Qt Undefined Reference to vtable

[ctote]

commented it out and i still get the same error

[Archimedes]

Post the last version of the code of jaus.h and jaus.cpp

[bmhautz]

It may be useful to post updated code with a note of what changed and the specific errors you are getting.

[ctote]

Here's my updated code:

#ifndef JAUS_H
#define JAUS_H
 
#include <QtNetwork>
#include <QUdpSocket>
#include <QObject>
 
struct Jaus_header
{
    unsigned short message_properties;
    unsigned short command_code;
    QByteArray dest_id[4];
    QByteArray source_id[4];
    unsigned short data_control;
    unsigned short sequence_num;
};
 
class Jaus_neighbor : public QObject
{
    Q_OBJECT
 
public:    
    void handshake();
    void capabilities_discover();
    void sys_management();
    void close_conn();
 
private:
    Jaus_header head;
 
    QUdpSocket *udpSocket;
 
private slots:
    Jaus_neighbor();
 
    void prepare_header();
    void read_jheader();
    void send_jheader();
 
    void do_command();
    void startBroadcasting();
    void stopBroadcasting();
    void sendDatagram();
    //void verifyDatagram();
};
 
#endif // JAUS_H

#ifndef JAUS_H
#define JAUS_H

#include <QtNetwork>
#include <QUdpSocket>
#include <QObject>

struct Jaus_header
{
    unsigned short message_properties;
    unsigned short command_code;
    QByteArray dest_id[4];
    QByteArray source_id[4];
    unsigned short data_control;
    unsigned short sequence_num;
};

class Jaus_neighbor : public QObject
{
    Q_OBJECT

public:    
    void handshake();
    void capabilities_discover();
    void sys_management();
    void close_conn();

private:
    Jaus_header head;

    QUdpSocket *udpSocket;

private slots:
    Jaus_neighbor();

    void prepare_header();
    void read_jheader();
    void send_jheader();

    void do_command();
    void startBroadcasting();
    void stopBroadcasting();
    void sendDatagram();
    //void verifyDatagram();
};

#endif // JAUS_H

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#include "jaus.h"
 
Jaus_neighbor::Jaus_neighbor()
{
    udpSocket = new QUdpSocket(this);
    for (int i = 0; i < 4; i++)
    {
        head.dest_id[i] = 0;
        head.source_id[i] = 0;
    }
    head.sequence_num = 0;
    head.data_control = 0;
    head.message_properties = 0;
    head.command_code = 0;
}
 
void Jaus_neighbor::startBroadcasting()
{
 
}
 
void Jaus_neighbor::stopBroadcasting()
{
 
}
 
void Jaus_neighbor::sendDatagram()
{
    //udpSocket->writeDatagram(message, QHostAddress::LocalHost, 9000);
}
 
 
void Jaus_neighbor::handshake()
{
    Jaus_neighbor::startBroadcasting();
}

#include "jaus.h"

Jaus_neighbor::Jaus_neighbor()
{
    udpSocket = new QUdpSocket(this);
    for (int i = 0; i < 4; i++)
    {
        head.dest_id[i] = 0;
        head.source_id[i] = 0;
    }
    head.sequence_num = 0;
    head.data_control = 0;
    head.message_properties = 0;
    head.command_code = 0;
}

void Jaus_neighbor::startBroadcasting()
{

}

void Jaus_neighbor::stopBroadcasting()
{

}

void Jaus_neighbor::sendDatagram()
{
    //udpSocket->writeDatagram(message, QHostAddress::LocalHost, 9000);
}


void Jaus_neighbor::handshake()
{
    Jaus_neighbor::startBroadcasting();
}

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#include <QtCore/QCoreApplication>
#include <iostream>
#include "jaus.h"
using namespace std;
 
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
 
    cout << "Initializing Jaus Connections..." << flush;
    //Jaus_neighbor cop;
 
    return a.exec();
}

#include <QtCore/QCoreApplication>
#include <iostream>
#include "jaus.h"
using namespace std;

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    cout << "Initializing Jaus Connections..." << flush;
    //Jaus_neighbor cop;

    return a.exec();
}

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I'm still getting the warnings -- but more importantly I think, is I'm getting the following error also: error: collect2: ld returned 1 exit status
If I comment out my default constructor, the app compiles fine.

[Archimedes]

You have your constructor in private slots, that means when you declare an Jaus_neighbor object you can't access the constructor cause it's private. So move it to public.
Also you're getting undefined references for the functions prepare_header(), read_jheader(), send_jheader() and do_command() because there aren't implementation for those functions in the jaus.cpp.

[ctote]

Thanks for the info -- I moved the constructor to public: but I still get the same error

[Archimedes]

I copy pasted the code you gave. I moved the constructor to public, provided the implementation for the functions I told in the previous post ( put in the .cpp file eg.
void Jaus_neighbor:repare_header() {} and so on) and compiled with success!

[ctote]

well that's just not fair then!

here's my new .cpp file (and i moved the constructor):

#include "jaus.h"
 
Jaus_neighbor::Jaus_neighbor()
{
    udpSocket = new QUdpSocket(this);
    for (int i = 0; i < 4; i++)
    {
        header.dest_id[i] = 0;
        header.source_id[i] = 0;
    }
    header.sequence_num = 0;
    header.data_control = 0;
    header.message_properties = 0;
    header.command_code = 0;
}
 
void Jaus_neighbor::startBroadcasting()
{
 
}
 
void Jaus_neighbor::stopBroadcasting()
{
 
}
 
void Jaus_neighbor::sendDatagram()
{
    //udpSocket->writeDatagram(message, QHostAddress::LocalHost, 9000);
}
 
 
void Jaus_neighbor::handshake()
{
    Jaus_neighbor::startBroadcasting();
}
 
void Jaus_neighbor::prepare_header(){}
void Jaus_neighbor::read_jheader(){}
void Jaus_neighbor::send_jheader(){}
void Jaus_neighbor::do_command(){}

#include "jaus.h"

Jaus_neighbor::Jaus_neighbor()
{
    udpSocket = new QUdpSocket(this);
    for (int i = 0; i < 4; i++)
    {
        header.dest_id[i] = 0;
        header.source_id[i] = 0;
    }
    header.sequence_num = 0;
    header.data_control = 0;
    header.message_properties = 0;
    header.command_code = 0;
}

void Jaus_neighbor::startBroadcasting()
{

}

void Jaus_neighbor::stopBroadcasting()
{

}

void Jaus_neighbor::sendDatagram()
{
    //udpSocket->writeDatagram(message, QHostAddress::LocalHost, 9000);
}


void Jaus_neighbor::handshake()
{
    Jaus_neighbor::startBroadcasting();
}

void Jaus_neighbor::prepare_header(){}
void Jaus_neighbor::read_jheader(){}
void Jaus_neighbor::send_jheader(){}
void Jaus_neighbor::do_command(){}

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Same error though

[Archimedes]

What are the differences with the code you'll find in the .zip??
Also did you rerun qmake?

[ctote]

Ok, here's what happened -- I ran your code and it compiled fine but no command line popped up, so I ran it again... now I get the same error every time with your code. I tried to run qmake, but it keeps saying unknown command.

This is frustrating

Also, I just noticed our .pro files are different... not sure if that matters:

mine:

# -------------------------------------------------
# Project created by QtCreator 2010-02-24T13:23:24
# -------------------------------------------------
QT += network
QT -= gui
TARGET = jausCommandLine
CONFIG += console
CONFIG -= app_bundle
TEMPLATE = app
SOURCES += main.cpp \
    jaus.cpp
HEADERS += jaus.h

# -------------------------------------------------
# Project created by QtCreator 2010-02-24T13:23:24
# -------------------------------------------------
QT += network
QT -= gui
TARGET = jausCommandLine
CONFIG += console
CONFIG -= app_bundle
TEMPLATE = app
SOURCES += main.cpp \
    jaus.cpp
HEADERS += jaus.h

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yours:

QT       += network
 
TARGET = jaus
TEMPLATE = app
 
 
SOURCES += main.cpp\
        jaus.cpp
 
HEADERS  += jaus.h

QT       += network

TARGET = jaus
TEMPLATE = app


SOURCES += main.cpp\
        jaus.cpp

HEADERS  += jaus.h

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[ctote]

Just changed my .pro file for yours (except I added the CONFIG section for my command line) -- it's working great now. Why? I'm very new to Qt and don't quite understand the requirements in the .pro file (as well as the requirements for object creation e.g., Q_OBJECT).

[squidge]

Typically, if you get "Undefined Reference to vtable" whilst building a project you need to ensure MOC is being run. The easiest way to ensure this is to simply run qmake from the QtCreator menu bar and then rebuild the project. Q_OBJECT is only required if your class needs signals or slots - these are then read by MOC and parsed into another file that it creates and automatically adds to your project. Without this file, you get the vtable error.