https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108836
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- Whatever we do it won't help them, as they're using libstdc++ headers from gcc 6.3 It's possible to have a gcc build that has limited support for threading, but not enough to support C++11 std::mutex, std::thread etc and in such cases it would be odd to have a no-op mutex. Another option might be to provide a very dumb mutex using atomic_flag for a spin lock.
