07235cc8f7
- fenv(3) - feclearexcept(3), fegetexceptflag(3), feraiseexcept(3), fesetexceptflag(3), fetestexcept(3) - fegetround(3), fesetround(3) - fegetenv(3), feholdexcept(3), fesetenv(3), feupdateenv(3) Reviewed by: standards@
114 lines
3.1 KiB
Groff
114 lines
3.1 KiB
Groff
.\" Copyright (c) 2004 David Schultz <das@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd May 8, 2004
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.Dt FEGETENV 3
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.Os
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.Sh NAME
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.Nm fegetenv ,
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.Nm feholdexcept ,
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.Nm fesetenv ,
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.Nm feupdateenv
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.Nd floating-point environment save and restore
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.Sh LIBRARY
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.Lb libm
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.Sh SYNOPSIS
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.In fenv.h
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.Fd "#pragma STDC FENV_ACCESS ON"
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.Ft int
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.Fn fegetenv "fenv_t *envp"
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.Ft int
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.Fn feholdexcept "fenv_t *envp"
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.Ft int
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.Fn fesetenv "const fenv_t *envp"
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.Ft int
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.Fn feupdateenv "const fenv_t *envp"
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.Sh DESCRIPTION
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The floating-point environment includes exception flags and masks, the
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current rounding mode, and other architecture-specific settings.
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However, it does not include the floating-point register file.
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.Pp
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The
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.Fn fegetenv
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function stores the current floating-point environment in the object
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pointed to by
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.Fa envp ,
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whereas
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.Fn feholdexcept
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saves the current environment, then clears all exception flags
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and masks all floating-point exceptions.
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.Pp
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The
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.Fn fesetenv
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function restores a previously saved environment.
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The
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.Fn feupdateenv
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function restores a saved environment as well, but it also
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raises any exceptions that were set in the environment it
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replaces.
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.Pp
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The
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.Fn feholdexcept
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function is often used with
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.Fn feupdateenv
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or
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.Fn fesetenv
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to suppress spurious exceptions that occur as a result of
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intermediate computations.
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An example in
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.Xr fenv 3
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demonstrates how to do this.
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.Sh RETURN VALUES
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The
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.Fn fegetenv ,
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.Fn feholdexcept ,
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.Fn fesetenv ,
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and
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.Fn feupdateenv
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functions return 0 if they succeed, and non-zero otherwise.
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.Sh SEE ALSO
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.Xr feclearexcept 3 ,
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.Xr fenv 3 ,
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.Xr feraiseexcept 3 ,
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.Xr fesetenv 3 ,
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.Xr fetestexcept 3 ,
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.Xr fpgetmask 3 ,
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.Xr fpgetprec 3 ,
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.Xr fpsetmask 3 ,
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.Xr fpsetprec 3
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.Sh STANDARDS
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The
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.Fn fegetenv ,
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.Fn feholdexcept ,
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.Fn fesetenv ,
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and
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.Fn feupdateenv
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functions conform to
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.St -isoC-99 .
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.Sh HISTORY
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These routines first appeared in
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.Fx 5.3 .
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