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};
25 use syntax::symbol::Symbol;
29 pub struct UnsafetyChecker<'a, 'tcx: 'a> {
32 source_scope_local_data: &'a IndexVec<SourceScope, SourceScopeLocalData>,
33 violations: Vec<UnsafetyViolation>,
34 source_info: SourceInfo,
35 tcx: TyCtxt<'a, 'tcx, 'tcx>,
36 param_env: ty::ParamEnv<'tcx>,
37 used_unsafe: FxHashSet<ast::NodeId>,
38 inherited_blocks: Vec<(ast::NodeId, bool)>,
41 impl<'a, 'gcx, 'tcx> UnsafetyChecker<'a, 'tcx> {
45 source_scope_local_data: &'a IndexVec<SourceScope, SourceScopeLocalData>,
46 tcx: TyCtxt<'a, 'tcx, 'tcx>,
47 param_env: ty::ParamEnv<'tcx>,
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 \
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::EndRegion(..) |
116 StatementKind::Validate(..) |
117 StatementKind::AscribeUserType(..) |
118 StatementKind::Nop => {
119 // safe (at least as emitted during MIR construction)
122 StatementKind::InlineAsm { .. } => {
123 self.require_unsafe("use of inline assembly",
124 "inline assembly is entirely unchecked and can cause undefined behavior")
127 self.super_statement(block, statement, location);
130 fn visit_rvalue(&mut self,
131 rvalue: &Rvalue<'tcx>,
134 if let &Rvalue::Aggregate(box ref aggregate, _) = rvalue {
136 &AggregateKind::Array(..) |
137 &AggregateKind::Tuple |
138 &AggregateKind::Adt(..) => {}
139 &AggregateKind::Closure(def_id, _) |
140 &AggregateKind::Generator(def_id, _, _) => {
141 let UnsafetyCheckResult {
142 violations, unsafe_blocks
143 } = self.tcx.unsafety_check_result(def_id);
144 self.register_violations(&violations, &unsafe_blocks);
148 self.super_rvalue(rvalue, location);
151 fn visit_place(&mut self,
153 context: PlaceContext<'tcx>,
154 location: Location) {
155 if let PlaceContext::Borrow { .. } = context {
156 if util::is_disaligned(self.tcx, self.mir, self.param_env, place) {
157 let source_info = self.source_info;
159 self.source_scope_local_data[source_info.scope].lint_root;
160 self.register_violations(&[UnsafetyViolation {
162 description: Symbol::intern("borrow of packed field").as_interned_str(),
164 Symbol::intern("fields of packed structs might be misaligned: \
165 dereferencing a misaligned pointer or even just creating a \
166 misaligned reference is undefined behavior")
168 kind: UnsafetyViolationKind::BorrowPacked(lint_root)
174 &Place::Projection(box Projection {
177 let old_source_info = self.source_info;
178 if let &Place::Local(local) = base {
179 if self.mir.local_decls[local].internal {
180 // Internal locals are used in the `move_val_init` desugaring.
181 // We want to check unsafety against the source info of the
182 // desugaring, rather than the source info of the RHS.
183 self.source_info = self.mir.local_decls[local].source_info;
186 let base_ty = base.ty(self.mir, self.tcx).to_ty(self.tcx);
189 self.require_unsafe("dereference of raw pointer",
190 "raw pointers may be NULL, dangling or unaligned; they can violate \
191 aliasing rules and cause data races: all of these are undefined \
196 if context == PlaceContext::Store ||
197 context == PlaceContext::AsmOutput ||
198 context == PlaceContext::Drop
200 let elem_ty = match elem {
201 &ProjectionElem::Field(_, ty) => ty,
203 self.source_info.span,
204 "non-field projection {:?} from union?",
207 if elem_ty.moves_by_default(self.tcx, self.param_env,
208 self.source_info.span) {
210 "assignment to non-`Copy` union field",
211 "the previous content of the field will be dropped, which \
212 causes undefined behavior if the field was not properly \
215 // write to non-move union, safe
218 self.require_unsafe("access to union field",
219 "the field may not be properly initialized: using \
220 uninitialized data will cause undefined behavior")
226 self.source_info = old_source_info;
228 &Place::Local(..) => {
231 &Place::Promoted(_) => {
232 bug!("unsafety checking should happen before promotion")
234 &Place::Static(box Static { def_id, ty: _ }) => {
235 if self.tcx.is_static(def_id) == Some(hir::Mutability::MutMutable) {
236 self.require_unsafe("use of mutable static",
237 "mutable statics can be mutated by multiple threads: aliasing violations \
238 or data races will cause undefined behavior");
239 } else if self.tcx.is_foreign_item(def_id) {
240 let source_info = self.source_info;
242 self.source_scope_local_data[source_info.scope].lint_root;
243 self.register_violations(&[UnsafetyViolation {
245 description: Symbol::intern("use of extern static").as_interned_str(),
247 Symbol::intern("extern statics are not controlled by the Rust type \
248 system: invalid data, aliasing violations or data \
249 races will cause undefined behavior")
251 kind: UnsafetyViolationKind::ExternStatic(lint_root)
256 self.super_place(place, context, location);
260 impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
261 fn require_unsafe(&mut self,
262 description: &'static str,
263 details: &'static str)
265 let source_info = self.source_info;
266 self.register_violations(&[UnsafetyViolation {
268 description: Symbol::intern(description).as_interned_str(),
269 details: Symbol::intern(details).as_interned_str(),
270 kind: UnsafetyViolationKind::General,
274 fn register_violations(&mut self,
275 violations: &[UnsafetyViolation],
276 unsafe_blocks: &[(ast::NodeId, bool)]) {
277 if self.min_const_fn {
278 for violation in violations {
279 let mut violation = violation.clone();
280 violation.kind = UnsafetyViolationKind::MinConstFn;
281 if !self.violations.contains(&violation) {
282 self.violations.push(violation)
286 let within_unsafe = match self.source_scope_local_data[self.source_info.scope].safety {
288 for violation in violations {
289 if !self.violations.contains(violation) {
290 self.violations.push(violation.clone())
295 Safety::BuiltinUnsafe | Safety::FnUnsafe => true,
296 Safety::ExplicitUnsafe(node_id) => {
297 if !violations.is_empty() {
298 self.used_unsafe.insert(node_id);
303 self.inherited_blocks.extend(unsafe_blocks.iter().map(|&(node_id, is_used)| {
304 (node_id, is_used && !within_unsafe)
309 pub(crate) fn provide(providers: &mut Providers) {
310 *providers = Providers {
311 unsafety_check_result,
312 unsafe_derive_on_repr_packed,
317 struct UnusedUnsafeVisitor<'a> {
318 used_unsafe: &'a FxHashSet<ast::NodeId>,
319 unsafe_blocks: &'a mut Vec<(ast::NodeId, bool)>,
322 impl<'a, 'tcx> hir::intravisit::Visitor<'tcx> for UnusedUnsafeVisitor<'a> {
323 fn nested_visit_map<'this>(&'this mut self) ->
324 hir::intravisit::NestedVisitorMap<'this, 'tcx>
326 hir::intravisit::NestedVisitorMap::None
329 fn visit_block(&mut self, block: &'tcx hir::Block) {
330 hir::intravisit::walk_block(self, block);
332 if let hir::UnsafeBlock(hir::UserProvided) = block.rules {
333 self.unsafe_blocks.push((block.id, self.used_unsafe.contains(&block.id)));
338 fn check_unused_unsafe<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
340 used_unsafe: &FxHashSet<ast::NodeId>,
341 unsafe_blocks: &'a mut Vec<(ast::NodeId, bool)>)
344 tcx.hir.as_local_node_id(def_id).and_then(|node_id| {
345 tcx.hir.maybe_body_owned_by(node_id)
348 let body_id = match body_id {
351 debug!("check_unused_unsafe({:?}) - no body found", def_id);
355 let body = tcx.hir.body(body_id);
356 debug!("check_unused_unsafe({:?}, body={:?}, used_unsafe={:?})",
357 def_id, body, used_unsafe);
359 let mut visitor = UnusedUnsafeVisitor { used_unsafe, unsafe_blocks };
360 hir::intravisit::Visitor::visit_body(&mut visitor, body);
363 fn unsafety_check_result<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
364 -> UnsafetyCheckResult
366 debug!("unsafety_violations({:?})", def_id);
368 // NB: this borrow is valid because all the consumers of
369 // `mir_built` force this.
370 let mir = &tcx.mir_built(def_id).borrow();
372 let source_scope_local_data = match mir.source_scope_local_data {
373 ClearCrossCrate::Set(ref data) => data,
374 ClearCrossCrate::Clear => {
375 debug!("unsafety_violations: {:?} - remote, skipping", def_id);
376 return UnsafetyCheckResult {
377 violations: Lrc::new([]),
378 unsafe_blocks: Lrc::new([])
383 let param_env = tcx.param_env(def_id);
384 let mut checker = UnsafetyChecker::new(
385 tcx.is_const_fn(def_id) && tcx.is_min_const_fn(def_id),
386 mir, source_scope_local_data, tcx, param_env);
387 checker.visit_mir(mir);
389 check_unused_unsafe(tcx, def_id, &checker.used_unsafe, &mut checker.inherited_blocks);
390 UnsafetyCheckResult {
391 violations: checker.violations.into(),
392 unsafe_blocks: checker.inherited_blocks.into()
396 fn unsafe_derive_on_repr_packed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
397 let lint_node_id = match tcx.hir.as_local_node_id(def_id) {
398 Some(node_id) => node_id,
399 None => bug!("checking unsafety for non-local def id {:?}", def_id)
402 // FIXME: when we make this a hard error, this should have its
404 let message = if tcx.generics_of(def_id).own_counts().types != 0 {
405 "#[derive] can't be used on a #[repr(packed)] struct with \
406 type parameters (error E0133)".to_string()
408 "#[derive] can't be used on a #[repr(packed)] struct that \
409 does not derive Copy (error E0133)".to_string()
411 tcx.lint_node(SAFE_PACKED_BORROWS,
413 tcx.def_span(def_id),
417 /// Return the NodeId for an enclosing scope that is also `unsafe`
418 fn is_enclosed(tcx: TyCtxt,
419 used_unsafe: &FxHashSet<ast::NodeId>,
420 id: ast::NodeId) -> Option<(String, ast::NodeId)> {
421 let parent_id = tcx.hir.get_parent_node(id);
423 if used_unsafe.contains(&parent_id) {
424 Some(("block".to_string(), parent_id))
425 } else if let Some(Node::Item(&hir::Item {
426 node: hir::ItemKind::Fn(_, header, _, _),
428 })) = tcx.hir.find(parent_id) {
429 match header.unsafety {
430 hir::Unsafety::Unsafe => Some(("fn".to_string(), parent_id)),
431 hir::Unsafety::Normal => None,
434 is_enclosed(tcx, used_unsafe, parent_id)
441 fn report_unused_unsafe(tcx: TyCtxt, used_unsafe: &FxHashSet<ast::NodeId>, id: ast::NodeId) {
442 let span = tcx.sess.source_map().def_span(tcx.hir.span(id));
443 let msg = "unnecessary `unsafe` block";
444 let mut db = tcx.struct_span_lint_node(UNUSED_UNSAFE, id, span, msg);
445 db.span_label(span, msg);
446 if let Some((kind, id)) = is_enclosed(tcx, used_unsafe, id) {
447 db.span_label(tcx.sess.source_map().def_span(tcx.hir.span(id)),
448 format!("because it's nested under this `unsafe` {}", kind));
453 fn builtin_derive_def_id<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> Option<DefId> {
454 debug!("builtin_derive_def_id({:?})", def_id);
455 if let Some(impl_def_id) = tcx.impl_of_method(def_id) {
456 if tcx.has_attr(impl_def_id, "automatically_derived") {
457 debug!("builtin_derive_def_id({:?}) - is {:?}", def_id, impl_def_id);
460 debug!("builtin_derive_def_id({:?}) - not automatically derived", def_id);
464 debug!("builtin_derive_def_id({:?}) - not a method", def_id);
469 pub fn check_unsafety<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
470 debug!("check_unsafety({:?})", def_id);
472 // closures are handled by their parent fn.
473 if tcx.is_closure(def_id) {
477 let UnsafetyCheckResult {
480 } = tcx.unsafety_check_result(def_id);
482 for &UnsafetyViolation {
483 source_info, description, details, kind
484 } in violations.iter() {
487 UnsafetyViolationKind::General => {
489 tcx.sess, source_info.span, E0133,
490 "{} is unsafe and requires unsafe function or block", description)
491 .span_label(source_info.span, &description.as_str()[..])
492 .note(&details.as_str()[..])
495 UnsafetyViolationKind::MinConstFn => {
496 tcx.sess.struct_span_err(
498 &format!("{} is unsafe and unsafe operations \
499 are not allowed in const fn", description))
500 .span_label(source_info.span, &description.as_str()[..])
501 .note(&details.as_str()[..])
504 UnsafetyViolationKind::ExternStatic(lint_node_id) => {
505 tcx.lint_node_note(SAFE_EXTERN_STATICS,
508 &format!("{} is unsafe and requires unsafe function or block \
509 (error E0133)", &description.as_str()[..]),
510 &details.as_str()[..]);
512 UnsafetyViolationKind::BorrowPacked(lint_node_id) => {
513 if let Some(impl_def_id) = builtin_derive_def_id(tcx, def_id) {
514 tcx.unsafe_derive_on_repr_packed(impl_def_id);
516 tcx.lint_node_note(SAFE_PACKED_BORROWS,
519 &format!("{} is unsafe and requires unsafe function or block \
520 (error E0133)", &description.as_str()[..]),
521 &details.as_str()[..]);
527 let mut unsafe_blocks: Vec<_> = unsafe_blocks.into_iter().collect();
528 unsafe_blocks.sort();
529 let used_unsafe: FxHashSet<_> = unsafe_blocks.iter()
530 .flat_map(|&&(id, used)| if used { Some(id) } else { None })
532 for &(block_id, is_used) in unsafe_blocks {
534 report_unused_unsafe(tcx, &used_unsafe, block_id);