Buffered stream output bug report

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CMU Common Lisp 19e (19E), running on gail
With core: /Users/sje/cmucl-19e-x86-darwin/lib/cmucl/lib/lisp.core
Dumped on: Thu, 2008-05-01 20:38:02-04:00 on macmini
See <http://www.cons.org/cmucl/> for support information.
Loaded subsystems:
    Python 1.1, target Intel x86
    CLOS based on Gerd's PCL 2004/04/14 03:32:47


Three related bugs:

(defun bug0 (my-stream)
  (write-char #\1 my-stream)
  (format my-stream "~D" 2)
  (write-char #\3 my-stream))

(defun bug1 (my-stream)
  (write-char #\1 my-stream)
  (format my-stream "~D" 2)
  (write-char #\3 my-stream)
  (finish-output my-stream))

(defun bug2 (my-stream)
  (write-char #\1 my-stream)
  (finish-output my-stream)
  (format my-stream "~D" 2)
  (finish-output my-stream)
  (write-char #\3 my-stream)
  (finish-output my-stream))

(bug0 t) -> should print "123".  It doesn't.

(bug1 t) -> should print "123".  It doesn't.

(bug2 t) -> should print "123".  It doesn't.

In fact, the outputs are all different.  GNU clisp seems to handle  
these okay, as does GNU gcl.

Thank you for your time.

== Steven