Support `#[rustc_align_static]` inside `thread_local!` #146281

Jules-Bertholet · 2025-09-06T17:01:11Z

Tracking issue: #146177

thread_local! {
    #[rustc_align_static(64)]
    static SO_ALIGNED: u64 = const { 0 };
}

This increases the amount of recursion the macro performs (once per attribute in addition to the previous once per item), making it easier to hit the recursion limit. I’ve added workarounds to limit the impact in the case of long doc comments, but this still needs a crater run just in case.

r? libs

@rustbot label A-attributes A-macros A-thread-locals F-static_align T-libs

rustbot · 2025-09-06T17:01:16Z

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rustbot · 2025-09-06T17:01:19Z

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann

Some changes occurred in compiler/rustc_codegen_gcc

cc @antoyo, @GuillaumeGomez

Some changes occurred to the CTFE machinery

cc @RalfJung, @oli-obk, @lcnr

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri, @RalfJung, @oli-obk, @lcnr

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

cc @jdonszelmann

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri

The Miri subtree was changed

cc @rust-lang/miri

jdonszelmann · 2025-09-10T18:59:51Z

@Jules-Bertholet would you mind rebasing? #146178 merged
@rustbot author

rustbot · 2025-09-10T18:59:57Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

Mark-Simulacrum · 2025-10-01T15:01:23Z

library/std/src/sys/thread_local/os.rs

+        }
+        unsafe {
+            ptr.write(Value { value: i.and_then(Option::take).unwrap_or_else(f), key });
+        }


I think ptr is going to be leaked here if get/set panic -- can that happen? It looks like those have a quite a bit of code that they're running...

Good catch, should be better now

Well, actually, if get/set specifically panic there will be a leak. I’m not sure if that’s possible, but in any case any issue here is preexisting and not made worse by this PR. f can definitely panic though, as can drop_in_place; my latest commit accounts for that.

Mark-Simulacrum · 2025-10-01T18:21:26Z

@bors r+

bors · 2025-10-01T18:21:30Z

📌 Commit 94f00f4 has been approved by Mark-Simulacrum

It is now in the queue for this repository.

…d-local, r=Mark-Simulacrum Support `#[rustc_align_static]` inside `thread_local!` Tracking issue: rust-lang#146177 ```rust thread_local! { #[rustc_align_static(64)] static SO_ALIGNED: u64 = const { 0 }; } ``` This increases the amount of recursion the macro performs (once per attribute in addition to the previous once per item), making it easier to hit the recursion limit. I’ve added workarounds to limit the impact in the case of long doc comments, but this still needs a crater run just in case. r? libs `@rustbot` label A-attributes A-macros A-thread-locals F-static_align T-libs

Rollup of 10 pull requests Successful merges: - #146281 (Support `#[rustc_align_static]` inside `thread_local!`) - #146535 (mbe: Implement `unsafe` attribute rules) - #146585 (indexing: reword help) - #147004 (Tweak handling of "struct like start" where a struct isn't supported) - #147221 (Forbid `//@ compile-flags: -Cincremental=` in tests) - #147225 (Don't enable shared memory by default with Wasm atomics) - #147227 (implement `Box::take`) - #147231 (Extending `#[rustc_force_inline]` to be applicable to inherent methods) - #147233 (Initialize llvm submodule if not already the case to run citool) - #147236 (Update books) r? `@ghost` `@rustbot` modify labels: rollup

…d-local, r=Mark-Simulacrum Support `#[rustc_align_static]` inside `thread_local!` Tracking issue: rust-lang#146177 ```rust thread_local! { #[rustc_align_static(64)] static SO_ALIGNED: u64 = const { 0 }; } ``` This increases the amount of recursion the macro performs (once per attribute in addition to the previous once per item), making it easier to hit the recursion limit. I’ve added workarounds to limit the impact in the case of long doc comments, but this still needs a crater run just in case. r? libs ``@rustbot`` label A-attributes A-macros A-thread-locals F-static_align T-libs

…d-local, r=Mark-Simulacrum Support `#[rustc_align_static]` inside `thread_local!` Tracking issue: rust-lang#146177 ```rust thread_local! { #[rustc_align_static(64)] static SO_ALIGNED: u64 = const { 0 }; } ``` This increases the amount of recursion the macro performs (once per attribute in addition to the previous once per item), making it easier to hit the recursion limit. I’ve added workarounds to limit the impact in the case of long doc comments, but this still needs a crater run just in case. r? libs `@rustbot` label A-attributes A-macros A-thread-locals F-static_align T-libs

Rollup of 9 pull requests Successful merges: - #146281 (Support `#[rustc_align_static]` inside `thread_local!`) - #146535 (mbe: Implement `unsafe` attribute rules) - #146585 (indexing: reword help) - #147004 (Tweak handling of "struct like start" where a struct isn't supported) - #147221 (Forbid `//@ compile-flags: -Cincremental=` in tests) - #147225 (Don't enable shared memory by default with Wasm atomics) - #147227 (implement `Box::take`) - #147233 (Initialize llvm submodule if not already the case to run citool) - #147236 (Update books) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #146281 - Jules-Bertholet:static-align-thread-local, r=Mark-Simulacrum Support `#[rustc_align_static]` inside `thread_local!` Tracking issue: #146177 ```rust thread_local! { #[rustc_align_static(64)] static SO_ALIGNED: u64 = const { 0 }; } ``` This increases the amount of recursion the macro performs (once per attribute in addition to the previous once per item), making it easier to hit the recursion limit. I’ve added workarounds to limit the impact in the case of long doc comments, but this still needs a crater run just in case. r? libs ``@rustbot`` label A-attributes A-macros A-thread-locals F-static_align T-libs

Rollup of 9 pull requests Successful merges: - rust-lang/rust#146281 (Support `#[rustc_align_static]` inside `thread_local!`) - rust-lang/rust#146535 (mbe: Implement `unsafe` attribute rules) - rust-lang/rust#146585 (indexing: reword help) - rust-lang/rust#147004 (Tweak handling of "struct like start" where a struct isn't supported) - rust-lang/rust#147221 (Forbid `//@ compile-flags: -Cincremental=` in tests) - rust-lang/rust#147225 (Don't enable shared memory by default with Wasm atomics) - rust-lang/rust#147227 (implement `Box::take`) - rust-lang/rust#147233 (Initialize llvm submodule if not already the case to run citool) - rust-lang/rust#147236 (Update books) r? `@ghost` `@rustbot` modify labels: rollup

rustbot assigned lcnr Sep 6, 2025

rustbot assigned jhpratt and unassigned lcnr Sep 6, 2025

Jules-Bertholet force-pushed the static-align-thread-local branch from 67db3cb to dd3475c Compare September 6, 2025 17:14

rustbot added A-LLVM Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues. and removed A-LLVM Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues. labels Sep 6, 2025

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Jules-Bertholet force-pushed the static-align-thread-local branch from dd3475c to 9cdfc77 Compare September 10, 2025 19:03

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Jules-Bertholet force-pushed the static-align-thread-local branch from ca8d8b3 to ff97f2a Compare September 24, 2025 21:45

Support #[rustc_align_static] inside thread_local!

a4e87e9

Jules-Bertholet force-pushed the static-align-thread-local branch from ff97f2a to a4e87e9 Compare September 26, 2025 17:51

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Hoist non-platform-specific code out of thread_local_inner!

4d32b9a

Jules-Bertholet force-pushed the static-align-thread-local branch from 52fd64d to 4d32b9a Compare September 27, 2025 21:05

Jules-Bertholet mentioned this pull request Sep 27, 2025

thread_local! doesn’t like types whose definitions cannot be written more than once #147103

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Mark-Simulacrum reviewed Oct 1, 2025

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Jules-Bertholet force-pushed the static-align-thread-local branch from d12cb9b to cafb91d Compare October 1, 2025 16:25

Fix memory leak in os impl

94f00f4

Jules-Bertholet force-pushed the static-align-thread-local branch from cafb91d to 94f00f4 Compare October 1, 2025 16:28

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-review Status: Awaiting review from the assignee but also interested parties. labels Oct 1, 2025

Zalathar mentioned this pull request Oct 2, 2025

Rollup of 10 pull requests #147253

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matthiaskrgr mentioned this pull request Oct 2, 2025

Rollup of 9 pull requests #147256

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jhpratt mentioned this pull request Oct 2, 2025

Rollup of 10 pull requests #147260

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matthiaskrgr mentioned this pull request Oct 2, 2025

Rollup of 9 pull requests #147261

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bors merged commit 92aac1b into rust-lang:master Oct 2, 2025
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rustbot added this to the 1.92.0 milestone Oct 2, 2025

Jules-Bertholet deleted the static-align-thread-local branch October 2, 2025 14:45

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Toolchain upgrade to nightly-2025-10-06 flux-rs/flux#1271

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