In contrast to what the C to Rust migration book is recommending (using FFI to integrate Rust with C), I've found it much easier to start from scratch. I recently finished a project where I rewrote Postgres in Rust[1]. For context, Postgres is about one million lines of C code.
On one attempt, I tried using c2rust to convert Postgres into unsafe Rust code. That attempt succeeded in terms of getting working "Rust" code, but any attempt to change any piece to safe rust, would require thousands of changes across codebase. Even though I had working Rust code, I found it infeasible to get to working idiomatic Rust code.
Instead what I found to be more effective was starting a new codebase and rewrite each file from the Postgres codebase into Rust one at a time. This allowed me to guarantee that at all times the new codebase was idiomatic and simultaneously I could make one pass over the Postgres codebase to get working idiomatic Rust.
YMMV, but I found it way easier to generate a whole new codebase from scratch rather than incrementally rewrite an existing codebase.
Starting from scratch also implies one major release where suddenly it's all Rust (so very risky). In contrast, we found that it's a much smoother transition for end-users and maintainers when we approach large codebases progressively, module by module, while the C engineers continue working on the C code and learn Rust in parallel.
Of course, each migration is different but I wanted to clarify with our field experience.
Coming from C I don’t think you’ll find Rust too foreign, once you internalize how the ownership rules work. In my experience the formal rules of Rust overlap a lot with behaviors that are good practice in C/C++ anyway, but there are some complicated concepts that you need to wrap your head around before expressing them in Rust becomes second nature.
Whether it would suit you, depends if you can learn to like Rust's approach of moving more work to the type system. In Rust you do certain things the Rust's way, period. Programmers used to C being unopinionated about everything find that objectionable.
Sounds right up my alley. Thanks to you (and other siblings) for the thoughtful replies.
Depends on platform for embedded. It not very pleasant to write rust if you have to think about binary size. For systems code - sure, use rust.
and cheadergen, Mainmatter's tool for the reverse direction