link-section

What's Changed

• Ensure hashes always compute 64-bit chunks by @mmastrac in #508
• Fix cross-crate section error on Rust versions 1.88-1.94 by @mmastrac in #509
• Fix WASM reference-section const cell layout by @silvanshine in #511
• Document crate_path and re-exports by @mmastrac in #514

Full Changelog: link-section-0.19.2...link-section-0.19.3

Changed

• Bump linktime-proc-macro dependency to 0.2.3 (consistent 64-bit hash chunks and cross-crate section-name fix).

Documentation

• Documented the crate_path override and surfaced the generated attribute reference (including crate_path) in the crate docs and README.

Fixed

• Fix cross-crate section-name error on Rust versions 1.88-1.94 (https://github.com/mmastrac/linktime/pull/509)
• Fix undefined behavior on WASM when a const item is submitted to a reference section: the item's cell lacked the fix-up slot the section-wide layout expects, so materialisation read past the cell and could write through a garbage slot pointer (https://github.com/mmastrac/linktime/pull/511).

What's Changed

• Bumped internal proc macro minimum version to pick up PR #495 (should not result in any downstream visible changes)

Full Changelog: link-section-0.19.1...link-section-0.19.2

Changed

• Bump linktime-proc-macro dependency to 0.2.1 (makes link-section names more stable).

Fixed

• Fix for semicolons accidentally inserted in WASM expression macro (generates a warning on nightly).

Fixed

• WASM: item counts no longer collapse under fat LTO. Items are gathered through address-significant intrusive list nodes that survive LTO. Fixes #488.

Changed

• WASM: the read_custom_section host import is no longer required. Sections are gathered in-module via .init_array.0 submissions and an .init_array.1 finalizer; the #[ctor] priority contract is unchanged.
• WASM: each item now lives in a single intrusive LinkCell<T> static (value plus trailing list metadata) instead of a separate value static and cell.

Removed

• Ref::as_ptr and MovableRef::as_ptr are now pub(crate). They exposed raw pointer plumbing that was never meant to be public API; use Deref (or offset_of for section-membership checks) instead. This is a breaking change.

Fixed

• Windows/COFF: section start/end pointers are now opacified with black_box, fixing a miscompile where an optimizing (LTO) build could prove a gathered slice (e.g. ScatteredSlice<&'static T>) reads as all-zero and fold it to null values, crashing on use (0xC0000005). Fixes #479.

Changed

• Empty sections are now automatically supported on all platforms other than AIX.

Changed

• Fixed WASM import module for read_custom_section and atexit.

Changed

• proc_macro feature is now required for any non-unsafe section.
• Non-unsafe sections now generate a unique ID for the submission site which allows multiple sections to share the same identifier.

Changed

• Fixed bug with submission of raw items to aux sections.

Added

• MovableRef and Ref implement Debug and Display if the referenced type does.

Changed

• Deprecated reference module in favor of Ref from the crate root.

Added

• reference sections support access both as a slice and as a reference at the submission site on all platforms (including WASM).
• movable sections support reordering and back-reference updates during startup initialization (allowing a "reference" to an item that may move during initialization at the submission site).
• typed and mutable sections have been split: typed allows for const and static items, while mutable allows for const items and as_mut_slice access.

Changed

• Bumped MSRV to 1.85.0.
• Significant rewrite to link-section's internal implementation.
• Sections require a type: #[section(typed)], #[section(untyped)], #[section(mutable)], #[section(movable)], or #[section(reference)].
• When submitting a fn() with a body to a typed link section, the function's body is not placed in any specific section. To restore the previous behavior, manually split function pointers and bodies:

#[section(untyped, aux(main = FN_ARRAY))]
pub static FN_BODIES: link_section::Section;

#[section(typed)]
pub static FN_ARRAY: link_section::TypedSection<fn()>;

#[in_section(FN_ARRAY)]
const _: fn() = linked_function;

#[in_section(FN_BODIES)]
pub fn linked_function() {
    eprintln!("linked_function");
}

Changed

• Repair MSRV breakage for WASM targets.

Added

• Support for AIX targets. Requires -C link-arg=-bdbg:namedsects:ss (or a recent Rust version that sets this automatically).

Added

• Support for const items in link sections.
• WASM now requires const items, and uses ctor-like initialization to copy data to a contiguous section. To access link-section slices in WASM in constructor functions, make sure to use priority = 1.
• Zero-sized types are no longer used in externs. Windows now uses a non-zero-sized alignment marker to align the start and end of the section. Other LLVM/GCC platforms use a u8.
• link-section is now no_std-compatible.

Changed

• WASM targets now use an extern read_custom_section function to read custom sections.

Changed

• Documentation polish and typo fixes.

Changed

• used_linker feature moved to --cfg linktime_used_linker flag.
• On macOS, fn items are placed in a __TEXT,__text,regular,pure_instructions section (fixes a linker warning in nightly).

Changed

• Macro attributes and crate features are auto-documented.

Added

• Included licenses in all files.
• Bumped proc-macro dependency versions.

Changed

• link-section crate no longer offers const section pointers.