https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113208
--- Comment #26 from Andrew Pinski <pinskia at gcc dot gnu.org> --- (In reply to Jan Hubicka from comment #25) > > If constexpr changes how the constructor is generated, isn't this violation > of ODR? Note the original code didn't have the constexpr change. And IIRC constexpr in libstdc++ might be different depending on the language, C++11 vs C++17 in many cases too.