https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78939 --- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> --- But that goes against http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-active.html#2446 So, I think GB 20 is in conflict with LWG2446, we can have just one of those.