2004-06-06 11:06:26 +01:00
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.\" 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 FECLEAREXCEPT 3
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.Os
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.Sh NAME
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.Nm feclearexcept ,
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.Nm fegetexceptflag ,
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.Nm feraiseexcept ,
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.Nm fesetexceptflag ,
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.Nm fetestexcept
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.Nd floating-point exception flag manipulation
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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 feclearexcept "int excepts"
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.Ft int
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.Fn fegetexceptflag "fexcept_t *flagp" "int excepts"
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.Ft int
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.Fn feraiseexcept "int excepts"
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.Ft int
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.Fn fesetexceptflag "const fexcept_t *flagp" "int excepts"
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.Ft int
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.Fn fetestexcept "int excepts"
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.Sh DESCRIPTION
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The
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.Fn feclearexcept
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routine clears the floating-point exception flags specified by
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.Fa excepts ,
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whereas
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.Fn feraiseexcept
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raises the specified exceptions.
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Raising an exception causes the corresponding flag to be set,
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2005-01-14 09:12:05 +00:00
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and a
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.Dv SIGFPE
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is delivered to the process if the exception is unmasked.
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2004-06-06 11:06:26 +01:00
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.Pp
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The
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.Fn fetestexcept
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function determines which flags are currently set, of those specified by
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.Fa excepts .
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.Pp
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The
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.Fn fegetexceptflag
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function stores the state of the exception flags specified in
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.Fa excepts
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in the opaque object pointed to by
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.Fa flagp .
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Similarly,
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.Fn fesetexceptflag
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changes the specified exception flags to reflect the state stored in
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the object pointed to by
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.Fa flagp .
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Note that the flags restored with
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.Fn fesetexceptflag
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must be a (not necessarily proper) subset of the flags recorded by
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a prior call to
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.Fn fegetexceptflag .
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.Pp
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For all of these functions, the possible types of exceptions
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include those described in
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.Xr fenv 3 .
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Some architectures may define other types of floating-point exceptions.
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.Sh IMPLEMENTATION NOTES
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On some architectures, raising an overflow or underflow exception
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also causes an inexact exception to be raised.
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In these cases, the overflow or underflow will be raised first.
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.Pp
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The
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.Fn fegetexceptflag
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and
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.Fn fesetexceptflag
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routines are preferred to
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.Fn fetestexcept
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and
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.Fn feraiseexcept ,
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respectively, for saving and restoring exception flags.
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The latter do not re-raise exceptions and may preserve
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architecture-specific information such as addresses where
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exceptions occurred.
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.Sh RETURN VALUES
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2005-01-11 20:50:51 +00:00
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The
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2004-06-06 11:06:26 +01:00
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.Fn feclearexcept ,
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.Fn fegetexceptflag ,
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.Fn feraiseexcept ,
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and
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.Fn fesetexceptflag
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functions return 0 upon success, and non-zero otherwise.
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The
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.Fn fetestexcept
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function returns the bitwise OR of the values of the current exception
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flags that were requested.
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.Sh SEE ALSO
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.Xr sigaction 2 ,
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.Xr feholdexcept 3 ,
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.Xr fenv 3 ,
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.Xr feupdateenv 3 ,
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.Xr fpgetsticky 3 ,
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.Xr fpresetsticky 3
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.Sh STANDARDS
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The
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.Fn feclearexcept ,
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.Fn fegetexceptflag ,
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.Fn feraiseexcept ,
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.Fn fesetexceptflag ,
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and
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.Fn fetestexcept
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routines conform to
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.St -isoC-99 .
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.Sh HISTORY
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These functions first appeared in
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.Fx 5.3 .
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