Question about call_c

Hi. I am trying to use call_c to interface with an external shared library
that creates its own objects.

If I want to do operations such as

         call_c(string_to_object("asdf"),Object)

and later (within the same goal invocation)

         call_c(object_to_string(Object),string(S)) ,

do I need to wrap O in a handle? (In reality, O is a pointer to the
object in question, whose memory is managed by the shared library code.)

If so, is there a default handler for pointers?

(Note that I want to call C functions from inside Eclipse; the embedding
and interfacing manual seems to address mostly the case where Eclipse is
called by C applications...)

Thanks, 

- Tomas