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Re: [Full-disclosure] Firefox 2.0.0.7 has a very serious calculation bug

From: Jimby Sharp (jimbysharpgmail.com)
Date: Fri Sep 28 2007 - 14:02:41 CDT


Michal

I don't get the same from C-style double arithmetics. Could you
provide a sample code that you believe should show the same behavior?

On 9/28/07, Michal Zalewski <lcamtufdione.cc> wrote:
> On Fri, 28 Sep 2007, carl hardwick wrote:
>
> > javascript:5.2-0.1
> > Firefox 2.0.0.7 result: 5.1000000000000005 (WRONG!)
>
> This is a proper behavior of IEEE 754 64-bit double float, which, IIRC, is
> precisely what ECMA standard mandates.
>
> You will get the same from any C-style 'double' arithmetics.
>
> > Internet Explorer 7 result: 5.1 (OK)
>
> They use a marginally higher precision. Now try 5.002-.001 - chances are,
> you will get 5.00999...
>
> Neither is a "very serious calculation bug". Javascript does not guarantee
> - and nowhere actually delivers - arbitrary GMP-style precision.
>
> /mz
>
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