I thought this was going to be about efficient overflow checking at a USER level. I want to be able to write efficient code something like

    bool SafeAddInts(int a, int b, int* out) {
      if (willOverFlowAdd(a,b)) {
        return false;
      }
      *out = a + b;
      return true;
    }

Or better

    bool SafeAddInts(int a, int b, int* out) {
      int temp = a + b;
      if (magicCheckProcessorFlagsForOverflow()) {
        return false;
      }
      *out = temp;
      return true;
    }

Or something along those lines.

It's all great the compiler can maybe generate code that crashes my program there's overflow but what's the efficient case for handling it at a user level given that overflow is undefined in the general case given the result is undefined?