Description
Summary
LMMS may crash on replacing instruments while playing notes. This also happens when loading preset to an instrument track while it's playing.
Steps to reproduce
- Open and the provided project file(alternatively, you can open any instrument and put a lot of notes there)
- Try replacing instruments until it crash
Since it's very hard to reproduce, you may want to modify the code like this:
diff --git a/src/tracks/InstrumentTrack.cpp b/src/tracks/InstrumentTrack.cpp
index 0e75c990a..942081917 100644
--- a/src/tracks/InstrumentTrack.cpp
+++ b/src/tracks/InstrumentTrack.cpp
@@ -1027,9 +1027,11 @@ Instrument * InstrumentTrack::loadInstrument(const QString & _plugin_name,
Q_ASSERT(!key);
silenceAllNotes( true );
+ QThread::msleep(100);
lock();
delete m_instrument;
+ QThread::msleep(100);
m_instrument = Instrument::instantiate(_plugin_name, this,
key, keyFromDnd);
unlock();Technical details
In InstrumentTrack::loadInstrument, m_instrument may be used while being deleted. Also, lock()ing after calling silenceAllNotes() doesn't prevent new notes to be added in between those two calls.
When a NotePlayHandle is added between two calls, it may try to use its m_instrumentTrack->instrument() during their deletion(or after deletion) since the returned value itself is not null.
In my cases, the crash always happened in InstrumentSoundShaping::releaseFrames , at the line calling m_instrumentTrack->instrument()->desiredReleaseFrames().
The same thing may happen in InstrumentTrack::loadTrackSpecificSettings, too.