File not found: mainwindow.obj

Question

I created a GUI Application -> QMainWindow
I added 1 item to the menu + the slot.
I created a new item -> QDialog
I the slot method i try to show the created dialog but i get this errors:

mainwindow.obj:-1: error: LNK2019: unresolved external symbol "public: __cdecl EditStudentDialog::EditStudentDialog(class QWidget *)" (??0EditStudentDialog@@QEAA@PEAVQWidget@@@Z) referenced in function "private: void __cdecl MainWindow::on_actionNew_triggered(void)" (?on_actionNew_triggered@MainWindow@@AEAAXXZ)

mainwindow.obj:-1: error: LNK2019: unresolved external symbol "public: virtual __cdecl EditStudentDialog::~EditStudentDialog(void)" (??1EditStudentDialog@@UEAA@XZ) referenced in function "private: void __cdecl MainWindow::on_actionNew_triggered(void)" (?on_actionNew_triggered@MainWindow@@AEAAXXZ)

This is the main window:

#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 slots:
    void on_actionNew_triggered();

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "editstudentdialog.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_actionNew_triggered()
{
    EditStudentDialog editDialog;
    editDialog.setModal(true);
    editDialog.exec();
}

This is the dialog ( just an empty one, no controls on it ):

#ifndef EDITSTUDENTDIALOG_H
#define EDITSTUDENTDIALOG_H

#include <QDialog>

namespace Ui {
class EditStudentDialog;
}

class EditStudentDialog : public QDialog
{
    Q_OBJECT

public:
    explicit EditStudentDialog(QWidget *parent = 0);
    ~EditStudentDialog();

private:
    Ui::EditStudentDialog *ui;
};

#endif // EDITSTUDENTDIALOG_H


#include "editstudentdialog.h"
#include "ui_editstudentdialog.h"

EditStudentDialog::EditStudentDialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::EditStudentDialog)
{
    ui->setupUi(this);
}

EditStudentDialog::~EditStudentDialog()
{
    delete ui;
}

What am I doing wrong?

EDIT: This is the .pro file

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = GUI1
TEMPLATE = app


SOURCES += main.cpp\
        mainwindow.cpp \
    editstudentdialog.cpp

HEADERS  += mainwindow.h \
    editstudentdialog.h

FORMS    += mainwindow.ui \
    editstudentdialog.ui

PS: I tried to clean the project and then build it but still the same issue.

EDIT 2: I am using Qt Creator 2.7 with Qt 5.0.2

score 23 · Answer 1 · edited Jun 11 '14 at 13:49

Solution

Right click on project > Clean
Right click on project > Run qmake
Right click on project > Build
Run - worked first time

Why it works

The reason this worked is because Run qmake updates your Makefile. For some reason qt is not automatically updating paths when you make changes to your project such as adding or removing files. Running qmake forces qt to update the paths for your project which enables it to find the mainwindow.obj file. You probably could just run qmake and your problem would be solved.

Effendi · Accepted Answer · 2013-06-04T09:26:06.757

6

It seems that editstudentdialog.obj file is not created properly. Try to clean the project (Build->Clean all) and the build it again. If it does not help check if editstudentdialog.cpp is added to the SOURCES variable in your .pro file. If still nothing happens please provide the .pro file.

EDIT: As was mentioned below, you may also try to delete the whole app and create it again.

edited Jun 04 '13 at 09:26

answered Apr 07 '13 at 17:00

Effendi

98
6

1

Your code builds fine, I have just checked it. Probably something may be wrong with the environment settings. If you are using QtCreator check 'Projects' tab that is on the left panel. You will find there 'Build settings', maybe you can notice something weird. Anyway try to create once again a new project and paste there your code. – Effendi Apr 07 '13 at 17:23
1

I deleted the app and then created it again and now it works. – Jack Willson Apr 07 '13 at 17:30

score 6 · Answer 3 · answered Apr 16 '13 at 22:01

6

I just experienced the same issue. "Build All", "Rebuild All", "Clean All" did not help me to solve the "unresolved external symbol" problem.

However, after I have completely deleted the build directory (in my case C:\dev\projects\qt\build-qt-gui-test-Desktop_Qt_5_0_2_MSVC2010_32bit-Debug) the rebuild worked as a charm.

Hope this help you, vladimir

answered Apr 16 '13 at 22:01

Vladimir L.

1,116
14
23

Yeah, I usually have to delete the shadow build directory for some of the weirder build breaks in Qt Creator. – kayleeFrye_onDeck Aug 17 '17 at 20:48

score 3 · Answer 4 · answered Jul 10 '14 at 19:56

3

I just wanted to add this answer for anyone else (mainly noobs) who had to create an entirely new project to resolve the issue:

I had an extra slot definition in my headers file which prevented the entire application from running, and gave me errors pointing to a function which was not the problem. FYI.

answered Jul 10 '14 at 19:56

Rachael

1,965
4
29
55

Faced with the same issue and only this answer helped. – semanser Feb 28 '18 at 15:17

score 1 · Answer 5 · answered Nov 18 '14 at 15:40

1

Another reason why this may occur is because the .pro file references something that is nonexistent. It happened to me and once I removed those references, the errors were gone.

answered Nov 18 '14 at 15:40

Admin Voter

251
1
12

score 1 · Answer 6 · answered Mar 17 '17 at 14:34

1

In my case the fix was to add a Q_OBJECT macro in the beginning of the QObject-deriving class that was mentioned in the error messages. I don't know why I didn't get messages that more specifically pointed me to the missing macro.

answered Mar 17 '17 at 14:34

Stefan Monov

11,332
10
63
120

score 0 · Answer 7 · answered Mar 13 '16 at 00:35

0

another reason this happens is if your function it's referencing is declared as an inline function in the header

answered Mar 13 '16 at 00:35

SteveEng

331
2
6

File not found: mainwindow.obj

7 Answers7

Solution

Why it works

Linked