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
_GLIBCXX_VISIBILITY(default)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