full-disclosure - Re: Major gcc 4.1.1 and up security issue

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Message-ID: <45AE65D7.7080105@shoplogistics.de>
Date: Wed, 17 Jan 2007 19:07:19 +0100
From: Marcus Graf <m.graf@...plogistics.de>
To: full-disclosure@...ts.grok.org.uk
Subject: Re: Major gcc 4.1.1 and up security issue

off topic thoughts:

> (twice 1.15 will likely be a bit or two different than 3.30).  As Fortran
> geeks have known for over half a century, a better way to code this is:
> 
> 	if (abs(a-b) < n*epsilon*a)
> 
> where 'epsilon' is the hardware constant defining the smallest number such
> that 1+a is different from 1, and 'n' controls how many significant digits
> we require in the test.

Hm...

assume a = b = -1.0

abs(a-b) is zero or maybe a little bit above
n*epsilon*a is negative (n>0, epsilon>0, a=-1)

Test fails :-(

Just my $0.02

Ciao
Marcus

-- 
Hail Eris! Hail Discordia!

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