[experiment] bootstrap: leverage cargo trim-paths by weihanglo · Pull Request #161049 · rust-lang/rust

weihanglo · 2026-08-13T13:08:46Z

What

Leverage Cargo's -Ztrim-paths to remap compiler and library. See rust-lang/cargo#17309.

I'll do some dist jobs and see if artifacts are remapped correctly.

try-jobs: dist-x86_64-msvc
try-jobs: dist-x86_64-linux
try-jobs: dist-aarch64-apple

🤖 LLM disclosure: I used LLM to do the first pass of bootstrap integration and temporary stage0 bump. The usage was signed off here on Zulip: #llm-reviews > Experiment with Cargo's trim-path in bootstrap

weihanglo · 2026-08-13T13:09:50Z

@bors try

[experiment] bootstrap: leverage cargo trim-paths

weihanglo · 2026-08-13T13:21:21Z

@bors try cancel

rust-bors · 2026-08-13T13:21:25Z

Try build cancelled. Cancelled workflows:

https://github.com/rust-lang/rust/actions/runs/31703558440

weihanglo · 2026-08-13T13:21:52Z

@bors try jobs=dist-x86_64-msvc,dist-x86_64-linux,dist-aarch64-apple

[experiment] bootstrap: leverage cargo trim-paths try-job: dist-x86_64-msvc try-job: dist-x86_64-linux try-job: dist-aarch64-apple

rust-bors · 2026-08-13T15:40:30Z

💔 Test for bd743b7 failed: CI. Failed jobs:

try - dist-aarch64-apple (web logs, enhanced plaintext logs)
try - dist-x86_64-linux (web logs, enhanced plaintext logs)
try - dist-x86_64-msvc (web logs, enhanced plaintext logs)

weihanglo · 2026-08-13T18:09:47Z

@bors try jobs=dist-x86_64-msvc,dist-x86_64-linux,dist-aarch64-apple

[experiment] bootstrap: leverage cargo trim-paths try-job: dist-x86_64-msvc try-job: dist-x86_64-linux try-job: dist-aarch64-apple

rust-bors · 2026-08-13T21:14:31Z

☀️ Try build successful (CI)
Build commit: 67c6105 (67c6105718f0714463e9014eca86d60e96ba0b12)
Base parent: ba28ff7 (ba28ff76f353a722f31c4f3dd2ac4e437d36411b)

weihanglo · 2026-08-14T01:46:27Z

@bors try jobs=dist-x86_64-msvc,dist-x86_64-linux,dist-aarch64-apple

[experiment] bootstrap: leverage cargo trim-paths try-job: dist-x86_64-msvc try-job: dist-x86_64-linux try-job: dist-aarch64-apple

This is effectively `library/=<to>/library` and `compiler/=<to>/compiler` in rustc bootstrap, when `__CARGO_RUSTC_BOOTSTRAP_WS_REMAP` is set. This isn't needed for normal cases because relative member paths are exactly what users want. See <rust-lang/rust#161049 (comment)>

With this, we get C dep remap for free when building in rustc bootstrap: See * rust-lang/rust#161049 * rust-lang/cargo#17309 * rust-lang/cc-rs#1794

This is effectively `library/=<to>/library` and `compiler/=<to>/compiler` in rustc bootstrap, when `__CARGO_RUSTC_BOOTSTRAP_WS_REMAP` is set. This isn't needed for normal cases because relative member paths are exactly what users want. See <rust-lang/rust#161049 (comment)>

chore: bump to cc@1.4.3 for rustc_llvm and library ### What is this? Old cc-rs derives this from the `-Clto` rustflag on its own. `cc@1.2.39` starts gating that behind `-Clinker-plugin-lto`, which bootstrap doesn't pass. Therefore, we need to pass this flag explicitly to keep LTO mode Previous efforts: * #146186 * #155438 I personally want this because of cc 1.3.0+ has the support of Cargo `-Ztrim-paths`, which helps what I am experimenting in <#161049>. ### How to review Commit by commit. To keep commits bisect-able, I added the first commit without cc bump. clang should be fine with duplicate `-flto` flags. One thing I am not certain is whether we should probe `-flto` flag in this case, or just make this fail if `-flto` isn't supported. (I assume `-flto` is quote widely supported) r? Kobzol --- 🤖 **LLM disclosure:** I used LLM for the experiment of <#161049>, but not the bootstrap LTO change in this PR.

This is effectively `library/=<to>/library` and `compiler/=<to>/compiler` in rustc bootstrap, when `__CARGO_RUSTC_BOOTSTRAP_WS_REMAP` is set. This isn't needed for normal cases because relative member paths are exactly what users want. See <rust-lang/rust#161049 (comment)>

chore: bump to cc@1.4.3 for rustc_llvm and library ### What is this? Old cc-rs derives this from the `-Clto` rustflag on its own. `cc@1.2.39` starts gating that behind `-Clinker-plugin-lto`, which bootstrap doesn't pass. Therefore, we need to pass this flag explicitly to keep LTO mode Previous efforts: * #146186 * #155438 I personally want this because of cc 1.3.0+ has the support of Cargo `-Ztrim-paths`, which helps what I am experimenting in <#161049>. ### How to review Commit by commit. To keep commits bisect-able, I added the first commit without cc bump. clang should be fine with duplicate `-flto` flags. One thing I am not certain is whether we should probe `-flto` flag in this case, or just make this fail if `-flto` isn't supported. (I assume `-flto` is quote widely supported) r? Kobzol --- 🤖 **LLM disclosure:** I used LLM for the experiment of <#161049>, but not the bootstrap LTO change in this PR.

Replace `RUSTC_DEBUGINFO_MAP` and `RUSTC_CARGO_REGISTRY_SRC_TO_REMAP` with cargo trim-paths and `__CARGO_RUSTC_BOOTSTRAP_WS_REMAP` override (See cargo#17309). The `RUSTC_DEBUGINFO_MAP` into `-ffile-prefix-map` in rustc_llvm will be covered cc@1.3.0+ natively (which inherits and forwards `CARGO_TRIM_PATHS_REMAP`)

The current dwarfdump checks cannot see `.rmeta` leaks: * The compiler keeps unremapped local paths in metadata unless the remap scope is `all` (see issue 159621) * std ships metadata as separate `.rmeta` via `-Zembed-metadata=no` so the leak does not even appear in the rlibs This commit enhances to also check rmeta files.

Registry dependencies are now remapped by cargo trim-paths as `/cargo/registry/{source-hash}/{pkg}-{ver}/`

The `-fdebug-prefix-map` flags in `cc_unhandled_cflags` served three kinds of consumers. * The cc-rs-driven C/C++ builds inside cargo: They now inherit the same remap pairs from cargo trim-paths so passing the flag through `CFLAGS` there is redundant. * The CMake-driven LLVM build: This is the one we need the remaps. * The remaining callers (`compiler_file` probing, cc detection, test fixtures): They never produce distributed artifacts.

weihanglo · 2026-08-22T11:58:11Z

@bors try jobs=dist-x86_64-msvc,dist-x86_64-linux,dist-aarch64-apple

[experiment] bootstrap: leverage cargo trim-paths try-job: dist-x86_64-msvc try-job: dist-x86_64-linux try-job: dist-aarch64-apple

rust-bors · 2026-08-22T14:32:31Z

☀️ Try build successful (CI)
Build commit: 0f3f6ba (0f3f6bab4b478ccba6ce0c6c6649899863d51eac)
Base parent: def3ee9 (def3ee9e4f0fe1429574f402bb624439bbd13fc6)

With this, we get C dep remap for free when building in rustc bootstrap: See * rust-lang#161049 * rust-lang/cargo#17309 * rust-lang/cc-rs#1794

rust-bors · 2026-08-24T17:13:13Z

☔ The latest upstream changes made this pull request unmergeable. Please resolve the merge conflicts by rebasing.

chore: bump to cc@1.4.3 for rustc_llvm and library ### What is this? Old cc-rs derives this from the `-Clto` rustflag on its own. `cc@1.2.39` starts gating that behind `-Clinker-plugin-lto`, which bootstrap doesn't pass. Therefore, we need to pass this flag explicitly to keep LTO mode Previous efforts: * rust-lang/rust#146186 * rust-lang/rust#155438 I personally want this because of cc 1.3.0+ has the support of Cargo `-Ztrim-paths`, which helps what I am experimenting in <rust-lang/rust#161049>. ### How to review Commit by commit. To keep commits bisect-able, I added the first commit without cc bump. clang should be fine with duplicate `-flto` flags. One thing I am not certain is whether we should probe `-flto` flag in this case, or just make this fail if `-flto` isn't supported. (I assume `-flto` is quote widely supported) r? Kobzol --- 🤖 **LLM disclosure:** I used LLM for the experiment of <rust-lang/rust#161049>, but not the bootstrap LTO change in this PR.

This is effectively `library/=<to>/library` and `compiler/=<to>/compiler` in rustc bootstrap, when `__CARGO_RUSTC_BOOTSTRAP_WS_REMAP` is set. This isn't needed for normal cases because relative member paths are exactly what users want. See <rust-lang/rust#161049 (comment)>

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rust-bors Bot pushed a commit that referenced this pull request Aug 13, 2026

Auto merge of #161049 - weihanglo:bootstrap-trim-paths-exp, r=<try>

e23bdd9

[experiment] bootstrap: leverage cargo trim-paths

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rust-bors Bot pushed a commit that referenced this pull request Aug 13, 2026

Auto merge of #161049 - weihanglo:bootstrap-trim-paths-exp, r=<try>

bd743b7

[experiment] bootstrap: leverage cargo trim-paths try-job: dist-x86_64-msvc try-job: dist-x86_64-linux try-job: dist-aarch64-apple

weihanglo mentioned this pull request Aug 13, 2026

Support custom remapping rules with trim-paths for bootstrap rust-lang/cargo#17309

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weihanglo force-pushed the bootstrap-trim-paths-exp branch from b0b31e6 to 9981c62 Compare August 13, 2026 16:17

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rust-bors Bot pushed a commit that referenced this pull request Aug 13, 2026

Auto merge of #161049 - weihanglo:bootstrap-trim-paths-exp, r=<try>

67c6105

[experiment] bootstrap: leverage cargo trim-paths try-job: dist-x86_64-msvc try-job: dist-x86_64-linux try-job: dist-aarch64-apple

weihanglo force-pushed the bootstrap-trim-paths-exp branch from 9981c62 to 21aed96 Compare August 13, 2026 22:52

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weihanglo force-pushed the bootstrap-trim-paths-exp branch from 21aed96 to 80d0ecc Compare August 14, 2026 01:45

rustbot added the A-LLVM Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues. label Aug 14, 2026

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rust-bors Bot pushed a commit that referenced this pull request Aug 14, 2026

Auto merge of #161049 - weihanglo:bootstrap-trim-paths-exp, r=<try>

f892cbb

[experiment] bootstrap: leverage cargo trim-paths try-job: dist-x86_64-msvc try-job: dist-x86_64-linux try-job: dist-aarch64-apple

weihanglo mentioned this pull request Aug 15, 2026

fix(trim-paths): custom workspace-relative member paths remap rust-lang/cargo#17366

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weihanglo mentioned this pull request Aug 17, 2026

chore: update to cc@1.4.3 rust-lang/miri#5259

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pull Bot pushed a commit to xtqqczze/rust-lang-miri that referenced this pull request Aug 17, 2026

chore: update to cc@1.4.3

1baabde

With this, we get C dep remap for free when building in rustc bootstrap: See * rust-lang/rust#161049 * rust-lang/cargo#17309 * rust-lang/cc-rs#1794

weihanglo mentioned this pull request Aug 17, 2026

chore: bump to cc@1.4.3 for rustc_llvm and library #161260

Merged

weihanglo added 5 commits August 21, 2026 23:10

tests: check $CARGO_HOME leaks

5cf3ce2

tests: switch remap prefix expectation to /cargo/registry

cb3818e

Registry dependencies are now remapped by cargo trim-paths as `/cargo/registry/{source-hash}/{pkg}-{ver}/`

weihanglo force-pushed the bootstrap-trim-paths-exp branch from e416b25 to 7d23b0e Compare August 22, 2026 03:11

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rust-bors Bot pushed a commit that referenced this pull request Aug 22, 2026

Auto merge of #161049 - weihanglo:bootstrap-trim-paths-exp, r=<try>

0f3f6ba

[experiment] bootstrap: leverage cargo trim-paths try-job: dist-x86_64-msvc try-job: dist-x86_64-linux try-job: dist-aarch64-apple

RalfJung pushed a commit to RalfJung/rust that referenced this pull request Aug 23, 2026

chore: update to cc@1.4.3

1df3fe0

With this, we get C dep remap for free when building in rustc bootstrap: See * rust-lang#161049 * rust-lang/cargo#17309 * rust-lang/cc-rs#1794

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