[Bug libstdc++/61519] Seemingly incorrect vtable reference when libstdc++ built with RTTI

[matthew at theiselins dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61519

--- Comment #2 from Matthew Iselin <matthew at theiselins dot net> ---
Where would I start in identifying what about the target is causing the issue?

The best I can come up with is an issue with the vtable prefix and/or the math
to determine the deepest object, but can't (yet) see how the target would
affect that.