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Add documentation for:
- 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@
This commit is contained in:
David Schultz
parent
7ab6d2aa74
commit
07235cc8f7
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=130148
137
lib/msun/man/feclearexcept.3
Normal file
137
lib/msun/man/feclearexcept.3
Normal file
@ -0,0 +1,137 @@
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.\" 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
|
||||
.\" documentation and/or other materials provided with the distribution.
|
||||
.\"
|
||||
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
||||
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
||||
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
||||
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
||||
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
||||
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
||||
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
||||
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
||||
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
||||
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
||||
.\" SUCH DAMAGE.
|
||||
.\"
|
||||
.\" $FreeBSD$
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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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and a SIGFPE is delivered to the process if the exception is unmasked.
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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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The
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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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113
lib/msun/man/fegetenv.3
Normal file
113
lib/msun/man/fegetenv.3
Normal file
@ -0,0 +1,113 @@
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.\" Copyright (c) 2004 David Schultz <das@FreeBSD.org>
|
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.\" 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
|
||||
.\" documentation and/or other materials provided with the distribution.
|
||||
.\"
|
||||
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
||||
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
||||
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
||||
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
||||
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
||||
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
||||
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
||||
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
||||
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
||||
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
||||
.\" SUCH DAMAGE.
|
||||
.\"
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||||
.\" $FreeBSD$
|
||||
.\"
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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 ,
|
||||
.Fn feholdexcept ,
|
||||
.Fn fesetenv ,
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||||
and
|
||||
.Fn feupdateenv
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||||
functions conform to
|
||||
.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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85
lib/msun/man/fegetround.3
Normal file
85
lib/msun/man/fegetround.3
Normal file
@ -0,0 +1,85 @@
|
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.\" 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
|
||||
.\" documentation and/or other materials provided with the distribution.
|
||||
.\"
|
||||
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
||||
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
||||
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
||||
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
||||
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
||||
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
||||
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
||||
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
||||
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
||||
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
||||
.\" SUCH DAMAGE.
|
||||
.\"
|
||||
.\" $FreeBSD$
|
||||
.\"
|
||||
.Dd May 8, 2004
|
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.Dt FEGETROUND 3
|
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.Os
|
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.Sh NAME
|
||||
.Nm fegetround ,
|
||||
.Nm fesetround
|
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.Nd floating-point rounding control
|
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.Sh LIBRARY
|
||||
.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 fegetround "void"
|
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.Ft int
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.Fn fesetround "int round"
|
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.Sh DESCRIPTION
|
||||
The
|
||||
.Fn fegetround
|
||||
function determines the current floating-point rounding mode,
|
||||
and the
|
||||
.Fn fesetround
|
||||
function sets the current rounding mode to
|
||||
.Fa round .
|
||||
The rounding mode is one of
|
||||
.Dv FE_TONEAREST ,
|
||||
.Dv FE_DOWNWARD ,
|
||||
.Dv FE_UPWARD ,
|
||||
or
|
||||
.Dv FE_TOWARDZERO ,
|
||||
as described in
|
||||
.Xr fenv 3 .
|
||||
.Sh RETURN VALUES
|
||||
The
|
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.Fn fegetround
|
||||
routine returns the current rounding mode.
|
||||
The
|
||||
.Fn fesetround
|
||||
function returns 0 on success and non-zero otherwise;
|
||||
however, the present implementation always succeeds.
|
||||
.Sh SEE ALSO
|
||||
.Xr fenv 3 ,
|
||||
.Xr fpgetround 3 ,
|
||||
.Xr fpsetround 3
|
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.Sh STANDARDS
|
||||
The
|
||||
.Fn fegetround
|
||||
and
|
||||
.Fn fesetround
|
||||
functions conform to
|
||||
.St -isoC-99 .
|
||||
.Sh HISTORY
|
||||
These routines first appeared in
|
||||
.Fx 5.3 .
|
||||
They supersede the non-standard
|
||||
.Xr fpgetround 3
|
||||
and
|
||||
.Xr fpsetround 3
|
||||
functions.
|
||||
266
lib/msun/man/fenv.3
Normal file
266
lib/msun/man/fenv.3
Normal file
@ -0,0 +1,266 @@
|
||||
.\" 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
|
||||
.\" documentation and/or other materials provided with the distribution.
|
||||
.\"
|
||||
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
||||
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
||||
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
||||
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
||||
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
||||
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
||||
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
||||
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
||||
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
||||
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
||||
.\" SUCH DAMAGE.
|
||||
.\"
|
||||
.\" $FreeBSD$
|
||||
.\"
|
||||
.Dd May 8, 2004
|
||||
.Dt FENV 3
|
||||
.Os
|
||||
.Sh NAME
|
||||
.Nm feclearexcept ,
|
||||
.Nm fegetexceptflag ,
|
||||
.Nm feraiseexcept ,
|
||||
.Nm fesetexceptflag ,
|
||||
.Nm fetestexcept ,
|
||||
.Nm fegetround ,
|
||||
.Nm fesetround ,
|
||||
.Nm fegetenv ,
|
||||
.Nm feholdexcept ,
|
||||
.Nm fesetenv ,
|
||||
.Nm feupdateenv
|
||||
.Nd floating-point environment control
|
||||
.Sh LIBRARY
|
||||
.Lb libm
|
||||
.Sh SYNOPSIS
|
||||
.In fenv.h
|
||||
.Fd "#pragma STDC FENV_ACCESS ON"
|
||||
.Ft int
|
||||
.Fn feclearexcept "int excepts"
|
||||
.Ft int
|
||||
.Fn fegetexceptflag "fexcept_t *flagp" "int excepts"
|
||||
.Ft int
|
||||
.Fn feraiseexcept "int excepts"
|
||||
.Ft int
|
||||
.Fn fesetexceptflag "const fexcept_t *flagp" "int excepts"
|
||||
.Ft int
|
||||
.Fn fetestexcept "int excepts"
|
||||
.Ft int
|
||||
.Fn fegetround "void"
|
||||
.Ft int
|
||||
.Fn fesetround "int round"
|
||||
.Ft int
|
||||
.Fn fegetenv "fenv_t *envp"
|
||||
.Ft int
|
||||
.Fn feholdexcept "fenv_t *envp"
|
||||
.Ft int
|
||||
.Fn fesetenv "const fenv_t *envp"
|
||||
.Ft int
|
||||
.Fn feupdateenv "const fenv_t *envp"
|
||||
.Sh DESCRIPTION
|
||||
The fenv routines manipulate the floating-point environment,
|
||||
which includes the exception flags and rounding modes defined in
|
||||
.St -ieee754 .
|
||||
.Ss Exceptions
|
||||
Exception flags are set as side-effects of floating-point arithmetic
|
||||
operations and math library routines, and they remain set until
|
||||
explicitly cleared.
|
||||
The following macros expand to bit flags of type
|
||||
.Vt int
|
||||
representing the five standard floating-point exceptions.
|
||||
.Bl -tag -width ".Dv FE_DIVBYZERO"
|
||||
.It Dv "FE_DIVBYZERO"
|
||||
A divide-by-zero exception occurs when the program attempts to
|
||||
divide a finite non-zero number by zero.
|
||||
.It Dv "FE_INEXACT"
|
||||
An inexact exception is raised whenever there is a loss of precision
|
||||
due to rounding.
|
||||
.It Dv "FE_INVALID"
|
||||
Invalid operation exceptions occur when a program attempts to
|
||||
perform calculations for which there is no reasonable representable
|
||||
answer.
|
||||
For instance, subtraction of infinities, division of zero by zero,
|
||||
ordered comparison involving
|
||||
.Na
|
||||
s, and taking the square root of a
|
||||
negative number are all invalid operations.
|
||||
.It Dv "FE_OVERFLOW"
|
||||
An overflow exception occurs when the magnitude of the result of a
|
||||
computation is too large to fit in the destination type.
|
||||
.It Dv "FE_UNDERFLOW"
|
||||
Underflow occurs when the result of a computation is too close to zero
|
||||
to be represented as a non-zero value in the destination type.
|
||||
.El
|
||||
.Pp
|
||||
Additionally, the
|
||||
.Dv FE_ALL_EXCEPT
|
||||
macro expands to the bitwise OR of the above flags and any
|
||||
architecture-specific flags.
|
||||
Combinations of these flags are passed to the
|
||||
.Fn feclearexcept ,
|
||||
.Fn fegetexceptflag ,
|
||||
.Fn feraiseexcept ,
|
||||
.Fn fesetexceptflag ,
|
||||
and
|
||||
.Fn fetestexcept
|
||||
functions to clear, save, raise, restore, and examine the
|
||||
processor's floating-point exception flags, respectively.
|
||||
.Ss Rounding Modes
|
||||
.St -ieee754
|
||||
specifies four rounding modes.
|
||||
These modes control the direction in which results are rounded
|
||||
from their exact values in order to fit them into binary
|
||||
floating-point variables.
|
||||
The four modes correspond with the following symbolic constants.
|
||||
.Bl -tag -width ".Dv FE_TOWARDZERO"
|
||||
.It Dv "FE_TONEAREST"
|
||||
Results are rounded to the closest representable value.
|
||||
If the exact result is exactly half way between two representable
|
||||
values, the value whose last binary digit is even (zero) is chosen.
|
||||
This is the default mode.
|
||||
.It Dv "FE_DOWNWARD"
|
||||
Results are rounded towards negative \*[If].
|
||||
.It Dv "FE_UPWARD"
|
||||
Results are rounded towards positive \*[If].
|
||||
.It Dv "FE_TOWARDZERO"
|
||||
Results are rounded towards zero.
|
||||
.El
|
||||
.Pp
|
||||
The
|
||||
.Fn fegetround
|
||||
and
|
||||
.Fn fesetround
|
||||
functions query and set the rounding mode.
|
||||
.Ss Environment Control
|
||||
The
|
||||
.Fn fegetenv
|
||||
and
|
||||
.Fn fesetenv
|
||||
functions save and restore the floating-point environment,
|
||||
which includes exception flags, the current exception mask,
|
||||
the rounding mode, and possibly other implementation-specific
|
||||
state.
|
||||
The
|
||||
.Fn feholdexcept
|
||||
function behaves like
|
||||
.Fn fegetenv ,
|
||||
but with the additional effect of clearing the exception flags and
|
||||
installing a
|
||||
.Em non-stop
|
||||
mode.
|
||||
In non-stop mode, floating-point operations will set exception flags
|
||||
as usual, but no
|
||||
.Dv SIGFPE
|
||||
signals will be generated as a result.
|
||||
Non-stop mode is the default, but it may be altered by
|
||||
non-standard mechanisms.
|
||||
.\" XXX Mention fe[gs]etmask() here after the interface is finalized
|
||||
.\" XXX and ready to be officially documented.
|
||||
The
|
||||
.Fn feupdateenv
|
||||
function restores a saved environment similarly to
|
||||
.Fn fesetenv ,
|
||||
but it also re-raises any floating-point exceptions from the old
|
||||
environment.
|
||||
.Pp
|
||||
The macro
|
||||
.Dv FE_DFL_ENV
|
||||
expands to a pointer to the default environment.
|
||||
.Sh CAVEATS
|
||||
The FENV_ACCESS pragma can be enabled with
|
||||
.Dl "#pragma STDC FENV_ACCESS ON"
|
||||
and disabled with the
|
||||
.Dl "#pragma STDC FENV_ACCESS OFF"
|
||||
directive.
|
||||
This lexically-scoped annotation tells the compiler that the program
|
||||
may access the floating-point environment, so optimizations that would
|
||||
violate strict IEEE-754 semantics are disabled.
|
||||
If execution reaches a block of code for which
|
||||
.Dv FENV_ACCESS
|
||||
is off, the floating-point environment will become undefined.
|
||||
.Sh EXAMPLES
|
||||
The following routine computes the square root function.
|
||||
It explicitly raises an invalid exception on appropriate inputs using
|
||||
.Fn feraiseexcept .
|
||||
It also defers inexact exceptions while it computes intermediate
|
||||
values, and then it allows an inexact exception to be raised only if
|
||||
the final answer is inexact.
|
||||
.Bd -literal -offset indent
|
||||
#pragma STDC FENV_ACCESS ON
|
||||
double sqrt(double n) {
|
||||
double x = 1.0;
|
||||
fenv_t env;
|
||||
|
||||
if (isnan(n) || n < 0.0) {
|
||||
feraiseexcept(FE_INVALID);
|
||||
return (NAN);
|
||||
}
|
||||
if (isinf(n) || n == 0.0)
|
||||
return (n);
|
||||
feholdexcept(&env);
|
||||
while (fabs((x * x) - n) > DBL_EPSILON * 2 * x)
|
||||
x = (x / 2) + (n / (2 * x));
|
||||
if (x * x == n)
|
||||
feclearexcept(FE_INEXACT);
|
||||
feupdateenv(&env);
|
||||
return (x);
|
||||
}
|
||||
.Ed
|
||||
.Sh SEE ALSO
|
||||
.Xr cc 1 ,
|
||||
.Xr feclearexcept 3 ,
|
||||
.Xr fegetenv 3 ,
|
||||
.Xr fegetexceptflag 3 ,
|
||||
.Xr fegetround 3 ,
|
||||
.Xr feholdexcept 3 ,
|
||||
.Xr feraiseexcept 3 ,
|
||||
.Xr fesetenv 3 ,
|
||||
.Xr fesetexceptflag 3 ,
|
||||
.Xr fesetround 3 ,
|
||||
.Xr fetestexcept 3 ,
|
||||
.Xr feupdateenv 3 ,
|
||||
.Xr fpgetmask 3 ,
|
||||
.Xr fpgetprec 3 ,
|
||||
.Xr fpgetsticky 3 ,
|
||||
.Xr fpgetround 3 ,
|
||||
.Xr fpresetsticky 3 ,
|
||||
.Xr fpsetmask 3 ,
|
||||
.Xr fpsetprec 3 ,
|
||||
.Xr fpsetround 3
|
||||
.Sh STANDARDS
|
||||
Except as noted below,
|
||||
.In fenv.h
|
||||
conforms to
|
||||
.St -isoC-99 .
|
||||
.Sh HISTORY
|
||||
The
|
||||
.In fenv.h
|
||||
header first appeared in
|
||||
.Fx 5.3 .
|
||||
It supersedes the non-standard routines defined in
|
||||
.In ieeefp.h
|
||||
and documented in
|
||||
.Xr fpgetround 3 .
|
||||
.Sh BUGS
|
||||
The
|
||||
.Dv FENV_ACCESS
|
||||
pragma is unimplemented in the system compiler.
|
||||
However, non-constant expressions generally produce the correct
|
||||
side-effects at low optimization levels.
|
||||
.Pp
|
||||
On the Alpha platform,
|
||||
.Xr cc 1
|
||||
must be passed the
|
||||
.Fl mieee-with-inexact mfp-rounding-mode=d
|
||||
options in order to generate code that has the standard
|
||||
side-effects and uses the specified rounding modes.
|
||||
Loading…
Reference in New Issue
Block a user