Date: Thu, 6 Apr 2000 09:30:04 -0700 (PDT) From: Julian Gilbey <J.D.Gilbey@qmw.ac.uk> To: freebsd-bugs@FreeBSD.org Subject: Re: bin/17824: [PATCH] /usr/bin/column has arithmetic overflows Message-ID: <200004061630.JAA56519@freefall.freebsd.org>
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The following reply was made to PR bin/17824; it has been noted by GNATS.
From: Julian Gilbey <J.D.Gilbey@qmw.ac.uk>
To: Sheldon Hearn <sheldonh@uunet.co.za>
Cc: freebsd-gnats-submit@FreeBSD.ORG
Subject: Re: bin/17824: [PATCH] /usr/bin/column has arithmetic overflows
Date: Thu, 6 Apr 2000 17:26:51 +0100
On Thu, Apr 06, 2000 at 02:25:53PM +0200, Sheldon Hearn wrote:
> On Thu, 06 Apr 2000 02:06:54 MST, jdg@debian.org wrote:
>
> > maxlength = (maxlength + TAB) & ~(TAB - 1);
> > numcols = termwidth / maxlength;
> > + if (!numcols) {
>
> I don't get it. You still don't seem to be protecting against
> divide-by-zero. Shouldn't you be testing the value of the dividend
> before dividing?
maxlength >= 0. So, assuming that TAB is 8 (which it presumably is),
the first line of the code rounds maxlength up to the next multiple of
8, so maxlength >= 8 after this step.
However, it is possible that numcols is zero if termwidth is less than
the new maxlength, in which case we get a divide by zero in the next
line (numrows = numlines / numcols or something like that). That's
why I test for numcols being zero and not maxlength.
Julian
--
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Julian Gilbey, Dept of Maths, QMW, Univ. of London. J.D.Gilbey@qmw.ac.uk
Debian GNU/Linux Developer, see http://www.debian.org/~jdg
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