libstdc++
experimental/bits/shared_ptr.h
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1 // Experimental shared_ptr with array support -*- C++ -*-
2 
3 // Copyright (C) 2015-2018 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10 
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15 
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19 
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24 
25 /** @file experimental/bits/shared_ptr.h
26  * This is an internal header file, included by other library headers.
27  * Do not attempt to use it directly. @headername{experimental/memory}
28  */
29 
30 #ifndef _GLIBCXX_EXPERIMENTAL_SHARED_PTR_H
31 #define _GLIBCXX_EXPERIMENTAL_SHARED_PTR_H 1
32 
33 #pragma GCC system_header
34 
35 #if __cplusplus >= 201402L
36 
37 #include <memory>
38 #include <experimental/type_traits>
39 
40 namespace std _GLIBCXX_VISIBILITY(default)
41 {
42 _GLIBCXX_BEGIN_NAMESPACE_VERSION
43 
44 namespace experimental
45 {
46 inline namespace fundamentals_v2
47 {
48  // 8.2.1
49 
50  template<typename _Tp> class shared_ptr;
51  template<typename _Tp> class weak_ptr;
52  template<typename _Tp> class enable_shared_from_this;
53 
54  template<typename _Yp, typename _Tp>
55  constexpr bool __sp_compatible_v
56  = std::__sp_compatible_with<_Yp*, _Tp*>::value;
57 
58  template<typename _Tp, typename _Yp>
59  constexpr bool __sp_is_constructible_v
60  = std::__sp_is_constructible<_Tp, _Yp>::value;
61 
62  template<typename _Tp>
63  class shared_ptr : public __shared_ptr<_Tp>
64  {
65  using _Base_type = __shared_ptr<_Tp>;
66 
67  public:
68  using element_type = typename _Base_type::element_type;
69 
70  private:
71  // Constraint for construction from a pointer of type _Yp*:
72  template<typename _Yp>
73  using _SafeConv = enable_if_t<__sp_is_constructible_v<_Tp, _Yp>>;
74 
75  template<typename _Tp1, typename _Res = void>
76  using _Compatible
77  = enable_if_t<__sp_compatible_v<_Tp1, _Tp>, _Res>;
78 
79  template<typename _Tp1, typename _Del,
80  typename _Ptr = typename unique_ptr<_Tp1, _Del>::pointer,
81  typename _Res = void>
82  using _UniqCompatible = enable_if_t<
83  __sp_compatible_v<_Tp1, _Tp>
84  && experimental::is_convertible_v<_Ptr, element_type*>,
85  _Res>;
86 
87  public:
88 
89  // 8.2.1.1, shared_ptr constructors
90  constexpr shared_ptr() noexcept = default;
91 
92  template<typename _Tp1, typename = _SafeConv<_Tp1>>
93  explicit
94  shared_ptr(_Tp1* __p) : _Base_type(__p)
95  { _M_enable_shared_from_this_with(__p); }
96 
97  template<typename _Tp1, typename _Deleter, typename = _SafeConv<_Tp1>>
98  shared_ptr(_Tp1* __p, _Deleter __d)
99  : _Base_type(__p, __d)
100  { _M_enable_shared_from_this_with(__p); }
101 
102  template<typename _Tp1, typename _Deleter, typename _Alloc,
103  typename = _SafeConv<_Tp1>>
104  shared_ptr(_Tp1* __p, _Deleter __d, _Alloc __a)
105  : _Base_type(__p, __d, __a)
106  { _M_enable_shared_from_this_with(__p); }
107 
108  template<typename _Deleter>
109  shared_ptr(nullptr_t __p, _Deleter __d)
110  : _Base_type(__p, __d) { }
111 
112  template<typename _Deleter, typename _Alloc>
113  shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
114  : _Base_type(__p, __d, __a) { }
115 
116  template<typename _Tp1>
117  shared_ptr(const shared_ptr<_Tp1>& __r, element_type* __p) noexcept
118  : _Base_type(__r, __p) { }
119 
120  shared_ptr(const shared_ptr& __r) noexcept
121  : _Base_type(__r) { }
122 
123  template<typename _Tp1, typename = _Compatible<_Tp1>>
124  shared_ptr(const shared_ptr<_Tp1>& __r) noexcept
125  : _Base_type(__r) { }
126 
127  shared_ptr(shared_ptr&& __r) noexcept
128  : _Base_type(std::move(__r)) { }
129 
130  template<typename _Tp1, typename = _Compatible<_Tp1>>
131  shared_ptr(shared_ptr<_Tp1>&& __r) noexcept
132  : _Base_type(std::move(__r)) { }
133 
134  template<typename _Tp1, typename = _Compatible<_Tp1>>
135  explicit
136  shared_ptr(const weak_ptr<_Tp1>& __r)
137  : _Base_type(__r) { }
138 
139 #if _GLIBCXX_USE_DEPRECATED
140  template<typename _Tp1, typename = _Compatible<_Tp1>>
141  shared_ptr(std::auto_ptr<_Tp1>&& __r)
142  : _Base_type(std::move(__r))
143  { _M_enable_shared_from_this_with(static_cast<_Tp1*>(this->get())); }
144 #endif
145 
146  template<typename _Tp1, typename _Del,
147  typename = _UniqCompatible<_Tp1, _Del>>
148  shared_ptr(unique_ptr<_Tp1, _Del>&& __r)
149  : _Base_type(std::move(__r))
150  {
151  // XXX assume conversion from __r.get() to this->get() to __elem_t*
152  // is a round trip, which might not be true in all cases.
153  using __elem_t = typename unique_ptr<_Tp1, _Del>::element_type;
154  _M_enable_shared_from_this_with(static_cast<__elem_t*>(this->get()));
155  }
156 
157  constexpr shared_ptr(nullptr_t __p)
158  : _Base_type(__p) { }
159 
160  // C++14 §20.8.2.2
161  ~shared_ptr() = default;
162 
163  // C++14 §20.8.2.3
164  shared_ptr& operator=(const shared_ptr&) noexcept = default;
165 
166  template <typename _Tp1>
167  _Compatible<_Tp1, shared_ptr&>
168  operator=(const shared_ptr<_Tp1>& __r) noexcept
169  {
170  _Base_type::operator=(__r);
171  return *this;
172  }
173 
174  shared_ptr&
175  operator=(shared_ptr&& __r) noexcept
176  {
177  _Base_type::operator=(std::move(__r));
178  return *this;
179  }
180 
181  template <typename _Tp1>
182  _Compatible<_Tp1, shared_ptr&>
183  operator=(shared_ptr<_Tp1>&& __r) noexcept
184  {
185  _Base_type::operator=(std::move(__r));
186  return *this;
187  }
188 
189 #if _GLIBCXX_USE_DEPRECATED
190  template<typename _Tp1>
191  _Compatible<_Tp1, shared_ptr&>
192  operator=(std::auto_ptr<_Tp1>&& __r)
193  {
194  __shared_ptr<_Tp>::operator=(std::move(__r));
195  return *this;
196  }
197 #endif
198 
199  template <typename _Tp1, typename _Del>
200  _UniqCompatible<_Tp1, _Del, shared_ptr&>
201  operator=(unique_ptr<_Tp1, _Del>&& __r)
202  {
203  _Base_type::operator=(std::move(__r));
204  return *this;
205  }
206 
207  // C++14 §20.8.2.2.4
208  // swap & reset
209  // 8.2.1.2 shared_ptr observers
210  // in __shared_ptr
211 
212  private:
213  template<typename _Alloc, typename... _Args>
214  shared_ptr(_Sp_make_shared_tag __tag, const _Alloc& __a,
215  _Args&&... __args)
216  : _Base_type(__tag, __a, std::forward<_Args>(__args)...)
217  { _M_enable_shared_from_this_with(this->get()); }
218 
219  template<typename _Tp1, typename _Alloc, typename... _Args>
220  friend shared_ptr<_Tp1>
221  allocate_shared(const _Alloc& __a, _Args&&... __args);
222 
223  shared_ptr(const weak_ptr<_Tp>& __r, std::nothrow_t)
224  : _Base_type(__r, std::nothrow) { }
225 
226  friend class weak_ptr<_Tp>;
227 
228  template<typename _Yp>
229  using __esft_base_t =
230  decltype(__expt_enable_shared_from_this_base(std::declval<_Yp*>()));
231 
232  // Detect an accessible and unambiguous enable_shared_from_this base.
233  template<typename _Yp, typename = void>
234  struct __has_esft_base
235  : false_type { };
236 
237  template<typename _Yp>
238  struct __has_esft_base<_Yp, __void_t<__esft_base_t<_Yp>>>
239  : __bool_constant<!is_array_v<_Tp>> { }; // ignore base for arrays
240 
241  template<typename _Yp>
242  typename enable_if<__has_esft_base<_Yp>::value>::type
243  _M_enable_shared_from_this_with(const _Yp* __p) noexcept
244  {
245  if (auto __base = __expt_enable_shared_from_this_base(__p))
246  {
247  __base->_M_weak_this
248  = shared_ptr<_Yp>(*this, const_cast<_Yp*>(__p));
249  }
250  }
251 
252  template<typename _Yp>
253  typename enable_if<!__has_esft_base<_Yp>::value>::type
254  _M_enable_shared_from_this_with(const _Yp*) noexcept
255  { }
256  };
257 
258  // C++14 §20.8.2.2.7 //DOING
259  template<typename _Tp1, typename _Tp2>
260  bool operator==(const shared_ptr<_Tp1>& __a,
261  const shared_ptr<_Tp2>& __b) noexcept
262  { return __a.get() == __b.get(); }
263 
264  template<typename _Tp>
265  inline bool
266  operator==(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
267  { return !__a; }
268 
269  template<typename _Tp>
270  inline bool
271  operator==(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
272  { return !__a; }
273 
274  template<typename _Tp1, typename _Tp2>
275  inline bool
276  operator!=(const shared_ptr<_Tp1>& __a,
277  const shared_ptr<_Tp2>& __b) noexcept
278  { return __a.get() != __b.get(); }
279 
280  template<typename _Tp>
281  inline bool
282  operator!=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
283  { return (bool)__a; }
284 
285  template<typename _Tp>
286  inline bool
287  operator!=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
288  { return (bool)__a; }
289 
290  template<typename _Tp1, typename _Tp2>
291  inline bool
292  operator<(const shared_ptr<_Tp1>& __a,
293  const shared_ptr<_Tp2>& __b) noexcept
294  {
295  using __elem_t1 = typename shared_ptr<_Tp1>::element_type;
296  using __elem_t2 = typename shared_ptr<_Tp2>::element_type;
297  using _CT = common_type_t<__elem_t1*, __elem_t2*>;
298  return std::less<_CT>()(__a.get(), __b.get());
299  }
300 
301  template<typename _Tp>
302  inline bool
303  operator<(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
304  {
305  using __elem_t = typename shared_ptr<_Tp>::element_type;
306  return std::less<__elem_t*>()(__a.get(), nullptr);
307  }
308 
309  template<typename _Tp>
310  inline bool
311  operator<(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
312  {
313  using __elem_t = typename shared_ptr<_Tp>::element_type;
314  return std::less<__elem_t*>()(nullptr, __a.get());
315  }
316 
317  template<typename _Tp1, typename _Tp2>
318  inline bool
319  operator<=(const shared_ptr<_Tp1>& __a,
320  const shared_ptr<_Tp2>& __b) noexcept
321  { return !(__b < __a); }
322 
323  template<typename _Tp>
324  inline bool
325  operator<=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
326  { return !(nullptr < __a); }
327 
328  template<typename _Tp>
329  inline bool
330  operator<=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
331  { return !(__a < nullptr); }
332 
333  template<typename _Tp1, typename _Tp2>
334  inline bool
335  operator>(const shared_ptr<_Tp1>& __a,
336  const shared_ptr<_Tp2>& __b) noexcept
337  { return (__b < __a); }
338 
339  template<typename _Tp>
340  inline bool
341  operator>(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
342  {
343  using __elem_t = typename shared_ptr<_Tp>::element_type;
344  return std::less<__elem_t*>()(nullptr, __a.get());
345  }
346 
347  template<typename _Tp>
348  inline bool
349  operator>(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
350  {
351  using __elem_t = typename shared_ptr<_Tp>::element_type;
352  return std::less<__elem_t*>()(__a.get(), nullptr);
353  }
354 
355  template<typename _Tp1, typename _Tp2>
356  inline bool
357  operator>=(const shared_ptr<_Tp1>& __a,
358  const shared_ptr<_Tp2>& __b) noexcept
359  { return !(__a < __b); }
360 
361  template<typename _Tp>
362  inline bool
363  operator>=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
364  { return !(__a < nullptr); }
365 
366  template<typename _Tp>
367  inline bool
368  operator>=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
369  { return !(nullptr < __a); }
370 
371  // C++14 §20.8.2.2.8
372  template<typename _Tp>
373  inline void
374  swap(shared_ptr<_Tp>& __a, shared_ptr<_Tp>& __b) noexcept
375  { __a.swap(__b); }
376 
377  // 8.2.1.3, shared_ptr casts
378  template<typename _Tp, typename _Tp1>
379  inline shared_ptr<_Tp>
380  static_pointer_cast(const shared_ptr<_Tp1>& __r) noexcept
381  {
382  using __elem_t = typename shared_ptr<_Tp>::element_type;
383  return shared_ptr<_Tp>(__r, static_cast<__elem_t*>(__r.get()));
384  }
385 
386  template<typename _Tp, typename _Tp1>
387  inline shared_ptr<_Tp>
388  dynamic_pointer_cast(const shared_ptr<_Tp1>& __r) noexcept
389  {
390  using __elem_t = typename shared_ptr<_Tp>::element_type;
391  if (_Tp* __p = dynamic_cast<__elem_t*>(__r.get()))
392  return shared_ptr<_Tp>(__r, __p);
393  return shared_ptr<_Tp>();
394  }
395 
396  template<typename _Tp, typename _Tp1>
397  inline shared_ptr<_Tp>
398  const_pointer_cast(const shared_ptr<_Tp1>& __r) noexcept
399  {
400  using __elem_t = typename shared_ptr<_Tp>::element_type;
401  return shared_ptr<_Tp>(__r, const_cast<__elem_t*>(__r.get()));
402  }
403 
404  template<typename _Tp, typename _Tp1>
405  inline shared_ptr<_Tp>
406  reinterpret_pointer_cast(const shared_ptr<_Tp1>& __r) noexcept
407  {
408  using __elem_t = typename shared_ptr<_Tp>::element_type;
409  return shared_ptr<_Tp>(__r, reinterpret_cast<__elem_t*>(__r.get()));
410  }
411 
412  // C++14 §20.8.2.3
413  template<typename _Tp>
414  class weak_ptr : public __weak_ptr<_Tp>
415  {
416  template<typename _Tp1, typename _Res = void>
417  using _Compatible = enable_if_t<__sp_compatible_v<_Tp1, _Tp>, _Res>;
418 
419  using _Base_type = __weak_ptr<_Tp>;
420 
421  public:
422  constexpr weak_ptr() noexcept = default;
423 
424  template<typename _Tp1, typename = _Compatible<_Tp1>>
425  weak_ptr(const shared_ptr<_Tp1>& __r) noexcept
426  : _Base_type(__r) { }
427 
428  weak_ptr(const weak_ptr&) noexcept = default;
429 
430  template<typename _Tp1, typename = _Compatible<_Tp1>>
431  weak_ptr(const weak_ptr<_Tp1>& __r) noexcept
432  : _Base_type(__r) { }
433 
434  weak_ptr(weak_ptr&&) noexcept = default;
435 
436  template<typename _Tp1, typename = _Compatible<_Tp1>>
437  weak_ptr(weak_ptr<_Tp1>&& __r) noexcept
438  : _Base_type(std::move(__r)) { }
439 
440  weak_ptr&
441  operator=(const weak_ptr& __r) noexcept = default;
442 
443  template<typename _Tp1>
444  _Compatible<_Tp1, weak_ptr&>
445  operator=(const weak_ptr<_Tp1>& __r) noexcept
446  {
447  this->_Base_type::operator=(__r);
448  return *this;
449  }
450 
451  template<typename _Tp1>
452  _Compatible<_Tp1, weak_ptr&>
453  operator=(const shared_ptr<_Tp1>& __r) noexcept
454  {
455  this->_Base_type::operator=(__r);
456  return *this;
457  }
458 
459  weak_ptr&
460  operator=(weak_ptr&& __r) noexcept = default;
461 
462  template<typename _Tp1>
463  _Compatible<_Tp1, weak_ptr&>
464  operator=(weak_ptr<_Tp1>&& __r) noexcept
465  {
466  this->_Base_type::operator=(std::move(__r));
467  return *this;
468  }
469 
470  shared_ptr<_Tp>
471  lock() const noexcept
472  { return shared_ptr<_Tp>(*this, std::nothrow); }
473 
474  friend class enable_shared_from_this<_Tp>;
475  };
476 
477  // C++14 §20.8.2.3.6
478  template<typename _Tp>
479  inline void
480  swap(weak_ptr<_Tp>& __a, weak_ptr<_Tp>& __b) noexcept
481  { __a.swap(__b); }
482 
483  /// C++14 §20.8.2.2.10
484  template<typename _Del, typename _Tp>
485  inline _Del*
486  get_deleter(const shared_ptr<_Tp>& __p) noexcept
487  { return std::get_deleter<_Del>(__p); }
488 
489  // C++14 §20.8.2.2.11
490  template<typename _Ch, typename _Tr, typename _Tp>
491  inline std::basic_ostream<_Ch, _Tr>&
492  operator<<(std::basic_ostream<_Ch, _Tr>& __os, const shared_ptr<_Tp>& __p)
493  {
494  __os << __p.get();
495  return __os;
496  }
497 
498  // C++14 §20.8.2.4
499  template<typename _Tp = void> class owner_less;
500 
501  /// Partial specialization of owner_less for shared_ptr.
502  template<typename _Tp>
503  struct owner_less<shared_ptr<_Tp>>
504  : public _Sp_owner_less<shared_ptr<_Tp>, weak_ptr<_Tp>>
505  { };
506 
507  /// Partial specialization of owner_less for weak_ptr.
508  template<typename _Tp>
509  struct owner_less<weak_ptr<_Tp>>
510  : public _Sp_owner_less<weak_ptr<_Tp>, shared_ptr<_Tp>>
511  { };
512 
513  template<>
514  class owner_less<void>
515  {
516  template<typename _Tp, typename _Up>
517  bool
518  operator()(shared_ptr<_Tp> const& __lhs,
519  shared_ptr<_Up> const& __rhs) const
520  { return __lhs.owner_before(__rhs); }
521 
522  template<typename _Tp, typename _Up>
523  bool
524  operator()(shared_ptr<_Tp> const& __lhs,
525  weak_ptr<_Up> const& __rhs) const
526  { return __lhs.owner_before(__rhs); }
527 
528  template<typename _Tp, typename _Up>
529  bool
530  operator()(weak_ptr<_Tp> const& __lhs,
531  shared_ptr<_Up> const& __rhs) const
532  { return __lhs.owner_before(__rhs); }
533 
534  template<typename _Tp, typename _Up>
535  bool
536  operator()(weak_ptr<_Tp> const& __lhs,
537  weak_ptr<_Up> const& __rhs) const
538  { return __lhs.owner_before(__rhs); }
539 
540  typedef void is_transparent;
541  };
542 
543  // C++14 §20.8.2.6
544  template<typename _Tp>
545  inline bool
546  atomic_is_lock_free(const shared_ptr<_Tp>* __p)
547  { return std::atomic_is_lock_free<_Tp, __default_lock_policy>(__p); }
548 
549  template<typename _Tp>
550  shared_ptr<_Tp> atomic_load(const shared_ptr<_Tp>* __p)
551  { return std::atomic_load<_Tp>(__p); }
552 
553  template<typename _Tp>
554  shared_ptr<_Tp>
555  atomic_load_explicit(const shared_ptr<_Tp>* __p, memory_order __mo)
556  { return std::atomic_load_explicit<_Tp>(__p, __mo); }
557 
558  template<typename _Tp>
559  void atomic_store(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r)
560  { return std::atomic_store<_Tp>(__p, __r); }
561 
562  template<typename _Tp>
563  shared_ptr<_Tp>
564  atomic_store_explicit(const shared_ptr<_Tp>* __p,
565  shared_ptr<_Tp> __r,
566  memory_order __mo)
567  { return std::atomic_store_explicit<_Tp>(__p, __r, __mo); }
568 
569  template<typename _Tp>
570  void atomic_exchange(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r)
571  { return std::atomic_exchange<_Tp>(__p, __r); }
572 
573  template<typename _Tp>
574  shared_ptr<_Tp>
575  atomic_exchange_explicit(const shared_ptr<_Tp>* __p,
576  shared_ptr<_Tp> __r,
577  memory_order __mo)
578  { return std::atomic_exchange_explicit<_Tp>(__p, __r, __mo); }
579 
580  template<typename _Tp>
581  bool atomic_compare_exchange_weak(shared_ptr<_Tp>* __p,
582  shared_ptr<_Tp>* __v,
583  shared_ptr<_Tp> __w)
584  { return std::atomic_compare_exchange_weak<_Tp>(__p, __v, __w); }
585 
586  template<typename _Tp>
587  bool atomic_compare_exchange_strong(shared_ptr<_Tp>* __p,
588  shared_ptr<_Tp>* __v,
589  shared_ptr<_Tp> __w)
590  { return std::atomic_compare_exchange_strong<_Tp>(__p, __v, __w); }
591 
592  template<typename _Tp>
593  bool atomic_compare_exchange_weak_explicit(shared_ptr<_Tp>* __p,
594  shared_ptr<_Tp>* __v,
595  shared_ptr<_Tp> __w,
596  memory_order __success,
597  memory_order __failure)
598  { return std::atomic_compare_exchange_weak_explicit<_Tp>(__p, __v, __w,
599  __success,
600  __failure); }
601 
602  template<typename _Tp>
603  bool atomic_compare_exchange_strong_explicit(shared_ptr<_Tp>* __p,
604  shared_ptr<_Tp>* __v,
605  shared_ptr<_Tp> __w,
606  memory_order __success,
607  memory_order __failure)
608  { return std::atomic_compare_exchange_strong_explicit<_Tp>(__p, __v, __w,
609  __success,
610  __failure); }
611 
612  //enable_shared_from_this
613  template<typename _Tp>
614  class enable_shared_from_this
615  {
616  protected:
617  constexpr enable_shared_from_this() noexcept { }
618 
619  enable_shared_from_this(const enable_shared_from_this&) noexcept { }
620 
621  enable_shared_from_this&
622  operator=(const enable_shared_from_this&) noexcept
623  { return *this; }
624 
625  ~enable_shared_from_this() { }
626 
627  public:
628  shared_ptr<_Tp>
629  shared_from_this()
630  { return shared_ptr<_Tp>(this->_M_weak_this); }
631 
632  shared_ptr<const _Tp>
633  shared_from_this() const
634  { return shared_ptr<const _Tp>(this->_M_weak_this); }
635 
636  weak_ptr<_Tp>
637  weak_from_this() noexcept
638  { return _M_weak_this; }
639 
640  weak_ptr<const _Tp>
641  weak_from_this() const noexcept
642  { return _M_weak_this; }
643 
644  private:
645  template<typename _Tp1>
646  void
647  _M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const noexcept
648  { _M_weak_this._M_assign(__p, __n); }
649 
650  // Found by ADL when this is an associated class.
651  friend const enable_shared_from_this*
652  __expt_enable_shared_from_this_base(const enable_shared_from_this* __p)
653  { return __p; }
654 
655  template<typename>
656  friend class shared_ptr;
657 
658  mutable weak_ptr<_Tp> _M_weak_this;
659  };
660 } // namespace fundamentals_v2
661 } // namespace experimental
662 
663  /// std::hash specialization for shared_ptr.
664  template<typename _Tp>
665  struct hash<experimental::shared_ptr<_Tp>>
666  : public __hash_base<size_t, experimental::shared_ptr<_Tp>>
667  {
668  size_t
669  operator()(const experimental::shared_ptr<_Tp>& __s) const noexcept
670  { return std::hash<_Tp*>()(__s.get()); }
671  };
672 
673 _GLIBCXX_END_NAMESPACE_VERSION
674 } // namespace std
675 
676 #endif // __cplusplus <= 201103L
677 
678 #endif // _GLIBCXX_EXPERIMENTAL_SHARED_PTR_H
std::weak_ptr
A smart pointer with weak semantics.
Definition: bits/shared_ptr.h:535
std::less
One of the comparison functors.
Definition: stl_function.h:340
std::lock
void lock(_L1 &__l1, _L2 &__l2, _L3 &... __l3)
Generic lock.
Definition: mutex:542
std::auto_ptr
A simple smart pointer providing strict ownership semantics.
Definition: auto_ptr.h:89
std::allocate_shared
shared_ptr< _Tp > allocate_shared(const _Alloc &__a, _Args &&... __args)
Create an object that is owned by a shared_ptr.
Definition: bits/shared_ptr.h:703
std::hash
Primary class template hash.
Definition: system_error:142
std::owner_less
Primary template owner_less.
Definition: bits/shared_ptr.h:616
std::hash< _Tp * >
Partial specializations for pointer types.
Definition: functional_hash.h:106
std::enable_if_t
typename enable_if< _Cond, _Tp >::type enable_if_t
Alias template for enable_if.
Definition: type_traits:2294
std::memory_order
memory_order
Enumeration for memory_order.
Definition: atomic_base.h:55
std
ISO C++ entities toplevel namespace is std.
std::basic_ostream
Template class basic_ostream.
Definition: iosfwd:86
std::operator<<
std::basic_ostream< _CharT, _Traits > & operator<<(std::basic_ostream< _CharT, _Traits > &__os, const bitset< _Nb > &__x)
Global I/O operators for bitsets.
Definition: bitset:1534
std::false_type
integral_constant< bool, false > false_type
The type used as a compile-time boolean with false value.
Definition: type_traits:78
std::shared_ptr
A smart pointer with reference-counted copy semantics.
Definition: bits/shared_ptr.h:103
std::forward
constexpr _Tp && forward(typename std::remove_reference< _Tp >::type &__t) noexcept
Forward an lvalue.
Definition: move.h:74