.\"	$OpenBSD: fegetenv.3,v 1.4 2018/03/16 16:58:26 schwarze Exp $
.\"
.\" Copyright (c) 2011 Martynas Venckus <martynas@openbsd.org>
.\"
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.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
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.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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.Dd $Mdocdate: March 16 2018 $
.Dt FEGETENV 3
.Os
.Sh NAME
.Nm fegetenv ,
.Nm feholdexcept ,
.Nm fesetenv ,
.Nm feupdateenv
.Nd manage floating-point environment
.Sh SYNOPSIS
.In fenv.h
.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
These functions manage the floating-point environment \(em status
flags, rounding direction modes and exception masks \(em as one entity.
The
.Fa envp
input argument is an object representing the floating-point environment.
The macro
.Dv FE_DFL_ENV
represents the default floating-point environment \(em the one installed
at program startup.
.Pp
The
.Fn fegetenv
function stores the current floating-point environment in the object
pointed to by
.Pa envp .
.Pp
The
.Fn feholdexcept
function saves the current floating-point environment in the object
pointed to by
.Pa envp ,
clears the floating-point status flags, and then installs a non-stop
(continue on floating-point exceptions) mode for all floating-point
exceptions.
.Pp
The
.Fn fesetenv
function establishes the floating-point environment represented by
the object pointed to by
.Pa envp .
The argument
.Pa envp
shall point to an object set by a call to
.Fn fegetenv
or
.Fn feholdexcept ,
or equal the macro
.Dv FE_DFL_ENV .
Note that
.Fn fesetenv
merely installs the state of the floating-point status flags
represented through its argument, and does not raise these
floating-point exceptions.
.Pp
The
.Fn feupdateenv
function saves the currently raised floating-point exceptions in
its automatic storage, installs the floating-point environment
represented by the object pointed to by
.Pa envp ,
and then raises the saved floating-point exceptions.
The argument
.Pa envp
shall point to an object set by a call to
.Fn feholdexcept
or
.Fn fegetenv ,
or equal the macro
.Dv FE_DFL_ENV .
.Sh RETURN VALUES
The
.Fn fegetenv ,
.Fn feholdexcept ,
.Fn fesetenv ,
and
.Fn feupdateenv
functions return zero on success, and non-zero if an error occurred.
.Sh SEE ALSO
.Xr feclearexcept 3 ,
.Xr feenableexcept 3 ,
.Xr fegetround 3
.Sh STANDARDS
The
.Fn fegetenv ,
.Fn feholdexcept ,
.Fn fesetenv ,
and
.Fn feupdateenv
functions conform to
.St -isoC-99 .
.Pp
The return types for
.Fn fegetenv ,
.Fn fesetenv ,
and
.Fn feupdateenv
are
.Vt int
for alignment with
.St -isoC-99
Defect Report #202.