http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51813
--- Comment #6 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-01-13 16:46:56 UTC --- Thanks for your help Jon. Note the issue isn't just about std::use_facet, is about std::codecvt too, any type we instantiate with mbstate_t.
