Question

The following code will crash, I found it was related to “new []”

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


    QPushButton *buttons = new QPushButton[5];
    for(int i=0;i<5;++i){
        buttons[i].setGeometry(0,0,30,40);
        buttons[i].setParent(this);
    }

}

after change new[] to normal array, it works fine

#mainwindow.h
QPushButton buttons[5];

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


    for(int i=0;i<5;++i){
        buttons[i].setGeometry(0,0,30,40);
        buttons[i].setParent(this);
    }

}

any ideas? thanks

Answer 1

I’m no Qt expert, but as far as I can tell, a QObject assumes ownership of all its child objects (it deletes them in the destructor).

If that is the case, you’re not supposed to do any of those things you’re doing – every QPushButton should be allocated dynamically and individually using new, and the fact that your second example doesn’t crash is what’s weird.