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std::allocation_result

Defined in header <memory> 
template< class Pointer, class SizeType = std::size_t >
struct allocation_result {
    Pointer ptr;
    SizeType count;
};
 (since C++23)

allocation_result specializations are returned from the allocate_at_least member function of appropriate Allocator types (e.g. std::allocator::allocate_at_least) and std::allocator_traits::allocate_at_least.

Every specialization of allocation_result has no base classes or declared members other than ptr and count, thus it is suitable for aggregate initialization and structured binding.

Template parameters

Pointer - typically std::allocator_traits<Alloc>::pointer, where Alloc is an Allocator type
SizeType - typically std::allocator_traits<Alloc>::size_type, where Alloc is an Allocator type

Member objects

ptr
(C++23)
typically used for the address of the first element in the storage allocated by allocate_at_least
(public member object)
count
(C++23)
typically used for the actual number of elements in the storage allocated by allocate_at_least
(public member object)

Notes

Pointer and SizeType are a pointer to an object type and std::make_unsigned_t<std::ptrdiff_t> (which is almost always same as std::size_t) by default.

Feature-test macro Value Std Feature
__cpp_lib_allocate_at_least 202302L (C++23) Size-feedback in the Allocator interface

Example

See also

(C++23)
allocates uninitialized storage at least as large as requested size
(public member function of std::allocator<T>)
[static] (C++23)
allocates storage at least as large as the requested size via an allocator
(public static member function of std::allocator_traits<Alloc>)

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