Error while deploying Qt5.10 App on linux

[Script22]

I'm trying to deploy a simple example on linux manually.

I copied the dependecies required by running

ldd ./binaryFile

inside the app directory

├── app.sh
├── lib
└── testApp

inside the lib directory I have

├──lib
  ├── plugins
  ├── qml
  └── other .so files from ldd

and then I run the bash script

#!/bin/sh
 export LD_LIBRARY_PATH=`pwd`/lib
 export QML_IMPORT_PATH=`pwd`/lib/qml
 export QML2_IMPORT_PATH=`pwd`/lib/qml
 export QT_QPA_PLATFORM_PLUGIN_PATH=`pwd`/lib/plugins/platforms
 #export QT_DEBUG_PLUGINS=0
 ./testApp

but I get this error

This application failed to start because it could not find or load the Qt platform plugin "xcb"
in "/home/zed/Desktop/testDep/lib/plugins/platforms".

Available platform plugins are: eglfs (from /home/zed/Desktop/testDep/lib/plugins/platforms), linuxfb (from /home/zed/Desktop/testDep/lib/plugins/platforms), minimal (from /home/zed/Desktop/testDep/lib/plugins/platforms), minimalegl (from /home/zed/Desktop/testDep/lib/plugins/platforms), offscreen (from /home/zed/Desktop/testDep/lib/plugins/platforms), vnc (from /home/zed/Desktop/testDep/lib/plugins/platforms), webgl (from /home/zed/Desktop/testDep/lib/plugins/platforms), xcb (from /home/zed/Desktop/testDep/lib/plugins/platforms).

Reinstalling the application may fix this problem.
./app.sh: line 7:  1948 Aborted                 (core dumped) ./testApp

Even though the "xcb" plugin is inside the platforms directory

when I run it using

export QT_DEBUG_PLUGINS=1

I get this debug message

Got keys from plugin meta data ("xcb")
QFactoryLoader::QFactoryLoader() checking directory path "/home/zed/Desktop/testDep" ...
QFactoryLoader::QFactoryLoader() looking at "/home/zed/Desktop/testDep/app.sh"
QElfParser: '/home/zed/Desktop/testDep/app.sh' is not an ELF object
"'/home/zed/Desktop/testDep/app.sh' is not an ELF object" 
         not a plugin
QFactoryLoader::QFactoryLoader() looking at "/home/zed/Desktop/testDep/testApp"
"Failed to extract plugin meta data from '/home/zed/Desktop/testDep/testApp'" 
         not a plugin
Cannot load library /home/zed/Desktop/testDep/lib/plugins/platforms/libqxcb.so: (/usr/lib/libQt5XcbQpa.so.5: symbol _ZNK15QPlatformWindow15safeAreaMarginsEv version Qt_5_PRIVATE_API not defined in file libQt5Gui.so.5 with link time reference)
QLibraryPrivate::loadPlugin failed on "/home/zed/Desktop/testDep/lib/plugins/platforms/libqxcb.so" : "Cannot load library /home/zed/Desktop/testDep/lib/plugins/platforms/libqxcb.so: (/usr/lib/libQt5XcbQpa.so.5: symbol _ZNK15QPlatformWindow15safeAreaMarginsEv version Qt_5_PRIVATE_API not defined in file libQt5Gui.so.5 with link time reference)"
QFactoryLoader::QFactoryLoader() checking directory path "/home/zed/Desktop/testDep/lib/plugins/platforms/platforms" ...
QFactoryLoader::QFactoryLoader() checking directory path "/home/zed/Desktop/testDep/platforms" ...
This application failed to start because it could not find or load the Qt platform plugin "xcb"
in "/home/zed/Desktop/testDep/lib/plugins/platforms".

Is there a way to fix this ?

PS:
Qt Version : 5.10
Compiled on : Kubuntu 18.4
Tested on : Manjaro XFCE 17.1

[Pablo J. Rogina]

@Script22 If I understood right, you developed your Qt app on Kubuntu 18.4 with Qt 5.10 and then you're deploying such app on Manjaro XFCE 17.1

It looks like you have a Qt libraries version mismatch. From your debug info, libqxcb.so that you deployed in target machine in turn is loading/depending on libQt5XcbQpa.so.5 which seems to be already in target machine

/home/zed/Desktop/testDep/lib/plugins/platforms/libqxcb.so: (/usr/lib/libQt5XcbQpa.so.5: ...

[Script22]

Yes, I developed on Kubuntu and deploying on manjaro.

So how to work around that ? I guess I should not replace that file as it would probably break something that manjaro uses, if I just copy it inside the libs directory would that work ?

[Pablo J. Rogina]

@Script22 said in Error while deploying Qt5.10 App on linux:

if I just copy it inside the libs directory would that work

I think so, but you should add that folder explicitly to the environment variable LD_LIBRARY_PATH, something like:

$> export LD_LIBRARY_PATH:/path/to/libs/folder:$LD_LIBRARY_PATH

[Script22]

Thanks @Pablo-J-Rogina !!
That fixed it, will pay more attention next time :)

[jsulm]

@Script22 You should take a look at http://doc.qt.io/qt-5/linux-deployment.html

[JinPark]

Hello, I actually exactly same error with @Script22
I downladed qt 5.15.2 source package.
and I located to /usr/local.

but in /usr/local/Qt-5.15.2/plugins/platforms, There is no libxcb.so here.
The result for ls on that folder is below.

jin@jin-PNVKB0A0-Samsung-DeskTop:/usr/local/Qt-5.15.2/plugins/platforms$ ls
libqeglfs.so libqminimalegl.so libqoffscreen.so libqwayland-egl.so libqwayland-xcomposite-egl.so libqwebgl.so
libqlinuxfb.so libqminimal.so libqvnc.so libqwayland-generic.so libqwayland-xcomposite-glx.so

So like @Script22 , I moved libxcb.so from /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms
Also I got error like him.

So I just decided to set Environment variable QT_QPA_PLATFORM_PLUGIN_PATH to /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms. But I got same error too.

How can I handle it ?

[jsulm]

@JinPark How exactly did you install Qt in /usr/local?
"I downladed qt 5.15.2 source package." - do you mean you downloaded Qt source code and build it by yourself?