On Mon, Jul 12, 2010 at 5:23 PM, Evan Laforge
Another hack I thought of:
- store ptr in a global MVar in haskell, pass it to C - C does its thing, ptr stays alive because haskell still has a reference - now when C calls the finalize funptr, it deletes the ptr from the haskell MVar, which releases haskell's hold on it
I would go with this path, however...
Effectively, this is using the global MVar as a GC root instead of the funptr itself. I'm much more confident that the GC is going to follow module level CAFs than some random funptrs allocated with a foreign "wrapper" call. However, the "wrapper" calls must serve as GC roots too, because otherwise what guarantees that variables captured in its closure stay alive? Right?
... I would try to avoid having the MVar/IOVar as a CAF because of its unpredictability. You can always encapsulate it as somewhere else (e.g. Reader monad). Hipmunk has a similar problem of having to keep things alive, and I just stash everything in a Data.Map inside a pure Haskell structure. But that's because in Hipmunk the objects are destroyed after they are explicitly removed, and this is done on Haskell land. I don't need to kill anything from C. Cheers, -- Felipe.