anchor.diff:  *current* error.
   ")
   
  +(eval-when (:compile-toplevel :load-toplevel :evaluate)
  +  (unless (fboundp 'print-backtrace-to-stream)
  +    (defun print-backtrace-to-stream (stream)
  +      (format stream "~&backtrace output unavailable.~%"))))
  
positive.code: ;; function
  (eval-when (:compile-toplevel :load-toplevel :execute)
    (when (find-symbol "*DEBUG-PRINT-VARIABLE-ALIST*" :sb-debug)
      (pushnew :hunchentoot-sbcl-debug-print-variable-alist *features*)))
  
  #+sbcl
  (defun print-backtrace-to-stream (stream)
    (let (#+:hunchentoot-sbcl-debug-print-variable-alist
  	(sb-debug:*debug-print-variable-alist*
  	 (list* '(*print-level* . nil)
  		'(*print-length* . nil)
  		sb-debug:*debug-print-variable-alist*))
  	#-:hunchentoot-sbcl-debug-print-variable-alist
  	(sb-debug:*debug-print-level* nil)
  	#-:hunchentoot-sbcl-debug-print-variable-alist
  	(sb-debug:*debug-print-length* nil))
      (sb-debug:backtrace most-positive-fixnum stream)))
  
  
negative.code:    "~@<An unhandled error condition has been signalled:~3I ~a~I~:@>~%~%"
     condition))
    
  (defun print-backtrace (error &key (output *debug-io*)
  			(if-exists :append)
  			(verbose nil))
    "Send a backtrace for the error `error` to `output`. 
  
  