[Solved] ERROR QOpenGLWidget example - Undefined symbol
I am working with Qt 5.4.0 embedded in remote debugging.
I have implemented an OpenGL project using QOpenGLWidget.
It should load an image but I am getting an error (see below 1).
I wanted to try the OpenGL examples and I am getting the same error when I am trying to run the QOpenGLWidget example (see below 2).
2Dpainting and HelloGL examples are working perfectly.
What can be the problem ?
1. Error from my project
Listening on port 10000
Remote debugging from host 192.168.101.122
Process /home/ubuntu/Documents/CrossCompilationTesting/Testv2 created; pid = 13638
Unable to find dynamic linker breakpoint function.
GDB will be unable to debug shared library initializers
and track explicitly loaded dynamic code./home/ubuntu/Documents/CrossCompilationTesting/Testv2: symbol lookup error: /home/ubuntu/Documents/CrossCompilationTesting/Testv2: undefined symbol: _ZN13QOpenGLWidget16staticMetaObjectE
Child exited with status 127
readchar: Got EOF
Debugging has finished@
2. Error when starting the example directly on the remote device
./openglwidget: symbol lookup error: ./qopenglwidget: undefined symbol: _ZN13QOpenGLWidget16staticMetaObjectE@
Maybe a silly question but do you have the QtOpenGL library installed on your target ?
When you said "installed" what do you mean ?
Right now, I just copied my QtOpenGL library inside my binary folder on my target. Is it correct to do it this way ?
Thank you for your help,
I checked if there was any QtOpenGL installed on my target on the Ubuntu Software Center and I have the Qt 5 OpenGL module (libqt5opengl5) installed...
Any ideas ?
By installed I mean did you deploy the Qt libraries and plugins on your target.
Just copying the library beside your binary is not enough. You would also need to set LD_LIBRARY_PATH to folder containing the Qt libraries.
No, I have not done that. I'm a self-learning so I probably missed this part.
What exactly is the process? Can I set LD_LIBRARY_PATH inside Qt Creator ? Where can I find some clear information about that?
Yes you can.
What is your target ?
Thanks a lot for your help.
My target is a linux (ubuntu 14.04) arm based. I am using the arm-linux-gnueabihf cross compiler.
Ok, as for the installation part, it's the last step after you called make
Sorry I do not understand...
Are you talking about adding a step inside QtCreator in the Build Steps after the "make" ?
Are you talking about the "make" after the ./configure ? So the "make install" step I presume ?
I am not able to find information on this LD_LIBRARY_PATH. Where am I supposed to set this variable ? Inside my .pro ? And to what ? Where ? On my target ? Or on my host ?
Is it supposed to be set to /usr/local/qt-embedded-5.4.0/lib or something like that ?
I am stuck on this error for several days. I tried so many things but none of them work... I will really appreciate your help.
Yes, make install after make after configure
LD_LIBRARY_PATH is not Qt specific it's a Linux environment variable that you can set in Qt Creator, in your current terminal or in a bash script that will start your application.
Since you are using Qt Creator and IIRC, you have the option to do it for your target. It must contain the path to where your custom built Qt can be found on the target.
Ok I see.
So if I understand correctly, I do NOT need to re-compile my custom built Qt or anything like that but I need to specify LD_LIBRARY_PATH in my QtCreator.
But when you say "It must contain the path to where your custom built Qt can be found on the target."
Does it mean that I need to copy my custom build Qt on my target ? It's 1.7GB, it's a lot for an embedded device. I only have it on my host right now.
I have a "qt5" folder inside my /usr/lib/arm-linux-gnueabihf on my target with inside three folders "libexec", "plugins" and "qml" but there is nothing about QOpenGL. libexec has QtWebPluginProcess and QtWebProcess. Is it the place where I should have my QOpenGL libraries ?
What am I missing ?
Since you only have it on your host, how do you expect your device to use it to run your application ? What device is it ? Currently most of them use e.g. sdcards that are generally big enough even for development.
You don't need to copy absolutely everything, the plugins/libraries your application is using would be enough
I copied the libQt5OpenGL.so.5.4.0 and I created the link of libQt5OpenGL.so on my target. I set the LD_LIBRARY_PATH in the Build environnement on Qt Creator to the folder where I copied the libraries but it is still not working...
What am I doing wrong ?
I don't understand why is it so difficult to get a QOpenGLWidget working. I search for it and the code is with the QtWidgets.
Why a QMessageBox will work perfectly and not a QOpenGLWidget ? What is the difference between them ?
It's the Run environment that you must update, it's when you run your application that LD_LIBRARY_PATH is used.
QMessageBox only relies on the widget module that seems to be properly deployed
I tried it, setting the LD_LIBRARY_PATH inside the Run Environment but I am still getting the error....
I also tried directly on the board by setting the LD_LIBRARY_PATH inside my terminal, running my binary file but I am still getting exactly the same error. Does it mean that I do not copy the good libraries ? What are they exactly ?
Which library did you copy exactly ?
Actually I solved the problems. I copied the libQt5Core.so.5, libQt5Gui.so.5, libQt5OpenGL.so.5 and libQt5Widgets.so.5 in the same directory of the binary file and I do not get the errors about the libraries.
Now I'm dealing with the plugins "xcb" or "eglfs".
First I do not know which one to use for an embedded device. I found somewhere that eglfs is the best. Is it right ?
I'm getting a "Could not create the egl surface: error = 0×300b" when using eglfs...
Any idea ? Should I create a new topic for that ?