anchor.diff:                                       #.sys.int::+object-tag-structure-object+)
                                       (1+ len))
                                      (#.sys.int::+object-tag-std-instance+ 3)
  -                                   (#.sys.int::+object-tag-stack-group+ (- 511 64))
  +                                   (#.sys.int::+object-tag-thread+ (- 511 64))
                                      (#.sys.int::+object-tag-symbol+ 6)
                                      ((#.sys.int::+object-tag-memory-array+
                                        #.sys.int::+object-tag-simple-string+
  
positive.code:                                      #.sys.int::+object-tag-simple-array+
                                       #.sys.int::+object-tag-array+)
                                      (+ 4 len))
                                     (#.sys.int::+object-tag-bignum+ 0))))
                     (map-object fn image seen-objects (image-word image (+ address (* i 8))))))))
            (#b1011) ; character
            (#b1101) ; single-float
  
negative.code:           (extract-image-array image address 32))
           (#.sys.int::+object-tag-std-instance+
            (cons (extract-image-object image (image-word image (+ address 8)))
                  (extract-image-object image (image-word image (+ address 16)))))
           (#.sys.int::+object-tag-function-reference+
            (format nil "#<FREF to ~S>" (extract-image-object image (image-word image (+ address 8)))))
           )))))
  
  (defun identify-symbols (image)
    "Detect all symbols in IMAGE, returning a list of (symbol-name address)."
  