Reduce library search path length in new build dir layout by ranger-ross · Pull Request #17191 · rust-lang/cargo

ranger-ross · 2026-07-09T13:52:01Z

What does this PR try to resolve?

This PR addresses #17183 by only adding dylib crates to the library search path (LD_LIBRARY_PATH on linux, PATH on windows)

Previously, deps would be added to the search path. With the new build dir layout, I naively added all out dirs which blew up the search path hitting OS limits.

See #17183 (comment) for more details.

How to test and review this PR?

See the included test. I also verified that Zed now properly compiles with the new build-dir layout (on Linux)

rustbot · 2026-07-09T13:52:06Z

r? @epage

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Owners of files modified in this PR: @ehuss, @epage, @weihanglo
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ranger-ross · 2026-07-11T13:58:29Z

I noticed the test was failing on stable, due to the behavior depending on rust-lang/rust@61f3e08 which still has not landed on stable.
I made the test nightly only until that commit lands on stable rust, in which case we can remove nightly only status

ranger-ross · 2026-07-11T14:01:27Z

Marking this as ready for review, the tests passed in CI and the CI failure appears to just be a spurious 503 from crates.io

weihanglo

Let me know when it is ready (pretty close I believe). Also, if we want to unblock rust-lang/rust#159076 we should do beta backport, right?

View changes since this review

weihanglo · 2026-07-12T05:15:24Z

BTW, I just got another idea: the current deps_output map collects every dylib output dir from every unit in the compilation session, which is not ideal. Some of the unit only need a subtree of it, and would be basically zero dylib path.

Anyway, I believe we don't need to put that much effort on this becuase dylibs are not that common as dependencies.

Hmmm yeah, good point. I probably added unit_graph.iter() to cast a wide net as possible.
I think we could construct lists per Unit instead of CompileKind.

Though, like you mentioned, dylibs usually don't make up a large percent of the crate graph so not sure if the effort for that optimization would be worth it

… the current target

ranger-ross · 2026-07-12T06:04:47Z

Let me know when it is ready (pretty close I believe). Also, if we want to unblock rust-lang/rust#159076 we should do beta backport, right?

I think its ready if it looks good to you.
Yeah, I think this will need to be backported.

I can raise a PR for that was well

weihanglo

Thanks!

Yeah would be nice to have a beta backport.

View changes since this review

@weihanglo

Backports: * #17191 * #17168 * #17179 Was only planning to backport #17191 but it builds on tests added in #17168 so was getting merge conflicts. Given they are both bug fixes and the new build-dir layout is still unstable, I figured it would be simpler to backport both fixes. r? @weihanglo

Update cargo submodule 29 commits in 59800466c5c41c444d264b1010b4d57e85a7117f..3efb1f477e99b42974b982d939fd100303cdf7db 2026-07-07 15:52:22 +0000 to 2026-07-17 23:53:19 +0000 - refactor(context): normalize in `homedir` instead (rust-lang/cargo#17222) - chore(ci): reflect doc folder move in book deployment (rust-lang/cargo#17235) - refactor(ops): Have cargo-metadata's ops match the command name (rust-lang/cargo#17233) - chore: Flatten src (rust-lang/cargo#17231) - chore: Flatten `src` (rust-lang/cargo#17230) - chore(ci): remove stale libsecret packages (rust-lang/cargo#17229) - perf: Lazily initialize git2 fetch transports (rust-lang/cargo#17226) - test(trim-paths): re-enable lldb debugger tests (rust-lang/cargo#17223) - Include SBOM outputs in fingerprints (rust-lang/cargo#17216) - Update cfg_aliases to 0.2.2 (rust-lang/cargo#17225) - test(trim-paths): exercise GDB on windows-gnu (rust-lang/cargo#17221) - feat(profile): Disable incremental compilation under CI by default (rust-lang/cargo#17220) - Remove myself from review rotation (rust-lang/cargo#17219) - Fix typo in comment in sync (rust-lang/cargo#17217) - docs(ref): Improve handing of built-in profiles (rust-lang/cargo#17213) - fix: dont apply host-config gating to stable behavior (rust-lang/cargo#17198) - chore(deps): update msrv (rust-lang/cargo#17192) - test: fix race in cargo_compile_with_invalid_code_in_deps (rust-lang/cargo#17203) - Rename `-Zno-embed-metadata` to `-Zembed-metadata=no` (rust-lang/cargo#17149) - fix(source): incorrect duplicate package warning (rust-lang/cargo#17204) - Fix manifest schema generation: `TomlDebugInfo` enum-variants doesn't renamed (rust-lang/cargo#17202) - Reduce library search path length in new build dir layout (rust-lang/cargo#17191) - fix(install): Move --debug to Compilation options (rust-lang/cargo#17199) - chore(ci): dogfood `build.warnings` (rust-lang/cargo#17195) - docs(lints): Better match clippy in lint section titles (rust-lang/cargo#17190) - chore: bump to 0.100.0; update changelog (rust-lang/cargo#17189) - docs(ref): Clarify MSRV for lints (rust-lang/cargo#17184) - docs(report): add missing entry for `cargo report future-incompatibilities` (rust-lang/cargo#17188) - Reduce rustc `-L` args used in the new `build-dir` layout (rust-lang/cargo#17168)

rustbot assigned epage Jul 9, 2026

rustbot added A-build-execution Area: anything dealing with executing the compiler S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 9, 2026

weihanglo reviewed Jul 9, 2026

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Comment thread tests/testsuite/build.rs

ranger-ross marked this pull request as draft July 11, 2026 01:03

rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 11, 2026

This was referenced Jul 11, 2026

Bump bootstrap to 1.98 beta rust-lang/rust#158888

Merged

dist-i686-msvc fails with STATUS_NO_MEMORY rust-lang/rust#159076

Open

ranger-ross force-pushed the reduce-ld-lib-path branch from 0b2d470 to 1411fd1 Compare July 11, 2026 13:35

ranger-ross changed the title ~~Reduce library search path length in build dir layout~~ Reduce library search path length in new build dir layout Jul 11, 2026

ranger-ross marked this pull request as ready for review July 11, 2026 14:00

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 11, 2026

weihanglo reviewed Jul 11, 2026

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Comment thread src/cargo/core/compiler/build_runner/mod.rs

Comment thread tests/testsuite/build.rs Outdated

Comment thread src/cargo/core/compiler/build_runner/mod.rs

ranger-ross mentioned this pull request Jul 12, 2026

build-dir legacy layout post stablization cleanup #17182

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weihanglo reviewed Jul 12, 2026

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Comment thread src/cargo/core/compiler/build_runner/mod.rs

ranger-ross force-pushed the reduce-ld-lib-path branch 2 times, most recently from 22939b2 to 50d9cbf Compare July 12, 2026 05:00

weihanglo reviewed Jul 12, 2026

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ranger-ross added 4 commits July 12, 2026 14:49

test: Added test to verify library search path has correct paths

18c88e7

fix: Only add dylib dependencies to library search path

d87df4c

test: Added test to verify cross target search paths behavior

09793a2

fix: Do not add unit output to search for units that do not belong to…

1b4c3e8

… the current target

ranger-ross force-pushed the reduce-ld-lib-path branch from 50d9cbf to 1b4c3e8 Compare July 12, 2026 05:52

weihanglo approved these changes Jul 12, 2026

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weihanglo added this pull request to the merge queue Jul 12, 2026

Merged via the queue into rust-lang:master with commit 6ff645c Jul 12, 2026
29 checks passed

rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 12, 2026

weihanglo added the beta-nominated Nominated to backport to the beta branch. label Jul 12, 2026

ranger-ross mentioned this pull request Jul 12, 2026

[beta 1.98] Backport new build-dir layout bug fixes #17207

Merged

ranger-ross mentioned this pull request Jul 17, 2026

Zed cannot be compiled with the new build dir layout #17183

Closed

weihanglo mentioned this pull request Jul 18, 2026

Update cargo submodule rust-lang/rust#159475

Merged

rustbot added this to the 1.99.0 milestone Jul 18, 2026

ranger-ross mentioned this pull request Jul 20, 2026

Re-organize build-dir by package + hash, rather than artifact type #15010

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Reduce library search path length in new build dir layout#17191

Reduce library search path length in new build dir layout#17191
weihanglo merged 4 commits into
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ranger-ross:reduce-ld-lib-path

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