83a82a1d86
The default level is always given in the declare_lint! macro, no need to add it inconsistently in the documentation.
78 lines
2.9 KiB
Rust
78 lines
2.9 KiB
Rust
//! Checks for uses of Mutex where an atomic value could be used
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//!
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//! This lint is **warn** by default
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use rustc::lint::{LintPass, LintArray, LateLintPass, LateContext};
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use rustc_front::hir::Expr;
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use syntax::ast;
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use rustc::middle::ty;
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use rustc::middle::subst::ParamSpace;
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use utils::{span_lint, MUTEX_PATH, match_type};
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/// **What it does:** This lint checks for usages of `Mutex<X>` where an atomic will do.
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///
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/// **Why is this bad?** Using a Mutex just to make access to a plain bool or reference sequential is shooting flies with cannons. `std::atomic::AtomicBool` and `std::atomic::AtomicPtr` are leaner and faster.
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///
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/// **Known problems:** This lint cannot detect if the Mutex is actually used for waiting before a critical section.
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///
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/// **Example:** `let x = Mutex::new(&y);`
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declare_lint! {
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pub MUTEX_ATOMIC,
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Warn,
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"using a Mutex where an atomic value could be used instead"
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}
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/// **What it does:** This lint checks for usages of `Mutex<X>` where `X` is an integral type.
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///
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/// **Why is this bad?** Using a Mutex just to make access to a plain integer sequential is shooting flies with cannons. `std::atomic::usize` is leaner and faster.
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///
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/// **Known problems:** This lint cannot detect if the Mutex is actually used for waiting before a critical section.
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///
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/// **Example:** `let x = Mutex::new(0usize);`
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declare_lint! {
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pub MUTEX_INTEGER,
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Allow,
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"using a Mutex for an integer type"
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}
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impl LintPass for MutexAtomic {
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fn get_lints(&self) -> LintArray {
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lint_array!(MUTEX_ATOMIC, MUTEX_INTEGER)
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}
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}
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pub struct MutexAtomic;
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impl LateLintPass for MutexAtomic {
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fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
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let ty = cx.tcx.expr_ty(expr);
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if let ty::TyStruct(_, subst) = ty.sty {
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if match_type(cx, ty, &MUTEX_PATH) {
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let mutex_param = &subst.types.get(ParamSpace::TypeSpace, 0).sty;
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if let Some(atomic_name) = get_atomic_name(mutex_param) {
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let msg = format!("Consider using an {} instead of a Mutex here. If you just want the locking \
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behaviour and not the internal type, consider using Mutex<()>.",
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atomic_name);
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match *mutex_param {
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ty::TyUint(t) if t != ast::TyUs => span_lint(cx, MUTEX_INTEGER, expr.span, &msg),
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ty::TyInt(t) if t != ast::TyIs => span_lint(cx, MUTEX_INTEGER, expr.span, &msg),
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_ => span_lint(cx, MUTEX_ATOMIC, expr.span, &msg),
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};
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}
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}
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}
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}
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}
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fn get_atomic_name(ty: &ty::TypeVariants) -> Option<(&'static str)> {
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match *ty {
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ty::TyBool => Some("AtomicBool"),
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ty::TyUint(_) => Some("AtomicUsize"),
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ty::TyInt(_) => Some("AtomicIsize"),
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ty::TyRawPtr(_) => Some("AtomicPtr"),
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_ => None,
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}
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}
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