1// auto_ptr implementation -*- C++ -*- 2 3// Copyright (C) 2007-2013 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 57 /** 58 * @brief A simple smart pointer providing strict ownership semantics. 59 * 60 * The Standard says: 61 * <pre> 62 * An @c auto_ptr owns the object it holds a pointer to. Copying 63 * an @c auto_ptr copies the pointer and transfers ownership to the 64 * destination. If more than one @c auto_ptr owns the same object 65 * at the same time the behavior of the program is undefined. 66 * 67 * The uses of @c auto_ptr include providing temporary 68 * exception-safety for dynamically allocated memory, passing 69 * ownership of dynamically allocated memory to a function, and 70 * returning dynamically allocated memory from a function. @c 71 * auto_ptr does not meet the CopyConstructible and Assignable 72 * requirements for Standard Library <a 73 * href="tables.html#65">container</a> elements and thus 74 * instantiating a Standard Library container with an @c auto_ptr 75 * results in undefined behavior. 76 * </pre> 77 * Quoted from [20.4.5]/3. 78 * 79 * Good examples of what can and cannot be done with auto_ptr can 80 * be found in the libstdc++ testsuite. 81 * 82 * _GLIBCXX_RESOLVE_LIB_DEFECTS 83 * 127. auto_ptr<> conversion issues 84 * These resolutions have all been incorporated. 85 */ 86 template<typename _Tp> 87 class auto_ptr 88 { 89 private: 90 _Tp* _M_ptr; 91 92 public: 93 /// The pointed-to type. 94 typedef _Tp element_type; 95 96 /** 97 * @brief An %auto_ptr is usually constructed from a raw pointer. 98 * @param __p A pointer (defaults to NULL). 99 * 100 * This object now @e owns the object pointed to by @a __p. 101 */ 102 explicit 103 auto_ptr(element_type* __p = 0) throw() : _M_ptr(__p) { } 104 105 /** 106 * @brief An %auto_ptr can be constructed from another %auto_ptr. 107 * @param __a Another %auto_ptr of the same type. 108 * 109 * This object now @e owns the object previously owned by @a __a, 110 * which has given up ownership. 111 */ 112 auto_ptr(auto_ptr& __a) throw() : _M_ptr(__a.release()) { } 113 114 /** 115 * @brief An %auto_ptr can be constructed from another %auto_ptr. 116 * @param __a Another %auto_ptr of a different but related type. 117 * 118 * A pointer-to-Tp1 must be convertible to a 119 * pointer-to-Tp/element_type. 120 * 121 * This object now @e owns the object previously owned by @a __a, 122 * which has given up ownership. 123 */ 124 template<typename _Tp1> 125 auto_ptr(auto_ptr<_Tp1>& __a) throw() : _M_ptr(__a.release()) { } 126 127 /** 128 * @brief %auto_ptr assignment operator. 129 * @param __a Another %auto_ptr of the same type. 130 * 131 * This object now @e owns the object previously owned by @a __a, 132 * which has given up ownership. The object that this one @e 133 * used to own and track has been deleted. 134 */ 135 auto_ptr& 136 operator=(auto_ptr& __a) throw() 137 { 138 reset(__a.release()); 139 return *this; 140 } 141 142 /** 143 * @brief %auto_ptr assignment operator. 144 * @param __a Another %auto_ptr of a different but related type. 145 * 146 * A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type. 147 * 148 * This object now @e owns the object previously owned by @a __a, 149 * which has given up ownership. The object that this one @e 150 * used to own and track has been deleted. 151 */ 152 template<typename _Tp1> 153 auto_ptr& 154 operator=(auto_ptr<_Tp1>& __a) throw() 155 { 156 reset(__a.release()); 157 return *this; 158 } 159 160 /** 161 * When the %auto_ptr goes out of scope, the object it owns is 162 * deleted. If it no longer owns anything (i.e., @c get() is 163 * @c NULL), then this has no effect. 164 * 165 * The C++ standard says there is supposed to be an empty throw 166 * specification here, but omitting it is standard conforming. Its 167 * presence can be detected only if _Tp::~_Tp() throws, but this is 168 * prohibited. [17.4.3.6]/2 169 */ 170 ~auto_ptr() { delete _M_ptr; } 171 172 /** 173 * @brief Smart pointer dereferencing. 174 * 175 * If this %auto_ptr no longer owns anything, then this 176 * operation will crash. (For a smart pointer, <em>no longer owns 177 * anything</em> is the same as being a null pointer, and you know 178 * what happens when you dereference one of those...) 179 */ 180 element_type& 181 operator*() const throw() 182 { 183 _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0); 184 return *_M_ptr; 185 } 186 187 /** 188 * @brief Smart pointer dereferencing. 189 * 190 * This returns the pointer itself, which the language then will 191 * automatically cause to be dereferenced. 192 */ 193 element_type* 194 operator->() const throw() 195 { 196 _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0); 197 return _M_ptr; 198 } 199 200 /** 201 * @brief Bypassing the smart pointer. 202 * @return The raw pointer being managed. 203 * 204 * You can get a copy of the pointer that this object owns, for 205 * situations such as passing to a function which only accepts 206 * a raw pointer. 207 * 208 * @note This %auto_ptr still owns the memory. 209 */ 210 element_type* 211 get() const throw() { return _M_ptr; } 212 213 /** 214 * @brief Bypassing the smart pointer. 215 * @return The raw pointer being managed. 216 * 217 * You can get a copy of the pointer that this object owns, for 218 * situations such as passing to a function which only accepts 219 * a raw pointer. 220 * 221 * @note This %auto_ptr no longer owns the memory. When this object 222 * goes out of scope, nothing will happen. 223 */ 224 element_type* 225 release() throw() 226 { 227 element_type* __tmp = _M_ptr; 228 _M_ptr = 0; 229 return __tmp; 230 } 231 232 /** 233 * @brief Forcibly deletes the managed object. 234 * @param __p A pointer (defaults to NULL). 235 * 236 * This object now @e owns the object pointed to by @a __p. The 237 * previous object has been deleted. 238 */ 239 void 240 reset(element_type* __p = 0) throw() 241 { 242 if (__p != _M_ptr) 243 { 244 delete _M_ptr; 245 _M_ptr = __p; 246 } 247 } 248 249 /** 250 * @brief Automatic conversions 251 * 252 * These operations convert an %auto_ptr into and from an auto_ptr_ref 253 * automatically as needed. This allows constructs such as 254 * @code 255 * auto_ptr<Derived> func_returning_auto_ptr(.....); 256 * ... 257 * auto_ptr<Base> ptr = func_returning_auto_ptr(.....); 258 * @endcode 259 */ 260 auto_ptr(auto_ptr_ref<element_type> __ref) throw() 261 : _M_ptr(__ref._M_ptr) { } 262 263 auto_ptr& 264 operator=(auto_ptr_ref<element_type> __ref) throw() 265 { 266 if (__ref._M_ptr != this->get()) 267 { 268 delete _M_ptr; 269 _M_ptr = __ref._M_ptr; 270 } 271 return *this; 272 } 273 274 template<typename _Tp1> 275 operator auto_ptr_ref<_Tp1>() throw() 276 { return auto_ptr_ref<_Tp1>(this->release()); } 277 278 template<typename _Tp1> 279 operator auto_ptr<_Tp1>() throw() 280 { return auto_ptr<_Tp1>(this->release()); } 281 } _GLIBCXX_DEPRECATED; 282 283 // _GLIBCXX_RESOLVE_LIB_DEFECTS 284 // 541. shared_ptr template assignment and void 285 template<> 286 class auto_ptr<void> 287 { 288 public: 289 typedef void element_type; 290 } _GLIBCXX_DEPRECATED; 291 292#if __cplusplus >= 201103L 293 template<_Lock_policy _Lp> 294 template<typename _Tp> 295 inline 296 __shared_count<_Lp>::__shared_count(std::auto_ptr<_Tp>&& __r) 297 : _M_pi(new _Sp_counted_ptr<_Tp*, _Lp>(__r.get())) 298 { __r.release(); } 299 300 template<typename _Tp, _Lock_policy _Lp> 301 template<typename _Tp1> 302 inline 303 __shared_ptr<_Tp, _Lp>::__shared_ptr(std::auto_ptr<_Tp1>&& __r) 304 : _M_ptr(__r.get()), _M_refcount() 305 { 306 __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>) 307 static_assert( sizeof(_Tp1) > 0, "incomplete type" ); 308 _Tp1* __tmp = __r.get(); 309 _M_refcount = __shared_count<_Lp>(std::move(__r)); 310 __enable_shared_from_this_helper(_M_refcount, __tmp, __tmp); 311 } 312 313 template<typename _Tp> 314 template<typename _Tp1> 315 inline 316 shared_ptr<_Tp>::shared_ptr(std::auto_ptr<_Tp1>&& __r) 317 : __shared_ptr<_Tp>(std::move(__r)) { } 318 319 template<typename _Tp, typename _Dp> 320 template<typename _Up, typename> 321 inline 322 unique_ptr<_Tp, _Dp>::unique_ptr(auto_ptr<_Up>&& __u) noexcept 323 : _M_t(__u.release(), deleter_type()) { } 324#endif 325 326_GLIBCXX_END_NAMESPACE_VERSION 327} // namespace 328 329#endif /* _BACKWARD_AUTO_PTR_H */ 330