undefined reference to vtable in Threads.

[prasanth.nvs]

In the following code i got compilation erros like below

/thread.cpp:20: undefined reference to `vtable for MyThread'

thread.cpp:6: undefined reference to `vtable for MyThread'

MyThread.h file is

#ifndef MYTHREAD_H
#define MYTHREAD_H
 
#include <QThread>
#include <QObject>
 
class MyThread:public QThread
{
    Q_OBJECT
public:
    MyThread(QWidget* aParent);
    ~MyThread();
 
public slots:
    void Finished();
 
protected:
    void run();
};
 
#endif //MYTHREAD_H

#ifndef MYTHREAD_H
#define MYTHREAD_H

#include <QThread>
#include <QObject>

class MyThread:public QThread
{
    Q_OBJECT
public:
    MyThread(QWidget* aParent);
    ~MyThread();

public slots:
    void Finished();

protected:
    void run();
};

#endif //MYTHREAD_H

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and MyThread.cpp is

#include "thread.h"
#include <iostream.h>
#include <QMetaType>
 
 
MyThread::MyThread(QWidget* aParent)
{
    qRegisterMetaType<MyThread*>("MyThread");
    QObject::connect(this,SIGNAL(finished()),this,SLOT(Finished()));
    if(!isRunning())
    {
        start();
    }
    else
    {
        return;
    }
}
 
MyThread::~MyThread()
{
 
}
 
 void MyThread::run()
{
    cout <<"Hello :" << endl;
}
 
 
void MyThread::Finished()
{
    cout << "In Finishes:" << endl;
}

#include "thread.h"
#include <iostream.h>
#include <QMetaType>


MyThread::MyThread(QWidget* aParent)
{
    qRegisterMetaType<MyThread*>("MyThread");
    QObject::connect(this,SIGNAL(finished()),this,SLOT(Finished()));
    if(!isRunning())
    {
        start();
    }
    else
    {
        return;
    }
}

MyThread::~MyThread()
{

}

 void MyThread::run()
{
    cout <<"Hello :" << endl;
}


void MyThread::Finished()
{
    cout << "In Finishes:" << endl;
}

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and main.cpp is

int main(int argc,char* argv[])
{
    QtopiaApplication app(argc,argv);
 
    QWidget* lWidget = new QWidget;
    lWidget->setGeometry(0,0,240,320);
 
    MyThread* lThread   = new MyThread(lWidget);
 
    Widget->show();
 
    return app.exec();
}

int main(int argc,char* argv[])
{
    QtopiaApplication app(argc,argv);

    QWidget* lWidget = new QWidget;
    lWidget->setGeometry(0,0,240,320);

    MyThread* lThread   = new MyThread(lWidget);

    Widget->show();

    return app.exec();
}

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Now whts the problem in above code and wts the reason for that.

[jpn]

Is thread.h listed in .pro? Did you re-run qmake after adding Q_OBJECT?

[jogeshwarakundi]

In the following code i got compilation erros like below

/thread.cpp:20: undefined reference to `vtable for MyThread'

thread.cpp:6: undefined reference to `vtable for MyThread'

MyThread.h file is

#ifndef MYTHREAD_H
#define MYTHREAD_H
 
#include <QThread>
#include <QObject>
 
class MyThread:public QThread
{
    Q_OBJECT
public:
    MyThread(QWidget* aParent);
    ~MyThread();
 
public slots:
    void Finished();
 
protected:
    void run();
};
 
#endif //MYTHREAD_H

#ifndef MYTHREAD_H
#define MYTHREAD_H

#include <QThread>
#include <QObject>

class MyThread:public QThread
{
    Q_OBJECT
public:
    MyThread(QWidget* aParent);
    ~MyThread();

public slots:
    void Finished();

protected:
    void run();
};

#endif //MYTHREAD_H

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and MyThread.cpp is

#include "thread.h"
#include <iostream.h>
#include <QMetaType>
 
 
MyThread::MyThread(QWidget* aParent)
{
    qRegisterMetaType<MyThread*>("MyThread");
    QObject::connect(this,SIGNAL(finished()),this,SLOT(Finished()));
    if(!isRunning())
    {
        start();
    }
    else
    {
        return;
    }
}
 
MyThread::~MyThread()
{
 
}
 
 void MyThread::run()
{
    cout <<"Hello :" << endl;
}
 
 
void MyThread::Finished()
{
    cout << "In Finishes:" << endl;
}

#include "thread.h"
#include <iostream.h>
#include <QMetaType>


MyThread::MyThread(QWidget* aParent)
{
    qRegisterMetaType<MyThread*>("MyThread");
    QObject::connect(this,SIGNAL(finished()),this,SLOT(Finished()));
    if(!isRunning())
    {
        start();
    }
    else
    {
        return;
    }
}

MyThread::~MyThread()
{

}

 void MyThread::run()
{
    cout <<"Hello :" << endl;
}


void MyThread::Finished()
{
    cout << "In Finishes:" << endl;
}

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and main.cpp is

int main(int argc,char* argv[])
{
    QtopiaApplication app(argc,argv);
 
    QWidget* lWidget = new QWidget;
    lWidget->setGeometry(0,0,240,320);
 
    MyThread* lThread   = new MyThread(lWidget);
 
    Widget->show();
 
    return app.exec();
}

int main(int argc,char* argv[])
{
    QtopiaApplication app(argc,argv);

    QWidget* lWidget = new QWidget;
    lWidget->setGeometry(0,0,240,320);

    MyThread* lThread   = new MyThread(lWidget);

    Widget->show();

    return app.exec();
}

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Now whts the problem in above code and wts the reason for that.

you are trying to call start() which in turn calls the void run() method from inside your MyThread constructor. this is not valid. before the object construction is complete, you cannot start calling the virtual methods of the object. this is a classic C++ error!

cheers!

[Yeshwin]

This problem occurs due to mistakes of Profile like Spellings of Variables.