Standard library header <fenv.h> (C99)

 

C

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Error handling

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Date and time utilities

Input/output support

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Concurrency support (C11)

Technical Specifications

Symbol index

 

Standard Library headers

<assert.h> <complex.h> (C99) <ctype.h> <errno.h> <fenv.h> (C99) <float.h> <inttypes.h> (C99)     <iso646.h> (C95) <limits.h> <locale.h> <math.h>

<setjmp.h> <signal.h> <stdalign.h> (C11*) <stdarg.h> <stdatomic.h> (C11)     <stdbit.h> (C23) <stdbool.h> (C99*) <stdckdint.h> (C23) <stddef.h> <stdint.h> (C99) <stdio.h>

<stdlib.h> <stdmchar.h> (C29) <stdnoreturn.h> (C11*) <string.h> <tgmath.h> (C99) <threads.h> (C11) <time.h> <uchar.h> (C11) <wchar.h> (C95) <wctype.h> (C95)

 

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

Types

Defined in header <fenv.h>
fenv_t	The type representing the entire floating-point environment
fexcept_t	The type representing all floating-point status flags collectively

Functions

feclearexcept (C99)	clears the specified floating-point status flags (function)
fetestexcept (C99)	determines which of the specified floating-point status flags are set (function)
feraiseexcept (C99)	raises the specified floating-point exceptions (function)
fegetexceptflagfesetexceptflag (C99)(C99)	copies the state of the specified floating-point status flags from or to the floating-point environment (function)
fegetroundfesetround (C99)(C99)	gets or sets rounding direction (function)
fegetenvfesetenv (C99)	saves or restores the current floating-point environment (function)
feholdexcept (C99)	saves the environment, clears all status flags and ignores all future errors (function)
feupdateenv (C99)	restores the floating-point environment and raises the previously raise exceptions (function)

Macros

FE_ALL_EXCEPTFE_DIVBYZEROFE_INEXACTFE_INVALIDFE_OVERFLOWFE_UNDERFLOW (C99)	floating-point exceptions (macro constant)
FE_DOWNWARDFE_TONEARESTFE_TOWARDZEROFE_UPWARD (C99)	floating-point rounding direction (macro constant)
FE_DFL_ENV (C99)	default floating-point environment (macro constant)

Synopsis

#define __STDC_VERSION_FENV_H__ 202311L

#define FE_ALL_EXCEPT         /* see description */
#define FE_DIVBYZERO          /* see description */
#define FE_INEXACT            /* see description */
#define FE_INVALID            /* see description */
#define FE_OVERFLOW           /* see description */
#define FE_UNDERFLOW          /* see description */
#define FE_DOWNWARD           /* see description */
#define FE_TONEARESTFROMZERO  /* see description */
#define FE_TONEAREST          /* see description */
#define FE_TOWARDZERO         /* see description */
#define FE_UPWARD             /* see description */
#define FE_DFL_ENV            /* see description */
#define FE_DFL_MODE           /* see description */

#define fenv_t                /* see description */
#define fexcept_t             /* see description */
#define femode_t              /* see description */

#pragma STDC FENV_ACCESS      /*on-off-switch*/
#pragma STDC FENV_ROUND       direction
#pragma STDC FENV_ROUND       FE_DYNAMIC

// functions
int feclearexcept(int excepts);
int fegetexceptflag(fexcept_t* flagp, int excepts);
int feraiseexcept(int excepts);
int fesetexcept(int excepts);
int fesetexceptflag(const fexcept_t* flagp, int excepts);
int fetestexceptflag(const fexcept_t* flagp, int excepts);
int fetestexcept(int excepts);
int fegetmode(femode_t* modep);
int fegetround(void);
int fesetmode(const femode_t* modep);
int fesetround(int rnd);
int fegetenv(fenv_t* envp);
int feholdexcept(fenv_t* envp);
int fesetenv(const fenv_t* envp);
int feupdateenv(const fenv_t* envp);

// Only if the implementation defines __STDC_IEC_60559_DFP__:
#define FE_DEC_DOWNWARD            /* implementation-defined */
#define FE_DEC_TONEARESTFROMZERO   /* implementation-defined */
#define FE_DEC_TONEAREST           /* implementation-defined */
#define FE_DEC_TOWARDZERO          /* implementation-defined */
#define FE_DEC_UPWARD              /* implementation-defined */

#pragma STDC FENV_DEC_ROUND /*dec-direction*/
int fe_dec_getround(void);
int fe_dec_setround(int rnd);

// Only if the implementation follows the recommended practice from F.2.2:
#define FE_SNANS_ALWAYS_SIGNAL /* implementation-defined */