use rustc_hir::def_id::LocalDefId; use rustc_middle::mir::visit::{PlaceContext, Visitor}; use rustc_middle::mir::*; use rustc_middle::ty::query::Providers; use rustc_middle::ty::{self, TyCtxt}; use rustc_session::lint::builtin::UNALIGNED_REFERENCES; use crate::util; use crate::MirLint; pub(crate) fn provide(providers: &mut Providers) { *providers = Providers { unsafe_derive_on_repr_packed, ..*providers }; } pub struct CheckPackedRef; impl<'tcx> MirLint<'tcx> for CheckPackedRef { fn run_lint(&self, tcx: TyCtxt<'tcx>, body: &Body<'tcx>) { let param_env = tcx.param_env(body.source.def_id()); let source_info = SourceInfo::outermost(body.span); let mut checker = PackedRefChecker { body, tcx, param_env, source_info }; checker.visit_body(&body); } } struct PackedRefChecker<'a, 'tcx> { body: &'a Body<'tcx>, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>, source_info: SourceInfo, } fn unsafe_derive_on_repr_packed(tcx: TyCtxt<'_>, def_id: LocalDefId) { let lint_hir_id = tcx.hir().local_def_id_to_hir_id(def_id); tcx.struct_span_lint_hir(UNALIGNED_REFERENCES, lint_hir_id, tcx.def_span(def_id), |lint| { // FIXME: when we make this a hard error, this should have its // own error code. let extra = if tcx.generics_of(def_id).own_requires_monomorphization() { "with type or const parameters" } else { "that does not derive `Copy`" }; let message = format!( "`{}` can't be derived on this `#[repr(packed)]` struct {}", tcx.item_name(tcx.trait_id_of_impl(def_id.to_def_id()).expect("derived trait name")), extra ); lint.build(message).emit(); }); } impl<'tcx> Visitor<'tcx> for PackedRefChecker<'_, 'tcx> { fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) { // Make sure we know where in the MIR we are. self.source_info = terminator.source_info; self.super_terminator(terminator, location); } fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) { // Make sure we know where in the MIR we are. self.source_info = statement.source_info; self.super_statement(statement, location); } fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, _location: Location) { if context.is_borrow() { if util::is_disaligned(self.tcx, self.body, self.param_env, *place) { let def_id = self.body.source.instance.def_id(); if let Some(impl_def_id) = self .tcx .impl_of_method(def_id) .filter(|&def_id| self.tcx.is_builtin_derive(def_id)) { // If a method is defined in the local crate, // the impl containing that method should also be. self.tcx.ensure().unsafe_derive_on_repr_packed(impl_def_id.expect_local()); } else { let source_info = self.source_info; let lint_root = self.body.source_scopes[source_info.scope] .local_data .as_ref() .assert_crate_local() .lint_root; self.tcx.struct_span_lint_hir( UNALIGNED_REFERENCES, lint_root, source_info.span, |lint| { lint.build("reference to packed field is unaligned") .note( "fields of packed structs are not properly aligned, and creating \ a misaligned reference is undefined behavior (even if that \ reference is never dereferenced)", ) .help( "copy the field contents to a local variable, or replace the \ reference with a raw pointer and use `read_unaligned`/`write_unaligned` \ (loads and stores via `*p` must be properly aligned even when using raw pointers)" ) .emit(); }, ); } } } } }