[Error] undefined symbol: _ZN7QWidget8qwsEventEP8QWSEvent

rocket42

hello everyone
i am using qt to develop apps for Beaglebone black board
My Desktop:

Ubuntu 14.04LTS
qt5.5.1 opensource, qtcreator 3.5.1 opensource
I already compile qt4.8.2 for Beaglebone black follow:
http://exploringbeaglebone.com/chapter6/
And i tried to compile a little app by command line, this little app run on beaglebone black very smoothly.
But now i want to develop on qtcreator ide. So i set up qtcreator follow:
http://developer.toradex.com/knowledge-base/how-to-set-up-qt-creator-to-cross-compile-for-embedded-linux#Configure_Qt_Creator
but when run app built by qtcreator. it emit error:
undefined symbol: _ZN7QWidget8qwsEventEP8QWSEvent
please show me how to solve it
i am waiting your response as soon as

SGaist

Hi,

Are you trying to build your Qt 4 code with Qt 5 ? If so the QWS related classes have been removed from Qt.

rocket42

thank SGaist
yes, i want to build Qt4 code base on Qt5.
please show me how to remove QWS related classes?

SGaist

Do you have any in your code ?

rocket42

i don't see QWS classe in my code

SGaist

Are you trying to run a Qt 4 build of your application against Qt 5 on your device ?

rocket42

@SGaist said:

Are you trying to run a Qt 4 build of your application against Qt 5 on your device ?

i still don't try it.
but i just have ran application with option -qws.
but it don't discard this error.

SGaist

What version of Qt do you have on your target ? What linux distribution are you running on it ?

rocket42

my target is using qt4
my linux distribution is ubuntu lts 14.04

SGaist

You also have an Ubuntu 14.04 running on your target ? If so, then you have a classic "desktop like" build of Qt on your target. That's why it can find the symbols related to QWS. Either rebuild your Qt without the embedded option or install your cross-compiled Qt on the target.

rocket42

No, my target use Angstrom os, which was distributed with board

SGaist

Then check how Qt was built for Angstrom but I suspect that it's a desktop like build rather than an embedded.

rocket42

I found cause of this error, but i dont know how to solve it. That is:
when create new project on Qt(Ctr+N). Qt automatically create new class called mainwindow
and automatically create code in main.cpp which show mainwindow. in main.cpp:
MainWindow w;
w.show();
if build, then run, this error raised
but i replace this two command in main.cpp as following:
...
#include <QMainWindow>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);

QMainWindow q;
q.show();

return a.exec();

}
it run ok.
we see that mainwindow class inherite from QMainWindow class.
when show QMainWindow is ok, but show mainwindow is not ok
that isn't understand

jsulm

Do you do something special in MainWindows constructor?

rocket42

No, Qt automatically create it. i don't change ever

SGaist

Silly question but, are you using the same kit for both projects ?

rocket42

yes, I use same kit for two

SGaist

Then as @jsulm asked, what are you doing in your MainWindow class that differs it from QMainWindow ?

rocket42

i don't change anything, MainWindow class is created automatically by Qt creator
let me post code here. i can't find how to attach it
mainwindow.h content:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

Mainwindow.cpp content:
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}

SGaist

Then there must be something else with your project.