On Thu, Jul 03, 2003 at 01:40:46AM -0400, Derek Elkins wrote:
On Thu, 3 Jul 2003 11:34:08 +0800 paul@theV.net wrote:
If a C function returns a (void*), let's say:
data MyObj = MyObj
foreign import ccall "static myobj_ffi.h new_obj" newMyObject :: IO (Ptr MyObj)
ptr <- newMyObject
should I free the ptr afterwards or not?
Assuming that it should be freed even in C and nothing else is managing it then I believe the answer is yes. You can use a finalizer to do it.
The wierd thing is, I cannot use the the function Foreign.Marshal.Alloc.free to free the ptr. I must use my own C function to do a simple free() call.
If I have another imported C function:
foreign import ccall "static myobj_ffi.h print_obj" printMyObject :: Ptr MyObj -> IO ()
Can I safely assume the C function print_obj(void *) always get the same pointer even if I call (printMyObject ptr) multiple times?
What other pointer would it pass?
The same Haskell ptr. I wonder if they'll ever change after creation. My question is, if Ptr is equivalent to a raw void* pointer in C, and pointers created in foreign language (which is later passed to Haskell as Ptr) has to be freed in the foreign language, then can I safely assume that Ptr isn't affected by Haskell's GC cycle? And what the real difference between Ptr and StablePtr? Regards, .paul.