\" $NetBSD: fegetenv.3,v 1.2 2010/08/04 18:58:18 wiz Exp $
\" Copyright (c) 2004 David Schultz <
[email protected]>
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Dd May 8, 2004
Dt FEGETENV 3
Os
Sh NAME
Nm fegetenv ,
Nm feholdexcept ,
Nm fesetenv ,
Nm feupdateenv
Nd floating-point environment save and restore
Sh LIBRARY
Lb libm
Sh SYNOPSIS
In fenv.h
Fd "#pragma STDC FENV_ACCESS ON"
Ft int
Fn fegetenv "fenv_t *envp"
Ft int
Fn feholdexcept "fenv_t *envp"
Ft int
Fn fesetenv "const fenv_t *envp"
Ft int
Fn feupdateenv "const fenv_t *envp"
Sh 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.
Pp
The
Fn fegetenv
function stores the current floating-point environment in the object
pointed to by
Fa envp ,
whereas
Fn feholdexcept
saves the current environment, then clears all exception flags
and masks all floating-point exceptions.
Pp
The
Fn fesetenv
function restores a previously saved environment.
The
Fn feupdateenv
function restores a saved environment as well, but it also
raises any exceptions that were set in the environment it
replaces.
Pp
The
Fn feholdexcept
function is often used with
Fn feupdateenv
or
Fn fesetenv
to suppress spurious exceptions that occur as a result of
intermediate computations.
An example in
Xr fenv 3
demonstrates how to do this.
Sh RETURN VALUES
The
Fn fegetenv ,
Fn feholdexcept ,
Fn fesetenv ,
and
Fn feupdateenv
functions return 0 if they succeed, and non-zero otherwise.
Sh SEE ALSO
Xr feclearexcept 3 ,
Xr fenv 3 ,
Xr feraiseexcept 3 ,
Xr fesetenv 3 ,
Xr fetestexcept 3 ,
Xr fpgetmask 3 ,
\"Xr fpgetprec 3 ,
Xr fpsetmask 3
\"Xr fpsetprec 3
Sh STANDARDS
The
Fn fegetenv ,
Fn feholdexcept ,
Fn fesetenv ,
and
Fn feupdateenv
functions conform to
St -isoC-99 .
Sh HISTORY
These routines first appeared in
Fx 5.3
and
Nx 6.0 .
