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Update link_section to use the attribute template #1903

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Update link_section to use the attribute template #1903

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1cefa15
Unwrap link_section
ehuss Jun 2, 2025
3eea3d6
Linkify attribute
ehuss Jun 2, 2025
54632d1
Move link_section example to the intro
ehuss Jun 2, 2025
45e5c16
Add link_section attribute template rules
ehuss Jun 3, 2025
a18b648
Reword abi.link_section.unsafe to match attribute template
ehuss Jun 3, 2025
a4ef1ce
Add abi.link_section.null
ehuss Jun 3, 2025
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40 changes: 30 additions & 10 deletions src/abi.md
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Expand Up @@ -90,27 +90,47 @@ r[abi.link_section]
## The `link_section` attribute

r[abi.link_section.intro]
The *`link_section` attribute* specifies the section of the object file that a
[function] or [static]'s content will be placed into.
The *`link_section` [attribute]* specifies the section of the object file that a [function] or [static]'s content will be placed into.

> [!EXAMPLE]
> <!-- no_run: don't link. The format of the section name is platform-specific. -->
> ```rust,no_run
> #[unsafe(no_mangle)]
> #[unsafe(link_section = ".example_section")]
> pub static VAR1: u32 = 1;
> ```

r[abi.link_section.syntax]
The `link_section` attribute uses the [MetaNameValueStr] syntax to specify the section name.

<!-- no_run: don't link. The format of the section name is platform-specific. -->
```rust,no_run
#[unsafe(no_mangle)]
#[unsafe(link_section = ".example_section")]
pub static VAR1: u32 = 1;
```
r[abi.link_section.allowed-positions]
The `link_section` attribute may only be applied to:

- [Static items][items.static]
- [Free functions][items.fn]
- [Inherent associated functions][items.associated.fn]
- [Trait impl functions][items.impl.trait]
- [Trait definition functions][items.traits] with a body

> [!NOTE]
> `rustc` currently warns in other positions, but this may be rejected in the future.

r[abi.link_section.duplicates]
Only the last instance of `link_section` on an item is honored. Previous `link_section` attributes are ignored.

> [!NOTE]
> `rustc` currently warns on preceding duplicate `link_section` attributes. This may become an error in the future.

r[abi.link_section.unsafe]
This attribute is unsafe as it allows users to place data and code into sections
of memory not expecting them, such as mutable data into read-only areas.
The `link_section` attribute must be marked with [`unsafe`][attributes.safety] because it allows users to place data and code into sections of memory not expecting them, such as mutable data into read-only areas.

r[abi.link_section.edition2024]
> [!EDITION-2024]
> Before the 2024 edition it is allowed to use the `link_section` attribute without the `unsafe` qualification.

r[abi.link_section.null]
The section name must not contain a [NUL] character.

r[abi.export_name]
## The `export_name` attribute

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