Hi there!
After porting our applications from Qt 5.4.2 to 5.5.0, I have strange crashes concerning icons coming from the QFileIconProvider set in QComboBoxes. Luckyli for me I can reproduce the crashes with your 'basicdrawing'-example, where I put two icons into the first two entries of the shapeComboBox, just changing the following lines of window.cpp:

//! [1]
Window::Window()
{
    QFileIconProvider provider;
    QIcon icon(provider.icon(QFileInfo("c:/Users/Harro Pahl/Pictures")));
    QIcon icon2(provider.icon(QFileInfo("c:/")));

    renderArea = new RenderArea;

    shapeComboBox = new QComboBox;
    shapeComboBox->addItem(icon, tr("Polygon"), RenderArea::Polygon);
    shapeComboBox->addItem(icon2, tr("Rectangle"), RenderArea::Rect);

This leads immediately to a crash when painting the combobox via QComboBox::paintEvent (the stack and variables are added as jpg to this ticket).

Thanks for your investigations in advance and greetings from Kiel!
Harro Pahl