Standard library header <memory>

This header is part of the dynamic memory management library.

Classes
Pointer traits
pointer_traits (C++11)	provides information about pointer-like types (class template)
Garbage collector support
pointer_safety (C++11)	lists pointer safety models (enum)
Allocators
allocator	the default allocator (class template)
allocator_traits (C++11)	provides information about allocator types (class template)
allocator_arg_t (C++11)	tag type used to select allocator-aware constructor overloads (class)
allocator_arg (C++11)	an object of type `std::allocator_arg_t` used to select allocator-aware constructors (constant)
uses_allocator (C++11)	checks if the specified type supports uses-allocator construction (class template)
Uninitialized storage
raw_storage_iterator (deprecated in C++17)(removed in C++20)	an iterator that allows standard algorithms to store results in uninitialized memory (class template)
Smart pointers
unique_ptr (C++11)	smart pointer with unique object ownership semantics (class template)
shared_ptr (C++11)	smart pointer with shared object ownership semantics (class template)
weak_ptr (C++11)	weak reference to an object managed by `std::shared_ptr` (class template)
auto_ptr (removed in C++17)	smart pointer with strict object ownership semantics (class template)
Helper classes
std::atomic<std::shared_ptr> (C++20)	atomic shared pointer (class template specialization)
std::atomic<std::weak_ptr> (C++20)	atomic weak pointer (class template specialization)
owner_less (C++11)	provides mixed-type owner-based ordering of shared and weak pointers (class template)
enable_shared_from_this (C++11)	allows an object to create a `shared_ptr` referring to itself (class template)
bad_weak_ptr (C++11)	exception thrown when accessing a `weak_ptr` which refers to already destroyed object (class)
default_delete (C++11)	default deleter for `unique_ptr` (class template)
std::hash<std::unique_ptr> (C++11)	hash support for `std::unique_ptr` (class template specialization)
std::hash<std::shared_ptr> (C++11)	hash support for `std::shared_ptr` (class template specialization)
Functions
Miscellaneous
to_address (C++20)	obtains a raw pointer from a pointer-like type (function template)
addressof (C++11)	obtains actual address of an object, even if the & operator is overloaded (function template)
align (C++11)	aligns a pointer in a buffer (function)
assume_aligned (C++20)	informs the compiler that a pointer is aligned (function template)
Garbage collector support
declare_reachable (C++11)	declares that an object can not be recycled (function)
undeclare_reachable (C++11)	declares that an object can be recycled (function template)
declare_no_pointers (C++11)	declares that a memory area does not contain traceable pointers (function)
undeclare_no_pointers (C++11)	cancels the effect of `std::declare_no_pointers` (function)
get_pointer_safety (C++11)	returns the current pointer safety model (function)
Uninitialized storage
uninitialized_copy	copies a range of objects to an uninitialized area of memory (function template)
uninitialized_copy_n (C++11)	copies a number of objects to an uninitialized area of memory (function template)
uninitialized_fill	copies an object to an uninitialized area of memory, defined by a range (function template)
uninitialized_fill_n	copies an object to an uninitialized area of memory, defined by a start and a count (function template)
uninitialized_move (C++17)	moves a range of objects to an uninitialized area of memory (function template)
uninitialized_move_n (C++17)	moves a number of objects to an uninitialized area of memory (function template)
uninitialized_default_construct (C++17)	constructs objects by default-initialization in an uninitialized area of memory, defined by a range (function template)
uninitialized_default_construct_n (C++17)	constructs objects by default-initialization in an uninitialized area of memory, defined by a start and a count (function template)
uninitialized_value_construct (C++17)	constructs objects by value-initialization in an uninitialized area of memory, defined by a range (function template)
uninitialized_value_construct_n (C++17)	constructs objects by value-initialization in an uninitialized area of memory, defined by a start and a count (function template)
destroy_at (C++17)	destroys an object at a given address (function template)
destroy (C++17)	destroys a range of objects (function template)
destroy_n (C++17)	destroys a number of objects in a range (function template)
get_temporary_buffer (deprecated in C++17)(removed in C++20)	obtains uninitialized storage (function template)
return_temporary_buffer (deprecated in C++17)(removed in C++20)	frees uninitialized storage (function template)
Smart pointer non-member operations
make_uniquemake_unique_default_init (C++14)(C++20)	creates a unique pointer that manages a new object (function template)
operator==operator!=operator<operator<=operator>operator>=	compares to another `unique_ptr` or with `nullptr` (function template)
make_sharedmake_shared_default_init (C++20)	creates a shared pointer that manages a new object (function template)
allocate_sharedallocate_shared_default_init (C++20)	creates a shared pointer that manages a new object allocated using an allocator (function template)
static_pointer_castdynamic_pointer_castconst_pointer_castreinterpret_pointer_cast (C++17)	applies `static_cast`, `dynamic_cast`, `const_cast`, or `reinterpret_cast` to the stored pointer (function template)
get_deleter	returns the deleter of specified type, if owned (function template)
operator==operator!=operator<operator<=operator>operator>=	compares with another `shared_ptr` or with `nullptr` (function template)
operator<<	outputs the value of the stored pointer to an output stream (function template)
std::swap(std::unique_ptr) (C++11)	specializes the `std::swap` algorithm (function template)
std::swap(std::weak_ptr) (C++11)	specializes the `std::swap` algorithm (function template)
std::swap(std::shared_ptr) (C++11)	specializes the `std::swap` algorithm (function template)

std::atomic_is_lock_free(std::shared_ptr)std::atomic_load(std::shared_ptr)std::atomic_load_explicit(std::shared_ptr)std::atomic_store(std::shared_ptr)std::atomic_store_explicit(std::shared_ptr)std::atomic_exchange(std::shared_ptr)std::atomic_exchange_explicit(std::shared_ptr)std::atomic_compare_exchange_weak(std::shared_ptr)std::atomic_compare_exchange_strong(std::shared_ptr)std::atomic_compare_exchange_weak_explicit(std::shared_ptr)std::atomic_compare_exchange_strong_explicit(std::shared_ptr)

(deprecated in C++20)

specializes atomic operations for std::shared_ptr
(function template)

Defined in namespace `std::ranges`
Niebloids
Uninitialized storage
uninitialized_copy (C++20)	copies a range of objects to an uninitialized area of memory (niebloid)
uninitialized_copy_n (C++20)	copies a number of objects to an uninitialized area of memory (niebloid)
uninitialized_fill (C++20)	copies an object to an uninitialized area of memory, defined by a range (niebloid)
uninitialized_fill_n (C++20)	copies an object to an uninitialized area of memory, defined by a start and a count (niebloid)
uninitialized_move (C++20)	moves a range of objects to an uninitialized area of memory (niebloid)
uninitialized_move_n (C++20)	moves a number of objects to an uninitialized area of memory (niebloid)
uninitialized_default_construct (C++20)	constructs objects by default-initialization in an uninitialized area of memory, defined by a range (niebloid)
uninitialized_default_construct_n (C++20)	constructs objects by default-initialization in an uninitialized area of memory, defined by a start and count (niebloid)
uninitialized_value_construct (C++20)	constructs objects by value-initialization in an uninitialized area of memory, defined by a range (niebloid)
uninitialized_value_construct_n (C++20)	constructs objects by value-initialization in an uninitialized area of memory, defined by a start and a count (niebloid)
destroy_at (C++20)	destroys an object at a given address (niebloid)
destroy (C++20)	destroys a range of objects (niebloid)
destroy_n (C++20)	destroys a number of objects in a range (niebloid)

Synopsis

namespace std {
  // pointer traits
  template<class Ptr> struct pointer_traits;
  template<class T> struct pointer_traits<T*>;
 
  // pointer conversion
  template<class T>
    constexpr T* to_address(T* p) noexcept;
  template<class Ptr>
    auto to_address(const Ptr& p) noexcept;
 
  // 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;
 
  // pointer alignment
  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);
 
  // allocator argument tag
  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;
 
  // uses-allocator construction
  template<class T, class Alloc, class... Args>
    auto uses_allocator_construction_args(const Alloc& alloc, Args&&... args)
      -> /* see definition */;
  template<class T, class Alloc, class Tuple1, class Tuple2>
    auto uses_allocator_construction_args(const Alloc& alloc, piecewise_construct_t,
                                          Tuple1&& x, Tuple2&& y)
      -> /* see definition */;
  template<class T, class Alloc>
    auto uses_allocator_construction_args(const Alloc& alloc) -> /* see definition */;
  template<class T, class Alloc, class U, class V>
    auto uses_allocator_construction_args(const Alloc& alloc, U&& u, V&& v)
      -> /* see definition */;
  template<class T, class Alloc, class U, class V>
    auto uses_allocator_construction_args(const Alloc& alloc, const pair<U,V>& pr)
      -> /* see definition */;
  template<class T, class Alloc, class U, class V>
    auto uses_allocator_construction_args(const Alloc& alloc, pair<U,V>&& pr)
      -> /* see definition */;
  template<class T, class Alloc, class... Args>
    T make_obj_using_allocator(const Alloc& alloc, Args&&... args);
  template<class T, class Alloc, class... Args>
    T* uninitialized_construct_using_allocator(T* p, const Alloc& alloc, Args&&... args);
 
  // allocator traits
  template<class Alloc> struct allocator_traits;
 
  // the default allocator
  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;
 
  // specialized algorithms
  // special memory concepts
  template<class I>
    concept __NoThrowInputIterator = /* see definition */;   // exposition only
  template<class I>
    concept __NoThrowForwardIterator = /* see definition */; // exposition only
  template<class S, class I>
    concept __NoThrowSentinel = /* see definition */;        // exposition only
  template<class R>
    concept __NoThrowInputRange = /* see definition */;      // exposition only
  template<class R>
    concept __NoThrowForwardRange = /* see definition */;    // exposition only
 
  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;
  }
 
  // class template 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 is not array
  template<class T>
    unique_ptr<T> make_unique(size_t n);                                // T is U[]
  template<class T, class... Args>
    /* unspecified */ make_unique(Args&&...) = delete;                  // T is U[N]
 
  template<class T>
    unique_ptr<T> make_unique_default_init();                           // T is not array
  template<class T>
    unique_ptr<T> make_unique_default_init(size_t n);                   // T is U[]
  template<class T, class... Args>
    /* unspecified */ make_unique_default_init(Args&&...) = delete;     // T is 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);
 
  // class bad_weak_ptr
  class bad_weak_ptr;
 
  // class template shared_ptr
  template<class T> class shared_ptr;
 
  // shared_ptr creation
  template<class T, class... Args>
    shared_ptr<T> make_shared(Args&&... args);                          // T is not array
  template<class T, class A, class... Args>
    shared_ptr<T> allocate_shared(const A& a, Args&&... args);          // T is not array
 
  template<class T>
    shared_ptr<T> make_shared(size_t N);                                // T is U[]
  template<class T, class A>
    shared_ptr<T> allocate_shared(const A& a, size_t N);                // T is U[]
 
  template<class T>
    shared_ptr<T> make_shared();                                        // T is U[N]
  template<class T, class A>
    shared_ptr<T> allocate_shared(const A& a);                          // T is U[N]
 
  template<class T>
    shared_ptr<T> make_shared(size_t N, const remove_extent_t<T>& u);   // T is U[]
  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[]
 
  template<class T>
    shared_ptr<T> make_shared(const remove_extent_t<T>& u);                 // T is U[N]
  template<class T, class A>
    shared_ptr<T> allocate_shared(const A& a, const remove_extent_t<T>& u); // T is U[N]
 
  template<class T>
    shared_ptr<T> make_shared_default_init();                           // T is not U[]
  template<class T, class A>
    shared_ptr<T> allocate_shared_default_init(const A& a);             // T is not U[]
 
  template<class T>
    shared_ptr<T> make_shared_default_init(size_t N);                   // T is U[]
  template<class T, class A>
    shared_ptr<T> allocate_shared_default_init(const A& a, size_t N);   // T is U[]
 
  // shared_ptr comparisons
  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 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(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);
 
  // class template weak_ptr
  template<class T> class weak_ptr;
 
  // weak_ptr specialized algorithms
  template<class T> void swap(weak_ptr<T>& a, weak_ptr<T>& b) noexcept;
 
  // class template owner_less
  template<class T = void> struct owner_less;
 
  // class template enable_shared_from_this
  template<class T> class enable_shared_from_this;
 
  // 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>>;
 
  // atomic smart pointers
  template<class T> struct atomic;
  template<class T> struct atomic<shared_ptr<T>>;
  template<class T> struct atomic<weak_ptr<T>>;
 
  // shared_ptr atomic access
  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);
}

Helper concepts

template<class I>
concept __NoThrowInputIterator = // exposition only
  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>; // exposition only
 
template<class R>
concept __NoThrowInputRange = // exposition only
  Range<R> &&
  __NoThrowInputIterator<iterator_t<R>> &&
  __NoThrowSentinel<sentinel_t<R>, iterator_t<R>>;
 
template<class I>
concept __NoThrowForwardIterator = // exposition only
  __NoThrowInputIterator<I> &&
  ForwardIterator<I> &&
  __NoThrowSentinel<I, I>;
 
template<class R>
concept __NoThrowForwardRange = // exposition only
  __NoThrowInputRange<R> &&
  __NoThrowForwardIterator<iterator_t<R>>;

Note: These names are only for exposition, they are not part of the interface.

Class template `std::pointer_traits`

namespace std {
  template <class Ptr> struct pointer_traits {
    using pointer = Ptr;
    using element_type = /* see definition */;
    using difference_type = /* see definition */;
    template <class U> using rebind = /* see definition */;
    static pointer pointer_to(/* see definition */ 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(/* see definition */ r) noexcept;
  };
}

Class `std::allocator_arg_t`

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

Class template `std::allocator_traits`

namespace std {
  template<class Alloc> struct allocator_traits {
    using allocator_type     = Alloc;
 
    using value_type         = typename Alloc::value_type;
 
    using pointer            = /* see definition */;
    using const_pointer      = /* see definition */;
    using void_pointer       = /* see definition */;
    using const_void_pointer = /* see definition */;
 
    using difference_type    = /* see definition */;
    using size_type          = /* see definition */;
 
    using propagate_on_container_copy_assignment = /* see definition */;
    using propagate_on_container_move_assignment = /* see definition */;
    using propagate_on_container_swap            = /* see definition */;
    using is_always_equal                        = /* see definition */;
 
    template<class T> using rebind_alloc = /* see definition */;
    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);
  };
}

Class template `std::allocator`

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);
  };
}

Class template `std::default_delete`

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;
  };
}

Class template `std::unique_ptr`

namespace std {
  template<class T, class D = default_delete<T>> class unique_ptr {
  public:
    using pointer      = /* see definition */;
    using element_type = T;
    using deleter_type = D;
 
    // constructors
    constexpr unique_ptr() noexcept;
    explicit unique_ptr(pointer p) noexcept;
    unique_ptr(pointer p, /* see definition */ d1) noexcept;
    unique_ptr(pointer p, /* see definition */ 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;
 
    // 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
    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;
 
    // modifiers
    pointer release() noexcept;
    void reset(pointer p = pointer()) noexcept;
    void swap(unique_ptr& u) noexcept;
 
    // disable copy from lvalue
    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      = /* see definition */;
    using element_type = T;
    using deleter_type = D;
 
    // constructors
    constexpr unique_ptr() noexcept;
    template<class U> explicit unique_ptr(U p) noexcept;
    template<class U> unique_ptr(U p, /* see definition */ d) noexcept;
    template<class U> unique_ptr(U p, /* see definition */ 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;
 
    // 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
    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;
    template<class U> void reset(U p) noexcept;
    void reset(nullptr_t = nullptr) noexcept;
    void swap(unique_ptr& u) noexcept;
 
    // disable copy from lvalue
    unique_ptr(const unique_ptr&) = delete;
    unique_ptr& operator=(const unique_ptr&) = delete;
  };
}

Class `std::bad_weak_ptr`

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

Class template `std::shared_ptr`

namespace std {
  template<class T> class shared_ptr {
  public:
    using element_type = remove_extent_t<T>;
    using weak_type    = weak_ptr<T>;
 
    // constructors
    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);
 
    // 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) noexcept;
    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
    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>;
}

Class template `std::weak_ptr`

namespace std {
  template<class T> class weak_ptr {
  public:
    using element_type = remove_extent_t<T>;
 
    // constructors
    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;
 
    // destructor
    ~weak_ptr();
 
    // assignment
    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;
 
    // 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(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>;
}

Class template `std::owner_less`

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 = /* unspecified */;
  };
}

Class template `std::enable_shared_from_this`

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;  // exposition only
  };
}

Class template `std::atomic`'s specialization for `std::shared_ptr`

namespace std {
  template<class T> struct atomic<shared_ptr<T>> {
    using value_type = shared_ptr<T>;
    static constexpr bool is_always_lock_free = /* implementation-defined */;
 
    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;            // exposition only
  };
}

Class template `std::atomic`'s specialization for `std::weak_ptr`

namespace std {
  template<class T> struct atomic<weak_ptr<T>> {
    using value_type = weak_ptr<T>;
    static constexpr bool is_always_lock_free = /* implementation-defined */;
 
    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;              // exposition only
  };
}

© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
http://en.cppreference.com/w/cpp/header/memory

Standard library header <memory>

Classes

Pointer traits

Garbage collector support

Allocators

Uninitialized storage

Smart pointers

Helper classes

Functions

Miscellaneous

Garbage collector support

Uninitialized storage

Smart pointer non-member operations

Niebloids

Uninitialized storage

Synopsis

Helper concepts

Class template std::pointer_traits

Class std::allocator_arg_t

Class template std::allocator_traits

Class template std::allocator

Class template std::default_delete

Class template std::unique_ptr

Class std::bad_weak_ptr

Class template std::shared_ptr

Class template std::weak_ptr

Class template std::owner_less

Class template std::enable_shared_from_this

Class template std::atomic's specialization for std::shared_ptr

Class template std::atomic's specialization for std::weak_ptr

Class template `std::pointer_traits`

Class `std::allocator_arg_t`

Class template `std::allocator_traits`

Class template `std::allocator`

Class template `std::default_delete`

Class template `std::unique_ptr`

Class `std::bad_weak_ptr`

Class template `std::shared_ptr`

Class template `std::weak_ptr`

Class template `std::owner_less`

Class template `std::enable_shared_from_this`

Class template `std::atomic`'s specialization for `std::shared_ptr`

Class template `std::atomic`'s specialization for `std::weak_ptr`