https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78420
--- Comment #19 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Jens Maurer from comment #16) > That means the standard library needs to do its homework to clearly specify > under which circumstances (which argument types) it expects a constexpr > function to be valid in a constant expression. That's LWG 2833.