[cells-devel] bug report w/patch for record-caller in link.lisp, in LWL 5.1

[Kenny Tilton]

Thanks, I'll put it in my working code base, but I have not committed to 
CVS in a while and not sure when I will again.

I have always hated that code. Not sure why I did not just use an 
integer and logical operations.

kt

Larry Clapp wrote:
> Bug report:
> 
> Running Stefano's Sudoku example from his cells-doc in Lispworks for
> Linux 5.1, got an error in record-caller:
> 
>   Error: The subscript 16 exceeds the limit 15 for the first dimension 
>   of the array #*1111111111111111.
>     1 (abort) Return to level 0.
>     2 Return to top loop level 0.
> 
> Lispworks said the offending code was at the indicated line:
> 
>   (handler-case
>       (setf (sbit (cd-usage *depender*) used-pos) 1)  ; <== ### here ###
>     (type-error (error)
>       (declare (ignorable error))
>       (setf (cd-usage *depender*)
>         (adjust-array (cd-usage *depender*) (+ used-pos 16) :initial-element 0))
>       (setf (sbit (cd-usage *depender*) used-pos) 1))))
> 
> Fix:
> 
> The condition reported was of type CONDITIONS:SUBSCRIPT-OUT-OF-BOUNDS.
> I added that to the handler-case, and then it worked:
> 
>   (handler-case
>       (setf (sbit (cd-usage *depender*) used-pos) 1)
>     ((or type-error conditions:subscript-out-of-bounds) (error)
>     ;^^^            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>       (declare (ignorable error))
>       (setf (cd-usage *depender*)
>         (adjust-array (cd-usage *depender*) (+ used-pos 16) :initial-element 0))
>       (setf (sbit (cd-usage *depender*) used-pos) 1))))
> 
> However, this seems like a demonstrably error-prone way to handle this
> particular situation, so I got rid of the handler-case entirely and
> tried this:
> 
>   (let ((cd-usage (cd-usage *depender*)))
>     (when (>= used-pos (array-dimension cd-usage 0))
>       (setf cd-usage
>             (setf (cd-usage *depender*)
>                   (adjust-array (cd-usage *depender*)
>                                 (+ used-pos 16)
>                                 :initial-element 0))))
>     (setf (sbit cd-usage used-pos) 1))
>       
> It works, doesn't depend on implementation-specific conditions, and in
> my limited testing (I ran the sudoku solver three times using each
> version), seems at least as fast, if not a tiny bit faster.
> 
> -- Larry
> 
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