From cppreference.com
< c‎ | numeric‎ | fenv
Defined in header <<fenv.h>>
int feholdexcept( fenv_t* envp );
(since C99)

First, saves the current floating-point environment to the object pointed to by envp (similar to fegetenv), then clears all floating-point status flags, and then installs the non-stop mode: future floating-point exceptions will not interrupt execution (will not trap), until the floating-point environment is restored by feupdateenv or fesetenv.

This function may be used in the beginning of a subroutine that must hide the floating-point exceptions it may raise from the caller. If only some exceptions must be suppressed, while others must be reported, the non-stop mode is usually ended with a call to feupdateenv after clearing the unwanted exceptions.


[edit] Parameters

envp - pointer to the object of type fenv_t where the floating-point environment will be stored

[edit] Return value

0 on success, non-zero otherwise.

[edit] Example

#include <stdio.h>
#include <fenv.h>
#include <float.h>
void show_fe_exceptions(void)
    printf("current exceptions raised: ");
    if(fetestexcept(FE_DIVBYZERO))     printf(" FE_DIVBYZERO");
    if(fetestexcept(FE_INEXACT))       printf(" FE_INEXACT");
    if(fetestexcept(FE_INVALID))       printf(" FE_INVALID");
    if(fetestexcept(FE_OVERFLOW))      printf(" FE_OVERFLOW");
    if(fetestexcept(FE_UNDERFLOW))     printf(" FE_UNDERFLOW");
    if(fetestexcept(FE_ALL_EXCEPT)==0) printf(" none");
double x2 (double x)   /* times two */
    fenv_t curr_excepts;
    /* Save and clear current f-p environment. */
    /* Raise inexact and overflow exceptions. */
    printf("In x2():  x = %f\n", x=x*2.0);
    feclearexcept(FE_INEXACT);   /* hide inexact exception from caller */
    /* Merge caller's exceptions (FE_INVALID)        */
    /* with remaining x2's exceptions (FE_OVERFLOW). */
    return x;
int main(void)
    feraiseexcept(FE_INVALID);   /* some computation with invalid argument */
    printf("x2(DBL_MAX) = %f\n", x2(DBL_MAX));
    return 0;


current exceptions raised:  FE_INVALID
In x2():  x = inf
current exceptions raised:  FE_INEXACT FE_OVERFLOW
x2(DBL_MAX) = inf
current exceptions raised:  FE_INVALID FE_OVERFLOW

[edit] See also

restores the floating-point environment and raises the previously raise exceptions
saves or restores the current floating point environment
default floating-point environment
(macro constant)
C++ documentation for feholdexcept