⚙️ cfg-expr

A parser and evaluator for Rust cfg() expressions. Targets as of Rust 1.43.1 are supported.

Alternatives

• cargo-platform
• parse_cfg

Usage

```rust use cfgexpr::{targets::getbuiltintargetby_triple, Expression, Predicate};

fn main() { let specific = Expression::parse( r#"all( targetos = "windows", targetarch = "x86", windows, targetenv = "msvc", targetfeature = "fxsr", targetfeature = "sse", targetfeature = "sse2", targetpointerwidth = "32", targetendian = "little", not(targetvendor = "uwp"), feature = "cool_thing", )"#, ) .unwrap();

// cfg_expr includes a list of every builtin target in rustc (as of 1.41)
let x86_win = get_builtin_target_by_triple("i686-pc-windows-msvc").unwrap();
let x86_pentium_win = get_builtin_target_by_triple("i586-pc-windows-msvc").unwrap();
let uwp_win = get_builtin_target_by_triple("i686-uwp-windows-msvc").unwrap();
let mac = get_builtin_target_by_triple("x86_64-apple-darwin").unwrap();

let avail_targ_feats = ["fxsr", "sse", "sse2"];

// This will satisfy all requirements
assert!(specific.eval(|pred| {
    match pred {
        Predicate::Target(tp) => tp.matches(x86_win),
        Predicate::TargetFeature(feat) => avail_targ_feats.contains(feat),
        Predicate::Feature(feat) => *feat == "cool_thing",
        _ => false,
    }
}));

// This won't, it doesnt' have the cool_thing feature!
assert!(!specific.eval(|pred| {
    match pred {
        Predicate::Target(tp) => tp.matches(x86_pentium_win),
        Predicate::TargetFeature(feat) => avail_targ_feats.contains(feat),
        _ => false,
    }
}));

// This will *not* satisfy the vendor predicate
assert!(!specific.eval(|pred| {
    match pred {
        Predicate::Target(tp) => tp.matches(uwp_win),
        Predicate::TargetFeature(feat) => avail_targ_feats.contains(feat),
        _ => false,
    }
}));

// This will *not* satisfy the vendor, os, or env predicates
assert!(!specific.eval(|pred| {
    match pred {
        Predicate::Target(tp) => tp.matches(mac),
        Predicate::TargetFeature(feat) => avail_targ_feats.contains(feat),
        _ => false,
    }
}));

} ```

Contributing

We welcome community contributions to this project.

Please read our Contributor Guide for more information on how to get started.

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.