I can't reproduce that.

If it is still reproducible if kdiff3 run directly from terminal?

Yes.

Output from commandline:
# kdiff3 -o /tmp/pgdg-fedora-all.repo -m /etc/yum.repos.d/pgdg-fedora-all.repo /etc/yum.repos.d/pgdg-fedora-all.repo.rpmnew 
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
kf.notifications: Failed to play sound with canberra: Not available
kf.notifications: Failed to play sound with canberra: Not available
KCrash: Application 'kdiff3' crashing...
KCrash: Attempting to start /usr/libexec/drkonqi
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
kf.kirigami: Failed to find a Kirigami platform plugin
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
file:///usr/lib64/qt5/qml/org/kde/kirigami.2/ContextDrawer.qml:135:9: QML ListView: Binding loop detected for property "topMargin"

Try to run it from user and not from root.

Still crashes :-( 

[kim@kim ~]$ kdiff3 -o /tmp/kde-kim/pgdg-fedora-all.repo -m /etc/yum.repos.d/pgdg-fedora-all.repo /etc/yum.repos.d/pgdg-fedora-all.repo.rpmnew
KCrash: Application 'kdiff3' crashing...
KCrash: Attempting to start /usr/libexec/drkonqi

[1]+  Stopped                 kdiff3 -o /tmp/kde-kim/pgdg-fedora-all.repo -m /etc/yum.repos.d/pgdg-fedora-all.repo /etc/yum.repos.d/pgdg-fedora-all.repo.rpmnew

I can reproduce the crash on exit just by diffing two files (attached).

[pilot:/tmp] kdiff3 License.txt License3.txt
Segmentation fault (core dumped)
Exit 139
[pilot:/tmp] 

This is a regression in kdiff3-1.10.5-1.fc38.x86_64. Downgrading to kdiff3-1.10.0-1.fc38.x86_64 fixes the crash.

Note that I am not using Wayland.

But the call stack is different than the original report:

Thread 1 "kdiff3" received signal SIGSEGV, Segmentation fault.
0x00007fffe489c880 in QXcbConnection::removeWindowEventListener(unsigned int) () from /lib64/libQt5XcbQpa.so.5
(gdb) bt
#0  0x00007fffe489c880 in QXcbConnection::removeWindowEventListener(unsigned int) () from /lib64/libQt5XcbQpa.so.5
#1  0x00007fffe48ac63d in QXcbWindow::destroy() () from /lib64/libQt5XcbQpa.so.5
#2  0x00007fffe48ac73d in QXcbWindow::~QXcbWindow() () from /lib64/libQt5XcbQpa.so.5
#3  0x00007ffff203471d in non-virtual thunk to QXcbGlxWindow::~QXcbGlxWindow() ()
   from /usr/lib64/qt5/plugins/xcbglintegrations/libqxcb-glx-integration.so
#4  0x00007ffff6b77871 in QWindowPrivate::destroy() () from /lib64/libQt5Gui.so.5
#5  0x00007ffff73d873d in QWidgetPrivate::deleteTLSysExtra() () from /lib64/libQt5Widgets.so.5
#6  0x00007ffff73e7698 in QWidget::destroy(bool, bool) () from /lib64/libQt5Widgets.so.5
#7  0x00007ffff73eed44 in QWidget::~QWidget() () from /lib64/libQt5Widgets.so.5
#8  0x000055555564a1e1 in std::shared_ptr<ProgressDialog>::~shared_ptr() [clone .lto_priv.0] ()
#9  0x00007ffff5e621e6 in __run_exit_handlers () from /lib64/libc.so.6
#10 0x00007ffff5e6232e in exit () from /lib64/libc.so.6
#11 0x00007ffff5e49b91 in __libc_start_call_main () from /lib64/libc.so.6
#12 0x00007ffff5e49c4b in __libc_start_main_impl () from /lib64/libc.so.6
#13 0x00005555555b9185 in _start ()

Created attachment 1990145 [details]
test file 1

Created attachment 1990146 [details]
test file 2

One other observation:
The crash only happens if I exit via the File->Quit menu or Ctrl-Q. It does not crash if I exit by closing the window via Ctrl-F4 or the mouse click.

This bug has been already fixed upstream on the "stable" 1.10.x branch in https://invent.kde.org/sdk/kdiff3/-/commit/5849ea6d7de19dcdb21534bdc63881e1d3cf274f. I verified locally that the fix works, but it is dependent on some previous commits, so it can't be easily patched to stock 1.10.5.

Thanks.
I will apply patch in next few days.

Seems problem solved in version 1.10.6.
Builds on the way.

FEDORA-2023-2c227920b9 has been submitted as an update to Fedora 38. https://bodhi.fedoraproject.org/updates/FEDORA-2023-2c227920b9

FEDORA-2023-96f5ef6ceb has been submitted as an update to Fedora 39. https://bodhi.fedoraproject.org/updates/FEDORA-2023-96f5ef6ceb

Thanks, kdiff3-1.10.6-1.fc38.x86_64 fixes this for me on Fedora 38.

FEDORA-2023-96f5ef6ceb has been pushed to the Fedora 39 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2023-96f5ef6ceb`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2023-96f5ef6ceb

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

FEDORA-2023-2c227920b9 has been pushed to the Fedora 38 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2023-2c227920b9`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2023-2c227920b9

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Thanks a lot!! :-)  I have tested the fix (new version) and it works as a charm.

FEDORA-2023-96f5ef6ceb has been pushed to the Fedora 39 stable repository.
If problem still persists, please make note of it in this bug report.

FEDORA-2023-2c227920b9 has been pushed to the Fedora 38 stable repository.
If problem still persists, please make note of it in this bug report.