Yi Lin

https://github.com/mmtk/mmtk-core/pull/864 further allows discontiguous VM space. > One leftover issue for the PR is that we need a way to tell if an object is in MMTk's heap (in internal...

The example does not explain why this is a problem. We allow off-heap `ObjectReference`, but it still needs to point to a valid object. If a VM uses 16 bytes...

> Currently no VM uses ActivePlan::vm_trace_object. To what I know, Julia and GHC use `vm_trace_object`.

> The problem in the current `is_in_mmtk_space(object)` is that it does not require `object` to be a valid object reference. `ObjectReference` has to be a valid object. This function is...

Adding another version of `ref_to_address()` for potential object reference sounds reasonable. But we already state that `ref_to_address` may have an invalid object reference. https://github.com/mmtk/mmtk-core/blob/e79e94e744660c486d5471f252ff05c4248bcea9/src/vm/object_model.rs#L444-L453 If I understand right, there are...

Related issue: https://github.com/mmtk/mmtk-core/issues/493

An alternative design is to allow re-entrance for `initialize_collection` and allow MMTk to check with the binding if a GC thread exists. For `initialize_collection`, if MMTk does not find GC...

For languages that use a special singleton object to represent its 'NULL' reference, can they use `Some(ObjectReference)` for the singleton object? When they allocate and initialize the object, they will...

> > For languages that use a special singleton object to represent its 'NULL' reference, can they use `Some(ObjectReference)` for the singleton object? When they allocate and initialize the object,...

> It may be worth mentioning those singleton objects in the comments. The main idea is, return `Some(objref)` if > > * The slot holds an object reference that can...