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|
//! This pass statically detects code which has undefined behaviour or is likely to be erroneous.
//! It can be used to locate problems in MIR building or optimizations. It assumes that all code
//! can be executed, so it has false positives.
use rustc_index::bit_set::BitSet;
use rustc_middle::mir::visit::{PlaceContext, Visitor};
use rustc_middle::mir::*;
use rustc_middle::ty::TyCtxt;
use rustc_mir_dataflow::impls::{MaybeStorageDead, MaybeStorageLive};
use rustc_mir_dataflow::storage::always_storage_live_locals;
use rustc_mir_dataflow::{Analysis, ResultsCursor};
use std::borrow::Cow;
pub fn lint_body<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>, when: String) {
let reachable_blocks = traversal::reachable_as_bitset(body);
let always_live_locals = &always_storage_live_locals(body);
let maybe_storage_live = MaybeStorageLive::new(Cow::Borrowed(always_live_locals))
.into_engine(tcx, body)
.iterate_to_fixpoint()
.into_results_cursor(body);
let maybe_storage_dead = MaybeStorageDead::new(Cow::Borrowed(always_live_locals))
.into_engine(tcx, body)
.iterate_to_fixpoint()
.into_results_cursor(body);
Lint {
tcx,
when,
body,
is_fn_like: tcx.def_kind(body.source.def_id()).is_fn_like(),
always_live_locals,
reachable_blocks,
maybe_storage_live,
maybe_storage_dead,
}
.visit_body(body);
}
struct Lint<'a, 'tcx> {
tcx: TyCtxt<'tcx>,
when: String,
body: &'a Body<'tcx>,
is_fn_like: bool,
always_live_locals: &'a BitSet<Local>,
reachable_blocks: BitSet<BasicBlock>,
maybe_storage_live: ResultsCursor<'a, 'tcx, MaybeStorageLive<'a>>,
maybe_storage_dead: ResultsCursor<'a, 'tcx, MaybeStorageDead<'a>>,
}
impl<'a, 'tcx> Lint<'a, 'tcx> {
#[track_caller]
fn fail(&self, location: Location, msg: impl AsRef<str>) {
let span = self.body.source_info(location).span;
self.tcx.sess.dcx().span_delayed_bug(
span,
format!(
"broken MIR in {:?} ({}) at {:?}:\n{}",
self.body.source.instance,
self.when,
location,
msg.as_ref()
),
);
}
}
impl<'a, 'tcx> Visitor<'tcx> for Lint<'a, 'tcx> {
fn visit_local(&mut self, local: Local, context: PlaceContext, location: Location) {
if self.reachable_blocks.contains(location.block) && context.is_use() {
self.maybe_storage_dead.seek_after_primary_effect(location);
if self.maybe_storage_dead.get().contains(local) {
self.fail(location, format!("use of local {local:?}, which has no storage here"));
}
}
}
fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
match statement.kind {
StatementKind::StorageLive(local) => {
if self.reachable_blocks.contains(location.block) {
self.maybe_storage_live.seek_before_primary_effect(location);
if self.maybe_storage_live.get().contains(local) {
self.fail(
location,
format!("StorageLive({local:?}) which already has storage here"),
);
}
}
}
_ => {}
}
self.super_statement(statement, location);
}
fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
match terminator.kind {
TerminatorKind::Return => {
if self.is_fn_like && self.reachable_blocks.contains(location.block) {
self.maybe_storage_live.seek_after_primary_effect(location);
for local in self.maybe_storage_live.get().iter() {
if !self.always_live_locals.contains(local) {
self.fail(
location,
format!(
"local {local:?} still has storage when returning from function"
),
);
}
}
}
}
_ => {}
}
self.super_terminator(terminator, location);
}
}
|
