libstdc++
shared_ptr_base.h
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1 // shared_ptr and weak_ptr implementation details -*- C++ -*-
2 
3 // Copyright (C) 2007-2018 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10 
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15 
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19 
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24 
25 // 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 #if __cpp_rtti
53 # include <typeinfo>
54 #endif
55 #include <bits/allocated_ptr.h>
56 #include <bits/refwrap.h>
57 #include <bits/stl_function.h>
58 #include <ext/aligned_buffer.h>
59 
60 namespace std _GLIBCXX_VISIBILITY(default)
61 {
62 #if !__cpp_rtti
63  class type_info;
64 #endif
65 
66 _GLIBCXX_BEGIN_NAMESPACE_VERSION
67 
68 #if _GLIBCXX_USE_DEPRECATED
69 #pragma GCC diagnostic push
70 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
71  template<typename> class auto_ptr;
72 #pragma GCC diagnostic pop
73 #endif
74 
75  /**
76  * @brief Exception possibly thrown by @c shared_ptr.
77  * @ingroup exceptions
78  */
80  {
81  public:
82  virtual char const* what() const noexcept;
83 
84  virtual ~bad_weak_ptr() noexcept;
85  };
86 
87  // Substitute for bad_weak_ptr object in the case of -fno-exceptions.
88  inline void
89  __throw_bad_weak_ptr()
90  { _GLIBCXX_THROW_OR_ABORT(bad_weak_ptr()); }
91 
92  using __gnu_cxx::_Lock_policy;
93  using __gnu_cxx::__default_lock_policy;
94  using __gnu_cxx::_S_single;
95  using __gnu_cxx::_S_mutex;
96  using __gnu_cxx::_S_atomic;
97 
98  // Empty helper class except when the template argument is _S_mutex.
99  template<_Lock_policy _Lp>
100  class _Mutex_base
101  {
102  protected:
103  // The atomic policy uses fully-fenced builtins, single doesn't care.
104  enum { _S_need_barriers = 0 };
105  };
106 
107  template<>
108  class _Mutex_base<_S_mutex>
109  : public __gnu_cxx::__mutex
110  {
111  protected:
112  // This policy is used when atomic builtins are not available.
113  // The replacement atomic operations might not have the necessary
114  // memory barriers.
115  enum { _S_need_barriers = 1 };
116  };
117 
118  template<_Lock_policy _Lp = __default_lock_policy>
119  class _Sp_counted_base
120  : public _Mutex_base<_Lp>
121  {
122  public:
123  _Sp_counted_base() noexcept
124  : _M_use_count(1), _M_weak_count(1) { }
125 
126  virtual
127  ~_Sp_counted_base() noexcept
128  { }
129 
130  // Called when _M_use_count drops to zero, to release the resources
131  // managed by *this.
132  virtual void
133  _M_dispose() noexcept = 0;
134 
135  // Called when _M_weak_count drops to zero.
136  virtual void
137  _M_destroy() noexcept
138  { delete this; }
139 
140  virtual void*
141  _M_get_deleter(const std::type_info&) noexcept = 0;
142 
143  void
144  _M_add_ref_copy()
145  { __gnu_cxx::__atomic_add_dispatch(&_M_use_count, 1); }
146 
147  void
148  _M_add_ref_lock();
149 
150  bool
151  _M_add_ref_lock_nothrow();
152 
153  void
154  _M_release() noexcept
155  {
156  // Be race-detector-friendly. For more info see bits/c++config.
157  _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_use_count);
158  if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, -1) == 1)
159  {
160  _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_use_count);
161  _M_dispose();
162  // There must be a memory barrier between dispose() and destroy()
163  // to ensure that the effects of dispose() are observed in the
164  // thread that runs destroy().
165  // See http://gcc.gnu.org/ml/libstdc++/2005-11/msg00136.html
166  if (_Mutex_base<_Lp>::_S_need_barriers)
167  {
168  __atomic_thread_fence (__ATOMIC_ACQ_REL);
169  }
170 
171  // Be race-detector-friendly. For more info see bits/c++config.
172  _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count);
173  if (__gnu_cxx::__exchange_and_add_dispatch(&_M_weak_count,
174  -1) == 1)
175  {
176  _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count);
177  _M_destroy();
178  }
179  }
180  }
181 
182  void
183  _M_weak_add_ref() noexcept
184  { __gnu_cxx::__atomic_add_dispatch(&_M_weak_count, 1); }
185 
186  void
187  _M_weak_release() noexcept
188  {
189  // Be race-detector-friendly. For more info see bits/c++config.
190  _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count);
191  if (__gnu_cxx::__exchange_and_add_dispatch(&_M_weak_count, -1) == 1)
192  {
193  _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count);
194  if (_Mutex_base<_Lp>::_S_need_barriers)
195  {
196  // See _M_release(),
197  // destroy() must observe results of dispose()
198  __atomic_thread_fence (__ATOMIC_ACQ_REL);
199  }
200  _M_destroy();
201  }
202  }
203 
204  long
205  _M_get_use_count() const noexcept
206  {
207  // No memory barrier is used here so there is no synchronization
208  // with other threads.
209  return __atomic_load_n(&_M_use_count, __ATOMIC_RELAXED);
210  }
211 
212  private:
213  _Sp_counted_base(_Sp_counted_base const&) = delete;
214  _Sp_counted_base& operator=(_Sp_counted_base const&) = delete;
215 
216  _Atomic_word _M_use_count; // #shared
217  _Atomic_word _M_weak_count; // #weak + (#shared != 0)
218  };
219 
220  template<>
221  inline void
222  _Sp_counted_base<_S_single>::
223  _M_add_ref_lock()
224  {
225  if (_M_use_count == 0)
226  __throw_bad_weak_ptr();
227  ++_M_use_count;
228  }
229 
230  template<>
231  inline void
232  _Sp_counted_base<_S_mutex>::
233  _M_add_ref_lock()
234  {
235  __gnu_cxx::__scoped_lock sentry(*this);
236  if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, 1) == 0)
237  {
238  _M_use_count = 0;
239  __throw_bad_weak_ptr();
240  }
241  }
242 
243  template<>
244  inline void
245  _Sp_counted_base<_S_atomic>::
246  _M_add_ref_lock()
247  {
248  // Perform lock-free add-if-not-zero operation.
249  _Atomic_word __count = _M_get_use_count();
250  do
251  {
252  if (__count == 0)
253  __throw_bad_weak_ptr();
254  // Replace the current counter value with the old value + 1, as
255  // long as it's not changed meanwhile.
256  }
257  while (!__atomic_compare_exchange_n(&_M_use_count, &__count, __count + 1,
258  true, __ATOMIC_ACQ_REL,
259  __ATOMIC_RELAXED));
260  }
261 
262  template<>
263  inline bool
264  _Sp_counted_base<_S_single>::
265  _M_add_ref_lock_nothrow()
266  {
267  if (_M_use_count == 0)
268  return false;
269  ++_M_use_count;
270  return true;
271  }
272 
273  template<>
274  inline bool
275  _Sp_counted_base<_S_mutex>::
276  _M_add_ref_lock_nothrow()
277  {
278  __gnu_cxx::__scoped_lock sentry(*this);
279  if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, 1) == 0)
280  {
281  _M_use_count = 0;
282  return false;
283  }
284  return true;
285  }
286 
287  template<>
288  inline bool
289  _Sp_counted_base<_S_atomic>::
290  _M_add_ref_lock_nothrow()
291  {
292  // Perform lock-free add-if-not-zero operation.
293  _Atomic_word __count = _M_get_use_count();
294  do
295  {
296  if (__count == 0)
297  return false;
298  // Replace the current counter value with the old value + 1, as
299  // long as it's not changed meanwhile.
300  }
301  while (!__atomic_compare_exchange_n(&_M_use_count, &__count, __count + 1,
302  true, __ATOMIC_ACQ_REL,
303  __ATOMIC_RELAXED));
304  return true;
305  }
306 
307  template<>
308  inline void
309  _Sp_counted_base<_S_single>::_M_add_ref_copy()
310  { ++_M_use_count; }
311 
312  template<>
313  inline void
314  _Sp_counted_base<_S_single>::_M_release() noexcept
315  {
316  if (--_M_use_count == 0)
317  {
318  _M_dispose();
319  if (--_M_weak_count == 0)
320  _M_destroy();
321  }
322  }
323 
324  template<>
325  inline void
326  _Sp_counted_base<_S_single>::_M_weak_add_ref() noexcept
327  { ++_M_weak_count; }
328 
329  template<>
330  inline void
331  _Sp_counted_base<_S_single>::_M_weak_release() noexcept
332  {
333  if (--_M_weak_count == 0)
334  _M_destroy();
335  }
336 
337  template<>
338  inline long
339  _Sp_counted_base<_S_single>::_M_get_use_count() const noexcept
340  { return _M_use_count; }
341 
342 
343  // Forward declarations.
344  template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
345  class __shared_ptr;
346 
347  template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
348  class __weak_ptr;
349 
350  template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
351  class __enable_shared_from_this;
352 
353  template<typename _Tp>
354  class shared_ptr;
355 
356  template<typename _Tp>
357  class weak_ptr;
358 
359  template<typename _Tp>
360  struct owner_less;
361 
362  template<typename _Tp>
363  class enable_shared_from_this;
364 
365  template<_Lock_policy _Lp = __default_lock_policy>
366  class __weak_count;
367 
368  template<_Lock_policy _Lp = __default_lock_policy>
369  class __shared_count;
370 
371 
372  // Counted ptr with no deleter or allocator support
373  template<typename _Ptr, _Lock_policy _Lp>
374  class _Sp_counted_ptr final : public _Sp_counted_base<_Lp>
375  {
376  public:
377  explicit
378  _Sp_counted_ptr(_Ptr __p) noexcept
379  : _M_ptr(__p) { }
380 
381  virtual void
382  _M_dispose() noexcept
383  { delete _M_ptr; }
384 
385  virtual void
386  _M_destroy() noexcept
387  { delete this; }
388 
389  virtual void*
390  _M_get_deleter(const std::type_info&) noexcept
391  { return nullptr; }
392 
393  _Sp_counted_ptr(const _Sp_counted_ptr&) = delete;
394  _Sp_counted_ptr& operator=(const _Sp_counted_ptr&) = delete;
395 
396  private:
397  _Ptr _M_ptr;
398  };
399 
400  template<>
401  inline void
402  _Sp_counted_ptr<nullptr_t, _S_single>::_M_dispose() noexcept { }
403 
404  template<>
405  inline void
406  _Sp_counted_ptr<nullptr_t, _S_mutex>::_M_dispose() noexcept { }
407 
408  template<>
409  inline void
410  _Sp_counted_ptr<nullptr_t, _S_atomic>::_M_dispose() noexcept { }
411 
412  template<int _Nm, typename _Tp,
413  bool __use_ebo = !__is_final(_Tp) && __is_empty(_Tp)>
414  struct _Sp_ebo_helper;
415 
416  /// Specialization using EBO.
417  template<int _Nm, typename _Tp>
418  struct _Sp_ebo_helper<_Nm, _Tp, true> : private _Tp
419  {
420  explicit _Sp_ebo_helper(const _Tp& __tp) : _Tp(__tp) { }
421  explicit _Sp_ebo_helper(_Tp&& __tp) : _Tp(std::move(__tp)) { }
422 
423  static _Tp&
424  _S_get(_Sp_ebo_helper& __eboh) { return static_cast<_Tp&>(__eboh); }
425  };
426 
427  /// Specialization not using EBO.
428  template<int _Nm, typename _Tp>
429  struct _Sp_ebo_helper<_Nm, _Tp, false>
430  {
431  explicit _Sp_ebo_helper(const _Tp& __tp) : _M_tp(__tp) { }
432  explicit _Sp_ebo_helper(_Tp&& __tp) : _M_tp(std::move(__tp)) { }
433 
434  static _Tp&
435  _S_get(_Sp_ebo_helper& __eboh)
436  { return __eboh._M_tp; }
437 
438  private:
439  _Tp _M_tp;
440  };
441 
442  // Support for custom deleter and/or allocator
443  template<typename _Ptr, typename _Deleter, typename _Alloc, _Lock_policy _Lp>
444  class _Sp_counted_deleter final : public _Sp_counted_base<_Lp>
445  {
446  class _Impl : _Sp_ebo_helper<0, _Deleter>, _Sp_ebo_helper<1, _Alloc>
447  {
448  typedef _Sp_ebo_helper<0, _Deleter> _Del_base;
449  typedef _Sp_ebo_helper<1, _Alloc> _Alloc_base;
450 
451  public:
452  _Impl(_Ptr __p, _Deleter __d, const _Alloc& __a) noexcept
453  : _M_ptr(__p), _Del_base(std::move(__d)), _Alloc_base(__a)
454  { }
455 
456  _Deleter& _M_del() noexcept { return _Del_base::_S_get(*this); }
457  _Alloc& _M_alloc() noexcept { return _Alloc_base::_S_get(*this); }
458 
459  _Ptr _M_ptr;
460  };
461 
462  public:
463  using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_deleter>;
464 
465  // __d(__p) must not throw.
466  _Sp_counted_deleter(_Ptr __p, _Deleter __d) noexcept
467  : _M_impl(__p, std::move(__d), _Alloc()) { }
468 
469  // __d(__p) must not throw.
470  _Sp_counted_deleter(_Ptr __p, _Deleter __d, const _Alloc& __a) noexcept
471  : _M_impl(__p, std::move(__d), __a) { }
472 
473  ~_Sp_counted_deleter() noexcept { }
474 
475  virtual void
476  _M_dispose() noexcept
477  { _M_impl._M_del()(_M_impl._M_ptr); }
478 
479  virtual void
480  _M_destroy() noexcept
481  {
482  __allocator_type __a(_M_impl._M_alloc());
483  __allocated_ptr<__allocator_type> __guard_ptr{ __a, this };
484  this->~_Sp_counted_deleter();
485  }
486 
487  virtual void*
488  _M_get_deleter(const std::type_info& __ti) noexcept
489  {
490 #if __cpp_rtti
491  // _GLIBCXX_RESOLVE_LIB_DEFECTS
492  // 2400. shared_ptr's get_deleter() should use addressof()
493  return __ti == typeid(_Deleter)
494  ? std::__addressof(_M_impl._M_del())
495  : nullptr;
496 #else
497  return nullptr;
498 #endif
499  }
500 
501  private:
502  _Impl _M_impl;
503  };
504 
505  // helpers for make_shared / allocate_shared
506 
507  struct _Sp_make_shared_tag
508  {
509 #if !__cpp_rtti
510  private:
511  template<typename _Tp, _Lock_policy _Lp>
512  friend class __shared_ptr;
513  template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
514  friend class _Sp_counted_ptr_inplace;
515 
516  static const type_info&
517  _S_ti() noexcept
518  {
519  static constexpr _Sp_make_shared_tag __tag;
520  return reinterpret_cast<const type_info&>(__tag);
521  }
522 #endif
523  };
524 
525  template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
526  class _Sp_counted_ptr_inplace final : public _Sp_counted_base<_Lp>
527  {
528  class _Impl : _Sp_ebo_helper<0, _Alloc>
529  {
530  typedef _Sp_ebo_helper<0, _Alloc> _A_base;
531 
532  public:
533  explicit _Impl(_Alloc __a) noexcept : _A_base(__a) { }
534 
535  _Alloc& _M_alloc() noexcept { return _A_base::_S_get(*this); }
536 
537  __gnu_cxx::__aligned_buffer<_Tp> _M_storage;
538  };
539 
540  public:
541  using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_ptr_inplace>;
542 
543  template<typename... _Args>
544  _Sp_counted_ptr_inplace(_Alloc __a, _Args&&... __args)
545  : _M_impl(__a)
546  {
547  // _GLIBCXX_RESOLVE_LIB_DEFECTS
548  // 2070. allocate_shared should use allocator_traits<A>::construct
550  std::forward<_Args>(__args)...); // might throw
551  }
552 
553  ~_Sp_counted_ptr_inplace() noexcept { }
554 
555  virtual void
556  _M_dispose() noexcept
557  {
558  allocator_traits<_Alloc>::destroy(_M_impl._M_alloc(), _M_ptr());
559  }
560 
561  // Override because the allocator needs to know the dynamic type
562  virtual void
563  _M_destroy() noexcept
564  {
565  __allocator_type __a(_M_impl._M_alloc());
566  __allocated_ptr<__allocator_type> __guard_ptr{ __a, this };
567  this->~_Sp_counted_ptr_inplace();
568  }
569 
570  // Sneaky trick so __shared_ptr can get the managed pointer
571  virtual void*
572  _M_get_deleter(const std::type_info& __ti) noexcept
573  {
574 #if __cpp_rtti
575  if (__ti == typeid(_Sp_make_shared_tag))
576 #else
577  if (&__ti == &_Sp_make_shared_tag::_S_ti())
578 #endif
579  return const_cast<typename remove_cv<_Tp>::type*>(_M_ptr());
580  return nullptr;
581  }
582 
583  private:
584  _Tp* _M_ptr() noexcept { return _M_impl._M_storage._M_ptr(); }
585 
586  _Impl _M_impl;
587  };
588 
589  // The default deleter for shared_ptr<T[]> and shared_ptr<T[N]>.
590  struct __sp_array_delete
591  {
592  template<typename _Yp>
593  void operator()(_Yp* __p) const { delete[] __p; }
594  };
595 
596  template<_Lock_policy _Lp>
597  class __shared_count
598  {
599  public:
600  constexpr __shared_count() noexcept : _M_pi(0)
601  { }
602 
603  template<typename _Ptr>
604  explicit
605  __shared_count(_Ptr __p) : _M_pi(0)
606  {
607  __try
608  {
609  _M_pi = new _Sp_counted_ptr<_Ptr, _Lp>(__p);
610  }
611  __catch(...)
612  {
613  delete __p;
614  __throw_exception_again;
615  }
616  }
617 
618  template<typename _Ptr>
619  __shared_count(_Ptr __p, /* is_array = */ false_type)
620  : __shared_count(__p)
621  { }
622 
623  template<typename _Ptr>
624  __shared_count(_Ptr __p, /* is_array = */ true_type)
625  : __shared_count(__p, __sp_array_delete{}, allocator<void>())
626  { }
627 
628  template<typename _Ptr, typename _Deleter>
629  __shared_count(_Ptr __p, _Deleter __d)
630  : __shared_count(__p, std::move(__d), allocator<void>())
631  { }
632 
633  template<typename _Ptr, typename _Deleter, typename _Alloc>
634  __shared_count(_Ptr __p, _Deleter __d, _Alloc __a) : _M_pi(0)
635  {
636  typedef _Sp_counted_deleter<_Ptr, _Deleter, _Alloc, _Lp> _Sp_cd_type;
637  __try
638  {
639  typename _Sp_cd_type::__allocator_type __a2(__a);
640  auto __guard = std::__allocate_guarded(__a2);
641  _Sp_cd_type* __mem = __guard.get();
642  ::new (__mem) _Sp_cd_type(__p, std::move(__d), std::move(__a));
643  _M_pi = __mem;
644  __guard = nullptr;
645  }
646  __catch(...)
647  {
648  __d(__p); // Call _Deleter on __p.
649  __throw_exception_again;
650  }
651  }
652 
653  template<typename _Tp, typename _Alloc, typename... _Args>
654  __shared_count(_Sp_make_shared_tag, _Tp*, const _Alloc& __a,
655  _Args&&... __args)
656  : _M_pi(0)
657  {
658  typedef _Sp_counted_ptr_inplace<_Tp, _Alloc, _Lp> _Sp_cp_type;
659  typename _Sp_cp_type::__allocator_type __a2(__a);
660  auto __guard = std::__allocate_guarded(__a2);
661  _Sp_cp_type* __mem = __guard.get();
662  ::new (__mem) _Sp_cp_type(std::move(__a),
663  std::forward<_Args>(__args)...);
664  _M_pi = __mem;
665  __guard = nullptr;
666  }
667 
668 #if _GLIBCXX_USE_DEPRECATED
669 #pragma GCC diagnostic push
670 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
671  // Special case for auto_ptr<_Tp> to provide the strong guarantee.
672  template<typename _Tp>
673  explicit
674  __shared_count(std::auto_ptr<_Tp>&& __r);
675 #pragma GCC diagnostic pop
676 #endif
677 
678  // Special case for unique_ptr<_Tp,_Del> to provide the strong guarantee.
679  template<typename _Tp, typename _Del>
680  explicit
681  __shared_count(std::unique_ptr<_Tp, _Del>&& __r) : _M_pi(0)
682  {
683  // _GLIBCXX_RESOLVE_LIB_DEFECTS
684  // 2415. Inconsistency between unique_ptr and shared_ptr
685  if (__r.get() == nullptr)
686  return;
687 
688  using _Ptr = typename unique_ptr<_Tp, _Del>::pointer;
689  using _Del2 = typename conditional<is_reference<_Del>::value,
690  reference_wrapper<typename remove_reference<_Del>::type>,
691  _Del>::type;
692  using _Sp_cd_type
693  = _Sp_counted_deleter<_Ptr, _Del2, allocator<void>, _Lp>;
694  using _Alloc = allocator<_Sp_cd_type>;
695  using _Alloc_traits = allocator_traits<_Alloc>;
696  _Alloc __a;
697  _Sp_cd_type* __mem = _Alloc_traits::allocate(__a, 1);
698  _Alloc_traits::construct(__a, __mem, __r.release(),
699  __r.get_deleter()); // non-throwing
700  _M_pi = __mem;
701  }
702 
703  // Throw bad_weak_ptr when __r._M_get_use_count() == 0.
704  explicit __shared_count(const __weak_count<_Lp>& __r);
705 
706  // Does not throw if __r._M_get_use_count() == 0, caller must check.
707  explicit __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t);
708 
709  ~__shared_count() noexcept
710  {
711  if (_M_pi != nullptr)
712  _M_pi->_M_release();
713  }
714 
715  __shared_count(const __shared_count& __r) noexcept
716  : _M_pi(__r._M_pi)
717  {
718  if (_M_pi != 0)
719  _M_pi->_M_add_ref_copy();
720  }
721 
722  __shared_count&
723  operator=(const __shared_count& __r) noexcept
724  {
725  _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
726  if (__tmp != _M_pi)
727  {
728  if (__tmp != 0)
729  __tmp->_M_add_ref_copy();
730  if (_M_pi != 0)
731  _M_pi->_M_release();
732  _M_pi = __tmp;
733  }
734  return *this;
735  }
736 
737  void
738  _M_swap(__shared_count& __r) noexcept
739  {
740  _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
741  __r._M_pi = _M_pi;
742  _M_pi = __tmp;
743  }
744 
745  long
746  _M_get_use_count() const noexcept
747  { return _M_pi != 0 ? _M_pi->_M_get_use_count() : 0; }
748 
749  bool
750  _M_unique() const noexcept
751  { return this->_M_get_use_count() == 1; }
752 
753  void*
754  _M_get_deleter(const std::type_info& __ti) const noexcept
755  { return _M_pi ? _M_pi->_M_get_deleter(__ti) : nullptr; }
756 
757  bool
758  _M_less(const __shared_count& __rhs) const noexcept
759  { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
760 
761  bool
762  _M_less(const __weak_count<_Lp>& __rhs) const noexcept
763  { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
764 
765  // Friend function injected into enclosing namespace and found by ADL
766  friend inline bool
767  operator==(const __shared_count& __a, const __shared_count& __b) noexcept
768  { return __a._M_pi == __b._M_pi; }
769 
770  private:
771  friend class __weak_count<_Lp>;
772 
773  _Sp_counted_base<_Lp>* _M_pi;
774  };
775 
776 
777  template<_Lock_policy _Lp>
778  class __weak_count
779  {
780  public:
781  constexpr __weak_count() noexcept : _M_pi(nullptr)
782  { }
783 
784  __weak_count(const __shared_count<_Lp>& __r) noexcept
785  : _M_pi(__r._M_pi)
786  {
787  if (_M_pi != nullptr)
788  _M_pi->_M_weak_add_ref();
789  }
790 
791  __weak_count(const __weak_count& __r) noexcept
792  : _M_pi(__r._M_pi)
793  {
794  if (_M_pi != nullptr)
795  _M_pi->_M_weak_add_ref();
796  }
797 
798  __weak_count(__weak_count&& __r) noexcept
799  : _M_pi(__r._M_pi)
800  { __r._M_pi = nullptr; }
801 
802  ~__weak_count() noexcept
803  {
804  if (_M_pi != nullptr)
805  _M_pi->_M_weak_release();
806  }
807 
808  __weak_count&
809  operator=(const __shared_count<_Lp>& __r) noexcept
810  {
811  _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
812  if (__tmp != nullptr)
813  __tmp->_M_weak_add_ref();
814  if (_M_pi != nullptr)
815  _M_pi->_M_weak_release();
816  _M_pi = __tmp;
817  return *this;
818  }
819 
820  __weak_count&
821  operator=(const __weak_count& __r) noexcept
822  {
823  _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
824  if (__tmp != nullptr)
825  __tmp->_M_weak_add_ref();
826  if (_M_pi != nullptr)
827  _M_pi->_M_weak_release();
828  _M_pi = __tmp;
829  return *this;
830  }
831 
832  __weak_count&
833  operator=(__weak_count&& __r) noexcept
834  {
835  if (_M_pi != nullptr)
836  _M_pi->_M_weak_release();
837  _M_pi = __r._M_pi;
838  __r._M_pi = nullptr;
839  return *this;
840  }
841 
842  void
843  _M_swap(__weak_count& __r) noexcept
844  {
845  _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
846  __r._M_pi = _M_pi;
847  _M_pi = __tmp;
848  }
849 
850  long
851  _M_get_use_count() const noexcept
852  { return _M_pi != nullptr ? _M_pi->_M_get_use_count() : 0; }
853 
854  bool
855  _M_less(const __weak_count& __rhs) const noexcept
856  { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
857 
858  bool
859  _M_less(const __shared_count<_Lp>& __rhs) const noexcept
860  { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
861 
862  // Friend function injected into enclosing namespace and found by ADL
863  friend inline bool
864  operator==(const __weak_count& __a, const __weak_count& __b) noexcept
865  { return __a._M_pi == __b._M_pi; }
866 
867  private:
868  friend class __shared_count<_Lp>;
869 
870  _Sp_counted_base<_Lp>* _M_pi;
871  };
872 
873  // Now that __weak_count is defined we can define this constructor:
874  template<_Lock_policy _Lp>
875  inline
876  __shared_count<_Lp>::__shared_count(const __weak_count<_Lp>& __r)
877  : _M_pi(__r._M_pi)
878  {
879  if (_M_pi != nullptr)
880  _M_pi->_M_add_ref_lock();
881  else
882  __throw_bad_weak_ptr();
883  }
884 
885  // Now that __weak_count is defined we can define this constructor:
886  template<_Lock_policy _Lp>
887  inline
888  __shared_count<_Lp>::
889  __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t)
890  : _M_pi(__r._M_pi)
891  {
892  if (_M_pi != nullptr)
893  if (!_M_pi->_M_add_ref_lock_nothrow())
894  _M_pi = nullptr;
895  }
896 
897 #define __cpp_lib_shared_ptr_arrays 201603
898 
899  // Helper traits for shared_ptr of array:
900 
901  // A pointer type Y* is said to be compatible with a pointer type T* when
902  // either Y* is convertible to T* or Y is U[N] and T is U cv [].
903  template<typename _Yp_ptr, typename _Tp_ptr>
904  struct __sp_compatible_with
905  : false_type
906  { };
907 
908  template<typename _Yp, typename _Tp>
909  struct __sp_compatible_with<_Yp*, _Tp*>
910  : is_convertible<_Yp*, _Tp*>::type
911  { };
912 
913  template<typename _Up, size_t _Nm>
914  struct __sp_compatible_with<_Up(*)[_Nm], _Up(*)[]>
915  : true_type
916  { };
917 
918  template<typename _Up, size_t _Nm>
919  struct __sp_compatible_with<_Up(*)[_Nm], const _Up(*)[]>
920  : true_type
921  { };
922 
923  template<typename _Up, size_t _Nm>
924  struct __sp_compatible_with<_Up(*)[_Nm], volatile _Up(*)[]>
925  : true_type
926  { };
927 
928  template<typename _Up, size_t _Nm>
929  struct __sp_compatible_with<_Up(*)[_Nm], const volatile _Up(*)[]>
930  : true_type
931  { };
932 
933  // Test conversion from Y(*)[N] to U(*)[N] without forming invalid type Y[N].
934  template<typename _Up, size_t _Nm, typename _Yp, typename = void>
935  struct __sp_is_constructible_arrN
936  : false_type
937  { };
938 
939  template<typename _Up, size_t _Nm, typename _Yp>
940  struct __sp_is_constructible_arrN<_Up, _Nm, _Yp, __void_t<_Yp[_Nm]>>
941  : is_convertible<_Yp(*)[_Nm], _Up(*)[_Nm]>::type
942  { };
943 
944  // Test conversion from Y(*)[] to U(*)[] without forming invalid type Y[].
945  template<typename _Up, typename _Yp, typename = void>
946  struct __sp_is_constructible_arr
947  : false_type
948  { };
949 
950  template<typename _Up, typename _Yp>
951  struct __sp_is_constructible_arr<_Up, _Yp, __void_t<_Yp[]>>
952  : is_convertible<_Yp(*)[], _Up(*)[]>::type
953  { };
954 
955  // Trait to check if shared_ptr<T> can be constructed from Y*.
956  template<typename _Tp, typename _Yp>
957  struct __sp_is_constructible;
958 
959  // When T is U[N], Y(*)[N] shall be convertible to T*;
960  template<typename _Up, size_t _Nm, typename _Yp>
961  struct __sp_is_constructible<_Up[_Nm], _Yp>
962  : __sp_is_constructible_arrN<_Up, _Nm, _Yp>::type
963  { };
964 
965  // when T is U[], Y(*)[] shall be convertible to T*;
966  template<typename _Up, typename _Yp>
967  struct __sp_is_constructible<_Up[], _Yp>
968  : __sp_is_constructible_arr<_Up, _Yp>::type
969  { };
970 
971  // otherwise, Y* shall be convertible to T*.
972  template<typename _Tp, typename _Yp>
973  struct __sp_is_constructible
974  : is_convertible<_Yp*, _Tp*>::type
975  { };
976 
977 
978  // Define operator* and operator-> for shared_ptr<T>.
979  template<typename _Tp, _Lock_policy _Lp,
980  bool = is_array<_Tp>::value, bool = is_void<_Tp>::value>
981  class __shared_ptr_access
982  {
983  public:
984  using element_type = _Tp;
985 
986  element_type&
987  operator*() const noexcept
988  {
989  __glibcxx_assert(_M_get() != nullptr);
990  return *_M_get();
991  }
992 
993  element_type*
994  operator->() const noexcept
995  {
996  _GLIBCXX_DEBUG_PEDASSERT(_M_get() != nullptr);
997  return _M_get();
998  }
999 
1000  private:
1001  element_type*
1002  _M_get() const noexcept
1003  { return static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get(); }
1004  };
1005 
1006  // Define operator-> for shared_ptr<cv void>.
1007  template<typename _Tp, _Lock_policy _Lp>
1008  class __shared_ptr_access<_Tp, _Lp, false, true>
1009  {
1010  public:
1011  using element_type = _Tp;
1012 
1013  element_type*
1014  operator->() const noexcept
1015  {
1016  auto __ptr = static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get();
1017  _GLIBCXX_DEBUG_PEDASSERT(__ptr != nullptr);
1018  return __ptr;
1019  }
1020  };
1021 
1022  // Define operator[] for shared_ptr<T[]> and shared_ptr<T[N]>.
1023  template<typename _Tp, _Lock_policy _Lp>
1024  class __shared_ptr_access<_Tp, _Lp, true, false>
1025  {
1026  public:
1027  using element_type = typename remove_extent<_Tp>::type;
1028 
1029 #if __cplusplus <= 201402L
1030  [[__deprecated__("shared_ptr<T[]>::operator* is absent from C++17")]]
1031  element_type&
1032  operator*() const noexcept
1033  {
1034  __glibcxx_assert(_M_get() != nullptr);
1035  return *_M_get();
1036  }
1037 
1038  [[__deprecated__("shared_ptr<T[]>::operator-> is absent from C++17")]]
1039  element_type*
1040  operator->() const noexcept
1041  {
1042  _GLIBCXX_DEBUG_PEDASSERT(_M_get() != nullptr);
1043  return _M_get();
1044  }
1045 #endif
1046 
1047  element_type&
1048  operator[](ptrdiff_t __i) const
1049  {
1050  __glibcxx_assert(_M_get() != nullptr);
1051  __glibcxx_assert(!extent<_Tp>::value || __i < extent<_Tp>::value);
1052  return _M_get()[__i];
1053  }
1054 
1055  private:
1056  element_type*
1057  _M_get() const noexcept
1058  { return static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get(); }
1059  };
1060 
1061  template<typename _Tp, _Lock_policy _Lp>
1062  class __shared_ptr
1063  : public __shared_ptr_access<_Tp, _Lp>
1064  {
1065  public:
1066  using element_type = typename remove_extent<_Tp>::type;
1067 
1068  private:
1069  // Constraint for taking ownership of a pointer of type _Yp*:
1070  template<typename _Yp>
1071  using _SafeConv
1072  = typename enable_if<__sp_is_constructible<_Tp, _Yp>::value>::type;
1073 
1074  // Constraint for construction from shared_ptr and weak_ptr:
1075  template<typename _Yp, typename _Res = void>
1076  using _Compatible = typename
1077  enable_if<__sp_compatible_with<_Yp*, _Tp*>::value, _Res>::type;
1078 
1079  // Constraint for assignment from shared_ptr and weak_ptr:
1080  template<typename _Yp>
1081  using _Assignable = _Compatible<_Yp, __shared_ptr&>;
1082 
1083  // Constraint for construction from unique_ptr:
1084  template<typename _Yp, typename _Del, typename _Res = void,
1085  typename _Ptr = typename unique_ptr<_Yp, _Del>::pointer>
1086  using _UniqCompatible = typename enable_if<__and_<
1087  __sp_compatible_with<_Yp*, _Tp*>, is_convertible<_Ptr, element_type*>
1088  >::value, _Res>::type;
1089 
1090  // Constraint for assignment from unique_ptr:
1091  template<typename _Yp, typename _Del>
1092  using _UniqAssignable = _UniqCompatible<_Yp, _Del, __shared_ptr&>;
1093 
1094  public:
1095 
1096 #if __cplusplus > 201402L
1097  using weak_type = __weak_ptr<_Tp, _Lp>;
1098 #endif
1099 
1100  constexpr __shared_ptr() noexcept
1101  : _M_ptr(0), _M_refcount()
1102  { }
1103 
1104  template<typename _Yp, typename = _SafeConv<_Yp>>
1105  explicit
1106  __shared_ptr(_Yp* __p)
1107  : _M_ptr(__p), _M_refcount(__p, typename is_array<_Tp>::type())
1108  {
1109  static_assert( !is_void<_Yp>::value, "incomplete type" );
1110  static_assert( sizeof(_Yp) > 0, "incomplete type" );
1111  _M_enable_shared_from_this_with(__p);
1112  }
1113 
1114  template<typename _Yp, typename _Deleter, typename = _SafeConv<_Yp>>
1115  __shared_ptr(_Yp* __p, _Deleter __d)
1116  : _M_ptr(__p), _M_refcount(__p, std::move(__d))
1117  {
1118  static_assert(__is_invocable<_Deleter&, _Yp*&>::value,
1119  "deleter expression d(p) is well-formed");
1120  _M_enable_shared_from_this_with(__p);
1121  }
1122 
1123  template<typename _Yp, typename _Deleter, typename _Alloc,
1124  typename = _SafeConv<_Yp>>
1125  __shared_ptr(_Yp* __p, _Deleter __d, _Alloc __a)
1126  : _M_ptr(__p), _M_refcount(__p, std::move(__d), std::move(__a))
1127  {
1128  static_assert(__is_invocable<_Deleter&, _Yp*&>::value,
1129  "deleter expression d(p) is well-formed");
1130  _M_enable_shared_from_this_with(__p);
1131  }
1132 
1133  template<typename _Deleter>
1134  __shared_ptr(nullptr_t __p, _Deleter __d)
1135  : _M_ptr(0), _M_refcount(__p, std::move(__d))
1136  { }
1137 
1138  template<typename _Deleter, typename _Alloc>
1139  __shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
1140  : _M_ptr(0), _M_refcount(__p, std::move(__d), std::move(__a))
1141  { }
1142 
1143  template<typename _Yp>
1144  __shared_ptr(const __shared_ptr<_Yp, _Lp>& __r,
1145  element_type* __p) noexcept
1146  : _M_ptr(__p), _M_refcount(__r._M_refcount) // never throws
1147  { }
1148 
1149  __shared_ptr(const __shared_ptr&) noexcept = default;
1150  __shared_ptr& operator=(const __shared_ptr&) noexcept = default;
1151  ~__shared_ptr() = default;
1152 
1153  template<typename _Yp, typename = _Compatible<_Yp>>
1154  __shared_ptr(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1155  : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount)
1156  { }
1157 
1158  __shared_ptr(__shared_ptr&& __r) noexcept
1159  : _M_ptr(__r._M_ptr), _M_refcount()
1160  {
1161  _M_refcount._M_swap(__r._M_refcount);
1162  __r._M_ptr = 0;
1163  }
1164 
1165  template<typename _Yp, typename = _Compatible<_Yp>>
1166  __shared_ptr(__shared_ptr<_Yp, _Lp>&& __r) noexcept
1167  : _M_ptr(__r._M_ptr), _M_refcount()
1168  {
1169  _M_refcount._M_swap(__r._M_refcount);
1170  __r._M_ptr = 0;
1171  }
1172 
1173  template<typename _Yp, typename = _Compatible<_Yp>>
1174  explicit __shared_ptr(const __weak_ptr<_Yp, _Lp>& __r)
1175  : _M_refcount(__r._M_refcount) // may throw
1176  {
1177  // It is now safe to copy __r._M_ptr, as
1178  // _M_refcount(__r._M_refcount) did not throw.
1179  _M_ptr = __r._M_ptr;
1180  }
1181 
1182  // If an exception is thrown this constructor has no effect.
1183  template<typename _Yp, typename _Del,
1184  typename = _UniqCompatible<_Yp, _Del>>
1185  __shared_ptr(unique_ptr<_Yp, _Del>&& __r)
1186  : _M_ptr(__r.get()), _M_refcount()
1187  {
1188  auto __raw = __to_address(__r.get());
1189  _M_refcount = __shared_count<_Lp>(std::move(__r));
1190  _M_enable_shared_from_this_with(__raw);
1191  }
1192 
1193 #if __cplusplus <= 201402L && _GLIBCXX_USE_DEPRECATED
1194  protected:
1195  // If an exception is thrown this constructor has no effect.
1196  template<typename _Tp1, typename _Del,
1197  typename enable_if<__and_<
1198  __not_<is_array<_Tp>>, is_array<_Tp1>,
1199  is_convertible<typename unique_ptr<_Tp1, _Del>::pointer, _Tp*>
1200  >::value, bool>::type = true>
1201  __shared_ptr(unique_ptr<_Tp1, _Del>&& __r, __sp_array_delete)
1202  : _M_ptr(__r.get()), _M_refcount()
1203  {
1204  auto __raw = __to_address(__r.get());
1205  _M_refcount = __shared_count<_Lp>(std::move(__r));
1206  _M_enable_shared_from_this_with(__raw);
1207  }
1208  public:
1209 #endif
1210 
1211 #if _GLIBCXX_USE_DEPRECATED
1212 #pragma GCC diagnostic push
1213 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
1214  // Postcondition: use_count() == 1 and __r.get() == 0
1215  template<typename _Yp, typename = _Compatible<_Yp>>
1216  __shared_ptr(auto_ptr<_Yp>&& __r);
1217 #pragma GCC diagnostic pop
1218 #endif
1219 
1220  constexpr __shared_ptr(nullptr_t) noexcept : __shared_ptr() { }
1221 
1222  template<typename _Yp>
1223  _Assignable<_Yp>
1224  operator=(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1225  {
1226  _M_ptr = __r._M_ptr;
1227  _M_refcount = __r._M_refcount; // __shared_count::op= doesn't throw
1228  return *this;
1229  }
1230 
1231 #if _GLIBCXX_USE_DEPRECATED
1232 #pragma GCC diagnostic push
1233 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
1234  template<typename _Yp>
1235  _Assignable<_Yp>
1236  operator=(auto_ptr<_Yp>&& __r)
1237  {
1238  __shared_ptr(std::move(__r)).swap(*this);
1239  return *this;
1240  }
1241 #pragma GCC diagnostic pop
1242 #endif
1243 
1244  __shared_ptr&
1245  operator=(__shared_ptr&& __r) noexcept
1246  {
1247  __shared_ptr(std::move(__r)).swap(*this);
1248  return *this;
1249  }
1250 
1251  template<class _Yp>
1252  _Assignable<_Yp>
1253  operator=(__shared_ptr<_Yp, _Lp>&& __r) noexcept
1254  {
1255  __shared_ptr(std::move(__r)).swap(*this);
1256  return *this;
1257  }
1258 
1259  template<typename _Yp, typename _Del>
1260  _UniqAssignable<_Yp, _Del>
1261  operator=(unique_ptr<_Yp, _Del>&& __r)
1262  {
1263  __shared_ptr(std::move(__r)).swap(*this);
1264  return *this;
1265  }
1266 
1267  void
1268  reset() noexcept
1269  { __shared_ptr().swap(*this); }
1270 
1271  template<typename _Yp>
1272  _SafeConv<_Yp>
1273  reset(_Yp* __p) // _Yp must be complete.
1274  {
1275  // Catch self-reset errors.
1276  __glibcxx_assert(__p == 0 || __p != _M_ptr);
1277  __shared_ptr(__p).swap(*this);
1278  }
1279 
1280  template<typename _Yp, typename _Deleter>
1281  _SafeConv<_Yp>
1282  reset(_Yp* __p, _Deleter __d)
1283  { __shared_ptr(__p, std::move(__d)).swap(*this); }
1284 
1285  template<typename _Yp, typename _Deleter, typename _Alloc>
1286  _SafeConv<_Yp>
1287  reset(_Yp* __p, _Deleter __d, _Alloc __a)
1288  { __shared_ptr(__p, std::move(__d), std::move(__a)).swap(*this); }
1289 
1290  element_type*
1291  get() const noexcept
1292  { return _M_ptr; }
1293 
1294  explicit operator bool() const // never throws
1295  { return _M_ptr == 0 ? false : true; }
1296 
1297  bool
1298  unique() const noexcept
1299  { return _M_refcount._M_unique(); }
1300 
1301  long
1302  use_count() const noexcept
1303  { return _M_refcount._M_get_use_count(); }
1304 
1305  void
1306  swap(__shared_ptr<_Tp, _Lp>& __other) noexcept
1307  {
1308  std::swap(_M_ptr, __other._M_ptr);
1309  _M_refcount._M_swap(__other._M_refcount);
1310  }
1311 
1312  template<typename _Tp1>
1313  bool
1314  owner_before(__shared_ptr<_Tp1, _Lp> const& __rhs) const noexcept
1315  { return _M_refcount._M_less(__rhs._M_refcount); }
1316 
1317  template<typename _Tp1>
1318  bool
1319  owner_before(__weak_ptr<_Tp1, _Lp> const& __rhs) const noexcept
1320  { return _M_refcount._M_less(__rhs._M_refcount); }
1321 
1322  protected:
1323  // This constructor is non-standard, it is used by allocate_shared.
1324  template<typename _Alloc, typename... _Args>
1325  __shared_ptr(_Sp_make_shared_tag __tag, const _Alloc& __a,
1326  _Args&&... __args)
1327  : _M_ptr(), _M_refcount(__tag, (_Tp*)0, __a,
1328  std::forward<_Args>(__args)...)
1329  {
1330  // _M_ptr needs to point to the newly constructed object.
1331  // This relies on _Sp_counted_ptr_inplace::_M_get_deleter.
1332 #if __cpp_rtti
1333  void* __p = _M_refcount._M_get_deleter(typeid(__tag));
1334 #else
1335  void* __p = _M_refcount._M_get_deleter(_Sp_make_shared_tag::_S_ti());
1336 #endif
1337  _M_ptr = static_cast<_Tp*>(__p);
1338  _M_enable_shared_from_this_with(_M_ptr);
1339  }
1340 
1341  template<typename _Tp1, _Lock_policy _Lp1, typename _Alloc,
1342  typename... _Args>
1343  friend __shared_ptr<_Tp1, _Lp1>
1344  __allocate_shared(const _Alloc& __a, _Args&&... __args);
1345 
1346  // This constructor is used by __weak_ptr::lock() and
1347  // shared_ptr::shared_ptr(const weak_ptr&, std::nothrow_t).
1348  __shared_ptr(const __weak_ptr<_Tp, _Lp>& __r, std::nothrow_t)
1349  : _M_refcount(__r._M_refcount, std::nothrow)
1350  {
1351  _M_ptr = _M_refcount._M_get_use_count() ? __r._M_ptr : nullptr;
1352  }
1353 
1354  friend class __weak_ptr<_Tp, _Lp>;
1355 
1356  private:
1357 
1358  template<typename _Yp>
1359  using __esft_base_t = decltype(__enable_shared_from_this_base(
1360  std::declval<const __shared_count<_Lp>&>(),
1361  std::declval<_Yp*>()));
1362 
1363  // Detect an accessible and unambiguous enable_shared_from_this base.
1364  template<typename _Yp, typename = void>
1365  struct __has_esft_base
1366  : false_type { };
1367 
1368  template<typename _Yp>
1369  struct __has_esft_base<_Yp, __void_t<__esft_base_t<_Yp>>>
1370  : __not_<is_array<_Tp>> { }; // No enable shared_from_this for arrays
1371 
1372  template<typename _Yp, typename _Yp2 = typename remove_cv<_Yp>::type>
1373  typename enable_if<__has_esft_base<_Yp2>::value>::type
1374  _M_enable_shared_from_this_with(_Yp* __p) noexcept
1375  {
1376  if (auto __base = __enable_shared_from_this_base(_M_refcount, __p))
1377  __base->_M_weak_assign(const_cast<_Yp2*>(__p), _M_refcount);
1378  }
1379 
1380  template<typename _Yp, typename _Yp2 = typename remove_cv<_Yp>::type>
1381  typename enable_if<!__has_esft_base<_Yp2>::value>::type
1382  _M_enable_shared_from_this_with(_Yp*) noexcept
1383  { }
1384 
1385  void*
1386  _M_get_deleter(const std::type_info& __ti) const noexcept
1387  { return _M_refcount._M_get_deleter(__ti); }
1388 
1389  template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
1390  template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
1391 
1392  template<typename _Del, typename _Tp1, _Lock_policy _Lp1>
1393  friend _Del* get_deleter(const __shared_ptr<_Tp1, _Lp1>&) noexcept;
1394 
1395  template<typename _Del, typename _Tp1>
1396  friend _Del* get_deleter(const shared_ptr<_Tp1>&) noexcept;
1397 
1398  element_type* _M_ptr; // Contained pointer.
1399  __shared_count<_Lp> _M_refcount; // Reference counter.
1400  };
1401 
1402 
1403  // 20.7.2.2.7 shared_ptr comparisons
1404  template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1405  inline bool
1406  operator==(const __shared_ptr<_Tp1, _Lp>& __a,
1407  const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1408  { return __a.get() == __b.get(); }
1409 
1410  template<typename _Tp, _Lock_policy _Lp>
1411  inline bool
1412  operator==(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1413  { return !__a; }
1414 
1415  template<typename _Tp, _Lock_policy _Lp>
1416  inline bool
1417  operator==(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1418  { return !__a; }
1419 
1420  template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1421  inline bool
1422  operator!=(const __shared_ptr<_Tp1, _Lp>& __a,
1423  const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1424  { return __a.get() != __b.get(); }
1425 
1426  template<typename _Tp, _Lock_policy _Lp>
1427  inline bool
1428  operator!=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1429  { return (bool)__a; }
1430 
1431  template<typename _Tp, _Lock_policy _Lp>
1432  inline bool
1433  operator!=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1434  { return (bool)__a; }
1435 
1436  template<typename _Tp, typename _Up, _Lock_policy _Lp>
1437  inline bool
1438  operator<(const __shared_ptr<_Tp, _Lp>& __a,
1439  const __shared_ptr<_Up, _Lp>& __b) noexcept
1440  {
1441  using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1442  using _Up_elt = typename __shared_ptr<_Up, _Lp>::element_type;
1443  using _Vp = typename common_type<_Tp_elt*, _Up_elt*>::type;
1444  return less<_Vp>()(__a.get(), __b.get());
1445  }
1446 
1447  template<typename _Tp, _Lock_policy _Lp>
1448  inline bool
1449  operator<(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1450  {
1451  using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1452  return less<_Tp_elt*>()(__a.get(), nullptr);
1453  }
1454 
1455  template<typename _Tp, _Lock_policy _Lp>
1456  inline bool
1457  operator<(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1458  {
1459  using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1460  return less<_Tp_elt*>()(nullptr, __a.get());
1461  }
1462 
1463  template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1464  inline bool
1465  operator<=(const __shared_ptr<_Tp1, _Lp>& __a,
1466  const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1467  { return !(__b < __a); }
1468 
1469  template<typename _Tp, _Lock_policy _Lp>
1470  inline bool
1471  operator<=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1472  { return !(nullptr < __a); }
1473 
1474  template<typename _Tp, _Lock_policy _Lp>
1475  inline bool
1476  operator<=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1477  { return !(__a < nullptr); }
1478 
1479  template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1480  inline bool
1481  operator>(const __shared_ptr<_Tp1, _Lp>& __a,
1482  const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1483  { return (__b < __a); }
1484 
1485  template<typename _Tp, _Lock_policy _Lp>
1486  inline bool
1487  operator>(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1488  { return nullptr < __a; }
1489 
1490  template<typename _Tp, _Lock_policy _Lp>
1491  inline bool
1492  operator>(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1493  { return __a < nullptr; }
1494 
1495  template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1496  inline bool
1497  operator>=(const __shared_ptr<_Tp1, _Lp>& __a,
1498  const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1499  { return !(__a < __b); }
1500 
1501  template<typename _Tp, _Lock_policy _Lp>
1502  inline bool
1503  operator>=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1504  { return !(__a < nullptr); }
1505 
1506  template<typename _Tp, _Lock_policy _Lp>
1507  inline bool
1508  operator>=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1509  { return !(nullptr < __a); }
1510 
1511  template<typename _Sp>
1512  struct _Sp_less : public binary_function<_Sp, _Sp, bool>
1513  {
1514  bool
1515  operator()(const _Sp& __lhs, const _Sp& __rhs) const noexcept
1516  {
1517  typedef typename _Sp::element_type element_type;
1518  return std::less<element_type*>()(__lhs.get(), __rhs.get());
1519  }
1520  };
1521 
1522  template<typename _Tp, _Lock_policy _Lp>
1523  struct less<__shared_ptr<_Tp, _Lp>>
1524  : public _Sp_less<__shared_ptr<_Tp, _Lp>>
1525  { };
1526 
1527  // 20.7.2.2.8 shared_ptr specialized algorithms.
1528  template<typename _Tp, _Lock_policy _Lp>
1529  inline void
1530  swap(__shared_ptr<_Tp, _Lp>& __a, __shared_ptr<_Tp, _Lp>& __b) noexcept
1531  { __a.swap(__b); }
1532 
1533  // 20.7.2.2.9 shared_ptr casts
1534 
1535  // The seemingly equivalent code:
1536  // shared_ptr<_Tp, _Lp>(static_cast<_Tp*>(__r.get()))
1537  // will eventually result in undefined behaviour, attempting to
1538  // delete the same object twice.
1539  /// static_pointer_cast
1540  template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1541  inline __shared_ptr<_Tp, _Lp>
1542  static_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1543  {
1544  using _Sp = __shared_ptr<_Tp, _Lp>;
1545  return _Sp(__r, static_cast<typename _Sp::element_type*>(__r.get()));
1546  }
1547 
1548  // The seemingly equivalent code:
1549  // shared_ptr<_Tp, _Lp>(const_cast<_Tp*>(__r.get()))
1550  // will eventually result in undefined behaviour, attempting to
1551  // delete the same object twice.
1552  /// const_pointer_cast
1553  template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1554  inline __shared_ptr<_Tp, _Lp>
1555  const_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1556  {
1557  using _Sp = __shared_ptr<_Tp, _Lp>;
1558  return _Sp(__r, const_cast<typename _Sp::element_type*>(__r.get()));
1559  }
1560 
1561  // The seemingly equivalent code:
1562  // shared_ptr<_Tp, _Lp>(dynamic_cast<_Tp*>(__r.get()))
1563  // will eventually result in undefined behaviour, attempting to
1564  // delete the same object twice.
1565  /// dynamic_pointer_cast
1566  template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1567  inline __shared_ptr<_Tp, _Lp>
1568  dynamic_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1569  {
1570  using _Sp = __shared_ptr<_Tp, _Lp>;
1571  if (auto* __p = dynamic_cast<typename _Sp::element_type*>(__r.get()))
1572  return _Sp(__r, __p);
1573  return _Sp();
1574  }
1575 
1576 #if __cplusplus > 201402L
1577  template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1578  inline __shared_ptr<_Tp, _Lp>
1579  reinterpret_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1580  {
1581  using _Sp = __shared_ptr<_Tp, _Lp>;
1582  return _Sp(__r, reinterpret_cast<typename _Sp::element_type*>(__r.get()));
1583  }
1584 #endif
1585 
1586  template<typename _Tp, _Lock_policy _Lp>
1587  class __weak_ptr
1588  {
1589  template<typename _Yp, typename _Res = void>
1590  using _Compatible = typename
1591  enable_if<__sp_compatible_with<_Yp*, _Tp*>::value, _Res>::type;
1592 
1593  // Constraint for assignment from shared_ptr and weak_ptr:
1594  template<typename _Yp>
1595  using _Assignable = _Compatible<_Yp, __weak_ptr&>;
1596 
1597  public:
1598  using element_type = typename remove_extent<_Tp>::type;
1599 
1600  constexpr __weak_ptr() noexcept
1601  : _M_ptr(nullptr), _M_refcount()
1602  { }
1603 
1604  __weak_ptr(const __weak_ptr&) noexcept = default;
1605 
1606  ~__weak_ptr() = default;
1607 
1608  // The "obvious" converting constructor implementation:
1609  //
1610  // template<typename _Tp1>
1611  // __weak_ptr(const __weak_ptr<_Tp1, _Lp>& __r)
1612  // : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws
1613  // { }
1614  //
1615  // has a serious problem.
1616  //
1617  // __r._M_ptr may already have been invalidated. The _M_ptr(__r._M_ptr)
1618  // conversion may require access to *__r._M_ptr (virtual inheritance).
1619  //
1620  // It is not possible to avoid spurious access violations since
1621  // in multithreaded programs __r._M_ptr may be invalidated at any point.
1622  template<typename _Yp, typename = _Compatible<_Yp>>
1623  __weak_ptr(const __weak_ptr<_Yp, _Lp>& __r) noexcept
1624  : _M_refcount(__r._M_refcount)
1625  { _M_ptr = __r.lock().get(); }
1626 
1627  template<typename _Yp, typename = _Compatible<_Yp>>
1628  __weak_ptr(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1629  : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount)
1630  { }
1631 
1632  __weak_ptr(__weak_ptr&& __r) noexcept
1633  : _M_ptr(__r._M_ptr), _M_refcount(std::move(__r._M_refcount))
1634  { __r._M_ptr = nullptr; }
1635 
1636  template<typename _Yp, typename = _Compatible<_Yp>>
1637  __weak_ptr(__weak_ptr<_Yp, _Lp>&& __r) noexcept
1638  : _M_ptr(__r.lock().get()), _M_refcount(std::move(__r._M_refcount))
1639  { __r._M_ptr = nullptr; }
1640 
1641  __weak_ptr&
1642  operator=(const __weak_ptr& __r) noexcept = default;
1643 
1644  template<typename _Yp>
1645  _Assignable<_Yp>
1646  operator=(const __weak_ptr<_Yp, _Lp>& __r) noexcept
1647  {
1648  _M_ptr = __r.lock().get();
1649  _M_refcount = __r._M_refcount;
1650  return *this;
1651  }
1652 
1653  template<typename _Yp>
1654  _Assignable<_Yp>
1655  operator=(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1656  {
1657  _M_ptr = __r._M_ptr;
1658  _M_refcount = __r._M_refcount;
1659  return *this;
1660  }
1661 
1662  __weak_ptr&
1663  operator=(__weak_ptr&& __r) noexcept
1664  {
1665  _M_ptr = __r._M_ptr;
1666  _M_refcount = std::move(__r._M_refcount);
1667  __r._M_ptr = nullptr;
1668  return *this;
1669  }
1670 
1671  template<typename _Yp>
1672  _Assignable<_Yp>
1673  operator=(__weak_ptr<_Yp, _Lp>&& __r) noexcept
1674  {
1675  _M_ptr = __r.lock().get();
1676  _M_refcount = std::move(__r._M_refcount);
1677  __r._M_ptr = nullptr;
1678  return *this;
1679  }
1680 
1681  __shared_ptr<_Tp, _Lp>
1682  lock() const noexcept
1683  { return __shared_ptr<element_type, _Lp>(*this, std::nothrow); }
1684 
1685  long
1686  use_count() const noexcept
1687  { return _M_refcount._M_get_use_count(); }
1688 
1689  bool
1690  expired() const noexcept
1691  { return _M_refcount._M_get_use_count() == 0; }
1692 
1693  template<typename _Tp1>
1694  bool
1695  owner_before(const __shared_ptr<_Tp1, _Lp>& __rhs) const noexcept
1696  { return _M_refcount._M_less(__rhs._M_refcount); }
1697 
1698  template<typename _Tp1>
1699  bool
1700  owner_before(const __weak_ptr<_Tp1, _Lp>& __rhs) const noexcept
1701  { return _M_refcount._M_less(__rhs._M_refcount); }
1702 
1703  void
1704  reset() noexcept
1705  { __weak_ptr().swap(*this); }
1706 
1707  void
1708  swap(__weak_ptr& __s) noexcept
1709  {
1710  std::swap(_M_ptr, __s._M_ptr);
1711  _M_refcount._M_swap(__s._M_refcount);
1712  }
1713 
1714  private:
1715  // Used by __enable_shared_from_this.
1716  void
1717  _M_assign(_Tp* __ptr, const __shared_count<_Lp>& __refcount) noexcept
1718  {
1719  if (use_count() == 0)
1720  {
1721  _M_ptr = __ptr;
1722  _M_refcount = __refcount;
1723  }
1724  }
1725 
1726  template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
1727  template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
1728  friend class __enable_shared_from_this<_Tp, _Lp>;
1729  friend class enable_shared_from_this<_Tp>;
1730 
1731  element_type* _M_ptr; // Contained pointer.
1732  __weak_count<_Lp> _M_refcount; // Reference counter.
1733  };
1734 
1735  // 20.7.2.3.6 weak_ptr specialized algorithms.
1736  template<typename _Tp, _Lock_policy _Lp>
1737  inline void
1738  swap(__weak_ptr<_Tp, _Lp>& __a, __weak_ptr<_Tp, _Lp>& __b) noexcept
1739  { __a.swap(__b); }
1740 
1741  template<typename _Tp, typename _Tp1>
1742  struct _Sp_owner_less : public binary_function<_Tp, _Tp, bool>
1743  {
1744  bool
1745  operator()(const _Tp& __lhs, const _Tp& __rhs) const noexcept
1746  { return __lhs.owner_before(__rhs); }
1747 
1748  bool
1749  operator()(const _Tp& __lhs, const _Tp1& __rhs) const noexcept
1750  { return __lhs.owner_before(__rhs); }
1751 
1752  bool
1753  operator()(const _Tp1& __lhs, const _Tp& __rhs) const noexcept
1754  { return __lhs.owner_before(__rhs); }
1755  };
1756 
1757  template<>
1758  struct _Sp_owner_less<void, void>
1759  {
1760  template<typename _Tp, typename _Up>
1761  auto
1762  operator()(const _Tp& __lhs, const _Up& __rhs) const noexcept
1763  -> decltype(__lhs.owner_before(__rhs))
1764  { return __lhs.owner_before(__rhs); }
1765 
1766  using is_transparent = void;
1767  };
1768 
1769  template<typename _Tp, _Lock_policy _Lp>
1770  struct owner_less<__shared_ptr<_Tp, _Lp>>
1771  : public _Sp_owner_less<__shared_ptr<_Tp, _Lp>, __weak_ptr<_Tp, _Lp>>
1772  { };
1773 
1774  template<typename _Tp, _Lock_policy _Lp>
1775  struct owner_less<__weak_ptr<_Tp, _Lp>>
1776  : public _Sp_owner_less<__weak_ptr<_Tp, _Lp>, __shared_ptr<_Tp, _Lp>>
1777  { };
1778 
1779 
1780  template<typename _Tp, _Lock_policy _Lp>
1781  class __enable_shared_from_this
1782  {
1783  protected:
1784  constexpr __enable_shared_from_this() noexcept { }
1785 
1786  __enable_shared_from_this(const __enable_shared_from_this&) noexcept { }
1787 
1788  __enable_shared_from_this&
1789  operator=(const __enable_shared_from_this&) noexcept
1790  { return *this; }
1791 
1792  ~__enable_shared_from_this() { }
1793 
1794  public:
1795  __shared_ptr<_Tp, _Lp>
1796  shared_from_this()
1797  { return __shared_ptr<_Tp, _Lp>(this->_M_weak_this); }
1798 
1799  __shared_ptr<const _Tp, _Lp>
1800  shared_from_this() const
1801  { return __shared_ptr<const _Tp, _Lp>(this->_M_weak_this); }
1802 
1803 #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
1804  __weak_ptr<_Tp, _Lp>
1805  weak_from_this() noexcept
1806  { return this->_M_weak_this; }
1807 
1808  __weak_ptr<const _Tp, _Lp>
1809  weak_from_this() const noexcept
1810  { return this->_M_weak_this; }
1811 #endif
1812 
1813  private:
1814  template<typename _Tp1>
1815  void
1816  _M_weak_assign(_Tp1* __p, const __shared_count<_Lp>& __n) const noexcept
1817  { _M_weak_this._M_assign(__p, __n); }
1818 
1819  friend const __enable_shared_from_this*
1820  __enable_shared_from_this_base(const __shared_count<_Lp>&,
1821  const __enable_shared_from_this* __p)
1822  { return __p; }
1823 
1824  template<typename, _Lock_policy>
1825  friend class __shared_ptr;
1826 
1827  mutable __weak_ptr<_Tp, _Lp> _M_weak_this;
1828  };
1829 
1830  template<typename _Tp, _Lock_policy _Lp, typename _Alloc, typename... _Args>
1831  inline __shared_ptr<_Tp, _Lp>
1832  __allocate_shared(const _Alloc& __a, _Args&&... __args)
1833  {
1834  return __shared_ptr<_Tp, _Lp>(_Sp_make_shared_tag(), __a,
1835  std::forward<_Args>(__args)...);
1836  }
1837 
1838  template<typename _Tp, _Lock_policy _Lp, typename... _Args>
1839  inline __shared_ptr<_Tp, _Lp>
1840  __make_shared(_Args&&... __args)
1841  {
1842  typedef typename std::remove_const<_Tp>::type _Tp_nc;
1843  return std::__allocate_shared<_Tp, _Lp>(std::allocator<_Tp_nc>(),
1844  std::forward<_Args>(__args)...);
1845  }
1846 
1847  /// std::hash specialization for __shared_ptr.
1848  template<typename _Tp, _Lock_policy _Lp>
1849  struct hash<__shared_ptr<_Tp, _Lp>>
1850  : public __hash_base<size_t, __shared_ptr<_Tp, _Lp>>
1851  {
1852  size_t
1853  operator()(const __shared_ptr<_Tp, _Lp>& __s) const noexcept
1854  {
1856  __s.get());
1857  }
1858  };
1859 
1860 _GLIBCXX_END_NAMESPACE_VERSION
1861 } // namespace
1862 
1863 #endif // _SHARED_PTR_BASE_H
void lock(_L1 &__l1, _L2 &__l2, _L3 &... __l3)
Generic lock.
Definition: mutex:542
Exception possibly thrown by shared_ptr.
Primary class template hash.
Definition: system_error:142
integral_constant< bool, false > false_type
The type used as a compile-time boolean with false value.
Definition: type_traits:90
Part of RTTI.
Definition: typeinfo:88
Scoped lock idiom.
Definition: concurrence.h:231
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition: move.h:47
Base class for all library exceptions.
Definition: exception.h:60
constexpr _Tp && forward(typename std::remove_reference< _Tp >::type &__t) noexcept
Forward an lvalue.
Definition: move.h:74
__allocated_ptr< _Alloc > __allocate_guarded(_Alloc &__a)
Allocate space for a single object using __a.
Definition: allocated_ptr.h:95
integral_constant< bool, true > true_type
The type used as a compile-time boolean with true value.
Definition: type_traits:87
One of the comparison functors.
Definition: stl_function.h:340
ISO C++ entities toplevel namespace is std.
The standard allocator, as per [20.4].
Definition: allocator.h:108
static auto construct(_Alloc &__a, _Tp *__p, _Args &&... __args) -> decltype(_S_construct(__a, __p, std::forward< _Args >(__args)...))
Construct an object of type _Tp.
20.7.1.2 unique_ptr for single objects.
Definition: unique_ptr.h:160
A simple smart pointer providing strict ownership semantics.
Definition: auto_ptr.h:89
static void destroy(_Alloc &__a, _Tp *__p)
Destroy an object of type _Tp.
virtual char const * what() const noexcept
complex< _Tp > operator*(const complex< _Tp > &__x, const complex< _Tp > &__y)
Return new complex value x times y.
Definition: complex:386