alt Hacker News> C++ actually did end up evolving the ability to define a zero-sized class without a unique memory address
Did it? Are you talking about the no_unique_address attribute (I had to go look that up because WG21 apparently doesn't care about consistently using or not using separators in attribute names) ? That attribute lets you do the same trick as empty base class but without the ceremony, however it doesn't let you make ZSTs.
Yes, that's what I'm talking about. It does expand on the empty base object optimization, though it is still not fully generic.
But you can now have multiple zero-sized types as siblings in a struct or class that can be zero-sized, the restriction is that they do have to be different types.