Preserve LLVM archive alternatives and add feature changelog - #878
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# Enable linker-managed ThinLTO on macOS Fix thin_lto feature on MacOS. # AG;DR ## Problem `--features=thin_lto` was silently ineffective on macOS: rules_cc only defines the ThinLTO feature on its non-Darwin path. Explicit `-flto=thin` compile and link flags work with Apple ld, but the toolchain did not provide them. Simply exposing the literal C++ `thin_lto` feature on Darwin is not sufficient. It activates Bazel's distributed indexing/backend path, which requires start/end-lib support and ELF indexing options that Apple ld does not provide. ## Fix - Translate configuration-level `--features=thin_lto` into linker-managed ThinLTO on Darwin, applying `-flto=thin` to compilation and linking without activating ELF indexing actions. - Respect explicit `--features=-thin_lto`, including when both enable and disable requests are present. - Keep target and execution configurations independent: build tools use `--host_features=thin_lto`. - Leave Linux's existing distributed ThinLTO behavior unchanged. - Document the macOS configuration-level scope: rule-local `features` attributes do not select this behavior. LLVM 23 still needs the existing native-linker override on macOS. ## Regression coverage - Analyze C compilation, C++ compilation, and linking; assert the flags are present only when enabled and no ELF-style indexing/backend actions are introduced. - Build and run a C/C++ cross-translation-unit probe with LLVM 23.1.2 and Apple ld. It contains an unresolved call that disappears only after optimization through both static libraries, so an ordinary non-LTO build cannot pass. - Verify the same probe fails with the expected undefined symbol when ThinLTO is disabled, and when only target features are enabled for an execution-configured tool. - Verify `--host_features=thin_lto` enables the tool independently of disabled target ThinLTO. - Add a required macOS CI job for Bazel 9/Bzlmod and Bazel 8/WORKSPACE, including the corresponding `required_checks_done.needs` entry. ## Local verification On Apple Silicon, repeated after rebasing onto merged #876 (`3764511`): - Bazel 9.0.0 / Bzlmod / LLVM 23.1.2: full `run_darwin_thin_lto_tests.sh` passed (six cached test results, both expected-failure checks, and the host-feature build). - Bazel 8.6.0 / WORKSPACE / LLVM 23.1.2: the same full regression script passed (six cached test results, both expected-failure checks, and the host-feature build). - #876's feature-matrix fixture: `--features=thin_lto //:selection_test` passed with Bazel 9 and Apple ld. - Root Bazel 9.0.0 `bazel test //... --nocache_test_results`: all 20 tests executed and passed. - `trunk check --no-fix` and the commit/push hooks passed. The Linux distributed ThinLTO fixture also passed in the existing container after #876's signed-feature API update. The rebase leaves the ThinLTO patch unchanged (`git range-diff` confirms this). ## CI cleanup follow-up during sequential merging - [#875's post-merge Ubuntu/Bazel 9 job](https://github.com/bazel-contrib/toolchains_llvm/actions/runs/36803938052/job/110184071511) passed its native tests, then failed deleting the shared repo contents cache before the WebAssembly phase: `Directory not empty`. - Its log shows separate root-workspace and tests-workspace Bazel servers, with an orphan Java process still alive after cleanup. Change the initial banner from `bazel version` to client-only `bazel --version`, removing that unnecessary idle root server. [Idle servers can run repo-cache garbage collection](https://github.com/bazelbuild/bazel/blob/master/src/main/java/com/google/devtools/build/lib/bazel/repository/RepositoryOptions.java), making this a likely source of the cleanup race. Compiler/linker configuration and cache-cleanup error handling are unchanged. - An isolated local probe verified that the old `version` command starts a server, while standalone `--version` succeeds on Bazel 8.6.0 and 9.0.0 without creating an output root. The probe server was shut down; `bash -n`, `git diff --check`, and the commit/push hooks passed. Current head: `0d84b16` (unchanged ThinLTO patch plus the CI banner fix). Fresh CI: [Tests run 36810263471](https://github.com/bazel-contrib/toolchains_llvm/actions/runs/36810263471). Protected squash auto-merge is enabled; #878 will be rebased only after this PR merges.
Keep xz, zstd, and gzip checksums in the extra-distributions helper, leaving archive compatibility decisions to the toolchain selector. Exercise the actual shell helper with offline release fixtures, extend the updater regression, and run both suites in required Linux/macOS CI. Correct stale updater documentation and add a release-heading changelog separating verified historical feature introductions from the planned 1.11.0 additions. Stacked on PR bazel-contrib#877.
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Fix the remaining xz/zstd mismatch in the single-release distribution helper and add a history-backed changelog.
AG;DR
Fix
#870 changed the Python updater to retain all archive formats and made the toolchain selector exclude zstd until Bazel can extract LLVM's large-window archives. The shell helper still had #836's old filter, which discarded xz whenever the same archive was available as zstd.
extra_distributions.sh.Changelog
Add
CHANGELOG.mdwith release headings and bullets, newest first. Historical feature introductions are checked against the first containing release tags; current changes are grouped under the version heading1.11.0. Distinguish earlier functionality from later enhancements, including Linux versus macOS ThinLTO, initial versus expanded dynamic-libstdc++ support, and MSan introduction versus correctness fixes.Regression coverage
required_checks_done.needs.Verification
python3 -m unittest discover -s utils -p '*_test.py' -v: all 8 tests pass on macOS.USE_BAZEL_VERSION=9.0.0 bazel test //... --test_output=errors --nocache_test_results: all 21 tests executed and passed on the rebased head.bash -nfor both shell entry points.git diff --check, and YAML validation that the required-check gate includes every declared job and has no unknown dependencies.Fresh CI: Tests run 36820892858. Protected squash auto-merge is enabled; this is the final PR in the #873 → #875 → #876 → #877 → #878 sequence. The changelog heading remains
## 1.11.0.