text: /* This testcase is part of GDB, the GNU debugger.
  
     Copyright 2004 Free Software Foundation, Inc.
  
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation; either version 2 of the License, or
     (at your option) any later version.
  
     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.
   
     You should have received a copy of the GNU General Public License
     along with this program; if not, write to the Free Software
     Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  
     Please email any bugs, comments, and/or additions to this file to:
     bug-gdb@prep.ai.mit.edu  */
  
  #include <signal.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <sys/time.h>
  
  enum level { MAIN, OUTER, INNER, LEAF, NR_LEVELS };
  
  /* Levels completed flag.  */
  volatile enum level level = NR_LEVELS;
  
  void catcher (int signal);
  
  void
  thrower (enum level next_level, int sig, int itimer, int on_stack)
  {
    level = next_level;
    /* Set up the signal handler.  */
    {
      struct sigaction act;
      memset (&act, 0, sizeof (act));
      act.sa_handler = catcher;
      act.sa_flags |= on_stack;
      sigaction (sig, &act, NULL);
    }
    /* Set up a one-off timer.  A timer, rather than SIGSEGV, is used as
       after a timer handler finishes the interrupted code can safely
       resume.  */
    {
      struct itimerval itime;
      memset (&itime, 0, sizeof (itime));
      itime.it_value.tv_usec = 250 * 1000;
      setitimer (itimer, &itime, NULL);
    }
    /* Wait.  */
    while (level != LEAF);
  }
  
  void
  catcher (int signal)
  {
    /* Find the next level.  */
    switch (level)
      {
      case MAIN:
        thrower (OUTER, SIGALRM, ITIMER_REAL, SA_ONSTACK);
        break;
      case OUTER:
        thrower (INNER, SIGVTALRM, ITIMER_VIRTUAL, SA_ONSTACK);
        break;
      case INNER:
        level = LEAF;
        return;
      }
  }
  
  
  main ()
  {
    /* Set up the altstack.  */
    {
      static char stack[SIGSTKSZ * NR_LEVELS];
      struct sigaltstack alt;
      memset (&alt, 0, sizeof (alt));
      alt.ss_sp = stack;
      alt.ss_size = SIGSTKSZ;
      alt.ss_flags = 0;
      if (sigaltstack (&alt, NULL) < 0)
        {
  	perror ("sigaltstack");
  	exit (0);
        }
    }
    level = MAIN;
    catcher (0);
  }
  