Bug#794959: kwin-x11: kwin crashes on startup

[Rostislav Pehlivanov <atomnuker@gmail.com>]

Package: kwin-x11
Version: 4:5.3.2-3
Severity: important

Dear Maintainer,

Kwin crashes on startup. This happens in every possible use:
1. Using kwin_x11 --replace to replace a window manager of another
desktop environment causes it to crash. The details tab just says it segfaults.

2. Starting plasma 5 normally through sddm or another display manager will simply
make Plamsa 5 freeze after the loading bar is full or once the wallpaper is loaded up.
There is no way to get a crash log here since no prompts show up nor does the sddm
service print an error to the journal nor does Kwin print to any log. The only
way I've confirmed that this is a kwin bug is:

3. Running startkde (by first stopping the sddm/display manager, running 'sudo Xorg` in
a VT terminal, switching to another terminal and running 'DISPLAY=:0 starkde'). This
causes Plamsa 5 to load up normally and display the bar which once again freezes once full.
Switching back to the VT with startkde, KCrash reports that kwin_x11 has crashed
with the reason being segfault.

I've also confirmed that this is not related in any way to the current Plasma 5 crashes on
Intel using the 'sna' accerelation method. Switching to 'uxa' has no effect on the kwin
crashes.
The crashes/startup freezes also occur for a completely new, just created user account, so it's
not a config problem.
When sddm is restarted and the normal startup procedure is attempted, switching back to a VT
once the freeze happens prints that libQt5Sql has segfaulted, though this does not always happen
so I don't think this is related.


-- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (900, 'unstable'), (800, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.2.0-rc4-youmu (SMP w/2 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages kwin-x11 depends on:
ii  kwin-common          4:5.3.2-3
ii  libc6                2.21-0experimental0
ii  libkf5i18n5          5.12.0-1
ii  libkf5windowsystem5  5.12.0-1
ii  libqt5core5a         5.4.2+dfsg-8
ii  libqt5gui5           5.4.2+dfsg-8
ii  libqt5widgets5       5.4.2+dfsg-8
ii  libqt5x11extras5     5.4.2-2
ii  libstdc++6           5.2.1-12
ii  libxcb1              1.10-3+b1

kwin-x11 recommends no packages.

kwin-x11 suggests no packages.

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