Update GCC to autoconf 2.69, automake 1.15.1

[Janne Blomqvist]

On Wed, Oct 31, 2018 at 9:12 AM Thomas Koenig <tkoenig@netcologne.de> wrote:

> > Makefile.am:48: warning: source file 'caf/single.c' is in a subdirectory,
> > Makefile.am:48: but option 'subdir-objects' is disabled
> > automake: warning: possible forward-incompatibility.
> > automake: At least a source file is in a subdirectory, but the
> 'subdir-objects'
> > automake: automake option hasn't been enabled.  For now, the
> corresponding output
> > automake: object file(s) will be placed in the top-level directory.
> However,
> > automake: this behaviour will change in future Automake versions: they
> > will
> > automake: unconditionally cause object files to be placed in the same
> subdirectory
> > automake: of the corresponding sources.
> > automake: You are advised to start using 'subdir-objects' option
> throughout your
> > automake: project, to avoid future incompatibilities.
> >
> > I think it's best for the relevant maintainers to add subdir-objects
> > and do any other associated Makefile.am changes needed.  In some cases
> > the paths in the warnings involved ../; I don't know if that adds any
> > extra complications to the use of subdir-objects.
>
> I'm not an automake expert, but I hope to be able to figure out
> what is needed.  If not, I guess I'll just ask :-)
>

My understanding is that we need to add 'subdir-objects' to
AM_INIT_AUTOMAKE in configure.ac.

See e.g. https://autotools.io/automake/options.html

(that site is pretty good for describing 'best practices' for modern
autotools; there's unfortunately a lot of very outdated autotools tutorials
around)

What is the plan for the previous branches?  Currently, it is necessary
> to keep around a special version of automake etc for
> --enable-maintainer-mode to work.  Backporting a patch which
> involves regeneration of files in libgfortran/generated from
> the files in libgfortan/m4 would then require keeping two versions
> of the relevant tools around, and switching between them.
>
> Would it make sense to backport because of this?
>

+1


-- 
Janne Blomqvist