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[MIT-Scheme-devel] Re: false positive: unreferenced bound variable

From: Joe Marshall
Subject: [MIT-Scheme-devel] Re: false positive: unreferenced bound variable
Date: Wed, 17 Mar 2010 02:59:48 -0700


 In cpress.scm,
;      Integrating procedure guarantee-buffer-space...
;Warning: Unreferenced bound variable: nb (guarantee-buffer-space)
;      ... done

The code is complex, but note this:
(define-integrable buffer-size-optimal? true)

(define (guarantee-buffer-space nb)
  ;; Make sure that the byte buffer has enough space to hold NB bytes.
  ;; If necessary, invalidate old commands until this is true.  If the
  ;; buffer size is optimal, this is never necessary, because the
  ;; buffer is big enough to hold all of the commands in the window.
  (if (and (not buffer-size-optimal?)
      (let ((end (bb-end byte-buffer)))
        (if (fix:< (let ((bp command-bp))
           ... lots of code elided ...

Since buffer-size-optimal? is true, the conditional can be eliminated and
this turns into
 (define (guarantee-buffer-space nb)

Which doesn't use nb.

In edwin\win32.scm there is this code:

(define (win32-screen/scroll-lines-down! screen xl xu yl yu amount)
  (and #f
       (win32-screen-vertical-scroll! (screen->handle screen)
                                      xl xu yl yu (fix:+ yl amount))))

The second arm of the AND is dead code, so the variables are not being used.

On Wed, Mar 17, 2010 at 12:57 AM, Chris Hanson <address@hidden> wrote:
> The new SF is generating unreferenced bound variables in situations
> where the variables are referenced.  In the two cases I looked at,
> both involved conditionals in which the variable was referenced on one
> arm of the conditional but not the other.


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