Boost C++ Libraries

A variation of the above is when a value is incremented/decremented beyond its domain.

#include <cassert>
#include <exception>
#include <iostream>

#include <boost/safe_numerics/safe_integer.hpp>

int main(int, const char *[]){
    std::cout << "example 2:";
    std::cout << "undetected overflow in data type" << std::endl;
    // problem: undetected overflow
    std::cout << "Not using safe numerics" << std::endl;
    try{
        int x = INT_MAX;
        // the following silently produces an incorrect result
        ++x;
        std::cout << x << " != " << INT_MAX << " + 1" << std::endl;
        std::cout << "error NOT detected!" << std::endl;
    }
    catch(std::exception){
        std::cout << "error detected!" << std::endl;
    }
    // solution: replace int with safe<int>
    std::cout << "Using safe numerics" << std::endl;
    try{
        using namespace boost::safe_numerics;
        safe<int> x = INT_MAX;
        // throws exception when result is past maximum possible 
        ++x;
        assert(false); // never arrive here
    }
    catch(std::exception & e){
        std::cout << e.what() << std::endl;
        std::cout << "error detected!" << std::endl;
    }
    return 0;
}

example 2:undetected overflow in data type
Not using safe numerics
-2147483648 != 2147483647 + 1
error NOT detected!
Using safe numerics
addition result too large
error detected!

When variables of unsigned integer type are decremented below zero, they "roll over" to the highest possible unsigned version of that integer type. This is a common problem which is generally never detected.