инициализировать и очистить набор сигналов (initialize and empty a signal set)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
sigemptyset — initialize and empty a signal set
Синопсис (Synopsis)
#include <signal.h>
int sigemptyset(sigset_t *set);
Описание (Description)
The sigemptyset() function initializes the signal set pointed to
by set, such that all signals defined in POSIX.1‐2008 are
excluded.
Возвращаемое значение (Return value)
Upon successful completion, sigemptyset() shall return 0;
otherwise, it shall return -1 and set errno to indicate the
error.
Ошибки (Error)
No errors are defined.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
None.
Обоснование (Rationale)
The implementation of the sigemptyset() (or sigfillset())
function could quite trivially clear (or set) all the bits in the
signal set. Alternatively, it would be reasonable to initialize
part of the structure, such as a version field, to permit binary-
compatibility between releases where the size of the set varies.
For such reasons, either sigemptyset() or sigfillset() must be
called prior to any other use of the signal set, even if such use
is read-only (for example, as an argument to sigpending()). This
function is not intended for dynamic allocation.
The sigfillset() and sigemptyset() functions require that the
resulting signal set include (or exclude) all the signals defined
in this volume of POSIX.1‐2017. Although it is outside the scope
of this volume of POSIX.1‐2017 to place this requirement on
signals that are implemented as extensions, it is recommended
that implementation-defined signals also be affected by these
functions. However, there may be a good reason for a particular
signal not to be affected. For example, blocking or ignoring an
implementation-defined signal may have undesirable side-effects,
whereas the default action for that signal is harmless. In such a
case, it would be preferable for such a signal to be excluded
from the signal set returned by sigfillset().
In early proposals there was no distinction between invalid and
unsupported signals (the names of optional signals that were not
supported by an implementation were not defined by that
implementation). The [EINVAL] error was thus specified as a
required error for invalid signals. With that distinction, it is
not necessary to require implementations of these functions to
determine whether an optional signal is actually supported, as
that could have a significant performance impact for little
value. The error could have been required for invalid signals and
optional for unsupported signals, but this seemed unnecessarily
complex. Thus, the error is optional in both cases.
Будущие направления (Future directions)
None.
Смотри также (See also)
Section 2.4, Signal Concepts, pthread_sigmask(3p), sigaction(3p),
sigaddset(3p), sigdelset(3p), sigfillset(3p), sigismember(3p),
sigpending(3p), sigsuspend(3p)
The Base Definitions volume of POSIX.1‐2017, signal.h(0p)
