ceph/src/boost/libs/safe_numerics/example/example4.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(){
  12     std::cout << "example 4: ";
  13     std::cout << "implicit conversions change data values" << std::endl;
  14     std::cout << "Not using safe numerics" << std::endl;
  15
  16     // problem: implicit conversions change data values
  17     try{
  18         signed int   a{-1};
  19         unsigned int b{1};
  20         std::cout << "a is " << a << " b is " << b << '\n';
  21         if(a < b){
  22             std::cout << "a is less than b\n";
  23         }
  24         else{
  25             std::cout << "b is less than a\n";
  26         }
  27         std::cout << "error NOT detected!" << std::endl;
  28     }
  29     catch(const std::exception &){
  30         // never arrive here - just produce the wrong answer!
  31         std::cout << "error detected!" << std::endl;
  32         return 1;
  33     }
  34
  35     // solution: replace int with safe<int> and unsigned int with safe<unsigned int>
  36     std::cout << "Using safe numerics" << std::endl;
  37     try{
  38         using namespace boost::safe_numerics;
  39         safe<signed int>   a{-1};
  40         safe<unsigned int> b{1};
  41         std::cout << "a is " << a << " b is " << b << '\n';
  42         if(a < b){
  43             std::cout << "a is less than b\n";
  44         }
  45         else{
  46             std::cout << "b is less than a\n";
  47         }
  48         std::cout << "error NOT detected!" << std::endl;
  49         return 1;
  50     }
  51     catch(const std::exception & e){
  52         // never arrive here - just produce the correct answer!
  53         std::cout << e.what() << std::endl;
  54         std::cout << "error detected!" << std::endl;
  55     }
  56     return 0;
  57 }