[Bug libstdc++/46914] std::atomic<int*>::exchange(...) doesn't store correct value.

["paolo.carlini at oracle dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46914

--- Comment #7 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-01-27 15:33:47 UTC ---
Ok. In any case we should not risk miscompiling stuff, better bailing out at
compile time. I see that in atomic_base.h the configure-time macros
_GLIBCXX_ATOMIC_BUILTINS_* are used and I se no uses of the
__GCC_HAVE_SYNC_COMPARE_AND_SWAP_* macros, the only one sensitive to the
command line switches. But apparently the PR is about compiling *without* any
special command line switch affecting the availability of the builtins, thus I
don't see how things could possibly go wrong. Something also to keep in mind is
that [GLIBCXX_ENABLE_ATOMIC_BUILTINS] in acinclude.m4 changed recently: I don't
think we want to go through big efforts fixing this issue affecting only C++0x
facilities in case it shows up only on 4.4.x, say, and it's fixed in mainline.
I'll also try to run further tests in mainline, multilib too.