1 // Move, forward and identity for C++11 + swap -*- C++ -*- 2 3 // Copyright (C) 2007-2018 Free Software Foundation, Inc. 4 // 5 // This file is part of the GNU ISO C++ Library. This library is free 6 // software; you can redistribute it and/or modify it under the 7 // terms of the GNU General Public License as published by the 8 // Free Software Foundation; either version 3, or (at your option) 9 // any later version. 10 11 // This library is distributed in the hope that it will be useful, 12 // but WITHOUT ANY WARRANTY; without even the implied warranty of 13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 // GNU General Public License for more details. 15 16 // Under Section 7 of GPL version 3, you are granted additional 17 // permissions described in the GCC Runtime Library Exception, version 18 // 3.1, as published by the Free Software Foundation. 19 20 // You should have received a copy of the GNU General Public License and 21 // a copy of the GCC Runtime Library Exception along with this program; 22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23 // <http://www.gnu.org/licenses/>. 24 25 /** @file bits/move.h 26 * This is an internal header file, included by other library headers. 27 * Do not attempt to use it directly. @headername{utility} 28 */ 29 30 #ifndef _MOVE_H 31 #define _MOVE_H 1 32 33 #include <bits/c++config.h> 34 #include <bits/concept_check.h> 35 36 namespace std _GLIBCXX_VISIBILITY(default) 37 { 38 _GLIBCXX_BEGIN_NAMESPACE_VERSION 39 40 // Used, in C++03 mode too, by allocators, etc. 41 /** 42 * @brief Same as C++11 std::addressof 43 * @ingroup utilities 44 */ 45 template<typename _Tp> 46 inline _GLIBCXX_CONSTEXPR _Tp* 47 __addressof(_Tp& __r) _GLIBCXX_NOEXCEPT 48 { return __builtin_addressof(__r); } 49 50 #if __cplusplus >= 201103L 51 52 _GLIBCXX_END_NAMESPACE_VERSION 53 } // namespace 54 55 #include <type_traits> // Brings in std::declval too. 56 57 namespace std _GLIBCXX_VISIBILITY(default) 58 { 59 _GLIBCXX_BEGIN_NAMESPACE_VERSION 60 61 /** 62 * @addtogroup utilities 63 * @{ 64 */ 65 66 /** 67 * @brief Forward an lvalue. 68 * @return The parameter cast to the specified type. 69 * 70 * This function is used to implement "perfect forwarding". 71 */ 72 template<typename _Tp> 73 constexpr _Tp&& 74 forward(typename std::remove_reference<_Tp>::type& __t) noexcept 75 { return static_cast<_Tp&&>(__t); } 76 77 /** 78 * @brief Forward an rvalue. 79 * @return The parameter cast to the specified type. 80 * 81 * This function is used to implement "perfect forwarding". 82 */ 83 template<typename _Tp> 84 constexpr _Tp&& 85 forward(typename std::remove_reference<_Tp>::type&& __t) noexcept 86 { 87 static_assert(!std::is_lvalue_reference<_Tp>::value, "template argument" 88 " substituting _Tp is an lvalue reference type"); 89 return static_cast<_Tp&&>(__t); 90 } 91 92 /** 93 * @brief Convert a value to an rvalue. 94 * @param __t A thing of arbitrary type. 95 * @return The parameter cast to an rvalue-reference to allow moving it. 96 */ 97 template<typename _Tp> 98 constexpr typename std::remove_reference<_Tp>::type&& 99 move(_Tp&& __t) noexcept 100 { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); } 101 102 103 template<typename _Tp> 104 struct __move_if_noexcept_cond 105 : public __and_<__not_<is_nothrow_move_constructible<_Tp>>, 106 is_copy_constructible<_Tp>>::type { }; 107 108 /** 109 * @brief Conditionally convert a value to an rvalue. 110 * @param __x A thing of arbitrary type. 111 * @return The parameter, possibly cast to an rvalue-reference. 112 * 113 * Same as std::move unless the type's move constructor could throw and the 114 * type is copyable, in which case an lvalue-reference is returned instead. 115 */ 116 template<typename _Tp> 117 constexpr typename 118 conditional<__move_if_noexcept_cond<_Tp>::value, const _Tp&, _Tp&&>::type 119 move_if_noexcept(_Tp& __x) noexcept 120 { return std::move(__x); } 121 122 // declval, from type_traits. 123 124 #if __cplusplus > 201402L 125 // _GLIBCXX_RESOLVE_LIB_DEFECTS 126 // 2296. std::addressof should be constexpr 127 # define __cpp_lib_addressof_constexpr 201603 128 #endif 129 /** 130 * @brief Returns the actual address of the object or function 131 * referenced by r, even in the presence of an overloaded 132 * operator&. 133 * @param __r Reference to an object or function. 134 * @return The actual address. 135 */ 136 template<typename _Tp> 137 inline _GLIBCXX17_CONSTEXPR _Tp* 138 addressof(_Tp& __r) noexcept 139 { return std::__addressof(__r); } 140 141 // _GLIBCXX_RESOLVE_LIB_DEFECTS 142 // 2598. addressof works on temporaries 143 template<typename _Tp> 144 const _Tp* addressof(const _Tp&&) = delete; 145 146 // C++11 version of std::exchange for internal use. 147 template <typename _Tp, typename _Up = _Tp> 148 inline _Tp 149 __exchange(_Tp& __obj, _Up&& __new_val) 150 { 151 _Tp __old_val = std::move(__obj); 152 __obj = std::forward<_Up>(__new_val); 153 return __old_val; 154 } 155 156 /// @} group utilities 157 158 #define _GLIBCXX_MOVE(__val) std::move(__val) 159 #define _GLIBCXX_FORWARD(_Tp, __val) std::forward<_Tp>(__val) 160 #else 161 #define _GLIBCXX_MOVE(__val) (__val) 162 #define _GLIBCXX_FORWARD(_Tp, __val) (__val) 163 #endif 164 165 /** 166 * @addtogroup utilities 167 * @{ 168 */ 169 170 /** 171 * @brief Swaps two values. 172 * @param __a A thing of arbitrary type. 173 * @param __b Another thing of arbitrary type. 174 * @return Nothing. 175 */ 176 template<typename _Tp> 177 inline 178 #if __cplusplus >= 201103L 179 typename enable_if<__and_<__not_<__is_tuple_like<_Tp>>, 180 is_move_constructible<_Tp>, 181 is_move_assignable<_Tp>>::value>::type 182 swap(_Tp& __a, _Tp& __b) 183 noexcept(__and_<is_nothrow_move_constructible<_Tp>, 184 is_nothrow_move_assignable<_Tp>>::value) 185 #else 186 void 187 swap(_Tp& __a, _Tp& __b) 188 #endif 189 { 190 // concept requirements 191 __glibcxx_function_requires(_SGIAssignableConcept<_Tp>) 192 193 _Tp __tmp = _GLIBCXX_MOVE(__a); 194 __a = _GLIBCXX_MOVE(__b); 195 __b = _GLIBCXX_MOVE(__tmp); 196 } 197 198 // _GLIBCXX_RESOLVE_LIB_DEFECTS 199 // DR 809. std::swap should be overloaded for array types. 200 /// Swap the contents of two arrays. 201 template<typename _Tp, size_t _Nm> 202 inline 203 #if __cplusplus >= 201103L 204 typename enable_if<__is_swappable<_Tp>::value>::type 205 swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm]) 206 noexcept(__is_nothrow_swappable<_Tp>::value) 207 #else 208 void 209 swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm]) 210 #endif 211 { 212 for (size_t __n = 0; __n < _Nm; ++__n) 213 swap(__a[__n], __b[__n]); 214 } 215 216 /// @} group utilities 217 _GLIBCXX_END_NAMESPACE_VERSION 218 } // namespace 219 220 #endif /* _MOVE_H */ 221