Boost C++ Libraries of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is the documentation for an old version of Boost. Click here to view this page for the latest version.
Library Documentation Index

Safe Numerics


Compile Time Arithmetic is Not Always Correct

If a divide by zero error occurs while a program is being compiled, there is not guarantee that it will be detected. This example shows a real example compiled with a recent version of CLang.

//  Copyright (c) 2018 Robert Ramey
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at

#include <stdexcept>
#include <iostream>

#include <boost/safe_numerics/safe_integer.hpp>

int main(int, const char *[]){
    // problem: cannot recover from arithmetic errors
    std::cout << "example 14: ";
    std::cout << "cannot detect compile time arithmetic errors" << std::endl;
    std::cout << "Not using safe numerics" << std::endl;

        const int x = 1;
        const int y = 0;
        // will emit warning at compile time
        // will leave an invalid result at runtime.
        std::cout << x / y; // will display "0"!
        std::cout << "error NOT detected!" << std::endl;
    catch(const std::exception &){
        std::cout << "error detected!" << std::endl;
    // solution: replace int with safe<int>
    std::cout << "Using safe numerics" << std::endl;
        using namespace boost::safe_numerics;
        const safe<int> x = 1;
        const safe<int> y = 0;
        // constexpr const safe<int> z = x / y; // note constexpr here!
        std::cout << x / y; // error would be detected at runtime
        std::cout << " error NOT detected!" << std::endl;
    catch(const std::exception & e){
        std::cout << "error detected:" << e.what() << std::endl;
    return 0;
example 8: cannot detect compile time arithmetic errors
Not using safe numerics
0error NOT detected!
Using safe numerics
error detected:positive overflow error
Program ended with exit code: 0