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Tracking Issue for #[repr(align(...))] on function items (fn_align) #82232

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repnop opened this issue Feb 17, 2021 · 4 comments
Open
1 of 3 tasks

Tracking Issue for #[repr(align(...))] on function items (fn_align) #82232

repnop opened this issue Feb 17, 2021 · 4 comments
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A-rust-for-linux Relevant for the Rust-for-Linux project C-tracking-issue Category: A tracking issue for an RFC or an unstable feature.

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@repnop
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repnop commented Feb 17, 2021 •
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This feature allows specifying an alignment for function items by adding the #[repr(align(...))] attribute to them.
The feature gate for the issue is #![feature(fn_align)]

Example

#[repr(align(16))]
fn requires_alignment() {
    // ...
}

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@repnop repnop added the C-tracking-issue Category: A tracking issue for an RFC or an unstable feature. label Feb 17, 2021
@repnop repnop changed the title Tracking Issue for #[repr(align = ...)] on function items (fn_align) Tracking Issue for #[repr(align(...))] on function items (fn_align) Feb 17, 2021
@memoryruins memoryruins mentioned this issue Apr 6, 2021
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@evanrichter
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Is it be possible to apply this to methods as well?

#![feature(fn_align)]

#[repr(align(1))]
fn main() {
    Bar::foo();
}

struct Bar;

impl Bar {
    #[repr(align(1))]
    fn foo() {
        println!("bar");
    }
}
error[E0517]: attribute should be applied to a struct, enum, function, or union
  --> src/main.rs:11:12
   |
11 |       #[repr(align(1))]
   |              ^^^^^^^^
12 | /     fn foo() {
13 | |         println!("bar");
14 | |     }
   | |_____- not a struct, enum, function, or union

For more information about this error, try `rustc --explain E0517`.
error: could not compile `asdf` due to previous error

@repnop
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repnop commented Aug 26, 2021

I don't see why not? (I'm surprised it doesn't work already honestly lol) I'll see if I can find some time to investigate that and make another PR to allow that 👍

@ghost ghost mentioned this issue Aug 12, 2022
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6 tasks
winksaville added a commit to winksaville/exper-borrowed-vs-owned-parameters that referenced this issue Dec 3, 2022
@winksaville
feat: Add MessageMf
e5f5f73 
MessageMf has "Many fields" making it able to see how borrowed and
owned scale differently.

Added benchmarking creating default instances of Message and
MessageMf.

Removed the xxx_loop() variants as they don't add information just more
noise. I would like to look at why xxx_idx_loop() is sometimes slower
than xxx_iter_loop().

NOTE: I believe some of the noise is caused by code alignment changes
as we tweak that where doing and change code.
See: https://www.google.com/search?q=benchmark sensitive to code alignment
and rust-lang/rust#82232
@bunnie
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bunnie commented Dec 25, 2022

Thanks for opening this, I just bumped my head into this exact problem as well!

@fee1-dead fee1-dead mentioned this issue Apr 14, 2023
Merged
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Apr 17, 2023
@matthiaskrgr
Rollup merge of rust-lang#110313 - fee1-dead-contrib:repr_align_metho…
eb05246 
…d, r=WaffleLapkin

allow `repr(align = x)` on inherent methods

Discussion: rust-lang#82232 (comment)
@jonathanpallant jonathanpallant mentioned this issue Nov 22, 2023
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@bazhenov bazhenov mentioned this issue Jan 20, 2024
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This was referenced Aug 8, 2024
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@workingjubilee
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This should come with a command-line flag to address the request made in #128830 for global code alignment control.

@workingjubilee workingjubilee added the A-rust-for-linux Relevant for the Rust-for-Linux project label Aug 8, 2024
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