C++ Interop Example

[ADKaster]

I took a crack at trying to create an example project for including a Swift library as a dependency to an existing C++ Zephyr project. Well by "existing" I mean, the app main is a C++ file, not that I have an existing Zephyr project to integrate with.

That example lives here: https://github.com/ADKaster/swift-embedded-export-zephyr

I based it off of some of the examples in this repository for Zephyr.

It's possible that "Zephyr + C++" is too tricky of a target to create this interop example for embedded from. But I doubt that this is a problem unique to me.

Would an example in a different operating environment be a good fit for this repo?

[rauhul]

Yeah this would be a good thing to include in an example attached to the integrate with zephyr guide in #140

[xtremekforever]

This seems interesting, @ADKaster do you want a crack at adding the example to the document or shall I have a look later?

[ADKaster]

@xtremekforever if my example worked, I wouldn't mind taking a crack at cleaning it up for use in your examples here. However, it doesn't quite build and I don't know enough about zephyr to fix all the compile errors I was seeing that are unrelated to Swift. They were mostly related to trying to use C++ in zephyr. Perhaps a non-zephyr example would be easier to handle?

I will note that the CMake files in my example repo are modified versions of what @etcwilde maintains at https://github.com/apple/swift-cmake-examples/tree/main/3_bidirectional_cxx_interop.

[ADKaster]

Also iirc I filed swiftlang/swift#80570 while playing with this example. Evan's CMake scripts attempt to extract information about target-specific include dirs and lib dirs from swiftc -print-target-info. But this completely falls over when using -enable-experimental-feature Embedded.

Relevant script lines:
https://github.com/ADKaster/swift-embedded-export-zephyr/blob/main/cmake/InitializeSwift.cmake#L39

[xtremekforever]

Oh okay, I thought the example was something that was already working. I could see a simple C++ interop example with embedded Swift could be more useful