GNU bug report logs - #14565
24.3.50; Error with byte-compiled function using backward-char

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Message #19 received at 14565 <at> debbugs.gnu.org (full text, mbox):

From: Stephen Berman <stephen.berman <at> gmx.net>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 14565 <at> debbugs.gnu.org
Subject: Re: bug#14565: 24.3.50;
	Error with byte-compiled function using backward-char
Date: Fri, 07 Jun 2013 11:40:23 +0200

On Thu, 06 Jun 2013 22:28:22 -0400 Glenn Morris <rgm <at> gnu.org> wrote:

> I suppose there could still be cases like
>
> (setq foo nil)
> (backward-char foo)

Yes, in fact, after seeing your fix, I realized that I had
oversimplified my test case; the code which revealed the bug actually
looks more like this (still simplified, but enough to raise the error
with your fix):

(defun my-test-3 ()
  (let (x)
    (backward-char (when x 2))))

> I wonder if these bytecomp handlers are worth keeping?

I don't see how to tweak byte-compile-backward-char to account for the
above cases, but I don't understand the bytecomp code well.  However, I
did test adding a case Bbackward_char to exec_byte_code parallel to
Bforward_char, and that handles the above cases as expected.  So that
may be the easiest fix.

Steve Berman

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