1 | // auto_ptr implementation -*- C++ -*- |
2 | |
3 | // Copyright (C) 2007-2024 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 backward/auto_ptr.h |
26 | * This is an internal header file, included by other library headers. |
27 | * Do not attempt to use it directly. @headername{memory} |
28 | */ |
29 | |
30 | #ifndef _BACKWARD_AUTO_PTR_H |
31 | #define _BACKWARD_AUTO_PTR_H 1 |
32 | |
33 | #include <bits/c++config.h> |
34 | #include <debug/debug.h> |
35 | |
36 | namespace std _GLIBCXX_VISIBILITY(default) |
37 | { |
38 | _GLIBCXX_BEGIN_NAMESPACE_VERSION |
39 | |
40 | /** |
41 | * A wrapper class to provide auto_ptr with reference semantics. |
42 | * For example, an auto_ptr can be assigned (or constructed from) |
43 | * the result of a function which returns an auto_ptr by value. |
44 | * |
45 | * All the auto_ptr_ref stuff should happen behind the scenes. |
46 | */ |
47 | template<typename _Tp1> |
48 | struct auto_ptr_ref |
49 | { |
50 | _Tp1* _M_ptr; |
51 | |
52 | explicit |
53 | auto_ptr_ref(_Tp1* __p): _M_ptr(__p) { } |
54 | } _GLIBCXX11_DEPRECATED; |
55 | |
56 | #pragma GCC diagnostic push |
57 | #pragma GCC diagnostic ignored "-Wdeprecated-declarations" |
58 | |
59 | /** |
60 | * @brief A simple smart pointer providing strict ownership semantics. |
61 | * |
62 | * The Standard says: |
63 | * <pre> |
64 | * An @c auto_ptr owns the object it holds a pointer to. Copying |
65 | * an @c auto_ptr copies the pointer and transfers ownership to the |
66 | * destination. If more than one @c auto_ptr owns the same object |
67 | * at the same time the behavior of the program is undefined. |
68 | * |
69 | * The uses of @c auto_ptr include providing temporary |
70 | * exception-safety for dynamically allocated memory, passing |
71 | * ownership of dynamically allocated memory to a function, and |
72 | * returning dynamically allocated memory from a function. @c |
73 | * auto_ptr does not meet the CopyConstructible and Assignable |
74 | * requirements for Standard Library <a |
75 | * href="tables.html#65">container</a> elements and thus |
76 | * instantiating a Standard Library container with an @c auto_ptr |
77 | * results in undefined behavior. |
78 | * </pre> |
79 | * Quoted from [20.4.5]/3. |
80 | * |
81 | * Good examples of what can and cannot be done with auto_ptr can |
82 | * be found in the libstdc++ testsuite. |
83 | * |
84 | * _GLIBCXX_RESOLVE_LIB_DEFECTS |
85 | * 127. auto_ptr<> conversion issues |
86 | * These resolutions have all been incorporated. |
87 | * |
88 | * @headerfile memory |
89 | * @deprecated Deprecated in C++11, no longer in the standard since C++17. |
90 | * Use `unique_ptr` instead. |
91 | */ |
92 | template<typename _Tp> |
93 | class auto_ptr |
94 | { |
95 | private: |
96 | _Tp* _M_ptr; |
97 | |
98 | public: |
99 | /// The pointed-to type. |
100 | typedef _Tp element_type; |
101 | |
102 | /** |
103 | * @brief An %auto_ptr is usually constructed from a raw pointer. |
104 | * @param __p A pointer (defaults to NULL). |
105 | * |
106 | * This object now @e owns the object pointed to by @a __p. |
107 | */ |
108 | explicit |
109 | auto_ptr(element_type* __p = 0) throw() : _M_ptr(__p) { } |
110 | |
111 | /** |
112 | * @brief An %auto_ptr can be constructed from another %auto_ptr. |
113 | * @param __a Another %auto_ptr of the same type. |
114 | * |
115 | * This object now @e owns the object previously owned by @a __a, |
116 | * which has given up ownership. |
117 | */ |
118 | auto_ptr(auto_ptr& __a) throw() : _M_ptr(__a.release()) { } |
119 | |
120 | /** |
121 | * @brief An %auto_ptr can be constructed from another %auto_ptr. |
122 | * @param __a Another %auto_ptr of a different but related type. |
123 | * |
124 | * A pointer-to-Tp1 must be convertible to a |
125 | * pointer-to-Tp/element_type. |
126 | * |
127 | * This object now @e owns the object previously owned by @a __a, |
128 | * which has given up ownership. |
129 | */ |
130 | template<typename _Tp1> |
131 | auto_ptr(auto_ptr<_Tp1>& __a) throw() : _M_ptr(__a.release()) { } |
132 | |
133 | /** |
134 | * @brief %auto_ptr assignment operator. |
135 | * @param __a Another %auto_ptr of the same type. |
136 | * |
137 | * This object now @e owns the object previously owned by @a __a, |
138 | * which has given up ownership. The object that this one @e |
139 | * used to own and track has been deleted. |
140 | */ |
141 | auto_ptr& |
142 | operator=(auto_ptr& __a) throw() |
143 | { |
144 | reset(p: __a.release()); |
145 | return *this; |
146 | } |
147 | |
148 | /** |
149 | * @brief %auto_ptr assignment operator. |
150 | * @param __a Another %auto_ptr of a different but related type. |
151 | * |
152 | * A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type. |
153 | * |
154 | * This object now @e owns the object previously owned by @a __a, |
155 | * which has given up ownership. The object that this one @e |
156 | * used to own and track has been deleted. |
157 | */ |
158 | template<typename _Tp1> |
159 | auto_ptr& |
160 | operator=(auto_ptr<_Tp1>& __a) throw() |
161 | { |
162 | reset(p: __a.release()); |
163 | return *this; |
164 | } |
165 | |
166 | /** |
167 | * When the %auto_ptr goes out of scope, the object it owns is |
168 | * deleted. If it no longer owns anything (i.e., @c get() is |
169 | * @c NULL), then this has no effect. |
170 | * |
171 | * The C++ standard says there is supposed to be an empty throw |
172 | * specification here, but omitting it is standard conforming. Its |
173 | * presence can be detected only if _Tp::~_Tp() throws, but this is |
174 | * prohibited. [17.4.3.6]/2 |
175 | */ |
176 | ~auto_ptr() { delete _M_ptr; } |
177 | |
178 | /** |
179 | * @brief Smart pointer dereferencing. |
180 | * |
181 | * If this %auto_ptr no longer owns anything, then this |
182 | * operation will crash. (For a smart pointer, <em>no longer owns |
183 | * anything</em> is the same as being a null pointer, and you know |
184 | * what happens when you dereference one of those...) |
185 | */ |
186 | element_type& |
187 | operator*() const throw() |
188 | { |
189 | __glibcxx_assert(_M_ptr != 0); |
190 | return *_M_ptr; |
191 | } |
192 | |
193 | /** |
194 | * @brief Smart pointer dereferencing. |
195 | * |
196 | * This returns the pointer itself, which the language then will |
197 | * automatically cause to be dereferenced. |
198 | */ |
199 | element_type* |
200 | operator->() const throw() |
201 | { |
202 | __glibcxx_assert(_M_ptr != 0); |
203 | return _M_ptr; |
204 | } |
205 | |
206 | /** |
207 | * @brief Bypassing the smart pointer. |
208 | * @return The raw pointer being managed. |
209 | * |
210 | * You can get a copy of the pointer that this object owns, for |
211 | * situations such as passing to a function which only accepts |
212 | * a raw pointer. |
213 | * |
214 | * @note This %auto_ptr still owns the memory. |
215 | */ |
216 | element_type* |
217 | get() const throw() { return _M_ptr; } |
218 | |
219 | /** |
220 | * @brief Bypassing the smart pointer. |
221 | * @return The raw pointer being managed. |
222 | * |
223 | * You can get a copy of the pointer that this object owns, for |
224 | * situations such as passing to a function which only accepts |
225 | * a raw pointer. |
226 | * |
227 | * @note This %auto_ptr no longer owns the memory. When this object |
228 | * goes out of scope, nothing will happen. |
229 | */ |
230 | element_type* |
231 | release() throw() |
232 | { |
233 | element_type* __tmp = _M_ptr; |
234 | _M_ptr = 0; |
235 | return __tmp; |
236 | } |
237 | |
238 | /** |
239 | * @brief Forcibly deletes the managed object. |
240 | * @param __p A pointer (defaults to NULL). |
241 | * |
242 | * This object now @e owns the object pointed to by @a __p. The |
243 | * previous object has been deleted. |
244 | */ |
245 | void |
246 | reset(element_type* __p = 0) throw() |
247 | { |
248 | if (__p != _M_ptr) |
249 | { |
250 | delete _M_ptr; |
251 | _M_ptr = __p; |
252 | } |
253 | } |
254 | |
255 | /** |
256 | * @brief Automatic conversions |
257 | * |
258 | * These operations are supposed to convert an %auto_ptr into and from |
259 | * an auto_ptr_ref automatically as needed. This would allow |
260 | * constructs such as |
261 | * @code |
262 | * auto_ptr<Derived> func_returning_auto_ptr(.....); |
263 | * ... |
264 | * auto_ptr<Base> ptr = func_returning_auto_ptr(.....); |
265 | * @endcode |
266 | * |
267 | * But it doesn't work, and won't be fixed. For further details see |
268 | * http://cplusplus.github.io/LWG/lwg-closed.html#463 |
269 | */ |
270 | auto_ptr(auto_ptr_ref<element_type> __ref) throw() |
271 | : _M_ptr(__ref._M_ptr) { } |
272 | |
273 | auto_ptr& |
274 | operator=(auto_ptr_ref<element_type> __ref) throw() |
275 | { |
276 | if (__ref._M_ptr != this->get()) |
277 | { |
278 | delete _M_ptr; |
279 | _M_ptr = __ref._M_ptr; |
280 | } |
281 | return *this; |
282 | } |
283 | |
284 | template<typename _Tp1> |
285 | operator auto_ptr_ref<_Tp1>() throw() |
286 | { return auto_ptr_ref<_Tp1>(this->release()); } |
287 | |
288 | template<typename _Tp1> |
289 | operator auto_ptr<_Tp1>() throw() |
290 | { return auto_ptr<_Tp1>(this->release()); } |
291 | } _GLIBCXX11_DEPRECATED_SUGGEST("std::unique_ptr" ); |
292 | |
293 | // _GLIBCXX_RESOLVE_LIB_DEFECTS |
294 | // 541. shared_ptr template assignment and void |
295 | template<> |
296 | class auto_ptr<void> |
297 | { |
298 | public: |
299 | typedef void element_type; |
300 | } _GLIBCXX11_DEPRECATED; |
301 | |
302 | #if __cplusplus >= 201103L |
303 | #if _GLIBCXX_HOSTED |
304 | template<_Lock_policy _Lp> |
305 | template<typename _Tp> |
306 | inline |
307 | __shared_count<_Lp>::__shared_count(std::auto_ptr<_Tp>&& __r) |
308 | : _M_pi(new _Sp_counted_ptr<_Tp*, _Lp>(__r.get())) |
309 | { __r.release(); } |
310 | |
311 | template<typename _Tp, _Lock_policy _Lp> |
312 | template<typename _Tp1, typename> |
313 | inline |
314 | __shared_ptr<_Tp, _Lp>::__shared_ptr(std::auto_ptr<_Tp1>&& __r) |
315 | : _M_ptr(__r.get()), _M_refcount() |
316 | { |
317 | __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>) |
318 | static_assert( sizeof(_Tp1) > 0, "incomplete type" ); |
319 | _Tp1* __tmp = __r.get(); |
320 | _M_refcount = __shared_count<_Lp>(std::move(__r)); |
321 | _M_enable_shared_from_this_with(__tmp); |
322 | } |
323 | |
324 | template<typename _Tp> |
325 | template<typename _Tp1, typename> |
326 | inline |
327 | shared_ptr<_Tp>::shared_ptr(std::auto_ptr<_Tp1>&& __r) |
328 | : __shared_ptr<_Tp>(std::move(__r)) { } |
329 | #endif // HOSTED |
330 | |
331 | template<typename _Tp, typename _Dp> |
332 | template<typename _Up, typename> |
333 | inline |
334 | unique_ptr<_Tp, _Dp>::unique_ptr(auto_ptr<_Up>&& __u) noexcept |
335 | : _M_t(__u.release(), deleter_type()) { } |
336 | #endif // C++11 |
337 | |
338 | #pragma GCC diagnostic pop |
339 | |
340 | _GLIBCXX_END_NAMESPACE_VERSION |
341 | } // namespace |
342 | |
343 | #endif /* _BACKWARD_AUTO_PTR_H */ |
344 | |