use `#[align]` attribute for `fn_align` #142507

folkertdev · 2025-06-14T14:26:28Z

Tracking issue: #82232

rust-lang/rfcs#3806 decides to add the #[align] attribute for alignment of various items. Right now it's used for functions with fn_align, in the future it will get more uses (statics, struct fields, etc.)

(the RFC finishes FCP today)

r? @ghost

folkertdev · 2025-06-15T11:15:06Z

@traviscross the FCP on #[align] is completed, but there is some discussion over there. I haven't seen anyone object to using #[align] though. Can we move forward with the attribute name change here (and then stabilize #140261), or should T-lang discuss the attribute change again first?

traviscross · 2025-06-15T18:42:41Z

Given the RFC acceptance, this change is good to go as a lang matter.

folkertdev

Nice, in that case

r? @jdonszelmann

compiler/rustc_passes/src/errors.rs

compiler/rustc_attr_parsing/src/attributes/repr.rs

rustbot · 2025-06-15T19:29:39Z

The Miri subtree was changed

cc @rust-lang/miri

Some changes occurred in compiler/rustc_codegen_ssa

cc @WaffleLapkin

Some changes occurred in compiler/rustc_codegen_ssa/src/codegen_attrs.rs

cc @jdonszelmann

Some changes occurred in compiler/rustc_passes/src/check_attr.rs

cc @jdonszelmann

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann

Some changes occurred in compiler/rustc_attr_data_structures

cc @jdonszelmann

jdonszelmann · 2025-06-15T20:19:43Z

On my to-do list! Will take a look somewhere this week :)

compiler/rustc_attr_parsing/src/attributes/repr.rs

jdonszelmann · 2025-06-15T22:29:16Z

compiler/rustc_attr_parsing/src/attributes/repr.rs

+        cx: &'c mut AcceptContext<'_, '_, S>,
+        args: &'c ArgParser<'_>,
+    ) {
+        // The builtin attributes parser already emits an error in this case.


by the template logic? I'd quite like to move those checks here at some point, including the templates. For converted attributes I usually have added an exception there to ignore attributes with new-style parsers so that these checks do do something, and all checks happen in one place. If you wouldn't mind, could you do the same for align?

With #138165 you don't need to make a new diagnostic for this either which should make your life easier.

by the template logic?

Exactly

If you wouldn't mind, could you do the same for align?

Do you have an example here? E.g ConfusablesParser also seems to ignore this case?

yea! I've been making exceptions to new attributes here:

rust/compiler/rustc_parse/src/validate_attr.rs

Line 288 in 1e8aac1

sym::inline

and then add proper validation for them here:

rust/compiler/rustc_attr_parsing/src/attributes/inline.rs

Line 24 in 1e8aac1

match args {

(n.b. I exhaustively match and error on all cases)

I think those links are to #138165? Should I rebase on that now? (happy to, but could also do a follow-up later)

I think rebasing would be nice, then this parser is in a much nicer state. Otherwise I'll go back to fix it next week again. That #138165 seems to make good progress.

compiler/rustc_attr_parsing/src/attributes/repr.rs

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

compiler/rustc_passes/src/check_attr.rs

jdonszelmann · 2025-06-15T22:39:09Z

compiler/rustc_passes/src/check_attr.rs

-                                    fluent::passes_repr_align_function,
-                                )
-                                .emit();
+                                self.dcx().emit_err(errors::ReprAlignShouldBeAlign {


love these helpful diagnostics :)

compiler/rustc_passes/src/errors.rs

bors · 2025-06-16T22:20:09Z

☔ The latest upstream changes (presumably #142589) made this pull request unmergeable. Please resolve the merge conflicts.

jdonszelmann · 2025-06-18T09:31:04Z

@folkertdev master now has these changes to diagnostics :)

Right now it's used for functions with `fn_align`, in the future it will get more uses (statics, struct fields, etc.)

jdonszelmann · 2025-06-18T12:00:25Z

much better

jdonszelmann · 2025-06-18T12:02:24Z

@bors rollup=always

bors · 2025-06-18T12:02:26Z

📌 Commit 1fdf2b5 has been approved by jdonszelmann

It is now in the queue for this repository.

rustbot added A-attributes Area: Attributes (`#[…]`, `#![…]`) T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jun 14, 2025

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folkertdev force-pushed the fn-align-align-attribute branch from 3d85cf8 to 8769e96 Compare June 14, 2025 15:24

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folkertdev force-pushed the fn-align-align-attribute branch from 8769e96 to 92fa35d Compare June 14, 2025 16:13

folkertdev commented Jun 15, 2025

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rustbot assigned jdonszelmann Jun 15, 2025

folkertdev marked this pull request as ready for review June 15, 2025 19:29

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 15, 2025

jdonszelmann mentioned this pull request Jun 15, 2025

Tracking issue: Attribute refactor #131229

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add #[align] attribute

1fdf2b5

Right now it's used for functions with `fn_align`, in the future it will get more uses (statics, struct fields, etc.)

folkertdev force-pushed the fn-align-align-attribute branch from ba3c409 to 1fdf2b5 Compare June 18, 2025 10:37

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 Jun 18, 2025

use #[align] attribute for fn_align #142507

Are you sure you want to change the base?

use #[align] attribute for fn_align #142507

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use `#[align]` attribute for `fn_align` #142507

use `#[align]` attribute for `fn_align` #142507

jdonszelmann commented Jun 18, 2025 •

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