How start compiler in Ubuntu 20

[mrjj]

Hi
What Qt version ?
And how did you install it ?

This i just experinced in older linux mint upgrading to Qt5.15

[Mikeeeeee]

I use Qt 5.15, I use online installer.
When installing on Windows, files did not arrive due to poor server speed and they had to be reinstalled. Maybe with Linux the same trouble.

[SGaist]

Hi,

Set QT_DEBUG_PLUGINS environment variable to 1 and restart your application. You shall have more information about why it fails to load.

[Mikeeeeee]

@SGaist said in How start compiler in Ubuntu 20:

QT_DEBUG_PLUGINS

I write in .pro file:

QT_DEBUG_PLUGINS = 1

But the debag didn't record anything else.

[mrjj]

@Mikeeeeee
Hi
You must do that in a shell.
Not in the .pro file

So open a shell
type
export QT_DEBUG_PLUGINS = 1
and then start creator in this shell.

If you dont know where creator is, you can right click its icon and edit it and see path there.

[Mikeeeeee]

I don't understand you. Do I need to register this in the console?

[JonB]

@Mikeeeeee
You need to do just what @mrjj stated:

1. Open a console/terminal.
2. Type: export QT_DEBUG_PLUGINS=1
3. Type the path to the Qt Creator executable to run it.

Because it has been run from a shell with that environment variable exported, you will get debug output showing you where it's looking for what, to diagnose your problem.

[Mikeeeeee]

@JonB said in How start compiler in Ubuntu 20:

export QT_DEBUG_PLUGINS = 1

this

export QT_DEBUG_PLUGINS = 1

return errors:

bash: export: «=»: this is an invalid identifier
bash: export: «1»: this is an invalid identifier

[JonB]

@Mikeeeeee said in How start compiler in Ubuntu 20:
I just copied what @mrjj typed. Correct is to remove the spaces:

export QT_DEBUG_PLUGINS=1

If it had been me, I would have typed man bash and searched for export for myself:

export [-fn] [name[=word]] ...

[Mikeeeeee]

I write this in folder "Qt", but qt did not issue any new errors. Still, maybe this is because the installer might not have downloaded the files?

[JonB]

@Mikeeeeee
Prior to the qt.qpa.plugin: Could not load ... error message, because of the environment variable you should have output (in the terminal) on where it looked for plugin xcb but failed to find it.

[Mikeeeeee]

It doesn't issue any more errors.
I have only this build log:

/home/admin1/Qt/5.15.0/gcc_64/bin/uic ../test/mainwindow.ui -o ui_mainwindow.h
g++ -c -pipe -g -std=gnu++11 -Wall -Wextra -D_REENTRANT -fPIC -DQT_DEPRECATED_WARNINGS -DQT_QML_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I../test -I. -I../../Qt/5.15.0/gcc_64/include -I../../Qt/5.15.0/gcc_64/include/QtWidgets -I../../Qt/5.15.0/gcc_64/include/QtGui -I../../Qt/5.15.0/gcc_64/include/QtCore -I. -isystem /usr/include/libdrm -I. -I../../Qt/5.15.0/gcc_64/mkspecs/linux-g++ -o main.o ../test/main.cpp
g++ -pipe -g -std=gnu++11 -Wall -Wextra -dM -E -o moc_predefs.h ../../Qt/5.15.0/gcc_64/mkspecs/features/data/dummy.cpp
g++ -c -pipe -g -std=gnu++11 -Wall -Wextra -D_REENTRANT -fPIC -DQT_DEPRECATED_WARNINGS -DQT_QML_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I../test -I. -I../../Qt/5.15.0/gcc_64/include -I../../Qt/5.15.0/gcc_64/include/QtWidgets -I../../Qt/5.15.0/gcc_64/include/QtGui -I../../Qt/5.15.0/gcc_64/include/QtCore -I. -isystem /usr/include/libdrm -I. -I../../Qt/5.15.0/gcc_64/mkspecs/linux-g++ -o mainwindow.o ../test/mainwindow.cpp
/home/admin1/Qt/5.15.0/gcc_64/bin/moc -DQT_DEPRECATED_WARNINGS -DQT_QML_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB --include /home/admin1/QtProjects/build-test-Desktop_Qt_5_15_0_GCC_64bit-Debug/moc_predefs.h -I/home/admin1/Qt/5.15.0/gcc_64/mkspecs/linux-g++ -I/home/admin1/QtProjects/test -I/home/admin1/Qt/5.15.0/gcc_64/include -I/home/admin1/Qt/5.15.0/gcc_64/include/QtWidgets -I/home/admin1/Qt/5.15.0/gcc_64/include/QtGui -I/home/admin1/Qt/5.15.0/gcc_64/include/QtCore -I. -I/usr/include/c++/9 -I/usr/include/x86_64-linux-gnu/c++/9 -I/usr/include/c++/9/backward -I/usr/lib/gcc/x86_64-linux-gnu/9/include -I/usr/local/include -I/usr/include/x86_64-linux-gnu -I/usr/include ../test/mainwindow.h -o moc_mainwindow.cpp
g++ -c -pipe -g -std=gnu++11 -Wall -Wextra -D_REENTRANT -fPIC -DQT_DEPRECATED_WARNINGS -DQT_QML_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I../test -I. -I../../Qt/5.15.0/gcc_64/include -I../../Qt/5.15.0/gcc_64/include/QtWidgets -I../../Qt/5.15.0/gcc_64/include/QtGui -I../../Qt/5.15.0/gcc_64/include/QtCore -I. -isystem /usr/include/libdrm -I. -I../../Qt/5.15.0/gcc_64/mkspecs/linux-g++ -o moc_mainwindow.o moc_mainwindow.cpp
g++ -Wl,-rpath,/home/admin1/Qt/5.15.0/gcc_64/lib -o test main.o mainwindow.o moc_mainwindow.o   /home/admin1/Qt/5.15.0/gcc_64/lib/libQt5Widgets.so /home/admin1/Qt/5.15.0/gcc_64/lib/libQt5Gui.so /home/admin1/Qt/5.15.0/gcc_64/lib/libQt5Core.so -lGL -lpthread   

[JonB]

@Mikeeeeee
I don't understand. Your output now shows a compilation. I thought your problem as reported by you was when you tried to start an application:

qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start ....

I have not seen you reproduce that error message with the environment variable switched on.

[Mikeeeeee]

This error persists. The error was always there and never changed.

[SGaist]

That's why we are asking you to start your application with the QT_DEBUG_PLUGINS environment variable set so that it provides more information at run time about what is happening to the xcb plugin.

[Mikeeeeee]

I started using QT_DEBUG_PLUGINS, but nothing has changed. QT_DEBUG_PLUGINS need to be registered in the "Qt" folder?

[SGaist]

How are you using exactly ?

[Mikeeeeee]

I write in folder "Qt" in console

export QT_DEBUG_PLUGINS=1

[SGaist]

The folder has no influence on that environment variable. And are you starting your application from the same terminal were you defined the variable ?

[Mikeeeeee]

I am restarted Qt.
Maybe I'm not there to change this variable. Explain in which folder I need to change this variable?