Other C++ features

You can make Rust subclasses of C++ classes - as these are mostly used to implement the Observer pattern, they're documented under calls from C++ to Rust.

Exceptions

Exceptions are not supported. If your C++ code is compiled with exceptions, you can expect serious runtime explosions. The underlying cxx crate has exception support, so it would be possible to add them.

Preprocessor symbols

#define and other preprocessor symbols will appear as constants. At present there is no way to do compile-time disablement of code (equivalent of #ifdef)¹.

String constants

Whether from a preprocessor symbol or from a C++ char* constant, strings appear as [u8] with a null terminator. To get a Rust string, do this:

#define BOB "Hello"

# mod ffi { pub static BOB: [u8; 6] = [72u8, 101u8, 108u8, 108u8, 111u8, 0u8]; }
assert_eq!(std::str::from_utf8(&ffi::BOB).unwrap().trim_end_matches(char::from(0)), "Hello");