99 lines
3.4 KiB
Rust
99 lines
3.4 KiB
Rust
//! Checks for uses of mutex where an atomic value could be used
|
|
//!
|
|
//! This lint is **warn** by default
|
|
|
|
use clippy_utils::diagnostics::span_lint;
|
|
use clippy_utils::ty::is_type_diagnostic_item;
|
|
use rustc_hir::Expr;
|
|
use rustc_lint::{LateContext, LateLintPass};
|
|
use rustc_middle::ty::{self, Ty};
|
|
use rustc_session::{declare_lint_pass, declare_tool_lint};
|
|
|
|
declare_clippy_lint! {
|
|
/// **What it does:** Checks for usages of `Mutex<X>` where an atomic will do.
|
|
///
|
|
/// **Why is this bad?** Using a mutex just to make access to a plain bool or
|
|
/// reference sequential is shooting flies with cannons.
|
|
/// `std::sync::atomic::AtomicBool` and `std::sync::atomic::AtomicPtr` are leaner and
|
|
/// faster.
|
|
///
|
|
/// **Known problems:** This lint cannot detect if the mutex is actually used
|
|
/// for waiting before a critical section.
|
|
///
|
|
/// **Example:**
|
|
/// ```rust
|
|
/// # let y = true;
|
|
///
|
|
/// // Bad
|
|
/// # use std::sync::Mutex;
|
|
/// let x = Mutex::new(&y);
|
|
///
|
|
/// // Good
|
|
/// # use std::sync::atomic::AtomicBool;
|
|
/// let x = AtomicBool::new(y);
|
|
/// ```
|
|
pub MUTEX_ATOMIC,
|
|
perf,
|
|
"using a mutex where an atomic value could be used instead"
|
|
}
|
|
|
|
declare_clippy_lint! {
|
|
/// **What it does:** Checks for usages of `Mutex<X>` where `X` is an integral
|
|
/// type.
|
|
///
|
|
/// **Why is this bad?** Using a mutex just to make access to a plain integer
|
|
/// sequential is
|
|
/// shooting flies with cannons. `std::sync::atomic::AtomicUsize` is leaner and faster.
|
|
///
|
|
/// **Known problems:** This lint cannot detect if the mutex is actually used
|
|
/// for waiting before a critical section.
|
|
///
|
|
/// **Example:**
|
|
/// ```rust
|
|
/// # use std::sync::Mutex;
|
|
/// let x = Mutex::new(0usize);
|
|
///
|
|
/// // Good
|
|
/// # use std::sync::atomic::AtomicUsize;
|
|
/// let x = AtomicUsize::new(0usize);
|
|
/// ```
|
|
pub MUTEX_INTEGER,
|
|
nursery,
|
|
"using a mutex for an integer type"
|
|
}
|
|
|
|
declare_lint_pass!(Mutex => [MUTEX_ATOMIC, MUTEX_INTEGER]);
|
|
|
|
impl<'tcx> LateLintPass<'tcx> for Mutex {
|
|
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
|
|
let ty = cx.typeck_results().expr_ty(expr);
|
|
if let ty::Adt(_, subst) = ty.kind() {
|
|
if is_type_diagnostic_item(cx, ty, sym!(mutex_type)) {
|
|
let mutex_param = subst.type_at(0);
|
|
if let Some(atomic_name) = get_atomic_name(mutex_param) {
|
|
let msg = format!(
|
|
"consider using an `{}` instead of a `Mutex` here; if you just want the locking \
|
|
behavior and not the internal type, consider using `Mutex<()>`",
|
|
atomic_name
|
|
);
|
|
match *mutex_param.kind() {
|
|
ty::Uint(t) if t != ty::UintTy::Usize => span_lint(cx, MUTEX_INTEGER, expr.span, &msg),
|
|
ty::Int(t) if t != ty::IntTy::Isize => span_lint(cx, MUTEX_INTEGER, expr.span, &msg),
|
|
_ => span_lint(cx, MUTEX_ATOMIC, expr.span, &msg),
|
|
};
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn get_atomic_name(ty: Ty<'_>) -> Option<&'static str> {
|
|
match ty.kind() {
|
|
ty::Bool => Some("AtomicBool"),
|
|
ty::Uint(_) => Some("AtomicUsize"),
|
|
ty::Int(_) => Some("AtomicIsize"),
|
|
ty::RawPtr(_) => Some("AtomicPtr"),
|
|
_ => None,
|
|
}
|
|
}
|