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shared_ptr.h
// shared_ptr and weak_ptr implementation -*- C++ -*- // Copyright (C) 2007-2022 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 <iosfwd> // std::basic_ostream #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 /// Write the stored pointer to an ostream. /// @relates shared_ptr 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 /// If `__p` has a deleter of type `_Del`, return a pointer to it. /// @relates shared_ptr 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 } /// @cond undocumented // Constraint for overloads taking non-array types. #if __cpp_concepts && __cpp_lib_type_trait_variable_templates template<typename _Tp> requires (!is_array_v<_Tp>) using _NonArray = _Tp; #else template<typename _Tp> using _NonArray = __enable_if_t<!is_array<_Tp>::value, _Tp>; #endif #if __cpp_lib_shared_ptr_arrays >= 201707L // Constraint for overloads taking array types with unknown bound, U[]. #if __cpp_concepts template<typename _Tp> requires is_array_v<_Tp> && (extent_v<_Tp> == 0) using _UnboundedArray = _Tp; #else template<typename _Tp> using _UnboundedArray = __enable_if_t<__is_array_unknown_bounds<_Tp>::value, _Tp>; #endif // Constraint for overloads taking array types with known bound, U[N]. #if __cpp_concepts template<typename _Tp> requires (extent_v<_Tp> != 0) using _BoundedArray = _Tp; #else template<typename _Tp> using _BoundedArray = __enable_if_t<__is_array_known_bounds<_Tp>::value, _Tp>; #endif #if __cpp_lib_smart_ptr_for_overwrite // Constraint for overloads taking either non-array or bounded array, U[N]. #if __cpp_concepts template<typename _Tp> requires (!is_array_v<_Tp>) || (extent_v<_Tp> != 0) using _NotUnboundedArray = _Tp; #else template<typename _Tp> using _NotUnboundedArray = __enable_if_t<!__is_array_unknown_bounds<_Tp>::value, _Tp>; #endif #endif // smart_ptr_for_overwrite #endif // shared_ptr_arrays /// @endcond /** * @brief A smart pointer with reference-counted copy semantics. * @headerfile memory * @since C++11 * * A `shared_ptr` object is either empty or _owns_ a pointer passed * to the constructor. Copies of a `shared_ptr` share ownership of * the same pointer. When the last `shared_ptr` that owns the pointer * is destroyed or reset, the owned pointer is freed (either by `delete` * or by invoking a custom deleter that was passed to the constructor). * * A `shared_ptr` also stores another pointer, which is usually * (but not always) the same pointer as it owns. The stored pointer * can be retrieved by calling the `get()` member function. * * The equality and relational operators for `shared_ptr` only compare * the stored pointer returned by `get()`, not the owned pointer. * To test whether two `shared_ptr` objects share ownership of the same * pointer see `std::shared_ptr::owner_before` and `std::owner_less`. */ 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: /// The type pointed to by the stored pointer, remove_extent_t<_Tp> using element_type = typename __shared_ptr<_Tp>::element_type; #if __cplusplus >= 201703L # define __cpp_lib_shared_ptr_weak_type 201606L /// The corresponding weak_ptr type for this shared_ptr /// @since C++17 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; ///< Copy constructor /** * @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 `__p` * and shares ownership with `__r`. * @param __r A `shared_ptr`. * @param __p A pointer that will remain valid while `*__r` is valid. * @post `get() == __p && use_count() == __r.use_count()` * * This can be used to construct a `shared_ptr` to a sub-object * of an object managed by an existing `shared_ptr`. The complete * object will remain valid while any `shared_ptr` owns it, even * if they don't store a pointer to the complete object. * * @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) { } #if __cplusplus > 201703L // _GLIBCXX_RESOLVE_LIB_DEFECTS // 2996. Missing rvalue overloads for shared_ptr operations /** * @brief Constructs a `shared_ptr` instance that stores `__p` * and shares ownership with `__r`. * @param __r A `shared_ptr`. * @param __p A pointer that will remain valid while `*__r` is valid. * @post `get() == __p && !__r.use_count() && !__r.get()` * @since C++17 * * This can be used to construct a `shared_ptr` to a sub-object * of an object managed by an existing `shared_ptr`. The complete * object will remain valid while any `shared_ptr` owns it, even * if they don't store a pointer to the complete object. * * @code * shared_ptr<pair<int,int>> pii(new pair<int,int>()); * shared_ptr<int> pi1(pii, &pii->first); * assert(pii.use_count() == 2); * shared_ptr<int> pi2(std::move(pii), &pii->second); * assert(pii.use_count() == 0); * @endcode */ template<typename _Yp> shared_ptr(shared_ptr<_Yp>&& __r, element_type* __p) noexcept : __shared_ptr<_Tp>(std::move(__r), __p) { } #endif /** * @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<_NonArray<_Yp>> allocate_shared(const _Alloc&, _Args&&...); template<typename _Yp, typename... _Args> friend shared_ptr<_NonArray<_Yp>> make_shared(_Args&&...); #if __cpp_lib_shared_ptr_arrays >= 201707L // This constructor is non-standard, it is used by allocate_shared<T[]>. template<typename _Alloc, typename _Init = const remove_extent_t<_Tp>*> shared_ptr(const _Sp_counted_array_base<_Alloc>& __a, _Init __init = nullptr) : __shared_ptr<_Tp>(__a, __init) { } template<typename _Yp, typename _Alloc> friend shared_ptr<_UnboundedArray<_Yp>> allocate_shared(const _Alloc&, size_t); template<typename _Yp> friend shared_ptr<_UnboundedArray<_Yp>> make_shared(size_t); template<typename _Yp, typename _Alloc> friend shared_ptr<_UnboundedArray<_Yp>> allocate_shared(const _Alloc&, size_t, const remove_extent_t<_Yp>&); template<typename _Yp> friend shared_ptr<_UnboundedArray<_Yp>> make_shared(size_t, const remove_extent_t<_Yp>&); template<typename _Yp, typename _Alloc> friend shared_ptr<_BoundedArray<_Yp>> allocate_shared(const _Alloc&); template<typename _Yp> friend shared_ptr<_BoundedArray<_Yp>> make_shared(); template<typename _Yp, typename _Alloc> friend shared_ptr<_BoundedArray<_Yp>> allocate_shared(const _Alloc&, const remove_extent_t<_Yp>&); template<typename _Yp> friend shared_ptr<_BoundedArray<_Yp>> make_shared(const remove_extent_t<_Yp>&); #if __cpp_lib_smart_ptr_for_overwrite template<typename _Yp, typename _Alloc> friend shared_ptr<_NotUnboundedArray<_Yp>> allocate_shared_for_overwrite(const _Alloc&); template<typename _Yp> friend shared_ptr<_NotUnboundedArray<_Yp>> make_shared_for_overwrite(); template<typename _Yp, typename _Alloc> friend shared_ptr<_UnboundedArray<_Yp>> allocate_shared_for_overwrite(const _Alloc&, size_t); template<typename _Yp> friend shared_ptr<_UnboundedArray<_Yp>> make_shared_for_overwrite(size_t); #endif #endif // This constructor is non-standard, it is used by weak_ptr::lock(). shared_ptr(const weak_ptr<_Tp>& __r, std::nothrow_t) noexcept : __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 /// @relates shared_ptr @{ /// Equality operator for shared_ptr objects, compares the stored pointers template<typename _Tp, typename _Up> _GLIBCXX_NODISCARD inline bool operator==(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept { return __a.get() == __b.get(); } /// shared_ptr comparison with nullptr template<typename _Tp> _GLIBCXX_NODISCARD inline bool operator==(const shared_ptr<_Tp>& __a, nullptr_t) noexcept { return !__a; } #ifdef __cpp_lib_three_way_comparison template<typename _Tp, typename _Up> inline strong_ordering operator<=>(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept { return compare_three_way()(__a.get(), __b.get()); } template<typename _Tp> inline strong_ordering operator<=>(const shared_ptr<_Tp>& __a, nullptr_t) noexcept { using pointer = typename shared_ptr<_Tp>::element_type*; return compare_three_way()(__a.get(), static_cast<pointer>(nullptr)); } #else /// shared_ptr comparison with nullptr template<typename _Tp> _GLIBCXX_NODISCARD inline bool operator==(nullptr_t, const shared_ptr<_Tp>& __a) noexcept { return !__a; } /// Inequality operator for shared_ptr objects, compares the stored pointers template<typename _Tp, typename _Up> _GLIBCXX_NODISCARD inline bool operator!=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept { return __a.get() != __b.get(); } /// shared_ptr comparison with nullptr template<typename _Tp> _GLIBCXX_NODISCARD inline bool operator!=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept { return (bool)__a; } /// shared_ptr comparison with nullptr template<typename _Tp> _GLIBCXX_NODISCARD inline bool operator!=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept { return (bool)__a; } /// Relational operator for shared_ptr objects, compares the stored pointers template<typename _Tp, typename _Up> _GLIBCXX_NODISCARD 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()); } /// shared_ptr comparison with nullptr template<typename _Tp> _GLIBCXX_NODISCARD 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); } /// shared_ptr comparison with nullptr template<typename _Tp> _GLIBCXX_NODISCARD 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()); } /// Relational operator for shared_ptr objects, compares the stored pointers template<typename _Tp, typename _Up> _GLIBCXX_NODISCARD inline bool operator<=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept { return !(__b < __a); } /// shared_ptr comparison with nullptr template<typename _Tp> _GLIBCXX_NODISCARD inline bool operator<=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept { return !(nullptr < __a); } /// shared_ptr comparison with nullptr template<typename _Tp> _GLIBCXX_NODISCARD inline bool operator<=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept { return !(__a < nullptr); } /// Relational operator for shared_ptr objects, compares the stored pointers template<typename _Tp, typename _Up> _GLIBCXX_NODISCARD inline bool operator>(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept { return (__b < __a); } /// shared_ptr comparison with nullptr template<typename _Tp> _GLIBCXX_NODISCARD inline bool operator>(const shared_ptr<_Tp>& __a, nullptr_t) noexcept { return nullptr < __a; } /// shared_ptr comparison with nullptr template<typename _Tp> _GLIBCXX_NODISCARD inline bool operator>(nullptr_t, const shared_ptr<_Tp>& __a) noexcept { return __a < nullptr; } /// Relational operator for shared_ptr objects, compares the stored pointers template<typename _Tp, typename _Up> _GLIBCXX_NODISCARD inline bool operator>=(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept { return !(__a < __b); } /// shared_ptr comparison with nullptr template<typename _Tp> _GLIBCXX_NODISCARD inline bool operator>=(const shared_ptr<_Tp>& __a, nullptr_t) noexcept { return !(__a < nullptr); } /// shared_ptr comparison with nullptr template<typename _Tp> _GLIBCXX_NODISCARD inline bool operator>=(nullptr_t, const shared_ptr<_Tp>& __a) noexcept { return !(nullptr < __a); } #endif // 20.7.2.2.8 shared_ptr specialized algorithms. /// Swap overload for shared_ptr 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. /// Convert type of `shared_ptr`, via `static_cast` 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())); } /// Convert type of `shared_ptr`, via `const_cast` 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())); } /// Convert type of `shared_ptr`, via `dynamic_cast` 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 >= 201703L /// Convert type of `shared_ptr`, via `reinterpret_cast` /// @since C++17 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())); } #if __cplusplus > 201703L // _GLIBCXX_RESOLVE_LIB_DEFECTS // 2996. Missing rvalue overloads for shared_ptr operations /// Convert type of `shared_ptr` rvalue, via `static_cast` /// @since C++20 template<typename _Tp, typename _Up> inline shared_ptr<_Tp> static_pointer_cast(shared_ptr<_Up>&& __r) noexcept { using _Sp = shared_ptr<_Tp>; return _Sp(std::move(__r), static_cast<typename _Sp::element_type*>(__r.get())); } /// Convert type of `shared_ptr` rvalue, via `const_cast` /// @since C++20 template<typename _Tp, typename _Up> inline shared_ptr<_Tp> const_pointer_cast(shared_ptr<_Up>&& __r) noexcept { using _Sp = shared_ptr<_Tp>; return _Sp(std::move(__r), const_cast<typename _Sp::element_type*>(__r.get())); } /// Convert type of `shared_ptr` rvalue, via `dynamic_cast` /// @since C++20 template<typename _Tp, typename _Up> inline shared_ptr<_Tp> dynamic_pointer_cast(shared_ptr<_Up>&& __r) noexcept { using _Sp = shared_ptr<_Tp>; if (auto* __p = dynamic_cast<typename _Sp::element_type*>(__r.get())) return _Sp(std::move(__r), __p); return _Sp(); } /// Convert type of `shared_ptr` rvalue, via `reinterpret_cast` /// @since C++20 template<typename _Tp, typename _Up> inline shared_ptr<_Tp> reinterpret_pointer_cast(shared_ptr<_Up>&& __r) noexcept { using _Sp = shared_ptr<_Tp>; return _Sp(std::move(__r), reinterpret_cast<typename _Sp::element_type*>(__r.get())); } #endif // C++20 #endif // C++17 /// @} /** * @brief A non-owning observer for a pointer owned by a shared_ptr * @headerfile memory * @since C++11 * * A weak_ptr provides a safe alternative to a raw pointer when you want * a non-owning reference to an object that is managed by a shared_ptr. * * Unlike a raw pointer, a weak_ptr can be converted to a new shared_ptr * that shares ownership with every other shared_ptr that already owns * the pointer. In other words you can upgrade from a non-owning "weak" * reference to an owning shared_ptr, without having access to any of * the existing shared_ptr objects. * * Also unlike a raw pointer, a weak_ptr does not become "dangling" after * the object it points to has been destroyed. Instead, a weak_ptr * becomes _expired_ and can no longer be converted to a shared_ptr that * owns the freed pointer, so you cannot accidentally access the pointed-to * object after it has been destroyed. */ 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. /// Swap overload for weak_ptr /// @relates weak_ptr 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 compares either shared_ptr or weak_ptr 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 the member function `shared_from_this`. * @headerfile memory * @since C++11 */ 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 201603L /** @{ * Get a `weak_ptr` referring to the object that has `*this` as its base. * @since C++17 */ 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; }; /// @relates shared_ptr @{ /** * @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<_NonArray<_Tp>> allocate_shared(const _Alloc& __a, _Args&&... __args) { 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<_NonArray<_Tp>> make_shared(_Args&&... __args) { using _Alloc = allocator<void>; _Alloc __a; return shared_ptr<_Tp>(_Sp_alloc_shared_tag<_Alloc>{__a}, std::forward<_Args>(__args)...); } #if __cpp_lib_shared_ptr_arrays >= 201707L /// @cond undocumented template<typename _Tp, typename _Alloc = allocator<void>> auto __make_shared_arr_tag(size_t __n, const _Alloc& __a = _Alloc()) noexcept { using _Up = remove_all_extents_t<_Tp>; using _UpAlloc = __alloc_rebind<_Alloc, _Up>; size_t __s = sizeof(remove_extent_t<_Tp>) / sizeof(_Up); if (__builtin_mul_overflow(__s, __n, &__n)) std::__throw_bad_array_new_length(); return _Sp_counted_array_base<_UpAlloc>{_UpAlloc(__a), __n}; } /// @endcond template<typename _Tp, typename _Alloc> inline shared_ptr<_UnboundedArray<_Tp>> allocate_shared(const _Alloc& __a, size_t __n) { return shared_ptr<_Tp>(std::__make_shared_arr_tag<_Tp>(__n, __a)); } template<typename _Tp> inline shared_ptr<_UnboundedArray<_Tp>> make_shared(size_t __n) { return shared_ptr<_Tp>(std::__make_shared_arr_tag<_Tp>(__n)); } template<typename _Tp, typename _Alloc> inline shared_ptr<_UnboundedArray<_Tp>> allocate_shared(const _Alloc& __a, size_t __n, const remove_extent_t<_Tp>& __u) { return shared_ptr<_Tp>(std::__make_shared_arr_tag<_Tp>(__n, __a), std::__addressof(__u)); } template<typename _Tp> inline shared_ptr<_UnboundedArray<_Tp>> make_shared(size_t __n, const remove_extent_t<_Tp>& __u) { return shared_ptr<_Tp>(std::__make_shared_arr_tag<_Tp>(__n), std::__addressof(__u)); } /// @cond undocumented template<typename _Tp, typename _Alloc = allocator<void>> auto __make_shared_arrN_tag(const _Alloc& __a = _Alloc()) noexcept { using _Up = remove_all_extents_t<_Tp>; using _UpAlloc = __alloc_rebind<_Alloc, _Up>; size_t __n = sizeof(_Tp) / sizeof(_Up); return _Sp_counted_array_base<_UpAlloc>{_UpAlloc(__a), __n}; } /// @endcond template<typename _Tp, typename _Alloc> inline shared_ptr<_BoundedArray<_Tp>> allocate_shared(const _Alloc& __a) { return shared_ptr<_Tp>(std::__make_shared_arrN_tag<_Tp>(__a)); } template<typename _Tp> inline shared_ptr<_BoundedArray<_Tp>> make_shared() { return shared_ptr<_Tp>(std::__make_shared_arrN_tag<_Tp>()); } template<typename _Tp, typename _Alloc> inline shared_ptr<_BoundedArray<_Tp>> allocate_shared(const _Alloc& __a, const remove_extent_t<_Tp>& __u) { return shared_ptr<_Tp>(std::__make_shared_arrN_tag<_Tp>(__a), std::__addressof(__u)); } template<typename _Tp> inline shared_ptr<_BoundedArray<_Tp>> make_shared(const remove_extent_t<_Tp>& __u) { return shared_ptr<_Tp>(std::__make_shared_arrN_tag<_Tp>(), std::__addressof(__u)); } #if __cpp_lib_smart_ptr_for_overwrite template<typename _Tp, typename _Alloc> inline shared_ptr<_NotUnboundedArray<_Tp>> allocate_shared_for_overwrite(const _Alloc& __a) { if constexpr (is_array_v<_Tp>) return shared_ptr<_Tp>(std::__make_shared_arrN_tag<_Tp>(__a), _Sp_overwrite_tag{}); else { // Rebind the allocator to _Sp_overwrite_tag, so that the // relevant _Sp_counted_ptr_inplace specialization is used. using _Alloc2 = __alloc_rebind<_Alloc, _Sp_overwrite_tag>; _Alloc2 __a2 = __a; return shared_ptr<_Tp>(_Sp_alloc_shared_tag<_Alloc2>{__a2}); } } template<typename _Tp> inline shared_ptr<_NotUnboundedArray<_Tp>> make_shared_for_overwrite() { if constexpr (is_array_v<_Tp>) return shared_ptr<_Tp>(std::__make_shared_arrN_tag<_Tp>(), _Sp_overwrite_tag{}); else { using _Alloc = allocator<_Sp_overwrite_tag>; return shared_ptr<_Tp>(_Sp_alloc_shared_tag<_Alloc>{{}}); } } template<typename _Tp, typename _Alloc> inline shared_ptr<_UnboundedArray<_Tp>> allocate_shared_for_overwrite(const _Alloc& __a, size_t __n) { return shared_ptr<_Tp>(std::__make_shared_arr_tag<_Tp>(__n, __a), _Sp_overwrite_tag{}); } template<typename _Tp> inline shared_ptr<_UnboundedArray<_Tp>> make_shared_for_overwrite(size_t __n) { return shared_ptr<_Tp>(std::__make_shared_arr_tag<_Tp>(__n), _Sp_overwrite_tag{}); } #endif // smart_ptr_for_overwrite #endif // shared_ptr_arrays /// 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()); } }; /// @} relates shared_ptr /// @} group pointer_abstractions #if __cplusplus >= 201703L namespace __detail::__variant { template<typename> struct _Never_valueless_alt; // see <variant> // Provide the strong exception-safety guarantee when emplacing a // shared_ptr into a variant. template<typename _Tp> struct _Never_valueless_alt<std::shared_ptr<_Tp>> : std::true_type { }; // Provide the strong exception-safety guarantee when emplacing a // weak_ptr into a variant. template<typename _Tp> struct _Never_valueless_alt<std::weak_ptr<_Tp>> : std::true_type { }; } // namespace __detail::__variant #endif // C++17 _GLIBCXX_END_NAMESPACE_VERSION } // namespace #endif // _SHARED_PTR_H