AC_CONFIG_SUBDIRS but immediately

[Gavin Smith]

I would like to configure in a subdirectory of a project.
AC_CONFIG_SUBDIRS accumulates its arguments and does them all at the
end, but I'd like it to be done right away.

I searched the archives of the mailing list and found a few
discussions, e.g.
http://lists.gnu.org/archive/html/autoconf/2008-05/msg00066.html.

What I have currently is

subdirs=tp/Texinfo/Convert/XSParagraph
_AC_OUTPUT_SUBDIRS

which uses an internal Autoconf macro. Obviously this is not ideal
because it could break for different versions of Autoconf.

Copying the code out of Autoconf to use isn't ideal either. if there
isn't an easy way to do this with public macros, could I add my
support for such a thing?

The reason I want to do this is to be able to test the subdirectory in
the configure script to see if building and running it worked, and to
be able to disable it if it didn't. The subdirectory contains a Perl
extension module that is to be dynamically linked into the Perl
interpreter. If it's detected that this doesn't work, the use of the
extension module will be disabled and a module written in interpreted
Perl will be used instead.

It also needs to be resilient against failure of the subsidiary
configure script. This happened due to the AC_PROG_CC macro
discovering that the C compiler didn't exist, or didn't work. This
compiler was the one that that Perl said it was compiled with (output
of "perl -V:cc"), so it's quite possible for it not to exist or not
work.

Advice welcome on how this could be accomplished.

(CC to Texinfo list)