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 private:
504 template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
505 friend class _Sp_counted_ptr_inplace;
506
507 static const type_info&
508 _S_ti() noexcept _GLIBCXX_VISIBILITY(default)
509 {
510 alignas(type_info) static constexpr char __tag[sizeof(type_info)] = { };
511 return reinterpret_cast<const type_info&>(__tag);
512 }
513 };
514
515 template<typename _Alloc>
516 struct _Sp_alloc_shared_tag
517 {
518 const _Alloc& _M_a;
519 };
520
521 template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
522 class _Sp_counted_ptr_inplace final : public _Sp_counted_base<_Lp>
523 {
524 class _Impl : _Sp_ebo_helper<0, _Alloc>
525 {
526 typedef _Sp_ebo_helper<0, _Alloc> _A_base;
527
528 public:
529 explicit _Impl(_Alloc __a) noexcept : _A_base(__a) { }
530
531 _Alloc& _M_alloc() noexcept { return _A_base::_S_get(*this); }
532
533 __gnu_cxx::__aligned_buffer<_Tp> _M_storage;
534 };
535
536 public:
537 using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_ptr_inplace>;
538
539 template<typename... _Args>
540 _Sp_counted_ptr_inplace(_Alloc __a, _Args&&... __args)
541 : _M_impl(__a)
542 {
543 // _GLIBCXX_RESOLVE_LIB_DEFECTS
544 // 2070. allocate_shared should use allocator_traits<A>::construct
545 allocator_traits<_Alloc>::construct(__a, _M_ptr(),
546 std::forward<_Args>(__args)...); // might throw
547 }
548
549 ~_Sp_counted_ptr_inplace() noexcept { }
550
551 virtual void
552 _M_dispose() noexcept
553 {
554 allocator_traits<_Alloc>::destroy(_M_impl._M_alloc(), _M_ptr());
555 }
556
557 // Override because the allocator needs to know the dynamic type
558 virtual void
559 _M_destroy() noexcept
560 {
561 __allocator_type __a(_M_impl._M_alloc());
562 __allocated_ptr<__allocator_type> __guard_ptr{ __a, this };
563 this->~_Sp_counted_ptr_inplace();
564 }
565
566 private:
567 friend class __shared_count<_Lp>; // To be able to call _M_ptr().
568
569 // No longer used, but code compiled against old libstdc++ headers
570 // might still call it from __shared_ptr ctor to get the pointer out.
571 virtual void*
572 _M_get_deleter(const std::type_info& __ti) noexcept override
573 {
574 // Check for the fake type_info first, so we don't try to access it
575 // as a real type_info object.
576 if (&__ti == &_Sp_make_shared_tag::_S_ti())
577 return const_cast<typename remove_cv<_Tp>::type*>(_M_ptr());
578#if __cpp_rtti
579 // Callers compiled with old libstdc++ headers and RTTI enabled
580 // might pass this instead:
581 else if (__ti == typeid(_Sp_make_shared_tag))
582 return const_cast<typename remove_cv<_Tp>::type*>(_M_ptr());
583#else
584 // Cannot detect a real type_info object. If the linker keeps a
585 // definition of this function compiled with -fno-rtti then callers
586 // that have RTTI enabled and pass a real type_info object will get
587 // a null pointer returned.
588#endif
589 return nullptr;
590 }
591
592 _Tp* _M_ptr() noexcept { return _M_impl._M_storage._M_ptr(); }
593
594 _Impl _M_impl;
595 };
596
597 // The default deleter for shared_ptr<T[]> and shared_ptr<T[N]>.
598 struct __sp_array_delete
599 {
600 template<typename _Yp>
601 void operator()(_Yp* __p) const { delete[] __p; }
602 };
603
604 template<_Lock_policy _Lp>
605 class __shared_count
606 {
607 template<typename _Tp>
608 struct __not_alloc_shared_tag { using type = void; };
609
610 template<typename _Tp>
611 struct __not_alloc_shared_tag<_Sp_alloc_shared_tag<_Tp>> { };
612
613 public:
614 constexpr __shared_count() noexcept : _M_pi(0)
615 { }
616
617 template<typename _Ptr>
618 explicit
619 __shared_count(_Ptr __p) : _M_pi(0)
620 {
621 __try
622 {
623 _M_pi = new _Sp_counted_ptr<_Ptr, _Lp>(__p);
624 }
625 __catch(...)
626 {
627 delete __p;
628 __throw_exception_again;
629 }
630 }
631
632 template<typename _Ptr>
633 __shared_count(_Ptr __p, /* is_array = */ false_type)
634 : __shared_count(__p)
635 { }
636
637 template<typename _Ptr>
638 __shared_count(_Ptr __p, /* is_array = */ true_type)
639 : __shared_count(__p, __sp_array_delete{}, allocator<void>())
640 { }
641
642 template<typename _Ptr, typename _Deleter,
643 typename = typename __not_alloc_shared_tag<_Deleter>::type>
644 __shared_count(_Ptr __p, _Deleter __d)
645 : __shared_count(__p, std::move(__d), allocator<void>())
646 { }
647
648 template<typename _Ptr, typename _Deleter, typename _Alloc,
649 typename = typename __not_alloc_shared_tag<_Deleter>::type>
650 __shared_count(_Ptr __p, _Deleter __d, _Alloc __a) : _M_pi(0)
651 {
652 typedef _Sp_counted_deleter<_Ptr, _Deleter, _Alloc, _Lp> _Sp_cd_type;
653 __try
654 {
655 typename _Sp_cd_type::__allocator_type __a2(__a);
656 auto __guard = std::__allocate_guarded(__a2);
657 _Sp_cd_type* __mem = __guard.get();
658 ::new (__mem) _Sp_cd_type(__p, std::move(__d), std::move(__a));
659 _M_pi = __mem;
660 __guard = nullptr;
661 }
662 __catch(...)
663 {
664 __d(__p); // Call _Deleter on __p.
665 __throw_exception_again;
666 }
667 }
668
669 template<typename _Tp, typename _Alloc, typename... _Args>
670 __shared_count(_Tp*& __p, _Sp_alloc_shared_tag<_Alloc> __a,
671 _Args&&... __args)
672 {
673 typedef _Sp_counted_ptr_inplace<_Tp, _Alloc, _Lp> _Sp_cp_type;
674 typename _Sp_cp_type::__allocator_type __a2(__a._M_a);
675 auto __guard = std::__allocate_guarded(__a2);
676 _Sp_cp_type* __mem = __guard.get();
677 auto __pi = ::new (__mem)
678 _Sp_cp_type(__a._M_a, std::forward<_Args>(__args)...);
679 __guard = nullptr;
680 _M_pi = __pi;
681 __p = __pi->_M_ptr();
682 }
683
684#if _GLIBCXX_USE_DEPRECATED
685#pragma GCC diagnostic push
686#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
687 // Special case for auto_ptr<_Tp> to provide the strong guarantee.
688 template<typename _Tp>
689 explicit
690 __shared_count(std::auto_ptr<_Tp>&& __r);
691#pragma GCC diagnostic pop
692#endif
693
694 // Special case for unique_ptr<_Tp,_Del> to provide the strong guarantee.
695 template<typename _Tp, typename _Del>
696 explicit
697 __shared_count(std::unique_ptr<_Tp, _Del>&& __r) : _M_pi(0)
698 {
699 // _GLIBCXX_RESOLVE_LIB_DEFECTS
700 // 2415. Inconsistency between unique_ptr and shared_ptr
701 if (__r.get() == nullptr)
702 return;
703
704 using _Ptr = typename unique_ptr<_Tp, _Del>::pointer;
705 using _Del2 = typename conditional<is_reference<_Del>::value,
706 reference_wrapper<typename remove_reference<_Del>::type>,
707 _Del>::type;
708 using _Sp_cd_type
709 = _Sp_counted_deleter<_Ptr, _Del2, allocator<void>, _Lp>;
710 using _Alloc = allocator<_Sp_cd_type>;
711 using _Alloc_traits = allocator_traits<_Alloc>;
712 _Alloc __a;
713 _Sp_cd_type* __mem = _Alloc_traits::allocate(__a, 1);
714 _Alloc_traits::construct(__a, __mem, __r.release(),
715 __r.get_deleter()); // non-throwing
716 _M_pi = __mem;
717 }
718
719 // Throw bad_weak_ptr when __r._M_get_use_count() == 0.
720 explicit __shared_count(const __weak_count<_Lp>& __r);
721
722 // Does not throw if __r._M_get_use_count() == 0, caller must check.
723 explicit __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t);
724
725 ~__shared_count() noexcept
726 {
727 if (_M_pi != nullptr)
728 _M_pi->_M_release();
729 }
730
731 __shared_count(const __shared_count& __r) noexcept
732 : _M_pi(__r._M_pi)
733 {
734 if (_M_pi != 0)
735 _M_pi->_M_add_ref_copy();
736 }
737
738 __shared_count&
739 operator=(const __shared_count& __r) noexcept
740 {
741 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
742 if (__tmp != _M_pi)
743 {
744 if (__tmp != 0)
745 __tmp->_M_add_ref_copy();
746 if (_M_pi != 0)
747 _M_pi->_M_release();
748 _M_pi = __tmp;
749 }
750 return *this;
751 }
752
753 void
754 _M_swap(__shared_count& __r) noexcept
755 {
756 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
757 __r._M_pi = _M_pi;
758 _M_pi = __tmp;
759 }
760
761 long
762 _M_get_use_count() const noexcept
763 { return _M_pi != 0 ? _M_pi->_M_get_use_count() : 0; }
764
765 bool
766 _M_unique() const noexcept
767 { return this->_M_get_use_count() == 1; }
768
769 void*
770 _M_get_deleter(const std::type_info& __ti) const noexcept
771 { return _M_pi ? _M_pi->_M_get_deleter(__ti) : nullptr; }
772
773 bool
774 _M_less(const __shared_count& __rhs) const noexcept
775 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
776
777 bool
778 _M_less(const __weak_count<_Lp>& __rhs) const noexcept
779 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
780
781 // Friend function injected into enclosing namespace and found by ADL
782 friend inline bool
783 operator==(const __shared_count& __a, const __shared_count& __b) noexcept
784 { return __a._M_pi == __b._M_pi; }
785
786 private:
787 friend class __weak_count<_Lp>;
788
789 _Sp_counted_base<_Lp>* _M_pi;
790 };
791
792
793 template<_Lock_policy _Lp>
794 class __weak_count
795 {
796 public:
797 constexpr __weak_count() noexcept : _M_pi(nullptr)
798 { }
799
800 __weak_count(const __shared_count<_Lp>& __r) noexcept
801 : _M_pi(__r._M_pi)
802 {
803 if (_M_pi != nullptr)
804 _M_pi->_M_weak_add_ref();
805 }
806
807 __weak_count(const __weak_count& __r) noexcept
808 : _M_pi(__r._M_pi)
809 {
810 if (_M_pi != nullptr)
811 _M_pi->_M_weak_add_ref();
812 }
813
814 __weak_count(__weak_count&& __r) noexcept
815 : _M_pi(__r._M_pi)
816 { __r._M_pi = nullptr; }
817
818 ~__weak_count() noexcept
819 {
820 if (_M_pi != nullptr)
821 _M_pi->_M_weak_release();
822 }
823
824 __weak_count&
825 operator=(const __shared_count<_Lp>& __r) noexcept
826 {
827 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
828 if (__tmp != nullptr)
829 __tmp->_M_weak_add_ref();
830 if (_M_pi != nullptr)
831 _M_pi->_M_weak_release();
832 _M_pi = __tmp;
833 return *this;
834 }
835
836 __weak_count&
837 operator=(const __weak_count& __r) noexcept
838 {
839 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
840 if (__tmp != nullptr)
841 __tmp->_M_weak_add_ref();
842 if (_M_pi != nullptr)
843 _M_pi->_M_weak_release();
844 _M_pi = __tmp;
845 return *this;
846 }
847
848 __weak_count&
849 operator=(__weak_count&& __r) noexcept
850 {
851 if (_M_pi != nullptr)
852 _M_pi->_M_weak_release();
853 _M_pi = __r._M_pi;
854 __r._M_pi = nullptr;
855 return *this;
856 }
857
858 void
859 _M_swap(__weak_count& __r) noexcept
860 {
861 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
862 __r._M_pi = _M_pi;
863 _M_pi = __tmp;
864 }
865
866 long
867 _M_get_use_count() const noexcept
868 { return _M_pi != nullptr ? _M_pi->_M_get_use_count() : 0; }
869
870 bool
871 _M_less(const __weak_count& __rhs) const noexcept
872 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
873
874 bool
875 _M_less(const __shared_count<_Lp>& __rhs) const noexcept
876 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
877
878 // Friend function injected into enclosing namespace and found by ADL
879 friend inline bool
880 operator==(const __weak_count& __a, const __weak_count& __b) noexcept
881 { return __a._M_pi == __b._M_pi; }
882
883 private:
884 friend class __shared_count<_Lp>;
885
886 _Sp_counted_base<_Lp>* _M_pi;
887 };
888
889 // Now that __weak_count is defined we can define this constructor:
890 template<_Lock_policy _Lp>
891 inline
892 __shared_count<_Lp>::__shared_count(const __weak_count<_Lp>& __r)
893 : _M_pi(__r._M_pi)
894 {
895 if (_M_pi != nullptr)
896 _M_pi->_M_add_ref_lock();
897 else
898 __throw_bad_weak_ptr();
899 }
900
901 // Now that __weak_count is defined we can define this constructor:
902 template<_Lock_policy _Lp>
903 inline
904 __shared_count<_Lp>::
905 __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t)
906 : _M_pi(__r._M_pi)
907 {
908 if (_M_pi != nullptr)
909 if (!_M_pi->_M_add_ref_lock_nothrow())
910 _M_pi = nullptr;
911 }
912
913#define __cpp_lib_shared_ptr_arrays 201603
914
915 // Helper traits for shared_ptr of array:
916
917 // A pointer type Y* is said to be compatible with a pointer type T* when
918 // either Y* is convertible to T* or Y is U[N] and T is U cv [].
919 template<typename _Yp_ptr, typename _Tp_ptr>
920 struct __sp_compatible_with
921 : false_type
922 { };
923
924 template<typename _Yp, typename _Tp>
925 struct __sp_compatible_with<_Yp*, _Tp*>
926 : is_convertible<_Yp*, _Tp*>::type
927 { };
928
929 template<typename _Up, size_t _Nm>
930 struct __sp_compatible_with<_Up(*)[_Nm], _Up(*)[]>
931 : true_type
932 { };
933
934 template<typename _Up, size_t _Nm>
935 struct __sp_compatible_with<_Up(*)[_Nm], const _Up(*)[]>
936 : true_type
937 { };
938
939 template<typename _Up, size_t _Nm>
940 struct __sp_compatible_with<_Up(*)[_Nm], volatile _Up(*)[]>
941 : true_type
942 { };
943
944 template<typename _Up, size_t _Nm>
945 struct __sp_compatible_with<_Up(*)[_Nm], const volatile _Up(*)[]>
946 : true_type
947 { };
948
949 // Test conversion from Y(*)[N] to U(*)[N] without forming invalid type Y[N].
950 template<typename _Up, size_t _Nm, typename _Yp, typename = void>
951 struct __sp_is_constructible_arrN
952 : false_type
953 { };
954
955 template<typename _Up, size_t _Nm, typename _Yp>
956 struct __sp_is_constructible_arrN<_Up, _Nm, _Yp, __void_t<_Yp[_Nm]>>
957 : is_convertible<_Yp(*)[_Nm], _Up(*)[_Nm]>::type
958 { };
959
960 // Test conversion from Y(*)[] to U(*)[] without forming invalid type Y[].
961 template<typename _Up, typename _Yp, typename = void>
962 struct __sp_is_constructible_arr
963 : false_type
964 { };
965
966 template<typename _Up, typename _Yp>
967 struct __sp_is_constructible_arr<_Up, _Yp, __void_t<_Yp[]>>
968 : is_convertible<_Yp(*)[], _Up(*)[]>::type
969 { };
970
971 // Trait to check if shared_ptr<T> can be constructed from Y*.
972 template<typename _Tp, typename _Yp>
973 struct __sp_is_constructible;
974
975 // When T is U[N], Y(*)[N] shall be convertible to T*;
976 template<typename _Up, size_t _Nm, typename _Yp>
977 struct __sp_is_constructible<_Up[_Nm], _Yp>
978 : __sp_is_constructible_arrN<_Up, _Nm, _Yp>::type
979 { };
980
981 // when T is U[], Y(*)[] shall be convertible to T*;
982 template<typename _Up, typename _Yp>
983 struct __sp_is_constructible<_Up[], _Yp>
984 : __sp_is_constructible_arr<_Up, _Yp>::type
985 { };
986
987 // otherwise, Y* shall be convertible to T*.
988 template<typename _Tp, typename _Yp>
989 struct __sp_is_constructible
990 : is_convertible<_Yp*, _Tp*>::type
991 { };
992
993
994 // Define operator* and operator-> for shared_ptr<T>.
995 template<typename _Tp, _Lock_policy _Lp,
996 bool = is_array<_Tp>::value, bool = is_void<_Tp>::value>
997 class __shared_ptr_access
998 {
999 public:
1000 using element_type = _Tp;
1001
1002 element_type&
1003 operator*() const noexcept
1004 {
1005 __glibcxx_assert(_M_get() != nullptr);
1006 return *_M_get();
1007 }
1008
1009 element_type*
1010 operator->() const noexcept
1011 {
1012 _GLIBCXX_DEBUG_PEDASSERT(_M_get() != nullptr);
1013 return _M_get();
1014 }
1015
1016 private:
1017 element_type*
1018 _M_get() const noexcept
1019 { return static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get(); }
1020 };
1021
1022 // Define operator-> for shared_ptr<cv void>.
1023 template<typename _Tp, _Lock_policy _Lp>
1024 class __shared_ptr_access<_Tp, _Lp, false, true>
1025 {
1026 public:
1027 using element_type = _Tp;
1028
1029 element_type*
1030 operator->() const noexcept
1031 {
1032 auto __ptr = static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get();
1033 _GLIBCXX_DEBUG_PEDASSERT(__ptr != nullptr);
1034 return __ptr;
1035 }
1036 };
1037
1038 // Define operator[] for shared_ptr<T[]> and shared_ptr<T[N]>.
1039 template<typename _Tp, _Lock_policy _Lp>
1040 class __shared_ptr_access<_Tp, _Lp, true, false>
1041 {
1042 public:
1043 using element_type = typename remove_extent<_Tp>::type;
1044
1045#if __cplusplus <= 201402L
1046 [[__deprecated__("shared_ptr<T[]>::operator* is absent from C++17")]]
1047 element_type&
1048 operator*() const noexcept
1049 {
1050 __glibcxx_assert(_M_get() != nullptr);
1051 return *_M_get();
1052 }
1053
1054 [[__deprecated__("shared_ptr<T[]>::operator-> is absent from C++17")]]
1055 element_type*
1056 operator->() const noexcept
1057 {
1058 _GLIBCXX_DEBUG_PEDASSERT(_M_get() != nullptr);
1059 return _M_get();
1060 }
1061#endif
1062
1063 element_type&
1064 operator[](ptrdiff_t __i) const
1065 {
1066 __glibcxx_assert(_M_get() != nullptr);
1067 __glibcxx_assert(!extent<_Tp>::value || __i < extent<_Tp>::value);
1068 return _M_get()[__i];
1069 }
1070
1071 private:
1072 element_type*
1073 _M_get() const noexcept
1074 { return static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get(); }
1075 };
1076
1077 template<typename _Tp, _Lock_policy _Lp>
1078 class __shared_ptr
1079 : public __shared_ptr_access<_Tp, _Lp>
1080 {
1081 public:
1082 using element_type = typename remove_extent<_Tp>::type;
1083
1084 private:
1085 // Constraint for taking ownership of a pointer of type _Yp*:
1086 template<typename _Yp>
1087 using _SafeConv
1088 = typename enable_if<__sp_is_constructible<_Tp, _Yp>::value>::type;
1089
1090 // Constraint for construction from shared_ptr and weak_ptr:
1091 template<typename _Yp, typename _Res = void>
1092 using _Compatible = typename
1093 enable_if<__sp_compatible_with<_Yp*, _Tp*>::value, _Res>::type;
1094
1095 // Constraint for assignment from shared_ptr and weak_ptr:
1096 template<typename _Yp>
1097 using _Assignable = _Compatible<_Yp, __shared_ptr&>;
1098
1099 // Constraint for construction from unique_ptr:
1100 template<typename _Yp, typename _Del, typename _Res = void,
1101 typename _Ptr = typename unique_ptr<_Yp, _Del>::pointer>
1102 using _UniqCompatible = typename enable_if<__and_<
1103 __sp_compatible_with<_Yp*, _Tp*>, is_convertible<_Ptr, element_type*>
1104 >::value, _Res>::type;
1105
1106 // Constraint for assignment from unique_ptr:
1107 template<typename _Yp, typename _Del>
1108 using _UniqAssignable = _UniqCompatible<_Yp, _Del, __shared_ptr&>;
1109
1110 public:
1111
1112#if __cplusplus > 201402L
1113 using weak_type = __weak_ptr<_Tp, _Lp>;
1114#endif
1115
1116 constexpr __shared_ptr() noexcept
1117 : _M_ptr(0), _M_refcount()
1118 { }
1119
1120 template<typename _Yp, typename = _SafeConv<_Yp>>
1121 explicit
1122 __shared_ptr(_Yp* __p)
1123 : _M_ptr(__p), _M_refcount(__p, typename is_array<_Tp>::type())
1124 {
1125 static_assert( !is_void<_Yp>::value, "incomplete type" );
1126 static_assert( sizeof(_Yp) > 0, "incomplete type" );
1127 _M_enable_shared_from_this_with(__p);
1128 }
1129
1130 template<typename _Yp, typename _Deleter, typename = _SafeConv<_Yp>>
1131 __shared_ptr(_Yp* __p, _Deleter __d)
1132 : _M_ptr(__p), _M_refcount(__p, std::move(__d))
1133 {
1134 static_assert(__is_invocable<_Deleter&, _Yp*&>::value,
1135 "deleter expression d(p) is well-formed");
1136 _M_enable_shared_from_this_with(__p);
1137 }
1138
1139 template<typename _Yp, typename _Deleter, typename _Alloc,
1140 typename = _SafeConv<_Yp>>
1141 __shared_ptr(_Yp* __p, _Deleter __d, _Alloc __a)
1142 : _M_ptr(__p), _M_refcount(__p, std::move(__d), std::move(__a))
1143 {
1144 static_assert(__is_invocable<_Deleter&, _Yp*&>::value,
1145 "deleter expression d(p) is well-formed");
1146 _M_enable_shared_from_this_with(__p);
1147 }
1148
1149 template<typename _Deleter>
1150 __shared_ptr(nullptr_t __p, _Deleter __d)
1151 : _M_ptr(0), _M_refcount(__p, std::move(__d))
1152 { }
1153
1154 template<typename _Deleter, typename _Alloc>
1155 __shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
1156 : _M_ptr(0), _M_refcount(__p, std::move(__d), std::move(__a))
1157 { }
1158
1159 template<typename _Yp>
1160 __shared_ptr(const __shared_ptr<_Yp, _Lp>& __r,
1161 element_type* __p) noexcept
1162 : _M_ptr(__p), _M_refcount(__r._M_refcount) // never throws
1163 { }
1164
1165 __shared_ptr(const __shared_ptr&) noexcept = default;
1166 __shared_ptr& operator=(const __shared_ptr&) noexcept = default;
1167 ~__shared_ptr() = default;
1168
1169 template<typename _Yp, typename = _Compatible<_Yp>>
1170 __shared_ptr(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1171 : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount)
1172 { }
1173
1174 __shared_ptr(__shared_ptr&& __r) noexcept
1175 : _M_ptr(__r._M_ptr), _M_refcount()
1176 {
1177 _M_refcount._M_swap(__r._M_refcount);
1178 __r._M_ptr = 0;
1179 }
1180
1181 template<typename _Yp, typename = _Compatible<_Yp>>
1182 __shared_ptr(__shared_ptr<_Yp, _Lp>&& __r) noexcept
1183 : _M_ptr(__r._M_ptr), _M_refcount()
1184 {
1185 _M_refcount._M_swap(__r._M_refcount);
1186 __r._M_ptr = 0;
1187 }
1188
1189 template<typename _Yp, typename = _Compatible<_Yp>>
1190 explicit __shared_ptr(const __weak_ptr<_Yp, _Lp>& __r)
1191 : _M_refcount(__r._M_refcount) // may throw
1192 {
1193 // It is now safe to copy __r._M_ptr, as
1194 // _M_refcount(__r._M_refcount) did not throw.
1195 _M_ptr = __r._M_ptr;
1196 }
1197
1198 // If an exception is thrown this constructor has no effect.
1199 template<typename _Yp, typename _Del,
1200 typename = _UniqCompatible<_Yp, _Del>>
1201 __shared_ptr(unique_ptr<_Yp, _Del>&& __r)
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
1209#if __cplusplus <= 201402L && _GLIBCXX_USE_DEPRECATED
1210 protected:
1211 // If an exception is thrown this constructor has no effect.
1212 template<typename _Tp1, typename _Del,
1213 typename enable_if<__and_<
1214 __not_<is_array<_Tp>>, is_array<_Tp1>,
1215 is_convertible<typename unique_ptr<_Tp1, _Del>::pointer, _Tp*>
1216 >::value, bool>::type = true>
1217 __shared_ptr(unique_ptr<_Tp1, _Del>&& __r, __sp_array_delete)
1218 : _M_ptr(__r.get()), _M_refcount()
1219 {
1220 auto __raw = __to_address(__r.get());
1221 _M_refcount = __shared_count<_Lp>(std::move(__r));
1222 _M_enable_shared_from_this_with(__raw);
1223 }
1224 public:
1225#endif
1226
1227#if _GLIBCXX_USE_DEPRECATED
1228#pragma GCC diagnostic push
1229#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
1230 // Postcondition: use_count() == 1 and __r.get() == 0
1231 template<typename _Yp, typename = _Compatible<_Yp>>
1232 __shared_ptr(auto_ptr<_Yp>&& __r);
1233#pragma GCC diagnostic pop
1234#endif
1235
1236 constexpr __shared_ptr(nullptr_t) noexcept : __shared_ptr() { }
1237
1238 template<typename _Yp>
1239 _Assignable<_Yp>
1240 operator=(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1241 {
1242 _M_ptr = __r._M_ptr;
1243 _M_refcount = __r._M_refcount; // __shared_count::op= doesn't throw
1244 return *this;
1245 }
1246
1247#if _GLIBCXX_USE_DEPRECATED
1248#pragma GCC diagnostic push
1249#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
1250 template<typename _Yp>
1251 _Assignable<_Yp>
1252 operator=(auto_ptr<_Yp>&& __r)
1253 {
1254 __shared_ptr(std::move(__r)).swap(*this);
1255 return *this;
1256 }
1257#pragma GCC diagnostic pop
1258#endif
1259
1260 __shared_ptr&
1261 operator=(__shared_ptr&& __r) noexcept
1262 {
1263 __shared_ptr(std::move(__r)).swap(*this);
1264 return *this;
1265 }
1266
1267 template<class _Yp>
1268 _Assignable<_Yp>
1269 operator=(__shared_ptr<_Yp, _Lp>&& __r) noexcept
1270 {
1271 __shared_ptr(std::move(__r)).swap(*this);
1272 return *this;
1273 }
1274
1275 template<typename _Yp, typename _Del>
1276 _UniqAssignable<_Yp, _Del>
1277 operator=(unique_ptr<_Yp, _Del>&& __r)
1278 {
1279 __shared_ptr(std::move(__r)).swap(*this);
1280 return *this;
1281 }
1282
1283 void
1284 reset() noexcept
1285 { __shared_ptr().swap(*this); }
1286
1287 template<typename _Yp>
1288 _SafeConv<_Yp>
1289 reset(_Yp* __p) // _Yp must be complete.
1290 {
1291 // Catch self-reset errors.
1292 __glibcxx_assert(__p == 0 || __p != _M_ptr);
1293 __shared_ptr(__p).swap(*this);
1294 }
1295
1296 template<typename _Yp, typename _Deleter>
1297 _SafeConv<_Yp>
1298 reset(_Yp* __p, _Deleter __d)
1299 { __shared_ptr(__p, std::move(__d)).swap(*this); }
1300
1301 template<typename _Yp, typename _Deleter, typename _Alloc>
1302 _SafeConv<_Yp>
1303 reset(_Yp* __p, _Deleter __d, _Alloc __a)
1304 { __shared_ptr(__p, std::move(__d), std::move(__a)).swap(*this); }
1305
1306 element_type*
1307 get() const noexcept
1308 { return _M_ptr; }
1309
1310 explicit operator bool() const // never throws
1311 { return _M_ptr == 0 ? false : true; }
1312
1313 bool
1314 unique() const noexcept
1315 { return _M_refcount._M_unique(); }
1316
1317 long
1318 use_count() const noexcept
1319 { return _M_refcount._M_get_use_count(); }
1320
1321 void
1322 swap(__shared_ptr<_Tp, _Lp>& __other) noexcept
1323 {
1324 std::swap(_M_ptr, __other._M_ptr);
1325 _M_refcount._M_swap(__other._M_refcount);
1326 }
1327
1328 template<typename _Tp1>
1329 bool
1330 owner_before(__shared_ptr<_Tp1, _Lp> const& __rhs) const noexcept
1331 { return _M_refcount._M_less(__rhs._M_refcount); }
1332
1333 template<typename _Tp1>
1334 bool
1335 owner_before(__weak_ptr<_Tp1, _Lp> const& __rhs) const noexcept
1336 { return _M_refcount._M_less(__rhs._M_refcount); }
1337
1338 protected:
1339 // This constructor is non-standard, it is used by allocate_shared.
1340 template<typename _Alloc, typename... _Args>
1341 __shared_ptr(_Sp_alloc_shared_tag<_Alloc> __tag, _Args&&... __args)
1342 : _M_ptr(), _M_refcount(_M_ptr, __tag, std::forward<_Args>(__args)...)
1343 { _M_enable_shared_from_this_with(_M_ptr); }
1344
1345 template<typename _Tp1, _Lock_policy _Lp1, typename _Alloc,
1346 typename... _Args>
1347 friend __shared_ptr<_Tp1, _Lp1>
1348 __allocate_shared(const _Alloc& __a, _Args&&... __args);
1349
1350 // This constructor is used by __weak_ptr::lock() and
1351 // shared_ptr::shared_ptr(const weak_ptr&, std::nothrow_t).
1352 __shared_ptr(const __weak_ptr<_Tp, _Lp>& __r, std::nothrow_t)
1353 : _M_refcount(__r._M_refcount, std::nothrow)
1354 {
1355 _M_ptr = _M_refcount._M_get_use_count() ? __r._M_ptr : nullptr;
1356 }
1357
1358 friend class __weak_ptr<_Tp, _Lp>;
1359
1360 private:
1361
1362 template<typename _Yp>
1363 using __esft_base_t = decltype(__enable_shared_from_this_base(
1364 std::declval<const __shared_count<_Lp>&>(),
1365 std::declval<_Yp*>()));
1366
1367 // Detect an accessible and unambiguous enable_shared_from_this base.
1368 template<typename _Yp, typename = void>
1369 struct __has_esft_base
1370 : false_type { };
1371
1372 template<typename _Yp>
1373 struct __has_esft_base<_Yp, __void_t<__esft_base_t<_Yp>>>
1374 : __not_<is_array<_Tp>> { }; // No enable shared_from_this for arrays
1375
1376 template<typename _Yp, typename _Yp2 = typename remove_cv<_Yp>::type>
1377 typename enable_if<__has_esft_base<_Yp2>::value>::type
1378 _M_enable_shared_from_this_with(_Yp* __p) noexcept
1379 {
1380 if (auto __base = __enable_shared_from_this_base(_M_refcount, __p))
1381 __base->_M_weak_assign(const_cast<_Yp2*>(__p), _M_refcount);
1382 }
1383
1384 template<typename _Yp, typename _Yp2 = typename remove_cv<_Yp>::type>
1385 typename enable_if<!__has_esft_base<_Yp2>::value>::type
1386 _M_enable_shared_from_this_with(_Yp*) noexcept
1387 { }
1388
1389 void*
1390 _M_get_deleter(const std::type_info& __ti) const noexcept
1391 { return _M_refcount._M_get_deleter(__ti); }
1392
1393 template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
1394 template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
1395
1396 template<typename _Del, typename _Tp1, _Lock_policy _Lp1>
1397 friend _Del* get_deleter(const __shared_ptr<_Tp1, _Lp1>&) noexcept;
1398
1399 template<typename _Del, typename _Tp1>
1400 friend _Del* get_deleter(const shared_ptr<_Tp1>&) noexcept;
1401
1402 element_type* _M_ptr; // Contained pointer.
1403 __shared_count<_Lp> _M_refcount; // Reference counter.
1404 };
1405
1406
1407 // 20.7.2.2.7 shared_ptr comparisons
1408 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1409 inline bool
1410 operator==(const __shared_ptr<_Tp1, _Lp>& __a,
1411 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1412 { return __a.get() == __b.get(); }
1413
1414 template<typename _Tp, _Lock_policy _Lp>
1415 inline bool
1416 operator==(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1417 { return !__a; }
1418
1419 template<typename _Tp, _Lock_policy _Lp>
1420 inline bool
1421 operator==(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1422 { return !__a; }
1423
1424 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1425 inline bool
1426 operator!=(const __shared_ptr<_Tp1, _Lp>& __a,
1427 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1428 { return __a.get() != __b.get(); }
1429
1430 template<typename _Tp, _Lock_policy _Lp>
1431 inline bool
1432 operator!=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1433 { return (bool)__a; }
1434
1435 template<typename _Tp, _Lock_policy _Lp>
1436 inline bool
1437 operator!=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1438 { return (bool)__a; }
1439
1440 template<typename _Tp, typename _Up, _Lock_policy _Lp>
1441 inline bool
1442 operator<(const __shared_ptr<_Tp, _Lp>& __a,
1443 const __shared_ptr<_Up, _Lp>& __b) noexcept
1444 {
1445 using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1446 using _Up_elt = typename __shared_ptr<_Up, _Lp>::element_type;
1447 using _Vp = typename common_type<_Tp_elt*, _Up_elt*>::type;
1448 return less<_Vp>()(__a.get(), __b.get());
1449 }
1450
1451 template<typename _Tp, _Lock_policy _Lp>
1452 inline bool
1453 operator<(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1454 {
1455 using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1456 return less<_Tp_elt*>()(__a.get(), nullptr);
1457 }
1458
1459 template<typename _Tp, _Lock_policy _Lp>
1460 inline bool
1461 operator<(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1462 {
1463 using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1464 return less<_Tp_elt*>()(nullptr, __a.get());
1465 }
1466
1467 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1468 inline bool
1469 operator<=(const __shared_ptr<_Tp1, _Lp>& __a,
1470 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1471 { return !(__b < __a); }
1472
1473 template<typename _Tp, _Lock_policy _Lp>
1474 inline bool
1475 operator<=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1476 { return !(nullptr < __a); }
1477
1478 template<typename _Tp, _Lock_policy _Lp>
1479 inline bool
1480 operator<=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1481 { return !(__a < nullptr); }
1482
1483 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1484 inline bool
1485 operator>(const __shared_ptr<_Tp1, _Lp>& __a,
1486 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1487 { return (__b < __a); }
1488
1489 template<typename _Tp, _Lock_policy _Lp>
1490 inline bool
1491 operator>(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1492 { return nullptr < __a; }
1493
1494 template<typename _Tp, _Lock_policy _Lp>
1495 inline bool
1496 operator>(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1497 { return __a < nullptr; }
1498
1499 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1500 inline bool
1501 operator>=(const __shared_ptr<_Tp1, _Lp>& __a,
1502 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1503 { return !(__a < __b); }
1504
1505 template<typename _Tp, _Lock_policy _Lp>
1506 inline bool
1507 operator>=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1508 { return !(__a < nullptr); }
1509
1510 template<typename _Tp, _Lock_policy _Lp>
1511 inline bool
1512 operator>=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1513 { return !(nullptr < __a); }
1514
1515 template<typename _Sp>
1516 struct _Sp_less : public binary_function<_Sp, _Sp, bool>
1517 {
1518 bool
1519 operator()(const _Sp& __lhs, const _Sp& __rhs) const noexcept
1520 {
1521 typedef typename _Sp::element_type element_type;
1522 return std::less<element_type*>()(__lhs.get(), __rhs.get());
1523 }
1524 };
1525
1526 template<typename _Tp, _Lock_policy _Lp>
1527 struct less<__shared_ptr<_Tp, _Lp>>
1528 : public _Sp_less<__shared_ptr<_Tp, _Lp>>
1529 { };
1530
1531 // 20.7.2.2.8 shared_ptr specialized algorithms.
1532 template<typename _Tp, _Lock_policy _Lp>
1533 inline void
1534 swap(__shared_ptr<_Tp, _Lp>& __a, __shared_ptr<_Tp, _Lp>& __b) noexcept
1535 { __a.swap(__b); }
1536
1537 // 20.7.2.2.9 shared_ptr casts
1538
1539 // The seemingly equivalent code:
1540 // shared_ptr<_Tp, _Lp>(static_cast<_Tp*>(__r.get()))
1541 // will eventually result in undefined behaviour, attempting to
1542 // delete the same object twice.
1543 /// static_pointer_cast
1544 template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1545 inline __shared_ptr<_Tp, _Lp>
1546 static_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1547 {
1548 using _Sp = __shared_ptr<_Tp, _Lp>;
1549 return _Sp(__r, static_cast<typename _Sp::element_type*>(__r.get()));
1550 }
1551
1552 // The seemingly equivalent code:
1553 // shared_ptr<_Tp, _Lp>(const_cast<_Tp*>(__r.get()))
1554 // will eventually result in undefined behaviour, attempting to
1555 // delete the same object twice.
1556 /// const_pointer_cast
1557 template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1558 inline __shared_ptr<_Tp, _Lp>
1559 const_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1560 {
1561 using _Sp = __shared_ptr<_Tp, _Lp>;
1562 return _Sp(__r, const_cast<typename _Sp::element_type*>(__r.get()));
1563 }
1564
1565 // The seemingly equivalent code:
1566 // shared_ptr<_Tp, _Lp>(dynamic_cast<_Tp*>(__r.get()))
1567 // will eventually result in undefined behaviour, attempting to
1568 // delete the same object twice.
1569 /// dynamic_pointer_cast
1570 template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1571 inline __shared_ptr<_Tp, _Lp>
1572 dynamic_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1573 {
1574 using _Sp = __shared_ptr<_Tp, _Lp>;
1575 if (auto* __p = dynamic_cast<typename _Sp::element_type*>(__r.get()))
1576 return _Sp(__r, __p);
1577 return _Sp();
1578 }
1579
1580#if __cplusplus > 201402L
1581 template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1582 inline __shared_ptr<_Tp, _Lp>
1583 reinterpret_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1584 {
1585 using _Sp = __shared_ptr<_Tp, _Lp>;
1586 return _Sp(__r, reinterpret_cast<typename _Sp::element_type*>(__r.get()));
1587 }
1588#endif
1589
1590 template<typename _Tp, _Lock_policy _Lp>
1591 class __weak_ptr
1592 {
1593 template<typename _Yp, typename _Res = void>
1594 using _Compatible = typename
1595 enable_if<__sp_compatible_with<_Yp*, _Tp*>::value, _Res>::type;
1596
1597 // Constraint for assignment from shared_ptr and weak_ptr:
1598 template<typename _Yp>
1599 using _Assignable = _Compatible<_Yp, __weak_ptr&>;
1600
1601 public:
1602 using element_type = typename remove_extent<_Tp>::type;
1603
1604 constexpr __weak_ptr() noexcept
1605 : _M_ptr(nullptr), _M_refcount()
1606 { }
1607
1608 __weak_ptr(const __weak_ptr&) noexcept = default;
1609
1610 ~__weak_ptr() = default;
1611
1612 // The "obvious" converting constructor implementation:
1613 //
1614 // template<typename _Tp1>
1615 // __weak_ptr(const __weak_ptr<_Tp1, _Lp>& __r)
1616 // : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws
1617 // { }
1618 //
1619 // has a serious problem.
1620 //
1621 // __r._M_ptr may already have been invalidated. The _M_ptr(__r._M_ptr)
1622 // conversion may require access to *__r._M_ptr (virtual inheritance).
1623 //
1624 // It is not possible to avoid spurious access violations since
1625 // in multithreaded programs __r._M_ptr may be invalidated at any point.
1626 template<typename _Yp, typename = _Compatible<_Yp>>
1627 __weak_ptr(const __weak_ptr<_Yp, _Lp>& __r) noexcept
1628 : _M_refcount(__r._M_refcount)
1629 { _M_ptr = __r.lock().get(); }
1630
1631 template<typename _Yp, typename = _Compatible<_Yp>>
1632 __weak_ptr(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1633 : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount)
1634 { }
1635
1636 __weak_ptr(__weak_ptr&& __r) noexcept
1637 : _M_ptr(__r._M_ptr), _M_refcount(std::move(__r._M_refcount))
1638 { __r._M_ptr = nullptr; }
1639
1640 template<typename _Yp, typename = _Compatible<_Yp>>
1641 __weak_ptr(__weak_ptr<_Yp, _Lp>&& __r) noexcept
1642 : _M_ptr(__r.lock().get()), _M_refcount(std::move(__r._M_refcount))
1643 { __r._M_ptr = nullptr; }
1644
1645 __weak_ptr&
1646 operator=(const __weak_ptr& __r) noexcept = default;
1647
1648 template<typename _Yp>
1649 _Assignable<_Yp>
1650 operator=(const __weak_ptr<_Yp, _Lp>& __r) noexcept
1651 {
1652 _M_ptr = __r.lock().get();
1653 _M_refcount = __r._M_refcount;
1654 return *this;
1655 }
1656
1657 template<typename _Yp>
1658 _Assignable<_Yp>
1659 operator=(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1660 {
1661 _M_ptr = __r._M_ptr;
1662 _M_refcount = __r._M_refcount;
1663 return *this;
1664 }
1665
1666 __weak_ptr&
1667 operator=(__weak_ptr&& __r) noexcept
1668 {
1669 _M_ptr = __r._M_ptr;
1670 _M_refcount = std::move(__r._M_refcount);
1671 __r._M_ptr = nullptr;
1672 return *this;
1673 }
1674
1675 template<typename _Yp>
1676 _Assignable<_Yp>
1677 operator=(__weak_ptr<_Yp, _Lp>&& __r) noexcept
1678 {
1679 _M_ptr = __r.lock().get();
1680 _M_refcount = std::move(__r._M_refcount);
1681 __r._M_ptr = nullptr;
1682 return *this;
1683 }
1684
1685 __shared_ptr<_Tp, _Lp>
1686 lock() const noexcept
1687 { return __shared_ptr<element_type, _Lp>(*this, std::nothrow); }
1688
1689 long
1690 use_count() const noexcept
1691 { return _M_refcount._M_get_use_count(); }
1692
1693 bool
1694 expired() const noexcept
1695 { return _M_refcount._M_get_use_count() == 0; }
1696
1697 template<typename _Tp1>
1698 bool
1699 owner_before(const __shared_ptr<_Tp1, _Lp>& __rhs) const noexcept
1700 { return _M_refcount._M_less(__rhs._M_refcount); }
1701
1702 template<typename _Tp1>
1703 bool
1704 owner_before(const __weak_ptr<_Tp1, _Lp>& __rhs) const noexcept
1705 { return _M_refcount._M_less(__rhs._M_refcount); }
1706
1707 void
1708 reset() noexcept
1709 { __weak_ptr().swap(*this); }
1710
1711 void
1712 swap(__weak_ptr& __s) noexcept
1713 {
1714 std::swap(_M_ptr, __s._M_ptr);
1715 _M_refcount._M_swap(__s._M_refcount);
1716 }
1717
1718 private:
1719 // Used by __enable_shared_from_this.
1720 void
1721 _M_assign(_Tp* __ptr, const __shared_count<_Lp>& __refcount) noexcept
1722 {
1723 if (use_count() == 0)
1724 {
1725 _M_ptr = __ptr;
1726 _M_refcount = __refcount;
1727 }
1728 }
1729
1730 template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
1731 template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
1732 friend class __enable_shared_from_this<_Tp, _Lp>;
1733 friend class enable_shared_from_this<_Tp>;
1734
1735 element_type* _M_ptr; // Contained pointer.
1736 __weak_count<_Lp> _M_refcount; // Reference counter.
1737 };
1738
1739 // 20.7.2.3.6 weak_ptr specialized algorithms.
1740 template<typename _Tp, _Lock_policy _Lp>
1741 inline void
1742 swap(__weak_ptr<_Tp, _Lp>& __a, __weak_ptr<_Tp, _Lp>& __b) noexcept
1743 { __a.swap(__b); }
1744
1745 template<typename _Tp, typename _Tp1>
1746 struct _Sp_owner_less : public binary_function<_Tp, _Tp, bool>
1747 {
1748 bool
1749 operator()(const _Tp& __lhs, const _Tp& __rhs) const noexcept
1750 { return __lhs.owner_before(__rhs); }
1751
1752 bool
1753 operator()(const _Tp& __lhs, const _Tp1& __rhs) const noexcept
1754 { return __lhs.owner_before(__rhs); }
1755
1756 bool
1757 operator()(const _Tp1& __lhs, const _Tp& __rhs) const noexcept
1758 { return __lhs.owner_before(__rhs); }
1759 };
1760
1761 template<>
1762 struct _Sp_owner_less<void, void>
1763 {
1764 template<typename _Tp, typename _Up>
1765 auto
1766 operator()(const _Tp& __lhs, const _Up& __rhs) const noexcept
1767 -> decltype(__lhs.owner_before(__rhs))
1768 { return __lhs.owner_before(__rhs); }
1769
1770 using is_transparent = void;
1771 };
1772
1773 template<typename _Tp, _Lock_policy _Lp>
1774 struct owner_less<__shared_ptr<_Tp, _Lp>>
1775 : public _Sp_owner_less<__shared_ptr<_Tp, _Lp>, __weak_ptr<_Tp, _Lp>>
1776 { };
1777
1778 template<typename _Tp, _Lock_policy _Lp>
1779 struct owner_less<__weak_ptr<_Tp, _Lp>>
1780 : public _Sp_owner_less<__weak_ptr<_Tp, _Lp>, __shared_ptr<_Tp, _Lp>>
1781 { };
1782
1783
1784 template<typename _Tp, _Lock_policy _Lp>
1785 class __enable_shared_from_this
1786 {
1787 protected:
1788 constexpr __enable_shared_from_this() noexcept { }
1789
1790 __enable_shared_from_this(const __enable_shared_from_this&) noexcept { }
1791
1792 __enable_shared_from_this&
1793 operator=(const __enable_shared_from_this&) noexcept
1794 { return *this; }
1795
1796 ~__enable_shared_from_this() { }
1797
1798 public:
1799 __shared_ptr<_Tp, _Lp>
1800 shared_from_this()
1801 { return __shared_ptr<_Tp, _Lp>(this->_M_weak_this); }
1802
1803 __shared_ptr<const _Tp, _Lp>
1804 shared_from_this() const
1805 { return __shared_ptr<const _Tp, _Lp>(this->_M_weak_this); }
1806
1807#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
1808 __weak_ptr<_Tp, _Lp>
1809 weak_from_this() noexcept
1810 { return this->_M_weak_this; }
1811
1812 __weak_ptr<const _Tp, _Lp>
1813 weak_from_this() const noexcept
1814 { return this->_M_weak_this; }
1815#endif
1816
1817 private:
1818 template<typename _Tp1>
1819 void
1820 _M_weak_assign(_Tp1* __p, const __shared_count<_Lp>& __n) const noexcept
1821 { _M_weak_this._M_assign(__p, __n); }
1822
1823 friend const __enable_shared_from_this*
1824 __enable_shared_from_this_base(const __shared_count<_Lp>&,
1825 const __enable_shared_from_this* __p)
1826 { return __p; }
1827
1828 template<typename, _Lock_policy>
1829 friend class __shared_ptr;
1830
1831 mutable __weak_ptr<_Tp, _Lp> _M_weak_this;
1832 };
1833
1834 template<typename _Tp, _Lock_policy _Lp, typename _Alloc, typename... _Args>
1835 inline __shared_ptr<_Tp, _Lp>
1836 __allocate_shared(const _Alloc& __a, _Args&&... __args)
1837 {
1838 return __shared_ptr<_Tp, _Lp>(_Sp_alloc_shared_tag<_Alloc>{__a},
1839 std::forward<_Args>(__args)...);
1840 }
1841
1842 template<typename _Tp, _Lock_policy _Lp, typename... _Args>
1843 inline __shared_ptr<_Tp, _Lp>
1844 __make_shared(_Args&&... __args)
1845 {
1846 typedef typename std::remove_const<_Tp>::type _Tp_nc;
1847 return std::__allocate_shared<_Tp, _Lp>(std::allocator<_Tp_nc>(),
1848 std::forward<_Args>(__args)...);
1849 }
1850
1851 /// std::hash specialization for __shared_ptr.
1852 template<typename _Tp, _Lock_policy _Lp>
1853 struct hash<__shared_ptr<_Tp, _Lp>>
1854 : public __hash_base<size_t, __shared_ptr<_Tp, _Lp>>
1855 {
1856 size_t
1857 operator()(const __shared_ptr<_Tp, _Lp>& __s) const noexcept
1858 {
1859 return hash<typename __shared_ptr<_Tp, _Lp>::element_type*>()(
1860 __s.get());
1861 }
1862 };
1863
1864_GLIBCXX_END_NAMESPACE_VERSION
1865} // namespace
1866
1867#endif // _SHARED_PTR_BASE_H
1868