qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.



  • Hello.
    After last qt5 update I'm getting this message:

    ~ $ qtcreator
    qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
    This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.
    
    Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, xcb.
    
    Aborted (core dumped)
    

    Here is strace log https://pastebin.com/1GfBFmUH

    Linux disto is manjaro which is based on archlinux. Any idea what is going on?

    Thank you and best regards.


  • Lifetime Qt Champion

    Hi,

    You should run your application with the QT_DEBUG_PLUGINS environment variable set to 1 to see what might go wrong when the plugin is loaded.



  • ~ $ export QT_DEBUG_PLUGINS=1
    ~ $ qtcreator
    QFactoryLoader::QFactoryLoader() checking directory path "/usr/lib/qt/plugins/platforms" ...
    QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/platforms/libqeglfs.so"
    Found metadata in lib /usr/lib/qt/plugins/platforms/libqeglfs.so, metadata=
    {
        "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
        "MetaData": {
            "Keys": [
                "eglfs"
            ]
        },
        "className": "QEglFSIntegrationPlugin",
        "debug": false,
        "version": 330497
    }
    
    
    Got keys from plugin meta data ("eglfs")
    QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/platforms/libqlinuxfb.so"
    Found metadata in lib /usr/lib/qt/plugins/platforms/libqlinuxfb.so, metadata=
    {
        "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
        "MetaData": {
            "Keys": [
                "linuxfb"
            ]
        },
        "className": "QLinuxFbIntegrationPlugin",
        "debug": false,
        "version": 330497
    }
    
    
    Got keys from plugin meta data ("linuxfb")
    QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/platforms/libqminimal.so"
    Found metadata in lib /usr/lib/qt/plugins/platforms/libqminimal.so, metadata=
    {
        "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
        "MetaData": {
            "Keys": [
                "minimal"
            ]
        },
        "className": "QMinimalIntegrationPlugin",
        "debug": false,
        "version": 330497
    }
    
    
    Got keys from plugin meta data ("minimal")
    QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/platforms/libqminimalegl.so"
    Found metadata in lib /usr/lib/qt/plugins/platforms/libqminimalegl.so, metadata=
    {
        "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
        "MetaData": {
            "Keys": [
                "minimalegl"
            ]
        },
        "className": "QMinimalEglIntegrationPlugin",
        "debug": false,
        "version": 330497
    }
    
    
    Got keys from plugin meta data ("minimalegl")
    QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/platforms/libqoffscreen.so"
    Found metadata in lib /usr/lib/qt/plugins/platforms/libqoffscreen.so, metadata=
    {
        "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
        "MetaData": {
            "Keys": [
                "offscreen"
            ]
        },
        "className": "QOffscreenIntegrationPlugin",
        "debug": false,
        "version": 330497
    }
    
    
    Got keys from plugin meta data ("offscreen")
    QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/platforms/libqvnc.so"
    Found metadata in lib /usr/lib/qt/plugins/platforms/libqvnc.so, metadata=
    {
        "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
        "MetaData": {
            "Keys": [
                "vnc"
            ]
        },
        "className": "QVncIntegrationPlugin",
        "debug": false,
        "version": 330497
    }
    
    
    Got keys from plugin meta data ("vnc")
    QFactoryLoader::QFactoryLoader() looking at "/usr/lib/qt/plugins/platforms/libqxcb.so"
    Found metadata in lib /usr/lib/qt/plugins/platforms/libqxcb.so, metadata=
    {
        "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
        "MetaData": {
            "Keys": [
                "xcb"
            ]
        },
        "className": "QXcbIntegrationPlugin",
        "debug": false,
        "version": 330497
    }
    
    
    Got keys from plugin meta data ("xcb")
    QFactoryLoader::QFactoryLoader() checking directory path "/usr/bin/platforms" ...
    Cannot load library /usr/lib/qt/plugins/platforms/libqxcb.so: (/usr/lib/libxcb-xinerama.so.0: invalid ELF header)
    QLibraryPrivate::loadPlugin failed on "/usr/lib/qt/plugins/platforms/libqxcb.so" : "Cannot load library /usr/lib/qt/plugins/platforms/libqxcb.so: (/usr/lib/libxcb-xinerama.so.0: invalid ELF header)"
    qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
    This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.
    
    Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, xcb.
    
    Aborted (core dumped)
    

    So my guess is that this is the key message:

    Got keys from plugin meta data ("xcb")
    QFactoryLoader::QFactoryLoader() checking directory path "/usr/bin/platforms" ...
    Cannot load library /usr/lib/qt/plugins/platforms/libqxcb.so: (/usr/lib/libxcb-xinerama.so.0: invalid ELF header)
    QLibraryPrivate::loadPlugin failed on "/usr/lib/qt/plugins/platforms/libqxcb.so" : "Cannot load library /usr/lib/qt/plugins/platforms/libqxcb.so: (/usr/lib/libxcb-xinerama.so.0: invalid ELF header)"
    
    /usr/lib/qt/plugins/platforms/libqxcb.so is owned by qt5-base 5.11.1-1
    

    so what now? do I need to reinstall qt5-base or do something else?

    Best regards.


  • Lifetime Qt Champion

    HI,

    Did you run ldd on your libraries and libxcb-xinerama versions ?



  • Hi
    Do you mean something like this?

    ~ $ pacman -Qo /usr/lib/libxcb-xinerama.so.0
    /usr/lib/libxcb-xinerama.so.0 is owned by libxcb 1.13-1
    

    and which file I should run this ldd on exactly?



  • Hi, try: ldd /usr/lib/qt/plugins/platforms/libqxcb.so


  • Lifetime Qt Champion

    You should try installing the corresponding dev packages on your system.



  • The same as before:

    ~ $ ldd /usr/lib/qt/plugins/platforms/libqxcb.so
    /usr/lib/qt/plugins/platforms/libqxcb.so: error while loading shared libraries: /usr/lib/libxcb-xinerama.so.0: invalid ELF header
    

    but after that

    ~ $ sudo pacman -S libxcb
    [sudo] password for tomasz: 
    warning: libxcb-1.13-1 is up to date -- reinstalling
    resolving dependencies...
    looking for conflicting packages...
    
    Packages (1) libxcb-1.13-1
    
    Total Download Size:   0.99 MiB
    Total Installed Size:  3.96 MiB
    Net Upgrade Size:      0.00 MiB
    
    :: Proceed with installation? [Y/n] Y
    :: Retrieving packages...
     libxcb-1.13-1-x86_64          1017.5 KiB   242K/s 00:04 [##############################] 100%
    (1/1) checking keys in keyring                           [##############################] 100%
    (1/1) checking package integrity                         [##############################] 100%
    (1/1) loading package files                              [##############################] 100%
    (1/1) checking for file conflicts                        [##############################] 100%
    (1/1) checking available disk space                      [##############################] 100%
    :: Processing package changes...
    (1/1) reinstalling libxcb                                [##############################] 100%
    :: Running post-transaction hooks...
    (1/1) Arming ConditionNeedsUpdate...
    ~ $ pacman -Qo /usr/lib/libxcb-xinerama.so.0
    /usr/lib/libxcb-xinerama.so.0 is owned by libxcb 1.13-1
    ~ $ ldd /usr/lib/qt/plugins/platforms/libqxcb.so
    	linux-vdso.so.1 (0x00007ffc93f56000)
    	libQt5XcbQpa.so.5 => /usr/lib/libQt5XcbQpa.so.5 (0x00007f730ea63000)
    	libQt5Gui.so.5 => /usr/lib/libQt5Gui.so.5 (0x00007f730e2d5000)
    	libQt5Core.so.5 => /usr/lib/libQt5Core.so.5 (0x00007f730dbd4000)
    	libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x00007f730d84b000)
    	libc.so.6 => /usr/lib/libc.so.6 (0x00007f730d48f000)
    	libfontconfig.so.1 => /usr/lib/libfontconfig.so.1 (0x00007f730d24c000)
    	libfreetype.so.6 => /usr/lib/libfreetype.so.6 (0x00007f730cf83000)
    	libQt5DBus.so.5 => /usr/lib/libQt5DBus.so.5 (0x00007f730ccf3000)
    	libpthread.so.0 => /usr/lib/libpthread.so.0 (0x00007f730cad5000)
    	libX11-xcb.so.1 => /usr/lib/libX11-xcb.so.1 (0x00007f730c8d3000)
    	libX11.so.6 => /usr/lib/libX11.so.6 (0x00007f730c594000)
    	libXi.so.6 => /usr/lib/libXi.so.6 (0x00007f730c383000)
    	libSM.so.6 => /usr/lib/libSM.so.6 (0x00007f730c17b000)
    	libICE.so.6 => /usr/lib/libICE.so.6 (0x00007f730bf5f000)
    	libXrender.so.1 => /usr/lib/libXrender.so.1 (0x00007f730bd54000)
    	libxcb-xkb.so.1 => /usr/lib/libxcb-xkb.so.1 (0x00007f730bb37000)
    	libxcb-render-util.so.0 => /usr/lib/libxcb-render-util.so.0 (0x00007f730b933000)
    	libxcb-render.so.0 => /usr/lib/libxcb-render.so.0 (0x00007f730b725000)
    	libxcb-sync.so.1 => /usr/lib/libxcb-sync.so.1 (0x00007f730b51e000)
    	libxcb-xfixes.so.0 => /usr/lib/libxcb-xfixes.so.0 (0x00007f730b316000)
    	libxcb-xinerama.so.0 => /usr/lib/libxcb-xinerama.so.0 (0x00007f730b113000)
    	libxcb-randr.so.0 => /usr/lib/libxcb-randr.so.0 (0x00007f730af03000)
    	libxcb-image.so.0 => /usr/lib/libxcb-image.so.0 (0x00007f730acfe000)
    	libxcb-shm.so.0 => /usr/lib/libxcb-shm.so.0 (0x00007f730aafa000)
    	libxcb-keysyms.so.1 => /usr/lib/libxcb-keysyms.so.1 (0x00007f730a8f7000)
    	libxcb-icccm.so.4 => /usr/lib/libxcb-icccm.so.4 (0x00007f730a6f2000)
    	libxcb.so.1 => /usr/lib/libxcb.so.1 (0x00007f730a4c9000)
    	libxcb-shape.so.0 => /usr/lib/libxcb-shape.so.0 (0x00007f730a2c5000)
    	libxkbcommon.so.0 => /usr/lib/libxkbcommon.so.0 (0x00007f730a086000)
    	libxkbcommon-x11.so.0 => /usr/lib/libxkbcommon-x11.so.0 (0x00007f7309e7f000)
    	libm.so.6 => /usr/lib/libm.so.6 (0x00007f7309aea000)
    	libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x00007f73098d2000)
    	libGL.so.1 => /usr/lib/libGL.so.1 (0x00007f7309647000)
    	libpng16.so.16 => /usr/lib/libpng16.so.16 (0x00007f7309411000)
    	libharfbuzz.so.0 => /usr/lib/libharfbuzz.so.0 (0x00007f7309165000)
    	libz.so.1 => /usr/lib/libz.so.1 (0x00007f7308f4e000)
    	libsystemd.so.0 => /usr/lib/libsystemd.so.0 (0x00007f7308cc4000)
    	libicui18n.so.61 => /usr/lib/libicui18n.so.61 (0x00007f7308819000)
    	libicuuc.so.61 => /usr/lib/libicuuc.so.61 (0x00007f730845f000)
    	libpcre2-16.so.0 => /usr/lib/libpcre2-16.so.0 (0x00007f73081e8000)
    	libdouble-conversion.so.1 => /usr/lib/libdouble-conversion.so.1 (0x00007f7307fd8000)
    	libdl.so.2 => /usr/lib/libdl.so.2 (0x00007f7307dd4000)
    	libglib-2.0.so.0 => /usr/lib/libglib-2.0.so.0 (0x00007f7307abd000)
    	/usr/lib64/ld-linux-x86-64.so.2 (0x00007f730efdd000)
    	libexpat.so.1 => /usr/lib/libexpat.so.1 (0x00007f730788b000)
    	libuuid.so.1 => /usr/lib/libuuid.so.1 (0x00007f7307684000)
    	libbz2.so.1.0 => /usr/lib/libbz2.so.1.0 (0x00007f7307474000)
    	libdbus-1.so.3 => /usr/lib/libdbus-1.so.3 (0x00007f7307223000)
    	libXext.so.6 => /usr/lib/libXext.so.6 (0x00007f7307011000)
    	libXau.so.6 => /usr/lib/libXau.so.6 (0x00007f7306e0d000)
    	libXdmcp.so.6 => /usr/lib/libXdmcp.so.6 (0x00007f7306c07000)
    	libxcb-util.so.1 => /usr/lib/libxcb-util.so.1 (0x00007f7306a01000)
    	libGLX.so.0 => /usr/lib/libGLX.so.0 (0x00007f73067d0000)
    	libGLdispatch.so.0 => /usr/lib/libGLdispatch.so.0 (0x00007f730651a000)
    	libgraphite2.so.3 => /usr/lib/libgraphite2.so.3 (0x00007f73062ee000)
    	librt.so.1 => /usr/lib/librt.so.1 (0x00007f73060e6000)
    	liblzma.so.5 => /usr/lib/liblzma.so.5 (0x00007f7305ec0000)
    	liblz4.so.1 => /usr/lib/liblz4.so.1 (0x00007f7305ca3000)
    	libgcrypt.so.20 => /usr/lib/libgcrypt.so.20 (0x00007f7305987000)
    	libicudata.so.61 => /usr/lib/libicudata.so.61 (0x00007f7303de2000)
    	libpcre.so.1 => /usr/lib/libpcre.so.1 (0x00007f7303b70000)
    	libgpg-error.so.0 => /usr/lib/libgpg-error.so.0 (0x00007f7303950000)
    ~ $ qtcreator
    QApplication: invalid style override passed, ignoring it.
    

    so it seems that reinstalling libxcb fixed the issue. So thank you very much guys.
    I own you really big beer :-)

    @SGaist
    there is no such thing on manjaro or archlinux which manjaro is baseed on



  • For those who could face the same issue and didn't solve by reinstalling libxcb: in my case the message was the same but it was caused by apps inside lxc unabling to open display, so, try to run another GUI app like xclock.



  • @DevAlone

    qt.qpa.xcb: could not connect to display <<-- Is that the message you're talking about?

    Could you explain a little better what was your problem and how did you fix it?

    What is lxc? And why to run another GUI app? I really didn't understand what you did to fix this problem.



  • @twar
    Hi, twar!
    I met the same error as yours, and I cannot solve it after using several methods.
    Can you tell me how to fix it more clearly? I'm new to geant4, so I cannot understand what you have said.
    Thank you!

    Best Wishes,
    jcren.



  • Hi
    I faced this problem and I got a new version of linuxdeployqt and now that error is gone.


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