NAME
fegetenv,
feholdexcept,
fesetenv,
feupdateenv —
floating-point environment save and restore
LIBRARY
Math Library (libm, -lm)
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),
fpsetmask(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 and
NetBSD 6.0.