https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117966
--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> --- This is not a G++ regression, it looks like this code has never been accepted. It's a library regression because we added a valid check which G++ can't compile. I will replace the check (it's redundant for a std::array anyway because we know it's a valid pointer of that size) but the G++ bug remains. It's probably a dup of an existing bug.
