[RFA] AiX: enable thread support only if libpthdebug is recent enough

[Andrew Cagney]

> (once more, with the patch this time, sorry)
> 
> Hello,
> 
> The build is broken for me on AiX 4.3.2.0 because aix-thread.c assumes
> a more recent version of lib pthdebug that is actually installed. I have
> therefore made the following changes to enable the thread support only
> if the pthread debug lib is at least version 3. 
> 
> I know the build works with version 3, and it may be that it works for
> version 2 as well. But I can't check this, so I played it safe for now.
> If it turns out that it works with version 2 as well, then we can very
> easily change it.
> 
> Since the build is also broken on the 5.3 branch for the same reason, 
> I suggest this patch be applied to the 5.3 branch as well.
> 
> 2002-11-27  J. Brobecker  <brobecker@gnat.com>
> 
>         * configure.in: Check that the pthdebug library is recent enough
>         before enable thread support on native AiX.
>         * configure: Regenerate.
> 
>         * config/powerpc/aix432.mh (NATDEPFILES): Remove aix-thread.o
>         from the list of object files as it is now appended by configure
>         if thread support is enabled.
>         (NAT_CLIBS): Removed as -lpthdebug is also appended by configure
>         if thread support is enabled.
> 
> Ok to commit? Ok for 5.3 as well?
> (I did not include the diff for configure, as this is a generated file)

Looks `safe' - can only hurts AIX - so yes, ok for both 5.3 and mainline.

Can you just, while you're at it, update the comment at the start of the 
containing switch so that it beter reflects current reality.

dnl See if thread_db library is around for Solaris thread debugging. 
Note that
dnl we must explicitly test for version 1 of the library because version 0
dnl (present on Solaris 2.4 or earlier) doesn't have the same API.

Andrew