Aegisub/m4macros/check_gnu_make.m4

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##### http://autoconf-archive.cryp.to/check_gnu_make.html
#
# SYNOPSIS
#
# CHECK_GNU_MAKE()
#
# DESCRIPTION
#
# This macro searches for a GNU version of make. If a match is found,
# the makefile variable `ifGNUmake' is set to the empty string,
# otherwise it is set to "#". This is useful for including a special
# features in a Makefile, which cannot be handled by other versions
# of make. The variable _cv_gnu_make_command is set to the command to
# invoke GNU make if it exists, the empty string otherwise.
#
# Here is an example of its use:
#
# Makefile.in might contain:
#
# # A failsafe way of putting a dependency rule into a makefile
# $(DEPEND):
# $(CC) -MM $(srcdir)/*.c > $(DEPEND)
#
# @ifGNUmake@ ifeq ($(DEPEND),$(wildcard $(DEPEND)))
# @ifGNUmake@ include $(DEPEND)
# @ifGNUmake@ endif
#
# Then configure.in would normally contain:
#
# CHECK_GNU_MAKE()
# AC_OUTPUT(Makefile)
#
# Then perhaps to cause gnu make to override any other make, we could
# do something like this (note that GNU make always looks for
# GNUmakefile first):
#
# if ! test x$_cv_gnu_make_command = x ; then
# mv Makefile GNUmakefile
# echo .DEFAULT: > Makefile ;
# echo \ $_cv_gnu_make_command \$@ >> Makefile;
# fi
#
# Then, if any (well almost any) other make is called, and GNU make
# also exists, then the other make wraps the GNU make.
#
# LAST MODIFICATION
#
# 2002-01-04
#
# COPYLEFT
#
# Copyright (c) 2002 John Darrington <j.darrington@elvis.murdoch.edu.au>
#
# Copying and distribution of this file, with or without
# modification, are permitted in any medium without royalty provided
# the copyright notice and this notice are preserved.
AC_DEFUN(
[CHECK_GNU_MAKE], [ AC_CACHE_CHECK( for GNU make,_cv_gnu_make_command,
_cv_gnu_make_command='' ;
dnl Search all the common names for GNU make
for a in "$MAKE" make gmake gnumake ; do
if test -z "$a" ; then continue ; fi ;
if ( sh -c "$a --version" 2> /dev/null | grep GNU 2>&1 > /dev/null ) ; then
_cv_gnu_make_command=$a ;
break;
fi
done ;
) ;
dnl If there was a GNU version, then set @ifGNUmake@ to the empty string, '#' otherwise
if test "x$_cv_gnu_make_command" != "x" ; then
ifGNUmake='' ;
else
ifGNUmake='#' ;
AC_MSG_RESULT("Not found");
fi
AC_SUBST(ifGNUmake)
] )