https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69259 --- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- The implementation follows the specification correctly, as far as I can see: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4099.html#fs.op.copy