> Note that the "safepointing" logic is exactly the same thing that's needed in refcounting to atomic replace a field.

No it's not, not even close.

> This article glosses over what I consider the hardest part - the enter/exit functionality around native functions may that block (but which must touch the allocator).

Yeah, that part is hard, and maybe I'll describe it in another post.

Look for `filc_enter` and `filc_exit` in https://github.com/pizlonator/fil-c/blob/deluge/libpas/src/l...