On 28/04/2008, at 7:23 PM, Bulat Ziganshin wrote:
Hello Verma,
Monday, April 28, 2008, 4:11:51 PM, you wrote:
newCString str
Now once I call this function from C code, I am freeing the allocated
memory using free function. I want to confirm that this is the right
thing to do.
yes, i've traced this function down to mallocArray -> mallocBytes ->
malloc() calls
Depending on how you feel about it, Bulat's response either entirely
answers your question or is neither here nor there.
If you want to write portable code, you should check with the FFI
spec. If you just want to write code that works with GHC as it
presently is, you can strace it or whatever.
As Bulat has already given you the pragmatic answer, allow me to grind
my axe a little. In the FFI spec on p33, we find:
newCString :: String -> IO CString
newCStringLen :: String -> IO CStringLen
Allocate a memory area for a Haskell string and marshal the string
into its C representation.
There are two variants of the routine, one for each supported string
representation. The
memory area allocated by these routines may be deallocated using
MarshalAlloc.free.
OK, so back on p19 we find:
free :: Ptr a -> IO ()
Free a block of memory that was allocated with malloc, mallocBytes,
realloc, reallocBytes,
or any of the allocation functions from MarshalArray (see Section
5.9).
and we can draw the inference (reading between the lines) that this
function need not have a relation to C's malloc. (Roughly, the
intention is to allow a Haskell implementation to use whatever memory
management it likes.)
So no, using C's free is not the right thing to do. It will probably
work in the real world, but you should try to use Haskell's free if
possible.
cheers
peter
_______________________________________________
Haskell-Cafe mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/haskell-cafe
