clippy_lints/src/atomic_ordering.rs

   1 use crate::utils::{match_def_path, span_lint_and_help};
   2 use if_chain::if_chain;
   3 use rustc_hir::def_id::DefId;
   4 use rustc_hir::{Expr, ExprKind};
   5 use rustc_lint::{LateContext, LateLintPass};
   6 use rustc_middle::ty;
   7 use rustc_session::{declare_lint_pass, declare_tool_lint};
   8
   9 declare_clippy_lint! {
  10     /// **What it does:** Checks for usage of invalid atomic
  11     /// ordering in atomic loads/stores/exchanges/updates and
  12     /// memory fences.
  13     ///
  14     /// **Why is this bad?** Using an invalid atomic ordering
  15     /// will cause a panic at run-time.
  16     ///
  17     /// **Known problems:** None.
  18     ///
  19     /// **Example:**
  20     /// ```rust,no_run
  21     /// # use std::sync::atomic::{self, AtomicU8, Ordering};
  22     ///
  23     /// let x = AtomicU8::new(0);
  24     ///
  25     /// // Bad: `Release` and `AcqRel` cannot be used for `load`.
  26     /// let _ = x.load(Ordering::Release);
  27     /// let _ = x.load(Ordering::AcqRel);
  28     ///
  29     /// // Bad: `Acquire` and `AcqRel` cannot be used for `store`.
  30     /// x.store(1, Ordering::Acquire);
  31     /// x.store(2, Ordering::AcqRel);
  32     ///
  33     /// // Bad: `Relaxed` cannot be used as a fence's ordering.
  34     /// atomic::fence(Ordering::Relaxed);
  35     /// atomic::compiler_fence(Ordering::Relaxed);
  36     ///
  37     /// // Bad: `Release` and `AcqRel` are both always invalid
  38     /// // for the failure ordering (the last arg).
  39     /// let _ = x.compare_exchange(1, 2, Ordering::SeqCst, Ordering::Release);
  40     /// let _ = x.compare_exchange_weak(2, 3, Ordering::AcqRel, Ordering::AcqRel);
  41     ///
  42     /// // Bad: The failure ordering is not allowed to be
  43     /// // stronger than the success order, and `SeqCst` is
  44     /// // stronger than `Relaxed`.
  45     /// let _ = x.fetch_update(Ordering::Relaxed, Ordering::SeqCst, |val| Some(val + val));
  46     /// ```
  47     pub INVALID_ATOMIC_ORDERING,
  48     correctness,
  49     "usage of invalid atomic ordering in atomic operations and memory fences"
  50 }
  51
  52 declare_lint_pass!(AtomicOrdering => [INVALID_ATOMIC_ORDERING]);
  53
  54 const ATOMIC_TYPES: [&str; 12] = [
  55     "AtomicBool",
  56     "AtomicI8",
  57     "AtomicI16",
  58     "AtomicI32",
  59     "AtomicI64",
  60     "AtomicIsize",
  61     "AtomicPtr",
  62     "AtomicU8",
  63     "AtomicU16",
  64     "AtomicU32",
  65     "AtomicU64",
  66     "AtomicUsize",
  67 ];
  68
  69 fn type_is_atomic(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
  70     if let ty::Adt(&ty::AdtDef { did, .. }, _) = cx.typeck_results().expr_ty(expr).kind() {
  71         ATOMIC_TYPES
  72             .iter()
  73             .any(|ty| match_def_path(cx, did, &["core", "sync", "atomic", ty]))
  74     } else {
  75         false
  76     }
  77 }
  78
  79 fn match_ordering_def_path(cx: &LateContext<'_>, did: DefId, orderings: &[&str]) -> bool {
  80     orderings
  81         .iter()
  82         .any(|ordering| match_def_path(cx, did, &["core", "sync", "atomic", "Ordering", ordering]))
  83 }
  84
  85 fn check_atomic_load_store(cx: &LateContext<'_>, expr: &Expr<'_>) {
  86     if_chain! {
  87         if let ExprKind::MethodCall(ref method_path, _, args, _) = &expr.kind;
  88         let method = method_path.ident.name.as_str();
  89         if type_is_atomic(cx, &args[0]);
  90         if method == "load" || method == "store";
  91         let ordering_arg = if method == "load" { &args[1] } else { &args[2] };
  92         if let ExprKind::Path(ref ordering_qpath) = ordering_arg.kind;
  93         if let Some(ordering_def_id) = cx.qpath_res(ordering_qpath, ordering_arg.hir_id).opt_def_id();
  94         then {
  95             if method == "load" &&
  96                 match_ordering_def_path(cx, ordering_def_id, &["Release", "AcqRel"]) {
  97                 span_lint_and_help(
  98                     cx,
  99                     INVALID_ATOMIC_ORDERING,
 100                     ordering_arg.span,
 101                     "atomic loads cannot have `Release` and `AcqRel` ordering",
 102                     None,
 103                     "consider using ordering modes `Acquire`, `SeqCst` or `Relaxed`"
 104                 );
 105             } else if method == "store" &&
 106                 match_ordering_def_path(cx, ordering_def_id, &["Acquire", "AcqRel"]) {
 107                 span_lint_and_help(
 108                     cx,
 109                     INVALID_ATOMIC_ORDERING,
 110                     ordering_arg.span,
 111                     "atomic stores cannot have `Acquire` and `AcqRel` ordering",
 112                     None,
 113                     "consider using ordering modes `Release`, `SeqCst` or `Relaxed`"
 114                 );
 115             }
 116         }
 117     }
 118 }
 119
 120 fn check_memory_fence(cx: &LateContext<'_>, expr: &Expr<'_>) {
 121     if_chain! {
 122         if let ExprKind::Call(ref func, ref args) = expr.kind;
 123         if let ExprKind::Path(ref func_qpath) = func.kind;
 124         if let Some(def_id) = cx.qpath_res(func_qpath, func.hir_id).opt_def_id();
 125         if ["fence", "compiler_fence"]
 126             .iter()
 127             .any(|func| match_def_path(cx, def_id, &["core", "sync", "atomic", func]));
 128         if let ExprKind::Path(ref ordering_qpath) = &args[0].kind;
 129         if let Some(ordering_def_id) = cx.qpath_res(ordering_qpath, args[0].hir_id).opt_def_id();
 130         if match_ordering_def_path(cx, ordering_def_id, &["Relaxed"]);
 131         then {
 132             span_lint_and_help(
 133                 cx,
 134                 INVALID_ATOMIC_ORDERING,
 135                 args[0].span,
 136                 "memory fences cannot have `Relaxed` ordering",
 137                 None,
 138                 "consider using ordering modes `Acquire`, `Release`, `AcqRel` or `SeqCst`"
 139             );
 140         }
 141     }
 142 }
 143
 144 fn opt_ordering_defid(cx: &LateContext<'_>, ord_arg: &Expr<'_>) -> Option<DefId> {
 145     if let ExprKind::Path(ref ord_qpath) = ord_arg.kind {
 146         cx.qpath_res(ord_qpath, ord_arg.hir_id).opt_def_id()
 147     } else {
 148         None
 149     }
 150 }
 151
 152 fn check_atomic_compare_exchange(cx: &LateContext<'_>, expr: &Expr<'_>) {
 153     if_chain! {
 154         if let ExprKind::MethodCall(ref method_path, _, args, _) = &expr.kind;
 155         let method = method_path.ident.name.as_str();
 156         if type_is_atomic(cx, &args[0]);
 157         if method == "compare_exchange" || method == "compare_exchange_weak" || method == "fetch_update";
 158         let (success_order_arg, failure_order_arg) = if method == "fetch_update" {
 159             (&args[1], &args[2])
 160         } else {
 161             (&args[3], &args[4])
 162         };
 163         if let Some(fail_ordering_def_id) = opt_ordering_defid(cx, failure_order_arg);
 164         then {
 165             // Helper type holding on to some checking and error reporting data. Has
 166             // - (success ordering name,
 167             // - list of failure orderings forbidden by the success order,
 168             // - suggestion message)
 169             type OrdLintInfo = (&'static str, &'static [&'static str], &'static str);
 170             let relaxed: OrdLintInfo = ("Relaxed", &["SeqCst", "Acquire"], "ordering mode `Relaxed`");
 171             let acquire: OrdLintInfo = ("Acquire", &["SeqCst"], "ordering modes `Acquire` or `Relaxed`");
 172             let seq_cst: OrdLintInfo = ("SeqCst", &[], "ordering modes `Acquire`, `SeqCst` or `Relaxed`");
 173             let release = ("Release", relaxed.1, relaxed.2);
 174             let acqrel = ("AcqRel", acquire.1, acquire.2);
 175             let search = [relaxed, acquire, seq_cst, release, acqrel];
 176
 177             let success_lint_info = opt_ordering_defid(cx, success_order_arg)
 178                 .and_then(|success_ord_def_id| -> Option<OrdLintInfo> {
 179                     search
 180                         .iter()
 181                         .find(|(ordering, ..)| {
 182                             match_def_path(cx, success_ord_def_id,
 183                                 &["core", "sync", "atomic", "Ordering", ordering])
 184                         })
 185                         .copied()
 186                 });
 187
 188             if match_ordering_def_path(cx, fail_ordering_def_id, &["Release", "AcqRel"]) {
 189                 // If we don't know the success order is, use what we'd suggest
 190                 // if it were maximally permissive.
 191                 let suggested = success_lint_info.unwrap_or(seq_cst).2;
 192                 span_lint_and_help(
 193                     cx,
 194                     INVALID_ATOMIC_ORDERING,
 195                     failure_order_arg.span,
 196                     &format!(
 197                         "{}'s failure ordering may not be `Release` or `AcqRel`",
 198                         method,
 199                     ),
 200                     None,
 201                     &format!("consider using {} instead", suggested),
 202                 );
 203             } else if let Some((success_ord_name, bad_ords_given_success, suggested)) = success_lint_info {
 204                 if match_ordering_def_path(cx, fail_ordering_def_id, bad_ords_given_success) {
 205                     span_lint_and_help(
 206                         cx,
 207                         INVALID_ATOMIC_ORDERING,
 208                         failure_order_arg.span,
 209                         &format!(
 210                             "{}'s failure ordering may not be stronger than the success ordering of `{}`",
 211                             method,
 212                             success_ord_name,
 213                         ),
 214                         None,
 215                         &format!("consider using {} instead", suggested),
 216                     );
 217                 }
 218             }
 219         }
 220     }
 221 }
 222
 223 impl<'tcx> LateLintPass<'tcx> for AtomicOrdering {
 224     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
 225         check_atomic_load_store(cx, expr);
 226         check_memory_fence(cx, expr);
 227         check_atomic_compare_exchange(cx, expr);
 228     }
 229 }