sysdeps/posix/sigset.c

   1 /* Copyright (C) 1998-2024 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
  27 sigset (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 }