Re: adding gnulib's sys_wait module to groff made Automake angry

[Bruno Haible]

Hi Branden,

> The Automake anger looks like this.
> 
> autoreconf: Entering directory `.'
> autoreconf: configure.ac: not using Gettext
> autoreconf: running: aclocal -I gnulib_m4 --force -I m4 -I gnulib_m4
> autoreconf: configure.ac: tracing
> autoreconf: configure.ac: not using Libtool
> autoreconf: running: /usr/bin/autoconf --include=gnulib_m4 --force
> autoreconf: running: /usr/bin/autoheader --include=gnulib_m4 --force
> autoreconf: running: automake --add-missing --copy --force-missing
> lib/gnulib.mk:1371: error: MOSTLYCLEANDIRS must be set with '=' before using 
> '+='
> Makefile.am:612:   'lib/gnulib.mk' included from here
> autoreconf: automake failed with exit status: 1
> ./bootstrap: autoreconf failed
> 
> Now, sure enough, adding
> 
> MOSTLYCLEANDIRS=
> 
> to Makefile.am right before our list of includes[1] fixes the build.

Good. This is also the way it's documented: [1] says that you need
to initialize MOSTLYCLEANDIRS in your Makefile.am.

> ...but I'm not sure how to explain the change.

It comes up now, because 'sys_wait' is the first Gnulib module that
you are requesting that creates a generated file in a subdirectory.

> Is there some auditing mode I can run automake or
> autoreconf in that will detect this sort of problem before a gnulib
> module sampled at random provokes it?

You could check whether all Makefile.am variables listed in [1]
are initialized in your top-level Makefile.am.

Bruno

[1] 
https://www.gnu.org/software/gnulib/manual/html_node/Modified-build-rules.html