NAME
feclearexcept,
fegetexceptflag,
feraiseexcept,
fesetexceptflag,
fetestexcept —
access floating-point status
flags
SYNOPSIS
#include
<fenv.h>
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
These functions provide access to the floating-point status flags. The excepts input argument is a bitmask specifying an exception type and containing any of the values listed below.
FE_DIVBYZERO- A divide-by-zero exception occurs when the program attempts to divide a finite non-zero number by zero.
FE_INEXACT- An inexact exception is raised whenever there is a loss of precision due to rounding.
FE_INVALID- Invalid operation exceptions occur when a program attempts to perform
calculations for which there is no reasonable representable answer.
For instance, subtraction of infinities, division of zero by zero, ordered comparison involving NaNs, and taking the square root of a negative number are all invalid operations.
FE_OVERFLOW- An overflow exception occurs when the magnitude of the result of a computation is too large to fit in the destination type.
FE_UNDERFLOW- Underflow occurs when the result of a computation is too close to zero to be represented as a non-zero value in the destination type.
FE_DENORMAL- Denormalization exception occurs when the result of a floating-point
expression is a denormalized number.
This is available only on the floating-point implementations of amd64 and i386 processors.
Additionally, the macro FE_ALL_EXCEPT is
simply the bitwise OR of all floating-point exception macros listed
above.
The
feclearexcept()
function clears the floating-point exceptions represented by
excepts.
The
fegetexceptflag()
function stores a representation of the states of the floating-point flags
indicated by excepts in the object pointed to by
flagp.
The
feraiseexcept()
function raises floating-point exceptions represented by
excepts.
The
fesetexceptflag()
function sets the floating-point status flags indicated by
excepts to the states stored in the object pointed
to by flagp. The value of
flagp shall have been set by a previous call to
fegetexceptflag() whose second argument represented
at least those floating-point exceptions represented by
excepts. This function does not raise floating-point
exceptions, but only sets the state of the flags.
The
fetesteexcept()
function determines which of a specified subset of the floating-point
exception flags are currently set. The excepts
specifies the floating-point status flags to be queried.
RETURN VALUES
The feclearexcept(),
fegetexceptflag(),
feraiseexcept(), and
fesetexceptflag() functions return zero on success,
and non-zero if an error occurred. The
fetestexcept() function returns a bitmask of a
specified subset of the floating-point exception flags which are currently
set.
SEE ALSO
STANDARDS
The feclearexcept(),
fegetexceptflag(),
feraiseexcept(),
fesetexceptflag(), and
fetestexcept() functions conform to
ISO/IEC 9899:1999
(“ISO C99”).
The return types for feclearexcept(),
fegetexceptflag(),
feraiseexcept(), and
fesetexceptflag() are int for
alignment with ISO/IEC 9899:1999
(“ISO C99”) Defect Report #202.
HISTORY
These functions first appeared in OpenBSD 5.0.
CAVEATS
On some architectures, feraiseexcept()
additionally raises the “inexact” floating-point exception
whenever it raises the “overflow” or “underflow”
floating-point exception.