SIGPENDING(2) Linux Programmer's Manual SIGPENDING(2)
sigpending, rt_sigpending - examine pending signals
int sigpending(sigset_t *set);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
sigpending() returns the set of signals that are pending for delivery
to the calling thread (i.e., the signals which have been raised while
blocked). The mask of pending signals is returned in set.
sigpending() returns 0 on success and -1 on error. In the event of an
error, errno is set to indicate the cause.
EFAULT set points to memory which is not a valid part of the process
See sigsetops(3) for details on manipulating signal sets.
If a signal is both blocked and has a disposition of "ignored", it is
not added to the mask of pending signals when generated.
The set of signals that is pending for a thread is the union of the set
of signals that is pending for that thread and the set of signals that
is pending for the process as a whole; see signal(7).
A child created via fork(2) initially has an empty pending signal set;
the pending signal set is preserved across an execve(2).
C library/kernel differences
The original Linux system call was named sigpending(). However, with
the addition of real-time signals in Linux 2.2, the fixed-size, 32-bit
sigset_t argument supported by that system call was no longer fit for
purpose. Consequently, a new system call, rt_sigpending(), was added
to support an enlarged sigset_t type. The new system call takes a sec‐
ond argument, size_t sigsetsize, which specifies the size in bytes of
the signal set in set. The glibc sigpending() wrapper function hides
these details from us, transparently calling rt_sigpending() when the
kernel provides it.
In versions of glibc up to and including 2.2.1, there is a bug in the
wrapper function for sigpending() which means that information about
pending real-time signals is not correctly returned.
kill(2), sigaction(2), signal(2), sigprocmask(2), sigsuspend(2), sigse‐
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Linux 2017-09-15 SIGPENDING(2)