Check for overflow condition in an arithmetic operation [duplicate]

Question

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Best way to detect integer overflow in C/C++

how do we check if any arithmetic operation like addition, multiplication or subtraction could result in an overflow?

Answer 1

Check the size of the operands first, and use std::numeric_limits. For example, for addition:

#include <limits>

unsigned int a, b;  // from somewhere

unsigned int diff = std::numeric_limits<unsigned int>::max() - a;

if (diff < b) { /* error, cannot add a + b */ }

You cannot generally and reliably detect arithmetic errors after the fact, so you have to do all the checking before.

You can easily template this approach to make it work with any numeric type.