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

Ajp1989

So I am trying to deploy my application to a machine have does not have Qt installed. I followed the instructions "X11 Deployment":http://qt-project.org/doc/qt-4.8/deployment-x11.html for shared libs.

Program works on dev system (Mint) but on a machine without Qt (Ubuntu 12.04) this error occurs:
@Failed to load platform plugin "xcb". Available platforms are:

Aborted (core dumped)
@

My application folder looks like this (ls -R)
@libQt5Core.so.5 libQt5Gui.so.5 libQt5Widgets.so.5 mg_linux.sh
libQt5DBus.so.5 libQt5Svg.so.5 mg_linux platforms

./platforms:
libqxcb.so@

I have checked the dependencies are installed with ldd on the executable and the libqxcb.so

I have looked through other solutions, such as
https://qt-project.org/forums/viewthread/22292/#155301
From which I thought goblincodings post/blog seemed relevant. For a test I downloaded his "app":http://goblincoding.com/2013/11/07/deploying-qt-5-applications-on-ubuntu-12-04/, ran the scripts for dependancies and still got an error:
@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.@

but this time it says xcb is availiable, which makes me think I have two probelms. Do I need to explicitly state the xcb is located in the platforms folder? Or should the release compile flag force this behaviour.

Thanks

JKSH

Hi,

As a general rule, you should use the Qt 5 documentation, not the Qt 4 one. In this case though, the Linux deployment page hasn't changed in a long time.

Did you copy the script in http://qt-project.org/doc/qt-5/linux-deployment.html that sets LD_LIBRARY_PATH? (this variable tells your system where to find the libraries for your app)

Ajp1989

Yes, I did follow the Qt 5 documentation, I just linked the wrong one here.

I have copied the script and renamed it. I know LD_LIBRARY_PATH is set correctly as program doesn't complain about missing libraries when run from script (gives xcb error). Running direclty gives an error about a missing lib.

JKSH

[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

SGaist

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

Ajp1989

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

Ajp1989

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.

JKSH

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

nike.niec

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

Ajp1989

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.

nike.niec

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

hskoglund

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.

nike.niec

Thanks,surely i will look into your blog