From:	Boon van der RJ <rjvdboon AT sloep03 DOT cs DOT vu DOT nl>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Help - Floating Point Exception
Date:	25 Sep 1998 11:33:25 GMT
Organization:	Fac. Wiskunde & Informatica, VU, Amsterdam
Lines:	46
Message-ID:	<6ufv25$a6e$1@star.cs.vu.nl>
References:	<GoldED DOT 199809242144148700 DOT enlar AT hidespam DOT iname DOT com>
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User-Agent:	tin/pre-1.4-980730 (UNIX) (SunOS/5.5.1 (sun4u))
Originator:	rjvdboon AT sloep03 DOT cs DOT vu DOT nl
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Eneko Lacunza <enlar AT hidespam DOT iname DOT com> wrote:
>     I'm having some problems with the following code:
> === Cut ===
> #define pi 3.1415926535897932385

> void build_table(void)
> {
> unsigned short xcont,ycont;
> float radio,angulo;

>      for(ycont=0;ycont<200;ycont++)
>          for(xcont=0;xcont<320;xcont++)
>          {
>              radio=sqrt((xcont-160)*(xcont-160)+(100-ycont)*(100-ycont));
>              angulo=atan2((xcont-160),(100-ycont));
atan2(0,0) might be handled not quite right, so that

>              table[xcont][ycont][0]=floor(radio);
>              table[xcont][ycont][1]=floor(255*angulo/(2*pi)); // FPE
floor crashes.

>          }
> }
>     This crashes at the point noted as //FPE with a Floating Point
> exception. This is quite tricky, because it doesn't crash in a shell (i.e.
> running it under rhide) and if I try to redir the crash, redir crashes when 
> the program has finished the above code and is doing something else.

In a dos-box under windows 95, you can mark the screen and paste in a
text-file, maybe that helps.

>     Could somebody tell me what does that exception mean, and how could I

Perhaps devide by zero.

> fix it (if this info is enough). I'm using GCC 2.7.2...

Do you compile with -lm, or do you use the standards in libc? libm
does some more checking (if I've understood correctly)
What type of computer do you use? (386/486/pentiumII?)

hth,
 Robert.
-- 
rjvdboon AT cs DOT vu DOT nl        | "En dat is niet waar!" sprak ex-Staatsecretaris-
www.cs.vu.nl/~rjvdboon   |    van-Onderwijs Netelenbos fel.

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