NAME
feclearexcept,
fegetexceptflag,
feraiseexcept,
fesetexceptflag,
fetestexcept —
floating-point exception flag
manipulation
LIBRARY
library “libm”
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
Thefeclearexcept()
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), fpresetsticky(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.