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#include <typeinfo>
53#include <bits/allocated_ptr.h>
54#include <bits/refwrap.h>
55#include <bits/stl_function.h>
56#include <ext/aligned_buffer.h>
57
58namespace std _GLIBCXX_VISIBILITY(default)
59{
60_GLIBCXX_BEGIN_NAMESPACE_VERSION
61
62#if _GLIBCXX_USE_DEPRECATED
63#pragma GCC diagnostic push
64#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
65 template<typename> class auto_ptr;
66#pragma GCC diagnostic pop
67#endif
68
69 /**
70 * @brief Exception possibly thrown by @c shared_ptr.
71 * @ingroup exceptions
72 */
73 class bad_weak_ptr : public std::exception
74 {
75 public:
76 virtual char const* what() const noexcept;
77
78 virtual ~bad_weak_ptr() noexcept;
79 };
80
81 // Substitute for bad_weak_ptr object in the case of -fno-exceptions.
82 inline void
83 __throw_bad_weak_ptr()
84 { _GLIBCXX_THROW_OR_ABORT(bad_weak_ptr()); }
85
86 using __gnu_cxx::_Lock_policy;
87 using __gnu_cxx::__default_lock_policy;
88 using __gnu_cxx::_S_single;
89 using __gnu_cxx::_S_mutex;
90 using __gnu_cxx::_S_atomic;
91
92 // Empty helper class except when the template argument is _S_mutex.
93 template<_Lock_policy _Lp>
94 class _Mutex_base
95 {
96 protected:
97 // The atomic policy uses fully-fenced builtins, single doesn't care.
98 enum { _S_need_barriers = 0 };
99 };
100
101 template<>
102 class _Mutex_base<_S_mutex>
103 : public __gnu_cxx::__mutex
104 {
105 protected:
106 // This policy is used when atomic builtins are not available.
107 // The replacement atomic operations might not have the necessary
108 // memory barriers.
109 enum { _S_need_barriers = 1 };
110 };
111
112 template<_Lock_policy _Lp = __default_lock_policy>
113 class _Sp_counted_base
114 : public _Mutex_base<_Lp>
115 {
116 public:
117 _Sp_counted_base() noexcept
118 : _M_use_count(1), _M_weak_count(1) { }
119
120 virtual
121 ~_Sp_counted_base() noexcept
122 { }
123
124 // Called when _M_use_count drops to zero, to release the resources
125 // managed by *this.
126 virtual void
127 _M_dispose() noexcept = 0;
128
129 // Called when _M_weak_count drops to zero.
130 virtual void
131 _M_destroy() noexcept
132 { delete this; }
133
134 virtual void*
135 _M_get_deleter(const std::type_info&) noexcept = 0;
136
137 void
138 _M_add_ref_copy()
139 { __gnu_cxx::__atomic_add_dispatch(&_M_use_count, 1); }
140
141 void
142 _M_add_ref_lock();
143
144 bool
145 _M_add_ref_lock_nothrow();
146
147 void
148 _M_release() noexcept
149 {
150 // Be race-detector-friendly. For more info see bits/c++config.
151 _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_use_count);
152 if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, -1) == 1)
153 {
154 _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_use_count);
155 _M_dispose();
156 // There must be a memory barrier between dispose() and destroy()
157 // to ensure that the effects of dispose() are observed in the
158 // thread that runs destroy().
159 // See http://gcc.gnu.org/ml/libstdc++/2005-11/msg00136.html
160 if (_Mutex_base<_Lp>::_S_need_barriers)
161 {
162 __atomic_thread_fence (__ATOMIC_ACQ_REL);
163 }
164
165 // Be race-detector-friendly. For more info see bits/c++config.
166 _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count);
167 if (__gnu_cxx::__exchange_and_add_dispatch(&_M_weak_count,
168 -1) == 1)
169 {
170 _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count);
171 _M_destroy();
172 }
173 }
174 }
175
176 void
177 _M_weak_add_ref() noexcept
178 { __gnu_cxx::__atomic_add_dispatch(&_M_weak_count, 1); }
179
180 void
181 _M_weak_release() noexcept
182 {
183 // Be race-detector-friendly. For more info see bits/c++config.
184 _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count);
185 if (__gnu_cxx::__exchange_and_add_dispatch(&_M_weak_count, -1) == 1)
186 {
187 _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count);
188 if (_Mutex_base<_Lp>::_S_need_barriers)
189 {
190 // See _M_release(),
191 // destroy() must observe results of dispose()
192 __atomic_thread_fence (__ATOMIC_ACQ_REL);
193 }
194 _M_destroy();
195 }
196 }
197
198 long
199 _M_get_use_count() const noexcept
200 {
201 // No memory barrier is used here so there is no synchronization
202 // with other threads.
203 return __atomic_load_n(&_M_use_count, __ATOMIC_RELAXED);
204 }
205
206 private:
207 _Sp_counted_base(_Sp_counted_base const&) = delete;
208 _Sp_counted_base& operator=(_Sp_counted_base const&) = delete;
209
210 _Atomic_word _M_use_count; // #shared
211 _Atomic_word _M_weak_count; // #weak + (#shared != 0)
212 };
213
214 template<>
215 inline void
216 _Sp_counted_base<_S_single>::
217 _M_add_ref_lock()
218 {
219 if (_M_use_count == 0)
220 __throw_bad_weak_ptr();
221 ++_M_use_count;
222 }
223
224 template<>
225 inline void
226 _Sp_counted_base<_S_mutex>::
227 _M_add_ref_lock()
228 {
229 __gnu_cxx::__scoped_lock sentry(*this);
230 if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, 1) == 0)
231 {
232 _M_use_count = 0;
233 __throw_bad_weak_ptr();
234 }
235 }
236
237 template<>
238 inline void
239 _Sp_counted_base<_S_atomic>::
240 _M_add_ref_lock()
241 {
242 // Perform lock-free add-if-not-zero operation.
243 _Atomic_word __count = _M_get_use_count();
244 do
245 {
246 if (__count == 0)
247 __throw_bad_weak_ptr();
248 // Replace the current counter value with the old value + 1, as
249 // long as it's not changed meanwhile.
250 }
251 while (!__atomic_compare_exchange_n(&_M_use_count, &__count, __count + 1,
252 true, __ATOMIC_ACQ_REL,
253 __ATOMIC_RELAXED));
254 }
255
256 template<>
257 inline bool
258 _Sp_counted_base<_S_single>::
259 _M_add_ref_lock_nothrow()
260 {
261 if (_M_use_count == 0)
262 return false;
263 ++_M_use_count;
264 return true;
265 }
266
267 template<>
268 inline bool
269 _Sp_counted_base<_S_mutex>::
270 _M_add_ref_lock_nothrow()
271 {
272 __gnu_cxx::__scoped_lock sentry(*this);
273 if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, 1) == 0)
274 {
275 _M_use_count = 0;
276 return false;
277 }
278 return true;
279 }
280
281 template<>
282 inline bool
283 _Sp_counted_base<_S_atomic>::
284 _M_add_ref_lock_nothrow()
285 {
286 // Perform lock-free add-if-not-zero operation.
287 _Atomic_word __count = _M_get_use_count();
288 do
289 {
290 if (__count == 0)
291 return false;
292 // Replace the current counter value with the old value + 1, as
293 // long as it's not changed meanwhile.
294 }
295 while (!__atomic_compare_exchange_n(&_M_use_count, &__count, __count + 1,
296 true, __ATOMIC_ACQ_REL,
297 __ATOMIC_RELAXED));
298 return true;
299 }
300
301 template<>
302 inline void
303 _Sp_counted_base<_S_single>::_M_add_ref_copy()
304 { ++_M_use_count; }
305
306 template<>
307 inline void
308 _Sp_counted_base<_S_single>::_M_release() noexcept
309 {
310 if (--_M_use_count == 0)
311 {
312 _M_dispose();
313 if (--_M_weak_count == 0)
314 _M_destroy();
315 }
316 }
317
318 template<>
319 inline void
320 _Sp_counted_base<_S_single>::_M_weak_add_ref() noexcept
321 { ++_M_weak_count; }
322
323 template<>
324 inline void
325 _Sp_counted_base<_S_single>::_M_weak_release() noexcept
326 {
327 if (--_M_weak_count == 0)
328 _M_destroy();
329 }
330
331 template<>
332 inline long
333 _Sp_counted_base<_S_single>::_M_get_use_count() const noexcept
334 { return _M_use_count; }
335
336
337 // Forward declarations.
338 template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
339 class __shared_ptr;
340
341 template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
342 class __weak_ptr;
343
344 template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
345 class __enable_shared_from_this;
346
347 template<typename _Tp>
348 class shared_ptr;
349
350 template<typename _Tp>
351 class weak_ptr;
352
353 template<typename _Tp>
354 struct owner_less;
355
356 template<typename _Tp>
357 class enable_shared_from_this;
358
359 template<_Lock_policy _Lp = __default_lock_policy>
360 class __weak_count;
361
362 template<_Lock_policy _Lp = __default_lock_policy>
363 class __shared_count;
364
365
366 // Counted ptr with no deleter or allocator support
367 template<typename _Ptr, _Lock_policy _Lp>
368 class _Sp_counted_ptr final : public _Sp_counted_base<_Lp>
369 {
370 public:
371 explicit
372 _Sp_counted_ptr(_Ptr __p) noexcept
373 : _M_ptr(__p) { }
374
375 virtual void
376 _M_dispose() noexcept
377 { delete _M_ptr; }
378
379 virtual void
380 _M_destroy() noexcept
381 { delete this; }
382
383 virtual void*
384 _M_get_deleter(const std::type_info&) noexcept
385 { return nullptr; }
386
387 _Sp_counted_ptr(const _Sp_counted_ptr&) = delete;
388 _Sp_counted_ptr& operator=(const _Sp_counted_ptr&) = delete;
389
390 private:
391 _Ptr _M_ptr;
392 };
393
394 template<>
395 inline void
396 _Sp_counted_ptr<nullptr_t, _S_single>::_M_dispose() noexcept { }
397
398 template<>
399 inline void
400 _Sp_counted_ptr<nullptr_t, _S_mutex>::_M_dispose() noexcept { }
401
402 template<>
403 inline void
404 _Sp_counted_ptr<nullptr_t, _S_atomic>::_M_dispose() noexcept { }
405
406 template<int _Nm, typename _Tp,
407 bool __use_ebo = !__is_final(_Tp) && __is_empty(_Tp)>
408 struct _Sp_ebo_helper;
409
410 /// Specialization using EBO.
411 template<int _Nm, typename _Tp>
412 struct _Sp_ebo_helper<_Nm, _Tp, true> : private _Tp
413 {
414 explicit _Sp_ebo_helper(const _Tp& __tp) : _Tp(__tp) { }
415 explicit _Sp_ebo_helper(_Tp&& __tp) : _Tp(std::move(__tp)) { }
416
417 static _Tp&
418 _S_get(_Sp_ebo_helper& __eboh) { return static_cast<_Tp&>(__eboh); }
419 };
420
421 /// Specialization not using EBO.
422 template<int _Nm, typename _Tp>
423 struct _Sp_ebo_helper<_Nm, _Tp, false>
424 {
425 explicit _Sp_ebo_helper(const _Tp& __tp) : _M_tp(__tp) { }
426 explicit _Sp_ebo_helper(_Tp&& __tp) : _M_tp(std::move(__tp)) { }
427
428 static _Tp&
429 _S_get(_Sp_ebo_helper& __eboh)
430 { return __eboh._M_tp; }
431
432 private:
433 _Tp _M_tp;
434 };
435
436 // Support for custom deleter and/or allocator
437 template<typename _Ptr, typename _Deleter, typename _Alloc, _Lock_policy _Lp>
438 class _Sp_counted_deleter final : public _Sp_counted_base<_Lp>
439 {
440 class _Impl : _Sp_ebo_helper<0, _Deleter>, _Sp_ebo_helper<1, _Alloc>
441 {
442 typedef _Sp_ebo_helper<0, _Deleter> _Del_base;
443 typedef _Sp_ebo_helper<1, _Alloc> _Alloc_base;
444
445 public:
446 _Impl(_Ptr __p, _Deleter __d, const _Alloc& __a) noexcept
447 : _M_ptr(__p), _Del_base(std::move(__d)), _Alloc_base(__a)
448 { }
449
450 _Deleter& _M_del() noexcept { return _Del_base::_S_get(*this); }
451 _Alloc& _M_alloc() noexcept { return _Alloc_base::_S_get(*this); }
452
453 _Ptr _M_ptr;
454 };
455
456 public:
457 using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_deleter>;
458
459 // __d(__p) must not throw.
460 _Sp_counted_deleter(_Ptr __p, _Deleter __d) noexcept
461 : _M_impl(__p, std::move(__d), _Alloc()) { }
462
463 // __d(__p) must not throw.
464 _Sp_counted_deleter(_Ptr __p, _Deleter __d, const _Alloc& __a) noexcept
465 : _M_impl(__p, std::move(__d), __a) { }
466
467 ~_Sp_counted_deleter() noexcept { }
468
469 virtual void
470 _M_dispose() noexcept
471 { _M_impl._M_del()(_M_impl._M_ptr); }
472
473 virtual void
474 _M_destroy() noexcept
475 {
476 __allocator_type __a(_M_impl._M_alloc());
477 __allocated_ptr<__allocator_type> __guard_ptr{ __a, this };
478 this->~_Sp_counted_deleter();
479 }
480
481 virtual void*
482 _M_get_deleter(const std::type_info& __ti) noexcept
483 {
484#if __cpp_rtti
485 // _GLIBCXX_RESOLVE_LIB_DEFECTS
486 // 2400. shared_ptr's get_deleter() should use addressof()
487 return __ti == typeid(_Deleter)
488 ? std::__addressof(_M_impl._M_del())
489 : nullptr;
490#else
491 return nullptr;
492#endif
493 }
494
495 private:
496 _Impl _M_impl;
497 };
498
499 // helpers for make_shared / allocate_shared
500
501 struct _Sp_make_shared_tag
502 {
503#if !__cpp_rtti
504 private:
505 template<typename _Tp, _Lock_policy _Lp>
506 friend class __shared_ptr;
507 template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
508 friend class _Sp_counted_ptr_inplace;
509
510 static const type_info&
511 _S_ti() noexcept _GLIBCXX_VISIBILITY(default)
512 {
513 alignas(type_info) static constexpr _Sp_make_shared_tag __tag;
514 return reinterpret_cast<const type_info&>(__tag);
515 }
516#endif
517 };
518
519 template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
520 class _Sp_counted_ptr_inplace final : public _Sp_counted_base<_Lp>
521 {
522 class _Impl : _Sp_ebo_helper<0, _Alloc>
523 {
524 typedef _Sp_ebo_helper<0, _Alloc> _A_base;
525
526 public:
527 explicit _Impl(_Alloc __a) noexcept : _A_base(__a) { }
528
529 _Alloc& _M_alloc() noexcept { return _A_base::_S_get(*this); }
530
531 __gnu_cxx::__aligned_buffer<_Tp> _M_storage;
532 };
533
534 public:
535 using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_ptr_inplace>;
536
537 template<typename... _Args>
538 _Sp_counted_ptr_inplace(_Alloc __a, _Args&&... __args)
539 : _M_impl(__a)
540 {
541 // _GLIBCXX_RESOLVE_LIB_DEFECTS
542 // 2070. allocate_shared should use allocator_traits<A>::construct
543 allocator_traits<_Alloc>::construct(__a, _M_ptr(),
544 std::forward<_Args>(__args)...); // might throw
545 }
546
547 ~_Sp_counted_ptr_inplace() noexcept { }
548
549 virtual void
550 _M_dispose() noexcept
551 {
552 allocator_traits<_Alloc>::destroy(_M_impl._M_alloc(), _M_ptr());
553 }
554
555 // Override because the allocator needs to know the dynamic type
556 virtual void
557 _M_destroy() noexcept
558 {
559 __allocator_type __a(_M_impl._M_alloc());
560 __allocated_ptr<__allocator_type> __guard_ptr{ __a, this };
561 this->~_Sp_counted_ptr_inplace();
562 }
563
564 // Sneaky trick so __shared_ptr can get the managed pointer
565 virtual void*
566 _M_get_deleter(const std::type_info& __ti) noexcept
567 {
568#if __cpp_rtti
569 if (__ti == typeid(_Sp_make_shared_tag))
570#else
571 if (&__ti == &_Sp_make_shared_tag::_S_ti())
572#endif
573 return const_cast<typename remove_cv<_Tp>::type*>(_M_ptr());
574 return nullptr;
575 }
576
577 private:
578 _Tp* _M_ptr() noexcept { return _M_impl._M_storage._M_ptr(); }
579
580 _Impl _M_impl;
581 };
582
583 // The default deleter for shared_ptr<T[]> and shared_ptr<T[N]>.
584 struct __sp_array_delete
585 {
586 template<typename _Yp>
587 void operator()(_Yp* __p) const { delete[] __p; }
588 };
589
590 template<_Lock_policy _Lp>
591 class __shared_count
592 {
593 public:
594 constexpr __shared_count() noexcept : _M_pi(0)
595 { }
596
597 template<typename _Ptr>
598 explicit
599 __shared_count(_Ptr __p) : _M_pi(0)
600 {
601 __try
602 {
603 _M_pi = new _Sp_counted_ptr<_Ptr, _Lp>(__p);
604 }
605 __catch(...)
606 {
607 delete __p;
608 __throw_exception_again;
609 }
610 }
611
612 template<typename _Ptr>
613 __shared_count(_Ptr __p, /* is_array = */ false_type)
614 : __shared_count(__p)
615 { }
616
617 template<typename _Ptr>
618 __shared_count(_Ptr __p, /* is_array = */ true_type)
619 : __shared_count(__p, __sp_array_delete{}, allocator<void>())
620 { }
621
622 template<typename _Ptr, typename _Deleter>
623 __shared_count(_Ptr __p, _Deleter __d)
624 : __shared_count(__p, std::move(__d), allocator<void>())
625 { }
626
627 template<typename _Ptr, typename _Deleter, typename _Alloc>
628 __shared_count(_Ptr __p, _Deleter __d, _Alloc __a) : _M_pi(0)
629 {
630 typedef _Sp_counted_deleter<_Ptr, _Deleter, _Alloc, _Lp> _Sp_cd_type;
631 __try
632 {
633 typename _Sp_cd_type::__allocator_type __a2(__a);
634 auto __guard = std::__allocate_guarded(__a2);
635 _Sp_cd_type* __mem = __guard.get();
636 ::new (__mem) _Sp_cd_type(__p, std::move(__d), std::move(__a));
637 _M_pi = __mem;
638 __guard = nullptr;
639 }
640 __catch(...)
641 {
642 __d(__p); // Call _Deleter on __p.
643 __throw_exception_again;
644 }
645 }
646
647 template<typename _Tp, typename _Alloc, typename... _Args>
648 __shared_count(_Sp_make_shared_tag, _Tp*, const _Alloc& __a,
649 _Args&&... __args)
650 : _M_pi(0)
651 {
652 typedef _Sp_counted_ptr_inplace<_Tp, _Alloc, _Lp> _Sp_cp_type;
653 typename _Sp_cp_type::__allocator_type __a2(__a);
654 auto __guard = std::__allocate_guarded(__a2);
655 _Sp_cp_type* __mem = __guard.get();
656 ::new (__mem) _Sp_cp_type(std::move(__a),
657 std::forward<_Args>(__args)...);
658 _M_pi = __mem;
659 __guard = nullptr;
660 }
661
662#if _GLIBCXX_USE_DEPRECATED
663#pragma GCC diagnostic push
664#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
665 // Special case for auto_ptr<_Tp> to provide the strong guarantee.
666 template<typename _Tp>
667 explicit
668 __shared_count(std::auto_ptr<_Tp>&& __r);
669#pragma GCC diagnostic pop
670#endif
671
672 // Special case for unique_ptr<_Tp,_Del> to provide the strong guarantee.
673 template<typename _Tp, typename _Del>
674 explicit
675 __shared_count(std::unique_ptr<_Tp, _Del>&& __r) : _M_pi(0)
676 {
677 // _GLIBCXX_RESOLVE_LIB_DEFECTS
678 // 2415. Inconsistency between unique_ptr and shared_ptr
679 if (__r.get() == nullptr)
680 return;
681
682 using _Ptr = typename unique_ptr<_Tp, _Del>::pointer;
683 using _Del2 = typename conditional<is_reference<_Del>::value,
684 reference_wrapper<typename remove_reference<_Del>::type>,
685 _Del>::type;
686 using _Sp_cd_type
687 = _Sp_counted_deleter<_Ptr, _Del2, allocator<void>, _Lp>;
688 using _Alloc = allocator<_Sp_cd_type>;
689 using _Alloc_traits = allocator_traits<_Alloc>;
690 _Alloc __a;
691 _Sp_cd_type* __mem = _Alloc_traits::allocate(__a, 1);
692 _Alloc_traits::construct(__a, __mem, __r.release(),
693 __r.get_deleter()); // non-throwing
694 _M_pi = __mem;
695 }
696
697 // Throw bad_weak_ptr when __r._M_get_use_count() == 0.
698 explicit __shared_count(const __weak_count<_Lp>& __r);
699
700 // Does not throw if __r._M_get_use_count() == 0, caller must check.
701 explicit __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t);
702
703 ~__shared_count() noexcept
704 {
705 if (_M_pi != nullptr)
706 _M_pi->_M_release();
707 }
708
709 __shared_count(const __shared_count& __r) noexcept
710 : _M_pi(__r._M_pi)
711 {
712 if (_M_pi != 0)
713 _M_pi->_M_add_ref_copy();
714 }
715
716 __shared_count&
717 operator=(const __shared_count& __r) noexcept
718 {
719 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
720 if (__tmp != _M_pi)
721 {
722 if (__tmp != 0)
723 __tmp->_M_add_ref_copy();
724 if (_M_pi != 0)
725 _M_pi->_M_release();
726 _M_pi = __tmp;
727 }
728 return *this;
729 }
730
731 void
732 _M_swap(__shared_count& __r) noexcept
733 {
734 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
735 __r._M_pi = _M_pi;
736 _M_pi = __tmp;
737 }
738
739 long
740 _M_get_use_count() const noexcept
741 { return _M_pi != 0 ? _M_pi->_M_get_use_count() : 0; }
742
743 bool
744 _M_unique() const noexcept
745 { return this->_M_get_use_count() == 1; }
746
747 void*
748 _M_get_deleter(const std::type_info& __ti) const noexcept
749 { return _M_pi ? _M_pi->_M_get_deleter(__ti) : nullptr; }
750
751 bool
752 _M_less(const __shared_count& __rhs) const noexcept
753 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
754
755 bool
756 _M_less(const __weak_count<_Lp>& __rhs) const noexcept
757 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
758
759 // Friend function injected into enclosing namespace and found by ADL
760 friend inline bool
761 operator==(const __shared_count& __a, const __shared_count& __b) noexcept
762 { return __a._M_pi == __b._M_pi; }
763
764 private:
765 friend class __weak_count<_Lp>;
766
767 _Sp_counted_base<_Lp>* _M_pi;
768 };
769
770
771 template<_Lock_policy _Lp>
772 class __weak_count
773 {
774 public:
775 constexpr __weak_count() noexcept : _M_pi(nullptr)
776 { }
777
778 __weak_count(const __shared_count<_Lp>& __r) noexcept
779 : _M_pi(__r._M_pi)
780 {
781 if (_M_pi != nullptr)
782 _M_pi->_M_weak_add_ref();
783 }
784
785 __weak_count(const __weak_count& __r) noexcept
786 : _M_pi(__r._M_pi)
787 {
788 if (_M_pi != nullptr)
789 _M_pi->_M_weak_add_ref();
790 }
791
792 __weak_count(__weak_count&& __r) noexcept
793 : _M_pi(__r._M_pi)
794 { __r._M_pi = nullptr; }
795
796 ~__weak_count() noexcept
797 {
798 if (_M_pi != nullptr)
799 _M_pi->_M_weak_release();
800 }
801
802 __weak_count&
803 operator=(const __shared_count<_Lp>& __r) noexcept
804 {
805 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
806 if (__tmp != nullptr)
807 __tmp->_M_weak_add_ref();
808 if (_M_pi != nullptr)
809 _M_pi->_M_weak_release();
810 _M_pi = __tmp;
811 return *this;
812 }
813
814 __weak_count&
815 operator=(const __weak_count& __r) noexcept
816 {
817 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
818 if (__tmp != nullptr)
819 __tmp->_M_weak_add_ref();
820 if (_M_pi != nullptr)
821 _M_pi->_M_weak_release();
822 _M_pi = __tmp;
823 return *this;
824 }
825
826 __weak_count&
827 operator=(__weak_count&& __r) noexcept
828 {
829 if (_M_pi != nullptr)
830 _M_pi->_M_weak_release();
831 _M_pi = __r._M_pi;
832 __r._M_pi = nullptr;
833 return *this;
834 }
835
836 void
837 _M_swap(__weak_count& __r) noexcept
838 {
839 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
840 __r._M_pi = _M_pi;
841 _M_pi = __tmp;
842 }
843
844 long
845 _M_get_use_count() const noexcept
846 { return _M_pi != nullptr ? _M_pi->_M_get_use_count() : 0; }
847
848 bool
849 _M_less(const __weak_count& __rhs) const noexcept
850 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
851
852 bool
853 _M_less(const __shared_count<_Lp>& __rhs) const noexcept
854 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
855
856 // Friend function injected into enclosing namespace and found by ADL
857 friend inline bool
858 operator==(const __weak_count& __a, const __weak_count& __b) noexcept
859 { return __a._M_pi == __b._M_pi; }
860
861 private:
862 friend class __shared_count<_Lp>;
863
864 _Sp_counted_base<_Lp>* _M_pi;
865 };
866
867 // Now that __weak_count is defined we can define this constructor:
868 template<_Lock_policy _Lp>
869 inline
870 __shared_count<_Lp>::__shared_count(const __weak_count<_Lp>& __r)
871 : _M_pi(__r._M_pi)
872 {
873 if (_M_pi != nullptr)
874 _M_pi->_M_add_ref_lock();
875 else
876 __throw_bad_weak_ptr();
877 }
878
879 // Now that __weak_count is defined we can define this constructor:
880 template<_Lock_policy _Lp>
881 inline
882 __shared_count<_Lp>::
883 __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t)
884 : _M_pi(__r._M_pi)
885 {
886 if (_M_pi != nullptr)
887 if (!_M_pi->_M_add_ref_lock_nothrow())
888 _M_pi = nullptr;
889 }
890
891#define __cpp_lib_shared_ptr_arrays 201603
892
893 // Helper traits for shared_ptr of array:
894
895 // A pointer type Y* is said to be compatible with a pointer type T* when
896 // either Y* is convertible to T* or Y is U[N] and T is U cv [].
897 template<typename _Yp_ptr, typename _Tp_ptr>
898 struct __sp_compatible_with
899 : false_type
900 { };
901
902 template<typename _Yp, typename _Tp>
903 struct __sp_compatible_with<_Yp*, _Tp*>
904 : is_convertible<_Yp*, _Tp*>::type
905 { };
906
907 template<typename _Up, size_t _Nm>
908 struct __sp_compatible_with<_Up(*)[_Nm], _Up(*)[]>
909 : true_type
910 { };
911
912 template<typename _Up, size_t _Nm>
913 struct __sp_compatible_with<_Up(*)[_Nm], const _Up(*)[]>
914 : true_type
915 { };
916
917 template<typename _Up, size_t _Nm>
918 struct __sp_compatible_with<_Up(*)[_Nm], volatile _Up(*)[]>
919 : true_type
920 { };
921
922 template<typename _Up, size_t _Nm>
923 struct __sp_compatible_with<_Up(*)[_Nm], const volatile _Up(*)[]>
924 : true_type
925 { };
926
927 // Test conversion from Y(*)[N] to U(*)[N] without forming invalid type Y[N].
928 template<typename _Up, size_t _Nm, typename _Yp, typename = void>
929 struct __sp_is_constructible_arrN
930 : false_type
931 { };
932
933 template<typename _Up, size_t _Nm, typename _Yp>
934 struct __sp_is_constructible_arrN<_Up, _Nm, _Yp, __void_t<_Yp[_Nm]>>
935 : is_convertible<_Yp(*)[_Nm], _Up(*)[_Nm]>::type
936 { };
937
938 // Test conversion from Y(*)[] to U(*)[] without forming invalid type Y[].
939 template<typename _Up, typename _Yp, typename = void>
940 struct __sp_is_constructible_arr
941 : false_type
942 { };
943
944 template<typename _Up, typename _Yp>
945 struct __sp_is_constructible_arr<_Up, _Yp, __void_t<_Yp[]>>
946 : is_convertible<_Yp(*)[], _Up(*)[]>::type
947 { };
948
949 // Trait to check if shared_ptr<T> can be constructed from Y*.
950 template<typename _Tp, typename _Yp>
951 struct __sp_is_constructible;
952
953 // When T is U[N], Y(*)[N] shall be convertible to T*;
954 template<typename _Up, size_t _Nm, typename _Yp>
955 struct __sp_is_constructible<_Up[_Nm], _Yp>
956 : __sp_is_constructible_arrN<_Up, _Nm, _Yp>::type
957 { };
958
959 // when T is U[], Y(*)[] shall be convertible to T*;
960 template<typename _Up, typename _Yp>
961 struct __sp_is_constructible<_Up[], _Yp>
962 : __sp_is_constructible_arr<_Up, _Yp>::type
963 { };
964
965 // otherwise, Y* shall be convertible to T*.
966 template<typename _Tp, typename _Yp>
967 struct __sp_is_constructible
968 : is_convertible<_Yp*, _Tp*>::type
969 { };
970
971
972 // Define operator* and operator-> for shared_ptr<T>.
973 template<typename _Tp, _Lock_policy _Lp,
974 bool = is_array<_Tp>::value, bool = is_void<_Tp>::value>
975 class __shared_ptr_access
976 {
977 public:
978 using element_type = _Tp;
979
980 element_type&
981 operator*() const noexcept
982 {
983 __glibcxx_assert(_M_get() != nullptr);
984 return *_M_get();
985 }
986
987 element_type*
988 operator->() const noexcept
989 {
990 _GLIBCXX_DEBUG_PEDASSERT(_M_get() != nullptr);
991 return _M_get();
992 }
993
994 private:
995 element_type*
996 _M_get() const noexcept
997 { return static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get(); }
998 };
999
1000 // Define operator-> for shared_ptr<cv void>.
1001 template<typename _Tp, _Lock_policy _Lp>
1002 class __shared_ptr_access<_Tp, _Lp, false, true>
1003 {
1004 public:
1005 using element_type = _Tp;
1006
1007 element_type*
1008 operator->() const noexcept
1009 {
1010 auto __ptr = static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get();
1011 _GLIBCXX_DEBUG_PEDASSERT(__ptr != nullptr);
1012 return __ptr;
1013 }
1014 };
1015
1016 // Define operator[] for shared_ptr<T[]> and shared_ptr<T[N]>.
1017 template<typename _Tp, _Lock_policy _Lp>
1018 class __shared_ptr_access<_Tp, _Lp, true, false>
1019 {
1020 public:
1021 using element_type = typename remove_extent<_Tp>::type;
1022
1023#if __cplusplus <= 201402L
1024 [[__deprecated__("shared_ptr<T[]>::operator* is absent from C++17")]]
1025 element_type&
1026 operator*() const noexcept
1027 {
1028 __glibcxx_assert(_M_get() != nullptr);
1029 return *_M_get();
1030 }
1031
1032 [[__deprecated__("shared_ptr<T[]>::operator-> is absent from C++17")]]
1033 element_type*
1034 operator->() const noexcept
1035 {
1036 _GLIBCXX_DEBUG_PEDASSERT(_M_get() != nullptr);
1037 return _M_get();
1038 }
1039#endif
1040
1041 element_type&
1042 operator[](ptrdiff_t __i) const
1043 {
1044 __glibcxx_assert(_M_get() != nullptr);
1045 __glibcxx_assert(!extent<_Tp>::value || __i < extent<_Tp>::value);
1046 return _M_get()[__i];
1047 }
1048
1049 private:
1050 element_type*
1051 _M_get() const noexcept
1052 { return static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get(); }
1053 };
1054
1055 template<typename _Tp, _Lock_policy _Lp>
1056 class __shared_ptr
1057 : public __shared_ptr_access<_Tp, _Lp>
1058 {
1059 public:
1060 using element_type = typename remove_extent<_Tp>::type;
1061
1062 private:
1063 // Constraint for taking ownership of a pointer of type _Yp*:
1064 template<typename _Yp>
1065 using _SafeConv
1066 = typename enable_if<__sp_is_constructible<_Tp, _Yp>::value>::type;
1067
1068 // Constraint for construction from shared_ptr and weak_ptr:
1069 template<typename _Yp, typename _Res = void>
1070 using _Compatible = typename
1071 enable_if<__sp_compatible_with<_Yp*, _Tp*>::value, _Res>::type;
1072
1073 // Constraint for assignment from shared_ptr and weak_ptr:
1074 template<typename _Yp>
1075 using _Assignable = _Compatible<_Yp, __shared_ptr&>;
1076
1077 // Constraint for construction from unique_ptr:
1078 template<typename _Yp, typename _Del, typename _Res = void,
1079 typename _Ptr = typename unique_ptr<_Yp, _Del>::pointer>
1080 using _UniqCompatible = typename enable_if<__and_<
1081 __sp_compatible_with<_Yp*, _Tp*>, is_convertible<_Ptr, element_type*>
1082 >::value, _Res>::type;
1083
1084 // Constraint for assignment from unique_ptr:
1085 template<typename _Yp, typename _Del>
1086 using _UniqAssignable = _UniqCompatible<_Yp, _Del, __shared_ptr&>;
1087
1088 public:
1089
1090#if __cplusplus > 201402L
1091 using weak_type = __weak_ptr<_Tp, _Lp>;
1092#endif
1093
1094 constexpr __shared_ptr() noexcept
1095 : _M_ptr(0), _M_refcount()
1096 { }
1097
1098 template<typename _Yp, typename = _SafeConv<_Yp>>
1099 explicit
1100 __shared_ptr(_Yp* __p)
1101 : _M_ptr(__p), _M_refcount(__p, typename is_array<_Tp>::type())
1102 {
1103 static_assert( !is_void<_Yp>::value, "incomplete type" );
1104 static_assert( sizeof(_Yp) > 0, "incomplete type" );
1105 _M_enable_shared_from_this_with(__p);
1106 }
1107
1108 template<typename _Yp, typename _Deleter, typename = _SafeConv<_Yp>>
1109 __shared_ptr(_Yp* __p, _Deleter __d)
1110 : _M_ptr(__p), _M_refcount(__p, std::move(__d))
1111 {
1112 static_assert(__is_invocable<_Deleter&, _Yp*&>::value,
1113 "deleter expression d(p) is well-formed");
1114 _M_enable_shared_from_this_with(__p);
1115 }
1116
1117 template<typename _Yp, typename _Deleter, typename _Alloc,
1118 typename = _SafeConv<_Yp>>
1119 __shared_ptr(_Yp* __p, _Deleter __d, _Alloc __a)
1120 : _M_ptr(__p), _M_refcount(__p, std::move(__d), std::move(__a))
1121 {
1122 static_assert(__is_invocable<_Deleter&, _Yp*&>::value,
1123 "deleter expression d(p) is well-formed");
1124 _M_enable_shared_from_this_with(__p);
1125 }
1126
1127 template<typename _Deleter>
1128 __shared_ptr(nullptr_t __p, _Deleter __d)
1129 : _M_ptr(0), _M_refcount(__p, std::move(__d))
1130 { }
1131
1132 template<typename _Deleter, typename _Alloc>
1133 __shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
1134 : _M_ptr(0), _M_refcount(__p, std::move(__d), std::move(__a))
1135 { }
1136
1137 template<typename _Yp>
1138 __shared_ptr(const __shared_ptr<_Yp, _Lp>& __r,
1139 element_type* __p) noexcept
1140 : _M_ptr(__p), _M_refcount(__r._M_refcount) // never throws
1141 { }
1142
1143 __shared_ptr(const __shared_ptr&) noexcept = default;
1144 __shared_ptr& operator=(const __shared_ptr&) noexcept = default;
1145 ~__shared_ptr() = default;
1146
1147 template<typename _Yp, typename = _Compatible<_Yp>>
1148 __shared_ptr(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1149 : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount)
1150 { }
1151
1152 __shared_ptr(__shared_ptr&& __r) noexcept
1153 : _M_ptr(__r._M_ptr), _M_refcount()
1154 {
1155 _M_refcount._M_swap(__r._M_refcount);
1156 __r._M_ptr = 0;
1157 }
1158
1159 template<typename _Yp, typename = _Compatible<_Yp>>
1160 __shared_ptr(__shared_ptr<_Yp, _Lp>&& __r) noexcept
1161 : _M_ptr(__r._M_ptr), _M_refcount()
1162 {
1163 _M_refcount._M_swap(__r._M_refcount);
1164 __r._M_ptr = 0;
1165 }
1166
1167 template<typename _Yp, typename = _Compatible<_Yp>>
1168 explicit __shared_ptr(const __weak_ptr<_Yp, _Lp>& __r)
1169 : _M_refcount(__r._M_refcount) // may throw
1170 {
1171 // It is now safe to copy __r._M_ptr, as
1172 // _M_refcount(__r._M_refcount) did not throw.
1173 _M_ptr = __r._M_ptr;
1174 }
1175
1176 // If an exception is thrown this constructor has no effect.
1177 template<typename _Yp, typename _Del,
1178 typename = _UniqCompatible<_Yp, _Del>>
1179 __shared_ptr(unique_ptr<_Yp, _Del>&& __r)
1180 : _M_ptr(__r.get()), _M_refcount()
1181 {
1182 auto __raw = __to_address(__r.get());
1183 _M_refcount = __shared_count<_Lp>(std::move(__r));
1184 _M_enable_shared_from_this_with(__raw);
1185 }
1186
1187#if __cplusplus <= 201402L && _GLIBCXX_USE_DEPRECATED
1188 protected:
1189 // If an exception is thrown this constructor has no effect.
1190 template<typename _Tp1, typename _Del,
1191 typename enable_if<__and_<
1192 __not_<is_array<_Tp>>, is_array<_Tp1>,
1193 is_convertible<typename unique_ptr<_Tp1, _Del>::pointer, _Tp*>
1194 >::value, bool>::type = true>
1195 __shared_ptr(unique_ptr<_Tp1, _Del>&& __r, __sp_array_delete)
1196 : _M_ptr(__r.get()), _M_refcount()
1197 {
1198 auto __raw = __to_address(__r.get());
1199 _M_refcount = __shared_count<_Lp>(std::move(__r));
1200 _M_enable_shared_from_this_with(__raw);
1201 }
1202 public:
1203#endif
1204
1205#if _GLIBCXX_USE_DEPRECATED
1206#pragma GCC diagnostic push
1207#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
1208 // Postcondition: use_count() == 1 and __r.get() == 0
1209 template<typename _Yp, typename = _Compatible<_Yp>>
1210 __shared_ptr(auto_ptr<_Yp>&& __r);
1211#pragma GCC diagnostic pop
1212#endif
1213
1214 constexpr __shared_ptr(nullptr_t) noexcept : __shared_ptr() { }
1215
1216 template<typename _Yp>
1217 _Assignable<_Yp>
1218 operator=(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1219 {
1220 _M_ptr = __r._M_ptr;
1221 _M_refcount = __r._M_refcount; // __shared_count::op= doesn't throw
1222 return *this;
1223 }
1224
1225#if _GLIBCXX_USE_DEPRECATED
1226#pragma GCC diagnostic push
1227#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
1228 template<typename _Yp>
1229 _Assignable<_Yp>
1230 operator=(auto_ptr<_Yp>&& __r)
1231 {
1232 __shared_ptr(std::move(__r)).swap(*this);
1233 return *this;
1234 }
1235#pragma GCC diagnostic pop
1236#endif
1237
1238 __shared_ptr&
1239 operator=(__shared_ptr&& __r) noexcept
1240 {
1241 __shared_ptr(std::move(__r)).swap(*this);
1242 return *this;
1243 }
1244
1245 template<class _Yp>
1246 _Assignable<_Yp>
1247 operator=(__shared_ptr<_Yp, _Lp>&& __r) noexcept
1248 {
1249 __shared_ptr(std::move(__r)).swap(*this);
1250 return *this;
1251 }
1252
1253 template<typename _Yp, typename _Del>
1254 _UniqAssignable<_Yp, _Del>
1255 operator=(unique_ptr<_Yp, _Del>&& __r)
1256 {
1257 __shared_ptr(std::move(__r)).swap(*this);
1258 return *this;
1259 }
1260
1261 void
1262 reset() noexcept
1263 { __shared_ptr().swap(*this); }
1264
1265 template<typename _Yp>
1266 _SafeConv<_Yp>
1267 reset(_Yp* __p) // _Yp must be complete.
1268 {
1269 // Catch self-reset errors.
1270 __glibcxx_assert(__p == 0 || __p != _M_ptr);
1271 __shared_ptr(__p).swap(*this);
1272 }
1273
1274 template<typename _Yp, typename _Deleter>
1275 _SafeConv<_Yp>
1276 reset(_Yp* __p, _Deleter __d)
1277 { __shared_ptr(__p, std::move(__d)).swap(*this); }
1278
1279 template<typename _Yp, typename _Deleter, typename _Alloc>
1280 _SafeConv<_Yp>
1281 reset(_Yp* __p, _Deleter __d, _Alloc __a)
1282 { __shared_ptr(__p, std::move(__d), std::move(__a)).swap(*this); }
1283
1284 element_type*
1285 get() const noexcept
1286 { return _M_ptr; }
1287
1288 explicit operator bool() const // never throws
1289 { return _M_ptr == 0 ? false : true; }
1290
1291 bool
1292 unique() const noexcept
1293 { return _M_refcount._M_unique(); }
1294
1295 long
1296 use_count() const noexcept
1297 { return _M_refcount._M_get_use_count(); }
1298
1299 void
1300 swap(__shared_ptr<_Tp, _Lp>& __other) noexcept
1301 {
1302 std::swap(_M_ptr, __other._M_ptr);
1303 _M_refcount._M_swap(__other._M_refcount);
1304 }
1305
1306 template<typename _Tp1>
1307 bool
1308 owner_before(__shared_ptr<_Tp1, _Lp> const& __rhs) const noexcept
1309 { return _M_refcount._M_less(__rhs._M_refcount); }
1310
1311 template<typename _Tp1>
1312 bool
1313 owner_before(__weak_ptr<_Tp1, _Lp> const& __rhs) const noexcept
1314 { return _M_refcount._M_less(__rhs._M_refcount); }
1315
1316 protected:
1317 // This constructor is non-standard, it is used by allocate_shared.
1318 template<typename _Alloc, typename... _Args>
1319 __shared_ptr(_Sp_make_shared_tag __tag, const _Alloc& __a,
1320 _Args&&... __args)
1321 : _M_ptr(), _M_refcount(__tag, (_Tp*)0, __a,
1322 std::forward<_Args>(__args)...)
1323 {
1324 // _M_ptr needs to point to the newly constructed object.
1325 // This relies on _Sp_counted_ptr_inplace::_M_get_deleter.
1326#if __cpp_rtti
1327 void* __p = _M_refcount._M_get_deleter(typeid(__tag));
1328#else
1329 void* __p = _M_refcount._M_get_deleter(_Sp_make_shared_tag::_S_ti());
1330#endif
1331 _M_ptr = static_cast<_Tp*>(__p);
1332 _M_enable_shared_from_this_with(_M_ptr);
1333 }
1334
1335 template<typename _Tp1, _Lock_policy _Lp1, typename _Alloc,
1336 typename... _Args>
1337 friend __shared_ptr<_Tp1, _Lp1>
1338 __allocate_shared(const _Alloc& __a, _Args&&... __args);
1339
1340 // This constructor is used by __weak_ptr::lock() and
1341 // shared_ptr::shared_ptr(const weak_ptr&, std::nothrow_t).
1342 __shared_ptr(const __weak_ptr<_Tp, _Lp>& __r, std::nothrow_t)
1343 : _M_refcount(__r._M_refcount, std::nothrow)
1344 {
1345 _M_ptr = _M_refcount._M_get_use_count() ? __r._M_ptr : nullptr;
1346 }
1347
1348 friend class __weak_ptr<_Tp, _Lp>;
1349
1350 private:
1351
1352 template<typename _Yp>
1353 using __esft_base_t = decltype(__enable_shared_from_this_base(
1354 std::declval<const __shared_count<_Lp>&>(),
1355 std::declval<_Yp*>()));
1356
1357 // Detect an accessible and unambiguous enable_shared_from_this base.
1358 template<typename _Yp, typename = void>
1359 struct __has_esft_base
1360 : false_type { };
1361
1362 template<typename _Yp>
1363 struct __has_esft_base<_Yp, __void_t<__esft_base_t<_Yp>>>
1364 : __not_<is_array<_Tp>> { }; // No enable shared_from_this for arrays
1365
1366 template<typename _Yp, typename _Yp2 = typename remove_cv<_Yp>::type>
1367 typename enable_if<__has_esft_base<_Yp2>::value>::type
1368 _M_enable_shared_from_this_with(_Yp* __p) noexcept
1369 {
1370 if (auto __base = __enable_shared_from_this_base(_M_refcount, __p))
1371 __base->_M_weak_assign(const_cast<_Yp2*>(__p), _M_refcount);
1372 }
1373
1374 template<typename _Yp, typename _Yp2 = typename remove_cv<_Yp>::type>
1375 typename enable_if<!__has_esft_base<_Yp2>::value>::type
1376 _M_enable_shared_from_this_with(_Yp*) noexcept
1377 { }
1378
1379 void*
1380 _M_get_deleter(const std::type_info& __ti) const noexcept
1381 { return _M_refcount._M_get_deleter(__ti); }
1382
1383 template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
1384 template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
1385
1386 template<typename _Del, typename _Tp1, _Lock_policy _Lp1>
1387 friend _Del* get_deleter(const __shared_ptr<_Tp1, _Lp1>&) noexcept;
1388
1389 template<typename _Del, typename _Tp1>
1390 friend _Del* get_deleter(const shared_ptr<_Tp1>&) noexcept;
1391
1392 element_type* _M_ptr; // Contained pointer.
1393 __shared_count<_Lp> _M_refcount; // Reference counter.
1394 };
1395
1396
1397 // 20.7.2.2.7 shared_ptr comparisons
1398 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1399 inline bool
1400 operator==(const __shared_ptr<_Tp1, _Lp>& __a,
1401 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1402 { return __a.get() == __b.get(); }
1403
1404 template<typename _Tp, _Lock_policy _Lp>
1405 inline bool
1406 operator==(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1407 { return !__a; }
1408
1409 template<typename _Tp, _Lock_policy _Lp>
1410 inline bool
1411 operator==(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1412 { return !__a; }
1413
1414 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1415 inline bool
1416 operator!=(const __shared_ptr<_Tp1, _Lp>& __a,
1417 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1418 { return __a.get() != __b.get(); }
1419
1420 template<typename _Tp, _Lock_policy _Lp>
1421 inline bool
1422 operator!=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1423 { return (bool)__a; }
1424
1425 template<typename _Tp, _Lock_policy _Lp>
1426 inline bool
1427 operator!=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1428 { return (bool)__a; }
1429
1430 template<typename _Tp, typename _Up, _Lock_policy _Lp>
1431 inline bool
1432 operator<(const __shared_ptr<_Tp, _Lp>& __a,
1433 const __shared_ptr<_Up, _Lp>& __b) noexcept
1434 {
1435 using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1436 using _Up_elt = typename __shared_ptr<_Up, _Lp>::element_type;
1437 using _Vp = typename common_type<_Tp_elt*, _Up_elt*>::type;
1438 return less<_Vp>()(__a.get(), __b.get());
1439 }
1440
1441 template<typename _Tp, _Lock_policy _Lp>
1442 inline bool
1443 operator<(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1444 {
1445 using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1446 return less<_Tp_elt*>()(__a.get(), nullptr);
1447 }
1448
1449 template<typename _Tp, _Lock_policy _Lp>
1450 inline bool
1451 operator<(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1452 {
1453 using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1454 return less<_Tp_elt*>()(nullptr, __a.get());
1455 }
1456
1457 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1458 inline bool
1459 operator<=(const __shared_ptr<_Tp1, _Lp>& __a,
1460 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1461 { return !(__b < __a); }
1462
1463 template<typename _Tp, _Lock_policy _Lp>
1464 inline bool
1465 operator<=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1466 { return !(nullptr < __a); }
1467
1468 template<typename _Tp, _Lock_policy _Lp>
1469 inline bool
1470 operator<=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1471 { return !(__a < nullptr); }
1472
1473 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1474 inline bool
1475 operator>(const __shared_ptr<_Tp1, _Lp>& __a,
1476 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1477 { return (__b < __a); }
1478
1479 template<typename _Tp, _Lock_policy _Lp>
1480 inline bool
1481 operator>(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1482 { return nullptr < __a; }
1483
1484 template<typename _Tp, _Lock_policy _Lp>
1485 inline bool
1486 operator>(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1487 { return __a < nullptr; }
1488
1489 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1490 inline bool
1491 operator>=(const __shared_ptr<_Tp1, _Lp>& __a,
1492 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1493 { return !(__a < __b); }
1494
1495 template<typename _Tp, _Lock_policy _Lp>
1496 inline bool
1497 operator>=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1498 { return !(__a < nullptr); }
1499
1500 template<typename _Tp, _Lock_policy _Lp>
1501 inline bool
1502 operator>=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1503 { return !(nullptr < __a); }
1504
1505 template<typename _Sp>
1506 struct _Sp_less : public binary_function<_Sp, _Sp, bool>
1507 {
1508 bool
1509 operator()(const _Sp& __lhs, const _Sp& __rhs) const noexcept
1510 {
1511 typedef typename _Sp::element_type element_type;
1512 return std::less<element_type*>()(__lhs.get(), __rhs.get());
1513 }
1514 };
1515
1516 template<typename _Tp, _Lock_policy _Lp>
1517 struct less<__shared_ptr<_Tp, _Lp>>
1518 : public _Sp_less<__shared_ptr<_Tp, _Lp>>
1519 { };
1520
1521 // 20.7.2.2.8 shared_ptr specialized algorithms.
1522 template<typename _Tp, _Lock_policy _Lp>
1523 inline void
1524 swap(__shared_ptr<_Tp, _Lp>& __a, __shared_ptr<_Tp, _Lp>& __b) noexcept
1525 { __a.swap(__b); }
1526
1527 // 20.7.2.2.9 shared_ptr casts
1528
1529 // The seemingly equivalent code:
1530 // shared_ptr<_Tp, _Lp>(static_cast<_Tp*>(__r.get()))
1531 // will eventually result in undefined behaviour, attempting to
1532 // delete the same object twice.
1533 /// static_pointer_cast
1534 template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1535 inline __shared_ptr<_Tp, _Lp>
1536 static_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1537 {
1538 using _Sp = __shared_ptr<_Tp, _Lp>;
1539 return _Sp(__r, static_cast<typename _Sp::element_type*>(__r.get()));
1540 }
1541
1542 // The seemingly equivalent code:
1543 // shared_ptr<_Tp, _Lp>(const_cast<_Tp*>(__r.get()))
1544 // will eventually result in undefined behaviour, attempting to
1545 // delete the same object twice.
1546 /// const_pointer_cast
1547 template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1548 inline __shared_ptr<_Tp, _Lp>
1549 const_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1550 {
1551 using _Sp = __shared_ptr<_Tp, _Lp>;
1552 return _Sp(__r, const_cast<typename _Sp::element_type*>(__r.get()));
1553 }
1554
1555 // The seemingly equivalent code:
1556 // shared_ptr<_Tp, _Lp>(dynamic_cast<_Tp*>(__r.get()))
1557 // will eventually result in undefined behaviour, attempting to
1558 // delete the same object twice.
1559 /// dynamic_pointer_cast
1560 template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1561 inline __shared_ptr<_Tp, _Lp>
1562 dynamic_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1563 {
1564 using _Sp = __shared_ptr<_Tp, _Lp>;
1565 if (auto* __p = dynamic_cast<typename _Sp::element_type*>(__r.get()))
1566 return _Sp(__r, __p);
1567 return _Sp();
1568 }
1569
1570#if __cplusplus > 201402L
1571 template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1572 inline __shared_ptr<_Tp, _Lp>
1573 reinterpret_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1574 {
1575 using _Sp = __shared_ptr<_Tp, _Lp>;
1576 return _Sp(__r, reinterpret_cast<typename _Sp::element_type*>(__r.get()));
1577 }
1578#endif
1579
1580 template<typename _Tp, _Lock_policy _Lp>
1581 class __weak_ptr
1582 {
1583 template<typename _Yp, typename _Res = void>
1584 using _Compatible = typename
1585 enable_if<__sp_compatible_with<_Yp*, _Tp*>::value, _Res>::type;
1586
1587 // Constraint for assignment from shared_ptr and weak_ptr:
1588 template<typename _Yp>
1589 using _Assignable = _Compatible<_Yp, __weak_ptr&>;
1590
1591 public:
1592 using element_type = typename remove_extent<_Tp>::type;
1593
1594 constexpr __weak_ptr() noexcept
1595 : _M_ptr(nullptr), _M_refcount()
1596 { }
1597
1598 __weak_ptr(const __weak_ptr&) noexcept = default;
1599
1600 ~__weak_ptr() = default;
1601
1602 // The "obvious" converting constructor implementation:
1603 //
1604 // template<typename _Tp1>
1605 // __weak_ptr(const __weak_ptr<_Tp1, _Lp>& __r)
1606 // : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws
1607 // { }
1608 //
1609 // has a serious problem.
1610 //
1611 // __r._M_ptr may already have been invalidated. The _M_ptr(__r._M_ptr)
1612 // conversion may require access to *__r._M_ptr (virtual inheritance).
1613 //
1614 // It is not possible to avoid spurious access violations since
1615 // in multithreaded programs __r._M_ptr may be invalidated at any point.
1616 template<typename _Yp, typename = _Compatible<_Yp>>
1617 __weak_ptr(const __weak_ptr<_Yp, _Lp>& __r) noexcept
1618 : _M_refcount(__r._M_refcount)
1619 { _M_ptr = __r.lock().get(); }
1620
1621 template<typename _Yp, typename = _Compatible<_Yp>>
1622 __weak_ptr(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1623 : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount)
1624 { }
1625
1626 __weak_ptr(__weak_ptr&& __r) noexcept
1627 : _M_ptr(__r._M_ptr), _M_refcount(std::move(__r._M_refcount))
1628 { __r._M_ptr = nullptr; }
1629
1630 template<typename _Yp, typename = _Compatible<_Yp>>
1631 __weak_ptr(__weak_ptr<_Yp, _Lp>&& __r) noexcept
1632 : _M_ptr(__r.lock().get()), _M_refcount(std::move(__r._M_refcount))
1633 { __r._M_ptr = nullptr; }
1634
1635 __weak_ptr&
1636 operator=(const __weak_ptr& __r) noexcept = default;
1637
1638 template<typename _Yp>
1639 _Assignable<_Yp>
1640 operator=(const __weak_ptr<_Yp, _Lp>& __r) noexcept
1641 {
1642 _M_ptr = __r.lock().get();
1643 _M_refcount = __r._M_refcount;
1644 return *this;
1645 }
1646
1647 template<typename _Yp>
1648 _Assignable<_Yp>
1649 operator=(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1650 {
1651 _M_ptr = __r._M_ptr;
1652 _M_refcount = __r._M_refcount;
1653 return *this;
1654 }
1655
1656 __weak_ptr&
1657 operator=(__weak_ptr&& __r) noexcept
1658 {
1659 _M_ptr = __r._M_ptr;
1660 _M_refcount = std::move(__r._M_refcount);
1661 __r._M_ptr = nullptr;
1662 return *this;
1663 }
1664
1665 template<typename _Yp>
1666 _Assignable<_Yp>
1667 operator=(__weak_ptr<_Yp, _Lp>&& __r) noexcept
1668 {
1669 _M_ptr = __r.lock().get();
1670 _M_refcount = std::move(__r._M_refcount);
1671 __r._M_ptr = nullptr;
1672 return *this;
1673 }
1674
1675 __shared_ptr<_Tp, _Lp>
1676 lock() const noexcept
1677 { return __shared_ptr<element_type, _Lp>(*this, std::nothrow); }
1678
1679 long
1680 use_count() const noexcept
1681 { return _M_refcount._M_get_use_count(); }
1682
1683 bool
1684 expired() const noexcept
1685 { return _M_refcount._M_get_use_count() == 0; }
1686
1687 template<typename _Tp1>
1688 bool
1689 owner_before(const __shared_ptr<_Tp1, _Lp>& __rhs) const noexcept
1690 { return _M_refcount._M_less(__rhs._M_refcount); }
1691
1692 template<typename _Tp1>
1693 bool
1694 owner_before(const __weak_ptr<_Tp1, _Lp>& __rhs) const noexcept
1695 { return _M_refcount._M_less(__rhs._M_refcount); }
1696
1697 void
1698 reset() noexcept
1699 { __weak_ptr().swap(*this); }
1700
1701 void
1702 swap(__weak_ptr& __s) noexcept
1703 {
1704 std::swap(_M_ptr, __s._M_ptr);
1705 _M_refcount._M_swap(__s._M_refcount);
1706 }
1707
1708 private:
1709 // Used by __enable_shared_from_this.
1710 void
1711 _M_assign(_Tp* __ptr, const __shared_count<_Lp>& __refcount) noexcept
1712 {
1713 if (use_count() == 0)
1714 {
1715 _M_ptr = __ptr;
1716 _M_refcount = __refcount;
1717 }
1718 }
1719
1720 template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
1721 template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
1722 friend class __enable_shared_from_this<_Tp, _Lp>;
1723 friend class enable_shared_from_this<_Tp>;
1724
1725 element_type* _M_ptr; // Contained pointer.
1726 __weak_count<_Lp> _M_refcount; // Reference counter.
1727 };
1728
1729 // 20.7.2.3.6 weak_ptr specialized algorithms.
1730 template<typename _Tp, _Lock_policy _Lp>
1731 inline void
1732 swap(__weak_ptr<_Tp, _Lp>& __a, __weak_ptr<_Tp, _Lp>& __b) noexcept
1733 { __a.swap(__b); }
1734
1735 template<typename _Tp, typename _Tp1>
1736 struct _Sp_owner_less : public binary_function<_Tp, _Tp, bool>
1737 {
1738 bool
1739 operator()(const _Tp& __lhs, const _Tp& __rhs) const noexcept
1740 { return __lhs.owner_before(__rhs); }
1741
1742 bool
1743 operator()(const _Tp& __lhs, const _Tp1& __rhs) const noexcept
1744 { return __lhs.owner_before(__rhs); }
1745
1746 bool
1747 operator()(const _Tp1& __lhs, const _Tp& __rhs) const noexcept
1748 { return __lhs.owner_before(__rhs); }
1749 };
1750
1751 template<>
1752 struct _Sp_owner_less<void, void>
1753 {
1754 template<typename _Tp, typename _Up>
1755 auto
1756 operator()(const _Tp& __lhs, const _Up& __rhs) const noexcept
1757 -> decltype(__lhs.owner_before(__rhs))
1758 { return __lhs.owner_before(__rhs); }
1759
1760 using is_transparent = void;
1761 };
1762
1763 template<typename _Tp, _Lock_policy _Lp>
1764 struct owner_less<__shared_ptr<_Tp, _Lp>>
1765 : public _Sp_owner_less<__shared_ptr<_Tp, _Lp>, __weak_ptr<_Tp, _Lp>>
1766 { };
1767
1768 template<typename _Tp, _Lock_policy _Lp>
1769 struct owner_less<__weak_ptr<_Tp, _Lp>>
1770 : public _Sp_owner_less<__weak_ptr<_Tp, _Lp>, __shared_ptr<_Tp, _Lp>>
1771 { };
1772
1773
1774 template<typename _Tp, _Lock_policy _Lp>
1775 class __enable_shared_from_this
1776 {
1777 protected:
1778 constexpr __enable_shared_from_this() noexcept { }
1779
1780 __enable_shared_from_this(const __enable_shared_from_this&) noexcept { }
1781
1782 __enable_shared_from_this&
1783 operator=(const __enable_shared_from_this&) noexcept
1784 { return *this; }
1785
1786 ~__enable_shared_from_this() { }
1787
1788 public:
1789 __shared_ptr<_Tp, _Lp>
1790 shared_from_this()
1791 { return __shared_ptr<_Tp, _Lp>(this->_M_weak_this); }
1792
1793 __shared_ptr<const _Tp, _Lp>
1794 shared_from_this() const
1795 { return __shared_ptr<const _Tp, _Lp>(this->_M_weak_this); }
1796
1797#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
1798 __weak_ptr<_Tp, _Lp>
1799 weak_from_this() noexcept
1800 { return this->_M_weak_this; }
1801
1802 __weak_ptr<const _Tp, _Lp>
1803 weak_from_this() const noexcept
1804 { return this->_M_weak_this; }
1805#endif
1806
1807 private:
1808 template<typename _Tp1>
1809 void
1810 _M_weak_assign(_Tp1* __p, const __shared_count<_Lp>& __n) const noexcept
1811 { _M_weak_this._M_assign(__p, __n); }
1812
1813 friend const __enable_shared_from_this*
1814 __enable_shared_from_this_base(const __shared_count<_Lp>&,
1815 const __enable_shared_from_this* __p)
1816 { return __p; }
1817
1818 template<typename, _Lock_policy>
1819 friend class __shared_ptr;
1820
1821 mutable __weak_ptr<_Tp, _Lp> _M_weak_this;
1822 };
1823
1824 template<typename _Tp, _Lock_policy _Lp, typename _Alloc, typename... _Args>
1825 inline __shared_ptr<_Tp, _Lp>
1826 __allocate_shared(const _Alloc& __a, _Args&&... __args)
1827 {
1828 return __shared_ptr<_Tp, _Lp>(_Sp_make_shared_tag(), __a,
1829 std::forward<_Args>(__args)...);
1830 }
1831
1832 template<typename _Tp, _Lock_policy _Lp, typename... _Args>
1833 inline __shared_ptr<_Tp, _Lp>
1834 __make_shared(_Args&&... __args)
1835 {
1836 typedef typename std::remove_const<_Tp>::type _Tp_nc;
1837 return std::__allocate_shared<_Tp, _Lp>(std::allocator<_Tp_nc>(),
1838 std::forward<_Args>(__args)...);
1839 }
1840
1841 /// std::hash specialization for __shared_ptr.
1842 template<typename _Tp, _Lock_policy _Lp>
1843 struct hash<__shared_ptr<_Tp, _Lp>>
1844 : public __hash_base<size_t, __shared_ptr<_Tp, _Lp>>
1845 {
1846 size_t
1847 operator()(const __shared_ptr<_Tp, _Lp>& __s) const noexcept
1848 {
1849 return hash<typename __shared_ptr<_Tp, _Lp>::element_type*>()(
1850 __s.get());
1851 }
1852 };
1853
1854_GLIBCXX_END_NAMESPACE_VERSION
1855} // namespace
1856
1857#endif // _SHARED_PTR_BASE_H
1858