Segfault and -dstg-lint errors using FFI and -XEmptyDataDecls

I encountered a segfault when working with some FFI code. I eventually discovered that this code also makes -dstg-lint complain.

With the below files, I can reproduce the segfault and -dstg-lint issues using ghc-6.12.1 and ghc-6.10.3 on OS X 10.6.2. The segfault goes away if I use -fvia-C, -O, or if I build on OS X 10.5.7.

The segfault also goes away if I use a unit type () instead of -XEmptyDataDecls.

$ ghc --make test-segfault.hs foreign.c -XForeignFunctionInterface \
        -XEmptyDataDecls -fforce-recomp && ./test-segfault 
[1 of 2] Compiling Types            ( Types.hs, Types.o )
[2 of 2] Compiling Main             ( test-segfault.hs, test-segfault.o )
Linking test-segfault ...
About to create...
Segmentation fault

foreign.c:

#include <stdio.h>
#include <stdlib.h>

void *
c_createFoo (int x) {
    fprintf(stderr,"Creating foo...\n");
    fflush(stderr);
    int *p = malloc(sizeof(int));
    *p = x;
    return p;
}

Types.hs:

module Types where

import Foreign.Ptr
import Foreign.C.Types

-- Replacing this line with the following one prevents the segfault,
-- but not the -dstg-lint error.
data Foo_
-- type Foo_ = ()

foreign import ccall safe c_createFoo :: CInt -> IO (Ptr Foo_)

createFoo :: Int -> IO (Ptr Foo_)
createFoo dtype = c_createFoo (toEnum dtype)

test-segfault.hs:

module Main where

import Types

main = do
    putStrLn "About to create..."
    createFoo 1
    putStrLn "Created."

The -dstg-lint error is somewhat long, but I can paste it if you're unable to reproduce it.

Trac metadata

Trac field	Value
Version	6.12.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (NCG)
Test case
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