Move `std::io::Error` into `core` by bushrat011899 · Pull Request #155625 · rust-lang/rust

bushrat011899 · 2026-04-21T23:54:37Z

ACP: rust-lang/libs-team#755
Tracking issue: #154046
Related: #155574
Related: #152918

Description

Moves std::io::Error into core, deferring Box-adjacent methods to incoherent implementations in alloc, and RawOsError methods to std. This requires some substantial changes to the internals of Error, but none of them are breaking changes or externally visible.

Notably, I've replaced usage of Box with a wrapper around a pointer and an appropriate drop function. This requires the addition of quite a few lines of unsafe, but is required to work around Box only being accessible from alloc. Additionally, an atomic pointer to a VTable is used for working with RawOsError in core, since we cannot know the required implementations without std.

Notes

This PR adopts the VTable technique from Move OS-dependent parts of std::io to alloc #152918
This PR builds on my previous PR Move std::io::RawOsError to core::io #155574
No AI tooling of any kind was used during the creation of this PR.

programmerjake · 2026-04-22T04:00:28Z

example of how to link from core's docs to std: https://doc.rust-lang.org/1.95.0/src/core/str/mod.rs.html#200

bushrat011899 · 2026-04-22T04:53:57Z

example of how to link from core's docs to std: https://doc.rust-lang.org/1.95.0/src/core/str/mod.rs.html#200

That's a clever trick I never knew about! Looks like it's also required for linking to incoherent implementations even within the file that creates them too.

programmerjake · 2026-04-22T07:11:54Z

label -O-unix
See

maybe just leave it until you get the PR to work, that way there's less comment spam.

rustbot · 2026-04-22T15:08:01Z

r? @Mark-Simulacrum

rustbot has assigned @Mark-Simulacrum.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

Owners of files modified in this PR: @scottmcm, libs
@scottmcm, libs expanded to 7 candidates
Random selection from Mark-Simulacrum, jhpratt, scottmcm

…ref, r=jhpratt Generalize IO Traits for `Arc<T>` where `&T: IoTrait` ACP: rust-lang/libs-team#755 Tracking issue: rust-lang#154046 Related: rust-lang#94744 ## Description After experimenting with rust-lang#155625, I noticed `Seek` and `SeekFrom` can almost be moved to `core::io`. Unfortunately, the implementation of `Seek` for `Arc<File>` is a blocker for such a move, since `Arc` is not a fundamental type. This PR attempts to resolve this potential blocker by replacing the implementation with a more general alternative. An internal trait `IoHandle` has been added which types can implement to opt-in to `Read`/`Write`/`Seek` implementations for `Arc<Self>` as long as `&Self` implements said trait. Note that `BufRead` is excluded as the signature for `fill_buf` would require returning from a temporary. Since this "blanket" implementation only applies to a single type which already implements the same traits, I believe this should have no user-facing impact. If this PR was merged, rust-lang#134190 could be replaced with a 2 line PR: ```rust impl IoHandle for TcpStream {} impl IoHandle for UnixStream {} ``` Likewise for any other types, a table of which can be found [here](rust-lang/libs-team#504 (comment)). This is out of scope for this PR to avoid the need for an ACP. --- ## Notes * See [this comment](rust-lang#154046 (comment)) for further details. * No AI tooling of any kind was used during the creation of this PR.

Rollup merge of #155684 - bushrat011899:blanket_io_seek_for_ref, r=jhpratt Generalize IO Traits for `Arc<T>` where `&T: IoTrait` ACP: rust-lang/libs-team#755 Tracking issue: #154046 Related: #94744 ## Description After experimenting with #155625, I noticed `Seek` and `SeekFrom` can almost be moved to `core::io`. Unfortunately, the implementation of `Seek` for `Arc<File>` is a blocker for such a move, since `Arc` is not a fundamental type. This PR attempts to resolve this potential blocker by replacing the implementation with a more general alternative. An internal trait `IoHandle` has been added which types can implement to opt-in to `Read`/`Write`/`Seek` implementations for `Arc<Self>` as long as `&Self` implements said trait. Note that `BufRead` is excluded as the signature for `fill_buf` would require returning from a temporary. Since this "blanket" implementation only applies to a single type which already implements the same traits, I believe this should have no user-facing impact. If this PR was merged, #134190 could be replaced with a 2 line PR: ```rust impl IoHandle for TcpStream {} impl IoHandle for UnixStream {} ``` Likewise for any other types, a table of which can be found [here](rust-lang/libs-team#504 (comment)). This is out of scope for this PR to avoid the need for an ACP. --- ## Notes * See [this comment](#154046 (comment)) for further details. * No AI tooling of any kind was used during the creation of this PR.

Viewing internals wont be possible from `std` once moved into `core`.

rustbot · 2026-04-27T00:30:18Z

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.

…pratt Generalize IO Traits for `Arc<T>` where `&T: IoTrait` ACP: rust-lang/libs-team#755 Tracking issue: rust-lang/rust#154046 Related: rust-lang/rust#94744 ## Description After experimenting with rust-lang/rust#155625, I noticed `Seek` and `SeekFrom` can almost be moved to `core::io`. Unfortunately, the implementation of `Seek` for `Arc<File>` is a blocker for such a move, since `Arc` is not a fundamental type. This PR attempts to resolve this potential blocker by replacing the implementation with a more general alternative. An internal trait `IoHandle` has been added which types can implement to opt-in to `Read`/`Write`/`Seek` implementations for `Arc<Self>` as long as `&Self` implements said trait. Note that `BufRead` is excluded as the signature for `fill_buf` would require returning from a temporary. Since this "blanket" implementation only applies to a single type which already implements the same traits, I believe this should have no user-facing impact. If this PR was merged, rust-lang/rust#134190 could be replaced with a 2 line PR: ```rust impl IoHandle for TcpStream {} impl IoHandle for UnixStream {} ``` Likewise for any other types, a table of which can be found [here](rust-lang/libs-team#504 (comment)). This is out of scope for this PR to avoid the need for an ACP. --- ## Notes * See [this comment](rust-lang/rust#154046 (comment)) for further details. * No AI tooling of any kind was used during the creation of this PR.

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Apr 21, 2026

This comment has been minimized.

Sign in to view

bushrat011899 force-pushed the core_io_error branch from b86f41f to c538e5d Compare April 22, 2026 00:16

This comment has been minimized.

Sign in to view

bushrat011899 force-pushed the core_io_error branch from 6c37f53 to 65d4011 Compare April 22, 2026 00:53

This comment has been minimized.

Sign in to view

bushrat011899 force-pushed the core_io_error branch from 65d4011 to 56a8e8c Compare April 22, 2026 01:43

programmerjake reviewed Apr 22, 2026

View reviewed changes

Comment thread library/core/src/io/error/os_functions_atomic.rs

bushrat011899 force-pushed the core_io_error branch 2 times, most recently from 93b1fa3 to d3835aa Compare April 22, 2026 03:06

programmerjake reviewed Apr 22, 2026

View reviewed changes

Comment thread library/core/src/io/error.rs Outdated

This comment has been minimized.

Sign in to view

bushrat011899 force-pushed the core_io_error branch from d3835aa to 8bfceb6 Compare April 22, 2026 04:52

rustbot added the O-unix Operating system: Unix-like label Apr 22, 2026

This comment has been minimized.

Sign in to view

rustbot removed the O-unix Operating system: Unix-like label Apr 22, 2026

This comment has been minimized.

Sign in to view

bushrat011899 force-pushed the core_io_error branch from 8bfceb6 to 96864eb Compare April 22, 2026 05:51

rustbot added the O-unix Operating system: Unix-like label Apr 22, 2026

This comment has been minimized.

Sign in to view

rustbot removed the O-unix Operating system: Unix-like label Apr 22, 2026

This comment has been minimized.

Sign in to view

bushrat011899 force-pushed the core_io_error branch from 96864eb to 7cad458 Compare April 22, 2026 07:05

rustbot added the O-unix Operating system: Unix-like label Apr 22, 2026

This comment has been minimized.

Sign in to view

rustbot removed the O-unix Operating system: Unix-like label Apr 22, 2026

This comment has been minimized.

Sign in to view

bushrat011899 force-pushed the core_io_error branch from 7cad458 to 0f0a783 Compare April 22, 2026 10:25

rustbot added the O-unix Operating system: Unix-like label Apr 22, 2026

bushrat011899 force-pushed the core_io_error branch from 0f0a783 to e4ed737 Compare April 22, 2026 13:22

bushrat011899 changed the title ~~[WIP]: Move std::io::Error into core~~ Move std::io::Error into core Apr 22, 2026

bushrat011899 marked this pull request as ready for review April 22, 2026 15:07

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 22, 2026

rustbot assigned Mark-Simulacrum Apr 22, 2026

rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Apr 22, 2026

programmerjake mentioned this pull request Apr 22, 2026

Move OS-dependent parts of std::io to alloc #152918

Open

bushrat011899 mentioned this pull request Apr 23, 2026

Generalize IO Traits for Arc<T> where &T: IoTrait #155684

Merged

bushrat011899 added 5 commits April 27, 2026 10:29

Adjust std::io::Error tests to only assess public API

a1f70ec

Viewing internals wont be possible from `std` once moved into `core`.

Adjust documentation to allow for incoherent implementations

01df53d

Setup alloc::io

14e95f2

Make std::io::Error compatible with core in-place

16d4e7d

Move std::io::Error and friends to core

4fe06e6

bushrat011899 force-pushed the core_io_error branch from e4ed737 to 4fe06e6 Compare April 27, 2026 00:30

bushrat011899 mentioned this pull request Apr 27, 2026

Move IoSlice and IoSliceMut to core::io #155849

Open

bushrat011899 mentioned this pull request Apr 28, 2026

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

Open

4 tasks

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Move `std::io::Error` into `core`#155625

Move `std::io::Error` into `core`#155625
bushrat011899 wants to merge 5 commits intorust-lang:mainfrom
bushrat011899:core_io_error

bushrat011899 commented Apr 21, 2026 •

edited by rustbot

Loading

Uh oh!

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

Uh oh!

Uh oh!

This comment has been minimized.

programmerjake commented Apr 22, 2026

Uh oh!

bushrat011899 commented Apr 22, 2026

Uh oh!

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

programmerjake commented Apr 22, 2026

Uh oh!

This comment has been minimized.

rustbot commented Apr 22, 2026

Uh oh!

rustbot commented Apr 27, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

Uh oh!

Conversation

bushrat011899 commented Apr 21, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Description

Notes

Uh oh!

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

Uh oh!

Uh oh!

This comment has been minimized.

programmerjake commented Apr 22, 2026

Uh oh!

bushrat011899 commented Apr 22, 2026

Uh oh!

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

programmerjake commented Apr 22, 2026

Uh oh!

This comment has been minimized.

rustbot commented Apr 22, 2026

Uh oh!

rustbot commented Apr 27, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

bushrat011899 commented Apr 21, 2026 •

edited by rustbot

Loading