Bug 458636

Additional output from gdb:
```
(gdb) frame 1
#1  0x00007fffe1b141ff in KrfbXCBEventFilter::KrfbXCBEventFilter (owner=0x5555556b1ed0, this=0x5555556b1fc0) at /usr/src/debug/krfb-22.08.0-2.fc36.x86_64/framebuffers/xcb/xcb_framebuffer.cpp:52
52          const xcb_query_extension_reply_t *xdamage_data = xcb_get_extension_data(
(gdb) list
47      KrfbXCBEventFilter::KrfbXCBEventFilter(XCBFrameBuffer *owner):
48          xdamageBaseEvent(0), xdamageBaseError(0),
49          xshmBaseEvent(0), xshmBaseError(0), xshmAvail(false),
50          fb_owner(owner)
51      {
52          const xcb_query_extension_reply_t *xdamage_data = xcb_get_extension_data(
53                      QX11Info::connection(), &xcb_damage_id);
54          if (xdamage_data) {
55              // also query extension version!
56              // ATTENTION: if we don't do that, xcb_damage_create() will always FAIL!
(gdb) p QX11Info::connection()
$1 = (xcb_connection_t *) 0x0
```

Why QX11Info::connection() is called in Wayland session, is it OK?

Output from `QT_LOGGING_RULES="krfb.krfb=true" krfb-virtualmonitor --name wireless --password 123 --resolution 1280x720 --port 5900`:
```
krfb.krfb: Loaded plugin with name  "pw"
krfb.krfb: Loaded plugin with name  "qt"
krfb.krfb: Loaded plugin with name  "xcb"
krfb.krfb: Using FrameBuffer: "xcb"
fish: Job 1, 'QT_LOGGING_RULES="krfb.krfb=tru…' terminated by signal SIGSEGV (Address boundary error
```

TLDR:
Default framebuffer plugin was set to xcb, if  krfb-virtualmonitor uses it under Wayland - it will crash.
Crash could be simply reproduced with: `rm -f ~/.config/krfbrc && krfb-virtualmonitor --name wireless --password 123 --resolution 2340x1080 --port 5900`.

Confirm issue.
krfb 22.11.90
OS: Kubuntu 22.10
KDE Plasma: 5.25.5
KDE Frameworks: 5.98.0
Qt: 5.15.6
Kernel version: 5.19.0-23-generic (64-бита)
Graphics Platform: Wayland
CPU: 12 × AMD Ryzen 5 5500U with Radeon Graphics
RAM: 30,7 ГиБ ОЗУ
Manufacturer: HP

Looks like this bug is gone.
It's still crashing after connect but with different stack trace.

Created attachment 164989 [details]
Archlinux - GDB output from jiriks74

I've encountered this bug when I tried to use the KDE Connect's Virtual Display feature.

I've ran `krfb` in GDB to see what causes the problem but I'm no smarter from the output. The GDB output is in attachments: https://bugs.kde.org/attachment.cgi?id=164989

The line that it gets SIGSEGV on is this one: 

#0  __memcpy_avx_unaligned_erms () at ../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S:660

I've tried changing the framebuffer module from `pw` to `qt` (as in settings it said that it's a slower fallback module but more stable) but then I saw that it doesn't work on Wayland in the output on `krfb` startup.

OS Info:
Operating System: EndeavourOS (Arch Linux)
KDE Plasma Version: 5.27.10
KDE Frameworks Version: 5.114.0
Qt Version: 5.15.12
Kernel Version: 6.7.0-zen3-1-zen (64-bit)
Graphics Platform: Wayland
Processors: 20 × 12th Gen Intel® Core™ i7-12700H
Memory: 15,3 GiB of RAM
Graphics Processor: Mesa Intel® Graphics

Can you retest this issue? There's been changes and as of 6.0.3 I can no longer cause krfb-virtualmonitor to crash nor can I use it to crash plasmashell.

Changing status to be more appropriate

Can't reproduce anymore with krfb-virtualmonitor version 24.02.1, Fedora 40.

I just tested this on NixOS `krfb-virtualmonitor` doesn't crash (I didn't check if it works) but `kfrb` does. 
krfb-virtualmonitor was ran as `krfb-virtualmonitor --name wireless --password 123 --resolution 1920x1200 --port 5900`

When running  `krfb 23.08.5` as `kfrb` I get:

> Wayland: Detected invalid configuration: preferredFrameBufferPlugin is not pipewire:  "xcb"
> Initializing D-Bus connectivity with XDG Desktop Portal
> DBus session created:  "/org/freedesktop/portal/desktop/request/1_143/krfb2891703386"
> kpipewire_dmabuf_logging: eglChooseConfig returned this many configs: 1
> Segmentation fault (core dumped)

Try to reset (delete) krfb config & try again.

(In reply to Yaroslav Sidlovsky from comment #12)
> Try to reset (delete) krfb config & try again.

Tried that already.