From owner-freebsd-hackers  Thu Mar  4 14:39:33 1999
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From: "Crist J. Clark" <cjc@cc942873-a.ewndsr1.nj.home.com>
Message-Id: <199903042248.RAA08114@cc942873-a.ewndsr1.nj.home.com>
Subject: FP Math Problem
To: freebsd-hackers@freebsd.org
Date: Thu, 4 Mar 1999 17:48:25 -0500 (EST)
Reply-To: cjclark@home.com
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I am trying to figure out why the following program produces a
floating point exception and core dumps.

#include <stdio.h>
#include <floatingpoint.h>
#include <float.h>

int main()
{

  double a = 1e200;
  double b;

  printf("fpgetmask:    %o\n",fpgetmask());

  printf("a:            %e\n",a);

  b = a*a;

  printf("isinf:        %d\n",isinf(b));

  printf("isnan:        %d\n",isnan(b));

  printf("b > DBL_MAX:  %d\n",b>DBL_MAX);

  printf("b:         %e\n",b);

  return 0;
}

My output is,

[112:~/tmp] ./dtest 
fpgetmask:    15
a:            1.000000e+200
isinf:        0
isnan:        0
Floating exception (core dumped)

I started with this on -questions and (although the thread got
sidetracked by a bad test program I presented at the beginning) other
FreeBSDers have not reproduced the error, but get what I would expect,

% ./dtest 
fpgetmask:    15
a:            1.000000e+200
isinf:        1
isnan:        0
b > DBL_MAX:  1
b:            inf

However, I get the FPE and core dump on my three FreeBSD machines
(different hardware on each). All are,

FreeBSD pc252.scitec.com 2.2.8-STABLE FreeBSD 2.2.8-STABLE #0: Mon Mar  1 14:25:39 EST 1999

Give or take a few days on the CVSup. (All were recently built to
2.2.8-S from 2.2.7-R.)

It has been suggested I have somehow mucked up my floating point,
but I do not know where to start and -questions did not
produce many leads.

Thanks for any help. More details can be provided; I would not know
where to start.
-- 
Crist J. Clark                           cjclark@home.com


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