1// shared_ptr and weak_ptr implementation details -*- C++ -*-
2
3// Copyright (C) 2007-2024 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library. This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
24
25// GCC Note: Based on files from version 1.32.0 of the Boost library.
26
27// shared_count.hpp
28// Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd.
29
30// shared_ptr.hpp
31// Copyright (C) 1998, 1999 Greg Colvin and Beman Dawes.
32// Copyright (C) 2001, 2002, 2003 Peter Dimov
33
34// weak_ptr.hpp
35// Copyright (C) 2001, 2002, 2003 Peter Dimov
36
37// enable_shared_from_this.hpp
38// Copyright (C) 2002 Peter Dimov
39
40// Distributed under the Boost Software License, Version 1.0. (See
41// accompanying file LICENSE_1_0.txt or copy at
42// http://www.boost.org/LICENSE_1_0.txt)
43
44/** @file bits/shared_ptr_base.h
45 * This is an internal header file, included by other library headers.
46 * Do not attempt to use it directly. @headername{memory}
47 */
48
49#ifndef _SHARED_PTR_BASE_H
50#define _SHARED_PTR_BASE_H 1
51
52#include <typeinfo>
53#include <bits/allocated_ptr.h>
54#include <bits/allocator.h>
55#include <bits/exception_defines.h>
56#include <bits/functional_hash.h>
57#include <bits/refwrap.h>
58#include <bits/stl_function.h> // std::less
59#include <bits/unique_ptr.h>
60#include <ext/aligned_buffer.h>
61#include <ext/atomicity.h>
62#include <ext/concurrence.h>
63#if __cplusplus >= 202002L
64# include <bit> // __bit_floor
65# include <compare>
66# include <bits/align.h> // std::align
67# include <bits/stl_uninitialized.h>
68#endif
69
70namespace std _GLIBCXX_VISIBILITY(default)
71{
72_GLIBCXX_BEGIN_NAMESPACE_VERSION
73
74#if _GLIBCXX_USE_DEPRECATED
75#pragma GCC diagnostic push
76#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
77 template<typename> class auto_ptr;
78#pragma GCC diagnostic pop
79#endif
80
81 /**
82 * @brief Exception possibly thrown by @c shared_ptr.
83 * @ingroup exceptions
84 */
85 class bad_weak_ptr : public std::exception
86 {
87 public:
88 virtual char const* what() const noexcept;
89
90 virtual ~bad_weak_ptr() noexcept;
91 };
92
93 // Substitute for bad_weak_ptr object in the case of -fno-exceptions.
94 inline void
95 __throw_bad_weak_ptr()
96 { _GLIBCXX_THROW_OR_ABORT(bad_weak_ptr()); }
97
98 using __gnu_cxx::_Lock_policy;
99 using __gnu_cxx::__default_lock_policy;
100 using __gnu_cxx::_S_single;
101 using __gnu_cxx::_S_mutex;
102 using __gnu_cxx::_S_atomic;
103
104 // Empty helper class except when the template argument is _S_mutex.
105 template<_Lock_policy _Lp>
106 class _Mutex_base
107 {
108 protected:
109 // The atomic policy uses fully-fenced builtins, single doesn't care.
110 enum { _S_need_barriers = 0 };
111 };
112
113 template<>
114 class _Mutex_base<_S_mutex>
115 : public __gnu_cxx::__mutex
116 {
117 protected:
118 // This policy is used when atomic builtins are not available.
119 // The replacement atomic operations might not have the necessary
120 // memory barriers.
121 enum { _S_need_barriers = 1 };
122 };
123
124 template<_Lock_policy _Lp = __default_lock_policy>
125 class _Sp_counted_base
126 : public _Mutex_base<_Lp>
127 {
128 public:
129 _Sp_counted_base() noexcept
130 : _M_use_count(1), _M_weak_count(1) { }
131
132 virtual
133 ~_Sp_counted_base() noexcept
134 { }
135
136 // Called when _M_use_count drops to zero, to release the resources
137 // managed by *this.
138 virtual void
139 _M_dispose() noexcept = 0;
140
141 // Called when _M_weak_count drops to zero.
142 virtual void
143 _M_destroy() noexcept
144 { delete this; }
145
146 virtual void*
147 _M_get_deleter(const std::type_info&) noexcept = 0;
148
149 // Increment the use count (used when the count is greater than zero).
150 void
151 _M_add_ref_copy()
152 { __gnu_cxx::__atomic_add_dispatch(mem: &_M_use_count, val: 1); }
153
154 // Increment the use count if it is non-zero, throw otherwise.
155 void
156 _M_add_ref_lock()
157 {
158 if (!_M_add_ref_lock_nothrow())
159 __throw_bad_weak_ptr();
160 }
161
162 // Increment the use count if it is non-zero.
163 bool
164 _M_add_ref_lock_nothrow() noexcept;
165
166 // Decrement the use count.
167 void
168 _M_release() noexcept;
169
170 // Called by _M_release() when the use count reaches zero.
171 void
172 _M_release_last_use() noexcept
173 {
174 _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_use_count);
175 _M_dispose();
176 // There must be a memory barrier between dispose() and destroy()
177 // to ensure that the effects of dispose() are observed in the
178 // thread that runs destroy().
179 // See http://gcc.gnu.org/ml/libstdc++/2005-11/msg00136.html
180 if (_Mutex_base<_Lp>::_S_need_barriers)
181 {
182 __atomic_thread_fence (__ATOMIC_ACQ_REL);
183 }
184
185 // Be race-detector-friendly. For more info see bits/c++config.
186 _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count);
187 if (__gnu_cxx::__exchange_and_add_dispatch(mem: &_M_weak_count,
188 val: -1) == 1)
189 {
190 _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count);
191 _M_destroy();
192 }
193 }
194
195 // As above, but 'noinline' to reduce code size on the cold path.
196 __attribute__((__noinline__))
197 void
198 _M_release_last_use_cold() noexcept
199 { _M_release_last_use(); }
200
201 // Increment the weak count.
202 void
203 _M_weak_add_ref() noexcept
204 { __gnu_cxx::__atomic_add_dispatch(mem: &_M_weak_count, val: 1); }
205
206 // Decrement the weak count.
207 void
208 _M_weak_release() noexcept
209 {
210 // Be race-detector-friendly. For more info see bits/c++config.
211 _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count);
212 if (__gnu_cxx::__exchange_and_add_dispatch(mem: &_M_weak_count, val: -1) == 1)
213 {
214 _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count);
215 if (_Mutex_base<_Lp>::_S_need_barriers)
216 {
217 // See _M_release(),
218 // destroy() must observe results of dispose()
219 __atomic_thread_fence (__ATOMIC_ACQ_REL);
220 }
221 _M_destroy();
222 }
223 }
224
225 long
226 _M_get_use_count() const noexcept
227 {
228 // No memory barrier is used here so there is no synchronization
229 // with other threads.
230 return __atomic_load_n(&_M_use_count, __ATOMIC_RELAXED);
231 }
232
233 private:
234 _Sp_counted_base(_Sp_counted_base const&) = delete;
235 _Sp_counted_base& operator=(_Sp_counted_base const&) = delete;
236
237 _Atomic_word _M_use_count; // #shared
238 _Atomic_word _M_weak_count; // #weak + (#shared != 0)
239 };
240
241 template<>
242 inline bool
243 _Sp_counted_base<_S_single>::
244 _M_add_ref_lock_nothrow() noexcept
245 {
246 if (_M_use_count == 0)
247 return false;
248 ++_M_use_count;
249 return true;
250 }
251
252 template<>
253 inline bool
254 _Sp_counted_base<_S_mutex>::
255 _M_add_ref_lock_nothrow() noexcept
256 {
257 __gnu_cxx::__scoped_lock sentry(*this);
258 if (__gnu_cxx::__exchange_and_add_dispatch(mem: &_M_use_count, val: 1) == 0)
259 {
260 _M_use_count = 0;
261 return false;
262 }
263 return true;
264 }
265
266 template<>
267 inline bool
268 _Sp_counted_base<_S_atomic>::
269 _M_add_ref_lock_nothrow() noexcept
270 {
271 // Perform lock-free add-if-not-zero operation.
272 _Atomic_word __count = _M_get_use_count();
273 do
274 {
275 if (__count == 0)
276 return false;
277 // Replace the current counter value with the old value + 1, as
278 // long as it's not changed meanwhile.
279 }
280 while (!__atomic_compare_exchange_n(&_M_use_count, &__count, __count + 1,
281 true, __ATOMIC_ACQ_REL,
282 __ATOMIC_RELAXED));
283 return true;
284 }
285
286 template<>
287 inline void
288 _Sp_counted_base<_S_single>::_M_add_ref_copy()
289 { ++_M_use_count; }
290
291 template<>
292 inline void
293 _Sp_counted_base<_S_single>::_M_release() noexcept
294 {
295 if (--_M_use_count == 0)
296 {
297 _M_dispose();
298 if (--_M_weak_count == 0)
299 _M_destroy();
300 }
301 }
302
303 template<>
304 inline void
305 _Sp_counted_base<_S_mutex>::_M_release() noexcept
306 {
307 // Be race-detector-friendly. For more info see bits/c++config.
308 _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_use_count);
309 if (__gnu_cxx::__exchange_and_add_dispatch(mem: &_M_use_count, val: -1) == 1)
310 {
311 _M_release_last_use();
312 }
313 }
314
315 template<>
316 inline void
317 _Sp_counted_base<_S_atomic>::_M_release() noexcept
318 {
319 _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_use_count);
320#if ! _GLIBCXX_TSAN
321 constexpr bool __lock_free
322 = __atomic_always_lock_free(sizeof(long long), 0)
323 && __atomic_always_lock_free(sizeof(_Atomic_word), 0);
324 constexpr bool __double_word
325 = sizeof(long long) == 2 * sizeof(_Atomic_word);
326 // The ref-count members follow the vptr, so are aligned to
327 // alignof(void*).
328 constexpr bool __aligned = __alignof(long long) <= alignof(void*);
329 if _GLIBCXX17_CONSTEXPR (__lock_free && __double_word && __aligned)
330 {
331 constexpr int __wordbits = __CHAR_BIT__ * sizeof(_Atomic_word);
332 constexpr int __shiftbits = __double_word ? __wordbits : 0;
333 constexpr long long __unique_ref = 1LL + (1LL << __shiftbits);
334 auto __both_counts = reinterpret_cast<long long*>(&_M_use_count);
335
336 _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count);
337 if (__atomic_load_n(__both_counts, __ATOMIC_ACQUIRE) == __unique_ref)
338 {
339 // Both counts are 1, so there are no weak references and
340 // we are releasing the last strong reference. No other
341 // threads can observe the effects of this _M_release()
342 // call (e.g. calling use_count()) without a data race.
343 _M_weak_count = _M_use_count = 0;
344 _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_use_count);
345 _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count);
346 _M_dispose();
347 _M_destroy();
348 return;
349 }
350 if (__gnu_cxx::__exchange_and_add_dispatch(mem: &_M_use_count, val: -1) == 1)
351 [[__unlikely__]]
352 {
353 _M_release_last_use_cold();
354 return;
355 }
356 }
357 else
358#endif
359 if (__gnu_cxx::__exchange_and_add_dispatch(mem: &_M_use_count, val: -1) == 1)
360 {
361 _M_release_last_use();
362 }
363 }
364
365 template<>
366 inline void
367 _Sp_counted_base<_S_single>::_M_weak_add_ref() noexcept
368 { ++_M_weak_count; }
369
370 template<>
371 inline void
372 _Sp_counted_base<_S_single>::_M_weak_release() noexcept
373 {
374 if (--_M_weak_count == 0)
375 _M_destroy();
376 }
377
378 template<>
379 inline long
380 _Sp_counted_base<_S_single>::_M_get_use_count() const noexcept
381 { return _M_use_count; }
382
383
384 // Forward declarations.
385 template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
386 class __shared_ptr;
387
388 template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
389 class __weak_ptr;
390
391 template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
392 class __enable_shared_from_this;
393
394 template<typename _Tp>
395 class shared_ptr;
396
397 template<typename _Tp>
398 class weak_ptr;
399
400 template<typename _Tp>
401 struct owner_less;
402
403 template<typename _Tp>
404 class enable_shared_from_this;
405
406 template<_Lock_policy _Lp = __default_lock_policy>
407 class __weak_count;
408
409 template<_Lock_policy _Lp = __default_lock_policy>
410 class __shared_count;
411
412#ifdef __glibcxx_atomic_shared_ptr
413 template<typename>
414 class _Sp_atomic;
415#endif
416
417 // Counted ptr with no deleter or allocator support
418 template<typename _Ptr, _Lock_policy _Lp>
419 class _Sp_counted_ptr final : public _Sp_counted_base<_Lp>
420 {
421 public:
422 explicit
423 _Sp_counted_ptr(_Ptr __p) noexcept
424 : _M_ptr(__p) { }
425
426 virtual void
427 _M_dispose() noexcept
428 { delete _M_ptr; }
429
430 virtual void
431 _M_destroy() noexcept
432 { delete this; }
433
434 virtual void*
435 _M_get_deleter(const std::type_info&) noexcept
436 { return nullptr; }
437
438 _Sp_counted_ptr(const _Sp_counted_ptr&) = delete;
439 _Sp_counted_ptr& operator=(const _Sp_counted_ptr&) = delete;
440
441 private:
442 _Ptr _M_ptr;
443 };
444
445 template<>
446 inline void
447 _Sp_counted_ptr<nullptr_t, _S_single>::_M_dispose() noexcept { }
448
449 template<>
450 inline void
451 _Sp_counted_ptr<nullptr_t, _S_mutex>::_M_dispose() noexcept { }
452
453 template<>
454 inline void
455 _Sp_counted_ptr<nullptr_t, _S_atomic>::_M_dispose() noexcept { }
456
457 // FIXME: once __has_cpp_attribute(__no_unique_address__)) is true for
458 // all supported compilers we can greatly simplify _Sp_ebo_helper.
459 // N.B. unconditionally applying the attribute could change layout for
460 // final types, which currently cannot use EBO so have a unique address.
461
462 template<int _Nm, typename _Tp,
463 bool __use_ebo = !__is_final(_Tp) && __is_empty(_Tp)>
464 struct _Sp_ebo_helper;
465
466 /// Specialization using EBO.
467 template<int _Nm, typename _Tp>
468 struct _Sp_ebo_helper<_Nm, _Tp, true> : private _Tp
469 {
470 explicit _Sp_ebo_helper(const _Tp& __tp) : _Tp(__tp) { }
471 explicit _Sp_ebo_helper(_Tp&& __tp) : _Tp(std::move(__tp)) { }
472
473 static _Tp&
474 _S_get(_Sp_ebo_helper& __eboh) { return static_cast<_Tp&>(__eboh); }
475 };
476
477 /// Specialization not using EBO.
478 template<int _Nm, typename _Tp>
479 struct _Sp_ebo_helper<_Nm, _Tp, false>
480 {
481 explicit _Sp_ebo_helper(const _Tp& __tp) : _M_tp(__tp) { }
482 explicit _Sp_ebo_helper(_Tp&& __tp) : _M_tp(std::move(__tp)) { }
483
484 static _Tp&
485 _S_get(_Sp_ebo_helper& __eboh)
486 { return __eboh._M_tp; }
487
488 private:
489 _Tp _M_tp;
490 };
491
492 // Support for custom deleter and/or allocator
493 template<typename _Ptr, typename _Deleter, typename _Alloc, _Lock_policy _Lp>
494 class _Sp_counted_deleter final : public _Sp_counted_base<_Lp>
495 {
496 class _Impl : _Sp_ebo_helper<0, _Deleter>, _Sp_ebo_helper<1, _Alloc>
497 {
498 typedef _Sp_ebo_helper<0, _Deleter> _Del_base;
499 typedef _Sp_ebo_helper<1, _Alloc> _Alloc_base;
500
501 public:
502 _Impl(_Ptr __p, _Deleter __d, const _Alloc& __a) noexcept
503 : _Del_base(std::move(__d)), _Alloc_base(__a), _M_ptr(__p)
504 { }
505
506 _Deleter& _M_del() noexcept { return _Del_base::_S_get(*this); }
507 _Alloc& _M_alloc() noexcept { return _Alloc_base::_S_get(*this); }
508
509 _Ptr _M_ptr;
510 };
511
512 public:
513 using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_deleter>;
514
515 // __d(__p) must not throw.
516 _Sp_counted_deleter(_Ptr __p, _Deleter __d) noexcept
517 : _M_impl(__p, std::move(__d), _Alloc()) { }
518
519 // __d(__p) must not throw.
520 _Sp_counted_deleter(_Ptr __p, _Deleter __d, const _Alloc& __a) noexcept
521 : _M_impl(__p, std::move(__d), __a) { }
522
523 ~_Sp_counted_deleter() noexcept { }
524
525 virtual void
526 _M_dispose() noexcept
527 { _M_impl._M_del()(_M_impl._M_ptr); }
528
529 virtual void
530 _M_destroy() noexcept
531 {
532 __allocator_type __a(_M_impl._M_alloc());
533 __allocated_ptr<__allocator_type> __guard_ptr{ __a, this };
534 this->~_Sp_counted_deleter();
535 }
536
537 virtual void*
538 _M_get_deleter(const type_info& __ti [[__gnu__::__unused__]]) noexcept
539 {
540#if __cpp_rtti
541 // _GLIBCXX_RESOLVE_LIB_DEFECTS
542 // 2400. shared_ptr's get_deleter() should use addressof()
543 return __ti == typeid(_Deleter)
544 ? std::__addressof(_M_impl._M_del())
545 : nullptr;
546#else
547 return nullptr;
548#endif
549 }
550
551 private:
552#ifdef __glibcxx_out_ptr
553 template<typename, typename, typename...> friend class out_ptr_t;
554#endif
555 _Impl _M_impl;
556 };
557
558 // helpers for make_shared / allocate_shared
559
560 struct _Sp_make_shared_tag
561 {
562 private:
563 template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
564 friend class _Sp_counted_ptr_inplace;
565
566 static const type_info&
567 _S_ti() noexcept _GLIBCXX_VISIBILITY(default)
568 {
569 alignas(type_info) static constexpr char __tag[sizeof(type_info)] = { };
570 return reinterpret_cast<const type_info&>(__tag);
571 }
572
573 static bool _S_eq(const type_info&) noexcept;
574 };
575
576 template<typename _Alloc>
577 struct _Sp_alloc_shared_tag
578 {
579 const _Alloc& _M_a;
580 };
581
582 template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
583 class _Sp_counted_ptr_inplace final : public _Sp_counted_base<_Lp>
584 {
585 class _Impl : _Sp_ebo_helper<0, _Alloc>
586 {
587 typedef _Sp_ebo_helper<0, _Alloc> _A_base;
588
589 public:
590 explicit _Impl(_Alloc __a) noexcept : _A_base(__a) { }
591
592 _Alloc& _M_alloc() noexcept { return _A_base::_S_get(*this); }
593
594 __gnu_cxx::__aligned_buffer<_Tp> _M_storage;
595 };
596
597 public:
598 using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_ptr_inplace>;
599
600 // Alloc parameter is not a reference so doesn't alias anything in __args
601 template<typename... _Args>
602 _Sp_counted_ptr_inplace(_Alloc __a, _Args&&... __args)
603 : _M_impl(__a)
604 {
605 // _GLIBCXX_RESOLVE_LIB_DEFECTS
606 // 2070. allocate_shared should use allocator_traits<A>::construct
607 allocator_traits<_Alloc>::construct(__a, _M_ptr(),
608 std::forward<_Args>(__args)...); // might throw
609 }
610
611 ~_Sp_counted_ptr_inplace() noexcept { }
612
613 virtual void
614 _M_dispose() noexcept
615 {
616 allocator_traits<_Alloc>::destroy(_M_impl._M_alloc(), _M_ptr());
617 }
618
619 // Override because the allocator needs to know the dynamic type
620 virtual void
621 _M_destroy() noexcept
622 {
623 __allocator_type __a(_M_impl._M_alloc());
624 __allocated_ptr<__allocator_type> __guard_ptr{ __a, this };
625 this->~_Sp_counted_ptr_inplace();
626 }
627
628 private:
629 friend class __shared_count<_Lp>; // To be able to call _M_ptr().
630
631 // No longer used, but code compiled against old libstdc++ headers
632 // might still call it from __shared_ptr ctor to get the pointer out.
633 virtual void*
634 _M_get_deleter(const std::type_info& __ti) noexcept override
635 {
636 auto __ptr = const_cast<typename remove_cv<_Tp>::type*>(_M_ptr());
637 // Check for the fake type_info first, so we don't try to access it
638 // as a real type_info object. Otherwise, check if it's the real
639 // type_info for this class. With RTTI enabled we can check directly,
640 // or call a library function to do it.
641 if (&__ti == &_Sp_make_shared_tag::_S_ti()
642 ||
643#if __cpp_rtti
644 __ti == typeid(_Sp_make_shared_tag)
645#else
646 _Sp_make_shared_tag::_S_eq(__ti)
647#endif
648 )
649 return __ptr;
650 return nullptr;
651 }
652
653 _Tp* _M_ptr() noexcept { return _M_impl._M_storage._M_ptr(); }
654
655 _Impl _M_impl;
656 };
657
658#ifdef __glibcxx_smart_ptr_for_overwrite // C++ >= 20 && HOSTED
659 struct _Sp_overwrite_tag { };
660
661 // Partial specialization used for make_shared_for_overwrite<non-array>().
662 // This partial specialization is used when the allocator's value type
663 // is the special _Sp_overwrite_tag type.
664#if __cpp_concepts
665 template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
666 requires is_same_v<typename _Alloc::value_type, _Sp_overwrite_tag>
667 class _Sp_counted_ptr_inplace<_Tp, _Alloc, _Lp> final
668#else
669 template<typename _Tp, template<typename> class _Alloc, _Lock_policy _Lp>
670 class _Sp_counted_ptr_inplace<_Tp, _Alloc<_Sp_overwrite_tag>, _Lp> final
671#endif
672 : public _Sp_counted_base<_Lp>
673 {
674 [[no_unique_address]] _Alloc _M_alloc;
675
676 union {
677 _Tp _M_obj;
678 char _M_unused;
679 };
680
681 friend class __shared_count<_Lp>; // To be able to call _M_ptr().
682
683 _Tp* _M_ptr() noexcept { return std::__addressof(_M_obj); }
684
685 public:
686 using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_ptr_inplace>;
687
688 _Sp_counted_ptr_inplace(const _Alloc& __a)
689 : _M_alloc(__a)
690 {
691 ::new((void*)_M_ptr()) _Tp; // default-initialized, for overwrite.
692 }
693
694 ~_Sp_counted_ptr_inplace() noexcept { }
695
696 virtual void
697 _M_dispose() noexcept
698 {
699 _M_obj.~_Tp();
700 }
701
702 // Override because the allocator needs to know the dynamic type
703 virtual void
704 _M_destroy() noexcept
705 {
706 using pointer = typename allocator_traits<__allocator_type>::pointer;
707 __allocator_type __a(_M_alloc);
708 auto __p = pointer_traits<pointer>::pointer_to(*this);
709 __allocated_ptr<__allocator_type> __guard_ptr{ __a, __p };
710 this->~_Sp_counted_ptr_inplace();
711 }
712
713 void*
714 _M_get_deleter(const std::type_info&) noexcept override
715 { return nullptr; }
716 };
717#endif // __glibcxx_smart_ptr_for_overwrite
718
719#if __glibcxx_shared_ptr_arrays >= 201707L // C++ >= 20 && HOSTED
720 struct _Sp_overwrite_tag;
721
722 // For make_shared<T[]>, make_shared<T[N]>, allocate_shared<T[]> etc.
723 template<typename _Alloc>
724 struct _Sp_counted_array_base
725 {
726 [[no_unique_address]] _Alloc _M_alloc{};
727 size_t _M_n = 0;
728 bool _M_overwrite = false;
729
730 typename allocator_traits<_Alloc>::pointer
731 _M_alloc_array(size_t __tail)
732 {
733 return allocator_traits<_Alloc>::allocate(_M_alloc, _M_n + __tail);
734 }
735
736 void
737 _M_dealloc_array(typename allocator_traits<_Alloc>::pointer __p,
738 size_t __tail)
739 {
740 allocator_traits<_Alloc>::deallocate(_M_alloc, __p, _M_n + __tail);
741 }
742
743 // Init the array elements
744 template<typename _Init>
745 void
746 _M_init(typename allocator_traits<_Alloc>::value_type* __p,
747 _Init __init)
748 {
749 using _Tp = remove_pointer_t<_Init>;
750 using _Up = typename allocator_traits<_Alloc>::value_type;
751
752 if constexpr (is_same_v<_Init, _Sp_overwrite_tag>)
753 {
754 std::uninitialized_default_construct_n(__p, _M_n);
755 _M_overwrite = true;
756 }
757 else if (__init == nullptr)
758 std::__uninitialized_default_n_a(__p, _M_n, _M_alloc);
759 else if constexpr (!is_array_v<_Tp>)
760 std::__uninitialized_fill_n_a(__p, _M_n, *__init, _M_alloc);
761 else
762 {
763#pragma GCC diagnostic push
764#pragma GCC diagnostic ignored "-Wunused-local-typedefs"
765 struct _Iter
766 {
767 using value_type = _Up;
768 using difference_type = ptrdiff_t;
769 using pointer = const _Up*;
770 using reference = const _Up&;
771 using iterator_category = forward_iterator_tag;
772
773 const _Up* _M_p;
774 size_t _M_len;
775 size_t _M_pos;
776
777 _Iter& operator++() { ++_M_pos; return *this; }
778 _Iter operator++(int) { auto __i(*this); ++_M_pos; return __i; }
779
780 reference operator*() const { return _M_p[_M_pos % _M_len]; }
781 pointer operator->() const { return _M_p + (_M_pos % _M_len); }
782
783 bool operator==(const _Iter& __i) const
784 { return _M_pos == __i._M_pos; }
785 };
786#pragma GCC diagnostic pop
787
788 _Iter __first{_S_first_elem(__init), sizeof(_Tp) / sizeof(_Up)};
789 _Iter __last = __first;
790 __last._M_pos = _M_n;
791 std::__uninitialized_copy_a(__first, __last, __p, _M_alloc);
792 }
793 }
794
795 protected:
796 // Destroy the array elements
797 void
798 _M_dispose_array(typename allocator_traits<_Alloc>::value_type* __p)
799 {
800 if (_M_overwrite)
801 std::destroy_n(__p, _M_n);
802 else
803 {
804 size_t __n = _M_n;
805 while (__n--)
806 allocator_traits<_Alloc>::destroy(_M_alloc, __p + __n);
807 }
808 }
809
810 private:
811 template<typename _Tp>
812 static _Tp*
813 _S_first_elem(_Tp* __p) { return __p; }
814
815 template<typename _Tp, size_t _Nm>
816 static auto
817 _S_first_elem(_Tp (*__p)[_Nm]) { return _S_first_elem(*__p); }
818 };
819
820 // Control block for make_shared<T[]>, make_shared<T[N]> etc. that will be
821 // placed into unused memory at the end of the array.
822 template<typename _Alloc, _Lock_policy _Lp>
823 class _Sp_counted_array final
824 : public _Sp_counted_base<_Lp>, _Sp_counted_array_base<_Alloc>
825 {
826 using pointer = typename allocator_traits<_Alloc>::pointer;
827
828 pointer _M_alloc_ptr;
829
830 auto _M_ptr() const noexcept { return std::to_address(_M_alloc_ptr); }
831
832 friend class __shared_count<_Lp>; // To be able to call _M_ptr().
833
834 public:
835 _Sp_counted_array(const _Sp_counted_array_base<_Alloc>& __a,
836 pointer __p) noexcept
837 : _Sp_counted_array_base<_Alloc>(__a), _M_alloc_ptr(__p)
838 { }
839
840 ~_Sp_counted_array() = default;
841
842 virtual void
843 _M_dispose() noexcept
844 {
845 if (this->_M_n)
846 this->_M_dispose_array(_M_ptr());
847 }
848
849 // Override because the allocator needs to know the dynamic type
850 virtual void
851 _M_destroy() noexcept
852 {
853 _Sp_counted_array_base<_Alloc> __a = *this;
854 pointer __p = _M_alloc_ptr;
855 this->~_Sp_counted_array();
856 __a._M_dealloc_array(__p, _S_tail());
857 }
858
859 // Returns the number of additional array elements that must be
860 // allocated in order to store a _Sp_counted_array at the end.
861 static constexpr size_t
862 _S_tail()
863 {
864 // The array elemenent type.
865 using _Tp = typename allocator_traits<_Alloc>::value_type;
866
867 // The space needed to store a _Sp_counted_array object.
868 size_t __bytes = sizeof(_Sp_counted_array);
869
870 // Add any padding needed for manual alignment within the buffer.
871 if constexpr (alignof(_Tp) < alignof(_Sp_counted_array))
872 __bytes += alignof(_Sp_counted_array) - alignof(_Tp);
873
874 return (__bytes + sizeof(_Tp) - 1) / sizeof(_Tp);
875 }
876
877 void*
878 _M_get_deleter(const std::type_info&) noexcept override
879 { return nullptr; }
880 };
881#endif // __glibcxx_shared_ptr_arrays >= 201707L
882
883 // The default deleter for shared_ptr<T[]> and shared_ptr<T[N]>.
884 struct __sp_array_delete
885 {
886 template<typename _Yp>
887 void operator()(_Yp* __p) const { delete[] __p; }
888 };
889
890 template<_Lock_policy _Lp>
891 class __shared_count
892 {
893 // Prevent _Sp_alloc_shared_tag from matching the shared_ptr(P, D) ctor.
894 template<typename _Tp>
895 struct __not_alloc_shared_tag { using type = void; };
896
897 template<typename _Tp>
898 struct __not_alloc_shared_tag<_Sp_alloc_shared_tag<_Tp>> { };
899
900#if __glibcxx_shared_ptr_arrays >= 201707L // C++ >= 20 && HOSTED
901 template<typename _Alloc>
902 struct __not_alloc_shared_tag<_Sp_counted_array_base<_Alloc>> { };
903#endif
904
905 public:
906 constexpr __shared_count() noexcept : _M_pi(0)
907 { }
908
909 template<typename _Ptr>
910 explicit
911 __shared_count(_Ptr __p) : _M_pi(0)
912 {
913 __try
914 {
915 _M_pi = new _Sp_counted_ptr<_Ptr, _Lp>(__p);
916 }
917 __catch(...)
918 {
919 delete __p;
920 __throw_exception_again;
921 }
922 }
923
924 template<typename _Ptr>
925 __shared_count(_Ptr __p, /* is_array = */ false_type)
926 : __shared_count(__p)
927 { }
928
929 template<typename _Ptr>
930 __shared_count(_Ptr __p, /* is_array = */ true_type)
931 : __shared_count(__p, __sp_array_delete{}, allocator<void>())
932 { }
933
934 template<typename _Ptr, typename _Deleter,
935 typename = typename __not_alloc_shared_tag<_Deleter>::type>
936 __shared_count(_Ptr __p, _Deleter __d)
937 : __shared_count(__p, std::move(__d), allocator<void>())
938 { }
939
940 template<typename _Ptr, typename _Deleter, typename _Alloc,
941 typename = typename __not_alloc_shared_tag<_Deleter>::type>
942 __shared_count(_Ptr __p, _Deleter __d, _Alloc __a) : _M_pi(0)
943 {
944 typedef _Sp_counted_deleter<_Ptr, _Deleter, _Alloc, _Lp> _Sp_cd_type;
945 __try
946 {
947 typename _Sp_cd_type::__allocator_type __a2(__a);
948 auto __guard = std::__allocate_guarded(__a2);
949 _Sp_cd_type* __mem = __guard.get();
950 ::new (__mem) _Sp_cd_type(__p, std::move(__d), std::move(__a));
951 _M_pi = __mem;
952 __guard = nullptr;
953 }
954 __catch(...)
955 {
956 __d(__p); // Call _Deleter on __p.
957 __throw_exception_again;
958 }
959 }
960
961 template<typename _Tp, typename _Alloc, typename... _Args>
962 __shared_count(_Tp*& __p, _Sp_alloc_shared_tag<_Alloc> __a,
963 _Args&&... __args)
964 {
965 typedef _Sp_counted_ptr_inplace<_Tp, _Alloc, _Lp> _Sp_cp_type;
966 typename _Sp_cp_type::__allocator_type __a2(__a._M_a);
967 auto __guard = std::__allocate_guarded(__a2);
968 _Sp_cp_type* __mem = __guard.get();
969 auto __pi = ::new (__mem)
970 _Sp_cp_type(__a._M_a, std::forward<_Args>(__args)...);
971 __guard = nullptr;
972 _M_pi = __pi;
973 __p = __pi->_M_ptr();
974 }
975
976#if __glibcxx_shared_ptr_arrays >= 201707L // C++ >= 20 && HOSTED
977 template<typename _Tp, typename _Alloc, typename _Init>
978 __shared_count(_Tp*& __p, const _Sp_counted_array_base<_Alloc>& __a,
979 _Init __init)
980 {
981 using _Up = remove_all_extents_t<_Tp>;
982 static_assert(is_same_v<_Up, typename _Alloc::value_type>);
983
984 using _Sp_ca_type = _Sp_counted_array<_Alloc, _Lp>;
985 const size_t __tail = _Sp_ca_type::_S_tail();
986
987 struct _Guarded_ptr : _Sp_counted_array_base<_Alloc>
988 {
989 typename allocator_traits<_Alloc>::pointer _M_ptr;
990
991 _Guarded_ptr(_Sp_counted_array_base<_Alloc> __a)
992 : _Sp_counted_array_base<_Alloc>(__a),
993 _M_ptr(this->_M_alloc_array(_Sp_ca_type::_S_tail()))
994 { }
995
996 ~_Guarded_ptr()
997 {
998 if (_M_ptr)
999 this->_M_dealloc_array(_M_ptr, _Sp_ca_type::_S_tail());
1000 }
1001 };
1002
1003 _Guarded_ptr __guard{__a};
1004 _Up* const __raw = std::to_address(__guard._M_ptr);
1005 __guard._M_init(__raw, __init); // might throw
1006
1007 void* __c = __raw + __a._M_n;
1008 if constexpr (alignof(_Up) < alignof(_Sp_ca_type))
1009 {
1010 size_t __space = sizeof(_Up) * __tail;
1011 __c = std::align(alignof(_Sp_ca_type), sizeof(_Sp_ca_type),
1012 __c, __space);
1013 }
1014 auto __pi = ::new(__c) _Sp_ca_type(__guard, __guard._M_ptr);
1015 __guard._M_ptr = nullptr;
1016 _M_pi = __pi;
1017 __p = reinterpret_cast<_Tp*>(__raw);
1018 }
1019#endif
1020
1021#if _GLIBCXX_USE_DEPRECATED
1022#pragma GCC diagnostic push
1023#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
1024 // Special case for auto_ptr<_Tp> to provide the strong guarantee.
1025 template<typename _Tp>
1026 explicit
1027 __shared_count(std::auto_ptr<_Tp>&& __r);
1028#pragma GCC diagnostic pop
1029#endif
1030
1031 // Special case for unique_ptr<_Tp,_Del> to provide the strong guarantee.
1032 template<typename _Tp, typename _Del>
1033 explicit
1034 __shared_count(std::unique_ptr<_Tp, _Del>&& __r) : _M_pi(0)
1035 {
1036 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1037 // 2415. Inconsistency between unique_ptr and shared_ptr
1038 if (__r.get() == nullptr)
1039 return;
1040
1041 using _Ptr = typename unique_ptr<_Tp, _Del>::pointer;
1042 using _Del2 = __conditional_t<is_reference<_Del>::value,
1043 reference_wrapper<typename remove_reference<_Del>::type>,
1044 _Del>;
1045 using _Sp_cd_type
1046 = _Sp_counted_deleter<_Ptr, _Del2, allocator<void>, _Lp>;
1047 using _Alloc = allocator<_Sp_cd_type>;
1048 using _Alloc_traits = allocator_traits<_Alloc>;
1049 _Alloc __a;
1050 _Sp_cd_type* __mem = _Alloc_traits::allocate(__a, 1);
1051 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1052 // 3548. shared_ptr construction from unique_ptr should move
1053 // (not copy) the deleter
1054 _Alloc_traits::construct(__a, __mem, __r.release(),
1055 std::forward<_Del>(__r.get_deleter()));
1056 _M_pi = __mem;
1057 }
1058
1059 // Throw bad_weak_ptr when __r._M_get_use_count() == 0.
1060 explicit __shared_count(const __weak_count<_Lp>& __r);
1061
1062 // Does not throw if __r._M_get_use_count() == 0, caller must check.
1063 explicit
1064 __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t) noexcept;
1065
1066 ~__shared_count() noexcept
1067 {
1068 if (_M_pi != nullptr)
1069 _M_pi->_M_release();
1070 }
1071
1072 __shared_count(const __shared_count& __r) noexcept
1073 : _M_pi(__r._M_pi)
1074 {
1075 if (_M_pi != nullptr)
1076 _M_pi->_M_add_ref_copy();
1077 }
1078
1079 __shared_count&
1080 operator=(const __shared_count& __r) noexcept
1081 {
1082 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
1083 if (__tmp != _M_pi)
1084 {
1085 if (__tmp != nullptr)
1086 __tmp->_M_add_ref_copy();
1087 if (_M_pi != nullptr)
1088 _M_pi->_M_release();
1089 _M_pi = __tmp;
1090 }
1091 return *this;
1092 }
1093
1094 void
1095 _M_swap(__shared_count& __r) noexcept
1096 {
1097 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
1098 __r._M_pi = _M_pi;
1099 _M_pi = __tmp;
1100 }
1101
1102 long
1103 _M_get_use_count() const noexcept
1104 { return _M_pi ? _M_pi->_M_get_use_count() : 0; }
1105
1106 bool
1107 _M_unique() const noexcept
1108 { return this->_M_get_use_count() == 1; }
1109
1110 void*
1111 _M_get_deleter(const std::type_info& __ti) const noexcept
1112 { return _M_pi ? _M_pi->_M_get_deleter(__ti) : nullptr; }
1113
1114 bool
1115 _M_less(const __shared_count& __rhs) const noexcept
1116 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
1117
1118 bool
1119 _M_less(const __weak_count<_Lp>& __rhs) const noexcept
1120 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
1121
1122 // Friend function injected into enclosing namespace and found by ADL
1123 friend inline bool
1124 operator==(const __shared_count& __a, const __shared_count& __b) noexcept
1125 { return __a._M_pi == __b._M_pi; }
1126
1127 private:
1128 friend class __weak_count<_Lp>;
1129#ifdef __glibcxx_atomic_shared_ptr
1130 template<typename> friend class _Sp_atomic;
1131#endif
1132#ifdef __glibcxx_out_ptr
1133 template<typename, typename, typename...> friend class out_ptr_t;
1134#endif
1135
1136 _Sp_counted_base<_Lp>* _M_pi;
1137 };
1138
1139
1140 template<_Lock_policy _Lp>
1141 class __weak_count
1142 {
1143 public:
1144 constexpr __weak_count() noexcept : _M_pi(nullptr)
1145 { }
1146
1147 __weak_count(const __shared_count<_Lp>& __r) noexcept
1148 : _M_pi(__r._M_pi)
1149 {
1150 if (_M_pi != nullptr)
1151 _M_pi->_M_weak_add_ref();
1152 }
1153
1154 __weak_count(const __weak_count& __r) noexcept
1155 : _M_pi(__r._M_pi)
1156 {
1157 if (_M_pi != nullptr)
1158 _M_pi->_M_weak_add_ref();
1159 }
1160
1161 __weak_count(__weak_count&& __r) noexcept
1162 : _M_pi(__r._M_pi)
1163 { __r._M_pi = nullptr; }
1164
1165 ~__weak_count() noexcept
1166 {
1167 if (_M_pi != nullptr)
1168 _M_pi->_M_weak_release();
1169 }
1170
1171 __weak_count&
1172 operator=(const __shared_count<_Lp>& __r) noexcept
1173 {
1174 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
1175 if (__tmp != nullptr)
1176 __tmp->_M_weak_add_ref();
1177 if (_M_pi != nullptr)
1178 _M_pi->_M_weak_release();
1179 _M_pi = __tmp;
1180 return *this;
1181 }
1182
1183 __weak_count&
1184 operator=(const __weak_count& __r) noexcept
1185 {
1186 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
1187 if (__tmp != nullptr)
1188 __tmp->_M_weak_add_ref();
1189 if (_M_pi != nullptr)
1190 _M_pi->_M_weak_release();
1191 _M_pi = __tmp;
1192 return *this;
1193 }
1194
1195 __weak_count&
1196 operator=(__weak_count&& __r) noexcept
1197 {
1198 if (_M_pi != nullptr)
1199 _M_pi->_M_weak_release();
1200 _M_pi = __r._M_pi;
1201 __r._M_pi = nullptr;
1202 return *this;
1203 }
1204
1205 void
1206 _M_swap(__weak_count& __r) noexcept
1207 {
1208 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
1209 __r._M_pi = _M_pi;
1210 _M_pi = __tmp;
1211 }
1212
1213 long
1214 _M_get_use_count() const noexcept
1215 { return _M_pi != nullptr ? _M_pi->_M_get_use_count() : 0; }
1216
1217 bool
1218 _M_less(const __weak_count& __rhs) const noexcept
1219 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
1220
1221 bool
1222 _M_less(const __shared_count<_Lp>& __rhs) const noexcept
1223 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
1224
1225 // Friend function injected into enclosing namespace and found by ADL
1226 friend inline bool
1227 operator==(const __weak_count& __a, const __weak_count& __b) noexcept
1228 { return __a._M_pi == __b._M_pi; }
1229
1230 private:
1231 friend class __shared_count<_Lp>;
1232#ifdef __glibcxx_atomic_shared_ptr
1233 template<typename> friend class _Sp_atomic;
1234#endif
1235
1236 _Sp_counted_base<_Lp>* _M_pi;
1237 };
1238
1239 // Now that __weak_count is defined we can define this constructor:
1240 template<_Lock_policy _Lp>
1241 inline
1242 __shared_count<_Lp>::__shared_count(const __weak_count<_Lp>& __r)
1243 : _M_pi(__r._M_pi)
1244 {
1245 if (_M_pi == nullptr || !_M_pi->_M_add_ref_lock_nothrow())
1246 __throw_bad_weak_ptr();
1247 }
1248
1249 // Now that __weak_count is defined we can define this constructor:
1250 template<_Lock_policy _Lp>
1251 inline
1252 __shared_count<_Lp>::
1253 __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t) noexcept
1254 : _M_pi(__r._M_pi)
1255 {
1256 if (_M_pi && !_M_pi->_M_add_ref_lock_nothrow())
1257 _M_pi = nullptr;
1258 }
1259
1260 // Helper traits for shared_ptr of array:
1261
1262 // A pointer type Y* is said to be compatible with a pointer type T* when
1263 // either Y* is convertible to T* or Y is U[N] and T is U cv [].
1264 template<typename _Yp_ptr, typename _Tp_ptr>
1265 struct __sp_compatible_with
1266 : false_type
1267 { };
1268
1269 template<typename _Yp, typename _Tp>
1270 struct __sp_compatible_with<_Yp*, _Tp*>
1271 : is_convertible<_Yp*, _Tp*>::type
1272 { };
1273
1274 template<typename _Up, size_t _Nm>
1275 struct __sp_compatible_with<_Up(*)[_Nm], _Up(*)[]>
1276 : true_type
1277 { };
1278
1279 template<typename _Up, size_t _Nm>
1280 struct __sp_compatible_with<_Up(*)[_Nm], const _Up(*)[]>
1281 : true_type
1282 { };
1283
1284 template<typename _Up, size_t _Nm>
1285 struct __sp_compatible_with<_Up(*)[_Nm], volatile _Up(*)[]>
1286 : true_type
1287 { };
1288
1289 template<typename _Up, size_t _Nm>
1290 struct __sp_compatible_with<_Up(*)[_Nm], const volatile _Up(*)[]>
1291 : true_type
1292 { };
1293
1294 // Test conversion from Y(*)[N] to U(*)[N] without forming invalid type Y[N].
1295 template<typename _Up, size_t _Nm, typename _Yp, typename = void>
1296 struct __sp_is_constructible_arrN
1297 : false_type
1298 { };
1299
1300 template<typename _Up, size_t _Nm, typename _Yp>
1301 struct __sp_is_constructible_arrN<_Up, _Nm, _Yp, __void_t<_Yp[_Nm]>>
1302 : is_convertible<_Yp(*)[_Nm], _Up(*)[_Nm]>::type
1303 { };
1304
1305 // Test conversion from Y(*)[] to U(*)[] without forming invalid type Y[].
1306 template<typename _Up, typename _Yp, typename = void>
1307 struct __sp_is_constructible_arr
1308 : false_type
1309 { };
1310
1311 template<typename _Up, typename _Yp>
1312 struct __sp_is_constructible_arr<_Up, _Yp, __void_t<_Yp[]>>
1313 : is_convertible<_Yp(*)[], _Up(*)[]>::type
1314 { };
1315
1316 // Trait to check if shared_ptr<T> can be constructed from Y*.
1317 template<typename _Tp, typename _Yp>
1318 struct __sp_is_constructible;
1319
1320 // When T is U[N], Y(*)[N] shall be convertible to T*;
1321 template<typename _Up, size_t _Nm, typename _Yp>
1322 struct __sp_is_constructible<_Up[_Nm], _Yp>
1323 : __sp_is_constructible_arrN<_Up, _Nm, _Yp>::type
1324 { };
1325
1326 // when T is U[], Y(*)[] shall be convertible to T*;
1327 template<typename _Up, typename _Yp>
1328 struct __sp_is_constructible<_Up[], _Yp>
1329 : __sp_is_constructible_arr<_Up, _Yp>::type
1330 { };
1331
1332 // otherwise, Y* shall be convertible to T*.
1333 template<typename _Tp, typename _Yp>
1334 struct __sp_is_constructible
1335 : is_convertible<_Yp*, _Tp*>::type
1336 { };
1337
1338
1339 // Define operator* and operator-> for shared_ptr<T>.
1340 template<typename _Tp, _Lock_policy _Lp,
1341 bool = is_array<_Tp>::value, bool = is_void<_Tp>::value>
1342 class __shared_ptr_access
1343 {
1344 public:
1345 using element_type = _Tp;
1346
1347 element_type&
1348 operator*() const noexcept
1349 {
1350 __glibcxx_assert(_M_get() != nullptr);
1351 return *_M_get();
1352 }
1353
1354 element_type*
1355 operator->() const noexcept
1356 {
1357 _GLIBCXX_DEBUG_PEDASSERT(_M_get() != nullptr);
1358 return _M_get();
1359 }
1360
1361 private:
1362 element_type*
1363 _M_get() const noexcept
1364 { return static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get(); }
1365 };
1366
1367 // Define operator-> for shared_ptr<cv void>.
1368 template<typename _Tp, _Lock_policy _Lp>
1369 class __shared_ptr_access<_Tp, _Lp, false, true>
1370 {
1371 public:
1372 using element_type = _Tp;
1373
1374 element_type*
1375 operator->() const noexcept
1376 {
1377 auto __ptr = static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get();
1378 _GLIBCXX_DEBUG_PEDASSERT(__ptr != nullptr);
1379 return __ptr;
1380 }
1381 };
1382
1383 // Define operator[] for shared_ptr<T[]> and shared_ptr<T[N]>.
1384 template<typename _Tp, _Lock_policy _Lp>
1385 class __shared_ptr_access<_Tp, _Lp, true, false>
1386 {
1387 public:
1388 using element_type = typename remove_extent<_Tp>::type;
1389
1390#if __cplusplus <= 201402L
1391 [[__deprecated__("shared_ptr<T[]>::operator* is absent from C++17")]]
1392 element_type&
1393 operator*() const noexcept
1394 {
1395 __glibcxx_assert(_M_get() != nullptr);
1396 return *_M_get();
1397 }
1398
1399 [[__deprecated__("shared_ptr<T[]>::operator-> is absent from C++17")]]
1400 element_type*
1401 operator->() const noexcept
1402 {
1403 _GLIBCXX_DEBUG_PEDASSERT(_M_get() != nullptr);
1404 return _M_get();
1405 }
1406#endif
1407
1408 element_type&
1409 operator[](ptrdiff_t __i) const noexcept
1410 {
1411 __glibcxx_assert(_M_get() != nullptr);
1412 __glibcxx_assert(!extent<_Tp>::value || __i < extent<_Tp>::value);
1413 return _M_get()[__i];
1414 }
1415
1416 private:
1417 element_type*
1418 _M_get() const noexcept
1419 { return static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get(); }
1420 };
1421
1422 template<typename _Tp, _Lock_policy _Lp>
1423 class __shared_ptr
1424 : public __shared_ptr_access<_Tp, _Lp>
1425 {
1426 public:
1427 using element_type = typename remove_extent<_Tp>::type;
1428
1429 private:
1430 // Constraint for taking ownership of a pointer of type _Yp*:
1431 template<typename _Yp>
1432 using _SafeConv
1433 = typename enable_if<__sp_is_constructible<_Tp, _Yp>::value>::type;
1434
1435 // Constraint for construction from shared_ptr and weak_ptr:
1436 template<typename _Yp, typename _Res = void>
1437 using _Compatible = typename
1438 enable_if<__sp_compatible_with<_Yp*, _Tp*>::value, _Res>::type;
1439
1440 // Constraint for assignment from shared_ptr and weak_ptr:
1441 template<typename _Yp>
1442 using _Assignable = _Compatible<_Yp, __shared_ptr&>;
1443
1444 // Constraint for construction from unique_ptr:
1445 template<typename _Yp, typename _Del, typename _Res = void,
1446 typename _Ptr = typename unique_ptr<_Yp, _Del>::pointer>
1447 using _UniqCompatible = __enable_if_t<__and_<
1448 __sp_compatible_with<_Yp*, _Tp*>,
1449 is_convertible<_Ptr, element_type*>,
1450 is_move_constructible<_Del>
1451 >::value, _Res>;
1452
1453 // Constraint for assignment from unique_ptr:
1454 template<typename _Yp, typename _Del>
1455 using _UniqAssignable = _UniqCompatible<_Yp, _Del, __shared_ptr&>;
1456
1457 public:
1458
1459#if __cplusplus > 201402L
1460 using weak_type = __weak_ptr<_Tp, _Lp>;
1461#endif
1462
1463 constexpr __shared_ptr() noexcept
1464 : _M_ptr(0), _M_refcount()
1465 { }
1466
1467 template<typename _Yp, typename = _SafeConv<_Yp>>
1468 explicit
1469 __shared_ptr(_Yp* __p)
1470 : _M_ptr(__p), _M_refcount(__p, typename is_array<_Tp>::type())
1471 {
1472 static_assert( !is_void<_Yp>::value, "incomplete type" );
1473 static_assert( sizeof(_Yp) > 0, "incomplete type" );
1474 _M_enable_shared_from_this_with(__p);
1475 }
1476
1477 template<typename _Yp, typename _Deleter, typename = _SafeConv<_Yp>>
1478 __shared_ptr(_Yp* __p, _Deleter __d)
1479 : _M_ptr(__p), _M_refcount(__p, std::move(__d))
1480 {
1481 static_assert(__is_invocable<_Deleter&, _Yp*&>::value,
1482 "deleter expression d(p) is well-formed");
1483 _M_enable_shared_from_this_with(__p);
1484 }
1485
1486 template<typename _Yp, typename _Deleter, typename _Alloc,
1487 typename = _SafeConv<_Yp>>
1488 __shared_ptr(_Yp* __p, _Deleter __d, _Alloc __a)
1489 : _M_ptr(__p), _M_refcount(__p, std::move(__d), std::move(__a))
1490 {
1491 static_assert(__is_invocable<_Deleter&, _Yp*&>::value,
1492 "deleter expression d(p) is well-formed");
1493 _M_enable_shared_from_this_with(__p);
1494 }
1495
1496 template<typename _Deleter>
1497 __shared_ptr(nullptr_t __p, _Deleter __d)
1498 : _M_ptr(0), _M_refcount(__p, std::move(__d))
1499 { }
1500
1501 template<typename _Deleter, typename _Alloc>
1502 __shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
1503 : _M_ptr(0), _M_refcount(__p, std::move(__d), std::move(__a))
1504 { }
1505
1506 // Aliasing constructor
1507 template<typename _Yp>
1508 __shared_ptr(const __shared_ptr<_Yp, _Lp>& __r,
1509 element_type* __p) noexcept
1510 : _M_ptr(__p), _M_refcount(__r._M_refcount) // never throws
1511 { }
1512
1513 // Aliasing constructor
1514 template<typename _Yp>
1515 __shared_ptr(__shared_ptr<_Yp, _Lp>&& __r,
1516 element_type* __p) noexcept
1517 : _M_ptr(__p), _M_refcount()
1518 {
1519 _M_refcount._M_swap(__r._M_refcount);
1520 __r._M_ptr = nullptr;
1521 }
1522
1523 __shared_ptr(const __shared_ptr&) noexcept = default;
1524 __shared_ptr& operator=(const __shared_ptr&) noexcept = default;
1525 ~__shared_ptr() = default;
1526
1527 template<typename _Yp, typename = _Compatible<_Yp>>
1528 __shared_ptr(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1529 : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount)
1530 { }
1531
1532 __shared_ptr(__shared_ptr&& __r) noexcept
1533 : _M_ptr(__r._M_ptr), _M_refcount()
1534 {
1535 _M_refcount._M_swap(__r._M_refcount);
1536 __r._M_ptr = nullptr;
1537 }
1538
1539 template<typename _Yp, typename = _Compatible<_Yp>>
1540 __shared_ptr(__shared_ptr<_Yp, _Lp>&& __r) noexcept
1541 : _M_ptr(__r._M_ptr), _M_refcount()
1542 {
1543 _M_refcount._M_swap(__r._M_refcount);
1544 __r._M_ptr = nullptr;
1545 }
1546
1547 template<typename _Yp, typename = _Compatible<_Yp>>
1548 explicit __shared_ptr(const __weak_ptr<_Yp, _Lp>& __r)
1549 : _M_refcount(__r._M_refcount) // may throw
1550 {
1551 // It is now safe to copy __r._M_ptr, as
1552 // _M_refcount(__r._M_refcount) did not throw.
1553 _M_ptr = __r._M_ptr;
1554 }
1555
1556 // If an exception is thrown this constructor has no effect.
1557 template<typename _Yp, typename _Del,
1558 typename = _UniqCompatible<_Yp, _Del>>
1559 __shared_ptr(unique_ptr<_Yp, _Del>&& __r)
1560 : _M_ptr(__r.get()), _M_refcount()
1561 {
1562 auto __raw = __to_address(__r.get());
1563 _M_refcount = __shared_count<_Lp>(std::move(__r));
1564 _M_enable_shared_from_this_with(__raw);
1565 }
1566
1567#if __cplusplus <= 201402L && _GLIBCXX_USE_DEPRECATED
1568 protected:
1569 // If an exception is thrown this constructor has no effect.
1570 template<typename _Tp1, typename _Del,
1571 typename enable_if<__and_<
1572 __not_<is_array<_Tp>>, is_array<_Tp1>,
1573 is_convertible<typename unique_ptr<_Tp1, _Del>::pointer, _Tp*>
1574 >::value, bool>::type = true>
1575 __shared_ptr(unique_ptr<_Tp1, _Del>&& __r, __sp_array_delete)
1576 : _M_ptr(__r.get()), _M_refcount()
1577 {
1578 auto __raw = __to_address(__r.get());
1579 _M_refcount = __shared_count<_Lp>(std::move(__r));
1580 _M_enable_shared_from_this_with(__raw);
1581 }
1582 public:
1583#endif
1584
1585#if _GLIBCXX_USE_DEPRECATED
1586#pragma GCC diagnostic push
1587#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
1588 // Postcondition: use_count() == 1 and __r.get() == 0
1589 template<typename _Yp, typename = _Compatible<_Yp>>
1590 __shared_ptr(auto_ptr<_Yp>&& __r);
1591#pragma GCC diagnostic pop
1592#endif
1593
1594 constexpr __shared_ptr(nullptr_t) noexcept : __shared_ptr() { }
1595
1596 template<typename _Yp>
1597 _Assignable<_Yp>
1598 operator=(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1599 {
1600 _M_ptr = __r._M_ptr;
1601 _M_refcount = __r._M_refcount; // __shared_count::op= doesn't throw
1602 return *this;
1603 }
1604
1605#if _GLIBCXX_USE_DEPRECATED
1606#pragma GCC diagnostic push
1607#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
1608 template<typename _Yp>
1609 _Assignable<_Yp>
1610 operator=(auto_ptr<_Yp>&& __r)
1611 {
1612 __shared_ptr(std::move(__r)).swap(*this);
1613 return *this;
1614 }
1615#pragma GCC diagnostic pop
1616#endif
1617
1618 __shared_ptr&
1619 operator=(__shared_ptr&& __r) noexcept
1620 {
1621 __shared_ptr(std::move(__r)).swap(*this);
1622 return *this;
1623 }
1624
1625 template<class _Yp>
1626 _Assignable<_Yp>
1627 operator=(__shared_ptr<_Yp, _Lp>&& __r) noexcept
1628 {
1629 __shared_ptr(std::move(__r)).swap(*this);
1630 return *this;
1631 }
1632
1633 template<typename _Yp, typename _Del>
1634 _UniqAssignable<_Yp, _Del>
1635 operator=(unique_ptr<_Yp, _Del>&& __r)
1636 {
1637 __shared_ptr(std::move(__r)).swap(*this);
1638 return *this;
1639 }
1640
1641 void
1642 reset() noexcept
1643 { __shared_ptr().swap(*this); }
1644
1645 template<typename _Yp>
1646 _SafeConv<_Yp>
1647 reset(_Yp* __p) // _Yp must be complete.
1648 {
1649 // Catch self-reset errors.
1650 __glibcxx_assert(__p == nullptr || __p != _M_ptr);
1651 __shared_ptr(__p).swap(*this);
1652 }
1653
1654 template<typename _Yp, typename _Deleter>
1655 _SafeConv<_Yp>
1656 reset(_Yp* __p, _Deleter __d)
1657 { __shared_ptr(__p, std::move(__d)).swap(*this); }
1658
1659 template<typename _Yp, typename _Deleter, typename _Alloc>
1660 _SafeConv<_Yp>
1661 reset(_Yp* __p, _Deleter __d, _Alloc __a)
1662 { __shared_ptr(__p, std::move(__d), std::move(__a)).swap(*this); }
1663
1664 /// Return the stored pointer.
1665 element_type*
1666 get() const noexcept
1667 { return _M_ptr; }
1668
1669 /// Return true if the stored pointer is not null.
1670 explicit operator bool() const noexcept
1671 { return _M_ptr != nullptr; }
1672
1673 /// Return true if use_count() == 1.
1674 bool
1675 unique() const noexcept
1676 { return _M_refcount._M_unique(); }
1677
1678 /// If *this owns a pointer, return the number of owners, otherwise zero.
1679 long
1680 use_count() const noexcept
1681 { return _M_refcount._M_get_use_count(); }
1682
1683 /// Exchange both the owned pointer and the stored pointer.
1684 void
1685 swap(__shared_ptr<_Tp, _Lp>& __other) noexcept
1686 {
1687 std::swap(_M_ptr, __other._M_ptr);
1688 _M_refcount._M_swap(__other._M_refcount);
1689 }
1690
1691 /** @brief Define an ordering based on ownership.
1692 *
1693 * This function defines a strict weak ordering between two shared_ptr
1694 * or weak_ptr objects, such that one object is less than the other
1695 * unless they share ownership of the same pointer, or are both empty.
1696 * @{
1697 */
1698 template<typename _Tp1>
1699 bool
1700 owner_before(__shared_ptr<_Tp1, _Lp> const& __rhs) const noexcept
1701 { return _M_refcount._M_less(__rhs._M_refcount); }
1702
1703 template<typename _Tp1>
1704 bool
1705 owner_before(__weak_ptr<_Tp1, _Lp> const& __rhs) const noexcept
1706 { return _M_refcount._M_less(__rhs._M_refcount); }
1707 /// @}
1708
1709 protected:
1710 // This constructor is non-standard, it is used by allocate_shared.
1711 template<typename _Alloc, typename... _Args>
1712 __shared_ptr(_Sp_alloc_shared_tag<_Alloc> __tag, _Args&&... __args)
1713 : _M_ptr(), _M_refcount(_M_ptr, __tag, std::forward<_Args>(__args)...)
1714 { _M_enable_shared_from_this_with(_M_ptr); }
1715
1716 template<typename _Tp1, _Lock_policy _Lp1, typename _Alloc,
1717 typename... _Args>
1718 friend __shared_ptr<_Tp1, _Lp1>
1719 __allocate_shared(const _Alloc& __a, _Args&&... __args);
1720
1721#if __glibcxx_shared_ptr_arrays >= 201707L // C++ >= 20 && HOSTED
1722 // This constructor is non-standard, it is used by allocate_shared<T[]>.
1723 template<typename _Alloc, typename _Init = const remove_extent_t<_Tp>*>
1724 __shared_ptr(const _Sp_counted_array_base<_Alloc>& __a,
1725 _Init __init = nullptr)
1726 : _M_ptr(), _M_refcount(_M_ptr, __a, __init)
1727 { }
1728#endif
1729
1730 // This constructor is used by __weak_ptr::lock() and
1731 // shared_ptr::shared_ptr(const weak_ptr&, std::nothrow_t).
1732 __shared_ptr(const __weak_ptr<_Tp, _Lp>& __r, std::nothrow_t) noexcept
1733 : _M_refcount(__r._M_refcount, std::nothrow)
1734 {
1735 _M_ptr = _M_refcount._M_get_use_count() ? __r._M_ptr : nullptr;
1736 }
1737
1738 friend class __weak_ptr<_Tp, _Lp>;
1739
1740 private:
1741
1742 template<typename _Yp>
1743 using __esft_base_t = decltype(__enable_shared_from_this_base(
1744 std::declval<const __shared_count<_Lp>&>(),
1745 std::declval<_Yp*>()));
1746
1747 // Detect an accessible and unambiguous enable_shared_from_this base.
1748 template<typename _Yp, typename = void>
1749 struct __has_esft_base
1750 : false_type { };
1751
1752 template<typename _Yp>
1753 struct __has_esft_base<_Yp, __void_t<__esft_base_t<_Yp>>>
1754 : __not_<is_array<_Tp>> { }; // No enable shared_from_this for arrays
1755
1756 template<typename _Yp, typename _Yp2 = typename remove_cv<_Yp>::type>
1757 typename enable_if<__has_esft_base<_Yp2>::value>::type
1758 _M_enable_shared_from_this_with(_Yp* __p) noexcept
1759 {
1760 if (auto __base = __enable_shared_from_this_base(_M_refcount, __p))
1761 __base->_M_weak_assign(const_cast<_Yp2*>(__p), _M_refcount);
1762 }
1763
1764 template<typename _Yp, typename _Yp2 = typename remove_cv<_Yp>::type>
1765 typename enable_if<!__has_esft_base<_Yp2>::value>::type
1766 _M_enable_shared_from_this_with(_Yp*) noexcept
1767 { }
1768
1769 void*
1770 _M_get_deleter(const std::type_info& __ti) const noexcept
1771 { return _M_refcount._M_get_deleter(__ti); }
1772
1773 template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
1774 template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
1775
1776 template<typename _Del, typename _Tp1, _Lock_policy _Lp1>
1777 friend _Del* get_deleter(const __shared_ptr<_Tp1, _Lp1>&) noexcept;
1778
1779 template<typename _Del, typename _Tp1>
1780 friend _Del* get_deleter(const shared_ptr<_Tp1>&) noexcept;
1781
1782#ifdef __glibcxx_atomic_shared_ptr
1783 friend _Sp_atomic<shared_ptr<_Tp>>;
1784#endif
1785#ifdef __glibcxx_out_ptr
1786 template<typename, typename, typename...> friend class out_ptr_t;
1787#endif
1788
1789 element_type* _M_ptr; // Contained pointer.
1790 __shared_count<_Lp> _M_refcount; // Reference counter.
1791 };
1792
1793
1794 // 20.7.2.2.7 shared_ptr comparisons
1795 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1796 inline bool
1797 operator==(const __shared_ptr<_Tp1, _Lp>& __a,
1798 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1799 { return __a.get() == __b.get(); }
1800
1801 template<typename _Tp, _Lock_policy _Lp>
1802 inline bool
1803 operator==(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1804 { return !__a; }
1805
1806#ifdef __cpp_lib_three_way_comparison
1807 template<typename _Tp, typename _Up, _Lock_policy _Lp>
1808 inline strong_ordering
1809 operator<=>(const __shared_ptr<_Tp, _Lp>& __a,
1810 const __shared_ptr<_Up, _Lp>& __b) noexcept
1811 { return compare_three_way()(__a.get(), __b.get()); }
1812
1813 template<typename _Tp, _Lock_policy _Lp>
1814 inline strong_ordering
1815 operator<=>(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1816 {
1817 using pointer = typename __shared_ptr<_Tp, _Lp>::element_type*;
1818 return compare_three_way()(__a.get(), static_cast<pointer>(nullptr));
1819 }
1820#else
1821 template<typename _Tp, _Lock_policy _Lp>
1822 inline bool
1823 operator==(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1824 { return !__a; }
1825
1826 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1827 inline bool
1828 operator!=(const __shared_ptr<_Tp1, _Lp>& __a,
1829 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1830 { return __a.get() != __b.get(); }
1831
1832 template<typename _Tp, _Lock_policy _Lp>
1833 inline bool
1834 operator!=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1835 { return (bool)__a; }
1836
1837 template<typename _Tp, _Lock_policy _Lp>
1838 inline bool
1839 operator!=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1840 { return (bool)__a; }
1841
1842 template<typename _Tp, typename _Up, _Lock_policy _Lp>
1843 inline bool
1844 operator<(const __shared_ptr<_Tp, _Lp>& __a,
1845 const __shared_ptr<_Up, _Lp>& __b) noexcept
1846 {
1847 using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1848 using _Up_elt = typename __shared_ptr<_Up, _Lp>::element_type;
1849 using _Vp = typename common_type<_Tp_elt*, _Up_elt*>::type;
1850 return less<_Vp>()(__a.get(), __b.get());
1851 }
1852
1853 template<typename _Tp, _Lock_policy _Lp>
1854 inline bool
1855 operator<(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1856 {
1857 using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1858 return less<_Tp_elt*>()(__a.get(), nullptr);
1859 }
1860
1861 template<typename _Tp, _Lock_policy _Lp>
1862 inline bool
1863 operator<(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1864 {
1865 using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1866 return less<_Tp_elt*>()(nullptr, __a.get());
1867 }
1868
1869 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1870 inline bool
1871 operator<=(const __shared_ptr<_Tp1, _Lp>& __a,
1872 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1873 { return !(__b < __a); }
1874
1875 template<typename _Tp, _Lock_policy _Lp>
1876 inline bool
1877 operator<=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1878 { return !(nullptr < __a); }
1879
1880 template<typename _Tp, _Lock_policy _Lp>
1881 inline bool
1882 operator<=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1883 { return !(__a < nullptr); }
1884
1885 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1886 inline bool
1887 operator>(const __shared_ptr<_Tp1, _Lp>& __a,
1888 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1889 { return (__b < __a); }
1890
1891 template<typename _Tp, _Lock_policy _Lp>
1892 inline bool
1893 operator>(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1894 { return nullptr < __a; }
1895
1896 template<typename _Tp, _Lock_policy _Lp>
1897 inline bool
1898 operator>(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1899 { return __a < nullptr; }
1900
1901 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1902 inline bool
1903 operator>=(const __shared_ptr<_Tp1, _Lp>& __a,
1904 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1905 { return !(__a < __b); }
1906
1907 template<typename _Tp, _Lock_policy _Lp>
1908 inline bool
1909 operator>=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1910 { return !(__a < nullptr); }
1911
1912 template<typename _Tp, _Lock_policy _Lp>
1913 inline bool
1914 operator>=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1915 { return !(nullptr < __a); }
1916#endif // three-way comparison
1917
1918 // 20.7.2.2.8 shared_ptr specialized algorithms.
1919 template<typename _Tp, _Lock_policy _Lp>
1920 inline void
1921 swap(__shared_ptr<_Tp, _Lp>& __a, __shared_ptr<_Tp, _Lp>& __b) noexcept
1922 { __a.swap(__b); }
1923
1924 // 20.7.2.2.9 shared_ptr casts
1925
1926 // The seemingly equivalent code:
1927 // shared_ptr<_Tp, _Lp>(static_cast<_Tp*>(__r.get()))
1928 // will eventually result in undefined behaviour, attempting to
1929 // delete the same object twice.
1930 /// static_pointer_cast
1931 template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1932 inline __shared_ptr<_Tp, _Lp>
1933 static_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1934 {
1935 using _Sp = __shared_ptr<_Tp, _Lp>;
1936 return _Sp(__r, static_cast<typename _Sp::element_type*>(__r.get()));
1937 }
1938
1939 // The seemingly equivalent code:
1940 // shared_ptr<_Tp, _Lp>(const_cast<_Tp*>(__r.get()))
1941 // will eventually result in undefined behaviour, attempting to
1942 // delete the same object twice.
1943 /// const_pointer_cast
1944 template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1945 inline __shared_ptr<_Tp, _Lp>
1946 const_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1947 {
1948 using _Sp = __shared_ptr<_Tp, _Lp>;
1949 return _Sp(__r, const_cast<typename _Sp::element_type*>(__r.get()));
1950 }
1951
1952 // The seemingly equivalent code:
1953 // shared_ptr<_Tp, _Lp>(dynamic_cast<_Tp*>(__r.get()))
1954 // will eventually result in undefined behaviour, attempting to
1955 // delete the same object twice.
1956 /// dynamic_pointer_cast
1957 template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1958 inline __shared_ptr<_Tp, _Lp>
1959 dynamic_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1960 {
1961 using _Sp = __shared_ptr<_Tp, _Lp>;
1962 if (auto* __p = dynamic_cast<typename _Sp::element_type*>(__r.get()))
1963 return _Sp(__r, __p);
1964 return _Sp();
1965 }
1966
1967#if __cplusplus > 201402L
1968 template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1969 inline __shared_ptr<_Tp, _Lp>
1970 reinterpret_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1971 {
1972 using _Sp = __shared_ptr<_Tp, _Lp>;
1973 return _Sp(__r, reinterpret_cast<typename _Sp::element_type*>(__r.get()));
1974 }
1975#endif
1976
1977 template<typename _Tp, _Lock_policy _Lp>
1978 class __weak_ptr
1979 {
1980 template<typename _Yp, typename _Res = void>
1981 using _Compatible = typename
1982 enable_if<__sp_compatible_with<_Yp*, _Tp*>::value, _Res>::type;
1983
1984 // Constraint for assignment from shared_ptr and weak_ptr:
1985 template<typename _Yp>
1986 using _Assignable = _Compatible<_Yp, __weak_ptr&>;
1987
1988 public:
1989 using element_type = typename remove_extent<_Tp>::type;
1990
1991 constexpr __weak_ptr() noexcept
1992 : _M_ptr(nullptr), _M_refcount()
1993 { }
1994
1995 __weak_ptr(const __weak_ptr&) noexcept = default;
1996
1997 ~__weak_ptr() = default;
1998
1999 // The "obvious" converting constructor implementation:
2000 //
2001 // template<typename _Tp1>
2002 // __weak_ptr(const __weak_ptr<_Tp1, _Lp>& __r)
2003 // : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws
2004 // { }
2005 //
2006 // has a serious problem.
2007 //
2008 // __r._M_ptr may already have been invalidated. The _M_ptr(__r._M_ptr)
2009 // conversion may require access to *__r._M_ptr (virtual inheritance).
2010 //
2011 // It is not possible to avoid spurious access violations since
2012 // in multithreaded programs __r._M_ptr may be invalidated at any point.
2013 template<typename _Yp, typename = _Compatible<_Yp>>
2014 __weak_ptr(const __weak_ptr<_Yp, _Lp>& __r) noexcept
2015 : _M_refcount(__r._M_refcount)
2016 { _M_ptr = __r.lock().get(); }
2017
2018 template<typename _Yp, typename = _Compatible<_Yp>>
2019 __weak_ptr(const __shared_ptr<_Yp, _Lp>& __r) noexcept
2020 : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount)
2021 { }
2022
2023 __weak_ptr(__weak_ptr&& __r) noexcept
2024 : _M_ptr(__r._M_ptr), _M_refcount(std::move(__r._M_refcount))
2025 { __r._M_ptr = nullptr; }
2026
2027 template<typename _Yp, typename = _Compatible<_Yp>>
2028 __weak_ptr(__weak_ptr<_Yp, _Lp>&& __r) noexcept
2029 : _M_ptr(__r.lock().get()), _M_refcount(std::move(__r._M_refcount))
2030 { __r._M_ptr = nullptr; }
2031
2032 __weak_ptr&
2033 operator=(const __weak_ptr& __r) noexcept = default;
2034
2035 template<typename _Yp>
2036 _Assignable<_Yp>
2037 operator=(const __weak_ptr<_Yp, _Lp>& __r) noexcept
2038 {
2039 _M_ptr = __r.lock().get();
2040 _M_refcount = __r._M_refcount;
2041 return *this;
2042 }
2043
2044 template<typename _Yp>
2045 _Assignable<_Yp>
2046 operator=(const __shared_ptr<_Yp, _Lp>& __r) noexcept
2047 {
2048 _M_ptr = __r._M_ptr;
2049 _M_refcount = __r._M_refcount;
2050 return *this;
2051 }
2052
2053 __weak_ptr&
2054 operator=(__weak_ptr&& __r) noexcept
2055 {
2056 __weak_ptr(std::move(__r)).swap(*this);
2057 return *this;
2058 }
2059
2060 template<typename _Yp>
2061 _Assignable<_Yp>
2062 operator=(__weak_ptr<_Yp, _Lp>&& __r) noexcept
2063 {
2064 _M_ptr = __r.lock().get();
2065 _M_refcount = std::move(__r._M_refcount);
2066 __r._M_ptr = nullptr;
2067 return *this;
2068 }
2069
2070 __shared_ptr<_Tp, _Lp>
2071 lock() const noexcept
2072 { return __shared_ptr<element_type, _Lp>(*this, std::nothrow); }
2073
2074 long
2075 use_count() const noexcept
2076 { return _M_refcount._M_get_use_count(); }
2077
2078 bool
2079 expired() const noexcept
2080 { return _M_refcount._M_get_use_count() == 0; }
2081
2082 template<typename _Tp1>
2083 bool
2084 owner_before(const __shared_ptr<_Tp1, _Lp>& __rhs) const noexcept
2085 { return _M_refcount._M_less(__rhs._M_refcount); }
2086
2087 template<typename _Tp1>
2088 bool
2089 owner_before(const __weak_ptr<_Tp1, _Lp>& __rhs) const noexcept
2090 { return _M_refcount._M_less(__rhs._M_refcount); }
2091
2092 void
2093 reset() noexcept
2094 { __weak_ptr().swap(*this); }
2095
2096 void
2097 swap(__weak_ptr& __s) noexcept
2098 {
2099 std::swap(_M_ptr, __s._M_ptr);
2100 _M_refcount._M_swap(__s._M_refcount);
2101 }
2102
2103 private:
2104 // Used by __enable_shared_from_this.
2105 void
2106 _M_assign(_Tp* __ptr, const __shared_count<_Lp>& __refcount) noexcept
2107 {
2108 if (use_count() == 0)
2109 {
2110 _M_ptr = __ptr;
2111 _M_refcount = __refcount;
2112 }
2113 }
2114
2115 template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
2116 template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
2117 friend class __enable_shared_from_this<_Tp, _Lp>;
2118 friend class enable_shared_from_this<_Tp>;
2119#ifdef __glibcxx_atomic_shared_ptr
2120 friend _Sp_atomic<weak_ptr<_Tp>>;
2121#endif
2122
2123 element_type* _M_ptr; // Contained pointer.
2124 __weak_count<_Lp> _M_refcount; // Reference counter.
2125 };
2126
2127 // 20.7.2.3.6 weak_ptr specialized algorithms.
2128 template<typename _Tp, _Lock_policy _Lp>
2129 inline void
2130 swap(__weak_ptr<_Tp, _Lp>& __a, __weak_ptr<_Tp, _Lp>& __b) noexcept
2131 { __a.swap(__b); }
2132
2133#pragma GCC diagnostic push
2134#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
2135 template<typename _Tp, typename _Tp1>
2136 struct _Sp_owner_less : public binary_function<_Tp, _Tp, bool>
2137 {
2138 bool
2139 operator()(const _Tp& __lhs, const _Tp& __rhs) const noexcept
2140 { return __lhs.owner_before(__rhs); }
2141
2142 bool
2143 operator()(const _Tp& __lhs, const _Tp1& __rhs) const noexcept
2144 { return __lhs.owner_before(__rhs); }
2145
2146 bool
2147 operator()(const _Tp1& __lhs, const _Tp& __rhs) const noexcept
2148 { return __lhs.owner_before(__rhs); }
2149 };
2150#pragma GCC diagnostic pop
2151
2152 template<>
2153 struct _Sp_owner_less<void, void>
2154 {
2155 template<typename _Tp, typename _Up>
2156 auto
2157 operator()(const _Tp& __lhs, const _Up& __rhs) const noexcept
2158 -> decltype(__lhs.owner_before(__rhs))
2159 { return __lhs.owner_before(__rhs); }
2160
2161 using is_transparent = void;
2162 };
2163
2164 template<typename _Tp, _Lock_policy _Lp>
2165 struct owner_less<__shared_ptr<_Tp, _Lp>>
2166 : public _Sp_owner_less<__shared_ptr<_Tp, _Lp>, __weak_ptr<_Tp, _Lp>>
2167 { };
2168
2169 template<typename _Tp, _Lock_policy _Lp>
2170 struct owner_less<__weak_ptr<_Tp, _Lp>>
2171 : public _Sp_owner_less<__weak_ptr<_Tp, _Lp>, __shared_ptr<_Tp, _Lp>>
2172 { };
2173
2174
2175 template<typename _Tp, _Lock_policy _Lp>
2176 class __enable_shared_from_this
2177 {
2178 protected:
2179 constexpr __enable_shared_from_this() noexcept { }
2180
2181 __enable_shared_from_this(const __enable_shared_from_this&) noexcept { }
2182
2183 __enable_shared_from_this&
2184 operator=(const __enable_shared_from_this&) noexcept
2185 { return *this; }
2186
2187 ~__enable_shared_from_this() { }
2188
2189 public:
2190 __shared_ptr<_Tp, _Lp>
2191 shared_from_this()
2192 { return __shared_ptr<_Tp, _Lp>(this->_M_weak_this); }
2193
2194 __shared_ptr<const _Tp, _Lp>
2195 shared_from_this() const
2196 { return __shared_ptr<const _Tp, _Lp>(this->_M_weak_this); }
2197
2198#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
2199 __weak_ptr<_Tp, _Lp>
2200 weak_from_this() noexcept
2201 { return this->_M_weak_this; }
2202
2203 __weak_ptr<const _Tp, _Lp>
2204 weak_from_this() const noexcept
2205 { return this->_M_weak_this; }
2206#endif
2207
2208 private:
2209 template<typename _Tp1>
2210 void
2211 _M_weak_assign(_Tp1* __p, const __shared_count<_Lp>& __n) const noexcept
2212 { _M_weak_this._M_assign(__p, __n); }
2213
2214 friend const __enable_shared_from_this*
2215 __enable_shared_from_this_base(const __shared_count<_Lp>&,
2216 const __enable_shared_from_this* __p)
2217 { return __p; }
2218
2219 template<typename, _Lock_policy>
2220 friend class __shared_ptr;
2221
2222 mutable __weak_ptr<_Tp, _Lp> _M_weak_this;
2223 };
2224
2225 template<typename _Tp, _Lock_policy _Lp = __default_lock_policy,
2226 typename _Alloc, typename... _Args>
2227 inline __shared_ptr<_Tp, _Lp>
2228 __allocate_shared(const _Alloc& __a, _Args&&... __args)
2229 {
2230 static_assert(!is_array<_Tp>::value, "make_shared<T[]> not supported");
2231
2232 return __shared_ptr<_Tp, _Lp>(_Sp_alloc_shared_tag<_Alloc>{__a},
2233 std::forward<_Args>(__args)...);
2234 }
2235
2236 template<typename _Tp, _Lock_policy _Lp = __default_lock_policy,
2237 typename... _Args>
2238 inline __shared_ptr<_Tp, _Lp>
2239 __make_shared(_Args&&... __args)
2240 {
2241 typedef typename std::remove_const<_Tp>::type _Tp_nc;
2242 return std::__allocate_shared<_Tp, _Lp>(std::allocator<_Tp_nc>(),
2243 std::forward<_Args>(__args)...);
2244 }
2245
2246 /// std::hash specialization for __shared_ptr.
2247 template<typename _Tp, _Lock_policy _Lp>
2248 struct hash<__shared_ptr<_Tp, _Lp>>
2249 : public __hash_base<size_t, __shared_ptr<_Tp, _Lp>>
2250 {
2251 size_t
2252 operator()(const __shared_ptr<_Tp, _Lp>& __s) const noexcept
2253 {
2254 return hash<typename __shared_ptr<_Tp, _Lp>::element_type*>()(
2255 __s.get());
2256 }
2257 };
2258
2259_GLIBCXX_END_NAMESPACE_VERSION
2260} // namespace
2261
2262#endif // _SHARED_PTR_BASE_H
2263