https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114933
--- Comment #8 from LIU Hao <lh_mouse at 126 dot com> --- Fixed in this commit: https://github.com/lhmouse/mcfgthread/commit/86ea295e41523183e7680c03cab35e6eb74c4857 It has actually been disallowed since C++98 (N1804) but as part of a different paragraph.
