Memory leak in FFI callback: GHC 6.6

[Simon Peyton-Jones]

Dear SevenThunders (if that is how you like to addressed)

Thanks for extracting a small program that exhibits the leak; that is
really helpful.  We'll look into it. Would you like to create a Trac bug
and attach your files?

Simon

| -----Original Message-----
| From: glasgow-haskell-users-bounces at haskell.org
[mailto:glasgow-haskell-users-bounces at haskell.org]
| On Behalf Of SevenThunders
| Sent: 03 November 2006 02:54
| To: glasgow-haskell-users at haskell.org
| Subject: Memory leak in FFI callback: GHC 6.6
| 
| 
| I'm not sure if this is a bug, but it sure seems that way to me.  When
using
| the "wrapper" technique for creating a Haskell callback function it
seems
| that freeHaskellFunPtr is not properly freeing the resource.
| 
| Here is an example program
| <leaky.hs>
| module Main where
| import Foreign
| import Foreign.Ptr
| import Foreign.Storable
| 
| -- | A convenient type synonym for storable arrays
| type Darr = Ptr (Double)
| -- | Function type for mapping doubles to doubles
| type Dfunc = Double -> Double
| -- | A convenient type synonym for  monad containing storable arrays
| type IODarr = IO (Darr)
| 
| 
| foreign import ccall "wrapper" mkDfunc :: Dfunc -> IO (FunPtr Dfunc)
| foreign import ccall "cleaky.h cfunc" cfunc :: (FunPtr Dfunc) -> IO (
Double
| )
| 
| 
| dadd :: Dfunc
| dadd x = x + 1.0
| 
| getleaky :: Dfunc -> IO ()
| getleaky cf = do
| 	pcf <- mkDfunc cf
| 	-- pd <- cfunc pcf
| 	print pcf
| 	freeHaskellFunPtr pcf
| 
| 
| main = sequence_ [getleaky dadd | q <- [1..500000]]
| 
| 
| It's compiled with
| ghc -fglasgow-exts -fffi -prof -auto -I. --make  leaky.hs cleaky.o
| 
| A possible cleaky.c and cleaky.h are
| #include <math.h>
| #include <stdio.h>
| #include "cleaky.h"
| 
| 
| double state = 1.0 ;
| 
| double cfunc(DFptr fptr)
| {
| // printf("In cfunc, fptr: %p\n", fptr) ;
| state = (*fptr) (state) ;
| // printf("state: %g\n", state) ;
| return(state) ;
| }
| 
| typedef double (*DFptr) (double) ;
| double cfunc(DFptr) ;
| 
| though they are not used.
| 
| leaky.exe grows the heap linearly without bound on windows XP 64.  The
| profiler never reports this correctly either.
| calling
| leaky +RTS -hc -RTS
| does not show the increase in the memory usage.
| 
| --
| View this message in context:
http://www.nabble.com/Memory-leak-in-FFI-callback%3A-GHC-6.6-
| tf2565446.html#a7150757
| Sent from the Haskell - Glasgow-haskell-users mailing list archive at
Nabble.com.
| 
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