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    Qt World Summit: Early-Bird Tickets

    [Solved] Qt5.2.1 Platform issue on deployment, could not find xcb plugin. Linux

    Installation and Deployment
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    • JKSH
      JKSH Moderators last edited by

      [quote]
      @
      This application failed to start because it could not find or load the Qt platform plugin "xcb".

      Available platform plugins are: xcb.

      Reinstalling the application may fix this problem.
      @
      [/quote]I've encountered this unintuitive message before. In my case, Ubuntu found libqxcb.so but failed to load it because one of its dependencies was missing.

      Follow the quick-and-dirty method in this guide to identify the missing dependenc(ies): http://qt-project.org/wiki/Deploy_an_Application_on_Windows It's written for Windows but also works on Linux. Just replace *.dll with *.so

      Qt Doc Search for browsers: forum.qt.io/topic/35616/web-browser-extension-for-improved-doc-searches

      1 Reply Last reply Reply Quote 0
      • SGaist
        SGaist Lifetime Qt Champion last edited by

        Hi,

        To add to JKSH, you can run ldd on your xcb plugin to see what libraries are linked and you'll also see if something is missing

        Interested in AI ? www.idiap.ch
        Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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        • A
          Ajp1989 last edited by

          Thanks for your responses. Think I am having some progress, or am doing it totally wrong.

          -So I orignally was using libqxcb.so from ~/Qt/5.2.1/gcc_64/plugins/platforms with no success. I thought perhaps this might be the incorrect library so I ran ldd on the source machine a picked out a version from where it was picking it's libs, /usr/lib/x86_64, this had more dependancies so I included them in the application directory.-
          -Now I get a different error-
          @
          ~Desktop/graph-deploy/./mg_linux: symbol lookup error: ~Desktop/graph-deploy/./mg_linux: undefined symbol: _ZN19QAbstractScrollArea19setSizeAdjustPolicyENS_16SizeAdjustPolicyE
          @
          -running cfilt identfies this as-
          @
          QAbstractScrollArea::setSizeAdjustPolicy(QAbstractScrollArea::SizeAdjustPolicy)
          @
          -Any ideas? Or have I gone the wrong way?-

          -Also I compiled the original on Mint 15 and am trying to get it to run on Ubuntu 12.04. Will this be an issue?-

          -I did notice that running-
          @ldd -d -r@

          -on the original libqxcb I was using returned no missing libraries but many undefined symbol references.-

          EDIT: ignore this rubbish!

          Needed to solve the symbol errors for the file libqxcb.so from /Qt/5.2.1/gcc_64/plugins/platforms

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          • A
            Ajp1989 last edited by

            Thanks JKSH for putting me on the way to the solution!
            [quote author="JKSH" date="1393037410"]
            Follow the quick-and-dirty method in this guide to identify the missing dependenc(ies): http://qt-project.org/wiki/Deploy_an_Application_on_Windows It's written for Windows but also works on Linux. Just replace *.dll with *.so[/quote]

            Here is a Linux version of the above for those who may have a similar problem.

            Firstly copy the required platform plugin libqxcb.so to a test directory ~/test_libs from /pathToQt/plugins/platforms in my case the pathToQt was ~/Qt/5.2.1/gcc_64/

            Then copy all of the libraries from /pathToQt/lib to ~/test_libs

            Set the LD_LIBRARY_PATH
            @
            LD_LIBRARY_PATH=~/test_libs
            export LD_LIBRARY_PATH
            @

            Then run
            @
            cd ~/test_libs
            ldd -r -d libqxcb.so
            @

            This should have no errors or undefined symbol messages.

            Then you can delete libraries from ~/test_libs whilst rerunning ldd to work out the required libs, or delete all the libraries that ldd does not list from the directory ~/test_libs.

            In my case libqxcb.so required the following libraries
            libicudata.so.51
            libicui18n.so.51
            libicuuc.so.51
            libQt5Core.so.5
            libQt5DBus.so.5
            libQt5Gui.so.5

            So I think my problem was that some incompatible libraries were found on the system so ldd didn't complain about them being missing.

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            • JKSH
              JKSH Moderators last edited by

              I'm glad that you've found a solution! Thank you for sharing your technique too.

              Qt Doc Search for browsers: forum.qt.io/topic/35616/web-browser-extension-for-improved-doc-searches

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              • N
                nike.niec last edited by

                Hi
                I am using CentOS 6.5 x86_64

                I created a GUI Application executable named "Graphitev1" using Qt5.2.1
                It is a Widget based application.

                Below are dependency for my executable:
                @
                ldd Graphitev1
                linux-vdso.so.1 => (0x00007fff2d5ff000)

                    libQt5PrintSupport.so.5 => /home/vedams/Qt5.2.1/5.2.1/gcc_64/lib/libQt5PrintSupport.so.5 (0x00007f4dc6bef000)

    libQt5Widgets.so.5 => /home/vedams/Qt5.2.1/5.2.1/gcc_64/lib/libQt5Widgets.so.5 (0x00007f4dc63a8000)

    libQt5Gui.so.5 => /home/vedams/Qt5.2.1/5.2.1/gcc_64/lib/libQt5Gui.so.5 (0x00007f4dc5d22000)

    libQt5Core.so.5 => /home/vedams/Qt5.2.1/5.2.1/gcc_64/lib/libQt5Core.so.5 (0x00007f4dc5654000)

    libGL.so.1 => /usr/lib64/libGL.so.1 (0x0000003195800000)

    libpthread.so.0 => /lib64/libpthread.so.0 (0x000000318a800000)

    libstdc++.so.6 => /usr/lib64/libstdc++.so.6 (0x0000003196400000)

    libm.so.6 => /lib64/libm.so.6 (0x000000318b400000)

    libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x0000003195000000)

    libc.so.6 => /lib64/libc.so.6 (0x000000318a000000)

    libgobject-2.0.so.0 => /lib64/libgobject-2.0.so.0 (0x000000318c800000)

    libglib-2.0.so.0 => /lib64/libglib-2.0.so.0 (0x000000318b800000)

    libX11.so.6 => /usr/lib64/libX11.so.6 (0x000000318e000000)

    libicui18n.so.51 => /home/vedams/Qt5.2.1/5.2.1/gcc_64/lib/libicui18n.so.51 (0x00007f4dc5226000)

    libicuuc.so.51 => /home/vedams/Qt5.2.1/5.2.1/gcc_64/lib/libicuuc.so.51 (0x00007f4dc4ea0000)

    libdl.so.2 => /lib64/libdl.so.2 (0x000000318a400000)

    libgthread-2.0.so.0 => /lib64/libgthread-2.0.so.0 (0x000000318cc00000)

    librt.so.1 => /lib64/librt.so.1 (0x000000318ac00000)
    /lib64/ld-linux-x86-64.so.2 (0x0000003189c00000)

    libglapi.so.0 => /usr/lib64/libglapi.so.0 (0x0000003197000000)

    libXext.so.6 => /usr/lib64/libXext.so.6 (0x000000318e800000)

    libXdamage.so.1 => /usr/lib64/libXdamage.so.1 (0x0000003191400000)

    libXfixes.so.3 => /usr/lib64/libXfixes.so.3 (0x0000003192000000)

    libX11-xcb.so.1 => /usr/lib64/libX11-xcb.so.1 (0x000000318f000000)

    libxcb-glx.so.0 => /usr/lib64/libxcb-glx.so.0 (0x0000003196c00000)

    libxcb-dri2.so.0 => /usr/lib64/libxcb-dri2.so.0 (0x0000003195c00000)

    libxcb.so.1 => /usr/lib64/libxcb.so.1 (0x000000318dc00000)

    libXxf86vm.so.1 => /usr/lib64/libXxf86vm.so.1 (0x0000003196000000)

    libdrm.so.2 => /usr/lib64/libdrm.so.2 (0x0000003196800000)

    libselinux.so.1 => /lib64/libselinux.so.1 (0x000000318bc00000)

    libicudata.so.51 => /home/vedams/Qt5.2.1/5.2.1/gcc_64

                /lib/libicudata.so.51 (0x00007f4dc3752000)

                    libXau.so.6 => /usr/lib64/libXau.so.6 (0x000000318d800000)

                @

                Now i am copying this executable "Graphitev1" with dependency in another CentOS 6.5 x86_64 machine and below is contents:

                @

                ls -lh
                -rwxrwxr-x. 1 vedams vedams 4.7M May 19 18:11 Graphitev1
                lrwxrwxrwx. 1 vedams vedams 18 May 19 18:19 libicudata.so.51 -> libicudata.so.51.1
                -rwxr-xr-x. 1 vedams vedams 22M May 19 18:11 libicudata.so.51.1
                lrwxrwxrwx. 1 vedams vedams 18 May 19 18:19 libicui18n.so.51 -> libicui18n.so.51.1
                -rwxr-xr-x. 1 vedams vedams 2.6M May 19 18:11 libicui18n.so.51.1
                lrwxrwxrwx. 1 vedams vedams 16 May 19 18:18 libicuuc.so.51 -> libicuuc.so.51.1
                -rwxr-xr-x. 1 vedams vedams 1.8M May 19 18:11 libicuuc.so.51.1
                lrwxrwxrwx. 1 vedams vedams 19 May 19 18:18 libQt5Core.so.5 -> libQt5Core.so.5.2.1
                -rwxr-xr-x. 1 vedams vedams 4.8M May 19 18:11 libQt5Core.so.5.2.1
                lrwxrwxrwx. 1 vedams vedams 19 May 19 18:17 libQt5DBus.so.5 -> libQt5DBus.so.5.2.1
                -rwxr-xr-x. 1 vedams vedams 523K May 19 18:11 libQt5DBus.so.5.2.1
                lrwxrwxrwx. 1 vedams vedams 18 May 19 18:17 libQt5Gui.so.5 -> libQt5Gui.so.5.2.1
                -rwxr-xr-x. 1 vedams vedams 4.6M May 19 18:11 libQt5Gui.so.5.2.1
                lrwxrwxrwx. 1 vedams vedams 27 May 19 18:16 libQt5PrintSupport.so.5 -> libQt5PrintSupport.so.5.2.1
                -rwxr-xr-x. 1 vedams vedams 412K May 19 18:11 libQt5PrintSupport.so.5.2.1
                lrwxrwxrwx. 1 vedams vedams 22 May 19 18:12 libQt5Widgets.so.5 -> libQt5Widgets.so.5.2.1
                -rwxr-xr-x. 1 vedams vedams 6.3M May 19 18:11 libQt5Widgets.so.5.2.1
                -rwxr-xr-x. 1 vedams vedams 1.4M May 19 18:11 libqxcb.so
                @

                now i exported the LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$PWD

                now when i ran the application, i got the error

                @

                This application failed to start because it could not find or load the Qt platform plugin "xcb".

                Reinstalling the application may fix this problem.
                Aborted (core dumped)
                @

                Please tell me in simple manner , how to resolve this error
                I m getting lost in above thread and following other links

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                • A
                  Ajp1989 last edited by

                  libqxcb.so needs to reside in a folder called platforms within the application source.

                  I found it very annoying when I had this error meassge to solve.

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                  • N
                    nike.niec last edited by

                    Thanks a lot Ajp1989.Its working
                    But can yu please explain the reason behind this

                    And can yu give the standard procedure to pack applcation to deliver it to client.Currently for testing purpose i hardcoded lot of things.
                    By Target Machine and development machines are CentOS-6.5 x86_64
                    And i am developing a Desktop Widget based Application

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                    • hskoglund
                      hskoglund last edited by

                      Hi, I also had problems before when deploying to Ubuntu machines. I wrote about it in 2 blog posts: "how to deploy":http://www.tripleboot.org/?p=138 (scroll down to Linux GCC...) and "why you need":http://www.tripleboot.org/?p=536 that platforms directory.

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                      • N
                        nike.niec last edited by

                        Thanks,surely i will look into your blog

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