libm/man/feclearexcept.3

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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 ,
.Xr fpresetsticky 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 .