[Python-Dev] Bumping autoconf from 2.68 to 2.69

[Trent Nelson]

On Tue, Oct 16, 2012 at 12:12:35AM -0700, R. David Murray wrote:
> On Mon, 15 Oct 2012 23:18:04 -0700, Ned Deily <nad at acm.org> wrote:
> > In article <20121016043352.GA21441 at snakebite.org>,
> >  Trent Nelson <trent at snakebite.org> wrote:
> > >     Any objections to regenerating configure with autoconf 2.69?  The
> > >     current version is based off 2.68, which was release on the 22nd
> > >     of September 2010.  2.69 was released on the 24th of April, 2012.
> > > 
> > >     (There are some fixes for the more esoteric UNIX platforms that
> > >      Snakebite will benefit from.  Also, I struggled to find a box
> > >      with 2.68 even installed when I needed to regenerate configure
> > >      this weekend; it seems all package management/ports have bumped
> > >      to 2.69.)
> > > 
> > >     If there are no objections, can it be applied across the board?
> > >     2.7, 3.2, 3.3 and 3.x?
> > 
> > I believe it is the case that we don't currently require a specific 
> > version of autoconf.  autoconf is only run when making a committer makes 
> > a change to configure.ac et al and then it is run on the committer's 
> > machine.  So whatever is checked in for those files reflects the version 
> > of autoconf that the committer used.
> 
> My understanding is that we use a specific version of autoconf.
> The reason is that otherwise we end up with useless churn in the repo
> as the generated file changes when different committers use different
> versions.  In the past we have had issues with a new autoconf version
> actually breaking the Python build, so we also need to test a new version
> before switching to it.

    Just to put this in perspective, here's a change I made to
    configure.ac over the weekend as part of #15819:

% hg diff configure.ac                               
diff -r 51ce9830d85a configure.ac
--- a/configure.ac      Sat Oct 13 11:58:23 2012 -0400
+++ b/configure.ac      Tue Oct 16 09:12:56 2012 +0000
@@ -9,6 +9,9 @@
 
 AC_INIT(python, PYTHON_VERSION, http://bugs.python.org/)
 
+BUILDDIR="`pwd`"
+AC_SUBST(BUILDDIR)
+
 AC_SUBST(HGVERSION)
 AC_SUBST(HGTAG)
 AC_SUBST(HGBRANCH)

    With the correct version of autoconf (2.68), this generates the
    following diff to configure:

% hg diff configure
diff -r 51ce9830d85a configure
--- a/configure Sat Oct 13 11:58:23 2012 -0400
+++ b/configure Tue Oct 16 09:15:04 2012 +0000
@@ -714,6 +714,7 @@
 HGBRANCH
 HGTAG
 HGVERSION
+BUILDDIR
 target_alias
 host_alias
 build_alias
@@ -2719,6 +2720,9 @@
 
 
 
+BUILDDIR="`pwd`"
+
+
 

    However, the 2.69 version of autoconf generates this monster of a
    configure diff:

        http://hydrogen.snakebite.net/~cpython/configure.diff

    As you can see, it's impossible to figure out what my configure.ac
    change was from that diff.  Which is why I'm proposing we leverage
    AC_PREREQ to prevent inadvertent autoconf version churn.

        Trent.