Fix macOS 27 SDK linking with Apple ld - #388
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LLVM 21's ld64.lld rejects TBD stubs that list arm64e.x1, so native macOS links fail with a cascade of missing libc++/libSystem symbols. Keep the override on the LLVM toolchain so wasm still uses wasm-ld. Co-authored-by: Cursor <cursoragent@cursor.com>
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🟡 Changes recommended
The MODULE.bazel change lacks the required regenerated MODULE.bazel.lock update.
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Pull request overview
Updates macOS LLVM linking to use Apple’s linker for MacOSX 27 SDK compatibility while preserving WASM’s wasm-ld.
Changes:
- Adds Darwin-specific
/usr/bin/ldflags. - Disables unsupported
--start-lib/--end-libusage on macOS. - Documents the workaround and removal conditions.
File summaries
| File | Description |
|---|---|
MODULE.bazel |
Configures Apple’s linker for Darwin LLVM toolchains. |
.bazelrc |
Disables supports_start_end_lib on macOS. |
docs/BUILD_SYSTEM.md |
Documents SDK and linker compatibility. |
Review details
- Files reviewed: 3/3 changed files
- Comments generated: 1
- Review effort level: Lite
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I saw some of these problems for a beta version but I did not think it made sense to fix them for before the official version was out.
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Summary
ld64.lldcannot parse MacOSX 27 SDK TBD stubs that listarm64e.x1, so native Darwin links fail with a cascade of missing libc++/libSystem symbols./usr/bin/ldviallvm.toolchain.extra_link_flags, scoped to the LLVM toolchain so wasm still useswasm-ld.supports_start_end_libon macOS hosts because Apple ld rejects LLD's--start-lib/--end-lib.Test plan
blaze build //library/tests/heuristic_sorting:minimal_new_test(previously failed at link)blaze test //library/tests/heuristic_sorting:minimal_new_testblaze aqueryconfirms wasm CppLink still usesemcc_link.sh(no/usr/bin/ld)ci_macos.ymlonmacos-26(bazelisk build //...andbazelisk test //...)Made with Cursor