mythread.cpp:(.text+0x89e): undefined reference to `vtable for ThreadDialog' error

[ashukla]

Dear Viewer!
How to solve this problem!

mythread.o: In function `ThreadDialog::startOrStopThreadB()':
mythread.cpp:(.text+0x259): undefined reference to `ThreadDialog::staticMetaObject'
mythread.cpp:(.text+0x2b7): undefined reference to `ThreadDialog::staticMetaObject'
mythread.o: In function `ThreadDialog::startOrStopThreadA()':
mythread.cpp:(.text+0x389): undefined reference to `ThreadDialog::staticMetaObject'
mythread.cpp:(.text+0x3e7): undefined reference to `ThreadDialog::staticMetaObject'
mythread.o: In function `ThreadDialog::ThreadDialog(QWidget*)':
mythread.cpp:(.text+0x4ae): undefined reference to `vtable for ThreadDialog'
mythread.cpp:(.text+0x4b5): undefined reference to `vtable for ThreadDialog'
mythread.cpp:(.text+0x57b): undefined reference to `ThreadDialog::staticMetaObject'
mythread.cpp:(.text+0x5de): undefined reference to `ThreadDialog::staticMetaObject'
mythread.cpp:(.text+0x641): undefined reference to `ThreadDialog::staticMetaObject'
mythread.o: In function `ThreadDialog::ThreadDialog(QWidget*)':
mythread.cpp:(.text+0x89e): undefined reference to `vtable for ThreadDialog'
mythread.cpp:(.text+0x8a5): undefined reference to `vtable for ThreadDialog'
mythread.cpp:(.text+0x96b): undefined reference to `ThreadDialog::staticMetaObject'
mythread.cpp:(.text+0x9ce): undefined reference to `ThreadDialog::staticMetaObject'
mythread.cpp:(.text+0xa31): undefined reference to `ThreadDialog::staticMetaObject'
mythread.o: In function `main':
mythread.cpp:(.text+0xcba): undefined reference to `vtable for ThreadDialog'
mythread.cpp:(.text+0xcc1): undefined reference to `vtable for ThreadDialog'
mythread.cpp:(.text+0xda2): undefined reference to `vtable for ThreadDialog'
mythread.cpp:(.text+0xda9): undefined reference to `vtable for ThreadDialog'
collect2: ld returned 1 exit status
make: *** [mythread] Error 1

The code is as follows;

/*mythread.h*/
#ifndef MYTHREAD_H
#define MYTHREAD_H
 
#include <QtGui>
#include <QString>
 
class MyThread : public QThread
{
    Q_OBJECT
 volatile bool stopped;
 QString msg;
 
public:
    MyThread(QObject *parent=0);
    void run(); // this is virtual method, we must implement it in our subclass of QThread
    void setMessage(const QString &message);
    void stop();
 
};
#endif
 
/*mythread.cpp*/
#include "mythread.h"
#include <iostream.h>
 
int i=0;
MyThread::MyThread(QObject *parent)
: QThread(parent)
{
	stopped = false;
 
	//run();
}
 
void MyThread::run()
{
   while (!stopped)
   {
 
          cerr << qPrintable(msg)<< endl;
          msleep(1000);
    	//if(++i==10)
    		//stop();
   }
 
 
 
 
}
 
void MyThread::stop()
{
    stopped = true;
}
void MyThread::setMessage(const QString &message)
{
	msg=message;
}
 
class ThreadDialog : public QDialog
{
    Q_OBJECT
public:
    ThreadDialog(QWidget *parent = 0);
protected:
    void closeEvent(QCloseEvent *event);
private slots:
    void startOrStopThreadA();
    void startOrStopThreadB();
private:
    MyThread threadA;
    MyThread threadB;
    QPushButton *threadAButton;
    QPushButton *threadBButton;
    QPushButton *quitButton;
};
 
ThreadDialog::ThreadDialog(QWidget *parent)
    : QDialog(parent)
{
    threadA.setMessage("Anurag");
    threadB.setMessage("Sonu");
    threadAButton = new QPushButton(tr("Start A"));
    threadBButton = new QPushButton(tr("Start B"));
    quitButton = new QPushButton(tr("Quit"));
    quitButton->setDefault(true);
    connect(threadAButton, SIGNAL(clicked()),
            this, SLOT(startOrStopThreadA()));
    connect(threadBButton, SIGNAL(clicked()),
            this, SLOT(startOrStopThreadB()));
 
}
 
void ThreadDialog::startOrStopThreadA()
{
    if (threadA.isRunning()) {
        threadA.stop();
        threadAButton->setText(tr("Start A"));
    } else {
        threadA.start();
        threadAButton->setText(tr("Stop A"));
    }
}
void ThreadDialog::startOrStopThreadB()
{
    if (threadB.isRunning()) {
        threadB.stop();
        threadBButton->setText(tr("Start B"));
    } else {
        threadB.start();
        threadBButton->setText(tr("Stop B"));
    }
}
 
void ThreadDialog::closeEvent(QCloseEvent *event)
{
    threadA.stop();
    threadB.stop();
    threadA.wait();
    threadB.wait();
    event->accept();
}
 
int main(int argc, char **argv)
{
	QApplication app(argc,argv);
	ThreadDialog t;
	return app.exec();	
}

/*mythread.h*/
#ifndef MYTHREAD_H
#define MYTHREAD_H
 
#include <QtGui>
#include <QString>
 
class MyThread : public QThread
{
    Q_OBJECT
 volatile bool stopped;
 QString msg;
 
public:
    MyThread(QObject *parent=0);
    void run(); // this is virtual method, we must implement it in our subclass of QThread
    void setMessage(const QString &message);
    void stop();
    
};
#endif

/*mythread.cpp*/
#include "mythread.h"
#include <iostream.h>

int i=0;
MyThread::MyThread(QObject *parent)
: QThread(parent)
{
	stopped = false;
	
	//run();
}
 
void MyThread::run()
{
   while (!stopped)
   {

          cerr << qPrintable(msg)<< endl;
          msleep(1000);
    	//if(++i==10)
    		//stop();
   }
   
   
   
   
}

void MyThread::stop()
{
    stopped = true;
}
void MyThread::setMessage(const QString &message)
{
	msg=message;
}

class ThreadDialog : public QDialog
{
    Q_OBJECT
public:
    ThreadDialog(QWidget *parent = 0);
protected:
    void closeEvent(QCloseEvent *event);
private slots:
    void startOrStopThreadA();
    void startOrStopThreadB();
private:
    MyThread threadA;
    MyThread threadB;
    QPushButton *threadAButton;
    QPushButton *threadBButton;
    QPushButton *quitButton;
};

ThreadDialog::ThreadDialog(QWidget *parent)
    : QDialog(parent)
{
    threadA.setMessage("Anurag");
    threadB.setMessage("Sonu");
    threadAButton = new QPushButton(tr("Start A"));
    threadBButton = new QPushButton(tr("Start B"));
    quitButton = new QPushButton(tr("Quit"));
    quitButton->setDefault(true);
    connect(threadAButton, SIGNAL(clicked()),
            this, SLOT(startOrStopThreadA()));
    connect(threadBButton, SIGNAL(clicked()),
            this, SLOT(startOrStopThreadB()));
    
}

void ThreadDialog::startOrStopThreadA()
{
    if (threadA.isRunning()) {
        threadA.stop();
        threadAButton->setText(tr("Start A"));
    } else {
        threadA.start();
        threadAButton->setText(tr("Stop A"));
    }
}
void ThreadDialog::startOrStopThreadB()
{
    if (threadB.isRunning()) {
        threadB.stop();
        threadBButton->setText(tr("Start B"));
    } else {
        threadB.start();
        threadBButton->setText(tr("Stop B"));
    }
}

void ThreadDialog::closeEvent(QCloseEvent *event)
{
    threadA.stop();
    threadB.stop();
    threadA.wait();
    threadB.wait();
    event->accept();
}

int main(int argc, char **argv)
{
	QApplication app(argc,argv);
	ThreadDialog t;
	return app.exec();	
}

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[caduel]

Make sure that your .pro file is uptodate.
(Esp. check that all your .h files are listed after HEADERS += ...;
and your .cpp files after SOURCES += ...)

Run qmake again it should work.

(This error almost always indicates to one of the following:
* forgotten Q_OBJECT in class declaration
* missing files in .pro file
* forgotten to update makefiles
Resulting in: moc not being run; no Qt-code being generated to implement signals and slots... thus the undefined references.)

HTH
Christoph

[ashukla]

I have not forgotten Q_OBJECT macro.
No files is missing to include in .pro files.
moc files is created as well.
but application is not running.

[jpn]

Is ThreadDialog declared in main.cpp? If so, add this:

#include "main.moc"

#include "main.moc"

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at the end of main.cpp and re-run qmake.

[babu198649]

hi
clean all the files created by qmake and make and compile freshly whenever u make a change that is realated with virtual table . i have accidently discovered this method ,but i dont know why this works.


i am using eclipse for qt and hence i dont have trouble in making and cleaning,
bye

[jacek]

clean all the files created by qmake and make and compile freshly whenever u make a change that is realated with virtual table . i have accidently discovered this method ,but i dont know why this works.

All you need is to re-run qmake and you have to do this every time you add or remove Q_OBJECT (or Q_GADGET) macro.