99 lines
3.2 KiB
Groff
99 lines
3.2 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 March 16, 2005
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.Dt FEENABLEEXCEPT 3
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.Os
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.Sh NAME
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.Nm feenableexcept ,
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.Nm fedisableexcept ,
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.Nm fegetexcept
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.Nd floating-point exception masking
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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 feenableexcept "int excepts"
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.Ft int
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.Fn fedisableexcept "int excepts"
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.Ft int
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.Fn fegetexcept "void"
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.Sh DESCRIPTION
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The
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.Fn feenableexcept
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and
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.Fn fedisableexcept
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functions
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unmask and mask (respectively) exceptions specified in
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.Fa excepts .
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The
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.Fn fegetexcept
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function
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returns the current exception mask.
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All exceptions are masked by default.
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.Pp
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Floating-point operations that produce unmasked exceptions will trap, and a
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.Dv SIGFPE
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will be delivered to the process.
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By installing a signal handler for
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.Dv SIGFPE ,
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applications can take appropriate action immediately without
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testing the exception flags after every operation.
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Note that the trap may not be immediate, but it should occur
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before the next floating-point instruction is executed.
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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 RETURN VALUES
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The
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.Fn feenableexcept ,
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.Fn fedisableexcept ,
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and
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.Fn fegetexcept
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functions return a bitmap of the exceptions that were unmasked
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prior to the call.
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.Sh SEE ALSO
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.Xr sigaction 2 ,
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.Xr feclearexcept 3 ,
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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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.Sh BUGS
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Functions in the standard library may trigger exceptions multiple
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times as a result of intermediate computations;
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however, they generally do not trigger spurious exceptions.
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.Pp
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No interface is provided to permit exceptions to be handled in
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nontrivial ways.
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There is no uniform way for an exception handler to access
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information about the exception-causing instruction, or
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to determine whether that instruction should be reexecuted
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after returning from the handler.
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