Wow, it looks odd that
(eq (cffi:null-pointer) (cffi:null-pointer))
(eql (cffi:null-pointer) (cffi:null-pointer))
(equal (cffi:null-pointer) (cffi:null-pointer))
(equalp (cffi:null-pointer) (cffi:null-pointer))
All give NIL as result.

Thanks, anyway, that's half of the problem, as %glfw:create-window returns a valid foreign pointer and cl-glfw3:create-window returns always a null pointer.



2013/11/25 Andreas Franke <andreas.franke@freemind-group.com>
>>   (let ((window (%glfw:create-window width height title monitor shared)))
>>     (if (eql (cffi:null-pointer) window)

>   #-sbcl (eql (cffi:null-pointer) window)
>   #+sbcl (and (sb-sys:system-area-pointer-p window)
>               (sb-sys:sap= (cffi:null-pointer) window))

Duh. It should be:
  (if (cffi:null-pointer-p window)
    ...

 :-)