Re: libtool problem on FreeBSD 4.1 with -pthread

[Ralf Wildenhues]

Hi Peter,

* Peter Ekberg wrote on Fri, Nov 05, 2004 at 08:59:09AM CET:
> 
> (I sent a message on this topic to bug-libtool a while back,
>  but it went by without any response whatsoever. Since I've
>  had more luck on this list lately, I'm resending here)

Yes, the topic has come up several times, see e.g. also these threads:
http://lists.gnu.org/archive/html/libtool/2004-10/msg00252.html
http://lists.gnu.org/archive/html/libtool/2004-10/msg00159.html

Sometimes bug reports just fly by because of time constraints,
and/or lack of knowledge.  Good-quality reports are also much
more likely to be answered (not to judge your earlier report,
that is).

> Background, in our project we build a library that uses
> pthreads if they are detected, and falls back to signals
> if pthreads are not detected. On Windows, Win32 threads are
> used. 
*snip*

See the ACX_PTHREAD macro on http://ac-archive.sourceforge.net/
for what else might be necessary.  It's also only a partial solution to
the problem, since C++ and Fortran compilers on AIX will have to be
changed as well.

> We would like -pthread to end up in the dependencies for the
> generated library, at least for FreeBSD, but as stated above
> the problem is probably bigger than FreeBSD/-pthread.
> 
> The attached patch adds any thread related flag to the
> dependencies, on the assumption that the app using the
> threaded lib will not be harmed by that flag when the
> lib was built with it in the first place.

Yes, but that's not enough.  I don't think your patch is a bad idea,
but it's surely not a portable solution to the problem.  The user of 
the library might have to use a different compiler driver on AIX.

Nevertheless, I think we should do something.  Issues:

- Peter mentioned using linker_inherited_flags for libtool-1.5
compatibility.
- There is currently an unused(?) libtool setting thread_safe_flag_spec,
together with a `libtool' option -thread-safe.  We could try and
actually make this useful.

Regards,
Ralf