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4.7.4 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 section 10.9 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 section 4.4 Outputting Files, for more information about AC_OUTPUT.

See section 14. Recreating a Configuration, for more examples of handling configuration-related dependencies.


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