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Edit File : shared_ptr.h \| Size : 22.88 KB
// shared_ptr and weak_ptr implementation -- C++ -- // Copyright (C) 2007-2018 Free Software Foundation, Inc. // // This file is part of the GNU ISO C++ Library. This library is free // software; you can redistribute it and/or modify it under the // terms of the GNU General Public License as published by the // Free Software Foundation; either version 3, or (at your option) // any later version. // This library is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // Under Section 7 of GPL version 3, you are granted additional // permissions described in the GCC Runtime Library Exception, version // 3.1, as published by the Free Software Foundation. // You should have received a copy of the GNU General Public License and // a copy of the GCC Runtime Library Exception along with this program; // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see // <http://www.gnu.org/licenses/>. // GCC Note: Based on files from version 1.32.0 of the Boost library. // shared_count.hpp // Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd. // shared_ptr.hpp // Copyright (C) 1998, 1999 Greg Colvin and Beman Dawes. // Copyright (C) 2001, 2002, 2003 Peter Dimov // weak_ptr.hpp // Copyright (C) 2001, 2002, 2003 Peter Dimov // enable_shared_from_this.hpp // Copyright (C) 2002 Peter Dimov // Distributed under the Boost Software License, Version 1.0. (See // accompanying file LICENSE_1_0.txt or copy at // http://www.boost.org/LICENSE_1_0.txt) /** @file * This is an internal header file, included by other library headers. * Do not attempt to use it directly. @headername{memory} / #ifndef _SHARED_PTR_H #define _SHARED_PTR_H 1 #include <bits/shared_ptr_base.h> namespace std _GLIBCXX_VISIBILITY(default) { _GLIBCXX_BEGIN_NAMESPACE_VERSION /* * @addtogroup pointer_abstractions * @{ / /// 20.7.2.2.11 shared_ptr I/O template<typename _Ch, typename _Tr, typename _Tp, _Lock_policy _Lp> inline std::basic_ostream<_Ch, _Tr>& operator<<(std::basic_ostream<_Ch, _Tr>& __os, const __shared_ptr<_Tp, _Lp>& __p) { __os << __p.get(); return __os; } template<typename _Del, typename _Tp, _Lock_policy _Lp> inline _Del get_deleter(const __shared_ptr<_Tp, _Lp>& __p) noexcept { #if __cpp_rtti return static_cast<_Del>(__p._M_get_deleter(typeid(_Del))); #else return 0; #endif } /// 20.7.2.2.10 shared_ptr get_deleter template<typename _Del, typename _Tp> inline _Del get_deleter(const shared_ptr<_Tp>& __p) noexcept { #if __cpp_rtti return static_cast<_Del>(__p._M_get_deleter(typeid(_Del))); #else return 0; #endif } /* * @brief A smart pointer with reference-counted copy semantics. * * The object pointed to is deleted when the last shared_ptr pointing to * it is destroyed or reset. / template<typename _Tp> class shared_ptr : public __shared_ptr<_Tp> { template<typename... _Args> using _Constructible = typename enable_if< is_constructible<__shared_ptr<_Tp>, _Args...>::value >::type; template<typename _Arg> using _Assignable = typename enable_if< is_assignable<__shared_ptr<_Tp>&, _Arg>::value, shared_ptr& >::type; public: using element_type = typename __shared_ptr<_Tp>::element_type; #if __cplusplus > 201402L # define __cpp_lib_shared_ptr_weak_type 201606 using weak_type = weak_ptr<_Tp>; #endif /* * @brief Construct an empty %shared_ptr. * @post use_count()==0 && get()==0 / constexpr shared_ptr() noexcept : __shared_ptr<_Tp>() { } shared_ptr(const shared_ptr&) noexcept = default; /* * @brief Construct a %shared_ptr that owns the pointer @a __p. * @param __p A pointer that is convertible to element_type. @post use_count() == 1 && get() == __p * @throw std::bad_alloc, in which case @c delete @a __p is called. / template<typename _Yp, typename = _Constructible<_Yp>> explicit shared_ptr(_Yp* __p) : __shared_ptr<_Tp>(__p) { } /** * @brief Construct a %shared_ptr that owns the pointer @a __p * and the deleter @a __d. * @param __p A pointer. * @param __d A deleter. * @post use_count() == 1 && get() == __p * @throw std::bad_alloc, in which case @a __d(__p) is called. * * Requirements: _Deleter's copy constructor and destructor must * not throw * * __shared_ptr will release __p by calling __d(__p) / template<typename _Yp, typename _Deleter, typename = _Constructible<_Yp, _Deleter>> shared_ptr(_Yp* __p, _Deleter __d) : __shared_ptr<_Tp>(__p, std::move(__d)) { } /** * @brief Construct a %shared_ptr that owns a null pointer * and the deleter @a __d. * @param __p A null pointer constant. * @param __d A deleter. * @post use_count() == 1 && get() == __p * @throw std::bad_alloc, in which case @a __d(__p) is called. * * Requirements: _Deleter's copy constructor and destructor must * not throw * * The last owner will call __d(__p) / template<typename _Deleter> shared_ptr(nullptr_t __p, _Deleter __d) : __shared_ptr<_Tp>(__p, std::move(__d)) { } /* * @brief Construct a %shared_ptr that owns the pointer @a __p * and the deleter @a __d. * @param __p A pointer. * @param __d A deleter. * @param __a An allocator. * @post use_count() == 1 && get() == __p * @throw std::bad_alloc, in which case @a __d(__p) is called. * * Requirements: _Deleter's copy constructor and destructor must * not throw _Alloc's copy constructor and destructor must not * throw. * * __shared_ptr will release __p by calling __d(__p) / template<typename _Yp, typename _Deleter, typename _Alloc, typename = _Constructible<_Yp, _Deleter, _Alloc>> shared_ptr(_Yp* __p, _Deleter __d, _Alloc __a) : __shared_ptr<_Tp>(__p, std::move(__d), std::move(__a)) { } /** * @brief Construct a %shared_ptr that owns a null pointer * and the deleter @a __d. * @param __p A null pointer constant. * @param __d A deleter. * @param __a An allocator. * @post use_count() == 1 && get() == __p * @throw std::bad_alloc, in which case @a __d(__p) is called. * * Requirements: _Deleter's copy constructor and destructor must * not throw _Alloc's copy constructor and destructor must not * throw. * * The last owner will call __d(__p) / template<typename _Deleter, typename _Alloc> shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a) : __shared_ptr<_Tp>(__p, std::move(__d), std::move(__a)) { } // Aliasing constructor /* * @brief Constructs a %shared_ptr instance that stores @a __p * and shares ownership with @a __r. * @param __r A %shared_ptr. * @param __p A pointer that will remain valid while @a __r is valid. @post get() == __p && use_count() == __r.use_count() * * This can be used to construct a @c shared_ptr to a sub-object * of an object managed by an existing @c shared_ptr. * * @code * shared_ptr< pair<int,int> > pii(new pair<int,int>()); * shared_ptr<int> pi(pii, &pii->first); * assert(pii.use_count() == 2); * @endcode / template<typename _Yp> shared_ptr(const shared_ptr<_Yp>& __r, element_type __p) noexcept : __shared_ptr<_Tp>(__r, __p) { } /** * @brief If @a __r is empty, constructs an empty %shared_ptr; * otherwise construct a %shared_ptr that shares ownership * with @a __r. * @param __r A %shared_ptr. * @post get() == __r.get() && use_count() == __r.use_count() / template<typename _Yp, typename = _Constructible<const shared_ptr<_Yp>&>> shared_ptr(const shared_ptr<_Yp>& __r) noexcept : __shared_ptr<_Tp>(__r) { } /* * @brief Move-constructs a %shared_ptr instance from @a __r. * @param __r A %shared_ptr rvalue. * @post this contains the old value of @a __r, @a __r is empty. / shared_ptr(shared_ptr&& __r) noexcept : __shared_ptr<_Tp>(std::move(__r)) { } /** * @brief Move-constructs a %shared_ptr instance from @a __r. * @param __r A %shared_ptr rvalue. * @post this contains the old value of @a __r, @a __r is empty. / template<typename _Yp, typename = _Constructible<shared_ptr<_Yp>>> shared_ptr(shared_ptr<_Yp>&& __r) noexcept : __shared_ptr<_Tp>(std::move(__r)) { } /** * @brief Constructs a %shared_ptr that shares ownership with @a __r * and stores a copy of the pointer stored in @a __r. * @param __r A weak_ptr. * @post use_count() == __r.use_count() * @throw bad_weak_ptr when __r.expired(), * in which case the constructor has no effect. / template<typename _Yp, typename = _Constructible<const weak_ptr<_Yp>&>> explicit shared_ptr(const weak_ptr<_Yp>& __r) : __shared_ptr<_Tp>(__r) { } #if _GLIBCXX_USE_DEPRECATED #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Wdeprecated-declarations" template<typename _Yp, typename = _Constructible<auto_ptr<_Yp>>> shared_ptr(auto_ptr<_Yp>&& __r); #pragma GCC diagnostic pop #endif // _GLIBCXX_RESOLVE_LIB_DEFECTS // 2399. shared_ptr's constructor from unique_ptr should be constrained template<typename _Yp, typename _Del, typename = _Constructible<unique_ptr<_Yp, _Del>>> shared_ptr(unique_ptr<_Yp, _Del>&& __r) : __shared_ptr<_Tp>(std::move(__r)) { } #if __cplusplus <= 201402L && _GLIBCXX_USE_DEPRECATED // This non-standard constructor exists to support conversions that // were possible in C++11 and C++14 but are ill-formed in C++17. // If an exception is thrown this constructor has no effect. template<typename _Yp, typename _Del, _Constructible<unique_ptr<_Yp, _Del>, __sp_array_delete> = 0> shared_ptr(unique_ptr<_Yp, _Del>&& __r) : __shared_ptr<_Tp>(std::move(__r), __sp_array_delete()) { } #endif /** * @brief Construct an empty %shared_ptr. * @post use_count() == 0 && get() == nullptr / constexpr shared_ptr(nullptr_t) noexcept : shared_ptr() { } shared_ptr& operator=(const shared_ptr&) noexcept = default; template<typename _Yp> _Assignable<const shared_ptr<_Yp>&> operator=(const shared_ptr<_Yp>& __r) noexcept { this->__shared_ptr<_Tp>::operator=(__r); return this; } #if _GLIBCXX_USE_DEPRECATED #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Wdeprecated-declarations" template<typename _Yp> _Assignable<auto_ptr<_Yp>> operator=(auto_ptr<_Yp>&& __r) { this->__shared_ptr<_Tp>::operator=(std::move(__r)); return this; } #pragma GCC diagnostic pop #endif shared_ptr& operator=(shared_ptr&& __r) noexcept { this->__shared_ptr<_Tp>::operator=(std::move(__r)); return this; } template<class _Yp> _Assignable<shared_ptr<_Yp>> operator=(shared_ptr<_Yp>&& __r) noexcept { this->__shared_ptr<_Tp>::operator=(std::move(__r)); return this; } template<typename _Yp, typename _Del> _Assignable<unique_ptr<_Yp, _Del>> operator=(unique_ptr<_Yp, _Del>&& __r) { this->__shared_ptr<_Tp>::operator=(std::move(__r)); return this; } private: // This constructor is non-standard, it is used by allocate_shared. template<typename _Alloc, typename... _Args> shared_ptr(_Sp_alloc_shared_tag<_Alloc> __tag, _Args&&... __args) : __shared_ptr<_Tp>(__tag, std::forward<_Args>(__args)...) { } template<typename _Yp, typename _Alloc, typename... _Args> friend shared_ptr<_Yp> allocate_shared(const _Alloc& __a, _Args&&... __args); // This constructor is non-standard, it is used by weak_ptr::lock(). shared_ptr(const weak_ptr<_Tp>& __r, std::nothrow_t) : __shared_ptr<_Tp>(__r, std::nothrow) { } friend class weak_ptr<_Tp>; }; #if __cpp_deduction_guides >= 201606 template<typename _Tp> shared_ptr(weak_ptr<_Tp>) -> shared_ptr<_Tp>; template<typename _Tp, typename _Del> shared_ptr(unique_ptr<_Tp, _Del>) -> shared_ptr<_Tp>; #endif // 20.7.2.2.7 shared_ptr comparisons template<typename _Tp, typename _Up> inline bool operator==(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept { return __a.get() == __b.get(); } template<typename _Tp> inline bool operator==(const shared_ptr<_Tp>& __a, nullptr_t) noexcept { return !__a; } template<typename _Tp> inline bool operator==(nullptr_t, const shared_ptr<_Tp>& __a) noexcept { return !__a; } template<typename _Tp, typename _Up> inline bool operator!=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept { return __a.get() != __b.get(); } template<typename _Tp> inline bool operator!=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept { return (bool)__a; } template<typename _Tp> inline bool operator!=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept { return (bool)__a; } template<typename _Tp, typename _Up> inline bool operator<(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept { using _Tp_elt = typename shared_ptr<_Tp>::element_type; using _Up_elt = typename shared_ptr<_Up>::element_type; using _Vp = typename common_type<_Tp_elt, _Up_elt>::type; return less<_Vp>()(__a.get(), __b.get()); } template<typename _Tp> inline bool operator<(const shared_ptr<_Tp>& __a, nullptr_t) noexcept { using _Tp_elt = typename shared_ptr<_Tp>::element_type; return less<_Tp_elt>()(__a.get(), nullptr); } template<typename _Tp> inline bool operator<(nullptr_t, const shared_ptr<_Tp>& __a) noexcept { using _Tp_elt = typename shared_ptr<_Tp>::element_type; return less<_Tp_elt>()(nullptr, __a.get()); } template<typename _Tp, typename _Up> inline bool operator<=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept { return !(__b < __a); } template<typename _Tp> inline bool operator<=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept { return !(nullptr < __a); } template<typename _Tp> inline bool operator<=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept { return !(__a < nullptr); } template<typename _Tp, typename _Up> inline bool operator>(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept { return (__b < __a); } template<typename _Tp> inline bool operator>(const shared_ptr<_Tp>& __a, nullptr_t) noexcept { return nullptr < __a; } template<typename _Tp> inline bool operator>(nullptr_t, const shared_ptr<_Tp>& __a) noexcept { return __a < nullptr; } template<typename _Tp, typename _Up> inline bool operator>=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept { return !(__a < __b); } template<typename _Tp> inline bool operator>=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept { return !(__a < nullptr); } template<typename _Tp> inline bool operator>=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept { return !(nullptr < __a); } template<typename _Tp> struct less<shared_ptr<_Tp>> : public _Sp_less<shared_ptr<_Tp>> { }; // 20.7.2.2.8 shared_ptr specialized algorithms. template<typename _Tp> inline void swap(shared_ptr<_Tp>& __a, shared_ptr<_Tp>& __b) noexcept { __a.swap(__b); } // 20.7.2.2.9 shared_ptr casts. template<typename _Tp, typename _Up> inline shared_ptr<_Tp> static_pointer_cast(const shared_ptr<_Up>& __r) noexcept { using _Sp = shared_ptr<_Tp>; return _Sp(__r, static_cast<typename _Sp::element_type>(__r.get())); } template<typename _Tp, typename _Up> inline shared_ptr<_Tp> const_pointer_cast(const shared_ptr<_Up>& __r) noexcept { using _Sp = shared_ptr<_Tp>; return _Sp(__r, const_cast<typename _Sp::element_type>(__r.get())); } template<typename _Tp, typename _Up> inline shared_ptr<_Tp> dynamic_pointer_cast(const shared_ptr<_Up>& __r) noexcept { using _Sp = shared_ptr<_Tp>; if (auto* __p = dynamic_cast<typename _Sp::element_type>(__r.get())) return _Sp(__r, __p); return _Sp(); } #if __cplusplus > 201402L template<typename _Tp, typename _Up> inline shared_ptr<_Tp> reinterpret_pointer_cast(const shared_ptr<_Up>& __r) noexcept { using _Sp = shared_ptr<_Tp>; return _Sp(__r, reinterpret_cast<typename _Sp::element_type>(__r.get())); } #endif /** * @brief A smart pointer with weak semantics. * * With forwarding constructors and assignment operators. / template<typename _Tp> class weak_ptr : public __weak_ptr<_Tp> { template<typename _Arg> using _Constructible = typename enable_if< is_constructible<__weak_ptr<_Tp>, _Arg>::value >::type; template<typename _Arg> using _Assignable = typename enable_if< is_assignable<__weak_ptr<_Tp>&, _Arg>::value, weak_ptr& >::type; public: constexpr weak_ptr() noexcept = default; template<typename _Yp, typename = _Constructible<const shared_ptr<_Yp>&>> weak_ptr(const shared_ptr<_Yp>& __r) noexcept : __weak_ptr<_Tp>(__r) { } weak_ptr(const weak_ptr&) noexcept = default; template<typename _Yp, typename = _Constructible<const weak_ptr<_Yp>&>> weak_ptr(const weak_ptr<_Yp>& __r) noexcept : __weak_ptr<_Tp>(__r) { } weak_ptr(weak_ptr&&) noexcept = default; template<typename _Yp, typename = _Constructible<weak_ptr<_Yp>>> weak_ptr(weak_ptr<_Yp>&& __r) noexcept : __weak_ptr<_Tp>(std::move(__r)) { } weak_ptr& operator=(const weak_ptr& __r) noexcept = default; template<typename _Yp> _Assignable<const weak_ptr<_Yp>&> operator=(const weak_ptr<_Yp>& __r) noexcept { this->__weak_ptr<_Tp>::operator=(__r); return this; } template<typename _Yp> _Assignable<const shared_ptr<_Yp>&> operator=(const shared_ptr<_Yp>& __r) noexcept { this->__weak_ptr<_Tp>::operator=(__r); return this; } weak_ptr& operator=(weak_ptr&& __r) noexcept = default; template<typename _Yp> _Assignable<weak_ptr<_Yp>> operator=(weak_ptr<_Yp>&& __r) noexcept { this->__weak_ptr<_Tp>::operator=(std::move(__r)); return this; } shared_ptr<_Tp> lock() const noexcept { return shared_ptr<_Tp>(this, std::nothrow); } }; #if __cpp_deduction_guides >= 201606 template<typename _Tp> weak_ptr(shared_ptr<_Tp>) -> weak_ptr<_Tp>; #endif // 20.7.2.3.6 weak_ptr specialized algorithms. template<typename _Tp> inline void swap(weak_ptr<_Tp>& __a, weak_ptr<_Tp>& __b) noexcept { __a.swap(__b); } /// Primary template owner_less template<typename _Tp = void> struct owner_less; /// Void specialization of owner_less template<> struct owner_less<void> : _Sp_owner_less<void, void> { }; /// Partial specialization of owner_less for shared_ptr. template<typename _Tp> struct owner_less<shared_ptr<_Tp>> : public _Sp_owner_less<shared_ptr<_Tp>, weak_ptr<_Tp>> { }; /// Partial specialization of owner_less for weak_ptr. template<typename _Tp> struct owner_less<weak_ptr<_Tp>> : public _Sp_owner_less<weak_ptr<_Tp>, shared_ptr<_Tp>> { }; /* * @brief Base class allowing use of member function shared_from_this. / template<typename _Tp> class enable_shared_from_this { protected: constexpr enable_shared_from_this() noexcept { } enable_shared_from_this(const enable_shared_from_this&) noexcept { } enable_shared_from_this& operator=(const enable_shared_from_this&) noexcept { return this; } ~enable_shared_from_this() { } public: shared_ptr<_Tp> shared_from_this() { return shared_ptr<_Tp>(this->_M_weak_this); } shared_ptr<const _Tp> shared_from_this() const { return shared_ptr<const _Tp>(this->_M_weak_this); } #if __cplusplus > 201402L \|\| !defined(__STRICT_ANSI__) // c++1z or gnu++11 #define __cpp_lib_enable_shared_from_this 201603 weak_ptr<_Tp> weak_from_this() noexcept { return this->_M_weak_this; } weak_ptr<const _Tp> weak_from_this() const noexcept { return this->_M_weak_this; } #endif private: template<typename _Tp1> void _M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const noexcept { _M_weak_this._M_assign(__p, __n); } // Found by ADL when this is an associated class. friend const enable_shared_from_this* __enable_shared_from_this_base(const __shared_count<>&, const enable_shared_from_this* __p) { return __p; } template<typename, _Lock_policy> friend class __shared_ptr; mutable weak_ptr<_Tp> _M_weak_this; }; /** * @brief Create an object that is owned by a shared_ptr. * @param __a An allocator. * @param __args Arguments for the @a _Tp object's constructor. * @return A shared_ptr that owns the newly created object. * @throw An exception thrown from @a _Alloc::allocate or from the * constructor of @a _Tp. * * A copy of @a __a will be used to allocate memory for the shared_ptr * and the new object. / template<typename _Tp, typename _Alloc, typename... _Args> inline shared_ptr<_Tp> allocate_shared(const _Alloc& __a, _Args&&... __args) { static_assert(!is_array<_Tp>::value, "make_shared<T[]> not supported"); return shared_ptr<_Tp>(_Sp_alloc_shared_tag<_Alloc>{__a}, std::forward<_Args>(__args)...); } /* * @brief Create an object that is owned by a shared_ptr. * @param __args Arguments for the @a _Tp object's constructor. * @return A shared_ptr that owns the newly created object. * @throw std::bad_alloc, or an exception thrown from the * constructor of @a _Tp. / template<typename _Tp, typename... _Args> inline shared_ptr<_Tp> make_shared(_Args&&... __args) { typedef typename std::remove_cv<_Tp>::type _Tp_nc; return std::allocate_shared<_Tp>(std::allocator<_Tp_nc>(), std::forward<_Args>(__args)...); } /// std::hash specialization for shared_ptr. template<typename _Tp> struct hash<shared_ptr<_Tp>> : public __hash_base<size_t, shared_ptr<_Tp>> { size_t operator()(const shared_ptr<_Tp>& __s) const noexcept { return std::hash<typename shared_ptr<_Tp>::element_type>()(__s.get()); } }; // @} group pointer_abstractions _GLIBCXX_END_NAMESPACE_VERSION } // namespace #endif // _SHARED_PTR_H Back

Edit File : shared_ptr.h | Size : 22.88 KB

// shared_ptr and weak_ptr implementation -*- C++ -*-

// Copyright (C) 2007-2018 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

// GCC Note: Based on files from version 1.32.0 of the Boost library.

//  shared_count.hpp
//  Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd.

//  shared_ptr.hpp
//  Copyright (C) 1998, 1999 Greg Colvin and Beman Dawes.
//  Copyright (C) 2001, 2002, 2003 Peter Dimov

//  weak_ptr.hpp
//  Copyright (C) 2001, 2002, 2003 Peter Dimov

//  enable_shared_from_this.hpp
//  Copyright (C) 2002 Peter Dimov

// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)

/** @file
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{memory}
 */

#ifndef _SHARED_PTR_H
#define _SHARED_PTR_H 1

#include <bits/shared_ptr_base.h>

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

/**
   * @addtogroup pointer_abstractions
   * @{
   */

/// 20.7.2.2.11 shared_ptr I/O
  template<typename _Ch, typename _Tr, typename _Tp, _Lock_policy _Lp>
    inline std::basic_ostream<_Ch, _Tr>&
    operator<<(std::basic_ostream<_Ch, _Tr>& __os,
	       const __shared_ptr<_Tp, _Lp>& __p)
    {
      __os << __p.get();
      return __os;
    }

template<typename _Del, typename _Tp, _Lock_policy _Lp>
    inline _Del*
    get_deleter(const __shared_ptr<_Tp, _Lp>& __p) noexcept
    {
#if __cpp_rtti
      return static_cast<_Del*>(__p._M_get_deleter(typeid(_Del)));
#else
      return 0;
#endif
    }

/// 20.7.2.2.10 shared_ptr get_deleter
  template<typename _Del, typename _Tp>
    inline _Del*
    get_deleter(const shared_ptr<_Tp>& __p) noexcept
    {
#if __cpp_rtti
      return static_cast<_Del*>(__p._M_get_deleter(typeid(_Del)));
#else
      return 0;
#endif
    }

/**
   *  @brief  A smart pointer with reference-counted copy semantics.
   *
   *  The object pointed to is deleted when the last shared_ptr pointing to
   *  it is destroyed or reset.
  */
  template<typename _Tp>
    class shared_ptr : public __shared_ptr<_Tp>
    {
      template<typename... _Args>
	using _Constructible = typename enable_if<
	  is_constructible<__shared_ptr<_Tp>, _Args...>::value
	>::type;

template<typename _Arg>
	using _Assignable = typename enable_if<
	  is_assignable<__shared_ptr<_Tp>&, _Arg>::value, shared_ptr&
	>::type;

public:

using element_type = typename __shared_ptr<_Tp>::element_type;

#if __cplusplus > 201402L
# define __cpp_lib_shared_ptr_weak_type 201606
      using weak_type = weak_ptr<_Tp>;
#endif
      /**
       *  @brief  Construct an empty %shared_ptr.
       *  @post   use_count()==0 && get()==0
       */
      constexpr shared_ptr() noexcept : __shared_ptr<_Tp>() { }

shared_ptr(const shared_ptr&) noexcept = default;

/**
       *  @brief  Construct a %shared_ptr that owns the pointer @a __p.
       *  @param  __p  A pointer that is convertible to element_type*.
       *  @post   use_count() == 1 && get() == __p
       *  @throw  std::bad_alloc, in which case @c delete @a __p is called.
       */
      template<typename _Yp, typename = _Constructible<_Yp*>>
	explicit
	shared_ptr(_Yp* __p) : __shared_ptr<_Tp>(__p) { }

/**
       *  @brief  Construct a %shared_ptr that owns the pointer @a __p
       *          and the deleter @a __d.
       *  @param  __p  A pointer.
       *  @param  __d  A deleter.
       *  @post   use_count() == 1 && get() == __p
       *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
       *
       *  Requirements: _Deleter's copy constructor and destructor must
       *  not throw
       *
       *  __shared_ptr will release __p by calling __d(__p)
       */
      template<typename _Yp, typename _Deleter,
	       typename = _Constructible<_Yp*, _Deleter>>
	shared_ptr(_Yp* __p, _Deleter __d)
        : __shared_ptr<_Tp>(__p, std::move(__d)) { }

/**
       *  @brief  Construct a %shared_ptr that owns a null pointer
       *          and the deleter @a __d.
       *  @param  __p  A null pointer constant.
       *  @param  __d  A deleter.
       *  @post   use_count() == 1 && get() == __p
       *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
       *
       *  Requirements: _Deleter's copy constructor and destructor must
       *  not throw
       *
       *  The last owner will call __d(__p)
       */
      template<typename _Deleter>
	shared_ptr(nullptr_t __p, _Deleter __d)
        : __shared_ptr<_Tp>(__p, std::move(__d)) { }

/**
       *  @brief  Construct a %shared_ptr that owns the pointer @a __p
       *          and the deleter @a __d.
       *  @param  __p  A pointer.
       *  @param  __d  A deleter.
       *  @param  __a  An allocator.
       *  @post   use_count() == 1 && get() == __p
       *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
       *
       *  Requirements: _Deleter's copy constructor and destructor must
       *  not throw _Alloc's copy constructor and destructor must not
       *  throw.
       *
       *  __shared_ptr will release __p by calling __d(__p)
       */
      template<typename _Yp, typename _Deleter, typename _Alloc,
	       typename = _Constructible<_Yp*, _Deleter, _Alloc>>
	shared_ptr(_Yp* __p, _Deleter __d, _Alloc __a)
	: __shared_ptr<_Tp>(__p, std::move(__d), std::move(__a)) { }

/**
       *  @brief  Construct a %shared_ptr that owns a null pointer
       *          and the deleter @a __d.
       *  @param  __p  A null pointer constant.
       *  @param  __d  A deleter.
       *  @param  __a  An allocator.
       *  @post   use_count() == 1 && get() == __p
       *  @throw  std::bad_alloc, in which case @a __d(__p) is called.
       *
       *  Requirements: _Deleter's copy constructor and destructor must
       *  not throw _Alloc's copy constructor and destructor must not
       *  throw.
       *
       *  The last owner will call __d(__p)
       */
      template<typename _Deleter, typename _Alloc>
	shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
	: __shared_ptr<_Tp>(__p, std::move(__d), std::move(__a)) { }

// Aliasing constructor

/**
       *  @brief  Constructs a %shared_ptr instance that stores @a __p
       *          and shares ownership with @a __r.
       *  @param  __r  A %shared_ptr.
       *  @param  __p  A pointer that will remain valid while @a *__r is valid.
       *  @post   get() == __p && use_count() == __r.use_count()
       *
       *  This can be used to construct a @c shared_ptr to a sub-object
       *  of an object managed by an existing @c shared_ptr.
       *
       * @code
       * shared_ptr< pair<int,int> > pii(new pair<int,int>());
       * shared_ptr<int> pi(pii, &pii->first);
       * assert(pii.use_count() == 2);
       * @endcode
       */
      template<typename _Yp>
	shared_ptr(const shared_ptr<_Yp>& __r, element_type* __p) noexcept
	: __shared_ptr<_Tp>(__r, __p) { }

/**
       *  @brief  If @a __r is empty, constructs an empty %shared_ptr;
       *          otherwise construct a %shared_ptr that shares ownership
       *          with @a __r.
       *  @param  __r  A %shared_ptr.
       *  @post   get() == __r.get() && use_count() == __r.use_count()
       */
      template<typename _Yp,
	       typename = _Constructible<const shared_ptr<_Yp>&>>
	shared_ptr(const shared_ptr<_Yp>& __r) noexcept
        : __shared_ptr<_Tp>(__r) { }

/**
       *  @brief  Move-constructs a %shared_ptr instance from @a __r.
       *  @param  __r  A %shared_ptr rvalue.
       *  @post   *this contains the old value of @a __r, @a __r is empty.
       */
      shared_ptr(shared_ptr&& __r) noexcept
      : __shared_ptr<_Tp>(std::move(__r)) { }

/**
       *  @brief  Move-constructs a %shared_ptr instance from @a __r.
       *  @param  __r  A %shared_ptr rvalue.
       *  @post   *this contains the old value of @a __r, @a __r is empty.
       */
      template<typename _Yp, typename = _Constructible<shared_ptr<_Yp>>>
	shared_ptr(shared_ptr<_Yp>&& __r) noexcept
	: __shared_ptr<_Tp>(std::move(__r)) { }

/**
       *  @brief  Constructs a %shared_ptr that shares ownership with @a __r
       *          and stores a copy of the pointer stored in @a __r.
       *  @param  __r  A weak_ptr.
       *  @post   use_count() == __r.use_count()
       *  @throw  bad_weak_ptr when __r.expired(),
       *          in which case the constructor has no effect.
       */
      template<typename _Yp, typename = _Constructible<const weak_ptr<_Yp>&>>
	explicit shared_ptr(const weak_ptr<_Yp>& __r)
	: __shared_ptr<_Tp>(__r) { }

#if _GLIBCXX_USE_DEPRECATED
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
      template<typename _Yp, typename = _Constructible<auto_ptr<_Yp>>>
	shared_ptr(auto_ptr<_Yp>&& __r);
#pragma GCC diagnostic pop
#endif

// _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 2399. shared_ptr's constructor from unique_ptr should be constrained
      template<typename _Yp, typename _Del,
	       typename = _Constructible<unique_ptr<_Yp, _Del>>>
	shared_ptr(unique_ptr<_Yp, _Del>&& __r)
	: __shared_ptr<_Tp>(std::move(__r)) { }

#if __cplusplus <= 201402L && _GLIBCXX_USE_DEPRECATED
      // This non-standard constructor exists to support conversions that
      // were possible in C++11 and C++14 but are ill-formed in C++17.
      // If an exception is thrown this constructor has no effect.
      template<typename _Yp, typename _Del,
		_Constructible<unique_ptr<_Yp, _Del>, __sp_array_delete>* = 0>
	shared_ptr(unique_ptr<_Yp, _Del>&& __r)
	: __shared_ptr<_Tp>(std::move(__r), __sp_array_delete()) { }
#endif

/**
       *  @brief  Construct an empty %shared_ptr.
       *  @post   use_count() == 0 && get() == nullptr
       */
      constexpr shared_ptr(nullptr_t) noexcept : shared_ptr() { }

shared_ptr& operator=(const shared_ptr&) noexcept = default;

template<typename _Yp>
	_Assignable<const shared_ptr<_Yp>&>
	operator=(const shared_ptr<_Yp>& __r) noexcept
	{
	  this->__shared_ptr<_Tp>::operator=(__r);
	  return *this;
	}

#if _GLIBCXX_USE_DEPRECATED
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
      template<typename _Yp>
	_Assignable<auto_ptr<_Yp>>
	operator=(auto_ptr<_Yp>&& __r)
	{
	  this->__shared_ptr<_Tp>::operator=(std::move(__r));
	  return *this;
	}
#pragma GCC diagnostic pop
#endif

shared_ptr&
      operator=(shared_ptr&& __r) noexcept
      {
	this->__shared_ptr<_Tp>::operator=(std::move(__r));
	return *this;
      }

template<class _Yp>
	_Assignable<shared_ptr<_Yp>>
	operator=(shared_ptr<_Yp>&& __r) noexcept
	{
	  this->__shared_ptr<_Tp>::operator=(std::move(__r));
	  return *this;
	}

template<typename _Yp, typename _Del>
	_Assignable<unique_ptr<_Yp, _Del>>
	operator=(unique_ptr<_Yp, _Del>&& __r)
	{
	  this->__shared_ptr<_Tp>::operator=(std::move(__r));
	  return *this;
	}

private:
      // This constructor is non-standard, it is used by allocate_shared.
      template<typename _Alloc, typename... _Args>
	shared_ptr(_Sp_alloc_shared_tag<_Alloc> __tag, _Args&&... __args)
	: __shared_ptr<_Tp>(__tag, std::forward<_Args>(__args)...)
	{ }

template<typename _Yp, typename _Alloc, typename... _Args>
	friend shared_ptr<_Yp>
	allocate_shared(const _Alloc& __a, _Args&&... __args);

// This constructor is non-standard, it is used by weak_ptr::lock().
      shared_ptr(const weak_ptr<_Tp>& __r, std::nothrow_t)
      : __shared_ptr<_Tp>(__r, std::nothrow) { }

friend class weak_ptr<_Tp>;
    };

#if __cpp_deduction_guides >= 201606
  template<typename _Tp>
    shared_ptr(weak_ptr<_Tp>) ->  shared_ptr<_Tp>;
  template<typename _Tp, typename _Del>
    shared_ptr(unique_ptr<_Tp, _Del>) ->  shared_ptr<_Tp>;
#endif

// 20.7.2.2.7 shared_ptr comparisons
  template<typename _Tp, typename _Up>
    inline bool
    operator==(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
    { return __a.get() == __b.get(); }

template<typename _Tp>
    inline bool
    operator==(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
    { return !__a; }

template<typename _Tp>
    inline bool
    operator==(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
    { return !__a; }

template<typename _Tp, typename _Up>
    inline bool
    operator!=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
    { return __a.get() != __b.get(); }

template<typename _Tp>
    inline bool
    operator!=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
    { return (bool)__a; }

template<typename _Tp>
    inline bool
    operator!=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
    { return (bool)__a; }

template<typename _Tp, typename _Up>
    inline bool
    operator<(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
    {
      using _Tp_elt = typename shared_ptr<_Tp>::element_type;
      using _Up_elt = typename shared_ptr<_Up>::element_type;
      using _Vp = typename common_type<_Tp_elt*, _Up_elt*>::type;
      return less<_Vp>()(__a.get(), __b.get());
    }

template<typename _Tp>
    inline bool
    operator<(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
    {
      using _Tp_elt = typename shared_ptr<_Tp>::element_type;
      return less<_Tp_elt*>()(__a.get(), nullptr);
    }

template<typename _Tp>
    inline bool
    operator<(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
    {
      using _Tp_elt = typename shared_ptr<_Tp>::element_type;
      return less<_Tp_elt*>()(nullptr, __a.get());
    }

template<typename _Tp, typename _Up>
    inline bool
    operator<=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
    { return !(__b < __a); }

template<typename _Tp>
    inline bool
    operator<=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
    { return !(nullptr < __a); }

template<typename _Tp>
    inline bool
    operator<=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
    { return !(__a < nullptr); }

template<typename _Tp, typename _Up>
    inline bool
    operator>(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
    { return (__b < __a); }

template<typename _Tp>
    inline bool
    operator>(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
    { return nullptr < __a; }

template<typename _Tp>
    inline bool
    operator>(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
    { return __a < nullptr; }

template<typename _Tp, typename _Up>
    inline bool
    operator>=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
    { return !(__a < __b); }

template<typename _Tp>
    inline bool
    operator>=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
    { return !(__a < nullptr); }

template<typename _Tp>
    inline bool
    operator>=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
    { return !(nullptr < __a); }

template<typename _Tp>
    struct less<shared_ptr<_Tp>> : public _Sp_less<shared_ptr<_Tp>>
    { };

// 20.7.2.2.8 shared_ptr specialized algorithms.
  template<typename _Tp>
    inline void
    swap(shared_ptr<_Tp>& __a, shared_ptr<_Tp>& __b) noexcept
    { __a.swap(__b); }

// 20.7.2.2.9 shared_ptr casts.
  template<typename _Tp, typename _Up>
    inline shared_ptr<_Tp>
    static_pointer_cast(const shared_ptr<_Up>& __r) noexcept
    {
      using _Sp = shared_ptr<_Tp>;
      return _Sp(__r, static_cast<typename _Sp::element_type*>(__r.get()));
    }

template<typename _Tp, typename _Up>
    inline shared_ptr<_Tp>
    const_pointer_cast(const shared_ptr<_Up>& __r) noexcept
    {
      using _Sp = shared_ptr<_Tp>;
      return _Sp(__r, const_cast<typename _Sp::element_type*>(__r.get()));
    }

template<typename _Tp, typename _Up>
    inline shared_ptr<_Tp>
    dynamic_pointer_cast(const shared_ptr<_Up>& __r) noexcept
    {
      using _Sp = shared_ptr<_Tp>;
      if (auto* __p = dynamic_cast<typename _Sp::element_type*>(__r.get()))
	return _Sp(__r, __p);
      return _Sp();
    }

#if __cplusplus > 201402L
  template<typename _Tp, typename _Up>
    inline shared_ptr<_Tp>
    reinterpret_pointer_cast(const shared_ptr<_Up>& __r) noexcept
    {
      using _Sp = shared_ptr<_Tp>;
      return _Sp(__r, reinterpret_cast<typename _Sp::element_type*>(__r.get()));
    }
#endif

/**
   *  @brief  A smart pointer with weak semantics.
   *
   *  With forwarding constructors and assignment operators.
   */
  template<typename _Tp>
    class weak_ptr : public __weak_ptr<_Tp>
    {
      template<typename _Arg>
	using _Constructible = typename enable_if<
	  is_constructible<__weak_ptr<_Tp>, _Arg>::value
	>::type;

template<typename _Arg>
	using _Assignable = typename enable_if<
	  is_assignable<__weak_ptr<_Tp>&, _Arg>::value, weak_ptr&
	>::type;

public:
      constexpr weak_ptr() noexcept = default;

template<typename _Yp,
	       typename = _Constructible<const shared_ptr<_Yp>&>>
	weak_ptr(const shared_ptr<_Yp>& __r) noexcept
	: __weak_ptr<_Tp>(__r) { }

weak_ptr(const weak_ptr&) noexcept = default;

template<typename _Yp, typename = _Constructible<const weak_ptr<_Yp>&>>
	weak_ptr(const weak_ptr<_Yp>& __r) noexcept
	: __weak_ptr<_Tp>(__r) { }

weak_ptr(weak_ptr&&) noexcept = default;

template<typename _Yp, typename = _Constructible<weak_ptr<_Yp>>>
	weak_ptr(weak_ptr<_Yp>&& __r) noexcept
	: __weak_ptr<_Tp>(std::move(__r)) { }

weak_ptr&
      operator=(const weak_ptr& __r) noexcept = default;

template<typename _Yp>
	_Assignable<const weak_ptr<_Yp>&>
	operator=(const weak_ptr<_Yp>& __r) noexcept
	{
	  this->__weak_ptr<_Tp>::operator=(__r);
	  return *this;
	}

template<typename _Yp>
	_Assignable<const shared_ptr<_Yp>&>
	operator=(const shared_ptr<_Yp>& __r) noexcept
	{
	  this->__weak_ptr<_Tp>::operator=(__r);
	  return *this;
	}

weak_ptr&
      operator=(weak_ptr&& __r) noexcept = default;

template<typename _Yp>
	_Assignable<weak_ptr<_Yp>>
	operator=(weak_ptr<_Yp>&& __r) noexcept
	{
	  this->__weak_ptr<_Tp>::operator=(std::move(__r));
	  return *this;
	}

shared_ptr<_Tp>
      lock() const noexcept
      { return shared_ptr<_Tp>(*this, std::nothrow); }
    };

#if __cpp_deduction_guides >= 201606
  template<typename _Tp>
    weak_ptr(shared_ptr<_Tp>) ->  weak_ptr<_Tp>;
#endif

// 20.7.2.3.6 weak_ptr specialized algorithms.
  template<typename _Tp>
    inline void
    swap(weak_ptr<_Tp>& __a, weak_ptr<_Tp>& __b) noexcept
    { __a.swap(__b); }

/// Primary template owner_less
  template<typename _Tp = void>
    struct owner_less;

/// Void specialization of owner_less
  template<>
    struct owner_less<void> : _Sp_owner_less<void, void>
    { };

/// Partial specialization of owner_less for shared_ptr.
  template<typename _Tp>
    struct owner_less<shared_ptr<_Tp>>
    : public _Sp_owner_less<shared_ptr<_Tp>, weak_ptr<_Tp>>
    { };

/// Partial specialization of owner_less for weak_ptr.
  template<typename _Tp>
    struct owner_less<weak_ptr<_Tp>>
    : public _Sp_owner_less<weak_ptr<_Tp>, shared_ptr<_Tp>>
    { };

/**
   *  @brief Base class allowing use of member function shared_from_this.
   */
  template<typename _Tp>
    class enable_shared_from_this
    {
    protected:
      constexpr enable_shared_from_this() noexcept { }

enable_shared_from_this(const enable_shared_from_this&) noexcept { }

enable_shared_from_this&
      operator=(const enable_shared_from_this&) noexcept
      { return *this; }

~enable_shared_from_this() { }

public:
      shared_ptr<_Tp>
      shared_from_this()
      { return shared_ptr<_Tp>(this->_M_weak_this); }

shared_ptr<const _Tp>
      shared_from_this() const
      { return shared_ptr<const _Tp>(this->_M_weak_this); }

#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
#define __cpp_lib_enable_shared_from_this 201603
      weak_ptr<_Tp>
      weak_from_this() noexcept
      { return this->_M_weak_this; }

weak_ptr<const _Tp>
      weak_from_this() const noexcept
      { return this->_M_weak_this; }
#endif

private:
      template<typename _Tp1>
	void
	_M_weak_assign(_Tp1* __p, const __shared_count<>& __n) const noexcept
	{ _M_weak_this._M_assign(__p, __n); }

// Found by ADL when this is an associated class.
      friend const enable_shared_from_this*
      __enable_shared_from_this_base(const __shared_count<>&,
				     const enable_shared_from_this* __p)
      { return __p; }

template<typename, _Lock_policy>
	friend class __shared_ptr;

mutable weak_ptr<_Tp>  _M_weak_this;
    };

/**
   *  @brief  Create an object that is owned by a shared_ptr.
   *  @param  __a     An allocator.
   *  @param  __args  Arguments for the @a _Tp object's constructor.
   *  @return A shared_ptr that owns the newly created object.
   *  @throw  An exception thrown from @a _Alloc::allocate or from the
   *          constructor of @a _Tp.
   *
   *  A copy of @a __a will be used to allocate memory for the shared_ptr
   *  and the new object.
   */
  template<typename _Tp, typename _Alloc, typename... _Args>
    inline shared_ptr<_Tp>
    allocate_shared(const _Alloc& __a, _Args&&... __args)
    {
      static_assert(!is_array<_Tp>::value, "make_shared<T[]> not supported");

return shared_ptr<_Tp>(_Sp_alloc_shared_tag<_Alloc>{__a},
			     std::forward<_Args>(__args)...);
    }

/**
   *  @brief  Create an object that is owned by a shared_ptr.
   *  @param  __args  Arguments for the @a _Tp object's constructor.
   *  @return A shared_ptr that owns the newly created object.
   *  @throw  std::bad_alloc, or an exception thrown from the
   *          constructor of @a _Tp.
   */
  template<typename _Tp, typename... _Args>
    inline shared_ptr<_Tp>
    make_shared(_Args&&... __args)
    {
      typedef typename std::remove_cv<_Tp>::type _Tp_nc;
      return std::allocate_shared<_Tp>(std::allocator<_Tp_nc>(),
				       std::forward<_Args>(__args)...);
    }

/// std::hash specialization for shared_ptr.
  template<typename _Tp>
    struct hash<shared_ptr<_Tp>>
    : public __hash_base<size_t, shared_ptr<_Tp>>
    {
      size_t
      operator()(const shared_ptr<_Tp>& __s) const noexcept
      {
	return std::hash<typename shared_ptr<_Tp>::element_type*>()(__s.get());
      }
    };

// @} group pointer_abstractions

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace

#endif // _SHARED_PTR_H

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