标准库头文件 <memory>

namespace std {
  // 指针特征
  template<class Ptr> struct pointer_traits;
  template<class T> struct pointer_traits<T*>;
 
  // 指针转换
  template<class T>
    constexpr T* to_address(T* p) noexcept;
  template<class Ptr>
    auto to_address(const Ptr& p) noexcept;
 
  // 指针安全
  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;
 
  // 指针对齐
  void* align(size_t alignment, size_t size, void*& ptr, size_t& space);
  template<size_t N, class T>
    [[nodiscard]] constexpr T* assume_aligned(T* ptr);
 
  // 分配器实参标签
  struct allocator_arg_t { explicit allocator_arg_t() = default; };
  inline constexpr allocator_arg_t allocator_arg{};
 
  // uses_allocator
  template<class T, class Alloc> struct uses_allocator;
 
  // uses_allocator
  template<class T, class Alloc>
    inline constexpr bool uses_allocator_v = uses_allocator<T, Alloc>::value;
 
  // 使用分配器构造
  template<class T, class Alloc, class... Args>
    constexpr auto uses_allocator_construction_args(const Alloc& alloc, Args&&... args)
      noexcept -> /* 见定义 */;
  template<class T, class Alloc, class Tuple1, class Tuple2>
    constexpr auto uses_allocator_construction_args(
      const Alloc& alloc, piecewise_construct_t, Tuple1&& x, Tuple2&& y)
      noexcept -> /* 见定义 */;
  template<class T, class Alloc>
    constexpr auto uses_allocator_construction_args(const Alloc& alloc)
      noexcept -> /* 见定义 */;
  template<class T, class Alloc, class U, class V>
    constexpr auto uses_allocator_construction_args(const Alloc& alloc, U&& u, V&& v)
      noexcept -> /* 见定义 */;
  template<class T, class Alloc, class U, class V>
    constexpr auto uses_allocator_construction_args(const Alloc& alloc,
      const pair<U,V>& pr)
      noexcept -> /* 见定义 */;
  template<class T, class Alloc, class U, class V>
    constexpr auto uses_allocator_construction_args(const Alloc& alloc, pair<U,V>&& pr)
      noexcept -> /* 见定义 */;
  template<class T, class Alloc, class... Args>
    constexpr T make_obj_using_allocator(const Alloc& alloc, Args&&... args);
 
  // 分配器特征
  template<class Alloc> struct allocator_traits;
 
  // 默认分配器
  template<class T> class allocator;
  template<class T, class U>
    bool operator==(const allocator<T>&, const allocator<U>&) noexcept;
  template<class T, class U>
    bool operator!=(const allocator<T>&, const allocator<U>&) noexcept;
 
  // 特化的算法
  // 特殊内存概念
  template<class I>
    concept __NoThrowInputIterator = /* 见定义 */;   // 仅用于阐释
  template<class I>
    concept __NoThrowForwardIterator = /* 见定义 */; // 仅用于阐释
  template<class S, class I>
    concept __NoThrowSentinel = /* 见定义 */;        // 仅用于阐释
  template<class R>
    concept __NoThrowInputRange = /* 见定义 */;      // 仅用于阐释
  template<class R>
    concept __NoThrowForwardRange = /* 见定义 */;    // 仅用于阐释
 
  template<class T>
    constexpr T* addressof(T& r) noexcept;
  template<class T>
    const T* addressof(const T&&) = delete;
  template<class ForwardIt>
    void uninitialized_default_construct(ForwardIt first, ForwardIt last);
  template<class ExecutionPolicy, class ForwardIt>
    void uninitialized_default_construct(ExecutionPolicy&& exec,
                                         ForwardIt first, ForwardIt last);
  template<class ForwardIt, class Size>
    ForwardIt uninitialized_default_construct_n(ForwardIt first, Size n);
  template<class ExecutionPolicy, class ForwardIt, class Size>
    ForwardIt uninitialized_default_construct_n(ExecutionPolicy&& exec,
                                                      ForwardIt first, Size n);
 
  namespace ranges {
    template<__NoThrowForwardIterator I, __NoThrowSentinel<I> S>
      requires DefaultConstructible<iter_value_t<I>>
        I uninitialized_default_construct(I first, S last);
    template<__NoThrowForwardRange R>
      requires DefaultConstructible<iter_value_t<iterator_t<R>>>
        safe_iterator_t<R> uninitialized_default_construct(R&& r);
 
    template<__NoThrowForwardIterator I>
      requires DefaultConstructible<iter_value_t<I>>
        I uninitialized_default_construct_n(I first, iter_difference_t<I> n);
  }
 
  template<class ForwardIt>
    void uninitialized_value_construct(ForwardIt first, ForwardIt last);
  template<class ExecutionPolicy, class ForwardIt>
    void uninitialized_value_construct(ExecutionPolicy&& exec,
                                       ForwardIt first, ForwardIt last);
  template<class ForwardIt, class Size>
    ForwardIt uninitialized_value_construct_n(ForwardIt first, Size n);
  template<class ExecutionPolicy, class ForwardIt, class Size>
    ForwardIt uninitialized_value_construct_n(ExecutionPolicy&& exec,
                                              ForwardIt first, Size n);
 
  namespace ranges {
    template<__NoThrowForwardIterator I, __NoThrowSentinel<I> S>
      requires DefaultConstructible<iter_value_t<I>>
        I uninitialized_value_construct(I first, S last);
    template<__NoThrowForwardRange R>
      requires DefaultConstructible<iter_value_t<iterator_t<R>>>
        safe_iterator_t<R> uninitialized_value_construct(R&& r);
 
    template<__NoThrowForwardIterator I>
      requires DefaultConstructible<iter_value_t<I>>
        I uninitialized_value_construct_n(I first, iter_difference_t<I> n);
  }
 
  template<class InputIt, class ForwardIt>
    ForwardIt uninitialized_copy(InputIt first, InputIt last, ForwardIt result);
  template<class ExecutionPolicy, class InputIt, class ForwardIt>
    ForwardIt uninitialized_copy(ExecutionPolicy&& exec,
                                 InputIt first, InputIt last, ForwardIt result);
  template<class InputIt, class Size, class ForwardIt>
    ForwardIt uninitialized_copy_n(InputIt first, Size n, ForwardIt result);
  template<class ExecutionPolicy, class InputIt, class Size, class ForwardIt>
    ForwardIt uninitialized_copy_n(ExecutionPolicy&& exec,
                                   InputIt first, Size n, ForwardIt result);
 
  namespace ranges {
    template<class I, class O>
    using uninitialized_copy_result = copy_result<I, O>;
    template<InputIterator I, Sentinel<I> S1,
             __NoThrowForwardIterator O, __NoThrowSentinel<O> S2>
      requires Constructible<iter_value_t<O>, iter_reference_t<I>>
        uninitialized_copy_result<I, O>
          uninitialized_copy(I ifirst, S1 ilast, O ofirst, S2 olast);
    template<InputRange IR, __NoThrowForwardRange OR>
      requires
        Constructible<iter_value_t<iterator_t<OR>>, iter_reference_t<iterator_t<IR>>>
        uninitialized_copy_result<safe_iterator_t<IR>, safe_iterator_t<OR>>
          uninitialized_copy(IR&& input_range, OR&& output_range);
 
    template<class I, class O>
      using uninitialized_copy_n_result = uninitialized_copy_result<I, O>;
    template<InputIterator I, __NoThrowForwardIterator O, __NoThrowSentinel<O> S>
      requires Constructible<iter_value_t<O>, iter_reference_t<I>>
        uninitialized_copy_n_result<I, O>
          uninitialized_copy_n(I ifirst, iter_difference_t<I> n, O ofirst, S olast);
  }
 
  template<class InputIt, class ForwardIt>
    ForwardIt uninitialized_move(InputIt first, InputIt last, ForwardIt result);
  template<class ExecutionPolicy, class InputIt, class ForwardIt>
    ForwardIt uninitialized_move(ExecutionPolicy&& exec,
                                 InputIt first, InputIt last, ForwardIt result);
  template<class InputIt, class Size, class ForwardIt>
    pair<InputIt, ForwardIt> uninitialized_move_n(InputIt first, Size n,
                                                  ForwardIt result);
  template<class ExecutionPolicy, class InputIt, class Size, class ForwardIt>
    pair<InputIt, ForwardIt> uninitialized_move_n(ExecutionPolicy&& exec,
                                                  InputIt first, Size n,
                                                  ForwardIt result);
 
  namespace ranges {
    template<class I, class O>
      using uninitialized_move_result = uninitialized_copy_result<I, O>;
    template<InputIterator I, Sentinel<I> S1,
             __NoThrowForwardIterator O, __NoThrowSentinel<O> S2>
      requires Constructible<iter_value_t<O>, iter_rvalue_reference_t<I>>
        uninitialized_move_result<I, O>
          uninitialized_move(I ifirst, S1 ilast, O ofirst, S2 olast);
    template<InputRange IR, __NoThrowForwardRange OR>
      requires Constructible<iter_value_t<iterator_t<OR>>,
                             iter_rvalue_reference_t<iterator_t<IR>>>
        uninitialized_move_result<safe_iterator_t<IR>, safe_iterator_t<OR>>
          uninitialized_move(IR&& input_range, OR&& output_range);
 
    template<class I, class O>
      using uninitialized_move_n_result = uninitialized_copy_result<I, O>;
    template<InputIterator I,
             __NoThrowForwardIterator O, __NoThrowSentinel<O> S>
      requires Constructible<iter_value_t<O>, iter_rvalue_reference_t<I>>
        uninitialized_move_n_result<I, O>
          uninitialized_move_n(I ifirst, iter_difference_t<I> n, O ofirst, S olast);
  }
 
  template<class ForwardIt, class T>
    void uninitialized_fill(ForwardIt first, ForwardIt last, const T& x);
  template<class ExecutionPolicy, class ForwardIt, class T>
    void uninitialized_fill(ExecutionPolicy&& exec,
                            ForwardIt first, ForwardIt last, const T& x);
  template<class ForwardIt, class Size, class T>
    ForwardIt uninitialized_fill_n(ForwardIt first, Size n, const T& x);
  template<class ExecutionPolicy, class ForwardIt, class Size, class T>
    ForwardIt uninitialized_fill_n(ExecutionPolicy&& exec,
                                   ForwardIt first, Size n, const T& x);
 
  namespace ranges {
    template<__NoThrowForwardIterator I, __NoThrowSentinel<I> S, class T>
      requires Constructible<iter_value_t<I>, const T&>
        I uninitialized_fill(I first, S last, const T& x);
    template<__NoThrowForwardRange R, class T>
      requires Constructible<iter_value_t<iterator_t<R>>, const T&>
        safe_iterator_t<R> uninitialized_fill(R&& r, const T& x);
 
    template<__NoThrowForwardIterator I, class T>
      requires Constructible<iter_value_t<I>, const T&>
        I uninitialized_fill_n(I first, iter_difference_t<I> n, const T& x);
  }
 
  template<class T>
    void destroy_at(T* location);
  template<class ForwardIt>
    void destroy(ForwardIt first, ForwardIt last);
  template<class ExecutionPolicy, class ForwardIt>
    void destroy(ExecutionPolicy&& exec,
                 ForwardIt first, ForwardIt last);
  template<class ForwardIt, class Size>
    ForwardIt destroy_n(ForwardIt first, Size n);
  template<class ExecutionPolicy, class ForwardIt, class Size>
    ForwardIt destroy_n(ExecutionPolicy&& exec,
                        ForwardIt first, Size n);
 
  namespace ranges {
    template<Destructible T>
      void destroy_at(T* location) noexcept;
 
    template<__NoThrowInputIterator I, __NoThrowSentinel<I> S>
      requires Destructible<iter_value_t<I>>
        I destroy(I first, S last) noexcept;
    template<__NoThrowInputRange R>
      requires Destructible<iter_value_t<iterator_t<R>>
        safe_iterator_t<R> destroy(R&& r) noexcept;
 
    template<__NoThrowInputIterator I>
      requires Destructible<iter_value_t<I>>
        I destroy_n(I first, iter_difference_t<I> n) noexcept;
  }
 
  // 类模板 unique_ptr
  template<class T> struct default_delete;
  template<class T> struct default_delete<T[]>;
  template<class T, class D = default_delete<T>> class unique_ptr;
  template<class T, class D> class unique_ptr<T[], D>;
 
  template<class T, class... Args>
    unique_ptr<T> make_unique(Args&&... args);                          // T 非数组
  template<class T>
    unique_ptr<T> make_unique(size_t n);                                // T 为 U[]
  template<class T, class... Args>
    /* 未指明 */ make_unique(Args&&...) = delete;                        // T 为 U[N]
 
  template<class T>
    unique_ptr<T> make_unique_default_init();                           // T 非数组
  template<class T>
    unique_ptr<T> make_unique_default_init(size_t n);                   // T 为 U[]
  template<class T, class... Args>
    /* 未指明 */ make_unique_default_init(Args&&...) = delete;           // T 为 U[N]
 
  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);
 
  template<class E, class T, class Y, class D>
    basic_ostream<E, T>& operator<<(basic_ostream<E, T>& os, const unique_ptr<Y, D>& p);
 
  // ç±» bad_weak_ptr
  class bad_weak_ptr;
 
  // 类模板 shared_ptr
  template<class T> class shared_ptr;
 
  // shared_ptr 创建
  template<class T, class... Args>
    shared_ptr<T> make_shared(Args&&... args);                          // T 非数组
  template<class T, class A, class... Args>
    shared_ptr<T> allocate_shared(const A& a, Args&&... args);          // T 非数组
 
  template<class T>
    shared_ptr<T> make_shared(size_t N);                                // T 为 U[]
  template<class T, class A>
    shared_ptr<T> allocate_shared(const A& a, size_t N);                // T 为 U[]
 
  template<class T>
    shared_ptr<T> make_shared();                                        // T 为 U[N]
  template<class T, class A>
    shared_ptr<T> allocate_shared(const A& a);                          // T 为 U[N]
 
  template<class T>
    shared_ptr<T> make_shared(size_t N, const remove_extent_t<T>& u);   // T 为 U[]
  template<class T, class A>
    shared_ptr<T> allocate_shared(const A& a, size_t N,
                                  const remove_extent_t<T>& u);         // T 为 U[]
 
  template<class T>
    shared_ptr<T> make_shared(const remove_extent_t<T>& u);                 // T 为 U[N]
  template<class T, class A>
    shared_ptr<T> allocate_shared(const A& a, const remove_extent_t<T>& u); // T 为 U[N]
 
  template<class T>
    shared_ptr<T> make_shared_default_init();                           // T 非 U[]
  template<class T, class A>
    shared_ptr<T> allocate_shared_default_init(const A& a);             // T 非 U[]
 
  template<class T>
    shared_ptr<T> make_shared_default_init(size_t N);                   // T 为 U[]
  template<class T, class A>
    shared_ptr<T> allocate_shared_default_init(const A& a, size_t N);   // T 为 U[]
 
  // shared_ptr 比较
  template<class T, class U>
    bool operator==(const shared_ptr<T>& a, const shared_ptr<U>& b) noexcept;
  template<class T, class U>
    bool operator!=(const shared_ptr<T>& a, const shared_ptr<U>& b) noexcept;
  template<class T, class U>
    bool operator<(const shared_ptr<T>& a, const shared_ptr<U>& b) noexcept;
  template<class T, class U>
    bool operator>(const shared_ptr<T>& a, const shared_ptr<U>& b) noexcept;
  template<class T, class U>
    bool operator<=(const shared_ptr<T>& a, const shared_ptr<U>& b) noexcept;
  template<class T, class U>
    bool operator>=(const shared_ptr<T>& a, const shared_ptr<U>& 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 特化算法
  template<class T>
    void swap(shared_ptr<T>& a, shared_ptr<T>& b) noexcept;
 
  // shared_ptr 转型
  template<class T, class U>
    shared_ptr<T> static_pointer_cast(const shared_ptr<U>& r) noexcept;
  template<class T, class U>
    shared_ptr<T> static_pointer_cast(shared_ptr<U>&& r) noexcept;
  template<class T, class U>
    shared_ptr<T> dynamic_pointer_cast(const shared_ptr<U>& r) noexcept;
  template<class T, class U>
    shared_ptr<T> dynamic_pointer_cast(shared_ptr<U>&& r) noexcept;
  template<class T, class U>
    shared_ptr<T> const_pointer_cast(const shared_ptr<U>& r) noexcept;
  template<class T, class U>
    shared_ptr<T> const_pointer_cast(shared_ptr<U>&& r) noexcept;
  template<class T, class U>
    shared_ptr<T> reinterpret_pointer_cast(const shared_ptr<U>& r) noexcept;
  template<class T, class U>
    shared_ptr<T> reinterpret_pointer_cast(shared_ptr<U>&& r) noexcept;
 
  // shared_ptr get_deleter
  template<class D, class T>
    D* get_deleter(const shared_ptr<T>& p) noexcept;
 
  // shared_ptr I/O
  template<class E, class T, class Y>
    basic_ostream<E, T>& operator<<(basic_ostream<E, T>& os, const shared_ptr<Y>& p);
 
  // 类模板 weak_ptr
  template<class T> class weak_ptr;
 
  // weak_ptr 特化算法
  template<class T> void swap(weak_ptr<T>& a, weak_ptr<T>& b) noexcept;
 
  // 类模板 owner_less
  template<class T = void> struct owner_less;
 
  // 类模板 enable_shared_from_this
  template<class T> class enable_shared_from_this;
 
  // 散列支持
  template<class T> struct hash;
  template<class T, class D> struct hash<unique_ptr<T, D>>;
  template<class T> struct hash<shared_ptr<T>>;
 
  // 原子智能指针
  template<class T> struct atomic;
  template<class T> struct atomic<shared_ptr<T>>;
  template<class T> struct atomic<weak_ptr<T>>;
 
  // shared_ptr 原子访问
  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);
}

template<class I>
concept __NoThrowInputIterator = // 仅用于阐释
  InputIterator<I> &&
  is_lvalue_reference_v<iter_reference_t<I>> &&
  Same<remove_cvref_t<iter_reference_t<I>>, iter_value_t<I>>;
 
template<class S, class I>
concept __NoThrowSentinel = Sentinel<S, I>; // 仅用于阐释
 
template<class R>
concept __NoThrowInputRange = // 仅用于阐释
  Range<R> &&
  __NoThrowInputIterator<iterator_t<R>> &&
  __NoThrowSentinel<sentinel_t<R>, iterator_t<R>>;
 
template<class I>
concept __NoThrowForwardIterator = // 仅用于阐释
  __NoThrowInputIterator<I> &&
  ForwardIterator<I> &&
  __NoThrowSentinel<I, I>;
 
template<class R>
concept __NoThrowForwardRange = // 仅用于阐释
  __NoThrowInputRange<R> &&
  __NoThrowForwardIterator<iterator_t<R>>;

namespace std {
  template <class Ptr> struct pointer_traits {
    using pointer = Ptr;
    using element_type = /* 见定义 */;
    using difference_type = /* 见定义 */;
    template <class U> using rebind = /* 见定义 */;
    static pointer pointer_to(/* 见定义 */ r);
  };
 
  template <class T> struct pointer_traits<T*> {
    using pointer = T*;
    using element_type = T;
    using difference_type = ptrdiff_t;
    template <class U> using rebind = U*;
    static constexpr pointer pointer_to(/* 见定义 */ r) noexcept;
  };
}

namespace std {
  struct allocator_arg_t { explicit allocator_arg_t() = default; };
  inline constexpr allocator_arg_t allocator_arg{};
}

namespace std {
  template<class Alloc> struct allocator_traits {
    using allocator_type     = Alloc;
 
    using value_type         = typename Alloc::value_type;
 
    using pointer            = /* 见定义 */;
    using const_pointer      = /* 见定义 */;
    using void_pointer       = /* 见定义 */;
    using const_void_pointer = /* 见定义 */;
 
    using difference_type    = /* 见定义 */;
    using size_type          = /* 见定义 */;
 
    using propagate_on_container_copy_assignment = /* 见定义 */;
    using propagate_on_container_move_assignment = /* 见定义 */;
    using propagate_on_container_swap            = /* 见定义 */;
    using is_always_equal                        = /* 见定义 */;
 
    template<class T> using rebind_alloc = /* 见定义 */;
    template<class T> using rebind_traits = allocator_traits<rebind_alloc<T>>;
 
    [[nodiscard]] static pointer allocate(Alloc& a, size_type n);
    [[nodiscard]] static pointer allocate(Alloc& a, size_type n, const_void_pointer hint);
 
    static void deallocate(Alloc& a, pointer p, size_type n);
 
    template<class T, class... Args>
      static void construct(Alloc& a, T* p, Args&&... args);
 
    template<class T>
      static void destroy(Alloc& a, T* p);
 
    static size_type max_size(const Alloc& a) noexcept;
 
    static Alloc select_on_container_copy_construction(const Alloc& rhs);
  };
}

namespace std {
  template<class T> class allocator {
   public:
    using value_type                             = T;
    using size_type                              = size_t;
    using difference_type                        = ptrdiff_t;
    using propagate_on_container_move_assignment = true_type;
    using is_always_equal                        = true_type;
 
    constexpr allocator() noexcept;
    constexpr allocator(const allocator&) noexcept;
    template<class U> constexpr allocator(const allocator<U>&) noexcept;
    ~allocator();
    allocator& operator=(const allocator&) = default;
 
    [[nodiscard]] T* allocate(size_t n);
    void deallocate(T* p, size_t n);
  };
}

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

namespace std {
  template<class T, class D = default_delete<T>> class unique_ptr {
  public:
    using pointer      = /* 见定义 */;
    using element_type = T;
    using deleter_type = D;
 
    // 构造函数
    constexpr unique_ptr() noexcept;
    explicit unique_ptr(pointer p) noexcept;
    unique_ptr(pointer p, /* 见定义 */ d1) noexcept;
    unique_ptr(pointer p, /* 见定义 */ d2) noexcept;
    unique_ptr(unique_ptr&& u) noexcept;
    constexpr unique_ptr(nullptr_t) noexcept;
    template<class U, class E>
      unique_ptr(unique_ptr<U, E>&& u) noexcept;
 
    // 析构函数
    ~unique_ptr();
 
    // 赋值
    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;
 
    // 探查函数
    add_lvalue_reference_t<T> 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;
 
    // 修改函数
    pointer release() noexcept;
    void reset(pointer p = pointer()) noexcept;
    void swap(unique_ptr& u) noexcept;
 
    // 禁用从左值复制
    unique_ptr(const unique_ptr&) = delete;
    unique_ptr& operator=(const unique_ptr&) = delete;
  };
 
  template<class T, class D> class unique_ptr<T[], D> {
  public:
    using pointer      = /* 见定义 */;
    using element_type = T;
    using deleter_type = D;
 
    // 构造函数
    constexpr unique_ptr() noexcept;
    template<class U> explicit unique_ptr(U p) noexcept;
    template<class U> unique_ptr(U p, /* 见定义 */ d) noexcept;
    template<class U> unique_ptr(U p, /* 见定义 */ d) noexcept;
    unique_ptr(unique_ptr&& u) noexcept;
    template<class U, class E>
      unique_ptr(unique_ptr<U, E>&& u) noexcept;
    constexpr unique_ptr(nullptr_t) noexcept;
 
    // 析构函数
    ~unique_ptr();
 
    // 赋值
    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;
 
    // 探察函数
    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;
 
    // 修改函数
    pointer release() noexcept;
    template<class U> void reset(U p) noexcept;
    void reset(nullptr_t = nullptr) noexcept;
    void swap(unique_ptr& u) noexcept;
 
    // 禁用从左值复制
    unique_ptr(const unique_ptr&) = delete;
    unique_ptr& operator=(const unique_ptr&) = delete;
  };
}

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

namespace std {
  template<class T> class shared_ptr {
  public:
    using element_type = remove_extent_t<T>;
    using weak_type    = weak_ptr<T>;
 
    // 构造函数
    constexpr shared_ptr() noexcept;
    constexpr shared_ptr(nullptr_t) noexcept : shared_ptr() { }
    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, element_type* p) noexcept;
    template<class Y>
      shared_ptr(shared_ptr<Y>&& r, element_type* 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, class D>
      shared_ptr(unique_ptr<Y, D>&& r);
 
    // 析构函数
    ~shared_ptr();
 
    // 赋值
    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) noexcept;
    template<class Y, class D>
      shared_ptr& operator=(unique_ptr<Y, D>&& r);
 
    // 修改函数
    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);
 
    // 探察函数
    element_type* get() const noexcept;
    T& operator*() const noexcept;
    T* operator->() const noexcept;
    element_type& operator[](ptrdiff_t i) const;
    long use_count() const noexcept;
    explicit operator bool() const noexcept;
    template<class U>
      bool owner_before(const shared_ptr<U>& b) const noexcept;
    template<class U>
      bool owner_before(const weak_ptr<U>& 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>;
}

namespace std {
  template<class T> class weak_ptr {
  public:
    using element_type = remove_extent_t<T>;
 
    // 构造函数
    constexpr weak_ptr() noexcept;
    template<class Y>
      weak_ptr(const shared_ptr<Y>& r) noexcept;
    weak_ptr(const weak_ptr& r) noexcept;
    template<class Y>
      weak_ptr(const weak_ptr<Y>& r) noexcept;
    weak_ptr(weak_ptr&& r) noexcept;
    template<class Y>
      weak_ptr(weak_ptr<Y>&& r) noexcept;
 
    // 析构函数
    ~weak_ptr();
 
    // 赋值
    weak_ptr& operator=(const weak_ptr& r) noexcept;
    template<class Y>
      weak_ptr& operator=(const weak_ptr<Y>& r) noexcept;
    template<class Y>
      weak_ptr& operator=(const shared_ptr<Y>& r) noexcept;
    weak_ptr& operator=(weak_ptr&& r) noexcept;
    template<class Y>
      weak_ptr& operator=(weak_ptr<Y>&& r) noexcept;
 
    // 修改函数
    void swap(weak_ptr& r) noexcept;
    void reset() noexcept;
 
    // 探察函数
    long use_count() const noexcept;
    bool expired() const noexcept;
    shared_ptr<T> lock() const noexcept;
    template<class U>
      bool owner_before(const shared_ptr<U>& b) const noexcept;
    template<class U>
      bool owner_before(const weak_ptr<U>& b) const noexcept;
  };
 
  template<class T>
    weak_ptr(shared_ptr<T>) -> weak_ptr<T>;
}

namespace std {
  template<class T = void> struct owner_less;
 
  template<class T> struct owner_less<shared_ptr<T>> {
    bool operator()(const shared_ptr<T>&, const shared_ptr<T>&) const noexcept;
    bool operator()(const shared_ptr<T>&, const weak_ptr<T>&) const noexcept;
    bool operator()(const weak_ptr<T>&, const shared_ptr<T>&) const noexcept;
  };
 
  template<class T> struct owner_less<weak_ptr<T>> {
    bool operator()(const weak_ptr<T>&, const weak_ptr<T>&) const noexcept;
    bool operator()(const shared_ptr<T>&, const weak_ptr<T>&) const noexcept;
    bool operator()(const weak_ptr<T>&, const shared_ptr<T>&) const noexcept;
  };
 
  template<> struct owner_less<void> {
    template<class T, class U>
      bool operator()(const shared_ptr<T>&, const shared_ptr<U>&) const noexcept;
    template<class T, class U>
      bool operator()(const shared_ptr<T>&, const weak_ptr<U>&) const noexcept;
    template<class T, class U>
      bool operator()(const weak_ptr<T>&, const shared_ptr<U>&) const noexcept;
    template<class T, class U>
      bool operator()(const weak_ptr<T>&, const weak_ptr<U>&) const noexcept;
 
    using is_transparent = /* 未指明 */;
  };
}

namespace std {
  template<class T> class enable_shared_from_this {
  protected:
    constexpr enable_shared_from_this() noexcept;
    enable_shared_from_this(const enable_shared_from_this&) noexcept;
    enable_shared_from_this& operator=(const enable_shared_from_this&) noexcept;
    ~enable_shared_from_this();
 
  public:
    shared_ptr<T> shared_from_this();
    shared_ptr<T const> shared_from_this() const;
    weak_ptr<T> weak_from_this() noexcept;
    weak_ptr<T const> weak_from_this() const noexcept;
 
  private:
    mutable weak_ptr<T> weak_this;  // 仅用于阐释
  };
}

namespace std {
  template<class T> struct atomic<shared_ptr<T>> {
    using value_type = shared_ptr<T>;
    static constexpr bool is_always_lock_free = /* 由实现定义 */;
 
    bool is_lock_free() const noexcept;
    void store(shared_ptr<T> desired, memory_order order = memory_order::seq_cst) noexcept;
    shared_ptr<T> load(memory_order order = memory_order::seq_cst) const noexcept;
    operator shared_ptr<T>() const noexcept;
 
    shared_ptr<T> exchange(shared_ptr<T> desired,
                           memory_order order = memory_order::seq_cst) noexcept;
 
    bool compare_exchange_weak(shared_ptr<T>& expected, shared_ptr<T> desired,
                               memory_order success, memory_order failure) noexcept;
    bool compare_exchange_strong(shared_ptr<T>& expected, shared_ptr<T> desired,
                                 memory_order success, memory_order failure) noexcept;
 
    bool compare_exchange_weak(shared_ptr<T>& expected, shared_ptr<T> desired,
                               memory_order order = memory_order::seq_cst) noexcept;
    bool compare_exchange_strong(shared_ptr<T>& expected, shared_ptr<T> desired,
                                 memory_order order = memory_order::seq_cst) noexcept;
 
    constexpr atomic() noexcept = default;
    atomic(shared_ptr<T> desired) noexcept;
    atomic(const atomic&) = delete;
    void operator=(const atomic&) = delete;
    void operator=(shared_ptr<T> desired) noexcept;
 
  private:
    shared_ptr<T> p;            // 仅用于阐释
  };
}

namespace std {
  template<class T> struct atomic<weak_ptr<T>> {
    using value_type = weak_ptr<T>;
    static constexpr bool is_always_lock_free = /* 由实现定义 */;
 
    bool is_lock_free() const noexcept;
    void store(weak_ptr<T> desired, memory_order order = memory_order::seq_cst) noexcept;
    weak_ptr<T> load(memory_order order = memory_order::seq_cst) const noexcept;
    operator weak_ptr<T>() const noexcept;
 
    weak_ptr<T> exchange(weak_ptr<T> desired,
                         memory_order order = memory_order::seq_cst) noexcept;
 
    bool compare_exchange_weak(weak_ptr<T>& expected, weak_ptr<T> desired,
                               memory_order success, memory_order failure) noexcept;
    bool compare_exchange_strong(weak_ptr<T>& expected, weak_ptr<T> desired,
                                 memory_order success, memory_order failure) noexcept;
 
    bool compare_exchange_weak(weak_ptr<T>& expected, weak_ptr<T> desired,
                               memory_order order = memory_order::seq_cst) noexcept;
    bool compare_exchange_strong(weak_ptr<T>& expected, weak_ptr<T> desired,
                                 memory_order order = memory_order::seq_cst) noexcept;
 
    constexpr atomic() noexcept = default;
    atomic(weak_ptr<T> desired) noexcept;
    atomic(const atomic&) = delete;
    void operator=(const atomic&) = delete;
    void operator=(weak_ptr<T> desired) noexcept;
 
  private:
    weak_ptr<T> p;              // 仅用于阐释
  };
}