QTableView SIGSEGV by repaint and destruction

[BUWNik94]

Hi everybody,
I am using a QTableView in my application for displaying some Information of E-Mails, which I want to analyze like shown in the screenshot below (in the second tab is currently no widget).

Before importing the Mails by using Chilkat-Library, there are no Problems.

After loading the data i get the following Problem:
If I change the Tab of the QTabView-Widget from "Mail-Liste" to Mail-Struktur" (or if the "Mail-Struktur"-Tab was active before loading the mails by changing to "Mail-Liste") I get a Segmentation fault in "qvariant_p.h", line 173. The same problem occurs if i Quit the program.

Here is the (shortened) sourcecode of my Model I use for the QTableView:

cmaillistmode.h:

#include <QAbstractTableModel>
#include <QList>
#include <QDebug>

#include "cmail.h"

/* DEFINES */
#define MAIL_LIST_TABLE_NUM_COLUMNS 6

class CMailListModel : public QAbstractTableModel
{
    Q_OBJECT
public:
    /* Konstruktor */
    CMailListModel();

    /* Destruktor */
    ~CMailListModel() override;

    /* Implementierung ehmals virtueller Funktionen */
    int rowCount(const QModelIndex &parent = QModelIndex()) const override;
    int columnCount(const QModelIndex &parent = QModelIndex()) const override;

    /* Daten für Tabelle abfragen */
    QVariant headerData(int section, Qt::Orientation orientation, int role) const;
    QVariant data(const QModelIndex &index, int role) const;

    /* Neue E-Mail hinzufügen */
    void appendMail(CMail* pNewMail);
    void appendMailOnce(CMail* pNewMail); /* Mail nur hinzufügen, wenn noch nicht in System ( bei message-ID)*/

private:
    QList<CMail*>*    m_pMailList;
};

#endif // CMAILLISTMODEL_H

cmaillistmodel.cpp

/* Modell für Darstellung und Abbildung der Liste aller geladenen / im Projekt enthaltenen Mails */

#include "cmaillistmodel.h"

CMailListModel::CMailListModel()
{
    /* Neue Mailliste erstellen */
    this->m_pMailList = new QList<CMail*>;
}

/* Destruktor */
CMailListModel::~CMailListModel()
{
   /* Delete list with CMail-Objects */
    for(int i=0; i<m_pMailList->count(); i++)
    {
        qDebug() << "Removing mail " << m_pMailList->at(i)->subject();
        delete m_pMailList->at(i);
    }
    qDebug() << "All mails removed.";
}

/* Anzahl der Reihen / Spalten abfragen */
int CMailListModel::rowCount(const QModelIndex &parent) const
{
    return this->m_pMailList->count();
}
int CMailListModel::columnCount(const QModelIndex &parent) const
{
    return MAIL_LIST_TABLE_NUM_COLUMNS;
}

/* Header abfragen */
QVariant CMailListModel::headerData(int section, Qt::Orientation orientation, int role) const
{
    if(role!=Qt::DisplayRole)
        return QVariant();

    if(orientation==Qt::Horizontal)
    {
        switch(section)
        {
            case 0:
                return tr("#");
            case 1:
                return tr("Zeitstempel");
            case 2:
                return tr("Betreff");
            case 3:
                return tr("Absender");
            case 4:
                return tr("Message-ID");
            case 5:
                return tr("Dep. Level");
            default:
                return {};
        }
    }
}

/* Daten abfragen */
QVariant CMailListModel::data(const QModelIndex &index, int role) const
{
    if(role != Qt::DisplayRole && role!=Qt::EditRole)
        return {};

    CMail* pMail = this->m_pMailList->at(index.row());

    switch(index.column())
    {
        case 0:
            return QString("%1").arg(index.row());
        case 1:
            return QString(pMail->emailDateStr());
        case 2:
            return QString(pMail->subject());
        case 3:
            return QString(pMail->ck_from());
        case 4:
            return QString(pMail->getHeaderField("Message-ID"));
        case 5:
            return QString("%1").arg(pMail->calculateDependencyLevelBySubject());
        default:
            return {};
    }
}

/* Neue E-Mail- anhängen */
void CMailListModel::appendMail(CMail *pNewMail)
{
    if(pNewMail!=NULL)
    {
        beginInsertRows({}, m_pMailList->count(), m_pMailList->count());
        this->m_pMailList->append(pNewMail);
        qDebug() << "Appending mail " << pNewMail->subject();
        endInsertRows();
    }
}

/* Neue Mail anhängen, wenn Sie noch nicht im System ist (Abgleich der Message-ID) */
void CMailListModel::appendMailOnce(CMail *pNewMail)
{
    if(pNewMail!=NULL)
    {
        bool bMailExists=false;
        for(int i=0;i<m_pMailList->count(); i++)
        {
            QString strNewMessageID, strCurrentMessageID;
            strNewMessageID = QString(pNewMail->getHeaderField("Message-ID"));
            strCurrentMessageID = QString(m_pMailList->at(i)->getHeaderField("Message-ID"));

            if(strNewMessageID==strCurrentMessageID)
            {
                bMailExists=true;
                break;
            }
        }
        if(!bMailExists)
        {
            this->appendMail(pNewMail);
        }
    }
}

CMail-Class is derived from CkEmail (here are the references like here:

class CMail : public CkEmail
{
public:
    /* Konstruktor */
    CMail();
};

The instance i use for processing the loaded mail-data is a member of my CMainWindow-Class. I set the model after creating the UI:

CMainWindow::CMainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::CMainWindow)
{
    /* Datenmodelle erzeugen */
    this->m_pMailListModel = new CMailListModel();

    ui->setupUi(this);

    /* Datenmodelle an Steuerelemente binden */
    ui->tblMailListView->setModel(this->m_pMailListModel);
}

And this is how it is destructed, but like i can see in my debug-output, if i quit the application, the CMainWindow-destructor is not called, the SIGSEGV occures before this.

CMainWindow::~CMainWindow()
{
    qDebug() << "Delete Mail-List-Model...";
    delete m_pMailListModel;
    qDebug() << "Mail-List-Model deleted.";

    qDebug() << "Delete UI...";
    delete ui;
    qDebug() << "UI deleted.";
}

I hope you have any idea how i can solve this problem.

[VRonin]

I get a Segmentation fault in "qvariant_p.h", line 173

Post the stack trace please

QList<CMail*>* m_pMailList;

You are leaking that variable, just allocate the list on the stack

~CMailListModel()

just use qDeleteAll

CMailListModel::rowCount / CMailListModel::columnCount

They should return 0; if parent.isValid() otherwise it's an infinitely deep tree

CMailListModel::data

Passing an invalid index causes segfault

CMailListModel::appendMail

Takes ownership of the object, are you sure you are not deleting it from the calling method?

[BUWNik94]

Thank you for the quick answer. I suggest, that the last thing you mentioned is where the failure occures, i will try to solve this (this is the point i notice that my last programming exercise is a few years ago).
The other point i have fixed also, thank you for this.