(define (do-trace procs)
  (for-each
   (lambda (s)
     (ensure procedure? s)
     (cond ((traced? s)
	    (warning "procedure already traced" s) )
	   (else
	    (let ((name (procedure-name s)))
	      (when (trace-verbose)
		(fprintf (current-error-port) "; tracing ~a~%" name))
	      (set! *traced-procedures* (cons (cons s name) *traced-procedures*))
	      (advise 
	       'around s
	       (lambda (next args)
		 (let ((results #f))
		   (dynamic-wind
		       (cut traced-procedure-entry name args)
		       (lambda () 
			 (call-with-values (cut apply next args)
			   (lambda rs
			     (set! results rs)
			     (apply values rs))))
		       (cut traced-procedure-exit name results))))
	       '*trace*)))))
   procs) )