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Merged
merged 2 commits into from
May 23, 2025

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@RalfJung RalfJung commented Jan 6, 2025

This fixes #134375 in a rather crude way, by making the example not build any more on aarch64-unknown-none-softfloat. That is a breaking change since the "neon" aarch64 target feature is stable, but this is justified as a soundness fix. Note that it's not "neon" which is problematic but "fp-armv8"; however, the two are tied together by rustc.

-Ctarget-feature=+neon still works, it just causes a warning (but one that we do hope to make a hard error eventually). Only #[target_feature="neon"] becomes a hard error with this PR.

More work on the LLVM side will be needed before we can let people use neon without impacting the ABI of float values (and, in particular, the ABI used by automatically inserted calls to libm functions, e.g. for int-to-float casts, which rustc has no control over).

Nominating for @rust-lang/lang since it is a breaking change. As-is this PR doesn't have a warning cycle; the hope is that the aarch64-unknown-none-softfloat target is sufficiently niche that there's no huge fallout and we can easily revert if it causes trouble. A warning cycle could be added but would need some dedicated rather hacky check in the target_feature attribute handling logic.

try-job: dist-various-1

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rustbot commented Jan 6, 2025

r? @Noratrieb

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@rustbot 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 Jan 6, 2025
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RalfJung commented Jan 6, 2025

Cc @Darksonn @Amanieu, please chime in if there are any aarch64 stakeholders that need #[target_feature(enable = "neon")] on aarch64-unknown-none-softfloat.

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Darksonn commented Jan 6, 2025

This change looks good to me. On the off chance that a kernel user comes up in the near future, they can use the "be careful" approach you mentioned in #134375 (comment).

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RalfJung commented Jan 6, 2025

Yeah, separately building some crates with aarch64-unknown-none-softfloat and some with aarch64-unknown-none and linking them together should work (but I have not tested this, you may need separate sysroots and then link them together as C-style object files). Once we have the target modifier system it should flag this as incompatible, but that can be unsafely overruled.

@traviscross traviscross added T-lang Relevant to the language team I-lang-nominated Nominated for discussion during a lang team meeting. labels Jan 6, 2025
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tgross35 commented Jan 6, 2025

Once we have the target modifier system it should flag this as incompatible, but that can be unsafely overruled.

Will that mean something like #[unsafe(target_feature(enable = "neon"))] can enable this back?

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RalfJung commented Jan 6, 2025

I don't think we should allow target features to do that (I was imagining target modifiers would introduce a new flag for overriding ABI-relevant target features, if there's any good use for that), and so far there was no proposal to allow overriding target modifiers on a per-function basis.

The text you quoted referred to -C flags, not attributes.

@RalfJung RalfJung force-pushed the aarch64-softfloat-not-neon branch from 2bd82d7 to bdf1e78 Compare January 6, 2025 23:01
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Amanieu commented Jan 7, 2025

I'm happy with this as long as we acknowledge that this is a temporary workaround until LLVM starts handling ABI independently of target features.

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RalfJung commented Jan 7, 2025

Fully agreed, the ideal end state is that we can use the FPU while sticking to a softfloat ABI (what clang and GCC do for -mfloat-abi=softfp on ARM-32). How temporary this will be depends on how long it takes until someone puts in the required work on the LLVM side.

@RalfJung RalfJung added the relnotes Marks issues that should be documented in the release notes of the next release. label Jan 14, 2025
@Noratrieb Noratrieb added S-waiting-on-team Status: Awaiting decision from the relevant subteam (see the T-<team> label). and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jan 17, 2025
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Was this discussed by T-lang prior to be approved? I assume yes since I see the release notes label, correct?

cc @traviscross probably knows

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RalfJung commented Jan 29, 2025

We are waiting for t-lang approval, hence the "I-lang-nominated" and "S-waiting-on-team" labels.

@tmandry tmandry removed the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Apr 23, 2025
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tmandry commented Apr 23, 2025

@rfcbot fcp merge

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rfcbot commented Apr 23, 2025

Team member @tmandry has proposed to merge this. The next step is review by the rest of the tagged team members:

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

cc @rust-lang/lang-advisors: FCP proposed for lang, please feel free to register concerns.
See this document for info about what commands tagged team members can give me.

@rfcbot rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Apr 23, 2025
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tmandry commented Apr 23, 2025

I would want relnotes to include a workaround (unfortunately, sounds like it's moving code into another crate and doing some cross-target shenanigans that cargo may not support). Since this is hitting an LLVM limitation it sounds like there's not much else we can do. But if there is any significant breakage we should revisit this decision.

@RalfJung RalfJung force-pushed the aarch64-softfloat-not-neon branch from bdf1e78 to 36f233c Compare April 24, 2025 08:30
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-Ctarget-feature=+neon still works, it just causes a warning (but one that we do hope to make a hard error eventually). Only #[target_feature="neon"] becomes a hard error with this PR.

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tmandry commented Apr 30, 2025

@rfcbot fcp cancel

rust-timer added a commit to rust-lang-ci/rust that referenced this pull request May 22, 2025
Rollup merge of rust-lang#141337 - RalfJung:stdarch, r=Amanieu

bump stdarch

This should unblock rust-lang#135160.
r? `@Amanieu`
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bors commented May 22, 2025

☔ The latest upstream changes (presumably #141379) made this pull request unmergeable. Please resolve the merge conflicts.

@RalfJung RalfJung force-pushed the aarch64-softfloat-not-neon branch from ceef31c to 3c020e5 Compare May 22, 2025 10:19
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@bors try

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bors commented May 22, 2025

⌛ Trying commit 3c020e5 with merge 4055942...

bors added a commit to rust-lang-ci/rust that referenced this pull request May 22, 2025
… r=<try>

aarch64-softfloat: forbid enabling the neon target feature

This fixes rust-lang#134375 in a rather crude way, by making [the example](https://godbolt.org/z/r56xWo8nT) not build any more on aarch64-unknown-none-softfloat. That is a breaking change since the "neon" aarch64 target feature is stable, but this is justified as a soundness fix. Note that it's not "neon" which is problematic but "fp-armv8"; however, the two are tied together by rustc.

`-Ctarget-feature=+neon` still works, it just causes a warning (but one that we do hope to make a hard error eventually). Only `#[target_feature="neon"]` becomes a hard error with this PR.

More work on the LLVM side will be needed before we can let people use neon without impacting the ABI of float values (and, in particular, the ABI used by automatically inserted calls to libm functions, e.g. for int-to-float casts, which rustc has no control over).

Nominating for `@rust-lang/lang` since it is a breaking change. As-is this PR doesn't have a warning cycle; the hope is that the aarch64-unknown-none-softfloat target is sufficiently niche that there's no huge fallout and we can easily revert if it causes trouble. A warning cycle could be added but would need some dedicated rather hacky check in the target_feature attribute handling logic.

try-job:  dist-various-1
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bors commented May 22, 2025

☀️ Try build successful - checks-actions
Build commit: 4055942 (4055942696f7b675e87ed2f111126f531b9fd1b5)

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@bors r=Noratrieb rollup=iffy

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bors commented May 22, 2025

📌 Commit 3c020e5 has been approved by Noratrieb

It is now in the queue for this repository.

@bors 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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels May 22, 2025
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@bors p=4

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bors commented May 23, 2025

⌛ Testing commit 3c020e5 with merge e7f4317...

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bors commented May 23, 2025

☀️ Test successful - checks-actions
Approved by: Noratrieb
Pushing e7f4317 to master...

@bors bors added the merged-by-bors This PR was explicitly merged by bors. label May 23, 2025
@bors bors merged commit e7f4317 into rust-lang:master May 23, 2025
7 checks passed
@rustbot rustbot added this to the 1.89.0 milestone May 23, 2025
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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 912981a (parent) -> e7f4317 (this PR)

Test differences

Show 282 test diffs

Stage 1

  • [ui] tests/ui/target-feature/abi-incompatible-target-feature-attribute-fcw.rs: [missing] -> pass (J0)
  • errors::verify_codegen_ssa_aarch64_softfloat_neon_142: [missing] -> pass (J1)

Stage 2

  • [ui] tests/ui/target-feature/abi-incompatible-target-feature-attribute-fcw.rs: [missing] -> pass (J2)

Additionally, 279 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 e7f4317ea0e891296163414c6f681ccec976abc3 --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

  1. dist-apple-various: 6436.2s -> 8665.5s (34.6%)
  2. dist-aarch64-apple: 5422.2s -> 6316.2s (16.5%)
  3. dist-x86_64-apple: 8690.3s -> 9534.0s (9.7%)
  4. x86_64-apple-2: 7269.9s -> 6683.2s (-8.1%)
  5. dist-loongarch64-linux: 6656.5s -> 6226.7s (-6.5%)
  6. dist-various-2: 3494.3s -> 3270.6s (-6.4%)
  7. x86_64-msvc-ext1: 7028.7s -> 7440.2s (5.9%)
  8. x86_64-apple-1: 7181.0s -> 7578.5s (5.5%)
  9. dist-x86_64-msvc: 6524.0s -> 6164.4s (-5.5%)
  10. dist-ohos-armv7: 4235.6s -> 4465.6s (5.4%)
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.

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Finished benchmarking commit (e7f4317): 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 -0.7%, secondary 2.6%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

mean range count
Regressions ❌
(primary)
- - 0
Regressions ❌
(secondary)
2.6% [2.6%, 2.6%] 1
Improvements ✅
(primary)
-0.7% [-0.7%, -0.7%] 1
Improvements ✅
(secondary)
- - 0
All ❌✅ (primary) -0.7% [-0.7%, -0.7%] 1

Cycles

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

Binary size

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

Bootstrap: 777.508s -> 778.581s (0.14%)
Artifact size: 365.50 MiB -> 365.44 MiB (-0.02%)

@RalfJung RalfJung deleted the aarch64-softfloat-not-neon branch May 23, 2025 05:56
github-actions bot pushed a commit to model-checking/verify-rust-std that referenced this pull request May 26, 2025
bump stdarch

This should unblock rust-lang#135160.
r? `@Amanieu`
@apiraino apiraino removed the to-announce Announce this issue on triage meeting label Jun 5, 2025
wip-sync pushed a commit to NetBSD/pkgsrc-wip that referenced this pull request Aug 11, 2025
Pkgsrc changes:
 * Adjust patches to adapt to upstream changes and new versions.
 * assosicated checksums

Upstream changes relative to 1.88.0:

Version 1.89.0 (2025-08-07)
==========================

Language
--------
- [Stabilize explicitly inferred const arguments (`feature(generic_arg_infer)`)]
  (rust-lang/rust#141610)
- [Add a warn-by-default `mismatched_lifetime_syntaxes` lint.]
  (rust-lang/rust#138677)
  This lint detects when the same lifetime is referred to by
  different syntax categories between function arguments and return
  values, which can be confusing to read, especially in unsafe
  code.  This lint supersedes the warn-by-default `elided_named_lifetimes`
  lint.
- [Expand `unpredictable_function_pointer_comparisons` to also lint
  on function pointer comparisons in external macros]
  (rust-lang/rust#134536)
- [Make the `dangerous_implicit_autorefs` lint deny-by-default]
  (rust-lang/rust#141661)
- [Stabilize the avx512 target features]
  (rust-lang/rust#138940)
- [Stabilize `kl` and `widekl` target features for x86]
  (rust-lang/rust#140766)
- [Stabilize `sha512`, `sm3` and `sm4` target features for x86]
  (rust-lang/rust#140767)
- [Stabilize LoongArch target features `f`, `d`, `frecipe`, `lasx`,
  `lbt`, `lsx`, and `lvz`]
  (rust-lang/rust#135015)
- [Remove `i128` and `u128` from `improper_ctypes_definitions`]
  (rust-lang/rust#137306)
- [Stabilize `repr128` (`#[repr(u128)]`, `#[repr(i128)]`)]
  (rust-lang/rust#138285)
- [Allow `#![doc(test(attr(..)))]` everywhere]
  (rust-lang/rust#140560)
- [Extend temporary lifetime extension to also go through tuple
  struct and tuple variant constructors]
  (rust-lang/rust#140593)

Compiler
--------
- [Default to non-leaf frame pointers on aarch64-linux]
  (rust-lang/rust#140832)
- [Enable non-leaf frame pointers for Arm64EC Windows]
  (rust-lang/rust#140862)
- [Set Apple frame pointers by architecture]
  (rust-lang/rust#141797)

Platform Support
----------------
- [Add new Tier-3 targets `loongarch32-unknown-none` and
  `loongarch32-unknown-none-softfloat`]
  (rust-lang/rust#142053)

Refer to Rust's [platform support page][platform-support-doc]
for more information on Rust's tiered platform support.

[platform-support-doc]: https://doc.rust-lang.org/rustc/platform-support.html

Libraries
---------
- [Specify the base path for `file!`]
  (rust-lang/rust#134442)
- [Allow storing `format_args!()` in a variable]
  (rust-lang/rust#140748)
- [Add `#[must_use]` to `[T; N]::map`]
  (rust-lang/rust#140957)
- [Implement `DerefMut` for `Lazy{Cell,Lock}`]
  (rust-lang/rust#129334)
- [Implement `Default` for `array::IntoIter`]
  (rust-lang/rust#141574)
- [Implement `Clone` for `slice::ChunkBy`]
  (rust-lang/rust#138016)
- [Implement `io::Seek` for `io::Take`]
  (rust-lang/rust#138023)

Stabilized APIs
---------------

- [`NonZero<char>`]
  (https://doc.rust-lang.org/stable/std/num/struct.NonZero.html)
- Many intrinsics for x86, not enumerated here
  - [AVX512 intrinsics](rust-lang/rust#111137)
  - [`SHA512`, `SM3` and `SM4` intrinsics]
    (rust-lang/rust#126624)
- [`File::lock`]
  (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.lock)
- [`File::lock_shared`]
  (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.lock_shared)
- [`File::try_lock`]
  (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.try_lock)
- [`File::try_lock_shared`]
  (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.try_lock_shared)
- [`File::unlock`]
  (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.unlock)
- [`NonNull::from_ref`]
  (https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.from_ref)
- [`NonNull::from_mut`]
  (https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.from_mut)
- [`NonNull::without_provenance`]
  (https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.without_provenance)
- [`NonNull::with_exposed_provenance`]
  (https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.with_exposed_provenance)
- [`NonNull::expose_provenance`]
  (https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.expose_provenance)
- [`OsString::leak`]
  (https://doc.rust-lang.org/stable/std/ffi/struct.OsString.html#method.leak)
- [`PathBuf::leak`]
  (https://doc.rust-lang.org/stable/std/path/struct.PathBuf.html#method.leak)
- [`Result::flatten`]
  (https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.flatten)
- [`std::os::linux::net::TcpStreamExt::quickack`]
  (https://doc.rust-lang.org/stable/std/os/linux/net/trait.TcpStreamExt.html#tymethod.quickack)
- [`std::os::linux::net::TcpStreamExt::set_quickack`]
  (https://doc.rust-lang.org/stable/std/os/linux/net/trait.TcpStreamExt.html#tymethod.set_quickack)

These previously stable APIs are now stable in const contexts:

- [`<[T; N]>::as_mut_slice`]
  (https://doc.rust-lang.org/stable/std/primitive.array.html#method.as_mut_slice)
- [`<[u8]>::eq_ignore_ascii_case`]
  (https://doc.rust-lang.org/stable/std/primitive.slice.html#impl-%5Bu8%5D/method.eq_ignore_ascii_case)
- [`str::eq_ignore_ascii_case`]
  (https://doc.rust-lang.org/stable/std/primitive.str.html#impl-str/method.eq_ignore_ascii_case)

Cargo
-----
- [`cargo fix` and `cargo clippy --fix` now default to the same
  Cargo target selection as other build commands.]
  (rust-lang/cargo#15192) Previously it
  would apply to all targets (like binaries, examples, tests, etc.).
  The `--edition` flag still applies to all targets.

- [Stabilize doctest-xcompile.]
  (rust-lang/cargo#15462) Doctests are
  now tested when cross-compiling. Just like other tests, it will
  use the [`runner` setting]
  (https://doc.rust-lang.org/cargo/reference/config.html#targettriplerunner)
  to run the tests. If you need to disable tests for a target, you
  can use the [ignore doctest attribute]
  (https://doc.rust-lang.org/rustdoc/write-documentation/documentation-tests.html#ignoring-targets)
  to specify the targets to ignore.

Rustdoc
-----
- [On mobile, make the sidebar full width and linewrap]
  (rust-lang/rust#139831). This makes long
  section and item names much easier to deal with on mobile.

Compatibility Notes
-------------------
- [Make `missing_fragment_specifier` an unconditional error]
  (rust-lang/rust#128425)
- [Enabling the `neon` target feature on `aarch64-unknown-none-softfloat`
  causes a warning]
  (rust-lang/rust#135160) because mixing
  code with and without that target feature is not properly supported
  by LLVM
- [Sized Hierarchy: Part I](rust-lang/rust#137944)
  - Introduces a small breaking change affecting `?Sized` bounds
    on impls on recursive types which contain associated type
    projections. It is not expected to affect any existing published
    crates. Can be fixed by refactoring the involved types or opting
    into the `sized_hierarchy` unstable feature. See the [FCP report]
    (rust-lang/rust#137944 (comment))
    for a code example.
- The warn-by-default `elided_named_lifetimes` lint is [superseded
  by the warn-by-default `mismatched_lifetime_syntaxes` lint.]
  (rust-lang/rust#138677)
- [Error on recursive opaque types earlier in the type checker]
  (rust-lang/rust#139419)
- [Type inference side effects from requiring element types of
  array repeat expressions are `Copy` are now only available at the
  end of type checking]
  (rust-lang/rust#139635)

- [The deprecated accidentally-stable
  `std::intrinsics::{copy,copy_nonoverlapping,write_bytes}` are now
  proper intrinsics]
  (rust-lang/rust#139916). There are no
  debug assertions guarding against UB, and they cannot be coerced
  to function pointers.
- [Remove long-deprecated `std::intrinsics::drop_in_place`]
  (rust-lang/rust#140151)
- [Make well-formedness predicates no longer coinductive]
  (rust-lang/rust#140208)
- [Remove hack when checking impl method compatibility]
  (rust-lang/rust#140557)
- [Remove unnecessary type inference due to built-in trait object impls]
  (rust-lang/rust#141352)
- [Lint against "stdcall", "fastcall", and "cdecl" on non-x86-32 targets]
  (rust-lang/rust#141435)
- [Future incompatibility warnings relating to the never type (`!`)
  are now reported in dependencies]
  (rust-lang/rust#141937)
- [Ensure `std::ptr::copy_*` intrinsics also perform the static
  self-init checks]
  (rust-lang/rust#142575)

Internal Changes
----------------

These changes do not affect any public interfaces of Rust, but they represent
significant improvements to the performance or internals of rustc and related
tools.

- [Correctly un-remap compiler sources paths with the `rustc-dev` component]
  (rust-lang/rust#142377)
tmeijn pushed a commit to tmeijn/dotfiles that referenced this pull request Aug 12, 2025
This MR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [rust](https://github.com/rust-lang/rust) | minor | `1.88.0` -> `1.89.0` |

MR created with the help of [el-capitano/tools/renovate-bot](https://gitlab.com/el-capitano/tools/renovate-bot).

**Proposed changes to behavior should be submitted there as MRs.**

---

### Release Notes

<details>
<summary>rust-lang/rust (rust)</summary>

### [`v1.89.0`](https://github.com/rust-lang/rust/blob/HEAD/RELEASES.md#Version-1890-2025-08-07)

[Compare Source](rust-lang/rust@1.88.0...1.89.0)

\==========================

<a id="1.89.0-Language"></a>

## Language

- [Stabilize explicitly inferred const arguments (`feature(generic_arg_infer)`)](rust-lang/rust#141610)
- [Add a warn-by-default `mismatched_lifetime_syntaxes` lint.](rust-lang/rust#138677)
  This lint detects when the same lifetime is referred to by different syntax categories between function arguments and return values, which can be confusing to read, especially in unsafe code.
  This lint supersedes the warn-by-default `elided_named_lifetimes` lint.
- [Expand `unpredictable_function_pointer_comparisons` to also lint on function pointer comparisons in external macros](rust-lang/rust#134536)
- [Make the `dangerous_implicit_autorefs` lint deny-by-default](rust-lang/rust#141661)
- [Stabilize the avx512 target features](rust-lang/rust#138940)
- [Stabilize `kl` and `widekl` target features for x86](rust-lang/rust#140766)
- [Stabilize `sha512`, `sm3` and `sm4` target features for x86](rust-lang/rust#140767)
- [Stabilize LoongArch target features `f`, `d`, `frecipe`, `lasx`, `lbt`, `lsx`, and `lvz`](rust-lang/rust#135015)
- [Remove `i128` and `u128` from `improper_ctypes_definitions`](rust-lang/rust#137306)
- [Stabilize `repr128` (`#[repr(u128)]`, `#[repr(i128)]`)](rust-lang/rust#138285)
- [Allow `#![doc(test(attr(..)))]` everywhere](rust-lang/rust#140560)
- [Extend temporary lifetime extension to also go through tuple struct and tuple variant constructors](rust-lang/rust#140593)
- [`extern "C"` functions on the `wasm32-unknown-unknown` target now have a standards compliant ABI](https://blog.rust-lang.org/2025/04/04/c-abi-changes-for-wasm32-unknown-unknown/)

<a id="1.89.0-Compiler"></a>

## Compiler

- [Default to non-leaf frame pointers on aarch64-linux](rust-lang/rust#140832)
- [Enable non-leaf frame pointers for Arm64EC Windows](rust-lang/rust#140862)
- [Set Apple frame pointers by architecture](rust-lang/rust#141797)

<a id="1.89.0-Platform-Support"></a>

## Platform Support

- [Add new Tier-3 targets `loongarch32-unknown-none` and `loongarch32-unknown-none-softfloat`](rust-lang/rust#142053)
- [`x86_64-apple-darwin` is in the process of being demoted to Tier 2 with host tools](rust-lang/rfcs#3841)

Refer to Rust's [platform support page][platform-support-doc]
for more information on Rust's tiered platform support.

[platform-support-doc]: https://doc.rust-lang.org/rustc/platform-support.html

<a id="1.89.0-Libraries"></a>

## Libraries

- [Specify the base path for `file!`](rust-lang/rust#134442)
- [Allow storing `format_args!()` in a variable](rust-lang/rust#140748)
- [Add `#[must_use]` to `[T; N]::map`](rust-lang/rust#140957)
- [Implement `DerefMut` for `Lazy{Cell,Lock}`](rust-lang/rust#129334)
- [Implement `Default` for `array::IntoIter`](rust-lang/rust#141574)
- [Implement `Clone` for `slice::ChunkBy`](rust-lang/rust#138016)
- [Implement `io::Seek` for `io::Take`](rust-lang/rust#138023)

<a id="1.89.0-Stabilized-APIs"></a>

## Stabilized APIs

- [`NonZero<char>`](https://doc.rust-lang.org/stable/std/num/struct.NonZero.html)
- Many intrinsics for x86, not enumerated here
  - [AVX512 intrinsics](rust-lang/rust#111137)
  - [`SHA512`, `SM3` and `SM4` intrinsics](rust-lang/rust#126624)
- [`File::lock`](https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.lock)
- [`File::lock_shared`](https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.lock_shared)
- [`File::try_lock`](https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.try_lock)
- [`File::try_lock_shared`](https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.try_lock_shared)
- [`File::unlock`](https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.unlock)
- [`NonNull::from_ref`](https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.from_ref)
- [`NonNull::from_mut`](https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.from_mut)
- [`NonNull::without_provenance`](https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.without_provenance)
- [`NonNull::with_exposed_provenance`](https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.with_exposed_provenance)
- [`NonNull::expose_provenance`](https://doc.rust-lang.org/stable/std/ptr/struct.NonNull.html#method.expose_provenance)
- [`OsString::leak`](https://doc.rust-lang.org/stable/std/ffi/struct.OsString.html#method.leak)
- [`PathBuf::leak`](https://doc.rust-lang.org/stable/std/path/struct.PathBuf.html#method.leak)
- [`Result::flatten`](https://doc.rust-lang.org/stable/std/result/enum.Result.html#method.flatten)
- [`std::os::linux::net::TcpStreamExt::quickack`](https://doc.rust-lang.org/stable/std/os/linux/net/trait.TcpStreamExt.html#tymethod.quickack)
- [`std::os::linux::net::TcpStreamExt::set_quickack`](https://doc.rust-lang.org/stable/std/os/linux/net/trait.TcpStreamExt.html#tymethod.set_quickack)

These previously stable APIs are now stable in const contexts:

- [`<[T; N]>::as_mut_slice`](https://doc.rust-lang.org/stable/std/primitive.array.html#method.as_mut_slice)
- [`<[u8]>::eq_ignore_ascii_case`](https://doc.rust-lang.org/stable/std/primitive.slice.html#impl-%5Bu8%5D/method.eq_ignore_ascii_case)
- [`str::eq_ignore_ascii_case`](https://doc.rust-lang.org/stable/std/primitive.str.html#impl-str/method.eq_ignore_ascii_case)

<a id="1.89.0-Cargo"></a>

## Cargo

- [`cargo fix` and `cargo clippy --fix` now default to the same Cargo target selection as other build commands.](rust-lang/cargo#15192) Previously it would apply to all targets (like binaries, examples, tests, etc.). The `--edition` flag still applies to all targets.
- [Stabilize doctest-xcompile.](rust-lang/cargo#15462) Doctests are now tested when cross-compiling. Just like other tests, it will use the [`runner` setting](https://doc.rust-lang.org/cargo/reference/config.html#targettriplerunner) to run the tests. If you need to disable tests for a target, you can use the [ignore doctest attribute](https://doc.rust-lang.org/rustdoc/write-documentation/documentation-tests.html#ignoring-targets) to specify the targets to ignore.

<a id="1.89.0-Rustdoc"></a>

## Rustdoc

- [On mobile, make the sidebar full width and linewrap](rust-lang/rust#139831). This makes long section and item names much easier to deal with on mobile.

<a id="1.89.0-Compatibility-Notes"></a>

## Compatibility Notes

- [Make `missing_fragment_specifier` an unconditional error](rust-lang/rust#128425)
- [Enabling the `neon` target feature on `aarch64-unknown-none-softfloat` causes a warning](rust-lang/rust#135160) because mixing code with and without that target feature is not properly supported by LLVM
- [Sized Hierarchy: Part I](rust-lang/rust#137944)
  - Introduces a small breaking change affecting `?Sized` bounds on impls on recursive types which contain associated type projections. It is not expected to affect any existing published crates. Can be fixed by refactoring the involved types or opting into the `sized_hierarchy` unstable feature. See the [FCP report](rust-lang/rust#137944 (comment)) for a code example.
- The warn-by-default `elided_named_lifetimes` lint is [superseded by the warn-by-default `mismatched_lifetime_syntaxes` lint.](rust-lang/rust#138677)
- [Error on recursive opaque types earlier in the type checker](rust-lang/rust#139419)
- [Type inference side effects from requiring element types of array repeat expressions are `Copy` are now only available at the end of type checking](rust-lang/rust#139635)
- [The deprecated accidentally-stable `std::intrinsics::{copy,copy_nonoverlapping,write_bytes}` are now proper intrinsics](rust-lang/rust#139916). There are no debug assertions guarding against UB, and they cannot be coerced to function pointers.
- [Remove long-deprecated `std::intrinsics::drop_in_place`](rust-lang/rust#140151)
- [Make well-formedness predicates no longer coinductive](rust-lang/rust#140208)
- [Remove hack when checking impl method compatibility](rust-lang/rust#140557)
- [Remove unnecessary type inference due to built-in trait object impls](rust-lang/rust#141352)
- [Lint against "stdcall", "fastcall", and "cdecl" on non-x86-32 targets](rust-lang/rust#141435)
- [Future incompatibility warnings relating to the never type (`!`) are now reported in dependencies](rust-lang/rust#141937)
- [Ensure `std::ptr::copy_*` intrinsics also perform the static self-init checks](rust-lang/rust#142575)
- [`extern "C"` functions on the `wasm32-unknown-unknown` target now have a standards compliant ABI](https://blog.rust-lang.org/2025/04/04/c-abi-changes-for-wasm32-unknown-unknown/)

<a id="1.89.0-Internal-Changes"></a>

## Internal Changes

These changes do not affect any public interfaces of Rust, but they represent
significant improvements to the performance or internals of rustc and related
tools.

- [Correctly un-remap compiler sources paths with the `rustc-dev` component](rust-lang/rust#142377)

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aarch64-unknown-none-softfloat: ABI unsoundness when enabling "neon" feature (tracking issue for aarch64_softfloat_neon)