Re: bug in CMU Common Lisp

[Mark Kantrowitz <Mark_Kantrowitz@GLINDA.OZ.CS.CMU.EDU>]

> Could you give more information on how to reproduce this?  What Lisp
> version on what machine, etc?

Python version 1.0(15b), VM version SPARCstation/Sun 4 on 15 JAN 92 05:57:46 pm.
Compiling:
/afs/cs.cmu.edu/project/oz/oz2/exp/system/source/class-integrated-sense-
model.lisp 15 JAN 92 02:42:53 pm    

The error file is in oz/oz2/exp/system/cmucl/class-integrated-sense-model.err

Here's an excerpt from the code that caused it:

 (let* ((class-sd (call query-property sd 'class))
	...
        (stable-qps nil)
	...)	
     (when (> base 0)
           (dolist (prop qp-check-list)
             (if (not (eq (call query-property sd prop)
                          (call query-property object prop)))
                 (setf base
                       (- base (max 1 (floor 4 (length qp-check-list)))))))
           (dolist (prop stable-qps)
             (if (not (eq (call query-property sd prop)
                          (call query-property object prop)))
                 (setf base
                       (- base (max 1 (floor 8 (length stable-qps))))))))
         (max 0 base)))

I didn't write this code, but it looks like stable-qps is always nil, so
(length stable-qps) is zero, leading to a divide by zero error, even though that
code is unreachable (i.e., it's in a dolist iterating on a null list). I'll send
mail to the author about this, but it looks like that's the cause of the
problem. 

--mark