Problem exporting Haskell to C via a DLL in GHC 6.6

Before I post this as a bug, I thought I'd check to make sure I'm not doing something wrong.
For this test case, on my windows XP machine I create a simple Haskell routine that counts the characters in a file,
create a DLL for that routine and call it from C.  The C code gives the correct answer (I think) but then
proceeds to hang and never terminate.  If the  readFile call is removed from this code, and a constant output is assigned to the variable ll, the code works fine and terminates correctly.  Thus the bug may possibly be some kind of interaction with the file IO routine, if it's a bug at all.

First the Haskell code:

baddll.hs:

module Bad
        where
import Foreign.Ptr
import Foreign.C.String
import Foreign.C.Types (CInt, CDouble )

foreign export stdcall badfunc :: CString -> IO (CInt)
--
-- | Conversion from Int to CInt
mkCInt :: Int -> CInt
mkCInt n = fromIntegral n

badfunc fstr = do
        file <- peekCAString fstr
        sstr <- readFile file
        let ll = length sstr
        return $ mkCInt ll

The C code:
#include <stdio.h>
__declspec(dllimport) int  __stdcall badfunc(char *outfile) ;


int main(int argc, char *argv)
{
int ll ;
ll = badfunc("bad.txt") ;
printf("ll = %d\n", ll) ;
return(1) ;
}

The .bat file used to compile everything.  (Assumes ghc and MS VC++ 6.0 is in my path)
baddll.bat:

ghc -O2 -static -c baddll.hs -fglasgow-exts
ghc -c dllBad.c
ghc --mk-dll -static -fglasgow-exts -o baddll.dll dllBad.o baddll.o baddll_stub.o -L"." -L"." -optdll--def -optdllbaddll.def  
lib /def:baddll.def /MACHINE:X86
cl baddll.c baddll.lib

The .def file used to create the dll export symbols.
baddll.def
LIBRARY baddll.dll
EXPORTS
        badfunc@4
        badfunc = badfunc@4

The boilerplate code to load and unload the Haskell runtime inside the DLL.
dllBad.c
#include <windows.h>
#include <Rts.h>

extern void __stginit_Bad(void);

static char* args[] = { "ghcDll", NULL };
                       /* N.B. argv arrays must end with NULL */
BOOL
STDCALL
DllMain
   ( HANDLE hModule
   , DWORD reason
   , void* reserved
   )
{
  if (reason == DLL_PROCESS_ATTACH) {
      /* By now, the RTS DLL should have been hoisted in, but we need to start it up. */
      startupHaskell(1, args, __stginit_Bad);
      return TRUE;
  }

  if (reason == DLL_PROCESS_DETACH) {
        shutdownHaskell();
        return TRUE;
  }

  return TRUE;
}


The text file I read in.
bad.txt:

Greetings Earthlings


If I recall correctly, from another piece of test code, this seemed to work OK in GHC 6.4.  However, I'll have to resurrect my GHC 6.4 installation to verify this.  If anyone sees an obvious problem with my code I'd love to be informed about this.