C++ Error Handling

1. #[cxx::bridge]
2. mod ffi {
3. unsafe extern "C++" {
4. include!("example/include/example.h");
5. fn fallible(depth: usize) -> Result<String>;
6. }
7. }

9. fn main() {
10. if let Err(err) = ffi::fallible(99) {
11. eprintln!("Error: {}", err);
12. process::exit(1);
13. }
14. }

• C++ functions declared to return a Result will catch any thrown exception on the C++ side and return it as an Err value to the calling Rust function.
• If an exception is thrown from an extern “C++” function that is not declared by the CXX bridge to return Result, the program calls C++’s std::terminate. The behavior is equivalent to the same exception being thrown through a noexcept C++ function.