std::fetestexcept

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Diagnostics library

Memory management library

Metaprogramming library (C++11)

General utilities library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library (C++17)

Concurrency support library (C++11)

Execution control library (C++26)

Technical specifications

Symbols index

External libraries

 

Numerics library

Common mathematical functions
Mathematical special functions (C++17)
Mathematical constants (C++20)
Basic linear algebra algorithms (C++26)
Data-parallel types (SIMD) (C++26)
Floating-point environment (C++11)
Complex numbers
Numeric array (valarray)
Pseudo-random number generation
Bit manipulation (C++20)
Saturation arithmetic (C++26)
Factor operations
gcd (C++17)	lcm (C++17)
Interpolations
midpoint (C++20)	lerp (C++20)
Generic numeric operations
iota (C++11) ranges::iota (C++23) accumulate inner_product adjacent_difference    partial_sum	reduce (C++17) transform_reduce (C++17) inclusive_scan (C++17) exclusive_scan (C++17) transform_inclusive_scan (C++17) transform_exclusive_scan (C++17)
C-style checked integer arithmetic
ckd_add (C++26) ckd_sub (C++26)	ckd_mul (C++26)

 

Floating-point environment

Functions

feclearexcept (C++11)

fetestexcept (C++11)

feraiseexcept (C++11)

fegetexceptflagfesetexceptflag (C++11)(C++11)

fegetroundfesetround (C++11)(C++11)

fegetenvfesetenv (C++11)(C++11)

feholdexcept (C++11)

feupdateenv (C++11)

Macro constants

FE_ALL_EXCEPTFE_DIVBYZEROFE_INEXACTFE_INVALIDFE_OVERFLOWFE_UNDERFLOW (C++11)(C++11)(C++11)(C++11)(C++11)(C++11)

FE_DOWNWARDFE_TONEARESTFE_TOWARDZEROFE_UPWARD (C++11)(C++11)(C++11)(C++11)

FE_DFL_ENV (C++11)

 

Defined in header <cfenv>
int fetestexcept( int excepts );		(since C++11)

Determines which of the specified subset of the floating point exceptions are currently set. The argument excepts is a bitwise OR of the floating point exception macros.

Parameters

excepts

-

bitmask listing the exception flags to test

Return value

Bitwise OR of the floating-point exception macros that are both included in excepts and correspond to floating-point exceptions currently set.

Example

Run this code

#include <cfenv>
#include <cmath>
#include <iostream>
 
/ #pragma STDC FENV_ACCESS ON
 
volatile double zero = 0.0; / volatile not needed where FENV_ACCESS is supported
volatile double one = 1.0;  / volatile not needed where FENV_ACCESS is supported
 
int main()
{
    std::feclearexcept(FE_ALL_EXCEPT);
    std::cout <<  "1.0/0.0 = " << 1.0 / zero << '\n';
    if (std::fetestexcept(FE_DIVBYZERO))
        std::cout << "division by zero reported\n";
    else
        std::cout << "division by zero not reported\n";
 
    std::feclearexcept(FE_ALL_EXCEPT);
    std::cout << "1.0/10 = " << one / 10 << '\n';
    if (std::fetestexcept(FE_INEXACT))
        std::cout << "inexact result reported\n";
    else
        std::cout << "inexact result not reported\n";
 
    std::feclearexcept(FE_ALL_EXCEPT);
    std::cout << "sqrt(-1) = " << std::sqrt(-1) << '\n';
    if (std::fetestexcept(FE_INVALID))
        std::cout << "invalid result reported\n";
    else
        std::cout << "invalid result not reported\n";
}

Possible output:

1.0/0.0 = inf
division by zero reported
1.0/10 = 0.1
inexact result reported
sqrt(-1) = -nan
invalid result reported

See also

feclearexcept (C++11)	clears the specified floating-point status flags (function)
C documentation for fetestexcept

Follow Lee on X/Twitter - Father, Husband, Serial builder creating AI, crypto, games & web tools. We are friends :) AI Will Come To Life!

Check out: eBank.nz (Art Generator) | Netwrck.com (AI Tools) | Text-Generator.io (AI API) | BitBank.nz (Crypto AI) | ReadingTime (Kids Reading) | RewordGame | BigMultiplayerChess | WebFiddle | How.nz | Helix AI Assistant