NAME¶

std::allocator_traits::allocate - std::allocator_traits::allocate

Synopsis¶

Defined in header <memory>
static pointer allocate( Alloc& a, size_type n (since C++11)
); (until C++20)
[[nodiscard]] static constexpr pointer allocate( (since C++20)
Alloc& a, size_type n );
static pointer allocate( Alloc& a, size_type n, (since C++11)
const_void_pointer hint (1) (until C++20)
);
[[nodiscard]] static constexpr pointer allocate( (2)
Alloc& a, size_type n, (since C++20)

const_void_pointer hint );

Uses the allocator a to allocate n * sizeof(Alloc::value_type) bytes of
uninitialized storage. An array of type Alloc::value_type[n] is created in the
storage, but none of its elements are constructed.

1) Calls a.allocate(n).
2) Additionally passes memory locality hint hint. Calls a.allocate(n, hint) if
possible. If not possible (e.g. a has no two-argument member function allocate),
calls a.allocate(n).

Parameters¶

a - allocator to use
n - the number of objects to allocate storage for
hint - pointer to a nearby memory location

Return value¶

The pointer returned by the call to a.allocate(n).

Notes¶

Alloc::allocate was not required to create array object until P0593R6, which made
using non-default allocator for std::vector and some other containers not
well-defined according to a strict reading of the core language specification.

After calling allocate and before construction of elements, pointer arithmetic of
Alloc::value_type* is well-defined within the allocated array, but the behavior is
undefined if elements are accessed.

Example¶

This section is incomplete
Reason: no example

See also¶

allocate allocates uninitialized storage
(public member function of std::allocator<T>)

Category:¶

* Todo no example