anchor.diff:    (labels ((collect-known (known subtree)
                (let ((caller  (car subtree))
                      (callees (strip-unknown (cdr subtree))))
  -               (if (graph-node-fn-name caller)
  +               (if (/= (graph-node-id caller) *unknown-id*)
                      (cons (cons caller callees) known)
                      (append callees known)))))
       (if call-graph
  
positive.code:     (write-string "ROOT[shape=\"rectangle\"]" stream)
      (terpri stream)
      (print-callees :root call-graph))
    (format stream "}~%"))
  
negative.code: 
  (defparameter *unknown-function-name* "<Unknown function>"
    "Bogus name of an unknown function")
  (defparameter *unknown-id* 0
    "ID of unknown function")
  
  ;; Just in case...
  (defmacro defvar-unbound (var-name &optional documentation)
  