1 // Move, forward and identity for C++11 + swap -*- C++ -*- 2 3 // Copyright (C) 2007-2020 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 #if __cplusplus < 201103L 35 # include <bits/concept_check.h> 36 #endif 37 38 namespace std _GLIBCXX_VISIBILITY(default) 39 { 40 _GLIBCXX_BEGIN_NAMESPACE_VERSION 41 42 // Used, in C++03 mode too, by allocators, etc. 43 /** 44 * @brief Same as C++11 std::addressof 45 * @ingroup utilities 46 */ 47 template<typename _Tp> 48 inline _GLIBCXX_CONSTEXPR _Tp* 49 __addressof(_Tp& __r) _GLIBCXX_NOEXCEPT 50 { return __builtin_addressof(__r); } 51 52 #if __cplusplus >= 201103L 53 54 _GLIBCXX_END_NAMESPACE_VERSION 55 } // namespace 56 57 #include <type_traits> // Brings in std::declval too. 58 59 namespace std _GLIBCXX_VISIBILITY(default) 60 { 61 _GLIBCXX_BEGIN_NAMESPACE_VERSION 62 63 /** 64 * @addtogroup utilities 65 * @{ 66 */ 67 68 /** 69 * @brief Forward an lvalue. 70 * @return The parameter cast to the specified type. 71 * 72 * This function is used to implement "perfect forwarding". 73 */ 74 template<typename _Tp> 75 constexpr _Tp&& 76 forward(typename std::remove_reference<_Tp>::type& __t) noexcept 77 { return static_cast<_Tp&&>(__t); } 78 79 /** 80 * @brief Forward an rvalue. 81 * @return The parameter cast to the specified type. 82 * 83 * This function is used to implement "perfect forwarding". 84 */ 85 template<typename _Tp> 86 constexpr _Tp&& 87 forward(typename std::remove_reference<_Tp>::type&& __t) noexcept 88 { 89 static_assert(!std::is_lvalue_reference<_Tp>::value, 90 "std::forward must not be used to convert an rvalue to an lvalue"); 91 return static_cast<_Tp&&>(__t); 92 } 93 94 /** 95 * @brief Convert a value to an rvalue. 96 * @param __t A thing of arbitrary type. 97 * @return The parameter cast to an rvalue-reference to allow moving it. 98 */ 99 template<typename _Tp> 100 constexpr typename std::remove_reference<_Tp>::type&& 101 move(_Tp&& __t) noexcept 102 { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); } 103 104 105 template<typename _Tp> 106 struct __move_if_noexcept_cond 107 : public __and_<__not_<is_nothrow_move_constructible<_Tp>>, 108 is_copy_constructible<_Tp>>::type { }; 109 110 /** 111 * @brief Conditionally convert a value to an rvalue. 112 * @param __x A thing of arbitrary type. 113 * @return The parameter, possibly cast to an rvalue-reference. 114 * 115 * Same as std::move unless the type's move constructor could throw and the 116 * type is copyable, in which case an lvalue-reference is returned instead. 117 */ 118 template<typename _Tp> 119 constexpr typename 120 conditional<__move_if_noexcept_cond<_Tp>::value, const _Tp&, _Tp&&>::type 121 move_if_noexcept(_Tp& __x) noexcept 122 { return std::move(__x); } 123 124 // declval, from type_traits. 125 126 #if __cplusplus > 201402L 127 // _GLIBCXX_RESOLVE_LIB_DEFECTS 128 // 2296. std::addressof should be constexpr 129 # define __cpp_lib_addressof_constexpr 201603 130 #endif 131 /** 132 * @brief Returns the actual address of the object or function 133 * referenced by r, even in the presence of an overloaded 134 * operator&. 135 * @param __r Reference to an object or function. 136 * @return The actual address. 137 */ 138 template<typename _Tp> 139 inline _GLIBCXX17_CONSTEXPR _Tp* 140 addressof(_Tp& __r) noexcept 141 { return std::__addressof(__r); } 142 143 // _GLIBCXX_RESOLVE_LIB_DEFECTS 144 // 2598. addressof works on temporaries 145 template<typename _Tp> 146 const _Tp* addressof(const _Tp&&) = delete; 147 148 // C++11 version of std::exchange for internal use. 149 template <typename _Tp, typename _Up = _Tp> 150 _GLIBCXX20_CONSTEXPR 151 inline _Tp 152 __exchange(_Tp& __obj, _Up&& __new_val) 153 { 154 _Tp __old_val = std::move(__obj); 155 __obj = std::forward<_Up>(__new_val); 156 return __old_val; 157 } 158 159 /// @} group utilities 160 161 #define _GLIBCXX_MOVE(__val) std::move(__val) 162 #define _GLIBCXX_FORWARD(_Tp, __val) std::forward<_Tp>(__val) 163 #else 164 #define _GLIBCXX_MOVE(__val) (__val) 165 #define _GLIBCXX_FORWARD(_Tp, __val) (__val) 166 #endif 167 168 /** 169 * @addtogroup utilities 170 * @{ 171 */ 172 173 /** 174 * @brief Swaps two values. 175 * @param __a A thing of arbitrary type. 176 * @param __b Another thing of arbitrary type. 177 * @return Nothing. 178 */ 179 template<typename _Tp> 180 _GLIBCXX20_CONSTEXPR 181 inline 182 #if __cplusplus >= 201103L 183 typename enable_if<__and_<__not_<__is_tuple_like<_Tp>>, 184 is_move_constructible<_Tp>, 185 is_move_assignable<_Tp>>::value>::type 186 #else 187 void 188 #endif 189 swap(_Tp& __a, _Tp& __b) 190 _GLIBCXX_NOEXCEPT_IF(__and_<is_nothrow_move_constructible<_Tp>, 191 is_nothrow_move_assignable<_Tp>>::value) 192 { 193 #if __cplusplus < 201103L 194 // concept requirements 195 __glibcxx_function_requires(_SGIAssignableConcept<_Tp>) 196 #endif 197 _Tp __tmp = _GLIBCXX_MOVE(__a); 198 __a = _GLIBCXX_MOVE(__b); 199 __b = _GLIBCXX_MOVE(__tmp); 200 } 201 202 // _GLIBCXX_RESOLVE_LIB_DEFECTS 203 // DR 809. std::swap should be overloaded for array types. 204 /// Swap the contents of two arrays. 205 template<typename _Tp, size_t _Nm> 206 _GLIBCXX20_CONSTEXPR 207 inline 208 #if __cplusplus >= 201103L 209 typename enable_if<__is_swappable<_Tp>::value>::type 210 #else 211 void 212 #endif 213 swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm]) 214 _GLIBCXX_NOEXCEPT_IF(__is_nothrow_swappable<_Tp>::value) 215 { 216 for (size_t __n = 0; __n < _Nm; ++__n) 217 swap(__a[__n], __b[__n]); 218 } 219 220 /// @} group utilities 221 _GLIBCXX_END_NAMESPACE_VERSION 222 } // namespace 223 224 #endif /* _MOVE_H */ 225