1 use rustc_data_structures::fx::FxHashSet;
2 use rustc_data_structures::indexed_vec::IndexVec;
3 use rustc_data_structures::sync::Lrc;
5 use rustc::ty::query::Providers;
6 use rustc::ty::{self, TyCtxt};
7 use rustc::ty::cast::CastTy;
10 use rustc::hir::def_id::DefId;
11 use rustc::lint::builtin::{SAFE_EXTERN_STATICS, SAFE_PACKED_BORROWS, UNUSED_UNSAFE};
13 use rustc::mir::visit::{PlaceContext, Visitor, MutatingUseContext};
15 use syntax::symbol::Symbol;
21 pub struct UnsafetyChecker<'a, 'tcx: 'a> {
25 source_scope_local_data: &'a IndexVec<SourceScope, SourceScopeLocalData>,
26 violations: Vec<UnsafetyViolation>,
27 source_info: SourceInfo,
28 tcx: TyCtxt<'a, 'tcx, 'tcx>,
29 param_env: ty::ParamEnv<'tcx>,
30 /// Mark an `unsafe` block as used, so we don't lint it.
31 used_unsafe: FxHashSet<hir::HirId>,
32 inherited_blocks: Vec<(hir::HirId, bool)>,
35 impl<'a, 'gcx, 'tcx> UnsafetyChecker<'a, 'tcx> {
40 source_scope_local_data: &'a IndexVec<SourceScope, SourceScopeLocalData>,
41 tcx: TyCtxt<'a, 'tcx, 'tcx>,
42 param_env: ty::ParamEnv<'tcx>,
46 assert!(const_context);
52 source_scope_local_data,
54 source_info: SourceInfo {
56 scope: OUTERMOST_SOURCE_SCOPE
60 used_unsafe: Default::default(),
61 inherited_blocks: vec![],
66 impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
67 fn visit_terminator(&mut self,
69 terminator: &Terminator<'tcx>,
72 self.source_info = terminator.source_info;
73 match terminator.kind {
74 TerminatorKind::Goto { .. } |
75 TerminatorKind::SwitchInt { .. } |
76 TerminatorKind::Drop { .. } |
77 TerminatorKind::Yield { .. } |
78 TerminatorKind::Assert { .. } |
79 TerminatorKind::DropAndReplace { .. } |
80 TerminatorKind::GeneratorDrop |
81 TerminatorKind::Resume |
82 TerminatorKind::Abort |
83 TerminatorKind::Return |
84 TerminatorKind::Unreachable |
85 TerminatorKind::FalseEdges { .. } |
86 TerminatorKind::FalseUnwind { .. } => {
87 // safe (at least as emitted during MIR construction)
90 TerminatorKind::Call { ref func, .. } => {
91 let func_ty = func.ty(self.mir, self.tcx);
92 let sig = func_ty.fn_sig(self.tcx);
93 if let hir::Unsafety::Unsafe = sig.unsafety() {
94 self.require_unsafe("call to unsafe function",
95 "consult the function's documentation for information on how to avoid \
96 undefined behavior", UnsafetyViolationKind::GeneralAndConstFn)
100 self.super_terminator(block, terminator, location);
103 fn visit_statement(&mut self,
105 statement: &Statement<'tcx>,
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::InlineAsm { .. } => {
122 self.require_unsafe("use of inline assembly",
123 "inline assembly is entirely unchecked and can cause undefined behavior",
124 UnsafetyViolationKind::General)
127 self.super_statement(block, statement, location);
130 fn visit_rvalue(&mut self,
131 rvalue: &Rvalue<'tcx>,
135 Rvalue::Aggregate(box ref aggregate, _) => {
137 &AggregateKind::Array(..) |
138 &AggregateKind::Tuple => {}
139 &AggregateKind::Adt(ref def, ..) => {
140 match self.tcx.layout_scalar_valid_range(def.did) {
141 (Bound::Unbounded, Bound::Unbounded) => {},
142 _ => self.require_unsafe(
143 "initializing type with `rustc_layout_scalar_valid_range` attr",
144 "initializing a layout restricted type's field with a value \
145 outside the valid range is undefined behavior",
146 UnsafetyViolationKind::GeneralAndConstFn,
150 &AggregateKind::Closure(def_id, _) |
151 &AggregateKind::Generator(def_id, _, _) => {
152 let UnsafetyCheckResult {
153 violations, unsafe_blocks
154 } = self.tcx.unsafety_check_result(def_id);
155 self.register_violations(&violations, &unsafe_blocks);
159 // casting pointers to ints is unsafe in const fn because the const evaluator cannot
160 // possibly know what the result of various operations like `address / 2` would be
161 // pointers during const evaluation have no integral address, only an abstract one
162 Rvalue::Cast(CastKind::Misc, ref operand, cast_ty)
163 if self.const_context && self.tcx.features().const_raw_ptr_to_usize_cast => {
164 let operand_ty = operand.ty(self.mir, self.tcx);
165 let cast_in = CastTy::from_ty(operand_ty).expect("bad input type for cast");
166 let cast_out = CastTy::from_ty(cast_ty).expect("bad output type for cast");
167 match (cast_in, cast_out) {
168 (CastTy::Ptr(_), CastTy::Int(_)) |
169 (CastTy::FnPtr, CastTy::Int(_)) => {
170 self.register_violations(&[UnsafetyViolation {
171 source_info: self.source_info,
172 description: Symbol::intern("cast of pointer to int").as_interned_str(),
173 details: Symbol::intern("casting pointers to integers in constants")
175 kind: UnsafetyViolationKind::General,
181 // raw pointer and fn pointer operations are unsafe as it is not clear whether one
182 // pointer would be "less" or "equal" to another, because we cannot know where llvm
183 // or the linker will place various statics in memory. Without this information the
184 // result of a comparison of addresses would differ between runtime and compile-time.
185 Rvalue::BinaryOp(_, ref lhs, _)
186 if self.const_context && self.tcx.features().const_compare_raw_pointers => {
187 if let ty::RawPtr(_) | ty::FnPtr(..) = lhs.ty(self.mir, self.tcx).sty {
188 self.register_violations(&[UnsafetyViolation {
189 source_info: self.source_info,
190 description: Symbol::intern("pointer operation").as_interned_str(),
191 details: Symbol::intern("operations on pointers in constants")
193 kind: UnsafetyViolationKind::General,
199 self.super_rvalue(rvalue, location);
202 fn visit_place(&mut self,
204 context: PlaceContext<'tcx>,
205 location: Location) {
207 &Place::Projection(box Projection {
210 if context.is_borrow() {
211 if util::is_disaligned(self.tcx, self.mir, self.param_env, place) {
212 let source_info = self.source_info;
214 self.source_scope_local_data[source_info.scope].lint_root;
215 self.register_violations(&[UnsafetyViolation {
217 description: Symbol::intern("borrow of packed field").as_interned_str(),
219 Symbol::intern("fields of packed structs might be misaligned: \
220 dereferencing a misaligned pointer or even just \
221 creating a misaligned reference is undefined \
224 kind: UnsafetyViolationKind::BorrowPacked(lint_root)
228 let is_borrow_of_interior_mut = context.is_borrow() && !base
229 .ty(self.mir, self.tcx)
231 .is_freeze(self.tcx, self.param_env, self.source_info.span);
235 // * `&x.field` if `field`'s type has interior mutability
236 // because either of these would allow modifying the layout constrained field and
237 // insert values that violate the layout constraints.
238 if context.is_mutating_use() || is_borrow_of_interior_mut {
239 self.check_mut_borrowing_layout_constrained_field(
240 place, context.is_mutating_use(),
243 let old_source_info = self.source_info;
244 if let &Place::Base(PlaceBase::Local(local)) = base {
245 if self.mir.local_decls[local].internal {
246 // Internal locals are used in the `move_val_init` desugaring.
247 // We want to check unsafety against the source info of the
248 // desugaring, rather than the source info of the RHS.
249 self.source_info = self.mir.local_decls[local].source_info;
252 let base_ty = base.ty(self.mir, self.tcx).ty;
255 self.require_unsafe("dereference of raw pointer",
256 "raw pointers may be NULL, dangling or unaligned; they can violate \
257 aliasing rules and cause data races: all of these are undefined \
258 behavior", UnsafetyViolationKind::General)
262 if context == PlaceContext::MutatingUse(MutatingUseContext::Store) ||
263 context == PlaceContext::MutatingUse(MutatingUseContext::Drop) ||
264 context == PlaceContext::MutatingUse(
265 MutatingUseContext::AsmOutput
268 let elem_ty = match elem {
269 &ProjectionElem::Field(_, ty) => ty,
271 self.source_info.span,
272 "non-field projection {:?} from union?",
275 if !elem_ty.is_copy_modulo_regions(
278 self.source_info.span,
281 "assignment to non-`Copy` union field",
282 "the previous content of the field will be dropped, which \
283 causes undefined behavior if the field was not properly \
284 initialized", UnsafetyViolationKind::General)
286 // write to non-move union, safe
289 self.require_unsafe("access to union field",
290 "the field may not be properly initialized: using \
291 uninitialized data will cause undefined behavior",
292 UnsafetyViolationKind::General)
298 self.source_info = old_source_info;
300 &Place::Base(PlaceBase::Local(..)) => {
303 &Place::Base(PlaceBase::Static(box Static { kind: StaticKind::Promoted(_), .. })) => {
304 bug!("unsafety checking should happen before promotion")
307 PlaceBase::Static(box Static { kind: StaticKind::Static(def_id), .. })
309 if self.tcx.is_mutable_static(def_id) {
310 self.require_unsafe("use of mutable static",
311 "mutable statics can be mutated by multiple threads: aliasing violations \
312 or data races will cause undefined behavior",
313 UnsafetyViolationKind::General);
314 } else if self.tcx.is_foreign_item(def_id) {
315 let source_info = self.source_info;
317 self.source_scope_local_data[source_info.scope].lint_root;
318 self.register_violations(&[UnsafetyViolation {
320 description: Symbol::intern("use of extern static").as_interned_str(),
322 Symbol::intern("extern statics are not controlled by the Rust type \
323 system: invalid data, aliasing violations or data \
324 races will cause undefined behavior")
326 kind: UnsafetyViolationKind::ExternStatic(lint_root)
331 self.super_place(place, context, location);
335 impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
338 description: &'static str,
339 details: &'static str,
340 kind: UnsafetyViolationKind,
342 let source_info = self.source_info;
343 self.register_violations(&[UnsafetyViolation {
345 description: Symbol::intern(description).as_interned_str(),
346 details: Symbol::intern(details).as_interned_str(),
351 fn register_violations(&mut self,
352 violations: &[UnsafetyViolation],
353 unsafe_blocks: &[(hir::HirId, bool)]) {
354 let safety = self.source_scope_local_data[self.source_info.scope].safety;
355 let within_unsafe = match safety {
356 // `unsafe` blocks are required in safe code
358 for violation in violations {
359 let mut violation = violation.clone();
360 match violation.kind {
361 UnsafetyViolationKind::GeneralAndConstFn |
362 UnsafetyViolationKind::General => {},
363 UnsafetyViolationKind::BorrowPacked(_) |
364 UnsafetyViolationKind::ExternStatic(_) => if self.min_const_fn {
365 // const fns don't need to be backwards compatible and can
366 // emit these violations as a hard error instead of a backwards
368 violation.kind = UnsafetyViolationKind::General;
371 if !self.violations.contains(&violation) {
372 self.violations.push(violation)
377 // `unsafe` function bodies allow unsafe without additional unsafe blocks
378 Safety::BuiltinUnsafe | Safety::FnUnsafe => true,
379 Safety::ExplicitUnsafe(hir_id) => {
380 // mark unsafe block as used if there are any unsafe operations inside
381 if !violations.is_empty() {
382 self.used_unsafe.insert(hir_id);
384 // only some unsafety is allowed in const fn
385 if self.min_const_fn {
386 for violation in violations {
387 match violation.kind {
388 // these unsafe things are stable in const fn
389 UnsafetyViolationKind::GeneralAndConstFn => {},
390 // these things are forbidden in const fns
391 UnsafetyViolationKind::General |
392 UnsafetyViolationKind::BorrowPacked(_) |
393 UnsafetyViolationKind::ExternStatic(_) => {
394 let mut violation = violation.clone();
395 // const fns don't need to be backwards compatible and can
396 // emit these violations as a hard error instead of a backwards
398 violation.kind = UnsafetyViolationKind::General;
399 if !self.violations.contains(&violation) {
400 self.violations.push(violation)
409 self.inherited_blocks.extend(unsafe_blocks.iter().map(|&(hir_id, is_used)| {
410 (hir_id, is_used && !within_unsafe)
413 fn check_mut_borrowing_layout_constrained_field(
415 mut place: &Place<'tcx>,
418 while let &Place::Projection(box Projection {
422 ProjectionElem::Field(..) => {
423 let ty = base.ty(&self.mir.local_decls, self.tcx).ty;
425 ty::Adt(def, _) => match self.tcx.layout_scalar_valid_range(def.did) {
426 (Bound::Unbounded, Bound::Unbounded) => {},
428 let (description, details) = if is_mut_use {
430 "mutation of layout constrained field",
431 "mutating layout constrained fields cannot statically be \
432 checked for valid values",
436 "borrow of layout constrained field with interior \
438 "references to fields of layout constrained fields \
439 lose the constraints. Coupled with interior mutability, \
440 the field can be changed to invalid values",
443 let source_info = self.source_info;
444 self.register_violations(&[UnsafetyViolation {
446 description: Symbol::intern(description).as_interned_str(),
447 details: Symbol::intern(details).as_interned_str(),
448 kind: UnsafetyViolationKind::GeneralAndConstFn,
462 pub(crate) fn provide(providers: &mut Providers<'_>) {
463 *providers = Providers {
464 unsafety_check_result,
465 unsafe_derive_on_repr_packed,
470 struct UnusedUnsafeVisitor<'a> {
471 used_unsafe: &'a FxHashSet<hir::HirId>,
472 unsafe_blocks: &'a mut Vec<(hir::HirId, bool)>,
475 impl<'a, 'tcx> hir::intravisit::Visitor<'tcx> for UnusedUnsafeVisitor<'a> {
476 fn nested_visit_map<'this>(&'this mut self) ->
477 hir::intravisit::NestedVisitorMap<'this, 'tcx>
479 hir::intravisit::NestedVisitorMap::None
482 fn visit_block(&mut self, block: &'tcx hir::Block) {
483 hir::intravisit::walk_block(self, block);
485 if let hir::UnsafeBlock(hir::UserProvided) = block.rules {
486 self.unsafe_blocks.push((block.hir_id, self.used_unsafe.contains(&block.hir_id)));
491 fn check_unused_unsafe<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
493 used_unsafe: &FxHashSet<hir::HirId>,
494 unsafe_blocks: &'a mut Vec<(hir::HirId, bool)>)
497 tcx.hir().as_local_hir_id(def_id).and_then(|hir_id| {
498 tcx.hir().maybe_body_owned_by_by_hir_id(hir_id)
501 let body_id = match body_id {
504 debug!("check_unused_unsafe({:?}) - no body found", def_id);
508 let body = tcx.hir().body(body_id);
509 debug!("check_unused_unsafe({:?}, body={:?}, used_unsafe={:?})",
510 def_id, body, used_unsafe);
512 let mut visitor = UnusedUnsafeVisitor { used_unsafe, unsafe_blocks };
513 hir::intravisit::Visitor::visit_body(&mut visitor, body);
516 fn unsafety_check_result<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
517 -> UnsafetyCheckResult
519 debug!("unsafety_violations({:?})", def_id);
521 // N.B., this borrow is valid because all the consumers of
522 // `mir_built` force this.
523 let mir = &tcx.mir_built(def_id).borrow();
525 let source_scope_local_data = match mir.source_scope_local_data {
526 ClearCrossCrate::Set(ref data) => data,
527 ClearCrossCrate::Clear => {
528 debug!("unsafety_violations: {:?} - remote, skipping", def_id);
529 return UnsafetyCheckResult {
530 violations: Lrc::new([]),
531 unsafe_blocks: Lrc::new([])
536 let param_env = tcx.param_env(def_id);
538 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
539 let (const_context, min_const_fn) = match tcx.hir().body_owner_kind_by_hir_id(id) {
540 hir::BodyOwnerKind::Closure => (false, false),
541 hir::BodyOwnerKind::Fn => (tcx.is_const_fn(def_id), tcx.is_min_const_fn(def_id)),
542 hir::BodyOwnerKind::Const |
543 hir::BodyOwnerKind::Static(_) => (true, false),
545 let mut checker = UnsafetyChecker::new(
546 const_context, min_const_fn,
547 mir, source_scope_local_data, tcx, param_env);
548 checker.visit_mir(mir);
550 check_unused_unsafe(tcx, def_id, &checker.used_unsafe, &mut checker.inherited_blocks);
551 UnsafetyCheckResult {
552 violations: checker.violations.into(),
553 unsafe_blocks: checker.inherited_blocks.into()
557 fn unsafe_derive_on_repr_packed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
558 let lint_hir_id = tcx.hir().as_local_hir_id(def_id).unwrap_or_else(||
559 bug!("checking unsafety for non-local def id {:?}", def_id));
561 // FIXME: when we make this a hard error, this should have its
563 let message = if tcx.generics_of(def_id).own_requires_monomorphization() {
564 "#[derive] can't be used on a #[repr(packed)] struct with \
565 type or const parameters (error E0133)".to_string()
567 "#[derive] can't be used on a #[repr(packed)] struct that \
568 does not derive Copy (error E0133)".to_string()
570 tcx.lint_hir(SAFE_PACKED_BORROWS,
572 tcx.def_span(def_id),
576 /// Returns the `HirId` for an enclosing scope that is also `unsafe`.
577 fn is_enclosed(tcx: TyCtxt<'_, '_, '_>,
578 used_unsafe: &FxHashSet<hir::HirId>,
579 id: hir::HirId) -> Option<(String, hir::HirId)> {
580 let parent_id = tcx.hir().get_parent_node_by_hir_id(id);
582 if used_unsafe.contains(&parent_id) {
583 Some(("block".to_string(), parent_id))
584 } else if let Some(Node::Item(&hir::Item {
585 node: hir::ItemKind::Fn(_, header, _, _),
587 })) = tcx.hir().find_by_hir_id(parent_id) {
588 match header.unsafety {
589 hir::Unsafety::Unsafe => Some(("fn".to_string(), parent_id)),
590 hir::Unsafety::Normal => None,
593 is_enclosed(tcx, used_unsafe, parent_id)
600 fn report_unused_unsafe(tcx: TyCtxt<'_, '_, '_>,
601 used_unsafe: &FxHashSet<hir::HirId>,
603 let span = tcx.sess.source_map().def_span(tcx.hir().span_by_hir_id(id));
604 let msg = "unnecessary `unsafe` block";
605 let mut db = tcx.struct_span_lint_hir(UNUSED_UNSAFE, id, span, msg);
606 db.span_label(span, msg);
607 if let Some((kind, id)) = is_enclosed(tcx, used_unsafe, id) {
608 db.span_label(tcx.sess.source_map().def_span(tcx.hir().span_by_hir_id(id)),
609 format!("because it's nested under this `unsafe` {}", kind));
614 fn builtin_derive_def_id<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> Option<DefId> {
615 debug!("builtin_derive_def_id({:?})", def_id);
616 if let Some(impl_def_id) = tcx.impl_of_method(def_id) {
617 if tcx.has_attr(impl_def_id, "automatically_derived") {
618 debug!("builtin_derive_def_id({:?}) - is {:?}", def_id, impl_def_id);
621 debug!("builtin_derive_def_id({:?}) - not automatically derived", def_id);
625 debug!("builtin_derive_def_id({:?}) - not a method", def_id);
630 pub fn check_unsafety<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
631 debug!("check_unsafety({:?})", def_id);
633 // closures are handled by their parent fn.
634 if tcx.is_closure(def_id) {
638 let UnsafetyCheckResult {
641 } = tcx.unsafety_check_result(def_id);
643 for &UnsafetyViolation {
644 source_info, description, details, kind
645 } in violations.iter() {
648 UnsafetyViolationKind::GeneralAndConstFn |
649 UnsafetyViolationKind::General => {
651 tcx.sess, source_info.span, E0133,
652 "{} is unsafe and requires unsafe function or block", description)
653 .span_label(source_info.span, &description.as_str()[..])
654 .note(&details.as_str()[..])
657 UnsafetyViolationKind::ExternStatic(lint_hir_id) => {
658 tcx.lint_node_note(SAFE_EXTERN_STATICS,
661 &format!("{} is unsafe and requires unsafe function or block \
662 (error E0133)", &description.as_str()[..]),
663 &details.as_str()[..]);
665 UnsafetyViolationKind::BorrowPacked(lint_hir_id) => {
666 if let Some(impl_def_id) = builtin_derive_def_id(tcx, def_id) {
667 tcx.unsafe_derive_on_repr_packed(impl_def_id);
669 tcx.lint_node_note(SAFE_PACKED_BORROWS,
672 &format!("{} is unsafe and requires unsafe function or block \
673 (error E0133)", &description.as_str()[..]),
674 &details.as_str()[..]);
680 let mut unsafe_blocks: Vec<_> = unsafe_blocks.into_iter().collect();
681 unsafe_blocks.sort_by_cached_key(|(hir_id, _)| tcx.hir().hir_to_node_id(*hir_id));
682 let used_unsafe: FxHashSet<_> = unsafe_blocks.iter()
683 .flat_map(|&&(id, used)| if used { Some(id) } else { None })
685 for &(block_id, is_used) in unsafe_blocks {
687 report_unused_unsafe(tcx, &used_unsafe, block_id);