Re: Rust front-end

[David Edelsohn <dje.gcc@gmail.com>]

On Mon, Jun 27, 2022 at 10:52 AM Philip Herron
<philip.herron@embecosm.com> wrote:
>
> Hi everyone,
>
> Since November 2020, I've worked full-time on the Rust front-end for
> GCC, thanks to Open Source Security, Inc and Embecosm. As a result, I
> am writing to this mailing list to seek feedback from the collective
> experience here early to plan a path for upstreaming the front-end
> into GCC.
>
> 1. What is the actual process of merging a prominent feature like this upstream
>   - How do we review this?
>   - Do we create a "mega-commit" patch
>   - How long should we expect this review process to take
>   - Is there anything we can do to make this easier?
>
> 2. What sort of quality does the GCC community expect?
>   - I think it is essential that we can compile valid test cases from
> a testsuite and real projects before merging.
>   - It seems reasonable that our error handling may not be 100% but be
> expected to improve over time
>   - Upon merging, can features like Rust be marked as experimental
>
> 3. How do GCC releases work?
>   - If you miss a window can we still merge code into the front-end?
>   - Can we merge without a borrow checker and backport this in the future?
>
> 4. What about the possibility of merging sooner rather than later,
> which would help the project gain interest through the increased
> visibility of it as part of the GCC family.
>   - Does this still allow for development churn, or will it cause friction?
>
> 5. Does anyone have prior experience or advice they could give us?
>
> For some context, my current project plan brings us to November 2022
> where we (unexpected events permitting) should be able to support
> valid Rust code targeting Rustc version ~1.40 and reuse libcore,
> liballoc and libstd. This date does not account for the borrow checker
> feature and the proc macro crate, which we have a plan to implement,
> but this will be a further six-month project.
>
> Regarding patch management, we currently do our development on GitHub:
> https://github.com/Rust-GCC/gccrs; this means we can integrate our
> issue tracking with the official Rust project by linking back to the
> official Rust project's RFC issues, for example. The downside is that
> when someone uses our compiler and hits an ICE, they will be directed
> to the GCC Bugzilla, which is correct but can lead to a mismatch in
> issue tracking. Nevertheless, I think it's essential to have the
> GitHub link here to integrate with the broader Rust community. I
> believe we can triage Rust issues on the Bugzilla and raise associated
> ones on Github to manage this.
>
> From my perspective as the lead on this front-end, we are currently
> under heavy development, so this means a fair amount of code churn
> still, and I don't see this changing until we can successfully compile
> the libcore crate later this year. Although I would love to see us
> merged into GCC 13, I want to make sure this project is a success for
> everyone, and this might mean pushing back to the next release window
> to make sure this is manageable to produce a quality front-end to sit
> alongside the others.
>
> I wish to thank you those in the GCC developer community, who have
> inspired me and helped me navigate my journey to this point in time.
>
> - Thomas Schwinge
> - Mark Wielaard
> - Tom Tromey
> - Ian Lance Taylor
> - David Edelsohn
> - David Malcolm
> - Martin Jambor

Congratulations! The GCC Steering Committee has voted to accept the
contribution of the Rust Frontend (aka GCC Rust) to GCC.  Please work
with the GCC Global Reviewers and GCC Release Managers for technical
review and technical approval of the patches.  We look forward to
including a preliminary, beta version of GCC Rust in GCC 13 as a
non-default language.

Thanks, David