ax_check_gnu_make (Autoconf Archive)

ax_check_gnu_make

Synopsis

AX_CHECK_GNU_MAKE([run-if-true],[run-if-false])

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 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:

  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.

Source Code

Download the latest version of ax_check_gnu_make.m4 or browse the macro’s revision history.

License

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.