Application: kdeinit5 ()
 (Compiled from sources)
Qt Version: 5.5.1
Operating System: Linux 4.3.2 x86_64

-- Information about the crash:
- What I was doing when the application crashed:

I am trying to log into a plasma desktop session.  I compiled plasma 5.5.0 from sources.  5.4.3 compiled from source works fine.

The crash can be reproduced every time.

-- Backtrace:
Application: KCMInit (kdeinit5), signal: Segmentation fault
Using host libthread_db library "/lib/libthread_db.so.1".
[Current thread is 1 (Thread 0x7fbfce27e840 (LWP 15388))]

Thread 2 (Thread 0x7fbfb5806700 (LWP 15390)):
#0  0x00007fbfcb000dbd in poll () from /lib/libc.so.6
#1  0x00007fbfc9dc90f2 in ?? () from /usr/lib/libxcb.so.1
#2  0x00007fbfc9dcac87 in xcb_wait_for_event () from /usr/lib/libxcb.so.1
#3  0x00007fbfb82dd4e9 in ?? () from /usr/lib/libQt5XcbQpa.so.5
#4  0x00007fbfcbbf41cf in ?? () from /usr/lib/libQt5Core.so.5
#5  0x00007fbfca23f3e4 in start_thread () from /lib/libpthread.so.0
#6  0x00007fbfcb009d0d in clone () from /lib/libc.so.6

Thread 1 (Thread 0x7fbfce27e840 (LWP 15388)):
[KCrash Handler]
#5  0x00007fbfba262f5c in XIFreeDeviceInfo () from /usr/lib/libXi.so.6
#6  0x00007fbfafb15b88 in MouseSettings::apply(bool) () from /usr/lib/qt5/plugins/kcm_input.so
#7  0x00007fbfafb19536 in kcminit_mouse () from /usr/lib/qt5/plugins/kcm_input.so
#8  0x00007fbfb878f152 in KCMInit::runModule(QString const&, QExplicitlySharedDataPointer<KService>) () from /usr/lib/libkdeinit5_kcminit_startup.so
#9  0x00007fbfb878f63b in KCMInit::runModules(int) () from /usr/lib/libkdeinit5_kcminit_startup.so
#10 0x00007fbfb8790330 in KCMInit::KCMInit(QCommandLineParser const&) () from /usr/lib/libkdeinit5_kcminit_startup.so
#11 0x00007fbfb8790b8a in kdemain () from /usr/lib/libkdeinit5_kcminit_startup.so
#12 0x0000000000408952 in ?? ()
#13 0x00000000004053d0 in main ()

Reported using DrKonqi