[Bug libstdc++/51906] thread lock test failures on darwin11 under Xcode 4.2

["redi at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51906

--- Comment #49 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-02-03 17:50:07 UTC ---
(In reply to comment #46)
> (In reply to comment #45)
> > Then I think we have to disable __GTHREAD_RECURSIVE_MUTEX_INIT unconditionally
> > on darwin.
> 
> I hope not.
> putting -mmacosx-version-min=10.6 - will cause the macro value to be 1060 - so
> defeating it.  One would not expect it to run on 10.7.

So using -mmacosx-version-min=10.6 without also using the 10.6 SDK is pilot
error?

But if I understand correctly, 10.6 didn't define
PTHREAD_MUTEX_RECURSIVE_INITIALIZER anyway, so using the 10.6 SDK would cause
it to be undefined, so why not just disable __GTHREAD_RECURSIVE_MUTEX_INIT
unconditionally?

The only system that defines it (10.7) can't use it.

> If one puts -mmacosx-version-min=10.6  and sysroots to the 10.6 SDK - *and*
> then transfers the executable to a 10.6 system - then that should work.  If
> not, then I agree.

Presumably it doesn't even need to be transferred to a 10.6 system, using the
10.6 SDK should mean the headers don't have the static initializer, so the
pthread_mutex_init_function() will always be used to create a recursive mutex,
and Greg says that works on 10.7