Pre-PEP: Rust for CPython

[emmatyping (Emma Smith)]

@rtpg

I think the argument to use Rust for CPython here would be much stronger if we could see standard_b64encode implemented in a way that takes advantage of Rust’s RAII to reduce the book-keeping we have to do in the C code right now.

Without a “Rust API” here for writing these extensions, this becomes purely a security argument (that I find fairly unconvincing at some level). If standard_b64encode was returning a Result and we were able to use ? and all this other stuff with a wrapper that did “the right thing” that would be, at least to me, much more interesting

One example of reducing mental bookkeeping is the BorrowedBuffer abstraction in the implementation cpython/Modules/_base64/src/lib.rs at c9deee600d60509c5da6ef538a9b530f7ba12e05 · emmatyping/cpython · GitHub. As mentioned previously, the current example is pretty bare-bones as it is a proof of concept. There is a large room for improvement in ergonomics. But even with raw FFI bindings, it’s possible to have a safe, idiomatic Rust core of an extension module then expose that via unsafe wrappers. And I think even that will improve the safety and utility of writing extensions in CPython.