| 1 | // Copyright (c) 2018 Robert Ramey |
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| 2 | // |
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| 3 | // Distributed under the Boost Software License, Version 1.0. (See |
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| 4 | // accompanying file LICENSE_1_0.txt or copy at |
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| 5 | // http://www.boost.org/LICENSE_1_0.txt) |
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| 6 | |
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| 7 | #include <iostream> |
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| 8 | |
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| 9 | #include <boost/safe_numerics/safe_integer.hpp> |
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| 10 | |
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| 11 | int main(int, const char *[]){ |
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| 12 | std::cout << "example 8:" ; |
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| 13 | std::cout << "undetected erroneous expression evaluation" << std::endl; |
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| 14 | std::cout << "Not using safe numerics" << std::endl; |
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| 15 | try{ |
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| 16 | unsigned int x = 127; |
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| 17 | unsigned int y = 2; |
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| 18 | unsigned int z; |
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| 19 | // this produces an invalid result ! |
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| 20 | z = y - x; |
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| 21 | std::cout << "error NOT detected!" << std::endl; |
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| 22 | std::cout << z << " != " << y << " - " << x << std::endl; |
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| 23 | } |
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| 24 | catch(const std::exception &){ |
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| 25 | std::cout << "error detected!" << std::endl; |
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| 26 | } |
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| 27 | // solution: replace int with safe<int> |
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| 28 | std::cout << "Using safe numerics" << std::endl; |
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| 29 | try{ |
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| 30 | using namespace boost::safe_numerics; |
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| 31 | safe<unsigned int> x = 127; |
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| 32 | safe<unsigned int> y = 2; |
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| 33 | safe<unsigned int> z; |
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| 34 | // rather than producing an invalid result an exception is thrown |
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| 35 | z = y - x; |
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| 36 | std::cout << "error NOT detected!" << std::endl; |
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| 37 | std::cout << z << " != " << y << " - " << x << std::endl; |
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| 38 | } |
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| 39 | catch(const std::exception & e){ |
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| 40 | // which we can catch here |
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| 41 | std::cout << "error detected:" << e.what() << std::endl; |
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| 42 | } |
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| 43 | return 0; |
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| 44 | } |
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| 45 | |
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