The floating-point environment includes exception flags and masks, the current rounding mode, and other architecture-specific settings. However, it does not include the floating-point register file.

fegetenv stores the current floating-point environment in the object pointed to by envp, whereas feholdexcept() saves the current environment, then clears all exception flags and masks all floating-point exceptions.

fesetenv restores a previously saved environment. feupdateenv() restores a saved environment as well, but it also raises any exceptions that were set in the environment it replaces.

feholdexcept is often used with feupdateenv or fesetenv to suppress spurious exceptions that occur as a result of intermediate computations. An example in fenv(3) demonstrates how to do this.

Library

Math Library (libm, -lm)

#include <fenv.h>
#pragma STDC FENV_ACCESS ON

int
fegetenv(fenv_t *envp);

int
feholdexcept(fenv_t *envp);

int
fesetenv(const fenv_t *envp);

int
feupdateenv(const fenv_t *envp);

Return Values

0 (zero)

Success.

Any other value

Failure.

Standards

feclearexcept(3), fenv(3), feraiseexcept(3), fesetenv(3), fetestexcept(3), fpgetmask(3), fpgetprec(3), fpsetmask(3), fpsetprec(3)

History

These routines first appeared in FreeBSD 5.3.