xref: /llvm-project/libcxx/include/__memory/shared_ptr.h (revision f69585235ec85d54e0f3fc41b2d5700430907f99) 
1 // -*- C++ -*-
2 //===----------------------------------------------------------------------===//
3 //
4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 // See https://llvm.org/LICENSE.txt for license information.
6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #ifndef _LIBCPP___MEMORY_SHARED_PTR_H
11 #define _LIBCPP___MEMORY_SHARED_PTR_H
12 
13 #include <__compare/compare_three_way.h>
14 #include <__compare/ordering.h>
15 #include <__config>
16 #include <__cstddef/nullptr_t.h>
17 #include <__cstddef/ptrdiff_t.h>
18 #include <__exception/exception.h>
19 #include <__functional/binary_function.h>
20 #include <__functional/operations.h>
21 #include <__functional/reference_wrapper.h>
22 #include <__fwd/ostream.h>
23 #include <__iterator/access.h>
24 #include <__memory/addressof.h>
25 #include <__memory/allocation_guard.h>
26 #include <__memory/allocator.h>
27 #include <__memory/allocator_destructor.h>
28 #include <__memory/allocator_traits.h>
29 #include <__memory/auto_ptr.h>
30 #include <__memory/compressed_pair.h>
31 #include <__memory/construct_at.h>
32 #include <__memory/pointer_traits.h>
33 #include <__memory/shared_count.h>
34 #include <__memory/uninitialized_algorithms.h>
35 #include <__memory/unique_ptr.h>
36 #include <__type_traits/add_lvalue_reference.h>
37 #include <__type_traits/conditional.h>
38 #include <__type_traits/conjunction.h>
39 #include <__type_traits/disjunction.h>
40 #include <__type_traits/enable_if.h>
41 #include <__type_traits/integral_constant.h>
42 #include <__type_traits/is_array.h>
43 #include <__type_traits/is_bounded_array.h>
44 #include <__type_traits/is_constructible.h>
45 #include <__type_traits/is_convertible.h>
46 #include <__type_traits/is_function.h>
47 #include <__type_traits/is_reference.h>
48 #include <__type_traits/is_same.h>
49 #include <__type_traits/is_unbounded_array.h>
50 #include <__type_traits/nat.h>
51 #include <__type_traits/negation.h>
52 #include <__type_traits/remove_cv.h>
53 #include <__type_traits/remove_extent.h>
54 #include <__type_traits/remove_reference.h>
55 #include <__utility/declval.h>
56 #include <__utility/forward.h>
57 #include <__utility/move.h>
58 #include <__utility/swap.h>
59 #include <__verbose_abort>
60 #include <typeinfo>
61 #if _LIBCPP_HAS_ATOMIC_HEADER
62 #  include <__atomic/memory_order.h>
63 #endif
64 
65 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
66 #  pragma GCC system_header
67 #endif
68 
69 _LIBCPP_PUSH_MACROS
70 #include <__undef_macros>
71 
72 _LIBCPP_BEGIN_NAMESPACE_STD
73 
74 class _LIBCPP_EXPORTED_FROM_ABI bad_weak_ptr : public std::exception {
75 public:
76   _LIBCPP_HIDE_FROM_ABI bad_weak_ptr() _NOEXCEPT                               = default;
77   _LIBCPP_HIDE_FROM_ABI bad_weak_ptr(const bad_weak_ptr&) _NOEXCEPT            = default;
78   _LIBCPP_HIDE_FROM_ABI bad_weak_ptr& operator=(const bad_weak_ptr&) _NOEXCEPT = default;
79   ~bad_weak_ptr() _NOEXCEPT override;
80   const char* what() const _NOEXCEPT override;
81 };
82 
83 [[__noreturn__]] inline _LIBCPP_HIDE_FROM_ABI void __throw_bad_weak_ptr() {
84 #if _LIBCPP_HAS_EXCEPTIONS
85   throw bad_weak_ptr();
86 #else
87   _LIBCPP_VERBOSE_ABORT("bad_weak_ptr was thrown in -fno-exceptions mode");
88 #endif
89 }
90 
91 template <class _Tp>
92 class _LIBCPP_TEMPLATE_VIS weak_ptr;
93 
94 template <class _Tp, class _Dp, class _Alloc>
95 class __shared_ptr_pointer : public __shared_weak_count {
96   _LIBCPP_COMPRESSED_TRIPLE(_Tp, __ptr_, _Dp, __deleter_, _Alloc, __alloc_);
97 
98 public:
99   _LIBCPP_HIDE_FROM_ABI __shared_ptr_pointer(_Tp __p, _Dp __d, _Alloc __a)
100       : __ptr_(__p), __deleter_(std::move(__d)), __alloc_(std::move(__a)) {}
101 
102 #if _LIBCPP_HAS_RTTI
103   _LIBCPP_HIDE_FROM_ABI_VIRTUAL const void* __get_deleter(const type_info&) const _NOEXCEPT override;
104 #endif
105 
106 private:
107   _LIBCPP_HIDE_FROM_ABI_VIRTUAL void __on_zero_shared() _NOEXCEPT override;
108   _LIBCPP_HIDE_FROM_ABI_VIRTUAL void __on_zero_shared_weak() _NOEXCEPT override;
109 };
110 
111 #if _LIBCPP_HAS_RTTI
112 
113 template <class _Tp, class _Dp, class _Alloc>
114 const void* __shared_ptr_pointer<_Tp, _Dp, _Alloc>::__get_deleter(const type_info& __t) const _NOEXCEPT {
115   return __t == typeid(_Dp) ? std::addressof(__deleter_) : nullptr;
116 }
117 
118 #endif // _LIBCPP_HAS_RTTI
119 
120 template <class _Tp, class _Dp, class _Alloc>
121 void __shared_ptr_pointer<_Tp, _Dp, _Alloc>::__on_zero_shared() _NOEXCEPT {
122   __deleter_(__ptr_);
123   __deleter_.~_Dp();
124 }
125 
126 template <class _Tp, class _Dp, class _Alloc>
127 void __shared_ptr_pointer<_Tp, _Dp, _Alloc>::__on_zero_shared_weak() _NOEXCEPT {
128   typedef typename __allocator_traits_rebind<_Alloc, __shared_ptr_pointer>::type _Al;
129   typedef allocator_traits<_Al> _ATraits;
130   typedef pointer_traits<typename _ATraits::pointer> _PTraits;
131 
132   _Al __a(__alloc_);
133   __alloc_.~_Alloc();
134   __a.deallocate(_PTraits::pointer_to(*this), 1);
135 }
136 
137 // This tag is used to instantiate an allocator type. The various shared_ptr control blocks
138 // detect that the allocator has been instantiated for this type and perform alternative
139 // initialization/destruction based on that.
140 struct __for_overwrite_tag {};
141 
142 template <class _Tp, class _Alloc>
143 struct __shared_ptr_emplace : __shared_weak_count {
144   using __value_type _LIBCPP_NODEBUG = __remove_cv_t<_Tp>;
145 
146   template <class... _Args,
147             class _Allocator                                                                         = _Alloc,
148             __enable_if_t<is_same<typename _Allocator::value_type, __for_overwrite_tag>::value, int> = 0>
149   _LIBCPP_HIDE_FROM_ABI explicit __shared_ptr_emplace(_Alloc __a, _Args&&...) : __storage_(std::move(__a)) {
150     static_assert(
151         sizeof...(_Args) == 0, "No argument should be provided to the control block when using _for_overwrite");
152     ::new (static_cast<void*>(__get_elem())) __value_type;
153   }
154 
155   template <class... _Args,
156             class _Allocator                                                                          = _Alloc,
157             __enable_if_t<!is_same<typename _Allocator::value_type, __for_overwrite_tag>::value, int> = 0>
158   _LIBCPP_HIDE_FROM_ABI explicit __shared_ptr_emplace(_Alloc __a, _Args&&... __args) : __storage_(std::move(__a)) {
159     using _TpAlloc = typename __allocator_traits_rebind<_Alloc, __value_type>::type;
160     _TpAlloc __tmp(*__get_alloc());
161     allocator_traits<_TpAlloc>::construct(__tmp, __get_elem(), std::forward<_Args>(__args)...);
162   }
163 
164   _LIBCPP_HIDE_FROM_ABI _Alloc* __get_alloc() _NOEXCEPT { return __storage_.__get_alloc(); }
165 
166   _LIBCPP_HIDE_FROM_ABI __value_type* __get_elem() _NOEXCEPT { return __storage_.__get_elem(); }
167 
168 private:
169   template <class _Allocator                                                                         = _Alloc,
170             __enable_if_t<is_same<typename _Allocator::value_type, __for_overwrite_tag>::value, int> = 0>
171   _LIBCPP_HIDE_FROM_ABI void __on_zero_shared_impl() _NOEXCEPT {
172     __get_elem()->~__value_type();
173   }
174 
175   template <class _Allocator                                                                          = _Alloc,
176             __enable_if_t<!is_same<typename _Allocator::value_type, __for_overwrite_tag>::value, int> = 0>
177   _LIBCPP_HIDE_FROM_ABI void __on_zero_shared_impl() _NOEXCEPT {
178     using _TpAlloc = typename __allocator_traits_rebind<_Allocator, __remove_cv_t<_Tp> >::type;
179     _TpAlloc __tmp(*__get_alloc());
180     allocator_traits<_TpAlloc>::destroy(__tmp, __get_elem());
181   }
182 
183   _LIBCPP_HIDE_FROM_ABI_VIRTUAL void __on_zero_shared() _NOEXCEPT override { __on_zero_shared_impl(); }
184 
185   _LIBCPP_HIDE_FROM_ABI_VIRTUAL void __on_zero_shared_weak() _NOEXCEPT override {
186     using _ControlBlockAlloc   = typename __allocator_traits_rebind<_Alloc, __shared_ptr_emplace>::type;
187     using _ControlBlockPointer = typename allocator_traits<_ControlBlockAlloc>::pointer;
188     _ControlBlockAlloc __tmp(*__get_alloc());
189     __storage_.~_Storage();
190     allocator_traits<_ControlBlockAlloc>::deallocate(__tmp, pointer_traits<_ControlBlockPointer>::pointer_to(*this), 1);
191   }
192 
193   // TODO: It should be possible to refactor this to remove `_Storage` entirely.
194   // This class implements the control block for non-array shared pointers created
195   // through `std::allocate_shared` and `std::make_shared`.
196   struct _Storage {
197     struct _Data {
198       _LIBCPP_COMPRESSED_PAIR(_Alloc, __alloc_, __value_type, __elem_);
199     };
200 
201     _ALIGNAS_TYPE(_Data) char __buffer_[sizeof(_Data)];
202 
203     _LIBCPP_HIDE_FROM_ABI explicit _Storage(_Alloc&& __a) { ::new ((void*)__get_alloc()) _Alloc(std::move(__a)); }
204     _LIBCPP_HIDE_FROM_ABI ~_Storage() { __get_alloc()->~_Alloc(); }
205 
206     _LIBCPP_HIDE_FROM_ABI _Alloc* __get_alloc() _NOEXCEPT {
207       return std::addressof(reinterpret_cast<_Data*>(__buffer_)->__alloc_);
208     }
209 
210     _LIBCPP_HIDE_FROM_ABI _LIBCPP_NO_CFI __value_type* __get_elem() _NOEXCEPT {
211       return std::addressof(reinterpret_cast<_Data*>(__buffer_)->__elem_);
212     }
213   };
214 
215   _Storage __storage_;
216 };
217 
218 struct __shared_ptr_dummy_rebind_allocator_type;
219 template <>
220 class _LIBCPP_TEMPLATE_VIS allocator<__shared_ptr_dummy_rebind_allocator_type> {
221 public:
222   template <class _Other>
223   struct rebind {
224     typedef allocator<_Other> other;
225   };
226 };
227 
228 template <class _Tp>
229 class _LIBCPP_TEMPLATE_VIS enable_shared_from_this;
230 
231 // http://eel.is/c++draft/util.sharedptr#util.smartptr.shared.general-6
232 // A pointer type Y* is said to be compatible with a pointer type T*
233 // when either Y* is convertible to T* or Y is U[N] and T is cv U[].
234 #if _LIBCPP_STD_VER >= 17
235 template <class _Yp, class _Tp>
236 struct __bounded_convertible_to_unbounded : false_type {};
237 
238 template <class _Up, std::size_t _Np, class _Tp>
239 struct __bounded_convertible_to_unbounded<_Up[_Np], _Tp> : is_same<__remove_cv_t<_Tp>, _Up[]> {};
240 
241 template <class _Yp, class _Tp>
242 struct __compatible_with : _Or< is_convertible<_Yp*, _Tp*>, __bounded_convertible_to_unbounded<_Yp, _Tp> > {};
243 #else
244 template <class _Yp, class _Tp>
245 struct __compatible_with : is_convertible<_Yp*, _Tp*> {};
246 #endif // _LIBCPP_STD_VER >= 17
247 
248 // Constructors that take raw pointers have a different set of "compatible" constraints
249 // http://eel.is/c++draft/util.sharedptr#util.smartptr.shared.const-9.1
250 // - If T is an array type, then either T is U[N] and Y(*)[N] is convertible to T*,
251 //   or T is U[] and Y(*)[] is convertible to T*.
252 // - If T is not an array type, then Y* is convertible to T*.
253 #if _LIBCPP_STD_VER >= 17
254 template <class _Yp, class _Tp, class = void>
255 struct __raw_pointer_compatible_with : _And< _Not<is_array<_Tp>>, is_convertible<_Yp*, _Tp*> > {};
256 
257 template <class _Yp, class _Up, std::size_t _Np>
258 struct __raw_pointer_compatible_with<_Yp, _Up[_Np], __enable_if_t< is_convertible<_Yp (*)[_Np], _Up (*)[_Np]>::value> >
259     : true_type {};
260 
261 template <class _Yp, class _Up>
262 struct __raw_pointer_compatible_with<_Yp, _Up[], __enable_if_t< is_convertible<_Yp (*)[], _Up (*)[]>::value> >
263     : true_type {};
264 
265 #else
266 template <class _Yp, class _Tp>
267 struct __raw_pointer_compatible_with : is_convertible<_Yp*, _Tp*> {};
268 #endif // _LIBCPP_STD_VER >= 17
269 
270 template <class _Ptr, class = void>
271 struct __is_deletable : false_type {};
272 template <class _Ptr>
273 struct __is_deletable<_Ptr, decltype(delete std::declval<_Ptr>())> : true_type {};
274 
275 template <class _Ptr, class = void>
276 struct __is_array_deletable : false_type {};
277 template <class _Ptr>
278 struct __is_array_deletable<_Ptr, decltype(delete[] std::declval<_Ptr>())> : true_type {};
279 
280 template <class _Dp, class _Pt, class = decltype(std::declval<_Dp>()(std::declval<_Pt>()))>
281 true_type __well_formed_deleter_test(int);
282 
283 template <class, class>
284 false_type __well_formed_deleter_test(...);
285 
286 template <class _Dp, class _Pt>
287 struct __well_formed_deleter : decltype(std::__well_formed_deleter_test<_Dp, _Pt>(0)) {};
288 
289 template <class _Dp, class _Yp, class _Tp>
290 struct __shared_ptr_deleter_ctor_reqs {
291   static const bool value = __raw_pointer_compatible_with<_Yp, _Tp>::value && is_move_constructible<_Dp>::value &&
292                             __well_formed_deleter<_Dp, _Yp*>::value;
293 };
294 
295 template <class _Dp>
296 using __shared_ptr_nullptr_deleter_ctor_reqs _LIBCPP_NODEBUG =
297     _And<is_move_constructible<_Dp>, __well_formed_deleter<_Dp, nullptr_t> >;
298 
299 #if defined(_LIBCPP_ABI_ENABLE_SHARED_PTR_TRIVIAL_ABI)
300 #  define _LIBCPP_SHARED_PTR_TRIVIAL_ABI __attribute__((__trivial_abi__))
301 #else
302 #  define _LIBCPP_SHARED_PTR_TRIVIAL_ABI
303 #endif
304 
305 template <class _Tp>
306 class _LIBCPP_SHARED_PTR_TRIVIAL_ABI _LIBCPP_TEMPLATE_VIS shared_ptr {
307   struct __nullptr_sfinae_tag {};
308 
309 public:
310 #if _LIBCPP_STD_VER >= 17
311   typedef weak_ptr<_Tp> weak_type;
312   typedef remove_extent_t<_Tp> element_type;
313 #else
314   typedef _Tp element_type;
315 #endif
316 
317   // A shared_ptr contains only two raw pointers which point to the heap and move constructing already doesn't require
318   // any bookkeeping, so it's always trivially relocatable.
319   using __trivially_relocatable _LIBCPP_NODEBUG = shared_ptr;
320 
321 private:
322   element_type* __ptr_;
323   __shared_weak_count* __cntrl_;
324 
325 public:
326   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR shared_ptr() _NOEXCEPT : __ptr_(nullptr), __cntrl_(nullptr) {}
327 
328   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR shared_ptr(nullptr_t) _NOEXCEPT : __ptr_(nullptr), __cntrl_(nullptr) {}
329 
330   template <class _Yp,
331             __enable_if_t< _And< __raw_pointer_compatible_with<_Yp, _Tp>
332   // In C++03 we get errors when trying to do SFINAE with the
333   // delete operator, so we always pretend that it's deletable.
334   // The same happens on GCC.
335 #if !defined(_LIBCPP_CXX03_LANG) && !defined(_LIBCPP_COMPILER_GCC)
336                                  ,
337                                  _If<is_array<_Tp>::value, __is_array_deletable<_Yp*>, __is_deletable<_Yp*> >
338 #endif
339                                  >::value,
340                            int> = 0>
341   _LIBCPP_HIDE_FROM_ABI explicit shared_ptr(_Yp* __p) : __ptr_(__p) {
342     unique_ptr<_Yp> __hold(__p);
343     typedef typename __shared_ptr_default_allocator<_Yp>::type _AllocT;
344     typedef __shared_ptr_pointer<_Yp*, __shared_ptr_default_delete<_Tp, _Yp>, _AllocT> _CntrlBlk;
345     __cntrl_ = new _CntrlBlk(__p, __shared_ptr_default_delete<_Tp, _Yp>(), _AllocT());
346     __hold.release();
347     __enable_weak_this(__p, __p);
348   }
349 
350   template <class _Yp, class _Dp, __enable_if_t<__shared_ptr_deleter_ctor_reqs<_Dp, _Yp, _Tp>::value, int> = 0>
351   _LIBCPP_HIDE_FROM_ABI shared_ptr(_Yp* __p, _Dp __d) : __ptr_(__p) {
352 #if _LIBCPP_HAS_EXCEPTIONS
353     try {
354 #endif // _LIBCPP_HAS_EXCEPTIONS
355       typedef typename __shared_ptr_default_allocator<_Yp>::type _AllocT;
356       typedef __shared_ptr_pointer<_Yp*, _Dp, _AllocT> _CntrlBlk;
357 #ifndef _LIBCPP_CXX03_LANG
358       __cntrl_ = new _CntrlBlk(__p, std::move(__d), _AllocT());
359 #else
360     __cntrl_ = new _CntrlBlk(__p, __d, _AllocT());
361 #endif // not _LIBCPP_CXX03_LANG
362       __enable_weak_this(__p, __p);
363 #if _LIBCPP_HAS_EXCEPTIONS
364     } catch (...) {
365       __d(__p);
366       throw;
367     }
368 #endif // _LIBCPP_HAS_EXCEPTIONS
369   }
370 
371   template <class _Yp,
372             class _Dp,
373             class _Alloc,
374             __enable_if_t<__shared_ptr_deleter_ctor_reqs<_Dp, _Yp, _Tp>::value, int> = 0>
375   _LIBCPP_HIDE_FROM_ABI shared_ptr(_Yp* __p, _Dp __d, _Alloc __a) : __ptr_(__p) {
376 #if _LIBCPP_HAS_EXCEPTIONS
377     try {
378 #endif // _LIBCPP_HAS_EXCEPTIONS
379       typedef __shared_ptr_pointer<_Yp*, _Dp, _Alloc> _CntrlBlk;
380       typedef typename __allocator_traits_rebind<_Alloc, _CntrlBlk>::type _A2;
381       typedef __allocator_destructor<_A2> _D2;
382       _A2 __a2(__a);
383       unique_ptr<_CntrlBlk, _D2> __hold2(__a2.allocate(1), _D2(__a2, 1));
384       ::new ((void*)std::addressof(*__hold2.get()))
385 #ifndef _LIBCPP_CXX03_LANG
386           _CntrlBlk(__p, std::move(__d), __a);
387 #else
388         _CntrlBlk(__p, __d, __a);
389 #endif // not _LIBCPP_CXX03_LANG
390       __cntrl_ = std::addressof(*__hold2.release());
391       __enable_weak_this(__p, __p);
392 #if _LIBCPP_HAS_EXCEPTIONS
393     } catch (...) {
394       __d(__p);
395       throw;
396     }
397 #endif // _LIBCPP_HAS_EXCEPTIONS
398   }
399 
400   template <class _Dp>
401   _LIBCPP_HIDE_FROM_ABI shared_ptr(
402       nullptr_t __p,
403       _Dp __d,
404       __enable_if_t<__shared_ptr_nullptr_deleter_ctor_reqs<_Dp>::value, __nullptr_sfinae_tag> = __nullptr_sfinae_tag())
405       : __ptr_(nullptr) {
406 #if _LIBCPP_HAS_EXCEPTIONS
407     try {
408 #endif // _LIBCPP_HAS_EXCEPTIONS
409       typedef typename __shared_ptr_default_allocator<_Tp>::type _AllocT;
410       typedef __shared_ptr_pointer<nullptr_t, _Dp, _AllocT> _CntrlBlk;
411 #ifndef _LIBCPP_CXX03_LANG
412       __cntrl_ = new _CntrlBlk(__p, std::move(__d), _AllocT());
413 #else
414     __cntrl_ = new _CntrlBlk(__p, __d, _AllocT());
415 #endif // not _LIBCPP_CXX03_LANG
416 #if _LIBCPP_HAS_EXCEPTIONS
417     } catch (...) {
418       __d(__p);
419       throw;
420     }
421 #endif // _LIBCPP_HAS_EXCEPTIONS
422   }
423 
424   template <class _Dp, class _Alloc>
425   _LIBCPP_HIDE_FROM_ABI shared_ptr(
426       nullptr_t __p,
427       _Dp __d,
428       _Alloc __a,
429       __enable_if_t<__shared_ptr_nullptr_deleter_ctor_reqs<_Dp>::value, __nullptr_sfinae_tag> = __nullptr_sfinae_tag())
430       : __ptr_(nullptr) {
431 #if _LIBCPP_HAS_EXCEPTIONS
432     try {
433 #endif // _LIBCPP_HAS_EXCEPTIONS
434       typedef __shared_ptr_pointer<nullptr_t, _Dp, _Alloc> _CntrlBlk;
435       typedef typename __allocator_traits_rebind<_Alloc, _CntrlBlk>::type _A2;
436       typedef __allocator_destructor<_A2> _D2;
437       _A2 __a2(__a);
438       unique_ptr<_CntrlBlk, _D2> __hold2(__a2.allocate(1), _D2(__a2, 1));
439       ::new ((void*)std::addressof(*__hold2.get()))
440 #ifndef _LIBCPP_CXX03_LANG
441           _CntrlBlk(__p, std::move(__d), __a);
442 #else
443         _CntrlBlk(__p, __d, __a);
444 #endif // not _LIBCPP_CXX03_LANG
445       __cntrl_ = std::addressof(*__hold2.release());
446 #if _LIBCPP_HAS_EXCEPTIONS
447     } catch (...) {
448       __d(__p);
449       throw;
450     }
451 #endif // _LIBCPP_HAS_EXCEPTIONS
452   }
453 
454   template <class _Yp>
455   _LIBCPP_HIDE_FROM_ABI shared_ptr(const shared_ptr<_Yp>& __r, element_type* __p) _NOEXCEPT
456       : __ptr_(__p),
457         __cntrl_(__r.__cntrl_) {
458     if (__cntrl_)
459       __cntrl_->__add_shared();
460   }
461 
462 // LWG-2996
463 // We don't backport because it is an evolutionary change.
464 #if _LIBCPP_STD_VER >= 20
465   template <class _Yp>
466   _LIBCPP_HIDE_FROM_ABI shared_ptr(shared_ptr<_Yp>&& __r, element_type* __p) noexcept
467       : __ptr_(__p), __cntrl_(__r.__cntrl_) {
468     __r.__ptr_   = nullptr;
469     __r.__cntrl_ = nullptr;
470   }
471 #endif
472 
473   _LIBCPP_HIDE_FROM_ABI shared_ptr(const shared_ptr& __r) _NOEXCEPT : __ptr_(__r.__ptr_), __cntrl_(__r.__cntrl_) {
474     if (__cntrl_)
475       __cntrl_->__add_shared();
476   }
477 
478   template <class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> = 0>
479   _LIBCPP_HIDE_FROM_ABI shared_ptr(const shared_ptr<_Yp>& __r) _NOEXCEPT : __ptr_(__r.__ptr_), __cntrl_(__r.__cntrl_) {
480     if (__cntrl_)
481       __cntrl_->__add_shared();
482   }
483 
484   _LIBCPP_HIDE_FROM_ABI shared_ptr(shared_ptr&& __r) _NOEXCEPT : __ptr_(__r.__ptr_), __cntrl_(__r.__cntrl_) {
485     __r.__ptr_   = nullptr;
486     __r.__cntrl_ = nullptr;
487   }
488 
489   template <class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> = 0>
490   _LIBCPP_HIDE_FROM_ABI shared_ptr(shared_ptr<_Yp>&& __r) _NOEXCEPT : __ptr_(__r.__ptr_), __cntrl_(__r.__cntrl_) {
491     __r.__ptr_   = nullptr;
492     __r.__cntrl_ = nullptr;
493   }
494 
495   template <class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> = 0>
496   _LIBCPP_HIDE_FROM_ABI explicit shared_ptr(const weak_ptr<_Yp>& __r)
497       : __ptr_(__r.__ptr_), __cntrl_(__r.__cntrl_ ? __r.__cntrl_->lock() : __r.__cntrl_) {
498     if (__cntrl_ == nullptr)
499       __throw_bad_weak_ptr();
500   }
501 
502 #if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
503   template <class _Yp, __enable_if_t<is_convertible<_Yp*, element_type*>::value, int> = 0>
504   _LIBCPP_HIDE_FROM_ABI shared_ptr(auto_ptr<_Yp>&& __r) : __ptr_(__r.get()) {
505     typedef __shared_ptr_pointer<_Yp*, default_delete<_Yp>, allocator<__remove_cv_t<_Yp> > > _CntrlBlk;
506     __cntrl_ = new _CntrlBlk(__r.get(), default_delete<_Yp>(), allocator<__remove_cv_t<_Yp> >());
507     __enable_weak_this(__r.get(), __r.get());
508     __r.release();
509   }
510 #endif
511 
512   template <class _Yp,
513             class _Dp,
514             __enable_if_t<!is_lvalue_reference<_Dp>::value && __compatible_with<_Yp, _Tp>::value &&
515                               is_convertible<typename unique_ptr<_Yp, _Dp>::pointer, element_type*>::value,
516                           int> = 0>
517   _LIBCPP_HIDE_FROM_ABI shared_ptr(unique_ptr<_Yp, _Dp>&& __r) : __ptr_(__r.get()) {
518 #if _LIBCPP_STD_VER >= 14
519     if (__ptr_ == nullptr)
520       __cntrl_ = nullptr;
521     else
522 #endif
523     {
524       typedef typename __shared_ptr_default_allocator<_Yp>::type _AllocT;
525       typedef __shared_ptr_pointer<typename unique_ptr<_Yp, _Dp>::pointer, _Dp, _AllocT> _CntrlBlk;
526       __cntrl_ = new _CntrlBlk(__r.get(), std::move(__r.get_deleter()), _AllocT());
527       __enable_weak_this(__r.get(), __r.get());
528     }
529     __r.release();
530   }
531 
532   template <class _Yp,
533             class _Dp,
534             class              = void,
535             __enable_if_t<is_lvalue_reference<_Dp>::value && __compatible_with<_Yp, _Tp>::value &&
536                               is_convertible<typename unique_ptr<_Yp, _Dp>::pointer, element_type*>::value,
537                           int> = 0>
538   _LIBCPP_HIDE_FROM_ABI shared_ptr(unique_ptr<_Yp, _Dp>&& __r) : __ptr_(__r.get()) {
539 #if _LIBCPP_STD_VER >= 14
540     if (__ptr_ == nullptr)
541       __cntrl_ = nullptr;
542     else
543 #endif
544     {
545       typedef typename __shared_ptr_default_allocator<_Yp>::type _AllocT;
546       typedef __shared_ptr_pointer<typename unique_ptr<_Yp, _Dp>::pointer,
547                                    reference_wrapper<__libcpp_remove_reference_t<_Dp> >,
548                                    _AllocT>
549           _CntrlBlk;
550       __cntrl_ = new _CntrlBlk(__r.get(), std::ref(__r.get_deleter()), _AllocT());
551       __enable_weak_this(__r.get(), __r.get());
552     }
553     __r.release();
554   }
555 
556   _LIBCPP_HIDE_FROM_ABI ~shared_ptr() {
557     if (__cntrl_)
558       __cntrl_->__release_shared();
559   }
560 
561   _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp>& operator=(const shared_ptr& __r) _NOEXCEPT {
562     shared_ptr(__r).swap(*this);
563     return *this;
564   }
565 
566   template <class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> = 0>
567   _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp>& operator=(const shared_ptr<_Yp>& __r) _NOEXCEPT {
568     shared_ptr(__r).swap(*this);
569     return *this;
570   }
571 
572   _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp>& operator=(shared_ptr&& __r) _NOEXCEPT {
573     shared_ptr(std::move(__r)).swap(*this);
574     return *this;
575   }
576 
577   template <class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> = 0>
578   _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp>& operator=(shared_ptr<_Yp>&& __r) {
579     shared_ptr(std::move(__r)).swap(*this);
580     return *this;
581   }
582 
583 #if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
584   template <class _Yp,
585             __enable_if_t<!is_array<_Yp>::value && is_convertible<_Yp*, typename shared_ptr<_Tp>::element_type*>::value,
586                           int> = 0>
587   _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp>& operator=(auto_ptr<_Yp>&& __r) {
588     shared_ptr(std::move(__r)).swap(*this);
589     return *this;
590   }
591 #endif
592 
593   template <class _Yp,
594             class _Dp,
595             __enable_if_t<_And< __compatible_with<_Yp, _Tp>,
596                                 is_convertible<typename unique_ptr<_Yp, _Dp>::pointer, element_type*> >::value,
597                           int> = 0>
598   _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp>& operator=(unique_ptr<_Yp, _Dp>&& __r) {
599     shared_ptr(std::move(__r)).swap(*this);
600     return *this;
601   }
602 
603   _LIBCPP_HIDE_FROM_ABI void swap(shared_ptr& __r) _NOEXCEPT {
604     std::swap(__ptr_, __r.__ptr_);
605     std::swap(__cntrl_, __r.__cntrl_);
606   }
607 
608   _LIBCPP_HIDE_FROM_ABI void reset() _NOEXCEPT { shared_ptr().swap(*this); }
609 
610   template <class _Yp, __enable_if_t<__raw_pointer_compatible_with<_Yp, _Tp>::value, int> = 0>
611   _LIBCPP_HIDE_FROM_ABI void reset(_Yp* __p) {
612     shared_ptr(__p).swap(*this);
613   }
614 
615   template <class _Yp, class _Dp, __enable_if_t<__shared_ptr_deleter_ctor_reqs<_Dp, _Yp, _Tp>::value, int> = 0>
616   _LIBCPP_HIDE_FROM_ABI void reset(_Yp* __p, _Dp __d) {
617     shared_ptr(__p, __d).swap(*this);
618   }
619 
620   template <class _Yp,
621             class _Dp,
622             class _Alloc,
623             __enable_if_t<__shared_ptr_deleter_ctor_reqs<_Dp, _Yp, _Tp>::value, int> = 0>
624   _LIBCPP_HIDE_FROM_ABI void reset(_Yp* __p, _Dp __d, _Alloc __a) {
625     shared_ptr(__p, __d, __a).swap(*this);
626   }
627 
628   _LIBCPP_HIDE_FROM_ABI element_type* get() const _NOEXCEPT { return __ptr_; }
629 
630   _LIBCPP_HIDE_FROM_ABI __add_lvalue_reference_t<element_type> operator*() const _NOEXCEPT { return *__ptr_; }
631 
632   _LIBCPP_HIDE_FROM_ABI element_type* operator->() const _NOEXCEPT {
633     static_assert(!is_array<_Tp>::value, "std::shared_ptr<T>::operator-> is only valid when T is not an array type.");
634     return __ptr_;
635   }
636 
637   _LIBCPP_HIDE_FROM_ABI long use_count() const _NOEXCEPT { return __cntrl_ ? __cntrl_->use_count() : 0; }
638 
639 #if _LIBCPP_STD_VER < 20 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_SHARED_PTR_UNIQUE)
640   _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_HIDE_FROM_ABI bool unique() const _NOEXCEPT { return use_count() == 1; }
641 #endif
642 
643   _LIBCPP_HIDE_FROM_ABI explicit operator bool() const _NOEXCEPT { return get() != nullptr; }
644 
645   template <class _Up>
646   _LIBCPP_HIDE_FROM_ABI bool owner_before(shared_ptr<_Up> const& __p) const _NOEXCEPT {
647     return __cntrl_ < __p.__cntrl_;
648   }
649 
650   template <class _Up>
651   _LIBCPP_HIDE_FROM_ABI bool owner_before(weak_ptr<_Up> const& __p) const _NOEXCEPT {
652     return __cntrl_ < __p.__cntrl_;
653   }
654 
655   _LIBCPP_HIDE_FROM_ABI bool __owner_equivalent(const shared_ptr& __p) const { return __cntrl_ == __p.__cntrl_; }
656 
657 #if _LIBCPP_STD_VER >= 17
658   _LIBCPP_HIDE_FROM_ABI __add_lvalue_reference_t<element_type> operator[](ptrdiff_t __i) const {
659     static_assert(is_array<_Tp>::value, "std::shared_ptr<T>::operator[] is only valid when T is an array type.");
660     return __ptr_[__i];
661   }
662 #endif
663 
664 #if _LIBCPP_HAS_RTTI
665   template <class _Dp>
666   _LIBCPP_HIDE_FROM_ABI _Dp* __get_deleter() const _NOEXCEPT {
667     return static_cast<_Dp*>(__cntrl_ ? const_cast<void*>(__cntrl_->__get_deleter(typeid(_Dp))) : nullptr);
668   }
669 #endif // _LIBCPP_HAS_RTTI
670 
671   template <class _Yp, class _CntrlBlk>
672   _LIBCPP_HIDE_FROM_ABI static shared_ptr<_Tp> __create_with_control_block(_Yp* __p, _CntrlBlk* __cntrl) _NOEXCEPT {
673     shared_ptr<_Tp> __r;
674     __r.__ptr_   = __p;
675     __r.__cntrl_ = __cntrl;
676     __r.__enable_weak_this(__r.__ptr_, __r.__ptr_);
677     return __r;
678   }
679 
680 private:
681   template <class _Yp, bool = is_function<_Yp>::value>
682   struct __shared_ptr_default_allocator {
683     typedef allocator<__remove_cv_t<_Yp> > type;
684   };
685 
686   template <class _Yp>
687   struct __shared_ptr_default_allocator<_Yp, true> {
688     typedef allocator<__shared_ptr_dummy_rebind_allocator_type> type;
689   };
690 
691   template <class _Yp,
692             class _OrigPtr,
693             __enable_if_t<is_convertible<_OrigPtr*, const enable_shared_from_this<_Yp>*>::value, int> = 0>
694   _LIBCPP_HIDE_FROM_ABI void __enable_weak_this(const enable_shared_from_this<_Yp>* __e, _OrigPtr* __ptr) _NOEXCEPT {
695     typedef __remove_cv_t<_Yp> _RawYp;
696     if (__e && __e->__weak_this_.expired()) {
697       __e->__weak_this_ = shared_ptr<_RawYp>(*this, const_cast<_RawYp*>(static_cast<const _Yp*>(__ptr)));
698     }
699   }
700 
701   _LIBCPP_HIDE_FROM_ABI void __enable_weak_this(...) _NOEXCEPT {}
702 
703   template <class, class _Yp>
704   struct __shared_ptr_default_delete : default_delete<_Yp> {};
705 
706   template <class _Yp, class _Un, size_t _Sz>
707   struct __shared_ptr_default_delete<_Yp[_Sz], _Un> : default_delete<_Yp[]> {};
708 
709   template <class _Yp, class _Un>
710   struct __shared_ptr_default_delete<_Yp[], _Un> : default_delete<_Yp[]> {};
711 
712   template <class _Up>
713   friend class _LIBCPP_TEMPLATE_VIS shared_ptr;
714   template <class _Up>
715   friend class _LIBCPP_TEMPLATE_VIS weak_ptr;
716 };
717 
718 #if _LIBCPP_STD_VER >= 17
719 template <class _Tp>
720 shared_ptr(weak_ptr<_Tp>) -> shared_ptr<_Tp>;
721 template <class _Tp, class _Dp>
722 shared_ptr(unique_ptr<_Tp, _Dp>) -> shared_ptr<_Tp>;
723 #endif
724 
725 //
726 // std::allocate_shared and std::make_shared
727 //
728 template <class _Tp, class _Alloc, class... _Args, __enable_if_t<!is_array<_Tp>::value, int> = 0>
729 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> allocate_shared(const _Alloc& __a, _Args&&... __args) {
730   using _ControlBlock          = __shared_ptr_emplace<_Tp, _Alloc>;
731   using _ControlBlockAllocator = typename __allocator_traits_rebind<_Alloc, _ControlBlock>::type;
732   __allocation_guard<_ControlBlockAllocator> __guard(__a, 1);
733   ::new ((void*)std::addressof(*__guard.__get())) _ControlBlock(__a, std::forward<_Args>(__args)...);
734   auto __control_block = __guard.__release_ptr();
735   return shared_ptr<_Tp>::__create_with_control_block(
736       (*__control_block).__get_elem(), std::addressof(*__control_block));
737 }
738 
739 template <class _Tp, class... _Args, __enable_if_t<!is_array<_Tp>::value, int> = 0>
740 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> make_shared(_Args&&... __args) {
741   return std::allocate_shared<_Tp>(allocator<__remove_cv_t<_Tp> >(), std::forward<_Args>(__args)...);
742 }
743 
744 #if _LIBCPP_STD_VER >= 20
745 
746 template <class _Tp, class _Alloc, __enable_if_t<!is_array<_Tp>::value, int> = 0>
747 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> allocate_shared_for_overwrite(const _Alloc& __a) {
748   using _ForOverwriteAllocator = __allocator_traits_rebind_t<_Alloc, __for_overwrite_tag>;
749   _ForOverwriteAllocator __alloc(__a);
750   return std::allocate_shared<_Tp>(__alloc);
751 }
752 
753 template <class _Tp, __enable_if_t<!is_array<_Tp>::value, int> = 0>
754 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> make_shared_for_overwrite() {
755   return std::allocate_shared_for_overwrite<_Tp>(allocator<__remove_cv_t<_Tp>>());
756 }
757 
758 #endif // _LIBCPP_STD_VER >= 20
759 
760 #if _LIBCPP_STD_VER >= 17
761 
762 template <size_t _Alignment>
763 struct __sp_aligned_storage {
764   alignas(_Alignment) char __storage[_Alignment];
765 };
766 
767 template <class _Tp, class _Alloc>
768 struct __unbounded_array_control_block;
769 
770 template <class _Tp, class _Alloc>
771 struct __unbounded_array_control_block<_Tp[], _Alloc> : __shared_weak_count {
772   _LIBCPP_HIDE_FROM_ABI constexpr _Tp* __get_data() noexcept { return __data_; }
773 
774   _LIBCPP_HIDE_FROM_ABI explicit __unbounded_array_control_block(
775       _Alloc const& __alloc, size_t __count, _Tp const& __arg)
776       : __alloc_(__alloc), __count_(__count) {
777     std::__uninitialized_allocator_fill_n_multidimensional(__alloc_, std::begin(__data_), __count_, __arg);
778   }
779 
780   _LIBCPP_HIDE_FROM_ABI explicit __unbounded_array_control_block(_Alloc const& __alloc, size_t __count)
781       : __alloc_(__alloc), __count_(__count) {
782 #  if _LIBCPP_STD_VER >= 20
783     if constexpr (is_same_v<typename _Alloc::value_type, __for_overwrite_tag>) {
784       // We are purposefully not using an allocator-aware default construction because the spec says so.
785       // There's currently no way of expressing default initialization in an allocator-aware manner anyway.
786       std::uninitialized_default_construct_n(std::begin(__data_), __count_);
787     } else {
788       std::__uninitialized_allocator_value_construct_n_multidimensional(__alloc_, std::begin(__data_), __count_);
789     }
790 #  else
791     std::__uninitialized_allocator_value_construct_n_multidimensional(__alloc_, std::begin(__data_), __count_);
792 #  endif
793   }
794 
795   // Returns the number of bytes required to store a control block followed by the given number
796   // of elements of _Tp, with the whole storage being aligned to a multiple of _Tp's alignment.
797   _LIBCPP_HIDE_FROM_ABI static constexpr size_t __bytes_for(size_t __elements) {
798     // When there's 0 elements, the control block alone is enough since it holds one element.
799     // Otherwise, we allocate one fewer element than requested because the control block already
800     // holds one. Also, we use the bitwise formula below to ensure that we allocate enough bytes
801     // for the whole allocation to be a multiple of _Tp's alignment. That formula is taken from [1].
802     //
803     // [1]: https://en.wikipedia.org/wiki/Data_structure_alignment#Computing_padding
804     size_t __bytes           = __elements == 0 ? sizeof(__unbounded_array_control_block)
805                                                : (__elements - 1) * sizeof(_Tp) + sizeof(__unbounded_array_control_block);
806     constexpr size_t __align = alignof(_Tp);
807     return (__bytes + __align - 1) & ~(__align - 1);
808   }
809 
810   _LIBCPP_HIDE_FROM_ABI_VIRTUAL
811   ~__unbounded_array_control_block() override {
812   } // can't be `= default` because of the sometimes-non-trivial union member __data_
813 
814 private:
815   _LIBCPP_HIDE_FROM_ABI_VIRTUAL void __on_zero_shared() _NOEXCEPT override {
816 #  if _LIBCPP_STD_VER >= 20
817     if constexpr (is_same_v<typename _Alloc::value_type, __for_overwrite_tag>) {
818       std::__reverse_destroy(__data_, __data_ + __count_);
819     } else {
820       __allocator_traits_rebind_t<_Alloc, _Tp> __value_alloc(__alloc_);
821       std::__allocator_destroy_multidimensional(__value_alloc, __data_, __data_ + __count_);
822     }
823 #  else
824     __allocator_traits_rebind_t<_Alloc, _Tp> __value_alloc(__alloc_);
825     std::__allocator_destroy_multidimensional(__value_alloc, __data_, __data_ + __count_);
826 #  endif
827   }
828 
829   _LIBCPP_HIDE_FROM_ABI_VIRTUAL void __on_zero_shared_weak() _NOEXCEPT override {
830     using _AlignedStorage = __sp_aligned_storage<alignof(__unbounded_array_control_block)>;
831     using _StorageAlloc   = __allocator_traits_rebind_t<_Alloc, _AlignedStorage>;
832     using _PointerTraits  = pointer_traits<typename allocator_traits<_StorageAlloc>::pointer>;
833 
834     _StorageAlloc __tmp(__alloc_);
835     __alloc_.~_Alloc();
836     size_t __size              = __unbounded_array_control_block::__bytes_for(__count_);
837     _AlignedStorage* __storage = reinterpret_cast<_AlignedStorage*>(this);
838     allocator_traits<_StorageAlloc>::deallocate(
839         __tmp, _PointerTraits::pointer_to(*__storage), __size / sizeof(_AlignedStorage));
840   }
841 
842   _LIBCPP_NO_UNIQUE_ADDRESS _Alloc __alloc_;
843   size_t __count_;
844   union {
845     _Tp __data_[1];
846   };
847 };
848 
849 template <class _Array, class _Alloc, class... _Arg>
850 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Array>
851 __allocate_shared_unbounded_array(const _Alloc& __a, size_t __n, _Arg&&... __arg) {
852   static_assert(__is_unbounded_array_v<_Array>);
853   // We compute the number of bytes necessary to hold the control block and the
854   // array elements. Then, we allocate an array of properly-aligned dummy structs
855   // large enough to hold the control block and array. This allows shifting the
856   // burden of aligning memory properly from us to the allocator.
857   using _ControlBlock   = __unbounded_array_control_block<_Array, _Alloc>;
858   using _AlignedStorage = __sp_aligned_storage<alignof(_ControlBlock)>;
859   using _StorageAlloc   = __allocator_traits_rebind_t<_Alloc, _AlignedStorage>;
860   __allocation_guard<_StorageAlloc> __guard(__a, _ControlBlock::__bytes_for(__n) / sizeof(_AlignedStorage));
861   _ControlBlock* __control_block = reinterpret_cast<_ControlBlock*>(std::addressof(*__guard.__get()));
862   std::__construct_at(__control_block, __a, __n, std::forward<_Arg>(__arg)...);
863   __guard.__release_ptr();
864   return shared_ptr<_Array>::__create_with_control_block(__control_block->__get_data(), __control_block);
865 }
866 
867 template <class _Tp, class _Alloc>
868 struct __bounded_array_control_block;
869 
870 template <class _Tp, size_t _Count, class _Alloc>
871 struct __bounded_array_control_block<_Tp[_Count], _Alloc> : __shared_weak_count {
872   _LIBCPP_HIDE_FROM_ABI constexpr _Tp* __get_data() noexcept { return __data_; }
873 
874   _LIBCPP_HIDE_FROM_ABI explicit __bounded_array_control_block(_Alloc const& __alloc, _Tp const& __arg)
875       : __alloc_(__alloc) {
876     std::__uninitialized_allocator_fill_n_multidimensional(__alloc_, std::addressof(__data_[0]), _Count, __arg);
877   }
878 
879   _LIBCPP_HIDE_FROM_ABI explicit __bounded_array_control_block(_Alloc const& __alloc) : __alloc_(__alloc) {
880 #  if _LIBCPP_STD_VER >= 20
881     if constexpr (is_same_v<typename _Alloc::value_type, __for_overwrite_tag>) {
882       // We are purposefully not using an allocator-aware default construction because the spec says so.
883       // There's currently no way of expressing default initialization in an allocator-aware manner anyway.
884       std::uninitialized_default_construct_n(std::addressof(__data_[0]), _Count);
885     } else {
886       std::__uninitialized_allocator_value_construct_n_multidimensional(__alloc_, std::addressof(__data_[0]), _Count);
887     }
888 #  else
889     std::__uninitialized_allocator_value_construct_n_multidimensional(__alloc_, std::addressof(__data_[0]), _Count);
890 #  endif
891   }
892 
893   _LIBCPP_HIDE_FROM_ABI_VIRTUAL
894   ~__bounded_array_control_block() override {
895   } // can't be `= default` because of the sometimes-non-trivial union member __data_
896 
897 private:
898   _LIBCPP_HIDE_FROM_ABI_VIRTUAL void __on_zero_shared() _NOEXCEPT override {
899 #  if _LIBCPP_STD_VER >= 20
900     if constexpr (is_same_v<typename _Alloc::value_type, __for_overwrite_tag>) {
901       std::__reverse_destroy(__data_, __data_ + _Count);
902     } else {
903       __allocator_traits_rebind_t<_Alloc, _Tp> __value_alloc(__alloc_);
904       std::__allocator_destroy_multidimensional(__value_alloc, __data_, __data_ + _Count);
905     }
906 #  else
907     __allocator_traits_rebind_t<_Alloc, _Tp> __value_alloc(__alloc_);
908     std::__allocator_destroy_multidimensional(__value_alloc, __data_, __data_ + _Count);
909 #  endif
910   }
911 
912   _LIBCPP_HIDE_FROM_ABI_VIRTUAL void __on_zero_shared_weak() _NOEXCEPT override {
913     using _ControlBlockAlloc = __allocator_traits_rebind_t<_Alloc, __bounded_array_control_block>;
914     using _PointerTraits     = pointer_traits<typename allocator_traits<_ControlBlockAlloc>::pointer>;
915 
916     _ControlBlockAlloc __tmp(__alloc_);
917     __alloc_.~_Alloc();
918     allocator_traits<_ControlBlockAlloc>::deallocate(__tmp, _PointerTraits::pointer_to(*this), 1);
919   }
920 
921   _LIBCPP_NO_UNIQUE_ADDRESS _Alloc __alloc_;
922   union {
923     _Tp __data_[_Count];
924   };
925 };
926 
927 template <class _Array, class _Alloc, class... _Arg>
928 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Array> __allocate_shared_bounded_array(const _Alloc& __a, _Arg&&... __arg) {
929   static_assert(__is_bounded_array_v<_Array>);
930   using _ControlBlock      = __bounded_array_control_block<_Array, _Alloc>;
931   using _ControlBlockAlloc = __allocator_traits_rebind_t<_Alloc, _ControlBlock>;
932 
933   __allocation_guard<_ControlBlockAlloc> __guard(__a, 1);
934   _ControlBlock* __control_block = reinterpret_cast<_ControlBlock*>(std::addressof(*__guard.__get()));
935   std::__construct_at(__control_block, __a, std::forward<_Arg>(__arg)...);
936   __guard.__release_ptr();
937   return shared_ptr<_Array>::__create_with_control_block(__control_block->__get_data(), __control_block);
938 }
939 
940 #endif // _LIBCPP_STD_VER >= 17
941 
942 #if _LIBCPP_STD_VER >= 20
943 
944 // bounded array variants
945 template <class _Tp, class _Alloc, __enable_if_t<is_bounded_array<_Tp>::value, int> = 0>
946 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> allocate_shared(const _Alloc& __a) {
947   return std::__allocate_shared_bounded_array<_Tp>(__a);
948 }
949 
950 template <class _Tp, class _Alloc, __enable_if_t<is_bounded_array<_Tp>::value, int> = 0>
951 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> allocate_shared(const _Alloc& __a, const remove_extent_t<_Tp>& __u) {
952   return std::__allocate_shared_bounded_array<_Tp>(__a, __u);
953 }
954 
955 template <class _Tp, class _Alloc, __enable_if_t<is_bounded_array<_Tp>::value, int> = 0>
956 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> allocate_shared_for_overwrite(const _Alloc& __a) {
957   using _ForOverwriteAllocator = __allocator_traits_rebind_t<_Alloc, __for_overwrite_tag>;
958   _ForOverwriteAllocator __alloc(__a);
959   return std::__allocate_shared_bounded_array<_Tp>(__alloc);
960 }
961 
962 template <class _Tp, __enable_if_t<is_bounded_array<_Tp>::value, int> = 0>
963 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> make_shared() {
964   return std::__allocate_shared_bounded_array<_Tp>(allocator<_Tp>());
965 }
966 
967 template <class _Tp, __enable_if_t<is_bounded_array<_Tp>::value, int> = 0>
968 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> make_shared(const remove_extent_t<_Tp>& __u) {
969   return std::__allocate_shared_bounded_array<_Tp>(allocator<_Tp>(), __u);
970 }
971 
972 template <class _Tp, __enable_if_t<is_bounded_array<_Tp>::value, int> = 0>
973 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> make_shared_for_overwrite() {
974   return std::__allocate_shared_bounded_array<_Tp>(allocator<__for_overwrite_tag>());
975 }
976 
977 // unbounded array variants
978 template <class _Tp, class _Alloc, __enable_if_t<is_unbounded_array<_Tp>::value, int> = 0>
979 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> allocate_shared(const _Alloc& __a, size_t __n) {
980   return std::__allocate_shared_unbounded_array<_Tp>(__a, __n);
981 }
982 
983 template <class _Tp, class _Alloc, __enable_if_t<is_unbounded_array<_Tp>::value, int> = 0>
984 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> allocate_shared(const _Alloc& __a, size_t __n, const remove_extent_t<_Tp>& __u) {
985   return std::__allocate_shared_unbounded_array<_Tp>(__a, __n, __u);
986 }
987 
988 template <class _Tp, class _Alloc, __enable_if_t<is_unbounded_array<_Tp>::value, int> = 0>
989 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> allocate_shared_for_overwrite(const _Alloc& __a, size_t __n) {
990   using _ForOverwriteAllocator = __allocator_traits_rebind_t<_Alloc, __for_overwrite_tag>;
991   _ForOverwriteAllocator __alloc(__a);
992   return std::__allocate_shared_unbounded_array<_Tp>(__alloc, __n);
993 }
994 
995 template <class _Tp, __enable_if_t<is_unbounded_array<_Tp>::value, int> = 0>
996 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> make_shared(size_t __n) {
997   return std::__allocate_shared_unbounded_array<_Tp>(allocator<_Tp>(), __n);
998 }
999 
1000 template <class _Tp, __enable_if_t<is_unbounded_array<_Tp>::value, int> = 0>
1001 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> make_shared(size_t __n, const remove_extent_t<_Tp>& __u) {
1002   return std::__allocate_shared_unbounded_array<_Tp>(allocator<_Tp>(), __n, __u);
1003 }
1004 
1005 template <class _Tp, __enable_if_t<is_unbounded_array<_Tp>::value, int> = 0>
1006 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> make_shared_for_overwrite(size_t __n) {
1007   return std::__allocate_shared_unbounded_array<_Tp>(allocator<__for_overwrite_tag>(), __n);
1008 }
1009 
1010 #endif // _LIBCPP_STD_VER >= 20
1011 
1012 template <class _Tp, class _Up>
1013 inline _LIBCPP_HIDE_FROM_ABI bool operator==(const shared_ptr<_Tp>& __x, const shared_ptr<_Up>& __y) _NOEXCEPT {
1014   return __x.get() == __y.get();
1015 }
1016 
1017 #if _LIBCPP_STD_VER <= 17
1018 
1019 template <class _Tp, class _Up>
1020 inline _LIBCPP_HIDE_FROM_ABI bool operator!=(const shared_ptr<_Tp>& __x, const shared_ptr<_Up>& __y) _NOEXCEPT {
1021   return !(__x == __y);
1022 }
1023 
1024 template <class _Tp, class _Up>
1025 inline _LIBCPP_HIDE_FROM_ABI bool operator<(const shared_ptr<_Tp>& __x, const shared_ptr<_Up>& __y) _NOEXCEPT {
1026 #  if _LIBCPP_STD_VER <= 11
1027   typedef typename common_type<_Tp*, _Up*>::type _Vp;
1028   return less<_Vp>()(__x.get(), __y.get());
1029 #  else
1030   return less<>()(__x.get(), __y.get());
1031 #  endif
1032 }
1033 
1034 template <class _Tp, class _Up>
1035 inline _LIBCPP_HIDE_FROM_ABI bool operator>(const shared_ptr<_Tp>& __x, const shared_ptr<_Up>& __y) _NOEXCEPT {
1036   return __y < __x;
1037 }
1038 
1039 template <class _Tp, class _Up>
1040 inline _LIBCPP_HIDE_FROM_ABI bool operator<=(const shared_ptr<_Tp>& __x, const shared_ptr<_Up>& __y) _NOEXCEPT {
1041   return !(__y < __x);
1042 }
1043 
1044 template <class _Tp, class _Up>
1045 inline _LIBCPP_HIDE_FROM_ABI bool operator>=(const shared_ptr<_Tp>& __x, const shared_ptr<_Up>& __y) _NOEXCEPT {
1046   return !(__x < __y);
1047 }
1048 
1049 #endif // _LIBCPP_STD_VER <= 17
1050 
1051 #if _LIBCPP_STD_VER >= 20
1052 template <class _Tp, class _Up>
1053 _LIBCPP_HIDE_FROM_ABI strong_ordering operator<=>(shared_ptr<_Tp> const& __x, shared_ptr<_Up> const& __y) noexcept {
1054   return compare_three_way()(__x.get(), __y.get());
1055 }
1056 #endif
1057 
1058 template <class _Tp>
1059 inline _LIBCPP_HIDE_FROM_ABI bool operator==(const shared_ptr<_Tp>& __x, nullptr_t) _NOEXCEPT {
1060   return !__x;
1061 }
1062 
1063 #if _LIBCPP_STD_VER <= 17
1064 
1065 template <class _Tp>
1066 inline _LIBCPP_HIDE_FROM_ABI bool operator==(nullptr_t, const shared_ptr<_Tp>& __x) _NOEXCEPT {
1067   return !__x;
1068 }
1069 
1070 template <class _Tp>
1071 inline _LIBCPP_HIDE_FROM_ABI bool operator!=(const shared_ptr<_Tp>& __x, nullptr_t) _NOEXCEPT {
1072   return static_cast<bool>(__x);
1073 }
1074 
1075 template <class _Tp>
1076 inline _LIBCPP_HIDE_FROM_ABI bool operator!=(nullptr_t, const shared_ptr<_Tp>& __x) _NOEXCEPT {
1077   return static_cast<bool>(__x);
1078 }
1079 
1080 template <class _Tp>
1081 inline _LIBCPP_HIDE_FROM_ABI bool operator<(const shared_ptr<_Tp>& __x, nullptr_t) _NOEXCEPT {
1082   return less<typename shared_ptr<_Tp>::element_type*>()(__x.get(), nullptr);
1083 }
1084 
1085 template <class _Tp>
1086 inline _LIBCPP_HIDE_FROM_ABI bool operator<(nullptr_t, const shared_ptr<_Tp>& __x) _NOEXCEPT {
1087   return less<typename shared_ptr<_Tp>::element_type*>()(nullptr, __x.get());
1088 }
1089 
1090 template <class _Tp>
1091 inline _LIBCPP_HIDE_FROM_ABI bool operator>(const shared_ptr<_Tp>& __x, nullptr_t) _NOEXCEPT {
1092   return nullptr < __x;
1093 }
1094 
1095 template <class _Tp>
1096 inline _LIBCPP_HIDE_FROM_ABI bool operator>(nullptr_t, const shared_ptr<_Tp>& __x) _NOEXCEPT {
1097   return __x < nullptr;
1098 }
1099 
1100 template <class _Tp>
1101 inline _LIBCPP_HIDE_FROM_ABI bool operator<=(const shared_ptr<_Tp>& __x, nullptr_t) _NOEXCEPT {
1102   return !(nullptr < __x);
1103 }
1104 
1105 template <class _Tp>
1106 inline _LIBCPP_HIDE_FROM_ABI bool operator<=(nullptr_t, const shared_ptr<_Tp>& __x) _NOEXCEPT {
1107   return !(__x < nullptr);
1108 }
1109 
1110 template <class _Tp>
1111 inline _LIBCPP_HIDE_FROM_ABI bool operator>=(const shared_ptr<_Tp>& __x, nullptr_t) _NOEXCEPT {
1112   return !(__x < nullptr);
1113 }
1114 
1115 template <class _Tp>
1116 inline _LIBCPP_HIDE_FROM_ABI bool operator>=(nullptr_t, const shared_ptr<_Tp>& __x) _NOEXCEPT {
1117   return !(nullptr < __x);
1118 }
1119 
1120 #endif // _LIBCPP_STD_VER <= 17
1121 
1122 #if _LIBCPP_STD_VER >= 20
1123 template <class _Tp>
1124 _LIBCPP_HIDE_FROM_ABI strong_ordering operator<=>(shared_ptr<_Tp> const& __x, nullptr_t) noexcept {
1125   return compare_three_way()(__x.get(), static_cast<typename shared_ptr<_Tp>::element_type*>(nullptr));
1126 }
1127 #endif
1128 
1129 template <class _Tp>
1130 inline _LIBCPP_HIDE_FROM_ABI void swap(shared_ptr<_Tp>& __x, shared_ptr<_Tp>& __y) _NOEXCEPT {
1131   __x.swap(__y);
1132 }
1133 
1134 template <class _Tp, class _Up>
1135 inline _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> static_pointer_cast(const shared_ptr<_Up>& __r) _NOEXCEPT {
1136   return shared_ptr<_Tp>(__r, static_cast< typename shared_ptr<_Tp>::element_type*>(__r.get()));
1137 }
1138 
1139 // LWG-2996
1140 // We don't backport because it is an evolutionary change.
1141 #if _LIBCPP_STD_VER >= 20
1142 template <class _Tp, class _Up>
1143 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> static_pointer_cast(shared_ptr<_Up>&& __r) noexcept {
1144   return shared_ptr<_Tp>(std::move(__r), static_cast<typename shared_ptr<_Tp>::element_type*>(__r.get()));
1145 }
1146 #endif
1147 
1148 template <class _Tp, class _Up>
1149 inline _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> dynamic_pointer_cast(const shared_ptr<_Up>& __r) _NOEXCEPT {
1150   typedef typename shared_ptr<_Tp>::element_type _ET;
1151   _ET* __p = dynamic_cast<_ET*>(__r.get());
1152   return __p ? shared_ptr<_Tp>(__r, __p) : shared_ptr<_Tp>();
1153 }
1154 
1155 // LWG-2996
1156 // We don't backport because it is an evolutionary change.
1157 #if _LIBCPP_STD_VER >= 20
1158 template <class _Tp, class _Up>
1159 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> dynamic_pointer_cast(shared_ptr<_Up>&& __r) noexcept {
1160   auto* __p = dynamic_cast<typename shared_ptr<_Tp>::element_type*>(__r.get());
1161   return __p ? shared_ptr<_Tp>(std::move(__r), __p) : shared_ptr<_Tp>();
1162 }
1163 #endif
1164 
1165 template <class _Tp, class _Up>
1166 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> const_pointer_cast(const shared_ptr<_Up>& __r) _NOEXCEPT {
1167   typedef typename shared_ptr<_Tp>::element_type _RTp;
1168   return shared_ptr<_Tp>(__r, const_cast<_RTp*>(__r.get()));
1169 }
1170 
1171 // LWG-2996
1172 // We don't backport because it is an evolutionary change.
1173 #if _LIBCPP_STD_VER >= 20
1174 template <class _Tp, class _Up>
1175 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> const_pointer_cast(shared_ptr<_Up>&& __r) noexcept {
1176   return shared_ptr<_Tp>(std::move(__r), const_cast<typename shared_ptr<_Tp>::element_type*>(__r.get()));
1177 }
1178 #endif
1179 
1180 template <class _Tp, class _Up>
1181 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> reinterpret_pointer_cast(const shared_ptr<_Up>& __r) _NOEXCEPT {
1182   return shared_ptr<_Tp>(__r, reinterpret_cast< typename shared_ptr<_Tp>::element_type*>(__r.get()));
1183 }
1184 
1185 // LWG-2996
1186 // We don't backport because it is an evolutionary change.
1187 #if _LIBCPP_STD_VER >= 20
1188 template <class _Tp, class _Up>
1189 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> reinterpret_pointer_cast(shared_ptr<_Up>&& __r) noexcept {
1190   return shared_ptr<_Tp>(std::move(__r), reinterpret_cast<typename shared_ptr<_Tp>::element_type*>(__r.get()));
1191 }
1192 #endif
1193 
1194 #if _LIBCPP_HAS_RTTI
1195 
1196 template <class _Dp, class _Tp>
1197 inline _LIBCPP_HIDE_FROM_ABI _Dp* get_deleter(const shared_ptr<_Tp>& __p) _NOEXCEPT {
1198   return __p.template __get_deleter<_Dp>();
1199 }
1200 
1201 #endif // _LIBCPP_HAS_RTTI
1202 
1203 template <class _Tp>
1204 class _LIBCPP_SHARED_PTR_TRIVIAL_ABI _LIBCPP_TEMPLATE_VIS weak_ptr {
1205 public:
1206 #if _LIBCPP_STD_VER >= 17
1207   typedef remove_extent_t<_Tp> element_type;
1208 #else
1209   typedef _Tp element_type;
1210 #endif
1211 
1212   // A weak_ptr contains only two raw pointers which point to the heap and move constructing already doesn't require
1213   // any bookkeeping, so it's always trivially relocatable.
1214   using __trivially_relocatable _LIBCPP_NODEBUG = weak_ptr;
1215 
1216 private:
1217   element_type* __ptr_;
1218   __shared_weak_count* __cntrl_;
1219 
1220 public:
1221   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR weak_ptr() _NOEXCEPT;
1222 
1223   template <class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> = 0>
1224   _LIBCPP_HIDE_FROM_ABI weak_ptr(shared_ptr<_Yp> const& __r) _NOEXCEPT;
1225 
1226   _LIBCPP_HIDE_FROM_ABI weak_ptr(weak_ptr const& __r) _NOEXCEPT;
1227 
1228   template <class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> = 0>
1229   _LIBCPP_HIDE_FROM_ABI weak_ptr(weak_ptr<_Yp> const& __r) _NOEXCEPT;
1230 
1231   _LIBCPP_HIDE_FROM_ABI weak_ptr(weak_ptr&& __r) _NOEXCEPT;
1232 
1233   template <class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> = 0>
1234   _LIBCPP_HIDE_FROM_ABI weak_ptr(weak_ptr<_Yp>&& __r) _NOEXCEPT;
1235 
1236   _LIBCPP_HIDE_FROM_ABI ~weak_ptr();
1237 
1238   _LIBCPP_HIDE_FROM_ABI weak_ptr& operator=(weak_ptr const& __r) _NOEXCEPT;
1239   template <class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> = 0>
1240   _LIBCPP_HIDE_FROM_ABI weak_ptr& operator=(weak_ptr<_Yp> const& __r) _NOEXCEPT;
1241 
1242   _LIBCPP_HIDE_FROM_ABI weak_ptr& operator=(weak_ptr&& __r) _NOEXCEPT;
1243   template <class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> = 0>
1244   _LIBCPP_HIDE_FROM_ABI weak_ptr& operator=(weak_ptr<_Yp>&& __r) _NOEXCEPT;
1245 
1246   template <class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> = 0>
1247   _LIBCPP_HIDE_FROM_ABI weak_ptr& operator=(shared_ptr<_Yp> const& __r) _NOEXCEPT;
1248 
1249   _LIBCPP_HIDE_FROM_ABI void swap(weak_ptr& __r) _NOEXCEPT;
1250   _LIBCPP_HIDE_FROM_ABI void reset() _NOEXCEPT;
1251 
1252   _LIBCPP_HIDE_FROM_ABI long use_count() const _NOEXCEPT { return __cntrl_ ? __cntrl_->use_count() : 0; }
1253   _LIBCPP_HIDE_FROM_ABI bool expired() const _NOEXCEPT { return __cntrl_ == nullptr || __cntrl_->use_count() == 0; }
1254   _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> lock() const _NOEXCEPT;
1255   template <class _Up>
1256   _LIBCPP_HIDE_FROM_ABI bool owner_before(const shared_ptr<_Up>& __r) const _NOEXCEPT {
1257     return __cntrl_ < __r.__cntrl_;
1258   }
1259   template <class _Up>
1260   _LIBCPP_HIDE_FROM_ABI bool owner_before(const weak_ptr<_Up>& __r) const _NOEXCEPT {
1261     return __cntrl_ < __r.__cntrl_;
1262   }
1263 
1264   template <class _Up>
1265   friend class _LIBCPP_TEMPLATE_VIS weak_ptr;
1266   template <class _Up>
1267   friend class _LIBCPP_TEMPLATE_VIS shared_ptr;
1268 };
1269 
1270 #if _LIBCPP_STD_VER >= 17
1271 template <class _Tp>
1272 weak_ptr(shared_ptr<_Tp>) -> weak_ptr<_Tp>;
1273 #endif
1274 
1275 template <class _Tp>
1276 inline _LIBCPP_CONSTEXPR weak_ptr<_Tp>::weak_ptr() _NOEXCEPT : __ptr_(nullptr), __cntrl_(nullptr) {}
1277 
1278 template <class _Tp>
1279 inline weak_ptr<_Tp>::weak_ptr(weak_ptr const& __r) _NOEXCEPT : __ptr_(__r.__ptr_), __cntrl_(__r.__cntrl_) {
1280   if (__cntrl_)
1281     __cntrl_->__add_weak();
1282 }
1283 
1284 template <class _Tp>
1285 template <class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> >
1286 inline weak_ptr<_Tp>::weak_ptr(shared_ptr<_Yp> const& __r) _NOEXCEPT : __ptr_(__r.__ptr_), __cntrl_(__r.__cntrl_) {
1287   if (__cntrl_)
1288     __cntrl_->__add_weak();
1289 }
1290 
1291 template <class _Tp>
1292 template <class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> >
1293 inline weak_ptr<_Tp>::weak_ptr(weak_ptr<_Yp> const& __r) _NOEXCEPT : __ptr_(nullptr), __cntrl_(nullptr) {
1294   shared_ptr<_Yp> __s = __r.lock();
1295   *this               = weak_ptr<_Tp>(__s);
1296 }
1297 
1298 template <class _Tp>
1299 inline weak_ptr<_Tp>::weak_ptr(weak_ptr&& __r) _NOEXCEPT : __ptr_(__r.__ptr_), __cntrl_(__r.__cntrl_) {
1300   __r.__ptr_   = nullptr;
1301   __r.__cntrl_ = nullptr;
1302 }
1303 
1304 template <class _Tp>
1305 template <class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> >
1306 inline weak_ptr<_Tp>::weak_ptr(weak_ptr<_Yp>&& __r) _NOEXCEPT : __ptr_(nullptr), __cntrl_(nullptr) {
1307   shared_ptr<_Yp> __s = __r.lock();
1308   *this               = weak_ptr<_Tp>(__s);
1309   __r.reset();
1310 }
1311 
1312 template <class _Tp>
1313 weak_ptr<_Tp>::~weak_ptr() {
1314   if (__cntrl_)
1315     __cntrl_->__release_weak();
1316 }
1317 
1318 template <class _Tp>
1319 inline weak_ptr<_Tp>& weak_ptr<_Tp>::operator=(weak_ptr const& __r) _NOEXCEPT {
1320   weak_ptr(__r).swap(*this);
1321   return *this;
1322 }
1323 
1324 template <class _Tp>
1325 template <class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> >
1326 inline weak_ptr<_Tp>& weak_ptr<_Tp>::operator=(weak_ptr<_Yp> const& __r) _NOEXCEPT {
1327   weak_ptr(__r).swap(*this);
1328   return *this;
1329 }
1330 
1331 template <class _Tp>
1332 inline weak_ptr<_Tp>& weak_ptr<_Tp>::operator=(weak_ptr&& __r) _NOEXCEPT {
1333   weak_ptr(std::move(__r)).swap(*this);
1334   return *this;
1335 }
1336 
1337 template <class _Tp>
1338 template <class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> >
1339 inline weak_ptr<_Tp>& weak_ptr<_Tp>::operator=(weak_ptr<_Yp>&& __r) _NOEXCEPT {
1340   weak_ptr(std::move(__r)).swap(*this);
1341   return *this;
1342 }
1343 
1344 template <class _Tp>
1345 template <class _Yp, __enable_if_t<__compatible_with<_Yp, _Tp>::value, int> >
1346 inline weak_ptr<_Tp>& weak_ptr<_Tp>::operator=(shared_ptr<_Yp> const& __r) _NOEXCEPT {
1347   weak_ptr(__r).swap(*this);
1348   return *this;
1349 }
1350 
1351 template <class _Tp>
1352 inline void weak_ptr<_Tp>::swap(weak_ptr& __r) _NOEXCEPT {
1353   std::swap(__ptr_, __r.__ptr_);
1354   std::swap(__cntrl_, __r.__cntrl_);
1355 }
1356 
1357 template <class _Tp>
1358 inline _LIBCPP_HIDE_FROM_ABI void swap(weak_ptr<_Tp>& __x, weak_ptr<_Tp>& __y) _NOEXCEPT {
1359   __x.swap(__y);
1360 }
1361 
1362 template <class _Tp>
1363 inline void weak_ptr<_Tp>::reset() _NOEXCEPT {
1364   weak_ptr().swap(*this);
1365 }
1366 
1367 template <class _Tp>
1368 shared_ptr<_Tp> weak_ptr<_Tp>::lock() const _NOEXCEPT {
1369   shared_ptr<_Tp> __r;
1370   __r.__cntrl_ = __cntrl_ ? __cntrl_->lock() : __cntrl_;
1371   if (__r.__cntrl_)
1372     __r.__ptr_ = __ptr_;
1373   return __r;
1374 }
1375 
1376 #if _LIBCPP_STD_VER >= 17
1377 template <class _Tp = void>
1378 struct owner_less;
1379 #else
1380 template <class _Tp>
1381 struct owner_less;
1382 #endif
1383 
1384 template <class _Tp>
1385 struct _LIBCPP_TEMPLATE_VIS owner_less<shared_ptr<_Tp> > : __binary_function<shared_ptr<_Tp>, shared_ptr<_Tp>, bool> {
1386   _LIBCPP_HIDE_FROM_ABI bool operator()(shared_ptr<_Tp> const& __x, shared_ptr<_Tp> const& __y) const _NOEXCEPT {
1387     return __x.owner_before(__y);
1388   }
1389   _LIBCPP_HIDE_FROM_ABI bool operator()(shared_ptr<_Tp> const& __x, weak_ptr<_Tp> const& __y) const _NOEXCEPT {
1390     return __x.owner_before(__y);
1391   }
1392   _LIBCPP_HIDE_FROM_ABI bool operator()(weak_ptr<_Tp> const& __x, shared_ptr<_Tp> const& __y) const _NOEXCEPT {
1393     return __x.owner_before(__y);
1394   }
1395 };
1396 
1397 template <class _Tp>
1398 struct _LIBCPP_TEMPLATE_VIS owner_less<weak_ptr<_Tp> > : __binary_function<weak_ptr<_Tp>, weak_ptr<_Tp>, bool> {
1399   _LIBCPP_HIDE_FROM_ABI bool operator()(weak_ptr<_Tp> const& __x, weak_ptr<_Tp> const& __y) const _NOEXCEPT {
1400     return __x.owner_before(__y);
1401   }
1402   _LIBCPP_HIDE_FROM_ABI bool operator()(shared_ptr<_Tp> const& __x, weak_ptr<_Tp> const& __y) const _NOEXCEPT {
1403     return __x.owner_before(__y);
1404   }
1405   _LIBCPP_HIDE_FROM_ABI bool operator()(weak_ptr<_Tp> const& __x, shared_ptr<_Tp> const& __y) const _NOEXCEPT {
1406     return __x.owner_before(__y);
1407   }
1408 };
1409 
1410 #if _LIBCPP_STD_VER >= 17
1411 template <>
1412 struct _LIBCPP_TEMPLATE_VIS owner_less<void> {
1413   template <class _Tp, class _Up>
1414   _LIBCPP_HIDE_FROM_ABI bool operator()(shared_ptr<_Tp> const& __x, shared_ptr<_Up> const& __y) const _NOEXCEPT {
1415     return __x.owner_before(__y);
1416   }
1417   template <class _Tp, class _Up>
1418   _LIBCPP_HIDE_FROM_ABI bool operator()(shared_ptr<_Tp> const& __x, weak_ptr<_Up> const& __y) const _NOEXCEPT {
1419     return __x.owner_before(__y);
1420   }
1421   template <class _Tp, class _Up>
1422   _LIBCPP_HIDE_FROM_ABI bool operator()(weak_ptr<_Tp> const& __x, shared_ptr<_Up> const& __y) const _NOEXCEPT {
1423     return __x.owner_before(__y);
1424   }
1425   template <class _Tp, class _Up>
1426   _LIBCPP_HIDE_FROM_ABI bool operator()(weak_ptr<_Tp> const& __x, weak_ptr<_Up> const& __y) const _NOEXCEPT {
1427     return __x.owner_before(__y);
1428   }
1429   typedef void is_transparent;
1430 };
1431 #endif
1432 
1433 template <class _Tp>
1434 class _LIBCPP_TEMPLATE_VIS enable_shared_from_this {
1435   mutable weak_ptr<_Tp> __weak_this_;
1436 
1437 protected:
1438   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR enable_shared_from_this() _NOEXCEPT {}
1439   _LIBCPP_HIDE_FROM_ABI enable_shared_from_this(enable_shared_from_this const&) _NOEXCEPT {}
1440   _LIBCPP_HIDE_FROM_ABI enable_shared_from_this& operator=(enable_shared_from_this const&) _NOEXCEPT { return *this; }
1441   _LIBCPP_HIDE_FROM_ABI ~enable_shared_from_this() {}
1442 
1443 public:
1444   _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> shared_from_this() { return shared_ptr<_Tp>(__weak_this_); }
1445   _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp const> shared_from_this() const { return shared_ptr<const _Tp>(__weak_this_); }
1446 
1447 #if _LIBCPP_STD_VER >= 17
1448   _LIBCPP_HIDE_FROM_ABI weak_ptr<_Tp> weak_from_this() _NOEXCEPT { return __weak_this_; }
1449 
1450   _LIBCPP_HIDE_FROM_ABI weak_ptr<const _Tp> weak_from_this() const _NOEXCEPT { return __weak_this_; }
1451 #endif // _LIBCPP_STD_VER >= 17
1452 
1453   template <class _Up>
1454   friend class shared_ptr;
1455 };
1456 
1457 template <class _Tp>
1458 struct _LIBCPP_TEMPLATE_VIS hash;
1459 
1460 template <class _Tp>
1461 struct _LIBCPP_TEMPLATE_VIS hash<shared_ptr<_Tp> > {
1462 #if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
1463   _LIBCPP_DEPRECATED_IN_CXX17 typedef shared_ptr<_Tp> argument_type;
1464   _LIBCPP_DEPRECATED_IN_CXX17 typedef size_t result_type;
1465 #endif
1466 
1467   _LIBCPP_HIDE_FROM_ABI size_t operator()(const shared_ptr<_Tp>& __ptr) const _NOEXCEPT {
1468     return hash<typename shared_ptr<_Tp>::element_type*>()(__ptr.get());
1469   }
1470 };
1471 
1472 template <class _CharT, class _Traits, class _Yp>
1473 inline _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
1474 operator<<(basic_ostream<_CharT, _Traits>& __os, shared_ptr<_Yp> const& __p);
1475 
1476 #if _LIBCPP_HAS_THREADS
1477 
1478 class _LIBCPP_EXPORTED_FROM_ABI __sp_mut {
1479   void* __lx_;
1480 
1481 public:
1482   void lock() _NOEXCEPT;
1483   void unlock() _NOEXCEPT;
1484 
1485 private:
1486   _LIBCPP_CONSTEXPR __sp_mut(void*) _NOEXCEPT;
1487   __sp_mut(const __sp_mut&);
1488   __sp_mut& operator=(const __sp_mut&);
1489 
1490   friend _LIBCPP_EXPORTED_FROM_ABI __sp_mut& __get_sp_mut(const void*);
1491 };
1492 
1493 _LIBCPP_EXPORTED_FROM_ABI __sp_mut& __get_sp_mut(const void*);
1494 
1495 template <class _Tp>
1496 inline _LIBCPP_HIDE_FROM_ABI bool atomic_is_lock_free(const shared_ptr<_Tp>*) {
1497   return false;
1498 }
1499 
1500 template <class _Tp>
1501 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> atomic_load(const shared_ptr<_Tp>* __p) {
1502   __sp_mut& __m = std::__get_sp_mut(__p);
1503   __m.lock();
1504   shared_ptr<_Tp> __q = *__p;
1505   __m.unlock();
1506   return __q;
1507 }
1508 
1509 template <class _Tp>
1510 inline _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> atomic_load_explicit(const shared_ptr<_Tp>* __p, memory_order) {
1511   return std::atomic_load(__p);
1512 }
1513 
1514 template <class _Tp>
1515 _LIBCPP_HIDE_FROM_ABI void atomic_store(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r) {
1516   __sp_mut& __m = std::__get_sp_mut(__p);
1517   __m.lock();
1518   __p->swap(__r);
1519   __m.unlock();
1520 }
1521 
1522 template <class _Tp>
1523 inline _LIBCPP_HIDE_FROM_ABI void atomic_store_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r, memory_order) {
1524   std::atomic_store(__p, __r);
1525 }
1526 
1527 template <class _Tp>
1528 _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp> atomic_exchange(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r) {
1529   __sp_mut& __m = std::__get_sp_mut(__p);
1530   __m.lock();
1531   __p->swap(__r);
1532   __m.unlock();
1533   return __r;
1534 }
1535 
1536 template <class _Tp>
1537 inline _LIBCPP_HIDE_FROM_ABI shared_ptr<_Tp>
1538 atomic_exchange_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r, memory_order) {
1539   return std::atomic_exchange(__p, __r);
1540 }
1541 
1542 template <class _Tp>
1543 _LIBCPP_HIDE_FROM_ABI bool
1544 atomic_compare_exchange_strong(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_ptr<_Tp> __w) {
1545   shared_ptr<_Tp> __temp;
1546   __sp_mut& __m = std::__get_sp_mut(__p);
1547   __m.lock();
1548   if (__p->__owner_equivalent(*__v)) {
1549     std::swap(__temp, *__p);
1550     *__p = __w;
1551     __m.unlock();
1552     return true;
1553   }
1554   std::swap(__temp, *__v);
1555   *__v = *__p;
1556   __m.unlock();
1557   return false;
1558 }
1559 
1560 template <class _Tp>
1561 inline _LIBCPP_HIDE_FROM_ABI bool
1562 atomic_compare_exchange_weak(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_ptr<_Tp> __w) {
1563   return std::atomic_compare_exchange_strong(__p, __v, __w);
1564 }
1565 
1566 template <class _Tp>
1567 inline _LIBCPP_HIDE_FROM_ABI bool atomic_compare_exchange_strong_explicit(
1568     shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_ptr<_Tp> __w, memory_order, memory_order) {
1569   return std::atomic_compare_exchange_strong(__p, __v, __w);
1570 }
1571 
1572 template <class _Tp>
1573 inline _LIBCPP_HIDE_FROM_ABI bool atomic_compare_exchange_weak_explicit(
1574     shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_ptr<_Tp> __w, memory_order, memory_order) {
1575   return std::atomic_compare_exchange_weak(__p, __v, __w);
1576 }
1577 
1578 #endif // _LIBCPP_HAS_THREADS
1579 
1580 _LIBCPP_END_NAMESPACE_STD
1581 
1582 _LIBCPP_POP_MACROS
1583 
1584 #endif // _LIBCPP___MEMORY_SHARED_PTR_H
1585