https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110061
--- Comment #14 from Wilco <wilco at gcc dot gnu.org> --- (In reply to Wilco from comment #13) > (In reply to Xi Ruoyao from comment #12) > > (In reply to Wilco from comment #11) > > > > > > Then the compiler (and the standard) is not what they consider. Such > > > > misunderstandings are everywhere and this has no difference. > > > > > > Where is int128 in "the standard"? > > > > Consider this: > > > > const _Atomic long double x = 0.1; > > > > int main() > > { > > double y = x; > > return y != 0.1; > > } > > > > If CAS is used here, the program will just segfault. Does the standard say > > this is ill-formed or not? > > I'd say this is ill formed yes. And it will crash on Atom laptops. Correction - it crashes on all AMD cpus too. Are you going to file bugreports for this?