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::{InternedString, sym};
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, '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,
68 terminator: &Terminator<'tcx>,
71 self.source_info = terminator.source_info;
72 match terminator.kind {
73 TerminatorKind::Goto { .. } |
74 TerminatorKind::SwitchInt { .. } |
75 TerminatorKind::Drop { .. } |
76 TerminatorKind::Yield { .. } |
77 TerminatorKind::Assert { .. } |
78 TerminatorKind::DropAndReplace { .. } |
79 TerminatorKind::GeneratorDrop |
80 TerminatorKind::Resume |
81 TerminatorKind::Abort |
82 TerminatorKind::Return |
83 TerminatorKind::Unreachable |
84 TerminatorKind::FalseEdges { .. } |
85 TerminatorKind::FalseUnwind { .. } => {
86 // safe (at least as emitted during MIR construction)
89 TerminatorKind::Call { ref func, .. } => {
90 let func_ty = func.ty(self.body, self.tcx);
91 let sig = func_ty.fn_sig(self.tcx);
92 if let hir::Unsafety::Unsafe = sig.unsafety() {
93 self.require_unsafe("call to unsafe function",
94 "consult the function's documentation for information on how to avoid \
95 undefined behavior", UnsafetyViolationKind::GeneralAndConstFn)
99 self.super_terminator(terminator, location);
102 fn visit_statement(&mut self,
103 statement: &Statement<'tcx>,
106 self.source_info = statement.source_info;
107 match statement.kind {
108 StatementKind::Assign(..) |
109 StatementKind::FakeRead(..) |
110 StatementKind::SetDiscriminant { .. } |
111 StatementKind::StorageLive(..) |
112 StatementKind::StorageDead(..) |
113 StatementKind::Retag { .. } |
114 StatementKind::AscribeUserType(..) |
115 StatementKind::Nop => {
116 // safe (at least as emitted during MIR construction)
119 StatementKind::InlineAsm { .. } => {
120 self.require_unsafe("use of inline assembly",
121 "inline assembly is entirely unchecked and can cause undefined behavior",
122 UnsafetyViolationKind::General)
125 self.super_statement(statement, location);
128 fn visit_rvalue(&mut self,
129 rvalue: &Rvalue<'tcx>,
133 Rvalue::Aggregate(box ref aggregate, _) => {
135 &AggregateKind::Array(..) |
136 &AggregateKind::Tuple => {}
137 &AggregateKind::Adt(ref def, ..) => {
138 match self.tcx.layout_scalar_valid_range(def.did) {
139 (Bound::Unbounded, Bound::Unbounded) => {},
140 _ => self.require_unsafe(
141 "initializing type with `rustc_layout_scalar_valid_range` attr",
142 "initializing a layout restricted type's field with a value \
143 outside the valid range is undefined behavior",
144 UnsafetyViolationKind::GeneralAndConstFn,
148 &AggregateKind::Closure(def_id, _) |
149 &AggregateKind::Generator(def_id, _, _) => {
150 let UnsafetyCheckResult {
151 violations, unsafe_blocks
152 } = self.tcx.unsafety_check_result(def_id);
153 self.register_violations(&violations, &unsafe_blocks);
157 // casting pointers to ints is unsafe in const fn because the const evaluator cannot
158 // possibly know what the result of various operations like `address / 2` would be
159 // pointers during const evaluation have no integral address, only an abstract one
160 Rvalue::Cast(CastKind::Misc, ref operand, cast_ty)
161 if self.const_context && self.tcx.features().const_raw_ptr_to_usize_cast => {
162 let operand_ty = operand.ty(self.body, self.tcx);
163 let cast_in = CastTy::from_ty(operand_ty).expect("bad input type for cast");
164 let cast_out = CastTy::from_ty(cast_ty).expect("bad output type for cast");
165 match (cast_in, cast_out) {
166 (CastTy::Ptr(_), CastTy::Int(_)) |
167 (CastTy::FnPtr, CastTy::Int(_)) => {
168 self.register_violations(&[UnsafetyViolation {
169 source_info: self.source_info,
170 description: InternedString::intern("cast of pointer to int"),
171 details: InternedString::intern(
172 "casting pointers to integers in constants"),
173 kind: UnsafetyViolationKind::General,
179 // raw pointer and fn pointer operations are unsafe as it is not clear whether one
180 // pointer would be "less" or "equal" to another, because we cannot know where llvm
181 // or the linker will place various statics in memory. Without this information the
182 // result of a comparison of addresses would differ between runtime and compile-time.
183 Rvalue::BinaryOp(_, ref lhs, _)
184 if self.const_context && self.tcx.features().const_compare_raw_pointers => {
185 if let ty::RawPtr(_) | ty::FnPtr(..) = lhs.ty(self.body, self.tcx).sty {
186 self.register_violations(&[UnsafetyViolation {
187 source_info: self.source_info,
188 description: InternedString::intern("pointer operation"),
189 details: InternedString::intern("operations on pointers in constants"),
190 kind: UnsafetyViolationKind::General,
196 self.super_rvalue(rvalue, location);
199 fn visit_place(&mut self,
201 context: PlaceContext,
202 _location: Location) {
203 place.iterate(|place_base, place_projections| {
205 PlaceBase::Local(..) => {
208 PlaceBase::Static(box Static { kind: StaticKind::Promoted(_), .. }) => {
209 bug!("unsafety checking should happen before promotion")
211 PlaceBase::Static(box Static { kind: StaticKind::Static(def_id), .. }) => {
212 if self.tcx.is_mutable_static(*def_id) {
213 self.require_unsafe("use of mutable static",
214 "mutable statics can be mutated by multiple threads: aliasing \
215 violations or data races will cause undefined behavior",
216 UnsafetyViolationKind::General);
217 } else if self.tcx.is_foreign_item(*def_id) {
218 let source_info = self.source_info;
220 self.source_scope_local_data[source_info.scope].lint_root;
221 self.register_violations(&[UnsafetyViolation {
223 description: InternedString::intern("use of extern static"),
224 details: InternedString::intern(
225 "extern statics are not controlled by the Rust type system: \
226 invalid data, aliasing violations or data races will cause \
227 undefined behavior"),
228 kind: UnsafetyViolationKind::ExternStatic(lint_root)
234 for proj in place_projections {
235 if context.is_borrow() {
236 if util::is_disaligned(self.tcx, self.body, self.param_env, place) {
237 let source_info = self.source_info;
239 self.source_scope_local_data[source_info.scope].lint_root;
240 self.register_violations(&[UnsafetyViolation {
242 description: InternedString::intern("borrow of packed field"),
243 details: InternedString::intern(
244 "fields of packed structs might be misaligned: dereferencing a \
245 misaligned pointer or even just creating a misaligned reference \
246 is undefined behavior"),
247 kind: UnsafetyViolationKind::BorrowPacked(lint_root)
251 let is_borrow_of_interior_mut = context.is_borrow() && !proj.base
252 .ty(self.body, self.tcx)
254 .is_freeze(self.tcx, self.param_env, self.source_info.span);
258 // * `&x.field` if `field`'s type has interior mutability
259 // because either of these would allow modifying the layout constrained field and
260 // insert values that violate the layout constraints.
261 if context.is_mutating_use() || is_borrow_of_interior_mut {
262 self.check_mut_borrowing_layout_constrained_field(
263 place, context.is_mutating_use(),
266 let old_source_info = self.source_info;
267 if let Place::Base(PlaceBase::Local(local)) = proj.base {
268 if self.body.local_decls[local].internal {
269 // Internal locals are used in the `move_val_init` desugaring.
270 // We want to check unsafety against the source info of the
271 // desugaring, rather than the source info of the RHS.
272 self.source_info = self.body.local_decls[local].source_info;
275 let base_ty = proj.base.ty(self.body, self.tcx).ty;
278 self.require_unsafe("dereference of raw pointer",
279 "raw pointers may be NULL, dangling or unaligned; they can violate \
280 aliasing rules and cause data races: all of these are undefined \
281 behavior", UnsafetyViolationKind::General)
285 if context == PlaceContext::MutatingUse(MutatingUseContext::Store) ||
286 context == PlaceContext::MutatingUse(MutatingUseContext::Drop) ||
287 context == PlaceContext::MutatingUse(
288 MutatingUseContext::AsmOutput
291 let elem_ty = match proj.elem {
292 ProjectionElem::Field(_, ty) => ty,
294 self.source_info.span,
295 "non-field projection {:?} from union?",
298 if !elem_ty.is_copy_modulo_regions(
301 self.source_info.span,
304 "assignment to non-`Copy` union field",
305 "the previous content of the field will be dropped, which \
306 causes undefined behavior if the field was not properly \
307 initialized", UnsafetyViolationKind::General)
309 // write to non-move union, safe
312 self.require_unsafe("access to union field",
313 "the field may not be properly initialized: using \
314 uninitialized data will cause undefined behavior",
315 UnsafetyViolationKind::General)
321 self.source_info = old_source_info;
327 impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
330 description: &'static str,
331 details: &'static str,
332 kind: UnsafetyViolationKind,
334 let source_info = self.source_info;
335 self.register_violations(&[UnsafetyViolation {
337 description: InternedString::intern(description),
338 details: InternedString::intern(details),
343 fn register_violations(&mut self,
344 violations: &[UnsafetyViolation],
345 unsafe_blocks: &[(hir::HirId, bool)]) {
346 let safety = self.source_scope_local_data[self.source_info.scope].safety;
347 let within_unsafe = match safety {
348 // `unsafe` blocks are required in safe code
350 for violation in violations {
351 let mut violation = violation.clone();
352 match violation.kind {
353 UnsafetyViolationKind::GeneralAndConstFn |
354 UnsafetyViolationKind::General => {},
355 UnsafetyViolationKind::BorrowPacked(_) |
356 UnsafetyViolationKind::ExternStatic(_) => if self.min_const_fn {
357 // const fns don't need to be backwards compatible and can
358 // emit these violations as a hard error instead of a backwards
360 violation.kind = UnsafetyViolationKind::General;
363 if !self.violations.contains(&violation) {
364 self.violations.push(violation)
369 // `unsafe` function bodies allow unsafe without additional unsafe blocks
370 Safety::BuiltinUnsafe | Safety::FnUnsafe => true,
371 Safety::ExplicitUnsafe(hir_id) => {
372 // mark unsafe block as used if there are any unsafe operations inside
373 if !violations.is_empty() {
374 self.used_unsafe.insert(hir_id);
376 // only some unsafety is allowed in const fn
377 if self.min_const_fn {
378 for violation in violations {
379 match violation.kind {
380 // these unsafe things are stable in const fn
381 UnsafetyViolationKind::GeneralAndConstFn => {},
382 // these things are forbidden in const fns
383 UnsafetyViolationKind::General |
384 UnsafetyViolationKind::BorrowPacked(_) |
385 UnsafetyViolationKind::ExternStatic(_) => {
386 let mut violation = violation.clone();
387 // const fns don't need to be backwards compatible and can
388 // emit these violations as a hard error instead of a backwards
390 violation.kind = UnsafetyViolationKind::General;
391 if !self.violations.contains(&violation) {
392 self.violations.push(violation)
401 self.inherited_blocks.extend(unsafe_blocks.iter().map(|&(hir_id, is_used)| {
402 (hir_id, is_used && !within_unsafe)
405 fn check_mut_borrowing_layout_constrained_field(
407 mut place: &Place<'tcx>,
410 while let &Place::Projection(box Projection {
414 ProjectionElem::Field(..) => {
415 let ty = base.ty(&self.body.local_decls, self.tcx).ty;
417 ty::Adt(def, _) => match self.tcx.layout_scalar_valid_range(def.did) {
418 (Bound::Unbounded, Bound::Unbounded) => {},
420 let (description, details) = if is_mut_use {
422 "mutation of layout constrained field",
423 "mutating layout constrained fields cannot statically be \
424 checked for valid values",
428 "borrow of layout constrained field with interior \
430 "references to fields of layout constrained fields \
431 lose the constraints. Coupled with interior mutability, \
432 the field can be changed to invalid values",
435 let source_info = self.source_info;
436 self.register_violations(&[UnsafetyViolation {
438 description: InternedString::intern(description),
439 details: InternedString::intern(details),
440 kind: UnsafetyViolationKind::GeneralAndConstFn,
454 pub(crate) fn provide(providers: &mut Providers<'_>) {
455 *providers = Providers {
456 unsafety_check_result,
457 unsafe_derive_on_repr_packed,
462 struct UnusedUnsafeVisitor<'a> {
463 used_unsafe: &'a FxHashSet<hir::HirId>,
464 unsafe_blocks: &'a mut Vec<(hir::HirId, bool)>,
467 impl<'a, 'tcx> hir::intravisit::Visitor<'tcx> for UnusedUnsafeVisitor<'a> {
468 fn nested_visit_map<'this>(&'this mut self) ->
469 hir::intravisit::NestedVisitorMap<'this, 'tcx>
471 hir::intravisit::NestedVisitorMap::None
474 fn visit_block(&mut self, block: &'tcx hir::Block) {
475 hir::intravisit::walk_block(self, block);
477 if let hir::UnsafeBlock(hir::UserProvided) = block.rules {
478 self.unsafe_blocks.push((block.hir_id, self.used_unsafe.contains(&block.hir_id)));
483 fn check_unused_unsafe<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
485 used_unsafe: &FxHashSet<hir::HirId>,
486 unsafe_blocks: &'a mut Vec<(hir::HirId, bool)>)
489 tcx.hir().as_local_hir_id(def_id).and_then(|hir_id| {
490 tcx.hir().maybe_body_owned_by_by_hir_id(hir_id)
493 let body_id = match body_id {
496 debug!("check_unused_unsafe({:?}) - no body found", def_id);
500 let body = tcx.hir().body(body_id);
501 debug!("check_unused_unsafe({:?}, body={:?}, used_unsafe={:?})",
502 def_id, body, used_unsafe);
504 let mut visitor = UnusedUnsafeVisitor { used_unsafe, unsafe_blocks };
505 hir::intravisit::Visitor::visit_body(&mut visitor, body);
508 fn unsafety_check_result<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
509 -> UnsafetyCheckResult
511 debug!("unsafety_violations({:?})", def_id);
513 // N.B., this borrow is valid because all the consumers of
514 // `mir_built` force this.
515 let body = &tcx.mir_built(def_id).borrow();
517 let source_scope_local_data = match body.source_scope_local_data {
518 ClearCrossCrate::Set(ref data) => data,
519 ClearCrossCrate::Clear => {
520 debug!("unsafety_violations: {:?} - remote, skipping", def_id);
521 return UnsafetyCheckResult {
522 violations: Lrc::new([]),
523 unsafe_blocks: Lrc::new([])
528 let param_env = tcx.param_env(def_id);
530 let id = tcx.hir().as_local_hir_id(def_id).unwrap();
531 let (const_context, min_const_fn) = match tcx.hir().body_owner_kind_by_hir_id(id) {
532 hir::BodyOwnerKind::Closure => (false, false),
533 hir::BodyOwnerKind::Fn => (tcx.is_const_fn(def_id), tcx.is_min_const_fn(def_id)),
534 hir::BodyOwnerKind::Const |
535 hir::BodyOwnerKind::Static(_) => (true, false),
537 let mut checker = UnsafetyChecker::new(
538 const_context, min_const_fn,
539 body, source_scope_local_data, tcx, param_env);
540 checker.visit_body(body);
542 check_unused_unsafe(tcx, def_id, &checker.used_unsafe, &mut checker.inherited_blocks);
543 UnsafetyCheckResult {
544 violations: checker.violations.into(),
545 unsafe_blocks: checker.inherited_blocks.into()
549 fn unsafe_derive_on_repr_packed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
550 let lint_hir_id = tcx.hir().as_local_hir_id(def_id).unwrap_or_else(||
551 bug!("checking unsafety for non-local def id {:?}", def_id));
553 // FIXME: when we make this a hard error, this should have its
555 let message = if tcx.generics_of(def_id).own_requires_monomorphization() {
556 "#[derive] can't be used on a #[repr(packed)] struct with \
557 type or const parameters (error E0133)".to_string()
559 "#[derive] can't be used on a #[repr(packed)] struct that \
560 does not derive Copy (error E0133)".to_string()
562 tcx.lint_hir(SAFE_PACKED_BORROWS,
564 tcx.def_span(def_id),
568 /// Returns the `HirId` for an enclosing scope that is also `unsafe`.
569 fn is_enclosed(tcx: TyCtxt<'_, '_, '_>,
570 used_unsafe: &FxHashSet<hir::HirId>,
571 id: hir::HirId) -> Option<(String, hir::HirId)> {
572 let parent_id = tcx.hir().get_parent_node_by_hir_id(id);
574 if used_unsafe.contains(&parent_id) {
575 Some(("block".to_string(), parent_id))
576 } else if let Some(Node::Item(&hir::Item {
577 node: hir::ItemKind::Fn(_, header, _, _),
579 })) = tcx.hir().find_by_hir_id(parent_id) {
580 match header.unsafety {
581 hir::Unsafety::Unsafe => Some(("fn".to_string(), parent_id)),
582 hir::Unsafety::Normal => None,
585 is_enclosed(tcx, used_unsafe, parent_id)
592 fn report_unused_unsafe(tcx: TyCtxt<'_, '_, '_>,
593 used_unsafe: &FxHashSet<hir::HirId>,
595 let span = tcx.sess.source_map().def_span(tcx.hir().span_by_hir_id(id));
596 let msg = "unnecessary `unsafe` block";
597 let mut db = tcx.struct_span_lint_hir(UNUSED_UNSAFE, id, span, msg);
598 db.span_label(span, msg);
599 if let Some((kind, id)) = is_enclosed(tcx, used_unsafe, id) {
600 db.span_label(tcx.sess.source_map().def_span(tcx.hir().span_by_hir_id(id)),
601 format!("because it's nested under this `unsafe` {}", kind));
606 fn builtin_derive_def_id<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> Option<DefId> {
607 debug!("builtin_derive_def_id({:?})", def_id);
608 if let Some(impl_def_id) = tcx.impl_of_method(def_id) {
609 if tcx.has_attr(impl_def_id, sym::automatically_derived) {
610 debug!("builtin_derive_def_id({:?}) - is {:?}", def_id, impl_def_id);
613 debug!("builtin_derive_def_id({:?}) - not automatically derived", def_id);
617 debug!("builtin_derive_def_id({:?}) - not a method", def_id);
622 pub fn check_unsafety<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
623 debug!("check_unsafety({:?})", def_id);
625 // closures are handled by their parent fn.
626 if tcx.is_closure(def_id) {
630 let UnsafetyCheckResult {
633 } = tcx.unsafety_check_result(def_id);
635 for &UnsafetyViolation {
636 source_info, description, details, kind
637 } in violations.iter() {
640 UnsafetyViolationKind::GeneralAndConstFn |
641 UnsafetyViolationKind::General => {
643 tcx.sess, source_info.span, E0133,
644 "{} is unsafe and requires unsafe function or block", description)
645 .span_label(source_info.span, &description.as_str()[..])
646 .note(&details.as_str()[..])
649 UnsafetyViolationKind::ExternStatic(lint_hir_id) => {
650 tcx.lint_node_note(SAFE_EXTERN_STATICS,
653 &format!("{} is unsafe and requires unsafe function or block \
654 (error E0133)", &description.as_str()[..]),
655 &details.as_str()[..]);
657 UnsafetyViolationKind::BorrowPacked(lint_hir_id) => {
658 if let Some(impl_def_id) = builtin_derive_def_id(tcx, def_id) {
659 tcx.unsafe_derive_on_repr_packed(impl_def_id);
661 tcx.lint_node_note(SAFE_PACKED_BORROWS,
664 &format!("{} is unsafe and requires unsafe function or block \
665 (error E0133)", &description.as_str()[..]),
666 &details.as_str()[..]);
672 let mut unsafe_blocks: Vec<_> = unsafe_blocks.into_iter().collect();
673 unsafe_blocks.sort_by_cached_key(|(hir_id, _)| tcx.hir().hir_to_node_id(*hir_id));
674 let used_unsafe: FxHashSet<_> = unsafe_blocks.iter()
675 .flat_map(|&&(id, used)| if used { Some(id) } else { None })
677 for &(block_id, is_used) in unsafe_blocks {
679 report_unused_unsafe(tcx, &used_unsafe, block_id);