137 lines
4.2 KiB
Rust
137 lines
4.2 KiB
Rust
use rustc::lint::*;
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use rustc::middle::const_val::ConstVal;
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use rustc::ty;
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use rustc_const_eval::EvalHint::ExprTypeChecked;
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use rustc_const_eval::ConstContext;
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use rustc_const_math::ConstInt;
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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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/// **What it does:** Checks for out of bounds array indexing with a constant 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_lint! {
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pub OUT_OF_BOUNDS_INDEXING,
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Deny,
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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_restriction_lint! {
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pub INDEXING_SLICING,
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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 = ConstInt::Infer(size as u128);
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let constcx = ConstContext::with_tables(cx.tcx, cx.tables);
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// Index is a constant uint
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let const_index = constcx.eval(index, ExprTypeChecked);
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if let Ok(ConstVal::Integral(const_index)) = const_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(index) {
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let start = range.start
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.map(|start| constcx.eval(start, ExprTypeChecked))
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.map(|v| v.ok());
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let end = range.end
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.map(|end| constcx.eval(end, ExprTypeChecked))
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.map(|v| v.ok());
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if let Some((start, end)) = to_const_range(start, end, range.limits, 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(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 the range.
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fn to_const_range(
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start: Option<Option<ConstVal>>,
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end: Option<Option<ConstVal>>,
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limits: RangeLimits,
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array_size: ConstInt
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) -> Option<(ConstInt, ConstInt)> {
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let start = match start {
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Some(Some(ConstVal::Integral(x))) => x,
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Some(_) => return None,
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None => ConstInt::Infer(0),
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};
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let end = match end {
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Some(Some(ConstVal::Integral(x))) => {
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if limits == RangeLimits::Closed {
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(x + ConstInt::Infer(1)).expect("such a big array is not realistic")
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} else {
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x
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}
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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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