libstdc++
bits/shared_ptr.h
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1// shared_ptr and weak_ptr implementation -*- C++ -*-
2
3// Copyright (C) 2007-2020 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
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_H
50#define _SHARED_PTR_H 1
51
53
54namespace std _GLIBCXX_VISIBILITY(default)
55{
56_GLIBCXX_BEGIN_NAMESPACE_VERSION
57
58 /**
59 * @addtogroup pointer_abstractions
60 * @{
61 */
62
63 // 20.7.2.2.11 shared_ptr I/O
64
65 /// Write the stored pointer to an ostream.
66 /// @relates shared_ptr
67 template<typename _Ch, typename _Tr, typename _Tp, _Lock_policy _Lp>
69 operator<<(std::basic_ostream<_Ch, _Tr>& __os,
70 const __shared_ptr<_Tp, _Lp>& __p)
71 {
72 __os << __p.get();
73 return __os;
74 }
75
76 template<typename _Del, typename _Tp, _Lock_policy _Lp>
77 inline _Del*
78 get_deleter(const __shared_ptr<_Tp, _Lp>& __p) noexcept
79 {
80#if __cpp_rtti
81 return static_cast<_Del*>(__p._M_get_deleter(typeid(_Del)));
82#else
83 return 0;
84#endif
85 }
86
87 /// 20.7.2.2.10 shared_ptr get_deleter
88
89 /// If `__p` has a deleter of type `_Del`, return a pointer to it.
90 /// @relates shared_ptr
91 template<typename _Del, typename _Tp>
92 inline _Del*
93 get_deleter(const shared_ptr<_Tp>& __p) noexcept
94 {
95#if __cpp_rtti
96 return static_cast<_Del*>(__p._M_get_deleter(typeid(_Del)));
97#else
98 return 0;
99#endif
100 }
101
102 /**
103 * @brief A smart pointer with reference-counted copy semantics.
104 *
105 * A `shared_ptr` object is either empty or _owns_ a pointer passed
106 * to the constructor. Copies of a `shared_ptr` share ownership of
107 * the same pointer. When the last `shared_ptr` that owns the pointer
108 * is destroyed or reset, the owned pointer is freed (either by `delete`
109 * or by invoking a custom deleter that was passed to the constructor).
110 *
111 * A `shared_ptr` also stores another pointer, which is usually
112 * (but not always) the same pointer as it owns. The stored pointer
113 * can be retrieved by calling the `get()` member function.
114 *
115 * The equality and relational operators for `shared_ptr` only compare
116 * the stored pointer returned by `get()`, not the owned pointer.
117 * To test whether two `shared_ptr` objects share ownership of the same
118 * pointer see `std::shared_ptr::owner_before` and `std::owner_less`.
119 */
120 template<typename _Tp>
121 class shared_ptr : public __shared_ptr<_Tp>
122 {
123 template<typename... _Args>
124 using _Constructible = typename enable_if<
125 is_constructible<__shared_ptr<_Tp>, _Args...>::value
126 >::type;
127
128 template<typename _Arg>
129 using _Assignable = typename enable_if<
131 >::type;
132
133 public:
134
135 /// The type pointed to by the stored pointer, remove_extent_t<_Tp>
136 using element_type = typename __shared_ptr<_Tp>::element_type;
137
138#if __cplusplus >= 201703L
139# define __cpp_lib_shared_ptr_weak_type 201606
140 /// The corresponding weak_ptr type for this shared_ptr
141 using weak_type = weak_ptr<_Tp>;
142#endif
143 /**
144 * @brief Construct an empty %shared_ptr.
145 * @post use_count()==0 && get()==0
146 */
147 constexpr shared_ptr() noexcept : __shared_ptr<_Tp>() { }
148
149 shared_ptr(const shared_ptr&) noexcept = default; ///< Copy constructor
150
151 /**
152 * @brief Construct a %shared_ptr that owns the pointer @a __p.
153 * @param __p A pointer that is convertible to element_type*.
154 * @post use_count() == 1 && get() == __p
155 * @throw std::bad_alloc, in which case @c delete @a __p is called.
156 */
157 template<typename _Yp, typename = _Constructible<_Yp*>>
158 explicit
159 shared_ptr(_Yp* __p) : __shared_ptr<_Tp>(__p) { }
160
161 /**
162 * @brief Construct a %shared_ptr that owns the pointer @a __p
163 * and the deleter @a __d.
164 * @param __p A pointer.
165 * @param __d A deleter.
166 * @post use_count() == 1 && get() == __p
167 * @throw std::bad_alloc, in which case @a __d(__p) is called.
168 *
169 * Requirements: _Deleter's copy constructor and destructor must
170 * not throw
171 *
172 * __shared_ptr will release __p by calling __d(__p)
173 */
174 template<typename _Yp, typename _Deleter,
175 typename = _Constructible<_Yp*, _Deleter>>
176 shared_ptr(_Yp* __p, _Deleter __d)
177 : __shared_ptr<_Tp>(__p, std::move(__d)) { }
178
179 /**
180 * @brief Construct a %shared_ptr that owns a null pointer
181 * and the deleter @a __d.
182 * @param __p A null pointer constant.
183 * @param __d A deleter.
184 * @post use_count() == 1 && get() == __p
185 * @throw std::bad_alloc, in which case @a __d(__p) is called.
186 *
187 * Requirements: _Deleter's copy constructor and destructor must
188 * not throw
189 *
190 * The last owner will call __d(__p)
191 */
192 template<typename _Deleter>
193 shared_ptr(nullptr_t __p, _Deleter __d)
194 : __shared_ptr<_Tp>(__p, std::move(__d)) { }
195
196 /**
197 * @brief Construct a %shared_ptr that owns the pointer @a __p
198 * and the deleter @a __d.
199 * @param __p A pointer.
200 * @param __d A deleter.
201 * @param __a An allocator.
202 * @post use_count() == 1 && get() == __p
203 * @throw std::bad_alloc, in which case @a __d(__p) is called.
204 *
205 * Requirements: _Deleter's copy constructor and destructor must
206 * not throw _Alloc's copy constructor and destructor must not
207 * throw.
208 *
209 * __shared_ptr will release __p by calling __d(__p)
210 */
211 template<typename _Yp, typename _Deleter, typename _Alloc,
212 typename = _Constructible<_Yp*, _Deleter, _Alloc>>
213 shared_ptr(_Yp* __p, _Deleter __d, _Alloc __a)
214 : __shared_ptr<_Tp>(__p, std::move(__d), std::move(__a)) { }
215
216 /**
217 * @brief Construct a %shared_ptr that owns a null pointer
218 * and the deleter @a __d.
219 * @param __p A null pointer constant.
220 * @param __d A deleter.
221 * @param __a An allocator.
222 * @post use_count() == 1 && get() == __p
223 * @throw std::bad_alloc, in which case @a __d(__p) is called.
224 *
225 * Requirements: _Deleter's copy constructor and destructor must
226 * not throw _Alloc's copy constructor and destructor must not
227 * throw.
228 *
229 * The last owner will call __d(__p)
230 */
231 template<typename _Deleter, typename _Alloc>
232 shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
233 : __shared_ptr<_Tp>(__p, std::move(__d), std::move(__a)) { }
234
235 // Aliasing constructor
236
237 /**
238 * @brief Constructs a `shared_ptr` instance that stores `__p`
239 * and shares ownership with `__r`.
240 * @param __r A `shared_ptr`.
241 * @param __p A pointer that will remain valid while `*__r` is valid.
242 * @post `get() == __p && use_count() == __r.use_count()`
243 *
244 * This can be used to construct a `shared_ptr` to a sub-object
245 * of an object managed by an existing `shared_ptr`. The complete
246 * object will remain valid while any `shared_ptr` owns it, even
247 * if they don't store a pointer to the complete object.
248 *
249 * @code
250 * shared_ptr<pair<int,int>> pii(new pair<int,int>());
251 * shared_ptr<int> pi(pii, &pii->first);
252 * assert(pii.use_count() == 2);
253 * @endcode
254 */
255 template<typename _Yp>
256 shared_ptr(const shared_ptr<_Yp>& __r, element_type* __p) noexcept
257 : __shared_ptr<_Tp>(__r, __p) { }
258
259#if __cplusplus > 201703L
260 // _GLIBCXX_RESOLVE_LIB_DEFECTS
261 // 2996. Missing rvalue overloads for shared_ptr operations
262 /**
263 * @brief Constructs a `shared_ptr` instance that stores `__p`
264 * and shares ownership with `__r`.
265 * @param __r A `shared_ptr`.
266 * @param __p A pointer that will remain valid while `*__r` is valid.
267 * @post `get() == __p && !__r.use_count() && !__r.get()`
268 *
269 * This can be used to construct a `shared_ptr` to a sub-object
270 * of an object managed by an existing `shared_ptr`. The complete
271 * object will remain valid while any `shared_ptr` owns it, even
272 * if they don't store a pointer to the complete object.
273 *
274 * @code
275 * shared_ptr<pair<int,int>> pii(new pair<int,int>());
276 * shared_ptr<int> pi1(pii, &pii->first);
277 * assert(pii.use_count() == 2);
278 * shared_ptr<int> pi2(std::move(pii), &pii->second);
279 * assert(pii.use_count() == 0);
280 * @endcode
281 */
282 template<typename _Yp>
283 shared_ptr(shared_ptr<_Yp>&& __r, element_type* __p) noexcept
284 : __shared_ptr<_Tp>(std::move(__r), __p) { }
285#endif
286 /**
287 * @brief If @a __r is empty, constructs an empty %shared_ptr;
288 * otherwise construct a %shared_ptr that shares ownership
289 * with @a __r.
290 * @param __r A %shared_ptr.
291 * @post get() == __r.get() && use_count() == __r.use_count()
292 */
293 template<typename _Yp,
294 typename = _Constructible<const shared_ptr<_Yp>&>>
295 shared_ptr(const shared_ptr<_Yp>& __r) noexcept
296 : __shared_ptr<_Tp>(__r) { }
297
298 /**
299 * @brief Move-constructs a %shared_ptr instance from @a __r.
300 * @param __r A %shared_ptr rvalue.
301 * @post *this contains the old value of @a __r, @a __r is empty.
302 */
303 shared_ptr(shared_ptr&& __r) noexcept
304 : __shared_ptr<_Tp>(std::move(__r)) { }
305
306 /**
307 * @brief Move-constructs a %shared_ptr instance from @a __r.
308 * @param __r A %shared_ptr rvalue.
309 * @post *this contains the old value of @a __r, @a __r is empty.
310 */
311 template<typename _Yp, typename = _Constructible<shared_ptr<_Yp>>>
313 : __shared_ptr<_Tp>(std::move(__r)) { }
314
315 /**
316 * @brief Constructs a %shared_ptr that shares ownership with @a __r
317 * and stores a copy of the pointer stored in @a __r.
318 * @param __r A weak_ptr.
319 * @post use_count() == __r.use_count()
320 * @throw bad_weak_ptr when __r.expired(),
321 * in which case the constructor has no effect.
322 */
323 template<typename _Yp, typename = _Constructible<const weak_ptr<_Yp>&>>
324 explicit shared_ptr(const weak_ptr<_Yp>& __r)
325 : __shared_ptr<_Tp>(__r) { }
326
327#if _GLIBCXX_USE_DEPRECATED
328#pragma GCC diagnostic push
329#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
330 template<typename _Yp, typename = _Constructible<auto_ptr<_Yp>>>
332#pragma GCC diagnostic pop
333#endif
334
335 // _GLIBCXX_RESOLVE_LIB_DEFECTS
336 // 2399. shared_ptr's constructor from unique_ptr should be constrained
337 template<typename _Yp, typename _Del,
338 typename = _Constructible<unique_ptr<_Yp, _Del>>>
340 : __shared_ptr<_Tp>(std::move(__r)) { }
341
342#if __cplusplus <= 201402L && _GLIBCXX_USE_DEPRECATED
343 // This non-standard constructor exists to support conversions that
344 // were possible in C++11 and C++14 but are ill-formed in C++17.
345 // If an exception is thrown this constructor has no effect.
346 template<typename _Yp, typename _Del,
347 _Constructible<unique_ptr<_Yp, _Del>, __sp_array_delete>* = 0>
348 shared_ptr(unique_ptr<_Yp, _Del>&& __r)
349 : __shared_ptr<_Tp>(std::move(__r), __sp_array_delete()) { }
350#endif
351
352 /**
353 * @brief Construct an empty %shared_ptr.
354 * @post use_count() == 0 && get() == nullptr
355 */
356 constexpr shared_ptr(nullptr_t) noexcept : shared_ptr() { }
357
358 shared_ptr& operator=(const shared_ptr&) noexcept = default;
359
360 template<typename _Yp>
361 _Assignable<const shared_ptr<_Yp>&>
362 operator=(const shared_ptr<_Yp>& __r) noexcept
363 {
364 this->__shared_ptr<_Tp>::operator=(__r);
365 return *this;
366 }
367
368#if _GLIBCXX_USE_DEPRECATED
369#pragma GCC diagnostic push
370#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
371 template<typename _Yp>
372 _Assignable<auto_ptr<_Yp>>
373 operator=(auto_ptr<_Yp>&& __r)
374 {
375 this->__shared_ptr<_Tp>::operator=(std::move(__r));
376 return *this;
377 }
378#pragma GCC diagnostic pop
379#endif
380
382 operator=(shared_ptr&& __r) noexcept
383 {
384 this->__shared_ptr<_Tp>::operator=(std::move(__r));
385 return *this;
386 }
387
388 template<class _Yp>
389 _Assignable<shared_ptr<_Yp>>
390 operator=(shared_ptr<_Yp>&& __r) noexcept
391 {
392 this->__shared_ptr<_Tp>::operator=(std::move(__r));
393 return *this;
394 }
395
396 template<typename _Yp, typename _Del>
397 _Assignable<unique_ptr<_Yp, _Del>>
398 operator=(unique_ptr<_Yp, _Del>&& __r)
399 {
400 this->__shared_ptr<_Tp>::operator=(std::move(__r));
401 return *this;
402 }
403
404 private:
405 // This constructor is non-standard, it is used by allocate_shared.
406 template<typename _Alloc, typename... _Args>
407 shared_ptr(_Sp_alloc_shared_tag<_Alloc> __tag, _Args&&... __args)
408 : __shared_ptr<_Tp>(__tag, std::forward<_Args>(__args)...)
409 { }
410
411 template<typename _Yp, typename _Alloc, typename... _Args>
412 friend shared_ptr<_Yp>
413 allocate_shared(const _Alloc& __a, _Args&&... __args);
414
415 // This constructor is non-standard, it is used by weak_ptr::lock().
416 shared_ptr(const weak_ptr<_Tp>& __r, std::nothrow_t)
417 : __shared_ptr<_Tp>(__r, std::nothrow) { }
418
419 friend class weak_ptr<_Tp>;
420 };
421
422#if __cpp_deduction_guides >= 201606
423 template<typename _Tp>
424 shared_ptr(weak_ptr<_Tp>) -> shared_ptr<_Tp>;
425 template<typename _Tp, typename _Del>
426 shared_ptr(unique_ptr<_Tp, _Del>) -> shared_ptr<_Tp>;
427#endif
428
429 // 20.7.2.2.7 shared_ptr comparisons
430
431 /// @relates shared_ptr @{
432
433 /// Equality operator for shared_ptr objects, compares the stored pointers
434 template<typename _Tp, typename _Up>
435 _GLIBCXX_NODISCARD inline bool
436 operator==(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
437 { return __a.get() == __b.get(); }
438
439 /// shared_ptr comparison with nullptr
440 template<typename _Tp>
441 _GLIBCXX_NODISCARD inline bool
442 operator==(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
443 { return !__a; }
444
445 /// shared_ptr comparison with nullptr
446 template<typename _Tp>
447 _GLIBCXX_NODISCARD inline bool
448 operator==(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
449 { return !__a; }
450
451 /// Inequality operator for shared_ptr objects, compares the stored pointers
452 template<typename _Tp, typename _Up>
453 _GLIBCXX_NODISCARD inline bool
454 operator!=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
455 { return __a.get() != __b.get(); }
456
457 /// shared_ptr comparison with nullptr
458 template<typename _Tp>
459 _GLIBCXX_NODISCARD inline bool
460 operator!=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
461 { return (bool)__a; }
462
463 /// shared_ptr comparison with nullptr
464 template<typename _Tp>
465 _GLIBCXX_NODISCARD inline bool
466 operator!=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
467 { return (bool)__a; }
468
469 /// Relational operator for shared_ptr objects, compares the stored pointers
470 template<typename _Tp, typename _Up>
471 _GLIBCXX_NODISCARD inline bool
472 operator<(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
473 {
474 using _Tp_elt = typename shared_ptr<_Tp>::element_type;
475 using _Up_elt = typename shared_ptr<_Up>::element_type;
476 using _Vp = typename common_type<_Tp_elt*, _Up_elt*>::type;
477 return less<_Vp>()(__a.get(), __b.get());
478 }
479
480 /// shared_ptr comparison with nullptr
481 template<typename _Tp>
482 _GLIBCXX_NODISCARD inline bool
483 operator<(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
484 {
485 using _Tp_elt = typename shared_ptr<_Tp>::element_type;
486 return less<_Tp_elt*>()(__a.get(), nullptr);
487 }
488
489 /// shared_ptr comparison with nullptr
490 template<typename _Tp>
491 _GLIBCXX_NODISCARD inline bool
492 operator<(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
493 {
494 using _Tp_elt = typename shared_ptr<_Tp>::element_type;
495 return less<_Tp_elt*>()(nullptr, __a.get());
496 }
497
498 /// Relational operator for shared_ptr objects, compares the stored pointers
499 template<typename _Tp, typename _Up>
500 _GLIBCXX_NODISCARD inline bool
501 operator<=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
502 { return !(__b < __a); }
503
504 /// shared_ptr comparison with nullptr
505 template<typename _Tp>
506 _GLIBCXX_NODISCARD inline bool
507 operator<=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
508 { return !(nullptr < __a); }
509
510 /// shared_ptr comparison with nullptr
511 template<typename _Tp>
512 _GLIBCXX_NODISCARD inline bool
513 operator<=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
514 { return !(__a < nullptr); }
515
516 /// Relational operator for shared_ptr objects, compares the stored pointers
517 template<typename _Tp, typename _Up>
518 _GLIBCXX_NODISCARD inline bool
519 operator>(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
520 { return (__b < __a); }
521
522 /// shared_ptr comparison with nullptr
523 template<typename _Tp>
524 _GLIBCXX_NODISCARD inline bool
525 operator>(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
526 { return nullptr < __a; }
527
528 /// shared_ptr comparison with nullptr
529 template<typename _Tp>
530 _GLIBCXX_NODISCARD inline bool
531 operator>(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
532 { return __a < nullptr; }
533
534 /// Relational operator for shared_ptr objects, compares the stored pointers
535 template<typename _Tp, typename _Up>
536 _GLIBCXX_NODISCARD inline bool
537 operator>=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
538 { return !(__a < __b); }
539
540 /// shared_ptr comparison with nullptr
541 template<typename _Tp>
542 _GLIBCXX_NODISCARD inline bool
543 operator>=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
544 { return !(__a < nullptr); }
545
546 /// shared_ptr comparison with nullptr
547 template<typename _Tp>
548 _GLIBCXX_NODISCARD inline bool
549 operator>=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
550 { return !(nullptr < __a); }
551
552 // 20.7.2.2.8 shared_ptr specialized algorithms.
553
554 /// Swap overload for shared_ptr
555 template<typename _Tp>
556 inline void
558 { __a.swap(__b); }
559
560 // 20.7.2.2.9 shared_ptr casts.
561
562 /// Convert type of `shared_ptr`, via `static_cast`
563 template<typename _Tp, typename _Up>
564 inline shared_ptr<_Tp>
566 {
567 using _Sp = shared_ptr<_Tp>;
568 return _Sp(__r, static_cast<typename _Sp::element_type*>(__r.get()));
569 }
570
571 /// Convert type of `shared_ptr`, via `const_cast`
572 template<typename _Tp, typename _Up>
573 inline shared_ptr<_Tp>
575 {
576 using _Sp = shared_ptr<_Tp>;
577 return _Sp(__r, const_cast<typename _Sp::element_type*>(__r.get()));
578 }
579
580 /// Convert type of `shared_ptr`, via `dynamic_cast`
581 template<typename _Tp, typename _Up>
582 inline shared_ptr<_Tp>
584 {
585 using _Sp = shared_ptr<_Tp>;
586 if (auto* __p = dynamic_cast<typename _Sp::element_type*>(__r.get()))
587 return _Sp(__r, __p);
588 return _Sp();
589 }
590
591#if __cplusplus >= 201703L
592 /// Convert type of `shared_ptr`, via `reinterpret_cast`
593 template<typename _Tp, typename _Up>
594 inline shared_ptr<_Tp>
595 reinterpret_pointer_cast(const shared_ptr<_Up>& __r) noexcept
596 {
597 using _Sp = shared_ptr<_Tp>;
598 return _Sp(__r, reinterpret_cast<typename _Sp::element_type*>(__r.get()));
599 }
600
601#if __cplusplus > 201703L
602 // _GLIBCXX_RESOLVE_LIB_DEFECTS
603 // 2996. Missing rvalue overloads for shared_ptr operations
604
605 /// Convert type of `shared_ptr` rvalue, via `static_cast`
606 template<typename _Tp, typename _Up>
607 inline shared_ptr<_Tp>
608 static_pointer_cast(shared_ptr<_Up>&& __r) noexcept
609 {
610 using _Sp = shared_ptr<_Tp>;
611 return _Sp(std::move(__r),
612 static_cast<typename _Sp::element_type*>(__r.get()));
613 }
614
615 /// Convert type of `shared_ptr` rvalue, via `const_cast`
616 template<typename _Tp, typename _Up>
617 inline shared_ptr<_Tp>
618 const_pointer_cast(shared_ptr<_Up>&& __r) noexcept
619 {
620 using _Sp = shared_ptr<_Tp>;
621 return _Sp(std::move(__r),
622 const_cast<typename _Sp::element_type*>(__r.get()));
623 }
624
625 /// Convert type of `shared_ptr` rvalue, via `dynamic_cast`
626 template<typename _Tp, typename _Up>
627 inline shared_ptr<_Tp>
628 dynamic_pointer_cast(shared_ptr<_Up>&& __r) noexcept
629 {
630 using _Sp = shared_ptr<_Tp>;
631 if (auto* __p = dynamic_cast<typename _Sp::element_type*>(__r.get()))
632 return _Sp(std::move(__r), __p);
633 return _Sp();
634 }
635
636 /// Convert type of `shared_ptr` rvalue, via `reinterpret_cast`
637 template<typename _Tp, typename _Up>
638 inline shared_ptr<_Tp>
639 reinterpret_pointer_cast(shared_ptr<_Up>&& __r) noexcept
640 {
641 using _Sp = shared_ptr<_Tp>;
642 return _Sp(std::move(__r),
643 reinterpret_cast<typename _Sp::element_type*>(__r.get()));
644 }
645#endif // C++20
646#endif // C++17
647
648 // @}
649
650 /**
651 * @brief A non-owning observer for a pointer owned by a shared_ptr
652 *
653 * A weak_ptr provides a safe alternative to a raw pointer when you want
654 * a non-owning reference to an object that is managed by a shared_ptr.
655 *
656 * Unlike a raw pointer, a weak_ptr can be converted to a new shared_ptr
657 * that shares ownership with every other shared_ptr that already owns
658 * the pointer. In other words you can upgrade from a non-owning "weak"
659 * reference to an owning shared_ptr, without having access to any of
660 * the existing shared_ptr objects.
661 *
662 * Also unlike a raw pointer, a weak_ptr does not become "dangling" after
663 * the object it points to has been destroyed. Instead, a weak_ptr
664 * becomes _expired_ and can no longer be converted to a shared_ptr that
665 * owns the freed pointer, so you cannot accidentally access the pointed-to
666 * object after it has been destroyed.
667 */
668 template<typename _Tp>
669 class weak_ptr : public __weak_ptr<_Tp>
670 {
671 template<typename _Arg>
672 using _Constructible = typename enable_if<
674 >::type;
675
676 template<typename _Arg>
677 using _Assignable = typename enable_if<
679 >::type;
680
681 public:
682 constexpr weak_ptr() noexcept = default;
683
684 template<typename _Yp,
685 typename = _Constructible<const shared_ptr<_Yp>&>>
686 weak_ptr(const shared_ptr<_Yp>& __r) noexcept
687 : __weak_ptr<_Tp>(__r) { }
688
689 weak_ptr(const weak_ptr&) noexcept = default;
690
691 template<typename _Yp, typename = _Constructible<const weak_ptr<_Yp>&>>
692 weak_ptr(const weak_ptr<_Yp>& __r) noexcept
693 : __weak_ptr<_Tp>(__r) { }
694
695 weak_ptr(weak_ptr&&) noexcept = default;
696
697 template<typename _Yp, typename = _Constructible<weak_ptr<_Yp>>>
698 weak_ptr(weak_ptr<_Yp>&& __r) noexcept
699 : __weak_ptr<_Tp>(std::move(__r)) { }
700
701 weak_ptr&
702 operator=(const weak_ptr& __r) noexcept = default;
703
704 template<typename _Yp>
705 _Assignable<const weak_ptr<_Yp>&>
706 operator=(const weak_ptr<_Yp>& __r) noexcept
707 {
708 this->__weak_ptr<_Tp>::operator=(__r);
709 return *this;
710 }
711
712 template<typename _Yp>
713 _Assignable<const shared_ptr<_Yp>&>
714 operator=(const shared_ptr<_Yp>& __r) noexcept
715 {
716 this->__weak_ptr<_Tp>::operator=(__r);
717 return *this;
718 }
719
720 weak_ptr&
721 operator=(weak_ptr&& __r) noexcept = default;
722
723 template<typename _Yp>
724 _Assignable<weak_ptr<_Yp>>
725 operator=(weak_ptr<_Yp>&& __r) noexcept
726 {
727 this->__weak_ptr<_Tp>::operator=(std::move(__r));
728 return *this;
729 }
730
732 lock() const noexcept
733 { return shared_ptr<_Tp>(*this, std::nothrow); }
734 };
735
736#if __cpp_deduction_guides >= 201606
737 template<typename _Tp>
739#endif
740
741 // 20.7.2.3.6 weak_ptr specialized algorithms.
742 /// Swap overload for weak_ptr
743 /// @relates weak_ptr
744 template<typename _Tp>
745 inline void
746 swap(weak_ptr<_Tp>& __a, weak_ptr<_Tp>& __b) noexcept
747 { __a.swap(__b); }
748
749
750 /// Primary template owner_less
751 template<typename _Tp = void>
753
754 /// Void specialization of owner_less compares either shared_ptr or weak_ptr
755 template<>
756 struct owner_less<void> : _Sp_owner_less<void, void>
757 { };
758
759 /// Partial specialization of owner_less for shared_ptr.
760 template<typename _Tp>
762 : public _Sp_owner_less<shared_ptr<_Tp>, weak_ptr<_Tp>>
763 { };
764
765 /// Partial specialization of owner_less for weak_ptr.
766 template<typename _Tp>
767 struct owner_less<weak_ptr<_Tp>>
768 : public _Sp_owner_less<weak_ptr<_Tp>, shared_ptr<_Tp>>
769 { };
770
771 /**
772 * @brief Base class allowing use of member function shared_from_this.
773 */
774 template<typename _Tp>
776 {
777 protected:
778 constexpr enable_shared_from_this() noexcept { }
779
781
783 operator=(const enable_shared_from_this&) noexcept
784 { return *this; }
785
787
788 public:
790 shared_from_this()
791 { return shared_ptr<_Tp>(this->_M_weak_this); }
792
794 shared_from_this() const
795 { return shared_ptr<const _Tp>(this->_M_weak_this); }
796
797#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
798#define __cpp_lib_enable_shared_from_this 201603
800 weak_from_this() noexcept
801 { return this->_M_weak_this; }
802
804 weak_from_this() const noexcept
805 { return this->_M_weak_this; }
806#endif
807
808 private:
809 template<typename _Tp1>
810 void
811 _M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const noexcept
812 { _M_weak_this._M_assign(__p, __n); }
813
814 // Found by ADL when this is an associated class.
815 friend const enable_shared_from_this*
816 __enable_shared_from_this_base(const __shared_count<>&,
817 const enable_shared_from_this* __p)
818 { return __p; }
819
820 template<typename, _Lock_policy>
821 friend class __shared_ptr;
822
823 mutable weak_ptr<_Tp> _M_weak_this;
824 };
825
826 /// @relates shared_ptr @{
827
828 /**
829 * @brief Create an object that is owned by a shared_ptr.
830 * @param __a An allocator.
831 * @param __args Arguments for the @a _Tp object's constructor.
832 * @return A shared_ptr that owns the newly created object.
833 * @throw An exception thrown from @a _Alloc::allocate or from the
834 * constructor of @a _Tp.
835 *
836 * A copy of @a __a will be used to allocate memory for the shared_ptr
837 * and the new object.
838 */
839 template<typename _Tp, typename _Alloc, typename... _Args>
840 inline shared_ptr<_Tp>
841 allocate_shared(const _Alloc& __a, _Args&&... __args)
842 {
843 return shared_ptr<_Tp>(_Sp_alloc_shared_tag<_Alloc>{__a},
844 std::forward<_Args>(__args)...);
845 }
846
847 /**
848 * @brief Create an object that is owned by a shared_ptr.
849 * @param __args Arguments for the @a _Tp object's constructor.
850 * @return A shared_ptr that owns the newly created object.
851 * @throw std::bad_alloc, or an exception thrown from the
852 * constructor of @a _Tp.
853 */
854 template<typename _Tp, typename... _Args>
855 inline shared_ptr<_Tp>
856 make_shared(_Args&&... __args)
857 {
858 typedef typename std::remove_cv<_Tp>::type _Tp_nc;
859 return std::allocate_shared<_Tp>(std::allocator<_Tp_nc>(),
860 std::forward<_Args>(__args)...);
861 }
862
863 /// std::hash specialization for shared_ptr.
864 template<typename _Tp>
865 struct hash<shared_ptr<_Tp>>
866 : public __hash_base<size_t, shared_ptr<_Tp>>
867 {
868 size_t
869 operator()(const shared_ptr<_Tp>& __s) const noexcept
870 {
872 }
873 };
874
875 // @} relates shared_ptr
876 // @} group pointer_abstractions
877
878#if __cplusplus >= 201703L
879 namespace __detail::__variant
880 {
881 template<typename> struct _Never_valueless_alt; // see <variant>
882
883 // Provide the strong exception-safety guarantee when emplacing a
884 // shared_ptr into a variant.
885 template<typename _Tp>
886 struct _Never_valueless_alt<std::shared_ptr<_Tp>>
888 { };
889
890 // Provide the strong exception-safety guarantee when emplacing a
891 // weak_ptr into a variant.
892 template<typename _Tp>
893 struct _Never_valueless_alt<std::weak_ptr<_Tp>>
895 { };
896 } // namespace __detail::__variant
897#endif // C++17
898
899_GLIBCXX_END_NAMESPACE_VERSION
900} // namespace
901
902#endif // _SHARED_PTR_H
shared_ptr< _Tp > make_shared(_Args &&... __args)
Create an object that is owned by a shared_ptr.
typename __shared_ptr< _Tp >::element_type element_type
The type pointed to by the stored pointer, remove_extent_t<_Tp>
shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
Construct a shared_ptr that owns a null pointer and the deleter __d.
shared_ptr(const shared_ptr< _Yp > &__r) noexcept
If __r is empty, constructs an empty shared_ptr; otherwise construct a shared_ptr that shares ownersh...
shared_ptr(shared_ptr< _Yp > &&__r) noexcept
Move-constructs a shared_ptr instance from __r.
shared_ptr(_Yp *__p, _Deleter __d, _Alloc __a)
Construct a shared_ptr that owns the pointer __p and the deleter __d.
bool operator!=(nullptr_t, const shared_ptr< _Tp > &__a) noexcept
shared_ptr comparison with nullptr
bool operator>(const shared_ptr< _Tp > &__a, nullptr_t) noexcept
shared_ptr comparison with nullptr
bool operator==(const shared_ptr< _Tp > &__a, nullptr_t) noexcept
shared_ptr comparison with nullptr
bool operator==(nullptr_t, const shared_ptr< _Tp > &__a) noexcept
shared_ptr comparison with nullptr
constexpr shared_ptr() noexcept
Construct an empty shared_ptr.
shared_ptr(const shared_ptr &) noexcept=default
Copy constructor.
shared_ptr< _Tp > static_pointer_cast(const shared_ptr< _Up > &__r) noexcept
Convert type of shared_ptr, via static_cast
bool operator!=(const shared_ptr< _Tp > &__a, const shared_ptr< _Up > &__b) noexcept
Inequality operator for shared_ptr objects, compares the stored pointers.
shared_ptr(shared_ptr &&__r) noexcept
Move-constructs a shared_ptr instance from __r.
_Del * get_deleter(const shared_ptr< _Tp > &__p) noexcept
20.7.2.2.10 shared_ptr get_deleter
bool operator==(const shared_ptr< _Tp > &__a, const shared_ptr< _Up > &__b) noexcept
bool operator>=(const shared_ptr< _Tp > &__a, nullptr_t) noexcept
shared_ptr comparison with nullptr
shared_ptr(_Yp *__p)
Construct a shared_ptr that owns the pointer __p.
void swap(weak_ptr< _Tp > &__a, weak_ptr< _Tp > &__b) noexcept
Swap overload for weak_ptr.
shared_ptr(nullptr_t __p, _Deleter __d)
Construct a shared_ptr that owns a null pointer and the deleter __d.
shared_ptr(_Yp *__p, _Deleter __d)
Construct a shared_ptr that owns the pointer __p and the deleter __d.
shared_ptr< _Tp > allocate_shared(const _Alloc &__a, _Args &&... __args)
Create an object that is owned by a shared_ptr.
shared_ptr(const shared_ptr< _Yp > &__r, element_type *__p) noexcept
Constructs a shared_ptr instance that stores __p and shares ownership with __r.
bool operator>(nullptr_t, const shared_ptr< _Tp > &__a) noexcept
shared_ptr comparison with nullptr
shared_ptr(const weak_ptr< _Yp > &__r)
Constructs a shared_ptr that shares ownership with __r and stores a copy of the pointer stored in __r...
bool operator>=(nullptr_t, const shared_ptr< _Tp > &__a) noexcept
shared_ptr comparison with nullptr
shared_ptr< _Tp > dynamic_pointer_cast(const shared_ptr< _Up > &__r) noexcept
Convert type of shared_ptr, via dynamic_cast
shared_ptr< _Tp > const_pointer_cast(const shared_ptr< _Up > &__r) noexcept
Convert type of shared_ptr, via const_cast
bool operator>(const shared_ptr< _Tp > &__a, const shared_ptr< _Up > &__b) noexcept
Relational operator for shared_ptr objects, compares the stored pointers.
bool operator>=(const shared_ptr< _Tp > &__a, const shared_ptr< _Up > &__b) noexcept
Relational operator for shared_ptr objects, compares the stored pointers.
constexpr shared_ptr(nullptr_t) noexcept
Construct an empty shared_ptr.
bool operator!=(const shared_ptr< _Tp > &__a, nullptr_t) noexcept
shared_ptr comparison with nullptr
void swap(shared_ptr< _Tp > &__a, shared_ptr< _Tp > &__b) noexcept
Swap overload for shared_ptr.
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition: move.h:101
constexpr _Tp && forward(typename std::remove_reference< _Tp >::type &__t) noexcept
Forward an lvalue.
Definition: move.h:76
ISO C++ entities toplevel namespace is std.
__shared_ptr< _Tp, _Lp > dynamic_pointer_cast(const __shared_ptr< _Tp1, _Lp > &__r) noexcept
dynamic_pointer_cast
__shared_ptr< _Tp, _Lp > static_pointer_cast(const __shared_ptr< _Tp1, _Lp > &__r) noexcept
static_pointer_cast
__shared_ptr< _Tp, _Lp > const_pointer_cast(const __shared_ptr< _Tp1, _Lp > &__r) noexcept
const_pointer_cast
Template class basic_ostream.
Definition: ostream:59
Primary class template hash.
integral_constant
Definition: type_traits:58
is_constructible
Definition: type_traits:908
is_assignable
Definition: type_traits:1059
Define a member typedef type only if a boolean constant is true.
Definition: type_traits:2170
common_type
Definition: type_traits:2202
The standard allocator, as per [20.4].
Definition: allocator.h:121
A smart pointer with reference-counted copy semantics.
A non-owning observer for a pointer owned by a shared_ptr.
Primary template owner_less.
Base class allowing use of member function shared_from_this.
One of the comparison functors.
Definition: stl_function.h:382
20.7.1.2 unique_ptr for single objects.
Definition: unique_ptr.h:242
A simple smart pointer providing strict ownership semantics.
Definition: auto_ptr.h:90