xref: /netbsd-src/lib/libm/man/fegetenv.3 (revision 3b43a9401a5b6f1de7e9441c24b1bb6da04181d3)

.\"	$NetBSD: fegetenv.3,v 1.2 2010/08/04 18:58:18 wiz Exp $
.\" Copyright (c) 2004 David Schultz <das@FreeBSD.org>
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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 .