Fix gc-native-roots failures on ARM Linux and macOS

[proggeramlug]

The scheduled gc-native-roots gate fails for two platform-specific reasons: Ubuntu ARM cannot compile the libyaml diagnostic pointer on targets where Rust's c_char is unsigned, and the macOS stock-toolchain step overwrites the LLVM 22 prefix with Homebrew's unversioned LLVM 23 before invoking the LLVM 22 in-process backend.

This casts libyaml's problem pointer through the target std::ffi::c_char type and preserves the LLVM_SYS_221_PREFIX exported by setup-llvm22. The stock-toolchain assertion still removes the external opt and clang overrides, while the in-process backend remains linked to the ABI required by llvm-sys 221.

Validation:

• ARM Linux target compile of the changed unsafe-libyaml diagnostic expression
• invalid Bun.YAML.parse compiled probe, including the full SyntaxError diagnostic
• corrected in-process RS4GC probe under LLVM 22: compact map present, raw stackmaps removed, output equal to the shadow-stack control, 75 copying minors and 15,391 objects moved, 12/12 functions reported as RS4GC
• perry-runtime: 3,242 passed, 4 ignored; doc tests: 8 ignored
• perry-stdlib: 132 passed
• all 64 local lint and compile gates passed; 2 CI-expression-only commands skipped
• actionlint reports one fewer finding than origin/main, with the remaining findings unchanged

Fixes #9915

Summary by CodeRabbit

• Bug Fixes

  • Restored scheduled native-roots validation on ARM Linux and macOS.
  • Improved platform-specific YAML parsing compatibility and error handling.
  • Ensured in-process LLVM builds use the configured LLVM 22 toolchain consistently.

• Documentation

  • Added changelog coverage for native-roots validation across supported platforms.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Team

Run ID: 1e78e941-4a91-4a26-add1-5c669d1449ed

📥 Commits

Reviewing files that changed from the base of the PR and between 504e180 and 49c63e5.

📒 Files selected for processing (3)

• .github/workflows/gc-native-roots.yml
• changelog.d/9920-gc-native-roots-platforms.md
• crates/perry-runtime/src/bun_compat/cli_utils.rs

Included review availability: Your plan provides up to 8 included reviews per hour; 3 remain after this review.

---

📝 Walkthrough

Walkthrough

The workflow preserves the setup-provided LLVM 22 prefix for in-process linking. The YAML parser error path adds an explicit c_char pointer cast. A changelog entry records the native-roots platform fixes.

Changes

Native-roots compatibility fixes

Layer / File(s)	Summary
Native-roots workflow toolchain .github/workflows/gc-native-roots.yml, changelog.d/9920-gc-native-roots-platforms.md	The in-process workflow step no longer overrides LLVM_SYS_221_PREFIX with Homebrew’s LLVM path. The changelog records the related platform fixes.
Parser error pointer conversion crates/perry-runtime/src/bun_compat/cli_utils.rs	parser.problem is cast to std::ffi::c_char before CStr::from_ptr receives it.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 49c63

This change restores native-roots compatibility checks on ARM Linux and macOS while preserving YAML diagnostic behavior. No merge-blocking risk remains.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files. (2 skipped: 2 …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the primary change: fixing gc-native-roots failures on ARM Linux and macOS.
Description check	✅ Passed	The description explains the failure causes, lists the code and workflow changes, references issue #9915, and provides detailed validation results. It omits the template headings and checklist, but th…
Linked Issues check	✅ Passed	The changes address the platform-specific failures described in issue #9915 by correcting ARM Linux libyaml pointer handling and preserving the LLVM 22 prefix for macOS in-process RS4GC validation. Th…
Out of Scope Changes check	✅ Passed	The workflow update, libyaml compatibility fix, and changelog entry are directly related to restoring the failing gc-native-roots gate. No unrelated code changes are identified.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files. (2 skipped: 2 unsupported.)

• Fix all pre-merge checks with AI

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[proggeramlug]

Landed on main via merge train #9923. Validated as a tree: 64/64 lint gates, and perry-runtime/codegen/hir/stdlib all green (5,962 tests, 0 failures). Thanks!