Thanks for your replies to my question, I was planning to go the trivial-garbage route and someone from CFFI-DEVEL kindly gave me this code to do GC automatically using my mat and del-mat functions (defstruct (cvmatrix (:constructor %make-cvmatrix)) (sap (mat) :type sb-sys:system-area-pointer :read-only t)) (defun make-cvmatrix () (let* ((matrix (%make-cvmatrix)) (sap (cvmatrix-sap matrix))) (tg:finalize matrix (lambda (x) (del-mat sap))) matrix)) When I run the make-cvmatrix function to create a matrix it outputs a struct instead of a pointer like i needed. I changed the last line of the make-cvmatrix function to be "sap" as below: (tg:finalize matrix (lambda (x) (del-mat sap))) sap)) ...and it appears to run poorly with only major variations in my ram levels which i suppose is just a result of lisps GC in process. Since I'm new to GC w/ trivial-garbage, I was hoping someone can verify first that the change to sap was an ok move. I was hoping someone could edit my code so I have a good example of Lisp GC with TG to work from and if I write a defcfun for this C wrapper : Mat* cv_create_Mat_typed(int rows, int cols, int type) { return new Mat(rows, cols, type); } eg: (defcfun ("cv_create_Mat_typed" mat-typed) (:pointer mat) "MAT constructor with a row, column and type parameter." (rows :int) (cols :int) (type :int)) show me where the rows cols type params get placed in an edited finalizer/constructor above..I would definately appreciate greatly:), concrete examples using the code I posted.