[bfgeek]

> the UAF-ish bugs are still bugs, and code poking at a GC-preserved object that the rest of the code doesn't really expect to still be alive might itself be pretty fraugh

For the LayoutObject heirarchy - the team doing that conversion added a NOT_DESTROYED() macro for this reason. It's gross, but was the least worst option.

As an aside - the performance of oilpan is broadly net positive now if you avoid some of the pitfalls. (The largest being a write into a Member<> requires a write-barrier). E.g. Things become trivially destructible, and no ref incrementing/decrementing, etc.