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| 1 | +use clippy_utils::{ |
| 2 | + diagnostics::span_lint_and_then, |
| 3 | + visitors::{for_each_expr_with_closures, Descend, Visitable}, |
| 4 | +}; |
| 5 | +use core::ops::ControlFlow::Continue; |
| 6 | +use hir::{ |
| 7 | + def::{DefKind, Res}, |
| 8 | + BlockCheckMode, ExprKind, QPath, UnOp, Unsafety, |
| 9 | +}; |
| 10 | +use rustc_ast::Mutability; |
| 11 | +use rustc_hir as hir; |
| 12 | +use rustc_lint::{LateContext, LateLintPass}; |
| 13 | +use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| 14 | +use rustc_span::Span; |
| 15 | + |
| 16 | +declare_clippy_lint! { |
| 17 | + /// ### What it does |
| 18 | + /// Checks for `unsafe` blocks that contain more than one unsafe operation. |
| 19 | + /// |
| 20 | + /// ### Why is this bad? |
| 21 | + /// Combined with `undocumented_unsafe_blocks`, |
| 22 | + /// this lint ensures that each unsafe operation must be independently justified. |
| 23 | + /// Combined with `unused_unsafe`, this lint also ensures |
| 24 | + /// elimination of unnecessary unsafe blocks through refactoring. |
| 25 | + /// |
| 26 | + /// ### Example |
| 27 | + /// ```rust |
| 28 | + /// /// Reads a `char` from the given pointer. |
| 29 | + /// /// |
| 30 | + /// /// # Safety |
| 31 | + /// /// |
| 32 | + /// /// `ptr` must point to four consecutive, initialized bytes which |
| 33 | + /// /// form a valid `char` when interpreted in the native byte order. |
| 34 | + /// fn read_char(ptr: *const u8) -> char { |
| 35 | + /// // SAFETY: The caller has guaranteed that the value pointed |
| 36 | + /// // to by `bytes` is a valid `char`. |
| 37 | + /// unsafe { char::from_u32_unchecked(*ptr.cast::<u32>()) } |
| 38 | + /// } |
| 39 | + /// ``` |
| 40 | + /// Use instead: |
| 41 | + /// ```rust |
| 42 | + /// /// Reads a `char` from the given pointer. |
| 43 | + /// /// |
| 44 | + /// /// # Safety |
| 45 | + /// /// |
| 46 | + /// /// - `ptr` must be 4-byte aligned, point to four consecutive |
| 47 | + /// /// initialized bytes, and be valid for reads of 4 bytes. |
| 48 | + /// /// - The bytes pointed to by `ptr` must represent a valid |
| 49 | + /// /// `char` when interpreted in the native byte order. |
| 50 | + /// fn read_char(ptr: *const u8) -> char { |
| 51 | + /// // SAFETY: `ptr` is 4-byte aligned, points to four consecutive |
| 52 | + /// // initialized bytes, and is valid for reads of 4 bytes. |
| 53 | + /// let int_value = unsafe { *ptr.cast::<u32>() }; |
| 54 | + /// |
| 55 | + /// // SAFETY: The caller has guaranteed that the four bytes |
| 56 | + /// // pointed to by `bytes` represent a valid `char`. |
| 57 | + /// unsafe { char::from_u32_unchecked(int_value) } |
| 58 | + /// } |
| 59 | + /// ``` |
| 60 | + #[clippy::version = "1.68.0"] |
| 61 | + pub MULTIPLE_UNSAFE_OPS_PER_BLOCK, |
| 62 | + restriction, |
| 63 | + "more than one unsafe operation per `unsafe` block" |
| 64 | +} |
| 65 | +declare_lint_pass!(MultipleUnsafeOpsPerBlock => [MULTIPLE_UNSAFE_OPS_PER_BLOCK]); |
| 66 | + |
| 67 | +impl<'tcx> LateLintPass<'tcx> for MultipleUnsafeOpsPerBlock { |
| 68 | + fn check_block(&mut self, cx: &LateContext<'tcx>, block: &'tcx hir::Block<'_>) { |
| 69 | + if !matches!(block.rules, BlockCheckMode::UnsafeBlock(_)) { |
| 70 | + return; |
| 71 | + } |
| 72 | + let mut unsafe_ops = vec![]; |
| 73 | + collect_unsafe_exprs(cx, block, &mut unsafe_ops); |
| 74 | + if unsafe_ops.len() > 1 { |
| 75 | + span_lint_and_then( |
| 76 | + cx, |
| 77 | + MULTIPLE_UNSAFE_OPS_PER_BLOCK, |
| 78 | + block.span, |
| 79 | + &format!( |
| 80 | + "this `unsafe` block contains {} unsafe operations, expected only one", |
| 81 | + unsafe_ops.len() |
| 82 | + ), |
| 83 | + |diag| { |
| 84 | + for (msg, span) in unsafe_ops { |
| 85 | + diag.span_note(span, msg); |
| 86 | + } |
| 87 | + }, |
| 88 | + ); |
| 89 | + } |
| 90 | + } |
| 91 | +} |
| 92 | + |
| 93 | +fn collect_unsafe_exprs<'tcx>( |
| 94 | + cx: &LateContext<'tcx>, |
| 95 | + node: impl Visitable<'tcx>, |
| 96 | + unsafe_ops: &mut Vec<(&'static str, Span)>, |
| 97 | +) { |
| 98 | + for_each_expr_with_closures(cx, node, |expr| { |
| 99 | + match expr.kind { |
| 100 | + ExprKind::InlineAsm(_) => unsafe_ops.push(("inline assembly used here", expr.span)), |
| 101 | + |
| 102 | + ExprKind::Field(e, _) => { |
| 103 | + if cx.typeck_results().expr_ty(e).is_union() { |
| 104 | + unsafe_ops.push(("union field access occurs here", expr.span)); |
| 105 | + } |
| 106 | + }, |
| 107 | + |
| 108 | + ExprKind::Path(QPath::Resolved( |
| 109 | + _, |
| 110 | + hir::Path { |
| 111 | + res: Res::Def(DefKind::Static(Mutability::Mut), _), |
| 112 | + .. |
| 113 | + }, |
| 114 | + )) => { |
| 115 | + unsafe_ops.push(("access of a mutable static occurs here", expr.span)); |
| 116 | + }, |
| 117 | + |
| 118 | + ExprKind::Unary(UnOp::Deref, e) if cx.typeck_results().expr_ty_adjusted(e).is_unsafe_ptr() => { |
| 119 | + unsafe_ops.push(("raw pointer dereference occurs here", expr.span)); |
| 120 | + }, |
| 121 | + |
| 122 | + ExprKind::Call(path_expr, _) => match path_expr.kind { |
| 123 | + ExprKind::Path(QPath::Resolved( |
| 124 | + _, |
| 125 | + hir::Path { |
| 126 | + res: Res::Def(kind, def_id), |
| 127 | + .. |
| 128 | + }, |
| 129 | + )) if kind.is_fn_like() => { |
| 130 | + let sig = cx.tcx.bound_fn_sig(*def_id); |
| 131 | + if sig.0.unsafety() == Unsafety::Unsafe { |
| 132 | + unsafe_ops.push(("unsafe function call occurs here", expr.span)); |
| 133 | + } |
| 134 | + }, |
| 135 | + |
| 136 | + ExprKind::Path(QPath::TypeRelative(..)) => { |
| 137 | + if let Some(sig) = cx |
| 138 | + .typeck_results() |
| 139 | + .type_dependent_def_id(path_expr.hir_id) |
| 140 | + .map(|def_id| cx.tcx.bound_fn_sig(def_id)) |
| 141 | + { |
| 142 | + if sig.0.unsafety() == Unsafety::Unsafe { |
| 143 | + unsafe_ops.push(("unsafe function call occurs here", expr.span)); |
| 144 | + } |
| 145 | + } |
| 146 | + }, |
| 147 | + |
| 148 | + _ => {}, |
| 149 | + }, |
| 150 | + |
| 151 | + ExprKind::MethodCall(..) => { |
| 152 | + if let Some(sig) = cx |
| 153 | + .typeck_results() |
| 154 | + .type_dependent_def_id(expr.hir_id) |
| 155 | + .map(|def_id| cx.tcx.bound_fn_sig(def_id)) |
| 156 | + { |
| 157 | + if sig.0.unsafety() == Unsafety::Unsafe { |
| 158 | + unsafe_ops.push(("unsafe method call occurs here", expr.span)); |
| 159 | + } |
| 160 | + } |
| 161 | + }, |
| 162 | + |
| 163 | + ExprKind::AssignOp(_, lhs, rhs) | ExprKind::Assign(lhs, rhs, _) => { |
| 164 | + if matches!( |
| 165 | + lhs.kind, |
| 166 | + ExprKind::Path(QPath::Resolved( |
| 167 | + _, |
| 168 | + hir::Path { |
| 169 | + res: Res::Def(DefKind::Static(Mutability::Mut), _), |
| 170 | + .. |
| 171 | + } |
| 172 | + )) |
| 173 | + ) { |
| 174 | + unsafe_ops.push(("modification of a mutable static occurs here", expr.span)); |
| 175 | + collect_unsafe_exprs(cx, rhs, unsafe_ops); |
| 176 | + return Continue(Descend::No); |
| 177 | + } |
| 178 | + }, |
| 179 | + |
| 180 | + _ => {}, |
| 181 | + }; |
| 182 | + |
| 183 | + Continue::<(), _>(Descend::Yes) |
| 184 | + }); |
| 185 | +} |
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