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glibc  2.9
Functions
fraiseexcpt.c File Reference
#include <fenv.h>
#include <math.h>

Go to the source code of this file.

Functions

int feraiseexcept (int excepts)

Function Documentation

int feraiseexcept ( int  excepts)

Definition at line 24 of file fraiseexcpt.c.

{
  /* Raise exceptions represented by EXPECTS.  But we must raise only
     one signal at a time.  It is important that if the overflow/underflow
     exception and the inexact exception are given at the same time,
     the overflow/underflow exception follows the inexact exception.  */

  /* First: invalid exception.  */
  if ((FE_INVALID & excepts) != 0)
    {
      /* One example of a invalid operation is 0.0 / 0.0.  */
      float f = 0.0;

      __asm__ __volatile__ ("divss %0, %0 " : : "x" (f));
      (void) &f;
    }

  /* Next: division by zero.  */
  if ((FE_DIVBYZERO & excepts) != 0)
    {
      float f = 1.0;
      float g = 0.0;

      __asm__ __volatile__ ("divss %1, %0" : : "x" (f), "x" (g));
      (void) &f;
    }

  /* Next: overflow.  */
  if ((FE_OVERFLOW & excepts) != 0)
    {
      /* XXX: Is it ok to only set the x87 FPU?  */
      /* There is no way to raise only the overflow flag.  Do it the
        hard way.  */
      fenv_t temp;

      /* Bah, we have to clear selected exceptions.  Since there is no
        `fldsw' instruction we have to do it the hard way.  */
      __asm__ __volatile__ ("fnstenv %0" : "=m" (*&temp));

      /* Set the relevant bits.  */
      temp.__status_word |= FE_OVERFLOW;

      /* Put the new data in effect.  */
      __asm__ __volatile__ ("fldenv %0" : : "m" (*&temp));

      /* And raise the exception.  */
      __asm__ __volatile__ ("fwait");
    }

  /* Next: underflow.  */
  if ((FE_UNDERFLOW & excepts) != 0)
    {
      /* XXX: Is it ok to only set the x87 FPU?  */
      /* There is no way to raise only the underflow flag.  Do it the
        hard way.  */
      fenv_t temp;

      /* Bah, we have to clear selected exceptions.  Since there is no
        `fldsw' instruction we have to do it the hard way.  */
      __asm__ __volatile__ ("fnstenv %0" : "=m" (*&temp));

      /* Set the relevant bits.  */
      temp.__status_word |= FE_UNDERFLOW;

      /* Put the new data in effect.  */
      __asm__ __volatile__ ("fldenv %0" : : "m" (*&temp));

      /* And raise the exception.  */
      __asm__ __volatile__ ("fwait");
    }

  /* Last: inexact.  */
  if ((FE_INEXACT & excepts) != 0)
    {
      /* XXX: Is it ok to only set the x87 FPU?  */
      /* There is no way to raise only the inexact flag.  Do it the
        hard way.  */
      fenv_t temp;

      /* Bah, we have to clear selected exceptions.  Since there is no
        `fldsw' instruction we have to do it the hard way.  */
      __asm__ __volatile__ ("fnstenv %0" : "=m" (*&temp));

      /* Set the relevant bits.  */
      temp.__status_word |= FE_INEXACT;

      /* Put the new data in effect.  */
      __asm__ __volatile__ ("fldenv %0" : : "m" (*&temp));

      /* And raise the exception.  */
      __asm__ __volatile__ ("fwait");
    }

  /* Success.  */
  return 0;
}

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