Re: floating point exception

[Richard B. Johnson]

On Tue, 15 Jan 2002, Zwane Mwaikambo wrote:

> On 14 Jan 2002, Christian Thalinger wrote:
> 
> > It seems the floating point exception is only raised with a new data
> > package. Is there a simple way to raise such a exception?
> 
> New data package? And does the same behaviour re-occur after the fpu
> exception? ie programs start segfaulting etc. Can you try doing a "dmesg"
> after the segfaults and fpu exception and see if there is anything in the
> kernel ring buffer too.
> 
> Regards,
> 	Zwane Mwaikambo

This will allow you to generate some math-errors and see if everything
works okay. By default, upon process creation, math errors like
/0 are masked.

/*
 *  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;
}

Cheers,
Dick Johnson

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