https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109305 --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- https://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2579 This copy only happens with _S_propagate_on_copy_assign which is true even.