gnulib/import/glthread/threadlib.c

   1 /* Multithreading primitives.
   2    Copyright (C) 2005-2019 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 3, or (at your option)
   7    any later version.
   8
   9    This program 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
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Bruno Haible <bruno@clisp.org>, 2005.  */
  18
  19 #include <config.h>
  20
  21 /* ========================================================================= */
  22
  23 #if USE_POSIX_THREADS || USE_ISOC_AND_POSIX_THREADS
  24
  25 /* Use the POSIX threads library.  */
  26
  27 # include <pthread.h>
  28 # include <stdlib.h>
  29
  30 # if PTHREAD_IN_USE_DETECTION_HARD
  31
  32 /* The function to be executed by a dummy thread.  */
  33 static void *
  34 dummy_thread_func (void *arg)
  35 {
  36   return arg;
  37 }
  38
  39 int
  40 glthread_in_use (void)
  41 {
  42   static int tested;
  43   static int result; /* 1: linked with -lpthread, 0: only with libc */
  44
  45   if (!tested)
  46     {
  47       pthread_t thread;
  48
  49       if (pthread_create (&thread, NULL, dummy_thread_func, NULL) != 0)
  50         /* Thread creation failed.  */
  51         result = 0;
  52       else
  53         {
  54           /* Thread creation works.  */
  55           void *retval;
  56           if (pthread_join (thread, &retval) != 0)
  57             abort ();
  58           result = 1;
  59         }
  60       tested = 1;
  61     }
  62   return result;
  63 }
  64
  65 # endif
  66
  67 #endif
  68
  69 /* ========================================================================= */
  70
  71 /* This declaration is solely to ensure that after preprocessing
  72    this file is never empty.  */
  73 typedef int dummy;