NAME
fegetenv,
feholdexcept, fesetenv,
feupdateenv —
floating-point environment save and
restore
LIBRARY
library “libm”
SYNOPSIS
#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);
DESCRIPTION
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.The
fegetenv()
function 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.
The
fesetenv()
function restores a previously saved environment. The
feupdateenv()
function restores a saved environment as well, but it also raises any
exceptions that were set in the environment it replaces.
The
feholdexcept()
function 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.
RETURN VALUES
The fegetenv(),
feholdexcept(), fesetenv(),
and feupdateenv() functions return 0 if they
succeed, and non-zero otherwise.
SEE ALSO
feclearexcept(3), fenv(3), feraiseexcept(3), fesetenv(3), fetestexcept(3), fpgetmask(3), fpgetprec(3), fpsetmask(3), fpsetprec(3)
STANDARDS
The fegetenv(),
feholdexcept(), fesetenv(),
and feupdateenv() functions conform to
ISO/IEC 9899:1999
(“ISO C99”).
HISTORY
These routines first appeared in FreeBSD 5.3.