LCOV - code coverage report
Current view: top level - usr/include/c++/9/bits - shared_ptr.h (source / functions) Hit Total Coverage
Test: ROSE Lines: 11 11 100.0 %
Date: 2022-12-08 13:48:47 Functions: 0 0 -
Legend: Lines: hit not hit

          Line data    Source code
       1             : // shared_ptr and weak_ptr implementation -*- C++ -*-
       2             : 
       3             : // Copyright (C) 2007-2019 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             : 
      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             :   template<typename _Del, typename _Tp, _Lock_policy _Lp>
      74             :     inline _Del*
      75             :     get_deleter(const __shared_ptr<_Tp, _Lp>& __p) noexcept
      76             :     {
      77             : #if __cpp_rtti
      78             :       return static_cast<_Del*>(__p._M_get_deleter(typeid(_Del)));
      79             : #else
      80             :       return 0;
      81             : #endif
      82             :     }
      83             : 
      84             :   /// 20.7.2.2.10 shared_ptr get_deleter
      85             :   template<typename _Del, typename _Tp>
      86             :     inline _Del*
      87             :     get_deleter(const shared_ptr<_Tp>& __p) noexcept
      88             :     {
      89             : #if __cpp_rtti
      90             :       return static_cast<_Del*>(__p._M_get_deleter(typeid(_Del)));
      91             : #else
      92             :       return 0;
      93             : #endif
      94             :     }
      95             : 
      96             :   /**
      97             :    *  @brief  A smart pointer with reference-counted copy semantics.
      98             :    *
      99             :    *  The object pointed to is deleted when the last shared_ptr pointing to
     100             :    *  it is destroyed or reset.
     101             :   */
     102             :   template<typename _Tp>
     103        1910 :     class shared_ptr : public __shared_ptr<_Tp>
     104             :     {
     105             :       template<typename... _Args>
     106             :         using _Constructible = typename enable_if<
     107             :           is_constructible<__shared_ptr<_Tp>, _Args...>::value
     108             :         >::type;
     109             : 
     110             :       template<typename _Arg>
     111             :         using _Assignable = typename enable_if<
     112             :           is_assignable<__shared_ptr<_Tp>&, _Arg>::value, shared_ptr&
     113             :         >::type;
     114             : 
     115             :     public:
     116             : 
     117             :       using element_type = typename __shared_ptr<_Tp>::element_type;
     118             : 
     119             : #if __cplusplus > 201402L
     120             : # define __cpp_lib_shared_ptr_weak_type 201606
     121             :       using weak_type = weak_ptr<_Tp>;
     122             : #endif
     123             :       /**
     124             :        *  @brief  Construct an empty %shared_ptr.
     125             :        *  @post   use_count()==0 && get()==0
     126             :        */
     127             :       constexpr shared_ptr() noexcept : __shared_ptr<_Tp>() { }
     128             : 
     129             :       shared_ptr(const shared_ptr&) noexcept = default;
     130             : 
     131             :       /**
     132             :        *  @brief  Construct a %shared_ptr that owns the pointer @a __p.
     133             :        *  @param  __p  A pointer that is convertible to element_type*.
     134             :        *  @post   use_count() == 1 && get() == __p
     135             :        *  @throw  std::bad_alloc, in which case @c delete @a __p is called.
     136             :        */
     137             :       template<typename _Yp, typename = _Constructible<_Yp*>>
     138             :         explicit
     139             :         shared_ptr(_Yp* __p) : __shared_ptr<_Tp>(__p) { }
     140             : 
     141             :       /**
     142             :        *  @brief  Construct a %shared_ptr that owns the pointer @a __p
     143             :        *          and the deleter @a __d.
     144             :        *  @param  __p  A pointer.
     145             :        *  @param  __d  A deleter.
     146             :        *  @post   use_count() == 1 && get() == __p
     147             :        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
     148             :        *
     149             :        *  Requirements: _Deleter's copy constructor and destructor must
     150             :        *  not throw
     151             :        *
     152             :        *  __shared_ptr will release __p by calling __d(__p)
     153             :        */
     154             :       template<typename _Yp, typename _Deleter,
     155             :                typename = _Constructible<_Yp*, _Deleter>>
     156             :         shared_ptr(_Yp* __p, _Deleter __d)
     157             :         : __shared_ptr<_Tp>(__p, std::move(__d)) { }
     158             : 
     159             :       /**
     160             :        *  @brief  Construct a %shared_ptr that owns a null pointer
     161             :        *          and the deleter @a __d.
     162             :        *  @param  __p  A null pointer constant.
     163             :        *  @param  __d  A deleter.
     164             :        *  @post   use_count() == 1 && get() == __p
     165             :        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
     166             :        *
     167             :        *  Requirements: _Deleter's copy constructor and destructor must
     168             :        *  not throw
     169             :        *
     170             :        *  The last owner will call __d(__p)
     171             :        */
     172             :       template<typename _Deleter>
     173             :         shared_ptr(nullptr_t __p, _Deleter __d)
     174             :         : __shared_ptr<_Tp>(__p, std::move(__d)) { }
     175             : 
     176             :       /**
     177             :        *  @brief  Construct a %shared_ptr that owns the pointer @a __p
     178             :        *          and the deleter @a __d.
     179             :        *  @param  __p  A pointer.
     180             :        *  @param  __d  A deleter.
     181             :        *  @param  __a  An allocator.
     182             :        *  @post   use_count() == 1 && get() == __p
     183             :        *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
     184             :        *
     185             :        *  Requirements: _Deleter's copy constructor and destructor must
     186             :        *  not throw _Alloc's copy constructor and destructor must not
     187             :        *  throw.
     188             :        *
     189             :        *  __shared_ptr will release __p by calling __d(__p)
     190             :        */
     191             :       template<typename _Yp, typename _Deleter, typename _Alloc,
     192             :                typename = _Constructible<_Yp*, _Deleter, _Alloc>>
     193             :         shared_ptr(_Yp* __p, _Deleter __d, _Alloc __a)
     194             :         : __shared_ptr<_Tp>(__p, std::move(__d), std::move(__a)) { }
     195             : 
     196             :       /**
     197             :        *  @brief  Construct a %shared_ptr that owns a null pointer
     198             :        *          and the deleter @a __d.
     199             :        *  @param  __p  A null pointer constant.
     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             :        *  The last owner will call __d(__p)
     210             :        */
     211             :       template<typename _Deleter, typename _Alloc>
     212             :         shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
     213             :         : __shared_ptr<_Tp>(__p, std::move(__d), std::move(__a)) { }
     214             : 
     215             :       // Aliasing constructor
     216             : 
     217             :       /**
     218             :        *  @brief  Constructs a %shared_ptr instance that stores @a __p
     219             :        *          and shares ownership with @a __r.
     220             :        *  @param  __r  A %shared_ptr.
     221             :        *  @param  __p  A pointer that will remain valid while @a *__r is valid.
     222             :        *  @post   get() == __p && use_count() == __r.use_count()
     223             :        *
     224             :        *  This can be used to construct a @c shared_ptr to a sub-object
     225             :        *  of an object managed by an existing @c shared_ptr.
     226             :        *
     227             :        * @code
     228             :        * shared_ptr< pair<int,int> > pii(new pair<int,int>());
     229             :        * shared_ptr<int> pi(pii, &pii->first);
     230             :        * assert(pii.use_count() == 2);
     231             :        * @endcode
     232             :        */
     233             :       template<typename _Yp>
     234             :         shared_ptr(const shared_ptr<_Yp>& __r, element_type* __p) noexcept
     235             :         : __shared_ptr<_Tp>(__r, __p) { }
     236             : 
     237             :       /**
     238             :        *  @brief  If @a __r is empty, constructs an empty %shared_ptr;
     239             :        *          otherwise construct a %shared_ptr that shares ownership
     240             :        *          with @a __r.
     241             :        *  @param  __r  A %shared_ptr.
     242             :        *  @post   get() == __r.get() && use_count() == __r.use_count()
     243             :        */
     244             :       template<typename _Yp,
     245             :                typename = _Constructible<const shared_ptr<_Yp>&>>
     246             :         shared_ptr(const shared_ptr<_Yp>& __r) noexcept
     247             :         : __shared_ptr<_Tp>(__r) { }
     248             : 
     249             :       /**
     250             :        *  @brief  Move-constructs a %shared_ptr instance from @a __r.
     251             :        *  @param  __r  A %shared_ptr rvalue.
     252             :        *  @post   *this contains the old value of @a __r, @a __r is empty.
     253             :        */
     254             :       shared_ptr(shared_ptr&& __r) noexcept
     255             :       : __shared_ptr<_Tp>(std::move(__r)) { }
     256             : 
     257             :       /**
     258             :        *  @brief  Move-constructs a %shared_ptr instance from @a __r.
     259             :        *  @param  __r  A %shared_ptr rvalue.
     260             :        *  @post   *this contains the old value of @a __r, @a __r is empty.
     261             :        */
     262             :       template<typename _Yp, typename = _Constructible<shared_ptr<_Yp>>>
     263         955 :         shared_ptr(shared_ptr<_Yp>&& __r) noexcept
     264         955 :         : __shared_ptr<_Tp>(std::move(__r)) { }
     265             : 
     266             :       /**
     267             :        *  @brief  Constructs a %shared_ptr that shares ownership with @a __r
     268             :        *          and stores a copy of the pointer stored in @a __r.
     269             :        *  @param  __r  A weak_ptr.
     270             :        *  @post   use_count() == __r.use_count()
     271             :        *  @throw  bad_weak_ptr when __r.expired(),
     272             :        *          in which case the constructor has no effect.
     273             :        */
     274             :       template<typename _Yp, typename = _Constructible<const weak_ptr<_Yp>&>>
     275             :         explicit shared_ptr(const weak_ptr<_Yp>& __r)
     276             :         : __shared_ptr<_Tp>(__r) { }
     277             : 
     278             : #if _GLIBCXX_USE_DEPRECATED
     279             : #pragma GCC diagnostic push
     280             : #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
     281             :       template<typename _Yp, typename = _Constructible<auto_ptr<_Yp>>>
     282             :         shared_ptr(auto_ptr<_Yp>&& __r);
     283             : #pragma GCC diagnostic pop
     284             : #endif
     285             : 
     286             :       // _GLIBCXX_RESOLVE_LIB_DEFECTS
     287             :       // 2399. shared_ptr's constructor from unique_ptr should be constrained
     288             :       template<typename _Yp, typename _Del,
     289             :                typename = _Constructible<unique_ptr<_Yp, _Del>>>
     290             :         shared_ptr(unique_ptr<_Yp, _Del>&& __r)
     291             :         : __shared_ptr<_Tp>(std::move(__r)) { }
     292             : 
     293             : #if __cplusplus <= 201402L && _GLIBCXX_USE_DEPRECATED
     294             :       // This non-standard constructor exists to support conversions that
     295             :       // were possible in C++11 and C++14 but are ill-formed in C++17.
     296             :       // If an exception is thrown this constructor has no effect.
     297             :       template<typename _Yp, typename _Del,
     298             :                 _Constructible<unique_ptr<_Yp, _Del>, __sp_array_delete>* = 0>
     299             :         shared_ptr(unique_ptr<_Yp, _Del>&& __r)
     300             :         : __shared_ptr<_Tp>(std::move(__r), __sp_array_delete()) { }
     301             : #endif
     302             : 
     303             :       /**
     304             :        *  @brief  Construct an empty %shared_ptr.
     305             :        *  @post   use_count() == 0 && get() == nullptr
     306             :        */
     307             :       constexpr shared_ptr(nullptr_t) noexcept : shared_ptr() { }
     308             : 
     309             :       shared_ptr& operator=(const shared_ptr&) noexcept = default;
     310             : 
     311             :       template<typename _Yp>
     312             :         _Assignable<const shared_ptr<_Yp>&>
     313             :         operator=(const shared_ptr<_Yp>& __r) noexcept
     314             :         {
     315             :           this->__shared_ptr<_Tp>::operator=(__r);
     316             :           return *this;
     317             :         }
     318             : 
     319             : #if _GLIBCXX_USE_DEPRECATED
     320             : #pragma GCC diagnostic push
     321             : #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
     322             :       template<typename _Yp>
     323             :         _Assignable<auto_ptr<_Yp>>
     324             :         operator=(auto_ptr<_Yp>&& __r)
     325             :         {
     326             :           this->__shared_ptr<_Tp>::operator=(std::move(__r));
     327             :           return *this;
     328             :         }
     329             : #pragma GCC diagnostic pop
     330             : #endif
     331             : 
     332             :       shared_ptr&
     333             :       operator=(shared_ptr&& __r) noexcept
     334             :       {
     335             :         this->__shared_ptr<_Tp>::operator=(std::move(__r));
     336             :         return *this;
     337             :       }
     338             : 
     339             :       template<class _Yp>
     340             :         _Assignable<shared_ptr<_Yp>>
     341             :         operator=(shared_ptr<_Yp>&& __r) noexcept
     342             :         {
     343             :           this->__shared_ptr<_Tp>::operator=(std::move(__r));
     344             :           return *this;
     345             :         }
     346             : 
     347             :       template<typename _Yp, typename _Del>
     348             :         _Assignable<unique_ptr<_Yp, _Del>>
     349             :         operator=(unique_ptr<_Yp, _Del>&& __r)
     350             :         {
     351             :           this->__shared_ptr<_Tp>::operator=(std::move(__r));
     352             :           return *this;
     353             :         }
     354             : 
     355             :     private:
     356             :       // This constructor is non-standard, it is used by allocate_shared.
     357             :       template<typename _Alloc, typename... _Args>
     358         955 :         shared_ptr(_Sp_alloc_shared_tag<_Alloc> __tag, _Args&&... __args)
     359        1910 :         : __shared_ptr<_Tp>(__tag, std::forward<_Args>(__args)...)
     360             :         { }
     361             : 
     362             :       template<typename _Yp, typename _Alloc, typename... _Args>
     363             :         friend shared_ptr<_Yp>
     364             :         allocate_shared(const _Alloc& __a, _Args&&... __args);
     365             : 
     366             :       // This constructor is non-standard, it is used by weak_ptr::lock().
     367             :       shared_ptr(const weak_ptr<_Tp>& __r, std::nothrow_t)
     368             :       : __shared_ptr<_Tp>(__r, std::nothrow) { }
     369             : 
     370             :       friend class weak_ptr<_Tp>;
     371             :     };
     372             : 
     373             : #if __cpp_deduction_guides >= 201606
     374             :   template<typename _Tp>
     375             :     shared_ptr(weak_ptr<_Tp>) ->  shared_ptr<_Tp>;
     376             :   template<typename _Tp, typename _Del>
     377             :     shared_ptr(unique_ptr<_Tp, _Del>) ->  shared_ptr<_Tp>;
     378             : #endif
     379             : 
     380             :   // 20.7.2.2.7 shared_ptr comparisons
     381             :   template<typename _Tp, typename _Up>
     382             :     _GLIBCXX_NODISCARD inline bool
     383             :     operator==(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
     384             :     { return __a.get() == __b.get(); }
     385             : 
     386             :   template<typename _Tp>
     387             :     _GLIBCXX_NODISCARD inline bool
     388         955 :     operator==(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
     389         955 :     { return !__a; }
     390             : 
     391             :   template<typename _Tp>
     392             :     _GLIBCXX_NODISCARD inline bool
     393             :     operator==(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
     394             :     { return !__a; }
     395             : 
     396             :   template<typename _Tp, typename _Up>
     397             :     _GLIBCXX_NODISCARD inline bool
     398             :     operator!=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
     399             :     { return __a.get() != __b.get(); }
     400             : 
     401             :   template<typename _Tp>
     402             :     _GLIBCXX_NODISCARD inline bool
     403             :     operator!=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
     404             :     { return (bool)__a; }
     405             : 
     406             :   template<typename _Tp>
     407             :     _GLIBCXX_NODISCARD inline bool
     408             :     operator!=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
     409             :     { return (bool)__a; }
     410             : 
     411             :   template<typename _Tp, typename _Up>
     412             :     _GLIBCXX_NODISCARD inline bool
     413             :     operator<(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
     414             :     {
     415             :       using _Tp_elt = typename shared_ptr<_Tp>::element_type;
     416             :       using _Up_elt = typename shared_ptr<_Up>::element_type;
     417             :       using _Vp = typename common_type<_Tp_elt*, _Up_elt*>::type;
     418             :       return less<_Vp>()(__a.get(), __b.get());
     419             :     }
     420             : 
     421             :   template<typename _Tp>
     422             :     _GLIBCXX_NODISCARD inline bool
     423             :     operator<(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
     424             :     {
     425             :       using _Tp_elt = typename shared_ptr<_Tp>::element_type;
     426             :       return less<_Tp_elt*>()(__a.get(), nullptr);
     427             :     }
     428             : 
     429             :   template<typename _Tp>
     430             :     _GLIBCXX_NODISCARD inline bool
     431             :     operator<(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
     432             :     {
     433             :       using _Tp_elt = typename shared_ptr<_Tp>::element_type;
     434             :       return less<_Tp_elt*>()(nullptr, __a.get());
     435             :     }
     436             : 
     437             :   template<typename _Tp, typename _Up>
     438             :     _GLIBCXX_NODISCARD inline bool
     439             :     operator<=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
     440             :     { return !(__b < __a); }
     441             : 
     442             :   template<typename _Tp>
     443             :     _GLIBCXX_NODISCARD inline bool
     444             :     operator<=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
     445             :     { return !(nullptr < __a); }
     446             : 
     447             :   template<typename _Tp>
     448             :     _GLIBCXX_NODISCARD inline bool
     449             :     operator<=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
     450             :     { return !(__a < nullptr); }
     451             : 
     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 (__b < __a); }
     456             : 
     457             :   template<typename _Tp>
     458             :     _GLIBCXX_NODISCARD inline bool
     459             :     operator>(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
     460             :     { return nullptr < __a; }
     461             : 
     462             :   template<typename _Tp>
     463             :     _GLIBCXX_NODISCARD inline bool
     464             :     operator>(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
     465             :     { return __a < nullptr; }
     466             : 
     467             :   template<typename _Tp, typename _Up>
     468             :     _GLIBCXX_NODISCARD inline bool
     469             :     operator>=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
     470             :     { return !(__a < __b); }
     471             : 
     472             :   template<typename _Tp>
     473             :     _GLIBCXX_NODISCARD inline bool
     474             :     operator>=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
     475             :     { return !(__a < nullptr); }
     476             : 
     477             :   template<typename _Tp>
     478             :     _GLIBCXX_NODISCARD inline bool
     479             :     operator>=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
     480             :     { return !(nullptr < __a); }
     481             : 
     482             :   // 20.7.2.2.8 shared_ptr specialized algorithms.
     483             :   template<typename _Tp>
     484             :     inline void
     485             :     swap(shared_ptr<_Tp>& __a, shared_ptr<_Tp>& __b) noexcept
     486             :     { __a.swap(__b); }
     487             : 
     488             :   // 20.7.2.2.9 shared_ptr casts.
     489             :   template<typename _Tp, typename _Up>
     490             :     inline shared_ptr<_Tp>
     491             :     static_pointer_cast(const shared_ptr<_Up>& __r) noexcept
     492             :     {
     493             :       using _Sp = shared_ptr<_Tp>;
     494             :       return _Sp(__r, static_cast<typename _Sp::element_type*>(__r.get()));
     495             :     }
     496             : 
     497             :   template<typename _Tp, typename _Up>
     498             :     inline shared_ptr<_Tp>
     499             :     const_pointer_cast(const shared_ptr<_Up>& __r) noexcept
     500             :     {
     501             :       using _Sp = shared_ptr<_Tp>;
     502             :       return _Sp(__r, const_cast<typename _Sp::element_type*>(__r.get()));
     503             :     }
     504             : 
     505             :   template<typename _Tp, typename _Up>
     506             :     inline shared_ptr<_Tp>
     507             :     dynamic_pointer_cast(const shared_ptr<_Up>& __r) noexcept
     508             :     {
     509             :       using _Sp = shared_ptr<_Tp>;
     510             :       if (auto* __p = dynamic_cast<typename _Sp::element_type*>(__r.get()))
     511             :         return _Sp(__r, __p);
     512             :       return _Sp();
     513             :     }
     514             : 
     515             : #if __cplusplus > 201402L
     516             :   template<typename _Tp, typename _Up>
     517             :     inline shared_ptr<_Tp>
     518             :     reinterpret_pointer_cast(const shared_ptr<_Up>& __r) noexcept
     519             :     {
     520             :       using _Sp = shared_ptr<_Tp>;
     521             :       return _Sp(__r, reinterpret_cast<typename _Sp::element_type*>(__r.get()));
     522             :     }
     523             : #endif
     524             : 
     525             :   /**
     526             :    *  @brief  A smart pointer with weak semantics.
     527             :    *
     528             :    *  With forwarding constructors and assignment operators.
     529             :    */
     530             :   template<typename _Tp>
     531             :     class weak_ptr : public __weak_ptr<_Tp>
     532             :     {
     533             :       template<typename _Arg>
     534             :         using _Constructible = typename enable_if<
     535             :           is_constructible<__weak_ptr<_Tp>, _Arg>::value
     536             :         >::type;
     537             : 
     538             :       template<typename _Arg>
     539             :         using _Assignable = typename enable_if<
     540             :           is_assignable<__weak_ptr<_Tp>&, _Arg>::value, weak_ptr&
     541             :         >::type;
     542             : 
     543             :     public:
     544             :       constexpr weak_ptr() noexcept = default;
     545             : 
     546             :       template<typename _Yp,
     547             :                typename = _Constructible<const shared_ptr<_Yp>&>>
     548             :         weak_ptr(const shared_ptr<_Yp>& __r) noexcept
     549             :         : __weak_ptr<_Tp>(__r) { }
     550             : 
     551             :       weak_ptr(const weak_ptr&) noexcept = default;
     552             : 
     553             :       template<typename _Yp, typename = _Constructible<const weak_ptr<_Yp>&>>
     554             :         weak_ptr(const weak_ptr<_Yp>& __r) noexcept
     555             :         : __weak_ptr<_Tp>(__r) { }
     556             : 
     557             :       weak_ptr(weak_ptr&&) noexcept = default;
     558             : 
     559             :       template<typename _Yp, typename = _Constructible<weak_ptr<_Yp>>>
     560             :         weak_ptr(weak_ptr<_Yp>&& __r) noexcept
     561             :         : __weak_ptr<_Tp>(std::move(__r)) { }
     562             : 
     563             :       weak_ptr&
     564             :       operator=(const weak_ptr& __r) noexcept = default;
     565             : 
     566             :       template<typename _Yp>
     567             :         _Assignable<const weak_ptr<_Yp>&>
     568             :         operator=(const weak_ptr<_Yp>& __r) noexcept
     569             :         {
     570             :           this->__weak_ptr<_Tp>::operator=(__r);
     571             :           return *this;
     572             :         }
     573             : 
     574             :       template<typename _Yp>
     575             :         _Assignable<const shared_ptr<_Yp>&>
     576             :         operator=(const shared_ptr<_Yp>& __r) noexcept
     577             :         {
     578             :           this->__weak_ptr<_Tp>::operator=(__r);
     579             :           return *this;
     580             :         }
     581             : 
     582             :       weak_ptr&
     583             :       operator=(weak_ptr&& __r) noexcept = default;
     584             : 
     585             :       template<typename _Yp>
     586             :         _Assignable<weak_ptr<_Yp>>
     587             :         operator=(weak_ptr<_Yp>&& __r) noexcept
     588             :         {
     589             :           this->__weak_ptr<_Tp>::operator=(std::move(__r));
     590             :           return *this;
     591             :         }
     592             : 
     593             :       shared_ptr<_Tp>
     594             :       lock() const noexcept
     595             :       { return shared_ptr<_Tp>(*this, std::nothrow); }
     596             :     };
     597             : 
     598             : #if __cpp_deduction_guides >= 201606
     599             :   template<typename _Tp>
     600             :     weak_ptr(shared_ptr<_Tp>) ->  weak_ptr<_Tp>;
     601             : #endif
     602             : 
     603             :   // 20.7.2.3.6 weak_ptr specialized algorithms.
     604             :   template<typename _Tp>
     605             :     inline void
     606             :     swap(weak_ptr<_Tp>& __a, weak_ptr<_Tp>& __b) noexcept
     607             :     { __a.swap(__b); }
     608             : 
     609             : 
     610             :   /// Primary template owner_less
     611             :   template<typename _Tp = void>
     612             :     struct owner_less;
     613             : 
     614             :   /// Void specialization of owner_less
     615             :   template<>
     616             :     struct owner_less<void> : _Sp_owner_less<void, void>
     617             :     { };
     618             : 
     619             :   /// Partial specialization of owner_less for shared_ptr.
     620             :   template<typename _Tp>
     621             :     struct owner_less<shared_ptr<_Tp>>
     622             :     : public _Sp_owner_less<shared_ptr<_Tp>, weak_ptr<_Tp>>
     623             :     { };
     624             : 
     625             :   /// Partial specialization of owner_less for weak_ptr.
     626             :   template<typename _Tp>
     627             :     struct owner_less<weak_ptr<_Tp>>
     628             :     : public _Sp_owner_less<weak_ptr<_Tp>, shared_ptr<_Tp>>
     629             :     { };
     630             : 
     631             :   /**
     632             :    *  @brief Base class allowing use of member function shared_from_this.
     633             :    */
     634             :   template<typename _Tp>
     635             :     class enable_shared_from_this
     636             :     {
     637             :     protected:
     638             :       constexpr enable_shared_from_this() noexcept { }
     639             : 
     640             :       enable_shared_from_this(const enable_shared_from_this&) noexcept { }
     641             : 
     642             :       enable_shared_from_this&
     643             :       operator=(const enable_shared_from_this&) noexcept
     644             :       { return *this; }
     645             : 
     646             :       ~enable_shared_from_this() { }
     647             : 
     648             :     public:
     649             :       shared_ptr<_Tp>
     650             :       shared_from_this()
     651             :       { return shared_ptr<_Tp>(this->_M_weak_this); }
     652             : 
     653             :       shared_ptr<const _Tp>
     654             :       shared_from_this() const
     655             :       { return shared_ptr<const _Tp>(this->_M_weak_this); }
     656             : 
     657             : #if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
     658             : #define __cpp_lib_enable_shared_from_this 201603
     659             :       weak_ptr<_Tp>
     660             :       weak_from_this() noexcept
     661             :       { return this->_M_weak_this; }
     662             : 
     663             :       weak_ptr<const _Tp>
     664             :       weak_from_this() const noexcept
     665             :       { return this->_M_weak_this; }
     666             : #endif
     667             : 
     668             :     private:
     669             :       template<typename _Tp1>
     670             :         void
     671             :         _M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const noexcept
     672             :         { _M_weak_this._M_assign(__p, __n); }
     673             : 
     674             :       // Found by ADL when this is an associated class.
     675             :       friend const enable_shared_from_this*
     676             :       __enable_shared_from_this_base(const __shared_count<>&,
     677             :                                      const enable_shared_from_this* __p)
     678             :       { return __p; }
     679             : 
     680             :       template<typename, _Lock_policy>
     681             :         friend class __shared_ptr;
     682             : 
     683             :       mutable weak_ptr<_Tp>  _M_weak_this;
     684             :     };
     685             : 
     686             :   /**
     687             :    *  @brief  Create an object that is owned by a shared_ptr.
     688             :    *  @param  __a     An allocator.
     689             :    *  @param  __args  Arguments for the @a _Tp object's constructor.
     690             :    *  @return A shared_ptr that owns the newly created object.
     691             :    *  @throw  An exception thrown from @a _Alloc::allocate or from the
     692             :    *          constructor of @a _Tp.
     693             :    *
     694             :    *  A copy of @a __a will be used to allocate memory for the shared_ptr
     695             :    *  and the new object.
     696             :    */
     697             :   template<typename _Tp, typename _Alloc, typename... _Args>
     698             :     inline shared_ptr<_Tp>
     699         955 :     allocate_shared(const _Alloc& __a, _Args&&... __args)
     700             :     {
     701             :       return shared_ptr<_Tp>(_Sp_alloc_shared_tag<_Alloc>{__a},
     702         955 :                              std::forward<_Args>(__args)...);
     703             :     }
     704             : 
     705             :   /**
     706             :    *  @brief  Create an object that is owned by a shared_ptr.
     707             :    *  @param  __args  Arguments for the @a _Tp object's constructor.
     708             :    *  @return A shared_ptr that owns the newly created object.
     709             :    *  @throw  std::bad_alloc, or an exception thrown from the
     710             :    *          constructor of @a _Tp.
     711             :    */
     712             :   template<typename _Tp, typename... _Args>
     713             :     inline shared_ptr<_Tp>
     714         955 :     make_shared(_Args&&... __args)
     715             :     {
     716             :       typedef typename std::remove_cv<_Tp>::type _Tp_nc;
     717             :       return std::allocate_shared<_Tp>(std::allocator<_Tp_nc>(),
     718         955 :                                        std::forward<_Args>(__args)...);
     719             :     }
     720             : 
     721             :   /// std::hash specialization for shared_ptr.
     722             :   template<typename _Tp>
     723             :     struct hash<shared_ptr<_Tp>>
     724             :     : public __hash_base<size_t, shared_ptr<_Tp>>
     725             :     {
     726             :       size_t
     727             :       operator()(const shared_ptr<_Tp>& __s) const noexcept
     728             :       {
     729             :         return std::hash<typename shared_ptr<_Tp>::element_type*>()(__s.get());
     730             :       }
     731             :     };
     732             : 
     733             :   /// @} group pointer_abstractions
     734             : 
     735             : #if __cplusplus >= 201703L
     736             :   namespace __detail::__variant
     737             :   {
     738             :     template<typename> struct _Never_valueless_alt; // see <variant>
     739             : 
     740             :     // Provide the strong exception-safety guarantee when emplacing a
     741             :     // shared_ptr into a variant.
     742             :     template<typename _Tp>
     743             :       struct _Never_valueless_alt<std::shared_ptr<_Tp>>
     744             :       : std::true_type
     745             :       { };
     746             : 
     747             :     // Provide the strong exception-safety guarantee when emplacing a
     748             :     // weak_ptr into a variant.
     749             :     template<typename _Tp>
     750             :       struct _Never_valueless_alt<std::weak_ptr<_Tp>>
     751             :       : std::true_type
     752             :       { };
     753             :   }  // namespace __detail::__variant
     754             : #endif // C++17
     755             : 
     756             : _GLIBCXX_END_NAMESPACE_VERSION
     757             : } // namespace
     758             : 
     759             : #endif // _SHARED_PTR_H

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