core: Add `BorrowedCursor::with_unfilled_buf` #142885

a1phyr · 2025-06-22T18:51:29Z

Implementation of rust-lang/libs-team#367.

This mainly adds BorrowedCursor::with_unfilled_buf, with enables using the unfilled part of a cursor as a BorrowedBuf.

Note that unlike the ACP, BorrowedCursor::unfilled_buf was moved to a From conversion. This is more consistent with other ways of creating a BorrowedBuf and hides a bit this conversion that requires unsafe code to be used correctly.

Cc #78485 #117693

rustbot · 2025-06-22T18:51:33Z

r? @Mark-Simulacrum

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library/core/src/io/borrowed_buf.rs

Implementation of rust-lang/libs-team#367. This mainly adds `BorrowedCursor::with_unfilled_buf`, with enables using the unfilled part of a cursor as a `BorrowedBuf`. Note that unlike the ACP, `BorrowedCursor::unfilled_buf` was moved to a `From` conversion. This is more consistent with other ways of creating a `BorrowedBuf` and hides a bit this conversion that requires unsafe code to be used correctly.

Mark-Simulacrum · 2025-07-13T12:06:22Z

@bors r+

bors · 2025-07-13T12:06:25Z

📌 Commit 136d24f has been approved by Mark-Simulacrum

It is now in the queue for this repository.

…ark-Simulacrum core: Add `BorrowedCursor::with_unfilled_buf` Implementation of rust-lang/libs-team#367. This mainly adds `BorrowedCursor::with_unfilled_buf`, with enables using the unfilled part of a cursor as a `BorrowedBuf`. Note that unlike the ACP, `BorrowedCursor::unfilled_buf` was moved to a `From` conversion. This is more consistent with other ways of creating a `BorrowedBuf` and hides a bit this conversion that requires unsafe code to be used correctly. Cc rust-lang#78485 rust-lang#117693

Rollup of 8 pull requests Successful merges: - #142885 (core: Add `BorrowedCursor::with_unfilled_buf`) - #143217 (Port #[link_ordinal] to the new attribute parsing infrastructure) - #143355 (wrapping shift: remove first bitmask and table) - #143448 (remote-test-client: Exit code `128 + <signal-number>` instead of `3`) - #143724 (Tidy cleanup) - #143820 (Fixed a core crate compilation failure when enabling the `optimize_for_size` feature on some targets) - #143850 (Compiletest: Simplify {Html,Json}DocCk directive handling) - #143880 (tests: Test line debuginfo for linebreaked function parameters) Failed merges: - #143630 (Drop `./x suggest`) - #143733 (Change bootstrap's `tool.TOOL_NAME.features` to work on any subcommand) r? `@ghost` `@rustbot` modify labels: rollup

…ark-Simulacrum core: Add `BorrowedCursor::with_unfilled_buf` Implementation of rust-lang/libs-team#367. This mainly adds `BorrowedCursor::with_unfilled_buf`, with enables using the unfilled part of a cursor as a `BorrowedBuf`. Note that unlike the ACP, `BorrowedCursor::unfilled_buf` was moved to a `From` conversion. This is more consistent with other ways of creating a `BorrowedBuf` and hides a bit this conversion that requires unsafe code to be used correctly. Cc rust-lang#78485 rust-lang#117693

Rollup of 16 pull requests Successful merges: - #142885 (core: Add `BorrowedCursor::with_unfilled_buf`) - #143217 (Port #[link_ordinal] to the new attribute parsing infrastructure) - #143355 (wrapping shift: remove first bitmask and table) - #143448 (remote-test-client: Exit code `128 + <signal-number>` instead of `3`) - #143592 (UWP: link ntdll functions using raw-dylib) - #143681 (bootstrap/miri: avoid rebuilds for test builds) - #143710 (Updates to random number generation APIs) - #143724 (Tidy cleanup) - #143820 (Fixed a core crate compilation failure when enabling the `optimize_for_size` feature on some targets) - #143850 (Compiletest: Simplify {Html,Json}DocCk directive handling) - #143855 (Port `#[omit_gdb_pretty_printer_section]` to the new attribute parsing) - #143868 (warn on align on fields to avoid breaking changes) - #143875 (update issue number for `const_trait_impl`) - #143881 (Use zero for initialized Once state) - #143887 (Run bootstrap tests sooner in the `x test` pipeline) - #143893 (Don't require `eh_personality` lang item on targets that have a personality) Failed merges: - #143878 (Port `#[pointee]` to the new attribute parsing infrastructure) - #143891 (Port `#[coverage]` to the new attribute system) r? `@ghost` `@rustbot` modify labels: rollup

…ark-Simulacrum core: Add `BorrowedCursor::with_unfilled_buf` Implementation of rust-lang/libs-team#367. This mainly adds `BorrowedCursor::with_unfilled_buf`, with enables using the unfilled part of a cursor as a `BorrowedBuf`. Note that unlike the ACP, `BorrowedCursor::unfilled_buf` was moved to a `From` conversion. This is more consistent with other ways of creating a `BorrowedBuf` and hides a bit this conversion that requires unsafe code to be used correctly. Cc rust-lang#78485 rust-lang#117693

Rollup of 17 pull requests Successful merges: - #142885 (core: Add `BorrowedCursor::with_unfilled_buf`) - #143217 (Port #[link_ordinal] to the new attribute parsing infrastructure) - #143355 (wrapping shift: remove first bitmask and table) - #143448 (remote-test-client: Exit code `128 + <signal-number>` instead of `3`) - #143681 (bootstrap/miri: avoid rebuilds for test builds) - #143710 (Updates to random number generation APIs) - #143724 (Tidy cleanup) - #143738 (Move several float tests to floats/mod.rs) - #143820 (Fixed a core crate compilation failure when enabling the `optimize_for_size` feature on some targets) - #143850 (Compiletest: Simplify {Html,Json}DocCk directive handling) - #143855 (Port `#[omit_gdb_pretty_printer_section]` to the new attribute parsing) - #143868 (warn on align on fields to avoid breaking changes) - #143875 (update issue number for `const_trait_impl`) - #143881 (Use zero for initialized Once state) - #143887 (Run bootstrap tests sooner in the `x test` pipeline) - #143893 (Don't require `eh_personality` lang item on targets that have a personality) - #143901 (Region constraint nits) Failed merges: - #143878 (Port `#[pointee]` to the new attribute parsing infrastructure) - #143891 (Port `#[coverage]` to the new attribute system) r? `@ghost` `@rustbot` modify labels: rollup

bors · 2025-07-14T23:45:21Z

⌛ Testing commit 136d24f with merge 7f2065a...

bors · 2025-07-15T02:46:26Z

☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing 7f2065a to master...

github-actions · 2025-07-15T02:49:40Z

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 a001497 (parent) -> 7f2065a (this PR)

Test differences

Show 5 test diffs

Stage 1

io::borrowed_buf::cursor_with_unfilled_buf: [missing] -> pass (J0)

Additionally, 4 doctest diffs were found. These are ignored, as they are noisy.

Job group index

J0: aarch64-apple, aarch64-gnu, aarch64-msvc-1, arm-android, armhf-gnu, dist-i586-gnu-i586-i686-musl, i686-gnu-1, i686-gnu-nopt-1, i686-msvc-1, pr-check-2, test-various, x86_64-apple-1, x86_64-gnu, x86_64-gnu-aux, x86_64-gnu-llvm-19-2, x86_64-gnu-llvm-19-3, x86_64-gnu-llvm-20-2, x86_64-gnu-llvm-20-3, x86_64-gnu-nopt, x86_64-gnu-stable, x86_64-mingw-1, x86_64-msvc-1

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 7f2065a4bae1faed5bab928c670964eafbf43b55 --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-aarch64-linux: 6071.9s -> 8199.1s (35.0%)
x86_64-apple-1: 7490.2s -> 10077.7s (34.5%)
aarch64-apple: 4936.8s -> 3820.7s (-22.6%)
dist-apple-various: 9048.0s -> 7510.5s (-17.0%)
dist-x86_64-apple: 10317.8s -> 9030.2s (-12.5%)
x86_64-gnu-llvm-20-1: 3702.2s -> 3286.7s (-11.2%)
x86_64-msvc-ext1: 7581.1s -> 6901.4s (-9.0%)
x86_64-apple-2: 5015.3s -> 4612.8s (-8.0%)
x86_64-msvc-1: 8616.6s -> 9232.2s (7.1%)
x86_64-mingw-2: 7527.7s -> 7000.3s (-7.0%)

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 · 2025-07-15T03:58:00Z

Finished benchmarking commit (7f2065a): 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)

Results (primary -2.3%)

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)	-	-	0
Improvements ✅ (primary)	-2.3%	[-3.6%, -1.2%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.3%	[-3.6%, -1.2%]	3

Cycles

Results (secondary -2.2%)

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)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.2%	[-2.2%, -2.2%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 464.247s -> 463.94s (-0.07%)
Artifact size: 374.71 MiB -> 374.74 MiB (0.01%)

rustbot assigned Mark-Simulacrum Jun 22, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jun 22, 2025

Mark-Simulacrum reviewed Jun 28, 2025

View reviewed changes

library/core/src/io/borrowed_buf.rs Show resolved Hide resolved

a1phyr force-pushed the borrowed_cursor_to_buf branch from 1b4a047 to 136d24f Compare July 1, 2025 12:06

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 Jul 13, 2025

a1phyr mentioned this pull request Jul 13, 2025

Trim BorrowedCursor API #143829

Open

matthiaskrgr mentioned this pull request Jul 13, 2025

Rollup of 8 pull requests #143899

Closed

fmease mentioned this pull request Jul 14, 2025

Rollup of 16 pull requests #143912

Closed

jhpratt mentioned this pull request Jul 14, 2025

Rollup of 17 pull requests #143916

Closed

bors added the merged-by-bors This PR was explicitly merged by bors. label Jul 15, 2025

bors merged commit 7f2065a into rust-lang:master Jul 15, 2025
11 checks passed

rustbot added this to the 1.90.0 milestone Jul 15, 2025

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core: Add `BorrowedCursor::with_unfilled_buf` #142885

core: Add `BorrowedCursor::with_unfilled_buf` #142885

a1phyr commented Jun 22, 2025 •

edited by rustbot

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core: Add BorrowedCursor::with_unfilled_buf #142885

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Test differences

Stage 1

Job duration changes

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rust-timer commented Jul 15, 2025

Overall result: no relevant changes - no action needed

Instruction count

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Binary size

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core: Add `BorrowedCursor::with_unfilled_buf` #142885

core: Add `BorrowedCursor::with_unfilled_buf` #142885

a1phyr commented Jun 22, 2025 •

edited by rustbot

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