\" $NetBSD: feclearexcept.3,v 1.2 2010/08/07 18:13:12 wiz Exp $
\" Copyright (c) 2004 David Schultz <
[email protected]>
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Dd May 8, 2004
Dt FECLEAREXCEPT 3
Os
Sh NAME
Nm feclearexcept ,
Nm fegetexceptflag ,
Nm feraiseexcept ,
Nm fesetexceptflag ,
Nm fetestexcept
Nd floating-point exception flag manipulation
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"
Sh DESCRIPTION
The
Fn feclearexcept
routine clears the floating-point exception flags specified by
Fa excepts ,
whereas
Fn feraiseexcept
raises the specified exceptions.
Raising an exception causes the corresponding flag to be set,
and a
Dv SIGFPE
is delivered to the process if the exception is unmasked.
Pp
The
Fn fetestexcept
function determines which flags are currently set, of those specified by
Fa excepts .
Pp
The
Fn fegetexceptflag
function stores the state of the exception flags specified in
Fa excepts
in the opaque object pointed to by
Fa flagp .
Similarly,
Fn fesetexceptflag
changes the specified exception flags to reflect the state stored in
the object pointed to by
Fa flagp .
Note that the flags restored with
Fn fesetexceptflag
must be a (not necessarily proper) subset of the flags recorded by
a prior call to
Fn fegetexceptflag .
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 IMPLEMENTATION NOTES
On some architectures, raising an overflow or underflow exception
also causes an inexact exception to be raised.
In these cases, the overflow or underflow will be raised first.
Pp
The
Fn fegetexceptflag
and
Fn fesetexceptflag
routines are preferred to
Fn fetestexcept
and
Fn feraiseexcept ,
respectively, for saving and restoring exception flags.
The latter do not re-raise exceptions and may preserve
architecture-specific information such as addresses where
exceptions occurred.
Sh RETURN VALUES
The
Fn feclearexcept ,
Fn fegetexceptflag ,
Fn feraiseexcept ,
and
Fn fesetexceptflag
functions return 0 upon success, and non-zero otherwise.
The
Fn fetestexcept
function returns the bitwise OR of the values of the current exception
flags that were requested.
Sh SEE ALSO
Xr sigaction 2 ,
Xr feholdexcept 3 ,
Xr fenv 3 ,
Xr feupdateenv 3 ,
Xr fpgetsticky 3
Sh STANDARDS
The
Fn feclearexcept ,
Fn fegetexceptflag ,
Fn feraiseexcept ,
Fn fesetexceptflag ,
and
Fn fetestexcept
routines conform to
St -isoC-99 .
Sh HISTORY
These functions first appeared in
Fx 5.3
and
Nx 6.0 .
