From cppreference.com
void*allocate_bytes(std::size_tnbytes,std::size_talignment=alignof(std::max_align_t));(since C++20)Allocates nbytes bytes of storage at specified alignment alignment using the underlying memory resource. Equivalent to returnresource()->allocate(nbytes,alignment);.
Parameters
nbytes - the number of bytes to allocate alignment - the alignment to use Return value
A pointer to the allocated storage.
Notes
This function was introduced for use with the fully-specialized allocator std::pmr::polymorphic_allocator<>, but it may be useful in any specialization.
The return type is void* (rather than, e.g., std::byte*) to support conversion to an arbitrary pointer type U* by static_cast<U*>.
Exceptions
May throw any exceptions thrown by the call to resource()->allocate.
See also
(C++20)
allocates raw memory suitable for an object or an array
(public member function)
(C++20)
allocates and constructs an object
(public member function)
allocate memory
(public member function)
[static]
allocates uninitialized storage using the allocator
(public static member function of std::allocator_traits<Alloc>)
allocates memory
(public member function of std::pmr::memory_resource)