Weird application crash

Hi to all!

I need help because I stumbled into pitfall I cannot solve. In my app module I have QTableView subclassed object which represents data from subclassed QStandardItemModel object. This QStandardItemModel subclassed object internally holds QList of some data. Now, when I empty this QList with clear() method and after I clear QTableView also using its inherited clear method with following code chunk:

Code:

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m_pShoppingCartView->order()->orders()->clear();    // reinits order list
    m_pShoppingCartView->shoppingCartModel()->clear();    // clears table view

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my app crashes with gdb error:

Code:

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warning: ASSERT: "i >= 0 && i < size()" in file ../../include/QtCore/../../src/corelib/tools/qbitarray.h, line 121

---

. The application crashes when I readd items to qlist and then render data of this qlist using model on table view. Why the app crashes?!

Sometimes I also get:

Code:

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warning: ASSERT: "i >= 0 && i < size()" in file ../../include/QtCore/../../src/corelib/tools/qbitarray.h, line 121
 
warning: QPaintEngine::setSystemClip: Should not be changed while engine is active
 
warning: QPaintEngine::setSystemClip: Should not be changed while engine is active
 
warning: QWidgetPrivate::beginSharedPainter: Painter is already active
 
warning: QPainter::begin: A paint device can only be painted by one painter at a time.
 
warning: QPainter::begin: A paint device can only be painted by one painter at a time.
 
warning: ASSERT: "sharedPainter ? sharedPainter->isActive() : true" in file kernel\qwidget.cpp, line 4420

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How is the order list related to the model? Do you emit proper signals when changing the model?

Well, here is model header:

Code:

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#ifndef CSHOPPINGCARTMODEL_H_
#define CSHOPPINGCARTMODEL_H_
 
// qt includes
//#include <QAbstractTableModel>
#include <QStandardItemModel>
#include <QModelIndex>
#include <QString>
 
#include "CMerchandizeOrder.h"
 
//class CShoppingCartModel : public QAbstractTableModel
class CShoppingCartModel : public QStandardItemModel
{
public:
    CShoppingCartModel(CMerchandizeOrder* pMerchandizeOrder,
                       QObject* pParent=0);
    int rowCount(const QModelIndex &parent = QModelIndex()) const;
    int columnCount (const QModelIndex & parent=QModelIndex()) const;
    QVariant data(const QModelIndex &index, int role) const;
/*
    bool setData(const QModelIndex &index,
                 const QVariant &value,
                 int role);
*/
 
    inline     CMerchandizeOrder* order()
        { return m_pMerchandizeOrder; };
private:
    CMerchandizeOrder* m_pMerchandizeOrder;
};
 
#endif /*CSHOPPINGCARTMODEL_H_*/

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and its implementation:

Code:

---

#include "CShoppingCartModel.h"
 
CShoppingCartModel::CShoppingCartModel(CMerchandizeOrder* pMerchandizeOrder,
                                       QObject* pParent)
//    : QAbstractTableModel(pParent), m_pMerchandizeOrder(pMerchandizeOrder)
    : QStandardItemModel(pParent), m_pMerchandizeOrder(pMerchandizeOrder)
{
    setColumnCount(1);    // sets column count
    setRowCount(pMerchandizeOrder->orders()->size());    // sets row count
}
 
int CShoppingCartModel::rowCount(const QModelIndex& parent) const
{
    return m_pMerchandizeOrder->orders()->size();
}
 
int CShoppingCartModel::columnCount (const QModelIndex& parent) const
{
    return 1;
}
 
QVariant CShoppingCartModel::data(const QModelIndex &index, int role) const
{
    if (!index.isValid())
        return QVariant();
    if(index.isValid() && role==Qt::DisplayRole)
        return m_pMerchandizeOrder->orders()->at(index.row()).strDisplayString;
        //QStandardItemModel::data(index, role);
    if(index.isValid() && role==Qt::FontRole)
        return QFont("Courier New",
                     18, 
                     QFont::Normal/*QFont::Bold*/);
    return QVariant();    // returns invalid record
}
 
/*
bool CShoppingCartModel::setData(const QModelIndex &index,
                                 const QVariant &value,
                                 int role)
{
    emit dataChanged(index, index);
    return true;
}
*/

---

You could try to use a debugger (e.g. gdb on linux) to pinpoint the exact location where the application crashes. This usually also reveals error that causes the crash.

Quote:

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Originally Posted by totycro

You could try to use a debugger (e.g. gdb on linux) to pinpoint the exact location where the application crashes. This usually also reveals error that causes the crash.

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Wll I did that, how could I otherwise show error strings ?!

What is the point of having a QStandardItemModel if you reimplement all of its functionality to operate on a list? Either use QStringListModel with a simple reimplementation to return another font (although you can do that on the view level) or use QStandardItemModel properly. The extra list is completely redundant here.

wysota, will fix that, now it is mandatory to make the code work. Here is the code that uses model:

Code:

---

// slot for choosing merchandize
void COperationWIndow::chooseMerchandize()
{
    structOrder tmpOrder;    // temp order
    QList<QStandardItem*> OrderItemList;    // order model item list
 
    qDebug() << "m_iSelected: " << m_pMerchandizeBrowser->m_iSelected;
    // FIXED: m_pMerchandizeBrowser->m_iSelected does not correctly show the index of selected image
/*
    tmpOrder.iMerchandizeID=1;
    tmpOrder.iMerchandizeQuantity=25;
    tmpOrder.rMerchandizePrice=4.00;
    tmpOrder.rSubtotal=tmpOrder.iMerchandizeQuantity*tmpOrder.rMerchandizePrice;
    tmpOrder.strMerchandizeName=QString("Testni Artikel");
    tmpOrder.strDisplayString=QString::number(tmpOrder.iMerchandizeID)+strMerchandizeSpaceDelimiter+\
                              QString(tmpOrder.strMerchandizeName)+strMerchandizeDelimiter+\
                              QString::number(tmpOrder.rMerchandizePrice, 'f', iMerchandizePricePrecision)+strMerchandizeSpaceDelimiter+\
                              QString::number(tmpOrder.iMerchandizeQuantity)+strMerchandizeSpaceDelimiter+\
                              QString::number(tmpOrder.rSubtotal, 'f', iMerchandizePricePrecision);
    qDebug() << "tmpOrder.strDisplayString=" << tmpOrder.strDisplayString;
*/
 
    // TODO: language id number must not be ignored in sql statement
    QString queryString("SELECT * from merchandize WHERE IdentificationNumber=%1 AND InUse=1;");
    int iMerchandizeId=m_pMerchandizeBrowser->m_iSelected+1;    // calcualtes id
    queryString=queryString.arg(iMerchandizeId);    // adds id to query string
    qDebug() << "Query: " << queryString;    // debug
    QSqlQuery query(queryString);    // sets up query from query string
    qDebug() << query.lastError().text();    // debug
    if (query.isActive())
    {
        while (query.next())
        {
            tmpOrder.iMerchandizeID=query.value(0).toInt();
            tmpOrder.iMerchandizeQuantity=1;
            tmpOrder.rMerchandizePrice=(qreal)query.value(3).toDouble();
            tmpOrder.rSubtotal=tmpOrder.iMerchandizeQuantity*tmpOrder.rMerchandizePrice;
            tmpOrder.strMerchandizeName=QString(query.value(2).toString());
            tmpOrder.strDisplayString=QString::number(tmpOrder.iMerchandizeID)+strMerchandizeSpaceDelimiter+\
                                      QString(tmpOrder.strMerchandizeName)+strMerchandizeDelimiter+\
                                      QString::number(tmpOrder.rMerchandizePrice, 'f', iMerchandizePricePrecision)+strMerchandizeSpaceDelimiter+\
                                      QString::number(tmpOrder.iMerchandizeQuantity)+strMerchandizeSpaceDelimiter+\
                                      QString::number(tmpOrder.rSubtotal, 'f', iMerchandizePricePrecision);
        }
 
 
        if(m_pShoppingCartView->order()->orders()->size()<=0)
        {
            // size of orders is zero, adds record to table
            m_pShoppingCartView->order()->orders()->append(tmpOrder);    // adds order to internal qlist
            QStandardItem* pItem=new QStandardItem(QString(tmpOrder.strDisplayString));
            Q_CHECK_PTR(pItem);    // checks creation
            m_pShoppingCartView->shoppingCartModel()->appendRow(pItem);
        }
        else
        {
            for(qint16 iIndex=0; iIndex<(qint16)m_pShoppingCartView->order()->orders()->size(); iIndex++)
            {
                qDebug() << " m_pShoppingCartView->order()->orders()->at((int)iIndex).iMerchandizeID (" \
                         << m_pShoppingCartView->order()->orders()->at((int)iIndex).iMerchandizeID << ")==" \
                         << "tmpOrder.iMerchandizeID (" << tmpOrder.iMerchandizeID << ")?";
                if(m_pShoppingCartView->order()->orders()->at((int)iIndex).iMerchandizeID==tmpOrder.iMerchandizeID)
/*
                qDebug() << " iMerchandizeId (" << iMerchandizeId \
                         << "tmpOrder.iMerchandizeID (" << tmpOrder.iMerchandizeID << ")?";
                if(iMerchandizeId==tmpOrder.iMerchandizeID)
*/
                {
                    // orderer merchandize found, so
                    tmpOrder.iMerchandizeQuantity++;    // update quantity
                    tmpOrder.rSubtotal=tmpOrder.iMerchandizeQuantity*tmpOrder.rMerchandizePrice;    // update total
                    tmpOrder.strDisplayString=QString::number(tmpOrder.iMerchandizeID)+strMerchandizeSpaceDelimiter+\
                                              QString(tmpOrder.strMerchandizeName)+strMerchandizeDelimiter+\
                                              QString::number(tmpOrder.rMerchandizePrice, 'f', iMerchandizePricePrecision)+strMerchandizeSpaceDelimiter+\
                                              QString::number(tmpOrder.iMerchandizeQuantity)+strMerchandizeSpaceDelimiter+\
                                              QString::number(tmpOrder.rSubtotal, 'f', iMerchandizePricePrecision);
                    m_pShoppingCartView->order()->orders()->replace((int)iIndex, tmpOrder);    // saves changes
                    m_pShoppingCartView->shoppingCartModel()->clear();    // clears table view
                    for(qint16 iIndex=0; iIndex<(qint16)m_pShoppingCartView->order()->orders()->size(); iIndex++)
                    {
                        QStandardItem* pItem=new QStandardItem(QString(tmpOrder.strDisplayString));    // creates new item from order
                        Q_CHECK_PTR(pItem);    // checks creation
                        OrderItemList.append(pItem);    // adds item to list
                        //m_pShoppingCartView->shoppingCartModel()->appendRow(pItem);    // adds items
                    }
                    m_pShoppingCartView->shoppingCartModel()->appendRow(OrderItemList);    // adds items
                    break;
                }
                else
                {
                    // ordered merchandize not found, so adds it
                    m_pShoppingCartView->order()->orders()->append(tmpOrder);    // adds order to internal qlist
                    QStandardItem* pItem=new QStandardItem(QString(tmpOrder.strDisplayString));    // creates new item from list
                    Q_CHECK_PTR(pItem);    // checks creation
                    m_pShoppingCartView->shoppingCartModel()->appendRow(pItem);
                    break;
                }    // for
            }    // for
        }    // if
/*
        m_pShoppingCartView->resizeColumnsToContents();
        m_pShoppingCartView->resizeRowsToContents();
*/
        if(m_pOrderButton->isEnabled()==false)
            m_pOrderButton->setEnabled(true);    // enables order buttn
    }    // if
}

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The code

Code:

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/*
        m_pShoppingCartView->resizeColumnsToContents();
        m_pShoppingCartView->resizeRowsToContents();
*/

---

is commented because here the app crashes by resizeRows. Why?!

You can't make an incorrect code work. Finding the real problem with a bad design will take more time than rewriting it using correct solutions. Either implement the model by subclassing from QAbstractListModel or switch to QStandardItemModel completely.

I've switched to QStandardItemModel, you saw it in the header file!!

And the order list simply cannot be redundant because I need it in other parts of project. So I cannot have QStandardModel with this list or what now?!

Quote:

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Originally Posted by MarkoSan

I've switched to QStandardItemModel, you saw it in the header file!!

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No, you didn't. You subclassed the model (and did it incorrectly) and not used it.

Quote:

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And the order list simply cannot be redundant because I need it in other parts of project. So I cannot have QStandardModel with this list or what now?!

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I don't know what can or can't be. I know all the functionality of your list is already in the standard item model. So either don't use the list or don't use QStandardItemModel. A proper approach is to get rid of QStandardItemModel, but it's more work to implement your own model instead of using the standard one.