libstdc++
shared_ptr_base.h
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1 // shared_ptr and weak_ptr implementation details -*- C++ -*-
2 
3 // Copyright (C) 2007-2025 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 bits/shared_ptr_base.h
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_BASE_H
50 #define _SHARED_PTR_BASE_H 1
51 
52 #include <typeinfo>
53 #include <bits/allocated_ptr.h>
54 #include <bits/allocator.h>
55 #include <bits/exception_defines.h>
56 #include <bits/functional_hash.h>
57 #include <bits/refwrap.h>
58 #include <bits/stl_function.h> // std::less
59 #include <bits/unique_ptr.h>
60 #include <ext/aligned_buffer.h>
61 #include <ext/atomicity.h>
62 #include <ext/concurrence.h>
63 #if __cplusplus >= 202002L
64 # include <compare>
65 # include <bits/align.h> // std::align
66 # include <bits/stl_uninitialized.h>
67 #endif
68 
69 namespace std _GLIBCXX_VISIBILITY(default)
70 {
71 _GLIBCXX_BEGIN_NAMESPACE_VERSION
72 
73 #if _GLIBCXX_USE_DEPRECATED
74 #pragma GCC diagnostic push
75 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
76  template<typename> class auto_ptr;
77 #pragma GCC diagnostic pop
78 #endif
79 
80  /**
81  * @brief Exception possibly thrown by @c shared_ptr.
82  * @ingroup exceptions
83  */
85  {
86  public:
87  virtual char const* what() const noexcept;
88 
89  virtual ~bad_weak_ptr() noexcept;
90  };
91 
92  // Substitute for bad_weak_ptr object in the case of -fno-exceptions.
93  inline void
94  __throw_bad_weak_ptr()
95  { _GLIBCXX_THROW_OR_ABORT(bad_weak_ptr()); }
96 
97  using __gnu_cxx::_Lock_policy;
98  using __gnu_cxx::__default_lock_policy;
99  using __gnu_cxx::_S_single;
100  using __gnu_cxx::_S_mutex;
101  using __gnu_cxx::_S_atomic;
102 
103  // Empty helper class except when the template argument is _S_mutex.
104  template<_Lock_policy _Lp>
105  class _Mutex_base
106  {
107  protected:
108  // The atomic policy uses fully-fenced builtins, single doesn't care.
109  enum { _S_need_barriers = 0 };
110  };
111 
112  template<>
113  class _Mutex_base<_S_mutex>
114  : public __gnu_cxx::__mutex
115  {
116  protected:
117  // This policy is used when atomic builtins are not available.
118  // The replacement atomic operations might not have the necessary
119  // memory barriers.
120  enum { _S_need_barriers = 1 };
121  };
122 
123  template<_Lock_policy _Lp = __default_lock_policy>
124  class _Sp_counted_base
125  : public _Mutex_base<_Lp>
126  {
127  public:
128  _Sp_counted_base() noexcept
129  : _M_use_count(1), _M_weak_count(1) { }
130 
131  virtual
132  ~_Sp_counted_base() noexcept
133  { }
134 
135  // Called when _M_use_count drops to zero, to release the resources
136  // managed by *this.
137  virtual void
138  _M_dispose() noexcept = 0;
139 
140  // Called when _M_weak_count drops to zero.
141  virtual void
142  _M_destroy() noexcept
143  { delete this; }
144 
145  virtual void*
146  _M_get_deleter(const std::type_info&) noexcept = 0;
147 
148  // Increment the use count (used when the count is greater than zero).
149  void
150  _M_add_ref_copy()
151  { __gnu_cxx::__atomic_add_dispatch(&_M_use_count, 1); }
152 
153  // Increment the use count if it is non-zero, throw otherwise.
154  void
155  _M_add_ref_lock()
156  {
157  if (!_M_add_ref_lock_nothrow())
158  __throw_bad_weak_ptr();
159  }
160 
161  // Increment the use count if it is non-zero.
162  bool
163  _M_add_ref_lock_nothrow() noexcept;
164 
165  // Decrement the use count.
166  void
167  _M_release() noexcept;
168 
169  // Called by _M_release() when the use count reaches zero.
170  void
171  _M_release_last_use() noexcept
172  {
173  _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_use_count);
174  _M_dispose();
175  // There must be a memory barrier between dispose() and destroy()
176  // to ensure that the effects of dispose() are observed in the
177  // thread that runs destroy().
178  // See http://gcc.gnu.org/ml/libstdc++/2005-11/msg00136.html
179  if (_Mutex_base<_Lp>::_S_need_barriers)
180  {
181  __atomic_thread_fence (__ATOMIC_ACQ_REL);
182  }
183 
184  // Be race-detector-friendly. For more info see bits/c++config.
185  _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count);
186  if (__gnu_cxx::__exchange_and_add_dispatch(&_M_weak_count,
187  -1) == 1)
188  {
189  _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count);
190  _M_destroy();
191  }
192  }
193 
194  // As above, but 'noinline' to reduce code size on the cold path.
195  __attribute__((__noinline__))
196  void
197  _M_release_last_use_cold() noexcept
198  { _M_release_last_use(); }
199 
200  // Increment the weak count.
201  void
202  _M_weak_add_ref() noexcept
203  { __gnu_cxx::__atomic_add_dispatch(&_M_weak_count, 1); }
204 
205  // Decrement the weak count.
206  void
207  _M_weak_release() noexcept
208  {
209  // Be race-detector-friendly. For more info see bits/c++config.
210  _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count);
211  if (__gnu_cxx::__exchange_and_add_dispatch(&_M_weak_count, -1) == 1)
212  {
213  _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count);
214  if (_Mutex_base<_Lp>::_S_need_barriers)
215  {
216  // See _M_release(),
217  // destroy() must observe results of dispose()
218  __atomic_thread_fence (__ATOMIC_ACQ_REL);
219  }
220  _M_destroy();
221  }
222  }
223 
224  long
225  _M_get_use_count() const noexcept
226  {
227  // No memory barrier is used here so there is no synchronization
228  // with other threads.
229  return __atomic_load_n(&_M_use_count, __ATOMIC_RELAXED);
230  }
231 
232  private:
233  _Sp_counted_base(_Sp_counted_base const&) = delete;
234  _Sp_counted_base& operator=(_Sp_counted_base const&) = delete;
235 
236  _Atomic_word _M_use_count; // #shared
237  _Atomic_word _M_weak_count; // #weak + (#shared != 0)
238  };
239 
240  template<>
241  inline bool
242  _Sp_counted_base<_S_single>::
243  _M_add_ref_lock_nothrow() noexcept
244  {
245  if (_M_use_count == 0)
246  return false;
247  ++_M_use_count;
248  return true;
249  }
250 
251  template<>
252  inline bool
253  _Sp_counted_base<_S_mutex>::
254  _M_add_ref_lock_nothrow() noexcept
255  {
256  __gnu_cxx::__scoped_lock sentry(*this);
257  if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, 1) == 0)
258  {
259  _M_use_count = 0;
260  return false;
261  }
262  return true;
263  }
264 
265  template<>
266  inline bool
267  _Sp_counted_base<_S_atomic>::
268  _M_add_ref_lock_nothrow() noexcept
269  {
270  // Perform lock-free add-if-not-zero operation.
271  _Atomic_word __count = _M_get_use_count();
272  do
273  {
274  if (__count == 0)
275  return false;
276  // Replace the current counter value with the old value + 1, as
277  // long as it's not changed meanwhile.
278  }
279  while (!__atomic_compare_exchange_n(&_M_use_count, &__count, __count + 1,
280  true, __ATOMIC_ACQ_REL,
281  __ATOMIC_RELAXED));
282  return true;
283  }
284 
285  template<>
286  inline void
287  _Sp_counted_base<_S_single>::_M_add_ref_copy()
288  { ++_M_use_count; }
289 
290  template<>
291  inline void
292  _Sp_counted_base<_S_single>::_M_release() noexcept
293  {
294  if (--_M_use_count == 0)
295  {
296  _M_dispose();
297  if (--_M_weak_count == 0)
298  _M_destroy();
299  }
300  }
301 
302  template<>
303  inline void
304  _Sp_counted_base<_S_mutex>::_M_release() noexcept
305  {
306  // Be race-detector-friendly. For more info see bits/c++config.
307  _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_use_count);
308  if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, -1) == 1)
309  {
310  _M_release_last_use();
311  }
312  }
313 
314  template<>
315  inline void
316  _Sp_counted_base<_S_atomic>::_M_release() noexcept
317  {
318  _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_use_count);
319 #if ! _GLIBCXX_TSAN
320  constexpr bool __lock_free
321  = __atomic_always_lock_free(sizeof(long long), 0)
322  && __atomic_always_lock_free(sizeof(_Atomic_word), 0);
323  constexpr bool __double_word
324  = sizeof(long long) == 2 * sizeof(_Atomic_word);
325  // The ref-count members follow the vptr, so are aligned to
326  // alignof(void*).
327  constexpr bool __aligned = __alignof(long long) <= alignof(void*);
328  if _GLIBCXX17_CONSTEXPR (__lock_free && __double_word && __aligned)
329  {
330  constexpr int __wordbits = __CHAR_BIT__ * sizeof(_Atomic_word);
331  constexpr int __shiftbits = __double_word ? __wordbits : 0;
332  constexpr long long __unique_ref = 1LL + (1LL << __shiftbits);
333  auto __both_counts = reinterpret_cast<long long*>(&_M_use_count);
334 
335  _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count);
336  if (__atomic_load_n(__both_counts, __ATOMIC_ACQUIRE) == __unique_ref)
337  {
338  // Both counts are 1, so there are no weak references and
339  // we are releasing the last strong reference. No other
340  // threads can observe the effects of this _M_release()
341  // call (e.g. calling use_count()) without a data race.
342  _M_weak_count = _M_use_count = 0;
343  _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_use_count);
344  _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count);
345  _M_dispose();
346  _M_destroy();
347  return;
348  }
349  if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, -1) == 1)
350  [[__unlikely__]]
351  {
352  _M_release_last_use_cold();
353  return;
354  }
355  }
356  else
357 #endif
358  if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, -1) == 1)
359  {
360  _M_release_last_use();
361  }
362  }
363 
364  template<>
365  inline void
366  _Sp_counted_base<_S_single>::_M_weak_add_ref() noexcept
367  { ++_M_weak_count; }
368 
369  template<>
370  inline void
371  _Sp_counted_base<_S_single>::_M_weak_release() noexcept
372  {
373  if (--_M_weak_count == 0)
374  _M_destroy();
375  }
376 
377  template<>
378  inline long
379  _Sp_counted_base<_S_single>::_M_get_use_count() const noexcept
380  { return _M_use_count; }
381 
382 
383  // Forward declarations.
384  template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
385  class __shared_ptr;
386 
387  template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
388  class __weak_ptr;
389 
390  template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
391  class __enable_shared_from_this;
392 
393  template<typename _Tp>
394  class shared_ptr;
395 
396  template<typename _Tp>
397  class weak_ptr;
398 
399  template<typename _Tp>
400  struct owner_less;
401 
402  template<typename _Tp>
403  class enable_shared_from_this;
404 
405  template<_Lock_policy _Lp = __default_lock_policy>
406  class __weak_count;
407 
408  template<_Lock_policy _Lp = __default_lock_policy>
409  class __shared_count;
410 
411 #ifdef __glibcxx_atomic_shared_ptr
412  template<typename>
413  class _Sp_atomic;
414 #endif
415 
416  // Counted ptr with no deleter or allocator support
417  template<typename _Ptr, _Lock_policy _Lp>
418  class _Sp_counted_ptr final : public _Sp_counted_base<_Lp>
419  {
420  public:
421  explicit
422  _Sp_counted_ptr(_Ptr __p) noexcept
423  : _M_ptr(__p) { }
424 
425  virtual void
426  _M_dispose() noexcept
427  { delete _M_ptr; }
428 
429  virtual void
430  _M_destroy() noexcept
431  { delete this; }
432 
433  virtual void*
434  _M_get_deleter(const std::type_info&) noexcept
435  { return nullptr; }
436 
437  _Sp_counted_ptr(const _Sp_counted_ptr&) = delete;
438  _Sp_counted_ptr& operator=(const _Sp_counted_ptr&) = delete;
439 
440  private:
441  _Ptr _M_ptr;
442  };
443 
444  template<>
445  inline void
446  _Sp_counted_ptr<nullptr_t, _S_single>::_M_dispose() noexcept { }
447 
448  template<>
449  inline void
450  _Sp_counted_ptr<nullptr_t, _S_mutex>::_M_dispose() noexcept { }
451 
452  template<>
453  inline void
454  _Sp_counted_ptr<nullptr_t, _S_atomic>::_M_dispose() noexcept { }
455 
456  // FIXME: once __has_cpp_attribute(__no_unique_address__)) is true for
457  // all supported compilers we can greatly simplify _Sp_ebo_helper.
458  // N.B. unconditionally applying the attribute could change layout for
459  // final types, which currently cannot use EBO so have a unique address.
460 
461  template<int _Nm, typename _Tp,
462  bool __use_ebo = !__is_final(_Tp) && __is_empty(_Tp)>
463  struct _Sp_ebo_helper;
464 
465  /// Specialization using EBO.
466  template<int _Nm, typename _Tp>
467  struct _Sp_ebo_helper<_Nm, _Tp, true> : private _Tp
468  {
469  explicit _Sp_ebo_helper(const _Tp& __tp) : _Tp(__tp) { }
470  explicit _Sp_ebo_helper(_Tp&& __tp) : _Tp(std::move(__tp)) { }
471 
472  static _Tp&
473  _S_get(_Sp_ebo_helper& __eboh) { return static_cast<_Tp&>(__eboh); }
474  };
475 
476  /// Specialization not using EBO.
477  template<int _Nm, typename _Tp>
478  struct _Sp_ebo_helper<_Nm, _Tp, false>
479  {
480  explicit _Sp_ebo_helper(const _Tp& __tp) : _M_tp(__tp) { }
481  explicit _Sp_ebo_helper(_Tp&& __tp) : _M_tp(std::move(__tp)) { }
482 
483  static _Tp&
484  _S_get(_Sp_ebo_helper& __eboh)
485  { return __eboh._M_tp; }
486 
487  private:
488  _Tp _M_tp;
489  };
490 
491  // Support for custom deleter and/or allocator
492  template<typename _Ptr, typename _Deleter, typename _Alloc, _Lock_policy _Lp>
493  class _Sp_counted_deleter final : public _Sp_counted_base<_Lp>
494  {
495  class _Impl : _Sp_ebo_helper<0, _Deleter>, _Sp_ebo_helper<1, _Alloc>
496  {
497  typedef _Sp_ebo_helper<0, _Deleter> _Del_base;
498  typedef _Sp_ebo_helper<1, _Alloc> _Alloc_base;
499 
500  public:
501  _Impl(_Ptr __p, _Deleter __d, const _Alloc& __a) noexcept
502  : _Del_base(std::move(__d)), _Alloc_base(__a), _M_ptr(__p)
503  { }
504 
505  _Deleter& _M_del() noexcept { return _Del_base::_S_get(*this); }
506  _Alloc& _M_alloc() noexcept { return _Alloc_base::_S_get(*this); }
507 
508  _Ptr _M_ptr;
509  };
510 
511  public:
512  using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_deleter>;
513 
514  // __d(__p) must not throw.
515  _Sp_counted_deleter(_Ptr __p, _Deleter __d) noexcept
516  : _M_impl(__p, std::move(__d), _Alloc()) { }
517 
518  // __d(__p) must not throw.
519  _Sp_counted_deleter(_Ptr __p, _Deleter __d, const _Alloc& __a) noexcept
520  : _M_impl(__p, std::move(__d), __a) { }
521 
522  ~_Sp_counted_deleter() noexcept { }
523 
524  virtual void
525  _M_dispose() noexcept
526  { _M_impl._M_del()(_M_impl._M_ptr); }
527 
528  virtual void
529  _M_destroy() noexcept
530  {
531  __allocator_type __a(_M_impl._M_alloc());
532  __allocated_ptr<__allocator_type> __guard_ptr{ __a, this };
533  this->~_Sp_counted_deleter();
534  }
535 
536  virtual void*
537  _M_get_deleter(const type_info& __ti [[__gnu__::__unused__]]) noexcept
538  {
539 #if __cpp_rtti
540  // _GLIBCXX_RESOLVE_LIB_DEFECTS
541  // 2400. shared_ptr's get_deleter() should use addressof()
542  return __ti == typeid(_Deleter)
543  ? std::__addressof(_M_impl._M_del())
544  : nullptr;
545 #else
546  return nullptr;
547 #endif
548  }
549 
550  private:
551 #ifdef __glibcxx_out_ptr
552  template<typename, typename, typename...> friend class out_ptr_t;
553 #endif
554  _Impl _M_impl;
555  };
556 
557  // helpers for make_shared / allocate_shared
558 
559  struct _Sp_make_shared_tag
560  {
561  private:
562  template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
563  friend class _Sp_counted_ptr_inplace;
564 
565  static const type_info&
566  _S_ti() noexcept _GLIBCXX_VISIBILITY(default)
567  {
568  alignas(type_info) static constexpr char __tag[sizeof(type_info)] = { };
569  return reinterpret_cast<const type_info&>(__tag);
570  }
571 
572  static bool _S_eq(const type_info&) noexcept;
573  };
574 
575  template<typename _Alloc>
576  struct _Sp_alloc_shared_tag
577  {
578  const _Alloc& _M_a;
579  };
580 
581  template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
582  class _Sp_counted_ptr_inplace final : public _Sp_counted_base<_Lp>
583  {
584  class _Impl : _Sp_ebo_helper<0, _Alloc>
585  {
586  typedef _Sp_ebo_helper<0, _Alloc> _A_base;
587 
588  public:
589  explicit _Impl(_Alloc __a) noexcept : _A_base(__a) { }
590 
591  _Alloc& _M_alloc() noexcept { return _A_base::_S_get(*this); }
592 
593  __gnu_cxx::__aligned_buffer<__remove_cv_t<_Tp>> _M_storage;
594  };
595 
596  public:
597  using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_ptr_inplace>;
598 
599  // Alloc parameter is not a reference so doesn't alias anything in __args
600  template<typename... _Args>
601  _Sp_counted_ptr_inplace(_Alloc __a, _Args&&... __args)
602  : _M_impl(__a)
603  {
604  // _GLIBCXX_RESOLVE_LIB_DEFECTS
605  // 2070. allocate_shared should use allocator_traits<A>::construct
607  std::forward<_Args>(__args)...); // might throw
608  }
609 
610  ~_Sp_counted_ptr_inplace() noexcept { }
611 
612  virtual void
613  _M_dispose() noexcept
614  {
615  allocator_traits<_Alloc>::destroy(_M_impl._M_alloc(), _M_ptr());
616  }
617 
618  // Override because the allocator needs to know the dynamic type
619  virtual void
620  _M_destroy() noexcept
621  {
622  __allocator_type __a(_M_impl._M_alloc());
623  __allocated_ptr<__allocator_type> __guard_ptr{ __a, this };
624  this->~_Sp_counted_ptr_inplace();
625  }
626 
627  private:
628  friend class __shared_count<_Lp>; // To be able to call _M_ptr().
629 
630  // No longer used, but code compiled against old libstdc++ headers
631  // might still call it from __shared_ptr ctor to get the pointer out.
632  virtual void*
633  _M_get_deleter(const std::type_info& __ti) noexcept override
634  {
635  // Check for the fake type_info first, so we don't try to access it
636  // as a real type_info object. Otherwise, check if it's the real
637  // type_info for this class. With RTTI enabled we can check directly,
638  // or call a library function to do it.
639  if (&__ti == &_Sp_make_shared_tag::_S_ti()
640  ||
641 #if __cpp_rtti
642  __ti == typeid(_Sp_make_shared_tag)
643 #else
644  _Sp_make_shared_tag::_S_eq(__ti)
645 #endif
646  )
647  return _M_ptr();
648  return nullptr;
649  }
650 
651  __remove_cv_t<_Tp>*
652  _M_ptr() noexcept { return _M_impl._M_storage._M_ptr(); }
653 
654  _Impl _M_impl;
655  };
656 
657 #ifdef __glibcxx_smart_ptr_for_overwrite // C++ >= 20 && HOSTED
658  struct _Sp_overwrite_tag { };
659 
660  // Partial specialization used for make_shared_for_overwrite<non-array>().
661  // This partial specialization is used when the allocator's value type
662  // is the special _Sp_overwrite_tag type.
663 #if __cpp_concepts
664  template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
665  requires is_same_v<typename _Alloc::value_type, _Sp_overwrite_tag>
666  class _Sp_counted_ptr_inplace<_Tp, _Alloc, _Lp> final
667 #else
668  template<typename _Tp, template<typename> class _Alloc, _Lock_policy _Lp>
669  class _Sp_counted_ptr_inplace<_Tp, _Alloc<_Sp_overwrite_tag>, _Lp> final
670 #endif
671  : public _Sp_counted_base<_Lp>
672  {
673  [[no_unique_address]] _Alloc _M_alloc;
674 
675  union {
676  remove_cv_t<_Tp> _M_obj;
677  char _M_unused;
678  };
679 
680  friend class __shared_count<_Lp>; // To be able to call _M_ptr().
681 
682  auto _M_ptr() noexcept { return std::__addressof(_M_obj); }
683 
684  public:
685  using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_ptr_inplace>;
686 
687  _Sp_counted_ptr_inplace(const _Alloc& __a)
688  : _M_alloc(__a)
689  {
690  ::new((void*)_M_ptr()) _Tp; // default-initialized, for overwrite.
691  }
692 
693  ~_Sp_counted_ptr_inplace() noexcept { }
694 
695  virtual void
696  _M_dispose() noexcept
697  {
698  _M_obj.~_Tp();
699  }
700 
701  // Override because the allocator needs to know the dynamic type
702  virtual void
703  _M_destroy() noexcept
704  {
705  using pointer = typename allocator_traits<__allocator_type>::pointer;
706  __allocator_type __a(_M_alloc);
707  auto __p = pointer_traits<pointer>::pointer_to(*this);
708  __allocated_ptr<__allocator_type> __guard_ptr{ __a, __p };
709  this->~_Sp_counted_ptr_inplace();
710  }
711 
712  void*
713  _M_get_deleter(const std::type_info&) noexcept override
714  { return nullptr; }
715  };
716 #endif // __glibcxx_smart_ptr_for_overwrite
717 
718 #if __glibcxx_shared_ptr_arrays >= 201707L // C++ >= 20 && HOSTED
719  struct _Sp_overwrite_tag;
720 
721  // For make_shared<T[]>, make_shared<T[N]>, allocate_shared<T[]> etc.
722  template<typename _Alloc>
723  struct _Sp_counted_array_base
724  {
725  [[no_unique_address]] _Alloc _M_alloc{};
726  size_t _M_n = 0;
727  bool _M_overwrite = false;
728 
730  _M_alloc_array(size_t __tail)
731  {
732  return allocator_traits<_Alloc>::allocate(_M_alloc, _M_n + __tail);
733  }
734 
735  void
736  _M_dealloc_array(typename allocator_traits<_Alloc>::pointer __p,
737  size_t __tail)
738  {
739  allocator_traits<_Alloc>::deallocate(_M_alloc, __p, _M_n + __tail);
740  }
741 
742  // Init the array elements
743  template<typename _Init>
744  void
745  _M_init(typename allocator_traits<_Alloc>::value_type* __p,
746  _Init __init)
747  {
748  using _Tp = remove_pointer_t<_Init>;
749  using _Up = typename allocator_traits<_Alloc>::value_type;
750 
751  if constexpr (is_same_v<_Init, _Sp_overwrite_tag>)
752  {
754  _M_overwrite = true;
755  }
756  else if (__init == nullptr)
757  std::__uninitialized_default_n_a(__p, _M_n, _M_alloc);
758  else if constexpr (!is_array_v<_Tp>)
759  std::__uninitialized_fill_n_a(__p, _M_n, *__init, _M_alloc);
760  else
761  {
762 #pragma GCC diagnostic push
763 #pragma GCC diagnostic ignored "-Wunused-local-typedefs"
764  struct _Iter
765  {
766  using value_type = _Up;
767  using difference_type = ptrdiff_t;
768  using pointer = const _Up*;
769  using reference = const _Up&;
770  using iterator_category = forward_iterator_tag;
771 
772  const _Up* _M_p;
773  size_t _M_len;
774  size_t _M_pos;
775 
776  _Iter& operator++() { ++_M_pos; return *this; }
777  _Iter operator++(int) { auto __i(*this); ++_M_pos; return __i; }
778 
779  reference operator*() const { return _M_p[_M_pos % _M_len]; }
780  pointer operator->() const { return _M_p + (_M_pos % _M_len); }
781 
782  bool operator==(const _Iter& __i) const
783  { return _M_pos == __i._M_pos; }
784  };
785 #pragma GCC diagnostic pop
786 
787  _Iter __first{_S_first_elem(__init), sizeof(_Tp) / sizeof(_Up)};
788  _Iter __last = __first;
789  __last._M_pos = _M_n;
790  std::__uninitialized_copy_a(__first, __last, __p, _M_alloc);
791  }
792  }
793 
794  protected:
795  // Destroy the array elements
796  void
797  _M_dispose_array(typename allocator_traits<_Alloc>::value_type* __p)
798  {
799  if (_M_overwrite)
800  std::destroy_n(__p, _M_n);
801  else
802  {
803  size_t __n = _M_n;
804  while (__n--)
805  allocator_traits<_Alloc>::destroy(_M_alloc, __p + __n);
806  }
807  }
808 
809  private:
810  template<typename _Tp>
811  static _Tp*
812  _S_first_elem(_Tp* __p) { return __p; }
813 
814  template<typename _Tp, size_t _Nm>
815  static auto
816  _S_first_elem(_Tp (*__p)[_Nm]) { return _S_first_elem(*__p); }
817  };
818 
819  // Control block for make_shared<T[]>, make_shared<T[N]> etc. that will be
820  // placed into unused memory at the end of the array.
821  template<typename _Alloc, _Lock_policy _Lp>
822  class _Sp_counted_array final
823  : public _Sp_counted_base<_Lp>, _Sp_counted_array_base<_Alloc>
824  {
825  using pointer = typename allocator_traits<_Alloc>::pointer;
826 
827  pointer _M_alloc_ptr;
828 
829  auto _M_ptr() const noexcept { return std::to_address(_M_alloc_ptr); }
830 
831  friend class __shared_count<_Lp>; // To be able to call _M_ptr().
832 
833  public:
834  _Sp_counted_array(const _Sp_counted_array_base<_Alloc>& __a,
835  pointer __p) noexcept
836  : _Sp_counted_array_base<_Alloc>(__a), _M_alloc_ptr(__p)
837  { }
838 
839  ~_Sp_counted_array() = default;
840 
841  virtual void
842  _M_dispose() noexcept
843  {
844  if (this->_M_n)
845  this->_M_dispose_array(_M_ptr());
846  }
847 
848  // Override because the allocator needs to know the dynamic type
849  virtual void
850  _M_destroy() noexcept
851  {
852  _Sp_counted_array_base<_Alloc> __a = *this;
853  pointer __p = _M_alloc_ptr;
854  this->~_Sp_counted_array();
855  __a._M_dealloc_array(__p, _S_tail());
856  }
857 
858  // Returns the number of additional array elements that must be
859  // allocated in order to store a _Sp_counted_array at the end.
860  static constexpr size_t
861  _S_tail()
862  {
863  // The array elemenent type.
864  using _Tp = typename allocator_traits<_Alloc>::value_type;
865 
866  // The space needed to store a _Sp_counted_array object.
867  size_t __bytes = sizeof(_Sp_counted_array);
868 
869  // Add any padding needed for manual alignment within the buffer.
870  if constexpr (alignof(_Tp) < alignof(_Sp_counted_array))
871  __bytes += alignof(_Sp_counted_array) - alignof(_Tp);
872 
873  return (__bytes + sizeof(_Tp) - 1) / sizeof(_Tp);
874  }
875 
876  void*
877  _M_get_deleter(const std::type_info&) noexcept override
878  { return nullptr; }
879  };
880 #endif // __glibcxx_shared_ptr_arrays >= 201707L
881 
882  // The default deleter for shared_ptr<T[]> and shared_ptr<T[N]>.
883  struct __sp_array_delete
884  {
885  template<typename _Yp>
886  void operator()(_Yp* __p) const { delete[] __p; }
887  };
888 
889  template<_Lock_policy _Lp>
890  class __shared_count
891  {
892  // Prevent _Sp_alloc_shared_tag from matching the shared_ptr(P, D) ctor.
893  template<typename _Tp>
894  struct __not_alloc_shared_tag { using type = void; };
895 
896  template<typename _Tp>
897  struct __not_alloc_shared_tag<_Sp_alloc_shared_tag<_Tp>> { };
898 
899 #if __glibcxx_shared_ptr_arrays >= 201707L // C++ >= 20 && HOSTED
900  template<typename _Alloc>
901  struct __not_alloc_shared_tag<_Sp_counted_array_base<_Alloc>> { };
902 #endif
903 
904  public:
905  constexpr __shared_count() noexcept : _M_pi(0)
906  { }
907 
908  template<typename _Ptr>
909  explicit
910  __shared_count(_Ptr __p) : _M_pi(0)
911  {
912  __try
913  {
914  _M_pi = new _Sp_counted_ptr<_Ptr, _Lp>(__p);
915  }
916  __catch(...)
917  {
918  delete __p;
919  __throw_exception_again;
920  }
921  }
922 
923  template<typename _Ptr>
924  __shared_count(_Ptr __p, /* is_array = */ false_type)
925  : __shared_count(__p)
926  { }
927 
928  template<typename _Ptr>
929  __shared_count(_Ptr __p, /* is_array = */ true_type)
930  : __shared_count(__p, __sp_array_delete{}, allocator<void>())
931  { }
932 
933  template<typename _Ptr, typename _Deleter,
934  typename = typename __not_alloc_shared_tag<_Deleter>::type>
935  __shared_count(_Ptr __p, _Deleter __d)
936  : __shared_count(__p, std::move(__d), allocator<void>())
937  { }
938 
939  template<typename _Ptr, typename _Deleter, typename _Alloc,
940  typename = typename __not_alloc_shared_tag<_Deleter>::type>
941  __shared_count(_Ptr __p, _Deleter __d, _Alloc __a) : _M_pi(0)
942  {
943  typedef _Sp_counted_deleter<_Ptr, _Deleter, _Alloc, _Lp> _Sp_cd_type;
944  __try
945  {
946  typename _Sp_cd_type::__allocator_type __a2(__a);
947  auto __guard = std::__allocate_guarded(__a2);
948  _Sp_cd_type* __mem = __guard.get();
949  ::new (__mem) _Sp_cd_type(__p, std::move(__d), std::move(__a));
950  _M_pi = __mem;
951  __guard = nullptr;
952  }
953  __catch(...)
954  {
955  __d(__p); // Call _Deleter on __p.
956  __throw_exception_again;
957  }
958  }
959 
960  template<typename _Tp, typename _Alloc, typename... _Args>
961  __shared_count(_Tp*& __p, _Sp_alloc_shared_tag<_Alloc> __a,
962  _Args&&... __args)
963  {
964  using _Tp2 = __remove_cv_t<_Tp>;
965  using _Sp_cp_type = _Sp_counted_ptr_inplace<_Tp2, _Alloc, _Lp>;
966  typename _Sp_cp_type::__allocator_type __a2(__a._M_a);
967  auto __guard = std::__allocate_guarded(__a2);
968  _Sp_cp_type* __mem = __guard.get();
969  auto __pi = ::new (__mem)
970  _Sp_cp_type(__a._M_a, std::forward<_Args>(__args)...);
971  __guard = nullptr;
972  _M_pi = __pi;
973  __p = __pi->_M_ptr();
974  }
975 
976 #if __glibcxx_shared_ptr_arrays >= 201707L // C++ >= 20 && HOSTED
977  template<typename _Tp, typename _Alloc, typename _Init>
978  __shared_count(_Tp*& __p, const _Sp_counted_array_base<_Alloc>& __a,
979  _Init __init)
980  {
981  using _Up = remove_all_extents_t<_Tp>;
982  static_assert(is_same_v<_Up, typename _Alloc::value_type>);
983 
984  using _Sp_ca_type = _Sp_counted_array<_Alloc, _Lp>;
985  const size_t __tail = _Sp_ca_type::_S_tail();
986 
987  struct _Guarded_ptr : _Sp_counted_array_base<_Alloc>
988  {
989  typename allocator_traits<_Alloc>::pointer _M_ptr;
990 
991  _Guarded_ptr(_Sp_counted_array_base<_Alloc> __a)
992  : _Sp_counted_array_base<_Alloc>(__a),
993  _M_ptr(this->_M_alloc_array(_Sp_ca_type::_S_tail()))
994  { }
995 
996  ~_Guarded_ptr()
997  {
998  if (_M_ptr)
999  this->_M_dealloc_array(_M_ptr, _Sp_ca_type::_S_tail());
1000  }
1001  };
1002 
1003  _Guarded_ptr __guard{__a};
1004  _Up* const __raw = std::to_address(__guard._M_ptr);
1005  __guard._M_init(__raw, __init); // might throw
1006 
1007  void* __c = __raw + __a._M_n;
1008  if constexpr (alignof(_Up) < alignof(_Sp_ca_type))
1009  {
1010  size_t __space = sizeof(_Up) * __tail;
1011  __c = std::align(alignof(_Sp_ca_type), sizeof(_Sp_ca_type),
1012  __c, __space);
1013  }
1014  auto __pi = ::new(__c) _Sp_ca_type(__guard, __guard._M_ptr);
1015  __guard._M_ptr = nullptr;
1016  _M_pi = __pi;
1017  __p = reinterpret_cast<_Tp*>(__raw);
1018  }
1019 #endif
1020 
1021 #if _GLIBCXX_USE_DEPRECATED
1022 #pragma GCC diagnostic push
1023 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
1024  // Special case for auto_ptr<_Tp> to provide the strong guarantee.
1025  template<typename _Tp>
1026  explicit
1027  __shared_count(std::auto_ptr<_Tp>&& __r);
1028 #pragma GCC diagnostic pop
1029 #endif
1030 
1031  // Special case for unique_ptr<_Tp,_Del> to provide the strong guarantee.
1032  template<typename _Tp, typename _Del>
1033  explicit
1034  __shared_count(std::unique_ptr<_Tp, _Del>&& __r) : _M_pi(0)
1035  {
1036  // _GLIBCXX_RESOLVE_LIB_DEFECTS
1037  // 2415. Inconsistency between unique_ptr and shared_ptr
1038  if (__r.get() == nullptr)
1039  return;
1040 
1041  using _Ptr = typename unique_ptr<_Tp, _Del>::pointer;
1042  using _Del2 = __conditional_t<is_reference<_Del>::value,
1043  reference_wrapper<typename remove_reference<_Del>::type>,
1044  _Del>;
1045  using _Sp_cd_type
1046  = _Sp_counted_deleter<_Ptr, _Del2, allocator<void>, _Lp>;
1047  using _Alloc = allocator<_Sp_cd_type>;
1048  using _Alloc_traits = allocator_traits<_Alloc>;
1049  _Alloc __a;
1050  _Sp_cd_type* __mem = _Alloc_traits::allocate(__a, 1);
1051  // _GLIBCXX_RESOLVE_LIB_DEFECTS
1052  // 3548. shared_ptr construction from unique_ptr should move
1053  // (not copy) the deleter
1054  _Alloc_traits::construct(__a, __mem, __r.release(),
1055  std::forward<_Del>(__r.get_deleter()));
1056  _M_pi = __mem;
1057  }
1058 
1059  // Throw bad_weak_ptr when __r._M_get_use_count() == 0.
1060  explicit __shared_count(const __weak_count<_Lp>& __r);
1061 
1062  // Does not throw if __r._M_get_use_count() == 0, caller must check.
1063  explicit
1064  __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t) noexcept;
1065 
1066  ~__shared_count() noexcept
1067  {
1068  if (_M_pi != nullptr)
1069  _M_pi->_M_release();
1070  }
1071 
1072  __shared_count(const __shared_count& __r) noexcept
1073  : _M_pi(__r._M_pi)
1074  {
1075  if (_M_pi != nullptr)
1076  _M_pi->_M_add_ref_copy();
1077  }
1078 
1079  __shared_count&
1080  operator=(const __shared_count& __r) noexcept
1081  {
1082  _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
1083  if (__tmp != _M_pi)
1084  {
1085  if (__tmp != nullptr)
1086  __tmp->_M_add_ref_copy();
1087  if (_M_pi != nullptr)
1088  _M_pi->_M_release();
1089  _M_pi = __tmp;
1090  }
1091  return *this;
1092  }
1093 
1094  void
1095  _M_swap(__shared_count& __r) noexcept
1096  {
1097  _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
1098  __r._M_pi = _M_pi;
1099  _M_pi = __tmp;
1100  }
1101 
1102  long
1103  _M_get_use_count() const noexcept
1104  { return _M_pi ? _M_pi->_M_get_use_count() : 0; }
1105 
1106  bool
1107  _M_unique() const noexcept
1108  { return this->_M_get_use_count() == 1; }
1109 
1110  void*
1111  _M_get_deleter(const std::type_info& __ti) const noexcept
1112  { return _M_pi ? _M_pi->_M_get_deleter(__ti) : nullptr; }
1113 
1114  bool
1115  _M_less(const __shared_count& __rhs) const noexcept
1116  { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
1117 
1118  bool
1119  _M_less(const __weak_count<_Lp>& __rhs) const noexcept
1120  { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
1121 
1122  // Friend function injected into enclosing namespace and found by ADL
1123  friend inline bool
1124  operator==(const __shared_count& __a, const __shared_count& __b) noexcept
1125  { return __a._M_pi == __b._M_pi; }
1126 
1127  private:
1128  friend class __weak_count<_Lp>;
1129 #ifdef __glibcxx_atomic_shared_ptr
1130  template<typename> friend class _Sp_atomic;
1131 #endif
1132 #ifdef __glibcxx_out_ptr
1133  template<typename, typename, typename...> friend class out_ptr_t;
1134 #endif
1135 
1136  _Sp_counted_base<_Lp>* _M_pi;
1137  };
1138 
1139 
1140  template<_Lock_policy _Lp>
1141  class __weak_count
1142  {
1143  public:
1144  constexpr __weak_count() noexcept : _M_pi(nullptr)
1145  { }
1146 
1147  __weak_count(const __shared_count<_Lp>& __r) noexcept
1148  : _M_pi(__r._M_pi)
1149  {
1150  if (_M_pi != nullptr)
1151  _M_pi->_M_weak_add_ref();
1152  }
1153 
1154  __weak_count(const __weak_count& __r) noexcept
1155  : _M_pi(__r._M_pi)
1156  {
1157  if (_M_pi != nullptr)
1158  _M_pi->_M_weak_add_ref();
1159  }
1160 
1161  __weak_count(__weak_count&& __r) noexcept
1162  : _M_pi(__r._M_pi)
1163  { __r._M_pi = nullptr; }
1164 
1165  ~__weak_count() noexcept
1166  {
1167  if (_M_pi != nullptr)
1168  _M_pi->_M_weak_release();
1169  }
1170 
1171  __weak_count&
1172  operator=(const __shared_count<_Lp>& __r) noexcept
1173  {
1174  _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
1175  if (__tmp != nullptr)
1176  __tmp->_M_weak_add_ref();
1177  if (_M_pi != nullptr)
1178  _M_pi->_M_weak_release();
1179  _M_pi = __tmp;
1180  return *this;
1181  }
1182 
1183  __weak_count&
1184  operator=(const __weak_count& __r) noexcept
1185  {
1186  _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
1187  if (__tmp != nullptr)
1188  __tmp->_M_weak_add_ref();
1189  if (_M_pi != nullptr)
1190  _M_pi->_M_weak_release();
1191  _M_pi = __tmp;
1192  return *this;
1193  }
1194 
1195  __weak_count&
1196  operator=(__weak_count&& __r) noexcept
1197  {
1198  if (_M_pi != nullptr)
1199  _M_pi->_M_weak_release();
1200  _M_pi = __r._M_pi;
1201  __r._M_pi = nullptr;
1202  return *this;
1203  }
1204 
1205  void
1206  _M_swap(__weak_count& __r) noexcept
1207  {
1208  _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
1209  __r._M_pi = _M_pi;
1210  _M_pi = __tmp;
1211  }
1212 
1213  long
1214  _M_get_use_count() const noexcept
1215  { return _M_pi != nullptr ? _M_pi->_M_get_use_count() : 0; }
1216 
1217  bool
1218  _M_less(const __weak_count& __rhs) const noexcept
1219  { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
1220 
1221  bool
1222  _M_less(const __shared_count<_Lp>& __rhs) const noexcept
1223  { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
1224 
1225  // Friend function injected into enclosing namespace and found by ADL
1226  friend inline bool
1227  operator==(const __weak_count& __a, const __weak_count& __b) noexcept
1228  { return __a._M_pi == __b._M_pi; }
1229 
1230  private:
1231  friend class __shared_count<_Lp>;
1232 #ifdef __glibcxx_atomic_shared_ptr
1233  template<typename> friend class _Sp_atomic;
1234 #endif
1235 
1236  _Sp_counted_base<_Lp>* _M_pi;
1237  };
1238 
1239  // Now that __weak_count is defined we can define this constructor:
1240  template<_Lock_policy _Lp>
1241  inline
1242  __shared_count<_Lp>::__shared_count(const __weak_count<_Lp>& __r)
1243  : _M_pi(__r._M_pi)
1244  {
1245  if (_M_pi == nullptr || !_M_pi->_M_add_ref_lock_nothrow())
1246  __throw_bad_weak_ptr();
1247  }
1248 
1249  // Now that __weak_count is defined we can define this constructor:
1250  template<_Lock_policy _Lp>
1251  inline
1252  __shared_count<_Lp>::
1253  __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t) noexcept
1254  : _M_pi(__r._M_pi)
1255  {
1256  if (_M_pi && !_M_pi->_M_add_ref_lock_nothrow())
1257  _M_pi = nullptr;
1258  }
1259 
1260  // Helper traits for shared_ptr of array:
1261 
1262  // A pointer type Y* is said to be compatible with a pointer type T* when
1263  // either Y* is convertible to T* or Y is U[N] and T is U cv [].
1264  template<typename _Yp_ptr, typename _Tp_ptr>
1265  struct __sp_compatible_with
1266  : false_type
1267  { };
1268 
1269  template<typename _Yp, typename _Tp>
1270  struct __sp_compatible_with<_Yp*, _Tp*>
1271  : is_convertible<_Yp*, _Tp*>::type
1272  { };
1273 
1274  template<typename _Up, size_t _Nm>
1275  struct __sp_compatible_with<_Up(*)[_Nm], _Up(*)[]>
1276  : true_type
1277  { };
1278 
1279  template<typename _Up, size_t _Nm>
1280  struct __sp_compatible_with<_Up(*)[_Nm], const _Up(*)[]>
1281  : true_type
1282  { };
1283 
1284  template<typename _Up, size_t _Nm>
1285  struct __sp_compatible_with<_Up(*)[_Nm], volatile _Up(*)[]>
1286  : true_type
1287  { };
1288 
1289  template<typename _Up, size_t _Nm>
1290  struct __sp_compatible_with<_Up(*)[_Nm], const volatile _Up(*)[]>
1291  : true_type
1292  { };
1293 
1294  // Test conversion from Y(*)[N] to U(*)[N] without forming invalid type Y[N].
1295  template<typename _Up, size_t _Nm, typename _Yp, typename = void>
1296  struct __sp_is_constructible_arrN
1297  : false_type
1298  { };
1299 
1300  template<typename _Up, size_t _Nm, typename _Yp>
1301  struct __sp_is_constructible_arrN<_Up, _Nm, _Yp, __void_t<_Yp[_Nm]>>
1302  : is_convertible<_Yp(*)[_Nm], _Up(*)[_Nm]>::type
1303  { };
1304 
1305  // Test conversion from Y(*)[] to U(*)[] without forming invalid type Y[].
1306  template<typename _Up, typename _Yp, typename = void>
1307  struct __sp_is_constructible_arr
1308  : false_type
1309  { };
1310 
1311  template<typename _Up, typename _Yp>
1312  struct __sp_is_constructible_arr<_Up, _Yp, __void_t<_Yp[]>>
1313  : is_convertible<_Yp(*)[], _Up(*)[]>::type
1314  { };
1315 
1316  // Trait to check if shared_ptr<T> can be constructed from Y*.
1317  template<typename _Tp, typename _Yp>
1318  struct __sp_is_constructible;
1319 
1320  // When T is U[N], Y(*)[N] shall be convertible to T*;
1321  template<typename _Up, size_t _Nm, typename _Yp>
1322  struct __sp_is_constructible<_Up[_Nm], _Yp>
1323  : __sp_is_constructible_arrN<_Up, _Nm, _Yp>::type
1324  { };
1325 
1326  // when T is U[], Y(*)[] shall be convertible to T*;
1327  template<typename _Up, typename _Yp>
1328  struct __sp_is_constructible<_Up[], _Yp>
1329  : __sp_is_constructible_arr<_Up, _Yp>::type
1330  { };
1331 
1332  // otherwise, Y* shall be convertible to T*.
1333  template<typename _Tp, typename _Yp>
1334  struct __sp_is_constructible
1335  : is_convertible<_Yp*, _Tp*>::type
1336  { };
1337 
1338 
1339  template<typename _Tp>
1340  [[__gnu__::__always_inline__]]
1341  inline _Tp*
1342  __shared_ptr_deref(_Tp* __p)
1343  {
1344  __glibcxx_assert(__p != nullptr);
1345  return __p;
1346  }
1347 
1348  // Define operator* and operator-> for shared_ptr<T>.
1349  template<typename _Tp, _Lock_policy _Lp,
1350  bool = is_array<_Tp>::value, bool = is_void<_Tp>::value>
1351  class __shared_ptr_access
1352  {
1353  public:
1354  using element_type = _Tp;
1355 
1356  element_type&
1357  operator*() const noexcept
1358  { return *std::__shared_ptr_deref(_M_get()); }
1359 
1360  element_type*
1361  operator->() const noexcept
1362  {
1363  _GLIBCXX_DEBUG_PEDASSERT(_M_get() != nullptr);
1364  return _M_get();
1365  }
1366 
1367  private:
1368  element_type*
1369  _M_get() const noexcept
1370  { return static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get(); }
1371  };
1372 
1373  // Define operator-> for shared_ptr<cv void>.
1374  template<typename _Tp, _Lock_policy _Lp>
1375  class __shared_ptr_access<_Tp, _Lp, false, true>
1376  {
1377  public:
1378  using element_type = _Tp;
1379 
1380  element_type*
1381  operator->() const noexcept
1382  {
1383  auto __ptr = static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get();
1384  _GLIBCXX_DEBUG_PEDASSERT(__ptr != nullptr);
1385  return __ptr;
1386  }
1387  };
1388 
1389  // Define operator[] for shared_ptr<T[]> and shared_ptr<T[N]>.
1390  template<typename _Tp, _Lock_policy _Lp>
1391  class __shared_ptr_access<_Tp, _Lp, true, false>
1392  {
1393  public:
1394  using element_type = typename remove_extent<_Tp>::type;
1395 
1396 #if __cplusplus <= 201402L
1397  [[__deprecated__("shared_ptr<T[]>::operator* is absent from C++17")]]
1398  element_type&
1399  operator*() const noexcept
1400  { return *std::__shared_ptr_deref(_M_get()); }
1401 
1402  [[__deprecated__("shared_ptr<T[]>::operator-> is absent from C++17")]]
1403  element_type*
1404  operator->() const noexcept
1405  {
1406  _GLIBCXX_DEBUG_PEDASSERT(_M_get() != nullptr);
1407  return _M_get();
1408  }
1409 #endif
1410 
1411 #pragma GCC diagnostic push
1412 #pragma GCC diagnostic ignored "-Wc++17-extensions"
1413  element_type&
1414  operator[](ptrdiff_t __i) const noexcept
1415  {
1416  if constexpr (extent<_Tp>::value)
1417  __glibcxx_assert(__i < extent<_Tp>::value);
1418  return std::__shared_ptr_deref(_M_get())[__i];
1419  }
1420 #pragma GCC diagnostic pop
1421 
1422  private:
1423  element_type*
1424  _M_get() const noexcept
1425  { return static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get(); }
1426  };
1427 
1428  template<typename _Tp, _Lock_policy _Lp>
1429  class __shared_ptr
1430  : public __shared_ptr_access<_Tp, _Lp>
1431  {
1432  public:
1433  using element_type = typename remove_extent<_Tp>::type;
1434 
1435  private:
1436  // Constraint for taking ownership of a pointer of type _Yp*:
1437  template<typename _Yp>
1438  using _SafeConv
1439  = typename enable_if<__sp_is_constructible<_Tp, _Yp>::value>::type;
1440 
1441  // Constraint for construction from shared_ptr and weak_ptr:
1442  template<typename _Yp, typename _Res = void>
1443  using _Compatible = typename
1444  enable_if<__sp_compatible_with<_Yp*, _Tp*>::value, _Res>::type;
1445 
1446  // Constraint for assignment from shared_ptr and weak_ptr:
1447  template<typename _Yp>
1448  using _Assignable = _Compatible<_Yp, __shared_ptr&>;
1449 
1450  // Constraint for construction from unique_ptr:
1451  template<typename _Yp, typename _Del, typename _Res = void,
1452  typename _Ptr = typename unique_ptr<_Yp, _Del>::pointer>
1453  using _UniqCompatible = __enable_if_t<__and_<
1454  __sp_compatible_with<_Yp*, _Tp*>,
1455  is_convertible<_Ptr, element_type*>,
1456  is_move_constructible<_Del>
1457  >::value, _Res>;
1458 
1459  // Constraint for assignment from unique_ptr:
1460  template<typename _Yp, typename _Del>
1461  using _UniqAssignable = _UniqCompatible<_Yp, _Del, __shared_ptr&>;
1462 
1463  public:
1464 
1465 #if __cplusplus > 201402L
1466  using weak_type = __weak_ptr<_Tp, _Lp>;
1467 #endif
1468 
1469  constexpr __shared_ptr() noexcept
1470  : _M_ptr(0), _M_refcount()
1471  { }
1472 
1473  template<typename _Yp, typename = _SafeConv<_Yp>>
1474  explicit
1475  __shared_ptr(_Yp* __p)
1476  : _M_ptr(__p), _M_refcount(__p, typename is_array<_Tp>::type())
1477  {
1478  static_assert( !is_void<_Yp>::value, "incomplete type" );
1479  static_assert( sizeof(_Yp) > 0, "incomplete type" );
1480  _M_enable_shared_from_this_with(__p);
1481  }
1482 
1483  template<typename _Yp, typename _Deleter, typename = _SafeConv<_Yp>>
1484  __shared_ptr(_Yp* __p, _Deleter __d)
1485  : _M_ptr(__p), _M_refcount(__p, std::move(__d))
1486  {
1487  static_assert(__is_invocable<_Deleter&, _Yp*&>::value,
1488  "deleter expression d(p) is well-formed");
1489  _M_enable_shared_from_this_with(__p);
1490  }
1491 
1492  template<typename _Yp, typename _Deleter, typename _Alloc,
1493  typename = _SafeConv<_Yp>>
1494  __shared_ptr(_Yp* __p, _Deleter __d, _Alloc __a)
1495  : _M_ptr(__p), _M_refcount(__p, std::move(__d), std::move(__a))
1496  {
1497  static_assert(__is_invocable<_Deleter&, _Yp*&>::value,
1498  "deleter expression d(p) is well-formed");
1499  _M_enable_shared_from_this_with(__p);
1500  }
1501 
1502  template<typename _Deleter>
1503  __shared_ptr(nullptr_t __p, _Deleter __d)
1504  : _M_ptr(0), _M_refcount(__p, std::move(__d))
1505  { }
1506 
1507  template<typename _Deleter, typename _Alloc>
1508  __shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
1509  : _M_ptr(0), _M_refcount(__p, std::move(__d), std::move(__a))
1510  { }
1511 
1512  // Aliasing constructor
1513  template<typename _Yp>
1514  __shared_ptr(const __shared_ptr<_Yp, _Lp>& __r,
1515  element_type* __p) noexcept
1516  : _M_ptr(__p), _M_refcount(__r._M_refcount) // never throws
1517  { }
1518 
1519  // Aliasing constructor
1520  template<typename _Yp>
1521  __shared_ptr(__shared_ptr<_Yp, _Lp>&& __r,
1522  element_type* __p) noexcept
1523  : _M_ptr(__p), _M_refcount()
1524  {
1525  _M_refcount._M_swap(__r._M_refcount);
1526  __r._M_ptr = nullptr;
1527  }
1528 
1529  __shared_ptr(const __shared_ptr&) noexcept = default;
1530  __shared_ptr& operator=(const __shared_ptr&) noexcept = default;
1531  ~__shared_ptr() = default;
1532 
1533  template<typename _Yp, typename = _Compatible<_Yp>>
1534  __shared_ptr(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1535  : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount)
1536  { }
1537 
1538  __shared_ptr(__shared_ptr&& __r) noexcept
1539  : _M_ptr(__r._M_ptr), _M_refcount()
1540  {
1541  _M_refcount._M_swap(__r._M_refcount);
1542  __r._M_ptr = nullptr;
1543  }
1544 
1545  template<typename _Yp, typename = _Compatible<_Yp>>
1546  __shared_ptr(__shared_ptr<_Yp, _Lp>&& __r) noexcept
1547  : _M_ptr(__r._M_ptr), _M_refcount()
1548  {
1549  _M_refcount._M_swap(__r._M_refcount);
1550  __r._M_ptr = nullptr;
1551  }
1552 
1553  template<typename _Yp, typename = _Compatible<_Yp>>
1554  explicit __shared_ptr(const __weak_ptr<_Yp, _Lp>& __r)
1555  : _M_refcount(__r._M_refcount) // may throw
1556  {
1557  // It is now safe to copy __r._M_ptr, as
1558  // _M_refcount(__r._M_refcount) did not throw.
1559  _M_ptr = __r._M_ptr;
1560  }
1561 
1562  // If an exception is thrown this constructor has no effect.
1563  template<typename _Yp, typename _Del,
1564  typename = _UniqCompatible<_Yp, _Del>>
1565  __shared_ptr(unique_ptr<_Yp, _Del>&& __r)
1566  : _M_ptr(__r.get()), _M_refcount()
1567  {
1568  auto __raw = std::__to_address(__r.get());
1569  _M_refcount = __shared_count<_Lp>(std::move(__r));
1570  _M_enable_shared_from_this_with(__raw);
1571  }
1572 
1573 #if __cplusplus <= 201402L && _GLIBCXX_USE_DEPRECATED
1574  protected:
1575  // If an exception is thrown this constructor has no effect.
1576  template<typename _Tp1, typename _Del,
1577  typename enable_if<__and_<
1578  __not_<is_array<_Tp>>, is_array<_Tp1>,
1579  is_convertible<typename unique_ptr<_Tp1, _Del>::pointer, _Tp*>
1580  >::value, bool>::type = true>
1581  __shared_ptr(unique_ptr<_Tp1, _Del>&& __r, __sp_array_delete)
1582  : _M_ptr(__r.get()), _M_refcount()
1583  {
1584  auto __raw = std::__to_address(__r.get());
1585  _M_refcount = __shared_count<_Lp>(std::move(__r));
1586  _M_enable_shared_from_this_with(__raw);
1587  }
1588  public:
1589 #endif
1590 
1591 #if _GLIBCXX_USE_DEPRECATED
1592 #pragma GCC diagnostic push
1593 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
1594  // Postcondition: use_count() == 1 and __r.get() == 0
1595  template<typename _Yp, typename = _Compatible<_Yp>>
1596  __shared_ptr(auto_ptr<_Yp>&& __r);
1597 #pragma GCC diagnostic pop
1598 #endif
1599 
1600  constexpr __shared_ptr(nullptr_t) noexcept : __shared_ptr() { }
1601 
1602  template<typename _Yp>
1603  _Assignable<_Yp>
1604  operator=(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1605  {
1606  _M_ptr = __r._M_ptr;
1607  _M_refcount = __r._M_refcount; // __shared_count::op= doesn't throw
1608  return *this;
1609  }
1610 
1611 #if _GLIBCXX_USE_DEPRECATED
1612 #pragma GCC diagnostic push
1613 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
1614  template<typename _Yp>
1615  _Assignable<_Yp>
1616  operator=(auto_ptr<_Yp>&& __r)
1617  {
1618  __shared_ptr(std::move(__r)).swap(*this);
1619  return *this;
1620  }
1621 #pragma GCC diagnostic pop
1622 #endif
1623 
1624  __shared_ptr&
1625  operator=(__shared_ptr&& __r) noexcept
1626  {
1627  __shared_ptr(std::move(__r)).swap(*this);
1628  return *this;
1629  }
1630 
1631  template<class _Yp>
1632  _Assignable<_Yp>
1633  operator=(__shared_ptr<_Yp, _Lp>&& __r) noexcept
1634  {
1635  __shared_ptr(std::move(__r)).swap(*this);
1636  return *this;
1637  }
1638 
1639  template<typename _Yp, typename _Del>
1640  _UniqAssignable<_Yp, _Del>
1641  operator=(unique_ptr<_Yp, _Del>&& __r)
1642  {
1643  __shared_ptr(std::move(__r)).swap(*this);
1644  return *this;
1645  }
1646 
1647  void
1648  reset() noexcept
1649  { __shared_ptr().swap(*this); }
1650 
1651  template<typename _Yp>
1652  _SafeConv<_Yp>
1653  reset(_Yp* __p) // _Yp must be complete.
1654  {
1655  // Catch self-reset errors.
1656  __glibcxx_assert(__p == nullptr || __p != _M_ptr);
1657  __shared_ptr(__p).swap(*this);
1658  }
1659 
1660  template<typename _Yp, typename _Deleter>
1661  _SafeConv<_Yp>
1662  reset(_Yp* __p, _Deleter __d)
1663  { __shared_ptr(__p, std::move(__d)).swap(*this); }
1664 
1665  template<typename _Yp, typename _Deleter, typename _Alloc>
1666  _SafeConv<_Yp>
1667  reset(_Yp* __p, _Deleter __d, _Alloc __a)
1668  { __shared_ptr(__p, std::move(__d), std::move(__a)).swap(*this); }
1669 
1670  /// Return the stored pointer.
1671  element_type*
1672  get() const noexcept
1673  { return _M_ptr; }
1674 
1675  /// Return true if the stored pointer is not null.
1676  explicit operator bool() const noexcept
1677  { return _M_ptr != nullptr; }
1678 
1679  /// Return true if use_count() == 1.
1680  bool
1681  unique() const noexcept
1682  { return _M_refcount._M_unique(); }
1683 
1684  /// If *this owns a pointer, return the number of owners, otherwise zero.
1685  long
1686  use_count() const noexcept
1687  { return _M_refcount._M_get_use_count(); }
1688 
1689  /// Exchange both the owned pointer and the stored pointer.
1690  void
1691  swap(__shared_ptr<_Tp, _Lp>& __other) noexcept
1692  {
1693  std::swap(_M_ptr, __other._M_ptr);
1694  _M_refcount._M_swap(__other._M_refcount);
1695  }
1696 
1697  /** @brief Define an ordering based on ownership.
1698  *
1699  * This function defines a strict weak ordering between two shared_ptr
1700  * or weak_ptr objects, such that one object is less than the other
1701  * unless they share ownership of the same pointer, or are both empty.
1702  * @{
1703  */
1704  template<typename _Tp1>
1705  bool
1706  owner_before(__shared_ptr<_Tp1, _Lp> const& __rhs) const noexcept
1707  { return _M_refcount._M_less(__rhs._M_refcount); }
1708 
1709  template<typename _Tp1>
1710  bool
1711  owner_before(__weak_ptr<_Tp1, _Lp> const& __rhs) const noexcept
1712  { return _M_refcount._M_less(__rhs._M_refcount); }
1713  /// @}
1714 
1715  protected:
1716  // This constructor is non-standard, it is used by allocate_shared.
1717  template<typename _Alloc, typename... _Args>
1718  __shared_ptr(_Sp_alloc_shared_tag<_Alloc> __tag, _Args&&... __args)
1719  : _M_ptr(), _M_refcount(_M_ptr, __tag, std::forward<_Args>(__args)...)
1720  { _M_enable_shared_from_this_with(_M_ptr); }
1721 
1722  template<typename _Tp1, _Lock_policy _Lp1, typename _Alloc,
1723  typename... _Args>
1724  friend __shared_ptr<_Tp1, _Lp1>
1725  __allocate_shared(const _Alloc& __a, _Args&&... __args);
1726 
1727 #if __glibcxx_shared_ptr_arrays >= 201707L // C++ >= 20 && HOSTED
1728  // This constructor is non-standard, it is used by allocate_shared<T[]>.
1729  template<typename _Alloc, typename _Init = const remove_extent_t<_Tp>*>
1730  __shared_ptr(const _Sp_counted_array_base<_Alloc>& __a,
1731  _Init __init = nullptr)
1732  : _M_ptr(), _M_refcount(_M_ptr, __a, __init)
1733  { }
1734 #endif
1735 
1736  // This constructor is used by __weak_ptr::lock() and
1737  // shared_ptr::shared_ptr(const weak_ptr&, std::nothrow_t).
1738  __shared_ptr(const __weak_ptr<_Tp, _Lp>& __r, std::nothrow_t) noexcept
1739  : _M_refcount(__r._M_refcount, std::nothrow)
1740  {
1741  _M_ptr = _M_refcount._M_get_use_count() ? __r._M_ptr : nullptr;
1742  }
1743 
1744  friend class __weak_ptr<_Tp, _Lp>;
1745 
1746  private:
1747 
1748  template<typename _Yp>
1749  using __esft_base_t = decltype(__enable_shared_from_this_base(
1750  std::declval<const __shared_count<_Lp>&>(),
1751  std::declval<_Yp*>()));
1752 
1753  // Detect an accessible and unambiguous enable_shared_from_this base.
1754  template<typename _Yp, typename = void>
1755  struct __has_esft_base
1756  : false_type { };
1757 
1758  template<typename _Yp>
1759  struct __has_esft_base<_Yp, __void_t<__esft_base_t<_Yp>>>
1760  : __not_<is_array<_Tp>> { }; // No enable shared_from_this for arrays
1761 
1762  template<typename _Yp, typename _Yp2 = typename remove_cv<_Yp>::type>
1763  typename enable_if<__has_esft_base<_Yp2>::value>::type
1764  _M_enable_shared_from_this_with(_Yp* __p) noexcept
1765  {
1766  if (auto __base = __enable_shared_from_this_base(_M_refcount, __p))
1767  __base->_M_weak_assign(const_cast<_Yp2*>(__p), _M_refcount);
1768  }
1769 
1770  template<typename _Yp, typename _Yp2 = typename remove_cv<_Yp>::type>
1771  typename enable_if<!__has_esft_base<_Yp2>::value>::type
1772  _M_enable_shared_from_this_with(_Yp*) noexcept
1773  { }
1774 
1775  void*
1776  _M_get_deleter(const std::type_info& __ti) const noexcept
1777  { return _M_refcount._M_get_deleter(__ti); }
1778 
1779  template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
1780  template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
1781 
1782  template<typename _Del, typename _Tp1, _Lock_policy _Lp1>
1783  friend _Del* get_deleter(const __shared_ptr<_Tp1, _Lp1>&) noexcept;
1784 
1785  template<typename _Del, typename _Tp1>
1786  friend _Del* get_deleter(const shared_ptr<_Tp1>&) noexcept;
1787 
1788 #ifdef __glibcxx_atomic_shared_ptr
1789  friend _Sp_atomic<shared_ptr<_Tp>>;
1790 #endif
1791 #ifdef __glibcxx_out_ptr
1792  template<typename, typename, typename...> friend class out_ptr_t;
1793 #endif
1794 
1795  element_type* _M_ptr; // Contained pointer.
1796  __shared_count<_Lp> _M_refcount; // Reference counter.
1797  };
1798 
1799 
1800  // 20.7.2.2.7 shared_ptr comparisons
1801  template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1802  inline bool
1803  operator==(const __shared_ptr<_Tp1, _Lp>& __a,
1804  const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1805  { return __a.get() == __b.get(); }
1806 
1807  template<typename _Tp, _Lock_policy _Lp>
1808  inline bool
1809  operator==(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1810  { return !__a; }
1811 
1812 #ifdef __cpp_lib_three_way_comparison
1813  template<typename _Tp, typename _Up, _Lock_policy _Lp>
1814  inline strong_ordering
1815  operator<=>(const __shared_ptr<_Tp, _Lp>& __a,
1816  const __shared_ptr<_Up, _Lp>& __b) noexcept
1817  { return compare_three_way()(__a.get(), __b.get()); }
1818 
1819  template<typename _Tp, _Lock_policy _Lp>
1820  inline strong_ordering
1821  operator<=>(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1822  {
1823  using pointer = typename __shared_ptr<_Tp, _Lp>::element_type*;
1824  return compare_three_way()(__a.get(), static_cast<pointer>(nullptr));
1825  }
1826 #else
1827  template<typename _Tp, _Lock_policy _Lp>
1828  inline bool
1829  operator==(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1830  { return !__a; }
1831 
1832  template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1833  inline bool
1834  operator!=(const __shared_ptr<_Tp1, _Lp>& __a,
1835  const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1836  { return __a.get() != __b.get(); }
1837 
1838  template<typename _Tp, _Lock_policy _Lp>
1839  inline bool
1840  operator!=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1841  { return (bool)__a; }
1842 
1843  template<typename _Tp, _Lock_policy _Lp>
1844  inline bool
1845  operator!=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1846  { return (bool)__a; }
1847 
1848  template<typename _Tp, typename _Up, _Lock_policy _Lp>
1849  inline bool
1850  operator<(const __shared_ptr<_Tp, _Lp>& __a,
1851  const __shared_ptr<_Up, _Lp>& __b) noexcept
1852  {
1853  using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1854  using _Up_elt = typename __shared_ptr<_Up, _Lp>::element_type;
1855  using _Vp = typename common_type<_Tp_elt*, _Up_elt*>::type;
1856  return less<_Vp>()(__a.get(), __b.get());
1857  }
1858 
1859  template<typename _Tp, _Lock_policy _Lp>
1860  inline bool
1861  operator<(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1862  {
1863  using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1864  return less<_Tp_elt*>()(__a.get(), nullptr);
1865  }
1866 
1867  template<typename _Tp, _Lock_policy _Lp>
1868  inline bool
1869  operator<(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1870  {
1871  using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1872  return less<_Tp_elt*>()(nullptr, __a.get());
1873  }
1874 
1875  template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1876  inline bool
1877  operator<=(const __shared_ptr<_Tp1, _Lp>& __a,
1878  const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1879  { return !(__b < __a); }
1880 
1881  template<typename _Tp, _Lock_policy _Lp>
1882  inline bool
1883  operator<=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1884  { return !(nullptr < __a); }
1885 
1886  template<typename _Tp, _Lock_policy _Lp>
1887  inline bool
1888  operator<=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1889  { return !(__a < nullptr); }
1890 
1891  template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1892  inline bool
1893  operator>(const __shared_ptr<_Tp1, _Lp>& __a,
1894  const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1895  { return (__b < __a); }
1896 
1897  template<typename _Tp, _Lock_policy _Lp>
1898  inline bool
1899  operator>(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1900  { return nullptr < __a; }
1901 
1902  template<typename _Tp, _Lock_policy _Lp>
1903  inline bool
1904  operator>(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1905  { return __a < nullptr; }
1906 
1907  template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1908  inline bool
1909  operator>=(const __shared_ptr<_Tp1, _Lp>& __a,
1910  const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1911  { return !(__a < __b); }
1912 
1913  template<typename _Tp, _Lock_policy _Lp>
1914  inline bool
1915  operator>=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1916  { return !(__a < nullptr); }
1917 
1918  template<typename _Tp, _Lock_policy _Lp>
1919  inline bool
1920  operator>=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1921  { return !(nullptr < __a); }
1922 #endif // three-way comparison
1923 
1924  // 20.7.2.2.8 shared_ptr specialized algorithms.
1925  template<typename _Tp, _Lock_policy _Lp>
1926  inline void
1927  swap(__shared_ptr<_Tp, _Lp>& __a, __shared_ptr<_Tp, _Lp>& __b) noexcept
1928  { __a.swap(__b); }
1929 
1930  // 20.7.2.2.9 shared_ptr casts
1931 
1932  // The seemingly equivalent code:
1933  // shared_ptr<_Tp, _Lp>(static_cast<_Tp*>(__r.get()))
1934  // will eventually result in undefined behaviour, attempting to
1935  // delete the same object twice.
1936  /// static_pointer_cast
1937  template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1938  inline __shared_ptr<_Tp, _Lp>
1939  static_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1940  {
1941  using _Sp = __shared_ptr<_Tp, _Lp>;
1942  return _Sp(__r, static_cast<typename _Sp::element_type*>(__r.get()));
1943  }
1944 
1945  // The seemingly equivalent code:
1946  // shared_ptr<_Tp, _Lp>(const_cast<_Tp*>(__r.get()))
1947  // will eventually result in undefined behaviour, attempting to
1948  // delete the same object twice.
1949  /// const_pointer_cast
1950  template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1951  inline __shared_ptr<_Tp, _Lp>
1952  const_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1953  {
1954  using _Sp = __shared_ptr<_Tp, _Lp>;
1955  return _Sp(__r, const_cast<typename _Sp::element_type*>(__r.get()));
1956  }
1957 
1958  // The seemingly equivalent code:
1959  // shared_ptr<_Tp, _Lp>(dynamic_cast<_Tp*>(__r.get()))
1960  // will eventually result in undefined behaviour, attempting to
1961  // delete the same object twice.
1962  /// dynamic_pointer_cast
1963  template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1964  inline __shared_ptr<_Tp, _Lp>
1965  dynamic_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1966  {
1967  using _Sp = __shared_ptr<_Tp, _Lp>;
1968  if (auto* __p = dynamic_cast<typename _Sp::element_type*>(__r.get()))
1969  return _Sp(__r, __p);
1970  return _Sp();
1971  }
1972 
1973 #if __cplusplus > 201402L
1974  template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1975  inline __shared_ptr<_Tp, _Lp>
1976  reinterpret_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1977  {
1978  using _Sp = __shared_ptr<_Tp, _Lp>;
1979  return _Sp(__r, reinterpret_cast<typename _Sp::element_type*>(__r.get()));
1980  }
1981 #endif
1982 
1983  template<typename _Tp, _Lock_policy _Lp>
1984  class __weak_ptr
1985  {
1986  template<typename _Yp, typename _Res = void>
1987  using _Compatible = typename
1988  enable_if<__sp_compatible_with<_Yp*, _Tp*>::value, _Res>::type;
1989 
1990  // Constraint for assignment from shared_ptr and weak_ptr:
1991  template<typename _Yp>
1992  using _Assignable = _Compatible<_Yp, __weak_ptr&>;
1993 
1994  public:
1995  using element_type = typename remove_extent<_Tp>::type;
1996 
1997  constexpr __weak_ptr() noexcept
1998  : _M_ptr(nullptr), _M_refcount()
1999  { }
2000 
2001  __weak_ptr(const __weak_ptr&) noexcept = default;
2002 
2003  ~__weak_ptr() = default;
2004 
2005  // The "obvious" converting constructor implementation:
2006  //
2007  // template<typename _Tp1>
2008  // __weak_ptr(const __weak_ptr<_Tp1, _Lp>& __r)
2009  // : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws
2010  // { }
2011  //
2012  // has a serious problem.
2013  //
2014  // __r._M_ptr may already have been invalidated. The _M_ptr(__r._M_ptr)
2015  // conversion may require access to *__r._M_ptr (virtual inheritance).
2016  //
2017  // It is not possible to avoid spurious access violations since
2018  // in multithreaded programs __r._M_ptr may be invalidated at any point.
2019  template<typename _Yp, typename = _Compatible<_Yp>>
2020  __weak_ptr(const __weak_ptr<_Yp, _Lp>& __r) noexcept
2021  : _M_refcount(__r._M_refcount)
2022  { _M_ptr = __r.lock().get(); }
2023 
2024  template<typename _Yp, typename = _Compatible<_Yp>>
2025  __weak_ptr(const __shared_ptr<_Yp, _Lp>& __r) noexcept
2026  : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount)
2027  { }
2028 
2029  __weak_ptr(__weak_ptr&& __r) noexcept
2030  : _M_ptr(__r._M_ptr), _M_refcount(std::move(__r._M_refcount))
2031  { __r._M_ptr = nullptr; }
2032 
2033  template<typename _Yp, typename = _Compatible<_Yp>>
2034  __weak_ptr(__weak_ptr<_Yp, _Lp>&& __r) noexcept
2035  : _M_ptr(__r.lock().get()), _M_refcount(std::move(__r._M_refcount))
2036  { __r._M_ptr = nullptr; }
2037 
2038  __weak_ptr&
2039  operator=(const __weak_ptr& __r) noexcept = default;
2040 
2041  template<typename _Yp>
2042  _Assignable<_Yp>
2043  operator=(const __weak_ptr<_Yp, _Lp>& __r) noexcept
2044  {
2045  _M_ptr = __r.lock().get();
2046  _M_refcount = __r._M_refcount;
2047  return *this;
2048  }
2049 
2050  template<typename _Yp>
2051  _Assignable<_Yp>
2052  operator=(const __shared_ptr<_Yp, _Lp>& __r) noexcept
2053  {
2054  _M_ptr = __r._M_ptr;
2055  _M_refcount = __r._M_refcount;
2056  return *this;
2057  }
2058 
2059  __weak_ptr&
2060  operator=(__weak_ptr&& __r) noexcept
2061  {
2062  __weak_ptr(std::move(__r)).swap(*this);
2063  return *this;
2064  }
2065 
2066  template<typename _Yp>
2067  _Assignable<_Yp>
2068  operator=(__weak_ptr<_Yp, _Lp>&& __r) noexcept
2069  {
2070  _M_ptr = __r.lock().get();
2071  _M_refcount = std::move(__r._M_refcount);
2072  __r._M_ptr = nullptr;
2073  return *this;
2074  }
2075 
2076  __shared_ptr<_Tp, _Lp>
2077  lock() const noexcept
2078  { return __shared_ptr<_Tp, _Lp>(*this, std::nothrow); }
2079 
2080  long
2081  use_count() const noexcept
2082  { return _M_refcount._M_get_use_count(); }
2083 
2084  bool
2085  expired() const noexcept
2086  { return _M_refcount._M_get_use_count() == 0; }
2087 
2088  template<typename _Tp1>
2089  bool
2090  owner_before(const __shared_ptr<_Tp1, _Lp>& __rhs) const noexcept
2091  { return _M_refcount._M_less(__rhs._M_refcount); }
2092 
2093  template<typename _Tp1>
2094  bool
2095  owner_before(const __weak_ptr<_Tp1, _Lp>& __rhs) const noexcept
2096  { return _M_refcount._M_less(__rhs._M_refcount); }
2097 
2098  void
2099  reset() noexcept
2100  { __weak_ptr().swap(*this); }
2101 
2102  void
2103  swap(__weak_ptr& __s) noexcept
2104  {
2105  std::swap(_M_ptr, __s._M_ptr);
2106  _M_refcount._M_swap(__s._M_refcount);
2107  }
2108 
2109  private:
2110  // Used by __enable_shared_from_this.
2111  void
2112  _M_assign(_Tp* __ptr, const __shared_count<_Lp>& __refcount) noexcept
2113  {
2114  if (use_count() == 0)
2115  {
2116  _M_ptr = __ptr;
2117  _M_refcount = __refcount;
2118  }
2119  }
2120 
2121  template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
2122  template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
2123  friend class __enable_shared_from_this<_Tp, _Lp>;
2124  friend class enable_shared_from_this<_Tp>;
2125 #ifdef __glibcxx_atomic_shared_ptr
2126  friend _Sp_atomic<weak_ptr<_Tp>>;
2127 #endif
2128 
2129  element_type* _M_ptr; // Contained pointer.
2130  __weak_count<_Lp> _M_refcount; // Reference counter.
2131  };
2132 
2133  // 20.7.2.3.6 weak_ptr specialized algorithms.
2134  template<typename _Tp, _Lock_policy _Lp>
2135  inline void
2136  swap(__weak_ptr<_Tp, _Lp>& __a, __weak_ptr<_Tp, _Lp>& __b) noexcept
2137  { __a.swap(__b); }
2138 
2139 #pragma GCC diagnostic push
2140 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
2141  template<typename _Tp, typename _Tp1>
2142  struct _Sp_owner_less : public binary_function<_Tp, _Tp, bool>
2143  {
2144  bool
2145  operator()(const _Tp& __lhs, const _Tp& __rhs) const noexcept
2146  { return __lhs.owner_before(__rhs); }
2147 
2148  bool
2149  operator()(const _Tp& __lhs, const _Tp1& __rhs) const noexcept
2150  { return __lhs.owner_before(__rhs); }
2151 
2152  bool
2153  operator()(const _Tp1& __lhs, const _Tp& __rhs) const noexcept
2154  { return __lhs.owner_before(__rhs); }
2155  };
2156 #pragma GCC diagnostic pop
2157 
2158  template<>
2159  struct _Sp_owner_less<void, void>
2160  {
2161  template<typename _Tp, typename _Up>
2162  auto
2163  operator()(const _Tp& __lhs, const _Up& __rhs) const noexcept
2164  -> decltype(__lhs.owner_before(__rhs))
2165  { return __lhs.owner_before(__rhs); }
2166 
2167  using is_transparent = void;
2168  };
2169 
2170  template<typename _Tp, _Lock_policy _Lp>
2171  struct owner_less<__shared_ptr<_Tp, _Lp>>
2172  : public _Sp_owner_less<__shared_ptr<_Tp, _Lp>, __weak_ptr<_Tp, _Lp>>
2173  { };
2174 
2175  template<typename _Tp, _Lock_policy _Lp>
2176  struct owner_less<__weak_ptr<_Tp, _Lp>>
2177  : public _Sp_owner_less<__weak_ptr<_Tp, _Lp>, __shared_ptr<_Tp, _Lp>>
2178  { };
2179 
2180 
2181  template<typename _Tp, _Lock_policy _Lp>
2182  class __enable_shared_from_this
2183  {
2184  protected:
2185  constexpr __enable_shared_from_this() noexcept { }
2186 
2187  __enable_shared_from_this(const __enable_shared_from_this&) noexcept { }
2188 
2189  __enable_shared_from_this&
2190  operator=(const __enable_shared_from_this&) noexcept
2191  { return *this; }
2192 
2193  ~__enable_shared_from_this() { }
2194 
2195  public:
2196  __shared_ptr<_Tp, _Lp>
2197  shared_from_this()
2198  { return __shared_ptr<_Tp, _Lp>(this->_M_weak_this); }
2199 
2200  __shared_ptr<const _Tp, _Lp>
2201  shared_from_this() const
2202  { return __shared_ptr<const _Tp, _Lp>(this->_M_weak_this); }
2203 
2204 #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
2205  __weak_ptr<_Tp, _Lp>
2206  weak_from_this() noexcept
2207  { return this->_M_weak_this; }
2208 
2209  __weak_ptr<const _Tp, _Lp>
2210  weak_from_this() const noexcept
2211  { return this->_M_weak_this; }
2212 #endif
2213 
2214  private:
2215  template<typename _Tp1>
2216  void
2217  _M_weak_assign(_Tp1* __p, const __shared_count<_Lp>& __n) const noexcept
2218  { _M_weak_this._M_assign(__p, __n); }
2219 
2220  friend const __enable_shared_from_this*
2221  __enable_shared_from_this_base(const __shared_count<_Lp>&,
2222  const __enable_shared_from_this* __p)
2223  { return __p; }
2224 
2225  template<typename, _Lock_policy>
2226  friend class __shared_ptr;
2227 
2228  mutable __weak_ptr<_Tp, _Lp> _M_weak_this;
2229  };
2230 
2231  template<typename _Tp, _Lock_policy _Lp = __default_lock_policy,
2232  typename _Alloc, typename... _Args>
2233  inline __shared_ptr<_Tp, _Lp>
2234  __allocate_shared(const _Alloc& __a, _Args&&... __args)
2235  {
2236  static_assert(!is_array<_Tp>::value, "make_shared<T[]> not supported");
2237 
2238  return __shared_ptr<_Tp, _Lp>(_Sp_alloc_shared_tag<_Alloc>{__a},
2239  std::forward<_Args>(__args)...);
2240  }
2241 
2242  template<typename _Tp, _Lock_policy _Lp = __default_lock_policy,
2243  typename... _Args>
2244  inline __shared_ptr<_Tp, _Lp>
2245  __make_shared(_Args&&... __args)
2246  {
2247  typedef typename std::remove_const<_Tp>::type _Tp_nc;
2248  return std::__allocate_shared<_Tp, _Lp>(std::allocator<_Tp_nc>(),
2249  std::forward<_Args>(__args)...);
2250  }
2251 
2252  /// std::hash specialization for __shared_ptr.
2253  template<typename _Tp, _Lock_policy _Lp>
2254  struct hash<__shared_ptr<_Tp, _Lp>>
2255  : public __hash_base<size_t, __shared_ptr<_Tp, _Lp>>
2256  {
2257  size_t
2258  operator()(const __shared_ptr<_Tp, _Lp>& __s) const noexcept
2259  {
2261  __s.get());
2262  }
2263  };
2264 
2265 _GLIBCXX_END_NAMESPACE_VERSION
2266 } // namespace
2267 
2268 #endif // _SHARED_PTR_BASE_H
constexpr bool operator<=(const duration< _Rep1, _Period1 > &__lhs, const duration< _Rep2, _Period2 > &__rhs)
Definition: chrono.h:859
constexpr bool operator>=(const duration< _Rep1, _Period1 > &__lhs, const duration< _Rep2, _Period2 > &__rhs)
Definition: chrono.h:873
constexpr bool operator<(const duration< _Rep1, _Period1 > &__lhs, const duration< _Rep2, _Period2 > &__rhs)
Definition: chrono.h:826
constexpr bool operator>(const duration< _Rep1, _Period1 > &__lhs, const duration< _Rep2, _Period2 > &__rhs)
Definition: chrono.h:866
constexpr complex< _Tp > operator*(const complex< _Tp > &__x, const complex< _Tp > &__y)
Return new complex value x times y.
Definition: complex:434
void * align(size_t __align, size_t __size, void *&__ptr, size_t &__space) noexcept
Fit aligned storage in buffer.
Definition: align.h:60
_GLIBCXX26_CONSTEXPR _ForwardIterator uninitialized_default_construct_n(_ForwardIterator __first, _Size __count)
Default-initializes objects in the range [first,first+count).
constexpr _Tp * to_address(_Tp *__ptr) noexcept
Obtain address referenced by a pointer to an object.
Definition: ptr_traits.h:232
__bool_constant< true > true_type
The type used as a compile-time boolean with true value.
Definition: type_traits:116
__bool_constant< false > false_type
The type used as a compile-time boolean with false value.
Definition: type_traits:119
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition: move.h:52
auto declval() noexcept -> decltype(__declval< _Tp >(0))
Definition: type_traits:2611
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition: move.h:138
constexpr _Tp && forward(typename std::remove_reference< _Tp >::type &__t) noexcept
Forward an lvalue.
Definition: move.h:72
void lock(_L1 &__l1, _L2 &__l2, _L3 &... __l3)
Generic lock.
Definition: mutex:700
ISO C++ entities toplevel namespace is std.
__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
constexpr _Iterator __base(_Iterator __it)
Part of RTTI.
Definition: typeinfo:94
Primary class template hash.
__detected_or_t< value_type *, __pointer, _Alloc > pointer
The allocator's pointer type.
static constexpr pointer allocate(_Alloc &__a, size_type __n)
Allocate memory.
static constexpr void destroy(_Alloc &__a, _Tp *__p) noexcept(_S_nothrow_destroy< _Tp >())
Destroy an object of type _Tp.
requires static constexpr __can_construct< _Alloc, _Tp, _Args... > void construct(_Alloc &__a, _Tp *__p, _Args &&... __args) noexcept(_S_nothrow_construct< _Tp, _Args... >())
Construct an object of type _Tp
_Alloc::value_type value_type
The allocated type.
static constexpr void deallocate(_Alloc &__a, pointer __p, size_type __n)
Deallocate memory.
The standard allocator, as per C++03 [20.4.1].
Definition: allocator.h:134
Base class for all library exceptions.
Definition: exception.h:62
A simple smart pointer providing strict ownership semantics.
Definition: auto_ptr.h:94
Exception possibly thrown by shared_ptr.
virtual char const * what() const noexcept
One of the comparison functors.
Definition: stl_function.h:401
A move-only smart pointer that manages unique ownership of a resource.
Definition: unique_ptr.h:272
Scoped lock idiom.
Definition: concurrence.h:234