1 // auto_ptr implementation -*- C++ -*- 2 3 // Copyright (C) 2007-2018 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 } _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