Add a new row to QTableWidget with initialized cells cause to segmentation fault

[SIFE]

I have this slot:

void MainWindow::addRow()
{
    int rows = ui->tableWidget->rowCount();
    ui->tableWidget->insertRow(rows);
    QTableWidgetItem *item;
    item = new QTableWidgetItem;
    item->setText(QString::number(0, 'f', 2));
    ui->tableWidget->setItem(rows - 1, 1, item);
    item = new QTableWidgetItem;
    item->setText(QString::number(0, 'f', 2));
    ui->tableWidget->setItem(rows - 1, 2, item);
}

void MainWindow::addRow()
{
    int rows = ui->tableWidget->rowCount();
    ui->tableWidget->insertRow(rows);
    QTableWidgetItem *item;
    item = new QTableWidgetItem;
    item->setText(QString::number(0, 'f', 2));
    ui->tableWidget->setItem(rows - 1, 1, item);
    item = new QTableWidgetItem;
    item->setText(QString::number(0, 'f', 2));
    ui->tableWidget->setItem(rows - 1, 2, item);
}

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When I add a new row, I get a segmentation fault, why?

[Lykurg]

ui->tableWidget->setItem(rows - 1, 1, item);
// [..]
ui->tableWidget->setItem(rows - 1, 2, item);

ui->tableWidget->setItem(rows - 1, 1, item);
// [..]
ui->tableWidget->setItem(rows - 1, 2, item);

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Musn't that be

ui->tableWidget->setItem(rows - 1, 0, item);
// [..]
ui->tableWidget->setItem(rows - 1, 1, item);

ui->tableWidget->setItem(rows - 1, 0, item);
// [..]
ui->tableWidget->setItem(rows - 1, 1, item);

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And use a debugger to see where exactly the application crashes.

[SIFE]

I tried this:

item = new QTableWidgetItem;
    item->setText(QString::number(0, 'f', 2));
    ui->tableWidget->setItem(rows, 0, item);
    /*item = new QTableWidgetItem;
    item->setText(QString::number(0, 'f', 2));
    ui->tableWidget->setItem(rows, 1, item);*/

item = new QTableWidgetItem;
    item->setText(QString::number(0, 'f', 2));
    ui->tableWidget->setItem(rows, 0, item);
    /*item = new QTableWidgetItem;
    item->setText(QString::number(0, 'f', 2));
    ui->tableWidget->setItem(rows, 1, item);*/

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This make first column initialized, but I need only the second and third columns to be initialized.

And use a debugger to see where exactly the application crashes.

Debugger didn't work with me in FreeBSD.

[Lykurg]

And you are using

ui->tableWidget->setItem(rows, 0, item);

ui->tableWidget->setItem(rows, 0, item);

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or

ui->tableWidget->setItem(rows-1, 0, item);

ui->tableWidget->setItem(rows-1, 0, item);

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? And if you don't use a debugger, what makes you sure this slot is causing the trouble? Comment all out and add it one by one to see where the crash happens.

[SIFE]

It 's appear like another slot cause the problem:

//connected signals
    connect(ui->tableWidget, SIGNAL(cellChanged(int,int)), this, SLOT(calc(int,int)));
 
 
void MainWindow::calc(int x,int y)
{
    if (y == 1)
    {
        float ttl = ui->tableWidget->item(x, y)->data(0).toFloat() * ui->tableWidget->item(x, 2)->data(0).toFloat();
        QTableWidgetItem *item = new QTableWidgetItem;
        item->setText(QString::number(ttl, 'f', 2));
        ui->tableWidget->setItem(x, 3, item);
        ttl = 0;
        int rows = ui->tableWidget->rowCount();
        for (int i = 0; i < rows; ++i)
        {
            ttl += ui->tableWidget->item(i, 3)->data(0).toFloat();
        }
 
        ui->totaleEdit->setText(QString::number(ttl, 'r', 2));
    }
    else if (y == 2)
    {
        float ttl = ui->tableWidget->item(x, y)->data(0).toFloat() * ui->tableWidget->item(x, 1)->data(0).toFloat();
        QTableWidgetItem *item = new QTableWidgetItem;
        item->setText(QString::number(ttl, 'f', 2));
        ui->tableWidget->setItem(x, 3, item);
        ttl = 0;
        int rows = ui->tableWidget->rowCount();
        for (int i = 0; i < rows; ++i)
        {
            ttl += ui->tableWidget->item(i, 3)->data(0).toFloat();
        }
 
        ui->totaleEdit->setText(QString::number(ttl, 'r', 2));
    }
}

//connected signals
    connect(ui->tableWidget, SIGNAL(cellChanged(int,int)), this, SLOT(calc(int,int)));


void MainWindow::calc(int x,int y)
{
    if (y == 1)
    {
        float ttl = ui->tableWidget->item(x, y)->data(0).toFloat() * ui->tableWidget->item(x, 2)->data(0).toFloat();
        QTableWidgetItem *item = new QTableWidgetItem;
        item->setText(QString::number(ttl, 'f', 2));
        ui->tableWidget->setItem(x, 3, item);
        ttl = 0;
        int rows = ui->tableWidget->rowCount();
        for (int i = 0; i < rows; ++i)
        {
            ttl += ui->tableWidget->item(i, 3)->data(0).toFloat();
        }

        ui->totaleEdit->setText(QString::number(ttl, 'r', 2));
    }
    else if (y == 2)
    {
        float ttl = ui->tableWidget->item(x, y)->data(0).toFloat() * ui->tableWidget->item(x, 1)->data(0).toFloat();
        QTableWidgetItem *item = new QTableWidgetItem;
        item->setText(QString::number(ttl, 'f', 2));
        ui->tableWidget->setItem(x, 3, item);
        ttl = 0;
        int rows = ui->tableWidget->rowCount();
        for (int i = 0; i < rows; ++i)
        {
            ttl += ui->tableWidget->item(i, 3)->data(0).toFloat();
        }

        ui->totaleEdit->setText(QString::number(ttl, 'r', 2));
    }
}

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So, I cheated with this condition:

if (y == 1 && ui->tableWidget->item(x, y)->data(0).toString() == "")

if (y == 1 && ui->tableWidget->item(x, y)->data(0).toString() == "")

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[Lykurg]

That's why a debugger is a good choice! Your code look also hard to maintain... and

ttl = 0;
int rows = ui->tableWidget->rowCount();
for (int i = 0; i < rows; ++i)
{
ttl += ui->tableWidget->item(i, 3)->data(0).toFloat();
}
 
ui->totaleEdit->setText(QString::number(ttl, 'r', 2));

ttl = 0;
int rows = ui->tableWidget->rowCount();
for (int i = 0; i < rows; ++i)
{
ttl += ui->tableWidget->item(i, 3)->data(0).toFloat();
}
 
ui->totaleEdit->setText(QString::number(ttl, 'r', 2));

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is madness for large tables. Better store the old value of (x,3) and calc the difference and only add/substract that from ui->totaleEdit.