GNU bug report logs - #22689
25.1.50; implement logcount

Previous Next

Package: emacs;

Reported by: Mark Oteiza <mvoteiza <at> udel.edu>

Date: Mon, 15 Feb 2016 23:20:01 UTC

Severity: wishlist

Found in version 25.1.50

Done: Mark Oteiza <mvoteiza <at> udel.edu>

Bug is archived. No further changes may be made.

Full log

View this message in rfc822 format

From: Benjamin Riefenstahl <b.riefenstahl <at> turtle-trading.net>
To: Mark Oteiza <mvoteiza <at> udel.edu>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 22689 <at> debbugs.gnu.org
Subject: bug#22689: [PATCH] Add logcount
Date: Sat, 30 Sep 2017 18:50:42 +0200

Hi Mark,

Just a drive-by note:

Mark Oteiza writes:
> +    {
> +      unsigned int count;
> +      for (count = 0; v; count++)
> +        {
> +          v &= v - 1;
> +        }
> +      XSETINT (res, v);
> +    }

Isn't this a fancy way of just saying "XSETINT (res, 0)"?  The variable
"count" is incremented but never used, so without it the loop
degenerates to

      while (v)
        {
          v &= v - 1;
        }

I other words, this just loops until "v == 0".

Maybe that assignment should be "XSETINT (res, count)"?  That would
actually use the variable "count".

benny
This bug report was last modified 7 years and 291 days ago.

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.