ceph/src/boost/libs/safe_numerics/example/example11.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 1:";
  13     std::cout << "undetected erroneous expression evaluation" << std::endl;
  14     std::cout << "Not using safe numerics" << std::endl;
  15     // problem: arithmetic operations can yield incorrect results.
  16     try{
  17         std::int8_t x = 127;
  18         std::int8_t y = 2;
  19         std::int8_t z;
  20         // this produces an invalid result !
  21         z = x + y;
  22         std::cout << z << " != " << x + y << std::endl;
  23         std::cout << "error NOT detected!" << std::endl;
  24     }
  25     catch(const std::exception &){
  26         std::cout << "error detected!" << std::endl;
  27     }
  28     // solution: replace std::int8_t with safe<std::int8_t>
  29     std::cout << "Using safe numerics" << std::endl;
  30     try{
  31         using namespace boost::safe_numerics;
  32         safe<std::int8_t> x = 127;
  33         safe<std::int8_t> y = 2;
  34         // rather than producing and invalid result an exception is thrown
  35         safe<std::int8_t> z = x + y;
  36     }
  37     catch(const std::exception & e){
  38         // which can catch here
  39         std::cout << e.what() << std::endl;
  40     }
  41     return 0;
  42 }