1 // auto_ptr implementation -*- C++ -*- 2 3 // Copyright (C) 2007-2022 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(__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(__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 template<_Lock_policy _Lp> 304 template<typename _Tp> 305 inline 306 __shared_count<_Lp>::__shared_count(std::auto_ptr<_Tp>&& __r) 307 : _M_pi(new _Sp_counted_ptr<_Tp*, _Lp>(__r.get())) 308 { __r.release(); } 309 310 template<typename _Tp, _Lock_policy _Lp> 311 template<typename _Tp1, typename> 312 inline 313 __shared_ptr<_Tp, _Lp>::__shared_ptr(std::auto_ptr<_Tp1>&& __r) 314 : _M_ptr(__r.get()), _M_refcount() 315 { 316 __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>) 317 static_assert( sizeof(_Tp1) > 0, "incomplete type" ); 318 _Tp1* __tmp = __r.get(); 319 _M_refcount = __shared_count<_Lp>(std::move(__r)); 320 _M_enable_shared_from_this_with(__tmp); 321 } 322 323 template<typename _Tp> 324 template<typename _Tp1, typename> 325 inline 326 shared_ptr<_Tp>::shared_ptr(std::auto_ptr<_Tp1>&& __r) 327 : __shared_ptr<_Tp>(std::move(__r)) { } 328 329 template<typename _Tp, typename _Dp> 330 template<typename _Up, typename> 331 inline 332 unique_ptr<_Tp, _Dp>::unique_ptr(auto_ptr<_Up>&& __u) noexcept 333 : _M_t(__u.release(), deleter_type()) { } 334 #endif 335 336 #pragma GCC diagnostic pop 337 338 _GLIBCXX_END_NAMESPACE_VERSION 339 } // namespace 340 341 #endif /* _BACKWARD_AUTO_PTR_H */ 342