http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59071
Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|ASSIGNED |NEW CC| |jakub at gcc dot gnu.org --- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> --- You would need constexpr int n = sizeof(__i128i) - N; to guarantee it is folded into a constant, otherwise there is no guarantee it will be, it is normal expression and it is purely an optimization issue (which you've requested not to be performed through -O0) whether it is evaluated as constant or not.