linux-kernel - Re: [PATCH] lib: gcd: prevent possible div by 0

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Date:	Mon, 10 Sep 2012 12:30:04 +0200
From:	Davidlohr Bueso <dave@....org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	stable@...r.kernel.org
Subject: Re: [PATCH] lib: gcd: prevent possible div by 0

On Mon, 2012-09-10 at 11:12 +0200, Eric Dumazet wrote:
> On Sun, 2012-09-09 at 17:03 +0200, Davidlohr Bueso wrote:
> > Account for properties when a and/or b are 0:
> > gcd(0, 0) = 0
> > gcd(a, 0) = a
> > gcd(0, b) = b
> > 
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Davidlohr Bueso <dave@....org>
> > ---
> >  lib/gcd.c |    3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/lib/gcd.c b/lib/gcd.c
> > index cce4f3c..7e163c6 100644
> > --- a/lib/gcd.c
> > +++ b/lib/gcd.c
> > @@ -7,6 +7,9 @@ unsigned long gcd(unsigned long a, unsigned long b)
> >  {
> >  	unsigned long r;
> >  
> > +	if (!a || !b)
> > +		return a | b;
> 
> This seems overkill

It might, but it reads better, IMHO.

> 
> > +
> >  	if (a < b)
> >  		swap(a, b);
> 
> better here to :
> 	if (!b)
> 		return a;
> 

Sure, I don't mind either way. I'll send a v2 shortly.

Thanks for reviewing.
Davidlohr


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