Re: Best practices to detect autoconf version in macro.

[Ralf Corsepius]

On 03/30/2010 04:41 PM, Eric Blake wrote:
> On 03/30/2010 03:13 AM, Konstantin Andreev wrote:
> > Hello.
> >
> > I need to write a macro, which will be expanded by various versions of
> > autoconf, including 2.13  :(
>
> Simultaneously targeting 2.59 and newer is moderately easy, and still
> supported by this list.  Supporting 2.50 and newer is a bit tougher, but
> not intractable.
Agreed.

> But simultaneously supporting 2.13 and 2.50+ is MUCH
> harder, with very few people even attempting it (my gut feel is that it
> is technically still doable, although I won't be the one doing it).
Testing is the problem.

Trying to say 2.13 compatible is likely doable for trivial configure 
scripts, but it easily becomes tedious for complex ones and .., close to 
impossible to test.

> If m4_version_compare is defined (added in 2.53, documented in 2.62),
> then use it.  Otherwise, you know that you are targeting an older autoconf.
>
> Read this thread for another person who attempted this feat for PHP, and
> later gave up, because the changes from 2.13 to 2.50 were so dramatic.
I could tell similar stories.

From my experience, it's way easier to "do the plunge once", i.e. to 
once convert all 2.13 anacronisms and bugward-compatibilities (which 
typically means exploits of autoconf-2.13 internal) to autoconf-2.50+.

At some point, very likely will want to take advantage of some 
autoconf-2.50+ features or finds that certain autoconf versions > 2.50 
provides a feature "one has always missed" in older autoconfs.

The lesson at least I've learnt, is not wanting to look back to 2.13.

BTW: Even more dramatic, similar considerations apply to automake.

Ralf