Stabilize unsafe_attributes

[carbotaniuman]

Stabilization report

Summary

This is a tracking issue for the RFC 3325: unsafe attributes

We are stabilizing #![feature(unsafe_attributes)], which makes certain attributes considered 'unsafe', meaning that they must be surrounded by an unsafe(...), as in #[unsafe(no_mangle)].

RFC: rust-lang/rfcs#3325
Tracking issue: #123757

What is stabilized

Summary of stabilization

Certain attributes will now be designated as unsafe attributes, namely, no_mangle, export_name, and link_section (stable only), and these attributes will need to be called by surrounding them in unsafe(...) syntax. On editions prior to 2024, this is simply an edition lint, but it will become a hard error in 2024. This also works in cfg_attr, but unsafe is not allowed for any other attributes, including proc-macros ones.

#[unsafe(no_mangle)]
fn a() {}

#[cfg_attr(any(), unsafe(export_name = "c"))]
fn b() {}

For a table showing the attributes that were considered to be included in the list to require unsafe, and subsequent reasoning about why each such attribute was or was not included, see this comment here

Tests

The relevant tests are in tests/ui/rust-2024/unsafe-attributes and tests/ui/attributes/unsafe.

[rustbot]

r? @nnethercote

rustbot has assigned @nnethercote.
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

[rustbot]

Some changes occurred in src/tools/rustfmt

cc @rust-lang/rustfmt

[traviscross]

@rustbot labels +I-lang-nominated

Let's discuss this edition-relevant stabilization and let's propose...

@rfcbot fcp merge

[traviscross]

@rfcbot fcp cancel

[rfcbot]

@traviscross proposal cancelled.

[traviscross]

@rfcbot fcp merge

[rfcbot]

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

• @joshtriplett
• @nikomatsakis
• @pnkfelix
• @scottmcm
• @tmandry
• @traviscross

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]

🔔 This is now entering its final comment period, as per the review above. 🔔

[nnethercote]

The code changes look fine. r=me once the FCP is finished.

[bors]

⌛ Testing commit de9b5c3 with merge 37d56da...

[bors]

☀️ Test successful - checks-actions
Approved by: nnethercote
Pushing 37d56da to master...

[rust-timer]

Finished benchmarking commit (37d56da): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.2%]	3
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 3.6%, secondary 4.1%)

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)	3.6%	[3.6%, 3.6%]	1
Regressions ❌ (secondary)	4.1%	[2.4%, 5.0%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	3.6%	[3.6%, 3.6%]	1

Cycles

Results (primary 2.7%)

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)	2.7%	[2.7%, 2.7%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.7%	[2.7%, 2.7%]	1

Binary size

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

Bootstrap: 749.471s -> 750.905s (0.19%)
Artifact size: 339.10 MiB -> 339.10 MiB (0.00%)