libc/signal/sigset.c

   1 /* Copyright (C) 1998, 2000, 2005 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    <http://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>
  23
  24 /* Set the disposition for SIG.  */
  25 __sighandler_t sigset (int sig, __sighandler_t disp)
  26 {
  27   struct sigaction act, oact;
  28   sigset_t set;
  29
  30   /* Check signal extents to protect __sigismember.  */
  31   if (disp == SIG_ERR || sig < 1 || sig >= NSIG)
  32     {
  33       __set_errno (EINVAL);
  34       return SIG_ERR;
  35     }
  36
  37 #ifdef SIG_HOLD
  38   /* Handle SIG_HOLD first.  */
  39   if (disp == SIG_HOLD)
  40     {
  41       __sigemptyset (&set);
  42       __sigaddset (&set, sig);
  43
  44       /* Add the signal set to the current signal mask.  */
  45       sigprocmask (SIG_BLOCK, &set, NULL); /* can't fail */
  46
  47       return SIG_HOLD;
  48     }
  49 #endif  /* SIG_HOLD */
  50
  51   memset(&act, 0, sizeof(act));
  52   act.sa_handler = disp;
  53   /* In Linux (as of 2.6.25), fails only if sig is SIGKILL or SIGSTOP */
  54   if (sigaction (sig, &act, &oact) < 0)
  55     return SIG_ERR;
  56
  57   /* Create an empty signal set. Add the specified signal.  */
  58   __sigemptyset (&set);
  59   __sigaddset (&set, sig);
  60
  61   /* Remove the signal set from the current signal mask.  */
  62   sigprocmask (SIG_UNBLOCK, &set, NULL); /* can't fail */
  63
  64   return oact.sa_handler;
  65 }