In article <ead7eb4e64962db8325e9305379508b3@localhost.localdomain>, Wolfgang Thaller <wolfgang.thaller@gmx.net> wrote:
Well now what if you want to pass two extra pointers? It's true you could "glue" them together [...]
Of course. That's what I have to do with all userData pointers I use in C, so if I use C finalizers, I'll put up with that...
The problem is that if you glue them together in Haskell using some tuple type, the native-code finaliser can't un-glue them without calling back into Haskell, which isn't in general allowed. So instead you have to call into native code to do the glue there. For instance, my Java VM reference finaliser needs the reference to finalise and also a "JVM-pointer". So when I'm constucting these things in Haskell, I need to take the JVM pointer and the reference, and call some C function that allocates a little structure of the two and returns a pointer to it. Then I can make a ForeignPtr with that. -- Ashley Yakeley, Seattle WA