Hi,

I haven't been able to reproduce this 100% of the time, but it happens
some of the time after logging in after rebooting.  I have a system
load monitor and have noticed that memory balloons and system
responsiveness drops right before the crash occurs.  Sorry for the
partially incomplete backtrace; libkf5configcore5-dbgsym wasn't
updated to 5.54.0-1+deb10u1 for some reason and is uninstallable.

Application: kdeinit5 (kdeinit5), signal: Segmentation fault
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[KCrash Handler]
#6  0x00007f966bfb6465 in QVector<unsigned long long>::reallocData (this=this@entry=0x5630f066f3a8, asize=268435452, aalloc=<optimized out>, options=...) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qarraydata.h:218
#7  0x00007f966bfba78e in QVector<unsigned long long>::append (t=<synthetic pointer>: <optimized out>, this=0x5630f066f3a8) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qrefcount.h:102
#8  QVector<unsigned long long>::operator<< (t=<synthetic pointer>: <optimized out>, this=0x5630f066f3a8) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qvector.h:283
#9  IdTreePostingIterator::next (this=0x5630f066f380) at ./src/engine/idtreedb.cpp:128
#10 0x00007f966bfa9444 in Baloo::AndPostingIterator::next (this=0x5630f0662de0) at ./src/engine/andpostingiterator.cpp:42
#11 Baloo::AndPostingIterator::next (this=0x5630f0662de0) at ./src/engine/andpostingiterator.cpp:45
#12 0x00007f966c18c4c1 in ?? () from /usr/lib/x86_64-linux-gnu/libKF5Baloo.so.5
#13 0x00007f966c17b190 in Baloo::Query::exec() () from /usr/lib/x86_64-linux-gnu/libKF5Baloo.so.5
#14 0x00007f967332f519 in ?? () from /usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kio/baloosearch.so
#15 0x00007f966e512f36 in KIO::SlaveBase::dispatch (this=0x7ffe684bffa0, command=71, data=...) at ./src/core/slavebase.cpp:1176
#16 0x00007f966e513876 in KIO::SlaveBase::dispatchLoop (this=0x7ffe684bffa0) at ./src/core/slavebase.cpp:325
#17 0x00007f967332fd07 in kdemain () from /usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kio/baloosearch.so
#18 0x00005630f0593e1c in launch (argc=4, _name=0x5630f0641248 "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kio/baloosearch.so", args=<optimized out>, cwd=<optimized out>, envc=0, envs=<optimized out>, reset_env=false, tty=0x0, avoid_loops=false, startup_id_str=0x5630f0597187 "0") at ./src/kdeinit/kinit.cpp:706
#19 0x00005630f0594eea in handle_launcher_request (sock=8, who=<optimized out>) at ./src/kdeinit/kinit.cpp:1146
#20 0x00005630f05958fb in handle_requests (waitForPid=0) at ./src/kdeinit/kinit.cpp:1339
#21 0x00005630f0590645 in main (argc=5, argv=<optimized out>) at ./src/kdeinit/kinit.cpp:1785
[Inferior 1 (process 2571) detached]

Wow, it was harder than expected to get the dbsym packages without a
security-debug suite.  Thanks to adsb and ansgar on #debian-qt-kde for
the help (adds additional steps to my easy useful backtraces for end
users plan).  Here it is:

Application: kdeinit5 (kdeinit5), signal: Segmentation fault
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[KCrash Handler]
#6  0x00007f966bfb6465 in QVector<unsigned long long>::reallocData (this=this@entry=0x5630f066f3a8, asize=268435452, aalloc=<optimized out>, options=...) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qarraydata.h:218
#7  0x00007f966bfba78e in QVector<unsigned long long>::append (t=<synthetic pointer>: <optimized out>, this=0x5630f066f3a8) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qrefcount.h:102
#8  QVector<unsigned long long>::operator<< (t=<synthetic pointer>: <optimized out>, this=0x5630f066f3a8) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qvector.h:283
#9  IdTreePostingIterator::next (this=0x5630f066f380) at ./src/engine/idtreedb.cpp:128
#10 0x00007f966bfa9444 in Baloo::AndPostingIterator::next (this=0x5630f0662de0) at ./src/engine/andpostingiterator.cpp:42
#11 Baloo::AndPostingIterator::next (this=0x5630f0662de0) at ./src/engine/andpostingiterator.cpp:45
#12 0x00007f966c18c4c1 in Baloo::SearchStore::exec (this=this@entry=0x7ffe684bfcb0, term=..., offset=<optimized out>, limit=<optimized out>, sortResults=<optimized out>) at ./src/lib/searchstore.cpp:127
#13 0x00007f966c17b190 in Baloo::Query::exec (this=this@entry=0x7ffe684bfd40) at ./src/lib/query.cpp:210
#14 0x00007f967332f519 in Baloo::SearchProtocol::listDir (this=0x7ffe684bffa0, url=...) at ./src/kioslaves/search/kio_search.cpp:120
#15 0x00007f966e512f36 in KIO::SlaveBase::dispatch (this=0x7ffe684bffa0, command=71, data=...) at ./src/core/slavebase.cpp:1176
#16 0x00007f966e513876 in KIO::SlaveBase::dispatchLoop (this=this@entry=0x7ffe684bffa0) at ./src/core/slavebase.cpp:325
#17 0x00007f967332fd07 in kdemain (argc=<optimized out>, argv=<optimized out>) at ./src/kioslaves/search/kio_search.cpp:218
#18 0x00005630f0593e1c in launch (argc=4, _name=0x5630f0641248 "/usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kio/baloosearch.so", args=<optimized out>, cwd=<optimized out>, envc=0, envs=<optimized out>, reset_env=false, tty=0x0, avoid_loops=false, startup_id_str=0x5630f0597187 "0") at ./src/kdeinit/kinit.cpp:706
#19 0x00005630f0594eea in handle_launcher_request (sock=8, who=<optimized out>) at ./src/kdeinit/kinit.cpp:1146
#20 0x00005630f05958fb in handle_requests (waitForPid=0) at ./src/kdeinit/kinit.cpp:1339
#21 0x00005630f0590645 in main (argc=5, argv=<optimized out>) at ./src/kdeinit/kinit.cpp:1785
[Inferior 1 (process 2571) detached]

I'm still not sure how to reliably reproduce this bug, but the
kdeinit5 crashes have continued to occur every ~30min today (within a
single session).

The memory usage spike I mentioned in a previous message seems to be
caused by baloosearch.so ... which didn't have this issue in stretch.
The backtrace seems to support a possible baloo<->kdeinit5
malinteraction.

P.S. I'm blacklisting most directories, because Baloo has always
choked when fed too much data.

After a big dist-upgrade I just did (and a reboot), I am not also experiencing
kdeinit5 crashes.  There's a notification popping up every now and then telling
me it crashed.  However it doesn't let me report a bug (looks like no bug
reporting URL is set, or so); so I am not sure how to even capture a stacktrace
of this.

; Ralf