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CheckObjCDealloc.cpp
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1 //==- CheckObjCDealloc.cpp - Check ObjC -dealloc implementation --*- C++ -*-==//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This checker analyzes Objective-C -dealloc methods and their callees
11 // to warn about improper releasing of instance variables that back synthesized
12 // properties. It warns about missing releases in the following cases:
13 // - When a class has a synthesized instance variable for a 'retain' or 'copy'
14 // property and lacks a -dealloc method in its implementation.
15 // - When a class has a synthesized instance variable for a 'retain'/'copy'
16 // property but the ivar is not released in -dealloc by either -release
17 // or by nilling out the property.
18 //
19 // It warns about extra releases in -dealloc (but not in callees) when a
20 // synthesized instance variable is released in the following cases:
21 // - When the property is 'assign' and is not 'readonly'.
22 // - When the property is 'weak'.
23 //
24 // This checker only warns for instance variables synthesized to back
25 // properties. Handling the more general case would require inferring whether
26 // an instance variable is stored retained or not. For synthesized properties,
27 // this is specified in the property declaration itself.
28 //
29 //===----------------------------------------------------------------------===//
30 
31 #include "ClangSACheckers.h"
32 #include "clang/AST/Attr.h"
33 #include "clang/AST/DeclObjC.h"
34 #include "clang/AST/Expr.h"
35 #include "clang/AST/ExprObjC.h"
37 #include "clang/Basic/TargetInfo.h"
48 #include "llvm/Support/raw_ostream.h"
49 
50 using namespace clang;
51 using namespace ento;
52 
53 /// Indicates whether an instance variable is required to be released in
54 /// -dealloc.
55 enum class ReleaseRequirement {
56  /// The instance variable must be released, either by calling
57  /// -release on it directly or by nilling it out with a property setter.
59 
60  /// The instance variable must not be directly released with -release.
62 
63  /// The requirement for the instance variable could not be determined.
64  Unknown
65 };
66 
67 /// Returns true if the property implementation is synthesized and the
68 /// type of the property is retainable.
70  const ObjCIvarDecl **ID,
71  const ObjCPropertyDecl **PD) {
72 
74  return false;
75 
76  (*ID) = I->getPropertyIvarDecl();
77  if (!(*ID))
78  return false;
79 
80  QualType T = (*ID)->getType();
81  if (!T->isObjCRetainableType())
82  return false;
83 
84  (*PD) = I->getPropertyDecl();
85  // Shouldn't be able to synthesize a property that doesn't exist.
86  assert(*PD);
87 
88  return true;
89 }
90 
91 namespace {
92 
93 class ObjCDeallocChecker
94  : public Checker<check::ASTDecl<ObjCImplementationDecl>,
95  check::PreObjCMessage, check::PostObjCMessage,
96  check::PreCall,
97  check::BeginFunction, check::EndFunction,
98  eval::Assume,
99  check::PointerEscape,
100  check::PreStmt<ReturnStmt>> {
101 
102  mutable IdentifierInfo *NSObjectII, *SenTestCaseII, *XCTestCaseII,
103  *Block_releaseII, *CIFilterII;
104 
105  mutable Selector DeallocSel, ReleaseSel;
106 
107  std::unique_ptr<BugType> MissingReleaseBugType;
108  std::unique_ptr<BugType> ExtraReleaseBugType;
109  std::unique_ptr<BugType> MistakenDeallocBugType;
110 
111 public:
112  ObjCDeallocChecker();
113 
114  void checkASTDecl(const ObjCImplementationDecl *D, AnalysisManager& Mgr,
115  BugReporter &BR) const;
116  void checkBeginFunction(CheckerContext &Ctx) const;
117  void checkPreObjCMessage(const ObjCMethodCall &M, CheckerContext &C) const;
118  void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
119  void checkPostObjCMessage(const ObjCMethodCall &M, CheckerContext &C) const;
120 
121  ProgramStateRef evalAssume(ProgramStateRef State, SVal Cond,
122  bool Assumption) const;
123 
124  ProgramStateRef checkPointerEscape(ProgramStateRef State,
125  const InvalidatedSymbols &Escaped,
126  const CallEvent *Call,
127  PointerEscapeKind Kind) const;
128  void checkPreStmt(const ReturnStmt *RS, CheckerContext &C) const;
129  void checkEndFunction(const ReturnStmt *RS, CheckerContext &Ctx) const;
130 
131 private:
132  void diagnoseMissingReleases(CheckerContext &C) const;
133 
134  bool diagnoseExtraRelease(SymbolRef ReleasedValue, const ObjCMethodCall &M,
135  CheckerContext &C) const;
136 
137  bool diagnoseMistakenDealloc(SymbolRef DeallocedValue,
138  const ObjCMethodCall &M,
139  CheckerContext &C) const;
140 
141  SymbolRef getValueReleasedByNillingOut(const ObjCMethodCall &M,
142  CheckerContext &C) const;
143 
144  const ObjCIvarRegion *getIvarRegionForIvarSymbol(SymbolRef IvarSym) const;
145  SymbolRef getInstanceSymbolFromIvarSymbol(SymbolRef IvarSym) const;
146 
147  const ObjCPropertyImplDecl*
148  findPropertyOnDeallocatingInstance(SymbolRef IvarSym,
149  CheckerContext &C) const;
150 
152  getDeallocReleaseRequirement(const ObjCPropertyImplDecl *PropImpl) const;
153 
154  bool isInInstanceDealloc(const CheckerContext &C, SVal &SelfValOut) const;
155  bool isInInstanceDealloc(const CheckerContext &C, const LocationContext *LCtx,
156  SVal &SelfValOut) const;
157  bool instanceDeallocIsOnStack(const CheckerContext &C,
158  SVal &InstanceValOut) const;
159 
160  bool isSuperDeallocMessage(const ObjCMethodCall &M) const;
161 
162  const ObjCImplDecl *getContainingObjCImpl(const LocationContext *LCtx) const;
163 
164  const ObjCPropertyDecl *
165  findShadowedPropertyDecl(const ObjCPropertyImplDecl *PropImpl) const;
166 
167  void transitionToReleaseValue(CheckerContext &C, SymbolRef Value) const;
168  ProgramStateRef removeValueRequiringRelease(ProgramStateRef State,
169  SymbolRef InstanceSym,
170  SymbolRef ValueSym) const;
171 
172  void initIdentifierInfoAndSelectors(ASTContext &Ctx) const;
173 
174  bool classHasSeparateTeardown(const ObjCInterfaceDecl *ID) const;
175 
176  bool isReleasedByCIFilterDealloc(const ObjCPropertyImplDecl *PropImpl) const;
177  bool isNibLoadedIvarWithoutRetain(const ObjCPropertyImplDecl *PropImpl) const;
178 };
179 } // End anonymous namespace.
180 
181 
182 /// Maps from the symbol for a class instance to the set of
183 /// symbols remaining that must be released in -dealloc.
185 REGISTER_MAP_WITH_PROGRAMSTATE(UnreleasedIvarMap, SymbolRef, SymbolSet)
186 
187 
188 /// An AST check that diagnose when the class requires a -dealloc method and
189 /// is missing one.
190 void ObjCDeallocChecker::checkASTDecl(const ObjCImplementationDecl *D,
191  AnalysisManager &Mgr,
192  BugReporter &BR) const {
193  assert(Mgr.getLangOpts().getGC() != LangOptions::GCOnly);
194  assert(!Mgr.getLangOpts().ObjCAutoRefCount);
195  initIdentifierInfoAndSelectors(Mgr.getASTContext());
196 
197  const ObjCInterfaceDecl *ID = D->getClassInterface();
198  // If the class is known to have a lifecycle with a separate teardown method
199  // then it may not require a -dealloc method.
200  if (classHasSeparateTeardown(ID))
201  return;
202 
203  // Does the class contain any synthesized properties that are retainable?
204  // If not, skip the check entirely.
205  const ObjCPropertyImplDecl *PropImplRequiringRelease = nullptr;
206  bool HasOthers = false;
207  for (const auto *I : D->property_impls()) {
208  if (getDeallocReleaseRequirement(I) == ReleaseRequirement::MustRelease) {
209  if (!PropImplRequiringRelease)
210  PropImplRequiringRelease = I;
211  else {
212  HasOthers = true;
213  break;
214  }
215  }
216  }
217 
218  if (!PropImplRequiringRelease)
219  return;
220 
221  const ObjCMethodDecl *MD = nullptr;
222 
223  // Scan the instance methods for "dealloc".
224  for (const auto *I : D->instance_methods()) {
225  if (I->getSelector() == DeallocSel) {
226  MD = I;
227  break;
228  }
229  }
230 
231  if (!MD) { // No dealloc found.
232  const char* Name = "Missing -dealloc";
233 
234  std::string Buf;
235  llvm::raw_string_ostream OS(Buf);
236  OS << "'" << *D << "' lacks a 'dealloc' instance method but "
237  << "must release '" << *PropImplRequiringRelease->getPropertyIvarDecl()
238  << "'";
239 
240  if (HasOthers)
241  OS << " and others";
242  PathDiagnosticLocation DLoc =
243  PathDiagnosticLocation::createBegin(D, BR.getSourceManager());
244 
245  BR.EmitBasicReport(D, this, Name, categories::CoreFoundationObjectiveC,
246  OS.str(), DLoc);
247  return;
248  }
249 }
250 
251 /// If this is the beginning of -dealloc, mark the values initially stored in
252 /// instance variables that must be released by the end of -dealloc
253 /// as unreleased in the state.
254 void ObjCDeallocChecker::checkBeginFunction(
255  CheckerContext &C) const {
256  initIdentifierInfoAndSelectors(C.getASTContext());
257 
258  // Only do this if the current method is -dealloc.
259  SVal SelfVal;
260  if (!isInInstanceDealloc(C, SelfVal))
261  return;
262 
263  SymbolRef SelfSymbol = SelfVal.getAsSymbol();
264 
265  const LocationContext *LCtx = C.getLocationContext();
266  ProgramStateRef InitialState = C.getState();
267 
268  ProgramStateRef State = InitialState;
269 
270  SymbolSet::Factory &F = State->getStateManager().get_context<SymbolSet>();
271 
272  // Symbols that must be released by the end of the -dealloc;
273  SymbolSet RequiredReleases = F.getEmptySet();
274 
275  // If we're an inlined -dealloc, we should add our symbols to the existing
276  // set from our subclass.
277  if (const SymbolSet *CurrSet = State->get<UnreleasedIvarMap>(SelfSymbol))
278  RequiredReleases = *CurrSet;
279 
280  for (auto *PropImpl : getContainingObjCImpl(LCtx)->property_impls()) {
281  ReleaseRequirement Requirement = getDeallocReleaseRequirement(PropImpl);
282  if (Requirement != ReleaseRequirement::MustRelease)
283  continue;
284 
285  SVal LVal = State->getLValue(PropImpl->getPropertyIvarDecl(), SelfVal);
286  Optional<Loc> LValLoc = LVal.getAs<Loc>();
287  if (!LValLoc)
288  continue;
289 
290  SVal InitialVal = State->getSVal(LValLoc.getValue());
291  SymbolRef Symbol = InitialVal.getAsSymbol();
292  if (!Symbol || !isa<SymbolRegionValue>(Symbol))
293  continue;
294 
295  // Mark the value as requiring a release.
296  RequiredReleases = F.add(RequiredReleases, Symbol);
297  }
298 
299  if (!RequiredReleases.isEmpty()) {
300  State = State->set<UnreleasedIvarMap>(SelfSymbol, RequiredReleases);
301  }
302 
303  if (State != InitialState) {
304  C.addTransition(State);
305  }
306 }
307 
308 /// Given a symbol for an ivar, return the ivar region it was loaded from.
309 /// Returns nullptr if the instance symbol cannot be found.
310 const ObjCIvarRegion *
311 ObjCDeallocChecker::getIvarRegionForIvarSymbol(SymbolRef IvarSym) const {
312  return dyn_cast_or_null<ObjCIvarRegion>(IvarSym->getOriginRegion());
313 }
314 
315 /// Given a symbol for an ivar, return a symbol for the instance containing
316 /// the ivar. Returns nullptr if the instance symbol cannot be found.
317 SymbolRef
318 ObjCDeallocChecker::getInstanceSymbolFromIvarSymbol(SymbolRef IvarSym) const {
319 
320  const ObjCIvarRegion *IvarRegion = getIvarRegionForIvarSymbol(IvarSym);
321  if (!IvarRegion)
322  return nullptr;
323 
324  return IvarRegion->getSymbolicBase()->getSymbol();
325 }
326 
327 /// If we are in -dealloc or -dealloc is on the stack, handle the call if it is
328 /// a release or a nilling-out property setter.
329 void ObjCDeallocChecker::checkPreObjCMessage(
330  const ObjCMethodCall &M, CheckerContext &C) const {
331  // Only run if -dealloc is on the stack.
332  SVal DeallocedInstance;
333  if (!instanceDeallocIsOnStack(C, DeallocedInstance))
334  return;
335 
336  SymbolRef ReleasedValue = nullptr;
337 
338  if (M.getSelector() == ReleaseSel) {
339  ReleasedValue = M.getReceiverSVal().getAsSymbol();
340  } else if (M.getSelector() == DeallocSel && !M.isReceiverSelfOrSuper()) {
341  if (diagnoseMistakenDealloc(M.getReceiverSVal().getAsSymbol(), M, C))
342  return;
343  }
344 
345  if (ReleasedValue) {
346  // An instance variable symbol was released with -release:
347  // [_property release];
348  if (diagnoseExtraRelease(ReleasedValue,M, C))
349  return;
350  } else {
351  // An instance variable symbol was released nilling out its property:
352  // self.property = nil;
353  ReleasedValue = getValueReleasedByNillingOut(M, C);
354  }
355 
356  if (!ReleasedValue)
357  return;
358 
359  transitionToReleaseValue(C, ReleasedValue);
360 }
361 
362 /// If we are in -dealloc or -dealloc is on the stack, handle the call if it is
363 /// call to Block_release().
364 void ObjCDeallocChecker::checkPreCall(const CallEvent &Call,
365  CheckerContext &C) const {
366  const IdentifierInfo *II = Call.getCalleeIdentifier();
367  if (II != Block_releaseII)
368  return;
369 
370  if (Call.getNumArgs() != 1)
371  return;
372 
373  SymbolRef ReleasedValue = Call.getArgSVal(0).getAsSymbol();
374  if (!ReleasedValue)
375  return;
376 
377  transitionToReleaseValue(C, ReleasedValue);
378 }
379 /// If the message was a call to '[super dealloc]', diagnose any missing
380 /// releases.
381 void ObjCDeallocChecker::checkPostObjCMessage(
382  const ObjCMethodCall &M, CheckerContext &C) const {
383  // We perform this check post-message so that if the super -dealloc
384  // calls a helper method and that this class overrides, any ivars released in
385  // the helper method will be recorded before checking.
386  if (isSuperDeallocMessage(M))
387  diagnoseMissingReleases(C);
388 }
389 
390 /// Check for missing releases even when -dealloc does not call
391 /// '[super dealloc]'.
392 void ObjCDeallocChecker::checkEndFunction(
393  const ReturnStmt *RS, CheckerContext &C) const {
394  diagnoseMissingReleases(C);
395 }
396 
397 /// Check for missing releases on early return.
398 void ObjCDeallocChecker::checkPreStmt(
399  const ReturnStmt *RS, CheckerContext &C) const {
400  diagnoseMissingReleases(C);
401 }
402 
403 /// When a symbol is assumed to be nil, remove it from the set of symbols
404 /// require to be nil.
405 ProgramStateRef ObjCDeallocChecker::evalAssume(ProgramStateRef State, SVal Cond,
406  bool Assumption) const {
407  if (State->get<UnreleasedIvarMap>().isEmpty())
408  return State;
409 
410  auto *CondBSE = dyn_cast_or_null<BinarySymExpr>(Cond.getAsSymExpr());
411  if (!CondBSE)
412  return State;
413 
414  BinaryOperator::Opcode OpCode = CondBSE->getOpcode();
415  if (Assumption) {
416  if (OpCode != BO_EQ)
417  return State;
418  } else {
419  if (OpCode != BO_NE)
420  return State;
421  }
422 
423  SymbolRef NullSymbol = nullptr;
424  if (auto *SIE = dyn_cast<SymIntExpr>(CondBSE)) {
425  const llvm::APInt &RHS = SIE->getRHS();
426  if (RHS != 0)
427  return State;
428  NullSymbol = SIE->getLHS();
429  } else if (auto *SIE = dyn_cast<IntSymExpr>(CondBSE)) {
430  const llvm::APInt &LHS = SIE->getLHS();
431  if (LHS != 0)
432  return State;
433  NullSymbol = SIE->getRHS();
434  } else {
435  return State;
436  }
437 
438  SymbolRef InstanceSymbol = getInstanceSymbolFromIvarSymbol(NullSymbol);
439  if (!InstanceSymbol)
440  return State;
441 
442  State = removeValueRequiringRelease(State, InstanceSymbol, NullSymbol);
443 
444  return State;
445 }
446 
447 /// If a symbol escapes conservatively assume unseen code released it.
448 ProgramStateRef ObjCDeallocChecker::checkPointerEscape(
449  ProgramStateRef State, const InvalidatedSymbols &Escaped,
450  const CallEvent *Call, PointerEscapeKind Kind) const {
451 
452  if (State->get<UnreleasedIvarMap>().isEmpty())
453  return State;
454 
455  // Don't treat calls to '[super dealloc]' as escaping for the purposes
456  // of this checker. Because the checker diagnoses missing releases in the
457  // post-message handler for '[super dealloc], escaping here would cause
458  // the checker to never warn.
459  auto *OMC = dyn_cast_or_null<ObjCMethodCall>(Call);
460  if (OMC && isSuperDeallocMessage(*OMC))
461  return State;
462 
463  for (const auto &Sym : Escaped) {
464  if (!Call || (Call && !Call->isInSystemHeader())) {
465  // If Sym is a symbol for an object with instance variables that
466  // must be released, remove these obligations when the object escapes
467  // unless via a call to a system function. System functions are
468  // very unlikely to release instance variables on objects passed to them,
469  // and are frequently called on 'self' in -dealloc (e.g., to remove
470  // observers) -- we want to avoid false negatives from escaping on
471  // them.
472  State = State->remove<UnreleasedIvarMap>(Sym);
473  }
474 
475 
476  SymbolRef InstanceSymbol = getInstanceSymbolFromIvarSymbol(Sym);
477  if (!InstanceSymbol)
478  continue;
479 
480  State = removeValueRequiringRelease(State, InstanceSymbol, Sym);
481  }
482 
483  return State;
484 }
485 
486 /// Report any unreleased instance variables for the current instance being
487 /// dealloced.
488 void ObjCDeallocChecker::diagnoseMissingReleases(CheckerContext &C) const {
489  ProgramStateRef State = C.getState();
490 
491  SVal SelfVal;
492  if (!isInInstanceDealloc(C, SelfVal))
493  return;
494 
495  const MemRegion *SelfRegion = SelfVal.castAs<loc::MemRegionVal>().getRegion();
496  const LocationContext *LCtx = C.getLocationContext();
497 
498  ExplodedNode *ErrNode = nullptr;
499 
500  SymbolRef SelfSym = SelfVal.getAsSymbol();
501  if (!SelfSym)
502  return;
503 
504  const SymbolSet *OldUnreleased = State->get<UnreleasedIvarMap>(SelfSym);
505  if (!OldUnreleased)
506  return;
507 
508  SymbolSet NewUnreleased = *OldUnreleased;
509  SymbolSet::Factory &F = State->getStateManager().get_context<SymbolSet>();
510 
511  ProgramStateRef InitialState = State;
512 
513  for (auto *IvarSymbol : *OldUnreleased) {
514  const TypedValueRegion *TVR =
515  cast<SymbolRegionValue>(IvarSymbol)->getRegion();
516  const ObjCIvarRegion *IvarRegion = cast<ObjCIvarRegion>(TVR);
517 
518  // Don't warn if the ivar is not for this instance.
519  if (SelfRegion != IvarRegion->getSuperRegion())
520  continue;
521 
522  const ObjCIvarDecl *IvarDecl = IvarRegion->getDecl();
523  // Prevent an inlined call to -dealloc in a super class from warning
524  // about the values the subclass's -dealloc should release.
525  if (IvarDecl->getContainingInterface() !=
526  cast<ObjCMethodDecl>(LCtx->getDecl())->getClassInterface())
527  continue;
528 
529  // Prevents diagnosing multiple times for the same instance variable
530  // at, for example, both a return and at the end of the function.
531  NewUnreleased = F.remove(NewUnreleased, IvarSymbol);
532 
533  if (State->getStateManager()
534  .getConstraintManager()
535  .isNull(State, IvarSymbol)
536  .isConstrainedTrue()) {
537  continue;
538  }
539 
540  // A missing release manifests as a leak, so treat as a non-fatal error.
541  if (!ErrNode)
542  ErrNode = C.generateNonFatalErrorNode();
543  // If we've already reached this node on another path, return without
544  // diagnosing.
545  if (!ErrNode)
546  return;
547 
548  std::string Buf;
549  llvm::raw_string_ostream OS(Buf);
550 
551  const ObjCInterfaceDecl *Interface = IvarDecl->getContainingInterface();
552  // If the class is known to have a lifecycle with teardown that is
553  // separate from -dealloc, do not warn about missing releases. We
554  // suppress here (rather than not tracking for instance variables in
555  // such classes) because these classes are rare.
556  if (classHasSeparateTeardown(Interface))
557  return;
558 
559  ObjCImplDecl *ImplDecl = Interface->getImplementation();
560 
561  const ObjCPropertyImplDecl *PropImpl =
562  ImplDecl->FindPropertyImplIvarDecl(IvarDecl->getIdentifier());
563 
564  const ObjCPropertyDecl *PropDecl = PropImpl->getPropertyDecl();
565 
566  assert(PropDecl->getSetterKind() == ObjCPropertyDecl::Copy ||
567  PropDecl->getSetterKind() == ObjCPropertyDecl::Retain);
568 
569  OS << "The '" << *IvarDecl << "' ivar in '" << *ImplDecl
570  << "' was ";
571 
572  if (PropDecl->getSetterKind() == ObjCPropertyDecl::Retain)
573  OS << "retained";
574  else
575  OS << "copied";
576 
577  OS << " by a synthesized property but not released"
578  " before '[super dealloc]'";
579 
580  std::unique_ptr<BugReport> BR(
581  new BugReport(*MissingReleaseBugType, OS.str(), ErrNode));
582 
583  C.emitReport(std::move(BR));
584  }
585 
586  if (NewUnreleased.isEmpty()) {
587  State = State->remove<UnreleasedIvarMap>(SelfSym);
588  } else {
589  State = State->set<UnreleasedIvarMap>(SelfSym, NewUnreleased);
590  }
591 
592  if (ErrNode) {
593  C.addTransition(State, ErrNode);
594  } else if (State != InitialState) {
595  C.addTransition(State);
596  }
597 
598  // Make sure that after checking in the top-most frame the list of
599  // tracked ivars is empty. This is intended to detect accidental leaks in
600  // the UnreleasedIvarMap program state.
601  assert(!LCtx->inTopFrame() || State->get<UnreleasedIvarMap>().isEmpty());
602 }
603 
604 /// Given a symbol, determine whether the symbol refers to an ivar on
605 /// the top-most deallocating instance. If so, find the property for that
606 /// ivar, if one exists. Otherwise return null.
607 const ObjCPropertyImplDecl *
608 ObjCDeallocChecker::findPropertyOnDeallocatingInstance(
609  SymbolRef IvarSym, CheckerContext &C) const {
610  SVal DeallocedInstance;
611  if (!isInInstanceDealloc(C, DeallocedInstance))
612  return nullptr;
613 
614  // Try to get the region from which the ivar value was loaded.
615  auto *IvarRegion = getIvarRegionForIvarSymbol(IvarSym);
616  if (!IvarRegion)
617  return nullptr;
618 
619  // Don't try to find the property if the ivar was not loaded from the
620  // given instance.
621  if (DeallocedInstance.castAs<loc::MemRegionVal>().getRegion() !=
622  IvarRegion->getSuperRegion())
623  return nullptr;
624 
625  const LocationContext *LCtx = C.getLocationContext();
626  const ObjCIvarDecl *IvarDecl = IvarRegion->getDecl();
627 
628  const ObjCImplDecl *Container = getContainingObjCImpl(LCtx);
629  const ObjCPropertyImplDecl *PropImpl =
630  Container->FindPropertyImplIvarDecl(IvarDecl->getIdentifier());
631  return PropImpl;
632 }
633 
634 /// Emits a warning if the current context is -dealloc and ReleasedValue
635 /// must not be directly released in a -dealloc. Returns true if a diagnostic
636 /// was emitted.
637 bool ObjCDeallocChecker::diagnoseExtraRelease(SymbolRef ReleasedValue,
638  const ObjCMethodCall &M,
639  CheckerContext &C) const {
640  // Try to get the region from which the released value was loaded.
641  // Note that, unlike diagnosing for missing releases, here we don't track
642  // values that must not be released in the state. This is because even if
643  // these values escape, it is still an error under the rules of MRR to
644  // release them in -dealloc.
645  const ObjCPropertyImplDecl *PropImpl =
646  findPropertyOnDeallocatingInstance(ReleasedValue, C);
647 
648  if (!PropImpl)
649  return false;
650 
651  // If the ivar belongs to a property that must not be released directly
652  // in dealloc, emit a warning.
653  if (getDeallocReleaseRequirement(PropImpl) !=
655  return false;
656  }
657 
658  // If the property is readwrite but it shadows a read-only property in its
659  // external interface, treat the property a read-only. If the outside
660  // world cannot write to a property then the internal implementation is free
661  // to make its own convention about whether the value is stored retained
662  // or not. We look up the shadow here rather than in
663  // getDeallocReleaseRequirement() because doing so can be expensive.
664  const ObjCPropertyDecl *PropDecl = findShadowedPropertyDecl(PropImpl);
665  if (PropDecl) {
666  if (PropDecl->isReadOnly())
667  return false;
668  } else {
669  PropDecl = PropImpl->getPropertyDecl();
670  }
671 
672  ExplodedNode *ErrNode = C.generateNonFatalErrorNode();
673  if (!ErrNode)
674  return false;
675 
676  std::string Buf;
677  llvm::raw_string_ostream OS(Buf);
678 
679  assert(PropDecl->getSetterKind() == ObjCPropertyDecl::Weak ||
680  (PropDecl->getSetterKind() == ObjCPropertyDecl::Assign &&
681  !PropDecl->isReadOnly()) ||
682  isReleasedByCIFilterDealloc(PropImpl)
683  );
684 
685  const ObjCImplDecl *Container = getContainingObjCImpl(C.getLocationContext());
686  OS << "The '" << *PropImpl->getPropertyIvarDecl()
687  << "' ivar in '" << *Container;
688 
689 
690  if (isReleasedByCIFilterDealloc(PropImpl)) {
691  OS << "' will be released by '-[CIFilter dealloc]' but also released here";
692  } else {
693  OS << "' was synthesized for ";
694 
695  if (PropDecl->getSetterKind() == ObjCPropertyDecl::Weak)
696  OS << "a weak";
697  else
698  OS << "an assign, readwrite";
699 
700  OS << " property but was released in 'dealloc'";
701  }
702 
703  std::unique_ptr<BugReport> BR(
704  new BugReport(*ExtraReleaseBugType, OS.str(), ErrNode));
705  BR->addRange(M.getOriginExpr()->getSourceRange());
706 
707  C.emitReport(std::move(BR));
708 
709  return true;
710 }
711 
712 /// Emits a warning if the current context is -dealloc and DeallocedValue
713 /// must not be directly dealloced in a -dealloc. Returns true if a diagnostic
714 /// was emitted.
715 bool ObjCDeallocChecker::diagnoseMistakenDealloc(SymbolRef DeallocedValue,
716  const ObjCMethodCall &M,
717  CheckerContext &C) const {
718 
719  // Find the property backing the instance variable that M
720  // is dealloc'ing.
721  const ObjCPropertyImplDecl *PropImpl =
722  findPropertyOnDeallocatingInstance(DeallocedValue, C);
723  if (!PropImpl)
724  return false;
725 
726  if (getDeallocReleaseRequirement(PropImpl) !=
728  return false;
729  }
730 
731  ExplodedNode *ErrNode = C.generateErrorNode();
732  if (!ErrNode)
733  return false;
734 
735  std::string Buf;
736  llvm::raw_string_ostream OS(Buf);
737 
738  OS << "'" << *PropImpl->getPropertyIvarDecl()
739  << "' should be released rather than deallocated";
740 
741  std::unique_ptr<BugReport> BR(
742  new BugReport(*MistakenDeallocBugType, OS.str(), ErrNode));
743  BR->addRange(M.getOriginExpr()->getSourceRange());
744 
745  C.emitReport(std::move(BR));
746 
747  return true;
748 }
749 
750 ObjCDeallocChecker::ObjCDeallocChecker()
751  : NSObjectII(nullptr), SenTestCaseII(nullptr), XCTestCaseII(nullptr),
752  CIFilterII(nullptr) {
753 
754  MissingReleaseBugType.reset(
755  new BugType(this, "Missing ivar release (leak)",
757 
758  ExtraReleaseBugType.reset(
759  new BugType(this, "Extra ivar release",
761 
762  MistakenDeallocBugType.reset(
763  new BugType(this, "Mistaken dealloc",
765 }
766 
767 void ObjCDeallocChecker::initIdentifierInfoAndSelectors(
768  ASTContext &Ctx) const {
769  if (NSObjectII)
770  return;
771 
772  NSObjectII = &Ctx.Idents.get("NSObject");
773  SenTestCaseII = &Ctx.Idents.get("SenTestCase");
774  XCTestCaseII = &Ctx.Idents.get("XCTestCase");
775  Block_releaseII = &Ctx.Idents.get("_Block_release");
776  CIFilterII = &Ctx.Idents.get("CIFilter");
777 
778  IdentifierInfo *DeallocII = &Ctx.Idents.get("dealloc");
779  IdentifierInfo *ReleaseII = &Ctx.Idents.get("release");
780  DeallocSel = Ctx.Selectors.getSelector(0, &DeallocII);
781  ReleaseSel = Ctx.Selectors.getSelector(0, &ReleaseII);
782 }
783 
784 /// Returns true if M is a call to '[super dealloc]'.
785 bool ObjCDeallocChecker::isSuperDeallocMessage(
786  const ObjCMethodCall &M) const {
788  return false;
789 
790  return M.getSelector() == DeallocSel;
791 }
792 
793 /// Returns the ObjCImplDecl containing the method declaration in LCtx.
794 const ObjCImplDecl *
795 ObjCDeallocChecker::getContainingObjCImpl(const LocationContext *LCtx) const {
796  auto *MD = cast<ObjCMethodDecl>(LCtx->getDecl());
797  return cast<ObjCImplDecl>(MD->getDeclContext());
798 }
799 
800 /// Returns the property that shadowed by PropImpl if one exists and
801 /// nullptr otherwise.
802 const ObjCPropertyDecl *ObjCDeallocChecker::findShadowedPropertyDecl(
803  const ObjCPropertyImplDecl *PropImpl) const {
804  const ObjCPropertyDecl *PropDecl = PropImpl->getPropertyDecl();
805 
806  // Only readwrite properties can shadow.
807  if (PropDecl->isReadOnly())
808  return nullptr;
809 
810  auto *CatDecl = dyn_cast<ObjCCategoryDecl>(PropDecl->getDeclContext());
811 
812  // Only class extensions can contain shadowing properties.
813  if (!CatDecl || !CatDecl->IsClassExtension())
814  return nullptr;
815 
816  IdentifierInfo *ID = PropDecl->getIdentifier();
817  DeclContext::lookup_result R = CatDecl->getClassInterface()->lookup(ID);
818  for (DeclContext::lookup_iterator I = R.begin(), E = R.end(); I != E; ++I) {
819  auto *ShadowedPropDecl = dyn_cast<ObjCPropertyDecl>(*I);
820  if (!ShadowedPropDecl)
821  continue;
822 
823  if (ShadowedPropDecl->isInstanceProperty()) {
824  assert(ShadowedPropDecl->isReadOnly());
825  return ShadowedPropDecl;
826  }
827  }
828 
829  return nullptr;
830 }
831 
832 /// Add a transition noting the release of the given value.
833 void ObjCDeallocChecker::transitionToReleaseValue(CheckerContext &C,
834  SymbolRef Value) const {
835  assert(Value);
836  SymbolRef InstanceSym = getInstanceSymbolFromIvarSymbol(Value);
837  if (!InstanceSym)
838  return;
839  ProgramStateRef InitialState = C.getState();
840 
841  ProgramStateRef ReleasedState =
842  removeValueRequiringRelease(InitialState, InstanceSym, Value);
843 
844  if (ReleasedState != InitialState) {
845  C.addTransition(ReleasedState);
846  }
847 }
848 
849 /// Remove the Value requiring a release from the tracked set for
850 /// Instance and return the resultant state.
851 ProgramStateRef ObjCDeallocChecker::removeValueRequiringRelease(
852  ProgramStateRef State, SymbolRef Instance, SymbolRef Value) const {
853  assert(Instance);
854  assert(Value);
855  const ObjCIvarRegion *RemovedRegion = getIvarRegionForIvarSymbol(Value);
856  if (!RemovedRegion)
857  return State;
858 
859  const SymbolSet *Unreleased = State->get<UnreleasedIvarMap>(Instance);
860  if (!Unreleased)
861  return State;
862 
863  // Mark the value as no longer requiring a release.
864  SymbolSet::Factory &F = State->getStateManager().get_context<SymbolSet>();
865  SymbolSet NewUnreleased = *Unreleased;
866  for (auto &Sym : *Unreleased) {
867  const ObjCIvarRegion *UnreleasedRegion = getIvarRegionForIvarSymbol(Sym);
868  assert(UnreleasedRegion);
869  if (RemovedRegion->getDecl() == UnreleasedRegion->getDecl()) {
870  NewUnreleased = F.remove(NewUnreleased, Sym);
871  }
872  }
873 
874  if (NewUnreleased.isEmpty()) {
875  return State->remove<UnreleasedIvarMap>(Instance);
876  }
877 
878  return State->set<UnreleasedIvarMap>(Instance, NewUnreleased);
879 }
880 
881 /// Determines whether the instance variable for \p PropImpl must or must not be
882 /// released in -dealloc or whether it cannot be determined.
883 ReleaseRequirement ObjCDeallocChecker::getDeallocReleaseRequirement(
884  const ObjCPropertyImplDecl *PropImpl) const {
885  const ObjCIvarDecl *IvarDecl;
886  const ObjCPropertyDecl *PropDecl;
887  if (!isSynthesizedRetainableProperty(PropImpl, &IvarDecl, &PropDecl))
889 
891 
892  switch (SK) {
893  // Retain and copy setters retain/copy their values before storing and so
894  // the value in their instance variables must be released in -dealloc.
897  if (isReleasedByCIFilterDealloc(PropImpl))
899 
900  if (isNibLoadedIvarWithoutRetain(PropImpl))
902 
904 
907 
909  // It is common for the ivars for read-only assign properties to
910  // always be stored retained, so their release requirement cannot be
911  // be determined.
912  if (PropDecl->isReadOnly())
914 
916  }
917  llvm_unreachable("Unrecognized setter kind");
918 }
919 
920 /// Returns the released value if M is a call a setter that releases
921 /// and nils out its underlying instance variable.
922 SymbolRef
923 ObjCDeallocChecker::getValueReleasedByNillingOut(const ObjCMethodCall &M,
924  CheckerContext &C) const {
925  SVal ReceiverVal = M.getReceiverSVal();
926  if (!ReceiverVal.isValid())
927  return nullptr;
928 
929  if (M.getNumArgs() == 0)
930  return nullptr;
931 
932  if (!M.getArgExpr(0)->getType()->isObjCRetainableType())
933  return nullptr;
934 
935  // Is the first argument nil?
936  SVal Arg = M.getArgSVal(0);
937  ProgramStateRef notNilState, nilState;
938  std::tie(notNilState, nilState) =
939  M.getState()->assume(Arg.castAs<DefinedOrUnknownSVal>());
940  if (!(nilState && !notNilState))
941  return nullptr;
942 
943  const ObjCPropertyDecl *Prop = M.getAccessedProperty();
944  if (!Prop)
945  return nullptr;
946 
947  ObjCIvarDecl *PropIvarDecl = Prop->getPropertyIvarDecl();
948  if (!PropIvarDecl)
949  return nullptr;
950 
951  ProgramStateRef State = C.getState();
952 
953  SVal LVal = State->getLValue(PropIvarDecl, ReceiverVal);
954  Optional<Loc> LValLoc = LVal.getAs<Loc>();
955  if (!LValLoc)
956  return nullptr;
957 
958  SVal CurrentValInIvar = State->getSVal(LValLoc.getValue());
959  return CurrentValInIvar.getAsSymbol();
960 }
961 
962 /// Returns true if the current context is a call to -dealloc and false
963 /// otherwise. If true, it also sets SelfValOut to the value of
964 /// 'self'.
965 bool ObjCDeallocChecker::isInInstanceDealloc(const CheckerContext &C,
966  SVal &SelfValOut) const {
967  return isInInstanceDealloc(C, C.getLocationContext(), SelfValOut);
968 }
969 
970 /// Returns true if LCtx is a call to -dealloc and false
971 /// otherwise. If true, it also sets SelfValOut to the value of
972 /// 'self'.
973 bool ObjCDeallocChecker::isInInstanceDealloc(const CheckerContext &C,
974  const LocationContext *LCtx,
975  SVal &SelfValOut) const {
976  auto *MD = dyn_cast<ObjCMethodDecl>(LCtx->getDecl());
977  if (!MD || !MD->isInstanceMethod() || MD->getSelector() != DeallocSel)
978  return false;
979 
980  const ImplicitParamDecl *SelfDecl = LCtx->getSelfDecl();
981  assert(SelfDecl && "No self in -dealloc?");
982 
983  ProgramStateRef State = C.getState();
984  SelfValOut = State->getSVal(State->getRegion(SelfDecl, LCtx));
985  return true;
986 }
987 
988 /// Returns true if there is a call to -dealloc anywhere on the stack and false
989 /// otherwise. If true, it also sets InstanceValOut to the value of
990 /// 'self' in the frame for -dealloc.
991 bool ObjCDeallocChecker::instanceDeallocIsOnStack(const CheckerContext &C,
992  SVal &InstanceValOut) const {
993  const LocationContext *LCtx = C.getLocationContext();
994 
995  while (LCtx) {
996  if (isInInstanceDealloc(C, LCtx, InstanceValOut))
997  return true;
998 
999  LCtx = LCtx->getParent();
1000  }
1001 
1002  return false;
1003 }
1004 
1005 /// Returns true if the ID is a class in which which is known to have
1006 /// a separate teardown lifecycle. In this case, -dealloc warnings
1007 /// about missing releases should be suppressed.
1008 bool ObjCDeallocChecker::classHasSeparateTeardown(
1009  const ObjCInterfaceDecl *ID) const {
1010  // Suppress if the class is not a subclass of NSObject.
1011  for ( ; ID ; ID = ID->getSuperClass()) {
1012  IdentifierInfo *II = ID->getIdentifier();
1013 
1014  if (II == NSObjectII)
1015  return false;
1016 
1017  // FIXME: For now, ignore classes that subclass SenTestCase and XCTestCase,
1018  // as these don't need to implement -dealloc. They implement tear down in
1019  // another way, which we should try and catch later.
1020  // http://llvm.org/bugs/show_bug.cgi?id=3187
1021  if (II == XCTestCaseII || II == SenTestCaseII)
1022  return true;
1023  }
1024 
1025  return true;
1026 }
1027 
1028 /// The -dealloc method in CIFilter highly unusual in that is will release
1029 /// instance variables belonging to its *subclasses* if the variable name
1030 /// starts with "input" or backs a property whose name starts with "input".
1031 /// Subclasses should not release these ivars in their own -dealloc method --
1032 /// doing so could result in an over release.
1033 ///
1034 /// This method returns true if the property will be released by
1035 /// -[CIFilter dealloc].
1036 bool ObjCDeallocChecker::isReleasedByCIFilterDealloc(
1037  const ObjCPropertyImplDecl *PropImpl) const {
1038  assert(PropImpl->getPropertyIvarDecl());
1039  StringRef PropName = PropImpl->getPropertyDecl()->getName();
1040  StringRef IvarName = PropImpl->getPropertyIvarDecl()->getName();
1041 
1042  const char *ReleasePrefix = "input";
1043  if (!(PropName.startswith(ReleasePrefix) ||
1044  IvarName.startswith(ReleasePrefix))) {
1045  return false;
1046  }
1047 
1048  const ObjCInterfaceDecl *ID =
1050  for ( ; ID ; ID = ID->getSuperClass()) {
1051  IdentifierInfo *II = ID->getIdentifier();
1052  if (II == CIFilterII)
1053  return true;
1054  }
1055 
1056  return false;
1057 }
1058 
1059 /// Returns whether the ivar backing the property is an IBOutlet that
1060 /// has its value set by nib loading code without retaining the value.
1061 ///
1062 /// On macOS, if there is no setter, the nib-loading code sets the ivar
1063 /// directly, without retaining the value,
1064 ///
1065 /// On iOS and its derivatives, the nib-loading code will call
1066 /// -setValue:forKey:, which retains the value before directly setting the ivar.
1067 bool ObjCDeallocChecker::isNibLoadedIvarWithoutRetain(
1068  const ObjCPropertyImplDecl *PropImpl) const {
1069  const ObjCIvarDecl *IvarDecl = PropImpl->getPropertyIvarDecl();
1070  if (!IvarDecl->hasAttr<IBOutletAttr>())
1071  return false;
1072 
1073  const llvm::Triple &Target =
1074  IvarDecl->getASTContext().getTargetInfo().getTriple();
1075 
1076  if (!Target.isMacOSX())
1077  return false;
1078 
1079  if (PropImpl->getPropertyDecl()->getSetterMethodDecl())
1080  return false;
1081 
1082  return true;
1083 }
1084 
1085 void ento::registerObjCDeallocChecker(CheckerManager &Mgr) {
1086  const LangOptions &LangOpts = Mgr.getLangOpts();
1087  // These checker only makes sense under MRR.
1088  if (LangOpts.getGC() == LangOptions::GCOnly || LangOpts.ObjCAutoRefCount)
1089  return;
1090 
1091  Mgr.registerChecker<ObjCDeallocChecker>();
1092 }
The receiver is the instance of the superclass object.
Definition: ExprObjC.h:1061
SVal getReceiverSVal() const
Returns the value of the receiver at the time of this call.
Definition: CallEvent.cpp:960
const char *const CoreFoundationObjectiveC
Smart pointer class that efficiently represents Objective-C method names.
A (possibly-)qualified type.
Definition: Type.h:642
ObjCIvarDecl * getPropertyIvarDecl() const
Definition: DeclObjC.h:2819
llvm::DenseSet< SymbolRef > InvalidatedSymbols
Definition: Store.h:52
const SymExpr * SymbolRef
const llvm::Triple & getTriple() const
Returns the target triple of the primary target.
Definition: TargetInfo.h:949
IntrusiveRefCntPtr< const ProgramState > ProgramStateRef
const TargetInfo & getTargetInfo() const
Definition: ASTContext.h:689
ObjCMethodDecl - Represents an instance or class method declaration.
Definition: DeclObjC.h:139
The instance variable must be released, either by calling -release on it directly or by nilling it ou...
const char *const MemoryCoreFoundationObjectiveC
IdentifierInfo * getIdentifier() const
Get the identifier that names this declaration, if there is one.
Definition: Decl.h:269
One of these records is kept for each identifier that is lexed.
Holds long-lived AST nodes (such as types and decls) that can be referred to throughout the semantic ...
Definition: ASTContext.h:154
The results of name lookup within a DeclContext.
Definition: DeclBase.h:1187
LineState State
SetterKind getSetterKind() const
getSetterKind - Return the method used for doing assignment in the property setter.
Definition: DeclObjC.h:886
instmeth_range instance_methods() const
Definition: DeclObjC.h:1046
ObjCMethodDecl * getSetterMethodDecl() const
Definition: DeclObjC.h:917
Keeps track of the various options that can be enabled, which controls the dialect of C or C++ that i...
Definition: LangOptions.h:50
IdentifierTable & Idents
Definition: ASTContext.h:565
BinaryOperatorKind
Represents any expression that calls an Objective-C method.
Definition: CallEvent.h:970
const ImplicitParamDecl * getSelfDecl() const
virtual bool inTopFrame() const
Return true if the current LocationContext has no caller context.
const LocationContext * getParent() const
bool isReadOnly() const
isReadOnly - Return true iff the property has a setter.
Definition: DeclObjC.h:855
Represents an ObjC class declaration.
Definition: DeclObjC.h:1164
ObjCPropertyImplDecl - Represents implementation declaration of a property in a class or category imp...
Definition: DeclObjC.h:2751
bool hasAttr() const
Definition: DeclBase.h:531
bool isReceiverSelfOrSuper() const
Checks if the receiver refers to &#39;self&#39; or &#39;super&#39;.
Definition: CallEvent.cpp:976
Defines the clang::LangOptions interface.
bool isObjCRetainableType() const
Definition: Type.cpp:3915
DeclContext * getDeclContext()
Definition: DeclBase.h:427
ObjCInterfaceDecl * getSuperClass() const
Definition: DeclObjC.cpp:338
QualType getType() const
Definition: Expr.h:128
propimpl_range property_impls() const
Definition: DeclObjC.h:2459
ReturnStmt - This represents a return, optionally of an expression: return; return 4;...
Definition: Stmt.h:2226
ReceiverKind getReceiverKind() const
Determine the kind of receiver that this message is being sent to.
Definition: ExprObjC.h:1188
static PathDiagnosticLocation createBegin(const Decl *D, const SourceManager &SM)
Create a location for the beginning of the declaration.
SelectorTable & Selectors
Definition: ASTContext.h:566
Kind
IdentifierInfo & get(StringRef Name)
Return the identifier token info for the specified named identifier.
#define REGISTER_MAP_WITH_PROGRAMSTATE(Name, Key, Value)
Declares an immutable map of type NameTy, suitable for placement into the ProgramState.
#define REGISTER_SET_FACTORY_WITH_PROGRAMSTATE(Name, Elem)
Declares an immutable set type Name and registers the factory for such sets in the program state...
ASTContext & getASTContext() const LLVM_READONLY
Definition: DeclBase.cpp:376
ObjCCategoryDecl - Represents a category declaration.
Definition: DeclObjC.h:2272
Represents one property declaration in an Objective-C interface.
Definition: DeclObjC.h:721
ObjCPropertyImplDecl * FindPropertyImplIvarDecl(IdentifierInfo *ivarId) const
FindPropertyImplIvarDecl - This method lookup the ivar in the list of properties implemented in this ...
Definition: DeclObjC.cpp:2098
ObjCImplementationDecl * getImplementation() const
Definition: DeclObjC.cpp:1549
virtual const ObjCMessageExpr * getOriginExpr() const
Definition: CallEvent.h:994
const ObjCInterfaceDecl * getClassInterface() const
Definition: DeclObjC.h:2432
Selector getSelector() const
Definition: CallEvent.h:1018
Dataflow Directional Tag Classes.
Kind getPropertyImplementation() const
Definition: DeclObjC.h:2815
const ObjCInterfaceDecl * getContainingInterface() const
Return the class interface that this ivar is logically contained in; this is either the interface whe...
Definition: DeclObjC.cpp:1790
const Decl * getDecl() const
PointerEscapeKind
Describes the different reasons a pointer escapes during analysis.
ObjCImplementationDecl - Represents a class definition - this is where method definitions are specifi...
Definition: DeclObjC.h:2544
The requirement for the instance variable could not be determined.
static bool isSynthesizedRetainableProperty(const ObjCPropertyImplDecl *I, const ObjCIvarDecl **ID, const ObjCPropertyDecl **PD)
Returns true if the property implementation is synthesized and the type of the property is retainable...
Selector getSelector(unsigned NumArgs, IdentifierInfo **IIV)
Can create any sort of selector.
unsigned getNumArgs() const override
Definition: CallEvent.h:1002
The instance variable must not be directly released with -release.
const Expr * getArgExpr(unsigned Index) const override
Definition: CallEvent.h:1006
ReleaseRequirement
Indicates whether an instance variable is required to be released in -dealloc.
ObjCIvarDecl - Represents an ObjC instance variable.
Definition: DeclObjC.h:1937
ObjCIvarDecl * getPropertyIvarDecl() const
Definition: DeclObjC.h:937
SourceRange getSourceRange() const LLVM_READONLY
SourceLocation tokens are not useful in isolation - they are low level value objects created/interpre...
Definition: Stmt.cpp:276
Defines the clang::TargetInfo interface.
StringRef getName() const
Get the name of identifier for this declaration as a StringRef.
Definition: Decl.h:275
const ObjCPropertyDecl * getAccessedProperty() const
Definition: CallEvent.cpp:1064
ObjCPropertyDecl * getPropertyDecl() const
Definition: DeclObjC.h:2810