Standard library header <cfenv> (C++11)

This header was originally in the C standard library as <fenv.h>.

This header is part of the floating-point environment library.

Types

fenv_t (C++11)	the type representing the entire floating-point environment (typedef)
fexcept_t (C++11)	the type representing all floating-point status flags collectively (typedef)

Functions

feclearexcept (C++11)	clears the specified floating-point status flags (function)
fetestexcept (C++11)	determines which of the specified floating-point status flags are set (function)
feraiseexcept (C++11)	raises the specified floating-point exceptions (function)
fegetexceptflagfesetexceptflag (C++11)(C++11)	copies the state of the specified floating-point status flags from or to the floating-point environment (function)
fegetroundfesetround (C++11)(C++11)	gets or sets rounding direction (function)
fegetenvfesetenv (C++11)	saves or restores the current floating-point environment (function)
feholdexcept (C++11)	saves the environment, clears all status flags and ignores all future errors (function)
feupdateenv (C++11)	restores the floating-point environment and raises the previously raised exceptions (function)

Macros

FE_ALL_EXCEPTFE_DIVBYZEROFE_INEXACTFE_INVALIDFE_OVERFLOWFE_UNDERFLOW (C++11)	floating-point exceptions (macro constant)
FE_DOWNWARDFE_TONEARESTFE_TOWARDZEROFE_UPWARD (C++11)	floating-point rounding direction (macro constant)
FE_DFL_ENV (C++11)	default floating-point environment (macro constant)

Synopsis

#define FE_ALL_EXCEPT /* see description */
#define FE_DIVBYZERO /* see description */    // optional
#define FE_INEXACT /* see description */      // optional
#define FE_INVALID /* see description */      // optional
#define FE_OVERFLOW /* see description */     // optional
#define FE_UNDERFLOW /* see description */    // optional

#define FE_DOWNWARD /* see description */     // optional
#define FE_TONEAREST /* see description */    // optional
#define FE_TOWARDZERO /* see description */   // optional
#define FE_UPWARD /* see description */       // optional

#define FE_DFL_ENV /* see description */

namespace std {
    // types
    using fenv_t    = /* object type */;
    using fexcept_t = /* object type */;

    // functions
    int feclearexcept(int except);
    int fegetexceptflag(fexcept_t* pflag, int except);
    int feraiseexcept(int except);
    int fesetexceptflag(const fexcept_t* pflag, int except);
    int fetestexcept(int except);
    int fegetround(void);
    int fesetround(int mode);
    int fegetenv(fenv_t* penv);
    int feholdexcept(fenv_t* penv);
    int fesetenv(const fenv_t* penv);
    int feupdateenv(const fenv_t* penv);
}

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 3905	C++11	std::fexcept_t must be an integer type	it is an object type