Bug 439832

This happens for me, too.

Perhaps I am wrong, but some file.so and thumbnail.so IO slave keeps that open.

I have encountered this issue with a recent AppImage also and have spent some time digging into it further--because I'm *so* close to being able to use Kate for working with Rust. :)

Summary:

 * A flatpak version that does not hang uses Qt 5.15.3 while an AppImage version that does hang uses Qt 5.15.2. (NB: When I looked on the GitHub Qt mirror there didn't appear to be a tag for Qt 5.15.3 AFAICT.)

 * A backtrace of the hung process:

```

Thread 1 "AppRun.wrapped" received signal SIGINT, Interrupt.
syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
38      ../sysdeps/unix/sysv/linux/x86_64/syscall.S: No such file or directory.
(gdb) bt
#0  syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
#1  0x00007ffff2a29224 in QSemaphore::acquire(int) () from /<path>/kate-appimage-extracted/squashfs-root/usr/bin/../lib/libQt5Core.so.5
#2  0x00007ffff2c6aa5e in void doActivate<false>(QObject*, int, void**) ()
   from /<path>/kate-appimage-extracted/squashfs-root/usr/bin/../lib/libQt5Core.so.5
#3  0x00007ffff2c63fff in QObject::destroyed(QObject*) () from /<path>/kate-appimage-extracted/squashfs-root/usr/bin/../lib/libQt5Core.so.5
#4  0x00007ffff2c688b4 in QObject::~QObject() () from /<path>/kate-appimage-extracted/squashfs-root/usr/bin/../lib/libQt5Core.so.5
#5  0x00007ffff2c2fa13 in QCoreApplication::~QCoreApplication() () from /<path>/kate-appimage-extracted/squashfs-root/usr/bin/../lib/libQt5Core.so.5
#6  0x00007ffff3226699 in QGuiApplication::~QGuiApplication() () from /<path>/kate-appimage-extracted/squashfs-root/usr/bin/../lib/libQt5Gui.so.5
#7  0x00007ffff3d32d1b in QApplication::~QApplication() () from /<path>/kate-appimage-extracted/squashfs-root/usr/bin/../lib/libQt5Widgets.so.5
#8  0x000055555558e688 in ?? ()
#9  0x00007ffff2217bf7 in __libc_start_main (main=0x55555558c2f0, argc=1, argv=0x7fffffffdd18, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>,
    stack_end=0x7fffffffdd08) at ../csu/libc-start.c:310
#10 0x000055555558fc6a in _start ()
(gdb) info threads
  Id   Target Id         Frame
* 1    Thread 0x7ffff7f9f900 (LWP 31069) "AppRun.wrapped" syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
  2    Thread 0x7fffe242a700 (LWP 31073) "QXcbEventQueue" 0x00007ffff230acb9 in __GI___poll (fds=0x7fffe2429ba8, nfds=1, timeout=-1)
    at ../sysdeps/unix/sysv/linux/poll.c:29
  3    Thread 0x7fffd5d8b700 (LWP 31074) "gmain" 0x00007ffff230acb9 in __GI___poll (fds=0x555555934490, nfds=2, timeout=-1) at ../sysdeps/unix/sysv/linux/poll.c:29
  4    Thread 0x7fffd5119700 (LWP 31075) "gdbus" 0x00007ffff230acb9 in __GI___poll (fds=0x5555559bbb90, nfds=2, timeout=-1) at ../sysdeps/unix/sysv/linux/poll.c:29

```

 * There does appear to be a possibly related code change in the surrounding area/version: https://github.com/qt/qtbase/commit/c1454d07cfc3f4cb8273fdb45b152c8942d04129

Suggestion for possible fix: Bump the Qt version used for the AppImage to Qt v5.15.3 and see if that solves the issue.

More system details:

> elementary OS 5.1.7 Hera (GNU/Linux 5.4.0-60-generic x86_64)
> Built on Ubuntu 18.04.6 LTS

[My apologies for the less than comprehensive details in this comment but I've just spent hours signing up for three different KDE accounts & working through various Bugzilla processes/issues on an *extremely* hot day, so wanted to share at least this much information before I ran out of momentum entirely. :)

I'll attempt to try to fill in some more details later if beneficial.]

Current nightmake uses Qt 5.15.8