Unexplained Segmentation Fault with QDialog::show() and QDialog::exec()

[powerofpi]

2) When a QObject are destroyed, it delete all children. You have not need to delete them explicitly

Thanks for that, I wasn't aware of it!

For the 1) I suggest you to define a difficulty() public methods that returns m_difficulty and call it after exec from calling code

I would definitely do that, if exec() didn't cause a segmentation fault

As some additional information, I tried to recreate the error with a very small program consisting of only a button with the same dialog window. In this case there was no seg fault and the window was displayed successfully. Could the complication of my program's main window (4 QDockWidgets and a QStatusBar) be causing the seg fault in my main program? Otherwise I used the same code and called it in the same way, so I'm getting more confused...

[mcosta]

Probably there is something wrong in your code. Check where you explicitly delete Widget and verify if there are logical errors.

[powerofpi]

Here is the relevant part of my main window code... I'm registering a generateNew slot to receive signals triggered by a new action. Then elsewhere I'm pressing the new button (in a dock widget), causing me to enter my generateNew() slot, and then the seg fault is always occurring on the call to exec(). Could there be a problem with a button press in a dock widget triggering an action and causing a dialog window in the main widget?

#include "mainwindow.h"
#include <QDesktopWidget>
#include <QApplication>
#include <QResizeEvent>
#include "engine/engine.h"
#include "storage/storage.h"
#include "gui/actionmanager.h"
 
MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
{
    //Test something manually
    //test();
 
    //Create actions
    createActions();
 
    //Create window internals
    createMainSceneAndView();
 
    //Create dock windows
    createDockWindows();
 
    //Additional Settings for this Window
    configureWindow();
 
    restoreSettings();
 
    show();
}
void MainWindow::createActions(){
 
    ActionManager::generateNewAction = new QAction(this);
    connect(ActionManager::generateNewAction, SIGNAL(triggered()), this, SLOT(generateNew()));
 
}
void MainWindow::generateNew(){
    qDebug() << "MainWindow got generate new event.";
 
    //Create a dialog window to get the requested difficulty
    this->generateNewDialog = new GenerateNewDialog(this);
    connect(this->generateNewDialog, SIGNAL(difficultySelected(int)), this, SLOT(generationDifficultySelected(int)));
 
    this->generateNewDialog->exec();
}

#include "mainwindow.h"
#include <QDesktopWidget>
#include <QApplication>
#include <QResizeEvent>
#include "engine/engine.h"
#include "storage/storage.h"
#include "gui/actionmanager.h"
 
MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
{
    //Test something manually
    //test();
 
    //Create actions
    createActions();
 
    //Create window internals
    createMainSceneAndView();
 
    //Create dock windows
    createDockWindows();
 
    //Additional Settings for this Window
    configureWindow();
 
    restoreSettings();
 
    show();
}
void MainWindow::createActions(){
 
    ActionManager::generateNewAction = new QAction(this);
    connect(ActionManager::generateNewAction, SIGNAL(triggered()), this, SLOT(generateNew()));
 
}
void MainWindow::generateNew(){
    qDebug() << "MainWindow got generate new event.";
 
    //Create a dialog window to get the requested difficulty
    this->generateNewDialog = new GenerateNewDialog(this);
    connect(this->generateNewDialog, SIGNAL(difficultySelected(int)), this, SLOT(generationDifficultySelected(int)));
 
    this->generateNewDialog->exec();
}

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[lauwe]

I am having similar problems with a class that inherits from QDialog. In my program i have a QVector<dialog*> with pointers to a number of different instances of the QDialog-derived class. I have a QComboBox that I want to use to activate (show()) these dialogs.

I have two items in the QComboBox and when I activate one dialog everything is fine. But opening the second one leads to a segmentation fault. Note that it does not matter which of the dialogs I open first. But the segmentation fault itself is not caused by me calling show()...

#0 0x00000008 in ?? () at c:/Qt/2010.05/qt/include/QtGui/../../src/gui/kernel/qwidget.h:487
#1 0x00bc0119 in QPainter (this=0x22d468, pd=0x9f504a0) at painting\qpainter.cpp:1489
#2 0x00aed236 in QWidgetPrivate::drawWidget (this=0x9f51600, pdev=0x9fa27c8, rgn=..., offset=..., flags=5, sharedPainter=0x0, backingStore=0x9fa2780) at kernel\qwidget.cpp:5397
#3 0x00c74b31 in QWidgetBackingStore::sync (this=0x9fa2780) at painting\qbackingstore.cpp:1328
#4 0x00ae4f50 in QWidgetPrivate::syncBackingStore (this=0x9f51600) at kernel\qwidget.cpp:1805
#5 0x00af4e75 in QWidget::event (this=0x9f50498, event=0x9f4d360) at kernel\qwidget.cpp:8480
#6 0x00aa9706 in QApplicationPrivate::notify_helper (this=0x3e4c18, receiver=0x9f50498, e=0x9f4d360) at kernel\qapplication.cpp:4396
#7 0x00aa9586 in QApplication::notify (this=0x22fe98, receiver=0x9f50498, e=0x9f4d360) at kernel\qapplication.cpp:4361
#8 0x6a1ff9dc in QCoreApplication::notifyInternal (this=0x22fe98, receiver=0x9f50498, event=0x9f4d360) at kernel\qcoreapplication.cpp:732
#9 0x6a265fbc in QCoreApplication::sendEvent (receiver=0x9f50498, event=0x9f4d360) at kernel//qcoreapplication.h:215
#10 0x6a200a87 in QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x3e5798) at kernel\qcoreapplication.cpp:1373
#11 0x6a222d2e in qt_internal_proc (hwnd=0x105026c, message=1025, wp=0, lp=0) at kernel\qeventdispatcher_win.cpp:503
#12 0x7e418734 in USER32!GetDC () from C:\WINDOWS\system32\user32.dll
#13 0x0105026c in QGraphicsScenePrivate::drawSubtreeRecursive (this=0x6a222a8a, item=0x105026c, painter=0x401, viewTransform=0x0, exposedRegion=0x0, widget=0x22fcdc, parentOpacity=1.6853403962263272e-307, effectTransform=0x14) at graphicsview\qgraphicsscene.cpp:4717
#14 0x7e418816 in USER32!GetDC () from C:\WINDOWS\system32\user32.dll
#15 0x6a222a8a in qt_fast_timer_proc (timerId=0, user=17105516) at kernel\qeventdispatcher_win.cpp:432
#16 0x7e4189cd in USER32!GetWindowLongW () from C:\WINDOWS\system32\user32.dll
#17 0x00000000 in ?? ()

The QDialog-derived class is generated using Qt Creator and has not been changed by me.