#13439: ForeignPtr finalizers not searched for reachable objects? -------------------------------------+------------------------------------- Reporter: | Owner: (none) facundo.dominguez | Type: bug | Status: new Priority: normal | Milestone: Component: | Version: 8.0.2 libraries/base | Keywords: ForeignPtr | Operating System: Unknown/Multiple finalizers | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The following program produces pairs of ForeignPtr's. The finalizer of the second ForeignPtr, uses the first ForeignPtr. When running this program it looks like the first ForeignPtr is finalized before the second one. {{{ import Control.Concurrent import Foreign.Concurrent (newForeignPtr) import Control.Monad import Foreign.ForeignPtr hiding (newForeignPtr) import Foreign.Ptr import System.Mem (performMajorGC) import Data.IORef import Data.Set as Set main = do rFinalized <- newIORef Set.empty forM_ [0..50000] $ \i -> do fp0 <- newForeignPtr nullPtr $ atomicModifyIORef' rFinalized (\s -> (Set.insert i s, ())) newForeignPtr nullPtr $ do finalized <- atomicModifyIORef' rFinalized (\s -> (Set.delete i s, Set.member i s)) when finalized $ putStrLn "fp0 was prematurely finalized" touchForeignPtr fp0 performMajorGC threadDelay 1000000 }}} {{{ $ ghc t.hs [1 of 1] Compiling Main ( t.hs, t.o ) Linking t ... $ ./t fp0 was prematurely finalized fp0 was prematurely finalized fp0 was prematurely finalized fp0 was prematurely finalized fp0 was prematurely finalized }}} Is this a bug in the implementation or an omission in the documentation of `Foreign.Concurrent.newForeignPtr`? Note that a more obvious program behaves correctly. {{{ main = do rFinalized <- newIORef False fp0 <- newForeignPtr nullPtr $ writeIORef rFinalized True newForeignPtr nullPtr $ do finalized <- readIORef rFinalized when finalized $ putStrLn "fp0 was prematurely finalized" touchForeignPtr fp0 performMajorGC threadDelay 1000000 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13439 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler