Don't leak sysroot crates through dependencies #149273

bjorn3 · 2025-11-24T15:31:01Z

Previously if a dependency of the current crate depended on a sysroot crate, then extern crate would in the current crate would pick the first loaded version of said sysroot crate even in case of an ambiguity. This is surprising and brittle. For -Ldependency= we already blocked this since #110229, but the fix didn't account for sysroot crates.

Should fix #147966

Previously if a dependency of the current crate depended on a sysroot crate, then extern crate would in the current crate would pick the first loaded version of said sysroot crate even in case of an ambiguity. This is surprising and brittle. For -Ldependency= we already blocked this, but the fix didn't account for sysroot crates.

rustbot · 2025-11-24T15:31:07Z

r? @chenyukang

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rustbot · 2025-11-24T19:22:44Z

The Miri subtree was changed

cc @rust-lang/miri

bjorn3 · 2025-11-24T21:24:27Z

We end up with two copies of rustc_macros in the stage1 sysroot. librustc_macros-ec6b51dc176f057f.so and librustc_macros.so. find build -iname 'librustc_macros*' | sort shows

build/aarch64-unknown-linux-gnu/stage0-sysroot/lib/rustlib/aarch64-unknown-linux-gnu/lib/librustc_macros-60ab85e5fc9a97c5.so
build/aarch64-unknown-linux-gnu/stage1-rustc-rmeta-artifacts/host/librustc_macros-60ab85e5fc9a97c5.so
build/aarch64-unknown-linux-gnu/stage1-rustc/release/deps/librustc_macros-60ab85e5fc9a97c5.so
build/aarch64-unknown-linux-gnu/stage1/lib/rustlib/aarch64-unknown-linux-gnu/lib/librustc_macros-ec6b51dc176f057f.so
build/aarch64-unknown-linux-gnu/stage1/lib/rustlib/aarch64-unknown-linux-gnu/lib/librustc_macros.so
build/aarch64-unknown-linux-gnu/stage2-rustc/release/deps/librustc_macros-7577fab33cd32388.so
build/aarch64-unknown-linux-gnu/stage2-rustc/release/deps/librustc_macros-ec6b51dc176f057f.so
build/aarch64-unknown-linux-gnu/stage2-rustc/release/librustc_macros.d
build/aarch64-unknown-linux-gnu/stage2-rustc/release/librustc_macros.so
build/aarch64-unknown-linux-gnu/stage2/lib/librustc_macros.so

     Running `/home/gh-bjorn3/rust/build/bootstrap/debug/rustc /home/gh-bjorn3/rust/build/bootstrap/debug/rustc --crate-name rustc_macros --edition=2024 compiler/rustc_macros/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --diagnostic-width=189 --crate-type proc-macro --emit=dep-info,link -C prefer-dynamic -C embed-bitcode=no -C debuginfo=1 -C overflow-checks=off --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values())' -C metadata=be7e7ca919dfe741 -C extra-filename=-ec6b51dc176f057f --out-dir /home/gh-bjorn3/rust/build/aarch64-unknown-linux-gnu/stage2-rustc/release/deps -L dependency=/home/gh-bjorn3/rust/build/aarch64-unknown-linux-gnu/stage2-rustc/release/deps --extern proc_macro2=/home/gh-bjorn3/rust/build/aarch64-unknown-linux-gnu/stage2-rustc/release/deps/libproc_macro2-f1b117abea6fea0b.rlib --extern quote=/home/gh-bjorn3/rust/build/aarch64-unknown-linux-gnu/stage2-rustc/release/deps/libquote-2b307f2bbd14d75c.rlib --extern syn=/home/gh-bjorn3/rust/build/aarch64-unknown-linux-gnu/stage2-rustc/release/deps/libsyn-dacac49cff7dc945.rlib --extern synstructure=/home/gh-bjorn3/rust/build/aarch64-unknown-linux-gnu/stage2-rustc/release/deps/libsynstructure-62471687b53f2245.rlib --extern proc_macro -Z binary-dep-depinfo`
     Running `/home/gh-bjorn3/rust/build/bootstrap/debug/rustc /home/gh-bjorn3/rust/build/bootstrap/debug/rustc --crate-name rustc_macros --edition=2024 compiler/rustc_macros/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --diagnostic-width=189 --crate-type proc-macro --emit=dep-info,link -C prefer-dynamic -C opt-level=3 -C embed-bitcode=no -C debuginfo=1 -C debug-assertions=on -C overflow-checks=off --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values())' -C metadata=5ad205a615dda1e1 -C extra-filename=-7577fab33cd32388 --out-dir /home/gh-bjorn3/rust/build/aarch64-unknown-linux-gnu/stage2-rustc/release/deps -L dependency=/home/gh-bjorn3/rust/build/aarch64-unknown-linux-gnu/stage2-rustc/release/deps --extern proc_macro2=/home/gh-bjorn3/rust/build/aarch64-unknown-linux-gnu/stage2-rustc/release/deps/libproc_macro2-f1b117abea6fea0b.rlib --extern quote=/home/gh-bjorn3/rust/build/aarch64-unknown-linux-gnu/stage2-rustc/release/deps/libquote-2b307f2bbd14d75c.rlib --extern syn=/home/gh-bjorn3/rust/build/aarch64-unknown-linux-gnu/stage2-rustc/release/deps/libsyn-dacac49cff7dc945.rlib --extern synstructure=/home/gh-bjorn3/rust/build/aarch64-unknown-linux-gnu/stage2-rustc/release/deps/libsynstructure-62471687b53f2245.rlib --extern proc_macro -Z binary-dep-depinfo`

I suspect cargo decided to built rustc_macros once as build dependency without optimizations and once as output artifact with optimizations because bootstrap passed -p rustc_macros.

compiler/rustc_metadata/src/creader.rs

compiler/rustc_metadata/src/locator.rs

bjorn3 · 2025-11-27T13:59:35Z

Checking how important the --extern fast path in existing_match is.

@bors try @rust-timer queue

Don't leak sysroot crates through dependencies

rust-bors · 2025-11-27T16:21:46Z

☀️ Try build successful (CI)
Build commit: c77897e (c77897e64048c8406614d7cc2520bd22084bf335, parent: 7b9905edb4df3aeaabd0d6cd0d4c09b183d7d965)

rust-timer · 2025-11-27T17:40:42Z

Finished benchmarking commit (c77897e): comparison URL.

Overall result: ✅ improvements - no action needed

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

@bors rollup=never
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.1%	[0.1%, 0.1%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.4%	[-2.7%, -0.4%]	9
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary -0.3%, secondary -5.4%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	1.5%	[1.5%, 1.5%]	1
Regressions ❌ (secondary)	4.8%	[4.8%, 4.8%]	1
Improvements ✅ (primary)	-2.1%	[-2.1%, -2.1%]	1
Improvements ✅ (secondary)	-7.9%	[-11.5%, -0.6%]	4
All ❌✅ (primary)	-0.3%	[-2.1%, 1.5%]	2

Cycles

Results (primary -2.0%, secondary 3.6%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.6%	[2.6%, 4.6%]	2
Improvements ✅ (primary)	-2.0%	[-2.1%, -1.9%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.0%	[-2.1%, -1.9%]	2

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 470.06s -> 469.991s (-0.01%)
Artifact size: 386.96 MiB -> 386.96 MiB (-0.00%)

bjorn3 · 2025-11-27T18:08:20Z

That turns out to be much better than I expected. It is a small perf win rather than a perf hit as I was afraid of. I've now cleaned up existing_match and made it immediately return None when no crate hash is given rather than still iterating over all crates, which should improve perf even more.

@rustbot ready

petrochenkov · 2025-11-28T12:18:53Z

Very nice.
@bors r+

bors · 2025-11-28T12:18:55Z

📌 Commit 871ec86 has been approved by petrochenkov

It is now in the queue for this repository.

bjorn3 · 2025-11-28T20:58:29Z

Oops, pushed to the wrong branch. Force pushed it back to the approved state.

@bors r=petrochenkov

bors · 2025-11-28T20:58:31Z

📌 Commit 871ec86 has been approved by petrochenkov

It is now in the queue for this repository.

…nkov Don't leak sysroot crates through dependencies Previously if a dependency of the current crate depended on a sysroot crate, then `extern crate` would in the current crate would pick the first loaded version of said sysroot crate even in case of an ambiguity. This is surprising and brittle. For `-Ldependency=` we already blocked this since #110229, but the fix didn't account for sysroot crates. Should fix #147966

bors · 2025-11-29T08:31:02Z

⌛ Testing commit 871ec86 with merge 8626569...

bors · 2025-11-29T09:00:02Z

💔 Test failed - checks-actions

…rate check

bjorn3 · 2025-11-29T09:07:12Z

@bors try jobs=dist-x86_64-msvc

Don't leak sysroot crates through dependencies try-job: dist-x86_64-msvc

rust-bors · 2025-11-29T11:51:02Z

☀️ Try build successful (CI)
Build commit: cee9c81 (cee9c8136595e0372e7b7e4f302efb0e26488aa5, parent: 3c5c55864f8f441054730037bc9f9901f9151398)

bjorn3 · 2025-11-29T14:51:08Z

@rustbot ready

petrochenkov · 2025-11-29T15:06:33Z

@bors r+

bors · 2025-11-29T15:06:35Z

📌 Commit 1ba6869 has been approved by petrochenkov

It is now in the queue for this repository.

…nkov Don't leak sysroot crates through dependencies Previously if a dependency of the current crate depended on a sysroot crate, then `extern crate` would in the current crate would pick the first loaded version of said sysroot crate even in case of an ambiguity. This is surprising and brittle. For `-Ldependency=` we already blocked this since #110229, but the fix didn't account for sysroot crates. Should fix #147966

bors · 2025-11-29T23:42:38Z

⌛ Testing commit 1ba6869 with merge f480fb1...

rust-log-analyzer · 2025-11-30T00:27:20Z

The job dist-powerpc64le-linux-gnu failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

bors · 2025-11-30T00:28:12Z

💔 Test failed - checks-actions

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tests/ui/allocator/no_std-alloc-error-handler* fail when download-rustc is enabled #108767

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bjorn3 force-pushed the crate_locator_improvements branch from 8d439c2 to f0a26f2 Compare November 25, 2025 12:34

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Auto merge of #149273 - bjorn3:crate_locator_improvements, r=<try>

c77897e

Don't leak sysroot crates through dependencies

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bjorn3 force-pushed the crate_locator_improvements branch from ac0aabb to e58a6df Compare November 27, 2025 18:07

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Handle windows producing two files for every dylib in the duplicate c…

1ba6869

…rate check

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Auto merge of #149273 - bjorn3:crate_locator_improvements, r=<try>

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Don't leak sysroot crates through dependencies try-job: dist-x86_64-msvc

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regression: ICE no resolution found for import #147966

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Overall result: ✅ improvements - no action needed

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