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

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bushrat011899 wants to merge 8 commits intorust-lang:mainfrom
bushrat011899:core_io_error
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Move std::io::Error into core#155625
bushrat011899 wants to merge 8 commits intorust-lang:mainfrom
bushrat011899:core_io_error

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@bushrat011899 bushrat011899 commented Apr 21, 2026 •
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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

@bushrat011899
Adjust Documentation for RawOsError
e1ef601 
The hyperlink to `std::io::Error` will not be valid when moved to `core::io`.
There is also a typo which I might as well fix while I'm here.
@bushrat011899
Adjust Usage of RawOsError
4cb72b3 
Inconsistently referenced through `std::sys` and `std::io`. Choosing `std::io` as the canonical source to make migration to `core::io` cleaner.
@bushrat011899
Move RawOsError to core::io
7653e5e
@rustbot 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
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programmerjake
programmerjake reviewed Apr 22, 2026
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Comment thread library/core/src/io/error/os_functions_atomic.rs
@bushrat011899 bushrat011899 force-pushed the core_io_error branch 2 times, most recently from 93b1fa3 to d3835aa Compare April 22, 2026 03:06
programmerjake
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Comment thread library/core/src/io/error.rs Outdated
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programmerjake commented Apr 22, 2026

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

@rustbot rustbot added the O-unix Operating system: Unix-like label Apr 22, 2026
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bushrat011899 commented Apr 22, 2026

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.

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

label -O-unix
See

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

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@rustbot rustbot added the O-unix Operating system: Unix-like label Apr 22, 2026
@bushrat011899 bushrat011899 changed the title [WIP]: Move std::io::Error into core Move std::io::Error into core Apr 22, 2026
@bushrat011899 bushrat011899 marked this pull request as ready for review April 22, 2026 15:07
@rustbot rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 22, 2026
@rustbot 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
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rustbot commented Apr 22, 2026

r? @Mark-Simulacrum

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The reviewer was selected based on:

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  • Random selection from Mark-Simulacrum, jhpratt, scottmcm

@programmerjake programmerjake mentioned this pull request Apr 22, 2026
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@bushrat011899 bushrat011899 mentioned this pull request Apr 23, 2026
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jhpratt added a commit to jhpratt/rust that referenced this pull request Apr 24, 2026
@jhpratt
Rollup merge of rust-lang#155684 - bushrat011899:blanket_io_seek_for_…
e002c6c 
…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.
rust-timer added a commit that referenced this pull request Apr 24, 2026
@rust-timer
Unrolled build for #155684
ed234f4 
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.
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