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The C and C++ Include Header Files
cat -n /usr/include/c++/15/bits/move.h
1 // Move, forward and identity for C++11 + swap -*- C++ -*- 2 3 // Copyright (C) 2007-2025 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 #else 37 # include <type_traits> // Brings in std::declval too. 38 #endif 39 40 namespace std _GLIBCXX_VISIBILITY(default) 41 { 42 _GLIBCXX_BEGIN_NAMESPACE_VERSION 43 44 // Used, in C++03 mode too, by allocators, etc. 45 /** 46 * @brief Same as C++11 std::addressof 47 * @ingroup utilities 48 */ 49 template<typename _Tp> 50 __attribute__((__always_inline__)) 51 inline _GLIBCXX_CONSTEXPR _Tp* 52 __addressof(_Tp& __r) _GLIBCXX_NOEXCEPT 53 { return __builtin_addressof(__r); } 54 55 #if __cplusplus >= 201103L 56 57 /** 58 * @addtogroup utilities 59 * @{ 60 */ 61 62 /** 63 * @brief Forward an lvalue. 64 * @return The parameter cast to the specified type. 65 * 66 * This function is used to implement "perfect forwarding". 67 * @since C++11 68 */ 69 template<typename _Tp> 70 [[__nodiscard__,__gnu__::__always_inline__]] 71 constexpr _Tp&& 72 forward(typename std::remove_reference<_Tp>::type& __t) noexcept 73 { return static_cast<_Tp&&>(__t); } 74 75 /** 76 * @brief Forward an rvalue. 77 * @return The parameter cast to the specified type. 78 * 79 * This function is used to implement "perfect forwarding". 80 * @since C++11 81 */ 82 template<typename _Tp> 83 [[__nodiscard__,__gnu__::__always_inline__]] 84 constexpr _Tp&& 85 forward(typename std::remove_reference<_Tp>::type&& __t) noexcept 86 { 87 static_assert(!std::is_lvalue_reference<_Tp>::value, 88 "std::forward must not be used to convert an rvalue to an lvalue"); 89 return static_cast<_Tp&&>(__t); 90 } 91 92 #if __glibcxx_forward_like // C++ >= 23 93 template<typename _Tp, typename _Up> 94 struct __like_impl; // _Tp must be a reference and _Up an lvalue reference 95 96 template<typename _Tp, typename _Up> 97 struct __like_impl<_Tp&, _Up&> 98 { using type = _Up&; }; 99 100 template<typename _Tp, typename _Up> 101 struct __like_impl<const _Tp&, _Up&> 102 { using type = const _Up&; }; 103 104 template<typename _Tp, typename _Up> 105 struct __like_impl<_Tp&&, _Up&> 106 { using type = _Up&&; }; 107 108 template<typename _Tp, typename _Up> 109 struct __like_impl<const _Tp&&, _Up&> 110 { using type = const _Up&&; }; 111 112 template<typename _Tp, typename _Up> 113 using __like_t = typename __like_impl<_Tp&&, _Up&>::type; 114 115 /** @brief Forward with the cv-qualifiers and value category of another type. 116 * @tparam _Tp An lvalue reference or rvalue reference. 117 * @tparam _Up An lvalue reference type deduced from the function argument. 118 * @param __x An lvalue. 119 * @return `__x` converted to match the qualifiers of `_Tp`. 120 * @since C++23 121 */ 122 template<typename _Tp, typename _Up> 123 [[nodiscard,__gnu__::__always_inline__]] 124 constexpr __like_t<_Tp, _Up> 125 forward_like(_Up&& __x) noexcept 126 { return static_cast<__like_t<_Tp, _Up>>(__x); } 127 #endif 128 129 /** 130 * @brief Convert a value to an rvalue. 131 * @param __t A thing of arbitrary type. 132 * @return The parameter cast to an rvalue-reference to allow moving it. 133 * @since C++11 134 */ 135 template<typename _Tp> 136 [[__nodiscard__,__gnu__::__always_inline__]] 137 constexpr typename std::remove_reference<_Tp>::type&& 138 move(_Tp&& __t) noexcept 139 { return static_cast<typename std::remove_reference<_Tp>::type&&>(__t); } 140 141 142 template<typename _Tp> 143 struct __move_if_noexcept_cond 144 : public __and_<__not_<is_nothrow_move_constructible<_Tp>>, 145 is_copy_constructible<_Tp>>::type { }; 146 147 /** 148 * @brief Conditionally convert a value to an rvalue. 149 * @param __x A thing of arbitrary type. 150 * @return The parameter, possibly cast to an rvalue-reference. 151 * 152 * Same as std::move unless the type's move constructor could throw and the 153 * type is copyable, in which case an lvalue-reference is returned instead. 154 * @since C++11 155 */ 156 template<typename _Tp> 157 [[__nodiscard__,__gnu__::__always_inline__]] 158 constexpr 159 __conditional_t<__move_if_noexcept_cond<_Tp>::value, const _Tp&, _Tp&&> 160 move_if_noexcept(_Tp& __x) noexcept 161 { return std::move(__x); } 162 163 // declval, from type_traits. 164 165 /** 166 * @brief Returns the actual address of the object or function 167 * referenced by r, even in the presence of an overloaded 168 * operator&. 169 * @param __r Reference to an object or function. 170 * @return The actual address. 171 * @since C++11 172 */ 173 template<typename _Tp> 174 [[__nodiscard__,__gnu__::__always_inline__]] 175 inline _GLIBCXX17_CONSTEXPR _Tp* 176 addressof(_Tp& __r) noexcept 177 { return std::__addressof(__r); } 178 179 // _GLIBCXX_RESOLVE_LIB_DEFECTS 180 // 2598. addressof works on temporaries 181 template<typename _Tp> 182 const _Tp* addressof(const _Tp&&) = delete; 183 184 // C++11 version of std::exchange for internal use. 185 template <typename _Tp, typename _Up = _Tp> 186 _GLIBCXX20_CONSTEXPR 187 inline _Tp 188 __exchange(_Tp& __obj, _Up&& __new_val) 189 { 190 _Tp __old_val = std::move(__obj); 191 __obj = std::forward<_Up>(__new_val); 192 return __old_val; 193 } 194 195 /// @} group utilities 196 197 #define _GLIBCXX_FWDREF(_Tp) _Tp&& 198 #define _GLIBCXX_MOVE(__val) std::move(__val) 199 #define _GLIBCXX_FORWARD(_Tp, __val) std::forward<_Tp>(__val) 200 #else 201 #define _GLIBCXX_FWDREF(_Tp) const _Tp& 202 #define _GLIBCXX_MOVE(__val) (__val) 203 #define _GLIBCXX_FORWARD(_Tp, __val) (__val) 204 #endif 205 206 /** 207 * @addtogroup utilities 208 * @{ 209 */ 210 211 /** 212 * @brief Swaps two values. 213 * @param __a A thing of arbitrary type. 214 * @param __b Another thing of arbitrary type. 215 * @return Nothing. 216 */ 217 template<typename _Tp> 218 _GLIBCXX20_CONSTEXPR 219 inline 220 #if __cplusplus >= 201103L 221 typename enable_if<__and_<__not_<__is_tuple_like<_Tp>>, 222 is_move_constructible<_Tp>, 223 is_move_assignable<_Tp>>::value>::type 224 #else 225 void 226 #endif 227 swap(_Tp& __a, _Tp& __b) 228 _GLIBCXX_NOEXCEPT_IF(__and_<is_nothrow_move_constructible<_Tp>, 229 is_nothrow_move_assignable<_Tp>>::value) 230 { 231 #if __cplusplus < 201103L 232 // concept requirements 233 __glibcxx_function_requires(_SGIAssignableConcept<_Tp>) 234 #endif 235 _Tp __tmp = _GLIBCXX_MOVE(__a); 236 __a = _GLIBCXX_MOVE(__b); 237 __b = _GLIBCXX_MOVE(__tmp); 238 } 239 240 // _GLIBCXX_RESOLVE_LIB_DEFECTS 241 // DR 809. std::swap should be overloaded for array types. 242 /// Swap the contents of two arrays. 243 template<typename _Tp, size_t _Nm> 244 _GLIBCXX20_CONSTEXPR 245 inline 246 #if __cplusplus >= 201103L 247 typename enable_if<__is_swappable<_Tp>::value>::type 248 #else 249 void 250 #endif 251 swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm]) 252 _GLIBCXX_NOEXCEPT_IF(__is_nothrow_swappable<_Tp>::value) 253 { 254 for (size_t __n = 0; __n < _Nm; ++__n) 255 swap(__a[__n], __b[__n]); 256 } 257 258 /// @} group utilities 259 _GLIBCXX_END_NAMESPACE_VERSION 260 } // namespace 261 262 #endif /* _MOVE_H */
