The benefits of Rust's (wonderful) model around references and lifetimes come at a significant cost to ergonomics when having to go into the Mordor of some C library and back. I usually find myself wishing I could have some macro where I just write in C and have it exposed as an unsafe back in Rust. I know I can do this by just writing a C dylib and integrating that, but now I've got two problems.
Even still, I prefer writing unsafe Rust to writing C. std::mem::ptr forces me to ask the right questions and reminds me of just how easy it is to fall into UB in C as well.