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

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

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

Contents

[edit] Types

fenv_t

(C++11)

the type representing the entire floating-point environment
(typedef) [edit]

fexcept_t

(C++11)

the type representing all floating-point status flags collectively
(typedef) [edit]

[edit] Functions

(C++11)

clears the specified floating-point status flags
(function) [edit]

(C++11)

determines which of the specified floating-point status flags are set
(function) [edit]

(C++11)

raises the specified floating-point exceptions
(function) [edit]

fegetexceptflagfesetexceptflag

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

copies the state of the specified floating-point status flags from or to the floating-point environment
(function) [edit]

fegetroundfesetround

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

gets or sets rounding direction
(function) [edit]

fegetenvfesetenv

(C++11)

saves or restores the current floating-point environment
(function) [edit]

(C++11)

saves the environment, clears all status flags and ignores all future errors
(function) [edit]

(C++11)

restores the floating-point environment and raises the previously raised exceptions
(function) [edit]

[edit] Macros

FE_ALL_EXCEPTFE_DIVBYZEROFE_INEXACTFE_INVALIDFE_OVERFLOWFE_UNDERFLOW

(C++11)

floating-point exceptions
(macro constant) [edit]

FE_DOWNWARDFE_TONEARESTFE_TOWARDZEROFE_UPWARD

(C++11)

floating-point rounding direction
(macro constant) [edit]

(C++11)

default floating-point environment
(macro constant) [edit]

[edit] 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);
}

[edit] 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

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