[Vm-dev] Detecting objects that point to an object

Hi folks. I need to know the objects (actually, only how many) that are pointing to any object. So...I take an object X, and I want to know how many objects are pointing to X.

The only possible I see in Squeak VM is to do a full mark over all objects in memory (or starting by the roots). This is time consuming and I even need (maybe) to do this check (to know how many objects are pointing to an object) for every single object.

So...is there a faster solution for this? The only thing I can imagine is to modify the object header, maybe create a new type, and add an array with the addresses of the objects that are pointing to that object. Or maybe just a counter that I can increase or decrease ?

Thanks for any tip.

Mariano