    {-# OPTIONS_GHC -XNoImplicitPrelude #-}
    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Foreign.Concurrent
    -- Copyright   :  (c) The University of Glasgow 2003
    -- License     :  BSD-style (see the file libraries/base/LICENSE)
    --
    -- Maintainer  :  ffi@haskell.org
    -- Stability   :  provisional
    -- Portability :  non-portable (requires concurrency)
    --
    -- FFI datatypes and operations that use or require concurrency (GHC only).
    --
    -----------------------------------------------------------------------------

    module Foreign.Concurrent
      (
            -- * Concurrency-based 'ForeignPtr' operations

            -- | These functions generalize their namesakes in the portable
            -- "Foreign.ForeignPtr" module by allowing arbitrary 'IO' actions
            -- as finalizers.  These finalizers necessarily run in a separate
            -- thread, cf. /Destructors, Finalizers and Synchronization/,
            -- by Hans Boehm, /POPL/, 2003.

            newForeignPtr,
            addForeignPtrFinalizer,
      ) where

    #ifdef __GLASGOW_HASKELL__
    import GHC.IOBase       ( IO )
    import GHC.Ptr          ( Ptr )
    import GHC.ForeignPtr   ( ForeignPtr )
    import qualified GHC.ForeignPtr
    #endif

    #ifdef __GLASGOW_HASKELL__
    newForeignPtr :: Ptr a -> IO () -> IO (ForeignPtr a)
    -- ^Turns a plain memory reference into a foreign object by associating
    -- a finalizer - given by the monadic operation - with the reference.
    -- The finalizer will be executed after the last reference to the
    -- foreign object is dropped.  Note that there is no guarantee on how
    -- soon the finalizer is executed after the last reference was dropped;
    -- this depends on the details of the Haskell storage manager.  The only
    -- guarantee is that the finalizer runs before the program terminates.
    newForeignPtr = GHC.ForeignPtr.newConcForeignPtr

    addForeignPtrFinalizer :: ForeignPtr a -> IO () -> IO ()
    -- ^This function adds a finalizer to the given 'ForeignPtr'.
    -- The finalizer will run after the last reference to the foreign object
    -- is dropped, but /before/ all previously registered finalizers for the
    -- same object.
    addForeignPtrFinalizer = GHC.ForeignPtr.addForeignPtrConcFinalizer
    #endif