1 use rustc_data_structures::fx::FxHashSet;
2 use rustc_errors::struct_span_err;
4 use rustc_hir::def_id::{DefId, LocalDefId};
5 use rustc_hir::hir_id::HirId;
6 use rustc_hir::intravisit;
8 use rustc_middle::mir::visit::{MutatingUseContext, PlaceContext, Visitor};
9 use rustc_middle::mir::*;
10 use rustc_middle::ty::cast::CastTy;
11 use rustc_middle::ty::query::Providers;
12 use rustc_middle::ty::{self, TyCtxt};
13 use rustc_session::lint::builtin::{SAFE_PACKED_BORROWS, UNSAFE_OP_IN_UNSAFE_FN, UNUSED_UNSAFE};
14 use rustc_session::lint::Level;
15 use rustc_span::symbol::sym;
19 use crate::const_eval::is_min_const_fn;
22 pub struct UnsafetyChecker<'a, 'tcx> {
27 violations: Vec<UnsafetyViolation>,
28 source_info: SourceInfo,
30 param_env: ty::ParamEnv<'tcx>,
31 /// Mark an `unsafe` block as used, so we don't lint it.
32 used_unsafe: FxHashSet<hir::HirId>,
33 inherited_blocks: Vec<(hir::HirId, bool)>,
36 impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
43 param_env: ty::ParamEnv<'tcx>,
47 assert!(const_context);
55 source_info: SourceInfo::outermost(body.span),
58 used_unsafe: Default::default(),
59 inherited_blocks: vec![],
64 impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
65 fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
66 self.source_info = terminator.source_info;
67 match terminator.kind {
68 TerminatorKind::Goto { .. }
69 | TerminatorKind::SwitchInt { .. }
70 | TerminatorKind::Drop { .. }
71 | TerminatorKind::Yield { .. }
72 | TerminatorKind::Assert { .. }
73 | TerminatorKind::DropAndReplace { .. }
74 | TerminatorKind::GeneratorDrop
75 | TerminatorKind::Resume
76 | TerminatorKind::Abort
77 | TerminatorKind::Return
78 | TerminatorKind::Unreachable
79 | TerminatorKind::FalseEdge { .. }
80 | TerminatorKind::FalseUnwind { .. } => {
81 // safe (at least as emitted during MIR construction)
84 TerminatorKind::Call { ref func, .. } => {
85 let func_ty = func.ty(self.body, self.tcx);
86 let sig = func_ty.fn_sig(self.tcx);
87 if let hir::Unsafety::Unsafe = sig.unsafety() {
89 UnsafetyViolationKind::GeneralAndConstFn,
90 UnsafetyViolationDetails::CallToUnsafeFunction,
94 if let ty::FnDef(func_id, _) = func_ty.kind {
95 self.check_target_features(func_id);
99 TerminatorKind::InlineAsm { .. } => self.require_unsafe(
100 UnsafetyViolationKind::General,
101 UnsafetyViolationDetails::UseOfInlineAssembly,
104 self.super_terminator(terminator, location);
107 fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
108 self.source_info = statement.source_info;
109 match statement.kind {
110 StatementKind::Assign(..)
111 | StatementKind::FakeRead(..)
112 | StatementKind::SetDiscriminant { .. }
113 | StatementKind::StorageLive(..)
114 | StatementKind::StorageDead(..)
115 | StatementKind::Retag { .. }
116 | StatementKind::AscribeUserType(..)
117 | StatementKind::Nop => {
118 // safe (at least as emitted during MIR construction)
121 StatementKind::LlvmInlineAsm { .. } => self.require_unsafe(
122 UnsafetyViolationKind::General,
123 UnsafetyViolationDetails::UseOfInlineAssembly,
126 self.super_statement(statement, location);
129 fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
131 Rvalue::Aggregate(box ref aggregate, _) => match aggregate {
132 &AggregateKind::Array(..) | &AggregateKind::Tuple => {}
133 &AggregateKind::Adt(ref def, ..) => {
134 match self.tcx.layout_scalar_valid_range(def.did) {
135 (Bound::Unbounded, Bound::Unbounded) => {}
136 _ => self.require_unsafe(
137 UnsafetyViolationKind::GeneralAndConstFn,
138 UnsafetyViolationDetails::InitializingTypeWith,
142 &AggregateKind::Closure(def_id, _) | &AggregateKind::Generator(def_id, _, _) => {
143 let UnsafetyCheckResult { violations, unsafe_blocks } =
144 self.tcx.unsafety_check_result(def_id.expect_local());
145 self.register_violations(&violations, &unsafe_blocks);
148 // casting pointers to ints is unsafe in const fn because the const evaluator cannot
149 // possibly know what the result of various operations like `address / 2` would be
150 // pointers during const evaluation have no integral address, only an abstract one
151 Rvalue::Cast(CastKind::Misc, ref operand, cast_ty)
152 if self.const_context && self.tcx.features().const_raw_ptr_to_usize_cast =>
154 let operand_ty = operand.ty(self.body, self.tcx);
155 let cast_in = CastTy::from_ty(operand_ty).expect("bad input type for cast");
156 let cast_out = CastTy::from_ty(cast_ty).expect("bad output type for cast");
157 match (cast_in, cast_out) {
158 (CastTy::Ptr(_) | CastTy::FnPtr, CastTy::Int(_)) => {
160 UnsafetyViolationKind::General,
161 UnsafetyViolationDetails::CastOfPointerToInt,
169 self.super_rvalue(rvalue, location);
172 fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, _location: Location) {
173 // On types with `scalar_valid_range`, prevent
176 // * `&x.field` if `field`'s type has interior mutability
177 // because either of these would allow modifying the layout constrained field and
178 // insert values that violate the layout constraints.
179 if context.is_mutating_use() || context.is_borrow() {
180 self.check_mut_borrowing_layout_constrained_field(*place, context.is_mutating_use());
183 if context.is_borrow() {
184 if util::is_disaligned(self.tcx, self.body, self.param_env, *place) {
186 UnsafetyViolationKind::BorrowPacked,
187 UnsafetyViolationDetails::BorrowOfPackedField,
192 for (i, elem) in place.projection.iter().enumerate() {
193 let proj_base = &place.projection[..i];
194 if context.is_borrow() {
195 if util::is_disaligned(self.tcx, self.body, self.param_env, *place) {
197 UnsafetyViolationKind::BorrowPacked,
198 UnsafetyViolationDetails::BorrowOfPackedField,
202 let source_info = self.source_info;
203 if let [] = proj_base {
204 let decl = &self.body.local_decls[place.local];
206 if let Some(box LocalInfo::StaticRef { def_id, .. }) = decl.local_info {
207 if self.tcx.is_mutable_static(def_id) {
209 UnsafetyViolationKind::General,
210 UnsafetyViolationDetails::UseOfMutableStatic,
213 } else if self.tcx.is_foreign_item(def_id) {
215 UnsafetyViolationKind::General,
216 UnsafetyViolationDetails::UseOfExternStatic,
221 // Internal locals are used in the `move_val_init` desugaring.
222 // We want to check unsafety against the source info of the
223 // desugaring, rather than the source info of the RHS.
224 self.source_info = self.body.local_decls[place.local].source_info;
228 let base_ty = Place::ty_from(place.local, proj_base, self.body, self.tcx).ty;
230 ty::RawPtr(..) => self.require_unsafe(
231 UnsafetyViolationKind::General,
232 UnsafetyViolationDetails::DerefOfRawPointer,
236 if context == PlaceContext::MutatingUse(MutatingUseContext::Store)
237 || context == PlaceContext::MutatingUse(MutatingUseContext::Drop)
238 || context == PlaceContext::MutatingUse(MutatingUseContext::AsmOutput)
240 let elem_ty = match elem {
241 ProjectionElem::Field(_, ty) => ty,
243 self.source_info.span,
244 "non-field projection {:?} from union?",
248 if !elem_ty.is_copy_modulo_regions(
249 self.tcx.at(self.source_info.span),
253 UnsafetyViolationKind::GeneralAndConstFn,
254 UnsafetyViolationDetails::AssignToNonCopyUnionField,
257 // write to non-move union, safe
261 UnsafetyViolationKind::GeneralAndConstFn,
262 UnsafetyViolationDetails::AccessToUnionField,
269 self.source_info = source_info;
274 impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
275 fn require_unsafe(&mut self, kind: UnsafetyViolationKind, details: UnsafetyViolationDetails) {
276 let source_info = self.source_info;
277 let lint_root = self.body.source_scopes[self.source_info.scope]
280 .assert_crate_local()
282 self.register_violations(
283 &[UnsafetyViolation { source_info, lint_root, kind, details }],
288 fn register_violations(
290 violations: &[UnsafetyViolation],
291 unsafe_blocks: &[(hir::HirId, bool)],
293 let safety = self.body.source_scopes[self.source_info.scope]
296 .assert_crate_local()
298 let within_unsafe = match safety {
299 // `unsafe` blocks are required in safe code
301 for violation in violations {
302 let mut violation = *violation;
303 match violation.kind {
304 UnsafetyViolationKind::GeneralAndConstFn
305 | UnsafetyViolationKind::General => {}
306 UnsafetyViolationKind::BorrowPacked => {
307 if self.min_const_fn {
308 // const fns don't need to be backwards compatible and can
309 // emit these violations as a hard error instead of a backwards
311 violation.kind = UnsafetyViolationKind::General;
314 UnsafetyViolationKind::UnsafeFn
315 | UnsafetyViolationKind::UnsafeFnBorrowPacked => {
316 bug!("`UnsafetyViolationKind::UnsafeFn` in an `Safe` context")
319 if !self.violations.contains(&violation) {
320 self.violations.push(violation)
325 // With the RFC 2585, no longer allow `unsafe` operations in `unsafe fn`s
326 Safety::FnUnsafe if self.tcx.features().unsafe_block_in_unsafe_fn => {
327 for violation in violations {
328 let mut violation = *violation;
330 if violation.kind == UnsafetyViolationKind::BorrowPacked {
331 violation.kind = UnsafetyViolationKind::UnsafeFnBorrowPacked;
333 violation.kind = UnsafetyViolationKind::UnsafeFn;
335 if !self.violations.contains(&violation) {
336 self.violations.push(violation)
341 // `unsafe` function bodies allow unsafe without additional unsafe blocks (before RFC 2585)
342 Safety::BuiltinUnsafe | Safety::FnUnsafe => true,
343 Safety::ExplicitUnsafe(hir_id) => {
344 // mark unsafe block as used if there are any unsafe operations inside
345 if !violations.is_empty() {
346 self.used_unsafe.insert(hir_id);
348 // only some unsafety is allowed in const fn
349 if self.min_const_fn {
350 for violation in violations {
351 match violation.kind {
352 // these unsafe things are stable in const fn
353 UnsafetyViolationKind::GeneralAndConstFn => {}
354 // these things are forbidden in const fns
355 UnsafetyViolationKind::General
356 | UnsafetyViolationKind::BorrowPacked => {
357 let mut violation = *violation;
358 // const fns don't need to be backwards compatible and can
359 // emit these violations as a hard error instead of a backwards
361 violation.kind = UnsafetyViolationKind::General;
362 if !self.violations.contains(&violation) {
363 self.violations.push(violation)
366 UnsafetyViolationKind::UnsafeFn
367 | UnsafetyViolationKind::UnsafeFnBorrowPacked => bug!(
368 "`UnsafetyViolationKind::UnsafeFn` in an `ExplicitUnsafe` context"
376 self.inherited_blocks.extend(
377 unsafe_blocks.iter().map(|&(hir_id, is_used)| (hir_id, is_used && !within_unsafe)),
380 fn check_mut_borrowing_layout_constrained_field(
385 let mut cursor = place.projection.as_ref();
386 while let &[ref proj_base @ .., elem] = cursor {
390 // Modifications behind a dereference don't affect the value of
392 ProjectionElem::Deref => return,
393 ProjectionElem::Field(..) => {
395 Place::ty_from(place.local, proj_base, &self.body.local_decls, self.tcx).ty;
396 if let ty::Adt(def, _) = ty.kind {
397 if self.tcx.layout_scalar_valid_range(def.did)
398 != (Bound::Unbounded, Bound::Unbounded)
400 let details = if is_mut_use {
401 UnsafetyViolationDetails::MutationOfLayoutConstrainedField
403 // Check `is_freeze` as late as possible to avoid cycle errors
404 // with opaque types.
406 .ty(self.body, self.tcx)
408 .is_freeze(self.tcx.at(self.source_info.span), self.param_env)
410 UnsafetyViolationDetails::BorrowOfLayoutConstrainedField
414 self.require_unsafe(UnsafetyViolationKind::GeneralAndConstFn, details);
423 /// Checks whether calling `func_did` needs an `unsafe` context or not, i.e. whether
424 /// the called function has target features the calling function hasn't.
425 fn check_target_features(&mut self, func_did: DefId) {
426 let callee_features = &self.tcx.codegen_fn_attrs(func_did).target_features;
427 let self_features = &self.tcx.codegen_fn_attrs(self.body_did).target_features;
429 // Is `callee_features` a subset of `calling_features`?
430 if !callee_features.iter().all(|feature| self_features.contains(feature)) {
432 UnsafetyViolationKind::GeneralAndConstFn,
433 UnsafetyViolationDetails::CallToFunctionWith,
439 pub(crate) fn provide(providers: &mut Providers) {
440 *providers = Providers {
441 unsafety_check_result: |tcx, def_id| {
442 unsafety_check_result(tcx, ty::WithOptConstParam::unknown(def_id))
444 unsafety_check_result_for_const_arg: |tcx, (did, param_did)| {
445 unsafety_check_result(
447 ty::WithOptConstParam { did, const_param_did: Some(param_did) },
450 unsafe_derive_on_repr_packed,
455 struct UnusedUnsafeVisitor<'a> {
456 used_unsafe: &'a FxHashSet<hir::HirId>,
457 unsafe_blocks: &'a mut Vec<(hir::HirId, bool)>,
460 impl<'a, 'tcx> intravisit::Visitor<'tcx> for UnusedUnsafeVisitor<'a> {
461 type Map = intravisit::ErasedMap<'tcx>;
463 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
464 intravisit::NestedVisitorMap::None
467 fn visit_block(&mut self, block: &'tcx hir::Block<'tcx>) {
468 intravisit::walk_block(self, block);
470 if let hir::BlockCheckMode::UnsafeBlock(hir::UnsafeSource::UserProvided) = block.rules {
471 self.unsafe_blocks.push((block.hir_id, self.used_unsafe.contains(&block.hir_id)));
476 fn check_unused_unsafe(
479 used_unsafe: &FxHashSet<hir::HirId>,
480 unsafe_blocks: &mut Vec<(hir::HirId, bool)>,
482 let body_id = tcx.hir().maybe_body_owned_by(tcx.hir().as_local_hir_id(def_id));
484 let body_id = match body_id {
487 debug!("check_unused_unsafe({:?}) - no body found", def_id);
491 let body = tcx.hir().body(body_id);
492 debug!("check_unused_unsafe({:?}, body={:?}, used_unsafe={:?})", def_id, body, used_unsafe);
494 let mut visitor = UnusedUnsafeVisitor { used_unsafe, unsafe_blocks };
495 intravisit::Visitor::visit_body(&mut visitor, body);
498 fn unsafety_check_result<'tcx>(
500 def: ty::WithOptConstParam<LocalDefId>,
501 ) -> &'tcx UnsafetyCheckResult {
502 if def.const_param_did.is_none() {
503 if let Some(param_did) = tcx.opt_const_param_of(def.did) {
504 return tcx.unsafety_check_result_for_const_arg((def.did, param_did));
508 debug!("unsafety_violations({:?})", def);
510 // N.B., this borrow is valid because all the consumers of
511 // `mir_built` force this.
512 let body = &tcx.mir_built(def).borrow();
514 let param_env = tcx.param_env(def.did);
516 let id = tcx.hir().as_local_hir_id(def.did);
517 let (const_context, min_const_fn) = match tcx.hir().body_owner_kind(id) {
518 hir::BodyOwnerKind::Closure => (false, false),
519 hir::BodyOwnerKind::Fn => {
520 (tcx.is_const_fn_raw(def.did.to_def_id()), is_min_const_fn(tcx, def.did.to_def_id()))
522 hir::BodyOwnerKind::Const | hir::BodyOwnerKind::Static(_) => (true, false),
525 UnsafetyChecker::new(const_context, min_const_fn, body, def.did, tcx, param_env);
526 checker.visit_body(&body);
528 check_unused_unsafe(tcx, def.did, &checker.used_unsafe, &mut checker.inherited_blocks);
530 tcx.arena.alloc(UnsafetyCheckResult {
531 violations: checker.violations.into(),
532 unsafe_blocks: checker.inherited_blocks.into(),
536 fn unsafe_derive_on_repr_packed(tcx: TyCtxt<'_>, def_id: LocalDefId) {
537 let lint_hir_id = tcx.hir().as_local_hir_id(def_id);
539 tcx.struct_span_lint_hir(SAFE_PACKED_BORROWS, lint_hir_id, tcx.def_span(def_id), |lint| {
540 // FIXME: when we make this a hard error, this should have its
542 let message = if tcx.generics_of(def_id).own_requires_monomorphization() {
543 "`#[derive]` can't be used on a `#[repr(packed)]` struct with \
544 type or const parameters (error E0133)"
547 "`#[derive]` can't be used on a `#[repr(packed)]` struct that \
548 does not derive Copy (error E0133)"
551 lint.build(&message).emit()
555 /// Returns the `HirId` for an enclosing scope that is also `unsafe`.
558 used_unsafe: &FxHashSet<hir::HirId>,
560 ) -> Option<(String, hir::HirId)> {
561 let parent_id = tcx.hir().get_parent_node(id);
563 if used_unsafe.contains(&parent_id) {
564 Some(("block".to_string(), parent_id))
565 } else if let Some(Node::Item(&hir::Item {
566 kind: hir::ItemKind::Fn(ref sig, _, _), ..
567 })) = tcx.hir().find(parent_id)
569 if sig.header.unsafety == hir::Unsafety::Unsafe
570 && !tcx.features().unsafe_block_in_unsafe_fn
572 Some(("fn".to_string(), parent_id))
577 is_enclosed(tcx, used_unsafe, parent_id)
584 fn report_unused_unsafe(tcx: TyCtxt<'_>, used_unsafe: &FxHashSet<hir::HirId>, id: hir::HirId) {
585 let span = tcx.sess.source_map().guess_head_span(tcx.hir().span(id));
586 tcx.struct_span_lint_hir(UNUSED_UNSAFE, id, span, |lint| {
587 let msg = "unnecessary `unsafe` block";
588 let mut db = lint.build(msg);
589 db.span_label(span, msg);
590 if let Some((kind, id)) = is_enclosed(tcx, used_unsafe, id) {
592 tcx.sess.source_map().guess_head_span(tcx.hir().span(id)),
593 format!("because it's nested under this `unsafe` {}", kind),
600 fn builtin_derive_def_id(tcx: TyCtxt<'_>, def_id: DefId) -> Option<DefId> {
601 debug!("builtin_derive_def_id({:?})", def_id);
602 if let Some(impl_def_id) = tcx.impl_of_method(def_id) {
603 if tcx.has_attr(impl_def_id, sym::automatically_derived) {
604 debug!("builtin_derive_def_id({:?}) - is {:?}", def_id, impl_def_id);
607 debug!("builtin_derive_def_id({:?}) - not automatically derived", def_id);
611 debug!("builtin_derive_def_id({:?}) - not a method", def_id);
616 pub fn check_unsafety(tcx: TyCtxt<'_>, def_id: LocalDefId) {
617 debug!("check_unsafety({:?})", def_id);
619 // closures are handled by their parent fn.
620 if tcx.is_closure(def_id.to_def_id()) {
624 let UnsafetyCheckResult { violations, unsafe_blocks } = tcx.unsafety_check_result(def_id);
626 for &UnsafetyViolation { source_info, lint_root, kind, details } in violations.iter() {
627 let (description, note) = details.description_and_note();
631 if unsafe_op_in_unsafe_fn_allowed(tcx, lint_root) { " function or" } else { "" };
634 UnsafetyViolationKind::GeneralAndConstFn | UnsafetyViolationKind::General => {
640 "{} is unsafe and requires unsafe{} block",
644 .span_label(source_info.span, description)
648 UnsafetyViolationKind::BorrowPacked => {
649 if let Some(impl_def_id) = builtin_derive_def_id(tcx, def_id.to_def_id()) {
650 // If a method is defined in the local crate,
651 // the impl containing that method should also be.
652 tcx.ensure().unsafe_derive_on_repr_packed(impl_def_id.expect_local());
654 tcx.struct_span_lint_hir(
660 "{} is unsafe and requires unsafe{} block (error E0133)",
661 description, unsafe_fn_msg,
669 UnsafetyViolationKind::UnsafeFn => tcx.struct_span_lint_hir(
670 UNSAFE_OP_IN_UNSAFE_FN,
675 "{} is unsafe and requires unsafe block (error E0133)",
678 .span_label(source_info.span, description)
683 UnsafetyViolationKind::UnsafeFnBorrowPacked => {
684 // When `unsafe_op_in_unsafe_fn` is disallowed, the behavior of safe and unsafe functions
685 // should be the same in terms of warnings and errors. Therefore, with `#[warn(safe_packed_borrows)]`,
686 // a safe packed borrow should emit a warning *but not an error* in an unsafe function,
687 // just like in a safe function, even if `unsafe_op_in_unsafe_fn` is `deny`.
689 // Also, `#[warn(unsafe_op_in_unsafe_fn)]` can't cause any new errors. Therefore, with
690 // `#[deny(safe_packed_borrows)]` and `#[warn(unsafe_op_in_unsafe_fn)]`, a packed borrow
691 // should only issue a warning for the sake of backwards compatibility.
693 // The solution those 2 expectations is to always take the minimum of both lints.
694 // This prevent any new errors (unless both lints are explicitely set to `deny`).
695 let lint = if tcx.lint_level_at_node(SAFE_PACKED_BORROWS, lint_root).0
696 <= tcx.lint_level_at_node(UNSAFE_OP_IN_UNSAFE_FN, lint_root).0
700 UNSAFE_OP_IN_UNSAFE_FN
702 tcx.struct_span_lint_hir(&lint, lint_root, source_info.span, |lint| {
704 "{} is unsafe and requires unsafe block (error E0133)",
707 .span_label(source_info.span, description)
715 let (mut unsafe_used, mut unsafe_unused): (FxHashSet<_>, Vec<_>) = Default::default();
716 for &(block_id, is_used) in unsafe_blocks.iter() {
718 unsafe_used.insert(block_id);
720 unsafe_unused.push(block_id);
723 // The unused unsafe blocks might not be in source order; sort them so that the unused unsafe
724 // error messages are properly aligned and the issue-45107 and lint-unused-unsafe tests pass.
725 unsafe_unused.sort_by_cached_key(|hir_id| tcx.hir().span(*hir_id));
727 for &block_id in &unsafe_unused {
728 report_unused_unsafe(tcx, &unsafe_used, block_id);
732 fn unsafe_op_in_unsafe_fn_allowed(tcx: TyCtxt<'_>, id: HirId) -> bool {
733 tcx.lint_level_at_node(UNSAFE_OP_IN_UNSAFE_FN, id).0 == Level::Allow