Isolate build script metadata progation between std and non-std crates#16489

ranger-ross · 2026-01-09T02:46:18Z

What does this PR try to resolve?

This PR fixes a regression found in rust-lang/rust#150739 that was introduced in #16436.

For -Zbuild-std std dependencies, we would panic due to the dependency not being present in Cargo.toml.
~~This PR adds handling fallback to the unit.pkg.name() if the unit both not present in Cargo.toml and is_std.~~ (see #16489 (comment))

This PR ensures that metadata propagation is only allowed between std->std crates and non-std->non-std crates.

How to test and review this PR?

cargo new foo
cd foo
cargo add cortex-m
cargo -Zbuild-std build

Previously we panic with

thread 'main' (4072127) panicked at src/cargo/core/compiler/custom_build.rs:472:21:
Dependency `compiler_builtins` not found in `foo`s dependencies
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

with this change we not compile successfully

r? @weihanglo

weihanglo · 2026-01-09T02:49:13Z

src/cargo/core/compiler/custom_build.rs

+                            // If the depenency is a build-std dependency, it might not be in
+                            // Cargo.toml. If its not present, we simply use the package name as we
+                            // know its not renamed.


See rust-lang/rust#150739 (comment)

Though they are not using any dep link metadata at this moment.

(I am a bit paranoid, sorry 😬)

I guess we can go the .filter() route mentioned in rust-lang/rust#150739 (comment) for now just to be safe?

That disables dep metadata propagation for the entire std graph, no?

Probably this filter(|dep| dep.unit.is_std == unit.is_std)?

ahh so allow propagation for std crate -> std crate but not std crate -> user crate?

I wonder if any std crates use the build std magic not include the dependencies in their Cargo.toml?
Hopefully not?

I wonder if any std crates use the build std magic not include the dependencies in Cargo.toml?

I guess not. std bootstrap doesn't use -Zbuild-std. It would be awkward if someone forked std and relied on -Zbuild-std attaching std root units to std units itself.

Updated the impl to add the std/nonstd boundary, as well as the PR tilte+description.

…crates

weihanglo

Thanks!

I guess it is fine we have no test for this because we are seeing more -Zbuild-std test in rust-lang/rust

View changes since this review

Update cargo submodule 27 commits in 94c368ad2b9db0f0da5bdd8421cea13786ce4412..8c133afcd5e0d69932fe11f5907683723f8d361d 2025-12-26 19:39:15 +0000 to 2026-01-09 03:50:15 +0000 - Isolate build script metadata progation between std and non-std crates (rust-lang/cargo#16489) - Add Clippy like lint groups (rust-lang/cargo#16464) - feat: in-memory only `Manifest` (rust-lang/cargo#16409) - Fixed incorrect version comparision during build script dependency selection (rust-lang/cargo#16486) - refactor: new type for unit index (rust-lang/cargo#16485) - feat(test): Make CARGO_BIN_EXE_ available at runtime (rust-lang/cargo#16421) - fix(package): detect dirty files when run from workspace member (rust-lang/cargo#16479) - fix(timing)!: remove `--timings=<FMT>` optional format values (rust-lang/cargo#16420) - docs(unstable): expand docs for `-Zbuild-analysis` (rust-lang/cargo#16476) - test: add `-Zunstable-options` with custom targets (rust-lang/cargo#16467) - feat(report): add cargo report rebuilds (rust-lang/cargo#16456) - feat(test-support): Use test name for dir when running tests (rust-lang/cargo#16121) - refactor: Migrate some cases to expect/reason (rust-lang/cargo#16461) - docs(build-script): clarify OUT_DIR is not cleaned between builds (rust-lang/cargo#16437) - chore: Update dependencies (rust-lang/cargo#16460) - Update handlebars to 6.4.0 (rust-lang/cargo#16457) - chore(deps): update alpine docker tag to v3.23 (rust-lang/cargo#16454) - Any build scripts can now use cargo::metadata=KEY=VALUE (rust-lang/cargo#16436) - fix(log): add `dependencies` field to `UnitRegistered` (rust-lang/cargo#16448) - Implement fine grain locking for `build-dir` (rust-lang/cargo#16155) - feat(resolver): List features when no close match (rust-lang/cargo#16445) - feat(report): new command `cargo report sessions` (rust-lang/cargo#16428) - feat (patch): Display where the patch was defined in patch-related error messages (rust-lang/cargo#16407) - test(build-rs): Reduce from 'build' to 'check' where possible (rust-lang/cargo#16444) - feat(toml): TOML 1.1 parse support (rust-lang/cargo#16415) - feat(report): support --manifest-path in `cargo report timings` (rust-lang/cargo#16441) - fix(vendor): recursively filter git files in subdirectories (rust-lang/cargo#16439)

This reverts rust-lang#16489 though currently only compiler_builtins has link metadata `-Zany-build-script-metadata` is not supported yet for build-std

Update cargo submodule 27 commits in 94c368ad2b9db0f0da5bdd8421cea13786ce4412..8c133afcd5e0d69932fe11f5907683723f8d361d 2025-12-26 19:39:15 +0000 to 2026-01-09 03:50:15 +0000 - Isolate build script metadata progation between std and non-std crates (rust-lang/cargo#16489) - Add Clippy like lint groups (rust-lang/cargo#16464) - feat: in-memory only `Manifest` (rust-lang/cargo#16409) - Fixed incorrect version comparision during build script dependency selection (rust-lang/cargo#16486) - refactor: new type for unit index (rust-lang/cargo#16485) - feat(test): Make CARGO_BIN_EXE_ available at runtime (rust-lang/cargo#16421) - fix(package): detect dirty files when run from workspace member (rust-lang/cargo#16479) - fix(timing)!: remove `--timings=<FMT>` optional format values (rust-lang/cargo#16420) - docs(unstable): expand docs for `-Zbuild-analysis` (rust-lang/cargo#16476) - test: add `-Zunstable-options` with custom targets (rust-lang/cargo#16467) - feat(report): add cargo report rebuilds (rust-lang/cargo#16456) - feat(test-support): Use test name for dir when running tests (rust-lang/cargo#16121) - refactor: Migrate some cases to expect/reason (rust-lang/cargo#16461) - docs(build-script): clarify OUT_DIR is not cleaned between builds (rust-lang/cargo#16437) - chore: Update dependencies (rust-lang/cargo#16460) - Update handlebars to 6.4.0 (rust-lang/cargo#16457) - chore(deps): update alpine docker tag to v3.23 (rust-lang/cargo#16454) - Any build scripts can now use cargo::metadata=KEY=VALUE (rust-lang/cargo#16436) - fix(log): add `dependencies` field to `UnitRegistered` (rust-lang/cargo#16448) - Implement fine grain locking for `build-dir` (rust-lang/cargo#16155) - feat(resolver): List features when no close match (rust-lang/cargo#16445) - feat(report): new command `cargo report sessions` (rust-lang/cargo#16428) - feat (patch): Display where the patch was defined in patch-related error messages (rust-lang/cargo#16407) - test(build-rs): Reduce from 'build' to 'check' where possible (rust-lang/cargo#16444) - feat(toml): TOML 1.1 parse support (rust-lang/cargo#16415) - feat(report): support --manifest-path in `cargo report timings` (rust-lang/cargo#16441) - fix(vendor): recursively filter git files in subdirectories (rust-lang/cargo#16439)

This reverts rust-lang#16489 though currently only compiler_builtins has link metadata `-Zany-build-script-metadata` is not supported yet for build-std

### What does this PR try to resolve? This reverts #16489 though currently only compiler_builtins has link metadata `-Zany-build-script-metadata` is not supported yet for build-std ### How to test and review this PR? Test passes.

Update cargo submodule 27 commits in 94c368ad2b9db0f0da5bdd8421cea13786ce4412..8c133afcd5e0d69932fe11f5907683723f8d361d 2025-12-26 19:39:15 +0000 to 2026-01-09 03:50:15 +0000 - Isolate build script metadata progation between std and non-std crates (rust-lang/cargo#16489) - Add Clippy like lint groups (rust-lang/cargo#16464) - feat: in-memory only `Manifest` (rust-lang/cargo#16409) - Fixed incorrect version comparision during build script dependency selection (rust-lang/cargo#16486) - refactor: new type for unit index (rust-lang/cargo#16485) - feat(test): Make CARGO_BIN_EXE_ available at runtime (rust-lang/cargo#16421) - fix(package): detect dirty files when run from workspace member (rust-lang/cargo#16479) - fix(timing)!: remove `--timings=<FMT>` optional format values (rust-lang/cargo#16420) - docs(unstable): expand docs for `-Zbuild-analysis` (rust-lang/cargo#16476) - test: add `-Zunstable-options` with custom targets (rust-lang/cargo#16467) - feat(report): add cargo report rebuilds (rust-lang/cargo#16456) - feat(test-support): Use test name for dir when running tests (rust-lang/cargo#16121) - refactor: Migrate some cases to expect/reason (rust-lang/cargo#16461) - docs(build-script): clarify OUT_DIR is not cleaned between builds (rust-lang/cargo#16437) - chore: Update dependencies (rust-lang/cargo#16460) - Update handlebars to 6.4.0 (rust-lang/cargo#16457) - chore(deps): update alpine docker tag to v3.23 (rust-lang/cargo#16454) - Any build scripts can now use cargo::metadata=KEY=VALUE (rust-lang/cargo#16436) - fix(log): add `dependencies` field to `UnitRegistered` (rust-lang/cargo#16448) - Implement fine grain locking for `build-dir` (rust-lang/cargo#16155) - feat(resolver): List features when no close match (rust-lang/cargo#16445) - feat(report): new command `cargo report sessions` (rust-lang/cargo#16428) - feat (patch): Display where the patch was defined in patch-related error messages (rust-lang/cargo#16407) - test(build-rs): Reduce from 'build' to 'check' where possible (rust-lang/cargo#16444) - feat(toml): TOML 1.1 parse support (rust-lang/cargo#16415) - feat(report): support --manifest-path in `cargo report timings` (rust-lang/cargo#16441) - fix(vendor): recursively filter git files in subdirectories (rust-lang/cargo#16439)

rustbot assigned weihanglo Jan 9, 2026

rustbot added A-build-scripts Area: build.rs scripts S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jan 9, 2026

ranger-ross mentioned this pull request Jan 9, 2026

Update cargo submodule rust-lang/rust#150739

Merged

weihanglo reviewed Jan 9, 2026

View reviewed changes

fix: Isolate build script metadata progation between std and non-std …

d5c1597

…crates

ranger-ross force-pushed the fix-build-std branch from 91f7862 to d5c1597 Compare January 9, 2026 03:19

ranger-ross changed the title ~~fix: Added handling for build-std when preparing build-script metadata~~ Isolate build script metadata progation between std and non-std crates Jan 9, 2026

weihanglo approved these changes Jan 9, 2026

View reviewed changes

weihanglo enabled auto-merge January 9, 2026 03:30

weihanglo added this pull request to the merge queue Jan 9, 2026

Merged via the queue into rust-lang:master with commit 8c133af Jan 9, 2026
29 checks passed

rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jan 9, 2026

rustbot added this to the 1.94.0 milestone Jan 9, 2026

ranger-ross mentioned this pull request Jan 10, 2026

custom_build.rs regression: Dependency not found in dependencies #16493

Closed

weihanglo added a commit to weihanglo/cargo that referenced this pull request Jan 10, 2026

test(build-std): regression test for rust-lang#16489

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weihanglo added a commit to weihanglo/cargo that referenced this pull request Jan 10, 2026

test(build-std): regression test for rust-lang#16489

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weihanglo mentioned this pull request Jan 10, 2026

fix(build-std): std link metadata propagate to user #16496

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weihanglo added a commit to weihanglo/cargo that referenced this pull request Jan 10, 2026

test(build-std): regression test for rust-lang#16489

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weihanglo added a commit to weihanglo/cargo that referenced this pull request Jan 12, 2026

test(build-std): regression test for rust-lang#16489

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Isolate build script metadata progation between std and non-std crates#16489

Isolate build script metadata progation between std and non-std crates#16489
weihanglo merged 1 commit intorust-lang:masterfrom
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