I'm not sure you need to? Rust references don't exist in C, after all. That being said I wouldn't be surprised if there were other factors that would weigh aga

I'm not sure you need to? Rust references don't exist in C, after all. That being said I wouldn't be surprised if there were other factors that would weigh against considering FFI calls to Fil-C safe by default (e.g., Fil-C's somewhat looser bounds on what is considered a valid pointer access).