clang  10.0.0svn
ObjCSuperDeallocChecker.cpp
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1 //===- ObjCSuperDeallocChecker.cpp - Check correct use of [super dealloc] -===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This defines ObjCSuperDeallocChecker, a builtin check that warns when
10 // self is used after a call to [super dealloc] in MRR mode.
11 //
12 //===----------------------------------------------------------------------===//
13 
21 
22 using namespace clang;
23 using namespace ento;
24 
25 namespace {
26 class ObjCSuperDeallocChecker
27  : public Checker<check::PostObjCMessage, check::PreObjCMessage,
28  check::PreCall, check::Location> {
29 
30  mutable IdentifierInfo *IIdealloc, *IINSObject;
31  mutable Selector SELdealloc;
32 
33  std::unique_ptr<BugType> DoubleSuperDeallocBugType;
34 
35  void initIdentifierInfoAndSelectors(ASTContext &Ctx) const;
36 
37  bool isSuperDeallocMessage(const ObjCMethodCall &M) const;
38 
39 public:
40  ObjCSuperDeallocChecker();
41  void checkPostObjCMessage(const ObjCMethodCall &M, CheckerContext &C) const;
42  void checkPreObjCMessage(const ObjCMethodCall &M, CheckerContext &C) const;
43 
44  void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
45 
46  void checkLocation(SVal l, bool isLoad, const Stmt *S,
47  CheckerContext &C) const;
48 
49 private:
50 
51  void diagnoseCallArguments(const CallEvent &CE, CheckerContext &C) const;
52 
53  void reportUseAfterDealloc(SymbolRef Sym, StringRef Desc, const Stmt *S,
54  CheckerContext &C) const;
55 };
56 
57 } // End anonymous namespace.
58 
59 // Remember whether [super dealloc] has previously been called on the
60 // SymbolRef for the receiver.
61 REGISTER_SET_WITH_PROGRAMSTATE(CalledSuperDealloc, SymbolRef)
62 
63 namespace {
64 class SuperDeallocBRVisitor final : public BugReporterVisitor {
65  SymbolRef ReceiverSymbol;
66  bool Satisfied;
67 
68 public:
69  SuperDeallocBRVisitor(SymbolRef ReceiverSymbol)
70  : ReceiverSymbol(ReceiverSymbol), Satisfied(false) {}
71 
72  PathDiagnosticPieceRef VisitNode(const ExplodedNode *Succ,
73  BugReporterContext &BRC,
74  PathSensitiveBugReport &BR) override;
75 
76  void Profile(llvm::FoldingSetNodeID &ID) const override {
77  ID.Add(ReceiverSymbol);
78  }
79 };
80 } // End anonymous namespace.
81 
82 void ObjCSuperDeallocChecker::checkPreObjCMessage(const ObjCMethodCall &M,
83  CheckerContext &C) const {
84 
85  ProgramStateRef State = C.getState();
86  SymbolRef ReceiverSymbol = M.getReceiverSVal().getAsSymbol();
87  if (!ReceiverSymbol) {
88  diagnoseCallArguments(M, C);
89  return;
90  }
91 
92  bool AlreadyCalled = State->contains<CalledSuperDealloc>(ReceiverSymbol);
93  if (!AlreadyCalled)
94  return;
95 
96  StringRef Desc;
97 
98  if (isSuperDeallocMessage(M)) {
99  Desc = "[super dealloc] should not be called multiple times";
100  } else {
101  Desc = StringRef();
102  }
103 
104  reportUseAfterDealloc(ReceiverSymbol, Desc, M.getOriginExpr(), C);
105 }
106 
107 void ObjCSuperDeallocChecker::checkPreCall(const CallEvent &Call,
108  CheckerContext &C) const {
109  diagnoseCallArguments(Call, C);
110 }
111 
112 void ObjCSuperDeallocChecker::checkPostObjCMessage(const ObjCMethodCall &M,
113  CheckerContext &C) const {
114  // Check for [super dealloc] method call.
115  if (!isSuperDeallocMessage(M))
116  return;
117 
118  ProgramStateRef State = C.getState();
119  SymbolRef ReceiverSymbol = M.getSelfSVal().getAsSymbol();
120  assert(ReceiverSymbol && "No receiver symbol at call to [super dealloc]?");
121 
122  // We add this transition in checkPostObjCMessage to avoid warning when
123  // we inline a call to [super dealloc] where the inlined call itself
124  // calls [super dealloc].
125  State = State->add<CalledSuperDealloc>(ReceiverSymbol);
126  C.addTransition(State);
127 }
128 
129 void ObjCSuperDeallocChecker::checkLocation(SVal L, bool IsLoad, const Stmt *S,
130  CheckerContext &C) const {
131  SymbolRef BaseSym = L.getLocSymbolInBase();
132  if (!BaseSym)
133  return;
134 
135  ProgramStateRef State = C.getState();
136 
137  if (!State->contains<CalledSuperDealloc>(BaseSym))
138  return;
139 
140  const MemRegion *R = L.getAsRegion();
141  if (!R)
142  return;
143 
144  // Climb the super regions to find the base symbol while recording
145  // the second-to-last region for error reporting.
146  const MemRegion *PriorSubRegion = nullptr;
147  while (const SubRegion *SR = dyn_cast<SubRegion>(R)) {
148  if (const SymbolicRegion *SymR = dyn_cast<SymbolicRegion>(SR)) {
149  BaseSym = SymR->getSymbol();
150  break;
151  } else {
152  R = SR->getSuperRegion();
153  PriorSubRegion = SR;
154  }
155  }
156 
157  StringRef Desc = StringRef();
158  auto *IvarRegion = dyn_cast_or_null<ObjCIvarRegion>(PriorSubRegion);
159 
160  std::string Buf;
161  llvm::raw_string_ostream OS(Buf);
162  if (IvarRegion) {
163  OS << "Use of instance variable '" << *IvarRegion->getDecl() <<
164  "' after 'self' has been deallocated";
165  Desc = OS.str();
166  }
167 
168  reportUseAfterDealloc(BaseSym, Desc, S, C);
169 }
170 
171 /// Report a use-after-dealloc on Sym. If not empty,
172 /// Desc will be used to describe the error; otherwise,
173 /// a default warning will be used.
174 void ObjCSuperDeallocChecker::reportUseAfterDealloc(SymbolRef Sym,
175  StringRef Desc,
176  const Stmt *S,
177  CheckerContext &C) const {
178  // We have a use of self after free.
179  // This likely causes a crash, so stop exploring the
180  // path by generating a sink.
181  ExplodedNode *ErrNode = C.generateErrorNode();
182  // If we've already reached this node on another path, return.
183  if (!ErrNode)
184  return;
185 
186  if (Desc.empty())
187  Desc = "Use of 'self' after it has been deallocated";
188 
189  // Generate the report.
190  auto BR = std::make_unique<PathSensitiveBugReport>(*DoubleSuperDeallocBugType,
191  Desc, ErrNode);
192  BR->addRange(S->getSourceRange());
193  BR->addVisitor(std::make_unique<SuperDeallocBRVisitor>(Sym));
194  C.emitReport(std::move(BR));
195 }
196 
197 /// Diagnose if any of the arguments to CE have already been
198 /// dealloc'd.
199 void ObjCSuperDeallocChecker::diagnoseCallArguments(const CallEvent &CE,
200  CheckerContext &C) const {
201  ProgramStateRef State = C.getState();
202  unsigned ArgCount = CE.getNumArgs();
203  for (unsigned I = 0; I < ArgCount; I++) {
204  SymbolRef Sym = CE.getArgSVal(I).getAsSymbol();
205  if (!Sym)
206  continue;
207 
208  if (State->contains<CalledSuperDealloc>(Sym)) {
209  reportUseAfterDealloc(Sym, StringRef(), CE.getArgExpr(I), C);
210  return;
211  }
212  }
213 }
214 
215 ObjCSuperDeallocChecker::ObjCSuperDeallocChecker()
216  : IIdealloc(nullptr), IINSObject(nullptr) {
217 
218  DoubleSuperDeallocBugType.reset(
219  new BugType(this, "[super dealloc] should not be called more than once",
221 }
222 
223 void
224 ObjCSuperDeallocChecker::initIdentifierInfoAndSelectors(ASTContext &Ctx) const {
225  if (IIdealloc)
226  return;
227 
228  IIdealloc = &Ctx.Idents.get("dealloc");
229  IINSObject = &Ctx.Idents.get("NSObject");
230 
231  SELdealloc = Ctx.Selectors.getSelector(0, &IIdealloc);
232 }
233 
234 bool
235 ObjCSuperDeallocChecker::isSuperDeallocMessage(const ObjCMethodCall &M) const {
236  if (M.getOriginExpr()->getReceiverKind() != ObjCMessageExpr::SuperInstance)
237  return false;
238 
239  ASTContext &Ctx = M.getState()->getStateManager().getContext();
240  initIdentifierInfoAndSelectors(Ctx);
241 
242  return M.getSelector() == SELdealloc;
243 }
244 
246 SuperDeallocBRVisitor::VisitNode(const ExplodedNode *Succ,
247  BugReporterContext &BRC,
248  PathSensitiveBugReport &) {
249  if (Satisfied)
250  return nullptr;
251 
252  ProgramStateRef State = Succ->getState();
253 
254  bool CalledNow =
255  Succ->getState()->contains<CalledSuperDealloc>(ReceiverSymbol);
256  bool CalledBefore =
257  Succ->getFirstPred()->getState()->contains<CalledSuperDealloc>(
258  ReceiverSymbol);
259 
260  // Is Succ the node on which the analyzer noted that [super dealloc] was
261  // called on ReceiverSymbol?
262  if (CalledNow && !CalledBefore) {
263  Satisfied = true;
264 
265  ProgramPoint P = Succ->getLocation();
266  PathDiagnosticLocation L =
267  PathDiagnosticLocation::create(P, BRC.getSourceManager());
268 
269  if (!L.isValid() || !L.asLocation().isValid())
270  return nullptr;
271 
272  return std::make_shared<PathDiagnosticEventPiece>(
273  L, "[super dealloc] called here");
274  }
275 
276  return nullptr;
277 }
278 
279 //===----------------------------------------------------------------------===//
280 // Checker Registration.
281 //===----------------------------------------------------------------------===//
282 
283 void ento::registerObjCSuperDeallocChecker(CheckerManager &Mgr) {
284  Mgr.registerChecker<ObjCSuperDeallocChecker>();
285 }
286 
287 bool ento::shouldRegisterObjCSuperDeallocChecker(const LangOptions &LO) {
288  return true;
289 }
SVal getSelfSVal() const
Return the value of &#39;self&#39; if available.
Definition: CallEvent.cpp:969
SVal getReceiverSVal() const
Returns the value of the receiver at the time of this call.
Definition: CallEvent.cpp:977
const char *const CoreFoundationObjectiveC
Smart pointer class that efficiently represents Objective-C method names.
Stmt - This represents one statement.
Definition: Stmt.h:66
IntrusiveRefCntPtr< const ProgramState > ProgramStateRef
StringRef P
One of these records is kept for each identifier that is lexed.
const SymExpr * SymbolRef
Definition: SymExpr.h:110
Holds long-lived AST nodes (such as types and decls) that can be referred to throughout the semantic ...
Definition: ASTContext.h:160
LineState State
Keeps track of the various options that can be enabled, which controls the dialect of C or C++ that i...
Definition: LangOptions.h:49
IdentifierTable & Idents
Definition: ASTContext.h:579
std::shared_ptr< PathDiagnosticPiece > PathDiagnosticPieceRef
Represents any expression that calls an Objective-C method.
Definition: CallEvent.h:938
ReceiverKind getReceiverKind() const
Determine the kind of receiver that this message is being sent to.
Definition: ExprObjC.h:1234
#define false
Definition: stdbool.h:17
SelectorTable & Selectors
Definition: ASTContext.h:580
IdentifierInfo & get(StringRef Name)
Return the identifier token info for the specified named identifier.
virtual const ObjCMessageExpr * getOriginExpr() const
Definition: CallEvent.h:962
#define REGISTER_SET_WITH_PROGRAMSTATE(Name, Elem)
Declares an immutable set of type NameTy, suitable for placement into the ProgramState.
Selector getSelector() const
Definition: CallEvent.h:986
Dataflow Directional Tag Classes.
std::unique_ptr< DiagnosticConsumer > create(StringRef OutputFile, DiagnosticOptions *Diags, bool MergeChildRecords=false)
Returns a DiagnosticConsumer that serializes diagnostics to a bitcode file.
Indicates that the tracking object is a descendant of a referenced-counted OSObject, used in the Darwin kernel.
Selector getSelector(unsigned NumArgs, IdentifierInfo **IIV)
Can create any sort of selector.
SourceRange getSourceRange() const LLVM_READONLY
SourceLocation tokens are not useful in isolation - they are low level value objects created/interpre...
Definition: Stmt.cpp:262