If you are using the main C++ distribution of wxWidgets, Feel free to ask any question related to wxWidgets development here. This means questions regarding to C++ and wxWidgets, not compile problems.
Make sure RenderCanvasLink is a valid pointer. It's possible Size events are sent before the window becomes initially visible, if you're not creating your RenderCanvasLink object before then, you'll be trying to dereference a bad pointer.
To confirm, you can try zeroing the pointer during RenderFrm's ctor and only dereference it if it's nonzero: