mutex (call_once): Remove parentheses to fix error in c++1y and gnu++1y mode.

	* include/std/mutex (call_once): Remove parentheses to fix error in
	c++1y and gnu++1y mode.
	* testsuite/30_threads/mutex/try_lock/2.cc: Call try_lock() in new
	thread to avoid undefined behaviour.

From-SVN: r199875

libstdc++-v3/ChangeLog

+2013-06-09  Jonathan Wakely  <jwakely.gcc@gmail.com>
+
+	* include/std/mutex (call_once): Remove parentheses to fix error in
+	c++1y and gnu++1y mode.
+	* testsuite/30_threads/mutex/try_lock/2.cc: Call try_lock() in new
+	thread to avoid undefined behaviour.
+
 2013-06-08  Ed Smith-Rowland  <3dw4rd@verizon.net>
 
 	Simplify and clean up library literals.

libstdc++-v3/include/std/mutex

@@ -783,7 +783,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       __set_once_functor_lock_ptr(&__functor_lock);
 #endif
 
-      int __e = __gthread_once(&(__once._M_once), &__once_proxy);
+      int __e = __gthread_once(&__once._M_once, &__once_proxy);
 
 #ifndef _GLIBCXX_HAVE_TLS
       if (__functor_lock)

libstdc++-v3/testsuite/30_threads/mutex/try_lock/2.cc

@@ -24,6 +24,7 @@
 
 
 #include <mutex>
+#include <thread>
 #include <system_error>
 #include <testsuite_hooks.h>
 
@@ -38,15 +39,18 @@ int main()
       m.lock();
       bool b;
 
-      try
-	{
-	  b = m.try_lock();
-	  VERIFY( !b );
-	}
-      catch (const std::system_error& e)
-	{
-	  VERIFY( false );
-	}
+      std::thread t([&] {
+        try
+          {
+            b = m.try_lock();
+          }
+        catch (const std::system_error& e)
+          {
+            VERIFY( false );
+          }
+      });
+      t.join();
+      VERIFY( !b );
 
       m.unlock();
     }