https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64867 --- Comment #8 from Andrew Pinski <pinskia at gcc dot gnu.org> --- See http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2342.htm . It does look like gcc is implementing the correct new pod rules and clang is not.