NAME
feclearexcept,
fegetexceptflag,
feraiseexcept,
fesetexceptflag,
fetestexcept —
floating-point
exception flag manipulation
LIBRARY
Math Library (libm, -lm)
SYNOPSIS
#include <fenv.h>
#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
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
excepts.
The
fegetexceptflag() function stores the state of the
exception flags specified in
excepts in the opaque
object pointed to by
flagp. Similarly,
fesetexceptflag() changes the specified exception flags to
reflect the state stored in the object pointed to by
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.
SEE ALSO
sigaction(2),
feholdexcept(3),
fenv(3),
feupdateenv(3),
fpgetsticky(3)
STANDARDS
The
feclearexcept(),
fegetexceptflag(),
feraiseexcept(),
fesetexceptflag(), and
fetestexcept() routines conform to
ISO/IEC
9899:1999 (“ISO C99”).
HISTORY
These functions first appeared in
FreeBSD 5.3 and
NetBSD 6.0.