1 // shared_ptr and weak_ptr implementation details -*- C++ -*-
2
3 // Copyright (C) 2007-2022 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
_GLIBCXX_VISIBILITY(default)70 namespace 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(&_M_use_count, 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(&_M_weak_count,
188 -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(&_M_weak_count, 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(&_M_weak_count, -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(&_M_use_count, 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(&_M_use_count, -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(&_M_use_count, -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(&_M_use_count, -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 #if __cplusplus >= 202002L
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 _Impl _M_impl;
553 };
554
555 // helpers for make_shared / allocate_shared
556
557 struct _Sp_make_shared_tag
558 {
559 private:
560 template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
561 friend class _Sp_counted_ptr_inplace;
562
563 static const type_info&
564 _S_ti() noexcept _GLIBCXX_VISIBILITY(default)
565 {
566 alignas(type_info) static constexpr char __tag[sizeof(type_info)] = { };
567 return reinterpret_cast<const type_info&>(__tag);
568 }
569
570 static bool _S_eq(const type_info&) noexcept;
571 };
572
573 template<typename _Alloc>
574 struct _Sp_alloc_shared_tag
575 {
576 const _Alloc& _M_a;
577 };
578
579 template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
580 class _Sp_counted_ptr_inplace final : public _Sp_counted_base<_Lp>
581 {
582 class _Impl : _Sp_ebo_helper<0, _Alloc>
583 {
584 typedef _Sp_ebo_helper<0, _Alloc> _A_base;
585
586 public:
587 explicit _Impl(_Alloc __a) noexcept : _A_base(__a) { }
588
589 _Alloc& _M_alloc() noexcept { return _A_base::_S_get(*this); }
590
591 __gnu_cxx::__aligned_buffer<_Tp> _M_storage;
592 };
593
594 public:
595 using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_ptr_inplace>;
596
597 // Alloc parameter is not a reference so doesn't alias anything in __args
598 template<typename... _Args>
599 _Sp_counted_ptr_inplace(_Alloc __a, _Args&&... __args)
600 : _M_impl(__a)
601 {
602 // _GLIBCXX_RESOLVE_LIB_DEFECTS
603 // 2070. allocate_shared should use allocator_traits<A>::construct
604 allocator_traits<_Alloc>::construct(__a, _M_ptr(),
605 std::forward<_Args>(__args)...); // might throw
606 }
607
608 ~_Sp_counted_ptr_inplace() noexcept { }
609
610 virtual void
611 _M_dispose() noexcept
612 {
613 allocator_traits<_Alloc>::destroy(_M_impl._M_alloc(), _M_ptr());
614 }
615
616 // Override because the allocator needs to know the dynamic type
617 virtual void
618 _M_destroy() noexcept
619 {
620 __allocator_type __a(_M_impl._M_alloc());
621 __allocated_ptr<__allocator_type> __guard_ptr{ __a, this };
622 this->~_Sp_counted_ptr_inplace();
623 }
624
625 private:
626 friend class __shared_count<_Lp>; // To be able to call _M_ptr().
627
628 // No longer used, but code compiled against old libstdc++ headers
629 // might still call it from __shared_ptr ctor to get the pointer out.
630 virtual void*
631 _M_get_deleter(const std::type_info& __ti) noexcept override
632 {
633 auto __ptr = const_cast<typename remove_cv<_Tp>::type*>(_M_ptr());
634 // Check for the fake type_info first, so we don't try to access it
635 // as a real type_info object. Otherwise, check if it's the real
636 // type_info for this class. With RTTI enabled we can check directly,
637 // or call a library function to do it.
638 if (&__ti == &_Sp_make_shared_tag::_S_ti()
639 ||
640 #if __cpp_rtti
641 __ti == typeid(_Sp_make_shared_tag)
642 #else
643 _Sp_make_shared_tag::_S_eq(__ti)
644 #endif
645 )
646 return __ptr;
647 return nullptr;
648 }
649
650 _Tp* _M_ptr() noexcept { return _M_impl._M_storage._M_ptr(); }
651
652 _Impl _M_impl;
653 };
654
655 #if __cplusplus >= 202002L
656 # define __cpp_lib_smart_ptr_for_overwrite 202002L
657 struct _Sp_overwrite_tag { };
658
659 // Partial specialization used for make_shared_for_overwrite<non-array>().
660 // This partial specialization is used when the allocator's value type
661 // is the special _Sp_overwrite_tag type.
662 #if __cpp_concepts
663 template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
664 requires is_same_v<typename _Alloc::value_type, _Sp_overwrite_tag>
665 class _Sp_counted_ptr_inplace<_Tp, _Alloc, _Lp> final
666 #else
667 template<typename _Tp, template<typename> class _Alloc, _Lock_policy _Lp>
668 class _Sp_counted_ptr_inplace<_Tp, _Alloc<_Sp_overwrite_tag>, _Lp> final
669 #endif
670 : public _Sp_counted_base<_Lp>
671 {
672 [[no_unique_address]] _Alloc _M_alloc;
673
674 union {
675 _Tp _M_obj;
676 char _M_unused;
677 };
678
679 friend class __shared_count<_Lp>; // To be able to call _M_ptr().
680
681 _Tp* _M_ptr() noexcept { return std::__addressof(_M_obj); }
682
683 public:
684 using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_ptr_inplace>;
685
686 _Sp_counted_ptr_inplace(const _Alloc& __a)
687 : _M_alloc(__a)
688 {
689 ::new((void*)_M_ptr()) _Tp; // default-initialized, for overwrite.
690 }
691
692 ~_Sp_counted_ptr_inplace() noexcept { }
693
694 virtual void
695 _M_dispose() noexcept
696 {
697 _M_obj.~_Tp();
698 }
699
700 // Override because the allocator needs to know the dynamic type
701 virtual void
702 _M_destroy() noexcept
703 {
704 using pointer = typename allocator_traits<__allocator_type>::pointer;
705 __allocator_type __a(_M_alloc);
706 auto __p = pointer_traits<pointer>::pointer_to(*this);
707 __allocated_ptr<__allocator_type> __guard_ptr{ __a, __p };
708 this->~_Sp_counted_ptr_inplace();
709 }
710
711 void*
712 _M_get_deleter(const std::type_info&) noexcept override
713 { return nullptr; }
714 };
715 #endif // C++20
716
717 #if __cplusplus <= 201703L
718 # define __cpp_lib_shared_ptr_arrays 201611L
719 #else
720 # define __cpp_lib_shared_ptr_arrays 201707L
721
722 struct _Sp_overwrite_tag;
723
724 // For make_shared<T[]>, make_shared<T[N]>, allocate_shared<T[]> etc.
725 template<typename _Alloc>
726 struct _Sp_counted_array_base
727 {
728 [[no_unique_address]] _Alloc _M_alloc{};
729 size_t _M_n = 0;
730 bool _M_overwrite = false;
731
732 typename allocator_traits<_Alloc>::pointer
733 _M_alloc_array(size_t __tail)
734 {
735 return allocator_traits<_Alloc>::allocate(_M_alloc, _M_n + __tail);
736 }
737
738 void
739 _M_dealloc_array(typename allocator_traits<_Alloc>::pointer __p,
740 size_t __tail)
741 {
742 allocator_traits<_Alloc>::deallocate(_M_alloc, __p, _M_n + __tail);
743 }
744
745 // Init the array elements
746 template<typename _Init>
747 void
748 _M_init(typename allocator_traits<_Alloc>::value_type* __p,
749 _Init __init)
750 {
751 using _Tp = remove_pointer_t<_Init>;
752 using _Up = typename allocator_traits<_Alloc>::value_type;
753
754 if constexpr (is_same_v<_Init, _Sp_overwrite_tag>)
755 {
756 std::uninitialized_default_construct_n(__p, _M_n);
757 _M_overwrite = true;
758 }
759 else if (__init == nullptr)
760 std::__uninitialized_default_n_a(__p, _M_n, _M_alloc);
761 else if constexpr (!is_array_v<_Tp>)
762 std::__uninitialized_fill_n_a(__p, _M_n, *__init, _M_alloc);
763 else
764 {
765 #pragma GCC diagnostic push
766 #pragma GCC diagnostic ignored "-Wunused-local-typedefs"
767 struct _Iter
768 {
769 using value_type = _Up;
770 using difference_type = ptrdiff_t;
771 using pointer = const _Up*;
772 using reference = const _Up&;
773 using iterator_category = forward_iterator_tag;
774
775 const _Up* _M_p;
776 size_t _M_len;
777 size_t _M_pos;
778
779 _Iter& operator++() { ++_M_pos; return *this; }
780 _Iter operator++(int) { auto __i(*this); ++_M_pos; return __i; }
781
782 reference operator*() const { return _M_p[_M_pos % _M_len]; }
783 pointer operator->() const { return _M_p + (_M_pos % _M_len); }
784
785 bool operator==(const _Iter& __i) const
786 { return _M_pos == __i._M_pos; }
787 };
788 #pragma GCC diagnostic pop
789
790 _Iter __first{_S_first_elem(__init), sizeof(_Tp) / sizeof(_Up)};
791 _Iter __last = __first;
792 __last._M_pos = _M_n;
793 std::__uninitialized_copy_a(__first, __last, __p, _M_alloc);
794 }
795 }
796
797 protected:
798 // Destroy the array elements
799 void
800 _M_dispose_array(typename allocator_traits<_Alloc>::value_type* __p)
801 {
802 if (_M_overwrite)
803 std::destroy_n(__p, _M_n);
804 else
805 {
806 size_t __n = _M_n;
807 while (__n--)
808 allocator_traits<_Alloc>::destroy(_M_alloc, __p + __n);
809 }
810 }
811
812 private:
813 template<typename _Tp>
814 static _Tp*
815 _S_first_elem(_Tp* __p) { return __p; }
816
817 template<typename _Tp, size_t _Nm>
818 static auto
819 _S_first_elem(_Tp (*__p)[_Nm]) { return _S_first_elem(*__p); }
820 };
821
822 // Control block for make_shared<T[]>, make_shared<T[N]> etc. that will be
823 // placed into unused memory at the end of the array.
824 template<typename _Alloc, _Lock_policy _Lp>
825 class _Sp_counted_array final
826 : public _Sp_counted_base<_Lp>, _Sp_counted_array_base<_Alloc>
827 {
828 using pointer = typename allocator_traits<_Alloc>::pointer;
829
830 pointer _M_alloc_ptr;
831
832 auto _M_ptr() const noexcept { return std::to_address(_M_alloc_ptr); }
833
834 friend class __shared_count<_Lp>; // To be able to call _M_ptr().
835
836 public:
837 _Sp_counted_array(const _Sp_counted_array_base<_Alloc>& __a,
838 pointer __p) noexcept
839 : _Sp_counted_array_base<_Alloc>(__a), _M_alloc_ptr(__p)
840 { }
841
842 ~_Sp_counted_array() = default;
843
844 virtual void
845 _M_dispose() noexcept
846 {
847 if (this->_M_n)
848 this->_M_dispose_array(_M_ptr());
849 }
850
851 // Override because the allocator needs to know the dynamic type
852 virtual void
853 _M_destroy() noexcept
854 {
855 _Sp_counted_array_base<_Alloc> __a = *this;
856 pointer __p = _M_alloc_ptr;
857 this->~_Sp_counted_array();
858 __a._M_dealloc_array(__p, _S_tail());
859 }
860
861 // Returns the number of additional array elements that must be
862 // allocated in order to store a _Sp_counted_array at the end.
863 static constexpr size_t
864 _S_tail()
865 {
866 // The array elemenent type.
867 using _Tp = typename allocator_traits<_Alloc>::value_type;
868
869 // The space needed to store a _Sp_counted_array object.
870 size_t __bytes = sizeof(_Sp_counted_array);
871
872 // Add any padding needed for manual alignment within the buffer.
873 if constexpr (alignof(_Tp) < alignof(_Sp_counted_array))
874 __bytes += alignof(_Sp_counted_array) - alignof(_Tp);
875
876 return (__bytes + sizeof(_Tp) - 1) / sizeof(_Tp);
877 }
878
879 void*
880 _M_get_deleter(const std::type_info&) noexcept override
881 { return nullptr; }
882 };
883 #endif // C++20
884
885 // The default deleter for shared_ptr<T[]> and shared_ptr<T[N]>.
886 struct __sp_array_delete
887 {
888 template<typename _Yp>
889 void operator()(_Yp* __p) const { delete[] __p; }
890 };
891
892 template<_Lock_policy _Lp>
893 class __shared_count
894 {
895 // Prevent _Sp_alloc_shared_tag from matching the shared_ptr(P, D) ctor.
896 template<typename _Tp>
897 struct __not_alloc_shared_tag { using type = void; };
898
899 template<typename _Tp>
900 struct __not_alloc_shared_tag<_Sp_alloc_shared_tag<_Tp>> { };
901
902 #if __cpp_lib_shared_ptr_arrays >= 201707L
903 template<typename _Alloc>
904 struct __not_alloc_shared_tag<_Sp_counted_array_base<_Alloc>> { };
905 #endif
906
907 public:
908 constexpr __shared_count() noexcept : _M_pi(0)
909 { }
910
911 template<typename _Ptr>
912 explicit
913 __shared_count(_Ptr __p) : _M_pi(0)
914 {
915 __try
916 {
917 _M_pi = new _Sp_counted_ptr<_Ptr, _Lp>(__p);
918 }
919 __catch(...)
920 {
921 delete __p;
922 __throw_exception_again;
923 }
924 }
925
926 template<typename _Ptr>
927 __shared_count(_Ptr __p, /* is_array = */ false_type)
928 : __shared_count(__p)
929 { }
930
931 template<typename _Ptr>
932 __shared_count(_Ptr __p, /* is_array = */ true_type)
933 : __shared_count(__p, __sp_array_delete{}, allocator<void>())
934 { }
935
936 template<typename _Ptr, typename _Deleter,
937 typename = typename __not_alloc_shared_tag<_Deleter>::type>
938 __shared_count(_Ptr __p, _Deleter __d)
939 : __shared_count(__p, std::move(__d), allocator<void>())
940 { }
941
942 template<typename _Ptr, typename _Deleter, typename _Alloc,
943 typename = typename __not_alloc_shared_tag<_Deleter>::type>
944 __shared_count(_Ptr __p, _Deleter __d, _Alloc __a) : _M_pi(0)
945 {
946 typedef _Sp_counted_deleter<_Ptr, _Deleter, _Alloc, _Lp> _Sp_cd_type;
947 __try
948 {
949 typename _Sp_cd_type::__allocator_type __a2(__a);
950 auto __guard = std::__allocate_guarded(__a2);
951 _Sp_cd_type* __mem = __guard.get();
952 ::new (__mem) _Sp_cd_type(__p, std::move(__d), std::move(__a));
953 _M_pi = __mem;
954 __guard = nullptr;
955 }
956 __catch(...)
957 {
958 __d(__p); // Call _Deleter on __p.
959 __throw_exception_again;
960 }
961 }
962
963 template<typename _Tp, typename _Alloc, typename... _Args>
964 __shared_count(_Tp*& __p, _Sp_alloc_shared_tag<_Alloc> __a,
965 _Args&&... __args)
966 {
967 typedef _Sp_counted_ptr_inplace<_Tp, _Alloc, _Lp> _Sp_cp_type;
968 typename _Sp_cp_type::__allocator_type __a2(__a._M_a);
969 auto __guard = std::__allocate_guarded(__a2);
970 _Sp_cp_type* __mem = __guard.get();
971 auto __pi = ::new (__mem)
972 _Sp_cp_type(__a._M_a, std::forward<_Args>(__args)...);
973 __guard = nullptr;
974 _M_pi = __pi;
975 __p = __pi->_M_ptr();
976 }
977
978 #if __cpp_lib_shared_ptr_arrays >= 201707L
979 template<typename _Tp, typename _Alloc, typename _Init>
980 __shared_count(_Tp*& __p, const _Sp_counted_array_base<_Alloc>& __a,
981 _Init __init)
982 {
983 using _Up = remove_all_extents_t<_Tp>;
984 static_assert(is_same_v<_Up, typename _Alloc::value_type>);
985
986 using _Sp_ca_type = _Sp_counted_array<_Alloc, _Lp>;
987 const size_t __tail = _Sp_ca_type::_S_tail();
988
989 struct _Guarded_ptr : _Sp_counted_array_base<_Alloc>
990 {
991 typename allocator_traits<_Alloc>::pointer _M_ptr;
992
993 _Guarded_ptr(_Sp_counted_array_base<_Alloc> __a)
994 : _Sp_counted_array_base<_Alloc>(__a),
995 _M_ptr(this->_M_alloc_array(_Sp_ca_type::_S_tail()))
996 { }
997
998 ~_Guarded_ptr()
999 {
1000 if (_M_ptr)
1001 this->_M_dealloc_array(_M_ptr, _Sp_ca_type::_S_tail());
1002 }
1003 };
1004
1005 _Guarded_ptr __guard{__a};
1006 _Up* const __raw = std::to_address(__guard._M_ptr);
1007 __guard._M_init(__raw, __init); // might throw
1008
1009 void* __c = __raw + __a._M_n;
1010 if constexpr (alignof(_Up) < alignof(_Sp_ca_type))
1011 {
1012 size_t __space = sizeof(_Up) * __tail;
1013 __c = std::align(alignof(_Sp_ca_type), sizeof(_Sp_ca_type),
1014 __c, __space);
1015 }
1016 auto __pi = ::new(__c) _Sp_ca_type(__guard, __guard._M_ptr);
1017 __guard._M_ptr = nullptr;
1018 _M_pi = __pi;
1019 __p = reinterpret_cast<_Tp*>(__raw);
1020 }
1021 #endif
1022
1023 #if _GLIBCXX_USE_DEPRECATED
1024 #pragma GCC diagnostic push
1025 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
1026 // Special case for auto_ptr<_Tp> to provide the strong guarantee.
1027 template<typename _Tp>
1028 explicit
1029 __shared_count(std::auto_ptr<_Tp>&& __r);
1030 #pragma GCC diagnostic pop
1031 #endif
1032
1033 // Special case for unique_ptr<_Tp,_Del> to provide the strong guarantee.
1034 template<typename _Tp, typename _Del>
1035 explicit
1036 __shared_count(std::unique_ptr<_Tp, _Del>&& __r) : _M_pi(0)
1037 {
1038 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1039 // 2415. Inconsistency between unique_ptr and shared_ptr
1040 if (__r.get() == nullptr)
1041 return;
1042
1043 using _Ptr = typename unique_ptr<_Tp, _Del>::pointer;
1044 using _Del2 = __conditional_t<is_reference<_Del>::value,
1045 reference_wrapper<typename remove_reference<_Del>::type>,
1046 _Del>;
1047 using _Sp_cd_type
1048 = _Sp_counted_deleter<_Ptr, _Del2, allocator<void>, _Lp>;
1049 using _Alloc = allocator<_Sp_cd_type>;
1050 using _Alloc_traits = allocator_traits<_Alloc>;
1051 _Alloc __a;
1052 _Sp_cd_type* __mem = _Alloc_traits::allocate(__a, 1);
1053 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1054 // 3548. shared_ptr construction from unique_ptr should move
1055 // (not copy) the deleter
1056 _Alloc_traits::construct(__a, __mem, __r.release(),
1057 std::forward<_Del>(__r.get_deleter()));
1058 _M_pi = __mem;
1059 }
1060
1061 // Throw bad_weak_ptr when __r._M_get_use_count() == 0.
1062 explicit __shared_count(const __weak_count<_Lp>& __r);
1063
1064 // Does not throw if __r._M_get_use_count() == 0, caller must check.
1065 explicit
1066 __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t) noexcept;
1067
1068 ~__shared_count() noexcept
1069 {
1070 if (_M_pi != nullptr)
1071 _M_pi->_M_release();
1072 }
1073
1074 __shared_count(const __shared_count& __r) noexcept
1075 : _M_pi(__r._M_pi)
1076 {
1077 if (_M_pi != nullptr)
1078 _M_pi->_M_add_ref_copy();
1079 }
1080
1081 __shared_count&
1082 operator=(const __shared_count& __r) noexcept
1083 {
1084 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
1085 if (__tmp != _M_pi)
1086 {
1087 if (__tmp != nullptr)
1088 __tmp->_M_add_ref_copy();
1089 if (_M_pi != nullptr)
1090 _M_pi->_M_release();
1091 _M_pi = __tmp;
1092 }
1093 return *this;
1094 }
1095
1096 void
1097 _M_swap(__shared_count& __r) noexcept
1098 {
1099 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
1100 __r._M_pi = _M_pi;
1101 _M_pi = __tmp;
1102 }
1103
1104 long
1105 _M_get_use_count() const noexcept
1106 { return _M_pi ? _M_pi->_M_get_use_count() : 0; }
1107
1108 bool
1109 _M_unique() const noexcept
1110 { return this->_M_get_use_count() == 1; }
1111
1112 void*
1113 _M_get_deleter(const std::type_info& __ti) const noexcept
1114 { return _M_pi ? _M_pi->_M_get_deleter(__ti) : nullptr; }
1115
1116 bool
1117 _M_less(const __shared_count& __rhs) const noexcept
1118 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
1119
1120 bool
1121 _M_less(const __weak_count<_Lp>& __rhs) const noexcept
1122 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
1123
1124 // Friend function injected into enclosing namespace and found by ADL
1125 friend inline bool
1126 operator==(const __shared_count& __a, const __shared_count& __b) noexcept
1127 { return __a._M_pi == __b._M_pi; }
1128
1129 private:
1130 friend class __weak_count<_Lp>;
1131 #if __cplusplus >= 202002L
1132 template<typename> friend class _Sp_atomic;
1133 #endif
1134
1135 _Sp_counted_base<_Lp>* _M_pi;
1136 };
1137
1138
1139 template<_Lock_policy _Lp>
1140 class __weak_count
1141 {
1142 public:
1143 constexpr __weak_count() noexcept : _M_pi(nullptr)
1144 { }
1145
1146 __weak_count(const __shared_count<_Lp>& __r) noexcept
1147 : _M_pi(__r._M_pi)
1148 {
1149 if (_M_pi != nullptr)
1150 _M_pi->_M_weak_add_ref();
1151 }
1152
1153 __weak_count(const __weak_count& __r) noexcept
1154 : _M_pi(__r._M_pi)
1155 {
1156 if (_M_pi != nullptr)
1157 _M_pi->_M_weak_add_ref();
1158 }
1159
1160 __weak_count(__weak_count&& __r) noexcept
1161 : _M_pi(__r._M_pi)
1162 { __r._M_pi = nullptr; }
1163
1164 ~__weak_count() noexcept
1165 {
1166 if (_M_pi != nullptr)
1167 _M_pi->_M_weak_release();
1168 }
1169
1170 __weak_count&
1171 operator=(const __shared_count<_Lp>& __r) noexcept
1172 {
1173 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
1174 if (__tmp != nullptr)
1175 __tmp->_M_weak_add_ref();
1176 if (_M_pi != nullptr)
1177 _M_pi->_M_weak_release();
1178 _M_pi = __tmp;
1179 return *this;
1180 }
1181
1182 __weak_count&
1183 operator=(const __weak_count& __r) noexcept
1184 {
1185 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
1186 if (__tmp != nullptr)
1187 __tmp->_M_weak_add_ref();
1188 if (_M_pi != nullptr)
1189 _M_pi->_M_weak_release();
1190 _M_pi = __tmp;
1191 return *this;
1192 }
1193
1194 __weak_count&
1195 operator=(__weak_count&& __r) noexcept
1196 {
1197 if (_M_pi != nullptr)
1198 _M_pi->_M_weak_release();
1199 _M_pi = __r._M_pi;
1200 __r._M_pi = nullptr;
1201 return *this;
1202 }
1203
1204 void
1205 _M_swap(__weak_count& __r) noexcept
1206 {
1207 _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
1208 __r._M_pi = _M_pi;
1209 _M_pi = __tmp;
1210 }
1211
1212 long
1213 _M_get_use_count() const noexcept
1214 { return _M_pi != nullptr ? _M_pi->_M_get_use_count() : 0; }
1215
1216 bool
1217 _M_less(const __weak_count& __rhs) const noexcept
1218 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
1219
1220 bool
1221 _M_less(const __shared_count<_Lp>& __rhs) const noexcept
1222 { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }
1223
1224 // Friend function injected into enclosing namespace and found by ADL
1225 friend inline bool
1226 operator==(const __weak_count& __a, const __weak_count& __b) noexcept
1227 { return __a._M_pi == __b._M_pi; }
1228
1229 private:
1230 friend class __shared_count<_Lp>;
1231 #if __cplusplus >= 202002L
1232 template<typename> friend class _Sp_atomic;
1233 #endif
1234
1235 _Sp_counted_base<_Lp>* _M_pi;
1236 };
1237
1238 // Now that __weak_count is defined we can define this constructor:
1239 template<_Lock_policy _Lp>
1240 inline
1241 __shared_count<_Lp>::__shared_count(const __weak_count<_Lp>& __r)
1242 : _M_pi(__r._M_pi)
1243 {
1244 if (_M_pi == nullptr || !_M_pi->_M_add_ref_lock_nothrow())
1245 __throw_bad_weak_ptr();
1246 }
1247
1248 // Now that __weak_count is defined we can define this constructor:
1249 template<_Lock_policy _Lp>
1250 inline
1251 __shared_count<_Lp>::
1252 __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t) noexcept
1253 : _M_pi(__r._M_pi)
1254 {
1255 if (_M_pi && !_M_pi->_M_add_ref_lock_nothrow())
1256 _M_pi = nullptr;
1257 }
1258
1259 // Helper traits for shared_ptr of array:
1260
1261 // A pointer type Y* is said to be compatible with a pointer type T* when
1262 // either Y* is convertible to T* or Y is U[N] and T is U cv [].
1263 template<typename _Yp_ptr, typename _Tp_ptr>
1264 struct __sp_compatible_with
1265 : false_type
1266 { };
1267
1268 template<typename _Yp, typename _Tp>
1269 struct __sp_compatible_with<_Yp*, _Tp*>
1270 : is_convertible<_Yp*, _Tp*>::type
1271 { };
1272
1273 template<typename _Up, size_t _Nm>
1274 struct __sp_compatible_with<_Up(*)[_Nm], _Up(*)[]>
1275 : true_type
1276 { };
1277
1278 template<typename _Up, size_t _Nm>
1279 struct __sp_compatible_with<_Up(*)[_Nm], const _Up(*)[]>
1280 : true_type
1281 { };
1282
1283 template<typename _Up, size_t _Nm>
1284 struct __sp_compatible_with<_Up(*)[_Nm], volatile _Up(*)[]>
1285 : true_type
1286 { };
1287
1288 template<typename _Up, size_t _Nm>
1289 struct __sp_compatible_with<_Up(*)[_Nm], const volatile _Up(*)[]>
1290 : true_type
1291 { };
1292
1293 // Test conversion from Y(*)[N] to U(*)[N] without forming invalid type Y[N].
1294 template<typename _Up, size_t _Nm, typename _Yp, typename = void>
1295 struct __sp_is_constructible_arrN
1296 : false_type
1297 { };
1298
1299 template<typename _Up, size_t _Nm, typename _Yp>
1300 struct __sp_is_constructible_arrN<_Up, _Nm, _Yp, __void_t<_Yp[_Nm]>>
1301 : is_convertible<_Yp(*)[_Nm], _Up(*)[_Nm]>::type
1302 { };
1303
1304 // Test conversion from Y(*)[] to U(*)[] without forming invalid type Y[].
1305 template<typename _Up, typename _Yp, typename = void>
1306 struct __sp_is_constructible_arr
1307 : false_type
1308 { };
1309
1310 template<typename _Up, typename _Yp>
1311 struct __sp_is_constructible_arr<_Up, _Yp, __void_t<_Yp[]>>
1312 : is_convertible<_Yp(*)[], _Up(*)[]>::type
1313 { };
1314
1315 // Trait to check if shared_ptr<T> can be constructed from Y*.
1316 template<typename _Tp, typename _Yp>
1317 struct __sp_is_constructible;
1318
1319 // When T is U[N], Y(*)[N] shall be convertible to T*;
1320 template<typename _Up, size_t _Nm, typename _Yp>
1321 struct __sp_is_constructible<_Up[_Nm], _Yp>
1322 : __sp_is_constructible_arrN<_Up, _Nm, _Yp>::type
1323 { };
1324
1325 // when T is U[], Y(*)[] shall be convertible to T*;
1326 template<typename _Up, typename _Yp>
1327 struct __sp_is_constructible<_Up[], _Yp>
1328 : __sp_is_constructible_arr<_Up, _Yp>::type
1329 { };
1330
1331 // otherwise, Y* shall be convertible to T*.
1332 template<typename _Tp, typename _Yp>
1333 struct __sp_is_constructible
1334 : is_convertible<_Yp*, _Tp*>::type
1335 { };
1336
1337
1338 // Define operator* and operator-> for shared_ptr<T>.
1339 template<typename _Tp, _Lock_policy _Lp,
1340 bool = is_array<_Tp>::value, bool = is_void<_Tp>::value>
1341 class __shared_ptr_access
1342 {
1343 public:
1344 using element_type = _Tp;
1345
1346 element_type&
1347 operator*() const noexcept
1348 {
1349 __glibcxx_assert(_M_get() != nullptr);
1350 return *_M_get();
1351 }
1352
1353 element_type*
1354 operator->() const noexcept
1355 {
1356 _GLIBCXX_DEBUG_PEDASSERT(_M_get() != nullptr);
1357 return _M_get();
1358 }
1359
1360 private:
1361 element_type*
1362 _M_get() const noexcept
1363 { return static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get(); }
1364 };
1365
1366 // Define operator-> for shared_ptr<cv void>.
1367 template<typename _Tp, _Lock_policy _Lp>
1368 class __shared_ptr_access<_Tp, _Lp, false, true>
1369 {
1370 public:
1371 using element_type = _Tp;
1372
1373 element_type*
1374 operator->() const noexcept
1375 {
1376 auto __ptr = static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get();
1377 _GLIBCXX_DEBUG_PEDASSERT(__ptr != nullptr);
1378 return __ptr;
1379 }
1380 };
1381
1382 // Define operator[] for shared_ptr<T[]> and shared_ptr<T[N]>.
1383 template<typename _Tp, _Lock_policy _Lp>
1384 class __shared_ptr_access<_Tp, _Lp, true, false>
1385 {
1386 public:
1387 using element_type = typename remove_extent<_Tp>::type;
1388
1389 #if __cplusplus <= 201402L
1390 [[__deprecated__("shared_ptr<T[]>::operator* is absent from C++17")]]
1391 element_type&
1392 operator*() const noexcept
1393 {
1394 __glibcxx_assert(_M_get() != nullptr);
1395 return *_M_get();
1396 }
1397
1398 [[__deprecated__("shared_ptr<T[]>::operator-> is absent from C++17")]]
1399 element_type*
1400 operator->() const noexcept
1401 {
1402 _GLIBCXX_DEBUG_PEDASSERT(_M_get() != nullptr);
1403 return _M_get();
1404 }
1405 #endif
1406
1407 element_type&
1408 operator[](ptrdiff_t __i) const noexcept
1409 {
1410 __glibcxx_assert(_M_get() != nullptr);
1411 __glibcxx_assert(!extent<_Tp>::value || __i < extent<_Tp>::value);
1412 return _M_get()[__i];
1413 }
1414
1415 private:
1416 element_type*
1417 _M_get() const noexcept
1418 { return static_cast<const __shared_ptr<_Tp, _Lp>*>(this)->get(); }
1419 };
1420
1421 template<typename _Tp, _Lock_policy _Lp>
1422 class __shared_ptr
1423 : public __shared_ptr_access<_Tp, _Lp>
1424 {
1425 public:
1426 using element_type = typename remove_extent<_Tp>::type;
1427
1428 private:
1429 // Constraint for taking ownership of a pointer of type _Yp*:
1430 template<typename _Yp>
1431 using _SafeConv
1432 = typename enable_if<__sp_is_constructible<_Tp, _Yp>::value>::type;
1433
1434 // Constraint for construction from shared_ptr and weak_ptr:
1435 template<typename _Yp, typename _Res = void>
1436 using _Compatible = typename
1437 enable_if<__sp_compatible_with<_Yp*, _Tp*>::value, _Res>::type;
1438
1439 // Constraint for assignment from shared_ptr and weak_ptr:
1440 template<typename _Yp>
1441 using _Assignable = _Compatible<_Yp, __shared_ptr&>;
1442
1443 // Constraint for construction from unique_ptr:
1444 template<typename _Yp, typename _Del, typename _Res = void,
1445 typename _Ptr = typename unique_ptr<_Yp, _Del>::pointer>
1446 using _UniqCompatible = __enable_if_t<__and_<
1447 __sp_compatible_with<_Yp*, _Tp*>,
1448 is_convertible<_Ptr, element_type*>,
1449 is_move_constructible<_Del>
1450 >::value, _Res>;
1451
1452 // Constraint for assignment from unique_ptr:
1453 template<typename _Yp, typename _Del>
1454 using _UniqAssignable = _UniqCompatible<_Yp, _Del, __shared_ptr&>;
1455
1456 public:
1457
1458 #if __cplusplus > 201402L
1459 using weak_type = __weak_ptr<_Tp, _Lp>;
1460 #endif
1461
1462 constexpr __shared_ptr() noexcept
1463 : _M_ptr(0), _M_refcount()
1464 { }
1465
1466 template<typename _Yp, typename = _SafeConv<_Yp>>
1467 explicit
1468 __shared_ptr(_Yp* __p)
1469 : _M_ptr(__p), _M_refcount(__p, typename is_array<_Tp>::type())
1470 {
1471 static_assert( !is_void<_Yp>::value, "incomplete type" );
1472 static_assert( sizeof(_Yp) > 0, "incomplete type" );
1473 _M_enable_shared_from_this_with(__p);
1474 }
1475
1476 template<typename _Yp, typename _Deleter, typename = _SafeConv<_Yp>>
1477 __shared_ptr(_Yp* __p, _Deleter __d)
1478 : _M_ptr(__p), _M_refcount(__p, std::move(__d))
1479 {
1480 static_assert(__is_invocable<_Deleter&, _Yp*&>::value,
1481 "deleter expression d(p) is well-formed");
1482 _M_enable_shared_from_this_with(__p);
1483 }
1484
1485 template<typename _Yp, typename _Deleter, typename _Alloc,
1486 typename = _SafeConv<_Yp>>
1487 __shared_ptr(_Yp* __p, _Deleter __d, _Alloc __a)
1488 : _M_ptr(__p), _M_refcount(__p, std::move(__d), std::move(__a))
1489 {
1490 static_assert(__is_invocable<_Deleter&, _Yp*&>::value,
1491 "deleter expression d(p) is well-formed");
1492 _M_enable_shared_from_this_with(__p);
1493 }
1494
1495 template<typename _Deleter>
1496 __shared_ptr(nullptr_t __p, _Deleter __d)
1497 : _M_ptr(0), _M_refcount(__p, std::move(__d))
1498 { }
1499
1500 template<typename _Deleter, typename _Alloc>
1501 __shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
1502 : _M_ptr(0), _M_refcount(__p, std::move(__d), std::move(__a))
1503 { }
1504
1505 // Aliasing constructor
1506 template<typename _Yp>
1507 __shared_ptr(const __shared_ptr<_Yp, _Lp>& __r,
1508 element_type* __p) noexcept
1509 : _M_ptr(__p), _M_refcount(__r._M_refcount) // never throws
1510 { }
1511
1512 // Aliasing constructor
1513 template<typename _Yp>
1514 __shared_ptr(__shared_ptr<_Yp, _Lp>&& __r,
1515 element_type* __p) noexcept
1516 : _M_ptr(__p), _M_refcount()
1517 {
1518 _M_refcount._M_swap(__r._M_refcount);
1519 __r._M_ptr = nullptr;
1520 }
1521
1522 __shared_ptr(const __shared_ptr&) noexcept = default;
1523 __shared_ptr& operator=(const __shared_ptr&) noexcept = default;
1524 ~__shared_ptr() = default;
1525
1526 template<typename _Yp, typename = _Compatible<_Yp>>
1527 __shared_ptr(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1528 : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount)
1529 { }
1530
1531 __shared_ptr(__shared_ptr&& __r) noexcept
1532 : _M_ptr(__r._M_ptr), _M_refcount()
1533 {
1534 _M_refcount._M_swap(__r._M_refcount);
1535 __r._M_ptr = nullptr;
1536 }
1537
1538 template<typename _Yp, typename = _Compatible<_Yp>>
1539 __shared_ptr(__shared_ptr<_Yp, _Lp>&& __r) noexcept
1540 : _M_ptr(__r._M_ptr), _M_refcount()
1541 {
1542 _M_refcount._M_swap(__r._M_refcount);
1543 __r._M_ptr = nullptr;
1544 }
1545
1546 template<typename _Yp, typename = _Compatible<_Yp>>
1547 explicit __shared_ptr(const __weak_ptr<_Yp, _Lp>& __r)
1548 : _M_refcount(__r._M_refcount) // may throw
1549 {
1550 // It is now safe to copy __r._M_ptr, as
1551 // _M_refcount(__r._M_refcount) did not throw.
1552 _M_ptr = __r._M_ptr;
1553 }
1554
1555 // If an exception is thrown this constructor has no effect.
1556 template<typename _Yp, typename _Del,
1557 typename = _UniqCompatible<_Yp, _Del>>
1558 __shared_ptr(unique_ptr<_Yp, _Del>&& __r)
1559 : _M_ptr(__r.get()), _M_refcount()
1560 {
1561 auto __raw = __to_address(__r.get());
1562 _M_refcount = __shared_count<_Lp>(std::move(__r));
1563 _M_enable_shared_from_this_with(__raw);
1564 }
1565
1566 #if __cplusplus <= 201402L && _GLIBCXX_USE_DEPRECATED
1567 protected:
1568 // If an exception is thrown this constructor has no effect.
1569 template<typename _Tp1, typename _Del,
1570 typename enable_if<__and_<
1571 __not_<is_array<_Tp>>, is_array<_Tp1>,
1572 is_convertible<typename unique_ptr<_Tp1, _Del>::pointer, _Tp*>
1573 >::value, bool>::type = true>
1574 __shared_ptr(unique_ptr<_Tp1, _Del>&& __r, __sp_array_delete)
1575 : _M_ptr(__r.get()), _M_refcount()
1576 {
1577 auto __raw = __to_address(__r.get());
1578 _M_refcount = __shared_count<_Lp>(std::move(__r));
1579 _M_enable_shared_from_this_with(__raw);
1580 }
1581 public:
1582 #endif
1583
1584 #if _GLIBCXX_USE_DEPRECATED
1585 #pragma GCC diagnostic push
1586 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
1587 // Postcondition: use_count() == 1 and __r.get() == 0
1588 template<typename _Yp, typename = _Compatible<_Yp>>
1589 __shared_ptr(auto_ptr<_Yp>&& __r);
1590 #pragma GCC diagnostic pop
1591 #endif
1592
1593 constexpr __shared_ptr(nullptr_t) noexcept : __shared_ptr() { }
1594
1595 template<typename _Yp>
1596 _Assignable<_Yp>
1597 operator=(const __shared_ptr<_Yp, _Lp>& __r) noexcept
1598 {
1599 _M_ptr = __r._M_ptr;
1600 _M_refcount = __r._M_refcount; // __shared_count::op= doesn't throw
1601 return *this;
1602 }
1603
1604 #if _GLIBCXX_USE_DEPRECATED
1605 #pragma GCC diagnostic push
1606 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
1607 template<typename _Yp>
1608 _Assignable<_Yp>
1609 operator=(auto_ptr<_Yp>&& __r)
1610 {
1611 __shared_ptr(std::move(__r)).swap(*this);
1612 return *this;
1613 }
1614 #pragma GCC diagnostic pop
1615 #endif
1616
1617 __shared_ptr&
1618 operator=(__shared_ptr&& __r) noexcept
1619 {
1620 __shared_ptr(std::move(__r)).swap(*this);
1621 return *this;
1622 }
1623
1624 template<class _Yp>
1625 _Assignable<_Yp>
1626 operator=(__shared_ptr<_Yp, _Lp>&& __r) noexcept
1627 {
1628 __shared_ptr(std::move(__r)).swap(*this);
1629 return *this;
1630 }
1631
1632 template<typename _Yp, typename _Del>
1633 _UniqAssignable<_Yp, _Del>
1634 operator=(unique_ptr<_Yp, _Del>&& __r)
1635 {
1636 __shared_ptr(std::move(__r)).swap(*this);
1637 return *this;
1638 }
1639
1640 void
1641 reset() noexcept
1642 { __shared_ptr().swap(*this); }
1643
1644 template<typename _Yp>
1645 _SafeConv<_Yp>
1646 reset(_Yp* __p) // _Yp must be complete.
1647 {
1648 // Catch self-reset errors.
1649 __glibcxx_assert(__p == nullptr || __p != _M_ptr);
1650 __shared_ptr(__p).swap(*this);
1651 }
1652
1653 template<typename _Yp, typename _Deleter>
1654 _SafeConv<_Yp>
1655 reset(_Yp* __p, _Deleter __d)
1656 { __shared_ptr(__p, std::move(__d)).swap(*this); }
1657
1658 template<typename _Yp, typename _Deleter, typename _Alloc>
1659 _SafeConv<_Yp>
1660 reset(_Yp* __p, _Deleter __d, _Alloc __a)
1661 { __shared_ptr(__p, std::move(__d), std::move(__a)).swap(*this); }
1662
1663 /// Return the stored pointer.
1664 element_type*
1665 get() const noexcept
1666 { return _M_ptr; }
1667
1668 /// Return true if the stored pointer is not null.
1669 #if __cplusplus >= 202002L
1670 [[__gnu__::__always_inline__]]
1671 #endif
1672 explicit operator bool() const noexcept
1673 { return _M_ptr != nullptr; }
1674
1675 /// Return true if use_count() == 1.
1676 bool
1677 unique() const noexcept
1678 { return _M_refcount._M_unique(); }
1679
1680 /// If *this owns a pointer, return the number of owners, otherwise zero.
1681 long
1682 use_count() const noexcept
1683 { return _M_refcount._M_get_use_count(); }
1684
1685 /// Exchange both the owned pointer and the stored pointer.
1686 void
1687 swap(__shared_ptr<_Tp, _Lp>& __other) noexcept
1688 {
1689 std::swap(_M_ptr, __other._M_ptr);
1690 _M_refcount._M_swap(__other._M_refcount);
1691 }
1692
1693 /** @brief Define an ordering based on ownership.
1694 *
1695 * This function defines a strict weak ordering between two shared_ptr
1696 * or weak_ptr objects, such that one object is less than the other
1697 * unless they share ownership of the same pointer, or are both empty.
1698 * @{
1699 */
1700 template<typename _Tp1>
1701 bool
1702 owner_before(__shared_ptr<_Tp1, _Lp> const& __rhs) const noexcept
1703 { return _M_refcount._M_less(__rhs._M_refcount); }
1704
1705 template<typename _Tp1>
1706 bool
1707 owner_before(__weak_ptr<_Tp1, _Lp> const& __rhs) const noexcept
1708 { return _M_refcount._M_less(__rhs._M_refcount); }
1709 /// @}
1710
1711 protected:
1712 // This constructor is non-standard, it is used by allocate_shared.
1713 template<typename _Alloc, typename... _Args>
1714 __shared_ptr(_Sp_alloc_shared_tag<_Alloc> __tag, _Args&&... __args)
1715 : _M_ptr(), _M_refcount(_M_ptr, __tag, std::forward<_Args>(__args)...)
1716 { _M_enable_shared_from_this_with(_M_ptr); }
1717
1718 template<typename _Tp1, _Lock_policy _Lp1, typename _Alloc,
1719 typename... _Args>
1720 friend __shared_ptr<_Tp1, _Lp1>
1721 __allocate_shared(const _Alloc& __a, _Args&&... __args);
1722
1723 #if __cpp_lib_shared_ptr_arrays >= 201707L
1724 // This constructor is non-standard, it is used by allocate_shared<T[]>.
1725 template<typename _Alloc, typename _Init = const remove_extent_t<_Tp>*>
1726 __shared_ptr(const _Sp_counted_array_base<_Alloc>& __a,
1727 _Init __init = nullptr)
1728 : _M_ptr(), _M_refcount(_M_ptr, __a, __init)
1729 { }
1730 #endif
1731
1732 // This constructor is used by __weak_ptr::lock() and
1733 // shared_ptr::shared_ptr(const weak_ptr&, std::nothrow_t).
1734 __shared_ptr(const __weak_ptr<_Tp, _Lp>& __r, std::nothrow_t) noexcept
1735 : _M_refcount(__r._M_refcount, std::nothrow)
1736 {
1737 _M_ptr = _M_refcount._M_get_use_count() ? __r._M_ptr : nullptr;
1738 }
1739
1740 friend class __weak_ptr<_Tp, _Lp>;
1741
1742 private:
1743
1744 template<typename _Yp>
1745 using __esft_base_t = decltype(__enable_shared_from_this_base(
1746 std::declval<const __shared_count<_Lp>&>(),
1747 std::declval<_Yp*>()));
1748
1749 // Detect an accessible and unambiguous enable_shared_from_this base.
1750 template<typename _Yp, typename = void>
1751 struct __has_esft_base
1752 : false_type { };
1753
1754 template<typename _Yp>
1755 struct __has_esft_base<_Yp, __void_t<__esft_base_t<_Yp>>>
1756 : __not_<is_array<_Tp>> { }; // No enable shared_from_this for arrays
1757
1758 template<typename _Yp, typename _Yp2 = typename remove_cv<_Yp>::type>
1759 typename enable_if<__has_esft_base<_Yp2>::value>::type
1760 _M_enable_shared_from_this_with(_Yp* __p) noexcept
1761 {
1762 if (auto __base = __enable_shared_from_this_base(_M_refcount, __p))
1763 __base->_M_weak_assign(const_cast<_Yp2*>(__p), _M_refcount);
1764 }
1765
1766 template<typename _Yp, typename _Yp2 = typename remove_cv<_Yp>::type>
1767 typename enable_if<!__has_esft_base<_Yp2>::value>::type
1768 _M_enable_shared_from_this_with(_Yp*) noexcept
1769 { }
1770
1771 void*
1772 _M_get_deleter(const std::type_info& __ti) const noexcept
1773 { return _M_refcount._M_get_deleter(__ti); }
1774
1775 template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
1776 template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
1777
1778 template<typename _Del, typename _Tp1, _Lock_policy _Lp1>
1779 friend _Del* get_deleter(const __shared_ptr<_Tp1, _Lp1>&) noexcept;
1780
1781 template<typename _Del, typename _Tp1>
1782 friend _Del* get_deleter(const shared_ptr<_Tp1>&) noexcept;
1783
1784 #if __cplusplus >= 202002L
1785 friend _Sp_atomic<shared_ptr<_Tp>>;
1786 #endif
1787
1788 element_type* _M_ptr; // Contained pointer.
1789 __shared_count<_Lp> _M_refcount; // Reference counter.
1790 };
1791
1792
1793 // 20.7.2.2.7 shared_ptr comparisons
1794 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1795 inline bool
1796 operator==(const __shared_ptr<_Tp1, _Lp>& __a,
1797 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1798 { return __a.get() == __b.get(); }
1799
1800 template<typename _Tp, _Lock_policy _Lp>
1801 inline bool
1802 operator==(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1803 { return !__a; }
1804
1805 #ifdef __cpp_lib_three_way_comparison
1806 template<typename _Tp, typename _Up, _Lock_policy _Lp>
1807 inline strong_ordering
1808 operator<=>(const __shared_ptr<_Tp, _Lp>& __a,
1809 const __shared_ptr<_Up, _Lp>& __b) noexcept
1810 { return compare_three_way()(__a.get(), __b.get()); }
1811
1812 template<typename _Tp, _Lock_policy _Lp>
1813 inline strong_ordering
1814 operator<=>(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1815 {
1816 using pointer = typename __shared_ptr<_Tp, _Lp>::element_type*;
1817 return compare_three_way()(__a.get(), static_cast<pointer>(nullptr));
1818 }
1819 #else
1820 template<typename _Tp, _Lock_policy _Lp>
1821 inline bool
1822 operator==(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1823 { return !__a; }
1824
1825 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1826 inline bool
1827 operator!=(const __shared_ptr<_Tp1, _Lp>& __a,
1828 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1829 { return __a.get() != __b.get(); }
1830
1831 template<typename _Tp, _Lock_policy _Lp>
1832 inline bool
1833 operator!=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1834 { return (bool)__a; }
1835
1836 template<typename _Tp, _Lock_policy _Lp>
1837 inline bool
1838 operator!=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1839 { return (bool)__a; }
1840
1841 template<typename _Tp, typename _Up, _Lock_policy _Lp>
1842 inline bool
1843 operator<(const __shared_ptr<_Tp, _Lp>& __a,
1844 const __shared_ptr<_Up, _Lp>& __b) noexcept
1845 {
1846 using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1847 using _Up_elt = typename __shared_ptr<_Up, _Lp>::element_type;
1848 using _Vp = typename common_type<_Tp_elt*, _Up_elt*>::type;
1849 return less<_Vp>()(__a.get(), __b.get());
1850 }
1851
1852 template<typename _Tp, _Lock_policy _Lp>
1853 inline bool
1854 operator<(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1855 {
1856 using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1857 return less<_Tp_elt*>()(__a.get(), nullptr);
1858 }
1859
1860 template<typename _Tp, _Lock_policy _Lp>
1861 inline bool
1862 operator<(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1863 {
1864 using _Tp_elt = typename __shared_ptr<_Tp, _Lp>::element_type;
1865 return less<_Tp_elt*>()(nullptr, __a.get());
1866 }
1867
1868 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1869 inline bool
1870 operator<=(const __shared_ptr<_Tp1, _Lp>& __a,
1871 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1872 { return !(__b < __a); }
1873
1874 template<typename _Tp, _Lock_policy _Lp>
1875 inline bool
1876 operator<=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1877 { return !(nullptr < __a); }
1878
1879 template<typename _Tp, _Lock_policy _Lp>
1880 inline bool
1881 operator<=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1882 { return !(__a < nullptr); }
1883
1884 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1885 inline bool
1886 operator>(const __shared_ptr<_Tp1, _Lp>& __a,
1887 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1888 { return (__b < __a); }
1889
1890 template<typename _Tp, _Lock_policy _Lp>
1891 inline bool
1892 operator>(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1893 { return nullptr < __a; }
1894
1895 template<typename _Tp, _Lock_policy _Lp>
1896 inline bool
1897 operator>(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1898 { return __a < nullptr; }
1899
1900 template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
1901 inline bool
1902 operator>=(const __shared_ptr<_Tp1, _Lp>& __a,
1903 const __shared_ptr<_Tp2, _Lp>& __b) noexcept
1904 { return !(__a < __b); }
1905
1906 template<typename _Tp, _Lock_policy _Lp>
1907 inline bool
1908 operator>=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
1909 { return !(__a < nullptr); }
1910
1911 template<typename _Tp, _Lock_policy _Lp>
1912 inline bool
1913 operator>=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
1914 { return !(nullptr < __a); }
1915 #endif // three-way comparison
1916
1917 // 20.7.2.2.8 shared_ptr specialized algorithms.
1918 template<typename _Tp, _Lock_policy _Lp>
1919 inline void
1920 swap(__shared_ptr<_Tp, _Lp>& __a, __shared_ptr<_Tp, _Lp>& __b) noexcept
1921 { __a.swap(__b); }
1922
1923 // 20.7.2.2.9 shared_ptr casts
1924
1925 // The seemingly equivalent code:
1926 // shared_ptr<_Tp, _Lp>(static_cast<_Tp*>(__r.get()))
1927 // will eventually result in undefined behaviour, attempting to
1928 // delete the same object twice.
1929 /// static_pointer_cast
1930 template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1931 inline __shared_ptr<_Tp, _Lp>
1932 static_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1933 {
1934 using _Sp = __shared_ptr<_Tp, _Lp>;
1935 return _Sp(__r, static_cast<typename _Sp::element_type*>(__r.get()));
1936 }
1937
1938 // The seemingly equivalent code:
1939 // shared_ptr<_Tp, _Lp>(const_cast<_Tp*>(__r.get()))
1940 // will eventually result in undefined behaviour, attempting to
1941 // delete the same object twice.
1942 /// const_pointer_cast
1943 template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1944 inline __shared_ptr<_Tp, _Lp>
1945 const_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1946 {
1947 using _Sp = __shared_ptr<_Tp, _Lp>;
1948 return _Sp(__r, const_cast<typename _Sp::element_type*>(__r.get()));
1949 }
1950
1951 // The seemingly equivalent code:
1952 // shared_ptr<_Tp, _Lp>(dynamic_cast<_Tp*>(__r.get()))
1953 // will eventually result in undefined behaviour, attempting to
1954 // delete the same object twice.
1955 /// dynamic_pointer_cast
1956 template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1957 inline __shared_ptr<_Tp, _Lp>
1958 dynamic_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1959 {
1960 using _Sp = __shared_ptr<_Tp, _Lp>;
1961 if (auto* __p = dynamic_cast<typename _Sp::element_type*>(__r.get()))
1962 return _Sp(__r, __p);
1963 return _Sp();
1964 }
1965
1966 #if __cplusplus > 201402L
1967 template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
1968 inline __shared_ptr<_Tp, _Lp>
1969 reinterpret_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
1970 {
1971 using _Sp = __shared_ptr<_Tp, _Lp>;
1972 return _Sp(__r, reinterpret_cast<typename _Sp::element_type*>(__r.get()));
1973 }
1974 #endif
1975
1976 template<typename _Tp, _Lock_policy _Lp>
1977 class __weak_ptr
1978 {
1979 template<typename _Yp, typename _Res = void>
1980 using _Compatible = typename
1981 enable_if<__sp_compatible_with<_Yp*, _Tp*>::value, _Res>::type;
1982
1983 // Constraint for assignment from shared_ptr and weak_ptr:
1984 template<typename _Yp>
1985 using _Assignable = _Compatible<_Yp, __weak_ptr&>;
1986
1987 public:
1988 using element_type = typename remove_extent<_Tp>::type;
1989
1990 constexpr __weak_ptr() noexcept
1991 : _M_ptr(nullptr), _M_refcount()
1992 { }
1993
1994 __weak_ptr(const __weak_ptr&) noexcept = default;
1995
1996 ~__weak_ptr() = default;
1997
1998 // The "obvious" converting constructor implementation:
1999 //
2000 // template<typename _Tp1>
2001 // __weak_ptr(const __weak_ptr<_Tp1, _Lp>& __r)
2002 // : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws
2003 // { }
2004 //
2005 // has a serious problem.
2006 //
2007 // __r._M_ptr may already have been invalidated. The _M_ptr(__r._M_ptr)
2008 // conversion may require access to *__r._M_ptr (virtual inheritance).
2009 //
2010 // It is not possible to avoid spurious access violations since
2011 // in multithreaded programs __r._M_ptr may be invalidated at any point.
2012 template<typename _Yp, typename = _Compatible<_Yp>>
2013 __weak_ptr(const __weak_ptr<_Yp, _Lp>& __r) noexcept
2014 : _M_refcount(__r._M_refcount)
2015 { _M_ptr = __r.lock().get(); }
2016
2017 template<typename _Yp, typename = _Compatible<_Yp>>
2018 __weak_ptr(const __shared_ptr<_Yp, _Lp>& __r) noexcept
2019 : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount)
2020 { }
2021
2022 __weak_ptr(__weak_ptr&& __r) noexcept
2023 : _M_ptr(__r._M_ptr), _M_refcount(std::move(__r._M_refcount))
2024 { __r._M_ptr = nullptr; }
2025
2026 template<typename _Yp, typename = _Compatible<_Yp>>
2027 __weak_ptr(__weak_ptr<_Yp, _Lp>&& __r) noexcept
2028 : _M_ptr(__r.lock().get()), _M_refcount(std::move(__r._M_refcount))
2029 { __r._M_ptr = nullptr; }
2030
2031 __weak_ptr&
2032 operator=(const __weak_ptr& __r) noexcept = default;
2033
2034 template<typename _Yp>
2035 _Assignable<_Yp>
2036 operator=(const __weak_ptr<_Yp, _Lp>& __r) noexcept
2037 {
2038 _M_ptr = __r.lock().get();
2039 _M_refcount = __r._M_refcount;
2040 return *this;
2041 }
2042
2043 template<typename _Yp>
2044 _Assignable<_Yp>
2045 operator=(const __shared_ptr<_Yp, _Lp>& __r) noexcept
2046 {
2047 _M_ptr = __r._M_ptr;
2048 _M_refcount = __r._M_refcount;
2049 return *this;
2050 }
2051
2052 __weak_ptr&
2053 operator=(__weak_ptr&& __r) noexcept
2054 {
2055 __weak_ptr(std::move(__r)).swap(*this);
2056 return *this;
2057 }
2058
2059 template<typename _Yp>
2060 _Assignable<_Yp>
2061 operator=(__weak_ptr<_Yp, _Lp>&& __r) noexcept
2062 {
2063 _M_ptr = __r.lock().get();
2064 _M_refcount = std::move(__r._M_refcount);
2065 __r._M_ptr = nullptr;
2066 return *this;
2067 }
2068
2069 __shared_ptr<_Tp, _Lp>
2070 lock() const noexcept
2071 { return __shared_ptr<element_type, _Lp>(*this, std::nothrow); }
2072
2073 long
2074 use_count() const noexcept
2075 { return _M_refcount._M_get_use_count(); }
2076
2077 bool
2078 expired() const noexcept
2079 { return _M_refcount._M_get_use_count() == 0; }
2080
2081 template<typename _Tp1>
2082 bool
2083 owner_before(const __shared_ptr<_Tp1, _Lp>& __rhs) const noexcept
2084 { return _M_refcount._M_less(__rhs._M_refcount); }
2085
2086 template<typename _Tp1>
2087 bool
2088 owner_before(const __weak_ptr<_Tp1, _Lp>& __rhs) const noexcept
2089 { return _M_refcount._M_less(__rhs._M_refcount); }
2090
2091 void
2092 reset() noexcept
2093 { __weak_ptr().swap(*this); }
2094
2095 void
2096 swap(__weak_ptr& __s) noexcept
2097 {
2098 std::swap(_M_ptr, __s._M_ptr);
2099 _M_refcount._M_swap(__s._M_refcount);
2100 }
2101
2102 private:
2103 // Used by __enable_shared_from_this.
2104 void
2105 _M_assign(_Tp* __ptr, const __shared_count<_Lp>& __refcount) noexcept
2106 {
2107 if (use_count() == 0)
2108 {
2109 _M_ptr = __ptr;
2110 _M_refcount = __refcount;
2111 }
2112 }
2113
2114 template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
2115 template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
2116 friend class __enable_shared_from_this<_Tp, _Lp>;
2117 friend class enable_shared_from_this<_Tp>;
2118 #if __cplusplus >= 202002L
2119 friend _Sp_atomic<weak_ptr<_Tp>>;
2120 #endif
2121
2122 element_type* _M_ptr; // Contained pointer.
2123 __weak_count<_Lp> _M_refcount; // Reference counter.
2124 };
2125
2126 // 20.7.2.3.6 weak_ptr specialized algorithms.
2127 template<typename _Tp, _Lock_policy _Lp>
2128 inline void
2129 swap(__weak_ptr<_Tp, _Lp>& __a, __weak_ptr<_Tp, _Lp>& __b) noexcept
2130 { __a.swap(__b); }
2131
2132 #pragma GCC diagnostic push
2133 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
2134 template<typename _Tp, typename _Tp1>
2135 struct _Sp_owner_less : public binary_function<_Tp, _Tp, bool>
2136 {
2137 bool
2138 operator()(const _Tp& __lhs, const _Tp& __rhs) const noexcept
2139 { return __lhs.owner_before(__rhs); }
2140
2141 bool
2142 operator()(const _Tp& __lhs, const _Tp1& __rhs) const noexcept
2143 { return __lhs.owner_before(__rhs); }
2144
2145 bool
2146 operator()(const _Tp1& __lhs, const _Tp& __rhs) const noexcept
2147 { return __lhs.owner_before(__rhs); }
2148 };
2149 #pragma GCC diagnostic pop
2150
2151 template<>
2152 struct _Sp_owner_less<void, void>
2153 {
2154 template<typename _Tp, typename _Up>
2155 auto
2156 operator()(const _Tp& __lhs, const _Up& __rhs) const noexcept
2157 -> decltype(__lhs.owner_before(__rhs))
2158 { return __lhs.owner_before(__rhs); }
2159
2160 using is_transparent = void;
2161 };
2162
2163 template<typename _Tp, _Lock_policy _Lp>
2164 struct owner_less<__shared_ptr<_Tp, _Lp>>
2165 : public _Sp_owner_less<__shared_ptr<_Tp, _Lp>, __weak_ptr<_Tp, _Lp>>
2166 { };
2167
2168 template<typename _Tp, _Lock_policy _Lp>
2169 struct owner_less<__weak_ptr<_Tp, _Lp>>
2170 : public _Sp_owner_less<__weak_ptr<_Tp, _Lp>, __shared_ptr<_Tp, _Lp>>
2171 { };
2172
2173
2174 template<typename _Tp, _Lock_policy _Lp>
2175 class __enable_shared_from_this
2176 {
2177 protected:
2178 constexpr __enable_shared_from_this() noexcept { }
2179
2180 __enable_shared_from_this(const __enable_shared_from_this&) noexcept { }
2181
2182 __enable_shared_from_this&
2183 operator=(const __enable_shared_from_this&) noexcept
2184 { return *this; }
2185
2186 ~__enable_shared_from_this() { }
2187
2188 public:
2189 __shared_ptr<_Tp, _Lp>
2190 shared_from_this()
2191 { return __shared_ptr<_Tp, _Lp>(this->_M_weak_this); }
2192
2193 __shared_ptr<const _Tp, _Lp>
2194 shared_from_this() const
2195 { return __shared_ptr<const _Tp, _Lp>(this->_M_weak_this); }
2196
2197 #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
2198 __weak_ptr<_Tp, _Lp>
2199 weak_from_this() noexcept
2200 { return this->_M_weak_this; }
2201
2202 __weak_ptr<const _Tp, _Lp>
2203 weak_from_this() const noexcept
2204 { return this->_M_weak_this; }
2205 #endif
2206
2207 private:
2208 template<typename _Tp1>
2209 void
2210 _M_weak_assign(_Tp1* __p, const __shared_count<_Lp>& __n) const noexcept
2211 { _M_weak_this._M_assign(__p, __n); }
2212
2213 friend const __enable_shared_from_this*
2214 __enable_shared_from_this_base(const __shared_count<_Lp>&,
2215 const __enable_shared_from_this* __p)
2216 { return __p; }
2217
2218 template<typename, _Lock_policy>
2219 friend class __shared_ptr;
2220
2221 mutable __weak_ptr<_Tp, _Lp> _M_weak_this;
2222 };
2223
2224 template<typename _Tp, _Lock_policy _Lp = __default_lock_policy,
2225 typename _Alloc, typename... _Args>
2226 inline __shared_ptr<_Tp, _Lp>
2227 __allocate_shared(const _Alloc& __a, _Args&&... __args)
2228 {
2229 static_assert(!is_array<_Tp>::value, "make_shared<T[]> not supported");
2230
2231 return __shared_ptr<_Tp, _Lp>(_Sp_alloc_shared_tag<_Alloc>{__a},
2232 std::forward<_Args>(__args)...);
2233 }
2234
2235 template<typename _Tp, _Lock_policy _Lp = __default_lock_policy,
2236 typename... _Args>
2237 inline __shared_ptr<_Tp, _Lp>
2238 __make_shared(_Args&&... __args)
2239 {
2240 typedef typename std::remove_const<_Tp>::type _Tp_nc;
2241 return std::__allocate_shared<_Tp, _Lp>(std::allocator<_Tp_nc>(),
2242 std::forward<_Args>(__args)...);
2243 }
2244
2245 /// std::hash specialization for __shared_ptr.
2246 template<typename _Tp, _Lock_policy _Lp>
2247 struct hash<__shared_ptr<_Tp, _Lp>>
2248 : public __hash_base<size_t, __shared_ptr<_Tp, _Lp>>
2249 {
2250 size_t
2251 operator()(const __shared_ptr<_Tp, _Lp>& __s) const noexcept
2252 {
2253 return hash<typename __shared_ptr<_Tp, _Lp>::element_type*>()(
2254 __s.get());
2255 }
2256 };
2257
2258 _GLIBCXX_END_NAMESPACE_VERSION
2259 } // namespace
2260
2261 #endif // _SHARED_PTR_BASE_H
2262