use rustc::middle::const_eval::{eval_const_expr_partial, ConstVal};
use rustc::middle::ty::TyArray;
use rustc_front::hir::*;
-use utils::span_lint;
+use syntax::ast::RangeLimits;
+use utils;
/// **What it does:** Check for out of bounds array indexing with a constant index.
///
/// let x = [1,2,3,4];
/// ...
/// x[9];
+/// &x[2..9];
/// ```
declare_lint! {
pub OUT_OF_BOUNDS_INDEXING,
"out of bound constant indexing"
}
+/// **What it does:** Check for usage of indexing or slicing.
+///
+/// **Why is this bad?** Usually, this can be safely allowed. However,
+/// in some domains such as kernel development, a panic can cause the
+/// whole operating system to crash.
+///
+/// **Known problems:** Hopefully none.
+///
+/// **Example:**
+///
+/// ```
+/// ...
+/// x[2];
+/// &x[0..2];
+/// ```
+declare_lint! {
+ pub INDEXING_SLICING,
+ Allow,
+ "indexing/slicing usage"
+}
+
#[derive(Copy,Clone)]
pub struct ArrayIndexing;
impl LintPass for ArrayIndexing {
fn get_lints(&self) -> LintArray {
- lint_array!(OUT_OF_BOUNDS_INDEXING)
+ lint_array!(INDEXING_SLICING, OUT_OF_BOUNDS_INDEXING)
}
}
impl LateLintPass for ArrayIndexing {
fn check_expr(&mut self, cx: &LateContext, e: &Expr) {
if let ExprIndex(ref array, ref index) = e.node {
+ // Array with known size can be checked statically
let ty = cx.tcx.expr_ty(array);
-
if let TyArray(_, size) = ty.sty {
- let index = eval_const_expr_partial(cx.tcx, &index, ExprTypeChecked, None);
- if let Ok(ConstVal::Uint(index)) = index {
- if size as u64 <= index {
- span_lint(cx, OUT_OF_BOUNDS_INDEXING, e.span, "const index-expr is out of bounds");
+ let size = size as u64;
+
+ // Index is a constant uint
+ let const_index = eval_const_expr_partial(cx.tcx, &index, ExprTypeChecked, None);
+ if let Ok(ConstVal::Uint(const_index)) = const_index {
+ if size <= const_index {
+ utils::span_lint(cx, OUT_OF_BOUNDS_INDEXING, e.span, "const index is out of bounds");
+ utils::span_lint(cx, INDEXING_SLICING, e.span, "indexing may panic");
+ } else {
+ // Index is within bounds
+ return;
}
}
+
+ // Index is a constant range
+ if let Some(range) = utils::unsugar_range(index) {
+ let start = range.start.map(|start|
+ eval_const_expr_partial(cx.tcx, start, ExprTypeChecked, None));
+ let end = range.end.map(|end|
+ eval_const_expr_partial(cx.tcx, end, ExprTypeChecked, None));
+
+ if let Some((start, end)) = to_const_range(start, end, range.limits, size) {
+ if start >= size && end >= size {
+ utils::span_lint(cx,
+ OUT_OF_BOUNDS_INDEXING,
+ e.span,
+ "range is out of bounds");
+ utils::span_lint(cx,
+ INDEXING_SLICING,
+ e.span,
+ "slicing may panic");
+ } else {
+ // Range is within bounds
+ return;
+ }
+ }
+ }
+ }
+
+ if let Some(range) = utils::unsugar_range(index) {
+ // Full ranges are always valid
+ if range.start.is_none() && range.end.is_none() {
+ return;
+ }
+
+ // Impossible to know if indexing or slicing is correct
+ utils::span_lint(cx, INDEXING_SLICING, e.span, "slicing may panic");
+ } else {
+ utils::span_lint(cx, INDEXING_SLICING, e.span, "indexing may panic");
}
}
}
}
+
+/// Returns an option containing a tuple with the start and end (exclusive) of the range
+///
+/// Note: we assume the start and the end of the range are unsigned, since array slicing
+/// works only on usize
+fn to_const_range<T>(start: Option<Result<ConstVal, T>>,
+ end: Option<Result<ConstVal, T>>,
+ limits: RangeLimits,
+ array_size: u64)
+ -> Option<(u64, u64)> {
+ let start = match start {
+ Some(Ok(ConstVal::Uint(x))) => x,
+ Some(_) => return None,
+ None => 0,
+ };
+
+ let end = match end {
+ Some(Ok(ConstVal::Uint(x))) => {
+ if limits == RangeLimits::Closed {
+ x
+ } else {
+ x - 1
+ }
+ }
+ Some(_) => return None,
+ None => array_size - 1,
+ };
+
+ Some((start, end))
+}
-#![feature(plugin)]
+#![feature(inclusive_range_syntax, plugin)]
#![plugin(clippy)]
+#![deny(indexing_slicing)]
#![deny(out_of_bounds_indexing)]
#![allow(no_effect)]
let x = [1,2,3,4];
x[0];
x[3];
- x[4]; //~ERROR: const index-expr is out of bounds
- x[1 << 3]; //~ERROR: const index-expr is out of bounds
+ x[4]; //~ERROR: indexing may panic
+ //~^ ERROR: const index is out of bounds
+ x[1 << 3]; //~ERROR: indexing may panic
+ //~^ ERROR: const index is out of bounds
+ &x[1..5]; //~ERROR: slicing may panic
+ //~^ ERROR: range is out of bounds
+ &x[0..3];
+ &x[0...4]; //~ERROR: slicing may panic
+ //~^ ERROR: range is out of bounds
+ &x[..];
+ &x[1..];
+ &x[..4];
+ &x[..5]; //~ERROR: slicing may panic
+ //~^ ERROR: range is out of bounds
+
+ let y = &x;
+ y[0]; //~ERROR: indexing may panic
+ &y[1..2]; //~ERROR: slicing may panic
+ &y[..];
+ &y[0...4]; //~ERROR: slicing may panic
}