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);
};
}Except for the destructor, member functions of the default allocator shall not introduce data races 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);
Returns: A pointer to the initial element of an array of storage of size n * sizeof(T), aligned appropriately for objects of type T.
Remarks: the storage is obtained by calling ::operator new, but it is unspecified when or how often this function is called.
void deallocate(T* p, size_t n);
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.
Remarks: Uses ::operator delete, but it is unspecified when this function is called.