Bug 1846191 ref-count MockCubeb to ensure that it lives as long as th…

…e audio thread might access it r=padenot

Differential Revision: https://phabricator.services.mozilla.com/D185027

dom/media/gtest/MockCubeb.cpp

@@ -137,7 +137,9 @@ void AddDevices(MockCubeb* mock, uint32_t device_count,
   }
 }
 
-void cubeb_mock_destroy(cubeb* context) { delete MockCubeb::AsMock(context); }
+void cubeb_mock_destroy(cubeb* context) {
+  MockCubeb::AsMock(context)->Destroy();
+}
 
 MockCubebStream::MockCubebStream(cubeb* aContext, cubeb_devid aInputDevice,
                                  cubeb_stream_params* aInputStreamParams,
@@ -405,16 +407,30 @@ void MockCubebStream::NotifyState(cubeb_state aState) {
 
 MockCubeb::MockCubeb() : ops(&mock_ops) {}
 
-MockCubeb::~MockCubeb() {
-  auto streams = mLiveStreams.Lock();
-  MOZ_ASSERT(streams->IsEmpty());
-  MOZ_ASSERT(!mFakeAudioThread);
-};
+MockCubeb::~MockCubeb() { MOZ_ASSERT(!mFakeAudioThread); };
 
-cubeb* MockCubeb::AsCubebContext() { return reinterpret_cast<cubeb*>(this); }
+void MockCubeb::Destroy() {
+  MOZ_ASSERT(mHasCubebContext);
+  {
+    auto streams = mLiveStreams.Lock();
+    MOZ_ASSERT(streams->IsEmpty());
+  }
+  mDestroyed = true;
+  Release();
+}
+
+cubeb* MockCubeb::AsCubebContext() {
+  MOZ_ASSERT(!mDestroyed);
+  if (mHasCubebContext.compareExchange(false, true)) {
+    AddRef();
+  }
+  return reinterpret_cast<cubeb*>(this);
+}
 
 MockCubeb* MockCubeb::AsMock(cubeb* aContext) {
-  return reinterpret_cast<MockCubeb*>(aContext);
+  auto* mockCubeb = reinterpret_cast<MockCubeb*>(aContext);
+  MOZ_ASSERT(!mockCubeb->mDestroyed);
+  return mockCubeb;
 }
 
 int MockCubeb::EnumerateDevices(cubeb_device_type aType,
@@ -623,6 +639,7 @@ void MockCubeb::StartStream(MockCubebStream* aStream) {
     streams->AppendElement(aStream->mSelf);
   }
   if (!mFakeAudioThread) {
+    AddRef();  // released when the thread exits
     mFakeAudioThread = WrapUnique(new std::thread(ThreadFunction_s, this));
   }
 }
@@ -665,6 +682,7 @@ void MockCubeb::ThreadFunction() {
     std::this_thread::sleep_for(
         std::chrono::microseconds(mFastMode ? 0 : 10 * PR_USEC_PER_MSEC));
   }
+  Release();
 }
 
 }  // namespace mozilla

dom/media/gtest/MockCubeb.h

@@ -290,13 +290,23 @@ class SmartMockCubebStream
 // backend, but is also controllable by the test code to decide what the backend
 // should do, depending on what is being tested.
 class MockCubeb {
+  // This needs to have the exact same memory layout as a real cubeb backend.
+  // It's very important for the `ops` member to be the very first member of
+  // the class, and for MockCubeb to not have any virtual members (to avoid
+  // having a vtable), so that AsMock() returns a pointer to this that can be
+  // used as a cubeb backend.
+  const cubeb_ops* ops;
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(MockCubeb);
+
  public:
   MockCubeb();
-  ~MockCubeb();
   // Cubeb backend implementation
   // This allows passing this class as a cubeb* instance.
+  // cubeb_destroy(context) should eventually be called on the return value
+  // iff this method is called.
   cubeb* AsCubebContext();
   static MockCubeb* AsMock(cubeb* aContext);
+  void Destroy();
   // Fill in the collection parameter with all devices of aType.
   int EnumerateDevices(cubeb_device_type aType,
                        cubeb_device_collection* aCollection);
@@ -389,11 +399,7 @@ class MockCubeb {
   void ThreadFunction();
 
  private:
-  // This needs to have the exact same memory layout as a real cubeb backend.
-  // It's very important for this `ops` member to be the very first member of
-  // the class, and to not have any virtual members (to avoid having a
-  // vtable).
-  const cubeb_ops* ops;
+  ~MockCubeb();
   // The callback to call when the device list has been changed.
   cubeb_device_collection_changed_callback
       mInputDeviceCollectionChangeCallback = nullptr;
@@ -413,6 +419,8 @@ class MockCubeb {
   // Whether the audio thread is forced, i.e., whether it remains active even
   // with no live streams.
   Atomic<bool> mForcedAudioThread{false};
+  Atomic<bool> mHasCubebContext{false};
+  Atomic<bool> mDestroyed{false};
   MozPromiseHolder<ForcedAudioThreadPromise> mForcedAudioThreadPromise;
   // Our input and output devices.
   nsTArray<cubeb_device_info> mInputDevices;