What is the lifespan of the captured stack allocated variables in lambda functions used as slots?

I need help understanding the way lambda functions work in order to prevent memory leaks when using them. More specifically, I would like to know when foo will be destroyed in the following case:

void MainWindow::onButtonClicked()
{
    QTimer *t(new QTimer(this));
    bool foo = false;

    t->setSingleShot(true);
    t->setInterval(1000);
    t->start();

    connect(t, &QTimer::timeout, [=](){
        delete t;
        qDebug() << foo;
    });
}

What about the case when [&] is used?