[C2hs] c2hs seems to ignore the types I give it when generating foreign import declarations

[Duncan Coutts]

On Sat, 2005-11-26 at 00:55 -0500, Cale Gibbard wrote:
> Hello, I've just started writing bindings to the Enlightenment
> Foundation Libraries, using c2hs. I've run into the following problem
> with the types in the foreign import declarations generated.
> 
> In Imlib2.h, there is a function prototype:
> int imlib_get_visual_depth(Display * display, Visual * visual);
> 
> In Imlib.chs, I have (among other things)
> import qualified Graphics.X11.Xlib.Types as Xlib
> -- ...
> {# fun imlib_get_visual_depth as getVisualDepth { id `Xlib.Display',
> id `Xlib.Visual' } -> `Int' #}
> 
> I run:
> c2hs -k /usr/local/include/Imlib2.h Imlib.chs
> 
> and in the resulting Imlib.hs, I get:
> 
> --- this part is correct:
> getVisualDepth :: Xlib.Display -> Xlib.Visual -> IO (Int)
> getVisualDepth a1 a2 =
>   let {a1' = id a1} in
>   let {a2' = id a2} in
>   getVisualDepth'_ a1' a2' >>= \res ->
>   let {res' = cIntConv res} in
>   return (res')
> 
> --- this part is not:
> foreign import ccall safe "Imlib.h imlib_get_visual_depth"
>   getVisualDepth'_ :: ((Ptr ()) -> ((Ptr ()) -> (IO CInt)))
> 
> Why did it choose the type Ptr (), when I gave the type Xlib.Display?

You need to tell c2hs about the relationship between C types and Haskell
types.

http://www.cse.unsw.edu.au/~chak/haskell/c2hs/docu/c2hs-3.html#ss3.10

You'll want to add something like:

{# pointer *Display -> Display #}
{# pointer *Visual  -> Visual #}

Note that c2hs doesn't yet accept qualified names like:
{# pointer *Display -> Xlib.Display #}

Duncan