sysdeps/posix/sigset.c

   1 /* Copyright (C) 1998, 2000, 2005, 2006 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, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <errno.h>
  20 #define __need_NULL
  21 #include <stddef.h>
  22 #include <signal.h>
  23 #include <string.h>     /* For the real memset prototype.  */
  24
  25
  26 /* Set the disposition for SIG.  */
  27 __sighandler_t
  28 sigset (sig, disp)
  29      int sig;
  30      __sighandler_t disp;
  31 {
  32   struct sigaction act;
  33   struct sigaction oact;
  34   sigset_t set;
  35   sigset_t oset;
  36
  37 #ifdef SIG_HOLD
  38   /* Handle SIG_HOLD first.  */
  39   if (disp == SIG_HOLD)
  40     {
  41       /* Create an empty signal set.  */
  42       if (__sigemptyset (&set) < 0)
  43         return SIG_ERR;
  44
  45       /* Add the specified signal.  */
  46       if (__sigaddset (&set, sig) < 0)
  47         return SIG_ERR;
  48
  49       /* Add the signal set to the current signal mask.  */
  50       if (__sigprocmask (SIG_BLOCK, &set, &oset) < 0)
  51         return SIG_ERR;
  52
  53       /* If the signal was already blocked signal this to the caller.  */
  54       if (__sigismember (&oset, sig))
  55         return SIG_HOLD;
  56
  57       /* We need to determine whether a specific handler is installed.  */
  58       if (__sigaction (sig, NULL, &oact) < 0)
  59         return SIG_ERR;
  60
  61       return oact.sa_handler;
  62     }
  63 #endif  /* SIG_HOLD */
  64
  65   /* Check signal extents to protect __sigismember.  */
  66   if (disp == SIG_ERR || sig < 1 || sig >= NSIG)
  67     {
  68       __set_errno (EINVAL);
  69       return SIG_ERR;
  70     }
  71
  72   act.sa_handler = disp;
  73   if (__sigemptyset (&act.sa_mask) < 0)
  74     return SIG_ERR;
  75   act.sa_flags = 0;
  76   if (__sigaction (sig, &act, &oact) < 0)
  77     return SIG_ERR;
  78
  79   /* Create an empty signal set.  */
  80   if (__sigemptyset (&set) < 0)
  81     return SIG_ERR;
  82
  83   /* Add the specified signal.  */
  84   if (__sigaddset (&set, sig) < 0)
  85     return SIG_ERR;
  86
  87   /* Remove the signal set from the current signal mask.  */
  88   if (__sigprocmask (SIG_UNBLOCK, &set, &oset) < 0)
  89     return SIG_ERR;
  90
  91   /* If the signal was already blocked return SIG_HOLD.  */
  92   return __sigismember (&oset, sig) ? SIG_HOLD : oact.sa_handler;
  93 }