private void assignVirtualBaseOffsets() throws PdbException {
		for (VirtualLayoutBaseClass base : virtualLayoutBaseClasses) {
			CppCompositeType cppBaseType = base.getBaseClassType();
			Long baseOffset = mainVbt.getBaseOffset(base.getOffetFromVbt());
			if (baseOffset == null) {
				throw new PdbException("Cannot place base class");
			}
			baseOffset += base.getBasePointerOffset();
			ClassID baseId = cppBaseType.getClassId();
			baseOffsetById.put(baseId, baseOffset);
		}
	}
Uses the main virtual base table to assign offsets for the virtual bases
@throws PdbException if a virtual base offset cannot be identified
Ghidra/Features/PDB/src/main/java/ghidra/app/util/pdb/pdbapplicator/CppCompositeType.java