sysdeps/posix/sigwait.c

   1 /* sigwait - implementation of sigwait function from POSIX.1c.
   2    Copyright (C) 1996 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Library General Public License as
   8    published by the Free Software Foundation; either version 2 of the
   9    License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Library General Public License for more details.
  15
  16    You should have received a copy of the GNU Library General Public
  17    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  18    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #include <assert.h>
  22 #include <errno.h>
  23 #include <signal.h>
  24
  25
  26 /* This is our dummy signal handler we use here.  */
  27 static void ignore_signal (int sig);
  28
  29 /* Place where to remember which signal we got.  Please note that this
  30    implementation cannot be used for the threaded libc.  The
  31    libpthread must provide an own version.  */
  32 static int was_sig;
  33
  34
  35 int
  36 __sigwait (const sigset_t *set, int *sig)
  37 {
  38   sigset_t tmp_mask;
  39   struct sigaction saved[NSIG];
  40   struct sigaction action;
  41   int save_errno;
  42   int this;
  43
  44   /* Prepare set.  */
  45   __sigfillset (&tmp_mask);
  46
  47   /* Unblock all signals in the SET and register our nice handler.  */
  48   action.sa_handler = ignore_signal;
  49   action.sa_flags = 0;
  50   __sigfillset (&action.sa_mask);       /* Block all signals for handler.  */
  51
  52   /* Make sure we recognize error conditions by setting WAS_SIG to a
  53      value which does not describe a legal signal number.  */
  54   was_sig = -1;
  55
  56   for (this = 0; this < NSIG; ++this)
  57     if (__sigismember (set, this))
  58       {
  59         /* Unblock this signal.  */
  60         __sigdelset (&tmp_mask, this);
  61
  62         /* Register temporary action handler.  */
  63         if (__sigaction (this, &action, &saved[this]) != 0)
  64           goto restore_handler;
  65       }
  66
  67   /* Now we can wait for signals.  */
  68   __sigsuspend (&tmp_mask);
  69
  70  restore_handler:
  71   save_errno = errno;
  72
  73   while (--this >= 0)
  74     if (__sigismember (set, this))
  75       /* We ignore errors here since we must restore all handlers.  */
  76       __sigaction (this, &saved[this], NULL);
  77
  78   __set_errno (save_errno);
  79
  80   /* Store the result and return.  */
  81   *sig = was_sig;
  82   return was_sig == -1 ? -1 : 0;
  83 }
  84 weak_alias (__sigwait, sigwait)
  85
  86
  87 static void
  88 ignore_signal (int sig)
  89 {
  90   /* Remember the signal.  */
  91   was_sig = sig;
  92 }