Oilpan: WebAudio: Prepare to move AudioProcessor hierarchy to Oilpan heap.

Source/modules/webaudio/AudioBasicProcessorNode.cpp

 /*
  * Copyright (C) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 27 matching lines @@
 
 AudioBasicProcessorNode::AudioBasicProcessorNode(AudioContext* context, float sampleRate)
     : AudioNode(context, sampleRate)
 {
     addInput();
     addOutput(AudioNodeOutput::create(this, 1));
 
     // The subclass must create m_processor.
 }
 
+void AudioBasicProcessorNode::trace(Visitor* visitor)
+{
+    visitor->trace(m_processor);
+    AudioNode::trace(visitor);
+}
+
 void AudioBasicProcessorNode::initialize()
 {
     if (isInitialized())
         return;
 
     ASSERT(processor());
     processor()->initialize();
 
     AudioNode::initialize();
 }
 
 void AudioBasicProcessorNode::uninitialize()

[haraken, 2014/07/23 03:09:49]

Hmm, this looks safe but fragile.

uninitialize() is sometimes called from destructors of the AudioNode hierarchy.
If this uninitialize() is called in some destructor, it causes a
touch-another-on-heap-object-in-destructor issue because it touches m_processor.
However, this uninitialize() is safe by accident because it is currently not
called in any destructor. It looks a bit fragile to rely on the assumption.

[tkent, 2014/07/23 03:38:41]

I'll add ~AudioBasicProcessorNode with ASSERT(!isInitialized()).

[haraken, 2014/07/23 03:41:03]

That's a nice idea.

 {
     if (!isInitialized())
         return;
 
     ASSERT(processor());
     processor()->uninitialize();
 
     AudioNode::uninitialize();
 }
 
@@ skipping 66 matching lines @@
 }
 
 double AudioBasicProcessorNode::latencyTime() const
 {
     return m_processor->latencyTime();
 }
 
 } // namespace blink
 
 #endif // ENABLE(WEB_AUDIO)