1 use rustc_hir::def_id::LocalDefId;
2 use rustc_middle::mir::visit::{PlaceContext, Visitor};
3 use rustc_middle::mir::*;
4 use rustc_middle::ty::query::Providers;
5 use rustc_middle::ty::{self, TyCtxt};
6 use rustc_session::lint::builtin::UNALIGNED_REFERENCES;
11 pub(crate) fn provide(providers: &mut Providers) {
12 *providers = Providers { unsafe_derive_on_repr_packed, ..*providers };
15 pub struct CheckPackedRef;
17 impl<'tcx> MirLint<'tcx> for CheckPackedRef {
18 fn run_lint(&self, tcx: TyCtxt<'tcx>, body: &Body<'tcx>) {
19 let param_env = tcx.param_env(body.source.def_id());
20 let source_info = SourceInfo::outermost(body.span);
21 let mut checker = PackedRefChecker { body, tcx, param_env, source_info };
22 checker.visit_body(&body);
26 struct PackedRefChecker<'a, 'tcx> {
29 param_env: ty::ParamEnv<'tcx>,
30 source_info: SourceInfo,
33 fn unsafe_derive_on_repr_packed(tcx: TyCtxt<'_>, def_id: LocalDefId) {
34 let lint_hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
36 // FIXME: when we make this a hard error, this should have its
39 let extra = if tcx.generics_of(def_id).own_requires_monomorphization() {
40 "with type or const parameters"
42 "that does not derive `Copy`"
44 let message = format!(
45 "`{}` can't be derived on this `#[repr(packed)]` struct {}",
46 tcx.item_name(tcx.trait_id_of_impl(def_id.to_def_id()).expect("derived trait name")),
50 tcx.struct_span_lint_hir(
59 impl<'tcx> Visitor<'tcx> for PackedRefChecker<'_, 'tcx> {
60 fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
61 // Make sure we know where in the MIR we are.
62 self.source_info = terminator.source_info;
63 self.super_terminator(terminator, location);
66 fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
67 // Make sure we know where in the MIR we are.
68 self.source_info = statement.source_info;
69 self.super_statement(statement, location);
72 fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, _location: Location) {
73 if context.is_borrow() {
74 if util::is_disaligned(self.tcx, self.body, self.param_env, *place) {
75 let def_id = self.body.source.instance.def_id();
76 if let Some(impl_def_id) = self
78 .impl_of_method(def_id)
79 .filter(|&def_id| self.tcx.is_builtin_derive(def_id))
81 // If a method is defined in the local crate,
82 // the impl containing that method should also be.
83 self.tcx.ensure().unsafe_derive_on_repr_packed(impl_def_id.expect_local());
85 let source_info = self.source_info;
86 let lint_root = self.body.source_scopes[source_info.scope]
91 self.tcx.struct_span_lint_hir(
95 "reference to packed field is unaligned",
99 "fields of packed structs are not properly aligned, and creating \
100 a misaligned reference is undefined behavior (even if that \
101 reference is never dereferenced)",
104 "copy the field contents to a local variable, or replace the \
105 reference with a raw pointer and use `read_unaligned`/`write_unaligned` \
106 (loads and stores via `*p` must be properly aligned even when using raw pointers)"