Help with callbacks

I am busy testing all the functions with callbacks in the SDL API 
and I am having trouble with a function in the Timer API.

Basically the idea is that you define a callback function, then pass 
that function to SDL with an interval value. SDL then calls that 
function at those intervals.

Here is the prototype for the function callback:

typedef Uint32 (*SDL_NewTimerCallback)(Uint32 interval, void *param);

(PROGN 
    (EXPORT 
        '(SDL_NEWTIMERCALLBACK)) 
    (DEFCTYPE SDL_NEWTIMERCALLBACK (:VOID *)))

And this is the prototype for the AddTimer function:

extern DECLSPEC SDL_TimerID SDL_AddTimer(Uint32 interval, 
SDL_NewTimerCallback callback, void *param);

(PROGN
    (EXPORT '(SDL_ADDTIMER))
    (DEFUN-DLL
        SDL_ADDTIMER
        ((INTERVAL UINT32)
            (CALLBACK SDL_NEWTIMERCALLBACK)
            (PARAM (:VOID *)))
        :RETURN-TYPE
        SDL_TIMERID
        :LIBRARY-NAME
        "SDL.dll"
        :ENTRY-NAME
        "SDL_AddTimer"
        :LINKAGE-TYPE
        :C))

Here is how I define the Lisp callback function:

(ct:defun-c-callback my-timer-func-1 ((interval Uint32) (param 
(:void *)))
    (fformat "Timer Fired, Yup."))

And this is how I call the timer:

(setf f-pointer (ct:create-foreign-ptr))
(setf var-1 (ct:malloc (ct:sizeof :LONG)))
(setf (ct:cpointer-value f-pointer) (ct:cpointer-value var-1))

(setf a-timer-1 (SDL_AddTimer 
        1000 
        (ct:get-callback-procinst 'my-timer-func-1) f-pointer))

However Corman crashes after the 1000ms when SDL tries to call the 
function. What am I doing wrong ?

-Luke




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