libstdc++-v3/testsuite/18_support/pthread_guard.cc

   1 //
   2 // Copyright (C) 2007-2020 Free Software Foundation, Inc.
   3 //
   4 // This file is part of the GNU ISO C++ Library.  This library is free
   5 // software; you can redistribute it and/or modify it under the
   6 // terms of the GNU General Public License as published by the
   7 // Free Software Foundation; either version 3, or (at your option)
   8 // any later version.
   9 //
  10 // This 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
  13 // GNU General Public License for more details.
  14 //
  15 // You should have received a copy of the GNU General Public License along
  16 // with this library; see the file COPYING3.  If not see
  17 // <http://www.gnu.org/licenses/>.
  18
  19 // { dg-do run }
  20 // { dg-options "-pthread"  }
  21 // { dg-require-effective-target pthread }
  22
  23 #include <cstdlib>
  24 #include <pthread.h>
  25
  26 // This used to deadlock with the old libstdc++ because there is only one
  27 // global mutex guarding initialization of statics and it is held during by
  28 // the initializer thread of a static until the variable is completely
  29 // initialized. If the initializer thread creates and waits for another thread
  30 // which also initializes a static variable, there will be a deadlock because
  31 // the first thread is holding the mutex and waiting for the second thread,
  32 // which is blocked when it is acquiring the mutex.
  33
  34 int
  35 get_bar (void)
  36 {
  37   return 1;
  38 }
  39
  40 void*
  41 do_something (void *arg)
  42 {
  43   static int bar __attribute__((unused)) = get_bar ();
  44   return 0;
  45 }
  46
  47 int
  48 get_foo (void)
  49 {
  50   pthread_t new_thread;
  51
  52   if (pthread_create (&new_thread, 0, do_something, 0) != 0)
  53     std::abort ();
  54
  55   if (pthread_join (new_thread, 0) != 0)
  56     std::abort ();
  57
  58   return 1;
  59 }
  60
  61 int
  62 main (int argc, char **argv)
  63 {
  64   static int foo __attribute__((unused)) = get_foo ();
  65   return 0;
  66 }