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| 1 | +//! Lint on use of `size_of` or `size_of_val` of T in an expression |
| 2 | +//! expecting a count of T |
| 3 | +
|
| 4 | +use crate::utils::{match_def_path, paths, span_lint_and_help}; |
| 5 | +use if_chain::if_chain; |
| 6 | +use rustc_hir::BinOpKind; |
| 7 | +use rustc_hir::{Expr, ExprKind}; |
| 8 | +use rustc_lint::{LateContext, LateLintPass}; |
| 9 | +use rustc_middle::ty::{self, Ty, TyS, TypeAndMut}; |
| 10 | +use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| 11 | + |
| 12 | +declare_clippy_lint! { |
| 13 | + /// **What it does:** Detects expressions where |
| 14 | + /// size_of::<T> or size_of_val::<T> is used as a |
| 15 | + /// count of elements of type T |
| 16 | + /// |
| 17 | + /// **Why is this bad?** These functions expect a count |
| 18 | + /// of T and not a number of bytes |
| 19 | + /// |
| 20 | + /// **Known problems:** None. |
| 21 | + /// |
| 22 | + /// **Example:** |
| 23 | + /// ```rust,no_run |
| 24 | + /// # use std::ptr::copy_nonoverlapping; |
| 25 | + /// # use std::mem::size_of; |
| 26 | + /// |
| 27 | + /// const SIZE: usize = 128; |
| 28 | + /// let x = [2u8; SIZE]; |
| 29 | + /// let mut y = [2u8; SIZE]; |
| 30 | + /// unsafe { copy_nonoverlapping(x.as_ptr(), y.as_mut_ptr(), size_of::<u8>() * SIZE) }; |
| 31 | + /// ``` |
| 32 | + pub SIZE_OF_IN_ELEMENT_COUNT, |
| 33 | + correctness, |
| 34 | + "using size_of::<T> or size_of_val::<T> where a count of elements of T is expected" |
| 35 | +} |
| 36 | + |
| 37 | +declare_lint_pass!(SizeOfInElementCount => [SIZE_OF_IN_ELEMENT_COUNT]); |
| 38 | + |
| 39 | +fn get_size_of_ty(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<Ty<'tcx>> { |
| 40 | + match expr.kind { |
| 41 | + ExprKind::Call(count_func, _func_args) => { |
| 42 | + if_chain! { |
| 43 | + if let ExprKind::Path(ref count_func_qpath) = count_func.kind; |
| 44 | + if let Some(def_id) = cx.qpath_res(count_func_qpath, count_func.hir_id).opt_def_id(); |
| 45 | + if match_def_path(cx, def_id, &paths::MEM_SIZE_OF) |
| 46 | + || match_def_path(cx, def_id, &paths::MEM_SIZE_OF_VAL); |
| 47 | + then { |
| 48 | + cx.typeck_results().node_substs(count_func.hir_id).types().next() |
| 49 | + } else { |
| 50 | + None |
| 51 | + } |
| 52 | + } |
| 53 | + }, |
| 54 | + ExprKind::Binary(op, left, right) if BinOpKind::Mul == op.node || BinOpKind::Div == op.node => { |
| 55 | + get_size_of_ty(cx, left).or_else(|| get_size_of_ty(cx, right)) |
| 56 | + }, |
| 57 | + ExprKind::Cast(expr, _) => get_size_of_ty(cx, expr), |
| 58 | + _ => None, |
| 59 | + } |
| 60 | +} |
| 61 | + |
| 62 | +fn get_pointee_ty_and_count_expr(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<(Ty<'tcx>, &'tcx Expr<'tcx>)> { |
| 63 | + const FUNCTIONS: [&[&str]; 8] = [ |
| 64 | + &paths::COPY_NONOVERLAPPING, |
| 65 | + &paths::COPY, |
| 66 | + &paths::WRITE_BYTES, |
| 67 | + &paths::PTR_SWAP_NONOVERLAPPING, |
| 68 | + &paths::PTR_SLICE_FROM_RAW_PARTS, |
| 69 | + &paths::PTR_SLICE_FROM_RAW_PARTS_MUT, |
| 70 | + &paths::SLICE_FROM_RAW_PARTS, |
| 71 | + &paths::SLICE_FROM_RAW_PARTS_MUT, |
| 72 | + ]; |
| 73 | + const METHODS: [&str; 11] = [ |
| 74 | + "write_bytes", |
| 75 | + "copy_to", |
| 76 | + "copy_from", |
| 77 | + "copy_to_nonoverlapping", |
| 78 | + "copy_from_nonoverlapping", |
| 79 | + "add", |
| 80 | + "wrapping_add", |
| 81 | + "sub", |
| 82 | + "wrapping_sub", |
| 83 | + "offset", |
| 84 | + "wrapping_offset", |
| 85 | + ]; |
| 86 | + |
| 87 | + if_chain! { |
| 88 | + // Find calls to ptr::{copy, copy_nonoverlapping} |
| 89 | + // and ptr::{swap_nonoverlapping, write_bytes}, |
| 90 | + if let ExprKind::Call(func, [.., count]) = expr.kind; |
| 91 | + if let ExprKind::Path(ref func_qpath) = func.kind; |
| 92 | + if let Some(def_id) = cx.qpath_res(func_qpath, func.hir_id).opt_def_id(); |
| 93 | + if FUNCTIONS.iter().any(|func_path| match_def_path(cx, def_id, func_path)); |
| 94 | + |
| 95 | + // Get the pointee type |
| 96 | + if let Some(pointee_ty) = cx.typeck_results().node_substs(func.hir_id).types().next(); |
| 97 | + then { |
| 98 | + return Some((pointee_ty, count)); |
| 99 | + } |
| 100 | + }; |
| 101 | + if_chain! { |
| 102 | + // Find calls to copy_{from,to}{,_nonoverlapping} and write_bytes methods |
| 103 | + if let ExprKind::MethodCall(method_path, _, [ptr_self, .., count], _) = expr.kind; |
| 104 | + let method_ident = method_path.ident.as_str(); |
| 105 | + if METHODS.iter().any(|m| *m == &*method_ident); |
| 106 | + |
| 107 | + // Get the pointee type |
| 108 | + if let ty::RawPtr(TypeAndMut { ty: pointee_ty, .. }) = |
| 109 | + cx.typeck_results().expr_ty(ptr_self).kind(); |
| 110 | + then { |
| 111 | + return Some((pointee_ty, count)); |
| 112 | + } |
| 113 | + }; |
| 114 | + None |
| 115 | +} |
| 116 | + |
| 117 | +impl<'tcx> LateLintPass<'tcx> for SizeOfInElementCount { |
| 118 | + fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { |
| 119 | + const HELP_MSG: &str = "use a count of elements instead of a count of bytes\ |
| 120 | + , it already gets multiplied by the size of the type"; |
| 121 | + |
| 122 | + const LINT_MSG: &str = "found a count of bytes \ |
| 123 | + instead of a count of elements of T"; |
| 124 | + |
| 125 | + if_chain! { |
| 126 | + // Find calls to functions with an element count parameter and get |
| 127 | + // the pointee type and count parameter expression |
| 128 | + if let Some((pointee_ty, count_expr)) = get_pointee_ty_and_count_expr(cx, expr); |
| 129 | + |
| 130 | + // Find a size_of call in the count parameter expression and |
| 131 | + // check that it's the same type |
| 132 | + if let Some(ty_used_for_size_of) = get_size_of_ty(cx, count_expr); |
| 133 | + if TyS::same_type(pointee_ty, ty_used_for_size_of); |
| 134 | + then { |
| 135 | + span_lint_and_help( |
| 136 | + cx, |
| 137 | + SIZE_OF_IN_ELEMENT_COUNT, |
| 138 | + count_expr.span, |
| 139 | + LINT_MSG, |
| 140 | + None, |
| 141 | + HELP_MSG |
| 142 | + ); |
| 143 | + } |
| 144 | + }; |
| 145 | + } |
| 146 | +} |
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