GCC Front-End For Rust

Alternative Rust Compiler for GCC

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May 2025 Monthly report

Overview

Thanks again to Open Source Security, inc and Embecosm for their ongoing support for this project.

Project update

The past month of development was mostly focused on community outreach, with a talk from Pierre-Emmanuel and Arthur at RustWeek in Utrecht, available here. Here, we met with Miguel Ojeda from the Rust-for-Linux project, who informed us that the kernel no longer relies on the alloc standard crate for its function. This makes our job easier, as we are now tasked with compiling core and the kernel’s implementation of alloc, rather than having to catch up with the standard library’s alloc crate.

In practice, this means that gccrs should be useful for Rust-for-Linux in a shorter span of time than originally planned, and we will start integrating the kernel’s source code to our testing infrastructure in our efforts to target those crates. We spent some time last month establishing these milestones, which will be worked on as part of a further 6 months of support from Open Source Security, inc, until the end of Stage 1 for GCC 16.1.

Our next efforts will focus on finishing our name resolution pass for core, and fixing the remaining macro expansion bugs. As part of Google Summer of Code, we will work on improving our pattern matching backend which will allow us to covers all of the patterns used in core. Once that work is complete, we will spend time exploring the Pin semantics and making sure gccrs handles them correctly, as this data structure is used everywhere in the Linux kernel. This will then allow us to start testing the compiler on the kernel crates, hopefully by the end of the summer.

Work also continued on the name resolution rewrite, which is now frustratingly close to replacing our previous implementation. We are resuming work on all areas of the compiler in June. The project received contributions from the usual suspects, with around 25 pull requests from external contributors this month. We are also starting work with our two GSoC students, Zhi Heng and Ryutaro Okada. They will be working on improving our pattern matching backend and on reimplementing certain Rust lints within our front-end rather than by depending on the GCC common compiler framework.

Community call

We will have our next monthly community call on the 9th of June at 9am UTC. You can subscribe to our calendar to see when the next one will be held. The call is open to everyone, even if you would just like to sit-in and listen. You can also subscribe to our mailing-list or join our Zulip chat to be notified of upcoming events.

Call for contribution

Completed Activities

Contributors this month

Overall Task Status

Category Last Month This Month Delta
TODO 477 471 -6
In Progress 118 114 -4
Completed 1056 1064 +8

Bugs

Category Last Month This Month Delta
TODO 209 207 -2
In Progress 56 56 -
Completed 519 521 +2

Test Cases

TestCases Last Month This Month Delta
Passing 10392 10631 +239
Failed - - -
XFAIL 73 73 -
XPASS - - -

Milestones Progress

Milestone Last Month This Month Delta Start Date Completion Date Target Target GCC
Name resolution 2.0 rework 100% 100% - 1st Jun 2024 - 1st Apr 2025 GCC 15.1
Macro expansion 100% 100% - 1st Jun 2024 - 1st Jan 2025 GCC 15.1
Remaining typecheck issues 100% 100% - 21st Oct 2024 - 1st Mar 2025 GCC 15.1
cfg-core 100% 100% - 1st Dec 2024 24th Mar 2025 1st Mar 2025 GCC 15.1
Codegen fixes 100% 100% - 7th Oct 2024 1st Apr 2025 1st Mar 2025 GCC 15.1
blackbox intrinsic 100% 100% - 28th Oct 2024 - 28th Jan 2025 GCC 15.1
let-else 100% 100% - 28th Jan 2025 - 28th Feb 2025 GCC 15.1
Specialization 100% 100% - 1st Jan 2025 1st Apr 2025 1st Mar 2025 GCC 15.1
cfg-rfl 100% 100% - 7th Jan 2025 19th Mar 2025 15th Feb 2025 GCC 15.1
Downgrade to Rust 1.49 100% 100% - 14th Mar 2025 26th Mar 2025 1st Apr 2025 GCC 15.1
Explicit generics with impl Trait 40% 55% +15% 28th Feb 2025 - 28th Mar 2025 GCC 15.1
Upcoming Milestone Last Month This Month Delta Start Date Completion Date Target Target GCC
Unstable RfL features 0% 0% - 7th Jan 2025 - 1st Aug 2025 GCC 16.1
offsetof!() builtin macro 0% 0% - 15th Mar 2025 - 15th Aug 2025 GCC 16.1
Generic Associated Types 0% 0% - 15th Mar 2025 - 15th Jun 2025 GCC 16.1
RfL const generics 0% 0% - 1st May 2025 - 15th Jun 2025 GCC 16.1
frontend plugin hooks 0% 0% - 15th May 2025 - 7th Jul 2025 GCC 16.1
Handling the testsuite issues 0% 0% - 15th Sep 2024 - 15th Sep 2025 GCC 16.1
main shim 0% 0% - 28th Jul 2025 - 15th Sep 2025 GCC 16.1
Past Milestone Last Month This Month Delta Start Date Completion Date Target Target GCC
Data Structures 1 - Core 100% 100% - 30th Nov 2020 27th Jan 2021 29th Jan 2021 GCC 14.1
Control Flow 1 - Core 100% 100% - 28th Jan 2021 10th Feb 2021 26th Feb 2021 GCC 14.1
Data Structures 2 - Generics 100% 100% - 11th Feb 2021 14th May 2021 28th May 2021 GCC 14.1
Data Structures 3 - Traits 100% 100% - 20th May 2021 17th Sep 2021 27th Aug 2021 GCC 14.1
Control Flow 2 - Pattern Matching 100% 100% - 20th Sep 2021 9th Dec 2021 29th Nov 2021 GCC 14.1
Macros and cfg expansion 100% 100% - 1st Dec 2021 31st Mar 2022 28th Mar 2022 GCC 14.1
Imports and Visibility 100% 100% - 29th Mar 2022 13th Jul 2022 27th May 2022 GCC 14.1
Const Generics 100% 100% - 30th May 2022 10th Oct 2022 17th Oct 2022 GCC 14.1
Initial upstream patches 100% 100% - 10th Oct 2022 13th Nov 2022 13th Nov 2022 GCC 14.1
Upstream initial patchset 100% 100% - 13th Nov 2022 13th Dec 2022 19th Dec 2022 GCC 14.1
Update GCC’s master branch 100% 100% - 1st Jan 2023 21st Feb 2023 3rd Mar 2023 GCC 14.1
Final set of upstream patches 100% 100% - 16th Nov 2022 1st May 2023 30th Apr 2023 GCC 14.1
Borrow Checking 1 100% 100% - TBD 8th Jan 2024 15th Aug 2023 GCC 14.1
Procedural Macros 1 100% 100% - 13th Apr 2023 6th Aug 2023 6th Aug 2023 GCC 14.1
GCC 13.2 Release 100% 100% - 13th Apr 2023 22nd Jul 2023 15th Jul 2023 GCC 14.1
GCC 14 Stage 3 100% 100% - 1st Sep 2023 20th Sep 2023 1st Nov 2023 GCC 14.1
GCC 14.1 Release 100% 100% - 2nd Jan 2024 2nd Jun 2024 15th Apr 2024 GCC 14.1
formatargs!() support 100% 100% - 15th Feb 2024 - 1st Apr 2024 GCC 14.1
GCC 14.2 100% 100% - 7th Jun 2024 15th Jun 2024 15th Jun 2024 GCC 14.2
GCC 15.1 100% 100% - 21st Jun 2024 31st Jun 2024 1st Jul 2024 GCC 15.1
Unhandled attributes 100% 100% - 1st Jul 2024 15th Aug 2024 15th Aug 2024 GCC 15.1
Inline assembly 100% 100% - 1st Jun 2024 26th Aug 2024 15th Sep 2024 GCC 15.1
Rustc Testsuite Adaptor 100% 100% - 1st Jun 2024 26th Aug 2024 15th Sep 2024 GCC 15.1
Borrow checker improvements 100% 100% - 1st Jun 2024 26th Aug 2024 15th Sep 2024 GCC 15.1
Deref and DerefMut improvements 100% 100% - 28th Sep 2024 25th Oct 2024 28th Dec 2024 GCC 15.1
Indexing fixes 100% 100% - 21st Jul 2024 25th Dec 2024 15th Nov 2024 GCC 15.1
Iterator fixes 100% 100% - 21st Jul 2024 25th Dec 2024 15th Nov 2024 GCC 15.1
Auto traits improvements 100% 100% - 15th Sep 2024 20th Jan 2025 21st Dec 2024 GCC 15.1
Lang items 100% 100% - 1st Jul 2024 10th Jan 2025 21st Nov 2024 GCC 15.1
alloc parser issues 100% 100% - 7th Jan 2025 31st Jun 2024 28th Jan 2025 GCC 15.1
std parser issues 100% 100% - 7th Jan 2025 31st Jun 2024 28th Jan 2025 GCC 16.1
Question mark operator 100% 100% - 15th Dec 2024 21st Feb 2025 21st Feb 2025 GCC 15.1

Planned Activities

Risks

We must establish the list of GCC-common changes we need, as we will have to send them upstream before the start of Stage 3 around November. This is the only risk which could incur further problems and prevent more gccrs features from landing in 16.1.