About a year ago I was wondering exactly the same things. I didn't find autoconf/automake/m4 stuff very easy. When I read your question I decided to make very basic example package that does the things you asked, so I have it documented for myself in the future as well.
Get it here if you are interested:
http://www.xs4all.nl/~heiky/myprog-0.1.tar.gz
It boils down to this:
Quote:
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1. How do I define a custom #define macro in config.h based on configure arguments? eg if I set --with-foo, I would like to have #define WITH_FOO 1 set in config.h
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In your package source directory create a file
"ac_foo.m4" that looks like this:
(this assumes --with-foo to specify a library directory, not "WITH_FOO 1", but you can figure out how to that from this. It will be easier I think)
Code:
AC_DEFUN([AC_FOO], [
AC_ARG_WITH([foo], AC_HELP_STRING([--with-foo=DIR], [Foo directory.]), [foo_dir=$withval])
dnl Do shell scripting here in most cross-platform
dnl compatible bourne shell (sh) code
dnl First make sure there's a default for the foo directory ($foo_dir)
dnl (if --with-foo is not given, m4 parameter here will be empty)
if test "x$foo_dir" = "x"
then
foo_dir=/usr/local/lib/foo
fi
dnl Make configure print a "Checking for..." message.
AC_MSG_CHECKING([for Foo library files])
dnl Find the directory of foo and check to see
dnl if $foo_dir contains what you expect from it.
if ! test -f $foo_dir/foo.so
then
dnl This will exit the configure script
AC_MSG_FAILURE(["Foo library not found!])
fi
dnl If did not exit before this line the foo lib dir is OK.
dnl Set CFLAGS according to what directory we have found
CFLAGS="$CFLAGS -L$foo_dir"
dnl Have configure say that it's OK
AC_MSG_RESULT([yes])
])
Also create a file called
"acinclude.m4" to make the above file known to autoconf. This file should look like this:
Code:
sinclude(ac_foo.m4)
And, to make sure "make dist" and "make distcheck" will package the new files in the distribution make sure this is in your
"Makefile.am":
Code:
EXTRA_DIST = ac_foo.m4
And finally call the new m4 macro (from the file "ac_foo.m4") from
"configure.ac":
Code:
AC_INIT([My Program], [0.1], [you@somewhere.com], [myprog])
AC_CONFIG_SRCDIR([main.c])
AM_INIT_AUTOMAKE
AC_CONFIG_HEADERS([config.h])
AC_PROG_CC
AC_PROG_INSTALL
AC_FOO
AC_CONFIG_FILES([Makefile])
AC_OUTPUT
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2. How do I make the directory variables (eg @includedir, @shareddir etc) visible to my code? I know how to achieve this by adding -D options to AM_CPPFLAGS in Makefile.am, but I would like to have the macros inside config.h. Can this be done?
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I found an m4 file that does this in the "autoconf archive" from the GNU site. It's called
"ac_define_dir:
Code:
dnl Taken from the autoconf archive (www.gnu.org)
dnl
dnl @synopsis AC_DEFINE_DIR(VARNAME, DIR [, DESCRIPTION])
dnl
dnl This macro _AC_DEFINEs VARNAME to the expansion of the DIR
dnl variable, taking care of fixing up ${prefix} and such.
dnl
dnl Note that the 3 argument form is only supported with autoconf 2.13 and
dnl later (i.e. only where _AC_DEFINE supports 3 arguments).
dnl
dnl Examples:
dnl
dnl AC_DEFINE_DIR(DATADIR, datadir)
dnl AC_DEFINE_DIR(PROG_PATH, bindir, [Location of installed binaries])
dnl
dnl @version $Id: ac_define_dir.m4,v 1.1 2002/12/31 02:15:21 heiko Exp $
dnl @author Guido Draheim <guidod@gmx.de>, original by Alexandre Oliva
AC_DEFUN([AC_DEFINE_DIR], [
test "x$prefix" = xNONE && prefix="$ac_default_prefix"
test "x$exec_prefix" = xNONE && exec_prefix='${prefix}'
ac_define_dir=`eval echo [$]$2`
ac_define_dir=`eval echo [$]ac_define_dir`
ifelse($3, ,
AC_DEFINE_UNQUOTED($1, "$ac_define_dir"),
AC_DEFINE_UNQUOTED($1, "$ac_define_dir", $3))
])
To use this, put this file also in your source directory, and like the --with-foo procedure above, mention it in the
"acinclude.m4" file:
Code:
sinclude(ac_foo.m4)
sinclude(ac_define_dir.m4)
..and in your Makefile.am:
Code:
EXTRA_DIST = ac_define_dir.m4 ac_foo.m4
(note that the "ac_foo.m4" stuff from before is also included)
And finally call it from
configure.ac". Here the datadir is #defined in config.h. (the datadir is the directory to store data used by your program. By default ./configure will make it: $PREFIX/share)
Code:
AC_DEFINE_DIR([DATADIR], [datadir], [Directory for data files.])
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3. How do I fail the configure script when a test fails. eg if AC_HEADER_STDC is not found, exit/fail the configure script.
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Use this (also see the first listing in this post):
Code:
AC_MSG_FAILURE(["Your custom error message"])
Like I already said, I've put a working example program package including all this on the web at:
http://www.xs4all.nl/~heiky/myprog-0.1.tar.gz
If you can improve or extend that, I'd be very interested!
