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Subject: Re: floating point exception
From: Christian Thalinger <e9625286@student.tuwien.ac.at>
To: "Richard B. Johnson" <root@chaos.analogic.com>
Cc: Zwane Mwaikambo <zwane@linux.realnet.co.sz>,
        linux-kernel <linux-kernel@vger.kernel.org>
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Date: 15 Jan 2002 19:49:11 +0100
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On Tue, 2002-01-15 at 19:31, Richard B. Johnson wrote:
> On 15 Jan 2002, Christian Thalinger wrote:
> 
> > On Tue, 2002-01-15 at 15:34, Zwane Mwaikambo wrote:
> > > On 14 Jan 2002, Christian Thalinger wrote:
> [SNIPPED...]
> 
> > 
> > Tried this:
> > 
> > #define _GNU_SOURCE 1
> > #include <fenv.h>
> > 
> > main() {
> >     double zero=0.0;
> >     double one=1.0;
> >     
> >     feenableexcept(FE_ALL_EXCEPT);
> >     
> >     one /=zero;
> > }
> > 
> Well, that won't even link. The source I showed previously
> compiles and link fine. It also shows a FPU exception when
> one divides by zero:
> 
> Script started on Tue Jan 15 13:27:05 2002
> # gcc -o zzz zzz.c -lm
> /tmp/ccjhyGHj.o: In function `main':
> /tmp/ccjhyGHj.o(.text+0x25): undefined reference to `feenableexcept'
> collect2: ld returned 1 exit status

This depends on the libc version. Seems you have 2.1. For me it's 2.2.

[root@sector17:/root/src]# cat fpu-exception.c
#define _GNU_SOURCE 1
#include <fenv.h>

main() {
    double zero=0.0;
    double one=1.0;
    
    feenableexcept(FE_ALL_EXCEPT);
    
    one /=zero;
}
[root@sector17:/root/src]# gcc -Wall -lm -o fpu-exception
fpu-exception.c
fpu-exception.c:4: warning: return type defaults to `int'
fpu-exception.c: In function `main':
fpu-exception.c:11: warning: control reaches end of non-void function
[root@sector17:/root/src]# ./fpu-exception  
Floating point exception
[root@sector17:/root/src]#