1# ===========================================================================
2#    https://www.gnu.org/software/autoconf-archive/ax_check_gnu_make.html
3# ===========================================================================
4#
5# SYNOPSIS
6#
7#   AX_CHECK_GNU_MAKE()
8#
9# DESCRIPTION
10#
11#   This macro searches for a GNU version of make. If a match is found:
12#
13#     * The makefile variable `ifGNUmake' is set to the empty string, otherwise
14#       it is set to "#". This is useful for including a special features in a
15#       Makefile, which cannot be handled by other versions of make.
16#     * The variable `_cv_gnu_make_command` is set to the command to invoke
17#       GNU make if it exists, the empty string otherwise.
18#     * The variable `ax_cv_gnu_make_command` is set to the command to invoke
19#       GNU make by copying `_cv_gnu_make_command`, otherwise it is unset.
20#     * If GNU Make is found, its version is extracted from the output of
21#       `make --version` as the last field of a record of space-separated
22#       columns and saved into the variable `ax_check_gnu_make_version`.
23#
24#   Here is an example of its use:
25#
26#   Makefile.in might contain:
27#
28#     # A failsafe way of putting a dependency rule into a makefile
29#     $(DEPEND):
30#             $(CC) -MM $(srcdir)/*.c > $(DEPEND)
31#
32#     @ifGNUmake@ ifeq ($(DEPEND),$(wildcard $(DEPEND)))
33#     @ifGNUmake@ include $(DEPEND)
34#     @ifGNUmake@ endif
35#
36#   Then configure.in would normally contain:
37#
38#     AX_CHECK_GNU_MAKE()
39#     AC_OUTPUT(Makefile)
40#
41#   Then perhaps to cause gnu make to override any other make, we could do
42#   something like this (note that GNU make always looks for GNUmakefile
43#   first):
44#
45#     if  ! test x$_cv_gnu_make_command = x ; then
46#             mv Makefile GNUmakefile
47#             echo .DEFAULT: > Makefile ;
48#             echo \  $_cv_gnu_make_command \$@ >> Makefile;
49#     fi
50#
51#   Then, if any (well almost any) other make is called, and GNU make also
52#   exists, then the other make wraps the GNU make.
53#
54# LICENSE
55#
56#   Copyright (c) 2008 John Darrington <j.darrington@elvis.murdoch.edu.au>
57#   Copyright (c) 2015 Enrico M. Crisostomo <enrico.m.crisostomo@gmail.com>
58#
59#   Copying and distribution of this file, with or without modification, are
60#   permitted in any medium without royalty provided the copyright notice
61#   and this notice are preserved. This file is offered as-is, without any
62#   warranty.
63
64#serial 9
65
66AC_DEFUN([AX_CHECK_GNU_MAKE],dnl
67  [AC_PROG_AWK
68  AC_CACHE_CHECK([for GNU make],[_cv_gnu_make_command],[dnl
69    _cv_gnu_make_command="" ;
70dnl Search all the common names for GNU make
71    for a in "$MAKE" make gmake gnumake ; do
72      if test -z "$a" ; then continue ; fi ;
73      if "$a" --version 2> /dev/null | grep GNU 2>&1 > /dev/null ; then
74        _cv_gnu_make_command=$a ;
75        AX_CHECK_GNU_MAKE_HEADLINE=$("$a" --version 2> /dev/null | grep "GNU Make")
76        ax_check_gnu_make_version=$(echo ${AX_CHECK_GNU_MAKE_HEADLINE} | ${AWK} -F " " '{ print $(NF); }')
77        break ;
78      fi
79    done ;])
80dnl If there was a GNU version, then set @ifGNUmake@ to the empty string, '#' otherwise
81  AS_VAR_IF([_cv_gnu_make_command], [""], [AS_VAR_SET([ifGNUmake], ["#"])],   [AS_VAR_SET([ifGNUmake], [""])])
82  AS_VAR_IF([_cv_gnu_make_command], [""], [AS_UNSET(ax_cv_gnu_make_command)], [AS_VAR_SET([ax_cv_gnu_make_command], [${_cv_gnu_make_command}])])
83  AC_SUBST([ifGNUmake])
84])
85