anchor.diff:  
   (defun gc ()
     "Calls the garbage collector."
  -  nil
  +  #-(or ccl clisp cmu sbcl) (error "~S: Missing a garbage collector call for ~S" 'gc (lisp-implementationt-type))
     #+ccl   (ccl:gc)
     #+clisp (ext:gc)
     #+cmu   (extensions:gc)
  
positive.code: ;;; Unfortunately, it looks like this is a primitive operation that
  ;;; cannot be implemented with just weak pointers.  CMUCL & SBCL are weak.
  
  #+(or cmu sbcl)
  (eval-when (:compile-toplevel :load-toplevel :execute)
    (format *error-output*
      "~2%WARNING: ~A: WEAK-OR-RELATION should be implemented ~
       as primitive in ~A~2%" 'closer-weak (lisp-implementation-type)))
  
  #-(and clisp (not debug-weak))
  (defstruct (weak-or-relation (:constructor %make-weak-or-relation)
  
negative.code:   (test/wl)
    (test/wht))
  
  #-sbcl (test)
  ;; #+sbcl (warn "~A: ~A fails weak-pointer garbage collection tests. Testing is disabled."
  ;;         'closer-weak (lisp-implementation-type))
  
  ;;;; THE END ;;;;
  