On Tue, Aug 21, 2018, 4:32 AM Simon Peyton Jones
That's explained in the paper. A StableName# is a pointer to a stable name object in the heap that *contains* an index into the stable name table. Basically, the garbage collector needs to know whether a stable name is alive or not, so it can work out when to clear it from the table.
Very good. But could it be explained in a Note too? The paper is from a long time ago, contains lots of surrounding explanation, and might well be out of date (even if it in fact is not out of date).
Certainly there should be a note, but as I mentioned in this thread, I think we can probably actually do better than we presently do.
So the entry in the table /also/ points to the same, heap-allocated StableName#? Doesn’t that keep it alive? Or is this akin to the treatment of weak pointers? (Which is part of the same paper.)
The stable name table is not in the root set. All its references are weak.
Do we anywhere keep a pointer to the object that this is a stable name of?
Yes. That's in the stable name table entry. It's also the key for the stable name hash table.