For a recent Uni project, I had to check user input for erroneous inputs. Since the program was adding together two integers, I needed to determine whether the resulting integer didn’t overflow – that is to say that the number is outside the range that can be represented by the computer. After some thinking, I settled on the following:

int will_overflow(int a, int b) { if ( (a > 0 && a > MAX_INT - b) || (a < 0 && a < MAX_INT - b)) return 1; return 0; }

The first check is for positive numbers, and the second is for negative, so this is a catch-all solution. The MAX_INT was defined asÂ 2147483647 using the #define compiler statement. It works because it checks whether the first number is greater than the largest representable number minus the second number.