mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-22 11:03:16 +00:00
91 lines
3 KiB
Rust
91 lines
3 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 crate::utils::{match_type, paths, span_lint};
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use rustc::hir::Expr;
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use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use rustc::ty::{self, Ty};
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use rustc::{declare_tool_lint, lint_array};
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use syntax::ast;
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/// **What it does:** 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
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/// reference sequential is shooting flies with cannons.
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/// `std::sync::atomic::AtomicBool` and `std::sync::atomic::AtomicPtr` are leaner and
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/// faster.
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///
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/// **Known problems:** This lint cannot detect if the mutex is actually used
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/// for waiting before a critical section.
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///
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/// **Example:**
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/// ```rust
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/// let x = Mutex::new(&y);
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/// ```
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declare_clippy_lint! {
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pub MUTEX_ATOMIC,
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perf,
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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:** Checks for usages of `Mutex<X>` where `X` is an integral
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/// type.
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///
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/// **Why is this bad?** Using a mutex just to make access to a plain integer
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/// sequential is
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/// shooting flies with cannons. `std::sync::atomic::AtomicUsize` is leaner and faster.
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///
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/// **Known problems:** This lint cannot detect if the mutex is actually used
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/// for waiting before a critical section.
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///
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/// **Example:**
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/// ```rust
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/// let x = Mutex::new(0usize);
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/// ```
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declare_clippy_lint! {
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pub MUTEX_INTEGER,
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nursery,
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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<'a, 'tcx> LateLintPass<'a, 'tcx> for MutexAtomic {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
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let ty = cx.tables.expr_ty(expr);
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if let ty::Adt(_, subst) = ty.sty {
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if match_type(cx, ty, &paths::MUTEX) {
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let mutex_param = subst.type_at(0);
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if let Some(atomic_name) = get_atomic_name(mutex_param) {
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let msg = format!(
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"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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);
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match mutex_param.sty {
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ty::Uint(t) if t != ast::UintTy::Usize => span_lint(cx, MUTEX_INTEGER, expr.span, &msg),
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ty::Int(t) if t != ast::IntTy::Isize => 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<'_>) -> Option<(&'static str)> {
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match ty.sty {
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ty::Bool => Some("AtomicBool"),
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ty::Uint(_) => Some("AtomicUsize"),
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ty::Int(_) => Some("AtomicIsize"),
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ty::RawPtr(_) => Some("AtomicPtr"),
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_ => None,
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}
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}
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