2013/6/19 Mikael <mikael.rcv@gmail.com>
.. 
            } else {
              // Reference from global variable etc.
              add_resolved_referencing_object(___ABSENT);
            }

___ABSENT showed to be unpractical as it behaves in an atypical way, so ___UNB1 better is a better choice. So:

              add_resolved_referencing_object(___UNB1);

By this reason, using ##resolve-referencing-objects looks slightly different now:

$ gsc
Gambit v4.6.9

> (define a "Hello world")
> (##resolve-referencing-objects a)
(#!unbound #!unbound #!unbound)
> (list a)
("Hello world")
> (##resolve-referencing-objects a)
(#!unbound #!unbound #!unbound ("Hello world"))