACRO
according to the FORMAT. Multiple `--trace' arguments can be used
to list several macros. Multiple `--trace' arguments for a single
macro are not cumulative; instead, you should just make FORMAT as
long as needed.
The FORMAT is a regular string, with newlines if desired, and
several special escape codes. It defaults to `$f:$l:$n:$%'; see
*note autom4te Invocation::, for details on the FORMAT.
`--initialization'
`-i'
By default, `--trace' does not trace the initialization of the
Autoconf macros (typically the `AC_DEFUN' definitions). This
results in a noticeable speedup, but can be disabled by this
option.
It is often necessary to check the content of a `configure.ac' file,
but parsing it yourself is extremely fragile and error-prone. It is
suggested that you rely upon `--trace' to scan `configure.ac'. For
instance, to find the list of variables that are substituted, use:
$ autoconf -t AC_SUBST
configure.ac:2:AC_SUBST:ECHO_C
configure.ac:2:AC_SUBST:ECHO_N
configure.ac:2:AC_SUBST:ECHO_T
More traces deleted
The example below highlights the difference between `$@', `$*', and
`$%'.
$ cat configure.ac
AC_DEFINE(This, is, [an
[example]])
$ autoconf -t 'AC_DEFINE:@: $@
*: $*
%: $%'
@: [This],[is],[an
[example]]
*: This,is,an
[example]
%: This:is:an [example]
The FORMAT gives you a lot of freedom:
$ autoconf -t 'AC_SUBST:$$ac_subst{"$1"} = "$f:$l";'
$ac_subst{"ECHO_C"} = "configure.ac:2";
$ac_subst{"ECHO_N"} = "configure.ac:2";
$ac_subst{"ECHO_T"} = "configure.ac:2";
More traces deleted
A long SEPARATOR can be used to improve the readability of complex
structures, and to ease their parsing (for instance when no single
character is suitable as a separator):
$ autoconf -t 'AM_MISSING_PROG:${|:::::|}*'
ACLOCAL|:::::|aclocal|:::::|$missing_dir
AUTOCONF|:::::|autoconf|:::::|$missing_dir
AUTOMAKE|:::::|automake|:::::|$missing_dir
More traces deleted
File: autoconf.info, Node: autoreconf Invocation, Prev: autoconf Invocation, Up: Making configure Scripts
3.5 Using `autoreconf' to Update `configure' Scripts
====================================================
Installing the various components of the GNU Build System can be
tedious: running `autopoint' for Gettext, `automake' for `Makefile.in'
etc. in each directory. It may be needed either because some tools
such as `automake' have been updated on your system, or because some of
the sources such as `configure.ac' have been updated, or finally,
simply in order to install the GNU Build System in a fresh tree.
`autoreconf' runs `autoconf', `autoheader', `aclocal', `automake',
`libtoolize', and `autopoint' (when appropriate) repeatedly to update
the GNU Build System in the specified directories and their
subdirectories (*note Subdirectories::). By default, it only remakes
those files that are older than their sources. The environment
variables `AUTOCONF', `AUTOHEADER', `AUTOMAKE', `ACLOCAL', `AUTOPOINT',
`LIBTOOLIZE', `M4', and `MAKE' may be used to override the invocation
of the respective tools.
If you install a new version of some tool, you can make `autoreconf'
remake _all_ of the files by giving it the `--force' option.
*Note Automatic Remaking::, for Make rules to automatically rebuild
`configure' scripts when their source files change. That method
handles the timestamps of configuration header templates properly, but
does not pass `--autoconf-dir=DIR' or `--localdir=DIR'.
Gettext supplies the `autopoint' command to add translation
infrastructure to a source package. If you use `autopoint', your
`configure.ac' should invoke both `AM_GNU_GETTEXT' and
`AM_GNU_GETTEXT_VERSION(GETTEXT-VERSION)'. *Note Invoking the
`autopoint' Program: (gettext)autopoint Invocation, for further details.
`autoreconf' accepts the following options:
`--help'
`-h'
Print a summary of the command line options and exit.
`--version'
`-V'
Print the version number of Autoconf and exit.
`--verbose'
`-V'
Print the name of each directory `autoreconf' examines and the
commands it runs. If given two or more times, pass `--verbose' to
subordinate tools that support it.
`--debug'
`-d'
Don't remove the temporary files.
`--force'
`-f'
Remake even `configure' scripts and configuration headers that are
newer than their input files (`configure.ac' and, if present,
`aclocal.m4').
`--install'
`-i'
Install the missing auxiliary files in the package. By default,
files are copied; this can be changed with `--symlink'.
If deemed appropriate, this option triggers calls to `automake
--add-missing', `libtoolize', `autopoint', etc.
`--no-recursive'
Do not rebuild files in subdirectories to configure (see *note
Subdirectories::, macro `AC_CONFIG_SUBDIRS').
`--symlink'
`-s'
When used with `--install', install symbolic links to the missing
auxiliary files instead of copying them.
`--make'
`-m'
When the directories were configured, update the configuration by
running `./config.status --recheck && ./config.status', and then
run `make'.
`--include=DIR'
`-I DIR'
Append DIR to the include path. Multiple invocations accumulate.
Passed on to `aclocal', `autoconf' and `autoheader' internally.
`--prepend-include=DIR'
`-B DIR'
Prepend DIR to the include path. Multiple invocations accumulate.
Passed on to `autoconf' and `autoheader' internally.
`--warnings=CATEGORY'
`-W CATEGORY'
Report the warnings related to CATEGORY (which can actually be a
comma separated list).
`cross'
related to cross compilation issues.
`obsolete'
report the uses of obsolete constructs.
`portability'
portability issues
`syntax'
dubious syntactic constructs.
`all'
report all the warnings
`none'
report none
`error'
treats warnings as errors
`no-CATEGORY'
disable warnings falling into CATEGORY
Warnings about `syntax' are enabled by default, and the environment
variable `WARNINGS', a comma separated list of categories, is
honored as well. Passing `-W CATEGORY' actually behaves as if you
had passed `--warnings syntax,$WARNINGS,CATEGORY'. To disable the
defaults and `WARNINGS', and then enable warnings about obsolete
constructs, use `-W none,obsolete'.
If you want `autoreconf' to pass flags that are not listed here on
to `aclocal', set `ACLOCAL_AMFLAGS' in your `Makefile.am'. Due to a
limitation in the Autoconf implementation these flags currently must be
set on a single line in `Makefile.am', without any backslash-newlines.
File: autoconf.info, Node: Setup, Next: Existing Tests, Prev: Making configure Scripts, Up: Top
4 Initialization and Output Files
*********************************
Autoconf-generated `configure' scripts need some information about how
to initialize, such as how to find the package's source files and about
the output files to produce. The following sections describe the
initialization and the creation of output files.
* Menu:
* Initializing configure:: Option processing etc.
* Versioning:: Dealing with Autoconf versions
* Notices:: Copyright, version numbers in `configure'
* Input:: Where Autoconf should find files
* Output:: Outputting results from the configuration
* Configuration Actions:: Preparing the output based on results
* Configuration Files:: Creating output files
* Makefile Substitutions:: Using output variables in makefiles
* Configuration Headers:: Creating a configuration header file
* Configuration Commands:: Running arbitrary instantiation commands
* Configuration Links:: Links depending on the configuration
* Subdirectories:: Configuring independent packages together
* Default Prefix:: Changing the default installation prefix
File: autoconf.info, Node: Initializing configure, Next: Versioning, Up: Setup
4.1 Initializing `configure'
============================
Every `configure' script must call `AC_INIT' before doing anything
else. The only other required macro is `AC_OUTPUT' (*note Output::).
-- Macro: AC_INIT (PACKAGE, VERSION, [BUG-REPORT], [TARNAME], [URL])
Process any command-line arguments and perform various
initializations and verifications.
Set the name of the PACKAGE and its VERSION. These are typically
used in `--version' support, including that of `configure'. The
optional argument BUG-REPORT should be the email to which users
should send bug reports. The package TARNAME differs from
PACKAGE: the latter designates the full package name (e.g., `GNU
Autoconf'), while the former is meant for distribution tar ball
names (e.g., `autoconf'). It defaults to PACKAGE with `GNU '
stripped, lower-cased, and all characters other than alphanumerics
and underscores are changed to `-'. If provided, URL should be
the home page for the package.
It is preferable that the arguments of `AC_INIT' be static, i.e.,
there should not be any shell computation, but they can be
computed by M4.
The following M4 macros (e.g., `AC_PACKAGE_NAME'), output variables
(e.g., `PACKAGE_NAME'), and preprocessor symbols (e.g.,
`PACKAGE_NAME'), are defined by `AC_INIT':
`AC_PACKAGE_NAME', `PACKAGE_NAME'
Exactly PACKAGE.
`AC_PACKAGE_TARNAME', `PACKAGE_TARNAME'
Exactly TARNAME, possibly generated from PACKAGE.
`AC_PACKAGE_VERSION', `PACKAGE_VERSION'
Exactly VERSION.
`AC_PACKAGE_STRING', `PACKAGE_STRING'
Exactly `PACKAGE VERSION'.
`AC_PACKAGE_BUGREPORT', `PACKAGE_BUGREPORT'
Exactly BUG-REPORT, if one was provided.
`AC_PACKAGE_URL', `PACKAGE_URL'
Exactly URL, if one was provided. If URL was empty, but
PACKAGE begins with `GNU ', then this defaults to
`http://www.gnu.org/software/TARNAME/', otherwise, no URL is
assumed.
If your `configure' script does its own option processing, it should
inspect `$@' or `$*' immediately after calling `AC_INIT', because other
Autoconf macros liberally use the `set' command to process strings, and
this has the side effect of updating `$@' and `$*'. However, we
suggest that you use standard macros like `AC_ARG_ENABLE' instead of
attempting to implement your own option processing. *Note Site
Configuration::.
File: autoconf.info, Node: Versioning, Next: Notices, Prev: Initializing configure, Up: Setup
4.2 Dealing with Autoconf versions
==================================
The following optional macros can be used to help choose the minimum
version of Autoconf that can successfully compile a given
`configure.ac'.
-- Macro: AC_PREREQ (VERSION)
Ensure that a recent enough version of Autoconf is being used. If
the version of Autoconf being used to create `configure' is
earlier than VERSION, print an error message to the standard error
output and exit with failure (exit status is 63). For example:
AC_PREREQ([2.64])
This macro is the only macro that may be used before `AC_INIT', but
for consistency, you are invited not to do so.
-- Macro: AC_AUTOCONF_VERSION
This macro was introduced in Autoconf 2.62. It identifies the
version of Autoconf that is currently parsing the input file, in a
format suitable for `m4_version_compare' (*note
m4_version_compare::); in other words, for this release of
Autoconf, its value is `2.64'. One potential use of this macro is
for writing conditional fallbacks based on when a feature was
added to Autoconf, rather than using `AC_PREREQ' to require the
newer version of Autoconf. However, remember that the Autoconf
philosophy favors feature checks over version checks.
You should not expand this macro directly; use
`m4_defn([AC_AUTOCONF_VERSION])' instead. This is because some
users might have a beta version of Autoconf installed, with
arbitrary letters included in its version string. This means it
is possible for the version string to contain the name of a
defined macro, such that expanding `AC_AUTOCONF_VERSION' would
trigger the expansion of that macro during rescanning, and change
the version string to be different than what you intended to check.
File: autoconf.info, Node: Notices, Next: Input, Prev: Versioning, Up: Setup
4.3 Notices in `configure'
==========================
The following macros manage version numbers for `configure' scripts.
Using them is optional.
-- Macro: AC_COPYRIGHT (COPYRIGHT-NOTICE)
State that, in addition to the Free Software Foundation's
copyright on the Autoconf macros, parts of your `configure' are
covered by the COPYRIGHT-NOTICE.
The COPYRIGHT-NOTICE shows up in both the head of `configure' and
in `configure --version'.
-- Macro: AC_REVISION (REVISION-INFO)
Copy revision stamp REVISION-INFO into the `configure' script,
with any dollar signs or double-quotes removed. This macro lets
you put a revision stamp from `configure.ac' into `configure'
without RCS or CVS changing it when you check in `configure'.
That way, you can determine easily which revision of
`configure.ac' a particular `configure' corresponds to.
For example, this line in `configure.ac':
AC_REVISION([$Revision: 1.30 $])
produces this in `configure':
#!/bin/sh
# From configure.ac Revision: 1.30
File: autoconf.info, Node: Input, Next: Output, Prev: Notices, Up: Setup
4.4 Finding `configure' Input
=============================
-- Macro: AC_CONFIG_SRCDIR (UNIQUE-FILE-IN-SOURCE-DIR)
UNIQUE-FILE-IN-SOURCE-DIR is some file that is in the package's
source directory; `configure' checks for this file's existence to
make sure that the directory that it is told contains the source
code in fact does. Occasionally people accidentally specify the
wrong directory with `--srcdir'; this is a safety check. *Note
configure Invocation::, for more information.
Packages that do manual configuration or use the `install' program
might need to tell `configure' where to find some other shell scripts
by calling `AC_CONFIG_AUX_DIR', though the default places it looks are
correct for most cases.
-- Macro: AC_CONFIG_AUX_DIR (DIR)
Use the auxiliary build tools (e.g., `install-sh', `config.sub',
`config.guess', Cygnus `configure', Automake and Libtool scripts,
etc.) that are in directory DIR. These are auxiliary files used
in configuration. DIR can be either absolute or relative to
`SRCDIR'. The default is `SRCDIR' or `SRCDIR/..' or
`SRCDIR/../..', whichever is the first that contains `install-sh'.
The other files are not checked for, so that using
`AC_PROG_INSTALL' does not automatically require distributing the
other auxiliary files. It checks for `install.sh' also, but that
name is obsolete because some `make' have a rule that creates
`install' from it if there is no makefile.
The auxiliary directory is commonly named `build-aux'. If you
need portability to DOS variants, do not name the auxiliary
directory `aux'. *Note File System Conventions::.
-- Macro: AC_REQUIRE_AUX_FILE (FILE)
Declares that FILE is expected in the directory defined above. In
Autoconf proper, this macro does nothing: its sole purpose is to be
traced by third-party tools to produce a list of expected auxiliary
files. For instance it is called by macros like `AC_PROG_INSTALL'
(*note Particular Programs::) or `AC_CANONICAL_BUILD' (*note
Canonicalizing::) to register the auxiliary files they need.
Similarly, packages that use `aclocal' should declare where local
macros can be found using `AC_CONFIG_MACRO_DIR'.
-- Macro: AC_CONFIG_MACRO_DIR (DIR)
Specify DIR as the location of additional local Autoconf macros.
This macro is intended for use by future versions of commands like
`autoreconf' that trace macro calls. It should be called directly
from `configure.ac' so that tools that install macros for
`aclocal' can find the macros' declarations.
Note that if you use `aclocal' from Automake to generate
`aclocal.m4', you must also set `ACLOCAL_AMFLAGS = -I DIR' in your
top-level `Makefile.am'. Due to a limitation in the Autoconf
implementation of `autoreconf', these include directives currently
must be set on a single line in `Makefile.am', without any
backslash-newlines.
File: autoconf.info, Node: Output, Next: Configuration Actions, Prev: Input, Up: Setup
4.5 Outputting Files
====================
Every Autoconf script, e.g., `configure.ac', should finish by calling
`AC_OUTPUT'. That is the macro that generates and runs
`config.status', which in turn creates the makefiles and any other
files resulting from configuration. This is the only required macro
besides `AC_INIT' (*note Input::).
-- Macro: AC_OUTPUT
Generate `config.status' and launch it. Call this macro once, at
the end of `configure.ac'.
`config.status' performs all the configuration actions: all the
output files (see *note Configuration Files::, macro
`AC_CONFIG_FILES'), header files (see *note Configuration
Headers::, macro `AC_CONFIG_HEADERS'), commands (see *note
Configuration Commands::, macro `AC_CONFIG_COMMANDS'), links (see
*note Configuration Links::, macro `AC_CONFIG_LINKS'),
subdirectories to configure (see *note Subdirectories::, macro
`AC_CONFIG_SUBDIRS') are honored.
The location of your `AC_OUTPUT' invocation is the exact point
where configuration actions are taken: any code afterwards is
executed by `configure' once `config.status' was run. If you want
to bind actions to `config.status' itself (independently of
whether `configure' is being run), see *note Running Arbitrary
Configuration Commands: Configuration Commands.
Historically, the usage of `AC_OUTPUT' was somewhat different.
*Note Obsolete Macros::, for a description of the arguments that
`AC_OUTPUT' used to support.
If you run `make' in subdirectories, you should run it using the
`make' variable `MAKE'. Most versions of `make' set `MAKE' to the name
of the `make' program plus any options it was given. (But many do not
include in it the values of any variables set on the command line, so
those are not passed on automatically.) Some old versions of `make' do
not set this variable. The following macro allows you to use it even
with those versions.
-- Macro: AC_PROG_MAKE_SET
If the Make command, `$MAKE' if set or else `make', predefines
`$(MAKE)', define output variable `SET_MAKE' to be empty.
Otherwise, define `SET_MAKE' to a macro definition that sets
`$(MAKE)', such as `MAKE=make'. Calls `AC_SUBST' for `SET_MAKE'.
If you use this macro, place a line like this in each `Makefile.in'
that runs `MAKE' on other directories:
@SET_MAKE@
File: autoconf.info, Node: Configuration Actions, Next: Configuration Files, Prev: Output, Up: Setup
4.6 Performing Configuration Actions
====================================
`configure' is designed so that it appears to do everything itself, but
there is actually a hidden slave: `config.status'. `configure' is in
charge of examining your system, but it is `config.status' that
actually takes the proper actions based on the results of `configure'.
The most typical task of `config.status' is to _instantiate_ files.
This section describes the common behavior of the four standard
instantiating macros: `AC_CONFIG_FILES', `AC_CONFIG_HEADERS',
`AC_CONFIG_COMMANDS' and `AC_CONFIG_LINKS'. They all have this
prototype:
AC_CONFIG_ITEMS(TAG..., [COMMANDS], [INIT-CMDS])
where the arguments are:
TAG...
A blank-or-newline-separated list of tags, which are typically the
names of the files to instantiate.
You are encouraged to use literals as TAGS. In particular, you
should avoid
... && my_foos="$my_foos fooo"
... && my_foos="$my_foos foooo"
AC_CONFIG_ITEMS([$my_foos])
and use this instead:
... && AC_CONFIG_ITEMS([fooo])
... && AC_CONFIG_ITEMS([foooo])
The macros `AC_CONFIG_FILES' and `AC_CONFIG_HEADERS' use special
TAG values: they may have the form `OUTPUT' or `OUTPUT:INPUTS'.
The file OUTPUT is instantiated from its templates, INPUTS
(defaulting to `OUTPUT.in').
`AC_CONFIG_FILES([Makefile:boiler/top.mk:boiler/bot.mk)]', for
example, asks for the creation of the file `Makefile' that
contains the expansion of the output variables in the
concatenation of `boiler/top.mk' and `boiler/bot.mk'.
The special value `-' might be used to denote the standard output
when used in OUTPUT, or the standard input when used in the
INPUTS. You most probably don't need to use this in
`configure.ac', but it is convenient when using the command line
interface of `./config.status', see *note config.status
Invocation::, for more details.
The INPUTS may be absolute or relative file names. In the latter
case they are first looked for in the build tree, and then in the
source tree. Input files should be text files, and a line length
below 2000 bytes should be safe.
COMMANDS
Shell commands output literally into `config.status', and
associated with a tag that the user can use to tell `config.status'
which commands to run. The commands are run each time a TAG
request is given to `config.status', typically each time the file
`TAG' is created.
The variables set during the execution of `configure' are _not_
available here: you first need to set them via the INIT-CMDS.
Nonetheless the following variables are precomputed:
`srcdir'
The name of the top source directory, assuming that the
working directory is the top build directory. This is what
the `configure' option `--srcdir' sets.
`ac_top_srcdir'
The name of the top source directory, assuming that the
working directory is the current build directory.
`ac_top_build_prefix'
The name of the top build directory, assuming that the working
directory is the current build directory. It can be empty,
or else ends with a slash, so that you may concatenate it.
`ac_srcdir'
The name of the corresponding source directory, assuming that
the working directory is the current build directory.
The "current" directory refers to the directory (or
pseudo-directory) containing the input part of TAGS. For
instance, running
AC_CONFIG_COMMANDS([deep/dir/out:in/in.in], [...], [...])
with `--srcdir=../package' produces the following values:
# Argument of --srcdir
srcdir='../package'
# Reversing deep/dir
ac_top_build_prefix='../../'
# Concatenation of $ac_top_build_prefix and srcdir
ac_top_srcdir='../../../package'
# Concatenation of $ac_top_srcdir and deep/dir
ac_srcdir='../../../package/deep/dir'
independently of `in/in.in'.
INIT-CMDS
Shell commands output _unquoted_ near the beginning of
`config.status', and executed each time `config.status' runs
(regardless of the tag). Because they are unquoted, for example,
`$var' is output as the value of `var'. INIT-CMDS is typically
used by `configure' to give `config.status' some variables it
needs to run the COMMANDS.
You should be extremely cautious in your variable names: all the
INIT-CMDS share the same name space and may overwrite each other
in unpredictable ways. Sorry...
All these macros can be called multiple times, with different TAG
values, of course!
File: autoconf.info, Node: Configuration Files, Next: Makefile Substitutions, Prev: Configuration Actions, Up: Setup
4.7 Creating Configuration Files
================================
Be sure to read the previous section, *note Configuration Actions::.
-- Macro: AC_CONFIG_FILES (FILE..., [CMDS], [INIT-CMDS])
Make `AC_OUTPUT' create each `FILE' by copying an input file (by
default `FILE.in'), substituting the output variable values. This
macro is one of the instantiating macros; see *note Configuration
Actions::. *Note Makefile Substitutions::, for more information
on using output variables. *Note Setting Output Variables::, for
more information on creating them. This macro creates the
directory that the file is in if it doesn't exist. Usually,
makefiles are created this way, but other files, such as
`.gdbinit', can be specified as well.
Typical calls to `AC_CONFIG_FILES' look like this:
AC_CONFIG_FILES([Makefile src/Makefile man/Makefile X/Imakefile])
AC_CONFIG_FILES([autoconf], [chmod +x autoconf])
You can override an input file name by appending to FILE a
colon-separated list of input files. Examples:
AC_CONFIG_FILES([Makefile:boiler/top.mk:boiler/bot.mk]
[lib/Makefile:boiler/lib.mk])
Doing this allows you to keep your file names acceptable to DOS
variants, or to prepend and/or append boilerplate to the file.
File: autoconf.info, Node: Makefile Substitutions, Next: Configuration Headers, Prev: Configuration Files, Up: Setup
4.8 Substitutions in Makefiles
==============================
Each subdirectory in a distribution that contains something to be
compiled or installed should come with a file `Makefile.in', from which
`configure' creates a file `Makefile' in that directory. To create
`Makefile', `configure' performs a simple variable substitution,
replacing occurrences of `@VARIABLE@' in `Makefile.in' with the value
that `configure' has determined for that variable. Variables that are
substituted into output files in this way are called "output
variables". They are ordinary shell variables that are set in
`configure'. To make `configure' substitute a particular variable into
the output files, the macro `AC_SUBST' must be called with that
variable name as an argument. Any occurrences of `@VARIABLE@' for
other variables are left unchanged. *Note Setting Output Variables::,
for more information on creating output variables with `AC_SUBST'.
A software package that uses a `configure' script should be
distributed with a file `Makefile.in', but no makefile; that way, the
user has to properly configure the package for the local system before
compiling it.
*Note Makefile Conventions: (standards)Makefile Conventions, for
more information on what to put in makefiles.
* Menu:
* Preset Output Variables:: Output variables that are always set
* Installation Directory Variables:: Other preset output variables
* Changed Directory Variables:: Warnings about `datarootdir'
* Build Directories:: Supporting multiple concurrent compiles
* Automatic Remaking:: Makefile rules for configuring
File: autoconf.info, Node: Preset Output Variables, Next: Installation Directory Variables, Up: Makefile Substitutions
4.8.1 Preset Output Variables
-----------------------------
Some output variables are preset by the Autoconf macros. Some of the
Autoconf macros set additional output variables, which are mentioned in
the descriptions for those macros. *Note Output Variable Index::, for a
complete list of output variables. *Note Installation Directory
Variables::, for the list of the preset ones related to installation
directories. Below are listed the other preset ones, many of which are
precious variables (*note Setting Output Variables::, `AC_ARG_VAR').
The preset variables which are available during `config.status'
(*note Configuration Actions::) may also be used during `configure'
tests. For example, it is permissible to reference `$srcdir' when
constructing a list of directories to pass via option `-I' during a
compiler feature check. When used in this manner, coupled with the
fact that `configure' is always run from the top build directory, it is
sufficient to use just `$srcdir' instead of `$top_srcdir'.
-- Variable: CFLAGS
Debugging and optimization options for the C compiler. If it is
not set in the environment when `configure' runs, the default
value is set when you call `AC_PROG_CC' (or empty if you don't).
`configure' uses this variable when compiling or linking programs
to test for C features.
If a compiler option affects only the behavior of the preprocessor
(e.g., `-D NAME'), it should be put into `CPPFLAGS' instead. If
it affects only the linker (e.g., `-L DIRECTORY'), it should be
put into `LDFLAGS' instead. If it affects only the compiler
proper, `CFLAGS' is the natural home for it. If an option affects
multiple phases of the compiler, though, matters get tricky. One
approach to put such options directly into `CC', e.g., `CC='gcc
-m64''. Another is to put them into both `CPPFLAGS' and
`LDFLAGS', but not into `CFLAGS'.
However, remember that some `Makefile' variables are reserved by
the GNU Coding Standards for the use of the "user"--the person
building the package. For instance, `CFLAGS' is one such variable.
Sometimes package developers are tempted to set user variables
such as `CFLAGS' because it appears to make their job easier.
However, the package itself should never set a user variable,
particularly not to include switches that are required for proper
compilation of the package. Since these variables are documented
as being for the package builder, that person rightfully expects
to be able to override any of these variables at build time. If
the package developer needs to add switches without interfering
with the user, the proper way to do that is to introduce an
additional variable. Automake makes this easy by introducing
`AM_CFLAGS' (*note Flag Variables Ordering: (automake)Flag
Variables Ordering.), but the concept is the same even if Automake
is not used.
-- Variable: configure_input
A comment saying that the file was generated automatically by
`configure' and giving the name of the input file. `AC_OUTPUT'
adds a comment line containing this variable to the top of every
makefile it creates. For other files, you should reference this
variable in a comment at the top of each input file. For example,
an input shell script should begin like this:
#!/bin/sh
# @configure_input@
The presence of that line also reminds people editing the file
that it needs to be processed by `configure' in order to be used.
-- Variable: CPPFLAGS
Preprocessor options for the C, C++, and Objective C preprocessors
and compilers. If it is not set in the environment when
`configure' runs, the default value is empty. `configure' uses
this variable when preprocessing or compiling programs to test for
C, C++, and Objective C features.
This variable's contents should contain options like `-I', `-D',
and `-U' that affect only the behavior of the preprocessor.
Please see the explanation of `CFLAGS' for what you can do if an
option affects other phases of the compiler as well.
Currently, `configure' always links as part of a single invocation
of the compiler that also preprocesses and compiles, so it uses
this variable also when linking programs. However, it is unwise to
depend on this behavior because the GNU Coding Standards do not
require it and many packages do not use `CPPFLAGS' when linking
programs.
*Note Special Chars in Variables::, for limitations that `CPPFLAGS'
might run into.
-- Variable: CXXFLAGS
Debugging and optimization options for the C++ compiler. It acts
like `CFLAGS', but for C++ instead of C.
-- Variable: DEFS
`-D' options to pass to the C compiler. If `AC_CONFIG_HEADERS' is
called, `configure' replaces `@DEFS@' with `-DHAVE_CONFIG_H'
instead (*note Configuration Headers::). This variable is not
defined while `configure' is performing its tests, only when
creating the output files. *Note Setting Output Variables::, for
how to check the results of previous tests.
-- Variable: ECHO_C
-- Variable: ECHO_N
-- Variable: ECHO_T
How does one suppress the trailing newline from `echo' for
question-answer message pairs? These variables provide a way:
echo $ECHO_N "And the winner is... $ECHO_C"
sleep 100000000000
echo "${ECHO_T}dead."
Some old and uncommon `echo' implementations offer no means to
achieve this, in which case `ECHO_T' is set to tab. You might not
want to use it.
-- Variable: ERLCFLAGS
Debugging and optimization options for the Erlang compiler. If it
is not set in the environment when `configure' runs, the default
value is empty. `configure' uses this variable when compiling
programs to test for Erlang features.
-- Variable: FCFLAGS
Debugging and optimization options for the Fortran compiler. If it
is not set in the environment when `configure' runs, the default
value is set when you call `AC_PROG_FC' (or empty if you don't).
`configure' uses this variable when compiling or linking programs
to test for Fortran features.
-- Variable: FFLAGS
Debugging and optimization options for the Fortran 77 compiler.
If it is not set in the environment when `configure' runs, the
default value is set when you call `AC_PROG_F77' (or empty if you
don't). `configure' uses this variable when compiling or linking
programs to test for Fortran 77 features.
-- Variable: LDFLAGS
Options for the linker. If it is not set in the environment when
`configure' runs, the default value is empty. `configure' uses
this variable when linking programs to test for C, C++, Objective
C, and Fortran features.
This variable's contents should contain options like `-s' and `-L'
that affect only the behavior of the linker. Please see the
explanation of `CFLAGS' for what you can do if an option also
affects other phases of the compiler.
Don't use this variable to pass library names (`-l') to the
linker; use `LIBS' instead.
-- Variable: LIBS
`-l' options to pass to the linker. The default value is empty,
but some Autoconf macros may prepend extra libraries to this
variable if those libraries are found and provide necessary
functions, see *note Libraries::. `configure' uses this variable
when linking programs to test for C, C++, and Fortran features.
-- Variable: OBJCFLAGS
Debugging and optimization options for the Objective C compiler.
It acts like `CFLAGS', but for Objective C instead of C.
-- Variable: builddir
Rigorously equal to `.'. Added for symmetry only.
-- Variable: abs_builddir
Absolute name of `builddir'.
-- Variable: top_builddir
The relative name of the top level of the current build tree. In
the top-level directory, this is the same as `builddir'.
-- Variable: top_build_prefix
The relative name of the top level of the current build tree with
final slash if nonemtpy. This is the same as `top_builddir',
except that it contains zero or more runs of `../', so it should
not be appended with a slash for concatenation. This helps for
`make' implementations that otherwise do not treat `./file' and
`file' as equal in the toplevel build directory.
-- Variable: abs_top_builddir
Absolute name of `top_builddir'.
-- Variable: srcdir
The name of the directory that contains the source code for that
makefile.
-- Variable: abs_srcdir
Absolute name of `srcdir'.
-- Variable: top_srcdir
The name of the top-level source code directory for the package.
In the top-level directory, this is the same as `srcdir'.
-- Variable: abs_top_srcdir
Absolute name of `top_srcdir'.
File: autoconf.info, Node: Installation Directory Variables, Next: Changed Directory Variables, Prev: Preset Output Variables, Up: Makefile Substitutions
4.8.2 Installation Directory Variables
--------------------------------------
The following variables specify the directories for package
installation, see *note Variables for Installation Directories:
(standards)Directory Variables, for more information. Each variable
corresponds to an argument of `configure'; trailing slashes are
stripped so that expressions such as `${prefix}/lib' expand with only
one slash between directory names. See the end of this section for
details on when and how to use these variables.
-- Variable: bindir
The directory for installing executables that users run.
-- Variable: datadir
The directory for installing idiosyncratic read-only
architecture-independent data.
-- Variable: datarootdir
The root of the directory tree for read-only
architecture-independent data files.
-- Variable: docdir
The directory for installing documentation files (other than Info
and man).
-- Variable: dvidir
The directory for installing documentation files in DVI format.
-- Variable: exec_prefix
The installation prefix for architecture-dependent files. By
default it's the same as PREFIX. You should avoid installing
anything directly to EXEC_PREFIX. However, the default value for
directories containing architecture-dependent files should be
relative to EXEC_PREFIX.
-- Variable: htmldir
The directory for installing HTML documentation.
-- Variable: includedir
The directory for installing C header files.
-- Variable: infodir
The directory for installing documentation in Info format.
-- Variable: libdir
The directory for installing object code libraries.
-- Variable: libexecdir
The directory for installing executables that other programs run.
-- Variable: localedir
The directory for installing locale-dependent but
architecture-independent data, such as message catalogs. This
directory usually has a subdirectory per locale.
-- Variable: localstatedir
The directory for installing modifiable single-machine data.
-- Variable: mandir
The top-level directory for installing documentation in man format.
-- Variable: oldincludedir
The directory for installing C header files for non-GCC compilers.
-- Variable: pdfdir
The directory for installing PDF documentation.
-- Variable: prefix
The common installation prefix for all files. If EXEC_PREFIX is
defined to a different value, PREFIX is used only for
architecture-independent files.
-- Variable: psdir
The directory for installing PostScript documentation.
-- Variable: sbindir
The directory for installing executables that system
administrators run.
-- Variable: sharedstatedir
The directory for installing modifiable architecture-independent
data.
-- Variable: sysconfdir
The directory for installing read-only single-machine data.
Most of these variables have values that rely on `prefix' or
`exec_prefix'. It is deliberate that the directory output variables
keep them unexpanded: typically `@datarootdir@' is replaced by
`${prefix}/share', not `/usr/local/share', and `@datadir@' is replaced
by `${datarootdir}'.
This behavior is mandated by the GNU Coding Standards, so that when
the user runs:
`make'
she can still specify a different prefix from the one specified to
`configure', in which case, if needed, the package should hard
code dependencies corresponding to the make-specified prefix.
`make install'
she can specify a different installation location, in which case
the package _must_ still depend on the location which was compiled
in (i.e., never recompile when `make install' is run). This is an
extremely important feature, as many people may decide to install
all the files of a package grouped together, and then install
links from the final locations to there.
In order to support these features, it is essential that
`datarootdir' remains defined as `${prefix}/share', so that its value
can be expanded based on the current value of `prefix'.
A corollary is that you should not use these variables except in
makefiles. For instance, instead of trying to evaluate `datadir' in
`configure' and hard-coding it in makefiles using e.g.,
`AC_DEFINE_UNQUOTED([DATADIR], ["$datadir"], [Data directory.])', you
should add `-DDATADIR='$(datadir)'' to your makefile's definition of
`CPPFLAGS' (`AM_CPPFLAGS' if you are also using Automake).
Similarly, you should not rely on `AC_CONFIG_FILES' to replace
`bindir' and friends in your shell scripts and other files; instead,
let `make' manage their replacement. For instance Autoconf ships
templates of its shell scripts ending with `.in', and uses a makefile
snippet similar to the following to build scripts like `autoheader' and
`autom4te':
edit = sed \
-e 's|@bindir[@]|$(bindir)|g' \
-e 's|@pkgdatadir[@]|$(pkgdatadir)|g' \
-e 's|@prefix[@]|$(prefix)|g'
autoheader autom4te: Makefile
rm -f $@ $@.tmp
srcdir=''; \
test -f ./$@.in || srcdir=$(srcdir)/; \
$(edit) $${srcdir}$@.in >$@.tmp
chmod +x $@.tmp
chmod a-w $@.tmp
mv $@.tmp $@
autoheader: $(srcdir)/autoheader.in
autom4te: $(srcdir)/autom4te.in
Some details are noteworthy:
`@bindir[@]'
The brackets prevent `configure' from replacing `@bindir@' in the
Sed expression itself. Brackets are preferable to a backslash
here, since Posix says `\@' is not portable.
`$(bindir)'
Don't use `@bindir@'! Use the matching makefile variable instead.
`$(pkgdatadir)'
The example takes advantage of the variable `$(pkgdatadir)'
provided by Automake; it is equivalent to `$(datadir)/$(PACKAGE)'.
`/'
Don't use `/' in the Sed expressions that replace file names since
most likely the variables you use, such as `$(bindir)', contain
`/'. Use a shell metacharacter instead, such as `|'.
special characters
File names, file name components, and the value of `VPATH' should
not contain shell metacharacters or white space. *Note Special
Chars in Variables::.
dependency on `Makefile'
Since `edit' uses values that depend on the configuration specific
values (`prefix', etc.) and not only on `VERSION' and so forth,
the output depends on `Makefile', not `configure.ac'.
`$@'
The main rule is generic, and uses `$@' extensively to avoid the
need for multiple copies of the rule.
Separated dependencies and single suffix rules
You can't use them! The above snippet cannot be (portably)
rewritten as:
autoconf autoheader: Makefile
.in:
rm -f $@ $@.tmp
$(edit) $< >$@.tmp
chmod +x $@.tmp
mv $@.tmp $@
*Note Single Suffix Rules::, for details.
`$(srcdir)'
Be sure to specify the name of the source directory, otherwise the
package won't support separated builds.
For the more specific installation of Erlang libraries, the
following variables are defined:
-- Variable: ERLANG_INSTALL_LIB_DIR
The common parent directory of Erlang library installation
directories. This variable is set by calling the
`AC_ERLANG_SUBST_INSTALL_LIB_DIR' macro in `configure.ac'.
-- Variable: ERLANG_INSTALL_LIB_DIR_LIBRARY
The installation directory for Erlang library LIBRARY. This
variable is set by using the `AC_ERLANG_SUBST_INSTALL_LIB_SUBDIR'
macro in `configure.ac'.
*Note Erlang Libraries::, for details.
File: autoconf.info, Node: Changed Directory Variables, Next: Build Directories, Prev: Installation Directory Variables, Up: Makefile Substitutions
4.8.3 Changed Directory Variables
---------------------------------
In Autoconf 2.60, the set of directory variables has changed, and the
defaults of some variables have been adjusted (*note Installation
Directory Variables::) to changes in the GNU Coding Standards.
Notably, `datadir', `infodir', and `mandir' are now expressed in terms
of `datarootdir'. If you are upgrading from an earlier Autoconf
version, you may need to adjust your files to ensure that the directory
variables are substituted correctly (*note Defining Directories::), and
that a definition of `datarootdir' is in place. For example, in a
`Makefile.in', adding
datarootdir = @datarootdir@
is usually sufficient. If you use Automake to create `Makefile.in', it
will add this for you.
To help with the transition, Autoconf warns about files that seem to
use `datarootdir' without defining it. In some cases, it then expands
the value of `$datarootdir' in substitutions of the directory
variables. The following example shows such a warning:
$ cat configure.ac
AC_INIT
AC_CONFIG_FILES([Makefile])
AC_OUTPUT
$ cat Makefile.in
prefix = @prefix@
datadir = @datadir@
$ autoconf
$ configure
configure: creating ./config.status
config.status: creating Makefile
config.status: WARNING:
Makefile.in seems to ignore the --datarootdir setting
$ cat Makefile
prefix = /usr/local
datadir = ${prefix}/share
Usually one can easily change the file to accommodate both older and
newer Autoconf releases:
$ cat Makefile.in
prefix = @prefix@
datarootdir = @datarootdir@
datadir = @datadir@
$ configure
configure: creating ./config.status
config.status: creating Makefile
$ cat Makefile
prefix = /usr/local
datarootdir = ${prefix}/share
datadir = ${datarootdir}
In some cases, however, the checks may not be able to detect that a
suitable initialization of `datarootdir' is in place, or they may fail
to detect that such an initialization is necessary in the output file.
If, after auditing your package, there are still spurious `configure'
warnings about `datarootdir', you may add the line
AC_DEFUN([AC_DATAROOTDIR_CHECKED])
to your `configure.ac' to disable the warnings. This is an exception
to the usual rule that you should not define a macro whose name begins
with `AC_' (*note Macro Names::).
File: autoconf.info, Node: Build Directories, Next: Automatic Remaking, Prev: Changed Directory Variables, Up: Makefile Substitutions
4.8.4 Build Directories
-----------------------
You can support compiling a software package for several architectures
simultaneously from the same copy of the source code. The object files
for each architecture are kept in their own directory.
To support doing this, `make' uses the `VPATH' variable to find the
files that are in the source directory. GNU Make can do this. Most
other recent `make' programs can do this as well, though they may have
difficulties and it is often simpler to recommend GNU `make' (*note
VPATH and Make::). Older `make' programs do not support `VPATH'; when
using them, the source code must be in the same directory as the object
files.
If you are using GNU Automake, the remaining details in this section
are already covered for you, based on the contents of your
`Makefile.am'. But if you are using Autoconf in isolation, then
supporting `VPATH' requires the following in your `Makefile.in':
srcdir = @srcdir@
VPATH = @srcdir@
Do not set `VPATH' to the value of another variable (*note Variables
listed in VPATH::.
`configure' substitutes the correct value for `srcdir' when it
produces `Makefile'.
Do not use the `make' variable `$<', which expands to the file name
of the file in the source directory (found with `VPATH'), except in
implicit rules. (An implicit rule is one such as `.c.o', which tells
how to create a `.o' file from a `.c' file.) Some versions of `make'
do not set `$<' in explicit rules; they expand it to an empty value.
Instead, Make command lines should always refer to source files by
prefixing them with `$(srcdir)/'. For example:
time.info: time.texinfo
$(MAKEINFO) '$(srcdir)/time.texinfo'
File: autoconf.info, Node: Automatic Remaking, Prev: Build Directories, Up: Makefile Substitutions
4.8.5 Automatic Remaking
------------------------
You can put rules like the following in the top-level `Makefile.in' for
a package to automatically update the configuration information when
you change the configuration files. This example includes all of the
optional files, such as `aclocal.m4' and those related to configuration
header files. Omit from the `Makefile.in' rules for any of these files
that your package does not use.
The `$(srcdir)/' prefix is included because of limitations in the
`VPATH' mechanism.
The `stamp-' files are necessary because the timestamps of
`config.h.in' and `config.h' are not changed if remaking them does not
change their contents. This feature avoids unnecessary recompilation.
You should include the file `stamp-h.in' in your package's
distribution, so that `make' considers `config.h.in' up to date. Don't
use `touch' (*note Limitations of Usual Tools: touch.); instead, use
`echo' (using `date' would cause needless differences, hence CVS
conflicts, etc.).
$(srcdir)/configure: configure.ac aclocal.m4
cd '$(srcdir)' && autoconf
# autoheader might not change config.h.in, so touch a stamp file.
$(srcdir)/config.h.in: stamp-h.in
$(srcdir)/stamp-h.in: configure.ac aclocal.m4
cd '$(srcdir)' && autoheader
echo timestamp > '$(srcdir)/stamp-h.in'
config.h: stamp-h
stamp-h: config.h.in config.status
./config.status
Makefile: Makefile.in config.status
./config.status
config.status: configure
./config.status --recheck
(Be careful if you copy these lines directly into your makefile, as you
need to convert the indented lines to start with the tab character.)
In addition, you should use
AC_CONFIG_FILES([stamp-h], [echo timestamp > stamp-h])
so `config.status' ensures that `config.h' is considered up to date.
*Note Output::, for more information about `AC_OUTPUT'.
*Note config.status Invocation::, for more examples of handling
configuration-related dependencies.
File: autoconf.info, Node: Configuration Headers, Next: Configuration Commands, Prev: Makefile Substitutions, Up: Setup
4.9 Configuration Header Files
==============================
When a package contains more than a few tests that define C preprocessor
symbols, the command lines to pass `-D' options to the compiler can get
quite long. This causes two problems. One is that the `make' output
is hard to visually scan for errors. More seriously, the command lines
can exceed the length limits of some operating systems. As an
alternative to passing `-D' options to the compiler, `configure'
scripts can create a C header file containing `#define' directives.
The `AC_CONFIG_HEADERS' macro selects this kind of output. Though it
can be called anywhere between `AC_INIT' and `AC_OUTPUT', it is
customary to call it right after `AC_INIT'.
The package should `#include' the configuration header file before
any other header files, to prevent inconsistencies in declarations (for
example, if it redefines `const').
To provide for VPATH builds, remember to pass the C compiler a `-I.'
option (or `-I..'; whichever directory contains `config.h'). Even if
you use `#include "config.h"', the preprocessor searches only the
directory of the currently read file, i.e., the source directory, not
the build directory.
With the appropriate `-I' option, you can use `#include '.
Actually, it's a good habit to use it, because in the rare case when
the source directory contains another `config.h', the build directory
should be searched first.
-- Macro: AC_CONFIG_HEADERS (HEADER ..., [CMDS], [INIT-CMDS])
This macro is one of the instantiating macros; see *note
Configuration Actions::. Make `AC_OUTPUT' create the file(s) in
the blank-or-newline-separated list HEADER containing C
preprocessor `#define' statements, and replace `@DEFS@' in
generated files with `-DHAVE_CONFIG_H' instead of the value of
`DEFS'. The usual name for HEADER is `config.h'.
If HEADER already exists and its contents are identical to what
`AC_OUTPUT' would put in it, it is left alone. Doing this allows
making some changes in the configuration without needlessly causing
object files that depend on the header file to be recompiled.
Usually the input file is named `HEADER.in'; however, you can
override the input file name by appending to HEADER a
colon-separated list of input files. For example, you might need
to make the input file name acceptable to DOS variants:
AC_CONFIG_HEADERS([config.h:config.hin])
-- Macro: AH_HEADER
This macro is defined as the name of the first declared config
header and undefined if no config headers have been declared up to
this point. A third-party macro may, for example, require use of
a config header without invoking AC_CONFIG_HEADERS twice, like
this:
AC_CONFIG_COMMANDS_PRE(
[m4_ifndef([AH_HEADER], [AC_CONFIG_HEADERS([config.h])])])
*Note Configuration Actions::, for more details on HEADER.
* Menu:
* Header Templates:: Input for the configuration headers
* autoheader Invocation:: How to create configuration templates
* Autoheader Macros:: How to specify CPP templates
File: autoconf.info, Node: Header Templates, Next: autoheader Invocation, Up: Configuration Headers
4.9.1 Configuration Header Templates
------------------------------------
Your distribution should contain a template file that looks as you want
the final header file to look, including comments, with `#undef'
statements which are used as hooks. For example, suppose your
`configure.ac' makes these calls:
AC_CONFIG_HEADERS([conf.h])
AC_CHECK_HEADERS([unistd.h])
Then you could have code like the following in `conf.h.in'. The
`conf.h' created by `configure' defines `HAVE_UNISTD_H' to 1, if and
only if the system has `unistd.h'.
/* Define as 1 if you have unistd.h. */
#undef HAVE_UNISTD_H
The format of the template file is stricter than what the C
preprocessor is required to accept. A directive line should contain
only whitespace, `#undef', and `HAVE_UNISTD_H'. The use of `#define'
instead of `#undef', or of comments on the same line as `#undef', is
strongly discouraged. Each hook should only be listed once. Other
preprocessor lines, such as `#ifdef' or `#include', are copied verbatim
from the template into the generated header.
Since it is a tedious task to keep a template header up to date, you
may use `autoheader' to generate it, see *note autoheader Invocation::.
During the instantiation of the header, each `#undef' line in the
template file for each symbol defined by `AC_DEFINE' is changed to an
appropriate `#define'. If the corresponding `AC_DEFINE' has not been
executed during the `configure' run, the `#undef' line is commented
out. (This is important, e.g., for `_POSIX_SOURCE': on many systems,
it can be implicitly defined by the compiler, and undefining it in the
header would then break compilation of subsequent headers.)
Currently, _all_ remaining `#undef' lines in the header template are
commented out, whether or not there was a corresponding `AC_DEFINE' for
the macro name; but this behavior is not guaranteed for future releases
of Autoconf.
Generally speaking, since you should not use `#define', and you
cannot guarantee whether a `#undef' directive in the header template
will be converted to a `#define' or commented out in the generated
header file, the template file cannot be used for conditional
definition effects. Consequently, if you need to use the construct
#ifdef THIS
# define THAT
#endif
you must place it outside of the template. If you absolutely need to
hook it to the config header itself, please put the directives to a
separate file, and `#include' that file from the config header
template. If you are using `autoheader', you would probably use
`AH_BOTTOM' to append the `#include' directive.
File: autoconf.info, Node: autoheader Invocation, Next: Autoheader Macros, Prev: Header Templates, Up: Configuration Headers
4.9.2 Using `autoheader' to Create `config.h.in'
------------------------------------------------
The `autoheader' program can create a template file of C `#define'
statements for `configure' to use. It searches for the first
invocation of `AC_CONFIG_HEADERS' in `configure' sources to determine
the name of the template. (If the first call of `AC_CONFIG_HEADERS'
specifies more than one input file name, `autoheader' uses the first
one.)
It is recommended that only one input file is used. If you want to
append a boilerplate code, it is preferable to use `AH_BOTTOM([#include
])'. File `conf_post.h' is not processed during the
configuration then, which make things clearer. Analogically, `AH_TOP'
can be used to prepend a boilerplate code.
In order to do its job, `autoheader' needs you to document all of
the symbols that you might use. Typically this is done via an
`AC_DEFINE' or `AC_DEFINE_UNQUOTED' call whose first argument is a
literal symbol and whose third argument describes the symbol (*note
Defining Symbols::). Alternatively, you can use `AH_TEMPLATE' (*note
Autoheader Macros::), or you can supply a suitable input file for a
subsequent configuration header file. Symbols defined by Autoconf's
builtin tests are already documented properly; you need to document
only those that you define yourself.
You might wonder why `autoheader' is needed: after all, why would
`configure' need to "patch" a `config.h.in' to produce a `config.h'
instead of just creating `config.h' from scratch? Well, when
everything rocks, the answer is just that we are wasting our time
maintaining `autoheader': generating `config.h' directly is all that is
needed. When things go wrong, however, you'll be thankful for the
existence of `autoheader'.
The fact that the symbols are documented is important in order to
_check_ that `config.h' makes sense. The fact that there is a
well-defined list of symbols that should be defined (or not) is also
important for people who are porting packages to environments where
`configure' cannot be run: they just have to _fill in the blanks_.
But let's come back to the point: the invocation of `autoheader'...
If you give `autoheader' an argument, it uses that file instead of
`configure.ac' and writes the header file to the standard output
instead of to `config.h.in'. If you give `autoheader' an argument of
`-', it reads the standard input instead of `configure.ac' and writes
the header file to the standard output.
`autoheader' accepts the following options:
`--help'
`-h'
Print a summary of the command line options and exit.
`--version'
`-V'
Print the version number of Autoconf and exit.
`--verbose'
`-v'
Report processing steps.
`--debug'
`-d'
Don't remove the temporary files.
`--force'
`-f'
Remake the template file even if newer than its input files.
`--include=DIR'
`-I DIR'
Append DIR to the include path. Multiple invocations accumulate.
`--prepend-include=DIR'
`-B DIR'
Prepend DIR to the include path. Multiple invocations accumulate.
`--warnings=CATEGORY'
`-W CATEGORY'
Report the warnings related to CATEGORY (which can actually be a
comma separated list). Current categories include:
`obsolete'
report the uses of obsolete constructs
`all'
report all the warnings
`none'
report none
`error'
treats warnings as errors
`no-CATEGORY'
disable warnings falling into CATEGORY
File: autoconf.info, Node: Autoheader Macros, Prev: autoheader Invocation, Up: Configuration Headers
4.9.3 Autoheader Macros
-----------------------
`autoheader' scans `configure.ac' and figures out which C preprocessor
symbols it might define. It knows how to generate templates for
symbols defined by `AC_CHECK_HEADERS', `AC_CHECK_FUNCS' etc., but if
you `AC_DEFINE' any additional symbol, you must define a template for
it. If there are missing templates, `autoheader' fails with an error
message.
The template for a SYMBOL is created by `autoheader' from the
DESCRIPTION argument to an `AC_DEFINE'; see *note Defining Symbols::.
For special needs, you can use the following macros.
-- Macro: AH_TEMPLATE (KEY, DESCRIPTION)
Tell `autoheader' to generate a template for KEY. This macro
generates standard templates just like `AC_DEFINE' when a
DESCRIPTION is given.
For example:
AH_TEMPLATE([CRAY_STACKSEG_END],
[Define to one of _getb67, GETB67, getb67
for Cray-2 and Cray-YMP systems. This
function is required for alloca.c support
on those systems.])
generates the following template, with the description properly
justified.
/* Define to one of _getb67, GETB67, getb67 for Cray-2 and
Cray-YMP systems. This function is required for alloca.c
support on those systems. */
#undef CRAY_STACKSEG_END
-- Macro: AH_VERBATIM (KEY, TEMPLATE)
Tell `autoheader' to include the TEMPLATE as-is in the header
template file. This TEMPLATE is associated with the KEY, which is
used to sort all the different templates and guarantee their
uniqueness. It should be a symbol that can be defined via
`AC_DEFINE'.
-- Macro: AH_TOP (TEXT)
Include TEXT at the top of the header template file.
-- Macro: AH_BOTTOM (TEXT)
Include TEXT at the bottom of the header template file.
Please note that TEXT gets included "verbatim" to the template file,
not to the resulting config header, so it can easily get mangled when
the template is processed. There is rarely a need for something other
than
AH_BOTTOM([#include ])
File: autoconf.info, Node: Configuration Commands, Next: Configuration Links, Prev: Configuration Headers, Up: Setup
4.10 Running Arbitrary Configuration Commands
=============================================
You can execute arbitrary commands before, during, and after
`config.status' is run. The three following macros accumulate the
commands to run when they are called multiple times.
`AC_CONFIG_COMMANDS' replaces the obsolete macro `AC_OUTPUT_COMMANDS';
see *note Obsolete Macros::, for details.
-- Macro: AC_CONFIG_COMMANDS (TAG..., [CMDS], [INIT-CMDS])
Specify additional shell commands to run at the end of
`config.status', and shell commands to initialize any variables
from `configure'. Associate the commands with TAG. Since
typically the CMDS create a file, TAG should naturally be the name
of that file. If needed, the directory hosting TAG is created.
This macro is one of the instantiating macros; see *note
Configuration Actions::.
Here is an unrealistic example:
fubar=42
AC_CONFIG_COMMANDS([fubar],
[echo this is extra $fubar, and so on.],
[fubar=$fubar])
Here is a better one:
AC_CONFIG_COMMANDS([timestamp], [date >timestamp])
The following two macros look similar, but in fact they are not of
the same breed: they are executed directly by `configure', so you
cannot use `config.status' to rerun them.
-- Macro: AC_CONFIG_COMMANDS_PRE (CMDS)
Execute the CMDS right before creating `config.status'.
This macro presents the last opportunity to call `AC_SUBST',
`AC_DEFINE', or `AC_CONFIG_ITEMS' macros.
-- Macro: AC_CONFIG_COMMANDS_POST (CMDS)
Execute the CMDS right after creating `config.status'.
File: autoconf.info, Node: Configuration Links, Next: Subdirectories, Prev: Configuration Commands, Up: Setup
4.11 Creating Configuration Links
=================================
You may find it convenient to create links whose destinations depend
upon results of tests. One can use `AC_CONFIG_COMMANDS' but the
creation of relative symbolic links can be delicate when the package is
built in a directory different from the source directory.
-- Macro: AC_CONFIG_LINKS (DEST:SOURCE..., [CMDS], [INIT-CMDS])
Make `AC_OUTPUT' link each of the existing files SOURCE to the
corresponding link name DEST. Makes a symbolic link if possible,
otherwise a hard link if possible, otherwise a copy. The DEST and
SOURCE names should be relative to the top level source or build
directory. This macro is one of the instantiating macros; see
*note Configuration Actions::.
For example, this call:
AC_CONFIG_LINKS([host.h:config/$machine.h
object.h:config/$obj_format.h])
creates in the current directory `host.h' as a link to
`SRCDIR/config/$machine.h', and `object.h' as a link to
`SRCDIR/config/$obj_format.h'.
The tempting value `.' for DEST is invalid: it makes it impossible
for `config.status' to guess the links to establish.
One can then run:
./config.status host.h object.h
to create the links.
File: autoconf.info, Node: Subdirectories, Next: Default Prefix, Prev: Configuration Links, Up: Setup
4.12 Configuring Other Packages in Subdirectories
=================================================
In most situations, calling `AC_OUTPUT' is sufficient to produce
makefiles in subdirectories. However, `configure' scripts that control
more than one independent package can use `AC_CONFIG_SUBDIRS' to run
`configure' scripts for other packages in subdirectories.
-- Macro: AC_CONFIG_SUBDIRS (DIR ...)
Make `AC_OUTPUT' run `configure' in each subdirectory DIR in the
given blank-or-newline-separated list. Each DIR should be a
literal, i.e., please do not use:
if test "x$package_foo_enabled" = xyes; then
$my_subdirs="$my_subdirs foo"
fi
AC_CONFIG_SUBDIRS([$my_subdirs])
because this prevents `./configure --help=recursive' from
displaying the options of the package `foo'. Instead, you should
write:
if test "x$package_foo_enabled" = xyes; then
AC_CONFIG_SUBDIRS([foo])
fi
If a given DIR is not found, an error is reported: if the
subdirectory is optional, write:
if test -d "$srcdir/foo"; then
AC_CONFIG_SUBDIRS([foo])
fi
If a given DIR contains `configure.gnu', it is run instead of
`configure'. This is for packages that might use a non-Autoconf
script `Configure', which can't be called through a wrapper
`configure' since it would be the same file on case-insensitive
file systems. Likewise, if a DIR contains `configure.in' but no
`configure', the Cygnus `configure' script found by
`AC_CONFIG_AUX_DIR' is used.
The subdirectory `configure' scripts are given the same command
line options that were given to this `configure' script, with minor
changes if needed, which include:
- adjusting a relative name for the cache file;
- adjusting a relative name for the source directory;
- propagating the current value of `$prefix', including if it
was defaulted, and if the default values of the top level and
of the subdirectory `configure' differ.
This macro also sets the output variable `subdirs' to the list of
directories `DIR ...'. Make rules can use this variable to
determine which subdirectories to recurse into.
This macro may be called multiple times.
File: autoconf.info, Node: Default Prefix, Prev: Subdirectories, Up: Setup
4.13 Default Prefix
===================
By default, `configure' sets the prefix for files it installs to
`/usr/local'. The user of `configure' can select a different prefix
using the `--prefix' and `--exec-prefix' options. There are two ways
to change the default: when creating `configure', and when running it.
Some software packages might want to install in a directory other
than `/usr/local' by default. To accomplish that, use the
`AC_PREFIX_DEFAULT' macro.
-- Macro: AC_PREFIX_DEFAULT (PREFIX)
Set the default installation prefix to PREFIX instead of
`/usr/local'.
It may be convenient for users to have `configure' guess the
installation prefix from the location of a related program that they
have already installed. If you wish to do that, you can call
`AC_PREFIX_PROGRAM'.
-- Macro: AC_PREFIX_PROGRAM (PROGRAM)
If the user did not specify an installation prefix (using the
`--prefix' option), guess a value for it by looking for PROGRAM in
`PATH', the way the shell does. If PROGRAM is found, set the
prefix to the parent of the directory containing PROGRAM, else
default the prefix as described above (`/usr/local' or
`AC_PREFIX_DEFAULT'). For example, if PROGRAM is `gcc' and the
`PATH' contains `/usr/local/gnu/bin/gcc', set the prefix to
`/usr/local/gnu'.
File: autoconf.info, Node: Existing Tests, Next: Writing Tests, Prev: Setup, Up: Top
5 Existing Tests
****************
These macros test for particular system features that packages might
need or want to use. If you need to test for a kind of feature that
none of these macros check for, you can probably do it by calling
primitive test macros with appropriate arguments (*note Writing
Tests::).
These tests print messages telling the user which feature they're
checking for, and what they find. They cache their results for future
`configure' runs (*note Caching Results::).
Some of these macros set output variables. *Note Makefile
Substitutions::, for how to get their values. The phrase "define NAME"
is used below as a shorthand to mean "define the C preprocessor symbol
NAME to the value 1". *Note Defining Symbols::, for how to get those
symbol definitions into your program.
* Menu:
* Common Behavior:: Macros' standard schemes
* Alternative Programs:: Selecting between alternative programs
* Files:: Checking for the existence of files
* Libraries:: Library archives that might be missing
* Library Functions:: C library functions that might be missing
* Header Files:: Header files that might be missing
* Declarations:: Declarations that may be missing
* Structures:: Structures or members that might be missing
* Types:: Types that might be missing
* Compilers and Preprocessors:: Checking for compiling programs
* System Services:: Operating system services
* Posix Variants:: Special kludges for specific Posix variants
* Erlang Libraries:: Checking for the existence of Erlang libraries
File: autoconf.info, Node: Common Behavior, Next: Alternative Programs, Up: Existing Tests
5.1 Common Behavior
===================
Much effort has been expended to make Autoconf easy to learn. The most
obvious way to reach this goal is simply to enforce standard interfaces
and behaviors, avoiding exceptions as much as possible. Because of
history and inertia, unfortunately, there are still too many exceptions
in Autoconf; nevertheless, this section describes some of the common
rules.
* Menu:
* Standard Symbols:: Symbols defined by the macros
* Default Includes:: Includes used by the generic macros
File: autoconf.info, Node: Standard Symbols, Next: Default Includes, Up: Common Behavior
5.1.1 Standard Symbols
----------------------
All the generic macros that `AC_DEFINE' a symbol as a result of their
test transform their ARGUMENT values to a standard alphabet. First,
ARGUMENT is converted to upper case and any asterisks (`*') are each
converted to `P'. Any remaining characters that are not alphanumeric
are converted to underscores.
For instance,
AC_CHECK_TYPES([struct $Expensive*])
defines the symbol `HAVE_STRUCT__EXPENSIVEP' if the check succeeds.
File: autoconf.info, Node: Default Includes, Prev: Standard Symbols, Up: Common Behavior
5.1.2 Default Includes
----------------------
Several tests depend upon a set of header files. Since these headers
are not universally available, tests actually have to provide a set of
protected includes, such as:
#ifdef TIME_WITH_SYS_TIME
# include
# include
#else
# ifdef HAVE_SYS_TIME_H
# include
# else
# include
# endif
#endif
Unless you know exactly what you are doing, you should avoid using
unconditional includes, and check the existence of the headers you
include beforehand (*note Header Files::).
Most generic macros use the following macro to provide the default
set of includes:
-- Macro: AC_INCLUDES_DEFAULT ([INCLUDE-DIRECTIVES])
Expand to INCLUDE-DIRECTIVES if defined, otherwise to:
#include
#ifdef HAVE_SYS_TYPES_H
# include
#endif
#ifdef HAVE_SYS_STAT_H
# include
#endif
#ifdef STDC_HEADERS
# include
# include
#else
# ifdef HAVE_STDLIB_H
# include
# endif
#endif
#ifdef HAVE_STRING_H
# if !defined STDC_HEADERS && defined HAVE_MEMORY_H
# include
# endif
# include
#endif
#ifdef HAVE_STRINGS_H
# include
#endif
#ifdef HAVE_INTTYPES_H
# include
#endif
#ifdef HAVE_STDINT_H
# include
#endif
#ifdef HAVE_UNISTD_H
# include
#endif
If the default includes are used, then check for the presence of
these headers and their compatibility, i.e., you don't need to run
`AC_HEADER_STDC', nor check for `stdlib.h' etc.
These headers are checked for in the same order as they are
included. For instance, on some systems `string.h' and
`strings.h' both exist, but conflict. Then `HAVE_STRING_H' is
defined, not `HAVE_STRINGS_H'.
File: autoconf.info, Node: Alternative Programs, Next: Files, Prev: Common Behavior, Up: Existing Tests
5.2 Alternative Programs
========================
These macros check for the presence or behavior of particular programs.
They are used to choose between several alternative programs and to
decide what to do once one has been chosen. If there is no macro
specifically defined to check for a program you need, and you don't need
to check for any special properties of it, then you can use one of the
general program-check macros.
* Menu:
* Particular Programs:: Special handling to find certain programs
* Generic Programs:: How to find other programs
File: autoconf.info, Node: Particular Programs, Next: Generic Programs, Up: Alternative Programs
5.2.1 Particular Program Checks
-------------------------------
These macros check for particular programs--whether they exist, and in
some cases whether they support certain features.
-- Macro: AC_PROG_AWK
Check for `gawk', `mawk', `nawk', and `awk', in that order, and
set output variable `AWK' to the first one that is found. It
tries `gawk' first because that is reported to be the best
implementation.
-- Macro: AC_PROG_GREP
Look for the best available `grep' or `ggrep' that accepts the
longest input lines possible, and that supports multiple `-e'
options. Set the output variable `GREP' to whatever is chosen.
*Note Limitations of Usual Tools: grep, for more information about
portability problems with the `grep' command family.
-- Macro: AC_PROG_EGREP
Check whether `$GREP -E' works, or else look for the best available
`egrep' or `gegrep' that accepts the longest input lines possible.
Set the output variable `EGREP' to whatever is chosen.
-- Macro: AC_PROG_FGREP
Check whether `$GREP -F' works, or else look for the best available
`fgrep' or `gfgrep' that accepts the longest input lines possible.
Set the output variable `FGREP' to whatever is chosen.
-- Macro: AC_PROG_INSTALL
Set output variable `INSTALL' to the name of a BSD-compatible
`install' program, if one is found in the current `PATH'.
Otherwise, set `INSTALL' to `DIR/install-sh -c', checking the
directories specified to `AC_CONFIG_AUX_DIR' (or its default
directories) to determine DIR (*note Output::). Also set the
variables `INSTALL_PROGRAM' and `INSTALL_SCRIPT' to `${INSTALL}'
and `INSTALL_DATA' to `${INSTALL} -m 644'.
`@INSTALL@' is special, as its value may vary for different
configuration files.
This macro screens out various instances of `install' known not to
work. It prefers to find a C program rather than a shell script,
for speed. Instead of `install-sh', it can also use `install.sh',
but that name is obsolete because some `make' programs have a rule
that creates `install' from it if there is no makefile. Further,
this macro requires `install' to be able to install multiple files
into a target directory in a single invocation.
Autoconf comes with a copy of `install-sh' that you can use. If
you use `AC_PROG_INSTALL', you must include either `install-sh' or
`install.sh' in your distribution; otherwise `configure' produces
an error message saying it can't find them--even if the system
you're on has a good `install' program. This check is a safety
measure to prevent you from accidentally leaving that file out,
which would prevent your package from installing on systems that
don't have a BSD-compatible `install' program.
If you need to use your own installation program because it has
features not found in standard `install' programs, there is no
reason to use `AC_PROG_INSTALL'; just put the file name of your
program into your `Makefile.in' files.
-- Macro: AC_PROG_MKDIR_P
Set output variable `MKDIR_P' to a program that ensures that for
each argument, a directory named by this argument exists, creating
it and its parent directories if needed, and without race
conditions when two instances of the program attempt to make the
same directory at nearly the same time.
This macro uses the `mkdir -p' command if possible. Otherwise, it
falls back on invoking `install-sh' with the `-d' option, so your
package should contain `install-sh' as described under
`AC_PROG_INSTALL'. An `install-sh' file that predates Autoconf
2.60 or Automake 1.10 is vulnerable to race conditions, so if you
want to support parallel installs from different packages into the
same directory you need to make sure you have an up-to-date
`install-sh'. In particular, be careful about using `autoreconf
-if' if your Automake predates Automake 1.10.
This macro is related to the `AS_MKDIR_P' macro (*note Programming
in M4sh::), but it sets an output variable intended for use in
other files, whereas `AS_MKDIR_P' is intended for use in scripts
like `configure'. Also, `AS_MKDIR_P' does not accept options, but
`MKDIR_P' supports the `-m' option, e.g., a makefile might invoke
`$(MKDIR_P) -m 0 dir' to create an inaccessible directory, and
conversely a makefile should use `$(MKDIR_P) -- $(FOO)' if FOO
might yield a value that begins with `-'. Finally, `AS_MKDIR_P'
does not check for race condition vulnerability, whereas
`AC_PROG_MKDIR_P' does.
`@MKDIR_P@' is special, as its value may vary for different
configuration files.
-- Macro: AC_PROG_LEX
If `flex' is found, set output variable `LEX' to `flex' and
`LEXLIB' to `-lfl', if that library is in a standard place.
Otherwise set `LEX' to `lex' and `LEXLIB' to `-ll', if found. If
neither variant is available, set `LEX' to `:'; for packages that
ship the generated `file.yy.c' alongside the source `file.l', this
default allows users without a lexer generator to still build the
package even if the timestamp for `file.l' is inadvertantly
changed.
Define `YYTEXT_POINTER' if `yytext' defaults to `char *' instead
of to `char []'. Also set output variable `LEX_OUTPUT_ROOT' to
the base of the file name that the lexer generates; usually
`lex.yy', but sometimes something else. These results vary
according to whether `lex' or `flex' is being used.
You are encouraged to use Flex in your sources, since it is both
more pleasant to use than plain Lex and the C source it produces
is portable. In order to ensure portability, however, you must
either provide a function `yywrap' or, if you don't use it (e.g.,
your scanner has no `#include'-like feature), simply include a
`%noyywrap' statement in the scanner's source. Once this done,
the scanner is portable (unless _you_ felt free to use nonportable
constructs) and does not depend on any library. In this case, and
in this case only, it is suggested that you use this Autoconf
snippet:
AC_PROG_LEX
if test "x$LEX" != xflex; then
LEX="$SHELL $missing_dir/missing flex"
AC_SUBST([LEX_OUTPUT_ROOT], [lex.yy])
AC_SUBST([LEXLIB], [''])
fi
The shell script `missing' can be found in the Automake
distribution.
Remember that the user may have supplied an alternate location in
`LEX', so if Flex is required, it is better to check that the user
provided something sufficient by parsing the output of `$LEX
--version' than by simply relying on `test "x$LEX" = xflex'.
To ensure backward compatibility, Automake's `AM_PROG_LEX' invokes
(indirectly) this macro twice, which causes an annoying but benign
"`AC_PROG_LEX' invoked multiple times" warning. Future versions
of Automake will fix this issue; meanwhile, just ignore this
message.
As part of running the test, this macro may delete any file in the
configuration directory named `lex.yy.c' or `lexyy.c'.
-- Macro: AC_PROG_LN_S
If `ln -s' works on the current file system (the operating system
and file system support symbolic links), set the output variable
`LN_S' to `ln -s'; otherwise, if `ln' works, set `LN_S' to `ln',
and otherwise set it to `cp -p'.
If you make a link in a directory other than the current
directory, its meaning depends on whether `ln' or `ln -s' is used.
To safely create links using `$(LN_S)', either find out which form
is used and adjust the arguments, or always invoke `ln' in the
directory where the link is to be created.
In other words, it does not work to do:
$(LN_S) foo /x/bar
Instead, do:
(cd /x && $(LN_S) foo bar)
-- Macro: AC_PROG_RANLIB
Set output variable `RANLIB' to `ranlib' if `ranlib' is found, and
otherwise to `:' (do nothing).
-- Macro: AC_PROG_SED
Set output variable `SED' to a Sed implementation that conforms to
Posix and does not have arbitrary length limits. Report an error
if no acceptable Sed is found. *Note Limitations of Usual Tools:
sed, for more information about portability problems with Sed.
-- Macro: AC_PROG_YACC
If `bison' is found, set output variable `YACC' to `bison -y'.
Otherwise, if `byacc' is found, set `YACC' to `byacc'. Otherwise
set `YACC' to `yacc'.
File: autoconf.info, Node: Generic Programs, Prev: Particular Programs, Up: Alternative Programs
5.2.2 Generic Program and File Checks
-------------------------------------
These macros are used to find programs not covered by the "particular"
test macros. If you need to check the behavior of a program as well as
find out whether it is present, you have to write your own test for it
(*note Writing Tests::). By default, these macros use the environment
variable `PATH'. If you need to check for a program that might not be
in the user's `PATH', you can pass a modified path to use instead, like
this:
AC_PATH_PROG([INETD], [inetd], [/usr/libexec/inetd],
[$PATH$PATH_SEPARATOR/usr/libexec$PATH_SEPARATOR]dnl
[/usr/sbin$PATH_SEPARATOR/usr/etc$PATH_SEPARATOR/etc])
You are strongly encouraged to declare the VARIABLE passed to
`AC_CHECK_PROG' etc. as precious, *Note Setting Output Variables::,
`AC_ARG_VAR', for more details.
-- Macro: AC_CHECK_PROG (VARIABLE, PROG-TO-CHECK-FOR, VALUE-IF-FOUND,
[VALUE-IF-NOT-FOUND], [PATH = `$PATH'], [REJECT])
Check whether program PROG-TO-CHECK-FOR exists in PATH. If it is
found, set VARIABLE to VALUE-IF-FOUND, otherwise to
VALUE-IF-NOT-FOUND, if given. Always pass over REJECT (an
absolute file name) even if it is the first found in the search
path; in that case, set VARIABLE using the absolute file name of
the PROG-TO-CHECK-FOR found that is not REJECT. If VARIABLE was
already set, do nothing. Calls `AC_SUBST' for VARIABLE.
-- Macro: AC_CHECK_PROGS (VARIABLE, PROGS-TO-CHECK-FOR,
[VALUE-IF-NOT-FOUND], [PATH = `$PATH'])
Check for each program in the blank-separated list
PROGS-TO-CHECK-FOR existing in the PATH. If one is found, set
VARIABLE to the name of that program. Otherwise, continue
checking the next program in the list. If none of the programs in
the list are found, set VARIABLE to VALUE-IF-NOT-FOUND; if
VALUE-IF-NOT-FOUND is not specified, the value of VARIABLE is not
changed. Calls `AC_SUBST' for VARIABLE.
-- Macro: AC_CHECK_TARGET_TOOL (VARIABLE, PROG-TO-CHECK-FOR,
[VALUE-IF-NOT-FOUND], [PATH = `$PATH'])
Like `AC_CHECK_PROG', but first looks for PROG-TO-CHECK-FOR with a
prefix of the target type as determined by `AC_CANONICAL_TARGET',
followed by a dash (*note Canonicalizing::). If the tool cannot
be found with a prefix, and if the build and target types are
equal, then it is also searched for without a prefix.
As noted in *note Specifying Target Triplets::, the target is
rarely specified, because most of the time it is the same as the
host: it is the type of system for which any compiler tool in the
package produces code. What this macro looks for is, for example,
_a tool (assembler, linker, etc.) that the compiler driver (`gcc'
for the GNU C Compiler) uses to produce objects, archives or
executables_.
-- Macro: AC_CHECK_TOOL (VARIABLE, PROG-TO-CHECK-FOR,
[VALUE-IF-NOT-FOUND], [PATH = `$PATH'])
Like `AC_CHECK_PROG', but first looks for PROG-TO-CHECK-FOR with a
prefix of the host type as specified by `--host', followed by a
dash. For example, if the user runs `configure --build=x86_64-gnu
--host=i386-gnu', then this call:
AC_CHECK_TOOL([RANLIB], [ranlib], [:])
sets `RANLIB' to `i386-gnu-ranlib' if that program exists in PATH,
or otherwise to `ranlib' if that program exists in PATH, or to `:'
if neither program exists.
When cross-compiling, this macro will issue a warning if no program
prefixed with the host type could be found. For more information,
see *note Specifying Target Triplets::.
-- Macro: AC_CHECK_TARGET_TOOLS (VARIABLE, PROGS-TO-CHECK-FOR,
[VALUE-IF-NOT-FOUND], [PATH = `$PATH'])
Like `AC_CHECK_TARGET_TOOL', each of the tools in the list
PROGS-TO-CHECK-FOR are checked with a prefix of the target type as
determined by `AC_CANONICAL_TARGET', followed by a dash (*note
Canonicalizing::). If none of the tools can be found with a
prefix, and if the build and target types are equal, then the
first one without a prefix is used. If a tool is found, set
VARIABLE to the name of that program. If none of the tools in the
list are found, set VARIABLE to VALUE-IF-NOT-FOUND; if
VALUE-IF-NOT-FOUND is not specified, the value of VARIABLE is not
changed. Calls `AC_SUBST' for VARIABLE.
-- Macro: AC_CHECK_TOOLS (VARIABLE, PROGS-TO-CHECK-FOR,
[VALUE-IF-NOT-FOUND], [PATH = `$PATH'])
Like `AC_CHECK_TOOL', each of the tools in the list
PROGS-TO-CHECK-FOR are checked with a prefix of the host type as
determined by `AC_CANONICAL_HOST', followed by a dash (*note
Canonicalizing::). If none of the tools can be found with a
prefix, then the first one without a prefix is used. If a tool is
found, set VARIABLE to the name of that program. If none of the
tools in the list are found, set VARIABLE to VALUE-IF-NOT-FOUND; if
VALUE-IF-NOT-FOUND is not specified, the value of VARIABLE is not
changed. Calls `AC_SUBST' for VARIABLE.
When cross-compiling, this macro will issue a warning if no program
prefixed with the host type could be found. For more information,
see *note Specifying Target Triplets::.
-- Macro: AC_PATH_PROG (VARIABLE, PROG-TO-CHECK-FOR,
[VALUE-IF-NOT-FOUND], [PATH = `$PATH'])
Like `AC_CHECK_PROG', but set VARIABLE to the absolute name of
PROG-TO-CHECK-FOR if found.
-- Macro: AC_PATH_PROGS (VARIABLE, PROGS-TO-CHECK-FOR,
[VALUE-IF-NOT-FOUND], [PATH = `$PATH'])
Like `AC_CHECK_PROGS', but if any of PROGS-TO-CHECK-FOR are found,
set VARIABLE to the absolute name of the program found.
-- Macro: AC_PATH_PROGS_FEATURE_CHECK (VARIABLE, PROGS-TO-CHECK-FOR,
FEATURE-TEST, [ACTION-IF-NOT-FOUND], [PATH = `$PATH'])
This macro was introduced in Autoconf 2.62. If VARIABLE is not
empty, then set the cache variable `$ac_cv_path_VARIABLE' to its
value. Otherwise, check for each program in the blank-separated
list PROGS-TO-CHECK-FOR existing in PATH. For each program found,
execute FEATURE-TEST with `$ac_path_VARIABLE' set to the absolute
name of the candidate program. If no invocation of FEATURE-TEST
sets the shell variable `$ac_cv_path_VARIABLE', then
ACTION-IF-NOT-FOUND is executed. FEATURE-TEST will be run even
when `ac_cv_path_VARIABLE' is set, to provide the ability to
choose a better candidate found later in PATH; to accept the
current setting and bypass all futher checks, FEATURE-TEST can
execute `ac_path_VARIABLE_found=:'.
Note that this macro has some subtle differences from
`AC_CHECK_PROGS'. It is designed to be run inside `AC_CACHE_VAL',
therefore, it should have no side effects. In particular,
VARIABLE is not set to the final value of `ac_cv_path_VARIABLE',
nor is `AC_SUBST' automatically run. Also, on failure, any action
can be performed, whereas `AC_CHECK_PROGS' only performs
`VARIABLE=VALUE-IF-NOT-FOUND'.
Here is an example, similar to what Autoconf uses in its own
configure script. It will search for an implementation of `m4'
that supports the `indir' builtin, even if it goes by the name
`gm4' or is not the first implementation on `PATH'.
AC_CACHE_CHECK([for m4 that supports indir], [ac_cv_path_M4],
[AC_PATH_PROGS_FEATURE_CHECK([M4], [m4 gm4],
[[m4out=`echo 'changequote([,])indir([divnum])' | $ac_path_M4`
test "x$m4out" = x0 \
&& ac_cv_path_M4=$ac_path_M4 ac_path_M4_found=:]],
[AC_MSG_ERROR([could not find m4 that supports indir])])])
AC_SUBST([M4], [$ac_cv_path_M4])
-- Macro: AC_PATH_TARGET_TOOL (VARIABLE, PROG-TO-CHECK-FOR,
[VALUE-IF-NOT-FOUND], [PATH = `$PATH'])
Like `AC_CHECK_TARGET_TOOL', but set VARIABLE to the absolute name
of the program if it is found.
-- Macro: AC_PATH_TOOL (VARIABLE, PROG-TO-CHECK-FOR,
[VALUE-IF-NOT-FOUND], [PATH = `$PATH'])
Like `AC_CHECK_TOOL', but set VARIABLE to the absolute name of the
program if it is found.
When cross-compiling, this macro will issue a warning if no program
prefixed with the host type could be found. For more information,
see *note Specifying Target Triplets::.
File: autoconf.info, Node: Files, Next: Libraries, Prev: Alternative Programs, Up: Existing Tests
5.3 Files
=========
You might also need to check for the existence of files. Before using
these macros, ask yourself whether a runtime test might not be a better
solution. Be aware that, like most Autoconf macros, they test a feature
of the host machine, and therefore, they die when cross-compiling.
-- Macro: AC_CHECK_FILE (FILE, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND])
Check whether file FILE exists on the native system. If it is
found, execute ACTION-IF-FOUND, otherwise do ACTION-IF-NOT-FOUND,
if given.
-- Macro: AC_CHECK_FILES (FILES, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND])
Executes `AC_CHECK_FILE' once for each file listed in FILES.
Additionally, defines `HAVE_FILE' (*note Standard Symbols::) for
each file found.
File: autoconf.info, Node: Libraries, Next: Library Functions, Prev: Files, Up: Existing Tests
5.4 Library Files
=================
The following macros check for the presence of certain C, C++, or
Fortran library archive files.
-- Macro: AC_CHECK_LIB (LIBRARY, FUNCTION, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND], [OTHER-LIBRARIES])
Test whether the library LIBRARY is available by trying to link a
test program that calls function FUNCTION with the library.
FUNCTION should be a function provided by the library. Use the
base name of the library; e.g., to check for `-lmp', use `mp' as
the LIBRARY argument.
ACTION-IF-FOUND is a list of shell commands to run if the link
with the library succeeds; ACTION-IF-NOT-FOUND is a list of shell
commands to run if the link fails. If ACTION-IF-FOUND is not
specified, the default action prepends `-lLIBRARY' to `LIBS' and
defines `HAVE_LIBLIBRARY' (in all capitals). This macro is
intended to support building `LIBS' in a right-to-left
(least-dependent to most-dependent) fashion such that library
dependencies are satisfied as a natural side effect of consecutive
tests. Linkers are sensitive to library ordering so the order in
which `LIBS' is generated is important to reliable detection of
libraries.
If linking with LIBRARY results in unresolved symbols that would
be resolved by linking with additional libraries, give those
libraries as the OTHER-LIBRARIES argument, separated by spaces:
e.g., `-lXt -lX11'. Otherwise, this macro fails to detect that
LIBRARY is present, because linking the test program always fails
with unresolved symbols. The OTHER-LIBRARIES argument should be
limited to cases where it is desirable to test for one library in
the presence of another that is not already in `LIBS'.
`AC_CHECK_LIB' requires some care in usage, and should be avoided
in some common cases. Many standard functions like `gethostbyname'
appear in the standard C library on some hosts, and in special
libraries like `nsl' on other hosts. On some hosts the special
libraries contain variant implementations that you may not want to
use. These days it is normally better to use
`AC_SEARCH_LIBS([gethostbyname], [nsl])' instead of
`AC_CHECK_LIB([nsl], [gethostbyname])'.
-- Macro: AC_SEARCH_LIBS (FUNCTION, SEARCH-LIBS, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND], [OTHER-LIBRARIES])
Search for a library defining FUNCTION if it's not already
available. This equates to calling
`AC_LINK_IFELSE([AC_LANG_CALL([], [FUNCTION])])' first with no
libraries, then for each library listed in SEARCH-LIBS.
Add `-lLIBRARY' to `LIBS' for the first library found to contain
FUNCTION, and run ACTION-IF-FOUND. If the function is not found,
run ACTION-IF-NOT-FOUND.
If linking with LIBRARY results in unresolved symbols that would
be resolved by linking with additional libraries, give those
libraries as the OTHER-LIBRARIES argument, separated by spaces:
e.g., `-lXt -lX11'. Otherwise, this macro fails to detect that
FUNCTION is present, because linking the test program always fails
with unresolved symbols.
File: autoconf.info, Node: Library Functions, Next: Header Files, Prev: Libraries, Up: Existing Tests
5.5 Library Functions
=====================
The following macros check for particular C library functions. If
there is no macro specifically defined to check for a function you need,
and you don't need to check for any special properties of it, then you
can use one of the general function-check macros.
* Menu:
* Function Portability:: Pitfalls with usual functions
* Particular Functions:: Special handling to find certain functions
* Generic Functions:: How to find other functions
File: autoconf.info, Node: Function Portability, Next: Particular Functions, Up: Library Functions
5.5.1 Portability of C Functions
--------------------------------
Most usual functions can either be missing, or be buggy, or be limited
on some architectures. This section tries to make an inventory of these
portability issues. By definition, this list always requires
additions. Please help us keeping it as complete as possible.
`exit'
On ancient hosts, `exit' returned `int'. This is because `exit'
predates `void', and there was a long tradition of it returning
`int'.
On current hosts, the problem more likely is that `exit' is not
declared, due to C++ problems of some sort or another. For this
reason we suggest that test programs not invoke `exit', but return
from `main' instead.
`free'
The C standard says a call `free (NULL)' does nothing, but some
old systems don't support this (e.g., NextStep).
`isinf'
`isnan'
The C99 standard says that `isinf' and `isnan' are macros. On
some systems just macros are available (e.g., HP-UX and Solaris
10), on some systems both macros and functions (e.g., glibc
2.3.2), and on some systems only functions (e.g., IRIX 6 and
Solaris 9). In some cases these functions are declared in
nonstandard headers like `' and defined in non-default
libraries like `-lm' or `-lsunmath'.
The C99 `isinf' and `isnan' macros work correctly with `long
double' arguments, but pre-C99 systems that use functions
typically assume `double' arguments. On such a system, `isinf'
incorrectly returns true for a finite `long double' argument that
is outside the range of `double'.
The best workaround for these issues is to use gnulib modules
`isinf' and `isnan' (*note Gnulib::). But a lighter weight
solution involves code like the following.
#include
#ifndef isnan
# define isnan(x) \
(sizeof (x) == sizeof (long double) ? isnan_ld (x) \
: sizeof (x) == sizeof (double) ? isnan_d (x) \
: isnan_f (x))
static inline int isnan_f (float x) { return x != x; }
static inline int isnan_d (double x) { return x != x; }
static inline int isnan_ld (long double x) { return x != x; }
#endif
#ifndef isinf
# define isinf(x) \
(sizeof (x) == sizeof (long double) ? isinf_ld (x) \
: sizeof (x) == sizeof (double) ? isinf_d (x) \
: isinf_f (x))
static inline int isinf_f (float x)
{ return !isnan (x) && isnan (x - x); }
static inline int isinf_d (double x)
{ return !isnan (x) && isnan (x - x); }
static inline int isinf_ld (long double x)
{ return !isnan (x) && isnan (x - x); }
#endif
Use `AC_C_INLINE' (*note C Compiler::) so that this code works on
compilers that lack the `inline' keyword. Some optimizing
compilers mishandle these definitions, but systems with that bug
typically have many other floating point corner-case compliance
problems anyway, so it's probably not worth worrying about.
`malloc'
The C standard says a call `malloc (0)' is implementation
dependent. It can return either `NULL' or a new non-null pointer.
The latter is more common (e.g., the GNU C Library) but is by no
means universal. `AC_FUNC_MALLOC' can be used to insist on
non-`NULL' (*note Particular Functions::).
`putenv'
Posix prefers `setenv' to `putenv'; among other things, `putenv'
is not required of all Posix implementations, but `setenv' is.
Posix specifies that `putenv' puts the given string directly in
`environ', but some systems make a copy of it instead (e.g., glibc
2.0, or BSD). And when a copy is made, `unsetenv' might not free
it, causing a memory leak (e.g., FreeBSD 4).
On some systems `putenv ("FOO")' removes `FOO' from the
environment, but this is not standard usage and it dumps core on
some systems (e.g., AIX).
On MinGW, a call `putenv ("FOO=")' removes `FOO' from the
environment, rather than inserting it with an empty value.
`realloc'
The C standard says a call `realloc (NULL, size)' is equivalent to
`malloc (size)', but some old systems don't support this (e.g.,
NextStep).
`signal' handler
Normally `signal' takes a handler function with a return type of
`void', but some old systems required `int' instead. Any actual
`int' value returned is not used; this is only a difference in the
function prototype demanded.
All systems we know of in current use return `void'. The `int'
was to support K&R C, where of course `void' is not available.
The obsolete macro `AC_TYPE_SIGNAL' (*note AC_TYPE_SIGNAL::) can
be used to establish the correct type in all cases.
In most cases, it is more robust to use `sigaction' when it is
available, rather than `signal'.
`snprintf'
The C99 standard says that if the output array isn't big enough
and if no other errors occur, `snprintf' and `vsnprintf' truncate
the output and return the number of bytes that ought to have been
produced. Some older systems return the truncated length (e.g.,
GNU C Library 2.0.x or IRIX 6.5), some a negative value (e.g.,
earlier GNU C Library versions), and some the buffer length
without truncation (e.g., 32-bit Solaris 7). Also, some buggy
older systems ignore the length and overrun the buffer (e.g.,
64-bit Solaris 7).
`sprintf'
The C standard says `sprintf' and `vsprintf' return the number of
bytes written. On some ancient systems (SunOS 4 for instance)
they return the buffer pointer instead, but these no longer need
to be worried about.
`sscanf'
On various old systems, e.g., HP-UX 9, `sscanf' requires that its
input string be writable (though it doesn't actually change it).
This can be a problem when using `gcc' since it normally puts
constant strings in read-only memory (*note Incompatibilities of
GCC: (gcc)Incompatibilities.). Apparently in some cases even
having format strings read-only can be a problem.
`strerror_r'
Posix specifies that `strerror_r' returns an `int', but many
systems (e.g., GNU C Library version 2.2.4) provide a different
version returning a `char *'. `AC_FUNC_STRERROR_R' can detect
which is in use (*note Particular Functions::).
`strnlen'
AIX 4.3 provides a broken version which produces the following
results:
strnlen ("foobar", 0) = 0
strnlen ("foobar", 1) = 3
strnlen ("foobar", 2) = 2
strnlen ("foobar", 3) = 1
strnlen ("foobar", 4) = 0
strnlen ("foobar", 5) = 6
strnlen ("foobar", 6) = 6
strnlen ("foobar", 7) = 6
strnlen ("foobar", 8) = 6
strnlen ("foobar", 9) = 6
`sysconf'
`_SC_PAGESIZE' is standard, but some older systems (e.g., HP-UX 9)
have `_SC_PAGE_SIZE' instead. This can be tested with `#ifdef'.
`unlink'
The Posix spec says that `unlink' causes the given file to be
removed only after there are no more open file handles for it.
Some non-Posix hosts have trouble with this requirement, though,
and some DOS variants even corrupt the file system.
`unsetenv'
On MinGW, `unsetenv' is not available, but a variable `FOO' can be
removed with a call `putenv ("FOO=")', as described under `putenv'
above.
`va_copy'
The C99 standard provides `va_copy' for copying `va_list'
variables. It may be available in older environments too, though
possibly as `__va_copy' (e.g., `gcc' in strict pre-C99 mode).
These can be tested with `#ifdef'. A fallback to `memcpy (&dst,
&src, sizeof (va_list))' gives maximum portability.
`va_list'
`va_list' is not necessarily just a pointer. It can be a `struct'
(e.g., `gcc' on Alpha), which means `NULL' is not portable. Or it
can be an array (e.g., `gcc' in some PowerPC configurations),
which means as a function parameter it can be effectively
call-by-reference and library routines might modify the value back
in the caller (e.g., `vsnprintf' in the GNU C Library 2.1).
Signed `>>'
Normally the C `>>' right shift of a signed type replicates the
high bit, giving a so-called "arithmetic" shift. But care should
be taken since Standard C doesn't require that behavior. On those
few processors without a native arithmetic shift (for instance Cray
vector systems) zero bits may be shifted in, the same as a shift
of an unsigned type.
Integer `/'
C divides signed integers by truncating their quotient toward zero,
yielding the same result as Fortran. However, before C99 the
standard allowed C implementations to take the floor or ceiling of
the quotient in some cases. Hardly any implementations took
advantage of this freedom, though, and it's probably not worth
worrying about this issue nowadays.
File: autoconf.info, Node: Particular Functions, Next: Generic Functions, Prev: Function Portability, Up: Library Functions
5.5.2 Particular Function Checks
--------------------------------
These macros check for particular C functions--whether they exist, and
in some cases how they respond when given certain arguments.
-- Macro: AC_FUNC_ALLOCA
Check how to get `alloca'. Tries to get a builtin version by
checking for `alloca.h' or the predefined C preprocessor macros
`__GNUC__' and `_AIX'. If this macro finds `alloca.h', it defines
`HAVE_ALLOCA_H'.
If those attempts fail, it looks for the function in the standard C
library. If any of those methods succeed, it defines
`HAVE_ALLOCA'. Otherwise, it sets the output variable `ALLOCA' to
`${LIBOBJDIR}alloca.o' and defines `C_ALLOCA' (so programs can
periodically call `alloca (0)' to garbage collect). This variable
is separate from `LIBOBJS' so multiple programs can share the
value of `ALLOCA' without needing to create an actual library, in
case only some of them use the code in `LIBOBJS'. The
`${LIBOBJDIR}' prefix serves the same purpose as in `LIBOBJS'
(*note AC_LIBOBJ vs LIBOBJS::).
This macro does not try to get `alloca' from the System V R3
`libPW' or the System V R4 `libucb' because those libraries
contain some incompatible functions that cause trouble. Some
versions do not even contain `alloca' or contain a buggy version.
If you still want to use their `alloca', use `ar' to extract
`alloca.o' from them instead of compiling `alloca.c'.
Source files that use `alloca' should start with a piece of code
like the following, to declare it properly.
#ifdef HAVE_ALLOCA_H
# include
#elif defined __GNUC__
# define alloca __builtin_alloca
#elif defined _AIX
# define alloca __alloca
#elif defined _MSC_VER
# include
# define alloca _alloca
#else
# include
# ifdef __cplusplus
extern "C"
# endif
void *alloca (size_t);
#endif
-- Macro: AC_FUNC_CHOWN
If the `chown' function is available and works (in particular, it
should accept `-1' for `uid' and `gid'), define `HAVE_CHOWN'.
-- Macro: AC_FUNC_CLOSEDIR_VOID
If the `closedir' function does not return a meaningful value,
define `CLOSEDIR_VOID'. Otherwise, callers ought to check its
return value for an error indicator.
Currently this test is implemented by running a test program. When
cross compiling the pessimistic assumption that `closedir' does not
return a meaningful value is made.
This macro is obsolescent, as `closedir' returns a meaningful value
on current systems. New programs need not use this macro.
-- Macro: AC_FUNC_ERROR_AT_LINE
If the `error_at_line' function is not found, require an
`AC_LIBOBJ' replacement of `error'.
-- Macro: AC_FUNC_FNMATCH
If the `fnmatch' function conforms to Posix, define
`HAVE_FNMATCH'. Detect common implementation bugs, for example,
the bugs in Solaris 2.4.
Unlike the other specific `AC_FUNC' macros, `AC_FUNC_FNMATCH' does
not replace a broken/missing `fnmatch'. This is for historical
reasons. See `AC_REPLACE_FNMATCH' below.
This macro is obsolescent. New programs should use Gnulib's
`fnmatch-posix' module. *Note Gnulib::.
-- Macro: AC_FUNC_FNMATCH_GNU
Behave like `AC_REPLACE_FNMATCH' (_replace_) but also test whether
`fnmatch' supports GNU extensions. Detect common implementation
bugs, for example, the bugs in the GNU C Library 2.1.
This macro is obsolescent. New programs should use Gnulib's
`fnmatch-gnu' module. *Note Gnulib::.
-- Macro: AC_FUNC_FORK
This macro checks for the `fork' and `vfork' functions. If a
working `fork' is found, define `HAVE_WORKING_FORK'. This macro
checks whether `fork' is just a stub by trying to run it.
If `vfork.h' is found, define `HAVE_VFORK_H'. If a working
`vfork' is found, define `HAVE_WORKING_VFORK'. Otherwise, define
`vfork' to be `fork' for backward compatibility with previous
versions of `autoconf'. This macro checks for several known
errors in implementations of `vfork' and considers the system to
not have a working `vfork' if it detects any of them. It is not
considered to be an implementation error if a child's invocation
of `signal' modifies the parent's signal handler, since child
processes rarely change their signal handlers.
Since this macro defines `vfork' only for backward compatibility
with previous versions of `autoconf' you're encouraged to define it
yourself in new code:
#ifndef HAVE_WORKING_VFORK
# define vfork fork
#endif
-- Macro: AC_FUNC_FSEEKO
If the `fseeko' function is available, define `HAVE_FSEEKO'.
Define `_LARGEFILE_SOURCE' if necessary to make the prototype
visible on some systems (e.g., glibc 2.2). Otherwise linkage
problems may occur when compiling with `AC_SYS_LARGEFILE' on
largefile-sensitive systems where `off_t' does not default to a
64bit entity. All systems with `fseeko' also supply `ftello'.
-- Macro: AC_FUNC_GETGROUPS
If the `getgroups' function is available and works (unlike on
Ultrix 4.3, where `getgroups (0, 0)' always fails), define
`HAVE_GETGROUPS'. Set `GETGROUPS_LIBS' to any libraries needed to
get that function. This macro runs `AC_TYPE_GETGROUPS'.
-- Macro: AC_FUNC_GETLOADAVG
Check how to get the system load averages. To perform its tests
properly, this macro needs the file `getloadavg.c'; therefore, be
sure to set the `AC_LIBOBJ' replacement directory properly (see
*note Generic Functions::, `AC_CONFIG_LIBOBJ_DIR').
If the system has the `getloadavg' function, define
`HAVE_GETLOADAVG', and set `GETLOADAVG_LIBS' to any libraries
necessary to get that function. Also add `GETLOADAVG_LIBS' to
`LIBS'. Otherwise, require an `AC_LIBOBJ' replacement for
`getloadavg' with source code in `DIR/getloadavg.c', and possibly
define several other C preprocessor macros and output variables:
1. Define `C_GETLOADAVG'.
2. Define `SVR4', `DGUX', `UMAX', or `UMAX4_3' if on those
systems.
3. If `nlist.h' is found, define `HAVE_NLIST_H'.
4. If `struct nlist' has an `n_un.n_name' member, define
`HAVE_STRUCT_NLIST_N_UN_N_NAME'. The obsolete symbol
`NLIST_NAME_UNION' is still defined, but do not depend upon
it.
5. Programs may need to be installed set-group-ID (or
set-user-ID) for `getloadavg' to work. In this case, define
`GETLOADAVG_PRIVILEGED', set the output variable `NEED_SETGID'
to `true' (and otherwise to `false'), and set `KMEM_GROUP' to
the name of the group that should own the installed program.
The `AC_FUNC_GETLOADAVG' macro is obsolescent. New programs should
use Gnulib's `getloadavg' module. *Note Gnulib::.
-- Macro: AC_FUNC_GETMNTENT
Check for `getmntent' in the standard C library, and then in the
`sun', `seq', and `gen' libraries, for UNICOS, IRIX 4, PTX, and
UnixWare, respectively. Then, if `getmntent' is available, define
`HAVE_GETMNTENT'.
-- Macro: AC_FUNC_GETPGRP
Define `GETPGRP_VOID' if it is an error to pass 0 to `getpgrp';
this is the Posix behavior. On older BSD systems, you must pass 0
to `getpgrp', as it takes an argument and behaves like Posix's
`getpgid'.
#ifdef GETPGRP_VOID
pid = getpgrp ();
#else
pid = getpgrp (0);
#endif
This macro does not check whether `getpgrp' exists at all; if you
need to work in that situation, first call `AC_CHECK_FUNC' for
`getpgrp'.
This macro is obsolescent, as current systems have a `getpgrp'
whose signature conforms to Posix. New programs need not use this
macro.
-- Macro: AC_FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK
If `link' is a symbolic link, then `lstat' should treat `link/'
the same as `link/.'. However, many older `lstat' implementations
incorrectly ignore trailing slashes.
It is safe to assume that if `lstat' incorrectly ignores trailing
slashes, then other symbolic-link-aware functions like `unlink'
also incorrectly ignore trailing slashes.
If `lstat' behaves properly, define
`LSTAT_FOLLOWS_SLASHED_SYMLINK', otherwise require an `AC_LIBOBJ'
replacement of `lstat'.
-- Macro: AC_FUNC_MALLOC
If the `malloc' function is compatible with the GNU C library
`malloc' (i.e., `malloc (0)' returns a valid pointer), define
`HAVE_MALLOC' to 1. Otherwise define `HAVE_MALLOC' to 0, ask for
an `AC_LIBOBJ' replacement for `malloc', and define `malloc' to
`rpl_malloc' so that the native `malloc' is not used in the main
project.
Typically, the replacement file `malloc.c' should look like (note
the `#undef malloc'):
#include
#undef malloc
#include
void *malloc ();
/* Allocate an N-byte block of memory from the heap.
If N is zero, allocate a 1-byte block. */
void *
rpl_malloc (size_t n)
{
if (n == 0)
n = 1;
return malloc (n);
}
-- Macro: AC_FUNC_MEMCMP
If the `memcmp' function is not available, or does not work on
8-bit data (like the one on SunOS 4.1.3), or fails when comparing
16 bytes or more and with at least one buffer not starting on a
4-byte boundary (such as the one on NeXT x86 OpenStep), require an
`AC_LIBOBJ' replacement for `memcmp'.
This macro is obsolescent, as current systems have a working
`memcmp'. New programs need not use this macro.
-- Macro: AC_FUNC_MBRTOWC
Define `HAVE_MBRTOWC' to 1 if the function `mbrtowc' and the type
`mbstate_t' are properly declared.
-- Macro: AC_FUNC_MKTIME
If the `mktime' function is not available, or does not work
correctly, require an `AC_LIBOBJ' replacement for `mktime'. For
the purposes of this test, `mktime' should conform to the Posix
standard and should be the inverse of `localtime'.
-- Macro: AC_FUNC_MMAP
If the `mmap' function exists and works correctly, define
`HAVE_MMAP'. This checks only private fixed mapping of
already-mapped memory.
-- Macro: AC_FUNC_OBSTACK
If the obstacks are found, define `HAVE_OBSTACK', else require an
`AC_LIBOBJ' replacement for `obstack'.
-- Macro: AC_FUNC_REALLOC
If the `realloc' function is compatible with the GNU C library
`realloc' (i.e., `realloc (NULL, 0)' returns a valid pointer),
define `HAVE_REALLOC' to 1. Otherwise define `HAVE_REALLOC' to 0,
ask for an `AC_LIBOBJ' replacement for `realloc', and define
`realloc' to `rpl_realloc' so that the native `realloc' is not
used in the main project. See `AC_FUNC_MALLOC' for details.
-- Macro: AC_FUNC_SELECT_ARGTYPES
Determines the correct type to be passed for each of the `select'
function's arguments, and defines those types in
`SELECT_TYPE_ARG1', `SELECT_TYPE_ARG234', and `SELECT_TYPE_ARG5'
respectively. `SELECT_TYPE_ARG1' defaults to `int',
`SELECT_TYPE_ARG234' defaults to `int *', and `SELECT_TYPE_ARG5'
defaults to `struct timeval *'.
This macro is obsolescent, as current systems have a `select' whose
signature conforms to Posix. New programs need not use this macro.
-- Macro: AC_FUNC_SETPGRP
If `setpgrp' takes no argument (the Posix version), define
`SETPGRP_VOID'. Otherwise, it is the BSD version, which takes two
process IDs as arguments. This macro does not check whether
`setpgrp' exists at all; if you need to work in that situation,
first call `AC_CHECK_FUNC' for `setpgrp'.
This macro is obsolescent, as current systems have a `setpgrp'
whose signature conforms to Posix. New programs need not use this
macro.
-- Macro: AC_FUNC_STAT
-- Macro: AC_FUNC_LSTAT
Determine whether `stat' or `lstat' have the bug that it succeeds
when given the zero-length file name as argument. The `stat' and
`lstat' from SunOS 4.1.4 and the Hurd (as of 1998-11-01) do this.
If it does, then define `HAVE_STAT_EMPTY_STRING_BUG' (or
`HAVE_LSTAT_EMPTY_STRING_BUG') and ask for an `AC_LIBOBJ'
replacement of it.
These macros are obsolescent, as no current systems have the bug.
New programs need not use these macros.
-- Macro: AC_FUNC_STRCOLL
If the `strcoll' function exists and works correctly, define
`HAVE_STRCOLL'. This does a bit more than
`AC_CHECK_FUNCS(strcoll)', because some systems have incorrect
definitions of `strcoll' that should not be used.
-- Macro: AC_FUNC_STRERROR_R
If `strerror_r' is available, define `HAVE_STRERROR_R', and if it
is declared, define `HAVE_DECL_STRERROR_R'. If it returns a `char
*' message, define `STRERROR_R_CHAR_P'; otherwise it returns an
`int' error number. The Thread-Safe Functions option of Posix
requires `strerror_r' to return `int', but many systems
(including, for example, version 2.2.4 of the GNU C Library)
return a `char *' value that is not necessarily equal to the
buffer argument.
-- Macro: AC_FUNC_STRFTIME
Check for `strftime' in the `intl' library, for SCO Unix. Then,
if `strftime' is available, define `HAVE_STRFTIME'.
This macro is obsolescent, as no current systems require the `intl'
library for `strftime'. New programs need not use this macro.
-- Macro: AC_FUNC_STRTOD
If the `strtod' function does not exist or doesn't work correctly,
ask for an `AC_LIBOBJ' replacement of `strtod'. In this case,
because `strtod.c' is likely to need `pow', set the output
variable `POW_LIB' to the extra library needed.
-- Macro: AC_FUNC_STRTOLD
If the `strtold' function exists and conforms to C99, define
`HAVE_STRTOLD'.
-- Macro: AC_FUNC_STRNLEN
If the `strnlen' function is not available, or is buggy (like the
one from AIX 4.3), require an `AC_LIBOBJ' replacement for it.
-- Macro: AC_FUNC_UTIME_NULL
If `utime (FILE, NULL)' sets FILE's timestamp to the present,
define `HAVE_UTIME_NULL'.
This macro is obsolescent, as all current systems have a `utime'
that behaves this way. New programs need not use this macro.
-- Macro: AC_FUNC_VPRINTF
If `vprintf' is found, define `HAVE_VPRINTF'. Otherwise, if
`_doprnt' is found, define `HAVE_DOPRNT'. (If `vprintf' is
available, you may assume that `vfprintf' and `vsprintf' are also
available.)
This macro is obsolescent, as all current systems have `vprintf'.
New programs need not use this macro.
-- Macro: AC_REPLACE_FNMATCH
If the `fnmatch' function does not conform to Posix (see
`AC_FUNC_FNMATCH'), ask for its `AC_LIBOBJ' replacement.
The files `fnmatch.c', `fnmatch_loop.c', and `fnmatch_.h' in the
`AC_LIBOBJ' replacement directory are assumed to contain a copy of
the source code of GNU `fnmatch'. If necessary, this source code
is compiled as an `AC_LIBOBJ' replacement, and the `fnmatch_.h'
file is linked to `fnmatch.h' so that it can be included in place
of the system `'.
This macro is obsolescent, as it assumes the use of particular
source files. New programs should use Gnulib's `fnmatch-posix'
module, which provides this macro along with the source files.
*Note Gnulib::.
File: autoconf.info, Node: Generic Functions, Prev: Particular Functions, Up: Library Functions
5.5.3 Generic Function Checks
-----------------------------
These macros are used to find functions not covered by the "particular"
test macros. If the functions might be in libraries other than the
default C library, first call `AC_CHECK_LIB' for those libraries. If
you need to check the behavior of a function as well as find out
whether it is present, you have to write your own test for it (*note
Writing Tests::).
-- Macro: AC_CHECK_FUNC (FUNCTION, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND])
If C function FUNCTION is available, run shell commands
ACTION-IF-FOUND, otherwise ACTION-IF-NOT-FOUND. If you just want
to define a symbol if the function is available, consider using
`AC_CHECK_FUNCS' instead. This macro checks for functions with C
linkage even when `AC_LANG(C++)' has been called, since C is more
standardized than C++. (*note Language Choice::, for more
information about selecting the language for checks.)
-- Macro: AC_CHECK_FUNCS (FUNCTION..., [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND])
For each FUNCTION enumerated in the blank-or-newline-separated
argument list, define `HAVE_FUNCTION' (in all capitals) if it is
available. If ACTION-IF-FOUND is given, it is additional shell
code to execute when one of the functions is found. You can give
it a value of `break' to break out of the loop on the first match.
If ACTION-IF-NOT-FOUND is given, it is executed when one of the
functions is not found.
-- Macro: AC_CHECK_FUNCS_ONCE (FUNCTION...)
For each FUNCTION enumerated in the blank-or-newline-separated
argument list, define `HAVE_FUNCTION' (in all capitals) if it is
available. This is a once-only variant of `AC_CHECK_FUNCS'. It
generates the checking code at most once, so that `configure' is
smaller and faster; but the checks cannot be conditionalized and
are always done once, early during the `configure' run.
Autoconf follows a philosophy that was formed over the years by those
who have struggled for portability: isolate the portability issues in
specific files, and then program as if you were in a Posix environment.
Some functions may be missing or unfixable, and your package must be
ready to replace them.
Suitable replacements for many such problem functions are available
from Gnulib (*note Gnulib::).
-- Macro: AC_LIBOBJ (FUNCTION)
Specify that `FUNCTION.c' must be included in the executables to
replace a missing or broken implementation of FUNCTION.
Technically, it adds `FUNCTION.$ac_objext' to the output variable
`LIBOBJS' if it is not already in, and calls `AC_LIBSOURCE' for
`FUNCTION.c'. You should not directly change `LIBOBJS', since
this is not traceable.
-- Macro: AC_LIBSOURCE (FILE)
Specify that FILE might be needed to compile the project. If you
need to know what files might be needed by a `configure.ac', you
should trace `AC_LIBSOURCE'. FILE must be a literal.
This macro is called automatically from `AC_LIBOBJ', but you must
call it explicitly if you pass a shell variable to `AC_LIBOBJ'. In
that case, since shell variables cannot be traced statically, you
must pass to `AC_LIBSOURCE' any possible files that the shell
variable might cause `AC_LIBOBJ' to need. For example, if you
want to pass a variable `$foo_or_bar' to `AC_LIBOBJ' that holds
either `"foo"' or `"bar"', you should do:
AC_LIBSOURCE([foo.c])
AC_LIBSOURCE([bar.c])
AC_LIBOBJ([$foo_or_bar])
There is usually a way to avoid this, however, and you are
encouraged to simply call `AC_LIBOBJ' with literal arguments.
Note that this macro replaces the obsolete `AC_LIBOBJ_DECL', with
slightly different semantics: the old macro took the function name,
e.g., `foo', as its argument rather than the file name.
-- Macro: AC_LIBSOURCES (FILES)
Like `AC_LIBSOURCE', but accepts one or more FILES in a
comma-separated M4 list. Thus, the above example might be
rewritten:
AC_LIBSOURCES([foo.c, bar.c])
AC_LIBOBJ([$foo_or_bar])
-- Macro: AC_CONFIG_LIBOBJ_DIR (DIRECTORY)
Specify that `AC_LIBOBJ' replacement files are to be found in
DIRECTORY, a name relative to the top level of the source tree.
The replacement directory defaults to `.', the top level
directory, and the most typical value is `lib', corresponding to
`AC_CONFIG_LIBOBJ_DIR([lib])'.
`configure' might need to know the replacement directory for the
following reasons: (i) some checks use the replacement files, (ii)
some macros bypass broken system headers by installing links to the
replacement headers (iii) when used in conjunction with Automake,
within each makefile, DIRECTORY is used as a relative path from
`$(top_srcdir)' to each object named in `LIBOBJS' and `LTLIBOBJS',
etc.
It is common to merely check for the existence of a function, and ask
for its `AC_LIBOBJ' replacement if missing. The following macro is a
convenient shorthand.
-- Macro: AC_REPLACE_FUNCS (FUNCTION...)
Like `AC_CHECK_FUNCS', but uses `AC_LIBOBJ(FUNCTION)' as
ACTION-IF-NOT-FOUND. You can declare your replacement function by
enclosing the prototype in `#ifndef HAVE_FUNCTION'. If the system
has the function, it probably declares it in a header file you
should be including, so you shouldn't redeclare it lest your
declaration conflict.
File: autoconf.info, Node: Header Files, Next: Declarations, Prev: Library Functions, Up: Existing Tests
5.6 Header Files
================
The following macros check for the presence of certain C header files.
If there is no macro specifically defined to check for a header file
you need, and you don't need to check for any special properties of it,
then you can use one of the general header-file check macros.
* Menu:
* Header Portability:: Collected knowledge on common headers
* Particular Headers:: Special handling to find certain headers
* Generic Headers:: How to find other headers
File: autoconf.info, Node: Header Portability, Next: Particular Headers, Up: Header Files
5.6.1 Portability of Headers
----------------------------
This section tries to collect knowledge about common headers, and the
problems they cause. By definition, this list always requires
additions. Please help us keeping it as complete as possible.
`limits.h'
C99 says that `limits.h' defines `LLONG_MIN', `LLONG_MAX', and
`ULLONG_MAX', but many almost-C99 environments (e.g., default GCC
4.0.2 + glibc 2.4) do not define them.
`inttypes.h' vs. `stdint.h'
The C99 standard says that `inttypes.h' includes `stdint.h', so
there's no need to include `stdint.h' separately in a standard
environment. Some implementations have `inttypes.h' but not
`stdint.h' (e.g., Solaris 7), but we don't know of any
implementation that has `stdint.h' but not `inttypes.h'.
`linux/irda.h'
It requires `linux/types.h' and `sys/socket.h'.
`linux/random.h'
It requires `linux/types.h'.
`net/if.h'
On Darwin, this file requires that `sys/socket.h' be included
beforehand. One should run:
AC_CHECK_HEADERS([sys/socket.h])
AC_CHECK_HEADERS([net/if.h], [], [],
[#include
#ifdef STDC_HEADERS
# include
# include
#else
# ifdef HAVE_STDLIB_H
# include
# endif
#endif
#ifdef HAVE_SYS_SOCKET_H
# include
#endif
])
`netinet/if_ether.h'
On Darwin, this file requires that `stdio.h' and `sys/socket.h' be
included beforehand. One should run:
AC_CHECK_HEADERS([sys/socket.h])
AC_CHECK_HEADERS([netinet/if_ether.h], [], [],
[#include
#ifdef STDC_HEADERS
# include
# include
#else
# ifdef HAVE_STDLIB_H
# include
# endif
#endif
#ifdef HAVE_SYS_SOCKET_H
# include
#endif
])
`stdint.h'
See above, item `inttypes.h' vs. `stdint.h'.
`stdlib.h'
On many systems (e.g., Darwin), `stdio.h' is a prerequisite.
`sys/mount.h'
On FreeBSD 4.8 on ia32 and using gcc version 2.95.4,
`sys/params.h' is a prerequisite.
`sys/ptem.h'
On Solaris 8, `sys/stream.h' is a prerequisite.
`sys/socket.h'
On Darwin, `stdlib.h' is a prerequisite.
`sys/ucred.h'
On Tru64 5.1, `sys/types.h' is a prerequisite.
`X11/extensions/scrnsaver.h'
Using XFree86, this header requires `X11/Xlib.h', which is probably
so required that you might not even consider looking for it.
AC_CHECK_HEADERS([X11/extensions/scrnsaver.h], [], [],
[[#include
]])
File: autoconf.info, Node: Particular Headers, Next: Generic Headers, Prev: Header Portability, Up: Header Files
5.6.2 Particular Header Checks
------------------------------
These macros check for particular system header files--whether they
exist, and in some cases whether they declare certain symbols.
-- Macro: AC_HEADER_ASSERT
Check whether to enable assertions in the style of `assert.h'.
Assertions are enabled by default, but the user can override this
by invoking `configure' with the `--disable-assert' option.
-- Macro: AC_HEADER_DIRENT
Check for the following header files. For the first one that is
found and defines `DIR', define the listed C preprocessor macro:
`dirent.h' `HAVE_DIRENT_H'
`sys/ndir.h' `HAVE_SYS_NDIR_H'
`sys/dir.h' `HAVE_SYS_DIR_H'
`ndir.h' `HAVE_NDIR_H'
The directory-library declarations in your source code should look
something like the following:
#include
#ifdef HAVE_DIRENT_H
# include
# define NAMLEN(dirent) strlen ((dirent)->d_name)
#else
# define dirent direct
# define NAMLEN(dirent) ((dirent)->d_namlen)
# ifdef HAVE_SYS_NDIR_H
# include
# endif
# ifdef HAVE_SYS_DIR_H
# include
# endif
# ifdef HAVE_NDIR_H
# include
# endif
#endif
Using the above declarations, the program would declare variables
to be of type `struct dirent', not `struct direct', and would
access the length of a directory entry name by passing a pointer
to a `struct dirent' to the `NAMLEN' macro.
This macro also checks for the SCO Xenix `dir' and `x' libraries.
This macro is obsolescent, as all current systems with directory
libraries have `'. New programs need not use this macro.
Also see `AC_STRUCT_DIRENT_D_INO' and `AC_STRUCT_DIRENT_D_TYPE'
(*note Particular Structures::).
-- Macro: AC_HEADER_MAJOR
If `sys/types.h' does not define `major', `minor', and `makedev',
but `sys/mkdev.h' does, define `MAJOR_IN_MKDEV'; otherwise, if
`sys/sysmacros.h' does, define `MAJOR_IN_SYSMACROS'.
-- Macro: AC_HEADER_RESOLV
Checks for header `resolv.h', checking for prerequisites first.
To properly use `resolv.h', your code should contain something like
the following:
#ifdef HAVE_SYS_TYPES_H
# include
#endif
#ifdef HAVE_NETINET_IN_H
# include /* inet_ functions / structs */
#endif
#ifdef HAVE_ARPA_NAMESER_H
# include /* DNS HEADER struct */
#endif
#ifdef HAVE_NETDB_H
# include
#endif
#include
-- Macro: AC_HEADER_STAT
If the macros `S_ISDIR', `S_ISREG', etc. defined in `sys/stat.h'
do not work properly (returning false positives), define
`STAT_MACROS_BROKEN'. This is the case on Tektronix UTekV, Amdahl
UTS and Motorola System V/88.
This macro is obsolescent, as no current systems have the bug.
New programs need not use this macro.
-- Macro: AC_HEADER_STDBOOL
If `stdbool.h' exists and conforms to C99, define `HAVE_STDBOOL_H'
to 1; if the type `_Bool' is defined, define `HAVE__BOOL' to 1.
To fulfill the C99 requirements, your `system.h' could contain the
following code:
#ifdef HAVE_STDBOOL_H
# include
#else
# ifndef HAVE__BOOL
# ifdef __cplusplus
typedef bool _Bool;
# else
# define _Bool signed char
# endif
# endif
# define bool _Bool
# define false 0
# define true 1
# define __bool_true_false_are_defined 1
#endif
Alternatively you can use the `stdbool' package of Gnulib (*note
Gnulib::); it packages the above code into a replacement header
and contains a few other bells and whistles.
-- Macro: AC_HEADER_STDC
Define `STDC_HEADERS' if the system has C header files conforming
to ANSI C89 (ISO C90). Specifically, this macro checks for
`stdlib.h', `stdarg.h', `string.h', and `float.h'; if the system
has those, it probably has the rest of the C89 header files. This
macro also checks whether `string.h' declares `memchr' (and thus
presumably the other `mem' functions), whether `stdlib.h' declare
`free' (and thus presumably `malloc' and other related functions),
and whether the `ctype.h' macros work on characters with the high
bit set, as the C standard requires.
If you use this macro, your code can refer to `STDC_HEADERS' to
determine whether the system has conforming header files (and
probably C library functions).
This macro is obsolescent, as current systems have conforming
header files. New programs need not use this macro.
Nowadays `string.h' is part of the C standard and declares
functions like `strcpy', and `strings.h' is standardized by Posix
and declares BSD functions like `bcopy'; but historically, string
functions were a major sticking point in this area. If you still
want to worry about portability to ancient systems without
standard headers, there is so much variation that it is probably
easier to declare the functions you use than to figure out exactly
what the system header files declare. Some ancient systems
contained a mix of functions from the C standard and from BSD;
some were mostly standard but lacked `memmove'; some defined the
BSD functions as macros in `string.h' or `strings.h'; some had
only the BSD functions but `string.h'; some declared the memory
functions in `memory.h', some in `string.h'; etc. It is probably
sufficient to check for one string function and one memory
function; if the library had the standard versions of those then
it probably had most of the others. If you put the following in
`configure.ac':
# This example is obsolescent.
# Nowadays you can omit these macro calls.
AC_HEADER_STDC
AC_CHECK_FUNCS([strchr memcpy])
then, in your code, you can use declarations like this:
/* This example is obsolescent.
Nowadays you can just #include . */
#ifdef STDC_HEADERS
# include
#else
# ifndef HAVE_STRCHR
# define strchr index
# define strrchr rindex
# endif
char *strchr (), *strrchr ();
# ifndef HAVE_MEMCPY
# define memcpy(d, s, n) bcopy ((s), (d), (n))
# define memmove(d, s, n) bcopy ((s), (d), (n))
# endif
#endif
If you use a function like `memchr', `memset', `strtok', or
`strspn', which have no BSD equivalent, then macros don't suffice
to port to ancient hosts; you must provide an implementation of
each function. An easy way to incorporate your implementations
only when needed (since the ones in system C libraries may be hand
optimized) is to, taking `memchr' for example, put it in
`memchr.c' and use `AC_REPLACE_FUNCS([memchr])'.
-- Macro: AC_HEADER_SYS_WAIT
If `sys/wait.h' exists and is compatible with Posix, define
`HAVE_SYS_WAIT_H'. Incompatibility can occur if `sys/wait.h' does
not exist, or if it uses the old BSD `union wait' instead of `int'
to store a status value. If `sys/wait.h' is not Posix compatible,
then instead of including it, define the Posix macros with their
usual interpretations. Here is an example:
#include
#ifdef HAVE_SYS_WAIT_H
# include
#endif
#ifndef WEXITSTATUS
# define WEXITSTATUS(stat_val) ((unsigned int) (stat_val) >> 8)
#endif
#ifndef WIFEXITED
# define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
#endif
This macro is obsolescent, as current systems are compatible with
Posix. New programs need not use this macro.
`_POSIX_VERSION' is defined when `unistd.h' is included on Posix
systems. If there is no `unistd.h', it is definitely not a Posix
system. However, some non-Posix systems do have `unistd.h'.
The way to check whether the system supports Posix is:
#ifdef HAVE_UNISTD_H
# include
# include
#endif
#ifdef _POSIX_VERSION
/* Code for Posix systems. */
#endif
-- Macro: AC_HEADER_TIME
If a program may include both `time.h' and `sys/time.h', define
`TIME_WITH_SYS_TIME'. On some ancient systems, `sys/time.h'
included `time.h', but `time.h' was not protected against multiple
inclusion, so programs could not explicitly include both files.
This macro is useful in programs that use, for example, `struct
timeval' as well as `struct tm'. It is best used in conjunction
with `HAVE_SYS_TIME_H', which can be checked for using
`AC_CHECK_HEADERS([sys/time.h])'.
#ifdef TIME_WITH_SYS_TIME
# include
# include
#else
# ifdef HAVE_SYS_TIME_H
# include
# else
# include
# endif
#endif
This macro is obsolescent, as current systems can include both
files when they exist. New programs need not use this macro.
-- Macro: AC_HEADER_TIOCGWINSZ
If the use of `TIOCGWINSZ' requires `', then define
`GWINSZ_IN_SYS_IOCTL'. Otherwise `TIOCGWINSZ' can be found in
`'.
Use:
#ifdef HAVE_TERMIOS_H
# include
#endif
#ifdef GWINSZ_IN_SYS_IOCTL
# include
#endif
File: autoconf.info, Node: Generic Headers, Prev: Particular Headers, Up: Header Files
5.6.3 Generic Header Checks
---------------------------
These macros are used to find system header files not covered by the
"particular" test macros. If you need to check the contents of a header
as well as find out whether it is present, you have to write your own
test for it (*note Writing Tests::).
-- Macro: AC_CHECK_HEADER (HEADER-FILE, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND], [INCLUDES])
If the system header file HEADER-FILE is compilable, execute shell
commands ACTION-IF-FOUND, otherwise execute ACTION-IF-NOT-FOUND.
If you just want to define a symbol if the header file is
available, consider using `AC_CHECK_HEADERS' instead.
INCLUDES is decoded to determine the appropriate include
directives. If omitted or empty, `configure' will check for both
header existence (with the preprocessor) and usability (with the
compiler), using `AC_INCLUDES_DEFAULT' for the compile test. If
there is a discrepancy between the results, a warning is issued to
the user, and the compiler results are favored (*note Present But
Cannot Be Compiled::). In general, favoring the compiler results
means that a header will be treated as not found even though the
file exists, because you did not provide enough prerequisites.
Providing a non-empty INCLUDES argument allows the code to provide
any prerequisites prior to including the header under test; it is
common to use the argument `AC_INCLUDES_DEFAULT' (*note Default
Includes::). With an explicit fourth argument, no preprocessor
test is needed. As a special case, an INCLUDES of exactly `-'
triggers the older preprocessor check, which merely determines
existence of the file in the preprocessor search path; this should
only be used as a last resort (it is safer to determine the actual
prerequisites and perform a compiler check, or else use
`AC_PREPROC_IFELSE' to make it obvious that only a preprocessor
check is desired).
-- Macro: AC_CHECK_HEADERS (HEADER-FILE..., [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND], [INCLUDES])
For each given system header file HEADER-FILE in the
blank-separated argument list that exists, define
`HAVE_HEADER-FILE' (in all capitals). If ACTION-IF-FOUND is
given, it is additional shell code to execute when one of the
header files is found. You can give it a value of `break' to
break out of the loop on the first match. If ACTION-IF-NOT-FOUND
is given, it is executed when one of the header files is not found.
INCLUDES is interpreted as in `AC_CHECK_HEADER', in order to
choose the set of preprocessor directives supplied before the
header under test.
Previous versions of Autoconf merely checked whether the header was
accepted by the preprocessor. This was changed because the old test was
inappropriate for typical uses. Headers are typically used to compile,
not merely to preprocess, and the old behavior sometimes accepted
headers that clashed at compile-time (*note Present But Cannot Be
Compiled::). If you need to check whether a header is preprocessable,
you can use `AC_PREPROC_IFELSE' (*note Running the Preprocessor::).
Actually requiring a header to compile improves the robustness of the
test, but it also requires that you make sure that headers that must be
included before the HEADER-FILE be part of the INCLUDES, (*note Default
Includes::). If looking for `bar.h', which requires that `foo.h' be
included before if it exists, we suggest the following scheme:
AC_CHECK_HEADERS([foo.h])
AC_CHECK_HEADERS([bar.h], [], [],
[#ifdef HAVE_FOO_H
# include
#endif
])
The following variant generates smaller, faster `configure' files if
you do not need the full power of `AC_CHECK_HEADERS'.
-- Macro: AC_CHECK_HEADERS_ONCE (HEADER-FILE...)
For each given system header file HEADER-FILE in the
blank-separated argument list that exists, define
`HAVE_HEADER-FILE' (in all capitals). This is a once-only variant
of `AC_CHECK_HEADERS'. It generates the checking code at most
once, so that `configure' is smaller and faster; but the checks
cannot be conditionalized and are always done once, early during
the `configure' run. Thus, this macro is only safe for checking
headers that do not have prerequisites beyond what
`AC_INCLUDES_DEFAULT' provides.
File: autoconf.info, Node: Declarations, Next: Structures, Prev: Header Files, Up: Existing Tests
5.7 Declarations
================
The following macros check for the declaration of variables and
functions. If there is no macro specifically defined to check for a
symbol you need, then you can use the general macros (*note Generic
Declarations::) or, for more complex tests, you may use
`AC_COMPILE_IFELSE' (*note Running the Compiler::).
* Menu:
* Particular Declarations:: Macros to check for certain declarations
* Generic Declarations:: How to find other declarations
File: autoconf.info, Node: Particular Declarations, Next: Generic Declarations, Up: Declarations
5.7.1 Particular Declaration Checks
-----------------------------------
There are no specific macros for declarations.
File: autoconf.info, Node: Generic Declarations, Prev: Particular Declarations, Up: Declarations
5.7.2 Generic Declaration Checks
--------------------------------
These macros are used to find declarations not covered by the
"particular" test macros.
-- Macro: AC_CHECK_DECL (SYMBOL, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND], [INCLUDES = `AC_INCLUDES_DEFAULT'])
If SYMBOL (a function, variable, or constant) is not declared in
INCLUDES and a declaration is needed, run the shell commands
ACTION-IF-NOT-FOUND, otherwise ACTION-IF-FOUND. INCLUDES is a
series of include directives, defaulting to `AC_INCLUDES_DEFAULT'
(*note Default Includes::), which are used prior to the
declaration under test.
This macro actually tests whether SYMBOL is defined as a macro or
can be used as an r-value, not whether it is really declared,
because it is much safer to avoid introducing extra declarations
when they are not needed.
-- Macro: AC_CHECK_DECLS (SYMBOLS, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND], [INCLUDES = `AC_INCLUDES_DEFAULT'])
For each of the SYMBOLS (_comma_-separated list), define
`HAVE_DECL_SYMBOL' (in all capitals) to `1' if SYMBOL is declared,
otherwise to `0'. If ACTION-IF-NOT-FOUND is given, it is
additional shell code to execute when one of the function
declarations is needed, otherwise ACTION-IF-FOUND is executed.
INCLUDES is a series of include directives, defaulting to
`AC_INCLUDES_DEFAULT' (*note Default Includes::), which are used
prior to the declarations under test.
This macro uses an M4 list as first argument:
AC_CHECK_DECLS([strdup])
AC_CHECK_DECLS([strlen])
AC_CHECK_DECLS([malloc, realloc, calloc, free])
AC_CHECK_DECLS([j0], [], [], [[#include ]])
Unlike the other `AC_CHECK_*S' macros, when a SYMBOL is not
declared, `HAVE_DECL_SYMBOL' is defined to `0' instead of leaving
`HAVE_DECL_SYMBOL' undeclared. When you are _sure_ that the check
was performed, use `HAVE_DECL_SYMBOL' in `#if':
#if !HAVE_DECL_SYMBOL
extern char *symbol;
#endif
If the test may have not been performed, however, because it is
safer _not_ to declare a symbol than to use a declaration that
conflicts with the system's one, you should use:
#if defined HAVE_DECL_MALLOC && !HAVE_DECL_MALLOC
void *malloc (size_t *s);
#endif
You fall into the second category only in extreme situations:
either your files may be used without being configured, or they
are used during the configuration. In most cases the traditional
approach is enough.
-- Macro: AC_CHECK_DECLS_ONCE (SYMBOLS)
For each of the SYMBOLS (_comma_-separated list), define
`HAVE_DECL_SYMBOL' (in all capitals) to `1' if SYMBOL is declared
in the default include files, otherwise to `0'. This is a
once-only variant of `AC_CHECK_DECLS'. It generates the checking
code at most once, so that `configure' is smaller and faster; but
the checks cannot be conditionalized and are always done once,
early during the `configure' run.
File: autoconf.info, Node: Structures, Next: Types, Prev: Declarations, Up: Existing Tests
5.8 Structures
==============
The following macros check for the presence of certain members in C
structures. If there is no macro specifically defined to check for a
member you need, then you can use the general structure-member macros
(*note Generic Structures::) or, for more complex tests, you may use
`AC_COMPILE_IFELSE' (*note Running the Compiler::).
* Menu:
* Particular Structures:: Macros to check for certain structure members
* Generic Structures:: How to find other structure members
File: autoconf.info, Node: Particular Structures, Next: Generic Structures, Up: Structures
5.8.1 Particular Structure Checks
---------------------------------
The following macros check for certain structures or structure members.
-- Macro: AC_STRUCT_DIRENT_D_INO
Perform all the actions of `AC_HEADER_DIRENT' (*note Particular
Headers::). Then, if `struct dirent' contains a `d_ino' member,
define `HAVE_STRUCT_DIRENT_D_INO'.
`HAVE_STRUCT_DIRENT_D_INO' indicates only the presence of `d_ino',
not whether its contents are always reliable. Traditionally, a
zero `d_ino' indicated a deleted directory entry, though current
systems hide this detail from the user and never return zero
`d_ino' values. Many current systems report an incorrect `d_ino'
for a directory entry that is a mount point.
-- Macro: AC_STRUCT_DIRENT_D_TYPE
Perform all the actions of `AC_HEADER_DIRENT' (*note Particular
Headers::). Then, if `struct dirent' contains a `d_type' member,
define `HAVE_STRUCT_DIRENT_D_TYPE'.
-- Macro: AC_STRUCT_ST_BLOCKS
If `struct stat' contains an `st_blocks' member, define
`HAVE_STRUCT_STAT_ST_BLOCKS'. Otherwise, require an `AC_LIBOBJ'
replacement of `fileblocks'. The former name, `HAVE_ST_BLOCKS' is
to be avoided, as its support will cease in the future.
-- Macro: AC_STRUCT_TM
If `time.h' does not define `struct tm', define `TM_IN_SYS_TIME',
which means that including `sys/time.h' had better define `struct
tm'.
This macro is obsolescent, as `time.h' defines `struct tm' in
current systems. New programs need not use this macro.
-- Macro: AC_STRUCT_TIMEZONE
Figure out how to get the current timezone. If `struct tm' has a
`tm_zone' member, define `HAVE_STRUCT_TM_TM_ZONE' (and the
obsoleted `HAVE_TM_ZONE'). Otherwise, if the external array
`tzname' is found, define `HAVE_TZNAME'; if it is declared, define
`HAVE_DECL_TZNAME'.
File: autoconf.info, Node: Generic Structures, Prev: Particular Structures, Up: Structures
5.8.2 Generic Structure Checks
------------------------------
These macros are used to find structure members not covered by the
"particular" test macros.
-- Macro: AC_CHECK_MEMBER (AGGREGATE.MEMBER, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND], [INCLUDES = `AC_INCLUDES_DEFAULT'])
Check whether MEMBER is a member of the aggregate AGGREGATE. If
no INCLUDES are specified, the default includes are used (*note
Default Includes::).
AC_CHECK_MEMBER([struct passwd.pw_gecos], [],
[AC_MSG_ERROR([We need `passwd.pw_gecos'!])],
[[#include ]])
You can use this macro for submembers:
AC_CHECK_MEMBER(struct top.middle.bot)
-- Macro: AC_CHECK_MEMBERS (MEMBERS, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND], [INCLUDES = `AC_INCLUDES_DEFAULT'])
Check for the existence of each `AGGREGATE.MEMBER' of MEMBERS
using the previous macro. When MEMBER belongs to AGGREGATE,
define `HAVE_AGGREGATE_MEMBER' (in all capitals, with spaces and
dots replaced by underscores). If ACTION-IF-FOUND is given, it is
executed for each of the found members. If ACTION-IF-NOT-FOUND is
given, it is executed for each of the members that could not be
found.
INCLUDES is a series of include directives, defaulting to
`AC_INCLUDES_DEFAULT' (*note Default Includes::), which are used
prior to the members under test.
This macro uses M4 lists:
AC_CHECK_MEMBERS([struct stat.st_rdev, struct stat.st_blksize])
File: autoconf.info, Node: Types, Next: Compilers and Preprocessors, Prev: Structures, Up: Existing Tests
5.9 Types
=========
The following macros check for C types, either builtin or typedefs. If
there is no macro specifically defined to check for a type you need, and
you don't need to check for any special properties of it, then you can
use a general type-check macro.
* Menu:
* Particular Types:: Special handling to find certain types
* Generic Types:: How to find other types
File: autoconf.info, Node: Particular Types, Next: Generic Types, Up: Types
5.9.1 Particular Type Checks
----------------------------
These macros check for particular C types in `sys/types.h', `stdlib.h',
`stdint.h', `inttypes.h' and others, if they exist.
The Gnulib `stdint' module is an alternate way to define many of
these symbols; it is useful if you prefer your code to assume a
C99-or-better environment. *Note Gnulib::.
-- Macro: AC_TYPE_GETGROUPS
Define `GETGROUPS_T' to be whichever of `gid_t' or `int' is the
base type of the array argument to `getgroups'.
-- Macro: AC_TYPE_INT8_T
If `stdint.h' or `inttypes.h' does not define the type `int8_t',
define `int8_t' to a signed integer type that is exactly 8 bits
wide and that uses two's complement representation, if such a type
exists. If you are worried about porting to hosts that lack such
a type, you can use the results of this macro in C89-or-later code
as follows:
#if HAVE_STDINT_H
# include
#endif
#if defined INT8_MAX || defined int8_t
_code using int8_t_
#else
_complicated alternative using >8-bit 'signed char'_
#endif
-- Macro: AC_TYPE_INT16_T
This is like `AC_TYPE_INT8_T', except for 16-bit integers.
-- Macro: AC_TYPE_INT32_T
This is like `AC_TYPE_INT8_T', except for 32-bit integers.
-- Macro: AC_TYPE_INT64_T
This is like `AC_TYPE_INT8_T', except for 64-bit integers.
-- Macro: AC_TYPE_INTMAX_T
If `stdint.h' or `inttypes.h' defines the type `intmax_t', define
`HAVE_INTMAX_T'. Otherwise, define `intmax_t' to the widest
signed integer type.
-- Macro: AC_TYPE_INTPTR_T
If `stdint.h' or `inttypes.h' defines the type `intptr_t', define
`HAVE_INTPTR_T'. Otherwise, define `intptr_t' to a signed integer
type wide enough to hold a pointer, if such a type exists.
-- Macro: AC_TYPE_LONG_DOUBLE
If the C compiler supports a working `long double' type, define
`HAVE_LONG_DOUBLE'. The `long double' type might have the same
range and precision as `double'.
This macro is obsolescent, as current C compilers support `long
double'. New programs need not use this macro.
-- Macro: AC_TYPE_LONG_DOUBLE_WIDER
If the C compiler supports a working `long double' type with more
range or precision than the `double' type, define
`HAVE_LONG_DOUBLE_WIDER'.
-- Macro: AC_TYPE_LONG_LONG_INT
If the C compiler supports a working `long long int' type, define
`HAVE_LONG_LONG_INT'. However, this test does not test `long long
int' values in preprocessor `#if' expressions, because too many
compilers mishandle such expressions. *Note Preprocessor
Arithmetic::.
-- Macro: AC_TYPE_MBSTATE_T
Define `HAVE_MBSTATE_T' if `' declares the `mbstate_t'
type. Also, define `mbstate_t' to be a type if `' does
not declare it.
-- Macro: AC_TYPE_MODE_T
Define `mode_t' to a suitable type, if standard headers do not
define it.
-- Macro: AC_TYPE_OFF_T
Define `off_t' to a suitable type, if standard headers do not
define it.
-- Macro: AC_TYPE_PID_T
Define `pid_t' to a suitable type, if standard headers do not
define it.
-- Macro: AC_TYPE_SIZE_T
Define `size_t' to a suitable type, if standard headers do not
define it.
-- Macro: AC_TYPE_SSIZE_T
Define `ssize_t' to a suitable type, if standard headers do not
define it.
-- Macro: AC_TYPE_UID_T
Define `uid_t' and `gid_t' to suitable types, if standard headers
do not define them.
-- Macro: AC_TYPE_UINT8_T
If `stdint.h' or `inttypes.h' does not define the type `uint8_t',
define `uint8_t' to an unsigned integer type that is exactly 8
bits wide, if such a type exists. This is like `AC_TYPE_INT8_T',
except for unsigned integers.
-- Macro: AC_TYPE_UINT16_T
This is like `AC_TYPE_UINT8_T', except for 16-bit integers.
-- Macro: AC_TYPE_UINT32_T
This is like `AC_TYPE_UINT8_T', except for 32-bit integers.
-- Macro: AC_TYPE_UINT64_T
This is like `AC_TYPE_UINT8_T', except for 64-bit integers.
-- Macro: AC_TYPE_UINTMAX_T
If `stdint.h' or `inttypes.h' defines the type `uintmax_t', define
`HAVE_UINTMAX_T'. Otherwise, define `uintmax_t' to the widest
unsigned integer type.
-- Macro: AC_TYPE_UINTPTR_T
If `stdint.h' or `inttypes.h' defines the type `uintptr_t', define
`HAVE_UINTPTR_T'. Otherwise, define `uintptr_t' to an unsigned
integer type wide enough to hold a pointer, if such a type exists.
-- Macro: AC_TYPE_UNSIGNED_LONG_LONG_INT
If the C compiler supports a working `unsigned long long int' type,
define `HAVE_UNSIGNED_LONG_LONG_INT'. However, this test does not
test `unsigned long long int' values in preprocessor `#if'
expressions, because too many compilers mishandle such expressions.
*Note Preprocessor Arithmetic::.
File: autoconf.info, Node: Generic Types, Prev: Particular Types, Up: Types
5.9.2 Generic Type Checks
-------------------------
These macros are used to check for types not covered by the "particular"
test macros.
-- Macro: AC_CHECK_TYPE (TYPE, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND], [INCLUDES = `AC_INCLUDES_DEFAULT'])
Check whether TYPE is defined. It may be a compiler builtin type
or defined by the INCLUDES. INCLUDES is a series of include
directives, defaulting to `AC_INCLUDES_DEFAULT' (*note Default
Includes::), which are used prior to the type under test.
In C, TYPE must be a type-name, so that the expression `sizeof
(TYPE)' is valid (but `sizeof ((TYPE))' is not). The same test is
applied when compiling for C++, which means that in C++ TYPE
should be a type-id and should not be an anonymous `struct' or
`union'.
-- Macro: AC_CHECK_TYPES (TYPES, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND], [INCLUDES = `AC_INCLUDES_DEFAULT'])
For each TYPE of the TYPES that is defined, define `HAVE_TYPE' (in
all capitals). Each TYPE must follow the rules of
`AC_CHECK_TYPE'. If no INCLUDES are specified, the default
includes are used (*note Default Includes::). If ACTION-IF-FOUND
is given, it is additional shell code to execute when one of the
types is found. If ACTION-IF-NOT-FOUND is given, it is executed
when one of the types is not found.
This macro uses M4 lists:
AC_CHECK_TYPES([ptrdiff_t])
AC_CHECK_TYPES([unsigned long long int, uintmax_t])
AC_CHECK_TYPES([float_t], [], [], [[#include ]])
Autoconf, up to 2.13, used to provide to another version of
`AC_CHECK_TYPE', broken by design. In order to keep backward
compatibility, a simple heuristic, quite safe but not totally, is
implemented. In case of doubt, read the documentation of the former
`AC_CHECK_TYPE', see *note Obsolete Macros::.
File: autoconf.info, Node: Compilers and Preprocessors, Next: System Services, Prev: Types, Up: Existing Tests
5.10 Compilers and Preprocessors
================================
All the tests for compilers (`AC_PROG_CC', `AC_PROG_CXX',
`AC_PROG_F77') define the output variable `EXEEXT' based on the output
of the compiler, typically to the empty string if Posix and `.exe' if a
DOS variant.
They also define the output variable `OBJEXT' based on the output of
the compiler, after `.c' files have been excluded, typically to `o' if
Posix, `obj' if a DOS variant.
If the compiler being used does not produce executables, the tests
fail. If the executables can't be run, and cross-compilation is not
enabled, they fail too. *Note Manual Configuration::, for more on
support for cross compiling.
* Menu:
* Specific Compiler Characteristics:: Some portability issues
* Generic Compiler Characteristics:: Language independent tests and features
* C Compiler:: Checking its characteristics
* C++ Compiler:: Likewise
* Objective C Compiler:: Likewise
* Erlang Compiler and Interpreter:: Likewise
* Fortran Compiler:: Likewise
File: autoconf.info, Node: Specific Compiler Characteristics, Next: Generic Compiler Characteristics, Up: Compilers and Preprocessors
5.10.1 Specific Compiler Characteristics
----------------------------------------
Some compilers exhibit different behaviors.
Static/Dynamic Expressions
Autoconf relies on a trick to extract one bit of information from
the C compiler: using negative array sizes. For instance the
following excerpt of a C source demonstrates how to test whether
`int' objects are 4 bytes wide:
static int test_array[sizeof (int) == 4 ? 1 : -1];
To our knowledge, there is a single compiler that does not support
this trick: the HP C compilers (the real ones, not only the
"bundled") on HP-UX 11.00. They incorrectly reject the above
program with the diagnostic "Variable-length arrays cannot have
static storage." This bug comes from HP compilers' mishandling of
`sizeof (int)', not from the `? 1 : -1', and Autoconf works around
this problem by casting `sizeof (int)' to `long int' before
comparing it.
File: autoconf.info, Node: Generic Compiler Characteristics, Next: C Compiler, Prev: Specific Compiler Characteristics, Up: Compilers and Preprocessors
5.10.2 Generic Compiler Characteristics
---------------------------------------
-- Macro: AC_CHECK_SIZEOF (TYPE-OR-EXPR, [UNUSED], [INCLUDES =
`AC_INCLUDES_DEFAULT'])
Define `SIZEOF_TYPE-OR-EXPR' (*note Standard Symbols::) to be the
size in bytes of TYPE-OR-EXPR, which may be either a type or an
expression returning a value that has a size. If the expression
`sizeof (TYPE-OR-EXPR)' is invalid, the result is 0. INCLUDES is
a series of include directives, defaulting to
`AC_INCLUDES_DEFAULT' (*note Default Includes::), which are used
prior to the expression under test.
This macro now works even when cross-compiling. The UNUSED
argument was used when cross-compiling.
For example, the call
AC_CHECK_SIZEOF([int *])
defines `SIZEOF_INT_P' to be 8 on DEC Alpha AXP systems.
-- Macro: AC_CHECK_ALIGNOF (TYPE, [INCLUDES = `AC_INCLUDES_DEFAULT'])
Define `ALIGNOF_TYPE' (*note Standard Symbols::) to be the
alignment in bytes of TYPE. `TYPE y;' must be valid as a
structure member declaration. If `type' is unknown, the result is
0. If no INCLUDES are specified, the default includes are used
(*note Default Includes::).
-- Macro: AC_COMPUTE_INT (VAR, EXPRESSION, [INCLUDES =
`AC_INCLUDES_DEFAULT'], [ACTION-IF-FAILS])
Store into the shell variable VAR the value of the integer
EXPRESSION. The value should fit in an initializer in a C
variable of type `signed long'. To support cross compilation (in
which case, the macro only works on hosts that use twos-complement
arithmetic), it should be possible to evaluate the expression at
compile-time. If no INCLUDES are specified, the default includes
are used (*note Default Includes::).
Execute ACTION-IF-FAILS if the value cannot be determined
correctly.
-- Macro: AC_LANG_WERROR
Normally Autoconf ignores warnings generated by the compiler,
linker, and preprocessor. If this macro is used, warnings count
as fatal errors for the current language. This macro is useful
when the results of configuration are used where warnings are
unacceptable; for instance, if parts of a program are built with
the GCC `-Werror' option. If the whole program is built using
`-Werror' it is often simpler to put `-Werror' in the compiler
flags (`CFLAGS', etc.).
-- Macro: AC_OPENMP
OpenMP (`http://www.openmp.org/') specifies extensions of C, C++,
and Fortran that simplify optimization of shared memory
parallelism, which is a common problem on multicore CPUs.
If the current language is C, the macro `AC_OPENMP' sets the
variable `OPENMP_CFLAGS' to the C compiler flags needed for
supporting OpenMP. `OPENMP_CFLAGS' is set to empty if the
compiler already supports OpenMP, if it has no way to activate
OpenMP support, or if the user rejects OpenMP support by invoking
`configure' with the `--disable-openmp' option.
`OPENMP_CFLAGS' needs to be used when compiling programs, when
preprocessing program source, and when linking programs.
Therefore you need to add `$(OPENMP_CFLAGS)' to the `CFLAGS' of C
programs that use OpenMP. If you preprocess OpenMP-specific C
code, you also need to add `$(OPENMP_CFLAGS)' to `CPPFLAGS'. The
presence of OpenMP support is revealed at compile time by the
preprocessor macro `_OPENMP'.
Linking a program with `OPENMP_CFLAGS' typically adds one more
shared library to the program's dependencies, so its use is
recommended only on programs that actually require OpenMP.
If the current language is C++, `AC_OPENMP' sets the variable
`OPENMP_CXXFLAGS', suitably for the C++ compiler. The same remarks
hold as for C.
If the current language is Fortran 77 or Fortran, `AC_OPENMP' sets
the variable `OPENMP_FFLAGS' or `OPENMP_FCFLAGS', respectively.
Similar remarks as for C hold, except that `CPPFLAGS' is not used
for Fortran, and no preprocessor macro signals OpenMP support.
For portability, it is best to avoid spaces between `#' and
`pragma omp'. That is, write `#pragma omp', not `# pragma omp'.
The Sun WorkShop 6.2 C compiler chokes on the latter.
File: autoconf.info, Node: C Compiler, Next: C++ Compiler, Prev: Generic Compiler Characteristics, Up: Compilers and Preprocessors
5.10.3 C Compiler Characteristics
---------------------------------
The following macros provide ways to find and exercise a C Compiler.
There are a few constructs that ought to be avoided, but do not deserve
being checked for, since they can easily be worked around.
Don't use lines containing solitary backslashes
They tickle a bug in the HP-UX C compiler (checked on HP-UX 10.20,
11.00, and 11i). When given the following source:
#ifdef __STDC__
/\
* A comment with backslash-newlines in it. %{ %} *\
\
/
char str[] = "\\
" A string with backslash-newlines in it %{ %} \\
"";
char apostrophe = '\\
\
'\
';
#endif
the compiler incorrectly fails with the diagnostics
"Non-terminating comment at end of file" and "Missing `#endif' at
end of file." Removing the lines with solitary backslashes solves
the problem.
Don't compile several files at once if output matters to you
Some compilers, such as HP's, report names of files being compiled
when given more than one file operand. For instance:
$ cc a.c b.c
a.c:
b.c:
This can cause problems if you observe the output of the compiler
to detect failures. Invoking `cc -c a.c && cc -c b.c && cc -o c
a.o b.o' solves the issue.
Don't rely on `#error' failing
The IRIX C compiler does not fail when #error is preprocessed; it
simply emits a diagnostic and continues, exiting successfully. So,
instead of an error directive like `#error "Unsupported word size"'
it is more portable to use an invalid directive like `#Unsupported
word size' in Autoconf tests. In ordinary source code, `#error' is
OK, since installers with inadequate compilers like IRIX can simply
examine these compilers' diagnostic output.
Don't rely on correct `#line' support
On Solaris, `c89' (at least Sun C 5.3 through 5.8) diagnoses
`#line' directives whose line numbers are greater than 32767.
Nothing in Posix makes this invalid. That is why Autoconf stopped
issuing `#line' directives.
-- Macro: AC_PROG_CC ([COMPILER-SEARCH-LIST])
Determine a C compiler to use. If `CC' is not already set in the
environment, check for `gcc' and `cc', then for other C compilers.
Set output variable `CC' to the name of the compiler found.
This macro may, however, be invoked with an optional first argument
which, if specified, must be a blank-separated list of C compilers
to search for. This just gives the user an opportunity to specify
an alternative search list for the C compiler. For example, if
you didn't like the default order, then you could invoke
`AC_PROG_CC' like this:
AC_PROG_CC([gcc cl cc])
If the C compiler does not handle function prototypes correctly by
default, try to add an option to output variable `CC' to make it
so. This macro tries various options that select
standard-conformance modes on various systems.
After calling this macro you can check whether the C compiler has
been set to accept ANSI C89 (ISO C90); if not, the shell variable
`ac_cv_prog_cc_c89' is set to `no'. See also `AC_C_PROTOTYPES'
below.
If using the GNU C compiler, set shell variable `GCC' to `yes'.
If output variable `CFLAGS' was not already set, set it to `-g
-O2' for the GNU C compiler (`-O2' on systems where GCC does not
accept `-g'), or `-g' for other compilers.
Many Autoconf macros use a compiler, and thus call
`AC_REQUIRE([AC_PROG_CC])' to ensure that the compiler has been
determined before the body of the outermost `AC_DEFUN' macro.
Although `AC_PROG_CC' is safe to directly expand multiple times, it
performs certain checks (such as the proper value of `EXEEXT') only
on the first invocation. Therefore, care must be used when
invoking this macro from within another macro rather than at the
top level (*note Expanded Before Required::).
-- Macro: AC_PROG_CC_C_O
If the C compiler does not accept the `-c' and `-o' options
simultaneously, define `NO_MINUS_C_MINUS_O'. This macro actually
tests both the compiler found by `AC_PROG_CC', and, if different,
the first `cc' in the path. The test fails if one fails. This
macro was created for GNU Make to choose the default C compilation
rule.
-- Macro: AC_PROG_CPP
Set output variable `CPP' to a command that runs the C
preprocessor. If `$CC -E' doesn't work, `/lib/cpp' is used. It
is only portable to run `CPP' on files with a `.c' extension.
Some preprocessors don't indicate missing include files by the
error status. For such preprocessors an internal variable is set
that causes other macros to check the standard error from the
preprocessor and consider the test failed if any warnings have
been reported. For most preprocessors, though, warnings do not
cause include-file tests to fail unless `AC_PROG_CPP_WERROR' is
also specified.
-- Macro: AC_PROG_CPP_WERROR
This acts like `AC_PROG_CPP', except it treats warnings from the
preprocessor as errors even if the preprocessor exit status
indicates success. This is useful for avoiding headers that
generate mandatory warnings, such as deprecation notices.
The following macros check for C compiler or machine architecture
features. To check for characteristics not listed here, use
`AC_COMPILE_IFELSE' (*note Running the Compiler::) or `AC_RUN_IFELSE'
(*note Runtime::).
-- Macro: AC_PROG_CC_STDC
If the C compiler cannot compile ISO Standard C (currently C99),
try to add an option to output variable `CC' to make it work. If
the compiler does not support C99, fall back to supporting ANSI
C89 (ISO C90).
After calling this macro you can check whether the C compiler has
been set to accept Standard C; if not, the shell variable
`ac_cv_prog_cc_stdc' is set to `no'.
-- Macro: AC_PROG_CC_C89
If the C compiler is not in ANSI C89 (ISO C90) mode by default,
try to add an option to output variable `CC' to make it so. This
macro tries various options that select ANSI C89 on some system or
another, preferring extended functionality modes over strict
conformance modes. It considers the compiler to be in ANSI C89
mode if it handles function prototypes correctly.
After calling this macro you can check whether the C compiler has
been set to accept ANSI C89; if not, the shell variable
`ac_cv_prog_cc_c89' is set to `no'.
This macro is called automatically by `AC_PROG_CC'.
-- Macro: AC_PROG_CC_C99
If the C compiler is not in C99 mode by default, try to add an
option to output variable `CC' to make it so. This macro tries
various options that select C99 on some system or another,
preferring extended functionality modes over strict conformance
modes. It considers the compiler to be in C99 mode if it handles
`_Bool', `//' comments, flexible array members, `inline', signed
and unsigned `long long int', mixed code and declarations, named
initialization of structs, `restrict', `va_copy', varargs macros,
variable declarations in `for' loops, and variable length arrays.
After calling this macro you can check whether the C compiler has
been set to accept C99; if not, the shell variable
`ac_cv_prog_cc_c99' is set to `no'.
-- Macro: AC_C_BACKSLASH_A
Define `HAVE_C_BACKSLASH_A' to 1 if the C compiler understands
`\a'.
This macro is obsolescent, as current C compilers understand `\a'.
New programs need not use this macro.
-- Macro: AC_C_BIGENDIAN ([ACTION-IF-TRUE], [ACTION-IF-FALSE],
[ACTION-IF-UNKNOWN], [ACTION-IF-UNIVERSAL])
If words are stored with the most significant byte first (like
Motorola and SPARC CPUs), execute ACTION-IF-TRUE. If words are
stored with the least significant byte first (like Intel and VAX
CPUs), execute ACTION-IF-FALSE.
This macro runs a test-case if endianness cannot be determined
from the system header files. When cross-compiling, the test-case
is not run but grep'ed for some magic values. ACTION-IF-UNKNOWN
is executed if the latter case fails to determine the byte sex of
the host system.
In some cases a single run of a compiler can generate code for
multiple architectures. This can happen, for example, when
generating Mac OS X universal binary files, which work on both
PowerPC and Intel architectures. In this case, the different
variants might be for different architectures whose endiannesses
differ. If `configure' detects this, it executes
ACTION-IF-UNIVERSAL instead of ACTION-IF-UNKNOWN.
The default for ACTION-IF-TRUE is to define `WORDS_BIGENDIAN'.
The default for ACTION-IF-FALSE is to do nothing. The default for
ACTION-IF-UNKNOWN is to abort configure and tell the installer how
to bypass this test. And finally, the default for
ACTION-IF-UNIVERSAL is to ensure that `WORDS_BIGENDIAN' is defined
if and only if a universal build is detected and the current code
is big-endian; this default works only if `autoheader' is used
(*note autoheader Invocation::).
If you use this macro without specifying ACTION-IF-UNIVERSAL, you
should also use `AC_CONFIG_HEADERS'; otherwise `WORDS_BIGENDIAN'
may be set incorrectly for Mac OS X universal binary files.
-- Macro: AC_C_CONST
If the C compiler does not fully support the `const' keyword,
define `const' to be empty. Some C compilers that do not define
`__STDC__' do support `const'; some compilers that define
`__STDC__' do not completely support `const'. Programs can simply
use `const' as if every C compiler supported it; for those that
don't, the makefile or configuration header file defines it as
empty.
Occasionally installers use a C++ compiler to compile C code,
typically because they lack a C compiler. This causes problems
with `const', because C and C++ treat `const' differently. For
example:
const int foo;
is valid in C but not in C++. These differences unfortunately
cannot be papered over by defining `const' to be empty.
If `autoconf' detects this situation, it leaves `const' alone, as
this generally yields better results in practice. However, using a
C++ compiler to compile C code is not recommended or supported, and
installers who run into trouble in this area should get a C
compiler like GCC to compile their C code.
This macro is obsolescent, as current C compilers support `const'.
New programs need not use this macro.
-- Macro: AC_C_RESTRICT
If the C compiler recognizes a variant spelling for the `restrict'
keyword (`__restrict', `__restrict__', or `_Restrict'), then
define `restrict' to that; this is more likely to do the right
thing with compilers that support language variants where plain
`restrict' is not a keyword. Otherwise, if the C compiler
recognizes the `restrict' keyword, don't do anything. Otherwise,
define `restrict' to be empty. Thus, programs may simply use
`restrict' as if every C compiler supported it; for those that do
not, the makefile or configuration header defines it away.
Although support in C++ for the `restrict' keyword is not
required, several C++ compilers do accept the keyword. This macro
works for them, too.
-- Macro: AC_C_VOLATILE
If the C compiler does not understand the keyword `volatile',
define `volatile' to be empty. Programs can simply use `volatile'
as if every C compiler supported it; for those that do not, the
makefile or configuration header defines it as empty.
If the correctness of your program depends on the semantics of
`volatile', simply defining it to be empty does, in a sense, break
your code. However, given that the compiler does not support
`volatile', you are at its mercy anyway. At least your program
compiles, when it wouldn't before. *Note Volatile Objects::, for
more about `volatile'.
In general, the `volatile' keyword is a standard C feature, so you
might expect that `volatile' is available only when `__STDC__' is
defined. However, Ultrix 4.3's native compiler does support
volatile, but does not define `__STDC__'.
This macro is obsolescent, as current C compilers support
`volatile'. New programs need not use this macro.
-- Macro: AC_C_INLINE
If the C compiler supports the keyword `inline', do nothing.
Otherwise define `inline' to `__inline__' or `__inline' if it
accepts one of those, otherwise define `inline' to be empty.
-- Macro: AC_C_CHAR_UNSIGNED
If the C type `char' is unsigned, define `__CHAR_UNSIGNED__',
unless the C compiler predefines it.
These days, using this macro is not necessary. The same
information can be determined by this portable alternative, thus
avoiding the use of preprocessor macros in the namespace reserved
for the implementation.
#include
#if CHAR_MIN == 0
# define CHAR_UNSIGNED 1
#endif
-- Macro: AC_C_STRINGIZE
If the C preprocessor supports the stringizing operator, define
`HAVE_STRINGIZE'. The stringizing operator is `#' and is found in
macros such as this:
#define x(y) #y
This macro is obsolescent, as current C compilers support the
stringizing operator. New programs need not use this macro.
-- Macro: AC_C_FLEXIBLE_ARRAY_MEMBER
If the C compiler supports flexible array members, define
`FLEXIBLE_ARRAY_MEMBER' to nothing; otherwise define it to 1.
That way, a declaration like this:
struct s
{
size_t n_vals;
double val[FLEXIBLE_ARRAY_MEMBER];
};
will let applications use the "struct hack" even with compilers
that do not support flexible array members. To allocate and use
such an object, you can use code like this:
size_t i;
size_t n = compute_value_count ();
struct s *p =
malloc (offsetof (struct s, val)
+ n * sizeof (double));
p->n_vals = n;
for (i = 0; i < n; i++)
p->val[i] = compute_value (i);
-- Macro: AC_C_VARARRAYS
If the C compiler supports variable-length arrays, define
`HAVE_C_VARARRAYS'. A variable-length array is an array of
automatic storage duration whose length is determined at run time,
when the array is declared.
-- Macro: AC_C_TYPEOF
If the C compiler supports GCC's `typeof' syntax either directly or
through a different spelling of the keyword (e.g., `__typeof__'),
define `HAVE_TYPEOF'. If the support is available only through a
different spelling, define `typeof' to that spelling.
-- Macro: AC_C_PROTOTYPES
If function prototypes are understood by the compiler (as
determined by `AC_PROG_CC'), define `PROTOTYPES' and
`__PROTOTYPES'. Defining `__PROTOTYPES' is for the benefit of
header files that cannot use macros that infringe on user name
space.
This macro is obsolescent, as current C compilers support
prototypes. New programs need not use this macro.
-- Macro: AC_PROG_GCC_TRADITIONAL
Add `-traditional' to output variable `CC' if using the GNU C
compiler and `ioctl' does not work properly without
`-traditional'. That usually happens when the fixed header files
have not been installed on an old system.
This macro is obsolescent, since current versions of the GNU C
compiler fix the header files automatically when installed.
File: autoconf.info, Node: C++ Compiler, Next: Objective C Compiler, Prev: C Compiler, Up: Compilers and Preprocessors
5.10.4 C++ Compiler Characteristics
-----------------------------------
-- Macro: AC_PROG_CXX ([COMPILER-SEARCH-LIST])
Determine a C++ compiler to use. Check whether the environment
variable `CXX' or `CCC' (in that order) is set; if so, then set
output variable `CXX' to its value.
Otherwise, if the macro is invoked without an argument, then
search for a C++ compiler under the likely names (first `g++' and
`c++' then other names). If none of those checks succeed, then as
a last resort set `CXX' to `g++'.
This macro may, however, be invoked with an optional first argument
which, if specified, must be a blank-separated list of C++
compilers to search for. This just gives the user an opportunity
to specify an alternative search list for the C++ compiler. For
example, if you didn't like the default order, then you could
invoke `AC_PROG_CXX' like this:
AC_PROG_CXX([gcc cl KCC CC cxx cc++ xlC aCC c++ g++])
If using the GNU C++ compiler, set shell variable `GXX' to `yes'.
If output variable `CXXFLAGS' was not already set, set it to `-g
-O2' for the GNU C++ compiler (`-O2' on systems where G++ does not
accept `-g'), or `-g' for other compilers.
-- Macro: AC_PROG_CXXCPP
Set output variable `CXXCPP' to a command that runs the C++
preprocessor. If `$CXX -E' doesn't work, `/lib/cpp' is used. It
is portable to run `CXXCPP' only on files with a `.c', `.C',
`.cc', or `.cpp' extension.
Some preprocessors don't indicate missing include files by the
error status. For such preprocessors an internal variable is set
that causes other macros to check the standard error from the
preprocessor and consider the test failed if any warnings have
been reported. However, it is not known whether such broken
preprocessors exist for C++.
-- Macro: AC_PROG_CXX_C_O
Test whether the C++ compiler accepts the options `-c' and `-o'
simultaneously, and define `CXX_NO_MINUS_C_MINUS_O', if it does
not.
File: autoconf.info, Node: Objective C Compiler, Next: Erlang Compiler and Interpreter, Prev: C++ Compiler, Up: Compilers and Preprocessors
5.10.5 Objective C Compiler Characteristics
-------------------------------------------
-- Macro: AC_PROG_OBJC ([COMPILER-SEARCH-LIST])
Determine an Objective C compiler to use. If `OBJC' is not already
set in the environment, check for Objective C compilers. Set
output variable `OBJC' to the name of the compiler found.
This macro may, however, be invoked with an optional first argument
which, if specified, must be a blank-separated list of Objective C
compilers to search for. This just gives the user an opportunity
to specify an alternative search list for the Objective C
compiler. For example, if you didn't like the default order, then
you could invoke `AC_PROG_OBJC' like this:
AC_PROG_OBJC([gcc objcc objc])
If using the GNU Objective C compiler, set shell variable `GOBJC'
to `yes'. If output variable `OBJCFLAGS' was not already set, set
it to `-g -O2' for the GNU Objective C compiler (`-O2' on systems
where `gcc' does not accept `-g'), or `-g' for other compilers.
-- Macro: AC_PROG_OBJCPP
Set output variable `OBJCPP' to a command that runs the Objective C
preprocessor. If `$OBJC -E' doesn't work, `/lib/cpp' is used.
File: autoconf.info, Node: Erlang Compiler and Interpreter, Next: Fortran Compiler, Prev: Objective C Compiler, Up: Compilers and Preprocessors
5.10.6 Erlang Compiler and Interpreter Characteristics
------------------------------------------------------
Autoconf defines the following macros for determining paths to the
essential Erlang/OTP programs:
-- Macro: AC_ERLANG_PATH_ERLC ([VALUE-IF-NOT-FOUND], [PATH = `$PATH'])
Determine an Erlang compiler to use. If `ERLC' is not already set
in the environment, check for `erlc'. Set output variable `ERLC'
to the complete path of the compiler command found. In addition,
if `ERLCFLAGS' is not set in the environment, set it to an empty
value.
The two optional arguments have the same meaning as the two last
arguments of macro `AC_PROG_PATH' for looking for the `erlc'
program. For example, to look for `erlc' only in the
`/usr/lib/erlang/bin' directory:
AC_ERLANG_PATH_ERLC([not found], [/usr/lib/erlang/bin])
-- Macro: AC_ERLANG_NEED_ERLC ([PATH = `$PATH'])
A simplified variant of the `AC_ERLANG_PATH_ERLC' macro, that
prints an error message and exits the `configure' script if the
`erlc' program is not found.
-- Macro: AC_ERLANG_PATH_ERL ([VALUE-IF-NOT-FOUND], [PATH = `$PATH'])
Determine an Erlang interpreter to use. If `ERL' is not already
set in the environment, check for `erl'. Set output variable
`ERL' to the complete path of the interpreter command found.
The two optional arguments have the same meaning as the two last
arguments of macro `AC_PROG_PATH' for looking for the `erl'
program. For example, to look for `erl' only in the
`/usr/lib/erlang/bin' directory:
AC_ERLANG_PATH_ERL([not found], [/usr/lib/erlang/bin])
-- Macro: AC_ERLANG_NEED_ERL ([PATH = `$PATH'])
A simplified variant of the `AC_ERLANG_PATH_ERL' macro, that
prints an error message and exits the `configure' script if the
`erl' program is not found.
File: autoconf.info, Node: Fortran Compiler, Prev: Erlang Compiler and Interpreter, Up: Compilers and Preprocessors
5.10.7 Fortran Compiler Characteristics
---------------------------------------
The Autoconf Fortran support is divided into two categories: legacy
Fortran 77 macros (`F77'), and modern Fortran macros (`FC'). The
former are intended for traditional Fortran 77 code, and have output
variables like `F77', `FFLAGS', and `FLIBS'. The latter are for newer
programs that can (or must) compile under the newer Fortran standards,
and have output variables like `FC', `FCFLAGS', and `FCLIBS'.
Except for two new macros `AC_FC_SRCEXT' and `AC_FC_FREEFORM' (see
below), the `FC' and `F77' macros behave almost identically, and so
they are documented together in this section.
-- Macro: AC_PROG_F77 ([COMPILER-SEARCH-LIST])
Determine a Fortran 77 compiler to use. If `F77' is not already
set in the environment, then check for `g77' and `f77', and then
some other names. Set the output variable `F77' to the name of
the compiler found.
This macro may, however, be invoked with an optional first argument
which, if specified, must be a blank-separated list of Fortran 77
compilers to search for. This just gives the user an opportunity
to specify an alternative search list for the Fortran 77 compiler.
For example, if you didn't like the default order, then you could
invoke `AC_PROG_F77' like this:
AC_PROG_F77([fl32 f77 fort77 xlf g77 f90 xlf90])
If using `g77' (the GNU Fortran 77 compiler), then set the shell
variable `G77' to `yes'. If the output variable `FFLAGS' was not
already set in the environment, then set it to `-g -02' for `g77'
(or `-O2' where `g77' does not accept `-g'). Otherwise, set
`FFLAGS' to `-g' for all other Fortran 77 compilers.
-- Macro: AC_PROG_FC ([COMPILER-SEARCH-LIST], [DIALECT])
Determine a Fortran compiler to use. If `FC' is not already set in
the environment, then `dialect' is a hint to indicate what Fortran
dialect to search for; the default is to search for the newest
available dialect. Set the output variable `FC' to the name of
the compiler found.
By default, newer dialects are preferred over older dialects, but
if `dialect' is specified then older dialects are preferred
starting with the specified dialect. `dialect' can currently be
one of Fortran 77, Fortran 90, or Fortran 95. However, this is
only a hint of which compiler _name_ to prefer (e.g., `f90' or
`f95'), and no attempt is made to guarantee that a particular
language standard is actually supported. Thus, it is preferable
that you avoid the `dialect' option, and use AC_PROG_FC only for
code compatible with the latest Fortran standard.
This macro may, alternatively, be invoked with an optional first
argument which, if specified, must be a blank-separated list of
Fortran compilers to search for, just as in `AC_PROG_F77'.
If the output variable `FCFLAGS' was not already set in the
environment, then set it to `-g -02' for GNU `g77' (or `-O2' where
`g77' does not accept `-g'). Otherwise, set `FCFLAGS' to `-g' for
all other Fortran compilers.
-- Macro: AC_PROG_F77_C_O
-- Macro: AC_PROG_FC_C_O
Test whether the Fortran compiler accepts the options `-c' and
`-o' simultaneously, and define `F77_NO_MINUS_C_MINUS_O' or
`FC_NO_MINUS_C_MINUS_O', respectively, if it does not.
The following macros check for Fortran compiler characteristics. To
check for characteristics not listed here, use `AC_COMPILE_IFELSE'
(*note Running the Compiler::) or `AC_RUN_IFELSE' (*note Runtime::),
making sure to first set the current language to Fortran 77 or Fortran
via `AC_LANG([Fortran 77])' or `AC_LANG(Fortran)' (*note Language
Choice::).
-- Macro: AC_F77_LIBRARY_LDFLAGS
-- Macro: AC_FC_LIBRARY_LDFLAGS
Determine the linker flags (e.g., `-L' and `-l') for the "Fortran
intrinsic and runtime libraries" that are required to successfully
link a Fortran program or shared library. The output variable
`FLIBS' or `FCLIBS' is set to these flags (which should be
included after `LIBS' when linking).
This macro is intended to be used in those situations when it is
necessary to mix, e.g., C++ and Fortran source code in a single
program or shared library (*note Mixing Fortran 77 With C and C++:
(automake)Mixing Fortran 77 With C and C++.).
For example, if object files from a C++ and Fortran compiler must
be linked together, then the C++ compiler/linker must be used for
linking (since special C++-ish things need to happen at link time
like calling global constructors, instantiating templates,
enabling exception support, etc.).
However, the Fortran intrinsic and runtime libraries must be
linked in as well, but the C++ compiler/linker doesn't know by
default how to add these Fortran 77 libraries. Hence, this macro
was created to determine these Fortran libraries.
The macros `AC_F77_DUMMY_MAIN' and `AC_FC_DUMMY_MAIN' or
`AC_F77_MAIN' and `AC_FC_MAIN' are probably also necessary to link
C/C++ with Fortran; see below.
-- Macro: AC_F77_DUMMY_MAIN ([ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
-- Macro: AC_FC_DUMMY_MAIN ([ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
With many compilers, the Fortran libraries detected by
`AC_F77_LIBRARY_LDFLAGS' or `AC_FC_LIBRARY_LDFLAGS' provide their
own `main' entry function that initializes things like Fortran
I/O, and which then calls a user-provided entry function named
(say) `MAIN__' to run the user's program. The `AC_F77_DUMMY_MAIN'
and `AC_FC_DUMMY_MAIN' or `AC_F77_MAIN' and `AC_FC_MAIN' macros
figure out how to deal with this interaction.
When using Fortran for purely numerical functions (no I/O, etc.)
often one prefers to provide one's own `main' and skip the Fortran
library initializations. In this case, however, one may still
need to provide a dummy `MAIN__' routine in order to prevent
linking errors on some systems. `AC_F77_DUMMY_MAIN' or
`AC_FC_DUMMY_MAIN' detects whether any such routine is _required_
for linking, and what its name is; the shell variable
`F77_DUMMY_MAIN' or `FC_DUMMY_MAIN' holds this name, `unknown'
when no solution was found, and `none' when no such dummy main is
needed.
By default, ACTION-IF-FOUND defines `F77_DUMMY_MAIN' or
`FC_DUMMY_MAIN' to the name of this routine (e.g., `MAIN__') _if_
it is required. ACTION-IF-NOT-FOUND defaults to exiting with an
error.
In order to link with Fortran routines, the user's C/C++ program
should then include the following code to define the dummy main if
it is needed:
#ifdef F77_DUMMY_MAIN
# ifdef __cplusplus
extern "C"
# endif
int F77_DUMMY_MAIN() { return 1; }
#endif
(Replace `F77' with `FC' for Fortran instead of Fortran 77.)
Note that this macro is called automatically from `AC_F77_WRAPPERS'
or `AC_FC_WRAPPERS'; there is generally no need to call it
explicitly unless one wants to change the default actions.
-- Macro: AC_F77_MAIN
-- Macro: AC_FC_MAIN
As discussed above, many Fortran libraries allow you to provide an
entry point called (say) `MAIN__' instead of the usual `main',
which is then called by a `main' function in the Fortran libraries
that initializes things like Fortran I/O. The `AC_F77_MAIN' and
`AC_FC_MAIN' macros detect whether it is _possible_ to utilize
such an alternate main function, and defines `F77_MAIN' and
`FC_MAIN' to the name of the function. (If no alternate main
function name is found, `F77_MAIN' and `FC_MAIN' are simply
defined to `main'.)
Thus, when calling Fortran routines from C that perform things
like I/O, one should use this macro and declare the "main"
function like so:
#ifdef __cplusplus
extern "C"
#endif
int F77_MAIN(int argc, char *argv[]);
(Again, replace `F77' with `FC' for Fortran instead of Fortran 77.)
-- Macro: AC_F77_WRAPPERS
-- Macro: AC_FC_WRAPPERS
Defines C macros `F77_FUNC (name, NAME)', `FC_FUNC (name, NAME)',
`F77_FUNC_(name, NAME)', and `FC_FUNC_(name, NAME)' to properly
mangle the names of C/C++ identifiers, and identifiers with
underscores, respectively, so that they match the name-mangling
scheme used by the Fortran compiler.
Fortran is case-insensitive, and in order to achieve this the
Fortran compiler converts all identifiers into a canonical case
and format. To call a Fortran subroutine from C or to write a C
function that is callable from Fortran, the C program must
explicitly use identifiers in the format expected by the Fortran
compiler. In order to do this, one simply wraps all C identifiers
in one of the macros provided by `AC_F77_WRAPPERS' or
`AC_FC_WRAPPERS'. For example, suppose you have the following
Fortran 77 subroutine:
subroutine foobar (x, y)
double precision x, y
y = 3.14159 * x
return
end
You would then declare its prototype in C or C++ as:
#define FOOBAR_F77 F77_FUNC (foobar, FOOBAR)
#ifdef __cplusplus
extern "C" /* prevent C++ name mangling */
#endif
void FOOBAR_F77(double *x, double *y);
Note that we pass both the lowercase and uppercase versions of the
function name to `F77_FUNC' so that it can select the right one.
Note also that all parameters to Fortran 77 routines are passed as
pointers (*note Mixing Fortran 77 With C and C++: (automake)Mixing
Fortran 77 With C and C++.).
(Replace `F77' with `FC' for Fortran instead of Fortran 77.)
Although Autoconf tries to be intelligent about detecting the
name-mangling scheme of the Fortran compiler, there may be Fortran
compilers that it doesn't support yet. In this case, the above
code generates a compile-time error, but some other behavior
(e.g., disabling Fortran-related features) can be induced by
checking whether `F77_FUNC' or `FC_FUNC' is defined.
Now, to call that routine from a C program, we would do something
like:
{
double x = 2.7183, y;
FOOBAR_F77 (&x, &y);
}
If the Fortran identifier contains an underscore (e.g., `foo_bar'),
you should use `F77_FUNC_' or `FC_FUNC_' instead of `F77_FUNC' or
`FC_FUNC' (with the same arguments). This is because some Fortran
compilers mangle names differently if they contain an underscore.
-- Macro: AC_F77_FUNC (NAME, [SHELLVAR])
-- Macro: AC_FC_FUNC (NAME, [SHELLVAR])
Given an identifier NAME, set the shell variable SHELLVAR to hold
the mangled version NAME according to the rules of the Fortran
linker (see also `AC_F77_WRAPPERS' or `AC_FC_WRAPPERS'). SHELLVAR
is optional; if it is not supplied, the shell variable is simply
NAME. The purpose of this macro is to give the caller a way to
access the name-mangling information other than through the C
preprocessor as above, for example, to call Fortran routines from
some language other than C/C++.
-- Macro: AC_FC_SRCEXT (EXT, [ACTION-IF-SUCCESS], [ACTION-IF-FAILURE])
By default, the `FC' macros perform their tests using a `.f'
extension for source-code files. Some compilers, however, only
enable newer language features for appropriately named files,
e.g., Fortran 90 features only for `.f90' files. On the other
hand, some other compilers expect all source files to end in `.f'
and require special flags to support other file name extensions.
The `AC_FC_SRCEXT' macro deals with both of these issues.
The `AC_FC_SRCEXT' tries to get the `FC' compiler to accept files
ending with the extension .EXT (i.e., EXT does _not_ contain the
dot). If any special compiler flags are needed for this, it
stores them in the output variable `FCFLAGS_'EXT. This extension
and these flags are then used for all subsequent `FC' tests (until
`AC_FC_SRCEXT' is called again).
For example, you would use `AC_FC_SRCEXT(f90)' to employ the
`.f90' extension in future tests, and it would set the
`FCFLAGS_f90' output variable with any extra flags that are needed
to compile such files.
The `FCFLAGS_'EXT can _not_ be simply absorbed into `FCFLAGS', for
two reasons based on the limitations of some compilers. First,
only one `FCFLAGS_'EXT can be used at a time, so files with
different extensions must be compiled separately. Second,
`FCFLAGS_'EXT must appear _immediately_ before the source-code
file name when compiling. So, continuing the example above, you
might compile a `foo.f90' file in your makefile with the command:
foo.o: foo.f90
$(FC) -c $(FCFLAGS) $(FCFLAGS_f90) '$(srcdir)/foo.f90'
If `AC_FC_SRCEXT' succeeds in compiling files with the EXT
extension, it calls ACTION-IF-SUCCESS (defaults to nothing). If
it fails, and cannot find a way to make the `FC' compiler accept
such files, it calls ACTION-IF-FAILURE (defaults to exiting with an
error message).
-- Macro: AC_FC_FREEFORM ([ACTION-IF-SUCCESS], [ACTION-IF-FAILURE])
The `AC_FC_FREEFORM' tries to ensure that the Fortran compiler
(`$FC') allows free-format source code (as opposed to the older
fixed-format style from Fortran 77). If necessary, it may add some
additional flags to `FCFLAGS'.
This macro is most important if you are using the default `.f'
extension, since many compilers interpret this extension as
indicating fixed-format source unless an additional flag is
supplied. If you specify a different extension with
`AC_FC_SRCEXT', such as `.f90' or `.f95', then `AC_FC_FREEFORM'
ordinarily succeeds without modifying `FCFLAGS'.
If `AC_FC_FREEFORM' succeeds in compiling free-form source, it
calls ACTION-IF-SUCCESS (defaults to nothing). If it fails, it
calls ACTION-IF-FAILURE (defaults to exiting with an error
message).
File: autoconf.info, Node: System Services, Next: Posix Variants, Prev: Compilers and Preprocessors, Up: Existing Tests
5.11 System Services
====================
The following macros check for operating system services or
capabilities.
-- Macro: AC_PATH_X
Try to locate the X Window System include files and libraries. If
the user gave the command line options `--x-includes=DIR' and
`--x-libraries=DIR', use those directories.
If either or both were not given, get the missing values by running
`xmkmf' (or an executable pointed to by the `XMKMF' environment
variable) on a trivial `Imakefile' and examining the makefile that
it produces. Setting `XMKMF' to `false' disables this method.
If this method fails to find the X Window System, `configure'
looks for the files in several directories where they often reside.
If either method is successful, set the shell variables
`x_includes' and `x_libraries' to their locations, unless they are
in directories the compiler searches by default.
If both methods fail, or the user gave the command line option
`--without-x', set the shell variable `no_x' to `yes'; otherwise
set it to the empty string.
-- Macro: AC_PATH_XTRA
An enhanced version of `AC_PATH_X'. It adds the C compiler flags
that X needs to output variable `X_CFLAGS', and the X linker flags
to `X_LIBS'. Define `X_DISPLAY_MISSING' if X is not available.
This macro also checks for special libraries that some systems
need in order to compile X programs. It adds any that the system
needs to output variable `X_EXTRA_LIBS'. And it checks for
special X11R6 libraries that need to be linked with before
`-lX11', and adds any found to the output variable `X_PRE_LIBS'.
-- Macro: AC_SYS_INTERPRETER
Check whether the system supports starting scripts with a line of
the form `#!/bin/sh' to select the interpreter to use for the
script. After running this macro, shell code in `configure.ac'
can check the shell variable `interpval'; it is set to `yes' if
the system supports `#!', `no' if not.
-- Macro: AC_SYS_LARGEFILE
Arrange for 64-bit file offsets, known as large-file support
(http://www.unix-systems.org/version2/whatsnew/lfs20mar.html). On
some hosts, one must use special compiler options to build
programs that can access large files. Append any such options to
the output variable `CC'. Define `_FILE_OFFSET_BITS' and
`_LARGE_FILES' if necessary.
Large-file support can be disabled by configuring with the
`--disable-largefile' option.
If you use this macro, check that your program works even when
`off_t' is wider than `long int', since this is common when
large-file support is enabled. For example, it is not correct to
print an arbitrary `off_t' value `X' with `printf ("%ld", (long
int) X)'.
The LFS introduced the `fseeko' and `ftello' functions to replace
their C counterparts `fseek' and `ftell' that do not use `off_t'.
Take care to use `AC_FUNC_FSEEKO' to make their prototypes
available when using them and large-file support is enabled.
-- Macro: AC_SYS_LONG_FILE_NAMES
If the system supports file names longer than 14 characters, define
`HAVE_LONG_FILE_NAMES'.
-- Macro: AC_SYS_POSIX_TERMIOS
Check to see if the Posix termios headers and functions are
available on the system. If so, set the shell variable
`ac_cv_sys_posix_termios' to `yes'. If not, set the variable to
`no'.
File: autoconf.info, Node: Posix Variants, Next: Erlang Libraries, Prev: System Services, Up: Existing Tests
5.12 Posix Variants
===================
The following macro makes it possible to use features of Posix that are
extensions to C, as well as platform extensions not defined by Posix.
-- Macro: AC_USE_SYSTEM_EXTENSIONS
This macro was introduced in Autoconf 2.60. If possible, enable
extensions to C or Posix on hosts that normally disable the
extensions, typically due to standards-conformance namespace
issues. This should be called before any macros that run the C
compiler. The following preprocessor macros are defined where
appropriate:
`_GNU_SOURCE'
Enable extensions on GNU/Linux.
`__EXTENSIONS__'
Enable general extensions on Solaris.
`_POSIX_PTHREAD_SEMANTICS'
Enable threading extensions on Solaris.
`_TANDEM_SOURCE'
Enable extensions for the HP NonStop platform.
`_ALL_SOURCE'
Enable extensions for AIX 3, and for Interix.
`_POSIX_SOURCE'
Enable Posix functions for Minix.
`_POSIX_1_SOURCE'
Enable additional Posix functions for Minix.
`_MINIX'
Identify Minix platform. This particular preprocessor macro
is obsolescent, and may be removed in a future release of
Autoconf.
File: autoconf.info, Node: Erlang Libraries, Prev: Posix Variants, Up: Existing Tests
5.13 Erlang Libraries
=====================
The following macros check for an installation of Erlang/OTP, and for
the presence of certain Erlang libraries. All those macros require the
configuration of an Erlang interpreter and an Erlang compiler (*note
Erlang Compiler and Interpreter::).
-- Macro: AC_ERLANG_SUBST_ERTS_VER
Set the output variable `ERLANG_ERTS_VER' to the version of the
Erlang runtime system (as returned by Erlang's
`erlang:system_info(version)' function). The result of this test
is cached if caching is enabled when running `configure'. The
`ERLANG_ERTS_VER' variable is not intended to be used for testing
for features of specific ERTS versions, but to be used for
substituting the ERTS version in Erlang/OTP release resource files
(`.rel' files), as shown below.
-- Macro: AC_ERLANG_SUBST_ROOT_DIR
Set the output variable `ERLANG_ROOT_DIR' to the path to the base
directory in which Erlang/OTP is installed (as returned by Erlang's
`code:root_dir/0' function). The result of this test is cached if
caching is enabled when running `configure'.
-- Macro: AC_ERLANG_SUBST_LIB_DIR
Set the output variable `ERLANG_LIB_DIR' to the path of the library
directory of Erlang/OTP (as returned by Erlang's `code:lib_dir/0'
function), which subdirectories each contain an installed
Erlang/OTP library. The result of this test is cached if caching
is enabled when running `configure'.
-- Macro: AC_ERLANG_CHECK_LIB (LIBRARY, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND])
Test whether the Erlang/OTP library LIBRARY is installed by
calling Erlang's `code:lib_dir/1' function. The result of this
test is cached if caching is enabled when running `configure'.
ACTION-IF-FOUND is a list of shell commands to run if the library
is installed; ACTION-IF-NOT-FOUND is a list of shell commands to
run if it is not. Additionally, if the library is installed, the
output variable `ERLANG_LIB_DIR_LIBRARY' is set to the path to the
library installation directory, and the output variable
`ERLANG_LIB_VER_LIBRARY' is set to the version number that is part
of the subdirectory name, if it is in the standard form
(`LIBRARY-VERSION'). If the directory name does not have a
version part, `ERLANG_LIB_VER_LIBRARY' is set to the empty string.
If the library is not installed, `ERLANG_LIB_DIR_LIBRARY' and
`ERLANG_LIB_VER_LIBRARY' are set to `"not found"'. For example,
to check if library `stdlib' is installed:
AC_ERLANG_CHECK_LIB([stdlib],
[echo "stdlib version \"$ERLANG_LIB_VER_stdlib\""
echo "is installed in \"$ERLANG_LIB_DIR_stdlib\""],
[AC_MSG_ERROR([stdlib was not found!])])
The `ERLANG_LIB_VER_LIBRARY' variables (set by
`AC_ERLANG_CHECK_LIB') and the `ERLANG_ERTS_VER' variable (set by
`AC_ERLANG_SUBST_ERTS_VER') are not intended to be used for
testing for features of specific versions of libraries or of the
Erlang runtime system. Those variables are intended to be
substituted in Erlang release resource files (`.rel' files). For
instance, to generate a `example.rel' file for an application
depending on the `stdlib' library, `configure.ac' could contain:
AC_ERLANG_SUBST_ERTS_VER
AC_ERLANG_CHECK_LIB([stdlib],
[],
[AC_MSG_ERROR([stdlib was not found!])])
AC_CONFIG_FILES([example.rel])
The `example.rel.in' file used to generate `example.rel' should
contain:
{release,
{"@PACKAGE@", "@VERSION@"},
{erts, "@ERLANG_ERTS_VER@"},
[{stdlib, "@ERLANG_LIB_VER_stdlib@"},
{@PACKAGE@, "@VERSION@"}]}.
In addition to the above macros, which test installed Erlang
libraries, the following macros determine the paths to the directories
into which newly built Erlang libraries are to be installed:
-- Macro: AC_ERLANG_SUBST_INSTALL_LIB_DIR
Set the `ERLANG_INSTALL_LIB_DIR' output variable to the directory
into which every built Erlang library should be installed in a
separate subdirectory. If this variable is not set in the
environment when `configure' runs, its default value is
`$ERLANG_LIB_DIR', which value is set by the
`AC_ERLANG_SUBST_LIB_DIR' macro.
-- Macro: AC_ERLANG_SUBST_INSTALL_LIB_SUBDIR (LIBRARY, VERSION)
Set the `ERLANG_INSTALL_LIB_DIR_LIBRARY' output variable to the
directory into which the built Erlang library LIBRARY version
VERSION should be installed. If this variable is not set in the
environment when `configure' runs, its default value is
`$ERLANG_INSTALL_LIB_DIR/LIBRARY-VERSION', the value of the
`ERLANG_INSTALL_LIB_DIR' variable being set by the
`AC_ERLANG_SUBST_INSTALL_LIB_DIR' macro.
File: autoconf.info, Node: Writing Tests, Next: Results, Prev: Existing Tests, Up: Top
6 Writing Tests
***************
If the existing feature tests don't do something you need, you have to
write new ones. These macros are the building blocks. They provide
ways for other macros to check whether various kinds of features are
available and report the results.
This chapter contains some suggestions and some of the reasons why
the existing tests are written the way they are. You can also learn a
lot about how to write Autoconf tests by looking at the existing ones.
If something goes wrong in one or more of the Autoconf tests, this
information can help you understand the assumptions behind them, which
might help you figure out how to best solve the problem.
These macros check the output of the compiler system of the current
language (*note Language Choice::). They do not cache the results of
their tests for future use (*note Caching Results::), because they don't
know enough about the information they are checking for to generate a
cache variable name. They also do not print any messages, for the same
reason. The checks for particular kinds of features call these macros
and do cache their results and print messages about what they're
checking for.
When you write a feature test that could be applicable to more than
one software package, the best thing to do is encapsulate it in a new
macro. *Note Writing Autoconf Macros::, for how to do that.
* Menu:
* Language Choice:: Selecting which language to use for testing
* Writing Test Programs:: Forging source files for compilers
* Running the Preprocessor:: Detecting preprocessor symbols
* Running the Compiler:: Detecting language or header features
* Running the Linker:: Detecting library features
* Runtime:: Testing for runtime features
* Systemology:: A zoology of operating systems
* Multiple Cases:: Tests for several possible values
File: autoconf.info, Node: Language Choice, Next: Writing Test Programs, Up: Writing Tests
6.1 Language Choice
===================
Autoconf-generated `configure' scripts check for the C compiler and its
features by default. Packages that use other programming languages
(maybe more than one, e.g., C and C++) need to test features of the
compilers for the respective languages. The following macros determine
which programming language is used in the subsequent tests in
`configure.ac'.
-- Macro: AC_LANG (LANGUAGE)
Do compilation tests using the compiler, preprocessor, and file
extensions for the specified LANGUAGE.
Supported languages are:
`C'
Do compilation tests using `CC' and `CPP' and use extension
`.c' for test programs. Use compilation flags: `CPPFLAGS'
with `CPP', and both `CPPFLAGS' and `CFLAGS' with `CC'.
`C++'
Do compilation tests using `CXX' and `CXXCPP' and use
extension `.C' for test programs. Use compilation flags:
`CPPFLAGS' with `CXXCPP', and both `CPPFLAGS' and `CXXFLAGS'
with `CXX'.
`Fortran 77'
Do compilation tests using `F77' and use extension `.f' for
test programs. Use compilation flags: `FFLAGS'.
`Fortran'
Do compilation tests using `FC' and use extension `.f' (or
whatever has been set by `AC_FC_SRCEXT') for test programs.
Use compilation flags: `FCFLAGS'.
`Erlang'
Compile and execute tests using `ERLC' and `ERL' and use
extension `.erl' for test Erlang modules. Use compilation
flags: `ERLCFLAGS'.
`Objective C'
Do compilation tests using `OBJC' and `OBJCPP' and use
extension `.m' for test programs. Use compilation flags:
`CPPFLAGS' with `OBJCPP', and both `CPPFLAGS' and `OBJCFLAGS'
with `OBJC'.
-- Macro: AC_LANG_PUSH (LANGUAGE)
Remember the current language (as set by `AC_LANG') on a stack, and
then select the LANGUAGE. Use this macro and `AC_LANG_POP' in
macros that need to temporarily switch to a particular language.
-- Macro: AC_LANG_POP ([LANGUAGE])
Select the language that is saved on the top of the stack, as set
by `AC_LANG_PUSH', and remove it from the stack.
If given, LANGUAGE specifies the language we just _quit_. It is a
good idea to specify it when it's known (which should be the
case...), since Autoconf detects inconsistencies.
AC_LANG_PUSH([Fortran 77])
# Perform some tests on Fortran 77.
# ...
AC_LANG_POP([Fortran 77])
-- Macro: AC_LANG_ASSERT (LANGUAGE)
Check statically that the current language is LANGUAGE. You
should use this in your language specific macros to avoid that
they be called with an inappropriate language.
This macro runs only at `autoconf' time, and incurs no cost at
`configure' time. Sadly enough and because Autoconf is a two
layer language (1), the macros `AC_LANG_PUSH' and `AC_LANG_POP'
cannot be "optimizing", therefore as much as possible you ought to
avoid using them to wrap your code, rather, require from the user
to run the macro with a correct current language, and check it
with `AC_LANG_ASSERT'. And anyway, that may help the user
understand she is running a Fortran macro while expecting a result
about her Fortran 77 compiler...
-- Macro: AC_REQUIRE_CPP
Ensure that whichever preprocessor would currently be used for
tests has been found. Calls `AC_REQUIRE' (*note Prerequisite
Macros::) with an argument of either `AC_PROG_CPP' or
`AC_PROG_CXXCPP', depending on which language is current.
---------- Footnotes ----------
(1) Because M4 is not aware of Sh code, especially conditionals,
some optimizations that look nice statically may produce incorrect
results at runtime.
File: autoconf.info, Node: Writing Test Programs, Next: Running the Preprocessor, Prev: Language Choice, Up: Writing Tests
6.2 Writing Test Programs
=========================
Autoconf tests follow a common scheme: feed some program with some
input, and most of the time, feed a compiler with some source file.
This section is dedicated to these source samples.
* Menu:
* Guidelines:: General rules for writing test programs
* Test Functions:: Avoiding pitfalls in test programs
* Generating Sources:: Source program boilerplate
File: autoconf.info, Node: Guidelines, Next: Test Functions, Up: Writing Test Programs
6.2.1 Guidelines for Test Programs
----------------------------------
The most important rule to follow when writing testing samples is:
_Look for realism._
This motto means that testing samples must be written with the same
strictness as real programs are written. In particular, you should
avoid "shortcuts" and simplifications.
Don't just play with the preprocessor if you want to prepare a
compilation. For instance, using `cpp' to check whether a header is
functional might let your `configure' accept a header which causes some
_compiler_ error. Do not hesitate to check a header with other headers
included before, especially required headers.
Make sure the symbols you use are properly defined, i.e., refrain
from simply declaring a function yourself instead of including the
proper header.
Test programs should not write to standard output. They should exit
with status 0 if the test succeeds, and with status 1 otherwise, so
that success can be distinguished easily from a core dump or other
failure; segmentation violations and other failures produce a nonzero
exit status. Unless you arrange for `exit' to be declared, test
programs should `return', not `exit', from `main', because on many
systems `exit' is not declared by default.
Test programs can use `#if' or `#ifdef' to check the values of
preprocessor macros defined by tests that have already run. For
example, if you call `AC_HEADER_STDBOOL', then later on in
`configure.ac' you can have a test program that includes `stdbool.h'
conditionally:
#ifdef HAVE_STDBOOL_H
# include
#endif
Both `#if HAVE_STDBOOL_H' and `#ifdef HAVE_STDBOOL_H' will work with
any standard C compiler. Some developers prefer `#if' because it is
easier to read, while others prefer `#ifdef' because it avoids
diagnostics with picky compilers like GCC with the `-Wundef' option.
If a test program needs to use or create a data file, give it a name
that starts with `conftest', such as `conftest.data'. The `configure'
script cleans up by running `rm -f -r conftest*' after running test
programs and if the script is interrupted.
File: autoconf.info, Node: Test Functions, Next: Generating Sources, Prev: Guidelines, Up: Writing Test Programs
6.2.2 Test Functions
--------------------
These days it's safe to assume support for function prototypes
(introduced in C89).
Functions that test programs declare should also be conditionalized
for C++, which requires `extern "C"' prototypes. Make sure to not
include any header files containing clashing prototypes.
#ifdef __cplusplus
extern "C"
#endif
void *valloc (size_t);
If a test program calls a function with invalid parameters (just to
see whether it exists), organize the program to ensure that it never
invokes that function. You can do this by calling it in another
function that is never invoked. You can't do it by putting it after a
call to `exit', because GCC version 2 knows that `exit' never returns
and optimizes out any code that follows it in the same block.
If you include any header files, be sure to call the functions
relevant to them with the correct number of arguments, even if they are
just 0, to avoid compilation errors due to prototypes. GCC version 2
has internal prototypes for several functions that it automatically
inlines; for example, `memcpy'. To avoid errors when checking for
them, either pass them the correct number of arguments or redeclare them
with a different return type (such as `char').
File: autoconf.info, Node: Generating Sources, Prev: Test Functions, Up: Writing Test Programs
6.2.3 Generating Sources
------------------------
Autoconf provides a set of macros that can be used to generate test
source files. They are written to be language generic, i.e., they
actually depend on the current language (*note Language Choice::) to
"format" the output properly.
-- Macro: AC_LANG_CONFTEST (SOURCE)
Save the SOURCE text in the current test source file:
`conftest.EXTENSION' where the EXTENSION depends on the current
language.
Note that the SOURCE is evaluated exactly once, like regular
Autoconf macro arguments, and therefore (i) you may pass a macro
invocation, (ii) if not, be sure to double quote if needed.
-- Macro: AC_LANG_SOURCE (SOURCE)
Expands into the SOURCE, with the definition of all the
`AC_DEFINE' performed so far.
For instance executing (observe the double quotation!):
AC_INIT([Hello], [1.0], [bug-hello@example.org])
AC_DEFINE([HELLO_WORLD], ["Hello, World\n"],
[Greetings string.])
AC_LANG(C)
AC_LANG_CONFTEST(
[AC_LANG_SOURCE([[const char hw[] = "Hello, World\n";]])])
gcc -E -dD -o - conftest.c
results in:
...
# 1 "conftest.c"
#define PACKAGE_NAME "Hello"
#define PACKAGE_TARNAME "hello"
#define PACKAGE_VERSION "1.0"
#define PACKAGE_STRING "Hello 1.0"
#define PACKAGE_BUGREPORT "bug-hello@example.org"
#define HELLO_WORLD "Hello, World\n"
const char hw[] = "Hello, World\n";
When the test language is Fortran or Erlang, the `AC_DEFINE'
definitions are not automatically translated into constants in the
source code by this macro.
-- Macro: AC_LANG_PROGRAM (PROLOGUE, BODY)
Expands into a source file which consists of the PROLOGUE, and
then BODY as body of the main function (e.g., `main' in C). Since
it uses `AC_LANG_SOURCE', the features of the latter are available.
For instance:
AC_INIT([Hello], [1.0], [bug-hello@example.org])
AC_DEFINE([HELLO_WORLD], ["Hello, World\n"],
[Greetings string.])
AC_LANG_CONFTEST(
[AC_LANG_PROGRAM([[const char hw[] = "Hello, World\n";]],
[[fputs (hw, stdout);]])])
gcc -E -dD -o - conftest.c
results in:
...
# 1 "conftest.c"
#define PACKAGE_NAME "Hello"
#define PACKAGE_TARNAME "hello"
#define PACKAGE_VERSION "1.0"
#define PACKAGE_STRING "Hello 1.0"
#define PACKAGE_BUGREPORT "bug-hello@example.org"
#define HELLO_WORLD "Hello, World\n"
const char hw[] = "Hello, World\n";
int
main ()
{
fputs (hw, stdout);
;
return 0;
}
In Erlang tests, the created source file is that of an Erlang module
called `conftest' (`conftest.erl'). This module defines and exports at
least one `start/0' function, which is called to perform the test. The
PROLOGUE is optional code that is inserted between the module header and
the `start/0' function definition. BODY is the body of the `start/0'
function without the final period (*note Runtime::, about constraints
on this function's behavior).
For instance:
AC_INIT([Hello], [1.0], [bug-hello@example.org])
AC_LANG(Erlang)
AC_LANG_CONFTEST(
[AC_LANG_PROGRAM([[-define(HELLO_WORLD, "Hello, world!").]],
[[io:format("~s~n", [?HELLO_WORLD])]])])
cat conftest.erl
results in:
-module(conftest).
-export([start/0]).
-define(HELLO_WORLD, "Hello, world!").
start() ->
io:format("~s~n", [?HELLO_WORLD])
.
-- Macro: AC_LANG_CALL (PROLOGUE, FUNCTION)
Expands into a source file which consists of the PROLOGUE, and
then a call to the FUNCTION as body of the main function (e.g.,
`main' in C). Since it uses `AC_LANG_PROGRAM', the feature of the
latter are available.
This function will probably be replaced in the future by a version
which would enable specifying the arguments. The use of this
macro is not encouraged, as it violates strongly the typing system.
This macro cannot be used for Erlang tests.
-- Macro: AC_LANG_FUNC_LINK_TRY (FUNCTION)
Expands into a source file which uses the FUNCTION in the body of
the main function (e.g., `main' in C). Since it uses
`AC_LANG_PROGRAM', the features of the latter are available.
As `AC_LANG_CALL', this macro is documented only for completeness.
It is considered to be severely broken, and in the future will be
removed in favor of actual function calls (with properly typed
arguments).
This macro cannot be used for Erlang tests.
File: autoconf.info, Node: Running the Preprocessor, Next: Running the Compiler, Prev: Writing Test Programs, Up: Writing Tests
6.3 Running the Preprocessor
============================
Sometimes one might need to run the preprocessor on some source file.
_Usually it is a bad idea_, as you typically need to _compile_ your
project, not merely run the preprocessor on it; therefore you certainly
want to run the compiler, not the preprocessor. Resist the temptation
of following the easiest path.
Nevertheless, if you need to run the preprocessor, then use
`AC_PREPROC_IFELSE'.
The macros described in this section cannot be used for tests in
Erlang or Fortran, since those languages require no preprocessor.
-- Macro: AC_PREPROC_IFELSE (INPUT, [ACTION-IF-TRUE],
[ACTION-IF-FALSE])
Run the preprocessor of the current language (*note Language
Choice::) on the INPUT, run the shell commands ACTION-IF-TRUE on
success, ACTION-IF-FALSE otherwise. The INPUT can be made by
`AC_LANG_PROGRAM' and friends.
This macro uses `CPPFLAGS', but not `CFLAGS', because `-g', `-O',
etc. are not valid options to many C preprocessors.
It is customary to report unexpected failures with
`AC_MSG_FAILURE'.
For instance:
AC_INIT([Hello], [1.0], [bug-hello@example.org])
AC_DEFINE([HELLO_WORLD], ["Hello, World\n"],
[Greetings string.])
AC_PREPROC_IFELSE(
[AC_LANG_PROGRAM([[const char hw[] = "Hello, World\n";]],
[[fputs (hw, stdout);]])],
[AC_MSG_RESULT([OK])],
[AC_MSG_FAILURE([unexpected preprocessor failure])])
results in:
checking for gcc... gcc
checking for C compiler default output file name... a.out
checking whether the C compiler works... yes
checking whether we are cross compiling... no
checking for suffix of executables...
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ISO C89... none needed
checking how to run the C preprocessor... gcc -E
OK
The macro `AC_TRY_CPP' (*note Obsolete Macros::) used to play the
role of `AC_PREPROC_IFELSE', but double quotes its argument, making it
impossible to use it to elaborate sources. You are encouraged to get
rid of your old use of the macro `AC_TRY_CPP' in favor of
`AC_PREPROC_IFELSE', but, in the first place, are you sure you need to
run the _preprocessor_ and not the compiler?
-- Macro: AC_EGREP_HEADER (PATTERN, HEADER-FILE, ACTION-IF-FOUND,
[ACTION-IF-NOT-FOUND])
If the output of running the preprocessor on the system header file
HEADER-FILE matches the extended regular expression PATTERN,
execute shell commands ACTION-IF-FOUND, otherwise execute
ACTION-IF-NOT-FOUND.
-- Macro: AC_EGREP_CPP (PATTERN, PROGRAM, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND])
PROGRAM is the text of a C or C++ program, on which shell
variable, back quote, and backslash substitutions are performed.
If the output of running the preprocessor on PROGRAM matches the
extended regular expression PATTERN, execute shell commands
ACTION-IF-FOUND, otherwise execute ACTION-IF-NOT-FOUND.
File: autoconf.info, Node: Running the Compiler, Next: Running the Linker, Prev: Running the Preprocessor, Up: Writing Tests
6.4 Running the Compiler
========================
To check for a syntax feature of the current language's (*note Language
Choice::) compiler, such as whether it recognizes a certain keyword, or
simply to try some library feature, use `AC_COMPILE_IFELSE' to try to
compile a small program that uses that feature.
-- Macro: AC_COMPILE_IFELSE (INPUT, [ACTION-IF-TRUE],
[ACTION-IF-FALSE])
Run the compiler and compilation flags of the current language
(*note Language Choice::) on the INPUT, run the shell commands
ACTION-IF-TRUE on success, ACTION-IF-FALSE otherwise. The INPUT
can be made by `AC_LANG_PROGRAM' and friends.
It is customary to report unexpected failures with
`AC_MSG_FAILURE'. This macro does not try to link; use
`AC_LINK_IFELSE' if you need to do that (*note Running the
Linker::).
This macro uses `AC_REQUIRE' for the compiler associated with the
current language, which means that if the compiler has not yet been
determined, the compiler determination will be made prior to the
body of the outermust `AC_DEFUN' macro that triggered this macro to
expand (*note Expanded Before Required::).
For tests in Erlang, the INPUT must be the source code of a module
named `conftest'. `AC_COMPILE_IFELSE' generates a `conftest.beam' file
that can be interpreted by the Erlang virtual machine (`ERL'). It is
recommended to use `AC_LANG_PROGRAM' to specify the test program, to
ensure that the Erlang module has the right name.
File: autoconf.info, Node: Running the Linker, Next: Runtime, Prev: Running the Compiler, Up: Writing Tests
6.5 Running the Linker
======================
To check for a library, a function, or a global variable, Autoconf
`configure' scripts try to compile and link a small program that uses
it. This is unlike Metaconfig, which by default uses `nm' or `ar' on
the C library to try to figure out which functions are available.
Trying to link with the function is usually a more reliable approach
because it avoids dealing with the variations in the options and output
formats of `nm' and `ar' and in the location of the standard libraries.
It also allows configuring for cross-compilation or checking a
function's runtime behavior if needed. On the other hand, it can be
slower than scanning the libraries once, but accuracy is more important
than speed.
`AC_LINK_IFELSE' is used to compile test programs to test for
functions and global variables. It is also used by `AC_CHECK_LIB' to
check for libraries (*note Libraries::), by adding the library being
checked for to `LIBS' temporarily and trying to link a small program.
-- Macro: AC_LINK_IFELSE (INPUT, [ACTION-IF-TRUE], [ACTION-IF-FALSE])
Run the compiler (and compilation flags) and the linker of the
current language (*note Language Choice::) on the INPUT, run the
shell commands ACTION-IF-TRUE on success, ACTION-IF-FALSE
otherwise. The INPUT can be made by `AC_LANG_PROGRAM' and friends.
`LDFLAGS' and `LIBS' are used for linking, in addition to the
current compilation flags.
It is customary to report unexpected failures with
`AC_MSG_FAILURE'. This macro does not try to execute the program;
use `AC_RUN_IFELSE' if you need to do that (*note Runtime::).
The `AC_LINK_IFELSE' macro cannot be used for Erlang tests, since
Erlang programs are interpreted and do not require linking.
File: autoconf.info, Node: Runtime, Next: Systemology, Prev: Running the Linker, Up: Writing Tests
6.6 Checking Runtime Behavior
=============================
Sometimes you need to find out how a system performs at runtime, such
as whether a given function has a certain capability or bug. If you
can, make such checks when your program runs instead of when it is
configured. You can check for things like the machine's endianness when
your program initializes itself.
If you really need to test for a runtime behavior while configuring,
you can write a test program to determine the result, and compile and
run it using `AC_RUN_IFELSE'. Avoid running test programs if possible,
because this prevents people from configuring your package for
cross-compiling.
-- Macro: AC_RUN_IFELSE (INPUT, [ACTION-IF-TRUE], [ACTION-IF-FALSE],
[ACTION-IF-CROSS-COMPILING])
If PROGRAM compiles and links successfully and returns an exit
status of 0 when executed, run shell commands ACTION-IF-TRUE.
Otherwise, run shell commands ACTION-IF-FALSE.
The INPUT can be made by `AC_LANG_PROGRAM' and friends. `LDFLAGS'
and `LIBS' are used for linking, in addition to the compilation
flags of the current language (*note Language Choice::).
If the compiler being used does not produce executables that run
on the system where `configure' is being run, then the test
program is not run. If the optional shell commands
ACTION-IF-CROSS-COMPILING are given, they are run instead.
Otherwise, `configure' prints an error message and exits.
In the ACTION-IF-FALSE section, the failing exit status is
available in the shell variable `$?'. This exit status might be
that of a failed compilation, or it might be that of a failed
program execution.
It is customary to report unexpected failures with
`AC_MSG_FAILURE'.
Try to provide a pessimistic default value to use when
cross-compiling makes runtime tests impossible. You do this by passing
the optional last argument to `AC_RUN_IFELSE'. `autoconf' prints a
warning message when creating `configure' each time it encounters a
call to `AC_RUN_IFELSE' with no ACTION-IF-CROSS-COMPILING argument
given. You may ignore the warning, though users cannot configure your
package for cross-compiling. A few of the macros distributed with
Autoconf produce this warning message.
To configure for cross-compiling you can also choose a value for
those parameters based on the canonical system name (*note Manual
Configuration::). Alternatively, set up a test results cache file with
the correct values for the host system (*note Caching Results::).
To provide a default for calls of `AC_RUN_IFELSE' that are embedded
in other macros, including a few of the ones that come with Autoconf,
you can test whether the shell variable `cross_compiling' is set to
`yes', and then use an alternate method to get the results instead of
calling the macros.
It is also permissible to temporarily assign to `cross_compiling' in
order to force tests to behave as though they are in a
cross-compilation environment, particularly since this provides a way to
test your ACTION-IF-CROSS-COMPILING even when you are not using a
cross-compiler.
# We temporarily set cross-compile mode to force AC_COMPUTE_INT
# to use the slow link-only method
save_cross_compiling=$cross_compiling
cross_compiling=yes
AC_COMPUTE_INT([...])
cross_compiling=$save_cross_compiling
A C or C++ runtime test should be portable. *Note Portable C and
C++::.
Erlang tests must exit themselves the Erlang VM by calling the
`halt/1' function: the given status code is used to determine the
success of the test (status is `0') or its failure (status is different
than `0'), as explained above. It must be noted that data output
through the standard output (e.g., using `io:format/2') may be
truncated when halting the VM. Therefore, if a test must output
configuration information, it is recommended to create and to output
data into the temporary file named `conftest.out', using the functions
of module `file'. The `conftest.out' file is automatically deleted by
the `AC_RUN_IFELSE' macro. For instance, a simplified implementation
of Autoconf's `AC_ERLANG_SUBST_LIB_DIR' macro is:
AC_INIT([LibdirTest], [1.0], [bug-libdirtest@example.org])
AC_ERLANG_NEED_ERL
AC_LANG(Erlang)
AC_RUN_IFELSE(
[AC_LANG_PROGRAM([], [dnl
file:write_file("conftest.out", code:lib_dir()),
halt(0)])],
[echo "code:lib_dir() returned: `cat conftest.out`"],
[AC_MSG_FAILURE([test Erlang program execution failed])])
File: autoconf.info, Node: Systemology, Next: Multiple Cases, Prev: Runtime, Up: Writing Tests
6.7 Systemology
===============
This section aims at presenting some systems and pointers to
documentation. It may help you addressing particular problems reported
by users.
Posix-conforming systems (http://www.opengroup.org/susv3) are
derived from the Unix operating system
(http://www.bell-labs.com/history/unix/).
The Rosetta Stone for Unix (http://bhami.com/rosetta.html) contains
a table correlating the features of various Posix-conforming systems.
Unix History (http://www.levenez.com/unix/) is a simplified diagram of
how many Unix systems were derived from each other.
The Heirloom Project (http://heirloom.sourceforge.net/) provides
some variants of traditional implementations of Unix utilities.
Darwin
Darwin is also known as Mac OS X. Beware that the file system
_can_ be case-preserving, but case insensitive. This can cause
nasty problems, since for instance the installation attempt for a
package having an `INSTALL' file can result in `make install'
report that nothing was to be done!
That's all dependent on whether the file system is a UFS (case
sensitive) or HFS+ (case preserving). By default Apple wants you
to install the OS on HFS+. Unfortunately, there are some pieces of
software which really need to be built on UFS. We may want to
rebuild Darwin to have both UFS and HFS+ available (and put the
/local/build tree on the UFS).
QNX 4.25
QNX is a realtime operating system running on Intel architecture
meant to be scalable from the small embedded systems to the hundred
processor super-computer. It claims to be Posix certified. More
information is available on the QNX home page
(http://www.qnx.com/).
Tru64
Documentation of several versions of Tru64
(http://h30097.www3.hp.com/docs/) is available in different
formats.
Unix version 7
Officially this was called the "Seventh Edition" of "the UNIX
time-sharing system" but we use the more-common name "Unix version
7". Documentation is available in the Unix Seventh Edition Manual
(http://plan9.bell-labs.com/7thEdMan/). Previous versions of Unix
are called "Unix version 6", etc., but they were not as widely
used.
File: autoconf.info, Node: Multiple Cases, Prev: Systemology, Up: Writing Tests
6.8 Multiple Cases
==================
Some operations are accomplished in several possible ways, depending on
the OS variant. Checking for them essentially requires a "case
statement". Autoconf does not directly provide one; however, it is
easy to simulate by using a shell variable to keep track of whether a
way to perform the operation has been found yet.
Here is an example that uses the shell variable `fstype' to keep
track of whether the remaining cases need to be checked. Note that
since the value of `fstype' is under our control, we don't have to use
the longer `test "x$fstype" = xno'.
AC_MSG_CHECKING([how to get file system type])
fstype=no
# The order of these tests is important.
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include
#include ]])],
[AC_DEFINE([FSTYPE_STATVFS], [1],
[Define if statvfs exists.])
fstype=SVR4])
if test $fstype = no; then
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include
#include ]])],
[AC_DEFINE([FSTYPE_USG_STATFS], [1],
[Define if USG statfs.])
fstype=SVR3])
fi
if test $fstype = no; then
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include
#include ]])]),
[AC_DEFINE([FSTYPE_AIX_STATFS], [1],
[Define if AIX statfs.])
fstype=AIX])
fi
# (more cases omitted here)
AC_MSG_RESULT([$fstype])
File: autoconf.info, Node: Results, Next: Programming in M4, Prev: Writing Tests, Up: Top
7 Results of Tests
******************
Once `configure' has determined whether a feature exists, what can it
do to record that information? There are four sorts of things it can
do: define a C preprocessor symbol, set a variable in the output files,
save the result in a cache file for future `configure' runs, and print
a message letting the user know the result of the test.
* Menu:
* Defining Symbols:: Defining C preprocessor symbols
* Setting Output Variables:: Replacing variables in output files
* Special Chars in Variables:: Characters to beware of in variables
* Caching Results:: Speeding up subsequent `configure' runs
* Printing Messages:: Notifying `configure' users
File: autoconf.info, Node: Defining Symbols, Next: Setting Output Variables, Up: Results
7.1 Defining C Preprocessor Symbols
===================================
A common action to take in response to a feature test is to define a C
preprocessor symbol indicating the results of the test. That is done by
calling `AC_DEFINE' or `AC_DEFINE_UNQUOTED'.
By default, `AC_OUTPUT' places the symbols defined by these macros
into the output variable `DEFS', which contains an option
`-DSYMBOL=VALUE' for each symbol defined. Unlike in Autoconf version
1, there is no variable `DEFS' defined while `configure' is running.
To check whether Autoconf macros have already defined a certain C
preprocessor symbol, test the value of the appropriate cache variable,
as in this example:
AC_CHECK_FUNC([vprintf], [AC_DEFINE([HAVE_VPRINTF], [1],
[Define if vprintf exists.])])
if test "x$ac_cv_func_vprintf" != xyes; then
AC_CHECK_FUNC([_doprnt], [AC_DEFINE([HAVE_DOPRNT], [1],
[Define if _doprnt exists.])])
fi
If `AC_CONFIG_HEADERS' has been called, then instead of creating
`DEFS', `AC_OUTPUT' creates a header file by substituting the correct
values into `#define' statements in a template file. *Note
Configuration Headers::, for more information about this kind of output.
-- Macro: AC_DEFINE (VARIABLE, VALUE, [DESCRIPTION])
-- Macro: AC_DEFINE (VARIABLE)
Define VARIABLE to VALUE (verbatim), by defining a C preprocessor
macro for VARIABLE. VARIABLE should be a C identifier, optionally
suffixed by a parenthesized argument list to define a C
preprocessor macro with arguments. The macro argument list, if
present, should be a comma-separated list of C identifiers,
possibly terminated by an ellipsis `...' if C99 syntax is employed.
VARIABLE should not contain comments, white space, trigraphs,
backslash-newlines, universal character names, or non-ASCII
characters.
VALUE may contain backslash-escaped newlines, which will be
preserved if you use `AC_CONFIG_HEADERS' but flattened if passed
via `@DEFS@' (with no effect on the compilation, since the
preprocessor sees only one line in the first place). VALUE should
not contain raw newlines. If you are not using
`AC_CONFIG_HEADERS', VALUE should not contain any `#' characters,
as `make' tends to eat them. To use a shell variable, use
`AC_DEFINE_UNQUOTED' instead.
DESCRIPTION is only useful if you are using `AC_CONFIG_HEADERS'.
In this case, DESCRIPTION is put into the generated `config.h.in'
as the comment before the macro define. The following example
defines the C preprocessor variable `EQUATION' to be the string
constant `"$a > $b"':
AC_DEFINE([EQUATION], ["$a > $b"],
[Equation string.])
If neither VALUE nor DESCRIPTION are given, then VALUE defaults to
1 instead of to the empty string. This is for backwards
compatibility with older versions of Autoconf, but this usage is
obsolescent and may be withdrawn in future versions of Autoconf.
If the VARIABLE is a literal string, it is passed to
`m4_pattern_allow' (*note Forbidden Patterns::).
If multiple `AC_DEFINE' statements are executed for the same
VARIABLE name (not counting any parenthesized argument list), the
last one wins.
-- Macro: AC_DEFINE_UNQUOTED (VARIABLE, VALUE, [DESCRIPTION])
-- Macro: AC_DEFINE_UNQUOTED (VARIABLE)
Like `AC_DEFINE', but three shell expansions are
performed--once--on VARIABLE and VALUE: variable expansion (`$'),
command substitution (``'), and backslash escaping (`\'), as if in
an unquoted here-document. Single and double quote characters in
the value have no special meaning. Use this macro instead of
`AC_DEFINE' when VARIABLE or VALUE is a shell variable. Examples:
AC_DEFINE_UNQUOTED([config_machfile], ["$machfile"],
[Configuration machine file.])
AC_DEFINE_UNQUOTED([GETGROUPS_T], [$ac_cv_type_getgroups],
[getgroups return type.])
AC_DEFINE_UNQUOTED([$ac_tr_hdr], [1],
[Translated header name.])
Due to a syntactical bizarreness of the Bourne shell, do not use
semicolons to separate `AC_DEFINE' or `AC_DEFINE_UNQUOTED' calls from
other macro calls or shell code; that can cause syntax errors in the
resulting `configure' script. Use either blanks or newlines. That is,
do this:
AC_CHECK_HEADER([elf.h],
[AC_DEFINE([SVR4], [1], [System V Release 4]) LIBS="-lelf $LIBS"])
or this:
AC_CHECK_HEADER([elf.h],
[AC_DEFINE([SVR4], [1], [System V Release 4])
LIBS="-lelf $LIBS"])
instead of this:
AC_CHECK_HEADER([elf.h],
[AC_DEFINE([SVR4], [1], [System V Release 4]); LIBS="-lelf $LIBS"])
File: autoconf.info, Node: Setting Output Variables, Next: Special Chars in Variables, Prev: Defining Symbols, Up: Results
7.2 Setting Output Variables
============================
Another way to record the results of tests is to set "output
variables", which are shell variables whose values are substituted into
files that `configure' outputs. The two macros below create new output
variables. *Note Preset Output Variables::, for a list of output
variables that are always available.
-- Macro: AC_SUBST (VARIABLE, [VALUE])
Create an output variable from a shell variable. Make `AC_OUTPUT'
substitute the variable VARIABLE into output files (typically one
or more makefiles). This means that `AC_OUTPUT' replaces
instances of `@VARIABLE@' in input files with the value that the
shell variable VARIABLE has when `AC_OUTPUT' is called. The value
can contain any non-`NUL' character, including newline. If you
are using Automake 1.11 or newer, for newlines in values you might
want to consider using `AM_SUBST_NOTMAKE' to prevent `automake'
from adding a line `VARIABLE = @VARIABLE@' to the `Makefile.in'
files (*note Automake: (automake)Optional.).
Variable occurrences should not overlap: e.g., an input file should
not contain `@VAR1@VAR2@' if VAR1 and VAR2 are variable names.
The substituted value is not rescanned for more output variables;
occurrences of `@VARIABLE@' in the value are inserted literally
into the output file. (The algorithm uses the special marker
`|#_!!_#|' internally, so neither the substituted value nor the
output file may contain `|#_!!_#|'.)
If VALUE is given, in addition assign it to VARIABLE.
The string VARIABLE is passed to `m4_pattern_allow' (*note
Forbidden Patterns::).
-- Macro: AC_SUBST_FILE (VARIABLE)
Another way to create an output variable from a shell variable.
Make `AC_OUTPUT' insert (without substitutions) the contents of
the file named by shell variable VARIABLE into output files. This
means that `AC_OUTPUT' replaces instances of `@VARIABLE@' in
output files (such as `Makefile.in') with the contents of the file
that the shell variable VARIABLE names when `AC_OUTPUT' is called.
Set the variable to `/dev/null' for cases that do not have a file
to insert. This substitution occurs only when the `@VARIABLE@' is
on a line by itself, optionally surrounded by spaces and tabs. The
substitution replaces the whole line, including the spaces, tabs,
and the terminating newline.
This macro is useful for inserting makefile fragments containing
special dependencies or other `make' directives for particular host
or target types into makefiles. For example, `configure.ac' could
contain:
AC_SUBST_FILE([host_frag])
host_frag=$srcdir/conf/sun4.mh
and then a `Makefile.in' could contain:
@host_frag@
The string VARIABLE is passed to `m4_pattern_allow' (*note
Forbidden Patterns::).
Running `configure' in varying environments can be extremely
dangerous. If for instance the user runs `CC=bizarre-cc ./configure',
then the cache, `config.h', and many other output files depend upon
`bizarre-cc' being the C compiler. If for some reason the user runs
`./configure' again, or if it is run via `./config.status --recheck',
(*Note Automatic Remaking::, and *note config.status Invocation::),
then the configuration can be inconsistent, composed of results
depending upon two different compilers.
Environment variables that affect this situation, such as `CC'
above, are called "precious variables", and can be declared as such by
`AC_ARG_VAR'.
-- Macro: AC_ARG_VAR (VARIABLE, DESCRIPTION)
Declare VARIABLE is a precious variable, and include its
DESCRIPTION in the variable section of `./configure --help'.
Being precious means that
- VARIABLE is substituted via `AC_SUBST'.
- The value of VARIABLE when `configure' was launched is saved
in the cache, including if it was not specified on the command
line but via the environment. Indeed, while `configure' can
notice the definition of `CC' in `./configure CC=bizarre-cc',
it is impossible to notice it in `CC=bizarre-cc ./configure',
which, unfortunately, is what most users do.
We emphasize that it is the _initial_ value of VARIABLE which
is saved, not that found during the execution of `configure'.
Indeed, specifying `./configure FOO=foo' and letting
`./configure' guess that `FOO' is `foo' can be two different
things.
- VARIABLE is checked for consistency between two `configure'
runs. For instance:
$ ./configure --silent --config-cache
$ CC=cc ./configure --silent --config-cache
configure: error: `CC' was not set in the previous run
configure: error: changes in the environment can compromise \
the build
configure: error: run `make distclean' and/or \
`rm config.cache' and start over
and similarly if the variable is unset, or if its content is
changed. If the content has white space changes only, then
the error is degraded to a warning only, but the old value is
reused.
- VARIABLE is kept during automatic reconfiguration (*note
config.status Invocation::) as if it had been passed as a
command line argument, including when no cache is used:
$ CC=/usr/bin/cc ./configure var=raboof --silent
$ ./config.status --recheck
running CONFIG_SHELL=/bin/sh /bin/sh ./configure var=raboof \
CC=/usr/bin/cc --no-create --no-recursion
File: autoconf.info, Node: Special Chars in Variables, Next: Caching Results, Prev: Setting Output Variables, Up: Results
7.3 Special Characters in Output Variables
==========================================
Many output variables are intended to be evaluated both by `make' and
by the shell. Some characters are expanded differently in these two
contexts, so to avoid confusion these variables' values should not
contain any of the following characters:
" # $ & ' ( ) * ; < > ? [ \ ^ ` |
Also, these variables' values should neither contain newlines, nor
start with `~', nor contain white space or `:' immediately followed by
`~'. The values can contain nonempty sequences of white space
characters like tabs and spaces, but each such sequence might
arbitrarily be replaced by a single space during substitution.
These restrictions apply both to the values that `configure'
computes, and to the values set directly by the user. For example, the
following invocations of `configure' are problematic, since they
attempt to use special characters within `CPPFLAGS' and white space
within `$(srcdir)':
CPPFLAGS='-DOUCH="&\"#$*?"' '../My Source/ouch-1.0/configure'
'../My Source/ouch-1.0/configure' CPPFLAGS='-DOUCH="&\"#$*?"'
File: autoconf.info, Node: Caching Results, Next: Printing Messages, Prev: Special Chars in Variables, Up: Results
7.4 Caching Results
===================
To avoid checking for the same features repeatedly in various
`configure' scripts (or in repeated runs of one script), `configure'
can optionally save the results of many checks in a "cache file" (*note
Cache Files::). If a `configure' script runs with caching enabled and
finds a cache file, it reads the results of previous runs from the
cache and avoids rerunning those checks. As a result, `configure' can
then run much faster than if it had to perform all of the checks every
time.
-- Macro: AC_CACHE_VAL (CACHE-ID, COMMANDS-TO-SET-IT)
Ensure that the results of the check identified by CACHE-ID are
available. If the results of the check were in the cache file
that was read, and `configure' was not given the `--quiet' or
`--silent' option, print a message saying that the result was
cached; otherwise, run the shell commands COMMANDS-TO-SET-IT. If
the shell commands are run to determine the value, the value is
saved in the cache file just before `configure' creates its output
files. *Note Cache Variable Names::, for how to choose the name
of the CACHE-ID variable.
The COMMANDS-TO-SET-IT _must have no side effects_ except for
setting the variable CACHE-ID, see below.
-- Macro: AC_CACHE_CHECK (MESSAGE, CACHE-ID, COMMANDS-TO-SET-IT)
A wrapper for `AC_CACHE_VAL' that takes care of printing the
messages. This macro provides a convenient shorthand for the most
common way to use these macros. It calls `AC_MSG_CHECKING' for
MESSAGE, then `AC_CACHE_VAL' with the CACHE-ID and COMMANDS
arguments, and `AC_MSG_RESULT' with CACHE-ID.
The COMMANDS-TO-SET-IT _must have no side effects_ except for
setting the variable CACHE-ID, see below.
It is common to find buggy macros using `AC_CACHE_VAL' or
`AC_CACHE_CHECK', because people are tempted to call `AC_DEFINE' in the
COMMANDS-TO-SET-IT. Instead, the code that _follows_ the call to
`AC_CACHE_VAL' should call `AC_DEFINE', by examining the value of the
cache variable. For instance, the following macro is broken:
AC_DEFUN([AC_SHELL_TRUE],
[AC_CACHE_CHECK([whether true(1) works], [my_cv_shell_true_works],
[my_cv_shell_true_works=no
(true) 2>/dev/null && my_cv_shell_true_works=yes
if test "x$my_cv_shell_true_works" = xyes; then
AC_DEFINE([TRUE_WORKS], [1],
[Define if `true(1)' works properly.])
fi])
])
This fails if the cache is enabled: the second time this macro is run,
`TRUE_WORKS' _will not be defined_. The proper implementation is:
AC_DEFUN([AC_SHELL_TRUE],
[AC_CACHE_CHECK([whether true(1) works], [my_cv_shell_true_works],
[my_cv_shell_true_works=no
(true) 2>/dev/null && my_cv_shell_true_works=yes])
if test "x$my_cv_shell_true_works" = xyes; then
AC_DEFINE([TRUE_WORKS], [1],
[Define if `true(1)' works properly.])
fi
])
Also, COMMANDS-TO-SET-IT should not print any messages, for example
with `AC_MSG_CHECKING'; do that before calling `AC_CACHE_VAL', so the
messages are printed regardless of whether the results of the check are
retrieved from the cache or determined by running the shell commands.
* Menu:
* Cache Variable Names:: Shell variables used in caches
* Cache Files:: Files `configure' uses for caching
* Cache Checkpointing:: Loading and saving the cache file
File: autoconf.info, Node: Cache Variable Names, Next: Cache Files, Up: Caching Results
7.4.1 Cache Variable Names
--------------------------
The names of cache variables should have the following format:
PACKAGE-PREFIX_cv_VALUE-TYPE_SPECIFIC-VALUE_[ADDITIONAL-OPTIONS]
for example, `ac_cv_header_stat_broken' or
`ac_cv_prog_gcc_traditional'. The parts of the variable name are:
PACKAGE-PREFIX
An abbreviation for your package or organization; the same prefix
you begin local Autoconf macros with, except lowercase by
convention. For cache values used by the distributed Autoconf
macros, this value is `ac'.
`_cv_'
Indicates that this shell variable is a cache value. This string
_must_ be present in the variable name, including the leading
underscore.
VALUE-TYPE
A convention for classifying cache values, to produce a rational
naming system. The values used in Autoconf are listed in *note
Macro Names::.
SPECIFIC-VALUE
Which member of the class of cache values this test applies to.
For example, which function (`alloca'), program (`gcc'), or output
variable (`INSTALL').
ADDITIONAL-OPTIONS
Any particular behavior of the specific member that this test
applies to. For example, `broken' or `set'. This part of the
name may be omitted if it does not apply.
The values assigned to cache variables may not contain newlines.
Usually, their values are Boolean (`yes' or `no') or the names of files
or functions; so this is not an important restriction.
File: autoconf.info, Node: Cache Files, Next: Cache Checkpointing, Prev: Cache Variable Names, Up: Caching Results
7.4.2 Cache Files
-----------------
A cache file is a shell script that caches the results of configure
tests run on one system so they can be shared between configure scripts
and configure runs. It is not useful on other systems. If its contents
are invalid for some reason, the user may delete or edit it.
By default, `configure' uses no cache file, to avoid problems caused
by accidental use of stale cache files.
To enable caching, `configure' accepts `--config-cache' (or `-C') to
cache results in the file `config.cache'. Alternatively,
`--cache-file=FILE' specifies that FILE be the cache file. The cache
file is created if it does not exist already. When `configure' calls
`configure' scripts in subdirectories, it uses the `--cache-file'
argument so that they share the same cache. *Note Subdirectories::,
for information on configuring subdirectories with the
`AC_CONFIG_SUBDIRS' macro.
`config.status' only pays attention to the cache file if it is given
the `--recheck' option, which makes it rerun `configure'.
It is wrong to try to distribute cache files for particular system
types. There is too much room for error in doing that, and too much
administrative overhead in maintaining them. For any features that
can't be guessed automatically, use the standard method of the canonical
system type and linking files (*note Manual Configuration::).
The site initialization script can specify a site-wide cache file to
use, instead of the usual per-program cache. In this case, the cache
file gradually accumulates information whenever someone runs a new
`configure' script. (Running `configure' merges the new cache results
with the existing cache file.) This may cause problems, however, if
the system configuration (e.g., the installed libraries or compilers)
changes and the stale cache file is not deleted.
File: autoconf.info, Node: Cache Checkpointing, Prev: Cache Files, Up: Caching Results
7.4.3 Cache Checkpointing
-------------------------
If your configure script, or a macro called from `configure.ac', happens
to abort the configure process, it may be useful to checkpoint the cache
a few times at key points using `AC_CACHE_SAVE'. Doing so reduces the
amount of time it takes to rerun the configure script with (hopefully)
the error that caused the previous abort corrected.
-- Macro: AC_CACHE_LOAD
Loads values from existing cache file, or creates a new cache file
if a cache file is not found. Called automatically from `AC_INIT'.
-- Macro: AC_CACHE_SAVE
Flushes all cached values to the cache file. Called automatically
from `AC_OUTPUT', but it can be quite useful to call
`AC_CACHE_SAVE' at key points in `configure.ac'.
For instance:
... AC_INIT, etc. ...
# Checks for programs.
AC_PROG_CC
AC_PROG_AWK
... more program checks ...
AC_CACHE_SAVE
# Checks for libraries.
AC_CHECK_LIB([nsl], [gethostbyname])
AC_CHECK_LIB([socket], [connect])
... more lib checks ...
AC_CACHE_SAVE
# Might abort...
AM_PATH_GTK([1.0.2], [], [AC_MSG_ERROR([GTK not in path])])
AM_PATH_GTKMM([0.9.5], [], [AC_MSG_ERROR([GTK not in path])])
... AC_OUTPUT, etc. ...
File: autoconf.info, Node: Printing Messages, Prev: Caching Results, Up: Results
7.5 Printing Messages
=====================
`configure' scripts need to give users running them several kinds of
information. The following macros print messages in ways appropriate
for each kind. The arguments to all of them get enclosed in shell
double quotes, so the shell performs variable and back-quote
substitution on them.
These macros are all wrappers around the `echo' shell command. They
direct output to the appropriate file descriptor (*note File Descriptor
Macros::). `configure' scripts should rarely need to run `echo'
directly to print messages for the user. Using these macros makes it
easy to change how and when each kind of message is printed; such
changes need only be made to the macro definitions and all the callers
change automatically.
To diagnose static issues, i.e., when `autoconf' is run, see *note
Diagnostic Macros::.
-- Macro: AC_MSG_CHECKING (FEATURE-DESCRIPTION)
Notify the user that `configure' is checking for a particular
feature. This macro prints a message that starts with `checking '
and ends with `...' and no newline. It must be followed by a call
to `AC_MSG_RESULT' to print the result of the check and the
newline. The FEATURE-DESCRIPTION should be something like
`whether the Fortran compiler accepts C++ comments' or `for c89'.
This macro prints nothing if `configure' is run with the `--quiet'
or `--silent' option.
-- Macro: AC_MSG_RESULT (RESULT-DESCRIPTION)
Notify the user of the results of a check. RESULT-DESCRIPTION is
almost always the value of the cache variable for the check,
typically `yes', `no', or a file name. This macro should follow a
call to `AC_MSG_CHECKING', and the RESULT-DESCRIPTION should be
the completion of the message printed by the call to
`AC_MSG_CHECKING'.
This macro prints nothing if `configure' is run with the `--quiet'
or `--silent' option.
-- Macro: AC_MSG_NOTICE (MESSAGE)
Deliver the MESSAGE to the user. It is useful mainly to print a
general description of the overall purpose of a group of feature
checks, e.g.,
AC_MSG_NOTICE([checking if stack overflow is detectable])
This macro prints nothing if `configure' is run with the `--quiet'
or `--silent' option.
-- Macro: AC_MSG_ERROR (ERROR-DESCRIPTION, [EXIT-STATUS = `$?/1'])
Notify the user of an error that prevents `configure' from
completing. This macro prints an error message to the standard
error output and exits `configure' with EXIT-STATUS (`$?' by
default, except that `0' is converted to `1'). ERROR-DESCRIPTION
should be something like `invalid value $HOME for \$HOME'.
The ERROR-DESCRIPTION should start with a lower-case letter, and
"cannot" is preferred to "can't".
-- Macro: AC_MSG_FAILURE (ERROR-DESCRIPTION, [EXIT-STATUS])
This `AC_MSG_ERROR' wrapper notifies the user of an error that
prevents `configure' from completing _and_ that additional details
are provided in `config.log'. This is typically used when
abnormal results are found during a compilation.
-- Macro: AC_MSG_WARN (PROBLEM-DESCRIPTION)
Notify the `configure' user of a possible problem. This macro
prints the message to the standard error output; `configure'
continues running afterward, so macros that call `AC_MSG_WARN'
should provide a default (back-up) behavior for the situations
they warn about. PROBLEM-DESCRIPTION should be something like `ln
-s seems to make hard links'.
File: autoconf.info, Node: Programming in M4, Next: Programming in M4sh, Prev: Results, Up: Top
8 Programming in M4
*******************
Autoconf is written on top of two layers: "M4sugar", which provides
convenient macros for pure M4 programming, and "M4sh", which provides
macros dedicated to shell script generation.
As of this version of Autoconf, these two layers still contain
experimental macros, whose interface might change in the future. As a
matter of fact, _anything that is not documented must not be used_.
* Menu:
* M4 Quotation:: Protecting macros from unwanted expansion
* Using autom4te:: The Autoconf executables backbone
* Programming in M4sugar:: Convenient pure M4 macros
* Debugging via autom4te:: Figuring out what M4 was doing
File: autoconf.info, Node: M4 Quotation, Next: Using autom4te, Up: Programming in M4
8.1 M4 Quotation
================
The most common problem with existing macros is an improper quotation.
This section, which users of Autoconf can skip, but which macro writers
_must_ read, first justifies the quotation scheme that was chosen for
Autoconf and then ends with a rule of thumb. Understanding the former
helps one to follow the latter.
* Menu:
* Active Characters:: Characters that change the behavior of M4
* One Macro Call:: Quotation and one macro call
* Quoting and Parameters:: M4 vs. shell parameters
* Quotation and Nested Macros:: Macros calling macros
* Changequote is Evil:: Worse than INTERCAL: M4 + changequote
* Quadrigraphs:: Another way to escape special characters
* Balancing Parentheses:: Dealing with unbalanced parentheses
* Quotation Rule Of Thumb:: One parenthesis, one quote
File: autoconf.info, Node: Active Characters, Next: One Macro Call, Up: M4 Quotation
8.1.1 Active Characters
-----------------------
To fully understand where proper quotation is important, you first need
to know what the special characters are in Autoconf: `#' introduces a
comment inside which no macro expansion is performed, `,' separates
arguments, `[' and `]' are the quotes themselves, `(' and `)' (which M4
tries to match by pairs), and finally `$' inside a macro definition.
In order to understand the delicate case of macro calls, we first
have to present some obvious failures. Below they are "obvious-ified",
but when you find them in real life, they are usually in disguise.
Comments, introduced by a hash and running up to the newline, are
opaque tokens to the top level: active characters are turned off, and
there is no macro expansion:
# define([def], ine)
=># define([def], ine)
Each time there can be a macro expansion, there is a quotation
expansion, i.e., one level of quotes is stripped:
int tab[10];
=>int tab10;
[int tab[10];]
=>int tab[10];
Without this in mind, the reader might try hopelessly to use her
macro `array':
define([array], [int tab[10];])
array
=>int tab10;
[array]
=>array
How can you correctly output the intended results(1)?
---------- Footnotes ----------
(1) Using `defn'.
File: autoconf.info, Node: One Macro Call, Next: Quoting and Parameters, Prev: Active Characters, Up: M4 Quotation
8.1.2 One Macro Call
--------------------
Let's proceed on the interaction between active characters and macros
with this small macro, which just returns its first argument:
define([car], [$1])
The two pairs of quotes above are not part of the arguments of
`define'; rather, they are understood by the top level when it tries to
find the arguments of `define'. Therefore, assuming `car' is not
already defined, it is equivalent to write:
define(car, $1)
But, while it is acceptable for a `configure.ac' to avoid unnecessary
quotes, it is bad practice for Autoconf macros which must both be more
robust and also advocate perfect style.
At the top level, there are only two possibilities: either you quote
or you don't:
car(foo, bar, baz)
=>foo
[car(foo, bar, baz)]
=>car(foo, bar, baz)
Let's pay attention to the special characters:
car(#)
error-->EOF in argument list
The closing parenthesis is hidden in the comment; with a hypothetical
quoting, the top level understood it this way:
car([#)]
Proper quotation, of course, fixes the problem:
car([#])
=>#
Here are more examples:
car(foo, bar)
=>foo
car([foo, bar])
=>foo, bar
car((foo, bar))
=>(foo, bar)
car([(foo], [bar)])
=>(foo
define([a], [b])
=>
car(a)
=>b
car([a])
=>b
car([[a]])
=>a
car([[[a]]])
=>[a]
File: autoconf.info, Node: Quoting and Parameters, Next: Quotation and Nested Macros, Prev: One Macro Call, Up: M4 Quotation
8.1.3 Quoting and Parameters
----------------------------
When M4 encounters `$' within a macro definition, followed immediately
by a character it recognizes (`0'...`9', `#', `@', or `*'), it will
perform M4 parameter expansion. This happens regardless of how many
layers of quotes the parameter expansion is nested within, or even if
it occurs in text that will be rescanned as a comment.
define([none], [$1])
=>
define([one], [[$1]])
=>
define([two], [[[$1]]])
=>
define([comment], [# $1])
=>
define([active], [ACTIVE])
=>
none([active])
=>ACTIVE
one([active])
=>active
two([active])
=>[active]
comment([active])
=># active
On the other hand, since autoconf generates shell code, you often
want to output shell variable expansion, rather than performing M4
parameter expansion. To do this, you must use M4 quoting to separate
the `$' from the next character in the definition of your macro. If
the macro definition occurs in single-quoted text, then insert another
level of quoting; if the usage is already inside a double-quoted
string, then split it into concatenated strings.
define([single], [a single-quoted $[]1 definition])
=>
define([double], [[a double-quoted $][1 definition]])
=>
single
=>a single-quoted $1 definition
double
=>a double-quoted $1 definition
Posix states that M4 implementations are free to provide
implementation extensions when `${' is encountered in a macro
definition. Autoconf reserves the longer sequence `${{' for use with
planned extensions that will be available in the future GNU M4 2.0, but
guarantees that all other instances of `${' will be output literally.
Therefore, this idiom can also be used to output shell code parameter
references:
define([first], [${1}])first
=>${1}
Posix also states that `$11' should expand to the first parameter
concatenated with a literal `1', although some versions of GNU M4
expand the eleventh parameter instead. For portability, you should
only use single-digit M4 parameter expansion.
With this in mind, we can explore the cases where macros invoke
macros...
File: autoconf.info, Node: Quotation and Nested Macros, Next: Changequote is Evil, Prev: Quoting and Parameters, Up: M4 Quotation
8.1.4 Quotation and Nested Macros
---------------------------------
The examples below use the following macros:
define([car], [$1])
define([active], [ACT, IVE])
define([array], [int tab[10]])
Each additional embedded macro call introduces other possible
interesting quotations:
car(active)
=>ACT
car([active])
=>ACT, IVE
car([[active]])
=>active
In the first case, the top level looks for the arguments of `car',
and finds `active'. Because M4 evaluates its arguments before applying
the macro, `active' is expanded, which results in:
car(ACT, IVE)
=>ACT
In the second case, the top level gives `active' as first and only
argument of `car', which results in:
active
=>ACT, IVE
i.e., the argument is evaluated _after_ the macro that invokes it. In
the third case, `car' receives `[active]', which results in:
[active]
=>active
exactly as we already saw above.
The example above, applied to a more realistic example, gives:
car(int tab[10];)
=>int tab10;
car([int tab[10];])
=>int tab10;
car([[int tab[10];]])
=>int tab[10];
Huh? The first case is easily understood, but why is the second wrong,
and the third right? To understand that, you must know that after M4
expands a macro, the resulting text is immediately subjected to macro
expansion and quote removal. This means that the quote removal occurs
twice--first before the argument is passed to the `car' macro, and
second after the `car' macro expands to the first argument.
As the author of the Autoconf macro `car', you then consider it to
be incorrect that your users have to double-quote the arguments of
`car', so you "fix" your macro. Let's call it `qar' for quoted car:
define([qar], [[$1]])
and check that `qar' is properly fixed:
qar([int tab[10];])
=>int tab[10];
Ahhh! That's much better.
But note what you've done: now that the result of `qar' is always a
literal string, the only time a user can use nested macros is if she
relies on an _unquoted_ macro call:
qar(active)
=>ACT
qar([active])
=>active
leaving no way for her to reproduce what she used to do with `car':
car([active])
=>ACT, IVE
Worse yet: she wants to use a macro that produces a set of `cpp' macros:
define([my_includes], [#include ])
car([my_includes])
=>#include
qar(my_includes)
error-->EOF in argument list
This macro, `qar', because it double quotes its arguments, forces
its users to leave their macro calls unquoted, which is dangerous.
Commas and other active symbols are interpreted by M4 before they are
given to the macro, often not in the way the users expect. Also,
because `qar' behaves differently from the other macros, it's an
exception that should be avoided in Autoconf.
File: autoconf.info, Node: Changequote is Evil, Next: Quadrigraphs, Prev: Quotation and Nested Macros, Up: M4 Quotation
8.1.5 `changequote' is Evil
---------------------------
The temptation is often high to bypass proper quotation, in particular
when it's late at night. Then, many experienced Autoconf hackers
finally surrender to the dark side of the force and use the ultimate
weapon: `changequote'.
The M4 builtin `changequote' belongs to a set of primitives that
allow one to adjust the syntax of the language to adjust it to one's
needs. For instance, by default M4 uses ``' and `'' as quotes, but in
the context of shell programming (and actually of most programming
languages), that's about the worst choice one can make: because of
strings and back-quoted expressions in shell code (such as `'this'' and
``that`'), and because of literal characters in usual programming
languages (as in `'0''), there are many unbalanced ``' and `''. Proper
M4 quotation then becomes a nightmare, if not impossible. In order to
make M4 useful in such a context, its designers have equipped it with
`changequote', which makes it possible to choose another pair of
quotes. M4sugar, M4sh, Autoconf, and Autotest all have chosen to use
`[' and `]'. Not especially because they are unlikely characters, but
_because they are characters unlikely to be unbalanced_.
There are other magic primitives, such as `changecom' to specify
what syntactic forms are comments (it is common to see `changecom()' when M4 is used to produce HTML pages), `changeword' and
`changesyntax' to change other syntactic details (such as the character
to denote the Nth argument, `$' by default, the parentheses around
arguments, etc.).
These primitives are really meant to make M4 more useful for specific
domains: they should be considered like command line options:
`--quotes', `--comments', `--words', and `--syntax'. Nevertheless,
they are implemented as M4 builtins, as it makes M4 libraries self
contained (no need for additional options).
There lies the problem...
The problem is that it is then tempting to use them in the middle of
an M4 script, as opposed to its initialization. This, if not carefully
thought out, can lead to disastrous effects: _you are changing the
language in the middle of the execution_. Changing and restoring the
syntax is often not enough: if you happened to invoke macros in between,
these macros are lost, as the current syntax is probably not the one
they were implemented with.
File: autoconf.info, Node: Quadrigraphs, Next: Balancing Parentheses, Prev: Changequote is Evil, Up: M4 Quotation
8.1.6 Quadrigraphs
------------------
When writing an Autoconf macro you may occasionally need to generate
special characters that are difficult to express with the standard
Autoconf quoting rules. For example, you may need to output the regular
expression `[^[]', which matches any character other than `['. This
expression contains unbalanced brackets so it cannot be put easily into
an M4 macro.
Additionally, there are a few m4sugar macros (such as `m4_split' and
`m4_expand') which internally use special markers in addition to the
regular quoting characters. If the arguments to these macros contain
the literal strings `-=<{(' or `)}>=-', the macros might behave
incorrectly.
You can work around these problems by using one of the following
"quadrigraphs":
`@<:@'
`['
`@:>@'
`]'
`@S|@'
`$'
`@%:@'
`#'
`@{:@'
`('
`@:}@'
`)'
`@&t@'
Expands to nothing.
Quadrigraphs are replaced at a late stage of the translation process,
after `m4' is run, so they do not get in the way of M4 quoting. For
example, the string `^@<:@', independently of its quotation, appears as
`^[' in the output.
The empty quadrigraph can be used:
- to mark trailing spaces explicitly
Trailing spaces are smashed by `autom4te'. This is a feature.
- to produce quadrigraphs and other strings reserved by m4sugar
For instance `@<@&t@:@' produces `@<:@'. For a more contrived
example:
m4_define([a], [A])m4_define([b], [B])m4_define([c], [C])dnl
m4_split([a )}>=- b -=<{( c])
=>[a], [], [B], [], [c]
m4_split([a )}@&t@>=- b -=<@&t@{( c])
=>[a], [)}>=-], [b], [-=<{(], [c]
- to escape _occurrences_ of forbidden patterns
For instance you might want to mention `AC_FOO' in a comment, while
still being sure that `autom4te' still catches unexpanded `AC_*'.
Then write `AC@&t@_FOO'.
The name `@&t@' was suggested by Paul Eggert:
I should give some credit to the `@&t@' pun. The `&' is my own
invention, but the `t' came from the source code of the ALGOL68C
compiler, written by Steve Bourne (of Bourne shell fame), and
which used `mt' to denote the empty string. In C, it would have
looked like something like:
char const mt[] = "";
but of course the source code was written in Algol 68.
I don't know where he got `mt' from: it could have been his own
invention, and I suppose it could have been a common pun around the
Cambridge University computer lab at the time.
File: autoconf.info, Node: Balancing Parentheses, Next: Quotation Rule Of Thumb, Prev: Quadrigraphs, Up: M4 Quotation
8.1.7 Dealing with unbalanced parentheses
-----------------------------------------
One of the pitfalls of portable shell programming is that `case'
statements require unbalanced parentheses (*note Limitations of Shell
Builtins: case.). With syntax highlighting editors, the presence of
unbalanced `)' can interfere with editors that perform syntax
highlighting of macro contents based on finding the matching `('.
Another concern is how much editing must be done when transferring code
snippets between shell scripts and macro definitions. But most
importantly, the presence of unbalanced parentheses can introduce
expansion bugs.
For an example, here is an underquoted attempt to use the macro
`my_case', which happens to expand to a portable `case' statement:
AC_DEFUN([my_case],
[case $file_name in
*.c) echo "C source code";;
esac])
AS_IF(:, my_case)
In the above example, the `AS_IF' call underquotes its arguments. As a
result, the unbalanced `)' generated by the premature expansion of
`my_case' results in expanding `AS_IF' with a truncated parameter, and
the expansion is syntactically invalid:
if :; then
case $file_name in
*.c
fi echo "C source code";;
esac)
If nothing else, this should emphasize the importance of the quoting
arguments to macro calls. On the other hand, there are several
variations for defining `my_case' to be more robust, even when used
without proper quoting, each with some benefits and some drawbacks.
Creative literal shell comment
AC_DEFUN([my_case],
[case $file_name in #(
*.c) echo "C source code";;
esac])
This version provides balanced parentheses to several editors, and
can be copied and pasted into a terminal as is. Unfortunately, it
is still unbalanced as an Autoconf argument, since `#(' is an M4
comment that masks the normal properties of `('.
Quadrigraph shell comment
AC_DEFUN([my_case],
[case $file_name in @%:@(
*.c) echo "C source code";;
esac])
This version provides balanced parentheses to even more editors,
and can be used as a balanced Autoconf argument. Unfortunately,
it requires some editing before it can be copied and pasted into a
terminal, and the use of the quadrigraph `@%:@' for `#' reduces
readability.
Quoting just the parenthesis
AC_DEFUN([my_case],
[case $file_name in
*.c[)] echo "C source code";;
esac])
This version quotes the `)', so that it can be used as a balanced
Autoconf argument. As written, this is not balanced to an editor,
but it can be coupled with `[#(]' to meet that need, too.
However, it still requires some edits before it can be copied and
pasted into a terminal.
Double-quoting the entire statement
AC_DEFUN([my_case],
[[case $file_name in #(
*.c) echo "C source code";;
esac]])
Since the entire macro is double-quoted, there is no problem with
using this as an Autoconf argument; and since the double-quoting
is over the entire statement, this code can be easily copied and
pasted into a terminal. However, the double quoting prevents the
expansion of any macros inside the case statement, which may cause
its own set of problems.
Using `AS_CASE'
AC_DEFUN([my_case],
[AS_CASE([$file_name],
[*.c], [echo "C source code"])])
This version avoids the balancing issue altogether, by relying on
`AS_CASE' (*note Common Shell Constructs::); it also allows for the
expansion of `AC_REQUIRE' to occur prior to the entire case
statement, rather than within a branch of the case statement that
might not be taken. However, the abstraction comes with a penalty
that it is no longer a quick copy, paste, and edit to get back to
shell code.
File: autoconf.info, Node: Quotation Rule Of Thumb, Prev: Balancing Parentheses, Up: M4 Quotation
8.1.8 Quotation Rule Of Thumb
-----------------------------
To conclude, the quotation rule of thumb is:
_One pair of quotes per pair of parentheses._
Never over-quote, never under-quote, in particular in the definition
of macros. In the few places where the macros need to use brackets
(usually in C program text or regular expressions), properly quote _the
arguments_!
It is common to read Autoconf programs with snippets like:
AC_TRY_LINK(
changequote(<<, >>)dnl
<<#include
#ifndef tzname /* For SGI. */
extern char *tzname[]; /* RS6000 and others reject char **tzname. */
#endif>>,
changequote([, ])dnl
[atoi (*tzname);], ac_cv_var_tzname=yes, ac_cv_var_tzname=no)
which is incredibly useless since `AC_TRY_LINK' is _already_ double
quoting, so you just need:
AC_TRY_LINK(
[#include
#ifndef tzname /* For SGI. */
extern char *tzname[]; /* RS6000 and others reject char **tzname. */
#endif],
[atoi (*tzname);],
[ac_cv_var_tzname=yes],
[ac_cv_var_tzname=no])
The M4-fluent reader might note that these two examples are rigorously
equivalent, since M4 swallows both the `changequote(<<, >>)' and `<<'
`>>' when it "collects" the arguments: these quotes are not part of the
arguments!
Simplified, the example above is just doing this:
changequote(<<, >>)dnl
<<[]>>
changequote([, ])dnl
instead of simply:
[[]]
With macros that do not double quote their arguments (which is the
rule), double-quote the (risky) literals:
AC_LINK_IFELSE([AC_LANG_PROGRAM(
[[#include
#ifndef tzname /* For SGI. */
extern char *tzname[]; /* RS6000 and others reject char **tzname. */
#endif]],
[atoi (*tzname);])],
[ac_cv_var_tzname=yes],
[ac_cv_var_tzname=no])
Please note that the macro `AC_TRY_LINK' is obsolete, so you really
should be using `AC_LINK_IFELSE' instead.
*Note Quadrigraphs::, for what to do if you run into a hopeless case
where quoting does not suffice.
When you create a `configure' script using newly written macros,
examine it carefully to check whether you need to add more quotes in
your macros. If one or more words have disappeared in the M4 output,
you need more quotes. When in doubt, quote.
However, it's also possible to put on too many layers of quotes. If
this happens, the resulting `configure' script may contain unexpanded
macros. The `autoconf' program checks for this problem by looking for
the string `AC_' in `configure'. However, this heuristic does not work
in general: for example, it does not catch overquoting in `AC_DEFINE'
descriptions.
File: autoconf.info, Node: Using autom4te, Next: Programming in M4sugar, Prev: M4 Quotation, Up: Programming in M4
8.2 Using `autom4te'
====================
The Autoconf suite, including M4sugar, M4sh, and Autotest, in addition
to Autoconf per se, heavily rely on M4. All these different uses
revealed common needs factored into a layer over M4: `autom4te'(1).
`autom4te' is a preprocessor that is like `m4'. It supports M4
extensions designed for use in tools like Autoconf.
* Menu:
* autom4te Invocation:: A GNU M4 wrapper
* Customizing autom4te:: Customizing the Autoconf package
---------- Footnotes ----------
(1) Yet another great name from Lars J. Aas.
File: autoconf.info, Node: autom4te Invocation, Next: Customizing autom4te, Up: Using autom4te
8.2.1 Invoking `autom4te'
-------------------------
The command line arguments are modeled after M4's:
autom4te OPTIONS FILES
where the FILES are directly passed to `m4'. By default, GNU M4 is
found during configuration, but the environment variable `M4' can be
set to tell `autom4te' where to look. In addition to the regular
expansion, it handles the replacement of the quadrigraphs (*note
Quadrigraphs::), and of `__oline__', the current line in the output.
It supports an extended syntax for the FILES:
`FILE.m4f'
This file is an M4 frozen file. Note that _all the previous files
are ignored_. See the option `--melt' for the rationale.
`FILE?'
If found in the library path, the FILE is included for expansion,
otherwise it is ignored instead of triggering a failure.
Of course, it supports the Autoconf common subset of options:
`--help'
`-h'
Print a summary of the command line options and exit.
`--version'
`-V'
Print the version number of Autoconf and exit.
`--verbose'
`-v'
Report processing steps.
`--debug'
`-d'
Don't remove the temporary files and be even more verbose.
`--include=DIR'
`-I DIR'
Also look for input files in DIR. Multiple invocations accumulate.
`--output=FILE'
`-o FILE'
Save output (script or trace) to FILE. The file `-' stands for
the standard output.
As an extension of `m4', it includes the following options:
`--warnings=CATEGORY'
`-W CATEGORY'
Report the warnings related to CATEGORY (which can actually be a
comma separated list). *Note Reporting Messages::, macro
`AC_DIAGNOSE', for a comprehensive list of categories. Special
values include:
`all'
report all the warnings
`none'
report none
`error'
treats warnings as errors
`no-CATEGORY'
disable warnings falling into CATEGORY
Warnings about `syntax' are enabled by default, and the environment
variable `WARNINGS', a comma separated list of categories, is
honored. `autom4te -W CATEGORY' actually behaves as if you had
run:
autom4te --warnings=syntax,$WARNINGS,CATEGORY
For example, if you want to disable defaults and `WARNINGS' of
`autom4te', but enable the warnings about obsolete constructs, you
would use `-W none,obsolete'.
`autom4te' displays a back trace for errors, but not for warnings;
if you want them, just pass `-W error'.
`--melt'
`-M'
Do not use frozen files. Any argument `FILE.m4f' is replaced by
`FILE.m4'. This helps tracing the macros which are executed only
when the files are frozen, typically `m4_define'. For instance,
running:
autom4te --melt 1.m4 2.m4f 3.m4 4.m4f input.m4
is roughly equivalent to running:
m4 1.m4 2.m4 3.m4 4.m4 input.m4
while
autom4te 1.m4 2.m4f 3.m4 4.m4f input.m4
is equivalent to:
m4 --reload-state=4.m4f input.m4
`--freeze'
`-F'
Produce a frozen state file. `autom4te' freezing is stricter than
M4's: it must produce no warnings, and no output other than empty
lines (a line with white space is _not_ empty) and comments
(starting with `#'). Unlike `m4''s similarly-named option, this
option takes no argument:
autom4te 1.m4 2.m4 3.m4 --freeze --output=3.m4f
corresponds to
m4 1.m4 2.m4 3.m4 --freeze-state=3.m4f
`--mode=OCTAL-MODE'
`-m OCTAL-MODE'
Set the mode of the non-traces output to OCTAL-MODE; by default
`0666'.
As another additional feature over `m4', `autom4te' caches its
results. GNU M4 is able to produce a regular output and traces at the
same time. Traces are heavily used in the GNU Build System:
`autoheader' uses them to build `config.h.in', `autoreconf' to
determine what GNU Build System components are used, `automake' to
"parse" `configure.ac' etc. To avoid recomputation, traces are cached
while performing regular expansion, and conversely. This cache is
(actually, the caches are) stored in the directory `autom4te.cache'.
_It can safely be removed_ at any moment (especially if for some reason
`autom4te' considers it trashed).
`--cache=DIRECTORY'
`-C DIRECTORY'
Specify the name of the directory where the result should be
cached. Passing an empty value disables caching. Be sure to pass
a relative file name, as for the time being, global caches are not
supported.
`--no-cache'
Don't cache the results.
`--force'
`-f'
If a cache is used, consider it obsolete (but update it anyway).
Because traces are so important to the GNU Build System, `autom4te'
provides high level tracing features as compared to M4, and helps
exploiting the cache:
`--trace=MACRO[:FORMAT]'
`-t MACRO[:FORMAT]'
Trace the invocations of MACRO according to the FORMAT. Multiple
`--trace' arguments can be used to list several macros. Multiple
`--trace' arguments for a single macro are not cumulative;
instead, you should just make FORMAT as long as needed.
The FORMAT is a regular string, with newlines if desired, and
several special escape codes. It defaults to `$f:$l:$n:$%'. It
can use the following special escapes:
`$$'
The character `$'.
`$f'
The file name from which MACRO is called.
`$l'
The line number from which MACRO is called.
`$d'
The depth of the MACRO call. This is an M4 technical detail
that you probably don't want to know about.
`$n'
The name of the MACRO.
`$NUM'
The NUMth argument of the call to MACRO.
`$@'
`$SEP@'
`${SEPARATOR}@'
All the arguments passed to MACRO, separated by the character
SEP or the string SEPARATOR (`,' by default). Each argument
is quoted, i.e., enclosed in a pair of square brackets.
`$*'
`$SEP*'
`${SEPARATOR}*'
As above, but the arguments are not quoted.
`$%'
`$SEP%'
`${SEPARATOR}%'
As above, but the arguments are not quoted, all new line
characters in the arguments are smashed, and the default
separator is `:'.
The escape `$%' produces single-line trace outputs (unless
you put newlines in the `separator'), while `$@' and `$*' do
not.
*Note autoconf Invocation::, for examples of trace uses.
`--preselect=MACRO'
`-p MACRO'
Cache the traces of MACRO, but do not enable traces. This is
especially important to save CPU cycles in the future. For
instance, when invoked, `autoconf' preselects all the macros that
`autoheader', `automake', `autoreconf', etc., trace, so that
running `m4' is not needed to trace them: the cache suffices.
This results in a huge speed-up.
Finally, `autom4te' introduces the concept of "Autom4te libraries".
They consists in a powerful yet extremely simple feature: sets of
combined command line arguments:
`--language=LANGUAGE'
`-l LANGUAGE'
Use the LANGUAGE Autom4te library. Current languages include:
`M4sugar'
create M4sugar output.
`M4sh'
create M4sh executable shell scripts.
`Autotest'
create Autotest executable test suites.
`Autoconf-without-aclocal-m4'
create Autoconf executable configure scripts without reading
`aclocal.m4'.
`Autoconf'
create Autoconf executable configure scripts. This language
inherits all the characteristics of
`Autoconf-without-aclocal-m4' and additionally reads
`aclocal.m4'.
`--prepend-include=DIR'
`-B DIR'
Prepend directory DIR to the search path. This is used to include
the language-specific files before any third-party macros.
As an example, if Autoconf is installed in its default location,
`/usr/local', the command `autom4te -l m4sugar foo.m4' is strictly
equivalent to the command:
autom4te --prepend-include /usr/local/share/autoconf \
m4sugar/m4sugar.m4f --warnings syntax foo.m4
Recursive expansion applies here: the command `autom4te -l m4sh foo.m4'
is the same as `autom4te --language M4sugar m4sugar/m4sh.m4f foo.m4',
i.e.:
autom4te --prepend-include /usr/local/share/autoconf \
m4sugar/m4sugar.m4f m4sugar/m4sh.m4f --mode 777 foo.m4
The definition of the languages is stored in `autom4te.cfg'.
File: autoconf.info, Node: Customizing autom4te, Prev: autom4te Invocation, Up: Using autom4te
8.2.2 Customizing `autom4te'
----------------------------
One can customize `autom4te' via `~/.autom4te.cfg' (i.e., as found in
the user home directory), and `./.autom4te.cfg' (i.e., as found in the
directory from which `autom4te' is run). The order is first reading
`autom4te.cfg', then `~/.autom4te.cfg', then `./.autom4te.cfg', and
finally the command line arguments.
In these text files, comments are introduced with `#', and empty
lines are ignored. Customization is performed on a per-language basis,
wrapped in between a `begin-language: "LANGUAGE"', `end-language:
"LANGUAGE"' pair.
Customizing a language stands for appending options (*note autom4te
Invocation::) to the current definition of the language. Options, and
more generally arguments, are introduced by `args: ARGUMENTS'. You may
use the traditional shell syntax to quote the ARGUMENTS.
As an example, to disable Autoconf caches (`autom4te.cache')
globally, include the following lines in `~/.autom4te.cfg':
## ------------------ ##
## User Preferences. ##
## ------------------ ##
begin-language: "Autoconf-without-aclocal-m4"
args: --no-cache
end-language: "Autoconf-without-aclocal-m4"
File: autoconf.info, Node: Programming in M4sugar, Next: Debugging via autom4te, Prev: Using autom4te, Up: Programming in M4
8.3 Programming in M4sugar
==========================
M4 by itself provides only a small, but sufficient, set of all-purpose
macros. M4sugar introduces additional generic macros. Its name was
coined by Lars J. Aas: "Readability And Greater Understanding Stands 4
M4sugar".
M4sugar reserves the macro namespace `^_m4_' for internal use, and
the macro namespace `^m4_' for M4sugar macros. You should not define
your own macros into these namespaces.
* Menu:
* Redefined M4 Macros:: M4 builtins changed in M4sugar
* Diagnostic Macros:: Diagnostic messages from M4sugar
* Diversion support:: Diversions in M4sugar
* Conditional constructs:: Conditions in M4
* Looping constructs:: Iteration in M4
* Evaluation Macros:: More quotation and evaluation control
* Text processing Macros:: String manipulation in M4
* Number processing Macros:: Arithmetic computation in M4
* Set manipulation Macros:: Set manipulation in M4
* Forbidden Patterns:: Catching unexpanded macros
File: autoconf.info, Node: Redefined M4 Macros, Next: Diagnostic Macros, Up: Programming in M4sugar
8.3.1 Redefined M4 Macros
-------------------------
With a few exceptions, all the M4 native macros are moved in the `m4_'
pseudo-namespace, e.g., M4sugar renames `define' as `m4_define' etc.
The list of macros unchanged from M4, except for their name, is:
- m4_builtin
- m4_changecom
- m4_changequote
- m4_debugfile
- m4_debugmode
- m4_decr
- m4_define
- m4_divnum
- m4_errprint
- m4_esyscmd
- m4_eval
- m4_format
- m4_ifdef
- m4_incr
- m4_index
- m4_indir
- m4_len
- m4_pushdef
- m4_shift
- m4_substr
- m4_syscmd
- m4_sysval
- m4_traceoff
- m4_traceon
- m4_translit
Some M4 macros are redefined, and are slightly incompatible with
their native equivalent.
-- Macro: __file__
-- Macro: __line__
All M4 macros starting with `__' retain their original name: for
example, no `m4__file__' is defined.
-- Macro: __oline__
This is not technically a macro, but a feature of Autom4te. The
sequence `__oline__' can be used similarly to the other m4sugar
location macros, but rather than expanding to the location of the
input file, it is translated to the line number where it appears
in the output file after all other M4 expansions.
-- Macro: dnl
This macro kept its original name: no `m4_dnl' is defined.
-- Macro: m4_bpatsubst (STRING, REGEXP, [REPLACEMENT])
This macro corresponds to `patsubst'. The name `m4_patsubst' is
kept for future versions of M4sugar, once GNU M4 2.0 is released
and supports extended regular expression syntax.
-- Macro: m4_bregexp (STRING, REGEXP, [REPLACEMENT])
This macro corresponds to `regexp'. The name `m4_regexp' is kept
for future versions of M4sugar, once GNU M4 2.0 is released and
supports extended regular expression syntax.
-- Macro: m4_copy (SOURCE, DEST)
-- Macro: m4_copy_force (SOURCE, DEST)
-- Macro: m4_rename (SOURCE, DEST)
-- Macro: m4_rename_force (SOURCE, DEST)
These macros aren't directly builtins, but are closely related to
`m4_pushdef' and `m4_defn'. `m4_copy' and `m4_rename' ensure that
DEST is undefined, while `m4_copy_force' and `m4_rename_force'
overwrite any existing definition. All four macros then proceed
to copy the entire pushdef stack of definitions of SOURCE over to
DEST. `m4_copy' and `m4_copy_force' preserve the source
(including in the special case where SOURCE is undefined), while
`m4_rename' and `m4_rename_force' undefine the original macro name
(making it an error to rename an undefined SOURCE).
Note that attempting to invoke a renamed macro might not work,
since the macro may have a dependence on helper macros accessed
via composition of `$0' but that were not also renamed; likewise,
other macros may have a hard-coded dependence on SOURCE and could
break if SOURCE has been deleted. On the other hand, it is always
safe to rename a macro to temporarily move it out of the way, then
rename it back later to restore original semantics.
-- Macro: m4_defn (MACRO...)
This macro fails if MACRO is not defined, even when using older
versions of M4 that did not warn. See `m4_undefine'.
Unfortunately, in order to support these older versions of M4,
there are some situations involving unbalanced quotes where
concatenating multiple macros together will work in newer M4 but
not in m4sugar; use quadrigraphs to work around this.
-- Macro: m4_divert (DIVERSION)
M4sugar relies heavily on diversions, so rather than behaving as a
primitive, `m4_divert' behaves like:
m4_divert_pop()m4_divert_push([DIVERSION])
*Note Diversion support::, for more details about the use of the
diversion stack.
-- Macro: m4_dumpdef (NAME...)
-- Macro: m4_dumpdefs (NAME...)
`m4_dumpdef' is like the M4 builtin, except that this version
requires at least one argument, output always goes to standard
error rather than the current debug file, no sorting is done on
multiple arguments, and an error is issued if any NAME is
undefined. `m4_dumpdefs' is a convenience macro that calls
`m4_dumpdef' for all of the `m4_pushdef' stack of definitions,
starting with the current, and silently does nothing if NAME is
undefined.
Unfortunately, due to a limitation in M4 1.4.x, any macro defined
as a builtin is output as the empty string. This behavior is
rectified by using M4 1.6 or newer. However, this behavior
difference means that `m4_dumpdef' should only be used while
developing m4sugar macros, and never in the final published form
of a macro.
-- Macro: m4_esyscmd_s (COMMAND)
Like `m4_esyscmd', this macro expands to the result of running
COMMAND in a shell. The difference is that any trailing newlines
are removed, so that the output behaves more like shell command
substitution.
-- Macro: m4_exit (EXIT-STATUS)
This macro corresponds to `m4exit'.
-- Macro: m4_if (COMMENT)
-- Macro: m4_if (STRING-1, STRING-2, EQUAL, [NOT-EQUAL])
-- Macro: m4_if (STRING-1, STRING-2, EQUAL-1, STRING-3, STRING-4,
EQUAL-2, ..., [NOT-EQUAL])
This macro corresponds to `ifelse'. STRING-1 and STRING-2 are
compared literally, so usually one of the two arguments is passed
unquoted. *Note Conditional constructs::, for more conditional
idioms.
-- Macro: m4_include (FILE)
-- Macro: m4_sinclude (FILE)
Like the M4 builtins, but warn against multiple inclusions of FILE.
-- Macro: m4_mkstemp (TEMPLATE)
-- Macro: m4_maketemp (TEMPLATE)
Posix requires `maketemp' to replace the trailing `X' characters
in TEMPLATE with the process id, without regards to the existence
of a file by that name, but this a security hole. When this was
pointed out to the Posix folks, they agreed to invent a new macro
`mkstemp' that always creates a uniquely named file, but not all
versions of GNU M4 support the new macro. In M4sugar,
`m4_maketemp' and `m4_mkstemp' are synonyms for each other, and
both have the secure semantics regardless of which macro the
underlying M4 provides.
-- Macro: m4_popdef (MACRO...)
This macro fails if MACRO is not defined, even when using older
versions of M4 that did not warn. See `m4_undefine'.
-- Macro: m4_undefine (MACRO...)
This macro fails if MACRO is not defined, even when using older
versions of M4 that did not warn. Use
m4_ifdef([MACRO], [m4_undefine([MACRO])])
if you are not sure whether MACRO is defined.
-- Macro: m4_undivert (DIVERSION...)
Unlike the M4 builtin, at least one DIVERSION must be specified.
Also, since the M4sugar diversion stack prefers named diversions,
the use of `m4_undivert' to include files is risky. *Note
Diversion support::, for more details about the use of the
diversion stack.
-- Macro: m4_wrap (TEXT)
-- Macro: m4_wrap_lifo (TEXT)
These macros correspond to `m4wrap'. Posix requires arguments of
multiple wrap calls to be reprocessed at EOF in the same order as
the original calls (first-in, first-out). GNU M4 versions through
1.4.10, however, reprocess them in reverse order (last-in,
first-out). Both orders are useful, therefore, you can rely on
`m4_wrap' to provide FIFO semantics and `m4_wrap_lifo' for LIFO
semantics, regardless of the underlying GNU M4 version.
Unlike the GNU M4 builtin, these macros only recognize one
argument, and avoid token pasting between consecutive invocations.
On the other hand, nested calls to `m4_wrap' from within wrapped
text work just as in the builtin.
File: autoconf.info, Node: Diagnostic Macros, Next: Diversion support, Prev: Redefined M4 Macros, Up: Programming in M4sugar
8.3.2 Diagnostic messages from M4sugar
--------------------------------------
When macros statically diagnose abnormal situations, benign or fatal,
they should report them using these macros. For issuing dynamic issues,
i.e., when `configure' is run, see *note Printing Messages::.
-- Macro: m4_assert (EXPRESSION, [EXIT-STATUS = `1'])
Assert that the arithmetic EXPRESSION evaluates to non-zero.
Otherwise, issue a fatal error, and exit `autom4te' with
EXIT-STATUS.
-- Macro: m4_errprintn (MESSAGE)
Similar to the builtin `m4_errprint', except that a newline is
guaranteed after MESSAGE.
-- Macro: m4_fatal (MESSAGE)
Report a severe error MESSAGE prefixed with the current location,
and have `autom4te' die.
-- Macro: m4_location
Useful as a prefix in a message line. Short for:
__file__:__line__
-- Macro: m4_warn (CATEGORY, MESSAGE)
Report MESSAGE as a warning (or as an error if requested by the
user) if warnings of the CATEGORY are turned on. If the message
is emitted, it is prefixed with the current location, and followed
by a call trace of all macros defined via `AC_DEFUN' used to get
to the current expansion. You are encouraged to use standard
categories, which currently include:
`all'
messages that don't fall into one of the following
categories. Use of an empty CATEGORY is equivalent.
`cross'
related to cross compilation issues.
`obsolete'
use of an obsolete construct.
`syntax'
dubious syntactic constructs, incorrectly ordered macro calls.
File: autoconf.info, Node: Diversion support, Next: Conditional constructs, Prev: Diagnostic Macros, Up: Programming in M4sugar
8.3.3 Diversion support
-----------------------
M4sugar makes heavy use of diversions, because it is often the case that
text that must appear early in the output is not discovered until late
in the input. Additionally, some of the topological sorting algorithms
used in resolving macro dependencies use diversions. However, most
macros should not need to change diversions directly, but rather rely on
higher-level M4sugar macros to manage diversions transparently.
In the rare case that it is necessary to write a macro that
explicitly outputs text to a different diversion, it is important to be
aware of an M4 limitation regarding diversions: text only goes to a
diversion if it is not part of argument collection. Therefore, any
macro that changes the current diversion cannot be used as an unquoted
argument to another macro, but must be expanded at the top level. The
macro `m4_expand' will diagnose any attempt to change diversions, since
it is generally useful only as an argument to another macro. The
following example shows what happens when diversion manipulation is
attempted within macro arguments:
m4_do([normal text]
m4_divert_push([KILL])unwanted[]m4_divert_pop([KILL])
[m4_divert_push([KILL])discarded[]m4_divert_pop([KILL])])dnl
=>normal text
=>unwanted
Notice that the unquoted text `unwanted' is output, even though it was
processed while the current diversion was `KILL', because it was
collected as part of the argument to `m4_do'. However, the text
`discarded' disappeared as desired, because the diversion changes were
single-quoted, and were not expanded until the top-level rescan of the
output of `m4_do'.
To make diversion management easier, M4sugar uses the concept of
named diversions. Rather than using diversion numbers directly, it is
nicer to associate a name with each diversion; the diversion number
associated with a particular diversion name is an implementation
detail, so you should only use diversion names. In general, you should
not output text to a named diversion until after calling the
appropriate initialization routine for your language (`m4_init',
`AS_INIT', `AT_INIT', ...), although there are some exceptions
documented below.
M4sugar defines two named diversions.
`KILL'
Text written to this diversion is discarded. This is the default
diversion once M4sugar is initialized.
`GROW'
This diversion is used behind the scenes by topological sorting
macros, such as `AC_REQUIRE'.
M4sh adds several more named diversions.
`BINSH'
This diversion is reserved for the `#!' interpreter line.
`HEADER-REVISION'
This diversion holds text from `AC_REVISION'.
`HEADER-COMMENT'
This diversion holds comments about the purpose of a file.
`HEADER-COPYRIGHT'
This diversion is managed by `AC_COPYRIGHT'.
`M4SH-SANITIZE'
This diversion contains M4sh sanitization code, used to ensure
M4sh is executing in a reasonable shell environment.
`M4SH-INIT'
This diversion contains M4sh initialization code, initializing
variables that are required by other M4sh macros.
`BODY'
This diversion contains the body of the shell code, and is the
default diversion once M4sh is initialized.
Autotest inherits diversions from M4sh, and changes the default
diversion from `BODY' back to `KILL'. It also adds several more named
diversions, with the following subset designed for developer use.
`PREPARE_TESTS'
This diversion contains initialization sequences which are executed
after `atconfig' and `atlocal', and after all command line
arguments have been parsed, but prior to running any tests. It
can be used to set up state that is required across all tests.
This diversion will work even before `AT_INIT'.
For now, the named diversions of Autoconf and Autoheader, and the
remaining diversions of Autotest, are not documented. In other words,
intentionally outputting text into an undocumented diversion is subject
to breakage in a future release of Autoconf.
-- Macro: m4_cleardivert (DIVERSION...)
Permanently discard any text that has been diverted into DIVERSION.
-- Macro: m4_divert_once (DIVERSION, [CONTENT])
Similar to `m4_divert_text', except that CONTENT is only output to
DIVERSION if this is the first time that `m4_divert_once' has been
called with its particular arguments.
-- Macro: m4_divert_pop ([DIVERSION])
If provided, check that the current diversion is indeed DIVERSION.
Then change to the diversion located earlier on the stack, giving
an error if an attempt is made to pop beyond the initial m4sugar
diversion of `KILL'.
-- Macro: m4_divert_push (DIVERSION)
Remember the former diversion on the diversion stack, and output
subsequent text into DIVERSION. M4sugar maintains a diversion
stack, and issues an error if there is not a matching pop for every
push.
-- Macro: m4_divert_text (DIVERSION, [CONTENT])
Output CONTENT and a newline into DIVERSION, without affecting the
current diversion. Shorthand for:
m4_divert_push([DIVERSION])CONTENT
m4_divert_pop([DIVERSION])dnl
-- Macro: m4_init
Initialize the M4sugar environment, setting up the default named
diversion to be `KILL'.
File: autoconf.info, Node: Conditional constructs, Next: Looping constructs, Prev: Diversion support, Up: Programming in M4sugar
8.3.4 Conditional constructs
----------------------------
The following macros provide additional conditional constructs as
convenience wrappers around `m4_if'.
-- Macro: m4_bmatch (STRING, REGEX-1, VALUE-1, [REGEX-2], [VALUE-2],
..., [DEFAULT])
The string STRING is repeatedly compared against a series of REGEX
arguments; if a match is found, the expansion is the corresponding
VALUE, otherwise, the macro moves on to the next REGEX. If no
REGEX match, then the result is the optional DEFAULT, or nothing.
-- Macro: m4_bpatsubsts (STRING, REGEX-1, SUBST-1, [REGEX-2],
[SUBST-2], ...)
The string STRING is altered by REGEX-1 and SUBST-1, as if by:
m4_bpatsubst([[STRING]], [REGEX], [SUBST])
The result of the substitution is then passed through the next set
of REGEX and SUBST, and so forth. An empty SUBST implies deletion
of any matched portions in the current string. Note that this
macro over-quotes STRING; this behavior is intentional, so that
the result of each step of the recursion remains as a quoted
string. However, it means that anchors (`^' and `$' in the REGEX
will line up with the extra quotations, and not the characters of
the original string. The overquoting is removed after the final
substitution.
-- Macro: m4_case (STRING, VALUE-1, IF-VALUE-1, [VALUE-2],
[IF-VALUE-2], ..., [DEFAULT])
Test STRING against multiple VALUE possibilities, resulting in the
first IF-VALUE for a match, or in the optional DEFAULT. This is
shorthand for:
m4_if([STRING], [VALUE-1], [IF-VALUE-1],
[STRING], [VALUE-2], [IF-VALUE-2], ...,
[DEFAULT])
-- Macro: m4_cond (TEST-1, VALUE-1, IF-VALUE-1, [TEST-2], [VALUE-2],
[IF-VALUE-2], ..., [DEFAULT])
This macro was introduced in Autoconf 2.62. Similar to `m4_if',
except that each TEST is expanded only when it is encountered.
This is useful for short-circuiting expensive tests; while `m4_if'
requires all its strings to be expanded up front before doing
comparisons, `m4_cond' only expands a TEST when all earlier tests
have failed.
For an example, these two sequences give the same result, but in
the case where `$1' does not contain a backslash, the `m4_cond'
version only expands `m4_index' once, instead of five times, for
faster computation if this is a common case for `$1'. Notice that
every third argument is unquoted for `m4_if', and quoted for
`m4_cond':
m4_if(m4_index([$1], [\]), [-1], [$2],
m4_eval(m4_index([$1], [\\]) >= 0), [1], [$2],
m4_eval(m4_index([$1], [\$]) >= 0), [1], [$2],
m4_eval(m4_index([$1], [\`]) >= 0), [1], [$3],
m4_eval(m4_index([$1], [\"]) >= 0), [1], [$3],
[$2])
m4_cond([m4_index([$1], [\])], [-1], [$2],
[m4_eval(m4_index([$1], [\\]) >= 0)], [1], [$2],
[m4_eval(m4_index([$1], [\$]) >= 0)], [1], [$2],
[m4_eval(m4_index([$1], [\`]) >= 0)], [1], [$3],
[m4_eval(m4_index([$1], [\"]) >= 0)], [1], [$3],
[$2])
-- Macro: m4_default (EXPR-1, EXPR-2)
-- Macro: m4_default_quoted (EXPR-1, EXPR-2)
-- Macro: m4_default_nblank (EXPR-1, [EXPR-2])
-- Macro: m4_default_nblank_quoted (EXPR-1, [EXPR-2])
If EXPR-1 contains text, use it. Otherwise, select EXPR-2.
`m4_default' expands the result, while `m4_default_quoted' does
not. Useful for providing a fixed default if the expression that
results in EXPR-1 would otherwise be empty. The difference
between `m4_default' and `m4_default_nblank' is whether an
argument consisting of just blanks (space, tab, newline) is
significant. When using the expanding versions, note that an
argument may contain text but still expand to an empty string.
m4_define([active], [ACTIVE])dnl
m4_define([empty], [])dnl
m4_define([demo1], [m4_default([$1], [$2])])dnl
m4_define([demo2], [m4_default_quoted([$1], [$2])])dnl
m4_define([demo3], [m4_default_nblank([$1], [$2])])dnl
m4_define([demo4], [m4_default_nblank_quoted([$1], [$2])])dnl
demo1([active], [default])
=>ACTIVE
demo1([], [active])
=>ACTIVE
demo1([empty], [text])
=>
-demo1([ ], [active])-
=>- -
demo2([active], [default])
=>active
demo2([], [active])
=>active
demo2([empty], [text])
=>empty
-demo2([ ], [active])-
=>- -
demo3([active], [default])
=>ACTIVE
demo3([], [active])
=>ACTIVE
demo3([empty], [text])
=>
-demo3([ ], [active])-
=>-ACTIVE-
demo4([active], [default])
=>active
demo4([], [active])
=>active
demo4([empty], [text])
=>empty
-demo4([ ], [active])-
=>-active-
-- Macro: m4_ifblank (COND, [IF-BLANK], [IF-TEXT])
-- Macro: m4_ifnblank (COND, [IF-TEXT], [IF-BLANK])
If COND is empty or consists only of blanks (space, tab, newline),
then expand IF-BLANK; otherwise, expand IF-TEXT. Two variants
exist, in order to make it easier to select the correct logical
sense when using only two parameters. Note that this is more
efficient than the equivalent behavior of:
m4_ifval(m4_normalize([COND]), IF-TEXT, IF-COND)
-- Macro: m4_ifndef (MACRO, IF-NOT-DEFINED, [IF-DEFINED])
This is shorthand for:
m4_ifdef([MACRO], [IF-DEFINED], [IF-NOT-DEFINED])
-- Macro: m4_ifset (MACRO, [IF-TRUE], [IF-FALSE])
If MACRO is undefined, or is defined as the empty string, expand
to IF-FALSE. Otherwise, expands to IF-TRUE. Similar to:
m4_ifval(m4_defn([MACRO]), [IF-TRUE], [IF-FALSE])
except that it is not an error if MACRO is undefined.
-- Macro: m4_ifval (COND, [IF-TRUE], [IF-FALSE])
Expands to IF-TRUE if COND is not empty, otherwise to IF-FALSE.
This is shorthand for:
m4_if([COND], [], [IF-TRUE], [IF-FALSE])
-- Macro: m4_ifvaln (COND, [IF-TRUE], [IF-FALSE])
Similar to `m4_ifval', except guarantee that a newline is present
after any non-empty expansion. Often followed by `dnl'.
-- Macro: m4_n (TEXT)
Expand to TEXT, and add a newline if TEXT is not empty. Often
followed by `dnl'.
File: autoconf.info, Node: Looping constructs, Next: Evaluation Macros, Prev: Conditional constructs, Up: Programming in M4sugar
8.3.5 Looping constructs
------------------------
The following macros are useful in implementing recursive algorithms in
M4, including loop operations. An M4 list is formed by quoting a list
of quoted elements; generally the lists are comma-separated, although
`m4_foreach_w' is whitespace-separated. For example, the list `[[a],
[b,c]]' contains two elements: `[a]' and `[b,c]'. It is common to see
lists with unquoted elements when those elements are not likely to be
macro names, as in `[fputc_unlocked, fgetc_unlocked]'.
Although not generally recommended, it is possible for quoted lists
to have side effects; all side effects are expanded only once, and
prior to visiting any list element. On the other hand, the fact that
unquoted macros are expanded exactly once means that macros without
side effects can be used to generate lists. For example,
m4_foreach([i], [[1], [2], [3]m4_errprintn([hi])], [i])
error-->hi
=>123
m4_define([list], [[1], [2], [3]])
=>
m4_foreach([i], [list], [i])
=>123
-- Macro: m4_argn (N, [ARG]...)
Extracts argument N (larger than 0) from the remaining arguments.
If there are too few arguments, the empty string is used. For any
N besides 1, this is more efficient than the similar
`m4_car(m4_shiftn([N], [], [ARG...]))'.
-- Macro: m4_car (ARG...)
Expands to the quoted first ARG. Can be used with `m4_cdr' to
recursively iterate through a list. Generally, when using quoted
lists of quoted elements, `m4_car' should be called without any
extra quotes.
-- Macro: m4_cdr (ARG...)
Expands to a quoted list of all but the first ARG, or the empty
string if there was only one argument. Generally, when using
quoted lists of quoted elements, `m4_cdr' should be called without
any extra quotes.
For example, this is a simple implementation of `m4_map'; note how
each iteration checks for the end of recursion, then merely
applies the first argument to the first element of the list, then
repeats with the rest of the list. (The actual implementation in
M4sugar is a bit more involved, to gain some speed and share code
with `m4_map_sep', and also to avoid expanding side effects in
`$2' twice).
m4_define([m4_map], [m4_ifval([$2],
[m4_apply([$1], m4_car($2))[]$0([$1], m4_cdr($2))])])dnl
m4_map([ m4_eval], [[[1]], [[1+1]], [[10],[16]]])
=> 1 2 a
-- Macro: m4_for (VAR, FIRST, LAST, [STEP], EXPRESSION)
Loop over the numeric values between FIRST and LAST including
bounds by increments of STEP. For each iteration, expand
EXPRESSION with the numeric value assigned to VAR. If STEP is
omitted, it defaults to `1' or `-1' depending on the order of the
limits. If given, STEP has to match this order. The number of
iterations is determined independently from definition of VAR;
iteration cannot be short-circuited or lengthened by modifying VAR
from within EXPRESSION.
-- Macro: m4_foreach (VAR, LIST, EXPRESSION)
Loop over the comma-separated M4 list LIST, assigning each value
to VAR, and expand EXPRESSION. The following example outputs two
lines:
m4_foreach([myvar], [[foo], [bar, baz]],
[echo myvar
])dnl
=>echo foo
=>echo bar, baz
Note that for some forms of EXPRESSION, it may be faster to use
`m4_map_args'.
-- Macro: m4_foreach_w (VAR, LIST, EXPRESSION)
Loop over the white-space-separated list LIST, assigning each value
to VAR, and expand EXPRESSION. If VAR is only referenced once in
EXPRESSION, it is more efficient to use `m4_map_args_w'.
The deprecated macro `AC_FOREACH' is an alias of `m4_foreach_w'.
-- Macro: m4_map (MACRO, LIST)
-- Macro: m4_mapall (MACRO, LIST)
-- Macro: m4_map_sep (MACRO, SEPARATOR, LIST)
-- Macro: m4_mapall_sep (MACRO, SEPARATOR, LIST)
Loop over the comma separated quoted list of argument descriptions
in LIST, and invoke MACRO with the arguments. An argument
description is in turn a comma-separated quoted list of quoted
elements, suitable for `m4_apply'. The macros `m4_map' and
`m4_map_sep' ignore empty argument descriptions, while `m4_mapall'
and `m4_mapall_sep' invoke MACRO with no arguments. The macros
`m4_map_sep' and `m4_mapall_sep' additionally expand SEPARATOR
between invocations of MACRO.
Note that SEPARATOR is expanded, unlike in `m4_join'. When
separating output with commas, this means that the map result can
be used as a series of arguments, by using a single-quoted comma as
SEPARATOR, or as a single string, by using a double-quoted comma.
m4_map([m4_count], [])
=>
m4_map([ m4_count], [[],
[[1]],
[[1], [2]]])
=> 1 2
m4_mapall([ m4_count], [[],
[[1]],
[[1], [2]]])
=> 0 1 2
m4_map_sep([m4_eval], [,], [[[1+2]],
[[10], [16]]])
=>3,a
m4_map_sep([m4_echo], [,], [[[a]], [[b]]])
=>a,b
m4_count(m4_map_sep([m4_echo], [,], [[[a]], [[b]]]))
=>2
m4_map_sep([m4_echo], [[,]], [[[a]], [[b]]])
=>a,b
m4_count(m4_map_sep([m4_echo], [[,]], [[[a]], [[b]]]))
=>1
-- Macro: m4_map_args (MACRO, ARG...)
Repeatedly invoke MACRO with each successive ARG as its only
argument. In the following example, three solutions are presented
with the same expansion; the solution using `m4_map_args' is the
most efficient.
m4_define([active], [ACTIVE])dnl
m4_foreach([var], [[plain], [active]], [ m4_echo(m4_defn([var]))])
=> plain active
m4_map([ m4_echo], [[[plain]], [[active]]])
=> plain active
m4_map_args([ m4_echo], [plain], [active])
=> plain active
In cases where it is useful to operate on additional parameters
besides the list elements, the macro `m4_curry' can be used in
MACRO to supply the argument currying necessary to generate the
desired argument list. In the following example, `list_add_n' is
more efficient than `list_add_x'. On the other hand, using
`m4_map_args_sep' can be even more efficient.
m4_define([list], [[1], [2], [3]])dnl
m4_define([add], [m4_eval(([$1]) + ([$2]))])dnl
dnl list_add_n(N, ARG...)
dnl Output a list consisting of each ARG added to N
m4_define([list_add_n],
[m4_shift(m4_map_args([,m4_curry([add], [$1])], m4_shift($@)))])dnl
list_add_n([1], list)
=>2,3,4
list_add_n([2], list)
=>3,4,5
m4_define([list_add_x],
[m4_shift(m4_foreach([var], m4_dquote(m4_shift($@)),
[,add([$1],m4_defn([var]))]))])dnl
list_add_x([1], list)
=>2,3,4
-- Macro: m4_map_args_pair (MACRO, [MACRO-END = `macro'], ARG...)
For every pair of arguments ARG, invoke MACRO with two arguments.
If there is an odd number of arguments, invoke MACRO-END, which
defaults to MACRO, with the remaining argument.
m4_map_args_pair([, m4_reverse], [], [1], [2], [3])
=>, 2, 1, 3
m4_map_args_pair([, m4_reverse], [, m4_dquote], [1], [2], [3])
=>, 2, 1, [3]
m4_map_args_pair([, m4_reverse], [, m4_dquote], [1], [2], [3], [4])
=>, 2, 1, 4, 3
-- Macro: m4_map_args_sep ([PRE], [POST], [SEP], ARG...)
Expand the sequence `PRE[ARG]POST' for each argument, additionally
expanding SEP between arguments. One common use of this macro is
constructing a macro call, where the opening and closing
parentheses are split between PRE and POST; in particular,
`m4_map_args([MACRO], [ARG])' is equivalent to
`m4_map_args_sep([MACRO(], [)], [], [ARG])'. This macro provides
the most efficient means for iterating over an arbitrary list of
arguments, particularly when repeatedly constructing a macro call
with more arguments than ARG.
-- Macro: m4_map_args_w (STRING, [PRE], [POST], [SEP])
Expand the sequence `PRE[word]POST' for each word in the
whitespace-separated STRING, additionally expanding SEP between
words. This macro provides the most efficient means for iterating
over a whitespace-separated string. In particular,
`m4_map_args_w([STRING], [ACTION(], [)])' is more efficient than
`m4_foreach_w([var], [STRING], [ACTION(m4_defn([var]))])'.
-- Macro: m4_shiftn (COUNT, ...)
-- Macro: m4_shift2 (...)
-- Macro: m4_shift3 (...)
`m4_shiftn' performs COUNT iterations of `m4_shift', along with
validation that enough arguments were passed in to match the shift
count, and that the count is positive. `m4_shift2' and
`m4_shift3' are specializations of `m4_shiftn', introduced in
Autoconf 2.62, and are more efficient for two and three shifts,
respectively.
-- Macro: m4_stack_foreach (MACRO, ACTION)
-- Macro: m4_stack_foreach_lifo (MACRO, ACTION)
For each of the `m4_pushdef' definitions of MACRO, expand ACTION
with the single argument of a definition of MACRO.
`m4_stack_foreach' starts with the oldest definition, while
`m4_stack_foreach_lifo' starts with the current definition.
ACTION should not push or pop definitions of MACRO, nor is there
any guarantee that the current definition of MACRO matches the
argument that was passed to ACTION. The macro `m4_curry' can be
used if ACTION needs more than one argument, although in that case
it is more efficient to use M4_STACK_FOREACH_SEP.
Due to technical limitations, there are a few low-level m4sugar
functions, such as `m4_pushdef', that cannot be used as the MACRO
argument.
m4_pushdef([a], [1])m4_pushdef([a], [2])dnl
m4_stack_foreach([a], [ m4_incr])
=> 2 3
m4_stack_foreach_lifo([a], [ m4_curry([m4_substr], [abcd])])
=> cd bcd
-- Macro: m4_stack_foreach_sep (MACRO, [PRE], [POST], [SEP])
-- Macro: m4_stack_foreach_sep_lifo (MACRO, [PRE], [POST], [SEP])
Expand the sequence `PRE[definition]POST' for each `m4_pushdef'
definition of MACRO, additionally expanding SEP between
definitions. `m4_stack_foreach_sep' visits the oldest definition
first, while `m4_stack_foreach_sep_lifo' visits the current
definition first. This macro provides the most efficient means
for iterating over a pushdef stack. In particular,
`m4_stack_foreach([MACRO], [ACTION])' is short for
`m4_stack_foreach_sep([MACRO], [ACTION(], [)])'.
File: autoconf.info, Node: Evaluation Macros, Next: Text processing Macros, Prev: Looping constructs, Up: Programming in M4sugar
8.3.6 Evaluation Macros
-----------------------
The following macros give some control over the order of the evaluation
by adding or removing levels of quotes.
-- Macro: m4_apply (MACRO, LIST)
Apply the elements of the quoted, comma-separated LIST as the
arguments to MACRO. If LIST is empty, invoke MACRO without
arguments. Note the difference between `m4_indir', which expects
its first argument to be a macro name but can use names that are
otherwise invalid, and `m4_apply', where MACRO can contain other
text, but must end in a valid macro name.
m4_apply([m4_count], [])
=>0
m4_apply([m4_count], [[]])
=>1
m4_apply([m4_count], [[1], [2]])
=>2
m4_apply([m4_join], [[|], [1], [2]])
=>1|2
-- Macro: m4_count (ARG, ...)
This macro returns the decimal count of the number of arguments it
was passed.
-- Macro: m4_curry (MACRO, ARG...)
This macro performs argument currying. The expansion of this
macro is another macro name that expects exactly one argument;
that argument is then appended to the ARG list, and then MACRO is
expanded with the resulting argument list.
m4_curry([m4_curry], [m4_reverse], [1])([2])([3])
=>3, 2, 1
Unfortunately, due to a limitation in M4 1.4.x, it is not possible
to pass the definition of a builtin macro as the argument to the
output of `m4_curry'; the empty string is used instead of the
builtin token. This behavior is rectified by using M4 1.6 or
newer.
-- Macro: m4_do (ARG, ...)
This macro loops over its arguments and expands each ARG in
sequence. Its main use is for readability; it allows the use of
indentation and fewer `dnl' to result in the same expansion. This
macro guarantees that no expansion will be concatenated with
subsequent text; to achieve full concatenation, use
`m4_unquote(m4_join([], ARG...))'.
m4_define([ab],[1])m4_define([bc],[2])m4_define([abc],[3])dnl
m4_do([a],[b])c
=>abc
m4_unquote(m4_join([],[a],[b]))c
=>3
m4_define([a],[A])m4_define([b],[B])m4_define([c],[C])dnl
m4_define([AB],[4])m4_define([BC],[5])m4_define([ABC],[6])dnl
m4_do([a],[b])c
=>ABC
m4_unquote(m4_join([],[a],[b]))c
=>3
-- Macro: m4_dquote (ARG, ...)
Return the arguments as a quoted list of quoted arguments.
Conveniently, if there is just one ARG, this effectively adds a
level of quoting.
-- Macro: m4_dquote_elt (ARG, ...)
Return the arguments as a series of double-quoted arguments.
Whereas `m4_dquote' returns a single argument, `m4_dquote_elt'
returns as many arguments as it was passed.
-- Macro: m4_echo (ARG, ...)
Return the arguments, with the same level of quoting. Other than
discarding whitespace after unquoted commas, this macro is a no-op.
-- Macro: m4_expand (ARG)
Return the expansion of ARG as a quoted string. Whereas
`m4_quote' is designed to collect expanded text into a single
argument, `m4_expand' is designed to perform one level of expansion
on quoted text. One distinction is in the treatment of whitespace
following a comma in the original ARG. Any time multiple
arguments are collected into one with `m4_quote', the M4 argument
collection rules discard the whitespace. However, with
`m4_expand', whitespace is preserved, even after the expansion of
macros contained in ARG. Additionally, `m4_expand' is able to
expand text that would involve an unterminated comment, whereas
expanding that same text as the argument to `m4_quote' runs into
difficulty in finding the end of the argument. Since manipulating
diversions during argument collection is inherently unsafe,
`m4_expand' issues an error if ARG attempts to change the current
diversion (*note Diversion support::).
m4_define([active], [ACT, IVE])dnl
m4_define([active2], [[ACT, IVE]])dnl
m4_quote(active, active)
=>ACT,IVE,ACT,IVE
m4_expand([active, active])
=>ACT, IVE, ACT, IVE
m4_quote(active2, active2)
=>ACT, IVE,ACT, IVE
m4_expand([active2, active2])
=>ACT, IVE, ACT, IVE
m4_expand([# m4_echo])
=># m4_echo
m4_quote(# m4_echo)
)
=># m4_echo)
=>
Note that `m4_expand' cannot handle an ARG that expands to literal
unbalanced quotes, but that quadrigraphs can be used when
unbalanced output is necessary. Likewise, unbalanced parentheses
should be supplied with double quoting or a quadrigraph.
m4_define([pattern], [[!@<:@]])dnl
m4_define([bar], [BAR])dnl
m4_expand([case $foo in
m4_defn([pattern])@:}@ bar ;;
*[)] blah ;;
esac])
=>case $foo in
=> [![]) BAR ;;
=> *) blah ;;
=>esac
-- Macro: m4_ignore (...)
This macro was introduced in Autoconf 2.62. Expands to nothing,
ignoring all of its arguments. By itself, this isn't very useful.
However, it can be used to conditionally ignore an arbitrary
number of arguments, by deciding which macro name to apply to a
list of arguments.
dnl foo outputs a message only if [debug] is defined.
m4_define([foo],
[m4_ifdef([debug],[AC_MSG_NOTICE],[m4_ignore])([debug message])])
Note that for earlier versions of Autoconf, the macro `__gnu__' can
serve the same purpose, although it is less readable.
-- Macro: m4_make_list (ARG, ...)
This macro exists to aid debugging of M4sugar algorithms. Its net
effect is similar to `m4_dquote'--it produces a quoted list of
quoted arguments, for each ARG. The difference is that this
version uses a comma-newline separator instead of just comma, to
improve readability of the list; with the result that it is less
efficient than `m4_dquote'.
m4_define([zero],[0])m4_define([one],[1])m4_define([two],[2])dnl
m4_dquote(zero, [one], [[two]])
=>[0],[one],[[two]]
m4_make_list(zero, [one], [[two]])
=>[0],
=>[one],
=>[[two]]
m4_foreach([number], m4_dquote(zero, [one], [[two]]), [ number])
=> 0 1 two
m4_foreach([number], m4_make_list(zero, [one], [[two]]), [ number])
=> 0 1 two
-- Macro: m4_quote (ARG, ...)
Return the arguments as a single entity, i.e., wrap them into a
pair of quotes. This effectively collapses multiple arguments
into one, although it loses whitespace after unquoted commas in
the process.
-- Macro: m4_reverse (ARG, ...)
Outputs each argument with the same level of quoting, but in
reverse order, and with space following each comma for readability.
m4_define([active], [ACT,IVE])
=>
m4_reverse(active, [active])
=>active, IVE, ACT
-- Macro: m4_unquote (ARG, ...)
This macro was introduced in Autoconf 2.62. Expand each argument,
separated by commas. For a single ARG, this effectively removes a
layer of quoting, and `m4_unquote([ARG])' is more efficient than
the equivalent `m4_do([ARG])'. For multiple arguments, this
results in an unquoted list of expansions. This is commonly used
with `m4_split', in order to convert a single quoted list into a
series of quoted elements.
The following example aims at emphasizing the difference between
several scenarios: not using these macros, using `m4_defn', using
`m4_quote', using `m4_dquote', and using `m4_expand'.
$ cat example.m4
dnl Overquote, so that quotes are visible.
m4_define([show], [$[]1 = [$1], $[]@ = [$@]])
m4_define([a], [A])
m4_define([mkargs], [1, 2[,] 3])
m4_define([arg1], [[$1]])
m4_divert([0])dnl
show(a, b)
show([a, b])
show(m4_quote(a, b))
show(m4_dquote(a, b))
show(m4_expand([a, b]))
arg1(mkargs)
arg1([mkargs])
arg1(m4_defn([mkargs]))
arg1(m4_quote(mkargs))
arg1(m4_dquote(mkargs))
arg1(m4_expand([mkargs]))
$ autom4te -l m4sugar example.m4
$1 = A, $@ = [A],[b]
$1 = a, b, $@ = [a, b]
$1 = A,b, $@ = [A,b]
$1 = [A],[b], $@ = [[A],[b]]
$1 = A, b, $@ = [A, b]
1
mkargs
1, 2[,] 3
1,2, 3
[1],[2, 3]
1, 2, 3
File: autoconf.info, Node: Text processing Macros, Next: Number processing Macros, Prev: Evaluation Macros, Up: Programming in M4sugar
8.3.7 String manipulation in M4
-------------------------------
The following macros may be used to manipulate strings in M4. Many of
the macros in this section intentionally result in quoted strings as
output, rather than subjecting the arguments to further expansions. As
a result, if you are manipulating text that contains active M4
characters, the arguments are passed with single quoting rather than
double.
-- Macro: m4_append (MACRO-NAME, STRING, [SEPARATOR])
-- Macro: m4_append_uniq (MACRO-NAME, STRING, [SEPARATOR] [IF-UNIQ],
[IF-DUPLICATE])
Redefine MACRO-NAME to its former contents with SEPARATOR and
STRING added at the end. If MACRO-NAME was undefined before (but
not if it was defined but empty), then no SEPARATOR is added. As
of Autoconf 2.62, neither STRING nor SEPARATOR are expanded during
this macro; instead, they are expanded when MACRO-NAME is invoked.
`m4_append' can be used to grow strings, and `m4_append_uniq' to
grow strings without duplicating substrings. Additionally,
`m4_append_uniq' takes two optional parameters as of Autoconf 2.62;
IF-UNIQ is expanded if STRING was appended, and IF-DUPLICATE is
expanded if STRING was already present. Also, `m4_append_uniq'
warns if SEPARATOR is not empty, but occurs within STRING, since
that can lead to duplicates.
Note that `m4_append' can scale linearly in the length of the final
string, depending on the quality of the underlying M4
implementation, while `m4_append_uniq' has an inherent quadratic
scaling factor. If an algorithm can tolerate duplicates in the
final string, use the former for speed. If duplicates must be
avoided, consider using `m4_set_add' instead (*note Set
manipulation Macros::).
m4_define([active], [ACTIVE])dnl
m4_append([sentence], [This is an])dnl
m4_append([sentence], [ active ])dnl
m4_append([sentence], [symbol.])dnl
sentence
=>This is an ACTIVE symbol.
m4_undefine([active])dnl
=>This is an active symbol.
m4_append_uniq([list], [one], [, ], [new], [existing])
=>new
m4_append_uniq([list], [one], [, ], [new], [existing])
=>existing
m4_append_uniq([list], [two], [, ], [new], [existing])
=>new
m4_append_uniq([list], [three], [, ], [new], [existing])
=>new
m4_append_uniq([list], [two], [, ], [new], [existing])
=>existing
list
=>one, two, three
m4_dquote(list)
=>[one],[two],[three]
m4_append([list2], [one], [[, ]])dnl
m4_append_uniq([list2], [two], [[, ]])dnl
m4_append([list2], [three], [[, ]])dnl
list2
=>one, two, three
m4_dquote(list2)
=>[one, two, three]
-- Macro: m4_append_uniq_w (MACRO-NAME, STRINGS)
This macro was introduced in Autoconf 2.62. It is similar to
`m4_append_uniq', but treats STRINGS as a whitespace separated
list of words to append, and only appends unique words.
MACRO-NAME is updated with a single space between new words.
m4_append_uniq_w([numbers], [1 1 2])dnl
m4_append_uniq_w([numbers], [ 2 3 ])dnl
numbers
=>1 2 3
-- Macro: m4_chomp (STRING)
-- Macro: m4_chomp_all (STRING)
Output STRING in quotes, but without a trailing newline. The
macro `m4_chomp' is slightly faster, and removes at most one
newline; the macro `m4_chomp_all' removes all consecutive trailing
newlines. Unlike `m4_flatten', embedded newlines are left intact,
and backslash does not influence the result.
-- Macro: m4_combine ([SEPARATOR], PREFIX-LIST, [INFIX], SUFFIX-1,
[SUFFIX-2], ...)
This macro produces a quoted string containing the pairwise
combination of every element of the quoted, comma-separated
PREFIX-LIST, and every element from the SUFFIX arguments. Each
pairwise combination is joined with INFIX in the middle, and
successive pairs are joined by SEPARATOR. No expansion occurs on
any of the arguments. No output occurs if either the PREFIX or
SUFFIX list is empty, but the lists can contain empty elements.
m4_define([a], [oops])dnl
m4_combine([, ], [[a], [b], [c]], [-], [1], [2], [3])
=>a-1, a-2, a-3, b-1, b-2, b-3, c-1, c-2, c-3
m4_combine([, ], [[a], [b]], [-])
=>
m4_combine([, ], [[a], [b]], [-], [])
=>a-, b-
m4_combine([, ], [], [-], [1], [2])
=>
m4_combine([, ], [[]], [-], [1], [2])
=>-1, -2
-- Macro: m4_flatten (STRING)
Flatten STRING into a single line. Delete all backslash-newline
pairs, and replace all remaining newlines with a space. The
result is still a quoted string.
-- Macro: m4_join ([SEPARATOR], ARGS...)
-- Macro: m4_joinall ([SEPARATOR], ARGS...)
Concatenate each ARG, separated by SEPARATOR. `joinall' uses
every argument, while `join' omits empty arguments so that there
are no back-to-back separators in the output. The result is a
quoted string.
m4_define([active], [ACTIVE])dnl
m4_join([|], [one], [], [active], [two])
=>one|active|two
m4_joinall([|], [one], [], [active], [two])
=>one||active|two
Note that if all you intend to do is join ARGS with commas between
them, to form a quoted list suitable for `m4_foreach', it is more
efficient to use `m4_dquote'.
-- Macro: m4_newline ([TEXT])
This macro was introduced in Autoconf 2.62, and expands to a
newline, followed by any TEXT. It is primarily useful for
maintaining macro formatting, and ensuring that M4 does not
discard leading whitespace during argument collection.
-- Macro: m4_normalize (STRING)
Remove leading and trailing spaces and tabs, sequences of
backslash-then-newline, and replace multiple spaces, tabs, and
newlines with a single space. This is a combination of
`m4_flatten' and `m4_strip'. To determine if STRING consists only
of bytes that would be removed by `m4_normalize', you can use
`m4_ifblank'.
-- Macro: m4_re_escape (STRING)
Backslash-escape all characters in STRING that are active in
regexps.
-- Macro: m4_split (STRING, [REGEXP = `[t ]+'])
Split STRING into an M4 list of elements quoted by `[' and `]',
while keeping white space at the beginning and at the end. If
REGEXP is given, use it instead of `[\t ]+' for splitting. If
STRING is empty, the result is an empty list.
-- Macro: m4_strip (STRING)
Strip whitespace from STRING. Sequences of spaces and tabs are
reduced to a single space, then leading and trailing spaces are
removed. The result is still a quoted string. Note that this
does not interfere with newlines; if you want newlines stripped as
well, consider `m4_flatten', or do it all at once with
`m4_normalize'. To quickly test if STRING has only whitespace,
use `m4_ifblank'.
-- Macro: m4_text_box (MESSAGE, [FRAME = `-'])
Add a text box around MESSAGE, using FRAME as the border character
above and below the message. The frame correctly accounts for the
subsequent expansion of MESSAGE. For example:
m4_define([macro], [abc])dnl
m4_text_box([macro])
=>## --- ##
=>## abc ##
=>## --- ##
The MESSAGE must contain balanced quotes and parentheses, although
quadrigraphs can be used to work around this.
-- Macro: m4_text_wrap (STRING, [PREFIX], [PREFIX1 = `PREFIX'], [WIDTH
= `79'])
Break STRING into a series of whitespace-separated words, then
output those words separated by spaces, and wrapping lines any
time the output would exceed WIDTH columns. If given, PREFIX1
begins the first line, and PREFIX begins all wrapped lines. If
PREFIX1 is longer than PREFIX, then the first line consists of
just PREFIX1. If PREFIX is longer than PREFIX1, padding is
inserted so that the first word of STRING begins at the same
indentation as all wrapped lines. Note that using literal tab
characters in any of the arguments will interfere with the
calculation of width. No expansions occur on PREFIX, PREFIX1, or
the words of STRING, although quadrigraphs are recognized.
For some examples:
m4_text_wrap([Short string */], [ ], [/* ], [20])
=>/* Short string */
m4_text_wrap([Much longer string */], [ ], [/* ], [20])
=>/* Much longer
=> string */
m4_text_wrap([Short doc.], [ ], [ --short ], [30])
=> --short Short doc.
m4_text_wrap([Short doc.], [ ], [ --too-wide ], [30])
=> --too-wide
=> Short doc.
m4_text_wrap([Super long documentation.], [ ],
[ --too-wide ], 30)
=> --too-wide
=> Super long
=> documentation.
-- Macro: m4_tolower (STRING)
-- Macro: m4_toupper (STRING)
Return STRING with letters converted to upper or lower case,
respectively.
File: autoconf.info, Node: Number processing Macros, Next: Set manipulation Macros, Prev: Text processing Macros, Up: Programming in M4sugar
8.3.8 Arithmetic computation in M4
----------------------------------
The following macros facilitate integer arithmetic operations. Where a
parameter is documented as taking an arithmetic expression, you can use
anything that can be parsed by `m4_eval'.
-- Macro: m4_cmp (EXPR-1, EXPR-2)
Compare the arithmetic expressions EXPR-1 and EXPR-2, and expand
to `-1' if EXPR-1 is smaller, `0' if they are equal, and `1' if
EXPR-1 is larger.
-- Macro: m4_list_cmp (LIST-1, LIST-2)
Compare the two M4 lists consisting of comma-separated arithmetic
expressions, left to right. Expand to `-1' for the first element
pairing where the value from LIST-1 is smaller, `1' where the
value from LIST-2 is smaller, or `0' if both lists have the same
values. If one list is shorter than the other, the remaining
elements of the longer list are compared against zero.
m4_list_cmp([1, 0], [1])
=>0
m4_list_cmp([1, [1 * 0]], [1, 0])
=>0
m4_list_cmp([1, 2], [1, 0])
=>1
m4_list_cmp([1, [1+1], 3],[1, 2])
=>1
m4_list_cmp([1, 2, -3], [1, 2])
=>-1
m4_list_cmp([1, 0], [1, 2])
=>-1
m4_list_cmp([1], [1, 2])
=>-1
-- Macro: m4_max (ARG, ...)
This macro was introduced in Autoconf 2.62. Expand to the decimal
value of the maximum arithmetic expression among all the arguments.
-- Macro: m4_min (ARG, ...)
This macro was introduced in Autoconf 2.62. Expand to the decimal
value of the minimum arithmetic expression among all the arguments.
-- Macro: m4_sign (EXPR)
Expand to `-1' if the arithmetic expression EXPR is negative, `1'
if it is positive, and `0' if it is zero.
-- Macro: m4_version_compare (VERSION-1, VERSION-2)
This macro was introduced in Autoconf 2.53, but had a number of
usability limitations that were not lifted until Autoconf 2.62.
Compare the version strings VERSION-1 and VERSION-2, and expand to
`-1' if VERSION-1 is smaller, `0' if they are the same, or `1'
VERSION-2 is smaller. Version strings must be a list of elements
separated by `.', `,' or `-', where each element is a number along
with optional case-insensitive letters designating beta releases.
The comparison stops at the leftmost element that contains a
difference, although a 0 element compares equal to a missing
element.
It is permissible to include commit identifiers in VERSION, such
as an abbreviated SHA1 of the commit, provided there is still a
monotonically increasing prefix to allow for accurate version-based
comparisons. For example, this paragraph was written when the
development snapshot of autoconf claimed to be at version
`2.61a-248-dc51', or 248 commits after the 2.61a release, with an
abbreviated commit identification of `dc51'.
m4_version_compare([1.1], [2.0])
=>-1
m4_version_compare([2.0b], [2.0a])
=>1
m4_version_compare([1.1.1], [1.1.1a])
=>-1
m4_version_compare([1.2], [1.1.1a])
=>1
m4_version_compare([1.0], [1])
=>0
m4_version_compare([1.1pre], [1.1PRE])
=>0
m4_version_compare([1.1a], [1,10])
=>-1
m4_version_compare([2.61a], [2.61a-248-dc51])
=>-1
m4_version_compare([2.61b], [2.61a-248-dc51])
=>1
-- Macro: m4_version_prereq (VERSION, [IF-NEW-ENOUGH], [IF-OLD =
`m4_fatal'])
Compares VERSION against the version of Autoconf currently
running. If the running version is at VERSION or newer, expand
IF-NEW-ENOUGH, but if VERSION is larger than the version currently
executing, expand IF-OLD, which defaults to printing an error
message and exiting m4sugar with status 63. When given only one
argument, this behaves like `AC_PREREQ' (*note Versioning::).
Remember that the autoconf philosophy favors feature checks over
version checks.
File: autoconf.info, Node: Set manipulation Macros, Next: Forbidden Patterns, Prev: Number processing Macros, Up: Programming in M4sugar
8.3.9 Set manipulation in M4
----------------------------
Sometimes, it is necessary to track a set of data, where the order does
not matter and where there are no duplicates in the set. The following
macros facilitate set manipulations. Each set is an opaque object,
which can only be accessed via these basic operations. The underlying
implementation guarantees linear scaling for set creation, which is more
efficient than using the quadratic `m4_append_uniq'. Both set names
and values can be arbitrary strings, except for unbalanced quotes.
This implementation ties up memory for removed elements until the next
operation that must traverse all the elements of a set; and although
that may slow down some operations until the memory for removed elements
is pruned, it still guarantees linear performance.
-- Macro: m4_set_add (SET, VALUE, [IF-UNIQ], [IF-DUP])
Adds the string VALUE as a member of set SET. Expand IF-UNIQ if
the element was added, or IF-DUP if it was previously in the set.
Operates in amortized constant time, so that set creation scales
linearly.
-- Macro: m4_set_add_all (SET, VALUE...)
Adds each VALUE to the set SET. This is slightly more efficient
than repeatedly invoking `m4_set_add'.
-- Macro: m4_set_contains (SET, VALUE, [IF-PRESENT], [IF-ABSENT])
Expands IF-PRESENT if the string VALUE is a member of SET,
otherwise IF-ABSENT.
m4_set_contains([a], [1], [yes], [no])
=>no
m4_set_add([a], [1], [added], [dup])
=>added
m4_set_add([a], [1], [added], [dup])
=>dup
m4_set_contains([a], [1], [yes], [no])
=>yes
m4_set_remove([a], [1], [removed], [missing])
=>removed
m4_set_contains([a], [1], [yes], [no])
=>no
m4_set_remove([a], [1], [removed], [missing])
=>missing
-- Macro: m4_set_contents (SET, [SEP])
-- Macro: m4_set_dump (SET, [SEP])
Expands to a single string consisting of all the members of the set
SET, each separated by SEP, which is not expanded.
`m4_set_contents' leaves the elements in SET but reclaims any
memory occupied by removed elements, while `m4_set_dump' is a
faster one-shot action that also deletes the set. No provision is
made for disambiguating members that contain a non-empty SEP as a
substring; use `m4_set_empty' to distinguish between an empty set
and the set containing only the empty string. The order of the
output is unspecified; in the current implementation, part of the
speed of `m4_set_dump' results from using a different output order
than `m4_set_contents'. These macros scale linearly in the size
of the set before memory pruning, and `m4_set_contents([SET],
[SEP])' is faster than `m4_joinall([SEP]m4_set_listc([SET]))'.
m4_set_add_all([a], [1], [2], [3])
=>
m4_set_contents([a], [-])
=>1-2-3
m4_joinall([-]m4_set_listc([a]))
=>1-2-3
m4_set_dump([a], [-])
=>3-2-1
m4_set_contents([a])
=>
m4_set_add([a], [])
=>
m4_set_contents([a], [-])
=>
-- Macro: m4_set_delete (SET)
Delete all elements and memory associated with SET. This is
linear in the set size, and faster than removing one element at a
time.
-- Macro: m4_set_difference (SETA, SETB)
-- Macro: m4_set_intersection (SETA, SETB)
-- Macro: m4_set_union (SETA, SETB)
Compute the relation between SETA and SETB, and output the result
as a list of quoted arguments without duplicates and with a
leading comma. Set difference selects the elements in SETA but
not SETB, intersection selects only elements in both sets, and
union selects elements in either set. These actions are linear in
the sum of the set sizes. The leading comma is necessary to
distinguish between no elements and the empty string as the only
element.
m4_set_add_all([a], [1], [2], [3])
=>
m4_set_add_all([b], [3], [], [4])
=>
m4_set_difference([a], [b])
=>,1,2
m4_set_difference([b], [a])
=>,,4
m4_set_intersection([a], [b])
=>,3
m4_set_union([a], [b])
=>,1,2,3,,4
-- Macro: m4_set_empty (SET, [IF-EMPTY], [IF-ELEMENTS])
Expand IF-EMPTY if the set SET has no elements, otherwise expand
IF-ELEMENTS. This macro operates in constant time. Using this
macro can help disambiguate output from `m4_set_contents' or
`m4_set_list'.
-- Macro: m4_set_foreach (SET, VARIABLE, ACTION)
For each element in the set SET, expand ACTION with the macro
VARIABLE defined as the set element. Behavior is unspecified if
ACTION recursively lists the contents of SET (although listing
other sets is acceptable), or if it modifies the set in any way
other than removing the element currently contained in VARIABLE.
This macro is faster than the corresponding `m4_foreach([VARIABLE],
m4_indir([m4_dquote]m4_set_listc([SET])), [ACTION])', although
`m4_set_map' might be faster still.
m4_set_add_all([a]m4_for([i], [1], [5], [], [,i]))
=>
m4_set_contents([a])
=>12345
m4_set_foreach([a], [i],
[m4_if(m4_eval(i&1), [0], [m4_set_remove([a], i, [i])])])
=>24
m4_set_contents([a])
=>135
-- Macro: m4_set_list (SET)
-- Macro: m4_set_listc (SET)
Produce a list of arguments, where each argument is a quoted
element from the set SET. The variant `m4_set_listc' is
unambiguous, by adding a leading comma if there are any set
elements, whereas the variant `m4_set_list' cannot distinguish
between an empty set and a set containing only the empty string.
These can be directly used in macros that take multiple arguments,
such as `m4_join' or `m4_set_add_all', or wrapped by `m4_dquote'
for macros that take a quoted list, such as `m4_map' or
`m4_foreach'. Any memory occupied by removed elements is
reclaimed during these macros.
m4_set_add_all([a], [1], [2], [3])
=>
m4_set_list([a])
=>1,2,3
m4_set_list([b])
=>
m4_set_listc([b])
=>
m4_count(m4_set_list([b]))
=>1
m4_set_empty([b], [0], [m4_count(m4_set_list([b]))])
=>0
m4_set_add([b], [])
=>
m4_set_list([b])
=>
m4_set_listc([b])
=>,
m4_count(m4_set_list([b]))
=>1
m4_set_empty([b], [0], [m4_count(m4_set_list([b]))])
=>1
-- Macro: m4_set_map (SET, ACTION)
For each element in the set SET, expand ACTION with a single
argument of the set element. Behavior is unspecified if ACTION
recursively lists the contents of SET (although listing other sets
is acceptable), or if it modifies the set in any way other than
removing the element passed as an argument. This macro is faster
than either corresponding counterpart of
`m4_map_args([ACTION]m4_set_listc([SET]))' or
`m4_set_foreach([SET], [var], [ACTION(m4_defn([var]))])'. It is
possible to use `m4_curry' if more than one argument is needed for
ACTION, although it is more efficient to use `m4_set_map_sep' in
that case.
-- Macro: m4_set_map_sep (SET, [PRE], [POST], [SEP])
For each element in the set SET, expand `PRE[element]POST',
additionally expanding SEP between elements. Behavior is
unspecified if the expansion recursively lists the contents of SET
(although listing other sets is acceptable), or if it modifies the
set in any way other than removing the element visited by the
expansion. This macro provides the most efficient means for
non-destructively visiting the elements of a set; in particular,
`m4_set_map([SET], [ACTION])' is equivalent to
`m4_set_map_sep([SET], [ACTION(], [)])'.
-- Macro: m4_set_remove (SET, VALUE, [IF-PRESENT], [IF-ABSENT])
If VALUE is an element in the set SET, then remove it and expand
IF-PRESENT. Otherwise expand IF-ABSENT. This macro operates in
constant time so that multiple removals will scale linearly rather
than quadratically; but when used outside of `m4_set_foreach' or
`m4_set_map', it leaves memory occupied until the set is later
compacted by `m4_set_contents' or `m4_set_list'. Several other
set operations are then less efficient between the time of element
removal and subsequent memory compaction, but still maintain their
guaranteed scaling performance.
-- Macro: m4_set_size (SET)
Expand to the size of the set SET. This implementation operates
in constant time, and is thus more efficient than
`m4_eval(m4_count(m4_set_listc([set])) - 1)'.
File: autoconf.info, Node: Forbidden Patterns, Prev: Set manipulation Macros, Up: Programming in M4sugar
8.3.10 Forbidden Patterns
-------------------------
M4sugar provides a means to define suspicious patterns, patterns
describing tokens which should not be found in the output. For
instance, if an Autoconf `configure' script includes tokens such as
`AC_DEFINE', or `dnl', then most probably something went wrong
(typically a macro was not evaluated because of overquotation).
M4sugar forbids all the tokens matching `^_?m4_' and `^dnl$'.
Additional layers, such as M4sh and Autoconf, add additional forbidden
patterns to the list.
-- Macro: m4_pattern_forbid (PATTERN)
Declare that no token matching PATTERN must be found in the output.
Comments are not checked; this can be a problem if, for instance,
you have some macro left unexpanded after an `#include'. No
consensus is currently found in the Autoconf community, as some
people consider it should be valid to name macros in comments
(which doesn't make sense to the authors of this documentation:
input, such as macros, should be documented by `dnl' comments;
reserving `#'-comments to document the output).
Of course, you might encounter exceptions to these generic rules, for
instance you might have to refer to `$m4_flags'.
-- Macro: m4_pattern_allow (PATTERN)
Any token matching PATTERN is allowed, including if it matches an
`m4_pattern_forbid' pattern.
File: autoconf.info, Node: Debugging via autom4te, Prev: Programming in M4sugar, Up: Programming in M4
8.4 Debugging via autom4te
==========================
At times, it is desirable to see what was happening inside m4, to see
why output was not matching expectations. However, post-processing done
by `autom4te' means that directly using the m4 builtin `m4_traceon' is
likely to interfere with operation. Also, frequent diversion changes
and the concept of forbidden tokens make it difficult to use `m4_defn'
to generate inline comments in the final output.
There are a couple of tools to help with this. One is the use of the
`--trace' option provided by `autom4te' (as well as each of the
programs that wrap `autom4te', such as `autoconf'), in order to inspect
when a macro is called and with which arguments. For example, when
this paragraph was written, the autoconf version could be found by:
$ autoconf --trace=AC_INIT
configure.ac:23:AC_INIT:GNU Autoconf:2.63b.95-3963:bug-autoconf@gnu.org
$ autoconf --trace='AC_INIT:version is $2'
version is 2.63b.95-3963
Another trick is to print out the expansion of various m4
expressions to standard error or to an independent file, with no
further m4 expansion, and without interfering with diversion changes or
the post-processing done to standard output. `m4_errprintn' shows a
given expression on standard error. For example, if you want to see
the expansion of an autoconf primitive or of one of your autoconf
macros, you can do it like this:
$ cat <<\EOF > configure.ac
AC_INIT
m4_errprintn([The definition of AC_DEFINE_UNQUOTED:])
m4_errprintn(m4_defn([AC_DEFINE_UNQUOTED]))
AC_OUTPUT
EOF
$ autoconf
error-->The definition of AC_DEFINE_UNQUOTED:
error-->_AC_DEFINE_Q([], $@)
File: autoconf.info, Node: Programming in M4sh, Next: Writing Autoconf Macros, Prev: Programming in M4, Up: Top
9 Programming in M4sh
*********************
M4sh, pronounced "mash", is aiming at producing portable Bourne shell
scripts. This name was coined by Lars J. Aas, who notes that,
according to the Webster's Revised Unabridged Dictionary (1913):
Mash \Mash\, n. [Akin to G. meisch, maisch, meische, maische,
mash, wash, and prob. to AS. miscian to mix. See "Mix".]
1. A mass of mixed ingredients reduced to a soft pulpy state by
beating or pressure...
2. A mixture of meal or bran and water fed to animals.
3. A mess; trouble. [Obs.] -Beau. & Fl.
M4sh reserves the M4 macro namespace `^_AS_' for internal use, and
the namespace `^AS_' for M4sh macros. It also reserves the shell and
environment variable namespace `^as_', and the here-document delimiter
namespace `^_AS[A-Z]' in the output file. You should not define your
own macros or output shell code that conflicts with these namespaces.
* Menu:
* Common Shell Constructs:: Portability layer for common shell constructs
* Polymorphic Variables:: Support for indirect variable names
* Initialization Macros:: Macros to establish a sane shell environment
* File Descriptor Macros:: File descriptor macros for input and output
File: autoconf.info, Node: Common Shell Constructs, Next: Polymorphic Variables, Up: Programming in M4sh
9.1 Common Shell Constructs
===========================
M4sh provides portable alternatives for some common shell constructs
that unfortunately are not portable in practice.
-- Macro: AS_CASE (WORD, [PATTERN1], [IF-MATCHED1], ..., [DEFAULT])
Expand into a shell `case' statement, where WORD is matched
against one or more patterns. IF-MATCHED is run if the
corresponding pattern matched WORD, else DEFAULT is run. Avoids
several portability issues (*note Limitations of Shell Builtins:
case.).
-- Macro: AS_ECHO (WORD)
Emits WORD to the standard output, followed by a newline. WORD
must be a single shell word (typically a quoted string). The
bytes of WORD are output as-is, even if it starts with "-" or
contains "\". Redirections can be placed outside the macro
invocation. This is much more portable than using `echo' (*note
Limitations of Shell Builtins: echo.).
-- Macro: AS_ECHO_N (WORD)
Emits WORD to the standard output, without a following newline.
WORD must be a single shell word (typically a quoted string) and,
for portability, should not include more than one newline. The
bytes of WORD are output as-is, even if it starts with "-" or
contains "\". Redirections can be placed outside the macro
invocation.
-- Macro: AS_ESCAPE (STRING, [CHARS = ``"$'])
Expands to STRING, with any characters in CHARS escaped with a
backslash (`\'). CHARS should be at most four bytes long, and
only contain characters from the set ``\"$'; however, characters
may be safely listed more than once in CHARS for the sake of
syntax highlighting editors. The current implementation expands
STRING after adding escapes; if STRING contains macro calls that
in turn expand to text needing shell quoting, you can use
`AS_ESCAPE(m4_dquote(m4_expand([string])))'.
The default for CHARS (`\"$`') is the set of characters needing
escapes when STRING will be used literally within double quotes.
One common variant is the set of characters to protect when STRING
will be used literally within back-ticks or an unquoted
here-document (`\$`'). Another common variant is `""', which can
be used to form a double-quoted string containing the same
expansions that would have occurred if STRING were expanded in an
unquoted here-document; however, when using this variant, care
must be taken that STRING does not use double quotes within
complex variable expansions (such as `${foo-`echo "hi"`}') that
would be broken with improper escapes.
This macro is often used with `AS_ECHO'. For an example, observe
the output generated by the shell code generated from this snippet:
foo=bar
AS_ECHO(["AS_ESCAPE(["$foo" = ])AS_ESCAPE(["$foo"], [""])"])
=>"$foo" = "bar"
m4_define([macro], [a, [\b]])
AS_ECHO(["AS_ESCAPE([[macro]])"])
=>macro
AS_ECHO(["AS_ESCAPE([macro])"])
=>a, b
AS_ECHO(["AS_ESCAPE(m4_dquote(m4_expand([macro])))"])
=>a, \b
To escape a string that will be placed within single quotes, use:
m4_bpatsubst([[STRING]], ['], ['\\''])
-- Macro: AS_EXIT ([STATUS = `$?'])
Emit code to exit the shell with STATUS, defaulting to `$?'. This
macro works around shells that see the exit status of the command
prior to `exit' inside a `trap 0' handler (*note Limitations of
Shell Builtins: trap.).
-- Macro: AS_IF (TEST1, [RUN-IF-TRUE1], ..., [RUN-IF-FALSE])
Run shell code TEST1. If TEST1 exits with a zero status then run
shell code RUN-IF-TRUE1, else examine further tests. If no test
exits with a zero status, run shell code RUN-IF-FALSE, with
simplifications if either RUN-IF-TRUE1 or RUN-IF-FALSE is empty.
For example,
AS_IF([test "x$foo" = xyes], [HANDLE_FOO([yes])],
[test "x$foo" != xno], [HANDLE_FOO([maybe])],
[echo foo not specified])
ensures any required macros of `HANDLE_FOO' are expanded before
the first test.
-- Macro: AS_MKDIR_P (FILE-NAME)
Make the directory FILE-NAME, including intervening directories as
necessary. This is equivalent to `mkdir -p -- FILE-NAME', except
that it is portable to older versions of `mkdir' that lack support
for the `-p' option or for the `--' delimiter (*note Limitations
of Usual Tools: mkdir.). Also, `AS_MKDIR_P' succeeds if FILE-NAME
is a symbolic link to an existing directory, even though Posix is
unclear whether `mkdir -p' should succeed in that case. If
creation of FILE-NAME fails, exit the script.
Also see the `AC_PROG_MKDIR_P' macro (*note Particular Programs::).
-- Macro: AS_SET_STATUS (STATUS)
Emit shell code to set the value of `$?' to STATUS, as efficiently
as possible. However, this is not guaranteed to abort a shell
running with `set -e' (*note Limitations of Shell Builtins: set.).
-- Macro: AS_TR_CPP (EXPRESSION)
Transform EXPRESSION into a valid right-hand side for a C
`#define'. For example:
# This outputs "#define HAVE_CHAR_P 1".
# Notice the m4 quoting around #, to prevent an m4 comment
type="char *"
echo "[#]define AS_TR_CPP([HAVE_$type]) 1"
-- Macro: AS_TR_SH (EXPRESSION)
Transform EXPRESSION into a valid shell variable name. For
example:
# This outputs "Have it!".
header="sys/some file.h"
AS_TR_SH([HAVE_$header])=yes
if test "x$HAVE_sys_some_file_h" = xyes; then echo "Have it!"; fi
-- Macro: AS_SET_CATFILE (VAR, DIR, FILE)
Set the shell variable VAR to DIR/FILE, but optimizing the common
cases (DIR or FILE is `.', FILE is absolute, etc.).
-- Macro: AS_UNSET (VAR)
Unsets the shell variable VAR, working around bugs in older shells
(*note Limitations of Shell Builtins: unset.). VAR can be a
literal or indirect variable name.
-- Macro: AS_VERSION_COMPARE (VERSION-1, VERSION-2, [ACTION-IF-LESS],
[ACTION-IF-EQUAL], [ACTION-IF-GREATER])
Compare two strings VERSION-1 and VERSION-2, possibly containing
shell variables, as version strings, and expand ACTION-IF-LESS,
ACTION-IF-EQUAL, or ACTION-IF-GREATER depending upon the result.
The algorithm to compare is similar to the one used by strverscmp
in glibc (*note String/Array Comparison: (libc)String/Array
Comparison.).
File: autoconf.info, Node: Polymorphic Variables, Next: Initialization Macros, Prev: Common Shell Constructs, Up: Programming in M4sh
9.2 Support for indirect variable names
=======================================
Often, it is convenient to write a macro that will emit shell code
operating on a shell variable. The simplest case is when the variable
name is known. But a more powerful idiom is writing shell code that can
work through an indirection, where another variable or command
substitution produces the name of the variable to actually manipulate.
M4sh supports the notion of polymorphic shell variables, making it easy
to write a macro that can deal with either literal or indirect variable
names and output shell code appropriate for both use cases. Behavior is
undefined if expansion of an indirect variable does not result in a
literal variable name.
-- Macro: AS_LITERAL_IF (EXPRESSION, [IF-LITERAL], [IF-NOT])
If the expansion of EXPRESSION is definitely a shell literal,
expand IF-LITERAL. If the expansion of EXPRESSION looks like it
might contain shell indirections (such as `$var' or ``expr`'),
then IF-NOT is expanded. In order to reduce the time spent
deciding whether an expression is literal, the implementation is
somewhat conservative (for example, `'[$]'' is a single-quoted
shell literal, but causes IF-NOT to be expanded). While this
macro is often used for recognizing shell variable names, it can
also be used in other contexts.
AC_DEFUN([MY_ACTION],
[AS_LITERAL_IF([$1],
[echo "$1"],
[AS_VAR_COPY([tmp], [$1])
echo "$tmp"])])
-- Macro: AS_VAR_APPEND (VAR, TEXT)
Emit shell code to append the shell expansion of TEXT to the end
of the current contents of the polymorphic shell variable VAR,
taking advantage of shells that provide the `+=' extension for more
efficient scaling.
For situations where the final contents of VAR are relatively
short (less than 256 bytes), it is more efficient to use the
simpler code sequence of `VAR=${VAR}TEXT' (or its polymorphic
equivalent of `AS_VAR_COPY([tmp], [VAR])' and `AS_VAR_SET([VAR],
["$tmp"TEXT])'). But in the case when the script will be
repeatedly appending text into `var', issues of scaling start to
become apparent. A naive implementation requires execution time
linear to the length of the current contents of VAR as well as the
length of TEXT for a single append, for an overall quadratic
scaling with multiple appends. This macro takes advantage of
shells which provide the extension `VAR+=TEXT', which can provide
amortized constant time for a single append, for an overall linear
scaling with multiple appends. Note that unlike `AS_VAR_SET',
this macro requires that TEXT be quoted properly to avoid field
splitting and file name expansion.
-- Macro: AS_VAR_ARITH (VAR, EXPRESSION)
Emit shell code to compute the arithmetic expansion of EXPRESSION,
assigning the result as the contents of the polymorphic shell
variable VAR. The code takes advantage of shells that provide
`$(())' for fewer forks, but uses `expr' as a fallback.
Therefore, the syntax for a valid EXPRESSION is rather limited:
all operators must occur as separate shell arguments and with
proper quoting, there is no portable equality operator, all
variables containing numeric values must be expanded prior to the
computation, all numeric values must be provided in decimal
without leading zeroes, and the first shell argument should not be
a negative number. In the following example, this snippet will
print `(2+3)*4 == 20'.
bar=3
AS_VAR_ARITH([foo], [\( 2 + $bar \) \* 4])
echo "(2+$bar)*4 == $foo"
-- Macro: AS_VAR_COPY (DEST, SOURCE)
Emit shell code to assign the contents of the polymorphic shell
variable SOURCE to the polymorphic shell variable DEST. For
example, executing this M4sh snippet will output `bar hi':
foo=bar bar=hi
AS_VAR_COPY([a], [foo])
AS_VAR_COPY([b], [$foo])
echo "$a $b"
When it is necessary to access the contents of an indirect variable
inside a shell double-quoted context, the recommended idiom is to
first copy the contents into a temporary literal shell variable.
for header in stdint_h inttypes_h ; do
AS_VAR_COPY([var], [ac_cv_header_$header])
echo "$header detected: $var"
done
-- Macro: AS_VAR_IF (VAR, [VALUE], [IF-EQUAL], [IF-NOT-EQUAL])
Output a shell conditional statement. If the contents of the
polymorphic shell variable VAR match the string VALUE, execute
IF-EQUAL; otherwise execute IF-NOT-EQUAL. Avoids shell bugs if an
interrupt signal arrives while a command substitution in VAR is
being expanded.
-- Macro: AS_VAR_PUSHDEF (M4-NAME, VALUE)
-- Macro: AS_VAR_POPDEF (M4-NAME)
A common M4sh idiom involves composing shell variable names from
an m4 argument (for example, writing a macro that uses a cache
variable). VALUE can be an arbitrary string, which will be
transliterated into a valid shell name by `AS_TR_SH'. In order to
access the composed variable name based on VALUE, it is easier to
declare a temporary m4 macro M4-NAME with `AS_VAR_PUSHDEF', then
use that macro as the argument to subsequent `AS_VAR' macros as a
polymorphic variable name, and finally free the temporary macro
with `AS_VAR_POPDEF'. These macros are often followed with `dnl',
to avoid excess newlines in the output.
Here is an involved example, that shows the power of writing
macros that can handle composed shell variable names:
m4_define([MY_CHECK_HEADER],
[AS_VAR_PUSHDEF([my_Header], [ac_cv_header_$1])dnl
AS_VAR_IF([my_Header], [yes], [echo "header $1 available"])dnl
AS_VAR_POPDEF([my_Header])dnl
])
MY_CHECK_HEADER([stdint.h])
for header in inttypes.h stdlib.h ; do
MY_CHECK_HEADER([$header])
done
In the above example, `MY_CHECK_HEADER' can operate on polymorphic
variable names. In the first invocation, the m4 argument is
`stdint.h', which transliterates into a literal `stdint_h'. As a
result, the temporary macro `my_Header' expands to the literal
shell name `ac_cv_header_stdint_h'. In the second invocation, the
m4 argument to `MY_CHECK_HEADER' is `$header', and the temporary
macro `my_Header' expands to the indirect shell name
`$as_my_Header'. During the shell execution of the for loop, when
`$header' contains `inttypes.h', then `$as_my_Header' contains
`ac_cv_header_inttypes_h'. If this script is then run on a
platform where all three headers have been previously detected, the
output of the script will include:
header stdint.h detected
header inttypes.h detected
header stdlib.h detected
-- Macro: AS_VAR_SET (VAR, [VALUE])
Emit shell code to assign the contents of the polymorphic shell
variable VAR to the shell expansion of VALUE. VALUE is not
subject to field splitting or file name expansion, so if command
substitution is used, it may be done with ``""`' rather than using
an intermediate variable (*note Shell Substitutions::). However,
VALUE does undergo rescanning for additional macro names; behavior
is unspecified if late expansion results in any shell
meta-characters.
-- Macro: AS_VAR_SET_IF (VAR, [IF-SET], [IF-UNDEF])
Emit a shell conditional statement, which executes IF-SET if the
polymorphic shell variable `var' is set to any value, and IF-UNDEF
otherwise.
-- Macro: AS_VAR_TEST_SET (VAR)
Emit a shell statement that results in a successful exit status
only if the polymorphic shell variable `var' is set.
File: autoconf.info, Node: Initialization Macros, Next: File Descriptor Macros, Prev: Polymorphic Variables, Up: Programming in M4sh
9.3 Initialization Macros
=========================
-- Macro: AS_BOURNE_COMPATIBLE
Set up the shell to be more compatible with the Bourne shell as
standardized by Posix, if possible. This may involve setting
environment variables, or setting options, or similar
implementation-specific actions. This macro is deprecated, since
`AS_INIT' already invokes it.
-- Macro: AS_INIT
Initialize the M4sh environment. This macro calls `m4_init', then
outputs the `#! /bin/sh' line, a notice about where the output was
generated from, and code to sanitize the environment for the rest
of the script. Among other initializations, this sets `SHELL' to
the shell chosen to run the script (*note CONFIG_SHELL::), and
`LC_ALL' to ensure the C locale. Finally, it changes the current
diversion to `BODY'.
-- Macro: AS_INIT_GENERATED (FILE, [COMMENT])
Emit shell code to start the creation of a subsidiary shell script
in FILE, including changing FILE to be executable. This macro
populates the child script with information learned from the parent
(thus, the emitted code is equivalent in effect, but more
efficient, than the code output by `AS_INIT',
`AS_BOURNE_COMPATIBLE', and `AS_SHELL_SANITIZE'). If present,
COMMENT is output near the beginning of the child, prior to the
shell initialization code, and is subject to parameter expansion,
command substitution, and backslash quote removal. The parent
script should check the exit status after this macro, in case FILE
could not be properly created (for example, if the disk was full).
If successfully created, the parent script can then proceed to
append additional M4sh constructs into the child script.
Note that the child script starts life without a log file open, so
if the parent script uses logging (*note AS_MESSAGE_LOG_FD::), you
must temporarily disable any attempts to use the log file until
after emitting code to open a log within the child. On the other
hand, if the parent script has `AS_MESSAGE_FD' redirected
somewhere besides `1', then the child script already has code that
copies stdout to that descriptor. Currently, the suggested idiom
for writing a M4sh shell script from within another script is:
AS_INIT_GENERATED([FILE], [[# My child script.
]]) || { AS_ECHO(["Failed to create child script"]); AS_EXIT; }
m4_pushdef([AS_MESSAGE_LOG_FD])dnl
cat >> "FILE" <<\__EOF__
# Code to initialize AS_MESSAGE_LOG_FD
m4_popdef([AS_MESSAGE_LOG_FD])dnl
# Additional code
__EOF__
This, however, may change in the future as the M4sh interface is
stabilized further.
Also, be aware that use of `LINENO' within the child script may
report line numbers relative to their location in the parent
script, even when using `AS_LINENO_PREPARE', if the parent script
was unable to locate a shell with working `LINENO' support.
-- Macro: AS_LINENO_PREPARE
Find a shell that supports the special variable `LINENO', which
contains the number of the currently executing line. This macro is
automatically invoked by `AC_INIT' in configure scripts.
-- Macro: AS_ME_PREPARE
Set up variable `as_me' to be the basename of the currently
executing script. This macro is automatically invoked by
`AC_INIT' in configure scripts.
-- Macro: AS_SHELL_SANITIZE
Initialize the shell suitably for `configure' scripts. This has
the effect of `AS_BOURNE_COMPATIBLE', and sets some other
environment variables for predictable results from configuration
tests. For example, it sets `LC_ALL' to change to the default C
locale. *Note Special Shell Variables::. This macro is
deprecated, since `AS_INIT' already invokes it.
File: autoconf.info, Node: File Descriptor Macros, Prev: Initialization Macros, Up: Programming in M4sh
9.4 File Descriptor Macros
==========================
The following macros define file descriptors used to output messages
(or input values) from `configure' scripts. For example:
echo "$wombats found" >&AS_MESSAGE_LOG_FD
echo 'Enter desired kangaroo count:' >&AS_MESSAGE_FD
read kangaroos <&AS_ORIGINAL_STDIN_FD`
However doing so is seldom needed, because Autoconf provides higher
level macros as described below.
-- Macro: AS_MESSAGE_FD
The file descriptor for `checking for...' messages and results.
By default, `AS_INIT' sets this to `1' for standalone M4sh
clients. However, `AC_INIT' shuffles things around to another file
descriptor, in order to allow the `-q' option of `configure' to
choose whether messages should go to the script's standard output
or be discarded.
If you want to display some messages, consider using one of the
printing macros (*note Printing Messages::) instead. Copies of
messages output via these macros are also recorded in `config.log'.
-- Macro: AS_MESSAGE_LOG_FD
This must either be empty, or expand to a file descriptor for log
messages. By default, `AS_INIT' sets this macro to the empty
string for standalone M4sh clients, thus disabling logging.
However, `AC_INIT' shuffles things around so that both `configure'
and `config.status' use `config.log' for log messages. Macros
that run tools, like `AC_COMPILE_IFELSE' (*note Running the
Compiler::), redirect all output to this descriptor. You may want
to do so if you develop such a low-level macro.
-- Macro: AS_ORIGINAL_STDIN_FD
This must expand to a file descriptor for the original standard
input. By default, `AS_INIT' sets this macro to `0' for standalone
M4sh clients. However, `AC_INIT' shuffles things around for
safety.
When `configure' runs, it may accidentally execute an interactive
command that has the same name as the non-interactive meant to be
used or checked. If the standard input was the terminal, such
interactive programs would cause `configure' to stop, pending some
user input. Therefore `configure' redirects its standard input
from `/dev/null' during its initialization. This is not normally
a problem, since `configure' normally does not need user input.
In the extreme case where your `configure' script really needs to
obtain some values from the original standard input, you can read
them explicitly from `AS_ORIGINAL_STDIN_FD'.
File: autoconf.info, Node: Writing Autoconf Macros, Next: Portable Shell, Prev: Programming in M4sh, Up: Top
10 Writing Autoconf Macros
**************************
When you write a feature test that could be applicable to more than one
software package, the best thing to do is encapsulate it in a new macro.
Here are some instructions and guidelines for writing Autoconf macros.
* Menu:
* Macro Definitions:: Basic format of an Autoconf macro
* Macro Names:: What to call your new macros
* Reporting Messages:: Notifying `autoconf' users
* Dependencies Between Macros:: What to do when macros depend on other macros
* Obsoleting Macros:: Warning about old ways of doing things
* Coding Style:: Writing Autoconf macros a` la Autoconf
File: autoconf.info, Node: Macro Definitions, Next: Macro Names, Up: Writing Autoconf Macros
10.1 Macro Definitions
======================
-- Macro: AC_DEFUN (NAME, [BODY])
Autoconf macros are defined using the `AC_DEFUN' macro, which is
similar to the M4 builtin `m4_define' macro; this creates a macro
named NAME and with BODY as its expansion. In addition to
defining a macro, `AC_DEFUN' adds to it some code that is used to
constrain the order in which macros are called, while avoiding
redundant output (*note Prerequisite Macros::).
An Autoconf macro definition looks like this:
AC_DEFUN(MACRO-NAME, MACRO-BODY)
You can refer to any arguments passed to the macro as `$1', `$2',
etc. *Note How to define new macros: (m4.info)Definitions, for more
complete information on writing M4 macros.
Most macros fall in one of two general categories. The first
category includes macros which take arguments, in order to generate
output parameterized by those arguments. Macros in this category are
designed to be directly expanded, often multiple times, and should not
be used as the argument to `AC_REQUIRE'. The other category includes
macros which are shorthand for a fixed block of text, and therefore do
not take arguments. For this category of macros, directly expanding
the macro multiple times results in redundant output, so it is more
common to use the macro as the argument to `AC_REQUIRE', or to declare
the macro with `AC_DEFUN_ONCE' (*note One-Shot Macros::).
Be sure to properly quote both the MACRO-BODY _and_ the MACRO-NAME
to avoid any problems if the macro happens to have been previously
defined.
Each macro should have a header comment that gives its prototype,
and a brief description. When arguments have default values, display
them in the prototype. For example:
# AC_MSG_ERROR(ERROR, [EXIT-STATUS = 1])
# --------------------------------------
m4_define([AC_MSG_ERROR],
[{ AS_MESSAGE([error: $1], [2])
exit m4_default([$2], [1]); }])
Comments about the macro should be left in the header comment. Most
other comments make their way into `configure', so just keep using `#'
to introduce comments.
If you have some special comments about pure M4 code, comments that
make no sense in `configure' and in the header comment, then use the
builtin `dnl': it causes M4 to discard the text through the next
newline.
Keep in mind that `dnl' is rarely needed to introduce comments;
`dnl' is more useful to get rid of the newlines following macros that
produce no output, such as `AC_REQUIRE'.
Public third-party macros need to use `AC_DEFUN', and not
`m4_define', in order to be found by `aclocal' (*note Extending
aclocal: (automake)Extending aclocal.). Additionally, if it is ever
determined that a macro should be made obsolete, it is easy to convert
from `AC_DEFUN' to `AU_DEFUN' in order to have `autoupdate' assist the
user in choosing a better alternative, but there is no corresponding
way to make `m4_define' issue an upgrade notice (*note AU_DEFUN::).
There is another subtle, but important, difference between using
`m4_define' and `AC_DEFUN': only the former is unaffected by
`AC_REQUIRE'. When writing a file, it is always safe to replace a
block of text with a `m4_define' macro that will expand to the same
text. But replacing a block of text with an `AC_DEFUN' macro with the
same content does not necessarily give the same results, because it
changes the location where any embedded but unsatisfied `AC_REQUIRE'
invocations within the block will be expanded. For an example of this,
see *note Expanded Before Required::.
File: autoconf.info, Node: Macro Names, Next: Reporting Messages, Prev: Macro Definitions, Up: Writing Autoconf Macros
10.2 Macro Names
================
All of the public Autoconf macros have all-uppercase names in the
namespace `^AC_' to prevent them from accidentally conflicting with
other text; Autoconf also reserves the namespace `^_AC_' for internal
macros. All shell variables that they use for internal purposes have
mostly-lowercase names starting with `ac_'. Autoconf also uses
here-document delimiters in the namespace `^_AC[A-Z]'. During
`configure', files produced by Autoconf make heavy use of the file
system namespace `^conf'.
Since Autoconf is built on top of M4sugar (*note Programming in
M4sugar::) and M4sh (*note Programming in M4sh::), you must also be
aware of those namespaces (`^_?\(m4\|AS\)_'). And since `configure.ac'
is also designed to be scanned by Autoheader, Autoscan, Autoupdate, and
Automake, you should be aware of the `^_?A[HNUM]_' namespaces. In
general, you _should not use_ the namespace of a package that does not
own the macro or shell code you are writing.
To ensure that your macros don't conflict with present or future
Autoconf macros, you should prefix your own macro names and any shell
variables they use with some other sequence. Possibilities include your
initials, or an abbreviation for the name of your organization or
software package. Historically, people have not always followed the
rule of using a namespace appropriate for their package, and this has
made it difficult for determining the origin of a macro (and where to
report bugs about that macro), as well as difficult for the true
namespace owner to add new macros without interference from pre-existing
uses of third-party macros. Perhaps the best example of this confusion
is the `AM_GNU_GETTEXT' macro, which belongs, not to Automake, but to
Gettext.
Most of the Autoconf macros' names follow a structured naming
convention that indicates the kind of feature check by the name. The
macro names consist of several words, separated by underscores, going
from most general to most specific. The names of their cache variables
use the same convention (*note Cache Variable Names::, for more
information on them).
The first word of the name after the namespace initials (such as
`AC_') usually tells the category of the feature being tested. Here
are the categories used in Autoconf for specific test macros, the kind
of macro that you are more likely to write. They are also used for
cache variables, in all-lowercase. Use them where applicable; where
they're not, invent your own categories.
`C'
C language builtin features.
`DECL'
Declarations of C variables in header files.
`FUNC'
Functions in libraries.
`GROUP'
Posix group owners of files.
`HEADER'
Header files.
`LIB'
C libraries.
`PROG'
The base names of programs.
`MEMBER'
Members of aggregates.
`SYS'
Operating system features.
`TYPE'
C builtin or declared types.
`VAR'
C variables in libraries.
After the category comes the name of the particular feature being
tested. Any further words in the macro name indicate particular aspects
of the feature. For example, `AC_PROG_CC_STDC' checks whether the C
compiler supports ISO Standard C.
An internal macro should have a name that starts with an underscore;
Autoconf internals should therefore start with `_AC_'. Additionally, a
macro that is an internal subroutine of another macro should have a
name that starts with an underscore and the name of that other macro,
followed by one or more words saying what the internal macro does. For
example, `AC_PATH_X' has internal macros `_AC_PATH_X_XMKMF' and
`_AC_PATH_X_DIRECT'.
File: autoconf.info, Node: Reporting Messages, Next: Dependencies Between Macros, Prev: Macro Names, Up: Writing Autoconf Macros
10.3 Reporting Messages
=======================
When macros statically diagnose abnormal situations, benign or fatal, it
is possible to make `autoconf' detect the problem, and refuse to create
`configure' in the case of an error. The macros in this section are
considered obsolescent, and new code should use M4sugar macros for this
purpose, see *note Diagnostic Macros::.
On the other hand, it is possible to want to detect errors when
`configure' is run, which are dependent on the environment of the user
rather than the maintainer. For dynamic diagnostics, see *note
Printing Messages::.
-- Macro: AC_DIAGNOSE (CATEGORY, MESSAGE)
Report MESSAGE as a warning (or as an error if requested by the
user) if warnings of the CATEGORY are turned on. This macro is
obsolescent; you are encouraged to use:
m4_warn([CATEGORY], [MESSAGE])
instead. *Note m4_warn::, for more details, including valid
CATEGORY names.
-- Macro: AC_WARNING (MESSAGE)
Report MESSAGE as a syntax warning. This macro is obsolescent;
you are encouraged to use:
m4_warn([syntax], [MESSAGE])
instead. *Note m4_warn::, for more details, as well as better
finer-grained categories of warnings (not all problems have to do
with syntax).
-- Macro: AC_FATAL (MESSAGE)
Report a severe error MESSAGE, and have `autoconf' die. This
macro is obsolescent; you are encouraged to use:
m4_fatal([MESSAGE])
instead. *Note m4_fatal::, for more details.
When the user runs `autoconf -W error', warnings from `m4_warn'
(including those issued through `AC_DIAGNOSE' and `AC_WARNING') are
reported as errors, see *note autoconf Invocation::.
File: autoconf.info, Node: Dependencies Between Macros, Next: Obsoleting Macros, Prev: Reporting Messages, Up: Writing Autoconf Macros
10.4 Dependencies Between Macros
================================
Some Autoconf macros depend on other macros having been called first in
order to work correctly. Autoconf provides a way to ensure that certain
macros are called if needed and a way to warn the user if macros are
called in an order that might cause incorrect operation.
* Menu:
* Prerequisite Macros:: Ensuring required information
* Suggested Ordering:: Warning about possible ordering problems
* One-Shot Macros:: Ensuring a macro is called only once
File: autoconf.info, Node: Prerequisite Macros, Next: Suggested Ordering, Up: Dependencies Between Macros
10.4.1 Prerequisite Macros
--------------------------
A macro that you write might need to use values that have previously
been computed by other macros. For example, `AC_DECL_YYTEXT' examines
the output of `flex' or `lex', so it depends on `AC_PROG_LEX' having
been called first to set the shell variable `LEX'.
Rather than forcing the user of the macros to keep track of the
dependencies between them, you can use the `AC_REQUIRE' macro to do it
automatically. `AC_REQUIRE' can ensure that a macro is only called if
it is needed, and only called once.
-- Macro: AC_REQUIRE (MACRO-NAME)
If the M4 macro MACRO-NAME has not already been called, call it
(without any arguments). Make sure to quote MACRO-NAME with
square brackets. MACRO-NAME must have been defined using
`AC_DEFUN' or else contain a call to `AC_PROVIDE' to indicate that
it has been called.
`AC_REQUIRE' must be used inside a macro defined by `AC_DEFUN'; it
must not be called from the top level. Also, it does not make
sense to require a macro that takes parameters.
`AC_REQUIRE' is often misunderstood. It really implements
dependencies between macros in the sense that if one macro depends upon
another, the latter is expanded _before_ the body of the former. To be
more precise, the required macro is expanded before the outermost
defined macro in the current expansion stack. In particular,
`AC_REQUIRE([FOO])' is not replaced with the body of `FOO'. For
instance, this definition of macros:
AC_DEFUN([TRAVOLTA],
[test "$body_temperature_in_celsius" -gt "38" &&
dance_floor=occupied])
AC_DEFUN([NEWTON_JOHN],
[test "x$hair_style" = xcurly &&
dance_floor=occupied])
AC_DEFUN([RESERVE_DANCE_FLOOR],
[if date | grep '^Sat.*pm' >/dev/null 2>&1; then
AC_REQUIRE([TRAVOLTA])
AC_REQUIRE([NEWTON_JOHN])
fi])
with this `configure.ac'
AC_INIT([Dance Manager], [1.0], [bug-dance@example.org])
RESERVE_DANCE_FLOOR
if test "x$dance_floor" = xoccupied; then
AC_MSG_ERROR([cannot pick up here, let's move])
fi
does not leave you with a better chance to meet a kindred soul at other
times than Saturday night since it expands into:
test "$body_temperature_in_Celsius" -gt "38" &&
dance_floor=occupied
test "x$hair_style" = xcurly &&
dance_floor=occupied
fi
if date | grep '^Sat.*pm' >/dev/null 2>&1; then
fi
This behavior was chosen on purpose: (i) it prevents messages in
required macros from interrupting the messages in the requiring macros;
(ii) it avoids bad surprises when shell conditionals are used, as in:
if ...; then
AC_REQUIRE([SOME_CHECK])
fi
...
SOME_CHECK
However, this implementation can lead to another class of problems.
Consider the case where an outer macro first expands, then indirectly
requires, an inner macro:
AC_DEFUN([TESTA], [[echo in A
if test -n "$SEEN_A" ; then echo duplicate ; fi
SEEN_A=:]])
AC_DEFUN([TESTB], [AC_REQUIRE([TESTA])[echo in B
if test -z "$SEEN_A" ; then echo bug ; fi]])
AC_DEFUN([TESTC], [AC_REQUIRE([TESTB])[echo in C]])
AC_DEFUN([OUTER], [[echo in OUTER]
A
C])
OUTER
Prior to Autoconf 2.64, the implementation of `AC_REQUIRE' recognized
that `TESTB' needed to be hoisted prior to the expansion of `OUTER',
but because `TESTA' had already been directly expanded, it failed to
hoist `TESTA'. Therefore, the expansion of `TESTB' occurs prior to its
prerequisites, leading to the following output:
in B
bug
in OUTER
in A
in C
Newer Autoconf is smart enough to recognize this situation, and hoists
`TESTA' even though it has already been expanded, but issues a syntax
warning in the process. This is because the hoisted expansion of
`TESTA' defeats the purpose of using `AC_REQUIRE' to avoid redundant
code, and causes its own set of problems if the hoisted macro is not
idempotent:
in A
in B
in OUTER
in A
duplicate
in C
The bug is not in Autoconf, but in the macro definitions. If you
ever pass a particular macro name to `AC_REQUIRE', then you are implying
that the macro only needs to be expanded once. But to enforce this,
either the macro must be declared with `AC_DEFUN_ONCE' (although this
only helps in Autoconf 2.64 or newer), or all uses of that macro should
be through `AC_REQUIRE'; directly expanding the macro defeats the point
of using `AC_REQUIRE' to eliminate redundant expansion. In the
example, this rule of thumb was violated because `TESTB' requires
`TESTA' while `OUTER' directly expands it. One way of fixing the bug
is to factor `TESTA' into two macros, the portion designed for direct
and repeated use (here, named `TESTA'), and the portion designed for
one-shot output and used only inside `AC_REQUIRE' (here, named
`TESTA_PREREQ'). Then, by fixing all clients to use the correct
calling convention according to their needs:
AC_DEFUN([TESTA], [AC_REQUIRE([TESTA_PREREQ])[echo in A]])
AC_DEFUN([TESTA_PREREQ], [[echo in A_PREREQ
if test -n "$SEEN_A" ; then echo duplicate ; fi
SEEN_A=:]])
AC_DEFUN([TESTB], [AC_REQUIRE([TESTA_PREREQ])[echo in B
if test -z "$SEEN_A" ; then echo bug ; fi]])
AC_DEFUN([TESTC], [AC_REQUIRE([TESTB])[echo in C]])
AC_DEFUN([OUTER], [[echo in OUTER]
TESTA
TESTC])
OUTER
the resulting output will then obey all dependency rules and avoid any
syntax warnings, whether the script is built with old or new Autoconf
versions:
in A_PREREQ
in B
in OUTER
in A
in C
The helper macros `AS_IF' and `AS_CASE' may be used to enforce
expansion of required macros outside of shell conditional constructs.
You are furthermore encouraged, although not required, to put all
`AC_REQUIRE' calls at the beginning of a macro. You can use `dnl' to
avoid the empty lines they leave.
File: autoconf.info, Node: Suggested Ordering, Next: One-Shot Macros, Prev: Prerequisite Macros, Up: Dependencies Between Macros
10.4.2 Suggested Ordering
-------------------------
Some macros should be run before another macro if both are called, but
neither _requires_ that the other be called. For example, a macro that
changes the behavior of the C compiler should be called before any
macros that run the C compiler. Many of these dependencies are noted in
the documentation.
Autoconf provides the `AC_BEFORE' macro to warn users when macros
with this kind of dependency appear out of order in a `configure.ac'
file. The warning occurs when creating `configure' from
`configure.ac', not when running `configure'.
For example, `AC_PROG_CPP' checks whether the C compiler can run the
C preprocessor when given the `-E' option. It should therefore be
called after any macros that change which C compiler is being used,
such as `AC_PROG_CC'. So `AC_PROG_CC' contains:
AC_BEFORE([$0], [AC_PROG_CPP])dnl
This warns the user if a call to `AC_PROG_CPP' has already occurred
when `AC_PROG_CC' is called.
-- Macro: AC_BEFORE (THIS-MACRO-NAME, CALLED-MACRO-NAME)
Make M4 print a warning message to the standard error output if
CALLED-MACRO-NAME has already been called. THIS-MACRO-NAME should
be the name of the macro that is calling `AC_BEFORE'. The macro
CALLED-MACRO-NAME must have been defined using `AC_DEFUN' or else
contain a call to `AC_PROVIDE' to indicate that it has been called.
File: autoconf.info, Node: One-Shot Macros, Prev: Suggested Ordering, Up: Dependencies Between Macros
10.4.3 One-Shot Macros
----------------------
Some macros should be called only once, either because calling them
multiple time is unsafe, or because it is bad style. For instance
Autoconf ensures that `AC_CANONICAL_BUILD' and cousins (*note
Canonicalizing::) are evaluated only once, because it makes no sense to
run these expensive checks more than once. Such one-shot macros can be
defined using `AC_DEFUN_ONCE'.
-- Macro: AC_DEFUN_ONCE (MACRO-NAME, MACRO-BODY)
Declare macro MACRO-NAME like `AC_DEFUN' would (*note Macro
Definitions::), but add additional logic that guarantees that only
the first use of the macro (whether by direct expansion or
`AC_REQUIRE') causes an expansion of MACRO-BODY; the expansion
will occur before the start of any enclosing macro defined by
`AC_DEFUN'. Subsequent expansions are silently ignored.
Generally, it does not make sense for MACRO-BODY to use parameters
such as `$1'.
Prior to Autoconf 2.64, a macro defined by `AC_DEFUN_ONCE' would
emit a warning if it was directly expanded a second time, so for
portability, it is better to use `AC_REQUIRE' than direct invocation of
MACRO-NAME inside a macro defined by `AC_DEFUN' (*note Prerequisite
Macros::).
File: autoconf.info, Node: Obsoleting Macros, Next: Coding Style, Prev: Dependencies Between Macros, Up: Writing Autoconf Macros
10.5 Obsoleting Macros
======================
Configuration and portability technology has evolved over the years.
Often better ways of solving a particular problem are developed, or
ad-hoc approaches are systematized. This process has occurred in many
parts of Autoconf. One result is that some of the macros are now
considered "obsolete"; they still work, but are no longer considered
the best thing to do, hence they should be replaced with more modern
macros. Ideally, `autoupdate' should replace the old macro calls with
their modern implementation.
Autoconf provides a simple means to obsolete a macro.
-- Macro: AU_DEFUN (OLD-MACRO, IMPLEMENTATION, [MESSAGE])
Define OLD-MACRO as IMPLEMENTATION. The only difference with
`AC_DEFUN' is that the user is warned that OLD-MACRO is now
obsolete.
If she then uses `autoupdate', the call to OLD-MACRO is replaced
by the modern IMPLEMENTATION. MESSAGE should include information
on what to do after running `autoupdate'; `autoupdate' prints it
as a warning, and includes it in the updated `configure.ac' file.
The details of this macro are hairy: if `autoconf' encounters an
`AU_DEFUN'ed macro, all macros inside its second argument are
expanded as usual. However, when `autoupdate' is run, only M4 and
M4sugar macros are expanded here, while all other macros are
disabled and appear literally in the updated `configure.ac'.
-- Macro: AU_ALIAS (OLD-NAME, NEW-NAME)
Used if the OLD-NAME is to be replaced by a call to NEW-MACRO with
the same parameters. This happens for example if the macro was
renamed.
File: autoconf.info, Node: Coding Style, Prev: Obsoleting Macros, Up: Writing Autoconf Macros
10.6 Coding Style
=================
The Autoconf macros follow a strict coding style. You are encouraged to
follow this style, especially if you intend to distribute your macro,
either by contributing it to Autoconf itself, or via other means.
The first requirement is to pay great attention to the quotation.
For more details, see *note Autoconf Language::, and *note M4
Quotation::.
Do not try to invent new interfaces. It is likely that there is a
macro in Autoconf that resembles the macro you are defining: try to
stick to this existing interface (order of arguments, default values,
etc.). We _are_ conscious that some of these interfaces are not
perfect; nevertheless, when harmless, homogeneity should be preferred
over creativity.
Be careful about clashes both between M4 symbols and between shell
variables.
If you stick to the suggested M4 naming scheme (*note Macro Names::),
you are unlikely to generate conflicts. Nevertheless, when you need to
set a special value, _avoid using a regular macro name_; rather, use an
"impossible" name. For instance, up to version 2.13, the macro
`AC_SUBST' used to remember what SYMBOL macros were already defined by
setting `AC_SUBST_SYMBOL', which is a regular macro name. But since
there is a macro named `AC_SUBST_FILE', it was just impossible to
`AC_SUBST(FILE)'! In this case, `AC_SUBST(SYMBOL)' or
`_AC_SUBST(SYMBOL)' should have been used (yes, with the parentheses).
No Autoconf macro should ever enter the user-variable name space;
i.e., except for the variables that are the actual result of running the
macro, all shell variables should start with `ac_'. In addition, small
macros or any macro that is likely to be embedded in other macros
should be careful not to use obvious names.
Do not use `dnl' to introduce comments: most of the comments you are
likely to write are either header comments which are not output anyway,
or comments that should make their way into `configure'. There are
exceptional cases where you do want to comment special M4 constructs,
in which case `dnl' is right, but keep in mind that it is unlikely.
M4 ignores the leading blanks and newlines before each argument.
Use this feature to indent in such a way that arguments are (more or
less) aligned with the opening parenthesis of the macro being called.
For instance, instead of
AC_CACHE_CHECK(for EMX OS/2 environment,
ac_cv_emxos2,
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM(, [return __EMX__;])],
[ac_cv_emxos2=yes], [ac_cv_emxos2=no])])
write
AC_CACHE_CHECK([for EMX OS/2 environment], [ac_cv_emxos2],
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [return __EMX__;])],
[ac_cv_emxos2=yes],
[ac_cv_emxos2=no])])
or even
AC_CACHE_CHECK([for EMX OS/2 environment],
[ac_cv_emxos2],
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],
[return __EMX__;])],
[ac_cv_emxos2=yes],
[ac_cv_emxos2=no])])
When using `AC_RUN_IFELSE' or any macro that cannot work when
cross-compiling, provide a pessimistic value (typically `no').
Feel free to use various tricks to prevent auxiliary tools, such as
syntax-highlighting editors, from behaving improperly. For instance,
instead of:
m4_bpatsubst([$1], [$"])
use
m4_bpatsubst([$1], [$""])
so that Emacsen do not open an endless "string" at the first quote.
For the same reasons, avoid:
test $[#] != 0
and use:
test $[@%:@] != 0
Otherwise, the closing bracket would be hidden inside a `#'-comment,
breaking the bracket-matching highlighting from Emacsen. Note the
preferred style to escape from M4: `$[1]', `$[@]', etc. Do not escape
when it is unnecessary. Common examples of useless quotation are
`[$]$1' (write `$$1'), `[$]var' (use `$var'), etc. If you add
portability issues to the picture, you'll prefer `${1+"$[@]"}' to
`"[$]@"', and you'll prefer do something better than hacking Autoconf
`:-)'.
When using `sed', don't use `-e' except for indenting purposes.
With the `s' and `y' commands, the preferred separator is `/' unless
`/' itself might appear in the pattern or replacement, in which case
you should use `|', or optionally `,' if you know the pattern and
replacement cannot contain a file name. If none of these characters
will do, choose a printable character that cannot appear in the pattern
or replacement. Characters from the set `"#$&'()*;<=>?`|~' are good
choices if the pattern or replacement might contain a file name, since
they have special meaning to the shell and are less likely to occur in
file names.
*Note Macro Definitions::, for details on how to define a macro. If
a macro doesn't use `AC_REQUIRE', is expected to never be the object of
an `AC_REQUIRE' directive, and macros required by other macros inside
arguments do not need to be expanded before this macro, then use
`m4_define'. In case of doubt, use `AC_DEFUN'. Also take into account
that public third-party macros need to use `AC_DEFUN' in order to be
found by `aclocal' (*note Extending aclocal: (automake)Extending
aclocal.). All the `AC_REQUIRE' statements should be at the beginning
of the macro, and each statement should be followed by `dnl'.
You should not rely on the number of arguments: instead of checking
whether an argument is missing, test that it is not empty. It provides
both a simpler and a more predictable interface to the user, and saves
room for further arguments.
Unless the macro is short, try to leave the closing `])' at the
beginning of a line, followed by a comment that repeats the name of the
macro being defined. This introduces an additional newline in
`configure'; normally, that is not a problem, but if you want to remove
it you can use `[]dnl' on the last line. You can similarly use `[]dnl'
after a macro call to remove its newline. `[]dnl' is recommended
instead of `dnl' to ensure that M4 does not interpret the `dnl' as
being attached to the preceding text or macro output. For example,
instead of:
AC_DEFUN([AC_PATH_X],
[AC_MSG_CHECKING([for X])
AC_REQUIRE_CPP()
# ...omitted...
AC_MSG_RESULT([libraries $x_libraries, headers $x_includes])
fi])
you would write:
AC_DEFUN([AC_PATH_X],
[AC_REQUIRE_CPP()[]dnl
AC_MSG_CHECKING([for X])
# ...omitted...
AC_MSG_RESULT([libraries $x_libraries, headers $x_includes])
fi[]dnl
])# AC_PATH_X
If the macro is long, try to split it into logical chunks.
Typically, macros that check for a bug in a function and prepare its
`AC_LIBOBJ' replacement should have an auxiliary macro to perform this
setup. Do not hesitate to introduce auxiliary macros to factor your
code.
In order to highlight the recommended coding style, here is a macro
written the old way:
dnl Check for EMX on OS/2.
dnl _AC_EMXOS2
AC_DEFUN(_AC_EMXOS2,
[AC_CACHE_CHECK(for EMX OS/2 environment, ac_cv_emxos2,
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM(, return __EMX__;)],
ac_cv_emxos2=yes, ac_cv_emxos2=no)])
test "x$ac_cv_emxos2" = xyes && EMXOS2=yes])
and the new way:
# _AC_EMXOS2
# ----------
# Check for EMX on OS/2.
m4_define([_AC_EMXOS2],
[AC_CACHE_CHECK([for EMX OS/2 environment], [ac_cv_emxos2],
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [return __EMX__;])],
[ac_cv_emxos2=yes],
[ac_cv_emxos2=no])])
test "x$ac_cv_emxos2" = xyes && EMXOS2=yes[]dnl
])# _AC_EMXOS2
File: autoconf.info, Node: Portable Shell, Next: Portable Make, Prev: Writing Autoconf Macros, Up: Top
11 Portable Shell Programming
*****************************
When writing your own checks, there are some shell-script programming
techniques you should avoid in order to make your code portable. The
Bourne shell and upward-compatible shells like the Korn shell and Bash
have evolved over the years, and many features added to the original
System7 shell are now supported on all interesting porting targets.
However, the following discussion between Russ Allbery and Robert Lipe
is worth reading:
Russ Allbery:
The GNU assumption that `/bin/sh' is the one and only shell leads
to a permanent deadlock. Vendors don't want to break users'
existing shell scripts, and there are some corner cases in the
Bourne shell that are not completely compatible with a Posix
shell. Thus, vendors who have taken this route will _never_
(OK..."never say never") replace the Bourne shell (as `/bin/sh')
with a Posix shell.
Robert Lipe:
This is exactly the problem. While most (at least most System
V's) do have a Bourne shell that accepts shell functions most
vendor `/bin/sh' programs are not the Posix shell.
So while most modern systems do have a shell _somewhere_ that
meets the Posix standard, the challenge is to find it.
For this reason, part of the job of M4sh (*note Programming in
M4sh::) is to find such a shell. But to prevent trouble, if you're not
using M4sh you should not take advantage of features that were added
after Unix version 7, circa 1977 (*note Systemology::); you should not
use aliases, negated character classes, or even `unset'. `#' comments,
while not in Unix version 7, were retrofitted in the original Bourne
shell and can be assumed to be part of the least common denominator.
On the other hand, if you're using M4sh you can assume that the shell
has the features that were added in SVR2 (circa 1984), including shell
functions, `return', `unset', and I/O redirection for builtins. For
more information, refer to `http://www.in-ulm.de/~mascheck/bourne/'.
However, some pitfalls have to be avoided for portable use of these
constructs; these will be documented in the rest of this chapter. See
in particular *note Shell Functions:: and *note Limitations of Shell
Builtins: Limitations of Builtins.
Some ancient systems have quite small limits on the length of the
`#!' line; for instance, 32 bytes (not including the newline) on SunOS
4. However, these ancient systems are no longer of practical concern.
The set of external programs you should run in a `configure' script
is fairly small. *Note Utilities in Makefiles: (standards)Utilities in
Makefiles, for the list. This restriction allows users to start out
with a fairly small set of programs and build the rest, avoiding too
many interdependencies between packages.
Some of these external utilities have a portable subset of features;
see *note Limitations of Usual Tools::.
There are other sources of documentation about shells. The
specification for the Posix Shell Command Language
(http://www.opengroup.org/susv3/utilities/xcu_chap02.html), though more
generous than the restrictive shell subset described above, is fairly
portable nowadays. Also please see the Shell FAQs
(http://www.faqs.org/faqs/unix-faq/shell/).
* Menu:
* Shellology:: A zoology of shells
* Here-Documents:: Quirks and tricks
* File Descriptors:: FDs and redirections
* File System Conventions:: File names
* Shell Pattern Matching:: Pattern matching
* Shell Substitutions:: Variable and command expansions
* Assignments:: Varying side effects of assignments
* Parentheses:: Parentheses in shell scripts
* Slashes:: Slashes in shell scripts
* Special Shell Variables:: Variables you should not change
* Shell Functions:: What to look out for if you use them
* Limitations of Builtins:: Portable use of not so portable /bin/sh
* Limitations of Usual Tools:: Portable use of portable tools
File: autoconf.info, Node: Shellology, Next: Here-Documents, Up: Portable Shell
11.1 Shellology
===============
There are several families of shells, most prominently the Bourne family
and the C shell family which are deeply incompatible. If you want to
write portable shell scripts, avoid members of the C shell family. The
the Shell difference FAQ
(http://www.faqs.org/faqs/unix-faq/shell/shell-differences/) includes a
small history of Posix shells, and a comparison between several of them.
Below we describe some of the members of the Bourne shell family.
Ash
Ash is often used on GNU/Linux and BSD systems as a light-weight
Bourne-compatible shell. Ash 0.2 has some bugs that are fixed in
the 0.3.x series, but portable shell scripts should work around
them, since version 0.2 is still shipped with many GNU/Linux
distributions.
To be compatible with Ash 0.2:
- don't use `$?' after expanding empty or unset variables, or
at the start of an `eval':
foo=
false
$foo
echo "Do not use it: $?"
false
eval 'echo "Do not use it: $?"'
- don't use command substitution within variable expansion:
cat ${FOO=`bar`}
- beware that single builtin substitutions are not performed by
a subshell, hence their effect applies to the current shell!
*Note Shell Substitutions::, item "Command Substitution".
Bash
To detect whether you are running Bash, test whether
`BASH_VERSION' is set. To require Posix compatibility, run `set
-o posix'. *Note Bash Posix Mode: (bash)Bash POSIX Mode, for
details.
Bash 2.05 and later
Versions 2.05 and later of Bash use a different format for the
output of the `set' builtin, designed to make evaluating its
output easier. However, this output is not compatible with earlier
versions of Bash (or with many other shells, probably). So if you
use Bash 2.05 or higher to execute `configure', you'll need to use
Bash 2.05 for all other build tasks as well.
Ksh
The Korn shell is compatible with the Bourne family and it mostly
conforms to Posix. It has two major variants commonly called
`ksh88' and `ksh93', named after the years of initial release. It
is usually called `ksh', but is called `sh' on some hosts if you
set your path appropriately.
Solaris systems have three variants: `/usr/bin/ksh' is `ksh88'; it
is standard on Solaris 2.0 and later. `/usr/xpg4/bin/sh' is a
Posix-compliant variant of `ksh88'; it is standard on Solaris 9
and later. `/usr/dt/bin/dtksh' is `ksh93'. Variants that are not
standard may be parts of optional packages. There is no extra
charge for these packages, but they are not part of a minimal OS
install and therefore some installations may not have it.
Starting with Tru64 Version 4.0, the Korn shell `/usr/bin/ksh' is
also available as `/usr/bin/posix/sh'. If the environment
variable `BIN_SH' is set to `xpg4', subsidiary invocations of the
standard shell conform to Posix.
Pdksh
A public-domain clone of the Korn shell called `pdksh' is widely
available: it has most of the `ksh88' features along with a few of
its own. It usually sets `KSH_VERSION', except if invoked as
`/bin/sh' on OpenBSD, and similarly to Bash you can require Posix
compatibility by running `set -o posix'. Unfortunately, with
`pdksh' 5.2.14 (the latest stable version as of January 2007)
Posix mode is buggy and causes `pdksh' to depart from Posix in at
least one respect:
$ echo "`echo \"hello\"`"
hello
$ set -o posix
$ echo "`echo \"hello\"`"
"hello"
The last line of output contains spurious quotes. This is yet
another reason why portable shell code should not contain
`"`...\"...\"...`"' constructs (*note Shell Substitutions::).
Zsh
To detect whether you are running `zsh', test whether
`ZSH_VERSION' is set. By default `zsh' is _not_ compatible with
the Bourne shell: you must execute `emulate sh', and for `zsh'
versions before 3.1.6-dev-18 you must also set `NULLCMD' to `:'.
*Note Compatibility: (zsh)Compatibility, for details.
The default Mac OS X `sh' was originally Zsh; it was changed to
Bash in Mac OS X 10.2.
File: autoconf.info, Node: Here-Documents, Next: File Descriptors, Prev: Shellology, Up: Portable Shell
11.2 Here-Documents
===================
Don't rely on `\' being preserved just because it has no special
meaning together with the next symbol. In the native `sh' on OpenBSD
2.7 `\"' expands to `"' in here-documents with unquoted delimiter. As
a general rule, if `\\' expands to `\' use `\\' to get `\'.
With OpenBSD 2.7's `sh'
$ cat < \" \\
> EOF
" \
and with Bash:
bash-2.04$ cat < \" \\
> EOF
\" \
Some shells mishandle large here-documents: for example, Solaris 10
`dtksh' and the UnixWare 7.1.1 Posix shell, which are derived from Korn
shell version M-12/28/93d, mishandle braced variable expansion that
crosses a 1024- or 4096-byte buffer boundary within a here-document.
Only the part of the variable name after the boundary is used. For
example, `${variable}' could be replaced by the expansion of `${ble}'.
If the end of the variable name is aligned with the block boundary, the
shell reports an error, as if you used `${}'. Instead of
`${variable-default}', the shell may expand `${riable-default}', or
even `${fault}'. This bug can often be worked around by omitting the
braces: `$variable'. The bug was fixed in `ksh93g' (1998-04-30) but as
of 2006 many operating systems were still shipping older versions with
the bug.
Many shells (including the Bourne shell) implement here-documents
inefficiently. In particular, some shells can be extremely inefficient
when a single statement contains many here-documents. For instance if
your `configure.ac' includes something like:
if ; then
assume this and that
else
check this
check that
check something else
...
on and on forever
...
fi
A shell parses the whole `if'/`fi' construct, creating temporary
files for each here-document in it. Some shells create links for such
here-documents on every `fork', so that the clean-up code they had
installed correctly removes them. It is creating the links that can
take the shell forever.
Moving the tests out of the `if'/`fi', or creating multiple
`if'/`fi' constructs, would improve the performance significantly.
Anyway, this kind of construct is not exactly the typical use of
Autoconf. In fact, it's even not recommended, because M4 macros can't
look into shell conditionals, so we may fail to expand a macro when it
was expanded before in a conditional path, and the condition turned out
to be false at runtime, and we end up not executing the macro at all.
File: autoconf.info, Node: File Descriptors, Next: File System Conventions, Prev: Here-Documents, Up: Portable Shell
11.3 File Descriptors
=====================
Most shells, if not all (including Bash, Zsh, Ash), output traces on
stderr, even for subshells. This might result in undesirable content
if you meant to capture the standard-error output of the inner command:
$ ash -x -c '(eval "echo foo >&2") 2>stderr'
$ cat stderr
+ eval echo foo >&2
+ echo foo
foo
$ bash -x -c '(eval "echo foo >&2") 2>stderr'
$ cat stderr
+ eval 'echo foo >&2'
++ echo foo
foo
$ zsh -x -c '(eval "echo foo >&2") 2>stderr'
# Traces on startup files deleted here.
$ cat stderr
+zsh:1> eval echo foo >&2
+zsh:1> echo foo
foo
One workaround is to grep out uninteresting lines, hoping not to remove
good ones.
If you intend to redirect both standard error and standard output,
redirect standard output first. This works better with HP-UX, since
its shell mishandles tracing if standard error is redirected first:
$ sh -x -c ': 2>err >out'
+ :
+ 2> err $ cat err
1> out
Don't try to redirect the standard error of a command substitution.
It must be done _inside_ the command substitution. When running `: `cd
/zorglub` 2>/dev/null' expect the error message to escape, while `: `cd
/zorglub 2>/dev/null`' works properly.
It is worth noting that Zsh (but not Ash nor Bash) makes it possible
in assignments though: `foo=`cd /zorglub` 2>/dev/null'.
Some shells, like `ash', don't recognize bi-directional redirection
(`<>'). And even on shells that recognize it, it is not portable to
use on fifos: Posix does not require read-write support for named
pipes, and Cygwin does not support it:
$ mkfifo fifo
$ exec 5<>fifo
$ echo hi >&5
bash: echo: write error: Communication error on send
When catering to old systems, don't redirect the same file descriptor
several times, as you are doomed to failure under Ultrix.
ULTRIX V4.4 (Rev. 69) System #31: Thu Aug 10 19:42:23 GMT 1995
UWS V4.4 (Rev. 11)
$ eval 'echo matter >fullness' >void
illegal io
$ eval '(echo matter >fullness)' >void
illegal io
$ (eval '(echo matter >fullness)') >void
Ambiguous output redirect.
In each case the expected result is of course `fullness' containing
`matter' and `void' being empty. However, this bug is probably not of
practical concern to modern platforms.
Solaris 10 `sh' will try to optimize away a `:' command in a loop
after the first iteration, even if it is redirected:
$ for i in 1 2 3 ; do : >x$i; done
$ ls
x1
As a workaround, `echo' or `eval' can be used.
Don't rely on file descriptors 0, 1, and 2 remaining closed in a
subsidiary program. If any of these descriptors is closed, the
operating system may open an unspecified file for the descriptor in the
new process image. Posix says this may be done only if the subsidiary
program is set-user-ID or set-group-ID, but HP-UX 11.23 does it even
for ordinary programs.
Don't rely on open file descriptors being open in child processes.
In `ksh', file descriptors above 2 which are opened using `exec N>file'
are closed by a subsequent `exec' (such as that involved in the
fork-and-exec which runs a program or script). Thus, using `sh', we
have:
$ cat ./descrips
#!/bin/sh -
echo hello >&5
$ exec 5>t
$ ./descrips
$ cat t
hello
$
But using ksh:
$ exec 5>t
$ ./descrips
hello
$ cat t
$
Within the process which runs the `descrips' script, file descriptor 5
is closed.
Don't rely on redirection to a closed file descriptor to cause an
error. With Solaris `/bin/sh', when the redirection fails, the output
goes to the original file descriptor.
$ bash -c 'echo hi >&3' 3>&-; echo $?
bash: 3: Bad file descriptor
1
$ /bin/sh -c 'echo hi >&3' 3>&-; echo $?
hi
0
DOS variants cannot rename or remove open files, such as in `mv foo
bar >foo' or `rm foo >foo', even though this is perfectly portable
among Posix hosts.
A few ancient systems reserved some file descriptors. By convention,
file descriptor 3 was opened to `/dev/tty' when you logged into Eighth
Edition (1985) through Tenth Edition Unix (1989). File descriptor 4
had a special use on the Stardent/Kubota Titan (circa 1990), though we
don't now remember what it was. Both these systems are obsolete, so
it's now safe to treat file descriptors 3 and 4 like any other file
descriptors.
File: autoconf.info, Node: File System Conventions, Next: Shell Pattern Matching, Prev: File Descriptors, Up: Portable Shell
11.4 File System Conventions
============================
Autoconf uses shell-script processing extensively, so the file names
that it processes should not contain characters that are special to the
shell. Special characters include space, tab, newline, NUL, and the
following:
" # $ & ' ( ) * ; < = > ? [ \ ` |
Also, file names should not begin with `~' or `-', and should
contain neither `-' immediately after `/' nor `~' immediately after
`:'. On Posix-like platforms, directory names should not contain `:',
as this runs afoul of `:' used as the path separator.
These restrictions apply not only to the files that you distribute,
but also to the absolute file names of your source, build, and
destination directories.
On some Posix-like platforms, `!' and `^' are special too, so they
should be avoided.
Posix lets implementations treat leading `//' specially, but
requires leading `///' and beyond to be equivalent to `/'. Most Unix
variants treat `//' like `/'. However, some treat `//' as a
"super-root" that can provide access to files that are not otherwise
reachable from `/'. The super-root tradition began with Apollo
Domain/OS, which died out long ago, but unfortunately Cygwin has
revived it.
While `autoconf' and friends are usually run on some Posix variety,
they can be used on other systems, most notably DOS variants. This
impacts several assumptions regarding file names.
For example, the following code:
case $foo_dir in
/*) # Absolute
;;
*)
foo_dir=$dots$foo_dir ;;
esac
fails to properly detect absolute file names on those systems, because
they can use a drivespec, and usually use a backslash as directory
separator. If you want to be portable to DOS variants (at the price of
rejecting valid but oddball Posix file names like `a:\b'), you can
check for absolute file names like this:
case $foo_dir in
[\\/]* | ?:[\\/]* ) # Absolute
;;
*)
foo_dir=$dots$foo_dir ;;
esac
Make sure you quote the brackets if appropriate and keep the backslash
as first character (*note Limitations of Shell Builtins: case.).
Also, because the colon is used as part of a drivespec, these
systems don't use it as path separator. When creating or accessing
paths, you can use the `PATH_SEPARATOR' output variable instead.
`configure' sets this to the appropriate value for the build system
(`:' or `;') when it starts up.
File names need extra care as well. While DOS variants that are
Posixy enough to run `autoconf' (such as DJGPP) are usually able to
handle long file names properly, there are still limitations that can
seriously break packages. Several of these issues can be easily
detected by the doschk
(ftp://ftp.gnu.org/gnu/non-gnu/doschk/doschk-1.1.tar.gz) package.
A short overview follows; problems are marked with SFN/LFN to
indicate where they apply: SFN means the issues are only relevant to
plain DOS, not to DOS under Microsoft Windows variants, while LFN
identifies problems that exist even under Microsoft Windows variants.
No multiple dots (SFN)
DOS cannot handle multiple dots in file names. This is an
especially important thing to remember when building a portable
configure script, as `autoconf' uses a .in suffix for template
files.
This is perfectly OK on Posix variants:
AC_CONFIG_HEADERS([config.h])
AC_CONFIG_FILES([source.c foo.bar])
AC_OUTPUT
but it causes problems on DOS, as it requires `config.h.in',
`source.c.in' and `foo.bar.in'. To make your package more portable
to DOS-based environments, you should use this instead:
AC_CONFIG_HEADERS([config.h:config.hin])
AC_CONFIG_FILES([source.c:source.cin foo.bar:foobar.in])
AC_OUTPUT
No leading dot (SFN)
DOS cannot handle file names that start with a dot. This is
usually not important for `autoconf'.
Case insensitivity (LFN)
DOS is case insensitive, so you cannot, for example, have both a
file called `INSTALL' and a directory called `install'. This also
affects `make'; if there's a file called `INSTALL' in the
directory, `make install' does nothing (unless the `install'
target is marked as PHONY).
The 8+3 limit (SFN)
Because the DOS file system only stores the first 8 characters of
the file name and the first 3 of the extension, those must be
unique. That means that `foobar-part1.c', `foobar-part2.c' and
`foobar-prettybird.c' all resolve to the same file name
(`FOOBAR-P.C'). The same goes for `foo.bar' and `foo.bartender'.
The 8+3 limit is not usually a problem under Microsoft Windows, as
it uses numeric tails in the short version of file names to make
them unique. However, a registry setting can turn this behavior
off. While this makes it possible to share file trees containing
long file names between SFN and LFN environments, it also means
the above problem applies there as well.
Invalid characters (LFN)
Some characters are invalid in DOS file names, and should therefore
be avoided. In a LFN environment, these are `/', `\', `?', `*',
`:', `<', `>', `|' and `"'. In a SFN environment, other
characters are also invalid. These include `+', `,', `[' and `]'.
Invalid names (LFN)
Some DOS file names are reserved, and cause problems if you try to
use files with those names. These names include `CON', `AUX',
`COM1', `COM2', `COM3', `COM4', `LPT1', `LPT2', `LPT3', `NUL', and
`PRN'. File names are case insensitive, so even names like
`aux/config.guess' are disallowed.
File: autoconf.info, Node: Shell Pattern Matching, Next: Shell Substitutions, Prev: File System Conventions, Up: Portable Shell
11.5 Shell Pattern Matching
===========================
Nowadays portable patterns can use negated character classes like
`[!-aeiou]'. The older syntax `[^-aeiou]' is supported by some shells
but not others; hence portable scripts should never use `^' as the
first character of a bracket pattern.
Outside the C locale, patterns like `[a-z]' are problematic since
they may match characters that are not lower-case letters.
File: autoconf.info, Node: Shell Substitutions, Next: Assignments, Prev: Shell Pattern Matching, Up: Portable Shell
11.6 Shell Substitutions
========================
Contrary to a persistent urban legend, the Bourne shell does not
systematically split variables and back-quoted expressions, in
particular on the right-hand side of assignments and in the argument of
`case'. For instance, the following code:
case "$given_srcdir" in
.) top_srcdir="`echo "$dots" | sed 's|/$||'`" ;;
*) top_srcdir="$dots$given_srcdir" ;;
esac
is more readable when written as:
case $given_srcdir in
.) top_srcdir=`echo "$dots" | sed 's|/$||'` ;;
*) top_srcdir=$dots$given_srcdir ;;
esac
and in fact it is even _more_ portable: in the first case of the first
attempt, the computation of `top_srcdir' is not portable, since not all
shells properly understand `"`..."..."...`"'. Worse yet, not all
shells understand `"`...\"...\"...`"' the same way. There is just no
portable way to use double-quoted strings inside double-quoted
back-quoted expressions (pfew!).
`$@'
One of the most famous shell-portability issues is related to
`"$@"'. When there are no positional arguments, Posix says that
`"$@"' is supposed to be equivalent to nothing, but the original
Unix version 7 Bourne shell treated it as equivalent to `""'
instead, and this behavior survives in later implementations like
Digital Unix 5.0.
The traditional way to work around this portability problem is to
use `${1+"$@"}'. Unfortunately this method does not work with Zsh
(3.x and 4.x), which is used on Mac OS X. When emulating the
Bourne shell, Zsh performs word splitting on `${1+"$@"}':
zsh $ emulate sh
zsh $ for i in "$@"; do echo $i; done
Hello World
!
zsh $ for i in ${1+"$@"}; do echo $i; done
Hello
World
!
Zsh handles plain `"$@"' properly, but we can't use plain `"$@"'
because of the portability problems mentioned above. One
workaround relies on Zsh's "global aliases" to convert `${1+"$@"}'
into `"$@"' by itself:
test "${ZSH_VERSION+set}" = set && alias -g '${1+"$@"}'='"$@"'
Zsh only recognizes this alias when a shell word matches it
exactly; `"foo"${1+"$@"}' remains subject to word splitting.
Since this case always yields at least one shell word, use plain
`"$@"'.
A more conservative workaround is to avoid `"$@"' if it is
possible that there may be no positional arguments. For example,
instead of:
cat conftest.c "$@"
you can use this instead:
case $# in
0) cat conftest.c;;
*) cat conftest.c "$@";;
esac
Autoconf macros often use the `set' command to update `$@', so if
you are writing shell code intended for `configure' you should not
assume that the value of `$@' persists for any length of time.
`${10}'
The 10th, 11th, ... positional parameters can be accessed only
after a `shift'. The 7th Edition shell reported an error if given
`${10}', and Solaris 10 `/bin/sh' still acts that way:
$ set 1 2 3 4 5 6 7 8 9 10
$ echo ${10}
bad substitution
`${VAR:-VALUE}'
Old BSD shells, including the Ultrix `sh', don't accept the colon
for any shell substitution, and complain and die. Similarly for
${VAR:=VALUE}, ${VAR:?VALUE}, etc.
`${VAR=LITERAL}'
Be sure to quote:
: ${var='Some words'}
otherwise some shells, such as on Digital Unix V 5.0, die because
of a "bad substitution".
Solaris `/bin/sh' has a frightening bug in its interpretation of
this. Imagine you need set a variable to a string containing `}'.
This `}' character confuses Solaris `/bin/sh' when the affected
variable was already set. This bug can be exercised by running:
$ unset foo
$ foo=${foo='}'}
$ echo $foo
}
$ foo=${foo='}' # no error; this hints to what the bug is
$ echo $foo
}
$ foo=${foo='}'}
$ echo $foo
}}
^ ugh!
It seems that `}' is interpreted as matching `${', even though it
is enclosed in single quotes. The problem doesn't happen using
double quotes.
`${VAR=EXPANDED-VALUE}'
On Ultrix, running
default="yu,yaa"
: ${var="$default"}
sets VAR to `M-yM-uM-,M-yM-aM-a', i.e., the 8th bit of each char
is set. You don't observe the phenomenon using a simple `echo
$var' since apparently the shell resets the 8th bit when it
expands $var. Here are two means to make this shell confess its
sins:
$ cat -v < broken
$ echo "`printf 'foo\r\n'`"" bar" | cmp - broken
- broken differ: char 4, line 1
Upon interrupt or SIGTERM, some shells may abort a command
substitution, replace it with a null string, and wrongly evaluate
the enclosing command before entering the trap or ending the
script. This can lead to spurious errors:
$ sh -c 'if test `sleep 5; echo hi` = hi; then echo yes; fi'
$ ^C
sh: test: hi: unexpected operator/operand
You can avoid this by assigning the command substitution to a
temporary variable:
$ sh -c 'res=`sleep 5; echo hi`
if test "x$res" = xhi; then echo yes; fi'
$ ^C
`$(COMMANDS)'
This construct is meant to replace ``COMMANDS`', and it has most
of the problems listed under ``COMMANDS`'.
This construct can be nested while this is impossible to do
portably with back quotes. Unfortunately it is not yet
universally supported. Most notably, even recent releases of
Solaris don't support it:
$ showrev -c /bin/sh | grep version
Command version: SunOS 5.10 Generic 121005-03 Oct 2006
$ echo $(echo blah)
syntax error: `(' unexpected
nor does IRIX 6.5's Bourne shell:
$ uname -a
IRIX firebird-image 6.5 07151432 IP22
$ echo $(echo blah)
$(echo blah)
If you do use `$(COMMANDS)', make sure that the commands do not
start with a parenthesis, as that would cause confusion with a
different notation `$((EXPRESSION))' that in modern shells is an
arithmetic expression not a command. To avoid the confusion,
insert a space between the two opening parentheses.
Avoid COMMANDS that contain unbalanced parentheses in
here-documents, comments, or case statement patterns, as many
shells mishandle them. For example, Bash 3.1, `ksh88', `pdksh'
5.2.14, and Zsh 4.2.6 all mishandle the following valid command:
echo $(case x in x) echo hello;; esac)
`$((EXPRESSION))'
Arithmetic expansion is not portable as some shells (most notably
Solaris 10 `/bin/sh') don't support it.
Among shells that do support `$(( ))', not all of them obey the
Posix rule that octal and hexadecimal constants must be recognized:
$ bash -c 'echo $(( 010 + 0x10 ))'
24
$ zsh -c 'echo $(( 010 + 0x10 ))'
26
$ zsh -c 'emulate sh; echo $(( 010 + 0x10 ))'
24
$ pdksh -c 'echo $(( 010 + 0x10 ))'
pdksh: 010 + 0x10 : bad number `0x10'
$ pdksh -c 'echo $(( 010 ))'
10
When it is available, using arithmetic expansion provides a
noticeable speedup in script execution; but testing for support
requires `eval' to avoid syntax errors. The following construct
is used by `AS_VAR_ARITH' to provide arithmetic computation when
all arguments are provided in decimal and without a leading zero,
and all operators are properly quoted and appear as distinct
arguments:
if ( eval 'test $(( 1 + 1 )) = 2' ) 2>/dev/null; then
eval 'func_arith ()
{
func_arith_result=$(( $* ))
}'
else
func_arith ()
{
func_arith_result=`expr "$@"`
}
fi
func_arith 1 + 1
foo=$func_arith_result
`^'
Always quote `^', otherwise traditional shells such as `/bin/sh'
on Solaris 10 treat this like `|'.
File: autoconf.info, Node: Assignments, Next: Parentheses, Prev: Shell Substitutions, Up: Portable Shell
11.7 Assignments
================
When setting several variables in a row, be aware that the order of the
evaluation is undefined. For instance `foo=1 foo=2; echo $foo' gives
`1' with Solaris `/bin/sh', but `2' with Bash. You must use `;' to
enforce the order: `foo=1; foo=2; echo $foo'.
Don't rely on the following to find `subdir/program':
PATH=subdir$PATH_SEPARATOR$PATH program
as this does not work with Zsh 3.0.6. Use something like this instead:
(PATH=subdir$PATH_SEPARATOR$PATH; export PATH; exec program)
Don't rely on the exit status of an assignment: Ash 0.2 does not
change the status and propagates that of the last statement:
$ false || foo=bar; echo $?
1
$ false || foo=`:`; echo $?
0
and to make things even worse, QNX 4.25 just sets the exit status to 0
in any case:
$ foo=`exit 1`; echo $?
0
To assign default values, follow this algorithm:
1. If the default value is a literal and does not contain any closing
brace, use:
: ${var='my literal'}
2. If the default value contains no closing brace, has to be
expanded, and the variable being initialized is not intended to be
IFS-split (i.e., it's not a list), then use:
: ${var="$default"}
3. If the default value contains no closing brace, has to be
expanded, and the variable being initialized is intended to be
IFS-split (i.e., it's a list), then use:
var=${var="$default"}
4. If the default value contains a closing brace, then use:
test "${var+set}" = set || var="has a '}'"
In most cases `var=${var="$default"}' is fine, but in case of doubt,
just use the last form. *Note Shell Substitutions::, items
`${VAR:-VALUE}' and `${VAR=VALUE}' for the rationale.
File: autoconf.info, Node: Parentheses, Next: Slashes, Prev: Assignments, Up: Portable Shell
11.8 Parentheses in Shell Scripts
=================================
Beware of two opening parentheses in a row, as many shell
implementations treat them specially. Posix requires that the command
`((cat))' must behave like `(cat)', but many shells, including Bash and
the Korn shell, treat `((cat))' as an arithmetic expression equivalent
to `let "cat"', and may or may not report an error when they detect
that `cat' is not a number. As another example, `pdksh' 5.2.14
misparses the following code:
if ((true) || false); then
echo ok
fi
To work around this problem, insert a space between the two opening
parentheses. There is a similar problem and workaround with `$(('; see
*note Shell Substitutions::.
File: autoconf.info, Node: Slashes, Next: Special Shell Variables, Prev: Parentheses, Up: Portable Shell
11.9 Slashes in Shell Scripts
=============================
Unpatched Tru64 5.1 `sh' omits the last slash of command-line arguments
that contain two trailing slashes:
$ echo / // /// //// .// //.
/ / // /// ./ //.
$ x=//
$ eval "echo \$x"
/
$ set -x
$ echo abc | tr -t ab //
+ echo abc
+ tr -t ab /
/bc
Unpatched Tru64 4.0 `sh' adds a slash after `"$var"' if the variable
is empty and the second double-quote is followed by a word that begins
and ends with slash:
$ sh -xc 'p=; echo "$p"/ouch/'
p=
+ echo //ouch/
//ouch/
However, our understanding is that patches are available, so perhaps
it's not worth worrying about working around these horrendous bugs.
File: autoconf.info, Node: Special Shell Variables, Next: Shell Functions, Prev: Slashes, Up: Portable Shell
11.10 Special Shell Variables
=============================
Some shell variables should not be used, since they can have a deep
influence on the behavior of the shell. In order to recover a sane
behavior from the shell, some variables should be unset; M4sh takes
care of this and provides fallback values, whenever needed, to cater
for a very old `/bin/sh' that does not support `unset'. (*note
Portable Shell Programming: Portable Shell.).
As a general rule, shell variable names containing a lower-case
letter are safe; you can define and use these variables without
worrying about their effect on the underlying system, and without
worrying about whether the shell changes them unexpectedly. (The
exception is the shell variable `status', as described below.)
Here is a list of names that are known to cause trouble. This list
is not exhaustive, but you should be safe if you avoid the name
`status' and names containing only upper-case letters and underscores.
`?'
Not all shells correctly reset `$?' after conditionals (*note
Limitations of Shell Builtins: if.). Not all shells manage `$?'
correctly in shell functions (*note Shell Functions::) or in traps
(*note Limitations of Shell Builtins: trap.). Not all shells reset
`$?' to zero after an empty command.
$ bash -c 'false; $empty; echo $?'
0
$ zsh -c 'false; $empty; echo $?'
1
`_'
Many shells reserve `$_' for various purposes, e.g., the name of
the last command executed.
`BIN_SH'
In Tru64, if `BIN_SH' is set to `xpg4', subsidiary invocations of
the standard shell conform to Posix.
`CDPATH'
When this variable is set it specifies a list of directories to
search when invoking `cd' with a relative file name that did not
start with `./' or `../'. Posix 1003.1-2001 says that if a
nonempty directory name from `CDPATH' is used successfully, `cd'
prints the resulting absolute file name. Unfortunately this
output can break idioms like `abs=`cd src && pwd`' because `abs'
receives the name twice. Also, many shells do not conform to this
part of Posix; for example, `zsh' prints the result only if a
directory name other than `.' was chosen from `CDPATH'.
In practice the shells that have this problem also support
`unset', so you can work around the problem as follows:
(unset CDPATH) >/dev/null 2>&1 && unset CDPATH
You can also avoid output by ensuring that your directory name is
absolute or anchored at `./', as in `abs=`cd ./src && pwd`'.
Configure scripts use M4sh, which automatically unsets `CDPATH' if
possible, so you need not worry about this problem in those
scripts.
`CLICOLOR_FORCE'
When this variable is set, some implementations of tools like `ls'
attempt to add color to their output via terminal escape
sequences, even when the output is not directed to a terminal, and
can thus cause spurious failures in scripts. Configure scripts
use M4sh, which automatically unsets this variable.
`DUALCASE'
In the MKS shell, case statements and file name generation are
case-insensitive unless `DUALCASE' is nonzero. Autoconf-generated
scripts export this variable when they start up.
`ENV'
`MAIL'
`MAILPATH'
`PS1'
`PS2'
`PS4'
These variables should not matter for shell scripts, since they are
supposed to affect only interactive shells. However, at least one
shell (the pre-3.0 UWIN Korn shell) gets confused about whether it
is interactive, which means that (for example) a `PS1' with a side
effect can unexpectedly modify `$?'. To work around this bug,
M4sh scripts (including `configure' scripts) do something like
this:
(unset ENV) >/dev/null 2>&1 && unset ENV MAIL MAILPATH
PS1='$ '
PS2='> '
PS4='+ '
(actually, there is some complication due to bugs in `unset'; see
*note Limitations of Shell Builtins: unset.).
`FPATH'
The Korn shell uses `FPATH' to find shell functions, so avoid
`FPATH' in portable scripts. `FPATH' is consulted after `PATH',
but you still need to be wary of tests that use `PATH' to find
whether a command exists, since they might report the wrong result
if `FPATH' is also set.
`GREP_OPTIONS'
When this variable is set, some implementations of `grep' honor
these options, even if the options include direction to enable
colored output via terminal escape sequences, and the result can
cause spurious failures when the output is not directed to a
terminal. Configure scripts use M4sh, which automatically unsets
this variable.
`IFS'
Long ago, shell scripts inherited `IFS' from the environment, but
this caused many problems so modern shells ignore any environment
settings for `IFS'.
Don't set the first character of `IFS' to backslash. Indeed,
Bourne shells use the first character (backslash) when joining the
components in `"$@"' and some shells then reinterpret (!) the
backslash escapes, so you can end up with backspace and other
strange characters.
The proper value for `IFS' (in regular code, not when performing
splits) is `'. The first character is especially
important, as it is used to join the arguments in `$*'; however,
note that traditional shells, but also bash-2.04, fail to adhere
to this and join with a space anyway.
`LANG'
`LC_ALL'
`LC_COLLATE'
`LC_CTYPE'
`LC_MESSAGES'
`LC_MONETARY'
`LC_NUMERIC'
`LC_TIME'
You should set all these variables to `C' because so much
configuration code assumes the C locale and Posix requires that
locale environment variables be set to `C' if the C locale is
desired; `configure' scripts and M4sh do that for you. Export
these variables after setting them.
`LANGUAGE'
`LANGUAGE' is not specified by Posix, but it is a GNU extension
that overrides `LC_ALL' in some cases, so you (or M4sh) should set
it too.
`LC_ADDRESS'
`LC_IDENTIFICATION'
`LC_MEASUREMENT'
`LC_NAME'
`LC_PAPER'
`LC_TELEPHONE'
These locale environment variables are GNU extensions. They are
treated like their Posix brethren (`LC_COLLATE', etc.) as
described above.
`LINENO'
Most modern shells provide the current line number in `LINENO'.
Its value is the line number of the beginning of the current
command. M4sh, and hence Autoconf, attempts to execute
`configure' with a shell that supports `LINENO'. If no such shell
is available, it attempts to implement `LINENO' with a Sed prepass
that replaces each instance of the string `$LINENO' (not followed
by an alphanumeric character) with the line's number. In M4sh
scripts you should execute `AS_LINENO_PREPARE' so that these
workarounds are included in your script; configure scripts do this
automatically in `AC_INIT'.
You should not rely on `LINENO' within `eval' or shell functions,
as the behavior differs in practice. The presence of a quoted
newline within simple commands can alter which line number is used
as the starting point for `$LINENO' substitutions within that
command. Also, the possibility of the Sed prepass means that you
should not rely on `$LINENO' when quoted, when in here-documents,
or when line continuations are used. Subshells should be OK,
though. In the following example, lines 1, 9, and 14 are
portable, but the other instances of `$LINENO' do not have
deterministic values:
$ cat lineno
echo 1. $LINENO
echo "2. $LINENO
3. $LINENO"
cat < N
> s,$,-,
> t loop
> :loop
> s,^\([0-9]*\)\(.*\)[$]LINENO\([^a-zA-Z0-9_]\),\1\2\1\3,
> t loop
> s,-$,,
> s,^[0-9]*\n,,
> ' |
> sh
1. 1
2. 2
3. 3
5. 5
6. 6
7. \7
9. 9
10. 10
11. 11
12. 12
13. 13
14. 14
15. 15
18. 16
18. 17
19. 20
In particular, note that `config.status' (and any other subsidiary
script created by `AS_INIT_GENERATED') might report line numbers
relative to the parent script as a result of the potential Sed
pass.
`NULLCMD'
When executing the command `>foo', `zsh' executes `$NULLCMD >foo'
unless it is operating in Bourne shell compatibility mode and the
`zsh' version is newer than 3.1.6-dev-18. If you are using an
older `zsh' and forget to set `NULLCMD', your script might be
suspended waiting for data on its standard input.
`PATH_SEPARATOR'
On DJGPP systems, the `PATH_SEPARATOR' environment variable can be
set to either `:' or `;' to control the path separator Bash uses
to set up certain environment variables (such as `PATH'). You can
set this variable to `;' if you want `configure' to use `;' as a
separator; this might be useful if you plan to use non-Posix
shells to execute files. *Note File System Conventions::, for
more information about `PATH_SEPARATOR'.
`PWD'
Posix 1003.1-2001 requires that `cd' and `pwd' must update the
`PWD' environment variable to point to the logical name of the
current directory, but traditional shells do not support this.
This can cause confusion if one shell instance maintains `PWD' but
a subsidiary and different shell does not know about `PWD' and
executes `cd'; in this case `PWD' points to the wrong directory.
Use ``pwd`' rather than `$PWD'.
`RANDOM'
Many shells provide `RANDOM', a variable that returns a different
integer each time it is used. Most of the time, its value does not
change when it is not used, but on IRIX 6.5 the value changes all
the time. This can be observed by using `set'. It is common
practice to use `$RANDOM' as part of a file name, but code
shouldn't rely on `$RANDOM' expanding to a nonempty string.
`status'
This variable is an alias to `$?' for `zsh' (at least 3.1.6),
hence read-only. Do not use it.
File: autoconf.info, Node: Shell Functions, Next: Limitations of Builtins, Prev: Special Shell Variables, Up: Portable Shell
11.11 Shell Functions
=====================
Nowadays, it is difficult to find a shell that does not support shell
functions at all. However, some differences should be expected.
Inside a shell function, you should not rely on the error status of a
subshell if the last command of that subshell was `exit' or `trap', as
this triggers bugs in zsh 4.x; while Autoconf tries to find a shell
that does not exhibit the bug, zsh might be the only shell present on
the user's machine.
Likewise, the state of `$?' is not reliable when entering a shell
function. This has the effect that using a function as the first
command in a `trap' handler can cause problems.
$ bash -c 'foo(){ echo $?; }; trap foo 0; (exit 2); exit 2'; echo $?
2
2
$ ash -c 'foo(){ echo $?; }; trap foo 0; (exit 2); exit 2'; echo $?
0
2
Not all shells treat shell functions as simple commands impacted by
`set -e', for example with Solaris 10 `bin/sh':
$ bash -c 'f(){ return 1; }; set -e; f; echo oops
$ /bin/sh -c 'f(){ return 1; }; set -e; f; echo oops
oops
Shell variables and functions may share the same namespace, for
example with Solaris 10 `/bin/sh':
$ f () { :; }; f=; f
f: not found
For this reason, Autoconf (actually M4sh, *note Programming in M4sh::)
uses the prefix `as_fn_' for its functions.
Handling of positional parameters and shell options varies among
shells. For example, Korn shells reset and restore trace output (`set
-x') and other options upon function entry and exit. Inside a function,
IRIX sh sets `$0' to the function name.
It is not portable to pass temporary environment variables to shell
functions. Solaris `/bin/sh' does not see the variable. Meanwhile,
not all shells follow the Posix rule that the assignment must affect
the current environment in the same manner as special built-ins.
$ /bin/sh -c 'func(){ echo $a;}; a=1 func; echo $a'
=>
=>
$ ash -c 'func(){ echo $a;}; a=1 func; echo $a'
=>1
=>
$ bash -c 'set -o posix; func(){ echo $a;}; a=1 func; echo $a'
=>1
=>1
Some ancient Bourne shell variants with function support did not
reset `$I, I >= 0', upon function exit, so effectively the arguments of
the script were lost after the first function invocation. It is
probably not worth worrying about these shells any more.
With AIX sh, a `trap' on 0 installed in a shell function triggers at
function exit rather than at script exit, see *Note Limitations of
Shell Builtins: trap.
File: autoconf.info, Node: Limitations of Builtins, Next: Limitations of Usual Tools, Prev: Shell Functions, Up: Portable Shell
11.12 Limitations of Shell Builtins
===================================
No, no, we are serious: some shells do have limitations! :)
You should always keep in mind that any builtin or command may
support options, and therefore differ in behavior with arguments
starting with a dash. For instance, even the innocent `echo "$word"'
can give unexpected results when `word' starts with a dash. It is
often possible to avoid this problem using `echo "x$word"', taking the
`x' into account later in the pipe. Many of these limitations can be
worked around using M4sh (*note Programming in M4sh::).
`.'
Use `.' only with regular files (use `test -f'). Bash 2.03, for
instance, chokes on `. /dev/null'. Remember that `.' uses `PATH'
if its argument contains no slashes. Also, some shells, including
bash 3.2, implicitly append the current directory to this `PATH'
search, even though Posix forbids it. So if you want to use `.'
on a file `foo' in the current directory, you must use `. ./foo'.
Not all shells gracefully handle syntax errors within a sourced
file. On one extreme, some non-interactive shells abort the
entire script. On the other, `zsh' 4.3.10 has a bug where it
fails to react to the syntax error.
$ echo 'fi' > syntax
$ bash -c '. ./syntax; echo $?'
./syntax: line 1: syntax error near unexpected token `fi'
./syntax: line 1: `fi'
1
$ ash -c '. ./syntax; echo $?'
./syntax: 1: Syntax error: "fi" unexpected
$ zsh -c '. ./syntax; echo $?'
./syntax:1: parse error near `fi'
0
`!'
The Unix version 7 shell did not support negating the exit status
of commands with `!', and this feature is still absent from some
shells (e.g., Solaris `/bin/sh'). Other shells, such as FreeBSD
`/bin/sh' or `ash', have bugs when using `!':
$ sh -c '! : | :'; echo $?
1
$ ash -c '! : | :'; echo $?
0
$ sh -c '! { :; }'; echo $?
1
$ ash -c '! { :; }'; echo $?
{: not found
Syntax error: "}" unexpected
2
Shell code like this:
if ! cmp file1 file2 >/dev/null 2>&1; then
echo files differ or trouble
fi
is therefore not portable in practice. Typically it is easy to
rewrite such code, e.g.:
cmp file1 file2 >/dev/null 2>&1 ||
echo files differ or trouble
More generally, one can always rewrite `! COMMAND' as:
if COMMAND; then (exit 1); else :; fi
`{...}'
Bash 3.2 (and earlier versions) sometimes does not properly set
`$?' when failing to write redirected output of a compound command.
This problem is most commonly observed with `{...}'; it does not
occur with `(...)'. For example:
$ bash -c '{ echo foo; } >/bad; echo $?'
bash: line 1: /bad: Permission denied
0
$ bash -c 'while :; do echo; done >/bad; echo $?'
bash: line 1: /bad: Permission denied
0
To work around the bug, prepend `:;':
$ bash -c ':;{ echo foo; } >/bad; echo $?'
bash: line 1: /bad: Permission denied
1
Posix requires a syntax error if a brace list has no contents.
However, not all shells obey this rule; and on shells where empty
lists are permitted, the effect on `$?' is inconsistent. To avoid
problems, ensure that a brace list is never empty.
$ bash -c 'false; { }; echo $?' || echo $?
bash: line 1: syntax error near unexpected token `}'
bash: line 1: `false; { }; echo $?'
2
$ zsh -c 'false; { }; echo $?' || echo $?
1
$ pdksh -c 'false; { }; echo $?' || echo $?
0
`break'
The use of `break 2' etc. is safe.
`case'
You don't need to quote the argument; no splitting is performed.
You don't need the final `;;', but you should use it.
Posix requires support for `case' patterns with opening
parentheses like this:
case $file_name in
(*.c) echo "C source code";;
esac
but the `(' in this example is not portable to many Bourne shell
implementations, which is a pity for those of us using tools that
rely on balanced parentheses. For instance, with Solaris
`/bin/sh':
$ case foo in (foo) echo foo;; esac
error-->syntax error: `(' unexpected
The leading `(' can be omitted safely. Unfortunately, there are
contexts where unbalanced parentheses cause other problems, such
as when using a syntax-highlighting editor that searches for the
balancing counterpart, or more importantly, when using a case
statement as an underquoted argument to an Autoconf macro. *Note
Balancing Parentheses::, for tradeoffs involved in various styles
of dealing with unbalanced `)'.
Zsh handles pattern fragments derived from parameter expansions or
command substitutions as though quoted:
$ pat=\?; case aa in ?$pat) echo match;; esac
$ pat=\?; case a? in ?$pat) echo match;; esac
match
Because of a bug in its `fnmatch', Bash fails to properly handle
backslashes in character classes:
bash-2.02$ case /tmp in [/\\]*) echo OK;; esac
bash-2.02$
This is extremely unfortunate, since you are likely to use this
code to handle Posix or MS-DOS absolute file names. To work
around this bug, always put the backslash first:
bash-2.02$ case '\TMP' in [\\/]*) echo OK;; esac
OK
bash-2.02$ case /tmp in [\\/]*) echo OK;; esac
OK
Many Bourne shells cannot handle closing brackets in character
classes correctly.
Some shells also have problems with backslash escaping in case you
do not want to match the backslash: both a backslash and the
escaped character match this pattern. To work around this,
specify the character class in a variable, so that quote removal
does not apply afterwards, and the special characters don't have
to be backslash-escaped:
$ case '\' in [\<]) echo OK;; esac
OK
$ scanset='[<]'; case '\' in $scanset) echo OK;; esac
$
Even with this, Solaris `ksh' matches a backslash if the set
contains any of the characters `|', `&', `(', or `)'.
Conversely, Tru64 `ksh' (circa 2003) erroneously always matches a
closing parenthesis if not specified in a character class:
$ case foo in *\)*) echo fail ;; esac
fail
$ case foo in *')'*) echo fail ;; esac
fail
Some shells, such as Ash 0.3.8, are confused by an empty
`case'/`esac':
ash-0.3.8 $ case foo in esac;
error-->Syntax error: ";" unexpected (expecting ")")
Posix requires `case' to give an exit status of 0 if no cases
match. However, `/bin/sh' in Solaris 10 does not obey this rule.
Meanwhile, it is unclear whether a case that matches, but contains
no statements, must also change the exit status to 0. The M4sh
macro `AS_CASE' works around these inconsistencies.
$ bash -c 'case `false` in ?) ;; esac; echo $?'
0
$ /bin/sh -c 'case `false` in ?) ;; esac; echo $?'
255
`cd'
Posix 1003.1-2001 requires that `cd' must support the `-L'
("logical") and `-P' ("physical") options, with `-L' being the
default. However, traditional shells do not support these
options, and their `cd' command has the `-P' behavior.
Portable scripts should assume neither option is supported, and
should assume neither behavior is the default. This can be a bit
tricky, since the Posix default behavior means that, for example,
`ls ..' and `cd ..' may refer to different directories if the
current logical directory is a symbolic link. It is safe to use
`cd DIR' if DIR contains no `..' components. Also,
Autoconf-generated scripts check for this problem when computing
variables like `ac_top_srcdir' (*note Configuration Actions::), so
it is safe to `cd' to these variables.
See *Note Special Shell Variables::, for portability problems
involving `cd' and the `CDPATH' environment variable. Also please
see the discussion of the `pwd' command.
`echo'
The simple `echo' is probably the most surprising source of
portability troubles. It is not possible to use `echo' portably
unless both options and escape sequences are omitted. Don't
expect any option.
Do not use backslashes in the arguments, as there is no consensus
on their handling. For `echo '\n' | wc -l', the `sh' of Solaris
outputs 2, but Bash and Zsh (in `sh' emulation mode) output 1.
The problem is truly `echo': all the shells understand `'\n'' as
the string composed of a backslash and an `n'. Within a command
substitution, `echo 'string\c'' will mess up the internal state of
ksh88 on AIX 6.1 so that it will print the first character `s'
only, followed by a newline, and then entirely drop the output of
the next echo in a command substitution.
Because of these problems, do not pass a string containing
arbitrary characters to `echo'. For example, `echo "$foo"' is safe
if you know that FOO's value cannot contain backslashes and cannot
start with `-', but otherwise you should use a here-document like
this:
cat </dev/null &&
ACTION
`expr "XFOO" : "XBAR"' is more robust than `echo "XFOO" | grep
"^XBAR"', because it avoids problems when `FOO' contains
backslashes.
`trap'
It is safe to trap at least the signals 1, 2, 13, and 15. You can
also trap 0, i.e., have the `trap' run when the script ends
(either via an explicit `exit', or the end of the script). The
trap for 0 should be installed outside of a shell function, or AIX
5.3 `/bin/sh' will invoke the trap at the end of this function.
Posix says that `trap - 1 2 13 15' resets the traps for the
specified signals to their default values, but many common shells
(e.g., Solaris `/bin/sh') misinterpret this and attempt to execute
a "command" named `-' when the specified conditions arise. Posix
2008 also added a requirement to support `trap 1 2 13 15' to reset
traps, as this is supported by a larger set of shells, but there
are still shells like `dash' that mistakenly try to execute `1'
instead of resetting the traps. Therefore, there is no portable
workaround, except for `trap - 0', for which `trap '' 0' is a
portable substitute.
Although Posix is not absolutely clear on this point, it is widely
admitted that when entering the trap `$?' should be set to the exit
status of the last command run before the trap. The ambiguity can
be summarized as: "when the trap is launched by an `exit', what is
the _last_ command run: that before `exit', or `exit' itself?"
Bash considers `exit' to be the last command, while Zsh and
Solaris `/bin/sh' consider that when the trap is run it is _still_
in the `exit', hence it is the previous exit status that the trap
receives:
$ cat trap.sh
trap 'echo $?' 0
(exit 42); exit 0
$ zsh trap.sh
42
$ bash trap.sh
0
The portable solution is then simple: when you want to `exit 42',
run `(exit 42); exit 42', the first `exit' being used to set the
exit status to 42 for Zsh, and the second to trigger the trap and
pass 42 as exit status for Bash. In M4sh, this is covered by using
`AS_EXIT'.
The shell in FreeBSD 4.0 has the following bug: `$?' is reset to 0
by empty lines if the code is inside `trap'.
$ trap 'false
echo $?' 0
$ exit
0
Fortunately, this bug only affects `trap'.
Several shells fail to execute an exit trap that is defined inside
a subshell, when the last command of that subshell is not a
builtin. A workaround is to use `exit $?' as the shell builtin.
$ bash -c '(trap "echo hi" 0; /bin/true)'
hi
$ /bin/sh -c '(trap "echo hi" 0; /bin/true)'
$ /bin/sh -c '(trap "echo hi" 0; /bin/true; exit $?)'
hi
Likewise, older implementations of `bash' failed to preserve `$?'
across an exit trap consisting of a single cleanup command.
$ bash -c 'trap "/bin/true" 0; exit 2'; echo $?
2
$ bash-2.05b -c 'trap "/bin/true" 0; exit 2'; echo $?
0
$ bash-2.05b -c 'trap ":; /bin/true" 0; exit 2'; echo $?
2
`true'
Don't worry: as far as we know `true' is portable. Nevertheless,
it's not always a builtin (e.g., Bash 1.x), and the portable shell
community tends to prefer using `:'. This has a funny side
effect: when asked whether `false' is more portable than `true'
Alexandre Oliva answered:
In a sense, yes, because if it doesn't exist, the shell will
produce an exit status of failure, which is correct for
`false', but not for `true'.
`unset'
In some nonconforming shells (e.g., Bash 2.05a), `unset FOO' fails
when `FOO' is not set. You can use
FOO=; unset FOO
if you are not sure that `FOO' is set.
A few ancient shells lack `unset' entirely. For some variables
such as `PS1', you can use a neutralizing value instead:
PS1='$ '
Usually, shells that do not support `unset' need less effort to
make the environment sane, so for example is not a problem if you
cannot unset `CDPATH' on those shells. However, Bash 2.01
mishandles `unset MAIL' in some cases and dumps core. So, you
should do something like
( (unset MAIL) || exit 1) >/dev/null 2>&1 && unset MAIL || :
*Note Special Shell Variables::, for some neutralizing values.
Also, see *note Limitations of Builtins: export, for the case of
environment variables.
`wait'
The exit status of `wait' is not always reliable.
File: autoconf.info, Node: Limitations of Usual Tools, Prev: Limitations of Builtins, Up: Portable Shell
11.13 Limitations of Usual Tools
================================
The small set of tools you can expect to find on any machine can still
include some limitations you should be aware of.
`awk'
Don't leave white space before the opening parenthesis in a user
function call. Posix does not allow this and GNU Awk rejects it:
$ gawk 'function die () { print "Aaaaarg!" }
BEGIN { die () }'
gawk: cmd. line:2: BEGIN { die () }
gawk: cmd. line:2: ^ parse error
$ gawk 'function die () { print "Aaaaarg!" }
BEGIN { die() }'
Aaaaarg!
Posix says that if a program contains only `BEGIN' actions, and
contains no instances of `getline', then the program merely
executes the actions without reading input. However, traditional
Awk implementations (such as Solaris 10 `awk') read and discard
input in this case. Portable scripts can redirect input from
`/dev/null' to work around the problem. For example:
awk 'BEGIN {print "hello world"}' printf "foo\n|foo\n" | $EGREP '^(|foo|bar)$'
|foo
> printf "bar\nbar|\n" | $EGREP '^(foo|bar|)$'
bar|
> printf "foo\nfoo|\n|bar\nbar\n" | $EGREP '^(foo||bar)$'
foo
|bar
`$EGREP' also suffers the limitations of `grep' (*note Limitations
of Usual Tools: grep.).
`expr'
Not all implementations obey the Posix rule that `--' separates
options from arguments; likewise, not all implementations provide
the extension to Posix that the first argument can be treated as
part of a valid expression rather than an invalid option if it
begins with `-'. When performing arithmetic, use `expr 0 + $var'
if `$var' might be a negative number, to keep `expr' from
interpreting it as an option.
No `expr' keyword starts with `X', so use `expr X"WORD" :
'XREGEX'' to keep `expr' from misinterpreting WORD.
Don't use `length', `substr', `match' and `index'.
`expr' (`|')
You can use `|'. Although Posix does require that `expr '''
return the empty string, it does not specify the result when you
`|' together the empty string (or zero) with the empty string. For
example:
expr '' \| ''
Posix 1003.2-1992 returns the empty string for this case, but
traditional Unix returns `0' (Solaris is one such example). In
Posix 1003.1-2001, the specification was changed to match
traditional Unix's behavior (which is bizarre, but it's too late
to fix this). Please note that the same problem does arise when
the empty string results from a computation, as in:
expr bar : foo \| foo : bar
Avoid this portability problem by avoiding the empty string.
`expr' (`:')
Portable `expr' regular expressions should use `\' to escape only
characters in the string `$()*.0123456789[\^n{}'. For example,
alternation, `\|', is common but Posix does not require its
support, so it should be avoided in portable scripts. Similarly,
`\+' and `\?' should be avoided.
Portable `expr' regular expressions should not begin with `^'.
Patterns are automatically anchored so leading `^' is not needed
anyway.
On the other hand, the behavior of the `$' anchor is not portable
on multi-line strings. Posix is ambiguous whether the anchor
applies to each line, as was done in older versions of GNU
Coreutils, or whether it applies only to the end of the overall
string, as in Coreutils 6.0 and most other implementations.
$ baz='foo
> bar'
$ expr "X$baz" : 'X\(foo\)$'
$ expr-5.97 "X$baz" : 'X\(foo\)$'
foo
The Posix standard is ambiguous as to whether `expr 'a' : '\(b\)''
outputs `0' or the empty string. In practice, it outputs the
empty string on most platforms, but portable scripts should not
assume this. For instance, the QNX 4.25 native `expr' returns `0'.
One might think that a way to get a uniform behavior would be to
use the empty string as a default value:
expr a : '\(b\)' \| ''
Unfortunately this behaves exactly as the original expression; see
the `expr' (`|') entry for more information.
Some ancient `expr' implementations (e.g., SunOS 4 `expr' and
Solaris 8 `/usr/ucb/expr') have a silly length limit that causes
`expr' to fail if the matched substring is longer than 120 bytes.
In this case, you might want to fall back on `echo|sed' if `expr'
fails. Nowadays this is of practical importance only for the rare
installer who mistakenly puts `/usr/ucb' before `/usr/bin' in
`PATH'.
On Mac OS X 10.4, `expr' mishandles the pattern `[^-]' in some
cases. For example, the command
expr Xpowerpc-apple-darwin8.1.0 : 'X[^-]*-[^-]*-\(.*\)'
outputs `apple-darwin8.1.0' rather than the correct `darwin8.1.0'.
This particular case can be worked around by substituting `[^--]'
for `[^-]'.
Don't leave, there is some more!
The QNX 4.25 `expr', in addition of preferring `0' to the empty
string, has a funny behavior in its exit status: it's always 1
when parentheses are used!
$ val=`expr 'a' : 'a'`; echo "$?: $val"
0: 1
$ val=`expr 'a' : 'b'`; echo "$?: $val"
1: 0
$ val=`expr 'a' : '\(a\)'`; echo "?: $val"
1: a
$ val=`expr 'a' : '\(b\)'`; echo "?: $val"
1: 0
In practice this can be a big problem if you are ready to catch
failures of `expr' programs with some other method (such as using
`sed'), since you may get twice the result. For instance
$ expr 'a' : '\(a\)' || echo 'a' | sed 's/^\(a\)$/\1/'
outputs `a' on most hosts, but `aa' on QNX 4.25. A simple
workaround consists of testing `expr' and using a variable set to
`expr' or to `false' according to the result.
Tru64 `expr' incorrectly treats the result as a number, if it can
be interpreted that way:
$ expr 00001 : '.*\(...\)'
1
On HP-UX 11, `expr' only supports a single sub-expression.
$ expr 'Xfoo' : 'X\(f\(oo\)*\)$'
expr: More than one '\(' was used.
`fgrep'
Posix 1003.1-2001 no longer requires `fgrep', but many hosts do
not yet support the Posix replacement `grep -F'. Also, some
traditional implementations do not work on long input lines. To
work around these problems, invoke `AC_PROG_FGREP' and then use
`$FGREP'.
`find'
The option `-maxdepth' seems to be GNU specific. Tru64 v5.1,
NetBSD 1.5 and Solaris `find' commands do not understand it.
The replacement of `{}' is guaranteed only if the argument is
exactly _{}_, not if it's only a part of an argument. For
instance on DU, and HP-UX 10.20 and HP-UX 11:
$ touch foo
$ find . -name foo -exec echo "{}-{}" \;
{}-{}
while GNU `find' reports `./foo-./foo'.
`grep'
Portable scripts can rely on the `grep' options `-c', `-l', `-n',
and `-v', but should avoid other options. For example, don't use
`-w', as Posix does not require it and Irix 6.5.16m's `grep' does
not support it. Also, portable scripts should not combine `-c'
with `-l', as Posix does not allow this.
Some of the options required by Posix are not portable in practice.
Don't use `grep -q' to suppress output, because many `grep'
implementations (e.g., Solaris) do not support `-q'. Don't use
`grep -s' to suppress output either, because Posix says `-s' does
not suppress output, only some error messages; also, the `-s'
option of traditional `grep' behaved like `-q' does in most modern
implementations. Instead, redirect the standard output and
standard error (in case the file doesn't exist) of `grep' to
`/dev/null'. Check the exit status of `grep' to determine whether
it found a match.
Some traditional `grep' implementations do not work on long input
lines. On AIX the default `grep' silently truncates long lines on
the input before matching.
Also, many implementations do not support multiple regexps with
`-e': they either reject `-e' entirely (e.g., Solaris) or honor
only the last pattern (e.g., IRIX 6.5 and NeXT). To work around
these problems, invoke `AC_PROG_GREP' and then use `$GREP'.
Another possible workaround for the multiple `-e' problem is to
separate the patterns by newlines, for example:
grep 'foo
bar' in.txt
except that this fails with traditional `grep' implementations and
with OpenBSD 3.8 `grep'.
Traditional `grep' implementations (e.g., Solaris) do not support
the `-E' or `-F' options. To work around these problems, invoke
`AC_PROG_EGREP' and then use `$EGREP', and similarly for
`AC_PROG_FGREP' and `$FGREP'. Even if you are willing to require
support for Posix `grep', your script should not use both `-E' and
`-F', since Posix does not allow this combination.
Portable `grep' regular expressions should use `\' only to escape
characters in the string `$()*.0123456789[\^{}'. For example,
alternation, `\|', is common but Posix does not require its
support in basic regular expressions, so it should be avoided in
portable scripts. Solaris and HP-UX `grep' do not support it.
Similarly, the following escape sequences should also be avoided:
`\<', `\>', `\+', `\?', `\`', `\'', `\B', `\b', `\S', `\s', `\W',
and `\w'.
Posix does not specify the behavior of `grep' on binary files. An
example where this matters is using BSD `grep' to search text that
includes embedded ANSI escape sequences for colored output to
terminals (`\033[m' is the sequence to restore normal output); the
behavior depends on whether input is seekable:
$ printf 'esc\033[mape\n' > sample
$ grep . sample
Binary file sample matches
$ cat sample | grep .
escape
`join'
Solaris 8 `join' has bugs when the second operand is standard
input, and when standard input is a pipe. For example, the
following shell script causes Solaris 8 `join' to loop forever:
cat >file <<'EOF'
1 x
2 y
EOF
cat file | join file -
Use `join - file' instead.
`ln'
Don't rely on `ln' having a `-f' option. Symbolic links are not
available on old systems; use `$(LN_S)' as a portable substitute.
For versions of the DJGPP before 2.04, `ln' emulates symbolic links
to executables by generating a stub that in turn calls the real
program. This feature also works with nonexistent files like in
the Posix spec. So `ln -s file link' generates `link.exe', which
attempts to call `file.exe' if run. But this feature only works
for executables, so `cp -p' is used instead for these systems.
DJGPP versions 2.04 and later have full support for symbolic links.
`ls'
The portable options are `-acdilrtu'. Current practice is for
`-l' to output both owner and group, even though ancient versions
of `ls' omitted the group.
On ancient hosts, `ls foo' sent the diagnostic `foo not found' to
standard output if `foo' did not exist. Hence a shell command
like `sources=`ls *.c 2>/dev/null`' did not always work, since it
was equivalent to `sources='*.c not found'' in the absence of `.c'
files. This is no longer a practical problem, since current `ls'
implementations send diagnostics to standard error.
The behavior of `ls' on a directory that is being concurrently
modified is not always predictable, because of a data race where
cached information returned by `readdir' does not match the current
directory state. In fact, MacOS 10.5 has an intermittent bug where
`readdir', and thus `ls', sometimes lists a file more than once if
other files were added or removed from the directory immediately
prior to the `ls' call. Since `ls' already sorts its output, the
duplicate entries can be avoided by piping the results through
`uniq'.
`mkdir'
No `mkdir' option is portable to older systems. Instead of `mkdir
-p FILE-NAME', you should use `AS_MKDIR_P(FILE-NAME)' (*note
Programming in M4sh::) or `AC_PROG_MKDIR_P' (*note Particular
Programs::).
Combining the `-m' and `-p' options, as in `mkdir -m go-w -p DIR',
often leads to trouble. FreeBSD `mkdir' incorrectly attempts to
change the permissions of DIR even if it already exists. HP-UX
11.23 and IRIX 6.5 `mkdir' often assign the wrong permissions to
any newly-created parents of DIR.
Posix does not clearly specify whether `mkdir -p foo' should
succeed when `foo' is a symbolic link to an already-existing
directory. The GNU Core Utilities 5.1.0 `mkdir' succeeds, but
Solaris `mkdir' fails.
Traditional `mkdir -p' implementations suffer from race conditions.
For example, if you invoke `mkdir -p a/b' and `mkdir -p a/c' at
the same time, both processes might detect that `a' is missing,
one might create `a', then the other might try to create `a' and
fail with a `File exists' diagnostic. The GNU Core Utilities
(`fileutils' version 4.1), FreeBSD 5.0, NetBSD 2.0.2, and OpenBSD
2.4 are known to be race-free when two processes invoke `mkdir -p'
simultaneously, but earlier versions are vulnerable. Solaris
`mkdir' is still vulnerable as of Solaris 10, and other
traditional Unix systems are probably vulnerable too. This
possible race is harmful in parallel builds when several Make
rules call `mkdir -p' to construct directories. You may use
`install-sh -d' as a safe replacement, provided this script is
recent enough; the copy shipped with Autoconf 2.60 and Automake
1.10 is OK, but copies from older versions are vulnerable.
`mkfifo'
`mknod'
The GNU Coding Standards state that `mknod' is safe to use on
platforms where it has been tested to exist; but it is generally
portable only for creating named FIFOs, since device numbers are
platform-specific. Autotest uses `mkfifo' to implement parallel
testsuites. Posix states that behavior is unspecified when
opening a named FIFO for both reading and writing; on at least
Cygwin, this results in failure on any attempt to read or write to
that file descriptor.
`mktemp'
Shell scripts can use temporary files safely with `mktemp', but it
does not exist on all systems. A portable way to create a safe
temporary file name is to create a temporary directory with mode
700 and use a file inside this directory. Both methods prevent
attackers from gaining control, though `mktemp' is far less likely
to fail gratuitously under attack.
Here is sample code to create a new temporary directory safely:
# Create a temporary directory $tmp in $TMPDIR (default /tmp).
# Use mktemp if possible; otherwise fall back on mkdir,
# with $RANDOM to make collisions less likely.
: ${TMPDIR=/tmp}
{
tmp=`
(umask 077 && mktemp -d "$TMPDIR/fooXXXXXX") 2>/dev/null
` &&
test -n "$tmp" && test -d "$tmp"
} || {
tmp=$TMPDIR/foo$$-$RANDOM
(umask 077 && mkdir "$tmp")
} || exit $?
`mv'
The only portable options are `-f' and `-i'.
Moving individual files between file systems is portable (it was
in Unix version 6), but it is not always atomic: when doing `mv
new existing', there's a critical section where neither the old
nor the new version of `existing' actually exists.
On some systems moving files from `/tmp' can sometimes cause
undesirable (but perfectly valid) warnings, even if you created
these files. This is because `/tmp' belongs to a group that
ordinary users are not members of, and files created in `/tmp'
inherit the group of `/tmp'. When the file is copied, `mv' issues
a diagnostic without failing:
$ touch /tmp/foo
$ mv /tmp/foo .
error-->mv: ./foo: set owner/group (was: 100/0): Operation not permitted
$ echo $?
0
$ ls foo
foo
This annoying behavior conforms to Posix, unfortunately.
Moving directories across mount points is not portable, use `cp'
and `rm'.
DOS variants cannot rename or remove open files, and do not
support commands like `mv foo bar >foo', even though this is
perfectly portable among Posix hosts.
`od'
In Mac OS X 10.3, `od' does not support the standard Posix options
`-A', `-j', `-N', or `-t', or the XSI option `-s'. The only
supported Posix option is `-v', and the only supported XSI options
are those in `-bcdox'. The BSD `hexdump' program can be used
instead.
This problem no longer exists in Mac OS X 10.4.3.
`rm'
The `-f' and `-r' options are portable.
It is not portable to invoke `rm' without operands. For example,
on many systems `rm -f -r' (with no other arguments) silently
succeeds without doing anything, but it fails with a diagnostic on
NetBSD 2.0.2.
A file might not be removed even if its parent directory is
writable and searchable. Many Posix hosts cannot remove a mount
point, a named stream, a working directory, or a last link to a
file that is being executed.
DOS variants cannot rename or remove open files, and do not
support commands like `rm foo >foo', even though this is perfectly
portable among Posix hosts.
`rmdir'
Just as with `rm', some platforms refuse to remove a working
directory.
`sed'
Patterns should not include the separator (unless escaped), even
as part of a character class. In conformance with Posix, the Cray
`sed' rejects `s/[^/]*$//': use `s,[^/]*$,,'.
Avoid empty patterns within parentheses (i.e., `\(\)'). Posix does
not require support for empty patterns, and Unicos 9 `sed' rejects
them.
Unicos 9 `sed' loops endlessly on patterns like `.*\n.*'.
Sed scripts should not use branch labels longer than 7 characters
and should not contain comments. HP-UX sed has a limit of 99
commands (not counting `:' commands) and 48 labels, which can not
be circumvented by using more than one script file. It can
execute up to 19 reads with the `r' command per cycle. Solaris
`/usr/ucb/sed' rejects usages that exceed a limit of about 6000
bytes for the internal representation of commands.
Avoid redundant `;', as some `sed' implementations, such as NetBSD
1.4.2's, incorrectly try to interpret the second `;' as a command:
$ echo a | sed 's/x/x/;;s/x/x/'
sed: 1: "s/x/x/;;s/x/x/": invalid command code ;
Input should not have unreasonably long lines, since some `sed'
implementations have an input buffer limited to 4000 bytes.
Likewise, not all `sed' implementations can handle embedded `NUL'
or a missing trailing newline.
Portable `sed' regular expressions should use `\' only to escape
characters in the string `$()*.0123456789[\^n{}'. For example,
alternation, `\|', is common but Posix does not require its
support, so it should be avoided in portable scripts. Solaris
`sed' does not support alternation; e.g., `sed '/a\|b/d'' deletes
only lines that contain the literal string `a|b'. Similarly, `\+'
and `\?' should be avoided.
Anchors (`^' and `$') inside groups are not portable.
Nested parentheses in patterns (e.g., `\(\(a*\)b*)\)') are quite
portable to current hosts, but was not supported by some ancient
`sed' implementations like SVR3.
Some `sed' implementations, e.g., Solaris, restrict the special
role of the asterisk to one-character regular expressions. This
may lead to unexpected behavior:
$ echo '1*23*4' | /usr/bin/sed 's/\(.\)*/x/g'
x2x4
$ echo '1*23*4' | /usr/xpg4/bin/sed 's/\(.\)*/x/g'
x
The `-e' option is mostly portable. However, its argument cannot
start with `a', `c', or `i', as this runs afoul of a Tru64 5.1 bug.
Also, its argument cannot be empty, as this fails on AIX 5.3.
Some people prefer to use `-e':
sed -e 'COMMAND-1' \
-e 'COMMAND-2'
as opposed to the equivalent:
sed '
COMMAND-1
COMMAND-2
'
The following usage is sometimes equivalent:
sed 'COMMAND-1;COMMAND-2'
but Posix says that this use of a semicolon has undefined effect if
COMMAND-1's verb is `{', `a', `b', `c', `i', `r', `t', `w', `:',
or `#', so you should use semicolon only with simple scripts that
do not use these verbs.
Commands inside { } brackets are further restricted. Posix says
that they cannot be preceded by addresses, `!', or `;', and that
each command must be followed immediately by a newline, without any
intervening blanks or semicolons. The closing bracket must be
alone on a line, other than white space preceding or following it.
Contrary to yet another urban legend, you may portably use `&' in
the replacement part of the `s' command to mean "what was
matched". All descendants of Unix version 7 `sed' (at least; we
don't have first hand experience with older `sed' implementations)
have supported it.
Posix requires that you must not have any white space between `!'
and the following command. It is OK to have blanks between the
address and the `!'. For instance, on Solaris:
$ echo "foo" | sed -n '/bar/ ! p'
error-->Unrecognized command: /bar/ ! p
$ echo "foo" | sed -n '/bar/! p'
error-->Unrecognized command: /bar/! p
$ echo "foo" | sed -n '/bar/ !p'
foo
Posix also says that you should not combine `!' and `;'. If you
use `!', it is best to put it on a command that is delimited by
newlines rather than `;'.
Also note that Posix requires that the `b', `t', `r', and `w'
commands be followed by exactly one space before their argument.
On the other hand, no white space is allowed between `:' and the
subsequent label name.
If a sed script is specified on the command line and ends in an
`a', `c', or `i' command, the last line of inserted text should be
followed by a newline. Otherwise some `sed' implementations
(e.g., OpenBSD 3.9) do not append a newline to the inserted text.
Many `sed' implementations (e.g., MacOS X 10.4, OpenBSD 3.9,
Solaris 10 `/usr/ucb/sed') strip leading white space from the text
of `a', `c', and `i' commands. Prepend a backslash to work around
this incompatibility with Posix:
$ echo flushleft | sed 'a\
> indented
> '
flushleft
indented
$ echo foo | sed 'a\
> \ indented
> '
flushleft
indented
Posix requires that with an empty regular expression, the last
non-empty regular expression from either an address specification
or substitution command is applied. However, busybox 1.6.1
complains when using a substitution command with a replacement
containing a back-reference to an empty regular expression; the
workaround is repeating the regular expression.
$ echo abc | busybox sed '/a\(b\)c/ s//\1/'
sed: No previous regexp.
$ echo abc | busybox sed '/a\(b\)c/ s/a\(b\)c/\1/'
b
`sed' (`t')
Some old systems have `sed' that "forget" to reset their `t' flag
when starting a new cycle. For instance on MIPS RISC/OS, and on
IRIX 5.3, if you run the following `sed' script (the line numbers
are not actual part of the texts):
s/keep me/kept/g # a
t end # b
s/.*/deleted/g # c
:end # d
on
delete me # 1
delete me # 2
keep me # 3
delete me # 4
you get
deleted
delete me
kept
deleted
instead of
deleted
deleted
kept
deleted
Why? When processing line 1, (c) matches, therefore sets the `t'
flag, and the output is produced. When processing line 2, the `t'
flag is still set (this is the bug). Command (a) fails to match,
but `sed' is not supposed to clear the `t' flag when a
substitution fails. Command (b) sees that the flag is set,
therefore it clears it, and jumps to (d), hence you get `delete me'
instead of `deleted'. When processing line (3), `t' is clear, (a)
matches, so the flag is set, hence (b) clears the flags and jumps.
Finally, since the flag is clear, line 4 is processed properly.
There are two things one should remember about `t' in `sed'.
Firstly, always remember that `t' jumps if _some_ substitution
succeeded, not only the immediately preceding substitution.
Therefore, always use a fake `t clear' followed by a `:clear' on
the next line, to reset the `t' flag where needed.
Secondly, you cannot rely on `sed' to clear the flag at each new
cycle.
One portable implementation of the script above is:
t clear
:clear
s/keep me/kept/g
t end
s/.*/deleted/g
:end
`sleep'
Using `sleep' is generally portable. However, remember that
adding a `sleep' to work around timestamp issues, with a minimum
granularity of one second, doesn't scale well for parallel builds
on modern machines with sub-second process completion.
`sort'
Remember that sort order is influenced by the current locale.
Inside `configure', the C locale is in effect, but in Makefile
snippets, you may need to specify `LC_ALL=C sort'.
`tar'
There are multiple file formats for `tar'; if you use Automake,
the macro `AM_INIT_AUTOMAKE' has some options controlling which
level of portability to use.
`touch'
If you specify the desired timestamp (e.g., with the `-r' option),
`touch' typically uses the `utime' or `utimes' system call, which
can result in the same kind of timestamp truncation problems that
`cp -p' has.
On ancient BSD systems, `touch' or any command that results in an
empty file does not update the timestamps, so use a command like
`echo' as a workaround. Also, GNU `touch' 3.16r (and presumably
all before that) fails to work on SunOS 4.1.3 when the empty file
is on an NFS-mounted 4.2 volume. However, these problems are no
longer of practical concern.
`tr'
Not all versions of `tr' handle all backslash character escapes.
For example, Solaris 10 `/usr/ucb/tr' falls over, even though
Solaris contains more modern `tr' in other locations. Therefore,
it is more portable to use octal escapes, even though this ties
the result to ASCII, when using `tr' to delete newlines or
carriage returns.
$ { echo moon; echo light; } | /usr/ucb/tr -d '\n' ; echo
moo
light
$ { echo moon; echo light; } | /usr/bin/tr -d '\n' ; echo
moonlight
$ { echo moon; echo light; } | /usr/ucb/tr -d '\012' ; echo
moonlight
Posix requires `tr' to operate on binary files. But at least
Solaris `/usr/ucb/tr' still fails to handle `\0' as the octal
escape for `NUL'. On Solaris, when using `tr' to neutralize a
binary file by converting `NUL' to a different character, it is
necessary to use `/usr/xpg4/bin/tr' instead.
$ printf 'a\0b\n' | /usr/ucb/tr '\0' '~' | wc -c
3
$ printf 'a\0b\n' | /usr/xpg4/bin/tr '\0' '~' | wc -c
4
File: autoconf.info, Node: Portable Make, Next: Portable C and C++, Prev: Portable Shell, Up: Top
12 Portable Make Programming
****************************
Writing portable makefiles is an art. Since a makefile's commands are
executed by the shell, you must consider the shell portability issues
already mentioned. However, other issues are specific to `make' itself.
* Menu:
* $< in Ordinary Make Rules:: $< in ordinary rules
* Failure in Make Rules:: Failing portably in rules
* Special Chars in Names:: Special Characters in Macro Names
* Backslash-Newline-Newline:: Empty last lines in macro definitions
* Backslash-Newline Comments:: Spanning comments across line boundaries
* Long Lines in Makefiles:: Line length limitations
* Macros and Submakes:: `make macro=value' and submakes
* The Make Macro MAKEFLAGS:: `$(MAKEFLAGS)' portability issues
* The Make Macro SHELL:: `$(SHELL)' portability issues
* Parallel Make:: Parallel `make' quirks
* Comments in Make Rules:: Other problems with Make comments
* obj/ and Make:: Don't name a subdirectory `obj'
* make -k Status:: Exit status of `make -k'
* VPATH and Make:: `VPATH' woes
* Single Suffix Rules:: Single suffix rules and separated dependencies
* Timestamps and Make:: Subsecond timestamp resolution
File: autoconf.info, Node: $< in Ordinary Make Rules, Next: Failure in Make Rules, Up: Portable Make
12.1 `$<' in Ordinary Make Rules
================================
Posix says that the `$<' construct in makefiles can be used only in
inference rules and in the `.DEFAULT' rule; its meaning in ordinary
rules is unspecified. Solaris `make' for instance replaces it with the
empty string. OpenBSD (3.0 and later) `make' diagnoses these uses and
errors out.
File: autoconf.info, Node: Failure in Make Rules, Next: Special Chars in Names, Prev: $< in Ordinary Make Rules, Up: Portable Make
12.2 Failure in Make Rules
==========================
Posix 2008 requires that `make' must invoke each command with the
equivalent of a `sh -e -c' subshell, which causes the subshell to exit
immediately if a subsidiary simple-command fails, although not all
`make' implementations have historically followed this rule. For
example, the command `touch T; rm -f U' may attempt to remove `U' even
if the `touch' fails, although this is not permitted with Posix make.
One way to work around failures in simple commands is to reword them so
that they always succeed, e.g., `touch T || :; rm -f U'. However, even
this approach can run into common bugs in BSD implementations of the
`-e' option of `sh' and `set' (*note Limitations of Shell Builtins:
set.), so if you are worried about porting to buggy BSD shells it may
be simpler to migrate complicated `make' actions into separate scripts.
File: autoconf.info, Node: Special Chars in Names, Next: Backslash-Newline-Newline, Prev: Failure in Make Rules, Up: Portable Make
12.3 Special Characters in Make Macro Names
===========================================
Posix limits macro names to nonempty strings containing only ASCII
letters and digits, `.', and `_'. Many `make' implementations allow a
wider variety of characters, but portable makefiles should avoid them.
It is portable to start a name with a special character, e.g.,
`$(.FOO)'.
Some ancient `make' implementations don't support leading
underscores in macro names. An example is NEWS-OS 4.2R.
$ cat Makefile
_am_include = #
_am_quote =
all:; @echo this is test
$ make
Make: Must be a separator on rules line 2. Stop.
$ cat Makefile2
am_include = #
am_quote =
all:; @echo this is test
$ make -f Makefile2
this is test
However, this problem is no longer of practical concern.
File: autoconf.info, Node: Backslash-Newline-Newline, Next: Backslash-Newline Comments, Prev: Special Chars in Names, Up: Portable Make
12.4 Backslash-Newline-Newline in Make Macro Values
===================================================
On some versions of HP-UX, `make' reads multiple newlines following a
backslash, continuing to the next non-empty line. For example,
FOO = one \
BAR = two
test:
: FOO is "$(FOO)"
: BAR is "$(BAR)"
shows `FOO' equal to `one BAR = two'. Other implementations sensibly
let a backslash continue only to the immediately following line.
File: autoconf.info, Node: Backslash-Newline Comments, Next: Long Lines in Makefiles, Prev: Backslash-Newline-Newline, Up: Portable Make
12.5 Backslash-Newline in Make Comments
=======================================
According to Posix, Make comments start with `#' and continue until an
unescaped newline is reached.
$ cat Makefile
# A = foo \
bar \
baz
all:
@echo ok
$ make # GNU make
ok
However this is not always the case. Some implementations discard
everything from `#' through the end of the line, ignoring any trailing
backslash.
$ pmake # BSD make
"Makefile", line 3: Need an operator
Fatal errors encountered -- cannot continue
Therefore, if you want to comment out a multi-line definition, prefix
each line with `#', not only the first.
# A = foo \
# bar \
# baz
File: autoconf.info, Node: Long Lines in Makefiles, Next: Macros and Submakes, Prev: Backslash-Newline Comments, Up: Portable Make
12.6 Long Lines in Makefiles
============================
Tru64 5.1's `make' has been reported to crash when given a makefile
with lines longer than around 20 kB. Earlier versions are reported to
exit with `Line too long' diagnostics.
File: autoconf.info, Node: Macros and Submakes, Next: The Make Macro MAKEFLAGS, Prev: Long Lines in Makefiles, Up: Portable Make
12.7 `make macro=value' and Submakes
====================================
A command-line variable definition such as `foo=bar' overrides any
definition of `foo' in a makefile. Some `make' implementations (such
as GNU `make') propagate this override to subsidiary invocations of
`make'. Some other implementations do not pass the substitution along
to submakes.
$ cat Makefile
foo = foo
one:
@echo $(foo)
$(MAKE) two
two:
@echo $(foo)
$ make foo=bar # GNU make 3.79.1
bar
make two
make[1]: Entering directory `/home/adl'
bar
make[1]: Leaving directory `/home/adl'
$ pmake foo=bar # BSD make
bar
pmake two
foo
You have a few possibilities if you do want the `foo=bar' override
to propagate to submakes. One is to use the `-e' option, which causes
all environment variables to have precedence over the makefile macro
definitions, and declare foo as an environment variable:
$ env foo=bar make -e
The `-e' option is propagated to submakes automatically, and since
the environment is inherited between `make' invocations, the `foo'
macro is overridden in submakes as expected.
This syntax (`foo=bar make -e') is portable only when used outside
of a makefile, for instance from a script or from the command line.
When run inside a `make' rule, GNU `make' 3.80 and prior versions
forget to propagate the `-e' option to submakes.
Moreover, using `-e' could have unexpected side effects if your
environment contains some other macros usually defined by the makefile.
(See also the note about `make -e' and `SHELL' below.)
Another way to propagate overrides to submakes is to do it manually,
from your makefile:
foo = foo
one:
@echo $(foo)
$(MAKE) foo=$(foo) two
two:
@echo $(foo)
You need to foresee all macros that a user might want to override if
you do that.
File: autoconf.info, Node: The Make Macro MAKEFLAGS, Next: The Make Macro SHELL, Prev: Macros and Submakes, Up: Portable Make
12.8 The Make Macro MAKEFLAGS
=============================
Posix requires `make' to use `MAKEFLAGS' to affect the current and
recursive invocations of make, but allows implementations several
formats for the variable. It is tricky to parse `$MAKEFLAGS' to
determine whether `-s' for silent execution or `-k' for continued
execution are in effect. For example, you cannot assume that the first
space-separated word in `$MAKEFLAGS' contains single-letter options,
since in the Cygwin version of GNU `make' it is either `--unix' or
`--win32' with the second word containing single-letter options.
$ cat Makefile
all:
@echo MAKEFLAGS = $(MAKEFLAGS)
$ make
MAKEFLAGS = --unix
$ make -k
MAKEFLAGS = --unix -k
File: autoconf.info, Node: The Make Macro SHELL, Next: Parallel Make, Prev: The Make Macro MAKEFLAGS, Up: Portable Make
12.9 The Make Macro `SHELL'
===========================
Posix-compliant `make' internally uses the `$(SHELL)' macro to spawn
shell processes and execute Make rules. This is a builtin macro
supplied by `make', but it can be modified by a makefile or by a
command-line argument.
Not all `make' implementations define this `SHELL' macro. Tru64
`make' is an example; this implementation always uses `/bin/sh'. So
it's a good idea to always define `SHELL' in your makefiles. If you
use Autoconf, do
SHELL = @SHELL@
If you use Automake, this is done for you.
Do not force `SHELL = /bin/sh' because that is not correct
everywhere. Remember, `/bin/sh' is not Posix compliant on many
systems, such as FreeBSD 4, NetBSD 3, AIX 3, Solaris 10, or Tru64.
Additionally, DJGPP lacks `/bin/sh', and when its GNU `make' port sees
such a setting it enters a special emulation mode where features like
pipes and redirections are emulated on top of DOS's `command.com'.
Unfortunately this emulation is incomplete; for instance it does not
handle command substitutions. Using `@SHELL@' means that your makefile
will benefit from the same improved shell, such as `bash' or `ksh',
that was discovered during `configure', so that you aren't fighting two
different sets of shell bugs between the two contexts.
Posix-compliant `make' should never acquire the value of $(SHELL)
from the environment, even when `make -e' is used (otherwise, think
about what would happen to your rules if `SHELL=/bin/tcsh').
However not all `make' implementations have this exception. For
instance it's not surprising that Tru64 `make' doesn't protect `SHELL',
since it doesn't use it.
$ cat Makefile
SHELL = /bin/sh
FOO = foo
all:
@echo $(SHELL)
@echo $(FOO)
$ env SHELL=/bin/tcsh FOO=bar make -e # Tru64 Make
/bin/tcsh
bar
$ env SHELL=/bin/tcsh FOO=bar gmake -e # GNU make
/bin/sh
bar
Conversely, `make' is not supposed to export any changes to the
macro `SHELL' to child processes. Again, many implementations break
this rule:
$ cat Makefile
all:
@echo $(SHELL)
@printenv SHELL
$ env SHELL=sh make -e SHELL=/bin/ksh # BSD Make, GNU make 3.80
/bin/ksh
/bin/ksh
$ env SHELL=sh gmake -e SHELL=/bin/ksh # GNU make 3.81
/bin/ksh
sh
File: autoconf.info, Node: Parallel Make, Next: Comments in Make Rules, Prev: The Make Macro SHELL, Up: Portable Make
12.10 Parallel Make
===================
Support for parallel execution in `make' implementation varies.
Generally, using GNU make is your best bet. When NetBSD `make' is
invoked with `-jN', it will reuse the same shell for multiple commands
within one recipe. This can have unexpected consequences.(1) For
example, change of directories or variables persist between commands:
all:
@var=value; cd /; pwd; echo $$var; echo $$$$
@pwd; echo $$var; echo $$$$
may output the following with `make -j1':
--- all ---
/
value
32235
/
value
32235
while without `-j1', or with `-B', the output looks less surprising:
/
value
32238
/tmp
32239
Another consequence of this is that, if one command in a recipe uses
`exit 0' to indicate a successful exit, the shell will be gone and the
remaining commands of this recipe will not be executed.
The above example also shows additional status output NetBSD `make'
produces in parallel mode for targets being updated.
Furthermore, parallel NetBSD `make' will route standard error from
commands that it spawns into its own standard output, and may remove
leading whitespace from output lines.
You can avoid these issues by using the `-B' option to enable
compatibility semantics. However, that will effectively also disable
all parallelism as that will cause prerequisites to be updated in the
order they are listed in a rule.
---------- Footnotes ----------
(1) Note that GNU make has heuristics to avoid spawning a shell at
all if the command is deemed safe to be executed directly.
File: autoconf.info, Node: Comments in Make Rules, Next: obj/ and Make, Prev: Parallel Make, Up: Portable Make
12.11 Comments in Make Rules
============================
Never put comments in a rule.
Some `make' treat anything starting with a tab as a command for the
current rule, even if the tab is immediately followed by a `#'. The
`make' from Tru64 Unix V5.1 is one of them. The following makefile
runs `# foo' through the shell.
all:
# foo
File: autoconf.info, Node: obj/ and Make, Next: make -k Status, Prev: Comments in Make Rules, Up: Portable Make
12.12 The `obj/' Subdirectory and Make
======================================
Never name one of your subdirectories `obj/' if you don't like
surprises.
If an `obj/' directory exists, BSD `make' enters it before reading
the makefile. Hence the makefile in the current directory is not read.
$ cat Makefile
all:
echo Hello
$ cat obj/Makefile
all:
echo World
$ make # GNU make
echo Hello
Hello
$ pmake # BSD make
echo World
World
File: autoconf.info, Node: make -k Status, Next: VPATH and Make, Prev: obj/ and Make, Up: Portable Make
12.13 Exit Status of `make -k'
==============================
Do not rely on the exit status of `make -k'. Some implementations
reflect whether they encountered an error in their exit status; other
implementations always succeed.
$ cat Makefile
all:
false
$ make -k; echo exit status: $? # GNU make
false
make: *** [all] Error 1
exit status: 2
$ pmake -k; echo exit status: $? # BSD make
false
*** Error code 1 (continuing)
exit status: 0
File: autoconf.info, Node: VPATH and Make, Next: Single Suffix Rules, Prev: make -k Status, Up: Portable Make
12.14 `VPATH' and Make
======================
Posix does not specify the semantics of `VPATH'. Typically, `make'
supports `VPATH', but its implementation is not consistent.
Autoconf and Automake support makefiles whose usages of `VPATH' are
portable to recent-enough popular implementations of `make', but to
keep the resulting makefiles portable, a package's makefile prototypes
must take the following issues into account. These issues are
complicated and are often poorly understood, and installers who use
`VPATH' should expect to find many bugs in this area. If you use
`VPATH', the simplest way to avoid these portability bugs is to stick
with GNU `make', since it is the most commonly-used `make' among
Autoconf users.
Here are some known issues with some `VPATH' implementations.
* Menu:
* Variables listed in VPATH:: `VPATH' must be literal on ancient hosts
* VPATH and Double-colon:: Problems with `::' on ancient hosts
* $< in Explicit Rules:: `$<' does not work in ordinary rules
* Automatic Rule Rewriting:: `VPATH' goes wild on Solaris
* Tru64 Directory Magic:: `mkdir' goes wild on Tru64
* Make Target Lookup:: More details about `VPATH' lookup
File: autoconf.info, Node: Variables listed in VPATH, Next: VPATH and Double-colon, Up: VPATH and Make
12.14.1 Variables listed in `VPATH'
-----------------------------------
Do not set `VPATH' to the value of another variable, for example `VPATH
= $(srcdir)', because some ancient versions of `make' do not do
variable substitutions on the value of `VPATH'. For example, use this
srcdir = @srcdir@
VPATH = @srcdir@
rather than `VPATH = $(srcdir)'. Note that with GNU Automake, there is
no need to set this yourself.
File: autoconf.info, Node: VPATH and Double-colon, Next: $< in Explicit Rules, Prev: Variables listed in VPATH, Up: VPATH and Make
12.14.2 `VPATH' and Double-colon Rules
--------------------------------------
With ancient versions of Sun `make', any assignment to `VPATH' causes
`make' to execute only the first set of double-colon rules. However,
this problem is no longer of practical concern.
File: autoconf.info, Node: $< in Explicit Rules, Next: Automatic Rule Rewriting, Prev: VPATH and Double-colon, Up: VPATH and Make
12.14.3 `$<' Not Supported in Explicit Rules
--------------------------------------------
Using `$<' in explicit rules is not portable. The prerequisite file
must be named explicitly in the rule. If you want to find the
prerequisite via a `VPATH' search, you have to code the whole thing
manually. *Note Build Directories::.
File: autoconf.info, Node: Automatic Rule Rewriting, Next: Tru64 Directory Magic, Prev: $< in Explicit Rules, Up: VPATH and Make
12.14.4 Automatic Rule Rewriting
--------------------------------
Some `make' implementations, such as Solaris and Tru64, search for
prerequisites in `VPATH' and then rewrite each occurrence as a plain
word in the rule. For instance:
# This isn't portable to GNU make.
VPATH = ../pkg/src
f.c: if.c
cp if.c f.c
executes `cp ../pkg/src/if.c f.c' if `if.c' is found in `../pkg/src'.
However, this rule leads to real problems in practice. For example,
if the source directory contains an ordinary file named `test' that is
used in a dependency, Solaris `make' rewrites commands like `if test -r
foo; ...' to `if ../pkg/src/test -r foo; ...', which is typically
undesirable. To avoid this problem, portable makefiles should never
mention a source file whose name is that of a shell keyword like
`until' or a shell command like `cat' or `gcc' or `test'.
Because of these problems GNU `make' and many other `make'
implementations do not rewrite commands, so portable makefiles should
search `VPATH' manually. It is tempting to write this:
# This isn't portable to Solaris make.
VPATH = ../pkg/src
f.c: if.c
cp `test -f if.c || echo $(VPATH)/`if.c f.c
However, the "prerequisite rewriting" still applies here. So if `if.c'
is in `../pkg/src', Solaris and Tru64 `make' execute
cp `test -f ../pkg/src/if.c || echo ../pkg/src/`if.c f.c
which reduces to
cp if.c f.c
and thus fails. Oops.
A simple workaround, and good practice anyway, is to use `$?' and
`$@' when possible:
VPATH = ../pkg/src
f.c: if.c
cp $? $@
but this does not generalize well to commands with multiple
prerequisites. A more general workaround is to rewrite the rule so that
the prerequisite `if.c' never appears as a plain word. For example,
these three rules would be safe, assuming `if.c' is in `../pkg/src' and
the other files are in the working directory:
VPATH = ../pkg/src
f.c: if.c f1.c
cat `test -f ./if.c || echo $(VPATH)/`if.c f1.c >$@
g.c: if.c g1.c
cat `test -f 'if.c' || echo $(VPATH)/`if.c g1.c >$@
h.c: if.c h1.c
cat `test -f "if.c" || echo $(VPATH)/`if.c h1.c >$@
Things get worse when your prerequisites are in a macro.
VPATH = ../pkg/src
HEADERS = f.h g.h h.h
install-HEADERS: $(HEADERS)
for i in $(HEADERS); do \
$(INSTALL) -m 644 \
`test -f $$i || echo $(VPATH)/`$$i \
$(DESTDIR)$(includedir)/$$i; \
done
The above `install-HEADERS' rule is not Solaris-proof because `for i
in $(HEADERS);' is expanded to `for i in f.h g.h h.h;' where `f.h' and
`g.h' are plain words and are hence subject to `VPATH' adjustments.
If the three files are in `../pkg/src', the rule is run as:
for i in ../pkg/src/f.h ../pkg/src/g.h h.h; do \
install -m 644 \
`test -f $i || echo ../pkg/src/`$i \
/usr/local/include/$i; \
done
where the two first `install' calls fail. For instance, consider
the `f.h' installation:
install -m 644 \
`test -f ../pkg/src/f.h || \
echo ../pkg/src/ \
`../pkg/src/f.h \
/usr/local/include/../pkg/src/f.h;
It reduces to:
install -m 644 \
../pkg/src/f.h \
/usr/local/include/../pkg/src/f.h;
Note that the manual `VPATH' search did not cause any problems here;
however this command installs `f.h' in an incorrect directory.
Trying to quote `$(HEADERS)' in some way, as we did for `foo.c' a
few makefiles ago, does not help:
install-HEADERS: $(HEADERS)
headers='$(HEADERS)'; \
for i in $$headers; do \
$(INSTALL) -m 644 \
`test -f $$i || echo $(VPATH)/`$$i \
$(DESTDIR)$(includedir)/$$i; \
done
Now, `headers='$(HEADERS)'' macro-expands to:
headers='f.h g.h h.h'
but `g.h' is still a plain word. (As an aside, the idiom
`headers='$(HEADERS)'; for i in $$headers;' is a good idea if
`$(HEADERS)' can be empty, because some shells diagnose a syntax error
on `for i in;'.)
One workaround is to strip this unwanted `../pkg/src/' prefix
manually:
VPATH = ../pkg/src
HEADERS = f.h g.h h.h
install-HEADERS: $(HEADERS)
headers='$(HEADERS)'; \
for i in $$headers; do \
i=`expr "$$i" : '$(VPATH)/\(.*\)'`;
$(INSTALL) -m 644 \
`test -f $$i || echo $(VPATH)/`$$i \
$(DESTDIR)$(includedir)/$$i; \
done
Automake does something similar. However the above hack works only
if the files listed in `HEADERS' are in the current directory or a
subdirectory; they should not be in an enclosing directory. If we had
`HEADERS = ../f.h', the above fragment would fail in a VPATH build with
Tru64 `make'. The reason is that not only does Tru64 `make' rewrite
dependencies, but it also simplifies them. Hence `../f.h' becomes
`../pkg/f.h' instead of `../pkg/src/../f.h'. This obviously defeats
any attempt to strip a leading `../pkg/src/' component.
The following example makes the behavior of Tru64 `make' more
apparent.
$ cat Makefile
VPATH = sub
all: ../foo
echo ../foo
$ ls
Makefile foo
$ make
echo foo
foo
Dependency `../foo' was found in `sub/../foo', but Tru64 `make'
simplified it as `foo'. (Note that the `sub/' directory does not even
exist, this just means that the simplification occurred before the file
was checked for.)
For the record here is how SunOS 4 `make' behaves on this example.
$ make
make: Fatal error: Don't know how to make target `../foo'
$ mkdir sub
$ make
echo sub/../foo
sub/../foo
File: autoconf.info, Node: Tru64 Directory Magic, Next: Make Target Lookup, Prev: Automatic Rule Rewriting, Up: VPATH and Make
12.14.5 Tru64 `make' Creates Prerequisite Directories Magically
---------------------------------------------------------------
When a prerequisite is a subdirectory of `VPATH', Tru64 `make' creates
it in the current directory.
$ mkdir -p foo/bar build
$ cd build
$ cat >Makefile <dest-stamp
File: autoconf.info, Node: Portable C and C++, Next: Manual Configuration, Prev: Portable Make, Up: Top
13 Portable C and C++ Programming
*********************************
C and C++ programs often use low-level features of the underlying
system, and therefore are often more difficult to make portable to other
platforms.
Several standards have been developed to help make your programs more
portable. If you write programs with these standards in mind, you can
have greater confidence that your programs work on a wide variety of
systems. *Note Language Standards Supported by GCC: (gcc)Standards,
for a list of C-related standards. Many programs also assume the Posix
standard (http://www.opengroup.org/susv3).
Some old code is written to be portable to K&R C, which predates any
C standard. K&R C compilers are no longer of practical interest,
though, and the rest of section assumes at least C89, the first C
standard.
Program portability is a huge topic, and this section can only
briefly introduce common pitfalls. *Note Portability between System
Types: (standards)System Portability, for more information.
* Menu:
* Varieties of Unportability:: How to make your programs unportable
* Integer Overflow:: When integers get too large
* Preprocessor Arithmetic:: `#if' expression problems
* Null Pointers:: Properties of null pointers
* Buffer Overruns:: Subscript errors and the like
* Volatile Objects:: `volatile' and signals
* Floating Point Portability:: Portable floating-point arithmetic
* Exiting Portably:: Exiting and the exit status
File: autoconf.info, Node: Varieties of Unportability, Next: Integer Overflow, Up: Portable C and C++
13.1 Varieties of Unportability
===============================
Autoconf tests and ordinary programs often need to test what is allowed
on a system, and therefore they may need to deliberately exceed the
boundaries of what the standards allow, if only to see whether an
optional feature is present. When you write such a program, you should
keep in mind the difference between constraints, unspecified behavior,
and undefined behavior.
In C, a "constraint" is a rule that the compiler must enforce. An
example constraint is that C programs must not declare a bit-field with
negative width. Tests can therefore reliably assume that programs with
negative-width bit-fields are rejected by a compiler that conforms to
the standard.
"Unspecified behavior" is valid behavior, where the standard allows
multiple possibilities. For example, the order of evaluation of
function arguments is unspecified. Some unspecified behavior is
"implementation-defined", i.e., documented by the implementation, but
since Autoconf tests cannot read the documentation they cannot
distinguish between implementation-defined and other unspecified
behavior. It is common for Autoconf tests to probe implementations to
determine otherwise-unspecified behavior.
"Undefined behavior" is invalid behavior, where the standard allows
the implementation to do anything it pleases. For example,
dereferencing a null pointer leads to undefined behavior. If possible,
test programs should avoid undefined behavior, since a program with
undefined behavior might succeed on a test that should fail.
The above rules apply to programs that are intended to conform to the
standard. However, strictly-conforming programs are quite rare, since
the standards are so limiting. A major goal of Autoconf is to support
programs that use implementation features not described by the standard,
and it is fairly common for test programs to violate the above rules, if
the programs work well enough in practice.
File: autoconf.info, Node: Integer Overflow, Next: Preprocessor Arithmetic, Prev: Varieties of Unportability, Up: Portable C and C++
13.2 Integer Overflow
=====================
In practice many portable C programs assume that signed integer
overflow wraps around reliably using two's complement arithmetic. Yet
the C standard says that program behavior is undefined on overflow, and
in a few cases C programs do not work on some modern implementations
because their overflows do not wrap around as their authors expected.
Conversely, in signed integer remainder, the C standard requires
overflow behavior that is commonly not implemented.
* Menu:
* Integer Overflow Basics:: Why integer overflow is a problem
* Signed Overflow Examples:: Examples of code assuming wraparound
* Optimization and Wraparound:: Optimizations that break uses of wraparound
* Signed Overflow Advice:: Practical advice for signed overflow issues
* Signed Integer Division:: `INT_MIN / -1' and `INT_MIN % -1'
File: autoconf.info, Node: Integer Overflow Basics, Next: Signed Overflow Examples, Up: Integer Overflow
13.2.1 Basics of Integer Overflow
---------------------------------
In languages like C, unsigned integer overflow reliably wraps around;
e.g., `UINT_MAX + 1' yields zero. This is guaranteed by the C standard
and is portable in practice, unless you specify aggressive, nonstandard
optimization options suitable only for special applications.
In contrast, the C standard says that signed integer overflow leads
to undefined behavior where a program can do anything, including dumping
core or overrunning a buffer. The misbehavior can even precede the
overflow. Such an overflow can occur during addition, subtraction,
multiplication, division, and left shift.
Despite this requirement of the standard, many C programs and
Autoconf tests assume that signed integer overflow silently wraps
around modulo a power of two, using two's complement arithmetic, so
long as you cast the resulting value to a signed integer type or store
it into a signed integer variable. If you use conservative
optimization flags, such programs are generally portable to the vast
majority of modern platforms, with a few exceptions discussed later.
For historical reasons the C standard also allows implementations
with ones' complement or signed magnitude arithmetic, but it is safe to
assume two's complement nowadays.
Also, overflow can occur when converting an out-of-range value to a
signed integer type. Here a standard implementation must define what
happens, but this might include raising an exception. In practice all
known implementations support silent wraparound in this case, so you
need not worry about other possibilities.
File: autoconf.info, Node: Signed Overflow Examples, Next: Optimization and Wraparound, Prev: Integer Overflow Basics, Up: Integer Overflow
13.2.2 Examples of Code Assuming Wraparound Overflow
----------------------------------------------------
There has long been a tension between what the C standard requires for
signed integer overflow, and what C programs commonly assume. The
standard allows aggressive optimizations based on assumptions that
overflow never occurs, but many practical C programs rely on overflow
wrapping around. These programs do not conform to the standard, but
they commonly work in practice because compiler writers are
understandably reluctant to implement optimizations that would break
many programs, unless perhaps a user specifies aggressive optimization.
The C Standard says that if a program has signed integer overflow its
behavior is undefined, and the undefined behavior can even precede the
overflow. To take an extreme example:
if (password == expected_password)
allow_superuser_privileges ();
else if (counter++ == INT_MAX)
abort ();
else
printf ("%d password mismatches\n", counter);
If the `int' variable `counter' equals `INT_MAX', `counter++' must
overflow and the behavior is undefined, so the C standard allows the
compiler to optimize away the test against `INT_MAX' and the `abort'
call. Worse, if an earlier bug in the program lets the compiler deduce
that `counter == INT_MAX' or that `counter' previously overflowed, the
C standard allows the compiler to optimize away the password test and
generate code that allows superuser privileges unconditionally.
Despite this requirement by the standard, it has long been common
for C code to assume wraparound arithmetic after signed overflow, and
all known practical C implementations support some C idioms that assume
wraparound signed arithmetic, even if the idioms do not conform
strictly to the standard. If your code looks like the following
examples it will almost surely work with real-world compilers.
Here is an example derived from the 7th Edition Unix implementation
of `atoi' (1979-01-10):
char *p;
int f, n;
...
while (*p >= '0' && *p <= '9')
n = n * 10 + *p++ - '0';
return (f ? -n : n);
Even if the input string is in range, on most modern machines this has
signed overflow when computing the most negative integer (the `-n'
overflows) or a value near an extreme integer (the first `+' overflows).
Here is another example, derived from the 7th Edition implementation
of `rand' (1979-01-10). Here the programmer expects both
multiplication and addition to wrap on overflow:
static long int randx = 1;
...
randx = randx * 1103515245 + 12345;
return (randx >> 16) & 077777;
In the following example, derived from the GNU C Library 2.5
implementation of `mktime' (2006-09-09), the code assumes wraparound
arithmetic in `+' to detect signed overflow:
time_t t, t1, t2;
int sec_requested, sec_adjustment;
...
t1 = t + sec_requested;
t2 = t1 + sec_adjustment;
if (((t1 < t) != (sec_requested < 0))
| ((t2 < t1) != (sec_adjustment < 0)))
return -1;
If your code looks like these examples, it is probably safe even
though it does not strictly conform to the C standard. This might lead
one to believe that one can generally assume wraparound on overflow,
but that is not always true, as can be seen in the next section.
File: autoconf.info, Node: Optimization and Wraparound, Next: Signed Overflow Advice, Prev: Signed Overflow Examples, Up: Integer Overflow
13.2.3 Optimizations That Break Wraparound Arithmetic
-----------------------------------------------------
Compilers sometimes generate code that is incompatible with wraparound
integer arithmetic. A simple example is an algebraic simplification: a
compiler might translate `(i * 2000) / 1000' to `i * 2' because it
assumes that `i * 2000' does not overflow. The translation is not
equivalent to the original when overflow occurs: e.g., in the typical
case of 32-bit signed two's complement wraparound `int', if `i' has
type `int' and value `1073742', the original expression returns
-2147483 but the optimized version returns the mathematically correct
value 2147484.
More subtly, loop induction optimizations often exploit the undefined
behavior of signed overflow. Consider the following contrived function
`sumc':
int
sumc (int lo, int hi)
{
int sum = 0;
int i;
for (i = lo; i <= hi; i++)
sum ^= i * 53;
return sum;
}
To avoid multiplying by 53 each time through the loop, an optimizing
compiler might internally transform `sumc' to the equivalent of the
following:
int
transformed_sumc (int lo, int hi)
{
int sum = 0;
int hic = hi * 53;
int ic;
for (ic = lo * 53; ic <= hic; ic += 53)
sum ^= ic;
return sum;
}
This transformation is allowed by the C standard, but it is invalid for
wraparound arithmetic when `INT_MAX / 53 < hi', because then the
overflow in computing expressions like `hi * 53' can cause the
expression `i <= hi' to yield a different value from the transformed
expression `ic <= hic'.
For this reason, compilers that use loop induction and similar
techniques often do not support reliable wraparound arithmetic when a
loop induction variable like `ic' is involved. Since loop induction
variables are generated by the compiler, and are not visible in the
source code, it is not always trivial to say whether the problem
affects your code.
Hardly any code actually depends on wraparound arithmetic in cases
like these, so in practice these loop induction optimizations are almost
always useful. However, edge cases in this area can cause problems.
For example:
int j;
for (j = 1; 0 < j; j *= 2)
test (j);
Here, the loop attempts to iterate through all powers of 2 that `int'
can represent, but the C standard allows a compiler to optimize away
the comparison and generate an infinite loop, under the argument that
behavior is undefined on overflow. As of this writing this
optimization is not done by any production version of GCC with `-O2',
but it might be performed by other compilers, or by more aggressive GCC
optimization options, and the GCC developers have not decided whether
it will continue to work with GCC and `-O2'.
File: autoconf.info, Node: Signed Overflow Advice, Next: Signed Integer Division, Prev: Optimization and Wraparound, Up: Integer Overflow
13.2.4 Practical Advice for Signed Overflow Issues
--------------------------------------------------
Ideally the safest approach is to avoid signed integer overflow
entirely. For example, instead of multiplying two signed integers, you
can convert them to unsigned integers, multiply the unsigned values,
then test whether the result is in signed range.
Rewriting code in this way will be inconvenient, though,
particularly if the signed values might be negative. Also, it may hurt
performance. Using unsigned arithmetic to check for overflow is
particularly painful to do portably and efficiently when dealing with an
integer type like `uid_t' whose width and signedness vary from platform
to platform.
Furthermore, many C applications pervasively assume wraparound
behavior and typically it is not easy to find and remove all these
assumptions. Hence it is often useful to maintain nonstandard code
that assumes wraparound on overflow, instead of rewriting the code.
The rest of this section attempts to give practical advice for this
situation.
If your code wants to detect signed integer overflow in `sum = a +
b', it is generally safe to use an expression like `(sum < a) != (b <
0)'.
If your code uses a signed loop index, make sure that the index
cannot overflow, along with all signed expressions derived from the
index. Here is a contrived example of problematic code with two
instances of overflow.
for (i = INT_MAX - 10; i <= INT_MAX; i++)
if (i + 1 < 0)
{
report_overflow ();
break;
}
Because of the two overflows, a compiler might optimize away or
transform the two comparisons in a way that is incompatible with the
wraparound assumption.
If your code uses an expression like `(i * 2000) / 1000' and you
actually want the multiplication to wrap around on overflow, use
unsigned arithmetic to do it, e.g., `((int) (i * 2000u)) / 1000'.
If your code assumes wraparound behavior and you want to insulate it
against any GCC optimizations that would fail to support that behavior,
you should use GCC's `-fwrapv' option, which causes signed overflow to
wrap around reliably (except for division and remainder, as discussed
in the next section).
If you need to port to platforms where signed integer overflow does
not reliably wrap around (e.g., due to hardware overflow checking, or to
highly aggressive optimizations), you should consider debugging with
GCC's `-ftrapv' option, which causes signed overflow to raise an
exception.
File: autoconf.info, Node: Signed Integer Division, Prev: Signed Overflow Advice, Up: Integer Overflow
13.2.5 Signed Integer Division and Integer Overflow
---------------------------------------------------
Overflow in signed integer division is not always harmless: for
example, on CPUs of the i386 family, dividing `INT_MIN' by `-1' yields
a SIGFPE signal which by default terminates the program. Worse, taking
the remainder of these two values typically yields the same signal on
these CPUs, even though the C standard requires `INT_MIN % -1' to yield
zero because the expression does not overflow.
File: autoconf.info, Node: Preprocessor Arithmetic, Next: Null Pointers, Prev: Integer Overflow, Up: Portable C and C++
13.3 Preprocessor Arithmetic
============================
In C99, preprocessor arithmetic, used for `#if' expressions, must be
evaluated as if all signed values are of type `intmax_t' and all
unsigned values of type `uintmax_t'. Many compilers are buggy in this
area, though. For example, as of 2007, Sun C mishandles `#if LLONG_MIN
< 0' on a platform with 32-bit `long int' and 64-bit `long long int'.
Also, some older preprocessors mishandle constants ending in `LL'. To
work around these problems, you can compute the value of expressions
like `LONG_MAX < LLONG_MAX' at `configure'-time rather than at
`#if'-time.
File: autoconf.info, Node: Null Pointers, Next: Buffer Overruns, Prev: Preprocessor Arithmetic, Up: Portable C and C++
13.4 Properties of Null Pointers
================================
Most modern hosts reliably fail when you attempt to dereference a null
pointer.
On almost all modern hosts, null pointers use an all-bits-zero
internal representation, so you can reliably use `memset' with 0 to set
all the pointers in an array to null values.
If `p' is a null pointer to an object type, the C expression `p + 0'
always evaluates to `p' on modern hosts, even though the standard says
that it has undefined behavior.
File: autoconf.info, Node: Buffer Overruns, Next: Volatile Objects, Prev: Null Pointers, Up: Portable C and C++
13.5 Buffer Overruns and Subscript Errors
=========================================
Buffer overruns and subscript errors are the most common dangerous
errors in C programs. They result in undefined behavior because storing
outside an array typically modifies storage that is used by some other
object, and most modern systems lack runtime checks to catch these
errors. Programs should not rely on buffer overruns being caught.
There is one exception to the usual rule that a portable program
cannot address outside an array. In C, it is valid to compute the
address just past an object, e.g., `&a[N]' where `a' has `N' elements,
so long as you do not dereference the resulting pointer. But it is not
valid to compute the address just before an object, e.g., `&a[-1]'; nor
is it valid to compute two past the end, e.g., `&a[N+1]'. On most
platforms `&a[-1] < &a[0] && &a[N] < &a[N+1]', but this is not reliable
in general, and it is usually easy enough to avoid the potential
portability problem, e.g., by allocating an extra unused array element
at the start or end.
Valgrind (http://valgrind.org/) can catch many overruns. GCC users
might also consider using the `-fmudflap' option to catch overruns.
Buffer overruns are usually caused by off-by-one errors, but there
are more subtle ways to get them.
Using `int' values to index into an array or compute array sizes
causes problems on typical 64-bit hosts where an array index might be
2^31 or larger. Index values of type `size_t' avoid this problem, but
cannot be negative. Index values of type `ptrdiff_t' are signed, and
are wide enough in practice.
If you add or multiply two numbers to calculate an array size, e.g.,
`malloc (x * sizeof y + z)', havoc ensues if the addition or
multiplication overflows.
Many implementations of the `alloca' function silently misbehave and
can generate buffer overflows if given sizes that are too large. The
size limits are implementation dependent, but are at least 4000 bytes
on all platforms that we know about.
The standard functions `asctime', `asctime_r', `ctime', `ctime_r',
and `gets' are prone to buffer overflows, and portable code should not
use them unless the inputs are known to be within certain limits. The
time-related functions can overflow their buffers if given timestamps
out of range (e.g., a year less than -999 or greater than 9999).
Time-related buffer overflows cannot happen with recent-enough versions
of the GNU C library, but are possible with other implementations. The
`gets' function is the worst, since it almost invariably overflows its
buffer when presented with an input line larger than the buffer.
File: autoconf.info, Node: Volatile Objects, Next: Floating Point Portability, Prev: Buffer Overruns, Up: Portable C and C++
13.6 Volatile Objects
=====================
The keyword `volatile' is often misunderstood in portable code. Its
use inhibits some memory-access optimizations, but programmers often
wish that it had a different meaning than it actually does.
`volatile' was designed for code that accesses special objects like
memory-mapped device registers whose contents spontaneously change.
Such code is inherently low-level, and it is difficult to specify
portably what `volatile' means in these cases. The C standard says,
"What constitutes an access to an object that has volatile-qualified
type is implementation-defined," so in theory each implementation is
supposed to fill in the gap by documenting what `volatile' means for
that implementation. In practice, though, this documentation is
usually absent or incomplete.
One area of confusion is the distinction between objects defined with
volatile types, and volatile lvalues. From the C standard's point of
view, an object defined with a volatile type has externally visible
behavior. You can think of such objects as having little oscilloscope
probes attached to them, so that the user can observe some properties of
accesses to them, just as the user can observe data written to output
files. However, the standard does not make it clear whether users can
observe accesses by volatile lvalues to ordinary objects. For example:
/* Declare and access a volatile object.
Accesses to X are "visible" to users. */
static int volatile x;
x = 1;
/* Access two ordinary objects via a volatile lvalue.
It's not clear whether accesses to *P are "visible". */
int y;
int *z = malloc (sizeof (int));
int volatile *p;
p = &y;
*p = 1;
p = z;
*p = 1;
Programmers often wish that `volatile' meant "Perform the memory
access here and now, without merging several memory accesses, without
changing the memory word size, and without reordering." But the C
standard does not require this. For objects defined with a volatile
type, accesses must be done before the next sequence point; but
otherwise merging, reordering, and word-size change is allowed. Worse,
it is not clear from the standard whether volatile lvalues provide more
guarantees in general than nonvolatile lvalues, if the underlying
objects are ordinary.
Even when accessing objects defined with a volatile type, the C
standard allows only extremely limited signal handlers: the behavior is
undefined if a signal handler reads any nonlocal object, or writes to
any nonlocal object whose type is not `sig_atomic_t volatile', or calls
any standard library function other than `abort', `signal', and (if C99)
`_Exit'. Hence C compilers need not worry about a signal handler
disturbing ordinary computation, unless the computation accesses a
`sig_atomic_t volatile' lvalue that is not a local variable. (There is
an obscure exception for accesses via a pointer to a volatile
character, since it may point into part of a `sig_atomic_t volatile'
object.) Posix adds to the list of library functions callable from a
portable signal handler, but otherwise is like the C standard in this
area.
Some C implementations allow memory-access optimizations within each
translation unit, such that actual behavior agrees with the behavior
required by the standard only when calling a function in some other
translation unit, and a signal handler acts like it was called from a
different translation unit. The C standard hints that in these
implementations, objects referred to by signal handlers "would require
explicit specification of `volatile' storage, as well as other
implementation-defined restrictions." But unfortunately even for this
special case these other restrictions are often not documented well.
*Note When is a Volatile Object Accessed?: (gcc)Volatiles, for some
restrictions imposed by GCC. *Note Defining Signal Handlers:
(libc)Defining Handlers, for some restrictions imposed by the GNU C
library. Restrictions differ on other platforms.
If possible, it is best to use a signal handler that fits within the
limits imposed by the C and Posix standards.
If this is not practical, you can try the following rules of thumb.
A signal handler should access only volatile lvalues, preferably lvalues
that refer to objects defined with a volatile type, and should not
assume that the accessed objects have an internally consistent state if
they are larger than a machine word. Furthermore, installers should
employ compilers and compiler options that are commonly used for
building operating system kernels, because kernels often need more from
`volatile' than the C Standard requires, and installers who compile an
application in a similar environment can sometimes benefit from the
extra constraints imposed by kernels on compilers. Admittedly we are
handwaving somewhat here, as there are few guarantees in this area; the
rules of thumb may help to fix some bugs but there is a good chance
that they will not fix them all.
For `volatile', C++ has the same problems that C does.
Multithreaded applications have even more problems with `volatile', but
they are beyond the scope of this section.
The bottom line is that using `volatile' typically hurts performance
but should not hurt correctness. In some cases its use does help
correctness, but these cases are often so poorly understood that all
too often adding `volatile' to a data structure merely alleviates some
symptoms of a bug while not fixing the bug in general.
File: autoconf.info, Node: Floating Point Portability, Next: Exiting Portably, Prev: Volatile Objects, Up: Portable C and C++
13.7 Floating Point Portability
===============================
Almost all modern systems use IEEE-754 floating point, and it is safe to
assume IEEE-754 in most portable code these days. For more information,
please see David Goldberg's classic paper What Every Computer Scientist
Should Know About Floating-Point Arithmetic
(http://www.validlab.com/goldberg/paper.pdf).
File: autoconf.info, Node: Exiting Portably, Prev: Floating Point Portability, Up: Portable C and C++
13.8 Exiting Portably
=====================
A C or C++ program can exit with status N by returning N from the
`main' function. Portable programs are supposed to exit either with
status 0 or `EXIT_SUCCESS' to succeed, or with status `EXIT_FAILURE' to
fail, but in practice it is portable to fail by exiting with status 1,
and test programs that assume Posix can fail by exiting with status
values from 1 through 255. Programs on SunOS 2.0 (1985) through 3.5.2
(1988) incorrectly exited with zero status when `main' returned
nonzero, but ancient systems like these are no longer of practical
concern.
A program can also exit with status N by passing N to the `exit'
function, and a program can fail by calling the `abort' function. If a
program is specialized to just some platforms, it can fail by calling
functions specific to those platforms, e.g., `_exit' (Posix) and
`_Exit' (C99). However, like other functions, an exit function should
be declared, typically by including a header. For example, if a C
program calls `exit', it should include `stdlib.h' either directly or
via the default includes (*note Default Includes::).
A program can fail due to undefined behavior such as dereferencing a
null pointer, but this is not recommended as undefined behavior allows
an implementation to do whatever it pleases and this includes exiting
successfully.
File: autoconf.info, Node: Manual Configuration, Next: Site Configuration, Prev: Portable C and C++, Up: Top
14 Manual Configuration
***********************
A few kinds of features can't be guessed automatically by running test
programs. For example, the details of the object-file format, or
special options that need to be passed to the compiler or linker. You
can check for such features using ad-hoc means, such as having
`configure' check the output of the `uname' program, or looking for
libraries that are unique to particular systems. However, Autoconf
provides a uniform method for handling unguessable features.
* Menu:
* Specifying Target Triplets:: Specifying target triplets
* Canonicalizing:: Getting the canonical system type
* Using System Type:: What to do with the system type
File: autoconf.info, Node: Specifying Target Triplets, Next: Canonicalizing, Up: Manual Configuration
14.1 Specifying target triplets
===============================
Autoconf-generated `configure' scripts can make decisions based on a
canonical name for the system type, or "target triplet", which has the
form: `CPU-VENDOR-OS', where OS can be `SYSTEM' or `KERNEL-SYSTEM'
`configure' can usually guess the canonical name for the type of
system it's running on. To do so it runs a script called
`config.guess', which infers the name using the `uname' command or
symbols predefined by the C preprocessor.
Alternately, the user can specify the system type with command line
arguments to `configure' (*note System Type::. Doing so is necessary
when cross-compiling. In the most complex case of cross-compiling,
three system types are involved. The options to specify them are:
`--build=BUILD-TYPE'
the type of system on which the package is being configured and
compiled. It defaults to the result of running `config.guess'.
`--host=HOST-TYPE'
the type of system on which the package runs. By default it is the
same as the build machine. Specifying it enables the
cross-compilation mode.
`--target=TARGET-TYPE'
the type of system for which any compiler tools in the package
produce code (rarely needed). By default, it is the same as host.
If you mean to override the result of `config.guess', use `--build',
not `--host', since the latter enables cross-compilation. For
historical reasons, whenever you specify `--host', be sure to specify
`--build' too; this will be fixed in the future. So, to enter
cross-compilation mode, use a command like this
./configure --build=i686-pc-linux-gnu --host=m68k-coff
Note that if you do not specify `--host', `configure' fails if it can't
run the code generated by the specified compiler. For example,
configuring as follows fails:
./configure CC=m68k-coff-gcc
When cross-compiling, `configure' will warn about any tools
(compilers, linkers, assemblers) whose name is not prefixed with the
host type. This is an aid to users performing cross-compilation.
Continuing the example above, if a cross-compiler named `cc' is used
with a native `pkg-config', then libraries found by `pkg-config' will
likely cause subtle build failures; but using the names `m68k-coff-cc'
and `m68k-coff-pkg-config' avoids any confusion. Avoiding the warning
is as simple as creating the correct symlinks naming the cross tools.
`configure' recognizes short aliases for many system types; for
example, `decstation' can be used instead of `mips-dec-ultrix4.2'.
`configure' runs a script called `config.sub' to canonicalize system
type aliases.
This section deliberately omits the description of the obsolete
interface; see *note Hosts and Cross-Compilation::.
File: autoconf.info, Node: Canonicalizing, Next: Using System Type, Prev: Specifying Target Triplets, Up: Manual Configuration
14.2 Getting the Canonical System Type
======================================
The following macros make the system type available to `configure'
scripts.
The variables `build_alias', `host_alias', and `target_alias' are
always exactly the arguments of `--build', `--host', and `--target'; in
particular, they are left empty if the user did not use them, even if
the corresponding `AC_CANONICAL' macro was run. Any configure script
may use these variables anywhere. These are the variables that should
be used when in interaction with the user.
If you need to recognize some special environments based on their
system type, run the following macros to get canonical system names.
These variables are not set before the macro call.
If you use these macros, you must distribute `config.guess' and
`config.sub' along with your source code. *Note Output::, for
information about the `AC_CONFIG_AUX_DIR' macro which you can use to
control in which directory `configure' looks for those scripts.
-- Macro: AC_CANONICAL_BUILD
Compute the canonical build-system type variable, `build', and its
three individual parts `build_cpu', `build_vendor', and `build_os'.
If `--build' was specified, then `build' is the canonicalization
of `build_alias' by `config.sub', otherwise it is determined by
the shell script `config.guess'.
-- Macro: AC_CANONICAL_HOST
Compute the canonical host-system type variable, `host', and its
three individual parts `host_cpu', `host_vendor', and `host_os'.
If `--host' was specified, then `host' is the canonicalization of
`host_alias' by `config.sub', otherwise it defaults to `build'.
-- Macro: AC_CANONICAL_TARGET
Compute the canonical target-system type variable, `target', and
its three individual parts `target_cpu', `target_vendor', and
`target_os'.
If `--target' was specified, then `target' is the canonicalization
of `target_alias' by `config.sub', otherwise it defaults to `host'.
Note that there can be artifacts due to the backward compatibility
code. See *Note Hosts and Cross-Compilation::, for more.
File: autoconf.info, Node: Using System Type, Prev: Canonicalizing, Up: Manual Configuration
14.3 Using the System Type
==========================
In `configure.ac' the system type is generally used by one or more
`case' statements to select system-specifics. Shell wildcards can be
used to match a group of system types.
For example, an extra assembler code object file could be chosen,
giving access to a CPU cycle counter register. `$(CYCLE_OBJ)' in the
following would be used in a makefile to add the object to a program or
library.
AS_CASE([$host],
[alpha*-*-*], [CYCLE_OBJ=rpcc.o],
[i?86-*-*], [CYCLE_OBJ=rdtsc.o],
[CYCLE_OBJ=""]
)
AC_SUBST([CYCLE_OBJ])
`AC_CONFIG_LINKS' (*note Configuration Links::) is another good way
to select variant source files, for example optimized code for some
CPUs. The configured CPU type doesn't always indicate exact CPU types,
so some runtime capability checks may be necessary too.
case $host in
alpha*-*-*) AC_CONFIG_LINKS([dither.c:alpha/dither.c]) ;;
powerpc*-*-*) AC_CONFIG_LINKS([dither.c:powerpc/dither.c]) ;;
*-*-*) AC_CONFIG_LINKS([dither.c:generic/dither.c]) ;;
esac
The host system type can also be used to find cross-compilation tools
with `AC_CHECK_TOOL' (*note Generic Programs::).
The above examples all show `$host', since this is where the code is
going to run. Only rarely is it necessary to test `$build' (which is
where the build is being done).
Whenever you're tempted to use `$host' it's worth considering
whether some sort of probe would be better. New system types come along
periodically or previously missing features are added. Well-written
probes can adapt themselves to such things, but hard-coded lists of
names can't. Here are some guidelines,
* Availability of libraries and library functions should always be
checked by probing.
* Variant behavior of system calls is best identified with runtime
tests if possible, but bug workarounds or obscure difficulties
might have to be driven from `$host'.
* Assembler code is inevitably highly CPU-specific and is best
selected according to `$host_cpu'.
* Assembler variations like underscore prefix on globals or ELF
versus COFF type directives are however best determined by
probing, perhaps even examining the compiler output.
`$target' is for use by a package creating a compiler or similar.
For ordinary packages it's meaningless and should not be used. It
indicates what the created compiler should generate code for, if it can
cross-compile. `$target' generally selects various hard-coded CPU and
system conventions, since usually the compiler or tools under
construction themselves determine how the target works.
File: autoconf.info, Node: Site Configuration, Next: Running configure Scripts, Prev: Manual Configuration, Up: Top
15 Site Configuration
*********************
`configure' scripts support several kinds of local configuration
decisions. There are ways for users to specify where external software
packages are, include or exclude optional features, install programs
under modified names, and set default values for `configure' options.
* Menu:
* Help Formatting:: Customizing `configure --help'
* External Software:: Working with other optional software
* Package Options:: Selecting optional features
* Pretty Help Strings:: Formatting help string
* Option Checking:: Controlling checking of `configure' options
* Site Details:: Configuring site details
* Transforming Names:: Changing program names when installing
* Site Defaults:: Giving `configure' local defaults
File: autoconf.info, Node: Help Formatting, Next: External Software, Up: Site Configuration
15.1 Controlling Help Output
============================
Users consult `configure --help' to learn of configuration decisions
specific to your package. By default, `configure' breaks this output
into sections for each type of option; within each section, help
strings appear in the order `configure.ac' defines them:
Optional Features:
...
--enable-bar include bar
Optional Packages:
...
--with-foo use foo
-- Macro: AC_PRESERVE_HELP_ORDER
Request an alternate `--help' format, in which options of all
types appear together, in the order defined. Call this macro
before any `AC_ARG_ENABLE' or `AC_ARG_WITH'.
Optional Features and Packages:
...
--enable-bar include bar
--with-foo use foo
File: autoconf.info, Node: External Software, Next: Package Options, Prev: Help Formatting, Up: Site Configuration
15.2 Working With External Software
===================================
Some packages require, or can optionally use, other software packages
that are already installed. The user can give `configure' command line
options to specify which such external software to use. The options
have one of these forms:
--with-PACKAGE[=ARG]
--without-PACKAGE
For example, `--with-gnu-ld' means work with the GNU linker instead
of some other linker. `--with-x' means work with The X Window System.
The user can give an argument by following the package name with `='
and the argument. Giving an argument of `no' is for packages that are
used by default; it says to _not_ use the package. An argument that is
neither `yes' nor `no' could include a name or number of a version of
the other package, to specify more precisely which other package this
program is supposed to work with. If no argument is given, it defaults
to `yes'. `--without-PACKAGE' is equivalent to `--with-PACKAGE=no'.
Normally `configure' scripts complain about `--with-PACKAGE' options
that they do not support. *Note Option Checking::, for details, and
for how to override the defaults.
For each external software package that may be used, `configure.ac'
should call `AC_ARG_WITH' to detect whether the `configure' user asked
to use it. Whether each package is used or not by default, and which
arguments are valid, is up to you.
-- Macro: AC_ARG_WITH (PACKAGE, HELP-STRING, [ACTION-IF-GIVEN],
[ACTION-IF-NOT-GIVEN])
If the user gave `configure' the option `--with-PACKAGE' or
`--without-PACKAGE', run shell commands ACTION-IF-GIVEN. If
neither option was given, run shell commands ACTION-IF-NOT-GIVEN.
The name PACKAGE indicates another software package that this
program should work with. It should consist only of alphanumeric
characters, dashes, and dots.
The option's argument is available to the shell commands
ACTION-IF-GIVEN in the shell variable `withval', which is actually
just the value of the shell variable named `with_PACKAGE', with
any non-alphanumeric characters in PACKAGE changed into `_'. You
may use that variable instead, if you wish.
The argument HELP-STRING is a description of the option that looks
like this:
--with-readline support fancy command line editing
HELP-STRING may be more than one line long, if more detail is
needed. Just make sure the columns line up in `configure --help'.
Avoid tabs in the help string. The easiest way to provide the
proper leading whitespace is to format your HELP-STRING with the
macro `AS_HELP_STRING' (*note Pretty Help Strings::).
The following example shows how to use the `AC_ARG_WITH' macro in
a common situation. You want to let the user decide whether to
enable support for an external library (e.g., the readline
library); if the user specified neither `--with-readline' nor
`--without-readline', you want to enable support for readline only
if the library is available on the system.
AC_ARG_WITH([readline],
[AS_HELP_STRING([--with-readline],
[support fancy command line editing @<:@default=check@:>@])],
[],
[with_readline=check])
LIBREADLINE=
AS_IF([test "x$with_readline" != xno],
[AC_CHECK_LIB([readline], [main],
[AC_SUBST([LIBREADLINE], ["-lreadline -lncurses"])
AC_DEFINE([HAVE_LIBREADLINE], [1],
[Define if you have libreadline])
],
[if test "x$with_readline" != xcheck; then
AC_MSG_FAILURE(
[--with-readline was given, but test for readline failed])
fi
], -lncurses)])
The next example shows how to use `AC_ARG_WITH' to give the user
the possibility to enable support for the readline library, in
case it is still experimental and not well tested, and is
therefore disabled by default.
AC_ARG_WITH([readline],
[AS_HELP_STRING([--with-readline],
[enable experimental support for readline])],
[],
[with_readline=no])
LIBREADLINE=
AS_IF([test "x$with_readline" != xno],
[AC_CHECK_LIB([readline], [main],
[AC_SUBST([LIBREADLINE], ["-lreadline -lncurses"])
AC_DEFINE([HAVE_LIBREADLINE], [1],
[Define if you have libreadline])
],
[AC_MSG_FAILURE(
[--with-readline was given, but test for readline failed])],
[-lncurses])])
The last example shows how to use `AC_ARG_WITH' to give the user
the possibility to disable support for the readline library, given
that it is an important feature and that it should be enabled by
default.
AC_ARG_WITH([readline],
[AS_HELP_STRING([--without-readline],
[disable support for readline])],
[],
[with_readline=yes])
LIBREADLINE=
AS_IF([test "x$with_readline" != xno],
[AC_CHECK_LIB([readline], [main],
[AC_SUBST([LIBREADLINE], ["-lreadline -lncurses"])
AC_DEFINE([HAVE_LIBREADLINE], [1],
[Define if you have libreadline])
],
[AC_MSG_FAILURE(
[readline test failed (--without-readline to disable)])],
[-lncurses])])
These three examples can be easily adapted to the case where
`AC_ARG_ENABLE' should be preferred to `AC_ARG_WITH' (see *note
Package Options::).
File: autoconf.info, Node: Package Options, Next: Pretty Help Strings, Prev: External Software, Up: Site Configuration
15.3 Choosing Package Options
=============================
If a software package has optional compile-time features, the user can
give `configure' command line options to specify whether to compile
them. The options have one of these forms:
--enable-FEATURE[=ARG]
--disable-FEATURE
These options allow users to choose which optional features to build
and install. `--enable-FEATURE' options should never make a feature
behave differently or cause one feature to replace another. They
should only cause parts of the program to be built rather than left out.
The user can give an argument by following the feature name with `='
and the argument. Giving an argument of `no' requests that the feature
_not_ be made available. A feature with an argument looks like
`--enable-debug=stabs'. If no argument is given, it defaults to `yes'.
`--disable-FEATURE' is equivalent to `--enable-FEATURE=no'.
Normally `configure' scripts complain about `--enable-PACKAGE'
options that they do not support. *Note Option Checking::, for
details, and for how to override the defaults.
For each optional feature, `configure.ac' should call
`AC_ARG_ENABLE' to detect whether the `configure' user asked to include
it. Whether each feature is included or not by default, and which
arguments are valid, is up to you.
-- Macro: AC_ARG_ENABLE (FEATURE, HELP-STRING, [ACTION-IF-GIVEN],
[ACTION-IF-NOT-GIVEN])
If the user gave `configure' the option `--enable-FEATURE' or
`--disable-FEATURE', run shell commands ACTION-IF-GIVEN. If
neither option was given, run shell commands ACTION-IF-NOT-GIVEN.
The name FEATURE indicates an optional user-level facility. It
should consist only of alphanumeric characters, dashes, and dots.
The option's argument is available to the shell commands
ACTION-IF-GIVEN in the shell variable `enableval', which is
actually just the value of the shell variable named
`enable_FEATURE', with any non-alphanumeric characters in FEATURE
changed into `_'. You may use that variable instead, if you wish.
The HELP-STRING argument is like that of `AC_ARG_WITH' (*note
External Software::).
You should format your HELP-STRING with the macro `AS_HELP_STRING'
(*note Pretty Help Strings::).
See the examples suggested with the definition of `AC_ARG_WITH'
(*note External Software::) to get an idea of possible
applications of `AC_ARG_ENABLE'.
File: autoconf.info, Node: Pretty Help Strings, Next: Option Checking, Prev: Package Options, Up: Site Configuration
15.4 Making Your Help Strings Look Pretty
=========================================
Properly formatting the `help strings' which are used in `AC_ARG_WITH'
(*note External Software::) and `AC_ARG_ENABLE' (*note Package
Options::) can be challenging. Specifically, you want your own `help
strings' to line up in the appropriate columns of `configure --help'
just like the standard Autoconf `help strings' do. This is the purpose
of the `AS_HELP_STRING' macro.
-- Macro: AS_HELP_STRING (LEFT-HAND-SIDE, RIGHT-HAND-SIDE
[INDENT-COLUMN = `26'], [WRAP-COLUMN = `79'])
Expands into a help string that looks pretty when the user executes
`configure --help'. It is typically used in `AC_ARG_WITH' (*note
External Software::) or `AC_ARG_ENABLE' (*note Package Options::).
The following example makes this clearer.
AC_ARG_WITH([foo],
[AS_HELP_STRING([--with-foo],
[use foo (default is no)])],
[use_foo=$withval],
[use_foo=no])
Then the last few lines of `configure --help' appear like this:
--enable and --with options recognized:
--with-foo use foo (default is no)
Macro expansion is performed on the first argument. However, the
second argument of `AS_HELP_STRING' is treated as a whitespace
separated list of text to be reformatted, and is not subject to
macro expansion. Since it is not expanded, it should not be
double quoted. *Note Autoconf Language::, for a more detailed
explanation.
The `AS_HELP_STRING' macro is particularly helpful when the
LEFT-HAND-SIDE and/or RIGHT-HAND-SIDE are composed of macro
arguments, as shown in the following example. Be aware that
LEFT-HAND-SIDE may not expand to unbalanced quotes, although
quadrigraphs can be used.
AC_DEFUN([MY_ARG_WITH],
[AC_ARG_WITH(m4_translit([[$1]], [_], [-]),
[AS_HELP_STRING([--with-m4_translit([$1], [_], [-])],
[use $1 (default is $2)])],
[use_[]$1=$withval],
[use_[]$1=$2])])
MY_ARG_WITH([a_b], [no])
Here, the last few lines of `configure --help' will include:
--enable and --with options recognized:
--with-a-b use a_b (default is no)
The parameters INDENT-COLUMN and WRAP-COLUMN were introduced in
Autoconf 2.62. Generally, they should not be specified; they exist
for fine-tuning of the wrapping.
AS_HELP_STRING([--option], [description of option])
=> --option description of option
AS_HELP_STRING([--option], [description of option], [15], [30])
=> --option description of
=> option
File: autoconf.info, Node: Option Checking, Next: Site Details, Prev: Pretty Help Strings, Up: Site Configuration
15.5 Controlling Checking of `configure' Options
================================================
The `configure' script checks its command-line options against a list
of known options, like `--help' or `--config-cache'. An unknown option
ordinarily indicates a mistake by the user and `configure' halts with
an error. However, by default unknown `--with-PACKAGE' and
`--enable-FEATURE' options elicit only a warning, to support
configuring entire source trees.
Source trees often contain multiple packages with a top-level
`configure' script that uses the `AC_CONFIG_SUBDIRS' macro (*note
Subdirectories::). Because the packages generally support different
`--with-PACKAGE' and `--enable-FEATURE' options, the GNU Coding
Standards say they must accept unrecognized options without halting.
Even a warning message is undesirable here, so `AC_CONFIG_SUBDIRS'
automatically disables the warnings.
This default behavior may be modified in two ways. First, the
installer can invoke `configure --disable-option-checking' to disable
these warnings, or invoke `configure --enable-option-checking=fatal'
options to turn them into fatal errors, respectively. Second, the
maintainer can use `AC_DISABLE_OPTION_CHECKING'.
-- Macro: AC_DISABLE_OPTION_CHECKING
By default, disable warnings related to any unrecognized
`--with-PACKAGE' or `--enable-FEATURE' options. This is implied
by `AC_CONFIG_SUBDIRS'.
The installer can override this behavior by passing
`--enable-option-checking' (enable warnings) or
`--enable-option-checking=fatal' (enable errors) to `configure'.
File: autoconf.info, Node: Site Details, Next: Transforming Names, Prev: Option Checking, Up: Site Configuration
15.6 Configuring Site Details
=============================
Some software packages require complex site-specific information. Some
examples are host names to use for certain services, company names, and
email addresses to contact. Since some configuration scripts generated
by Metaconfig ask for such information interactively, people sometimes
wonder how to get that information in Autoconf-generated configuration
scripts, which aren't interactive.
Such site configuration information should be put in a file that is
edited _only by users_, not by programs. The location of the file can
either be based on the `prefix' variable, or be a standard location
such as the user's home directory. It could even be specified by an
environment variable. The programs should examine that file at
runtime, rather than at compile time. Runtime configuration is more
convenient for users and makes the configuration process simpler than
getting the information while configuring. *Note Variables for
Installation Directories: (standards)Directory Variables, for more
information on where to put data files.
File: autoconf.info, Node: Transforming Names, Next: Site Defaults, Prev: Site Details, Up: Site Configuration
15.7 Transforming Program Names When Installing
===============================================
Autoconf supports changing the names of programs when installing them.
In order to use these transformations, `configure.ac' must call the
macro `AC_ARG_PROGRAM'.
-- Macro: AC_ARG_PROGRAM
Place in output variable `program_transform_name' a sequence of
`sed' commands for changing the names of installed programs.
If any of the options described below are given to `configure',
program names are transformed accordingly. Otherwise, if
`AC_CANONICAL_TARGET' has been called and a `--target' value is
given, the target type followed by a dash is used as a prefix.
Otherwise, no program name transformation is done.
* Menu:
* Transformation Options:: `configure' options to transform names
* Transformation Examples:: Sample uses of transforming names
* Transformation Rules:: Makefile uses of transforming names
File: autoconf.info, Node: Transformation Options, Next: Transformation Examples, Up: Transforming Names
15.7.1 Transformation Options
-----------------------------
You can specify name transformations by giving `configure' these
command line options:
`--program-prefix=PREFIX'
prepend PREFIX to the names;
`--program-suffix=SUFFIX'
append SUFFIX to the names;
`--program-transform-name=EXPRESSION'
perform `sed' substitution EXPRESSION on the names.
File: autoconf.info, Node: Transformation Examples, Next: Transformation Rules, Prev: Transformation Options, Up: Transforming Names
15.7.2 Transformation Examples
------------------------------
These transformations are useful with programs that can be part of a
cross-compilation development environment. For example, a
cross-assembler running on a Sun 4 configured with
`--target=i960-vxworks' is normally installed as `i960-vxworks-as',
rather than `as', which could be confused with a native Sun 4 assembler.
You can force a program name to begin with `g', if you don't want
GNU programs installed on your system to shadow other programs with the
same name. For example, if you configure GNU `diff' with
`--program-prefix=g', then when you run `make install' it is installed
as `/usr/local/bin/gdiff'.
As a more sophisticated example, you could use
--program-transform-name='s/^/g/; s/^gg/g/; s/^gless/less/'
to prepend `g' to most of the program names in a source tree,
excepting those like `gdb' that already have one and those like `less'
and `lesskey' that aren't GNU programs. (That is assuming that you
have a source tree containing those programs that is set up to use this
feature.)
One way to install multiple versions of some programs simultaneously
is to append a version number to the name of one or both. For example,
if you want to keep Autoconf version 1 around for awhile, you can
configure Autoconf version 2 using `--program-suffix=2' to install the
programs as `/usr/local/bin/autoconf2', `/usr/local/bin/autoheader2',
etc. Nevertheless, pay attention that only the binaries are renamed,
therefore you'd have problems with the library files which might
overlap.
File: autoconf.info, Node: Transformation Rules, Prev: Transformation Examples, Up: Transforming Names
15.7.3 Transformation Rules
---------------------------
Here is how to use the variable `program_transform_name' in a
`Makefile.in':
PROGRAMS = cp ls rm
transform = @program_transform_name@
install:
for p in $(PROGRAMS); do \
$(INSTALL_PROGRAM) $$p $(DESTDIR)$(bindir)/`echo $$p | \
sed '$(transform)'`; \
done
uninstall:
for p in $(PROGRAMS); do \
rm -f $(DESTDIR)$(bindir)/`echo $$p | sed '$(transform)'`; \
done
It is guaranteed that `program_transform_name' is never empty, and
that there are no useless separators. Therefore you may safely embed
`program_transform_name' within a sed program using `;':
transform = @program_transform_name@
transform_exe = s/$(EXEEXT)$$//;$(transform);s/$$/$(EXEEXT)/
Whether to do the transformations on documentation files (Texinfo or
`man') is a tricky question; there seems to be no perfect answer, due
to the several reasons for name transforming. Documentation is not
usually particular to a specific architecture, and Texinfo files do not
conflict with system documentation. But they might conflict with
earlier versions of the same files, and `man' pages sometimes do
conflict with system documentation. As a compromise, it is probably
best to do name transformations on `man' pages but not on Texinfo
manuals.
File: autoconf.info, Node: Site Defaults, Prev: Transforming Names, Up: Site Configuration
15.8 Setting Site Defaults
==========================
Autoconf-generated `configure' scripts allow your site to provide
default values for some configuration values. You do this by creating
site- and system-wide initialization files.
If the environment variable `CONFIG_SITE' is set, `configure' uses
its value as the name of a shell script to read. Otherwise, it reads
the shell script `PREFIX/share/config.site' if it exists, then
`PREFIX/etc/config.site' if it exists. Thus, settings in
machine-specific files override those in machine-independent ones in
case of conflict.
Site files can be arbitrary shell scripts, but only certain kinds of
code are really appropriate to be in them. Because `configure' reads
any cache file after it has read any site files, a site file can define
a default cache file to be shared between all Autoconf-generated
`configure' scripts run on that system (*note Cache Files::). If you
set a default cache file in a site file, it is a good idea to also set
the output variable `CC' in that site file, because the cache file is
only valid for a particular compiler, but many systems have several
available.
You can examine or override the value set by a command line option to
`configure' in a site file; options set shell variables that have the
same names as the options, with any dashes turned into underscores.
The exceptions are that `--without-' and `--disable-' options are like
giving the corresponding `--with-' or `--enable-' option and the value
`no'. Thus, `--cache-file=localcache' sets the variable `cache_file'
to the value `localcache'; `--enable-warnings=no' or
`--disable-warnings' sets the variable `enable_warnings' to the value
`no'; `--prefix=/usr' sets the variable `prefix' to the value `/usr';
etc.
Site files are also good places to set default values for other
output variables, such as `CFLAGS', if you need to give them non-default
values: anything you would normally do, repetitively, on the command
line. If you use non-default values for PREFIX or EXEC_PREFIX
(wherever you locate the site file), you can set them in the site file
if you specify it with the `CONFIG_SITE' environment variable.
You can set some cache values in the site file itself. Doing this is
useful if you are cross-compiling, where it is impossible to check
features that require running a test program. You could "prime the
cache" by setting those values correctly for that system in
`PREFIX/etc/config.site'. To find out the names of the cache variables
you need to set, look for shell variables with `_cv_' in their names in
the affected `configure' scripts, or in the Autoconf M4 source code for
those macros.
The cache file is careful to not override any variables set in the
site files. Similarly, you should not override command-line options in
the site files. Your code should check that variables such as `prefix'
and `cache_file' have their default values (as set near the top of
`configure') before changing them.
Here is a sample file `/usr/share/local/gnu/share/config.site'. The
command `configure --prefix=/usr/share/local/gnu' would read this file
(if `CONFIG_SITE' is not set to a different file).
# /usr/share/local/gnu/share/config.site for configure
#
# Change some defaults.
test "$prefix" = NONE && prefix=/usr/share/local/gnu
test "$exec_prefix" = NONE && exec_prefix=/usr/local/gnu
test "$sharedstatedir" = '${prefix}/com' && sharedstatedir=/var
test "$localstatedir" = '${prefix}/var' && localstatedir=/var
# Give Autoconf 2.x generated configure scripts a shared default
# cache file for feature test results, architecture-specific.
if test "$cache_file" = /dev/null; then
cache_file="$prefix/var/config.cache"
# A cache file is only valid for one C compiler.
CC=gcc
fi
Another use of `config.site' is for priming the directory variables
in a manner consistent with the Filesystem Hierarchy Standard (FHS).
Once the following file is installed at `/usr/share/config.site', a
user can execute simply `./configure --prefix=/usr' to get all the
directories chosen in the locations recommended by FHS.
# /usr/share/config.site for FHS defaults when installing below /usr,
# and the respective settings were not changed on the command line.
if test "$prefix" = /usr; then
test "$sysconfdir" = '${prefix}/etc' && sysconfdir=/etc
test "$sharedstatedir" = '${prefix}/com' && sharedstatedir=/var
test "$localstatedir" = '${prefix}/var' && localstatedir=/var
fi
Likewise, on platforms where 64-bit libraries are built by default,
then installed in `/usr/local/lib64' instead of `/usr/local/lib', it is
appropriate to install `/usr/local/share/config.site':
# /usr/local/share/config.site for platforms that prefer
# the directory /usr/local/lib64 over /usr/local/lib.
test "$libdir" = '${exec_prefix}/lib' && libdir='${exec_prefix}/lib64'
File: autoconf.info, Node: Running configure Scripts, Next: config.status Invocation, Prev: Site Configuration, Up: Top
16 Running `configure' Scripts
******************************
Below are instructions on how to configure a package that uses a
`configure' script, suitable for inclusion as an `INSTALL' file in the
package. A plain-text version of `INSTALL' which you may use comes
with Autoconf.
* Menu:
* Basic Installation:: Instructions for typical cases
* Compilers and Options:: Selecting compilers and optimization
* Multiple Architectures:: Compiling for multiple architectures at once
* Installation Names:: Installing in different directories
* Optional Features:: Selecting optional features
* Particular Systems:: Particular systems
* System Type:: Specifying the system type
* Sharing Defaults:: Setting site-wide defaults for `configure'
* Defining Variables:: Specifying the compiler etc.
* configure Invocation:: Changing how `configure' runs
File: autoconf.info, Node: Basic Installation, Next: Compilers and Options, Up: Running configure Scripts
16.1 Basic Installation
=======================
Briefly, the shell commands `./configure; make; make install' should
configure, build, and install this package. The following
more-detailed instructions are generic; see the `README' file for
instructions specific to this package. More recommendations for GNU
packages can be found in *note Makefile Conventions:
(standards)Makefile Conventions.
The `configure' shell script attempts to guess correct values for
various system-dependent variables used during compilation. It uses
those values to create a `Makefile' in each directory of the package.
It may also create one or more `.h' files containing system-dependent
definitions. Finally, it creates a shell script `config.status' that
you can run in the future to recreate the current configuration, and a
file `config.log' containing compiler output (useful mainly for
debugging `configure').
It can also use an optional file (typically called `config.cache'
and enabled with `--cache-file=config.cache' or simply `-C') that saves
the results of its tests to speed up reconfiguring. Caching is
disabled by default to prevent problems with accidental use of stale
cache files.
If you need to do unusual things to compile the package, please try
to figure out how `configure' could check whether to do them, and mail
diffs or instructions to the address given in the `README' so they can
be considered for the next release. If you are using the cache, and at
some point `config.cache' contains results you don't want to keep, you
may remove or edit it.
The file `configure.ac' (or `configure.in') is used to create
`configure' by a program called `autoconf'. You need `configure.ac' if
you want to change it or regenerate `configure' using a newer version
of `autoconf'.
The simplest way to compile this package is:
1. `cd' to the directory containing the package's source code and type
`./configure' to configure the package for your system.
Running `configure' might take a while. While running, it prints
some messages telling which features it is checking for.
2. Type `make' to compile the package.
3. Optionally, type `make check' to run any self-tests that come with
the package, generally using the just-built uninstalled binaries.
4. Type `make install' to install the programs and any data files and
documentation. When installing into a prefix owned by root, it is
recommended that the package be configured and built as a regular
user, and only the `make install' phase executed with root
privileges.
5. Optionally, type `make installcheck' to repeat any self-tests, but
this time using the binaries in their final installed location.
6. You can remove the program binaries and object files from the
source code directory by typing `make clean'. To also remove the
files that `configure' created (so you can compile the package for
a different kind of computer), type `make distclean'. There is
also a `make maintainer-clean' target, but that is intended mainly
for the package's developers. If you use it, you may have to get
all sorts of other programs in order to regenerate files that came
with the distribution.
7. Often, you can also type `make uninstall' to remove the installed
files again. In practice, not all packages have tested that
uninstallation works correctly, even though it is required by the
GNU Coding Standards.
8. Some packages, particularly those that use Automake, provide `make
distcheck', which can by used by developers to test that all other
targets like `make install' and `make uninstall' work correctly.
This target is generally not run by end users.
File: autoconf.info, Node: Compilers and Options, Next: Multiple Architectures, Prev: Basic Installation, Up: Running configure Scripts
16.2 Compilers and Options
==========================
Some systems require unusual options for compilation or linking that the
`configure' script does not know about. Run `./configure --help' for
details on some of the pertinent environment variables.
You can give `configure' initial values for configuration parameters
by setting variables in the command line or in the environment. Here
is an example:
./configure CC=c99 CFLAGS=-g LIBS=-lposix
*Note Defining Variables::, for more details.
File: autoconf.info, Node: Multiple Architectures, Next: Installation Names, Prev: Compilers and Options, Up: Running configure Scripts
16.3 Compiling For Multiple Architectures
=========================================
You can compile the package for more than one kind of computer at the
same time, by placing the object files for each architecture in their
own directory. To do this, you can use GNU `make'. `cd' to the
directory where you want the object files and executables to go and run
the `configure' script. `configure' automatically checks for the
source code in the directory that `configure' is in and in `..'. This
is known as a "VPATH" build.
With a non-GNU `make', it is safer to compile the package for one
architecture at a time in the source code directory. After you have
installed the package for one architecture, use `make distclean' before
reconfiguring for another architecture.
On MacOS X 10.5 and later systems, you can create libraries and
executables that work on multiple system types--known as "fat" or
"universal" binaries--by specifying multiple `-arch' options to the
compiler but only a single `-arch' option to the preprocessor. Like
this:
./configure CC="gcc -arch i386 -arch x86_64 -arch ppc -arch ppc64" \
CXX="g++ -arch i386 -arch x86_64 -arch ppc -arch ppc64" \
CPP="gcc -E" CXXCPP="g++ -E"
This is not guaranteed to produce working output in all cases, you
may have to build one architecture at a time and combine the results
using the `lipo' tool if you have problems.
File: autoconf.info, Node: Installation Names, Next: Optional Features, Prev: Multiple Architectures, Up: Running configure Scripts
16.4 Installation Names
=======================
By default, `make install' installs the package's commands under
`/usr/local/bin', include files under `/usr/local/include', etc. You
can specify an installation prefix other than `/usr/local' by giving
`configure' the option `--prefix=PREFIX', where PREFIX must be an
absolute path.
You can specify separate installation prefixes for
architecture-specific files and architecture-independent files. If you
pass the option `--exec-prefix=PREFIX' to `configure', the package uses
PREFIX as the prefix for installing programs and libraries.
Documentation and other data files still use the regular prefix.
In addition, if you use an unusual directory layout you can give
options like `--bindir=DIR' to specify different values for particular
kinds of files. Run `configure --help' for a list of the directories
you can set and what kinds of files go in them. In general, the
default for these options is expressed in terms of `${prefix}', so that
specifying just `--prefix' will affect all of the other directory
specifications.
The most portable way to affect installation locations is to pass the
correct locations to `configure'; however, many packages provide one or
both of the following shortcuts of passing variable assignments to the
`make install' command line to change installation locations without
having to reconfigure or recompile.
The first method involves providing an override variable for each
affected directory. For example, `make install
prefix=/path/to/alternate' will choose an alternate location, as well as
influencing all other directory configuration variables that were
expressed in terms of `${prefix}' (or, put another way, all directories
specified during `configure' but not in terms of the common prefix must
each be overridden at install time for the entire installation to be
relocated). The approach of makefile variable overrides for each
directory variable is required by the GNU Coding Standards, and ideally
causes no recompilation. However, some platforms have known
limitations with the semantics of shared libraries that end up
requiring recompilation when using this method, particularly noticeable
in packages that use GNU Libtool.
The second method involves providing the `DESTDIR' variable. For
example, `make install DESTDIR=/path/to/alternate' will prepend
`/path/to/alternate' before all installation paths. The approach of
`DESTDIR' overrides is not required by the GNU Coding Standards, and
does not work on platforms that have drive letters. On the other hand,
it does better at avoiding recompilation issues, and works well even
when some directory options were not specified in terms of `${prefix}'
at `configure' time. For packages which support `DESTDIR', the
variable should remain undefined during `configure' and `make all', and
only be specified during `make install'.
File: autoconf.info, Node: Optional Features, Next: Particular Systems, Prev: Installation Names, Up: Running configure Scripts
16.5 Optional Features
======================
If the package supports it, you can cause programs to be installed with
an extra prefix or suffix on their names by giving `configure' the
option `--program-prefix=PREFIX' or `--program-suffix=SUFFIX'.
Some packages pay attention to `--enable-FEATURE' options to
`configure', where FEATURE indicates an optional part of the package.
They may also pay attention to `--with-PACKAGE' options, where PACKAGE
is something like `gnu-as' or `x' (for the X Window System). The
`README' should mention any `--enable-' and `--with-' options that the
package recognizes.
For packages that use the X Window System, `configure' can usually
find the X include and library files automatically, but if it doesn't,
you can use the `configure' options `--x-includes=DIR' and
`--x-libraries=DIR' to specify their locations.
Some packages offer the ability to configure how verbose the
execution of `make' will be. For these packages, running `./configure
--enable-silent-rules' sets the default to minimal output, which can be
overridden with `make V=1'; while running `./configure
--disable-silent-rules' sets the default to verbose, which can be
overridden with `make V=0'.
File: autoconf.info, Node: Particular Systems, Next: System Type, Prev: Optional Features, Up: Running configure Scripts
16.6 Particular systems
=======================
On HP-UX, the default C compiler is not ANSI C compatible. If GNU CC is
not installed, it is recommended to use the following options in order
to use an ANSI C compiler:
./configure CC="cc -Ae -D_XOPEN_SOURCE=500"
and if that doesn't work, install pre-built binaries of GCC for HP-UX.
On OSF/1 a.k.a. Tru64, some versions of the default C compiler cannot
parse its `' header file. The option `-nodtk' can be used as
a workaround. If GNU CC is not installed, it is therefore recommended
to try
./configure CC="cc"
and if that doesn't work, try
./configure CC="cc -nodtk"
On Solaris, don't put `/usr/ucb' early in your `PATH'. This
directory contains several dysfunctional programs; working variants of
these programs are available in `/usr/bin'. So, if you need `/usr/ucb'
in your `PATH', put it _after_ `/usr/bin'.
On Haiku, software installed for all users goes in `/boot/common',
not `/usr/local'. It is recommended to use the following options:
./configure --prefix=/boot/common
File: autoconf.info, Node: System Type, Next: Sharing Defaults, Prev: Particular Systems, Up: Running configure Scripts
16.7 Specifying the System Type
===============================
There may be some features `configure' cannot figure out automatically,
but needs to determine by the type of machine the package will run on.
Usually, assuming the package is built to be run on the _same_
architectures, `configure' can figure that out, but if it prints a
message saying it cannot guess the machine type, give it the
`--build=TYPE' option. TYPE can either be a short name for the system
type, such as `sun4', or a canonical name which has the form:
CPU-COMPANY-SYSTEM
where SYSTEM can have one of these forms:
OS
KERNEL-OS
See the file `config.sub' for the possible values of each field. If
`config.sub' isn't included in this package, then this package doesn't
need to know the machine type.
If you are _building_ compiler tools for cross-compiling, you should
use the option `--target=TYPE' to select the type of system they will
produce code for.
If you want to _use_ a cross compiler, that generates code for a
platform different from the build platform, you should specify the
"host" platform (i.e., that on which the generated programs will
eventually be run) with `--host=TYPE'.
File: autoconf.info, Node: Sharing Defaults, Next: Defining Variables, Prev: System Type, Up: Running configure Scripts
16.8 Sharing Defaults
=====================
If you want to set default values for `configure' scripts to share, you
can create a site shell script called `config.site' that gives default
values for variables like `CC', `cache_file', and `prefix'.
`configure' looks for `PREFIX/share/config.site' if it exists, then
`PREFIX/etc/config.site' if it exists. Or, you can set the
`CONFIG_SITE' environment variable to the location of the site script.
A warning: not all `configure' scripts look for a site script.
File: autoconf.info, Node: Defining Variables, Next: configure Invocation, Prev: Sharing Defaults, Up: Running configure Scripts
16.9 Defining Variables
=======================
Variables not defined in a site shell script can be set in the
environment passed to `configure'. However, some packages may run
configure again during the build, and the customized values of these
variables may be lost. In order to avoid this problem, you should set
them in the `configure' command line, using `VAR=value'. For example:
./configure CC=/usr/local2/bin/gcc
causes the specified `gcc' to be used as the C compiler (unless it is
overridden in the site shell script).
Unfortunately, this technique does not work for `CONFIG_SHELL' due to
an Autoconf bug. Until the bug is fixed you can use this workaround:
CONFIG_SHELL=/bin/bash /bin/bash ./configure CONFIG_SHELL=/bin/bash
File: autoconf.info, Node: configure Invocation, Prev: Defining Variables, Up: Running configure Scripts
16.10 `configure' Invocation
============================
`configure' recognizes the following options to control how it operates.
`--help'
`-h'
Print a summary of all of the options to `configure', and exit.
`--help=short'
`--help=recursive'
Print a summary of the options unique to this package's
`configure', and exit. The `short' variant lists options used
only in the top level, while the `recursive' variant lists options
also present in any nested packages.
`--version'
`-V'
Print the version of Autoconf used to generate the `configure'
script, and exit.
`--cache-file=FILE'
Enable the cache: use and save the results of the tests in FILE,
traditionally `config.cache'. FILE defaults to `/dev/null' to
disable caching.
`--config-cache'
`-C'
Alias for `--cache-file=config.cache'.
`--quiet'
`--silent'
`-q'
Do not print messages saying which checks are being made. To
suppress all normal output, redirect it to `/dev/null' (any error
messages will still be shown).
`--srcdir=DIR'
Look for the package's source code in directory DIR. Usually
`configure' can determine that directory automatically.
`--prefix=DIR'
Use DIR as the installation prefix. *note Installation Names::
for more details, including other options available for fine-tuning
the installation locations.
`--no-create'
`-n'
Run the configure checks, but stop before creating any output
files.
`configure' also accepts some other, not widely useful, options. Run
`configure --help' for more details.
File: autoconf.info, Node: config.status Invocation, Next: Obsolete Constructs, Prev: Running configure Scripts, Up: Top
17 config.status Invocation
***************************
The `configure' script creates a file named `config.status', which
actually configures, "instantiates", the template files. It also
records the configuration options that were specified when the package
was last configured in case reconfiguring is needed.
Synopsis:
./config.status [OPTION]... [TAG]...
It configures each TAG; if none are specified, all the templates are
instantiated. A TAG refers to a file or other tag associated with a
configuration action, as specified by an `AC_CONFIG_ITEMS' macro (*note
Configuration Actions::). The files must be specified without their
dependencies, as in
./config.status foobar
not
./config.status foobar:foo.in:bar.in
The supported options are:
`--help'
`-h'
Print a summary of the command line options, the list of the
template files, and exit.
`--version'
`-V'
Print the version number of Autoconf and the configuration
settings, and exit.
`--silent'
`--quiet'
`-q'
Do not print progress messages.
`--debug'
`-d'
Don't remove the temporary files.
`--file=FILE[:TEMPLATE]'
Require that FILE be instantiated as if
`AC_CONFIG_FILES(FILE:TEMPLATE)' was used. Both FILE and TEMPLATE
may be `-' in which case the standard output and/or standard
input, respectively, is used. If a TEMPLATE file name is
relative, it is first looked for in the build tree, and then in
the source tree. *Note Configuration Actions::, for more details.
This option and the following ones provide one way for separately
distributed packages to share the values computed by `configure'.
Doing so can be useful if some of the packages need a superset of
the features that one of them, perhaps a common library, does.
These options allow a `config.status' file to create files other
than the ones that its `configure.ac' specifies, so it can be used
for a different package, or for extracting a subset of values.
For example,
echo '@CC@' | ./config.status --file=-
provides the value of `@CC@' on standard output.
`--header=FILE[:TEMPLATE]'
Same as `--file' above, but with `AC_CONFIG_HEADERS'.
`--recheck'
Ask `config.status' to update itself and exit (no instantiation).
This option is useful if you change `configure', so that the
results of some tests might be different from the previous run.
The `--recheck' option reruns `configure' with the same arguments
you used before, plus the `--no-create' option, which prevents
`configure' from running `config.status' and creating `Makefile'
and other files, and the `--no-recursion' option, which prevents
`configure' from running other `configure' scripts in
subdirectories. (This is so other Make rules can run
`config.status' when it changes; *note Automatic Remaking::, for
an example).
`config.status' checks several optional environment variables that
can alter its behavior:
-- Variable: CONFIG_SHELL
The shell with which to run `configure' for the `--recheck'
option. It must be Bourne-compatible. The default is a shell that
supports `LINENO' if available, and `/bin/sh' otherwise. Invoking
`configure' by hand bypasses this setting, so you may need to use
a command like `CONFIG_SHELL=/bin/bash /bin/bash ./configure' to
insure that the same shell is used everywhere. The absolute name
of the shell should be passed.
-- Variable: CONFIG_STATUS
The file name to use for the shell script that records the
configuration. The default is `./config.status'. This variable is
useful when one package uses parts of another and the `configure'
scripts shouldn't be merged because they are maintained separately.
You can use `./config.status' in your makefiles. For example, in
the dependencies given above (*note Automatic Remaking::),
`config.status' is run twice when `configure.ac' has changed. If that
bothers you, you can make each run only regenerate the files for that
rule:
config.h: stamp-h
stamp-h: config.h.in config.status
./config.status config.h
echo > stamp-h
Makefile: Makefile.in config.status
./config.status Makefile
The calling convention of `config.status' has changed; see *note
Obsolete config.status Use::, for details.
File: autoconf.info, Node: Obsolete Constructs, Next: Using Autotest, Prev: config.status Invocation, Up: Top
18 Obsolete Constructs
**********************
Autoconf changes, and throughout the years some constructs have been
obsoleted. Most of the changes involve the macros, but in some cases
the tools themselves, or even some concepts, are now considered
obsolete.
You may completely skip this chapter if you are new to Autoconf. Its
intention is mainly to help maintainers updating their packages by
understanding how to move to more modern constructs.
* Menu:
* Obsolete config.status Use:: Obsolete convention for `config.status'
* acconfig Header:: Additional entries in `config.h.in'
* autoupdate Invocation:: Automatic update of `configure.ac'
* Obsolete Macros:: Backward compatibility macros
* Autoconf 1:: Tips for upgrading your files
* Autoconf 2.13:: Some fresher tips
File: autoconf.info, Node: Obsolete config.status Use, Next: acconfig Header, Up: Obsolete Constructs
18.1 Obsolete `config.status' Invocation
========================================
`config.status' now supports arguments to specify the files to
instantiate; see *note config.status Invocation::, for more details.
Before, environment variables had to be used.
-- Variable: CONFIG_COMMANDS
The tags of the commands to execute. The default is the arguments
given to `AC_OUTPUT' and `AC_CONFIG_COMMANDS' in `configure.ac'.
-- Variable: CONFIG_FILES
The files in which to perform `@VARIABLE@' substitutions. The
default is the arguments given to `AC_OUTPUT' and
`AC_CONFIG_FILES' in `configure.ac'.
-- Variable: CONFIG_HEADERS
The files in which to substitute C `#define' statements. The
default is the arguments given to `AC_CONFIG_HEADERS'; if that
macro was not called, `config.status' ignores this variable.
-- Variable: CONFIG_LINKS
The symbolic links to establish. The default is the arguments
given to `AC_CONFIG_LINKS'; if that macro was not called,
`config.status' ignores this variable.
In *note config.status Invocation::, using this old interface, the
example would be:
config.h: stamp-h
stamp-h: config.h.in config.status
CONFIG_COMMANDS= CONFIG_LINKS= CONFIG_FILES= \
CONFIG_HEADERS=config.h ./config.status
echo > stamp-h
Makefile: Makefile.in config.status
CONFIG_COMMANDS= CONFIG_LINKS= CONFIG_HEADERS= \
CONFIG_FILES=Makefile ./config.status
(If `configure.ac' does not call `AC_CONFIG_HEADERS', there is no need
to set `CONFIG_HEADERS' in the `make' rules. Equally for
`CONFIG_COMMANDS', etc.)
File: autoconf.info, Node: acconfig Header, Next: autoupdate Invocation, Prev: Obsolete config.status Use, Up: Obsolete Constructs
18.2 `acconfig.h'
=================
In order to produce `config.h.in', `autoheader' needs to build or to
find templates for each symbol. Modern releases of Autoconf use
`AH_VERBATIM' and `AH_TEMPLATE' (*note Autoheader Macros::), but in
older releases a file, `acconfig.h', contained the list of needed
templates. `autoheader' copied comments and `#define' and `#undef'
statements from `acconfig.h' in the current directory, if present.
This file used to be mandatory if you `AC_DEFINE' any additional
symbols.
Modern releases of Autoconf also provide `AH_TOP' and `AH_BOTTOM' if
you need to prepend/append some information to `config.h.in'. Ancient
versions of Autoconf had a similar feature: if `./acconfig.h' contains
the string `@TOP@', `autoheader' copies the lines before the line
containing `@TOP@' into the top of the file that it generates.
Similarly, if `./acconfig.h' contains the string `@BOTTOM@',
`autoheader' copies the lines after that line to the end of the file it
generates. Either or both of those strings may be omitted. An even
older alternate way to produce the same effect in ancient versions of
Autoconf is to create the files `FILE.top' (typically `config.h.top')
and/or `FILE.bot' in the current directory. If they exist,
`autoheader' copies them to the beginning and end, respectively, of its
output.
In former versions of Autoconf, the files used in preparing a
software package for distribution were:
configure.ac --. .------> autoconf* -----> configure
+---+
[aclocal.m4] --+ `---.
[acsite.m4] ---' |
+--> [autoheader*] -> [config.h.in]
[acconfig.h] ----. |
+-----'
[config.h.top] --+
[config.h.bot] --'
Using only the `AH_' macros, `configure.ac' should be
self-contained, and should not depend upon `acconfig.h' etc.
File: autoconf.info, Node: autoupdate Invocation, Next: Obsolete Macros, Prev: acconfig Header, Up: Obsolete Constructs
18.3 Using `autoupdate' to Modernize `configure.ac'
===================================================
The `autoupdate' program updates a `configure.ac' file that calls
Autoconf macros by their old names to use the current macro names. In
version 2 of Autoconf, most of the macros were renamed to use a more
uniform and descriptive naming scheme. *Note Macro Names::, for a
description of the new scheme. Although the old names still work
(*note Obsolete Macros::, for a list of the old macros and the
corresponding new names), you can make your `configure.ac' files more
readable and make it easier to use the current Autoconf documentation
if you update them to use the new macro names.
If given no arguments, `autoupdate' updates `configure.ac', backing
up the original version with the suffix `~' (or the value of the
environment variable `SIMPLE_BACKUP_SUFFIX', if that is set). If you
give `autoupdate' an argument, it reads that file instead of
`configure.ac' and writes the updated file to the standard output.
`autoupdate' accepts the following options:
`--help'
`-h'
Print a summary of the command line options and exit.
`--version'
`-V'
Print the version number of Autoconf and exit.
`--verbose'
`-v'
Report processing steps.
`--debug'
`-d'
Don't remove the temporary files.
`--force'
`-f'
Force the update even if the file has not changed. Disregard the
cache.
`--include=DIR'
`-I DIR'
Also look for input files in DIR. Multiple invocations accumulate.
Directories are browsed from last to first.
`--prepend-include=DIR'
`-B DIR'
Prepend directory DIR to the search path. This is used to include
the language-specific files before any third-party macros.
File: autoconf.info, Node: Obsolete Macros, Next: Autoconf 1, Prev: autoupdate Invocation, Up: Obsolete Constructs
18.4 Obsolete Macros
====================
Several macros are obsoleted in Autoconf, for various reasons (typically
they failed to quote properly, couldn't be extended for more recent
issues, etc.). They are still supported, but deprecated: their use
should be avoided.
During the jump from Autoconf version 1 to version 2, most of the
macros were renamed to use a more uniform and descriptive naming scheme,
but their signature did not change. *Note Macro Names::, for a
description of the new naming scheme. Below, if there is just the
mapping from old names to new names for these macros, the reader is
invited to refer to the definition of the new macro for the signature
and the description.
-- Macro: AC_AIX
This macro is a platform-specific subset of
`AC_USE_SYSTEM_EXTENSIONS' (*note AC_USE_SYSTEM_EXTENSIONS::).
-- Macro: AC_ALLOCA
Replaced by `AC_FUNC_ALLOCA' (*note AC_FUNC_ALLOCA::).
-- Macro: AC_ARG_ARRAY
Removed because of limited usefulness.
-- Macro: AC_C_CROSS
This macro is obsolete; it does nothing.
-- Macro: AC_C_LONG_DOUBLE
If the C compiler supports a working `long double' type with more
range or precision than the `double' type, define
`HAVE_LONG_DOUBLE'.
You should use `AC_TYPE_LONG_DOUBLE' or
`AC_TYPE_LONG_DOUBLE_WIDER' instead. *Note Particular Types::.
-- Macro: AC_CANONICAL_SYSTEM
Determine the system type and set output variables to the names of
the canonical system types. *Note Canonicalizing::, for details
about the variables this macro sets.
The user is encouraged to use either `AC_CANONICAL_BUILD', or
`AC_CANONICAL_HOST', or `AC_CANONICAL_TARGET', depending on the
needs. Using `AC_CANONICAL_TARGET' is enough to run the two other
macros (*note Canonicalizing::).
-- Macro: AC_CHAR_UNSIGNED
Replaced by `AC_C_CHAR_UNSIGNED' (*note AC_C_CHAR_UNSIGNED::).
-- Macro: AC_CHECK_TYPE (TYPE, DEFAULT)
Autoconf, up to 2.13, used to provide this version of
`AC_CHECK_TYPE', deprecated because of its flaws. First, although
it is a member of the `CHECK' clan, it does more than just
checking. Secondly, missing types are defined using `#define',
not `typedef', and this can lead to problems in the case of
pointer types.
This use of `AC_CHECK_TYPE' is obsolete and discouraged; see *note
Generic Types::, for the description of the current macro.
If the type TYPE is not defined, define it to be the C (or C++)
builtin type DEFAULT, e.g., `short int' or `unsigned int'.
This macro is equivalent to:
AC_CHECK_TYPE([TYPE], [],
[AC_DEFINE_UNQUOTED([TYPE], [DEFAULT],
[Define to `DEFAULT'
if does not define.])])
In order to keep backward compatibility, the two versions of
`AC_CHECK_TYPE' are implemented, selected using these heuristics:
1. If there are three or four arguments, the modern version is
used.
2. If the second argument appears to be a C or C++ type, then the
obsolete version is used. This happens if the argument is a
C or C++ _builtin_ type or a C identifier ending in `_t',
optionally followed by one of `[(* ' and then by a string of
zero or more characters taken from the set `[]()* _a-zA-Z0-9'.
3. If the second argument is spelled with the alphabet of valid
C and C++ types, the user is warned and the modern version is
used.
4. Otherwise, the modern version is used.
You are encouraged either to use a valid builtin type, or to use
the equivalent modern code (see above), or better yet, to use
`AC_CHECK_TYPES' together with
#ifndef HAVE_LOFF_T
typedef loff_t off_t;
#endif
-- Macro: AC_CHECKING (FEATURE-DESCRIPTION)
Same as
AC_MSG_NOTICE([checking FEATURE-DESCRIPTION...]
*Note AC_MSG_NOTICE::.
-- Macro: AC_COMPILE_CHECK (ECHO-TEXT, INCLUDES, FUNCTION-BODY,
ACTION-IF-TRUE, [ACTION-IF-FALSE])
This is an obsolete version of `AC_TRY_COMPILE' itself replaced by
`AC_COMPILE_IFELSE' (*note Running the Compiler::), with the
addition that it prints `checking for ECHO-TEXT' to the standard
output first, if ECHO-TEXT is non-empty. Use `AC_MSG_CHECKING'
and `AC_MSG_RESULT' instead to print messages (*note Printing
Messages::).
-- Macro: AC_CONST
Replaced by `AC_C_CONST' (*note AC_C_CONST::).
-- Macro: AC_CROSS_CHECK
Same as `AC_C_CROSS', which is obsolete too, and does nothing
`:-)'.
-- Macro: AC_CYGWIN
Check for the Cygwin environment in which case the shell variable
`CYGWIN' is set to `yes'. Don't use this macro, the dignified
means to check the nature of the host is using `AC_CANONICAL_HOST'
(*note Canonicalizing::). As a matter of fact this macro is
defined as:
AC_REQUIRE([AC_CANONICAL_HOST])[]dnl
case $host_os in
*cygwin* ) CYGWIN=yes;;
* ) CYGWIN=no;;
esac
Beware that the variable `CYGWIN' has a special meaning when
running Cygwin, and should not be changed. That's yet another
reason not to use this macro.
-- Macro: AC_DECL_SYS_SIGLIST
Same as:
AC_CHECK_DECLS([sys_siglist], [], [],
[#include
/* NetBSD declares sys_siglist in unistd.h. */
#ifdef HAVE_UNISTD_H
# include
#endif
])
*Note AC_CHECK_DECLS::.
-- Macro: AC_DECL_YYTEXT
Does nothing, now integrated in `AC_PROG_LEX' (*note
AC_PROG_LEX::).
-- Macro: AC_DIR_HEADER
Like calling `AC_FUNC_CLOSEDIR_VOID' (*note
AC_FUNC_CLOSEDIR_VOID::) and `AC_HEADER_DIRENT' (*note
AC_HEADER_DIRENT::), but defines a different set of C preprocessor
macros to indicate which header file is found:
Header Old Symbol New Symbol
`dirent.h' `DIRENT' `HAVE_DIRENT_H'
`sys/ndir.h' `SYSNDIR' `HAVE_SYS_NDIR_H'
`sys/dir.h' `SYSDIR' `HAVE_SYS_DIR_H'
`ndir.h' `NDIR' `HAVE_NDIR_H'
-- Macro: AC_DYNIX_SEQ
If on DYNIX/ptx, add `-lseq' to output variable `LIBS'. This
macro used to be defined as
AC_CHECK_LIB([seq], [getmntent], [LIBS="-lseq $LIBS"])
now it is just `AC_FUNC_GETMNTENT' (*note AC_FUNC_GETMNTENT::).
-- Macro: AC_EXEEXT
Defined the output variable `EXEEXT' based on the output of the
compiler, which is now done automatically. Typically set to empty
string if Posix and `.exe' if a DOS variant.
-- Macro: AC_EMXOS2
Similar to `AC_CYGWIN' but checks for the EMX environment on OS/2
and sets `EMXOS2'. Don't use this macro, the dignified means to
check the nature of the host is using `AC_CANONICAL_HOST' (*note
Canonicalizing::).
-- Macro: AC_ENABLE (FEATURE, ACTION-IF-GIVEN, [ACTION-IF-NOT-GIVEN])
This is an obsolete version of `AC_ARG_ENABLE' that does not
support providing a help string (*note AC_ARG_ENABLE::).
-- Macro: AC_ERROR
Replaced by `AC_MSG_ERROR' (*note AC_MSG_ERROR::).
-- Macro: AC_FIND_X
Replaced by `AC_PATH_X' (*note AC_PATH_X::).
-- Macro: AC_FIND_XTRA
Replaced by `AC_PATH_XTRA' (*note AC_PATH_XTRA::).
-- Macro: AC_FOREACH
Replaced by `m4_foreach_w' (*note m4_foreach_w::).
-- Macro: AC_FUNC_CHECK
Replaced by `AC_CHECK_FUNC' (*note AC_CHECK_FUNC::).
-- Macro: AC_FUNC_SETVBUF_REVERSED
Do nothing. Formerly, this macro checked whether `setvbuf' takes
the buffering type as its second argument and the buffer pointer
as the third, instead of the other way around, and defined
`SETVBUF_REVERSED'. However, the last systems to have the problem
were those based on SVR2, which became obsolete in 1987, and the
macro is no longer needed.
-- Macro: AC_FUNC_WAIT3
If `wait3' is found and fills in the contents of its third argument
(a `struct rusage *'), which HP-UX does not do, define
`HAVE_WAIT3'.
These days portable programs should use `waitpid', not `wait3', as
`wait3' has been removed from Posix.
-- Macro: AC_GCC_TRADITIONAL
Replaced by `AC_PROG_GCC_TRADITIONAL' (*note
AC_PROG_GCC_TRADITIONAL::).
-- Macro: AC_GETGROUPS_T
Replaced by `AC_TYPE_GETGROUPS' (*note AC_TYPE_GETGROUPS::).
-- Macro: AC_GETLOADAVG
Replaced by `AC_FUNC_GETLOADAVG' (*note AC_FUNC_GETLOADAVG::).
-- Macro: AC_GNU_SOURCE
This macro is a platform-specific subset of
`AC_USE_SYSTEM_EXTENSIONS' (*note AC_USE_SYSTEM_EXTENSIONS::).
-- Macro: AC_HAVE_FUNCS
Replaced by `AC_CHECK_FUNCS' (*note AC_CHECK_FUNCS::).
-- Macro: AC_HAVE_HEADERS
Replaced by `AC_CHECK_HEADERS' (*note AC_CHECK_HEADERS::).
-- Macro: AC_HAVE_LIBRARY (LIBRARY, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND], [OTHER-LIBRARIES])
This macro is equivalent to calling `AC_CHECK_LIB' with a FUNCTION
argument of `main'. In addition, LIBRARY can be written as any of
`foo', `-lfoo', or `libfoo.a'. In all of those cases, the
compiler is passed `-lfoo'. However, LIBRARY cannot be a shell
variable; it must be a literal name. *Note AC_CHECK_LIB::.
-- Macro: AC_HAVE_POUNDBANG
Replaced by `AC_SYS_INTERPRETER' (*note AC_SYS_INTERPRETER::).
-- Macro: AC_HEADER_CHECK
Replaced by `AC_CHECK_HEADER' (*note AC_CHECK_HEADER::).
-- Macro: AC_HEADER_EGREP
Replaced by `AC_EGREP_HEADER' (*note AC_EGREP_HEADER::).
-- Macro: AC_HELP_STRING
Replaced by `AS_HELP_STRING' (*note AS_HELP_STRING::).
-- Macro: AC_INIT (UNIQUE-FILE-IN-SOURCE-DIR)
Formerly `AC_INIT' used to have a single argument, and was
equivalent to:
AC_INIT
AC_CONFIG_SRCDIR(UNIQUE-FILE-IN-SOURCE-DIR)
See *note AC_INIT:: and *note AC_CONFIG_SRCDIR::.
-- Macro: AC_INLINE
Replaced by `AC_C_INLINE' (*note AC_C_INLINE::).
-- Macro: AC_INT_16_BITS
If the C type `int' is 16 bits wide, define `INT_16_BITS'. Use
`AC_CHECK_SIZEOF(int)' instead (*note AC_CHECK_SIZEOF::).
-- Macro: AC_IRIX_SUN
If on IRIX (Silicon Graphics Unix), add `-lsun' to output `LIBS'.
If you were using it to get `getmntent', use `AC_FUNC_GETMNTENT'
instead. If you used it for the NIS versions of the password and
group functions, use `AC_CHECK_LIB(sun, getpwnam)'. Up to
Autoconf 2.13, it used to be
AC_CHECK_LIB([sun], [getmntent], [LIBS="-lsun $LIBS"])
now it is defined as
AC_FUNC_GETMNTENT
AC_CHECK_LIB([sun], [getpwnam])
See *note AC_FUNC_GETMNTENT:: and *note AC_CHECK_LIB::.
-- Macro: AC_ISC_POSIX
This macro adds `-lcposix' to output variable `LIBS' if necessary
for Posix facilities. Sun dropped support for the obsolete
INTERACTIVE Systems Corporation Unix on 2006-07-23. New programs
need not use this macro. It is implemented as
`AC_SEARCH_LIBS([strerror], [cposix])' (*note AC_SEARCH_LIBS::).
-- Macro: AC_LANG_C
Same as `AC_LANG([C])' (*note AC_LANG::).
-- Macro: AC_LANG_CPLUSPLUS
Same as `AC_LANG([C++])' (*note AC_LANG::).
-- Macro: AC_LANG_FORTRAN77
Same as `AC_LANG([Fortran 77])' (*note AC_LANG::).
-- Macro: AC_LANG_RESTORE
Select the LANGUAGE that is saved on the top of the stack, as set
by `AC_LANG_SAVE', remove it from the stack, and call
`AC_LANG(LANGUAGE)'. *Note Language Choice::, for the preferred
way to change languages.
-- Macro: AC_LANG_SAVE
Remember the current language (as set by `AC_LANG') on a stack.
The current language does not change. `AC_LANG_PUSH' is preferred
(*note AC_LANG_PUSH::).
-- Macro: AC_LINK_FILES (SOURCE..., DEST...)
This is an obsolete version of `AC_CONFIG_LINKS' (*note
AC_CONFIG_LINKS::. An updated version of:
AC_LINK_FILES(config/$machine.h config/$obj_format.h,
host.h object.h)
is:
AC_CONFIG_LINKS([host.h:config/$machine.h
object.h:config/$obj_format.h])
-- Macro: AC_LN_S
Replaced by `AC_PROG_LN_S' (*note AC_PROG_LN_S::).
-- Macro: AC_LONG_64_BITS
Define `LONG_64_BITS' if the C type `long int' is 64 bits wide.
Use the generic macro `AC_CHECK_SIZEOF([long int])' instead (*note
AC_CHECK_SIZEOF::).
-- Macro: AC_LONG_DOUBLE
If the C compiler supports a working `long double' type with more
range or precision than the `double' type, define
`HAVE_LONG_DOUBLE'.
You should use `AC_TYPE_LONG_DOUBLE' or
`AC_TYPE_LONG_DOUBLE_WIDER' instead. *Note Particular Types::.
-- Macro: AC_LONG_FILE_NAMES
Replaced by
AC_SYS_LONG_FILE_NAMES
*Note AC_SYS_LONG_FILE_NAMES::.
-- Macro: AC_MAJOR_HEADER
Replaced by `AC_HEADER_MAJOR' (*note AC_HEADER_MAJOR::).
-- Macro: AC_MEMORY_H
Used to define `NEED_MEMORY_H' if the `mem' functions were defined
in `memory.h'. Today it is equivalent to
`AC_CHECK_HEADERS([memory.h])' (*note AC_CHECK_HEADERS::). Adjust
your code to depend upon `HAVE_MEMORY_H', not `NEED_MEMORY_H'; see
*note Standard Symbols::.
-- Macro: AC_MINGW32
Similar to `AC_CYGWIN' but checks for the MinGW compiler
environment and sets `MINGW32'. Don't use this macro, the
dignified means to check the nature of the host is using
`AC_CANONICAL_HOST' (*note Canonicalizing::).
-- Macro: AC_MINIX
This macro is a platform-specific subset of
`AC_USE_SYSTEM_EXTENSIONS' (*note AC_USE_SYSTEM_EXTENSIONS::).
-- Macro: AC_MINUS_C_MINUS_O
Replaced by `AC_PROG_CC_C_O' (*note AC_PROG_CC_C_O::).
-- Macro: AC_MMAP
Replaced by `AC_FUNC_MMAP' (*note AC_FUNC_MMAP::).
-- Macro: AC_MODE_T
Replaced by `AC_TYPE_MODE_T' (*note AC_TYPE_MODE_T::).
-- Macro: AC_OBJEXT
Defined the output variable `OBJEXT' based on the output of the
compiler, after .c files have been excluded. Typically set to `o'
if Posix, `obj' if a DOS variant. Now the compiler checking
macros handle this automatically.
-- Macro: AC_OBSOLETE (THIS-MACRO-NAME, [SUGGESTION])
Make M4 print a message to the standard error output warning that
THIS-MACRO-NAME is obsolete, and giving the file and line number
where it was called. THIS-MACRO-NAME should be the name of the
macro that is calling `AC_OBSOLETE'. If SUGGESTION is given, it
is printed at the end of the warning message; for example, it can
be a suggestion for what to use instead of THIS-MACRO-NAME.
For instance
AC_OBSOLETE([$0], [; use AC_CHECK_HEADERS(unistd.h) instead])dnl
You are encouraged to use `AU_DEFUN' instead, since it gives better
services to the user (*note AU_DEFUN::).
-- Macro: AC_OFF_T
Replaced by `AC_TYPE_OFF_T' (*note AC_TYPE_OFF_T::).
-- Macro: AC_OUTPUT ([FILE]..., [EXTRA-CMDS], [INIT-CMDS])
The use of `AC_OUTPUT' with arguments is deprecated. This
obsoleted interface is equivalent to:
AC_CONFIG_FILES(FILE...)
AC_CONFIG_COMMANDS([default],
EXTRA-CMDS, INIT-CMDS)
AC_OUTPUT
See *note AC_CONFIG_FILES::, *note AC_CONFIG_COMMANDS::, and *note
AC_OUTPUT::.
-- Macro: AC_OUTPUT_COMMANDS (EXTRA-CMDS, [INIT-CMDS])
Specify additional shell commands to run at the end of
`config.status', and shell commands to initialize any variables
from `configure'. This macro may be called multiple times. It is
obsolete, replaced by `AC_CONFIG_COMMANDS' (*note
AC_CONFIG_COMMANDS::).
Here is an unrealistic example:
fubar=27
AC_OUTPUT_COMMANDS([echo this is extra $fubar, and so on.],
[fubar=$fubar])
AC_OUTPUT_COMMANDS([echo this is another, extra, bit],
[echo init bit])
Aside from the fact that `AC_CONFIG_COMMANDS' requires an
additional key, an important difference is that
`AC_OUTPUT_COMMANDS' is quoting its arguments twice, unlike
`AC_CONFIG_COMMANDS'. This means that `AC_CONFIG_COMMANDS' can
safely be given macro calls as arguments:
AC_CONFIG_COMMANDS(foo, [my_FOO()])
Conversely, where one level of quoting was enough for literal
strings with `AC_OUTPUT_COMMANDS', you need two with
`AC_CONFIG_COMMANDS'. The following lines are equivalent:
AC_OUTPUT_COMMANDS([echo "Square brackets: []"])
AC_CONFIG_COMMANDS([default], [[echo "Square brackets: []"]])
-- Macro: AC_PID_T
Replaced by `AC_TYPE_PID_T' (*note AC_TYPE_PID_T::).
-- Macro: AC_PREFIX
Replaced by `AC_PREFIX_PROGRAM' (*note AC_PREFIX_PROGRAM::).
-- Macro: AC_PROGRAMS_CHECK
Replaced by `AC_CHECK_PROGS' (*note AC_CHECK_PROGS::).
-- Macro: AC_PROGRAMS_PATH
Replaced by `AC_PATH_PROGS' (*note AC_PATH_PROGS::).
-- Macro: AC_PROGRAM_CHECK
Replaced by `AC_CHECK_PROG' (*note AC_CHECK_PROG::).
-- Macro: AC_PROGRAM_EGREP
Replaced by `AC_EGREP_CPP' (*note AC_EGREP_CPP::).
-- Macro: AC_PROGRAM_PATH
Replaced by `AC_PATH_PROG' (*note AC_PATH_PROG::).
-- Macro: AC_REMOTE_TAPE
Removed because of limited usefulness.
-- Macro: AC_RESTARTABLE_SYSCALLS
This macro was renamed `AC_SYS_RESTARTABLE_SYSCALLS'. However,
these days portable programs should use `sigaction' with
`SA_RESTART' if they want restartable system calls. They should
not rely on `HAVE_RESTARTABLE_SYSCALLS', since nowadays whether a
system call is restartable is a dynamic issue, not a
configuration-time issue.
-- Macro: AC_RETSIGTYPE
Replaced by `AC_TYPE_SIGNAL' (*note AC_TYPE_SIGNAL::), which itself
is obsolete when assuming C89 or better.
-- Macro: AC_RSH
Removed because of limited usefulness.
-- Macro: AC_SCO_INTL
If on SCO Unix, add `-lintl' to output variable `LIBS'. This
macro used to do this:
AC_CHECK_LIB([intl], [strftime], [LIBS="-lintl $LIBS"])
Now it just calls `AC_FUNC_STRFTIME' instead (*note
AC_FUNC_STRFTIME::).
-- Macro: AC_SETVBUF_REVERSED
Replaced by
AC_FUNC_SETVBUF_REVERSED
*Note AC_FUNC_SETVBUF_REVERSED::.
-- Macro: AC_SET_MAKE
Replaced by `AC_PROG_MAKE_SET' (*note AC_PROG_MAKE_SET::).
-- Macro: AC_SIZEOF_TYPE
Replaced by `AC_CHECK_SIZEOF' (*note AC_CHECK_SIZEOF::).
-- Macro: AC_SIZE_T
Replaced by `AC_TYPE_SIZE_T' (*note AC_TYPE_SIZE_T::).
-- Macro: AC_STAT_MACROS_BROKEN
Replaced by `AC_HEADER_STAT' (*note AC_HEADER_STAT::).
-- Macro: AC_STDC_HEADERS
Replaced by `AC_HEADER_STDC' (*note AC_HEADER_STDC::).
-- Macro: AC_STRCOLL
Replaced by `AC_FUNC_STRCOLL' (*note AC_FUNC_STRCOLL::).
-- Macro: AC_STRUCT_ST_BLKSIZE
If `struct stat' contains an `st_blksize' member, define
`HAVE_STRUCT_STAT_ST_BLKSIZE'. The former name, `HAVE_ST_BLKSIZE'
is to be avoided, as its support will cease in the future. This
macro is obsoleted, and should be replaced by
AC_CHECK_MEMBERS([struct stat.st_blksize])
*Note AC_CHECK_MEMBERS::.
-- Macro: AC_STRUCT_ST_RDEV
If `struct stat' contains an `st_rdev' member, define
`HAVE_STRUCT_STAT_ST_RDEV'. The former name for this macro,
`HAVE_ST_RDEV', is to be avoided as it will cease to be supported
in the future. Actually, even the new macro is obsolete and
should be replaced by:
AC_CHECK_MEMBERS([struct stat.st_rdev])
*Note AC_CHECK_MEMBERS::.
-- Macro: AC_ST_BLKSIZE
Replaced by `AC_CHECK_MEMBERS' (*note AC_CHECK_MEMBERS::).
-- Macro: AC_ST_BLOCKS
Replaced by `AC_STRUCT_ST_BLOCKS' (*note AC_STRUCT_ST_BLOCKS::).
-- Macro: AC_ST_RDEV
Replaced by `AC_CHECK_MEMBERS' (*note AC_CHECK_MEMBERS::).
-- Macro: AC_SYS_RESTARTABLE_SYSCALLS
If the system automatically restarts a system call that is
interrupted by a signal, define `HAVE_RESTARTABLE_SYSCALLS'. This
macro does not check whether system calls are restarted in
general--it checks whether a signal handler installed with
`signal' (but not `sigaction') causes system calls to be
restarted. It does not check whether system calls can be
restarted when interrupted by signals that have no handler.
These days portable programs should use `sigaction' with
`SA_RESTART' if they want restartable system calls. They should
not rely on `HAVE_RESTARTABLE_SYSCALLS', since nowadays whether a
system call is restartable is a dynamic issue, not a
configuration-time issue.
-- Macro: AC_SYS_SIGLIST_DECLARED
This macro was renamed `AC_DECL_SYS_SIGLIST'. However, even that
name is obsolete, as the same functionality is now acheived via
`AC_CHECK_DECLS' (*note AC_CHECK_DECLS::).
-- Macro: AC_TEST_CPP
This macro was renamed `AC_TRY_CPP', which in turn was replaced by
`AC_PREPROC_IFELSE' (*note AC_PREPROC_IFELSE::).
-- Macro: AC_TEST_PROGRAM
This macro was renamed `AC_TRY_RUN', which in turn was replaced by
`AC_RUN_IFELSE' (*note AC_RUN_IFELSE::).
-- Macro: AC_TIMEZONE
Replaced by `AC_STRUCT_TIMEZONE' (*note AC_STRUCT_TIMEZONE::).
-- Macro: AC_TIME_WITH_SYS_TIME
Replaced by `AC_HEADER_TIME' (*note AC_HEADER_TIME::).
-- Macro: AC_TRY_COMPILE (INCLUDES, FUNCTION-BODY, [ACTION-IF-TRUE],
[ACTION-IF-FALSE])
Same as:
AC_COMPILE_IFELSE(
[AC_LANG_PROGRAM([[INCLUDES]],
[[FUNCTION-BODY]])],
[ACTION-IF-TRUE],
[ACTION-IF-FALSE])
*Note Running the Compiler::.
This macro double quotes both INCLUDES and FUNCTION-BODY.
For C and C++, INCLUDES is any `#include' statements needed by the
code in FUNCTION-BODY (INCLUDES is ignored if the currently
selected language is Fortran or Fortran 77). The compiler and
compilation flags are determined by the current language (*note
Language Choice::).
-- Macro: AC_TRY_CPP (INPUT, [ACTION-IF-TRUE], [ACTION-IF-FALSE])
Same as:
AC_PREPROC_IFELSE(
[AC_LANG_SOURCE([[INPUT]])],
[ACTION-IF-TRUE],
[ACTION-IF-FALSE])
*Note Running the Preprocessor::.
This macro double quotes the INPUT.
-- Macro: AC_TRY_LINK (INCLUDES, FUNCTION-BODY, [ACTION-IF-TRUE],
[ACTION-IF-FALSE])
Same as:
AC_LINK_IFELSE(
[AC_LANG_PROGRAM([[INCLUDES]],
[[FUNCTION-BODY]])],
[ACTION-IF-TRUE],
[ACTION-IF-FALSE])
*Note Running the Compiler::.
This macro double quotes both INCLUDES and FUNCTION-BODY.
Depending on the current language (*note Language Choice::),
create a test program to see whether a function whose body
consists of FUNCTION-BODY can be compiled and linked. If the file
compiles and links successfully, run shell commands
ACTION-IF-FOUND, otherwise run ACTION-IF-NOT-FOUND.
This macro double quotes both INCLUDES and FUNCTION-BODY.
For C and C++, INCLUDES is any `#include' statements needed by the
code in FUNCTION-BODY (INCLUDES is ignored if the currently
selected language is Fortran or Fortran 77). The compiler and
compilation flags are determined by the current language (*note
Language Choice::), and in addition `LDFLAGS' and `LIBS' are used
for linking.
-- Macro: AC_TRY_LINK_FUNC (FUNCTION, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND])
This macro is equivalent to
AC_LINK_IFELSE([AC_LANG_CALL([], [FUNCTION])],
[ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
*Note AC_LINK_IFELSE::.
-- Macro: AC_TRY_RUN (PROGRAM, [ACTION-IF-TRUE], [ACTION-IF-FALSE],
[ACTION-IF-CROSS-COMPILING])
Same as:
AC_RUN_IFELSE(
[AC_LANG_SOURCE([[PROGRAM]])],
[ACTION-IF-TRUE],
[ACTION-IF-FALSE],
[ACTION-IF-CROSS-COMPILING])
*Note Runtime::.
-- Macro: AC_TYPE_SIGNAL
If `signal.h' declares `signal' as returning a pointer to a
function returning `void', define `RETSIGTYPE' to be `void';
otherwise, define it to be `int'. These days, it is portable to
assume C89, and that signal handlers return `void', without
needing to use this macro or `RETSIGTYPE'.
When targetting older K&R C, it is possible to define signal
handlers as returning type `RETSIGTYPE', and omit a return
statement:
RETSIGTYPE
hup_handler ()
{
...
}
-- Macro: AC_UID_T
Replaced by `AC_TYPE_UID_T' (*note AC_TYPE_UID_T::).
-- Macro: AC_UNISTD_H
Same as `AC_CHECK_HEADERS([unistd.h])' (*note AC_CHECK_HEADERS::).
-- Macro: AC_USG
Define `USG' if the BSD string functions are defined in
`strings.h'. You should no longer depend upon `USG', but on
`HAVE_STRING_H'; see *note Standard Symbols::.
-- Macro: AC_UTIME_NULL
Replaced by `AC_FUNC_UTIME_NULL' (*note AC_FUNC_UTIME_NULL::).
-- Macro: AC_VALIDATE_CACHED_SYSTEM_TUPLE ([CMD])
If the cache file is inconsistent with the current host, target and
build system types, it used to execute CMD or print a default
error message. This is now handled by default.
-- Macro: AC_VERBOSE (RESULT-DESCRIPTION)
Replaced by `AC_MSG_RESULT' (*note AC_MSG_RESULT::).
-- Macro: AC_VFORK
Replaced by `AC_FUNC_FORK' (*note AC_FUNC_FORK::).
-- Macro: AC_VPRINTF
Replaced by `AC_FUNC_VPRINTF' (*note AC_FUNC_VPRINTF::).
-- Macro: AC_WAIT3
This macro was renamed `AC_FUNC_WAIT3'. However, these days
portable programs should use `waitpid', not `wait3', as `wait3'
has been removed from Posix.
-- Macro: AC_WARN
Replaced by `AC_MSG_WARN' (*note AC_MSG_WARN::).
-- Macro: AC_WITH (PACKAGE, ACTION-IF-GIVEN, [ACTION-IF-NOT-GIVEN])
This is an obsolete version of `AC_ARG_WITH' that does not support
providing a help string (*note AC_ARG_WITH::).
-- Macro: AC_WORDS_BIGENDIAN
Replaced by `AC_C_BIGENDIAN' (*note AC_C_BIGENDIAN::).
-- Macro: AC_XENIX_DIR
This macro used to add `-lx' to output variable `LIBS' if on
Xenix. Also, if `dirent.h' is being checked for, added `-ldir' to
`LIBS'. Now it is merely an alias of `AC_HEADER_DIRENT' instead,
plus some code to detect whether running XENIX on which you should
not depend:
AC_MSG_CHECKING([for Xenix])
AC_EGREP_CPP([yes],
[#if defined M_XENIX && !defined M_UNIX
yes
#endif],
[AC_MSG_RESULT([yes]); XENIX=yes],
[AC_MSG_RESULT([no]); XENIX=])
Don't use this macro, the dignified means to check the nature of
the host is using `AC_CANONICAL_HOST' (*note Canonicalizing::).
-- Macro: AC_YYTEXT_POINTER
This macro was renamed `AC_DECL_YYTEXT', which in turn was
integrated into `AC_PROG_LEX' (*note AC_PROG_LEX::).
File: autoconf.info, Node: Autoconf 1, Next: Autoconf 2.13, Prev: Obsolete Macros, Up: Obsolete Constructs
18.5 Upgrading From Version 1
=============================
Autoconf version 2 is mostly backward compatible with version 1.
However, it introduces better ways to do some things, and doesn't
support some of the ugly things in version 1. So, depending on how
sophisticated your `configure.ac' files are, you might have to do some
manual work in order to upgrade to version 2. This chapter points out
some problems to watch for when upgrading. Also, perhaps your
`configure' scripts could benefit from some of the new features in
version 2; the changes are summarized in the file `NEWS' in the
Autoconf distribution.
* Menu:
* Changed File Names:: Files you might rename
* Changed Makefiles:: New things to put in `Makefile.in'
* Changed Macros:: Macro calls you might replace
* Changed Results:: Changes in how to check test results
* Changed Macro Writing:: Better ways to write your own macros
File: autoconf.info, Node: Changed File Names, Next: Changed Makefiles, Up: Autoconf 1
18.5.1 Changed File Names
-------------------------
If you have an `aclocal.m4' installed with Autoconf (as opposed to in a
particular package's source directory), you must rename it to
`acsite.m4'. *Note autoconf Invocation::.
If you distribute `install.sh' with your package, rename it to
`install-sh' so `make' builtin rules don't inadvertently create a file
called `install' from it. `AC_PROG_INSTALL' looks for the script under
both names, but it is best to use the new name.
If you were using `config.h.top', `config.h.bot', or `acconfig.h',
you still can, but you have less clutter if you use the `AH_' macros.
*Note Autoheader Macros::.
File: autoconf.info, Node: Changed Makefiles, Next: Changed Macros, Prev: Changed File Names, Up: Autoconf 1
18.5.2 Changed Makefiles
------------------------
Add `@CFLAGS@', `@CPPFLAGS@', and `@LDFLAGS@' in your `Makefile.in'
files, so they can take advantage of the values of those variables in
the environment when `configure' is run. Doing this isn't necessary,
but it's a convenience for users.
Also add `@configure_input@' in a comment to each input file for
`AC_OUTPUT', so that the output files contain a comment saying they
were produced by `configure'. Automatically selecting the right
comment syntax for all the kinds of files that people call `AC_OUTPUT'
on became too much work.
Add `config.log' and `config.cache' to the list of files you remove
in `distclean' targets.
If you have the following in `Makefile.in':
prefix = /usr/local
exec_prefix = $(prefix)
you must change it to:
prefix = @prefix@
exec_prefix = @exec_prefix@
The old behavior of replacing those variables without `@' characters
around them has been removed.
File: autoconf.info, Node: Changed Macros, Next: Changed Results, Prev: Changed Makefiles, Up: Autoconf 1
18.5.3 Changed Macros
---------------------
Many of the macros were renamed in Autoconf version 2. You can still
use the old names, but the new ones are clearer, and it's easier to find
the documentation for them. *Note Obsolete Macros::, for a table
showing the new names for the old macros. Use the `autoupdate' program
to convert your `configure.ac' to using the new macro names. *Note
autoupdate Invocation::.
Some macros have been superseded by similar ones that do the job
better, but are not call-compatible. If you get warnings about calling
obsolete macros while running `autoconf', you may safely ignore them,
but your `configure' script generally works better if you follow the
advice that is printed about what to replace the obsolete macros with.
In particular, the mechanism for reporting the results of tests has
changed. If you were using `echo' or `AC_VERBOSE' (perhaps via
`AC_COMPILE_CHECK'), your `configure' script's output looks better if
you switch to `AC_MSG_CHECKING' and `AC_MSG_RESULT'. *Note Printing
Messages::. Those macros work best in conjunction with cache
variables. *Note Caching Results::.
File: autoconf.info, Node: Changed Results, Next: Changed Macro Writing, Prev: Changed Macros, Up: Autoconf 1
18.5.4 Changed Results
----------------------
If you were checking the results of previous tests by examining the
shell variable `DEFS', you need to switch to checking the values of the
cache variables for those tests. `DEFS' no longer exists while
`configure' is running; it is only created when generating output
files. This difference from version 1 is because properly quoting the
contents of that variable turned out to be too cumbersome and
inefficient to do every time `AC_DEFINE' is called. *Note Cache
Variable Names::.
For example, here is a `configure.ac' fragment written for Autoconf
version 1:
AC_HAVE_FUNCS(syslog)
case "$DEFS" in
*-DHAVE_SYSLOG*) ;;
*) # syslog is not in the default libraries. See if it's in some other.
saved_LIBS="$LIBS"
for lib in bsd socket inet; do
AC_CHECKING(for syslog in -l$lib)
LIBS="-l$lib $saved_LIBS"
AC_HAVE_FUNCS(syslog)
case "$DEFS" in
*-DHAVE_SYSLOG*) break ;;
*) ;;
esac
LIBS="$saved_LIBS"
done ;;
esac
Here is a way to write it for version 2:
AC_CHECK_FUNCS([syslog])
if test "x$ac_cv_func_syslog" = xno; then
# syslog is not in the default libraries. See if it's in some other.
for lib in bsd socket inet; do
AC_CHECK_LIB([$lib], [syslog], [AC_DEFINE([HAVE_SYSLOG])
LIBS="-l$lib $LIBS"; break])
done
fi
If you were working around bugs in `AC_DEFINE_UNQUOTED' by adding
backslashes before quotes, you need to remove them. It now works
predictably, and does not treat quotes (except back quotes) specially.
*Note Setting Output Variables::.
All of the Boolean shell variables set by Autoconf macros now use
`yes' for the true value. Most of them use `no' for false, though for
backward compatibility some use the empty string instead. If you were
relying on a shell variable being set to something like 1 or `t' for
true, you need to change your tests.
File: autoconf.info, Node: Changed Macro Writing, Prev: Changed Results, Up: Autoconf 1
18.5.5 Changed Macro Writing
----------------------------
When defining your own macros, you should now use `AC_DEFUN' instead of
`define'. `AC_DEFUN' automatically calls `AC_PROVIDE' and ensures that
macros called via `AC_REQUIRE' do not interrupt other macros, to
prevent nested `checking...' messages on the screen. There's no actual
harm in continuing to use the older way, but it's less convenient and
attractive. *Note Macro Definitions::.
You probably looked at the macros that came with Autoconf as a guide
for how to do things. It would be a good idea to take a look at the new
versions of them, as the style is somewhat improved and they take
advantage of some new features.
If you were doing tricky things with undocumented Autoconf internals
(macros, variables, diversions), check whether you need to change
anything to account for changes that have been made. Perhaps you can
even use an officially supported technique in version 2 instead of
kludging. Or perhaps not.
To speed up your locally written feature tests, add caching to them.
See whether any of your tests are of general enough usefulness to
encapsulate them into macros that you can share.
File: autoconf.info, Node: Autoconf 2.13, Prev: Autoconf 1, Up: Obsolete Constructs
18.6 Upgrading From Version 2.13
================================
The introduction of the previous section (*note Autoconf 1::) perfectly
suits this section...
Autoconf version 2.50 is mostly backward compatible with version
2.13. However, it introduces better ways to do some things, and
doesn't support some of the ugly things in version 2.13. So,
depending on how sophisticated your `configure.ac' files are, you
might have to do some manual work in order to upgrade to version
2.50. This chapter points out some problems to watch for when
upgrading. Also, perhaps your `configure' scripts could benefit
from some of the new features in version 2.50; the changes are
summarized in the file `NEWS' in the Autoconf distribution.
* Menu:
* Changed Quotation:: Broken code which used to work
* New Macros:: Interaction with foreign macros
* Hosts and Cross-Compilation:: Bugward compatibility kludges
* AC_LIBOBJ vs LIBOBJS:: LIBOBJS is a forbidden token
* AC_ACT_IFELSE vs AC_TRY_ACT:: A more generic scheme for testing sources
File: autoconf.info, Node: Changed Quotation, Next: New Macros, Up: Autoconf 2.13
18.6.1 Changed Quotation
------------------------
The most important changes are invisible to you: the implementation of
most macros have completely changed. This allowed more factorization of
the code, better error messages, a higher uniformity of the user's
interface etc. Unfortunately, as a side effect, some construct which
used to (miraculously) work might break starting with Autoconf 2.50.
The most common culprit is bad quotation.
For instance, in the following example, the message is not properly
quoted:
AC_INIT
AC_CHECK_HEADERS(foo.h, ,
AC_MSG_ERROR(cannot find foo.h, bailing out))
AC_OUTPUT
Autoconf 2.13 simply ignores it:
$ autoconf-2.13; ./configure --silent
creating cache ./config.cache
configure: error: cannot find foo.h
$
while Autoconf 2.50 produces a broken `configure':
$ autoconf-2.50; ./configure --silent
configure: error: cannot find foo.h
./configure: exit: bad non-numeric arg `bailing'
./configure: exit: bad non-numeric arg `bailing'
$
The message needs to be quoted, and the `AC_MSG_ERROR' invocation
too!
AC_INIT([Example], [1.0], [bug-example@example.org])
AC_CHECK_HEADERS([foo.h], [],
[AC_MSG_ERROR([cannot find foo.h, bailing out])])
AC_OUTPUT
Many many (and many more) Autoconf macros were lacking proper
quotation, including no less than... `AC_DEFUN' itself!
$ cat configure.in
AC_DEFUN([AC_PROG_INSTALL],
[# My own much better version
])
AC_INIT
AC_PROG_INSTALL
AC_OUTPUT
$ autoconf-2.13
autoconf: Undefined macros:
***BUG in Autoconf--please report*** AC_FD_MSG
***BUG in Autoconf--please report*** AC_EPI
configure.in:1:AC_DEFUN([AC_PROG_INSTALL],
configure.in:5:AC_PROG_INSTALL
$ autoconf-2.50
$
File: autoconf.info, Node: New Macros, Next: Hosts and Cross-Compilation, Prev: Changed Quotation, Up: Autoconf 2.13
18.6.2 New Macros
-----------------
While Autoconf was relatively dormant in the late 1990s, Automake
provided Autoconf-like macros for a while. Starting with Autoconf 2.50
in 2001, Autoconf provided versions of these macros, integrated in the
`AC_' namespace, instead of `AM_'. But in order to ease the upgrading
via `autoupdate', bindings to such `AM_' macros are provided.
Unfortunately older versions of Automake (e.g., Automake 1.4) did
not quote the names of these macros. Therefore, when `m4' finds
something like `AC_DEFUN(AM_TYPE_PTRDIFF_T, ...)' in `aclocal.m4',
`AM_TYPE_PTRDIFF_T' is expanded, replaced with its Autoconf definition.
Fortunately Autoconf catches pre-`AC_INIT' expansions, and
complains, in its own words:
$ cat configure.ac
AC_INIT([Example], [1.0], [bug-example@example.org])
AM_TYPE_PTRDIFF_T
$ aclocal-1.4
$ autoconf
aclocal.m4:17: error: m4_defn: undefined macro: _m4_divert_diversion
aclocal.m4:17: the top level
autom4te: m4 failed with exit status: 1
$
Modern versions of Automake no longer define most of these macros,
and properly quote the names of the remaining macros. If you must use
an old Automake, do not depend upon macros from Automake as it is
simply not its job to provide macros (but the one it requires itself):
$ cat configure.ac
AC_INIT([Example], [1.0], [bug-example@example.org])
AM_TYPE_PTRDIFF_T
$ rm aclocal.m4
$ autoupdate
autoupdate: `configure.ac' is updated
$ cat configure.ac
AC_INIT([Example], [1.0], [bug-example@example.org])
AC_CHECK_TYPES([ptrdiff_t])
$ aclocal-1.4
$ autoconf
$
File: autoconf.info, Node: Hosts and Cross-Compilation, Next: AC_LIBOBJ vs LIBOBJS, Prev: New Macros, Up: Autoconf 2.13
18.6.3 Hosts and Cross-Compilation
----------------------------------
Based on the experience of compiler writers, and after long public
debates, many aspects of the cross-compilation chain have changed:
- the relationship between the build, host, and target architecture
types,
- the command line interface for specifying them to `configure',
- the variables defined in `configure',
- the enabling of cross-compilation mode.
The relationship between build, host, and target have been cleaned
up: the chain of default is now simply: target defaults to host, host to
build, and build to the result of `config.guess'. Nevertheless, in
order to ease the transition from 2.13 to 2.50, the following
transition scheme is implemented. _Do not rely on it_, as it will be
completely disabled in a couple of releases (we cannot keep it, as it
proves to cause more problems than it cures).
They all default to the result of running `config.guess', unless you
specify either `--build' or `--host'. In this case, the default
becomes the system type you specified. If you specify both, and
they're different, `configure' enters cross compilation mode, so it
doesn't run any tests that require execution.
Hint: if you mean to override the result of `config.guess', prefer
`--build' over `--host'. In the future, `--host' will not override the
name of the build system type. Whenever you specify `--host', be sure
to specify `--build' too.
For backward compatibility, `configure' accepts a system type as an
option by itself. Such an option overrides the defaults for build,
host, and target system types. The following configure statement
configures a cross toolchain that runs on NetBSD/alpha but generates
code for GNU Hurd/sparc, which is also the build platform.
./configure --host=alpha-netbsd sparc-gnu
In Autoconf 2.13 and before, the variables `build', `host', and
`target' had a different semantics before and after the invocation of
`AC_CANONICAL_BUILD' etc. Now, the argument of `--build' is strictly
copied into `build_alias', and is left empty otherwise. After the
`AC_CANONICAL_BUILD', `build' is set to the canonicalized build type.
To ease the transition, before, its contents is the same as that of
`build_alias'. Do _not_ rely on this broken feature.
For consistency with the backward compatibility scheme exposed above,
when `--host' is specified but `--build' isn't, the build system is
assumed to be the same as `--host', and `build_alias' is set to that
value. Eventually, this historically incorrect behavior will go away.
The former scheme to enable cross-compilation proved to cause more
harm than good, in particular, it used to be triggered too easily,
leaving regular end users puzzled in front of cryptic error messages.
`configure' could even enter cross-compilation mode only because the
compiler was not functional. This is mainly because `configure' used
to try to detect cross-compilation, instead of waiting for an explicit
flag from the user.
Now, `configure' enters cross-compilation mode if and only if
`--host' is passed.
That's the short documentation. To ease the transition between 2.13
and its successors, a more complicated scheme is implemented. _Do not
rely on the following_, as it will be removed in the near future.
If you specify `--host', but not `--build', when `configure'
performs the first compiler test it tries to run an executable produced
by the compiler. If the execution fails, it enters cross-compilation
mode. This is fragile. Moreover, by the time the compiler test is
performed, it may be too late to modify the build-system type: other
tests may have already been performed. Therefore, whenever you specify
`--host', be sure to specify `--build' too.
./configure --build=i686-pc-linux-gnu --host=m68k-coff
enters cross-compilation mode. The former interface, which consisted
in setting the compiler to a cross-compiler without informing
`configure' is obsolete. For instance, `configure' fails if it can't
run the code generated by the specified compiler if you configure as
follows:
./configure CC=m68k-coff-gcc
File: autoconf.info, Node: AC_LIBOBJ vs LIBOBJS, Next: AC_ACT_IFELSE vs AC_TRY_ACT, Prev: Hosts and Cross-Compilation, Up: Autoconf 2.13
18.6.4 `AC_LIBOBJ' vs. `LIBOBJS'
--------------------------------
Up to Autoconf 2.13, the replacement of functions was triggered via the
variable `LIBOBJS'. Since Autoconf 2.50, the macro `AC_LIBOBJ' should
be used instead (*note Generic Functions::). Starting at Autoconf
2.53, the use of `LIBOBJS' is an error.
This change is mandated by the unification of the GNU Build System
components. In particular, the various fragile techniques used to parse
a `configure.ac' are all replaced with the use of traces. As a
consequence, any action must be traceable, which obsoletes critical
variable assignments. Fortunately, `LIBOBJS' was the only problem, and
it can even be handled gracefully (read, "without your having to change
something").
There were two typical uses of `LIBOBJS': asking for a replacement
function, and adjusting `LIBOBJS' for Automake and/or Libtool.
As for function replacement, the fix is immediate: use `AC_LIBOBJ'.
For instance:
LIBOBJS="$LIBOBJS fnmatch.o"
LIBOBJS="$LIBOBJS malloc.$ac_objext"
should be replaced with:
AC_LIBOBJ([fnmatch])
AC_LIBOBJ([malloc])
When used with Automake 1.10 or newer, a suitable value for
`LIBOBJDIR' is set so that the `LIBOBJS' and `LTLIBOBJS' can be
referenced from any `Makefile.am'. Even without Automake, arranging
for `LIBOBJDIR' to be set correctly enables referencing `LIBOBJS' and
`LTLIBOBJS' in another directory. The `LIBOBJDIR' feature is
experimental.
File: autoconf.info, Node: AC_ACT_IFELSE vs AC_TRY_ACT, Prev: AC_LIBOBJ vs LIBOBJS, Up: Autoconf 2.13
18.6.5 `AC_ACT_IFELSE' vs. `AC_TRY_ACT'
---------------------------------------
Since Autoconf 2.50, internal codes uses `AC_PREPROC_IFELSE',
`AC_COMPILE_IFELSE', `AC_LINK_IFELSE', and `AC_RUN_IFELSE' on one hand
and `AC_LANG_SOURCES', and `AC_LANG_PROGRAM' on the other hand instead
of the deprecated `AC_TRY_CPP', `AC_TRY_COMPILE', `AC_TRY_LINK', and
`AC_TRY_RUN'. The motivations where:
- a more consistent interface: `AC_TRY_COMPILE' etc. were double
quoting their arguments;
- the combinatoric explosion is solved by decomposing on the one
hand the generation of sources, and on the other hand executing
the program;
- this scheme helps supporting more languages than plain C and C++.
In addition to the change of syntax, the philosophy has changed too:
while emphasis was put on speed at the expense of accuracy, today's
Autoconf promotes accuracy of the testing framework at, ahem..., the
expense of speed.
As a perfect example of what is _not_ to be done, here is how to
find out whether a header file contains a particular declaration, such
as a typedef, a structure, a structure member, or a function. Use
`AC_EGREP_HEADER' instead of running `grep' directly on the header
file; on some systems the symbol might be defined in another header
file that the file you are checking includes.
As a (bad) example, here is how you should not check for C
preprocessor symbols, either defined by header files or predefined by
the C preprocessor: using `AC_EGREP_CPP':
AC_EGREP_CPP(yes,
[#ifdef _AIX
yes
#endif
], is_aix=yes, is_aix=no)
The above example, properly written would (i) use `AC_LANG_PROGRAM',
and (ii) run the compiler:
AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
[[#ifndef _AIX
error: This isn't AIX!
#endif
]])],
[is_aix=yes],
[is_aix=no])
File: autoconf.info, Node: Using Autotest, Next: FAQ, Prev: Obsolete Constructs, Up: Top
19 Generating Test Suites with Autotest
***************************************
*N.B.: This section describes a feature which is still
stabilizing. Although we believe that Autotest is useful as-is, this
documentation describes an interface which might change in the future:
do not depend upon Autotest without subscribing to the Autoconf mailing
lists.*
It is paradoxical that portable projects depend on nonportable tools
to run their test suite. Autoconf by itself is the paragon of this
problem: although it aims at perfectly portability, up to 2.13 its test
suite was using DejaGNU, a rich and complex testing framework, but
which is far from being standard on Posix systems. Worse yet, it was
likely to be missing on the most fragile platforms, the very platforms
that are most likely to torture Autoconf and exhibit deficiencies.
To circumvent this problem, many package maintainers have developed
their own testing framework, based on simple shell scripts whose sole
outputs are exit status values describing whether the test succeeded.
Most of these tests share common patterns, and this can result in lots
of duplicated code and tedious maintenance.
Following exactly the same reasoning that yielded to the inception of
Autoconf, Autotest provides a test suite generation framework, based on
M4 macros building a portable shell script. The suite itself is
equipped with automatic logging and tracing facilities which greatly
diminish the interaction with bug reporters, and simple timing reports.
Autoconf itself has been using Autotest for years, and we do attest
that it has considerably improved the strength of the test suite and the
quality of bug reports. Other projects are known to use some generation
of Autotest, such as Bison, Free Recode, Free Wdiff, GNU Tar, each of
them with different needs, and this usage has validated Autotest as a
general testing framework.
Nonetheless, compared to DejaGNU, Autotest is inadequate for
interactive tool testing, which is probably its main limitation.
* Menu:
* Using an Autotest Test Suite:: Autotest and the user
* Writing Testsuites:: Autotest macros
* testsuite Invocation:: Running `testsuite' scripts
* Making testsuite Scripts:: Using autom4te to create `testsuite'
File: autoconf.info, Node: Using an Autotest Test Suite, Next: Writing Testsuites, Up: Using Autotest
19.1 Using an Autotest Test Suite
=================================
* Menu:
* testsuite Scripts:: The concepts of Autotest
* Autotest Logs:: Their contents
File: autoconf.info, Node: testsuite Scripts, Next: Autotest Logs, Up: Using an Autotest Test Suite
19.1.1 `testsuite' Scripts
--------------------------
Generating testing or validation suites using Autotest is rather easy.
The whole validation suite is held in a file to be processed through
`autom4te', itself using GNU M4 under the scene, to produce a
stand-alone Bourne shell script which then gets distributed. Neither
`autom4te' nor GNU M4 are needed at the installer's end.
Each test of the validation suite should be part of some test group.
A "test group" is a sequence of interwoven tests that ought to be
executed together, usually because one test in the group creates data
files than a later test in the same group needs to read. Complex test
groups make later debugging more tedious. It is much better to keep
only a few tests per test group. Ideally there is only one test per
test group.
For all but the simplest packages, some file such as `testsuite.at'
does not fully hold all test sources, as these are often easier to
maintain in separate files. Each of these separate files holds a single
test group, or a sequence of test groups all addressing some common
functionality in the package. In such cases, `testsuite.at' merely
initializes the validation suite, and sometimes does elementary health
checking, before listing include statements for all other test files.
The special file `package.m4', containing the identification of the
package, is automatically included if found.
A convenient alternative consists in moving all the global issues
(local Autotest macros, elementary health checking, and `AT_INIT'
invocation) into the file `local.at', and making `testsuite.at' be a
simple list of `m4_include' of sub test suites. In such case,
generating the whole test suite or pieces of it is only a matter of
choosing the `autom4te' command line arguments.
The validation scripts that Autotest produces are by convention
called `testsuite'. When run, `testsuite' executes each test group in
turn, producing only one summary line per test to say if that
particular test succeeded or failed. At end of all tests, summarizing
counters get printed. One debugging directory is left for each test
group which failed, if any: such directories are named
`testsuite.dir/NN', where NN is the sequence number of the test group,
and they include:
* a debugging script named `run' which reruns the test in "debug
mode" (*note testsuite Invocation::). The automatic generation of
debugging scripts has the purpose of easing the chase for bugs.
* all the files created with `AT_DATA'
* a log of the run, named `testsuite.log'
In the ideal situation, none of the tests fail, and consequently no
debugging directory is left behind for validation.
It often happens in practice that individual tests in the validation
suite need to get information coming out of the configuration process.
Some of this information, common for all validation suites, is provided
through the file `atconfig', automatically created by
`AC_CONFIG_TESTDIR'. For configuration informations which your testing
environment specifically needs, you might prepare an optional file
named `atlocal.in', instantiated by `AC_CONFIG_FILES'. The
configuration process produces `atconfig' and `atlocal' out of these
two input files, and these two produced files are automatically read by
the `testsuite' script.
Here is a diagram showing the relationship between files.
Files used in preparing a software package for distribution:
[package.m4] -->.
\
subfile-1.at ->. [local.at] ---->+
... \ \
subfile-i.at ---->-- testsuite.at -->-- autom4te* -->testsuite
... /
subfile-n.at ->'
Files used in configuring a software package:
.--> atconfig
/
[atlocal.in] --> config.status* --<
\
`--> [atlocal]
Files created during the test suite execution:
atconfig -->. .--> testsuite.log
\ /
>-- testsuite* --<
/ \
[atlocal] ->' `--> [testsuite.dir]
File: autoconf.info, Node: Autotest Logs, Prev: testsuite Scripts, Up: Using an Autotest Test Suite
19.1.2 Autotest Logs
--------------------
When run, the test suite creates a log file named after itself, e.g., a
test suite named `testsuite' creates `testsuite.log'. It contains a
lot of information, usually more than maintainers actually need, but
therefore most of the time it contains all that is needed:
command line arguments
A bad but unfortunately widespread habit consists of setting
environment variables before the command, such as in
`CC=my-home-grown-cc ./testsuite'. The test suite does not know
this change, hence (i) it cannot report it to you, and (ii) it
cannot preserve the value of `CC' for subsequent runs. Autoconf
faced exactly the same problem, and solved it by asking users to
pass the variable definitions as command line arguments. Autotest
requires this rule, too, but has no means to enforce it; the log
then contains a trace of the variables that were changed by the
user.
`ChangeLog' excerpts
The topmost lines of all the `ChangeLog' files found in the source
hierarchy. This is especially useful when bugs are reported
against development versions of the package, since the version
string does not provide sufficient information to know the exact
state of the sources the user compiled. Of course, this relies on
the use of a `ChangeLog'.
build machine
Running a test suite in a cross-compile environment is not an easy
task, since it would mean having the test suite run on a machine
BUILD, while running programs on a machine HOST. It is much
simpler to run both the test suite and the programs on HOST, but
then, from the point of view of the test suite, there remains a
single environment, HOST = BUILD. The log contains relevant
information on the state of the build machine, including some
important environment variables.
tested programs
The absolute file name and answers to `--version' of the tested
programs (see *note Writing Testsuites::, `AT_TESTED').
configuration log
The contents of `config.log', as created by `configure', are
appended. It contains the configuration flags and a detailed
report on the configuration itself.
File: autoconf.info, Node: Writing Testsuites, Next: testsuite Invocation, Prev: Using an Autotest Test Suite, Up: Using Autotest
19.2 Writing `testsuite.at'
===========================
The `testsuite.at' is a Bourne shell script making use of special
Autotest M4 macros. It often contains a call to `AT_INIT' near its
beginning followed by one call to `m4_include' per source file for
tests. Each such included file, or the remainder of `testsuite.at' if
include files are not used, contain a sequence of test groups. Each
test group begins with a call to `AT_SETUP', then an arbitrary number
of shell commands or calls to `AT_CHECK', and then completes with a
call to `AT_CLEANUP'. Multiple test groups can be categorized by a
call to `AT_BANNER'.
All of the public Autotest macros have all-uppercase names in the
namespace `^AT_' to prevent them from accidentally conflicting with
other text; Autoconf also reserves the namespace `^_AT_' for internal
macros. All shell variables used in the testsuite for internal
purposes have mostly-lowercase names starting with `at_'. Autotest
also uses here-document delimiters in the namespace `^_AT[A-Z]', and
makes use of the file system namespace `^at-'.
Since Autoconf is built on top of M4sugar (*note Programming in
M4sugar::) and M4sh (*note Programming in M4sh::), you must also be
aware of those namespaces (`^_?\(m4\|AS\)_'). In general, you _should
not use_ the namespace of a package that does not own the macro or
shell code you are writing.
-- Macro: AT_INIT ([NAME])
Initialize Autotest. Giving a NAME to the test suite is
encouraged if your package includes several test suites. Before
this macro is called, `AT_PACKAGE_STRING' and
`AT_PACKAGE_BUGREPORT' must be defined, which are used to display
information about the testsuite to the user. Typically, these
macros are provided by a file `package.m4' built by `make' (*note
Making testsuite Scripts::), in order to inherit the package name,
version, and bug reporting address from `configure.ac'.
-- Macro: AT_COPYRIGHT (COPYRIGHT-NOTICE)
State that, in addition to the Free Software Foundation's
copyright on the Autotest macros, parts of your test suite are
covered by COPYRIGHT-NOTICE.
The COPYRIGHT-NOTICE shows up in both the head of `testsuite' and
in `testsuite --version'.
-- Macro: AT_TESTED (EXECUTABLES)
Log the file name and answer to `--version' of each program in
space-separated list EXECUTABLES. Several invocations register
new executables, in other words, don't fear registering one program
several times.
Autotest test suites rely on `PATH' to find the tested program.
This avoids the need to generate absolute names of the various tools,
and makes it possible to test installed programs. Therefore, knowing
which programs are being exercised is crucial to understanding problems
in the test suite itself, or its occasional misuses. It is a good idea
to also subscribe foreign programs you depend upon, to avoid
incompatible diagnostics.
-- Macro: AT_BANNER (TEST-CATEGORY-NAME)
This macro identifies the start of a category of related test
groups. When the resulting `testsuite' is invoked with more than
one test group to run, its output will include a banner containing
TEST-CATEGORY-NAME prior to any tests run from that category. The
banner should be no more than about 40 or 50 characters. A blank
banner will not print, effectively ending a category and letting
subsequent test groups behave as though they are uncategorized
when run in isolation.
-- Macro: AT_SETUP (TEST-GROUP-NAME)
This macro starts a group of related tests, all to be executed in
the same subshell. It accepts a single argument, which holds a
few words (no more than about 30 or 40 characters) quickly
describing the purpose of the test group being started.
TEST-GROUP-NAME must not expand to unbalanced quotes, although
quadrigraphs can be used.
-- Macro: AT_KEYWORDS (KEYWORDS)
Associate the space-separated list of KEYWORDS to the enclosing
test group. This makes it possible to run "slices" of the test
suite. For instance, if some of your test groups exercise some
`foo' feature, then using `AT_KEYWORDS(foo)' lets you run
`./testsuite -k foo' to run exclusively these test groups. The
TITLE of the test group is automatically recorded to `AT_KEYWORDS'.
Several invocations within a test group accumulate new keywords.
In other words, don't fear registering the same keyword several
times in a test group.
-- Macro: AT_CAPTURE_FILE (FILE)
If the current test group fails, log the contents of FILE.
Several identical calls within one test group have no additional
effect.
-- Macro: AT_FAIL_IF (SHELL-CONDITION)
Make the test group fail and skip the rest of its execution, if
SHELL-CONDITION is true. SHELL-CONDITION is a shell expression
such as a `test' command. Tests before `AT_FAIL_IF' will be
executed and may still cause the test group to be skipped. You
can instantiate this macro many times from within the same test
group.
You should use this macro only for very simple failure conditions.
If the SHELL-CONDITION could emit any kind of output you should
instead use `AT_CHECK' like
AT_CHECK([if SHELL-CONDITION; then exit 99; fi])
so that such output is properly recorded in the `testsuite.log'
file.
-- Macro: AT_SKIP_IF (SHELL-CONDITION)
Determine whether the test should be skipped because it requires
features that are unsupported on the machine under test.
SHELL-CONDITION is a shell expression such as a `test' command.
Tests before `AT_SKIP_IF' will be executed and may still cause the
test group to fail. You can instantiate this macro many times
from within the same test group.
You should use this macro only for very simple skip conditions.
If the SHELL-CONDITION could emit any kind of output you should
instead use `AT_CHECK' like
AT_CHECK([if SHELL-CONDITION; then exit 77; fi])
so that such output is properly recorded in the `testsuite.log'
file.
-- Macro: AT_XFAIL_IF (SHELL-CONDITION)
Determine whether the test is expected to fail because it is a
known bug (for unsupported features, you should skip the test).
SHELL-CONDITION is a shell expression such as a `test' command;
you can instantiate this macro many times from within the same
test group, and one of the conditions is enough to turn the test
into an expected failure.
-- Macro: AT_CLEANUP
End the current test group.
-- Macro: AT_DATA (FILE, CONTENTS)
Initialize an input data FILE with given CONTENTS. Of course, the
CONTENTS have to be properly quoted between square brackets to
protect against included commas or spurious M4 expansion. The
contents must end with an end of line. FILE must be a single
shell word that expands into a single file name.
-- Macro: AT_CHECK (COMMANDS, [STATUS = `0'], [STDOUT], [STDERR],
[RUN-IF-FAIL], [RUN-IF-PASS])
-- Macro: AT_CHECK_UNQUOTED (COMMANDS, [STATUS = `0'], [STDOUT],
[STDERR], [RUN-IF-FAIL], [RUN-IF-PASS])
Execute a test by performing given shell COMMANDS. COMMANDS is
output as-is, so shell expansions are honored. These commands
should normally exit with STATUS, while producing expected STDOUT
and STDERR contents. If COMMANDS exit with unexpected status 77,
then the rest of the test group is skipped. If COMMANDS exit with
unexpected status 99, then the test group is immediately failed.
Otherwise, if this test fails, run shell commands RUN-IF-FAIL or,
if this test passes, run shell commands RUN-IF-PASS.
This macro must be invoked in between `AT_SETUP' and `AT_CLEANUP'.
If STATUS is the literal `ignore', then the corresponding exit
status is not checked, except for the special cases of 77 (skip)
and 99 (hard failure). The existence of hard failures allows one
to mark a test as an expected failure with `AT_XFAIL_IF' because a
feature has not yet been implemented, but to still distinguish
between gracefully handling the missing feature and dumping core.
A hard failure also inhibits post-test actions in RUN-IF-FAIL.
If the value of the STDOUT or STDERR parameter is one of the
literals in the following table, then the test treats the output
according to the rules of that literal. Otherwise, the value of
the parameter is treated as text that must exactly match the
output given by COMMANDS on standard out and standard error
(including an empty parameter for no output); any differences are
captured in the testsuite log and the test is failed (unless an
unexpected exit status of 77 skipped the test instead). The
difference between `AT_CHECK' and `AT_CHECK_UNQUOTED' is that only
the latter performs shell variable expansion (`$'), command
substitution (``'), and backslash escaping (`\') on comparison
text given in the STDOUT and STDERR arguments; if the text
includes a trailing newline, this would be the same as if it were
specified via an unquoted here-document. (However, there is no
difference in the interpretation of COMMANDS).
`ignore'
The content of the output is ignored, but still captured in
the test group log (if the testsuite is run with option `-v',
the test group log is displayed as the test is run; if the
test group later fails, the test group log is also copied
into the overall testsuite log). This action is valid for
both STDOUT and STDERR.
`ignore-nolog'
The content of the output is ignored, and nothing is captured
in the log files. If COMMANDS are likely to produce binary
output (including long lines) or large amounts of output,
then logging the output can make it harder to locate details
related to subsequent tests within the group, and could
potentially corrupt terminal display of a user running
`testsuite -v'.
`stdout'
For the STDOUT parameter, capture the content of standard
output to both the file `stdout' and the test group log.
Subsequent commands in the test group can then post-process
the file. This action is often used when it is desired to
use `grep' to look for a substring in the output, or when the
output must be post-processed to normalize error messages
into a common form.
`stderr'
Like `stdout', except that it only works for the STDERR
parameter, and the standard error capture file will be named
`stderr'.
`stdout-nolog'
`stderr-nolog'
Like `stdout' or `stderr', except that the captured output is
not duplicated into the test group log. This action is
particularly useful for an intermediate check that produces
large amounts of data, which will be followed by another
check that filters down to the relevant data, as it makes it
easier to locate details in the log.
`expout'
For the STDOUT parameter, compare standard output contents
with the previously created file `expout', and list any
differences in the testsuite log.
`experr'
Like `expout', except that it only works for the STDERR
parameter, and the standard error contents are compared with
`experr'.
File: autoconf.info, Node: testsuite Invocation, Next: Making testsuite Scripts, Prev: Writing Testsuites, Up: Using Autotest
19.3 Running `testsuite' Scripts
================================
Autotest test suites support the following arguments:
`--help'
`-h'
Display the list of options and exit successfully.
`--version'
`-V'
Display the version of the test suite and exit successfully.
`--directory=DIR'
`-C DIR'
Change the current directory to DIR before creating any files.
Useful for running the testsuite in a subdirectory from a top-level
Makefile.
`--jobs[=N]'
`-j[N]'
Run N tests in parallel, if possible. If N is not given, run all
given tests in parallel. Note that there should be no space
before the argument to `-j', as `-j NUMBER' denotes the separate
arguments `-j' and `NUMBER', see below.
In parallel mode, the standard input device of the testsuite
script is not available to commands inside a test group.
Furthermore, banner lines are not printed, and the summary line
for each test group is output after the test group completes.
Summary lines may appear unordered. If verbose and trace output
are enabled (see below), they may appear intermixed from
concurrently running tests.
Parallel mode requires the `mkfifo' command to work, and will be
silently disabled otherwise.
`--clean'
`-c'
Remove all the files the test suite might have created and exit.
Meant for `clean' Make targets.
`--list'
`-l'
List all the tests (or only the selection), including their
possible keywords.
By default all tests are performed (or described with `--list') in
the default environment first silently, then verbosely, but the
environment, set of tests, and verbosity level can be tuned:
`VARIABLE=VALUE'
Set the environment VARIABLE to VALUE. Use this rather than
`FOO=foo ./testsuite' as debugging scripts would then run in a
different environment.
The variable `AUTOTEST_PATH' specifies the testing path to prepend
to `PATH'. Relative directory names (not starting with `/') are
considered to be relative to the top level of the package being
built. All directories are made absolute, first starting from the
top level _build_ tree, then from the _source_ tree. For instance
`./testsuite AUTOTEST_PATH=tests:bin' for a `/src/foo-1.0' source
package built in `/tmp/foo' results in
`/tmp/foo/tests:/tmp/foo/bin' and then
`/src/foo-1.0/tests:/src/foo-1.0/bin' being prepended to `PATH'.
`NUMBER'
`NUMBER-NUMBER'
`NUMBER-'
`-NUMBER'
Add the corresponding test groups, with obvious semantics, to the
selection.
`--keywords=KEYWORDS'
`-k KEYWORDS'
Add to the selection the test groups with title or keywords
(arguments to `AT_SETUP' or `AT_KEYWORDS') that match _all_
keywords of the comma separated list KEYWORDS, case-insensitively.
Use `!' immediately before the keyword to invert the selection for
this keyword. By default, the keywords match whole words; enclose
them in `.*' to also match parts of words.
For example, running
./testsuite -k 'autoupdate,.*FUNC.*'
selects all tests tagged `autoupdate' _and_ with tags containing
`FUNC' (as in `AC_CHECK_FUNC', `AC_FUNC_ALLOCA', etc.), while
./testsuite -k '!autoupdate' -k '.*FUNC.*'
selects all tests not tagged `autoupdate' _or_ with tags
containing `FUNC'.
`--errexit'
`-e'
If any test fails, immediately abort testing. It implies
`--debug': post test group clean up, and top-level logging are
inhibited. This option is meant for the full test suite, it is
not really useful for generated debugging scripts. If the
testsuite is run in parallel mode using `--jobs', then
concurrently running tests will finish before exiting.
`--verbose'
`-v'
Force more verbosity in the detailed output of what is being done.
This is the default for debugging scripts.
`--debug'
`-d'
Do not remove the files after a test group was performed --but
they are still removed _before_, therefore using this option is
sane when running several test groups. Create debugging scripts.
Do not overwrite the top-level log (in order to preserve
supposedly existing full log file). This is the default for
debugging scripts, but it can also be useful to debug the
testsuite itself.
`--trace'
`-x'
Trigger shell tracing of the test groups.
File: autoconf.info, Node: Making testsuite Scripts, Prev: testsuite Invocation, Up: Using Autotest
19.4 Making `testsuite' Scripts
===============================
For putting Autotest into movement, you need some configuration and
makefile machinery. We recommend, at least if your package uses deep or
shallow hierarchies, that you use `tests/' as the name of the directory
holding all your tests and their makefile. Here is a check list of
things to do.
- Make sure to create the file `package.m4', which defines the
identity of the package. It must define `AT_PACKAGE_STRING', the
full signature of the package, and `AT_PACKAGE_BUGREPORT', the
address to which bug reports should be sent. For sake of
completeness, we suggest that you also define `AT_PACKAGE_NAME',
`AT_PACKAGE_TARNAME', `AT_PACKAGE_VERSION', and `AT_PACKAGE_URL'.
*Note Initializing configure::, for a description of these
variables. Be sure to distribute `package.m4' and to put it into
the source hierarchy: the test suite ought to be shipped! See
below for an example `Makefile' excerpt.
- Invoke `AC_CONFIG_TESTDIR'.
-- Macro: AC_CONFIG_TESTDIR (DIRECTORY, [TEST-PATH = `directory'])
An Autotest test suite is to be configured in DIRECTORY. This
macro requires the instantiation of `DIRECTORY/atconfig' from
`DIRECTORY/atconfig.in', and sets the default `AUTOTEST_PATH'
to TEST-PATH (*note testsuite Invocation::).
- Still within `configure.ac', as appropriate, ensure that some
`AC_CONFIG_FILES' command includes substitution for
`tests/atlocal'.
- The appropriate `Makefile' should be modified so the validation in
your package is triggered by `make check'. An example is provided
below.
With Automake, here is a minimal example for inclusion in
`tests/Makefile.am', in order to link `make check' with a validation
suite.
# The `:;' works around a Bash 3.2 bug when the output is not writeable.
$(srcdir)/package.m4: $(top_srcdir)/configure.ac
:;{ \
echo '# Signature of the current package.' && \
echo 'm4_define([AT_PACKAGE_NAME],' && \
echo ' [@PACKAGE_NAME@])' && \
echo 'm4_define([AT_PACKAGE_TARNAME],' && \
echo ' [@PACKAGE_TARNAME@])' && \
echo 'm4_define([AT_PACKAGE_VERSION],' && \
echo ' [@PACKAGE_VERSION@])' && \
echo 'm4_define([AT_PACKAGE_STRING],' && \
echo ' [@PACKAGE_STRING@])' && \
echo 'm4_define([AT_PACKAGE_BUGREPORT],' && \
echo ' [@PACKAGE_BUGREPORT@])'; \
echo 'm4_define([AT_PACKAGE_URL],' && \
echo ' [@PACKAGE_URL@])'; \
} >'$(srcdir)/package.m4'
EXTRA_DIST = testsuite.at $(srcdir)/package.m4 $(TESTSUITE) atlocal.in
TESTSUITE = $(srcdir)/testsuite
check-local: atconfig atlocal $(TESTSUITE)
$(SHELL) '$(TESTSUITE)' $(TESTSUITEFLAGS)
installcheck-local: atconfig atlocal $(TESTSUITE)
$(SHELL) '$(TESTSUITE)' AUTOTEST_PATH='$(bindir)' \
$(TESTSUITEFLAGS)
clean-local:
test ! -f '$(TESTSUITE)' || \
$(SHELL) '$(TESTSUITE)' --clean
AUTOM4TE = $(SHELL) $(srcdir)/build-aux/missing --run autom4te
AUTOTEST = $(AUTOM4TE) --language=autotest
$(TESTSUITE): $(srcdir)/testsuite.at $(srcdir)/package.m4
$(AUTOTEST) -I '$(srcdir)' -o $@.tmp $@.at
mv $@.tmp $@
Note that the built testsuite is distributed; this is necessary
because users might not have Autoconf installed, and thus would not be
able to rebuild it. Likewise, the use of `missing' provides the user
with a nicer error message if they modify a source file to the
testsuite, and accidentally trigger the rebuild rules.
You might want to list explicitly the dependencies, i.e., the list of
the files `testsuite.at' includes.
If you don't use Automake, you should include the above example in
`tests/Makefile.in', along with additional lines inspired from the
following:
subdir = tests
atconfig: $(top_builddir)/config.status
cd $(top_builddir) && \
$(SHELL) ./config.status $(subdir)/$@
atlocal: $(srcdir)/atlocal.in $(top_builddir)/config.status
cd $(top_builddir) && \
$(SHELL) ./config.status $(subdir)/$@
and manage to have `$(EXTRA_DIST)' distributed. You will also want to
distribute the file `build-aux/missing' from the Automake project; a
copy of this file resides in the Autoconf source.
With all this in place, and if you have not initialized
`TESTSUITEFLAGS' within your makefile, you can fine-tune test suite
execution with this variable, for example:
make check TESTSUITEFLAGS='-v -d -x 75 -k AC_PROG_CC CFLAGS=-g'
File: autoconf.info, Node: FAQ, Next: History, Prev: Using Autotest, Up: Top
20 Frequent Autoconf Questions, with answers
********************************************
Several questions about Autoconf come up occasionally. Here some of
them are addressed.
* Menu:
* Distributing:: Distributing `configure' scripts
* Why GNU M4:: Why not use the standard M4?
* Bootstrapping:: Autoconf and GNU M4 require each other?
* Why Not Imake:: Why GNU uses `configure' instead of Imake
* Defining Directories:: Passing `datadir' to program
* Autom4te Cache:: What is it? Can I remove it?
* Present But Cannot Be Compiled:: Compiler and Preprocessor Disagree
* Expanded Before Required:: Expanded Before Required
File: autoconf.info, Node: Distributing, Next: Why GNU M4, Up: FAQ
20.1 Distributing `configure' Scripts
=====================================
What are the restrictions on distributing `configure'
scripts that Autoconf generates? How does that affect my
programs that use them?
There are no restrictions on how the configuration scripts that
Autoconf produces may be distributed or used. In Autoconf version 1,
they were covered by the GNU General Public License. We still encourage
software authors to distribute their work under terms like those of the
GPL, but doing so is not required to use Autoconf.
Of the other files that might be used with `configure',
`config.h.in' is under whatever copyright you use for your
`configure.ac'. `config.sub' and `config.guess' have an exception to
the GPL when they are used with an Autoconf-generated `configure'
script, which permits you to distribute them under the same terms as
the rest of your package. `install-sh' is from the X Consortium and is
not copyrighted.
File: autoconf.info, Node: Why GNU M4, Next: Bootstrapping, Prev: Distributing, Up: FAQ
20.2 Why Require GNU M4?
========================
Why does Autoconf require GNU M4?
Many M4 implementations have hard-coded limitations on the size and
number of macros that Autoconf exceeds. They also lack several builtin
macros that it would be difficult to get along without in a
sophisticated application like Autoconf, including:
m4_builtin
m4_indir
m4_bpatsubst
__file__
__line__
Autoconf requires version 1.4.6 or later of GNU M4.
Since only software maintainers need to use Autoconf, and since GNU
M4 is simple to configure and install, it seems reasonable to require
GNU M4 to be installed also. Many maintainers of GNU and other free
software already have most of the GNU utilities installed, since they
prefer them.
File: autoconf.info, Node: Bootstrapping, Next: Why Not Imake, Prev: Why GNU M4, Up: FAQ
20.3 How Can I Bootstrap?
=========================
If Autoconf requires GNU M4 and GNU M4 has an Autoconf
`configure' script, how do I bootstrap? It seems like a chicken
and egg problem!
This is a misunderstanding. Although GNU M4 does come with a
`configure' script produced by Autoconf, Autoconf is not required in
order to run the script and install GNU M4. Autoconf is only required
if you want to change the M4 `configure' script, which few people have
to do (mainly its maintainer).
File: autoconf.info, Node: Why Not Imake, Next: Defining Directories, Prev: Bootstrapping, Up: FAQ
20.4 Why Not Imake?
===================
Why not use Imake instead of `configure' scripts?
Several people have written addressing this question, so I include
adaptations of their explanations here.
The following answer is based on one written by Richard Pixley:
Autoconf generated scripts frequently work on machines that it has
never been set up to handle before. That is, it does a good job of
inferring a configuration for a new system. Imake cannot do this.
Imake uses a common database of host specific data. For X11, this
makes sense because the distribution is made as a collection of
tools, by one central authority who has control over the database.
GNU tools are not released this way. Each GNU tool has a
maintainer; these maintainers are scattered across the world.
Using a common database would be a maintenance nightmare.
Autoconf may appear to be this kind of database, but in fact it is
not. Instead of listing host dependencies, it lists program
requirements.
If you view the GNU suite as a collection of native tools, then the
problems are similar. But the GNU development tools can be
configured as cross tools in almost any host+target permutation.
All of these configurations can be installed concurrently. They
can even be configured to share host independent files across
hosts. Imake doesn't address these issues.
Imake templates are a form of standardization. The GNU coding
standards address the same issues without necessarily imposing the
same restrictions.
Here is some further explanation, written by Per Bothner:
One of the advantages of Imake is that it easy to generate large
makefiles using the `#include' and macro mechanisms of `cpp'.
However, `cpp' is not programmable: it has limited conditional
facilities, and no looping. And `cpp' cannot inspect its
environment.
All of these problems are solved by using `sh' instead of `cpp'.
The shell is fully programmable, has macro substitution, can
execute (or source) other shell scripts, and can inspect its
environment.
Paul Eggert elaborates more:
With Autoconf, installers need not assume that Imake itself is
already installed and working well. This may not seem like much
of an advantage to people who are accustomed to Imake. But on
many hosts Imake is not installed or the default installation is
not working well, and requiring Imake to install a package hinders
the acceptance of that package on those hosts. For example, the
Imake template and configuration files might not be installed
properly on a host, or the Imake build procedure might wrongly
assume that all source files are in one big directory tree, or the
Imake configuration might assume one compiler whereas the package
or the installer needs to use another, or there might be a version
mismatch between the Imake expected by the package and the Imake
supported by the host. These problems are much rarer with
Autoconf, where each package comes with its own independent
configuration processor.
Also, Imake often suffers from unexpected interactions between
`make' and the installer's C preprocessor. The fundamental problem
here is that the C preprocessor was designed to preprocess C
programs, not makefiles. This is much less of a problem with
Autoconf, which uses the general-purpose preprocessor M4, and
where the package's author (rather than the installer) does the
preprocessing in a standard way.
Finally, Mark Eichin notes:
Imake isn't all that extensible, either. In order to add new
features to Imake, you need to provide your own project template,
and duplicate most of the features of the existing one. This
means that for a sophisticated project, using the vendor-provided
Imake templates fails to provide any leverage--since they don't
cover anything that your own project needs (unless it is an X11
program).
On the other side, though:
The one advantage that Imake has over `configure': `Imakefile'
files tend to be much shorter (likewise, less redundant) than
`Makefile.in' files. There is a fix to this, however--at least
for the Kerberos V5 tree, we've modified things to call in common
`post.in' and `pre.in' makefile fragments for the entire tree.
This means that a lot of common things don't have to be
duplicated, even though they normally are in `configure' setups.
File: autoconf.info, Node: Defining Directories, Next: Autom4te Cache, Prev: Why Not Imake, Up: FAQ
20.5 How Do I `#define' Installation Directories?
=================================================
My program needs library files, installed in `datadir' and
similar. If I use
AC_DEFINE_UNQUOTED([DATADIR], [$datadir],
[Define to the read-only architecture-independent
data directory.])
I get
#define DATADIR "${prefix}/share"
As already explained, this behavior is on purpose, mandated by the GNU
Coding Standards, see *note Installation Directory Variables::. There
are several means to achieve a similar goal:
- Do not use `AC_DEFINE' but use your makefile to pass the actual
value of `datadir' via compilation flags. *Note Installation
Directory Variables::, for the details.
- This solution can be simplified when compiling a program: you may
either extend the `CPPFLAGS':
CPPFLAGS = -DDATADIR='"$(datadir)"' @CPPFLAGS@
If you are using Automake, you should use `AM_CPPFLAGS' instead:
AM_CPPFLAGS = -DDATADIR='"$(datadir)"'
Alternatively, create a dedicated header file:
DISTCLEANFILES = myprog-paths.h
myprog-paths.h: Makefile
echo '#define DATADIR "$(datadir)"' >$@
- Use `AC_DEFINE' but have `configure' compute the literal value of
`datadir' and others. Many people have wrapped macros to automate
this task; for an example, see the macro `AC_DEFINE_DIR' from the
Autoconf Macro Archive (http://autoconf-archive.cryp.to/).
This solution does not conform to the GNU Coding Standards.
- Note that all the previous solutions hard wire the absolute name of
these directories in the executables, which is not a good
property. You may try to compute the names relative to `prefix',
and try to find `prefix' at runtime, this way your package is
relocatable.
File: autoconf.info, Node: Autom4te Cache, Next: Present But Cannot Be Compiled, Prev: Defining Directories, Up: FAQ
20.6 What is `autom4te.cache'?
==============================
What is this directory `autom4te.cache'? Can I safely remove it?
In the GNU Build System, `configure.ac' plays a central role and is
read by many tools: `autoconf' to create `configure', `autoheader' to
create `config.h.in', `automake' to create `Makefile.in', `autoscan' to
check the completeness of `configure.ac', `autoreconf' to check the GNU
Build System components that are used. To "read `configure.ac'"
actually means to compile it with M4, which can be a long process for
complex `configure.ac'.
This is why all these tools, instead of running directly M4, invoke
`autom4te' (*note autom4te Invocation::) which, while answering to a
specific demand, stores additional information in `autom4te.cache' for
future runs. For instance, if you run `autoconf', behind the scenes,
`autom4te' also stores information for the other tools, so that when
you invoke `autoheader' or `automake' etc., reprocessing `configure.ac'
is not needed. The speed up is frequently 30%, and is increasing with
the size of `configure.ac'.
But it is and remains being simply a cache: you can safely remove it.
Can I permanently get rid of it?
The creation of this cache can be disabled from `~/.autom4te.cfg',
see *note Customizing autom4te::, for more details. You should be
aware that disabling the cache slows down the Autoconf test suite by
40%. The more GNU Build System components are used, the more the cache
is useful; for instance running `autoreconf -f' on the Core Utilities
is twice slower without the cache _although `--force' implies that the
cache is not fully exploited_, and eight times slower than without
`--force'.
File: autoconf.info, Node: Present But Cannot Be Compiled, Next: Expanded Before Required, Prev: Autom4te Cache, Up: FAQ
20.7 Header Present But Cannot Be Compiled
==========================================
The most important guideline to bear in mind when checking for features
is to mimic as much as possible the intended use. Unfortunately, old
versions of `AC_CHECK_HEADER' and `AC_CHECK_HEADERS' failed to follow
this idea, and called the preprocessor, instead of the compiler, to
check for headers. As a result, incompatibilities between headers went
unnoticed during configuration, and maintainers finally had to deal
with this issue elsewhere.
The transition began with Autoconf 2.56. As of Autoconf 2.64 both
checks are performed, and `configure' complains loudly if the compiler
and the preprocessor do not agree. However, only the compiler result
is considered.
Consider the following example:
$ cat number.h
typedef int number;
$ cat pi.h
const number pi = 3;
$ cat configure.ac
AC_INIT([Example], [1.0], [bug-example@example.org])
AC_CHECK_HEADERS([pi.h])
$ autoconf -Wall
$ ./configure
checking for gcc... gcc
checking for C compiler default output file name... a.out
checking whether the C compiler works... yes
checking whether we are cross compiling... no
checking for suffix of executables...
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ISO C89... none needed
checking how to run the C preprocessor... gcc -E
checking for grep that handles long lines and -e... grep
checking for egrep... grep -E
checking for ANSI C header files... yes
checking for sys/types.h... yes
checking for sys/stat.h... yes
checking for stdlib.h... yes
checking for string.h... yes
checking for memory.h... yes
checking for strings.h... yes
checking for inttypes.h... yes
checking for stdint.h... yes
checking for unistd.h... yes
checking pi.h usability... no
checking pi.h presence... yes
configure: WARNING: pi.h: present but cannot be compiled
configure: WARNING: pi.h: check for missing prerequisite headers?
configure: WARNING: pi.h: see the Autoconf documentation
configure: WARNING: pi.h: section "Present But Cannot Be Compiled"
configure: WARNING: pi.h: proceeding with the compiler's result
configure: WARNING: ## -------------------------------------- ##
configure: WARNING: ## Report this to bug-example@example.org ##
configure: WARNING: ## -------------------------------------- ##
checking for pi.h... yes
The proper way the handle this case is using the fourth argument (*note
Generic Headers::):
$ cat configure.ac
AC_INIT([Example], [1.0], [bug-example@example.org])
AC_CHECK_HEADERS([number.h pi.h], [], [],
[[#ifdef HAVE_NUMBER_H
# include
#endif
]])
$ autoconf -Wall
$ ./configure
checking for gcc... gcc
checking for C compiler default output... a.out
checking whether the C compiler works... yes
checking whether we are cross compiling... no
checking for suffix of executables...
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ANSI C... none needed
checking for number.h... yes
checking for pi.h... yes
See *note Particular Headers::, for a list of headers with their
prerequisites.
File: autoconf.info, Node: Expanded Before Required, Prev: Present But Cannot Be Compiled, Up: FAQ
20.8 Expanded Before Required
=============================
Older versions of Autoconf silently built files with incorrect ordering
between dependent macros if an outer macro first expanded, then later
indirectly required, an inner macro. Starting with Autoconf 2.64, this
situation no longer generates out-of-order code, but results in
duplicate output and a syntax warning:
$ cat configure.ac
=>AC_DEFUN([TESTA], [[echo in A
=>if test -n "$SEEN_A" ; then echo duplicate ; fi
=>SEEN_A=:]])
=>AC_DEFUN([TESTB], [AC_REQUIRE([TESTA])[echo in B
=>if test -z "$SEEN_A" ; then echo bug ; fi]])
=>AC_DEFUN([TESTC], [AC_REQUIRE([TESTB])[echo in C]])
=>AC_DEFUN([OUTER], [[echo in OUTER]
=>TESTA
=>TESTC])
=>AC_INIT
=>OUTER
=>AC_OUTPUT
$ autoconf
=>configure.ac:11: warning: AC_REQUIRE:
=> `TESTA' was expanded before it was required
=>configure.ac:4: TESTB is expanded from...
=>configure.ac:6: TESTC is expanded from...
=>configure.ac:7: OUTER is expanded from...
=>configure.ac:11: the top level
To avoid this warning, decide what purpose the macro in question serves.
If it only needs to be expanded once (for example, if it provides
initialization text used by later macros), then the simplest fix is to
change the macro to be declared with `AC_DEFUN_ONCE' (*note One-Shot
Macros::), although this only works in Autoconf 2.64 and newer. A more
portable fix is to change all instances of direct calls to instead go
through `AC_REQUIRE' (*note Prerequisite Macros::). If, instead, the
macro is parameterized by arguments or by the current definition of
other macros in the m4 environment, then the macro should always be
directly expanded instead of required.
For another case study, consider this example trimmed down from an
actual package. Originally, the package contained shell code and
multiple macro invocations at the top level of `configure.ac':
AC_DEFUN([FOO], [AC_COMPILE_IFELSE([...])])
foobar=
AC_PROG_CC
FOO
but that was getting complex, so the author wanted to offload some of
the text into a new macro in another file included via `aclocal.m4'.
The nai"ve approach merely wraps the text in a new macro:
AC_DEFUN([FOO], [AC_COMPILE_IFELSE([...])])
AC_DEFUN([BAR], [
foobar=
AC_PROG_CC
FOO
])
BAR
With older versions of Autoconf, the setting of `foobar=' occurs before
the single compiler check, as the author intended. But with Autoconf
2.64, this issues the "expanded before it was required" warning for
`AC_PROG_CC', and outputs two copies of the compiler check, one before
`foobar=', and one after. To understand why this is happening,
remember that the use of `AC_COMPILE_IFELSE' includes a call to
`AC_REQUIRE([AC_PROG_CC])' under the hood. According to the documented
semantics of `AC_REQUIRE', this means that `AC_PROG_CC' _must_ occur
before the body of the outermost `AC_DEFUN', which in this case is
`BAR', thus preceeding the use of `foobar='. The older versions of
Autoconf were broken with regards to the rules of `AC_REQUIRE', which
explains why the code changed from one over to two copies of
`AC_PROG_CC' when upgrading autoconf. In other words, the author was
unknowingly relying on a bug exploit to get the desired results, and
that exploit broke once the bug was fixed.
So, what recourse does the author have, to restore their intended
semantics of setting `foobar=' prior to a single compiler check,
regardless of whether Autoconf 2.63 or 2.64 is used? One idea is to
remember that only `AC_DEFUN' is impacted by `AC_REQUIRE'; there is
always the possibility of using the lower-level `m4_define':
AC_DEFUN([FOO], [AC_COMPILE_IFELSE([...])])
m4_define([BAR], [
foobar=
AC_PROG_CC
FOO
])
BAR
This works great if everything is in the same file. However, it does
not help in the case where the author wants to have `aclocal' find the
definition of `BAR' from its own file, since `aclocal' requires the use
of `AC_DEFUN'. In this case, a better fix is to recognize that if
`BAR' also uses `AC_REQUIRE', then there will no longer be direct
expansion prior to a subsequent require. Then, by creating yet another
helper macro, the author can once again guarantee a single invocation of
`AC_PROG_CC', which will still occur after `foobar='. The author can
also use `AC_BEFORE' to make sure no other macro appearing before `BAR'
has triggered an unwanted expansion of `AC_PROG_CC'.
AC_DEFUN([FOO], [AC_COMPILE_IFELSE([...])])
AC_DEFUN([BEFORE_CC], [
foobar=
])
AC_DEFUN([BAR], [
AC_BEFORE([$0], [AC_PROG_CC])dnl
AC_REQUIRE([BEFORE_CC])dnl
AC_REQUIRE([AC_PROG_CC])dnl
FOO
])
BAR
File: autoconf.info, Node: History, Next: GNU Free Documentation License, Prev: FAQ, Up: Top
21 History of Autoconf
**********************
You may be wondering, Why was Autoconf originally written? How did it
get into its present form? (Why does it look like gorilla spit?) If
you're not wondering, then this chapter contains no information useful
to you, and you might as well skip it. If you _are_ wondering, then
let there be light...
* Menu:
* Genesis:: Prehistory and naming of `configure'
* Exodus:: The plagues of M4 and Perl
* Leviticus:: The priestly code of portability arrives
* Numbers:: Growth and contributors
* Deuteronomy:: Approaching the promises of easy configuration
File: autoconf.info, Node: Genesis, Next: Exodus, Up: History
21.1 Genesis
============
In June 1991 I was maintaining many of the GNU utilities for the Free
Software Foundation. As they were ported to more platforms and more
programs were added, the number of `-D' options that users had to
select in the makefile (around 20) became burdensome. Especially for
me--I had to test each new release on a bunch of different systems. So
I wrote a little shell script to guess some of the correct settings for
the fileutils package, and released it as part of fileutils 2.0. That
`configure' script worked well enough that the next month I adapted it
(by hand) to create similar `configure' scripts for several other GNU
utilities packages. Brian Berliner also adapted one of my scripts for
his CVS revision control system.
Later that summer, I learned that Richard Stallman and Richard Pixley
were developing similar scripts to use in the GNU compiler tools; so I
adapted my `configure' scripts to support their evolving interface:
using the file name `Makefile.in' as the templates; adding `+srcdir',
the first option (of many); and creating `config.status' files.
File: autoconf.info, Node: Exodus, Next: Leviticus, Prev: Genesis, Up: History
21.2 Exodus
===========
As I got feedback from users, I incorporated many improvements, using
Emacs to search and replace, cut and paste, similar changes in each of
the scripts. As I adapted more GNU utilities packages to use
`configure' scripts, updating them all by hand became impractical.
Rich Murphey, the maintainer of the GNU graphics utilities, sent me
mail saying that the `configure' scripts were great, and asking if I
had a tool for generating them that I could send him. No, I thought,
but I should! So I started to work out how to generate them. And the
journey from the slavery of hand-written `configure' scripts to the
abundance and ease of Autoconf began.
Cygnus `configure', which was being developed at around that time,
is table driven; it is meant to deal mainly with a discrete number of
system types with a small number of mainly unguessable features (such as
details of the object file format). The automatic configuration system
that Brian Fox had developed for Bash takes a similar approach. For
general use, it seems to me a hopeless cause to try to maintain an
up-to-date database of which features each variant of each operating
system has. It's easier and more reliable to check for most features on
the fly--especially on hybrid systems that people have hacked on
locally or that have patches from vendors installed.
I considered using an architecture similar to that of Cygnus
`configure', where there is a single `configure' script that reads
pieces of `configure.in' when run. But I didn't want to have to
distribute all of the feature tests with every package, so I settled on
having a different `configure' made from each `configure.in' by a
preprocessor. That approach also offered more control and flexibility.
I looked briefly into using the Metaconfig package, by Larry Wall,
Harlan Stenn, and Raphael Manfredi, but I decided not to for several
reasons. The `Configure' scripts it produces are interactive, which I
find quite inconvenient; I didn't like the ways it checked for some
features (such as library functions); I didn't know that it was still
being maintained, and the `Configure' scripts I had seen didn't work on
many modern systems (such as System V R4 and NeXT); it wasn't flexible
in what it could do in response to a feature's presence or absence; I
found it confusing to learn; and it was too big and complex for my
needs (I didn't realize then how much Autoconf would eventually have to
grow).
I considered using Perl to generate my style of `configure' scripts,
but decided that M4 was better suited to the job of simple textual
substitutions: it gets in the way less, because output is implicit.
Plus, everyone already has it. (Initially I didn't rely on the GNU
extensions to M4.) Also, some of my friends at the University of
Maryland had recently been putting M4 front ends on several programs,
including `tvtwm', and I was interested in trying out a new language.
File: autoconf.info, Node: Leviticus, Next: Numbers, Prev: Exodus, Up: History
21.3 Leviticus
==============
Since my `configure' scripts determine the system's capabilities
automatically, with no interactive user intervention, I decided to call
the program that generates them Autoconfig. But with a version number
tacked on, that name would be too long for old Unix file systems, so I
shortened it to Autoconf.
In the fall of 1991 I called together a group of fellow questers
after the Holy Grail of portability (er, that is, alpha testers) to
give me feedback as I encapsulated pieces of my handwritten scripts in
M4 macros and continued to add features and improve the techniques used
in the checks. Prominent among the testers were Franc,ois Pinard, who
came up with the idea of making an Autoconf shell script to run M4 and
check for unresolved macro calls; Richard Pixley, who suggested running
the compiler instead of searching the file system to find include files
and symbols, for more accurate results; Karl Berry, who got Autoconf to
configure TeX and added the macro index to the documentation; and Ian
Lance Taylor, who added support for creating a C header file as an
alternative to putting `-D' options in a makefile, so he could use
Autoconf for his UUCP package. The alpha testers cheerfully adjusted
their files again and again as the names and calling conventions of the
Autoconf macros changed from release to release. They all contributed
many specific checks, great ideas, and bug fixes.
File: autoconf.info, Node: Numbers, Next: Deuteronomy, Prev: Leviticus, Up: History
21.4 Numbers
============
In July 1992, after months of alpha testing, I released Autoconf 1.0,
and converted many GNU packages to use it. I was surprised by how
positive the reaction to it was. More people started using it than I
could keep track of, including people working on software that wasn't
part of the GNU Project (such as TCL, FSP, and Kerberos V5). Autoconf
continued to improve rapidly, as many people using the `configure'
scripts reported problems they encountered.
Autoconf turned out to be a good torture test for M4 implementations.
Unix M4 started to dump core because of the length of the macros that
Autoconf defined, and several bugs showed up in GNU M4 as well.
Eventually, we realized that we needed to use some features that only
GNU M4 has. 4.3BSD M4, in particular, has an impoverished set of
builtin macros; the System V version is better, but still doesn't
provide everything we need.
More development occurred as people put Autoconf under more stresses
(and to uses I hadn't anticipated). Karl Berry added checks for X11.
david zuhn contributed C++ support. Franc,ois Pinard made it diagnose
invalid arguments. Jim Blandy bravely coerced it into configuring GNU
Emacs, laying the groundwork for several later improvements. Roland
McGrath got it to configure the GNU C Library, wrote the `autoheader'
script to automate the creation of C header file templates, and added a
`--verbose' option to `configure'. Noah Friedman added the
`--autoconf-dir' option and `AC_MACRODIR' environment variable. (He
also coined the term "autoconfiscate" to mean "adapt a software package
to use Autoconf".) Roland and Noah improved the quoting protection in
`AC_DEFINE' and fixed many bugs, especially when I got sick of dealing
with portability problems from February through June, 1993.
File: autoconf.info, Node: Deuteronomy, Prev: Numbers, Up: History
21.5 Deuteronomy
================
A long wish list for major features had accumulated, and the effect of
several years of patching by various people had left some residual
cruft. In April 1994, while working for Cygnus Support, I began a major
revision of Autoconf. I added most of the features of the Cygnus
`configure' that Autoconf had lacked, largely by adapting the relevant
parts of Cygnus `configure' with the help of david zuhn and Ken
Raeburn. These features include support for using `config.sub',
`config.guess', `--host', and `--target'; making links to files; and
running `configure' scripts in subdirectories. Adding these features
enabled Ken to convert GNU `as', and Rob Savoye to convert DejaGNU, to
using Autoconf.
I added more features in response to other peoples' requests. Many
people had asked for `configure' scripts to share the results of the
checks between runs, because (particularly when configuring a large
source tree, like Cygnus does) they were frustratingly slow. Mike
Haertel suggested adding site-specific initialization scripts. People
distributing software that had to unpack on MS-DOS asked for a way to
override the `.in' extension on the file names, which produced file
names like `config.h.in' containing two dots. Jim Avera did an
extensive examination of the problems with quoting in `AC_DEFINE' and
`AC_SUBST'; his insights led to significant improvements. Richard
Stallman asked that compiler output be sent to `config.log' instead of
`/dev/null', to help people debug the Emacs `configure' script.
I made some other changes because of my dissatisfaction with the
quality of the program. I made the messages showing results of the
checks less ambiguous, always printing a result. I regularized the
names of the macros and cleaned up coding style inconsistencies. I
added some auxiliary utilities that I had developed to help convert
source code packages to use Autoconf. With the help of Franc,ois
Pinard, I made the macros not interrupt each others' messages. (That
feature revealed some performance bottlenecks in GNU M4, which he
hastily corrected!) I reorganized the documentation around problems
people want to solve. And I began a test suite, because experience had
shown that Autoconf has a pronounced tendency to regress when we change
it.
Again, several alpha testers gave invaluable feedback, especially
Franc,ois Pinard, Jim Meyering, Karl Berry, Rob Savoye, Ken Raeburn,
and Mark Eichin.
Finally, version 2.0 was ready. And there was much rejoicing. (And
I have free time again. I think. Yeah, right.)
File: autoconf.info, Node: GNU Free Documentation License, Next: Indices, Prev: History, Up: Top
Appendix A GNU Free Documentation License
*****************************************
Version 1.3, 3 November 2008
Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
`http://fsf.org/'
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
0. PREAMBLE
The purpose of this License is to make a manual, textbook, or other
functional and useful document "free" in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or
noncommercially. Secondarily, this License preserves for the
author and publisher a way to get credit for their work, while not
being considered responsible for modifications made by others.
This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense.
It complements the GNU General Public License, which is a copyleft
license designed for free software.
We have designed this License in order to use it for manuals for
free software, because free software needs free documentation: a
free program should come with manuals providing the same freedoms
that the software does. But this License is not limited to
software manuals; it can be used for any textual work, regardless
of subject matter or whether it is published as a printed book.
We recommend this License principally for works whose purpose is
instruction or reference.
1. APPLICABILITY AND DEFINITIONS
This License applies to any manual or other work, in any medium,
that contains a notice placed by the copyright holder saying it
can be distributed under the terms of this License. Such a notice
grants a world-wide, royalty-free license, unlimited in duration,
to use that work under the conditions stated herein. The
"Document", below, refers to any such manual or work. Any member
of the public is a licensee, and is addressed as "you". You
accept the license if you copy, modify or distribute the work in a
way requiring permission under copyright law.
A "Modified Version" of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.
A "Secondary Section" is a named appendix or a front-matter section
of the Document that deals exclusively with the relationship of the
publishers or authors of the Document to the Document's overall
subject (or to related matters) and contains nothing that could
fall directly within that overall subject. (Thus, if the Document
is in part a textbook of mathematics, a Secondary Section may not
explain any mathematics.) The relationship could be a matter of
historical connection with the subject or with related matters, or
of legal, commercial, philosophical, ethical or political position
regarding them.
The "Invariant Sections" are certain Secondary Sections whose
titles are designated, as being those of Invariant Sections, in
the notice that says that the Document is released under this
License. If a section does not fit the above definition of
Secondary then it is not allowed to be designated as Invariant.
The Document may contain zero Invariant Sections. If the Document
does not identify any Invariant Sections then there are none.
The "Cover Texts" are certain short passages of text that are
listed, as Front-Cover Texts or Back-Cover Texts, in the notice
that says that the Document is released under this License. A
Front-Cover Text may be at most 5 words, and a Back-Cover Text may
be at most 25 words.
A "Transparent" copy of the Document means a machine-readable copy,
represented in a format whose specification is available to the
general public, that is suitable for revising the document
straightforwardly with generic text editors or (for images
composed of pixels) generic paint programs or (for drawings) some
widely available drawing editor, and that is suitable for input to
text formatters or for automatic translation to a variety of
formats suitable for input to text formatters. A copy made in an
otherwise Transparent file format whose markup, or absence of
markup, has been arranged to thwart or discourage subsequent
modification by readers is not Transparent. An image format is
not Transparent if used for any substantial amount of text. A
copy that is not "Transparent" is called "Opaque".
Examples of suitable formats for Transparent copies include plain
ASCII without markup, Texinfo input format, LaTeX input format,
SGML or XML using a publicly available DTD, and
standard-conforming simple HTML, PostScript or PDF designed for
human modification. Examples of transparent image formats include
PNG, XCF and JPG. Opaque formats include proprietary formats that
can be read and edited only by proprietary word processors, SGML or
XML for which the DTD and/or processing tools are not generally
available, and the machine-generated HTML, PostScript or PDF
produced by some word processors for output purposes only.
The "Title Page" means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the
material this License requires to appear in the title page. For
works in formats which do not have any title page as such, "Title
Page" means the text near the most prominent appearance of the
work's title, preceding the beginning of the body of the text.
The "publisher" means any person or entity that distributes copies
of the Document to the public.
A section "Entitled XYZ" means a named subunit of the Document
whose title either is precisely XYZ or contains XYZ in parentheses
following text that translates XYZ in another language. (Here XYZ
stands for a specific section name mentioned below, such as
"Acknowledgements", "Dedications", "Endorsements", or "History".)
To "Preserve the Title" of such a section when you modify the
Document means that it remains a section "Entitled XYZ" according
to this definition.
The Document may include Warranty Disclaimers next to the notice
which states that this License applies to the Document. These
Warranty Disclaimers are considered to be included by reference in
this License, but only as regards disclaiming warranties: any other
implication that these Warranty Disclaimers may have is void and
has no effect on the meaning of this License.
2. VERBATIM COPYING
You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License
applies to the Document are reproduced in all copies, and that you
add no other conditions whatsoever to those of this License. You
may not use technical measures to obstruct or control the reading
or further copying of the copies you make or distribute. However,
you may accept compensation in exchange for copies. If you
distribute a large enough number of copies you must also follow
the conditions in section 3.
You may also lend copies, under the same conditions stated above,
and you may publicly display copies.
3. COPYING IN QUANTITY
If you publish printed copies (or copies in media that commonly
have printed covers) of the Document, numbering more than 100, and
the Document's license notice requires Cover Texts, you must
enclose the copies in covers that carry, clearly and legibly, all
these Cover Texts: Front-Cover Texts on the front cover, and
Back-Cover Texts on the back cover. Both covers must also clearly
and legibly identify you as the publisher of these copies. The
front cover must present the full title with all words of the
title equally prominent and visible. You may add other material
on the covers in addition. Copying with changes limited to the
covers, as long as they preserve the title of the Document and
satisfy these conditions, can be treated as verbatim copying in
other respects.
If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto
adjacent pages.
If you publish or distribute Opaque copies of the Document
numbering more than 100, you must either include a
machine-readable Transparent copy along with each Opaque copy, or
state in or with each Opaque copy a computer-network location from
which the general network-using public has access to download
using public-standard network protocols a complete Transparent
copy of the Document, free of added material. If you use the
latter option, you must take reasonably prudent steps, when you
begin distribution of Opaque copies in quantity, to ensure that
this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you
distribute an Opaque copy (directly or through your agents or
retailers) of that edition to the public.
It is requested, but not required, that you contact the authors of
the Document well before redistributing any large number of
copies, to give them a chance to provide you with an updated
version of the Document.
4. MODIFICATIONS
You may copy and distribute a Modified Version of the Document
under the conditions of sections 2 and 3 above, provided that you
release the Modified Version under precisely this License, with
the Modified Version filling the role of the Document, thus
licensing distribution and modification of the Modified Version to
whoever possesses a copy of it. In addition, you must do these
things in the Modified Version:
A. Use in the Title Page (and on the covers, if any) a title
distinct from that of the Document, and from those of
previous versions (which should, if there were any, be listed
in the History section of the Document). You may use the
same title as a previous version if the original publisher of
that version gives permission.
B. List on the Title Page, as authors, one or more persons or
entities responsible for authorship of the modifications in
the Modified Version, together with at least five of the
principal authors of the Document (all of its principal
authors, if it has fewer than five), unless they release you
from this requirement.
C. State on the Title page the name of the publisher of the
Modified Version, as the publisher.
D. Preserve all the copyright notices of the Document.
E. Add an appropriate copyright notice for your modifications
adjacent to the other copyright notices.
F. Include, immediately after the copyright notices, a license
notice giving the public permission to use the Modified
Version under the terms of this License, in the form shown in
the Addendum below.
G. Preserve in that license notice the full lists of Invariant
Sections and required Cover Texts given in the Document's
license notice.
H. Include an unaltered copy of this License.
I. Preserve the section Entitled "History", Preserve its Title,
and add to it an item stating at least the title, year, new
authors, and publisher of the Modified Version as given on
the Title Page. If there is no section Entitled "History" in
the Document, create one stating the title, year, authors,
and publisher of the Document as given on its Title Page,
then add an item describing the Modified Version as stated in
the previous sentence.
J. Preserve the network location, if any, given in the Document
for public access to a Transparent copy of the Document, and
likewise the network locations given in the Document for
previous versions it was based on. These may be placed in
the "History" section. You may omit a network location for a
work that was published at least four years before the
Document itself, or if the original publisher of the version
it refers to gives permission.
K. For any section Entitled "Acknowledgements" or "Dedications",
Preserve the Title of the section, and preserve in the
section all the substance and tone of each of the contributor
acknowledgements and/or dedications given therein.
L. Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles. Section numbers
or the equivalent are not considered part of the section
titles.
M. Delete any section Entitled "Endorsements". Such a section
may not be included in the Modified Version.
N. Do not retitle any existing section to be Entitled
"Endorsements" or to conflict in title with any Invariant
Section.
O. Preserve any Warranty Disclaimers.
If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no
material copied from the Document, you may at your option
designate some or all of these sections as invariant. To do this,
add their titles to the list of Invariant Sections in the Modified
Version's license notice. These titles must be distinct from any
other section titles.
You may add a section Entitled "Endorsements", provided it contains
nothing but endorsements of your Modified Version by various
parties--for example, statements of peer review or that the text
has been approved by an organization as the authoritative
definition of a standard.
You may add a passage of up to five words as a Front-Cover Text,
and a passage of up to 25 words as a Back-Cover Text, to the end
of the list of Cover Texts in the Modified Version. Only one
passage of Front-Cover Text and one of Back-Cover Text may be
added by (or through arrangements made by) any one entity. If the
Document already includes a cover text for the same cover,
previously added by you or by arrangement made by the same entity
you are acting on behalf of, you may not add another; but you may
replace the old one, on explicit permission from the previous
publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this
License give permission to use their names for publicity for or to
assert or imply endorsement of any Modified Version.
5. COMBINING DOCUMENTS
You may combine the Document with other documents released under
this License, under the terms defined in section 4 above for
modified versions, provided that you include in the combination
all of the Invariant Sections of all of the original documents,
unmodified, and list them all as Invariant Sections of your
combined work in its license notice, and that you preserve all
their Warranty Disclaimers.
The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy. If there are multiple Invariant Sections with the same name
but different contents, make the title of each such section unique
by adding at the end of it, in parentheses, the name of the
original author or publisher of that section if known, or else a
unique number. Make the same adjustment to the section titles in
the list of Invariant Sections in the license notice of the
combined work.
In the combination, you must combine any sections Entitled
"History" in the various original documents, forming one section
Entitled "History"; likewise combine any sections Entitled
"Acknowledgements", and any sections Entitled "Dedications". You
must delete all sections Entitled "Endorsements."
6. COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other
documents released under this License, and replace the individual
copies of this License in the various documents with a single copy
that is included in the collection, provided that you follow the
rules of this License for verbatim copying of each of the
documents in all other respects.
You may extract a single document from such a collection, and
distribute it individually under this License, provided you insert
a copy of this License into the extracted document, and follow
this License in all other respects regarding verbatim copying of
that document.
7. AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other
separate and independent documents or works, in or on a volume of
a storage or distribution medium, is called an "aggregate" if the
copyright resulting from the compilation is not used to limit the
legal rights of the compilation's users beyond what the individual
works permit. When the Document is included in an aggregate, this
License does not apply to the other works in the aggregate which
are not themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half
of the entire aggregate, the Document's Cover Texts may be placed
on covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic
form. Otherwise they must appear on printed covers that bracket
the whole aggregate.
8. TRANSLATION
Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section
4. Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections. You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also
include the original English version of this License and the
original versions of those notices and disclaimers. In case of a
disagreement between the translation and the original version of
this License or a notice or disclaimer, the original version will
prevail.
If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section 4) to
Preserve its Title (section 1) will typically require changing the
actual title.
9. TERMINATION
You may not copy, modify, sublicense, or distribute the Document
except as expressly provided under this License. Any attempt
otherwise to copy, modify, sublicense, or distribute it is void,
and will automatically terminate your rights under this License.
However, if you cease all violation of this License, then your
license from a particular copyright holder is reinstated (a)
provisionally, unless and until the copyright holder explicitly
and finally terminates your license, and (b) permanently, if the
copyright holder fails to notify you of the violation by some
reasonable means prior to 60 days after the cessation.
Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from
that copyright holder, and you cure the violation prior to 30 days
after your receipt of the notice.
Termination of your rights under this section does not terminate
the licenses of parties who have received copies or rights from
you under this License. If your rights have been terminated and
not permanently reinstated, receipt of a copy of some or all of
the same material does not give you any rights to use it.
10. FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions of
the GNU Free Documentation License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns. See
`http://www.gnu.org/copyleft/'.
Each version of the License is given a distinguishing version
number. If the Document specifies that a particular numbered
version of this License "or any later version" applies to it, you
have the option of following the terms and conditions either of
that specified version or of any later version that has been
published (not as a draft) by the Free Software Foundation. If
the Document does not specify a version number of this License,
you may choose any version ever published (not as a draft) by the
Free Software Foundation. If the Document specifies that a proxy
can decide which future versions of this License can be used, that
proxy's public statement of acceptance of a version permanently
authorizes you to choose that version for the Document.
11. RELICENSING
"Massive Multiauthor Collaboration Site" (or "MMC Site") means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works. A
public wiki that anybody can edit is an example of such a server.
A "Massive Multiauthor Collaboration" (or "MMC") contained in the
site means any set of copyrightable works thus published on the MMC
site.
"CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
published by that same organization.
"Incorporate" means to publish or republish a Document, in whole or
in part, as part of another Document.
An MMC is "eligible for relicensing" if it is licensed under this
License, and if all works that were first published under this
License somewhere other than this MMC, and subsequently
incorporated in whole or in part into the MMC, (1) had no cover
texts or invariant sections, and (2) were thus incorporated prior
to November 1, 2008.
The operator of an MMC Site may republish an MMC contained in the
site under CC-BY-SA on the same site at any time before August 1,
2009, provided the MMC is eligible for relicensing.
ADDENDUM: How to use this License for your documents
====================================================
To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:
Copyright (C) YEAR YOUR NAME.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts." line with this:
with the Invariant Sections being LIST THEIR TITLES, with
the Front-Cover Texts being LIST, and with the Back-Cover Texts
being LIST.
If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.
If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License, to
permit their use in free software.
File: autoconf.info, Node: Indices, Prev: GNU Free Documentation License, Up: Top
Appendix B Indices
******************
* Menu:
* Environment Variable Index:: Index of environment variables used
* Output Variable Index:: Index of variables set in output files
* Preprocessor Symbol Index:: Index of C preprocessor symbols defined
* Autoconf Macro Index:: Index of Autoconf macros
* M4 Macro Index:: Index of M4, M4sugar, and M4sh macros
* Autotest Macro Index:: Index of Autotest macros
* Program & Function Index:: Index of those with portability problems
* Concept Index:: General index
File: autoconf.info, Node: Environment Variable Index, Next: Output Variable Index, Up: Indices
B.1 Environment Variable Index
==============================
This is an alphabetical list of the environment variables that might
influence Autoconf checks.
[index ]
* Menu:
* _: Special Shell Variables.
(line 36)
* BIN_SH: Special Shell Variables.
(line 40)
* CC: C Compiler. (line 61)
* CDPATH: Special Shell Variables.
(line 44)
* CFLAGS <1>: C Compiler. (line 61)
* CFLAGS: Preset Output Variables.
(line 23)
* CLICOLOR_FORCE: Special Shell Variables.
(line 67)
* CONFIG_COMMANDS: Obsolete config.status Use.
(line 11)
* CONFIG_FILES: Obsolete config.status Use.
(line 15)
* CONFIG_HEADERS: Obsolete config.status Use.
(line 20)
* CONFIG_LINKS: Obsolete config.status Use.
(line 25)
* CONFIG_SHELL: config.status Invocation.
(line 88)
* CONFIG_SITE: Site Defaults. (line 10)
* CONFIG_STATUS: config.status Invocation.
(line 97)
* CPP: C Compiler. (line 107)
* CPPFLAGS: Preset Output Variables.
(line 72)
* CXX: C++ Compiler. (line 7)
* CXXCPP: C++ Compiler. (line 31)
* CXXFLAGS <1>: Preset Output Variables.
(line 94)
* CXXFLAGS: C++ Compiler. (line 7)
* CYGWIN: Obsolete Macros. (line 124)
* DUALCASE: Special Shell Variables.
(line 74)
* ENV: Special Shell Variables.
(line 84)
* ERL: Erlang Compiler and Interpreter.
(line 29)
* ERLC: Erlang Compiler and Interpreter.
(line 10)
* ERLCFLAGS <1>: Preset Output Variables.
(line 120)
* ERLCFLAGS: Erlang Compiler and Interpreter.
(line 10)
* F77: Fortran Compiler. (line 18)
* FC: Fortran Compiler. (line 39)
* FCFLAGS <1>: Preset Output Variables.
(line 126)
* FCFLAGS: Fortran Compiler. (line 39)
* FFLAGS <1>: Fortran Compiler. (line 18)
* FFLAGS: Preset Output Variables.
(line 133)
* FPATH: Special Shell Variables.
(line 101)
* GREP_OPTIONS: Special Shell Variables.
(line 108)
* IFS: Special Shell Variables.
(line 116)
* LANG: Special Shell Variables.
(line 140)
* LANGUAGE: Special Shell Variables.
(line 147)
* LC_ADDRESS: Special Shell Variables.
(line 157)
* LC_ALL <1>: Initialization Macros.
(line 14)
* LC_ALL: Special Shell Variables.
(line 140)
* LC_COLLATE: Special Shell Variables.
(line 140)
* LC_CTYPE: Special Shell Variables.
(line 140)
* LC_IDENTIFICATION: Special Shell Variables.
(line 157)
* LC_MEASUREMENT: Special Shell Variables.
(line 157)
* LC_MESSAGES: Special Shell Variables.
(line 140)
* LC_MONETARY: Special Shell Variables.
(line 140)
* LC_NAME: Special Shell Variables.
(line 157)
* LC_NUMERIC: Special Shell Variables.
(line 140)
* LC_PAPER: Special Shell Variables.
(line 157)
* LC_TELEPHONE: Special Shell Variables.
(line 157)
* LC_TIME: Special Shell Variables.
(line 140)
* LDFLAGS: Preset Output Variables.
(line 140)
* LIBS: Preset Output Variables.
(line 154)
* LINENO <1>: Initialization Macros.
(line 64)
* LINENO: Special Shell Variables.
(line 162)
* M4: autom4te Invocation. (line 10)
* MAIL: Special Shell Variables.
(line 84)
* MAILPATH: Special Shell Variables.
(line 84)
* NULLCMD: Special Shell Variables.
(line 291)
* OBJC: Objective C Compiler.
(line 7)
* OBJCFLAGS <1>: Objective C Compiler.
(line 7)
* OBJCFLAGS: Preset Output Variables.
(line 161)
* OBJCPP: Objective C Compiler.
(line 26)
* PATH_SEPARATOR: Special Shell Variables.
(line 298)
* PS1: Special Shell Variables.
(line 84)
* PS2: Special Shell Variables.
(line 84)
* PS4: Special Shell Variables.
(line 84)
* PWD: Special Shell Variables.
(line 307)
* RANDOM: Special Shell Variables.
(line 316)
* SHELL: Initialization Macros.
(line 14)
* SIMPLE_BACKUP_SUFFIX: autoupdate Invocation.
(line 16)
* status: Special Shell Variables.
(line 324)
* WARNINGS <1>: autom4te Invocation. (line 58)
* WARNINGS <2>: autoheader Invocation.
(line 83)
* WARNINGS <3>: autoconf Invocation. (line 62)
* WARNINGS: autoreconf Invocation.
(line 97)
* XMKMF: System Services. (line 10)
* YACC: Particular Programs. (line 178)
* YFLAGS: Particular Programs. (line 178)
File: autoconf.info, Node: Output Variable Index, Next: Preprocessor Symbol Index, Prev: Environment Variable Index, Up: Indices
B.2 Output Variable Index
=========================
This is an alphabetical list of the variables that Autoconf can
substitute into files that it creates, typically one or more makefiles.
*Note Setting Output Variables::, for more information on how this is
done.
[index ]
* Menu:
* abs_builddir: Preset Output Variables.
(line 168)
* abs_srcdir: Preset Output Variables.
(line 190)
* abs_top_builddir: Preset Output Variables.
(line 183)
* abs_top_srcdir: Preset Output Variables.
(line 197)
* ALLOCA: Particular Functions.
(line 10)
* AWK: Particular Programs. (line 10)
* bindir: Installation Directory Variables.
(line 15)
* build: Canonicalizing. (line 26)
* build_alias: Canonicalizing. (line 9)
* build_cpu: Canonicalizing. (line 26)
* build_os: Canonicalizing. (line 26)
* build_vendor: Canonicalizing. (line 26)
* builddir: Preset Output Variables.
(line 165)
* CC <1>: C Compiler. (line 350)
* CC: System Services. (line 49)
* CFLAGS <1>: Preset Output Variables.
(line 23)
* CFLAGS: C Compiler. (line 61)
* configure_input: Preset Output Variables.
(line 58)
* CPP: C Compiler. (line 107)
* CPPFLAGS: Preset Output Variables.
(line 72)
* cross_compiling: Runtime. (line 56)
* CXX: C++ Compiler. (line 7)
* CXXCPP: C++ Compiler. (line 31)
* CXXFLAGS <1>: C++ Compiler. (line 7)
* CXXFLAGS: Preset Output Variables.
(line 94)
* datadir: Installation Directory Variables.
(line 18)
* datarootdir: Installation Directory Variables.
(line 22)
* DEFS: Preset Output Variables.
(line 98)
* docdir: Installation Directory Variables.
(line 26)
* dvidir: Installation Directory Variables.
(line 30)
* ECHO_C: Preset Output Variables.
(line 108)
* ECHO_N: Preset Output Variables.
(line 108)
* ECHO_T: Preset Output Variables.
(line 108)
* EGREP: Particular Programs. (line 23)
* ERL <1>: Running the Compiler.
(line 29)
* ERL <2>: Language Choice. (line 40)
* ERL: Erlang Compiler and Interpreter.
(line 29)
* ERLANG_ERTS_VER: Erlang Libraries. (line 12)
* ERLANG_INSTALL_LIB_DIR <1>: Installation Directory Variables.
(line 201)
* ERLANG_INSTALL_LIB_DIR: Erlang Libraries. (line 86)
* ERLANG_INSTALL_LIB_DIR_LIBRARY <1>: Installation Directory Variables.
(line 206)
* ERLANG_INSTALL_LIB_DIR_LIBRARY: Erlang Libraries. (line 94)
* ERLANG_LIB_DIR: Erlang Libraries. (line 28)
* ERLANG_LIB_DIR_LIBRARY: Erlang Libraries. (line 36)
* ERLANG_LIB_VER_LIBRARY: Erlang Libraries. (line 36)
* ERLANG_ROOT_DIR: Erlang Libraries. (line 22)
* ERLC <1>: Erlang Compiler and Interpreter.
(line 10)
* ERLC: Language Choice. (line 40)
* ERLCFLAGS <1>: Erlang Compiler and Interpreter.
(line 10)
* ERLCFLAGS <2>: Preset Output Variables.
(line 120)
* ERLCFLAGS: Language Choice. (line 40)
* exec_prefix: Installation Directory Variables.
(line 33)
* EXEEXT <1>: Compilers and Preprocessors.
(line 6)
* EXEEXT: Obsolete Macros. (line 178)
* F77: Fortran Compiler. (line 18)
* FC: Fortran Compiler. (line 39)
* FCFLAGS <1>: Preset Output Variables.
(line 126)
* FCFLAGS: Fortran Compiler. (line 39)
* FCLIBS: Fortran Compiler. (line 79)
* FFLAGS <1>: Preset Output Variables.
(line 133)
* FFLAGS: Fortran Compiler. (line 18)
* FGREP: Particular Programs. (line 28)
* FLIBS: Fortran Compiler. (line 79)
* GETGROUPS_LIBS: Particular Functions.
(line 124)
* GETLOADAVG_LIBS: Particular Functions.
(line 130)
* GREP: Particular Programs. (line 16)
* host: Canonicalizing. (line 34)
* host_alias: Canonicalizing. (line 9)
* host_cpu: Canonicalizing. (line 34)
* host_os: Canonicalizing. (line 34)
* host_vendor: Canonicalizing. (line 34)
* htmldir: Installation Directory Variables.
(line 40)
* includedir: Installation Directory Variables.
(line 43)
* infodir: Installation Directory Variables.
(line 46)
* INSTALL: Particular Programs. (line 33)
* INSTALL_DATA: Particular Programs. (line 33)
* INSTALL_PROGRAM: Particular Programs. (line 33)
* INSTALL_SCRIPT: Particular Programs. (line 33)
* KMEM_GROUP: Particular Functions.
(line 130)
* LDFLAGS: Preset Output Variables.
(line 140)
* LEX: Particular Programs. (line 98)
* LEX_OUTPUT_ROOT: Particular Programs. (line 98)
* LEXLIB: Particular Programs. (line 98)
* libdir: Installation Directory Variables.
(line 49)
* libexecdir: Installation Directory Variables.
(line 52)
* LIBOBJDIR: AC_LIBOBJ vs LIBOBJS.
(line 35)
* LIBOBJS <1>: Particular Structures.
(line 26)
* LIBOBJS <2>: Particular Functions.
(line 130)
* LIBOBJS <3>: Generic Functions. (line 113)
* LIBOBJS <4>: Particular Functions.
(line 246)
* LIBOBJS: Generic Functions. (line 52)
* LIBS <1>: Obsolete Macros. (line 489)
* LIBS <2>: Preset Output Variables.
(line 154)
* LIBS: Obsolete Macros. (line 295)
* LN_S: Particular Programs. (line 149)
* localedir: Installation Directory Variables.
(line 55)
* localstatedir: Installation Directory Variables.
(line 60)
* mandir: Installation Directory Variables.
(line 63)
* MKDIR_P: Particular Programs. (line 67)
* NEED_SETGID: Particular Functions.
(line 130)
* OBJC: Objective C Compiler.
(line 7)
* OBJCFLAGS <1>: Objective C Compiler.
(line 7)
* OBJCFLAGS: Preset Output Variables.
(line 161)
* OBJCPP: Objective C Compiler.
(line 26)
* OBJEXT <1>: Obsolete Macros. (line 384)
* OBJEXT: Compilers and Preprocessors.
(line 11)
* oldincludedir: Installation Directory Variables.
(line 66)
* OPENMP_CFLAGS: Generic Compiler Characteristics.
(line 56)
* OPENMP_CXXFLAGS: Generic Compiler Characteristics.
(line 56)
* OPENMP_FCFLAGS: Generic Compiler Characteristics.
(line 56)
* OPENMP_FFLAGS: Generic Compiler Characteristics.
(line 56)
* PACKAGE_BUGREPORT: Initializing configure.
(line 45)
* PACKAGE_NAME: Initializing configure.
(line 33)
* PACKAGE_STRING: Initializing configure.
(line 42)
* PACKAGE_TARNAME: Initializing configure.
(line 36)
* PACKAGE_URL: Initializing configure.
(line 48)
* PACKAGE_VERSION: Initializing configure.
(line 39)
* pdfdir: Installation Directory Variables.
(line 69)
* POW_LIB: Particular Functions.
(line 327)
* prefix: Installation Directory Variables.
(line 72)
* program_transform_name: Transforming Names. (line 11)
* psdir: Installation Directory Variables.
(line 77)
* RANLIB: Particular Programs. (line 168)
* sbindir: Installation Directory Variables.
(line 80)
* SED: Particular Programs. (line 172)
* SET_MAKE: Output. (line 45)
* sharedstatedir: Installation Directory Variables.
(line 84)
* srcdir: Preset Output Variables.
(line 186)
* subdirs: Subdirectories. (line 12)
* sysconfdir: Installation Directory Variables.
(line 88)
* target: Canonicalizing. (line 41)
* target_alias: Canonicalizing. (line 9)
* target_cpu: Canonicalizing. (line 41)
* target_os: Canonicalizing. (line 41)
* target_vendor: Canonicalizing. (line 41)
* top_build_prefix: Preset Output Variables.
(line 175)
* top_builddir: Preset Output Variables.
(line 171)
* top_srcdir: Preset Output Variables.
(line 193)
* X_CFLAGS: System Services. (line 30)
* X_EXTRA_LIBS: System Services. (line 30)
* X_LIBS: System Services. (line 30)
* X_PRE_LIBS: System Services. (line 30)
* YACC: Particular Programs. (line 178)
File: autoconf.info, Node: Preprocessor Symbol Index, Next: Autoconf Macro Index, Prev: Output Variable Index, Up: Indices
B.3 Preprocessor Symbol Index
=============================
This is an alphabetical list of the C preprocessor symbols that the
Autoconf macros define. To work with Autoconf, C source code needs to
use these names in `#if' or `#ifdef' directives.
[index ]
* Menu:
* __CHAR_UNSIGNED__: C Compiler. (line 280)
* __EXTENSIONS__: Posix Variants. (line 10)
* __PROTOTYPES: C Compiler. (line 340)
* _ALL_SOURCE <1>: Posix Variants. (line 10)
* _ALL_SOURCE: Obsolete Macros. (line 20)
* _FILE_OFFSET_BITS: System Services. (line 49)
* _GNU_SOURCE <1>: Obsolete Macros. (line 234)
* _GNU_SOURCE: Posix Variants. (line 10)
* _LARGE_FILES: System Services. (line 49)
* _LARGEFILE_SOURCE: Particular Functions.
(line 116)
* _MINIX <1>: Posix Variants. (line 10)
* _MINIX: Obsolete Macros. (line 371)
* _OPENMP: Generic Compiler Characteristics.
(line 56)
* _POSIX_1_SOURCE <1>: Obsolete Macros. (line 371)
* _POSIX_1_SOURCE: Posix Variants. (line 10)
* _POSIX_PTHREAD_SEMANTICS: Posix Variants. (line 10)
* _POSIX_SOURCE <1>: Posix Variants. (line 10)
* _POSIX_SOURCE: Obsolete Macros. (line 371)
* _POSIX_VERSION: Particular Headers. (line 206)
* _TANDEM_SOURCE: Posix Variants. (line 10)
* ALIGNOF_TYPE: Generic Compiler Characteristics.
(line 26)
* C_ALLOCA: Particular Functions.
(line 10)
* C_GETLOADAVG: Particular Functions.
(line 130)
* CLOSEDIR_VOID: Particular Functions.
(line 58)
* const: C Compiler. (line 211)
* CXX_NO_MINUS_C_MINUS_O: C++ Compiler. (line 44)
* DGUX: Particular Functions.
(line 130)
* DIRENT: Obsolete Macros. (line 158)
* F77_DUMMY_MAIN: Fortran Compiler. (line 107)
* F77_FUNC: Fortran Compiler. (line 173)
* F77_FUNC_: Fortran Compiler. (line 173)
* F77_MAIN: Fortran Compiler. (line 150)
* F77_NO_MINUS_C_MINUS_O: Fortran Compiler. (line 66)
* FC_FUNC: Fortran Compiler. (line 173)
* FC_FUNC_: Fortran Compiler. (line 173)
* FC_MAIN: Fortran Compiler. (line 150)
* FC_NO_MINUS_C_MINUS_O: Fortran Compiler. (line 66)
* FLEXIBLE_ARRAY_MEMBER: C Compiler. (line 304)
* GETGROUPS_T: Particular Types. (line 14)
* GETLOADAVG_PRIVILEGED: Particular Functions.
(line 130)
* GETPGRP_VOID: Particular Functions.
(line 170)
* gid_t: Particular Types. (line 99)
* GWINSZ_IN_SYS_IOCTL: Particular Headers. (line 246)
* HAVE__BOOL: Particular Headers. (line 91)
* HAVE_AGGREGATE_MEMBER: Generic Structures. (line 25)
* HAVE_ALLOCA_H: Particular Functions.
(line 10)
* HAVE_C_BACKSLASH_A: C Compiler. (line 170)
* HAVE_C_VARARRAYS: C Compiler. (line 328)
* HAVE_CHOWN: Particular Functions.
(line 54)
* HAVE_CONFIG_H: Configuration Headers.
(line 33)
* HAVE_DECL_STRERROR_R: Particular Functions.
(line 310)
* HAVE_DECL_SYMBOL: Generic Declarations.
(line 25)
* HAVE_DECL_TZNAME: Particular Structures.
(line 40)
* HAVE_DIRENT_H: Particular Headers. (line 15)
* HAVE_DOPRNT: Particular Functions.
(line 348)
* HAVE_FSEEKO: Particular Functions.
(line 116)
* HAVE_FUNCTION: Generic Functions. (line 25)
* HAVE_GETGROUPS: Particular Functions.
(line 124)
* HAVE_GETMNTENT: Particular Functions.
(line 164)
* HAVE_HEADER: Generic Headers. (line 42)
* HAVE_INT16_T: Particular Types. (line 35)
* HAVE_INT32_T: Particular Types. (line 38)
* HAVE_INT64_T: Particular Types. (line 41)
* HAVE_INT8_T: Particular Types. (line 18)
* HAVE_INTMAX_T: Particular Types. (line 44)
* HAVE_INTPTR_T: Particular Types. (line 49)
* HAVE_LONG_DOUBLE <1>: Particular Types. (line 54)
* HAVE_LONG_DOUBLE: Obsolete Macros. (line 33)
* HAVE_LONG_DOUBLE_WIDER: Particular Types. (line 62)
* HAVE_LONG_FILE_NAMES: System Services. (line 71)
* HAVE_LONG_LONG_INT: Particular Types. (line 67)
* HAVE_LSTAT_EMPTY_STRING_BUG: Particular Functions.
(line 292)
* HAVE_MALLOC: Particular Functions.
(line 203)
* HAVE_MBRTOWC: Particular Functions.
(line 242)
* HAVE_MMAP: Particular Functions.
(line 252)
* HAVE_NDIR_H: Particular Headers. (line 15)
* HAVE_NLIST_H: Particular Functions.
(line 130)
* HAVE_OBSTACK: Particular Functions.
(line 257)
* HAVE_REALLOC: Particular Functions.
(line 261)
* HAVE_RESOLV_H: Particular Headers. (line 63)
* HAVE_RESTARTABLE_SYSCALLS: Obsolete Macros. (line 548)
* HAVE_ST_BLKSIZE: Obsolete Macros. (line 521)
* HAVE_ST_BLOCKS: Particular Structures.
(line 26)
* HAVE_ST_RDEV: Obsolete Macros. (line 530)
* HAVE_STAT_EMPTY_STRING_BUG: Particular Functions.
(line 292)
* HAVE_STDBOOL_H: Particular Headers. (line 91)
* HAVE_STRCOLL: Particular Functions.
(line 304)
* HAVE_STRERROR_R: Particular Functions.
(line 310)
* HAVE_STRFTIME: Particular Functions.
(line 320)
* HAVE_STRINGIZE: C Compiler. (line 294)
* HAVE_STRNLEN: Particular Functions.
(line 337)
* HAVE_STRTOLD: Particular Functions.
(line 333)
* HAVE_STRUCT_DIRENT_D_INO: Particular Structures.
(line 9)
* HAVE_STRUCT_DIRENT_D_TYPE: Particular Structures.
(line 21)
* HAVE_STRUCT_STAT_ST_BLKSIZE: Obsolete Macros. (line 521)
* HAVE_STRUCT_STAT_ST_BLOCKS: Particular Structures.
(line 26)
* HAVE_STRUCT_STAT_ST_RDEV: Obsolete Macros. (line 530)
* HAVE_STRUCT_TM_TM_ZONE: Particular Structures.
(line 40)
* HAVE_SYS_DIR_H: Particular Headers. (line 15)
* HAVE_SYS_NDIR_H: Particular Headers. (line 15)
* HAVE_SYS_WAIT_H: Particular Headers. (line 185)
* HAVE_TM_ZONE: Particular Structures.
(line 40)
* HAVE_TYPE: Generic Types. (line 24)
* HAVE_TYPEOF: C Compiler. (line 334)
* HAVE_TZNAME: Particular Structures.
(line 40)
* HAVE_UINT16_T: Particular Types. (line 109)
* HAVE_UINT32_T: Particular Types. (line 112)
* HAVE_UINT64_T: Particular Types. (line 115)
* HAVE_UINT8_T: Particular Types. (line 103)
* HAVE_UINTMAX_T: Particular Types. (line 118)
* HAVE_UINTPTR_T: Particular Types. (line 123)
* HAVE_UNSIGNED_LONG_LONG_INT: Particular Types. (line 128)
* HAVE_UTIME_NULL: Particular Functions.
(line 341)
* HAVE_VFORK_H: Particular Functions.
(line 94)
* HAVE_VPRINTF: Particular Functions.
(line 348)
* HAVE_WAIT3: Obsolete Macros. (line 216)
* HAVE_WORKING_FORK: Particular Functions.
(line 94)
* HAVE_WORKING_VFORK: Particular Functions.
(line 94)
* inline: C Compiler. (line 275)
* int16_t: Particular Types. (line 35)
* int32_t: Particular Types. (line 38)
* int64_t: Particular Types. (line 41)
* int8_t: Particular Types. (line 18)
* INT_16_BITS: Obsolete Macros. (line 275)
* intmax_t: Particular Types. (line 44)
* intptr_t: Particular Types. (line 49)
* LONG_64_BITS: Obsolete Macros. (line 337)
* LSTAT_FOLLOWS_SLASHED_SYMLINK: Particular Functions.
(line 190)
* MAJOR_IN_MKDEV: Particular Headers. (line 58)
* MAJOR_IN_SYSMACROS: Particular Headers. (line 58)
* malloc: Particular Functions.
(line 203)
* mbstate_t: Particular Types. (line 74)
* mode_t: Particular Types. (line 79)
* NDEBUG: Particular Headers. (line 10)
* NDIR: Obsolete Macros. (line 158)
* NEED_MEMORY_H: Obsolete Macros. (line 358)
* NEED_SETGID: Particular Functions.
(line 130)
* NLIST_NAME_UNION: Particular Functions.
(line 130)
* NO_MINUS_C_MINUS_O: C Compiler. (line 99)
* off_t: Particular Types. (line 83)
* PACKAGE_BUGREPORT: Initializing configure.
(line 45)
* PACKAGE_NAME: Initializing configure.
(line 33)
* PACKAGE_STRING: Initializing configure.
(line 42)
* PACKAGE_TARNAME: Initializing configure.
(line 36)
* PACKAGE_URL: Initializing configure.
(line 48)
* PACKAGE_VERSION: Initializing configure.
(line 39)
* PARAMS: C Compiler. (line 340)
* pid_t: Particular Types. (line 87)
* PROTOTYPES: C Compiler. (line 340)
* realloc: Particular Functions.
(line 261)
* restrict: C Compiler. (line 239)
* RETSIGTYPE: Obsolete Macros. (line 662)
* SELECT_TYPE_ARG1: Particular Functions.
(line 269)
* SELECT_TYPE_ARG234: Particular Functions.
(line 269)
* SELECT_TYPE_ARG5: Particular Functions.
(line 269)
* SETPGRP_VOID: Particular Functions.
(line 280)
* SETVBUF_REVERSED: Obsolete Macros. (line 208)
* size_t: Particular Types. (line 91)
* SIZEOF_TYPE-OR-EXPR: Generic Compiler Characteristics.
(line 8)
* ssize_t: Particular Types. (line 95)
* STAT_MACROS_BROKEN: Particular Headers. (line 82)
* STDC_HEADERS: Particular Headers. (line 118)
* STRERROR_R_CHAR_P: Particular Functions.
(line 310)
* SVR4: Particular Functions.
(line 130)
* SYS_SIGLIST_DECLARED: Obsolete Macros. (line 141)
* SYSDIR: Obsolete Macros. (line 158)
* SYSNDIR: Obsolete Macros. (line 158)
* TIME_WITH_SYS_TIME: Particular Headers. (line 222)
* TM_IN_SYS_TIME: Particular Structures.
(line 32)
* typeof: C Compiler. (line 334)
* uid_t: Particular Types. (line 99)
* uint16_t: Particular Types. (line 109)
* uint32_t: Particular Types. (line 112)
* uint64_t: Particular Types. (line 115)
* uint8_t: Particular Types. (line 103)
* uintmax_t: Particular Types. (line 118)
* uintptr_t: Particular Types. (line 123)
* UMAX: Particular Functions.
(line 130)
* UMAX4_3: Particular Functions.
(line 130)
* USG: Obsolete Macros. (line 685)
* VARIABLE: Defining Symbols. (line 74)
* vfork: Particular Functions.
(line 94)
* volatile: C Compiler. (line 254)
* WORDS_BIGENDIAN: C Compiler. (line 178)
* X_DISPLAY_MISSING: System Services. (line 30)
* YYTEXT_POINTER: Particular Programs. (line 98)
File: autoconf.info, Node: Autoconf Macro Index, Next: M4 Macro Index, Prev: Preprocessor Symbol Index, Up: Indices
B.4 Autoconf Macro Index
========================
This is an alphabetical list of the Autoconf macros.
[index ]
* Menu:
* AC_ACT_IFELSE: AC_ACT_IFELSE vs AC_TRY_ACT.
(line 6)
* AC_AIX: Obsolete Macros. (line 20)
* AC_ALLOCA: Obsolete Macros. (line 24)
* AC_ARG_ARRAY: Obsolete Macros. (line 27)
* AC_ARG_ENABLE: Package Options. (line 35)
* AC_ARG_PROGRAM: Transforming Names. (line 11)
* AC_ARG_VAR: Setting Output Variables.
(line 79)
* AC_ARG_WITH: External Software. (line 36)
* AC_AUTOCONF_VERSION: Versioning. (line 22)
* AC_BEFORE: Suggested Ordering. (line 28)
* AC_C_BACKSLASH_A: C Compiler. (line 170)
* AC_C_BIGENDIAN: C Compiler. (line 178)
* AC_C_CHAR_UNSIGNED: C Compiler. (line 280)
* AC_C_CONST: C Compiler. (line 211)
* AC_C_CROSS: Obsolete Macros. (line 30)
* AC_C_FLEXIBLE_ARRAY_MEMBER: C Compiler. (line 304)
* AC_C_INLINE: C Compiler. (line 275)
* AC_C_LONG_DOUBLE: Obsolete Macros. (line 33)
* AC_C_PROTOTYPES: C Compiler. (line 340)
* AC_C_RESTRICT: C Compiler. (line 239)
* AC_C_STRINGIZE: C Compiler. (line 294)
* AC_C_TYPEOF: C Compiler. (line 334)
* AC_C_VARARRAYS: C Compiler. (line 328)
* AC_C_VOLATILE: C Compiler. (line 254)
* AC_CACHE_CHECK: Caching Results. (line 30)
* AC_CACHE_LOAD: Cache Checkpointing. (line 13)
* AC_CACHE_SAVE: Cache Checkpointing. (line 17)
* AC_CACHE_VAL: Caching Results. (line 16)
* AC_CANONICAL_BUILD: Canonicalizing. (line 26)
* AC_CANONICAL_HOST: Canonicalizing. (line 34)
* AC_CANONICAL_SYSTEM: Obsolete Macros. (line 41)
* AC_CANONICAL_TARGET: Canonicalizing. (line 41)
* AC_CHAR_UNSIGNED: Obsolete Macros. (line 51)
* AC_CHECK_ALIGNOF: Generic Compiler Characteristics.
(line 26)
* AC_CHECK_DECL: Generic Declarations.
(line 11)
* AC_CHECK_DECLS: Generic Declarations.
(line 25)
* AC_CHECK_DECLS_ONCE: Generic Declarations.
(line 64)
* AC_CHECK_FILE: Files. (line 13)
* AC_CHECK_FILES: Files. (line 19)
* AC_CHECK_FUNC: Generic Functions. (line 15)
* AC_CHECK_FUNCS: Generic Functions. (line 25)
* AC_CHECK_FUNCS_ONCE: Generic Functions. (line 34)
* AC_CHECK_HEADER: Generic Headers. (line 13)
* AC_CHECK_HEADERS: Generic Headers. (line 42)
* AC_CHECK_HEADERS_ONCE: Generic Headers. (line 79)
* AC_CHECK_LIB: Libraries. (line 11)
* AC_CHECK_MEMBER: Generic Structures. (line 11)
* AC_CHECK_MEMBERS: Generic Structures. (line 25)
* AC_CHECK_PROG: Generic Programs. (line 24)
* AC_CHECK_PROGS: Generic Programs. (line 34)
* AC_CHECK_SIZEOF: Generic Compiler Characteristics.
(line 8)
* AC_CHECK_TARGET_TOOL: Generic Programs. (line 44)
* AC_CHECK_TARGET_TOOLS: Generic Programs. (line 75)
* AC_CHECK_TOOL: Generic Programs. (line 60)
* AC_CHECK_TOOLS: Generic Programs. (line 88)
* AC_CHECK_TYPE <1>: Obsolete Macros. (line 54)
* AC_CHECK_TYPE: Generic Types. (line 11)
* AC_CHECK_TYPES: Generic Types. (line 24)
* AC_CHECKING: Obsolete Macros. (line 101)
* AC_COMPILE_CHECK: Obsolete Macros. (line 109)
* AC_COMPILE_IFELSE: Running the Compiler.
(line 13)
* AC_COMPUTE_INT: Generic Compiler Characteristics.
(line 34)
* AC_CONFIG_AUX_DIR: Input. (line 20)
* AC_CONFIG_COMMANDS: Configuration Commands.
(line 13)
* AC_CONFIG_COMMANDS_POST: Configuration Commands.
(line 41)
* AC_CONFIG_COMMANDS_PRE: Configuration Commands.
(line 35)
* AC_CONFIG_FILES: Configuration Files. (line 9)
* AC_CONFIG_HEADERS: Configuration Headers.
(line 33)
* AC_CONFIG_ITEMS: Configuration Actions.
(line 12)
* AC_CONFIG_LIBOBJ_DIR: Generic Functions. (line 93)
* AC_CONFIG_LINKS: Configuration Links. (line 12)
* AC_CONFIG_MACRO_DIR: Input. (line 48)
* AC_CONFIG_SRCDIR: Input. (line 7)
* AC_CONFIG_SUBDIRS: Subdirectories. (line 12)
* AC_CONFIG_TESTDIR: Making testsuite Scripts.
(line 26)
* AC_CONST: Obsolete Macros. (line 117)
* AC_COPYRIGHT: Notices. (line 10)
* AC_CROSS_CHECK: Obsolete Macros. (line 120)
* AC_CYGWIN: Obsolete Macros. (line 124)
* AC_DATAROOTDIR_CHECKED: Changed Directory Variables.
(line 58)
* AC_DECL_SYS_SIGLIST: Obsolete Macros. (line 141)
* AC_DECL_YYTEXT: Obsolete Macros. (line 154)
* AC_DEFINE: Defining Symbols. (line 32)
* AC_DEFINE_UNQUOTED: Defining Symbols. (line 74)
* AC_DEFUN: Macro Definitions. (line 7)
* AC_DEFUN_ONCE: One-Shot Macros. (line 14)
* AC_DIAGNOSE: Reporting Messages. (line 18)
* AC_DIR_HEADER: Obsolete Macros. (line 158)
* AC_DISABLE_OPTION_CHECKING: Option Checking. (line 28)
* AC_DYNIX_SEQ: Obsolete Macros. (line 170)
* AC_EGREP_CPP: Running the Preprocessor.
(line 73)
* AC_EGREP_HEADER: Running the Preprocessor.
(line 66)
* AC_EMXOS2: Obsolete Macros. (line 183)
* AC_ENABLE: Obsolete Macros. (line 189)
* AC_ERLANG_CHECK_LIB: Erlang Libraries. (line 36)
* AC_ERLANG_NEED_ERL: Erlang Compiler and Interpreter.
(line 41)
* AC_ERLANG_NEED_ERLC: Erlang Compiler and Interpreter.
(line 24)
* AC_ERLANG_PATH_ERL: Erlang Compiler and Interpreter.
(line 29)
* AC_ERLANG_PATH_ERLC: Erlang Compiler and Interpreter.
(line 10)
* AC_ERLANG_SUBST_ERTS_VER: Erlang Libraries. (line 12)
* AC_ERLANG_SUBST_INSTALL_LIB_DIR <1>: Erlang Libraries. (line 86)
* AC_ERLANG_SUBST_INSTALL_LIB_DIR: Installation Directory Variables.
(line 201)
* AC_ERLANG_SUBST_INSTALL_LIB_SUBDIR <1>: Installation Directory Variables.
(line 206)
* AC_ERLANG_SUBST_INSTALL_LIB_SUBDIR: Erlang Libraries. (line 94)
* AC_ERLANG_SUBST_LIB_DIR: Erlang Libraries. (line 28)
* AC_ERLANG_SUBST_ROOT_DIR: Erlang Libraries. (line 22)
* AC_ERROR: Obsolete Macros. (line 193)
* AC_EXEEXT: Obsolete Macros. (line 178)
* AC_F77_DUMMY_MAIN: Fortran Compiler. (line 107)
* AC_F77_FUNC: Fortran Compiler. (line 233)
* AC_F77_LIBRARY_LDFLAGS: Fortran Compiler. (line 79)
* AC_F77_MAIN: Fortran Compiler. (line 150)
* AC_F77_WRAPPERS: Fortran Compiler. (line 173)
* AC_FATAL: Reporting Messages. (line 34)
* AC_FC_FREEFORM: Fortran Compiler. (line 282)
* AC_FC_FUNC: Fortran Compiler. (line 233)
* AC_FC_LIBRARY_LDFLAGS: Fortran Compiler. (line 79)
* AC_FC_MAIN: Fortran Compiler. (line 150)
* AC_FC_SRCEXT: Fortran Compiler. (line 243)
* AC_FC_WRAPPERS: Fortran Compiler. (line 173)
* AC_FIND_X: Obsolete Macros. (line 196)
* AC_FIND_XTRA: Obsolete Macros. (line 199)
* AC_FOREACH: Obsolete Macros. (line 202)
* AC_FUNC_ALLOCA: Particular Functions.
(line 10)
* AC_FUNC_CHECK: Obsolete Macros. (line 205)
* AC_FUNC_CHOWN: Particular Functions.
(line 54)
* AC_FUNC_CLOSEDIR_VOID: Particular Functions.
(line 58)
* AC_FUNC_ERROR_AT_LINE: Particular Functions.
(line 70)
* AC_FUNC_FNMATCH: Particular Functions.
(line 74)
* AC_FUNC_FNMATCH_GNU: Particular Functions.
(line 86)
* AC_FUNC_FORK: Particular Functions.
(line 94)
* AC_FUNC_FSEEKO: Particular Functions.
(line 116)
* AC_FUNC_GETGROUPS: Particular Functions.
(line 124)
* AC_FUNC_GETLOADAVG: Particular Functions.
(line 130)
* AC_FUNC_GETMNTENT: Particular Functions.
(line 164)
* AC_FUNC_GETPGRP: Particular Functions.
(line 170)
* AC_FUNC_LSTAT: Particular Functions.
(line 292)
* AC_FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK: Particular Functions.
(line 190)
* AC_FUNC_MALLOC: Particular Functions.
(line 203)
* AC_FUNC_MBRTOWC: Particular Functions.
(line 242)
* AC_FUNC_MEMCMP: Particular Functions.
(line 232)
* AC_FUNC_MKTIME: Particular Functions.
(line 246)
* AC_FUNC_MMAP: Particular Functions.
(line 252)
* AC_FUNC_OBSTACK: Particular Functions.
(line 257)
* AC_FUNC_REALLOC: Particular Functions.
(line 261)
* AC_FUNC_SELECT_ARGTYPES: Particular Functions.
(line 269)
* AC_FUNC_SETPGRP: Particular Functions.
(line 280)
* AC_FUNC_SETVBUF_REVERSED: Obsolete Macros. (line 208)
* AC_FUNC_STAT: Particular Functions.
(line 292)
* AC_FUNC_STRCOLL: Particular Functions.
(line 304)
* AC_FUNC_STRERROR_R: Particular Functions.
(line 310)
* AC_FUNC_STRFTIME: Particular Functions.
(line 320)
* AC_FUNC_STRNLEN: Particular Functions.
(line 337)
* AC_FUNC_STRTOD: Particular Functions.
(line 327)
* AC_FUNC_STRTOLD: Particular Functions.
(line 333)
* AC_FUNC_UTIME_NULL: Particular Functions.
(line 341)
* AC_FUNC_VPRINTF: Particular Functions.
(line 348)
* AC_FUNC_WAIT3: Obsolete Macros. (line 216)
* AC_GCC_TRADITIONAL: Obsolete Macros. (line 224)
* AC_GETGROUPS_T: Obsolete Macros. (line 228)
* AC_GETLOADAVG: Obsolete Macros. (line 231)
* AC_GNU_SOURCE: Obsolete Macros. (line 234)
* AC_HAVE_FUNCS: Obsolete Macros. (line 238)
* AC_HAVE_HEADERS: Obsolete Macros. (line 241)
* AC_HAVE_LIBRARY: Obsolete Macros. (line 245)
* AC_HAVE_POUNDBANG: Obsolete Macros. (line 252)
* AC_HEADER_ASSERT: Particular Headers. (line 10)
* AC_HEADER_CHECK: Obsolete Macros. (line 255)
* AC_HEADER_DIRENT: Particular Headers. (line 15)
* AC_HEADER_EGREP: Obsolete Macros. (line 258)
* AC_HEADER_MAJOR: Particular Headers. (line 58)
* AC_HEADER_RESOLV: Particular Headers. (line 63)
* AC_HEADER_STAT: Particular Headers. (line 82)
* AC_HEADER_STDBOOL: Particular Headers. (line 91)
* AC_HEADER_STDC: Particular Headers. (line 118)
* AC_HEADER_SYS_WAIT: Particular Headers. (line 185)
* AC_HEADER_TIME: Particular Headers. (line 222)
* AC_HEADER_TIOCGWINSZ: Particular Headers. (line 246)
* AC_HELP_STRING: Obsolete Macros. (line 261)
* AC_INCLUDES_DEFAULT: Default Includes. (line 29)
* AC_INIT <1>: Initializing configure.
(line 10)
* AC_INIT: Obsolete Macros. (line 264)
* AC_INLINE: Obsolete Macros. (line 272)
* AC_INT_16_BITS: Obsolete Macros. (line 275)
* AC_IRIX_SUN: Obsolete Macros. (line 279)
* AC_ISC_POSIX: Obsolete Macros. (line 295)
* AC_LANG_ASSERT: Language Choice. (line 69)
* AC_LANG_C: Obsolete Macros. (line 302)
* AC_LANG_CALL: Generating Sources. (line 115)
* AC_LANG_CONFTEST: Generating Sources. (line 12)
* AC_LANG_CPLUSPLUS: Obsolete Macros. (line 305)
* AC_LANG_FORTRAN77: Obsolete Macros. (line 308)
* AC_LANG_FUNC_LINK_TRY: Generating Sources. (line 127)
* AC_LANG_POP: Language Choice. (line 56)
* AC_LANG_PROGRAM: Generating Sources. (line 53)
* AC_LANG_PUSH: Language Choice. (line 51)
* AC_LANG_RESTORE: Obsolete Macros. (line 311)
* AC_LANG_SAVE: Obsolete Macros. (line 317)
* AC_LANG_SOURCE: Generating Sources. (line 21)
* AC_LANG_WERROR: Generic Compiler Characteristics.
(line 46)
* AC_LIBOBJ: Generic Functions. (line 52)
* AC_LIBSOURCE: Generic Functions. (line 61)
* AC_LIBSOURCES: Generic Functions. (line 85)
* AC_LINK_FILES: Obsolete Macros. (line 322)
* AC_LINK_IFELSE: Running the Linker. (line 24)
* AC_LN_S: Obsolete Macros. (line 334)
* AC_LONG_64_BITS: Obsolete Macros. (line 337)
* AC_LONG_DOUBLE: Obsolete Macros. (line 342)
* AC_LONG_FILE_NAMES: Obsolete Macros. (line 350)
* AC_MAJOR_HEADER: Obsolete Macros. (line 355)
* AC_MEMORY_H: Obsolete Macros. (line 358)
* AC_MINGW32: Obsolete Macros. (line 365)
* AC_MINIX: Obsolete Macros. (line 371)
* AC_MINUS_C_MINUS_O: Obsolete Macros. (line 375)
* AC_MMAP: Obsolete Macros. (line 378)
* AC_MODE_T: Obsolete Macros. (line 381)
* AC_MSG_CHECKING: Printing Messages. (line 24)
* AC_MSG_ERROR: Printing Messages. (line 56)
* AC_MSG_FAILURE: Printing Messages. (line 66)
* AC_MSG_NOTICE: Printing Messages. (line 46)
* AC_MSG_RESULT: Printing Messages. (line 35)
* AC_MSG_WARN: Printing Messages. (line 72)
* AC_OBJEXT: Obsolete Macros. (line 384)
* AC_OBSOLETE: Obsolete Macros. (line 390)
* AC_OFF_T: Obsolete Macros. (line 405)
* AC_OPENMP: Generic Compiler Characteristics.
(line 56)
* AC_OUTPUT <1>: Obsolete Macros. (line 408)
* AC_OUTPUT: Output. (line 13)
* AC_OUTPUT_COMMANDS: Obsolete Macros. (line 420)
* AC_PACKAGE_BUGREPORT: Initializing configure.
(line 45)
* AC_PACKAGE_NAME: Initializing configure.
(line 33)
* AC_PACKAGE_STRING: Initializing configure.
(line 42)
* AC_PACKAGE_TARNAME: Initializing configure.
(line 36)
* AC_PACKAGE_URL: Initializing configure.
(line 48)
* AC_PACKAGE_VERSION: Initializing configure.
(line 39)
* AC_PATH_PROG: Generic Programs. (line 104)
* AC_PATH_PROGS: Generic Programs. (line 109)
* AC_PATH_PROGS_FEATURE_CHECK: Generic Programs. (line 114)
* AC_PATH_TARGET_TOOL: Generic Programs. (line 150)
* AC_PATH_TOOL: Generic Programs. (line 155)
* AC_PATH_X: System Services. (line 10)
* AC_PATH_XTRA: System Services. (line 30)
* AC_PID_T: Obsolete Macros. (line 450)
* AC_PREFIX: Obsolete Macros. (line 453)
* AC_PREFIX_DEFAULT: Default Prefix. (line 16)
* AC_PREFIX_PROGRAM: Default Prefix. (line 25)
* AC_PREPROC_IFELSE: Running the Preprocessor.
(line 20)
* AC_PREREQ: Versioning. (line 11)
* AC_PRESERVE_HELP_ORDER: Help Formatting. (line 20)
* AC_PROG_AWK: Particular Programs. (line 10)
* AC_PROG_CC: C Compiler. (line 61)
* AC_PROG_CC_C89: C Compiler. (line 141)
* AC_PROG_CC_C99: C Compiler. (line 155)
* AC_PROG_CC_C_O: C Compiler. (line 99)
* AC_PROG_CC_STDC: C Compiler. (line 131)
* AC_PROG_CPP: C Compiler. (line 107)
* AC_PROG_CPP_WERROR: C Compiler. (line 120)
* AC_PROG_CXX: C++ Compiler. (line 7)
* AC_PROG_CXX_C_O: C++ Compiler. (line 44)
* AC_PROG_CXXCPP: C++ Compiler. (line 31)
* AC_PROG_EGREP: Particular Programs. (line 23)
* AC_PROG_F77: Fortran Compiler. (line 18)
* AC_PROG_F77_C_O: Fortran Compiler. (line 66)
* AC_PROG_FC: Fortran Compiler. (line 39)
* AC_PROG_FC_C_O: Fortran Compiler. (line 66)
* AC_PROG_FGREP: Particular Programs. (line 28)
* AC_PROG_GCC_TRADITIONAL: C Compiler. (line 350)
* AC_PROG_GREP: Particular Programs. (line 16)
* AC_PROG_INSTALL: Particular Programs. (line 33)
* AC_PROG_LEX: Particular Programs. (line 98)
* AC_PROG_LN_S: Particular Programs. (line 149)
* AC_PROG_MAKE_SET: Output. (line 45)
* AC_PROG_MKDIR_P: Particular Programs. (line 67)
* AC_PROG_OBJC: Objective C Compiler.
(line 7)
* AC_PROG_OBJCPP: Objective C Compiler.
(line 26)
* AC_PROG_RANLIB: Particular Programs. (line 168)
* AC_PROG_SED: Particular Programs. (line 172)
* AC_PROG_YACC: Particular Programs. (line 178)
* AC_PROGRAM_CHECK: Obsolete Macros. (line 462)
* AC_PROGRAM_EGREP: Obsolete Macros. (line 465)
* AC_PROGRAM_PATH: Obsolete Macros. (line 468)
* AC_PROGRAMS_CHECK: Obsolete Macros. (line 456)
* AC_PROGRAMS_PATH: Obsolete Macros. (line 459)
* AC_REMOTE_TAPE: Obsolete Macros. (line 471)
* AC_REPLACE_FNMATCH: Particular Functions.
(line 357)
* AC_REPLACE_FUNCS: Generic Functions. (line 113)
* AC_REQUIRE: Prerequisite Macros. (line 17)
* AC_REQUIRE_AUX_FILE: Input. (line 37)
* AC_REQUIRE_CPP: Language Choice. (line 84)
* AC_RESTARTABLE_SYSCALLS: Obsolete Macros. (line 474)
* AC_RETSIGTYPE: Obsolete Macros. (line 482)
* AC_REVISION: Notices. (line 18)
* AC_RSH: Obsolete Macros. (line 486)
* AC_RUN_IFELSE: Runtime. (line 20)
* AC_SCO_INTL: Obsolete Macros. (line 489)
* AC_SEARCH_LIBS: Libraries. (line 49)
* AC_SET_MAKE: Obsolete Macros. (line 503)
* AC_SETVBUF_REVERSED: Obsolete Macros. (line 498)
* AC_SIZE_T: Obsolete Macros. (line 509)
* AC_SIZEOF_TYPE: Obsolete Macros. (line 506)
* AC_ST_BLKSIZE: Obsolete Macros. (line 539)
* AC_ST_BLOCKS: Obsolete Macros. (line 542)
* AC_ST_RDEV: Obsolete Macros. (line 545)
* AC_STAT_MACROS_BROKEN: Obsolete Macros. (line 512)
* AC_STDC_HEADERS: Obsolete Macros. (line 515)
* AC_STRCOLL: Obsolete Macros. (line 518)
* AC_STRUCT_DIRENT_D_INO: Particular Structures.
(line 9)
* AC_STRUCT_DIRENT_D_TYPE: Particular Structures.
(line 21)
* AC_STRUCT_ST_BLKSIZE: Obsolete Macros. (line 521)
* AC_STRUCT_ST_BLOCKS: Particular Structures.
(line 26)
* AC_STRUCT_ST_RDEV: Obsolete Macros. (line 530)
* AC_STRUCT_TIMEZONE: Particular Structures.
(line 40)
* AC_STRUCT_TM: Particular Structures.
(line 32)
* AC_SUBST: Setting Output Variables.
(line 13)
* AC_SUBST_FILE: Setting Output Variables.
(line 38)
* AC_SYS_INTERPRETER: System Services. (line 42)
* AC_SYS_LARGEFILE: System Services. (line 49)
* AC_SYS_LONG_FILE_NAMES: System Services. (line 71)
* AC_SYS_POSIX_TERMIOS: System Services. (line 75)
* AC_SYS_RESTARTABLE_SYSCALLS: Obsolete Macros. (line 548)
* AC_SYS_SIGLIST_DECLARED: Obsolete Macros. (line 563)
* AC_TEST_CPP: Obsolete Macros. (line 568)
* AC_TEST_PROGRAM: Obsolete Macros. (line 572)
* AC_TIME_WITH_SYS_TIME: Obsolete Macros. (line 579)
* AC_TIMEZONE: Obsolete Macros. (line 576)
* AC_TRY_ACT: AC_ACT_IFELSE vs AC_TRY_ACT.
(line 6)
* AC_TRY_COMPILE: Obsolete Macros. (line 583)
* AC_TRY_CPP: Obsolete Macros. (line 602)
* AC_TRY_LINK: Obsolete Macros. (line 615)
* AC_TRY_LINK_FUNC: Obsolete Macros. (line 644)
* AC_TRY_RUN: Obsolete Macros. (line 651)
* AC_TYPE_GETGROUPS: Particular Types. (line 14)
* AC_TYPE_INT16_T: Particular Types. (line 35)
* AC_TYPE_INT32_T: Particular Types. (line 38)
* AC_TYPE_INT64_T: Particular Types. (line 41)
* AC_TYPE_INT8_T: Particular Types. (line 18)
* AC_TYPE_INTMAX_T: Particular Types. (line 44)
* AC_TYPE_INTPTR_T: Particular Types. (line 49)
* AC_TYPE_LONG_DOUBLE: Particular Types. (line 54)
* AC_TYPE_LONG_DOUBLE_WIDER: Particular Types. (line 62)
* AC_TYPE_LONG_LONG_INT: Particular Types. (line 67)
* AC_TYPE_MBSTATE_T: Particular Types. (line 74)
* AC_TYPE_MODE_T: Particular Types. (line 79)
* AC_TYPE_OFF_T: Particular Types. (line 83)
* AC_TYPE_PID_T: Particular Types. (line 87)
* AC_TYPE_SIGNAL: Obsolete Macros. (line 662)
* AC_TYPE_SIZE_T: Particular Types. (line 91)
* AC_TYPE_SSIZE_T: Particular Types. (line 95)
* AC_TYPE_UID_T: Particular Types. (line 99)
* AC_TYPE_UINT16_T: Particular Types. (line 109)
* AC_TYPE_UINT32_T: Particular Types. (line 112)
* AC_TYPE_UINT64_T: Particular Types. (line 115)
* AC_TYPE_UINT8_T: Particular Types. (line 103)
* AC_TYPE_UINTMAX_T: Particular Types. (line 118)
* AC_TYPE_UINTPTR_T: Particular Types. (line 123)
* AC_TYPE_UNSIGNED_LONG_LONG_INT: Particular Types. (line 128)
* AC_UID_T: Obsolete Macros. (line 679)
* AC_UNISTD_H: Obsolete Macros. (line 682)
* AC_USE_SYSTEM_EXTENSIONS: Posix Variants. (line 10)
* AC_USG: Obsolete Macros. (line 685)
* AC_UTIME_NULL: Obsolete Macros. (line 690)
* AC_VALIDATE_CACHED_SYSTEM_TUPLE: Obsolete Macros. (line 693)
* AC_VERBOSE: Obsolete Macros. (line 698)
* AC_VFORK: Obsolete Macros. (line 701)
* AC_VPRINTF: Obsolete Macros. (line 704)
* AC_WAIT3: Obsolete Macros. (line 707)
* AC_WARN: Obsolete Macros. (line 712)
* AC_WARNING: Reporting Messages. (line 26)
* AC_WITH: Obsolete Macros. (line 715)
* AC_WORDS_BIGENDIAN: Obsolete Macros. (line 719)
* AC_XENIX_DIR: Obsolete Macros. (line 722)
* AC_YYTEXT_POINTER: Obsolete Macros. (line 739)
* AH_BOTTOM: Autoheader Macros. (line 50)
* AH_HEADER: Configuration Headers.
(line 54)
* AH_TEMPLATE: Autoheader Macros. (line 19)
* AH_TOP: Autoheader Macros. (line 47)
* AH_VERBATIM: Autoheader Macros. (line 40)
* AU_ALIAS: Obsoleting Macros. (line 34)
* AU_DEFUN: Obsoleting Macros. (line 18)
File: autoconf.info, Node: M4 Macro Index, Next: Autotest Macro Index, Prev: Autoconf Macro Index, Up: Indices
B.5 M4 Macro Index
==================
This is an alphabetical list of the M4, M4sugar, and M4sh macros.
[index ]
* Menu:
* __file__: Redefined M4 Macros. (line 65)
* __line__: Redefined M4 Macros. (line 65)
* __oline__: Redefined M4 Macros. (line 69)
* AS_APPEND: Polymorphic Variables.
(line 35)
* AS_ARITH: Polymorphic Variables.
(line 57)
* AS_BOURNE_COMPATIBLE: Initialization Macros.
(line 7)
* AS_CASE: Common Shell Constructs.
(line 10)
* AS_ECHO: Common Shell Constructs.
(line 17)
* AS_ECHO_N: Common Shell Constructs.
(line 25)
* AS_ESCAPE: Common Shell Constructs.
(line 33)
* AS_EXIT: Common Shell Constructs.
(line 73)
* AS_HELP_STRING: Pretty Help Strings. (line 15)
* AS_IF: Common Shell Constructs.
(line 79)
* AS_INIT: Initialization Macros.
(line 14)
* AS_INIT_GENERATED: Initialization Macros.
(line 23)
* AS_LINENO_PREPARE: Initialization Macros.
(line 64)
* AS_LITERAL_IF: Polymorphic Variables.
(line 18)
* AS_ME_PREPARE: Initialization Macros.
(line 69)
* AS_MESSAGE_FD: File Descriptor Macros.
(line 17)
* AS_MESSAGE_LOG_FD: File Descriptor Macros.
(line 29)
* AS_MKDIR_P: Common Shell Constructs.
(line 93)
* AS_ORIGINAL_STDIN_FD: File Descriptor Macros.
(line 39)
* AS_SET_CATFILE: Common Shell Constructs.
(line 128)
* AS_SET_STATUS: Common Shell Constructs.
(line 105)
* AS_SHELL_SANITIZE: Initialization Macros.
(line 74)
* AS_TR_CPP: Common Shell Constructs.
(line 110)
* AS_TR_SH: Common Shell Constructs.
(line 119)
* AS_UNSET: Common Shell Constructs.
(line 132)
* AS_VAR_COPY: Polymorphic Variables.
(line 75)
* AS_VAR_IF: Polymorphic Variables.
(line 94)
* AS_VAR_POPDEF: Polymorphic Variables.
(line 102)
* AS_VAR_PUSHDEF: Polymorphic Variables.
(line 102)
* AS_VAR_SET: Polymorphic Variables.
(line 144)
* AS_VAR_SET_IF: Polymorphic Variables.
(line 154)
* AS_VAR_TEST_SET: Polymorphic Variables.
(line 159)
* AS_VERSION_COMPARE: Common Shell Constructs.
(line 138)
* dnl: Redefined M4 Macros. (line 76)
* m4_append: Text processing Macros.
(line 16)
* m4_append_uniq: Text processing Macros.
(line 16)
* m4_append_uniq_w: Text processing Macros.
(line 69)
* m4_apply: Evaluation Macros. (line 10)
* m4_argn: Looping constructs. (line 29)
* m4_assert: Diagnostic Macros. (line 11)
* m4_bmatch: Conditional constructs.
(line 11)
* m4_bpatsubst: Redefined M4 Macros. (line 79)
* m4_bpatsubsts: Conditional constructs.
(line 18)
* m4_bregexp: Redefined M4 Macros. (line 84)
* m4_builtin: Redefined M4 Macros. (line 6)
* m4_car: Looping constructs. (line 35)
* m4_case: Conditional constructs.
(line 33)
* m4_cdr: Looping constructs. (line 41)
* m4_changecom: Redefined M4 Macros. (line 6)
* m4_changequote: Redefined M4 Macros. (line 6)
* m4_chomp: Text processing Macros.
(line 80)
* m4_chomp_all: Text processing Macros.
(line 80)
* m4_cleardivert: Diversion support. (line 97)
* m4_cmp: Number processing Macros.
(line 11)
* m4_combine: Text processing Macros.
(line 88)
* m4_cond: Conditional constructs.
(line 42)
* m4_copy: Redefined M4 Macros. (line 92)
* m4_copy_force: Redefined M4 Macros. (line 92)
* m4_count: Evaluation Macros. (line 26)
* m4_curry: Evaluation Macros. (line 30)
* m4_debugfile: Redefined M4 Macros. (line 6)
* m4_debugmode: Redefined M4 Macros. (line 6)
* m4_decr: Redefined M4 Macros. (line 6)
* m4_default: Conditional constructs.
(line 73)
* m4_default_nblank: Conditional constructs.
(line 73)
* m4_default_nblank_quoted: Conditional constructs.
(line 73)
* m4_default_quoted: Conditional constructs.
(line 73)
* m4_define: Redefined M4 Macros. (line 6)
* m4_defn: Redefined M4 Macros. (line 111)
* m4_divert: Redefined M4 Macros. (line 119)
* m4_divert_once: Diversion support. (line 100)
* m4_divert_pop: Diversion support. (line 105)
* m4_divert_push: Diversion support. (line 111)
* m4_divert_text: Diversion support. (line 117)
* m4_divnum: Redefined M4 Macros. (line 6)
* m4_do: Evaluation Macros. (line 45)
* m4_dquote: Evaluation Macros. (line 65)
* m4_dquote_elt: Evaluation Macros. (line 70)
* m4_dumpdef: Redefined M4 Macros. (line 127)
* m4_dumpdefs: Redefined M4 Macros. (line 127)
* m4_echo: Evaluation Macros. (line 75)
* m4_errprint: Redefined M4 Macros. (line 6)
* m4_errprintn: Diagnostic Macros. (line 16)
* m4_esyscmd: Redefined M4 Macros. (line 6)
* m4_esyscmd_s: Redefined M4 Macros. (line 144)
* m4_eval: Redefined M4 Macros. (line 6)
* m4_exit: Redefined M4 Macros. (line 150)
* m4_expand: Evaluation Macros. (line 79)
* m4_fatal: Diagnostic Macros. (line 20)
* m4_flatten: Text processing Macros.
(line 108)
* m4_for: Looping constructs. (line 59)
* m4_foreach: Looping constructs. (line 69)
* m4_foreach_w: Looping constructs. (line 83)
* m4_format: Redefined M4 Macros. (line 6)
* m4_if: Redefined M4 Macros. (line 156)
* m4_ifblank: Conditional constructs.
(line 123)
* m4_ifdef: Redefined M4 Macros. (line 6)
* m4_ifnblank: Conditional constructs.
(line 123)
* m4_ifndef: Conditional constructs.
(line 131)
* m4_ifset: Conditional constructs.
(line 135)
* m4_ifval: Conditional constructs.
(line 141)
* m4_ifvaln: Conditional constructs.
(line 146)
* m4_ignore: Evaluation Macros. (line 129)
* m4_include: Redefined M4 Macros. (line 163)
* m4_incr: Redefined M4 Macros. (line 6)
* m4_index: Redefined M4 Macros. (line 6)
* m4_indir: Redefined M4 Macros. (line 6)
* m4_init: Diversion support. (line 123)
* m4_join: Text processing Macros.
(line 114)
* m4_joinall: Text processing Macros.
(line 114)
* m4_len: Redefined M4 Macros. (line 6)
* m4_list_cmp: Number processing Macros.
(line 16)
* m4_location: Diagnostic Macros. (line 24)
* m4_make_list: Evaluation Macros. (line 142)
* m4_maketemp: Redefined M4 Macros. (line 167)
* m4_map: Looping constructs. (line 93)
* m4_map_args: Looping constructs. (line 130)
* m4_map_args_pair: Looping constructs. (line 166)
* m4_map_args_sep: Looping constructs. (line 178)
* m4_map_args_w: Looping constructs. (line 189)
* m4_map_sep: Looping constructs. (line 93)
* m4_mapall: Looping constructs. (line 93)
* m4_mapall_sep: Looping constructs. (line 93)
* m4_max: Number processing Macros.
(line 38)
* m4_min: Number processing Macros.
(line 42)
* m4_mkstemp: Redefined M4 Macros. (line 167)
* m4_n: Conditional constructs.
(line 150)
* m4_newline: Text processing Macros.
(line 129)
* m4_normalize: Text processing Macros.
(line 135)
* m4_pattern_allow: Forbidden Patterns. (line 30)
* m4_pattern_forbid: Forbidden Patterns. (line 17)
* m4_popdef: Redefined M4 Macros. (line 178)
* m4_pushdef: Redefined M4 Macros. (line 6)
* m4_quote: Evaluation Macros. (line 161)
* m4_re_escape: Text processing Macros.
(line 143)
* m4_rename: Redefined M4 Macros. (line 92)
* m4_rename_force: Redefined M4 Macros. (line 92)
* m4_reverse: Evaluation Macros. (line 167)
* m4_set_add: Set manipulation Macros.
(line 19)
* m4_set_add_all: Set manipulation Macros.
(line 25)
* m4_set_contains: Set manipulation Macros.
(line 29)
* m4_set_contents: Set manipulation Macros.
(line 49)
* m4_set_delete: Set manipulation Macros.
(line 79)
* m4_set_difference: Set manipulation Macros.
(line 86)
* m4_set_dump: Set manipulation Macros.
(line 49)
* m4_set_empty: Set manipulation Macros.
(line 109)
* m4_set_foreach: Set manipulation Macros.
(line 115)
* m4_set_intersection: Set manipulation Macros.
(line 86)
* m4_set_list: Set manipulation Macros.
(line 136)
* m4_set_listc: Set manipulation Macros.
(line 136)
* m4_set_map: Set manipulation Macros.
(line 171)
* m4_set_map_sep: Set manipulation Macros.
(line 184)
* m4_set_remove: Set manipulation Macros.
(line 195)
* m4_set_size: Set manipulation Macros.
(line 206)
* m4_set_union: Set manipulation Macros.
(line 86)
* m4_shift: Redefined M4 Macros. (line 6)
* m4_shift2: Looping constructs. (line 199)
* m4_shift3: Looping constructs. (line 199)
* m4_shiftn: Looping constructs. (line 199)
* m4_sign: Number processing Macros.
(line 46)
* m4_sinclude: Redefined M4 Macros. (line 163)
* m4_split: Text processing Macros.
(line 147)
* m4_stack_foreach: Looping constructs. (line 208)
* m4_stack_foreach_lifo: Looping constructs. (line 208)
* m4_stack_foreach_sep: Looping constructs. (line 230)
* m4_stack_foreach_sep_lifo: Looping constructs. (line 230)
* m4_strip: Text processing Macros.
(line 153)
* m4_substr: Redefined M4 Macros. (line 6)
* m4_syscmd: Redefined M4 Macros. (line 6)
* m4_sysval: Redefined M4 Macros. (line 6)
* m4_text_box: Text processing Macros.
(line 162)
* m4_text_wrap: Text processing Macros.
(line 176)
* m4_tolower: Text processing Macros.
(line 207)
* m4_toupper: Text processing Macros.
(line 207)
* m4_traceoff: Redefined M4 Macros. (line 6)
* m4_traceon: Redefined M4 Macros. (line 6)
* m4_translit: Redefined M4 Macros. (line 6)
* m4_undefine: Redefined M4 Macros. (line 182)
* m4_undivert: Redefined M4 Macros. (line 190)
* m4_unquote: Evaluation Macros. (line 176)
* m4_version_compare: Number processing Macros.
(line 50)
* m4_version_prereq: Number processing Macros.
(line 90)
* m4_warn: Diagnostic Macros. (line 28)
* m4_wrap: Redefined M4 Macros. (line 198)
* m4_wrap_lifo: Redefined M4 Macros. (line 198)
File: autoconf.info, Node: Autotest Macro Index, Next: Program & Function Index, Prev: M4 Macro Index, Up: Indices
B.6 Autotest Macro Index
========================
This is an alphabetical list of the Autotest macros.
[index ]
* Menu:
* AT_BANNER: Writing Testsuites. (line 64)
* AT_CAPTURE_FILE: Writing Testsuites. (line 94)
* AT_CHECK: Writing Testsuites. (line 151)
* AT_CHECK_UNQUOTED: Writing Testsuites. (line 151)
* AT_CLEANUP: Writing Testsuites. (line 137)
* AT_COPYRIGHT: Writing Testsuites. (line 41)
* AT_DATA: Writing Testsuites. (line 141)
* AT_FAIL_IF: Writing Testsuites. (line 99)
* AT_INIT: Writing Testsuites. (line 31)
* AT_KEYWORDS: Writing Testsuites. (line 82)
* AT_PACKAGE_BUGREPORT: Making testsuite Scripts.
(line 12)
* AT_PACKAGE_NAME: Making testsuite Scripts.
(line 12)
* AT_PACKAGE_STRING: Making testsuite Scripts.
(line 12)
* AT_PACKAGE_TARNAME: Making testsuite Scripts.
(line 12)
* AT_PACKAGE_URL: Making testsuite Scripts.
(line 12)
* AT_PACKAGE_VERSION: Making testsuite Scripts.
(line 12)
* AT_SETUP: Writing Testsuites. (line 74)
* AT_SKIP_IF: Writing Testsuites. (line 114)
* AT_TESTED: Writing Testsuites. (line 49)
* AT_XFAIL_IF: Writing Testsuites. (line 129)
File: autoconf.info, Node: Program & Function Index, Next: Concept Index, Prev: Autotest Macro Index, Up: Indices
B.7 Program and Function Index
==============================
This is an alphabetical list of the programs and functions whose
portability is discussed in this document.
[index ]
* Menu:
* !: Limitations of Builtins.
(line 41)
* .: Limitations of Builtins.
(line 17)
* /usr/bin/ksh on Solaris: Shellology. (line 63)
* /usr/dt/bin/dtksh on Solaris: Shellology. (line 66)
* /usr/xpg4/bin/sh on Solaris: Shellology. (line 64)
* alloca: Particular Functions.
(line 10)
* alloca.h: Particular Functions.
(line 10)
* assert.h: Particular Headers. (line 10)
* awk: Limitations of Usual Tools.
(line 10)
* basename: Limitations of Usual Tools.
(line 140)
* break: Limitations of Builtins.
(line 107)
* case: Limitations of Builtins.
(line 110)
* cat: Limitations of Usual Tools.
(line 144)
* cc: Limitations of Usual Tools.
(line 147)
* cd: Limitations of Builtins.
(line 203)
* chgrp: Limitations of Usual Tools.
(line 181)
* chmod: Limitations of Usual Tools.
(line 185)
* chown <1>: Limitations of Usual Tools.
(line 181)
* chown: Particular Functions.
(line 54)
* closedir: Particular Functions.
(line 58)
* cmp: Limitations of Usual Tools.
(line 195)
* cp: Limitations of Usual Tools.
(line 202)
* ctype.h: Particular Headers. (line 118)
* date: Limitations of Usual Tools.
(line 254)
* diff: Limitations of Usual Tools.
(line 264)
* dirent.h: Particular Headers. (line 15)
* dirname: Limitations of Usual Tools.
(line 270)
* echo: Limitations of Builtins.
(line 223)
* egrep: Limitations of Usual Tools.
(line 277)
* error_at_line: Particular Functions.
(line 70)
* eval: Limitations of Builtins.
(line 255)
* exec: Limitations of Builtins.
(line 300)
* exit <1>: Limitations of Builtins.
(line 340)
* exit: Function Portability.
(line 12)
* export: Limitations of Builtins.
(line 365)
* expr: Limitations of Usual Tools.
(line 335)
* expr (|): Limitations of Usual Tools.
(line 316)
* false: Limitations of Builtins.
(line 401)
* fgrep: Limitations of Usual Tools.
(line 425)
* find: Limitations of Usual Tools.
(line 432)
* float.h: Particular Headers. (line 118)
* fnmatch: Particular Functions.
(line 74)
* fnmatch.h: Particular Functions.
(line 357)
* for: Limitations of Builtins.
(line 405)
* fork: Particular Functions.
(line 94)
* free: Function Portability.
(line 22)
* fseeko: Particular Functions.
(line 116)
* ftello: Particular Functions.
(line 116)
* getgroups: Particular Functions.
(line 124)
* getloadavg: Particular Functions.
(line 130)
* getmntent: Particular Functions.
(line 164)
* getpgid: Particular Functions.
(line 170)
* getpgrp: Particular Functions.
(line 170)
* grep: Limitations of Usual Tools.
(line 446)
* if: Limitations of Builtins.
(line 431)
* inttypes.h <1>: Particular Types. (line 6)
* inttypes.h: Header Portability. (line 16)
* isinf: Function Portability.
(line 27)
* isnan: Function Portability.
(line 27)
* join: Limitations of Usual Tools.
(line 510)
* ksh: Shellology. (line 57)
* ksh88: Shellology. (line 57)
* ksh93: Shellology. (line 57)
* linux/irda.h: Header Portability. (line 23)
* linux/random.h: Header Portability. (line 26)
* ln: Limitations of Usual Tools.
(line 523)
* ls: Limitations of Usual Tools.
(line 535)
* lstat: Particular Functions.
(line 190)
* make: Portable Make. (line 6)
* malloc <1>: Function Portability.
(line 77)
* malloc: Particular Functions.
(line 203)
* mbrtowc: Particular Functions.
(line 242)
* memcmp: Particular Functions.
(line 232)
* mkdir: Limitations of Usual Tools.
(line 557)
* mkfifo: Limitations of Usual Tools.
(line 591)
* mknod: Limitations of Usual Tools.
(line 591)
* mktemp: Limitations of Usual Tools.
(line 601)
* mktime: Particular Functions.
(line 246)
* mmap: Particular Functions.
(line 252)
* mv: Limitations of Usual Tools.
(line 625)
* ndir.h: Particular Headers. (line 15)
* net/if.h: Header Portability. (line 29)
* netinet/if_ether.h: Header Portability. (line 49)
* nlist.h: Particular Functions.
(line 147)
* od: Limitations of Usual Tools.
(line 657)
* pdksh: Shellology. (line 77)
* printf: Limitations of Builtins.
(line 470)
* putenv: Function Portability.
(line 84)
* pwd: Limitations of Builtins.
(line 494)
* read: Limitations of Builtins.
(line 525)
* realloc <1>: Function Portability.
(line 100)
* realloc: Particular Functions.
(line 261)
* resolv.h: Particular Headers. (line 63)
* rm: Limitations of Usual Tools.
(line 666)
* rmdir: Limitations of Usual Tools.
(line 683)
* sed: Limitations of Usual Tools.
(line 687)
* sed (t): Limitations of Usual Tools.
(line 829)
* select: Particular Functions.
(line 269)
* set: Limitations of Builtins.
(line 529)
* setpgrp: Particular Functions.
(line 280)
* setvbuf: Obsolete Macros. (line 208)
* shift: Limitations of Builtins.
(line 651)
* sigaction: Function Portability.
(line 105)
* signal: Function Portability.
(line 105)
* signal.h: Obsolete Macros. (line 662)
* sleep: Limitations of Usual Tools.
(line 889)
* snprintf: Function Portability.
(line 119)
* sort: Limitations of Usual Tools.
(line 895)
* source: Limitations of Builtins.
(line 659)
* sprintf: Function Portability.
(line 130)
* sscanf: Function Portability.
(line 136)
* stat: Particular Functions.
(line 292)
* stdarg.h: Particular Headers. (line 118)
* stdbool.h: Particular Headers. (line 91)
* stdint.h <1>: Particular Types. (line 6)
* stdint.h: Header Portability. (line 16)
* stdlib.h <1>: Particular Headers. (line 118)
* stdlib.h <2>: Header Portability. (line 72)
* stdlib.h: Particular Types. (line 6)
* strcoll: Particular Functions.
(line 304)
* strerror_r <1>: Particular Functions.
(line 310)
* strerror_r: Function Portability.
(line 144)
* strftime: Particular Functions.
(line 320)
* string.h: Particular Headers. (line 118)
* strings.h: Particular Headers. (line 135)
* strnlen <1>: Particular Functions.
(line 337)
* strnlen: Function Portability.
(line 150)
* strtod: Particular Functions.
(line 327)
* strtold: Particular Functions.
(line 333)
* sys/dir.h: Particular Headers. (line 15)
* sys/ioctl.h: Particular Headers. (line 246)
* sys/mkdev.h: Particular Headers. (line 58)
* sys/mount.h: Header Portability. (line 75)
* sys/ndir.h: Particular Headers. (line 15)
* sys/ptem.h: Header Portability. (line 79)
* sys/socket.h: Header Portability. (line 82)
* sys/stat.h: Particular Headers. (line 82)
* sys/sysmacros.h: Particular Headers. (line 58)
* sys/time.h <1>: Particular Headers. (line 222)
* sys/time.h: Particular Structures.
(line 32)
* sys/types.h: Particular Types. (line 6)
* sys/ucred.h: Header Portability. (line 85)
* sys/wait.h: Particular Headers. (line 185)
* sysconf: Function Portability.
(line 165)
* system.h: Particular Headers. (line 91)
* tar: Limitations of Usual Tools.
(line 900)
* termios.h: Particular Headers. (line 246)
* test: Limitations of Builtins.
(line 663)
* time.h <1>: Particular Structures.
(line 32)
* time.h: Particular Headers. (line 222)
* touch: Limitations of Usual Tools.
(line 905)
* tr: Limitations of Usual Tools.
(line 918)
* trap: Limitations of Builtins.
(line 751)
* true: Limitations of Builtins.
(line 825)
* unistd.h: Particular Headers. (line 206)
* unlink: Function Portability.
(line 169)
* unset: Limitations of Builtins.
(line 836)
* unsetenv: Function Portability.
(line 175)
* utime: Particular Functions.
(line 341)
* va_copy: Function Portability.
(line 180)
* va_list: Function Portability.
(line 187)
* vfork: Particular Functions.
(line 94)
* vfork.h: Particular Functions.
(line 94)
* vprintf: Particular Functions.
(line 348)
* vsnprintf: Function Portability.
(line 119)
* vsprintf <1>: Particular Functions.
(line 348)
* vsprintf: Function Portability.
(line 130)
* wait: Limitations of Builtins.
(line 861)
* wait3: Obsolete Macros. (line 216)
* wchar.h: Particular Types. (line 74)
* X11/extensions/scrnsaver.h: Header Portability. (line 88)
* {...}: Limitations of Builtins.
(line 74)
File: autoconf.info, Node: Concept Index, Prev: Program & Function Index, Up: Indices
B.8 Concept Index
=================
This is an alphabetical list of the files, tools, and concepts
introduced in this document.
[index ]
* Menu:
* "$@": Shell Substitutions. (line 31)
* $((EXPRESSION)): Shell Substitutions. (line 263)
* $(COMMANDS): Shell Substitutions. (line 230)
* $<, explicit rules, and VPATH: $< in Explicit Rules.
(line 6)
* ${#VAR}: Shell Substitutions. (line 176)
* ${VAR##WORD}: Shell Substitutions. (line 176)
* ${VAR#WORD}: Shell Substitutions. (line 176)
* ${VAR%%WORD}: Shell Substitutions. (line 176)
* ${VAR%WORD}: Shell Substitutions. (line 176)
* ${VAR=EXPANDED-VALUE}: Shell Substitutions. (line 126)
* ${VAR=LITERAL}: Shell Substitutions. (line 96)
* 64-bit libraries: Site Defaults. (line 94)
* @&t@: Quadrigraphs. (line 6)
* @S|@: Quadrigraphs. (line 6)
* ^ quoting: Shell Substitutions. (line 303)
* _m4_divert_diversion: New Macros. (line 6)
* `COMMANDS`: Shell Substitutions. (line 184)
* absolute file names, detect: File System Conventions.
(line 52)
* acconfig.h: acconfig Header. (line 6)
* aclocal.m4: Making configure Scripts.
(line 6)
* Ash: Shellology. (line 16)
* autoconf: autoconf Invocation. (line 6)
* Autoconf upgrading <1>: Autoconf 1. (line 6)
* Autoconf upgrading: Autoconf 2.13. (line 6)
* Autoconf version: Versioning. (line 6)
* autoheader: autoheader Invocation.
(line 6)
* Autoheader macros: Autoheader Macros. (line 6)
* autom4te debugging tips: Debugging via autom4te.
(line 6)
* Autom4te Library: autom4te Invocation. (line 225)
* autom4te.cache: autom4te Invocation. (line 130)
* autom4te.cfg: autom4te Invocation. (line 258)
* Automake: Automake. (line 19)
* Automatic remaking: Automatic Remaking. (line 6)
* automatic rule rewriting and VPATH: Automatic Rule Rewriting.
(line 6)
* autopoint: autoreconf Invocation.
(line 30)
* autoreconf: autoreconf Invocation.
(line 6)
* autoscan: autoscan Invocation. (line 6)
* Autotest: Using Autotest. (line 6)
* AUTOTEST_PATH: testsuite Invocation.
(line 60)
* autoupdate: autoupdate Invocation.
(line 6)
* Back trace <1>: autom4te Invocation. (line 86)
* Back trace: autoconf Invocation. (line 86)
* balancing parentheses: Balancing Parentheses.
(line 6)
* Bash: Shellology. (line 43)
* Bash 2.05 and later: Shellology. (line 49)
* Bootstrap: Bootstrapping. (line 6)
* BSD make and obj/: obj/ and Make. (line 6)
* buffer overruns: Buffer Overruns. (line 6)
* Build directories: Build Directories. (line 6)
* C function portability: Function Portability.
(line 6)
* C types: Types. (line 6)
* Cache: Caching Results. (line 6)
* Cache variable: Cache Variable Names.
(line 6)
* Cache, enabling: configure Invocation.
(line 25)
* Canonical system type: Canonicalizing. (line 6)
* carriage return, deleting: Limitations of Usual Tools.
(line 918)
* changequote: Changequote is Evil. (line 6)
* Coding style: Coding Style. (line 6)
* Command Substitution: Shell Substitutions. (line 184)
* Commands for configuration: Configuration Commands.
(line 6)
* Comments in Makefile rules: Comments in Make Rules.
(line 6)
* Common autoconf behavior: Common Behavior. (line 6)
* Compilers: Compilers and Preprocessors.
(line 6)
* composing variable names: Polymorphic Variables.
(line 102)
* config.h: Configuration Headers.
(line 6)
* config.h.bot: acconfig Header. (line 6)
* config.h.in: Header Templates. (line 6)
* config.h.top: acconfig Header. (line 6)
* config.site: Site Defaults. (line 6)
* config.status: config.status Invocation.
(line 6)
* config.sub: Specifying Target Triplets.
(line 56)
* Configuration actions: Configuration Actions.
(line 6)
* Configuration commands: Configuration Commands.
(line 6)
* Configuration file creation: Configuration Files. (line 6)
* Configuration Header: Configuration Headers.
(line 6)
* Configuration Header Template: Header Templates. (line 6)
* Configuration links: Configuration Links. (line 6)
* configure <1>: Making configure Scripts.
(line 6)
* configure: Running configure Scripts.
(line 6)
* Configure subdirectories: Subdirectories. (line 6)
* configure.ac: Making configure Scripts.
(line 27)
* configure.in: Making configure Scripts.
(line 27)
* Copyright Notice <1>: Writing Testsuites. (line 41)
* Copyright Notice: Notices. (line 10)
* Creating configuration files: Configuration Files. (line 6)
* Creating temporary files: Limitations of Usual Tools.
(line 601)
* Cross compilation: Hosts and Cross-Compilation.
(line 6)
* Darwin: Systemology. (line 23)
* Data structure, set: Set manipulation Macros.
(line 6)
* datarootdir: Changed Directory Variables.
(line 6)
* debugging tips: Debugging via autom4te.
(line 6)
* Declaration, checking: Declarations. (line 6)
* Default includes: Default Includes. (line 6)
* deleting carriage return: Limitations of Usual Tools.
(line 918)
* Dependencies between macros: Dependencies Between Macros.
(line 6)
* Descriptors: File Descriptors. (line 6)
* descriptors: File Descriptor Macros.
(line 6)
* Directories, build: Build Directories. (line 6)
* Directories, installation: Installation Directory Variables.
(line 6)
* division, integer: Signed Integer Division.
(line 6)
* dnl <1>: Coding Style. (line 40)
* dnl: Macro Definitions. (line 51)
* double-colon rules and VPATH: VPATH and Double-colon.
(line 6)
* Endianness: C Compiler. (line 178)
* Erlang: Erlang Compiler and Interpreter.
(line 6)
* Erlang, Library, checking: Erlang Libraries. (line 6)
* exiting portably: Exiting Portably. (line 6)
* expanded before required: Expanded Before Required.
(line 6)
* explicit rules, $<, and VPATH: $< in Explicit Rules.
(line 6)
* External software: External Software. (line 6)
* F77: Fortran Compiler. (line 6)
* FHS: Site Defaults. (line 80)
* file descriptors: File Descriptor Macros.
(line 6)
* File descriptors: File Descriptors. (line 6)
* File system conventions: File System Conventions.
(line 6)
* File, checking: Files. (line 6)
* Filesystem Hierarchy Standard: Site Defaults. (line 80)
* floating point: Floating Point Portability.
(line 6)
* Forbidden patterns: Forbidden Patterns. (line 6)
* Fortran: Fortran Compiler. (line 6)
* Function, checking: Particular Functions.
(line 6)
* Gettext: autoreconf Invocation.
(line 30)
* GNU build system: The GNU Build System.
(line 6)
* Gnulib: Gnulib. (line 11)
* Header portability: Header Portability. (line 6)
* Header templates: Header Templates. (line 6)
* Header, checking: Header Files. (line 6)
* Help strings: Pretty Help Strings. (line 6)
* Here-documents: Here-Documents. (line 6)
* History of autoconf: History. (line 6)
* ifnames: ifnames Invocation. (line 6)
* Imake: Why Not Imake. (line 6)
* Includes, default: Default Includes. (line 6)
* indirection, variable name: Polymorphic Variables.
(line 6)
* input: File Descriptor Macros.
(line 6)
* Install prefix: Default Prefix. (line 6)
* Installation directories: Installation Directory Variables.
(line 6)
* Instantiation: Output. (line 13)
* integer overflow <1>: Signed Overflow Examples.
(line 6)
* integer overflow <2>: Integer Overflow Basics.
(line 6)
* integer overflow <3>: Signed Overflow Advice.
(line 6)
* integer overflow: Integer Overflow. (line 6)
* Introduction: Introduction. (line 6)
* Korn shell: Shellology. (line 57)
* Ksh: Shellology. (line 57)
* Language: Language Choice. (line 6)
* Large file support: System Services. (line 49)
* LFS: System Services. (line 49)
* lib64: Site Defaults. (line 94)
* Library, checking: Libraries. (line 6)
* Libtool: Libtool. (line 14)
* License: Distributing. (line 6)
* Limitations of make: Portable Make. (line 6)
* Limitations of shell builtins: Limitations of Builtins.
(line 6)
* Limitations of usual tools: Limitations of Usual Tools.
(line 6)
* Links: Configuration Links. (line 12)
* Links for configuration: Configuration Links. (line 6)
* Listing directories: Limitations of Usual Tools.
(line 535)
* loop induction: Optimization and Wraparound.
(line 6)
* low-level output: File Descriptor Macros.
(line 6)
* M4: Programming in M4. (line 6)
* M4 quotation: M4 Quotation. (line 6)
* M4sugar: Programming in M4sugar.
(line 6)
* m4sugar debugging tips: Debugging via autom4te.
(line 6)
* Macro invocation stack <1>: autom4te Invocation. (line 86)
* Macro invocation stack: autoconf Invocation. (line 86)
* Macros, called once: One-Shot Macros. (line 6)
* Macros, obsoleting: Obsoleting Macros. (line 6)
* Macros, ordering: Suggested Ordering. (line 6)
* Macros, prerequisites: Prerequisite Macros. (line 6)
* make -k: make -k Status. (line 6)
* make and MAKEFLAGS: The Make Macro MAKEFLAGS.
(line 6)
* make and SHELL: The Make Macro SHELL.
(line 6)
* Makefile rules and comments: Comments in Make Rules.
(line 6)
* Makefile substitutions: Makefile Substitutions.
(line 6)
* MAKEFLAGS and make: The Make Macro MAKEFLAGS.
(line 6)
* Making directories: Limitations of Usual Tools.
(line 557)
* Messages, from autoconf: Reporting Messages. (line 6)
* Messages, from configure: Printing Messages. (line 6)
* Messages, from M4sugar: Diagnostic Macros. (line 6)
* Moving open files: Limitations of Usual Tools.
(line 625)
* Notices in configure: Notices. (line 6)
* null pointers: Null Pointers. (line 6)
* obj/, subdirectory: obj/ and Make. (line 6)
* Obsolete constructs: Obsolete Constructs. (line 6)
* Obsoleting macros: Obsoleting Macros. (line 6)
* obstack: Particular Functions.
(line 257)
* One-shot macros: One-Shot Macros. (line 6)
* Options, package: Package Options. (line 6)
* Options, Package: Option Checking. (line 6)
* Ordering macros: Suggested Ordering. (line 6)
* Output variables <1>: Setting Output Variables.
(line 6)
* Output variables: Preset Output Variables.
(line 6)
* Output variables, special characters in: Special Chars in Variables.
(line 6)
* output, low-level: File Descriptor Macros.
(line 6)
* Outputting files: Output. (line 6)
* overflow, signed integer <1>: Integer Overflow. (line 6)
* overflow, signed integer <2>: Signed Overflow Examples.
(line 6)
* overflow, signed integer <3>: Signed Overflow Advice.
(line 6)
* overflow, signed integer: Integer Overflow Basics.
(line 6)
* Package options: Package Options. (line 6)
* package.m4: Making testsuite Scripts.
(line 12)
* Parallel make: Parallel Make. (line 6)
* parentheses, balancing: Balancing Parentheses.
(line 6)
* Patterns, forbidden: Forbidden Patterns. (line 6)
* polymorphic variable name: Polymorphic Variables.
(line 6)
* portability: Varieties of Unportability.
(line 6)
* Portability of C functions: Function Portability.
(line 6)
* Portability of headers: Header Portability. (line 6)
* Portable C and C++ programming: Portable C and C++. (line 6)
* Portable shell programming: Portable Shell. (line 6)
* positional parameters: Shell Substitutions. (line 82)
* Posix termios headers: System Services. (line 75)
* Precious Variable: Setting Output Variables.
(line 65)
* Prefix for install: Default Prefix. (line 6)
* preprocessor arithmetic: Preprocessor Arithmetic.
(line 6)
* Preprocessors: Compilers and Preprocessors.
(line 6)
* prerequisite directories and VPATH: Tru64 Directory Magic.
(line 6)
* Prerequisite macros: Prerequisite Macros. (line 6)
* Program names, transforming: Transforming Names. (line 6)
* Programs, checking: Alternative Programs.
(line 6)
* QNX 4.25: Systemology. (line 37)
* quadrigraphs: Quadrigraphs. (line 6)
* quotation <1>: Autoconf Language. (line 6)
* quotation: M4 Quotation. (line 6)
* Remaking automatically: Automatic Remaking. (line 6)
* Revision: Notices. (line 18)
* Rule, Single Suffix Inference: Single Suffix Rules. (line 6)
* Separated Dependencies: Single Suffix Rules. (line 9)
* set -b: Limitations of Builtins.
(line 626)
* set -e: Limitations of Builtins.
(line 554)
* set -m: Limitations of Builtins.
(line 626)
* Set manipulation: Set manipulation Macros.
(line 6)
* SHELL and make: The Make Macro SHELL.
(line 6)
* Shell assignments: Assignments. (line 6)
* Shell builtins: Limitations of Builtins.
(line 6)
* Shell file descriptors: File Descriptors. (line 6)
* Shell Functions: Shell Functions. (line 6)
* Shell here-documents: Here-Documents. (line 6)
* Shell parentheses: Parentheses. (line 6)
* Shell pattern matching: Shell Pattern Matching.
(line 6)
* Shell slashes: Slashes. (line 6)
* Shell substitutions: Shell Substitutions. (line 6)
* Shell variables: Special Shell Variables.
(line 6)
* Shellology: Shellology. (line 6)
* signed integer overflow <1>: Signed Overflow Advice.
(line 6)
* signed integer overflow <2>: Integer Overflow Basics.
(line 6)
* signed integer overflow <3>: Integer Overflow. (line 6)
* signed integer overflow: Signed Overflow Examples.
(line 6)
* Single Suffix Inference Rule: Single Suffix Rules. (line 6)
* Site defaults: Site Defaults. (line 6)
* Site details: Site Details. (line 6)
* Special shell variables: Special Shell Variables.
(line 6)
* standard input: File Descriptor Macros.
(line 6)
* Standard symbols: Standard Symbols. (line 6)
* Structure, checking: Structures. (line 6)
* Subdirectory configure: Subdirectories. (line 6)
* Substitutions in makefiles: Makefile Substitutions.
(line 6)
* Symbolic links: Limitations of Usual Tools.
(line 523)
* System type <1>: Specifying Target Triplets.
(line 6)
* System type: Canonicalizing. (line 6)
* Systemology: Systemology. (line 6)
* Target triplet: Specifying Target Triplets.
(line 6)
* termios Posix headers: System Services. (line 75)
* test group: testsuite Scripts. (line 12)
* testsuite <1>: testsuite Invocation.
(line 6)
* testsuite: testsuite Scripts. (line 6)
* timestamp resolution <1>: Limitations of Usual Tools.
(line 217)
* timestamp resolution: Timestamps and Make. (line 6)
* Transforming program names: Transforming Names. (line 6)
* Tru64: Systemology. (line 44)
* Types: Types. (line 6)
* unbalanced parentheses, managing: Balancing Parentheses.
(line 6)
* undefined macro: New Macros. (line 6)
* Unix version 7: Systemology. (line 49)
* Unordered set manipulation: Set manipulation Macros.
(line 6)
* Upgrading autoconf <1>: Autoconf 2.13. (line 6)
* Upgrading autoconf: Autoconf 1. (line 6)
* V7: Systemology. (line 49)
* variable name indirection: Polymorphic Variables.
(line 6)
* variable names, composing: Polymorphic Variables.
(line 102)
* Variable, Precious: Setting Output Variables.
(line 65)
* variables and VPATH: Variables listed in VPATH.
(line 6)
* Version: Versioning. (line 11)
* version, Autoconf: Versioning. (line 6)
* volatile objects: Volatile Objects. (line 6)
* VPATH: VPATH and Make. (line 6)
* VPATH and automatic rule rewriting: Automatic Rule Rewriting.
(line 6)
* VPATH and double-colon rules: VPATH and Double-colon.
(line 6)
* VPATH and prerequisite directories: Tru64 Directory Magic.
(line 6)
* VPATH and variables: Variables listed in VPATH.
(line 6)
* VPATH, explicit rules, and $<: $< in Explicit Rules.
(line 6)
* VPATH, resolving target pathnames: Make Target Lookup. (line 6)
* wraparound arithmetic <1>: Signed Overflow Examples.
(line 6)
* wraparound arithmetic <2>: Integer Overflow. (line 6)
* wraparound arithmetic <3>: Signed Overflow Advice.
(line 6)
* wraparound arithmetic: Integer Overflow Basics.
(line 6)
* X Window System: System Services. (line 10)
* Zsh: Shellology. (line 97)
Tag Table:
Node: Top2286
Node: Introduction21046
Node: The GNU Build System27548
Node: Automake28527
Node: Gnulib30476
Node: Libtool31785
Node: Pointers33207
Ref: Pointers-Footnote-134508
Node: Making configure Scripts34668
Node: Writing Autoconf Input37703
Node: Shell Script Compiler39166
Node: Autoconf Language41527
Node: Autoconf Input Layout47402
Node: autoscan Invocation48810
Node: ifnames Invocation51366
Node: autoconf Invocation52566
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Ref: AC_INIT64204
Node: Versioning66482
Node: Notices68422
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Ref: AC_CONFIG_SRCDIR69738
Node: Output72685
Ref: AC_OUTPUT73120
Ref: AC_PROG_MAKE_SET74738
Node: Configuration Actions75163
Node: Configuration Files80063
Ref: AC_CONFIG_FILES80324
Node: Makefile Substitutions81543
Node: Preset Output Variables83285
Node: Installation Directory Variables92410
Node: Changed Directory Variables100248
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Node: Configuration Headers106865
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Node: autoheader Invocation112902
Node: Autoheader Macros116544
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Node: Subdirectories122030
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Node: Preprocessor Arithmetic652704
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End Tag Table
autoconf2.64-2.64/doc/make-stds.texi 0000644 0002024 0002024 00000132465 11233202134 016511 0 ustar arthur arthur @comment This file is included by both standards.texi and make.texinfo.
@comment It was broken out of standards.texi on 1/6/93 by roland.
@node Makefile Conventions
@chapter Makefile Conventions
@comment standards.texi does not print an index, but make.texinfo does.
@cindex makefile, conventions for
@cindex conventions for makefiles
@cindex standards for makefiles
@c Copyright 1992, 1993, 1994, 1995, 1996, 1997, 1998, 2000, 2001,
@c 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
@c
@c Permission is granted to copy, distribute and/or modify this document
@c under the terms of the GNU Free Documentation License, Version 1.3
@c or any later version published by the Free Software Foundation;
@c with no Invariant Sections, with no
@c Front-Cover Texts, and with no Back-Cover Texts.
@c A copy of the license is included in the section entitled ``GNU
@c Free Documentation License''.
This
@ifinfo
node
@end ifinfo
@iftex
@ifset CODESTD
section
@end ifset
@ifclear CODESTD
chapter
@end ifclear
@end iftex
describes conventions for writing the Makefiles for GNU programs.
Using Automake will help you write a Makefile that follows these
conventions. For more information on portable Makefiles, see
@sc{posix} and @ref{Portable Make, Portable Make Programming,, autoconf,
Autoconf}.
@menu
* Makefile Basics:: General conventions for Makefiles.
* Utilities in Makefiles:: Utilities to be used in Makefiles.
* Command Variables:: Variables for specifying commands.
* DESTDIR:: Supporting staged installs.
* Directory Variables:: Variables for installation directories.
* Standard Targets:: Standard targets for users.
* Install Command Categories:: Three categories of commands in the `install'
rule: normal, pre-install and post-install.
@end menu
@node Makefile Basics
@section General Conventions for Makefiles
Every Makefile should contain this line:
@example
SHELL = /bin/sh
@end example
@noindent
to avoid trouble on systems where the @code{SHELL} variable might be
inherited from the environment. (This is never a problem with GNU
@code{make}.)
Different @code{make} programs have incompatible suffix lists and
implicit rules, and this sometimes creates confusion or misbehavior. So
it is a good idea to set the suffix list explicitly using only the
suffixes you need in the particular Makefile, like this:
@example
.SUFFIXES:
.SUFFIXES: .c .o
@end example
@noindent
The first line clears out the suffix list, the second introduces all
suffixes which may be subject to implicit rules in this Makefile.
Don't assume that @file{.} is in the path for command execution. When
you need to run programs that are a part of your package during the
make, please make sure that it uses @file{./} if the program is built as
part of the make or @file{$(srcdir)/} if the file is an unchanging part
of the source code. Without one of these prefixes, the current search
path is used.
The distinction between @file{./} (the @dfn{build directory}) and
@file{$(srcdir)/} (the @dfn{source directory}) is important because
users can build in a separate directory using the @samp{--srcdir} option
to @file{configure}. A rule of the form:
@smallexample
foo.1 : foo.man sedscript
sed -e sedscript foo.man > foo.1
@end smallexample
@noindent
will fail when the build directory is not the source directory, because
@file{foo.man} and @file{sedscript} are in the source directory.
When using GNU @code{make}, relying on @samp{VPATH} to find the source
file will work in the case where there is a single dependency file,
since the @code{make} automatic variable @samp{$<} will represent the
source file wherever it is. (Many versions of @code{make} set @samp{$<}
only in implicit rules.) A Makefile target like
@smallexample
foo.o : bar.c
$(CC) -I. -I$(srcdir) $(CFLAGS) -c bar.c -o foo.o
@end smallexample
@noindent
should instead be written as
@smallexample
foo.o : bar.c
$(CC) -I. -I$(srcdir) $(CFLAGS) -c $< -o $@@
@end smallexample
@noindent
in order to allow @samp{VPATH} to work correctly. When the target has
multiple dependencies, using an explicit @samp{$(srcdir)} is the easiest
way to make the rule work well. For example, the target above for
@file{foo.1} is best written as:
@smallexample
foo.1 : foo.man sedscript
sed -e $(srcdir)/sedscript $(srcdir)/foo.man > $@@
@end smallexample
GNU distributions usually contain some files which are not source
files---for example, Info files, and the output from Autoconf, Automake,
Bison or Flex. Since these files normally appear in the source
directory, they should always appear in the source directory, not in the
build directory. So Makefile rules to update them should put the
updated files in the source directory.
However, if a file does not appear in the distribution, then the
Makefile should not put it in the source directory, because building a
program in ordinary circumstances should not modify the source directory
in any way.
Try to make the build and installation targets, at least (and all their
subtargets) work correctly with a parallel @code{make}.
@node Utilities in Makefiles
@section Utilities in Makefiles
Write the Makefile commands (and any shell scripts, such as
@code{configure}) to run under @code{sh} (both the traditional Bourne
shell and the @sc{posix} shell), not @code{csh}. Don't use any
special features of @code{ksh} or @code{bash}, or @sc{posix} features
not widely supported in traditional Bourne @code{sh}.
The @code{configure} script and the Makefile rules for building and
installation should not use any utilities directly except these:
@c dd find
@c gunzip gzip md5sum
@c mkfifo mknod tee uname
@example
awk cat cmp cp diff echo egrep expr false grep install-info
ln ls mkdir mv pwd rm rmdir sed sleep sort tar test touch tr true
@end example
Compression programs such as @code{gzip} can be used in the
@code{dist} rule.
Generally, stick to the widely-supported (usually
@sc{posix}-specified) options and features of these programs. For
example, don't use @samp{mkdir -p}, convenient as it may be, because a
few systems don't support it at all and with others, it is not safe
for parallel execution. For a list of known incompatibilities, see
@ref{Portable Shell, Portable Shell Programming,, autoconf, Autoconf}.
It is a good idea to avoid creating symbolic links in makefiles, since a
few file systems don't support them.
The Makefile rules for building and installation can also use compilers
and related programs, but should do so via @code{make} variables so that the
user can substitute alternatives. Here are some of the programs we
mean:
@example
ar bison cc flex install ld ldconfig lex
make makeinfo ranlib texi2dvi yacc
@end example
Use the following @code{make} variables to run those programs:
@example
$(AR) $(BISON) $(CC) $(FLEX) $(INSTALL) $(LD) $(LDCONFIG) $(LEX)
$(MAKE) $(MAKEINFO) $(RANLIB) $(TEXI2DVI) $(YACC)
@end example
When you use @code{ranlib} or @code{ldconfig}, you should make sure
nothing bad happens if the system does not have the program in question.
Arrange to ignore an error from that command, and print a message before
the command to tell the user that failure of this command does not mean
a problem. (The Autoconf @samp{AC_PROG_RANLIB} macro can help with
this.)
If you use symbolic links, you should implement a fallback for systems
that don't have symbolic links.
Additional utilities that can be used via Make variables are:
@example
chgrp chmod chown mknod
@end example
It is ok to use other utilities in Makefile portions (or scripts)
intended only for particular systems where you know those utilities
exist.
@node Command Variables
@section Variables for Specifying Commands
Makefiles should provide variables for overriding certain commands, options,
and so on.
In particular, you should run most utility programs via variables.
Thus, if you use Bison, have a variable named @code{BISON} whose default
value is set with @samp{BISON = bison}, and refer to it with
@code{$(BISON)} whenever you need to use Bison.
File management utilities such as @code{ln}, @code{rm}, @code{mv}, and
so on, need not be referred to through variables in this way, since users
don't need to replace them with other programs.
Each program-name variable should come with an options variable that is
used to supply options to the program. Append @samp{FLAGS} to the
program-name variable name to get the options variable name---for
example, @code{BISONFLAGS}. (The names @code{CFLAGS} for the C
compiler, @code{YFLAGS} for yacc, and @code{LFLAGS} for lex, are
exceptions to this rule, but we keep them because they are standard.)
Use @code{CPPFLAGS} in any compilation command that runs the
preprocessor, and use @code{LDFLAGS} in any compilation command that
does linking as well as in any direct use of @code{ld}.
If there are C compiler options that @emph{must} be used for proper
compilation of certain files, do not include them in @code{CFLAGS}.
Users expect to be able to specify @code{CFLAGS} freely themselves.
Instead, arrange to pass the necessary options to the C compiler
independently of @code{CFLAGS}, by writing them explicitly in the
compilation commands or by defining an implicit rule, like this:
@smallexample
CFLAGS = -g
ALL_CFLAGS = -I. $(CFLAGS)
.c.o:
$(CC) -c $(CPPFLAGS) $(ALL_CFLAGS) $<
@end smallexample
Do include the @samp{-g} option in @code{CFLAGS}, because that is not
@emph{required} for proper compilation. You can consider it a default
that is only recommended. If the package is set up so that it is
compiled with GCC by default, then you might as well include @samp{-O}
in the default value of @code{CFLAGS} as well.
Put @code{CFLAGS} last in the compilation command, after other variables
containing compiler options, so the user can use @code{CFLAGS} to
override the others.
@code{CFLAGS} should be used in every invocation of the C compiler,
both those which do compilation and those which do linking.
Every Makefile should define the variable @code{INSTALL}, which is the
basic command for installing a file into the system.
Every Makefile should also define the variables @code{INSTALL_PROGRAM}
and @code{INSTALL_DATA}. (The default for @code{INSTALL_PROGRAM} should
be @code{$(INSTALL)}; the default for @code{INSTALL_DATA} should be
@code{$@{INSTALL@} -m 644}.) Then it should use those variables as the
commands for actual installation, for executables and non-executables
respectively. Minimal use of these variables is as follows:
@example
$(INSTALL_PROGRAM) foo $(bindir)/foo
$(INSTALL_DATA) libfoo.a $(libdir)/libfoo.a
@end example
However, it is preferable to support a @code{DESTDIR} prefix on the
target files, as explained in the next section.
It is acceptable, but not required, to install multiple files in one
command, with the final argument being a directory, as in:
@example
$(INSTALL_PROGRAM) foo bar baz $(bindir)
@end example
@node DESTDIR
@section @code{DESTDIR}: support for staged installs
@vindex DESTDIR
@cindex staged installs
@cindex installations, staged
@code{DESTDIR} is a variable prepended to each installed target file,
like this:
@example
$(INSTALL_PROGRAM) foo $(DESTDIR)$(bindir)/foo
$(INSTALL_DATA) libfoo.a $(DESTDIR)$(libdir)/libfoo.a
@end example
The @code{DESTDIR} variable is specified by the user on the @code{make}
command line as an absolute file name. For example:
@example
make DESTDIR=/tmp/stage install
@end example
@noindent
@code{DESTDIR} should be supported only in the @code{install*} and
@code{uninstall*} targets, as those are the only targets where it is
useful.
If your installation step would normally install
@file{/usr/local/bin/foo} and @file{/usr/local/lib/libfoo.a}, then an
installation invoked as in the example above would install
@file{/tmp/stage/usr/local/bin/foo} and
@file{/tmp/stage/usr/local/lib/libfoo.a} instead.
Prepending the variable @code{DESTDIR} to each target in this way
provides for @dfn{staged installs}, where the installed files are not
placed directly into their expected location but are instead copied
into a temporary location (@code{DESTDIR}). However, installed files
maintain their relative directory structure and any embedded file names
will not be modified.
You should not set the value of @code{DESTDIR} in your @file{Makefile}
at all; then the files are installed into their expected locations by
default. Also, specifying @code{DESTDIR} should not change the
operation of the software in any way, so its value should not be
included in any file contents.
@code{DESTDIR} support is commonly used in package creation. It is
also helpful to users who want to understand what a given package will
install where, and to allow users who don't normally have permissions
to install into protected areas to build and install before gaining
those permissions. Finally, it can be useful with tools such as
@code{stow}, where code is installed in one place but made to appear
to be installed somewhere else using symbolic links or special mount
operations. So, we strongly recommend GNU packages support
@code{DESTDIR}, though it is not an absolute requirement.
@node Directory Variables
@section Variables for Installation Directories
Installation directories should always be named by variables, so it is
easy to install in a nonstandard place. The standard names for these
variables and the values they should have in GNU packages are
described below. They are based on a standard file system layout;
variants of it are used in GNU/Linux and other modern operating
systems.
Installers are expected to override these values when calling
@command{make} (e.g., @kbd{make prefix=/usr install} or
@command{configure} (e.g., @kbd{configure --prefix=/usr}). GNU
packages should not try to guess which value should be appropriate for
these variables on the system they are being installed onto: use the
default settings specified here so that all GNU packages behave
identically, allowing the installer to achieve any desired layout.
These first two variables set the root for the installation. All the
other installation directories should be subdirectories of one of
these two, and nothing should be directly installed into these two
directories.
@table @code
@item prefix
@vindex prefix
A prefix used in constructing the default values of the variables listed
below. The default value of @code{prefix} should be @file{/usr/local}.
When building the complete GNU system, the prefix will be empty and
@file{/usr} will be a symbolic link to @file{/}.
(If you are using Autoconf, write it as @samp{@@prefix@@}.)
Running @samp{make install} with a different value of @code{prefix} from
the one used to build the program should @emph{not} recompile the
program.
@item exec_prefix
@vindex exec_prefix
A prefix used in constructing the default values of some of the
variables listed below. The default value of @code{exec_prefix} should
be @code{$(prefix)}.
(If you are using Autoconf, write it as @samp{@@exec_prefix@@}.)
Generally, @code{$(exec_prefix)} is used for directories that contain
machine-specific files (such as executables and subroutine libraries),
while @code{$(prefix)} is used directly for other directories.
Running @samp{make install} with a different value of @code{exec_prefix}
from the one used to build the program should @emph{not} recompile the
program.
@end table
Executable programs are installed in one of the following directories.
@table @code
@item bindir
@vindex bindir
The directory for installing executable programs that users can run.
This should normally be @file{/usr/local/bin}, but write it as
@file{$(exec_prefix)/bin}.
(If you are using Autoconf, write it as @samp{@@bindir@@}.)
@item sbindir
@vindex sbindir
The directory for installing executable programs that can be run from
the shell, but are only generally useful to system administrators. This
should normally be @file{/usr/local/sbin}, but write it as
@file{$(exec_prefix)/sbin}.
(If you are using Autoconf, write it as @samp{@@sbindir@@}.)
@item libexecdir
@vindex libexecdir
@comment This paragraph adjusted to avoid overfull hbox --roland 5jul94
The directory for installing executable programs to be run by other
programs rather than by users. This directory should normally be
@file{/usr/local/libexec}, but write it as @file{$(exec_prefix)/libexec}.
(If you are using Autoconf, write it as @samp{@@libexecdir@@}.)
The definition of @samp{libexecdir} is the same for all packages, so
you should install your data in a subdirectory thereof. Most packages
install their data under @file{$(libexecdir)/@var{package-name}/},
possibly within additional subdirectories thereof, such as
@file{$(libexecdir)/@var{package-name}/@var{machine}/@var{version}}.
@end table
Data files used by the program during its execution are divided into
categories in two ways.
@itemize @bullet
@item
Some files are normally modified by programs; others are never normally
modified (though users may edit some of these).
@item
Some files are architecture-independent and can be shared by all
machines at a site; some are architecture-dependent and can be shared
only by machines of the same kind and operating system; others may never
be shared between two machines.
@end itemize
This makes for six different possibilities. However, we want to
discourage the use of architecture-dependent files, aside from object
files and libraries. It is much cleaner to make other data files
architecture-independent, and it is generally not hard.
Here are the variables Makefiles should use to specify directories
to put these various kinds of files in:
@table @samp
@item datarootdir
The root of the directory tree for read-only architecture-independent
data files. This should normally be @file{/usr/local/share}, but
write it as @file{$(prefix)/share}. (If you are using Autoconf, write
it as @samp{@@datarootdir@@}.) @samp{datadir}'s default value is
based on this variable; so are @samp{infodir}, @samp{mandir}, and
others.
@item datadir
The directory for installing idiosyncratic read-only
architecture-independent data files for this program. This is usually
the same place as @samp{datarootdir}, but we use the two separate
variables so that you can move these program-specific files without
altering the location for Info files, man pages, etc.
This should normally be @file{/usr/local/share}, but write it as
@file{$(datarootdir)}. (If you are using Autoconf, write it as
@samp{@@datadir@@}.)
The definition of @samp{datadir} is the same for all packages, so you
should install your data in a subdirectory thereof. Most packages
install their data under @file{$(datadir)/@var{package-name}/}.
@item sysconfdir
The directory for installing read-only data files that pertain to a
single machine--that is to say, files for configuring a host. Mailer
and network configuration files, @file{/etc/passwd}, and so forth belong
here. All the files in this directory should be ordinary ASCII text
files. This directory should normally be @file{/usr/local/etc}, but
write it as @file{$(prefix)/etc}.
(If you are using Autoconf, write it as @samp{@@sysconfdir@@}.)
Do not install executables here in this directory (they probably belong
in @file{$(libexecdir)} or @file{$(sbindir)}). Also do not install
files that are modified in the normal course of their use (programs
whose purpose is to change the configuration of the system excluded).
Those probably belong in @file{$(localstatedir)}.
@item sharedstatedir
The directory for installing architecture-independent data files which
the programs modify while they run. This should normally be
@file{/usr/local/com}, but write it as @file{$(prefix)/com}.
(If you are using Autoconf, write it as @samp{@@sharedstatedir@@}.)
@item localstatedir
The directory for installing data files which the programs modify while
they run, and that pertain to one specific machine. Users should never
need to modify files in this directory to configure the package's
operation; put such configuration information in separate files that go
in @file{$(datadir)} or @file{$(sysconfdir)}. @file{$(localstatedir)}
should normally be @file{/usr/local/var}, but write it as
@file{$(prefix)/var}.
(If you are using Autoconf, write it as @samp{@@localstatedir@@}.)
@end table
These variables specify the directory for installing certain specific
types of files, if your program has them. Every GNU package should
have Info files, so every program needs @samp{infodir}, but not all
need @samp{libdir} or @samp{lispdir}.
@table @samp
@item includedir
@c rewritten to avoid overfull hbox --roland
The directory for installing header files to be included by user
programs with the C @samp{#include} preprocessor directive. This
should normally be @file{/usr/local/include}, but write it as
@file{$(prefix)/include}.
(If you are using Autoconf, write it as @samp{@@includedir@@}.)
Most compilers other than GCC do not look for header files in directory
@file{/usr/local/include}. So installing the header files this way is
only useful with GCC. Sometimes this is not a problem because some
libraries are only really intended to work with GCC. But some libraries
are intended to work with other compilers. They should install their
header files in two places, one specified by @code{includedir} and one
specified by @code{oldincludedir}.
@item oldincludedir
The directory for installing @samp{#include} header files for use with
compilers other than GCC. This should normally be @file{/usr/include}.
(If you are using Autoconf, you can write it as @samp{@@oldincludedir@@}.)
The Makefile commands should check whether the value of
@code{oldincludedir} is empty. If it is, they should not try to use
it; they should cancel the second installation of the header files.
A package should not replace an existing header in this directory unless
the header came from the same package. Thus, if your Foo package
provides a header file @file{foo.h}, then it should install the header
file in the @code{oldincludedir} directory if either (1) there is no
@file{foo.h} there or (2) the @file{foo.h} that exists came from the Foo
package.
To tell whether @file{foo.h} came from the Foo package, put a magic
string in the file---part of a comment---and @code{grep} for that string.
@item docdir
The directory for installing documentation files (other than Info) for
this package. By default, it should be
@file{/usr/local/share/doc/@var{yourpkg}}, but it should be written as
@file{$(datarootdir)/doc/@var{yourpkg}}. (If you are using Autoconf,
write it as @samp{@@docdir@@}.) The @var{yourpkg} subdirectory, which
may include a version number, prevents collisions among files with
common names, such as @file{README}.
@item infodir
The directory for installing the Info files for this package. By
default, it should be @file{/usr/local/share/info}, but it should be
written as @file{$(datarootdir)/info}. (If you are using Autoconf,
write it as @samp{@@infodir@@}.) @code{infodir} is separate from
@code{docdir} for compatibility with existing practice.
@item htmldir
@itemx dvidir
@itemx pdfdir
@itemx psdir
Directories for installing documentation files in the particular
format. They should all be set to @code{$(docdir)} by default. (If
you are using Autoconf, write them as @samp{@@htmldir@@},
@samp{@@dvidir@@}, etc.) Packages which supply several translations
of their documentation should install them in
@samp{$(htmldir)/}@var{ll}, @samp{$(pdfdir)/}@var{ll}, etc. where
@var{ll} is a locale abbreviation such as @samp{en} or @samp{pt_BR}.
@item libdir
The directory for object files and libraries of object code. Do not
install executables here, they probably ought to go in @file{$(libexecdir)}
instead. The value of @code{libdir} should normally be
@file{/usr/local/lib}, but write it as @file{$(exec_prefix)/lib}.
(If you are using Autoconf, write it as @samp{@@libdir@@}.)
@item lispdir
The directory for installing any Emacs Lisp files in this package. By
default, it should be @file{/usr/local/share/emacs/site-lisp}, but it
should be written as @file{$(datarootdir)/emacs/site-lisp}.
If you are using Autoconf, write the default as @samp{@@lispdir@@}.
In order to make @samp{@@lispdir@@} work, you need the following lines
in your @file{configure.in} file:
@example
lispdir='$@{datarootdir@}/emacs/site-lisp'
AC_SUBST(lispdir)
@end example
@item localedir
The directory for installing locale-specific message catalogs for this
package. By default, it should be @file{/usr/local/share/locale}, but
it should be written as @file{$(datarootdir)/locale}. (If you are
using Autoconf, write it as @samp{@@localedir@@}.) This directory
usually has a subdirectory per locale.
@end table
Unix-style man pages are installed in one of the following:
@table @samp
@item mandir
The top-level directory for installing the man pages (if any) for this
package. It will normally be @file{/usr/local/share/man}, but you
should write it as @file{$(datarootdir)/man}. (If you are using
Autoconf, write it as @samp{@@mandir@@}.)
@item man1dir
The directory for installing section 1 man pages. Write it as
@file{$(mandir)/man1}.
@item man2dir
The directory for installing section 2 man pages. Write it as
@file{$(mandir)/man2}
@item @dots{}
@strong{Don't make the primary documentation for any GNU software be a
man page. Write a manual in Texinfo instead. Man pages are just for
the sake of people running GNU software on Unix, which is a secondary
application only.}
@item manext
The file name extension for the installed man page. This should contain
a period followed by the appropriate digit; it should normally be @samp{.1}.
@item man1ext
The file name extension for installed section 1 man pages.
@item man2ext
The file name extension for installed section 2 man pages.
@item @dots{}
Use these names instead of @samp{manext} if the package needs to install man
pages in more than one section of the manual.
@end table
And finally, you should set the following variable:
@table @samp
@item srcdir
The directory for the sources being compiled. The value of this
variable is normally inserted by the @code{configure} shell script.
(If you are using Autoconf, use @samp{srcdir = @@srcdir@@}.)
@end table
For example:
@smallexample
@c I have changed some of the comments here slightly to fix an overfull
@c hbox, so the make manual can format correctly. --roland
# Common prefix for installation directories.
# NOTE: This directory must exist when you start the install.
prefix = /usr/local
datarootdir = $(prefix)/share
datadir = $(datarootdir)
exec_prefix = $(prefix)
# Where to put the executable for the command `gcc'.
bindir = $(exec_prefix)/bin
# Where to put the directories used by the compiler.
libexecdir = $(exec_prefix)/libexec
# Where to put the Info files.
infodir = $(datarootdir)/info
@end smallexample
If your program installs a large number of files into one of the
standard user-specified directories, it might be useful to group them
into a subdirectory particular to that program. If you do this, you
should write the @code{install} rule to create these subdirectories.
Do not expect the user to include the subdirectory name in the value of
any of the variables listed above. The idea of having a uniform set of
variable names for installation directories is to enable the user to
specify the exact same values for several different GNU packages. In
order for this to be useful, all the packages must be designed so that
they will work sensibly when the user does so.
At times, not all of these variables may be implemented in the current
release of Autoconf and/or Automake; but as of Autoconf@tie{}2.60, we
believe all of them are. When any are missing, the descriptions here
serve as specifications for what Autoconf will implement. As a
programmer, you can either use a development version of Autoconf or
avoid using these variables until a stable release is made which
supports them.
@node Standard Targets
@section Standard Targets for Users
All GNU programs should have the following targets in their Makefiles:
@table @samp
@item all
Compile the entire program. This should be the default target. This
target need not rebuild any documentation files; Info files should
normally be included in the distribution, and DVI (and other
documentation format) files should be made only when explicitly asked
for.
By default, the Make rules should compile and link with @samp{-g}, so
that executable programs have debugging symbols. Users who don't mind
being helpless can strip the executables later if they wish.
@item install
Compile the program and copy the executables, libraries, and so on to
the file names where they should reside for actual use. If there is a
simple test to verify that a program is properly installed, this target
should run that test.
Do not strip executables when installing them. Devil-may-care users can
use the @code{install-strip} target to do that.
If possible, write the @code{install} target rule so that it does not
modify anything in the directory where the program was built, provided
@samp{make all} has just been done. This is convenient for building the
program under one user name and installing it under another.
The commands should create all the directories in which files are to be
installed, if they don't already exist. This includes the directories
specified as the values of the variables @code{prefix} and
@code{exec_prefix}, as well as all subdirectories that are needed.
One way to do this is by means of an @code{installdirs} target
as described below.
Use @samp{-} before any command for installing a man page, so that
@code{make} will ignore any errors. This is in case there are systems
that don't have the Unix man page documentation system installed.
The way to install Info files is to copy them into @file{$(infodir)}
with @code{$(INSTALL_DATA)} (@pxref{Command Variables}), and then run
the @code{install-info} program if it is present. @code{install-info}
is a program that edits the Info @file{dir} file to add or update the
menu entry for the given Info file; it is part of the Texinfo package.
Here is a sample rule to install an Info file:
@comment This example has been carefully formatted for the Make manual.
@comment Please do not reformat it without talking to bug-make@gnu.org.
@smallexample
$(DESTDIR)$(infodir)/foo.info: foo.info
$(POST_INSTALL)
# There may be a newer info file in . than in srcdir.
-if test -f foo.info; then d=.; \
else d=$(srcdir); fi; \
$(INSTALL_DATA) $$d/foo.info $(DESTDIR)$@@; \
# Run install-info only if it exists.
# Use `if' instead of just prepending `-' to the
# line so we notice real errors from install-info.
# We use `$(SHELL) -c' because some shells do not
# fail gracefully when there is an unknown command.
if $(SHELL) -c 'install-info --version' \
>/dev/null 2>&1; then \
install-info --dir-file=$(DESTDIR)$(infodir)/dir \
$(DESTDIR)$(infodir)/foo.info; \
else true; fi
@end smallexample
When writing the @code{install} target, you must classify all the
commands into three categories: normal ones, @dfn{pre-installation}
commands and @dfn{post-installation} commands. @xref{Install Command
Categories}.
@item install-html
@itemx install-dvi
@itemx install-pdf
@itemx install-ps
These targets install documentation in formats other than Info;
they're intended to be called explicitly by the person installing the
package, if that format is desired. GNU prefers Info files, so these
must be installed by the @code{install} target.
When you have many documentation files to install, we recommend that
you avoid collisions and clutter by arranging for these targets to
install in subdirectories of the appropriate installation directory,
such as @code{htmldir}. As one example, if your package has multiple
manuals, and you wish to install HTML documentation with many files
(such as the ``split'' mode output by @code{makeinfo --html}), you'll
certainly want to use subdirectories, or two nodes with the same name
in different manuals will overwrite each other.
Please make these @code{install-@var{format}} targets invoke the
commands for the @var{format} target, for example, by making
@var{format} a dependency.
@item uninstall
Delete all the installed files---the copies that the @samp{install}
and @samp{install-*} targets create.
This rule should not modify the directories where compilation is done,
only the directories where files are installed.
The uninstallation commands are divided into three categories, just like
the installation commands. @xref{Install Command Categories}.
@item install-strip
Like @code{install}, but strip the executable files while installing
them. In simple cases, this target can use the @code{install} target in
a simple way:
@smallexample
install-strip:
$(MAKE) INSTALL_PROGRAM='$(INSTALL_PROGRAM) -s' \
install
@end smallexample
But if the package installs scripts as well as real executables, the
@code{install-strip} target can't just refer to the @code{install}
target; it has to strip the executables but not the scripts.
@code{install-strip} should not strip the executables in the build
directory which are being copied for installation. It should only strip
the copies that are installed.
Normally we do not recommend stripping an executable unless you are sure
the program has no bugs. However, it can be reasonable to install a
stripped executable for actual execution while saving the unstripped
executable elsewhere in case there is a bug.
@comment The gratuitous blank line here is to make the table look better
@comment in the printed Make manual. Please leave it in.
@item clean
Delete all files in the current directory that are normally created by
building the program. Also delete files in other directories if they
are created by this makefile. However, don't delete the files that
record the configuration. Also preserve files that could be made by
building, but normally aren't because the distribution comes with
them. There is no need to delete parent directories that were created
with @samp{mkdir -p}, since they could have existed anyway.
Delete @file{.dvi} files here if they are not part of the distribution.
@item distclean
Delete all files in the current directory (or created by this
makefile) that are created by configuring or building the program. If
you have unpacked the source and built the program without creating
any other files, @samp{make distclean} should leave only the files
that were in the distribution. However, there is no need to delete
parent directories that were created with @samp{mkdir -p}, since they
could have existed anyway.
@item mostlyclean
Like @samp{clean}, but may refrain from deleting a few files that people
normally don't want to recompile. For example, the @samp{mostlyclean}
target for GCC does not delete @file{libgcc.a}, because recompiling it
is rarely necessary and takes a lot of time.
@item maintainer-clean
Delete almost everything that can be reconstructed with this Makefile.
This typically includes everything deleted by @code{distclean}, plus
more: C source files produced by Bison, tags tables, Info files, and
so on.
The reason we say ``almost everything'' is that running the command
@samp{make maintainer-clean} should not delete @file{configure} even
if @file{configure} can be remade using a rule in the Makefile. More
generally, @samp{make maintainer-clean} should not delete anything
that needs to exist in order to run @file{configure} and then begin to
build the program. Also, there is no need to delete parent
directories that were created with @samp{mkdir -p}, since they could
have existed anyway. These are the only exceptions;
@code{maintainer-clean} should delete everything else that can be
rebuilt.
The @samp{maintainer-clean} target is intended to be used by a maintainer of
the package, not by ordinary users. You may need special tools to
reconstruct some of the files that @samp{make maintainer-clean} deletes.
Since these files are normally included in the distribution, we don't
take care to make them easy to reconstruct. If you find you need to
unpack the full distribution again, don't blame us.
To help make users aware of this, the commands for the special
@code{maintainer-clean} target should start with these two:
@smallexample
@@echo 'This command is intended for maintainers to use; it'
@@echo 'deletes files that may need special tools to rebuild.'
@end smallexample
@item TAGS
Update a tags table for this program.
@c ADR: how?
@item info
Generate any Info files needed. The best way to write the rules is as
follows:
@smallexample
info: foo.info
foo.info: foo.texi chap1.texi chap2.texi
$(MAKEINFO) $(srcdir)/foo.texi
@end smallexample
@noindent
You must define the variable @code{MAKEINFO} in the Makefile. It should
run the @code{makeinfo} program, which is part of the Texinfo
distribution.
Normally a GNU distribution comes with Info files, and that means the
Info files are present in the source directory. Therefore, the Make
rule for an info file should update it in the source directory. When
users build the package, ordinarily Make will not update the Info files
because they will already be up to date.
@item dvi
@itemx html
@itemx pdf
@itemx ps
Generate documentation files in the given format. These targets
should always exist, but any or all can be a no-op if the given output
format cannot be generated. These targets should not be dependencies
of the @code{all} target; the user must manually invoke them.
Here's an example rule for generating DVI files from Texinfo:
@smallexample
dvi: foo.dvi
foo.dvi: foo.texi chap1.texi chap2.texi
$(TEXI2DVI) $(srcdir)/foo.texi
@end smallexample
@noindent
You must define the variable @code{TEXI2DVI} in the Makefile. It should
run the program @code{texi2dvi}, which is part of the Texinfo
distribution.@footnote{@code{texi2dvi} uses @TeX{} to do the real work
of formatting. @TeX{} is not distributed with Texinfo.} Alternatively,
write just the dependencies, and allow GNU @code{make} to provide the command.
Here's another example, this one for generating HTML from Texinfo:
@smallexample
html: foo.html
foo.html: foo.texi chap1.texi chap2.texi
$(TEXI2HTML) $(srcdir)/foo.texi
@end smallexample
@noindent
Again, you would define the variable @code{TEXI2HTML} in the Makefile;
for example, it might run @code{makeinfo --no-split --html}
(@command{makeinfo} is part of the Texinfo distribution).
@item dist
Create a distribution tar file for this program. The tar file should be
set up so that the file names in the tar file start with a subdirectory
name which is the name of the package it is a distribution for. This
name can include the version number.
For example, the distribution tar file of GCC version 1.40 unpacks into
a subdirectory named @file{gcc-1.40}.
The easiest way to do this is to create a subdirectory appropriately
named, use @code{ln} or @code{cp} to install the proper files in it, and
then @code{tar} that subdirectory.
Compress the tar file with @code{gzip}. For example, the actual
distribution file for GCC version 1.40 is called @file{gcc-1.40.tar.gz}.
It is ok to support other free compression formats as well, such as
@code{bzip2} and @code{lzma}.
The @code{dist} target should explicitly depend on all non-source files
that are in the distribution, to make sure they are up to date in the
distribution.
@ifset CODESTD
@xref{Releases, , Making Releases}.
@end ifset
@ifclear CODESTD
@xref{Releases, , Making Releases, standards, GNU Coding Standards}.
@end ifclear
@item check
Perform self-tests (if any). The user must build the program before
running the tests, but need not install the program; you should write
the self-tests so that they work when the program is built but not
installed.
@end table
The following targets are suggested as conventional names, for programs
in which they are useful.
@table @code
@item installcheck
Perform installation tests (if any). The user must build and install
the program before running the tests. You should not assume that
@file{$(bindir)} is in the search path.
@item installdirs
It's useful to add a target named @samp{installdirs} to create the
directories where files are installed, and their parent directories.
There is a script called @file{mkinstalldirs} which is convenient for
this; you can find it in the Texinfo package.
@c It's in /gd/gnu/lib/mkinstalldirs.
You can use a rule like this:
@comment This has been carefully formatted to look decent in the Make manual.
@comment Please be sure not to make it extend any further to the right.--roland
@smallexample
# Make sure all installation directories (e.g. $(bindir))
# actually exist by making them if necessary.
installdirs: mkinstalldirs
$(srcdir)/mkinstalldirs $(bindir) $(datadir) \
$(libdir) $(infodir) \
$(mandir)
@end smallexample
@noindent
or, if you wish to support @env{DESTDIR},
@smallexample
# Make sure all installation directories (e.g. $(bindir))
# actually exist by making them if necessary.
installdirs: mkinstalldirs
$(srcdir)/mkinstalldirs \
$(DESTDIR)$(bindir) $(DESTDIR)$(datadir) \
$(DESTDIR)$(libdir) $(DESTDIR)$(infodir) \
$(DESTDIR)$(mandir)
@end smallexample
This rule should not modify the directories where compilation is done.
It should do nothing but create installation directories.
@end table
@node Install Command Categories
@section Install Command Categories
@cindex pre-installation commands
@cindex post-installation commands
When writing the @code{install} target, you must classify all the
commands into three categories: normal ones, @dfn{pre-installation}
commands and @dfn{post-installation} commands.
Normal commands move files into their proper places, and set their
modes. They may not alter any files except the ones that come entirely
from the package they belong to.
Pre-installation and post-installation commands may alter other files;
in particular, they can edit global configuration files or data bases.
Pre-installation commands are typically executed before the normal
commands, and post-installation commands are typically run after the
normal commands.
The most common use for a post-installation command is to run
@code{install-info}. This cannot be done with a normal command, since
it alters a file (the Info directory) which does not come entirely and
solely from the package being installed. It is a post-installation
command because it needs to be done after the normal command which
installs the package's Info files.
Most programs don't need any pre-installation commands, but we have the
feature just in case it is needed.
To classify the commands in the @code{install} rule into these three
categories, insert @dfn{category lines} among them. A category line
specifies the category for the commands that follow.
A category line consists of a tab and a reference to a special Make
variable, plus an optional comment at the end. There are three
variables you can use, one for each category; the variable name
specifies the category. Category lines are no-ops in ordinary execution
because these three Make variables are normally undefined (and you
@emph{should not} define them in the makefile).
Here are the three possible category lines, each with a comment that
explains what it means:
@smallexample
$(PRE_INSTALL) # @r{Pre-install commands follow.}
$(POST_INSTALL) # @r{Post-install commands follow.}
$(NORMAL_INSTALL) # @r{Normal commands follow.}
@end smallexample
If you don't use a category line at the beginning of the @code{install}
rule, all the commands are classified as normal until the first category
line. If you don't use any category lines, all the commands are
classified as normal.
These are the category lines for @code{uninstall}:
@smallexample
$(PRE_UNINSTALL) # @r{Pre-uninstall commands follow.}
$(POST_UNINSTALL) # @r{Post-uninstall commands follow.}
$(NORMAL_UNINSTALL) # @r{Normal commands follow.}
@end smallexample
Typically, a pre-uninstall command would be used for deleting entries
from the Info directory.
If the @code{install} or @code{uninstall} target has any dependencies
which act as subroutines of installation, then you should start
@emph{each} dependency's commands with a category line, and start the
main target's commands with a category line also. This way, you can
ensure that each command is placed in the right category regardless of
which of the dependencies actually run.
Pre-installation and post-installation commands should not run any
programs except for these:
@example
[ basename bash cat chgrp chmod chown cmp cp dd diff echo
egrep expand expr false fgrep find getopt grep gunzip gzip
hostname install install-info kill ldconfig ln ls md5sum
mkdir mkfifo mknod mv printenv pwd rm rmdir sed sort tee
test touch true uname xargs yes
@end example
@cindex binary packages
The reason for distinguishing the commands in this way is for the sake
of making binary packages. Typically a binary package contains all the
executables and other files that need to be installed, and has its own
method of installing them---so it does not need to run the normal
installation commands. But installing the binary package does need to
execute the pre-installation and post-installation commands.
Programs to build binary packages work by extracting the
pre-installation and post-installation commands. Here is one way of
extracting the pre-installation commands (the @option{-s} option to
@command{make} is needed to silence messages about entering
subdirectories):
@smallexample
make -s -n install -o all \
PRE_INSTALL=pre-install \
POST_INSTALL=post-install \
NORMAL_INSTALL=normal-install \
| gawk -f pre-install.awk
@end smallexample
@noindent
where the file @file{pre-install.awk} could contain this:
@smallexample
$0 ~ /^(normal-install|post-install)[ \t]*$/ @{on = 0@}
on @{print $0@}
$0 ~ /^pre-install[ \t]*$/ @{on = 1@}
@end smallexample
autoconf2.64-2.64/doc/autoconf.texi 0000644 0002024 0002024 00003264654 11233213512 016452 0 ustar arthur arthur \input texinfo @c -*-texinfo-*-
@comment ========================================================
@comment %**start of header
@setfilename autoconf.info
@include version.texi
@settitle Autoconf
@setchapternewpage odd
@ifnothtml
@setcontentsaftertitlepage
@end ifnothtml
@finalout
@c @ovar(ARG)
@c ----------
@c The ARG is an optional argument. To be used for macro arguments in
@c their documentation (@defmac).
@macro ovar{varname}
@r{[}@var{\varname\}@r{]}@c
@end macro
@c @dvar(ARG, DEFAULT)
@c -------------------
@c The ARG is an optional argument, defaulting to DEFAULT. To be used
@c for macro arguments in their documentation (@defmac).
@macro dvar{varname, default}
@r{[}@var{\varname\} = @samp{\default\}@r{]}@c
@end macro
@c Handling the indexes with Texinfo yields several different problems.
@c
@c Because we want to drop out the AC_ part of the macro names in the
@c printed manual, but not in the other outputs, we need a layer above
@c the usual @acindex{} etc. That's why we first define indexes such as
@c acx meant to become the macro @acindex. First of all, using ``ac_''
@c does not work with makeinfo, and using ``ac1'' doesn't work with TeX.
@c So use something more regular ``acx''. Then you finish with a printed
@c index saying ``index is not existent''. Of course: you ought to use
@c two letters :( So you use capitals.
@c
@c Second, when defining a macro in the TeX world, following spaces are
@c eaten. But then, since we embed @acxindex commands that use the end
@c of line as an end marker, the whole things wrecks itself. So make
@c sure you do *force* an additional end of line, add a ``@c''.
@c
@c Finally, you might want to get rid of TeX expansion, using --expand
@c with texi2dvi. But then you wake up an old problem: we use macros
@c in @defmac etc. where TeX does perform the expansion, but not makeinfo.
@c Define an environment variable index.
@defcodeindex ev
@c Define an output variable index.
@defcodeindex ov
@c Define a CPP variable index.
@defcodeindex cv
@c Define an Autoconf macro index that @defmac doesn't write to.
@defcodeindex AC
@c Define an Autotest macro index that @defmac doesn't write to.
@defcodeindex AT
@c Define an M4sugar macro index that @defmac doesn't write to.
@defcodeindex MS
@c Define an index for *foreign* programs: `mv' etc. Used for the
@c portability sections and so on.
@defindex pr
@c shortindexflag
@c --------------
@c Shall we factor AC_ out of the Autoconf macro index etc.?
@iftex
@set shortindexflag
@end iftex
@c @acindex{MACRO}
@c ---------------
@c Registering an AC_\MACRO\.
@ifset shortindexflag
@macro acindex{macro}
@ACindex \macro\
@c
@end macro
@end ifset
@ifclear shortindexflag
@macro acindex{macro}
@ACindex AC_\macro\
@end macro
@end ifclear
@c @ahindex{MACRO}
@c ---------------
@c Registering an AH_\MACRO\.
@macro ahindex{macro}
@ACindex AH_\macro\
@c
@end macro
@c @asindex{MACRO}
@c ---------------
@c Registering an AS_\MACRO\.
@ifset shortindexflag
@macro asindex{macro}
@MSindex \macro\
@c
@end macro
@end ifset
@ifclear shortindexflag
@macro asindex{macro}
@MSindex AS_\macro\
@end macro
@end ifclear
@c @atindex{MACRO}
@c ---------------
@c Registering an AT_\MACRO\.
@ifset shortindexflag
@macro atindex{macro}
@ATindex \macro\
@c
@end macro
@end ifset
@ifclear shortindexflag
@macro atindex{macro}
@ATindex AT_\macro\
@end macro
@end ifclear
@c @auindex{MACRO}
@c ---------------
@c Registering an AU_\MACRO\.
@macro auindex{macro}
@ACindex AU_\macro\
@c
@end macro
@c @hdrindex{MACRO}
@c ----------------
@c Indexing a header.
@macro hdrindex{macro}
@prindex @file{\macro\}
@c
@end macro
@c @msindex{MACRO}
@c ---------------
@c Registering an m4_\MACRO\.
@ifset shortindexflag
@macro msindex{macro}
@MSindex \macro\
@c
@end macro
@end ifset
@ifclear shortindexflag
@macro msindex{macro}
@MSindex m4_\macro\
@end macro
@end ifclear
@c Define an index for functions: `alloca' etc. Used for the
@c portability sections and so on. We can't use `fn' (aka `fnindex),
@c since `@defmac' goes into it => we'd get all the macros too.
@c FIXME: Aaarg! It seems there are too many indices for TeX :(
@c
@c ! No room for a new @write .
@c l.112 @defcodeindex fu
@c
@c so don't define yet another one :( Just put some tags before each
@c @prindex which is actually a @funindex.
@c
@c @defcodeindex fu
@c
@c
@c @c Put the programs and functions into their own index.
@c @syncodeindex fu pr
@comment %**end of header
@comment ========================================================
@copying
This manual (@value{UPDATED}) is for @acronym{GNU} Autoconf
(version @value{VERSION}),
a package for creating scripts to configure source code packages using
templates and an M4 macro package.
Copyright @copyright{} 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000,
2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software
Foundation, Inc.
@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the @acronym{GNU} Free Documentation License,
Version 1.3 or any later version published by the Free Software
Foundation; with no Invariant Sections, with the Front-Cover texts
being ``A @acronym{GNU} Manual,'' and with the Back-Cover Texts as in
(a) below. A copy of the license is included in the section entitled
``@acronym{GNU} Free Documentation License.''
(a) The FSF's Back-Cover Text is: ``You have the freedom to copy and
modify this @acronym{GNU} manual. Buying copies from the @acronym{FSF}
supports it in developing @acronym{GNU} and promoting software
freedom.''
@end quotation
@end copying
@dircategory Software development
@direntry
* Autoconf: (autoconf). Create source code configuration scripts.
@end direntry
@dircategory Individual utilities
@direntry
* autoscan: (autoconf)autoscan Invocation.
Semi-automatic @file{configure.ac} writing
* ifnames: (autoconf)ifnames Invocation. Listing conditionals in source.
* autoconf-invocation: (autoconf)autoconf Invocation.
How to create configuration scripts
* autoreconf: (autoconf)autoreconf Invocation.
Remaking multiple @command{configure} scripts
* autoheader: (autoconf)autoheader Invocation.
How to create configuration templates
* autom4te: (autoconf)autom4te Invocation.
The Autoconf executables backbone
* configure: (autoconf)configure Invocation. Configuring a package.
* autoupdate: (autoconf)autoupdate Invocation.
Automatic update of @file{configure.ac}
* config.status: (autoconf)config.status Invocation. Recreating configurations.
* testsuite: (autoconf)testsuite Invocation. Running an Autotest test suite.
@end direntry
@titlepage
@title Autoconf
@subtitle Creating Automatic Configuration Scripts
@subtitle for version @value{VERSION}, @value{UPDATED}
@author David MacKenzie
@author Ben Elliston
@author Akim Demaille
@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage
@contents
@ifnottex
@node Top
@top Autoconf
@insertcopying
@end ifnottex
@c The master menu, created with texinfo-master-menu, goes here.
@menu
* Introduction:: Autoconf's purpose, strengths, and weaknesses
* The GNU Build System:: A set of tools for portable software packages
* Making configure Scripts:: How to organize and produce Autoconf scripts
* Setup:: Initialization and output
* Existing Tests:: Macros that check for particular features
* Writing Tests:: How to write new feature checks
* Results:: What to do with results from feature checks
* Programming in M4:: Layers on top of which Autoconf is written
* Programming in M4sh:: Shell portability layer
* Writing Autoconf Macros:: Adding new macros to Autoconf
* Portable Shell:: Shell script portability pitfalls
* Portable Make:: Makefile portability pitfalls
* Portable C and C++:: C and C++ portability pitfalls
* Manual Configuration:: Selecting features that can't be guessed
* Site Configuration:: Local defaults for @command{configure}
* Running configure Scripts:: How to use the Autoconf output
* config.status Invocation:: Recreating a configuration
* Obsolete Constructs:: Kept for backward compatibility
* Using Autotest:: Creating portable test suites
* FAQ:: Frequent Autoconf Questions, with answers
* History:: History of Autoconf
* GNU Free Documentation License:: License for copying this manual
* Indices:: Indices of symbols, concepts, etc.
@detailmenu
--- The Detailed Node Listing ---
The @acronym{GNU} Build System
* Automake:: Escaping makefile hell
* Gnulib:: The @acronym{GNU} portability library
* Libtool:: Building libraries portably
* Pointers:: More info on the @acronym{GNU} build system
Making @command{configure} Scripts
* Writing Autoconf Input:: What to put in an Autoconf input file
* autoscan Invocation:: Semi-automatic @file{configure.ac} writing
* ifnames Invocation:: Listing the conditionals in source code
* autoconf Invocation:: How to create configuration scripts
* autoreconf Invocation:: Remaking multiple @command{configure} scripts
Writing @file{configure.ac}
* Shell Script Compiler:: Autoconf as solution of a problem
* Autoconf Language:: Programming in Autoconf
* Autoconf Input Layout:: Standard organization of @file{configure.ac}
Initialization and Output Files
* Initializing configure:: Option processing etc.
* Versioning:: Dealing with Autoconf versions
* Notices:: Copyright, version numbers in @command{configure}
* Input:: Where Autoconf should find files
* Output:: Outputting results from the configuration
* Configuration Actions:: Preparing the output based on results
* Configuration Files:: Creating output files
* Makefile Substitutions:: Using output variables in makefiles
* Configuration Headers:: Creating a configuration header file
* Configuration Commands:: Running arbitrary instantiation commands
* Configuration Links:: Links depending on the configuration
* Subdirectories:: Configuring independent packages together
* Default Prefix:: Changing the default installation prefix
Substitutions in Makefiles
* Preset Output Variables:: Output variables that are always set
* Installation Directory Variables:: Other preset output variables
* Changed Directory Variables:: Warnings about @file{datarootdir}
* Build Directories:: Supporting multiple concurrent compiles
* Automatic Remaking:: Makefile rules for configuring
Configuration Header Files
* Header Templates:: Input for the configuration headers
* autoheader Invocation:: How to create configuration templates
* Autoheader Macros:: How to specify CPP templates
Existing Tests
* Common Behavior:: Macros' standard schemes
* Alternative Programs:: Selecting between alternative programs
* Files:: Checking for the existence of files
* Libraries:: Library archives that might be missing
* Library Functions:: C library functions that might be missing
* Header Files:: Header files that might be missing
* Declarations:: Declarations that may be missing
* Structures:: Structures or members that might be missing
* Types:: Types that might be missing
* Compilers and Preprocessors:: Checking for compiling programs
* System Services:: Operating system services
* Posix Variants:: Special kludges for specific Posix variants
* Erlang Libraries:: Checking for the existence of Erlang libraries
Common Behavior
* Standard Symbols:: Symbols defined by the macros
* Default Includes:: Includes used by the generic macros
Alternative Programs
* Particular Programs:: Special handling to find certain programs
* Generic Programs:: How to find other programs
Library Functions
* Function Portability:: Pitfalls with usual functions
* Particular Functions:: Special handling to find certain functions
* Generic Functions:: How to find other functions
Header Files
* Header Portability:: Collected knowledge on common headers
* Particular Headers:: Special handling to find certain headers
* Generic Headers:: How to find other headers
Declarations
* Particular Declarations:: Macros to check for certain declarations
* Generic Declarations:: How to find other declarations
Structures
* Particular Structures:: Macros to check for certain structure members
* Generic Structures:: How to find other structure members
Types
* Particular Types:: Special handling to find certain types
* Generic Types:: How to find other types
Compilers and Preprocessors
* Specific Compiler Characteristics:: Some portability issues
* Generic Compiler Characteristics:: Language independent tests and features
* C Compiler:: Checking its characteristics
* C++ Compiler:: Likewise
* Objective C Compiler:: Likewise
* Erlang Compiler and Interpreter:: Likewise
* Fortran Compiler:: Likewise
Writing Tests
* Language Choice:: Selecting which language to use for testing
* Writing Test Programs:: Forging source files for compilers
* Running the Preprocessor:: Detecting preprocessor symbols
* Running the Compiler:: Detecting language or header features
* Running the Linker:: Detecting library features
* Runtime:: Testing for runtime features
* Systemology:: A zoology of operating systems
* Multiple Cases:: Tests for several possible values
Writing Test Programs
* Guidelines:: General rules for writing test programs
* Test Functions:: Avoiding pitfalls in test programs
* Generating Sources:: Source program boilerplate
Results of Tests
* Defining Symbols:: Defining C preprocessor symbols
* Setting Output Variables:: Replacing variables in output files
* Special Chars in Variables:: Characters to beware of in variables
* Caching Results:: Speeding up subsequent @command{configure} runs
* Printing Messages:: Notifying @command{configure} users
Caching Results
* Cache Variable Names:: Shell variables used in caches
* Cache Files:: Files @command{configure} uses for caching
* Cache Checkpointing:: Loading and saving the cache file
Programming in M4
* M4 Quotation:: Protecting macros from unwanted expansion
* Using autom4te:: The Autoconf executables backbone
* Programming in M4sugar:: Convenient pure M4 macros
* Debugging via autom4te:: Figuring out what M4 was doing
Programming in M4sh
* Common Shell Constructs:: Portability layer for common shell constructs
* Polymorphic Variables:: Support for indirect variable names
* Initialization Macros:: Macros to establish a sane shell environment
* File Descriptor Macros:: File descriptor macros for input and output
M4 Quotation
* Active Characters:: Characters that change the behavior of M4
* One Macro Call:: Quotation and one macro call
* Quoting and Parameters:: M4 vs. shell parameters
* Quotation and Nested Macros:: Macros calling macros
* Changequote is Evil:: Worse than INTERCAL: M4 + changequote
* Quadrigraphs:: Another way to escape special characters
* Balancing Parentheses:: Dealing with unbalanced parentheses
* Quotation Rule Of Thumb:: One parenthesis, one quote
Using @command{autom4te}
* autom4te Invocation:: A @acronym{GNU} M4 wrapper
* Customizing autom4te:: Customizing the Autoconf package
Programming in M4sugar
* Redefined M4 Macros:: M4 builtins changed in M4sugar
* Diagnostic Macros:: Diagnostic messages from M4sugar
* Diversion support:: Diversions in M4sugar
* Conditional constructs:: Conditions in M4
* Looping constructs:: Iteration in M4
* Evaluation Macros:: More quotation and evaluation control
* Text processing Macros:: String manipulation in M4
* Number processing Macros:: Arithmetic computation in M4
* Set manipulation Macros:: Set manipulation in M4
* Forbidden Patterns:: Catching unexpanded macros
Writing Autoconf Macros
* Macro Definitions:: Basic format of an Autoconf macro
* Macro Names:: What to call your new macros
* Reporting Messages:: Notifying @command{autoconf} users
* Dependencies Between Macros:: What to do when macros depend on other macros
* Obsoleting Macros:: Warning about old ways of doing things
* Coding Style:: Writing Autoconf macros @`a la Autoconf
Dependencies Between Macros
* Prerequisite Macros:: Ensuring required information
* Suggested Ordering:: Warning about possible ordering problems
* One-Shot Macros:: Ensuring a macro is called only once
Portable Shell Programming
* Shellology:: A zoology of shells
* Here-Documents:: Quirks and tricks
* File Descriptors:: FDs and redirections
* File System Conventions:: File names
* Shell Pattern Matching:: Pattern matching
* Shell Substitutions:: Variable and command expansions
* Assignments:: Varying side effects of assignments
* Parentheses:: Parentheses in shell scripts
* Slashes:: Slashes in shell scripts
* Special Shell Variables:: Variables you should not change
* Shell Functions:: What to look out for if you use them
* Limitations of Builtins:: Portable use of not so portable /bin/sh
* Limitations of Usual Tools:: Portable use of portable tools
Portable Make Programming
* $< in Ordinary Make Rules:: $< in ordinary rules
* Failure in Make Rules:: Failing portably in rules
* Special Chars in Names:: Special Characters in Macro Names
* Backslash-Newline-Newline:: Empty last lines in macro definitions
* Backslash-Newline Comments:: Spanning comments across line boundaries
* Long Lines in Makefiles:: Line length limitations
* Macros and Submakes:: @code{make macro=value} and submakes
* The Make Macro MAKEFLAGS:: @code{$(MAKEFLAGS)} portability issues
* The Make Macro SHELL:: @code{$(SHELL)} portability issues
* Parallel Make:: Parallel @command{make} quirks
* Comments in Make Rules:: Other problems with Make comments
* obj/ and Make:: Don't name a subdirectory @file{obj}
* make -k Status:: Exit status of @samp{make -k}
* VPATH and Make:: @code{VPATH} woes
* Single Suffix Rules:: Single suffix rules and separated dependencies
* Timestamps and Make:: Subsecond timestamp resolution
@code{VPATH} and Make
* Variables listed in VPATH:: @code{VPATH} must be literal on ancient hosts
* VPATH and Double-colon:: Problems with @samp{::} on ancient hosts
* $< in Explicit Rules:: @code{$<} does not work in ordinary rules
* Automatic Rule Rewriting:: @code{VPATH} goes wild on Solaris
* Tru64 Directory Magic:: @command{mkdir} goes wild on Tru64
* Make Target Lookup:: More details about @code{VPATH} lookup
Portable C and C++ Programming
* Varieties of Unportability:: How to make your programs unportable
* Integer Overflow:: When integers get too large
* Preprocessor Arithmetic:: @code{#if} expression problems
* Null Pointers:: Properties of null pointers
* Buffer Overruns:: Subscript errors and the like
* Volatile Objects:: @code{volatile} and signals
* Floating Point Portability:: Portable floating-point arithmetic
* Exiting Portably:: Exiting and the exit status
Manual Configuration
* Specifying Target Triplets:: Specifying target triplets
* Canonicalizing:: Getting the canonical system type
* Using System Type:: What to do with the system type
Site Configuration
* Help Formatting:: Customizing @samp{configure --help}
* External Software:: Working with other optional software
* Package Options:: Selecting optional features
* Pretty Help Strings:: Formatting help string
* Option Checking:: Controlling checking of @command{configure} options
* Site Details:: Configuring site details
* Transforming Names:: Changing program names when installing
* Site Defaults:: Giving @command{configure} local defaults
Transforming Program Names When Installing
* Transformation Options:: @command{configure} options to transform names
* Transformation Examples:: Sample uses of transforming names
* Transformation Rules:: Makefile uses of transforming names
Running @command{configure} Scripts
* Basic Installation:: Instructions for typical cases
* Compilers and Options:: Selecting compilers and optimization
* Multiple Architectures:: Compiling for multiple architectures at once
* Installation Names:: Installing in different directories
* Optional Features:: Selecting optional features
* Particular Systems:: Particular systems
* System Type:: Specifying the system type
* Sharing Defaults:: Setting site-wide defaults for @command{configure}
* Defining Variables:: Specifying the compiler etc.
* configure Invocation:: Changing how @command{configure} runs
Obsolete Constructs
* Obsolete config.status Use:: Obsolete convention for @command{config.status}
* acconfig Header:: Additional entries in @file{config.h.in}
* autoupdate Invocation:: Automatic update of @file{configure.ac}
* Obsolete Macros:: Backward compatibility macros
* Autoconf 1:: Tips for upgrading your files
* Autoconf 2.13:: Some fresher tips
Upgrading From Version 1
* Changed File Names:: Files you might rename
* Changed Makefiles:: New things to put in @file{Makefile.in}
* Changed Macros:: Macro calls you might replace
* Changed Results:: Changes in how to check test results
* Changed Macro Writing:: Better ways to write your own macros
Upgrading From Version 2.13
* Changed Quotation:: Broken code which used to work
* New Macros:: Interaction with foreign macros
* Hosts and Cross-Compilation:: Bugward compatibility kludges
* AC_LIBOBJ vs LIBOBJS:: LIBOBJS is a forbidden token
* AC_ACT_IFELSE vs AC_TRY_ACT:: A more generic scheme for testing sources
Generating Test Suites with Autotest
* Using an Autotest Test Suite:: Autotest and the user
* Writing Testsuites:: Autotest macros
* testsuite Invocation:: Running @command{testsuite} scripts
* Making testsuite Scripts:: Using autom4te to create @command{testsuite}
Using an Autotest Test Suite
* testsuite Scripts:: The concepts of Autotest
* Autotest Logs:: Their contents
Frequent Autoconf Questions, with answers
* Distributing:: Distributing @command{configure} scripts
* Why GNU M4:: Why not use the standard M4?
* Bootstrapping:: Autoconf and @acronym{GNU} M4 require each other?
* Why Not Imake:: Why @acronym{GNU} uses @command{configure} instead of Imake
* Defining Directories:: Passing @code{datadir} to program
* Autom4te Cache:: What is it? Can I remove it?
* Present But Cannot Be Compiled:: Compiler and Preprocessor Disagree
* Expanded Before Required:: Expanded Before Required
History of Autoconf
* Genesis:: Prehistory and naming of @command{configure}
* Exodus:: The plagues of M4 and Perl
* Leviticus:: The priestly code of portability arrives
* Numbers:: Growth and contributors
* Deuteronomy:: Approaching the promises of easy configuration
Indices
* Environment Variable Index:: Index of environment variables used
* Output Variable Index:: Index of variables set in output files
* Preprocessor Symbol Index:: Index of C preprocessor symbols defined
* Autoconf Macro Index:: Index of Autoconf macros
* M4 Macro Index:: Index of M4, M4sugar, and M4sh macros
* Autotest Macro Index:: Index of Autotest macros
* Program & Function Index:: Index of those with portability problems
* Concept Index:: General index
@end detailmenu
@end menu
@c ============================================================= Introduction.
@node Introduction
@chapter Introduction
@cindex Introduction
@flushright
A physicist, an engineer, and a computer scientist were discussing the
nature of God. ``Surely a Physicist,'' said the physicist, ``because
early in the Creation, God made Light; and you know, Maxwell's
equations, the dual nature of electromagnetic waves, the relativistic
consequences@enddots{}'' ``An Engineer!,'' said the engineer, ``because
before making Light, God split the Chaos into Land and Water; it takes a
hell of an engineer to handle that big amount of mud, and orderly
separation of solids from liquids@enddots{}'' The computer scientist
shouted: ``And the Chaos, where do you think it was coming from, hmm?''
---Anonymous
@end flushright
@c (via Franc,ois Pinard)
Autoconf is a tool for producing shell scripts that automatically
configure software source code packages to adapt to many kinds of
Posix-like systems. The configuration scripts produced by Autoconf
are independent of Autoconf when they are run, so their users do not
need to have Autoconf.
The configuration scripts produced by Autoconf require no manual user
intervention when run; they do not normally even need an argument
specifying the system type. Instead, they individually test for the
presence of each feature that the software package they are for might need.
(Before each check, they print a one-line message stating what they are
checking for, so the user doesn't get too bored while waiting for the
script to finish.) As a result, they deal well with systems that are
hybrids or customized from the more common Posix variants. There is
no need to maintain files that list the features supported by each
release of each variant of Posix.
For each software package that Autoconf is used with, it creates a
configuration script from a template file that lists the system features
that the package needs or can use. After the shell code to recognize
and respond to a system feature has been written, Autoconf allows it to
be shared by many software packages that can use (or need) that feature.
If it later turns out that the shell code needs adjustment for some
reason, it needs to be changed in only one place; all of the
configuration scripts can be regenerated automatically to take advantage
of the updated code.
@c "Those who do not understand Unix are condemned to reinvent it, poorly."
@c --Henry Spencer, 1987 (see http://en.wikipedia.org/wiki/Unix_philosophy)
Those who do not understand Autoconf are condemned to reinvent it, poorly.
The primary goal of Autoconf is making the @emph{user's} life easier;
making the @emph{maintainer's} life easier is only a secondary goal.
Put another way, the primary goal is not to make the generation of
@file{configure} automatic for package maintainers (although patches
along that front are welcome, since package maintainers form the user
base of Autoconf); rather, the goal is to make @file{configure}
painless, portable, and predictable for the end user of each
@dfn{autoconfiscated} package. And to this degree, Autoconf is highly
successful at its goal --- most complaints to the Autoconf list are
about difficulties in writing Autoconf input, and not in the behavior of
the resulting @file{configure}. Even packages that don't use Autoconf
will generally provide a @file{configure} script, and the most common
complaint about these alternative home-grown scripts is that they fail
to meet one or more of the @acronym{GNU} Coding Standards that users
have come to expect from Autoconf-generated @file{configure} scripts.
The Metaconfig package is similar in purpose to Autoconf, but the
scripts it produces require manual user intervention, which is quite
inconvenient when configuring large source trees. Unlike Metaconfig
scripts, Autoconf scripts can support cross-compiling, if some care is
taken in writing them.
Autoconf does not solve all problems related to making portable
software packages---for a more complete solution, it should be used in
concert with other @acronym{GNU} build tools like Automake and
Libtool. These other tools take on jobs like the creation of a
portable, recursive makefile with all of the standard targets,
linking of shared libraries, and so on. @xref{The GNU Build System},
for more information.
Autoconf imposes some restrictions on the names of macros used with
@code{#if} in C programs (@pxref{Preprocessor Symbol Index}).
Autoconf requires @acronym{GNU} M4 version 1.4.6 or later in order to
generate the scripts. It uses features that some versions of M4,
including @acronym{GNU} M4 1.3, do not have. Autoconf works better
with @acronym{GNU} M4 version 1.4.13 or later, though this is not
required.
@xref{Autoconf 1}, for information about upgrading from version 1.
@xref{History}, for the story of Autoconf's development. @xref{FAQ},
for answers to some common questions about Autoconf.
See the @uref{http://@/www.gnu.org/@/software/@/autoconf/,
Autoconf web page} for up-to-date information, details on the mailing
lists, pointers to a list of known bugs, etc.
Mail suggestions to @email{autoconf@@gnu.org, the Autoconf mailing
list}. Past suggestions are
@uref{http://@/lists.gnu.org/@/archive/@/html/@/autoconf/, archived}.
Mail bug reports to @email{bug-autoconf@@gnu.org, the
Autoconf Bugs mailing list}. Past bug reports are
@uref{http://@/lists.gnu.org/@/archive/@/html/@/bug-autoconf/, archived}.
If possible, first check that your bug is
not already solved in current development versions, and that it has not
been reported yet. Be sure to include all the needed information and a
short @file{configure.ac} that demonstrates the problem.
Autoconf's development tree is accessible via @command{git}; see the
@uref{http://@/savannah.gnu.org/@/projects/@/autoconf/, Autoconf
Summary} for details, or view
@uref{http://@/git.sv.gnu.org/@/gitweb/@/?p=autoconf.git, the actual
repository}. Anonymous @acronym{CVS} access is also available, see
@file{README} for more details. Patches relative to the
current @command{git} version can be sent for review to the
@email{autoconf-patches@@gnu.org, Autoconf Patches mailing list}, with
discussion on prior patches
@uref{http://@/lists.gnu.org/@/archive/@/html/@/autoconf-@/patches/,
archived}; and all commits are posted in the read-only
@email{autoconf-commit@@gnu.org, Autoconf Commit mailing list}, which is
also @uref{http://@/lists.gnu.org/@/archive/@/html/@/autoconf-commit/,
archived}.
Because of its mission, the Autoconf package itself
includes only a set of often-used
macros that have already demonstrated their usefulness. Nevertheless,
if you wish to share your macros, or find existing ones, see the
@uref{http://@/autoconf-archive.cryp.to/, Autoconf Macro
Archive}, which is kindly run by @email{simons@@cryp.to,
Peter Simons}.
@c ================================================= The GNU Build System
@node The GNU Build System
@chapter The @acronym{GNU} Build System
@cindex @acronym{GNU} build system
Autoconf solves an important problem---reliable discovery of
system-specific build and runtime information---but this is only one
piece of the puzzle for the development of portable software. To this
end, the @acronym{GNU} project has developed a suite of integrated
utilities to finish the job Autoconf started: the @acronym{GNU} build
system, whose most important components are Autoconf, Automake, and
Libtool. In this chapter, we introduce you to those tools, point you
to sources of more information, and try to convince you to use the
entire @acronym{GNU} build system for your software.
@menu
* Automake:: Escaping makefile hell
* Gnulib:: The @acronym{GNU} portability library
* Libtool:: Building libraries portably
* Pointers:: More info on the @acronym{GNU} build system
@end menu
@node Automake
@section Automake
The ubiquity of @command{make} means that a makefile is almost the
only viable way to distribute automatic build rules for software, but
one quickly runs into its numerous limitations. Its lack of
support for automatic dependency tracking, recursive builds in
subdirectories, reliable timestamps (e.g., for network file systems), and
so on, mean that developers must painfully (and often incorrectly)
reinvent the wheel for each project. Portability is non-trivial, thanks
to the quirks of @command{make} on many systems. On top of all this is the
manual labor required to implement the many standard targets that users
have come to expect (@code{make install}, @code{make distclean},
@code{make uninstall}, etc.). Since you are, of course, using Autoconf,
you also have to insert repetitive code in your @file{Makefile.in} to
recognize @code{@@CC@@}, @code{@@CFLAGS@@}, and other substitutions
provided by @command{configure}. Into this mess steps @dfn{Automake}.
@cindex Automake
Automake allows you to specify your build needs in a @file{Makefile.am}
file with a vastly simpler and more powerful syntax than that of a plain
makefile, and then generates a portable @file{Makefile.in} for
use with Autoconf. For example, the @file{Makefile.am} to build and
install a simple ``Hello world'' program might look like:
@example
bin_PROGRAMS = hello
hello_SOURCES = hello.c
@end example
@noindent
The resulting @file{Makefile.in} (~400 lines) automatically supports all
the standard targets, the substitutions provided by Autoconf, automatic
dependency tracking, @code{VPATH} building, and so on. @command{make}
builds the @code{hello} program, and @code{make install} installs it
in @file{/usr/local/bin} (or whatever prefix was given to
@command{configure}, if not @file{/usr/local}).
The benefits of Automake increase for larger packages (especially ones
with subdirectories), but even for small programs the added convenience
and portability can be substantial. And that's not all@enddots{}
@node Gnulib
@section Gnulib
@acronym{GNU} software has a well-deserved reputation for running on
many different types of systems. While our primary goal is to write
software for the @acronym{GNU} system, many users and developers have
been introduced to us through the systems that they were already using.
@cindex Gnulib
Gnulib is a central location for common @acronym{GNU} code, intended to
be shared among free software packages. Its components are typically
shared at the source level, rather than being a library that gets built,
installed, and linked against. The idea is to copy files from Gnulib
into your own source tree. There is no distribution tarball; developers
should just grab source modules from the repository. The source files
are available online, under various licenses, mostly @acronym{GNU}
@acronym{GPL} or @acronym{GNU} @acronym{LGPL}.
Gnulib modules typically contain C source code along with Autoconf
macros used to configure the source code. For example, the Gnulib
@code{stdbool} module implements a @file{stdbool.h} header that nearly
conforms to C99, even on old-fashioned hosts that lack @file{stdbool.h}.
This module contains a source file for the replacement header, along
with an Autoconf macro that arranges to use the replacement header on
old-fashioned systems.
@node Libtool
@section Libtool
Often, one wants to build not only programs, but libraries, so that
other programs can benefit from the fruits of your labor. Ideally, one
would like to produce @emph{shared} (dynamically linked) libraries,
which can be used by multiple programs without duplication on disk or in
memory and can be updated independently of the linked programs.
Producing shared libraries portably, however, is the stuff of
nightmares---each system has its own incompatible tools, compiler flags,
and magic incantations. Fortunately, @acronym{GNU} provides a solution:
@dfn{Libtool}.
@cindex Libtool
Libtool handles all the requirements of building shared libraries for
you, and at this time seems to be the @emph{only} way to do so with any
portability. It also handles many other headaches, such as: the
interaction of Make rules with the variable suffixes of
shared libraries, linking reliably with shared libraries before they are
installed by the superuser, and supplying a consistent versioning system
(so that different versions of a library can be installed or upgraded
without breaking binary compatibility). Although Libtool, like
Autoconf, can be used without Automake, it is most simply utilized in
conjunction with Automake---there, Libtool is used automatically
whenever shared libraries are needed, and you need not know its syntax.
@node Pointers
@section Pointers
Developers who are used to the simplicity of @command{make} for small
projects on a single system might be daunted at the prospect of
learning to use Automake and Autoconf. As your software is
distributed to more and more users, however, you otherwise
quickly find yourself putting lots of effort into reinventing the
services that the @acronym{GNU} build tools provide, and making the
same mistakes that they once made and overcame. (Besides, since
you're already learning Autoconf, Automake is a piece of cake.)
There are a number of places that you can go to for more information on
the @acronym{GNU} build tools.
@itemize @minus
@item Web
The project home pages for
@uref{http://@/www@/.gnu@/.org/@/software/@/autoconf/, Autoconf},
@uref{http://@/www@/.gnu@/.org/@/software/@/automake/, Automake},
@uref{http://@/www@/.gnu@/.org/@/software/@/gnulib/, Gnulib}, and
@uref{http://@/www@/.gnu@/.org/@/software/@/libtool/, Libtool}.
@item Automake Manual
@xref{Top, , Automake, automake, @acronym{GNU} Automake}, for more
information on Automake.
@item Books
The book @cite{@acronym{GNU} Autoconf, Automake and
Libtool}@footnote{@cite{@acronym{GNU} Autoconf, Automake and Libtool},
by G. V. Vaughan, B. Elliston, T. Tromey, and I. L. Taylor. SAMS (originally
New Riders), 2000, ISBN 1578701902.} describes the complete @acronym{GNU}
build environment. You can also find
@uref{http://@/sources.redhat.com/@/autobook/, the entire book on-line}.
@end itemize
@c ================================================= Making configure Scripts.
@node Making configure Scripts
@chapter Making @command{configure} Scripts
@cindex @file{aclocal.m4}
@cindex @command{configure}
The configuration scripts that Autoconf produces are by convention
called @command{configure}. When run, @command{configure} creates several
files, replacing configuration parameters in them with appropriate
values. The files that @command{configure} creates are:
@itemize @minus
@item
one or more @file{Makefile} files, usually one in each subdirectory of the
package (@pxref{Makefile Substitutions});
@item
optionally, a C header file, the name of which is configurable,
containing @code{#define} directives (@pxref{Configuration Headers});
@item
a shell script called @file{config.status} that, when run, recreates
the files listed above (@pxref{config.status Invocation});
@item
an optional shell script normally called @file{config.cache}
(created when using @samp{configure --config-cache}) that
saves the results of running many of the tests (@pxref{Cache Files});
@item
a file called @file{config.log} containing any messages produced by
compilers, to help debugging if @command{configure} makes a mistake.
@end itemize
@cindex @file{configure.in}
@cindex @file{configure.ac}
To create a @command{configure} script with Autoconf, you need to write an
Autoconf input file @file{configure.ac} (or @file{configure.in}) and run
@command{autoconf} on it. If you write your own feature tests to
supplement those that come with Autoconf, you might also write files
called @file{aclocal.m4} and @file{acsite.m4}. If you use a C header
file to contain @code{#define} directives, you might also run
@command{autoheader}, and you can distribute the generated file
@file{config.h.in} with the package.
Here is a diagram showing how the files that can be used in
configuration are produced. Programs that are executed are suffixed by
@samp{*}. Optional files are enclosed in square brackets (@samp{[]}).
@command{autoconf} and @command{autoheader} also read the installed Autoconf
macro files (by reading @file{autoconf.m4}).
@noindent
Files used in preparing a software package for distribution:
@example
your source files --> [autoscan*] --> [configure.scan] --> configure.ac
@group
configure.ac --.
| .------> autoconf* -----> configure
[aclocal.m4] --+---+
| `-----> [autoheader*] --> [config.h.in]
[acsite.m4] ---'
@end group
Makefile.in -------------------------------> Makefile.in
@end example
@noindent
Files used in configuring a software package:
@example
@group
.-------------> [config.cache]
configure* ------------+-------------> config.log
|
[config.h.in] -. v .-> [config.h] -.
+--> config.status* -+ +--> make*
Makefile.in ---' `-> Makefile ---'
@end group
@end example
@menu
* Writing Autoconf Input:: What to put in an Autoconf input file
* autoscan Invocation:: Semi-automatic @file{configure.ac} writing
* ifnames Invocation:: Listing the conditionals in source code
* autoconf Invocation:: How to create configuration scripts
* autoreconf Invocation:: Remaking multiple @command{configure} scripts
@end menu
@node Writing Autoconf Input
@section Writing @file{configure.ac}
To produce a @command{configure} script for a software package, create a
file called @file{configure.ac} that contains invocations of the
Autoconf macros that test the system features your package needs or can
use. Autoconf macros already exist to check for many features; see
@ref{Existing Tests}, for their descriptions. For most other features,
you can use Autoconf template macros to produce custom checks; see
@ref{Writing Tests}, for information about them. For especially tricky
or specialized features, @file{configure.ac} might need to contain some
hand-crafted shell commands; see @ref{Portable Shell, , Portable Shell
Programming}. The @command{autoscan} program can give you a good start
in writing @file{configure.ac} (@pxref{autoscan Invocation}, for more
information).
Previous versions of Autoconf promoted the name @file{configure.in},
which is somewhat ambiguous (the tool needed to process this file is not
described by its extension), and introduces a slight confusion with
@file{config.h.in} and so on (for which @samp{.in} means ``to be
processed by @command{configure}''). Using @file{configure.ac} is now
preferred.
@menu
* Shell Script Compiler:: Autoconf as solution of a problem
* Autoconf Language:: Programming in Autoconf
* Autoconf Input Layout:: Standard organization of @file{configure.ac}
@end menu
@node Shell Script Compiler
@subsection A Shell Script Compiler
Just as for any other computer language, in order to properly program
@file{configure.ac} in Autoconf you must understand @emph{what} problem
the language tries to address and @emph{how} it does so.
The problem Autoconf addresses is that the world is a mess. After all,
you are using Autoconf in order to have your package compile easily on
all sorts of different systems, some of them being extremely hostile.
Autoconf itself bears the price for these differences: @command{configure}
must run on all those systems, and thus @command{configure} must limit itself
to their lowest common denominator of features.
Naturally, you might then think of shell scripts; who needs
@command{autoconf}? A set of properly written shell functions is enough to
make it easy to write @command{configure} scripts by hand. Sigh!
Unfortunately, even in 2008, where shells without any function support are
far and few between, there are pitfalls to avoid when making use of them.
Also, finding a Bourne shell that accepts shell functions is not trivial,
even though there is almost always one on interesting porting targets.
So, what is really needed is some kind of compiler, @command{autoconf},
that takes an Autoconf program, @file{configure.ac}, and transforms it
into a portable shell script, @command{configure}.
How does @command{autoconf} perform this task?
There are two obvious possibilities: creating a brand new language or
extending an existing one. The former option is attractive: all
sorts of optimizations could easily be implemented in the compiler and
many rigorous checks could be performed on the Autoconf program
(e.g., rejecting any non-portable construct). Alternatively, you can
extend an existing language, such as the @code{sh} (Bourne shell)
language.
Autoconf does the latter: it is a layer on top of @code{sh}. It was
therefore most convenient to implement @command{autoconf} as a macro
expander: a program that repeatedly performs @dfn{macro expansions} on
text input, replacing macro calls with macro bodies and producing a pure
@code{sh} script in the end. Instead of implementing a dedicated
Autoconf macro expander, it is natural to use an existing
general-purpose macro language, such as M4, and implement the extensions
as a set of M4 macros.
@node Autoconf Language
@subsection The Autoconf Language
@cindex quotation
The Autoconf language differs from many other computer
languages because it treats actual code the same as plain text. Whereas
in C, for instance, data and instructions have different syntactic
status, in Autoconf their status is rigorously the same. Therefore, we
need a means to distinguish literal strings from text to be expanded:
quotation.
When calling macros that take arguments, there must not be any white
space between the macro name and the open parenthesis. Arguments should
be enclosed within the M4 quote characters @samp{[} and @samp{]}, and be
separated by commas. Any leading blanks or newlines in arguments are ignored,
unless they are quoted. You should always quote an argument that
might contain a macro name, comma, parenthesis, or a leading blank or
newline. This rule applies recursively for every macro
call, including macros called from other macros.
For instance:
@example
AC_CHECK_HEADER([stdio.h],
[AC_DEFINE([HAVE_STDIO_H], [1],
[Define to 1 if you have .])],
[AC_MSG_ERROR([Sorry, can't do anything for you])])
@end example
@noindent
is quoted properly. You may safely simplify its quotation to:
@example
AC_CHECK_HEADER([stdio.h],
[AC_DEFINE([HAVE_STDIO_H], 1,
[Define to 1 if you have .])],
[AC_MSG_ERROR([Sorry, can't do anything for you])])
@end example
@noindent
because @samp{1} cannot contain a macro call. Here, the argument of
@code{AC_MSG_ERROR} must be quoted; otherwise, its comma would be
interpreted as an argument separator. Also, the second and third arguments
of @samp{AC_CHECK_HEADER} must be quoted, since they contain
macro calls. The three arguments @samp{HAVE_STDIO_H}, @samp{stdio.h},
and @samp{Define to 1 if you have .} do not need quoting, but
if you unwisely defined a macro with a name like @samp{Define} or
@samp{stdio} then they would need quoting. Cautious Autoconf users
would keep the quotes, but many Autoconf users find such precautions
annoying, and would rewrite the example as follows:
@example
AC_CHECK_HEADER(stdio.h,
[AC_DEFINE(HAVE_STDIO_H, 1,
[Define to 1 if you have .])],
[AC_MSG_ERROR([Sorry, can't do anything for you])])
@end example
@noindent
This is safe, so long as you adopt good naming conventions and do not
define macros with names like @samp{HAVE_STDIO_H}, @samp{stdio}, or
@samp{h}. Though it is also safe here to omit the quotes around
@samp{Define to 1 if you have .} this is not recommended, as
message strings are more likely to inadvertently contain commas.
The following example is wrong and dangerous, as it is underquoted:
@example
AC_CHECK_HEADER(stdio.h,
AC_DEFINE(HAVE_STDIO_H, 1,
Define to 1 if you have .),
AC_MSG_ERROR([Sorry, can't do anything for you]))
@end example
In other cases, you may have to use text that also resembles a macro
call. You must quote that text even when it is not passed as a macro
argument:
@example
echo "Hard rock was here! --[AC_DC]"
@end example
@noindent
which results in:
@example
echo "Hard rock was here! --AC_DC"
@end example
@noindent
When you use the same text in a macro argument, you must therefore have
an extra quotation level (since one is stripped away by the macro
substitution). In general, then, it is a good idea to @emph{use double
quoting for all literal string arguments}:
@example
AC_MSG_WARN([[AC_DC stinks --Iron Maiden]])
@end example
You are now able to understand one of the constructs of Autoconf that
has been continually misunderstood@enddots{} The rule of thumb is that
@emph{whenever you expect macro expansion, expect quote expansion};
i.e., expect one level of quotes to be lost. For instance:
@example
AC_COMPILE_IFELSE([char b[10];], [], [AC_MSG_ERROR([you lose])])
@end example
@noindent
is incorrect: here, the first argument of @code{AC_COMPILE_IFELSE} is
@samp{char b[10];} and is expanded once, which results in
@samp{char b10;}. (There was an idiom common in Autoconf's past to
address this issue via the M4 @code{changequote} primitive, but do not
use it!) Let's take a closer look: the author meant the first argument
to be understood as a literal, and therefore it must be quoted twice:
@example
AC_COMPILE_IFELSE([[char b[10];]], [], [AC_MSG_ERROR([you lose])])
@end example
@noindent
Voil@`a, you actually produce @samp{char b[10];} this time!
On the other hand, descriptions (e.g., the last parameter of
@code{AC_DEFINE} or @code{AS_HELP_STRING}) are not literals---they
are subject to line breaking, for example---and should not be double quoted.
Even if these descriptions are short and are not actually broken, double
quoting them yields weird results.
Some macros take optional arguments, which this documentation represents
as @ovar{arg} (not to be confused with the quote characters). You may
just leave them empty, or use @samp{[]} to make the emptiness of the
argument explicit, or you may simply omit the trailing commas. The
three lines below are equivalent:
@example
AC_CHECK_HEADERS([stdio.h], [], [], [])
AC_CHECK_HEADERS([stdio.h],,,)
AC_CHECK_HEADERS([stdio.h])
@end example
It is best to put each macro call on its own line in
@file{configure.ac}. Most of the macros don't add extra newlines; they
rely on the newline after the macro call to terminate the commands.
This approach makes the generated @command{configure} script a little
easier to read by not inserting lots of blank lines. It is generally
safe to set shell variables on the same line as a macro call, because
the shell allows assignments without intervening newlines.
You can include comments in @file{configure.ac} files by starting them
with the @samp{#}. For example, it is helpful to begin
@file{configure.ac} files with a line like this:
@example
# Process this file with autoconf to produce a configure script.
@end example
@node Autoconf Input Layout
@subsection Standard @file{configure.ac} Layout
The order in which @file{configure.ac} calls the Autoconf macros is not
important, with a few exceptions. Every @file{configure.ac} must
contain a call to @code{AC_INIT} before the checks, and a call to
@code{AC_OUTPUT} at the end (@pxref{Output}). Additionally, some macros
rely on other macros having been called first, because they check
previously set values of some variables to decide what to do. These
macros are noted in the individual descriptions (@pxref{Existing
Tests}), and they also warn you when @command{configure} is created if they
are called out of order.
To encourage consistency, here is a suggested order for calling the
Autoconf macros. Generally speaking, the things near the end of this
list are those that could depend on things earlier in it. For example,
library functions could be affected by types and libraries.
@display
@group
Autoconf requirements
@code{AC_INIT(@var{package}, @var{version}, @var{bug-report-address})}
information on the package
checks for programs
checks for libraries
checks for header files
checks for types
checks for structures
checks for compiler characteristics
checks for library functions
checks for system services
@code{AC_CONFIG_FILES(@r{[}@var{file@dots{}}@r{]})}
@code{AC_OUTPUT}
@end group
@end display
@node autoscan Invocation
@section Using @command{autoscan} to Create @file{configure.ac}
@cindex @command{autoscan}
The @command{autoscan} program can help you create and/or maintain a
@file{configure.ac} file for a software package. @command{autoscan}
examines source files in the directory tree rooted at a directory given
as a command line argument, or the current directory if none is given.
It searches the source files for common portability problems and creates
a file @file{configure.scan} which is a preliminary @file{configure.ac}
for that package, and checks a possibly existing @file{configure.ac} for
completeness.
When using @command{autoscan} to create a @file{configure.ac}, you
should manually examine @file{configure.scan} before renaming it to
@file{configure.ac}; it probably needs some adjustments.
Occasionally, @command{autoscan} outputs a macro in the wrong order
relative to another macro, so that @command{autoconf} produces a warning;
you need to move such macros manually. Also, if you want the package to
use a configuration header file, you must add a call to
@code{AC_CONFIG_HEADERS} (@pxref{Configuration Headers}). You might
also have to change or add some @code{#if} directives to your program in
order to make it work with Autoconf (@pxref{ifnames Invocation}, for
information about a program that can help with that job).
When using @command{autoscan} to maintain a @file{configure.ac}, simply
consider adding its suggestions. The file @file{autoscan.log}
contains detailed information on why a macro is requested.
@command{autoscan} uses several data files (installed along with Autoconf)
to determine which macros to output when it finds particular symbols in
a package's source files. These data files all have the same format:
each line consists of a symbol, one or more blanks, and the Autoconf macro to
output if that symbol is encountered. Lines starting with @samp{#} are
comments.
@command{autoscan} accepts the following options:
@table @option
@item --help
@itemx -h
Print a summary of the command line options and exit.
@item --version
@itemx -V
Print the version number of Autoconf and exit.
@item --verbose
@itemx -v
Print the names of the files it examines and the potentially interesting
symbols it finds in them. This output can be voluminous.
@item --debug
@itemx -d
Don't remove temporary files.
@item --include=@var{dir}
@itemx -I @var{dir}
Append @var{dir} to the include path. Multiple invocations accumulate.
@item --prepend-include=@var{dir}
@itemx -B @var{dir}
Prepend @var{dir} to the include path. Multiple invocations accumulate.
@end table
@node ifnames Invocation
@section Using @command{ifnames} to List Conditionals
@cindex @command{ifnames}
@command{ifnames} can help you write @file{configure.ac} for a software
package. It prints the identifiers that the package already uses in C
preprocessor conditionals. If a package has already been set up to have
some portability, @command{ifnames} can thus help you figure out what its
@command{configure} needs to check for. It may help fill in some gaps in a
@file{configure.ac} generated by @command{autoscan} (@pxref{autoscan
Invocation}).
@command{ifnames} scans all of the C source files named on the command line
(or the standard input, if none are given) and writes to the standard
output a sorted list of all the identifiers that appear in those files
in @code{#if}, @code{#elif}, @code{#ifdef}, or @code{#ifndef}
directives. It prints each identifier on a line, followed by a
space-separated list of the files in which that identifier occurs.
@noindent
@command{ifnames} accepts the following options:
@table @option
@item --help
@itemx -h
Print a summary of the command line options and exit.
@item --version
@itemx -V
Print the version number of Autoconf and exit.
@end table
@node autoconf Invocation
@section Using @command{autoconf} to Create @command{configure}
@cindex @command{autoconf}
To create @command{configure} from @file{configure.ac}, run the
@command{autoconf} program with no arguments. @command{autoconf} processes
@file{configure.ac} with the M4 macro processor, using the
Autoconf macros. If you give @command{autoconf} an argument, it reads that
file instead of @file{configure.ac} and writes the configuration script
to the standard output instead of to @command{configure}. If you give
@command{autoconf} the argument @option{-}, it reads from the standard
input instead of @file{configure.ac} and writes the configuration script
to the standard output.
The Autoconf macros are defined in several files. Some of the files are
distributed with Autoconf; @command{autoconf} reads them first. Then it
looks for the optional file @file{acsite.m4} in the directory that
contains the distributed Autoconf macro files, and for the optional file
@file{aclocal.m4} in the current directory. Those files can contain
your site's or the package's own Autoconf macro definitions
(@pxref{Writing Autoconf Macros}, for more information). If a macro is
defined in more than one of the files that @command{autoconf} reads, the
last definition it reads overrides the earlier ones.
@command{autoconf} accepts the following options:
@table @option
@item --help
@itemx -h
Print a summary of the command line options and exit.
@item --version
@itemx -V
Print the version number of Autoconf and exit.
@item --verbose
@itemx -v
Report processing steps.
@item --debug
@itemx -d
Don't remove the temporary files.
@item --force
@itemx -f
Remake @file{configure} even if newer than its input files.
@item --include=@var{dir}
@itemx -I @var{dir}
Append @var{dir} to the include path. Multiple invocations accumulate.
@item --prepend-include=@var{dir}
@itemx -B @var{dir}
Prepend @var{dir} to the include path. Multiple invocations accumulate.
@item --output=@var{file}
@itemx -o @var{file}
Save output (script or trace) to @var{file}. The file @option{-} stands
for the standard output.
@item --warnings=@var{category}
@itemx -W @var{category}
@evindex WARNINGS
Report the warnings related to @var{category} (which can actually be a
comma separated list). @xref{Reporting Messages}, macro
@code{AC_DIAGNOSE}, for a comprehensive list of categories. Special
values include:
@table @samp
@item all
report all the warnings
@item none
report none
@item error
treats warnings as errors
@item no-@var{category}
disable warnings falling into @var{category}
@end table
Warnings about @samp{syntax} are enabled by default, and the environment
variable @env{WARNINGS}, a comma separated list of categories, is
honored as well. Passing @option{-W @var{category}} actually behaves as if
you had passed @option{--warnings syntax,$WARNINGS,@var{category}}. To
disable the defaults and @env{WARNINGS}, and then
enable warnings about obsolete constructs, use @option{-W
none,obsolete}.
@cindex Back trace
@cindex Macro invocation stack
Because @command{autoconf} uses @command{autom4te} behind the scenes, it
displays a back trace for errors, but not for warnings; if you want
them, just pass @option{-W error}. @xref{autom4te Invocation}, for some
examples.
@item --trace=@var{macro}[:@var{format}]
@itemx -t @var{macro}[:@var{format}]
Do not create the @command{configure} script, but list the calls to
@var{macro} according to the @var{format}. Multiple @option{--trace}
arguments can be used to list several macros. Multiple @option{--trace}
arguments for a single macro are not cumulative; instead, you should
just make @var{format} as long as needed.
The @var{format} is a regular string, with newlines if desired, and
several special escape codes. It defaults to @samp{$f:$l:$n:$%}; see
@ref{autom4te Invocation}, for details on the @var{format}.
@item --initialization
@itemx -i
By default, @option{--trace} does not trace the initialization of the
Autoconf macros (typically the @code{AC_DEFUN} definitions). This
results in a noticeable speedup, but can be disabled by this option.
@end table
It is often necessary to check the content of a @file{configure.ac}
file, but parsing it yourself is extremely fragile and error-prone. It
is suggested that you rely upon @option{--trace} to scan
@file{configure.ac}. For instance, to find the list of variables that
are substituted, use:
@example
@group
$ @kbd{autoconf -t AC_SUBST}
configure.ac:2:AC_SUBST:ECHO_C
configure.ac:2:AC_SUBST:ECHO_N
configure.ac:2:AC_SUBST:ECHO_T
@i{More traces deleted}
@end group
@end example
@noindent
The example below highlights the difference between @samp{$@@},
@samp{$*}, and @samp{$%}.
@example
@group
$ @kbd{cat configure.ac}
AC_DEFINE(This, is, [an
[example]])
$ @kbd{autoconf -t 'AC_DEFINE:@@: $@@}
*: $*
%: $%'
@@: [This],[is],[an
[example]]
*: This,is,an
[example]
%: This:is:an [example]
@end group
@end example
@noindent
The @var{format} gives you a lot of freedom:
@example
@group
$ @kbd{autoconf -t 'AC_SUBST:$$ac_subst@{"$1"@} = "$f:$l";'}
$ac_subst@{"ECHO_C"@} = "configure.ac:2";
$ac_subst@{"ECHO_N"@} = "configure.ac:2";
$ac_subst@{"ECHO_T"@} = "configure.ac:2";
@i{More traces deleted}
@end group
@end example
@noindent
A long @var{separator} can be used to improve the readability of complex
structures, and to ease their parsing (for instance when no single
character is suitable as a separator):
@example
@group
$ @kbd{autoconf -t 'AM_MISSING_PROG:$@{|:::::|@}*'}
ACLOCAL|:::::|aclocal|:::::|$missing_dir
AUTOCONF|:::::|autoconf|:::::|$missing_dir
AUTOMAKE|:::::|automake|:::::|$missing_dir
@i{More traces deleted}
@end group
@end example
@node autoreconf Invocation
@section Using @command{autoreconf} to Update @command{configure} Scripts
@cindex @command{autoreconf}
Installing the various components of the @acronym{GNU} Build System can be
tedious: running @command{autopoint} for Gettext, @command{automake} for
@file{Makefile.in} etc.@: in each directory. It may be needed either
because some tools such as @command{automake} have been updated on your
system, or because some of the sources such as @file{configure.ac} have
been updated, or finally, simply in order to install the @acronym{GNU} Build
System in a fresh tree.
@command{autoreconf} runs @command{autoconf}, @command{autoheader},
@command{aclocal}, @command{automake}, @command{libtoolize}, and
@command{autopoint} (when appropriate) repeatedly to update the
@acronym{GNU} Build System in the specified directories and their
subdirectories (@pxref{Subdirectories}). By default, it only remakes
those files that are older than their sources. The environment variables
@env{AUTOCONF}, @env{AUTOHEADER}, @env{AUTOMAKE}, @env{ACLOCAL},
@env{AUTOPOINT}, @env{LIBTOOLIZE}, @env{M4}, and @env{MAKE} may be used
to override the invocation of the respective tools.
If you install a new version of some tool, you can make
@command{autoreconf} remake @emph{all} of the files by giving it the
@option{--force} option.
@xref{Automatic Remaking}, for Make rules to automatically
rebuild @command{configure} scripts when their source files change. That
method handles the timestamps of configuration header templates
properly, but does not pass @option{--autoconf-dir=@var{dir}} or
@option{--localdir=@var{dir}}.
@cindex Gettext
@cindex @command{autopoint}
Gettext supplies the @command{autopoint} command to add translation
infrastructure to a source package. If you use @command{autopoint},
your @file{configure.ac} should invoke both @code{AM_GNU_GETTEXT} and
@code{AM_GNU_GETTEXT_VERSION(@var{gettext-version})}. @xref{autopoint
Invocation, , Invoking the @code{autopoint} Program, gettext,
@acronym{GNU} @code{gettext} utilities}, for further details.
@noindent
@command{autoreconf} accepts the following options:
@table @option
@item --help
@itemx -h
Print a summary of the command line options and exit.
@item --version
@itemx -V
Print the version number of Autoconf and exit.
@item --verbose
@itemx -V
Print the name of each directory @command{autoreconf} examines and the
commands it runs. If given two or more times, pass @option{--verbose}
to subordinate tools that support it.
@item --debug
@itemx -d
Don't remove the temporary files.
@item --force
@itemx -f
Remake even @file{configure} scripts and configuration headers that are
newer than their input files (@file{configure.ac} and, if present,
@file{aclocal.m4}).
@item --install
@itemx -i
Install the missing auxiliary files in the package. By default, files
are copied; this can be changed with @option{--symlink}.
If deemed appropriate, this option triggers calls to
@samp{automake --add-missing},
@samp{libtoolize}, @samp{autopoint}, etc.
@item --no-recursive
Do not rebuild files in subdirectories to configure (see @ref{Subdirectories},
macro @code{AC_CONFIG_SUBDIRS}).
@item --symlink
@itemx -s
When used with @option{--install}, install symbolic links to the missing
auxiliary files instead of copying them.
@item --make
@itemx -m
When the directories were configured, update the configuration by
running @samp{./config.status --recheck && ./config.status}, and then
run @samp{make}.
@item --include=@var{dir}
@itemx -I @var{dir}
Append @var{dir} to the include path. Multiple invocations accumulate.
Passed on to @command{aclocal}, @command{autoconf} and
@command{autoheader} internally.
@item --prepend-include=@var{dir}
@itemx -B @var{dir}
Prepend @var{dir} to the include path. Multiple invocations accumulate.
Passed on to @command{autoconf} and @command{autoheader} internally.
@item --warnings=@var{category}
@itemx -W @var{category}
@evindex WARNINGS
Report the warnings related to @var{category} (which can actually be a
comma separated list).
@table @samp
@item cross
related to cross compilation issues.
@item obsolete
report the uses of obsolete constructs.
@item portability
portability issues
@item syntax
dubious syntactic constructs.
@item all
report all the warnings
@item none
report none
@item error
treats warnings as errors
@item no-@var{category}
disable warnings falling into @var{category}
@end table
Warnings about @samp{syntax} are enabled by default, and the environment
variable @env{WARNINGS}, a comma separated list of categories, is
honored as well. Passing @option{-W @var{category}} actually behaves as if
you had passed @option{--warnings syntax,$WARNINGS,@var{category}}. To
disable the defaults and @env{WARNINGS}, and then
enable warnings about obsolete constructs, use @option{-W
none,obsolete}.
@end table
If you want @command{autoreconf} to pass flags that are not listed here
on to @command{aclocal}, set @code{ACLOCAL_AMFLAGS} in your @file{Makefile.am}.
Due to a limitation in the Autoconf implementation these flags currently
must be set on a single line in @file{Makefile.am}, without any
backslash-newlines.
@c ========================================= Initialization and Output Files.
@node Setup
@chapter Initialization and Output Files
Autoconf-generated @command{configure} scripts need some information about
how to initialize, such as how to find the package's source files and
about the output files to produce. The following sections describe the
initialization and the creation of output files.
@menu
* Initializing configure:: Option processing etc.
* Versioning:: Dealing with Autoconf versions
* Notices:: Copyright, version numbers in @command{configure}
* Input:: Where Autoconf should find files
* Output:: Outputting results from the configuration
* Configuration Actions:: Preparing the output based on results
* Configuration Files:: Creating output files
* Makefile Substitutions:: Using output variables in makefiles
* Configuration Headers:: Creating a configuration header file
* Configuration Commands:: Running arbitrary instantiation commands
* Configuration Links:: Links depending on the configuration
* Subdirectories:: Configuring independent packages together
* Default Prefix:: Changing the default installation prefix
@end menu
@node Initializing configure
@section Initializing @command{configure}
Every @command{configure} script must call @code{AC_INIT} before doing
anything else. The only other required macro is @code{AC_OUTPUT}
(@pxref{Output}).
@anchor{AC_INIT}
@defmac AC_INIT (@var{package}, @var{version}, @ovar{bug-report}, @
@ovar{tarname}, @ovar{url})
@acindex{INIT}
Process any command-line arguments and perform various initializations
and verifications.
Set the name of the @var{package} and its @var{version}. These are
typically used in @option{--version} support, including that of
@command{configure}. The optional argument @var{bug-report} should be
the email to which users should send bug reports. The package
@var{tarname} differs from @var{package}: the latter designates the full
package name (e.g., @samp{GNU Autoconf}), while the former is meant for
distribution tar ball names (e.g., @samp{autoconf}). It defaults to
@var{package} with @samp{GNU } stripped, lower-cased, and all characters
other than alphanumerics and underscores are changed to @samp{-}. If
provided, @var{url} should be the home page for the package.
It is preferable that the arguments of @code{AC_INIT} be static, i.e.,
there should not be any shell computation, but they can be computed by
M4.
The following M4 macros (e.g., @code{AC_PACKAGE_NAME}), output variables
(e.g., @code{PACKAGE_NAME}), and preprocessor symbols (e.g.,
@code{PACKAGE_NAME}), are defined by @code{AC_INIT}:
@table @asis
@item @code{AC_PACKAGE_NAME}, @code{PACKAGE_NAME}
@acindex{PACKAGE_NAME}
@ovindex PACKAGE_NAME
@cvindex PACKAGE_NAME
Exactly @var{package}.
@item @code{AC_PACKAGE_TARNAME}, @code{PACKAGE_TARNAME}
@acindex{PACKAGE_TARNAME}
@ovindex PACKAGE_TARNAME
@cvindex PACKAGE_TARNAME
Exactly @var{tarname}, possibly generated from @var{package}.
@item @code{AC_PACKAGE_VERSION}, @code{PACKAGE_VERSION}
@acindex{PACKAGE_VERSION}
@ovindex PACKAGE_VERSION
@cvindex PACKAGE_VERSION
Exactly @var{version}.
@item @code{AC_PACKAGE_STRING}, @code{PACKAGE_STRING}
@acindex{PACKAGE_STRING}
@ovindex PACKAGE_STRING
@cvindex PACKAGE_STRING
Exactly @samp{@var{package} @var{version}}.
@item @code{AC_PACKAGE_BUGREPORT}, @code{PACKAGE_BUGREPORT}
@acindex{PACKAGE_BUGREPORT}
@ovindex PACKAGE_BUGREPORT
@cvindex PACKAGE_BUGREPORT
Exactly @var{bug-report}, if one was provided.
@item @code{AC_PACKAGE_URL}, @code{PACKAGE_URL}
@acindex{PACKAGE_URL}
@ovindex PACKAGE_URL
@cvindex PACKAGE_URL
Exactly @var{url}, if one was provided. If @var{url} was empty, but
@var{package} begins with @samp{GNU }, then this defaults to
@samp{http://@/www.gnu.org/@/software/@/@var{tarname}/}, otherwise, no URL is
assumed.
@end table
@end defmac
If your @command{configure} script does its own option processing, it
should inspect @samp{$@@} or @samp{$*} immediately after calling
@code{AC_INIT}, because other Autoconf macros liberally use the
@command{set} command to process strings, and this has the side effect
of updating @samp{$@@} and @samp{$*}. However, we suggest that you use
standard macros like @code{AC_ARG_ENABLE} instead of attempting to
implement your own option processing. @xref{Site Configuration}.
@node Versioning
@section Dealing with Autoconf versions
@cindex Autoconf version
@cindex version, Autoconf
The following optional macros can be used to help choose the minimum
version of Autoconf that can successfully compile a given
@file{configure.ac}.
@defmac AC_PREREQ (@var{version})
@acindex{PREREQ}
@cindex Version
Ensure that a recent enough version of Autoconf is being used. If the
version of Autoconf being used to create @command{configure} is
earlier than @var{version}, print an error message to the standard
error output and exit with failure (exit status is 63). For example:
@example
AC_PREREQ([@value{VERSION}])
@end example
This macro is the only macro that may be used before @code{AC_INIT}, but
for consistency, you are invited not to do so.
@end defmac
@defmac AC_AUTOCONF_VERSION
@acindex{AUTOCONF_VERSION}
This macro was introduced in Autoconf 2.62. It identifies the version
of Autoconf that is currently parsing the input file, in a format
suitable for @code{m4_version_compare} (@pxref{m4_version_compare}); in
other words, for this release of Autoconf, its value is
@samp{@value{VERSION}}. One potential use of this macro is for writing
conditional fallbacks based on when a feature was added to Autoconf,
rather than using @code{AC_PREREQ} to require the newer version of
Autoconf. However, remember that the Autoconf philosophy favors feature
checks over version checks.
You should not expand this macro directly; use
@samp{m4_defn([AC_AUTOCONF_VERSION])} instead. This is because some
users might
have a beta version of Autoconf installed, with arbitrary letters
included in its version string. This means it is possible for the
version string to contain the name of a defined macro, such that
expanding @code{AC_AUTOCONF_VERSION} would trigger the expansion of that
macro during rescanning, and change the version string to be different
than what you intended to check.
@end defmac
@node Notices
@section Notices in @command{configure}
@cindex Notices in @command{configure}
The following macros manage version numbers for @command{configure}
scripts. Using them is optional.
@defmac AC_COPYRIGHT (@var{copyright-notice})
@acindex{COPYRIGHT}
@cindex Copyright Notice
State that, in addition to the Free Software Foundation's copyright on
the Autoconf macros, parts of your @command{configure} are covered by the
@var{copyright-notice}.
The @var{copyright-notice} shows up in both the head of
@command{configure} and in @samp{configure --version}.
@end defmac
@defmac AC_REVISION (@var{revision-info})
@acindex{REVISION}
@cindex Revision
Copy revision stamp @var{revision-info} into the @command{configure}
script, with any dollar signs or double-quotes removed. This macro lets
you put a revision stamp from @file{configure.ac} into @command{configure}
without @acronym{RCS} or @acronym{CVS} changing it when you check in
@command{configure}. That way, you can determine easily which revision of
@file{configure.ac} a particular @command{configure} corresponds to.
For example, this line in @file{configure.ac}:
@c The @w prevents RCS from changing the example in the manual.
@example
AC_REVISION([@w{$}Revision: 1.30 $])
@end example
@noindent
produces this in @command{configure}:
@example
#!/bin/sh
# From configure.ac Revision: 1.30
@end example
@end defmac
@node Input
@section Finding @command{configure} Input
@anchor{AC_CONFIG_SRCDIR}
@defmac AC_CONFIG_SRCDIR (@var{unique-file-in-source-dir})
@acindex{CONFIG_SRCDIR}
@var{unique-file-in-source-dir} is some file that is in the package's
source directory; @command{configure} checks for this file's existence to
make sure that the directory that it is told contains the source code in
fact does. Occasionally people accidentally specify the wrong directory
with @option{--srcdir}; this is a safety check. @xref{configure
Invocation}, for more information.
@end defmac
@c FIXME: Remove definitively once --install explained.
@c
@c Small packages may store all their macros in @code{aclocal.m4}. As the
@c set of macros grows, or for maintenance reasons, a maintainer may prefer
@c to split the macros in several files. In this case, Autoconf must be
@c told which files to load, and in which order.
@c
@c @defmac AC_INCLUDE (@var{file}@dots{})
@c @acindex{INCLUDE}
@c @c FIXME: There is no longer shell globbing.
@c Read the macro definitions that appear in the listed files. A list of
@c space-separated file names or shell globbing patterns is expected. The
@c files are read in the order they're listed.
@c
@c Because the order of definition of macros is important (only the last
@c definition of a macro is used), beware that it is @code{AC_INIT} that
@c loads @file{acsite.m4} and @file{aclocal.m4}. Note that
@c @code{AC_INCLUDE}ing a file before @code{AC_INIT} or within
@c @file{aclocal.m4} is different from doing so after @code{AC_INIT}: in
@c the latter case, non-macro lines from included files may end up in the
@c @file{configure} script, whereas in the former case, they'd be discarded
@c just like any text that appear before @code{AC_INIT}.
@c @end defmac
Packages that do manual configuration or use the @command{install} program
might need to tell @command{configure} where to find some other shell
scripts by calling @code{AC_CONFIG_AUX_DIR}, though the default places
it looks are correct for most cases.
@defmac AC_CONFIG_AUX_DIR (@var{dir})
@acindex{CONFIG_AUX_DIR}
Use the auxiliary build tools (e.g., @file{install-sh},
@file{config.sub}, @file{config.guess}, Cygnus @command{configure},
Automake and Libtool scripts, etc.)@: that are in directory @var{dir}.
These are auxiliary files used in configuration. @var{dir} can be
either absolute or relative to @file{@var{srcdir}}. The default is
@file{@var{srcdir}} or @file{@var{srcdir}/..} or
@file{@var{srcdir}/../..}, whichever is the first that contains
@file{install-sh}. The other files are not checked for, so that using
@code{AC_PROG_INSTALL} does not automatically require distributing the
other auxiliary files. It checks for @file{install.sh} also, but that
name is obsolete because some @command{make} have a rule that creates
@file{install} from it if there is no makefile.
The auxiliary directory is commonly named @file{build-aux}.
If you need portability to @acronym{DOS} variants, do not name the
auxiliary directory @file{aux}. @xref{File System Conventions}.
@end defmac
@defmac AC_REQUIRE_AUX_FILE (@var{file})
@acindex{REQUIRE_AUX_FILE}
Declares that @var{file} is expected in the directory defined above. In
Autoconf proper, this macro does nothing: its sole purpose is to be
traced by third-party tools to produce a list of expected auxiliary
files. For instance it is called by macros like @code{AC_PROG_INSTALL}
(@pxref{Particular Programs}) or @code{AC_CANONICAL_BUILD}
(@pxref{Canonicalizing}) to register the auxiliary files they need.
@end defmac
Similarly, packages that use @command{aclocal} should declare where
local macros can be found using @code{AC_CONFIG_MACRO_DIR}.
@defmac AC_CONFIG_MACRO_DIR (@var{dir})
@acindex{CONFIG_MACRO_DIR}
Specify @var{dir} as the location of additional local Autoconf macros.
This macro is intended for use by future versions of commands like
@command{autoreconf} that trace macro calls. It should be called
directly from @file{configure.ac} so that tools that install macros for
@command{aclocal} can find the macros' declarations.
Note that if you use @command{aclocal} from Automake to generate
@file{aclocal.m4}, you must also set @code{ACLOCAL_AMFLAGS = -I
@var{dir}} in your top-level @file{Makefile.am}. Due to a limitation in
the Autoconf implementation of @command{autoreconf}, these include
directives currently must be set on a single line in @file{Makefile.am},
without any backslash-newlines.
@end defmac
@node Output
@section Outputting Files
@cindex Outputting files
Every Autoconf script, e.g., @file{configure.ac}, should finish by
calling @code{AC_OUTPUT}. That is the macro that generates and runs
@file{config.status}, which in turn creates the makefiles and any
other files resulting from configuration. This is the only required
macro besides @code{AC_INIT} (@pxref{Input}).
@anchor{AC_OUTPUT}
@defmac AC_OUTPUT
@acindex{OUTPUT}
@cindex Instantiation
Generate @file{config.status} and launch it. Call this macro once, at
the end of @file{configure.ac}.
@file{config.status} performs all the configuration actions: all the
output files (see @ref{Configuration Files}, macro
@code{AC_CONFIG_FILES}), header files (see @ref{Configuration Headers},
macro @code{AC_CONFIG_HEADERS}), commands (see @ref{Configuration
Commands}, macro @code{AC_CONFIG_COMMANDS}), links (see
@ref{Configuration Links}, macro @code{AC_CONFIG_LINKS}), subdirectories
to configure (see @ref{Subdirectories}, macro @code{AC_CONFIG_SUBDIRS})
are honored.
The location of your @code{AC_OUTPUT} invocation is the exact point
where configuration actions are taken: any code afterwards is
executed by @command{configure} once @command{config.status} was run. If
you want to bind actions to @command{config.status} itself
(independently of whether @command{configure} is being run), see
@ref{Configuration Commands, , Running Arbitrary Configuration
Commands}.
@end defmac
Historically, the usage of @code{AC_OUTPUT} was somewhat different.
@xref{Obsolete Macros}, for a description of the arguments that
@code{AC_OUTPUT} used to support.
If you run @command{make} in subdirectories, you should run it using the
@command{make} variable @code{MAKE}. Most versions of @command{make} set
@code{MAKE} to the name of the @command{make} program plus any options it
was given. (But many do not include in it the values of any variables
set on the command line, so those are not passed on automatically.)
Some old versions of @command{make} do not set this variable. The
following macro allows you to use it even with those versions.
@anchor{AC_PROG_MAKE_SET}
@defmac AC_PROG_MAKE_SET
@acindex{PROG_MAKE_SET}
@ovindex SET_MAKE
If the Make command, @code{$MAKE} if set or else @samp{make}, predefines
@code{$(MAKE)}, define output variable @code{SET_MAKE} to be empty.
Otherwise, define @code{SET_MAKE} to a macro definition that sets
@code{$(MAKE)}, such as @samp{MAKE=make}. Calls @code{AC_SUBST} for
@code{SET_MAKE}.
@end defmac
If you use this macro, place a line like this in each @file{Makefile.in}
that runs @command{MAKE} on other directories:
@example
@@SET_MAKE@@
@end example
@node Configuration Actions
@section Performing Configuration Actions
@cindex Configuration actions
@file{configure} is designed so that it appears to do everything itself,
but there is actually a hidden slave: @file{config.status}.
@file{configure} is in charge of examining your system, but it is
@file{config.status} that actually takes the proper actions based on the
results of @file{configure}. The most typical task of
@file{config.status} is to @emph{instantiate} files.
@acindex{CONFIG_@var{ITEMS}}
This section describes the common behavior of the four standard
instantiating macros: @code{AC_CONFIG_FILES}, @code{AC_CONFIG_HEADERS},
@code{AC_CONFIG_COMMANDS} and @code{AC_CONFIG_LINKS}. They all
have this prototype:
@c FIXME: Can't use @ovar here, Texinfo 4.0 goes lunatic and emits something
@c awful.
@example
AC_CONFIG_@var{ITEMS}(@var{tag}@dots{}, [@var{commands}], [@var{init-cmds}])
@end example
@noindent
where the arguments are:
@table @var
@item tag@dots{}
A blank-or-newline-separated list of tags, which are typically the names of
the files to instantiate.
You are encouraged to use literals as @var{tags}. In particular, you
should avoid
@example
@dots{} && my_foos="$my_foos fooo"
@dots{} && my_foos="$my_foos foooo"
AC_CONFIG_@var{ITEMS}([$my_foos])
@end example
@noindent
and use this instead:
@example
@dots{} && AC_CONFIG_@var{ITEMS}([fooo])
@dots{} && AC_CONFIG_@var{ITEMS}([foooo])
@end example
The macros @code{AC_CONFIG_FILES} and @code{AC_CONFIG_HEADERS} use
special @var{tag} values: they may have the form @samp{@var{output}} or
@samp{@var{output}:@var{inputs}}. The file @var{output} is instantiated
from its templates, @var{inputs} (defaulting to @samp{@var{output}.in}).
@samp{AC_CONFIG_FILES([Makefile:boiler/top.mk:boiler/bot.mk)]},
for example, asks for
the creation of the file @file{Makefile} that contains the expansion of the
output variables in the concatenation of @file{boiler/top.mk} and
@file{boiler/bot.mk}.
The special value @samp{-} might be used to denote the standard output
when used in @var{output}, or the standard input when used in the
@var{inputs}. You most probably don't need to use this in
@file{configure.ac}, but it is convenient when using the command line
interface of @file{./config.status}, see @ref{config.status Invocation},
for more details.
The @var{inputs} may be absolute or relative file names. In the latter
case they are first looked for in the build tree, and then in the source
tree. Input files should be text files, and a line length below 2000
bytes should be safe.
@item commands
Shell commands output literally into @file{config.status}, and
associated with a tag that the user can use to tell @file{config.status}
which commands to run. The commands are run each time a @var{tag}
request is given to @file{config.status}, typically each time the file
@file{@var{tag}} is created.
The variables set during the execution of @command{configure} are
@emph{not} available here: you first need to set them via the
@var{init-cmds}. Nonetheless the following variables are precomputed:
@table @code
@item srcdir
The name of the top source directory, assuming that the working
directory is the top build directory. This
is what the @command{configure} option @option{--srcdir} sets.
@item ac_top_srcdir
The name of the top source directory, assuming that the working
directory is the current build directory.
@item ac_top_build_prefix
The name of the top build directory, assuming that the working
directory is the current build directory.
It can be empty, or else ends with a slash, so that you may concatenate
it.
@item ac_srcdir
The name of the corresponding source directory, assuming that the
working directory is the current build directory.
@end table
@noindent
The @dfn{current} directory refers to the directory (or
pseudo-directory) containing the input part of @var{tags}. For
instance, running
@example
AC_CONFIG_COMMANDS([deep/dir/out:in/in.in], [@dots{}], [@dots{}])
@end example
@noindent
with @option{--srcdir=../package} produces the following values:
@example
# Argument of --srcdir
srcdir='../package'
# Reversing deep/dir
ac_top_build_prefix='../../'
# Concatenation of $ac_top_build_prefix and srcdir
ac_top_srcdir='../../../package'
# Concatenation of $ac_top_srcdir and deep/dir
ac_srcdir='../../../package/deep/dir'
@end example
@noindent
independently of @samp{in/in.in}.
@item init-cmds
Shell commands output @emph{unquoted} near the beginning of
@file{config.status}, and executed each time @file{config.status} runs
(regardless of the tag). Because they are unquoted, for example,
@samp{$var} is output as the value of @code{var}. @var{init-cmds}
is typically used by @file{configure} to give @file{config.status} some
variables it needs to run the @var{commands}.
You should be extremely cautious in your variable names: all the
@var{init-cmds} share the same name space and may overwrite each other
in unpredictable ways. Sorry@enddots{}
@end table
All these macros can be called multiple times, with different
@var{tag} values, of course!
@node Configuration Files
@section Creating Configuration Files
@cindex Creating configuration files
@cindex Configuration file creation
Be sure to read the previous section, @ref{Configuration Actions}.
@anchor{AC_CONFIG_FILES}
@defmac AC_CONFIG_FILES (@var{file}@dots{}, @ovar{cmds}, @ovar{init-cmds})
@acindex{CONFIG_FILES}
Make @code{AC_OUTPUT} create each @file{@var{file}} by copying an input
file (by default @file{@var{file}.in}), substituting the output variable
values.
@c Before we used to have this feature, which was later rejected
@c because it complicates the writing of makefiles:
@c If the file would be unchanged, it is left untouched, to preserve
@c timestamp.
This macro is one of the instantiating macros; see @ref{Configuration
Actions}. @xref{Makefile Substitutions}, for more information on using
output variables. @xref{Setting Output Variables}, for more information
on creating them. This macro creates the directory that the file is in
if it doesn't exist. Usually, makefiles are created this way,
but other files, such as @file{.gdbinit}, can be specified as well.
Typical calls to @code{AC_CONFIG_FILES} look like this:
@example
AC_CONFIG_FILES([Makefile src/Makefile man/Makefile X/Imakefile])
AC_CONFIG_FILES([autoconf], [chmod +x autoconf])
@end example
You can override an input file name by appending to @var{file} a
colon-separated list of input files. Examples:
@example
AC_CONFIG_FILES([Makefile:boiler/top.mk:boiler/bot.mk]
[lib/Makefile:boiler/lib.mk])
@end example
@noindent
Doing this allows you to keep your file names acceptable to
@acronym{DOS} variants, or
to prepend and/or append boilerplate to the file.
@end defmac
@node Makefile Substitutions
@section Substitutions in Makefiles
@cindex Substitutions in makefiles
@cindex Makefile substitutions
Each subdirectory in a distribution that contains something to be
compiled or installed should come with a file @file{Makefile.in}, from
which @command{configure} creates a file @file{Makefile} in that directory.
To create @file{Makefile}, @command{configure} performs a simple variable
substitution, replacing occurrences of @samp{@@@var{variable}@@} in
@file{Makefile.in} with the value that @command{configure} has determined
for that variable. Variables that are substituted into output files in
this way are called @dfn{output variables}. They are ordinary shell
variables that are set in @command{configure}. To make @command{configure}
substitute a particular variable into the output files, the macro
@code{AC_SUBST} must be called with that variable name as an argument.
Any occurrences of @samp{@@@var{variable}@@} for other variables are
left unchanged. @xref{Setting Output Variables}, for more information
on creating output variables with @code{AC_SUBST}.
A software package that uses a @command{configure} script should be
distributed with a file @file{Makefile.in}, but no makefile; that
way, the user has to properly configure the package for the local system
before compiling it.
@xref{Makefile Conventions, , Makefile Conventions, standards, The
@acronym{GNU} Coding Standards}, for more information on what to put in
makefiles.
@menu
* Preset Output Variables:: Output variables that are always set
* Installation Directory Variables:: Other preset output variables
* Changed Directory Variables:: Warnings about @file{datarootdir}
* Build Directories:: Supporting multiple concurrent compiles
* Automatic Remaking:: Makefile rules for configuring
@end menu
@node Preset Output Variables
@subsection Preset Output Variables
@cindex Output variables
Some output variables are preset by the Autoconf macros. Some of the
Autoconf macros set additional output variables, which are mentioned in
the descriptions for those macros. @xref{Output Variable Index}, for a
complete list of output variables. @xref{Installation Directory
Variables}, for the list of the preset ones related to installation
directories. Below are listed the other preset ones, many of which are
precious variables (@pxref{Setting Output Variables},
@code{AC_ARG_VAR}).
The preset variables which are available during @file{config.status}
(@pxref{Configuration Actions}) may also be used during
@command{configure} tests. For example, it is permissible to reference
@samp{$srcdir} when constructing a list of directories to pass via
option @option{-I} during a compiler feature check. When used in this
manner, coupled with the fact that @command{configure} is always run
from the top build directory, it is sufficient to use just
@samp{$srcdir} instead of @samp{$top_srcdir}.
@c Just say no to ASCII sorting! We're humans, not computers.
@c These variables are listed as they would be in a dictionary:
@c actor
@c Actress
@c actress
@defvar CFLAGS
@evindex CFLAGS
@ovindex CFLAGS
Debugging and optimization options for the C compiler. If it is not set
in the environment when @command{configure} runs, the default value is set
when you call @code{AC_PROG_CC} (or empty if you don't). @command{configure}
uses this variable when compiling or linking programs to test for C features.
If a compiler option affects only the behavior of the preprocessor
(e.g., @option{-D @var{name}}), it should be put into @code{CPPFLAGS}
instead. If it affects only the linker (e.g., @option{-L
@var{directory}}), it should be put into @code{LDFLAGS} instead. If it
affects only the compiler proper, @code{CFLAGS} is the natural home for
it. If an option affects multiple phases of the compiler, though,
matters get tricky. One approach to put such options directly into
@code{CC}, e.g., @code{CC='gcc -m64'}. Another is to put them into both
@code{CPPFLAGS} and @code{LDFLAGS}, but not into @code{CFLAGS}.
However, remember that some @file{Makefile} variables are reserved by
the @acronym{GNU} Coding Standards for the use of the ``user''---the person
building the package. For instance, @code{CFLAGS} is one such variable.
Sometimes package developers are tempted to set user variables such as
@code{CFLAGS} because it appears to make their job easier. However, the
package itself should never set a user variable, particularly not to
include switches that are required for proper compilation of the
package. Since these variables are documented as being for the package
builder, that person rightfully expects to be able to override any of
these variables at build time. If the package developer needs to add
switches without interfering with the user, the proper way to do that is
to introduce an additional variable. Automake makes this easy by
introducing @code{AM_CFLAGS} (@pxref{Flag Variables Ordering, , ,
automake, @acronym{GNU} Automake}), but the concept is the same even if
Automake is not used.
@end defvar
@defvar configure_input
@ovindex configure_input
A comment saying that the file was generated automatically by
@command{configure} and giving the name of the input file.
@code{AC_OUTPUT} adds a comment line containing this variable to the top
of every makefile it creates. For other files, you should
reference this variable in a comment at the top of each input file. For
example, an input shell script should begin like this:
@example
#!/bin/sh
# @@configure_input@@
@end example
@noindent
The presence of that line also reminds people editing the file that it
needs to be processed by @command{configure} in order to be used.
@end defvar
@defvar CPPFLAGS
@evindex CPPFLAGS
@ovindex CPPFLAGS
Preprocessor options for the C, C++, and Objective C preprocessors and
compilers. If
it is not set in the environment when @command{configure} runs, the default
value is empty. @command{configure} uses this variable when preprocessing
or compiling programs to test for C, C++, and Objective C features.
This variable's contents should contain options like @option{-I},
@option{-D}, and @option{-U} that affect only the behavior of the
preprocessor. Please see the explanation of @code{CFLAGS} for what you
can do if an option affects other phases of the compiler as well.
Currently, @command{configure} always links as part of a single
invocation of the compiler that also preprocesses and compiles, so it
uses this variable also when linking programs. However, it is unwise to
depend on this behavior because the @acronym{GNU} Coding Standards do
not require it and many packages do not use @code{CPPFLAGS} when linking
programs.
@xref{Special Chars in Variables}, for limitations that @code{CPPFLAGS}
might run into.
@end defvar
@defvar CXXFLAGS
@evindex CXXFLAGS
@ovindex CXXFLAGS
Debugging and optimization options for the C++ compiler. It acts like
@code{CFLAGS}, but for C++ instead of C.
@end defvar
@defvar DEFS
@ovindex DEFS
@option{-D} options to pass to the C compiler. If @code{AC_CONFIG_HEADERS}
is called, @command{configure} replaces @samp{@@DEFS@@} with
@option{-DHAVE_CONFIG_H} instead (@pxref{Configuration Headers}). This
variable is not defined while @command{configure} is performing its tests,
only when creating the output files. @xref{Setting Output Variables}, for
how to check the results of previous tests.
@end defvar
@defvar ECHO_C
@defvarx ECHO_N
@defvarx ECHO_T
@ovindex ECHO_C
@ovindex ECHO_N
@ovindex ECHO_T
How does one suppress the trailing newline from @command{echo} for
question-answer message pairs? These variables provide a way:
@example
echo $ECHO_N "And the winner is... $ECHO_C"
sleep 100000000000
echo "$@{ECHO_T@}dead."
@end example
@noindent
Some old and uncommon @command{echo} implementations offer no means to
achieve this, in which case @code{ECHO_T} is set to tab. You might not
want to use it.
@end defvar
@defvar ERLCFLAGS
@evindex ERLCFLAGS
@ovindex ERLCFLAGS
Debugging and optimization options for the Erlang compiler. If it is not set
in the environment when @command{configure} runs, the default value is empty.
@command{configure} uses this variable when compiling
programs to test for Erlang features.
@end defvar
@defvar FCFLAGS
@evindex FCFLAGS
@ovindex FCFLAGS
Debugging and optimization options for the Fortran compiler. If it
is not set in the environment when @command{configure} runs, the default
value is set when you call @code{AC_PROG_FC} (or empty if you don't).
@command{configure} uses this variable when compiling or linking
programs to test for Fortran features.
@end defvar
@defvar FFLAGS
@evindex FFLAGS
@ovindex FFLAGS
Debugging and optimization options for the Fortran 77 compiler. If it
is not set in the environment when @command{configure} runs, the default
value is set when you call @code{AC_PROG_F77} (or empty if you don't).
@command{configure} uses this variable when compiling or linking
programs to test for Fortran 77 features.
@end defvar
@defvar LDFLAGS
@evindex LDFLAGS
@ovindex LDFLAGS
Options for the linker. If it is not set
in the environment when @command{configure} runs, the default value is empty.
@command{configure} uses this variable when linking programs to test for
C, C++, Objective C, and Fortran features.
This variable's contents should contain options like @option{-s} and
@option{-L} that affect only the behavior of the linker. Please see the
explanation of @code{CFLAGS} for what you can do if an option also
affects other phases of the compiler.
Don't use this variable to pass library names
(@option{-l}) to the linker; use @code{LIBS} instead.
@end defvar
@defvar LIBS
@evindex LIBS
@ovindex LIBS
@option{-l} options to pass to the linker. The default value is empty,
but some Autoconf macros may prepend extra libraries to this variable if
those libraries are found and provide necessary functions, see
@ref{Libraries}. @command{configure} uses this variable when linking
programs to test for C, C++, and Fortran features.
@end defvar
@defvar OBJCFLAGS
@evindex OBJCFLAGS
@ovindex OBJCFLAGS
Debugging and optimization options for the Objective C compiler. It
acts like @code{CFLAGS}, but for Objective C instead of C.
@end defvar
@defvar builddir
@ovindex builddir
Rigorously equal to @samp{.}. Added for symmetry only.
@end defvar
@defvar abs_builddir
@ovindex abs_builddir
Absolute name of @code{builddir}.
@end defvar
@defvar top_builddir
@ovindex top_builddir
The relative name of the top level of the current build tree. In the
top-level directory, this is the same as @code{builddir}.
@end defvar
@defvar top_build_prefix
@ovindex top_build_prefix
The relative name of the top level of the current build tree with final
slash if nonemtpy. This is the same as @code{top_builddir}, except that
it contains zero or more runs of @code{../}, so it should not be
appended with a slash for concatenation. This helps for @command{make}
implementations that otherwise do not treat @file{./file} and @file{file}
as equal in the toplevel build directory.
@end defvar
@defvar abs_top_builddir
@ovindex abs_top_builddir
Absolute name of @code{top_builddir}.
@end defvar
@defvar srcdir
@ovindex srcdir
The name of the directory that contains the source code for
that makefile.
@end defvar
@defvar abs_srcdir
@ovindex abs_srcdir
Absolute name of @code{srcdir}.
@end defvar
@defvar top_srcdir
@ovindex top_srcdir
The name of the top-level source code directory for the
package. In the top-level directory, this is the same as @code{srcdir}.
@end defvar
@defvar abs_top_srcdir
@ovindex abs_top_srcdir
Absolute name of @code{top_srcdir}.
@end defvar
@node Installation Directory Variables
@subsection Installation Directory Variables
@cindex Installation directories
@cindex Directories, installation
The following variables specify the directories for
package installation, see @ref{Directory Variables, , Variables for
Installation Directories, standards, The @acronym{GNU} Coding
Standards}, for more information. Each variable corresponds to an
argument of @command{configure}; trailing slashes are stripped so that
expressions such as @samp{$@{prefix@}/lib} expand with only one slash
between directory names. See the end of this section for
details on when and how to use these variables.
@defvar bindir
@ovindex bindir
The directory for installing executables that users run.
@end defvar
@defvar datadir
@ovindex datadir
The directory for installing idiosyncratic read-only
architecture-independent data.
@end defvar
@defvar datarootdir
@ovindex datarootdir
The root of the directory tree for read-only architecture-independent
data files.
@end defvar
@defvar docdir
@ovindex docdir
The directory for installing documentation files (other than Info and
man).
@end defvar
@defvar dvidir
@ovindex dvidir
The directory for installing documentation files in DVI format.
@end defvar
@defvar exec_prefix
@ovindex exec_prefix
The installation prefix for architecture-dependent files. By default
it's the same as @var{prefix}. You should avoid installing anything
directly to @var{exec_prefix}. However, the default value for
directories containing architecture-dependent files should be relative
to @var{exec_prefix}.
@end defvar
@defvar htmldir
@ovindex htmldir
The directory for installing HTML documentation.
@end defvar
@defvar includedir
@ovindex includedir
The directory for installing C header files.
@end defvar
@defvar infodir
@ovindex infodir
The directory for installing documentation in Info format.
@end defvar
@defvar libdir
@ovindex libdir
The directory for installing object code libraries.
@end defvar
@defvar libexecdir
@ovindex libexecdir
The directory for installing executables that other programs run.
@end defvar
@defvar localedir
@ovindex localedir
The directory for installing locale-dependent but
architecture-independent data, such as message catalogs. This directory
usually has a subdirectory per locale.
@end defvar
@defvar localstatedir
@ovindex localstatedir
The directory for installing modifiable single-machine data.
@end defvar
@defvar mandir
@ovindex mandir
The top-level directory for installing documentation in man format.
@end defvar
@defvar oldincludedir
@ovindex oldincludedir
The directory for installing C header files for non-@acronym{GCC} compilers.
@end defvar
@defvar pdfdir
@ovindex pdfdir
The directory for installing PDF documentation.
@end defvar
@defvar prefix
@ovindex prefix
The common installation prefix for all files. If @var{exec_prefix}
is defined to a different value, @var{prefix} is used only for
architecture-independent files.
@end defvar
@defvar psdir
@ovindex psdir
The directory for installing PostScript documentation.
@end defvar
@defvar sbindir
@ovindex sbindir
The directory for installing executables that system
administrators run.
@end defvar
@defvar sharedstatedir
@ovindex sharedstatedir
The directory for installing modifiable architecture-independent data.
@end defvar
@defvar sysconfdir
@ovindex sysconfdir
The directory for installing read-only single-machine data.
@end defvar
Most of these variables have values that rely on @code{prefix} or
@code{exec_prefix}. It is deliberate that the directory output
variables keep them unexpanded: typically @samp{@@datarootdir@@} is
replaced by @samp{$@{prefix@}/share}, not @samp{/usr/local/share}, and
@samp{@@datadir@@} is replaced by @samp{$@{datarootdir@}}.
This behavior is mandated by the @acronym{GNU} Coding Standards, so that when
the user runs:
@table @samp
@item make
she can still specify a different prefix from the one specified to
@command{configure}, in which case, if needed, the package should hard
code dependencies corresponding to the make-specified prefix.
@item make install
she can specify a different installation location, in which case the
package @emph{must} still depend on the location which was compiled in
(i.e., never recompile when @samp{make install} is run). This is an
extremely important feature, as many people may decide to install all
the files of a package grouped together, and then install links from
the final locations to there.
@end table
In order to support these features, it is essential that
@code{datarootdir} remains defined as @samp{$@{prefix@}/share},
so that its value can be expanded based
on the current value of @code{prefix}.
A corollary is that you should not use these variables except in
makefiles. For instance, instead of trying to evaluate @code{datadir}
in @file{configure} and hard-coding it in makefiles using
e.g., @samp{AC_DEFINE_UNQUOTED([DATADIR], ["$datadir"], [Data directory.])},
you should add
@option{-DDATADIR='$(datadir)'} to your makefile's definition of
@code{CPPFLAGS} (@code{AM_CPPFLAGS} if you are also using Automake).
Similarly, you should not rely on @code{AC_CONFIG_FILES} to replace
@code{bindir} and friends in your shell scripts and other files; instead,
let @command{make} manage their replacement. For instance Autoconf
ships templates of its shell scripts ending with @samp{.in}, and uses a
makefile snippet similar to the following to build scripts like
@command{autoheader} and @command{autom4te}:
@example
@group
edit = sed \
-e 's|@@bindir[@@]|$(bindir)|g' \
-e 's|@@pkgdatadir[@@]|$(pkgdatadir)|g' \
-e 's|@@prefix[@@]|$(prefix)|g'
@end group
@group
autoheader autom4te: Makefile
rm -f $@@ $@@.tmp
srcdir=''; \
test -f ./$@@.in || srcdir=$(srcdir)/; \
$(edit) $$@{srcdir@}$@@.in >$@@.tmp
chmod +x $@@.tmp
chmod a-w $@@.tmp
mv $@@.tmp $@@
@end group
@group
autoheader: $(srcdir)/autoheader.in
autom4te: $(srcdir)/autom4te.in
@end group
@end example
Some details are noteworthy:
@table @asis
@item @samp{@@bindir[@@]}
The brackets prevent @command{configure} from replacing
@samp{@@bindir@@} in the Sed expression itself.
Brackets are preferable to a backslash here, since
Posix says @samp{\@@} is not portable.
@item @samp{$(bindir)}
Don't use @samp{@@bindir@@}! Use the matching makefile variable
instead.
@item @samp{$(pkgdatadir)}
The example takes advantage of the variable @samp{$(pkgdatadir)}
provided by Automake; it is equivalent to @samp{$(datadir)/$(PACKAGE)}.
@item @samp{/}
Don't use @samp{/} in the Sed expressions that replace file names since
most likely the
variables you use, such as @samp{$(bindir)}, contain @samp{/}.
Use a shell metacharacter instead, such as @samp{|}.
@item special characters
File names, file name components, and the value of @code{VPATH} should
not contain shell metacharacters or white
space. @xref{Special Chars in Variables}.
@item dependency on @file{Makefile}
Since @code{edit} uses values that depend on the configuration specific
values (@code{prefix}, etc.)@: and not only on @code{VERSION} and so forth,
the output depends on @file{Makefile}, not @file{configure.ac}.
@item @samp{$@@}
The main rule is generic, and uses @samp{$@@} extensively to
avoid the need for multiple copies of the rule.
@item Separated dependencies and single suffix rules
You can't use them! The above snippet cannot be (portably) rewritten
as:
@example
autoconf autoheader: Makefile
@group
.in:
rm -f $@@ $@@.tmp
$(edit) $< >$@@.tmp
chmod +x $@@.tmp
mv $@@.tmp $@@
@end group
@end example
@xref{Single Suffix Rules}, for details.
@item @samp{$(srcdir)}
Be sure to specify the name of the source directory,
otherwise the package won't support separated builds.
@end table
For the more specific installation of Erlang libraries, the following variables
are defined:
@defvar ERLANG_INSTALL_LIB_DIR
@ovindex ERLANG_INSTALL_LIB_DIR
@acindex{ERLANG_SUBST_INSTALL_LIB_DIR}
The common parent directory of Erlang library installation directories.
This variable is set by calling the @code{AC_ERLANG_SUBST_INSTALL_LIB_DIR}
macro in @file{configure.ac}.
@end defvar
@defvar ERLANG_INSTALL_LIB_DIR_@var{library}
@ovindex ERLANG_INSTALL_LIB_DIR_@var{library}
@acindex{ERLANG_SUBST_INSTALL_LIB_SUBDIR}
The installation directory for Erlang library @var{library}.
This variable is set by using the
@samp{AC_ERLANG_SUBST_INSTALL_LIB_SUBDIR}
macro in @file{configure.ac}.
@end defvar
@xref{Erlang Libraries}, for details.
@node Changed Directory Variables
@subsection Changed Directory Variables
@cindex @file{datarootdir}
In Autoconf 2.60, the set of directory variables has changed, and the
defaults of some variables have been adjusted
(@pxref{Installation Directory Variables}) to changes in the
@acronym{GNU} Coding Standards. Notably, @file{datadir}, @file{infodir}, and
@file{mandir} are now expressed in terms of @file{datarootdir}. If you are
upgrading from an earlier Autoconf version, you may need to adjust your files
to ensure that the directory variables are substituted correctly
(@pxref{Defining Directories}), and that a definition of @file{datarootdir} is
in place. For example, in a @file{Makefile.in}, adding
@example
datarootdir = @@datarootdir@@
@end example
@noindent
is usually sufficient. If you use Automake to create @file{Makefile.in},
it will add this for you.
To help with the transition, Autoconf warns about files that seem to use
@code{datarootdir} without defining it. In some cases, it then expands
the value of @code{$datarootdir} in substitutions of the directory
variables. The following example shows such a warning:
@example
$ @kbd{cat configure.ac}
AC_INIT
AC_CONFIG_FILES([Makefile])
AC_OUTPUT
$ @kbd{cat Makefile.in}
prefix = @@prefix@@
datadir = @@datadir@@
$ @kbd{autoconf}
$ @kbd{configure}
configure: creating ./config.status
config.status: creating Makefile
config.status: WARNING:
Makefile.in seems to ignore the --datarootdir setting
$ @kbd{cat Makefile}
prefix = /usr/local
datadir = $@{prefix@}/share
@end example
Usually one can easily change the file to accommodate both older and newer
Autoconf releases:
@example
$ @kbd{cat Makefile.in}
prefix = @@prefix@@
datarootdir = @@datarootdir@@
datadir = @@datadir@@
$ @kbd{configure}
configure: creating ./config.status
config.status: creating Makefile
$ @kbd{cat Makefile}
prefix = /usr/local
datarootdir = $@{prefix@}/share
datadir = $@{datarootdir@}
@end example
@acindex{DATAROOTDIR_CHECKED}
In some cases, however, the checks may not be able to detect that a suitable
initialization of @code{datarootdir} is in place, or they may fail to detect
that such an initialization is necessary in the output file. If, after
auditing your package, there are still spurious @file{configure} warnings about
@code{datarootdir}, you may add the line
@example
AC_DEFUN([AC_DATAROOTDIR_CHECKED])
@end example
@noindent
to your @file{configure.ac} to disable the warnings. This is an exception
to the usual rule that you should not define a macro whose name begins with
@code{AC_} (@pxref{Macro Names}).
@node Build Directories
@subsection Build Directories
@cindex Build directories
@cindex Directories, build
You can support compiling a software package for several architectures
simultaneously from the same copy of the source code. The object files
for each architecture are kept in their own directory.
To support doing this, @command{make} uses the @code{VPATH} variable to
find the files that are in the source directory. @acronym{GNU} Make
can do this. Most other recent @command{make} programs can do this as
well, though they may have difficulties and it is often simpler to
recommend @acronym{GNU} @command{make} (@pxref{VPATH and Make}). Older
@command{make} programs do not support @code{VPATH}; when using them, the
source code must be in the same directory as the object files.
If you are using @acronym{GNU} Automake, the remaining details in this
section are already covered for you, based on the contents of your
@file{Makefile.am}. But if you are using Autoconf in isolation, then
supporting @code{VPATH} requires the following in your
@file{Makefile.in}:
@example
srcdir = @@srcdir@@
VPATH = @@srcdir@@
@end example
Do not set @code{VPATH} to the value of another variable (@pxref{Variables
listed in VPATH}.
@command{configure} substitutes the correct value for @code{srcdir} when
it produces @file{Makefile}.
Do not use the @command{make} variable @code{$<}, which expands to the
file name of the file in the source directory (found with @code{VPATH}),
except in implicit rules. (An implicit rule is one such as @samp{.c.o},
which tells how to create a @file{.o} file from a @file{.c} file.) Some
versions of @command{make} do not set @code{$<} in explicit rules; they
expand it to an empty value.
Instead, Make command lines should always refer to source
files by prefixing them with @samp{$(srcdir)/}. For example:
@example
time.info: time.texinfo
$(MAKEINFO) '$(srcdir)/time.texinfo'
@end example
@node Automatic Remaking
@subsection Automatic Remaking
@cindex Automatic remaking
@cindex Remaking automatically
You can put rules like the following in the top-level @file{Makefile.in}
for a package to automatically update the configuration information when
you change the configuration files. This example includes all of the
optional files, such as @file{aclocal.m4} and those related to
configuration header files. Omit from the @file{Makefile.in} rules for
any of these files that your package does not use.
The @samp{$(srcdir)/} prefix is included because of limitations in the
@code{VPATH} mechanism.
The @file{stamp-} files are necessary because the timestamps of
@file{config.h.in} and @file{config.h} are not changed if remaking
them does not change their contents. This feature avoids unnecessary
recompilation. You should include the file @file{stamp-h.in} in your
package's distribution, so that @command{make} considers
@file{config.h.in} up to date. Don't use @command{touch}
(@pxref{touch, , Limitations of Usual Tools}); instead, use
@command{echo} (using
@command{date} would cause needless differences, hence @acronym{CVS}
conflicts, etc.).
@example
@group
$(srcdir)/configure: configure.ac aclocal.m4
cd '$(srcdir)' && autoconf
# autoheader might not change config.h.in, so touch a stamp file.
$(srcdir)/config.h.in: stamp-h.in
$(srcdir)/stamp-h.in: configure.ac aclocal.m4
cd '$(srcdir)' && autoheader
echo timestamp > '$(srcdir)/stamp-h.in'
config.h: stamp-h
stamp-h: config.h.in config.status
./config.status
Makefile: Makefile.in config.status
./config.status
config.status: configure
./config.status --recheck
@end group
@end example
@noindent
(Be careful if you copy these lines directly into your makefile, as you
need to convert the indented lines to start with the tab character.)
In addition, you should use
@example
AC_CONFIG_FILES([stamp-h], [echo timestamp > stamp-h])
@end example
@noindent
so @file{config.status} ensures that @file{config.h} is considered up to
date. @xref{Output}, for more information about @code{AC_OUTPUT}.
@xref{config.status Invocation}, for more examples of handling
configuration-related dependencies.
@node Configuration Headers
@section Configuration Header Files
@cindex Configuration Header
@cindex @file{config.h}
When a package contains more than a few tests that define C preprocessor
symbols, the command lines to pass @option{-D} options to the compiler
can get quite long. This causes two problems. One is that the
@command{make} output is hard to visually scan for errors. More
seriously, the command lines can exceed the length limits of some
operating systems. As an alternative to passing @option{-D} options to
the compiler, @command{configure} scripts can create a C header file
containing @samp{#define} directives. The @code{AC_CONFIG_HEADERS}
macro selects this kind of output. Though it can be called anywhere
between @code{AC_INIT} and @code{AC_OUTPUT}, it is customary to call
it right after @code{AC_INIT}.
The package should @samp{#include} the configuration header file before
any other header files, to prevent inconsistencies in declarations (for
example, if it redefines @code{const}).
To provide for VPATH builds, remember to pass the C compiler a @option{-I.}
option (or @option{-I..}; whichever directory contains @file{config.h}).
Even if you use @samp{#include "config.h"}, the preprocessor searches only
the directory of the currently read file, i.e., the source directory, not
the build directory.
With the appropriate @option{-I} option, you can use
@samp{#include }. Actually, it's a good habit to use it,
because in the rare case when the source directory contains another
@file{config.h}, the build directory should be searched first.
@defmac AC_CONFIG_HEADERS (@var{header} @dots{}, @ovar{cmds}, @ovar{init-cmds})
@acindex{CONFIG_HEADERS}
@cvindex HAVE_CONFIG_H
This macro is one of the instantiating macros; see @ref{Configuration
Actions}. Make @code{AC_OUTPUT} create the file(s) in the
blank-or-newline-separated list @var{header} containing C preprocessor
@code{#define} statements, and replace @samp{@@DEFS@@} in generated
files with @option{-DHAVE_CONFIG_H} instead of the value of @code{DEFS}.
The usual name for @var{header} is @file{config.h}.
If @var{header} already exists and its contents are identical to what
@code{AC_OUTPUT} would put in it, it is left alone. Doing this allows
making some changes in the configuration without needlessly causing
object files that depend on the header file to be recompiled.
Usually the input file is named @file{@var{header}.in}; however, you can
override the input file name by appending to @var{header} a
colon-separated list of input files. For example, you might need to make
the input file name acceptable to @acronym{DOS} variants:
@example
AC_CONFIG_HEADERS([config.h:config.hin])
@end example
@end defmac
@defmac AH_HEADER
@ahindex{HEADER}
This macro is defined as the name of the first declared config header
and undefined if no config headers have been declared up to this point.
A third-party macro may, for example, require use of a config header
without invoking AC_CONFIG_HEADERS twice, like this:
@example
AC_CONFIG_COMMANDS_PRE(
[m4_ifndef([AH_HEADER], [AC_CONFIG_HEADERS([config.h])])])
@end example
@end defmac
@xref{Configuration Actions}, for more details on @var{header}.
@menu
* Header Templates:: Input for the configuration headers
* autoheader Invocation:: How to create configuration templates
* Autoheader Macros:: How to specify CPP templates
@end menu
@node Header Templates
@subsection Configuration Header Templates
@cindex Configuration Header Template
@cindex Header templates
@cindex @file{config.h.in}
Your distribution should contain a template file that looks as you want
the final header file to look, including comments, with @code{#undef}
statements which are used as hooks. For example, suppose your
@file{configure.ac} makes these calls:
@example
AC_CONFIG_HEADERS([conf.h])
AC_CHECK_HEADERS([unistd.h])
@end example
@noindent
Then you could have code like the following in @file{conf.h.in}.
The @file{conf.h} created by @command{configure} defines @samp{HAVE_UNISTD_H}
to 1, if and only if the system has @file{unistd.h}.
@example
@group
/* Define as 1 if you have unistd.h. */
#undef HAVE_UNISTD_H
@end group
@end example
The format of the template file is stricter than what the C preprocessor
is required to accept. A directive line should contain only whitespace,
@samp{#undef}, and @samp{HAVE_UNISTD_H}. The use of @samp{#define}
instead of @samp{#undef}, or of comments on the same line as
@samp{#undef}, is strongly discouraged. Each hook should only be listed
once. Other preprocessor lines, such as @samp{#ifdef} or
@samp{#include}, are copied verbatim from the template into the
generated header.
Since it is a tedious task to keep a template header up to date, you may
use @command{autoheader} to generate it, see @ref{autoheader Invocation}.
During the instantiation of the header, each @samp{#undef} line in the
template file for each symbol defined by @samp{AC_DEFINE} is changed to an
appropriate @samp{#define}. If the corresponding @samp{AC_DEFINE} has not
been executed during the @command{configure} run, the @samp{#undef} line is
commented out. (This is important, e.g., for @samp{_POSIX_SOURCE}:
on many systems, it can be implicitly defined by the compiler, and
undefining it in the header would then break compilation of subsequent
headers.)
Currently, @emph{all} remaining @samp{#undef} lines in the header
template are commented out, whether or not there was a corresponding
@samp{AC_DEFINE} for the macro name; but this behavior is not guaranteed
for future releases of Autoconf.
Generally speaking, since you should not use @samp{#define}, and you
cannot guarantee whether a @samp{#undef} directive in the header
template will be converted to a @samp{#define} or commented out in the
generated header file, the template file cannot be used for conditional
definition effects. Consequently, if you need to use the construct
@example
@group
#ifdef THIS
# define THAT
#endif
@end group
@end example
@noindent
you must place it outside of the template.
If you absolutely need to hook it to the config header itself, please put
the directives to a separate file, and @samp{#include} that file from the
config header template. If you are using @command{autoheader}, you would
probably use @samp{AH_BOTTOM} to append the @samp{#include} directive.
@node autoheader Invocation
@subsection Using @command{autoheader} to Create @file{config.h.in}
@cindex @command{autoheader}
The @command{autoheader} program can create a template file of C
@samp{#define} statements for @command{configure} to use.
It searches for the first invocation of @code{AC_CONFIG_HEADERS} in
@file{configure} sources to determine the name of the template.
(If the first call of @code{AC_CONFIG_HEADERS} specifies more than one
input file name, @command{autoheader} uses the first one.)
It is recommended that only one input file is used. If you want to append
a boilerplate code, it is preferable to use
@samp{AH_BOTTOM([#include ])}.
File @file{conf_post.h} is not processed during the configuration then,
which make things clearer. Analogically, @code{AH_TOP} can be used to
prepend a boilerplate code.
In order to do its job, @command{autoheader} needs you to document all
of the symbols that you might use. Typically this is done via an
@code{AC_DEFINE} or @code{AC_DEFINE_UNQUOTED} call whose first argument
is a literal symbol and whose third argument describes the symbol
(@pxref{Defining Symbols}). Alternatively, you can use
@code{AH_TEMPLATE} (@pxref{Autoheader Macros}), or you can supply a
suitable input file for a subsequent configuration header file.
Symbols defined by Autoconf's builtin tests are already documented properly;
you need to document only those that you
define yourself.
You might wonder why @command{autoheader} is needed: after all, why
would @command{configure} need to ``patch'' a @file{config.h.in} to
produce a @file{config.h} instead of just creating @file{config.h} from
scratch? Well, when everything rocks, the answer is just that we are
wasting our time maintaining @command{autoheader}: generating
@file{config.h} directly is all that is needed. When things go wrong,
however, you'll be thankful for the existence of @command{autoheader}.
The fact that the symbols are documented is important in order to
@emph{check} that @file{config.h} makes sense. The fact that there is a
well-defined list of symbols that should be defined (or not) is
also important for people who are porting packages to environments where
@command{configure} cannot be run: they just have to @emph{fill in the
blanks}.
But let's come back to the point: the invocation of @command{autoheader}@dots{}
If you give @command{autoheader} an argument, it uses that file instead
of @file{configure.ac} and writes the header file to the standard output
instead of to @file{config.h.in}. If you give @command{autoheader} an
argument of @option{-}, it reads the standard input instead of
@file{configure.ac} and writes the header file to the standard output.
@command{autoheader} accepts the following options:
@table @option
@item --help
@itemx -h
Print a summary of the command line options and exit.
@item --version
@itemx -V
Print the version number of Autoconf and exit.
@item --verbose
@itemx -v
Report processing steps.
@item --debug
@itemx -d
Don't remove the temporary files.
@item --force
@itemx -f
Remake the template file even if newer than its input files.
@item --include=@var{dir}
@itemx -I @var{dir}
Append @var{dir} to the include path. Multiple invocations accumulate.
@item --prepend-include=@var{dir}
@itemx -B @var{dir}
Prepend @var{dir} to the include path. Multiple invocations accumulate.
@item --warnings=@var{category}
@itemx -W @var{category}
@evindex WARNINGS
Report the warnings related to @var{category} (which can actually be a
comma separated list). Current categories include:
@table @samp
@item obsolete
report the uses of obsolete constructs
@item all
report all the warnings
@item none
report none
@item error
treats warnings as errors
@item no-@var{category}
disable warnings falling into @var{category}
@end table
@end table
@node Autoheader Macros
@subsection Autoheader Macros
@cindex Autoheader macros
@command{autoheader} scans @file{configure.ac} and figures out which C
preprocessor symbols it might define. It knows how to generate
templates for symbols defined by @code{AC_CHECK_HEADERS},
@code{AC_CHECK_FUNCS} etc., but if you @code{AC_DEFINE} any additional
symbol, you must define a template for it. If there are missing
templates, @command{autoheader} fails with an error message.
The template for a @var{symbol} is created
by @command{autoheader} from
the @var{description} argument to an @code{AC_DEFINE};
see @ref{Defining Symbols}.
For special needs, you can use the following macros.
@defmac AH_TEMPLATE (@var{key}, @var{description})
@ahindex{TEMPLATE}
Tell @command{autoheader} to generate a template for @var{key}. This macro
generates standard templates just like @code{AC_DEFINE} when a
@var{description} is given.
For example:
@example
AH_TEMPLATE([CRAY_STACKSEG_END],
[Define to one of _getb67, GETB67, getb67
for Cray-2 and Cray-YMP systems. This
function is required for alloca.c support
on those systems.])
@end example
@noindent
generates the following template, with the description properly
justified.
@example
/* Define to one of _getb67, GETB67, getb67 for Cray-2 and
Cray-YMP systems. This function is required for alloca.c
support on those systems. */
#undef CRAY_STACKSEG_END
@end example
@end defmac
@defmac AH_VERBATIM (@var{key}, @var{template})
@ahindex{VERBATIM}
Tell @command{autoheader} to include the @var{template} as-is in the header
template file. This @var{template} is associated with the @var{key},
which is used to sort all the different templates and guarantee their
uniqueness. It should be a symbol that can be defined via @code{AC_DEFINE}.
@end defmac
@defmac AH_TOP (@var{text})
@ahindex{TOP}
Include @var{text} at the top of the header template file.
@end defmac
@defmac AH_BOTTOM (@var{text})
@ahindex{BOTTOM}
Include @var{text} at the bottom of the header template file.
@end defmac
Please note that @var{text} gets included ``verbatim'' to the template file,
not to the resulting config header, so it can easily get mangled when the
template is processed. There is rarely a need for something other than
@example
AH_BOTTOM([#include ])
@end example
@node Configuration Commands
@section Running Arbitrary Configuration Commands
@cindex Configuration commands
@cindex Commands for configuration
You can execute arbitrary commands before, during, and after
@file{config.status} is run. The three following macros accumulate the
commands to run when they are called multiple times.
@code{AC_CONFIG_COMMANDS} replaces the obsolete macro
@code{AC_OUTPUT_COMMANDS}; see @ref{Obsolete Macros}, for details.
@anchor{AC_CONFIG_COMMANDS}
@defmac AC_CONFIG_COMMANDS (@var{tag}@dots{}, @ovar{cmds}, @ovar{init-cmds})
@acindex{CONFIG_COMMANDS}
Specify additional shell commands to run at the end of
@file{config.status}, and shell commands to initialize any variables
from @command{configure}. Associate the commands with @var{tag}.
Since typically the @var{cmds} create a file, @var{tag} should
naturally be the name of that file. If needed, the directory hosting
@var{tag} is created. This macro is one of the instantiating macros;
see @ref{Configuration Actions}.
Here is an unrealistic example:
@example
fubar=42
AC_CONFIG_COMMANDS([fubar],
[echo this is extra $fubar, and so on.],
[fubar=$fubar])
@end example
Here is a better one:
@example
AC_CONFIG_COMMANDS([timestamp], [date >timestamp])
@end example
@end defmac
The following two macros look similar, but in fact they are not of the same
breed: they are executed directly by @file{configure}, so you cannot use
@file{config.status} to rerun them.
@c Yet it is good to leave them here. The user sees them together and
@c decides which best fits their needs.
@defmac AC_CONFIG_COMMANDS_PRE (@var{cmds})
@acindex{CONFIG_COMMANDS_PRE}
Execute the @var{cmds} right before creating @file{config.status}.
This macro presents the last opportunity to call @code{AC_SUBST},
@code{AC_DEFINE}, or @code{AC_CONFIG_@var{ITEMS}} macros.
@end defmac
@defmac AC_CONFIG_COMMANDS_POST (@var{cmds})
@acindex{CONFIG_COMMANDS_POST}
Execute the @var{cmds} right after creating @file{config.status}.
@end defmac
@node Configuration Links
@section Creating Configuration Links
@cindex Configuration links
@cindex Links for configuration
You may find it convenient to create links whose destinations depend upon
results of tests. One can use @code{AC_CONFIG_COMMANDS} but the
creation of relative symbolic links can be delicate when the package is
built in a directory different from the source directory.
@anchor{AC_CONFIG_LINKS}
@defmac AC_CONFIG_LINKS (@var{dest}:@var{source}@dots{}, @ovar{cmds}, @
@ovar{init-cmds})
@acindex{CONFIG_LINKS}
@cindex Links
Make @code{AC_OUTPUT} link each of the existing files @var{source} to
the corresponding link name @var{dest}. Makes a symbolic link if
possible, otherwise a hard link if possible, otherwise a copy. The
@var{dest} and @var{source} names should be relative to the top level
source or build directory. This macro is one of the instantiating
macros; see @ref{Configuration Actions}.
For example, this call:
@example
AC_CONFIG_LINKS([host.h:config/$machine.h
object.h:config/$obj_format.h])
@end example
@noindent
creates in the current directory @file{host.h} as a link to
@file{@var{srcdir}/config/$machine.h}, and @file{object.h} as a
link to @file{@var{srcdir}/config/$obj_format.h}.
The tempting value @samp{.} for @var{dest} is invalid: it makes it
impossible for @samp{config.status} to guess the links to establish.
One can then run:
@example
./config.status host.h object.h
@end example
@noindent
to create the links.
@end defmac
@node Subdirectories
@section Configuring Other Packages in Subdirectories
@cindex Configure subdirectories
@cindex Subdirectory configure
In most situations, calling @code{AC_OUTPUT} is sufficient to produce
makefiles in subdirectories. However, @command{configure} scripts
that control more than one independent package can use
@code{AC_CONFIG_SUBDIRS} to run @command{configure} scripts for other
packages in subdirectories.
@defmac AC_CONFIG_SUBDIRS (@var{dir} @dots{})
@acindex{CONFIG_SUBDIRS}
@ovindex subdirs
Make @code{AC_OUTPUT} run @command{configure} in each subdirectory
@var{dir} in the given blank-or-newline-separated list. Each @var{dir} should
be a literal, i.e., please do not use:
@example
if test "x$package_foo_enabled" = xyes; then
$my_subdirs="$my_subdirs foo"
fi
AC_CONFIG_SUBDIRS([$my_subdirs])
@end example
@noindent
because this prevents @samp{./configure --help=recursive} from
displaying the options of the package @code{foo}. Instead, you should
write:
@example
if test "x$package_foo_enabled" = xyes; then
AC_CONFIG_SUBDIRS([foo])
fi
@end example
If a given @var{dir} is not found, an error is reported: if the
subdirectory is optional, write:
@example
if test -d "$srcdir/foo"; then
AC_CONFIG_SUBDIRS([foo])
fi
@end example
@c NB: Yes, below we mean configure.in, not configure.ac.
If a given @var{dir} contains @command{configure.gnu}, it is run instead
of @command{configure}. This is for packages that might use a
non-Autoconf script @command{Configure}, which can't be called through a
wrapper @command{configure} since it would be the same file on
case-insensitive file systems. Likewise, if a @var{dir} contains
@file{configure.in} but no @command{configure}, the Cygnus
@command{configure} script found by @code{AC_CONFIG_AUX_DIR} is used.
The subdirectory @command{configure} scripts are given the same command
line options that were given to this @command{configure} script, with minor
changes if needed, which include:
@itemize @minus
@item
adjusting a relative name for the cache file;
@item
adjusting a relative name for the source directory;
@item
propagating the current value of @code{$prefix}, including if it was
defaulted, and if the default values of the top level and of the subdirectory
@file{configure} differ.
@end itemize
This macro also sets the output variable @code{subdirs} to the list of
directories @samp{@var{dir} @dots{}}. Make rules can use
this variable to determine which subdirectories to recurse into.
This macro may be called multiple times.
@end defmac
@node Default Prefix
@section Default Prefix
@cindex Install prefix
@cindex Prefix for install
By default, @command{configure} sets the prefix for files it installs to
@file{/usr/local}. The user of @command{configure} can select a different
prefix using the @option{--prefix} and @option{--exec-prefix} options.
There are two ways to change the default: when creating
@command{configure}, and when running it.
Some software packages might want to install in a directory other than
@file{/usr/local} by default. To accomplish that, use the
@code{AC_PREFIX_DEFAULT} macro.
@defmac AC_PREFIX_DEFAULT (@var{prefix})
@acindex{PREFIX_DEFAULT}
Set the default installation prefix to @var{prefix} instead of
@file{/usr/local}.
@end defmac
It may be convenient for users to have @command{configure} guess the
installation prefix from the location of a related program that they
have already installed. If you wish to do that, you can call
@code{AC_PREFIX_PROGRAM}.
@anchor{AC_PREFIX_PROGRAM}
@defmac AC_PREFIX_PROGRAM (@var{program})
@acindex{PREFIX_PROGRAM}
If the user did not specify an installation prefix (using the
@option{--prefix} option), guess a value for it by looking for
@var{program} in @env{PATH}, the way the shell does. If @var{program}
is found, set the prefix to the parent of the directory containing
@var{program}, else default the prefix as described above
(@file{/usr/local} or @code{AC_PREFIX_DEFAULT}). For example, if
@var{program} is @code{gcc} and the @env{PATH} contains
@file{/usr/local/gnu/bin/gcc}, set the prefix to @file{/usr/local/gnu}.
@end defmac
@c ======================================================== Existing tests
@node Existing Tests
@chapter Existing Tests
These macros test for particular system features that packages might
need or want to use. If you need to test for a kind of feature that
none of these macros check for, you can probably do it by calling
primitive test macros with appropriate arguments (@pxref{Writing
Tests}).
These tests print messages telling the user which feature they're
checking for, and what they find. They cache their results for future
@command{configure} runs (@pxref{Caching Results}).
Some of these macros set output variables. @xref{Makefile
Substitutions}, for how to get their values. The phrase ``define
@var{name}'' is used below as a shorthand to mean ``define the C
preprocessor symbol @var{name} to the value 1''. @xref{Defining
Symbols}, for how to get those symbol definitions into your program.
@menu
* Common Behavior:: Macros' standard schemes
* Alternative Programs:: Selecting between alternative programs
* Files:: Checking for the existence of files
* Libraries:: Library archives that might be missing
* Library Functions:: C library functions that might be missing
* Header Files:: Header files that might be missing
* Declarations:: Declarations that may be missing
* Structures:: Structures or members that might be missing
* Types:: Types that might be missing
* Compilers and Preprocessors:: Checking for compiling programs
* System Services:: Operating system services
* Posix Variants:: Special kludges for specific Posix variants
* Erlang Libraries:: Checking for the existence of Erlang libraries
@end menu
@node Common Behavior
@section Common Behavior
@cindex Common autoconf behavior
Much effort has been expended to make Autoconf easy to learn. The most
obvious way to reach this goal is simply to enforce standard interfaces
and behaviors, avoiding exceptions as much as possible. Because of
history and inertia, unfortunately, there are still too many exceptions
in Autoconf; nevertheless, this section describes some of the common
rules.
@menu
* Standard Symbols:: Symbols defined by the macros
* Default Includes:: Includes used by the generic macros
@end menu
@node Standard Symbols
@subsection Standard Symbols
@cindex Standard symbols
All the generic macros that @code{AC_DEFINE} a symbol as a result of
their test transform their @var{argument} values to a standard alphabet.
First, @var{argument} is converted to upper case and any asterisks
(@samp{*}) are each converted to @samp{P}. Any remaining characters
that are not alphanumeric are converted to underscores.
For instance,
@example
AC_CHECK_TYPES([struct $Expensive*])
@end example
@noindent
defines the symbol @samp{HAVE_STRUCT__EXPENSIVEP} if the check
succeeds.
@node Default Includes
@subsection Default Includes
@cindex Default includes
@cindex Includes, default
Several tests depend upon a set of header files. Since these headers
are not universally available, tests actually have to provide a set of
protected includes, such as:
@example
@group
#ifdef TIME_WITH_SYS_TIME
# include
# include
#else
# ifdef HAVE_SYS_TIME_H
# include
# else
# include
# endif
#endif
@end group
@end example
@noindent
Unless you know exactly what you are doing, you should avoid using
unconditional includes, and check the existence of the headers you
include beforehand (@pxref{Header Files}).
Most generic macros use the following macro to provide the default set
of includes:
@defmac AC_INCLUDES_DEFAULT (@ovar{include-directives})
@acindex{INCLUDES_DEFAULT}
Expand to @var{include-directives} if defined, otherwise to:
@example
@group
#include
#ifdef HAVE_SYS_TYPES_H
# include
#endif
#ifdef HAVE_SYS_STAT_H
# include
#endif
#ifdef STDC_HEADERS
# include
# include
#else
# ifdef HAVE_STDLIB_H
# include
# endif
#endif
#ifdef HAVE_STRING_H
# if !defined STDC_HEADERS && defined HAVE_MEMORY_H
# include
# endif
# include
#endif
#ifdef HAVE_STRINGS_H
# include
#endif
#ifdef HAVE_INTTYPES_H
# include
#endif
#ifdef HAVE_STDINT_H
# include
#endif
#ifdef HAVE_UNISTD_H
# include
#endif
@end group
@end example
If the default includes are used, then check for the presence of these
headers and their compatibility, i.e., you don't need to run
@code{AC_HEADER_STDC}, nor check for @file{stdlib.h} etc.
These headers are checked for in the same order as they are included.
For instance, on some systems @file{string.h} and @file{strings.h} both
exist, but conflict. Then @code{HAVE_STRING_H} is defined, not
@code{HAVE_STRINGS_H}.
@end defmac
@node Alternative Programs
@section Alternative Programs
@cindex Programs, checking
These macros check for the presence or behavior of particular programs.
They are used to choose between several alternative programs and to
decide what to do once one has been chosen. If there is no macro
specifically defined to check for a program you need, and you don't need
to check for any special properties of it, then you can use one of the
general program-check macros.
@menu
* Particular Programs:: Special handling to find certain programs
* Generic Programs:: How to find other programs
@end menu
@node Particular Programs
@subsection Particular Program Checks
These macros check for particular programs---whether they exist, and
in some cases whether they support certain features.
@defmac AC_PROG_AWK
@acindex{PROG_AWK}
@ovindex AWK
Check for @code{gawk}, @code{mawk}, @code{nawk}, and @code{awk}, in that
order, and set output variable @code{AWK} to the first one that is found.
It tries @code{gawk} first because that is reported to be the
best implementation.
@end defmac
@defmac AC_PROG_GREP
@acindex{PROG_GREP}
@ovindex GREP
Look for the best available @code{grep} or @code{ggrep} that accepts the
longest input lines possible, and that supports multiple @option{-e} options.
Set the output variable @code{GREP} to whatever is chosen.
@xref{grep, , Limitations of Usual Tools}, for more information about
portability problems with the @command{grep} command family.
@end defmac
@defmac AC_PROG_EGREP
@acindex{PROG_EGREP}
@ovindex EGREP
Check whether @code{$GREP -E} works, or else look for the best available
@code{egrep} or @code{gegrep} that accepts the longest input lines possible.
Set the output variable @code{EGREP} to whatever is chosen.
@end defmac
@defmac AC_PROG_FGREP
@acindex{PROG_FGREP}
@ovindex FGREP
Check whether @code{$GREP -F} works, or else look for the best available
@code{fgrep} or @code{gfgrep} that accepts the longest input lines possible.
Set the output variable @code{FGREP} to whatever is chosen.
@end defmac
@defmac AC_PROG_INSTALL
@acindex{PROG_INSTALL}
@ovindex INSTALL
@ovindex INSTALL_PROGRAM
@ovindex INSTALL_DATA
@ovindex INSTALL_SCRIPT
Set output variable @code{INSTALL} to the name of a @acronym{BSD}-compatible
@command{install} program, if one is found in the current @env{PATH}.
Otherwise, set @code{INSTALL} to @samp{@var{dir}/install-sh -c},
checking the directories specified to @code{AC_CONFIG_AUX_DIR} (or its
default directories) to determine @var{dir} (@pxref{Output}). Also set
the variables @code{INSTALL_PROGRAM} and @code{INSTALL_SCRIPT} to
@samp{$@{INSTALL@}} and @code{INSTALL_DATA} to @samp{$@{INSTALL@} -m 644}.
@samp{@@INSTALL@@} is special, as its value may vary for different
configuration files.
This macro screens out various instances of @command{install} known not to
work. It prefers to find a C program rather than a shell script, for
speed. Instead of @file{install-sh}, it can also use @file{install.sh},
but that name is obsolete because some @command{make} programs have a rule
that creates @file{install} from it if there is no makefile. Further, this
macro requires @command{install} to be able to install multiple files into a
target directory in a single invocation.
Autoconf comes with a copy of @file{install-sh} that you can use. If
you use @code{AC_PROG_INSTALL}, you must include either
@file{install-sh} or @file{install.sh} in your distribution; otherwise
@command{configure} produces an error message saying it can't find
them---even if the system you're on has a good @command{install} program.
This check is a safety measure to prevent you from accidentally leaving
that file out, which would prevent your package from installing on
systems that don't have a @acronym{BSD}-compatible @command{install} program.
If you need to use your own installation program because it has features
not found in standard @command{install} programs, there is no reason to use
@code{AC_PROG_INSTALL}; just put the file name of your program into your
@file{Makefile.in} files.
@end defmac
@defmac AC_PROG_MKDIR_P
@acindex{PROG_MKDIR_P}
@ovindex MKDIR_P
Set output variable @code{MKDIR_P} to a program that ensures that for
each argument, a directory named by this argument exists, creating it
and its parent directories if needed, and without race conditions when
two instances of the program attempt to make the same directory at
nearly the same time.
This macro uses the @samp{mkdir -p} command if possible. Otherwise, it
falls back on invoking @command{install-sh} with the @option{-d} option,
so your package should
contain @file{install-sh} as described under @code{AC_PROG_INSTALL}.
An @file{install-sh} file that predates Autoconf 2.60 or Automake 1.10
is vulnerable to race conditions, so if you want to support parallel
installs from
different packages into the same directory you need to make sure you
have an up-to-date @file{install-sh}. In particular, be careful about
using @samp{autoreconf -if} if your Automake predates Automake 1.10.
This macro is related to the @code{AS_MKDIR_P} macro (@pxref{Programming
in M4sh}), but it sets an output variable intended for use in other
files, whereas @code{AS_MKDIR_P} is intended for use in scripts like
@command{configure}. Also, @code{AS_MKDIR_P} does not accept options,
but @code{MKDIR_P} supports the @option{-m} option, e.g., a makefile
might invoke @code{$(MKDIR_P) -m 0 dir} to create an inaccessible
directory, and conversely a makefile should use @code{$(MKDIR_P) --
$(FOO)} if @var{FOO} might yield a value that begins with @samp{-}.
Finally, @code{AS_MKDIR_P} does not check for race condition
vulnerability, whereas @code{AC_PROG_MKDIR_P} does.
@samp{@@MKDIR_P@@} is special, as its value may vary for different
configuration files.
@end defmac
@anchor{AC_PROG_LEX}
@defmac AC_PROG_LEX
@acindex{PROG_LEX}
@ovindex LEX
@ovindex LEXLIB
@cvindex YYTEXT_POINTER
@ovindex LEX_OUTPUT_ROOT
If @code{flex} is found, set output variable @code{LEX} to @samp{flex}
and @code{LEXLIB} to @option{-lfl}, if that library is in a standard
place. Otherwise set @code{LEX} to @samp{lex} and @code{LEXLIB} to
@option{-ll}, if found. If neither variant is available, set @code{LEX}
to @samp{:}; for packages that ship the generated @file{file.yy.c}
alongside the source @file{file.l}, this default allows users without a
lexer generator to still build the package even if the timestamp for
@file{file.l} is inadvertantly changed.
Define @code{YYTEXT_POINTER} if @code{yytext} defaults to @samp{char *} instead
of to @samp{char []}. Also set output variable @code{LEX_OUTPUT_ROOT} to
the base of the file name that the lexer generates; usually
@file{lex.yy}, but sometimes something else. These results vary
according to whether @code{lex} or @code{flex} is being used.
You are encouraged to use Flex in your sources, since it is both more
pleasant to use than plain Lex and the C source it produces is portable.
In order to ensure portability, however, you must either provide a
function @code{yywrap} or, if you don't use it (e.g., your scanner has
no @samp{#include}-like feature), simply include a @samp{%noyywrap}
statement in the scanner's source. Once this done, the scanner is
portable (unless @emph{you} felt free to use nonportable constructs) and
does not depend on any library. In this case, and in this case only, it
is suggested that you use this Autoconf snippet:
@example
AC_PROG_LEX
if test "x$LEX" != xflex; then
LEX="$SHELL $missing_dir/missing flex"
AC_SUBST([LEX_OUTPUT_ROOT], [lex.yy])
AC_SUBST([LEXLIB], [''])
fi
@end example
The shell script @command{missing} can be found in the Automake
distribution.
Remember that the user may have supplied an alternate location in
@env{LEX}, so if Flex is required, it is better to check that the user
provided something sufficient by parsing the output of @samp{$LEX
--version} than by simply relying on @code{test "x$LEX" = xflex}.
To ensure backward compatibility, Automake's @code{AM_PROG_LEX} invokes
(indirectly) this macro twice, which causes an annoying but benign
``@code{AC_PROG_LEX} invoked multiple times'' warning. Future versions
of Automake will fix this issue; meanwhile, just ignore this message.
As part of running the test, this macro may delete any file in the
configuration directory named @file{lex.yy.c} or @file{lexyy.c}.
@end defmac
@anchor{AC_PROG_LN_S}
@defmac AC_PROG_LN_S
@acindex{PROG_LN_S}
@ovindex LN_S
If @samp{ln -s} works on the current file system (the operating system
and file system support symbolic links), set the output variable
@code{LN_S} to @samp{ln -s}; otherwise, if @samp{ln} works, set
@code{LN_S} to @samp{ln}, and otherwise set it to @samp{cp -p}.
If you make a link in a directory other than the current directory, its
meaning depends on whether @samp{ln} or @samp{ln -s} is used. To safely
create links using @samp{$(LN_S)}, either find out which form is used
and adjust the arguments, or always invoke @code{ln} in the directory
where the link is to be created.
In other words, it does not work to do:
@example
$(LN_S) foo /x/bar
@end example
Instead, do:
@example
(cd /x && $(LN_S) foo bar)
@end example
@end defmac
@defmac AC_PROG_RANLIB
@acindex{PROG_RANLIB}
@ovindex RANLIB
Set output variable @code{RANLIB} to @samp{ranlib} if @code{ranlib}
is found, and otherwise to @samp{:} (do nothing).
@end defmac
@defmac AC_PROG_SED
@acindex{PROG_SED}
@ovindex SED
Set output variable @code{SED} to a Sed implementation that conforms to
Posix and does not have arbitrary length limits. Report an error if no
acceptable Sed is found. @xref{sed, , Limitations of Usual Tools}, for more
information about portability problems with Sed.
@end defmac
@defmac AC_PROG_YACC
@acindex{PROG_YACC}
@evindex YACC
@evindex YFLAGS
@ovindex YACC
If @code{bison} is found, set output variable @code{YACC} to @samp{bison
-y}. Otherwise, if @code{byacc} is found, set @code{YACC} to
@samp{byacc}. Otherwise set @code{YACC} to @samp{yacc}.
@end defmac
@node Generic Programs
@subsection Generic Program and File Checks
These macros are used to find programs not covered by the ``particular''
test macros. If you need to check the behavior of a program as well as
find out whether it is present, you have to write your own test for it
(@pxref{Writing Tests}). By default, these macros use the environment
variable @env{PATH}. If you need to check for a program that might not
be in the user's @env{PATH}, you can pass a modified path to use
instead, like this:
@example
AC_PATH_PROG([INETD], [inetd], [/usr/libexec/inetd],
[$PATH$PATH_SEPARATOR/usr/libexec$PATH_SEPARATOR]dnl
[/usr/sbin$PATH_SEPARATOR/usr/etc$PATH_SEPARATOR/etc])
@end example
You are strongly encouraged to declare the @var{variable} passed to
@code{AC_CHECK_PROG} etc.@: as precious, @xref{Setting Output Variables},
@code{AC_ARG_VAR}, for more details.
@anchor{AC_CHECK_PROG}
@defmac AC_CHECK_PROG (@var{variable}, @var{prog-to-check-for}, @
@var{value-if-found}, @ovar{value-if-not-found}, @dvar{path, $PATH}, @
@ovar{reject})
@acindex{CHECK_PROG}
Check whether program @var{prog-to-check-for} exists in @var{path}. If
it is found, set @var{variable} to @var{value-if-found}, otherwise to
@var{value-if-not-found}, if given. Always pass over @var{reject} (an
absolute file name) even if it is the first found in the search path; in
that case, set @var{variable} using the absolute file name of the
@var{prog-to-check-for} found that is not @var{reject}. If
@var{variable} was already set, do nothing. Calls @code{AC_SUBST} for
@var{variable}.
@end defmac
@anchor{AC_CHECK_PROGS}
@defmac AC_CHECK_PROGS (@var{variable}, @var{progs-to-check-for}, @
@ovar{value-if-not-found}, @dvar{path, $PATH})
@acindex{CHECK_PROGS}
Check for each program in the blank-separated list
@var{progs-to-check-for} existing in the @var{path}. If one is found, set
@var{variable} to the name of that program. Otherwise, continue
checking the next program in the list. If none of the programs in the
list are found, set @var{variable} to @var{value-if-not-found}; if
@var{value-if-not-found} is not specified, the value of @var{variable}
is not changed. Calls @code{AC_SUBST} for @var{variable}.
@end defmac
@defmac AC_CHECK_TARGET_TOOL (@var{variable}, @var{prog-to-check-for}, @
@ovar{value-if-not-found}, @dvar{path, $PATH})
@acindex{CHECK_TARGET_TOOL}
Like @code{AC_CHECK_PROG}, but first looks for @var{prog-to-check-for}
with a prefix of the target type as determined by
@code{AC_CANONICAL_TARGET}, followed by a dash (@pxref{Canonicalizing}).
If the tool cannot be found with a prefix, and if the build and target
types are equal, then it is also searched for without a prefix.
As noted in @ref{Specifying Target Triplets}, the
target is rarely specified, because most of the time it is the same
as the host: it is the type of system for which any compiler tool in
the package produces code. What this macro looks for is,
for example, @emph{a tool @r{(assembler, linker, etc.)}@: that the
compiler driver @r{(@command{gcc} for the @acronym{GNU} C Compiler)}
uses to produce objects, archives or executables}.
@end defmac
@defmac AC_CHECK_TOOL (@var{variable}, @var{prog-to-check-for}, @
@ovar{value-if-not-found}, @dvar{path, $PATH})
@acindex{CHECK_TOOL}
Like @code{AC_CHECK_PROG}, but first looks for @var{prog-to-check-for}
with a prefix of the host type as specified by @option{--host}, followed by a
dash. For example, if the user runs
@samp{configure --build=x86_64-gnu --host=i386-gnu}, then this call:
@example
AC_CHECK_TOOL([RANLIB], [ranlib], [:])
@end example
@noindent
sets @code{RANLIB} to @file{i386-gnu-ranlib} if that program exists in
@var{path}, or otherwise to @samp{ranlib} if that program exists in
@var{path}, or to @samp{:} if neither program exists.
When cross-compiling, this macro will issue a warning if no program
prefixed with the host type could be found.
For more information, see @ref{Specifying Target Triplets}.
@end defmac
@defmac AC_CHECK_TARGET_TOOLS (@var{variable}, @var{progs-to-check-for}, @
@ovar{value-if-not-found}, @dvar{path, $PATH})
@acindex{CHECK_TARGET_TOOLS}
Like @code{AC_CHECK_TARGET_TOOL}, each of the tools in the list
@var{progs-to-check-for} are checked with a prefix of the target type as
determined by @code{AC_CANONICAL_TARGET}, followed by a dash
(@pxref{Canonicalizing}). If none of the tools can be found with a
prefix, and if the build and target types are equal, then the first one
without a prefix is used. If a tool is found, set @var{variable} to
the name of that program. If none of the tools in the list are found,
set @var{variable} to @var{value-if-not-found}; if @var{value-if-not-found}
is not specified, the value of @var{variable} is not changed. Calls
@code{AC_SUBST} for @var{variable}.
@end defmac
@defmac AC_CHECK_TOOLS (@var{variable}, @var{progs-to-check-for}, @
@ovar{value-if-not-found}, @dvar{path, $PATH})
@acindex{CHECK_TOOLS}
Like @code{AC_CHECK_TOOL}, each of the tools in the list
@var{progs-to-check-for} are checked with a prefix of the host type as
determined by @code{AC_CANONICAL_HOST}, followed by a dash
(@pxref{Canonicalizing}). If none of the tools can be found with a
prefix, then the first one without a prefix is used. If a tool is found,
set @var{variable} to the name of that program. If none of the tools in
the list are found, set @var{variable} to @var{value-if-not-found}; if
@var{value-if-not-found} is not specified, the value of @var{variable}
is not changed. Calls @code{AC_SUBST} for @var{variable}.
When cross-compiling, this macro will issue a warning if no program
prefixed with the host type could be found.
For more information, see @ref{Specifying Target Triplets}.
@end defmac
@anchor{AC_PATH_PROG}
@defmac AC_PATH_PROG (@var{variable}, @var{prog-to-check-for}, @
@ovar{value-if-not-found}, @dvar{path, $PATH})
@acindex{PATH_PROG}
Like @code{AC_CHECK_PROG}, but set @var{variable} to the absolute
name of @var{prog-to-check-for} if found.
@end defmac
@anchor{AC_PATH_PROGS}
@defmac AC_PATH_PROGS (@var{variable}, @var{progs-to-check-for}, @
@ovar{value-if-not-found}, @dvar{path, $PATH})
@acindex{PATH_PROGS}
Like @code{AC_CHECK_PROGS}, but if any of @var{progs-to-check-for}
are found, set @var{variable} to the absolute name of the program
found.
@end defmac
@defmac AC_PATH_PROGS_FEATURE_CHECK (@var{variable}, @
@var{progs-to-check-for}, @var{feature-test}, @
@ovar{action-if-not-found}, @dvar{path, $PATH})
@acindex{PATH_PROGS_FEATURE_CHECK}
This macro was introduced in Autoconf 2.62. If @var{variable} is not
empty, then set the cache variable @code{$ac_cv_path_@var{variable}} to
its value. Otherwise, check for each program in the blank-separated
list @var{progs-to-check-for} existing in @var{path}. For each program
found, execute @var{feature-test} with @code{$ac_path_@var{variable}}
set to the absolute name of the candidate program. If no invocation of
@var{feature-test} sets the shell variable
@code{$ac_cv_path_@var{variable}}, then @var{action-if-not-found} is
executed. @var{feature-test} will be run even when
@code{ac_cv_path_@var{variable}} is set, to provide the ability to
choose a better candidate found later in @var{path}; to accept the
current setting and bypass all futher checks, @var{feature-test} can
execute @code{ac_path_@var{variable}_found=:}.
Note that this macro has some subtle differences from
@code{AC_CHECK_PROGS}. It is designed to be run inside
@code{AC_CACHE_VAL}, therefore, it should have no side effects. In
particular, @var{variable} is not set to the final value of
@code{ac_cv_path_@var{variable}}, nor is @code{AC_SUBST} automatically
run. Also, on failure, any action can be performed, whereas
@code{AC_CHECK_PROGS} only performs
@code{@var{variable}=@var{value-if-not-found}}.
Here is an example, similar to what Autoconf uses in its own configure
script. It will search for an implementation of @command{m4} that
supports the @code{indir} builtin, even if it goes by the name
@command{gm4} or is not the first implementation on @env{PATH}.
@example
AC_CACHE_CHECK([for m4 that supports indir], [ac_cv_path_M4],
[AC_PATH_PROGS_FEATURE_CHECK([M4], [m4 gm4],
[[m4out=`echo 'changequote([,])indir([divnum])' | $ac_path_M4`
test "x$m4out" = x0 \
&& ac_cv_path_M4=$ac_path_M4 ac_path_M4_found=:]],
[AC_MSG_ERROR([could not find m4 that supports indir])])])
AC_SUBST([M4], [$ac_cv_path_M4])
@end example
@end defmac
@defmac AC_PATH_TARGET_TOOL (@var{variable}, @var{prog-to-check-for}, @
@ovar{value-if-not-found}, @dvar{path, $PATH})
@acindex{PATH_TARGET_TOOL}
Like @code{AC_CHECK_TARGET_TOOL}, but set @var{variable} to the absolute
name of the program if it is found.
@end defmac
@defmac AC_PATH_TOOL (@var{variable}, @var{prog-to-check-for}, @
@ovar{value-if-not-found}, @dvar{path, $PATH})
@acindex{PATH_TOOL}
Like @code{AC_CHECK_TOOL}, but set @var{variable} to the absolute
name of the program if it is found.
When cross-compiling, this macro will issue a warning if no program
prefixed with the host type could be found.
For more information, see @ref{Specifying Target Triplets}.
@end defmac
@node Files
@section Files
@cindex File, checking
You might also need to check for the existence of files. Before using
these macros, ask yourself whether a runtime test might not be a better
solution. Be aware that, like most Autoconf macros, they test a feature
of the host machine, and therefore, they die when cross-compiling.
@defmac AC_CHECK_FILE (@var{file}, @ovar{action-if-found}, @
@ovar{action-if-not-found})
@acindex{CHECK_FILE}
Check whether file @var{file} exists on the native system. If it is
found, execute @var{action-if-found}, otherwise do
@var{action-if-not-found}, if given.
@end defmac
@defmac AC_CHECK_FILES (@var{files}, @ovar{action-if-found}, @
@ovar{action-if-not-found})
@acindex{CHECK_FILES}
Executes @code{AC_CHECK_FILE} once for each file listed in @var{files}.
Additionally, defines @samp{HAVE_@var{file}} (@pxref{Standard Symbols})
for each file found.
@end defmac
@node Libraries
@section Library Files
@cindex Library, checking
The following macros check for the presence of certain C, C++, or Fortran
library archive files.
@anchor{AC_CHECK_LIB}
@defmac AC_CHECK_LIB (@var{library}, @var{function}, @
@ovar{action-if-found}, @ovar{action-if-not-found}, @ovar{other-libraries})
@acindex{CHECK_LIB}
Test whether the library @var{library} is available by trying to link
a test program that calls function @var{function} with the library.
@var{function} should be a function provided by the library.
Use the base
name of the library; e.g., to check for @option{-lmp}, use @samp{mp} as
the @var{library} argument.
@var{action-if-found} is a list of shell commands to run if the link
with the library succeeds; @var{action-if-not-found} is a list of shell
commands to run if the link fails. If @var{action-if-found} is not
specified, the default action prepends @option{-l@var{library}} to
@code{LIBS} and defines @samp{HAVE_LIB@var{library}} (in all
capitals). This macro is intended to support building @code{LIBS} in
a right-to-left (least-dependent to most-dependent) fashion such that
library dependencies are satisfied as a natural side effect of
consecutive tests. Linkers are sensitive to library ordering
so the order in which @code{LIBS} is generated is important to reliable
detection of libraries.
If linking with @var{library} results in unresolved symbols that would
be resolved by linking with additional libraries, give those libraries
as the @var{other-libraries} argument, separated by spaces:
e.g., @option{-lXt -lX11}. Otherwise, this macro fails to detect
that @var{library} is present, because linking the test program
always fails with unresolved symbols. The @var{other-libraries} argument
should be limited to cases where it is desirable to test for one library
in the presence of another that is not already in @code{LIBS}.
@code{AC_CHECK_LIB} requires some care in usage, and should be avoided
in some common cases. Many standard functions like @code{gethostbyname}
appear in the standard C library on some hosts, and in special libraries
like @code{nsl} on other hosts. On some hosts the special libraries
contain variant implementations that you may not want to use. These
days it is normally better to use @code{AC_SEARCH_LIBS([gethostbyname],
[nsl])} instead of @code{AC_CHECK_LIB([nsl], [gethostbyname])}.
@end defmac
@anchor{AC_SEARCH_LIBS}
@defmac AC_SEARCH_LIBS (@var{function}, @var{search-libs}, @
@ovar{action-if-found}, @ovar{action-if-not-found}, @ovar{other-libraries})
@acindex{SEARCH_LIBS}
Search for a library defining @var{function} if it's not already
available. This equates to calling
@samp{AC_LINK_IFELSE([AC_LANG_CALL([], [@var{function}])])} first with
no libraries, then for each library listed in @var{search-libs}.
Add @option{-l@var{library}} to @code{LIBS} for the first library found
to contain @var{function}, and run @var{action-if-found}. If the
function is not found, run @var{action-if-not-found}.
If linking with @var{library} results in unresolved symbols that would
be resolved by linking with additional libraries, give those libraries
as the @var{other-libraries} argument, separated by spaces:
e.g., @option{-lXt -lX11}. Otherwise, this macro fails to detect
that @var{function} is present, because linking the test program
always fails with unresolved symbols.
@end defmac
@node Library Functions
@section Library Functions
The following macros check for particular C library functions.
If there is no macro specifically defined to check for a function you need,
and you don't need to check for any special properties of
it, then you can use one of the general function-check macros.
@menu
* Function Portability:: Pitfalls with usual functions
* Particular Functions:: Special handling to find certain functions
* Generic Functions:: How to find other functions
@end menu
@node Function Portability
@subsection Portability of C Functions
@cindex Portability of C functions
@cindex C function portability
Most usual functions can either be missing, or be buggy, or be limited
on some architectures. This section tries to make an inventory of these
portability issues. By definition, this list always requires
additions. Please help us keeping it as complete as possible.
@table @asis
@item @code{exit}
@c @fuindex exit
@prindex @code{exit}
On ancient hosts, @code{exit} returned @code{int}.
This is because @code{exit} predates @code{void}, and there was a long
tradition of it returning @code{int}.
On current hosts, the problem more likely is that @code{exit} is not
declared, due to C++ problems of some sort or another. For this reason
we suggest that test programs not invoke @code{exit}, but return from
@code{main} instead.
@item @code{free}
@c @fuindex free
@prindex @code{free}
The C standard says a call @code{free (NULL)} does nothing, but
some old systems don't support this (e.g., NextStep).
@item @code{isinf}
@itemx @code{isnan}
@c @fuindex isinf
@c @fuindex isnan
@prindex @code{isinf}
@prindex @code{isnan}
The C99 standard says that @code{isinf} and @code{isnan} are
macros. On some systems just macros are available
(e.g., @acronym{HP-UX} and Solaris 10), on
some systems both macros and functions (e.g., glibc 2.3.2), and on some
systems only functions (e.g., IRIX 6 and Solaris 9). In some cases
these functions are declared in nonstandard headers like
@code{} and defined in non-default libraries like
@option{-lm} or @option{-lsunmath}.
The C99 @code{isinf} and @code{isnan} macros work correctly with
@code{long double} arguments, but pre-C99 systems that use functions
typically assume @code{double} arguments. On such a system,
@code{isinf} incorrectly returns true for a finite @code{long double}
argument that is outside the range of @code{double}.
The best workaround for these issues is to use gnulib modules
@code{isinf} and @code{isnan} (@pxref{Gnulib}). But a lighter weight
solution involves code like the following.
@smallexample
#include
#ifndef isnan
# define isnan(x) \
(sizeof (x) == sizeof (long double) ? isnan_ld (x) \
: sizeof (x) == sizeof (double) ? isnan_d (x) \
: isnan_f (x))
static inline int isnan_f (float x) @{ return x != x; @}
static inline int isnan_d (double x) @{ return x != x; @}
static inline int isnan_ld (long double x) @{ return x != x; @}
#endif
#ifndef isinf
# define isinf(x) \
(sizeof (x) == sizeof (long double) ? isinf_ld (x) \
: sizeof (x) == sizeof (double) ? isinf_d (x) \
: isinf_f (x))
static inline int isinf_f (float x)
@{ return !isnan (x) && isnan (x - x); @}
static inline int isinf_d (double x)
@{ return !isnan (x) && isnan (x - x); @}
static inline int isinf_ld (long double x)
@{ return !isnan (x) && isnan (x - x); @}
#endif
@end smallexample
Use @code{AC_C_INLINE} (@pxref{C Compiler}) so that this code works on
compilers that lack the @code{inline} keyword. Some optimizing
compilers mishandle these definitions, but systems with that bug
typically have many other floating point corner-case compliance problems
anyway, so it's probably not worth worrying about.
@item @code{malloc}
@c @fuindex malloc
@prindex @code{malloc}
The C standard says a call @code{malloc (0)} is implementation
dependent. It can return either @code{NULL} or a new non-null pointer.
The latter is more common (e.g., the @acronym{GNU} C Library) but is by
no means universal. @code{AC_FUNC_MALLOC}
can be used to insist on non-@code{NULL} (@pxref{Particular Functions}).
@item @code{putenv}
@c @fuindex putenv
@prindex @code{putenv}
Posix prefers @code{setenv} to @code{putenv}; among other things,
@code{putenv} is not required of all Posix implementations, but
@code{setenv} is.
Posix specifies that @code{putenv} puts the given string directly in
@code{environ}, but some systems make a copy of it instead (e.g.,
glibc 2.0, or @acronym{BSD}). And when a copy is made, @code{unsetenv} might
not free it, causing a memory leak (e.g., Free@acronym{BSD} 4).
On some systems @code{putenv ("FOO")} removes @samp{FOO} from the
environment, but this is not standard usage and it dumps core
on some systems (e.g., AIX).
On MinGW, a call @code{putenv ("FOO=")} removes @samp{FOO} from the
environment, rather than inserting it with an empty value.
@item @code{realloc}
@c @fuindex realloc
@prindex @code{realloc}
The C standard says a call @code{realloc (NULL, size)} is equivalent
to @code{malloc (size)}, but some old systems don't support this (e.g.,
NextStep).
@item @code{signal} handler
@c @fuindex signal
@prindex @code{signal}
@prindex @code{sigaction}
Normally @code{signal} takes a handler function with a return type of
@code{void}, but some old systems required @code{int} instead. Any
actual @code{int} value returned is not used; this is only a
difference in the function prototype demanded.
All systems we know of in current use return @code{void}. The
@code{int} was to support K&R C, where of course @code{void} is not
available. The obsolete macro @code{AC_TYPE_SIGNAL}
(@pxref{AC_TYPE_SIGNAL}) can be used to establish the correct type in
all cases.
In most cases, it is more robust to use @code{sigaction} when it is
available, rather than @code{signal}.
@item @code{snprintf}
@c @fuindex snprintf
@prindex @code{snprintf}
@c @fuindex vsnprintf
@prindex @code{vsnprintf}
The C99 standard says that if the output array isn't big enough
and if no other errors occur, @code{snprintf} and @code{vsnprintf}
truncate the output and return the number of bytes that ought to have
been produced. Some older systems return the truncated length (e.g.,
@acronym{GNU} C Library 2.0.x or @sc{irix} 6.5), some a negative value
(e.g., earlier @acronym{GNU} C Library versions), and some the buffer
length without truncation (e.g., 32-bit Solaris 7). Also, some buggy
older systems ignore the length and overrun the buffer (e.g., 64-bit
Solaris 7).
@item @code{sprintf}
@c @fuindex sprintf
@prindex @code{sprintf}
@c @fuindex vsprintf
@prindex @code{vsprintf}
The C standard says @code{sprintf} and @code{vsprintf} return the
number of bytes written. On some ancient systems (SunOS 4 for
instance) they return the buffer pointer instead, but these no
longer need to be worried about.
@item @code{sscanf}
@c @fuindex sscanf
@prindex @code{sscanf}
On various old systems, e.g., @acronym{HP-UX} 9, @code{sscanf} requires
that its
input string be writable (though it doesn't actually change it). This
can be a problem when using @command{gcc} since it normally puts
constant strings in read-only memory (@pxref{Incompatibilities,
Incompatibilities of @acronym{GCC}, , gcc, Using and
Porting the @acronym{GNU} Compiler Collection}). Apparently in some cases even
having format strings read-only can be a problem.
@item @code{strerror_r}
@c @fuindex strerror_r
@prindex @code{strerror_r}
Posix specifies that @code{strerror_r} returns an @code{int}, but many
systems (e.g., @acronym{GNU} C Library version 2.2.4) provide a
different version returning a @code{char *}. @code{AC_FUNC_STRERROR_R}
can detect which is in use (@pxref{Particular Functions}).
@item @code{strnlen}
@c @fuindex strnlen
@prindex @code{strnlen}
@acronym{AIX} 4.3 provides a broken version which produces the
following results:
@example
strnlen ("foobar", 0) = 0
strnlen ("foobar", 1) = 3
strnlen ("foobar", 2) = 2
strnlen ("foobar", 3) = 1
strnlen ("foobar", 4) = 0
strnlen ("foobar", 5) = 6
strnlen ("foobar", 6) = 6
strnlen ("foobar", 7) = 6
strnlen ("foobar", 8) = 6
strnlen ("foobar", 9) = 6
@end example
@item @code{sysconf}
@c @fuindex sysconf
@prindex @code{sysconf}
@code{_SC_PAGESIZE} is standard, but some older systems (e.g., @acronym{HP-UX}
9) have @code{_SC_PAGE_SIZE} instead. This can be tested with
@code{#ifdef}.
@item @code{unlink}
@c @fuindex unlink
@prindex @code{unlink}
The Posix spec says that @code{unlink} causes the given file to be
removed only after there are no more open file handles for it. Some
non-Posix hosts have trouble with this requirement, though,
and some @acronym{DOS} variants even corrupt the file system.
@item @code{unsetenv}
@c @fuindex unsetenv
@prindex @code{unsetenv}
On MinGW, @code{unsetenv} is not available, but a variable @samp{FOO}
can be removed with a call @code{putenv ("FOO=")}, as described under
@code{putenv} above.
@item @code{va_copy}
@c @fuindex va_copy
@prindex @code{va_copy}
The C99 standard provides @code{va_copy} for copying
@code{va_list} variables. It may be available in older environments
too, though possibly as @code{__va_copy} (e.g., @command{gcc} in strict
pre-C99 mode). These can be tested with @code{#ifdef}. A fallback to
@code{memcpy (&dst, &src, sizeof (va_list))} gives maximum
portability.
@item @code{va_list}
@c @fuindex va_list
@prindex @code{va_list}
@code{va_list} is not necessarily just a pointer. It can be a
@code{struct} (e.g., @command{gcc} on Alpha), which means @code{NULL} is
not portable. Or it can be an array (e.g., @command{gcc} in some
PowerPC configurations), which means as a function parameter it can be
effectively call-by-reference and library routines might modify the
value back in the caller (e.g., @code{vsnprintf} in the @acronym{GNU} C Library
2.1).
@item Signed @code{>>}
Normally the C @code{>>} right shift of a signed type replicates the
high bit, giving a so-called ``arithmetic'' shift. But care should be
taken since Standard C doesn't require that behavior. On those
few processors without a native arithmetic shift (for instance Cray
vector systems) zero bits may be shifted in, the same as a shift of an
unsigned type.
@item Integer @code{/}
C divides signed integers by truncating their quotient toward zero,
yielding the same result as Fortran. However, before C99 the standard
allowed C implementations to take the floor or ceiling of the quotient
in some cases. Hardly any implementations took advantage of this
freedom, though, and it's probably not worth worrying about this issue
nowadays.
@end table
@node Particular Functions
@subsection Particular Function Checks
@cindex Function, checking
These macros check for particular C functions---whether they exist, and
in some cases how they respond when given certain arguments.
@anchor{AC_FUNC_ALLOCA}
@defmac AC_FUNC_ALLOCA
@acindex{FUNC_ALLOCA}
@cvindex C_ALLOCA
@cvindex HAVE_ALLOCA_H
@ovindex ALLOCA
@c @fuindex alloca
@prindex @code{alloca}
@hdrindex{alloca.h}
Check how to get @code{alloca}. Tries to get a builtin version by
checking for @file{alloca.h} or the predefined C preprocessor macros
@code{__GNUC__} and @code{_AIX}. If this macro finds @file{alloca.h},
it defines @code{HAVE_ALLOCA_H}.
If those attempts fail, it looks for the function in the standard C
library. If any of those methods succeed, it defines
@code{HAVE_ALLOCA}. Otherwise, it sets the output variable
@code{ALLOCA} to @samp{$@{LIBOBJDIR@}alloca.o} and defines
@code{C_ALLOCA} (so programs can periodically call @samp{alloca (0)} to
garbage collect). This variable is separate from @code{LIBOBJS} so
multiple programs can share the value of @code{ALLOCA} without needing
to create an actual library, in case only some of them use the code in
@code{LIBOBJS}. The @samp{$@{LIBOBJDIR@}} prefix serves the same
purpose as in @code{LIBOBJS} (@pxref{AC_LIBOBJ vs LIBOBJS}).
This macro does not try to get @code{alloca} from the System V R3
@file{libPW} or the System V R4 @file{libucb} because those libraries
contain some incompatible functions that cause trouble. Some versions
do not even contain @code{alloca} or contain a buggy version. If you
still want to use their @code{alloca}, use @code{ar} to extract
@file{alloca.o} from them instead of compiling @file{alloca.c}.
Source files that use @code{alloca} should start with a piece of code
like the following, to declare it properly.
@example
@group
#ifdef HAVE_ALLOCA_H
# include
#elif defined __GNUC__
# define alloca __builtin_alloca
#elif defined _AIX
# define alloca __alloca
#elif defined _MSC_VER
# include
# define alloca _alloca
#else
# include
# ifdef __cplusplus
extern "C"
# endif
void *alloca (size_t);
#endif
@end group
@end example
@end defmac
@defmac AC_FUNC_CHOWN
@acindex{FUNC_CHOWN}
@cvindex HAVE_CHOWN
@c @fuindex chown
@prindex @code{chown}
If the @code{chown} function is available and works (in particular, it
should accept @option{-1} for @code{uid} and @code{gid}), define
@code{HAVE_CHOWN}.
@end defmac
@anchor{AC_FUNC_CLOSEDIR_VOID}
@defmac AC_FUNC_CLOSEDIR_VOID
@acindex{FUNC_CLOSEDIR_VOID}
@cvindex CLOSEDIR_VOID
@c @fuindex closedir
@prindex @code{closedir}
If the @code{closedir} function does not return a meaningful value,
define @code{CLOSEDIR_VOID}. Otherwise, callers ought to check its
return value for an error indicator.
Currently this test is implemented by running a test program. When
cross compiling the pessimistic assumption that @code{closedir} does not
return a meaningful value is made.
This macro is obsolescent, as @code{closedir} returns a meaningful value
on current systems. New programs need not use this macro.
@end defmac
@defmac AC_FUNC_ERROR_AT_LINE
@acindex{FUNC_ERROR_AT_LINE}
@c @fuindex error_at_line
@prindex @code{error_at_line}
If the @code{error_at_line} function is not found, require an
@code{AC_LIBOBJ} replacement of @samp{error}.
@end defmac
@defmac AC_FUNC_FNMATCH
@acindex{FUNC_FNMATCH}
@c @fuindex fnmatch
@prindex @code{fnmatch}
If the @code{fnmatch} function conforms to Posix, define
@code{HAVE_FNMATCH}. Detect common implementation bugs, for example,
the bugs in Solaris 2.4.
Unlike the other specific
@code{AC_FUNC} macros, @code{AC_FUNC_FNMATCH} does not replace a
broken/missing @code{fnmatch}. This is for historical reasons.
See @code{AC_REPLACE_FNMATCH} below.
This macro is obsolescent. New programs should use Gnulib's
@code{fnmatch-posix} module. @xref{Gnulib}.
@end defmac
@defmac AC_FUNC_FNMATCH_GNU
@acindex{FUNC_FNMATCH_GNU}
@c @fuindex fnmatch
@prindex @code{fnmatch}
Behave like @code{AC_REPLACE_FNMATCH} (@emph{replace}) but also test
whether @code{fnmatch} supports @acronym{GNU} extensions. Detect common
implementation bugs, for example, the bugs in the @acronym{GNU} C
Library 2.1.
This macro is obsolescent. New programs should use Gnulib's
@code{fnmatch-gnu} module. @xref{Gnulib}.
@end defmac
@anchor{AC_FUNC_FORK}
@defmac AC_FUNC_FORK
@acindex{FUNC_FORK}
@cvindex HAVE_VFORK_H
@cvindex HAVE_WORKING_FORK
@cvindex HAVE_WORKING_VFORK
@cvindex vfork
@c @fuindex fork
@prindex @code{fork}
@c @fuindex vfork
@prindex @code{vfork}
@hdrindex{vfork.h}
This macro checks for the @code{fork} and @code{vfork} functions. If a
working @code{fork} is found, define @code{HAVE_WORKING_FORK}. This macro
checks whether @code{fork} is just a stub by trying to run it.
If @file{vfork.h} is found, define @code{HAVE_VFORK_H}. If a working
@code{vfork} is found, define @code{HAVE_WORKING_VFORK}. Otherwise,
define @code{vfork} to be @code{fork} for backward compatibility with
previous versions of @command{autoconf}. This macro checks for several known
errors in implementations of @code{vfork} and considers the system to not
have a working @code{vfork} if it detects any of them. It is not considered
to be an implementation error if a child's invocation of @code{signal}
modifies the parent's signal handler, since child processes rarely change
their signal handlers.
Since this macro defines @code{vfork} only for backward compatibility with
previous versions of @command{autoconf} you're encouraged to define it
yourself in new code:
@example
@group
#ifndef HAVE_WORKING_VFORK
# define vfork fork
#endif
@end group
@end example
@end defmac
@defmac AC_FUNC_FSEEKO
@acindex{FUNC_FSEEKO}
@cvindex _LARGEFILE_SOURCE
@cvindex HAVE_FSEEKO
@c @fuindex fseeko
@prindex @code{fseeko}
@c @fuindex ftello
@prindex @code{ftello}
If the @code{fseeko} function is available, define @code{HAVE_FSEEKO}.
Define @code{_LARGEFILE_SOURCE} if necessary to make the prototype
visible on some systems (e.g., glibc 2.2). Otherwise linkage problems
may occur when compiling with @code{AC_SYS_LARGEFILE} on
largefile-sensitive systems where @code{off_t} does not default to a
64bit entity. All systems with @code{fseeko} also supply @code{ftello}.
@end defmac
@defmac AC_FUNC_GETGROUPS
@acindex{FUNC_GETGROUPS}
@cvindex HAVE_GETGROUPS
@ovindex GETGROUPS_LIBS
@c @fuindex getgroups
@prindex @code{getgroups}
If the @code{getgroups} function is available and works (unlike on
Ultrix 4.3, where @samp{getgroups (0, 0)} always fails), define
@code{HAVE_GETGROUPS}. Set @code{GETGROUPS_LIBS} to any libraries
needed to get that function. This macro runs @code{AC_TYPE_GETGROUPS}.
@end defmac
@anchor{AC_FUNC_GETLOADAVG}
@defmac AC_FUNC_GETLOADAVG
@acindex{FUNC_GETLOADAVG}
@cvindex SVR4
@cvindex DGUX
@cvindex UMAX
@cvindex UMAX4_3
@cvindex HAVE_NLIST_H
@cvindex NLIST_NAME_UNION
@cvindex GETLOADAVG_PRIVILEGED
@cvindex NEED_SETGID
@cvindex C_GETLOADAVG
@ovindex LIBOBJS
@ovindex NEED_SETGID
@ovindex KMEM_GROUP
@ovindex GETLOADAVG_LIBS
@c @fuindex getloadavg
@prindex @code{getloadavg}
Check how to get the system load averages. To perform its tests
properly, this macro needs the file @file{getloadavg.c}; therefore, be
sure to set the @code{AC_LIBOBJ} replacement directory properly (see
@ref{Generic Functions}, @code{AC_CONFIG_LIBOBJ_DIR}).
If the system has the @code{getloadavg} function, define
@code{HAVE_GETLOADAVG}, and set @code{GETLOADAVG_LIBS} to any libraries
necessary to get that function. Also add @code{GETLOADAVG_LIBS} to
@code{LIBS}. Otherwise, require an @code{AC_LIBOBJ} replacement for
@samp{getloadavg} with source code in @file{@var{dir}/getloadavg.c}, and
possibly define several other C preprocessor macros and output
variables:
@enumerate
@item
Define @code{C_GETLOADAVG}.
@item
Define @code{SVR4}, @code{DGUX}, @code{UMAX}, or @code{UMAX4_3} if on
those systems.
@item
@hdrindex{nlist.h}
If @file{nlist.h} is found, define @code{HAVE_NLIST_H}.
@item
If @samp{struct nlist} has an @samp{n_un.n_name} member, define
@code{HAVE_STRUCT_NLIST_N_UN_N_NAME}. The obsolete symbol
@code{NLIST_NAME_UNION} is still defined, but do not depend upon it.
@item
Programs may need to be installed set-group-ID (or set-user-ID) for
@code{getloadavg} to work. In this case, define
@code{GETLOADAVG_PRIVILEGED}, set the output variable @code{NEED_SETGID}
to @samp{true} (and otherwise to @samp{false}), and set
@code{KMEM_GROUP} to the name of the group that should own the installed
program.
@end enumerate
The @code{AC_FUNC_GETLOADAVG} macro is obsolescent. New programs should
use Gnulib's @code{getloadavg} module. @xref{Gnulib}.
@end defmac
@anchor{AC_FUNC_GETMNTENT}
@defmac AC_FUNC_GETMNTENT
@acindex{FUNC_GETMNTENT}
@cvindex HAVE_GETMNTENT
@c @fuindex getmntent
@prindex @code{getmntent}
Check for @code{getmntent} in the standard C library, and then in the
@file{sun}, @file{seq}, and @file{gen} libraries, for @sc{unicos},
@sc{irix} 4, @sc{ptx}, and UnixWare, respectively. Then, if
@code{getmntent} is available, define @code{HAVE_GETMNTENT}.
@end defmac
@defmac AC_FUNC_GETPGRP
@acindex{FUNC_GETPGRP}
@cvindex GETPGRP_VOID
@c @fuindex getpgid
@c @fuindex getpgrp
@prindex @code{getpgid}
@prindex @code{getpgrp}
Define @code{GETPGRP_VOID} if it is an error to pass 0 to
@code{getpgrp}; this is the Posix behavior. On older @acronym{BSD}
systems, you must pass 0 to @code{getpgrp}, as it takes an argument and
behaves like Posix's @code{getpgid}.
@example
#ifdef GETPGRP_VOID
pid = getpgrp ();
#else
pid = getpgrp (0);
#endif
@end example
This macro does not check whether
@code{getpgrp} exists at all; if you need to work in that situation,
first call @code{AC_CHECK_FUNC} for @code{getpgrp}.
This macro is obsolescent, as current systems have a @code{getpgrp}
whose signature conforms to Posix. New programs need not use this macro.
@end defmac
@defmac AC_FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK
@acindex{FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK}
@cvindex LSTAT_FOLLOWS_SLASHED_SYMLINK
@c @fuindex lstat
@prindex @code{lstat}
If @file{link} is a symbolic link, then @code{lstat} should treat
@file{link/} the same as @file{link/.}. However, many older
@code{lstat} implementations incorrectly ignore trailing slashes.
It is safe to assume that if @code{lstat} incorrectly ignores
trailing slashes, then other symbolic-link-aware functions like
@code{unlink} also incorrectly ignore trailing slashes.
If @code{lstat} behaves properly, define
@code{LSTAT_FOLLOWS_SLASHED_SYMLINK}, otherwise require an
@code{AC_LIBOBJ} replacement of @code{lstat}.
@end defmac
@defmac AC_FUNC_MALLOC
@acindex{FUNC_MALLOC}
@cvindex HAVE_MALLOC
@cvindex malloc
@c @fuindex malloc
@prindex @code{malloc}
If the @code{malloc} function is compatible with the @acronym{GNU} C
library @code{malloc} (i.e., @samp{malloc (0)} returns a valid
pointer), define @code{HAVE_MALLOC} to 1. Otherwise define
@code{HAVE_MALLOC} to 0, ask for an @code{AC_LIBOBJ} replacement for
@samp{malloc}, and define @code{malloc} to @code{rpl_malloc} so that the
native @code{malloc} is not used in the main project.
Typically, the replacement file @file{malloc.c} should look like (note
the @samp{#undef malloc}):
@verbatim
#include
#undef malloc
#include
void *malloc ();
/* Allocate an N-byte block of memory from the heap.
If N is zero, allocate a 1-byte block. */
void *
rpl_malloc (size_t n)
{
if (n == 0)
n = 1;
return malloc (n);
}
@end verbatim
@end defmac
@defmac AC_FUNC_MEMCMP
@acindex{FUNC_MEMCMP}
@ovindex LIBOBJS
@c @fuindex memcmp
@prindex @code{memcmp}
If the @code{memcmp} function is not available, or does not work on
8-bit data (like the one on SunOS 4.1.3), or fails when comparing 16
bytes or more and with at least one buffer not starting on a 4-byte
boundary (such as the one on NeXT x86 OpenStep), require an
@code{AC_LIBOBJ} replacement for @samp{memcmp}.
This macro is obsolescent, as current systems have a working
@code{memcmp}. New programs need not use this macro.
@end defmac
@defmac AC_FUNC_MBRTOWC
@acindex{FUNC_MBRTOWC}
@cvindex HAVE_MBRTOWC
@c @fuindex mbrtowc
@prindex @code{mbrtowc}
Define @code{HAVE_MBRTOWC} to 1 if the function @code{mbrtowc} and the
type @code{mbstate_t} are properly declared.
@end defmac
@defmac AC_FUNC_MKTIME
@acindex{FUNC_MKTIME}
@ovindex LIBOBJS
@c @fuindex mktime
@prindex @code{mktime}
If the @code{mktime} function is not available, or does not work
correctly, require an @code{AC_LIBOBJ} replacement for @samp{mktime}.
For the purposes of this test, @code{mktime} should conform to the
Posix standard and should be the inverse of
@code{localtime}.
@end defmac
@anchor{AC_FUNC_MMAP}
@defmac AC_FUNC_MMAP
@acindex{FUNC_MMAP}
@cvindex HAVE_MMAP
@c @fuindex mmap
@prindex @code{mmap}
If the @code{mmap} function exists and works correctly, define
@code{HAVE_MMAP}. This checks only private fixed mapping of already-mapped
memory.
@end defmac
@defmac AC_FUNC_OBSTACK
@acindex{FUNC_OBSTACK}
@cvindex HAVE_OBSTACK
@cindex obstack
If the obstacks are found, define @code{HAVE_OBSTACK}, else require an
@code{AC_LIBOBJ} replacement for @samp{obstack}.
@end defmac
@defmac AC_FUNC_REALLOC
@acindex{FUNC_REALLOC}
@cvindex HAVE_REALLOC
@cvindex realloc
@c @fuindex realloc
@prindex @code{realloc}
If the @code{realloc} function is compatible with the @acronym{GNU} C
library @code{realloc} (i.e., @samp{realloc (NULL, 0)} returns a
valid pointer), define @code{HAVE_REALLOC} to 1. Otherwise define
@code{HAVE_REALLOC} to 0, ask for an @code{AC_LIBOBJ} replacement for
@samp{realloc}, and define @code{realloc} to @code{rpl_realloc} so that
the native @code{realloc} is not used in the main project. See
@code{AC_FUNC_MALLOC} for details.
@end defmac
@defmac AC_FUNC_SELECT_ARGTYPES
@acindex{FUNC_SELECT_ARGTYPES}
@cvindex SELECT_TYPE_ARG1
@cvindex SELECT_TYPE_ARG234
@cvindex SELECT_TYPE_ARG5
@c @fuindex select
@prindex @code{select}
Determines the correct type to be passed for each of the
@code{select} function's arguments, and defines those types
in @code{SELECT_TYPE_ARG1}, @code{SELECT_TYPE_ARG234}, and
@code{SELECT_TYPE_ARG5} respectively. @code{SELECT_TYPE_ARG1} defaults
to @samp{int}, @code{SELECT_TYPE_ARG234} defaults to @samp{int *},
and @code{SELECT_TYPE_ARG5} defaults to @samp{struct timeval *}.
This macro is obsolescent, as current systems have a @code{select} whose
signature conforms to Posix. New programs need not use this macro.
@end defmac
@defmac AC_FUNC_SETPGRP
@acindex{FUNC_SETPGRP}
@cvindex SETPGRP_VOID
@c @fuindex setpgrp
@prindex @code{setpgrp}
If @code{setpgrp} takes no argument (the Posix version), define
@code{SETPGRP_VOID}. Otherwise, it is the @acronym{BSD} version, which takes
two process IDs as arguments. This macro does not check whether
@code{setpgrp} exists at all; if you need to work in that situation,
first call @code{AC_CHECK_FUNC} for @code{setpgrp}.
This macro is obsolescent, as current systems have a @code{setpgrp}
whose signature conforms to Posix. New programs need not use this macro.
@end defmac
@defmac AC_FUNC_STAT
@defmacx AC_FUNC_LSTAT
@acindex{FUNC_STAT}
@acindex{FUNC_LSTAT}
@cvindex HAVE_STAT_EMPTY_STRING_BUG
@cvindex HAVE_LSTAT_EMPTY_STRING_BUG
@c @fuindex stat
@prindex @code{stat}
@c @fuindex lstat
@prindex @code{lstat}
Determine whether @code{stat} or @code{lstat} have the bug that it
succeeds when given the zero-length file name as argument. The @code{stat}
and @code{lstat} from SunOS 4.1.4 and the Hurd (as of 1998-11-01) do
this.
If it does, then define @code{HAVE_STAT_EMPTY_STRING_BUG} (or
@code{HAVE_LSTAT_EMPTY_STRING_BUG}) and ask for an @code{AC_LIBOBJ}
replacement of it.
These macros are obsolescent, as no current systems have the bug.
New programs need not use these macros.
@end defmac
@anchor{AC_FUNC_STRCOLL}
@defmac AC_FUNC_STRCOLL
@acindex{FUNC_STRCOLL}
@cvindex HAVE_STRCOLL
@c @fuindex strcoll
@prindex @code{strcoll}
If the @code{strcoll} function exists and works correctly, define
@code{HAVE_STRCOLL}. This does a bit more than
@samp{AC_CHECK_FUNCS(strcoll)}, because some systems have incorrect
definitions of @code{strcoll} that should not be used.
@end defmac
@defmac AC_FUNC_STRERROR_R
@acindex{FUNC_STRERROR_R}
@cvindex HAVE_STRERROR_R
@cvindex HAVE_DECL_STRERROR_R
@cvindex STRERROR_R_CHAR_P
@c @fuindex strerror_r
@prindex @code{strerror_r}
If @code{strerror_r} is available, define @code{HAVE_STRERROR_R}, and if
it is declared, define @code{HAVE_DECL_STRERROR_R}. If it returns a
@code{char *} message, define @code{STRERROR_R_CHAR_P}; otherwise it
returns an @code{int} error number. The Thread-Safe Functions option of
Posix requires @code{strerror_r} to return @code{int}, but
many systems (including, for example, version 2.2.4 of the @acronym{GNU} C
Library) return a @code{char *} value that is not necessarily equal to
the buffer argument.
@end defmac
@anchor{AC_FUNC_STRFTIME}
@defmac AC_FUNC_STRFTIME
@acindex{FUNC_STRFTIME}
@cvindex HAVE_STRFTIME
@c @fuindex strftime
@prindex @code{strftime}
Check for @code{strftime} in the @file{intl} library, for SCO Unix.
Then, if @code{strftime} is available, define @code{HAVE_STRFTIME}.
This macro is obsolescent, as no current systems require the @file{intl}
library for @code{strftime}. New programs need not use this macro.
@end defmac
@defmac AC_FUNC_STRTOD
@acindex{FUNC_STRTOD}
@ovindex POW_LIB
@c @fuindex strtod
@prindex @code{strtod}
If the @code{strtod} function does not exist or doesn't work correctly,
ask for an @code{AC_LIBOBJ} replacement of @samp{strtod}. In this case,
because @file{strtod.c} is likely to need @samp{pow}, set the output
variable @code{POW_LIB} to the extra library needed.
@end defmac
@defmac AC_FUNC_STRTOLD
@acindex{FUNC_STRTOLD}
@cvindex HAVE_STRTOLD
@prindex @code{strtold}
If the @code{strtold} function exists and conforms to C99, define
@code{HAVE_STRTOLD}.
@end defmac
@defmac AC_FUNC_STRNLEN
@acindex{FUNC_STRNLEN}
@cvindex HAVE_STRNLEN
@c @fuindex strnlen
@prindex @code{strnlen}
If the @code{strnlen} function is not available, or is buggy (like the one
from @acronym{AIX} 4.3), require an @code{AC_LIBOBJ} replacement for it.
@end defmac
@anchor{AC_FUNC_UTIME_NULL}
@defmac AC_FUNC_UTIME_NULL
@acindex{FUNC_UTIME_NULL}
@cvindex HAVE_UTIME_NULL
@c @fuindex utime
@prindex @code{utime}
If @samp{utime (@var{file}, NULL)} sets @var{file}'s timestamp to
the present, define @code{HAVE_UTIME_NULL}.
This macro is obsolescent, as all current systems have a @code{utime}
that behaves this way. New programs need not use this macro.
@end defmac
@anchor{AC_FUNC_VPRINTF}
@defmac AC_FUNC_VPRINTF
@acindex{FUNC_VPRINTF}
@cvindex HAVE_VPRINTF
@cvindex HAVE_DOPRNT
@c @fuindex vprintf
@prindex @code{vprintf}
@c @fuindex vsprintf
@prindex @code{vsprintf}
If @code{vprintf} is found, define @code{HAVE_VPRINTF}. Otherwise, if
@code{_doprnt} is found, define @code{HAVE_DOPRNT}. (If @code{vprintf}
is available, you may assume that @code{vfprintf} and @code{vsprintf}
are also available.)
This macro is obsolescent, as all current systems have @code{vprintf}.
New programs need not use this macro.
@end defmac
@defmac AC_REPLACE_FNMATCH
@acindex{REPLACE_FNMATCH}
@c @fuindex fnmatch
@prindex @code{fnmatch}
@hdrindex{fnmatch.h}
If the @code{fnmatch} function does not conform to Posix (see
@code{AC_FUNC_FNMATCH}), ask for its @code{AC_LIBOBJ} replacement.
The files @file{fnmatch.c}, @file{fnmatch_loop.c}, and @file{fnmatch_.h}
in the @code{AC_LIBOBJ} replacement directory are assumed to contain a
copy of the source code of @acronym{GNU} @code{fnmatch}. If necessary,
this source code is compiled as an @code{AC_LIBOBJ} replacement, and the
@file{fnmatch_.h} file is linked to @file{fnmatch.h} so that it can be
included in place of the system @code{}.
This macro is obsolescent, as it assumes the use of particular source
files. New programs should use Gnulib's @code{fnmatch-posix} module,
which provides this macro along with the source files. @xref{Gnulib}.
@end defmac
@node Generic Functions
@subsection Generic Function Checks
These macros are used to find functions not covered by the ``particular''
test macros. If the functions might be in libraries other than the
default C library, first call @code{AC_CHECK_LIB} for those libraries.
If you need to check the behavior of a function as well as find out
whether it is present, you have to write your own test for
it (@pxref{Writing Tests}).
@anchor{AC_CHECK_FUNC}
@defmac AC_CHECK_FUNC (@var{function}, @ovar{action-if-found}, @
@ovar{action-if-not-found})
@acindex{CHECK_FUNC}
If C function @var{function} is available, run shell commands
@var{action-if-found}, otherwise @var{action-if-not-found}. If you just
want to define a symbol if the function is available, consider using
@code{AC_CHECK_FUNCS} instead. This macro checks for functions with C
linkage even when @code{AC_LANG(C++)} has been called, since C is more
standardized than C++. (@pxref{Language Choice}, for more information
about selecting the language for checks.)
@end defmac
@anchor{AC_CHECK_FUNCS}
@defmac AC_CHECK_FUNCS (@var{function}@dots{}, @ovar{action-if-found}, @
@ovar{action-if-not-found})
@acindex{CHECK_FUNCS}
@cvindex HAVE_@var{function}
For each @var{function} enumerated in the blank-or-newline-separated argument
list, define @code{HAVE_@var{function}} (in all capitals) if it is available.
If @var{action-if-found} is given, it is additional shell code to
execute when one of the functions is found. You can give it a value of
@samp{break} to break out of the loop on the first match. If
@var{action-if-not-found} is given, it is executed when one of the
functions is not found.
@end defmac
@defmac AC_CHECK_FUNCS_ONCE (@var{function}@dots{})
@acindex{CHECK_FUNCS_ONCE}
@cvindex HAVE_@var{function}
For each @var{function} enumerated in the blank-or-newline-separated argument
list, define @code{HAVE_@var{function}} (in all capitals) if it is available.
This is a once-only variant of @code{AC_CHECK_FUNCS}. It generates the
checking code at most once, so that @command{configure} is smaller and
faster; but the checks cannot be conditionalized and are always done once,
early during the @command{configure} run.
@end defmac
@sp 1
Autoconf follows a philosophy that was formed over the years by those
who have struggled for portability: isolate the portability issues in
specific files, and then program as if you were in a Posix
environment. Some functions may be missing or unfixable, and your
package must be ready to replace them.
Suitable replacements for many such problem functions are available from
Gnulib (@pxref{Gnulib}).
@defmac AC_LIBOBJ (@var{function})
@acindex{LIBOBJ}
@ovindex LIBOBJS
Specify that @samp{@var{function}.c} must be included in the executables
to replace a missing or broken implementation of @var{function}.
Technically, it adds @samp{@var{function}.$ac_objext} to the output
variable @code{LIBOBJS} if it is not already in, and calls
@code{AC_LIBSOURCE} for @samp{@var{function}.c}. You should not
directly change @code{LIBOBJS}, since this is not traceable.
@end defmac
@defmac AC_LIBSOURCE (@var{file})
@acindex{LIBSOURCE}
Specify that @var{file} might be needed to compile the project. If you
need to know what files might be needed by a @file{configure.ac}, you
should trace @code{AC_LIBSOURCE}. @var{file} must be a literal.
This macro is called automatically from @code{AC_LIBOBJ}, but you must
call it explicitly if you pass a shell variable to @code{AC_LIBOBJ}. In
that case, since shell variables cannot be traced statically, you must
pass to @code{AC_LIBSOURCE} any possible files that the shell variable
might cause @code{AC_LIBOBJ} to need. For example, if you want to pass
a variable @code{$foo_or_bar} to @code{AC_LIBOBJ} that holds either
@code{"foo"} or @code{"bar"}, you should do:
@example
AC_LIBSOURCE([foo.c])
AC_LIBSOURCE([bar.c])
AC_LIBOBJ([$foo_or_bar])
@end example
@noindent
There is usually a way to avoid this, however, and you are encouraged to
simply call @code{AC_LIBOBJ} with literal arguments.
Note that this macro replaces the obsolete @code{AC_LIBOBJ_DECL}, with
slightly different semantics: the old macro took the function name,
e.g., @code{foo}, as its argument rather than the file name.
@end defmac
@defmac AC_LIBSOURCES (@var{files})
@acindex{LIBSOURCES}
Like @code{AC_LIBSOURCE}, but accepts one or more @var{files} in a
comma-separated M4 list. Thus, the above example might be rewritten:
@example
AC_LIBSOURCES([foo.c, bar.c])
AC_LIBOBJ([$foo_or_bar])
@end example
@end defmac
@defmac AC_CONFIG_LIBOBJ_DIR (@var{directory})
@acindex{CONFIG_LIBOBJ_DIR}
Specify that @code{AC_LIBOBJ} replacement files are to be found in
@var{directory}, a name relative to the top level of the
source tree. The replacement directory defaults to @file{.}, the top
level directory, and the most typical value is @file{lib}, corresponding
to @samp{AC_CONFIG_LIBOBJ_DIR([lib])}.
@command{configure} might need to know the replacement directory for the
following reasons: (i) some checks use the replacement files, (ii) some
macros bypass broken system headers by installing links to the
replacement headers (iii) when used in conjunction with Automake,
within each makefile, @var{directory} is used as a relative path
from @code{$(top_srcdir)} to each object named in @code{LIBOBJS} and
@code{LTLIBOBJS}, etc.
@end defmac
@sp 1
It is common to merely check for the existence of a function, and ask
for its @code{AC_LIBOBJ} replacement if missing. The following macro is
a convenient shorthand.
@defmac AC_REPLACE_FUNCS (@var{function}@dots{})
@acindex{REPLACE_FUNCS}
@cvindex HAVE_@var{function}
@ovindex LIBOBJS
Like @code{AC_CHECK_FUNCS}, but uses @samp{AC_LIBOBJ(@var{function})} as
@var{action-if-not-found}. You can declare your replacement function by
enclosing the prototype in @samp{#ifndef HAVE_@var{function}}. If the
system has the function, it probably declares it in a header file you
should be including, so you shouldn't redeclare it lest your declaration
conflict.
@end defmac
@node Header Files
@section Header Files
@cindex Header, checking
The following macros check for the presence of certain C header files.
If there is no macro specifically defined to check for a header file you need,
and you don't need to check for any special properties of
it, then you can use one of the general header-file check macros.
@menu
* Header Portability:: Collected knowledge on common headers
* Particular Headers:: Special handling to find certain headers
* Generic Headers:: How to find other headers
@end menu
@node Header Portability
@subsection Portability of Headers
@cindex Portability of headers
@cindex Header portability
This section tries to collect knowledge about common headers, and the
problems they cause. By definition, this list always requires
additions. Please help us keeping it as complete as possible.
@table @asis
@item @file{limits.h}
C99 says that @file{limits.h} defines @code{LLONG_MIN},
@code{LLONG_MAX}, and @code{ULLONG_MAX}, but many almost-C99
environments (e.g., default @acronym{GCC} 4.0.2 + glibc 2.4) do not
define them.
@item @file{inttypes.h} vs.@: @file{stdint.h}
@hdrindex{inttypes.h}
@hdrindex{stdint.h}
The C99 standard says that @file{inttypes.h} includes
@file{stdint.h}, so there's no need to include @file{stdint.h}
separately in a standard environment. Some implementations have
@file{inttypes.h} but not @file{stdint.h} (e.g., Solaris 7), but we don't
know of any implementation that has @file{stdint.h} but not
@file{inttypes.h}.
@item @file{linux/irda.h}
@hdrindex{linux/irda.h}
It requires @file{linux/types.h} and @file{sys/socket.h}.
@item @file{linux/random.h}
@hdrindex{linux/random.h}
It requires @file{linux/types.h}.
@item @file{net/if.h}
@hdrindex{net/if.h}
On Darwin, this file requires that @file{sys/socket.h} be included
beforehand. One should run:
@example
AC_CHECK_HEADERS([sys/socket.h])
AC_CHECK_HEADERS([net/if.h], [], [],
[#include
#ifdef STDC_HEADERS
# include
# include
#else
# ifdef HAVE_STDLIB_H
# include
# endif
#endif
#ifdef HAVE_SYS_SOCKET_H
# include
#endif
])
@end example
@item @file{netinet/if_ether.h}
@hdrindex{netinet/if_ether.h}
On Darwin, this file requires that @file{stdio.h} and
@file{sys/socket.h} be included beforehand. One should run:
@example
AC_CHECK_HEADERS([sys/socket.h])
AC_CHECK_HEADERS([netinet/if_ether.h], [], [],
[#include
#ifdef STDC_HEADERS
# include
# include
#else
# ifdef HAVE_STDLIB_H
# include
# endif
#endif
#ifdef HAVE_SYS_SOCKET_H
# include
#endif
])
@end example
@item @file{stdint.h}
See above, item @file{inttypes.h} vs.@: @file{stdint.h}.
@item @file{stdlib.h}
@hdrindex{stdlib.h}
On many systems (e.g., Darwin), @file{stdio.h} is a prerequisite.
@item @file{sys/mount.h}
@hdrindex{sys/mount.h}
On Free@acronym{BSD} 4.8 on ia32 and using gcc version 2.95.4,
@file{sys/params.h} is a prerequisite.
@item @file{sys/ptem.h}
@hdrindex{sys/ptem.h}
On Solaris 8, @file{sys/stream.h} is a prerequisite.
@item @file{sys/socket.h}
@hdrindex{sys/socket.h}
On Darwin, @file{stdlib.h} is a prerequisite.
@item @file{sys/ucred.h}
@hdrindex{sys/ucred.h}
On Tru64 5.1, @file{sys/types.h} is a prerequisite.
@item @file{X11/extensions/scrnsaver.h}
@hdrindex{X11/extensions/scrnsaver.h}
Using XFree86, this header requires @file{X11/Xlib.h}, which is probably
so required that you might not even consider looking for it.
@example
AC_CHECK_HEADERS([X11/extensions/scrnsaver.h], [], [],
[[#include
]])
@end example
@end table
@node Particular Headers
@subsection Particular Header Checks
These macros check for particular system header files---whether they
exist, and in some cases whether they declare certain symbols.
@defmac AC_HEADER_ASSERT
@acindex{HEADER_ASSERT}
@cvindex NDEBUG
@hdrindex{assert.h}
Check whether to enable assertions in the style of @file{assert.h}.
Assertions are enabled by default, but the user can override this by
invoking @command{configure} with the @option{--disable-assert} option.
@end defmac
@anchor{AC_HEADER_DIRENT}
@defmac AC_HEADER_DIRENT
@acindex{HEADER_DIRENT}
@cvindex HAVE_DIRENT_H
@cvindex HAVE_NDIR_H
@cvindex HAVE_SYS_DIR_H
@cvindex HAVE_SYS_NDIR_H
@hdrindex{dirent.h}
@hdrindex{sys/ndir.h}
@hdrindex{sys/dir.h}
@hdrindex{ndir.h}
Check for the following header files. For the first one that is
found and defines @samp{DIR}, define the listed C preprocessor macro:
@multitable {@file{sys/ndir.h}} {@code{HAVE_SYS_NDIR_H}}
@item @file{dirent.h} @tab @code{HAVE_DIRENT_H}
@item @file{sys/ndir.h} @tab @code{HAVE_SYS_NDIR_H}
@item @file{sys/dir.h} @tab @code{HAVE_SYS_DIR_H}
@item @file{ndir.h} @tab @code{HAVE_NDIR_H}
@end multitable
The directory-library declarations in your source code should look
something like the following:
@example
@group
#include
#ifdef HAVE_DIRENT_H
# include
# define NAMLEN(dirent) strlen ((dirent)->d_name)
#else
# define dirent direct
# define NAMLEN(dirent) ((dirent)->d_namlen)
# ifdef HAVE_SYS_NDIR_H
# include
# endif
# ifdef HAVE_SYS_DIR_H
# include
# endif
# ifdef HAVE_NDIR_H
# include
# endif
#endif
@end group
@end example
Using the above declarations, the program would declare variables to be
of type @code{struct dirent}, not @code{struct direct}, and would access
the length of a directory entry name by passing a pointer to a
@code{struct dirent} to the @code{NAMLEN} macro.
This macro also checks for the SCO Xenix @file{dir} and @file{x} libraries.
This macro is obsolescent, as all current systems with directory
libraries have @code{}. New programs need not use this macro.
Also see @code{AC_STRUCT_DIRENT_D_INO} and
@code{AC_STRUCT_DIRENT_D_TYPE} (@pxref{Particular Structures}).
@end defmac
@anchor{AC_HEADER_MAJOR}
@defmac AC_HEADER_MAJOR
@acindex{HEADER_MAJOR}
@cvindex MAJOR_IN_MKDEV
@cvindex MAJOR_IN_SYSMACROS
@hdrindex{sys/mkdev.h}
@hdrindex{sys/sysmacros.h}
If @file{sys/types.h} does not define @code{major}, @code{minor}, and
@code{makedev}, but @file{sys/mkdev.h} does, define
@code{MAJOR_IN_MKDEV}; otherwise, if @file{sys/sysmacros.h} does, define
@code{MAJOR_IN_SYSMACROS}.
@end defmac
@defmac AC_HEADER_RESOLV
@acindex{HEADER_RESOLV}
@cvindex HAVE_RESOLV_H
@hdrindex{resolv.h}
Checks for header @file{resolv.h}, checking for prerequisites first.
To properly use @file{resolv.h}, your code should contain something like
the following:
@verbatim
#ifdef HAVE_SYS_TYPES_H
# include
#endif
#ifdef HAVE_NETINET_IN_H
# include /* inet_ functions / structs */
#endif
#ifdef HAVE_ARPA_NAMESER_H
# include /* DNS HEADER struct */
#endif
#ifdef HAVE_NETDB_H
# include
#endif
#include
@end verbatim
@end defmac
@anchor{AC_HEADER_STAT}
@defmac AC_HEADER_STAT
@acindex{HEADER_STAT}
@cvindex STAT_MACROS_BROKEN
@hdrindex{sys/stat.h}
If the macros @code{S_ISDIR}, @code{S_ISREG}, etc.@: defined in
@file{sys/stat.h} do not work properly (returning false positives),
define @code{STAT_MACROS_BROKEN}. This is the case on Tektronix UTekV,
Amdahl UTS and Motorola System V/88.
This macro is obsolescent, as no current systems have the bug.
New programs need not use this macro.
@end defmac
@defmac AC_HEADER_STDBOOL
@acindex{HEADER_STDBOOL}
@cvindex HAVE_STDBOOL_H
@cvindex HAVE__BOOL
@hdrindex{stdbool.h}
@hdrindex{system.h}
If @file{stdbool.h} exists and conforms to C99, define
@code{HAVE_STDBOOL_H} to 1; if the type @code{_Bool} is defined, define
@code{HAVE__BOOL} to 1. To fulfill the C99 requirements, your
@file{system.h} could contain the following code:
@verbatim
#ifdef HAVE_STDBOOL_H
# include
#else
# ifndef HAVE__BOOL
# ifdef __cplusplus
typedef bool _Bool;
# else
# define _Bool signed char
# endif
# endif
# define bool _Bool
# define false 0
# define true 1
# define __bool_true_false_are_defined 1
#endif
@end verbatim
Alternatively you can use the @samp{stdbool} package of Gnulib
(@pxref{Gnulib}); it packages the above code into a replacement header
and contains a few other bells and whistles.
@end defmac
@anchor{AC_HEADER_STDC}
@defmac AC_HEADER_STDC
@acindex{HEADER_STDC}
@cvindex STDC_HEADERS
@hdrindex{stdlib.h}
@hdrindex{stdarg.h}
@hdrindex{string.h}
@hdrindex{float.h}
@hdrindex{ctype.h}
Define @code{STDC_HEADERS} if the system has C header files
conforming to @acronym{ANSI} C89 (@acronym{ISO} C90).
Specifically, this macro checks for @file{stdlib.h}, @file{stdarg.h},
@file{string.h}, and @file{float.h}; if the system has those, it
probably has the rest of the C89 header files. This macro also
checks whether @file{string.h} declares @code{memchr} (and thus
presumably the other @code{mem} functions), whether @file{stdlib.h}
declare @code{free} (and thus presumably @code{malloc} and other related
functions), and whether the @file{ctype.h} macros work on characters
with the high bit set, as the C standard requires.
If you use this macro, your code can refer to @code{STDC_HEADERS} to
determine whether the system has conforming header files (and probably C
library functions).
This macro is obsolescent, as current systems have conforming header
files. New programs need not use this macro.
@hdrindex{string.h}
@hdrindex{strings.h}
Nowadays @file{string.h} is part of the C standard and declares functions like
@code{strcpy}, and @file{strings.h} is standardized by Posix and declares
@acronym{BSD} functions like @code{bcopy}; but
historically, string functions were a major sticking point in this area.
If you still want to worry about portability to ancient systems without
standard headers, there is so much variation
that it is probably easier to declare the functions you use than to
figure out exactly what the system header files declare. Some ancient systems
contained a mix of functions from the C standard and from @acronym{BSD};
some were mostly standard but lacked @samp{memmove}; some defined the
@acronym{BSD} functions as macros in @file{string.h} or
@file{strings.h}; some had only the @acronym{BSD} functions but
@file{string.h}; some declared the memory functions in @file{memory.h},
some in @file{string.h}; etc. It is probably sufficient to check for
one string function and one memory function; if the library had the
standard versions of those then it probably had most of the others.
If you put the following in @file{configure.ac}:
@example
# This example is obsolescent.
# Nowadays you can omit these macro calls.
AC_HEADER_STDC
AC_CHECK_FUNCS([strchr memcpy])
@end example
@noindent
then, in your code, you can use declarations like this:
@example
@group
/* This example is obsolescent.
Nowadays you can just #include . */
#ifdef STDC_HEADERS
# include
#else
# ifndef HAVE_STRCHR
# define strchr index
# define strrchr rindex
# endif
char *strchr (), *strrchr ();
# ifndef HAVE_MEMCPY
# define memcpy(d, s, n) bcopy ((s), (d), (n))
# define memmove(d, s, n) bcopy ((s), (d), (n))
# endif
#endif
@end group
@end example
@noindent
If you use a function like @code{memchr}, @code{memset}, @code{strtok},
or @code{strspn}, which have no @acronym{BSD} equivalent, then macros don't
suffice to port to ancient hosts; you must provide an implementation of
each function. An easy
way to incorporate your implementations only when needed (since the ones
in system C libraries may be hand optimized) is to, taking @code{memchr}
for example, put it in @file{memchr.c} and use
@samp{AC_REPLACE_FUNCS([memchr])}.
@end defmac
@defmac AC_HEADER_SYS_WAIT
@acindex{HEADER_SYS_WAIT}
@cvindex HAVE_SYS_WAIT_H
@hdrindex{sys/wait.h}
If @file{sys/wait.h} exists and is compatible with Posix, define
@code{HAVE_SYS_WAIT_H}. Incompatibility can occur if @file{sys/wait.h}
does not exist, or if it uses the old @acronym{BSD} @code{union wait} instead
of @code{int} to store a status value. If @file{sys/wait.h} is not
Posix compatible, then instead of including it, define the
Posix macros with their usual interpretations. Here is an
example:
@example
@group
#include
#ifdef HAVE_SYS_WAIT_H
# include
#endif
#ifndef WEXITSTATUS
# define WEXITSTATUS(stat_val) ((unsigned int) (stat_val) >> 8)
#endif
#ifndef WIFEXITED
# define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
#endif
@end group
@end example
@noindent
This macro is obsolescent, as current systems are compatible with Posix.
New programs need not use this macro.
@end defmac
@cvindex _POSIX_VERSION
@hdrindex{unistd.h}
@code{_POSIX_VERSION} is defined when @file{unistd.h} is included on
Posix systems. If there is no @file{unistd.h}, it is definitely
not a Posix system. However, some non-Posix systems do
have @file{unistd.h}.
The way to check whether the system supports Posix is:
@example
@group
#ifdef HAVE_UNISTD_H
# include
# include
#endif
#ifdef _POSIX_VERSION
/* Code for Posix systems. */
#endif
@end group
@end example
@anchor{AC_HEADER_TIME}
@defmac AC_HEADER_TIME
@acindex{HEADER_TIME}
@cvindex TIME_WITH_SYS_TIME
@hdrindex{time.h}
@hdrindex{sys/time.h}
If a program may include both @file{time.h} and @file{sys/time.h},
define @code{TIME_WITH_SYS_TIME}. On some ancient systems,
@file{sys/time.h} included @file{time.h}, but @file{time.h} was not
protected against multiple inclusion, so programs could not explicitly
include both files. This macro is useful in programs that use, for
example, @code{struct timeval} as well as
@code{struct tm}. It is best used in conjunction with
@code{HAVE_SYS_TIME_H}, which can be checked for using
@code{AC_CHECK_HEADERS([sys/time.h])}.
@example
@group
#ifdef TIME_WITH_SYS_TIME
# include
# include
#else
# ifdef HAVE_SYS_TIME_H
# include
# else
# include
# endif
#endif
@end group
@end example
@noindent
This macro is obsolescent, as current systems can include both files
when they exist. New programs need not use this macro.
@end defmac
@defmac AC_HEADER_TIOCGWINSZ
@acindex{HEADER_TIOCGWINSZ}
@cvindex GWINSZ_IN_SYS_IOCTL
@hdrindex{sys/ioctl.h}
@hdrindex{termios.h}
@c FIXME: I need clarifications from Jim.
If the use of @code{TIOCGWINSZ} requires @file{}, then
define @code{GWINSZ_IN_SYS_IOCTL}. Otherwise @code{TIOCGWINSZ} can be
found in @file{}.
Use:
@example
@group
#ifdef HAVE_TERMIOS_H
# include
#endif
#ifdef GWINSZ_IN_SYS_IOCTL
# include
#endif
@end group
@end example
@end defmac
@node Generic Headers
@subsection Generic Header Checks
These macros are used to find system header files not covered by the
``particular'' test macros. If you need to check the contents of a header
as well as find out whether it is present, you have to write your own
test for it (@pxref{Writing Tests}).
@anchor{AC_CHECK_HEADER}
@defmac AC_CHECK_HEADER (@var{header-file}, @ovar{action-if-found}, @
@ovar{action-if-not-found}, @ovar{includes})
@acindex{CHECK_HEADER}
If the system header file @var{header-file} is compilable, execute shell
commands @var{action-if-found}, otherwise execute
@var{action-if-not-found}. If you just want to define a symbol if the
header file is available, consider using @code{AC_CHECK_HEADERS}
instead.
@var{includes} is decoded to determine the appropriate include
directives. If omitted or empty, @file{configure} will check for both header
existence (with the preprocessor) and usability (with the compiler),
using @code{AC_INCLUDES_DEFAULT} for the compile test. If
there is a discrepancy between the results, a warning is issued to the
user, and the compiler results are favored (@pxref{Present But
Cannot Be Compiled}). In general, favoring the compiler results means
that a header will be treated as not found even though the file exists,
because you did not provide enough prerequisites.
Providing a non-empty @var{includes} argument allows the code to provide
any prerequisites prior to including the header under test; it is common
to use the argument @code{AC_INCLUDES_DEFAULT} (@pxref{Default
Includes}). With an explicit fourth argument, no preprocessor test is
needed. As a special case, an @var{includes} of exactly @samp{-}
triggers the older preprocessor check, which merely determines existence
of the file in the preprocessor search path; this should only be used as
a last resort (it is safer to determine the actual prerequisites and
perform a compiler check, or else use @code{AC_PREPROC_IFELSE} to make
it obvious that only a preprocessor check is desired).
@end defmac
@anchor{AC_CHECK_HEADERS}
@defmac AC_CHECK_HEADERS (@var{header-file}@dots{}, @
@ovar{action-if-found}, @ovar{action-if-not-found}, @
@ovar{includes})
@acindex{CHECK_HEADERS}
@cvindex HAVE_@var{header}
For each given system header file @var{header-file} in the
blank-separated argument list that exists, define
@code{HAVE_@var{header-file}} (in all capitals). If @var{action-if-found}
is given, it is additional shell code to execute when one of the header
files is found. You can give it a value of @samp{break} to break out of
the loop on the first match. If @var{action-if-not-found} is given, it
is executed when one of the header files is not found.
@var{includes} is interpreted as in @code{AC_CHECK_HEADER}, in order to
choose the set of preprocessor directives supplied before the header
under test.
@end defmac
Previous versions of Autoconf merely checked whether the header was
accepted by the preprocessor. This was changed because the old test was
inappropriate for typical uses. Headers are typically used to compile,
not merely to preprocess, and the old behavior sometimes accepted
headers that clashed at compile-time (@pxref{Present But Cannot Be
Compiled}). If you need to check whether a header is preprocessable,
you can use @code{AC_PREPROC_IFELSE} (@pxref{Running the Preprocessor}).
Actually requiring a header to compile improves the robustness of the
test, but it also requires
that you make sure that headers that must be included before the
@var{header-file} be part of the @var{includes}, (@pxref{Default
Includes}). If looking for @file{bar.h}, which requires that
@file{foo.h} be included before if it exists, we suggest the following
scheme:
@verbatim
AC_CHECK_HEADERS([foo.h])
AC_CHECK_HEADERS([bar.h], [], [],
[#ifdef HAVE_FOO_H
# include
#endif
])
@end verbatim
The following variant generates smaller, faster @command{configure}
files if you do not need the full power of @code{AC_CHECK_HEADERS}.
@defmac AC_CHECK_HEADERS_ONCE (@var{header-file}@dots{})
@acindex{CHECK_HEADERS_ONCE}
@cvindex HAVE_@var{header}
For each given system header file @var{header-file} in the
blank-separated argument list that exists, define
@code{HAVE_@var{header-file}} (in all capitals).
This is a once-only variant of @code{AC_CHECK_HEADERS}. It generates the
checking code at most once, so that @command{configure} is smaller and
faster; but the checks cannot be conditionalized and are always done once,
early during the @command{configure} run. Thus, this macro is only safe
for checking headers that do not have prerequisites beyond what
@code{AC_INCLUDES_DEFAULT} provides.
@end defmac
@node Declarations
@section Declarations
@cindex Declaration, checking
The following macros check for the declaration of variables and
functions. If there is no macro specifically defined to check for a
symbol you need, then you can use the general macros (@pxref{Generic
Declarations}) or, for more complex tests, you may use
@code{AC_COMPILE_IFELSE} (@pxref{Running the Compiler}).
@menu
* Particular Declarations:: Macros to check for certain declarations
* Generic Declarations:: How to find other declarations
@end menu
@node Particular Declarations
@subsection Particular Declaration Checks
There are no specific macros for declarations.
@node Generic Declarations
@subsection Generic Declaration Checks
These macros are used to find declarations not covered by the ``particular''
test macros.
@defmac AC_CHECK_DECL (@var{symbol}, @ovar{action-if-found}, @
@ovar{action-if-not-found}, @dvar{includes, AC_INCLUDES_DEFAULT})
@acindex{CHECK_DECL}
If @var{symbol} (a function, variable, or constant) is not declared in
@var{includes} and a declaration is needed, run the shell commands
@var{action-if-not-found}, otherwise @var{action-if-found}.
@var{includes} is a series of include directives, defaulting to
@code{AC_INCLUDES_DEFAULT} (@pxref{Default Includes}), which are used
prior to the declaration under test.
This macro actually tests whether @var{symbol} is defined as a macro or
can be used as an r-value, not whether it is really declared, because it
is much safer to avoid
introducing extra declarations when they are not needed.
@end defmac
@anchor{AC_CHECK_DECLS}
@defmac AC_CHECK_DECLS (@var{symbols}, @ovar{action-if-found}, @
@ovar{action-if-not-found}, @dvar{includes, AC_INCLUDES_DEFAULT})
@acindex{CHECK_DECLS}
@cvindex HAVE_DECL_@var{symbol}
For each of the @var{symbols} (@emph{comma}-separated list), define
@code{HAVE_DECL_@var{symbol}} (in all capitals) to @samp{1} if
@var{symbol} is declared, otherwise to @samp{0}. If
@var{action-if-not-found} is given, it is additional shell code to
execute when one of the function declarations is needed, otherwise
@var{action-if-found} is executed.
@var{includes} is a series of include directives, defaulting to
@code{AC_INCLUDES_DEFAULT} (@pxref{Default Includes}), which are used
prior to the declarations under test.
This macro uses an M4 list as first argument:
@example
AC_CHECK_DECLS([strdup])
AC_CHECK_DECLS([strlen])
AC_CHECK_DECLS([malloc, realloc, calloc, free])
AC_CHECK_DECLS([j0], [], [], [[#include ]])
@end example
Unlike the other @samp{AC_CHECK_*S} macros, when a @var{symbol} is not
declared, @code{HAVE_DECL_@var{symbol}} is defined to @samp{0} instead
of leaving @code{HAVE_DECL_@var{symbol}} undeclared. When you are
@emph{sure} that the check was performed, use
@code{HAVE_DECL_@var{symbol}} in @code{#if}:
@example
#if !HAVE_DECL_SYMBOL
extern char *symbol;
#endif
@end example
@noindent
If the test may have not been performed, however, because it is safer
@emph{not} to declare a symbol than to use a declaration that conflicts
with the system's one, you should use:
@example
#if defined HAVE_DECL_MALLOC && !HAVE_DECL_MALLOC
void *malloc (size_t *s);
#endif
@end example
@noindent
You fall into the second category only in extreme situations: either
your files may be used without being configured, or they are used during
the configuration. In most cases the traditional approach is enough.
@end defmac
@defmac AC_CHECK_DECLS_ONCE (@var{symbols})
@acindex{CHECK_DECLS_ONCE}
@cvindex HAVE_DECL_@var{symbol}
For each of the @var{symbols} (@emph{comma}-separated list), define
@code{HAVE_DECL_@var{symbol}} (in all capitals) to @samp{1} if
@var{symbol} is declared in the default include files, otherwise to
@samp{0}. This is a once-only variant of @code{AC_CHECK_DECLS}. It
generates the checking code at most once, so that @command{configure} is
smaller and faster; but the checks cannot be conditionalized and are
always done once, early during the @command{configure} run.
@end defmac
@node Structures
@section Structures
@cindex Structure, checking
The following macros check for the presence of certain members in C
structures. If there is no macro specifically defined to check for a
member you need, then you can use the general structure-member macros
(@pxref{Generic Structures}) or, for more complex tests, you may use
@code{AC_COMPILE_IFELSE} (@pxref{Running the Compiler}).
@menu
* Particular Structures:: Macros to check for certain structure members
* Generic Structures:: How to find other structure members
@end menu
@node Particular Structures
@subsection Particular Structure Checks
The following macros check for certain structures or structure members.
@defmac AC_STRUCT_DIRENT_D_INO
@acindex{STRUCT_DIRENT_D_INO}
@cvindex HAVE_STRUCT_DIRENT_D_INO
Perform all the actions of @code{AC_HEADER_DIRENT} (@pxref{Particular
Headers}). Then, if @code{struct dirent} contains a @code{d_ino}
member, define @code{HAVE_STRUCT_DIRENT_D_INO}.
@code{HAVE_STRUCT_DIRENT_D_INO} indicates only the presence of
@code{d_ino}, not whether its contents are always reliable.
Traditionally, a zero @code{d_ino} indicated a deleted directory entry,
though current systems hide this detail from the user and never return
zero @code{d_ino} values.
Many current systems report an incorrect @code{d_ino} for a directory
entry that is a mount point.
@end defmac
@defmac AC_STRUCT_DIRENT_D_TYPE
@acindex{STRUCT_DIRENT_D_TYPE}
@cvindex HAVE_STRUCT_DIRENT_D_TYPE
Perform all the actions of @code{AC_HEADER_DIRENT} (@pxref{Particular
Headers}). Then, if @code{struct dirent} contains a @code{d_type}
member, define @code{HAVE_STRUCT_DIRENT_D_TYPE}.
@end defmac
@anchor{AC_STRUCT_ST_BLOCKS}
@defmac AC_STRUCT_ST_BLOCKS
@acindex{STRUCT_ST_BLOCKS}
@cvindex HAVE_STRUCT_STAT_ST_BLOCKS
@cvindex HAVE_ST_BLOCKS
@ovindex LIBOBJS
If @code{struct stat} contains an @code{st_blocks} member, define
@code{HAVE_STRUCT_STAT_ST_BLOCKS}. Otherwise, require an
@code{AC_LIBOBJ} replacement of @samp{fileblocks}. The former name,
@code{HAVE_ST_BLOCKS} is to be avoided, as its support will cease in the
future.
@end defmac
@defmac AC_STRUCT_TM
@acindex{STRUCT_TM}
@cvindex TM_IN_SYS_TIME
@hdrindex{time.h}
@hdrindex{sys/time.h}
If @file{time.h} does not define @code{struct tm}, define
@code{TM_IN_SYS_TIME}, which means that including @file{sys/time.h}
had better define @code{struct tm}.
This macro is obsolescent, as @file{time.h} defines @code{struct tm} in
current systems. New programs need not use this macro.
@end defmac
@anchor{AC_STRUCT_TIMEZONE}
@defmac AC_STRUCT_TIMEZONE
@acindex{STRUCT_TIMEZONE}
@cvindex HAVE_DECL_TZNAME
@cvindex HAVE_STRUCT_TM_TM_ZONE
@cvindex HAVE_TM_ZONE
@cvindex HAVE_TZNAME
Figure out how to get the current timezone. If @code{struct tm} has a
@code{tm_zone} member, define @code{HAVE_STRUCT_TM_TM_ZONE} (and the
obsoleted @code{HAVE_TM_ZONE}). Otherwise, if the external array
@code{tzname} is found, define @code{HAVE_TZNAME}; if it is declared,
define @code{HAVE_DECL_TZNAME}.
@end defmac
@node Generic Structures
@subsection Generic Structure Checks
These macros are used to find structure members not covered by the
``particular'' test macros.
@defmac AC_CHECK_MEMBER (@var{aggregate}.@var{member}, @
@ovar{action-if-found}, @ovar{action-if-not-found}, @
@dvar{includes, AC_INCLUDES_DEFAULT})
@acindex{CHECK_MEMBER}
Check whether @var{member} is a member of the aggregate @var{aggregate}.
If no @var{includes} are specified, the default includes are used
(@pxref{Default Includes}).
@example
AC_CHECK_MEMBER([struct passwd.pw_gecos], [],
[AC_MSG_ERROR([We need `passwd.pw_gecos'!])],
[[#include ]])
@end example
You can use this macro for submembers:
@example
AC_CHECK_MEMBER(struct top.middle.bot)
@end example
@end defmac
@anchor{AC_CHECK_MEMBERS}
@defmac AC_CHECK_MEMBERS (@var{members}, @ovar{action-if-found}, @
@ovar{action-if-not-found}, @dvar{includes, AC_INCLUDES_DEFAULT})
@acindex{CHECK_MEMBERS}
@cvindex HAVE_@var{aggregate}_@var{member}
Check for the existence of each @samp{@var{aggregate}.@var{member}} of
@var{members} using the previous macro. When @var{member} belongs to
@var{aggregate}, define @code{HAVE_@var{aggregate}_@var{member}} (in all
capitals, with spaces and dots replaced by underscores). If
@var{action-if-found} is given, it is executed for each of the found
members. If @var{action-if-not-found} is given, it is executed for each
of the members that could not be found.
@var{includes} is a series of include directives, defaulting to
@code{AC_INCLUDES_DEFAULT} (@pxref{Default Includes}), which are used
prior to the members under test.
This macro uses M4 lists:
@example
AC_CHECK_MEMBERS([struct stat.st_rdev, struct stat.st_blksize])
@end example
@end defmac
@node Types
@section Types
@cindex Types
@cindex C types
The following macros check for C types, either builtin or typedefs. If
there is no macro specifically defined to check for a type you need, and
you don't need to check for any special properties of it, then you can
use a general type-check macro.
@menu
* Particular Types:: Special handling to find certain types
* Generic Types:: How to find other types
@end menu
@node Particular Types
@subsection Particular Type Checks
@hdrindex{sys/types.h}
@hdrindex{stdlib.h}
@hdrindex{stdint.h}
@hdrindex{inttypes.h}
These macros check for particular C types in @file{sys/types.h},
@file{stdlib.h}, @file{stdint.h}, @file{inttypes.h} and others, if they
exist.
The Gnulib @code{stdint} module is an alternate way to define many of
these symbols; it is useful if you prefer your code to assume a
C99-or-better environment. @xref{Gnulib}.
@anchor{AC_TYPE_GETGROUPS}
@defmac AC_TYPE_GETGROUPS
@acindex{TYPE_GETGROUPS}
@cvindex GETGROUPS_T
Define @code{GETGROUPS_T} to be whichever of @code{gid_t} or @code{int}
is the base type of the array argument to @code{getgroups}.
@end defmac
@defmac AC_TYPE_INT8_T
@acindex{TYPE_INT8_T}
@cvindex HAVE_INT8_T
@cvindex int8_t
If @file{stdint.h} or @file{inttypes.h} does not define the type
@code{int8_t}, define @code{int8_t} to a signed
integer type that is exactly 8 bits wide and that uses two's complement
representation, if such a type exists.
If you are worried about porting to hosts that lack such a type, you can
use the results of this macro in C89-or-later code as follows:
@example
#if HAVE_STDINT_H
# include
#endif
#if defined INT8_MAX || defined int8_t
@emph{code using int8_t}
#else
@emph{complicated alternative using >8-bit 'signed char'}
#endif
@end example
@end defmac
@defmac AC_TYPE_INT16_T
@acindex{TYPE_INT16_T}
@cvindex HAVE_INT16_T
@cvindex int16_t
This is like @code{AC_TYPE_INT8_T}, except for 16-bit integers.
@end defmac
@defmac AC_TYPE_INT32_T
@acindex{TYPE_INT32_T}
@cvindex HAVE_INT32_T
@cvindex int32_t
This is like @code{AC_TYPE_INT8_T}, except for 32-bit integers.
@end defmac
@defmac AC_TYPE_INT64_T
@acindex{TYPE_INT64_T}
@cvindex HAVE_INT64_T
@cvindex int64_t
This is like @code{AC_TYPE_INT8_T}, except for 64-bit integers.
@end defmac
@defmac AC_TYPE_INTMAX_T
@acindex{TYPE_INTMAX_T}
@cvindex HAVE_INTMAX_T
@cvindex intmax_t
If @file{stdint.h} or @file{inttypes.h} defines the type @code{intmax_t},
define @code{HAVE_INTMAX_T}. Otherwise, define @code{intmax_t} to the
widest signed integer type.
@end defmac
@defmac AC_TYPE_INTPTR_T
@acindex{TYPE_INTPTR_T}
@cvindex HAVE_INTPTR_T
@cvindex intptr_t
If @file{stdint.h} or @file{inttypes.h} defines the type @code{intptr_t},
define @code{HAVE_INTPTR_T}. Otherwise, define @code{intptr_t} to a
signed integer type wide enough to hold a pointer, if such a type
exists.
@end defmac
@defmac AC_TYPE_LONG_DOUBLE
@acindex{TYPE_LONG_DOUBLE}
@cvindex HAVE_LONG_DOUBLE
If the C compiler supports a working @code{long double} type, define
@code{HAVE_LONG_DOUBLE}. The @code{long double} type might have the
same range and precision as @code{double}.
This macro is obsolescent, as current C compilers support @code{long
double}. New programs need not use this macro.
@end defmac
@defmac AC_TYPE_LONG_DOUBLE_WIDER
@acindex{TYPE_LONG_DOUBLE_WIDER}
@cvindex HAVE_LONG_DOUBLE_WIDER
If the C compiler supports a working @code{long double} type with more
range or precision than the @code{double} type, define
@code{HAVE_LONG_DOUBLE_WIDER}.
@end defmac
@defmac AC_TYPE_LONG_LONG_INT
@acindex{TYPE_LONG_LONG_INT}
@cvindex HAVE_LONG_LONG_INT
If the C compiler supports a working @code{long long int} type, define
@code{HAVE_LONG_LONG_INT}. However, this test does not test
@code{long long int} values in preprocessor @code{#if} expressions,
because too many compilers mishandle such expressions.
@xref{Preprocessor Arithmetic}.
@end defmac
@defmac AC_TYPE_MBSTATE_T
@acindex{TYPE_MBSTATE_T}
@cvindex mbstate_t
@hdrindex{wchar.h}
Define @code{HAVE_MBSTATE_T} if @code{} declares the
@code{mbstate_t} type. Also, define @code{mbstate_t} to be a type if
@code{} does not declare it.
@end defmac
@anchor{AC_TYPE_MODE_T}
@defmac AC_TYPE_MODE_T
@acindex{TYPE_MODE_T}
@cvindex mode_t
Define @code{mode_t} to a suitable type, if standard headers do not
define it.
@end defmac
@anchor{AC_TYPE_OFF_T}
@defmac AC_TYPE_OFF_T
@acindex{TYPE_OFF_T}
@cvindex off_t
Define @code{off_t} to a suitable type, if standard headers do not
define it.
@end defmac
@anchor{AC_TYPE_PID_T}
@defmac AC_TYPE_PID_T
@acindex{TYPE_PID_T}
@cvindex pid_t
Define @code{pid_t} to a suitable type, if standard headers do not
define it.
@end defmac
@anchor{AC_TYPE_SIZE_T}
@defmac AC_TYPE_SIZE_T
@acindex{TYPE_SIZE_T}
@cvindex size_t
Define @code{size_t} to a suitable type, if standard headers do not
define it.
@end defmac
@defmac AC_TYPE_SSIZE_T
@acindex{TYPE_SSIZE_T}
@cvindex ssize_t
Define @code{ssize_t} to a suitable type, if standard headers do not
define it.
@end defmac
@anchor{AC_TYPE_UID_T}
@defmac AC_TYPE_UID_T
@acindex{TYPE_UID_T}
@cvindex uid_t
@cvindex gid_t
Define @code{uid_t} and @code{gid_t} to suitable types, if standard
headers do not define them.
@end defmac
@defmac AC_TYPE_UINT8_T
@acindex{TYPE_UINT8_T}
@cvindex HAVE_UINT8_T
@cvindex uint8_t
If @file{stdint.h} or @file{inttypes.h} does not define the type
@code{uint8_t}, define @code{uint8_t} to an
unsigned integer type that is exactly 8 bits wide, if such a type
exists.
This is like @code{AC_TYPE_INT8_T}, except for unsigned integers.
@end defmac
@defmac AC_TYPE_UINT16_T
@acindex{TYPE_UINT16_T}
@cvindex HAVE_UINT16_T
@cvindex uint16_t
This is like @code{AC_TYPE_UINT8_T}, except for 16-bit integers.
@end defmac
@defmac AC_TYPE_UINT32_T
@acindex{TYPE_UINT32_T}
@cvindex HAVE_UINT32_T
@cvindex uint32_t
This is like @code{AC_TYPE_UINT8_T}, except for 32-bit integers.
@end defmac
@defmac AC_TYPE_UINT64_T
@acindex{TYPE_UINT64_T}
@cvindex HAVE_UINT64_T
@cvindex uint64_t
This is like @code{AC_TYPE_UINT8_T}, except for 64-bit integers.
@end defmac
@defmac AC_TYPE_UINTMAX_T
@acindex{TYPE_UINTMAX_T}
@cvindex HAVE_UINTMAX_T
@cvindex uintmax_t
If @file{stdint.h} or @file{inttypes.h} defines the type @code{uintmax_t},
define @code{HAVE_UINTMAX_T}. Otherwise, define @code{uintmax_t} to the
widest unsigned integer type.
@end defmac
@defmac AC_TYPE_UINTPTR_T
@acindex{TYPE_UINTPTR_T}
@cvindex HAVE_UINTPTR_T
@cvindex uintptr_t
If @file{stdint.h} or @file{inttypes.h} defines the type @code{uintptr_t},
define @code{HAVE_UINTPTR_T}. Otherwise, define @code{uintptr_t} to an
unsigned integer type wide enough to hold a pointer, if such a type
exists.
@end defmac
@defmac AC_TYPE_UNSIGNED_LONG_LONG_INT
@acindex{TYPE_UNSIGNED_LONG_LONG_INT}
@cvindex HAVE_UNSIGNED_LONG_LONG_INT
If the C compiler supports a working @code{unsigned long long int} type,
define @code{HAVE_UNSIGNED_LONG_LONG_INT}. However, this test does not test
@code{unsigned long long int} values in preprocessor @code{#if} expressions,
because too many compilers mishandle such expressions.
@xref{Preprocessor Arithmetic}.
@end defmac
@node Generic Types
@subsection Generic Type Checks
These macros are used to check for types not covered by the ``particular''
test macros.
@defmac AC_CHECK_TYPE (@var{type}, @ovar{action-if-found}, @
@ovar{action-if-not-found}, @dvar{includes, AC_INCLUDES_DEFAULT})
@acindex{CHECK_TYPE}
Check whether @var{type} is defined. It may be a compiler builtin type
or defined by the @var{includes}. @var{includes} is a series of include
directives, defaulting to @code{AC_INCLUDES_DEFAULT} (@pxref{Default
Includes}), which are used prior to the type under test.
In C, @var{type} must be a type-name, so that the expression @samp{sizeof
(@var{type})} is valid (but @samp{sizeof ((@var{type}))} is not). The
same test is applied when compiling for C++, which means that in C++
@var{type} should be a type-id and should not be an anonymous
@samp{struct} or @samp{union}.
@end defmac
@defmac AC_CHECK_TYPES (@var{types}, @ovar{action-if-found}, @
@ovar{action-if-not-found}, @dvar{includes, AC_INCLUDES_DEFAULT})
@acindex{CHECK_TYPES}
@cvindex HAVE_@var{type}
For each @var{type} of the @var{types} that is defined, define
@code{HAVE_@var{type}} (in all capitals). Each @var{type} must follow
the rules of @code{AC_CHECK_TYPE}. If no @var{includes} are
specified, the default includes are used (@pxref{Default Includes}). If
@var{action-if-found} is given, it is additional shell code to execute
when one of the types is found. If @var{action-if-not-found} is given,
it is executed when one of the types is not found.
This macro uses M4 lists:
@example
AC_CHECK_TYPES([ptrdiff_t])
AC_CHECK_TYPES([unsigned long long int, uintmax_t])
AC_CHECK_TYPES([float_t], [], [], [[#include ]])
@end example
@end defmac
Autoconf, up to 2.13, used to provide to another version of
@code{AC_CHECK_TYPE}, broken by design. In order to keep backward
compatibility, a simple heuristic, quite safe but not totally, is
implemented. In case of doubt, read the documentation of the former
@code{AC_CHECK_TYPE}, see @ref{Obsolete Macros}.
@node Compilers and Preprocessors
@section Compilers and Preprocessors
@cindex Compilers
@cindex Preprocessors
@ovindex EXEEXT
All the tests for compilers (@code{AC_PROG_CC}, @code{AC_PROG_CXX},
@code{AC_PROG_F77}) define the output variable @code{EXEEXT} based on
the output of the compiler, typically to the empty string if
Posix and @samp{.exe} if a @acronym{DOS} variant.
@ovindex OBJEXT
They also define the output variable @code{OBJEXT} based on the
output of the compiler, after @file{.c} files have been excluded, typically
to @samp{o} if Posix, @samp{obj} if a @acronym{DOS} variant.
If the compiler being used does not produce executables, the tests fail. If
the executables can't be run, and cross-compilation is not enabled, they
fail too. @xref{Manual Configuration}, for more on support for cross
compiling.
@menu
* Specific Compiler Characteristics:: Some portability issues
* Generic Compiler Characteristics:: Language independent tests and features
* C Compiler:: Checking its characteristics
* C++ Compiler:: Likewise
* Objective C Compiler:: Likewise
* Erlang Compiler and Interpreter:: Likewise
* Fortran Compiler:: Likewise
@end menu
@node Specific Compiler Characteristics
@subsection Specific Compiler Characteristics
Some compilers exhibit different behaviors.
@table @asis
@item Static/Dynamic Expressions
Autoconf relies on a trick to extract one bit of information from the C
compiler: using negative array sizes. For instance the following
excerpt of a C source demonstrates how to test whether @samp{int} objects are 4
bytes wide:
@example
static int test_array[sizeof (int) == 4 ? 1 : -1];
@end example
@noindent
To our knowledge, there is a single compiler that does not support this
trick: the @acronym{HP} C compilers (the real ones, not only the
``bundled'') on @acronym{HP-UX} 11.00.
They incorrectly reject the above program with the diagnostic
``Variable-length arrays cannot have static storage.''
This bug comes from @acronym{HP} compilers' mishandling of @code{sizeof (int)},
not from the @code{? 1 : -1}, and
Autoconf works around this problem by casting @code{sizeof (int)} to
@code{long int} before comparing it.
@end table
@node Generic Compiler Characteristics
@subsection Generic Compiler Characteristics
@anchor{AC_CHECK_SIZEOF}
@defmac AC_CHECK_SIZEOF (@var{type-or-expr}, @ovar{unused}, @
@dvar{includes, AC_INCLUDES_DEFAULT})
@acindex{CHECK_SIZEOF}
@cvindex SIZEOF_@var{type-or-expr}
Define @code{SIZEOF_@var{type-or-expr}} (@pxref{Standard Symbols}) to be
the size in bytes of @var{type-or-expr}, which may be either a type or
an expression returning a value that has a size. If the expression
@samp{sizeof (@var{type-or-expr})} is invalid, the result is 0.
@var{includes} is a series of include directives, defaulting to
@code{AC_INCLUDES_DEFAULT} (@pxref{Default Includes}), which are used
prior to the expression under test.
This macro now works even when cross-compiling. The @var{unused}
argument was used when cross-compiling.
For example, the call
@example
AC_CHECK_SIZEOF([int *])
@end example
@noindent
defines @code{SIZEOF_INT_P} to be 8 on DEC Alpha AXP systems.
@end defmac
@defmac AC_CHECK_ALIGNOF (@var{type}, @dvar{includes, AC_INCLUDES_DEFAULT})
@acindex{CHECK_ALIGNOF}
@cvindex ALIGNOF_@var{type}
Define @code{ALIGNOF_@var{type}} (@pxref{Standard Symbols}) to be the
alignment in bytes of @var{type}. @samp{@var{type} y;} must be valid as
a structure member declaration. If @samp{type} is unknown, the result
is 0. If no @var{includes} are specified, the default includes are used
(@pxref{Default Includes}).
@end defmac
@defmac AC_COMPUTE_INT (@var{var}, @var{expression}, @
@dvar{includes, AC_INCLUDES_DEFAULT}, @ovar{action-if-fails})
@acindex{COMPUTE_INT}
Store into the shell variable @var{var} the value of the integer
@var{expression}. The
value should fit in an initializer in a C variable of type @code{signed
long}. To support cross compilation (in which case, the macro only works on
hosts that use twos-complement arithmetic), it should be possible to evaluate
the expression at compile-time. If no @var{includes} are specified, the
default includes are used (@pxref{Default Includes}).
Execute @var{action-if-fails} if the value cannot be determined correctly.
@end defmac
@defmac AC_LANG_WERROR
@acindex{LANG_WERROR}
Normally Autoconf ignores warnings generated by the compiler, linker, and
preprocessor. If this macro is used, warnings count as fatal
errors for the current language. This macro is useful when the
results of configuration are used where warnings are unacceptable; for
instance, if parts of a program are built with the @acronym{GCC}
@option{-Werror}
option. If the whole program is built using @option{-Werror} it is
often simpler to put @option{-Werror} in the compiler flags (@code{CFLAGS},
etc.).
@end defmac
@defmac AC_OPENMP
@acindex{OPENMP}
@cvindex _OPENMP
@ovindex OPENMP_CFLAGS
@ovindex OPENMP_CXXFLAGS
@ovindex OPENMP_FFLAGS
@ovindex OPENMP_FCFLAGS
OpenMP (@url{http://@/www.openmp.org/}) specifies extensions of C, C++,
and Fortran that simplify optimization of shared memory parallelism,
which is a common problem on multicore CPUs.
If the current language is C, the macro @code{AC_OPENMP} sets the
variable @code{OPENMP_CFLAGS} to the C compiler flags needed for
supporting OpenMP@. @code{OPENMP_CFLAGS} is set to empty if the
compiler already supports OpenMP, if it has no way to activate OpenMP
support, or if the user rejects OpenMP support by invoking
@samp{configure} with the @samp{--disable-openmp} option.
@code{OPENMP_CFLAGS} needs to be used when compiling programs, when
preprocessing program source, and when linking programs. Therefore you
need to add @code{$(OPENMP_CFLAGS)} to the @code{CFLAGS} of C programs
that use OpenMP@. If you preprocess OpenMP-specific C code, you also
need to add @code{$(OPENMP_CFLAGS)} to @code{CPPFLAGS}. The presence of
OpenMP support is revealed at compile time by the preprocessor macro
@code{_OPENMP}.
Linking a program with @code{OPENMP_CFLAGS} typically adds one more
shared library to the program's dependencies, so its use is recommended
only on programs that actually require OpenMP.
If the current language is C++, @code{AC_OPENMP} sets the variable
@code{OPENMP_CXXFLAGS}, suitably for the C++ compiler. The same remarks
hold as for C.
If the current language is Fortran 77 or Fortran, @code{AC_OPENMP} sets
the variable @code{OPENMP_FFLAGS} or @code{OPENMP_FCFLAGS},
respectively. Similar remarks as for C hold, except that
@code{CPPFLAGS} is not used for Fortran, and no preprocessor macro
signals OpenMP support.
For portability, it is best to avoid spaces between @samp{#} and
@samp{pragma omp}. That is, write @samp{#pragma omp}, not
@samp{# pragma omp}. The Sun WorkShop 6.2 C compiler chokes on the
latter.
@end defmac
@node C Compiler
@subsection C Compiler Characteristics
The following macros provide ways to find and exercise a C Compiler.
There are a few constructs that ought to be avoided, but do not deserve
being checked for, since they can easily be worked around.
@table @asis
@item Don't use lines containing solitary backslashes
They tickle a bug in the @acronym{HP-UX} C compiler (checked on
@acronym{HP-UX} 10.20,
11.00, and 11i). When given the following source:
@example
#ifdef __STDC__
/\
* A comment with backslash-newlines in it. %@{ %@} *\
\
/
char str[] = "\\
" A string with backslash-newlines in it %@{ %@} \\
"";
char apostrophe = '\\
\
'\
';
#endif
@end example
@noindent
the compiler incorrectly fails with the diagnostics ``Non-terminating
comment at end of file'' and ``Missing @samp{#endif} at end of file.''
Removing the lines with solitary backslashes solves the problem.
@item Don't compile several files at once if output matters to you
Some compilers, such as @acronym{HP}'s, report names of files being
compiled when given more than one file operand. For instance:
@example
$ @kbd{cc a.c b.c}
a.c:
b.c:
@end example
@noindent
This can cause problems if you observe the output of the compiler to
detect failures. Invoking @samp{cc -c a.c && cc -c b.c && cc -o c a.o
b.o} solves the issue.
@item Don't rely on @code{#error} failing
The @sc{irix} C compiler does not fail when #error is preprocessed; it
simply emits a diagnostic and continues, exiting successfully. So,
instead of an error directive like @code{#error "Unsupported word size"}
it is more portable to use an invalid directive like @code{#Unsupported
word size} in Autoconf tests. In ordinary source code, @code{#error} is
OK, since installers with inadequate compilers like @sc{irix} can simply
examine these compilers' diagnostic output.
@item Don't rely on correct @code{#line} support
On Solaris, @command{c89} (at least Sun C 5.3 through 5.8)
diagnoses @code{#line} directives whose line
numbers are greater than 32767. Nothing in Posix
makes this invalid. That is why Autoconf stopped issuing
@code{#line} directives.
@end table
@defmac AC_PROG_CC (@ovar{compiler-search-list})
@acindex{PROG_CC}
@evindex CC
@evindex CFLAGS
@ovindex CC
@ovindex CFLAGS
Determine a C compiler to use. If @code{CC} is not already set in the
environment, check for @code{gcc} and @code{cc}, then for other C
compilers. Set output variable @code{CC} to the name of the compiler
found.
This macro may, however, be invoked with an optional first argument
which, if specified, must be a blank-separated list of C compilers to
search for. This just gives the user an opportunity to specify an
alternative search list for the C compiler. For example, if you didn't
like the default order, then you could invoke @code{AC_PROG_CC} like
this:
@example
AC_PROG_CC([gcc cl cc])
@end example
If the C compiler does not handle function prototypes correctly by
default, try to add an option to output variable @code{CC} to make it
so. This macro tries various options that select standard-conformance
modes on various systems.
After calling this macro you can check whether the C compiler has been
set to accept @acronym{ANSI} C89 (@acronym{ISO} C90); if not, the shell
variable
@code{ac_cv_prog_cc_c89} is set to @samp{no}. See also
@code{AC_C_PROTOTYPES} below.
If using the @acronym{GNU} C compiler, set shell variable @code{GCC} to
@samp{yes}. If output variable @code{CFLAGS} was not already set, set
it to @option{-g -O2} for the @acronym{GNU} C compiler (@option{-O2} on systems
where @acronym{GCC} does not accept @option{-g}), or @option{-g} for
other compilers.
Many Autoconf macros use a compiler, and thus call
@samp{AC_REQUIRE([AC_PROG_CC])} to ensure that the compiler has been
determined before the body of the outermost @code{AC_DEFUN} macro.
Although @code{AC_PROG_CC} is safe to directly expand multiple times, it
performs certain checks (such as the proper value of @env{EXEEXT}) only
on the first invocation. Therefore, care must be used when invoking
this macro from within another macro rather than at the top level
(@pxref{Expanded Before Required}).
@end defmac
@anchor{AC_PROG_CC_C_O}
@defmac AC_PROG_CC_C_O
@acindex{PROG_CC_C_O}
@cvindex NO_MINUS_C_MINUS_O
If the C compiler does not accept the @option{-c} and @option{-o} options
simultaneously, define @code{NO_MINUS_C_MINUS_O}. This macro actually
tests both the compiler found by @code{AC_PROG_CC}, and, if different,
the first @code{cc} in the path. The test fails if one fails. This
macro was created for @acronym{GNU} Make to choose the default C compilation
rule.
@end defmac
@defmac AC_PROG_CPP
@acindex{PROG_CPP}
@evindex CPP
@ovindex CPP
Set output variable @code{CPP} to a command that runs the
C preprocessor. If @samp{$CC -E} doesn't work, @file{/lib/cpp} is used.
It is only portable to run @code{CPP} on files with a @file{.c}
extension.
Some preprocessors don't indicate missing include files by the error
status. For such preprocessors an internal variable is set that causes
other macros to check the standard error from the preprocessor and
consider the test failed if any warnings have been reported.
For most preprocessors, though, warnings do not cause include-file
tests to fail unless @code{AC_PROG_CPP_WERROR} is also specified.
@end defmac
@defmac AC_PROG_CPP_WERROR
@acindex{PROG_CPP_WERROR}
@ovindex CPP
This acts like @code{AC_PROG_CPP}, except it treats warnings from the
preprocessor as errors even if the preprocessor exit status indicates
success. This is useful for avoiding headers that generate mandatory
warnings, such as deprecation notices.
@end defmac
The following macros check for C compiler or machine architecture
features. To check for characteristics not listed here, use
@code{AC_COMPILE_IFELSE} (@pxref{Running the Compiler}) or
@code{AC_RUN_IFELSE} (@pxref{Runtime}).
@defmac AC_PROG_CC_STDC
@acindex{PROG_CC_STDC}
If the C compiler cannot compile @acronym{ISO} Standard C (currently
C99), try to add an option to output variable @code{CC} to make it work.
If the compiler does not support C99, fall back to supporting
@acronym{ANSI} C89 (@acronym{ISO} C90).
After calling this macro you can check whether the C compiler has been
set to accept Standard C; if not, the shell variable
@code{ac_cv_prog_cc_stdc} is set to @samp{no}.
@end defmac
@defmac AC_PROG_CC_C89
@acindex{PROG_CC_C89}
If the C compiler is not in @acronym{ANSI} C89 (@acronym{ISO} C90) mode by
default, try to add an option to output variable @code{CC} to make it
so. This macro tries various options that select @acronym{ANSI} C89 on
some system or another, preferring extended functionality modes over
strict conformance modes. It considers the compiler to be in
@acronym{ANSI} C89 mode if it handles function prototypes correctly.
After calling this macro you can check whether the C compiler has been
set to accept @acronym{ANSI} C89; if not, the shell variable
@code{ac_cv_prog_cc_c89} is set to @samp{no}.
This macro is called automatically by @code{AC_PROG_CC}.
@end defmac
@defmac AC_PROG_CC_C99
@acindex{PROG_CC_C99}
If the C compiler is not in C99 mode by default, try to add an
option to output variable @code{CC} to make it so. This macro tries
various options that select C99 on some system or another, preferring
extended functionality modes over strict conformance modes. It
considers the compiler to be in C99 mode if it handles @code{_Bool},
@code{//} comments, flexible array members, @code{inline}, signed and
unsigned @code{long long int}, mixed code and declarations, named
initialization of structs,
@code{restrict}, @code{va_copy}, varargs macros, variable declarations
in @code{for} loops, and variable length arrays.
After calling this macro you can check whether the C compiler has been
set to accept C99; if not, the shell variable
@code{ac_cv_prog_cc_c99} is set to @samp{no}.
@end defmac
@defmac AC_C_BACKSLASH_A
@acindex{C_BACKSLASH_A}
@cvindex HAVE_C_BACKSLASH_A
Define @samp{HAVE_C_BACKSLASH_A} to 1 if the C compiler understands
@samp{\a}.
This macro is obsolescent, as current C compilers understand @samp{\a}.
New programs need not use this macro.
@end defmac
@anchor{AC_C_BIGENDIAN}
@defmac AC_C_BIGENDIAN (@ovar{action-if-true}, @ovar{action-if-false}, @
@ovar{action-if-unknown}, @ovar{action-if-universal})
@acindex{C_BIGENDIAN}
@cvindex WORDS_BIGENDIAN
@cindex Endianness
If words are stored with the most significant byte first (like Motorola
and SPARC CPUs), execute @var{action-if-true}. If words are stored with
the least significant byte first (like Intel and VAX CPUs), execute
@var{action-if-false}.
This macro runs a test-case if endianness cannot be determined from the
system header files. When cross-compiling, the test-case is not run but
grep'ed for some magic values. @var{action-if-unknown} is executed if
the latter case fails to determine the byte sex of the host system.
In some cases a single run of a compiler can generate code for multiple
architectures. This can happen, for example, when generating Mac OS X
universal binary files, which work on both PowerPC and Intel
architectures. In this case, the different variants might be for
different architectures whose endiannesses differ. If
@command{configure} detects this, it executes @var{action-if-universal}
instead of @var{action-if-unknown}.
The default for @var{action-if-true} is to define
@samp{WORDS_BIGENDIAN}. The default for @var{action-if-false} is to do
nothing. The default for @var{action-if-unknown} is to
abort configure and tell the installer how to bypass this test.
And finally, the default for @var{action-if-universal} is to ensure that
@samp{WORDS_BIGENDIAN} is defined if and only if a universal build is
detected and the current code is big-endian; this default works only if
@command{autoheader} is used (@pxref{autoheader Invocation}).
If you use this macro without specifying @var{action-if-universal}, you
should also use @code{AC_CONFIG_HEADERS}; otherwise
@samp{WORDS_BIGENDIAN} may be set incorrectly for Mac OS X universal
binary files.
@end defmac
@anchor{AC_C_CONST}
@defmac AC_C_CONST
@acindex{C_CONST}
@cvindex const
If the C compiler does not fully support the @code{const} keyword,
define @code{const} to be empty. Some C compilers that do
not define @code{__STDC__} do support @code{const}; some compilers that
define @code{__STDC__} do not completely support @code{const}. Programs
can simply use @code{const} as if every C compiler supported it; for
those that don't, the makefile or configuration header file
defines it as empty.
Occasionally installers use a C++ compiler to compile C code, typically
because they lack a C compiler. This causes problems with @code{const},
because C and C++ treat @code{const} differently. For example:
@example
const int foo;
@end example
@noindent
is valid in C but not in C++. These differences unfortunately cannot be
papered over by defining @code{const} to be empty.
If @command{autoconf} detects this situation, it leaves @code{const} alone,
as this generally yields better results in practice. However, using a
C++ compiler to compile C code is not recommended or supported, and
installers who run into trouble in this area should get a C compiler
like @acronym{GCC} to compile their C code.
This macro is obsolescent, as current C compilers support @code{const}.
New programs need not use this macro.
@end defmac
@defmac AC_C_RESTRICT
@acindex{C_RESTRICT}
@cvindex restrict
If the C compiler recognizes a variant spelling for the @code{restrict}
keyword (@code{__restrict}, @code{__restrict__}, or @code{_Restrict}),
then define @code{restrict} to that; this is more likely to do the right
thing with compilers that support language variants where plain
@code{restrict} is not a keyword. Otherwise, if the C compiler
recognizes the @code{restrict} keyword, don't do anything.
Otherwise, define @code{restrict} to be empty.
Thus, programs may simply use @code{restrict} as if every C compiler
supported it; for those that do not, the makefile
or configuration header defines it away.
Although support in C++ for the @code{restrict} keyword is not
required, several C++ compilers do accept the keyword.
This macro works for them, too.
@end defmac
@defmac AC_C_VOLATILE
@acindex{C_VOLATILE}
@cvindex volatile
If the C compiler does not understand the keyword @code{volatile},
define @code{volatile} to be empty. Programs can simply use
@code{volatile} as if every C compiler supported it; for those that do
not, the makefile or configuration header defines it as
empty.
If the correctness of your program depends on the semantics of
@code{volatile}, simply defining it to be empty does, in a sense, break
your code. However, given that the compiler does not support
@code{volatile}, you are at its mercy anyway. At least your
program compiles, when it wouldn't before.
@xref{Volatile Objects}, for more about @code{volatile}.
In general, the @code{volatile} keyword is a standard C feature, so
you might expect that @code{volatile} is available only when
@code{__STDC__} is defined. However, Ultrix 4.3's native compiler does
support volatile, but does not define @code{__STDC__}.
This macro is obsolescent, as current C compilers support @code{volatile}.
New programs need not use this macro.
@end defmac
@anchor{AC_C_INLINE}
@defmac AC_C_INLINE
@acindex{C_INLINE}
@cvindex inline
If the C compiler supports the keyword @code{inline}, do nothing.
Otherwise define @code{inline} to @code{__inline__} or @code{__inline}
if it accepts one of those, otherwise define @code{inline} to be empty.
@end defmac
@anchor{AC_C_CHAR_UNSIGNED}
@defmac AC_C_CHAR_UNSIGNED
@acindex{C_CHAR_UNSIGNED}
@cvindex __CHAR_UNSIGNED__
If the C type @code{char} is unsigned, define @code{__CHAR_UNSIGNED__},
unless the C compiler predefines it.
These days, using this macro is not necessary. The same information can
be determined by this portable alternative, thus avoiding the use of
preprocessor macros in the namespace reserved for the implementation.
@example
#include
#if CHAR_MIN == 0
# define CHAR_UNSIGNED 1
#endif
@end example
@end defmac
@defmac AC_C_STRINGIZE
@acindex{C_STRINGIZE}
@cvindex HAVE_STRINGIZE
If the C preprocessor supports the stringizing operator, define
@code{HAVE_STRINGIZE}. The stringizing operator is @samp{#} and is
found in macros such as this:
@example
#define x(y) #y
@end example
This macro is obsolescent, as current C compilers support the
stringizing operator. New programs need not use this macro.
@end defmac
@defmac AC_C_FLEXIBLE_ARRAY_MEMBER
@acindex{C_FLEXIBLE_ARRAY_MEMBER}
@cvindex FLEXIBLE_ARRAY_MEMBER
If the C compiler supports flexible array members, define
@code{FLEXIBLE_ARRAY_MEMBER} to nothing; otherwise define it to 1.
That way, a declaration like this:
@example
struct s
@{
size_t n_vals;
double val[FLEXIBLE_ARRAY_MEMBER];
@};
@end example
@noindent
will let applications use the ``struct hack'' even with compilers that
do not support flexible array members. To allocate and use such an
object, you can use code like this:
@example
size_t i;
size_t n = compute_value_count ();
struct s *p =
malloc (offsetof (struct s, val)
+ n * sizeof (double));
p->n_vals = n;
for (i = 0; i < n; i++)
p->val[i] = compute_value (i);
@end example
@end defmac
@defmac AC_C_VARARRAYS
@acindex{C_VARARRAYS}
@cvindex HAVE_C_VARARRAYS
If the C compiler supports variable-length arrays, define
@code{HAVE_C_VARARRAYS}. A variable-length array is an array of automatic
storage duration whose length is determined at run time, when the array
is declared.
@end defmac
@defmac AC_C_TYPEOF
@acindex{C_TYPEOF}
@cvindex HAVE_TYPEOF
@cvindex typeof
If the C compiler supports @acronym{GCC}'s @code{typeof} syntax either
directly or
through a different spelling of the keyword (e.g., @code{__typeof__}),
define @code{HAVE_TYPEOF}. If the support is available only through a
different spelling, define @code{typeof} to that spelling.
@end defmac
@defmac AC_C_PROTOTYPES
@acindex{C_PROTOTYPES}
@cvindex PROTOTYPES
@cvindex __PROTOTYPES
@cvindex PARAMS
If function prototypes are understood by the compiler (as determined by
@code{AC_PROG_CC}), define @code{PROTOTYPES} and @code{__PROTOTYPES}.
Defining @code{__PROTOTYPES} is for the benefit of
header files that cannot use macros that infringe on user name space.
This macro is obsolescent, as current C compilers support prototypes.
New programs need not use this macro.
@end defmac
@anchor{AC_PROG_GCC_TRADITIONAL}
@defmac AC_PROG_GCC_TRADITIONAL
@acindex{PROG_GCC_TRADITIONAL}
@ovindex CC
Add @option{-traditional} to output variable @code{CC} if using the
@acronym{GNU} C compiler and @code{ioctl} does not work properly without
@option{-traditional}. That usually happens when the fixed header files
have not been installed on an old system.
This macro is obsolescent, since current versions of the @acronym{GNU} C
compiler fix the header files automatically when installed.
@end defmac
@node C++ Compiler
@subsection C++ Compiler Characteristics
@defmac AC_PROG_CXX (@ovar{compiler-search-list})
@acindex{PROG_CXX}
@evindex CXX
@evindex CXXFLAGS
@ovindex CXX
@ovindex CXXFLAGS
Determine a C++ compiler to use. Check whether the environment variable
@code{CXX} or @code{CCC} (in that order) is set; if so, then set output
variable @code{CXX} to its value.
Otherwise, if the macro is invoked without an argument, then search for
a C++ compiler under the likely names (first @code{g++} and @code{c++}
then other names). If none of those checks succeed, then as a last
resort set @code{CXX} to @code{g++}.
This macro may, however, be invoked with an optional first argument
which, if specified, must be a blank-separated list of C++ compilers to
search for. This just gives the user an opportunity to specify an
alternative search list for the C++ compiler. For example, if you
didn't like the default order, then you could invoke @code{AC_PROG_CXX}
like this:
@example
AC_PROG_CXX([gcc cl KCC CC cxx cc++ xlC aCC c++ g++])
@end example
If using the @acronym{GNU} C++ compiler, set shell variable @code{GXX} to
@samp{yes}. If output variable @code{CXXFLAGS} was not already set, set
it to @option{-g -O2} for the @acronym{GNU} C++ compiler (@option{-O2} on
systems where G++ does not accept @option{-g}), or @option{-g} for other
compilers.
@end defmac
@defmac AC_PROG_CXXCPP
@acindex{PROG_CXXCPP}
@evindex CXXCPP
@ovindex CXXCPP
Set output variable @code{CXXCPP} to a command that runs the C++
preprocessor. If @samp{$CXX -E} doesn't work, @file{/lib/cpp} is used.
It is portable to run @code{CXXCPP} only on files with a @file{.c},
@file{.C}, @file{.cc}, or @file{.cpp} extension.
Some preprocessors don't indicate missing include files by the error
status. For such preprocessors an internal variable is set that causes
other macros to check the standard error from the preprocessor and
consider the test failed if any warnings have been reported. However,
it is not known whether such broken preprocessors exist for C++.
@end defmac
@defmac AC_PROG_CXX_C_O
@acindex{PROG_CXX_C_O}
@cvindex CXX_NO_MINUS_C_MINUS_O
Test whether the C++ compiler accepts the options @option{-c} and
@option{-o} simultaneously, and define @code{CXX_NO_MINUS_C_MINUS_O},
if it does not.
@end defmac
@node Objective C Compiler
@subsection Objective C Compiler Characteristics
@defmac AC_PROG_OBJC (@ovar{compiler-search-list})
@acindex{PROG_OBJC}
@evindex OBJC
@evindex OBJCFLAGS
@ovindex OBJC
@ovindex OBJCFLAGS
Determine an Objective C compiler to use. If @code{OBJC} is not already
set in the environment, check for Objective C compilers. Set output
variable @code{OBJC} to the name of the compiler found.
This macro may, however, be invoked with an optional first argument
which, if specified, must be a blank-separated list of Objective C compilers to
search for. This just gives the user an opportunity to specify an
alternative search list for the Objective C compiler. For example, if you
didn't like the default order, then you could invoke @code{AC_PROG_OBJC}
like this:
@example
AC_PROG_OBJC([gcc objcc objc])
@end example
If using the @acronym{GNU} Objective C compiler, set shell variable
@code{GOBJC} to @samp{yes}. If output variable @code{OBJCFLAGS} was not
already set, set it to @option{-g -O2} for the @acronym{GNU} Objective C
compiler (@option{-O2} on systems where @command{gcc} does not accept
@option{-g}), or @option{-g} for other compilers.
@end defmac
@defmac AC_PROG_OBJCPP
@acindex{PROG_OBJCPP}
@evindex OBJCPP
@ovindex OBJCPP
Set output variable @code{OBJCPP} to a command that runs the Objective C
preprocessor. If @samp{$OBJC -E} doesn't work, @file{/lib/cpp} is used.
@end defmac
@node Erlang Compiler and Interpreter
@subsection Erlang Compiler and Interpreter Characteristics
@cindex Erlang
Autoconf defines the following macros for determining paths to the essential
Erlang/OTP programs:
@defmac AC_ERLANG_PATH_ERLC (@ovar{value-if-not-found}, @dvar{path, $PATH})
@acindex{ERLANG_PATH_ERLC}
@evindex ERLC
@evindex ERLCFLAGS
@ovindex ERLC
@ovindex ERLCFLAGS
Determine an Erlang compiler to use. If @code{ERLC} is not already set in the
environment, check for @command{erlc}. Set output variable @code{ERLC} to the
complete path of the compiler command found. In addition, if @code{ERLCFLAGS}
is not set in the environment, set it to an empty value.
The two optional arguments have the same meaning as the two last arguments of
macro @code{AC_PROG_PATH} for looking for the @command{erlc} program. For
example, to look for @command{erlc} only in the @file{/usr/lib/erlang/bin}
directory:
@example
AC_ERLANG_PATH_ERLC([not found], [/usr/lib/erlang/bin])
@end example
@end defmac
@defmac AC_ERLANG_NEED_ERLC (@dvar{path, $PATH})
@acindex{ERLANG_NEED_ERLC}
A simplified variant of the @code{AC_ERLANG_PATH_ERLC} macro, that prints an
error message and exits the @command{configure} script if the @command{erlc}
program is not found.
@end defmac
@defmac AC_ERLANG_PATH_ERL (@ovar{value-if-not-found}, @dvar{path, $PATH})
@acindex{ERLANG_PATH_ERL}
@evindex ERL
@ovindex ERL
Determine an Erlang interpreter to use. If @code{ERL} is not already
set in the
environment, check for @command{erl}. Set output variable @code{ERL} to the
complete path of the interpreter command found.
The two optional arguments have the same meaning as the two last arguments of
macro @code{AC_PROG_PATH} for looking for the @command{erl} program. For
example, to look for @command{erl} only in the @file{/usr/lib/erlang/bin}
directory:
@example
AC_ERLANG_PATH_ERL([not found], [/usr/lib/erlang/bin])
@end example
@end defmac
@defmac AC_ERLANG_NEED_ERL (@dvar{path, $PATH})
@acindex{ERLANG_NEED_ERL}
A simplified variant of the @code{AC_ERLANG_PATH_ERL} macro, that prints an
error message and exits the @command{configure} script if the @command{erl}
program is not found.
@end defmac
@node Fortran Compiler
@subsection Fortran Compiler Characteristics
@cindex Fortran
@cindex F77
The Autoconf Fortran support is divided into two categories: legacy
Fortran 77 macros (@code{F77}), and modern Fortran macros (@code{FC}).
The former are intended for traditional Fortran 77 code, and have output
variables like @code{F77}, @code{FFLAGS}, and @code{FLIBS}. The latter
are for newer programs that can (or must) compile under the newer
Fortran standards, and have output variables like @code{FC},
@code{FCFLAGS}, and @code{FCLIBS}.
Except for two new macros @code{AC_FC_SRCEXT} and
@code{AC_FC_FREEFORM} (see below), the @code{FC} and @code{F77} macros
behave almost identically, and so they are documented together in this
section.
@defmac AC_PROG_F77 (@ovar{compiler-search-list})
@acindex{PROG_F77}
@evindex F77
@evindex FFLAGS
@ovindex F77
@ovindex FFLAGS
Determine a Fortran 77 compiler to use. If @code{F77} is not already
set in the environment, then check for @code{g77} and @code{f77}, and
then some other names. Set the output variable @code{F77} to the name
of the compiler found.
This macro may, however, be invoked with an optional first argument
which, if specified, must be a blank-separated list of Fortran 77
compilers to search for. This just gives the user an opportunity to
specify an alternative search list for the Fortran 77 compiler. For
example, if you didn't like the default order, then you could invoke
@code{AC_PROG_F77} like this:
@example
AC_PROG_F77([fl32 f77 fort77 xlf g77 f90 xlf90])
@end example
If using @code{g77} (the @acronym{GNU} Fortran 77 compiler), then
set the shell variable @code{G77} to @samp{yes}.
If the output variable @code{FFLAGS} was not already set in the
environment, then set it to @option{-g -02} for @code{g77} (or @option{-O2}
where @code{g77} does not accept @option{-g}). Otherwise, set
@code{FFLAGS} to @option{-g} for all other Fortran 77 compilers.
@end defmac
@defmac AC_PROG_FC (@ovar{compiler-search-list}, @ovar{dialect})
@acindex{PROG_FC}
@evindex FC
@evindex FCFLAGS
@ovindex FC
@ovindex FCFLAGS
Determine a Fortran compiler to use. If @code{FC} is not already set in
the environment, then @code{dialect} is a hint to indicate what Fortran
dialect to search for; the default is to search for the newest available
dialect. Set the output variable @code{FC} to the name of the compiler
found.
By default, newer dialects are preferred over older dialects, but if
@code{dialect} is specified then older dialects are preferred starting
with the specified dialect. @code{dialect} can currently be one of
Fortran 77, Fortran 90, or Fortran 95. However, this is only a hint of
which compiler @emph{name} to prefer (e.g., @code{f90} or @code{f95}),
and no attempt is made to guarantee that a particular language standard
is actually supported. Thus, it is preferable that you avoid the
@code{dialect} option, and use AC_PROG_FC only for code compatible with
the latest Fortran standard.
This macro may, alternatively, be invoked with an optional first argument
which, if specified, must be a blank-separated list of Fortran
compilers to search for, just as in @code{AC_PROG_F77}.
If the output variable @code{FCFLAGS} was not already set in the
environment, then set it to @option{-g -02} for @acronym{GNU} @code{g77} (or
@option{-O2} where @code{g77} does not accept @option{-g}). Otherwise,
set @code{FCFLAGS} to @option{-g} for all other Fortran compilers.
@end defmac
@defmac AC_PROG_F77_C_O
@defmacx AC_PROG_FC_C_O
@acindex{PROG_F77_C_O}
@acindex{PROG_FC_C_O}
@cvindex F77_NO_MINUS_C_MINUS_O
@cvindex FC_NO_MINUS_C_MINUS_O
Test whether the Fortran compiler accepts the options @option{-c} and
@option{-o} simultaneously, and define @code{F77_NO_MINUS_C_MINUS_O} or
@code{FC_NO_MINUS_C_MINUS_O}, respectively, if it does not.
@end defmac
The following macros check for Fortran compiler characteristics.
To check for characteristics not listed here, use
@code{AC_COMPILE_IFELSE} (@pxref{Running the Compiler}) or
@code{AC_RUN_IFELSE} (@pxref{Runtime}), making sure to first set the
current language to Fortran 77 or Fortran via @code{AC_LANG([Fortran 77])}
or @code{AC_LANG(Fortran)} (@pxref{Language Choice}).
@defmac AC_F77_LIBRARY_LDFLAGS
@defmacx AC_FC_LIBRARY_LDFLAGS
@acindex{F77_LIBRARY_LDFLAGS}
@ovindex FLIBS
@acindex{FC_LIBRARY_LDFLAGS}
@ovindex FCLIBS
Determine the linker flags (e.g., @option{-L} and @option{-l}) for the
@dfn{Fortran intrinsic and runtime libraries} that are required to
successfully link a Fortran program or shared library. The output
variable @code{FLIBS} or @code{FCLIBS} is set to these flags (which
should be included after @code{LIBS} when linking).
This macro is intended to be used in those situations when it is
necessary to mix, e.g., C++ and Fortran source code in a single
program or shared library (@pxref{Mixing Fortran 77 With C and C++, , ,
automake, @acronym{GNU} Automake}).
For example, if object files from a C++ and Fortran compiler must be
linked together, then the C++ compiler/linker must be used for linking
(since special C++-ish things need to happen at link time like calling
global constructors, instantiating templates, enabling exception
support, etc.).
However, the Fortran intrinsic and runtime libraries must be linked in
as well, but the C++ compiler/linker doesn't know by default how to add
these Fortran 77 libraries. Hence, this macro was created to determine
these Fortran libraries.
The macros @code{AC_F77_DUMMY_MAIN} and @code{AC_FC_DUMMY_MAIN} or
@code{AC_F77_MAIN} and @code{AC_FC_MAIN} are probably also necessary to
link C/C++ with Fortran; see below.
@end defmac
@defmac AC_F77_DUMMY_MAIN (@ovar{action-if-found}, @ovar{action-if-not-found})
@defmacx AC_FC_DUMMY_MAIN (@ovar{action-if-found}, @ovar{action-if-not-found})
@acindex{F77_DUMMY_MAIN}
@cvindex F77_DUMMY_MAIN
With many compilers, the Fortran libraries detected by
@code{AC_F77_LIBRARY_LDFLAGS} or @code{AC_FC_LIBRARY_LDFLAGS} provide
their own @code{main} entry function that initializes things like
Fortran I/O, and which then calls a user-provided entry function named
(say) @code{MAIN__} to run the user's program. The
@code{AC_F77_DUMMY_MAIN} and @code{AC_FC_DUMMY_MAIN} or
@code{AC_F77_MAIN} and @code{AC_FC_MAIN} macros figure out how to deal with
this interaction.
When using Fortran for purely numerical functions (no I/O, etc.)@: often
one prefers to provide one's own @code{main} and skip the Fortran
library initializations. In this case, however, one may still need to
provide a dummy @code{MAIN__} routine in order to prevent linking errors
on some systems. @code{AC_F77_DUMMY_MAIN} or @code{AC_FC_DUMMY_MAIN}
detects whether any such routine is @emph{required} for linking, and
what its name is; the shell variable @code{F77_DUMMY_MAIN} or
@code{FC_DUMMY_MAIN} holds this name, @code{unknown} when no solution
was found, and @code{none} when no such dummy main is needed.
By default, @var{action-if-found} defines @code{F77_DUMMY_MAIN} or
@code{FC_DUMMY_MAIN} to the name of this routine (e.g., @code{MAIN__})
@emph{if} it is required. @var{action-if-not-found} defaults to
exiting with an error.
In order to link with Fortran routines, the user's C/C++ program should
then include the following code to define the dummy main if it is
needed:
@example
#ifdef F77_DUMMY_MAIN
# ifdef __cplusplus
extern "C"
# endif
int F77_DUMMY_MAIN() @{ return 1; @}
#endif
@end example
(Replace @code{F77} with @code{FC} for Fortran instead of Fortran 77.)
Note that this macro is called automatically from @code{AC_F77_WRAPPERS}
or @code{AC_FC_WRAPPERS}; there is generally no need to call it
explicitly unless one wants to change the default actions.
@end defmac
@defmac AC_F77_MAIN
@defmacx AC_FC_MAIN
@acindex{F77_MAIN}
@cvindex F77_MAIN
@acindex{FC_MAIN}
@cvindex FC_MAIN
As discussed above, many Fortran libraries allow you to provide an entry
point called (say) @code{MAIN__} instead of the usual @code{main}, which
is then called by a @code{main} function in the Fortran libraries that
initializes things like Fortran I/O@. The
@code{AC_F77_MAIN} and @code{AC_FC_MAIN} macros detect whether it is
@emph{possible} to utilize such an alternate main function, and defines
@code{F77_MAIN} and @code{FC_MAIN} to the name of the function. (If no
alternate main function name is found, @code{F77_MAIN} and @code{FC_MAIN} are
simply defined to @code{main}.)
Thus, when calling Fortran routines from C that perform things like I/O,
one should use this macro and declare the "main" function like so:
@example
#ifdef __cplusplus
extern "C"
#endif
int F77_MAIN(int argc, char *argv[]);
@end example
(Again, replace @code{F77} with @code{FC} for Fortran instead of Fortran 77.)
@end defmac
@defmac AC_F77_WRAPPERS
@defmacx AC_FC_WRAPPERS
@acindex{F77_WRAPPERS}
@cvindex F77_FUNC
@cvindex F77_FUNC_
@acindex{FC_WRAPPERS}
@cvindex FC_FUNC
@cvindex FC_FUNC_
Defines C macros @code{F77_FUNC (name, NAME)}, @code{FC_FUNC (name, NAME)},
@code{F77_FUNC_(name, NAME)}, and @code{FC_FUNC_(name, NAME)} to properly
mangle the names of C/C++ identifiers, and identifiers with underscores,
respectively, so that they match the name-mangling scheme used by the
Fortran compiler.
Fortran is case-insensitive, and in order to achieve this the Fortran
compiler converts all identifiers into a canonical case and format. To
call a Fortran subroutine from C or to write a C function that is
callable from Fortran, the C program must explicitly use identifiers in
the format expected by the Fortran compiler. In order to do this, one
simply wraps all C identifiers in one of the macros provided by
@code{AC_F77_WRAPPERS} or @code{AC_FC_WRAPPERS}. For example, suppose
you have the following Fortran 77 subroutine:
@example
subroutine foobar (x, y)
double precision x, y
y = 3.14159 * x
return
end
@end example
You would then declare its prototype in C or C++ as:
@example
#define FOOBAR_F77 F77_FUNC (foobar, FOOBAR)
#ifdef __cplusplus
extern "C" /* prevent C++ name mangling */
#endif
void FOOBAR_F77(double *x, double *y);
@end example
Note that we pass both the lowercase and uppercase versions of the
function name to @code{F77_FUNC} so that it can select the right one.
Note also that all parameters to Fortran 77 routines are passed as
pointers (@pxref{Mixing Fortran 77 With C and C++, , , automake, @acronym{GNU}
Automake}).
(Replace @code{F77} with @code{FC} for Fortran instead of Fortran 77.)
Although Autoconf tries to be intelligent about detecting the
name-mangling scheme of the Fortran compiler, there may be Fortran
compilers that it doesn't support yet. In this case, the above code
generates a compile-time error, but some other behavior
(e.g., disabling Fortran-related features) can be induced by checking
whether @code{F77_FUNC} or @code{FC_FUNC} is defined.
Now, to call that routine from a C program, we would do something like:
@example
@{
double x = 2.7183, y;
FOOBAR_F77 (&x, &y);
@}
@end example
If the Fortran identifier contains an underscore (e.g., @code{foo_bar}),
you should use @code{F77_FUNC_} or @code{FC_FUNC_} instead of
@code{F77_FUNC} or @code{FC_FUNC} (with the same arguments). This is
because some Fortran compilers mangle names differently if they contain
an underscore.
@end defmac
@defmac AC_F77_FUNC (@var{name}, @ovar{shellvar})
@defmacx AC_FC_FUNC (@var{name}, @ovar{shellvar})
@acindex{F77_FUNC}
@acindex{FC_FUNC}
Given an identifier @var{name}, set the shell variable @var{shellvar} to
hold the mangled version @var{name} according to the rules of the
Fortran linker (see also @code{AC_F77_WRAPPERS} or
@code{AC_FC_WRAPPERS}). @var{shellvar} is optional; if it is not
supplied, the shell variable is simply @var{name}. The purpose of
this macro is to give the caller a way to access the name-mangling
information other than through the C preprocessor as above, for example,
to call Fortran routines from some language other than C/C++.
@end defmac
@defmac AC_FC_SRCEXT (@var{ext}, @ovar{action-if-success}, @
@ovar{action-if-failure})
@acindex{FC_SRCEXT}
By default, the @code{FC} macros perform their tests using a @file{.f}
extension for source-code files. Some compilers, however, only enable
newer language features for appropriately named files, e.g., Fortran 90
features only for @file{.f90} files. On the other hand, some other
compilers expect all source files to end in @file{.f} and require
special flags to support other file name extensions. The
@code{AC_FC_SRCEXT} macro deals with both of these issues.
The @code{AC_FC_SRCEXT} tries to get the @code{FC} compiler to accept files
ending with the extension .@var{ext} (i.e., @var{ext} does @emph{not}
contain the dot). If any special compiler flags are needed for this, it
stores them in the output variable @code{FCFLAGS_}@var{ext}. This
extension and these flags are then used for all subsequent @code{FC} tests
(until @code{AC_FC_SRCEXT} is called again).
For example, you would use @code{AC_FC_SRCEXT(f90)} to employ the
@file{.f90} extension in future tests, and it would set the
@code{FCFLAGS_f90} output variable with any extra flags that are needed
to compile such files.
The @code{FCFLAGS_}@var{ext} can @emph{not} be simply absorbed into
@code{FCFLAGS}, for two reasons based on the limitations of some
compilers. First, only one @code{FCFLAGS_}@var{ext} can be used at a
time, so files with different extensions must be compiled separately.
Second, @code{FCFLAGS_}@var{ext} must appear @emph{immediately} before
the source-code file name when compiling. So, continuing the example
above, you might compile a @file{foo.f90} file in your makefile with the
command:
@example
foo.o: foo.f90
$(FC) -c $(FCFLAGS) $(FCFLAGS_f90) '$(srcdir)/foo.f90'
@end example
If @code{AC_FC_SRCEXT} succeeds in compiling files with the @var{ext}
extension, it calls @var{action-if-success} (defaults to nothing). If
it fails, and cannot find a way to make the @code{FC} compiler accept such
files, it calls @var{action-if-failure} (defaults to exiting with an
error message).
@end defmac
@defmac AC_FC_FREEFORM (@ovar{action-if-success}, @ovar{action-if-failure})
@acindex{FC_FREEFORM}
The @code{AC_FC_FREEFORM} tries to ensure that the Fortran compiler
(@code{$FC}) allows free-format source code (as opposed to the older
fixed-format style from Fortran 77). If necessary, it may add some
additional flags to @code{FCFLAGS}.
This macro is most important if you are using the default @file{.f}
extension, since many compilers interpret this extension as indicating
fixed-format source unless an additional flag is supplied. If you
specify a different extension with @code{AC_FC_SRCEXT}, such as
@file{.f90} or @file{.f95}, then @code{AC_FC_FREEFORM} ordinarily
succeeds without modifying @code{FCFLAGS}.
If @code{AC_FC_FREEFORM} succeeds in compiling free-form source, it
calls @var{action-if-success} (defaults to nothing). If it fails, it
calls @var{action-if-failure} (defaults to exiting with an error
message).
@end defmac
@node System Services
@section System Services
The following macros check for operating system services or capabilities.
@anchor{AC_PATH_X}
@defmac AC_PATH_X
@acindex{PATH_X}
@evindex XMKMF
@cindex X Window System
Try to locate the X Window System include files and libraries. If the
user gave the command line options @option{--x-includes=@var{dir}} and
@option{--x-libraries=@var{dir}}, use those directories.
If either or both were not given, get the missing values by running
@code{xmkmf} (or an executable pointed to by the @code{XMKMF}
environment variable) on a trivial @file{Imakefile} and examining the
makefile that it produces. Setting @code{XMKMF} to @samp{false}
disables this method.
If this method fails to find the X Window System, @command{configure}
looks for the files in several directories where they often reside.
If either method is successful, set the shell variables
@code{x_includes} and @code{x_libraries} to their locations, unless they
are in directories the compiler searches by default.
If both methods fail, or the user gave the command line option
@option{--without-x}, set the shell variable @code{no_x} to @samp{yes};
otherwise set it to the empty string.
@end defmac
@anchor{AC_PATH_XTRA}
@defmac AC_PATH_XTRA
@acindex{PATH_XTRA}
@ovindex X_CFLAGS
@ovindex X_LIBS
@ovindex X_EXTRA_LIBS
@ovindex X_PRE_LIBS
@cvindex X_DISPLAY_MISSING
An enhanced version of @code{AC_PATH_X}. It adds the C compiler flags
that X needs to output variable @code{X_CFLAGS}, and the X linker flags
to @code{X_LIBS}. Define @code{X_DISPLAY_MISSING} if X is not
available.
This macro also checks for special libraries that some systems need in
order to compile X programs. It adds any that the system needs to
output variable @code{X_EXTRA_LIBS}. And it checks for special X11R6
libraries that need to be linked with before @option{-lX11}, and adds
any found to the output variable @code{X_PRE_LIBS}.
@c This is an incomplete kludge. Make a real way to do it.
@c If you need to check for other X functions or libraries yourself, then
@c after calling this macro, add the contents of @code{X_EXTRA_LIBS} to
@c @code{LIBS} temporarily, like this: (FIXME - add example)
@end defmac
@anchor{AC_SYS_INTERPRETER}
@defmac AC_SYS_INTERPRETER
@acindex{SYS_INTERPRETER}
Check whether the system supports starting scripts with a line of the
form @samp{#!/bin/sh} to select the interpreter to use for the script.
After running this macro, shell code in @file{configure.ac} can check
the shell variable @code{interpval}; it is set to @samp{yes}
if the system supports @samp{#!}, @samp{no} if not.
@end defmac
@defmac AC_SYS_LARGEFILE
@acindex{SYS_LARGEFILE}
@cvindex _FILE_OFFSET_BITS
@cvindex _LARGE_FILES
@ovindex CC
@cindex Large file support
@cindex LFS
Arrange for 64-bit file offsets, known as
@uref{http://@/www.unix-systems@/.org/@/version2/@/whatsnew/@/lfs20mar.html,
large-file support}. On some hosts, one must use special compiler
options to build programs that can access large files. Append any such
options to the output variable @code{CC}. Define
@code{_FILE_OFFSET_BITS} and @code{_LARGE_FILES} if necessary.
Large-file support can be disabled by configuring with the
@option{--disable-largefile} option.
If you use this macro, check that your program works even when
@code{off_t} is wider than @code{long int}, since this is common when
large-file support is enabled. For example, it is not correct to print
an arbitrary @code{off_t} value @code{X} with @code{printf ("%ld",
(long int) X)}.
The LFS introduced the @code{fseeko} and @code{ftello} functions to
replace their C counterparts @code{fseek} and @code{ftell} that do not
use @code{off_t}. Take care to use @code{AC_FUNC_FSEEKO} to make their
prototypes available when using them and large-file support is
enabled.
@end defmac
@anchor{AC_SYS_LONG_FILE_NAMES}
@defmac AC_SYS_LONG_FILE_NAMES
@acindex{SYS_LONG_FILE_NAMES}
@cvindex HAVE_LONG_FILE_NAMES
If the system supports file names longer than 14 characters, define
@code{HAVE_LONG_FILE_NAMES}.
@end defmac
@defmac AC_SYS_POSIX_TERMIOS
@acindex{SYS_POSIX_TERMIOS}
@cindex Posix termios headers
@cindex termios Posix headers
Check to see if the Posix termios headers and functions are available on the
system. If so, set the shell variable @code{ac_cv_sys_posix_termios} to
@samp{yes}. If not, set the variable to @samp{no}.
@end defmac
@node Posix Variants
@section Posix Variants
The following macro makes it possible to use features of Posix that are
extensions to C, as well as platform extensions not defined by Posix.
@anchor{AC_USE_SYSTEM_EXTENSIONS}
@defmac AC_USE_SYSTEM_EXTENSIONS
@acindex{USE_SYSTEM_EXTENSIONS}
@cvindex _ALL_SOURCE
@cvindex _GNU_SOURCE
@cvindex _MINIX
@cvindex _POSIX_1_SOURCE
@cvindex _POSIX_PTHREAD_SEMANTICS
@cvindex _POSIX_SOURCE
@cvindex _TANDEM_SOURCE
@cvindex __EXTENSIONS__
This macro was introduced in Autoconf 2.60. If possible, enable
extensions to C or Posix on hosts that normally disable the extensions,
typically due to standards-conformance namespace issues. This should be
called before any macros that run the C compiler. The following
preprocessor macros are defined where appropriate:
@table @code
@item _GNU_SOURCE
Enable extensions on @acronym{GNU}/Linux.
@item __EXTENSIONS__
Enable general extensions on Solaris.
@item _POSIX_PTHREAD_SEMANTICS
Enable threading extensions on Solaris.
@item _TANDEM_SOURCE
Enable extensions for the @acronym{HP} NonStop platform.
@item _ALL_SOURCE
Enable extensions for @acronym{AIX} 3, and for Interix.
@item _POSIX_SOURCE
Enable Posix functions for Minix.
@item _POSIX_1_SOURCE
Enable additional Posix functions for Minix.
@item _MINIX
Identify Minix platform. This particular preprocessor macro is
obsolescent, and may be removed in a future release of Autoconf.
@end table
@end defmac
@node Erlang Libraries
@section Erlang Libraries
@cindex Erlang, Library, checking
The following macros check for an installation of Erlang/OTP, and for the
presence of certain Erlang libraries. All those macros require the
configuration of an Erlang interpreter and an Erlang compiler
(@pxref{Erlang Compiler and Interpreter}).
@defmac AC_ERLANG_SUBST_ERTS_VER
@acindex{ERLANG_SUBST_ERTS_VER}
@ovindex ERLANG_ERTS_VER
Set the output variable @code{ERLANG_ERTS_VER} to the version of the
Erlang runtime system (as returned by Erlang's
@code{erlang:system_info(version)} function). The result of this test
is cached if caching is enabled when running @command{configure}. The
@code{ERLANG_ERTS_VER} variable is not intended to be used for testing
for features of specific ERTS versions, but to be used for substituting
the ERTS version in Erlang/OTP release resource files (@code{.rel}
files), as shown below.
@end defmac
@defmac AC_ERLANG_SUBST_ROOT_DIR
@acindex{ERLANG_SUBST_ROOT_DIR}
@ovindex ERLANG_ROOT_DIR
Set the output variable @code{ERLANG_ROOT_DIR} to the path to the base
directory in which Erlang/OTP is installed (as returned by Erlang's
@code{code:root_dir/0} function). The result of this test is cached if
caching is enabled when running @command{configure}.
@end defmac
@defmac AC_ERLANG_SUBST_LIB_DIR
@acindex{ERLANG_SUBST_LIB_DIR}
@ovindex ERLANG_LIB_DIR
Set the output variable @code{ERLANG_LIB_DIR} to the path of the library
directory of Erlang/OTP (as returned by Erlang's
@code{code:lib_dir/0} function), which subdirectories each contain an installed
Erlang/OTP library. The result of this test is cached if caching is enabled
when running @command{configure}.
@end defmac
@defmac AC_ERLANG_CHECK_LIB (@var{library}, @ovar{action-if-found}, @
@ovar{action-if-not-found})
@acindex{ERLANG_CHECK_LIB}
@ovindex ERLANG_LIB_DIR_@var{library}
@ovindex ERLANG_LIB_VER_@var{library}
Test whether the Erlang/OTP library @var{library} is installed by
calling Erlang's @code{code:lib_dir/1} function. The result of this
test is cached if caching is enabled when running @command{configure}.
@var{action-if-found} is a list of shell commands to run if the library
is installed; @var{action-if-not-found} is a list of shell commands to
run if it is not. Additionally, if the library is installed, the output
variable @samp{ERLANG_LIB_DIR_@var{library}} is set to the path to the
library installation directory, and the output variable
@samp{ERLANG_LIB_VER_@var{library}} is set to the version number that is
part of the subdirectory name, if it is in the standard form
(@code{@var{library}-@var{version}}). If the directory name does not
have a version part, @samp{ERLANG_LIB_VER_@var{library}} is set to the
empty string. If the library is not installed,
@samp{ERLANG_LIB_DIR_@var{library}} and
@samp{ERLANG_LIB_VER_@var{library}} are set to @code{"not found"}. For
example, to check if library @code{stdlib} is installed:
@example
AC_ERLANG_CHECK_LIB([stdlib],
[echo "stdlib version \"$ERLANG_LIB_VER_stdlib\""
echo "is installed in \"$ERLANG_LIB_DIR_stdlib\""],
[AC_MSG_ERROR([stdlib was not found!])])
@end example
The @samp{ERLANG_LIB_VER_@var{library}} variables (set by
@code{AC_ERLANG_CHECK_LIB}) and the @code{ERLANG_ERTS_VER} variable (set
by @code{AC_ERLANG_SUBST_ERTS_VER}) are not intended to be used for
testing for features of specific versions of libraries or of the Erlang
runtime system. Those variables are intended to be substituted in
Erlang release resource files (@code{.rel} files). For instance, to
generate a @file{example.rel} file for an application depending on the
@code{stdlib} library, @file{configure.ac} could contain:
@example
AC_ERLANG_SUBST_ERTS_VER
AC_ERLANG_CHECK_LIB([stdlib],
[],
[AC_MSG_ERROR([stdlib was not found!])])
AC_CONFIG_FILES([example.rel])
@end example
@noindent
The @file{example.rel.in} file used to generate @file{example.rel}
should contain:
@example
@{release,
@{"@@PACKAGE@@", "@@VERSION@@"@},
@{erts, "@@ERLANG_ERTS_VER@@"@},
[@{stdlib, "@@ERLANG_LIB_VER_stdlib@@"@},
@{@@PACKAGE@@, "@@VERSION@@"@}]@}.
@end example
@end defmac
In addition to the above macros, which test installed Erlang libraries, the
following macros determine the paths to the directories into which newly built
Erlang libraries are to be installed:
@defmac AC_ERLANG_SUBST_INSTALL_LIB_DIR
@acindex{ERLANG_SUBST_INSTALL_LIB_DIR}
@ovindex ERLANG_INSTALL_LIB_DIR
Set the @code{ERLANG_INSTALL_LIB_DIR} output variable to the directory into
which every built Erlang library should be installed in a separate
subdirectory.
If this variable is not set in the environment when @command{configure} runs,
its default value is @code{$ERLANG_LIB_DIR}, which value is set by the
@code{AC_ERLANG_SUBST_LIB_DIR} macro.
@end defmac
@defmac AC_ERLANG_SUBST_INSTALL_LIB_SUBDIR (@var{library}, @var{version})
@acindex{ERLANG_SUBST_INSTALL_LIB_SUBDIR}
@ovindex ERLANG_INSTALL_LIB_DIR_@var{library}
Set the @samp{ERLANG_INSTALL_LIB_DIR_@var{library}} output variable to the
directory into which the built Erlang library @var{library} version
@var{version} should be installed. If this variable is not set in the
environment when @command{configure} runs, its default value is
@samp{$ERLANG_INSTALL_LIB_DIR/@var{library}-@var{version}}, the value of the
@code{ERLANG_INSTALL_LIB_DIR} variable being set by the
@code{AC_ERLANG_SUBST_INSTALL_LIB_DIR} macro.
@end defmac
@c ========================================================= Writing Tests
@node Writing Tests
@chapter Writing Tests
If the existing feature tests don't do something you need, you have to
write new ones. These macros are the building blocks. They provide
ways for other macros to check whether various kinds of features are
available and report the results.
This chapter contains some suggestions and some of the reasons why the
existing tests are written the way they are. You can also learn a lot
about how to write Autoconf tests by looking at the existing ones. If
something goes wrong in one or more of the Autoconf tests, this
information can help you understand the assumptions behind them, which
might help you figure out how to best solve the problem.
These macros check the output of the compiler system of the current
language (@pxref{Language Choice}). They do not cache the results of
their tests for future use (@pxref{Caching Results}), because they don't
know enough about the information they are checking for to generate a
cache variable name. They also do not print any messages, for the same
reason. The checks for particular kinds of features call these macros
and do cache their results and print messages about what they're
checking for.
When you write a feature test that could be applicable to more than one
software package, the best thing to do is encapsulate it in a new macro.
@xref{Writing Autoconf Macros}, for how to do that.
@menu
* Language Choice:: Selecting which language to use for testing
* Writing Test Programs:: Forging source files for compilers
* Running the Preprocessor:: Detecting preprocessor symbols
* Running the Compiler:: Detecting language or header features
* Running the Linker:: Detecting library features
* Runtime:: Testing for runtime features
* Systemology:: A zoology of operating systems
* Multiple Cases:: Tests for several possible values
@end menu
@node Language Choice
@section Language Choice
@cindex Language
Autoconf-generated @command{configure} scripts check for the C compiler and
its features by default. Packages that use other programming languages
(maybe more than one, e.g., C and C++) need to test features of the
compilers for the respective languages. The following macros determine
which programming language is used in the subsequent tests in
@file{configure.ac}.
@anchor{AC_LANG}
@defmac AC_LANG (@var{language})
Do compilation tests using the compiler, preprocessor, and file
extensions for the specified @var{language}.
Supported languages are:
@table @samp
@item C
Do compilation tests using @code{CC} and @code{CPP} and use extension
@file{.c} for test programs. Use compilation flags: @code{CPPFLAGS} with
@code{CPP}, and both @code{CPPFLAGS} and @code{CFLAGS} with @code{CC}.
@item C++
Do compilation tests using @code{CXX} and @code{CXXCPP} and use
extension @file{.C} for test programs. Use compilation flags:
@code{CPPFLAGS} with @code{CXXCPP}, and both @code{CPPFLAGS} and
@code{CXXFLAGS} with @code{CXX}.
@item Fortran 77
Do compilation tests using @code{F77} and use extension @file{.f} for
test programs. Use compilation flags: @code{FFLAGS}.
@item Fortran
Do compilation tests using @code{FC} and use extension @file{.f} (or
whatever has been set by @code{AC_FC_SRCEXT}) for test programs. Use
compilation flags: @code{FCFLAGS}.
@item Erlang
@ovindex ERLC
@ovindex ERL
@ovindex ERLCFLAGS
Compile and execute tests using @code{ERLC} and @code{ERL} and use extension
@file{.erl} for test Erlang modules. Use compilation flags: @code{ERLCFLAGS}.
@item Objective C
Do compilation tests using @code{OBJC} and @code{OBJCPP} and use
extension @file{.m} for test programs. Use compilation flags:
@code{CPPFLAGS} with @code{OBJCPP}, and both @code{CPPFLAGS} and
@code{OBJCFLAGS} with @code{OBJC}.
@end table
@end defmac
@anchor{AC_LANG_PUSH}
@defmac AC_LANG_PUSH (@var{language})
@acindex{LANG_PUSH}
Remember the current language (as set by @code{AC_LANG}) on a stack, and
then select the @var{language}. Use this macro and @code{AC_LANG_POP}
in macros that need to temporarily switch to a particular language.
@end defmac
@defmac AC_LANG_POP (@ovar{language})
@acindex{LANG_POP}
Select the language that is saved on the top of the stack, as set by
@code{AC_LANG_PUSH}, and remove it from the stack.
If given, @var{language} specifies the language we just @emph{quit}. It
is a good idea to specify it when it's known (which should be the
case@dots{}), since Autoconf detects inconsistencies.
@example
AC_LANG_PUSH([Fortran 77])
# Perform some tests on Fortran 77.
# @dots{}
AC_LANG_POP([Fortran 77])
@end example
@end defmac
@defmac AC_LANG_ASSERT (@var{language})
@acindex{LANG_ASSERT} Check statically that the current language is
@var{language}. You should use this in your language specific macros
to avoid that they be called with an inappropriate language.
This macro runs only at @command{autoconf} time, and incurs no cost at
@command{configure} time. Sadly enough and because Autoconf is a two
layer language @footnote{Because M4 is not aware of Sh code,
especially conditionals, some optimizations that look nice statically
may produce incorrect results at runtime.}, the macros
@code{AC_LANG_PUSH} and @code{AC_LANG_POP} cannot be ``optimizing'',
therefore as much as possible you ought to avoid using them to wrap
your code, rather, require from the user to run the macro with a
correct current language, and check it with @code{AC_LANG_ASSERT}.
And anyway, that may help the user understand she is running a Fortran
macro while expecting a result about her Fortran 77 compiler@enddots{}
@end defmac
@defmac AC_REQUIRE_CPP
@acindex{REQUIRE_CPP}
Ensure that whichever preprocessor would currently be used for tests has
been found. Calls @code{AC_REQUIRE} (@pxref{Prerequisite Macros}) with an
argument of either @code{AC_PROG_CPP} or @code{AC_PROG_CXXCPP},
depending on which language is current.
@end defmac
@node Writing Test Programs
@section Writing Test Programs
Autoconf tests follow a common scheme: feed some program with some
input, and most of the time, feed a compiler with some source file.
This section is dedicated to these source samples.
@menu
* Guidelines:: General rules for writing test programs
* Test Functions:: Avoiding pitfalls in test programs
* Generating Sources:: Source program boilerplate
@end menu
@node Guidelines
@subsection Guidelines for Test Programs
The most important rule to follow when writing testing samples is:
@center @emph{Look for realism.}
This motto means that testing samples must be written with the same
strictness as real programs are written. In particular, you should
avoid ``shortcuts'' and simplifications.
Don't just play with the preprocessor if you want to prepare a
compilation. For instance, using @command{cpp} to check whether a header is
functional might let your @command{configure} accept a header which
causes some @emph{compiler} error. Do not hesitate to check a header with
other headers included before, especially required headers.
Make sure the symbols you use are properly defined, i.e., refrain from
simply declaring a function yourself instead of including the proper
header.
Test programs should not write to standard output. They
should exit with status 0 if the test succeeds, and with status 1
otherwise, so that success
can be distinguished easily from a core dump or other failure;
segmentation violations and other failures produce a nonzero exit
status. Unless you arrange for @code{exit} to be declared, test
programs should @code{return}, not @code{exit}, from @code{main},
because on many systems @code{exit} is not declared by default.
Test programs can use @code{#if} or @code{#ifdef} to check the values of
preprocessor macros defined by tests that have already run. For
example, if you call @code{AC_HEADER_STDBOOL}, then later on in
@file{configure.ac} you can have a test program that includes
@file{stdbool.h} conditionally:
@example
@group
#ifdef HAVE_STDBOOL_H
# include
#endif
@end group
@end example
Both @code{#if HAVE_STDBOOL_H} and @code{#ifdef HAVE_STDBOOL_H} will
work with any standard C compiler. Some developers prefer @code{#if}
because it is easier to read, while others prefer @code{#ifdef} because
it avoids diagnostics with picky compilers like @acronym{GCC} with the
@option{-Wundef} option.
If a test program needs to use or create a data file, give it a name
that starts with @file{conftest}, such as @file{conftest.data}. The
@command{configure} script cleans up by running @samp{rm -f -r conftest*}
after running test programs and if the script is interrupted.
@node Test Functions
@subsection Test Functions
These days it's safe to assume support for function prototypes
(introduced in C89).
Functions that test programs declare should also be conditionalized for
C++, which requires @samp{extern "C"} prototypes. Make sure to not
include any header files containing clashing prototypes.
@example
#ifdef __cplusplus
extern "C"
#endif
void *valloc (size_t);
@end example
If a test program calls a function with invalid parameters (just to see
whether it exists), organize the program to ensure that it never invokes
that function. You can do this by calling it in another function that is
never invoked. You can't do it by putting it after a call to
@code{exit}, because @acronym{GCC} version 2 knows that @code{exit}
never returns
and optimizes out any code that follows it in the same block.
If you include any header files, be sure to call the functions
relevant to them with the correct number of arguments, even if they are
just 0, to avoid compilation errors due to prototypes. @acronym{GCC}
version 2
has internal prototypes for several functions that it automatically
inlines; for example, @code{memcpy}. To avoid errors when checking for
them, either pass them the correct number of arguments or redeclare them
with a different return type (such as @code{char}).
@node Generating Sources
@subsection Generating Sources
Autoconf provides a set of macros that can be used to generate test
source files. They are written to be language generic, i.e., they
actually depend on the current language (@pxref{Language Choice}) to
``format'' the output properly.
@defmac AC_LANG_CONFTEST (@var{source})
@acindex{LANG_CONFTEST}
Save the @var{source} text in the current test source file:
@file{conftest.@var{extension}} where the @var{extension} depends on the
current language.
Note that the @var{source} is evaluated exactly once, like regular
Autoconf macro arguments, and therefore (i) you may pass a macro
invocation, (ii) if not, be sure to double quote if needed.
@end defmac
@defmac AC_LANG_SOURCE (@var{source})
@acindex{LANG_SOURCE}
Expands into the @var{source}, with the definition of
all the @code{AC_DEFINE} performed so far.
@end defmac
For instance executing (observe the double quotation!):
@example
AC_INIT([Hello], [1.0], [bug-hello@@example.org])
AC_DEFINE([HELLO_WORLD], ["Hello, World\n"],
[Greetings string.])
AC_LANG(C)
AC_LANG_CONFTEST(
[AC_LANG_SOURCE([[const char hw[] = "Hello, World\n";]])])
gcc -E -dD -o - conftest.c
@end example
@noindent
results in:
@example
@dots{}
# 1 "conftest.c"
#define PACKAGE_NAME "Hello"
#define PACKAGE_TARNAME "hello"
#define PACKAGE_VERSION "1.0"
#define PACKAGE_STRING "Hello 1.0"
#define PACKAGE_BUGREPORT "bug-hello@@example.org"
#define HELLO_WORLD "Hello, World\n"
const char hw[] = "Hello, World\n";
@end example
When the test language is Fortran or Erlang, the @code{AC_DEFINE} definitions
are not automatically translated into constants in the source code by this
macro.
@defmac AC_LANG_PROGRAM (@var{prologue}, @var{body})
@acindex{LANG_PROGRAM}
Expands into a source file which consists of the @var{prologue}, and
then @var{body} as body of the main function (e.g., @code{main} in
C). Since it uses @code{AC_LANG_SOURCE}, the features of the latter are
available.
@end defmac
For instance:
@example
AC_INIT([Hello], [1.0], [bug-hello@@example.org])
AC_DEFINE([HELLO_WORLD], ["Hello, World\n"],
[Greetings string.])
AC_LANG_CONFTEST(
[AC_LANG_PROGRAM([[const char hw[] = "Hello, World\n";]],
[[fputs (hw, stdout);]])])
gcc -E -dD -o - conftest.c
@end example
@noindent
results in:
@example
@dots{}
# 1 "conftest.c"
#define PACKAGE_NAME "Hello"
#define PACKAGE_TARNAME "hello"
#define PACKAGE_VERSION "1.0"
#define PACKAGE_STRING "Hello 1.0"
#define PACKAGE_BUGREPORT "bug-hello@@example.org"
#define HELLO_WORLD "Hello, World\n"
const char hw[] = "Hello, World\n";
int
main ()
@{
fputs (hw, stdout);
;
return 0;
@}
@end example
In Erlang tests, the created source file is that of an Erlang module called
@code{conftest} (@file{conftest.erl}). This module defines and exports
at least
one @code{start/0} function, which is called to perform the test. The
@var{prologue} is optional code that is inserted between the module header and
the @code{start/0} function definition. @var{body} is the body of the
@code{start/0} function without the final period (@pxref{Runtime}, about
constraints on this function's behavior).
For instance:
@example
AC_INIT([Hello], [1.0], [bug-hello@@example.org])
AC_LANG(Erlang)
AC_LANG_CONFTEST(
[AC_LANG_PROGRAM([[-define(HELLO_WORLD, "Hello, world!").]],
[[io:format("~s~n", [?HELLO_WORLD])]])])
cat conftest.erl
@end example
@noindent
results in:
@example
-module(conftest).
-export([start/0]).
-define(HELLO_WORLD, "Hello, world!").
start() ->
io:format("~s~n", [?HELLO_WORLD])
.
@end example
@defmac AC_LANG_CALL (@var{prologue}, @var{function})
@acindex{LANG_CALL}
Expands into a source file which consists of the @var{prologue}, and
then a call to the @var{function} as body of the main function (e.g.,
@code{main} in C). Since it uses @code{AC_LANG_PROGRAM}, the feature
of the latter are available.
This function will probably be replaced in the future by a version
which would enable specifying the arguments. The use of this macro is
not encouraged, as it violates strongly the typing system.
This macro cannot be used for Erlang tests.
@end defmac
@defmac AC_LANG_FUNC_LINK_TRY (@var{function})
@acindex{LANG_FUNC_LINK_TRY}
Expands into a source file which uses the @var{function} in the body of
the main function (e.g., @code{main} in C). Since it uses
@code{AC_LANG_PROGRAM}, the features of the latter are available.
As @code{AC_LANG_CALL}, this macro is documented only for completeness.
It is considered to be severely broken, and in the future will be
removed in favor of actual function calls (with properly typed
arguments).
This macro cannot be used for Erlang tests.
@end defmac
@node Running the Preprocessor
@section Running the Preprocessor
Sometimes one might need to run the preprocessor on some source file.
@emph{Usually it is a bad idea}, as you typically need to @emph{compile}
your project, not merely run the preprocessor on it; therefore you
certainly want to run the compiler, not the preprocessor. Resist the
temptation of following the easiest path.
Nevertheless, if you need to run the preprocessor, then use
@code{AC_PREPROC_IFELSE}.
The macros described in this section cannot be used for tests in Erlang or
Fortran, since those languages require no preprocessor.
@anchor{AC_PREPROC_IFELSE}
@defmac AC_PREPROC_IFELSE (@var{input}, @ovar{action-if-true}, @
@ovar{action-if-false})
@acindex{PREPROC_IFELSE}
Run the preprocessor of the current language (@pxref{Language Choice})
on the @var{input}, run the shell commands @var{action-if-true} on
success, @var{action-if-false} otherwise. The @var{input} can be made
by @code{AC_LANG_PROGRAM} and friends.
This macro uses @code{CPPFLAGS}, but not @code{CFLAGS}, because
@option{-g}, @option{-O}, etc.@: are not valid options to many C
preprocessors.
It is customary to report unexpected failures with
@code{AC_MSG_FAILURE}.
@end defmac
For instance:
@example
AC_INIT([Hello], [1.0], [bug-hello@@example.org])
AC_DEFINE([HELLO_WORLD], ["Hello, World\n"],
[Greetings string.])
AC_PREPROC_IFELSE(
[AC_LANG_PROGRAM([[const char hw[] = "Hello, World\n";]],
[[fputs (hw, stdout);]])],
[AC_MSG_RESULT([OK])],
[AC_MSG_FAILURE([unexpected preprocessor failure])])
@end example
@noindent
results in:
@example
checking for gcc... gcc
checking for C compiler default output file name... a.out
checking whether the C compiler works... yes
checking whether we are cross compiling... no
checking for suffix of executables...
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ISO C89... none needed
checking how to run the C preprocessor... gcc -E
OK
@end example
@sp 1
The macro @code{AC_TRY_CPP} (@pxref{Obsolete Macros}) used to play the
role of @code{AC_PREPROC_IFELSE}, but double quotes its argument, making
it impossible to use it to elaborate sources. You are encouraged to
get rid of your old use of the macro @code{AC_TRY_CPP} in favor of
@code{AC_PREPROC_IFELSE}, but, in the first place, are you sure you need
to run the @emph{preprocessor} and not the compiler?
@anchor{AC_EGREP_HEADER}
@defmac AC_EGREP_HEADER (@var{pattern}, @var{header-file}, @
@var{action-if-found}, @ovar{action-if-not-found})
@acindex{EGREP_HEADER}
If the output of running the preprocessor on the system header file
@var{header-file} matches the extended regular expression
@var{pattern}, execute shell commands @var{action-if-found}, otherwise
execute @var{action-if-not-found}.
@end defmac
@anchor{AC_EGREP_CPP}
@defmac AC_EGREP_CPP (@var{pattern}, @var{program}, @
@ovar{action-if-found}, @ovar{action-if-not-found})
@acindex{EGREP_CPP}
@var{program} is the text of a C or C++ program, on which shell
variable, back quote, and backslash substitutions are performed. If the
output of running the preprocessor on @var{program} matches the
extended regular expression @var{pattern}, execute shell commands
@var{action-if-found}, otherwise execute @var{action-if-not-found}.
@end defmac
@node Running the Compiler
@section Running the Compiler
To check for a syntax feature of the current language's (@pxref{Language
Choice}) compiler, such as whether it recognizes a certain keyword, or
simply to try some library feature, use @code{AC_COMPILE_IFELSE} to try
to compile a small program that uses that feature.
@defmac AC_COMPILE_IFELSE (@var{input}, @ovar{action-if-true}, @
@ovar{action-if-false})
@acindex{COMPILE_IFELSE}
Run the compiler and compilation flags of the current language
(@pxref{Language Choice}) on the @var{input}, run the shell commands
@var{action-if-true} on success, @var{action-if-false} otherwise. The
@var{input} can be made by @code{AC_LANG_PROGRAM} and friends.
It is customary to report unexpected failures with
@code{AC_MSG_FAILURE}. This macro does not try to link; use
@code{AC_LINK_IFELSE} if you need to do that (@pxref{Running the
Linker}).
This macro uses @code{AC_REQUIRE} for the compiler associated with the
current language, which means that if the compiler has not yet been
determined, the compiler determination will be made prior to the body of
the outermust @code{AC_DEFUN} macro that triggered this macro to
expand (@pxref{Expanded Before Required}).
@end defmac
@ovindex ERL
For tests in Erlang, the @var{input} must be the source code of a module named
@code{conftest}. @code{AC_COMPILE_IFELSE} generates a @file{conftest.beam}
file that can be interpreted by the Erlang virtual machine (@code{ERL}). It is
recommended to use @code{AC_LANG_PROGRAM} to specify the test program,
to ensure that the Erlang module has the right name.
@node Running the Linker
@section Running the Linker
To check for a library, a function, or a global variable, Autoconf
@command{configure} scripts try to compile and link a small program that
uses it. This is unlike Metaconfig, which by default uses @code{nm} or
@code{ar} on the C library to try to figure out which functions are
available. Trying to link with the function is usually a more reliable
approach because it avoids dealing with the variations in the options
and output formats of @code{nm} and @code{ar} and in the location of the
standard libraries. It also allows configuring for cross-compilation or
checking a function's runtime behavior if needed. On the other hand,
it can be slower than scanning the libraries once, but accuracy is more
important than speed.
@code{AC_LINK_IFELSE} is used to compile test programs to test for
functions and global variables. It is also used by @code{AC_CHECK_LIB}
to check for libraries (@pxref{Libraries}), by adding the library being
checked for to @code{LIBS} temporarily and trying to link a small
program.
@anchor{AC_LINK_IFELSE}
@defmac AC_LINK_IFELSE (@var{input}, @ovar{action-if-true}, @
@ovar{action-if-false})
@acindex{LINK_IFELSE}
Run the compiler (and compilation flags) and the linker of the current
language (@pxref{Language Choice}) on the @var{input}, run the shell
commands @var{action-if-true} on success, @var{action-if-false}
otherwise. The @var{input} can be made by @code{AC_LANG_PROGRAM} and
friends.
@code{LDFLAGS} and @code{LIBS} are used for linking, in addition to the
current compilation flags.
It is customary to report unexpected failures with
@code{AC_MSG_FAILURE}. This macro does not try to execute the program;
use @code{AC_RUN_IFELSE} if you need to do that (@pxref{Runtime}).
@end defmac
The @code{AC_LINK_IFELSE} macro cannot be used for Erlang tests, since Erlang
programs are interpreted and do not require linking.
@node Runtime
@section Checking Runtime Behavior
Sometimes you need to find out how a system performs at runtime, such
as whether a given function has a certain capability or bug. If you
can, make such checks when your program runs instead of when it is
configured. You can check for things like the machine's endianness when
your program initializes itself.
If you really need to test for a runtime behavior while configuring,
you can write a test program to determine the result, and compile and
run it using @code{AC_RUN_IFELSE}. Avoid running test programs if
possible, because this prevents people from configuring your package for
cross-compiling.
@anchor{AC_RUN_IFELSE}
@defmac AC_RUN_IFELSE (@var{input}, @ovar{action-if-true}, @
@ovar{action-if-false}, @ovar{action-if-cross-compiling})
@acindex{RUN_IFELSE}
If @var{program} compiles and links successfully and returns an exit
status of 0 when executed, run shell commands @var{action-if-true}.
Otherwise, run shell commands @var{action-if-false}.
The @var{input} can be made by @code{AC_LANG_PROGRAM} and friends.
@code{LDFLAGS} and @code{LIBS} are used for linking, in addition to the
compilation flags of the current language (@pxref{Language Choice}).
If the compiler being used does not produce executables that run on the
system where @command{configure} is being run, then the test program is
not run. If the optional shell commands @var{action-if-cross-compiling}
are given, they are run instead. Otherwise, @command{configure} prints
an error message and exits.
In the @var{action-if-false} section, the failing exit status is
available in the shell variable @samp{$?}. This exit status might be
that of a failed compilation, or it might be that of a failed program
execution.
It is customary to report unexpected failures with
@code{AC_MSG_FAILURE}.
@end defmac
Try to provide a pessimistic default value to use when cross-compiling
makes runtime tests impossible. You do this by passing the optional
last argument to @code{AC_RUN_IFELSE}. @command{autoconf} prints a
warning message when creating @command{configure} each time it
encounters a call to @code{AC_RUN_IFELSE} with no
@var{action-if-cross-compiling} argument given. You may ignore the
warning, though users cannot configure your package for
cross-compiling. A few of the macros distributed with Autoconf produce
this warning message.
To configure for cross-compiling you can also choose a value for those
parameters based on the canonical system name (@pxref{Manual
Configuration}). Alternatively, set up a test results cache file with
the correct values for the host system (@pxref{Caching Results}).
@ovindex cross_compiling
To provide a default for calls of @code{AC_RUN_IFELSE} that are embedded
in other macros, including a few of the ones that come with Autoconf,
you can test whether the shell variable @code{cross_compiling} is set to
@samp{yes}, and then use an alternate method to get the results instead
of calling the macros.
It is also permissible to temporarily assign to @code{cross_compiling}
in order to force tests to behave as though they are in a
cross-compilation environment, particularly since this provides a way to
test your @var{action-if-cross-compiling} even when you are not using a
cross-compiler.
@example
# We temporarily set cross-compile mode to force AC_COMPUTE_INT
# to use the slow link-only method
save_cross_compiling=$cross_compiling
cross_compiling=yes
AC_COMPUTE_INT([@dots{}])
cross_compiling=$save_cross_compiling
@end example
A C or C++ runtime test should be portable.
@xref{Portable C and C++}.
Erlang tests must exit themselves the Erlang VM by calling the @code{halt/1}
function: the given status code is used to determine the success of the test
(status is @code{0}) or its failure (status is different than @code{0}), as
explained above. It must be noted that data output through the standard output
(e.g., using @code{io:format/2}) may be truncated when halting the VM.
Therefore, if a test must output configuration information, it is recommended
to create and to output data into the temporary file named @file{conftest.out},
using the functions of module @code{file}. The @code{conftest.out} file is
automatically deleted by the @code{AC_RUN_IFELSE} macro. For instance, a
simplified implementation of Autoconf's @code{AC_ERLANG_SUBST_LIB_DIR}
macro is:
@example
AC_INIT([LibdirTest], [1.0], [bug-libdirtest@@example.org])
AC_ERLANG_NEED_ERL
AC_LANG(Erlang)
AC_RUN_IFELSE(
[AC_LANG_PROGRAM([], [dnl
file:write_file("conftest.out", code:lib_dir()),
halt(0)])],
[echo "code:lib_dir() returned: `cat conftest.out`"],
[AC_MSG_FAILURE([test Erlang program execution failed])])
@end example
@node Systemology
@section Systemology
@cindex Systemology
This section aims at presenting some systems and pointers to
documentation. It may help you addressing particular problems reported
by users.
@uref{http://@/www.opengroup.org/@/susv3, Posix-conforming systems} are
derived from the @uref{http://@/www.bell-labs.com/@/history/@/unix/, Unix
operating system}.
The @uref{http://@/bhami.com/@/rosetta.html, Rosetta Stone for Unix}
contains a table correlating the features of various Posix-conforming
systems. @uref{http://@/www.levenez.com/@/unix/, Unix History} is a
simplified diagram of how many Unix systems were derived from each
other.
@uref{http://@/heirloom.sourceforge.net/, The Heirloom Project}
provides some variants of traditional implementations of Unix utilities.
@table @asis
@item Darwin
@cindex Darwin
Darwin is also known as Mac OS X@. Beware that the file system @emph{can} be
case-preserving, but case insensitive. This can cause nasty problems,
since for instance the installation attempt for a package having an
@file{INSTALL} file can result in @samp{make install} report that
nothing was to be done!
That's all dependent on whether the file system is a UFS (case
sensitive) or HFS+ (case preserving). By default Apple wants you to
install the OS on HFS+. Unfortunately, there are some pieces of
software which really need to be built on UFS@. We may want to rebuild
Darwin to have both UFS and HFS+ available (and put the /local/build
tree on the UFS).
@item @acronym{QNX} 4.25
@cindex @acronym{QNX} 4.25
@c FIXME: Please, if you feel like writing something more precise,
@c it'd be great. In particular, I can't understand the difference with
@c QNX Neutrino.
@acronym{QNX} is a realtime operating system running on Intel architecture
meant to be scalable from the small embedded systems to the hundred
processor super-computer. It claims to be Posix certified. More
information is available on the
@uref{http://@/www.qnx.com/, @acronym{QNX} home page}.
@item Tru64
@cindex Tru64
@uref{http://@/h30097.www3.hp.com/@/docs/,
Documentation of several versions of Tru64} is available in different
formats.
@item Unix version 7
@cindex Unix version 7
@cindex V7
Officially this was called the ``Seventh Edition'' of ``the @sc{unix}
time-sharing system'' but we use the more-common name ``Unix version 7''.
Documentation is available in the
@uref{http://@/plan9.bell-labs.com/@/7thEdMan/, Unix Seventh Edition Manual}.
Previous versions of Unix are called ``Unix version 6'', etc., but
they were not as widely used.
@end table
@node Multiple Cases
@section Multiple Cases
Some operations are accomplished in several possible ways, depending on
the OS variant. Checking for them essentially requires a ``case
statement''. Autoconf does not directly provide one; however, it is
easy to simulate by using a shell variable to keep track of whether a
way to perform the operation has been found yet.
Here is an example that uses the shell variable @code{fstype} to keep
track of whether the remaining cases need to be checked. Note that
since the value of @code{fstype} is under our control, we don't have to
use the longer @samp{test "x$fstype" = xno}.
@example
@group
AC_MSG_CHECKING([how to get file system type])
fstype=no
# The order of these tests is important.
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include
#include ]])],
[AC_DEFINE([FSTYPE_STATVFS], [1],
[Define if statvfs exists.])
fstype=SVR4])
if test $fstype = no; then
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include
#include ]])],
[AC_DEFINE([FSTYPE_USG_STATFS], [1],
[Define if USG statfs.])
fstype=SVR3])
fi
if test $fstype = no; then
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include
#include ]])]),
[AC_DEFINE([FSTYPE_AIX_STATFS], [1],
[Define if AIX statfs.])
fstype=AIX])
fi
# (more cases omitted here)
AC_MSG_RESULT([$fstype])
@end group
@end example
@c ====================================================== Results of Tests.
@node Results
@chapter Results of Tests
Once @command{configure} has determined whether a feature exists, what can
it do to record that information? There are four sorts of things it can
do: define a C preprocessor symbol, set a variable in the output files,
save the result in a cache file for future @command{configure} runs, and
print a message letting the user know the result of the test.
@menu
* Defining Symbols:: Defining C preprocessor symbols
* Setting Output Variables:: Replacing variables in output files
* Special Chars in Variables:: Characters to beware of in variables
* Caching Results:: Speeding up subsequent @command{configure} runs
* Printing Messages:: Notifying @command{configure} users
@end menu
@node Defining Symbols
@section Defining C Preprocessor Symbols
A common action to take in response to a feature test is to define a C
preprocessor symbol indicating the results of the test. That is done by
calling @code{AC_DEFINE} or @code{AC_DEFINE_UNQUOTED}.
By default, @code{AC_OUTPUT} places the symbols defined by these macros
into the output variable @code{DEFS}, which contains an option
@option{-D@var{symbol}=@var{value}} for each symbol defined. Unlike in
Autoconf version 1, there is no variable @code{DEFS} defined while
@command{configure} is running. To check whether Autoconf macros have
already defined a certain C preprocessor symbol, test the value of the
appropriate cache variable, as in this example:
@example
AC_CHECK_FUNC([vprintf], [AC_DEFINE([HAVE_VPRINTF], [1],
[Define if vprintf exists.])])
if test "x$ac_cv_func_vprintf" != xyes; then
AC_CHECK_FUNC([_doprnt], [AC_DEFINE([HAVE_DOPRNT], [1],
[Define if _doprnt exists.])])
fi
@end example
If @code{AC_CONFIG_HEADERS} has been called, then instead of creating
@code{DEFS}, @code{AC_OUTPUT} creates a header file by substituting the
correct values into @code{#define} statements in a template file.
@xref{Configuration Headers}, for more information about this kind of
output.
@defmac AC_DEFINE (@var{variable}, @var{value}, @ovar{description})
@defmacx AC_DEFINE (@var{variable})
@cvindex @var{variable}
@acindex{DEFINE}
Define @var{variable} to @var{value} (verbatim), by defining a C
preprocessor macro for @var{variable}. @var{variable} should be a C
identifier, optionally suffixed by a parenthesized argument list to
define a C preprocessor macro with arguments. The macro argument list,
if present, should be a comma-separated list of C identifiers, possibly
terminated by an ellipsis @samp{...} if C99 syntax is employed.
@var{variable} should not contain comments, white space, trigraphs,
backslash-newlines, universal character names, or non-@acronym{ASCII}
characters.
@var{value} may contain backslash-escaped newlines, which will be
preserved if you use @code{AC_CONFIG_HEADERS} but flattened if passed
via @code{@@DEFS@@} (with no effect on the compilation, since the
preprocessor sees only one line in the first place). @var{value} should
not contain raw newlines. If you are not using
@code{AC_CONFIG_HEADERS}, @var{value} should not contain any @samp{#}
characters, as @command{make} tends to eat them. To use a shell
variable, use @code{AC_DEFINE_UNQUOTED} instead.
@var{description} is only useful if you are using
@code{AC_CONFIG_HEADERS}. In this case, @var{description} is put into
the generated @file{config.h.in} as the comment before the macro define.
The following example defines the C preprocessor variable
@code{EQUATION} to be the string constant @samp{"$a > $b"}:
@example
AC_DEFINE([EQUATION], ["$a > $b"],
[Equation string.])
@end example
If neither @var{value} nor @var{description} are given, then
@var{value} defaults to 1 instead of to the empty string. This is for
backwards compatibility with older versions of Autoconf, but this usage
is obsolescent and may be withdrawn in future versions of Autoconf.
If the @var{variable} is a literal string, it is passed to
@code{m4_pattern_allow} (@pxref{Forbidden Patterns}).
If multiple @code{AC_DEFINE} statements are executed for the same
@var{variable} name (not counting any parenthesized argument list),
the last one wins.
@end defmac
@defmac AC_DEFINE_UNQUOTED (@var{variable}, @var{value}, @ovar{description})
@defmacx AC_DEFINE_UNQUOTED (@var{variable})
@acindex{DEFINE_UNQUOTED}
@cvindex @var{variable}
Like @code{AC_DEFINE}, but three shell expansions are
performed---once---on @var{variable} and @var{value}: variable expansion
(@samp{$}), command substitution (@samp{`}), and backslash escaping
(@samp{\}), as if in an unquoted here-document. Single and double quote
characters in the value have no
special meaning. Use this macro instead of @code{AC_DEFINE} when
@var{variable} or @var{value} is a shell variable. Examples:
@example
AC_DEFINE_UNQUOTED([config_machfile], ["$machfile"],
[Configuration machine file.])
AC_DEFINE_UNQUOTED([GETGROUPS_T], [$ac_cv_type_getgroups],
[getgroups return type.])
AC_DEFINE_UNQUOTED([$ac_tr_hdr], [1],
[Translated header name.])
@end example
@end defmac
Due to a syntactical bizarreness of the Bourne shell, do not use
semicolons to separate @code{AC_DEFINE} or @code{AC_DEFINE_UNQUOTED}
calls from other macro calls or shell code; that can cause syntax errors
in the resulting @command{configure} script. Use either blanks or
newlines. That is, do this:
@example
AC_CHECK_HEADER([elf.h],
[AC_DEFINE([SVR4], [1], [System V Release 4]) LIBS="-lelf $LIBS"])
@end example
@noindent
or this:
@example
AC_CHECK_HEADER([elf.h],
[AC_DEFINE([SVR4], [1], [System V Release 4])
LIBS="-lelf $LIBS"])
@end example
@noindent
instead of this:
@example
AC_CHECK_HEADER([elf.h],
[AC_DEFINE([SVR4], [1], [System V Release 4]); LIBS="-lelf $LIBS"])
@end example
@node Setting Output Variables
@section Setting Output Variables
@cindex Output variables
Another way to record the results of tests is to set @dfn{output
variables}, which are shell variables whose values are substituted into
files that @command{configure} outputs. The two macros below create new
output variables. @xref{Preset Output Variables}, for a list of output
variables that are always available.
@defmac AC_SUBST (@var{variable}, @ovar{value})
@acindex{SUBST}
Create an output variable from a shell variable. Make @code{AC_OUTPUT}
substitute the variable @var{variable} into output files (typically one
or more makefiles). This means that @code{AC_OUTPUT}
replaces instances of @samp{@@@var{variable}@@} in input files with the
value that the shell variable @var{variable} has when @code{AC_OUTPUT}
is called. The value can contain any non-@code{NUL} character, including
newline. If you are using Automake 1.11 or newer, for newlines in values
you might want to consider using @code{AM_SUBST_NOTMAKE} to prevent
@command{automake} from adding a line @code{@var{variable} =
@@@var{variable}@@} to the @file{Makefile.in} files (@pxref{Optional, ,
Automake, automake, Other things Automake recognizes}).
Variable occurrences should not overlap: e.g., an input file should
not contain @samp{@@@var{var1}@@@var{var2}@@} if @var{var1} and @var{var2}
are variable names.
The substituted value is not rescanned for more output variables;
occurrences of @samp{@@@var{variable}@@} in the value are inserted
literally into the output file. (The algorithm uses the special marker
@code{|#_!!_#|} internally, so neither the substituted value nor the
output file may contain @code{|#_!!_#|}.)
If @var{value} is given, in addition assign it to @var{variable}.
The string @var{variable} is passed to @code{m4_pattern_allow}
(@pxref{Forbidden Patterns}).
@end defmac
@defmac AC_SUBST_FILE (@var{variable})
@acindex{SUBST_FILE}
Another way to create an output variable from a shell variable. Make
@code{AC_OUTPUT} insert (without substitutions) the contents of the file
named by shell variable @var{variable} into output files. This means
that @code{AC_OUTPUT} replaces instances of
@samp{@@@var{variable}@@} in output files (such as @file{Makefile.in})
with the contents of the file that the shell variable @var{variable}
names when @code{AC_OUTPUT} is called. Set the variable to
@file{/dev/null} for cases that do not have a file to insert.
This substitution occurs only when the @samp{@@@var{variable}@@} is on a
line by itself, optionally surrounded by spaces and tabs. The
substitution replaces the whole line, including the spaces, tabs, and
the terminating newline.
This macro is useful for inserting makefile fragments containing
special dependencies or other @command{make} directives for particular host
or target types into makefiles. For example, @file{configure.ac}
could contain:
@example
AC_SUBST_FILE([host_frag])
host_frag=$srcdir/conf/sun4.mh
@end example
@noindent
and then a @file{Makefile.in} could contain:
@example
@@host_frag@@
@end example
The string @var{variable} is passed to @code{m4_pattern_allow}
(@pxref{Forbidden Patterns}).
@end defmac
@cindex Precious Variable
@cindex Variable, Precious
Running @command{configure} in varying environments can be extremely
dangerous. If for instance the user runs @samp{CC=bizarre-cc
./configure}, then the cache, @file{config.h}, and many other output
files depend upon @command{bizarre-cc} being the C compiler. If
for some reason the user runs @command{./configure} again, or if it is
run via @samp{./config.status --recheck}, (@xref{Automatic Remaking},
and @pxref{config.status Invocation}), then the configuration can be
inconsistent, composed of results depending upon two different
compilers.
Environment variables that affect this situation, such as @samp{CC}
above, are called @dfn{precious variables}, and can be declared as such
by @code{AC_ARG_VAR}.
@defmac AC_ARG_VAR (@var{variable}, @var{description})
@acindex{ARG_VAR}
Declare @var{variable} is a precious variable, and include its
@var{description} in the variable section of @samp{./configure --help}.
Being precious means that
@itemize @minus
@item
@var{variable} is substituted via @code{AC_SUBST}.
@item
The value of @var{variable} when @command{configure} was launched is
saved in the cache, including if it was not specified on the command
line but via the environment. Indeed, while @command{configure} can
notice the definition of @code{CC} in @samp{./configure CC=bizarre-cc},
it is impossible to notice it in @samp{CC=bizarre-cc ./configure},
which, unfortunately, is what most users do.
We emphasize that it is the @emph{initial} value of @var{variable} which
is saved, not that found during the execution of @command{configure}.
Indeed, specifying @samp{./configure FOO=foo} and letting
@samp{./configure} guess that @code{FOO} is @code{foo} can be two
different things.
@item
@var{variable} is checked for consistency between two
@command{configure} runs. For instance:
@example
$ @kbd{./configure --silent --config-cache}
$ @kbd{CC=cc ./configure --silent --config-cache}
configure: error: `CC' was not set in the previous run
configure: error: changes in the environment can compromise \
the build
configure: error: run `make distclean' and/or \
`rm config.cache' and start over
@end example
@noindent
and similarly if the variable is unset, or if its content is changed.
If the content has white space changes only, then the error is degraded
to a warning only, but the old value is reused.
@item
@var{variable} is kept during automatic reconfiguration
(@pxref{config.status Invocation}) as if it had been passed as a command
line argument, including when no cache is used:
@example
$ @kbd{CC=/usr/bin/cc ./configure var=raboof --silent}
$ @kbd{./config.status --recheck}
running CONFIG_SHELL=/bin/sh /bin/sh ./configure var=raboof \
CC=/usr/bin/cc --no-create --no-recursion
@end example
@end itemize
@end defmac
@node Special Chars in Variables
@section Special Characters in Output Variables
@cindex Output variables, special characters in
Many output variables are intended to be evaluated both by
@command{make} and by the shell. Some characters are expanded
differently in these two contexts, so to avoid confusion these
variables' values should not contain any of the following characters:
@example
" # $ & ' ( ) * ; < > ? [ \ ^ ` |
@end example
Also, these variables' values should neither contain newlines, nor start
with @samp{~}, nor contain white space or @samp{:} immediately followed
by @samp{~}. The values can contain nonempty sequences of white space
characters like tabs and spaces, but each such sequence might
arbitrarily be replaced by a single space during substitution.
These restrictions apply both to the values that @command{configure}
computes, and to the values set directly by the user. For example, the
following invocations of @command{configure} are problematic, since they
attempt to use special characters within @code{CPPFLAGS} and white space
within @code{$(srcdir)}:
@example
CPPFLAGS='-DOUCH="&\"#$*?"' '../My Source/ouch-1.0/configure'
'../My Source/ouch-1.0/configure' CPPFLAGS='-DOUCH="&\"#$*?"'
@end example
@node Caching Results
@section Caching Results
@cindex Cache
To avoid checking for the same features repeatedly in various
@command{configure} scripts (or in repeated runs of one script),
@command{configure} can optionally save the results of many checks in a
@dfn{cache file} (@pxref{Cache Files}). If a @command{configure} script
runs with caching enabled and finds a cache file, it reads the results
of previous runs from the cache and avoids rerunning those checks. As a
result, @command{configure} can then run much faster than if it had to
perform all of the checks every time.
@defmac AC_CACHE_VAL (@var{cache-id}, @var{commands-to-set-it})
@acindex{CACHE_VAL}
Ensure that the results of the check identified by @var{cache-id} are
available. If the results of the check were in the cache file that was
read, and @command{configure} was not given the @option{--quiet} or
@option{--silent} option, print a message saying that the result was
cached; otherwise, run the shell commands @var{commands-to-set-it}. If
the shell commands are run to determine the value, the value is
saved in the cache file just before @command{configure} creates its output
files. @xref{Cache Variable Names}, for how to choose the name of the
@var{cache-id} variable.
The @var{commands-to-set-it} @emph{must have no side effects} except for
setting the variable @var{cache-id}, see below.
@end defmac
@defmac AC_CACHE_CHECK (@var{message}, @var{cache-id}, @
@var{commands-to-set-it})
@acindex{CACHE_CHECK}
A wrapper for @code{AC_CACHE_VAL} that takes care of printing the
messages. This macro provides a convenient shorthand for the most
common way to use these macros. It calls @code{AC_MSG_CHECKING} for
@var{message}, then @code{AC_CACHE_VAL} with the @var{cache-id} and
@var{commands} arguments, and @code{AC_MSG_RESULT} with @var{cache-id}.
The @var{commands-to-set-it} @emph{must have no side effects} except for
setting the variable @var{cache-id}, see below.
@end defmac
It is common to find buggy macros using @code{AC_CACHE_VAL} or
@code{AC_CACHE_CHECK}, because people are tempted to call
@code{AC_DEFINE} in the @var{commands-to-set-it}. Instead, the code that
@emph{follows} the call to @code{AC_CACHE_VAL} should call
@code{AC_DEFINE}, by examining the value of the cache variable. For
instance, the following macro is broken:
@example
@group
AC_DEFUN([AC_SHELL_TRUE],
[AC_CACHE_CHECK([whether true(1) works], [my_cv_shell_true_works],
[my_cv_shell_true_works=no
(true) 2>/dev/null && my_cv_shell_true_works=yes
if test "x$my_cv_shell_true_works" = xyes; then
AC_DEFINE([TRUE_WORKS], [1],
[Define if `true(1)' works properly.])
fi])
])
@end group
@end example
@noindent
This fails if the cache is enabled: the second time this macro is run,
@code{TRUE_WORKS} @emph{will not be defined}. The proper implementation
is:
@example
@group
AC_DEFUN([AC_SHELL_TRUE],
[AC_CACHE_CHECK([whether true(1) works], [my_cv_shell_true_works],
[my_cv_shell_true_works=no
(true) 2>/dev/null && my_cv_shell_true_works=yes])
if test "x$my_cv_shell_true_works" = xyes; then
AC_DEFINE([TRUE_WORKS], [1],
[Define if `true(1)' works properly.])
fi
])
@end group
@end example
Also, @var{commands-to-set-it} should not print any messages, for
example with @code{AC_MSG_CHECKING}; do that before calling
@code{AC_CACHE_VAL}, so the messages are printed regardless of whether
the results of the check are retrieved from the cache or determined by
running the shell commands.
@menu
* Cache Variable Names:: Shell variables used in caches
* Cache Files:: Files @command{configure} uses for caching
* Cache Checkpointing:: Loading and saving the cache file
@end menu
@node Cache Variable Names
@subsection Cache Variable Names
@cindex Cache variable
The names of cache variables should have the following format:
@example
@var{package-prefix}_cv_@var{value-type}_@var{specific-value}_@ovar{additional-options}
@end example
@noindent
for example, @samp{ac_cv_header_stat_broken} or
@samp{ac_cv_prog_gcc_traditional}. The parts of the variable name are:
@table @asis
@item @var{package-prefix}
An abbreviation for your package or organization; the same prefix you
begin local Autoconf macros with, except lowercase by convention.
For cache values used by the distributed Autoconf macros, this value is
@samp{ac}.
@item @code{_cv_}
Indicates that this shell variable is a cache value. This string
@emph{must} be present in the variable name, including the leading
underscore.
@item @var{value-type}
A convention for classifying cache values, to produce a rational naming
system. The values used in Autoconf are listed in @ref{Macro Names}.
@item @var{specific-value}
Which member of the class of cache values this test applies to.
For example, which function (@samp{alloca}), program (@samp{gcc}), or
output variable (@samp{INSTALL}).
@item @var{additional-options}
Any particular behavior of the specific member that this test applies to.
For example, @samp{broken} or @samp{set}. This part of the name may
be omitted if it does not apply.
@end table
The values assigned to cache variables may not contain newlines.
Usually, their values are Boolean (@samp{yes} or @samp{no}) or the
names of files or functions; so this is not an important restriction.
@node Cache Files
@subsection Cache Files
A cache file is a shell script that caches the results of configure
tests run on one system so they can be shared between configure scripts
and configure runs. It is not useful on other systems. If its contents
are invalid for some reason, the user may delete or edit it.
By default, @command{configure} uses no cache file,
to avoid problems caused by accidental
use of stale cache files.
To enable caching, @command{configure} accepts @option{--config-cache} (or
@option{-C}) to cache results in the file @file{config.cache}.
Alternatively, @option{--cache-file=@var{file}} specifies that
@var{file} be the cache file. The cache file is created if it does not
exist already. When @command{configure} calls @command{configure} scripts in
subdirectories, it uses the @option{--cache-file} argument so that they
share the same cache. @xref{Subdirectories}, for information on
configuring subdirectories with the @code{AC_CONFIG_SUBDIRS} macro.
@file{config.status} only pays attention to the cache file if it is
given the @option{--recheck} option, which makes it rerun
@command{configure}.
It is wrong to try to distribute cache files for particular system types.
There is too much room for error in doing that, and too much
administrative overhead in maintaining them. For any features that
can't be guessed automatically, use the standard method of the canonical
system type and linking files (@pxref{Manual Configuration}).
The site initialization script can specify a site-wide cache file to
use, instead of the usual per-program cache. In this case, the cache
file gradually accumulates information whenever someone runs a new
@command{configure} script. (Running @command{configure} merges the new cache
results with the existing cache file.) This may cause problems,
however, if the system configuration (e.g., the installed libraries or
compilers) changes and the stale cache file is not deleted.
@node Cache Checkpointing
@subsection Cache Checkpointing
If your configure script, or a macro called from @file{configure.ac}, happens
to abort the configure process, it may be useful to checkpoint the cache
a few times at key points using @code{AC_CACHE_SAVE}. Doing so
reduces the amount of time it takes to rerun the configure script with
(hopefully) the error that caused the previous abort corrected.
@c FIXME: Do we really want to document this guy?
@defmac AC_CACHE_LOAD
@acindex{CACHE_LOAD}
Loads values from existing cache file, or creates a new cache file if a
cache file is not found. Called automatically from @code{AC_INIT}.
@end defmac
@defmac AC_CACHE_SAVE
@acindex{CACHE_SAVE}
Flushes all cached values to the cache file. Called automatically from
@code{AC_OUTPUT}, but it can be quite useful to call
@code{AC_CACHE_SAVE} at key points in @file{configure.ac}.
@end defmac
For instance:
@example
@r{ @dots{} AC_INIT, etc. @dots{}}
@group
# Checks for programs.
AC_PROG_CC
AC_PROG_AWK
@r{ @dots{} more program checks @dots{}}
AC_CACHE_SAVE
@end group
@group
# Checks for libraries.
AC_CHECK_LIB([nsl], [gethostbyname])
AC_CHECK_LIB([socket], [connect])
@r{ @dots{} more lib checks @dots{}}
AC_CACHE_SAVE
@end group
@group
# Might abort@dots{}
AM_PATH_GTK([1.0.2], [], [AC_MSG_ERROR([GTK not in path])])
AM_PATH_GTKMM([0.9.5], [], [AC_MSG_ERROR([GTK not in path])])
@end group
@r{ @dots{} AC_OUTPUT, etc. @dots{}}
@end example
@node Printing Messages
@section Printing Messages
@cindex Messages, from @command{configure}
@command{configure} scripts need to give users running them several kinds
of information. The following macros print messages in ways appropriate
for each kind. The arguments to all of them get enclosed in shell
double quotes, so the shell performs variable and back-quote
substitution on them.
These macros are all wrappers around the @command{echo} shell command.
They direct output to the appropriate file descriptor (@pxref{File
Descriptor Macros}).
@command{configure} scripts should rarely need to run @command{echo} directly
to print messages for the user. Using these macros makes it easy to
change how and when each kind of message is printed; such changes need
only be made to the macro definitions and all the callers change
automatically.
To diagnose static issues, i.e., when @command{autoconf} is run, see
@ref{Diagnostic Macros}.
@defmac AC_MSG_CHECKING (@var{feature-description})
@acindex{MSG_CHECKING}
Notify the user that @command{configure} is checking for a particular
feature. This macro prints a message that starts with @samp{checking }
and ends with @samp{...} and no newline. It must be followed by a call
to @code{AC_MSG_RESULT} to print the result of the check and the
newline. The @var{feature-description} should be something like
@samp{whether the Fortran compiler accepts C++ comments} or @samp{for
c89}.
This macro prints nothing if @command{configure} is run with the
@option{--quiet} or @option{--silent} option.
@end defmac
@anchor{AC_MSG_RESULT}
@defmac AC_MSG_RESULT (@var{result-description})
@acindex{MSG_RESULT}
Notify the user of the results of a check. @var{result-description} is
almost always the value of the cache variable for the check, typically
@samp{yes}, @samp{no}, or a file name. This macro should follow a call
to @code{AC_MSG_CHECKING}, and the @var{result-description} should be
the completion of the message printed by the call to
@code{AC_MSG_CHECKING}.
This macro prints nothing if @command{configure} is run with the
@option{--quiet} or @option{--silent} option.
@end defmac
@anchor{AC_MSG_NOTICE}
@defmac AC_MSG_NOTICE (@var{message})
@acindex{MSG_NOTICE}
Deliver the @var{message} to the user. It is useful mainly to print a
general description of the overall purpose of a group of feature checks,
e.g.,
@example
AC_MSG_NOTICE([checking if stack overflow is detectable])
@end example
This macro prints nothing if @command{configure} is run with the
@option{--quiet} or @option{--silent} option.
@end defmac
@anchor{AC_MSG_ERROR}
@defmac AC_MSG_ERROR (@var{error-description}, @dvar{exit-status, $?/1})
@acindex{MSG_ERROR}
Notify the user of an error that prevents @command{configure} from
completing. This macro prints an error message to the standard error
output and exits @command{configure} with @var{exit-status} (@samp{$?}
by default, except that @samp{0} is converted to @samp{1}).
@var{error-description} should be something like @samp{invalid value
$HOME for \$HOME}.
The @var{error-description} should start with a lower-case letter, and
``cannot'' is preferred to ``can't''.
@end defmac
@defmac AC_MSG_FAILURE (@var{error-description}, @ovar{exit-status})
@acindex{MSG_FAILURE}
This @code{AC_MSG_ERROR} wrapper notifies the user of an error that
prevents @command{configure} from completing @emph{and} that additional
details are provided in @file{config.log}. This is typically used when
abnormal results are found during a compilation.
@end defmac
@anchor{AC_MSG_WARN}
@defmac AC_MSG_WARN (@var{problem-description})
@acindex{MSG_WARN}
Notify the @command{configure} user of a possible problem. This macro
prints the message to the standard error output; @command{configure}
continues running afterward, so macros that call @code{AC_MSG_WARN} should
provide a default (back-up) behavior for the situations they warn about.
@var{problem-description} should be something like @samp{ln -s seems to
make hard links}.
@end defmac
@c ====================================================== Programming in M4.
@node Programming in M4
@chapter Programming in M4
@cindex M4
Autoconf is written on top of two layers: @dfn{M4sugar}, which provides
convenient macros for pure M4 programming, and @dfn{M4sh}, which
provides macros dedicated to shell script generation.
As of this version of Autoconf, these two layers still contain
experimental macros, whose interface might change in the future. As a
matter of fact, @emph{anything that is not documented must not be used}.
@menu
* M4 Quotation:: Protecting macros from unwanted expansion
* Using autom4te:: The Autoconf executables backbone
* Programming in M4sugar:: Convenient pure M4 macros
* Debugging via autom4te:: Figuring out what M4 was doing
@end menu
@node M4 Quotation
@section M4 Quotation
@cindex M4 quotation
@cindex quotation
The most common problem with existing macros is an improper quotation.
This section, which users of Autoconf can skip, but which macro writers
@emph{must} read, first justifies the quotation scheme that was chosen
for Autoconf and then ends with a rule of thumb. Understanding the
former helps one to follow the latter.
@menu
* Active Characters:: Characters that change the behavior of M4
* One Macro Call:: Quotation and one macro call
* Quoting and Parameters:: M4 vs. shell parameters
* Quotation and Nested Macros:: Macros calling macros
* Changequote is Evil:: Worse than INTERCAL: M4 + changequote
* Quadrigraphs:: Another way to escape special characters
* Balancing Parentheses:: Dealing with unbalanced parentheses
* Quotation Rule Of Thumb:: One parenthesis, one quote
@end menu
@node Active Characters
@subsection Active Characters
To fully understand where proper quotation is important, you first need
to know what the special characters are in Autoconf: @samp{#} introduces
a comment inside which no macro expansion is performed, @samp{,}
separates arguments, @samp{[} and @samp{]} are the quotes themselves,
@samp{(} and @samp{)} (which M4 tries to match by pairs), and finally
@samp{$} inside a macro definition.
In order to understand the delicate case of macro calls, we first have
to present some obvious failures. Below they are ``obvious-ified'',
but when you find them in real life, they are usually in disguise.
Comments, introduced by a hash and running up to the newline, are opaque
tokens to the top level: active characters are turned off, and there is
no macro expansion:
@example
# define([def], ine)
@result{}# define([def], ine)
@end example
Each time there can be a macro expansion, there is a quotation
expansion, i.e., one level of quotes is stripped:
@example
int tab[10];
@result{}int tab10;
[int tab[10];]
@result{}int tab[10];
@end example
Without this in mind, the reader might try hopelessly to use her macro
@code{array}:
@example
define([array], [int tab[10];])
array
@result{}int tab10;
[array]
@result{}array
@end example
@noindent
How can you correctly output the intended results@footnote{Using
@code{defn}.}?
@node One Macro Call
@subsection One Macro Call
Let's proceed on the interaction between active characters and macros
with this small macro, which just returns its first argument:
@example
define([car], [$1])
@end example
@noindent
The two pairs of quotes above are not part of the arguments of
@code{define}; rather, they are understood by the top level when it
tries to find the arguments of @code{define}. Therefore, assuming
@code{car} is not already defined, it is equivalent to write:
@example
define(car, $1)
@end example
@noindent
But, while it is acceptable for a @file{configure.ac} to avoid unnecessary
quotes, it is bad practice for Autoconf macros which must both be more
robust and also advocate perfect style.
At the top level, there are only two possibilities: either you
quote or you don't:
@example
car(foo, bar, baz)
@result{}foo
[car(foo, bar, baz)]
@result{}car(foo, bar, baz)
@end example
Let's pay attention to the special characters:
@example
car(#)
@error{}EOF in argument list
@end example
The closing parenthesis is hidden in the comment; with a hypothetical
quoting, the top level understood it this way:
@example
car([#)]
@end example
@noindent
Proper quotation, of course, fixes the problem:
@example
car([#])
@result{}#
@end example
Here are more examples:
@example
car(foo, bar)
@result{}foo
car([foo, bar])
@result{}foo, bar
car((foo, bar))
@result{}(foo, bar)
car([(foo], [bar)])
@result{}(foo
define([a], [b])
@result{}
car(a)
@result{}b
car([a])
@result{}b
car([[a]])
@result{}a
car([[[a]]])
@result{}[a]
@end example
@node Quoting and Parameters
@subsection Quoting and Parameters
When M4 encounters @samp{$} within a macro definition, followed
immediately by a character it recognizes (@samp{0}@dots{}@samp{9},
@samp{#}, @samp{@@}, or @samp{*}), it will perform M4 parameter
expansion. This happens regardless of how many layers of quotes the
parameter expansion is nested within, or even if it occurs in text that
will be rescanned as a comment.
@example
define([none], [$1])
@result{}
define([one], [[$1]])
@result{}
define([two], [[[$1]]])
@result{}
define([comment], [# $1])
@result{}
define([active], [ACTIVE])
@result{}
none([active])
@result{}ACTIVE
one([active])
@result{}active
two([active])
@result{}[active]
comment([active])
@result{}# active
@end example
On the other hand, since autoconf generates shell code, you often want
to output shell variable expansion, rather than performing M4 parameter
expansion. To do this, you must use M4 quoting to separate the @samp{$}
from the next character in the definition of your macro. If the macro
definition occurs in single-quoted text, then insert another level of
quoting; if the usage is already inside a double-quoted string, then
split it into concatenated strings.
@example
define([single], [a single-quoted $[]1 definition])
@result{}
define([double], [[a double-quoted $][1 definition]])
@result{}
single
@result{}a single-quoted $1 definition
double
@result{}a double-quoted $1 definition
@end example
Posix states that M4 implementations are free to provide implementation
extensions when @samp{$@{} is encountered in a macro definition.
Autoconf reserves the longer sequence @samp{$@{@{} for use with planned
extensions that will be available in the future @acronym{GNU} M4 2.0,
but guarantees that all other instances of @samp{$@{} will be output
literally. Therefore, this idiom can also be used to output shell code
parameter references:
@example
define([first], [$@{1@}])first
@result{}$@{1@}
@end example
Posix also states that @samp{$11} should expand to the first parameter
concatenated with a literal @samp{1}, although some versions of
@acronym{GNU} M4 expand the eleventh parameter instead. For
portability, you should only use single-digit M4 parameter expansion.
With this in mind, we can explore the cases where macros invoke
macros@enddots{}
@node Quotation and Nested Macros
@subsection Quotation and Nested Macros
The examples below use the following macros:
@example
define([car], [$1])
define([active], [ACT, IVE])
define([array], [int tab[10]])
@end example
Each additional embedded macro call introduces other possible
interesting quotations:
@example
car(active)
@result{}ACT
car([active])
@result{}ACT, IVE
car([[active]])
@result{}active
@end example
In the first case, the top level looks for the arguments of @code{car},
and finds @samp{active}. Because M4 evaluates its arguments
before applying the macro, @samp{active} is expanded, which results in:
@example
car(ACT, IVE)
@result{}ACT
@end example
@noindent
In the second case, the top level gives @samp{active} as first and only
argument of @code{car}, which results in:
@example
active
@result{}ACT, IVE
@end example
@noindent
i.e., the argument is evaluated @emph{after} the macro that invokes it.
In the third case, @code{car} receives @samp{[active]}, which results in:
@example
[active]
@result{}active
@end example
@noindent
exactly as we already saw above.
The example above, applied to a more realistic example, gives:
@example
car(int tab[10];)
@result{}int tab10;
car([int tab[10];])
@result{}int tab10;
car([[int tab[10];]])
@result{}int tab[10];
@end example
@noindent
Huh? The first case is easily understood, but why is the second wrong,
and the third right? To understand that, you must know that after
M4 expands a macro, the resulting text is immediately subjected
to macro expansion and quote removal. This means that the quote removal
occurs twice---first before the argument is passed to the @code{car}
macro, and second after the @code{car} macro expands to the first
argument.
As the author of the Autoconf macro @code{car}, you then consider it to
be incorrect that your users have to double-quote the arguments of
@code{car}, so you ``fix'' your macro. Let's call it @code{qar} for
quoted car:
@example
define([qar], [[$1]])
@end example
@noindent
and check that @code{qar} is properly fixed:
@example
qar([int tab[10];])
@result{}int tab[10];
@end example
@noindent
Ahhh! That's much better.
But note what you've done: now that the result of @code{qar} is always
a literal string, the only time a user can use nested macros is if she
relies on an @emph{unquoted} macro call:
@example
qar(active)
@result{}ACT
qar([active])
@result{}active
@end example
@noindent
leaving no way for her to reproduce what she used to do with @code{car}:
@example
car([active])
@result{}ACT, IVE
@end example
@noindent
Worse yet: she wants to use a macro that produces a set of @code{cpp}
macros:
@example
define([my_includes], [#include ])
car([my_includes])
@result{}#include
qar(my_includes)
@error{}EOF in argument list
@end example
This macro, @code{qar}, because it double quotes its arguments, forces
its users to leave their macro calls unquoted, which is dangerous.
Commas and other active symbols are interpreted by M4 before
they are given to the macro, often not in the way the users expect.
Also, because @code{qar} behaves differently from the other macros,
it's an exception that should be avoided in Autoconf.
@node Changequote is Evil
@subsection @code{changequote} is Evil
@cindex @code{changequote}
The temptation is often high to bypass proper quotation, in particular
when it's late at night. Then, many experienced Autoconf hackers
finally surrender to the dark side of the force and use the ultimate
weapon: @code{changequote}.
The M4 builtin @code{changequote} belongs to a set of primitives that
allow one to adjust the syntax of the language to adjust it to one's
needs. For instance, by default M4 uses @samp{`} and @samp{'} as
quotes, but in the context of shell programming (and actually of most
programming languages), that's about the worst choice one can make:
because of strings and back-quoted expressions in shell code (such as
@samp{'this'} and @samp{`that`}), and because of literal characters in usual
programming languages (as in @samp{'0'}), there are many unbalanced
@samp{`} and @samp{'}. Proper M4 quotation then becomes a nightmare, if
not impossible. In order to make M4 useful in such a context, its
designers have equipped it with @code{changequote}, which makes it
possible to choose another pair of quotes. M4sugar, M4sh, Autoconf, and
Autotest all have chosen to use @samp{[} and @samp{]}. Not especially
because they are unlikely characters, but @emph{because they are
characters unlikely to be unbalanced}.
There are other magic primitives, such as @code{changecom} to specify
what syntactic forms are comments (it is common to see
@samp{changecom()} when M4 is used to produce HTML pages),
@code{changeword} and @code{changesyntax} to change other syntactic
details (such as the character to denote the @var{n}th argument, @samp{$} by
default, the parentheses around arguments, etc.).
These primitives are really meant to make M4 more useful for specific
domains: they should be considered like command line options:
@option{--quotes}, @option{--comments}, @option{--words}, and
@option{--syntax}. Nevertheless, they are implemented as M4 builtins, as
it makes M4 libraries self contained (no need for additional options).
There lies the problem@enddots{}
@sp 1
The problem is that it is then tempting to use them in the middle of an
M4 script, as opposed to its initialization. This, if not carefully
thought out, can lead to disastrous effects: @emph{you are changing the
language in the middle of the execution}. Changing and restoring the
syntax is often not enough: if you happened to invoke macros in between,
these macros are lost, as the current syntax is probably not
the one they were implemented with.
@c FIXME: I've been looking for a short, real case example, but I
@c lost them all :(
@node Quadrigraphs
@subsection Quadrigraphs
@cindex quadrigraphs
@cindex @samp{@@S|@@}
@cindex @samp{@@&t@@}
@c Info cannot handle `:' in index entries.
@c @cindex @samp{@@<:@@}
@c @cindex @samp{@@:>@@}
@c @cindex @samp{@@%:@@}
@c @cindex @samp{@@@{:@@}
@c @cindex @samp{@@:@}@@}
When writing an Autoconf macro you may occasionally need to generate
special characters that are difficult to express with the standard
Autoconf quoting rules. For example, you may need to output the regular
expression @samp{[^[]}, which matches any character other than @samp{[}.
This expression contains unbalanced brackets so it cannot be put easily
into an M4 macro.
Additionally, there are a few m4sugar macros (such as @code{m4_split}
and @code{m4_expand}) which internally use special markers in addition
to the regular quoting characters. If the arguments to these macros
contain the literal strings @samp{-=<@{(} or @samp{)@}>=-}, the macros
might behave incorrectly.
You can work around these problems by using one of the following
@dfn{quadrigraphs}:
@table @samp
@item @@<:@@
@samp{[}
@item @@:>@@
@samp{]}
@item @@S|@@
@samp{$}
@item @@%:@@
@samp{#}
@item @@@{:@@
@samp{(}
@item @@:@}@@
@samp{)}
@item @@&t@@
Expands to nothing.
@end table
Quadrigraphs are replaced at a late stage of the translation process,
after @command{m4} is run, so they do not get in the way of M4 quoting.
For example, the string @samp{^@@<:@@}, independently of its quotation,
appears as @samp{^[} in the output.
The empty quadrigraph can be used:
@itemize @minus
@item to mark trailing spaces explicitly
Trailing spaces are smashed by @command{autom4te}. This is a feature.
@item to produce quadrigraphs and other strings reserved by m4sugar
For instance @samp{@@<@@&t@@:@@} produces @samp{@@<:@@}. For a more
contrived example:
@example
m4_define([a], [A])m4_define([b], [B])m4_define([c], [C])dnl
m4_split([a )@}>=- b -=<@{( c])
@result{}[a], [], [B], [], [c]
m4_split([a )@}@@&t@@>=- b -=<@@&t@@@{( c])
@result{}[a], [)@}>=-], [b], [-=<@{(], [c]
@end example
@item to escape @emph{occurrences} of forbidden patterns
For instance you might want to mention @code{AC_FOO} in a comment, while
still being sure that @command{autom4te} still catches unexpanded
@samp{AC_*}. Then write @samp{AC@@&t@@_FOO}.
@end itemize
The name @samp{@@&t@@} was suggested by Paul Eggert:
@quotation
I should give some credit to the @samp{@@&t@@} pun. The @samp{&} is my
own invention, but the @samp{t} came from the source code of the
@sc{algol68c} compiler, written by Steve Bourne (of Bourne shell fame),
and which used @samp{mt} to denote the empty string. In C, it would
have looked like something like:
@example
char const mt[] = "";
@end example
@noindent
but of course the source code was written in Algol 68.
I don't know where he got @samp{mt} from: it could have been his own
invention, and I suppose it could have been a common pun around the
Cambridge University computer lab at the time.
@end quotation
@node Balancing Parentheses
@subsection Dealing with unbalanced parentheses
@cindex balancing parentheses
@cindex parentheses, balancing
@cindex unbalanced parentheses, managing
One of the pitfalls of portable shell programming is that @command{case}
statements require unbalanced parentheses (@pxref{case, , Limitations of
Shell Builtins}). With syntax highlighting
editors, the presence of unbalanced @samp{)} can interfere with editors
that perform syntax highlighting of macro contents based on finding the
matching @samp{(}. Another concern is how much editing must be done
when transferring code snippets between shell scripts and macro
definitions. But most importantly, the presence of unbalanced
parentheses can introduce expansion bugs.
For an example, here is an underquoted attempt to use the macro
@code{my_case}, which happens to expand to a portable @command{case}
statement:
@example
AC_DEFUN([my_case],
[case $file_name in
*.c) echo "C source code";;
esac])
AS_IF(:, my_case)
@end example
@noindent
In the above example, the @code{AS_IF} call underquotes its arguments.
As a result, the unbalanced @samp{)} generated by the premature
expansion of @code{my_case} results in expanding @code{AS_IF} with a
truncated parameter, and the expansion is syntactically invalid:
@example
if :; then
case $file_name in
*.c
fi echo "C source code";;
esac)
@end example
If nothing else, this should emphasize the importance of the quoting
arguments to macro calls. On the other hand, there are several
variations for defining @code{my_case} to be more robust, even when used
without proper quoting, each with some benefits and some drawbacks.
@itemize @w{}
@item Creative literal shell comment
@example
AC_DEFUN([my_case],
[case $file_name in #(
*.c) echo "C source code";;
esac])
@end example
@noindent
This version provides balanced parentheses to several editors, and can
be copied and pasted into a terminal as is. Unfortunately, it is still
unbalanced as an Autoconf argument, since @samp{#(} is an M4 comment
that masks the normal properties of @samp{(}.
@item Quadrigraph shell comment
@example
AC_DEFUN([my_case],
[case $file_name in @@%:@@(
*.c) echo "C source code";;
esac])
@end example
@noindent
This version provides balanced parentheses to even more editors, and can
be used as a balanced Autoconf argument. Unfortunately, it requires
some editing before it can be copied and pasted into a terminal, and the
use of the quadrigraph @samp{@@%:@@} for @samp{#} reduces readability.
@item Quoting just the parenthesis
@example
AC_DEFUN([my_case],
[case $file_name in
*.c[)] echo "C source code";;
esac])
@end example
@noindent
This version quotes the @samp{)}, so that it can be used as a balanced
Autoconf argument. As written, this is not balanced to an editor, but
it can be coupled with @samp{[#(]} to meet that need, too. However, it
still requires some edits before it can be copied and pasted into a
terminal.
@item Double-quoting the entire statement
@example
AC_DEFUN([my_case],
[[case $file_name in #(
*.c) echo "C source code";;
esac]])
@end example
@noindent
Since the entire macro is double-quoted, there is no problem with using
this as an Autoconf argument; and since the double-quoting is over the
entire statement, this code can be easily copied and pasted into a
terminal. However, the double quoting prevents the expansion of any
macros inside the case statement, which may cause its own set of
problems.
@item Using @code{AS_CASE}
@example
AC_DEFUN([my_case],
[AS_CASE([$file_name],
[*.c], [echo "C source code"])])
@end example
@noindent
This version avoids the balancing issue altogether, by relying on
@code{AS_CASE} (@pxref{Common Shell Constructs}); it also allows for the
expansion of @code{AC_REQUIRE} to occur prior to the entire case
statement, rather than within a branch of the case statement that might
not be taken. However, the abstraction comes with a penalty that it is
no longer a quick copy, paste, and edit to get back to shell code.
@end itemize
@node Quotation Rule Of Thumb
@subsection Quotation Rule Of Thumb
To conclude, the quotation rule of thumb is:
@center @emph{One pair of quotes per pair of parentheses.}
Never over-quote, never under-quote, in particular in the definition of
macros. In the few places where the macros need to use brackets
(usually in C program text or regular expressions), properly quote
@emph{the arguments}!
It is common to read Autoconf programs with snippets like:
@example
AC_TRY_LINK(
changequote(<<, >>)dnl
<<#include
#ifndef tzname /* For SGI. */
extern char *tzname[]; /* RS6000 and others reject char **tzname. */
#endif>>,
changequote([, ])dnl
[atoi (*tzname);], ac_cv_var_tzname=yes, ac_cv_var_tzname=no)
@end example
@noindent
which is incredibly useless since @code{AC_TRY_LINK} is @emph{already}
double quoting, so you just need:
@example
AC_TRY_LINK(
[#include
#ifndef tzname /* For SGI. */
extern char *tzname[]; /* RS6000 and others reject char **tzname. */
#endif],
[atoi (*tzname);],
[ac_cv_var_tzname=yes],
[ac_cv_var_tzname=no])
@end example
@noindent
The M4-fluent reader might note that these two examples are rigorously
equivalent, since M4 swallows both the @samp{changequote(<<, >>)}
and @samp{<<} @samp{>>} when it @dfn{collects} the arguments: these
quotes are not part of the arguments!
Simplified, the example above is just doing this:
@example
changequote(<<, >>)dnl
<<[]>>
changequote([, ])dnl
@end example
@noindent
instead of simply:
@example
[[]]
@end example
With macros that do not double quote their arguments (which is the
rule), double-quote the (risky) literals:
@example
AC_LINK_IFELSE([AC_LANG_PROGRAM(
[[#include
#ifndef tzname /* For SGI. */
extern char *tzname[]; /* RS6000 and others reject char **tzname. */
#endif]],
[atoi (*tzname);])],
[ac_cv_var_tzname=yes],
[ac_cv_var_tzname=no])
@end example
Please note that the macro @code{AC_TRY_LINK} is obsolete, so you really
should be using @code{AC_LINK_IFELSE} instead.
@xref{Quadrigraphs}, for what to do if you run into a hopeless case
where quoting does not suffice.
When you create a @command{configure} script using newly written macros,
examine it carefully to check whether you need to add more quotes in
your macros. If one or more words have disappeared in the M4
output, you need more quotes. When in doubt, quote.
However, it's also possible to put on too many layers of quotes. If
this happens, the resulting @command{configure} script may contain
unexpanded macros. The @command{autoconf} program checks for this problem
by looking for the string @samp{AC_} in @file{configure}. However, this
heuristic does not work in general: for example, it does not catch
overquoting in @code{AC_DEFINE} descriptions.
@c ---------------------------------------- Using autom4te
@node Using autom4te
@section Using @command{autom4te}
The Autoconf suite, including M4sugar, M4sh, and Autotest, in addition
to Autoconf per se, heavily rely on M4. All these different uses
revealed common needs factored into a layer over M4:
@command{autom4te}@footnote{
@c
Yet another great name from Lars J. Aas.
@c
}.
@command{autom4te} is a preprocessor that is like @command{m4}.
It supports M4 extensions designed for use in tools like Autoconf.
@menu
* autom4te Invocation:: A @acronym{GNU} M4 wrapper
* Customizing autom4te:: Customizing the Autoconf package
@end menu
@node autom4te Invocation
@subsection Invoking @command{autom4te}
The command line arguments are modeled after M4's:
@example
autom4te @var{options} @var{files}
@end example
@noindent
@evindex M4
where the @var{files} are directly passed to @command{m4}. By default,
@acronym{GNU} M4 is found during configuration, but the environment
variable
@env{M4} can be set to tell @command{autom4te} where to look. In addition
to the regular expansion, it handles the replacement of the quadrigraphs
(@pxref{Quadrigraphs}), and of @samp{__oline__}, the current line in the
output. It supports an extended syntax for the @var{files}:
@table @file
@item @var{file}.m4f
This file is an M4 frozen file. Note that @emph{all the previous files
are ignored}. See the option @option{--melt} for the rationale.
@item @var{file}?
If found in the library path, the @var{file} is included for expansion,
otherwise it is ignored instead of triggering a failure.
@end table
@sp 1
Of course, it supports the Autoconf common subset of options:
@table @option
@item --help
@itemx -h
Print a summary of the command line options and exit.
@item --version
@itemx -V
Print the version number of Autoconf and exit.
@item --verbose
@itemx -v
Report processing steps.
@item --debug
@itemx -d
Don't remove the temporary files and be even more verbose.
@item --include=@var{dir}
@itemx -I @var{dir}
Also look for input files in @var{dir}. Multiple invocations
accumulate.
@item --output=@var{file}
@itemx -o @var{file}
Save output (script or trace) to @var{file}. The file @option{-} stands
for the standard output.
@end table
@sp 1
As an extension of @command{m4}, it includes the following options:
@table @option
@item --warnings=@var{category}
@itemx -W @var{category}
@evindex WARNINGS
@c FIXME: Point to the M4sugar macros, not Autoconf's.
Report the warnings related to @var{category} (which can actually be a
comma separated list). @xref{Reporting Messages}, macro
@code{AC_DIAGNOSE}, for a comprehensive list of categories. Special
values include:
@table @samp
@item all
report all the warnings
@item none
report none
@item error
treats warnings as errors
@item no-@var{category}
disable warnings falling into @var{category}
@end table
Warnings about @samp{syntax} are enabled by default, and the environment
variable @env{WARNINGS}, a comma separated list of categories, is
honored. @samp{autom4te -W @var{category}} actually
behaves as if you had run:
@example
autom4te --warnings=syntax,$WARNINGS,@var{category}
@end example
@noindent
For example, if you want to disable defaults and @env{WARNINGS}
of @command{autom4te}, but enable the warnings about obsolete
constructs, you would use @option{-W none,obsolete}.
@cindex Back trace
@cindex Macro invocation stack
@command{autom4te} displays a back trace for errors, but not for
warnings; if you want them, just pass @option{-W error}.
@item --melt
@itemx -M
Do not use frozen files. Any argument @code{@var{file}.m4f} is
replaced by @code{@var{file}.m4}. This helps tracing the macros which
are executed only when the files are frozen, typically
@code{m4_define}. For instance, running:
@example
autom4te --melt 1.m4 2.m4f 3.m4 4.m4f input.m4
@end example
@noindent
is roughly equivalent to running:
@example
m4 1.m4 2.m4 3.m4 4.m4 input.m4
@end example
@noindent
while
@example
autom4te 1.m4 2.m4f 3.m4 4.m4f input.m4
@end example
@noindent
is equivalent to:
@example
m4 --reload-state=4.m4f input.m4
@end example
@item --freeze
@itemx -F
Produce a frozen state file. @command{autom4te} freezing is stricter
than M4's: it must produce no warnings, and no output other than empty
lines (a line with white space is @emph{not} empty) and comments
(starting with @samp{#}). Unlike @command{m4}'s similarly-named option,
this option takes no argument:
@example
autom4te 1.m4 2.m4 3.m4 --freeze --output=3.m4f
@end example
@noindent
corresponds to
@example
m4 1.m4 2.m4 3.m4 --freeze-state=3.m4f
@end example
@item --mode=@var{octal-mode}
@itemx -m @var{octal-mode}
Set the mode of the non-traces output to @var{octal-mode}; by default
@samp{0666}.
@end table
@sp 1
@cindex @file{autom4te.cache}
As another additional feature over @command{m4}, @command{autom4te}
caches its results. @acronym{GNU} M4 is able to produce a regular
output and traces at the same time. Traces are heavily used in the
@acronym{GNU} Build System: @command{autoheader} uses them to build
@file{config.h.in}, @command{autoreconf} to determine what
@acronym{GNU} Build System components are used, @command{automake} to
``parse'' @file{configure.ac} etc. To avoid recomputation,
traces are cached while performing regular expansion,
and conversely. This cache is (actually, the caches are) stored in
the directory @file{autom4te.cache}. @emph{It can safely be removed}
at any moment (especially if for some reason @command{autom4te}
considers it trashed).
@table @option
@item --cache=@var{directory}
@itemx -C @var{directory}
Specify the name of the directory where the result should be cached.
Passing an empty value disables caching. Be sure to pass a relative
file name, as for the time being, global caches are not supported.
@item --no-cache
Don't cache the results.
@item --force
@itemx -f
If a cache is used, consider it obsolete (but update it anyway).
@end table
@sp 1
Because traces are so important to the @acronym{GNU} Build System,
@command{autom4te} provides high level tracing features as compared to
M4, and helps exploiting the cache:
@table @option
@item --trace=@var{macro}[:@var{format}]
@itemx -t @var{macro}[:@var{format}]
Trace the invocations of @var{macro} according to the @var{format}.
Multiple @option{--trace} arguments can be used to list several macros.
Multiple @option{--trace} arguments for a single macro are not
cumulative; instead, you should just make @var{format} as long as
needed.
The @var{format} is a regular string, with newlines if desired, and
several special escape codes. It defaults to @samp{$f:$l:$n:$%}. It can
use the following special escapes:
@table @samp
@item $$
The character @samp{$}.
@item $f
The file name from which @var{macro} is called.
@item $l
The line number from which @var{macro} is called.
@item $d
The depth of the @var{macro} call. This is an M4 technical detail that
you probably don't want to know about.
@item $n
The name of the @var{macro}.
@item $@var{num}
The @var{num}th argument of the call to @var{macro}.
@item $@@
@itemx $@var{sep}@@
@itemx $@{@var{separator}@}@@
All the arguments passed to @var{macro}, separated by the character
@var{sep} or the string @var{separator} (@samp{,} by default). Each
argument is quoted, i.e., enclosed in a pair of square brackets.
@item $*
@itemx $@var{sep}*
@itemx $@{@var{separator}@}*
As above, but the arguments are not quoted.
@item $%
@itemx $@var{sep}%
@itemx $@{@var{separator}@}%
As above, but the arguments are not quoted, all new line characters in
the arguments are smashed, and the default separator is @samp{:}.
The escape @samp{$%} produces single-line trace outputs (unless you put
newlines in the @samp{separator}), while @samp{$@@} and @samp{$*} do
not.
@end table
@xref{autoconf Invocation}, for examples of trace uses.
@item --preselect=@var{macro}
@itemx -p @var{macro}
Cache the traces of @var{macro}, but do not enable traces. This is
especially important to save CPU cycles in the future. For instance,
when invoked, @command{autoconf} preselects all the macros that
@command{autoheader}, @command{automake}, @command{autoreconf}, etc.,
trace, so that running @command{m4} is not needed to trace them: the
cache suffices. This results in a huge speed-up.
@end table
@sp 1
@cindex Autom4te Library
Finally, @command{autom4te} introduces the concept of @dfn{Autom4te
libraries}. They consists in a powerful yet extremely simple feature:
sets of combined command line arguments:
@table @option
@item --language=@var{language}
@itemx -l @var{language}
Use the @var{language} Autom4te library. Current languages include:
@table @code
@item M4sugar
create M4sugar output.
@item M4sh
create M4sh executable shell scripts.
@item Autotest
create Autotest executable test suites.
@item Autoconf-without-aclocal-m4
create Autoconf executable configure scripts without
reading @file{aclocal.m4}.
@item Autoconf
create Autoconf executable configure scripts. This language inherits
all the characteristics of @code{Autoconf-without-aclocal-m4} and
additionally reads @file{aclocal.m4}.
@end table
@item --prepend-include=@var{dir}
@itemx -B @var{dir}
Prepend directory @var{dir} to the search path. This is used to include
the language-specific files before any third-party macros.
@end table
@cindex @file{autom4te.cfg}
As an example, if Autoconf is installed in its default location,
@file{/usr/local}, the command @samp{autom4te -l m4sugar foo.m4} is
strictly equivalent to the command:
@example
autom4te --prepend-include /usr/local/share/autoconf \
m4sugar/m4sugar.m4f --warnings syntax foo.m4
@end example
@noindent
Recursive expansion applies here: the command @samp{autom4te -l m4sh foo.m4}
is the same as @samp{autom4te --language M4sugar m4sugar/m4sh.m4f
foo.m4}, i.e.:
@example
autom4te --prepend-include /usr/local/share/autoconf \
m4sugar/m4sugar.m4f m4sugar/m4sh.m4f --mode 777 foo.m4
@end example
@noindent
The definition of the languages is stored in @file{autom4te.cfg}.
@node Customizing autom4te
@subsection Customizing @command{autom4te}
One can customize @command{autom4te} via @file{~/.autom4te.cfg} (i.e.,
as found in the user home directory), and @file{./.autom4te.cfg} (i.e.,
as found in the directory from which @command{autom4te} is run). The
order is first reading @file{autom4te.cfg}, then @file{~/.autom4te.cfg},
then @file{./.autom4te.cfg}, and finally the command line arguments.
In these text files, comments are introduced with @code{#}, and empty
lines are ignored. Customization is performed on a per-language basis,
wrapped in between a @samp{begin-language: "@var{language}"},
@samp{end-language: "@var{language}"} pair.
Customizing a language stands for appending options (@pxref{autom4te
Invocation}) to the current definition of the language. Options, and
more generally arguments, are introduced by @samp{args:
@var{arguments}}. You may use the traditional shell syntax to quote the
@var{arguments}.
As an example, to disable Autoconf caches (@file{autom4te.cache})
globally, include the following lines in @file{~/.autom4te.cfg}:
@verbatim
## ------------------ ##
## User Preferences. ##
## ------------------ ##
begin-language: "Autoconf-without-aclocal-m4"
args: --no-cache
end-language: "Autoconf-without-aclocal-m4"
@end verbatim
@node Programming in M4sugar
@section Programming in M4sugar
@cindex M4sugar
M4 by itself provides only a small, but sufficient, set of all-purpose
macros. M4sugar introduces additional generic macros. Its name was
coined by Lars J. Aas: ``Readability And Greater Understanding Stands 4
M4sugar''.
M4sugar reserves the macro namespace @samp{^_m4_} for internal use, and
the macro namespace @samp{^m4_} for M4sugar macros. You should not
define your own macros into these namespaces.
@menu
* Redefined M4 Macros:: M4 builtins changed in M4sugar
* Diagnostic Macros:: Diagnostic messages from M4sugar
* Diversion support:: Diversions in M4sugar
* Conditional constructs:: Conditions in M4
* Looping constructs:: Iteration in M4
* Evaluation Macros:: More quotation and evaluation control
* Text processing Macros:: String manipulation in M4
* Number processing Macros:: Arithmetic computation in M4
* Set manipulation Macros:: Set manipulation in M4
* Forbidden Patterns:: Catching unexpanded macros
@end menu
@node Redefined M4 Macros
@subsection Redefined M4 Macros
@msindex{builtin}
@msindex{changecom}
@msindex{changequote}
@msindex{debugfile}
@msindex{debugmode}
@msindex{decr}
@msindex{define}
@msindex{divnum}
@msindex{errprint}
@msindex{esyscmd}
@msindex{eval}
@msindex{format}
@msindex{ifdef}
@msindex{incr}
@msindex{index}
@msindex{indir}
@msindex{len}
@msindex{pushdef}
@msindex{shift}
@msindex{substr}
@msindex{syscmd}
@msindex{sysval}
@msindex{traceoff}
@msindex{traceon}
@msindex{translit}
With a few exceptions, all the M4 native macros are moved in the
@samp{m4_} pseudo-namespace, e.g., M4sugar renames @code{define} as
@code{m4_define} etc.
The list of macros unchanged from M4, except for their name, is:
@itemize @minus
@item m4_builtin
@item m4_changecom
@item m4_changequote
@item m4_debugfile
@item m4_debugmode
@item m4_decr
@item m4_define
@item m4_divnum
@item m4_errprint
@item m4_esyscmd
@item m4_eval
@item m4_format
@item m4_ifdef
@item m4_incr
@item m4_index
@item m4_indir
@item m4_len
@item m4_pushdef
@item m4_shift
@item m4_substr
@item m4_syscmd
@item m4_sysval
@item m4_traceoff
@item m4_traceon
@item m4_translit
@end itemize
Some M4 macros are redefined, and are slightly incompatible with their
native equivalent.
@defmac __file__
@defmacx __line__
@MSindex __file__
@MSindex __line__
All M4 macros starting with @samp{__} retain their original name: for
example, no @code{m4__file__} is defined.
@end defmac
@defmac __oline__
@MSindex __oline__
This is not technically a macro, but a feature of Autom4te. The
sequence @code{__oline__} can be used similarly to the other m4sugar
location macros, but rather than expanding to the location of the input
file, it is translated to the line number where it appears in the output
file after all other M4 expansions.
@end defmac
@defmac dnl
@MSindex dnl
This macro kept its original name: no @code{m4_dnl} is defined.
@end defmac
@defmac m4_bpatsubst (@var{string}, @var{regexp}, @ovar{replacement})
@msindex{bpatsubst}
This macro corresponds to @code{patsubst}. The name @code{m4_patsubst}
is kept for future versions of M4sugar, once @acronym{GNU} M4 2.0 is
released and supports extended regular expression syntax.
@end defmac
@defmac m4_bregexp (@var{string}, @var{regexp}, @ovar{replacement})
@msindex{bregexp}
This macro corresponds to @code{regexp}. The name @code{m4_regexp}
is kept for future versions of M4sugar, once @acronym{GNU} M4 2.0 is
released and supports extended regular expression syntax.
@end defmac
@defmac m4_copy (@var{source}, @var{dest})
@defmacx m4_copy_force (@var{source}, @var{dest})
@defmacx m4_rename (@var{source}, @var{dest})
@defmacx m4_rename_force (@var{source}, @var{dest})
@msindex{copy}
@msindex{copy_force}
@msindex{rename}
@msindex{rename_force}
These macros aren't directly builtins, but are closely related to
@code{m4_pushdef} and @code{m4_defn}. @code{m4_copy} and
@code{m4_rename} ensure that @var{dest} is undefined, while
@code{m4_copy_force} and @code{m4_rename_force} overwrite any existing
definition. All four macros then proceed to copy the entire pushdef
stack of definitions of @var{source} over to @var{dest}. @code{m4_copy}
and @code{m4_copy_force} preserve the source (including in the special
case where @var{source} is undefined), while @code{m4_rename} and
@code{m4_rename_force} undefine the original macro name (making it an
error to rename an undefined @var{source}).
Note that attempting to invoke a renamed macro might not work, since the
macro may have a dependence on helper macros accessed via composition of
@samp{$0} but that were not also renamed; likewise, other macros may
have a hard-coded dependence on @var{source} and could break if
@var{source} has been deleted. On the other hand, it is always safe to
rename a macro to temporarily move it out of the way, then rename it
back later to restore original semantics.
@end defmac
@defmac m4_defn (@var{macro}@dots{})
@msindex{defn}
This macro fails if @var{macro} is not defined, even when using older
versions of M4 that did not warn. See @code{m4_undefine}.
Unfortunately, in order to support these older versions of M4, there are
some situations involving unbalanced quotes where concatenating multiple
macros together will work in newer M4 but not in m4sugar; use
quadrigraphs to work around this.
@end defmac
@defmac m4_divert (@var{diversion})
@msindex{divert}
M4sugar relies heavily on diversions, so rather than behaving as a
primitive, @code{m4_divert} behaves like:
@example
m4_divert_pop()m4_divert_push([@var{diversion}])
@end example
@noindent
@xref{Diversion support}, for more details about the use of the
diversion stack.
@end defmac
@defmac m4_dumpdef (@var{name}@dots{})
@defmacx m4_dumpdefs (@var{name}@dots{})
@msindex{dumpdef}
@msindex{dumpdefs}
@code{m4_dumpdef} is like the M4 builtin, except that this version
requires at least one argument, output always goes to standard error
rather than the current debug file, no sorting is done on multiple
arguments, and an error is issued if any
@var{name} is undefined. @code{m4_dumpdefs} is a convenience macro that
calls @code{m4_dumpdef} for all of the
@code{m4_pushdef} stack of definitions, starting with the current, and
silently does nothing if @var{name} is undefined.
Unfortunately, due to a limitation in M4 1.4.x, any macro defined as a
builtin is output as the empty string. This behavior is rectified by
using M4 1.6 or newer. However, this behavior difference means that
@code{m4_dumpdef} should only be used while developing m4sugar macros,
and never in the final published form of a macro.
@end defmac
@defmac m4_esyscmd_s (@var{command})
@msindex{esyscmd_s}
Like @code{m4_esyscmd}, this macro expands to the result of running
@var{command} in a shell. The difference is that any trailing newlines
are removed, so that the output behaves more like shell command
substitution.
@end defmac
@defmac m4_exit (@var{exit-status})
@msindex{exit}
This macro corresponds to @code{m4exit}.
@end defmac
@defmac m4_if (@var{comment})
@defmacx m4_if (@var{string-1}, @var{string-2}, @var{equal}, @ovar{not-equal})
@defmacx m4_if (@var{string-1}, @var{string-2}, @var{equal-1}, @
@var{string-3}, @var{string-4}, @var{equal-2}, @dots{}, @ovar{not-equal})
@msindex{if}
This macro corresponds to @code{ifelse}. @var{string-1} and
@var{string-2} are compared literally, so usually one of the two
arguments is passed unquoted. @xref{Conditional constructs}, for more
conditional idioms.
@end defmac
@defmac m4_include (@var{file})
@defmacx m4_sinclude (@var{file})
@msindex{include}
@msindex{sinclude}
Like the M4 builtins, but warn against multiple inclusions of @var{file}.
@end defmac
@defmac m4_mkstemp (@var{template})
@defmacx m4_maketemp (@var{template})
@msindex{maketemp}
@msindex{mkstemp}
Posix requires @code{maketemp} to replace the trailing @samp{X}
characters in @var{template} with the process id, without regards to the
existence of a file by that name, but this a security hole. When this
was pointed out to the Posix folks, they agreed to invent a new macro
@code{mkstemp} that always creates a uniquely named file, but not all
versions of @acronym{GNU} M4 support the new macro. In M4sugar,
@code{m4_maketemp} and @code{m4_mkstemp} are synonyms for each other,
and both have the secure semantics regardless of which macro the
underlying M4 provides.
@end defmac
@defmac m4_popdef (@var{macro}@dots{})
@msindex{popdef}
This macro fails if @var{macro} is not defined, even when using older
versions of M4 that did not warn. See @code{m4_undefine}.
@end defmac
@defmac m4_undefine (@var{macro}@dots{})
@msindex{undefine}
This macro fails if @var{macro} is not defined, even when using older
versions of M4 that did not warn. Use
@example
m4_ifdef([@var{macro}], [m4_undefine([@var{macro}])])
@end example
@noindent
if you are not sure whether @var{macro} is defined.
@end defmac
@defmac m4_undivert (@var{diversion}@dots{})
@msindex{undivert}
Unlike the M4 builtin, at least one @var{diversion} must be specified.
Also, since the M4sugar diversion stack prefers named
diversions, the use of @code{m4_undivert} to include files is risky.
@xref{Diversion support}, for more details about the use of the
diversion stack.
@end defmac
@defmac m4_wrap (@var{text})
@defmacx m4_wrap_lifo (@var{text})
@msindex{wrap}
@msindex{wrap_lifo}
These macros correspond to @code{m4wrap}. Posix requires arguments of
multiple wrap calls to be reprocessed at @acronym{EOF} in the same order
as the original calls (first-in, first-out). @acronym{GNU} M4 versions
through 1.4.10, however, reprocess them in reverse order (last-in,
first-out). Both orders are useful, therefore, you can rely on
@code{m4_wrap} to provide FIFO semantics and @code{m4_wrap_lifo} for
LIFO semantics, regardless of the underlying @acronym{GNU} M4 version.
Unlike the @acronym{GNU} M4 builtin, these macros only recognize one
argument, and avoid token pasting between consecutive invocations. On
the other hand, nested calls to @code{m4_wrap} from within wrapped text
work just as in the builtin.
@end defmac
@node Diagnostic Macros
@subsection Diagnostic messages from M4sugar
@cindex Messages, from @command{M4sugar}
When macros statically diagnose abnormal situations, benign or fatal,
they should report them using these macros. For issuing dynamic issues,
i.e., when @command{configure} is run, see @ref{Printing Messages}.
@defmac m4_assert (@var{expression}, @dvar{exit-status, 1})
@msindex{assert}
Assert that the arithmetic @var{expression} evaluates to non-zero.
Otherwise, issue a fatal error, and exit @command{autom4te} with
@var{exit-status}.
@end defmac
@defmac m4_errprintn (@var{message})
@msindex{errprintn}
Similar to the builtin @code{m4_errprint}, except that a newline is
guaranteed after @var{message}.
@end defmac
@anchor{m4_fatal}
@defmac m4_fatal (@var{message})
@msindex{fatal}
Report a severe error @var{message} prefixed with the current location,
and have @command{autom4te} die.
@end defmac
@defmac m4_location
@msindex{location}
Useful as a prefix in a message line. Short for:
@example
__file__:__line__
@end example
@end defmac
@anchor{m4_warn}
@defmac m4_warn (@var{category}, @var{message})
@msindex{warn}
Report @var{message} as a warning (or as an error if requested by the
user) if warnings of the @var{category} are turned on. If the message
is emitted, it is prefixed with the current location, and followed by a
call trace of all macros defined via @code{AC_DEFUN} used to get to the
current expansion. You are encouraged to use standard categories, which
currently include:
@table @samp
@item all
messages that don't fall into one of the following categories. Use of an
empty @var{category} is equivalent.
@item cross
related to cross compilation issues.
@item obsolete
use of an obsolete construct.
@item syntax
dubious syntactic constructs, incorrectly ordered macro calls.
@end table
@end defmac
@node Diversion support
@subsection Diversion support
M4sugar makes heavy use of diversions, because it is often the case that
text that must appear early in the output is not discovered until late
in the input. Additionally, some of the topological sorting algorithms
used in resolving macro dependencies use diversions. However, most
macros should not need to change diversions directly, but rather rely on
higher-level M4sugar macros to manage diversions transparently.
In the rare case that it is necessary to write a macro that explicitly
outputs text to a different diversion, it is important to be aware of an
M4 limitation regarding diversions: text only goes to a diversion if it
is not part of argument collection. Therefore, any macro that changes
the current diversion cannot be used as an unquoted argument to another
macro, but must be expanded at the top level. The macro
@code{m4_expand} will diagnose any attempt to change diversions, since
it is generally useful only as an argument to another macro. The
following example shows what happens when diversion manipulation is
attempted within macro arguments:
@example
m4_do([normal text]
m4_divert_push([KILL])unwanted[]m4_divert_pop([KILL])
[m4_divert_push([KILL])discarded[]m4_divert_pop([KILL])])dnl
@result{}normal text
@result{}unwanted
@end example
@noindent
Notice that the unquoted text @code{unwanted} is output, even though it
was processed while the current diversion was @code{KILL}, because it
was collected as part of the argument to @code{m4_do}. However, the
text @code{discarded} disappeared as desired, because the diversion
changes were single-quoted, and were not expanded until the top-level
rescan of the output of @code{m4_do}.
To make diversion management easier, M4sugar uses the concept of named
diversions. Rather than using diversion numbers directly, it is nicer
to associate a name with each diversion; the diversion number associated
with a particular diversion name is an implementation detail, so you
should only use diversion names. In general, you should not output text
to a named diversion until after calling the appropriate initialization
routine for your language (@code{m4_init}, @code{AS_INIT},
@code{AT_INIT}, @dots{}), although there are some exceptions documented
below.
M4sugar defines two named diversions.
@table @code
@item KILL
Text written to this diversion is discarded. This is the default
diversion once M4sugar is initialized.
@item GROW
This diversion is used behind the scenes by topological sorting macros,
such as @code{AC_REQUIRE}.
@end table
M4sh adds several more named diversions.
@table @code
@item BINSH
This diversion is reserved for the @samp{#!} interpreter line.
@item HEADER-REVISION
This diversion holds text from @code{AC_REVISION}.
@item HEADER-COMMENT
This diversion holds comments about the purpose of a file.
@item HEADER-COPYRIGHT
This diversion is managed by @code{AC_COPYRIGHT}.
@item M4SH-SANITIZE
This diversion contains M4sh sanitization code, used to ensure M4sh is
executing in a reasonable shell environment.
@item M4SH-INIT
This diversion contains M4sh initialization code, initializing variables
that are required by other M4sh macros.
@item BODY
This diversion contains the body of the shell code, and is the default
diversion once M4sh is initialized.
@end table
Autotest inherits diversions from M4sh, and changes the default
diversion from @code{BODY} back to @code{KILL}. It also adds several
more named diversions, with the following subset designed for developer
use.
@table @code
@item PREPARE_TESTS
This diversion contains initialization sequences which are executed
after @file{atconfig} and @file{atlocal}, and after all command line
arguments have been parsed, but prior to running any tests. It can be
used to set up state that is required across all tests. This diversion
will work even before @code{AT_INIT}.
@end table
For now, the named diversions of Autoconf and Autoheader, and the
remaining diversions of Autotest, are not documented. In other words,
intentionally outputting text into an undocumented diversion is subject
to breakage in a future release of Autoconf.
@defmac m4_cleardivert (@var{diversion}@dots{})
@msindex{cleardivert}
Permanently discard any text that has been diverted into
@var{diversion}.
@end defmac
@defmac m4_divert_once (@var{diversion}, @ovar{content})
@msindex{divert_once}
Similar to @code{m4_divert_text}, except that @var{content} is only
output to @var{diversion} if this is the first time that
@code{m4_divert_once} has been called with its particular arguments.
@end defmac
@defmac m4_divert_pop (@ovar{diversion})
@msindex{divert_pop}
If provided, check that the current diversion is indeed @var{diversion}.
Then change to the diversion located earlier on the stack, giving an
error if an attempt is made to pop beyond the initial m4sugar diversion
of @code{KILL}.
@end defmac
@defmac m4_divert_push (@var{diversion})
@msindex{divert_push}
Remember the former diversion on the diversion stack, and output
subsequent text into @var{diversion}. M4sugar maintains a diversion
stack, and issues an error if there is not a matching pop for every
push.
@end defmac
@defmac m4_divert_text (@var{diversion}, @ovar{content})
@msindex{divert_text}
Output @var{content} and a newline into @var{diversion}, without
affecting the current diversion. Shorthand for:
@example
m4_divert_push([@var{diversion}])@var{content}
m4_divert_pop([@var{diversion}])dnl
@end example
@end defmac
@defmac m4_init
@msindex{init}
Initialize the M4sugar environment, setting up the default named
diversion to be @code{KILL}.
@end defmac
@node Conditional constructs
@subsection Conditional constructs
The following macros provide additional conditional constructs as
convenience wrappers around @code{m4_if}.
@defmac m4_bmatch (@var{string}, @var{regex-1}, @var{value-1}, @
@ovar{regex-2}, @ovar{value-2}, @dots{}, @ovar{default})
@msindex{bmatch}
The string @var{string} is repeatedly compared against a series of
@var{regex} arguments; if a match is found, the expansion is the
corresponding @var{value}, otherwise, the macro moves on to the next
@var{regex}. If no @var{regex} match, then the result is the optional
@var{default}, or nothing.
@end defmac
@defmac m4_bpatsubsts (@var{string}, @var{regex-1}, @var{subst-1}, @
@ovar{regex-2}, @ovar{subst-2}, @dots{})
@msindex{bpatsubsts}
The string @var{string} is altered by @var{regex-1} and @var{subst-1},
as if by:
@example
m4_bpatsubst([[@var{string}]], [@var{regex}], [@var{subst}])
@end example
@noindent
The result of the substitution is then passed through the next set of
@var{regex} and @var{subst}, and so forth. An empty @var{subst} implies
deletion of any matched portions in the current string. Note that this
macro over-quotes @var{string}; this behavior is intentional, so that
the result of each step of the recursion remains as a quoted string.
However, it means that anchors (@samp{^} and @samp{$} in the @var{regex}
will line up with the extra quotations, and not the characters of the
original string. The overquoting is removed after the final
substitution.
@end defmac
@defmac m4_case (@var{string}, @var{value-1}, @var{if-value-1}, @
@ovar{value-2}, @ovar{if-value-2}, @dots{}, @ovar{default})
@msindex{case}
Test @var{string} against multiple @var{value} possibilities, resulting
in the first @var{if-value} for a match, or in the optional
@var{default}. This is shorthand for:
@example
m4_if([@var{string}], [@var{value-1}], [@var{if-value-1}],
[@var{string}], [@var{value-2}], [@var{if-value-2}], @dots{},
[@var{default}])
@end example
@end defmac
@defmac m4_cond (@var{test-1}, @var{value-1}, @var{if-value-1}, @
@ovar{test-2}, @ovar{value-2}, @ovar{if-value-2}, @dots{}, @ovar{default})
@msindex{cond}
This macro was introduced in Autoconf 2.62. Similar to @code{m4_if},
except that each @var{test} is expanded only when it is encountered.
This is useful for short-circuiting expensive tests; while @code{m4_if}
requires all its strings to be expanded up front before doing
comparisons, @code{m4_cond} only expands a @var{test} when all earlier
tests have failed.
For an example, these two sequences give the same result, but in the
case where @samp{$1} does not contain a backslash, the @code{m4_cond}
version only expands @code{m4_index} once, instead of five times, for
faster computation if this is a common case for @samp{$1}. Notice that
every third argument is unquoted for @code{m4_if}, and quoted for
@code{m4_cond}:
@example
m4_if(m4_index([$1], [\]), [-1], [$2],
m4_eval(m4_index([$1], [\\]) >= 0), [1], [$2],
m4_eval(m4_index([$1], [\$]) >= 0), [1], [$2],
m4_eval(m4_index([$1], [\`]) >= 0), [1], [$3],
m4_eval(m4_index([$1], [\"]) >= 0), [1], [$3],
[$2])
m4_cond([m4_index([$1], [\])], [-1], [$2],
[m4_eval(m4_index([$1], [\\]) >= 0)], [1], [$2],
[m4_eval(m4_index([$1], [\$]) >= 0)], [1], [$2],
[m4_eval(m4_index([$1], [\`]) >= 0)], [1], [$3],
[m4_eval(m4_index([$1], [\"]) >= 0)], [1], [$3],
[$2])
@end example
@end defmac
@defmac m4_default (@var{expr-1}, @var{expr-2})
@defmacx m4_default_quoted (@var{expr-1}, @var{expr-2})
@defmacx m4_default_nblank (@var{expr-1}, @ovar{expr-2})
@defmacx m4_default_nblank_quoted (@var{expr-1}, @ovar{expr-2})
@msindex{default}
@msindex{default_quoted}
@msindex{default_nblank}
@msindex{default_nblank_quoted}
If @var{expr-1} contains text, use it. Otherwise, select @var{expr-2}.
@code{m4_default} expands the result, while @code{m4_default_quoted}
does not. Useful for providing a fixed default if the expression that
results in @var{expr-1} would otherwise be empty. The difference
between @code{m4_default} and @code{m4_default_nblank} is whether an
argument consisting of just blanks (space, tab, newline) is
significant. When using the expanding versions, note that an argument
may contain text but still expand to an empty string.
@example
m4_define([active], [ACTIVE])dnl
m4_define([empty], [])dnl
m4_define([demo1], [m4_default([$1], [$2])])dnl
m4_define([demo2], [m4_default_quoted([$1], [$2])])dnl
m4_define([demo3], [m4_default_nblank([$1], [$2])])dnl
m4_define([demo4], [m4_default_nblank_quoted([$1], [$2])])dnl
demo1([active], [default])
@result{}ACTIVE
demo1([], [active])
@result{}ACTIVE
demo1([empty], [text])
@result{}
-demo1([ ], [active])-
@result{}- -
demo2([active], [default])
@result{}active
demo2([], [active])
@result{}active
demo2([empty], [text])
@result{}empty
-demo2([ ], [active])-
@result{}- -
demo3([active], [default])
@result{}ACTIVE
demo3([], [active])
@result{}ACTIVE
demo3([empty], [text])
@result{}
-demo3([ ], [active])-
@result{}-ACTIVE-
demo4([active], [default])
@result{}active
demo4([], [active])
@result{}active
demo4([empty], [text])
@result{}empty
-demo4([ ], [active])-
@result{}-active-
@end example
@end defmac
@defmac m4_ifblank (@var{cond}, @ovar{if-blank}, @ovar{if-text})
@defmacx m4_ifnblank (@var{cond}, @ovar{if-text}, @ovar{if-blank})
@msindex{ifblank}
@msindex{ifnblank}
If @var{cond} is empty or consists only of blanks (space, tab, newline),
then expand @var{if-blank}; otherwise, expand @var{if-text}. Two
variants exist, in order to make it easier to select the correct logical
sense when using only two parameters. Note that this is more efficient
than the equivalent behavior of:
@example
m4_ifval(m4_normalize([@var{cond}]), @var{if-text}, @var{if-cond})
@end example
@end defmac
@defmac m4_ifndef (@var{macro}, @var{if-not-defined}, @ovar{if-defined})
@msindex{ifndef}
This is shorthand for:
@example
m4_ifdef([@var{macro}], [@var{if-defined}], [@var{if-not-defined}])
@end example
@end defmac
@defmac m4_ifset (@var{macro}, @ovar{if-true}, @ovar{if-false})
@msindex{ifset}
If @var{macro} is undefined, or is defined as the empty string, expand
to @var{if-false}. Otherwise, expands to @var{if-true}. Similar to:
@example
m4_ifval(m4_defn([@var{macro}]), [@var{if-true}], [@var{if-false}])
@end example
@noindent
except that it is not an error if @var{macro} is undefined.
@end defmac
@defmac m4_ifval (@var{cond}, @ovar{if-true}, @ovar{if-false})
@msindex{ifval}
Expands to @var{if-true} if @var{cond} is not empty, otherwise to
@var{if-false}. This is shorthand for:
@example
m4_if([@var{cond}], [], [@var{if-true}], [@var{if-false}])
@end example
@end defmac
@defmac m4_ifvaln (@var{cond}, @ovar{if-true}, @ovar{if-false})
@msindex{ifvaln}
Similar to @code{m4_ifval}, except guarantee that a newline is present
after any non-empty expansion. Often followed by @code{dnl}.
@end defmac
@defmac m4_n (@var{text})
@msindex{n}
Expand to @var{text}, and add a newline if @var{text} is not empty.
Often followed by @code{dnl}.
@end defmac
@node Looping constructs
@subsection Looping constructs
The following macros are useful in implementing recursive algorithms in
M4, including loop operations. An M4 list is formed by quoting a list
of quoted elements; generally the lists are comma-separated, although
@code{m4_foreach_w} is whitespace-separated. For example, the list
@samp{[[a], [b,c]]} contains two elements: @samp{[a]} and @samp{[b,c]}.
It is common to see lists with unquoted elements when those elements are
not likely to be macro names, as in @samp{[fputc_unlocked,
fgetc_unlocked]}.
Although not generally recommended, it is possible for quoted lists to
have side effects; all side effects are expanded only once, and prior to
visiting any list element. On the other hand, the fact that unquoted
macros are expanded exactly once means that macros without side effects
can be used to generate lists. For example,
@example
m4_foreach([i], [[1], [2], [3]m4_errprintn([hi])], [i])
@error{}hi
@result{}123
m4_define([list], [[1], [2], [3]])
@result{}
m4_foreach([i], [list], [i])
@result{}123
@end example
@defmac m4_argn (@var{n}, @ovar{arg}@dots{})
@msindex{argn}
Extracts argument @var{n} (larger than 0) from the remaining arguments.
If there are too few arguments, the empty string is used. For any
@var{n} besides 1, this is more efficient than the similar
@samp{m4_car(m4_shiftn([@var{n}], [], [@var{arg}@dots{}]))}.
@end defmac
@defmac m4_car (@var{arg}@dots{})
@msindex{car}
Expands to the quoted first @var{arg}. Can be used with @code{m4_cdr}
to recursively iterate
through a list. Generally, when using quoted lists of quoted elements,
@code{m4_car} should be called without any extra quotes.
@end defmac
@defmac m4_cdr (@var{arg}@dots{})
@msindex{cdr}
Expands to a quoted list of all but the first @var{arg}, or the empty
string if there was only one argument. Generally, when using quoted
lists of quoted elements, @code{m4_cdr} should be called without any
extra quotes.
For example, this is a simple implementation of @code{m4_map}; note how
each iteration checks for the end of recursion, then merely applies the
first argument to the first element of the list, then repeats with the
rest of the list. (The actual implementation in M4sugar is a bit more
involved, to gain some speed and share code with @code{m4_map_sep}, and
also to avoid expanding side effects in @samp{$2} twice).
@example
m4_define([m4_map], [m4_ifval([$2],
[m4_apply([$1], m4_car($2))[]$0([$1], m4_cdr($2))])])dnl
m4_map([ m4_eval], [[[1]], [[1+1]], [[10],[16]]])
@result{} 1 2 a
@end example
@end defmac
@defmac m4_for (@var{var}, @var{first}, @var{last}, @ovar{step}, @
@var{expression})
@msindex{for}
Loop over the numeric values between @var{first} and @var{last}
including bounds by increments of @var{step}. For each iteration,
expand @var{expression} with the numeric value assigned to @var{var}.
If @var{step} is omitted, it defaults to @samp{1} or @samp{-1} depending
on the order of the limits. If given, @var{step} has to match this
order. The number of iterations is determined independently from
definition of @var{var}; iteration cannot be short-circuited or
lengthened by modifying @var{var} from within @var{expression}.
@end defmac
@defmac m4_foreach (@var{var}, @var{list}, @var{expression})
@msindex{foreach}
Loop over the comma-separated M4 list @var{list}, assigning each value
to @var{var}, and expand @var{expression}. The following example
outputs two lines:
@example
m4_foreach([myvar], [[foo], [bar, baz]],
[echo myvar
])dnl
@result{}echo foo
@result{}echo bar, baz
@end example
Note that for some forms of @var{expression}, it may be faster to use
@code{m4_map_args}.
@end defmac
@anchor{m4_foreach_w}
@defmac m4_foreach_w (@var{var}, @var{list}, @var{expression})
@msindex{foreach_w}
Loop over the white-space-separated list @var{list}, assigning each value
to @var{var}, and expand @var{expression}. If @var{var} is only
referenced once in @var{expression}, it is more efficient to use
@code{m4_map_args_w}.
The deprecated macro @code{AC_FOREACH} is an alias of
@code{m4_foreach_w}.
@end defmac
@defmac m4_map (@var{macro}, @var{list})
@defmacx m4_mapall (@var{macro}, @var{list})
@defmacx m4_map_sep (@var{macro}, @var{separator}, @var{list})
@defmacx m4_mapall_sep (@var{macro}, @var{separator}, @var{list})
@msindex{map}
@msindex{mapall}
@msindex{map_sep}
@msindex{mapall_sep}
Loop over the comma separated quoted list of argument descriptions in
@var{list}, and invoke @var{macro} with the arguments. An argument
description is in turn a comma-separated quoted list of quoted elements,
suitable for @code{m4_apply}. The macros @code{m4_map} and
@code{m4_map_sep} ignore empty argument descriptions, while
@code{m4_mapall} and @code{m4_mapall_sep} invoke @var{macro} with no
arguments. The macros @code{m4_map_sep} and @code{m4_mapall_sep}
additionally expand @var{separator} between invocations of @var{macro}.
Note that @var{separator} is expanded, unlike in @code{m4_join}. When
separating output with commas, this means that the map result can be
used as a series of arguments, by using a single-quoted comma as
@var{separator}, or as a single string, by using a double-quoted comma.
@example
m4_map([m4_count], [])
@result{}
m4_map([ m4_count], [[],
[[1]],
[[1], [2]]])
@result{} 1 2
m4_mapall([ m4_count], [[],
[[1]],
[[1], [2]]])
@result{} 0 1 2
m4_map_sep([m4_eval], [,], [[[1+2]],
[[10], [16]]])
@result{}3,a
m4_map_sep([m4_echo], [,], [[[a]], [[b]]])
@result{}a,b
m4_count(m4_map_sep([m4_echo], [,], [[[a]], [[b]]]))
@result{}2
m4_map_sep([m4_echo], [[,]], [[[a]], [[b]]])
@result{}a,b
m4_count(m4_map_sep([m4_echo], [[,]], [[[a]], [[b]]]))
@result{}1
@end example
@end defmac
@defmac m4_map_args (@var{macro}, @var{arg}@dots{})
@msindex{map_args}
Repeatedly invoke @var{macro} with each successive @var{arg} as its only
argument. In the following example, three solutions are presented with
the same expansion; the solution using @code{m4_map_args} is the most
efficient.
@example
m4_define([active], [ACTIVE])dnl
m4_foreach([var], [[plain], [active]], [ m4_echo(m4_defn([var]))])
@result{} plain active
m4_map([ m4_echo], [[[plain]], [[active]]])
@result{} plain active
m4_map_args([ m4_echo], [plain], [active])
@result{} plain active
@end example
In cases where it is useful to operate on additional parameters besides
the list elements, the macro @code{m4_curry} can be used in @var{macro}
to supply the argument currying necessary to generate the desired
argument list. In the following example, @code{list_add_n} is more
efficient than @code{list_add_x}. On the other hand, using
@code{m4_map_args_sep} can be even more efficient.
@example
m4_define([list], [[1], [2], [3]])dnl
m4_define([add], [m4_eval(([$1]) + ([$2]))])dnl
dnl list_add_n(N, ARG...)
dnl Output a list consisting of each ARG added to N
m4_define([list_add_n],
[m4_shift(m4_map_args([,m4_curry([add], [$1])], m4_shift($@@)))])dnl
list_add_n([1], list)
@result{}2,3,4
list_add_n([2], list)
@result{}3,4,5
m4_define([list_add_x],
[m4_shift(m4_foreach([var], m4_dquote(m4_shift($@@)),
[,add([$1],m4_defn([var]))]))])dnl
list_add_x([1], list)
@result{}2,3,4
@end example
@end defmac
@defmac m4_map_args_pair (@var{macro}, @dvar{macro-end, macro}, @
@var{arg}@dots{})
@msindex{map_args_pair}
For every pair of arguments @var{arg}, invoke @var{macro} with two
arguments. If there is an odd number of arguments, invoke
@var{macro-end}, which defaults to @var{macro}, with the remaining
argument.
@example
m4_map_args_pair([, m4_reverse], [], [1], [2], [3])
@result{}, 2, 1, 3
m4_map_args_pair([, m4_reverse], [, m4_dquote], [1], [2], [3])
@result{}, 2, 1, [3]
m4_map_args_pair([, m4_reverse], [, m4_dquote], [1], [2], [3], [4])
@result{}, 2, 1, 4, 3
@end example
@end defmac
@defmac m4_map_args_sep (@ovar{pre}, @ovar{post}, @ovar{sep}, @var{arg}@dots{})
@msindex{map_args_sep}
Expand the sequence @code{@var{pre}[@var{arg}]@var{post}} for each
argument, additionally expanding @var{sep} between arguments. One
common use of this macro is constructing a macro call, where the opening
and closing parentheses are split between @var{pre} and @var{post}; in
particular, @code{m4_map_args([@var{macro}], [@var{arg}])} is equivalent
to @code{m4_map_args_sep([@var{macro}(], [)], [], [@var{arg}])}. This
macro provides the most efficient means for iterating over an arbitrary
list of arguments, particularly when repeatedly constructing a macro
call with more arguments than @var{arg}.
@end defmac
@defmac m4_map_args_w (@var{string}, @ovar{pre}, @ovar{post}, @ovar{sep})
@msindex{map_args_w}
Expand the sequence @code{@var{pre}[word]@var{post}} for each word in
the whitespace-separated @var{string}, additionally expanding @var{sep}
between words. This macro provides the most efficient means for
iterating over a whitespace-separated string. In particular,
@code{m4_map_args_w([@var{string}], [@var{action}(], [)])} is more
efficient than @code{m4_foreach_w([var], [@var{string}],
[@var{action}(m4_defn([var]))])}.
@end defmac
@defmac m4_shiftn (@var{count}, @dots{})
@defmacx m4_shift2 (@dots{})
@defmacx m4_shift3 (@dots{})
@msindex{shift2}
@msindex{shift3}
@msindex{shiftn}
@code{m4_shiftn} performs @var{count} iterations of @code{m4_shift},
along with validation that enough arguments were passed in to match the
shift count, and that the count is positive. @code{m4_shift2} and
@code{m4_shift3} are specializations
of @code{m4_shiftn}, introduced in Autoconf 2.62, and are more efficient
for two and three shifts, respectively.
@end defmac
@defmac m4_stack_foreach (@var{macro}, @var{action})
@defmacx m4_stack_foreach_lifo (@var{macro}, @var{action})
@msindex{stack_foreach}
@msindex{stack_foreach_lifo}
For each of the @code{m4_pushdef} definitions of @var{macro}, expand
@var{action} with the single argument of a definition of @var{macro}.
@code{m4_stack_foreach} starts with the oldest definition, while
@code{m4_stack_foreach_lifo} starts with the current definition.
@var{action} should not push or pop definitions of @var{macro}, nor is
there any guarantee that the current definition of @var{macro} matches
the argument that was passed to @var{action}. The macro @code{m4_curry}
can be used if @var{action} needs more than one argument, although in
that case it is more efficient to use @var{m4_stack_foreach_sep}.
Due to technical limitations, there are a few low-level m4sugar
functions, such as @code{m4_pushdef}, that cannot be used as the
@var{macro} argument.
@example
m4_pushdef([a], [1])m4_pushdef([a], [2])dnl
m4_stack_foreach([a], [ m4_incr])
@result{} 2 3
m4_stack_foreach_lifo([a], [ m4_curry([m4_substr], [abcd])])
@result{} cd bcd
@end example
@end defmac
@defmac m4_stack_foreach_sep (@var{macro}, @ovar{pre}, @ovar{post}, @ovar{sep})
@defmacx m4_stack_foreach_sep_lifo (@var{macro}, @ovar{pre}, @ovar{post}, @
@ovar{sep})
@msindex{stack_foreach_sep}
@msindex{stack_foreach_sep_lifo}
Expand the sequence @code{@var{pre}[definition]@var{post}} for each
@code{m4_pushdef} definition of @var{macro}, additionally expanding
@var{sep} between definitions. @code{m4_stack_foreach_sep} visits the
oldest definition first, while @code{m4_stack_foreach_sep_lifo} visits
the current definition first. This macro provides the most efficient
means for iterating over a pushdef stack. In particular,
@code{m4_stack_foreach([@var{macro}], [@var{action}])} is short for
@code{m4_stack_foreach_sep([@var{macro}], [@var{action}(], [)])}.
@end defmac
@node Evaluation Macros
@subsection Evaluation Macros
The following macros give some control over the order of the evaluation
by adding or removing levels of quotes.
@defmac m4_apply (@var{macro}, @var{list})
@msindex{apply}
Apply the elements of the quoted, comma-separated @var{list} as the
arguments to @var{macro}. If @var{list} is empty, invoke @var{macro}
without arguments. Note the difference between @code{m4_indir}, which
expects its first argument to be a macro name but can use names that are
otherwise invalid, and @code{m4_apply}, where @var{macro} can contain
other text, but must end in a valid macro name.
@example
m4_apply([m4_count], [])
@result{}0
m4_apply([m4_count], [[]])
@result{}1
m4_apply([m4_count], [[1], [2]])
@result{}2
m4_apply([m4_join], [[|], [1], [2]])
@result{}1|2
@end example
@end defmac
@defmac m4_count (@var{arg}, @dots{})
@msindex{count}
This macro returns the decimal count of the number of arguments it was
passed.
@end defmac
@defmac m4_curry (@var{macro}, @var{arg}@dots{})
@msindex{curry}
This macro performs argument currying. The expansion of this macro is
another macro name that expects exactly one argument; that argument is
then appended to the @var{arg} list, and then @var{macro} is expanded
with the resulting argument list.
@example
m4_curry([m4_curry], [m4_reverse], [1])([2])([3])
@result{}3, 2, 1
@end example
Unfortunately, due to a limitation in M4 1.4.x, it is not possible to
pass the definition of a builtin macro as the argument to the output of
@code{m4_curry}; the empty string is used instead of the builtin token.
This behavior is rectified by using M4 1.6 or newer.
@end defmac
@defmac m4_do (@var{arg}, @dots{})
@msindex{do}
This macro loops over its arguments and expands each @var{arg} in
sequence. Its main use is for readability; it allows the use of
indentation and fewer @code{dnl} to result in the same expansion. This
macro guarantees that no expansion will be concatenated with subsequent
text; to achieve full concatenation, use @code{m4_unquote(m4_join([],
@var{arg@dots{}}))}.
@example
m4_define([ab],[1])m4_define([bc],[2])m4_define([abc],[3])dnl
m4_do([a],[b])c
@result{}abc
m4_unquote(m4_join([],[a],[b]))c
@result{}3
m4_define([a],[A])m4_define([b],[B])m4_define([c],[C])dnl
m4_define([AB],[4])m4_define([BC],[5])m4_define([ABC],[6])dnl
m4_do([a],[b])c
@result{}ABC
m4_unquote(m4_join([],[a],[b]))c
@result{}3
@end example
@end defmac
@defmac m4_dquote (@var{arg}, @dots{})
@msindex{dquote}
Return the arguments as a quoted list of quoted arguments.
Conveniently, if there is just one @var{arg}, this effectively adds a
level of quoting.
@end defmac
@defmac m4_dquote_elt (@var{arg}, @dots{})
@msindex{dquote_elt}
Return the arguments as a series of double-quoted arguments. Whereas
@code{m4_dquote} returns a single argument, @code{m4_dquote_elt} returns
as many arguments as it was passed.
@end defmac
@defmac m4_echo (@var{arg}, @dots{})
@msindex{echo}
Return the arguments, with the same level of quoting. Other than
discarding whitespace after unquoted commas, this macro is a no-op.
@end defmac
@defmac m4_expand (@var{arg})
@msindex{expand}
Return the expansion of @var{arg} as a quoted string. Whereas
@code{m4_quote} is designed to collect expanded text into a single
argument, @code{m4_expand} is designed to perform one level of expansion
on quoted text. One distinction is in the treatment of whitespace
following a comma in the original @var{arg}. Any time multiple
arguments are collected into one with @code{m4_quote}, the M4 argument
collection rules discard the whitespace. However, with @code{m4_expand},
whitespace is preserved, even after the expansion of macros contained in
@var{arg}. Additionally, @code{m4_expand} is able to expand text that
would involve an unterminated comment, whereas expanding that same text
as the argument to @code{m4_quote} runs into difficulty in finding the
end of the argument. Since manipulating diversions during argument
collection is inherently unsafe, @code{m4_expand} issues an error if
@var{arg} attempts to change the current diversion (@pxref{Diversion
support}).
@example
m4_define([active], [ACT, IVE])dnl
m4_define([active2], [[ACT, IVE]])dnl
m4_quote(active, active)
@result{}ACT,IVE,ACT,IVE
m4_expand([active, active])
@result{}ACT, IVE, ACT, IVE
m4_quote(active2, active2)
@result{}ACT, IVE,ACT, IVE
m4_expand([active2, active2])
@result{}ACT, IVE, ACT, IVE
m4_expand([# m4_echo])
@result{}# m4_echo
m4_quote(# m4_echo)
)
@result{}# m4_echo)
@result{}
@end example
Note that @code{m4_expand} cannot handle an @var{arg} that expands to
literal unbalanced quotes, but that quadrigraphs can be used when
unbalanced output is necessary. Likewise, unbalanced parentheses should
be supplied with double quoting or a quadrigraph.
@example
m4_define([pattern], [[!@@<:@@]])dnl
m4_define([bar], [BAR])dnl
m4_expand([case $foo in
m4_defn([pattern])@@:@}@@ bar ;;
*[)] blah ;;
esac])
@result{}case $foo in
@result{} [![]) BAR ;;
@result{} *) blah ;;
@result{}esac
@end example
@end defmac
@defmac m4_ignore (@dots{})
@msindex{ignore}
This macro was introduced in Autoconf 2.62. Expands to nothing,
ignoring all of its arguments. By itself, this isn't very useful.
However, it can be used to conditionally ignore an arbitrary number of
arguments, by deciding which macro name to apply to a list of arguments.
@example
dnl foo outputs a message only if [debug] is defined.
m4_define([foo],
[m4_ifdef([debug],[AC_MSG_NOTICE],[m4_ignore])([debug message])])
@end example
Note that for earlier versions of Autoconf, the macro @code{__gnu__} can
serve the same purpose, although it is less readable.
@end defmac
@defmac m4_make_list (@var{arg}, @dots{})
@msindex{make_list}
This macro exists to aid debugging of M4sugar algorithms. Its net
effect is similar to @code{m4_dquote}---it produces a quoted list of
quoted arguments, for each @var{arg}. The difference is that this
version uses a comma-newline separator instead of just comma, to improve
readability of the list; with the result that it is less efficient than
@code{m4_dquote}.
@example
m4_define([zero],[0])m4_define([one],[1])m4_define([two],[2])dnl
m4_dquote(zero, [one], [[two]])
@result{}[0],[one],[[two]]
m4_make_list(zero, [one], [[two]])
@result{}[0],
@result{}[one],
@result{}[[two]]
m4_foreach([number], m4_dquote(zero, [one], [[two]]), [ number])
@result{} 0 1 two
m4_foreach([number], m4_make_list(zero, [one], [[two]]), [ number])
@result{} 0 1 two
@end example
@end defmac
@c m4_noquote is too dangerous to document - it invokes macros that
@c probably rely on @samp{[]} nested quoting for proper operation. The
@c user should generally prefer m4_unquote instead.
@defmac m4_quote (@var{arg}, @dots{})
@msindex{quote}
Return the arguments as a single entity, i.e., wrap them into a pair of
quotes. This effectively collapses multiple arguments into one,
although it loses whitespace after unquoted commas in the process.
@end defmac
@defmac m4_reverse (@var{arg}, @dots{})
@msindex{reverse}
Outputs each argument with the same level of quoting, but in reverse
order, and with space following each comma for readability.
@example
m4_define([active], [ACT,IVE])
@result{}
m4_reverse(active, [active])
@result{}active, IVE, ACT
@end example
@end defmac
@defmac m4_unquote (@var{arg}, @dots{})
@msindex{unquote}
This macro was introduced in Autoconf 2.62. Expand each argument,
separated by commas. For a single @var{arg}, this effectively removes a
layer of quoting, and @code{m4_unquote([@var{arg}])} is more efficient
than the equivalent @code{m4_do([@var{arg}])}. For multiple arguments,
this results in an unquoted list of expansions. This is commonly used
with @code{m4_split}, in order to convert a single quoted list into a
series of quoted elements.
@end defmac
The following example aims at emphasizing the difference between several
scenarios: not using these macros, using @code{m4_defn}, using
@code{m4_quote}, using @code{m4_dquote}, and using @code{m4_expand}.
@example
$ @kbd{cat example.m4}
dnl Overquote, so that quotes are visible.
m4_define([show], [$[]1 = [$1], $[]@@ = [$@@]])
m4_define([a], [A])
m4_define([mkargs], [1, 2[,] 3])
m4_define([arg1], [[$1]])
m4_divert([0])dnl
show(a, b)
show([a, b])
show(m4_quote(a, b))
show(m4_dquote(a, b))
show(m4_expand([a, b]))
arg1(mkargs)
arg1([mkargs])
arg1(m4_defn([mkargs]))
arg1(m4_quote(mkargs))
arg1(m4_dquote(mkargs))
arg1(m4_expand([mkargs]))
$ @kbd{autom4te -l m4sugar example.m4}
$1 = A, $@@ = [A],[b]
$1 = a, b, $@@ = [a, b]
$1 = A,b, $@@ = [A,b]
$1 = [A],[b], $@@ = [[A],[b]]
$1 = A, b, $@@ = [A, b]
1
mkargs
1, 2[,] 3
1,2, 3
[1],[2, 3]
1, 2, 3
@end example
@node Text processing Macros
@subsection String manipulation in M4
The following macros may be used to manipulate strings in M4. Many of
the macros in this section intentionally result in quoted strings as
output, rather than subjecting the arguments to further expansions. As
a result, if you are manipulating text that contains active M4
characters, the arguments are passed with single quoting rather than
double.
@defmac m4_append (@var{macro-name}, @var{string}, @ovar{separator})
@defmacx m4_append_uniq (@var{macro-name}, @var{string}, @ovar{separator} @
@ovar{if-uniq}, @ovar{if-duplicate})
@msindex{append}
@msindex{append_uniq}
Redefine @var{macro-name} to its former contents with @var{separator}
and @var{string} added at the end. If @var{macro-name} was undefined
before (but not if it was defined but empty), then no @var{separator} is
added. As of Autoconf 2.62, neither @var{string} nor @var{separator}
are expanded during this macro; instead, they are expanded when
@var{macro-name} is invoked.
@code{m4_append} can be used to grow strings, and @code{m4_append_uniq}
to grow strings without duplicating substrings. Additionally,
@code{m4_append_uniq} takes two optional parameters as of Autoconf 2.62;
@var{if-uniq} is expanded if @var{string} was appended, and
@var{if-duplicate} is expanded if @var{string} was already present.
Also, @code{m4_append_uniq} warns if @var{separator} is not empty, but
occurs within @var{string}, since that can lead to duplicates.
Note that @code{m4_append} can scale linearly in the length of the final
string, depending on the quality of the underlying M4 implementation,
while @code{m4_append_uniq} has an inherent quadratic scaling factor.
If an algorithm can tolerate duplicates in the final string, use the
former for speed. If duplicates must be avoided, consider using
@code{m4_set_add} instead (@pxref{Set manipulation Macros}).
@example
m4_define([active], [ACTIVE])dnl
m4_append([sentence], [This is an])dnl
m4_append([sentence], [ active ])dnl
m4_append([sentence], [symbol.])dnl
sentence
@result{}This is an ACTIVE symbol.
m4_undefine([active])dnl
@result{}This is an active symbol.
m4_append_uniq([list], [one], [, ], [new], [existing])
@result{}new
m4_append_uniq([list], [one], [, ], [new], [existing])
@result{}existing
m4_append_uniq([list], [two], [, ], [new], [existing])
@result{}new
m4_append_uniq([list], [three], [, ], [new], [existing])
@result{}new
m4_append_uniq([list], [two], [, ], [new], [existing])
@result{}existing
list
@result{}one, two, three
m4_dquote(list)
@result{}[one],[two],[three]
m4_append([list2], [one], [[, ]])dnl
m4_append_uniq([list2], [two], [[, ]])dnl
m4_append([list2], [three], [[, ]])dnl
list2
@result{}one, two, three
m4_dquote(list2)
@result{}[one, two, three]
@end example
@end defmac
@defmac m4_append_uniq_w (@var{macro-name}, @var{strings})
@msindex{append_uniq_w}
This macro was introduced in Autoconf 2.62. It is similar to
@code{m4_append_uniq}, but treats @var{strings} as a whitespace
separated list of words to append, and only appends unique words.
@var{macro-name} is updated with a single space between new words.
@example
m4_append_uniq_w([numbers], [1 1 2])dnl
m4_append_uniq_w([numbers], [ 2 3 ])dnl
numbers
@result{}1 2 3
@end example
@end defmac
@defmac m4_chomp (@var{string})
@defmacx m4_chomp_all (@var{string})
@msindex{chomp}
@msindex{chomp_all}
Output @var{string} in quotes, but without a trailing newline. The
macro @code{m4_chomp} is slightly faster, and removes at most one
newline; the macro @code{m4_chomp_all} removes all consecutive trailing
newlines. Unlike @code{m4_flatten}, embedded newlines are left intact,
and backslash does not influence the result.
@end defmac
@defmac m4_combine (@ovar{separator}, @var{prefix-list}, @ovar{infix}, @
@var{suffix-1}, @ovar{suffix-2}, @dots{})
@msindex{combine}
This macro produces a quoted string containing the pairwise combination
of every element of the quoted, comma-separated @var{prefix-list}, and
every element from the @var{suffix} arguments. Each pairwise
combination is joined with @var{infix} in the middle, and successive
pairs are joined by @var{separator}. No expansion occurs on any of the
arguments. No output occurs if either the @var{prefix} or @var{suffix}
list is empty, but the lists can contain empty elements.
@example
m4_define([a], [oops])dnl
m4_combine([, ], [[a], [b], [c]], [-], [1], [2], [3])
@result{}a-1, a-2, a-3, b-1, b-2, b-3, c-1, c-2, c-3
m4_combine([, ], [[a], [b]], [-])
@result{}
m4_combine([, ], [[a], [b]], [-], [])
@result{}a-, b-
m4_combine([, ], [], [-], [1], [2])
@result{}
m4_combine([, ], [[]], [-], [1], [2])
@result{}-1, -2
@end example
@end defmac
@defmac m4_flatten (@var{string})
@msindex{flatten}
Flatten @var{string} into a single line. Delete all backslash-newline
pairs, and replace all remaining newlines with a space. The result is
still a quoted string.
@end defmac
@defmac m4_join (@ovar{separator}, @var{args}@dots{})
@defmacx m4_joinall (@ovar{separator}, @var{args}@dots{})
@msindex{join}
@msindex{joinall}
Concatenate each @var{arg}, separated by @var{separator}.
@code{joinall} uses every argument, while @code{join} omits empty
arguments so that there are no back-to-back separators in the output.
The result is a quoted string.
@example
m4_define([active], [ACTIVE])dnl
m4_join([|], [one], [], [active], [two])
@result{}one|active|two
m4_joinall([|], [one], [], [active], [two])
@result{}one||active|two
@end example
Note that if all you intend to do is join @var{args} with commas between
them, to form a quoted list suitable for @code{m4_foreach}, it is more
efficient to use @code{m4_dquote}.
@end defmac
@defmac m4_newline (@ovar{text})
@msindex{newline}
This macro was introduced in Autoconf 2.62, and expands to a newline,
followed by any @var{text}.
It is primarily useful for maintaining macro formatting, and ensuring
that M4 does not discard leading whitespace during argument collection.
@end defmac
@defmac m4_normalize (@var{string})
@msindex{normalize}
Remove leading and trailing spaces and tabs, sequences of
backslash-then-newline, and replace multiple spaces, tabs, and newlines
with a single space. This is a combination of @code{m4_flatten} and
@code{m4_strip}. To determine if @var{string} consists only of bytes
that would be removed by @code{m4_normalize}, you can use
@code{m4_ifblank}.
@end defmac
@defmac m4_re_escape (@var{string})
@msindex{re_escape}
Backslash-escape all characters in @var{string} that are active in
regexps.
@end defmac
@defmac m4_split (@var{string}, @dvar{regexp, [\t ]+})
@msindex{split}
Split @var{string} into an M4 list of elements quoted by @samp{[} and
@samp{]}, while keeping white space at the beginning and at the end.
If @var{regexp} is given, use it instead of @samp{[\t ]+} for splitting.
If @var{string} is empty, the result is an empty list.
@end defmac
@defmac m4_strip (@var{string})
@msindex{strip}
Strip whitespace from @var{string}. Sequences of spaces and tabs are
reduced to a single space, then leading and trailing spaces are removed.
The result is still a quoted string. Note that this does not interfere
with newlines; if you want newlines stripped as well, consider
@code{m4_flatten}, or do it all at once with @code{m4_normalize}. To
quickly test if @var{string} has only whitespace, use @code{m4_ifblank}.
@end defmac
@defmac m4_text_box (@var{message}, @dvar{frame, -})
@msindex{text_box}
Add a text box around @var{message}, using @var{frame} as the border
character above and below the message. The frame correctly accounts for
the subsequent expansion of @var{message}. For example:
@example
m4_define([macro], [abc])dnl
m4_text_box([macro])
@result{}## --- ##
@result{}## abc ##
@result{}## --- ##
@end example
The @var{message} must contain balanced quotes and parentheses, although
quadrigraphs can be used to work around this.
@end defmac
@defmac m4_text_wrap (@var{string}, @ovar{prefix}, @
@dvar{prefix1, @var{prefix}}, @dvar{width, 79})
@msindex{text_wrap}
Break @var{string} into a series of whitespace-separated words, then
output those words separated by spaces, and wrapping lines any time the
output would exceed @var{width} columns. If given, @var{prefix1} begins
the first line, and @var{prefix} begins all wrapped lines. If
@var{prefix1} is longer than @var{prefix}, then the first line consists
of just @var{prefix1}. If @var{prefix} is longer than @var{prefix1},
padding is inserted so that the first word of @var{string} begins at the
same indentation as all wrapped lines. Note that using literal tab
characters in any of the arguments will interfere with the calculation
of width. No expansions occur on @var{prefix}, @var{prefix1}, or the
words of @var{string}, although quadrigraphs are recognized.
For some examples:
@example
m4_text_wrap([Short string */], [ ], [/* ], [20])
@result{}/* Short string */
m4_text_wrap([Much longer string */], [ ], [/* ], [20])
@result{}/* Much longer
@result{} string */
m4_text_wrap([Short doc.], [ ], [ --short ], [30])
@result{} --short Short doc.
m4_text_wrap([Short doc.], [ ], [ --too-wide ], [30])
@result{} --too-wide
@result{} Short doc.
m4_text_wrap([Super long documentation.], [ ],
[ --too-wide ], 30)
@result{} --too-wide
@result{} Super long
@result{} documentation.
@end example
@end defmac
@defmac m4_tolower (@var{string})
@defmacx m4_toupper (@var{string})
@msindex{tolower}
@msindex{toupper}
Return @var{string} with letters converted to upper or lower case,
respectively.
@end defmac
@node Number processing Macros
@subsection Arithmetic computation in M4
The following macros facilitate integer arithmetic operations.
Where a parameter is documented as taking an arithmetic expression, you
can use anything that can be parsed by @code{m4_eval}.
@defmac m4_cmp (@var{expr-1}, @var{expr-2})
@msindex{cmp}
Compare the arithmetic expressions @var{expr-1} and @var{expr-2}, and
expand to @samp{-1} if @var{expr-1} is smaller, @samp{0} if they are
equal, and @samp{1} if @var{expr-1} is larger.
@end defmac
@defmac m4_list_cmp (@var{list-1}, @var{list-2})
@msindex{list_cmp}
Compare the two M4 lists consisting of comma-separated arithmetic
expressions, left to right. Expand to @samp{-1} for the first element
pairing where the value from @var{list-1} is smaller, @samp{1} where the
value from @var{list-2} is smaller, or @samp{0} if both lists have the
same values. If one list is shorter than the other, the remaining
elements of the longer list are compared against zero.
@example
m4_list_cmp([1, 0], [1])
@result{}0
m4_list_cmp([1, [1 * 0]], [1, 0])
@result{}0
m4_list_cmp([1, 2], [1, 0])
@result{}1
m4_list_cmp([1, [1+1], 3],[1, 2])
@result{}1
m4_list_cmp([1, 2, -3], [1, 2])
@result{}-1
m4_list_cmp([1, 0], [1, 2])
@result{}-1
m4_list_cmp([1], [1, 2])
@result{}-1
@end example
@end defmac
@defmac m4_max (@var{arg}, @dots{})
@msindex{max}
This macro was introduced in Autoconf 2.62. Expand to the decimal value
of the maximum arithmetic expression among all the arguments.
@end defmac
@defmac m4_min (@var{arg}, @dots{})
@msindex{min}
This macro was introduced in Autoconf 2.62. Expand to the decimal value
of the minimum arithmetic expression among all the arguments.
@end defmac
@defmac m4_sign (@var{expr})
@msindex{sign}
Expand to @samp{-1} if the arithmetic expression @var{expr} is negative,
@samp{1} if it is positive, and @samp{0} if it is zero.
@end defmac
@anchor{m4_version_compare}
@defmac m4_version_compare (@var{version-1}, @var{version-2})
@msindex{version_compare}
This macro was introduced in Autoconf 2.53, but had a number of
usability limitations that were not lifted until Autoconf 2.62. Compare
the version strings @var{version-1} and @var{version-2}, and expand to
@samp{-1} if @var{version-1} is smaller, @samp{0} if they are the same,
or @samp{1} @var{version-2} is smaller. Version strings must be a list
of elements separated by @samp{.}, @samp{,} or @samp{-}, where each
element is a number along with optional case-insensitive letters
designating beta releases. The comparison stops at the leftmost element
that contains a difference, although a 0 element compares equal to a
missing element.
It is permissible to include commit identifiers in @var{version}, such
as an abbreviated SHA1 of the commit, provided there is still a
monotonically increasing prefix to allow for accurate version-based
comparisons. For example, this paragraph was written when the
development snapshot of autoconf claimed to be at version
@samp{2.61a-248-dc51}, or 248 commits after the 2.61a release, with an
abbreviated commit identification of @samp{dc51}.
@example
m4_version_compare([1.1], [2.0])
@result{}-1
m4_version_compare([2.0b], [2.0a])
@result{}1
m4_version_compare([1.1.1], [1.1.1a])
@result{}-1
m4_version_compare([1.2], [1.1.1a])
@result{}1
m4_version_compare([1.0], [1])
@result{}0
m4_version_compare([1.1pre], [1.1PRE])
@result{}0
m4_version_compare([1.1a], [1,10])
@result{}-1
m4_version_compare([2.61a], [2.61a-248-dc51])
@result{}-1
m4_version_compare([2.61b], [2.61a-248-dc51])
@result{}1
@end example
@end defmac
@defmac m4_version_prereq (@var{version}, @ovar{if-new-enough}, @
@dvar{if-old, m4_fatal})
@msindex{version_prereq}
Compares @var{version} against the version of Autoconf currently
running. If the running version is at @var{version} or newer, expand
@var{if-new-enough}, but if @var{version} is larger than the version
currently executing, expand @var{if-old}, which defaults to printing an
error message and exiting m4sugar with status 63. When given only one
argument, this behaves like @code{AC_PREREQ} (@pxref{Versioning}).
Remember that the autoconf philosophy favors feature checks over version
checks.
@end defmac
@node Set manipulation Macros
@subsection Set manipulation in M4
@cindex Set manipulation
@cindex Data structure, set
@cindex Unordered set manipulation
Sometimes, it is necessary to track a set of data, where the order does
not matter and where there are no duplicates in the set. The following
macros facilitate set manipulations. Each set is an opaque object,
which can only be accessed via these basic operations. The underlying
implementation guarantees linear scaling for set creation, which is more
efficient than using the quadratic @code{m4_append_uniq}. Both set
names and values can be arbitrary strings, except for unbalanced quotes.
This implementation ties up memory for removed elements until the next
operation that must traverse all the elements of a set; and although
that may slow down some operations until the memory for removed elements
is pruned, it still guarantees linear performance.
@defmac m4_set_add (@var{set}, @var{value}, @ovar{if-uniq}, @ovar{if-dup})
@msindex{set_add}
Adds the string @var{value} as a member of set @var{set}. Expand
@var{if-uniq} if the element was added, or @var{if-dup} if it was
previously in the set. Operates in amortized constant time, so that set
creation scales linearly.
@end defmac
@defmac m4_set_add_all (@var{set}, @var{value}@dots{})
@msindex{set_add_all}
Adds each @var{value} to the set @var{set}. This is slightly more
efficient than repeatedly invoking @code{m4_set_add}.
@end defmac
@defmac m4_set_contains (@var{set}, @var{value}, @ovar{if-present}, @
@ovar{if-absent})
@msindex{set_contains}
Expands @var{if-present} if the string @var{value} is a member of
@var{set}, otherwise @var{if-absent}.
@example
m4_set_contains([a], [1], [yes], [no])
@result{}no
m4_set_add([a], [1], [added], [dup])
@result{}added
m4_set_add([a], [1], [added], [dup])
@result{}dup
m4_set_contains([a], [1], [yes], [no])
@result{}yes
m4_set_remove([a], [1], [removed], [missing])
@result{}removed
m4_set_contains([a], [1], [yes], [no])
@result{}no
m4_set_remove([a], [1], [removed], [missing])
@result{}missing
@end example
@end defmac
@defmac m4_set_contents (@var{set}, @ovar{sep})
@defmacx m4_set_dump (@var{set}, @ovar{sep})
@msindex{set_contents}
@msindex{set_dump}
Expands to a single string consisting of all the members of the set
@var{set}, each separated by @var{sep}, which is not expanded.
@code{m4_set_contents} leaves the elements in @var{set} but reclaims any
memory occupied by removed elements, while @code{m4_set_dump} is a
faster one-shot action that also deletes the set. No provision is made
for disambiguating members that contain a non-empty @var{sep} as a
substring; use @code{m4_set_empty} to distinguish between an empty set
and the set containing only the empty string. The order of the output
is unspecified; in the current implementation, part of the speed of
@code{m4_set_dump} results from using a different output order than
@code{m4_set_contents}. These macros scale linearly in the size of the
set before memory pruning, and @code{m4_set_contents([@var{set}],
[@var{sep}])} is faster than
@code{m4_joinall([@var{sep}]m4_set_listc([@var{set}]))}.
@example
m4_set_add_all([a], [1], [2], [3])
@result{}
m4_set_contents([a], [-])
@result{}1-2-3
m4_joinall([-]m4_set_listc([a]))
@result{}1-2-3
m4_set_dump([a], [-])
@result{}3-2-1
m4_set_contents([a])
@result{}
m4_set_add([a], [])
@result{}
m4_set_contents([a], [-])
@result{}
@end example
@end defmac
@defmac m4_set_delete (@var{set})
@msindex{set_delete}
Delete all elements and memory associated with @var{set}. This is
linear in the set size, and faster than removing one element at a time.
@end defmac
@defmac m4_set_difference (@var{seta}, @var{setb})
@defmacx m4_set_intersection (@var{seta}, @var{setb})
@defmacx m4_set_union (@var{seta}, @var{setb})
@msindex{set_difference}
@msindex{set_intersection}
@msindex{set_union}
Compute the relation between @var{seta} and @var{setb}, and output the
result as a list of quoted arguments without duplicates and with a
leading comma. Set difference selects the elements in @var{seta} but
not @var{setb}, intersection selects only elements in both sets, and
union selects elements in either set. These actions are linear in the
sum of the set sizes. The leading comma is necessary to distinguish
between no elements and the empty string as the only element.
@example
m4_set_add_all([a], [1], [2], [3])
@result{}
m4_set_add_all([b], [3], [], [4])
@result{}
m4_set_difference([a], [b])
@result{},1,2
m4_set_difference([b], [a])
@result{},,4
m4_set_intersection([a], [b])
@result{},3
m4_set_union([a], [b])
@result{},1,2,3,,4
@end example
@end defmac
@defmac m4_set_empty (@var{set}, @ovar{if-empty}, @ovar{if-elements})
@msindex{set_empty}
Expand @var{if-empty} if the set @var{set} has no elements, otherwise
expand @var{if-elements}. This macro operates in constant time. Using
this macro can help disambiguate output from @code{m4_set_contents} or
@code{m4_set_list}.
@end defmac
@defmac m4_set_foreach (@var{set}, @var{variable}, @var{action})
@msindex{set_foreach}
For each element in the set @var{set}, expand @var{action} with the
macro @var{variable} defined as the set element. Behavior is
unspecified if @var{action} recursively lists the contents of @var{set}
(although listing other sets is acceptable), or if it modifies the set
in any way other than removing the element currently contained in
@var{variable}. This macro is faster than the corresponding
@code{m4_foreach([@var{variable}],
m4_indir([m4_dquote]m4_set_listc([@var{set}])), [@var{action}])},
although @code{m4_set_map} might be faster still.
@example
m4_set_add_all([a]m4_for([i], [1], [5], [], [,i]))
@result{}
m4_set_contents([a])
@result{}12345
m4_set_foreach([a], [i],
[m4_if(m4_eval(i&1), [0], [m4_set_remove([a], i, [i])])])
@result{}24
m4_set_contents([a])
@result{}135
@end example
@end defmac
@defmac m4_set_list (@var{set})
@defmacx m4_set_listc (@var{set})
@msindex{set_list}
@msindex{set_listc}
Produce a list of arguments, where each argument is a quoted element
from the set @var{set}. The variant @code{m4_set_listc} is unambiguous,
by adding a leading comma if there are any set elements, whereas the
variant @code{m4_set_list} cannot distinguish between an empty set and a
set containing only the empty string. These can be directly used in
macros that take multiple arguments, such as @code{m4_join} or
@code{m4_set_add_all}, or wrapped by @code{m4_dquote} for macros that
take a quoted list, such as @code{m4_map} or @code{m4_foreach}. Any
memory occupied by removed elements is reclaimed during these macros.
@example
m4_set_add_all([a], [1], [2], [3])
@result{}
m4_set_list([a])
@result{}1,2,3
m4_set_list([b])
@result{}
m4_set_listc([b])
@result{}
m4_count(m4_set_list([b]))
@result{}1
m4_set_empty([b], [0], [m4_count(m4_set_list([b]))])
@result{}0
m4_set_add([b], [])
@result{}
m4_set_list([b])
@result{}
m4_set_listc([b])
@result{},
m4_count(m4_set_list([b]))
@result{}1
m4_set_empty([b], [0], [m4_count(m4_set_list([b]))])
@result{}1
@end example
@end defmac
@defmac m4_set_map (@var{set}, @var{action})
@msindex{set_map}
For each element in the set @var{set}, expand @var{action} with a single
argument of the set element. Behavior is unspecified if @var{action}
recursively lists the contents of @var{set} (although listing other sets
is acceptable), or if it modifies the set in any way other than removing
the element passed as an argument. This macro is faster than either
corresponding counterpart of
@code{m4_map_args([@var{action}]m4_set_listc([@var{set}]))} or
@code{m4_set_foreach([@var{set}], [var],
[@var{action}(m4_defn([var]))])}. It is possible to use @code{m4_curry}
if more than one argument is needed for @var{action}, although it is
more efficient to use @code{m4_set_map_sep} in that case.
@end defmac
@defmac m4_set_map_sep (@var{set}, @ovar{pre}, @ovar{post}, @ovar{sep})
@msindex{set_map_sep}
For each element in the set @var{set}, expand
@code{@var{pre}[element]@var{post}}, additionally expanding @var{sep}
between elements. Behavior is unspecified if the expansion recursively
lists the contents of @var{set} (although listing other sets
is acceptable), or if it modifies the set in any way other than removing
the element visited by the expansion. This macro provides the most
efficient means for non-destructively visiting the elements of a set; in
particular, @code{m4_set_map([@var{set}], [@var{action}])} is equivalent
to @code{m4_set_map_sep([@var{set}], [@var{action}(], [)])}.
@end defmac
@defmac m4_set_remove (@var{set}, @var{value}, @ovar{if-present}, @
@ovar{if-absent})
@msindex{set_remove}
If @var{value} is an element in the set @var{set}, then remove it and
expand @var{if-present}. Otherwise expand @var{if-absent}. This macro
operates in constant time so that multiple removals will scale linearly
rather than quadratically; but when used outside of
@code{m4_set_foreach} or @code{m4_set_map}, it leaves memory occupied
until the set is later
compacted by @code{m4_set_contents} or @code{m4_set_list}. Several
other set operations are then less efficient between the time of element
removal and subsequent memory compaction, but still maintain their
guaranteed scaling performance.
@end defmac
@defmac m4_set_size (@var{set})
@msindex{set_size}
Expand to the size of the set @var{set}. This implementation operates
in constant time, and is thus more efficient than
@code{m4_eval(m4_count(m4_set_listc([set])) - 1)}.
@end defmac
@node Forbidden Patterns
@subsection Forbidden Patterns
@cindex Forbidden patterns
@cindex Patterns, forbidden
M4sugar provides a means to define suspicious patterns, patterns
describing tokens which should not be found in the output. For
instance, if an Autoconf @file{configure} script includes tokens such as
@samp{AC_DEFINE}, or @samp{dnl}, then most probably something went
wrong (typically a macro was not evaluated because of overquotation).
M4sugar forbids all the tokens matching @samp{^_?m4_} and @samp{^dnl$}.
Additional layers, such as M4sh and Autoconf, add additional forbidden
patterns to the list.
@defmac m4_pattern_forbid (@var{pattern})
@msindex{pattern_forbid}
Declare that no token matching @var{pattern} must be found in the output.
Comments are not checked; this can be a problem if, for instance, you
have some macro left unexpanded after an @samp{#include}. No consensus
is currently found in the Autoconf community, as some people consider it
should be valid to name macros in comments (which doesn't make sense to
the authors of this documentation: input, such as macros, should be
documented by @samp{dnl} comments; reserving @samp{#}-comments to
document the output).
@end defmac
Of course, you might encounter exceptions to these generic rules, for
instance you might have to refer to @samp{$m4_flags}.
@defmac m4_pattern_allow (@var{pattern})
@msindex{pattern_allow}
Any token matching @var{pattern} is allowed, including if it matches an
@code{m4_pattern_forbid} pattern.
@end defmac
@node Debugging via autom4te
@section Debugging via autom4te
@cindex debugging tips
@cindex autom4te debugging tips
@cindex m4sugar debugging tips
At times, it is desirable to see what was happening inside m4, to see
why output was not matching expectations. However, post-processing done
by @command{autom4te} means that directly using the m4 builtin
@code{m4_traceon} is likely to interfere with operation. Also, frequent
diversion changes and the concept of forbidden tokens make it difficult
to use @code{m4_defn} to generate inline comments in the final output.
There are a couple of tools to help with this. One is the use of the
@option{--trace} option provided by @command{autom4te} (as well as each
of the programs that wrap @command{autom4te}, such as
@command{autoconf}), in order to inspect when a macro is called and with
which arguments. For example, when this paragraph was written, the
autoconf version could be found by:
@example
$ @kbd{autoconf --trace=AC_INIT}
configure.ac:23:AC_INIT:GNU Autoconf:2.63b.95-3963:bug-autoconf@@gnu.org
$ @kbd{autoconf --trace='AC_INIT:version is $2'}
version is 2.63b.95-3963
@end example
Another trick is to print out the expansion of various m4 expressions to
standard error or to an independent file, with no further m4 expansion,
and without interfering with diversion changes or the post-processing
done to standard output. @code{m4_errprintn} shows a given expression
on standard error. For example, if you want to see the expansion of an
autoconf primitive or of one of your autoconf macros, you can do it like
this:
@example
$ @kbd{cat <<\EOF > configure.ac}
AC_INIT
m4_errprintn([The definition of AC_DEFINE_UNQUOTED:])
m4_errprintn(m4_defn([AC_DEFINE_UNQUOTED]))
AC_OUTPUT
EOF
$ @kbd{autoconf}
@error{}The definition of AC_DEFINE_UNQUOTED:
@error{}_AC_DEFINE_Q([], $@@)
@end example
@node Programming in M4sh
@chapter Programming in M4sh
M4sh, pronounced ``mash'', is aiming at producing portable Bourne shell
scripts. This name was coined by Lars J. Aas, who notes that,
according to the Webster's Revised Unabridged Dictionary (1913):
@quotation
Mash \Mash\, n. [Akin to G. meisch, maisch, meische, maische, mash,
wash, and prob.@: to AS. miscian to mix. See ``Mix''.]
@enumerate 1
@item
A mass of mixed ingredients reduced to a soft pulpy state by beating or
pressure@enddots{}
@item
A mixture of meal or bran and water fed to animals.
@item
A mess; trouble. [Obs.] --Beau.@: & Fl.
@end enumerate
@end quotation
M4sh reserves the M4 macro namespace @samp{^_AS_} for internal use, and
the namespace @samp{^AS_} for M4sh macros. It also reserves the shell
and environment variable namespace @samp{^as_}, and the here-document
delimiter namespace @samp{^_AS[A-Z]} in the output file. You should not
define your own macros or output shell code that conflicts with these
namespaces.
@menu
* Common Shell Constructs:: Portability layer for common shell constructs
* Polymorphic Variables:: Support for indirect variable names
* Initialization Macros:: Macros to establish a sane shell environment
* File Descriptor Macros:: File descriptor macros for input and output
@end menu
@node Common Shell Constructs
@section Common Shell Constructs
M4sh provides portable alternatives for some common shell constructs
that unfortunately are not portable in practice.
@c Deprecated, to be replaced by a better API
@ignore
@defmac AS_BASENAME (@var{file-name})
@asindex{BASENAME}
Output the non-directory portion of @var{file-name}. For example,
if @code{$file} is @samp{/one/two/three}, the command
@code{base=`AS_BASENAME(["$file"])`} sets @code{base} to @samp{three}.
@end defmac
@end ignore
@defmac AS_CASE (@var{word}, @ovar{pattern1}, @ovar{if-matched1}, @
@dots{}, @ovar{default})
@asindex{CASE}
Expand into a shell @samp{case} statement, where @var{word} is matched
against one or more patterns. @var{if-matched} is run if the
corresponding pattern matched @var{word}, else @var{default} is run.
Avoids several portability issues (@pxref{case, , Limitations of Shell
Builtins}).
@end defmac
@c Deprecated, to be replaced by a better API
@ignore
@defmac AS_DIRNAME (@var{file-name})
@asindex{DIRNAME}
Output the directory portion of @var{file-name}. For example,
if @code{$file} is @samp{/one/two/three}, the command
@code{dir=`AS_DIRNAME(["$file"])`} sets @code{dir} to @samp{/one/two}.
@end defmac
@end ignore
@defmac AS_ECHO (@var{word})
@asindex{ECHO}
Emits @var{word} to the standard output, followed by a newline. @var{word}
must be a single shell word (typically a quoted string). The bytes of
@var{word} are output as-is, even if it starts with "-" or contains "\".
Redirections can be placed outside the macro invocation. This is much
more portable than using @command{echo} (@pxref{echo, , Limitations of
Shell Builtins}).
@end defmac
@defmac AS_ECHO_N (@var{word})
@asindex{ECHO_N}
Emits @var{word} to the standard output, without a following newline.
@var{word} must be a single shell word (typically a quoted string) and,
for portability, should not include more than one newline. The bytes of
@var{word} are output as-is, even if it starts with "-" or contains "\".
Redirections can be placed outside the macro invocation.
@end defmac
@defmac AS_ESCAPE (@var{string}, @dvar{chars, `\"$})
@asindex{ESCAPE}
Expands to @var{string}, with any characters in @var{chars} escaped with
a backslash (@samp{\}). @var{chars} should be at most four bytes long,
and only contain characters from the set @samp{`\"$}; however,
characters may be safely listed more than once in @var{chars} for the
sake of syntax highlighting editors. The current implementation expands
@var{string} after adding escapes; if @var{string} contains macro calls
that in turn expand to text needing shell quoting, you can use
@code{AS_ESCAPE(m4_dquote(m4_expand([string])))}.
The default for @var{chars} (@samp{\"$`}) is the set of characters
needing escapes when @var{string} will be used literally within double
quotes. One common variant is the set of characters to protect when
@var{string} will be used literally within back-ticks or an unquoted
here-document (@samp{\$`}). Another common variant is @samp{""}, which can
be used to form a double-quoted string containing the same expansions
that would have occurred if @var{string} were expanded in an unquoted
here-document; however, when using this variant, care must be taken that
@var{string} does not use double quotes within complex variable
expansions (such as @samp{$@{foo-`echo "hi"`@}}) that would be broken
with improper escapes.
This macro is often used with @code{AS_ECHO}. For an example, observe
the output generated by the shell code generated from this snippet:
@example
foo=bar
AS_ECHO(["AS_ESCAPE(["$foo" = ])AS_ESCAPE(["$foo"], [""])"])
@result{}"$foo" = "bar"
m4_define([macro], [a, [\b]])
AS_ECHO(["AS_ESCAPE([[macro]])"])
@result{}macro
AS_ECHO(["AS_ESCAPE([macro])"])
@result{}a, b
AS_ECHO(["AS_ESCAPE(m4_dquote(m4_expand([macro])))"])
@result{}a, \b
@end example
@comment Should we add AS_ESCAPE_SINGLE? If we do, we can optimize in
@comment the case of @var{string} that does not contain '.
To escape a string that will be placed within single quotes, use:
@example
m4_bpatsubst([[@var{string}]], ['], ['\\''])
@end example
@end defmac
@defmac AS_EXIT (@dvar{status, $?})
@asindex{EXIT}
Emit code to exit the shell with @var{status}, defaulting to @samp{$?}.
This macro
works around shells that see the exit status of the command prior to
@code{exit} inside a @samp{trap 0} handler (@pxref{trap, , Limitations
of Shell Builtins}).
@end defmac
@defmac AS_IF (@var{test1}, @ovar{run-if-true1}, @dots{}, @ovar{run-if-false})
@asindex{IF}
Run shell code @var{test1}. If @var{test1} exits with a zero status then
run shell code @var{run-if-true1}, else examine further tests. If no test
exits with a zero status, run shell code @var{run-if-false}, with
simplifications if either @var{run-if-true1} or @var{run-if-false}
is empty. For example,
@example
AS_IF([test "x$foo" = xyes], [HANDLE_FOO([yes])],
[test "x$foo" != xno], [HANDLE_FOO([maybe])],
[echo foo not specified])
@end example
@noindent
ensures any required macros of @code{HANDLE_FOO}
are expanded before the first test.
@end defmac
@defmac AS_MKDIR_P (@var{file-name})
@asindex{MKDIR_P}
Make the directory @var{file-name}, including intervening directories
as necessary. This is equivalent to @samp{mkdir -p -- @var{file-name}},
except that it is portable to older versions of @command{mkdir} that
lack support for the @option{-p} option or for the @option{--}
delimiter (@pxref{mkdir, , Limitations of Usual Tools}). Also,
@code{AS_MKDIR_P}
succeeds if @var{file-name} is a symbolic link to an existing directory,
even though Posix is unclear whether @samp{mkdir -p} should
succeed in that case. If creation of @var{file-name} fails, exit the
script.
Also see the @code{AC_PROG_MKDIR_P} macro (@pxref{Particular Programs}).
@end defmac
@defmac AS_SET_STATUS (@var{status})
@asindex{SET_STATUS}
Emit shell code to set the value of @samp{$?} to @var{status}, as
efficiently as possible. However, this is not guaranteed to abort a
shell running with @code{set -e} (@pxref{set, , Limitations of Shell
Builtins}).
@end defmac
@defmac AS_TR_CPP (@var{expression})
@asindex{TR_CPP}
Transform @var{expression} into a valid right-hand side for a C @code{#define}.
For example:
@example
# This outputs "#define HAVE_CHAR_P 1".
# Notice the m4 quoting around #, to prevent an m4 comment
type="char *"
echo "[#]define AS_TR_CPP([HAVE_$type]) 1"
@end example
@end defmac
@defmac AS_TR_SH (@var{expression})
@asindex{TR_SH}
Transform @var{expression} into a valid shell variable name. For example:
@example
# This outputs "Have it!".
header="sys/some file.h"
AS_TR_SH([HAVE_$header])=yes
if test "x$HAVE_sys_some_file_h" = xyes; then echo "Have it!"; fi
@end example
@end defmac
@defmac AS_SET_CATFILE (@var{var}, @var{dir}, @var{file})
@asindex{SET_CATFILE}
Set the shell variable @var{var} to @var{dir}/@var{file}, but
optimizing the common cases (@var{dir} or @var{file} is @samp{.},
@var{file} is absolute, etc.).
@end defmac
@defmac AS_UNSET (@var{var})
@asindex{UNSET}
Unsets the shell variable @var{var}, working around bugs in older
shells (@pxref{unset, , Limitations of Shell
Builtins}). @var{var} can be a literal or indirect variable name.
@end defmac
@defmac AS_VERSION_COMPARE (@var{version-1}, @var{version-2}, @
@ovar{action-if-less}, @ovar{action-if-equal}, @ovar{action-if-greater})
@asindex{VERSION_COMPARE}
Compare two strings @var{version-1} and @var{version-2}, possibly
containing shell variables, as version strings, and expand
@var{action-if-less}, @var{action-if-equal}, or @var{action-if-greater}
depending upon the result.
The algorithm to compare is similar to the one used by strverscmp in
glibc (@pxref{String/Array Comparison, , String/Array Comparison, libc,
The @acronym{GNU} C Library}).
@end defmac
@node Polymorphic Variables
@section Support for indirect variable names
@cindex variable name indirection
@cindex polymorphic variable name
@cindex indirection, variable name
Often, it is convenient to write a macro that will emit shell code
operating on a shell variable. The simplest case is when the variable
name is known. But a more powerful idiom is writing shell code that can
work through an indirection, where another variable or command
substitution produces the name of the variable to actually manipulate.
M4sh supports the notion of polymorphic shell variables, making it easy
to write a macro that can deal with either literal or indirect variable
names and output shell code appropriate for both use cases. Behavior is
undefined if expansion of an indirect variable does not result in a
literal variable name.
@defmac AS_LITERAL_IF (@var{expression}, @ovar{if-literal}, @ovar{if-not})
@asindex{LITERAL_IF}
If the expansion of @var{expression} is definitely a shell literal,
expand @var{if-literal}. If the expansion of @var{expression} looks
like it might contain shell indirections (such as @code{$var} or
@code{`expr`}), then @var{if-not} is expanded. In order to reduce the
time spent deciding whether an expression is literal, the implementation
is somewhat conservative (for example, @samp{'[$]'} is a single-quoted
shell literal, but causes @var{if-not} to be expanded). While this
macro is often used for recognizing shell variable names, it can also be
used in other contexts.
@example
AC_DEFUN([MY_ACTION],
[AS_LITERAL_IF([$1],
[echo "$1"],
[AS_VAR_COPY([tmp], [$1])
echo "$tmp"])])
@end example
@end defmac
@defmac AS_VAR_APPEND (@var{var}, @var{text})
@asindex{APPEND}
Emit shell code to append the shell expansion of @var{text} to the end
of the current contents of the polymorphic shell variable @var{var},
taking advantage of shells that provide the @samp{+=} extension for more
efficient scaling.
For situations where the final contents of @var{var} are relatively
short (less than 256 bytes), it is more efficient to use the simpler
code sequence of @code{@var{var}=$@{@var{var}@}@var{text}} (or its
polymorphic equivalent of @code{AS_VAR_COPY([tmp], [@var{var}])} and
@code{AS_VAR_SET([@var{var}], ["$tmp"@var{text}])}). But in the case
when the script will be repeatedly appending text into @code{var},
issues of scaling start to become apparent. A naive implementation
requires execution time linear to the length of the current contents of
@var{var} as well as the length of @var{text} for a single append, for
an overall quadratic scaling with multiple appends. This macro takes
advantage of shells which provide the extension
@code{@var{var}+=@var{text}}, which can provide amortized constant time
for a single append, for an overall linear scaling with multiple
appends. Note that unlike @code{AS_VAR_SET}, this macro requires that
@var{text} be quoted properly to avoid field splitting and file name
expansion.
@end defmac
@defmac AS_VAR_ARITH (@var{var}, @var{expression})
@asindex{ARITH}
Emit shell code to compute the arithmetic expansion of @var{expression},
assigning the result as the contents of the polymorphic shell variable
@var{var}. The code takes advantage of shells that provide @samp{$(())}
for fewer forks, but uses @command{expr} as a fallback. Therefore, the
syntax for a valid @var{expression} is rather limited: all operators
must occur as separate shell arguments and with proper quoting, there is
no portable equality operator, all variables containing numeric values
must be expanded prior to the computation, all numeric values must be
provided in decimal without leading zeroes, and the first shell argument
should not be a negative number. In the following example, this snippet
will print @samp{(2+3)*4 == 20}.
@example
bar=3
AS_VAR_ARITH([foo], [\( 2 + $bar \) \* 4])
echo "(2+$bar)*4 == $foo"
@end example
@end defmac
@defmac AS_VAR_COPY (@var{dest}, @var{source})
@asindex{VAR_COPY}
Emit shell code to assign the contents of the polymorphic shell variable
@var{source} to the polymorphic shell variable @var{dest}. For example,
executing this M4sh snippet will output @samp{bar hi}:
@example
foo=bar bar=hi
AS_VAR_COPY([a], [foo])
AS_VAR_COPY([b], [$foo])
echo "$a $b"
@end example
When it is necessary to access the contents of an indirect variable
inside a shell double-quoted context, the recommended idiom is to first
copy the contents into a temporary literal shell variable.
@smallexample
for header in stdint_h inttypes_h ; do
AS_VAR_COPY([var], [ac_cv_header_$header])
echo "$header detected: $var"
done
@end smallexample
@end defmac
@comment AS_VAR_GET is intentionally undocumented; it can't handle
@comment trailing newlines uniformly, and forks too much.
@defmac AS_VAR_IF (@var{var}, @ovar{value}, @ovar{if-equal}, @
@ovar{if-not-equal})
@asindex{VAR_IF}
Output a shell conditional statement. If the contents of the
polymorphic shell variable @var{var} match the string @var{value},
execute @var{if-equal}; otherwise execute @var{if-not-equal}. Avoids
shell bugs if an interrupt signal arrives while a command substitution
in @var{var} is being expanded.
@end defmac
@defmac AS_VAR_PUSHDEF (@var{m4-name}, @var{value})
@defmacx AS_VAR_POPDEF (@var{m4-name})
@asindex{VAR_PUSHDEF}
@asindex{VAR_POPDEF}
@cindex composing variable names
@cindex variable names, composing
A common M4sh idiom involves composing shell variable names from an m4
argument (for example, writing a macro that uses a cache variable).
@var{value} can be an arbitrary string, which will be transliterated
into a valid shell name by @code{AS_TR_SH}. In order to access the
composed variable name based on @var{value}, it is easier to declare a
temporary m4 macro @var{m4-name} with @code{AS_VAR_PUSHDEF}, then use
that macro as the argument to subsequent @code{AS_VAR} macros as a
polymorphic variable name, and finally free the temporary macro with
@code{AS_VAR_POPDEF}. These macros are often followed with @code{dnl},
to avoid excess newlines in the output.
Here is an involved example, that shows the power of writing macros that
can handle composed shell variable names:
@example
m4_define([MY_CHECK_HEADER],
[AS_VAR_PUSHDEF([my_Header], [ac_cv_header_$1])dnl
AS_VAR_IF([my_Header], [yes], [echo "header $1 available"])dnl
AS_VAR_POPDEF([my_Header])dnl
])
MY_CHECK_HEADER([stdint.h])
for header in inttypes.h stdlib.h ; do
MY_CHECK_HEADER([$header])
done
@end example
@noindent
In the above example, @code{MY_CHECK_HEADER} can operate on polymorphic
variable names. In the first invocation, the m4 argument is
@code{stdint.h}, which transliterates into a literal @code{stdint_h}.
As a result, the temporary macro @code{my_Header} expands to the literal
shell name @samp{ac_cv_header_stdint_h}. In the second invocation, the
m4 argument to @code{MY_CHECK_HEADER} is @code{$header}, and the
temporary macro @code{my_Header} expands to the indirect shell name
@samp{$as_my_Header}. During the shell execution of the for loop, when
@samp{$header} contains @samp{inttypes.h}, then @samp{$as_my_Header}
contains @samp{ac_cv_header_inttypes_h}. If this script is then run on a
platform where all three headers have been previously detected, the
output of the script will include:
@smallexample
header stdint.h detected
header inttypes.h detected
header stdlib.h detected
@end smallexample
@end defmac
@defmac AS_VAR_SET (@var{var}, @ovar{value})
@asindex{VAR_SET}
Emit shell code to assign the contents of the polymorphic shell variable
@var{var} to the shell expansion of @var{value}. @var{value} is not
subject to field splitting or file name expansion, so if command
substitution is used, it may be done with @samp{`""`} rather than using
an intermediate variable (@pxref{Shell Substitutions}). However,
@var{value} does undergo rescanning for additional macro names; behavior
is unspecified if late expansion results in any shell meta-characters.
@end defmac
@defmac AS_VAR_SET_IF (@var{var}, @ovar{if-set}, @ovar{if-undef})
@asindex{VAR_SET_IF}
Emit a shell conditional statement, which executes @var{if-set} if the
polymorphic shell variable @code{var} is set to any value, and
@var{if-undef} otherwise.
@end defmac
@defmac AS_VAR_TEST_SET (@var{var})
@asindex{VAR_TEST_SET}
Emit a shell statement that results in a successful exit status only if
the polymorphic shell variable @code{var} is set.
@end defmac
@node Initialization Macros
@section Initialization Macros
@defmac AS_BOURNE_COMPATIBLE
@asindex{BOURNE_COMPATIBLE}
Set up the shell to be more compatible with the Bourne shell as
standardized by Posix, if possible. This may involve setting
environment variables, or setting options, or similar
implementation-specific actions. This macro is deprecated, since
@code{AS_INIT} already invokes it.
@end defmac
@defmac AS_INIT
@asindex{INIT}
@evindex LC_ALL
@evindex SHELL
Initialize the M4sh environment. This macro calls @code{m4_init}, then
outputs the @code{#! /bin/sh} line, a notice about where the output was
generated from, and code to sanitize the environment for the rest of the
script. Among other initializations, this sets @env{SHELL} to the shell
chosen to run the script (@pxref{CONFIG_SHELL}), and @env{LC_ALL} to
ensure the C locale. Finally, it changes the current diversion to
@code{BODY}.
@end defmac
@defmac AS_INIT_GENERATED (@var{file}, @ovar{comment})
@asindex{INIT_GENERATED}
Emit shell code to start the creation of a subsidiary shell script in
@var{file}, including changing @var{file} to be executable. This macro
populates the child script with information learned from the parent
(thus, the emitted code is equivalent in effect, but more efficient,
than the code output by @code{AS_INIT}, @code{AS_BOURNE_COMPATIBLE}, and
@code{AS_SHELL_SANITIZE}). If present, @var{comment} is output near the
beginning of the child, prior to the shell initialization code, and is
subject to parameter expansion, command substitution, and backslash
quote removal. The
parent script should check the exit status after this macro, in case
@var{file} could not be properly created (for example, if the disk was
full). If successfully created, the parent script can then proceed to
append additional M4sh constructs into the child script.
Note that the child script starts life without a log file open, so if
the parent script uses logging (@pxref{AS_MESSAGE_LOG_FD}), you
must temporarily disable any attempts to use the log file until after
emitting code to open a log within the child. On the other hand, if the
parent script has @code{AS_MESSAGE_FD} redirected somewhere besides
@samp{1}, then the child script already has code that copies stdout to
that descriptor. Currently, the suggested
idiom for writing a M4sh shell script from within another script is:
@example
AS_INIT_GENERATED([@var{file}], [[# My child script.
]]) || @{ AS_ECHO(["Failed to create child script"]); AS_EXIT; @}
m4_pushdef([AS_MESSAGE_LOG_FD])dnl
cat >> "@var{file}" <<\__EOF__
# Code to initialize AS_MESSAGE_LOG_FD
m4_popdef([AS_MESSAGE_LOG_FD])dnl
# Additional code
__EOF__
@end example
This, however, may change in the future as the M4sh interface is
stabilized further.
Also, be aware that use of @env{LINENO} within the child script may
report line numbers relative to their location in the parent script,
even when using @code{AS_LINENO_PREPARE}, if the parent script was
unable to locate a shell with working @env{LINENO} support.
@end defmac
@defmac AS_LINENO_PREPARE
@asindex{LINENO_PREPARE}
@evindex LINENO
Find a shell that supports the special variable @env{LINENO}, which
contains the number of the currently executing line. This macro is
automatically invoked by @code{AC_INIT} in configure scripts.
@end defmac
@defmac AS_ME_PREPARE
@asindex{ME_PREPARE}
Set up variable @env{as_me} to be the basename of the currently executing
script. This macro is automatically invoked by @code{AC_INIT} in
configure scripts.
@end defmac
@defmac AS_SHELL_SANITIZE
@asindex{SHELL_SANITIZE}
Initialize the shell suitably for @command{configure} scripts. This has
the effect of @code{AS_BOURNE_COMPATIBLE}, and sets some other
environment variables for predictable results from configuration tests.
For example, it sets @env{LC_ALL} to change to the default C locale.
@xref{Special Shell Variables}. This macro is deprecated, since
@code{AS_INIT} already invokes it.
@end defmac
@node File Descriptor Macros
@section File Descriptor Macros
@cindex input
@cindex standard input
@cindex file descriptors
@cindex descriptors
@cindex low-level output
@cindex output, low-level
The following macros define file descriptors used to output messages
(or input values) from @file{configure} scripts.
For example:
@example
echo "$wombats found" >&AS_MESSAGE_LOG_FD
echo 'Enter desired kangaroo count:' >&AS_MESSAGE_FD
read kangaroos <&AS_ORIGINAL_STDIN_FD`
@end example
@noindent
However doing so is seldom needed, because Autoconf provides higher
level macros as described below.
@defmac AS_MESSAGE_FD
@asindex{MESSAGE_FD}
The file descriptor for @samp{checking for...} messages and results.
By default, @code{AS_INIT} sets this to @samp{1} for standalone M4sh
clients. However, @code{AC_INIT} shuffles things around to another file
descriptor, in order to allow the @option{-q} option of
@command{configure} to choose whether messages should go to the script's
standard output or be discarded.
If you want to display some messages, consider using one of the printing
macros (@pxref{Printing Messages}) instead. Copies of messages output
via these macros are also recorded in @file{config.log}.
@end defmac
@anchor{AS_MESSAGE_LOG_FD}
@defmac AS_MESSAGE_LOG_FD
@asindex{MESSAGE_LOG_FD}
This must either be empty, or expand to a file descriptor for log
messages. By default, @code{AS_INIT} sets this macro to the empty
string for standalone M4sh clients, thus disabling logging. However,
@code{AC_INIT} shuffles things around so that both @command{configure}
and @command{config.status} use @file{config.log} for log messages.
Macros that run tools, like @code{AC_COMPILE_IFELSE} (@pxref{Running the
Compiler}), redirect all output to this descriptor. You may want to do
so if you develop such a low-level macro.
@end defmac
@defmac AS_ORIGINAL_STDIN_FD
@asindex{ORIGINAL_STDIN_FD}
This must expand to a file descriptor for the original standard input.
By default, @code{AS_INIT} sets this macro to @samp{0} for standalone
M4sh clients. However, @code{AC_INIT} shuffles things around for
safety.
When @command{configure} runs, it may accidentally execute an
interactive command that has the same name as the non-interactive meant
to be used or checked. If the standard input was the terminal, such
interactive programs would cause @command{configure} to stop, pending
some user input. Therefore @command{configure} redirects its standard
input from @file{/dev/null} during its initialization. This is not
normally a problem, since @command{configure} normally does not need
user input.
In the extreme case where your @file{configure} script really needs to
obtain some values from the original standard input, you can read them
explicitly from @code{AS_ORIGINAL_STDIN_FD}.
@end defmac
@c =================================================== Writing Autoconf Macros.
@node Writing Autoconf Macros
@chapter Writing Autoconf Macros
When you write a feature test that could be applicable to more than one
software package, the best thing to do is encapsulate it in a new macro.
Here are some instructions and guidelines for writing Autoconf macros.
@menu
* Macro Definitions:: Basic format of an Autoconf macro
* Macro Names:: What to call your new macros
* Reporting Messages:: Notifying @command{autoconf} users
* Dependencies Between Macros:: What to do when macros depend on other macros
* Obsoleting Macros:: Warning about old ways of doing things
* Coding Style:: Writing Autoconf macros @`a la Autoconf
@end menu
@node Macro Definitions
@section Macro Definitions
@defmac AC_DEFUN (@var{name}, @ovar{body})
@acindex{DEFUN}
Autoconf macros are defined using the @code{AC_DEFUN} macro, which is
similar to the M4 builtin @code{m4_define} macro; this creates a macro
named @var{name} and with @var{body} as its expansion. In addition to
defining a macro, @code{AC_DEFUN} adds to it some code that is used to
constrain the order in which macros are called, while avoiding redundant
output (@pxref{Prerequisite Macros}).
@end defmac
An Autoconf macro definition looks like this:
@example
AC_DEFUN(@var{macro-name}, @var{macro-body})
@end example
You can refer to any arguments passed to the macro as @samp{$1},
@samp{$2}, etc. @xref{Definitions, , How to define new macros, m4.info,
@acronym{GNU} M4}, for more complete information on writing M4 macros.
Most macros fall in one of two general categories. The first category
includes macros which take arguments, in order to generate output
parameterized by those arguments. Macros in this category are designed
to be directly expanded, often multiple times, and should not be used as
the argument to @code{AC_REQUIRE}. The other category includes macros
which are shorthand for a fixed block of text, and therefore do not take
arguments. For this category of macros, directly expanding the macro
multiple times results in redundant output, so it is more common to use
the macro as the argument to @code{AC_REQUIRE}, or to declare the macro
with @code{AC_DEFUN_ONCE} (@pxref{One-Shot Macros}).
Be sure to properly quote both the @var{macro-body} @emph{and} the
@var{macro-name} to avoid any problems if the macro happens to have
been previously defined.
Each macro should have a header comment that gives its prototype, and a
brief description. When arguments have default values, display them in
the prototype. For example:
@example
# AC_MSG_ERROR(ERROR, [EXIT-STATUS = 1])
# --------------------------------------
m4_define([AC_MSG_ERROR],
[@{ AS_MESSAGE([error: $1], [2])
exit m4_default([$2], [1]); @}])
@end example
Comments about the macro should be left in the header comment. Most
other comments make their way into @file{configure}, so just keep
using @samp{#} to introduce comments.
@cindex @code{dnl}
If you have some special comments about pure M4 code, comments
that make no sense in @file{configure} and in the header comment, then
use the builtin @code{dnl}: it causes M4 to discard the text
through the next newline.
Keep in mind that @code{dnl} is rarely needed to introduce comments;
@code{dnl} is more useful to get rid of the newlines following macros
that produce no output, such as @code{AC_REQUIRE}.
Public third-party macros need to use @code{AC_DEFUN}, and not
@code{m4_define}, in order to be found by @command{aclocal}
(@pxref{Extending aclocal,,, automake, @acronym{GNU} Automake}).
Additionally, if it is ever determined that a macro should be made
obsolete, it is easy to convert from @code{AC_DEFUN} to @code{AU_DEFUN}
in order to have @command{autoupdate} assist the user in choosing a
better alternative, but there is no corresponding way to make
@code{m4_define} issue an upgrade notice (@pxref{AU_DEFUN}).
There is another subtle, but important, difference between using
@code{m4_define} and @code{AC_DEFUN}: only the former is unaffected by
@code{AC_REQUIRE}. When writing a file, it is always safe to replace a
block of text with a @code{m4_define} macro that will expand to the same
text. But replacing a block of text with an @code{AC_DEFUN} macro with
the same content does not necessarily give the same results, because it
changes the location where any embedded but unsatisfied
@code{AC_REQUIRE} invocations within the block will be expanded. For an
example of this, see @ref{Expanded Before Required}.
@node Macro Names
@section Macro Names
All of the public Autoconf macros have all-uppercase names in the
namespace @samp{^AC_} to prevent them from accidentally conflicting with
other text; Autoconf also reserves the namespace @samp{^_AC_} for
internal macros. All shell variables that they use for internal
purposes have mostly-lowercase names starting with @samp{ac_}. Autoconf
also uses here-document delimiters in the namespace @samp{^_AC[A-Z]}. During
@command{configure}, files produced by Autoconf make heavy use of the
file system namespace @samp{^conf}.
Since Autoconf is built on top of M4sugar (@pxref{Programming in
M4sugar}) and M4sh (@pxref{Programming in M4sh}), you must also be aware
of those namespaces (@samp{^_?\(m4\|AS\)_}). And since
@file{configure.ac} is also designed to be scanned by Autoheader,
Autoscan, Autoupdate, and Automake, you should be aware of the
@samp{^_?A[HNUM]_} namespaces. In general, you @emph{should not use}
the namespace of a package that does not own the macro or shell code you
are writing.
To ensure that your macros don't conflict with present or future
Autoconf macros, you should prefix your own macro names and any shell
variables they use with some other sequence. Possibilities include your
initials, or an abbreviation for the name of your organization or
software package. Historically, people have not always followed the
rule of using a namespace appropriate for their package, and this has
made it difficult for determining the origin of a macro (and where to
report bugs about that macro), as well as difficult for the true
namespace owner to add new macros without interference from pre-existing
uses of third-party macros. Perhaps the best example of this confusion
is the @code{AM_GNU_GETTEXT} macro, which belongs, not to Automake, but
to Gettext.
Most of the Autoconf macros' names follow a structured naming convention
that indicates the kind of feature check by the name. The macro names
consist of several words, separated by underscores, going from most
general to most specific. The names of their cache variables use the
same convention (@pxref{Cache Variable Names}, for more information on
them).
The first word of the name after the namespace initials (such as
@samp{AC_}) usually tells the category
of the feature being tested. Here are the categories used in Autoconf for
specific test macros, the kind of macro that you are more likely to
write. They are also used for cache variables, in all-lowercase. Use
them where applicable; where they're not, invent your own categories.
@table @code
@item C
C language builtin features.
@item DECL
Declarations of C variables in header files.
@item FUNC
Functions in libraries.
@item GROUP
Posix group owners of files.
@item HEADER
Header files.
@item LIB
C libraries.
@item PROG
The base names of programs.
@item MEMBER
Members of aggregates.
@item SYS
Operating system features.
@item TYPE
C builtin or declared types.
@item VAR
C variables in libraries.
@end table
After the category comes the name of the particular feature being
tested. Any further words in the macro name indicate particular aspects
of the feature. For example, @code{AC_PROG_CC_STDC} checks whether the
C compiler supports @acronym{ISO} Standard C.
An internal macro should have a name that starts with an underscore;
Autoconf internals should therefore start with @samp{_AC_}.
Additionally, a macro that is an internal subroutine of another macro
should have a name that starts with an underscore and the name of that
other macro, followed by one or more words saying what the internal
macro does. For example, @code{AC_PATH_X} has internal macros
@code{_AC_PATH_X_XMKMF} and @code{_AC_PATH_X_DIRECT}.
@node Reporting Messages
@section Reporting Messages
@cindex Messages, from @command{autoconf}
When macros statically diagnose abnormal situations, benign or fatal, it
is possible to make @command{autoconf} detect the problem, and refuse to
create @file{configure} in the case of an error. The macros in this
section are considered obsolescent, and new code should use M4sugar
macros for this purpose, see @ref{Diagnostic Macros}.
On the other hand, it is possible to want to detect errors when
@command{configure} is run, which are dependent on the environment of
the user rather than the maintainer. For dynamic diagnostics, see
@ref{Printing Messages}.
@defmac AC_DIAGNOSE (@var{category}, @var{message})
@acindex{DIAGNOSE}
Report @var{message} as a warning (or as an error if requested by the
user) if warnings of the @var{category} are turned on. This macro is
obsolescent; you are encouraged to use:
@example
m4_warn([@var{category}], [@var{message}])
@end example
@noindent
instead. @xref{m4_warn}, for more details, including valid
@var{category} names.
@end defmac
@defmac AC_WARNING (@var{message})
@acindex{WARNING}
Report @var{message} as a syntax warning. This macro is obsolescent;
you are encouraged to use:
@example
m4_warn([syntax], [@var{message}])
@end example
@noindent
instead. @xref{m4_warn}, for more details, as well as better
finer-grained categories of warnings (not all problems have to do with
syntax).
@end defmac
@defmac AC_FATAL (@var{message})
@acindex{FATAL}
Report a severe error @var{message}, and have @command{autoconf} die.
This macro is obsolescent; you are encouraged to use:
@example
m4_fatal([@var{message}])
@end example
@noindent
instead. @xref{m4_fatal}, for more details.
@end defmac
When the user runs @samp{autoconf -W error}, warnings from
@code{m4_warn} (including those issued through @code{AC_DIAGNOSE} and
@code{AC_WARNING}) are reported as errors, see @ref{autoconf Invocation}.
@node Dependencies Between Macros
@section Dependencies Between Macros
@cindex Dependencies between macros
Some Autoconf macros depend on other macros having been called first in
order to work correctly. Autoconf provides a way to ensure that certain
macros are called if needed and a way to warn the user if macros are
called in an order that might cause incorrect operation.
@menu
* Prerequisite Macros:: Ensuring required information
* Suggested Ordering:: Warning about possible ordering problems
* One-Shot Macros:: Ensuring a macro is called only once
@end menu
@node Prerequisite Macros
@subsection Prerequisite Macros
@cindex Prerequisite macros
@cindex Macros, prerequisites
A macro that you write might need to use values that have previously
been computed by other macros. For example, @code{AC_DECL_YYTEXT}
examines the output of @code{flex} or @code{lex}, so it depends on
@code{AC_PROG_LEX} having been called first to set the shell variable
@code{LEX}.
Rather than forcing the user of the macros to keep track of the
dependencies between them, you can use the @code{AC_REQUIRE} macro to do
it automatically. @code{AC_REQUIRE} can ensure that a macro is only
called if it is needed, and only called once.
@defmac AC_REQUIRE (@var{macro-name})
@acindex{REQUIRE}
If the M4 macro @var{macro-name} has not already been called, call it
(without any arguments). Make sure to quote @var{macro-name} with
square brackets. @var{macro-name} must have been defined using
@code{AC_DEFUN} or else contain a call to @code{AC_PROVIDE} to indicate
that it has been called.
@code{AC_REQUIRE} must be used inside a macro defined by @code{AC_DEFUN}; it
must not be called from the top level. Also, it does not make sense to
require a macro that takes parameters.
@end defmac
@code{AC_REQUIRE} is often misunderstood. It really implements
dependencies between macros in the sense that if one macro depends upon
another, the latter is expanded @emph{before} the body of the
former. To be more precise, the required macro is expanded before
the outermost defined macro in the current expansion stack.
In particular, @samp{AC_REQUIRE([FOO])} is not replaced with the body of
@code{FOO}. For instance, this definition of macros:
@example
@group
AC_DEFUN([TRAVOLTA],
[test "$body_temperature_in_celsius" -gt "38" &&
dance_floor=occupied])
AC_DEFUN([NEWTON_JOHN],
[test "x$hair_style" = xcurly &&
dance_floor=occupied])
@end group
@group
AC_DEFUN([RESERVE_DANCE_FLOOR],
[if date | grep '^Sat.*pm' >/dev/null 2>&1; then
AC_REQUIRE([TRAVOLTA])
AC_REQUIRE([NEWTON_JOHN])
fi])
@end group
@end example
@noindent
with this @file{configure.ac}
@example
AC_INIT([Dance Manager], [1.0], [bug-dance@@example.org])
RESERVE_DANCE_FLOOR
if test "x$dance_floor" = xoccupied; then
AC_MSG_ERROR([cannot pick up here, let's move])
fi
@end example
@noindent
does not leave you with a better chance to meet a kindred soul at
other times than Saturday night since it expands into:
@example
@group
test "$body_temperature_in_Celsius" -gt "38" &&
dance_floor=occupied
test "x$hair_style" = xcurly &&
dance_floor=occupied
fi
if date | grep '^Sat.*pm' >/dev/null 2>&1; then
fi
@end group
@end example
This behavior was chosen on purpose: (i) it prevents messages in
required macros from interrupting the messages in the requiring macros;
(ii) it avoids bad surprises when shell conditionals are used, as in:
@example
@group
if @dots{}; then
AC_REQUIRE([SOME_CHECK])
fi
@dots{}
SOME_CHECK
@end group
@end example
However, this implementation can lead to another class of problems.
Consider the case where an outer macro first expands, then indirectly
requires, an inner macro:
@example
AC_DEFUN([TESTA], [[echo in A
if test -n "$SEEN_A" ; then echo duplicate ; fi
SEEN_A=:]])
AC_DEFUN([TESTB], [AC_REQUIRE([TESTA])[echo in B
if test -z "$SEEN_A" ; then echo bug ; fi]])
AC_DEFUN([TESTC], [AC_REQUIRE([TESTB])[echo in C]])
AC_DEFUN([OUTER], [[echo in OUTER]
A
C])
OUTER
@end example
@noindent
Prior to Autoconf 2.64, the implementation of @code{AC_REQUIRE}
recognized that @code{TESTB} needed to be hoisted prior to the expansion
of @code{OUTER}, but because @code{TESTA} had already been directly
expanded, it failed to hoist @code{TESTA}. Therefore, the expansion of
@code{TESTB} occurs prior to its prerequisites, leading to the following
output:
@example
in B
bug
in OUTER
in A
in C
@end example
@noindent
Newer Autoconf is smart enough to recognize this situation, and hoists
@code{TESTA} even though it has already been expanded, but issues a
syntax warning in the process. This is because the hoisted expansion of
@code{TESTA} defeats the purpose of using @code{AC_REQUIRE} to avoid
redundant code, and causes its own set of problems if the hoisted macro
is not idempotent:
@example
in A
in B
in OUTER
in A
duplicate
in C
@end example
The bug is not in Autoconf, but in the macro definitions. If you ever
pass a particular macro name to @code{AC_REQUIRE}, then you are implying
that the macro only needs to be expanded once. But to enforce this,
either the macro must be declared with @code{AC_DEFUN_ONCE} (although
this only helps in Autoconf 2.64 or newer), or all
uses of that macro should be through @code{AC_REQUIRE}; directly
expanding the macro defeats the point of using @code{AC_REQUIRE} to
eliminate redundant expansion. In the example, this rule of thumb was
violated because @code{TESTB} requires @code{TESTA} while @code{OUTER}
directly expands it. One way of fixing the bug is to factor
@code{TESTA} into two macros, the portion designed for direct and
repeated use (here, named @code{TESTA}), and the portion designed for
one-shot output and used only inside @code{AC_REQUIRE} (here, named
@code{TESTA_PREREQ}). Then, by fixing all clients to use the correct
calling convention according to their needs:
@example
AC_DEFUN([TESTA], [AC_REQUIRE([TESTA_PREREQ])[echo in A]])
AC_DEFUN([TESTA_PREREQ], [[echo in A_PREREQ
if test -n "$SEEN_A" ; then echo duplicate ; fi
SEEN_A=:]])
AC_DEFUN([TESTB], [AC_REQUIRE([TESTA_PREREQ])[echo in B
if test -z "$SEEN_A" ; then echo bug ; fi]])
AC_DEFUN([TESTC], [AC_REQUIRE([TESTB])[echo in C]])
AC_DEFUN([OUTER], [[echo in OUTER]
TESTA
TESTC])
OUTER
@end example
@noindent
the resulting output will then obey all dependency rules and avoid any
syntax warnings, whether the script is built with old or new Autoconf
versions:
@example
in A_PREREQ
in B
in OUTER
in A
in C
@end example
The helper macros @code{AS_IF} and @code{AS_CASE} may be used to
enforce expansion of required macros outside of shell conditional
constructs. You are furthermore encouraged, although not required, to
put all @code{AC_REQUIRE} calls
at the beginning of a macro. You can use @code{dnl} to avoid the empty
lines they leave.
@node Suggested Ordering
@subsection Suggested Ordering
@cindex Macros, ordering
@cindex Ordering macros
Some macros should be run before another macro if both are called, but
neither @emph{requires} that the other be called. For example, a macro
that changes the behavior of the C compiler should be called before any
macros that run the C compiler. Many of these dependencies are noted in
the documentation.
Autoconf provides the @code{AC_BEFORE} macro to warn users when macros
with this kind of dependency appear out of order in a
@file{configure.ac} file. The warning occurs when creating
@command{configure} from @file{configure.ac}, not when running
@command{configure}.
For example, @code{AC_PROG_CPP} checks whether the C compiler
can run the C preprocessor when given the @option{-E} option. It should
therefore be called after any macros that change which C compiler is
being used, such as @code{AC_PROG_CC}. So @code{AC_PROG_CC} contains:
@example
AC_BEFORE([$0], [AC_PROG_CPP])dnl
@end example
@noindent
This warns the user if a call to @code{AC_PROG_CPP} has already occurred
when @code{AC_PROG_CC} is called.
@defmac AC_BEFORE (@var{this-macro-name}, @var{called-macro-name})
@acindex{BEFORE}
Make M4 print a warning message to the standard error output if
@var{called-macro-name} has already been called. @var{this-macro-name}
should be the name of the macro that is calling @code{AC_BEFORE}. The
macro @var{called-macro-name} must have been defined using
@code{AC_DEFUN} or else contain a call to @code{AC_PROVIDE} to indicate
that it has been called.
@end defmac
@node One-Shot Macros
@subsection One-Shot Macros
@cindex One-shot macros
@cindex Macros, called once
Some macros should be called only once, either because calling them
multiple time is unsafe, or because it is bad style. For instance
Autoconf ensures that @code{AC_CANONICAL_BUILD} and cousins
(@pxref{Canonicalizing}) are evaluated only once, because it makes no
sense to run these expensive checks more than once. Such one-shot
macros can be defined using @code{AC_DEFUN_ONCE}.
@defmac AC_DEFUN_ONCE (@var{macro-name}, @var{macro-body})
@acindex{DEFUN_ONCE}
Declare macro @var{macro-name} like @code{AC_DEFUN} would (@pxref{Macro
Definitions}), but add additional logic that guarantees that only the
first use of the macro (whether by direct expansion or
@code{AC_REQUIRE}) causes an expansion of @var{macro-body}; the
expansion will occur before the start of any enclosing macro defined by
@code{AC_DEFUN}. Subsequent expansions are silently ignored.
Generally, it does not make sense for @var{macro-body} to use parameters
such as @code{$1}.
@end defmac
Prior to Autoconf 2.64, a macro defined by @code{AC_DEFUN_ONCE} would
emit a warning if it was directly expanded a second time, so for
portability, it is better to use @code{AC_REQUIRE} than direct
invocation of @var{macro-name} inside a macro defined by @code{AC_DEFUN}
(@pxref{Prerequisite Macros}).
@node Obsoleting Macros
@section Obsoleting Macros
@cindex Obsoleting macros
@cindex Macros, obsoleting
Configuration and portability technology has evolved over the years.
Often better ways of solving a particular problem are developed, or
ad-hoc approaches are systematized. This process has occurred in many
parts of Autoconf. One result is that some of the macros are now
considered @dfn{obsolete}; they still work, but are no longer considered
the best thing to do, hence they should be replaced with more modern
macros. Ideally, @command{autoupdate} should replace the old macro calls
with their modern implementation.
Autoconf provides a simple means to obsolete a macro.
@anchor{AU_DEFUN}
@defmac AU_DEFUN (@var{old-macro}, @var{implementation}, @ovar{message})
@auindex{DEFUN}
Define @var{old-macro} as @var{implementation}. The only difference
with @code{AC_DEFUN} is that the user is warned that
@var{old-macro} is now obsolete.
If she then uses @command{autoupdate}, the call to @var{old-macro} is
replaced by the modern @var{implementation}. @var{message} should
include information on what to do after running @command{autoupdate};
@command{autoupdate} prints it as a warning, and includes it
in the updated @file{configure.ac} file.
The details of this macro are hairy: if @command{autoconf} encounters an
@code{AU_DEFUN}ed macro, all macros inside its second argument are expanded
as usual. However, when @command{autoupdate} is run, only M4 and M4sugar
macros are expanded here, while all other macros are disabled and
appear literally in the updated @file{configure.ac}.
@end defmac
@defmac AU_ALIAS (@var{old-name}, @var{new-name})
@auindex{ALIAS}
Used if the @var{old-name} is to be replaced by a call to @var{new-macro}
with the same parameters. This happens for example if the macro was renamed.
@end defmac
@node Coding Style
@section Coding Style
@cindex Coding style
The Autoconf macros follow a strict coding style. You are encouraged to
follow this style, especially if you intend to distribute your macro,
either by contributing it to Autoconf itself, or via other means.
The first requirement is to pay great attention to the quotation. For
more details, see @ref{Autoconf Language}, and @ref{M4 Quotation}.
Do not try to invent new interfaces. It is likely that there is a macro
in Autoconf that resembles the macro you are defining: try to stick to
this existing interface (order of arguments, default values, etc.). We
@emph{are} conscious that some of these interfaces are not perfect;
nevertheless, when harmless, homogeneity should be preferred over
creativity.
Be careful about clashes both between M4 symbols and between shell
variables.
If you stick to the suggested M4 naming scheme (@pxref{Macro Names}),
you are unlikely to generate conflicts. Nevertheless, when you need to
set a special value, @emph{avoid using a regular macro name}; rather,
use an ``impossible'' name. For instance, up to version 2.13, the macro
@code{AC_SUBST} used to remember what @var{symbol} macros were already defined
by setting @code{AC_SUBST_@var{symbol}}, which is a regular macro name.
But since there is a macro named @code{AC_SUBST_FILE}, it was just
impossible to @samp{AC_SUBST(FILE)}! In this case,
@code{AC_SUBST(@var{symbol})} or @code{_AC_SUBST(@var{symbol})} should
have been used (yes, with the parentheses).
@c or better yet, high-level macros such as @code{m4_expand_once}
No Autoconf macro should ever enter the user-variable name space; i.e.,
except for the variables that are the actual result of running the
macro, all shell variables should start with @code{ac_}. In
addition, small macros or any macro that is likely to be embedded in
other macros should be careful not to use obvious names.
@cindex @code{dnl}
Do not use @code{dnl} to introduce comments: most of the comments you
are likely to write are either header comments which are not output
anyway, or comments that should make their way into @file{configure}.
There are exceptional cases where you do want to comment special M4
constructs, in which case @code{dnl} is right, but keep in mind that it
is unlikely.
M4 ignores the leading blanks and newlines before each argument.
Use this feature to
indent in such a way that arguments are (more or less) aligned with the
opening parenthesis of the macro being called. For instance, instead of
@example
AC_CACHE_CHECK(for EMX OS/2 environment,
ac_cv_emxos2,
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM(, [return __EMX__;])],
[ac_cv_emxos2=yes], [ac_cv_emxos2=no])])
@end example
@noindent
write
@example
AC_CACHE_CHECK([for EMX OS/2 environment], [ac_cv_emxos2],
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [return __EMX__;])],
[ac_cv_emxos2=yes],
[ac_cv_emxos2=no])])
@end example
@noindent
or even
@example
AC_CACHE_CHECK([for EMX OS/2 environment],
[ac_cv_emxos2],
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],
[return __EMX__;])],
[ac_cv_emxos2=yes],
[ac_cv_emxos2=no])])
@end example
When using @code{AC_RUN_IFELSE} or any macro that cannot work when
cross-compiling, provide a pessimistic value (typically @samp{no}).
Feel free to use various tricks to prevent auxiliary tools, such as
syntax-highlighting editors, from behaving improperly. For instance,
instead of:
@example
m4_bpatsubst([$1], [$"])
@end example
@noindent
use
@example
m4_bpatsubst([$1], [$""])
@end example
@noindent
so that Emacsen do not open an endless ``string'' at the first quote.
For the same reasons, avoid:
@example
test $[#] != 0
@end example
@noindent
and use:
@example
test $[@@%:@@] != 0
@end example
@noindent
Otherwise, the closing bracket would be hidden inside a @samp{#}-comment,
breaking the bracket-matching highlighting from Emacsen. Note the
preferred style to escape from M4: @samp{$[1]}, @samp{$[@@]}, etc. Do
not escape when it is unnecessary. Common examples of useless quotation
are @samp{[$]$1} (write @samp{$$1}), @samp{[$]var} (use @samp{$var}),
etc. If you add portability issues to the picture, you'll prefer
@samp{$@{1+"$[@@]"@}} to @samp{"[$]@@"}, and you'll prefer do something
better than hacking Autoconf @code{:-)}.
When using @command{sed}, don't use @option{-e} except for indenting
purposes. With the @code{s} and @code{y} commands, the preferred
separator is @samp{/} unless @samp{/} itself might appear in the pattern
or replacement, in which case you should use @samp{|}, or optionally
@samp{,} if you know the pattern and replacement cannot contain a file
name. If none of these characters will do, choose a printable character
that cannot appear in the pattern or replacement. Characters from the
set @samp{"#$&'()*;<=>?`|~} are good choices if the pattern or
replacement might contain a file name, since they have special meaning
to the shell and are less likely to occur in file names.
@xref{Macro Definitions}, for details on how to define a macro. If a
macro doesn't use @code{AC_REQUIRE}, is expected to never be the object
of an @code{AC_REQUIRE} directive, and macros required by other macros
inside arguments do not need to be expanded before this macro, then
use @code{m4_define}. In case of doubt, use @code{AC_DEFUN}.
Also take into account that public third-party macros need to use
@code{AC_DEFUN} in order to be found by @command{aclocal}
(@pxref{Extending aclocal,,, automake, @acronym{GNU} Automake}).
All the @code{AC_REQUIRE} statements should be at the beginning of the
macro, and each statement should be followed by @code{dnl}.
You should not rely on the number of arguments: instead of checking
whether an argument is missing, test that it is not empty. It provides
both a simpler and a more predictable interface to the user, and saves
room for further arguments.
Unless the macro is short, try to leave the closing @samp{])} at the
beginning of a line, followed by a comment that repeats the name of the
macro being defined. This introduces an additional newline in
@command{configure}; normally, that is not a problem, but if you want to
remove it you can use @samp{[]dnl} on the last line. You can similarly
use @samp{[]dnl} after a macro call to remove its newline. @samp{[]dnl}
is recommended instead of @samp{dnl} to ensure that M4 does not
interpret the @samp{dnl} as being attached to the preceding text or
macro output. For example, instead of:
@example
AC_DEFUN([AC_PATH_X],
[AC_MSG_CHECKING([for X])
AC_REQUIRE_CPP()
@r{# @dots{}omitted@dots{}}
AC_MSG_RESULT([libraries $x_libraries, headers $x_includes])
fi])
@end example
@noindent
you would write:
@example
AC_DEFUN([AC_PATH_X],
[AC_REQUIRE_CPP()[]dnl
AC_MSG_CHECKING([for X])
@r{# @dots{}omitted@dots{}}
AC_MSG_RESULT([libraries $x_libraries, headers $x_includes])
fi[]dnl
])# AC_PATH_X
@end example
If the macro is long, try to split it into logical chunks. Typically,
macros that check for a bug in a function and prepare its
@code{AC_LIBOBJ} replacement should have an auxiliary macro to perform
this setup. Do not hesitate to introduce auxiliary macros to factor
your code.
In order to highlight the recommended coding style, here is a macro
written the old way:
@example
dnl Check for EMX on OS/2.
dnl _AC_EMXOS2
AC_DEFUN(_AC_EMXOS2,
[AC_CACHE_CHECK(for EMX OS/2 environment, ac_cv_emxos2,
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM(, return __EMX__;)],
ac_cv_emxos2=yes, ac_cv_emxos2=no)])
test "x$ac_cv_emxos2" = xyes && EMXOS2=yes])
@end example
@noindent
and the new way:
@example
# _AC_EMXOS2
# ----------
# Check for EMX on OS/2.
m4_define([_AC_EMXOS2],
[AC_CACHE_CHECK([for EMX OS/2 environment], [ac_cv_emxos2],
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [return __EMX__;])],
[ac_cv_emxos2=yes],
[ac_cv_emxos2=no])])
test "x$ac_cv_emxos2" = xyes && EMXOS2=yes[]dnl
])# _AC_EMXOS2
@end example
@c ============================================= Portable Shell Programming
@node Portable Shell
@chapter Portable Shell Programming
@cindex Portable shell programming
When writing your own checks, there are some shell-script programming
techniques you should avoid in order to make your code portable. The
Bourne shell and upward-compatible shells like the Korn shell and Bash
have evolved over the years, and many features added to the original
System7 shell are now supported on all interesting porting targets.
However, the following discussion between Russ Allbery and Robert Lipe
is worth reading:
@noindent
Russ Allbery:
@quotation
The @acronym{GNU} assumption that @command{/bin/sh} is the one and only shell
leads to a permanent deadlock. Vendors don't want to break users'
existing shell scripts, and there are some corner cases in the Bourne
shell that are not completely compatible with a Posix shell. Thus,
vendors who have taken this route will @emph{never} (OK@dots{}``never say
never'') replace the Bourne shell (as @command{/bin/sh}) with a
Posix shell.
@end quotation
@noindent
Robert Lipe:
@quotation
This is exactly the problem. While most (at least most System V's) do
have a Bourne shell that accepts shell functions most vendor
@command{/bin/sh} programs are not the Posix shell.
So while most modern systems do have a shell @emph{somewhere} that meets the
Posix standard, the challenge is to find it.
@end quotation
For this reason, part of the job of M4sh (@pxref{Programming in M4sh})
is to find such a shell. But to prevent trouble, if you're not using
M4sh you should not take advantage of features that were added after Unix
version 7, circa 1977 (@pxref{Systemology}); you should not use aliases,
negated character classes, or even @command{unset}. @code{#} comments,
while not in Unix version 7, were retrofitted in the original Bourne
shell and can be assumed to be part of the least common denominator.
On the other hand, if you're using M4sh you can assume that the shell
has the features that were added in SVR2 (circa 1984), including shell
functions,
@command{return}, @command{unset}, and I/O redirection for builtins. For
more information, refer to @uref{http://@/www.in-ulm.de/@/~mascheck/@/bourne/}.
However, some pitfalls have to be avoided for portable use of these
constructs; these will be documented in the rest of this chapter.
See in particular @ref{Shell Functions} and @ref{Limitations of
Builtins, , Limitations of Shell Builtins}.
Some ancient systems have quite
small limits on the length of the @samp{#!} line; for instance, 32
bytes (not including the newline) on SunOS 4.
However, these ancient systems are no longer of practical concern.
The set of external programs you should run in a @command{configure} script
is fairly small. @xref{Utilities in Makefiles, , Utilities in
Makefiles, standards, @acronym{GNU} Coding Standards}, for the list. This
restriction allows users to start out with a fairly small set of
programs and build the rest, avoiding too many interdependencies between
packages.
Some of these external utilities have a portable subset of features; see
@ref{Limitations of Usual Tools}.
There are other sources of documentation about shells. The
specification for the Posix
@uref{http://@/www.opengroup.org/@/susv3/@/utilities/@/xcu_chap02@/.html, Shell
Command Language}, though more generous than the restrictive shell
subset described above, is fairly portable nowadays. Also please see
@uref{http://@/www.faqs.org/@/faqs/@/unix-faq/@/shell/, the Shell FAQs}.
@menu
* Shellology:: A zoology of shells
* Here-Documents:: Quirks and tricks
* File Descriptors:: FDs and redirections
* File System Conventions:: File names
* Shell Pattern Matching:: Pattern matching
* Shell Substitutions:: Variable and command expansions
* Assignments:: Varying side effects of assignments
* Parentheses:: Parentheses in shell scripts
* Slashes:: Slashes in shell scripts
* Special Shell Variables:: Variables you should not change
* Shell Functions:: What to look out for if you use them
* Limitations of Builtins:: Portable use of not so portable /bin/sh
* Limitations of Usual Tools:: Portable use of portable tools
@end menu
@node Shellology
@section Shellology
@cindex Shellology
There are several families of shells, most prominently the Bourne family
and the C shell family which are deeply incompatible. If you want to
write portable shell scripts, avoid members of the C shell family. The
@uref{http://@/www.faqs.org/@/faqs/@/unix-faq/@/shell/@/shell-differences/, the
Shell difference FAQ} includes a small history of Posix shells, and a
comparison between several of them.
Below we describe some of the members of the Bourne shell family.
@table @asis
@item Ash
@cindex Ash
Ash is often used on @acronym{GNU}/Linux and @acronym{BSD}
systems as a light-weight Bourne-compatible shell. Ash 0.2 has some
bugs that are fixed in the 0.3.x series, but portable shell scripts
should work around them, since version 0.2 is still shipped with many
@acronym{GNU}/Linux distributions.
To be compatible with Ash 0.2:
@itemize @minus
@item
don't use @samp{$?} after expanding empty or unset variables,
or at the start of an @command{eval}:
@example
foo=
false
$foo
echo "Do not use it: $?"
false
eval 'echo "Do not use it: $?"'
@end example
@item
don't use command substitution within variable expansion:
@example
cat $@{FOO=`bar`@}
@end example
@item
beware that single builtin substitutions are not performed by a
subshell, hence their effect applies to the current shell! @xref{Shell
Substitutions}, item ``Command Substitution''.
@end itemize
@item Bash
@cindex Bash
To detect whether you are running Bash, test whether
@code{BASH_VERSION} is set. To require
Posix compatibility, run @samp{set -o posix}. @xref{Bash POSIX
Mode, , Bash Posix Mode, bash, The @acronym{GNU} Bash Reference
Manual}, for details.
@item Bash 2.05 and later
@cindex Bash 2.05 and later
Versions 2.05 and later of Bash use a different format for the
output of the @command{set} builtin, designed to make evaluating its
output easier. However, this output is not compatible with earlier
versions of Bash (or with many other shells, probably). So if
you use Bash 2.05 or higher to execute @command{configure},
you'll need to use Bash 2.05 for all other build tasks as well.
@item Ksh
@cindex Ksh
@cindex Korn shell
@prindex @samp{ksh}
@prindex @samp{ksh88}
@prindex @samp{ksh93}
The Korn shell is compatible with the Bourne family and it mostly
conforms to Posix. It has two major variants commonly
called @samp{ksh88} and @samp{ksh93}, named after the years of initial
release. It is usually called @command{ksh}, but is called @command{sh}
on some hosts if you set your path appropriately.
Solaris systems have three variants:
@prindex @command{/usr/bin/ksh} on Solaris
@command{/usr/bin/ksh} is @samp{ksh88}; it is
standard on Solaris 2.0 and later.
@prindex @command{/usr/xpg4/bin/sh} on Solaris
@command{/usr/xpg4/bin/sh} is a Posix-compliant variant of
@samp{ksh88}; it is standard on Solaris 9 and later.
@prindex @command{/usr/dt/bin/dtksh} on Solaris
@command{/usr/dt/bin/dtksh} is @samp{ksh93}.
Variants that are not standard may be parts of optional
packages. There is no extra charge for these packages, but they are
not part of a minimal OS install and therefore some installations may
not have it.
Starting with Tru64 Version 4.0, the Korn shell @command{/usr/bin/ksh}
is also available as @command{/usr/bin/posix/sh}. If the environment
variable @env{BIN_SH} is set to @code{xpg4}, subsidiary invocations of
the standard shell conform to Posix.
@item Pdksh
@prindex @samp{pdksh}
A public-domain clone of the Korn shell called @command{pdksh} is widely
available: it has most of the @samp{ksh88} features along with a few of
its own. It usually sets @code{KSH_VERSION}, except if invoked as
@command{/bin/sh} on Open@acronym{BSD}, and similarly to Bash you can require
Posix compatibility by running @samp{set -o posix}. Unfortunately, with
@command{pdksh} 5.2.14 (the latest stable version as of January 2007)
Posix mode is buggy and causes @command{pdksh} to depart from Posix in
at least one respect:
@example
$ @kbd{echo "`echo \"hello\"`"}
hello
$ @kbd{set -o posix}
$ @kbd{echo "`echo \"hello\"`"}
"hello"
@end example
The last line of output contains spurious quotes. This is yet another
reason why portable shell code should not contain
@code{"`@dots{}\"@dots{}\"@dots{}`"} constructs (@pxref{Shell
Substitutions}).
@item Zsh
@cindex Zsh
To detect whether you are running @command{zsh}, test whether
@code{ZSH_VERSION} is set. By default @command{zsh} is @emph{not}
compatible with the Bourne shell: you must execute @samp{emulate sh},
and for @command{zsh} versions before 3.1.6-dev-18 you must also
set @code{NULLCMD} to @samp{:}. @xref{Compatibility, , Compatibility,
zsh, The Z Shell Manual}, for details.
The default Mac OS X @command{sh} was originally Zsh; it was changed to
Bash in Mac OS X 10.2.
@end table
@node Here-Documents
@section Here-Documents
@cindex Here-documents
@cindex Shell here-documents
Don't rely on @samp{\} being preserved just because it has no special
meaning together with the next symbol. In the native @command{sh}
on Open@acronym{BSD} 2.7 @samp{\"} expands to @samp{"} in here-documents with
unquoted delimiter. As a general rule, if @samp{\\} expands to @samp{\}
use @samp{\\} to get @samp{\}.
With Open@acronym{BSD} 2.7's @command{sh}
@example
@group
$ @kbd{cat < \" \\
> EOF}
" \
@end group
@end example
@noindent
and with Bash:
@example
@group
bash-2.04$ @kbd{cat < \" \\
> EOF}
\" \
@end group
@end example
Some shells mishandle large here-documents: for example,
Solaris 10 @command{dtksh} and the UnixWare 7.1.1 Posix shell, which are
derived from Korn shell version M-12/28/93d, mishandle braced variable
expansion that crosses a 1024- or 4096-byte buffer boundary
within a here-document. Only the part of the variable name after the boundary
is used. For example, @code{$@{variable@}} could be replaced by the expansion
of @code{$@{ble@}}. If the end of the variable name is aligned with the block
boundary, the shell reports an error, as if you used @code{$@{@}}.
Instead of @code{$@{variable-default@}}, the shell may expand
@code{$@{riable-default@}}, or even @code{$@{fault@}}. This bug can often
be worked around by omitting the braces: @code{$variable}. The bug was
fixed in
@samp{ksh93g} (1998-04-30) but as of 2006 many operating systems were
still shipping older versions with the bug.
Many shells (including the Bourne shell) implement here-documents
inefficiently. In particular, some shells can be extremely inefficient when
a single statement contains many here-documents. For instance if your
@file{configure.ac} includes something like:
@example
@group
if ; then
assume this and that
else
check this
check that
check something else
@dots{}
on and on forever
@dots{}
fi
@end group
@end example
A shell parses the whole @code{if}/@code{fi} construct, creating
temporary files for each here-document in it. Some shells create links
for such here-documents on every @code{fork}, so that the clean-up code
they had installed correctly removes them. It is creating the links
that can take the shell forever.
Moving the tests out of the @code{if}/@code{fi}, or creating multiple
@code{if}/@code{fi} constructs, would improve the performance
significantly. Anyway, this kind of construct is not exactly the
typical use of Autoconf. In fact, it's even not recommended, because M4
macros can't look into shell conditionals, so we may fail to expand a
macro when it was expanded before in a conditional path, and the
condition turned out to be false at runtime, and we end up not
executing the macro at all.
@node File Descriptors
@section File Descriptors
@cindex Descriptors
@cindex File descriptors
@cindex Shell file descriptors
Most shells, if not all (including Bash, Zsh, Ash), output traces on
stderr, even for subshells. This might result in undesirable content
if you meant to capture the standard-error output of the inner command:
@example
$ @kbd{ash -x -c '(eval "echo foo >&2") 2>stderr'}
$ @kbd{cat stderr}
+ eval echo foo >&2
+ echo foo
foo
$ @kbd{bash -x -c '(eval "echo foo >&2") 2>stderr'}
$ @kbd{cat stderr}
+ eval 'echo foo >&2'
++ echo foo
foo
$ @kbd{zsh -x -c '(eval "echo foo >&2") 2>stderr'}
@i{# Traces on startup files deleted here.}
$ @kbd{cat stderr}
+zsh:1> eval echo foo >&2
+zsh:1> echo foo
foo
@end example
@noindent
One workaround is to grep out uninteresting lines, hoping not to remove
good ones.
If you intend to redirect both standard error and standard output,
redirect standard output first. This works better with @acronym{HP-UX},
since its shell mishandles tracing if standard error is redirected
first:
@example
$ @kbd{sh -x -c ': 2>err >out'}
+ :
+ 2> err $ @kbd{cat err}
1> out
@end example
Don't try to redirect the standard error of a command substitution. It
must be done @emph{inside} the command substitution. When running
@samp{: `cd /zorglub` 2>/dev/null} expect the error message to
escape, while @samp{: `cd /zorglub 2>/dev/null`} works properly.
It is worth noting that Zsh (but not Ash nor Bash) makes it possible
in assignments though: @samp{foo=`cd /zorglub` 2>/dev/null}.
Some shells, like @command{ash}, don't recognize bi-directional
redirection (@samp{<>}). And even on shells that recognize it, it is
not portable to use on fifos: Posix does not require read-write support
for named pipes, and Cygwin does not support it:
@example
$ @kbd{mkfifo fifo}
$ @kbd{exec 5<>fifo}
$ @kbd{echo hi >&5}
bash: echo: write error: Communication error on send
@end example
When catering to old systems, don't redirect the same file descriptor
several times, as you are doomed to failure under Ultrix.
@example
ULTRIX V4.4 (Rev. 69) System #31: Thu Aug 10 19:42:23 GMT 1995
UWS V4.4 (Rev. 11)
$ @kbd{eval 'echo matter >fullness' >void}
illegal io
$ @kbd{eval '(echo matter >fullness)' >void}
illegal io
$ @kbd{(eval '(echo matter >fullness)') >void}
Ambiguous output redirect.
@end example
@noindent
In each case the expected result is of course @file{fullness} containing
@samp{matter} and @file{void} being empty. However, this bug is
probably not of practical concern to modern platforms.
Solaris 10 @command{sh} will try to optimize away a @command{:} command
in a loop after the first iteration, even if it is redirected:
@example
$ @kbd{for i in 1 2 3 ; do : >x$i; done}
$ @kbd{ls}
x1
@end example
@noindent
As a workaround, @command{echo} or @command{eval} can be used.
Don't rely on file descriptors 0, 1, and 2 remaining closed in a
subsidiary program. If any of these descriptors is closed, the
operating system may open an unspecified file for the descriptor in the
new process image. Posix says this may be done only if the subsidiary
program is set-user-ID or set-group-ID, but @acronym{HP-UX} 11.23 does
it even for ordinary programs.
Don't rely on open file descriptors being open in child processes. In
@command{ksh}, file descriptors above 2 which are opened using
@samp{exec @var{n}>file} are closed by a subsequent @samp{exec} (such as
that involved in the fork-and-exec which runs a program or script).
Thus, using @command{sh}, we have:
@example
$ @kbd{cat ./descrips}
#!/bin/sh -
echo hello >&5
$ @kbd{exec 5>t}
$ @kbd{./descrips}
$ @kbd{cat t}
hello
$
@end example
@noindent
But using ksh:
@example
$ @kbd{exec 5>t}
$ @kbd{./descrips}
hello
$ @kbd{cat t}
$
@end example
@noindent
Within the process which runs the @samp{descrips} script, file
descriptor 5 is closed.
Don't rely on redirection to a closed file descriptor to cause an
error. With Solaris @command{/bin/sh}, when the redirection fails, the
output goes to the original file descriptor.
@example
$ @kbd{bash -c 'echo hi >&3' 3>&-; echo $?}
bash: 3: Bad file descriptor
1
$ @kbd{/bin/sh -c 'echo hi >&3' 3>&-; echo $?}
hi
0
@end example
@acronym{DOS} variants cannot rename or remove open files, such as in
@samp{mv foo bar >foo} or @samp{rm foo >foo}, even though this is
perfectly portable among Posix hosts.
A few ancient systems reserved some file descriptors. By convention,
file descriptor 3 was opened to @file{/dev/tty} when you logged into
Eighth Edition (1985) through Tenth Edition Unix (1989). File
descriptor 4 had a special use on the Stardent/Kubota Titan (circa
1990), though we don't now remember what it was. Both these systems are
obsolete, so it's now safe to treat file descriptors 3 and 4 like any
other file descriptors.
@node File System Conventions
@section File System Conventions
@cindex File system conventions
Autoconf uses shell-script processing extensively, so the file names
that it processes should not contain characters that are special to the
shell. Special characters include space, tab, newline, @sc{nul}, and
the following:
@example
" # $ & ' ( ) * ; < = > ? [ \ ` |
@end example
Also, file names should not begin with @samp{~} or @samp{-}, and should
contain neither @samp{-} immediately after @samp{/} nor @samp{~}
immediately after @samp{:}. On Posix-like platforms, directory names
should not contain @samp{:}, as this runs afoul of @samp{:} used as the
path separator.
These restrictions apply not only to the files that you distribute, but
also to the absolute file names of your source, build, and destination
directories.
On some Posix-like platforms, @samp{!} and @samp{^} are special too, so
they should be avoided.
Posix lets implementations treat leading @file{//} specially, but
requires leading @file{///} and beyond to be equivalent to @file{/}.
Most Unix variants treat @file{//} like @file{/}. However, some treat
@file{//} as a ``super-root'' that can provide access to files that are
not otherwise reachable from @file{/}. The super-root tradition began
with Apollo Domain/OS, which died out long ago, but unfortunately Cygwin
has revived it.
While @command{autoconf} and friends are usually run on some Posix
variety, they can be used on other systems, most notably @acronym{DOS}
variants. This impacts several assumptions regarding file names.
@noindent
For example, the following code:
@example
case $foo_dir in
/*) # Absolute
;;
*)
foo_dir=$dots$foo_dir ;;
esac
@end example
@noindent
fails to properly detect absolute file names on those systems, because
they can use a drivespec, and usually use a backslash as directory
separator. If you want to be portable to @acronym{DOS} variants (at the
price of rejecting valid but oddball Posix file names like @file{a:\b}),
you can check for absolute file names like this:
@cindex absolute file names, detect
@example
case $foo_dir in
[\\/]* | ?:[\\/]* ) # Absolute
;;
*)
foo_dir=$dots$foo_dir ;;
esac
@end example
@noindent
Make sure you quote the brackets if appropriate and keep the backslash as
first character (@pxref{case, , Limitations of Shell Builtins}).
Also, because the colon is used as part of a drivespec, these systems don't
use it as path separator. When creating or accessing paths, you can use the
@code{PATH_SEPARATOR} output variable instead. @command{configure} sets this
to the appropriate value for the build system (@samp{:} or @samp{;}) when it
starts up.
File names need extra care as well. While @acronym{DOS} variants
that are Posixy enough to run @command{autoconf} (such as @acronym{DJGPP})
are usually able to handle long file names properly, there are still
limitations that can seriously break packages. Several of these issues
can be easily detected by the
@uref{ftp://@/ftp.gnu.org/@/gnu/@/non-gnu/@/doschk/@/doschk-1.1.tar.gz, doschk}
package.
A short overview follows; problems are marked with @sc{sfn}/@sc{lfn} to
indicate where they apply: @sc{sfn} means the issues are only relevant to
plain @acronym{DOS}, not to @acronym{DOS} under Microsoft Windows
variants, while @sc{lfn} identifies problems that exist even under
Microsoft Windows variants.
@table @asis
@item No multiple dots (@sc{sfn})
@acronym{DOS} cannot handle multiple dots in file names. This is an especially
important thing to remember when building a portable configure script,
as @command{autoconf} uses a .in suffix for template files.
This is perfectly OK on Posix variants:
@example
AC_CONFIG_HEADERS([config.h])
AC_CONFIG_FILES([source.c foo.bar])
AC_OUTPUT
@end example
@noindent
but it causes problems on @acronym{DOS}, as it requires @samp{config.h.in},
@samp{source.c.in} and @samp{foo.bar.in}. To make your package more portable
to @acronym{DOS}-based environments, you should use this instead:
@example
AC_CONFIG_HEADERS([config.h:config.hin])
AC_CONFIG_FILES([source.c:source.cin foo.bar:foobar.in])
AC_OUTPUT
@end example
@item No leading dot (@sc{sfn})
@acronym{DOS} cannot handle file names that start with a dot. This is usually
not important for @command{autoconf}.
@item Case insensitivity (@sc{lfn})
@acronym{DOS} is case insensitive, so you cannot, for example, have both a
file called @samp{INSTALL} and a directory called @samp{install}. This
also affects @command{make}; if there's a file called @samp{INSTALL} in
the directory, @samp{make install} does nothing (unless the
@samp{install} target is marked as PHONY).
@item The 8+3 limit (@sc{sfn})
Because the @acronym{DOS} file system only stores the first 8 characters of
the file name and the first 3 of the extension, those must be unique.
That means that @file{foobar-part1.c}, @file{foobar-part2.c} and
@file{foobar-prettybird.c} all resolve to the same file name
(@file{FOOBAR-P.C}). The same goes for @file{foo.bar} and
@file{foo.bartender}.
The 8+3 limit is not usually a problem under Microsoft Windows, as it
uses numeric
tails in the short version of file names to make them unique. However, a
registry setting can turn this behavior off. While this makes it
possible to share file trees containing long file names between @sc{sfn}
and @sc{lfn} environments, it also means the above problem applies there
as well.
@item Invalid characters (@sc{lfn})
Some characters are invalid in @acronym{DOS} file names, and should therefore
be avoided. In a @sc{lfn} environment, these are @samp{/}, @samp{\},
@samp{?}, @samp{*}, @samp{:}, @samp{<}, @samp{>}, @samp{|} and @samp{"}.
In a @sc{sfn} environment, other characters are also invalid. These
include @samp{+}, @samp{,}, @samp{[} and @samp{]}.
@item Invalid names (@sc{lfn})
Some @acronym{DOS} file names are reserved, and cause problems if you
try to use files with those names. These names include @file{CON},
@file{AUX}, @file{COM1}, @file{COM2}, @file{COM3}, @file{COM4},
@file{LPT1}, @file{LPT2}, @file{LPT3}, @file{NUL}, and @file{PRN}.
File names are case insensitive, so even names like
@file{aux/config.guess} are disallowed.
@end table
@node Shell Pattern Matching
@section Shell Pattern Matching
@cindex Shell pattern matching
Nowadays portable patterns can use negated character classes like
@samp{[!-aeiou]}. The older syntax @samp{[^-aeiou]} is supported by
some shells but not others; hence portable scripts should never use
@samp{^} as the first character of a bracket pattern.
Outside the C locale, patterns like @samp{[a-z]} are problematic since
they may match characters that are not lower-case letters.
@node Shell Substitutions
@section Shell Substitutions
@cindex Shell substitutions
Contrary to a persistent urban legend, the Bourne shell does not
systematically split variables and back-quoted expressions, in particular
on the right-hand side of assignments and in the argument of @code{case}.
For instance, the following code:
@example
case "$given_srcdir" in
.) top_srcdir="`echo "$dots" | sed 's|/$||'`" ;;
*) top_srcdir="$dots$given_srcdir" ;;
esac
@end example
@noindent
is more readable when written as:
@example
case $given_srcdir in
.) top_srcdir=`echo "$dots" | sed 's|/$||'` ;;
*) top_srcdir=$dots$given_srcdir ;;
esac
@end example
@noindent
and in fact it is even @emph{more} portable: in the first case of the
first attempt, the computation of @code{top_srcdir} is not portable,
since not all shells properly understand @code{"`@dots{}"@dots{}"@dots{}`"}.
Worse yet, not all shells understand @code{"`@dots{}\"@dots{}\"@dots{}`"}
the same way. There is just no portable way to use double-quoted
strings inside double-quoted back-quoted expressions (pfew!).
@table @code
@item $@@
@cindex @samp{"$@@"}
One of the most famous shell-portability issues is related to
@samp{"$@@"}. When there are no positional arguments, Posix says
that @samp{"$@@"} is supposed to be equivalent to nothing, but the
original Unix version 7 Bourne shell treated it as equivalent to
@samp{""} instead, and this behavior survives in later implementations
like Digital Unix 5.0.
The traditional way to work around this portability problem is to use
@samp{$@{1+"$@@"@}}. Unfortunately this method does not work with
Zsh (3.x and 4.x), which is used on Mac OS X@. When emulating
the Bourne shell, Zsh performs word splitting on @samp{$@{1+"$@@"@}}:
@example
zsh $ @kbd{emulate sh}
zsh $ @kbd{for i in "$@@"; do echo $i; done}
Hello World
!
zsh $ @kbd{for i in $@{1+"$@@"@}; do echo $i; done}
Hello
World
!
@end example
@noindent
Zsh handles plain @samp{"$@@"} properly, but we can't use plain
@samp{"$@@"} because of the portability problems mentioned above.
One workaround relies on Zsh's ``global aliases'' to convert
@samp{$@{1+"$@@"@}} into @samp{"$@@"} by itself:
@example
test "$@{ZSH_VERSION+set@}" = set && alias -g '$@{1+"$@@"@}'='"$@@"'
@end example
Zsh only recognizes this alias when a shell word matches it exactly;
@samp{"foo"$@{1+"$@@"@}} remains subject to word splitting. Since this
case always yields at least one shell word, use plain @samp{"$@@"}.
A more conservative workaround is to avoid @samp{"$@@"} if it is
possible that there may be no positional arguments. For example,
instead of:
@example
cat conftest.c "$@@"
@end example
you can use this instead:
@example
case $# in
0) cat conftest.c;;
*) cat conftest.c "$@@";;
esac
@end example
Autoconf macros often use the @command{set} command to update
@samp{$@@}, so if you are writing shell code intended for
@command{configure} you should not assume that the value of @samp{$@@}
persists for any length of time.
@item $@{10@}
@cindex positional parameters
The 10th, 11th, @dots{} positional parameters can be accessed only after
a @code{shift}. The 7th Edition shell reported an error if given
@code{$@{10@}}, and
Solaris 10 @command{/bin/sh} still acts that way:
@example
$ @kbd{set 1 2 3 4 5 6 7 8 9 10}
$ @kbd{echo $@{10@}}
bad substitution
@end example
@item $@{@var{var}:-@var{value}@}
@c Info cannot handle `:' in index entries.
@c @cindex $@{@var{var}:-@var{value}@}
Old @acronym{BSD} shells, including the Ultrix @code{sh}, don't accept the
colon for any shell substitution, and complain and die.
Similarly for $@{@var{var}:=@var{value}@}, $@{@var{var}:?@var{value}@}, etc.
@item $@{@var{var}=@var{literal}@}
@cindex $@{@var{var}=@var{literal}@}
Be sure to quote:
@example
: $@{var='Some words'@}
@end example
@noindent
otherwise some shells, such as on Digital Unix V 5.0, die because
of a ``bad substitution''.
@sp 1
Solaris @command{/bin/sh} has a frightening bug in its interpretation
of this. Imagine you need set a variable to a string containing
@samp{@}}. This @samp{@}} character confuses Solaris @command{/bin/sh}
when the affected variable was already set. This bug can be exercised
by running:
@example
$ @kbd{unset foo}
$ @kbd{foo=$@{foo='@}'@}}
$ @kbd{echo $foo}
@}
$ @kbd{foo=$@{foo='@}' # no error; this hints to what the bug is}
$ @kbd{echo $foo}
@}
$ @kbd{foo=$@{foo='@}'@}}
$ @kbd{echo $foo}
@}@}
^ ugh!
@end example
It seems that @samp{@}} is interpreted as matching @samp{$@{}, even
though it is enclosed in single quotes. The problem doesn't happen
using double quotes.
@item $@{@var{var}=@var{expanded-value}@}
@cindex $@{@var{var}=@var{expanded-value}@}
On Ultrix,
running
@example
default="yu,yaa"
: $@{var="$default"@}
@end example
@noindent
sets @var{var} to @samp{M-yM-uM-,M-yM-aM-a}, i.e., the 8th bit of
each char is set. You don't observe the phenomenon using a simple
@samp{echo $var} since apparently the shell resets the 8th bit when it
expands $var. Here are two means to make this shell confess its sins:
@example
$ @kbd{cat -v < broken}
$ @kbd{echo "`printf 'foo\r\n'`"" bar" | cmp - broken}
- broken differ: char 4, line 1
@end example
Upon interrupt or SIGTERM, some shells may abort a command substitution,
replace it with a null string, and wrongly evaluate the enclosing
command before entering the trap or ending the script. This can lead to
spurious errors:
@example
$ @kbd{sh -c 'if test `sleep 5; echo hi` = hi; then echo yes; fi'}
$ @kbd{^C}
sh: test: hi: unexpected operator/operand
@end example
@noindent
You can avoid this by assigning the command substitution to a temporary
variable:
@example
$ @kbd{sh -c 'res=`sleep 5; echo hi`
if test "x$res" = xhi; then echo yes; fi'}
$ @kbd{^C}
@end example
@item $(@var{commands})
@cindex $(@var{commands})
This construct is meant to replace @samp{`@var{commands}`},
and it has most of the problems listed under @code{`@var{commands}`}.
This construct can be
nested while this is impossible to do portably with back quotes.
Unfortunately it is not yet universally supported. Most notably, even recent
releases of Solaris don't support it:
@example
$ @kbd{showrev -c /bin/sh | grep version}
Command version: SunOS 5.10 Generic 121005-03 Oct 2006
$ @kbd{echo $(echo blah)}
syntax error: `(' unexpected
@end example
@noindent
nor does @sc{irix} 6.5's Bourne shell:
@example
$ @kbd{uname -a}
IRIX firebird-image 6.5 07151432 IP22
$ @kbd{echo $(echo blah)}
$(echo blah)
@end example
If you do use @samp{$(@var{commands})}, make sure that the commands
do not start with a parenthesis, as that would cause confusion with
a different notation @samp{$((@var{expression}))} that in modern
shells is an arithmetic expression not a command. To avoid the
confusion, insert a space between the two opening parentheses.
Avoid @var{commands} that contain unbalanced parentheses in
here-documents, comments, or case statement patterns, as many shells
mishandle them. For example, Bash 3.1, @samp{ksh88}, @command{pdksh}
5.2.14, and Zsh 4.2.6 all mishandle the following valid command:
@example
echo $(case x in x) echo hello;; esac)
@end example
@item $((@var{expression}))
@cindex $((@var{expression}))
Arithmetic expansion is not portable as some shells (most
notably Solaris 10 @command{/bin/sh}) don't support it.
Among shells that do support @samp{$(( ))}, not all of them obey the
Posix rule that octal and hexadecimal constants must be recognized:
@example
$ @kbd{bash -c 'echo $(( 010 + 0x10 ))'}
24
$ @kbd{zsh -c 'echo $(( 010 + 0x10 ))'}
26
$ @kbd{zsh -c 'emulate sh; echo $(( 010 + 0x10 ))'}
24
$ @kbd{pdksh -c 'echo $(( 010 + 0x10 ))'}
pdksh: 010 + 0x10 : bad number `0x10'
$ @kbd{pdksh -c 'echo $(( 010 ))'}
10
@end example
When it is available, using arithmetic expansion provides a noticeable
speedup in script execution; but testing for support requires
@command{eval} to avoid syntax errors. The following construct is used
by @code{AS_VAR_ARITH} to provide arithmetic computation when all
arguments are provided in decimal and without a leading zero, and all
operators are properly quoted and appear as distinct arguments:
@example
if ( eval 'test $(( 1 + 1 )) = 2' ) 2>/dev/null; then
eval 'func_arith ()
@{
func_arith_result=$(( $* ))
@}'
else
func_arith ()
@{
func_arith_result=`expr "$@@"`
@}
fi
func_arith 1 + 1
foo=$func_arith_result
@end example
@item ^
@cindex ^ quoting
Always quote @samp{^}, otherwise traditional shells such as
@command{/bin/sh} on Solaris 10 treat this like @samp{|}.
@end table
@node Assignments
@section Assignments
@cindex Shell assignments
When setting several variables in a row, be aware that the order of the
evaluation is undefined. For instance @samp{foo=1 foo=2; echo $foo}
gives @samp{1} with Solaris @command{/bin/sh}, but @samp{2} with Bash.
You must use
@samp{;} to enforce the order: @samp{foo=1; foo=2; echo $foo}.
Don't rely on the following to find @file{subdir/program}:
@example
PATH=subdir$PATH_SEPARATOR$PATH program
@end example
@noindent
as this does not work with Zsh 3.0.6. Use something like this
instead:
@example
(PATH=subdir$PATH_SEPARATOR$PATH; export PATH; exec program)
@end example
Don't rely on the exit status of an assignment: Ash 0.2 does not change
the status and propagates that of the last statement:
@example
$ @kbd{false || foo=bar; echo $?}
1
$ @kbd{false || foo=`:`; echo $?}
0
@end example
@noindent
and to make things even worse, @acronym{QNX} 4.25 just sets the exit status
to 0 in any case:
@example
$ @kbd{foo=`exit 1`; echo $?}
0
@end example
To assign default values, follow this algorithm:
@enumerate
@item
If the default value is a literal and does not contain any closing
brace, use:
@example
: $@{var='my literal'@}
@end example
@item
If the default value contains no closing brace, has to be expanded, and
the variable being initialized is not intended to be IFS-split
(i.e., it's not a list), then use:
@example
: $@{var="$default"@}
@end example
@item
If the default value contains no closing brace, has to be expanded, and
the variable being initialized is intended to be IFS-split (i.e., it's a list),
then use:
@example
var=$@{var="$default"@}
@end example
@item
If the default value contains a closing brace, then use:
@example
test "$@{var+set@}" = set || var="has a '@}'"
@end example
@end enumerate
In most cases @samp{var=$@{var="$default"@}} is fine, but in case of
doubt, just use the last form. @xref{Shell Substitutions}, items
@samp{$@{@var{var}:-@var{value}@}} and @samp{$@{@var{var}=@var{value}@}}
for the rationale.
@node Parentheses
@section Parentheses in Shell Scripts
@cindex Shell parentheses
Beware of two opening parentheses in a row, as many shell
implementations treat them specially. Posix requires that the command
@samp{((cat))} must behave like @samp{(cat)}, but many shells, including
Bash and the Korn shell, treat @samp{((cat))} as an arithmetic
expression equivalent to @samp{let "cat"}, and may or may not report an
error when they detect that @samp{cat} is not a number. As another
example, @samp{pdksh} 5.2.14 misparses the following code:
@example
if ((true) || false); then
echo ok
fi
@end example
@noindent
To work around this problem, insert a space between the two opening
parentheses. There is a similar problem and workaround with
@samp{$((}; see @ref{Shell Substitutions}.
@node Slashes
@section Slashes in Shell Scripts
@cindex Shell slashes
Unpatched Tru64 5.1 @command{sh} omits the last slash of command-line
arguments that contain two trailing slashes:
@example
$ @kbd{echo / // /// //// .// //.}
/ / // /// ./ //.
$ @kbd{x=//}
$ @kbd{eval "echo \$x"}
/
$ @kbd{set -x}
$ @kbd{echo abc | tr -t ab //}
+ echo abc
+ tr -t ab /
/bc
@end example
Unpatched Tru64 4.0 @command{sh} adds a slash after @samp{"$var"} if the
variable is empty and the second double-quote is followed by a word that
begins and ends with slash:
@example
$ @kbd{sh -xc 'p=; echo "$p"/ouch/'}
p=
+ echo //ouch/
//ouch/
@end example
However, our understanding is that patches are available, so perhaps
it's not worth worrying about working around these horrendous bugs.
@node Special Shell Variables
@section Special Shell Variables
@cindex Shell variables
@cindex Special shell variables
Some shell variables should not be used, since they can have a deep
influence on the behavior of the shell. In order to recover a sane
behavior from the shell, some variables should be unset; M4sh takes
care of this and provides fallback values, whenever needed, to cater
for a very old @file{/bin/sh} that does not support @command{unset}.
(@pxref{Portable Shell, , Portable Shell Programming}).
As a general rule, shell variable names containing a lower-case letter
are safe; you can define and use these variables without worrying about
their effect on the underlying system, and without worrying about
whether the shell changes them unexpectedly. (The exception is the
shell variable @code{status}, as described below.)
Here is a list of names that are known to cause trouble. This list is
not exhaustive, but you should be safe if you avoid the name
@code{status} and names containing only upper-case letters and
underscores.
@c Alphabetical order, case insensitive, `A' before `a'.
@table @code
@item ?
Not all shells correctly reset @samp{$?} after conditionals (@pxref{if,
, Limitations of Shell Builtins}). Not all shells manage @samp{$?}
correctly in shell functions (@pxref{Shell Functions}) or in traps
(@pxref{trap, , Limitations of Shell Builtins}). Not all shells reset
@samp{$?} to zero after an empty command.
@example
$ @kbd{bash -c 'false; $empty; echo $?'}
0
$ @kbd{zsh -c 'false; $empty; echo $?'}
1
@end example
@item _
@evindex _
Many shells reserve @samp{$_} for various purposes, e.g., the name of
the last command executed.
@item BIN_SH
@evindex BIN_SH
In Tru64, if @env{BIN_SH} is set to @code{xpg4}, subsidiary invocations of
the standard shell conform to Posix.
@item CDPATH
@evindex CDPATH
When this variable is set it specifies a list of directories to search
when invoking @code{cd} with a relative file name that did not start
with @samp{./} or @samp{../}. Posix
1003.1-2001 says that if a nonempty directory name from @env{CDPATH}
is used successfully, @code{cd} prints the resulting absolute
file name. Unfortunately this output can break idioms like
@samp{abs=`cd src && pwd`} because @code{abs} receives the name twice.
Also, many shells do not conform to this part of Posix; for
example, @command{zsh} prints the result only if a directory name
other than @file{.} was chosen from @env{CDPATH}.
In practice the shells that have this problem also support
@command{unset}, so you can work around the problem as follows:
@example
(unset CDPATH) >/dev/null 2>&1 && unset CDPATH
@end example
You can also avoid output by ensuring that your directory name is
absolute or anchored at @samp{./}, as in @samp{abs=`cd ./src && pwd`}.
Configure scripts use M4sh, which automatically unsets @env{CDPATH} if
possible, so you need not worry about this problem in those scripts.
@item CLICOLOR_FORCE
@evindex CLICOLOR_FORCE
When this variable is set, some implementations of tools like
@command{ls} attempt to add color to their output via terminal escape
sequences, even when the output is not directed to a terminal, and can
thus cause spurious failures in scripts. Configure scripts use M4sh,
which automatically unsets this variable.
@item DUALCASE
@evindex DUALCASE
In the MKS shell, case statements and file name generation are
case-insensitive unless @env{DUALCASE} is nonzero.
Autoconf-generated scripts export this variable when they start up.
@item ENV
@itemx MAIL
@itemx MAILPATH
@itemx PS1
@itemx PS2
@itemx PS4
@evindex ENV
@evindex MAIL
@evindex MAILPATH
@evindex PS1
@evindex PS2
@evindex PS4
These variables should not matter for shell scripts, since they are
supposed to affect only interactive shells. However, at least one
shell (the pre-3.0 @sc{uwin} Korn shell) gets confused about
whether it is interactive, which means that (for example) a @env{PS1}
with a side effect can unexpectedly modify @samp{$?}. To work around
this bug, M4sh scripts (including @file{configure} scripts) do something
like this:
@example
(unset ENV) >/dev/null 2>&1 && unset ENV MAIL MAILPATH
PS1='$ '
PS2='> '
PS4='+ '
@end example
@noindent
(actually, there is some complication due to bugs in @command{unset};
see @pxref{unset, , Limitations of Shell Builtins}).
@item FPATH
@evindex FPATH
The Korn shell uses @env{FPATH} to find shell functions, so avoid
@env{FPATH} in portable scripts. @env{FPATH} is consulted after
@env{PATH}, but you still need to be wary of tests that use @env{PATH}
to find whether a command exists, since they might report the wrong
result if @env{FPATH} is also set.
@item GREP_OPTIONS
@evindex GREP_OPTIONS
When this variable is set, some implementations of @command{grep} honor
these options, even if the options include direction to enable colored
output via terminal escape sequences, and the result can cause spurious
failures when the output is not directed to a terminal. Configure
scripts use M4sh, which automatically unsets this variable.
@item IFS
@evindex IFS
Long ago, shell scripts inherited @env{IFS} from the environment,
but this caused many problems so modern shells ignore any environment
settings for @env{IFS}.
Don't set the first character of @code{IFS} to backslash. Indeed,
Bourne shells use the first character (backslash) when joining the
components in @samp{"$@@"} and some shells then reinterpret (!)@: the
backslash escapes, so you can end up with backspace and other strange
characters.
The proper value for @code{IFS} (in regular code, not when performing
splits) is @samp{@key{SPC}@key{TAB}@key{RET}}. The first character is
especially important, as it is used to join the arguments in @samp{$*};
however, note that traditional shells, but also bash-2.04, fail to adhere
to this and join with a space anyway.
@item LANG
@itemx LC_ALL
@itemx LC_COLLATE
@itemx LC_CTYPE
@itemx LC_MESSAGES
@itemx LC_MONETARY
@itemx LC_NUMERIC
@itemx LC_TIME
@evindex LANG
@evindex LC_ALL
@evindex LC_COLLATE
@evindex LC_CTYPE
@evindex LC_MESSAGES
@evindex LC_MONETARY
@evindex LC_NUMERIC
@evindex LC_TIME
You should set all these variables to @samp{C} because so much
configuration code assumes the C locale and Posix requires that locale
environment variables be set to @samp{C} if the C locale is desired;
@file{configure} scripts and M4sh do that for you.
Export these variables after setting them.
@c However, some older, nonstandard
@c systems (notably @acronym{SCO}) break if locale environment variables
@c are set to @samp{C}, so when running on these systems
@c Autoconf-generated scripts unset the variables instead.
@item LANGUAGE
@evindex LANGUAGE
@env{LANGUAGE} is not specified by Posix, but it is a @acronym{GNU}
extension that overrides @env{LC_ALL} in some cases, so you (or M4sh)
should set it too.
@item LC_ADDRESS
@itemx LC_IDENTIFICATION
@itemx LC_MEASUREMENT
@itemx LC_NAME
@itemx LC_PAPER
@itemx LC_TELEPHONE
@evindex LC_ADDRESS
@evindex LC_IDENTIFICATION
@evindex LC_MEASUREMENT
@evindex LC_NAME
@evindex LC_PAPER
@evindex LC_TELEPHONE
These locale environment variables are @acronym{GNU} extensions. They
are treated like their Posix brethren (@env{LC_COLLATE},
etc.)@: as described above.
@item LINENO
@evindex LINENO
Most modern shells provide the current line number in @code{LINENO}.
Its value is the line number of the beginning of the current command.
M4sh, and hence Autoconf, attempts to execute @command{configure} with
a shell that supports @code{LINENO}. If no such shell is available, it
attempts to implement @code{LINENO} with a Sed prepass that replaces each
instance of the string @code{$LINENO} (not followed by an alphanumeric
character) with the line's number. In M4sh scripts you should execute
@code{AS_LINENO_PREPARE} so that these workarounds are included in
your script; configure scripts do this automatically in @code{AC_INIT}.
You should not rely on @code{LINENO} within @command{eval} or shell
functions, as the behavior differs in practice. The presence of a
quoted newline within simple commands can alter which line number is
used as the starting point for @code{$LINENO} substitutions within that
command. Also, the possibility of the Sed prepass means that you should
not rely on @code{$LINENO} when quoted, when in here-documents, or when
line continuations are used. Subshells should be OK, though. In the
following example, lines 1, 9, and 14 are portable, but the other
instances of @code{$LINENO} do not have deterministic values:
@example
@group
$ @kbd{cat lineno}
echo 1. $LINENO
echo "2. $LINENO
3. $LINENO"
cat < @kbd{ N}
> @kbd{ s,$,-,}
> @kbd{ t loop}
> @kbd{ :loop}
> @kbd{ s,^\([0-9]*\)\(.*\)[$]LINENO\([^a-zA-Z0-9_]\),\1\2\1\3,}
> @kbd{ t loop}
> @kbd{ s,-$,,}
> @kbd{ s,^[0-9]*\n,,}
> @kbd{ ' |}
> @kbd{ sh}
1. 1
2. 2
3. 3
5. 5
6. 6
7. \7
9. 9
10. 10
11. 11
12. 12
13. 13
14. 14
15. 15
18. 16
18. 17
19. 20
@end group
@end example
In particular, note that @file{config.status} (and any other subsidiary
script created by @code{AS_INIT_GENERATED}) might report line numbers
relative to the parent script as a result of the potential Sed pass.
@item NULLCMD
@evindex NULLCMD
When executing the command @samp{>foo}, @command{zsh} executes
@samp{$NULLCMD >foo} unless it is operating in Bourne shell
compatibility mode and the @command{zsh} version is newer
than 3.1.6-dev-18. If you are using an older @command{zsh}
and forget to set @env{NULLCMD},
your script might be suspended waiting for data on its standard input.
@item PATH_SEPARATOR
@evindex PATH_SEPARATOR
On @acronym{DJGPP} systems, the @env{PATH_SEPARATOR} environment
variable can be set to either @samp{:} or @samp{;} to control the path
separator Bash uses to set up certain environment variables (such as
@env{PATH}). You can set this variable to @samp{;} if you want
@command{configure} to use @samp{;} as a separator; this might be useful
if you plan to use non-Posix shells to execute files. @xref{File System
Conventions}, for more information about @code{PATH_SEPARATOR}.
@item PWD
@evindex PWD
Posix 1003.1-2001 requires that @command{cd} and
@command{pwd} must update the @env{PWD} environment variable to point
to the logical name of the current directory, but traditional shells
do not support this. This can cause confusion if one shell instance
maintains @env{PWD} but a subsidiary and different shell does not know
about @env{PWD} and executes @command{cd}; in this case @env{PWD}
points to the wrong directory. Use @samp{`pwd`} rather than
@samp{$PWD}.
@item RANDOM
@evindex RANDOM
Many shells provide @code{RANDOM}, a variable that returns a different
integer each time it is used. Most of the time, its value does not
change when it is not used, but on @sc{irix} 6.5 the value changes all
the time. This can be observed by using @command{set}. It is common
practice to use @code{$RANDOM} as part of a file name, but code
shouldn't rely on @code{$RANDOM} expanding to a nonempty string.
@item status
@evindex status
This variable is an alias to @samp{$?} for @code{zsh} (at least 3.1.6),
hence read-only. Do not use it.
@end table
@node Shell Functions
@section Shell Functions
@cindex Shell Functions
Nowadays, it is difficult to find a shell that does not support
shell functions at all. However, some differences should be expected.
Inside a shell function, you should not rely on the error status of a
subshell if the last command of that subshell was @code{exit} or
@code{trap}, as this triggers bugs in zsh 4.x; while Autoconf tries to
find a shell that does not exhibit the bug, zsh might be the only shell
present on the user's machine.
Likewise, the state of @samp{$?} is not reliable when entering a shell
function. This has the effect that using a function as the first
command in a @command{trap} handler can cause problems.
@example
$ @kbd{bash -c 'foo()@{ echo $?; @}; trap foo 0; (exit 2); exit 2'; echo $?}
2
2
$ @kbd{ash -c 'foo()@{ echo $?; @}; trap foo 0; (exit 2); exit 2'; echo $?}
0
2
@end example
Not all shells treat shell functions as simple commands impacted by
@samp{set -e}, for example with Solaris 10 @command{bin/sh}:
@example
$ @kbd{bash -c 'f()@{ return 1; @}; set -e; f; echo oops}
$ @kbd{/bin/sh -c 'f()@{ return 1; @}; set -e; f; echo oops}
oops
@end example
Shell variables and functions may share the same namespace, for example
with Solaris 10 @command{/bin/sh}:
@example
$ @kbd{f () @{ :; @}; f=; f}
f: not found
@end example
@noindent
For this reason, Autoconf (actually M4sh, @pxref{Programming in M4sh})
uses the prefix @samp{as_fn_} for its functions.
Handling of positional parameters and shell options varies among shells.
For example, Korn shells reset and restore trace output (@samp{set -x})
and other options upon function entry and exit. Inside a function,
@acronym{IRIX} sh sets @samp{$0} to the function name.
It is not portable to pass temporary environment variables to shell
functions. Solaris @command{/bin/sh} does not see the variable.
Meanwhile, not all shells follow the Posix rule that the assignment must
affect the current environment in the same manner as special built-ins.
@example
$ @kbd{/bin/sh -c 'func()@{ echo $a;@}; a=1 func; echo $a'}
@result{}
@result{}
$ @kbd{ash -c 'func()@{ echo $a;@}; a=1 func; echo $a'}
@result{}1
@result{}
$ @kbd{bash -c 'set -o posix; func()@{ echo $a;@}; a=1 func; echo $a'}
@result{}1
@result{}1
@end example
Some ancient Bourne shell variants with function support did not reset
@samp{$@var{i}, @var{i} >= 0}, upon function exit, so effectively the
arguments of the script were lost after the first function invocation.
It is probably not worth worrying about these shells any more.
With @acronym{AIX} sh, a @command{trap} on 0 installed in a shell function
triggers at function exit rather than at script exit, see @xref{trap, ,
Limitations of Shell Builtins}.
@node Limitations of Builtins
@section Limitations of Shell Builtins
@cindex Shell builtins
@cindex Limitations of shell builtins
No, no, we are serious: some shells do have limitations! :)
You should always keep in mind that any builtin or command may support
options, and therefore differ in behavior with arguments
starting with a dash. For instance, even the innocent @samp{echo "$word"}
can give unexpected results when @code{word} starts with a dash. It is
often possible to avoid this problem using @samp{echo "x$word"}, taking
the @samp{x} into account later in the pipe. Many of these limitations
can be worked around using M4sh (@pxref{Programming in M4sh}).
@c This table includes things like `@command{test} (files)', so we can't
@c use @table @command.
@table @asis
@item @command{.}
@c --------------
@prindex @command{.}
Use @command{.} only with regular files (use @samp{test -f}). Bash
2.03, for instance, chokes on @samp{. /dev/null}. Remember that
@command{.} uses @env{PATH} if its argument contains no slashes. Also,
some shells, including bash 3.2, implicitly append the current directory
to this @env{PATH} search, even though Posix forbids it. So if you want
to use @command{.} on a file @file{foo} in the current directory, you
must use @samp{. ./foo}.
Not all shells gracefully handle syntax errors within a sourced file.
On one extreme, some non-interactive shells abort the entire script. On
the other, @command{zsh} 4.3.10 has a bug where it fails to react to the
syntax error.
@example
$ @kbd{echo 'fi' > syntax}
$ @kbd{bash -c '. ./syntax; echo $?'}
./syntax: line 1: syntax error near unexpected token `fi'
./syntax: line 1: `fi'
1
$ @kbd{ash -c '. ./syntax; echo $?'}
./syntax: 1: Syntax error: "fi" unexpected
$ @kbd{zsh -c '. ./syntax; echo $?'}
./syntax:1: parse error near `fi'
0
@end example
@item @command{!}
@c --------------
@prindex @command{!}
The Unix version 7 shell did not support
negating the exit status of commands with @command{!}, and this feature
is still absent from some shells (e.g., Solaris @command{/bin/sh}).
Other shells, such as FreeBSD @command{/bin/sh} or @command{ash}, have
bugs when using @command{!}:
@example
$ @kbd{sh -c '! : | :'; echo $?}
1
$ @kbd{ash -c '! : | :'; echo $?}
0
$ @kbd{sh -c '! @{ :; @}'; echo $?}
1
$ @kbd{ash -c '! @{ :; @}'; echo $?}
@{: not found
Syntax error: "@}" unexpected
2
@end example
Shell code like this:
@example
if ! cmp file1 file2 >/dev/null 2>&1; then
echo files differ or trouble
fi
@end example
is therefore not portable in practice. Typically it is easy to rewrite
such code, e.g.:
@example
cmp file1 file2 >/dev/null 2>&1 ||
echo files differ or trouble
@end example
More generally, one can always rewrite @samp{! @var{command}} as:
@example
if @var{command}; then (exit 1); else :; fi
@end example
@item @command{@{...@}}
@c --------------------
@prindex @command{@{...@}}
Bash 3.2 (and earlier versions) sometimes does not properly set
@samp{$?} when failing to write redirected output of a compound command.
This problem is most commonly observed with @samp{@{@dots{}@}}; it does
not occur with @samp{(@dots{})}. For example:
@example
$ @kbd{bash -c '@{ echo foo; @} >/bad; echo $?'}
bash: line 1: /bad: Permission denied
0
$ @kbd{bash -c 'while :; do echo; done >/bad; echo $?'}
bash: line 1: /bad: Permission denied
0
@end example
To work around the bug, prepend @samp{:;}:
@example
$ @kbd{bash -c ':;@{ echo foo; @} >/bad; echo $?'}
bash: line 1: /bad: Permission denied
1
@end example
Posix requires a syntax error if a brace list has no contents. However,
not all shells obey this rule; and on shells where empty lists are
permitted, the effect on @samp{$?} is inconsistent. To avoid problems,
ensure that a brace list is never empty.
@example
$ @kbd{bash -c 'false; @{ @}; echo $?' || echo $?}
bash: line 1: syntax error near unexpected token `@}'
bash: line 1: `false; @{ @}; echo $?'
2
$ @kbd{zsh -c 'false; @{ @}; echo $?' || echo $?}
1
$ @kbd{pdksh -c 'false; @{ @}; echo $?' || echo $?}
0
@end example
@item @command{break}
@c ------------------
@prindex @command{break}
The use of @samp{break 2} etc.@: is safe.
@anchor{case}
@item @command{case}
@c -----------------
@prindex @command{case}
You don't need to quote the argument; no splitting is performed.
You don't need the final @samp{;;}, but you should use it.
Posix requires support for @code{case} patterns with opening
parentheses like this:
@example
case $file_name in
(*.c) echo "C source code";;
esac
@end example
@noindent
but the @code{(} in this example is not portable to many Bourne
shell implementations, which is a pity for those of us using tools that
rely on balanced parentheses. For instance, with Solaris
@command{/bin/sh}:
@example
$ @kbd{case foo in (foo) echo foo;; esac}
@error{}syntax error: `(' unexpected
@end example
@noindent
The leading @samp{(} can be omitted safely. Unfortunately, there are
contexts where unbalanced parentheses cause other problems, such as when
using a syntax-highlighting editor that searches for the balancing
counterpart, or more importantly, when using a case statement as an
underquoted argument to an Autoconf macro. @xref{Balancing
Parentheses}, for tradeoffs involved in various styles of dealing with
unbalanced @samp{)}.
Zsh handles pattern fragments derived from parameter expansions or
command substitutions as though quoted:
@example
$ pat=\?; case aa in ?$pat) echo match;; esac
$ pat=\?; case a? in ?$pat) echo match;; esac
match
@end example
@noindent
Because of a bug in its @code{fnmatch}, Bash fails to properly
handle backslashes in character classes:
@example
bash-2.02$ @kbd{case /tmp in [/\\]*) echo OK;; esac}
bash-2.02$
@end example
@noindent
This is extremely unfortunate, since you are likely to use this code to
handle Posix or @sc{ms-dos} absolute file names. To work around this
bug, always put the backslash first:
@example
bash-2.02$ @kbd{case '\TMP' in [\\/]*) echo OK;; esac}
OK
bash-2.02$ @kbd{case /tmp in [\\/]*) echo OK;; esac}
OK
@end example
Many Bourne shells cannot handle closing brackets in character classes
correctly.
Some shells also have problems with backslash escaping in case you do not want
to match the backslash: both a backslash and the escaped character match this
pattern. To work around this, specify the character class in a variable, so
that quote removal does not apply afterwards, and the special characters don't
have to be backslash-escaped:
@example
$ @kbd{case '\' in [\<]) echo OK;; esac}
OK
$ @kbd{scanset='[<]'; case '\' in $scanset) echo OK;; esac}
$
@end example
Even with this, Solaris @command{ksh} matches a backslash if the set
contains any
of the characters @samp{|}, @samp{&}, @samp{(}, or @samp{)}.
Conversely, Tru64 @command{ksh} (circa 2003) erroneously always matches
a closing parenthesis if not specified in a character class:
@example
$ @kbd{case foo in *\)*) echo fail ;; esac}
fail
$ @kbd{case foo in *')'*) echo fail ;; esac}
fail
@end example
Some shells, such as Ash 0.3.8, are confused by an empty
@code{case}/@code{esac}:
@example
ash-0.3.8 $ @kbd{case foo in esac;}
@error{}Syntax error: ";" unexpected (expecting ")")
@end example
Posix requires @command{case} to give an exit status of 0 if no cases
match. However, @command{/bin/sh} in Solaris 10 does not obey this
rule. Meanwhile, it is unclear whether a case that matches, but
contains no statements, must also change the exit status to 0. The M4sh
macro @code{AS_CASE} works around these inconsistencies.
@example
$ @kbd{bash -c 'case `false` in ?) ;; esac; echo $?'}
0
$ @kbd{/bin/sh -c 'case `false` in ?) ;; esac; echo $?'}
255
@end example
@item @command{cd}
@c ---------------
@prindex @command{cd}
Posix 1003.1-2001 requires that @command{cd} must support
the @option{-L} (``logical'') and @option{-P} (``physical'') options,
with @option{-L} being the default. However, traditional shells do
not support these options, and their @command{cd} command has the
@option{-P} behavior.
Portable scripts should assume neither option is supported, and should
assume neither behavior is the default. This can be a bit tricky,
since the Posix default behavior means that, for example,
@samp{ls ..} and @samp{cd ..} may refer to different directories if
the current logical directory is a symbolic link. It is safe to use
@code{cd @var{dir}} if @var{dir} contains no @file{..} components.
Also, Autoconf-generated scripts check for this problem when computing
variables like @code{ac_top_srcdir} (@pxref{Configuration Actions}),
so it is safe to @command{cd} to these variables.
See @xref{Special Shell Variables}, for portability problems involving
@command{cd} and the @env{CDPATH} environment variable.
Also please see the discussion of the @command{pwd} command.
@anchor{echo}
@item @command{echo}
@c -----------------
@prindex @command{echo}
The simple @command{echo} is probably the most surprising source of
portability troubles. It is not possible to use @samp{echo} portably
unless both options and escape sequences are omitted. Don't expect any
option.
Do not use backslashes in the arguments, as there is no consensus on
their handling. For @samp{echo '\n' | wc -l}, the @command{sh} of
Solaris outputs 2, but Bash and Zsh (in @command{sh} emulation mode) output 1.
The problem is truly @command{echo}: all the shells
understand @samp{'\n'} as the string composed of a backslash and an
@samp{n}. Within a command substitution, @samp{echo 'string\c'} will
mess up the internal state of ksh88 on AIX 6.1 so that it will print
the first character @samp{s} only, followed by a newline, and then
entirely drop the output of the next echo in a command substitution.
Because of these problems, do not pass a string containing arbitrary
characters to @command{echo}. For example, @samp{echo "$foo"} is safe
if you know that @var{foo}'s value cannot contain backslashes and cannot
start with @samp{-}, but otherwise you should use a here-document like
this:
@example
cat </dev/null &&
@var{action}
@end example
@samp{expr "X@var{foo}" : "X@var{bar}"} is more robust than @samp{echo
"X@var{foo}" | grep "^X@var{bar}"}, because it avoids problems when
@samp{@var{foo}} contains backslashes.
@anchor{trap}
@item @command{trap}
@c -----------------
@prindex @command{trap}
It is safe to trap at least the signals 1, 2, 13, and 15. You can also
trap 0, i.e., have the @command{trap} run when the script ends (either via an
explicit @command{exit}, or the end of the script). The trap for 0 should be
installed outside of a shell function, or @acronym{AIX} 5.3 @command{/bin/sh}
will invoke the trap at the end of this function.
Posix says that @samp{trap - 1 2 13 15} resets the traps for the
specified signals to their default values, but many common shells (e.g.,
Solaris @command{/bin/sh}) misinterpret this and attempt to execute a
``command'' named @command{-} when the specified conditions arise.
Posix 2008 also added a requirement to support @samp{trap 1 2 13 15} to
reset traps, as this is supported by a larger set of shells, but there
are still shells like @command{dash} that mistakenly try to execute
@command{1} instead of resetting the traps. Therefore, there is no
portable workaround, except for @samp{trap - 0}, for which
@samp{trap '' 0} is a portable substitute.
Although Posix is not absolutely clear on this point, it is widely
admitted that when entering the trap @samp{$?} should be set to the exit
status of the last command run before the trap. The ambiguity can be
summarized as: ``when the trap is launched by an @command{exit}, what is
the @emph{last} command run: that before @command{exit}, or
@command{exit} itself?''
Bash considers @command{exit} to be the last command, while Zsh and
Solaris @command{/bin/sh} consider that when the trap is run it is
@emph{still} in the @command{exit}, hence it is the previous exit status
that the trap receives:
@example
$ @kbd{cat trap.sh}
trap 'echo $?' 0
(exit 42); exit 0
$ @kbd{zsh trap.sh}
42
$ @kbd{bash trap.sh}
0
@end example
The portable solution is then simple: when you want to @samp{exit 42},
run @samp{(exit 42); exit 42}, the first @command{exit} being used to
set the exit status to 42 for Zsh, and the second to trigger the trap
and pass 42 as exit status for Bash. In M4sh, this is covered by using
@code{AS_EXIT}.
The shell in Free@acronym{BSD} 4.0 has the following bug: @samp{$?} is
reset to 0 by empty lines if the code is inside @command{trap}.
@example
$ @kbd{trap 'false}
echo $?' 0
$ @kbd{exit}
0
@end example
@noindent
Fortunately, this bug only affects @command{trap}.
Several shells fail to execute an exit trap that is defined inside a
subshell, when the last command of that subshell is not a builtin. A
workaround is to use @samp{exit $?} as the shell builtin.
@example
$ @kbd{bash -c '(trap "echo hi" 0; /bin/true)'}
hi
$ @kbd{/bin/sh -c '(trap "echo hi" 0; /bin/true)'}
$ @kbd{/bin/sh -c '(trap "echo hi" 0; /bin/true; exit $?)'}
hi
@end example
@noindent
Likewise, older implementations of @command{bash} failed to preserve
@samp{$?} across an exit trap consisting of a single cleanup command.
@example
$ @kbd{bash -c 'trap "/bin/true" 0; exit 2'; echo $?}
2
$ @kbd{bash-2.05b -c 'trap "/bin/true" 0; exit 2'; echo $?}
0
$ @kbd{bash-2.05b -c 'trap ":; /bin/true" 0; exit 2'; echo $?}
2
@end example
@item @command{true}
@c -----------------
@prindex @command{true}
@c Info cannot handle `:' in index entries.
@c @prindex @command{:}
Don't worry: as far as we know @command{true} is portable.
Nevertheless, it's not always a builtin (e.g., Bash 1.x), and the
portable shell community tends to prefer using @command{:}. This has a
funny side effect: when asked whether @command{false} is more portable
than @command{true} Alexandre Oliva answered:
@quotation
In a sense, yes, because if it doesn't exist, the shell will produce an
exit status of failure, which is correct for @command{false}, but not
for @command{true}.
@end quotation
@anchor{unset}
@item @command{unset}
@c ------------------
@prindex @command{unset}
In some nonconforming shells (e.g., Bash 2.05a), @code{unset FOO} fails
when @code{FOO} is not set. You can use
@smallexample
FOO=; unset FOO
@end smallexample
if you are not sure that @code{FOO} is set.
A few ancient shells lack @command{unset} entirely. For some variables
such as @code{PS1}, you can use a neutralizing value instead:
@smallexample
PS1='$ '
@end smallexample
Usually, shells that do not support @command{unset} need less effort to
make the environment sane, so for example is not a problem if you cannot
unset @command{CDPATH} on those shells. However, Bash 2.01 mishandles
@code{unset MAIL} in some cases and dumps core. So, you should do
something like
@smallexample
( (unset MAIL) || exit 1) >/dev/null 2>&1 && unset MAIL || :
@end smallexample
@noindent
@xref{Special Shell Variables}, for some neutralizing values. Also, see
@ref{export, , Limitations of Builtins}, for
the case of environment variables.
@item @command{wait}
@c -----------------
@prindex @command{wait}
The exit status of @command{wait} is not always reliable.
@end table
@node Limitations of Usual Tools
@section Limitations of Usual Tools
@cindex Limitations of usual tools
The small set of tools you can expect to find on any machine can still
include some limitations you should be aware of.
@comment Between this list and the list of builtins above, we should
@comment mention all the tools in GNU Coding Standards ``Utilities in
@comment Makefiles''.
@c This table includes things like `@command{expr} (|)', so we can't
@c use @table @command.
@table @asis
@item @command{awk}
@c ----------------
@prindex @command{awk}
Don't leave white space before the opening parenthesis in a user function call.
Posix does not allow this and @acronym{GNU} Awk rejects it:
@example
$ @kbd{gawk 'function die () @{ print "Aaaaarg!" @}
BEGIN @{ die () @}'}
gawk: cmd. line:2: BEGIN @{ die () @}
gawk: cmd. line:2: ^ parse error
$ @kbd{gawk 'function die () @{ print "Aaaaarg!" @}
BEGIN @{ die() @}'}
Aaaaarg!
@end example
Posix says that if a program contains only @samp{BEGIN} actions, and
contains no instances of @code{getline}, then the program merely
executes the actions without reading input. However, traditional Awk
implementations (such as Solaris 10 @command{awk}) read and discard
input in this case. Portable scripts can redirect input from
@file{/dev/null} to work around the problem. For example:
@example
awk 'BEGIN @{print "hello world"@}' printf "foo\n|foo\n" | $EGREP '^(|foo|bar)$'
|foo
> printf "bar\nbar|\n" | $EGREP '^(foo|bar|)$'
bar|
> printf "foo\nfoo|\n|bar\nbar\n" | $EGREP '^(foo||bar)$'
foo
|bar
@end example
@command{$EGREP} also suffers the limitations of @command{grep}
(@pxref{grep, , Limitations of Usual Tools}).
@item @command{expr}
@c -----------------
@prindex @command{expr}
Not all implementations obey the Posix rule that @samp{--} separates
options from arguments; likewise, not all implementations provide the
extension to Posix that the first argument can be treated as part of a
valid expression rather than an invalid option if it begins with
@samp{-}. When performing arithmetic, use @samp{expr 0 + $var} if
@samp{$var} might be a negative number, to keep @command{expr} from
interpreting it as an option.
No @command{expr} keyword starts with @samp{X}, so use @samp{expr
X"@var{word}" : 'X@var{regex}'} to keep @command{expr} from
misinterpreting @var{word}.
Don't use @code{length}, @code{substr}, @code{match} and @code{index}.
@item @command{expr} (@samp{|})
@prindex @command{expr} (@samp{|})
You can use @samp{|}. Although Posix does require that @samp{expr
''} return the empty string, it does not specify the result when you
@samp{|} together the empty string (or zero) with the empty string. For
example:
@example
expr '' \| ''
@end example
Posix 1003.2-1992 returns the empty string
for this case, but traditional Unix returns @samp{0} (Solaris is
one such example). In Posix 1003.1-2001, the specification was
changed to match traditional Unix's behavior (which is
bizarre, but it's too late to fix this). Please note that the same
problem does arise when the empty string results from a computation,
as in:
@example
expr bar : foo \| foo : bar
@end example
@noindent
Avoid this portability problem by avoiding the empty string.
@item @command{expr} (@samp{:})
@c ----------------------------
@prindex @command{expr}
Portable @command{expr} regular expressions should use @samp{\} to
escape only characters in the string @samp{$()*.0123456789[\^n@{@}}.
For example, alternation, @samp{\|}, is common but Posix does not
require its support, so it should be avoided in portable scripts.
Similarly, @samp{\+} and @samp{\?} should be avoided.
Portable @command{expr} regular expressions should not begin with
@samp{^}. Patterns are automatically anchored so leading @samp{^} is
not needed anyway.
On the other hand, the behavior of the @samp{$} anchor is not portable
on multi-line strings. Posix is ambiguous whether the anchor applies to
each line, as was done in older versions of @acronym{GNU} Coreutils, or
whether it applies only to the end of the overall string, as in
Coreutils 6.0 and most other implementations.
@example
$ @kbd{baz='foo}
> @kbd{bar'}
$ @kbd{expr "X$baz" : 'X\(foo\)$'}
$ @kbd{expr-5.97 "X$baz" : 'X\(foo\)$'}
foo
@end example
The Posix standard is ambiguous as to whether
@samp{expr 'a' : '\(b\)'} outputs @samp{0} or the empty string.
In practice, it outputs the empty string on most platforms, but portable
scripts should not assume this. For instance, the @acronym{QNX} 4.25 native
@command{expr} returns @samp{0}.
One might think that a way to get a uniform behavior would be to use
the empty string as a default value:
@example
expr a : '\(b\)' \| ''
@end example
@noindent
Unfortunately this behaves exactly as the original expression; see the
@command{expr} (@samp{|}) entry for more information.
Some ancient @command{expr} implementations (e.g., SunOS 4 @command{expr} and
Solaris 8 @command{/usr/ucb/expr}) have a silly length limit that causes
@command{expr} to fail if the matched substring is longer than 120
bytes. In this case, you might want to fall back on @samp{echo|sed} if
@command{expr} fails. Nowadays this is of practical importance only for
the rare installer who mistakenly puts @file{/usr/ucb} before
@file{/usr/bin} in @env{PATH}.
On Mac OS X 10.4, @command{expr} mishandles the pattern @samp{[^-]} in
some cases. For example, the command
@example
expr Xpowerpc-apple-darwin8.1.0 : 'X[^-]*-[^-]*-\(.*\)'
@end example
@noindent
outputs @samp{apple-darwin8.1.0} rather than the correct @samp{darwin8.1.0}.
This particular case can be worked around by substituting @samp{[^--]}
for @samp{[^-]}.
Don't leave, there is some more!
The @acronym{QNX} 4.25 @command{expr}, in addition of preferring @samp{0} to
the empty string, has a funny behavior in its exit status: it's always 1
when parentheses are used!
@example
$ @kbd{val=`expr 'a' : 'a'`; echo "$?: $val"}
0: 1
$ @kbd{val=`expr 'a' : 'b'`; echo "$?: $val"}
1: 0
$ @kbd{val=`expr 'a' : '\(a\)'`; echo "?: $val"}
1: a
$ @kbd{val=`expr 'a' : '\(b\)'`; echo "?: $val"}
1: 0
@end example
@noindent
In practice this can be a big problem if you are ready to catch failures
of @command{expr} programs with some other method (such as using
@command{sed}), since you may get twice the result. For instance
@example
$ @kbd{expr 'a' : '\(a\)' || echo 'a' | sed 's/^\(a\)$/\1/'}
@end example
@noindent
outputs @samp{a} on most hosts, but @samp{aa} on @acronym{QNX} 4.25. A
simple workaround consists of testing @command{expr} and using a variable
set to @command{expr} or to @command{false} according to the result.
Tru64 @command{expr} incorrectly treats the result as a number, if it
can be interpreted that way:
@example
$ @kbd{expr 00001 : '.*\(...\)'}
1
@end example
On @acronym{HP-UX} 11, @command{expr} only supports a single
sub-expression.
@example
$ @kbd{expr 'Xfoo' : 'X\(f\(oo\)*\)$'}
expr: More than one '\(' was used.
@end example
@item @command{fgrep}
@c ------------------
@prindex @command{fgrep}
Posix 1003.1-2001 no longer requires @command{fgrep},
but many hosts do not yet support the Posix
replacement @code{grep -F}. Also, some traditional implementations do
not work on long input lines. To work around these problems, invoke
@code{AC_PROG_FGREP} and then use @code{$FGREP}.
@item @command{find}
@c -----------------
@prindex @command{find}
The option @option{-maxdepth} seems to be @acronym{GNU} specific.
Tru64 v5.1, Net@acronym{BSD} 1.5 and Solaris @command{find}
commands do not understand it.
The replacement of @samp{@{@}} is guaranteed only if the argument is
exactly @emph{@{@}}, not if it's only a part of an argument. For
instance on DU, and @acronym{HP-UX} 10.20 and @acronym{HP-UX} 11:
@example
$ @kbd{touch foo}
$ @kbd{find . -name foo -exec echo "@{@}-@{@}" \;}
@{@}-@{@}
@end example
@noindent
while @acronym{GNU} @command{find} reports @samp{./foo-./foo}.
@anchor{grep}
@item @command{grep}
@c -----------------
@prindex @command{grep}
Portable scripts can rely on the @command{grep} options @option{-c},
@option{-l}, @option{-n}, and @option{-v}, but should avoid other
options. For example, don't use @option{-w}, as Posix does not require
it and Irix 6.5.16m's @command{grep} does not support it. Also,
portable scripts should not combine @option{-c} with @option{-l},
as Posix does not allow this.
Some of the options required by Posix are not portable in practice.
Don't use @samp{grep -q} to suppress output, because many @command{grep}
implementations (e.g., Solaris) do not support @option{-q}.
Don't use @samp{grep -s} to suppress output either, because Posix
says @option{-s} does not suppress output, only some error messages;
also, the @option{-s} option of traditional @command{grep} behaved
like @option{-q} does in most modern implementations. Instead,
redirect the standard output and standard error (in case the file
doesn't exist) of @code{grep} to @file{/dev/null}. Check the exit
status of @code{grep} to determine whether it found a match.
Some traditional @command{grep} implementations do not work on long
input lines. On AIX the default @code{grep} silently truncates long
lines on the input before matching.
Also, many implementations do not support multiple regexps
with @option{-e}: they either reject @option{-e} entirely (e.g., Solaris)
or honor only the last pattern (e.g., @acronym{IRIX} 6.5 and NeXT). To
work around these problems, invoke @code{AC_PROG_GREP} and then use
@code{$GREP}.
Another possible workaround for the multiple @option{-e} problem is to
separate the patterns by newlines, for example:
@example
grep 'foo
bar' in.txt
@end example
@noindent
except that this fails with traditional @command{grep}
implementations and with Open@acronym{BSD} 3.8 @command{grep}.
Traditional @command{grep} implementations (e.g., Solaris) do not
support the @option{-E} or @option{-F} options. To work around these
problems, invoke @code{AC_PROG_EGREP} and then use @code{$EGREP}, and
similarly for @code{AC_PROG_FGREP} and @code{$FGREP}. Even if you are
willing to require support for Posix @command{grep}, your script should
not use both @option{-E} and @option{-F}, since Posix does not allow
this combination.
Portable @command{grep} regular expressions should use @samp{\} only to
escape characters in the string @samp{$()*.0123456789[\^@{@}}. For example,
alternation, @samp{\|}, is common but Posix does not require its
support in basic regular expressions, so it should be avoided in
portable scripts. Solaris and HP-UX @command{grep} do not support it.
Similarly, the following escape sequences should also be avoided:
@samp{\<}, @samp{\>}, @samp{\+}, @samp{\?}, @samp{\`}, @samp{\'},
@samp{\B}, @samp{\b}, @samp{\S}, @samp{\s}, @samp{\W}, and @samp{\w}.
Posix does not specify the behavior of @command{grep} on binary files.
An example where this matters is using @acronym{BSD} @command{grep} to
search text that includes embedded @acronym{ANSI} escape sequences for
colored output to terminals (@samp{\033[m} is the sequence to restore
normal output); the behavior depends on whether input is seekable:
@example
$ @kbd{printf 'esc\033[mape\n' > sample}
$ @kbd{grep . sample}
Binary file sample matches
$ @kbd{cat sample | grep .}
escape
@end example
@item @command{join}
@c -----------------
@prindex @command{join}
Solaris 8 @command{join} has bugs when the second operand is standard
input, and when standard input is a pipe. For example, the following
shell script causes Solaris 8 @command{join} to loop forever:
@example
cat >file <<'EOF'
1 x
2 y
EOF
cat file | join file -
@end example
Use @samp{join - file} instead.
@item @command{ln}
@c ---------------
@prindex @command{ln}
@cindex Symbolic links
Don't rely on @command{ln} having a @option{-f} option. Symbolic links
are not available on old systems; use @samp{$(LN_S)} as a portable substitute.
For versions of the @acronym{DJGPP} before 2.04,
@command{ln} emulates symbolic links
to executables by generating a stub that in turn calls the real
program. This feature also works with nonexistent files like in the
Posix spec. So @samp{ln -s file link} generates @file{link.exe},
which attempts to call @file{file.exe} if run. But this feature only
works for executables, so @samp{cp -p} is used instead for these
systems. @acronym{DJGPP} versions 2.04 and later have full support
for symbolic links.
@item @command{ls}
@c ---------------
@prindex @command{ls}
@cindex Listing directories
The portable options are @option{-acdilrtu}. Current practice is for
@option{-l} to output both owner and group, even though ancient versions
of @command{ls} omitted the group.
On ancient hosts, @samp{ls foo} sent the diagnostic @samp{foo not found}
to standard output if @file{foo} did not exist. Hence a shell command
like @samp{sources=`ls *.c 2>/dev/null`} did not always work, since it
was equivalent to @samp{sources='*.c not found'} in the absence of
@samp{.c} files. This is no longer a practical problem, since current
@command{ls} implementations send diagnostics to standard error.
The behavior of @command{ls} on a directory that is being concurrently
modified is not always predictable, because of a data race where cached
information returned by @code{readdir} does not match the current
directory state. In fact, MacOS 10.5 has an intermittent bug where
@code{readdir}, and thus @command{ls}, sometimes lists a file more than
once if other files were added or removed from the directory immediately
prior to the @command{ls} call. Since @command{ls} already sorts its
output, the duplicate entries can be avoided by piping the results
through @code{uniq}.
@anchor{mkdir}
@item @command{mkdir}
@c ------------------
@prindex @command{mkdir}
@cindex Making directories
No @command{mkdir} option is portable to older systems. Instead of
@samp{mkdir -p @var{file-name}}, you should use
@code{AS_MKDIR_P(@var{file-name})} (@pxref{Programming in M4sh})
or @code{AC_PROG_MKDIR_P} (@pxref{Particular Programs}).
Combining the @option{-m} and @option{-p} options, as in @samp{mkdir -m
go-w -p @var{dir}}, often leads to trouble. Free@acronym{BSD}
@command{mkdir} incorrectly attempts to change the permissions of
@var{dir} even if it already exists. @acronym{HP-UX} 11.23 and
@acronym{IRIX} 6.5 @command{mkdir} often assign the wrong permissions to
any newly-created parents of @var{dir}.
Posix does not clearly specify whether @samp{mkdir -p foo}
should succeed when @file{foo} is a symbolic link to an already-existing
directory. The @acronym{GNU} Core Utilities 5.1.0 @command{mkdir}
succeeds, but Solaris @command{mkdir} fails.
Traditional @code{mkdir -p} implementations suffer from race conditions.
For example, if you invoke @code{mkdir -p a/b} and @code{mkdir -p a/c}
at the same time, both processes might detect that @file{a} is missing,
one might create @file{a}, then the other might try to create @file{a}
and fail with a @code{File exists} diagnostic. The @acronym{GNU} Core
Utilities (@samp{fileutils} version 4.1), Free@acronym{BSD} 5.0,
Net@acronym{BSD} 2.0.2, and Open@acronym{BSD} 2.4 are known to be
race-free when two processes invoke @code{mkdir -p} simultaneously, but
earlier versions are vulnerable. Solaris @command{mkdir} is still
vulnerable as of Solaris 10, and other traditional Unix systems are
probably vulnerable too. This possible race is harmful in parallel
builds when several Make rules call @code{mkdir -p} to
construct directories. You may use
@code{install-sh -d} as a safe replacement, provided this script is
recent enough; the copy shipped with Autoconf 2.60 and Automake 1.10 is
OK, but copies from older versions are vulnerable.
@item @command{mkfifo}
@itemx @command{mknod}
@c -------------------
@prindex @command{mkfifo}
@prindex @command{mknod}
The @acronym{GNU} Coding Standards state that @command{mknod} is safe to use on
platforms where it has been tested to exist; but it is generally portable
only for creating named FIFOs, since device numbers are
platform-specific. Autotest uses @command{mkfifo} to implement parallel
testsuites. Posix states that behavior is unspecified when opening a
named FIFO for both reading and writing; on at least Cygwin, this
results in failure on any attempt to read or write to that file
descriptor.
@item @command{mktemp}
@c -------------------
@prindex @command{mktemp}
@cindex Creating temporary files
Shell scripts can use temporary files safely with @command{mktemp}, but
it does not exist on all systems. A portable way to create a safe
temporary file name is to create a temporary directory with mode 700 and
use a file inside this directory. Both methods prevent attackers from
gaining control, though @command{mktemp} is far less likely to fail
gratuitously under attack.
Here is sample code to create a new temporary directory safely:
@example
# Create a temporary directory $tmp in $TMPDIR (default /tmp).
# Use mktemp if possible; otherwise fall back on mkdir,
# with $RANDOM to make collisions less likely.
: $@{TMPDIR=/tmp@}
@{
tmp=`
(umask 077 && mktemp -d "$TMPDIR/fooXXXXXX") 2>/dev/null
` &&
test -n "$tmp" && test -d "$tmp"
@} || @{
tmp=$TMPDIR/foo$$-$RANDOM
(umask 077 && mkdir "$tmp")
@} || exit $?
@end example
@item @command{mv}
@c ---------------
@prindex @command{mv}
@cindex Moving open files
The only portable options are @option{-f} and @option{-i}.
Moving individual files between file systems is portable (it was in Unix
version 6),
but it is not always atomic: when doing @samp{mv new existing}, there's
a critical section where neither the old nor the new version of
@file{existing} actually exists.
On some systems moving files from @file{/tmp} can sometimes cause
undesirable (but perfectly valid) warnings, even if you created these
files. This is because @file{/tmp} belongs to a group that ordinary
users are not members of, and files created in @file{/tmp} inherit
the group of @file{/tmp}. When the file is copied, @command{mv} issues
a diagnostic without failing:
@smallexample
$ @kbd{touch /tmp/foo}
$ @kbd{mv /tmp/foo .}
@error{}mv: ./foo: set owner/group (was: 100/0): Operation not permitted
$ @kbd{echo $?}
0
$ @kbd{ls foo}
foo
@end smallexample
@noindent
This annoying behavior conforms to Posix, unfortunately.
Moving directories across mount points is not portable, use @command{cp}
and @command{rm}.
@acronym{DOS} variants cannot rename or remove open files, and do not
support commands like @samp{mv foo bar >foo}, even though this is
perfectly portable among Posix hosts.
@item @command{od}
@c ---------------
@prindex @command{od}
In Mac OS X 10.3, @command{od} does not support the
standard Posix options @option{-A}, @option{-j}, @option{-N}, or
@option{-t}, or the @acronym{XSI} option @option{-s}. The only
supported Posix option is @option{-v}, and the only supported
@acronym{XSI} options are those in @option{-bcdox}. The @acronym{BSD}
@command{hexdump} program can be used instead.
This problem no longer exists in Mac OS X 10.4.3.
@item @command{rm}
@c ---------------
@prindex @command{rm}
The @option{-f} and @option{-r} options are portable.
It is not portable to invoke @command{rm} without operands. For
example, on many systems @samp{rm -f -r} (with no other arguments)
silently succeeds without doing anything, but it fails with a diagnostic
on Net@acronym{BSD} 2.0.2.
A file might not be removed even if its parent directory is writable
and searchable. Many Posix hosts cannot remove a mount point, a named
stream, a working directory, or a last link to a file that is being
executed.
@acronym{DOS} variants cannot rename or remove open files, and do not
support commands like @samp{rm foo >foo}, even though this is
perfectly portable among Posix hosts.
@item @command{rmdir}
@c ------------------
@prindex @command{rmdir}
Just as with @command{rm}, some platforms refuse to remove a working
directory.
@anchor{sed}
@item @command{sed}
@c ----------------
@prindex @command{sed}
Patterns should not include the separator (unless escaped), even as part
of a character class. In conformance with Posix, the Cray
@command{sed} rejects @samp{s/[^/]*$//}: use @samp{s,[^/]*$,,}.
Avoid empty patterns within parentheses (i.e., @samp{\(\)}). Posix does
not require support for empty patterns, and Unicos 9 @command{sed} rejects
them.
Unicos 9 @command{sed} loops endlessly on patterns like @samp{.*\n.*}.
Sed scripts should not use branch labels longer than 7 characters and
should not contain comments. @acronym{HP-UX} sed has a limit of 99 commands
(not counting @samp{:} commands) and
48 labels, which can not be circumvented by using more than one script
file. It can execute up to 19 reads with the @samp{r} command per cycle.
Solaris @command{/usr/ucb/sed} rejects usages that exceed a limit of
about 6000 bytes for the internal representation of commands.
Avoid redundant @samp{;}, as some @command{sed} implementations, such as
Net@acronym{BSD} 1.4.2's, incorrectly try to interpret the second
@samp{;} as a command:
@example
$ @kbd{echo a | sed 's/x/x/;;s/x/x/'}
sed: 1: "s/x/x/;;s/x/x/": invalid command code ;
@end example
Input should not have unreasonably long lines, since some @command{sed}
implementations have an input buffer limited to 4000 bytes. Likewise,
not all @command{sed} implementations can handle embedded @code{NUL} or
a missing trailing newline.
Portable @command{sed} regular expressions should use @samp{\} only to escape
characters in the string @samp{$()*.0123456789[\^n@{@}}. For example,
alternation, @samp{\|}, is common but Posix does not require its
support, so it should be avoided in portable scripts. Solaris
@command{sed} does not support alternation; e.g., @samp{sed '/a\|b/d'}
deletes only lines that contain the literal string @samp{a|b}.
Similarly, @samp{\+} and @samp{\?} should be avoided.
Anchors (@samp{^} and @samp{$}) inside groups are not portable.
Nested parentheses in patterns (e.g., @samp{\(\(a*\)b*)\)}) are
quite portable to current hosts, but was not supported by some ancient
@command{sed} implementations like SVR3.
Some @command{sed} implementations, e.g., Solaris,
restrict the special role of the asterisk to one-character regular expressions.
This may lead to unexpected behavior:
@example
$ @kbd{echo '1*23*4' | /usr/bin/sed 's/\(.\)*/x/g'}
x2x4
$ @kbd{echo '1*23*4' | /usr/xpg4/bin/sed 's/\(.\)*/x/g'}
x
@end example
The @option{-e} option is mostly portable.
However, its argument
cannot start with @samp{a}, @samp{c}, or @samp{i},
as this runs afoul of a Tru64 5.1 bug.
Also, its argument cannot be empty, as this fails on @acronym{AIX} 5.3.
Some people prefer to use @samp{-e}:
@example
sed -e '@var{command-1}' \
-e '@var{command-2}'
@end example
@noindent
as opposed to the equivalent:
@example
sed '
@var{command-1}
@var{command-2}
'
@end example
@noindent
The following usage is sometimes equivalent:
@example
sed '@var{command-1};@var{command-2}'
@end example
but Posix says that this use of a semicolon has undefined effect if
@var{command-1}'s verb is @samp{@{}, @samp{a}, @samp{b}, @samp{c},
@samp{i}, @samp{r}, @samp{t}, @samp{w}, @samp{:}, or @samp{#}, so you
should use semicolon only with simple scripts that do not use these
verbs.
Commands inside @{ @} brackets are further restricted. Posix says that
they cannot be preceded by addresses, @samp{!}, or @samp{;}, and that
each command must be followed immediately by a newline, without any
intervening blanks or semicolons. The closing bracket must be alone on
a line, other than white space preceding or following it.
Contrary to yet another urban legend, you may portably use @samp{&} in
the replacement part of the @code{s} command to mean ``what was
matched''. All descendants of Unix version 7 @command{sed}
(at least; we
don't have first hand experience with older @command{sed} implementations) have
supported it.
Posix requires that you must not have any white space between
@samp{!} and the following command. It is OK to have blanks between
the address and the @samp{!}. For instance, on Solaris:
@example
$ @kbd{echo "foo" | sed -n '/bar/ ! p'}
@error{}Unrecognized command: /bar/ ! p
$ @kbd{echo "foo" | sed -n '/bar/! p'}
@error{}Unrecognized command: /bar/! p
$ @kbd{echo "foo" | sed -n '/bar/ !p'}
foo
@end example
Posix also says that you should not combine @samp{!} and @samp{;}. If
you use @samp{!}, it is best to put it on a command that is delimited by
newlines rather than @samp{;}.
Also note that Posix requires that the @samp{b}, @samp{t}, @samp{r}, and
@samp{w} commands be followed by exactly one space before their argument.
On the other hand, no white space is allowed between @samp{:} and the
subsequent label name.
If a sed script is specified on the command line and ends in an
@samp{a}, @samp{c}, or @samp{i} command, the last line of inserted text
should be followed by a newline. Otherwise some @command{sed}
implementations (e.g., Open@acronym{BSD} 3.9) do not append a newline to the
inserted text.
Many @command{sed} implementations (e.g., MacOS X 10.4,
Open@acronym{BSD} 3.9, Solaris 10
@command{/usr/ucb/sed}) strip leading white space from the text of
@samp{a}, @samp{c}, and @samp{i} commands. Prepend a backslash to
work around this incompatibility with Posix:
@example
$ @kbd{echo flushleft | sed 'a\}
> @kbd{ indented}
> @kbd{'}
flushleft
indented
$ @kbd{echo foo | sed 'a\}
> @kbd{\ indented}
> @kbd{'}
flushleft
indented
@end example
Posix requires that with an empty regular expression, the last non-empty
regular expression from either an address specification or substitution
command is applied. However, busybox 1.6.1 complains when using a
substitution command with a replacement containing a back-reference to
an empty regular expression; the workaround is repeating the regular
expression.
@example
$ @kbd{echo abc | busybox sed '/a\(b\)c/ s//\1/'}
sed: No previous regexp.
$ @kbd{echo abc | busybox sed '/a\(b\)c/ s/a\(b\)c/\1/'}
b
@end example
@item @command{sed} (@samp{t})
@c ---------------------------
@prindex @command{sed} (@samp{t})
Some old systems have @command{sed} that ``forget'' to reset their
@samp{t} flag when starting a new cycle. For instance on @acronym{MIPS
RISC/OS}, and on @sc{irix} 5.3, if you run the following @command{sed}
script (the line numbers are not actual part of the texts):
@example
s/keep me/kept/g # a
t end # b
s/.*/deleted/g # c
:end # d
@end example
@noindent
on
@example
delete me # 1
delete me # 2
keep me # 3
delete me # 4
@end example
@noindent
you get
@example
deleted
delete me
kept
deleted
@end example
@noindent
instead of
@example
deleted
deleted
kept
deleted
@end example
Why? When processing line 1, (c) matches, therefore sets the @samp{t}
flag, and the output is produced. When processing
line 2, the @samp{t} flag is still set (this is the bug). Command (a)
fails to match, but @command{sed} is not supposed to clear the @samp{t}
flag when a substitution fails. Command (b) sees that the flag is set,
therefore it clears it, and jumps to (d), hence you get @samp{delete me}
instead of @samp{deleted}. When processing line (3), @samp{t} is clear,
(a) matches, so the flag is set, hence (b) clears the flags and jumps.
Finally, since the flag is clear, line 4 is processed properly.
There are two things one should remember about @samp{t} in @command{sed}.
Firstly, always remember that @samp{t} jumps if @emph{some} substitution
succeeded, not only the immediately preceding substitution. Therefore,
always use a fake @samp{t clear} followed by a @samp{:clear} on the next
line, to reset the @samp{t} flag where needed.
Secondly, you cannot rely on @command{sed} to clear the flag at each new
cycle.
One portable implementation of the script above is:
@example
t clear
:clear
s/keep me/kept/g
t end
s/.*/deleted/g
:end
@end example
@item @command{sleep}
@c ------------------
@prindex @command{sleep}
Using @command{sleep} is generally portable. However, remember that
adding a @command{sleep} to work around timestamp issues, with a minimum
granularity of one second, doesn't scale well for parallel builds on
modern machines with sub-second process completion.
@item @command{sort}
@c -----------------
@prindex @command{sort}
Remember that sort order is influenced by the current locale. Inside
@file{configure}, the C locale is in effect, but in Makefile snippets,
you may need to specify @code{LC_ALL=C sort}.
@item @command{tar}
@c ----------------
@prindex @command{tar}
There are multiple file formats for @command{tar}; if you use Automake,
the macro @code{AM_INIT_AUTOMAKE} has some options controlling which
level of portability to use.
@anchor{touch}
@item @command{touch}
@c ------------------
@prindex @command{touch}
@cindex timestamp resolution
If you specify the desired timestamp (e.g., with the @option{-r}
option), @command{touch} typically uses the @code{utime} or
@code{utimes} system call, which can result in the same kind of
timestamp truncation problems that @samp{cp -p} has.
On ancient @acronym{BSD} systems, @command{touch} or any command that
results in an empty file does not update the timestamps, so use a
command like @command{echo} as a workaround.
Also,
@acronym{GNU} @command{touch} 3.16r (and presumably all before that)
fails to work on SunOS 4.1.3 when the empty file is on an
@acronym{NFS}-mounted 4.2 volume.
However, these problems are no longer of practical concern.
@item @command{tr}
@c ---------------
@prindex @command{tr}
@cindex carriage return, deleting
@cindex deleting carriage return
Not all versions of @command{tr} handle all backslash character escapes.
For example, Solaris 10 @command{/usr/ucb/tr} falls over, even though
Solaris contains more modern @command{tr} in other locations.
Therefore, it is more portable to use octal escapes, even though this
ties the result to @acronym{ASCII}, when using @command{tr} to delete
newlines or carriage returns.
@example
$ @kbd{@{ echo moon; echo light; @} | /usr/ucb/tr -d '\n' ; echo}
moo
light
$ @kbd{@{ echo moon; echo light; @} | /usr/bin/tr -d '\n' ; echo}
moonlight
$ @kbd{@{ echo moon; echo light; @} | /usr/ucb/tr -d '\012' ; echo}
moonlight
@end example
Posix requires @command{tr} to operate on binary files. But at least
Solaris @command{/usr/ucb/tr} still fails to handle @samp{\0} as the
octal escape for @code{NUL}. On Solaris, when using @command{tr} to
neutralize a binary file by converting @code{NUL} to a different
character, it is necessary to use @command{/usr/xpg4/bin/tr} instead.
@example
$ @kbd{printf 'a\0b\n' | /usr/ucb/tr '\0' '~' | wc -c}
3
$ @kbd{printf 'a\0b\n' | /usr/xpg4/bin/tr '\0' '~' | wc -c}
4
@end example
@end table
@node Portable Make
@chapter Portable Make Programming
@prindex @command{make}
@cindex Limitations of @command{make}
Writing portable makefiles is an art. Since a makefile's commands are
executed by the shell, you must consider the shell portability issues
already mentioned. However, other issues are specific to @command{make}
itself.
@menu
* $< in Ordinary Make Rules:: $< in ordinary rules
* Failure in Make Rules:: Failing portably in rules
* Special Chars in Names:: Special Characters in Macro Names
* Backslash-Newline-Newline:: Empty last lines in macro definitions
* Backslash-Newline Comments:: Spanning comments across line boundaries
* Long Lines in Makefiles:: Line length limitations
* Macros and Submakes:: @code{make macro=value} and submakes
* The Make Macro MAKEFLAGS:: @code{$(MAKEFLAGS)} portability issues
* The Make Macro SHELL:: @code{$(SHELL)} portability issues
* Parallel Make:: Parallel @command{make} quirks
* Comments in Make Rules:: Other problems with Make comments
* obj/ and Make:: Don't name a subdirectory @file{obj}
* make -k Status:: Exit status of @samp{make -k}
* VPATH and Make:: @code{VPATH} woes
* Single Suffix Rules:: Single suffix rules and separated dependencies
* Timestamps and Make:: Subsecond timestamp resolution
@end menu
@node $< in Ordinary Make Rules
@section @code{$<} in Ordinary Make Rules
Posix says that the @samp{$<} construct in makefiles can be
used only in inference rules and in the @samp{.DEFAULT} rule; its
meaning in ordinary rules is unspecified. Solaris @command{make}
for instance replaces it with the empty string. Open@acronym{BSD} (3.0 and
later) @command{make} diagnoses these uses and errors out.
@node Failure in Make Rules
@section Failure in Make Rules
Posix 2008 requires that @command{make} must invoke each command with
the equivalent of a @samp{sh -e -c} subshell, which causes the
subshell to exit immediately if a subsidiary simple-command fails,
although not all @command{make} implementations have historically
followed this rule. For
example, the command @samp{touch T; rm -f U} may attempt to
remove @file{U} even if the @command{touch} fails, although this is not
permitted with Posix make. One way to work around failures in simple
commands is to reword them so that they always succeed, e.g., @samp{touch
T || :; rm -f U}.
However, even this approach can run into common bugs in @acronym{BSD}
implementations of the @option{-e} option of @command{sh} and
@command{set} (@pxref{set, , Limitations of Shell Builtins}), so if you
are worried
about porting to buggy @acronym{BSD} shells it may be simpler to migrate
complicated @command{make} actions into separate scripts.
@node Special Chars in Names
@section Special Characters in Make Macro Names
Posix limits macro names to nonempty strings containing only
@acronym{ASCII} letters and digits, @samp{.}, and @samp{_}. Many
@command{make} implementations allow a wider variety of characters, but
portable makefiles should avoid them. It is portable to start a name
with a special character, e.g., @samp{$(.FOO)}.
Some ancient @command{make} implementations don't support leading
underscores in macro names. An example is @acronym{NEWS-OS} 4.2R.
@example
$ @kbd{cat Makefile}
_am_include = #
_am_quote =
all:; @@echo this is test
$ @kbd{make}
Make: Must be a separator on rules line 2. Stop.
$ @kbd{cat Makefile2}
am_include = #
am_quote =
all:; @@echo this is test
$ @kbd{make -f Makefile2}
this is test
@end example
@noindent
However, this problem is no longer of practical concern.
@node Backslash-Newline-Newline
@section Backslash-Newline-Newline in Make Macro Values
@c This has been seen on ia64 hpux 11.20, and on one hppa hpux 10.20,
@c but another hppa hpux 10.20 didn't have it. Bob Proulx
@c thinks it was in hpux 8.0 too.
On some versions of @acronym{HP-UX}, @command{make} reads multiple newlines
following a backslash, continuing to the next non-empty line. For
example,
@example
FOO = one \
BAR = two
test:
: FOO is "$(FOO)"
: BAR is "$(BAR)"
@end example
@noindent
shows @code{FOO} equal to @code{one BAR = two}. Other implementations
sensibly let a backslash continue only to the immediately following
line.
@node Backslash-Newline Comments
@section Backslash-Newline in Make Comments
According to Posix, Make comments start with @code{#}
and continue until an unescaped newline is reached.
@example
$ @kbd{cat Makefile}
# A = foo \
bar \
baz
all:
@@echo ok
$ @kbd{make} # GNU make
ok
@end example
@noindent
However this is not always the case. Some implementations
discard everything from @code{#} through the end of the line, ignoring any
trailing backslash.
@example
$ @kbd{pmake} # BSD make
"Makefile", line 3: Need an operator
Fatal errors encountered -- cannot continue
@end example
@noindent
Therefore, if you want to comment out a multi-line definition, prefix each
line with @code{#}, not only the first.
@example
# A = foo \
# bar \
# baz
@end example
@node Long Lines in Makefiles
@section Long Lines in Makefiles
Tru64 5.1's @command{make} has been reported to crash when given a
makefile with lines longer than around 20 kB. Earlier versions are
reported to exit with @code{Line too long} diagnostics.
@node Macros and Submakes
@section @code{make macro=value} and Submakes
A command-line variable definition such as @code{foo=bar} overrides any
definition of @code{foo} in a makefile. Some @command{make}
implementations (such as @acronym{GNU} @command{make}) propagate this
override to subsidiary invocations of @command{make}. Some other
implementations do not pass the substitution along to submakes.
@example
$ @kbd{cat Makefile}
foo = foo
one:
@@echo $(foo)
$(MAKE) two
two:
@@echo $(foo)
$ @kbd{make foo=bar} # GNU make 3.79.1
bar
make two
make[1]: Entering directory `/home/adl'
bar
make[1]: Leaving directory `/home/adl'
$ @kbd{pmake foo=bar} # BSD make
bar
pmake two
foo
@end example
You have a few possibilities if you do want the @code{foo=bar} override
to propagate to submakes. One is to use the @option{-e}
option, which causes all environment variables to have precedence over
the makefile macro definitions, and declare foo as an environment
variable:
@example
$ @kbd{env foo=bar make -e}
@end example
The @option{-e} option is propagated to submakes automatically,
and since the environment is inherited between @command{make}
invocations, the @code{foo} macro is overridden in
submakes as expected.
This syntax (@code{foo=bar make -e}) is portable only when used
outside of a makefile, for instance from a script or from the
command line. When run inside a @command{make} rule, @acronym{GNU}
@command{make} 3.80 and prior versions forget to propagate the
@option{-e} option to submakes.
Moreover, using @option{-e} could have unexpected side effects if your
environment contains some other macros usually defined by the
makefile. (See also the note about @code{make -e} and @code{SHELL}
below.)
Another way to propagate overrides to submakes is to do it
manually, from your makefile:
@example
foo = foo
one:
@@echo $(foo)
$(MAKE) foo=$(foo) two
two:
@@echo $(foo)
@end example
You need to foresee all macros that a user might want to override if
you do that.
@node The Make Macro MAKEFLAGS
@section The Make Macro MAKEFLAGS
@cindex @code{MAKEFLAGS} and @command{make}
@cindex @command{make} and @code{MAKEFLAGS}
Posix requires @command{make} to use @code{MAKEFLAGS} to affect the
current and recursive invocations of make, but allows implementations
several formats for the variable. It is tricky to parse
@code{$MAKEFLAGS} to determine whether @option{-s} for silent execution
or @option{-k} for continued execution are in effect. For example, you
cannot assume that the first space-separated word in @code{$MAKEFLAGS}
contains single-letter options, since in the Cygwin version of
@acronym{GNU} @command{make} it is either @option{--unix} or
@option{--win32} with the second word containing single-letter options.
@example
$ @kbd{cat Makefile}
all:
@@echo MAKEFLAGS = $(MAKEFLAGS)
$ @kbd{make}
MAKEFLAGS = --unix
$ @kbd{make -k}
MAKEFLAGS = --unix -k
@end example
@node The Make Macro SHELL
@section The Make Macro @code{SHELL}
@cindex @code{SHELL} and @command{make}
@cindex @command{make} and @code{SHELL}
Posix-compliant @command{make} internally uses the @code{$(SHELL)}
macro to spawn shell processes and execute Make rules. This
is a builtin macro supplied by @command{make}, but it can be modified
by a makefile or by a command-line argument.
Not all @command{make} implementations define this @code{SHELL} macro.
Tru64
@command{make} is an example; this implementation always uses
@code{/bin/sh}. So it's a good idea to always define @code{SHELL} in
your makefiles. If you use Autoconf, do
@example
SHELL = @@SHELL@@
@end example
@noindent
If you use Automake, this is done for you.
Do not force @code{SHELL = /bin/sh} because that is not correct
everywhere. Remember, @file{/bin/sh} is not Posix compliant on many
systems, such as FreeBSD 4, NetBSD 3, AIX 3, Solaris 10, or Tru64.
Additionally, @acronym{DJGPP} lacks @code{/bin/sh}, and when its
@acronym{GNU} @command{make} port sees such a setting it enters a
special emulation mode where features like pipes and redirections are
emulated on top of DOS's @command{command.com}. Unfortunately this
emulation is incomplete; for instance it does not handle command
substitutions. Using @code{@@SHELL@@} means that your makefile will
benefit from the same improved shell, such as @command{bash} or
@command{ksh}, that was discovered during @command{configure}, so that
you aren't fighting two different sets of shell bugs between the two
contexts.
Posix-compliant @command{make} should never acquire the value of
$(SHELL) from the environment, even when @code{make -e} is used
(otherwise, think about what would happen to your rules if
@code{SHELL=/bin/tcsh}).
However not all @command{make} implementations have this exception.
For instance it's not surprising that Tru64 @command{make} doesn't
protect @code{SHELL}, since it doesn't use it.
@example
$ @kbd{cat Makefile}
SHELL = /bin/sh
FOO = foo
all:
@@echo $(SHELL)
@@echo $(FOO)
$ @kbd{env SHELL=/bin/tcsh FOO=bar make -e} # Tru64 Make
/bin/tcsh
bar
$ @kbd{env SHELL=/bin/tcsh FOO=bar gmake -e} # GNU make
/bin/sh
bar
@end example
Conversely, @command{make} is not supposed to export any changes to the
macro @code{SHELL} to child processes. Again, many implementations
break this rule:
@example
$ @kbd{cat Makefile}
all:
@@echo $(SHELL)
@@printenv SHELL
$ @kbd{env SHELL=sh make -e SHELL=/bin/ksh} # BSD Make, GNU make 3.80
/bin/ksh
/bin/ksh
$ @kbd{env SHELL=sh gmake -e SHELL=/bin/ksh} # GNU make 3.81
/bin/ksh
sh
@end example
@node Parallel Make
@section Parallel Make
@cindex Parallel @command{make}
Support for parallel execution in @command{make} implementation varies.
Generally, using @acronym{GNU} make is your best bet. When NetBSD
@command{make} is invoked with @option{-j@var{N}}, it will reuse the
same shell for multiple commands within one recipe. This can have
unexpected consequences.@footnote{Note that @acronym{GNU} make has
heuristics to avoid spawning a shell at all if the command is deemed
safe to be executed directly.} For example, change of directories or
variables persist between commands:
@example
all:
@@var=value; cd /; pwd; echo $$var; echo $$$$
@@pwd; echo $$var; echo $$$$
@end example
@noindent
may output the following with @code{make -j1}:
@example
--- all ---
/
value
32235
/
value
32235
@end example
while without @option{-j1}, or with @option{-B}, the output looks less
surprising:
@example
/
value
32238
/tmp
32239
@end example
Another consequence of this is that, if one command in a recipe uses
@code{exit 0} to indicate a successful exit, the shell will be gone
and the remaining commands of this recipe will not be executed.
The above example also shows additional status output NetBSD
@command{make} produces in parallel mode for targets being updated.
Furthermore, parallel NetBSD @command{make} will route standard error
from commands that it spawns into its own standard output, and may
remove leading whitespace from output lines.
You can avoid these issues by using the @option{-B} option to enable
compatibility semantics. However, that will effectively also disable
all parallelism as that will cause prerequisites to be updated in the
order they are listed in a rule.
@node Comments in Make Rules
@section Comments in Make Rules
@cindex Comments in @file{Makefile} rules
@cindex @file{Makefile} rules and comments
Never put comments in a rule.
Some @command{make} treat anything starting with a tab as a command for
the current rule, even if the tab is immediately followed by a @code{#}.
The @command{make} from Tru64 Unix V5.1 is one of them. The following
makefile runs @code{# foo} through the shell.
@example
all:
# foo
@end example
@node obj/ and Make
@section The @file{obj/} Subdirectory and Make
@cindex @file{obj/}, subdirectory
@cindex @acronym{BSD} @command{make} and @file{obj/}
Never name one of your subdirectories @file{obj/} if you don't like
surprises.
If an @file{obj/} directory exists, @acronym{BSD} @command{make} enters it
before reading the makefile. Hence the makefile in the
current directory is not read.
@example
$ @kbd{cat Makefile}
all:
echo Hello
$ @kbd{cat obj/Makefile}
all:
echo World
$ @kbd{make} # GNU make
echo Hello
Hello
$ @kbd{pmake} # BSD make
echo World
World
@end example
@node make -k Status
@section Exit Status of @code{make -k}
@cindex @code{make -k}
Do not rely on the exit status of @code{make -k}. Some implementations
reflect whether they encountered an error in their exit status; other
implementations always succeed.
@example
$ @kbd{cat Makefile}
all:
false
$ @kbd{make -k; echo exit status: $?} # GNU make
false
make: *** [all] Error 1
exit status: 2
$ @kbd{pmake -k; echo exit status: $?} # BSD make
false
*** Error code 1 (continuing)
exit status: 0
@end example
@node VPATH and Make
@section @code{VPATH} and Make
@cindex @code{VPATH}
Posix does not specify the semantics of @code{VPATH}. Typically,
@command{make} supports @code{VPATH}, but its implementation is not
consistent.
Autoconf and Automake support makefiles whose usages of @code{VPATH} are
portable to recent-enough popular implementations of @command{make}, but
to keep the resulting makefiles portable, a package's makefile
prototypes must take the following issues into account. These issues
are complicated and are often poorly understood, and installers who use
@code{VPATH} should expect to find many bugs in this area. If you use
@code{VPATH}, the simplest way to avoid these portability bugs is to
stick with @acronym{GNU} @command{make}, since it is the most
commonly-used @command{make} among Autoconf users.
Here are some known issues with some @code{VPATH}
implementations.
@menu
* Variables listed in VPATH:: @code{VPATH} must be literal on ancient hosts
* VPATH and Double-colon:: Problems with @samp{::} on ancient hosts
* $< in Explicit Rules:: @code{$<} does not work in ordinary rules
* Automatic Rule Rewriting:: @code{VPATH} goes wild on Solaris
* Tru64 Directory Magic:: @command{mkdir} goes wild on Tru64
* Make Target Lookup:: More details about @code{VPATH} lookup
@end menu
@node Variables listed in VPATH
@subsection Variables listed in @code{VPATH}
@cindex @code{VPATH} and variables
@cindex variables and @code{VPATH}
Do not set @code{VPATH} to the value of another variable, for example
@samp{VPATH = $(srcdir)}, because some ancient versions of
@command{make} do not do variable substitutions on the value of
@code{VPATH}. For example, use this
@example
srcdir = @@srcdir@@
VPATH = @@srcdir@@
@end example
@noindent
rather than @samp{VPATH = $(srcdir)}. Note that with @acronym{GNU}
Automake, there is no need to set this yourself.
@node VPATH and Double-colon
@subsection @code{VPATH} and Double-colon Rules
@cindex @code{VPATH} and double-colon rules
@cindex double-colon rules and @code{VPATH}
With ancient versions of Sun @command{make},
any assignment to @code{VPATH} causes @command{make} to execute only
the first set of double-colon rules.
However, this problem is no longer of practical concern.
@node $< in Explicit Rules
@subsection @code{$<} Not Supported in Explicit Rules
@cindex explicit rules, @code{$<}, and @code{VPATH}
@cindex @code{$<}, explicit rules, and @code{VPATH}
@cindex @code{VPATH}, explicit rules, and @code{$<}
Using @code{$<} in explicit rules is not portable.
The prerequisite file must be named explicitly in the rule. If you want
to find the prerequisite via a @code{VPATH} search, you have to code the
whole thing manually. @xref{Build Directories}.
@node Automatic Rule Rewriting
@subsection Automatic Rule Rewriting
@cindex @code{VPATH} and automatic rule rewriting
@cindex automatic rule rewriting and @code{VPATH}
Some @command{make} implementations, such as Solaris and Tru64,
search for prerequisites in @code{VPATH} and
then rewrite each occurrence as a plain word in the rule.
For instance:
@example
# This isn't portable to GNU make.
VPATH = ../pkg/src
f.c: if.c
cp if.c f.c
@end example
@noindent
executes @code{cp ../pkg/src/if.c f.c} if @file{if.c} is
found in @file{../pkg/src}.
However, this rule leads to real problems in practice. For example, if
the source directory contains an ordinary file named @file{test} that is
used in a dependency, Solaris @command{make} rewrites commands like
@samp{if test -r foo; @dots{}} to @samp{if ../pkg/src/test -r foo;
@dots{}}, which is typically undesirable. To avoid this problem,
portable makefiles should never mention a source file whose name is that
of a shell keyword like @file{until} or a shell command like
@command{cat} or @command{gcc} or @command{test}.
Because of these problems @acronym{GNU} @command{make} and many other
@command{make} implementations do not rewrite commands, so portable
makefiles should
search @code{VPATH} manually. It is tempting to write this:
@smallexample
# This isn't portable to Solaris make.
VPATH = ../pkg/src
f.c: if.c
cp `test -f if.c || echo $(VPATH)/`if.c f.c
@end smallexample
@noindent
However, the ``prerequisite rewriting'' still applies here. So if
@file{if.c} is in @file{../pkg/src}, Solaris and Tru64 @command{make}
execute
@smallexample
cp `test -f ../pkg/src/if.c || echo ../pkg/src/`if.c f.c
@end smallexample
@noindent
which reduces to
@example
cp if.c f.c
@end example
@noindent
and thus fails. Oops.
A simple workaround, and good practice anyway, is to use @samp{$?} and
@samp{$@@} when possible:
@smallexample
VPATH = ../pkg/src
f.c: if.c
cp $? $@@
@end smallexample
@noindent
but this does not generalize well to commands with multiple
prerequisites. A more general workaround is to rewrite the rule so that
the prerequisite @file{if.c} never appears as a plain word. For
example, these three rules would be safe, assuming @file{if.c} is in
@file{../pkg/src} and the other files are in the working directory:
@smallexample
VPATH = ../pkg/src
f.c: if.c f1.c
cat `test -f ./if.c || echo $(VPATH)/`if.c f1.c >$@@
g.c: if.c g1.c
cat `test -f 'if.c' || echo $(VPATH)/`if.c g1.c >$@@
h.c: if.c h1.c
cat `test -f "if.c" || echo $(VPATH)/`if.c h1.c >$@@
@end smallexample
Things get worse when your prerequisites are in a macro.
@example
VPATH = ../pkg/src
HEADERS = f.h g.h h.h
install-HEADERS: $(HEADERS)
for i in $(HEADERS); do \
$(INSTALL) -m 644 \
`test -f $$i || echo $(VPATH)/`$$i \
$(DESTDIR)$(includedir)/$$i; \
done
@end example
The above @code{install-HEADERS} rule is not Solaris-proof because @code{for
i in $(HEADERS);} is expanded to @code{for i in f.h g.h h.h;}
where @code{f.h} and @code{g.h} are plain words and are hence
subject to @code{VPATH} adjustments.
If the three files are in @file{../pkg/src}, the rule is run as:
@example
for i in ../pkg/src/f.h ../pkg/src/g.h h.h; do \
install -m 644 \
`test -f $i || echo ../pkg/src/`$i \
/usr/local/include/$i; \
done
@end example
where the two first @command{install} calls fail. For instance,
consider the @code{f.h} installation:
@example
install -m 644 \
`test -f ../pkg/src/f.h || \
echo ../pkg/src/ \
`../pkg/src/f.h \
/usr/local/include/../pkg/src/f.h;
@end example
@noindent
It reduces to:
@example
install -m 644 \
../pkg/src/f.h \
/usr/local/include/../pkg/src/f.h;
@end example
Note that the manual @code{VPATH} search did not cause any problems here;
however this command installs @file{f.h} in an incorrect directory.
Trying to quote @code{$(HEADERS)} in some way, as we did for
@code{foo.c} a few makefiles ago, does not help:
@example
install-HEADERS: $(HEADERS)
headers='$(HEADERS)'; \
for i in $$headers; do \
$(INSTALL) -m 644 \
`test -f $$i || echo $(VPATH)/`$$i \
$(DESTDIR)$(includedir)/$$i; \
done
@end example
Now, @code{headers='$(HEADERS)'} macro-expands to:
@example
headers='f.h g.h h.h'
@end example
@noindent
but @code{g.h} is still a plain word. (As an aside, the idiom
@code{headers='$(HEADERS)'; for i in $$headers;} is a good
idea if @code{$(HEADERS)} can be empty, because some shells diagnose a
syntax error on @code{for i in;}.)
One workaround is to strip this unwanted @file{../pkg/src/} prefix manually:
@example
VPATH = ../pkg/src
HEADERS = f.h g.h h.h
install-HEADERS: $(HEADERS)
headers='$(HEADERS)'; \
for i in $$headers; do \
i=`expr "$$i" : '$(VPATH)/\(.*\)'`;
$(INSTALL) -m 644 \
`test -f $$i || echo $(VPATH)/`$$i \
$(DESTDIR)$(includedir)/$$i; \
done
@end example
Automake does something similar. However the above hack works only if
the files listed in @code{HEADERS} are in the current directory or a
subdirectory; they should not be in an enclosing directory. If we had
@code{HEADERS = ../f.h}, the above fragment would fail in a VPATH
build with Tru64 @command{make}. The reason is that not only does
Tru64 @command{make} rewrite dependencies, but it also simplifies
them. Hence @code{../f.h} becomes @code{../pkg/f.h} instead of
@code{../pkg/src/../f.h}. This obviously defeats any attempt to strip
a leading @file{../pkg/src/} component.
The following example makes the behavior of Tru64 @command{make}
more apparent.
@example
$ @kbd{cat Makefile}
VPATH = sub
all: ../foo
echo ../foo
$ @kbd{ls}
Makefile foo
$ @kbd{make}
echo foo
foo
@end example
@noindent
Dependency @file{../foo} was found in @file{sub/../foo}, but Tru64
@command{make} simplified it as @file{foo}. (Note that the @file{sub/}
directory does not even exist, this just means that the simplification
occurred before the file was checked for.)
For the record here is how SunOS 4 @command{make} behaves on this
example.
@smallexample
$ @kbd{make}
make: Fatal error: Don't know how to make target `../foo'
$ @kbd{mkdir sub}
$ @kbd{make}
echo sub/../foo
sub/../foo
@end smallexample
@node Tru64 Directory Magic
@subsection Tru64 @command{make} Creates Prerequisite Directories Magically
@cindex @code{VPATH} and prerequisite directories
@cindex prerequisite directories and @code{VPATH}
When a prerequisite is a subdirectory of @code{VPATH}, Tru64
@command{make} creates it in the current directory.
@example
$ @kbd{mkdir -p foo/bar build}
$ @kbd{cd build}
$ @kbd{cat >Makefile <dest-stamp
@end example
@c ======================================== Portable C and C++ Programming
@node Portable C and C++
@chapter Portable C and C++ Programming
@cindex Portable C and C++ programming
C and C++ programs often use low-level features of the underlying
system, and therefore are often more difficult to make portable to other
platforms.
Several standards have been developed to help make your programs more
portable. If you write programs with these standards in mind, you can
have greater confidence that your programs work on a wide variety
of systems. @xref{Standards, , Language Standards Supported by
@acronym{GCC}, gcc, Using the @acronym{GNU} Compiler Collection
(@acronym{GCC})}, for a list of C-related
standards. Many programs also assume the
@uref{http://@/www.opengroup.org/@/susv3, Posix standard}.
Some old code is written to be portable to K&R C, which predates any C
standard. K&R C compilers are no longer of practical interest, though,
and the rest of section assumes at least C89, the first C standard.
Program portability is a huge topic, and this section can only briefly
introduce common pitfalls. @xref{System Portability, , Portability
between System Types, standards, @acronym{GNU} Coding Standards}, for
more information.
@menu
* Varieties of Unportability:: How to make your programs unportable
* Integer Overflow:: When integers get too large
* Preprocessor Arithmetic:: @code{#if} expression problems
* Null Pointers:: Properties of null pointers
* Buffer Overruns:: Subscript errors and the like
* Volatile Objects:: @code{volatile} and signals
* Floating Point Portability:: Portable floating-point arithmetic
* Exiting Portably:: Exiting and the exit status
@end menu
@node Varieties of Unportability
@section Varieties of Unportability
@cindex portability
Autoconf tests and ordinary programs often need to test what is allowed
on a system, and therefore they may need to deliberately exceed the
boundaries of what the standards allow, if only to see whether an
optional feature is present. When you write such a program, you should
keep in mind the difference between constraints, unspecified behavior,
and undefined behavior.
In C, a @dfn{constraint} is a rule that the compiler must enforce. An
example constraint is that C programs must not declare a bit-field with
negative width. Tests can therefore reliably assume that programs with
negative-width bit-fields are rejected by a compiler that conforms
to the standard.
@dfn{Unspecified behavior} is valid behavior, where the standard allows
multiple possibilities. For example, the order of evaluation of
function arguments is unspecified. Some unspecified behavior is
@dfn{implementation-defined}, i.e., documented by the implementation,
but since Autoconf tests cannot read the documentation they cannot
distinguish between implementation-defined and other unspecified
behavior. It is common for Autoconf tests to probe implementations to
determine otherwise-unspecified behavior.
@dfn{Undefined behavior} is invalid behavior, where the standard allows
the implementation to do anything it pleases. For example,
dereferencing a null pointer leads to undefined behavior. If possible,
test programs should avoid undefined behavior, since a program with
undefined behavior might succeed on a test that should fail.
The above rules apply to programs that are intended to conform to the
standard. However, strictly-conforming programs are quite rare, since
the standards are so limiting. A major goal of Autoconf is to support
programs that use implementation features not described by the standard,
and it is fairly common for test programs to violate the above rules, if
the programs work well enough in practice.
@node Integer Overflow
@section Integer Overflow
@cindex integer overflow
@cindex overflow, signed integer
@cindex signed integer overflow
@cindex wraparound arithmetic
In practice many portable C programs assume that signed integer overflow wraps
around reliably using two's complement arithmetic. Yet the C standard
says that program behavior is undefined on overflow, and in a few cases
C programs do not work on some modern implementations because their
overflows do not wrap around as their authors expected. Conversely, in
signed integer remainder, the C standard requires overflow
behavior that is commonly not implemented.
@menu
* Integer Overflow Basics:: Why integer overflow is a problem
* Signed Overflow Examples:: Examples of code assuming wraparound
* Optimization and Wraparound:: Optimizations that break uses of wraparound
* Signed Overflow Advice:: Practical advice for signed overflow issues
* Signed Integer Division:: @code{INT_MIN / -1} and @code{INT_MIN % -1}
@end menu
@node Integer Overflow Basics
@subsection Basics of Integer Overflow
@cindex integer overflow
@cindex overflow, signed integer
@cindex signed integer overflow
@cindex wraparound arithmetic
In languages like C, unsigned integer overflow reliably wraps around;
e.g., @code{UINT_MAX + 1} yields zero.
This is guaranteed by the C standard and is
portable in practice, unless you specify aggressive,
nonstandard optimization options
suitable only for special applications.
In contrast, the C standard says that signed integer overflow leads to
undefined behavior where a program can do anything, including dumping
core or overrunning a buffer. The misbehavior can even precede the
overflow. Such an overflow can occur during addition, subtraction,
multiplication, division, and left shift.
Despite this requirement of the standard, many C programs and Autoconf
tests assume that signed integer overflow silently wraps around modulo a
power of two, using two's complement arithmetic, so long as you cast the
resulting value to a signed integer type or store it into a signed
integer variable. If you use conservative optimization flags, such
programs are generally portable to the vast majority of modern
platforms, with a few exceptions discussed later.
For historical reasons the C standard also allows implementations with
ones' complement or signed magnitude arithmetic, but it is safe to
assume two's complement nowadays.
Also, overflow can occur when converting an out-of-range value to a
signed integer type. Here a standard implementation must define what
happens, but this might include raising an exception. In practice all
known implementations support silent wraparound in this case, so you need
not worry about other possibilities.
@node Signed Overflow Examples
@subsection Examples of Code Assuming Wraparound Overflow
@cindex integer overflow
@cindex overflow, signed integer
@cindex signed integer overflow
@cindex wraparound arithmetic
There has long been a tension between what the C standard requires for
signed integer overflow, and what C programs commonly assume. The
standard allows aggressive optimizations based on assumptions that
overflow never occurs, but many practical C programs rely on overflow
wrapping around. These programs do not conform to the standard, but
they commonly work in practice because compiler writers are
understandably reluctant to implement optimizations that would break
many programs, unless perhaps a user specifies aggressive optimization.
The C Standard says that if a program has signed integer overflow its
behavior is undefined, and the undefined behavior can even precede the
overflow. To take an extreme example:
@c Inspired by Robert Dewar's example in
@c (2007-01-01).
@example
if (password == expected_password)
allow_superuser_privileges ();
else if (counter++ == INT_MAX)
abort ();
else
printf ("%d password mismatches\n", counter);
@end example
@noindent
If the @code{int} variable @code{counter} equals @code{INT_MAX},
@code{counter++} must overflow and the behavior is undefined, so the C
standard allows the compiler to optimize away the test against
@code{INT_MAX} and the @code{abort} call.
Worse, if an earlier bug in the program lets the compiler deduce that
@code{counter == INT_MAX} or that @code{counter} previously overflowed,
the C standard allows the compiler to optimize away the password test
and generate code that allows superuser privileges unconditionally.
Despite this requirement by the standard, it has long been common for C
code to assume wraparound arithmetic after signed overflow, and all
known practical C implementations support some C idioms that assume
wraparound signed arithmetic, even if the idioms do not conform
strictly to the standard. If your code looks like the following
examples it will almost surely work with real-world compilers.
Here is an example derived from the 7th Edition Unix implementation of
@code{atoi} (1979-01-10):
@example
char *p;
int f, n;
@dots{}
while (*p >= '0' && *p <= '9')
n = n * 10 + *p++ - '0';
return (f ? -n : n);
@end example
@noindent
Even if the input string is in range, on most modern machines this has
signed overflow when computing the most negative integer (the @code{-n}
overflows) or a value near an extreme integer (the first @code{+}
overflows).
Here is another example, derived from the 7th Edition implementation of
@code{rand} (1979-01-10). Here the programmer expects both
multiplication and addition to wrap on overflow:
@example
static long int randx = 1;
@dots{}
randx = randx * 1103515245 + 12345;
return (randx >> 16) & 077777;
@end example
In the following example, derived from the @acronym{GNU} C Library 2.5
implementation of @code{mktime} (2006-09-09), the code assumes
wraparound arithmetic in @code{+} to detect signed overflow:
@example
time_t t, t1, t2;
int sec_requested, sec_adjustment;
@dots{}
t1 = t + sec_requested;
t2 = t1 + sec_adjustment;
if (((t1 < t) != (sec_requested < 0))
| ((t2 < t1) != (sec_adjustment < 0)))
return -1;
@end example
If your code looks like these examples, it is probably safe even though
it does not strictly conform to the C standard. This might lead one to
believe that one can generally assume wraparound on overflow, but that
is not always true, as can be seen in the next section.
@node Optimization and Wraparound
@subsection Optimizations That Break Wraparound Arithmetic
@cindex loop induction
Compilers sometimes generate code that is incompatible with wraparound
integer arithmetic. A simple example is an algebraic simplification: a
compiler might translate @code{(i * 2000) / 1000} to @code{i * 2}
because it assumes that @code{i * 2000} does not overflow. The
translation is not equivalent to the original when overflow occurs:
e.g., in the typical case of 32-bit signed two's complement wraparound
@code{int}, if @code{i} has type @code{int} and value @code{1073742},
the original expression returns @minus{}2147483 but the optimized
version returns the mathematically correct value 2147484.
More subtly, loop induction optimizations often exploit the undefined
behavior of signed overflow. Consider the following contrived function
@code{sumc}:
@example
int
sumc (int lo, int hi)
@{
int sum = 0;
int i;
for (i = lo; i <= hi; i++)
sum ^= i * 53;
return sum;
@}
@end example
@noindent
To avoid multiplying by 53 each time through the loop, an optimizing
compiler might internally transform @code{sumc} to the equivalent of the
following:
@example
int
transformed_sumc (int lo, int hi)
@{
int sum = 0;
int hic = hi * 53;
int ic;
for (ic = lo * 53; ic <= hic; ic += 53)
sum ^= ic;
return sum;
@}
@end example
@noindent
This transformation is allowed by the C standard, but it is invalid for
wraparound arithmetic when @code{INT_MAX / 53 < hi}, because then the
overflow in computing expressions like @code{hi * 53} can cause the
expression @code{i <= hi} to yield a different value from the
transformed expression @code{ic <= hic}.
For this reason, compilers that use loop induction and similar
techniques often do not support reliable wraparound arithmetic when a
loop induction variable like @code{ic} is involved. Since loop
induction variables are generated by the compiler, and are not visible
in the source code, it is not always trivial to say whether the problem
affects your code.
Hardly any code actually depends on wraparound arithmetic in cases like
these, so in practice these loop induction optimizations are almost
always useful. However, edge cases in this area can cause problems.
For example:
@example
int j;
for (j = 1; 0 < j; j *= 2)
test (j);
@end example
@noindent
Here, the loop attempts to iterate through all powers of 2 that
@code{int} can represent, but the C standard allows a compiler to
optimize away the comparison and generate an infinite loop,
under the argument that behavior is undefined on overflow. As of this
writing this optimization is not done by any production version of
@acronym{GCC} with @option{-O2}, but it might be performed by other
compilers, or by more aggressive @acronym{GCC} optimization options,
and the @acronym{GCC} developers have not decided whether it will
continue to work with @acronym{GCC} and @option{-O2}.
@node Signed Overflow Advice
@subsection Practical Advice for Signed Overflow Issues
@cindex integer overflow
@cindex overflow, signed integer
@cindex signed integer overflow
@cindex wraparound arithmetic
Ideally the safest approach is to avoid signed integer overflow
entirely. For example, instead of multiplying two signed integers, you
can convert them to unsigned integers, multiply the unsigned values,
then test whether the result is in signed range.
Rewriting code in this way will be inconvenient, though, particularly if
the signed values might be negative. Also, it may hurt
performance. Using unsigned arithmetic to check for overflow is
particularly painful to do portably and efficiently when dealing with an
integer type like @code{uid_t} whose width and signedness vary from
platform to platform.
Furthermore, many C applications pervasively assume wraparound behavior
and typically it is not easy to find and remove all these assumptions.
Hence it is often useful to maintain nonstandard code that assumes
wraparound on overflow, instead of rewriting the code. The rest of this
section attempts to give practical advice for this situation.
If your code wants to detect signed integer overflow in @code{sum = a +
b}, it is generally safe to use an expression like @code{(sum < a) != (b
< 0)}.
If your code uses a signed loop index, make sure that the index cannot
overflow, along with all signed expressions derived from the index.
Here is a contrived example of problematic code with two instances of
overflow.
@example
for (i = INT_MAX - 10; i <= INT_MAX; i++)
if (i + 1 < 0)
@{
report_overflow ();
break;
@}
@end example
@noindent
Because of the two overflows, a compiler might optimize away or
transform the two comparisons in a way that is incompatible with the
wraparound assumption.
If your code uses an expression like @code{(i * 2000) / 1000} and you
actually want the multiplication to wrap around on overflow, use
unsigned arithmetic
to do it, e.g., @code{((int) (i * 2000u)) / 1000}.
If your code assumes wraparound behavior and you want to insulate it
against any @acronym{GCC} optimizations that would fail to support that
behavior, you should use @acronym{GCC}'s @option{-fwrapv} option, which
causes signed overflow to wrap around reliably (except for division and
remainder, as discussed in the next section).
If you need to port to platforms where signed integer overflow does not
reliably wrap around (e.g., due to hardware overflow checking, or to
highly aggressive optimizations), you should consider debugging with
@acronym{GCC}'s @option{-ftrapv} option, which causes signed overflow to
raise an exception.
@node Signed Integer Division
@subsection Signed Integer Division and Integer Overflow
@cindex division, integer
Overflow in signed
integer division is not always harmless: for example, on CPUs of the
i386 family, dividing @code{INT_MIN} by @code{-1} yields a SIGFPE signal
which by default terminates the program. Worse, taking the remainder
of these two values typically yields the same signal on these CPUs,
even though the C standard requires @code{INT_MIN % -1} to yield zero
because the expression does not overflow.
@node Preprocessor Arithmetic
@section Preprocessor Arithmetic
@cindex preprocessor arithmetic
In C99, preprocessor arithmetic, used for @code{#if} expressions, must
be evaluated as if all signed values are of type @code{intmax_t} and all
unsigned values of type @code{uintmax_t}. Many compilers are buggy in
this area, though. For example, as of 2007, Sun C mishandles @code{#if
LLONG_MIN < 0} on a platform with 32-bit @code{long int} and 64-bit
@code{long long int}. Also, some older preprocessors mishandle
constants ending in @code{LL}. To work around these problems, you can
compute the value of expressions like @code{LONG_MAX < LLONG_MAX} at
@code{configure}-time rather than at @code{#if}-time.
@node Null Pointers
@section Properties of Null Pointers
@cindex null pointers
Most modern hosts reliably fail when you attempt to dereference a null
pointer.
On almost all modern hosts, null pointers use an all-bits-zero internal
representation, so you can reliably use @code{memset} with 0 to set all
the pointers in an array to null values.
If @code{p} is a null pointer to an object type, the C expression
@code{p + 0} always evaluates to @code{p} on modern hosts, even though
the standard says that it has undefined behavior.
@node Buffer Overruns
@section Buffer Overruns and Subscript Errors
@cindex buffer overruns
Buffer overruns and subscript errors are the most common dangerous
errors in C programs. They result in undefined behavior because storing
outside an array typically modifies storage that is used by some other
object, and most modern systems lack runtime checks to catch these
errors. Programs should not rely on buffer overruns being caught.
There is one exception to the usual rule that a portable program cannot
address outside an array. In C, it is valid to compute the address just
past an object, e.g., @code{&a[N]} where @code{a} has @code{N} elements,
so long as you do not dereference the resulting pointer. But it is not
valid to compute the address just before an object, e.g., @code{&a[-1]};
nor is it valid to compute two past the end, e.g., @code{&a[N+1]}. On
most platforms @code{&a[-1] < &a[0] && &a[N] < &a[N+1]}, but this is not
reliable in general, and it is usually easy enough to avoid the
potential portability problem, e.g., by allocating an extra unused array
element at the start or end.
@uref{http://@/valgrind.org/, Valgrind} can catch many overruns.
@acronym{GCC}
users might also consider using the @option{-fmudflap} option to catch
overruns.
Buffer overruns are usually caused by off-by-one errors, but there are
more subtle ways to get them.
Using @code{int} values to index into an array or compute array sizes
causes problems on typical 64-bit hosts where an array index might
be @math{2^31} or larger. Index values of type @code{size_t} avoid this
problem, but cannot be negative. Index values of type @code{ptrdiff_t}
are signed, and are wide enough in practice.
If you add or multiply two numbers to calculate an array size, e.g.,
@code{malloc (x * sizeof y + z)}, havoc ensues if the addition or
multiplication overflows.
Many implementations of the @code{alloca} function silently misbehave
and can generate buffer overflows if given sizes that are too large.
The size limits are implementation dependent, but are at least 4000
bytes on all platforms that we know about.
The standard functions @code{asctime}, @code{asctime_r}, @code{ctime},
@code{ctime_r}, and @code{gets} are prone to buffer overflows, and
portable code should not use them unless the inputs are known to be
within certain limits. The time-related functions can overflow their
buffers if given timestamps out of range (e.g., a year less than -999
or greater than 9999). Time-related buffer overflows cannot happen with
recent-enough versions of the @acronym{GNU} C library, but are possible
with other
implementations. The @code{gets} function is the worst, since it almost
invariably overflows its buffer when presented with an input line larger
than the buffer.
@node Volatile Objects
@section Volatile Objects
@cindex volatile objects
The keyword @code{volatile} is often misunderstood in portable code.
Its use inhibits some memory-access optimizations, but programmers often
wish that it had a different meaning than it actually does.
@code{volatile} was designed for code that accesses special objects like
memory-mapped device registers whose contents spontaneously change.
Such code is inherently low-level, and it is difficult to specify
portably what @code{volatile} means in these cases. The C standard
says, ``What constitutes an access to an object that has
volatile-qualified type is implementation-defined,'' so in theory each
implementation is supposed to fill in the gap by documenting what
@code{volatile} means for that implementation. In practice, though,
this documentation is usually absent or incomplete.
One area of confusion is the distinction between objects defined with
volatile types, and volatile lvalues. From the C standard's point of
view, an object defined with a volatile type has externally visible
behavior. You can think of such objects as having little oscilloscope
probes attached to them, so that the user can observe some properties of
accesses to them, just as the user can observe data written to output
files. However, the standard does not make it clear whether users can
observe accesses by volatile lvalues to ordinary objects. For example:
@example
/* Declare and access a volatile object.
Accesses to X are "visible" to users. */
static int volatile x;
x = 1;
/* Access two ordinary objects via a volatile lvalue.
It's not clear whether accesses to *P are "visible". */
int y;
int *z = malloc (sizeof (int));
int volatile *p;
p = &y;
*p = 1;
p = z;
*p = 1;
@end example
Programmers often wish that @code{volatile} meant ``Perform the memory
access here and now, without merging several memory accesses, without
changing the memory word size, and without reordering.'' But the C
standard does not require this. For objects defined with a volatile
type, accesses must be done before the next sequence point; but
otherwise merging, reordering, and word-size change is allowed. Worse,
it is not clear from the standard whether volatile lvalues provide more
guarantees in general than nonvolatile lvalues, if the underlying
objects are ordinary.
Even when accessing objects defined with a volatile type,
the C standard allows only
extremely limited signal handlers: the behavior is undefined if a signal
handler reads any nonlocal object, or writes to any nonlocal object
whose type is not @code{sig_atomic_t volatile}, or calls any standard
library function other than @code{abort}, @code{signal}, and (if C99)
@code{_Exit}. Hence C compilers need not worry about a signal handler
disturbing ordinary computation, unless the computation accesses a
@code{sig_atomic_t volatile} lvalue that is not a local variable.
(There is an obscure exception for accesses via a pointer to a volatile
character, since it may point into part of a @code{sig_atomic_t
volatile} object.) Posix
adds to the list of library functions callable from a portable signal
handler, but otherwise is like the C standard in this area.
Some C implementations allow memory-access optimizations within each
translation unit, such that actual behavior agrees with the behavior
required by the standard only when calling a function in some other
translation unit, and a signal handler acts like it was called from a
different translation unit. The C standard hints that in these
implementations, objects referred to by signal handlers ``would require
explicit specification of @code{volatile} storage, as well as other
implementation-defined restrictions.'' But unfortunately even for this
special case these other restrictions are often not documented well.
@xref{Volatiles, , When is a Volatile Object Accessed?, gcc, Using the
@acronym{GNU} Compiler Collection (@acronym{GCC})}, for some
restrictions imposed by @acronym{GCC}. @xref{Defining Handlers, ,
Defining Signal Handlers, libc, The @acronym{GNU} C Library}, for some
restrictions imposed by the @acronym{GNU} C library. Restrictions
differ on other platforms.
If possible, it is best to use a signal handler that fits within the
limits imposed by the C and Posix standards.
If this is not practical, you can try the following rules of thumb. A
signal handler should access only volatile lvalues, preferably lvalues
that refer to objects defined with a volatile type, and should not
assume that the accessed objects have an internally consistent state
if they are larger than a machine word. Furthermore, installers
should employ compilers and compiler options that are commonly used
for building operating system kernels, because kernels often need more
from @code{volatile} than the C Standard requires, and installers who
compile an application in a similar environment can sometimes benefit
from the extra constraints imposed by kernels on compilers.
Admittedly we are handwaving somewhat here, as there are few
guarantees in this area; the rules of thumb may help to fix some bugs
but there is a good chance that they will not fix them all.
For @code{volatile}, C++ has the same problems that C does.
Multithreaded applications have even more problems with @code{volatile},
but they are beyond the scope of this section.
The bottom line is that using @code{volatile} typically hurts
performance but should not hurt correctness. In some cases its use
does help correctness, but these cases are often so poorly understood
that all too often adding @code{volatile} to a data structure merely
alleviates some symptoms of a bug while not fixing the bug in general.
@node Floating Point Portability
@section Floating Point Portability
@cindex floating point
Almost all modern systems use IEEE-754 floating point, and it is safe to
assume IEEE-754 in most portable code these days. For more information,
please see David Goldberg's classic paper
@uref{http://@/www.validlab.com/@/goldberg/@/paper.pdf, What Every Computer
Scientist Should Know About Floating-Point Arithmetic}.
@node Exiting Portably
@section Exiting Portably
@cindex exiting portably
A C or C++ program can exit with status @var{N} by returning
@var{N} from the @code{main} function. Portable programs are supposed
to exit either with status 0 or @code{EXIT_SUCCESS} to succeed, or with
status @code{EXIT_FAILURE} to fail, but in practice it is portable to
fail by exiting with status 1, and test programs that assume Posix can
fail by exiting with status values from 1 through 255. Programs on
SunOS 2.0 (1985) through 3.5.2 (1988) incorrectly exited with zero
status when @code{main} returned nonzero, but ancient systems like these
are no longer of practical concern.
A program can also exit with status @var{N} by passing @var{N} to the
@code{exit} function, and a program can fail by calling the @code{abort}
function. If a program is specialized to just some platforms, it can fail
by calling functions specific to those platforms, e.g., @code{_exit}
(Posix) and @code{_Exit} (C99). However, like other functions, an exit
function should be declared, typically by including a header. For
example, if a C program calls @code{exit}, it should include @file{stdlib.h}
either directly or via the default includes (@pxref{Default Includes}).
A program can fail due to undefined behavior such as dereferencing a null
pointer, but this is not recommended as undefined behavior allows an
implementation to do whatever it pleases and this includes exiting
successfully.
@c ================================================== Manual Configuration
@node Manual Configuration
@chapter Manual Configuration
A few kinds of features can't be guessed automatically by running test
programs. For example, the details of the object-file format, or
special options that need to be passed to the compiler or linker. You
can check for such features using ad-hoc means, such as having
@command{configure} check the output of the @code{uname} program, or
looking for libraries that are unique to particular systems. However,
Autoconf provides a uniform method for handling unguessable features.
@menu
* Specifying Target Triplets:: Specifying target triplets
* Canonicalizing:: Getting the canonical system type
* Using System Type:: What to do with the system type
@end menu
@node Specifying Target Triplets
@section Specifying target triplets
@cindex System type
@cindex Target triplet
@c This node used to be named Specifying Names. The @anchor allows old
@c links to still work.
@anchor{Specifying Names}
Autoconf-generated
@command{configure} scripts can make decisions based on a canonical name
for the system type, or @dfn{target triplet}, which has the form:
@samp{@var{cpu}-@var{vendor}-@var{os}}, where @var{os} can be
@samp{@var{system}} or @samp{@var{kernel}-@var{system}}
@command{configure} can usually guess the canonical name for the type of
system it's running on. To do so it runs a script called
@command{config.guess}, which infers the name using the @code{uname}
command or symbols predefined by the C preprocessor.
Alternately, the user can specify the system type with command line
arguments to @command{configure} (@pxref{System Type}. Doing so is
necessary when
cross-compiling. In the most complex case of cross-compiling, three
system types are involved. The options to specify them are:
@table @option
@item --build=@var{build-type}
the type of system on which the package is being configured and
compiled. It defaults to the result of running @command{config.guess}.
@item --host=@var{host-type}
the type of system on which the package runs. By default it is the
same as the build machine. Specifying it enables the cross-compilation
mode.
@item --target=@var{target-type}
the type of system for which any compiler tools in the package
produce code (rarely needed). By default, it is the same as host.
@end table
If you mean to override the result of @command{config.guess}, use
@option{--build}, not @option{--host}, since the latter enables
cross-compilation. For historical reasons,
whenever you specify @option{--host},
be sure to specify @option{--build} too; this will be fixed in the
future. So, to enter cross-compilation mode, use a command like this
@example
./configure --build=i686-pc-linux-gnu --host=m68k-coff
@end example
@noindent
Note that if you do not specify @option{--host}, @command{configure}
fails if it can't run the code generated by the specified compiler. For
example, configuring as follows fails:
@example
./configure CC=m68k-coff-gcc
@end example
When cross-compiling, @command{configure} will warn about any tools
(compilers, linkers, assemblers) whose name is not prefixed with the
host type. This is an aid to users performing cross-compilation.
Continuing the example above, if a cross-compiler named @command{cc} is
used with a native @command{pkg-config}, then libraries found by
@command{pkg-config} will likely cause subtle build failures; but using
the names @command{m68k-coff-cc} and @command{m68k-coff-pkg-config}
avoids any confusion. Avoiding the warning is as simple as creating the
correct symlinks naming the cross tools.
@cindex @command{config.sub}
@command{configure} recognizes short aliases for many system types; for
example, @samp{decstation} can be used instead of
@samp{mips-dec-ultrix4.2}. @command{configure} runs a script called
@command{config.sub} to canonicalize system type aliases.
This section deliberately omits the description of the obsolete
interface; see @ref{Hosts and Cross-Compilation}.
@node Canonicalizing
@section Getting the Canonical System Type
@cindex System type
@cindex Canonical system type
The following macros make the system type available to @command{configure}
scripts.
@ovindex build_alias
@ovindex host_alias
@ovindex target_alias
The variables @samp{build_alias}, @samp{host_alias}, and
@samp{target_alias} are always exactly the arguments of @option{--build},
@option{--host}, and @option{--target}; in particular, they are left empty
if the user did not use them, even if the corresponding
@code{AC_CANONICAL} macro was run. Any configure script may use these
variables anywhere. These are the variables that should be used when in
interaction with the user.
If you need to recognize some special environments based on their system
type, run the following macros to get canonical system names. These
variables are not set before the macro call.
If you use these macros, you must distribute @command{config.guess} and
@command{config.sub} along with your source code. @xref{Output}, for
information about the @code{AC_CONFIG_AUX_DIR} macro which you can use
to control in which directory @command{configure} looks for those scripts.
@defmac AC_CANONICAL_BUILD
@acindex{CANONICAL_BUILD}
@ovindex build
@ovindex build_cpu
@ovindex build_vendor
@ovindex build_os
Compute the canonical build-system type variable, @code{build}, and its
three individual parts @code{build_cpu}, @code{build_vendor}, and
@code{build_os}.
If @option{--build} was specified, then @code{build} is the
canonicalization of @code{build_alias} by @command{config.sub},
otherwise it is determined by the shell script @command{config.guess}.
@end defmac
@defmac AC_CANONICAL_HOST
@acindex{CANONICAL_HOST}
@ovindex host
@ovindex host_cpu
@ovindex host_vendor
@ovindex host_os
Compute the canonical host-system type variable, @code{host}, and its
three individual parts @code{host_cpu}, @code{host_vendor}, and
@code{host_os}.
If @option{--host} was specified, then @code{host} is the
canonicalization of @code{host_alias} by @command{config.sub},
otherwise it defaults to @code{build}.
@end defmac
@defmac AC_CANONICAL_TARGET
@acindex{CANONICAL_TARGET}
@ovindex target
@ovindex target_cpu
@ovindex target_vendor
@ovindex target_os
Compute the canonical target-system type variable, @code{target}, and its
three individual parts @code{target_cpu}, @code{target_vendor}, and
@code{target_os}.
If @option{--target} was specified, then @code{target} is the
canonicalization of @code{target_alias} by @command{config.sub},
otherwise it defaults to @code{host}.
@end defmac
Note that there can be artifacts due to the backward compatibility
code. See @xref{Hosts and Cross-Compilation}, for more.
@node Using System Type
@section Using the System Type
In @file{configure.ac} the system type is generally used by one or more
@code{case} statements to select system-specifics. Shell wildcards can
be used to match a group of system types.
For example, an extra assembler code object file could be chosen, giving
access to a CPU cycle counter register. @code{$(CYCLE_OBJ)} in the
following would be used in a makefile to add the object to a
program or library.
@example
AS_CASE([$host],
[alpha*-*-*], [CYCLE_OBJ=rpcc.o],
[i?86-*-*], [CYCLE_OBJ=rdtsc.o],
[CYCLE_OBJ=""]
)
AC_SUBST([CYCLE_OBJ])
@end example
@code{AC_CONFIG_LINKS} (@pxref{Configuration Links}) is another good way
to select variant source files, for example optimized code for some
CPUs. The configured CPU type doesn't always indicate exact CPU types,
so some runtime capability checks may be necessary too.
@example
case $host in
alpha*-*-*) AC_CONFIG_LINKS([dither.c:alpha/dither.c]) ;;
powerpc*-*-*) AC_CONFIG_LINKS([dither.c:powerpc/dither.c]) ;;
*-*-*) AC_CONFIG_LINKS([dither.c:generic/dither.c]) ;;
esac
@end example
The host system type can also be used to find cross-compilation tools
with @code{AC_CHECK_TOOL} (@pxref{Generic Programs}).
The above examples all show @samp{$host}, since this is where the code
is going to run. Only rarely is it necessary to test @samp{$build}
(which is where the build is being done).
Whenever you're tempted to use @samp{$host} it's worth considering
whether some sort of probe would be better. New system types come along
periodically or previously missing features are added. Well-written
probes can adapt themselves to such things, but hard-coded lists of
names can't. Here are some guidelines,
@itemize @bullet
@item
Availability of libraries and library functions should always be checked
by probing.
@item
Variant behavior of system calls is best identified with runtime tests
if possible, but bug workarounds or obscure difficulties might have to
be driven from @samp{$host}.
@item
Assembler code is inevitably highly CPU-specific and is best selected
according to @samp{$host_cpu}.
@item
Assembler variations like underscore prefix on globals or ELF versus
COFF type directives are however best determined by probing, perhaps
even examining the compiler output.
@end itemize
@samp{$target} is for use by a package creating a compiler or similar.
For ordinary packages it's meaningless and should not be used. It
indicates what the created compiler should generate code for, if it can
cross-compile. @samp{$target} generally selects various hard-coded CPU
and system conventions, since usually the compiler or tools under
construction themselves determine how the target works.
@c ===================================================== Site Configuration.
@node Site Configuration
@chapter Site Configuration
@command{configure} scripts support several kinds of local configuration
decisions. There are ways for users to specify where external software
packages are, include or exclude optional features, install programs
under modified names, and set default values for @command{configure}
options.
@menu
* Help Formatting:: Customizing @samp{configure --help}
* External Software:: Working with other optional software
* Package Options:: Selecting optional features
* Pretty Help Strings:: Formatting help string
* Option Checking:: Controlling checking of @command{configure} options
* Site Details:: Configuring site details
* Transforming Names:: Changing program names when installing
* Site Defaults:: Giving @command{configure} local defaults
@end menu
@node Help Formatting
@section Controlling Help Output
Users consult @samp{configure --help} to learn of configuration
decisions specific to your package. By default, @command{configure}
breaks this output into sections for each type of option; within each
section, help strings appear in the order @file{configure.ac} defines
them:
@example
Optional Features:
@dots{}
--enable-bar include bar
Optional Packages:
@dots{}
--with-foo use foo
@end example
@defmac AC_PRESERVE_HELP_ORDER
@acindex{PRESERVE_HELP_ORDER}
Request an alternate @option{--help} format, in which options of all
types appear together, in the order defined. Call this macro before any
@code{AC_ARG_ENABLE} or @code{AC_ARG_WITH}.
@example
Optional Features and Packages:
@dots{}
--enable-bar include bar
--with-foo use foo
@end example
@end defmac
@node External Software
@section Working With External Software
@cindex External software
Some packages require, or can optionally use, other software packages
that are already installed. The user can give @command{configure}
command line options to specify which such external software to use.
The options have one of these forms:
@c FIXME: Can't use @ovar here, Texinfo 4.0 goes lunatic and emits something
@c awful.
@example
--with-@var{package}[=@var{arg}]
--without-@var{package}
@end example
For example, @option{--with-gnu-ld} means work with the @acronym{GNU} linker
instead of some other linker. @option{--with-x} means work with The X
Window System.
The user can give an argument by following the package name with
@samp{=} and the argument. Giving an argument of @samp{no} is for
packages that are used by default; it says to @emph{not} use the
package. An argument that is neither @samp{yes} nor @samp{no} could
include a name or number of a version of the other package, to specify
more precisely which other package this program is supposed to work
with. If no argument is given, it defaults to @samp{yes}.
@option{--without-@var{package}} is equivalent to
@option{--with-@var{package}=no}.
Normally @command{configure} scripts complain about
@option{--with-@var{package}} options that they do not support.
@xref{Option Checking}, for details, and for how to override the
defaults.
For each external software package that may be used, @file{configure.ac}
should call @code{AC_ARG_WITH} to detect whether the @command{configure}
user asked to use it. Whether each package is used or not by default,
and which arguments are valid, is up to you.
@anchor{AC_ARG_WITH}
@defmac AC_ARG_WITH (@var{package}, @var{help-string}, @
@ovar{action-if-given}, @ovar{action-if-not-given})
@acindex{ARG_WITH}
If the user gave @command{configure} the option @option{--with-@var{package}}
or @option{--without-@var{package}}, run shell commands
@var{action-if-given}. If neither option was given, run shell commands
@var{action-if-not-given}. The name @var{package} indicates another
software package that this program should work with. It should consist
only of alphanumeric characters, dashes, and dots.
The option's argument is available to the shell commands
@var{action-if-given} in the shell variable @code{withval}, which is
actually just the value of the shell variable named
@code{with_@var{package}}, with any non-alphanumeric characters in
@var{package} changed into @samp{_}. You may use that variable instead,
if you wish.
The argument @var{help-string} is a description of the option that
looks like this:
@example
--with-readline support fancy command line editing
@end example
@noindent
@var{help-string} may be more than one line long, if more detail is
needed. Just make sure the columns line up in @samp{configure
--help}. Avoid tabs in the help string. The easiest way to provide the
proper leading whitespace is to format your @var{help-string} with the macro
@code{AS_HELP_STRING} (@pxref{Pretty Help Strings}).
The following example shows how to use the @code{AC_ARG_WITH} macro in
a common situation. You want to let the user decide whether to enable
support for an external library (e.g., the readline library); if the user
specified neither @option{--with-readline} nor @option{--without-readline},
you want to enable support for readline only if the library is available
on the system.
@c FIXME: Remove AS_IF when the problem of AC_REQUIRE within `if' is solved.
@example
AC_ARG_WITH([readline],
[AS_HELP_STRING([--with-readline],
[support fancy command line editing @@<:@@default=check@@:>@@])],
[],
[with_readline=check])
LIBREADLINE=
AS_IF([test "x$with_readline" != xno],
[AC_CHECK_LIB([readline], [main],
[AC_SUBST([LIBREADLINE], ["-lreadline -lncurses"])
AC_DEFINE([HAVE_LIBREADLINE], [1],
[Define if you have libreadline])
],
[if test "x$with_readline" != xcheck; then
AC_MSG_FAILURE(
[--with-readline was given, but test for readline failed])
fi
], -lncurses)])
@end example
The next example shows how to use @code{AC_ARG_WITH} to give the user the
possibility to enable support for the readline library, in case it is still
experimental and not well tested, and is therefore disabled by default.
@c FIXME: Remove AS_IF when the problem of AC_REQUIRE within `if' is solved.
@example
AC_ARG_WITH([readline],
[AS_HELP_STRING([--with-readline],
[enable experimental support for readline])],
[],
[with_readline=no])
LIBREADLINE=
AS_IF([test "x$with_readline" != xno],
[AC_CHECK_LIB([readline], [main],
[AC_SUBST([LIBREADLINE], ["-lreadline -lncurses"])
AC_DEFINE([HAVE_LIBREADLINE], [1],
[Define if you have libreadline])
],
[AC_MSG_FAILURE(
[--with-readline was given, but test for readline failed])],
[-lncurses])])
@end example
The last example shows how to use @code{AC_ARG_WITH} to give the user the
possibility to disable support for the readline library, given that it is
an important feature and that it should be enabled by default.
@c FIXME: Remove AS_IF when the problem of AC_REQUIRE within `if' is solved.
@example
AC_ARG_WITH([readline],
[AS_HELP_STRING([--without-readline],
[disable support for readline])],
[],
[with_readline=yes])
LIBREADLINE=
AS_IF([test "x$with_readline" != xno],
[AC_CHECK_LIB([readline], [main],
[AC_SUBST([LIBREADLINE], ["-lreadline -lncurses"])
AC_DEFINE([HAVE_LIBREADLINE], [1],
[Define if you have libreadline])
],
[AC_MSG_FAILURE(
[readline test failed (--without-readline to disable)])],
[-lncurses])])
@end example
These three examples can be easily adapted to the case where
@code{AC_ARG_ENABLE} should be preferred to @code{AC_ARG_WITH} (see
@ref{Package Options}).
@end defmac
@node Package Options
@section Choosing Package Options
@cindex Package options
@cindex Options, package
If a software package has optional compile-time features, the user can
give @command{configure} command line options to specify whether to
compile them. The options have one of these forms:
@c FIXME: Can't use @ovar here, Texinfo 4.0 goes lunatic and emits something
@c awful.
@example
--enable-@var{feature}[=@var{arg}]
--disable-@var{feature}
@end example
These options allow users to choose which optional features to build and
install. @option{--enable-@var{feature}} options should never make a
feature behave differently or cause one feature to replace another.
They should only cause parts of the program to be built rather than left
out.
The user can give an argument by following the feature name with
@samp{=} and the argument. Giving an argument of @samp{no} requests
that the feature @emph{not} be made available. A feature with an
argument looks like @option{--enable-debug=stabs}. If no argument is
given, it defaults to @samp{yes}. @option{--disable-@var{feature}} is
equivalent to @option{--enable-@var{feature}=no}.
Normally @command{configure} scripts complain about
@option{--enable-@var{package}} options that they do not support.
@xref{Option Checking}, for details, and for how to override the
defaults.
For each optional feature, @file{configure.ac} should call
@code{AC_ARG_ENABLE} to detect whether the @command{configure} user asked
to include it. Whether each feature is included or not by default, and
which arguments are valid, is up to you.
@anchor{AC_ARG_ENABLE}
@defmac AC_ARG_ENABLE (@var{feature}, @var{help-string}, @
@ovar{action-if-given}, @ovar{action-if-not-given})
@acindex{ARG_ENABLE}
If the user gave @command{configure} the option
@option{--enable-@var{feature}} or @option{--disable-@var{feature}}, run
shell commands @var{action-if-given}. If neither option was given, run
shell commands @var{action-if-not-given}. The name @var{feature}
indicates an optional user-level facility. It should consist only of
alphanumeric characters, dashes, and dots.
The option's argument is available to the shell commands
@var{action-if-given} in the shell variable @code{enableval}, which is
actually just the value of the shell variable named
@code{enable_@var{feature}}, with any non-alphanumeric characters in
@var{feature} changed into @samp{_}. You may use that variable instead,
if you wish. The @var{help-string} argument is like that of
@code{AC_ARG_WITH} (@pxref{External Software}).
You should format your @var{help-string} with the macro
@code{AS_HELP_STRING} (@pxref{Pretty Help Strings}).
See the examples suggested with the definition of @code{AC_ARG_WITH}
(@pxref{External Software}) to get an idea of possible applications of
@code{AC_ARG_ENABLE}.
@end defmac
@node Pretty Help Strings
@section Making Your Help Strings Look Pretty
@cindex Help strings
Properly formatting the @samp{help strings} which are used in
@code{AC_ARG_WITH} (@pxref{External Software}) and @code{AC_ARG_ENABLE}
(@pxref{Package Options}) can be challenging. Specifically, you want
your own @samp{help strings} to line up in the appropriate columns of
@samp{configure --help} just like the standard Autoconf @samp{help
strings} do. This is the purpose of the @code{AS_HELP_STRING} macro.
@anchor{AS_HELP_STRING}
@defmac AS_HELP_STRING (@var{left-hand-side}, @var{right-hand-side} @
@dvar{indent-column, 26}, @dvar{wrap-column, 79})
@asindex{HELP_STRING}
Expands into a help string that looks pretty when the user executes
@samp{configure --help}. It is typically used in @code{AC_ARG_WITH}
(@pxref{External Software}) or @code{AC_ARG_ENABLE} (@pxref{Package
Options}). The following example makes this clearer.
@example
AC_ARG_WITH([foo],
[AS_HELP_STRING([--with-foo],
[use foo (default is no)])],
[use_foo=$withval],
[use_foo=no])
@end example
Then the last few lines of @samp{configure --help} appear like
this:
@example
--enable and --with options recognized:
--with-foo use foo (default is no)
@end example
Macro expansion is performed on the first argument. However, the second
argument of @code{AS_HELP_STRING} is treated as a whitespace separated
list of text to be reformatted, and is not subject to macro expansion.
Since it is not expanded, it should not be double quoted.
@xref{Autoconf Language}, for a more detailed explanation.
The @code{AS_HELP_STRING} macro is particularly helpful when the
@var{left-hand-side} and/or @var{right-hand-side} are composed of macro
arguments, as shown in the following example. Be aware that
@var{left-hand-side} may not expand to unbalanced quotes,
although quadrigraphs can be used.
@example
AC_DEFUN([MY_ARG_WITH],
[AC_ARG_WITH(m4_translit([[$1]], [_], [-]),
[AS_HELP_STRING([--with-m4_translit([$1], [_], [-])],
[use $1 (default is $2)])],
[use_[]$1=$withval],
[use_[]$1=$2])])
MY_ARG_WITH([a_b], [no])
@end example
@noindent
Here, the last few lines of @samp{configure --help} will include:
@example
--enable and --with options recognized:
--with-a-b use a_b (default is no)
@end example
The parameters @var{indent-column} and @var{wrap-column} were introduced
in Autoconf 2.62. Generally, they should not be specified; they exist
for fine-tuning of the wrapping.
@example
AS_HELP_STRING([--option], [description of option])
@result{} --option description of option
AS_HELP_STRING([--option], [description of option], [15], [30])
@result{} --option description of
@result{} option
@end example
@end defmac
@node Option Checking
@section Controlling Checking of @command{configure} Options
@cindex Options, Package
The @command{configure} script checks its command-line options against a
list of known options, like @option{--help} or @option{--config-cache}.
An unknown option ordinarily indicates a mistake by the user and
@command{configure} halts with an error. However, by default unknown
@option{--with-@var{package}} and @option{--enable-@var{feature}}
options elicit only a warning, to support configuring entire source
trees.
Source trees often contain multiple packages with a top-level
@command{configure} script that uses the @code{AC_CONFIG_SUBDIRS} macro
(@pxref{Subdirectories}). Because the packages generally support
different @option{--with-@var{package}} and
@option{--enable-@var{feature}} options, the @acronym{GNU} Coding
Standards say they must accept unrecognized options without halting.
Even a warning message is undesirable here, so @code{AC_CONFIG_SUBDIRS}
automatically disables the warnings.
This default behavior may be modified in two ways. First, the installer
can invoke @code{configure --disable-option-checking} to disable
these warnings, or invoke @code{configure --enable-option-checking=fatal}
options to turn them into fatal errors, respectively. Second, the
maintainer can use @code{AC_DISABLE_OPTION_CHECKING}.
@defmac AC_DISABLE_OPTION_CHECKING
@acindex{DISABLE_OPTION_CHECKING}
By default, disable warnings related to any unrecognized
@option{--with-@var{package}} or @option{--enable-@var{feature}}
options. This is implied by @code{AC_CONFIG_SUBDIRS}.
The installer can override this behavior by passing
@option{--enable-option-checking} (enable warnings) or
@option{--enable-option-checking=fatal} (enable errors) to
@command{configure}.
@end defmac
@node Site Details
@section Configuring Site Details
@cindex Site details
Some software packages require complex site-specific information. Some
examples are host names to use for certain services, company names, and
email addresses to contact. Since some configuration scripts generated
by Metaconfig ask for such information interactively, people sometimes
wonder how to get that information in Autoconf-generated configuration
scripts, which aren't interactive.
Such site configuration information should be put in a file that is
edited @emph{only by users}, not by programs. The location of the file
can either be based on the @code{prefix} variable, or be a standard
location such as the user's home directory. It could even be specified
by an environment variable. The programs should examine that file at
runtime, rather than at compile time. Runtime configuration is more
convenient for users and makes the configuration process simpler than
getting the information while configuring. @xref{Directory Variables, ,
Variables for Installation Directories, standards, @acronym{GNU} Coding
Standards}, for more information on where to put data files.
@node Transforming Names
@section Transforming Program Names When Installing
@cindex Transforming program names
@cindex Program names, transforming
Autoconf supports changing the names of programs when installing them.
In order to use these transformations, @file{configure.ac} must call the
macro @code{AC_ARG_PROGRAM}.
@defmac AC_ARG_PROGRAM
@acindex{ARG_PROGRAM}
@ovindex program_transform_name
Place in output variable @code{program_transform_name} a sequence of
@code{sed} commands for changing the names of installed programs.
If any of the options described below are given to @command{configure},
program names are transformed accordingly. Otherwise, if
@code{AC_CANONICAL_TARGET} has been called and a @option{--target} value
is given, the target type followed by a dash is used as a prefix.
Otherwise, no program name transformation is done.
@end defmac
@menu
* Transformation Options:: @command{configure} options to transform names
* Transformation Examples:: Sample uses of transforming names
* Transformation Rules:: Makefile uses of transforming names
@end menu
@node Transformation Options
@subsection Transformation Options
You can specify name transformations by giving @command{configure} these
command line options:
@table @option
@item --program-prefix=@var{prefix}
prepend @var{prefix} to the names;
@item --program-suffix=@var{suffix}
append @var{suffix} to the names;
@item --program-transform-name=@var{expression}
perform @code{sed} substitution @var{expression} on the names.
@end table
@node Transformation Examples
@subsection Transformation Examples
These transformations are useful with programs that can be part of a
cross-compilation development environment. For example, a
cross-assembler running on a Sun 4 configured with
@option{--target=i960-vxworks} is normally installed as
@file{i960-vxworks-as}, rather than @file{as}, which could be confused
with a native Sun 4 assembler.
You can force a program name to begin with @file{g}, if you don't want
@acronym{GNU} programs installed on your system to shadow other programs with
the same name. For example, if you configure @acronym{GNU} @code{diff} with
@option{--program-prefix=g}, then when you run @samp{make install} it is
installed as @file{/usr/local/bin/gdiff}.
As a more sophisticated example, you could use
@example
--program-transform-name='s/^/g/; s/^gg/g/; s/^gless/less/'
@end example
@noindent
to prepend @samp{g} to most of the program names in a source tree,
excepting those like @code{gdb} that already have one and those like
@code{less} and @code{lesskey} that aren't @acronym{GNU} programs. (That is
assuming that you have a source tree containing those programs that is
set up to use this feature.)
One way to install multiple versions of some programs simultaneously is
to append a version number to the name of one or both. For example, if
you want to keep Autoconf version 1 around for awhile, you can configure
Autoconf version 2 using @option{--program-suffix=2} to install the
programs as @file{/usr/local/bin/autoconf2},
@file{/usr/local/bin/autoheader2}, etc. Nevertheless, pay attention
that only the binaries are renamed, therefore you'd have problems with
the library files which might overlap.
@node Transformation Rules
@subsection Transformation Rules
Here is how to use the variable @code{program_transform_name} in a
@file{Makefile.in}:
@example
PROGRAMS = cp ls rm
transform = @@program_transform_name@@
install:
for p in $(PROGRAMS); do \
$(INSTALL_PROGRAM) $$p $(DESTDIR)$(bindir)/`echo $$p | \
sed '$(transform)'`; \
done
uninstall:
for p in $(PROGRAMS); do \
rm -f $(DESTDIR)$(bindir)/`echo $$p | sed '$(transform)'`; \
done
@end example
It is guaranteed that @code{program_transform_name} is never empty, and
that there are no useless separators. Therefore you may safely embed
@code{program_transform_name} within a sed program using @samp{;}:
@example
transform = @@program_transform_name@@
transform_exe = s/$(EXEEXT)$$//;$(transform);s/$$/$(EXEEXT)/
@end example
Whether to do the transformations on documentation files (Texinfo or
@code{man}) is a tricky question; there seems to be no perfect answer,
due to the several reasons for name transforming. Documentation is not
usually particular to a specific architecture, and Texinfo files do not
conflict with system documentation. But they might conflict with
earlier versions of the same files, and @code{man} pages sometimes do
conflict with system documentation. As a compromise, it is probably
best to do name transformations on @code{man} pages but not on Texinfo
manuals.
@node Site Defaults
@section Setting Site Defaults
@cindex Site defaults
@cindex config.site
Autoconf-generated @command{configure} scripts allow your site to provide
default values for some configuration values. You do this by creating
site- and system-wide initialization files.
@evindex CONFIG_SITE
If the environment variable @code{CONFIG_SITE} is set, @command{configure}
uses its value as the name of a shell script to read. Otherwise, it
reads the shell script @file{@var{prefix}/share/config.site} if it exists,
then @file{@var{prefix}/etc/config.site} if it exists. Thus,
settings in machine-specific files override those in machine-independent
ones in case of conflict.
Site files can be arbitrary shell scripts, but only certain kinds of
code are really appropriate to be in them. Because @command{configure}
reads any cache file after it has read any site files, a site file can
define a default cache file to be shared between all Autoconf-generated
@command{configure} scripts run on that system (@pxref{Cache Files}). If
you set a default cache file in a site file, it is a good idea to also
set the output variable @code{CC} in that site file, because the cache
file is only valid for a particular compiler, but many systems have
several available.
You can examine or override the value set by a command line option to
@command{configure} in a site file; options set shell variables that have
the same names as the options, with any dashes turned into underscores.
The exceptions are that @option{--without-} and @option{--disable-} options
are like giving the corresponding @option{--with-} or @option{--enable-}
option and the value @samp{no}. Thus, @option{--cache-file=localcache}
sets the variable @code{cache_file} to the value @samp{localcache};
@option{--enable-warnings=no} or @option{--disable-warnings} sets the variable
@code{enable_warnings} to the value @samp{no}; @option{--prefix=/usr} sets the
variable @code{prefix} to the value @samp{/usr}; etc.
Site files are also good places to set default values for other output
variables, such as @code{CFLAGS}, if you need to give them non-default
values: anything you would normally do, repetitively, on the command
line. If you use non-default values for @var{prefix} or
@var{exec_prefix} (wherever you locate the site file), you can set them
in the site file if you specify it with the @code{CONFIG_SITE}
environment variable.
You can set some cache values in the site file itself. Doing this is
useful if you are cross-compiling, where it is impossible to check features
that require running a test program. You could ``prime the cache'' by
setting those values correctly for that system in
@file{@var{prefix}/etc/config.site}. To find out the names of the cache
variables you need to set, look for shell variables with @samp{_cv_} in
their names in the affected @command{configure} scripts, or in the Autoconf
M4 source code for those macros.
The cache file is careful to not override any variables set in the site
files. Similarly, you should not override command-line options in the
site files. Your code should check that variables such as @code{prefix}
and @code{cache_file} have their default values (as set near the top of
@command{configure}) before changing them.
Here is a sample file @file{/usr/share/local/@/gnu/share/@/config.site}. The
command @samp{configure --prefix=/usr/share/local/gnu} would read this
file (if @code{CONFIG_SITE} is not set to a different file).
@example
# /usr/share/local/gnu/share/config.site for configure
#
# Change some defaults.
test "$prefix" = NONE && prefix=/usr/share/local/gnu
test "$exec_prefix" = NONE && exec_prefix=/usr/local/gnu
test "$sharedstatedir" = '$@{prefix@}/com' && sharedstatedir=/var
test "$localstatedir" = '$@{prefix@}/var' && localstatedir=/var
# Give Autoconf 2.x generated configure scripts a shared default
# cache file for feature test results, architecture-specific.
if test "$cache_file" = /dev/null; then
cache_file="$prefix/var/config.cache"
# A cache file is only valid for one C compiler.
CC=gcc
fi
@end example
@cindex Filesystem Hierarchy Standard
@cindex FHS
Another use of @file{config.site} is for priming the directory variables
in a manner consistent with the Filesystem Hierarchy Standard
(@acronym{FHS}). Once the following file is installed at
@file{/usr/share/config.site}, a user can execute simply
@code{./configure --prefix=/usr} to get all the directories chosen in
the locations recommended by @acronym{FHS}.
@example
# /usr/share/config.site for FHS defaults when installing below /usr,
# and the respective settings were not changed on the command line.
if test "$prefix" = /usr; then
test "$sysconfdir" = '$@{prefix@}/etc' && sysconfdir=/etc
test "$sharedstatedir" = '$@{prefix@}/com' && sharedstatedir=/var
test "$localstatedir" = '$@{prefix@}/var' && localstatedir=/var
fi
@end example
@cindex lib64
@cindex 64-bit libraries
Likewise, on platforms where 64-bit libraries are built by default, then
installed in @file{/usr/local/@/lib64} instead of @file{/usr/local/@/lib},
it is appropriate to install @file{/usr/local/@/share/config.site}:
@example
# /usr/local/share/config.site for platforms that prefer
# the directory /usr/local/lib64 over /usr/local/lib.
test "$libdir" = '$@{exec_prefix@}/lib' && libdir='$@{exec_prefix@}/lib64'
@end example
@c ============================================== Running configure Scripts.
@node Running configure Scripts
@chapter Running @command{configure} Scripts
@cindex @command{configure}
Below are instructions on how to configure a package that uses a
@command{configure} script, suitable for inclusion as an @file{INSTALL}
file in the package. A plain-text version of @file{INSTALL} which you
may use comes with Autoconf.
@menu
* Basic Installation:: Instructions for typical cases
* Compilers and Options:: Selecting compilers and optimization
* Multiple Architectures:: Compiling for multiple architectures at once
* Installation Names:: Installing in different directories
* Optional Features:: Selecting optional features
* Particular Systems:: Particular systems
* System Type:: Specifying the system type
* Sharing Defaults:: Setting site-wide defaults for @command{configure}
* Defining Variables:: Specifying the compiler etc.
* configure Invocation:: Changing how @command{configure} runs
@end menu
@set autoconf
@include install.texi
@c ============================================== config.status Invocation
@node config.status Invocation
@chapter config.status Invocation
@cindex @command{config.status}
The @command{configure} script creates a file named @file{config.status},
which actually configures, @dfn{instantiates}, the template files. It
also records the configuration options that were specified when the
package was last configured in case reconfiguring is needed.
Synopsis:
@example
./config.status @ovar{option}@dots{} @ovar{tag}@dots{}
@end example
It configures each @var{tag}; if none are specified, all the templates
are instantiated. A @var{tag} refers to a file or other tag associated
with a configuration action, as specified by an @code{AC_CONFIG_@var{ITEMS}}
macro (@pxref{Configuration Actions}). The files must be specified
without their dependencies, as in
@example
./config.status foobar
@end example
@noindent
not
@example
./config.status foobar:foo.in:bar.in
@end example
The supported options are:
@table @option
@item --help
@itemx -h
Print a summary of the command line options, the list of the template
files, and exit.
@item --version
@itemx -V
Print the version number of Autoconf and the configuration settings,
and exit.
@item --silent
@itemx --quiet
@itemx -q
Do not print progress messages.
@item --debug
@itemx -d
Don't remove the temporary files.
@item --file=@var{file}[:@var{template}]
Require that @var{file} be instantiated as if
@samp{AC_CONFIG_FILES(@var{file}:@var{template})} was used. Both
@var{file} and @var{template} may be @samp{-} in which case the standard
output and/or standard input, respectively, is used. If a
@var{template} file name is relative, it is first looked for in the build
tree, and then in the source tree. @xref{Configuration Actions}, for
more details.
This option and the following ones provide one way for separately
distributed packages to share the values computed by @command{configure}.
Doing so can be useful if some of the packages need a superset of the
features that one of them, perhaps a common library, does. These
options allow a @file{config.status} file to create files other than the
ones that its @file{configure.ac} specifies, so it can be used for a
different package, or for extracting a subset of values. For example,
@example
echo '@@CC@@' | ./config.status --file=-
@end example
@noindent
provides the value of @code{@@CC@@} on standard output.
@item --header=@var{file}[:@var{template}]
Same as @option{--file} above, but with @samp{AC_CONFIG_HEADERS}.
@item --recheck
Ask @file{config.status} to update itself and exit (no instantiation).
This option is useful if you change @command{configure}, so that the
results of some tests might be different from the previous run. The
@option{--recheck} option reruns @command{configure} with the same arguments
you used before, plus the @option{--no-create} option, which prevents
@command{configure} from running @file{config.status} and creating
@file{Makefile} and other files, and the @option{--no-recursion} option,
which prevents @command{configure} from running other @command{configure}
scripts in subdirectories. (This is so other Make rules can
run @file{config.status} when it changes; @pxref{Automatic Remaking},
for an example).
@end table
@file{config.status} checks several optional environment variables that
can alter its behavior:
@anchor{CONFIG_SHELL}
@defvar CONFIG_SHELL
@evindex CONFIG_SHELL
The shell with which to run @command{configure} for the @option{--recheck}
option. It must be Bourne-compatible. The default is a shell that
supports @code{LINENO} if available, and @file{/bin/sh} otherwise.
Invoking @command{configure} by hand bypasses this setting, so you may
need to use a command like @samp{CONFIG_SHELL=/bin/bash /bin/bash ./configure}
to insure that the same shell is used everywhere. The absolute name of the
shell should be passed.
@end defvar
@defvar CONFIG_STATUS
@evindex CONFIG_STATUS
The file name to use for the shell script that records the
configuration. The default is @file{./config.status}. This variable is
useful when one package uses parts of another and the @command{configure}
scripts shouldn't be merged because they are maintained separately.
@end defvar
You can use @file{./config.status} in your makefiles. For example, in
the dependencies given above (@pxref{Automatic Remaking}),
@file{config.status} is run twice when @file{configure.ac} has changed.
If that bothers you, you can make each run only regenerate the files for
that rule:
@example
@group
config.h: stamp-h
stamp-h: config.h.in config.status
./config.status config.h
echo > stamp-h
Makefile: Makefile.in config.status
./config.status Makefile
@end group
@end example
The calling convention of @file{config.status} has changed; see
@ref{Obsolete config.status Use}, for details.
@c =================================================== Obsolete Constructs
@node Obsolete Constructs
@chapter Obsolete Constructs
@cindex Obsolete constructs
Autoconf changes, and throughout the years some constructs have been
obsoleted. Most of the changes involve the macros, but in some cases
the tools themselves, or even some concepts, are now considered
obsolete.
You may completely skip this chapter if you are new to Autoconf. Its
intention is mainly to help maintainers updating their packages by
understanding how to move to more modern constructs.
@menu
* Obsolete config.status Use:: Obsolete convention for @command{config.status}
* acconfig Header:: Additional entries in @file{config.h.in}
* autoupdate Invocation:: Automatic update of @file{configure.ac}
* Obsolete Macros:: Backward compatibility macros
* Autoconf 1:: Tips for upgrading your files
* Autoconf 2.13:: Some fresher tips
@end menu
@node Obsolete config.status Use
@section Obsolete @file{config.status} Invocation
@file{config.status} now supports arguments to specify the files to
instantiate; see @ref{config.status Invocation}, for more details.
Before, environment variables had to be used.
@defvar CONFIG_COMMANDS
@evindex CONFIG_COMMANDS
The tags of the commands to execute. The default is the arguments given
to @code{AC_OUTPUT} and @code{AC_CONFIG_COMMANDS} in
@file{configure.ac}.
@end defvar
@defvar CONFIG_FILES
@evindex CONFIG_FILES
The files in which to perform @samp{@@@var{variable}@@} substitutions.
The default is the arguments given to @code{AC_OUTPUT} and
@code{AC_CONFIG_FILES} in @file{configure.ac}.
@end defvar
@defvar CONFIG_HEADERS
@evindex CONFIG_HEADERS
The files in which to substitute C @code{#define} statements. The
default is the arguments given to @code{AC_CONFIG_HEADERS}; if that
macro was not called, @file{config.status} ignores this variable.
@end defvar
@defvar CONFIG_LINKS
@evindex CONFIG_LINKS
The symbolic links to establish. The default is the arguments given to
@code{AC_CONFIG_LINKS}; if that macro was not called,
@file{config.status} ignores this variable.
@end defvar
In @ref{config.status Invocation}, using this old interface, the example
would be:
@example
@group
config.h: stamp-h
stamp-h: config.h.in config.status
CONFIG_COMMANDS= CONFIG_LINKS= CONFIG_FILES= \
CONFIG_HEADERS=config.h ./config.status
echo > stamp-h
Makefile: Makefile.in config.status
CONFIG_COMMANDS= CONFIG_LINKS= CONFIG_HEADERS= \
CONFIG_FILES=Makefile ./config.status
@end group
@end example
@noindent
(If @file{configure.ac} does not call @code{AC_CONFIG_HEADERS}, there is
no need to set @code{CONFIG_HEADERS} in the @command{make} rules. Equally
for @code{CONFIG_COMMANDS}, etc.)
@node acconfig Header
@section @file{acconfig.h}
@cindex @file{acconfig.h}
@cindex @file{config.h.top}
@cindex @file{config.h.bot}
In order to produce @file{config.h.in}, @command{autoheader} needs to
build or to find templates for each symbol. Modern releases of Autoconf
use @code{AH_VERBATIM} and @code{AH_TEMPLATE} (@pxref{Autoheader
Macros}), but in older releases a file, @file{acconfig.h}, contained the
list of needed templates. @command{autoheader} copied comments and
@code{#define} and @code{#undef} statements from @file{acconfig.h} in
the current directory, if present. This file used to be mandatory if
you @code{AC_DEFINE} any additional symbols.
Modern releases of Autoconf also provide @code{AH_TOP} and
@code{AH_BOTTOM} if you need to prepend/append some information to
@file{config.h.in}. Ancient versions of Autoconf had a similar feature:
if @file{./acconfig.h} contains the string @samp{@@TOP@@},
@command{autoheader} copies the lines before the line containing
@samp{@@TOP@@} into the top of the file that it generates. Similarly,
if @file{./acconfig.h} contains the string @samp{@@BOTTOM@@},
@command{autoheader} copies the lines after that line to the end of the
file it generates. Either or both of those strings may be omitted. An
even older alternate way to produce the same effect in ancient versions
of Autoconf is to create the files @file{@var{file}.top} (typically
@file{config.h.top}) and/or @file{@var{file}.bot} in the current
directory. If they exist, @command{autoheader} copies them to the
beginning and end, respectively, of its output.
In former versions of Autoconf, the files used in preparing a software
package for distribution were:
@example
@group
configure.ac --. .------> autoconf* -----> configure
+---+
[aclocal.m4] --+ `---.
[acsite.m4] ---' |
+--> [autoheader*] -> [config.h.in]
[acconfig.h] ----. |
+-----'
[config.h.top] --+
[config.h.bot] --'
@end group
@end example
Using only the @code{AH_} macros, @file{configure.ac} should be
self-contained, and should not depend upon @file{acconfig.h} etc.
@node autoupdate Invocation
@section Using @command{autoupdate} to Modernize @file{configure.ac}
@cindex @command{autoupdate}
The @command{autoupdate} program updates a @file{configure.ac} file that
calls Autoconf macros by their old names to use the current macro names.
In version 2 of Autoconf, most of the macros were renamed to use a more
uniform and descriptive naming scheme. @xref{Macro Names}, for a
description of the new scheme. Although the old names still work
(@pxref{Obsolete Macros}, for a list of the old macros and the corresponding
new names), you can make your @file{configure.ac} files more readable
and make it easier to use the current Autoconf documentation if you
update them to use the new macro names.
@evindex SIMPLE_BACKUP_SUFFIX
If given no arguments, @command{autoupdate} updates @file{configure.ac},
backing up the original version with the suffix @file{~} (or the value
of the environment variable @code{SIMPLE_BACKUP_SUFFIX}, if that is
set). If you give @command{autoupdate} an argument, it reads that file
instead of @file{configure.ac} and writes the updated file to the
standard output.
@noindent
@command{autoupdate} accepts the following options:
@table @option
@item --help
@itemx -h
Print a summary of the command line options and exit.
@item --version
@itemx -V
Print the version number of Autoconf and exit.
@item --verbose
@itemx -v
Report processing steps.
@item --debug
@itemx -d
Don't remove the temporary files.
@item --force
@itemx -f
Force the update even if the file has not changed. Disregard the cache.
@item --include=@var{dir}
@itemx -I @var{dir}
Also look for input files in @var{dir}. Multiple invocations accumulate.
Directories are browsed from last to first.
@item --prepend-include=@var{dir}
@itemx -B @var{dir}
Prepend directory @var{dir} to the search path. This is used to include
the language-specific files before any third-party macros.
@end table
@node Obsolete Macros
@section Obsolete Macros
Several macros are obsoleted in Autoconf, for various reasons (typically
they failed to quote properly, couldn't be extended for more recent
issues, etc.). They are still supported, but deprecated: their use
should be avoided.
During the jump from Autoconf version 1 to version 2, most of the
macros were renamed to use a more uniform and descriptive naming scheme,
but their signature did not change. @xref{Macro Names}, for a
description of the new naming scheme. Below, if there is just the mapping
from old names to new names for these macros, the reader is invited to
refer to the definition of the new macro for the signature and the
description.
@defmac AC_AIX
@acindex{AIX}
@cvindex _ALL_SOURCE
This macro is a platform-specific subset of
@code{AC_USE_SYSTEM_EXTENSIONS} (@pxref{AC_USE_SYSTEM_EXTENSIONS}).
@end defmac
@defmac AC_ALLOCA
@acindex{ALLOCA}
Replaced by @code{AC_FUNC_ALLOCA} (@pxref{AC_FUNC_ALLOCA}).
@end defmac
@defmac AC_ARG_ARRAY
@acindex{ARG_ARRAY}
Removed because of limited usefulness.
@end defmac
@defmac AC_C_CROSS
@acindex{C_CROSS}
This macro is obsolete; it does nothing.
@end defmac
@defmac AC_C_LONG_DOUBLE
@acindex{C_LONG_DOUBLE}
@cvindex HAVE_LONG_DOUBLE
If the C compiler supports a working @code{long double} type with more
range or precision than the @code{double} type, define
@code{HAVE_LONG_DOUBLE}.
You should use @code{AC_TYPE_LONG_DOUBLE} or
@code{AC_TYPE_LONG_DOUBLE_WIDER} instead. @xref{Particular Types}.
@end defmac
@defmac AC_CANONICAL_SYSTEM
@acindex{CANONICAL_SYSTEM}
Determine the system type and set output variables to the names of the
canonical system types. @xref{Canonicalizing}, for details about the
variables this macro sets.
The user is encouraged to use either @code{AC_CANONICAL_BUILD}, or
@code{AC_CANONICAL_HOST}, or @code{AC_CANONICAL_TARGET}, depending on
the needs. Using @code{AC_CANONICAL_TARGET} is enough to run the two
other macros (@pxref{Canonicalizing}).
@end defmac
@defmac AC_CHAR_UNSIGNED
@acindex{CHAR_UNSIGNED}
Replaced by @code{AC_C_CHAR_UNSIGNED} (@pxref{AC_C_CHAR_UNSIGNED}).
@end defmac
@defmac AC_CHECK_TYPE (@var{type}, @var{default})
@acindex{CHECK_TYPE}
Autoconf, up to 2.13, used to provide this version of
@code{AC_CHECK_TYPE}, deprecated because of its flaws. First, although
it is a member of the @code{CHECK} clan, it does
more than just checking. Secondly, missing types are defined
using @code{#define}, not @code{typedef}, and this can lead to
problems in the case of pointer types.
This use of @code{AC_CHECK_TYPE} is obsolete and discouraged; see
@ref{Generic Types}, for the description of the current macro.
If the type @var{type} is not defined, define it to be the C (or C++)
builtin type @var{default}, e.g., @samp{short int} or @samp{unsigned int}.
This macro is equivalent to:
@example
AC_CHECK_TYPE([@var{type}], [],
[AC_DEFINE_UNQUOTED([@var{type}], [@var{default}],
[Define to `@var{default}'
if does not define.])])
@end example
In order to keep backward compatibility, the two versions of
@code{AC_CHECK_TYPE} are implemented, selected using these heuristics:
@enumerate
@item
If there are three or four arguments, the modern version is used.
@item
If the second argument appears to be a C or C++ type, then the
obsolete version is used. This happens if the argument is a C or C++
@emph{builtin} type or a C identifier ending in @samp{_t}, optionally
followed by one of @samp{[(* } and then by a string of zero or more
characters taken from the set @samp{[]()* _a-zA-Z0-9}.
@item
If the second argument is spelled with the alphabet of valid C and C++
types, the user is warned and the modern version is used.
@item
Otherwise, the modern version is used.
@end enumerate
@noindent
You are encouraged either to use a valid builtin type, or to use the
equivalent modern code (see above), or better yet, to use
@code{AC_CHECK_TYPES} together with
@example
#ifndef HAVE_LOFF_T
typedef loff_t off_t;
#endif
@end example
@end defmac
@c end of AC_CHECK_TYPE
@defmac AC_CHECKING (@var{feature-description})
@acindex{CHECKING}
Same as
@example
AC_MSG_NOTICE([checking @var{feature-description}@dots{}]
@end example
@noindent
@xref{AC_MSG_NOTICE}.
@end defmac
@defmac AC_COMPILE_CHECK (@var{echo-text}, @var{includes}, @
@var{function-body}, @var{action-if-true}, @ovar{action-if-false})
@acindex{COMPILE_CHECK}
This is an obsolete version of @code{AC_TRY_COMPILE} itself replaced by
@code{AC_COMPILE_IFELSE} (@pxref{Running the Compiler}), with the
addition that it prints @samp{checking for @var{echo-text}} to the
standard output first, if @var{echo-text} is non-empty. Use
@code{AC_MSG_CHECKING} and @code{AC_MSG_RESULT} instead to print
messages (@pxref{Printing Messages}).
@end defmac
@defmac AC_CONST
@acindex{CONST}
Replaced by @code{AC_C_CONST} (@pxref{AC_C_CONST}).
@end defmac
@defmac AC_CROSS_CHECK
@acindex{CROSS_CHECK}
Same as @code{AC_C_CROSS}, which is obsolete too, and does nothing
@code{:-)}.
@end defmac
@defmac AC_CYGWIN
@acindex{CYGWIN}
@evindex CYGWIN
Check for the Cygwin environment in which case the shell variable
@code{CYGWIN} is set to @samp{yes}. Don't use this macro, the dignified
means to check the nature of the host is using @code{AC_CANONICAL_HOST}
(@pxref{Canonicalizing}). As a matter of fact this macro is defined as:
@example
AC_REQUIRE([AC_CANONICAL_HOST])[]dnl
case $host_os in
*cygwin* ) CYGWIN=yes;;
* ) CYGWIN=no;;
esac
@end example
Beware that the variable @env{CYGWIN} has a special meaning when
running Cygwin, and should not be changed. That's yet another reason
not to use this macro.
@end defmac
@defmac AC_DECL_SYS_SIGLIST
@acindex{DECL_SYS_SIGLIST}
@cvindex SYS_SIGLIST_DECLARED
Same as:
@example
AC_CHECK_DECLS([sys_siglist], [], [],
[#include