Custom Qt widget example in Qt Creator errors

Question

I'm a Qt beginner, I have the 5.2.1 version and I was trying to learn Qt/QML from a book on Github. However, this is one of the most basic examples:

#ifndef CUSTOMWIDGET_H
#define CUSTOMWIDGET_H

#include <QtWidgets>

class CustomWidget : public QWidget
{
    Q_OBJECT
public:
    explicit CustomWidget(QWidget *parent = 0);
    void paintEvent(QPaintEvent *event);
   void mousePressEvent(QMouseEvent *event);
   void mouseMoveEvent(QMouseEvent *event);
private:
     QPoint m_lastPos;
};

#endif // CUSTOMWIDGET_H

And here are the errors I get:

ln function `_start'

undefined reference to `main'

collect2: ld returned 1 exit status

I have no idea what any of these mean, so any help would be appreciated. I made the project as a Qt Quick Application.

These are included in the .pro file

QT += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

Probably you copied *.h and *.cpp files belong to the CustomWidget class and didn't copy main.cpp so linker cannot find entry point — folibis, Jul 22 '15 at 13:48

score 1 · Accepted Answer · edited May 23 '17 at 11:44

First you should go to google and look for the errors, you can find them and the solution, and some solutions are here in stackoverflow too.

For what I can help and hope it helps you:

ln function _start' With only that I don't know what does it mean, can you copy the full error? Maybe this can help you
undefined reference to main' Basically you are doing a example in a new project I supose so there is no main() function, which is basic for any program to run. You can add a main.cpp or declare it globaly like void main() {}Try looking at this and this
collect2: ld returned 1 exit status means that something was wrong (there are errors before this line), so that's why is the last error.

Custom Qt widget example in Qt Creator errors

1 Answers1