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  1. Qt
  2. QTBUG-97603

Qt5/ Qt6 applications crash with Segmentation fault on wacom tablet touch input



    • Bug
    • Resolution: Unresolved
    • P3: Somewhat important
    • None
    • 5.15.2, 5.15.3, 5.15.5, 6.3.1
    • None
    • Linux/X11


      I have a Lenovo m14t monitor with multitouch and stylus. It has a wacom tablet, and the stylus is an active one with battery, pressure sensitivity and two buttons: One "stylus button" and the other turns it into an eraser.

      When I use it under Xorg with the wacom driver from the xf86-input-wacom project, any Qt5 based application I tried so far crashes with a Segmentation fault as soon as I touch the touchscreen with my finger (it does not so on stylus input).

      This tried for the following software:

      • marble-qt, version 2.2.20,
      • kate, version 21.08.2.
      • krusader, version 2.7.2,
      • dolphin, version 21.08.2,
      • digikam, version 7.3.01,
      • qt5ct, version 1.5.

      Underlying qt5-base libraries are version 5.15.2+kde+r237, from Artix Linux; see below under "Environment".

      As an example, here for marble-qt a gdb run:

      Start it with gdb marble-qt, input run on gdb's command line, waiting until the programme is up, produces the following output:

      Starting program: /usr/bin/marble-qt
      [Thread debugging using libthread_db enabled]
      Using host libthread_db library "/usr/lib/libthread_db.so.1".
      [New Thread 0x7fffda7e5640 (LWP 10845)]
      [New Thread 0x7fffc8151640 (LWP 10846)]
      [New Thread 0x7fffbffff640 (LWP 10847)]
      [New Thread 0x7fffb3fff640 (LWP 10848)]
      [New Thread 0x7fffa7fff640 (LWP 10849)]
      [New Thread 0x7fff9bfff640 (LWP 10850)]
      [Thread 0x7fff9bfff640 (LWP 10850) exited]
      [New Thread 0x7fff9bfff640 (LWP 10851)]
      [Detaching after fork from child process 10852]
      [Detaching after fork from child process 10853]
      [Detaching after fork from child process 10854]
      [New Thread 0x7fff8ffff640 (LWP 10857)]
      [New Thread 0x7fff83fff640 (LWP 10858)]
      [New Thread 0x7fff77fff640 (LWP 10859)]
      [New Thread 0x7fff6bfff640 (LWP 10860)]
      [New Thread 0x7fff5ffff640 (LWP 10861)]
      [New Thread 0x7fff5bffe640 (LWP 10862)]
      [New Thread 0x7fff3fffd640 (LWP 10865)]
      [New Thread 0x7fff47fff640 (LWP 10863)]
      [New Thread 0x7fff43ffe640 (LWP 10864)]
      [New Thread 0x7fff37ffb640 (LWP 10867)]
      [New Thread 0x7fff3bffc640 (LWP 10866)]
      [New Thread 0x7fff23fff640 (LWP 10868)]
      [New Thread 0x7fff17fff640 (LWP 10869)]
      [New Thread 0x7fff03fff640 (LWP 10870)]
      [Thread 0x7fff03fff640 (LWP 10870) exited]
      [New Thread 0x7fff03fff640 (LWP 10871)]
      [Thread 0x7fff03fff640 (LWP 10871) exited]
      [New Thread 0x7fff03fff640 (LWP 10872)]
      [New Thread 0x7ffeffffe640 (LWP 10873)]
      [New Thread 0x7ffef3fff640 (LWP 10874)]
      [Detaching after fork from child process 10875]
      [New Thread 0x7ffee7fff640 (LWP 10876)]
      [New Thread 0x7ffedbfff640 (LWP 10881)]
      [New Thread 0x7ffecffff640 (LWP 10885)]
      [New Thread 0x7ffec3fff640 (LWP 10894)]
      [New Thread 0x7ffeb7fff640 (LWP 10909)]
      [New Thread 0x7ffeabfff640 (LWP 10910)]
      [New Thread 0x7ffe9ffff640 (LWP 10911)]
      [New Thread 0x7ffe93fff640 (LWP 10912)]
      [New Thread 0x7ffe8fffe640 (LWP 10913)]
      [Thread 0x7ffe9ffff640 (LWP 10911) exited]
      [New Thread 0x7ffe9ffff640 (LWP 10914)]
      [New Thread 0x7ffe83fff640 (LWP 10915)]
      [Thread 0x7ffe93fff640 (LWP 10912) exited]
      [New Thread 0x7ffe93fff640 (LWP 10916)]
      [New Thread 0x7ffe77fff640 (LWP 10917)]
      [Thread 0x7ffe9ffff640 (LWP 10914) exited]
      [New Thread 0x7ffe9ffff640 (LWP 10918)]
      [Thread 0x7ffe93fff640 (LWP 10916) exited]
      [New Thread 0x7ffe73ffe640 (LWP 10919)]
      [New Thread 0x7ffe93fff640 (LWP 10920)]
      [Thread 0x7ffe73ffe640 (LWP 10919) exited]
      [New Thread 0x7ffe73ffe640 (LWP 10921)]
      [Thread 0x7ffe93fff640 (LWP 10920) exited]
      [Thread 0x7ffe73ffe640 (LWP 10921) exited]
      [New Thread 0x7ffe73ffe640 (LWP 10925)]
      [Thread 0x7ffeb7fff640 (LWP 10909) exited]
      [New Thread 0x7ffeb7fff640 (LWP 10937)]
      [New Thread 0x7ffe93fff640 (LWP 10938)]
      [New Thread 0x7ffe6fffd640 (LWP 10939)]
      [New Thread 0x7ffe6bffc640 (LWP 10940)]
      [New Thread 0x7ffe67ffb640 (LWP 10941)]
      [New Thread 0x7ffe63ffa640 (LWP 10942)]
      [New Thread 0x7ffe5fff9640 (LWP 10943)]
      [Thread 0x7ffe9ffff640 (LWP 10918) exited]
      [Thread 0x7ffe83fff640 (LWP 10915) exited]
      [Thread 0x7ffe8fffe640 (LWP 10913) exited]
      [Thread 0x7ffe77fff640 (LWP 10917) exited]
      [Thread 0x7fff3bffc640 (LWP 10866) exited]
      [Thread 0x7fff5bffe640 (LWP 10862) exited]
      [Thread 0x7fff5ffff640 (LWP 10861) exited]
      [Thread 0x7fff43ffe640 (LWP 10864) exited]
      [New Thread 0x7fff43ffe640 (LWP 11056)]
      [Thread 0x7fff43ffe640 (LWP 11056) exited]

      Now, when I touch the programme with my finger on the touchscreen, the following output comes:

      Thread 1 "marble-qt" received signal SIGSEGV, Segmentation fault.
      0x00007fffda91ab27 in QXcbConnection::xi2ProcessTouch(void*, QXcbWindow*) () from /usr/lib/libQt5XcbQpa.so.5

      Then, in the gdb command line, typing bt for "backtrace", yields the following:

      #0  0x00007fffda91ab27 in QXcbConnection::xi2ProcessTouch(void*, QXcbWindow*) () at /usr/lib/libQt5XcbQpa.so.5#1  0x00007fffda8e6dcf in QXcbConnection::handleXcbEvent(xcb_generic_event_t*) () at /usr/lib/libQt5XcbQpa.so.5#2  0x00007fffda8e82d1 in QXcbConnection::processXcbEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/libQt5XcbQpa.so.5#3  0x00007fffda90f7f8 in  () at /usr/lib/libQt5XcbQpa.so.5#4  0x00007ffff4e6909c in g_main_context_dispatch () at /usr/lib/libglib-2.0.so.0#5  0x00007ffff4ebe7f9 in  () at /usr/lib/libglib-2.0.so.0#6  0x00007ffff4e666e5 in g_main_context_iteration () at /usr/lib/libglib-2.0.so.0#7  0x00007ffff6661a8a in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/libQt5Core.so.5#8  0x00007ffff6606a1b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/libQt5Core.so.5#9  0x00007ffff660f208 in QCoreApplication::exec() () at /usr/lib/libQt5Core.so.5#10 0x000055555556a090 in  ()#11 0x00007ffff5f6eb25 in __libc_start_main () at /usr/lib/libc.so.6#12 0x000055555556ac8e in  ()

      Typing cont for "continue" in gdb's command line then yields the following (leading to quitting of the software):

      Couldn't get registers: No such process.
      Couldn't get registers: No such process.
      (gdb) [Thread 0x7ffe5fff9640 (LWP 10943) exited]
      [Thread 0x7ffe63ffa640 (LWP 10942) exited]
      [Thread 0x7ffe67ffb640 (LWP 10941) exited]
      [Thread 0x7ffe6bffc640 (LWP 10940) exited]
      [Thread 0x7ffe6fffd640 (LWP 10939) exited]
      [Thread 0x7ffe93fff640 (LWP 10938) exited]
      [Thread 0x7ffeb7fff640 (LWP 10937) exited]
      [Thread 0x7ffe73ffe640 (LWP 10925) exited]
      [Thread 0x7ffeabfff640 (LWP 10910) exited]
      [Thread 0x7ffec3fff640 (LWP 10894) exited]
      [Thread 0x7ffecffff640 (LWP 10885) exited]
      [Thread 0x7ffedbfff640 (LWP 10881) exited]
      [Thread 0x7ffee7fff640 (LWP 10876) exited]
      [Thread 0x7ffef3fff640 (LWP 10874) exited]
      [Thread 0x7ffeffffe640 (LWP 10873) exited]
      [Thread 0x7fff03fff640 (LWP 10872) exited]
      [Thread 0x7fff17fff640 (LWP 10869) exited]
      [Thread 0x7fff23fff640 (LWP 10868) exited]
      [Thread 0x7fff37ffb640 (LWP 10867) exited]
      [Thread 0x7fff3fffd640 (LWP 10865) exited]
      [Thread 0x7fff47fff640 (LWP 10863) exited]
      [Thread 0x7fff6bfff640 (LWP 10860) exited]
      [Thread 0x7fff77fff640 (LWP 10859) exited]
      [Thread 0x7fff83fff640 (LWP 10858) exited]
      [Thread 0x7fff8ffff640 (LWP 10857) exited]
      [Thread 0x7fff9bfff640 (LWP 10851) exited]
      [Thread 0x7fffa7fff640 (LWP 10849) exited]
      [Thread 0x7fffb3fff640 (LWP 10848) exited]
      [Thread 0x7fffc8151640 (LWP 10846) exited]
      [Thread 0x7fffda7e5640 (LWP 10845) exited]
      [Thread 0x7fffdb1d8140 (LWP 10838) exited]

      Then when I want to quit gdb it still prints the warning

      A debugging session is active.

      Inferior 1 [process 10838] will be killed.

      Quit anyway? (y or n)

      but the only useful to do I seem to find is to just quit.


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            srutledg Shawn Rutledge
            dreieck Drei Eck
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