segmentation fault on closing

**harakiri** · 7th July 2009, 11:02

hello,

i've got the following implementation:

Qt Code:

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int main() {
 
  GUI gui;
  gui.start();
 
}

int main() {

  GUI gui;
  gui.start();

}

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Qt Code:

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void GUI::start(){
 
  int argc = 0;
  char** argv = 0;
  m_Application = new QApplication( argc, argv );
 
  m_MainWindow = new MainWindow();
 
  m_MainWindow->show();
  m_Application->exec();
 
}

void GUI::start(){

  int argc = 0;
  char** argv = 0;
  m_Application = new QApplication( argc, argv );

  m_MainWindow = new MainWindow();

  m_MainWindow->show();
  m_Application->exec();

}

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so far, everything works fine. but as soon as i call the following function:

Qt Code:

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void MainWindow::startDetection() {
 
    ImageWindow* edgeDetectedImageWindow = new ImageWindow(this, m_ImageName, resultLocation, name);
    edgeDetectedImageWindow->show();
  }

void MainWindow::startDetection() {

    ImageWindow* edgeDetectedImageWindow = new ImageWindow(this, m_ImageName, resultLocation, name);
    edgeDetectedImageWindow->show();
  }

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the whole application ist still working fine unless i close it: Segmentation fault
the debugger says:
(gdb) bt
#0 0xb5c28326 in ?? () from /lib/tls/i686/cmov/libc.so.6
#1 0xb5c28fc0 in ?? () from /lib/tls/i686/cmov/libc.so.6
#2 0xb5be9c1a in exit () from /lib/tls/i686/cmov/libc.so.6
#3 0xb5bd177d in __libc_start_main () from /lib/tls/i686/cmov/libc.so.6
#4 0x08056161 in _start () at ../sysdeps/i386/elf/start.S:119

anyone can help me with this matter?

here are the headers of the classes:

Qt Code:

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#ifndef GUI_H
#define GUI_H
 
#include <QSplashScreen>
#include <QApplication>
 
#include "MainWindow/MainWindow.h"
 
#define THIS GUI
 
using namespace std;
 
class THIS{
 
//   Q_OBJECT;
 
public:
  THIS();
  ~THIS();
  void start();
 
private:
  MainWindow* m_MainWindow;
  QApplication* m_Application;
 
};
 
#undef THIS
 
#endif /*GUI_H*/

#ifndef GUI_H
#define GUI_H

#include <QSplashScreen>
#include <QApplication>

#include "MainWindow/MainWindow.h"

#define THIS GUI

using namespace std;

class THIS{

//   Q_OBJECT;

public:
  THIS();
  ~THIS();
  void start();

private:
  MainWindow* m_MainWindow;
  QApplication* m_Application;

};

#undef THIS

#endif /*GUI_H*/

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Qt Code:

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#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QMainWindow>
#include <QStatusBar>
#include <QDir>
#include <QFrame>
#include <QHBoxLayout>
#include <QVBoxLayout>
#include <QPushButton>
#include <QScrollArea>
#include <QLabel>
#include <QFileDialog>
#include <QMessageBox>
#include <QMenuBar>
#include <QMenu>
#include <QAction>
#include <QString>
#include <QIcon>
 
#include "../../Modules/NevedgModule/NevedgModule.h"
#include "../../Modules/Obj2PgmModule/Obj2PgmModule.h"
#include "../../Modules/HystlineModule/HystlineModule.h"
#include "../../Modules/PumaToQTConverterModule/PumaToQTConverterModule.h"
#include "../../Modules/HasplitModule/HasplitModule.h"
#include "../../Modules/FindRectangleModule/FindRectangleModule.h"
#include "../../Modules/FindCircleModule/FindCircleModule.h"
#include "../../Modules/GeometricObjectConverterModule/GeometricObjectConverterModule.h"
 
#include "ImageWindow/ImageWindow.h"
#include "GraphicsWindow/GraphicsWindow.h"
 
#define THIS MainWindow
 
using namespace std;
 
class MainWindow : public QMainWindow {
 
  Q_OBJECT;
 
public:
 
  THIS();
  ~THIS();
 
private:
 
  QString m_AppName;
  QString m_ImageName;
  QString m_ImageBaseName;
  QString m_ImagePath;
 
  void loadModules();
    NevedgModule* m_NevedgModule;
    Obj2PgmModule* m_Obj2PgmModule;
    HystlineModule* m_HystlineModule;
    PumaToQTConverterModule* m_PumaToQTConverterModule;
    HasplitModule* m_HasplitModule;
    FindRectangleModule* m_FindRectangleModule;
    FindCircleModule* m_FindCircleModule;
    GeometricObjectConverterModule* m_GeometricObjectConverterModule;
 
  void createMainWidget();
    QFrame* m_MainFrame;
    QHBoxLayout* m_MainLayout;
      QFrame* m_OperationsFrame;
      QVBoxLayout* m_OperationsLayout;
        QPushButton* m_LoadImagePushButton;
        QPushButton* m_StartDetectionPushButton;
      QScrollArea* m_InitialScrollArea;
      QLabel* m_InitialLabel;
 
  void createMenus();
    QMenu* m_FileMenu;
      QAction* m_LoadImageAction;
      QAction* m_ExitAct;
    QMenu* m_EditMenu;
    QMenu* m_ViewMenu;
    QMenu* m_HelpMenu;
 
public slots:
 
  void openImage();
  void loadImage(const QString &fileName);
  void startDetection();
 
};
 
#undef THIS
 
#endif

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QStatusBar>
#include <QDir>
#include <QFrame>
#include <QHBoxLayout>
#include <QVBoxLayout>
#include <QPushButton>
#include <QScrollArea>
#include <QLabel>
#include <QFileDialog>
#include <QMessageBox>
#include <QMenuBar>
#include <QMenu>
#include <QAction>
#include <QString>
#include <QIcon>

#include "../../Modules/NevedgModule/NevedgModule.h"
#include "../../Modules/Obj2PgmModule/Obj2PgmModule.h"
#include "../../Modules/HystlineModule/HystlineModule.h"
#include "../../Modules/PumaToQTConverterModule/PumaToQTConverterModule.h"
#include "../../Modules/HasplitModule/HasplitModule.h"
#include "../../Modules/FindRectangleModule/FindRectangleModule.h"
#include "../../Modules/FindCircleModule/FindCircleModule.h"
#include "../../Modules/GeometricObjectConverterModule/GeometricObjectConverterModule.h"

#include "ImageWindow/ImageWindow.h"
#include "GraphicsWindow/GraphicsWindow.h"

#define THIS MainWindow

using namespace std;

class MainWindow : public QMainWindow {

  Q_OBJECT;

public:

  THIS();
  ~THIS();

private:

  QString m_AppName;
  QString m_ImageName;
  QString m_ImageBaseName;
  QString m_ImagePath;

  void loadModules();
    NevedgModule* m_NevedgModule;
    Obj2PgmModule* m_Obj2PgmModule;
    HystlineModule* m_HystlineModule;
    PumaToQTConverterModule* m_PumaToQTConverterModule;
    HasplitModule* m_HasplitModule;
    FindRectangleModule* m_FindRectangleModule;
    FindCircleModule* m_FindCircleModule;
    GeometricObjectConverterModule* m_GeometricObjectConverterModule;

  void createMainWidget();
    QFrame* m_MainFrame;
    QHBoxLayout* m_MainLayout;
      QFrame* m_OperationsFrame;
      QVBoxLayout* m_OperationsLayout;
        QPushButton* m_LoadImagePushButton;
        QPushButton* m_StartDetectionPushButton;
      QScrollArea* m_InitialScrollArea;
      QLabel* m_InitialLabel;

  void createMenus();
    QMenu* m_FileMenu;
      QAction* m_LoadImageAction;
      QAction* m_ExitAct;
    QMenu* m_EditMenu;
    QMenu* m_ViewMenu;
    QMenu* m_HelpMenu;

public slots:

  void openImage();
  void loadImage(const QString &fileName);
  void startDetection();

};

#undef THIS

#endif

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Qt Code:

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#ifndef IMAGEWINDOW_H
#define IMAGEWINDOW_H
 
#include <QMainWindow>
#include <QWidget>
#include <QString>
#include <QDir>
#include <QIcon>
#include <QScrollArea>
#include <QLabel>
#include <QMessageBox>
 
#define THIS ImageWindow
 
using namespace std;
 
class ImageWindow : public QMainWindow {
 
  Q_OBJECT;
 
public:
 
  THIS(QWidget* parent, QString &imageName, QString &imagePath, QString &operation);
  ~THIS();
 
private:
 
  QString m_ImageName;
  QString m_ImagePath;
  QString m_Operation;
 
  QScrollArea *m_ImageScrollArea;
  QLabel* m_ImageLabel;
 
public slots:
 
};
 
#undef THIS
 
#endif

#ifndef IMAGEWINDOW_H
#define IMAGEWINDOW_H

#include <QMainWindow>
#include <QWidget>
#include <QString>
#include <QDir>
#include <QIcon>
#include <QScrollArea>
#include <QLabel>
#include <QMessageBox>

#define THIS ImageWindow

using namespace std;

class ImageWindow : public QMainWindow {

  Q_OBJECT;

public:

  THIS(QWidget* parent, QString &imageName, QString &imagePath, QString &operation);
  ~THIS();

private:

  QString m_ImageName;
  QString m_ImagePath;
  QString m_Operation;

  QScrollArea *m_ImageScrollArea;
  QLabel* m_ImageLabel;

public slots:

};

#undef THIS

#endif

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**nish** · 7th July 2009, 11:26

why cant you put your qapplication on stack in main()?

**harakiri** · 7th July 2009, 11:34

Originally Posted by MrDeath

why cant you put your qapplication on stack in main()?

the programm can be started without a gui, but i could skip that step using the GUI file

EDIT:
deleted the GUI file, main():

Qt Code:

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int main() {
 
  int argc = 0;
  char** argv = 0;
  QApplication* m_Application = new QApplication( argc, argv );
 
  MainWindow* m_MainWindow = new MainWindow();
 
  m_MainWindow->show();
  m_Application->exec();
 
}

int main() {

  int argc = 0;
  char** argv = 0;
  QApplication* m_Application = new QApplication( argc, argv );

  MainWindow* m_MainWindow = new MainWindow();

  m_MainWindow->show();
  m_Application->exec();

}

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segmentation fault still appears on closing

**nish** · 7th July 2009, 13:59

first of all make argc and argv the parameters of main().. secondly use QApplication instead of QApplication*... third.. use a debugger to debug your app.. it will land the exact point where your app crashes... then see the call stack to trace the error.

**harakiri** · 7th July 2009, 16:47

Originally Posted by MrDeath

first of all make argc and argv the parameters of main().. secondly use QApplication instead of QApplication*... third.. use a debugger to debug your app.. it will land the exact point where your app crashes... then see the call stack to trace the error.

Qt Code:

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int main(int argc, char *argv[]) {
 
  QApplication m_Application( argc, argv );
 
  MainWindow* m_MainWindow = new MainWindow();
 
  m_MainWindow->show();
 
  return m_Application.exec();
 
}

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

  QApplication m_Application( argc, argv );

  MainWindow* m_MainWindow = new MainWindow();

  m_MainWindow->show();

  return m_Application.exec();

}

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debugger result:

Qt Code:

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(gdb) bt
#0  0xb5cec2ed in ?? () from /lib/tls/i686/cmov/libc.so.6
#1  0xb5cecfc0 in ?? () from /lib/tls/i686/cmov/libc.so.6
#2  0xb5cadc1a in exit () from /lib/tls/i686/cmov/libc.so.6
#3  0xb5c9577d in __libc_start_main () from /lib/tls/i686/cmov/libc.so.6
#4  0x08056021 in _start () at ../sysdeps/i386/elf/start.S:119

(gdb) bt
#0  0xb5cec2ed in ?? () from /lib/tls/i686/cmov/libc.so.6
#1  0xb5cecfc0 in ?? () from /lib/tls/i686/cmov/libc.so.6
#2  0xb5cadc1a in exit () from /lib/tls/i686/cmov/libc.so.6
#3  0xb5c9577d in __libc_start_main () from /lib/tls/i686/cmov/libc.so.6
#4  0x08056021 in _start () at ../sysdeps/i386/elf/start.S:119

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**nish** · 8th July 2009, 01:06

ok .. the debugger is not helpful...

to trace the error... place a breakpoint in mainwindow destructor. then single step.. if it passes well.. then place on other destructors... if any destructor is not called than you have a problem.

**harakiri** · 8th July 2009, 13:54

ok i'll test that, ty

EDIT:

that worked, thank you!

Qt Code:

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void GraphicsWindow::closeEvent(QCloseEvent *event) {
 
  delete this;
  event->accept();
 
}

void GraphicsWindow::closeEvent(QCloseEvent *event) {

  delete this;
  event->accept();

}

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fixed it, now the destructor is called

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