private void addPlaceholderVirtualBaseTableEntry(PlaceholderVirtualBaseTable ptable,
			MsVxtManager vxtManager, VirtualLayoutBaseClass base, long baseOffset) {
		long basePtrOffset = base.getBasePointerOffset();
		if (ptable.getPtrOffsetInClass() != basePtrOffset) {
			// error
			return;
		}
		PlaceholderVirtualBaseTableEntry e = ptable.getEntry(base.getOffetFromVbt());
		if (e != null) {
			e.setOffset(baseOffset);
			return;
		}
		ClassID baseId = base.getBaseClassType().getClassId();
		ptable.setBaseClassOffsetAndId(base.getOffetFromVbt(), baseOffset, baseId);
	}
Provides the Virtual Base Table to be used for placing virtual bases of this class
@throws PdbException upon unrecognized vbt type
Ghidra/Features/PDB/src/main/java/ghidra/app/util/pdb/pdbapplicator/CppCompositeType.java