"Luís" == Luís Oliveira luismbo@gmail.com:
Luís> "Hoehle, Joerg-Cyril" Joerg-Cyril.Hoehle@t-systems.com writes:
In CLISP, every closure can be turned into a callback, and this is valuable since it allows to retrieve context information out of the closure. Is cffi's limitation caused by some implementations?
Luís> To my knowledge, yes. AFAICT, only SBCL/x86 and CLISP support Luís> that.
Luís> Regarding the behaviour of CFFI:DEFCALLBACK as a non-toplevel Luís> form, not only will it set it globally, the callback itself won't Luís> be generated at runtime on most Lisp, IIRC.
I've just ran into the same problem. I really really need closures as callbacks. I've tried the naive approach:
(defmacro object-event-callback-add (obj type function) `(foreign-funcall "evas_object_event_callback_add" :pointer ,obj callback-type ,(foreign-enum-value 'callback-type type) :pointer (get-callback (defcallback ,(gensym "CB") :void ((data :pointer) (cb-e evas) (cb-obj object) (cb-event :pointer)) (funcall ,function cb-e cb-obj cb-event))) :pointer (null-pointer)))
... but that's a half-baked solution with too many limitations and only works in a simple example that you run once.
What are the problems with unnamed callbacks? My guess was that they will never get garbage-collected, but how about storing all of these in a table somewhere and explicitly freeing them after they are no longer needed? In my case I do have a way of finding out when a callback is no longer needed, and I suspect this is the case for many other applications.
I mostly develop on SBCL/x86 and ECL, so even if a solution worked on these platforms only, I'd be really happy.
--J.