You're on the right track, but this parenthetical comment:
> the output is compatible with CLM's filter generator
refers to the Snd version of CLM, not the CL version. In CL, you need to use
the "butter" macro from butterworth.cl:
(outa i (* amp (butter flt (oscil os))))
That memory fault is the sort of thing that made me give up on CL many years ago.