[Bug libstdc++/58938] [4.7/4.8/4.9 Regression] std::exception_ptr is missing on architectures with incomplete atomic int support

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58938

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
So why is this a regression?  Does ARM define _GLIBCXX_ATOMIC_BUILTINS_4 but
ATOMIC_INT_LOCK_FREE=1 ? That seems like a bug in those definitions.