1 // nonstandard construct and destroy functions -*- C++ -*- 2 3 // Copyright (C) 2001-2020 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 /* 26 * 27 * Copyright (c) 1994 28 * Hewlett-Packard Company 29 * 30 * Permission to use, copy, modify, distribute and sell this software 31 * and its documentation for any purpose is hereby granted without fee, 32 * provided that the above copyright notice appear in all copies and 33 * that both that copyright notice and this permission notice appear 34 * in supporting documentation. Hewlett-Packard Company makes no 35 * representations about the suitability of this software for any 36 * purpose. It is provided "as is" without express or implied warranty. 37 * 38 * 39 * Copyright (c) 1996,1997 40 * Silicon Graphics Computer Systems, Inc. 41 * 42 * Permission to use, copy, modify, distribute and sell this software 43 * and its documentation for any purpose is hereby granted without fee, 44 * provided that the above copyright notice appear in all copies and 45 * that both that copyright notice and this permission notice appear 46 * in supporting documentation. Silicon Graphics makes no 47 * representations about the suitability of this software for any 48 * purpose. It is provided "as is" without express or implied warranty. 49 */ 50 51 /** @file bits/stl_construct.h 52 * This is an internal header file, included by other library headers. 53 * Do not attempt to use it directly. @headername{memory} 54 */ 55 56 #ifndef _STL_CONSTRUCT_H 57 #define _STL_CONSTRUCT_H 1 58 59 #include <new> 60 #include <bits/move.h> 61 #include <bits/stl_iterator_base_types.h> // for iterator_traits 62 #include <bits/stl_iterator_base_funcs.h> // for advance 63 64 /* This file provides the C++17 functions std::destroy_at, std::destroy, and 65 * std::destroy_n, and the C++20 function std::construct_at. 66 * It also provides std::_Construct, std::_Destroy,and std::_Destroy_n functions 67 * which are defined in all standard modes and so can be used in C++98-14 code. 68 * The _Destroy functions will dispatch to destroy_at during constant 69 * evaluation, because calls to that function are intercepted by the compiler 70 * to allow use in constant expressions. 71 */ 72 73 namespace std _GLIBCXX_VISIBILITY(default) 74 { 75 _GLIBCXX_BEGIN_NAMESPACE_VERSION 76 77 #if __cplusplus >= 201703L 78 template <typename _Tp> 79 _GLIBCXX20_CONSTEXPR inline void 80 destroy_at(_Tp* __location) 81 { 82 if constexpr (__cplusplus > 201703L && is_array_v<_Tp>) 83 { 84 for (auto& __x : *__location) 85 std::destroy_at(std::__addressof(__x)); 86 } 87 else 88 __location->~_Tp(); 89 } 90 91 #if __cplusplus > 201703L 92 template<typename _Tp, typename... _Args> 93 constexpr auto 94 construct_at(_Tp* __location, _Args&&... __args) 95 noexcept(noexcept(::new((void*)0) _Tp(std::declval<_Args>()...))) 96 -> decltype(::new((void*)0) _Tp(std::declval<_Args>()...)) 97 { return ::new((void*)__location) _Tp(std::forward<_Args>(__args)...); } 98 #endif // C++20 99 #endif// C++17 100 101 /** 102 * Constructs an object in existing memory by invoking an allocated 103 * object's constructor with an initializer. 104 */ 105 #if __cplusplus >= 201103L 106 template<typename _Tp, typename... _Args> 107 inline void 108 _Construct(_Tp* __p, _Args&&... __args) 109 { ::new(static_cast<void*>(__p)) _Tp(std::forward<_Args>(__args)...); } 110 #else 111 template<typename _T1, typename _T2> 112 inline void 113 _Construct(_T1* __p, const _T2& __value) 114 { 115 // _GLIBCXX_RESOLVE_LIB_DEFECTS 116 // 402. wrong new expression in [some_]allocator::construct 117 ::new(static_cast<void*>(__p)) _T1(__value); 118 } 119 #endif 120 121 template<typename _T1> 122 inline void 123 _Construct_novalue(_T1* __p) 124 { ::new(static_cast<void*>(__p)) _T1; } 125 126 template<typename _ForwardIterator> 127 _GLIBCXX20_CONSTEXPR void 128 _Destroy(_ForwardIterator __first, _ForwardIterator __last); 129 130 /** 131 * Destroy the object pointed to by a pointer type. 132 */ 133 template<typename _Tp> 134 _GLIBCXX14_CONSTEXPR inline void 135 _Destroy(_Tp* __pointer) 136 { 137 #if __cplusplus > 201703L 138 std::destroy_at(__pointer); 139 #else 140 __pointer->~_Tp(); 141 #endif 142 } 143 144 template<bool> 145 struct _Destroy_aux 146 { 147 template<typename _ForwardIterator> 148 static _GLIBCXX20_CONSTEXPR void 149 __destroy(_ForwardIterator __first, _ForwardIterator __last) 150 { 151 for (; __first != __last; ++__first) 152 std::_Destroy(std::__addressof(*__first)); 153 } 154 }; 155 156 template<> 157 struct _Destroy_aux<true> 158 { 159 template<typename _ForwardIterator> 160 static void 161 __destroy(_ForwardIterator, _ForwardIterator) { } 162 }; 163 164 /** 165 * Destroy a range of objects. If the value_type of the object has 166 * a trivial destructor, the compiler should optimize all of this 167 * away, otherwise the objects' destructors must be invoked. 168 */ 169 template<typename _ForwardIterator> 170 _GLIBCXX20_CONSTEXPR inline void 171 _Destroy(_ForwardIterator __first, _ForwardIterator __last) 172 { 173 typedef typename iterator_traits<_ForwardIterator>::value_type 174 _Value_type; 175 #if __cplusplus >= 201103L 176 // A deleted destructor is trivial, this ensures we reject such types: 177 static_assert(is_destructible<_Value_type>::value, 178 "value type is destructible"); 179 #endif 180 #if __cplusplus > 201703L && defined __cpp_lib_is_constant_evaluated 181 if (std::is_constant_evaluated()) 182 return _Destroy_aux<false>::__destroy(__first, __last); 183 #endif 184 std::_Destroy_aux<__has_trivial_destructor(_Value_type)>:: 185 __destroy(__first, __last); 186 } 187 188 template<bool> 189 struct _Destroy_n_aux 190 { 191 template<typename _ForwardIterator, typename _Size> 192 static _GLIBCXX20_CONSTEXPR _ForwardIterator 193 __destroy_n(_ForwardIterator __first, _Size __count) 194 { 195 for (; __count > 0; (void)++__first, --__count) 196 std::_Destroy(std::__addressof(*__first)); 197 return __first; 198 } 199 }; 200 201 template<> 202 struct _Destroy_n_aux<true> 203 { 204 template<typename _ForwardIterator, typename _Size> 205 static _ForwardIterator 206 __destroy_n(_ForwardIterator __first, _Size __count) 207 { 208 std::advance(__first, __count); 209 return __first; 210 } 211 }; 212 213 /** 214 * Destroy a range of objects. If the value_type of the object has 215 * a trivial destructor, the compiler should optimize all of this 216 * away, otherwise the objects' destructors must be invoked. 217 */ 218 template<typename _ForwardIterator, typename _Size> 219 _GLIBCXX20_CONSTEXPR inline _ForwardIterator 220 _Destroy_n(_ForwardIterator __first, _Size __count) 221 { 222 typedef typename iterator_traits<_ForwardIterator>::value_type 223 _Value_type; 224 #if __cplusplus >= 201103L 225 // A deleted destructor is trivial, this ensures we reject such types: 226 static_assert(is_destructible<_Value_type>::value, 227 "value type is destructible"); 228 #endif 229 #if __cplusplus > 201703L && defined __cpp_lib_is_constant_evaluated 230 if (std::is_constant_evaluated()) 231 return _Destroy_n_aux<false>::__destroy_n(__first, __count); 232 #endif 233 return std::_Destroy_n_aux<__has_trivial_destructor(_Value_type)>:: 234 __destroy_n(__first, __count); 235 } 236 237 #if __cplusplus >= 201703L 238 template <typename _ForwardIterator> 239 _GLIBCXX20_CONSTEXPR inline void 240 destroy(_ForwardIterator __first, _ForwardIterator __last) 241 { 242 std::_Destroy(__first, __last); 243 } 244 245 template <typename _ForwardIterator, typename _Size> 246 _GLIBCXX20_CONSTEXPR inline _ForwardIterator 247 destroy_n(_ForwardIterator __first, _Size __count) 248 { 249 return std::_Destroy_n(__first, __count); 250 } 251 #endif // C++17 252 253 _GLIBCXX_END_NAMESPACE_VERSION 254 } // namespace std 255 256 #endif /* _STL_CONSTRUCT_H */ 257