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From: deb@kea.wpd.sgi.com (Deb Ryan)
Newsgroups: comp.sys.sgi
Subject: Re: SIGFPE
Summary: trap handler info
Message-ID: <46227@sgi.sgi.com>
Date: 13 Dec 89 01:05:06 GMT
References: <8912111534.AA25453@prism.gatech.edu> <624@chem.ucsd.EDU>
Sender: deb@kea.wpd.sgi.com
Organization: Silicon Graphics, Inc., Mountain View, CA
Lines: 72

In article <624@chem.ucsd.EDU>, tps@chem.ucsd.edu (Tom Stockfisch) writes:
> With 3.2 floating point exceptions are ignored, with NaN's and Infinity's
> propagated through floating point exceptions, presumably according to
> IEEE rules.  I happen to prefer that all exceptions result in SIGFPE
> being raised, so that a process stops right away and either aborts
> or calls a signal()-specified error handler.
> 
> How can I achieve this?
> -- 
> 
> || Tom Stockfisch, UCSD Chemistry	tps@chem.ucsd.edu


You two choices:

1. Wait for the trap handler, comming out in the aspen release.
   This will make it easy to core dump, or do anything your heart can code
   in a subroutine .


2. If all you really want to do is coredump, this  Fortran
   callable C routine will show you what to do.  signal (2) will also
   allow you to specify your own handler, but you will be pretty limited
   without information about the exception.

----------------------------------cut here -------------------------------------
#include <stdio.h>
#include <signal.h>
#include <sys/fpu.h>

/* this code uses information from the manpages fpc(3c) and signal(2)

   set_traps is a fortran callable subroutine which will enable
   foating point exceptions, and coredump upon recieving one
 */
set_traps_() {
union fpc_csr fpstat;

/* enable the floating point traps
 */
 fpstat.fc_word = get_fpc_csr();
 fpstat.fc_word |= (FPCSR_ENABLES | FPCSR_EXCEPTIONS);
 set_fpc_csr (fpstat.fc_word);

/* abort upon recieving floating point trap 
 */
signal (SIGFPE, SIG_DFL);
}


/* test routine for set_traps
 */
main() {

float zero=0.0;
float one=1.0;
float result;

	set_traps_();

	/* divide by zero */
	printf( "\n\ndividing by zero:\n");
	result = one/zero;
	printf("one/zero yields %e\n",result);
}


--

					-Deb
					 deb@sgi.com
 					 Deborah Ryan Caruso @ Silicon Graphics