2016-07-15 17:25:44 -05:00
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//! Checks for uses of mutex where an atomic value could be used
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2015-10-06 18:17:57 -05:00
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//!
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//! This lint is **warn** by default
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2021-03-25 13:29:11 -05:00
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use clippy_utils::diagnostics::span_lint;
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use clippy_utils::ty::is_type_diagnostic_item;
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2020-01-06 10:39:50 -06:00
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use rustc_hir::Expr;
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2020-01-12 00:08:41 -06:00
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use rustc_lint::{LateContext, LateLintPass};
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2020-03-30 04:02:14 -05:00
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use rustc_middle::ty::{self, Ty};
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2020-01-11 05:37:08 -06:00
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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2015-10-06 18:17:57 -05:00
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2018-03-28 08:24:26 -05:00
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declare_clippy_lint! {
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2021-07-29 05:16:06 -05:00
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/// ### What it does
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/// Checks for usages of `Mutex<X>` where an atomic will do.
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2019-03-05 10:50:33 -06:00
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///
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2021-07-29 05:16:06 -05:00
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/// ### Why is this bad?
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/// Using a mutex just to make access to a plain bool or
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2019-03-05 10:50:33 -06:00
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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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2021-07-29 05:16:06 -05:00
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/// ### Known problems
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/// This lint cannot detect if the mutex is actually used
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2019-03-05 10:50:33 -06:00
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/// for waiting before a critical section.
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///
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2021-07-29 05:16:06 -05:00
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/// ### Example
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2019-03-05 10:50:33 -06:00
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/// ```rust
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2020-06-09 09:36:01 -05:00
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/// # let y = true;
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///
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/// // Bad
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2019-08-03 01:01:27 -05:00
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/// # use std::sync::Mutex;
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2019-03-05 10:50:33 -06:00
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/// let x = Mutex::new(&y);
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2020-06-09 09:36:01 -05:00
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///
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/// // Good
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/// # use std::sync::atomic::AtomicBool;
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/// let x = AtomicBool::new(y);
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2019-03-05 10:50:33 -06:00
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/// ```
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2015-10-06 18:17:57 -05:00
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pub MUTEX_ATOMIC,
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2018-03-28 08:24:26 -05:00
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perf,
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2016-07-15 17:25:44 -05:00
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"using a mutex where an atomic value could be used instead"
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2015-10-06 18:17:57 -05:00
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}
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2018-03-28 08:24:26 -05:00
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declare_clippy_lint! {
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2021-07-29 05:16:06 -05:00
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/// ### What it does
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/// Checks for usages of `Mutex<X>` where `X` is an integral
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2019-03-05 10:50:33 -06:00
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/// type.
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///
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2021-07-29 05:16:06 -05:00
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/// ### Why is this bad?
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/// Using a mutex just to make access to a plain integer
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2019-03-05 10:50:33 -06:00
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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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2021-07-29 05:16:06 -05:00
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/// ### Known problems
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/// This lint cannot detect if the mutex is actually used
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2019-03-05 10:50:33 -06:00
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/// for waiting before a critical section.
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///
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2021-07-29 05:16:06 -05:00
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/// ### Example
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2019-03-05 10:50:33 -06:00
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/// ```rust
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2019-08-03 14:01:23 -05:00
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/// # use std::sync::Mutex;
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2019-03-05 10:50:33 -06:00
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/// let x = Mutex::new(0usize);
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2020-06-09 09:36:01 -05:00
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///
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/// // Good
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/// # use std::sync::atomic::AtomicUsize;
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/// let x = AtomicUsize::new(0usize);
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2019-03-05 10:50:33 -06:00
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/// ```
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2015-10-07 15:58:34 -05:00
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pub MUTEX_INTEGER,
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2018-03-29 06:41:53 -05:00
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nursery,
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2016-07-15 17:25:44 -05:00
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"using a mutex for an integer type"
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2015-10-07 15:58:34 -05:00
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}
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2019-04-08 15:43:55 -05:00
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declare_lint_pass!(Mutex => [MUTEX_ATOMIC, MUTEX_INTEGER]);
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2019-01-26 13:40:55 -06:00
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2020-06-25 15:41:36 -05:00
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impl<'tcx> LateLintPass<'tcx> for Mutex {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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2020-07-17 03:47:04 -05:00
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let ty = cx.typeck_results().expr_ty(expr);
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2020-08-03 17:18:29 -05:00
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if let ty::Adt(_, subst) = ty.kind() {
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2020-04-23 01:09:42 -05:00
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if is_type_diagnostic_item(cx, ty, sym!(mutex_type)) {
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2017-06-10 21:57:25 -05:00
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let mutex_param = subst.type_at(0);
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2015-10-06 18:17:57 -05:00
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if let Some(atomic_name) = get_atomic_name(mutex_param) {
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2017-08-09 02:30:56 -05:00
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let msg = format!(
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2020-08-28 09:10:16 -05:00
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"consider using an `{}` instead of a `Mutex` here; if you just want the locking \
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behavior and not the internal type, consider using `Mutex<()>`",
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2017-08-09 02:30:56 -05:00
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atomic_name
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);
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2020-08-03 17:18:29 -05:00
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match *mutex_param.kind() {
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2020-12-12 08:32:45 -06:00
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ty::Uint(t) if t != ty::UintTy::Usize => span_lint(cx, MUTEX_INTEGER, expr.span, &msg),
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ty::Int(t) if t != ty::IntTy::Isize => span_lint(cx, MUTEX_INTEGER, expr.span, &msg),
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2016-01-03 22:26:12 -06:00
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_ => span_lint(cx, MUTEX_ATOMIC, expr.span, &msg),
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2015-12-31 14:39:03 -06:00
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};
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2015-10-06 18:17:57 -05:00
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}
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}
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}
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}
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}
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2019-11-05 08:51:56 -06:00
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fn get_atomic_name(ty: Ty<'_>) -> Option<&'static str> {
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2020-08-03 17:18:29 -05:00
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match ty.kind() {
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2018-08-22 16:34:52 -05:00
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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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2016-01-03 22:26:12 -06:00
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_ => None,
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2015-10-06 18:17:57 -05:00
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}
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}
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