https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71892
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- Both examples you give are undefined behaviour according to the C++ standard. You can claim the code is valid, but that doesn't make it true. You seem to be confusing "it worked OK until now" with "this code is valid according to the language standard".
