[Dune] Autotools build system, minimum requirements

[Christoph Grüninger]

Hi Bård,
I think nobody really checks the minimum requirements for the build 
tools unless one runs into trouble. I try to keep the build system free 
of warnings for the most recent versions but I don't keep old version 
for testing.
I had a problem with RHEL 5 and dune 2.3-svn, too. But autoconf 2.59 was 
released almost 10 years ago in December 2003 (RHEL 5 is from 2007). I 
don't see how we can stay compatible that long.
I expect that the situation becomes worse. automake announced to change 
their version scheme and the plan to release major versions "which can 
introduce new big features [..], removal of deprecated features, 
backward-incompatible changes of behaviour" every 18 or 24 months. [1]


> I'll solve that locally, but the bigger issues is that there seems to be
> a little confusion and/or inconsistency in the way the minimum
> requirements are encoded in the configure.ac and *.m4 files.  Searching
> through the source trees I can only find
>
>          AC_PREREQ([2.50])
>
> (with and without the quotes) including in "duneproject" but not in
> dunecontrol's DUNE_AC_INIT macro.  Is not encoding the actual minimum
> requirements an oversight or a conscious decision?

I would quote it, too. And you are right, we should update the required 
version to the one in our documentation. Maybe we can lower the required 
version, but someone has to check that it works.

> For the record, the first build obstacle I encountered that is
> definitely related to minimum Autoconf version was the unconditional use
> of AC_PROG_MKDIR_P (introduced, as far as I can tell, in dune-common's
> commit 6f87a45).  I haven't been able to trace the history of that
> macro, but it was *definitely* introduced after Autoconf 2.59.

It was introduced in autoconf 2.60 in June 2006, see [2].

Bye
Christoph

[1] http://lists.gnu.org/archive/html/automake/2013-06/msg00040.html
[2] 
http://lists.gnu.org/archive/html/autotools-announce/2006-06/msg00002.html

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