Garbage Collector : Ignoring a reference

[ciechowoj via Digitalmars-d-learn]

> Thus, i need a way to tell the gc to ignore the reference ( or 
> something similar ) in that hashmap.

So, having pointer that doesn't hold a reference isn't that hard 
(store it in memory region that is unreachable to gc), but don't 
you need a way to tell if that pointer ins't dangling, beyond 
initial problem?