Why does setSubSymbol causes QGIS to crash?

Question

I am having problems creating a multilayer line symbol with this code :

symbol = QgsLineSymbolV2.createSimple({})
symbol.deleteSymbolLayer(0)

symbolLine = QgsSimpleLineSymbolLayerV2()
symbol.appendSymbolLayer(symbolLine)

symbolArrow = QgsMarkerSymbolV2.createSimple({})
symbolArrow.deleteSymbolLayer(0)

symbolArrowLayer = QgsSimpleMarkerSymbolLayerV2()
symbolArrow.appendSymbolLayer(symbolArrowLayer)

symbolLineArrow = QgsMarkerLineSymbolLayerV2()
symbolLineArrow.setSubSymbol(symbolArrow) # Causes crash !!!

symbol.appendSymbolLayer(symbolLineArrow)

Is there something wrong in this code ? Has anybody already had this issue ?

Answer 1

Looks like you hit a bug in QGIS. I've fixed it now, and the fix will be included in the next point releases.

In the meantime, you can work around it by making symbolArrow a global variable, so that it will not be garbage collected by python.