I just tried it recently, worked well enough, including support for std vector, string etc. You can loop over std vector items using a standard Swift loop, for example. It´s clear Apple needs and uses this internally too.

Not sure about Arduino specific code, but including C/C++ is fairly easy. See Swift Embedded Examples [1] (check Sources/Support)

[1]: https://github.com/apple/swift-embedded-examples/tree/main/p...

they even show this in the video, apparently it’s supposed to be straightforward