> undefined behavior in C/C++ is that it simplifies the compiler’s job, making it possible to generate very efficient code in certain situations.<p>I've been growing more skeptical of this claim over time. First, more evidence would be nice instead of "some loops". What is a program (not a benchmark) that has an observable performance difference when compiled with and without -fwrap?<p>Second, it seems counter productive. The word is now out that if you use signed ints, the compiler is going to fuck you over. So now everybody is (or should be) using unsigned ints, and whatever optimization the compiler was performing, now it can't. A lot of grief for no progress.