Re: [Chicken-users] c-callbacks

[felix winkelmann]

On 8/17/07, Bastian Müller <address@hidden> wrote:
>
> ODE uses the following callback:
>    typedef void dNearCallback (void *data, dGeomID o1, dGeomID o2);
> that I interfaced by
>    (define-foreign-type dNearCallback (function void (c-pointer
> dGeomID dGeomID)))
>
> For the collision detection call
>    void dSpaceCollide (dSpaceID space, void *data, dNearCallback
> *callback);
> I used
>    (define ode-space-collide
>      (foreign-lambda void "dSpaceCollide" dSpaceID c-pointer
> dNearCallback))
>
> As an example callback I defined:
>    (define-external (foobar (c-pointer data) (dGeomID geom1) (dGeomID
> geom2)) void
>      (printf "collision") (newline))
>
> Finally, I tried to do the actual call.
> First, I tried:
>    (ode-space-collide space (null-pointer) foobar)
> and during the simulation I got an
>    Error: bad argument count - received -2 but expected 3: error in
> error
>    graphics.scm: 76   ode-space-collide    <--

This has nothing to do with arguments, instead it means that the runtime
system is completely screwed up. I assume it  is due to "ode-space-collide":
You *MUST* (_MUST_, /MUST/) use "foreign-safe-lambda[*]", instead
of "foreign-lambda[*]" for foreign procedures that invoke, or may invoke
callbacks.


cheers,
felix