1// auto_ptr implementation -*- C++ -*- 
2 
3// Copyright (C) 2007-2019 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 
36namespace 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 } _GLIBCXX_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 template<typename _Tp> 
89 class auto_ptr 
90 { 
91 private: 
92 _Tp* _M_ptr; 
93  
94 public: 
95 /// The pointed-to type. 
96 typedef _Tp element_type; 
97  
98 /** 
99 * @brief An %auto_ptr is usually constructed from a raw pointer. 
100 * @param __p A pointer (defaults to NULL). 
101 * 
102 * This object now @e owns the object pointed to by @a __p. 
103 */ 
104 explicit 
105 auto_ptr(element_type* __p = 0) throw() : _M_ptr(__p) { } 
106 
107 /** 
108 * @brief An %auto_ptr can be constructed from another %auto_ptr. 
109 * @param __a Another %auto_ptr of the same type. 
110 * 
111 * This object now @e owns the object previously owned by @a __a, 
112 * which has given up ownership. 
113 */ 
114 auto_ptr(auto_ptr& __a) throw() : _M_ptr(__a.release()) { } 
115 
116 /** 
117 * @brief An %auto_ptr can be constructed from another %auto_ptr. 
118 * @param __a Another %auto_ptr of a different but related type. 
119 * 
120 * A pointer-to-Tp1 must be convertible to a 
121 * pointer-to-Tp/element_type. 
122 * 
123 * This object now @e owns the object previously owned by @a __a, 
124 * which has given up ownership. 
125 */ 
126 template<typename _Tp1> 
127 auto_ptr(auto_ptr<_Tp1>& __a) throw() : _M_ptr(__a.release()) { } 
128 
129 /** 
130 * @brief %auto_ptr assignment operator. 
131 * @param __a Another %auto_ptr of the same type. 
132 * 
133 * This object now @e owns the object previously owned by @a __a, 
134 * which has given up ownership. The object that this one @e 
135 * used to own and track has been deleted. 
136 */ 
137 auto_ptr& 
138 operator=(auto_ptr& __a) throw() 
139 { 
140 reset(__a.release()); 
141 return *this; 
142 } 
143 
144 /** 
145 * @brief %auto_ptr assignment operator. 
146 * @param __a Another %auto_ptr of a different but related type. 
147 * 
148 * A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type. 
149 * 
150 * This object now @e owns the object previously owned by @a __a, 
151 * which has given up ownership. The object that this one @e 
152 * used to own and track has been deleted. 
153 */ 
154 template<typename _Tp1> 
155 auto_ptr& 
156 operator=(auto_ptr<_Tp1>& __a) throw() 
157 { 
158 reset(__a.release()); 
159 return *this; 
160 } 
161 
162 /** 
163 * When the %auto_ptr goes out of scope, the object it owns is 
164 * deleted. If it no longer owns anything (i.e., @c get() is 
165 * @c NULL), then this has no effect. 
166 * 
167 * The C++ standard says there is supposed to be an empty throw 
168 * specification here, but omitting it is standard conforming. Its 
169 * presence can be detected only if _Tp::~_Tp() throws, but this is 
170 * prohibited. [17.4.3.6]/2 
171 */ 
172 ~auto_ptr() { delete _M_ptr; } 
173  
174 /** 
175 * @brief Smart pointer dereferencing. 
176 * 
177 * If this %auto_ptr no longer owns anything, then this 
178 * operation will crash. (For a smart pointer, <em>no longer owns 
179 * anything</em> is the same as being a null pointer, and you know 
180 * what happens when you dereference one of those...) 
181 */ 
182 element_type& 
183 operator*() const throw()  
184 { 
185 __glibcxx_assert(_M_ptr != 0); 
186 return *_M_ptr;  
187 } 
188  
189 /** 
190 * @brief Smart pointer dereferencing. 
191 * 
192 * This returns the pointer itself, which the language then will 
193 * automatically cause to be dereferenced. 
194 */ 
195 element_type* 
196 operator->() const throw()  
197 { 
198 __glibcxx_assert(_M_ptr != 0); 
199 return _M_ptr;  
200 } 
201  
202 /** 
203 * @brief Bypassing the smart pointer. 
204 * @return The raw pointer being managed. 
205 * 
206 * You can get a copy of the pointer that this object owns, for 
207 * situations such as passing to a function which only accepts 
208 * a raw pointer. 
209 * 
210 * @note This %auto_ptr still owns the memory. 
211 */ 
212 element_type* 
213 get() const throw() { return _M_ptr; } 
214  
215 /** 
216 * @brief Bypassing the smart pointer. 
217 * @return The raw pointer being managed. 
218 * 
219 * You can get a copy of the pointer that this object owns, for 
220 * situations such as passing to a function which only accepts 
221 * a raw pointer. 
222 * 
223 * @note This %auto_ptr no longer owns the memory. When this object 
224 * goes out of scope, nothing will happen. 
225 */ 
226 element_type* 
227 release() throw() 
228 { 
229 element_type* __tmp = _M_ptr; 
230 _M_ptr = 0; 
231 return __tmp; 
232 } 
233  
234 /** 
235 * @brief Forcibly deletes the managed object. 
236 * @param __p A pointer (defaults to NULL). 
237 * 
238 * This object now @e owns the object pointed to by @a __p. The 
239 * previous object has been deleted. 
240 */ 
241 void 
242 reset(element_type* __p = 0) throw() 
243 { 
244 if (__p != _M_ptr) 
245 { 
246 delete _M_ptr; 
247 _M_ptr = __p; 
248 } 
249 } 
250  
251 /**  
252 * @brief Automatic conversions 
253 * 
254 * These operations are supposed to convert an %auto_ptr into and from 
255 * an auto_ptr_ref automatically as needed. This would allow 
256 * constructs such as 
257 * @code 
258 * auto_ptr<Derived> func_returning_auto_ptr(.....); 
259 * ... 
260 * auto_ptr<Base> ptr = func_returning_auto_ptr(.....); 
261 * @endcode 
262 * 
263 * But it doesn't work, and won't be fixed. For further details see 
264 * http://cplusplus.github.io/LWG/lwg-closed.html#463 
265 */ 
266 auto_ptr(auto_ptr_ref<element_type> __ref) throw() 
267 : _M_ptr(__ref._M_ptr) { } 
268  
269 auto_ptr& 
270 operator=(auto_ptr_ref<element_type> __ref) throw() 
271 { 
272 if (__ref._M_ptr != this->get()) 
273 { 
274 delete _M_ptr; 
275 _M_ptr = __ref._M_ptr; 
276 } 
277 return *this; 
278 } 
279  
280 template<typename _Tp1> 
281 operator auto_ptr_ref<_Tp1>() throw() 
282 { return auto_ptr_ref<_Tp1>(this->release()); } 
283 
284 template<typename _Tp1> 
285 operator auto_ptr<_Tp1>() throw() 
286 { return auto_ptr<_Tp1>(this->release()); } 
287 } _GLIBCXX_DEPRECATED; 
288 
289 // _GLIBCXX_RESOLVE_LIB_DEFECTS 
290 // 541. shared_ptr template assignment and void 
291 template<> 
292 class auto_ptr<void> 
293 { 
294 public: 
295 typedef void element_type; 
296 } _GLIBCXX_DEPRECATED; 
297 
298#if __cplusplus >= 201103L 
299 template<_Lock_policy _Lp> 
300 template<typename _Tp> 
301 inline 
302 __shared_count<_Lp>::__shared_count(std::auto_ptr<_Tp>&& __r) 
303 : _M_pi(new _Sp_counted_ptr<_Tp*, _Lp>(__r.get())) 
304 { __r.release(); } 
305 
306 template<typename _Tp, _Lock_policy _Lp> 
307 template<typename _Tp1, typename> 
308 inline 
309 __shared_ptr<_Tp, _Lp>::__shared_ptr(std::auto_ptr<_Tp1>&& __r) 
310 : _M_ptr(__r.get()), _M_refcount() 
311 { 
312 __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>) 
313 static_assert( sizeof(_Tp1) > 0, "incomplete type" ); 
314 _Tp1* __tmp = __r.get(); 
315 _M_refcount = __shared_count<_Lp>(std::move(__r)); 
316 _M_enable_shared_from_this_with(__tmp); 
317 } 
318 
319 template<typename _Tp> 
320 template<typename _Tp1, typename> 
321 inline 
322 shared_ptr<_Tp>::shared_ptr(std::auto_ptr<_Tp1>&& __r) 
323 : __shared_ptr<_Tp>(std::move(__r)) { } 
324 
325 template<typename _Tp, typename _Dp> 
326 template<typename _Up, typename> 
327 inline 
328 unique_ptr<_Tp, _Dp>::unique_ptr(auto_ptr<_Up>&& __u) noexcept 
329 : _M_t(__u.release(), deleter_type()) { } 
330#endif 
331 
332#pragma GCC diagnostic pop 
333 
334_GLIBCXX_END_NAMESPACE_VERSION 
335} // namespace 
336 
337#endif /* _BACKWARD_AUTO_PTR_H */ 
338