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 makefile variable `ifnGNUmake' is set to #, otherwise it is set to the empty string. This is useful for including a special features in a Makefile, which can be handled by other versions of make or to specify else like clause. * 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`. * Additionally if GNU Make is found, run shell code run-if-true else run shell code run-if-false.
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 $(DEPEND) @ifGNUmake@ else fallback code @ifGNUmake@ endif
Then configure.in would normally contain:
Then perhaps to cause gnu make to override any other make, we could do something like this (note that GNU make always looks for GNUmakefile first):
if ! test x$_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.
Download the latest version of ax_check_gnu_make.m4 or browse the macro’s revision history.
Copyright © 2008 John Darrington email@example.com
Copyright © 2015 Enrico M. Crisostomo firstname.lastname@example.org
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