abi::__base_class_info's public_mask

[Jeffrey D. Oldham]

\S 2.9.5.6.c of the C++ ABI for IA-64 specifies that
abi::__base_class_info has a __public_mask enumeration constant
implying that __vmi_class_type_info has entries for non-public direct
base classes.  Are these non-public base classes included just for
completeness or are they necessary to implement dynamic_cast or some
other algorithm?

Am I correct in assuming that the \S 2.9.7 dynamic cast algorithm only
looks at public base classes?

Thanks for the information,
Jeffrey D. Oldham
oldham at codesourcery.com