|  | 
            Obtain an executor with the default allocator
            property.
          
basic_system_executor< Blocking, Relationship, std::allocator< void > > require( execution::allocator_t< void > ) const;
            Do not call this function directly. It is intended for use with the
            require
            customisation point.
          
For example:
asio::system_executor ex1; auto ex2 = asio::require(ex1, asio::execution::allocator);