[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

With this we get remap for free when building in rustc bootstrap: See * rust-lang/rust#161049 * rust-lang#17309

### What does this PR try to resolve? With this we get remap for free when building in rustc bootstrap: See * rust-lang/rust#161049 * rust-lang#17309 * rust-lang/cc-rs#1794 ### How to test and review this PR?

rust-bors · 2026-08-15T04:57:06Z

☀️ Try build successful (CI)
Build commit: 62cf67c (62cf67c121864e5bfc57b32497dc24e22b7a91a0)
Base parent: d453bdd (d453bdd8f092d099bc336f0bda4163f809ad18e0)

Urgau · 2026-08-15T12:25:51Z

-                    // When building the standard library sources, we want to apply the std remap scheme.
-                    let map = [
-                        // Cargo use relative paths for workspace members, so let's remap those.
-                        format!("library/={map_to}/library"),


Seems like this remapping isn't done anymore.

$ rustc +62cf67c121864e5bfc57b32497dc24e22b7a91a0 diag.rs error[E0277]: the trait bound `{integer}: AsRef<Path>` is not satisfied --> diag.rs:2:37 | 2 | let a = std::fs::read_to_string(12).unwrap(); | ----------------------- ^^ the trait `AsRef<Path>` is not implemented for `{integer}` | | | required by a bound introduced by this call | note: required by a bound in `std::fs::read_to_string` --> library/std/src/fs.rs:383:0 error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0277`.

View changes since the review

Ah, we forgot library=<map_to>/library remap, which its relative form not covered by Cargo's <absolute-workspace-root>=<map_to>

Yeah, the same is probably also not done for compiler.

Posted rust-lang/cargo#17366

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)

This comment has been minimized.

Sign in to view

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

This comment has been minimized.

Sign in to view

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

Open

This comment has been minimized.

Sign in to view

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

This comment has been minimized.

Sign in to view

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

This comment has been minimized.

Sign in to view

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

This comment has been minimized.

Sign in to view

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

rust-bors Bot pushed a commit that referenced this pull request Aug 15, 2026

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

62cf67c

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

pull Bot pushed a commit to Mattlk13/cargo that referenced this pull request Aug 15, 2026

chore: update to cc@1.4.3

1d19d0c

With this we get remap for free when building in rustc bootstrap: See * rust-lang/rust#161049 * rust-lang#17309

Urgau reviewed Aug 15, 2026

View reviewed changes

This comment has been minimized.

Sign in to view

weihanglo mentioned this pull request Aug 15, 2026

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

Open

weihanglo mentioned this pull request Aug 17, 2026

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

Merged

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

This comment has been minimized.

Sign in to view

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

Uh oh!

Uh oh!

Conversation

weihanglo commented Aug 13, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

What

Uh oh!

weihanglo commented Aug 13, 2026

Uh oh!

This comment has been minimized.

This comment has been minimized.

weihanglo commented Aug 13, 2026

Uh oh!

rust-bors Bot commented Aug 13, 2026

Uh oh!

weihanglo commented Aug 13, 2026

Uh oh!

This comment has been minimized.

This comment has been minimized.

rust-bors Bot commented Aug 13, 2026

Uh oh!

This comment has been minimized.

weihanglo commented Aug 13, 2026

Uh oh!

This comment has been minimized.

rust-bors Bot commented Aug 13, 2026

Uh oh!

This comment has been minimized.

weihanglo commented Aug 14, 2026

Uh oh!

This comment has been minimized.

rust-bors Bot commented Aug 15, 2026

Uh oh!

Urgau Aug 15, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

weihanglo Aug 15, 2026

Choose a reason for hiding this comment

Uh oh!

Urgau Aug 15, 2026

Choose a reason for hiding this comment

Uh oh!

weihanglo Aug 15, 2026

Choose a reason for hiding this comment

Uh oh!

This comment has been minimized.

weihanglo commented Aug 22, 2026

Uh oh!

This comment has been minimized.

rust-bors Bot commented Aug 22, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

weihanglo commented Aug 13, 2026 •

edited by rustbot

Loading

Urgau Aug 15, 2026 •

edited by rustbot

Loading