include/memory

// -*- C++ -*-
//===-------------------------- memory ------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_MEMORY
#define _LIBCPP_MEMORY

/*
    memory synopsis

namespace std
{

struct allocator_arg_t { };
inline constexpr allocator_arg_t allocator_arg = allocator_arg_t();

template <class T, class Alloc> struct uses_allocator;

template <class Ptr>
struct pointer_traits
{
    typedef Ptr pointer;
    typedef <details> element_type;
    typedef <details> difference_type;

    template <class U> using rebind = <details>;

    static pointer pointer_to(<details>);
};

template <class T>
struct pointer_traits<T*>
{
    typedef T* pointer;
    typedef T element_type;
    typedef ptrdiff_t difference_type;

    template <class U> using rebind = U*;

    static pointer pointer_to(<details>) noexcept; // constexpr in C++20
};

template <class T> constexpr T* to_address(T* p) noexcept; // C++20
template <class Ptr> auto to_address(const Ptr& p) noexcept; // C++20

template <class Alloc>
struct allocator_traits
{
    typedef Alloc                        allocator_type;
    typedef typename allocator_type::value_type
                                         value_type;

    typedef Alloc::pointer | value_type* pointer;
    typedef Alloc::const_pointer
          | pointer_traits<pointer>::rebind<const value_type>
                                         const_pointer;
    typedef Alloc::void_pointer
          | pointer_traits<pointer>::rebind<void>
                                         void_pointer;
    typedef Alloc::const_void_pointer
          | pointer_traits<pointer>::rebind<const void>
                                         const_void_pointer;
    typedef Alloc::difference_type
          | pointer_traits<pointer>::difference_type
                                         difference_type;
    typedef Alloc::size_type
          | make_unsigned<difference_type>::type
                                         size_type;
    typedef Alloc::propagate_on_container_copy_assignment
          | false_type                   propagate_on_container_copy_assignment;
    typedef Alloc::propagate_on_container_move_assignment
          | false_type                   propagate_on_container_move_assignment;
    typedef Alloc::propagate_on_container_swap
          | false_type                   propagate_on_container_swap;
    typedef Alloc::is_always_equal
          | is_empty                     is_always_equal;

    template <class T> using rebind_alloc  = Alloc::rebind<T>::other | Alloc<T, Args...>;
    template <class T> using rebind_traits = allocator_traits<rebind_alloc<T>>;

    static pointer allocate(allocator_type& a, size_type n);                          // constexpr and [[nodiscard]] in C++20
    static pointer allocate(allocator_type& a, size_type n, const_void_pointer hint); // constexpr and [[nodiscard]] in C++20

    static void deallocate(allocator_type& a, pointer p, size_type n) noexcept; // constexpr in C++20

    template <class T, class... Args>
    static void construct(allocator_type& a, T* p, Args&&... args); // constexpr in C++20

    template <class T>
    static void destroy(allocator_type& a, T* p); // constexpr in C++20

    static size_type max_size(const allocator_type& a); // noexcept in C++14, constexpr in C++20
    static allocator_type select_on_container_copy_construction(const allocator_type& a); // constexpr in C++20
};

template <>
class allocator<void> // deprecated in C++17, removed in C++20
{
public:
    typedef void*                                 pointer;
    typedef const void*                           const_pointer;
    typedef void                                  value_type;

    template <class _Up> struct rebind {typedef allocator<_Up> other;};
};

template <class T>
class allocator
{
public:
    typedef size_t    size_type;
    typedef ptrdiff_t difference_type;
    typedef T*        pointer;                           // deprecated in C++17, removed in C++20
    typedef const T*  const_pointer;                     // deprecated in C++17, removed in C++20
    typedef typename add_lvalue_reference<T>::type
                      reference;                         // deprecated in C++17, removed in C++20
    typedef typename add_lvalue_reference<const T>::type
                      const_reference;                   // deprecated in C++17, removed in C++20

    typedef T         value_type;

    template <class U> struct rebind {typedef allocator<U> other;}; // deprecated in C++17, removed in C++20

    typedef true_type propagate_on_container_move_assignment;
    typedef true_type is_always_equal;

    constexpr allocator() noexcept;                      // constexpr in C++20
    constexpr allocator(const allocator&) noexcept;      // constexpr in C++20
    template <class U>
      constexpr allocator(const allocator<U>&) noexcept; // constexpr in C++20
    ~allocator();                                        // constexpr in C++20
    pointer address(reference x) const noexcept;             // deprecated in C++17, removed in C++20
    const_pointer address(const_reference x) const noexcept; // deprecated in C++17, removed in C++20
    T* allocate(size_t n, const void* hint);          // deprecated in C++17, removed in C++20
    T* allocate(size_t n);                              // constexpr in C++20
    void deallocate(T* p, size_t n) noexcept;           // constexpr in C++20
    size_type max_size() const noexcept;              // deprecated in C++17, removed in C++20
    template<class U, class... Args>
        void construct(U* p, Args&&... args);         // deprecated in C++17, removed in C++20
    template <class U>
        void destroy(U* p);                           // deprecated in C++17, removed in C++20
};

template <class T, class U>
bool operator==(const allocator<T>&, const allocator<U>&) noexcept; // constexpr in C++20

template <class T, class U>
bool operator!=(const allocator<T>&, const allocator<U>&) noexcept; // constexpr in C++20

template <class OutputIterator, class T>
class raw_storage_iterator
    : public iterator<output_iterator_tag,
                      T,                               // purposefully not C++03
                      ptrdiff_t,                       // purposefully not C++03
                      T*,                              // purposefully not C++03
                      raw_storage_iterator&>           // purposefully not C++03
{
public:
    explicit raw_storage_iterator(OutputIterator x);
    raw_storage_iterator& operator*();
    raw_storage_iterator& operator=(const T& element);
    raw_storage_iterator& operator++();
    raw_storage_iterator  operator++(int);
};

template <class T> pair<T*,ptrdiff_t> get_temporary_buffer(ptrdiff_t n) noexcept;
template <class T> void               return_temporary_buffer(T* p) noexcept;

template <class T> T* addressof(T& r) noexcept;
template <class T> T* addressof(const T&& r) noexcept = delete;

template <class InputIterator, class ForwardIterator>
ForwardIterator
uninitialized_copy(InputIterator first, InputIterator last, ForwardIterator result);

template <class InputIterator, class Size, class ForwardIterator>
ForwardIterator
uninitialized_copy_n(InputIterator first, Size n, ForwardIterator result);

template <class ForwardIterator, class T>
void uninitialized_fill(ForwardIterator first, ForwardIterator last, const T& x);

template <class ForwardIterator, class Size, class T>
ForwardIterator
uninitialized_fill_n(ForwardIterator first, Size n, const T& x);

template <class T, class ...Args>
constexpr T* construct_at(T* location, Args&& ...args); // since C++20

template <class T>
void destroy_at(T* location); // constexpr in C++20

template <class ForwardIterator>
void destroy(ForwardIterator first, ForwardIterator last); // constexpr in C++20

template <class ForwardIterator, class Size>
ForwardIterator destroy_n(ForwardIterator first, Size n); // constexpr in C++20

template <class InputIterator, class ForwardIterator>
 ForwardIterator uninitialized_move(InputIterator first, InputIterator last, ForwardIterator result);

template <class InputIterator, class Size, class ForwardIterator>
 pair<InputIterator,ForwardIterator> uninitialized_move_n(InputIterator first, Size n, ForwardIterator result);

template <class ForwardIterator>
 void uninitialized_value_construct(ForwardIterator first, ForwardIterator last);

template <class ForwardIterator, class Size>
 ForwardIterator uninitialized_value_construct_n(ForwardIterator first, Size n);

template <class ForwardIterator>
 void uninitialized_default_construct(ForwardIterator first, ForwardIterator last);

template <class ForwardIterator, class Size>
 ForwardIterator uninitialized_default_construct_n(ForwardIterator first, Size n);

template <class Y> struct auto_ptr_ref {};      // deprecated in C++11, removed in C++17

template<class X>
class auto_ptr                                  // deprecated in C++11, removed in C++17
{
public:
    typedef X element_type;

    explicit auto_ptr(X* p =0) throw();
    auto_ptr(auto_ptr&) throw();
    template<class Y> auto_ptr(auto_ptr<Y>&) throw();
    auto_ptr& operator=(auto_ptr&) throw();
    template<class Y> auto_ptr& operator=(auto_ptr<Y>&) throw();
    auto_ptr& operator=(auto_ptr_ref<X> r) throw();
    ~auto_ptr() throw();

    typename add_lvalue_reference<X>::type operator*() const throw();
    X* operator->() const throw();
    X* get() const throw();
    X* release() throw();
    void reset(X* p =0) throw();

    auto_ptr(auto_ptr_ref<X>) throw();
    template<class Y> operator auto_ptr_ref<Y>() throw();
    template<class Y> operator auto_ptr<Y>() throw();
};

template <class T>
struct default_delete
{
    constexpr default_delete() noexcept = default;
    template <class U> default_delete(const default_delete<U>&) noexcept;

    void operator()(T*) const noexcept;
};

template <class T>
struct default_delete<T[]>
{
    constexpr default_delete() noexcept = default;
    void operator()(T*) const noexcept;
    template <class U> void operator()(U*) const = delete;
};

template <class T, class D = default_delete<T>>
class unique_ptr
{
public:
    typedef see below pointer;
    typedef T element_type;
    typedef D deleter_type;

    // constructors
    constexpr unique_ptr() noexcept;
    explicit unique_ptr(pointer p) noexcept;
    unique_ptr(pointer p, see below d1) noexcept;
    unique_ptr(pointer p, see below d2) noexcept;
    unique_ptr(unique_ptr&& u) noexcept;
    unique_ptr(nullptr_t) noexcept : unique_ptr() { }
    template <class U, class E>
        unique_ptr(unique_ptr<U, E>&& u) noexcept;
    template <class U>
        unique_ptr(auto_ptr<U>&& u) noexcept;       // removed in C++17

    // destructor
    ~unique_ptr();

    // assignment
    unique_ptr& operator=(unique_ptr&& u) noexcept;
    template <class U, class E> unique_ptr& operator=(unique_ptr<U, E>&& u) noexcept;
    unique_ptr& operator=(nullptr_t) noexcept;

    // observers
    typename add_lvalue_reference<T>::type operator*() const;
    pointer operator->() const noexcept;
    pointer get() const noexcept;
    deleter_type& get_deleter() noexcept;
    const deleter_type& get_deleter() const noexcept;
    explicit operator bool() const noexcept;

    // modifiers
    pointer release() noexcept;
    void reset(pointer p = pointer()) noexcept;
    void swap(unique_ptr& u) noexcept;
};

template <class T, class D>
class unique_ptr<T[], D>
{
public:
    typedef implementation-defined pointer;
    typedef T element_type;
    typedef D deleter_type;

    // constructors
    constexpr unique_ptr() noexcept;
    explicit unique_ptr(pointer p) noexcept;
    unique_ptr(pointer p, see below d) noexcept;
    unique_ptr(pointer p, see below d) noexcept;
    unique_ptr(unique_ptr&& u) noexcept;
    unique_ptr(nullptr_t) noexcept : unique_ptr() { }

    // destructor
    ~unique_ptr();

    // assignment
    unique_ptr& operator=(unique_ptr&& u) noexcept;
    unique_ptr& operator=(nullptr_t) noexcept;

    // observers
    T& operator[](size_t i) const;
    pointer get() const noexcept;
    deleter_type& get_deleter() noexcept;
    const deleter_type& get_deleter() const noexcept;
    explicit operator bool() const noexcept;

    // modifiers
    pointer release() noexcept;
    void reset(pointer p = pointer()) noexcept;
    void reset(nullptr_t) noexcept;
  template <class U> void reset(U) = delete;
    void swap(unique_ptr& u) noexcept;
};

template <class T, class D>
    void swap(unique_ptr<T, D>& x, unique_ptr<T, D>& y) noexcept;

template <class T1, class D1, class T2, class D2>
    bool operator==(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
template <class T1, class D1, class T2, class D2>
    bool operator!=(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
template <class T1, class D1, class T2, class D2>
    bool operator<(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
template <class T1, class D1, class T2, class D2>
    bool operator<=(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
template <class T1, class D1, class T2, class D2>
    bool operator>(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);
template <class T1, class D1, class T2, class D2>
    bool operator>=(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);

template <class T, class D>
    bool operator==(const unique_ptr<T, D>& x, nullptr_t) noexcept;
template <class T, class D>
    bool operator==(nullptr_t, const unique_ptr<T, D>& y) noexcept;
template <class T, class D>
    bool operator!=(const unique_ptr<T, D>& x, nullptr_t) noexcept;
template <class T, class D>
    bool operator!=(nullptr_t, const unique_ptr<T, D>& y) noexcept;

template <class T, class D>
    bool operator<(const unique_ptr<T, D>& x, nullptr_t);
template <class T, class D>
    bool operator<(nullptr_t, const unique_ptr<T, D>& y);
template <class T, class D>
    bool operator<=(const unique_ptr<T, D>& x, nullptr_t);
template <class T, class D>
    bool operator<=(nullptr_t, const unique_ptr<T, D>& y);
template <class T, class D>
    bool operator>(const unique_ptr<T, D>& x, nullptr_t);
template <class T, class D>
    bool operator>(nullptr_t, const unique_ptr<T, D>& y);
template <class T, class D>
    bool operator>=(const unique_ptr<T, D>& x, nullptr_t);
template <class T, class D>
    bool operator>=(nullptr_t, const unique_ptr<T, D>& y);

class bad_weak_ptr
    : public std::exception
{
    bad_weak_ptr() noexcept;
};

template<class T, class... Args> unique_ptr<T> make_unique(Args&&... args);     // C++14
template<class T>                unique_ptr<T> make_unique(size_t n);           // C++14
template<class T, class... Args> unspecified   make_unique(Args&&...) = delete; // C++14, T == U[N]

template<class E, class T, class Y, class D>
    basic_ostream<E, T>& operator<< (basic_ostream<E, T>& os, unique_ptr<Y, D> const& p);

template<class T>
class shared_ptr
{
public:
    typedef T element_type;
    typedef weak_ptr<T> weak_type; // C++17

    // constructors:
    constexpr shared_ptr() noexcept;
    template<class Y> explicit shared_ptr(Y* p);
    template<class Y, class D> shared_ptr(Y* p, D d);
    template<class Y, class D, class A> shared_ptr(Y* p, D d, A a);
    template <class D> shared_ptr(nullptr_t p, D d);
    template <class D, class A> shared_ptr(nullptr_t p, D d, A a);
    template<class Y> shared_ptr(const shared_ptr<Y>& r, T *p) noexcept;
    shared_ptr(const shared_ptr& r) noexcept;
    template<class Y> shared_ptr(const shared_ptr<Y>& r) noexcept;
    shared_ptr(shared_ptr&& r) noexcept;
    template<class Y> shared_ptr(shared_ptr<Y>&& r) noexcept;
    template<class Y> explicit shared_ptr(const weak_ptr<Y>& r);
    template<class Y> shared_ptr(auto_ptr<Y>&& r);          // removed in C++17
    template <class Y, class D> shared_ptr(unique_ptr<Y, D>&& r);
    shared_ptr(nullptr_t) : shared_ptr() { }

    // destructor:
    ~shared_ptr();

    // assignment:
    shared_ptr& operator=(const shared_ptr& r) noexcept;
    template<class Y> shared_ptr& operator=(const shared_ptr<Y>& r) noexcept;
    shared_ptr& operator=(shared_ptr&& r) noexcept;
    template<class Y> shared_ptr& operator=(shared_ptr<Y>&& r);
    template<class Y> shared_ptr& operator=(auto_ptr<Y>&& r); // removed in C++17
    template <class Y, class D> shared_ptr& operator=(unique_ptr<Y, D>&& r);

    // modifiers:
    void swap(shared_ptr& r) noexcept;
    void reset() noexcept;
    template<class Y> void reset(Y* p);
    template<class Y, class D> void reset(Y* p, D d);
    template<class Y, class D, class A> void reset(Y* p, D d, A a);

    // observers:
    T* get() const noexcept;
    T& operator*() const noexcept;
    T* operator->() const noexcept;
    long use_count() const noexcept;
    bool unique() const noexcept;
    explicit operator bool() const noexcept;
    template<class U> bool owner_before(shared_ptr<U> const& b) const noexcept;
    template<class U> bool owner_before(weak_ptr<U> const& b) const noexcept;
};

template<class T>
shared_ptr(weak_ptr<T>) -> shared_ptr<T>;
template<class T, class D>
shared_ptr(unique_ptr<T, D>) -> shared_ptr<T>;

// shared_ptr comparisons:
template<class T, class U>
    bool operator==(shared_ptr<T> const& a, shared_ptr<U> const& b) noexcept;
template<class T, class U>
    bool operator!=(shared_ptr<T> const& a, shared_ptr<U> const& b) noexcept;
template<class T, class U>
    bool operator<(shared_ptr<T> const& a, shared_ptr<U> const& b) noexcept;
template<class T, class U>
    bool operator>(shared_ptr<T> const& a, shared_ptr<U> const& b) noexcept;
template<class T, class U>
    bool operator<=(shared_ptr<T> const& a, shared_ptr<U> const& b) noexcept;
template<class T, class U>
    bool operator>=(shared_ptr<T> const& a, shared_ptr<U> const& b) noexcept;

template <class T>
    bool operator==(const shared_ptr<T>& x, nullptr_t) noexcept;
template <class T>
    bool operator==(nullptr_t, const shared_ptr<T>& y) noexcept;
template <class T>
    bool operator!=(const shared_ptr<T>& x, nullptr_t) noexcept;
template <class T>
    bool operator!=(nullptr_t, const shared_ptr<T>& y) noexcept;
template <class T>
    bool operator<(const shared_ptr<T>& x, nullptr_t) noexcept;
template <class T>
bool operator<(nullptr_t, const shared_ptr<T>& y) noexcept;
template <class T>
    bool operator<=(const shared_ptr<T>& x, nullptr_t) noexcept;
template <class T>
    bool operator<=(nullptr_t, const shared_ptr<T>& y) noexcept;
template <class T>
    bool operator>(const shared_ptr<T>& x, nullptr_t) noexcept;
template <class T>
    bool operator>(nullptr_t, const shared_ptr<T>& y) noexcept;
template <class T>
    bool operator>=(const shared_ptr<T>& x, nullptr_t) noexcept;
template <class T>
    bool operator>=(nullptr_t, const shared_ptr<T>& y) noexcept;

// shared_ptr specialized algorithms:
template<class T> void swap(shared_ptr<T>& a, shared_ptr<T>& b) noexcept;

// shared_ptr casts:
template<class T, class U>
    shared_ptr<T> static_pointer_cast(shared_ptr<U> const& r) noexcept;
template<class T, class U>
    shared_ptr<T> dynamic_pointer_cast(shared_ptr<U> const& r) noexcept;
template<class T, class U>
    shared_ptr<T> const_pointer_cast(shared_ptr<U> const& r) noexcept;

// shared_ptr I/O:
template<class E, class T, class Y>
    basic_ostream<E, T>& operator<< (basic_ostream<E, T>& os, shared_ptr<Y> const& p);

// shared_ptr get_deleter:
template<class D, class T> D* get_deleter(shared_ptr<T> const& p) noexcept;

template<class T, class... Args>
    shared_ptr<T> make_shared(Args&&... args);
template<class T, class A, class... Args>
    shared_ptr<T> allocate_shared(const A& a, Args&&... args);

template<class T>
class weak_ptr
{
public:
    typedef T element_type;

    // constructors
    constexpr weak_ptr() noexcept;
    template<class Y> weak_ptr(shared_ptr<Y> const& r) noexcept;
    weak_ptr(weak_ptr const& r) noexcept;
    template<class Y> weak_ptr(weak_ptr<Y> const& r) noexcept;
    weak_ptr(weak_ptr&& r) noexcept;                      // C++14
    template<class Y> weak_ptr(weak_ptr<Y>&& r) noexcept; // C++14

    // destructor
    ~weak_ptr();

    // assignment
    weak_ptr& operator=(weak_ptr const& r) noexcept;
    template<class Y> weak_ptr& operator=(weak_ptr<Y> const& r) noexcept;
    template<class Y> weak_ptr& operator=(shared_ptr<Y> const& r) noexcept;
    weak_ptr& operator=(weak_ptr&& r) noexcept;                      // C++14
    template<class Y> weak_ptr& operator=(weak_ptr<Y>&& r) noexcept; // C++14

    // modifiers
    void swap(weak_ptr& r) noexcept;
    void reset() noexcept;

    // observers
    long use_count() const noexcept;
    bool expired() const noexcept;
    shared_ptr<T> lock() const noexcept;
    template<class U> bool owner_before(shared_ptr<U> const& b) const noexcept;
    template<class U> bool owner_before(weak_ptr<U> const& b) const noexcept;
};

template<class T>
weak_ptr(shared_ptr<T>) -> weak_ptr<T>;

// weak_ptr specialized algorithms:
template<class T> void swap(weak_ptr<T>& a, weak_ptr<T>& b) noexcept;

// class owner_less:
template<class T> struct owner_less;

template<class T>
struct owner_less<shared_ptr<T> >
    : binary_function<shared_ptr<T>, shared_ptr<T>, bool>
{
    typedef bool result_type;
    bool operator()(shared_ptr<T> const&, shared_ptr<T> const&) const noexcept;
    bool operator()(shared_ptr<T> const&, weak_ptr<T> const&) const noexcept;
    bool operator()(weak_ptr<T> const&, shared_ptr<T> const&) const noexcept;
};

template<class T>
struct owner_less<weak_ptr<T> >
    : binary_function<weak_ptr<T>, weak_ptr<T>, bool>
{
    typedef bool result_type;
    bool operator()(weak_ptr<T> const&, weak_ptr<T> const&) const noexcept;
    bool operator()(shared_ptr<T> const&, weak_ptr<T> const&) const noexcept;
    bool operator()(weak_ptr<T> const&, shared_ptr<T> const&) const noexcept;
};

template <>  // Added in C++14
struct owner_less<void>
{
    template <class _Tp, class _Up>
    bool operator()( shared_ptr<_Tp> const& __x, shared_ptr<_Up> const& __y) const noexcept;
    template <class _Tp, class _Up>
    bool operator()( shared_ptr<_Tp> const& __x,   weak_ptr<_Up> const& __y) const noexcept;
    template <class _Tp, class _Up>
    bool operator()(   weak_ptr<_Tp> const& __x, shared_ptr<_Up> const& __y) const noexcept;
    template <class _Tp, class _Up>
    bool operator()(   weak_ptr<_Tp> const& __x,   weak_ptr<_Up> const& __y) const noexcept;

    typedef void is_transparent;
};

template<class T>
class enable_shared_from_this
{
protected:
    constexpr enable_shared_from_this() noexcept;
    enable_shared_from_this(enable_shared_from_this const&) noexcept;
    enable_shared_from_this& operator=(enable_shared_from_this const&) noexcept;
    ~enable_shared_from_this();
public:
    shared_ptr<T> shared_from_this();
    shared_ptr<T const> shared_from_this() const;
};

template<class T>
    bool atomic_is_lock_free(const shared_ptr<T>* p);
template<class T>
    shared_ptr<T> atomic_load(const shared_ptr<T>* p);
template<class T>
    shared_ptr<T> atomic_load_explicit(const shared_ptr<T>* p, memory_order mo);
template<class T>
    void atomic_store(shared_ptr<T>* p, shared_ptr<T> r);
template<class T>
    void atomic_store_explicit(shared_ptr<T>* p, shared_ptr<T> r, memory_order mo);
template<class T>
    shared_ptr<T> atomic_exchange(shared_ptr<T>* p, shared_ptr<T> r);
template<class T>
    shared_ptr<T>
    atomic_exchange_explicit(shared_ptr<T>* p, shared_ptr<T> r, memory_order mo);
template<class T>
    bool
    atomic_compare_exchange_weak(shared_ptr<T>* p, shared_ptr<T>* v, shared_ptr<T> w);
template<class T>
    bool
    atomic_compare_exchange_strong( shared_ptr<T>* p, shared_ptr<T>* v, shared_ptr<T> w);
template<class T>
    bool
    atomic_compare_exchange_weak_explicit(shared_ptr<T>* p, shared_ptr<T>* v,
                                          shared_ptr<T> w, memory_order success,
                                          memory_order failure);
template<class T>
    bool
    atomic_compare_exchange_strong_explicit(shared_ptr<T>* p, shared_ptr<T>* v,
                                            shared_ptr<T> w, memory_order success,
                                            memory_order failure);
// Hash support
template <class T> struct hash;
template <class T, class D> struct hash<unique_ptr<T, D> >;
template <class T> struct hash<shared_ptr<T> >;

template <class T, class Alloc>
  inline constexpr bool uses_allocator_v = uses_allocator<T, Alloc>::value;

// Pointer safety
enum class pointer_safety { relaxed, preferred, strict };
void declare_reachable(void *p);
template <class T> T *undeclare_reachable(T *p);
void declare_no_pointers(char *p, size_t n);
void undeclare_no_pointers(char *p, size_t n);
pointer_safety get_pointer_safety() noexcept;

void* align(size_t alignment, size_t size, void*& ptr, size_t& space);

}  // std

*/

#include <__config>
#include <type_traits>
#include <typeinfo>
#include <cstddef>
#include <cstdint>
#include <new>
#include <utility>
#include <limits>
#include <iterator>
#include <__functional_base>
#include <iosfwd>
#include <tuple>
#include <stdexcept>
#include <cstring>
#if !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
#  include <atomic>
#endif
#include <version>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

_LIBCPP_PUSH_MACROS
#include <__undef_macros>


_LIBCPP_BEGIN_NAMESPACE_STD

template <class _ValueType>
inline _LIBCPP_INLINE_VISIBILITY
_ValueType __libcpp_relaxed_load(_ValueType const* __value) {
#if !defined(_LIBCPP_HAS_NO_THREADS) && \
    defined(__ATOMIC_RELAXED) &&        \
    (__has_builtin(__atomic_load_n) || defined(_LIBCPP_COMPILER_GCC))
    return __atomic_load_n(__value, __ATOMIC_RELAXED);
#else
    return *__value;
#endif
}

template <class _ValueType>
inline _LIBCPP_INLINE_VISIBILITY
_ValueType __libcpp_acquire_load(_ValueType const* __value) {
#if !defined(_LIBCPP_HAS_NO_THREADS) && \
    defined(__ATOMIC_ACQUIRE) &&        \
    (__has_builtin(__atomic_load_n) || defined(_LIBCPP_COMPILER_GCC))
    return __atomic_load_n(__value, __ATOMIC_ACQUIRE);
#else
    return *__value;
#endif
}

// addressof moved to <type_traits>

template <class _Tp> class allocator;

#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_MEMBERS)
template <>
class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX17 allocator<void>
{
public:
    typedef void*             pointer;
    typedef const void*       const_pointer;
    typedef void              value_type;

    template <class _Up> struct rebind {typedef allocator<_Up> other;};
};

template <>
class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX17 allocator<const void>
{
public:
    typedef const void*       pointer;
    typedef const void*       const_pointer;
    typedef const void        value_type;

    template <class _Up> struct rebind {typedef allocator<_Up> other;};
};
#endif

// pointer_traits

template <class _Tp, class = void>
struct __has_element_type : false_type {};

template <class _Tp>
struct __has_element_type<_Tp,
              typename __void_t<typename _Tp::element_type>::type> : true_type {};

template <class _Ptr, bool = __has_element_type<_Ptr>::value>
struct __pointer_traits_element_type;

template <class _Ptr>
struct __pointer_traits_element_type<_Ptr, true>
{
    typedef _LIBCPP_NODEBUG_TYPE typename _Ptr::element_type type;
};

template <template <class, class...> class _Sp, class _Tp, class ..._Args>
struct __pointer_traits_element_type<_Sp<_Tp, _Args...>, true>
{
    typedef _LIBCPP_NODEBUG_TYPE typename _Sp<_Tp, _Args...>::element_type type;
};

template <template <class, class...> class _Sp, class _Tp, class ..._Args>
struct __pointer_traits_element_type<_Sp<_Tp, _Args...>, false>
{
    typedef _LIBCPP_NODEBUG_TYPE _Tp type;
};

template <class _Tp, class = void>
struct __has_difference_type : false_type {};

template <class _Tp>
struct __has_difference_type<_Tp,
            typename __void_t<typename _Tp::difference_type>::type> : true_type {};

template <class _Ptr, bool = __has_difference_type<_Ptr>::value>
struct __pointer_traits_difference_type
{
    typedef _LIBCPP_NODEBUG_TYPE ptrdiff_t type;
};

template <class _Ptr>
struct __pointer_traits_difference_type<_Ptr, true>
{
    typedef _LIBCPP_NODEBUG_TYPE typename _Ptr::difference_type type;
};

template <class _Tp, class _Up>
struct __has_rebind
{
private:
    struct __two {char __lx; char __lxx;};
    template <class _Xp> static __two __test(...);
    _LIBCPP_SUPPRESS_DEPRECATED_PUSH
    template <class _Xp> static char __test(typename _Xp::template rebind<_Up>* = 0);
    _LIBCPP_SUPPRESS_DEPRECATED_POP
public:
    static const bool value = sizeof(__test<_Tp>(0)) == 1;
};

template <class _Tp, class _Up, bool = __has_rebind<_Tp, _Up>::value>
struct __pointer_traits_rebind
{
#ifndef _LIBCPP_CXX03_LANG
    typedef _LIBCPP_NODEBUG_TYPE typename _Tp::template rebind<_Up> type;
#else
    typedef _LIBCPP_NODEBUG_TYPE typename _Tp::template rebind<_Up>::other type;
#endif
};

template <template <class, class...> class _Sp, class _Tp, class ..._Args, class _Up>
struct __pointer_traits_rebind<_Sp<_Tp, _Args...>, _Up, true>
{
#ifndef _LIBCPP_CXX03_LANG
    typedef _LIBCPP_NODEBUG_TYPE typename _Sp<_Tp, _Args...>::template rebind<_Up> type;
#else
    typedef _LIBCPP_NODEBUG_TYPE typename _Sp<_Tp, _Args...>::template rebind<_Up>::other type;
#endif
};

template <template <class, class...> class _Sp, class _Tp, class ..._Args, class _Up>
struct __pointer_traits_rebind<_Sp<_Tp, _Args...>, _Up, false>
{
    typedef _Sp<_Up, _Args...> type;
};

template <class _Ptr>
struct _LIBCPP_TEMPLATE_VIS pointer_traits
{
    typedef _Ptr                                                     pointer;
    typedef typename __pointer_traits_element_type<pointer>::type    element_type;
    typedef typename __pointer_traits_difference_type<pointer>::type difference_type;

#ifndef _LIBCPP_CXX03_LANG
    template <class _Up> using rebind = typename __pointer_traits_rebind<pointer, _Up>::type;
#else
    template <class _Up> struct rebind
        {typedef typename __pointer_traits_rebind<pointer, _Up>::type other;};
#endif  // _LIBCPP_CXX03_LANG

private:
    struct __nat {};
public:
    _LIBCPP_INLINE_VISIBILITY
    static pointer pointer_to(typename conditional<is_void<element_type>::value,
                                           __nat, element_type>::type& __r)
        {return pointer::pointer_to(__r);}
};

template <class _Tp>
struct _LIBCPP_TEMPLATE_VIS pointer_traits<_Tp*>
{
    typedef _Tp*      pointer;
    typedef _Tp       element_type;
    typedef ptrdiff_t difference_type;

#ifndef _LIBCPP_CXX03_LANG
    template <class _Up> using rebind = _Up*;
#else
    template <class _Up> struct rebind {typedef _Up* other;};
#endif

private:
    struct __nat {};
public:
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    static pointer pointer_to(typename conditional<is_void<element_type>::value,
                                      __nat, element_type>::type& __r) _NOEXCEPT
        {return _VSTD::addressof(__r);}
};

template <class _From, class _To>
struct __rebind_pointer {
#ifndef _LIBCPP_CXX03_LANG
    typedef typename pointer_traits<_From>::template rebind<_To>        type;
#else
    typedef typename pointer_traits<_From>::template rebind<_To>::other type;
#endif
};

// construct_at

#if _LIBCPP_STD_VER > 17

template<class _Tp>
_LIBCPP_CONSTEXPR_AFTER_CXX17 void* __voidify(_Tp& __ptr) noexcept {
    return const_cast<void*>(static_cast<const volatile void*>(_VSTD::addressof(__ptr)));
}

template<class _Tp, class ..._Args, class = decltype(
    ::new (_VSTD::declval<void*>()) _Tp(_VSTD::declval<_Args>()...)
)>
_LIBCPP_INLINE_VISIBILITY
constexpr _Tp* construct_at(_Tp* __location, _Args&& ...__args) {
    _LIBCPP_ASSERT(__location, "null pointer given to construct_at");
    return ::new (_VSTD::__voidify(*__location)) _Tp(_VSTD::forward<_Args>(__args)...);
}

#endif

// destroy_at

#if _LIBCPP_STD_VER > 14

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
void destroy_at(_Tp* __loc) {
    _LIBCPP_ASSERT(__loc, "null pointer given to destroy_at");
    __loc->~_Tp();
}

#endif

// allocator_traits

template <class _Tp, class = void>
struct __has_pointer_type : false_type {};

template <class _Tp>
struct __has_pointer_type<_Tp,
          typename __void_t<typename _Tp::pointer>::type> : true_type {};

namespace __pointer_type_imp
{

template <class _Tp, class _Dp, bool = __has_pointer_type<_Dp>::value>
struct __pointer_type
{
    typedef _LIBCPP_NODEBUG_TYPE typename _Dp::pointer type;
};

template <class _Tp, class _Dp>
struct __pointer_type<_Tp, _Dp, false>
{
    typedef _LIBCPP_NODEBUG_TYPE _Tp* type;
};

}  // __pointer_type_imp

template <class _Tp, class _Dp>
struct __pointer_type
{
    typedef _LIBCPP_NODEBUG_TYPE typename __pointer_type_imp::__pointer_type<_Tp, typename remove_reference<_Dp>::type>::type type;
};

template <class _Tp, class = void>
struct __has_const_pointer : false_type {};

template <class _Tp>
struct __has_const_pointer<_Tp,
            typename __void_t<typename _Tp::const_pointer>::type> : true_type {};

template <class _Tp, class _Ptr, class _Alloc, bool = __has_const_pointer<_Alloc>::value>
struct __const_pointer
{
    typedef _LIBCPP_NODEBUG_TYPE typename _Alloc::const_pointer type;
};

template <class _Tp, class _Ptr, class _Alloc>
struct __const_pointer<_Tp, _Ptr, _Alloc, false>
{
#ifndef _LIBCPP_CXX03_LANG
    typedef _LIBCPP_NODEBUG_TYPE typename pointer_traits<_Ptr>::template rebind<const _Tp> type;
#else
    typedef typename pointer_traits<_Ptr>::template rebind<const _Tp>::other type;
#endif
};

template <class _Tp, class = void>
struct __has_void_pointer : false_type {};

template <class _Tp>
struct __has_void_pointer<_Tp,
               typename __void_t<typename _Tp::void_pointer>::type> : true_type {};

template <class _Ptr, class _Alloc, bool = __has_void_pointer<_Alloc>::value>
struct __void_pointer
{
    typedef _LIBCPP_NODEBUG_TYPE typename _Alloc::void_pointer type;
};

template <class _Ptr, class _Alloc>
struct __void_pointer<_Ptr, _Alloc, false>
{
#ifndef _LIBCPP_CXX03_LANG
    typedef _LIBCPP_NODEBUG_TYPE typename pointer_traits<_Ptr>::template rebind<void> type;
#else
    typedef _LIBCPP_NODEBUG_TYPE typename pointer_traits<_Ptr>::template rebind<void>::other type;
#endif
};

template <class _Tp, class = void>
struct __has_const_void_pointer : false_type {};

template <class _Tp>
struct __has_const_void_pointer<_Tp,
            typename __void_t<typename _Tp::const_void_pointer>::type> : true_type {};

template <class _Ptr, class _Alloc, bool = __has_const_void_pointer<_Alloc>::value>
struct __const_void_pointer
{
    typedef _LIBCPP_NODEBUG_TYPE typename _Alloc::const_void_pointer type;
};

template <class _Ptr, class _Alloc>
struct __const_void_pointer<_Ptr, _Alloc, false>
{
#ifndef _LIBCPP_CXX03_LANG
    typedef _LIBCPP_NODEBUG_TYPE typename pointer_traits<_Ptr>::template rebind<const void> type;
#else
    typedef _LIBCPP_NODEBUG_TYPE typename pointer_traits<_Ptr>::template rebind<const void>::other type;
#endif
};


template <bool _UsePointerTraits> struct __to_address_helper;

template <> struct __to_address_helper<true> {
    template <class _Pointer>
    using __return_type = decltype(pointer_traits<_Pointer>::to_address(std::declval<const _Pointer&>()));

    template <class _Pointer>
    _LIBCPP_CONSTEXPR
    static __return_type<_Pointer>
    __do_it(const _Pointer &__p) _NOEXCEPT { return pointer_traits<_Pointer>::to_address(__p); }
};

template <class _Pointer, bool _Dummy = true>
using __choose_to_address = __to_address_helper<_IsValidExpansion<__to_address_helper<_Dummy>::template __return_type, _Pointer>::value>;


template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
_Tp*
__to_address(_Tp* __p) _NOEXCEPT
{
    static_assert(!is_function<_Tp>::value, "_Tp is a function type");
    return __p;
}

template <class _Pointer>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename __choose_to_address<_Pointer>::template __return_type<_Pointer>
__to_address(const _Pointer& __p) _NOEXCEPT {
  return __choose_to_address<_Pointer>::__do_it(__p);
}

template <> struct __to_address_helper<false> {
    template <class _Pointer>
    using __return_type = typename pointer_traits<_Pointer>::element_type*;

    template <class _Pointer>
    _LIBCPP_CONSTEXPR
    static __return_type<_Pointer>
    __do_it(const _Pointer &__p) _NOEXCEPT { return std::__to_address(__p.operator->()); }
};


#if _LIBCPP_STD_VER > 17
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY constexpr
_Tp*
to_address(_Tp* __p) _NOEXCEPT
{
    static_assert(!is_function_v<_Tp>, "_Tp is a function type");
    return __p;
}

template <class _Pointer>
inline _LIBCPP_INLINE_VISIBILITY
auto
to_address(const _Pointer& __p) _NOEXCEPT
{
    return _VSTD::__to_address(__p);
}
#endif

template <class _Tp, class = void>
struct __has_size_type : false_type {};

template <class _Tp>
struct __has_size_type<_Tp,
               typename __void_t<typename _Tp::size_type>::type> : true_type {};

template <class _Alloc, class _DiffType, bool = __has_size_type<_Alloc>::value>
struct __size_type
{
    typedef _LIBCPP_NODEBUG_TYPE typename make_unsigned<_DiffType>::type type;
};

template <class _Alloc, class _DiffType>
struct __size_type<_Alloc, _DiffType, true>
{
    typedef _LIBCPP_NODEBUG_TYPE typename _Alloc::size_type type;
};

template <class _Tp, class = void>
struct __has_propagate_on_container_copy_assignment : false_type {};

template <class _Tp>
struct __has_propagate_on_container_copy_assignment<_Tp,
    typename __void_t<typename _Tp::propagate_on_container_copy_assignment>::type>
        : true_type {};

template <class _Alloc, bool = __has_propagate_on_container_copy_assignment<_Alloc>::value>
struct __propagate_on_container_copy_assignment
{
    typedef _LIBCPP_NODEBUG_TYPE false_type type;
};

template <class _Alloc>
struct __propagate_on_container_copy_assignment<_Alloc, true>
{
    typedef _LIBCPP_NODEBUG_TYPE typename _Alloc::propagate_on_container_copy_assignment type;
};

template <class _Tp, class = void>
struct __has_propagate_on_container_move_assignment : false_type {};

template <class _Tp>
struct __has_propagate_on_container_move_assignment<_Tp,
           typename __void_t<typename _Tp::propagate_on_container_move_assignment>::type>
               : true_type {};

template <class _Alloc, bool = __has_propagate_on_container_move_assignment<_Alloc>::value>
struct __propagate_on_container_move_assignment
{
    typedef false_type type;
};

template <class _Alloc>
struct __propagate_on_container_move_assignment<_Alloc, true>
{
    typedef _LIBCPP_NODEBUG_TYPE typename _Alloc::propagate_on_container_move_assignment type;
};

template <class _Tp, class = void>
struct __has_propagate_on_container_swap : false_type {};

template <class _Tp>
struct __has_propagate_on_container_swap<_Tp,
           typename __void_t<typename _Tp::propagate_on_container_swap>::type>
               : true_type {};

template <class _Alloc, bool = __has_propagate_on_container_swap<_Alloc>::value>
struct __propagate_on_container_swap
{
    typedef false_type type;
};

template <class _Alloc>
struct __propagate_on_container_swap<_Alloc, true>
{
    typedef _LIBCPP_NODEBUG_TYPE typename _Alloc::propagate_on_container_swap type;
};

template <class _Tp, class = void>
struct __has_is_always_equal : false_type {};

template <class _Tp>
struct __has_is_always_equal<_Tp,
           typename __void_t<typename _Tp::is_always_equal>::type>
               : true_type {};

template <class _Alloc, bool = __has_is_always_equal<_Alloc>::value>
struct __is_always_equal
{
    typedef _LIBCPP_NODEBUG_TYPE typename _VSTD::is_empty<_Alloc>::type type;
};

template <class _Alloc>
struct __is_always_equal<_Alloc, true>
{
    typedef _LIBCPP_NODEBUG_TYPE typename _Alloc::is_always_equal type;
};

template <class _Tp, class _Up, bool = __has_rebind<_Tp, _Up>::value>
struct __has_rebind_other
{
private:
    struct __two {char __lx; char __lxx;};
    template <class _Xp> static __two __test(...);
    _LIBCPP_SUPPRESS_DEPRECATED_PUSH
    template <class _Xp> static char __test(typename _Xp::template rebind<_Up>::other* = 0);
    _LIBCPP_SUPPRESS_DEPRECATED_POP
public:
    static const bool value = sizeof(__test<_Tp>(0)) == 1;
};

template <class _Tp, class _Up>
struct __has_rebind_other<_Tp, _Up, false>
{
    static const bool value = false;
};

template <class _Tp, class _Up, bool = __has_rebind_other<_Tp, _Up>::value>
struct __allocator_traits_rebind
{
    _LIBCPP_SUPPRESS_DEPRECATED_PUSH
    typedef _LIBCPP_NODEBUG_TYPE typename _Tp::template rebind<_Up>::other type;
    _LIBCPP_SUPPRESS_DEPRECATED_POP
};

template <template <class, class...> class _Alloc, class _Tp, class ..._Args, class _Up>
struct __allocator_traits_rebind<_Alloc<_Tp, _Args...>, _Up, true>
{
    _LIBCPP_SUPPRESS_DEPRECATED_PUSH
    typedef _LIBCPP_NODEBUG_TYPE typename _Alloc<_Tp, _Args...>::template rebind<_Up>::other type;
    _LIBCPP_SUPPRESS_DEPRECATED_POP
};

template <template <class, class...> class _Alloc, class _Tp, class ..._Args, class _Up>
struct __allocator_traits_rebind<_Alloc<_Tp, _Args...>, _Up, false>
{
    typedef _LIBCPP_NODEBUG_TYPE _Alloc<_Up, _Args...> type;
};

#ifndef _LIBCPP_CXX03_LANG

_LIBCPP_SUPPRESS_DEPRECATED_PUSH
template <class _Alloc, class _SizeType, class _ConstVoidPtr>
auto
__has_allocate_hint_test(_Alloc&& __a, _SizeType&& __sz, _ConstVoidPtr&& __p)
    -> decltype((void)__a.allocate(__sz, __p), true_type());
_LIBCPP_SUPPRESS_DEPRECATED_POP

template <class _Alloc, class _SizeType, class _ConstVoidPtr>
auto
__has_allocate_hint_test(const _Alloc& __a, _SizeType&& __sz, _ConstVoidPtr&& __p)
    -> false_type;

template <class _Alloc, class _SizeType, class _ConstVoidPtr>
struct __has_allocate_hint
    : decltype(_VSTD::__has_allocate_hint_test(declval<_Alloc>(),
                                               declval<_SizeType>(),
                                               declval<_ConstVoidPtr>()))
{
};

#else  // _LIBCPP_CXX03_LANG

template <class _Alloc, class _SizeType, class _ConstVoidPtr>
struct __has_allocate_hint
    : true_type
{
};

#endif  // _LIBCPP_CXX03_LANG

_LIBCPP_SUPPRESS_DEPRECATED_PUSH
template <class _Alloc, class ..._Args,
    class = decltype(_VSTD::declval<_Alloc>().construct(_VSTD::declval<_Args>()...))>
static true_type __test_has_construct(int);
_LIBCPP_SUPPRESS_DEPRECATED_POP

template <class _Alloc, class...>
static false_type __test_has_construct(...);

template <class _Alloc, class ..._Args>
struct __has_construct : decltype(__test_has_construct<_Alloc, _Args...>(0)) {};

#if !defined(_LIBCPP_CXX03_LANG)

_LIBCPP_SUPPRESS_DEPRECATED_PUSH
template <class _Alloc, class _Pointer>
auto
__has_destroy_test(_Alloc&& __a, _Pointer&& __p)
    -> decltype(__a.destroy(__p), true_type());
_LIBCPP_SUPPRESS_DEPRECATED_POP

template <class _Alloc, class _Pointer>
auto
__has_destroy_test(const _Alloc& __a, _Pointer&& __p)
    -> false_type;

template <class _Alloc, class _Pointer>
struct __has_destroy
    : decltype(_VSTD::__has_destroy_test(declval<_Alloc>(),
                                         declval<_Pointer>()))
{
};

_LIBCPP_SUPPRESS_DEPRECATED_PUSH
template <class _Alloc>
auto
__has_max_size_test(_Alloc&& __a)
    -> decltype(__a.max_size(), true_type());
_LIBCPP_SUPPRESS_DEPRECATED_POP

template <class _Alloc>
auto
__has_max_size_test(const volatile _Alloc& __a)
    -> false_type;

template <class _Alloc>
struct __has_max_size
    : decltype(_VSTD::__has_max_size_test(declval<_Alloc&>()))
{
};

template <class _Alloc>
auto
__has_select_on_container_copy_construction_test(_Alloc&& __a)
    -> decltype(__a.select_on_container_copy_construction(), true_type());

template <class _Alloc>
auto
__has_select_on_container_copy_construction_test(const volatile _Alloc& __a)
    -> false_type;

template <class _Alloc>
struct __has_select_on_container_copy_construction
    : decltype(_VSTD::__has_select_on_container_copy_construction_test(declval<_Alloc&>()))
{
};

#else  // _LIBCPP_CXX03_LANG

template <class _Alloc, class _Pointer, class = void>
struct __has_destroy : false_type {};

template <class _Alloc, class _Pointer>
struct __has_destroy<_Alloc, _Pointer, typename __void_t<
    decltype(_VSTD::declval<_Alloc>().destroy(_VSTD::declval<_Pointer>()))
>::type> : std::true_type {};

template <class _Alloc>
struct __has_max_size
    : true_type
{
};

template <class _Alloc>
struct __has_select_on_container_copy_construction
    : false_type
{
};

#endif  // _LIBCPP_CXX03_LANG

template <class _Alloc, class _Ptr, bool = __has_difference_type<_Alloc>::value>
struct __alloc_traits_difference_type
{
    typedef _LIBCPP_NODEBUG_TYPE typename pointer_traits<_Ptr>::difference_type type;
};

template <class _Alloc, class _Ptr>
struct __alloc_traits_difference_type<_Alloc, _Ptr, true>
{
    typedef _LIBCPP_NODEBUG_TYPE typename _Alloc::difference_type type;
};

template <class _Tp>
struct __is_default_allocator : false_type {};

template <class _Tp>
struct __is_default_allocator<_VSTD::allocator<_Tp> > : true_type {};



template <class _Alloc,
    bool = __has_construct<_Alloc, typename _Alloc::value_type*,  typename _Alloc::value_type&&>::value && !__is_default_allocator<_Alloc>::value
    >
struct __is_cpp17_move_insertable;
template <class _Alloc>
struct __is_cpp17_move_insertable<_Alloc, true> : std::true_type {};
template <class _Alloc>
struct __is_cpp17_move_insertable<_Alloc, false> : std::is_move_constructible<typename _Alloc::value_type> {};

template <class _Alloc,
    bool = __has_construct<_Alloc, typename _Alloc::value_type*, const typename _Alloc::value_type&>::value && !__is_default_allocator<_Alloc>::value
    >
struct __is_cpp17_copy_insertable;
template <class _Alloc>
struct __is_cpp17_copy_insertable<_Alloc, true> : __is_cpp17_move_insertable<_Alloc> {};
template <class _Alloc>
struct __is_cpp17_copy_insertable<_Alloc, false> : integral_constant<bool,
    std::is_copy_constructible<typename _Alloc::value_type>::value &&
    __is_cpp17_move_insertable<_Alloc>::value>
  {};



template <class _Alloc>
struct _LIBCPP_TEMPLATE_VIS allocator_traits
{
    typedef _Alloc                              allocator_type;
    typedef typename allocator_type::value_type value_type;

    typedef typename __pointer_type<value_type, allocator_type>::type pointer;
    typedef typename __const_pointer<value_type, pointer, allocator_type>::type const_pointer;
    typedef typename __void_pointer<pointer, allocator_type>::type void_pointer;
    typedef typename __const_void_pointer<pointer, allocator_type>::type const_void_pointer;

    typedef typename __alloc_traits_difference_type<allocator_type, pointer>::type difference_type;
    typedef typename __size_type<allocator_type, difference_type>::type size_type;

    typedef typename __propagate_on_container_copy_assignment<allocator_type>::type
                     propagate_on_container_copy_assignment;
    typedef typename __propagate_on_container_move_assignment<allocator_type>::type
                     propagate_on_container_move_assignment;
    typedef typename __propagate_on_container_swap<allocator_type>::type
                     propagate_on_container_swap;
    typedef typename __is_always_equal<allocator_type>::type
                     is_always_equal;

#ifndef _LIBCPP_CXX03_LANG
    template <class _Tp> using rebind_alloc =
                  typename __allocator_traits_rebind<allocator_type, _Tp>::type;
    template <class _Tp> using rebind_traits = allocator_traits<rebind_alloc<_Tp> >;
#else  // _LIBCPP_CXX03_LANG
    template <class _Tp> struct rebind_alloc
        {typedef typename __allocator_traits_rebind<allocator_type, _Tp>::type other;};
    template <class _Tp> struct rebind_traits
        {typedef allocator_traits<typename rebind_alloc<_Tp>::other> other;};
#endif  // _LIBCPP_CXX03_LANG

    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    static pointer allocate(allocator_type& __a, size_type __n)
        {return __a.allocate(__n);}
    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    static pointer allocate(allocator_type& __a, size_type __n, const_void_pointer __hint)
        {return __allocate(__a, __n, __hint,
            __has_allocate_hint<allocator_type, size_type, const_void_pointer>());}

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    static void deallocate(allocator_type& __a, pointer __p, size_type __n) _NOEXCEPT
        {__a.deallocate(__p, __n);}

    template <class _Tp, class... _Args>
        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
        static void construct(allocator_type& __a, _Tp* __p, _Args&&... __args)
            {__construct(__has_construct<allocator_type, _Tp*, _Args...>(),
                         __a, __p, _VSTD::forward<_Args>(__args)...);}

    template <class _Tp>
        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
        static void destroy(allocator_type& __a, _Tp* __p)
            {__destroy(__has_destroy<allocator_type, _Tp*>(), __a, __p);}

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    static size_type max_size(const allocator_type& __a) _NOEXCEPT
        {return __max_size(__has_max_size<const allocator_type>(), __a);}

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    static allocator_type
        select_on_container_copy_construction(const allocator_type& __a)
            {return __select_on_container_copy_construction(
                __has_select_on_container_copy_construction<const allocator_type>(),
                __a);}

    template <class _Ptr>
        _LIBCPP_INLINE_VISIBILITY
        static
        void
        __construct_forward_with_exception_guarantees(allocator_type& __a, _Ptr __begin1, _Ptr __end1, _Ptr& __begin2)
        {
            static_assert(__is_cpp17_move_insertable<allocator_type>::value,
              "The specified type does not meet the requirements of Cpp17MoveInsertible");
            for (; __begin1 != __end1; ++__begin1, (void) ++__begin2)
              construct(__a, _VSTD::__to_address(__begin2),
#ifdef _LIBCPP_NO_EXCEPTIONS
                        _VSTD::move(*__begin1)
#else
                        _VSTD::move_if_noexcept(*__begin1)
#endif
                        );
        }

    template <class _Tp>
        _LIBCPP_INLINE_VISIBILITY
        static
        typename enable_if
        <
            (__is_default_allocator<allocator_type>::value
                || !__has_construct<allocator_type, _Tp*, _Tp>::value) &&
             is_trivially_move_constructible<_Tp>::value,
            void
        >::type
        __construct_forward_with_exception_guarantees(allocator_type&, _Tp* __begin1, _Tp* __end1, _Tp*& __begin2)
        {
            ptrdiff_t _Np = __end1 - __begin1;
            if (_Np > 0)
            {
                _VSTD::memcpy(__begin2, __begin1, _Np * sizeof(_Tp));
                __begin2 += _Np;
            }
        }

    template <class _Iter, class _Ptr>
        _LIBCPP_INLINE_VISIBILITY
        static
        void
        __construct_range_forward(allocator_type& __a, _Iter __begin1, _Iter __end1, _Ptr& __begin2)
        {
            for (; __begin1 != __end1; ++__begin1, (void) ++__begin2)
                construct(__a, _VSTD::__to_address(__begin2), *__begin1);
        }

    template <class _SourceTp, class _DestTp,
              class _RawSourceTp = typename remove_const<_SourceTp>::type,
              class _RawDestTp = typename remove_const<_DestTp>::type>
        _LIBCPP_INLINE_VISIBILITY
        static
        typename enable_if
        <
            is_trivially_copy_constructible<_DestTp>::value &&
            is_same<_RawSourceTp, _RawDestTp>::value &&
            (__is_default_allocator<allocator_type>::value ||
             !__has_construct<allocator_type, _DestTp*, _SourceTp&>::value),
            void
        >::type
        __construct_range_forward(allocator_type&, _SourceTp* __begin1, _SourceTp* __end1, _DestTp*& __begin2)
        {
            ptrdiff_t _Np = __end1 - __begin1;
            if (_Np > 0)
            {
                _VSTD::memcpy(const_cast<_RawDestTp*>(__begin2), __begin1, _Np * sizeof(_DestTp));
                __begin2 += _Np;
            }
        }

    template <class _Ptr>
        _LIBCPP_INLINE_VISIBILITY
        static
        void
        __construct_backward_with_exception_guarantees(allocator_type& __a, _Ptr __begin1, _Ptr __end1, _Ptr& __end2)
        {
            static_assert(__is_cpp17_move_insertable<allocator_type>::value,
              "The specified type does not meet the requirements of Cpp17MoveInsertable");
            while (__end1 != __begin1)
            {
              construct(__a, _VSTD::__to_address(__end2 - 1),
#ifdef _LIBCPP_NO_EXCEPTIONS
                        _VSTD::move(*--__end1)
#else
                        _VSTD::move_if_noexcept(*--__end1)
#endif
                        );
              --__end2;
            }
        }

    template <class _Tp>
        _LIBCPP_INLINE_VISIBILITY
        static
        typename enable_if
        <
            (__is_default_allocator<allocator_type>::value
                || !__has_construct<allocator_type, _Tp*, _Tp>::value) &&
             is_trivially_move_constructible<_Tp>::value,
            void
        >::type
        __construct_backward_with_exception_guarantees(allocator_type&, _Tp* __begin1, _Tp* __end1, _Tp*& __end2)
        {
            ptrdiff_t _Np = __end1 - __begin1;
            __end2 -= _Np;
            if (_Np > 0)
                _VSTD::memcpy(__end2, __begin1, _Np * sizeof(_Tp));
        }

private:

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    static pointer __allocate(allocator_type& __a, size_type __n,
        const_void_pointer __hint, true_type)
        {
            _LIBCPP_SUPPRESS_DEPRECATED_PUSH
            return __a.allocate(__n, __hint);
            _LIBCPP_SUPPRESS_DEPRECATED_POP
        }
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    static pointer __allocate(allocator_type& __a, size_type __n,
        const_void_pointer, false_type)
        {return __a.allocate(__n);}

    template <class _Tp, class... _Args>
        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
        static void __construct(true_type, allocator_type& __a, _Tp* __p, _Args&&... __args)
            {
                _LIBCPP_SUPPRESS_DEPRECATED_PUSH
                __a.construct(__p, _VSTD::forward<_Args>(__args)...);
                _LIBCPP_SUPPRESS_DEPRECATED_POP
            }

    template <class _Tp, class... _Args>
        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
        static void __construct(false_type, allocator_type&, _Tp* __p, _Args&&... __args)
            {
#if _LIBCPP_STD_VER > 17
                _VSTD::construct_at(__p, _VSTD::forward<_Args>(__args)...);
#else
                ::new ((void*)__p) _Tp(_VSTD::forward<_Args>(__args)...);
#endif
            }

    template <class _Tp>
        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
        static void __destroy(true_type, allocator_type& __a, _Tp* __p)
            {
                _LIBCPP_SUPPRESS_DEPRECATED_PUSH
                __a.destroy(__p);
                _LIBCPP_SUPPRESS_DEPRECATED_POP
            }
    template <class _Tp>
        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
        static void __destroy(false_type, allocator_type&, _Tp* __p)
            {
#if _LIBCPP_STD_VER > 17
                _VSTD::destroy_at(__p);
#else
                __p->~_Tp();
#endif
            }

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    static size_type __max_size(true_type, const allocator_type& __a) _NOEXCEPT
            {
                _LIBCPP_SUPPRESS_DEPRECATED_PUSH
                return __a.max_size();
                _LIBCPP_SUPPRESS_DEPRECATED_POP
            }

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    static size_type __max_size(false_type, const allocator_type&) _NOEXCEPT
            {return numeric_limits<size_type>::max() / sizeof(value_type);}

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    static allocator_type
        __select_on_container_copy_construction(true_type, const allocator_type& __a)
            {return __a.select_on_container_copy_construction();}
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    static allocator_type
        __select_on_container_copy_construction(false_type, const allocator_type& __a)
            {return __a;}
};

template <class _Traits, class _Tp>
struct __rebind_alloc_helper
{
#ifndef _LIBCPP_CXX03_LANG
    typedef _LIBCPP_NODEBUG_TYPE typename _Traits::template rebind_alloc<_Tp>        type;
#else
    typedef typename _Traits::template rebind_alloc<_Tp>::other type;
#endif
};

// allocator

template <class _Tp>
class _LIBCPP_TEMPLATE_VIS allocator
{
public:
    typedef size_t      size_type;
    typedef ptrdiff_t   difference_type;
    typedef _Tp         value_type;
    typedef true_type   propagate_on_container_move_assignment;
    typedef true_type   is_always_equal;

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    allocator() _NOEXCEPT { }

    template <class _Up>
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    allocator(const allocator<_Up>&) _NOEXCEPT { }

    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    _Tp* allocate(size_t __n) {
        if (__n > allocator_traits<allocator>::max_size(*this))
            __throw_length_error("allocator<T>::allocate(size_t n)"
                                 " 'n' exceeds maximum supported size");
        return static_cast<_Tp*>(_VSTD::__libcpp_allocate(__n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp)));
    }

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    void deallocate(_Tp* __p, size_t __n) _NOEXCEPT {
        _VSTD::__libcpp_deallocate((void*)__p, __n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp));
    }

    // C++20 Removed members
#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_MEMBERS)
    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp*       pointer;
    _LIBCPP_DEPRECATED_IN_CXX17 typedef const _Tp* const_pointer;
    _LIBCPP_DEPRECATED_IN_CXX17 typedef _Tp&       reference;
    _LIBCPP_DEPRECATED_IN_CXX17 typedef const _Tp& const_reference;

    template <class _Up>
    struct _LIBCPP_DEPRECATED_IN_CXX17 rebind {
        typedef allocator<_Up> other;
    };

    _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY
    pointer address(reference __x) const _NOEXCEPT {
        return _VSTD::addressof(__x);
    }
    _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY
    const_pointer address(const_reference __x) const _NOEXCEPT {
        return _VSTD::addressof(__x);
    }

    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY _LIBCPP_DEPRECATED_IN_CXX17
    _Tp* allocate(size_t __n, const void*) {
        return allocate(__n);
    }

    _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY size_type max_size() const _NOEXCEPT {
        return size_type(~0) / sizeof(_Tp);
    }

    template <class _Up, class... _Args>
    _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY
    void construct(_Up* __p, _Args&&... __args) {
        ::new((void*)__p) _Up(_VSTD::forward<_Args>(__args)...);
    }

    _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY
    void destroy(pointer __p) {
        __p->~_Tp();
    }
#endif
};

template <class _Tp>
class _LIBCPP_TEMPLATE_VIS allocator<const _Tp>
{
public:
    typedef size_t      size_type;
    typedef ptrdiff_t   difference_type;
    typedef const _Tp   value_type;
    typedef true_type   propagate_on_container_move_assignment;
    typedef true_type   is_always_equal;

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    allocator() _NOEXCEPT { }

    template <class _Up>
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    allocator(const allocator<_Up>&) _NOEXCEPT { }

    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    const _Tp* allocate(size_t __n) {
        if (__n > allocator_traits<allocator>::max_size(*this))
            __throw_length_error("allocator<const T>::allocate(size_t n)"
                                 " 'n' exceeds maximum supported size");
        return static_cast<const _Tp*>(_VSTD::__libcpp_allocate(__n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp)));
    }

    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
    void deallocate(const _Tp* __p, size_t __n) {
        _VSTD::__libcpp_deallocate((void*) const_cast<_Tp *>(__p), __n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp));
    }

    // C++20 Removed members
#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_MEMBERS)
    _LIBCPP_DEPRECATED_IN_CXX17 typedef const _Tp* pointer;
    _LIBCPP_DEPRECATED_IN_CXX17 typedef const _Tp* const_pointer;
    _LIBCPP_DEPRECATED_IN_CXX17 typedef const _Tp& reference;
    _LIBCPP_DEPRECATED_IN_CXX17 typedef const _Tp& const_reference;

    template <class _Up>
    struct _LIBCPP_DEPRECATED_IN_CXX17 rebind {
        typedef allocator<_Up> other;
    };

    _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY
    const_pointer address(const_reference __x) const _NOEXCEPT {
        return _VSTD::addressof(__x);
    }

    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY _LIBCPP_DEPRECATED_IN_CXX17
    const _Tp* allocate(size_t __n, const void*) {
        return allocate(__n);
    }

    _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY size_type max_size() const _NOEXCEPT {
        return size_type(~0) / sizeof(_Tp);
    }

    template <class _Up, class... _Args>
    _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY
    void construct(_Up* __p, _Args&&... __args) {
        ::new((void*)__p) _Up(_VSTD::forward<_Args>(__args)...);
    }

    _LIBCPP_DEPRECATED_IN_CXX17 _LIBCPP_INLINE_VISIBILITY
    void destroy(pointer __p) {
        __p->~_Tp();
    }
#endif
};

template <class _Tp, class _Up>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
bool operator==(const allocator<_Tp>&, const allocator<_Up>&) _NOEXCEPT {return true;}

template <class _Tp, class _Up>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
bool operator!=(const allocator<_Tp>&, const allocator<_Up>&) _NOEXCEPT {return false;}

template <class _OutputIterator, class _Tp>
class _LIBCPP_TEMPLATE_VIS raw_storage_iterator
    : public iterator<output_iterator_tag,
                      _Tp,                                         // purposefully not C++03
                      ptrdiff_t,                                   // purposefully not C++03
                      _Tp*,                                        // purposefully not C++03
                      raw_storage_iterator<_OutputIterator, _Tp>&> // purposefully not C++03
{
private:
    _OutputIterator __x_;
public:
    _LIBCPP_INLINE_VISIBILITY explicit raw_storage_iterator(_OutputIterator __x) : __x_(__x) {}
    _LIBCPP_INLINE_VISIBILITY raw_storage_iterator& operator*() {return *this;}
    _LIBCPP_INLINE_VISIBILITY raw_storage_iterator& operator=(const _Tp& __element)
        {::new(_VSTD::addressof(*__x_)) _Tp(__element); return *this;}
#if _LIBCPP_STD_VER >= 14
    _LIBCPP_INLINE_VISIBILITY raw_storage_iterator& operator=(_Tp&& __element)
        {::new(_VSTD::addressof(*__x_)) _Tp(_VSTD::move(__element)); return *this;}
#endif
    _LIBCPP_INLINE_VISIBILITY raw_storage_iterator& operator++() {++__x_; return *this;}
    _LIBCPP_INLINE_VISIBILITY raw_storage_iterator  operator++(int)
        {raw_storage_iterator __t(*this); ++__x_; return __t;}
#if _LIBCPP_STD_VER >= 14
    _LIBCPP_INLINE_VISIBILITY _OutputIterator base() const { return __x_; }
#endif
};

template <class _Tp>
_LIBCPP_NODISCARD_EXT _LIBCPP_NO_CFI
pair<_Tp*, ptrdiff_t>
get_temporary_buffer(ptrdiff_t __n) _NOEXCEPT
{
    pair<_Tp*, ptrdiff_t> __r(0, 0);
    const ptrdiff_t __m = (~ptrdiff_t(0) ^
                           ptrdiff_t(ptrdiff_t(1) << (sizeof(ptrdiff_t) * __CHAR_BIT__ - 1)))
                           / sizeof(_Tp);
    if (__n > __m)
        __n = __m;
    while (__n > 0)
    {
#if !defined(_LIBCPP_HAS_NO_ALIGNED_ALLOCATION)
    if (__is_overaligned_for_new(_LIBCPP_ALIGNOF(_Tp)))
        {
            std::align_val_t __al =
                std::align_val_t(std::alignment_of<_Tp>::value);
            __r.first = static_cast<_Tp*>(::operator new(
                __n * sizeof(_Tp), __al, nothrow));
        } else {
            __r.first = static_cast<_Tp*>(::operator new(
                __n * sizeof(_Tp), nothrow));
        }
#else
    if (__is_overaligned_for_new(_LIBCPP_ALIGNOF(_Tp)))
        {
            // Since aligned operator new is unavailable, return an empty
            // buffer rather than one with invalid alignment.
            return __r;
        }

        __r.first = static_cast<_Tp*>(::operator new(__n * sizeof(_Tp), nothrow));
#endif

        if (__r.first)
        {
            __r.second = __n;
            break;
        }
        __n /= 2;
    }
    return __r;
}

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
void return_temporary_buffer(_Tp* __p) _NOEXCEPT
{
  _VSTD::__libcpp_deallocate_unsized((void*)__p, _LIBCPP_ALIGNOF(_Tp));
}

#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
template <class _Tp>
struct _LIBCPP_DEPRECATED_IN_CXX11 auto_ptr_ref
{
    _Tp* __ptr_;
};

template<class _Tp>
class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 auto_ptr
{
private:
    _Tp* __ptr_;
public:
    typedef _Tp element_type;

    _LIBCPP_INLINE_VISIBILITY explicit auto_ptr(_Tp* __p = 0) _NOEXCEPT : __ptr_(__p) {}
    _LIBCPP_INLINE_VISIBILITY auto_ptr(auto_ptr& __p) _NOEXCEPT : __ptr_(__p.release()) {}
    template<class _Up> _LIBCPP_INLINE_VISIBILITY auto_ptr(auto_ptr<_Up>& __p) _NOEXCEPT
        : __ptr_(__p.release()) {}
    _LIBCPP_INLINE_VISIBILITY auto_ptr& operator=(auto_ptr& __p) _NOEXCEPT
        {reset(__p.release()); return *this;}
    template<class _Up> _LIBCPP_INLINE_VISIBILITY auto_ptr& operator=(auto_ptr<_Up>& __p) _NOEXCEPT
        {reset(__p.release()); return *this;}
    _LIBCPP_INLINE_VISIBILITY auto_ptr& operator=(auto_ptr_ref<_Tp> __p) _NOEXCEPT
        {reset(__p.__ptr_); return *this;}
    _LIBCPP_INLINE_VISIBILITY ~auto_ptr() _NOEXCEPT {delete __ptr_;}

    _LIBCPP_INLINE_VISIBILITY _Tp& operator*() const _NOEXCEPT
        {return *__ptr_;}
    _LIBCPP_INLINE_VISIBILITY _Tp* operator->() const _NOEXCEPT {return __ptr_;}
    _LIBCPP_INLINE_VISIBILITY _Tp* get() const _NOEXCEPT {return __ptr_;}
    _LIBCPP_INLINE_VISIBILITY _Tp* release() _NOEXCEPT
    {
        _Tp* __t = __ptr_;
        __ptr_ = 0;
        return __t;
    }
    _LIBCPP_INLINE_VISIBILITY void reset(_Tp* __p = 0) _NOEXCEPT
    {
        if (__ptr_ != __p)
            delete __ptr_;
        __ptr_ = __p;
    }

    _LIBCPP_INLINE_VISIBILITY auto_ptr(auto_ptr_ref<_Tp> __p) _NOEXCEPT : __ptr_(__p.__ptr_) {}
    template<class _Up> _LIBCPP_INLINE_VISIBILITY operator auto_ptr_ref<_Up>() _NOEXCEPT
        {auto_ptr_ref<_Up> __t; __t.__ptr_ = release(); return __t;}
    template<class _Up> _LIBCPP_INLINE_VISIBILITY operator auto_ptr<_Up>() _NOEXCEPT
        {return auto_ptr<_Up>(release());}
};

template <>
class _LIBCPP_TEMPLATE_VIS _LIBCPP_DEPRECATED_IN_CXX11 auto_ptr<void>
{
public:
    typedef void element_type;
};
#endif

// Tag used to default initialize one or both of the pair's elements.
struct __default_init_tag {};
struct __value_init_tag {};

template <class _Tp, int _Idx,
          bool _CanBeEmptyBase =
              is_empty<_Tp>::value && !__libcpp_is_final<_Tp>::value>
struct __compressed_pair_elem {
  typedef _Tp _ParamT;
  typedef _Tp& reference;
  typedef const _Tp& const_reference;

  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
  __compressed_pair_elem(__default_init_tag) {}
  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
  __compressed_pair_elem(__value_init_tag) : __value_() {}

  template <class _Up, class = typename enable_if<
      !is_same<__compressed_pair_elem, typename decay<_Up>::type>::value
  >::type>
  _LIBCPP_INLINE_VISIBILITY
  _LIBCPP_CONSTEXPR explicit
  __compressed_pair_elem(_Up&& __u)
      : __value_(_VSTD::forward<_Up>(__u))
    {
    }


#ifndef _LIBCPP_CXX03_LANG
  template <class... _Args, size_t... _Indexes>
  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
  __compressed_pair_elem(piecewise_construct_t, tuple<_Args...> __args,
                         __tuple_indices<_Indexes...>)
      : __value_(_VSTD::forward<_Args>(_VSTD::get<_Indexes>(__args))...) {}
#endif


  _LIBCPP_INLINE_VISIBILITY reference __get() _NOEXCEPT { return __value_; }
  _LIBCPP_INLINE_VISIBILITY
  const_reference __get() const _NOEXCEPT { return __value_; }

private:
  _Tp __value_;
};

template <class _Tp, int _Idx>
struct __compressed_pair_elem<_Tp, _Idx, true> : private _Tp {
  typedef _Tp _ParamT;
  typedef _Tp& reference;
  typedef const _Tp& const_reference;
  typedef _Tp __value_type;

  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR __compressed_pair_elem() = default;
  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
  __compressed_pair_elem(__default_init_tag) {}
  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
  __compressed_pair_elem(__value_init_tag) : __value_type() {}

  template <class _Up, class = typename enable_if<
        !is_same<__compressed_pair_elem, typename decay<_Up>::type>::value
  >::type>
  _LIBCPP_INLINE_VISIBILITY
  _LIBCPP_CONSTEXPR explicit
  __compressed_pair_elem(_Up&& __u)
      : __value_type(_VSTD::forward<_Up>(__u))
  {}

#ifndef _LIBCPP_CXX03_LANG
  template <class... _Args, size_t... _Indexes>
  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
  __compressed_pair_elem(piecewise_construct_t, tuple<_Args...> __args,
                         __tuple_indices<_Indexes...>)
      : __value_type(_VSTD::forward<_Args>(_VSTD::get<_Indexes>(__args))...) {}
#endif

  _LIBCPP_INLINE_VISIBILITY reference __get() _NOEXCEPT { return *this; }
  _LIBCPP_INLINE_VISIBILITY
  const_reference __get() const _NOEXCEPT { return *this; }
};

template <class _T1, class _T2>
class __compressed_pair : private __compressed_pair_elem<_T1, 0>,
                          private __compressed_pair_elem<_T2, 1> {
  typedef _LIBCPP_NODEBUG_TYPE __compressed_pair_elem<_T1, 0> _Base1;
  typedef _LIBCPP_NODEBUG_TYPE __compressed_pair_elem<_T2, 1> _Base2;

  // NOTE: This static assert should never fire because __compressed_pair
  // is *almost never* used in a scenario where it's possible for T1 == T2.
  // (The exception is std::function where it is possible that the function
  //  object and the allocator have the same type).
  static_assert((!is_same<_T1, _T2>::value),
    "__compressed_pair cannot be instantated when T1 and T2 are the same type; "
    "The current implementation is NOT ABI-compatible with the previous "
    "implementation for this configuration");

public:
    template <bool _Dummy = true,
      class = typename enable_if<
          __dependent_type<is_default_constructible<_T1>, _Dummy>::value &&
          __dependent_type<is_default_constructible<_T2>, _Dummy>::value
      >::type
  >
  _LIBCPP_INLINE_VISIBILITY
  _LIBCPP_CONSTEXPR __compressed_pair() : _Base1(__value_init_tag()), _Base2(__value_init_tag()) {}

  template <class _U1, class _U2>
  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
  __compressed_pair(_U1&& __t1, _U2&& __t2)
      : _Base1(std::forward<_U1>(__t1)), _Base2(std::forward<_U2>(__t2)) {}

#ifndef _LIBCPP_CXX03_LANG
  template <class... _Args1, class... _Args2>
  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
  __compressed_pair(piecewise_construct_t __pc, tuple<_Args1...> __first_args,
                    tuple<_Args2...> __second_args)
      : _Base1(__pc, _VSTD::move(__first_args),
               typename __make_tuple_indices<sizeof...(_Args1)>::type()),
        _Base2(__pc, _VSTD::move(__second_args),
               typename __make_tuple_indices<sizeof...(_Args2)>::type()) {}
#endif

  _LIBCPP_INLINE_VISIBILITY
  typename _Base1::reference first() _NOEXCEPT {
    return static_cast<_Base1&>(*this).__get();
  }

  _LIBCPP_INLINE_VISIBILITY
  typename _Base1::const_reference first() const _NOEXCEPT {
    return static_cast<_Base1 const&>(*this).__get();
  }

  _LIBCPP_INLINE_VISIBILITY
  typename _Base2::reference second() _NOEXCEPT {
    return static_cast<_Base2&>(*this).__get();
  }

  _LIBCPP_INLINE_VISIBILITY
  typename _Base2::const_reference second() const _NOEXCEPT {
    return static_cast<_Base2 const&>(*this).__get();
  }

  _LIBCPP_INLINE_VISIBILITY
  void swap(__compressed_pair& __x)
    _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
               __is_nothrow_swappable<_T2>::value)
  {
    using std::swap;
    swap(first(), __x.first());
    swap(second(), __x.second());
  }
};

template <class _T1, class _T2>
inline _LIBCPP_INLINE_VISIBILITY
void swap(__compressed_pair<_T1, _T2>& __x, __compressed_pair<_T1, _T2>& __y)
    _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
               __is_nothrow_swappable<_T2>::value) {
  __x.swap(__y);
}

// default_delete

template <class _Tp>
struct _LIBCPP_TEMPLATE_VIS default_delete {
    static_assert(!is_function<_Tp>::value,
                  "default_delete cannot be instantiated for function types");
#ifndef _LIBCPP_CXX03_LANG
  _LIBCPP_INLINE_VISIBILITY constexpr default_delete() _NOEXCEPT = default;
#else
  _LIBCPP_INLINE_VISIBILITY default_delete() {}
#endif
  template <class _Up>
  _LIBCPP_INLINE_VISIBILITY
  default_delete(const default_delete<_Up>&,
                 typename enable_if<is_convertible<_Up*, _Tp*>::value>::type* =
                     0) _NOEXCEPT {}

  _LIBCPP_INLINE_VISIBILITY void operator()(_Tp* __ptr) const _NOEXCEPT {
    static_assert(sizeof(_Tp) > 0,
                  "default_delete can not delete incomplete type");
    static_assert(!is_void<_Tp>::value,
                  "default_delete can not delete incomplete type");
    delete __ptr;
  }
};

template <class _Tp>
struct _LIBCPP_TEMPLATE_VIS default_delete<_Tp[]> {
private:
  template <class _Up>
  struct _EnableIfConvertible
      : enable_if<is_convertible<_Up(*)[], _Tp(*)[]>::value> {};

public:
#ifndef _LIBCPP_CXX03_LANG
  _LIBCPP_INLINE_VISIBILITY constexpr default_delete() _NOEXCEPT = default;
#else
  _LIBCPP_INLINE_VISIBILITY default_delete() {}
#endif

  template <class _Up>
  _LIBCPP_INLINE_VISIBILITY
  default_delete(const default_delete<_Up[]>&,
                 typename _EnableIfConvertible<_Up>::type* = 0) _NOEXCEPT {}

  template <class _Up>
  _LIBCPP_INLINE_VISIBILITY
  typename _EnableIfConvertible<_Up>::type
  operator()(_Up* __ptr) const _NOEXCEPT {
    static_assert(sizeof(_Tp) > 0,
                  "default_delete can not delete incomplete type");
    static_assert(!is_void<_Tp>::value,
                  "default_delete can not delete void type");
    delete[] __ptr;
  }
};

template <class _Deleter>
struct __unique_ptr_deleter_sfinae {
  static_assert(!is_reference<_Deleter>::value, "incorrect specialization");
  typedef const _Deleter& __lval_ref_type;
  typedef _Deleter&& __good_rval_ref_type;
  typedef true_type __enable_rval_overload;
};

template <class _Deleter>
struct __unique_ptr_deleter_sfinae<_Deleter const&> {
  typedef const _Deleter& __lval_ref_type;
  typedef const _Deleter&& __bad_rval_ref_type;
  typedef false_type __enable_rval_overload;
};

template <class _Deleter>
struct __unique_ptr_deleter_sfinae<_Deleter&> {
  typedef _Deleter& __lval_ref_type;
  typedef _Deleter&& __bad_rval_ref_type;
  typedef false_type __enable_rval_overload;
};

#if defined(_LIBCPP_ABI_ENABLE_UNIQUE_PTR_TRIVIAL_ABI)
#  define _LIBCPP_UNIQUE_PTR_TRIVIAL_ABI __attribute__((trivial_abi))
#else
#  define _LIBCPP_UNIQUE_PTR_TRIVIAL_ABI
#endif

template <class _Tp, class _Dp = default_delete<_Tp> >
class _LIBCPP_UNIQUE_PTR_TRIVIAL_ABI _LIBCPP_TEMPLATE_VIS unique_ptr {
public:
  typedef _Tp element_type;
  typedef _Dp deleter_type;
  typedef _LIBCPP_NODEBUG_TYPE typename __pointer_type<_Tp, deleter_type>::type pointer;

  static_assert(!is_rvalue_reference<deleter_type>::value,
                "the specified deleter type cannot be an rvalue reference");

private:
  __compressed_pair<pointer, deleter_type> __ptr_;

  struct __nat { int __for_bool_; };

  typedef _LIBCPP_NODEBUG_TYPE __unique_ptr_deleter_sfinae<_Dp> _DeleterSFINAE;

  template <bool _Dummy>
  using _LValRefType _LIBCPP_NODEBUG_TYPE =
      typename __dependent_type<_DeleterSFINAE, _Dummy>::__lval_ref_type;

  template <bool _Dummy>
  using _GoodRValRefType _LIBCPP_NODEBUG_TYPE =
      typename __dependent_type<_DeleterSFINAE, _Dummy>::__good_rval_ref_type;

  template <bool _Dummy>
  using _BadRValRefType _LIBCPP_NODEBUG_TYPE  =
      typename __dependent_type<_DeleterSFINAE, _Dummy>::__bad_rval_ref_type;

  template <bool _Dummy, class _Deleter = typename __dependent_type<
                             __identity<deleter_type>, _Dummy>::type>
  using _EnableIfDeleterDefaultConstructible _LIBCPP_NODEBUG_TYPE =
      typename enable_if<is_default_constructible<_Deleter>::value &&
                         !is_pointer<_Deleter>::value>::type;

  template <class _ArgType>
  using _EnableIfDeleterConstructible _LIBCPP_NODEBUG_TYPE  =
      typename enable_if<is_constructible<deleter_type, _ArgType>::value>::type;

  template <class _UPtr, class _Up>
  using _EnableIfMoveConvertible _LIBCPP_NODEBUG_TYPE  = typename enable_if<
      is_convertible<typename _UPtr::pointer, pointer>::value &&
      !is_array<_Up>::value
  >::type;

  template <class _UDel>
  using _EnableIfDeleterConvertible _LIBCPP_NODEBUG_TYPE  = typename enable_if<
      (is_reference<_Dp>::value && is_same<_Dp, _UDel>::value) ||
      (!is_reference<_Dp>::value && is_convertible<_UDel, _Dp>::value)
    >::type;

  template <class _UDel>
  using _EnableIfDeleterAssignable = typename enable_if<
      is_assignable<_Dp&, _UDel&&>::value
    >::type;

public:
  template <bool _Dummy = true,
            class = _EnableIfDeleterDefaultConstructible<_Dummy> >
  _LIBCPP_INLINE_VISIBILITY
  _LIBCPP_CONSTEXPR unique_ptr() _NOEXCEPT : __ptr_(pointer(), __default_init_tag()) {}

  template <bool _Dummy = true,
            class = _EnableIfDeleterDefaultConstructible<_Dummy> >
  _LIBCPP_INLINE_VISIBILITY
  _LIBCPP_CONSTEXPR unique_ptr(nullptr_t) _NOEXCEPT : __ptr_(pointer(), __default_init_tag()) {}

  template <bool _Dummy = true,
            class = _EnableIfDeleterDefaultConstructible<_Dummy> >
  _LIBCPP_INLINE_VISIBILITY
  explicit unique_ptr(pointer __p) _NOEXCEPT : __ptr_(__p, __default_init_tag()) {}

  template <bool _Dummy = true,
            class = _EnableIfDeleterConstructible<_LValRefType<_Dummy> > >
  _LIBCPP_INLINE_VISIBILITY
  unique_ptr(pointer __p, _LValRefType<_Dummy> __d) _NOEXCEPT
      : __ptr_(__p, __d) {}

  template <bool _Dummy = true,
            class = _EnableIfDeleterConstructible<_GoodRValRefType<_Dummy> > >
  _LIBCPP_INLINE_VISIBILITY
  unique_ptr(pointer __p, _GoodRValRefType<_Dummy> __d) _NOEXCEPT
      : __ptr_(__p, _VSTD::move(__d)) {
    static_assert(!is_reference<deleter_type>::value,
                  "rvalue deleter bound to reference");
  }

  template <bool _Dummy = true,
            class = _EnableIfDeleterConstructible<_BadRValRefType<_Dummy> > >
  _LIBCPP_INLINE_VISIBILITY
  unique_ptr(pointer __p, _BadRValRefType<_Dummy> __d) = delete;

  _LIBCPP_INLINE_VISIBILITY
  unique_ptr(unique_ptr&& __u) _NOEXCEPT
      : __ptr_(__u.release(), _VSTD::forward<deleter_type>(__u.get_deleter())) {
  }

  template <class _Up, class _Ep,
      class = _EnableIfMoveConvertible<unique_ptr<_Up, _Ep>, _Up>,
      class = _EnableIfDeleterConvertible<_Ep>
  >
  _LIBCPP_INLINE_VISIBILITY
  unique_ptr(unique_ptr<_Up, _Ep>&& __u) _NOEXCEPT
      : __ptr_(__u.release(), _VSTD::forward<_Ep>(__u.get_deleter())) {}

#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
  template <class _Up>
  _LIBCPP_INLINE_VISIBILITY
  unique_ptr(auto_ptr<_Up>&& __p,
             typename enable_if<is_convertible<_Up*, _Tp*>::value &&
                                    is_same<_Dp, default_delete<_Tp> >::value,
                                __nat>::type = __nat()) _NOEXCEPT
      : __ptr_(__p.release(), __default_init_tag()) {}
#endif

  _LIBCPP_INLINE_VISIBILITY
  unique_ptr& operator=(unique_ptr&& __u) _NOEXCEPT {
    reset(__u.release());
    __ptr_.second() = _VSTD::forward<deleter_type>(__u.get_deleter());
    return *this;
  }

  template <class _Up, class _Ep,
      class = _EnableIfMoveConvertible<unique_ptr<_Up, _Ep>, _Up>,
      class = _EnableIfDeleterAssignable<_Ep>
  >
  _LIBCPP_INLINE_VISIBILITY
  unique_ptr& operator=(unique_ptr<_Up, _Ep>&& __u) _NOEXCEPT {
    reset(__u.release());
    __ptr_.second() = _VSTD::forward<_Ep>(__u.get_deleter());
    return *this;
  }

#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
  template <class _Up>
  _LIBCPP_INLINE_VISIBILITY
      typename enable_if<is_convertible<_Up*, _Tp*>::value &&
                             is_same<_Dp, default_delete<_Tp> >::value,
                         unique_ptr&>::type
      operator=(auto_ptr<_Up> __p) {
    reset(__p.release());
    return *this;
  }
#endif

#ifdef _LIBCPP_CXX03_LANG
  unique_ptr(unique_ptr const&) = delete;
  unique_ptr& operator=(unique_ptr const&) = delete;
#endif


  _LIBCPP_INLINE_VISIBILITY
  ~unique_ptr() { reset(); }

  _LIBCPP_INLINE_VISIBILITY
  unique_ptr& operator=(nullptr_t) _NOEXCEPT {
    reset();
    return *this;
  }

  _LIBCPP_INLINE_VISIBILITY
  typename add_lvalue_reference<_Tp>::type
  operator*() const {
    return *__ptr_.first();
  }
  _LIBCPP_INLINE_VISIBILITY
  pointer operator->() const _NOEXCEPT {
    return __ptr_.first();
  }
  _LIBCPP_INLINE_VISIBILITY
  pointer get() const _NOEXCEPT {
    return __ptr_.first();
  }
  _LIBCPP_INLINE_VISIBILITY
  deleter_type& get_deleter() _NOEXCEPT {
    return __ptr_.second();
  }
  _LIBCPP_INLINE_VISIBILITY
  const deleter_type& get_deleter() const _NOEXCEPT {
    return __ptr_.second();
  }
  _LIBCPP_INLINE_VISIBILITY
  _LIBCPP_EXPLICIT operator bool() const _NOEXCEPT {
    return __ptr_.first() != nullptr;
  }

  _LIBCPP_INLINE_VISIBILITY
  pointer release() _NOEXCEPT {
    pointer __t = __ptr_.first();
    __ptr_.first() = pointer();
    return __t;
  }

  _LIBCPP_INLINE_VISIBILITY
  void reset(pointer __p = pointer()) _NOEXCEPT {
    pointer __tmp = __ptr_.first();
    __ptr_.first() = __p;
    if (__tmp)
      __ptr_.second()(__tmp);
  }

  _LIBCPP_INLINE_VISIBILITY
  void swap(unique_ptr& __u) _NOEXCEPT {
    __ptr_.swap(__u.__ptr_);
  }
};


template <class _Tp, class _Dp>
class _LIBCPP_UNIQUE_PTR_TRIVIAL_ABI _LIBCPP_TEMPLATE_VIS unique_ptr<_Tp[], _Dp> {
public:
  typedef _Tp element_type;
  typedef _Dp deleter_type;
  typedef typename __pointer_type<_Tp, deleter_type>::type pointer;

private:
  __compressed_pair<pointer, deleter_type> __ptr_;

  template <class _From>
  struct _CheckArrayPointerConversion : is_same<_From, pointer> {};

  template <class _FromElem>
  struct _CheckArrayPointerConversion<_FromElem*>
      : integral_constant<bool,
          is_same<_FromElem*, pointer>::value ||
            (is_same<pointer, element_type*>::value &&
             is_convertible<_FromElem(*)[], element_type(*)[]>::value)
      >
  {};

  typedef __unique_ptr_deleter_sfinae<_Dp> _DeleterSFINAE;

  template <bool _Dummy>
  using _LValRefType _LIBCPP_NODEBUG_TYPE =
      typename __dependent_type<_DeleterSFINAE, _Dummy>::__lval_ref_type;

  template <bool _Dummy>
  using _GoodRValRefType _LIBCPP_NODEBUG_TYPE =
      typename __dependent_type<_DeleterSFINAE, _Dummy>::__good_rval_ref_type;

  template <bool _Dummy>
  using _BadRValRefType _LIBCPP_NODEBUG_TYPE =
      typename __dependent_type<_DeleterSFINAE, _Dummy>::__bad_rval_ref_type;

  template <bool _Dummy, class _Deleter = typename __dependent_type<
                             __identity<deleter_type>, _Dummy>::type>
  using _EnableIfDeleterDefaultConstructible _LIBCPP_NODEBUG_TYPE  =
      typename enable_if<is_default_constructible<_Deleter>::value &&
                         !is_pointer<_Deleter>::value>::type;

  template <class _ArgType>
  using _EnableIfDeleterConstructible _LIBCPP_NODEBUG_TYPE  =
      typename enable_if<is_constructible<deleter_type, _ArgType>::value>::type;

  template <class _Pp>
  using _EnableIfPointerConvertible _LIBCPP_NODEBUG_TYPE  = typename enable_if<
      _CheckArrayPointerConversion<_Pp>::value
  >::type;

  template <class _UPtr, class _Up,
        class _ElemT = typename _UPtr::element_type>
  using _EnableIfMoveConvertible _LIBCPP_NODEBUG_TYPE  = typename enable_if<
      is_array<_Up>::value &&
      is_same<pointer, element_type*>::value &&
      is_same<typename _UPtr::pointer, _ElemT*>::value &&
      is_convertible<_ElemT(*)[], element_type(*)[]>::value
    >::type;

  template <class _UDel>
  using _EnableIfDeleterConvertible _LIBCPP_NODEBUG_TYPE  = typename enable_if<
      (is_reference<_Dp>::value && is_same<_Dp, _UDel>::value) ||
      (!is_reference<_Dp>::value && is_convertible<_UDel, _Dp>::value)
    >::type;

  template <class _UDel>
  using _EnableIfDeleterAssignable _LIBCPP_NODEBUG_TYPE  = typename enable_if<
      is_assignable<_Dp&, _UDel&&>::value
    >::type;

public:
  template <bool _Dummy = true,
            class = _EnableIfDeleterDefaultConstructible<_Dummy> >
  _LIBCPP_INLINE_VISIBILITY
  _LIBCPP_CONSTEXPR unique_ptr() _NOEXCEPT : __ptr_(pointer(), __default_init_tag()) {}

  template <bool _Dummy = true,
            class = _EnableIfDeleterDefaultConstructible<_Dummy> >
  _LIBCPP_INLINE_VISIBILITY
  _LIBCPP_CONSTEXPR unique_ptr(nullptr_t) _NOEXCEPT : __ptr_(pointer(), __default_init_tag()) {}

  template <class _Pp, bool _Dummy = true,
            class = _EnableIfDeleterDefaultConstructible<_Dummy>,
            class = _EnableIfPointerConvertible<_Pp> >
  _LIBCPP_INLINE_VISIBILITY
  explicit unique_ptr(_Pp __p) _NOEXCEPT
      : __ptr_(__p, __default_init_tag()) {}

  template <class _Pp, bool _Dummy = true,
            class = _EnableIfDeleterConstructible<_LValRefType<_Dummy> >,
            class = _EnableIfPointerConvertible<_Pp> >
  _LIBCPP_INLINE_VISIBILITY
  unique_ptr(_Pp __p, _LValRefType<_Dummy> __d) _NOEXCEPT
      : __ptr_(__p, __d) {}

  template <bool _Dummy = true,
            class = _EnableIfDeleterConstructible<_LValRefType<_Dummy> > >
  _LIBCPP_INLINE_VISIBILITY
  unique_ptr(nullptr_t, _LValRefType<_Dummy> __d) _NOEXCEPT
      : __ptr_(nullptr, __d) {}

  template <class _Pp, bool _Dummy = true,
            class = _EnableIfDeleterConstructible<_GoodRValRefType<_Dummy> >,
            class = _EnableIfPointerConvertible<_Pp> >
  _LIBCPP_INLINE_VISIBILITY
  unique_ptr(_Pp __p, _GoodRValRefType<_Dummy> __d) _NOEXCEPT
      : __ptr_(__p, _VSTD::move(__d)) {
    static_assert(!is_reference<deleter_type>::value,
                  "rvalue deleter bound to reference");
  }

  template <bool _Dummy = true,
            class = _EnableIfDeleterConstructible<_GoodRValRefType<_Dummy> > >
  _LIBCPP_INLINE_VISIBILITY
  unique_ptr(nullptr_t, _GoodRValRefType<_Dummy> __d) _NOEXCEPT
      : __ptr_(nullptr, _VSTD::move(__d)) {
    static_assert(!is_reference<deleter_type>::value,
                  "rvalue deleter bound to reference");
  }

  template <class _Pp, bool _Dummy = true,
            class = _EnableIfDeleterConstructible<_BadRValRefType<_Dummy> >,
            class = _EnableIfPointerConvertible<_Pp> >
  _LIBCPP_INLINE_VISIBILITY
  unique_ptr(_Pp __p, _BadRValRefType<_Dummy> __d) = delete;

  _LIBCPP_INLINE_VISIBILITY
  unique_ptr(unique_ptr&& __u) _NOEXCEPT
      : __ptr_(__u.release(), _VSTD::forward<deleter_type>(__u.get_deleter())) {
  }

  _LIBCPP_INLINE_VISIBILITY
  unique_ptr& operator=(unique_ptr&& __u) _NOEXCEPT {
    reset(__u.release());
    __ptr_.second() = _VSTD::forward<deleter_type>(__u.get_deleter());
    return *this;
  }

  template <class _Up, class _Ep,
      class = _EnableIfMoveConvertible<unique_ptr<_Up, _Ep>, _Up>,
      class = _EnableIfDeleterConvertible<_Ep>
  >
  _LIBCPP_INLINE_VISIBILITY
  unique_ptr(unique_ptr<_Up, _Ep>&& __u) _NOEXCEPT
      : __ptr_(__u.release(), _VSTD::forward<_Ep>(__u.get_deleter())) {
  }

  template <class _Up, class _Ep,
      class = _EnableIfMoveConvertible<unique_ptr<_Up, _Ep>, _Up>,
      class = _EnableIfDeleterAssignable<_Ep>
  >
  _LIBCPP_INLINE_VISIBILITY
  unique_ptr&
  operator=(unique_ptr<_Up, _Ep>&& __u) _NOEXCEPT {
    reset(__u.release());
    __ptr_.second() = _VSTD::forward<_Ep>(__u.get_deleter());
    return *this;
  }

#ifdef _LIBCPP_CXX03_LANG
  unique_ptr(unique_ptr const&) = delete;
  unique_ptr& operator=(unique_ptr const&) = delete;
#endif

public:
  _LIBCPP_INLINE_VISIBILITY
  ~unique_ptr() { reset(); }

  _LIBCPP_INLINE_VISIBILITY
  unique_ptr& operator=(nullptr_t) _NOEXCEPT {
    reset();
    return *this;
  }

  _LIBCPP_INLINE_VISIBILITY
  typename add_lvalue_reference<_Tp>::type
  operator[](size_t __i) const {
    return __ptr_.first()[__i];
  }
  _LIBCPP_INLINE_VISIBILITY
  pointer get() const _NOEXCEPT {
    return __ptr_.first();
  }

  _LIBCPP_INLINE_VISIBILITY
  deleter_type& get_deleter() _NOEXCEPT {
    return __ptr_.second();
  }

  _LIBCPP_INLINE_VISIBILITY
  const deleter_type& get_deleter() const _NOEXCEPT {
    return __ptr_.second();
  }
  _LIBCPP_INLINE_VISIBILITY
  _LIBCPP_EXPLICIT operator bool() const _NOEXCEPT {
    return __ptr_.first() != nullptr;
  }

  _LIBCPP_INLINE_VISIBILITY
  pointer release() _NOEXCEPT {
    pointer __t = __ptr_.first();
    __ptr_.first() = pointer();
    return __t;
  }

  template <class _Pp>
  _LIBCPP_INLINE_VISIBILITY
  typename enable_if<
      _CheckArrayPointerConversion<_Pp>::value
  >::type
  reset(_Pp __p) _NOEXCEPT {
    pointer __tmp = __ptr_.first();
    __ptr_.first() = __p;
    if (__tmp)
      __ptr_.second()(__tmp);
  }

  _LIBCPP_INLINE_VISIBILITY
  void reset(nullptr_t = nullptr) _NOEXCEPT {
    pointer __tmp = __ptr_.first();
    __ptr_.first() = nullptr;
    if (__tmp)
      __ptr_.second()(__tmp);
  }

  _LIBCPP_INLINE_VISIBILITY
  void swap(unique_ptr& __u) _NOEXCEPT {
    __ptr_.swap(__u.__ptr_);
  }

};

template <class _Tp, class _Dp>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if<
    __is_swappable<_Dp>::value,
    void
>::type
swap(unique_ptr<_Tp, _Dp>& __x, unique_ptr<_Tp, _Dp>& __y) _NOEXCEPT {__x.swap(__y);}

template <class _T1, class _D1, class _T2, class _D2>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(const unique_ptr<_T1, _D1>& __x, const unique_ptr<_T2, _D2>& __y) {return __x.get() == __y.get();}

template <class _T1, class _D1, class _T2, class _D2>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const unique_ptr<_T1, _D1>& __x, const unique_ptr<_T2, _D2>& __y) {return !(__x == __y);}

template <class _T1, class _D1, class _T2, class _D2>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator< (const unique_ptr<_T1, _D1>& __x, const unique_ptr<_T2, _D2>& __y)
{
    typedef typename unique_ptr<_T1, _D1>::pointer _P1;
    typedef typename unique_ptr<_T2, _D2>::pointer _P2;
    typedef typename common_type<_P1, _P2>::type _Vp;
    return less<_Vp>()(__x.get(), __y.get());
}

template <class _T1, class _D1, class _T2, class _D2>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator> (const unique_ptr<_T1, _D1>& __x, const unique_ptr<_T2, _D2>& __y) {return __y < __x;}

template <class _T1, class _D1, class _T2, class _D2>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(const unique_ptr<_T1, _D1>& __x, const unique_ptr<_T2, _D2>& __y) {return !(__y < __x);}

template <class _T1, class _D1, class _T2, class _D2>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>=(const unique_ptr<_T1, _D1>& __x, const unique_ptr<_T2, _D2>& __y) {return !(__x < __y);}

template <class _T1, class _D1>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(const unique_ptr<_T1, _D1>& __x, nullptr_t) _NOEXCEPT
{
    return !__x;
}

template <class _T1, class _D1>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(nullptr_t, const unique_ptr<_T1, _D1>& __x) _NOEXCEPT
{
    return !__x;
}

template <class _T1, class _D1>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const unique_ptr<_T1, _D1>& __x, nullptr_t) _NOEXCEPT
{
    return static_cast<bool>(__x);
}

template <class _T1, class _D1>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(nullptr_t, const unique_ptr<_T1, _D1>& __x) _NOEXCEPT
{
    return static_cast<bool>(__x);
}

template <class _T1, class _D1>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<(const unique_ptr<_T1, _D1>& __x, nullptr_t)
{
    typedef typename unique_ptr<_T1, _D1>::pointer _P1;
    return less<_P1>()(__x.get(), nullptr);
}

template <class _T1, class _D1>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<(nullptr_t, const unique_ptr<_T1, _D1>& __x)
{
    typedef typename unique_ptr<_T1, _D1>::pointer _P1;
    return less<_P1>()(nullptr, __x.get());
}

template <class _T1, class _D1>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>(const unique_ptr<_T1, _D1>& __x, nullptr_t)
{
    return nullptr < __x;
}

template <class _T1, class _D1>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>(nullptr_t, const unique_ptr<_T1, _D1>& __x)
{
    return __x < nullptr;
}

template <class _T1, class _D1>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(const unique_ptr<_T1, _D1>& __x, nullptr_t)
{
    return !(nullptr < __x);
}

template <class _T1, class _D1>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(nullptr_t, const unique_ptr<_T1, _D1>& __x)
{
    return !(__x < nullptr);
}

template <class _T1, class _D1>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>=(const unique_ptr<_T1, _D1>& __x, nullptr_t)
{
    return !(__x < nullptr);
}

template <class _T1, class _D1>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>=(nullptr_t, const unique_ptr<_T1, _D1>& __x)
{
    return !(nullptr < __x);
}

#if _LIBCPP_STD_VER > 11

template<class _Tp>
struct __unique_if
{
    typedef unique_ptr<_Tp> __unique_single;
};

template<class _Tp>
struct __unique_if<_Tp[]>
{
    typedef unique_ptr<_Tp[]> __unique_array_unknown_bound;
};

template<class _Tp, size_t _Np>
struct __unique_if<_Tp[_Np]>
{
    typedef void __unique_array_known_bound;
};

template<class _Tp, class... _Args>
inline _LIBCPP_INLINE_VISIBILITY
typename __unique_if<_Tp>::__unique_single
make_unique(_Args&&... __args)
{
    return unique_ptr<_Tp>(new _Tp(_VSTD::forward<_Args>(__args)...));
}

template<class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
typename __unique_if<_Tp>::__unique_array_unknown_bound
make_unique(size_t __n)
{
    typedef typename remove_extent<_Tp>::type _Up;
    return unique_ptr<_Tp>(new _Up[__n]());
}

template<class _Tp, class... _Args>
    typename __unique_if<_Tp>::__unique_array_known_bound
    make_unique(_Args&&...) = delete;

#endif  // _LIBCPP_STD_VER > 11

template <class _Tp, class _Dp>
#ifdef _LIBCPP_CXX03_LANG
struct _LIBCPP_TEMPLATE_VIS hash<unique_ptr<_Tp, _Dp> >
#else
struct _LIBCPP_TEMPLATE_VIS hash<__enable_hash_helper<
    unique_ptr<_Tp, _Dp>, typename unique_ptr<_Tp, _Dp>::pointer> >
#endif
{
    typedef unique_ptr<_Tp, _Dp> argument_type;
    typedef size_t               result_type;
    _LIBCPP_INLINE_VISIBILITY
    result_type operator()(const argument_type& __ptr) const
    {
        typedef typename argument_type::pointer pointer;
        return hash<pointer>()(__ptr.get());
    }
};

struct __destruct_n
{
private:
    size_t __size_;

    template <class _Tp>
    _LIBCPP_INLINE_VISIBILITY void __process(_Tp* __p, false_type) _NOEXCEPT
        {for (size_t __i = 0; __i < __size_; ++__i, ++__p) __p->~_Tp();}

    template <class _Tp>
    _LIBCPP_INLINE_VISIBILITY void __process(_Tp*, true_type) _NOEXCEPT
        {}

    _LIBCPP_INLINE_VISIBILITY void __incr(false_type) _NOEXCEPT
        {++__size_;}
    _LIBCPP_INLINE_VISIBILITY void __incr(true_type) _NOEXCEPT
        {}

    _LIBCPP_INLINE_VISIBILITY void __set(size_t __s, false_type) _NOEXCEPT
        {__size_ = __s;}
    _LIBCPP_INLINE_VISIBILITY void __set(size_t, true_type) _NOEXCEPT
        {}
public:
    _LIBCPP_INLINE_VISIBILITY explicit __destruct_n(size_t __s) _NOEXCEPT
        : __size_(__s) {}

    template <class _Tp>
    _LIBCPP_INLINE_VISIBILITY void __incr(_Tp*) _NOEXCEPT
        {__incr(integral_constant<bool, is_trivially_destructible<_Tp>::value>());}

    template <class _Tp>
    _LIBCPP_INLINE_VISIBILITY void __set(size_t __s, _Tp*) _NOEXCEPT
        {__set(__s, integral_constant<bool, is_trivially_destructible<_Tp>::value>());}

    template <class _Tp>
    _LIBCPP_INLINE_VISIBILITY void operator()(_Tp* __p) _NOEXCEPT
        {__process(__p, integral_constant<bool, is_trivially_destructible<_Tp>::value>());}
};

template <class _Alloc>
class __allocator_destructor
{
    typedef _LIBCPP_NODEBUG_TYPE allocator_traits<_Alloc> __alloc_traits;
public:
    typedef _LIBCPP_NODEBUG_TYPE typename __alloc_traits::pointer pointer;
    typedef _LIBCPP_NODEBUG_TYPE typename __alloc_traits::size_type size_type;
private:
    _Alloc& __alloc_;
    size_type __s_;
public:
    _LIBCPP_INLINE_VISIBILITY __allocator_destructor(_Alloc& __a, size_type __s)
             _NOEXCEPT
        : __alloc_(__a), __s_(__s) {}
    _LIBCPP_INLINE_VISIBILITY
    void operator()(pointer __p) _NOEXCEPT
        {__alloc_traits::deallocate(__alloc_, __p, __s_);}
};

template <class _InputIterator, class _ForwardIterator>
_ForwardIterator
uninitialized_copy(_InputIterator __f, _InputIterator __l, _ForwardIterator __r)
{
    typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
#ifndef _LIBCPP_NO_EXCEPTIONS
    _ForwardIterator __s = __r;
    try
    {
#endif
        for (; __f != __l; ++__f, (void) ++__r)
            ::new (static_cast<void*>(_VSTD::addressof(*__r))) value_type(*__f);
#ifndef _LIBCPP_NO_EXCEPTIONS
    }
    catch (...)
    {
        for (; __s != __r; ++__s)
            __s->~value_type();
        throw;
    }
#endif
    return __r;
}

template <class _InputIterator, class _Size, class _ForwardIterator>
_ForwardIterator
uninitialized_copy_n(_InputIterator __f, _Size __n, _ForwardIterator __r)
{
    typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
#ifndef _LIBCPP_NO_EXCEPTIONS
    _ForwardIterator __s = __r;
    try
    {
#endif
        for (; __n > 0; ++__f, (void) ++__r, (void) --__n)
            ::new (static_cast<void*>(_VSTD::addressof(*__r))) value_type(*__f);
#ifndef _LIBCPP_NO_EXCEPTIONS
    }
    catch (...)
    {
        for (; __s != __r; ++__s)
            __s->~value_type();
        throw;
    }
#endif
    return __r;
}

template <class _ForwardIterator, class _Tp>
void
uninitialized_fill(_ForwardIterator __f, _ForwardIterator __l, const _Tp& __x)
{
    typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
#ifndef _LIBCPP_NO_EXCEPTIONS
    _ForwardIterator __s = __f;
    try
    {
#endif
        for (; __f != __l; ++__f)
            ::new (static_cast<void*>(_VSTD::addressof(*__f))) value_type(__x);
#ifndef _LIBCPP_NO_EXCEPTIONS
    }
    catch (...)
    {
        for (; __s != __f; ++__s)
            __s->~value_type();
        throw;
    }
#endif
}

template <class _ForwardIterator, class _Size, class _Tp>
_ForwardIterator
uninitialized_fill_n(_ForwardIterator __f, _Size __n, const _Tp& __x)
{
    typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
#ifndef _LIBCPP_NO_EXCEPTIONS
    _ForwardIterator __s = __f;
    try
    {
#endif
        for (; __n > 0; ++__f, (void) --__n)
            ::new (static_cast<void*>(_VSTD::addressof(*__f))) value_type(__x);
#ifndef _LIBCPP_NO_EXCEPTIONS
    }
    catch (...)
    {
        for (; __s != __f; ++__s)
            __s->~value_type();
        throw;
    }
#endif
    return __f;
}

#if _LIBCPP_STD_VER > 14

template <class _ForwardIterator>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
void destroy(_ForwardIterator __first, _ForwardIterator __last) {
    for (; __first != __last; ++__first)
        _VSTD::destroy_at(_VSTD::addressof(*__first));
}

template <class _ForwardIterator, class _Size>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
_ForwardIterator destroy_n(_ForwardIterator __first, _Size __n) {
    for (; __n > 0; (void)++__first, --__n)
        _VSTD::destroy_at(_VSTD::addressof(*__first));
    return __first;
}

template <class _ForwardIterator>
inline _LIBCPP_INLINE_VISIBILITY
void uninitialized_default_construct(_ForwardIterator __first, _ForwardIterator __last) {
    using _Vt = typename iterator_traits<_ForwardIterator>::value_type;
    auto __idx = __first;
#ifndef _LIBCPP_NO_EXCEPTIONS
    try {
#endif
    for (; __idx != __last; ++__idx)
        ::new((void*)_VSTD::addressof(*__idx)) _Vt;
#ifndef _LIBCPP_NO_EXCEPTIONS
    } catch (...) {
        _VSTD::destroy(__first, __idx);
        throw;
    }
#endif
}

template <class _ForwardIterator, class _Size>
inline _LIBCPP_INLINE_VISIBILITY
_ForwardIterator uninitialized_default_construct_n(_ForwardIterator __first, _Size __n) {
    using _Vt = typename iterator_traits<_ForwardIterator>::value_type;
    auto __idx = __first;
#ifndef _LIBCPP_NO_EXCEPTIONS
    try {
#endif
    for (; __n > 0; (void)++__idx, --__n)
        ::new((void*)_VSTD::addressof(*__idx)) _Vt;
    return __idx;
#ifndef _LIBCPP_NO_EXCEPTIONS
    } catch (...) {
        _VSTD::destroy(__first, __idx);
        throw;
    }
#endif
}


template <class _ForwardIterator>
inline _LIBCPP_INLINE_VISIBILITY
void uninitialized_value_construct(_ForwardIterator __first, _ForwardIterator __last) {
    using _Vt = typename iterator_traits<_ForwardIterator>::value_type;
    auto __idx = __first;
#ifndef _LIBCPP_NO_EXCEPTIONS
    try {
#endif
    for (; __idx != __last; ++__idx)
        ::new((void*)_VSTD::addressof(*__idx)) _Vt();
#ifndef _LIBCPP_NO_EXCEPTIONS
    } catch (...) {
        _VSTD::destroy(__first, __idx);
        throw;
    }
#endif
}

template <class _ForwardIterator, class _Size>
inline _LIBCPP_INLINE_VISIBILITY
_ForwardIterator uninitialized_value_construct_n(_ForwardIterator __first, _Size __n) {
    using _Vt = typename iterator_traits<_ForwardIterator>::value_type;
    auto __idx = __first;
#ifndef _LIBCPP_NO_EXCEPTIONS
    try {
#endif
    for (; __n > 0; (void)++__idx, --__n)
        ::new((void*)_VSTD::addressof(*__idx)) _Vt();
    return __idx;
#ifndef _LIBCPP_NO_EXCEPTIONS
    } catch (...) {
        _VSTD::destroy(__first, __idx);
        throw;
    }
#endif
}


template <class _InputIt, class _ForwardIt>
inline _LIBCPP_INLINE_VISIBILITY
_ForwardIt uninitialized_move(_InputIt __first, _InputIt __last, _ForwardIt __first_res) {
    using _Vt = typename iterator_traits<_ForwardIt>::value_type;
    auto __idx = __first_res;
#ifndef _LIBCPP_NO_EXCEPTIONS
    try {
#endif
    for (; __first != __last; (void)++__idx, ++__first)
        ::new((void*)_VSTD::addressof(*__idx)) _Vt(std::move(*__first));
    return __idx;
#ifndef _LIBCPP_NO_EXCEPTIONS
    } catch (...) {
        _VSTD::destroy(__first_res, __idx);
        throw;
    }
#endif
}

template <class _InputIt, class _Size, class _ForwardIt>
inline _LIBCPP_INLINE_VISIBILITY
pair<_InputIt, _ForwardIt>
uninitialized_move_n(_InputIt __first, _Size __n, _ForwardIt __first_res) {
    using _Vt = typename iterator_traits<_ForwardIt>::value_type;
    auto __idx = __first_res;
#ifndef _LIBCPP_NO_EXCEPTIONS
    try {
#endif
    for (; __n > 0; ++__idx, (void)++__first, --__n)
        ::new((void*)_VSTD::addressof(*__idx)) _Vt(std::move(*__first));
    return {__first, __idx};
#ifndef _LIBCPP_NO_EXCEPTIONS
    } catch (...) {
        _VSTD::destroy(__first_res, __idx);
        throw;
    }
#endif
}


#endif // _LIBCPP_STD_VER > 14

// NOTE: Relaxed and acq/rel atomics (for increment and decrement respectively)
// should be sufficient for thread safety.
// See https://bugs.llvm.org/show_bug.cgi?id=22803
#if defined(__clang__) && __has_builtin(__atomic_add_fetch)          \
                       && defined(__ATOMIC_RELAXED)                  \
                       && defined(__ATOMIC_ACQ_REL)
#   define _LIBCPP_HAS_BUILTIN_ATOMIC_SUPPORT
#elif defined(_LIBCPP_COMPILER_GCC)
#   define _LIBCPP_HAS_BUILTIN_ATOMIC_SUPPORT
#endif

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY _Tp
__libcpp_atomic_refcount_increment(_Tp& __t) _NOEXCEPT
{
#if defined(_LIBCPP_HAS_BUILTIN_ATOMIC_SUPPORT) && !defined(_LIBCPP_HAS_NO_THREADS)
    return __atomic_add_fetch(&__t, 1, __ATOMIC_RELAXED);
#else
    return __t += 1;
#endif
}

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY _Tp
__libcpp_atomic_refcount_decrement(_Tp& __t) _NOEXCEPT
{
#if defined(_LIBCPP_HAS_BUILTIN_ATOMIC_SUPPORT) && !defined(_LIBCPP_HAS_NO_THREADS)
    return __atomic_add_fetch(&__t, -1, __ATOMIC_ACQ_REL);
#else
    return __t -= 1;
#endif
}

class _LIBCPP_EXCEPTION_ABI bad_weak_ptr
    : public std::exception
{
public:
    bad_weak_ptr() _NOEXCEPT = default;
    bad_weak_ptr(const bad_weak_ptr&) _NOEXCEPT = default;
    virtual ~bad_weak_ptr() _NOEXCEPT;
    virtual const char* what() const  _NOEXCEPT;
};

_LIBCPP_NORETURN inline _LIBCPP_INLINE_VISIBILITY
void __throw_bad_weak_ptr()
{
#ifndef _LIBCPP_NO_EXCEPTIONS
    throw bad_weak_ptr();
#else
    _VSTD::abort();
#endif
}

template<class _Tp> class _LIBCPP_TEMPLATE_VIS weak_ptr;

class _LIBCPP_TYPE_VIS __shared_count
{
    __shared_count(const __shared_count&);
    __shared_count& operator=(const __shared_count&);

protected:
    long __shared_owners_;
    virtual ~__shared_count();
private:
    virtual void __on_zero_shared() _NOEXCEPT = 0;

public:
    _LIBCPP_INLINE_VISIBILITY
    explicit __shared_count(long __refs = 0) _NOEXCEPT
        : __shared_owners_(__refs) {}

#if defined(_LIBCPP_BUILDING_LIBRARY) && \
    defined(_LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS)
    void __add_shared() _NOEXCEPT;
    bool __release_shared() _NOEXCEPT;
#else
    _LIBCPP_INLINE_VISIBILITY
    void __add_shared() _NOEXCEPT {
      __libcpp_atomic_refcount_increment(__shared_owners_);
    }
    _LIBCPP_INLINE_VISIBILITY
    bool __release_shared() _NOEXCEPT {
      if (__libcpp_atomic_refcount_decrement(__shared_owners_) == -1) {
        __on_zero_shared();
        return true;
      }
      return false;
    }
#endif
    _LIBCPP_INLINE_VISIBILITY
    long use_count() const _NOEXCEPT {
        return __libcpp_relaxed_load(&__shared_owners_) + 1;
    }
};

class _LIBCPP_TYPE_VIS __shared_weak_count
    : private __shared_count
{
    long __shared_weak_owners_;

public:
    _LIBCPP_INLINE_VISIBILITY
    explicit __shared_weak_count(long __refs = 0) _NOEXCEPT
        : __shared_count(__refs),
          __shared_weak_owners_(__refs) {}
protected:
    virtual ~__shared_weak_count();

public:
#if defined(_LIBCPP_BUILDING_LIBRARY) && \
    defined(_LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS)
    void __add_shared() _NOEXCEPT;
    void __add_weak() _NOEXCEPT;
    void __release_shared() _NOEXCEPT;
#else
    _LIBCPP_INLINE_VISIBILITY
    void __add_shared() _NOEXCEPT {
      __shared_count::__add_shared();
    }
    _LIBCPP_INLINE_VISIBILITY
    void __add_weak() _NOEXCEPT {
      __libcpp_atomic_refcount_increment(__shared_weak_owners_);
    }
    _LIBCPP_INLINE_VISIBILITY
    void __release_shared() _NOEXCEPT {
      if (__shared_count::__release_shared())
        __release_weak();
    }
#endif
    void __release_weak() _NOEXCEPT;
    _LIBCPP_INLINE_VISIBILITY
    long use_count() const _NOEXCEPT {return __shared_count::use_count();}
    __shared_weak_count* lock() _NOEXCEPT;

    // Define the function out only if we build static libc++ without RTTI.
    // Otherwise we may break clients who need to compile their projects with
    // -fno-rtti and yet link against a libc++.dylib compiled
    // without -fno-rtti.
#if !defined(_LIBCPP_NO_RTTI) || !defined(_LIBCPP_BUILD_STATIC)
    virtual const void* __get_deleter(const type_info&) const _NOEXCEPT;
#endif
private:
    virtual void __on_zero_shared_weak() _NOEXCEPT = 0;
};

template <class _Tp, class _Dp, class _Alloc>
class __shared_ptr_pointer
    : public __shared_weak_count
{
    __compressed_pair<__compressed_pair<_Tp, _Dp>, _Alloc> __data_;
public:
    _LIBCPP_INLINE_VISIBILITY
    __shared_ptr_pointer(_Tp __p, _Dp __d, _Alloc __a)
        :  __data_(__compressed_pair<_Tp, _Dp>(__p, _VSTD::move(__d)), _VSTD::move(__a)) {}

#ifndef _LIBCPP_NO_RTTI
    virtual const void* __get_deleter(const type_info&) const _NOEXCEPT;
#endif

private:
    virtual void __on_zero_shared() _NOEXCEPT;
    virtual void __on_zero_shared_weak() _NOEXCEPT;
};

#ifndef _LIBCPP_NO_RTTI

template <class _Tp, class _Dp, class _Alloc>
const void*
__shared_ptr_pointer<_Tp, _Dp, _Alloc>::__get_deleter(const type_info& __t) const _NOEXCEPT
{
    return __t == typeid(_Dp) ? _VSTD::addressof(__data_.first().second()) : nullptr;
}

#endif  // _LIBCPP_NO_RTTI

template <class _Tp, class _Dp, class _Alloc>
void
__shared_ptr_pointer<_Tp, _Dp, _Alloc>::__on_zero_shared() _NOEXCEPT
{
    __data_.first().second()(__data_.first().first());
    __data_.first().second().~_Dp();
}

template <class _Tp, class _Dp, class _Alloc>
void
__shared_ptr_pointer<_Tp, _Dp, _Alloc>::__on_zero_shared_weak() _NOEXCEPT
{
    typedef typename __allocator_traits_rebind<_Alloc, __shared_ptr_pointer>::type _Al;
    typedef allocator_traits<_Al> _ATraits;
    typedef pointer_traits<typename _ATraits::pointer> _PTraits;

    _Al __a(__data_.second());
    __data_.second().~_Alloc();
    __a.deallocate(_PTraits::pointer_to(*this), 1);
}

template <class _Tp, class _Alloc>
class __shared_ptr_emplace
    : public __shared_weak_count
{
    __compressed_pair<_Alloc, _Tp> __data_;
public:

    _LIBCPP_INLINE_VISIBILITY
    __shared_ptr_emplace(_Alloc __a)
        :  __data_(_VSTD::move(__a), __value_init_tag()) {}

#ifndef _LIBCPP_CXX03_LANG
    template <class ..._Args>
        _LIBCPP_INLINE_VISIBILITY
        __shared_ptr_emplace(_Alloc __a, _Args&& ...__args)
            :  __data_(piecewise_construct, _VSTD::forward_as_tuple(__a),
                   _VSTD::forward_as_tuple(_VSTD::forward<_Args>(__args)...)) {}
#else
    template <class ..._Args>
        _LIBCPP_INLINE_VISIBILITY
        __shared_ptr_emplace(_Alloc __a, _Args&& ...__args)
            :  __data_(__a, _Tp(_VSTD::forward<_Args>(__args)...)) {}
#endif

private:
    virtual void __on_zero_shared() _NOEXCEPT;
    virtual void __on_zero_shared_weak() _NOEXCEPT;
public:
    _LIBCPP_INLINE_VISIBILITY
    _Tp* get() _NOEXCEPT {return _VSTD::addressof(__data_.second());}
};

template <class _Tp, class _Alloc>
void
__shared_ptr_emplace<_Tp, _Alloc>::__on_zero_shared() _NOEXCEPT
{
    __data_.second().~_Tp();
}

template <class _Tp, class _Alloc>
void
__shared_ptr_emplace<_Tp, _Alloc>::__on_zero_shared_weak() _NOEXCEPT
{
    typedef typename __allocator_traits_rebind<_Alloc, __shared_ptr_emplace>::type _Al;
    typedef allocator_traits<_Al> _ATraits;
    typedef pointer_traits<typename _ATraits::pointer> _PTraits;
    _Al __a(__data_.first());
    __data_.first().~_Alloc();
    __a.deallocate(_PTraits::pointer_to(*this), 1);
}

struct __shared_ptr_dummy_rebind_allocator_type;
template <>
class _LIBCPP_TEMPLATE_VIS allocator<__shared_ptr_dummy_rebind_allocator_type>
{
public:
    template <class _Other>
    struct rebind
    {
        typedef allocator<_Other> other;
    };
};

template<class _Tp> class _LIBCPP_TEMPLATE_VIS enable_shared_from_this;

template<class _Tp, class _Up>
struct __compatible_with
#if _LIBCPP_STD_VER > 14
    : is_convertible<remove_extent_t<_Tp>*, remove_extent_t<_Up>*> {};
#else
    : is_convertible<_Tp*, _Up*> {};
#endif // _LIBCPP_STD_VER > 14

#if defined(_LIBCPP_ABI_ENABLE_SHARED_PTR_TRIVIAL_ABI)
#  define _LIBCPP_SHARED_PTR_TRIVIAL_ABI __attribute__((trivial_abi))
#else
#  define _LIBCPP_SHARED_PTR_TRIVIAL_ABI
#endif

template<class _Tp>
class _LIBCPP_SHARED_PTR_TRIVIAL_ABI _LIBCPP_TEMPLATE_VIS shared_ptr
{
public:
#if _LIBCPP_STD_VER > 14
    typedef weak_ptr<_Tp> weak_type;
    typedef remove_extent_t<_Tp> element_type;
#else
    typedef _Tp element_type;
#endif

private:
    element_type*      __ptr_;
    __shared_weak_count* __cntrl_;

    struct __nat {int __for_bool_;};
public:
    _LIBCPP_INLINE_VISIBILITY
    _LIBCPP_CONSTEXPR shared_ptr() _NOEXCEPT;
    _LIBCPP_INLINE_VISIBILITY
    _LIBCPP_CONSTEXPR shared_ptr(nullptr_t) _NOEXCEPT;
    template<class _Yp>
        explicit shared_ptr(_Yp* __p,
                            typename enable_if<__compatible_with<_Yp, element_type>::value, __nat>::type = __nat());
    template<class _Yp, class _Dp>
        shared_ptr(_Yp* __p, _Dp __d,
                   typename enable_if<__compatible_with<_Yp, element_type>::value, __nat>::type = __nat());
    template<class _Yp, class _Dp, class _Alloc>
        shared_ptr(_Yp* __p, _Dp __d, _Alloc __a,
                   typename enable_if<__compatible_with<_Yp, element_type>::value, __nat>::type = __nat());
    template <class _Dp> shared_ptr(nullptr_t __p, _Dp __d);
    template <class _Dp, class _Alloc> shared_ptr(nullptr_t __p, _Dp __d, _Alloc __a);
    template<class _Yp> _LIBCPP_INLINE_VISIBILITY shared_ptr(const shared_ptr<_Yp>& __r, element_type* __p) _NOEXCEPT;
    _LIBCPP_INLINE_VISIBILITY
    shared_ptr(const shared_ptr& __r) _NOEXCEPT;
    template<class _Yp>
        _LIBCPP_INLINE_VISIBILITY
        shared_ptr(const shared_ptr<_Yp>& __r,
                   typename enable_if<__compatible_with<_Yp, element_type>::value, __nat>::type = __nat())
                       _NOEXCEPT;
    _LIBCPP_INLINE_VISIBILITY
    shared_ptr(shared_ptr&& __r) _NOEXCEPT;
    template<class _Yp> _LIBCPP_INLINE_VISIBILITY  shared_ptr(shared_ptr<_Yp>&& __r,
                   typename enable_if<__compatible_with<_Yp, element_type>::value, __nat>::type = __nat())
                       _NOEXCEPT;
    template<class _Yp> explicit shared_ptr(const weak_ptr<_Yp>& __r,
                   typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type= __nat());
#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
    template<class _Yp>
        shared_ptr(auto_ptr<_Yp>&& __r,
                   typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type = __nat());
#endif
    template <class _Yp, class _Dp>
        shared_ptr(unique_ptr<_Yp, _Dp>&&,
                   typename enable_if
                   <
                       !is_lvalue_reference<_Dp>::value &&
                       !is_array<_Yp>::value &&
                       is_convertible<typename unique_ptr<_Yp, _Dp>::pointer, element_type*>::value,
                       __nat
                   >::type = __nat());
    template <class _Yp, class _Dp>
        shared_ptr(unique_ptr<_Yp, _Dp>&&,
                   typename enable_if
                   <
                       is_lvalue_reference<_Dp>::value &&
                       !is_array<_Yp>::value &&
                       is_convertible<typename unique_ptr<_Yp, _Dp>::pointer, element_type*>::value,
                       __nat
                   >::type = __nat());

    ~shared_ptr();

    _LIBCPP_INLINE_VISIBILITY
    shared_ptr& operator=(const shared_ptr& __r) _NOEXCEPT;
    template<class _Yp>
        typename enable_if
        <
            __compatible_with<_Yp, element_type>::value,
            shared_ptr&
        >::type
        _LIBCPP_INLINE_VISIBILITY
        operator=(const shared_ptr<_Yp>& __r) _NOEXCEPT;
    _LIBCPP_INLINE_VISIBILITY
    shared_ptr& operator=(shared_ptr&& __r) _NOEXCEPT;
    template<class _Yp>
        typename enable_if
        <
            __compatible_with<_Yp, element_type>::value,
            shared_ptr&
        >::type
        _LIBCPP_INLINE_VISIBILITY
        operator=(shared_ptr<_Yp>&& __r);
#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
    template<class _Yp>
        _LIBCPP_INLINE_VISIBILITY
        typename enable_if
        <
            !is_array<_Yp>::value &&
            is_convertible<_Yp*, element_type*>::value,
            shared_ptr
        >::type&
        operator=(auto_ptr<_Yp>&& __r);
#endif
    template <class _Yp, class _Dp>
        typename enable_if
        <
            !is_array<_Yp>::value &&
            is_convertible<typename unique_ptr<_Yp, _Dp>::pointer, element_type*>::value,
            shared_ptr&
        >::type
        _LIBCPP_INLINE_VISIBILITY
        operator=(unique_ptr<_Yp, _Dp>&& __r);

    _LIBCPP_INLINE_VISIBILITY
    void swap(shared_ptr& __r) _NOEXCEPT;
    _LIBCPP_INLINE_VISIBILITY
    void reset() _NOEXCEPT;
    template<class _Yp>
        typename enable_if
        <
            __compatible_with<_Yp, element_type>::value,
            void
        >::type
        _LIBCPP_INLINE_VISIBILITY
        reset(_Yp* __p);
    template<class _Yp, class _Dp>
        typename enable_if
        <
            __compatible_with<_Yp, element_type>::value,
            void
        >::type
        _LIBCPP_INLINE_VISIBILITY
        reset(_Yp* __p, _Dp __d);
    template<class _Yp, class _Dp, class _Alloc>
        typename enable_if
        <
            __compatible_with<_Yp, element_type>::value,
            void
        >::type
        _LIBCPP_INLINE_VISIBILITY
        reset(_Yp* __p, _Dp __d, _Alloc __a);

    _LIBCPP_INLINE_VISIBILITY
    element_type* get() const _NOEXCEPT {return __ptr_;}
    _LIBCPP_INLINE_VISIBILITY
    typename add_lvalue_reference<element_type>::type operator*() const _NOEXCEPT
        {return *__ptr_;}
    _LIBCPP_INLINE_VISIBILITY
    element_type* operator->() const _NOEXCEPT
    {
        static_assert(!_VSTD::is_array<_Tp>::value,
                      "std::shared_ptr<T>::operator-> is only valid when T is not an array type.");
        return __ptr_;
    }
    _LIBCPP_INLINE_VISIBILITY
    long use_count() const _NOEXCEPT {return __cntrl_ ? __cntrl_->use_count() : 0;}
    _LIBCPP_INLINE_VISIBILITY
    bool unique() const _NOEXCEPT {return use_count() == 1;}
    _LIBCPP_INLINE_VISIBILITY
    _LIBCPP_EXPLICIT operator bool() const _NOEXCEPT {return get() != 0;}
    template <class _Up>
        _LIBCPP_INLINE_VISIBILITY
        bool owner_before(shared_ptr<_Up> const& __p) const _NOEXCEPT
        {return __cntrl_ < __p.__cntrl_;}
    template <class _Up>
        _LIBCPP_INLINE_VISIBILITY
        bool owner_before(weak_ptr<_Up> const& __p) const _NOEXCEPT
        {return __cntrl_ < __p.__cntrl_;}
    _LIBCPP_INLINE_VISIBILITY
    bool
    __owner_equivalent(const shared_ptr& __p) const
        {return __cntrl_ == __p.__cntrl_;}

#if _LIBCPP_STD_VER > 14
    typename add_lvalue_reference<element_type>::type
    _LIBCPP_INLINE_VISIBILITY
    operator[](ptrdiff_t __i) const
    {
            static_assert(_VSTD::is_array<_Tp>::value,
                          "std::shared_ptr<T>::operator[] is only valid when T is an array type.");
            return __ptr_[__i];
    }
#endif

#ifndef _LIBCPP_NO_RTTI
    template <class _Dp>
        _LIBCPP_INLINE_VISIBILITY
        _Dp* __get_deleter() const _NOEXCEPT
            {return static_cast<_Dp*>(__cntrl_
                    ? const_cast<void *>(__cntrl_->__get_deleter(typeid(_Dp)))
                      : nullptr);}
#endif  // _LIBCPP_NO_RTTI

    template<class _Yp, class _CntrlBlk>
    static shared_ptr<_Tp>
    __create_with_control_block(_Yp* __p, _CntrlBlk* __cntrl) _NOEXCEPT
    {
        shared_ptr<_Tp> __r;
        __r.__ptr_ = __p;
        __r.__cntrl_ = __cntrl;
        __r.__enable_weak_this(__r.__ptr_, __r.__ptr_);
        return __r;
    }

private:
    template <class _Yp, bool = is_function<_Yp>::value>
        struct __shared_ptr_default_allocator
        {
            typedef allocator<_Yp> type;
        };

    template <class _Yp>
        struct __shared_ptr_default_allocator<_Yp, true>
        {
            typedef allocator<__shared_ptr_dummy_rebind_allocator_type> type;
        };

    template <class _Yp, class _OrigPtr>
        _LIBCPP_INLINE_VISIBILITY
        typename enable_if<is_convertible<_OrigPtr*,
                                          const enable_shared_from_this<_Yp>*
        >::value,
            void>::type
        __enable_weak_this(const enable_shared_from_this<_Yp>* __e,
                           _OrigPtr* __ptr) _NOEXCEPT
        {
            typedef typename remove_cv<_Yp>::type _RawYp;
            if (__e && __e->__weak_this_.expired())
            {
                __e->__weak_this_ = shared_ptr<_RawYp>(*this,
                    const_cast<_RawYp*>(static_cast<const _Yp*>(__ptr)));
            }
        }

    _LIBCPP_INLINE_VISIBILITY void __enable_weak_this(...) _NOEXCEPT {}

    template <class, class _Yp>
        struct __shared_ptr_default_delete
            : default_delete<_Yp> {};

    template <class _Yp, class _Un, size_t _Sz>
        struct __shared_ptr_default_delete<_Yp[_Sz], _Un>
            : default_delete<_Yp[]> {};

    template <class _Yp, class _Un>
        struct __shared_ptr_default_delete<_Yp[], _Un>
            : default_delete<_Yp[]> {};

    template <class _Up> friend class _LIBCPP_TEMPLATE_VIS shared_ptr;
    template <class _Up> friend class _LIBCPP_TEMPLATE_VIS weak_ptr;
};

#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
template<class _Tp>
shared_ptr(weak_ptr<_Tp>) -> shared_ptr<_Tp>;
template<class _Tp, class _Dp>
shared_ptr(unique_ptr<_Tp, _Dp>) -> shared_ptr<_Tp>;
#endif

template<class _Tp>
inline
_LIBCPP_CONSTEXPR
shared_ptr<_Tp>::shared_ptr() _NOEXCEPT
    : __ptr_(0),
      __cntrl_(0)
{
}

template<class _Tp>
inline
_LIBCPP_CONSTEXPR
shared_ptr<_Tp>::shared_ptr(nullptr_t) _NOEXCEPT
    : __ptr_(0),
      __cntrl_(0)
{
}

template<class _Tp>
template<class _Yp>
shared_ptr<_Tp>::shared_ptr(_Yp* __p,
                            typename enable_if<__compatible_with<_Yp, element_type>::value, __nat>::type)
    : __ptr_(__p)
{
    unique_ptr<_Yp> __hold(__p);
    typedef typename __shared_ptr_default_allocator<_Yp>::type _AllocT;
    typedef __shared_ptr_pointer<_Yp*, __shared_ptr_default_delete<_Tp, _Yp>, _AllocT > _CntrlBlk;
    __cntrl_ = new _CntrlBlk(__p, __shared_ptr_default_delete<_Tp, _Yp>(), _AllocT());
    __hold.release();
    __enable_weak_this(__p, __p);
}

template<class _Tp>
template<class _Yp, class _Dp>
shared_ptr<_Tp>::shared_ptr(_Yp* __p, _Dp __d,
                            typename enable_if<__compatible_with<_Yp, element_type>::value, __nat>::type)
    : __ptr_(__p)
{
#ifndef _LIBCPP_NO_EXCEPTIONS
    try
    {
#endif  // _LIBCPP_NO_EXCEPTIONS
        typedef typename __shared_ptr_default_allocator<_Yp>::type _AllocT;
        typedef __shared_ptr_pointer<_Yp*, _Dp, _AllocT > _CntrlBlk;
        __cntrl_ = new _CntrlBlk(__p, __d, _AllocT());
        __enable_weak_this(__p, __p);
#ifndef _LIBCPP_NO_EXCEPTIONS
    }
    catch (...)
    {
        __d(__p);
        throw;
    }
#endif  // _LIBCPP_NO_EXCEPTIONS
}

template<class _Tp>
template<class _Dp>
shared_ptr<_Tp>::shared_ptr(nullptr_t __p, _Dp __d)
    : __ptr_(0)
{
#ifndef _LIBCPP_NO_EXCEPTIONS
    try
    {
#endif  // _LIBCPP_NO_EXCEPTIONS
        typedef typename __shared_ptr_default_allocator<_Tp>::type _AllocT;
        typedef __shared_ptr_pointer<nullptr_t, _Dp, _AllocT > _CntrlBlk;
        __cntrl_ = new _CntrlBlk(__p, __d, _AllocT());
#ifndef _LIBCPP_NO_EXCEPTIONS
    }
    catch (...)
    {
        __d(__p);
        throw;
    }
#endif  // _LIBCPP_NO_EXCEPTIONS
}

template<class _Tp>
template<class _Yp, class _Dp, class _Alloc>
shared_ptr<_Tp>::shared_ptr(_Yp* __p, _Dp __d, _Alloc __a,
                            typename enable_if<__compatible_with<_Yp, element_type>::value, __nat>::type)
    : __ptr_(__p)
{
#ifndef _LIBCPP_NO_EXCEPTIONS
    try
    {
#endif  // _LIBCPP_NO_EXCEPTIONS
        typedef __shared_ptr_pointer<_Yp*, _Dp, _Alloc> _CntrlBlk;
        typedef typename __allocator_traits_rebind<_Alloc, _CntrlBlk>::type _A2;
        typedef __allocator_destructor<_A2> _D2;
        _A2 __a2(__a);
        unique_ptr<_CntrlBlk, _D2> __hold2(__a2.allocate(1), _D2(__a2, 1));
        ::new(static_cast<void*>(_VSTD::addressof(*__hold2.get())))
            _CntrlBlk(__p, __d, __a);
        __cntrl_ = _VSTD::addressof(*__hold2.release());
        __enable_weak_this(__p, __p);
#ifndef _LIBCPP_NO_EXCEPTIONS
    }
    catch (...)
    {
        __d(__p);
        throw;
    }
#endif  // _LIBCPP_NO_EXCEPTIONS
}

template<class _Tp>
template<class _Dp, class _Alloc>
shared_ptr<_Tp>::shared_ptr(nullptr_t __p, _Dp __d, _Alloc __a)
    : __ptr_(0)
{
#ifndef _LIBCPP_NO_EXCEPTIONS
    try
    {
#endif  // _LIBCPP_NO_EXCEPTIONS
        typedef __shared_ptr_pointer<nullptr_t, _Dp, _Alloc> _CntrlBlk;
        typedef typename __allocator_traits_rebind<_Alloc, _CntrlBlk>::type _A2;
        typedef __allocator_destructor<_A2> _D2;
        _A2 __a2(__a);
        unique_ptr<_CntrlBlk, _D2> __hold2(__a2.allocate(1), _D2(__a2, 1));
        ::new(static_cast<void*>(_VSTD::addressof(*__hold2.get())))
            _CntrlBlk(__p, __d, __a);
        __cntrl_ = _VSTD::addressof(*__hold2.release());
#ifndef _LIBCPP_NO_EXCEPTIONS
    }
    catch (...)
    {
        __d(__p);
        throw;
    }
#endif  // _LIBCPP_NO_EXCEPTIONS
}

template<class _Tp>
template<class _Yp>
inline
shared_ptr<_Tp>::shared_ptr(const shared_ptr<_Yp>& __r, element_type *__p) _NOEXCEPT
    : __ptr_(__p),
      __cntrl_(__r.__cntrl_)
{
    if (__cntrl_)
        __cntrl_->__add_shared();
}

template<class _Tp>
inline
shared_ptr<_Tp>::shared_ptr(const shared_ptr& __r) _NOEXCEPT
    : __ptr_(__r.__ptr_),
      __cntrl_(__r.__cntrl_)
{
    if (__cntrl_)
        __cntrl_->__add_shared();
}

template<class _Tp>
template<class _Yp>
inline
shared_ptr<_Tp>::shared_ptr(const shared_ptr<_Yp>& __r,
                            typename enable_if<__compatible_with<_Yp, element_type>::value, __nat>::type)
         _NOEXCEPT
    : __ptr_(__r.__ptr_),
      __cntrl_(__r.__cntrl_)
{
    if (__cntrl_)
        __cntrl_->__add_shared();
}

template<class _Tp>
inline
shared_ptr<_Tp>::shared_ptr(shared_ptr&& __r) _NOEXCEPT
    : __ptr_(__r.__ptr_),
      __cntrl_(__r.__cntrl_)
{
    __r.__ptr_ = 0;
    __r.__cntrl_ = 0;
}

template<class _Tp>
template<class _Yp>
inline
shared_ptr<_Tp>::shared_ptr(shared_ptr<_Yp>&& __r,
                            typename enable_if<__compatible_with<_Yp, element_type>::value, __nat>::type)
         _NOEXCEPT
    : __ptr_(__r.__ptr_),
      __cntrl_(__r.__cntrl_)
{
    __r.__ptr_ = 0;
    __r.__cntrl_ = 0;
}

#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
template<class _Tp>
template<class _Yp>
shared_ptr<_Tp>::shared_ptr(auto_ptr<_Yp>&& __r,
                            typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type)
    : __ptr_(__r.get())
{
    typedef __shared_ptr_pointer<_Yp*, default_delete<_Yp>, allocator<_Yp> > _CntrlBlk;
    __cntrl_ = new _CntrlBlk(__r.get(), default_delete<_Yp>(), allocator<_Yp>());
    __enable_weak_this(__r.get(), __r.get());
    __r.release();
}
#endif

template<class _Tp>
template <class _Yp, class _Dp>
shared_ptr<_Tp>::shared_ptr(unique_ptr<_Yp, _Dp>&& __r,
                            typename enable_if
                            <
                                !is_lvalue_reference<_Dp>::value &&
                                !is_array<_Yp>::value &&
                                is_convertible<typename unique_ptr<_Yp, _Dp>::pointer, element_type*>::value,
                                __nat
                            >::type)
    : __ptr_(__r.get())
{
#if _LIBCPP_STD_VER > 11
    if (__ptr_ == nullptr)
        __cntrl_ = nullptr;
    else
#endif
    {
        typedef typename __shared_ptr_default_allocator<_Yp>::type _AllocT;
        typedef __shared_ptr_pointer<_Yp*, _Dp, _AllocT > _CntrlBlk;
        __cntrl_ = new _CntrlBlk(__r.get(), __r.get_deleter(), _AllocT());
        __enable_weak_this(__r.get(), __r.get());
    }
    __r.release();
}

template<class _Tp>
template <class _Yp, class _Dp>
shared_ptr<_Tp>::shared_ptr(unique_ptr<_Yp, _Dp>&& __r,
                            typename enable_if
                            <
                                is_lvalue_reference<_Dp>::value &&
                                !is_array<_Yp>::value &&
                                is_convertible<typename unique_ptr<_Yp, _Dp>::pointer, element_type*>::value,
                                __nat
                            >::type)
    : __ptr_(__r.get())
{
#if _LIBCPP_STD_VER > 11
    if (__ptr_ == nullptr)
        __cntrl_ = nullptr;
    else
#endif
    {
        typedef typename __shared_ptr_default_allocator<_Yp>::type _AllocT;
        typedef __shared_ptr_pointer<_Yp*,
                                     reference_wrapper<typename remove_reference<_Dp>::type>,
                                     _AllocT > _CntrlBlk;
        __cntrl_ = new _CntrlBlk(__r.get(), _VSTD::ref(__r.get_deleter()), _AllocT());
        __enable_weak_this(__r.get(), __r.get());
    }
    __r.release();
}

template<class _Tp>
shared_ptr<_Tp>::~shared_ptr()
{
    if (__cntrl_)
        __cntrl_->__release_shared();
}

template<class _Tp>
inline
shared_ptr<_Tp>&
shared_ptr<_Tp>::operator=(const shared_ptr& __r) _NOEXCEPT
{
    shared_ptr(__r).swap(*this);
    return *this;
}

template<class _Tp>
template<class _Yp>
inline
typename enable_if
<
    __compatible_with<_Yp, typename shared_ptr<_Tp>::element_type>::value,
    shared_ptr<_Tp>&
>::type
shared_ptr<_Tp>::operator=(const shared_ptr<_Yp>& __r) _NOEXCEPT
{
    shared_ptr(__r).swap(*this);
    return *this;
}

template<class _Tp>
inline
shared_ptr<_Tp>&
shared_ptr<_Tp>::operator=(shared_ptr&& __r) _NOEXCEPT
{
    shared_ptr(_VSTD::move(__r)).swap(*this);
    return *this;
}

template<class _Tp>
template<class _Yp>
inline
typename enable_if
<
    __compatible_with<_Yp, typename shared_ptr<_Tp>::element_type>::value,
    shared_ptr<_Tp>&
>::type
shared_ptr<_Tp>::operator=(shared_ptr<_Yp>&& __r)
{
    shared_ptr(_VSTD::move(__r)).swap(*this);
    return *this;
}

#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
template<class _Tp>
template<class _Yp>
inline
typename enable_if
<
    !is_array<_Yp>::value &&
    is_convertible<_Yp*, typename shared_ptr<_Tp>::element_type*>::value,
    shared_ptr<_Tp>
>::type&
shared_ptr<_Tp>::operator=(auto_ptr<_Yp>&& __r)
{
    shared_ptr(_VSTD::move(__r)).swap(*this);
    return *this;
}
#endif

template<class _Tp>
template <class _Yp, class _Dp>
inline
typename enable_if
<
    !is_array<_Yp>::value &&
    is_convertible<typename unique_ptr<_Yp, _Dp>::pointer,
                   typename shared_ptr<_Tp>::element_type*>::value,
    shared_ptr<_Tp>&
>::type
shared_ptr<_Tp>::operator=(unique_ptr<_Yp, _Dp>&& __r)
{
    shared_ptr(_VSTD::move(__r)).swap(*this);
    return *this;
}

template<class _Tp>
inline
void
shared_ptr<_Tp>::swap(shared_ptr& __r) _NOEXCEPT
{
    _VSTD::swap(__ptr_, __r.__ptr_);
    _VSTD::swap(__cntrl_, __r.__cntrl_);
}

template<class _Tp>
inline
void
shared_ptr<_Tp>::reset() _NOEXCEPT
{
    shared_ptr().swap(*this);
}

template<class _Tp>
template<class _Yp>
inline
typename enable_if
<
    __compatible_with<_Yp, typename shared_ptr<_Tp>::element_type>::value,
    void
>::type
shared_ptr<_Tp>::reset(_Yp* __p)
{
    shared_ptr(__p).swap(*this);
}

template<class _Tp>
template<class _Yp, class _Dp>
inline
typename enable_if
<
    __compatible_with<_Yp, typename shared_ptr<_Tp>::element_type>::value,
    void
>::type
shared_ptr<_Tp>::reset(_Yp* __p, _Dp __d)
{
    shared_ptr(__p, __d).swap(*this);
}

template<class _Tp>
template<class _Yp, class _Dp, class _Alloc>
inline
typename enable_if
<
    __compatible_with<_Yp, typename shared_ptr<_Tp>::element_type>::value,
    void
>::type
shared_ptr<_Tp>::reset(_Yp* __p, _Dp __d, _Alloc __a)
{
    shared_ptr(__p, __d, __a).swap(*this);
}

template<class _Tp, class ..._Args>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_array<_Tp>::value,
    shared_ptr<_Tp>
>::type
make_shared(_Args&& ...__args)
{
    static_assert(is_constructible<_Tp, _Args...>::value, "Can't construct object in make_shared");
    typedef __shared_ptr_emplace<_Tp, allocator<_Tp> > _CntrlBlk;
    typedef allocator<_CntrlBlk> _A2;
    typedef __allocator_destructor<_A2> _D2;

    _A2 __a2;
    unique_ptr<_CntrlBlk, _D2> __hold2(__a2.allocate(1), _D2(__a2, 1));
    ::new(__hold2.get()) _CntrlBlk(__a2, _VSTD::forward<_Args>(__args)...);

    _Tp *__ptr = __hold2.get()->get();
    return shared_ptr<_Tp>::__create_with_control_block(__ptr, __hold2.release());
}

template<class _Tp, class _Alloc, class ..._Args>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_array<_Tp>::value,
    shared_ptr<_Tp>
>::type
allocate_shared(const _Alloc& __a, _Args&& ...__args)
{
    static_assert( is_constructible<_Tp, _Args...>::value, "Can't construct object in allocate_shared");

    typedef __shared_ptr_emplace<_Tp, _Alloc> _CntrlBlk;
    typedef typename __allocator_traits_rebind<_Alloc, _CntrlBlk>::type _A2;
    typedef __allocator_destructor<_A2> _D2;

    _A2 __a2(__a);
    unique_ptr<_CntrlBlk, _D2> __hold2(__a2.allocate(1), _D2(__a2, 1));
    ::new(static_cast<void*>(_VSTD::addressof(*__hold2.get())))
        _CntrlBlk(__a, _VSTD::forward<_Args>(__args)...);

    typename shared_ptr<_Tp>::element_type *__p = __hold2.get()->get();
    return shared_ptr<_Tp>::__create_with_control_block(__p, _VSTD::addressof(*__hold2.release()));
}

template<class _Tp, class _Up>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(const shared_ptr<_Tp>& __x, const shared_ptr<_Up>& __y) _NOEXCEPT
{
    return __x.get() == __y.get();
}

template<class _Tp, class _Up>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const shared_ptr<_Tp>& __x, const shared_ptr<_Up>& __y) _NOEXCEPT
{
    return !(__x == __y);
}

template<class _Tp, class _Up>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<(const shared_ptr<_Tp>& __x, const shared_ptr<_Up>& __y) _NOEXCEPT
{
#if _LIBCPP_STD_VER <= 11
    typedef typename common_type<_Tp*, _Up*>::type _Vp;
    return less<_Vp>()(__x.get(), __y.get());
#else
    return less<>()(__x.get(), __y.get());
#endif

}

template<class _Tp, class _Up>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>(const shared_ptr<_Tp>& __x, const shared_ptr<_Up>& __y) _NOEXCEPT
{
    return __y < __x;
}

template<class _Tp, class _Up>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(const shared_ptr<_Tp>& __x, const shared_ptr<_Up>& __y) _NOEXCEPT
{
    return !(__y < __x);
}

template<class _Tp, class _Up>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>=(const shared_ptr<_Tp>& __x, const shared_ptr<_Up>& __y) _NOEXCEPT
{
    return !(__x < __y);
}

template<class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(const shared_ptr<_Tp>& __x, nullptr_t) _NOEXCEPT
{
    return !__x;
}

template<class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator==(nullptr_t, const shared_ptr<_Tp>& __x) _NOEXCEPT
{
    return !__x;
}

template<class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(const shared_ptr<_Tp>& __x, nullptr_t) _NOEXCEPT
{
    return static_cast<bool>(__x);
}

template<class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator!=(nullptr_t, const shared_ptr<_Tp>& __x) _NOEXCEPT
{
    return static_cast<bool>(__x);
}

template<class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<(const shared_ptr<_Tp>& __x, nullptr_t) _NOEXCEPT
{
    return less<_Tp*>()(__x.get(), nullptr);
}

template<class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<(nullptr_t, const shared_ptr<_Tp>& __x) _NOEXCEPT
{
    return less<_Tp*>()(nullptr, __x.get());
}

template<class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>(const shared_ptr<_Tp>& __x, nullptr_t) _NOEXCEPT
{
    return nullptr < __x;
}

template<class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>(nullptr_t, const shared_ptr<_Tp>& __x) _NOEXCEPT
{
    return __x < nullptr;
}

template<class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(const shared_ptr<_Tp>& __x, nullptr_t) _NOEXCEPT
{
    return !(nullptr < __x);
}

template<class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator<=(nullptr_t, const shared_ptr<_Tp>& __x) _NOEXCEPT
{
    return !(__x < nullptr);
}

template<class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>=(const shared_ptr<_Tp>& __x, nullptr_t) _NOEXCEPT
{
    return !(__x < nullptr);
}

template<class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
bool
operator>=(nullptr_t, const shared_ptr<_Tp>& __x) _NOEXCEPT
{
    return !(nullptr < __x);
}

template<class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
void
swap(shared_ptr<_Tp>& __x, shared_ptr<_Tp>& __y) _NOEXCEPT
{
    __x.swap(__y);
}

template<class _Tp, class _Up>
inline _LIBCPP_INLINE_VISIBILITY
shared_ptr<_Tp>
static_pointer_cast(const shared_ptr<_Up>& __r) _NOEXCEPT
{
    return shared_ptr<_Tp>(__r,
                           static_cast<
                               typename shared_ptr<_Tp>::element_type*>(__r.get()));
}

template<class _Tp, class _Up>
inline _LIBCPP_INLINE_VISIBILITY
shared_ptr<_Tp>
dynamic_pointer_cast(const shared_ptr<_Up>& __r) _NOEXCEPT
{
    typedef typename shared_ptr<_Tp>::element_type _ET;
    _ET* __p = dynamic_cast<_ET*>(__r.get());
    return __p ? shared_ptr<_Tp>(__r, __p) : shared_ptr<_Tp>();
}

template<class _Tp, class _Up>
shared_ptr<_Tp>
const_pointer_cast(const shared_ptr<_Up>& __r) _NOEXCEPT
{
    typedef typename shared_ptr<_Tp>::element_type _RTp;
    return shared_ptr<_Tp>(__r, const_cast<_RTp*>(__r.get()));
}

template<class _Tp, class _Up>
shared_ptr<_Tp>
reinterpret_pointer_cast(const shared_ptr<_Up>& __r) _NOEXCEPT
{
    return shared_ptr<_Tp>(__r,
                           reinterpret_cast<
                               typename shared_ptr<_Tp>::element_type*>(__r.get()));
}

#ifndef _LIBCPP_NO_RTTI

template<class _Dp, class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
_Dp*
get_deleter(const shared_ptr<_Tp>& __p) _NOEXCEPT
{
    return __p.template __get_deleter<_Dp>();
}

#endif  // _LIBCPP_NO_RTTI

template<class _Tp>
class _LIBCPP_SHARED_PTR_TRIVIAL_ABI _LIBCPP_TEMPLATE_VIS weak_ptr
{
public:
    typedef _Tp element_type;
private:
    element_type*        __ptr_;
    __shared_weak_count* __cntrl_;

public:
    _LIBCPP_INLINE_VISIBILITY
    _LIBCPP_CONSTEXPR weak_ptr() _NOEXCEPT;
    template<class _Yp> _LIBCPP_INLINE_VISIBILITY weak_ptr(shared_ptr<_Yp> const& __r,
                   typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat*>::type = 0)
                        _NOEXCEPT;
    _LIBCPP_INLINE_VISIBILITY
    weak_ptr(weak_ptr const& __r) _NOEXCEPT;
    template<class _Yp> _LIBCPP_INLINE_VISIBILITY weak_ptr(weak_ptr<_Yp> const& __r,
                   typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat*>::type = 0)
                         _NOEXCEPT;

    _LIBCPP_INLINE_VISIBILITY
    weak_ptr(weak_ptr&& __r) _NOEXCEPT;
    template<class _Yp> _LIBCPP_INLINE_VISIBILITY weak_ptr(weak_ptr<_Yp>&& __r,
                   typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat*>::type = 0)
                         _NOEXCEPT;
    ~weak_ptr();

    _LIBCPP_INLINE_VISIBILITY
    weak_ptr& operator=(weak_ptr const& __r) _NOEXCEPT;
    template<class _Yp>
        typename enable_if
        <
            is_convertible<_Yp*, element_type*>::value,
            weak_ptr&
        >::type
        _LIBCPP_INLINE_VISIBILITY
        operator=(weak_ptr<_Yp> const& __r) _NOEXCEPT;

    _LIBCPP_INLINE_VISIBILITY
    weak_ptr& operator=(weak_ptr&& __r) _NOEXCEPT;
    template<class _Yp>
        typename enable_if
        <
            is_convertible<_Yp*, element_type*>::value,
            weak_ptr&
        >::type
        _LIBCPP_INLINE_VISIBILITY
        operator=(weak_ptr<_Yp>&& __r) _NOEXCEPT;

    template<class _Yp>
        typename enable_if
        <
            is_convertible<_Yp*, element_type*>::value,
            weak_ptr&
        >::type
        _LIBCPP_INLINE_VISIBILITY
        operator=(shared_ptr<_Yp> const& __r) _NOEXCEPT;

    _LIBCPP_INLINE_VISIBILITY
    void swap(weak_ptr& __r) _NOEXCEPT;
    _LIBCPP_INLINE_VISIBILITY
    void reset() _NOEXCEPT;

    _LIBCPP_INLINE_VISIBILITY
    long use_count() const _NOEXCEPT
        {return __cntrl_ ? __cntrl_->use_count() : 0;}
    _LIBCPP_INLINE_VISIBILITY
    bool expired() const _NOEXCEPT
        {return __cntrl_ == 0 || __cntrl_->use_count() == 0;}
    shared_ptr<_Tp> lock() const _NOEXCEPT;
    template<class _Up>
        _LIBCPP_INLINE_VISIBILITY
        bool owner_before(const shared_ptr<_Up>& __r) const _NOEXCEPT
        {return __cntrl_ < __r.__cntrl_;}
    template<class _Up>
        _LIBCPP_INLINE_VISIBILITY
        bool owner_before(const weak_ptr<_Up>& __r) const _NOEXCEPT
        {return __cntrl_ < __r.__cntrl_;}

    template <class _Up> friend class _LIBCPP_TEMPLATE_VIS weak_ptr;
    template <class _Up> friend class _LIBCPP_TEMPLATE_VIS shared_ptr;
};

#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
template<class _Tp>
weak_ptr(shared_ptr<_Tp>) -> weak_ptr<_Tp>;
#endif

template<class _Tp>
inline
_LIBCPP_CONSTEXPR
weak_ptr<_Tp>::weak_ptr() _NOEXCEPT
    : __ptr_(0),
      __cntrl_(0)
{
}

template<class _Tp>
inline
weak_ptr<_Tp>::weak_ptr(weak_ptr const& __r) _NOEXCEPT
    : __ptr_(__r.__ptr_),
      __cntrl_(__r.__cntrl_)
{
    if (__cntrl_)
        __cntrl_->__add_weak();
}

template<class _Tp>
template<class _Yp>
inline
weak_ptr<_Tp>::weak_ptr(shared_ptr<_Yp> const& __r,
                        typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat*>::type)
                         _NOEXCEPT
    : __ptr_(__r.__ptr_),
      __cntrl_(__r.__cntrl_)
{
    if (__cntrl_)
        __cntrl_->__add_weak();
}

template<class _Tp>
template<class _Yp>
inline
weak_ptr<_Tp>::weak_ptr(weak_ptr<_Yp> const& __r,
                        typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat*>::type)
         _NOEXCEPT
    : __ptr_(__r.__ptr_),
      __cntrl_(__r.__cntrl_)
{
    if (__cntrl_)
        __cntrl_->__add_weak();
}

template<class _Tp>
inline
weak_ptr<_Tp>::weak_ptr(weak_ptr&& __r) _NOEXCEPT
    : __ptr_(__r.__ptr_),
      __cntrl_(__r.__cntrl_)
{
    __r.__ptr_ = 0;
    __r.__cntrl_ = 0;
}

template<class _Tp>
template<class _Yp>
inline
weak_ptr<_Tp>::weak_ptr(weak_ptr<_Yp>&& __r,
                        typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat*>::type)
         _NOEXCEPT
    : __ptr_(__r.__ptr_),
      __cntrl_(__r.__cntrl_)
{
    __r.__ptr_ = 0;
    __r.__cntrl_ = 0;
}

template<class _Tp>
weak_ptr<_Tp>::~weak_ptr()
{
    if (__cntrl_)
        __cntrl_->__release_weak();
}

template<class _Tp>
inline
weak_ptr<_Tp>&
weak_ptr<_Tp>::operator=(weak_ptr const& __r) _NOEXCEPT
{
    weak_ptr(__r).swap(*this);
    return *this;
}

template<class _Tp>
template<class _Yp>
inline
typename enable_if
<
    is_convertible<_Yp*, _Tp*>::value,
    weak_ptr<_Tp>&
>::type
weak_ptr<_Tp>::operator=(weak_ptr<_Yp> const& __r) _NOEXCEPT
{
    weak_ptr(__r).swap(*this);
    return *this;
}

template<class _Tp>
inline
weak_ptr<_Tp>&
weak_ptr<_Tp>::operator=(weak_ptr&& __r) _NOEXCEPT
{
    weak_ptr(_VSTD::move(__r)).swap(*this);
    return *this;
}

template<class _Tp>
template<class _Yp>
inline
typename enable_if
<
    is_convertible<_Yp*, _Tp*>::value,
    weak_ptr<_Tp>&
>::type
weak_ptr<_Tp>::operator=(weak_ptr<_Yp>&& __r) _NOEXCEPT
{
    weak_ptr(_VSTD::move(__r)).swap(*this);
    return *this;
}

template<class _Tp>
template<class _Yp>
inline
typename enable_if
<
    is_convertible<_Yp*, _Tp*>::value,
    weak_ptr<_Tp>&
>::type
weak_ptr<_Tp>::operator=(shared_ptr<_Yp> const& __r) _NOEXCEPT
{
    weak_ptr(__r).swap(*this);
    return *this;
}

template<class _Tp>
inline
void
weak_ptr<_Tp>::swap(weak_ptr& __r) _NOEXCEPT
{
    _VSTD::swap(__ptr_, __r.__ptr_);
    _VSTD::swap(__cntrl_, __r.__cntrl_);
}

template<class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
void
swap(weak_ptr<_Tp>& __x, weak_ptr<_Tp>& __y) _NOEXCEPT
{
    __x.swap(__y);
}

template<class _Tp>
inline
void
weak_ptr<_Tp>::reset() _NOEXCEPT
{
    weak_ptr().swap(*this);
}

template<class _Tp>
template<class _Yp>
shared_ptr<_Tp>::shared_ptr(const weak_ptr<_Yp>& __r,
                            typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type)
    : __ptr_(__r.__ptr_),
      __cntrl_(__r.__cntrl_ ? __r.__cntrl_->lock() : __r.__cntrl_)
{
    if (__cntrl_ == 0)
        __throw_bad_weak_ptr();
}

template<class _Tp>
shared_ptr<_Tp>
weak_ptr<_Tp>::lock() const _NOEXCEPT
{
    shared_ptr<_Tp> __r;
    __r.__cntrl_ = __cntrl_ ? __cntrl_->lock() : __cntrl_;
    if (__r.__cntrl_)
        __r.__ptr_ = __ptr_;
    return __r;
}

#if _LIBCPP_STD_VER > 14
template <class _Tp = void> struct owner_less;
#else
template <class _Tp> struct owner_less;
#endif

template <class _Tp>
struct _LIBCPP_TEMPLATE_VIS owner_less<shared_ptr<_Tp> >
    : binary_function<shared_ptr<_Tp>, shared_ptr<_Tp>, bool>
{
    typedef bool result_type;
    _LIBCPP_INLINE_VISIBILITY
    bool operator()(shared_ptr<_Tp> const& __x, shared_ptr<_Tp> const& __y) const _NOEXCEPT
        {return __x.owner_before(__y);}
    _LIBCPP_INLINE_VISIBILITY
    bool operator()(shared_ptr<_Tp> const& __x,   weak_ptr<_Tp> const& __y) const _NOEXCEPT
        {return __x.owner_before(__y);}
    _LIBCPP_INLINE_VISIBILITY
    bool operator()(  weak_ptr<_Tp> const& __x, shared_ptr<_Tp> const& __y) const _NOEXCEPT
        {return __x.owner_before(__y);}
};

template <class _Tp>
struct _LIBCPP_TEMPLATE_VIS owner_less<weak_ptr<_Tp> >
    : binary_function<weak_ptr<_Tp>, weak_ptr<_Tp>, bool>
{
    typedef bool result_type;
    _LIBCPP_INLINE_VISIBILITY
    bool operator()(  weak_ptr<_Tp> const& __x,   weak_ptr<_Tp> const& __y) const _NOEXCEPT
        {return __x.owner_before(__y);}
    _LIBCPP_INLINE_VISIBILITY
    bool operator()(shared_ptr<_Tp> const& __x,   weak_ptr<_Tp> const& __y) const _NOEXCEPT
        {return __x.owner_before(__y);}
    _LIBCPP_INLINE_VISIBILITY
    bool operator()(  weak_ptr<_Tp> const& __x, shared_ptr<_Tp> const& __y) const _NOEXCEPT
        {return __x.owner_before(__y);}
};

#if _LIBCPP_STD_VER > 14
template <>
struct _LIBCPP_TEMPLATE_VIS owner_less<void>
{
    template <class _Tp, class _Up>
    _LIBCPP_INLINE_VISIBILITY
    bool operator()( shared_ptr<_Tp> const& __x, shared_ptr<_Up> const& __y) const _NOEXCEPT
        {return __x.owner_before(__y);}
    template <class _Tp, class _Up>
    _LIBCPP_INLINE_VISIBILITY
    bool operator()( shared_ptr<_Tp> const& __x,   weak_ptr<_Up> const& __y) const _NOEXCEPT
        {return __x.owner_before(__y);}
    template <class _Tp, class _Up>
    _LIBCPP_INLINE_VISIBILITY
    bool operator()(   weak_ptr<_Tp> const& __x, shared_ptr<_Up> const& __y) const _NOEXCEPT
        {return __x.owner_before(__y);}
    template <class _Tp, class _Up>
    _LIBCPP_INLINE_VISIBILITY
    bool operator()(   weak_ptr<_Tp> const& __x,   weak_ptr<_Up> const& __y) const _NOEXCEPT
        {return __x.owner_before(__y);}
    typedef void is_transparent;
};
#endif

template<class _Tp>
class _LIBCPP_TEMPLATE_VIS enable_shared_from_this
{
    mutable weak_ptr<_Tp> __weak_this_;
protected:
    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
    enable_shared_from_this() _NOEXCEPT {}
    _LIBCPP_INLINE_VISIBILITY
    enable_shared_from_this(enable_shared_from_this const&) _NOEXCEPT {}
    _LIBCPP_INLINE_VISIBILITY
    enable_shared_from_this& operator=(enable_shared_from_this const&) _NOEXCEPT
        {return *this;}
    _LIBCPP_INLINE_VISIBILITY
    ~enable_shared_from_this() {}
public:
    _LIBCPP_INLINE_VISIBILITY
    shared_ptr<_Tp> shared_from_this()
        {return shared_ptr<_Tp>(__weak_this_);}
    _LIBCPP_INLINE_VISIBILITY
    shared_ptr<_Tp const> shared_from_this() const
        {return shared_ptr<const _Tp>(__weak_this_);}

#if _LIBCPP_STD_VER > 14
    _LIBCPP_INLINE_VISIBILITY
    weak_ptr<_Tp> weak_from_this() _NOEXCEPT
       { return __weak_this_; }

    _LIBCPP_INLINE_VISIBILITY
    weak_ptr<const _Tp> weak_from_this() const _NOEXCEPT
        { return __weak_this_; }
#endif // _LIBCPP_STD_VER > 14

    template <class _Up> friend class shared_ptr;
};

template <class _Tp>
struct _LIBCPP_TEMPLATE_VIS hash<shared_ptr<_Tp> >
{
    typedef shared_ptr<_Tp>      argument_type;
    typedef size_t               result_type;

    _LIBCPP_INLINE_VISIBILITY
    result_type operator()(const argument_type& __ptr) const _NOEXCEPT
    {
        return hash<typename shared_ptr<_Tp>::element_type*>()(__ptr.get());
    }
};

template<class _CharT, class _Traits, class _Yp>
inline _LIBCPP_INLINE_VISIBILITY
basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os, shared_ptr<_Yp> const& __p);


#if !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)

class _LIBCPP_TYPE_VIS __sp_mut
{
    void* __lx;
public:
    void lock() _NOEXCEPT;
    void unlock() _NOEXCEPT;

private:
    _LIBCPP_CONSTEXPR __sp_mut(void*) _NOEXCEPT;
    __sp_mut(const __sp_mut&);
    __sp_mut& operator=(const __sp_mut&);

    friend _LIBCPP_FUNC_VIS __sp_mut& __get_sp_mut(const void*);
};

_LIBCPP_FUNC_VIS _LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
__sp_mut& __get_sp_mut(const void*);

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
bool
atomic_is_lock_free(const shared_ptr<_Tp>*)
{
    return false;
}

template <class _Tp>
_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
shared_ptr<_Tp>
atomic_load(const shared_ptr<_Tp>* __p)
{
    __sp_mut& __m = __get_sp_mut(__p);
    __m.lock();
    shared_ptr<_Tp> __q = *__p;
    __m.unlock();
    return __q;
}

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
shared_ptr<_Tp>
atomic_load_explicit(const shared_ptr<_Tp>* __p, memory_order)
{
    return atomic_load(__p);
}

template <class _Tp>
_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
void
atomic_store(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r)
{
    __sp_mut& __m = __get_sp_mut(__p);
    __m.lock();
    __p->swap(__r);
    __m.unlock();
}

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
void
atomic_store_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r, memory_order)
{
    atomic_store(__p, __r);
}

template <class _Tp>
_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
shared_ptr<_Tp>
atomic_exchange(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r)
{
    __sp_mut& __m = __get_sp_mut(__p);
    __m.lock();
    __p->swap(__r);
    __m.unlock();
    return __r;
}

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
shared_ptr<_Tp>
atomic_exchange_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r, memory_order)
{
    return atomic_exchange(__p, __r);
}

template <class _Tp>
_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
bool
atomic_compare_exchange_strong(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_ptr<_Tp> __w)
{
    shared_ptr<_Tp> __temp;
    __sp_mut& __m = __get_sp_mut(__p);
    __m.lock();
    if (__p->__owner_equivalent(*__v))
    {
        _VSTD::swap(__temp, *__p);
        *__p = __w;
        __m.unlock();
        return true;
    }
    _VSTD::swap(__temp, *__v);
    *__v = *__p;
    __m.unlock();
    return false;
}

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
bool
atomic_compare_exchange_weak(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_ptr<_Tp> __w)
{
    return atomic_compare_exchange_strong(__p, __v, __w);
}

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
bool
atomic_compare_exchange_strong_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v,
                                        shared_ptr<_Tp> __w, memory_order, memory_order)
{
    return atomic_compare_exchange_strong(__p, __v, __w);
}

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
bool
atomic_compare_exchange_weak_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v,
                                      shared_ptr<_Tp> __w, memory_order, memory_order)
{
    return atomic_compare_exchange_weak(__p, __v, __w);
}

#endif  // !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)

//enum class
#if defined(_LIBCPP_ABI_POINTER_SAFETY_ENUM_TYPE)
# ifndef _LIBCPP_CXX03_LANG
enum class pointer_safety : unsigned char {
  relaxed,
  preferred,
  strict
};
# endif
#else
struct _LIBCPP_TYPE_VIS pointer_safety
{
    enum __lx
    {
        relaxed,
        preferred,
        strict
    };

    __lx __v_;

    _LIBCPP_INLINE_VISIBILITY
    pointer_safety() : __v_() {}

    _LIBCPP_INLINE_VISIBILITY
    pointer_safety(__lx __v) : __v_(__v) {}
    _LIBCPP_INLINE_VISIBILITY
    operator int() const {return __v_;}
};
#endif

#if !defined(_LIBCPP_ABI_POINTER_SAFETY_ENUM_TYPE) && \
    defined(_LIBCPP_BUILDING_LIBRARY)
_LIBCPP_FUNC_VIS pointer_safety get_pointer_safety() _NOEXCEPT;
#else
// This function is only offered in C++03 under ABI v1.
# if !defined(_LIBCPP_ABI_POINTER_SAFETY_ENUM_TYPE) || !defined(_LIBCPP_CXX03_LANG)
inline _LIBCPP_INLINE_VISIBILITY
pointer_safety get_pointer_safety() _NOEXCEPT {
  return pointer_safety::relaxed;
}
# endif
#endif


_LIBCPP_FUNC_VIS void declare_reachable(void* __p);
_LIBCPP_FUNC_VIS void declare_no_pointers(char* __p, size_t __n);
_LIBCPP_FUNC_VIS void undeclare_no_pointers(char* __p, size_t __n);
_LIBCPP_FUNC_VIS void* __undeclare_reachable(void* __p);

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
_Tp*
undeclare_reachable(_Tp* __p)
{
    return static_cast<_Tp*>(__undeclare_reachable(__p));
}

_LIBCPP_FUNC_VIS void* align(size_t __align, size_t __sz, void*& __ptr, size_t& __space);

// --- Helper for container swap --
template <typename _Alloc>
inline _LIBCPP_INLINE_VISIBILITY
void __swap_allocator(_Alloc & __a1, _Alloc & __a2)
#if _LIBCPP_STD_VER >= 14
    _NOEXCEPT
#else
    _NOEXCEPT_(__is_nothrow_swappable<_Alloc>::value)
#endif
{
    __swap_allocator(__a1, __a2,
      integral_constant<bool, _VSTD::allocator_traits<_Alloc>::propagate_on_container_swap::value>());
}

template <typename _Alloc>
_LIBCPP_INLINE_VISIBILITY
void __swap_allocator(_Alloc & __a1, _Alloc & __a2, true_type)
#if _LIBCPP_STD_VER >= 14
    _NOEXCEPT
#else
    _NOEXCEPT_(__is_nothrow_swappable<_Alloc>::value)
#endif
{
    using _VSTD::swap;
    swap(__a1, __a2);
}

template <typename _Alloc>
inline _LIBCPP_INLINE_VISIBILITY
void __swap_allocator(_Alloc &, _Alloc &, false_type) _NOEXCEPT {}

template <typename _Alloc, typename _Traits=allocator_traits<_Alloc> >
struct __noexcept_move_assign_container : public integral_constant<bool,
    _Traits::propagate_on_container_move_assignment::value
#if _LIBCPP_STD_VER > 14
        || _Traits::is_always_equal::value
#else
        && is_nothrow_move_assignable<_Alloc>::value
#endif
    > {};


template <class _Tp, class _Alloc>
struct __temp_value {
    typedef allocator_traits<_Alloc> _Traits;

    typename aligned_storage<sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp)>::type __v;
    _Alloc &__a;

    _Tp *__addr() { return reinterpret_cast<_Tp *>(addressof(__v)); }
    _Tp &   get() { return *__addr(); }

    template<class... _Args>
    _LIBCPP_NO_CFI
    __temp_value(_Alloc &__alloc, _Args&& ... __args) : __a(__alloc) {
      _Traits::construct(__a, reinterpret_cast<_Tp*>(addressof(__v)),
                         _VSTD::forward<_Args>(__args)...);
    }

    ~__temp_value() { _Traits::destroy(__a, __addr()); }
    };

template<typename _Alloc, typename = void, typename = void>
struct __is_allocator : false_type {};

template<typename _Alloc>
struct __is_allocator<_Alloc,
       typename __void_t<typename _Alloc::value_type>::type,
       typename __void_t<decltype(_VSTD::declval<_Alloc&>().allocate(size_t(0)))>::type
     >
   : true_type {};

// __builtin_new_allocator -- A non-templated helper for allocating and
// deallocating memory using __builtin_operator_new and
// __builtin_operator_delete. It should be used in preference to
// `std::allocator<T>` to avoid additional instantiations.
struct __builtin_new_allocator {
  struct __builtin_new_deleter {
    typedef void* pointer_type;

    _LIBCPP_CONSTEXPR explicit __builtin_new_deleter(size_t __size, size_t __align)
        : __size_(__size), __align_(__align) {}

    void operator()(void* p) const _NOEXCEPT {
        std::__libcpp_deallocate(p, __size_, __align_);
    }

   private:
    size_t __size_;
    size_t __align_;
  };

  typedef unique_ptr<void, __builtin_new_deleter> __holder_t;

  static __holder_t __allocate_bytes(size_t __s, size_t __align) {
      return __holder_t(std::__libcpp_allocate(__s, __align),
                     __builtin_new_deleter(__s, __align));
  }

  static void __deallocate_bytes(void* __p, size_t __s,
                                 size_t __align) _NOEXCEPT {
      std::__libcpp_deallocate(__p, __s, __align);
  }

  template <class _Tp>
  _LIBCPP_NODEBUG _LIBCPP_ALWAYS_INLINE
  static __holder_t __allocate_type(size_t __n) {
      return __allocate_bytes(__n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp));
  }

  template <class _Tp>
  _LIBCPP_NODEBUG _LIBCPP_ALWAYS_INLINE
  static void __deallocate_type(void* __p, size_t __n) _NOEXCEPT {
      __deallocate_bytes(__p, __n * sizeof(_Tp), _LIBCPP_ALIGNOF(_Tp));
  }
};


_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#if defined(_LIBCPP_HAS_PARALLEL_ALGORITHMS) && _LIBCPP_STD_VER >= 17
#   include <__pstl_memory>
#endif

#endif  // _LIBCPP_MEMORY