libstdc++
stl_construct.h
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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 _Construct and _Destroy functions will dispatch to construct_at and
69 * destroy_at during constant evaluation, because calls to those functions are
70 * intercepted by the compiler to allow use in constant expressions.
71 */
72
73namespace 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 constexpr _Tp*
108 _Construct(_Tp* __p, _Args&&... __args)
109 {
110#if __cplusplus > 201703L
111 return std::construct_at(__p, std::forward<_Args>(__args)...);
112#else
113 return ::new(static_cast<void*>(__p)) _Tp(std::forward<_Args>(__args)...);
114#endif
115 }
116#else
117 template<typename _T1, typename _T2>
118 inline _T1*
119 _Construct(_T1* __p, const _T2& __value)
120 {
121 // _GLIBCXX_RESOLVE_LIB_DEFECTS
122 // 402. wrong new expression in [some_]allocator::construct
123 return ::new(static_cast<void*>(__p)) _T1(__value);
124 }
125#endif
126
127 template<typename _T1>
128 inline void
129 _Construct_novalue(_T1* __p)
130 { ::new(static_cast<void*>(__p)) _T1; }
131
132 template<typename _ForwardIterator>
133 _GLIBCXX20_CONSTEXPR void
134 _Destroy(_ForwardIterator __first, _ForwardIterator __last);
135
136 /**
137 * Destroy the object pointed to by a pointer type.
138 */
139 template<typename _Tp>
140 _GLIBCXX14_CONSTEXPR inline void
141 _Destroy(_Tp* __pointer)
142 {
143#if __cplusplus > 201703L
144 std::destroy_at(__pointer);
145#else
146 __pointer->~_Tp();
147#endif
148 }
149
150 template<bool>
151 struct _Destroy_aux
152 {
153 template<typename _ForwardIterator>
154 static _GLIBCXX20_CONSTEXPR void
155 __destroy(_ForwardIterator __first, _ForwardIterator __last)
156 {
157 for (; __first != __last; ++__first)
159 }
160 };
161
162 template<>
163 struct _Destroy_aux<true>
164 {
165 template<typename _ForwardIterator>
166 static void
167 __destroy(_ForwardIterator, _ForwardIterator) { }
168 };
169
170 /**
171 * Destroy a range of objects. If the value_type of the object has
172 * a trivial destructor, the compiler should optimize all of this
173 * away, otherwise the objects' destructors must be invoked.
174 */
175 template<typename _ForwardIterator>
176 _GLIBCXX20_CONSTEXPR inline void
177 _Destroy(_ForwardIterator __first, _ForwardIterator __last)
178 {
180 _Value_type;
181#if __cplusplus >= 201103L
182 // A deleted destructor is trivial, this ensures we reject such types:
184 "value type is destructible");
185#endif
186#if __cplusplus > 201703L && defined __cpp_lib_is_constant_evaluated
187 if (std::is_constant_evaluated())
188 return _Destroy_aux<false>::__destroy(__first, __last);
189#endif
190 std::_Destroy_aux<__has_trivial_destructor(_Value_type)>::
191 __destroy(__first, __last);
192 }
193
194 template<bool>
195 struct _Destroy_n_aux
196 {
197 template<typename _ForwardIterator, typename _Size>
198 static _GLIBCXX20_CONSTEXPR _ForwardIterator
199 __destroy_n(_ForwardIterator __first, _Size __count)
200 {
201 for (; __count > 0; (void)++__first, --__count)
203 return __first;
204 }
205 };
206
207 template<>
208 struct _Destroy_n_aux<true>
209 {
210 template<typename _ForwardIterator, typename _Size>
211 static _ForwardIterator
212 __destroy_n(_ForwardIterator __first, _Size __count)
213 {
214 std::advance(__first, __count);
215 return __first;
216 }
217 };
218
219 /**
220 * Destroy a range of objects. If the value_type of the object has
221 * a trivial destructor, the compiler should optimize all of this
222 * away, otherwise the objects' destructors must be invoked.
223 */
224 template<typename _ForwardIterator, typename _Size>
225 _GLIBCXX20_CONSTEXPR inline _ForwardIterator
226 _Destroy_n(_ForwardIterator __first, _Size __count)
227 {
229 _Value_type;
230#if __cplusplus >= 201103L
231 // A deleted destructor is trivial, this ensures we reject such types:
233 "value type is destructible");
234#endif
235#if __cplusplus > 201703L && defined __cpp_lib_is_constant_evaluated
236 if (std::is_constant_evaluated())
237 return _Destroy_n_aux<false>::__destroy_n(__first, __count);
238#endif
239 return std::_Destroy_n_aux<__has_trivial_destructor(_Value_type)>::
240 __destroy_n(__first, __count);
241 }
242
243#if __cplusplus >= 201703L
244 template <typename _ForwardIterator>
245 _GLIBCXX20_CONSTEXPR inline void
246 destroy(_ForwardIterator __first, _ForwardIterator __last)
247 {
248 std::_Destroy(__first, __last);
249 }
250
251 template <typename _ForwardIterator, typename _Size>
252 _GLIBCXX20_CONSTEXPR inline _ForwardIterator
253 destroy_n(_ForwardIterator __first, _Size __count)
254 {
255 return std::_Destroy_n(__first, __count);
256 }
257#endif // C++17
258
259_GLIBCXX_END_NAMESPACE_VERSION
260} // namespace std
261
262#endif /* _STL_CONSTRUCT_H */
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition: move.h:49
ISO C++ entities toplevel namespace is std.
constexpr _ForwardIterator _Destroy_n(_ForwardIterator __first, _Size __count)
constexpr void advance(_InputIterator &__i, _Distance __n)
A generalization of pointer arithmetic.
void _Destroy(_ForwardIterator __first, _ForwardIterator __last, _Allocator &__alloc)
constexpr _Tp * _Construct(_Tp *__p, _Args &&... __args)
is_destructible
Definition: type_traits:843
Traits class for iterators.