August 2025 Monthly report

Overview

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

Project update

The month of August was focused on bug fixing for building core, once again. We identified some issues in our macro expansion and reworked our ExpandVisitor, a piece of code we had originally written 3 years ago which contained some shortcomings and would not expand macro invocations in all places required. We implemented a new visitor to visit nodes from their container, and potentially reseat their pointer - which fixed a lot of the issues and increased the completeness of the compiler. We then transformed all of our mutating visitors into visitors inheriting from this container visitor, which resulted in a cleaner codebase and a more correct front end.

Google Summer of Code also came to an end, with both our students Ryutaro Okada and Zhi Heng successfully completing their projects and earning top scores in their final evaluations. It was a joy to work alongside them on their projects, and we hope to see them contribute in the future.

As a reminder, our current objective is to get gccrs to a state where it can compile the Linux kernel’s Rust parts. The Rust-for-Linux project does not depend on the entire Rust standard library (std), but only on core - like a lot of Rust embedded projects. However, because the project wants to benefit from all of Rust’s functionalities, they are reimplementing parts of the standard library using the kernel’s memory allocator - this enables Rust kernel module developers to use types such as Vec<T>, or String. As such, the milestones we worked on this summer are aimed at two objectives:

1. Compile Rust’s core library, as it is the sole dependency of the Linux kernel’s Rust crate
2. Compile the Rust kernel crate

In order to do this, we had to implement some new Rust features over the summer: namely, try blocks and while-let loops, both used in core and within the kernel. The kernel makes use of more recent Rust features that are not present in the version we target, so we must implement them as well - for example, the offset_of macro.

Our first objective is the kernel’s alloc crate, a reimplementation of parts of the Rust std crate responsible for implementing dynamically allocated types. Thanks to the work of our contributors over the summer, we were able to implement all of the required language features mentioned above. We are now debugging a few remaining bugs in our name resolution and macro expansion passes.

The next two weeks of work on the project will be focused on these bugs, and the last two weeks of the month of September will be solely dedicated to compiling the Linux kernel’s alloc crate.

We are currently interviewing two interns who would contribute to the project for the period of September to January - we are currently designing milestones for them, so that they may contribute meaningfully to the project while gaining work experience within our company Embecosm SAS.

Finally, we will also be present at three major conferences in September:

• Oxidize in Berlin, Germany
• Kangrejos in Oviedo, Spain
• GNU Cauldron in Port, Portugal

Pierre-Emmanuel and Arthur will be giving talks at these three venues and we hope to meet with everyone interested in the project!

Community call

We will have our next monthly community call on the 8th of September 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.

• Jitsi link
• Calendar ID: 7060a0923ffebd3cb52b1afef35a28ff7b64f05962c9af84c23b1847f1f5f894@group.calendar.google.com
• Google calendar link
• iCal link

Call for contribution

• https://github.com/Rust-GCC/gccrs/issues/2500

• https://github.com/Rust-GCC/gccrs/issues/2376

Completed Activities

• gccrs: Fix segv when handling invalid array capacities PR4120
• More const generics development PR4119
• Get rid of TyTy::BaseType can_eq interface PR4118
• Unify path-to-type handling in Late resolver PR4113
• Recognize rustc_allow_const_fn_unstable PR4111
• nr1.0: Remove chunks of resolution phase PR4110
• nr1.0: Remove support in expansion phase PR4109
• Implement missing var decl binding & read-only checker cases for TuplePatternItemsHasRest PR4106
• Emit error on lonely self use declaration PR4103
• Do not dump the AST if the parser emit errors PR4101
• Separate strip information from internal state PR4100
• Avoid std::unique_ptr<std::string> in Token PR4097
• gccrs: Refactor AST Patterns that hold multiple pattern items PR4096
• Remove Parser::parse_tuple_index_expr_float PR4095
• nr1.0: Remove support in privacy checker PR4094
• nr1.0: Remove support in pattern checker PR4093
• nr1.0: Remove support in borrow checker PR4092
• nr1.0: Remove support in rust-session-manager.cc PR4091
• Eagerly expand format_args macro PR4089
• ci: Fix arm64 ci PR4088
• Remove Parser::parse_path_in_expression_pratt PR4087
• Partial eq fn field PR4084
• Expect identifier subpatterns to be non-alt PR4083
• gccrs: fix ICE for empty enum variant PR4081
• Add AST::PointerVisitor PR4079
• gccrs: fix ICE by skipping invalid (non-FNDEF) candidates PR4078
• Reject empty cfg_attr PR4077
• Handle patterns in macro expansion PR4076
• nr2.0: Fix ChangeLog entry PR4075
• Improve libformat_parser FFI PR4074
• Fix Self macro and partial macro invocation parsing null check PR4073
• Finish up subpattern codegen support for identifier patterns PR4072
• Wildcard use declaration PR4070
• Replace old read-only checker with new one. PR4069
• CfgStrip AST nodes marked with #[test] PR4067
• Collect lang items after expansion PR4066
• Remove #[simd_test] support PR4065
• Improve handling of non-final path segments PR4063
• gccrs: Implement rest pattern support for slice patterns PR4062
• Fix Macro builtins asm clobber infinite loop PR4061
• gccrs: fix ICE in convert_tree for tuple destructuring with ref PR4059
• Allow early resolution to use the language prelude PR4058
• Detect failure to match an ident metavariable PR4057
• Add checks to ExpandVisitor PR4052
• gccrs: Fix ICE on exclusive_rangepattern lowering PR4049
• Exclude some inline assembly test PR4048
• Misc fixes in headers PR4045
• Improve handling of AttrInputLiteral PR4044
• Sync with upstream fa099f248e2462ecd5ab8b0cadd348aaf11bb093 PR4043
• Recognize rustc_args_required_const attribute PR4042
• Remove undefined behavior with static_cast PR4041
• Handle attributes in expression macros PR4040
• gccrs: Refactor HIR::PatternItem class and its derivatives PR4039
• Explicitely create empty vector PR4029
• Add offset_of!() evaluation PR4021
• Make AttributeParser rely more on Parser PR4018
• ci: Bump from macos-13 to macos-15 PR4001
• Implement readonly checker on HIR PR3881
• Fix ICE when trying to compile enums with non-const discriminants. PR3681
• Fix Error Code for Attempted to call something which isn’t a function nor a method. PR3496

Contributors this month

• Zhi Heng
• Ryutaro Okada
• Lishin
• Marc Poulhiès
• Owen Avery
• Pierre-Emmanuel Patry
• Philip Herron
• Arthur Cohen

Overall Task Status

Bugs

Test Cases

Milestones Progress

Planned Activities

• Finish debugging core
• Start experimenting with the kernel’s Rust code