-Wabi is misdesigned (answers the wrong question)

[Joe Buck]

I think that -Wabi as currently implemented is useless.

The picture I had in mind when we first talked about it was this:
if -Wabi is on, we would compute the layout of a class using the
3.2 algorithm and the ABI-compliant (modulo unknown bugs) algorithm,
and object iff there is a difference.

However, -Wabi as implemented doesn't do that: it objects to any
usage that potentially *might* tweak an algorithm difference.