Yeah, you're definitely right that a lot of C and C++ code is written assuming signed overflow won't be optimized away. I think it was a mistake of GCC to do th

Yeah, you're definitely right that a lot of C and C++ code is written assuming signed overflow won't be optimized away. I think it was a mistake of GCC to do this optimization without some explicit flag like "-fremove-signed-overflow". I wish they didn't do that, but it's not up to me what they do. It's necessary for optimizations like loop unrolling, auto-vectorization, and compiling "for (int i = 0; i < N; i++)" as if it were written "for (size_t i = 0; i < N; i++)" when it's more efficient to do so, but again, I think this should be opt-in, and either -fwrapv or -ftrapv should be default on the generic -O1, -O2, -O3 levels.