fix panic when rustc tries to reduce intermediate filenames len with utf8 by tardyp · Pull Request #148018 · rust-lang/rust

tardyp · 2025-10-23T08:26:19Z

The issue cannot be reproduced with the former testcase of creating external crates because rust refuses to use "external crate 28_找出字符串中第一个匹配项的下标" because it is not a valid indentifier (starts with number, and contain non ascii chars)

But still using 28_找出字符串中第一个匹配项的下标.rs as a filename is accepted by previous rustc releases So we consider it valid, and add an integration test for it to catch any regression on other code related to non ascii filenames.

Fix#147975

rustbot · 2025-10-23T08:26:23Z

r? @jieyouxu

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tardyp · 2025-10-23T08:37:40Z

not sure of the process for urgent beta fixes.

I uploaded two versions of this patch, this one against master and #148019 against beta

apiraino · 2025-10-23T10:04:41Z

not sure of the process for urgent beta fixes.
I uploaded two versions of this patch, this one against master and #148019 against beta

Thanks @tardyp! Patches for regressions can either be fixed on the master branch (like this one) or directly on the beta branch. In practice I think there is no big difference; fixing stuff on master obviously needs a backport patch to beta (which you have already submitted).

In both case they are nominated for backport approval (see docs) and discussed during the weekly T-compiler triage meeting (in ~4 hours from now 🙂 )

jieyouxu · 2025-10-23T10:28:10Z

r? compiler (wont get to this soon)

Noratrieb · 2025-10-23T11:05:39Z

I've nominates this one for backport and will close the other PR to follow our standard process of nominating PRs against master and then letting the release team cherry pick approved backports. Thank you for the quick fix!

JonathanBrouwer · 2025-10-23T11:19:09Z

+ .char_indices()
+ .find(|(i, _)| *i >= stripped_bytes)
+ .map(|(i, _)| i)
+ .unwrap_or(filename.len());


I believe that the 5 lines above are equivalent to:
let split_at = filename.ceil_char_boundary(stripped_bytes);

JonathanBrouwer · 2025-10-23T11:42:18Z

r=me after the comment above is resolved
@rustbot author

rustbot · 2025-10-23T11:51:35Z

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

tardyp · 2025-10-23T12:07:02Z

@rustbot ready

tardyp · 2025-10-23T12:14:53Z

@thanks @JonathanBrouwer for the thoughtful suggestion on this recently out of nightly api.

Note that I took the opportunity of this rework to replace the boring "28_找出字符串中第一个匹配项的下标" by more entertaining "ⴻⵎⵎⴻⵎ_ⴷⵉⵎⴰ_ⵖⴻⴼ_ⵢⵉⵙⴻⴽⴽⵉⵍⴻⵏ_ⵏ_ⵡⴰⵟⴰⵙ_ⵏ_ⵢⵉⴱⵢⵜⴻⵏ" which more adequately watches for multi byte character issues.

JonathanBrouwer · 2025-10-23T13:10:25Z

Thank you so much for the quick fix!
@bors r+ rollup

bors · 2025-10-23T13:10:28Z

📌 Commit a968930 has been approved by JonathanBrouwer

It is now in the queue for this repository.

…th multi byte chars The issue cannot be reproduced with the former testcase of creating external crates because rust refuses to use "external crate 28_找出字符串中第一个匹配项的下标" because it is not a valid indentifier (starts with number, and contain non ascii chars) But still using 28_找出字符串中第一个匹配项的下标.rs as a filename is accepted by previous rustc releases So we consider it valid, and add an integration test for it to catch any regression on other code related to non ascii filenames.

JonathanBrouwer · 2025-10-24T14:24:40Z

@bors try jobs=x86_64-mingw-,i686-msvc-
Would be really suprised if it fails now but lets run it anyways to be sure.
@tardyp Thanks so much for your quick fixes!

fix panic when rustc tries to reduce intermediate filenames len with utf8 try-job: x86_64-mingw-* try-job: i686-msvc-*

tardyp · 2025-10-24T14:37:33Z

I'll be in vacation tomorrow for a week, mostly afk, so I wouldn't be able to be so reactive. hopefully we can finish this today!

rust-bors · 2025-10-24T17:27:57Z

☀️ Try build successful (CI)
Build commit: 3634e54 (3634e54c8b3d8bb839bbda831a265ababb9de237, parent: 8aab621cd56bdc704f73c9d9aaa9f35ab5ee55b0)

cuviper · 2025-10-24T17:37:58Z

Let's boost this so we can get to the beta backport too...

@bors r=JonathanBrouwer p=5

bors · 2025-10-24T17:38:01Z

📌 Commit c6acffe has been approved by JonathanBrouwer

It is now in the queue for this repository.

bors · 2025-10-24T18:23:13Z

⌛ Testing commit c6acffe with merge 2aaa62b...

bors · 2025-10-24T21:38:20Z

☀️ Test successful - checks-actions
Approved by: JonathanBrouwer
Pushing 2aaa62b to master...

github-actions · 2025-10-24T21:41:54Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing ab92564 (parent) -> 2aaa62b (this PR)

Test differences

Show 6 test diffs

Stage 1

[run-make] tests/run-make/lto-long-filenames_cn: [missing] -> pass (J3)

Stage 2

[run-make] tests/run-make/lto-long-filenames_cn: [missing] -> ignore (ignored when cross-compiling) (J0)
[run-make] tests/run-make/lto-long-filenames_cn: [missing] -> ignore (ignored when the operating system and target environment are windows-gnu) (J1)
[run-make] tests/run-make/lto-long-filenames_cn: [missing] -> pass (J2)

Additionally, 2 doctest diffs were found. These are ignored, as they are noisy.

Job group index

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
test-dashboard 2aaa62b89d22b570e560731b03e3d2d6f5c3bbce --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

pr-check-1: 1500.5s -> 1906.0s (27.0%)
x86_64-gnu-miri: 4103.7s -> 4847.8s (18.1%)
x86_64-rust-for-linux: 2461.8s -> 2903.0s (17.9%)
x86_64-gnu-llvm-20-1: 3296.6s -> 3860.5s (17.1%)
x86_64-gnu-debug: 6137.5s -> 7180.2s (17.0%)
x86_64-gnu-gcc: 3033.5s -> 3525.8s (16.2%)
i686-gnu-2: 5392.9s -> 6243.6s (15.8%)
x86_64-gnu-llvm-20: 2428.1s -> 2808.3s (15.7%)
aarch64-gnu: 6019.0s -> 6857.0s (13.9%)
dist-various-1: 3645.2s -> 4134.8s (13.4%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

cuviper · 2025-10-24T22:16:56Z

+ let stripped_bytes = filename.len().saturating_sub(allowed_suffix);
+
+ // ensure we don't cut in a middle of a char
+ let split_at = filename.ceil_char_boundary(stripped_bytes);


FYI, I needed to bootstrap the round_char_boundary feature for this:
1e668e0#diff-a984c7e4fd6f10b956c673e00529f4f80cecdd5572d349ce1fda61b7ce63c5aa
(not a problem, just noting the difference in backport)

rust-timer · 2025-10-24T22:50:33Z

Finished benchmarking commit (2aaa62b): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

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

Max RSS (memory usage)

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

Cycles

Results (secondary -2.0%)

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)	4.8%	[4.8%, 4.8%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.9%	[-3.6%, -1.7%]	7
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 474.337s -> 475.049s (0.15%)
Artifact size: 390.48 MiB -> 390.50 MiB (0.00%)

[beta] backports - Revert constification of `AsRef for Cow` due to inference failure #148011 - Revert constification of `Borrow` and `Deref for Cow` due to inference failure #148016 - Revert "fix: Filter suggestion parts that match existing code" #148043 - Revert "feat: implement `hash_map!` macro" #148049 - fix panic when rustc tries to reduce intermediate filenames len with utf8 #148018 r? cuviper

…thanBrouwer fix panic when rustc tries to reduce intermediate filenames len with utf8 The issue cannot be reproduced with the former testcase of creating external crates because rust refuses to use "external crate 28_找出字符串中第一个匹配项的下标" because it is not a valid indentifier (starts with number, and contain non ascii chars) But still using 28_找出字符串中第一个匹配项的下标.rs as a filename is accepted by previous rustc releases So we consider it valid, and add an integration test for it to catch any regression on other code related to non ascii filenames. Fixrust-lang#147975

rustbot assigned jieyouxu Oct 23, 2025

rustbot added A-run-make Area: port run-make Makefiles to rmake.rs 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. labels Oct 23, 2025

tardyp changed the title ~~fix panic when rustc tries to reduce intermediate filenames length wi…~~fix panic when rustc tries to reduce intermediate filenames len with utf8Oct 23, 2025

rustbot assigned petrochenkov and unassigned jieyouxu Oct 23, 2025

Noratrieb added the beta-nominated Nominated for backporting to the compiler in the beta channel. label Oct 23, 2025

Noratrieb mentioned this pull request Oct 23, 2025
[beta] fix panic when rustc tries to reduce intermediate filenames length #148019
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JonathanBrouwer requested changes Oct 23, 2025
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JonathanBrouwer assigned JonathanBrouwer and unassigned petrochenkov Oct 23, 2025

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Oct 23, 2025

tardyp force-pushed the lto_big_filesize_utf8 branch from 96868ac to a968930Compare October 23, 2025 12:03

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Oct 23, 2025

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Oct 23, 2025

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Comment threadtests/run-make/lto-long-filenames_cn/rmake.rs Outdated

tardyp force-pushed the lto_big_filesize_utf8 branch from d73e0b8 to c6acffeCompare October 24, 2025 14:20

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rust-borsBot added a commit that referenced this pull request Oct 24, 2025
Auto merge of#148018- tardyp:lto_big_filesize_utf8, r=<try>
3634e54
fix panic when rustc tries to reduce intermediate filenames len with utf8 try-job: x86_64-mingw-* try-job: i686-msvc-*

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Oct 24, 2025

This was referenced Oct 24, 2025
test(frontmatter): Rename tests to make coverage more obvious #148073
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[beta] backports #148075
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bors added the merged-by-bors This PR was explicitly merged by bors. label Oct 24, 2025

bors merged commit 2aaa62b into rust-lang:masterOct 24, 2025
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rustbot added this to the 1.92.0 milestone Oct 24, 2025

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cuviper modified the milestones: 1.92.0, 1.91.0 Oct 24, 2025

cuviper removed the beta-nominated Nominated for backporting to the compiler in the beta channel. label Oct 24, 2025

theemathas mentioned this pull request Oct 25, 2025
regression: ICE byte index is not a char boundary #147975
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