https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57136
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- clang started to accept this code in clang 10.
pinskia at gcc dot gnu.org via Gcc-bugs Mon, 26 Jul 2021 19:06:06 -0700
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57136
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- clang started to accept this code in clang 10.