Crate rucc_gnu 

The GNU compatibility surface: features.toml, attributes, builtins, pragmas.

Design: spec/13-gnu-compat.md. Layer rank 4, see spec/18-package-layout.md.

Status

The matrix is real. features.toml next to this file is the source of truth for what the compiler claims to support, build.rs turns it into the table below, and the __has_* family in the preprocessor answers out of it. The attributes and builtins themselves land with the parser, and every row that says unimplemented says so because it is.

The rule that makes the table worth having is in section 13.2: answering __has_builtin untruthfully is worse than answering no, because a header that gets a yes and then fails to compile is much harder to diagnose than one that takes its fallback path. So only a row marked implemented answers yes, and a row marked implemented with no test named against it fails the build.

use rucc_gnu::{Kind, Status};

assert_eq!(rucc_gnu::has_feature("__has_include"), 1);
assert_eq!(rucc_gnu::has_attribute("cleanup"), 0, "not until the parser lands");
assert_eq!(rucc_gnu::has_attribute("no_such_attribute"), 0);

// The armoured spelling is the same question.
assert_eq!(rucc_gnu::lookup(Kind::Attribute, "__packed__").map(|f| f.name), Some("packed"));

// Nested functions are refused rather than pending, and the table says which.
let nested = rucc_gnu::lookup(Kind::Extension, "nested_functions").unwrap();
assert_eq!(nested.status, Status::Rejected);

Every crate in the workspace is published, and publishing implies a promise. This one is tier 3: its Rust API is explicitly unstable and will change without a major version bump. Depend on the rucc binary’s behaviour, not on this.

Structs

Feature

One row of the matrix.

Enums

Answer

What happens when the compiler meets something this row describes and cannot do it.

Kind

What kind of thing a row of the matrix describes.

Status

How far along a row is.

Constants

MILESTONE

The milestone in spec/17-milestones.md that fills this crate in.

Statics

FEATURES

Every row of the matrix, sorted by kind and then by name.

Functions

features

The whole matrix, sorted by kind and then by name.

has_attribute

What __has_attribute(name) answers.

has_builtin

What __has_builtin(name) answers.

has_c_attribute

What __has_c_attribute(name) answers, which is the number the standard gives the attribute rather than one.

has_extension

What __has_extension(name) answers.

has_feature

What __has_feature(name) answers.

lookup

The row for a name, if the matrix has one.