Using Rust for kernel development

Posted Sep 28, 2021 12:41 UTC (Tue) by alonz (subscriber, #815)
In reply to: Using Rust for kernel development by jgg
Parent article: Using Rust for kernel development

Upgrading C to C++ (and C++03 to C++11) is somewhat of a joke; the language is generally 99.9% identical, and the only "conversion" required is often just to replace identifiers which conflict with keywords in the other language with something else. (And even then, in some such "uplifted" codebases I have seen, the resulting identifiers were jarring and clearly not what a human programmer would choose to use.)

Conversion between languages with larger semantic differences - such as the case with Rust - would indeed be a feat worthy of a Nobel-prize-equivalent. And that's even before you try to care about readability of the resulting code. (I had myself written two such "transpilers" in my career; both were very special-purpose, targeting very limited code-bases, and both produced code that was nearly impossible to maintain.)

Using Rust for kernel development

Posted Sep 28, 2021 13:41 UTC (Tue) by jgg (subscriber, #55211) [Link]

Just making C compile in a C++ compiler is not at all what I mean by upgrade. Proper C++11 code looks and operates very differently from C code. Human led, machine assisted incremental improvement is required to get from C to C++11 stuff. This is things like converting to use unique_ptr/smart_ptr, changing open coded containers into STL stuff, relying on the language to do cleanup, using move semantics, references, etc/etc. This is where the code becomes safer and more understandable.

My point is there is a proven path from C code to high quality C++11 code that is incremental and auditable (and a wack of human work). It starts with a lightweight 'transpile' to get C code into the C++ compiler in the first place, and no, it doesn't completely destroy the readability of the code base.

To my mind this should be the gold standard. This approach to add Rust parallel to C without any sane migration path is not. The fact that C to Rust, to even get started on the human-led incremental improvement, is basically impossible is not inherent. It comes from the deliberate design of Rust.

Despite Al's virtrol, I think there is merit in exploring what an ideal language upgrade for the kernel would be like - at least we can understand how far away this Rust proposal is.