Node:Automatic Remaking, Previous:Build Directories, Up:Makefile Substitutions

Automatic Remaking

You can put rules like the following in the top-level Makefile.in for a package to automatically update the configuration information when you change the configuration files. This example includes all of the optional files, such as aclocal.m4 and those related to configuration header files. Omit from the Makefile.in rules for any of these files that your package does not use.

The $(srcdir)/ prefix is included because of limitations in the VPATH mechanism.

The stamp- files are necessary because the timestamps of config.h.in and config.h will not be changed if remaking them does not change their contents. This feature avoids unnecessary recompilation. You should include the file stamp-h.in your package's distribution, so make will consider config.h.in up to date. Don't use touch (see Limitations of Usual Tools), rather use echo (using date would cause needless differences, hence CVS conflicts etc.).

$(srcdir)/configure: configure.ac aclocal.m4
        cd $(srcdir) && autoconf

# autoheader might not change config.h.in, so touch a stamp file.
$(srcdir)/config.h.in: stamp-h.in
$(srcdir)/stamp-h.in: configure.ac aclocal.m4
        cd $(srcdir) && autoheader
        echo timestamp > $(srcdir)/stamp-h.in

config.h: stamp-h
stamp-h: config.h.in config.status
        ./config.status

Makefile: Makefile.in config.status
        ./config.status

config.status: configure
        ./config.status --recheck

(Be careful if you copy these lines directly into your Makefile, as you will need to convert the indented lines to start with the tab character.)

In addition, you should use AC_CONFIG_FILES([stamp-h], [echo timestamp > stamp-h]) so config.status will ensure that config.h is considered up to date. See Output, for more information about AC_OUTPUT.

See config.status Invocation, for more examples of handling configuration-related dependencies.