20 General utilities library [utilities]

20.6 Memory [memory]

20.6.3 Pointer traits [pointer.traits]

The class template pointer_traits supplies a uniform interface to certain attributes of pointer-like types.

namespace std {
  template <class Ptr> struct pointer_traits {
    typedef Ptr       pointer;
    typedef see below element_type;
    typedef see below difference_type;

    template <class U> using rebind = see below;

    static pointer pointer_to(see below r);
  };

  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(see below r) noexcept;
  };
}

20.6.3.1 Pointer traits member types [pointer.traits.types]

typedef see below element_type;

Type: Ptr::element_type if such a type exists; otherwise, T if Ptr is a class template instantiation of the form SomePointer<T, Args>, where Args is zero or more type arguments; otherwise, the specialization is ill-formed.

typedef see below difference_type;

Type: Ptr::difference_type if such a type exists; otherwise, std::ptrdiff_t.

template <class U> using rebind = see below;

Alias template: Ptr::rebind<U> if such a type exists; otherwise, SomePointer<U, Args> if Ptr is a class template instantiation of the form SomePointer<T, Args>, where Args is zero or more type arguments; otherwise, the instantiation of rebind is ill-formed.

20.6.3.2 Pointer traits member functions [pointer.traits.functions]

static pointer pointer_traits::pointer_to(see below r); static pointer pointer_traits<T*>::pointer_to(see below r) noexcept;

Remark: if element_type is (possibly cv-qualified) void, the type of r is unspecified; otherwise, it is element_type&.

Returns: The first member function returns a dereferenceable pointer to r obtained by calling Ptr::pointer_to(r); an instantiation of this function is ill-formed if Ptr does not have a matching pointer_to static member function. The second member function returns std::addressof(r).