Re: floating point exception

[Richard B. Johnson]

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
# gcc -o zzz fpu.c
# zzz
Floating point exception (core dumped)
# cat fpu.c
/*
 *  Note FPU control only exists per process. Therefore, you have
 *  to set up the FPU before you use it in any program.
 */
#include <i386/fpu_control.h>

#define FPU_MASK (_FPU_MASK_IM |\
                  _FPU_MASK_DM |\
                  _FPU_MASK_ZM |\
                  _FPU_MASK_OM |\
                  _FPU_MASK_UM |\
                  _FPU_MASK_PM)

void fpu()
{
    __setfpucw(_FPU_DEFAULT & ~FPU_MASK);
}

main() {
   double zero=0.0;
   double one=1.0;
   fpu();

   one /=zero;
}

# cat zzz.c

#define _GNU_SOURCE 1
#include <fenv.h>

main() {
    double zero=0.0;
    double one=1.0;
    
    feenableexcept(FE_ALL_EXCEPT);
    
    one /=zero;
}

You have new mail in /var/spool/mail/root
# exit
exit

Script done on Tue Jan 15 13:28:32 2002

Cheers,
Dick Johnson

Penguin : Linux version 2.4.1 on an i686 machine (797.90 BogoMips).

    I was going to compile a list of innovations that could be
    attributed to Microsoft. Once I realized that Ctrl-Alt-Del
    was handled in the BIOS, I found that there aren't any.