| 1 | // Copyright 2010, Niels Dekker. |
| 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 | // Test program for boost::initialized<T>. |
| 8 | // |
| 9 | // 2 May 2010 (Created) Niels Dekker |
| 10 | |
| 11 | #include <boost/utility/value_init.hpp> |
| 12 | #include <boost/detail/lightweight_test.hpp> |
| 13 | |
| 14 | #include <string> |
| 15 | |
| 16 | namespace |
| 17 | { |
| 18 | // Typical use case for boost::initialized<T>: A generic class that |
| 19 | // holds a value of type T, which must be initialized by either |
| 20 | // value-initialization or direct-initialization. |
| 21 | template <class T> class key_value_pair |
| 22 | { |
| 23 | std::string m_key; |
| 24 | boost::initialized<T> m_value; |
| 25 | public: |
| 26 | |
| 27 | // Value-initializes the object held by m_value. |
| 28 | key_value_pair() { } |
| 29 | |
| 30 | // Value-initializes the object held by m_value. |
| 31 | explicit key_value_pair(const std::string& key) |
| 32 | : |
| 33 | m_key(key) |
| 34 | { |
| 35 | } |
| 36 | |
| 37 | // Direct-initializes the object held by m_value. |
| 38 | key_value_pair(const std::string& key, const T& value) |
| 39 | : |
| 40 | m_key(key), m_value(value) |
| 41 | { |
| 42 | } |
| 43 | |
| 44 | const T& get_value() const |
| 45 | { |
| 46 | return m_value; |
| 47 | } |
| 48 | }; |
| 49 | |
| 50 | |
| 51 | // Tells whether the argument is value-initialized. |
| 52 | bool is_value_initialized(const int& arg) |
| 53 | { |
| 54 | return arg == 0; |
| 55 | } |
| 56 | |
| 57 | |
| 58 | // Tells whether the argument is value-initialized. |
| 59 | bool is_value_initialized(const std::string& arg) |
| 60 | { |
| 61 | return arg.empty(); |
| 62 | } |
| 63 | |
| 64 | struct foo |
| 65 | { |
| 66 | int data; |
| 67 | }; |
| 68 | |
| 69 | bool operator==(const foo& lhs, const foo& rhs) |
| 70 | { |
| 71 | return lhs.data == rhs.data; |
| 72 | } |
| 73 | |
| 74 | |
| 75 | // Tells whether the argument is value-initialized. |
| 76 | bool is_value_initialized(const foo& arg) |
| 77 | { |
| 78 | return arg.data == 0; |
| 79 | } |
| 80 | |
| 81 | |
| 82 | template <class T> |
| 83 | void test_key_value_pair(const T& magic_value) |
| 84 | { |
| 85 | // The value component of a default key_value_pair must be value-initialized. |
| 86 | key_value_pair<T> default_key_value_pair; |
| 87 | BOOST_TEST( is_value_initialized(default_key_value_pair.get_value() ) ); |
| 88 | |
| 89 | // The value component of a key_value_pair that only has its key explicitly specified |
| 90 | // must also be value-initialized. |
| 91 | BOOST_TEST( is_value_initialized(key_value_pair<T>("key").get_value()) ); |
| 92 | |
| 93 | // However, the value component of the following key_value_pair must be |
| 94 | // "magic_value", as it must be direct-initialized. |
| 95 | BOOST_TEST( key_value_pair<T>("key", magic_value).get_value() == magic_value ); |
| 96 | } |
| 97 | } |
| 98 | |
| 99 | |
| 100 | // Tests boost::initialize for a fundamental type, a type with a |
| 101 | // user-defined constructor, and a user-defined type without |
| 102 | // a user-defined constructor. |
| 103 | int main() |
| 104 | { |
| 105 | |
| 106 | const int magic_number = 42; |
| 107 | test_key_value_pair(magic_number); |
| 108 | |
| 109 | const std::string magic_string = "magic value"; |
| 110 | test_key_value_pair(magic_string); |
| 111 | |
| 112 | const foo magic_foo = { 42 }; |
| 113 | test_key_value_pair(magic_foo); |
| 114 | |
| 115 | return boost::report_errors(); |
| 116 | } |