Date: Tue, 10 Apr 2018 17:41:46 -0300 From: "dgutson ." <danielgutson@...il.com> To: musl@...ts.openwall.com Subject: Re: catan errors On Tue, Apr 10, 2018 at 5:32 PM, Rich Felker <dalias@...c.org> wrote: > 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? > - if (a == 0.0) - goto ovrf; t = y + 1.0; a = (x2 + t * t)/a; The check you removed does not look correct for me because what I mentioned. However, shouldn't you check, before the division, that a is not the nearest to zero (+ or -) denormalized representable double, in order to avoid ending in inf? > > Rich > -- Who’s got the sweetest disposition? One guess, that’s who? Who’d never, ever start an argument? Who never shows a bit of temperament? Who's never wrong but always right? Who'd never dream of starting a fight? Who get stuck with all the bad luck? Content of type "text/html" skipped
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