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;
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 /// mark an `unsafe` block as used, so we don't lint it
38 used_unsafe: FxHashSet<ast::NodeId>,
39 inherited_blocks: Vec<(ast::NodeId, bool)>,
42 impl<'a, 'gcx, 'tcx> UnsafetyChecker<'a, 'tcx> {
46 source_scope_local_data: &'a IndexVec<SourceScope, SourceScopeLocalData>,
47 tcx: TyCtxt<'a, 'tcx, 'tcx>,
48 param_env: ty::ParamEnv<'tcx>,
53 source_scope_local_data,
55 source_info: SourceInfo {
57 scope: OUTERMOST_SOURCE_SCOPE
61 used_unsafe: Default::default(),
62 inherited_blocks: vec![],
67 impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
68 fn visit_terminator(&mut self,
70 terminator: &Terminator<'tcx>,
73 self.source_info = terminator.source_info;
74 match terminator.kind {
75 TerminatorKind::Goto { .. } |
76 TerminatorKind::SwitchInt { .. } |
77 TerminatorKind::Drop { .. } |
78 TerminatorKind::Yield { .. } |
79 TerminatorKind::Assert { .. } |
80 TerminatorKind::DropAndReplace { .. } |
81 TerminatorKind::GeneratorDrop |
82 TerminatorKind::Resume |
83 TerminatorKind::Abort |
84 TerminatorKind::Return |
85 TerminatorKind::Unreachable |
86 TerminatorKind::FalseEdges { .. } |
87 TerminatorKind::FalseUnwind { .. } => {
88 // safe (at least as emitted during MIR construction)
91 TerminatorKind::Call { ref func, .. } => {
92 let func_ty = func.ty(self.mir, self.tcx);
93 let sig = func_ty.fn_sig(self.tcx);
94 if let hir::Unsafety::Unsafe = sig.unsafety() {
95 self.require_unsafe("call to unsafe function",
96 "consult the function's documentation for information on how to avoid \
97 undefined behavior", UnsafetyViolationKind::MinConstFn)
101 self.super_terminator(block, terminator, location);
104 fn visit_statement(&mut self,
106 statement: &Statement<'tcx>,
109 self.source_info = statement.source_info;
110 match statement.kind {
111 StatementKind::Assign(..) |
112 StatementKind::FakeRead(..) |
113 StatementKind::SetDiscriminant { .. } |
114 StatementKind::StorageLive(..) |
115 StatementKind::StorageDead(..) |
116 StatementKind::Retag { .. } |
117 StatementKind::EscapeToRaw { .. } |
118 StatementKind::AscribeUserType(..) |
119 StatementKind::Nop => {
120 // safe (at least as emitted during MIR construction)
123 StatementKind::InlineAsm { .. } => {
124 self.require_unsafe("use of inline assembly",
125 "inline assembly is entirely unchecked and can cause undefined behavior",
126 UnsafetyViolationKind::General)
129 self.super_statement(block, statement, location);
132 fn visit_rvalue(&mut self,
133 rvalue: &Rvalue<'tcx>,
136 if let &Rvalue::Aggregate(box ref aggregate, _) = rvalue {
138 &AggregateKind::Array(..) |
139 &AggregateKind::Tuple |
140 &AggregateKind::Adt(..) => {}
141 &AggregateKind::Closure(def_id, _) |
142 &AggregateKind::Generator(def_id, _, _) => {
143 let UnsafetyCheckResult {
144 violations, unsafe_blocks
145 } = self.tcx.unsafety_check_result(def_id);
146 self.register_violations(&violations, &unsafe_blocks);
150 self.super_rvalue(rvalue, location);
153 fn visit_place(&mut self,
155 context: PlaceContext<'tcx>,
156 location: Location) {
157 if context.is_borrow() {
158 if util::is_disaligned(self.tcx, self.mir, self.param_env, place) {
159 let source_info = self.source_info;
161 self.source_scope_local_data[source_info.scope].lint_root;
162 self.register_violations(&[UnsafetyViolation {
164 description: Symbol::intern("borrow of packed field").as_interned_str(),
166 Symbol::intern("fields of packed structs might be misaligned: \
167 dereferencing a misaligned pointer or even just creating a \
168 misaligned reference is undefined behavior")
170 kind: UnsafetyViolationKind::BorrowPacked(lint_root)
176 &Place::Projection(box Projection {
179 let old_source_info = self.source_info;
180 if let &Place::Local(local) = base {
181 if self.mir.local_decls[local].internal {
182 // Internal locals are used in the `move_val_init` desugaring.
183 // We want to check unsafety against the source info of the
184 // desugaring, rather than the source info of the RHS.
185 self.source_info = self.mir.local_decls[local].source_info;
188 let base_ty = base.ty(self.mir, self.tcx).to_ty(self.tcx);
191 self.require_unsafe("dereference of raw pointer",
192 "raw pointers may be NULL, dangling or unaligned; they can violate \
193 aliasing rules and cause data races: all of these are undefined \
194 behavior", UnsafetyViolationKind::General)
198 if context == PlaceContext::MutatingUse(MutatingUseContext::Store) ||
199 context == PlaceContext::MutatingUse(MutatingUseContext::Drop) ||
200 context == PlaceContext::MutatingUse(
201 MutatingUseContext::AsmOutput
204 let elem_ty = match elem {
205 &ProjectionElem::Field(_, ty) => ty,
207 self.source_info.span,
208 "non-field projection {:?} from union?",
211 if elem_ty.moves_by_default(self.tcx, self.param_env,
212 self.source_info.span) {
214 "assignment to non-`Copy` union field",
215 "the previous content of the field will be dropped, which \
216 causes undefined behavior if the field was not properly \
217 initialized", UnsafetyViolationKind::General)
219 // write to non-move union, safe
222 self.require_unsafe("access to union field",
223 "the field may not be properly initialized: using \
224 uninitialized data will cause undefined behavior",
225 UnsafetyViolationKind::General)
231 self.source_info = old_source_info;
233 &Place::Local(..) => {
236 &Place::Promoted(_) => {
237 bug!("unsafety checking should happen before promotion")
239 &Place::Static(box Static { def_id, ty: _ }) => {
240 if self.tcx.is_static(def_id) == Some(hir::Mutability::MutMutable) {
241 self.require_unsafe("use of mutable static",
242 "mutable statics can be mutated by multiple threads: aliasing violations \
243 or data races will cause undefined behavior",
244 UnsafetyViolationKind::General);
245 } else if self.tcx.is_foreign_item(def_id) {
246 let source_info = self.source_info;
248 self.source_scope_local_data[source_info.scope].lint_root;
249 self.register_violations(&[UnsafetyViolation {
251 description: Symbol::intern("use of extern static").as_interned_str(),
253 Symbol::intern("extern statics are not controlled by the Rust type \
254 system: invalid data, aliasing violations or data \
255 races will cause undefined behavior")
257 kind: UnsafetyViolationKind::ExternStatic(lint_root)
262 self.super_place(place, context, location);
266 impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
269 description: &'static str,
270 details: &'static str,
271 kind: UnsafetyViolationKind,
273 let source_info = self.source_info;
274 self.register_violations(&[UnsafetyViolation {
276 description: Symbol::intern(description).as_interned_str(),
277 details: Symbol::intern(details).as_interned_str(),
282 fn register_violations(&mut self,
283 violations: &[UnsafetyViolation],
284 unsafe_blocks: &[(ast::NodeId, bool)]) {
285 let safety = self.source_scope_local_data[self.source_info.scope].safety;
286 let within_unsafe = match (safety, self.min_const_fn) {
287 // Erring on the safe side, pun intended
288 (Safety::BuiltinUnsafe, true) |
289 // mir building encodes const fn bodies as safe, even for `const unsafe fn`
290 (Safety::FnUnsafe, true) => bug!("const unsafe fn body treated as inherently unsafe"),
291 // `unsafe` blocks are required in safe code
292 (Safety::Safe, _) => {
293 for violation in violations {
294 let mut violation = violation.clone();
295 if self.min_const_fn {
296 // overwrite unsafety violation in const fn with a single hard error kind
297 violation.kind = UnsafetyViolationKind::MinConstFn;
298 } else if let UnsafetyViolationKind::MinConstFn = violation.kind {
299 // outside of const fns we treat `MinConstFn` and `General` the same
300 violation.kind = UnsafetyViolationKind::General;
302 if !self.violations.contains(&violation) {
303 self.violations.push(violation)
308 // regular `unsafe` function bodies allow unsafe without additional unsafe blocks
309 (Safety::BuiltinUnsafe, false) | (Safety::FnUnsafe, false) => true,
310 (Safety::ExplicitUnsafe(node_id), _) => {
311 // mark unsafe block as used if there are any unsafe operations inside
312 if !violations.is_empty() {
313 self.used_unsafe.insert(node_id);
315 // only some unsafety is allowed in const fn
316 if self.min_const_fn {
317 for violation in violations {
318 match violation.kind {
320 UnsafetyViolationKind::MinConstFn
321 // if `#![feature(min_const_unsafe_fn)]` is active
322 if self.tcx.sess.features_untracked().min_const_unsafe_fn => {},
324 let mut violation = violation.clone();
325 // overwrite unsafety violation in const fn with a hard error
326 violation.kind = UnsafetyViolationKind::MinConstFn;
327 if !self.violations.contains(&violation) {
328 self.violations.push(violation)
337 self.inherited_blocks.extend(unsafe_blocks.iter().map(|&(node_id, is_used)| {
338 (node_id, is_used && !within_unsafe)
343 pub(crate) fn provide(providers: &mut Providers) {
344 *providers = Providers {
345 unsafety_check_result,
346 unsafe_derive_on_repr_packed,
351 struct UnusedUnsafeVisitor<'a> {
352 used_unsafe: &'a FxHashSet<ast::NodeId>,
353 unsafe_blocks: &'a mut Vec<(ast::NodeId, bool)>,
356 impl<'a, 'tcx> hir::intravisit::Visitor<'tcx> for UnusedUnsafeVisitor<'a> {
357 fn nested_visit_map<'this>(&'this mut self) ->
358 hir::intravisit::NestedVisitorMap<'this, 'tcx>
360 hir::intravisit::NestedVisitorMap::None
363 fn visit_block(&mut self, block: &'tcx hir::Block) {
364 hir::intravisit::walk_block(self, block);
366 if let hir::UnsafeBlock(hir::UserProvided) = block.rules {
367 self.unsafe_blocks.push((block.id, self.used_unsafe.contains(&block.id)));
372 fn check_unused_unsafe<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
374 used_unsafe: &FxHashSet<ast::NodeId>,
375 unsafe_blocks: &'a mut Vec<(ast::NodeId, bool)>)
378 tcx.hir.as_local_node_id(def_id).and_then(|node_id| {
379 tcx.hir.maybe_body_owned_by(node_id)
382 let body_id = match body_id {
385 debug!("check_unused_unsafe({:?}) - no body found", def_id);
389 let body = tcx.hir.body(body_id);
390 debug!("check_unused_unsafe({:?}, body={:?}, used_unsafe={:?})",
391 def_id, body, used_unsafe);
393 let mut visitor = UnusedUnsafeVisitor { used_unsafe, unsafe_blocks };
394 hir::intravisit::Visitor::visit_body(&mut visitor, body);
397 fn unsafety_check_result<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
398 -> UnsafetyCheckResult
400 debug!("unsafety_violations({:?})", def_id);
402 // NB: this borrow is valid because all the consumers of
403 // `mir_built` force this.
404 let mir = &tcx.mir_built(def_id).borrow();
406 let source_scope_local_data = match mir.source_scope_local_data {
407 ClearCrossCrate::Set(ref data) => data,
408 ClearCrossCrate::Clear => {
409 debug!("unsafety_violations: {:?} - remote, skipping", def_id);
410 return UnsafetyCheckResult {
411 violations: Lrc::new([]),
412 unsafe_blocks: Lrc::new([])
417 let param_env = tcx.param_env(def_id);
418 let mut checker = UnsafetyChecker::new(
419 tcx.is_const_fn(def_id) && tcx.is_min_const_fn(def_id),
420 mir, source_scope_local_data, tcx, param_env);
421 checker.visit_mir(mir);
423 check_unused_unsafe(tcx, def_id, &checker.used_unsafe, &mut checker.inherited_blocks);
424 UnsafetyCheckResult {
425 violations: checker.violations.into(),
426 unsafe_blocks: checker.inherited_blocks.into()
430 fn unsafe_derive_on_repr_packed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
431 let lint_node_id = match tcx.hir.as_local_node_id(def_id) {
432 Some(node_id) => node_id,
433 None => bug!("checking unsafety for non-local def id {:?}", def_id)
436 // FIXME: when we make this a hard error, this should have its
438 let message = if tcx.generics_of(def_id).own_counts().types != 0 {
439 "#[derive] can't be used on a #[repr(packed)] struct with \
440 type parameters (error E0133)".to_string()
442 "#[derive] can't be used on a #[repr(packed)] struct that \
443 does not derive Copy (error E0133)".to_string()
445 tcx.lint_node(SAFE_PACKED_BORROWS,
447 tcx.def_span(def_id),
451 /// Return the NodeId for an enclosing scope that is also `unsafe`
452 fn is_enclosed(tcx: TyCtxt,
453 used_unsafe: &FxHashSet<ast::NodeId>,
454 id: ast::NodeId) -> Option<(String, ast::NodeId)> {
455 let parent_id = tcx.hir.get_parent_node(id);
457 if used_unsafe.contains(&parent_id) {
458 Some(("block".to_string(), parent_id))
459 } else if let Some(Node::Item(&hir::Item {
460 node: hir::ItemKind::Fn(_, header, _, _),
462 })) = tcx.hir.find(parent_id) {
463 match header.unsafety {
464 hir::Unsafety::Unsafe => Some(("fn".to_string(), parent_id)),
465 hir::Unsafety::Normal => None,
468 is_enclosed(tcx, used_unsafe, parent_id)
475 fn report_unused_unsafe(tcx: TyCtxt, used_unsafe: &FxHashSet<ast::NodeId>, id: ast::NodeId) {
476 let span = tcx.sess.source_map().def_span(tcx.hir.span(id));
477 let msg = "unnecessary `unsafe` block";
478 let mut db = tcx.struct_span_lint_node(UNUSED_UNSAFE, id, span, msg);
479 db.span_label(span, msg);
480 if let Some((kind, id)) = is_enclosed(tcx, used_unsafe, id) {
481 db.span_label(tcx.sess.source_map().def_span(tcx.hir.span(id)),
482 format!("because it's nested under this `unsafe` {}", kind));
487 fn builtin_derive_def_id<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> Option<DefId> {
488 debug!("builtin_derive_def_id({:?})", def_id);
489 if let Some(impl_def_id) = tcx.impl_of_method(def_id) {
490 if tcx.has_attr(impl_def_id, "automatically_derived") {
491 debug!("builtin_derive_def_id({:?}) - is {:?}", def_id, impl_def_id);
494 debug!("builtin_derive_def_id({:?}) - not automatically derived", def_id);
498 debug!("builtin_derive_def_id({:?}) - not a method", def_id);
503 pub fn check_unsafety<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
504 debug!("check_unsafety({:?})", def_id);
506 // closures are handled by their parent fn.
507 if tcx.is_closure(def_id) {
511 let UnsafetyCheckResult {
514 } = tcx.unsafety_check_result(def_id);
516 for &UnsafetyViolation {
517 source_info, description, details, kind
518 } in violations.iter() {
521 UnsafetyViolationKind::General => {
523 tcx.sess, source_info.span, E0133,
524 "{} is unsafe and requires unsafe function or block", description)
525 .span_label(source_info.span, &description.as_str()[..])
526 .note(&details.as_str()[..])
529 UnsafetyViolationKind::MinConstFn => {
530 tcx.sess.struct_span_err(
532 &format!("{} is unsafe and unsafe operations \
533 are not allowed in const fn", description))
534 .span_label(source_info.span, &description.as_str()[..])
535 .note(&details.as_str()[..])
538 UnsafetyViolationKind::ExternStatic(lint_node_id) => {
539 tcx.lint_node_note(SAFE_EXTERN_STATICS,
542 &format!("{} is unsafe and requires unsafe function or block \
543 (error E0133)", &description.as_str()[..]),
544 &details.as_str()[..]);
546 UnsafetyViolationKind::BorrowPacked(lint_node_id) => {
547 if let Some(impl_def_id) = builtin_derive_def_id(tcx, def_id) {
548 tcx.unsafe_derive_on_repr_packed(impl_def_id);
550 tcx.lint_node_note(SAFE_PACKED_BORROWS,
553 &format!("{} is unsafe and requires unsafe function or block \
554 (error E0133)", &description.as_str()[..]),
555 &details.as_str()[..]);
561 let mut unsafe_blocks: Vec<_> = unsafe_blocks.into_iter().collect();
562 unsafe_blocks.sort();
563 let used_unsafe: FxHashSet<_> = unsafe_blocks.iter()
564 .flat_map(|&&(id, used)| if used { Some(id) } else { None })
566 for &(block_id, is_used) in unsafe_blocks {
568 report_unused_unsafe(tcx, &used_unsafe, block_id);