Each COM interface pointer has a reference count which is used by the server to control its lifetime. The function add-ref
should be called whenever an extra reference to the interface pointer is being made. The function invokes the COM method IUnknown::AddRef
so the form (add-ref ptr)
is equivalent to using call-com-interface
as follows:
(call-com-interface (ptr i-unknown add-ref))
LispWorks COM/Automation User Guide and Reference Manual - 14 Feb 2015