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rust-clippy/clippy_lints/src/array_indexing.rs
2017-03-05 10:27:20 +01:00

154 lines
5.5 KiB
Rust

use rustc::lint::*;
use rustc::middle::const_val::ConstVal;
use rustc::ty;
use rustc_const_eval::ConstContext;
use rustc_const_math::{ConstUsize, ConstIsize, ConstInt};
use rustc::hir;
use syntax::ast::RangeLimits;
use utils::{self, higher};
/// **What it does:** Checks for out of bounds array indexing with a constant index.
///
/// **Why is this bad?** This will always panic at runtime.
///
/// **Known problems:** Hopefully none.
///
/// **Example:**
/// ```rust
/// let x = [1,2,3,4];
/// ...
/// x[9];
/// &x[2..9];
/// ```
declare_lint! {
pub OUT_OF_BOUNDS_INDEXING,
Deny,
"out of bounds constant indexing"
}
/// **What it does:** Checks 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:**
/// ```rust
/// ...
/// x[2];
/// &x[0..2];
/// ```
declare_restriction_lint! {
pub INDEXING_SLICING,
"indexing/slicing usage"
}
#[derive(Copy,Clone)]
pub struct ArrayIndexing;
impl LintPass for ArrayIndexing {
fn get_lints(&self) -> LintArray {
lint_array!(INDEXING_SLICING, OUT_OF_BOUNDS_INDEXING)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ArrayIndexing {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx hir::Expr) {
if let hir::ExprIndex(ref array, ref index) = e.node {
// Array with known size can be checked statically
let ty = cx.tables.expr_ty(array);
if let ty::TyArray(_, size) = ty.sty {
let size = ConstInt::Usize(ConstUsize::new(size as u64, cx.sess().target.uint_type)
.expect("array size is invalid"));
let constcx = ConstContext::with_tables(cx.tcx, cx.tables);
// Index is a constant uint
let const_index = constcx.eval(index);
if let Ok(ConstVal::Integral(const_index)) = const_index {
if size <= const_index {
utils::span_lint(cx, OUT_OF_BOUNDS_INDEXING, e.span, "const index is out of bounds");
}
return;
}
// Index is a constant range
if let Some(range) = higher::range(index) {
let start = range.start
.map(|start| constcx.eval(start))
.map(|v| v.ok());
let end = range.end
.map(|end| constcx.eval(end))
.map(|v| v.ok());
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");
}
return;
}
}
}
if let Some(range) = higher::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.
fn to_const_range(
start: &Option<Option<ConstVal>>,
end: &Option<Option<ConstVal>>,
limits: RangeLimits,
array_size: ConstInt
) -> Option<(ConstInt, ConstInt)> {
let start = match *start {
Some(Some(ConstVal::Integral(x))) => x,
Some(_) => return None,
None => ConstInt::U8(0),
};
let end = match *end {
Some(Some(ConstVal::Integral(x))) => {
if limits == RangeLimits::Closed {
match x {
ConstInt::U8(_) => (x + ConstInt::U8(1)),
ConstInt::U16(_) => (x + ConstInt::U16(1)),
ConstInt::U32(_) => (x + ConstInt::U32(1)),
ConstInt::U64(_) => (x + ConstInt::U64(1)),
ConstInt::U128(_) => (x + ConstInt::U128(1)),
ConstInt::Usize(ConstUsize::Us16(_)) => (x + ConstInt::Usize(ConstUsize::Us16(1))),
ConstInt::Usize(ConstUsize::Us32(_)) => (x + ConstInt::Usize(ConstUsize::Us32(1))),
ConstInt::Usize(ConstUsize::Us64(_)) => (x + ConstInt::Usize(ConstUsize::Us64(1))),
ConstInt::I8(_) => (x + ConstInt::I8(1)),
ConstInt::I16(_) => (x + ConstInt::I16(1)),
ConstInt::I32(_) => (x + ConstInt::I32(1)),
ConstInt::I64(_) => (x + ConstInt::I64(1)),
ConstInt::I128(_) => (x + ConstInt::I128(1)),
ConstInt::Isize(ConstIsize::Is16(_)) => (x + ConstInt::Isize(ConstIsize::Is16(1))),
ConstInt::Isize(ConstIsize::Is32(_)) => (x + ConstInt::Isize(ConstIsize::Is32(1))),
ConstInt::Isize(ConstIsize::Is64(_)) => (x + ConstInt::Isize(ConstIsize::Is64(1))),
}
.expect("such a big array is not realistic")
} else {
x
}
},
Some(_) => return None,
None => array_size,
};
Some((start, end))
}