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|
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);
// 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
);
tcx.struct_span_lint_hir(
UNALIGNED_REFERENCES,
lint_hir_id,
tcx.def_span(def_id),
message,
|lint| lint,
);
}
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,
"reference to packed field is unaligned",
|lint| {
lint
.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)"
)
},
);
}
}
}
}
}
|
