full-disclosure - Re: Firefox 2.0.0.7 has a very serious calculation bug

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Message-ID: <Pine.LNX.4.58.0709282106580.16489@dione.cc>
Date: Fri, 28 Sep 2007 21:09:02 +0200 (CEST)
From: Michal Zalewski <lcamtuf@...ne.cc>
To: Jimby Sharp <jimbysharp@...il.com>
Cc: full-disclosure@...ts.grok.org.uk, carl hardwick <hardwick.carl@...il.com>
Subject: Re: Firefox 2.0.0.7 has a very serious
 calculation bug

On Sat, 29 Sep 2007, Jimby Sharp wrote:

> 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?

If you don't, it's presumably because the subtraction is optimized out by
the compiler, or because you printf() with an insufficient precision in
format spec. The following should do the trick:

volatile double a = 5.2;
volatile double b = 0.1;
main() { printf("%.16lf\n",a-b); }

/mz

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