[Bug libstdc++/60645] locale::facet::_S_get_c_locale does not handle __gthread_once error codes.

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60645

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I would not be opposed to a patch improving error handling of such functions,
the calls in atexit_thread.cc are certainly allowed to fail and we should
handle it.

What is the right thing to do there though? If __gthread_key_create() fails
then the once flag will still be set, so key_s::key_s() will never be run
again, and the __cxa_thread_atexit feature is basically unusable. Is that
acceptable?