zig/lib/libcxx/include/memory

// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// 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

// clang-format off

/*
    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> constexpr 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

    [[nodiscard]] static constexpr allocation_result<pointer, size_type>
      allocate_at_least(Alloc& a, size_type n);                                 // Since C++23

    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 Pointer, class SizeType = size_t>
struct allocation_result {
    Pointer ptr;
    SizeType count;
}; // Since C++23

template <>
class allocator<void> // 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;                   // Deprecated in C++23, removed in C++26

    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; // removed in C++20

template <class OutputIterator, class T>
class raw_storage_iterator // deprecated in C++17, removed in C++20
    : public iterator<output_iterator_tag, void, void, void, void> // until C++17
{
public:
    typedef output_iterator_tag iterator_category;
    typedef void                value_type;
    typedef void                difference_type; // until C++20
    typedef ptrdiff_t           difference_type; // since C++20
    typedef void                pointer;
    typedef void                reference;

    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);

namespace ranges {

template<class InputIterator, class OutputIterator>
using uninitialized_copy_result = in_out_result<InputIterator, OutputIterator>; // since C++20

template<input_iterator InputIterator, sentinel-for<InputIterator> Sentinel1, nothrow-forward-iterator OutputIterator, nothrow-sentinel-for<OutputIterator> Sentinel2>
  requires constructible_from<iter_value_t<OutputIterator>, iter_reference_t<InputIterator>>
uninitialized_copy_result<InputIterator, OutputIterator>
uninitialized_copy(InputIterator ifirst, Sentinel1 ilast, OutputIterator ofirst, Sentinel2 olast); // since C++20

template<input_range InputRange, nothrow-forward-range OutputRange>
  requires constructible_from<range_value_t<OutputRange>, range_reference_t<InputRange>>
uninitialized_copy_result<borrowed_iterator_t<InputRange>, borrowed_iterator_t<OutputRange>>
uninitialized_copy(InputRange&& in_range, OutputRange&& out_range); // since C++20

}

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

namespace ranges {

template<class InputIterator, class OutputIterator>
using uninitialized_copy_n_result = in_out_result<InputIterator, OutputIterator>; // since C++20

template<input_iterator InputIterator, nothrow-forward-iterator OutputIterator, nothrow-sentinel-for<OutputIterator> Sentinel>
  requires constructible_from<iter_value_t<OutputIterator>, iter_reference_t<InputIterator>>
uninitialized_copy_n_result<InputIterator, OutputIterator>
uninitialized_copy_n(InputIterator ifirst, iter_difference_t<InputIterator> n, OutputIterator ofirst, Sentinel olast); // since C++20

}

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

namespace ranges {

template <nothrow-forward-iterator ForwardIterator, nothrow-sentinel-for<ForwardIterator> Sentinel, class T>
  requires constructible_from<iter_value_t<ForwardIterator>, const T&>
ForwardIterator uninitialized_fill(ForwardIterator first, Sentinel last, const T& x); // since C++20

template <nothrow-forward-range ForwardRange, class T>
  requires constructible_from<range_value_t<ForwardRange>, const T&>
borrowed_iterator_t<ForwardRange> uninitialized_fill(ForwardRange&& range, const T& x); // since C++20

}

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

namespace ranges {

template <nothrow-forward-iterator ForwardIterator, class T>
  requires constructible_from<iter_value_t<ForwardIterator>, const T&>
ForwardIterator uninitialized_fill_n(ForwardIterator first, iter_difference_t<ForwardIterator> n); // since C++20

}

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

namespace ranges {
  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

namespace ranges {
  template<destructible T>
    constexpr void destroy_at(T* location) noexcept; // since C++20
}

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

namespace ranges {
  template<nothrow-input-iterator InputIterator, nothrow-sentinel-for<InputIterator> Sentinel>
    requires destructible<iter_value_t<InputIterator>>
    constexpr InputIterator destroy(InputIterator first, Sentinel last) noexcept; // since C++20
  template<nothrow-input-range InputRange>
    requires destructible<range_value_t<InputRange>>
    constexpr borrowed_iterator_t<InputRange> destroy(InputRange&& range) noexcept; // since C++20
}

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

namespace ranges {
  template<nothrow-input-iterator InputIterator>
    requires destructible<iter_value_t<InputIterator>>
    constexpr InputIterator destroy_n(InputIterator first, iter_difference_t<InputIterator> n) noexcept; // since C++20
}

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

namespace ranges {

template<class InputIterator, class OutputIterator>
using uninitialized_move_result = in_out_result<InputIterator, OutputIterator>; // since C++20

template <input_iterator InputIterator, sentinel_for<InputIterator> Sentinel1, nothrow-forward-iterator OutputIterator, nothrow-sentinel-for<O> Sentinel2>
  requires constructible_from<iter_value_t<OutputIterator>, iter_rvalue_reference_t<InputIterator>>
uninitialized_move_result<InputIterator, OutputIterator>
uninitialized_move(InputIterator ifirst, Sentinel1 ilast, OutputIterator ofirst, Sentinel2 olast); // since C++20

template<input_range InputRange, nothrow-forward-range OutputRange>
  requires constructible_from<range_value_t<OutputRange>, range_rvalue_reference_t<InputRange>>
uninitialized_move_result<borrowed_iterator_t<InputRange>, borrowed_iterator_t<OutputRange>>
uninitialized_move(InputRange&& in_range, OutputRange&& out_range); // since C++20

}

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

namespace ranges {

template<class InputIterator, class OutputIterator>
using uninitialized_move_n_result = in_out_result<InputIterator, OutputIterator>; // since C++20

template<input_iterator InputIterator, nothrow-forward-iterator OutputIterator, nothrow-sentinel-for<OutputIterator> Sentinel>
  requires constructible_from<iter_value_t<OutputIterator>, iter_rvalue_reference_t<InputIterator>>
uninitialized_move_n_result<InputIterator, OutputIterator>
uninitialized_move_n(InputIterator ifirst, iter_difference_t<InputIterator> n, OutputIterator ofirst, Sentinel olast); // since C++20

}

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

namespace ranges {

template <nothrow-forward-iterator ForwardIterator, nothrow-sentinel-for<ForwardIterator> Sentinel>
  requires default_initializable<iter_value_t<ForwardIterator>>
 ForwardIterator uninitialized_value_construct(ForwardIterator first, Sentinel last); // since C++20

template <nothrow-forward-range ForwardRange>
  requires default_initializable<range_value_t<ForwardRange>>
 borrowed_iterator_t<ForwardRange> uninitialized_value_construct(ForwardRange&& r); // since C++20

}

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

namespace ranges {

template <nothrow-forward-iterator ForwardIterator>
  requires default_initializable<iter_value_t<ForwardIterator>>
 ForwardIterator uninitialized_value_construct_n(ForwardIterator first, iter_difference_t<ForwardIterator> n); // since C++20

}

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

namespace ranges {

template <nothrow-forward-iterator ForwardIterator, nothrow-sentinel-for<ForwardIterator> Sentinel>
  requires default_initializable<iter_value_t<ForwardIterator>>
 ForwardIterator uninitialized_default_construct(ForwardIterator first, Sentinel last); // since C++20

template <nothrow-forward-range ForwardRange>
  requires default_initializable<range_value_t<ForwardRange>>
 borrowed_iterator_t<ForwardRange> uninitialized_default_construct(ForwardRange&& r); // since C++20

}

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

namespace ranges {

template <nothrow-forward-iterator ForwardIterator>
  requires default_initializable<iter_value_t<ForwardIterator>>
 ForwardIterator uninitialized_default_construct_n(ForwardIterator first, iter_difference_t<ForwardIterator> n); // since C++20

}

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> constexpr default_delete(const default_delete<U>&) noexcept; // constexpr since C++23

    constexpr void operator()(T*) const noexcept;                                   // constexpr since C++23
};

template <class T>
struct default_delete<T[]>
{
    constexpr default_delete() noexcept = default;
    template <class U> constexpr default_delete(const default_delete <U[]>&) noexcept; // constexpr since C++23
    constexpr void operator()(T*) const noexcept;                                      // constexpr since C++23
    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;
    constexpr explicit unique_ptr(pointer p) noexcept;           // constexpr since C++23
    constexpr unique_ptr(pointer p, see below d1) noexcept;      // constexpr since C++23
    constexpr unique_ptr(pointer p, see below d2) noexcept;      // constexpr since C++23
    constexpr unique_ptr(unique_ptr&& u) noexcept;               // constexpr since C++23
    constexpr unique_ptr(nullptr_t) noexcept : unique_ptr() { }
    template <class U, class E>
        constexpr unique_ptr(unique_ptr<U, E>&& u) noexcept;     // constexpr since C++23
    template <class U>
        unique_ptr(auto_ptr<U>&& u) noexcept;                    // removed in C++17

    // destructor
    constexpr ~unique_ptr();                                     // constexpr since C++23

    // assignment
    constexpr unique_ptr& operator=(unique_ptr&& u) noexcept;                         // constexpr since C++23
    template <class U, class E>
    constexpr unique_ptr& operator=(unique_ptr<U, E>&& u) noexcept;                   // constexpr since C++23
    constexpr unique_ptr& operator=(nullptr_t) noexcept;                              // constexpr since C++23

    // observers
    constexpr
    add_lvalue_reference<T>::type operator*() const noexcept(see below);              // constexpr since C++23
    constexpr pointer operator->() const noexcept;                                    // constexpr since C++23
    constexpr pointer get() const noexcept;                                           // constexpr since C++23
    constexpr deleter_type& get_deleter() noexcept;                                   // constexpr since C++23
    constexpr const deleter_type& get_deleter() const noexcept;                       // constexpr since C++23
    constexpr explicit operator bool() const noexcept;                                // constexpr since C++23

    // modifiers
    constexpr pointer release() noexcept;                                             // constexpr since C++23
    constexpr void reset(pointer p = pointer()) noexcept;                             // constexpr since C++23
    constexpr void swap(unique_ptr& u) noexcept;                                      // constexpr since C++23
};

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;
    constexpr explicit unique_ptr(pointer p) noexcept;          // constexpr since C++23
    constexpr unique_ptr(pointer p, see below d) noexcept;      // constexpr since C++23
    constexpr unique_ptr(pointer p, see below d) noexcept;      // constexpr since C++23
    constexpr unique_ptr(unique_ptr&& u) noexcept;              // constexpr since C++23
    template <class U, class E>
    constexpr unique_ptr(unique_ptr <U, E>&& u) noexcept;       // constexpr since C++23
    constexpr unique_ptr(nullptr_t) noexcept : unique_ptr() { }

    // destructor
    constexpr ~unique_ptr();                                    // constexpr since C++23

    // assignment
    constexpr unique_ptr& operator=(unique_ptr&& u) noexcept;        // constexpr since C++23
    template <class U, class E>
    constexpr unique_ptr& operator=(unique_ptr <U, E>&& u) noexcept; // constexpr since C++23
    constexpr unique_ptr& operator=(nullptr_t) noexcept;             // constexpr since C++23

    // observers
    constexpr T& operator[](size_t i) const;                    // constexpr since C++23
    constexpr pointer get() const noexcept;                     // constexpr since C++23
    constexpr deleter_type& get_deleter() noexcept;             // constexpr since C++23
    constexpr const deleter_type& get_deleter() const noexcept; // constexpr since C++23
    constexpr explicit operator bool() const noexcept;          // constexpr since C++23

    // modifiers
    constexpr pointer release() noexcept;                       // constexpr since C++23
    constexpr void reset(pointer p = pointer()) noexcept;       // constexpr since C++23
    constexpr void reset(nullptr_t) noexcept;                   // constexpr since C++23
  template <class U> void reset(U) = delete;
    constexpr void swap(unique_ptr& u) noexcept;                // constexpr since C++23
};

template <class T, class D>
    constexpr void swap(unique_ptr<T, D>& x, unique_ptr<T, D>& y) noexcept;                 // constexpr since C++23

template <class T1, class D1, class T2, class D2>
    constexpr bool operator==(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);    // constexpr since C++23
template <class T1, class D1, class T2, class D2>
    bool operator!=(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);              // removed in C++20
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>
  requires three_way_comparable_with<typename unique_ptr<T1, D1>::pointer,
                                     typename unique_ptr<T2, D2>::pointer>
  compare_three_way_result_t<typename unique_ptr<T1, D1>::pointer,
                             typename unique_ptr<T2, D2>::pointer>
    operator<=>(const unique_ptr<T1, D1>& x, const unique_ptr<T2, D2>& y);      // C++20

template <class T, class D>
    constexpr bool operator==(const unique_ptr<T, D>& x, nullptr_t) noexcept;   // constexpr since C++23
template <class T, class D>
    bool operator==(nullptr_t, const unique_ptr<T, D>& y) noexcept;             // removed in C++20
template <class T, class D>
    bool operator!=(const unique_ptr<T, D>& x, nullptr_t) noexcept;             // removed in C++20
template <class T, class D>
    bool operator!=(nullptr_t, const unique_ptr<T, D>& y) noexcept;             // removed in C++20

template <class T, class D>
    constexpr bool operator<(const unique_ptr<T, D>& x, nullptr_t);     // constexpr since C++23
template <class T, class D>
    constexpr bool operator<(nullptr_t, const unique_ptr<T, D>& y);     // constexpr since C++23
template <class T, class D>
    constexpr bool operator<=(const unique_ptr<T, D>& x, nullptr_t);    // constexpr since C++23
template <class T, class D>
    constexpr bool operator<=(nullptr_t, const unique_ptr<T, D>& y);    // constexpr since C++23
template <class T, class D>
    constexpr bool operator>(const unique_ptr<T, D>& x, nullptr_t);     // constexpr since C++23
template <class T, class D>
    constexpr bool operator>(nullptr_t, const unique_ptr<T, D>& y);     // constexpr since C++23
template <class T, class D>
    constexpr bool operator>=(const unique_ptr<T, D>& x, nullptr_t);    // constexpr since C++23
template <class T, class D>
    constexpr bool operator>=(nullptr_t, const unique_ptr<T, D>& y);    // constexpr since C++23
template<class T, class D>
  requires three_way_comparable<typename unique_ptr<T, D>::pointer>
  compare_three_way_result_t<typename unique_ptr<T, D>::pointer>
    constexpr operator<=>(const unique_ptr<T, D>& x, nullptr_t);        // C++20, constexpr since C++23

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

template<class T, class... Args>
constexpr unique_ptr<T> make_unique(Args&&... args);                            // C++14, constexpr since C++23
template<class T>
constexpr unique_ptr<T> make_unique(size_t n);                                  // C++14, constexpr since C++23
template<class T, class... Args> unspecified   make_unique(Args&&...) = delete; // C++14, T == U[N]

template<class T>
  constexpr unique_ptr<T> make_unique_for_overwrite();                        // T is not array, C++20, constexpr since C++23
template<class T>
  constexpr unique_ptr<T> make_unique_for_overwrite(size_t n);                // T is U[], C++20, constexpr since C++23
template<class T, class... Args>
  unspecified make_unique_for_overwrite(Args&&...) = delete;                  // T is U[N], C++20

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; // until C++17
    typedef remove_extent_t<T> element_type; // since C++17
    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;  // deprected in C++17, removed in C++20
    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;               // removed in C++20
template<class T, class U>
    bool operator<(shared_ptr<T> const& a, shared_ptr<U> const& b) noexcept;                // removed in C++20
template<class T, class U>
    bool operator>(shared_ptr<T> const& a, shared_ptr<U> const& b) noexcept;                // removed in C++20
template<class T, class U>
    bool operator<=(shared_ptr<T> const& a, shared_ptr<U> const& b) noexcept;               // removed in C++20
template<class T, class U>
    bool operator>=(shared_ptr<T> const& a, shared_ptr<U> const& b) noexcept;               // removed in C++20
template<class T, class U>
    strong_ordering operator<=>(shared_ptr<T> const& a, shared_ptr<U> const& b) noexcept;   // C++20

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;               // removed in C++20
template <class T>
    bool operator!=(const shared_ptr<T>& x, nullptr_t) noexcept;               // removed in C++20
template <class T>
    bool operator!=(nullptr_t, const shared_ptr<T>& y) noexcept;               // removed in C++20
template <class T>
    bool operator<(const shared_ptr<T>& x, nullptr_t) noexcept;                // removed in C++20
template <class T>
    bool operator<(nullptr_t, const shared_ptr<T>& y) noexcept;                // removed in C++20
template <class T>
    bool operator<=(const shared_ptr<T>& x, nullptr_t) noexcept;               // removed in C++20
template <class T>
    bool operator<=(nullptr_t, const shared_ptr<T>& y) noexcept;               // removed in C++20
template <class T>
    bool operator>(const shared_ptr<T>& x, nullptr_t) noexcept;                // removed in C++20
template <class T>
    bool operator>(nullptr_t, const shared_ptr<T>& y) noexcept;                // removed in C++20
template <class T>
    bool operator>=(const shared_ptr<T>& x, nullptr_t) noexcept;               // removed in C++20
template <class T>
    bool operator>=(nullptr_t, const shared_ptr<T>& y) noexcept;               // removed in C++20
template<class T>
    strong_ordering operator<=>(shared_ptr<T> const& x, nullptr_t) noexcept;   // C++20

// 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); // T is not an array
template<class T, class A, class... Args>
    shared_ptr<T> allocate_shared(const A& a, Args&&... args); // T is not an array

template<class T>
    shared_ptr<T> make_shared(size_t N); // T is U[] (since C++20)
template<class T, class A>
    shared_ptr<T> allocate_shared(const A& a, size_t N); // T is U[] (since C++20)

template<class T>
    shared_ptr<T> make_shared(); // T is U[N] (since C++20)
template<class T, class A>
    shared_ptr<T> allocate_shared(const A& a); // T is U[N] (since C++20)

template<class T>
    shared_ptr<T> make_shared(size_t N, const remove_extent_t<T>& u); // T is U[] (since C++20)
template<class T, class A>
    shared_ptr<T> allocate_shared(const A& a, size_t N, const remove_extent_t<T>& u); // T is U[] (since C++20)

template<class T> shared_ptr<T>
    make_shared(const remove_extent_t<T>& u); // T is U[N] (since C++20)
template<class T, class A>
    shared_ptr<T> allocate_shared(const A& a, const remove_extent_t<T>& u); // T is U[N] (since C++20)

template<class T>
  shared_ptr<T> make_shared_for_overwrite();                                  // T is not U[], C++20
template<class T, class A>
  shared_ptr<T> allocate_shared_for_overwrite(const A& a);                    // T is not U[], C++20

template<class T>
  shared_ptr<T> make_shared_for_overwrite(size_t N);                          // T is U[], C++20
template<class T, class A>
  shared_ptr<T> allocate_shared_for_overwrite(const A& a, size_t N);          // T is U[], C++20

template<class T>
class weak_ptr
{
public:
    typedef T element_type; // until C++17
    typedef remove_extent_t<T> element_type; // since C++17

    // 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;

// [allocator.uses.construction], uses-allocator construction
template<class T, class Alloc, class... Args>
  constexpr auto uses_allocator_construction_args(const Alloc& alloc,             // since C++20
                                                  Args&&... args) noexcept;
template<class T, class Alloc, class Tuple1, class Tuple2>
  constexpr auto uses_allocator_construction_args(const Alloc& alloc,             // since C++20
                                                  piecewise_construct_t,
                                                  Tuple1&& x, Tuple2&& y) noexcept;
template<class T, class Alloc>
  constexpr auto uses_allocator_construction_args(const Alloc& alloc) noexcept;   // since C++20
template<class T, class Alloc, class U, class V>
  constexpr auto uses_allocator_construction_args(const Alloc& alloc,             // since C++20
                                                  U&& u, V&& v) noexcept;
template<class T, class Alloc, class U, class V>
  constexpr auto uses_allocator_construction_args(const Alloc& alloc,             // since C++23
                                                  pair<U, V>& pr) noexcept;
template<class T, class Alloc, class U, class V>
  constexpr auto uses_allocator_construction_args(const Alloc& alloc,             // since C++20
                                                  const pair<U, V>& pr) noexcept;
template<class T, class Alloc, class U, class V>
  constexpr auto uses_allocator_construction_args(const Alloc& alloc,             // since C++20
                                                  pair<U, V>&& pr) noexcept;
template<class T, class Alloc, class U, class V>
  constexpr auto uses_allocator_construction_args(const Alloc& alloc,             // since C++23
                                                  const pair<U, V>&& pr) noexcept;
template<class T, class Alloc, pair-like P>
  constexpr auto uses_allocator_construction_args(const Alloc& alloc,             // since C++20
                                                  P&& p) noexcept;
template<class T, class Alloc, class U>
  constexpr auto uses_allocator_construction_args(const Alloc& alloc,             // since C++20
                                                  U&& u) noexcept;
template<class T, class Alloc, class... Args>
  constexpr T make_obj_using_allocator(const Alloc& alloc, Args&&... args);       // since C++20
template<class T, class Alloc, class... Args>
  constexpr T* uninitialized_construct_using_allocator(T* p,                      // since C++20
                                                         const Alloc& alloc, Args&&... args);

// [ptr.align]
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); // since C++20

// [out.ptr.t], class template out_ptr_t
template<class Smart, class Pointer, class... Args>
  class out_ptr_t;                                          // since c++23

// [out.ptr], function template out_ptr
template<class Pointer = void, class Smart, class... Args>
  auto out_ptr(Smart& s, Args&&... args);                   // since c++23

// [inout.ptr.t], class template inout_ptr_t
template<class Smart, class Pointer, class... Args>
  class inout_ptr_t;                                        // since c++23

// [inout.ptr], function template inout_ptr
template<class Pointer = void, class Smart, class... Args>
  auto inout_ptr(Smart& s, Args&&... args);                 // since c++23

}  // std

*/

// clang-format on

#include <__config>
#include <__memory/addressof.h>
#include <__memory/align.h>
#include <__memory/allocator.h>
#include <__memory/allocator_arg_t.h>
#include <__memory/allocator_traits.h>
#include <__memory/auto_ptr.h>
#include <__memory/inout_ptr.h>
#include <__memory/out_ptr.h>
#include <__memory/pointer_traits.h>
#include <__memory/raw_storage_iterator.h>
#include <__memory/shared_ptr.h>
#include <__memory/temporary_buffer.h>
#include <__memory/uninitialized_algorithms.h>
#include <__memory/unique_ptr.h>
#include <__memory/uses_allocator.h>

// standard-mandated includes

#if _LIBCPP_STD_VER >= 17
#  include <__memory/construct_at.h>
#endif

#if _LIBCPP_STD_VER >= 20
#  include <__memory/assume_aligned.h>
#  include <__memory/concepts.h>
#  include <__memory/ranges_construct_at.h>
#  include <__memory/ranges_uninitialized_algorithms.h>
#  include <__memory/uses_allocator_construction.h>
#endif

#if _LIBCPP_STD_VER >= 23
#  include <__memory/allocate_at_least.h>
#endif

#include <version>

// [memory.syn]
#include <compare>

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

#if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
#  include <atomic>
#  include <concepts>
#  include <cstddef>
#  include <cstdint>
#  include <cstdlib>
#  include <cstring>
#  include <iosfwd>
#  include <iterator>
#  include <new>
#  include <stdexcept>
#  include <tuple>
#  include <type_traits>
#  include <typeinfo>
#  include <utility>
#endif

#endif // _LIBCPP_MEMORY