minix/lib/libm/man/feenableexcept.3
Ben Gras 2fe8fb192f Full switch to clang/ELF. Drop ack. Simplify.
There is important information about booting non-ack images in
docs/UPDATING. ack/aout-format images can't be built any more, and
booting clang/ELF-format ones is a little different. Updating to the
new boot monitor is recommended.

Changes in this commit:

	. drop boot monitor -> allowing dropping ack support
	. facility to copy ELF boot files to /boot so that old boot monitor
	  can still boot fairly easily, see UPDATING
	. no more ack-format libraries -> single-case libraries
	. some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases
	. drop several ack toolchain commands, but not all support
	  commands (e.g. aal is gone but acksize is not yet).
	. a few libc files moved to netbsd libc dir
	. new /bin/date as minix date used code in libc/
	. test compile fix
	. harmonize includes
	. /usr/lib is no longer special: without ack, /usr/lib plays no
	  kind of special bootstrapping role any more and bootstrapping
	  is done exclusively through packages, so releases depend even
	  less on the state of the machine making them now.
	. rename nbsd_lib* to lib*
	. reduce mtree
2012-02-14 14:52:02 +01:00

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.\" $NetBSD: feenableexcept.3,v 1.1 2010/07/31 21:47:53 joerg Exp $
.\" Copyright (c) 2004 David Schultz <das@FreeBSD.org>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.Dd March 16, 2005
.Dt FEENABLEEXCEPT 3
.Os
.Sh NAME
.Nm feenableexcept ,
.Nm fedisableexcept ,
.Nm fegetexcept
.Nd floating-point exception masking
.Sh LIBRARY
.Lb libm
.Sh SYNOPSIS
.In fenv.h
.Fd "#pragma STDC FENV_ACCESS ON"
.Ft int
.Fn feenableexcept "int excepts"
.Ft int
.Fn fedisableexcept "int excepts"
.Ft int
.Fn fegetexcept "void"
.Sh DESCRIPTION
The
.Fn feenableexcept
and
.Fn fedisableexcept
functions
unmask and mask (respectively) exceptions specified in
.Fa excepts .
The
.Fn fegetexcept
function
returns the current exception mask.
All exceptions are masked by default.
.Pp
Floating-point operations that produce unmasked exceptions will trap, and a
.Dv SIGFPE
will be delivered to the process.
By installing a signal handler for
.Dv SIGFPE ,
applications can take appropriate action immediately without
testing the exception flags after every operation.
Note that the trap may not be immediate, but it should occur
before the next floating-point instruction is executed.
.Pp
For all of these functions, the possible types of exceptions
include those described in
.Xr fenv 3 .
Some architectures may define other types of floating-point exceptions.
.Sh RETURN VALUES
The
.Fn feenableexcept ,
.Fn fedisableexcept ,
and
.Fn fegetexcept
functions return a bitmap of the exceptions that were unmasked
prior to the call.
.Sh SEE ALSO
.Xr sigaction 2 ,
.Xr feclearexcept 3 ,
.Xr feholdexcept 3 ,
.Xr fenv 3 ,
.Xr feupdateenv 3
.Sh BUGS
Functions in the standard library may trigger exceptions multiple
times as a result of intermediate computations;
however, they generally do not trigger spurious exceptions.
.Pp
No interface is provided to permit exceptions to be handled in
nontrivial ways.
There is no uniform way for an exception handler to access
information about the exception-causing instruction, or
to determine whether that instruction should be reexecuted
after returning from the handler.