bug#7860: recursive autoreconf breaks AM_COND_IF conditionalization of AC_CONFIG_FILES

[Ralf Wildenhues]

* Dave Hart wrote on Tue, Jan 18, 2011 at 10:13:21PM CET:
> When invoked by autoreconf of a project with nested configure.ac
> files, automake does not respect the disabling of AC_CONFIG_FILES by
> the top-level configure.ac using AM_COND_IF, resulting in an incorrect
> Makefile.  Re-running autoreconf from within the nested project
> produces correct output.

I think the underlying issue is the following:
  AM_COND_IF([COND], [... AC_CONFIG_FILES([M]) ...])

can only help to conditionalize the regeneration rules for M that are
produced by automake; that is a decision that can be done at configure
run time.  What you need is something that is decided at automake run
time, more precisely at autoconf --trace'ing time.  AM_COND_IF cannot be
that, because COND is by definition only decided at configure time.

You'd need something like

m4_if([my_m4_variable], [value],
      [AC_CONFIG_FILES([M])])

with a condition that is evaluated at m4 run time.
I don't think you need AM_COND_IF then at all.

Hope that helps.

Cheers,
Ralf