Move `std::io::buffered` to `alloc::io` by bushrat011899 · Pull Request #158547 · rust-lang/rust

bushrat011899 · 2026-06-29T05:48:35Z

ACP: rust-lang/libs-team#755
Tracking issue: #154046
Split From: #156527
~~Blocked On: #158546~~

Description

Moves std::io::BufReader/BufWriter/LineWriter/etc. to alloc::io. This is effectively a direct cut and paste. Blocked on #158546.

Notes

No AI tooling of any kind was used during the creation of this PR.
Please see Tracking Issue for alloc::io and core::io #154046 (comment) for a review order and broader context for this PR.

rustbot · 2026-06-29T05:48:41Z

r? @JohnTitor

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Owners of files modified in this PR: @ChrisDenton, libs
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bushrat011899 · 2026-06-29T05:48:45Z

@rustbot blocked

Move `std::io::buffered` to `alloc::io`

rust-bors · 2026-07-20T14:22:23Z

☀️ Try build successful (CI)
Build commit: b404afe (b404afe496973d61ac2deb36a68e7664b110decd)
Base parent: 14ead7d (14ead7d3d509f50efe9afb84673e65885dfd4d07)

rust-timer · 2026-07-20T15:11:37Z

Finished benchmarking commit (b404afe): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking means the PR may be perf-sensitive. Consider adding rollup=never if this change is not fit for rolling up.

@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

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

Max RSS (memory usage)

Results (primary 2.9%, secondary 0.7%)

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

	mean	range	count
Regressions ❌ (primary)	6.6%	[6.6%, 6.6%]	1
Regressions ❌ (secondary)	5.9%	[4.6%, 7.2%]	4
Improvements ✅ (primary)	-0.9%	[-0.9%, -0.9%]	1
Improvements ✅ (secondary)	-4.5%	[-6.5%, -3.1%]	4
All ❌✅ (primary)	2.9%	[-0.9%, 6.6%]	2

Cycles

Results (primary -0.5%)

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

	mean	range	count
Regressions ❌ (primary)	2.0%	[2.0%, 2.0%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-3.1%	[-3.1%, -3.1%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.5%	[-3.1%, 2.0%]	2

Binary size

Results (primary 0.0%, secondary 0.0%)

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

	mean	range	count
Regressions ❌ (primary)	0.0%	[0.0%, 0.0%]	4
Regressions ❌ (secondary)	0.0%	[0.0%, 0.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[0.0%, 0.0%]	4

Bootstrap: 485.673s -> 485.443s (-0.05%)
Artifact size: 391.74 MiB -> 392.41 MiB (0.17%)

clarfonthey · 2026-07-20T17:49:21Z

@bors r+ rollup

rust-bors · 2026-07-20T17:49:24Z

📌 Commit 6ef1cf3 has been approved by clarfonthey

It is now in the queue for this repository.

…=clarfonthey Move `std::io::buffered` to `alloc::io` ACP: rust-lang/libs-team#755 Tracking issue: rust-lang#154046 Split From: rust-lang#156527 ~~Blocked On: rust-lang#158546 ## Description Moves `std::io::BufReader`/`BufWriter`/`LineWriter`/etc. to `alloc::io`. This is effectively a direct cut and paste. Blocked on rust-lang#158546. --- ## Notes * No AI tooling of any kind was used during the creation of this PR. * Please see rust-lang#154046 (comment) for a review order and broader context for this PR.

…uwer Rollup of 7 pull requests Successful merges: - #159582 (Sync from portable simd 2026 07 20) - #157270 (ergonomic_clones_dotuse_capture_by_ref: Capture upvar by ref for `.use` in non-move closures) - #158496 (Move `check_rustc_pub_transparent` into the attribute parser) - #158547 (Move `std::io::buffered` to `alloc::io`) - #159505 (make rustdoc::bare_urls strip trailing periods from url) - #159578 (Extract coroutine closure helper functions) - #159613 (Set the rustc lib path for unstable-book-gen)

Rollup of 14 pull requests Successful merges: - #159307 (Improve cross-namespace name diagnostics) - #159543 (Remove extra semicolons in parsing item lists) - #157270 (ergonomic_clones_dotuse_capture_by_ref: Capture upvar by ref for `.use` in non-move closures) - #158496 (Move `check_rustc_pub_transparent` into the attribute parser) - #158547 (Move `std::io::buffered` to `alloc::io`) - #158808 (Filter host libstdc++ ABI flag in rustc_llvm cross builds) - #159362 (Add regression test for #120328) - #159472 (Support creating float constants in rustc_public mir) - #159505 (make rustdoc::bare_urls strip trailing periods from url) - #159568 (Suggest close compiler options) - #159578 (Extract coroutine closure helper functions) - #159601 (Make `TokenTreeCursor` private) - #159613 (Set the rustc lib path for unstable-book-gen) - #159616 (Clarify the comment about stage1/stage2 discrepancy in input-stats test)

Rollup merge of #158547 - bushrat011899:alloc_io_buffered, r=clarfonthey Move `std::io::buffered` to `alloc::io` ACP: rust-lang/libs-team#755 Tracking issue: #154046 Split From: #156527 ~~Blocked On: #158546 ## Description Moves `std::io::BufReader`/`BufWriter`/`LineWriter`/etc. to `alloc::io`. This is effectively a direct cut and paste. Blocked on #158546. --- ## Notes * No AI tooling of any kind was used during the creation of this PR. * Please see #154046 (comment) for a review order and broader context for this PR.

Rollup of 14 pull requests Successful merges: - rust-lang/rust#159307 (Improve cross-namespace name diagnostics) - rust-lang/rust#159543 (Remove extra semicolons in parsing item lists) - rust-lang/rust#157270 (ergonomic_clones_dotuse_capture_by_ref: Capture upvar by ref for `.use` in non-move closures) - rust-lang/rust#158496 (Move `check_rustc_pub_transparent` into the attribute parser) - rust-lang/rust#158547 (Move `std::io::buffered` to `alloc::io`) - rust-lang/rust#158808 (Filter host libstdc++ ABI flag in rustc_llvm cross builds) - rust-lang/rust#159362 (Add regression test for rust-lang/rust#120328) - rust-lang/rust#159472 (Support creating float constants in rustc_public mir) - rust-lang/rust#159505 (make rustdoc::bare_urls strip trailing periods from url) - rust-lang/rust#159568 (Suggest close compiler options) - rust-lang/rust#159578 (Extract coroutine closure helper functions) - rust-lang/rust#159601 (Make `TokenTreeCursor` private) - rust-lang/rust#159613 (Set the rustc lib path for unstable-book-gen) - rust-lang/rust#159616 (Clarify the comment about stage1/stage2 discrepancy in input-stats test)

rust-lang#158547 moved `std::io::BufWriter` to `alloc::io::BufWriter`. That allows it to be used in `no-std` configurations, and in particular on platforms where unwinding isn't supported. However one of the doc tests uses `catch_unwind`, which fails on platforms which cannot unwind. Fix this by copying the magic incantation from a similar doctest in library/core/src/range.rs

… r=clarfonthey Mark a doctest as requiring unwinding rust-lang#158547 moved `std::io::BufWriter` to `alloc::io::BufWriter`. That allows it to be used in `no-std` configurations, and in particular on platforms where unwinding isn't supported. However one of the doc tests uses `catch_unwind`, which fails on platforms which cannot unwind. Fix this by copying the magic incantation from a similar doctest in library/core/src/range.rs

Rollup merge of #160151 - fs-rachel:unwind-in-alloc-doctest, r=clarfonthey Mark a doctest as requiring unwinding #158547 moved `std::io::BufWriter` to `alloc::io::BufWriter`. That allows it to be used in `no-std` configurations, and in particular on platforms where unwinding isn't supported. However one of the doc tests uses `catch_unwind`, which fails on platforms which cannot unwind. Fix this by copying the magic incantation from a similar doctest in library/core/src/range.rs

rust-lang#158547 moved `std::io::BufWriter` to `alloc::io::BufWriter`. That allows it to be used in `no-std` configurations, and in particular on platforms where unwinding isn't supported. However one of the doc tests uses `catch_unwind`, which fails on platforms which cannot unwind. Fix this by copying the magic incantation from a similar doctest in library/core/src/range.rs

…als, r=clarfonthey Move `std::io::copy` to `alloc::io` ACP: rust-lang/libs-team#755 Tracking issue: rust-lang#154046 Split From: rust-lang#156527 ~~Blocked On: rust-lang#158547 ## Description Moves `std::io::copy` into `alloc::io`. Blocked on rust-lang#158547. This relies on specialization to allow `std` to provide optimised copy implementations for its types where appropriate. The exact technique involves defining a new trait, `alloc::io::SpecCopy`: ```rust #[doc(hidden)] #[unstable(feature = "core_io_internals", reason = "exposed only for libstd", issue = "none")] #[rustc_specialization_trait] pub trait SpecCopy: Read { /// Attempt to copy from this reader to the provided writer using a specialized /// process. fn copy<R: Read + ?Sized, W: Write + ?Sized>( _reader: &mut R, _writer: &mut W, ) -> Result<CopyState>; } ``` Since optimised copying requires both the reader and writer to support the operation between each other, we can choose one of them to be the implementer of the copy algorithm, and delegate specialization to it. In this case, I've chosen the reader to be the provider of the specialized copy implementation arbitrarily. Note that the `SpecCopy::copy` function is generic over the reader specifically to allow wrappers like `Take<R>` to be visible to the implementation of `copy`. Because this introduces a new layer of specialization to `io::copy`, I think this PR should be benchmarked to make sure performance characteristics aren't too different. I am expecting compilation time to be slightly worse, since there's just more specialization happening, but the actual code run _should_ be the same. --- ## Notes * No AI tooling of any kind was used during the creation of this PR. * Please see rust-lang#154046 (comment) for a review order and broader context for this PR.

Rollup merge of #158548 - bushrat011899:alloc_io_copy_internals, r=clarfonthey Move `std::io::copy` to `alloc::io` ACP: rust-lang/libs-team#755 Tracking issue: #154046 Split From: #156527 ~~Blocked On: #158547 ## Description Moves `std::io::copy` into `alloc::io`. Blocked on #158547. This relies on specialization to allow `std` to provide optimised copy implementations for its types where appropriate. The exact technique involves defining a new trait, `alloc::io::SpecCopy`: ```rust #[doc(hidden)] #[unstable(feature = "core_io_internals", reason = "exposed only for libstd", issue = "none")] #[rustc_specialization_trait] pub trait SpecCopy: Read { /// Attempt to copy from this reader to the provided writer using a specialized /// process. fn copy<R: Read + ?Sized, W: Write + ?Sized>( _reader: &mut R, _writer: &mut W, ) -> Result<CopyState>; } ``` Since optimised copying requires both the reader and writer to support the operation between each other, we can choose one of them to be the implementer of the copy algorithm, and delegate specialization to it. In this case, I've chosen the reader to be the provider of the specialized copy implementation arbitrarily. Note that the `SpecCopy::copy` function is generic over the reader specifically to allow wrappers like `Take<R>` to be visible to the implementation of `copy`. Because this introduces a new layer of specialization to `io::copy`, I think this PR should be benchmarked to make sure performance characteristics aren't too different. I am expecting compilation time to be slightly worse, since there's just more specialization happening, but the actual code run _should_ be the same. --- ## Notes * No AI tooling of any kind was used during the creation of this PR. * Please see #154046 (comment) for a review order and broader context for this PR.

rustbot assigned JohnTitor Jun 29, 2026

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. labels Jun 29, 2026

rustbot added S-blocked Status: Blocked on something else such as an RFC or other implementation work. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 29, 2026

This was referenced Jun 29, 2026

Tracking Issue for alloc::io and core::io #154046

Open

Move std::io::copy to alloc::io #158548

Merged