https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65861
--- Comment #13 from Andrew Pinski <pinskia at gcc dot gnu.org> --- (In reply to Jonathan Wakely from comment #11) > (In reply to Andrew Pinski from comment #10) > > GCC 10+ started to reject the code just the same as CLANG does. > > Clang doesn't reject it, libc++ does. Clang with libstdc++ accepts it, and > so does GCC trunk (you just need some more headers for recent versions): I should have known the more headers for recent versions :).