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- // Copyright (c) 2018 Robert Ramey
- //
- // Distributed under the Boost Software License, Version 1.0. (See
- // accompanying file LICENSE_1_0.txt or copy at
- // http://www.boost.org/LICENSE_1_0.txt)
- #include <iostream>
- #include <boost/safe_numerics/safe_integer.hpp>
- int main(int, const char *[]){
- std::cout << "example 3:";
- std::cout << "undetected underflow in data type" << std::endl;
- std::cout << "Not using safe numerics" << std::endl;
- // problem: decrement can yield incorrect result
- try{
- unsigned int x = 0;
- // the following silently produces an incorrect result
- --x;
- std::cout << x << " != " << -1 << std::endl;
- // when comparing int and unsigned int, C++ converts
- // the int to unsigned int so the following assertion
- // fails to detect the above error!
- assert(x == -1);
- std::cout << "error NOT detected!" << std::endl;
- }
- catch(const std::exception &){
- // never arrive here
- std::cout << "error detected!" << std::endl;
- }
- // solution: replace unsigned int with safe<unsigned int>
- std::cout << "Using safe numerics" << std::endl;
- try{
- using namespace boost::safe_numerics;
- safe<unsigned int> x = 0;
- // decrement unsigned to less than zero throws exception
- --x;
- assert(false); // never arrive here
- }
- catch(const std::exception & e){
- std::cout << e.what() << std::endl;
- std::cout << "error detected!" << std::endl;
- }
- return 0;
- }
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