That would not prevent the overflow from actually happening, which would be technically UB if the sum is a signed type. It is possible to catch overflow in the

That would not prevent the overflow from actually happening, which would be technically UB if the sum is a signed type. It is possible to catch overflow in the last instant like this (in the last instant before executing the addition instruction) but the test is more involved. It's a pity that there are no standardized tools (AFAIK) but it's not possible to write a substantial piece of code in this way, anyway. What you would generally do is assume that x and y can't be overflow. I.e. you need to have a rough idea what quantities you will process. And put a few checks and assertions in strategic locations.