Please consider adding an overload to ::PrintSelf()
which defaults to one of the standard output streams and does not require an ostream reference. As far as I can tell [1, 2], the current signature
PrintSelf (std::ostream &os, Indent indent) const
cannot be called from a debugger because it is not possible to get a reference to any std ostream (at least not in lldb, which is de facto the only debugger these days on macOS). In some situations, the debugger’s pretty-printer is not sufficient (or sometimes broken due to failed lookup of elided symbols).
If this is acceptable, I could make the appropriate MR.