[kbenson]

Isn't Swift compiled? I'm not sure it's relevant to the specific problems faced here, unless a library written and compiled in earlier versions of Swift won't be usable in a Swift 4 project.

[ori_b]

That's the case. Swift is currently not abi compatible, so libraries compiled with one Swift version only work with that version.

[kbenson]

Ah, I see. I assume you could compile to a C compatible library, but they you would have to deal with marshaling costs where the types mismatch, correct?