Don Fisher wrote:
> For the alpha I see many compiler flags that control how floating point errors
> are handled. Examples are
>
> -mfp-trap-mode=TRAP MODE
> -mfp-rounding-mode=ROUNDING MODE
> -mtrap-precision=TRAP PRECISION
>
> How are these functions implemented for the i386? I would like to be able to
> ignore or trap to an exception handler things like floating underflow, division
> by zero etc.
AFAIK, you have to manipulate the FPU control word directly, e.g.
#include <stdio.h>
int main(void)
{
unsigned short cw = 0;
double one = 1.0, zero = 0.0;
/* print the CW */
asm("fstcw %0" : "=m" (cw));
printf("CW=%04x\n", cw);
/* divide by zero: shouldn't generate SIGFPE */
printf("1/0 = ");
printf("%f\n", one/zero);
/* clear the ZM (divide-by-zero mask) bit */
cw &= ~0x0004;
asm("fldcw %0" : "=m" (cw));
/* print the CW */
asm("fstcw %0" : "=m" (cw));
printf("CW=%04x\n", cw);
/* divide by zero: should generate SIGFPE */
printf("1/0 = ");
printf("%f\n", one/zero);
return 0;
}
--
Glynn Clements <[EMAIL PROTECTED]>
