mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-21 02:23:19 +00:00
123 lines
3.7 KiB
Rust
123 lines
3.7 KiB
Rust
use rustc::lint::*;
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use rustc::ty;
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use rustc::hir;
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use syntax::ast::RangeLimits;
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use utils::{self, higher};
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use utils::higher::Range;
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use consts::{constant, Constant};
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/// **What it does:** Checks for out of bounds array indexing with a constant
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/// index.
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///
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/// **Why is this bad?** This will always panic at runtime.
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///
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/// **Known problems:** Hopefully none.
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///
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/// **Example:**
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/// ```rust
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/// let x = [1,2,3,4];
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/// ...
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/// x[9];
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/// &x[2..9];
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/// ```
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declare_clippy_lint! {
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pub OUT_OF_BOUNDS_INDEXING,
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correctness,
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"out of bounds constant indexing"
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}
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/// **What it does:** Checks for usage of indexing or slicing.
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///
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/// **Why is this bad?** Usually, this can be safely allowed. However, in some
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/// domains such as kernel development, a panic can cause the whole operating
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/// system to crash.
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///
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/// **Known problems:** Hopefully none.
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///
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/// **Example:**
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/// ```rust
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/// ...
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/// x[2];
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/// &x[0..2];
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/// ```
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declare_clippy_lint! {
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pub INDEXING_SLICING,
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restriction,
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"indexing/slicing usage"
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}
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#[derive(Copy, Clone)]
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pub struct ArrayIndexing;
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impl LintPass for ArrayIndexing {
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fn get_lints(&self) -> LintArray {
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lint_array!(INDEXING_SLICING, OUT_OF_BOUNDS_INDEXING)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ArrayIndexing {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx hir::Expr) {
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if let hir::ExprIndex(ref array, ref index) = e.node {
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// Array with known size can be checked statically
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let ty = cx.tables.expr_ty(array);
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if let ty::TyArray(_, size) = ty.sty {
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let size = size.assert_usize(cx.tcx).unwrap().into();
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// Index is a constant uint
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if let Some((Constant::Int(const_index), _)) = constant(cx, cx.tables, index) {
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if size <= const_index {
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utils::span_lint(cx, OUT_OF_BOUNDS_INDEXING, e.span, "const index is out of bounds");
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}
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return;
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}
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// Index is a constant range
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if let Some(range) = higher::range(cx, index) {
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if let Some((start, end)) = to_const_range(cx, range, size) {
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if start > size || end > size {
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utils::span_lint(cx, OUT_OF_BOUNDS_INDEXING, e.span, "range is out of bounds");
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}
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return;
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}
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}
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}
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if let Some(range) = higher::range(cx, index) {
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// Full ranges are always valid
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if range.start.is_none() && range.end.is_none() {
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return;
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}
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// Impossible to know if indexing or slicing is correct
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utils::span_lint(cx, INDEXING_SLICING, e.span, "slicing may panic");
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} else {
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utils::span_lint(cx, INDEXING_SLICING, e.span, "indexing may panic");
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}
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}
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}
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}
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/// Returns an option containing a tuple with the start and end (exclusive) of
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/// the range.
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fn to_const_range<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, range: Range, array_size: u128) -> Option<(u128, u128)> {
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let s = range.start.map(|expr| constant(cx, cx.tables, expr).map(|(c, _)| c));
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let start = match s {
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Some(Some(Constant::Int(x))) => x,
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Some(_) => return None,
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None => 0,
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};
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let e = range.end.map(|expr| constant(cx, cx.tables, expr).map(|(c, _)| c));
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let end = match e {
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Some(Some(Constant::Int(x))) => if range.limits == RangeLimits::Closed {
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x + 1
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} else {
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x
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},
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Some(_) => return None,
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None => array_size,
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};
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Some((start, end))
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}
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