It varies a lot depending on your needs. Here are a few options. Parts of postgres just heavily document the allowed range and expected domain of such function

It varies a lot depending on your needs. Here are a few options. Parts of postgres just heavily document the allowed range and expected domain of such functions (effectively encoding a type system into the comments and relying on a human to enforce it). I've seen people drop down into assembly to prevent UB. Note that checking the overflow flag doesn't necessarily suffice; the problem happens during compilation -- e.g. if you write `x = (x-MIN_INT)+MAX_INT;` the compiler might be able to reason that the only value for x which wouldn't have UB is MIN_INT. Consequently the result must be MAX_INT, and the compiler can inline that constant anywhere else it's used without ever issuing the instructions so that you could check an overflow flag if you wanted to. If you do those calculations in assembly then you have a lot more freedom in that regard. Some projects do manually check every arithmetic call (or more commonly they'll lean on the pre-processor to do that kind of busywork for them), or at least they'll do so out of some small, core kernel which is more heavily vetted and can't afford the overhead.