startplasmacompositor and Applications Launcher: Cannot mix incompatible Qt library (version 0x50902) with this library (version 0x50901)

[kliu128]

Issue description

Between nixpkgs of two days ago and nixpkgs today, it seems the Applications Menu in KDE and the Plasma wayland session crash on start, likely due to Qt downgrade from #31357. startplasmacompositor shows the cursor for a split second, then crashes, while the Applications Menu crashes plasmashell.

Log opening Applications Menu in X:

Nov 10 07:29:44 rem xsession[31304]: KAStatsFavoritesModel::setFavorites is ignored                                          
Nov 10 07:29:44 rem xsession[31304]: [KASTATSFAVS]  0x5d521a0 0x0 "no client ID yet"   initForClient "org.kde.plasma.kickoff.
favorites.instance-165"                                                                                                      
Nov 10 07:29:44 rem xsession[31304]: [KASTATSFAVS]  0x5d521a0 0x611b7e0 "org.kde.plasma.kickoff.favorites.instance-165"   Loa
ding the ordering  ("preferred://browser", "systemsettings.desktop", "org.kde.dolphin.desktop", "org.kde.kate.desktop", "org.
kde.discover.desktop")                                                                                                       
Nov 10 07:29:44 rem xsession[31304]: [KASTATSFAVS]  0x5d521a0 0x611b7e0 "org.kde.plasma.kickoff.favorites.instance-165"   Que
ry is Query { Select: LinkedResources, Type: (":any"), Agent: ("org.kde.plasma.favorites.applications", "org.kde.plasma.favor
ites.contacts", "org.kde.plasma.favorites.documents"), Activity: (":current", ":global"), Url: ("*"), Order: HighScore, Limit
: 0 }                                                                                                                        
Nov 10 07:29:44 rem xsession[31304]: Cannot mix incompatible Qt library (version 0x50902) with this library (version 0x50901)

Log starting Plasma wayland session (long):

removed '/home/kevin/.cache/icon-cache.kcache'
startplasmacompositor: Starting up...
Activating service name='org.freedesktop.systemd1'
Activated service 'org.freedesktop.systemd1' failed: Process org.freedesktop.systemd1 exited with status 1
dbus-update-activation-environment: warning: error sending to systemd: org.freedesktop.DBus.Error.Spawn.ChildExited: Process org.freedesktop.systemd1 exited with status 1
No backend specified through command line argument, trying auto resolution
Icon theme "ubuntu-mono-dark" not found.
Icon theme "Mint-X" not found.
Icon theme "elementary" not found.
Icon theme "gnome" not found.
OpenGL vendor string:                   X.Org
OpenGL renderer string:                 Radeon RX 580 Series (AMD POLARIS10 / DRM 3.18.0 / 4.13.12, LLVM 5.0.0)
OpenGL version string:                  4.5 (Core Profile) Mesa 17.2.4
OpenGL shading language version string: 4.50
Driver:                                 Unknown
GPU class:                              Unknown
OpenGL version:                         4.5
GLSL version:                           4.50
Mesa version:                           17.2.4
Linux kernel version:                   4.13.12
Requires strict binding:                no
GLSL shaders:                           yes
Texture NPOT support:                   yes
Virtual Machine:                        no
_XSERVTransSocketUNIXCreateListener: ...SocketCreateListener() failed
_XSERVTransMakeAllCOTSServerListeners: server already running
_XSERVTransSocketUNIXCreateListener: ...SocketCreateListener() failed
_XSERVTransMakeAllCOTSServerListeners: server already running
glamor: EGL version 1.5 (DRI2):
X-Server started on display :2
This application failed to start because it could not find or load the Qt platform plugin "xcb"
in "".

Available platform plugins are: minimal, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, xcb, wayland-org.kde.kwin.qpa, minimal, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, xcb.

Reinstalling the application may fix this problem.
org.kde.kwindowsystem: Could not find any platform plugin
Configuring Lock Action
file:///run/current-system/sw/share/kwin/virtualkeyboard/main.qml:21:1: module "QtQuick.VirtualKeyboard" is not installed 
     import QtQuick.VirtualKeyboard 2.1 
     ^
kf5.kcoreaddons.desktopparser: Property type "Url" is not a known QVariant type. Found while parsing property definition for "X-KWin-Video-Url" in "/run/current-system/sw/share/kservicetypes5/kwin-effect.desktop"
Session path: "/org/freedesktop/login1/session/_32"
The XKEYBOARD keymap compiler (xkbcomp) reports:
> Error:            Key <CAPS> added to map for multiple modifiers
>                   Using Control, ignoring Lock.
Errors from xkbcomp are not fatal to the X server
QObject::connect: invalid null parameter
xkbcommon: ERROR: Key "<CAPS>" added to modifier map for multiple modifiers; Using Control, ignoring Lock
Using Wayland-EGL
QObject::connect: invalid null parameter
xkbcommon: ERROR: Key "<CAPS>" added to modifier map for multiple modifiers; Using Control, ignoring Lock
Icon theme "ubuntu-mono-dark" not found.
Icon theme "Mint-X" not found.
Icon theme "elementary" not found.
Icon theme "gnome" not found.
QObject::connect: invalid null parameter
xkbcommon: ERROR: Key "<CAPS>" added to modifier map for multiple modifiers; Using Control, ignoring Lock
Config timer connecting...
Icon theme "ubuntu-mono-dark" not found.
Icon theme "Mint-X" not found.
Icon theme "elementary" not found.
Icon theme "gnome" not found.
Setting the name of  0x1f1a4e0  to  "org.kde.ActivityManager.ActivityTemplates"
Setting the name of  0x1f10f80  to  "org.kde.ActivityManager.RunApplication"
Setting the name of  0x1f0b400  to  "org.kde.ActivityManager.Resources.Scoring"
Creating directory:  "/home/kevin/.local/share/kactivitymanagerd/resources/"
Cannot mix incompatible Qt library (version 0x50902) with this library (version 0x50901)
libpng warning: iCCP: known incorrect sRGB profile
KActivities: FATAL ERROR: Failed to contact the activity manager daemon
Service started, version: 
Cleaning up...
file:///home/kevin/.local/share/plasma/look-and-feel/com.github.varlesh.arc-dark/contents/splash/Splash.qml:89: ReferenceError: bottomRect is not defined
file:///home/kevin/.local/share/plasma/look-and-feel/com.github.varlesh.arc-dark/contents/splash/Splash.qml:88: ReferenceError: bottomRect is not defined
file:///home/kevin/.local/share/plasma/look-and-feel/com.github.varlesh.arc-dark/contents/splash/Splash.qml:89: ReferenceError: bottomRect is not defined
Using the 'wl-shell' shell integration
file:///home/kevin/.local/share/plasma/look-and-feel/com.github.varlesh.arc-dark/contents/splash/Splash.qml:89: ReferenceError: bottomRect is not defined
file:///home/kevin/.local/share/plasma/look-and-feel/com.github.varlesh.arc-dark/contents/splash/Splash.qml:88: ReferenceError: bottomRect is not defined
file:///home/kevin/.local/share/plasma/look-and-feel/com.github.varlesh.arc-dark/contents/splash/Splash.qml:89: ReferenceError: bottomRect is not defined
file:///home/kevin/.local/share/plasma/look-and-feel/com.github.varlesh.arc-dark/contents/splash/Splash.qml:88: ReferenceError: bottomRect is not defined
file:///home/kevin/.local/share/plasma/look-and-feel/com.github.varlesh.arc-dark/contents/splash/Splash.qml:89: ReferenceError: bottomRect is not defined
/nix/store/868wx8sw0a1nxrjap6gj89bnhknzi2va-plasma-workspace-5.11.3-bin/lib/libexec/startplasma: line 89: mkfontdir: command not found
startplasma: Starting up...
/nix/store/868wx8sw0a1nxrjap6gj89bnhknzi2va-plasma-workspace-5.11.3-bin/lib/libexec/startplasma: line 122: /nix/store/r3xizrv8nc5zrz990a67m26h12dxnsva-plasma-workspace-5.11.3/lib/libexec/kf5/start_kdeinit_wrapper: No such file or directory
startplasma: Could not start kdeinit5. Check your installation.
/nix/store/868wx8sw0a1nxrjap6gj89bnhknzi2va-plasma-workspace-5.11.3-bin/lib/libexec/startplasma: line 127: xmessage: command not found
glamor: EGL version 1.5 (DRI2):
This application failed to start because it could not find or load the Qt platform plugin "xcb"
in "".

Available platform plugins are: minimal, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, xcb, wayland-org.kde.kwin.qpa, minimal, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, xcb.

Reinstalling the application may fix this problem.
QSocketNotifier: Invalid socket 51 with type Read, disabling...
startplasmacompositor: Shutting down...
/nix/store/ky7100hcmgzjazgnwsjvx3f3qbcq12cb-xprop-1.2.2/bin/xprop:  unable to open display ''
/nix/store/ky7100hcmgzjazgnwsjvx3f3qbcq12cb-xprop-1.2.2/bin/xprop:  unable to open display ''
startplasmacompositor: Done.

Steps to reproduce

Open the Applications Menu (in X) or try to start a plasma wayland session with startplasmacompositor.

Technical details

• System: 18.03.git.3c56820 (Impala)
• Nix version: nix-env (Nix) 1.11.15
• Nixpkgs version: "18.03.git.3c56820469"
• Sandboxing enabled: build-use-sandbox = false

(Running some out-of-tree patches that don't touch Qt/Plasma stuff, but currently based off of 7ebacd1.)

[orivej]

You may be able to identify which packages needs to be reinstalled with nix-store -q --referrers /nix/store/*-qt*-5.9.2 after nix-collect-garbage -d, or you may reinstall everything that has changed with nix-env -u --always.

[kliu128]

It seems just collecting garbage solved the problem?? Weird! Well, I guess that's solved. Is this normal for a library up/downgrade?

[orivej]

Nobody else has reported that collecting garbage helps, I didn't expect that and I don't have an explanation. Personally I have never experienced this issue. I've linked this to another report in #30551.