.\" Copyright (c) 2011, Apple Inc.
.Dd May 9, 2011
.Dt FEGETENV 3
.Os
.Sh NAME
.Nm fegetenv, feholdexcept, fesetenv, feupdateenv
.Nd functions providing access to the floating-point environment.
.Sh SYNOPSIS
.Fd #include <fenv.h>
.Fd #pragma STDC FENV_ACCESS ON
.Ft int
.Fn fegetenv "fenv_t *envp"
.Ft int
.Fn feholdexcept "fenvt_t *envp"
.Ft int
.Fn fesetenv "fenv_t *envp"
.Ft int
.Fn feupdateenv "fenv_t *envp"
.Sh DESCRIPTION
These functions provide the means to manage the entire floating-point
environment--including both status flags and control modes--as a single entity.
.Pp
The
.Fn fegetenv
function attempts to store the current floating-point environment in the object
pointed to by
.Fa envp .
It returns zero if the environment was successfully stored, and a nonzero value
otherwise.
.Pp
The
.Fn feholdexcept
function saves the current floating-point environment in the object pointed to
by
.Fa envp ,
clears the floating-point status flags, and then installs a "non-stop" mode, if
available, under which no traps are taken for floating-point exceptions (as is
the case in default IEEE-754 floating-point execution).  It returns zero if and
only if such a mode was successfully installed.
.Pp
The
.Fn fesetenv
function attempts to establish the floating-point environment represented by
the object pointed to by
.Fa envp .
This object shall have been set by a call to
.Fn fegetenv 
or
.Fn feholdexcept ,
or be equal to a floating-point environment macro defined in <fenv.h>.  Note
that this function merely installs the floating-point status flags represented
by its argument, and does not raise the corresponding floating-point exceptions.
It returns zero if and only if the environment pointed to by 
.Fa envp
was successfully installed.
.Pp
The
.Fn feupdateenv
function attempts to save the currently raised floating-point flags, install 
the floating-point environment represented by 
.Fa *envp ,
and then raise the floating-point exceptions corresponding to the saved flags.
The object pointed to by
.Fa envp
shall have been set by a call to
.Fn fegetenv 
or
.Fn feholdexcept ,
or be equal to a floating-point environment macro defined in <fenv.h>.  It
returns zero if and only if all of the specified actions were successfully
carried out.
.Sh SEE ALSO
.Xr fenv 3 ,
.Xr feclearexcept 3 ,
.Xr fegetexceptflag 3 ,
.Xr fegetround 3 ,
.Xr feraiseexcept 3 ,
.Xr fesetexceptflag 3 ,
.Xr fesetround 3 ,
.Xr feraiseexcept 3
.Sh STANDARDS
These functions conform to ISO/IEC 9899:TC3.