NAME
feenableexcept,
fedisableexcept,
fegetexcept —
floating-point
exception masking
LIBRARY
Math Library (libm, -lm)
SYNOPSIS
#include <fenv.h>
#pragma STDC FENV_ACCESS ON
int
feenableexcept(
int
excepts);
int
fedisableexcept(
int
excepts);
int
fegetexcept(
void);
DESCRIPTION
The
feenableexcept() and
fedisableexcept()
functions unmask and mask (respectively) exceptions specified in
excepts. The
fegetexcept() function
returns the current exception mask. All exceptions are masked by default.
Floating-point operations that produce unmasked exceptions will trap, and a
SIGFPE
will be delivered to the process. By installing
a signal handler for
SIGFPE
, applications can take
appropriate action immediately without testing the exception flags after every
operation. Note that the trap may not be immediate, but it should occur before
the next floating-point instruction is executed.
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.
RETURN VALUES
The
feenableexcept(),
fedisableexcept(), and
fegetexcept() functions return a bitmap of the exceptions
that were unmasked prior to the call.
SEE ALSO
sigaction(2),
feclearexcept(3),
feholdexcept(3),
fenv(3),
feupdateenv(3)
BUGS
Functions in the standard library may trigger exceptions multiple times as a
result of intermediate computations; however, they generally do not trigger
spurious exceptions.
No interface is provided to permit exceptions to be handled in nontrivial ways.
There is no uniform way for an exception handler to access information about
the exception-causing instruction, or to determine whether that instruction
should be reexecuted after returning from the handler.