From owner-freebsd-hackers  Tue Apr 25  0: 5:38 2000
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Date: Tue, 25 Apr 2000 00:05:23 -0700
From: Brooks Davis <brooks@one-eyed-alien.net>
To: Nate Lawson <nate@elite.net>
Cc: freebsd-hackers@FreeBSD.ORG, freebsd-ports@FreeBSD.ORG,
	davidm@hpl.hp.com
Subject: Re: floating point exceptions
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On Mon, Apr 24, 2000 at 11:44:59PM -0700, Nate Lawson wrote:
> I am running FreeBSD 4.0-RELEASE on x86 with gcc 2.95.2 and the
> httperf-0.6 port gives a SIGFPE and dumps core when run against a system
> that has no web server running.  (The default behavior is to measure
> localhost when no arguments are specified). 
> 
> It seems this is caused by a divide by zero error since the delta between 
> connections ends up being zero.  The author suggest that the divide 
> should return a defined value, Inf, according to the IEEE floating point 
> standard.  FreeBSD generates SIGFPE.  I temporarily patched the code 
> locally to check for a delta of zero and arbitrarily set it to 1.0 so 
> that the divide succeeds and everything comes out ok without crashing.
> 
> Is FreeBSD's behavior correct?  Why or why not?  You can use the included 
> code snippet to verify that this occurs.

FreeBSD has traditionaly violated the IEEE FP standard in this regard.
This is fixed in 5.0 and I think in 4.0-STABLE (though I can't remember
what file this is in so I can't check.)  If upgrading to -stable isn't
an option you can add a call to fpsetmask(3) in the application as
follows (this will work on Solaris and Irix as well):

#include <ieeefp.h>
<...>
main() {
	<declare things>

	fpsetmask(0);
	<...>
}

-- Brooks

-- 
Any statement of the form "X is the one, true Y" is FALSE.


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