Expand description
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 1.54.0 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_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,
}
}));Re-exports
pub use error::ParseError;pub use expr::Expression;pub use expr::Predicate;pub use expr::TargetPredicate;