[favorited]

There are different ways to design it, but a simple version could be a function that takes 2 operands and 1 result pointer as inputs, and returns boolean (true if success, false if it overflowed):

    bool SafeAddIntInt(int32_t x, int32_t y, int32_t *r);

so the caller could say

    int32_t result;
    if (SafeAddIntInt(x, y, &result)) {
      // do something with result
    } else {
      // handle overflow
    }

An even simpler version could just abort on over/underflow.

[tsimionescu]

Note that there is no such thing as integer underflow. INT_MIN-1 is an overflow just as much as INT_MAX+1.

Only floats can suffer from underflow, which happens when you want to represent a number whose absolute value is smaller than the floating point precision can allow (e.g. trying to represent 1/2^32 in a 32-bit float).