There is no undefined behaviour, '#pragma GCC optimize("wrapv")' takes care of that. EDIT: It seems that clang doesn't support #pragma GCC optimize, so it's a

There is no undefined behaviour, '#pragma GCC optimize("wrapv")' takes care of that. EDIT: It seems that clang doesn't support #pragma GCC optimize, so it's a no-op in that snippet. It doesn't change the result though. If you pass -fwrapv flag to clang, it will be optimized in exactly the same way.