Hi all, I'd like to attach a finalizer to FunPtrs (which point to JIT-compiled functions that need to be deallocated). However, the act of running the finalizer (no matter what it does) results in a segfault. Here's a minimal example: {-# LANGUAGE UnboxedTuples, MagicHash #-} import GHC.Exts (FunPtr(..)) import GHC.Base import Foreign.Ptr import System.Mem attachFinalizer :: FunPtr a -> IO () -> IO () attachFinalizer fptr@(FunPtr addr) (IO fin) = IO $ \s0 -> case mkWeak# addr fptr fin s0 of (# s1, _ #) -> (# s1, () #) foreign import ccall "wrapper" mkIO :: IO () -> IO (FunPtr (IO ())) main = do fptr <- mkIO $ return () attachFinalizer fptr $ do -- The exact contents of the finalizer doesn't seem to matter putStrLn "+++ finalizer ran" freeHaskellFunPtr fptr putStrLn "+++ attached successfully" performGC Is there a proper way to do this? (GHC 8.6.5) Roman