1 files changed, 84 insertions, 0 deletions

diff --git a/m4/ax_check_gnu_make.m4 b/m4/ax_check_gnu_make.m4
new file mode 100644
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+++ b/m4/ax_check_gnu_make.m4
@@ -0,0 +1,84 @@
+# ===========================================================================
+#     http://www.gnu.org/software/autoconf-archive/ax_check_gnu_make.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_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.
+#     * The variable `ax_cv_gnu_make_command` is set to the command to invoke
+#       GNU make by copying `_cv_gnu_make_command`, otherwise it is unset.
+#     * If GNU Make is found, its version is extracted from the output of
+#       `make --version` as the last field of a record of space-separated
+#       columns and saved into the variable `ax_check_gnu_make_version`.
+#
+#   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 $(DEPEND)
+#     @ifGNUmake@ endif
+#
+#   Then configure.in would normally contain:
+#
+#     AX_CHECK_GNU_MAKE()
+#     AC_OUTPUT(Makefile)
+#
+#   Then perhaps to cause gnu make to override any other make, we could do
+#   something like this (note that GNU make always looks for GNUmakefile
+#   first):
+#
+#     if  ! test x$_cv_gnu_make_command = x ; then
+#             mv Makefile GNUmakefile
+#             echo .DEFAULT: > Makefile ;
+#             echo \  $_cv_gnu_make_command \$@ >> Makefile;
+#     fi
+#
+#   Then, if any (well almost any) other make is called, and GNU make also
+#   exists, then the other make wraps the GNU make.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 John Darrington <j.darrington@elvis.murdoch.edu.au>
+#   Copyright (c) 2015 Enrico M. Crisostomo <enrico.m.crisostomo@gmail.com>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 8
+
+AC_DEFUN([AX_CHECK_GNU_MAKE],dnl
+  [AC_PROG_AWK
+  AC_CACHE_CHECK([for GNU make],[_cv_gnu_make_command],[dnl
+    _cv_gnu_make_command="" ;
+dnl Search all the common names for GNU make
+    for a in "$MAKE" make gmake gnumake ; do
+      if test -z "$a" ; then continue ; fi ;
+      if "$a" --version 2> /dev/null | grep GNU 2>&1 > /dev/null ; then
+        _cv_gnu_make_command=$a ;
+        AX_CHECK_GNU_MAKE_HEADLINE=$("$a" --version 2> /dev/null | grep "GNU Make")
+        ax_check_gnu_make_version=$(echo ${AX_CHECK_GNU_MAKE_HEADLINE} | ${AWK} -F " " '{ print $(NF); }')
+        break ;
+      fi
+    done ;])
+dnl If there was a GNU version, then set @ifGNUmake@ to the empty string, '#' otherwise
+  AS_VAR_IF([_cv_gnu_make_command], [""], [AS_VAR_SET([ifGNUmake], ["#"])],   [AS_VAR_SET([ifGNUmake], [""])])
+  AS_VAR_IF([_cv_gnu_make_command], [""], [AS_UNSET(ax_cv_gnu_make_command)], [AS_VAR_SET([ax_cv_gnu_make_command], [${_cv_gnu_make_command}])])
+  AC_SUBST([ifGNUmake])
+])