This descibes possible causes for a rare crasher with effects.

[daschuer]

I have experienced a crasher during testing of #2618

Probably related:
https://bugs.launchpad.net/mixxx/+bug/1775497

Here is the log, unfortunately it has not happen to me under GDB.

QML debugging is enabled. Only use this in a safe environment.
Loading resources from  "/home/daniel/workspace/2.3/res/"
Configuration file is at version "2.3.0-beta" instead of the current "2.4.0-alpha-pre"
BroadcastSettings - Found 1 profile(s)
Loading resources from  "/home/daniel/workspace/2.3/res/"
Found and will use default keyboard mapping "/home/daniel/workspace/2.3/res/keyboard/en_US.kbd.cfg"
Loading resources from  "/home/daniel/workspace/2.3/res/"
Loaded skin "Shade"
DBus screensaver  org.freedesktop.ScreenSaver  inhibited
ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear
ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe
ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side
ALSA lib pcm_route.c:869:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:869:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:869:(find_matching_chmap) Found no matching channel map
ALSA lib pcm_route.c:869:(find_matching_chmap) Found no matching channel map
Cannot connect to server socket err = Datei oder Verzeichnis nicht gefunden
Cannot connect to server request channel
jack server is not running or cannot be started
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
Cannot connect to server socket err = Datei oder Verzeichnis nicht gefunden
Cannot connect to server request channel
jack server is not running or cannot be started
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
ALSA lib pcm_oss.c:377:(_snd_pcm_oss_open) Unknown field port
ALSA lib pcm_oss.c:377:(_snd_pcm_oss_open) Unknown field port
ALSA lib pcm_usb_stream.c:486:(_snd_pcm_usb_stream_open) Invalid type for card
ALSA lib pcm_usb_stream.c:486:(_snd_pcm_usb_stream_open) Invalid type for card
Cannot connect to server socket err = Datei oder Verzeichnis nicht gefunden
Cannot connect to server request channel
jack server is not running or cannot be started
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
warning [Main] Library - Skipping access check for missing or invalid directory QFileInfo(/home/daniel/Öffen)
warning [BrowseThread] MetadataSourceTagLib - Cannot import track metadata from file "/home/daniel/Musik/Mixxx/Recordings/2021-03-16_15h27m08s.aac" with unknown or unsupported type 0
warning [BrowseThread] MetadataSourceTagLib - Cannot import track metadata from file "/home/daniel/Musik/Mixxx/Recordings/2021-03-16_15h26m32s.aac" with unknown or unsupported type 0
warning [BrowseThread] MetadataSourceTagLib - Cannot import track metadata from file "/home/daniel/Musik/Mixxx/Recordings/2021-03-16_15h26m02s.aac" with unknown or unsupported type 0
warning [Main] ControlDoublePrivate::getControl returning NULL for ( "[Master]" , "skin_settings" )
Abgebrochen (Speicherabzug geschrieben)

[Be-ing]

This code hasn't changed since you reviewed it years ago in #1254 besides adding documentation. This is unrelated to #2618 and I think it's inappropriate to open this PR as if these preexisting bugs are somehow a justification for not merging a 3.5 year old branch.

[ronso0]

I don't see a comment that this blocks #2618...
It's just ToDos been added.

[Swiftb0y]

It doesn't matter whether this PR is related to #2618 or not. It contains useful information for posterity and thats why we should merge it. But it should not block the merge of #2618!!

[Be-ing]

I don't know if this really contains useful information. We have a bug report and some guesses what causes the bug but it does not seem to be known for sure. I do not think it is appropriate to add potentially misleading comments to the code.

[ywwg]

Here is the log, unfortunately it has not happen to me under GDB.

can you get the crash to occur reliably without gdb? If so you should be able to enable corefile dumps and attach gdb to the corefile. (That's how I was able to find the controller shutdown bug)

[daschuer]

I have not yet found a pattern to reproduce that crash. It did not happen in my latest tests.
I think core dumps are enabled by default on Ubuntu. However I have no experience to use it for debugging. Probably a good Idea to learn it. Thank you for the hint.

[Holzhaus]

I have not yet found a pattern to reproduce that crash. It did not happen in my latest tests.
I think core dumps are enabled by default on Ubuntu. However I have no experience to use it for debugging. Probably a good Idea to learn it. Thank you for the hint.

If Ubuntu uses systemd's coredump mechanism, you can usecoredumpctl to open a gdb instance for the latest coredump:

$ coredump -1 gdb

[daschuer]

Ubuntu uses Apport

[Be-ing]

https://blogs.gnome.org/mcatanzaro/2021/09/18/creating-quality-backtraces-for-crash-reports/

[daschuer]

Reopened at: #4487