1/* Copyright (C) 1998-2022 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include <errno.h>
19#define __need_NULL
20#include <stddef.h>
21#include <signal.h>
22#include <string.h> /* For the real memset prototype. */
23#include <sigsetops.h>
24
25/* Set the disposition for SIG. */
26__sighandler_t
27sigset (int sig, __sighandler_t disp)
28{
29 struct sigaction act;
30 struct sigaction oact;
31 sigset_t set;
32 sigset_t oset;
33
34 __sigemptyset (&set);
35 if (sigaddset (&set, sig) < 0)
36 return SIG_ERR;
37
38 if (disp == SIG_HOLD)
39 {
40 /* Add the signal to the current signal mask. */
41 if (__sigprocmask (SIG_BLOCK, &set, &oset) < 0)
42 return SIG_ERR;
43
44 /* If the signal was already blocked signal this to the caller. */
45 if (__sigismember (&oset, sig))
46 return SIG_HOLD;
47
48 /* We need to determine whether a specific handler is installed. */
49 if (__sigaction (sig, NULL, &oact) < 0)
50 return SIG_ERR;
51
52 return oact.sa_handler;
53 }
54 else
55 {
56 act.sa_handler = disp;
57 __sigemptyset (&act.sa_mask);
58 act.sa_flags = 0;
59 if (__sigaction (sig, &act, &oact) < 0)
60 return SIG_ERR;
61
62 /* Remove the signal from the current signal mask. */
63 if (__sigprocmask (SIG_UNBLOCK, &set, &oset) < 0)
64 return SIG_ERR;
65
66 /* If the signal was already blocked return SIG_HOLD. */
67 return __sigismember (&oset, sig) ? SIG_HOLD : oact.sa_handler;
68 }
69}
70

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