QTableManager Removing All Rows Crashes Application with Bad Access



  • I have a QTableWidget that I drew in QT Creator, as well as added rows there. I tried using the following techniques...

    http://stackoverflow.com/questions/15848086/how-to-delete-all-rows-from-qtablewidget

    ...but the application crashes with a bad access after it removes all the rows.

    However, if I leave one row behind, it doesn't crash. For instance:

    ui->myTable->model()->removeRows(0,ui->myTable->rowCount()-1);
    // leaves a row, but doesn't crash; remove -1 and it removes all rows and crashes
    

    ...and...

    for (int i = 0; i<= ui->myTable->rowCount(); i++) {
        ui->myTable->removeRow(0);
    }
    // leaves a row, but doesn't crash; set i = -1 and it removes all rows and crashes
    

    Did I stumble upon a huge showstopper bug in Qt 5.5?

    EDIT: Hang on...may be because later on in the code I'm trying to select a row that no longer exists....



  • @maximo
    Hello.
    I rapidly draw an application designing a QTableView with QDesigner adding 2 rows and a PushButton with the following code
    void MainWindow::on_pushButton_clicked()
    {
    ui->tableWidget->model()->removeRows(0,ui->tableWidget->rowCount());
    }

    I have no crash.

    In fact you use to remove the model rows with the rowCount of the Table. Perhaps you may try to use ui->myTable->model()->removeRows(0,ui->myTable->model()->rowCount()); to be coherent.

    But is the model of your QTableWidget or your QTableWidget itself connected to another QObjet?



  • @Olivier-Ronat Thanks for checking, Olivier. Sorry to detain you to do that when I found it was my own fault. However, I learned some things and got a little better at debugging in Qt Creator.

    I found the cause. I had a signal attached to the selectionModel of each row. Here's how I found out (note, I'm a newbie). On my Mac, I got the crash report and clicked a button to see what it was. This showed a callstack. I was able to see that it was complaining about setting text() from on_SelRow, and then I recalled that I had a signal connected on rows. So, I changed my code like so:

    ui->myTable->selectionModel()->disconnect();
    ui->myTable->model()->removeRows(0,ui->myTable->rowCount());
    

    I was then able to remove rows without a crash. I just need to remember to add the signal back to the table when I add rows again.

    P.S.

    You may also be wondering why I was intercepting a selected row. The reason was because then I could show a box above the table that showed the item detail in an easier to read format than having to scroll horizontally in the table to see all the columns. I was doing it like so:

    connect(ui->myTable->selectionModel(), SIGNAL(currentRowChanged(QModelIndex,QModelIndex)),
                    this, SLOT(on_SelRow(QModelIndex,QModelIndex)));
    

    ...and then I had a class method like so:

    void MainWindow::on_SelRow(QModelIndex oCurrRow, QModelIndex oPrevRow)
    {
        QTableWidget *t = dynamic_cast<QTableWidget *>(QObject::sender()->parent());
        int y = oCurrRow.row();
       // do something with t (table) and y (row index) variables
    }
    


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