Fix other cause of intermittent timing-dependent crash at shutdown...

... AudioIO holds a weak pointer to its listener so there is no dangling
pointer

src/AudioIO.cpp

@@ -977,7 +977,6 @@ AudioIO::AudioIO()
    mNumCaptureChannels = 0;
    mPaused = false;
 
-   mListener = NULL;
    mUpdateMeters = false;
    mUpdatingMeters = false;
 
@@ -1445,9 +1444,10 @@ void AudioIO::StartMonitoring( const AudioIOStartStreamOptions &options )
    mLastPaError = Pa_StartStream( mPortStreamV19 );
 
    // Update UI display only now, after all possibilities for error are past.
-   if ((mLastPaError == paNoError) && mListener) {
+   auto pListener = GetListener();
+   if ((mLastPaError == paNoError) && pListener) {
       // advertise the chosen I/O sample rate to the UI
-      mListener->OnAudioIORate((int)mRate);
+      pListener->OnAudioIORate((int)mRate);
    }
 }
 
@@ -1570,7 +1570,9 @@ int AudioIO::StartStream(const TransportTracks &tracks,
    unsigned int captureChannels = 0;
    sampleFormat captureFormat = floatSample;
 
-   if (tracks.playbackTracks.size() > 0 
+   auto pListener = GetListener();
+
+   if (tracks.playbackTracks.size() > 0
 #ifdef EXPERIMENTAL_MIDI_OUT
       || tracks.midiTracks.size() > 0
 #endif
@@ -1595,8 +1597,8 @@ int AudioIO::StartStream(const TransportTracks &tracks,
       captureFormat = mCaptureTracks[0]->GetSampleFormat();
 
       // Tell project that we are about to start recording
-      if (mListener)
-         mListener->OnAudioIOStartRecording();
+      if (pListener)
+         pListener->OnAudioIOStartRecording();
    }
 
    bool successAudio;
@@ -1619,8 +1621,8 @@ int AudioIO::StartStream(const TransportTracks &tracks,
 #endif
 
    if (!successAudio) {
-      if (mListener && captureChannels > 0)
-         mListener->OnAudioIOStopRecording();
+      if (pListener && captureChannels > 0)
+         pListener->OnAudioIOStopRecording();
       mStreamToken = 0;
 
       return 0;
@@ -1751,8 +1753,8 @@ int AudioIO::StartStream(const TransportTracks &tracks,
       {
          mStreamToken = 0;
          mAudioThreadFillBuffersLoopRunning = false;
-         if (mListener && mNumCaptureChannels > 0)
-            mListener->OnAudioIOStopRecording();
+         if (pListener && mNumCaptureChannels > 0)
+            pListener->OnAudioIOStopRecording();
          StartStreamCleanup();
          AudacityMessageBox(LAT1CTOWX(Pa_GetErrorText(err)));
          return 0;
@@ -1760,9 +1762,9 @@ int AudioIO::StartStream(const TransportTracks &tracks,
    }
 
    // Update UI display only now, after all possibilities for error are past.
-   if (mListener) {
+   if (pListener) {
       // advertise the chosen I/O sample rate to the UI
-      mListener->OnAudioIORate((int)mRate);
+      pListener->OnAudioIORate((int)mRate);
    }
 
    if (mNumPlaybackChannels > 0)
@@ -2277,6 +2279,8 @@ void AudioIO::StopStream()
    }
 #endif
 
+   auto pListener = GetListener();
+   
    // If there's no token, we were just monitoring, so we can
    // skip this next part...
    if (mStreamToken > 0) {
@@ -2354,8 +2358,8 @@ void AudioIO::StopStream()
             }
          }
 
-         if (mListener)
-            mListener->OnCommitRecording();
+         if (pListener)
+            pListener->OnCommitRecording();
       }
    }
 
@@ -2369,8 +2373,8 @@ void AudioIO::StopStream()
    mOutputMeter.Release();
    mOwningProject = nullptr;
 
-   if (mListener && mNumCaptureChannels > 0)
-      mListener->OnAudioIOStopRecording();
+   if (pListener && mNumCaptureChannels > 0)
+      pListener->OnAudioIOStopRecording();
 
    //
    // Only set token to 0 after we're totally finished with everything
@@ -2390,9 +2394,9 @@ void AudioIO::StopStream()
    mScrubState.reset();
 #endif
 
-   if (mListener) {
+   if (pListener) {
       // Tell UI to hide sample rate
-      mListener->OnAudioIORate(0);
+      pListener->OnAudioIORate(0);
    }
 
    // Don't cause a busy wait in the audio thread after stopping scrubbing
@@ -2983,8 +2987,9 @@ void AudioIO::FillBuffers()
             mRecordingSchedule.mPosition += avail / mRate;
             mRecordingSchedule.mLatencyCorrected = latencyCorrected;
 
-            if (mListener && !blockFileLog.IsEmpty())
-               mListener->OnAudioIONewBlockFiles(blockFileLog);
+            auto pListener = GetListener();
+            if (pListener && !blockFileLog.IsEmpty())
+               pListener->OnAudioIONewBlockFiles(blockFileLog);
          }
          // end of record buffering
       },
@@ -3004,7 +3009,8 @@ void AudioIO::FillBuffers()
    );
 }
 
-void AudioIO::SetListener(AudioIOListener* listener)
+void AudioIoCallback::SetListener(
+   const std::shared_ptr< AudioIOListener > &listener)
 {
    if (IsBusy())
       return;
@@ -3683,8 +3689,9 @@ void AudioIoCallback::CheckSoundActivatedRecordingLevel( const void *inputBuffer
    bool bShouldBePaused = mInputMeter->GetMaxPeak() < mSilenceLevel;
    if( bShouldBePaused != IsPaused())
    {
-      if ( mListener )
-         mListener->OnSoundActivationThreshold();
+      auto pListener = GetListener();
+      if ( pListener )
+         pListener->OnSoundActivationThreshold();
    }
 }
 

src/AudioIO.h

@@ -19,6 +19,7 @@
 
 #include "Experimental.h"
 
+#include <memory>
 #include <utility>
 #include <wx/atomic.h> // member variable
 
@@ -249,6 +250,10 @@ public:
       const PaStreamCallbackTimeInfo *timeInfo,
       const PaStreamCallbackFlags statusFlags, void *userData);
 
+   std::shared_ptr< AudioIOListener > GetListener() const
+      { return mListener.lock(); }
+   void SetListener( const std::shared_ptr< AudioIOListener > &listener);
+   
    // Part of the callback
    PaStreamCallbackResult CallbackDoSeek();
 
@@ -469,7 +474,7 @@ protected:
    bool                mUpdateMeters;
    volatile bool       mUpdatingMeters;
 
-   AudioIOListener*    mListener;
+   std::weak_ptr< AudioIOListener > mListener;
 
    friend class AudioThread;
 #ifdef EXPERIMENTAL_MIDI_OUT
@@ -558,9 +563,6 @@ public:
    // This might return null during application startup or shutdown
    static AudioIO *Get();
 
-   AudioIOListener* GetListener() { return mListener; }
-   void SetListener(AudioIOListener* listener);
-
    /** \brief Start up Portaudio for capture and recording as needed for
     * input monitoring and software playthrough only
     *

src/AudioIOBase.h

@@ -74,7 +74,6 @@ struct AudioIOStartStreamOptions
    AudioIOStartStreamOptions(AudacityProject *pProject_, double rate_)
       : pProject{ pProject_ }
       , envelope(nullptr)
-      , listener(NULL)
       , rate(rate_)
       , playLooped(false)
       , cutPreviewGapStart(0.0)
@@ -86,7 +85,7 @@ struct AudioIOStartStreamOptions
    AudacityProject *pProject{};
    MeterPanelBase *captureMeter{}, *playbackMeter{};
    BoundedEnvelope *envelope; // for time warping
-   AudioIOListener* listener;
+   std::shared_ptr< AudioIOListener > listener;
    double rate;
    bool playLooped;
    double cutPreviewGapStart;

src/ProjectAudioManager.cpp

@@ -201,7 +201,7 @@ DefaultPlayOptions( AudacityProject &project )
    options.playbackMeter = projectAudioIO.GetPlaybackMeter();
    auto timeTrack = *TrackList::Get( project ).Any<TimeTrack>().begin();
    options.envelope = timeTrack ? timeTrack->GetEnvelope() : nullptr;
-   options.listener = &ProjectAudioManager::Get( project );
+   options.listener = ProjectAudioManager::Get( project ).shared_from_this();
    return options;
 }
 
@@ -220,6 +220,6 @@ DefaultSpeedPlayOptions( AudacityProject &project )
    options.playbackMeter = projectAudioIO.GetPlaybackMeter();
    auto timeTrack = *TrackList::Get( project ).Any<TimeTrack>().begin();
    options.envelope = timeTrack ? timeTrack->GetEnvelope() : nullptr;
-   options.listener = &ProjectAudioManager::Get( project );
+   options.listener = ProjectAudioManager::Get( project ).shared_from_this();
    return options;
 }

src/ProjectAudioManager.h

@@ -20,6 +20,7 @@ struct AudioIOStartStreamOptions;
 class ProjectAudioManager final
    : public ClientData::Base
    , public AudioIOListener
+   , public std::enable_shared_from_this< ProjectAudioManager >
 {
 public:
    static ProjectAudioManager &Get( AudacityProject &project );

src/ProjectManager.cpp

@@ -383,7 +383,8 @@ AudacityProject *ProjectManager::New()
    
    //Initialise the Listeners
    auto gAudioIO = AudioIO::Get();
-   gAudioIO->SetListener( &ProjectAudioManager::Get( project ) );
+   gAudioIO->SetListener(
+      ProjectAudioManager::Get( project ).shared_from_this() );
    auto &projectSelectionManager = ProjectSelectionManager::Get( project );
    SelectionBar::Get( project ).SetListener( &projectSelectionManager );
 #ifdef EXPERIMENTAL_SPECTRAL_EDITING
@@ -599,10 +600,14 @@ void ProjectManager::OnCloseWindow(wxCloseEvent & event)
 
    // Since we're going to be destroyed, make sure we're not to
    // receive audio notifications anymore.
-   if ( gAudioIO->GetListener() == &ProjectAudioManager::Get( project ) ) {
+   // PRL:  Maybe all this is unnecessary now that the listener is managed
+   // by a weak pointer.
+   if ( gAudioIO->GetListener().get() == &ProjectAudioManager::Get( project ) ) {
       auto active = GetActiveProject();
       gAudioIO->SetListener(
-         active ? &ProjectAudioManager::Get( *active ) : nullptr
+         active
+            ? ProjectAudioManager::Get( *active ).shared_from_this()
+            : nullptr
       );
    }