- Add assertions in MutexLocker/MonitorLocker to ensure that the code enclosed

runtime/vm/os_thread_macos.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"  // NOLINT
 #if defined(TARGET_OS_MACOS)
 
 #include "vm/os_thread.h"
 
 #include <sys/errno.h>  // NOLINT
@@ skipping 317 matching lines @@
 #endif  // defined(DEBUG)
 
   int result = pthread_mutex_destroy(data_.mutex());
   VALIDATE_PTHREAD_RESULT(result);
 
   result = pthread_cond_destroy(data_.cond());
   VALIDATE_PTHREAD_RESULT(result);
 }
 
 
+bool Monitor::TryEnter() {
+  int result = pthread_mutex_trylock(data_.mutex());
+  // Return false if the lock is busy and locking failed.
+  if ((result == EBUSY) || (result == EDEADLK)) {
+    return false;
+  }
+  ASSERT_PTHREAD_SUCCESS(result);  // Verify no other errors.
+#if defined(DEBUG)
+  // When running with assertions enabled we track the owner.
+  ASSERT(owner_ == OSThread::kInvalidThreadId);
+  owner_ = OSThread::GetCurrentThreadId();
+#endif  // defined(DEBUG)
+  return true;
+}
+
+
 void Monitor::Enter() {
   int result = pthread_mutex_lock(data_.mutex());
   VALIDATE_PTHREAD_RESULT(result);
 
 #if defined(DEBUG)
   // When running with assertions enabled we track the owner.
   ASSERT(owner_ == OSThread::kInvalidThreadId);
   owner_ = OSThread::GetCurrentThreadId();
 #endif  // defined(DEBUG)
 }
@@ skipping 70 matching lines @@
 void Monitor::NotifyAll() {
   // When running with assertions enabled we track the owner.
   ASSERT(IsOwnedByCurrentThread());
   int result = pthread_cond_broadcast(data_.cond());
   VALIDATE_PTHREAD_RESULT(result);
 }
 
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_MACOS)