Query the current value of the allocator
property.
template< typename OtherAllocator> constexpr Allocator query( execution::allocator_t< OtherAllocator > ) const;
Do not call this function directly. It is intended for use with the
query
customisation point.
For example:
asio::system_executor ex; auto alloc = asio::query(ex, asio::execution::allocator);