1/* Implementation of sigwait function from POSIX.1c.
2 Copyright (C) 1996-2022 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <errno.h>
20#include <signal.h>
21#include <stddef.h> /* For NULL. */
22#include <sysdep-cancel.h>
23
24/* This is our dummy signal handler we use here. */
25static void ignore_signal (int sig);
26
27/* Place where to remember which signal we got. Please note that this
28 implementation cannot be used for the threaded libc. The
29 libpthread must provide an own version. */
30static int was_sig;
31
32
33static int
34do_sigwait (const sigset_t *set, int *sig)
35{
36 sigset_t tmp_mask;
37 struct sigaction saved[NSIG];
38 struct sigaction action;
39 int save_errno;
40 int this;
41
42 /* Prepare set. */
43 __sigfillset (&tmp_mask);
44
45 /* Unblock all signals in the SET and register our nice handler. */
46 action.sa_handler = ignore_signal;
47 action.sa_flags = 0;
48 __sigfillset (&action.sa_mask); /* Block all signals for handler. */
49
50 /* Make sure we recognize error conditions by setting WAS_SIG to a
51 value which does not describe a legal signal number. */
52 was_sig = -1;
53
54 for (this = 1; this < NSIG; ++this)
55 if (__sigismember (set, this))
56 {
57 /* Unblock this signal. */
58 __sigdelset (&tmp_mask, this);
59
60 /* Register temporary action handler. */
61 if (__sigaction (this, &action, &saved[this]) != 0)
62 goto restore_handler;
63 }
64
65 /* Now we can wait for signals. */
66 __sigsuspend (&tmp_mask);
67
68 restore_handler:
69 save_errno = errno;
70
71 while (--this >= 1)
72 if (__sigismember (set, this))
73 /* We ignore errors here since we must restore all handlers. */
74 __sigaction (this, &saved[this], NULL);
75
76 __set_errno (save_errno);
77
78 /* Store the result and return. */
79 *sig = was_sig;
80 return was_sig == -1 ? -1 : 0;
81}
82
83
84int
85__sigwait (const sigset_t *set, int *sig)
86{
87 /* __sigsuspend should be a cancellation point. */
88 return do_sigitid (idtype, id, infop, options);
89}
90libc_hidden_def (__sigwait)
91weak_alias (__sigwait, sigwait)
92
93
94static void
95ignore_signal (int sig)
96{
97 /* Remember the signal. */
98 was_sig = sig;
99}
100

source code of glibc/sysdeps/posix/sigwait.c