T-compiler Meeting Agenda 2025-07-17

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Announcements

Reminder: if you see a PR/issue that seems like there might be legal implications due to copyright/IP/etc, please let us know (or at least message @davidtwco or @Wesley Wiser so we can pass it along).

MCPs/FCPs

New MCPs (take a look, see if you like them!)
- “Tier 3 target proposal: riscv64a23-unknown-linux-gnu” compiler-team#894 (Zulip)
- “Flag -Zindirect-branch-cs-prefix (retpoline mitigation)” compiler-team#899 (Zulip)
Old MCPs (stale MCP might be closed as per MCP procedure)
- None at this time
Old MCPs (not seconded, take a look)
- “Add hygiene attributes to compile expanded source code” compiler-team#692 (Zulip) (last review activity: about 30 days ago)
  - concern: path-to-stabilization
- “Policy change around adding new unstable flags” compiler-team#787 (Zulip) (last review activity: 9 months ago)
- “Rename “dylib” crate type to “rdylib” (keep old name but deprecate it), and maybe do the same for “staticlib” → “cstaticlib”” compiler-team#825 (Zulip) (last review activity: about 13 days ago)
  - concern: needs-a-sufficiently-long-deprecation-timeline
  - concern: broad-change-needs-tlang-buy-in-possibly-fcp
  - concern: needs-a-blog-post
- “Compile UI tests as libraries by default” compiler-team#842 (Zulip) (last review activity: 4 months ago)
- “Basic target naming rules” compiler-team#850 (Zulip) (last review activity: about 1 days ago)
  - concern: wont-stop-target-names-from-proliferating
- “Unify ui test inline error annotation style” compiler-team#859 (Zulip) (last review activity: 3 months ago)
- “Promote tier 3 riscv32 ESP-IDF targets to tier 2” compiler-team#864 (Zulip) (last review activity: about 34 days ago)
- “Add support for specifying split-debuginfo=unpacked output directory” compiler-team#871 (Zulip) (last review activity: 2 months ago)
- “WebAssembly for procedural macros” compiler-team#876 (Zulip) (last review activity: about 0 days ago)
  - concern: proposal-wording
- “Promote armv7-unknown-linux-musleabihf to tier 2 with host tools” compiler-team#888 (Zulip) (last review activity: about 1 days ago)
  - concern: lack-of-maintainers
Pending FCP requests (check your boxes!)
- merge: Begin enforcing Tier 2 target maintainer requirements (compiler-team#896)
  - @|116266 @|125250 @|116107 @|119031 @|248906 @|426609 @|116118 @|444933 @_|353056
  - no pending concerns
- merge: sanitizers: Stabilize AddressSanitizer and LeakSanitizer for the Tier 1 targets (rust#123617)
  - no pending checkboxes
  - concerns: stabilization-scope (by wesleywiser)
- merge: Fix backtraces with -C panic=abort on linux; emit unwind tables by default (rust#143613)
  - @|116266 @|125250 @|116107 @|248906 @|426609 @|116122 @|116118 @|444933 @_|353056
  - no pending concerns
Things in FCP (make sure you’re good with it)
- “Add Hotpatch flag” compiler-team#745 (Zulip)
- “Proposal for Adapt Stack Protector for Rust” compiler-team#841 (Zulip)
  - concern: lose-debuginfo-data
  - concern: impl-at-mir-level
  - concern: inhibit-opts
- “Make the UI test suite more amenable to multiple editions” compiler-team#861 (Zulip)
- “Upgrade *-linux-musl targets to musl 1.2.5” compiler-team#887 (Zulip)
- “Policy: Empower reviewers to reject burdensome PRs” compiler-team#893 (Zulip)
  - concern: ai-should-still-be-mentioned-in-motivation
  - concern: resolve ai-should-still-be-mentioned-in-motivation
  - concern: wording-nits
- “Add target_env = "macabi" and target_env = "sim"” rust#139451
Accepted MCPs
- “setup typos check in CI (for rust repo)” compiler-team#817 (Zulip)
- “Add one more “late metadata”/“digest” file to rlib archives” compiler-team#853 (Zulip)
- “Constrain process required for some user-facing changes to lower support tier targets” compiler-team#884 (Zulip)
- “Expose target_abi = "elfv{1,2}" on powerpc64-any-unixy-elfy targets” compiler-team#885 (Zulip)
- “use separate build directory for rust-analyzer to use” compiler-team#889 (Zulip)
- “Create rustc_target::spec::Target from a Builder” compiler-team#890 (Zulip)
- “Run more tests for rustc_codegen_gcc in the CI” compiler-team#891 (Zulip)
- “Auto-create tracking issues for accepted MCPs” compiler-team#892 (Zulip)
MCPs blocked on unresolved concerns
Finalized FCPs (disposition merge)
- “Use lld by default on x86_64-unknown-linux-gnu stable” rust#140525
Other teams finalized FCPs
- “Allow #[must_use] on associated types to warn on unused values in generic contexts” rust#142590

Backport nominations

T-compiler beta / T-compiler stable

:beta: “Taint body on invalid call ABI” rust#142983
- Authored by compiler-errors
- Voting Zulip topic
:beta: “Reword mismatched-lifetime-syntaxes text based on feedback” rust#143914
- Authored by shepmaster
- Voting Zulip topic
:beta: “trait_sel: MetaSized always holds temporarily” rust#144016
- Authored by davidtwco
- Voting Zulip topic
No stable nominations for T-compiler this time.

T-types beta / T-types stable

No beta nominations for T-types this time.
No stable nominations for T-types this time.

PRs S-waiting-on-team

T-compiler

“Tracking Issue for bare_link_kind” rust#132061
“Stabilize fn_align: #[align(N)] on functions” rust#140261
“Add new function_casts_as_integer lint” rust#141470
“Stabilize -Cmin-function-alignment” rust#142824
“Fix backtraces with -C panic=abort on linux; emit unwind tables by default” rust#143613
Issues in progress or waiting on other teams