Re: New substitution: top_build_prefix

[Benoit Sigoure]

On Nov 10, 2007, at 12:00 PM, Ralf Wildenhues wrote:

> * Ralf Wildenhues wrote on Thu, Nov 08, 2007 at 09:05:24PM CET:
> >   LIBLTDL = ${top_builddir}/ltdl/libltdl.la
> [...]
> >     New config files output variable `top_build_prefix'.
>
> Thanks to Paul and Benoit for reviewing my Autoconf patch.
>
> Here's what I could think of for Libtool.  It's a bit ugly in that it
> depends on the Autoconf version, and thus will fix the issue for AIX
> make only once Autoconf 2.62 is used.
>
> Hmm, do you think I could make the version comparison be against
> `2.61a.265'?  Do you see a more straightforward way to find out  
> whether
> Autoconf substitutes top_build_prefix, i.e., can I access `autom4te
> --trace' results from within macro files?  I could define a helper  
> macro
> in Autoconf, but that wouldn't feel much nicer either.
>
> I'll wait for comments a couple of days before applying.

Hi Ralf,
thanks for addressing this.  I must admit that I can't think of  
anything better than this (that is, doing the version comparison).  I  
don't know whether you can access the trace result from within a  
macro, I don't think that's possible.

Your last solution has a very small advantage.  Correct me if I'm  
wrong but basically the idea is to have some sort of witness macro in  
autoconf (_AC_HAVE_TOP_BUILD_PREFIX, or whatever) and libtool would  
try to expand it (if it expands => you can use ${top_build_prefix} /  
otherwise => fall back on ${top_builddir}) is that right?  Well, this  
has the advantage that if this patch is backported by some  
distribution to an older version, libtool will correctly guess that $ 
{top_build_prefix} is usable even though you have an older autoconf.   
I think it might also help people that still deal with CVS autoconf  
(where the version number might be inaccurate or unreliable, as we  
have seen in Patrick's report yesterday).

All in all, either solution is sort of kludgy, but I have a slight  
preference for the helper macro in Autoconf.

> 2007-11-10  Ralf Wildenhues  <address@hidden>
>
>         Use `${top_build_prefix}' for better compatibility with non-GNU make.
>         * libltdl/m4/ltdl.m4 (_LT_BUILD_PREFIX): New macro.
>         If the Autoconf version used is >= 2.62, then expand to
>         `${top_build_prefix}', otherwise to `${top_builddir}/'.
>         (LTDL_CONVENIENCE, LTDL_INSTALLABLE): Use it for defining
>         LIBLTDL.  Fixes a build failure with AIX make in a package
>         using convenience libltdl in nonrecursive mode.
>         * doc/libtool.texi (Distributing libltdl): Document requirements
>         to define `top_build_prefix' if Automake is not used.
>         Report by Bob Friesenhahn.

Yeah, otherwise this also looks fine by me.

--
Benoit Sigoure aka Tsuna
EPITA Research and Development Laboratory

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