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SubjectRe: floating point exception
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.


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