4.78 <fenv.h> floating-point environment access in C99

The C99 standard header file <fenv.h> provides access to an IEEE 754-compliant floating-point environment for numerical programming.

The library introduces two types and numerous macros and functions for managing and controlling floating-point state.
The new types supported are:
  • fenv_t, representing the entire floating-point environment.
  • fexcept_t, representing the floating-point state.
New macros supported include:
  • FE_DIVBYZERO, FE_INEXACT, FE_INVALID, FE_OVERFLOW and FE_UNDERFLOW for managing floating-point exceptions.
  • FE_DOWNWARD, FE_TONEAREST, FE_TOWARDZERO, FE_UPWARD for managing rounding in the represented rounding direction.
  • FE_DFL_ENV, representing the default floating-point environment.
New functions include:
int feclearexcept(int ex); // clear floating-point exceptions selected by ex
int feraiseexcept(int ex); // raise floating point exceptions selected by ex
int fetestexcept(int ex); // test floating point exceptions selected by ex
int fegetround(void); // return the current rounding mode
int fesetround(int mode); // set the current rounding mode given by mode
int fegetenv(fenv_t *penv); return the floating-point environment in penv
int fesetenv(const fenv_t *penv); // set the floating-point environment to penv
Related concepts
4.60 New library features of C99
4.74 Additional <math.h> library functions in C99
4.75 Complex numbers in C99
4.76 Boolean type and <stdbool.h> in C99
4.77 Extended integer types and functions in <inttypes.h> and <stdint.h> in C99
4.79 <stdio.h> snprintf family of functions in C99
4.80 <tgmath.h> type-generic math macros in C99
4.81 <wchar.h> wide character I/O functions in C99
Related information
Institute of Electrical and Electronics Engineers
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