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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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