A parser and evaluator for Rust cfg() expressions. Targets as of Rust 1.58.0 are supported.
cfg-expr is a crate that can be used to parse and evaluate Rust cfg() expressions, both as declarable in Rust code itself, as well in cargo manifests' [target.'cfg()'.dependencies] sections.
It contains a list of all builtin targets known to rustc as of 1.58.0 that can be used to determine if a particular cfg expression is satisfiable.
use cfg_expr::{targets::get_builtin_target_by_triple, Expression, Predicate};
let specific = Expression::parse(
r#"all(
target_os = "windows",
target_arch = "x86",
windows,
target_env = "msvc",
target_feature = "fxsr",
target_feature = "sse",
target_feature = "sse2",
target_pointer_width = "32",
target_endian = "little",
not(target_vendor = "uwp"),
feature = "cool_thing",
)"#,
).unwrap();
// cfg_expr includes a list of every builtin target in rustc
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_target_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_target_feats.contains(feat),
Predicate::Feature(feat) => *feat == "cool_thing",
_ => false,
}
}));
// This won't, it doesn't have the cool_thing feature!
assert!(!specific.eval(|pred| {
match pred {
Predicate::Target(tp) => tp.matches(x86_pentium_win),
Predicate::TargetFeature(feat) => avail_target_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_target_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_target_feats.contains(feat),
_ => false,
}
}));We welcome community contributions to this project.
Please read our Contributor Guide for more information on how to get started.
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.
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.