Tobias Hunger Software Engineer at SixtyFPS GmbH Rust was designed to interoperate with other languages, but this interoperability is primarily based on C data structures and functions. This is limiting for C++ applications, because instances of C++ classes do not have a standardized representation in C. How can we expose Rust interfaces to C++ and the other way around? At Slint we develop a UI toolkit in and for Rust. We also provide quality C++ bindings and integrate with existing C++ libraries. We do have to deal with interoperability issues on a regular basis. In this presentation we are going to review the crates we use to achieve interoperability, as well as the tricks we learned using C++ libraries and how we expose a modern C++ API to our Rust code, including a first-class CMake integration.