mrustc VS gccrs

No, you don't. Existential proof: mrustc ignores lifetimes. Just flat out simply ignores. It changes some corner-cases related to HRBT, yet rustc compiled by mrustc works (that's BTW mrustc exist: to bootsrap the rustc compiler).

Incidentally C++ is the only way to bootstrap rust without rust today.

https://github.com/thepowersgang/mrustc

Well, there is mrustc[0], a Rust compiler that doesn't include a borrow-checker, so it's possible to compile (at least some versions of) Rust without a borrow checker, though it might not result in the most optimized code.

AFAIK there are some optimization like the infamous `noalias` optimization (which took several tries to get turned on[1]) that uses information established during borrow checking.

I'm also not sure what the relation with NLL (non-lexical lifetimes) is, where I would assume you would need at least a primitive borrow-checker to establish some information that the backend might be interested in. Then again, mrustc compiles Rust versions that have NLL features without a borrow-checker, so it's again probably more on the optimization side than being essential.

[0]: https://github.com/thepowersgang/mrustc

[1]: https://stackoverflow.com/a/57259339

> Maybe another memory safe language, but Rust has severe bootstrapping issues which is a hard sell for distros that care about source to binary transparency.

It is possible to bootstrap rustc from just GCC relatively easily, although it's a little bit time consuming.

You can use mrustc to bootstrap Rust 1.54: https://github.com/thepowersgang/mrustc

And from then you can go through each version all the way to the current 1.72. (Each new Rust version officially needs the previous one to compile.)

Have you tried this route : https://github.com/thepowersgang/mrustc ?

Mrustc supports Rust 1.54.0 today

There are three. The official one, mrustc (no borrow checker, but can essentially compile the official rustc) and GCC (can't really compile anything substantial yet). Only rustc is production-ready though.

That probably depends on what you mean by problematic. Having an ever increasing chain of dependencies isn’t the most desirable situation so there has been some work to trim the bootstrap chain. In 2018, when the blogpost I linked above was written, mrustc was used to bootstrap rust 1.19.0; now mrustc can bootstrap rust 1.54.0 so the chain to recent versions is much shorter than if all those intervening versions back through 1.19.0 needed to be built. https://github.com/thepowersgang/mrustc

There is a Rust front-end for GCC that is under active development [1]. If the chip vendors are not willing to develop and upstream a LLVM back-end then they can feel free to start contributing to it.

[1] https://rust-gcc.github.io/

That's why gccrs doesn't even consider lifetime checking a part of the language (they plan to use Polonius, too).

There's ongoing work on a Rust front-end for GCC (https://github.com/Rust-GCC/gccrs). Bit barebones right now -- ie, even core doesn't compile -- but there's funding, demand, and regular progress, so it'll only get better from there. Once gccrs can compile core, it should be ready to compile most of Rust, and thus if you've taught the calling conventions for C to GCC, you're golden.

I recommend checking out the GCC Rust frontend project.

That is what theyre refering to, yes. The GitHub is named https://github.com/Rust-GCC/gccrs

- But this misses so much extra context information

3. Macro invocations there are really subtle rules on how you treat macro invocations such as this which is not documented at all https://github.com/Rust-GCC/gccrs/blob/master/gcc/rust/expan...

Some day I personally want to write a blog post about how complicated and under spec'd Rust is, then write one about the stuff i do like it such as iterators being part of libcore so i don't need reactive extensions.

(Speaking of which, Rust-GCC (or gcc-rs or gccrs or whichever other of their names they decide is the primary one) isn't even going to be a complete C++ implementation. Their plan is to implement enough to compile Polonius (the NLL 2.0 borrow checker being developed in Rust for rustc) and then share that since borrow-checking isn't necessary for codegen... only to identify and reject invalid programs... making the C++ portion of it not that different in scope from mrustc.)

That bridge will be crossed with gccrs (compiling Rust with gcc directly, coming next month with GCC 13) and rust_codegen_gcc (rustc frontend, GCC backend, works now but just doesn’t yet have an “easy” setup)