Fix vec iter zst alignment #149272

DrAsu33 · 2025-11-24T15:05:24Z

rustbot · 2025-11-24T15:05:27Z

This PR modifies tests/ui/issues/. If this PR is adding new tests to tests/ui/issues/,
please refrain from doing so, and instead add it to more descriptive subdirectories.

rustbot · 2025-11-24T15:05:29Z

r? @fee1-dead

rustbot has assigned @fee1-dead.
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reddevilmidzy · 2025-11-24T16:39:47Z

tests/ui/issues/issue-zst-nthback-148682.rs

It looks like the file name needs to be changed.

https://rustc-dev-guide.rust-lang.org/tests/best-practices.html#test-naming

Instead of using the issues directory, please refer to this and choose a more appropriate location.

reddevilmidzy · 2025-11-24T16:46:03Z

tests/ui/issues/issue-148682.rs

@@ -0,0 +1,9 @@
+// check-pass


Suggested change

// check-pass

//@ check-pass

Kivooeo · 2025-11-24T23:44:55Z

r? libs

DrAsu33 · 2025-11-25T01:35:08Z

@reddevilmidzy Thanks! Updated as requested.

reddevilmidzy

and please squash

View changes since this review

reddevilmidzy · 2025-11-25T02:19:32Z

tests/ui/issues/issue-zst-nthback-148682.rs

+// @ check-pass
+//test Intolter::nth_back does not cause UB for ZSTs with high alignment


Please remove leading spaces from commands, and add a space before comments.

Suggested change

// @ check-pass

//test Intolter::nth_back does not cause UB for ZSTs with high alignment

//@ check-pass

// test Intolter::nth_back does not cause UB for ZSTs with high alignment

Thanks！It seems that all the CI tests are passed

reddevilmidzy · 2025-11-25T02:23:42Z

tests/ui/issues/issue-zst-nthback-148682.rs

Instead of using the issues directory, please refer to this and choose a more appropriate location.

library/alloc/src/vec/into_iter.rs

reddevilmidzy · 2025-11-25T15:02:39Z

Could you please add close: #148682 to the PR description?(without backtick) GitHub will then automatically close the issue.
and please squash

rustbot · 2025-11-26T00:36:29Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

DrAsu33 · 2025-11-28T01:37:01Z

@rustbot ready

RalfJung · 2025-11-29T09:12:42Z

library/alloctests/tests/vec.rs

+// Regression test for Undefined Behavior (UB) caused by IntoIter::nth_back (#148682)
+// when dealing with high-aligned Zero-Sized Types (ZSTs).
 #[test] 
 #[cfg(miri)] 


Why do you only enable this test in Miri?

Sorry, I thought that the UB could only be detected by miri. I have modified that.

Yeah, only Miri will detect UB. But the test should still pass without Miri, and in particular this enures it gets type-checked.

RalfJung · 2025-11-29T09:20:07Z

Also, please run ./x test tidy --bless before committing. No need to wait for CI for simple tidy issues. :)

DrAsu33 · 2025-12-03T07:22:21Z

Builds are green and I've addressed all feedback (moved test to library/alloc/tests/vec.rs).

@rustbot ready

Mark-Simulacrum

r=me with extra tests added

View changes since this review

rustbot · 2025-12-08T00:29:34Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

Mark-Simulacrum · 2025-12-08T00:29:50Z

library/alloctests/tests/vec.rs

+// Regression test for Undefined Behavior (UB) caused by IntoIter::nth_back (#148682)
+// when dealing with high-aligned Zero-Sized Types (ZSTs).
+#[test]
+fn zst_vec_iter_nth_back_regression() {


Can you add tests for other collections that I suspect may well have the same bug? At the very least VecDeque, BTreeMap, HashMap, and BinaryHeap all seem likely to be potentially at risk.

This commit consolidates all changes, including the core logic fix for IntoIter::nth_back and the addition of the Miri regression test in `library/alloctests/tests/vec.rs`, to prevent Undefined Behavior (UB) when dealing with highly-aligned Zero-Sized Types.

DrAsu33 · 2025-12-09T10:20:13Z

Thanks for the review! @Mark-Simulacrum I've addressed your comments and pushed the changes. Let me know if there's anything else needed.
@rustbot ready

Mark-Simulacrum · 2025-12-13T22:21:36Z

@bors r+

bors · 2025-12-13T22:21:39Z

📌 Commit 34392a9 has been approved by Mark-Simulacrum

It is now in the queue for this repository.

…-148682, r=Mark-Simulacrum Fix vec iter zst alignment Closes rust-lang#148682

Rollup of 8 pull requests Successful merges: - #148755 (Constify `DropGuard::dismiss` and trait impls) - #148825 (Add SystemTime::{MIN, MAX}) - #149272 (Fix vec iter zst alignment) - #149417 (tidy: Detect outdated workspaces in workspace list) - #149437 (Fix trailing newline in JUnit formatter) - #149773 (fix va_list test by adding a llvmir signext check) - #149894 (Update to mdbook 0.5) - #149955 (Fix typo in armv7a-vex-v5 documentation) r? `@ghost` `@rustbot` modify labels: rollup

…-148682, r=Mark-Simulacrum Fix vec iter zst alignment Closes rust-lang#148682

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Nov 24, 2025

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library/alloc/src/vec/into_iter.rs Outdated Show resolved Hide resolved

Kivooeo changed the title ~~Fix vec iter zst alignment 148682~~ Fix vec iter zst alignment Nov 25, 2025

DrAsu33 force-pushed the fix-vec-iter-zst-alignment-148682 branch from ceb3c6f to 069f53f Compare November 26, 2025 00:36

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DrAsu33 force-pushed the fix-vec-iter-zst-alignment-148682 branch from 069f53f to d94bb76 Compare November 26, 2025 00:39

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DrAsu33 force-pushed the fix-vec-iter-zst-alignment-148682 branch from e608b3a to ef2ceec Compare November 29, 2025 11:38

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DrAsu33 force-pushed the fix-vec-iter-zst-alignment-148682 branch from ef2ceec to 89b4b30 Compare November 29, 2025 11:44

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DrAsu33 force-pushed the fix-vec-iter-zst-alignment-148682 branch from a246d47 to 34392a9 Compare December 9, 2025 07:57

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ChrisDenton added a commit to ChrisDenton/rust that referenced this pull request Dec 14, 2025

Rollup merge of rust-lang#149272 - DrAsu33:fix-vec-iter-zst-alignment…

22df403

…-148682, r=Mark-Simulacrum Fix vec iter zst alignment Closes rust-lang#148682

ChrisDenton mentioned this pull request Dec 14, 2025

Rollup of 8 pull requests #149975

Closed

ChrisDenton added a commit to ChrisDenton/rust that referenced this pull request Dec 14, 2025

Rollup merge of rust-lang#149272 - DrAsu33:fix-vec-iter-zst-alignment…

735c45e

…-148682, r=Mark-Simulacrum Fix vec iter zst alignment Closes rust-lang#148682

ChrisDenton mentioned this pull request Dec 14, 2025

Rollup of 8 pull requests #149979

Open

		// @ check-pass
		//test Intolter::nth_back does not cause UB for ZSTs with high alignment

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Fix vec iter zst alignment #149272

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Fix vec iter zst alignment #149272

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