Turbo C matherr() function

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2 total messages Started by Bernie Roehl Wed, 01 Aug 1990 12:53

#1762

Author: Bernie Roehl
Date: Wed, 01 Aug 1990 12:53

23 lines
1159 bytes

The problem is simple... maybe the solution will be, too.
I'm trying to define my own matherr() function, as described on page 242 of
the Reference Guide.

#include <math.h>

int matherr(struct exception *e)
	{
	fprintf(stderr, "Hello, world!\n");
	return 1;
	}

I then write a short program that just divides by zero, link it with the above,
and run it.  Instead of "Hello, world!\n", I get the standard Turboc C
"Floating point error: Divide by 0".

Any ideas/suggestions/etc will be much appreciated.  Thanks in advance...

-- 
	Bernie Roehl, University of Waterloo Electrical Engineering Dept
	Mail: broehl@watserv1.waterloo.edu OR broehl@watserv1.UWaterloo.ca
	BangPath: {allegra,decvax,utzoo,clyde}!watmath!watserv1!broehl
	Voice:  (519) 885-1211 x 2607 [work]

Re: Turbo C matherr() function

#1773

Author: Pete Holzmann
Date: Fri, 03 Aug 1990 13:13

28 lines
1746 bytes

broehl@watserv1.waterloo.edu (Bernie Roehl) writes:
>The problem is simple... maybe the solution will be, too.
>I'm trying to define my own matherr() function, as described on page 242 of
>the Reference Guide.
>
>I then write a short program that just divides by zero, link it with the above,
>and run it.  Instead of "Hello, world!\n", I get the standard Turboc C
>"Floating point error: Divide by 0".
>
>Any ideas/suggestions/etc will be much appreciated.  Thanks in advance...

Unfortunately, the solution is not as simple as you would like.

matherr() only deals with the errors that it is documented to deal
with. Basically, it is only called when an error is generated within
the trig/exponential functions.

To handle divide by zero and a host of other problems, you must set
up a signal handler for SIG_FPE (see signal()). This also requires 
careful use of setjmp() and longjmp(). Which can be truly a pain in
the neck!

Pete
-- 
Peter Holzmann, Octopus Enterprises   |(if you're a techie Christian & are
19611 La Mar Ct., Cupertino, CA 95014 |interested in helping w/ the Great
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