libstdc++
bits/shared_ptr.h
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1 // shared_ptr and weak_ptr implementation -*- C++ -*-
2 
3 // Copyright (C) 2007-2021 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 // GCC Note: Based on files from version 1.32.0 of the Boost library.
26 
27 // shared_count.hpp
28 // Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd.
29 
30 // shared_ptr.hpp
31 // Copyright (C) 1998, 1999 Greg Colvin and Beman Dawes.
32 // Copyright (C) 2001, 2002, 2003 Peter Dimov
33 
34 // weak_ptr.hpp
35 // Copyright (C) 2001, 2002, 2003 Peter Dimov
36 
37 // enable_shared_from_this.hpp
38 // Copyright (C) 2002 Peter Dimov
39 
40 // Distributed under the Boost Software License, Version 1.0. (See
41 // accompanying file LICENSE_1_0.txt or copy at
42 // http://www.boost.org/LICENSE_1_0.txt)
43 
44 /** @file
45  * This is an internal header file, included by other library headers.
46  * Do not attempt to use it directly. @headername{memory}
47  */
48 
49 #ifndef _SHARED_PTR_H
50 #define _SHARED_PTR_H 1
51 
52 #include <iosfwd> // std::basic_ostream
53 #include <bits/shared_ptr_base.h>
54 
55 namespace std _GLIBCXX_VISIBILITY(default)
56 {
57 _GLIBCXX_BEGIN_NAMESPACE_VERSION
58 
59  /**
60  * @addtogroup pointer_abstractions
61  * @{
62  */
63 
64  // 20.7.2.2.11 shared_ptr I/O
65 
66  /// Write the stored pointer to an ostream.
67  /// @relates shared_ptr
68  template<typename _Ch, typename _Tr, typename _Tp, _Lock_policy _Lp>
71  const __shared_ptr<_Tp, _Lp>& __p)
72  {
73  __os << __p.get();
74  return __os;
75  }
76 
77  template<typename _Del, typename _Tp, _Lock_policy _Lp>
78  inline _Del*
79  get_deleter(const __shared_ptr<_Tp, _Lp>& __p) noexcept
80  {
81 #if __cpp_rtti
82  return static_cast<_Del*>(__p._M_get_deleter(typeid(_Del)));
83 #else
84  return 0;
85 #endif
86  }
87 
88  /// 20.7.2.2.10 shared_ptr get_deleter
89 
90  /// If `__p` has a deleter of type `_Del`, return a pointer to it.
91  /// @relates shared_ptr
92  template<typename _Del, typename _Tp>
93  inline _Del*
94  get_deleter(const shared_ptr<_Tp>& __p) noexcept
95  {
96 #if __cpp_rtti
97  return static_cast<_Del*>(__p._M_get_deleter(typeid(_Del)));
98 #else
99  return 0;
100 #endif
101  }
102 
103  /**
104  * @brief A smart pointer with reference-counted copy semantics.
105  *
106  * A `shared_ptr` object is either empty or _owns_ a pointer passed
107  * to the constructor. Copies of a `shared_ptr` share ownership of
108  * the same pointer. When the last `shared_ptr` that owns the pointer
109  * is destroyed or reset, the owned pointer is freed (either by `delete`
110  * or by invoking a custom deleter that was passed to the constructor).
111  *
112  * A `shared_ptr` also stores another pointer, which is usually
113  * (but not always) the same pointer as it owns. The stored pointer
114  * can be retrieved by calling the `get()` member function.
115  *
116  * The equality and relational operators for `shared_ptr` only compare
117  * the stored pointer returned by `get()`, not the owned pointer.
118  * To test whether two `shared_ptr` objects share ownership of the same
119  * pointer see `std::shared_ptr::owner_before` and `std::owner_less`.
120  */
121  template<typename _Tp>
122  class shared_ptr : public __shared_ptr<_Tp>
123  {
124  template<typename... _Args>
125  using _Constructible = typename enable_if<
126  is_constructible<__shared_ptr<_Tp>, _Args...>::value
127  >::type;
128 
129  template<typename _Arg>
130  using _Assignable = typename enable_if<
132  >::type;
133 
134  public:
135 
136  /// The type pointed to by the stored pointer, remove_extent_t<_Tp>
137  using element_type = typename __shared_ptr<_Tp>::element_type;
138 
139 #if __cplusplus >= 201703L
140 # define __cpp_lib_shared_ptr_weak_type 201606
141  /// The corresponding weak_ptr type for this shared_ptr
143 #endif
144  /**
145  * @brief Construct an empty %shared_ptr.
146  * @post use_count()==0 && get()==0
147  */
148  constexpr shared_ptr() noexcept : __shared_ptr<_Tp>() { }
149 
150  shared_ptr(const shared_ptr&) noexcept = default; ///< Copy constructor
151 
152  /**
153  * @brief Construct a %shared_ptr that owns the pointer @a __p.
154  * @param __p A pointer that is convertible to element_type*.
155  * @post use_count() == 1 && get() == __p
156  * @throw std::bad_alloc, in which case @c delete @a __p is called.
157  */
158  template<typename _Yp, typename = _Constructible<_Yp*>>
159  explicit
160  shared_ptr(_Yp* __p) : __shared_ptr<_Tp>(__p) { }
161 
162  /**
163  * @brief Construct a %shared_ptr that owns the pointer @a __p
164  * and the deleter @a __d.
165  * @param __p A pointer.
166  * @param __d A deleter.
167  * @post use_count() == 1 && get() == __p
168  * @throw std::bad_alloc, in which case @a __d(__p) is called.
169  *
170  * Requirements: _Deleter's copy constructor and destructor must
171  * not throw
172  *
173  * __shared_ptr will release __p by calling __d(__p)
174  */
175  template<typename _Yp, typename _Deleter,
176  typename = _Constructible<_Yp*, _Deleter>>
177  shared_ptr(_Yp* __p, _Deleter __d)
178  : __shared_ptr<_Tp>(__p, std::move(__d)) { }
179 
180  /**
181  * @brief Construct a %shared_ptr that owns a null pointer
182  * and the deleter @a __d.
183  * @param __p A null pointer constant.
184  * @param __d A deleter.
185  * @post use_count() == 1 && get() == __p
186  * @throw std::bad_alloc, in which case @a __d(__p) is called.
187  *
188  * Requirements: _Deleter's copy constructor and destructor must
189  * not throw
190  *
191  * The last owner will call __d(__p)
192  */
193  template<typename _Deleter>
194  shared_ptr(nullptr_t __p, _Deleter __d)
195  : __shared_ptr<_Tp>(__p, std::move(__d)) { }
196 
197  /**
198  * @brief Construct a %shared_ptr that owns the pointer @a __p
199  * and the deleter @a __d.
200  * @param __p A pointer.
201  * @param __d A deleter.
202  * @param __a An allocator.
203  * @post use_count() == 1 && get() == __p
204  * @throw std::bad_alloc, in which case @a __d(__p) is called.
205  *
206  * Requirements: _Deleter's copy constructor and destructor must
207  * not throw _Alloc's copy constructor and destructor must not
208  * throw.
209  *
210  * __shared_ptr will release __p by calling __d(__p)
211  */
212  template<typename _Yp, typename _Deleter, typename _Alloc,
213  typename = _Constructible<_Yp*, _Deleter, _Alloc>>
214  shared_ptr(_Yp* __p, _Deleter __d, _Alloc __a)
215  : __shared_ptr<_Tp>(__p, std::move(__d), std::move(__a)) { }
216 
217  /**
218  * @brief Construct a %shared_ptr that owns a null pointer
219  * and the deleter @a __d.
220  * @param __p A null pointer constant.
221  * @param __d A deleter.
222  * @param __a An allocator.
223  * @post use_count() == 1 && get() == __p
224  * @throw std::bad_alloc, in which case @a __d(__p) is called.
225  *
226  * Requirements: _Deleter's copy constructor and destructor must
227  * not throw _Alloc's copy constructor and destructor must not
228  * throw.
229  *
230  * The last owner will call __d(__p)
231  */
232  template<typename _Deleter, typename _Alloc>
233  shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
234  : __shared_ptr<_Tp>(__p, std::move(__d), std::move(__a)) { }
235 
236  // Aliasing constructor
237 
238  /**
239  * @brief Constructs a `shared_ptr` instance that stores `__p`
240  * and shares ownership with `__r`.
241  * @param __r A `shared_ptr`.
242  * @param __p A pointer that will remain valid while `*__r` is valid.
243  * @post `get() == __p && use_count() == __r.use_count()`
244  *
245  * This can be used to construct a `shared_ptr` to a sub-object
246  * of an object managed by an existing `shared_ptr`. The complete
247  * object will remain valid while any `shared_ptr` owns it, even
248  * if they don't store a pointer to the complete object.
249  *
250  * @code
251  * shared_ptr<pair<int,int>> pii(new pair<int,int>());
252  * shared_ptr<int> pi(pii, &pii->first);
253  * assert(pii.use_count() == 2);
254  * @endcode
255  */
256  template<typename _Yp>
257  shared_ptr(const shared_ptr<_Yp>& __r, element_type* __p) noexcept
258  : __shared_ptr<_Tp>(__r, __p) { }
259 
260 #if __cplusplus > 201703L
261  // _GLIBCXX_RESOLVE_LIB_DEFECTS
262  // 2996. Missing rvalue overloads for shared_ptr operations
263  /**
264  * @brief Constructs a `shared_ptr` instance that stores `__p`
265  * and shares ownership with `__r`.
266  * @param __r A `shared_ptr`.
267  * @param __p A pointer that will remain valid while `*__r` is valid.
268  * @post `get() == __p && !__r.use_count() && !__r.get()`
269  *
270  * This can be used to construct a `shared_ptr` to a sub-object
271  * of an object managed by an existing `shared_ptr`. The complete
272  * object will remain valid while any `shared_ptr` owns it, even
273  * if they don't store a pointer to the complete object.
274  *
275  * @code
276  * shared_ptr<pair<int,int>> pii(new pair<int,int>());
277  * shared_ptr<int> pi1(pii, &pii->first);
278  * assert(pii.use_count() == 2);
279  * shared_ptr<int> pi2(std::move(pii), &pii->second);
280  * assert(pii.use_count() == 0);
281  * @endcode
282  */
283  template<typename _Yp>
284  shared_ptr(shared_ptr<_Yp>&& __r, element_type* __p) noexcept
285  : __shared_ptr<_Tp>(std::move(__r), __p) { }
286 #endif
287  /**
288  * @brief If @a __r is empty, constructs an empty %shared_ptr;
289  * otherwise construct a %shared_ptr that shares ownership
290  * with @a __r.
291  * @param __r A %shared_ptr.
292  * @post get() == __r.get() && use_count() == __r.use_count()
293  */
294  template<typename _Yp,
295  typename = _Constructible<const shared_ptr<_Yp>&>>
296  shared_ptr(const shared_ptr<_Yp>& __r) noexcept
297  : __shared_ptr<_Tp>(__r) { }
298 
299  /**
300  * @brief Move-constructs a %shared_ptr instance from @a __r.
301  * @param __r A %shared_ptr rvalue.
302  * @post *this contains the old value of @a __r, @a __r is empty.
303  */
304  shared_ptr(shared_ptr&& __r) noexcept
305  : __shared_ptr<_Tp>(std::move(__r)) { }
306 
307  /**
308  * @brief Move-constructs a %shared_ptr instance from @a __r.
309  * @param __r A %shared_ptr rvalue.
310  * @post *this contains the old value of @a __r, @a __r is empty.
311  */
312  template<typename _Yp, typename = _Constructible<shared_ptr<_Yp>>>
313  shared_ptr(shared_ptr<_Yp>&& __r) noexcept
314  : __shared_ptr<_Tp>(std::move(__r)) { }
315 
316  /**
317  * @brief Constructs a %shared_ptr that shares ownership with @a __r
318  * and stores a copy of the pointer stored in @a __r.
319  * @param __r A weak_ptr.
320  * @post use_count() == __r.use_count()
321  * @throw bad_weak_ptr when __r.expired(),
322  * in which case the constructor has no effect.
323  */
324  template<typename _Yp, typename = _Constructible<const weak_ptr<_Yp>&>>
325  explicit shared_ptr(const weak_ptr<_Yp>& __r)
326  : __shared_ptr<_Tp>(__r) { }
327 
328 #if _GLIBCXX_USE_DEPRECATED
329 #pragma GCC diagnostic push
330 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
331  template<typename _Yp, typename = _Constructible<auto_ptr<_Yp>>>
332  shared_ptr(auto_ptr<_Yp>&& __r);
333 #pragma GCC diagnostic pop
334 #endif
335 
336  // _GLIBCXX_RESOLVE_LIB_DEFECTS
337  // 2399. shared_ptr's constructor from unique_ptr should be constrained
338  template<typename _Yp, typename _Del,
339  typename = _Constructible<unique_ptr<_Yp, _Del>>>
341  : __shared_ptr<_Tp>(std::move(__r)) { }
342 
343 #if __cplusplus <= 201402L && _GLIBCXX_USE_DEPRECATED
344  // This non-standard constructor exists to support conversions that
345  // were possible in C++11 and C++14 but are ill-formed in C++17.
346  // If an exception is thrown this constructor has no effect.
347  template<typename _Yp, typename _Del,
348  _Constructible<unique_ptr<_Yp, _Del>, __sp_array_delete>* = 0>
349  shared_ptr(unique_ptr<_Yp, _Del>&& __r)
350  : __shared_ptr<_Tp>(std::move(__r), __sp_array_delete()) { }
351 #endif
352 
353  /**
354  * @brief Construct an empty %shared_ptr.
355  * @post use_count() == 0 && get() == nullptr
356  */
357  constexpr shared_ptr(nullptr_t) noexcept : shared_ptr() { }
358 
359  shared_ptr& operator=(const shared_ptr&) noexcept = default;
360 
361  template<typename _Yp>
362  _Assignable<const shared_ptr<_Yp>&>
363  operator=(const shared_ptr<_Yp>& __r) noexcept
364  {
365  this->__shared_ptr<_Tp>::operator=(__r);
366  return *this;
367  }
368 
369 #if _GLIBCXX_USE_DEPRECATED
370 #pragma GCC diagnostic push
371 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
372  template<typename _Yp>
373  _Assignable<auto_ptr<_Yp>>
374  operator=(auto_ptr<_Yp>&& __r)
375  {
376  this->__shared_ptr<_Tp>::operator=(std::move(__r));
377  return *this;
378  }
379 #pragma GCC diagnostic pop
380 #endif
381 
382  shared_ptr&
383  operator=(shared_ptr&& __r) noexcept
384  {
385  this->__shared_ptr<_Tp>::operator=(std::move(__r));
386  return *this;
387  }
388 
389  template<class _Yp>
390  _Assignable<shared_ptr<_Yp>>
391  operator=(shared_ptr<_Yp>&& __r) noexcept
392  {
393  this->__shared_ptr<_Tp>::operator=(std::move(__r));
394  return *this;
395  }
396 
397  template<typename _Yp, typename _Del>
398  _Assignable<unique_ptr<_Yp, _Del>>
399  operator=(unique_ptr<_Yp, _Del>&& __r)
400  {
401  this->__shared_ptr<_Tp>::operator=(std::move(__r));
402  return *this;
403  }
404 
405  private:
406  // This constructor is non-standard, it is used by allocate_shared.
407  template<typename _Alloc, typename... _Args>
408  shared_ptr(_Sp_alloc_shared_tag<_Alloc> __tag, _Args&&... __args)
409  : __shared_ptr<_Tp>(__tag, std::forward<_Args>(__args)...)
410  { }
411 
412  template<typename _Yp, typename _Alloc, typename... _Args>
413  friend shared_ptr<_Yp>
414  allocate_shared(const _Alloc& __a, _Args&&... __args);
415 
416  // This constructor is non-standard, it is used by weak_ptr::lock().
417  shared_ptr(const weak_ptr<_Tp>& __r, std::nothrow_t) noexcept
418  : __shared_ptr<_Tp>(__r, std::nothrow) { }
419 
420  friend class weak_ptr<_Tp>;
421  };
422 
423 #if __cpp_deduction_guides >= 201606
424  template<typename _Tp>
425  shared_ptr(weak_ptr<_Tp>) -> shared_ptr<_Tp>;
426  template<typename _Tp, typename _Del>
427  shared_ptr(unique_ptr<_Tp, _Del>) -> shared_ptr<_Tp>;
428 #endif
429 
430  // 20.7.2.2.7 shared_ptr comparisons
431 
432  /// @relates shared_ptr @{
433 
434  /// Equality operator for shared_ptr objects, compares the stored pointers
435  template<typename _Tp, typename _Up>
436  _GLIBCXX_NODISCARD inline bool
437  operator==(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
438  { return __a.get() == __b.get(); }
439 
440  /// shared_ptr comparison with nullptr
441  template<typename _Tp>
442  _GLIBCXX_NODISCARD inline bool
443  operator==(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
444  { return !__a; }
445 
446 #ifdef __cpp_lib_three_way_comparison
447  template<typename _Tp, typename _Up>
448  inline strong_ordering
449  operator<=>(const shared_ptr<_Tp>& __a,
450  const shared_ptr<_Up>& __b) noexcept
451  { return compare_three_way()(__a.get(), __b.get()); }
452 
453  template<typename _Tp>
454  inline strong_ordering
455  operator<=>(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
456  {
457  using pointer = typename shared_ptr<_Tp>::element_type*;
458  return compare_three_way()(__a.get(), static_cast<pointer>(nullptr));
459  }
460 #else
461  /// shared_ptr comparison with nullptr
462  template<typename _Tp>
463  _GLIBCXX_NODISCARD inline bool
464  operator==(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
465  { return !__a; }
466 
467  /// Inequality operator for shared_ptr objects, compares the stored pointers
468  template<typename _Tp, typename _Up>
469  _GLIBCXX_NODISCARD inline bool
470  operator!=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
471  { return __a.get() != __b.get(); }
472 
473  /// shared_ptr comparison with nullptr
474  template<typename _Tp>
475  _GLIBCXX_NODISCARD inline bool
476  operator!=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
477  { return (bool)__a; }
478 
479  /// shared_ptr comparison with nullptr
480  template<typename _Tp>
481  _GLIBCXX_NODISCARD inline bool
482  operator!=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
483  { return (bool)__a; }
484 
485  /// Relational operator for shared_ptr objects, compares the stored pointers
486  template<typename _Tp, typename _Up>
487  _GLIBCXX_NODISCARD inline bool
488  operator<(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
489  {
490  using _Tp_elt = typename shared_ptr<_Tp>::element_type;
491  using _Up_elt = typename shared_ptr<_Up>::element_type;
492  using _Vp = typename common_type<_Tp_elt*, _Up_elt*>::type;
493  return less<_Vp>()(__a.get(), __b.get());
494  }
495 
496  /// shared_ptr comparison with nullptr
497  template<typename _Tp>
498  _GLIBCXX_NODISCARD inline bool
499  operator<(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
500  {
501  using _Tp_elt = typename shared_ptr<_Tp>::element_type;
502  return less<_Tp_elt*>()(__a.get(), nullptr);
503  }
504 
505  /// shared_ptr comparison with nullptr
506  template<typename _Tp>
507  _GLIBCXX_NODISCARD inline bool
508  operator<(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
509  {
510  using _Tp_elt = typename shared_ptr<_Tp>::element_type;
511  return less<_Tp_elt*>()(nullptr, __a.get());
512  }
513 
514  /// Relational operator for shared_ptr objects, compares the stored pointers
515  template<typename _Tp, typename _Up>
516  _GLIBCXX_NODISCARD inline bool
517  operator<=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
518  { return !(__b < __a); }
519 
520  /// shared_ptr comparison with nullptr
521  template<typename _Tp>
522  _GLIBCXX_NODISCARD inline bool
523  operator<=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
524  { return !(nullptr < __a); }
525 
526  /// shared_ptr comparison with nullptr
527  template<typename _Tp>
528  _GLIBCXX_NODISCARD inline bool
529  operator<=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
530  { return !(__a < nullptr); }
531 
532  /// Relational operator for shared_ptr objects, compares the stored pointers
533  template<typename _Tp, typename _Up>
534  _GLIBCXX_NODISCARD inline bool
535  operator>(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
536  { return (__b < __a); }
537 
538  /// shared_ptr comparison with nullptr
539  template<typename _Tp>
540  _GLIBCXX_NODISCARD inline bool
541  operator>(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
542  { return nullptr < __a; }
543 
544  /// shared_ptr comparison with nullptr
545  template<typename _Tp>
546  _GLIBCXX_NODISCARD inline bool
547  operator>(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
548  { return __a < nullptr; }
549 
550  /// Relational operator for shared_ptr objects, compares the stored pointers
551  template<typename _Tp, typename _Up>
552  _GLIBCXX_NODISCARD inline bool
553  operator>=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
554  { return !(__a < __b); }
555 
556  /// shared_ptr comparison with nullptr
557  template<typename _Tp>
558  _GLIBCXX_NODISCARD inline bool
559  operator>=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
560  { return !(__a < nullptr); }
561 
562  /// shared_ptr comparison with nullptr
563  template<typename _Tp>
564  _GLIBCXX_NODISCARD inline bool
565  operator>=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
566  { return !(nullptr < __a); }
567 #endif
568 
569  // 20.7.2.2.8 shared_ptr specialized algorithms.
570 
571  /// Swap overload for shared_ptr
572  template<typename _Tp>
573  inline void
574  swap(shared_ptr<_Tp>& __a, shared_ptr<_Tp>& __b) noexcept
575  { __a.swap(__b); }
576 
577  // 20.7.2.2.9 shared_ptr casts.
578 
579  /// Convert type of `shared_ptr`, via `static_cast`
580  template<typename _Tp, typename _Up>
581  inline shared_ptr<_Tp>
583  {
584  using _Sp = shared_ptr<_Tp>;
585  return _Sp(__r, static_cast<typename _Sp::element_type*>(__r.get()));
586  }
587 
588  /// Convert type of `shared_ptr`, via `const_cast`
589  template<typename _Tp, typename _Up>
590  inline shared_ptr<_Tp>
591  const_pointer_cast(const shared_ptr<_Up>& __r) noexcept
592  {
593  using _Sp = shared_ptr<_Tp>;
594  return _Sp(__r, const_cast<typename _Sp::element_type*>(__r.get()));
595  }
596 
597  /// Convert type of `shared_ptr`, via `dynamic_cast`
598  template<typename _Tp, typename _Up>
599  inline shared_ptr<_Tp>
601  {
602  using _Sp = shared_ptr<_Tp>;
603  if (auto* __p = dynamic_cast<typename _Sp::element_type*>(__r.get()))
604  return _Sp(__r, __p);
605  return _Sp();
606  }
607 
608 #if __cplusplus >= 201703L
609  /// Convert type of `shared_ptr`, via `reinterpret_cast`
610  template<typename _Tp, typename _Up>
611  inline shared_ptr<_Tp>
613  {
614  using _Sp = shared_ptr<_Tp>;
615  return _Sp(__r, reinterpret_cast<typename _Sp::element_type*>(__r.get()));
616  }
617 
618 #if __cplusplus > 201703L
619  // _GLIBCXX_RESOLVE_LIB_DEFECTS
620  // 2996. Missing rvalue overloads for shared_ptr operations
621 
622  /// Convert type of `shared_ptr` rvalue, via `static_cast`
623  template<typename _Tp, typename _Up>
624  inline shared_ptr<_Tp>
625  static_pointer_cast(shared_ptr<_Up>&& __r) noexcept
626  {
627  using _Sp = shared_ptr<_Tp>;
628  return _Sp(std::move(__r),
629  static_cast<typename _Sp::element_type*>(__r.get()));
630  }
631 
632  /// Convert type of `shared_ptr` rvalue, via `const_cast`
633  template<typename _Tp, typename _Up>
634  inline shared_ptr<_Tp>
635  const_pointer_cast(shared_ptr<_Up>&& __r) noexcept
636  {
637  using _Sp = shared_ptr<_Tp>;
638  return _Sp(std::move(__r),
639  const_cast<typename _Sp::element_type*>(__r.get()));
640  }
641 
642  /// Convert type of `shared_ptr` rvalue, via `dynamic_cast`
643  template<typename _Tp, typename _Up>
644  inline shared_ptr<_Tp>
645  dynamic_pointer_cast(shared_ptr<_Up>&& __r) noexcept
646  {
647  using _Sp = shared_ptr<_Tp>;
648  if (auto* __p = dynamic_cast<typename _Sp::element_type*>(__r.get()))
649  return _Sp(std::move(__r), __p);
650  return _Sp();
651  }
652 
653  /// Convert type of `shared_ptr` rvalue, via `reinterpret_cast`
654  template<typename _Tp, typename _Up>
655  inline shared_ptr<_Tp>
656  reinterpret_pointer_cast(shared_ptr<_Up>&& __r) noexcept
657  {
658  using _Sp = shared_ptr<_Tp>;
659  return _Sp(std::move(__r),
660  reinterpret_cast<typename _Sp::element_type*>(__r.get()));
661  }
662 #endif // C++20
663 #endif // C++17
664 
665  /// @}
666 
667  /**
668  * @brief A non-owning observer for a pointer owned by a shared_ptr
669  *
670  * A weak_ptr provides a safe alternative to a raw pointer when you want
671  * a non-owning reference to an object that is managed by a shared_ptr.
672  *
673  * Unlike a raw pointer, a weak_ptr can be converted to a new shared_ptr
674  * that shares ownership with every other shared_ptr that already owns
675  * the pointer. In other words you can upgrade from a non-owning "weak"
676  * reference to an owning shared_ptr, without having access to any of
677  * the existing shared_ptr objects.
678  *
679  * Also unlike a raw pointer, a weak_ptr does not become "dangling" after
680  * the object it points to has been destroyed. Instead, a weak_ptr
681  * becomes _expired_ and can no longer be converted to a shared_ptr that
682  * owns the freed pointer, so you cannot accidentally access the pointed-to
683  * object after it has been destroyed.
684  */
685  template<typename _Tp>
686  class weak_ptr : public __weak_ptr<_Tp>
687  {
688  template<typename _Arg>
689  using _Constructible = typename enable_if<
691  >::type;
692 
693  template<typename _Arg>
694  using _Assignable = typename enable_if<
695  is_assignable<__weak_ptr<_Tp>&, _Arg>::value, weak_ptr&
696  >::type;
697 
698  public:
699  constexpr weak_ptr() noexcept = default;
700 
701  template<typename _Yp,
702  typename = _Constructible<const shared_ptr<_Yp>&>>
703  weak_ptr(const shared_ptr<_Yp>& __r) noexcept
704  : __weak_ptr<_Tp>(__r) { }
705 
706  weak_ptr(const weak_ptr&) noexcept = default;
707 
708  template<typename _Yp, typename = _Constructible<const weak_ptr<_Yp>&>>
709  weak_ptr(const weak_ptr<_Yp>& __r) noexcept
710  : __weak_ptr<_Tp>(__r) { }
711 
712  weak_ptr(weak_ptr&&) noexcept = default;
713 
714  template<typename _Yp, typename = _Constructible<weak_ptr<_Yp>>>
715  weak_ptr(weak_ptr<_Yp>&& __r) noexcept
716  : __weak_ptr<_Tp>(std::move(__r)) { }
717 
718  weak_ptr&
719  operator=(const weak_ptr& __r) noexcept = default;
720 
721  template<typename _Yp>
722  _Assignable<const weak_ptr<_Yp>&>
723  operator=(const weak_ptr<_Yp>& __r) noexcept
724  {
725  this->__weak_ptr<_Tp>::operator=(__r);
726  return *this;
727  }
728 
729  template<typename _Yp>
730  _Assignable<const shared_ptr<_Yp>&>
731  operator=(const shared_ptr<_Yp>& __r) noexcept
732  {
733  this->__weak_ptr<_Tp>::operator=(__r);
734  return *this;
735  }
736 
737  weak_ptr&
738  operator=(weak_ptr&& __r) noexcept = default;
739 
740  template<typename _Yp>
741  _Assignable<weak_ptr<_Yp>>
742  operator=(weak_ptr<_Yp>&& __r) noexcept
743  {
744  this->__weak_ptr<_Tp>::operator=(std::move(__r));
745  return *this;
746  }
747 
749  lock() const noexcept
750  { return shared_ptr<_Tp>(*this, std::nothrow); }
751  };
752 
753 #if __cpp_deduction_guides >= 201606
754  template<typename _Tp>
756 #endif
757 
758  // 20.7.2.3.6 weak_ptr specialized algorithms.
759  /// Swap overload for weak_ptr
760  /// @relates weak_ptr
761  template<typename _Tp>
762  inline void
763  swap(weak_ptr<_Tp>& __a, weak_ptr<_Tp>& __b) noexcept
764  { __a.swap(__b); }
765 
766 
767  /// Primary template owner_less
768  template<typename _Tp = void>
769  struct owner_less;
770 
771  /// Void specialization of owner_less compares either shared_ptr or weak_ptr
772  template<>
773  struct owner_less<void> : _Sp_owner_less<void, void>
774  { };
775 
776  /// Partial specialization of owner_less for shared_ptr.
777  template<typename _Tp>
778  struct owner_less<shared_ptr<_Tp>>
779  : public _Sp_owner_less<shared_ptr<_Tp>, weak_ptr<_Tp>>
780  { };
781 
782  /// Partial specialization of owner_less for weak_ptr.
783  template<typename _Tp>
784  struct owner_less<weak_ptr<_Tp>>
785  : public _Sp_owner_less<weak_ptr<_Tp>, shared_ptr<_Tp>>
786  { };
787 
788  /**
789  * @brief Base class allowing use of member function shared_from_this.
790  */
791  template<typename _Tp>
793  {
794  protected:
795  constexpr enable_shared_from_this() noexcept { }
796 
798 
800  operator=(const enable_shared_from_this&) noexcept
801  { return *this; }
802 
804 
805  public:
807  shared_from_this()
808  { return shared_ptr<_Tp>(this->_M_weak_this); }
809 
811  shared_from_this() const
812  { return shared_ptr<const _Tp>(this->_M_weak_this); }
813 
814 #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
815 #define __cpp_lib_enable_shared_from_this 201603
817  weak_from_this() noexcept
818  { return this->_M_weak_this; }
819 
821  weak_from_this() const noexcept
822  { return this->_M_weak_this; }
823 #endif
824 
825  private:
826  template<typename _Tp1>
827  void
828  _M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const noexcept
829  { _M_weak_this._M_assign(__p, __n); }
830 
831  // Found by ADL when this is an associated class.
832  friend const enable_shared_from_this*
833  __enable_shared_from_this_base(const __shared_count<>&,
834  const enable_shared_from_this* __p)
835  { return __p; }
836 
837  template<typename, _Lock_policy>
838  friend class __shared_ptr;
839 
840  mutable weak_ptr<_Tp> _M_weak_this;
841  };
842 
843  /// @relates shared_ptr @{
844 
845  /**
846  * @brief Create an object that is owned by a shared_ptr.
847  * @param __a An allocator.
848  * @param __args Arguments for the @a _Tp object's constructor.
849  * @return A shared_ptr that owns the newly created object.
850  * @throw An exception thrown from @a _Alloc::allocate or from the
851  * constructor of @a _Tp.
852  *
853  * A copy of @a __a will be used to allocate memory for the shared_ptr
854  * and the new object.
855  */
856  template<typename _Tp, typename _Alloc, typename... _Args>
857  inline shared_ptr<_Tp>
858  allocate_shared(const _Alloc& __a, _Args&&... __args)
859  {
860  static_assert(!is_array<_Tp>::value, "make_shared<T[]> not supported");
861 
862  return shared_ptr<_Tp>(_Sp_alloc_shared_tag<_Alloc>{__a},
863  std::forward<_Args>(__args)...);
864  }
865 
866  /**
867  * @brief Create an object that is owned by a shared_ptr.
868  * @param __args Arguments for the @a _Tp object's constructor.
869  * @return A shared_ptr that owns the newly created object.
870  * @throw std::bad_alloc, or an exception thrown from the
871  * constructor of @a _Tp.
872  */
873  template<typename _Tp, typename... _Args>
874  inline shared_ptr<_Tp>
875  make_shared(_Args&&... __args)
876  {
877  typedef typename std::remove_cv<_Tp>::type _Tp_nc;
878  return std::allocate_shared<_Tp>(std::allocator<_Tp_nc>(),
879  std::forward<_Args>(__args)...);
880  }
881 
882  /// std::hash specialization for shared_ptr.
883  template<typename _Tp>
884  struct hash<shared_ptr<_Tp>>
885  : public __hash_base<size_t, shared_ptr<_Tp>>
886  {
887  size_t
888  operator()(const shared_ptr<_Tp>& __s) const noexcept
889  {
891  }
892  };
893 
894  /// @} relates shared_ptr
895  /// @} group pointer_abstractions
896 
897 #if __cplusplus >= 201703L
898  namespace __detail::__variant
899  {
900  template<typename> struct _Never_valueless_alt; // see <variant>
901 
902  // Provide the strong exception-safety guarantee when emplacing a
903  // shared_ptr into a variant.
904  template<typename _Tp>
905  struct _Never_valueless_alt<std::shared_ptr<_Tp>>
907  { };
908 
909  // Provide the strong exception-safety guarantee when emplacing a
910  // weak_ptr into a variant.
911  template<typename _Tp>
912  struct _Never_valueless_alt<std::weak_ptr<_Tp>>
914  { };
915  } // namespace __detail::__variant
916 #endif // C++17
917 
918 _GLIBCXX_END_NAMESPACE_VERSION
919 } // namespace
920 
921 #endif // _SHARED_PTR_H
shared_ptr< _Tp > make_shared(_Args &&... __args)
Create an object that is owned by a shared_ptr.
bool operator!=(nullptr_t, const shared_ptr< _Tp > &__a) noexcept
shared_ptr comparison with nullptr
bool operator>(const shared_ptr< _Tp > &__a, nullptr_t) noexcept
shared_ptr comparison with nullptr
bool operator==(const shared_ptr< _Tp > &__a, nullptr_t) noexcept
shared_ptr comparison with nullptr
bool operator==(nullptr_t, const shared_ptr< _Tp > &__a) noexcept
shared_ptr comparison with nullptr
shared_ptr< _Tp > static_pointer_cast(const shared_ptr< _Up > &__r) noexcept
Convert type of shared_ptr, via static_cast
bool operator!=(const shared_ptr< _Tp > &__a, const shared_ptr< _Up > &__b) noexcept
Inequality operator for shared_ptr objects, compares the stored pointers.
_Del * get_deleter(const shared_ptr< _Tp > &__p) noexcept
20.7.2.2.10 shared_ptr get_deleter
bool operator==(const shared_ptr< _Tp > &__a, const shared_ptr< _Up > &__b) noexcept
shared_ptr< _Tp > reinterpret_pointer_cast(const shared_ptr< _Up > &__r) noexcept
Convert type of shared_ptr, via reinterpret_cast
bool operator>=(const shared_ptr< _Tp > &__a, nullptr_t) noexcept
shared_ptr comparison with nullptr
void swap(weak_ptr< _Tp > &__a, weak_ptr< _Tp > &__b) noexcept
Swap overload for weak_ptr.
shared_ptr< _Tp > allocate_shared(const _Alloc &__a, _Args &&... __args)
Create an object that is owned by a shared_ptr.
bool operator>(nullptr_t, const shared_ptr< _Tp > &__a) noexcept
shared_ptr comparison with nullptr
bool operator>=(nullptr_t, const shared_ptr< _Tp > &__a) noexcept
shared_ptr comparison with nullptr
shared_ptr< _Tp > dynamic_pointer_cast(const shared_ptr< _Up > &__r) noexcept
Convert type of shared_ptr, via dynamic_cast
shared_ptr< _Tp > const_pointer_cast(const shared_ptr< _Up > &__r) noexcept
Convert type of shared_ptr, via const_cast
bool operator>(const shared_ptr< _Tp > &__a, const shared_ptr< _Up > &__b) noexcept
Relational operator for shared_ptr objects, compares the stored pointers.
bool operator>=(const shared_ptr< _Tp > &__a, const shared_ptr< _Up > &__b) noexcept
Relational operator for shared_ptr objects, compares the stored pointers.
bool operator!=(const shared_ptr< _Tp > &__a, nullptr_t) noexcept
shared_ptr comparison with nullptr
void swap(shared_ptr< _Tp > &__a, shared_ptr< _Tp > &__b) noexcept
Swap overload for shared_ptr.
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition: move.h:104
constexpr _Tp && forward(typename std::remove_reference< _Tp >::type &__t) noexcept
Forward an lvalue.
Definition: move.h:77
ISO C++ entities toplevel namespace is std.
std::basic_ostream< _CharT, _Traits > & operator<<(std::basic_ostream< _CharT, _Traits > &__os, const bitset< _Nb > &__x)
Global I/O operators for bitsets.
Definition: bitset:1540
__shared_ptr< _Tp, _Lp > static_pointer_cast(const __shared_ptr< _Tp1, _Lp > &__r) noexcept
static_pointer_cast
__shared_ptr< _Tp, _Lp > const_pointer_cast(const __shared_ptr< _Tp1, _Lp > &__r) noexcept
const_pointer_cast
__shared_ptr< _Tp, _Lp > dynamic_pointer_cast(const __shared_ptr< _Tp1, _Lp > &__r) noexcept
dynamic_pointer_cast
Template class basic_ostream.
Definition: ostream:59
Primary class template hash.
integral_constant
Definition: type_traits:66
is_array
Definition: type_traits:429
is_constructible
Definition: type_traits:954
is_assignable
Definition: type_traits:1088
Define a member typedef type only if a boolean constant is true.
Definition: type_traits:2200
common_type
Definition: type_traits:2236
The standard allocator, as per C++03 [20.4.1].
Definition: allocator.h:141
A smart pointer with reference-counted copy semantics.
typename __shared_ptr< _Tp >::element_type element_type
The type pointed to by the stored pointer, remove_extent_t<_Tp>
shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
Construct a shared_ptr that owns a null pointer and the deleter __d.
shared_ptr(const shared_ptr< _Yp > &__r) noexcept
If __r is empty, constructs an empty shared_ptr; otherwise construct a shared_ptr that shares ownersh...
shared_ptr(shared_ptr< _Yp > &&__r) noexcept
Move-constructs a shared_ptr instance from __r.
weak_ptr< _Tp > weak_type
The corresponding weak_ptr type for this shared_ptr.
shared_ptr(_Yp *__p, _Deleter __d, _Alloc __a)
Construct a shared_ptr that owns the pointer __p and the deleter __d.
constexpr shared_ptr() noexcept
Construct an empty shared_ptr.
shared_ptr(const shared_ptr &) noexcept=default
Copy constructor.
shared_ptr(shared_ptr &&__r) noexcept
Move-constructs a shared_ptr instance from __r.
shared_ptr(_Yp *__p)
Construct a shared_ptr that owns the pointer __p.
shared_ptr(nullptr_t __p, _Deleter __d)
Construct a shared_ptr that owns a null pointer and the deleter __d.
shared_ptr(_Yp *__p, _Deleter __d)
Construct a shared_ptr that owns the pointer __p and the deleter __d.
shared_ptr(const shared_ptr< _Yp > &__r, element_type *__p) noexcept
Constructs a shared_ptr instance that stores __p and shares ownership with __r.
shared_ptr(const weak_ptr< _Yp > &__r)
Constructs a shared_ptr that shares ownership with __r and stores a copy of the pointer stored in __r...
constexpr shared_ptr(nullptr_t) noexcept
Construct an empty shared_ptr.
A non-owning observer for a pointer owned by a shared_ptr.
Primary template owner_less.
Base class allowing use of member function shared_from_this.
One of the comparison functors.
Definition: stl_function.h:382
20.7.1.2 unique_ptr for single objects.
Definition: unique_ptr.h:243
A simple smart pointer providing strict ownership semantics.
Definition: auto_ptr.h:90