libstdc++
shared_ptr.h
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1 // shared_ptr and weak_ptr implementation -*- C++ -*-
2 
3 // Copyright (C) 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10 
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15 
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19 
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24 
25 // GCC Note: Based on files from version 1.32.0 of the Boost library.
26 
27 // shared_count.hpp
28 // Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd.
29 
30 // shared_ptr.hpp
31 // Copyright (C) 1998, 1999 Greg Colvin and Beman Dawes.
32 // Copyright (C) 2001, 2002, 2003 Peter Dimov
33 
34 // weak_ptr.hpp
35 // Copyright (C) 2001, 2002, 2003 Peter Dimov
36 
37 // enable_shared_from_this.hpp
38 // Copyright (C) 2002 Peter Dimov
39 
40 // Distributed under the Boost Software License, Version 1.0. (See
41 // accompanying file LICENSE_1_0.txt or copy at
42 // http://www.boost.org/LICENSE_1_0.txt)
43 
44 /** @file bits/shared_ptr.h
45  * This is an internal header file, included by other library headers.
46  * Do not attempt to use it directly. @headername{memory}
47  */
48 
49 #ifndef _SHARED_PTR_H
50 #define _SHARED_PTR_H 1
51 
52 #include <bits/shared_ptr_base.h>
53 
54 namespace std _GLIBCXX_VISIBILITY(default)
55 {
56 _GLIBCXX_BEGIN_NAMESPACE_VERSION
57 
58  /**
59  * @addtogroup pointer_abstractions
60  * @{
61  */
62 
63  /// 2.2.3.7 shared_ptr I/O
64  template<typename _Ch, typename _Tr, typename _Tp, _Lock_policy _Lp>
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  /// 2.2.3.10 shared_ptr get_deleter (experimental)
74  template<typename _Del, typename _Tp, _Lock_policy _Lp>
75  inline _Del*
76  get_deleter(const __shared_ptr<_Tp, _Lp>& __p) noexcept
77  {
78 #ifdef __GXX_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  public:
96  /**
97  * @brief Construct an empty %shared_ptr.
98  * @post use_count()==0 && get()==0
99  */
100  constexpr shared_ptr() noexcept
101  : __shared_ptr<_Tp>() { }
102 
103  shared_ptr(const shared_ptr&) noexcept = default;
104 
105  /**
106  * @brief Construct a %shared_ptr that owns the pointer @a __p.
107  * @param __p A pointer that is convertible to element_type*.
108  * @post use_count() == 1 && get() == __p
109  * @throw std::bad_alloc, in which case @c delete @a __p is called.
110  */
111  template<typename _Tp1>
112  explicit shared_ptr(_Tp1* __p)
113  : __shared_ptr<_Tp>(__p) { }
114 
115  /**
116  * @brief Construct a %shared_ptr that owns the pointer @a __p
117  * and the deleter @a __d.
118  * @param __p A pointer.
119  * @param __d A deleter.
120  * @post use_count() == 1 && get() == __p
121  * @throw std::bad_alloc, in which case @a __d(__p) is called.
122  *
123  * Requirements: _Deleter's copy constructor and destructor must
124  * not throw
125  *
126  * __shared_ptr will release __p by calling __d(__p)
127  */
128  template<typename _Tp1, typename _Deleter>
129  shared_ptr(_Tp1* __p, _Deleter __d)
130  : __shared_ptr<_Tp>(__p, __d) { }
131 
132  /**
133  * @brief Construct a %shared_ptr that owns a null pointer
134  * and the deleter @a __d.
135  * @param __p A null pointer constant.
136  * @param __d A deleter.
137  * @post use_count() == 1 && get() == __p
138  * @throw std::bad_alloc, in which case @a __d(__p) is called.
139  *
140  * Requirements: _Deleter's copy constructor and destructor must
141  * not throw
142  *
143  * The last owner will call __d(__p)
144  */
145  template<typename _Deleter>
146  shared_ptr(nullptr_t __p, _Deleter __d)
147  : __shared_ptr<_Tp>(__p, __d) { }
148 
149  /**
150  * @brief Construct a %shared_ptr that owns the pointer @a __p
151  * and the deleter @a __d.
152  * @param __p A pointer.
153  * @param __d A deleter.
154  * @param __a An allocator.
155  * @post use_count() == 1 && get() == __p
156  * @throw std::bad_alloc, in which case @a __d(__p) is called.
157  *
158  * Requirements: _Deleter's copy constructor and destructor must
159  * not throw _Alloc's copy constructor and destructor must not
160  * throw.
161  *
162  * __shared_ptr will release __p by calling __d(__p)
163  */
164  template<typename _Tp1, typename _Deleter, typename _Alloc>
165  shared_ptr(_Tp1* __p, _Deleter __d, _Alloc __a)
166  : __shared_ptr<_Tp>(__p, __d, std::move(__a)) { }
167 
168  /**
169  * @brief Construct a %shared_ptr that owns a null pointer
170  * and the deleter @a __d.
171  * @param __p A null pointer constant.
172  * @param __d A deleter.
173  * @param __a An allocator.
174  * @post use_count() == 1 && get() == __p
175  * @throw std::bad_alloc, in which case @a __d(__p) is called.
176  *
177  * Requirements: _Deleter's copy constructor and destructor must
178  * not throw _Alloc's copy constructor and destructor must not
179  * throw.
180  *
181  * The last owner will call __d(__p)
182  */
183  template<typename _Deleter, typename _Alloc>
184  shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
185  : __shared_ptr<_Tp>(__p, __d, std::move(__a)) { }
186 
187  // Aliasing constructor
188 
189  /**
190  * @brief Constructs a %shared_ptr instance that stores @a __p
191  * and shares ownership with @a __r.
192  * @param __r A %shared_ptr.
193  * @param __p A pointer that will remain valid while @a *__r is valid.
194  * @post get() == __p && use_count() == __r.use_count()
195  *
196  * This can be used to construct a @c shared_ptr to a sub-object
197  * of an object managed by an existing @c shared_ptr.
198  *
199  * @code
200  * shared_ptr< pair<int,int> > pii(new pair<int,int>());
201  * shared_ptr<int> pi(pii, &pii->first);
202  * assert(pii.use_count() == 2);
203  * @endcode
204  */
205  template<typename _Tp1>
206  shared_ptr(const shared_ptr<_Tp1>& __r, _Tp* __p) noexcept
207  : __shared_ptr<_Tp>(__r, __p) { }
208 
209  /**
210  * @brief If @a __r is empty, constructs an empty %shared_ptr;
211  * otherwise construct a %shared_ptr that shares ownership
212  * with @a __r.
213  * @param __r A %shared_ptr.
214  * @post get() == __r.get() && use_count() == __r.use_count()
215  */
216  template<typename _Tp1, typename = typename
218  shared_ptr(const shared_ptr<_Tp1>& __r) noexcept
219  : __shared_ptr<_Tp>(__r) { }
220 
221  /**
222  * @brief Move-constructs a %shared_ptr instance from @a __r.
223  * @param __r A %shared_ptr rvalue.
224  * @post *this contains the old value of @a __r, @a __r is empty.
225  */
226  shared_ptr(shared_ptr&& __r) noexcept
227  : __shared_ptr<_Tp>(std::move(__r)) { }
228 
229  /**
230  * @brief Move-constructs a %shared_ptr instance from @a __r.
231  * @param __r A %shared_ptr rvalue.
232  * @post *this contains the old value of @a __r, @a __r is empty.
233  */
234  template<typename _Tp1, typename = typename
236  shared_ptr(shared_ptr<_Tp1>&& __r) noexcept
237  : __shared_ptr<_Tp>(std::move(__r)) { }
238 
239  /**
240  * @brief Constructs a %shared_ptr that shares ownership with @a __r
241  * and stores a copy of the pointer stored in @a __r.
242  * @param __r A weak_ptr.
243  * @post use_count() == __r.use_count()
244  * @throw bad_weak_ptr when __r.expired(),
245  * in which case the constructor has no effect.
246  */
247  template<typename _Tp1>
248  explicit shared_ptr(const weak_ptr<_Tp1>& __r)
249  : __shared_ptr<_Tp>(__r) { }
250 
251 #if _GLIBCXX_USE_DEPRECATED
252  template<typename _Tp1>
254  : __shared_ptr<_Tp>(std::move(__r)) { }
255 #endif
256 
257  template<typename _Tp1, typename _Del>
259  : __shared_ptr<_Tp>(std::move(__r)) { }
260 
261  /**
262  * @brief Construct an empty %shared_ptr.
263  * @param __p A null pointer constant.
264  * @post use_count() == 0 && get() == nullptr
265  */
266  constexpr shared_ptr(nullptr_t __p) noexcept
267  : __shared_ptr<_Tp>(__p) { }
268 
269  shared_ptr& operator=(const shared_ptr&) noexcept = default;
270 
271  template<typename _Tp1>
272  shared_ptr&
273  operator=(const shared_ptr<_Tp1>& __r) noexcept
274  {
275  this->__shared_ptr<_Tp>::operator=(__r);
276  return *this;
277  }
278 
279 #if _GLIBCXX_USE_DEPRECATED
280  template<typename _Tp1>
281  shared_ptr&
282  operator=(std::auto_ptr<_Tp1>&& __r)
283  {
284  this->__shared_ptr<_Tp>::operator=(std::move(__r));
285  return *this;
286  }
287 #endif
288 
289  shared_ptr&
290  operator=(shared_ptr&& __r) noexcept
291  {
292  this->__shared_ptr<_Tp>::operator=(std::move(__r));
293  return *this;
294  }
295 
296  template<class _Tp1>
297  shared_ptr&
298  operator=(shared_ptr<_Tp1>&& __r) noexcept
299  {
300  this->__shared_ptr<_Tp>::operator=(std::move(__r));
301  return *this;
302  }
303 
304  template<typename _Tp1, typename _Del>
305  shared_ptr&
306  operator=(std::unique_ptr<_Tp1, _Del>&& __r)
307  {
308  this->__shared_ptr<_Tp>::operator=(std::move(__r));
309  return *this;
310  }
311 
312  private:
313  // This constructor is non-standard, it is used by allocate_shared.
314  template<typename _Alloc, typename... _Args>
315  shared_ptr(_Sp_make_shared_tag __tag, const _Alloc& __a,
316  _Args&&... __args)
317  : __shared_ptr<_Tp>(__tag, __a, std::forward<_Args>(__args)...)
318  { }
319 
320  template<typename _Tp1, typename _Alloc, typename... _Args>
321  friend shared_ptr<_Tp1>
322  allocate_shared(const _Alloc& __a, _Args&&... __args);
323  };
324 
325  // 20.8.13.2.7 shared_ptr comparisons
326  template<typename _Tp1, typename _Tp2>
327  inline bool
328  operator==(const shared_ptr<_Tp1>& __a,
329  const shared_ptr<_Tp2>& __b) noexcept
330  { return __a.get() == __b.get(); }
331 
332  template<typename _Tp>
333  inline bool
334  operator==(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
335  { return !__a; }
336 
337  template<typename _Tp>
338  inline bool
339  operator==(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
340  { return !__a; }
341 
342  template<typename _Tp1, typename _Tp2>
343  inline bool
344  operator!=(const shared_ptr<_Tp1>& __a,
345  const shared_ptr<_Tp2>& __b) noexcept
346  { return __a.get() != __b.get(); }
347 
348  template<typename _Tp>
349  inline bool
350  operator!=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
351  { return (bool)__a; }
352 
353  template<typename _Tp>
354  inline bool
355  operator!=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
356  { return (bool)__a; }
357 
358  template<typename _Tp1, typename _Tp2>
359  inline bool
360  operator<(const shared_ptr<_Tp1>& __a,
361  const shared_ptr<_Tp2>& __b) noexcept
362  {
363  typedef typename std::common_type<_Tp1*, _Tp2*>::type _CT;
364  return std::less<_CT>()(__a.get(), __b.get());
365  }
366 
367  template<typename _Tp>
368  inline bool
369  operator<(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
370  { return std::less<_Tp*>()(__a.get(), nullptr); }
371 
372  template<typename _Tp>
373  inline bool
374  operator<(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
375  { return std::less<_Tp*>()(nullptr, __a.get()); }
376 
377  template<typename _Tp1, typename _Tp2>
378  inline bool
379  operator<=(const shared_ptr<_Tp1>& __a,
380  const shared_ptr<_Tp2>& __b) noexcept
381  { return !(__b < __a); }
382 
383  template<typename _Tp>
384  inline bool
385  operator<=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
386  { return !(nullptr < __a); }
387 
388  template<typename _Tp>
389  inline bool
390  operator<=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
391  { return !(__a < nullptr); }
392 
393  template<typename _Tp1, typename _Tp2>
394  inline bool
395  operator>(const shared_ptr<_Tp1>& __a,
396  const shared_ptr<_Tp2>& __b) noexcept
397  { return (__b < __a); }
398 
399  template<typename _Tp>
400  inline bool
401  operator>(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
402  { return std::less<_Tp*>()(nullptr, __a.get()); }
403 
404  template<typename _Tp>
405  inline bool
406  operator>(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
407  { return std::less<_Tp*>()(__a.get(), nullptr); }
408 
409  template<typename _Tp1, typename _Tp2>
410  inline bool
411  operator>=(const shared_ptr<_Tp1>& __a,
412  const shared_ptr<_Tp2>& __b) noexcept
413  { return !(__a < __b); }
414 
415  template<typename _Tp>
416  inline bool
417  operator>=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
418  { return !(__a < nullptr); }
419 
420  template<typename _Tp>
421  inline bool
422  operator>=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
423  { return !(nullptr < __a); }
424 
425  template<typename _Tp>
426  struct less<shared_ptr<_Tp>> : public _Sp_less<shared_ptr<_Tp>>
427  { };
428 
429  // 20.8.13.2.9 shared_ptr specialized algorithms.
430  template<typename _Tp>
431  inline void
432  swap(shared_ptr<_Tp>& __a, shared_ptr<_Tp>& __b) noexcept
433  { __a.swap(__b); }
434 
435  // 20.8.13.2.10 shared_ptr casts.
436  template<typename _Tp, typename _Tp1>
437  inline shared_ptr<_Tp>
438  static_pointer_cast(const shared_ptr<_Tp1>& __r) noexcept
439  { return shared_ptr<_Tp>(__r, static_cast<_Tp*>(__r.get())); }
440 
441  template<typename _Tp, typename _Tp1>
442  inline shared_ptr<_Tp>
443  const_pointer_cast(const shared_ptr<_Tp1>& __r) noexcept
444  { return shared_ptr<_Tp>(__r, const_cast<_Tp*>(__r.get())); }
445 
446  template<typename _Tp, typename _Tp1>
447  inline shared_ptr<_Tp>
448  dynamic_pointer_cast(const shared_ptr<_Tp1>& __r) noexcept
449  {
450  if (_Tp* __p = dynamic_cast<_Tp*>(__r.get()))
451  return shared_ptr<_Tp>(__r, __p);
452  return shared_ptr<_Tp>();
453  }
454 
455 
456  /**
457  * @brief A smart pointer with weak semantics.
458  *
459  * With forwarding constructors and assignment operators.
460  */
461  template<typename _Tp>
462  class weak_ptr : public __weak_ptr<_Tp>
463  {
464  public:
465  constexpr weak_ptr() noexcept
466  : __weak_ptr<_Tp>() { }
467 
468  template<typename _Tp1, typename = typename
470  weak_ptr(const weak_ptr<_Tp1>& __r) noexcept
471  : __weak_ptr<_Tp>(__r) { }
472 
473  template<typename _Tp1, typename = typename
475  weak_ptr(const shared_ptr<_Tp1>& __r) noexcept
476  : __weak_ptr<_Tp>(__r) { }
477 
478  template<typename _Tp1>
479  weak_ptr&
480  operator=(const weak_ptr<_Tp1>& __r) noexcept
481  {
482  this->__weak_ptr<_Tp>::operator=(__r);
483  return *this;
484  }
485 
486  template<typename _Tp1>
487  weak_ptr&
488  operator=(const shared_ptr<_Tp1>& __r) noexcept
489  {
490  this->__weak_ptr<_Tp>::operator=(__r);
491  return *this;
492  }
493 
495  lock() const noexcept
496  {
497 #ifdef __GTHREADS
498  if (this->expired())
499  return shared_ptr<_Tp>();
500 
501  __try
502  {
503  return shared_ptr<_Tp>(*this);
504  }
505  __catch(const bad_weak_ptr&)
506  {
507  return shared_ptr<_Tp>();
508  }
509 #else
510  return this->expired() ? shared_ptr<_Tp>() : shared_ptr<_Tp>(*this);
511 #endif
512  }
513  };
514 
515  // 20.8.13.3.7 weak_ptr specialized algorithms.
516  template<typename _Tp>
517  inline void
518  swap(weak_ptr<_Tp>& __a, weak_ptr<_Tp>& __b) noexcept
519  { __a.swap(__b); }
520 
521 
522  /// Primary template owner_less
523  template<typename _Tp>
524  struct owner_less;
525 
526  /// Partial specialization of owner_less for shared_ptr.
527  template<typename _Tp>
528  struct owner_less<shared_ptr<_Tp>>
529  : public _Sp_owner_less<shared_ptr<_Tp>, weak_ptr<_Tp>>
530  { };
531 
532  /// Partial specialization of owner_less for weak_ptr.
533  template<typename _Tp>
534  struct owner_less<weak_ptr<_Tp>>
535  : public _Sp_owner_less<weak_ptr<_Tp>, shared_ptr<_Tp>>
536  { };
537 
538  /**
539  * @brief Base class allowing use of member function shared_from_this.
540  */
541  template<typename _Tp>
543  {
544  protected:
545  constexpr enable_shared_from_this() noexcept { }
546 
548 
550  operator=(const enable_shared_from_this&) noexcept
551  { return *this; }
552 
554 
555  public:
557  shared_from_this()
558  { return shared_ptr<_Tp>(this->_M_weak_this); }
559 
561  shared_from_this() const
562  { return shared_ptr<const _Tp>(this->_M_weak_this); }
563 
564  private:
565  template<typename _Tp1>
566  void
567  _M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const noexcept
568  { _M_weak_this._M_assign(__p, __n); }
569 
570  template<typename _Tp1>
571  friend void
572  __enable_shared_from_this_helper(const __shared_count<>& __pn,
573  const enable_shared_from_this* __pe,
574  const _Tp1* __px) noexcept
575  {
576  if (__pe != 0)
577  __pe->_M_weak_assign(const_cast<_Tp1*>(__px), __pn);
578  }
579 
580  mutable weak_ptr<_Tp> _M_weak_this;
581  };
582 
583  /**
584  * @brief Create an object that is owned by a shared_ptr.
585  * @param __a An allocator.
586  * @param __args Arguments for the @a _Tp object's constructor.
587  * @return A shared_ptr that owns the newly created object.
588  * @throw An exception thrown from @a _Alloc::allocate or from the
589  * constructor of @a _Tp.
590  *
591  * A copy of @a __a will be used to allocate memory for the shared_ptr
592  * and the new object.
593  */
594  template<typename _Tp, typename _Alloc, typename... _Args>
595  inline shared_ptr<_Tp>
596  allocate_shared(const _Alloc& __a, _Args&&... __args)
597  {
598  return shared_ptr<_Tp>(_Sp_make_shared_tag(), __a,
599  std::forward<_Args>(__args)...);
600  }
601 
602  /**
603  * @brief Create an object that is owned by a shared_ptr.
604  * @param __args Arguments for the @a _Tp object's constructor.
605  * @return A shared_ptr that owns the newly created object.
606  * @throw std::bad_alloc, or an exception thrown from the
607  * constructor of @a _Tp.
608  */
609  template<typename _Tp, typename... _Args>
610  inline shared_ptr<_Tp>
611  make_shared(_Args&&... __args)
612  {
613  typedef typename std::remove_const<_Tp>::type _Tp_nc;
614  return std::allocate_shared<_Tp>(std::allocator<_Tp_nc>(),
615  std::forward<_Args>(__args)...);
616  }
617 
618  /// std::hash specialization for shared_ptr.
619  template<typename _Tp>
620  struct hash<shared_ptr<_Tp>>
621  : public __hash_base<size_t, shared_ptr<_Tp>>
622  {
623  size_t
624  operator()(const shared_ptr<_Tp>& __s) const noexcept
625  { return std::hash<_Tp*>()(__s.get()); }
626  };
627 
628  // @} group pointer_abstractions
629 
630 _GLIBCXX_END_NAMESPACE_VERSION
631 } // namespace
632 
633 #endif // _SHARED_PTR_H