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Date: Tue, 10 Apr 2018 16:32:06 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: catan errors

On Tue, Apr 10, 2018 at 05:23:12PM -0300, dgutson . wrote:
> On Tue, Apr 10, 2018 at 4:50 PM, Rich Felker <dalias@...c.org> wrote:
> 
> > The OpenBSD catan implementation we're using has a number of
> > nonsensical "overflow" (goto ovrf) conditions that aren't errors,
> > reported by mepholic on irc. I think the attached patch fixes them
> > without introducing new problems, but I'm not sure if any other
> > problems remain.
> >
> > Note that, of the three cases removed:
> >
> > 1. Is not an exceptional case at all, and made no sense to begin with.
> >
> > 2. Is only exceptional if x and a are both zero; atan(2x,0) is
> >    perfectly well-defined.
> >
> > 3. Is only possible if y==1.0 and x==0.0, which is the only real
> >    exceptional case for atan: z==I.
> >
> 
> 
> Besides the trigonometric case, are you considering de-normalized numbers,
> such as 4.94066e-324 as divisor?
> For example:
>     double x = 1.0;
>     double y = 5E-324;
> x / y is inf, and y != 0.0.
> Shouldn't 'a' be checked against that number or its absolute value >=
> minimum?

Can you clarify where you think something goes wrong?

Rich

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