[ forwarded to ffi@haskell.org ]
In the current implementation there is no way to force finalization of the foreign ptr if there are still references to it. In this scenario the finalization will be executed during the next garbage collection. In some cases it is known that the foreign pointer value is not used anymore but the references still exist in the stack and they cannot be freed from the collector. In such cases I want to be able to explicitly finalize the foreign pointers. For that reason I wrote the following simple function:
module FinalizeForeignPtr(finalizeForeignPtr) where
import GHC.ForeignPtr import Data.IORef
finalizeForeignPtr :: ForeignPtr a -> IO () finalizeForeignPtr foreignPtr = do finalizers <- readIORef refFinalizers sequence_ finalizers writeIORef refFinalizers [] where refFinalizers = case foreignPtr of (ForeignPtr _ ref) -> ref (MallocPtr _ ref) -> ref
There's a race condition between multiple finalizeForeignPtrs, but apart from that it looks fine. I don't see any reason why we shouldn't have this. GHC's weak pointer interface has a similar function for running the finalizer early. Cheers, Simon