libm/man/fegetenv.3

.\" Copyright (c) 2004 David Schultz <das@FreeBSD.org>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD: src/lib/msun/man/fegetenv.3,v 1.1 2004/06/06 10:06:26 das Exp $
.\"
.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 .