Both are great tech but solve the problem of safety differently. I would say Fil-c is great for non-performance-critical (think like somewhere between c and go/java, still very fast) existing C programs where compatibility with the existing program / security is a big concern. think ffmpeg, nginx, sudo.

Fil-c:

- You have a great existing c program that may have memory bugs, and you wanna make it safer.

- Or you wanna write a new program in c, and be extra sure it's safe and don't mind a little performance penalty.

- Or you wanna find subtle memory bugs by building your c program with fil-c (asan style) and disable it for performance in your release build.

Rust is great when you want to build a new codebase from scratch, and have the time and patience to deal with the borrow checker. It also gives you some thread safety, (which is different from memory safety) at the development time cost of dealing with the borrow checker. Rust:

- A new codebase where you need multithreading and safety, and want excellent performance

- You need a broad ecosystem of existing packages

- Your problem space benefits from a robust type system.

FYI nginx and Apache and Postgres using shared memory across processes make them hard to use with Fil-C. Lighttpd works well though!