feclearexceptfegetexceptflagferaiseexceptfesetexceptflagfetestexcept
- floating-point exception flag manipulation
LIBRARY
Lb libm
SYNOPSIS
#include <fenv.h>
Fd #pragma STDC FENV_ACCESS ON
int
feclearexcept (int excepts); int
fegetexceptflag (fexcept_t *flagp int excepts); int
feraiseexcept (int excepts); int
fesetexceptflag (const fexcept_t *flagp int excepts); int
fetestexcept (int excepts);
DESCRIPTION
The
feclearexcept ();
routine clears the floating-point exception flags specified by
Fa excepts ,
whereas
feraiseexcept ();
raises the specified exceptions.
Raising an exception causes the corresponding flag to be set,
and a
SIGFPE
is delivered to the process if the exception is unmasked.
The
fetestexcept ();
function determines which flags are currently set, of those specified by
Fa excepts .
The
fegetexceptflag ();
function stores the state of the exception flags specified in
Fa excepts
in the opaque object pointed to by
Fa flagp .
Similarly,
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
fesetexceptflag ();
must be a (not necessarily proper) subset of the flags recorded by
a prior call to
fegetexceptflag (.);
For all of these functions, the possible types of exceptions
include those described in
fenv(3).
Some architectures may define other types of floating-point exceptions.
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.
The
fegetexceptflag ();
and
fesetexceptflag ();
routines are preferred to
fetestexcept ();
and
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.
RETURN VALUES
The
feclearexcept (,);
fegetexceptflag (,);
feraiseexcept (,);
and
fesetexceptflag ();
functions return 0 upon success, and non-zero otherwise.
The
fetestexcept ();
function returns the bitwise OR of the values of the current exception
flags that were requested.
