The following warning exists in collection.h:
E:\workspace\mongo\src\mongo/db/catalog/collection.h(726): warning C4373: 'mongo::Collection::aboutToDeleteCapped': virtual function overrides 'mongo::CappedCallback::aboutToDeleteCapped', previous versions of the compiler did not override when parameters only differed by const/vol atile qualifiers E:\workspace\mongo\src\mongo/db/storage/capped_callback.h(53): note: see declaration of 'mongo::CappedCallback::aboutToDeleteCapped'
I believe it is not necessary to have aboutToDeleteCapped in the Collection class.