Rollup of 6 pull requests by JonathanBrouwer · Pull Request #163754 · rust-lang/rust

JonathanBrouwer · 2026-10-04T12:24:55Z

Successful merges:

FCW for #[panic_handler] on unsafe fn. #162974 (FCW for #[panic_handler] on unsafe fn.)
Add documentation for the no_main and repr attributes #163627 (Add documentation for the no_main and repr attributes)
Add --frontend-threads option to ./x perf #163671 (Add --frontend-threads option to ./x perf)
c_str_alloc_error test: mention why this is mostly Miri-only #163694 (c_str_alloc_error test: mention why this is mostly Miri-only)
Stabilize CStr::display #163711 (Stabilize CStr::display)
[tiny] Remove useless .into() calls #163723 ([tiny] Remove useless .into() calls)

Fix test-tidy review changes review changes review changes fix llvm build ignore attribute documentation example fix tidy use no_run instead of ignore

…r, r=mejrs FCW for `#[panic_handler]` on `unsafe fn`. Mitigates rust-lang#162967. A function annotated with `#[panic_handler]` can be called by the compiler from anywhere. So, such functions must not have any safety preconditions. A [github search](https://github.com/search?q=language%3Arust+%2F%23%5C%5Bpanic_handler%5C%5D%5Cnunsafe%2F&type=code) shows many crates that would run into this, so a hard error seems infeasible. If needed, I can modify the code in order to run crater to check how much code would be flagged by this FCW. ~~I have not yet created a proper tracking issue for the FCW. If this PR seems like the right direction, I will do so before merging.~~ I've created a tracking issue for this FCW at rust-lang#163263 An LLM pointed me towards `check_panic_info_fn` and `emit_node_span_lint` (which I verified to be right). However, this PR is otherwise written manually.

…ttribute, r=bushrat011899,JonathanBrouwer Add documentation for the `no_main` and `repr` attributes Part of rust-lang#157604. This PR documents `no_main` and `repr` attributes in `library/core/src/attribute_docs.rs` with some examples. Tested with: `./x doc`

…opt, r=Kobzol Add `--frontend-threads` option to `./x perf` This just adds an option to pass through the `--frontend-threads` option to `rustc-perf` through `./x perf` (which option is documented in the [`rustc-perf` repo](https://github.com/rust-lang/rustc-perf/blob/main/collector/README.md#benchmarking-options). Before this, `./x perf` had no way of telling `rustc-perf` how many frontend threads to use, so it always defaulted to 1. This made it a bit more difficult to test perf-related chnages to the parallel frontend. I tested this option locally and it seems to work perfectly fine.

@bjorn3

…fonthey c_str_alloc_error test: mention why this is mostly Miri-only This was explained at the top of the file but I missed it there. Seems worth repeating at the attribute? Or am I just too blind? Cc @bjorn3 -- is it expected that `#[global_allocator]` does not work in alloctests?

…itor Stabilize `CStr::display` Passed FCP in rust-lang#139984. (closes rust-lang#139984) cc rust-lang#163710

…enyukang [tiny] Remove useless `.into()` calls

JonathanBrouwer · 2026-10-04T12:25:04Z

@bors r+ p=5 force

Trying commonly failed jobs
@bors try jobs=dist-various-1,test-various,test-x86_64-gnu-aux,test-x86_64-msvc-1,test-aarch64-apple-1,test-aarch64-apple-2,test-x86_64-mingw-1,test-i686-msvc,test-armhf-gnu

rust-bors · 2026-10-04T12:25:07Z

📌 Commit 1afe421 has been approved by JonathanBrouwer

It is now in the queue for this repository.

Rollup of 6 pull requests try-job: dist-various-1 try-job: test-various try-job: test-x86_64-gnu-aux try-job: test-x86_64-msvc-1 try-job: test-aarch64-apple-1 try-job: test-aarch64-apple-2 try-job: test-x86_64-mingw-1 try-job: test-i686-msvc try-job: test-armhf-gnu

rust-bors · 2026-10-04T15:21:43Z

☀️ Try build successful (CI)
Build commit: 054a7f3 (054a7f3e274478933a69116055e3d9a4a179355c)
Base parent: 4ddbc06 (4ddbc06ea09abcda34f80baf31cc9bc2686b0ae6)

rust-bors · 2026-10-04T17:47:24Z

☀️ Test successful - CI
Approved by: JonathanBrouwer
Duration: 3h 48s
Pushing f48b3e6 to main...

github-actions · 2026-10-04T17:51:04Z

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 a639ea0 (parent) -> f48b3e6 (this PR)

Test differences

Show 131 test diffs

Stage 1

[ui (polonius)] tests/ui/panic-handler/unsafe_panic_handler.rs: [missing] -> pass (J0)
[ui] tests/ui/panic-handler/unsafe_panic_handler.rs: [missing] -> pass (J2)

Stage 2

[ui] tests/ui/panic-handler/unsafe_panic_handler.rs: [missing] -> pass (J1)

Additionally, 128 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 f48b3e61eeece268609bd920fcca1ded047db7ca --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

dist-i686-msvc: 32m 25s -> 52m 51s (+63.0%)
dist-loongarch64-linux: 1h 21m -> 2h 8m (+58.5%)
test-x86_64-gnu-aux: 2h 37m -> 1h 30m (-42.8%)
test-arm-android: 1h 16m -> 1h 49m (+42.6%)
test-i686-gnu-nopt-2: 2h 21m -> 1h 23m (-41.0%)
test-x86_64-gnu-stable: 1h 52m -> 2h 36m (+38.7%)
dist-x86_64-musl: 1h 43m -> 2h 21m (+37.2%)
test-x86_64-msvc-ext3: 1h 29m -> 2h 1m (+35.4%)
test-x86_64-gnu-debug: 2h 4m -> 1h 21m (-34.4%)
test-pr-check-1: 39m 1s -> 25m 48s (-33.9%)

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.

rust-timer · 2026-10-04T18:30:59Z

Finished benchmarking commit (f48b3e6): comparison URL.

Overall result: ❌✅ regressions and improvements - no action needed

@rustbot label: -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)	0.4%	[0.4%, 0.4%]	1
Improvements ✅ (primary)	-0.3%	[-0.3%, -0.3%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.3%	[-0.3%, -0.3%]	1

Max RSS (memory usage)

Results (secondary 1.4%)

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)	9.1%	[9.1%, 9.1%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.5%	[-3.0%, -2.1%]	2
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary -0.9%)

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)	1.6%	[1.6%, 1.6%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.3%	[-3.3%, -3.3%]	1
All ❌✅ (primary)	-	-	0

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 489.631s -> 490.122s (0.10%)
Artifact size: 408.63 MiB -> 408.65 MiB (0.00%)

rust-bors · 2026-10-04T19:00:20Z

📌 Perf builds for each rolled up PR:

PR#	Message	Perf Build Sha
#162974	FCW for `#[panic_handler]` on `unsafe fn`.	`00e4dad1632b46dbf956648311908bad107f6788` (link)
#163627	Add documentation for the `no_main` and `repr` attributes	`5059fc013879e512c60ad81fab297466ea8fba46` (link)
#163671	Add `--frontend-threads` option to `./x perf`	`31394a5198a6d8972163f3cae450d87887f0f357` (link)
#163694	c_str_alloc_error test: mention why this is mostly Miri-only	`ea6a18759383d9e52dc185d2b0a23ddcb5dd74ef` (link)
#163711	Stabilize `CStr::display`	`909b0296a7743d13460b71b56ed4e9249003a0e0` (link)
#163723	[tiny] Remove useless `.into()` calls	`2d7373f038d538fd6ba9b60a25fc057c3c188cba` (link)

parent commit: a639ea0890

In the case of a perf regression, run the following command with the SHAs of each PR you suspect might be the cause: @rust-timer triage $SHA $SHA $SHA..., or run @rust-timer triage all to benchmark all rollup members.

itsjunetime and others added 15 commits October 2, 2026 11:28

Add option to pass --frontend-threads to rustc-perf

a010cc6

Regenerate completions

0050bb2

Stabilize CStr::display

6749841

c_str_alloc_error test: mention why this is mostly Miri-only

4cc87c1

Add documentation for the and attributes

17f3f9c

Fix test-tidy review changes review changes review changes fix llvm build ignore attribute documentation example fix tidy use no_run instead of ignore

Remove useless .into() calls

59a2426

Another useless into

8cb6fca

Another useless into

c7ebf41

FCW for #[panic_handler] on unsafe fn.

0ed52fa

Rollup merge of rust-lang#163711 - clarfonthey:c-str-display, r=JohnT…

c0403d4

…itor Stabilize `CStr::display` Passed FCP in rust-lang#139984. (closes rust-lang#139984) cc rust-lang#163710

Rollup merge of rust-lang#163723 - estebank:remove-useless-into, r=ch…

1afe421

…enyukang [tiny] Remove useless `.into()` calls

rust-bors Bot added the rollup A PR which is a rollup label Oct 4, 2026

rust-bors Bot 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 4, 2026

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rust-bors Bot added the merged-by-bors This PR was explicitly merged by bors. label Oct 4, 2026

rust-bors Bot removed the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label Oct 4, 2026

rust-bors Bot merged commit f48b3e6 into rust-lang:main Oct 4, 2026
16 checks passed

rustbot added this to the 1.101.0 milestone Oct 4, 2026

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Rollup of 6 pull requests - #163754

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Test differences

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rust-timer commented Oct 4, 2026

Overall result: ❌✅ regressions and improvements - no action needed

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