ceph/src/boost/libs/safe_numerics/example/example8.cpp

   1 //  Copyright (c) 2018 Robert Ramey
   2 //
   3 // Distributed under the Boost Software License, Version 1.0. (See
   4 // accompanying file LICENSE_1_0.txt or copy at
   5 // http://www.boost.org/LICENSE_1_0.txt)
   6
   7 #include <iostream>
   8
   9 #include <boost/safe_numerics/safe_integer.hpp>
  10
  11 int main(int, const char *[]){
  12     std::cout << "example 8:";
  13     std::cout << "undetected erroneous expression evaluation" << std::endl;
  14     std::cout << "Not using safe numerics" << std::endl;
  15     try{
  16         unsigned int x = 127;
  17         unsigned int y = 2;
  18         unsigned int z;
  19         // this produces an invalid result !
  20         z = y - x;
  21         std::cout << "error NOT detected!" << std::endl;
  22         std::cout << z << " != " << y << " - " << x << std::endl;
  23     }
  24     catch(const std::exception &){
  25         std::cout << "error detected!" << std::endl;
  26     }
  27     // solution: replace int with safe<int>
  28     std::cout << "Using safe numerics" << std::endl;
  29     try{
  30         using namespace boost::safe_numerics;
  31         safe<unsigned int> x = 127;
  32         safe<unsigned int> y = 2;
  33         safe<unsigned int> z;
  34         // rather than producing an invalid result an exception is thrown
  35         z = y - x;
  36         std::cout << "error NOT detected!" << std::endl;
  37         std::cout << z << " != " << y << " - " << x << std::endl;
  38     }
  39     catch(const std::exception & e){
  40         // which we can catch here
  41         std::cout << "error detected:" << e.what() << std::endl;
  42     }
  43     return 0;
  44 }