Client crash on MIDI mixdown when using multiple connections

[falkTX]

I'm having a crash (assertion failure) in latest git jack2 code.

it crashes during jack_port_get_buffer function.
Running the app normally prints to terminal:
jack_midi_dump: ../common/JackMidiPort.cpp:130: void Jack::MidiBufferMixdown(void*, void**, int, jack_nframes_t): Assertion next_event != 0' failed.and through GDB:0x00007ffff6af2302 in __GI___assert_fail (assertion=0x7fffe92e8fbb "next_event != 0", file=0x7fffe92e8fa0 "../common/JackMidiPort.cpp", line=130, function=0x7fffe92e8fe0 "void Jack::MidiBufferMixdown(void*, void**, int, jack_nframes_t)") at assert.c:101`

I was able to get a simple test for the crash (in Linux).

1. run any kind of jack-midi generator (sequencer, keyboard, etc)
2. run another client that has jack-midi-out, but this one doesn't need to output any events.
(I'm using "jack_midiseq EmptySequencer 1 24000 0 60")
3. run "jack_midi_dump" twice
4. connect the midi generator out port to both midi-monitor in ports, same thing for midiseq
5. generate/play some events for a few seconds

a single or both jack_midi_dump tools will abort due to an assertion failure.

[falkTX]

screenshot of the connections required for the crash

[sletz]

Dmitry Baikov wrote this code… back in 2007. Not sure he even read this list anymore.

Any way for you to debug the code yourself with the test case you have?

Stéphane

Le 21 déc. 2013 à 05:41, falkTX notifications@github.com a écrit :

I'm having a crash (assertion failure) in latest git jack2 code.

it crashes during jack_port_get_buffer function.
Running the app normally prints to terminal:
jack_midi_dump: ../common/JackMidiPort.cpp:130: void Jack::MidiBufferMixdown(void_, void__, int, jack_nframes_t): Assertion `next_event != 0' failed.
and through GDB:
0x00007ffff6af2302 in _GI___assert_fail (assertion=0x7fffe92e8fbb "next_event != 0", file=0x7fffe92e8fa0 "../common/JackMidiPort.cpp", line=130, function=0x7fffe92e8fe0 "void Jack::MidiBufferMixdown(void, void**, int, jack_nframes_t)") at assert.c:101

I was able to get a simple test for the crash (in Linux).

1. run any kind of jack-midi generator (sequencer, keyboard, etc)
2. run another client that has jack-midi-out, but this one doesn't need to output any events.
   (I'm using "jack_midiseq EmptySequencer 1 24000 0 60")
3. run "jack_midi_dump" twice
4. connect the midi generator out port to both midi-monitor in ports, same thing for midiseq
5. generate/play some events for a few seconds

a single or both jack_midi_dump tools will abort due to an assertion failure.

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[falkTX]

I'll build jack2 in debug mode and see what I can find about this.
I'm not sure what's the best way to debug this though, any tips?

[7890]

@falkTX the described setup seems to work (now) as expected in jackd 1.9.12, please confirm.

[falkTX]

Ah yes, this was handled in fb87a14
assert in a library used by others is not very nice..