[Xcb] [libpthread-stubs] fix semaphore signal safety

[Jamey Sharp]

On Sat, Sep 26, 2009 at 6:52 AM, Samuel Thibault
<samuel.thibault at ens-lyon.org> wrote:
> I've just realized that sem_post() is allowed to be called from a signal
> handler, so the semaphore implementation has to be signal-safe, here is
> a patch.

Huh, I missed something when the original patches went by. Why do
these stubs need to do anything? pthread_mutex_lock, for instance, is
a complete no-op.

Is this because "The mutex functions are not async-signal safe"
(pthread_mutex_lock(3)) so can't possibly be used in a single-threaded
program, but the semaphore functions apparently can?

Still, it seems to me that if somebody expects the semaphore functions
to actually do something, they should link with pthread.

Jamey