* README: Document signed integer overflow situation more

[gnulib.git] / lib / lock.c

diff --git a/lib/lock.c b/lib/lock.c
index 5c14fa3..34a59ab 100644 (file)
--- a/lib/lock.c
+++ b/lib/lock.c
@@ -1,28 +1,25 @@
 /* Locking in multithreaded situations.
-   Copyright (C) 2005 Free Software Foundation, Inc.
+   Copyright (C) 2005-2006 Free Software Foundation, Inc.
 
-   This program is free software; you can redistribute it and/or modify it
-   under the terms of the GNU Library General Public License as published
-   by the Free Software Foundation; either version 2, or (at your option)
+   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, 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
-   Library General Public License for more details.
+   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 Library General Public
-   License along with this program; if not, write to the Free Software
-   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
-   USA.  */
+   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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
 
 /* Written by Bruno Haible <bruno@clisp.org>, 2005.
    Based on GCC's gthr-posix.h, gthr-posix95.h, gthr-solaris.h,
    gthr-win32.h.  */
 
-#ifdef HAVE_CONFIG_H
-# include <config.h>
-#endif
+#include <config.h>
 
 #include "lock.h"
 
@@ -32,6 +29,43 @@
 
 /* Use the POSIX threads library.  */
 
+# if PTHREAD_IN_USE_DETECTION_HARD
+
+/* The function to be executed by a dummy thread.  */
+static void *
+dummy_thread_func (void *arg)
+{
+  return arg;
+}
+
+int
+glthread_in_use (void)
+{
+  static int tested;
+  static int result; /* 1: linked with -lpthread, 0: only with libc */
+
+  if (!tested)
+    {
+      pthread_t thread;
+
+      if (pthread_create (&thread, NULL, dummy_thread_func, NULL) != 0)
+       /* Thread creation failed.  */
+       result = 0;
+      else
+       {
+         /* Thread creation works.  */
+         void *retval;
+         if (pthread_join (thread, &retval) != 0)
+           abort ();
+         result = 1;
+       }
+      tested = 1;
+    }
+  return result;
+}
+
+# endif
+
 /* -------------------------- gl_lock_t datatype -------------------------- */
 
 /* ------------------------- gl_rwlock_t datatype ------------------------- */