bug with -O -ffi and multiple module

Okay, here's a weird one.  There's something wrong with the ffi when using
-O and the foreign imports are from another module.  For example, our
foreign module, foo.c contains functions:

   void* openFile(char*fn);
   void closeFile(void*f);
   float readFloat(void*f);

which are interfaced from foo.h.  We have a FooIntr.hs interface file,
which looks like:

   foreign import ccall "foo.h openFile"  c__openFile  :: Ptr CChar -> IO
       (Ptr ())
   foreign import ccall "foo.h closeFile" c__closeFile :: Ptr () -> IO ()
   foreign import ccall "foo.h readFloat" c__readFloat :: Ptr () -> IO
       CFloat

openFile fn = cstring fn >>= c__openFile
closeFile = c__closeFile
readFloat h = do CFloat f <- c__readFloat h; return f

(plus helper definition of cstring)

Now, in our Foo.hs main file, we have:

  main = do
     [fn] <- getArgs
     h <- openFile fn
     f1 <- readFloat h
     f2 <- readFloat h
     closeFile h
     print (f1,f2)

In a file "bar", we have "1.234 5.678".

We compile foo.c via 'gcc -c foo.c' which works fine, then compile Foo.hs
using 

  ghc --make -ffi Foo.hs foo.o -o foo

we then run

  ./foo bar

and everything works fine.  We erase the intermediate files and recompile
with:

  ghc --make -ffi Foo.hs foo.o -o foo -O

and then run

  ./foo bar

and the results are random (seemingly) numbers.

Interestingly, if we include FooIntr into Foo and don't have Foo import it
anymore, everything works fine with -O on.

I've attached the actual files in a tar so someone can take a look.

 - Hal

--
Hal Daume III

 "Computer science is no more about computers    | hdaume@xxxxxxx
  than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume

bug.tar.gz
Description: Binary data