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feclearexcept

From cppreference.com
< c‎ | numeric‎ | fenv
 
C
 
Numerics
 
Floating-point environment
 
Defined in header <fenv.h>
int feclearexcept( int excepts );
 (since C99)

Attempts to clear the floating-point exceptions that are listed in the bitmask argument excepts, which is a bitwise OR of the floating-point exception macros.

Contents

[edit] Parameters

excepts - bitmask listing the exception flags to clear

[edit] Return value

​0​ if all indicated exceptions were successfully cleared or if excepts is zero. Returns a non-zero value on error.

[edit] Example

Run this code
#include <fenv.h>
#include <stdio.h>
#include <math.h>
#include <float.h>
 
/*
 * A possible implementation of hypot which makes use of many advanced
 * floating-point features.
 */
double hypot_demo(double a, double b) {
  const int range_problem = FE_OVERFLOW | FE_UNDERFLOW;
  feclearexcept(range_problem);
  // try a fast algorithm
  double result = sqrt(a * a + b * b);
  if (!fetestexcept(range_problem))  // no overflow or underflow
    return result;                   // return the fast result
  // do a more complicated calculation to avoid overflow or underflow
  int a_exponent,b_exponent;
  frexp(a, &a_exponent);
  frexp(b, &b_exponent);
 
  if (a_exponent - b_exponent > DBL_MAX_EXP)
    return fabs(a) + fabs(b);        // we can ignore the smaller value
  // scale so that fabs(a) is near 1
  double a_scaled = scalbn(a, -a_exponent);
  double b_scaled = scalbn(b, -a_exponent);
  // overflow and underflow is now impossible 
  result = sqrt(a_scaled * a_scaled + b_scaled * b_scaled);
  // undo scaling
  return scalbn(result, a_exponent);
}
 
int main(void)
{
  // Normal case takes the fast route