[project @ 2001-03-13 21:21:27 by qrczak]

Add 'destruct :: Ptr a -> IO ()' method to class Storable. Thanks
Wojciech Moczydlowski <khaliff@astercity.net> for the suggestion.

It should free memory associated with the object (except the object
pointer itself). A default definition does nothing, but will be
non-trivial for some C structs.

The canonical ForeignPtr finalizer for a malloced data object would be
'destruct p >> free p'.

diff --git a/ghc/lib/std/PrelStorable.lhs b/ghc/lib/std/PrelStorable.lhs
index f02b832..0786954 100644 (file)
--- a/ghc/lib/std/PrelStorable.lhs
+++ b/ghc/lib/std/PrelStorable.lhs
@@ -1,5 +1,5 @@
 % -----------------------------------------------------------------------------
-% $Id: PrelStorable.lhs,v 1.3 2001/02/28 00:01:03 qrczak Exp $
+% $Id: PrelStorable.lhs,v 1.4 2001/03/13 21:21:27 qrczak Exp $
 %
 % (c) The FFI task force, 2000
 %
@@ -18,7 +18,8 @@ module PrelStorable
             peekByteOff,    -- :: Ptr b -> Int      -> IO a
             pokeByteOff,    -- :: Ptr b -> Int -> a -> IO ()
             peek,           -- :: Ptr a             -> IO a
-            poke)           -- :: Ptr a        -> a -> IO ()
+            poke,           -- :: Ptr a        -> a -> IO ()
+            destruct)       -- :: Ptr a             -> IO ()
         ) where
 \end{code}
 
@@ -64,6 +65,10 @@ class Storable a where
    peek        :: Ptr a      -> IO a
    poke        :: Ptr a -> a -> IO ()
 
+   -- free memory associated with the object
+   -- (except the object pointer itself)
+   destruct    :: Ptr a -> IO ()
+
    -- circular default instances
    peekElemOff = peekElemOff_ undefined
       where peekElemOff_ :: a -> Ptr a -> Int -> IO a
@@ -75,6 +80,8 @@ class Storable a where
 
    peek ptr = peekElemOff ptr 0
    poke ptr = pokeElemOff ptr 0
+
+   destruct _ = return ()
 \end{code}
 
 System-dependent, but rather obvious instances