linuxthreads/Examples/ex8.c

   1 /* Tests for fork in multi-threaded environment.
   2    Copyright (C) 2000 Free Software Foundation, Inc.
   3    Contributed by Ulrich Drepper <drepper@cygnus.com>, 2000.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <errno.h>
  21 #include <error.h>
  22 #include <stdlib.h>
  23 #include <pthread.h>
  24 #include <unistd.h>
  25 #include <sys/wait.h>
  26
  27 enum
  28 {
  29   PREPARE_BIT = 1,
  30   PARENT_BIT = 2,
  31   CHILD_BIT = 4
  32 };
  33
  34 static int var;
  35
  36 static void
  37 prepare (void)
  38 {
  39   var |= PREPARE_BIT;
  40 }
  41
  42 static void
  43 parent (void)
  44 {
  45   var |= PARENT_BIT;
  46 }
  47
  48 static void
  49 child (void)
  50 {
  51   var |= CHILD_BIT;
  52 }
  53
  54
  55 static void *thread (void *arg);
  56
  57
  58 int
  59 main (void)
  60 {
  61   pthread_t th;
  62   void *res;
  63
  64   pthread_atfork (prepare, parent, child);
  65
  66   if (pthread_create (&th, NULL, thread, NULL) != 0)
  67     error (EXIT_FAILURE, 0, "cannot create thread");
  68
  69   pthread_join (th, &res);
  70
  71   return (int) (long int) res;
  72 }
  73
  74
  75 static void *
  76 thread (void *arg)
  77 {
  78   int status;
  79   pid_t pid;
  80
  81   pid = fork ();
  82   if (pid == 0)
  83     {
  84       /* We check whether the `prepare' and `child' function ran.  */
  85       exit (var != (PREPARE_BIT | CHILD_BIT));
  86     }
  87   else if (pid == (pid_t) -1)
  88     error (EXIT_FAILURE, errno, "cannot fork");
  89
  90   if (waitpid (pid, &status, 0) != pid)
  91     error (EXIT_FAILURE, errno, "wrong child");
  92
  93   if (WTERMSIG (status) != 0)
  94     error (EXIT_FAILURE, 0, "Child terminated incorrectly");
  95   status = WEXITSTATUS (status);
  96
  97   if (status == 0)
  98     status = var != (PREPARE_BIT | PARENT_BIT);
  99
 100   return (void *) (long int) status;
 101 }