Inconsistent and unintended behavior of different ordering tags

After creating a grid function space, I usually print out the number of degrees of freedom associated with the space. If the space is a non-leaf space, e.g. a composite grid function space, I also print out the number of degrees of freedom of its children since I consider this an interesting information; in particular for multi domain simulations.

While adapting my code to PDELab 2.0 and its new ordering mechanism, I stumbled upon two problems:

1. The size of child spaces does not seem to be available when using a composite grid function space together with the EntityBlockedOrderingTag (calling child_gfs.size() results in a GridFunctionSpaceHierarchyError: "Size cannot be calculated at this point in the GFS tree), while it is available for the LexicographicOrderingTag.
2. When using a composite grid function space together with the EntityBlockedOrderingTag, composite_gfs.ordering() yields an instance of GridViewOrdering which inherits from OrderingBase. Since OrderingBase provides methods like

     typename Traits::SizeType size(const typename Traits::SizeType child_index) const

   GridViewOrdering provides those methods as well. But OrderingBase implements its own update() method which overrides the update method from OrderingBase. Some inherited class members which are required by inherited methods (like the size method mentioned above) are thus left in an uninitialized state, yielding undefined behavior. For example, calling

     composite_gfs.ordering().size(child_index)

   results in a segfault. The method accesses the elements of the uninitialized inherited class member OrderingBase::_child_size_offsets which is an empty std::vector.

I would try to deal with the issue myself, but I would have to understand the code of the new ordering mechanism first. Trying to do so unfortunately turned out to be a little hard without having a reasonably detailed description of the mechanism and the ideas of its implementation at hand.