could not find or load the Qt platform plugun "xcb"

b108463

Hi all,
I try to run my executable file which is compiled by Qt. It shows a error message as below

root@tegra-ubuntu:/home/ubuntu# ./SMPCodeReader1_ARM_exec
Fatal: This application failed to start because it could not find or load the Qt platform plugin "xcb"
in "".

Reinstalling the application may fix this problem. (:0)
Aborted
root@tegra-ubuntu:/home/ubuntu#

May I learn why this problem happened ? Thanks a lot.

Note The packages are listed as below has installed on my TK1 platform.
libx11-xcb-dev:armhf install
libx11-xcb1:armhf install
libx11-xcb1-dbg:armhf install
libxcb-dri2-0:armhf install
libxcb-dri2-0-dev:armhf install
libxcb-dri3-0:armhf install
libxcb-dri3-dev:armhf install
libxcb-glx0:armhf install
libxcb-glx0-dev:armhf install
libxcb-icccm4:armhf install
libxcb-image0:armhf install
libxcb-keysyms1:armhf install
libxcb-present-dev:armhf install
libxcb-present0:armhf install
libxcb-randr0:armhf install
libxcb-randr0-dev:armhf install
libxcb-render-util0:armhf install
libxcb-render0:armhf install
libxcb-render0-dev:armhf install
libxcb-shape0:armhf install
libxcb-shape0-dev:armhf install
libxcb-shm0:armhf install
libxcb-sync-dev:armhf install
libxcb-sync1:armhf install
libxcb-util0:armhf install
libxcb-xfixes0:armhf install
libxcb-xfixes0-dev:armhf install
libxcb-xinerama0:armhf install
libxcb-xinerama0-dev:armhf install
libxcb-xkb1:armhf install
libxcb1:armhf install
libxcb1-dev:armhf install

ambershark

@b108463 Your application can't find the xcb plugin for qt. It should be in /your/qt/path/plugins/platforms/libqxcb.so or something like that. You can install it for your application by using the dir structure:

myapp
plugins/
   platforms/
      libqxcb.so

Or you can use a qt.conf file to point your plugins dir to your qt installation.

Keep in mind this qt install has to match the architecture you are running, in this case I noticed you are using an ARM platform. So make sure your Qt is built for ARM.

b108463

@ambershark Thanks, but I don't understand it clearly.

I found my libqxcb.so in /usr/lib/arm-linux-gnueabihf/qt5/plugins/platforms/libqxcb.so

2.I found the qt.conf in several paths
/usr/share/qtchooser/qt5-arm-linux-gnueabihf.conf
/usr/share/qtchooser/qt4-arm-linux-gnueabihf.conf
/usr/lib/arm-linux-gnueabihf/qtchooser/qt5.conf
/usr/lib/arm-linux-gnueabihf/qtchooser/qt4.conf

Should I add the path of libqxcb.so in theses qt.conf?

ambershark

@b108463 No you need to set it in the same directory as your binary.. i.e.

$ cd /your/path/to/your/app
$ echo "[Paths]" > qt.conf
$ echo "Plugins = /usr/lib/arm-linux-gnueabihf/qt5/plugins" >> qt.conf

Note, that will require your plugins to always be at that directory. Which they probably won't. So the better option for distribution is to make a bundle that contains the libs and plugins you need.

b108463

@ambershark

It seems to create a qt.conf in the same folder as myapp,right?
For 3rd step, it only write the "/usr/lib/arm-linux-gnueabihf/qt5/plugins" to qt.conf , not "/usr/lib/arm-linux-gnueabihf/qt5/plugins/platforms" ?

Sorry,I am a new user, so please forgive me to ask some basic questions. Thanks a lot.

b108463

Add more informatio as below

root@tegra-ubuntu:/home/ubuntu/SMPEXEC# ls -al
total 13448
drwxr-xr-x 2 root root 4096 Dec 29 06:50 .
drwxr-xr-x 24 ubuntu ubuntu 4096 Dec 29 06:49 ..
-rw-r--r-- 1 root root 57 Dec 29 06:50 qt.conf
-rwxrwxrwx 1 root root 4630503 Dec 28 11:14 SMPCodeReader1_ARM_exec
-rwxrwxrwx 1 root root 4502863 Dec 28 11:14 SMPCodeReader_ARM_exec
-rwxrwxrwx 1 root root 4618254 Dec 27 10:03 SMPCodeReader_exe
root@tegra-ubuntu:/home/ubuntu/SMPEXEC# cat qt.conf
[Paths]
Plugins=/usr/lib/arm-linux-gnueabihf/qt5/plugins
root@tegra-ubuntu:/home/ubuntu/SMPEXEC# ls -al /usr/lib/arm-linux-gnueabihf/qt5/plugins/platforms/libqxcb.so -al
-rw-r--r-- 1 root root 441360 Apr 1 2015 /usr/lib/arm-linux-gnueabihf/qt5/plugins/platforms/libqxcb.so
root@tegra-ubuntu:/home/ubuntu/SMPEXEC# ./SMPCodeReader_ARM_exec
Fatal: This application failed to start because it could not find or load the Qt platform plugin "xcb"
in "".

Reinstalling the application may fix this problem. (:0)
Aborted
root@tegra-ubuntu:/home/ubuntu/SMPEXEC#

ambershark

@b108463 said in could not find or load the Qt platform plugun "xcb":

Add more informatio as below

root@tegra-ubuntu:/home/ubuntu/SMPEXEC# ls -al
total 13448
drwxr-xr-x 2 root root 4096 Dec 29 06:50 .
drwxr-xr-x 24 ubuntu ubuntu 4096 Dec 29 06:49 ..
-rw-r--r-- 1 root root 57 Dec 29 06:50 qt.conf
-rwxrwxrwx 1 root root 4630503 Dec 28 11:14 SMPCodeReader1_ARM_exec
-rwxrwxrwx 1 root root 4502863 Dec 28 11:14 SMPCodeReader_ARM_exec
-rwxrwxrwx 1 root root 4618254 Dec 27 10:03 SMPCodeReader_exe
root@tegra-ubuntu:/home/ubuntu/SMPEXEC# cat qt.conf
[Paths]
Plugins=/usr/lib/arm-linux-gnueabihf/qt5/plugins
root@tegra-ubuntu:/home/ubuntu/SMPEXEC# ls -al /usr/lib/arm-linux-gnueabihf/qt5/plugins/platforms/libqxcb.so -al
-rw-r--r-- 1 root root 441360 Apr 1 2015 /usr/lib/arm-linux-gnueabihf/qt5/plugins/platforms/libqxcb.so
root@tegra-ubuntu:/home/ubuntu/SMPEXEC# ./SMPCodeReader_ARM_exec
Fatal: This application failed to start because it could not find or load the Qt platform plugin "xcb"
in "".

Reinstalling the application may fix this problem. (:0)
Aborted
root@tegra-ubuntu:/home/ubuntu/SMPEXEC#

Weird it's not picking up your path from qt.conf. Try putting a space before and after the = sign as I showed in my echo command above.

And to answer your other question you only want the path to plugins, it will looks for platforms/libxxx underneath that.

Here's an example of a linux distribution for one of my applications:

.
./resources
./resources/APP-64.png
./resources/APP-32.png
./resources/messages.xml
./bin
./bin/myapp
./bin/qt.conf
./myapp
./INSTALL
./README
./libs
./libs/libstdc++.so.6
./libs/libQt5Core.so.5
./libs/libQt5Xml.so.5
./libs/libQt5Widgets.so.5
./libs/libsharkcore.so
./libs/libQt5XcbQpa.so.5
./libs/libQt5DBus.so.5
./libs/libgcc_s.so.1
./libs/libsharkcore.so.1.7.3
./libs/libQt5Network.so.5
./libs/libquazip.so.1.0.0
./libs/libQt5XmlPatterns.so.5
./libs/plugins
./libs/plugins/platforms
./libs/plugins/platforms/libqxcb.so
./libs/libQt5Gui.so.5
./libs/libQt5SerialPort.so.5

And in qt.conf:

[Paths]
Plugins = ../libs/plugins

And finally a startup script myapp:

#!/bin/sh

dir="$(dirname `readlink -f $0`)"
LD_LIBRARY_PATH="$dir/libs:$LD_LIBRARY_PATH"
export LD_LIBRARY_PATH
exec $dir/bin/myapp "$@"

Hopefully that helps clear things up on how to distribute apps for linux with Qt.