Hi Simon, I'm looking at object unloading code in CheckUnload.c. My understanding of how unloading works is: - When unloading of an object is requested the object is added to `unloaded_objects`. - When `unloaded_objects` is not empty, after GC, we scan the heap for any references to objects. This is done in `searchHeapBlocks` called by `checkUnload`. - When `searchHeapBlocks` finds a reference to an object code it marks the object code. - After scanning the heap any objects in `unloaded_objects` that are not marked are unloaded. Does this sound right so far? What I'm confused about is `searchHeapBlocks`. As far as I can see it just skips all objects other than stacks. For example here's the code for scanning a constructor: case CONSTR: case CONSTR_NOCAF: case CONSTR_1_0: case CONSTR_0_1: case CONSTR_1_1: case CONSTR_0_2: case CONSTR_2_0: size = sizeW_fromITBL(info); break; So if I see a constructor with a reference to an object code in its payload I'll not mark the object code. This looks wrong to me. I don't understand why we only care about stacks and nothing else. Could you comment on this? Thanks, Ömer