1 // Copyright 2017 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 use rustc_data_structures::fx::FxHashSet;
12 use rustc_data_structures::indexed_vec::IndexVec;
13 use rustc_data_structures::sync::Lrc;
15 use rustc::ty::query::Providers;
16 use rustc::ty::{self, TyCtxt};
19 use rustc::hir::def_id::DefId;
20 use rustc::lint::builtin::{SAFE_EXTERN_STATICS, SAFE_PACKED_BORROWS, UNUSED_UNSAFE};
22 use rustc::mir::visit::{PlaceContext, Visitor, MutatingUseContext};
25 use syntax::symbol::Symbol;
31 pub struct UnsafetyChecker<'a, 'tcx: 'a> {
34 source_scope_local_data: &'a IndexVec<SourceScope, SourceScopeLocalData>,
35 violations: Vec<UnsafetyViolation>,
36 source_info: SourceInfo,
37 tcx: TyCtxt<'a, 'tcx, 'tcx>,
38 param_env: ty::ParamEnv<'tcx>,
39 /// mark an `unsafe` block as used, so we don't lint it
40 used_unsafe: FxHashSet<ast::NodeId>,
41 inherited_blocks: Vec<(ast::NodeId, bool)>,
44 impl<'a, 'gcx, 'tcx> UnsafetyChecker<'a, 'tcx> {
48 source_scope_local_data: &'a IndexVec<SourceScope, SourceScopeLocalData>,
49 tcx: TyCtxt<'a, 'tcx, 'tcx>,
50 param_env: ty::ParamEnv<'tcx>,
55 source_scope_local_data,
57 source_info: SourceInfo {
59 scope: OUTERMOST_SOURCE_SCOPE
63 used_unsafe: Default::default(),
64 inherited_blocks: vec![],
69 impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
70 fn visit_terminator(&mut self,
72 terminator: &Terminator<'tcx>,
75 self.source_info = terminator.source_info;
76 match terminator.kind {
77 TerminatorKind::Goto { .. } |
78 TerminatorKind::SwitchInt { .. } |
79 TerminatorKind::Drop { .. } |
80 TerminatorKind::Yield { .. } |
81 TerminatorKind::Assert { .. } |
82 TerminatorKind::DropAndReplace { .. } |
83 TerminatorKind::GeneratorDrop |
84 TerminatorKind::Resume |
85 TerminatorKind::Abort |
86 TerminatorKind::Return |
87 TerminatorKind::Unreachable |
88 TerminatorKind::FalseEdges { .. } |
89 TerminatorKind::FalseUnwind { .. } => {
90 // safe (at least as emitted during MIR construction)
93 TerminatorKind::Call { ref func, .. } => {
94 let func_ty = func.ty(self.mir, self.tcx);
95 let sig = func_ty.fn_sig(self.tcx);
96 if let hir::Unsafety::Unsafe = sig.unsafety() {
97 self.require_unsafe("call to unsafe function",
98 "consult the function's documentation for information on how to avoid \
99 undefined behavior", UnsafetyViolationKind::MinConstFn)
103 self.super_terminator(block, terminator, location);
106 fn visit_statement(&mut self,
108 statement: &Statement<'tcx>,
111 self.source_info = statement.source_info;
112 match statement.kind {
113 StatementKind::Assign(..) |
114 StatementKind::FakeRead(..) |
115 StatementKind::SetDiscriminant { .. } |
116 StatementKind::StorageLive(..) |
117 StatementKind::StorageDead(..) |
118 StatementKind::Retag { .. } |
119 StatementKind::EscapeToRaw { .. } |
120 StatementKind::AscribeUserType(..) |
121 StatementKind::Nop => {
122 // safe (at least as emitted during MIR construction)
125 StatementKind::InlineAsm { .. } => {
126 self.require_unsafe("use of inline assembly",
127 "inline assembly is entirely unchecked and can cause undefined behavior",
128 UnsafetyViolationKind::General)
131 self.super_statement(block, statement, location);
134 fn visit_rvalue(&mut self,
135 rvalue: &Rvalue<'tcx>,
138 if let &Rvalue::Aggregate(box ref aggregate, _) = rvalue {
140 &AggregateKind::Array(..) |
141 &AggregateKind::Tuple => {}
142 &AggregateKind::Adt(ref def, ..) => {
143 match self.tcx.layout_scalar_valid_range(def.did) {
144 (Bound::Unbounded, Bound::Unbounded) => {},
145 _ => self.require_unsafe(
146 "initializing type with `rustc_layout_scalar_valid_range` attr",
147 "initializing a layout restricted type's field with a value outside \
148 the valid range is undefined behavior",
149 UnsafetyViolationKind::MinConstFn,
153 &AggregateKind::Closure(def_id, _) |
154 &AggregateKind::Generator(def_id, _, _) => {
155 let UnsafetyCheckResult {
156 violations, unsafe_blocks
157 } = self.tcx.unsafety_check_result(def_id);
158 self.register_violations(&violations, &unsafe_blocks);
162 self.super_rvalue(rvalue, location);
165 fn visit_place(&mut self,
167 context: PlaceContext<'tcx>,
168 location: Location) {
170 &Place::Projection(box Projection {
173 if context.is_borrow() {
174 if util::is_disaligned(self.tcx, self.mir, self.param_env, place) {
175 let source_info = self.source_info;
177 self.source_scope_local_data[source_info.scope].lint_root;
178 self.register_violations(&[UnsafetyViolation {
180 description: Symbol::intern("borrow of packed field").as_interned_str(),
182 Symbol::intern("fields of packed structs might be misaligned: \
183 dereferencing a misaligned pointer or even just \
184 creating a misaligned reference is undefined \
187 kind: UnsafetyViolationKind::BorrowPacked(lint_root)
191 let is_borrow_of_interior_mut = context.is_borrow() && !base
192 .ty(self.mir, self.tcx)
194 .is_freeze(self.tcx, self.param_env, self.source_info.span);
198 // * `&x.field` if `field`'s type has interior mutability
199 // because either of these would allow modifying the layout constrained field and
200 // insert values that violate the layout constraints.
201 if context.is_mutating_use() || is_borrow_of_interior_mut {
202 self.check_mut_borrowing_layout_constrained_field(
203 place, context.is_mutating_use(),
206 let old_source_info = self.source_info;
207 if let &Place::Local(local) = base {
208 if self.mir.local_decls[local].internal {
209 // Internal locals are used in the `move_val_init` desugaring.
210 // We want to check unsafety against the source info of the
211 // desugaring, rather than the source info of the RHS.
212 self.source_info = self.mir.local_decls[local].source_info;
215 let base_ty = base.ty(self.mir, self.tcx).to_ty(self.tcx);
218 self.require_unsafe("dereference of raw pointer",
219 "raw pointers may be NULL, dangling or unaligned; they can violate \
220 aliasing rules and cause data races: all of these are undefined \
221 behavior", UnsafetyViolationKind::General)
225 if context == PlaceContext::MutatingUse(MutatingUseContext::Store) ||
226 context == PlaceContext::MutatingUse(MutatingUseContext::Drop) ||
227 context == PlaceContext::MutatingUse(
228 MutatingUseContext::AsmOutput
231 let elem_ty = match elem {
232 &ProjectionElem::Field(_, ty) => ty,
234 self.source_info.span,
235 "non-field projection {:?} from union?",
238 if elem_ty.moves_by_default(self.tcx, self.param_env,
239 self.source_info.span) {
241 "assignment to non-`Copy` union field",
242 "the previous content of the field will be dropped, which \
243 causes undefined behavior if the field was not properly \
244 initialized", UnsafetyViolationKind::General)
246 // write to non-move union, safe
249 self.require_unsafe("access to union field",
250 "the field may not be properly initialized: using \
251 uninitialized data will cause undefined behavior",
252 UnsafetyViolationKind::General)
258 self.source_info = old_source_info;
260 &Place::Local(..) => {
263 &Place::Promoted(_) => {
264 bug!("unsafety checking should happen before promotion")
266 &Place::Static(box Static { def_id, ty: _ }) => {
267 if self.tcx.is_static(def_id) == Some(hir::Mutability::MutMutable) {
268 self.require_unsafe("use of mutable static",
269 "mutable statics can be mutated by multiple threads: aliasing violations \
270 or data races will cause undefined behavior",
271 UnsafetyViolationKind::General);
272 } else if self.tcx.is_foreign_item(def_id) {
273 let source_info = self.source_info;
275 self.source_scope_local_data[source_info.scope].lint_root;
276 self.register_violations(&[UnsafetyViolation {
278 description: Symbol::intern("use of extern static").as_interned_str(),
280 Symbol::intern("extern statics are not controlled by the Rust type \
281 system: invalid data, aliasing violations or data \
282 races will cause undefined behavior")
284 kind: UnsafetyViolationKind::ExternStatic(lint_root)
289 self.super_place(place, context, location);
293 impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
296 description: &'static str,
297 details: &'static str,
298 kind: UnsafetyViolationKind,
300 let source_info = self.source_info;
301 self.register_violations(&[UnsafetyViolation {
303 description: Symbol::intern(description).as_interned_str(),
304 details: Symbol::intern(details).as_interned_str(),
309 fn register_violations(&mut self,
310 violations: &[UnsafetyViolation],
311 unsafe_blocks: &[(ast::NodeId, bool)]) {
312 let safety = self.source_scope_local_data[self.source_info.scope].safety;
313 let within_unsafe = match (safety, self.min_const_fn) {
314 // Erring on the safe side, pun intended
315 (Safety::BuiltinUnsafe, true) |
316 // mir building encodes const fn bodies as safe, even for `const unsafe fn`
317 (Safety::FnUnsafe, true) => bug!("const unsafe fn body treated as inherently unsafe"),
318 // `unsafe` blocks are required in safe code
319 (Safety::Safe, _) => {
320 for violation in violations {
321 let mut violation = violation.clone();
322 if self.min_const_fn {
323 // overwrite unsafety violation in const fn with a single hard error kind
324 violation.kind = UnsafetyViolationKind::MinConstFn;
325 } else if let UnsafetyViolationKind::MinConstFn = violation.kind {
326 // outside of const fns we treat `MinConstFn` and `General` the same
327 violation.kind = UnsafetyViolationKind::General;
329 if !self.violations.contains(&violation) {
330 self.violations.push(violation)
335 // regular `unsafe` function bodies allow unsafe without additional unsafe blocks
336 (Safety::BuiltinUnsafe, false) | (Safety::FnUnsafe, false) => true,
337 (Safety::ExplicitUnsafe(node_id), _) => {
338 // mark unsafe block as used if there are any unsafe operations inside
339 if !violations.is_empty() {
340 self.used_unsafe.insert(node_id);
342 // only some unsafety is allowed in const fn
343 if self.min_const_fn {
344 for violation in violations {
345 match violation.kind {
347 UnsafetyViolationKind::MinConstFn
348 // if `#![feature(min_const_unsafe_fn)]` is active
349 if self.tcx.sess.features_untracked().min_const_unsafe_fn => {},
351 let mut violation = violation.clone();
352 // overwrite unsafety violation in const fn with a hard error
353 violation.kind = UnsafetyViolationKind::MinConstFn;
354 if !self.violations.contains(&violation) {
355 self.violations.push(violation)
364 self.inherited_blocks.extend(unsafe_blocks.iter().map(|&(node_id, is_used)| {
365 (node_id, is_used && !within_unsafe)
368 fn check_mut_borrowing_layout_constrained_field(
370 mut place: &Place<'tcx>,
373 while let &Place::Projection(box Projection {
377 ProjectionElem::Field(..) => {
378 let ty = base.ty(&self.mir.local_decls, self.tcx).to_ty(self.tcx);
380 ty::Adt(def, _) => match self.tcx.layout_scalar_valid_range(def.did) {
381 (Bound::Unbounded, Bound::Unbounded) => {},
383 let (description, details) = if is_mut_use {
385 "mutation of layout constrained field",
386 "mutating layout constrained fields cannot statically be \
387 checked for valid values",
391 "borrow of layout constrained field with interior \
393 "references to fields of layout constrained fields \
394 lose the constraints. Coupled with interior mutability, \
395 the field can be changed to invalid values",
398 let source_info = self.source_info;
399 self.register_violations(&[UnsafetyViolation {
401 description: Symbol::intern(description).as_interned_str(),
402 details: Symbol::intern(details).as_interned_str(),
403 kind: UnsafetyViolationKind::MinConstFn,
417 pub(crate) fn provide(providers: &mut Providers) {
418 *providers = Providers {
419 unsafety_check_result,
420 unsafe_derive_on_repr_packed,
425 struct UnusedUnsafeVisitor<'a> {
426 used_unsafe: &'a FxHashSet<ast::NodeId>,
427 unsafe_blocks: &'a mut Vec<(ast::NodeId, bool)>,
430 impl<'a, 'tcx> hir::intravisit::Visitor<'tcx> for UnusedUnsafeVisitor<'a> {
431 fn nested_visit_map<'this>(&'this mut self) ->
432 hir::intravisit::NestedVisitorMap<'this, 'tcx>
434 hir::intravisit::NestedVisitorMap::None
437 fn visit_block(&mut self, block: &'tcx hir::Block) {
438 hir::intravisit::walk_block(self, block);
440 if let hir::UnsafeBlock(hir::UserProvided) = block.rules {
441 self.unsafe_blocks.push((block.id, self.used_unsafe.contains(&block.id)));
446 fn check_unused_unsafe<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
448 used_unsafe: &FxHashSet<ast::NodeId>,
449 unsafe_blocks: &'a mut Vec<(ast::NodeId, bool)>)
452 tcx.hir.as_local_node_id(def_id).and_then(|node_id| {
453 tcx.hir.maybe_body_owned_by(node_id)
456 let body_id = match body_id {
459 debug!("check_unused_unsafe({:?}) - no body found", def_id);
463 let body = tcx.hir.body(body_id);
464 debug!("check_unused_unsafe({:?}, body={:?}, used_unsafe={:?})",
465 def_id, body, used_unsafe);
467 let mut visitor = UnusedUnsafeVisitor { used_unsafe, unsafe_blocks };
468 hir::intravisit::Visitor::visit_body(&mut visitor, body);
471 fn unsafety_check_result<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
472 -> UnsafetyCheckResult
474 debug!("unsafety_violations({:?})", def_id);
476 // NB: this borrow is valid because all the consumers of
477 // `mir_built` force this.
478 let mir = &tcx.mir_built(def_id).borrow();
480 let source_scope_local_data = match mir.source_scope_local_data {
481 ClearCrossCrate::Set(ref data) => data,
482 ClearCrossCrate::Clear => {
483 debug!("unsafety_violations: {:?} - remote, skipping", def_id);
484 return UnsafetyCheckResult {
485 violations: Lrc::new([]),
486 unsafe_blocks: Lrc::new([])
491 let param_env = tcx.param_env(def_id);
492 let mut checker = UnsafetyChecker::new(
493 tcx.is_const_fn(def_id) && tcx.is_min_const_fn(def_id),
494 mir, source_scope_local_data, tcx, param_env);
495 checker.visit_mir(mir);
497 check_unused_unsafe(tcx, def_id, &checker.used_unsafe, &mut checker.inherited_blocks);
498 UnsafetyCheckResult {
499 violations: checker.violations.into(),
500 unsafe_blocks: checker.inherited_blocks.into()
504 fn unsafe_derive_on_repr_packed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
505 let lint_node_id = match tcx.hir.as_local_node_id(def_id) {
506 Some(node_id) => node_id,
507 None => bug!("checking unsafety for non-local def id {:?}", def_id)
510 // FIXME: when we make this a hard error, this should have its
512 let message = if tcx.generics_of(def_id).own_counts().types != 0 {
513 "#[derive] can't be used on a #[repr(packed)] struct with \
514 type parameters (error E0133)".to_string()
516 "#[derive] can't be used on a #[repr(packed)] struct that \
517 does not derive Copy (error E0133)".to_string()
519 tcx.lint_node(SAFE_PACKED_BORROWS,
521 tcx.def_span(def_id),
525 /// Return the NodeId for an enclosing scope that is also `unsafe`
526 fn is_enclosed(tcx: TyCtxt,
527 used_unsafe: &FxHashSet<ast::NodeId>,
528 id: ast::NodeId) -> Option<(String, ast::NodeId)> {
529 let parent_id = tcx.hir.get_parent_node(id);
531 if used_unsafe.contains(&parent_id) {
532 Some(("block".to_string(), parent_id))
533 } else if let Some(Node::Item(&hir::Item {
534 node: hir::ItemKind::Fn(_, header, _, _),
536 })) = tcx.hir.find(parent_id) {
537 match header.unsafety {
538 hir::Unsafety::Unsafe => Some(("fn".to_string(), parent_id)),
539 hir::Unsafety::Normal => None,
542 is_enclosed(tcx, used_unsafe, parent_id)
549 fn report_unused_unsafe(tcx: TyCtxt, used_unsafe: &FxHashSet<ast::NodeId>, id: ast::NodeId) {
550 let span = tcx.sess.source_map().def_span(tcx.hir.span(id));
551 let msg = "unnecessary `unsafe` block";
552 let mut db = tcx.struct_span_lint_node(UNUSED_UNSAFE, id, span, msg);
553 db.span_label(span, msg);
554 if let Some((kind, id)) = is_enclosed(tcx, used_unsafe, id) {
555 db.span_label(tcx.sess.source_map().def_span(tcx.hir.span(id)),
556 format!("because it's nested under this `unsafe` {}", kind));
561 fn builtin_derive_def_id<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> Option<DefId> {
562 debug!("builtin_derive_def_id({:?})", def_id);
563 if let Some(impl_def_id) = tcx.impl_of_method(def_id) {
564 if tcx.has_attr(impl_def_id, "automatically_derived") {
565 debug!("builtin_derive_def_id({:?}) - is {:?}", def_id, impl_def_id);
568 debug!("builtin_derive_def_id({:?}) - not automatically derived", def_id);
572 debug!("builtin_derive_def_id({:?}) - not a method", def_id);
577 pub fn check_unsafety<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
578 debug!("check_unsafety({:?})", def_id);
580 // closures are handled by their parent fn.
581 if tcx.is_closure(def_id) {
585 let UnsafetyCheckResult {
588 } = tcx.unsafety_check_result(def_id);
590 for &UnsafetyViolation {
591 source_info, description, details, kind
592 } in violations.iter() {
595 UnsafetyViolationKind::General => {
597 tcx.sess, source_info.span, E0133,
598 "{} is unsafe and requires unsafe function or block", description)
599 .span_label(source_info.span, &description.as_str()[..])
600 .note(&details.as_str()[..])
603 UnsafetyViolationKind::MinConstFn => {
604 tcx.sess.struct_span_err(
606 &format!("{} is unsafe and unsafe operations \
607 are not allowed in const fn", description))
608 .span_label(source_info.span, &description.as_str()[..])
609 .note(&details.as_str()[..])
612 UnsafetyViolationKind::ExternStatic(lint_node_id) => {
613 tcx.lint_node_note(SAFE_EXTERN_STATICS,
616 &format!("{} is unsafe and requires unsafe function or block \
617 (error E0133)", &description.as_str()[..]),
618 &details.as_str()[..]);
620 UnsafetyViolationKind::BorrowPacked(lint_node_id) => {
621 if let Some(impl_def_id) = builtin_derive_def_id(tcx, def_id) {
622 tcx.unsafe_derive_on_repr_packed(impl_def_id);
624 tcx.lint_node_note(SAFE_PACKED_BORROWS,
627 &format!("{} is unsafe and requires unsafe function or block \
628 (error E0133)", &description.as_str()[..]),
629 &details.as_str()[..]);
635 let mut unsafe_blocks: Vec<_> = unsafe_blocks.into_iter().collect();
636 unsafe_blocks.sort();
637 let used_unsafe: FxHashSet<_> = unsafe_blocks.iter()
638 .flat_map(|&&(id, used)| if used { Some(id) } else { None })
640 for &(block_id, is_used) in unsafe_blocks {
642 report_unused_unsafe(tcx, &used_unsafe, block_id);