20 General utilities library [utilities]

20.10 Memory [memory]

20.10.9 The default allocator [default.allocator]

1

All specializations of the default allocator satisfy the allocator completeness requirements [allocator.requirements.completeness].

namespace std {
  template <class T> class allocator {
   public:
    using value_type      = T;
    using propagate_on_container_move_assignment = true_type;
    using is_always_equal = true_type;

    allocator() noexcept;
    allocator(const allocator&) noexcept;
    template <class U> allocator(const allocator<U>&) noexcept;
   ~allocator();

    T* allocate(size_t n);
    void deallocate(T* p, size_t n);
  };
}

20.10.9.1 allocator members [allocator.members]

1

Except for the destructor, member functions of the default allocator shall not introduce data races ([intro.multithread]) as a result of concurrent calls to those member functions from different threads. Calls to these functions that allocate or deallocate a particular unit of storage shall occur in a single total order, and each such deallocation call shall happen before the next allocation (if any) in this order.

T* allocate(size_t n);

2

Returns: A pointer to the initial element of an array of storage of size n * sizeof(T), aligned appropriately for objects of type T.

3

Remarks: the storage is obtained by calling ::operator new ([new.delete]), but it is unspecified when or how often this function is called.

4

Throws: bad_alloc if the storage cannot be obtained.

void deallocate(T* p, size_t n);

5

Requires: p shall be a pointer value obtained from allocate(). n shall equal the value passed as the first argument to the invocation of allocate which returned p.

6

Effects: Deallocates the storage referenced by p .

7

Remarks: Uses ::operator delete ([new.delete]), but it is unspecified when this function is called.

20.10.9.2 allocator globals [allocator.globals]

template <class T, class U> bool operator==(const allocator<T>&, const allocator<U>&) noexcept;

1

Returns: true.

template <class T, class U> bool operator!=(const allocator<T>&, const allocator<U>&) noexcept;

2

Returns: false.