1 // shared_ptr and weak_ptr implementation -*- C++ -*-
2
3 // Copyright (C) 2007-2016 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
52 #include <bits/shared_ptr_base.h>
53
_GLIBCXX_VISIBILITY(default)54 namespace 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 template<typename _Ch, typename _Tr, typename _Tp, _Lock_policy _Lp>
65 inline std::basic_ostream<_Ch, _Tr>&
66 operator<<(std::basic_ostream<_Ch, _Tr>& __os,
67 const __shared_ptr<_Tp, _Lp>& __p)
68 {
69 __os << __p.get();
70 return __os;
71 }
72
73 /// 20.7.2.2.10 shared_ptr get_deleter
74 template<typename _Del, typename _Tp, _Lock_policy _Lp>
75 inline _Del*
76 get_deleter(const __shared_ptr<_Tp, _Lp>& __p) noexcept
77 {
78 #if __cpp_rtti
79 return static_cast<_Del*>(__p._M_get_deleter(typeid(_Del)));
80 #else
81 return 0;
82 #endif
83 }
84
85
86 /**
87 * @brief A smart pointer with reference-counted copy semantics.
88 *
89 * The object pointed to is deleted when the last shared_ptr pointing to
90 * it is destroyed or reset.
91 */
92 template<typename _Tp>
93 class shared_ptr : public __shared_ptr<_Tp>
94 {
95 template<typename _Ptr>
96 using _Convertible
97 = typename enable_if<is_convertible<_Ptr, _Tp*>::value>::type;
98
99 public:
100 /**
101 * @brief Construct an empty %shared_ptr.
102 * @post use_count()==0 && get()==0
103 */
104 constexpr shared_ptr() noexcept
105 : __shared_ptr<_Tp>() { }
106
107 shared_ptr(const shared_ptr&) noexcept = default;
108
109 /**
110 * @brief Construct a %shared_ptr that owns the pointer @a __p.
111 * @param __p A pointer that is convertible to element_type*.
112 * @post use_count() == 1 && get() == __p
113 * @throw std::bad_alloc, in which case @c delete @a __p is called.
114 */
115 template<typename _Tp1>
116 explicit shared_ptr(_Tp1* __p)
117 : __shared_ptr<_Tp>(__p) { }
118
119 /**
120 * @brief Construct a %shared_ptr that owns the pointer @a __p
121 * and the deleter @a __d.
122 * @param __p A pointer.
123 * @param __d A deleter.
124 * @post use_count() == 1 && get() == __p
125 * @throw std::bad_alloc, in which case @a __d(__p) is called.
126 *
127 * Requirements: _Deleter's copy constructor and destructor must
128 * not throw
129 *
130 * __shared_ptr will release __p by calling __d(__p)
131 */
132 template<typename _Tp1, typename _Deleter>
133 shared_ptr(_Tp1* __p, _Deleter __d)
134 : __shared_ptr<_Tp>(__p, __d) { }
135
136 /**
137 * @brief Construct a %shared_ptr that owns a null pointer
138 * and the deleter @a __d.
139 * @param __p A null pointer constant.
140 * @param __d A deleter.
141 * @post use_count() == 1 && get() == __p
142 * @throw std::bad_alloc, in which case @a __d(__p) is called.
143 *
144 * Requirements: _Deleter's copy constructor and destructor must
145 * not throw
146 *
147 * The last owner will call __d(__p)
148 */
149 template<typename _Deleter>
150 shared_ptr(nullptr_t __p, _Deleter __d)
151 : __shared_ptr<_Tp>(__p, __d) { }
152
153 /**
154 * @brief Construct a %shared_ptr that owns the pointer @a __p
155 * and the deleter @a __d.
156 * @param __p A pointer.
157 * @param __d A deleter.
158 * @param __a An allocator.
159 * @post use_count() == 1 && get() == __p
160 * @throw std::bad_alloc, in which case @a __d(__p) is called.
161 *
162 * Requirements: _Deleter's copy constructor and destructor must
163 * not throw _Alloc's copy constructor and destructor must not
164 * throw.
165 *
166 * __shared_ptr will release __p by calling __d(__p)
167 */
168 template<typename _Tp1, typename _Deleter, typename _Alloc>
169 shared_ptr(_Tp1* __p, _Deleter __d, _Alloc __a)
170 : __shared_ptr<_Tp>(__p, __d, std::move(__a)) { }
171
172 /**
173 * @brief Construct a %shared_ptr that owns a null pointer
174 * and the deleter @a __d.
175 * @param __p A null pointer constant.
176 * @param __d A deleter.
177 * @param __a An allocator.
178 * @post use_count() == 1 && get() == __p
179 * @throw std::bad_alloc, in which case @a __d(__p) is called.
180 *
181 * Requirements: _Deleter's copy constructor and destructor must
182 * not throw _Alloc's copy constructor and destructor must not
183 * throw.
184 *
185 * The last owner will call __d(__p)
186 */
187 template<typename _Deleter, typename _Alloc>
188 shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
189 : __shared_ptr<_Tp>(__p, __d, std::move(__a)) { }
190
191 // Aliasing constructor
192
193 /**
194 * @brief Constructs a %shared_ptr instance that stores @a __p
195 * and shares ownership with @a __r.
196 * @param __r A %shared_ptr.
197 * @param __p A pointer that will remain valid while @a *__r is valid.
198 * @post get() == __p && use_count() == __r.use_count()
199 *
200 * This can be used to construct a @c shared_ptr to a sub-object
201 * of an object managed by an existing @c shared_ptr.
202 *
203 * @code
204 * shared_ptr< pair<int,int> > pii(new pair<int,int>());
205 * shared_ptr<int> pi(pii, &pii->first);
206 * assert(pii.use_count() == 2);
207 * @endcode
208 */
209 template<typename _Tp1>
210 shared_ptr(const shared_ptr<_Tp1>& __r, _Tp* __p) noexcept
211 : __shared_ptr<_Tp>(__r, __p) { }
212
213 /**
214 * @brief If @a __r is empty, constructs an empty %shared_ptr;
215 * otherwise construct a %shared_ptr that shares ownership
216 * with @a __r.
217 * @param __r A %shared_ptr.
218 * @post get() == __r.get() && use_count() == __r.use_count()
219 */
220 template<typename _Tp1, typename = _Convertible<_Tp1*>>
221 shared_ptr(const shared_ptr<_Tp1>& __r) noexcept
222 : __shared_ptr<_Tp>(__r) { }
223
224 /**
225 * @brief Move-constructs a %shared_ptr instance from @a __r.
226 * @param __r A %shared_ptr rvalue.
227 * @post *this contains the old value of @a __r, @a __r is empty.
228 */
229 shared_ptr(shared_ptr&& __r) noexcept
230 : __shared_ptr<_Tp>(std::move(__r)) { }
231
232 /**
233 * @brief Move-constructs a %shared_ptr instance from @a __r.
234 * @param __r A %shared_ptr rvalue.
235 * @post *this contains the old value of @a __r, @a __r is empty.
236 */
237 template<typename _Tp1, typename = _Convertible<_Tp1*>>
238 shared_ptr(shared_ptr<_Tp1>&& __r) noexcept
239 : __shared_ptr<_Tp>(std::move(__r)) { }
240
241 /**
242 * @brief Constructs a %shared_ptr that shares ownership with @a __r
243 * and stores a copy of the pointer stored in @a __r.
244 * @param __r A weak_ptr.
245 * @post use_count() == __r.use_count()
246 * @throw bad_weak_ptr when __r.expired(),
247 * in which case the constructor has no effect.
248 */
249 template<typename _Tp1>
250 explicit shared_ptr(const weak_ptr<_Tp1>& __r)
251 : __shared_ptr<_Tp>(__r) { }
252
253 #if _GLIBCXX_USE_DEPRECATED
254 template<typename _Tp1>
255 shared_ptr(std::auto_ptr<_Tp1>&& __r);
256 #endif
257
258 // _GLIBCXX_RESOLVE_LIB_DEFECTS
259 // 2399. shared_ptr's constructor from unique_ptr should be constrained
260 template<typename _Tp1, typename _Del, typename
261 = _Convertible<typename unique_ptr<_Tp1, _Del>::pointer>>
262 shared_ptr(std::unique_ptr<_Tp1, _Del>&& __r)
263 : __shared_ptr<_Tp>(std::move(__r)) { }
264
265 /**
266 * @brief Construct an empty %shared_ptr.
267 * @post use_count() == 0 && get() == nullptr
268 */
269 constexpr shared_ptr(nullptr_t) noexcept : shared_ptr() { }
270
271 shared_ptr& operator=(const shared_ptr&) noexcept = default;
272
273 template<typename _Tp1>
274 shared_ptr&
275 operator=(const shared_ptr<_Tp1>& __r) noexcept
276 {
277 this->__shared_ptr<_Tp>::operator=(__r);
278 return *this;
279 }
280
281 #if _GLIBCXX_USE_DEPRECATED
282 template<typename _Tp1>
283 shared_ptr&
284 operator=(std::auto_ptr<_Tp1>&& __r)
285 {
286 this->__shared_ptr<_Tp>::operator=(std::move(__r));
287 return *this;
288 }
289 #endif
290
291 shared_ptr&
292 operator=(shared_ptr&& __r) noexcept
293 {
294 this->__shared_ptr<_Tp>::operator=(std::move(__r));
295 return *this;
296 }
297
298 template<class _Tp1>
299 shared_ptr&
300 operator=(shared_ptr<_Tp1>&& __r) noexcept
301 {
302 this->__shared_ptr<_Tp>::operator=(std::move(__r));
303 return *this;
304 }
305
306 template<typename _Tp1, typename _Del>
307 shared_ptr&
308 operator=(std::unique_ptr<_Tp1, _Del>&& __r)
309 {
310 this->__shared_ptr<_Tp>::operator=(std::move(__r));
311 return *this;
312 }
313
314 private:
315 // This constructor is non-standard, it is used by allocate_shared.
316 template<typename _Alloc, typename... _Args>
317 shared_ptr(_Sp_make_shared_tag __tag, const _Alloc& __a,
318 _Args&&... __args)
319 : __shared_ptr<_Tp>(__tag, __a, std::forward<_Args>(__args)...)
320 { }
321
322 template<typename _Tp1, typename _Alloc, typename... _Args>
323 friend shared_ptr<_Tp1>
324 allocate_shared(const _Alloc& __a, _Args&&... __args);
325
326 // This constructor is non-standard, it is used by weak_ptr::lock().
327 shared_ptr(const weak_ptr<_Tp>& __r, std::nothrow_t)
328 : __shared_ptr<_Tp>(__r, std::nothrow) { }
329
330 friend class weak_ptr<_Tp>;
331 };
332
333 // 20.7.2.2.7 shared_ptr comparisons
334 template<typename _Tp1, typename _Tp2>
335 inline bool
336 operator==(const shared_ptr<_Tp1>& __a,
337 const shared_ptr<_Tp2>& __b) noexcept
338 { return __a.get() == __b.get(); }
339
340 template<typename _Tp>
341 inline bool
342 operator==(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
343 { return !__a; }
344
345 template<typename _Tp>
346 inline bool
347 operator==(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
348 { return !__a; }
349
350 template<typename _Tp1, typename _Tp2>
351 inline bool
352 operator!=(const shared_ptr<_Tp1>& __a,
353 const shared_ptr<_Tp2>& __b) noexcept
354 { return __a.get() != __b.get(); }
355
356 template<typename _Tp>
357 inline bool
358 operator!=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
359 { return (bool)__a; }
360
361 template<typename _Tp>
362 inline bool
363 operator!=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
364 { return (bool)__a; }
365
366 template<typename _Tp1, typename _Tp2>
367 inline bool
368 operator<(const shared_ptr<_Tp1>& __a,
369 const shared_ptr<_Tp2>& __b) noexcept
370 {
371 typedef typename std::common_type<_Tp1*, _Tp2*>::type _CT;
372 return std::less<_CT>()(__a.get(), __b.get());
373 }
374
375 template<typename _Tp>
376 inline bool
377 operator<(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
378 { return std::less<_Tp*>()(__a.get(), nullptr); }
379
380 template<typename _Tp>
381 inline bool
382 operator<(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
383 { return std::less<_Tp*>()(nullptr, __a.get()); }
384
385 template<typename _Tp1, typename _Tp2>
386 inline bool
387 operator<=(const shared_ptr<_Tp1>& __a,
388 const shared_ptr<_Tp2>& __b) noexcept
389 { return !(__b < __a); }
390
391 template<typename _Tp>
392 inline bool
393 operator<=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
394 { return !(nullptr < __a); }
395
396 template<typename _Tp>
397 inline bool
398 operator<=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
399 { return !(__a < nullptr); }
400
401 template<typename _Tp1, typename _Tp2>
402 inline bool
403 operator>(const shared_ptr<_Tp1>& __a,
404 const shared_ptr<_Tp2>& __b) noexcept
405 { return (__b < __a); }
406
407 template<typename _Tp>
408 inline bool
409 operator>(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
410 { return std::less<_Tp*>()(nullptr, __a.get()); }
411
412 template<typename _Tp>
413 inline bool
414 operator>(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
415 { return std::less<_Tp*>()(__a.get(), nullptr); }
416
417 template<typename _Tp1, typename _Tp2>
418 inline bool
419 operator>=(const shared_ptr<_Tp1>& __a,
420 const shared_ptr<_Tp2>& __b) noexcept
421 { return !(__a < __b); }
422
423 template<typename _Tp>
424 inline bool
425 operator>=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
426 { return !(__a < nullptr); }
427
428 template<typename _Tp>
429 inline bool
430 operator>=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
431 { return !(nullptr < __a); }
432
433 template<typename _Tp>
434 struct less<shared_ptr<_Tp>> : public _Sp_less<shared_ptr<_Tp>>
435 { };
436
437 // 20.7.2.2.8 shared_ptr specialized algorithms.
438 template<typename _Tp>
439 inline void
440 swap(shared_ptr<_Tp>& __a, shared_ptr<_Tp>& __b) noexcept
441 { __a.swap(__b); }
442
443 // 20.7.2.2.9 shared_ptr casts.
444 template<typename _Tp, typename _Tp1>
445 inline shared_ptr<_Tp>
446 static_pointer_cast(const shared_ptr<_Tp1>& __r) noexcept
447 { return shared_ptr<_Tp>(__r, static_cast<_Tp*>(__r.get())); }
448
449 template<typename _Tp, typename _Tp1>
450 inline shared_ptr<_Tp>
451 const_pointer_cast(const shared_ptr<_Tp1>& __r) noexcept
452 { return shared_ptr<_Tp>(__r, const_cast<_Tp*>(__r.get())); }
453
454 template<typename _Tp, typename _Tp1>
455 inline shared_ptr<_Tp>
456 dynamic_pointer_cast(const shared_ptr<_Tp1>& __r) noexcept
457 {
458 if (_Tp* __p = dynamic_cast<_Tp*>(__r.get()))
459 return shared_ptr<_Tp>(__r, __p);
460 return shared_ptr<_Tp>();
461 }
462
463
464 /**
465 * @brief A smart pointer with weak semantics.
466 *
467 * With forwarding constructors and assignment operators.
468 */
469 template<typename _Tp>
470 class weak_ptr : public __weak_ptr<_Tp>
471 {
472 template<typename _Ptr>
473 using _Convertible
474 = typename enable_if<is_convertible<_Ptr, _Tp*>::value>::type;
475
476 public:
477 constexpr weak_ptr() noexcept = default;
478
479 template<typename _Tp1, typename = _Convertible<_Tp1*>>
480 weak_ptr(const shared_ptr<_Tp1>& __r) noexcept
481 : __weak_ptr<_Tp>(__r) { }
482
483 weak_ptr(const weak_ptr&) noexcept = default;
484
485 template<typename _Tp1, typename = _Convertible<_Tp1*>>
486 weak_ptr(const weak_ptr<_Tp1>& __r) noexcept
487 : __weak_ptr<_Tp>(__r) { }
488
489 weak_ptr(weak_ptr&&) noexcept = default;
490
491 template<typename _Tp1, typename = _Convertible<_Tp1*>>
492 weak_ptr(weak_ptr<_Tp1>&& __r) noexcept
493 : __weak_ptr<_Tp>(std::move(__r)) { }
494
495 weak_ptr&
496 operator=(const weak_ptr& __r) noexcept = default;
497
498 template<typename _Tp1>
499 weak_ptr&
500 operator=(const weak_ptr<_Tp1>& __r) noexcept
501 {
502 this->__weak_ptr<_Tp>::operator=(__r);
503 return *this;
504 }
505
506 template<typename _Tp1>
507 weak_ptr&
508 operator=(const shared_ptr<_Tp1>& __r) noexcept
509 {
510 this->__weak_ptr<_Tp>::operator=(__r);
511 return *this;
512 }
513
514 weak_ptr&
515 operator=(weak_ptr&& __r) noexcept = default;
516
517 template<typename _Tp1>
518 weak_ptr&
519 operator=(weak_ptr<_Tp1>&& __r) noexcept
520 {
521 this->__weak_ptr<_Tp>::operator=(std::move(__r));
522 return *this;
523 }
524
525 shared_ptr<_Tp>
526 lock() const noexcept
527 { return shared_ptr<_Tp>(*this, std::nothrow); }
528 };
529
530 // 20.7.2.3.6 weak_ptr specialized algorithms.
531 template<typename _Tp>
532 inline void
533 swap(weak_ptr<_Tp>& __a, weak_ptr<_Tp>& __b) noexcept
534 { __a.swap(__b); }
535
536
537 /// Primary template owner_less
538 template<typename _Tp>
539 struct owner_less;
540
541 /// Partial specialization of owner_less for shared_ptr.
542 template<typename _Tp>
543 struct owner_less<shared_ptr<_Tp>>
544 : public _Sp_owner_less<shared_ptr<_Tp>, weak_ptr<_Tp>>
545 { };
546
547 /// Partial specialization of owner_less for weak_ptr.
548 template<typename _Tp>
549 struct owner_less<weak_ptr<_Tp>>
550 : public _Sp_owner_less<weak_ptr<_Tp>, shared_ptr<_Tp>>
551 { };
552
553 /**
554 * @brief Base class allowing use of member function shared_from_this.
555 */
556 template<typename _Tp>
557 class enable_shared_from_this
558 {
559 protected:
560 constexpr enable_shared_from_this() noexcept { }
561
562 enable_shared_from_this(const enable_shared_from_this&) noexcept { }
563
564 enable_shared_from_this&
565 operator=(const enable_shared_from_this&) noexcept
566 { return *this; }
567
568 ~enable_shared_from_this() { }
569
570 public:
571 shared_ptr<_Tp>
572 shared_from_this()
573 { return shared_ptr<_Tp>(this->_M_weak_this); }
574
575 shared_ptr<const _Tp>
576 shared_from_this() const
577 { return shared_ptr<const _Tp>(this->_M_weak_this); }
578
579 private:
580 template<typename _Tp1>
581 void
582 _M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const noexcept
583 { _M_weak_this._M_assign(__p, __n); }
584
585 template<typename _Tp1, typename _Tp2>
586 friend void
587 __enable_shared_from_this_helper(const __shared_count<>&,
588 const enable_shared_from_this<_Tp1>*,
589 const _Tp2*) noexcept;
590
591 mutable weak_ptr<_Tp> _M_weak_this;
592 };
593
594 template<typename _Tp1, typename _Tp2>
595 inline void
596 __enable_shared_from_this_helper(const __shared_count<>& __pn,
597 const enable_shared_from_this<_Tp1>*
598 __pe, const _Tp2* __px) noexcept
599 {
600 if (__pe != nullptr)
601 __pe->_M_weak_assign(const_cast<_Tp2*>(__px), __pn);
602 }
603
604 /**
605 * @brief Create an object that is owned by a shared_ptr.
606 * @param __a An allocator.
607 * @param __args Arguments for the @a _Tp object's constructor.
608 * @return A shared_ptr that owns the newly created object.
609 * @throw An exception thrown from @a _Alloc::allocate or from the
610 * constructor of @a _Tp.
611 *
612 * A copy of @a __a will be used to allocate memory for the shared_ptr
613 * and the new object.
614 */
615 template<typename _Tp, typename _Alloc, typename... _Args>
616 inline shared_ptr<_Tp>
617 allocate_shared(const _Alloc& __a, _Args&&... __args)
618 {
619 return shared_ptr<_Tp>(_Sp_make_shared_tag(), __a,
620 std::forward<_Args>(__args)...);
621 }
622
623 /**
624 * @brief Create an object that is owned by a shared_ptr.
625 * @param __args Arguments for the @a _Tp object's constructor.
626 * @return A shared_ptr that owns the newly created object.
627 * @throw std::bad_alloc, or an exception thrown from the
628 * constructor of @a _Tp.
629 */
630 template<typename _Tp, typename... _Args>
631 inline shared_ptr<_Tp>
632 make_shared(_Args&&... __args)
633 {
634 typedef typename std::remove_const<_Tp>::type _Tp_nc;
635 return std::allocate_shared<_Tp>(std::allocator<_Tp_nc>(),
636 std::forward<_Args>(__args)...);
637 }
638
639 /// std::hash specialization for shared_ptr.
640 template<typename _Tp>
641 struct hash<shared_ptr<_Tp>>
642 : public __hash_base<size_t, shared_ptr<_Tp>>
643 {
644 size_t
645 operator()(const shared_ptr<_Tp>& __s) const noexcept
646 { return std::hash<_Tp*>()(__s.get()); }
647 };
648
649 // @} group pointer_abstractions
650
651 _GLIBCXX_END_NAMESPACE_VERSION
652 } // namespace
653
654 #endif // _SHARED_PTR_H
655