On Sun, 2009-11-29 at 18:00 +0100, El Barto wrote:
Hello, I get a segfault when I do str <- peekCString ptr free ptr return (Just str)
As Thomas says, you've not really given us enough info here. I'll make some guesses and observations anyway :-)
But not when I don't free the C pointer.
Are you sure the C code does not also free the memory? That would lead to a double-free which can easily manifest as a segfault.
I also get the same behaviour with ByteString.packCString...
That's pretty odd since packCString does not free the C string, it makes a copy. I suppose it could possibly segfault if your C string was not actually null terminated (as C strings must be). There are also variants that do not copy, such as unsafePackMallocCString. See the docs for a description.
Could you please tell me if the memory is correctly freed by GHC when I don't do it myself? And how can I specify a custom free function (i.e. xmlFree function in libxml2)?
See the documentation for ForeignPtr.
Maybe I should use a data type with two fields : the String/ByteString and the ForeignPtr to the CString?
Is your C String supposed to be freed using the C free() function, or is it supposed to be freed using xmlFree() or something? Duncan