[swift-evolution] ABI in Layman's terms?

[Jonathan Hull]

Could someone explain in simple terms what the ABI is and what sorts of things might affect it?

I had thought it was the layout in memory of structs/classes/etc… and how the program knows where to go to find a particular field.  This seems to be incorrect though, as I have seen many features that I would assume have some affect on this layout ruled “out of scope for phase 1”.  For example, I would think that many generics features would have an impact on the ABI, or the idea of COW (via secret boxing) for structs, or even union types.

At the very least, I would think that mix-ins would have a fairly significant effect.

I am obviously missing something here, and I want to provide constructive effort to the community (as opposed to distracting from the task at hand), so I would appreciate some clarification/guidance...

Thanks,
Jon