Unhandled Exception

[dougbroadwell]

(Reposted with code inserted)

Windows, Qt Creator 1.0.0, Qt 4.5.0

I'm creating a little SQL input form. In the main window constructor, I create a QSqlTableModel and when I try to associate it with a QTableView created in QDesigner I get the runtime error:

Unhandled exception at 0x00f8a5be in Forecast1.exe: 0xC0000005: Access violation reading location 0x00000004

The arrow in the following code is where it is occurring.


void MainWindow::SetupHeaderWidget()
{
// Set up the ForecastHeader (database) table Model //

HeaderModel = new QSqlTableModel(this);
HeaderModel->setTable("ForecastHeader");
HeaderModel->setSort (Head_ForecastDate_Col, Qt::AscendingOrder);
HeaderModel->setHeaderData(Head_Agency_Col, Qt::Horizontal, "Agency");
HeaderModel->setHeaderData(Head_ForecastDate_Col, Qt::Horizontal, "Forecast Date");
HeaderModel->setHeaderData(Head_ForecastPercent_Col, Qt::Horizontal, "Percent");
HeaderModel->setHeaderData(Head_Note_Col, Qt::Horizontal, "Note");
HeaderModel->select(); // Suck the data into this model.

// Set up the ForecastHeader (database) table View //

--> tvForecastHeader->setModel(HeaderModel);
tvForecastHeader->setSelectionMode(QAbstractItemView::SingleSelectio n);
...


In running in the debugger traces it to the lines below, at (in qwidget.h line 144):

QWidgetPrivate *pd = parent->d_func();

is where it happens, when I step a message displayed is: ' stopped: "signal received" ' and the debugger will not go beyond the "Q_DECLARE_PRIVATE(QWidget)" line in the last section.


void QWidget::releaseDC(HDC hdc) const
{
Q_D(const QWidget);
// If its the widgets own dc, it will be released elsewhere. If
// its a different HDC we release it and issue a warning if it
// fails.
--> if (hdc != d->hd && !ReleaseDC(winId(), hdc))
qErrnoWarning("QWidget::releaseDC(): failed to release HDC");
}
#else
...


WId QWidget::winId() const
{
if (!testAttribute(Qt::WA_WState_Created) || !internalWinId()) {
QWidget *that = const_cast<QWidget*>(this);
that->setAttribute(Qt::WA_NativeWindow);
--> that->d_func()->createWinId();
return that->data->winid;
}
return data->winid;
}


void QWidgetPrivate::createWinId(WId winid)
{
Q_Q(QWidget);
const bool forceNativeWindow = q->testAttribute(Qt::WA_NativeWindow);
if (!q->testAttribute(Qt::WA_WState_Created) || (forceNativeWindow && !q->internalWinId())) {
if (!q->isWindow()) {
QWidget *parent = q->parentWidget();
--> QWidgetPrivate *pd = parent->d_func();
if (forceNativeWindow && !q->testAttribute(Qt::WA_DontCreateNativeAncestors))
parent->setAttribute(Qt::WA_NativeWindow);
...


class Q_GUI_EXPORT QWidget : public QObject, public QPaintDevice
{
Q_OBJECT
--> Q_DECLARE_PRIVATE(QWidget)
Q_PROPERTY(bool modal READ isModal)
Q_PROPERTY(Qt::WindowModality windowModality READ windowModality WRITE setWindowModality)
Q_PROPERTY(bool enabled READ isEnabled WRITE setEnabled)


Thanks,
Doug

[dougbroadwell]

Another Datapoint:

I'm using multiple inheritance to use graphic objects generated from QDesigner, in this case in the file ui_mainwindow.h (I have used the multiple inheritance approach in other projects without experiencing this problem). If I replace the:


tvForecastHeader->setModel(HeaderModel);

where tvForecastHeader is created in the object defined in ui_mainwindow.h and instantiated in the mainwindow constructor:


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

with a locally created one as in:


DetailView = new QTableView();
DetailView->setModel(HeaderModel);


It doesn't crash. But I can't see what's different from this and the instatiation in MainWindowObject.

?? Doug

[dougbroadwell]

Well, I switched from using the Multiple Inheritance method to the Single Inheritance method and now it works !?!?!

So I'll consider this a fix for now but would sure like to know if I was doing something wrong or if it was a bug.

Regards,
Doug