[kmonsen]

I think, as a generalization, most communication between languages goes through C. For example Rust or Switft to C++ would go Rust -> C -> C++. Or Switft -> C -> Rust as examples. I think Swift is trying to make C++ bindings, but in general most languages can talk to/from C.

Of course there are other mechanisms, but for direct bindings I think C bindings are by far the most common.

[nly]

Actually for Swift <-> C++ you tend to go via Objective C++, which as easy as renaming your .cpp file to .mm, and calling in to Swift via a bridging header