xref: /llvm-project/clang/lib/StaticAnalyzer/Checkers/MallocChecker.cpp (revision 8dc53af5dcbbcbb00faf3ed3cc3e62c982007144)
1 //=== MallocChecker.cpp - A malloc/free checker -------------------*- 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 file defines malloc/free checker, which checks for potential memory
11 // leaks, double free, and use-after-free problems.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "ClangSACheckers.h"
16 #include "InterCheckerAPI.h"
17 #include "clang/StaticAnalyzer/Core/Checker.h"
18 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
19 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
20 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
21 #include "clang/StaticAnalyzer/Core/PathSensitive/ObjCMessage.h"
22 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
23 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
24 #include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
25 #include "clang/Basic/SourceManager.h"
26 #include "llvm/ADT/ImmutableMap.h"
27 #include "llvm/ADT/SmallString.h"
28 #include "llvm/ADT/STLExtras.h"
29 #include <climits>
30 
31 using namespace clang;
32 using namespace ento;
33 
34 namespace {
35 
36 class RefState {
37   enum Kind { AllocateUnchecked, AllocateFailed, Released, Escaped,
38               Relinquished } K;
39   const Stmt *S;
40 
41 public:
42   RefState(Kind k, const Stmt *s) : K(k), S(s) {}
43 
44   bool isAllocated() const { return K == AllocateUnchecked; }
45   bool isReleased() const { return K == Released; }
46 
47   const Stmt *getStmt() const { return S; }
48 
49   bool operator==(const RefState &X) const {
50     return K == X.K && S == X.S;
51   }
52 
53   static RefState getAllocateUnchecked(const Stmt *s) {
54     return RefState(AllocateUnchecked, s);
55   }
56   static RefState getAllocateFailed() {
57     return RefState(AllocateFailed, 0);
58   }
59   static RefState getReleased(const Stmt *s) { return RefState(Released, s); }
60   static RefState getEscaped(const Stmt *s) { return RefState(Escaped, s); }
61   static RefState getRelinquished(const Stmt *s) {
62     return RefState(Relinquished, s);
63   }
64 
65   void Profile(llvm::FoldingSetNodeID &ID) const {
66     ID.AddInteger(K);
67     ID.AddPointer(S);
68   }
69 };
70 
71 struct ReallocPair {
72   SymbolRef ReallocatedSym;
73   bool IsFreeOnFailure;
74   ReallocPair(SymbolRef S, bool F) : ReallocatedSym(S), IsFreeOnFailure(F) {}
75   void Profile(llvm::FoldingSetNodeID &ID) const {
76     ID.AddInteger(IsFreeOnFailure);
77     ID.AddPointer(ReallocatedSym);
78   }
79   bool operator==(const ReallocPair &X) const {
80     return ReallocatedSym == X.ReallocatedSym &&
81            IsFreeOnFailure == X.IsFreeOnFailure;
82   }
83 };
84 
85 class MallocChecker : public Checker<check::DeadSymbols,
86                                      check::EndPath,
87                                      check::PreStmt<ReturnStmt>,
88                                      check::PreStmt<CallExpr>,
89                                      check::PostStmt<CallExpr>,
90                                      check::Location,
91                                      check::Bind,
92                                      eval::Assume,
93                                      check::RegionChanges>
94 {
95   mutable OwningPtr<BugType> BT_DoubleFree;
96   mutable OwningPtr<BugType> BT_Leak;
97   mutable OwningPtr<BugType> BT_UseFree;
98   mutable OwningPtr<BugType> BT_BadFree;
99   mutable IdentifierInfo *II_malloc, *II_free, *II_realloc, *II_calloc,
100                          *II_valloc, *II_reallocf, *II_strndup, *II_strdup;
101 
102   static const unsigned InvalidArgIndex = UINT_MAX;
103 
104 public:
105   MallocChecker() : II_malloc(0), II_free(0), II_realloc(0), II_calloc(0),
106                     II_valloc(0), II_reallocf(0), II_strndup(0), II_strdup(0) {}
107 
108   /// In pessimistic mode, the checker assumes that it does not know which
109   /// functions might free the memory.
110   struct ChecksFilter {
111     DefaultBool CMallocPessimistic;
112     DefaultBool CMallocOptimistic;
113   };
114 
115   ChecksFilter Filter;
116 
117   void checkPreStmt(const CallExpr *S, CheckerContext &C) const;
118   void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
119   void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;
120   void checkEndPath(CheckerContext &C) const;
121   void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const;
122   ProgramStateRef evalAssume(ProgramStateRef state, SVal Cond,
123                             bool Assumption) const;
124   void checkLocation(SVal l, bool isLoad, const Stmt *S,
125                      CheckerContext &C) const;
126   void checkBind(SVal location, SVal val, const Stmt*S,
127                  CheckerContext &C) const;
128   ProgramStateRef
129   checkRegionChanges(ProgramStateRef state,
130                      const StoreManager::InvalidatedSymbols *invalidated,
131                      ArrayRef<const MemRegion *> ExplicitRegions,
132                      ArrayRef<const MemRegion *> Regions,
133                      const CallOrObjCMessage *Call) const;
134   bool wantsRegionChangeUpdate(ProgramStateRef state) const {
135     return true;
136   }
137 
138 private:
139   void initIdentifierInfo(ASTContext &C) const;
140 
141   /// Check if this is one of the functions which can allocate/reallocate memory
142   /// pointed to by one of its arguments.
143   bool isMemFunction(const FunctionDecl *FD, ASTContext &C) const;
144 
145   static ProgramStateRef MallocMemReturnsAttr(CheckerContext &C,
146                                               const CallExpr *CE,
147                                               const OwnershipAttr* Att);
148   static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
149                                      const Expr *SizeEx, SVal Init,
150                                      ProgramStateRef state) {
151     return MallocMemAux(C, CE,
152                         state->getSVal(SizeEx, C.getLocationContext()),
153                         Init, state);
154   }
155 
156   static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
157                                      SVal SizeEx, SVal Init,
158                                      ProgramStateRef state);
159 
160   /// Update the RefState to reflect the new memory allocation.
161   static ProgramStateRef MallocUpdateRefState(CheckerContext &C,
162                                               const CallExpr *CE,
163                                               ProgramStateRef state);
164 
165   ProgramStateRef FreeMemAttr(CheckerContext &C, const CallExpr *CE,
166                               const OwnershipAttr* Att) const;
167   ProgramStateRef FreeMemAux(CheckerContext &C, const CallExpr *CE,
168                                  ProgramStateRef state, unsigned Num,
169                                  bool Hold) const;
170 
171   ProgramStateRef ReallocMem(CheckerContext &C, const CallExpr *CE,
172                              bool FreesMemOnFailure) const;
173   static ProgramStateRef CallocMem(CheckerContext &C, const CallExpr *CE);
174 
175   bool checkEscape(SymbolRef Sym, const Stmt *S, CheckerContext &C) const;
176   bool checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
177                          const Stmt *S = 0) const;
178 
179   /// Check if the function is not known to us. So, for example, we could
180   /// conservatively assume it can free/reallocate it's pointer arguments.
181   bool doesNotFreeMemory(const CallOrObjCMessage *Call,
182                          ProgramStateRef State) const;
183 
184   static bool SummarizeValue(raw_ostream &os, SVal V);
185   static bool SummarizeRegion(raw_ostream &os, const MemRegion *MR);
186   void ReportBadFree(CheckerContext &C, SVal ArgVal, SourceRange range) const;
187 
188   /// Find the location of the allocation for Sym on the path leading to the
189   /// exploded node N.
190   const Stmt *getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
191                                 CheckerContext &C) const;
192 
193   void reportLeak(SymbolRef Sym, ExplodedNode *N, CheckerContext &C) const;
194 
195   /// The bug visitor which allows us to print extra diagnostics along the
196   /// BugReport path. For example, showing the allocation site of the leaked
197   /// region.
198   class MallocBugVisitor : public BugReporterVisitor {
199   protected:
200     enum NotificationMode {
201       Normal,
202       Complete,
203       ReallocationFailed
204     };
205 
206     // The allocated region symbol tracked by the main analysis.
207     SymbolRef Sym;
208     NotificationMode Mode;
209 
210   public:
211     MallocBugVisitor(SymbolRef S) : Sym(S), Mode(Normal) {}
212     virtual ~MallocBugVisitor() {}
213 
214     void Profile(llvm::FoldingSetNodeID &ID) const {
215       static int X = 0;
216       ID.AddPointer(&X);
217       ID.AddPointer(Sym);
218     }
219 
220     inline bool isAllocated(const RefState *S, const RefState *SPrev,
221                             const Stmt *Stmt) {
222       // Did not track -> allocated. Other state (released) -> allocated.
223       return (Stmt && isa<CallExpr>(Stmt) &&
224               (S && S->isAllocated()) && (!SPrev || !SPrev->isAllocated()));
225     }
226 
227     inline bool isReleased(const RefState *S, const RefState *SPrev,
228                            const Stmt *Stmt) {
229       // Did not track -> released. Other state (allocated) -> released.
230       return (Stmt && isa<CallExpr>(Stmt) &&
231               (S && S->isReleased()) && (!SPrev || !SPrev->isReleased()));
232     }
233 
234     inline bool isReallocFailedCheck(const RefState *S, const RefState *SPrev,
235                                      const Stmt *Stmt) {
236       // If the expression is not a call, and the state change is
237       // released -> allocated, it must be the realloc return value
238       // check. If we have to handle more cases here, it might be cleaner just
239       // to track this extra bit in the state itself.
240       return ((!Stmt || !isa<CallExpr>(Stmt)) &&
241               (S && S->isAllocated()) && (SPrev && !SPrev->isAllocated()));
242     }
243 
244     PathDiagnosticPiece *VisitNode(const ExplodedNode *N,
245                                    const ExplodedNode *PrevN,
246                                    BugReporterContext &BRC,
247                                    BugReport &BR);
248   };
249 };
250 } // end anonymous namespace
251 
252 typedef llvm::ImmutableMap<SymbolRef, RefState> RegionStateTy;
253 typedef llvm::ImmutableMap<SymbolRef, ReallocPair > ReallocMap;
254 class RegionState {};
255 class ReallocPairs {};
256 namespace clang {
257 namespace ento {
258   template <>
259   struct ProgramStateTrait<RegionState>
260     : public ProgramStatePartialTrait<RegionStateTy> {
261     static void *GDMIndex() { static int x; return &x; }
262   };
263 
264   template <>
265   struct ProgramStateTrait<ReallocPairs>
266     : public ProgramStatePartialTrait<ReallocMap> {
267     static void *GDMIndex() { static int x; return &x; }
268   };
269 }
270 }
271 
272 namespace {
273 class StopTrackingCallback : public SymbolVisitor {
274   ProgramStateRef state;
275 public:
276   StopTrackingCallback(ProgramStateRef st) : state(st) {}
277   ProgramStateRef getState() const { return state; }
278 
279   bool VisitSymbol(SymbolRef sym) {
280     state = state->remove<RegionState>(sym);
281     return true;
282   }
283 };
284 } // end anonymous namespace
285 
286 void MallocChecker::initIdentifierInfo(ASTContext &Ctx) const {
287   if (!II_malloc)
288     II_malloc = &Ctx.Idents.get("malloc");
289   if (!II_free)
290     II_free = &Ctx.Idents.get("free");
291   if (!II_realloc)
292     II_realloc = &Ctx.Idents.get("realloc");
293   if (!II_reallocf)
294     II_reallocf = &Ctx.Idents.get("reallocf");
295   if (!II_calloc)
296     II_calloc = &Ctx.Idents.get("calloc");
297   if (!II_valloc)
298     II_valloc = &Ctx.Idents.get("valloc");
299   if (!II_strdup)
300     II_strdup = &Ctx.Idents.get("strdup");
301   if (!II_strndup)
302     II_strndup = &Ctx.Idents.get("strndup");
303 }
304 
305 bool MallocChecker::isMemFunction(const FunctionDecl *FD, ASTContext &C) const {
306   if (!FD)
307     return false;
308   IdentifierInfo *FunI = FD->getIdentifier();
309   if (!FunI)
310     return false;
311 
312   initIdentifierInfo(C);
313 
314   if (FunI == II_malloc || FunI == II_free || FunI == II_realloc ||
315       FunI == II_reallocf || FunI == II_calloc || FunI == II_valloc ||
316       FunI == II_strdup || FunI == II_strndup)
317     return true;
318 
319   if (Filter.CMallocOptimistic && FD->hasAttrs() &&
320       FD->specific_attr_begin<OwnershipAttr>() !=
321           FD->specific_attr_end<OwnershipAttr>())
322     return true;
323 
324 
325   return false;
326 }
327 
328 void MallocChecker::checkPostStmt(const CallExpr *CE, CheckerContext &C) const {
329   const FunctionDecl *FD = C.getCalleeDecl(CE);
330   if (!FD)
331     return;
332 
333   initIdentifierInfo(C.getASTContext());
334   IdentifierInfo *FunI = FD->getIdentifier();
335   if (!FunI)
336     return;
337 
338   ProgramStateRef State = C.getState();
339   if (FunI == II_malloc || FunI == II_valloc) {
340     State = MallocMemAux(C, CE, CE->getArg(0), UndefinedVal(), State);
341   } else if (FunI == II_realloc) {
342     State = ReallocMem(C, CE, false);
343   } else if (FunI == II_reallocf) {
344     State = ReallocMem(C, CE, true);
345   } else if (FunI == II_calloc) {
346     State = CallocMem(C, CE);
347   } else if (FunI == II_free) {
348     State = FreeMemAux(C, CE, C.getState(), 0, false);
349   } else if (FunI == II_strdup) {
350     State = MallocUpdateRefState(C, CE, State);
351   } else if (FunI == II_strndup) {
352     State = MallocUpdateRefState(C, CE, State);
353   } else if (Filter.CMallocOptimistic) {
354     // Check all the attributes, if there are any.
355     // There can be multiple of these attributes.
356     if (FD->hasAttrs())
357       for (specific_attr_iterator<OwnershipAttr>
358           i = FD->specific_attr_begin<OwnershipAttr>(),
359           e = FD->specific_attr_end<OwnershipAttr>();
360           i != e; ++i) {
361         switch ((*i)->getOwnKind()) {
362         case OwnershipAttr::Returns:
363           State = MallocMemReturnsAttr(C, CE, *i);
364           break;
365         case OwnershipAttr::Takes:
366         case OwnershipAttr::Holds:
367           State = FreeMemAttr(C, CE, *i);
368           break;
369         }
370       }
371   }
372   C.addTransition(State);
373 }
374 
375 ProgramStateRef MallocChecker::MallocMemReturnsAttr(CheckerContext &C,
376                                                     const CallExpr *CE,
377                                                     const OwnershipAttr* Att) {
378   if (Att->getModule() != "malloc")
379     return 0;
380 
381   OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
382   if (I != E) {
383     return MallocMemAux(C, CE, CE->getArg(*I), UndefinedVal(), C.getState());
384   }
385   return MallocMemAux(C, CE, UnknownVal(), UndefinedVal(), C.getState());
386 }
387 
388 ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C,
389                                            const CallExpr *CE,
390                                            SVal Size, SVal Init,
391                                            ProgramStateRef state) {
392   // Get the return value.
393   SVal retVal = state->getSVal(CE, C.getLocationContext());
394 
395   // We expect the malloc functions to return a pointer.
396   if (!isa<Loc>(retVal))
397     return 0;
398 
399   // Fill the region with the initialization value.
400   state = state->bindDefault(retVal, Init);
401 
402   // Set the region's extent equal to the Size parameter.
403   const SymbolicRegion *R =
404       dyn_cast_or_null<SymbolicRegion>(retVal.getAsRegion());
405   if (!R)
406     return 0;
407   if (isa<DefinedOrUnknownSVal>(Size)) {
408     SValBuilder &svalBuilder = C.getSValBuilder();
409     DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder);
410     DefinedOrUnknownSVal DefinedSize = cast<DefinedOrUnknownSVal>(Size);
411     DefinedOrUnknownSVal extentMatchesSize =
412         svalBuilder.evalEQ(state, Extent, DefinedSize);
413 
414     state = state->assume(extentMatchesSize, true);
415     assert(state);
416   }
417 
418   return MallocUpdateRefState(C, CE, state);
419 }
420 
421 ProgramStateRef MallocChecker::MallocUpdateRefState(CheckerContext &C,
422                                                     const CallExpr *CE,
423                                                     ProgramStateRef state) {
424   // Get the return value.
425   SVal retVal = state->getSVal(CE, C.getLocationContext());
426 
427   // We expect the malloc functions to return a pointer.
428   if (!isa<Loc>(retVal))
429     return 0;
430 
431   SymbolRef Sym = retVal.getAsLocSymbol();
432   assert(Sym);
433 
434   // Set the symbol's state to Allocated.
435   return state->set<RegionState>(Sym, RefState::getAllocateUnchecked(CE));
436 
437 }
438 
439 ProgramStateRef MallocChecker::FreeMemAttr(CheckerContext &C,
440                                            const CallExpr *CE,
441                                            const OwnershipAttr* Att) const {
442   if (Att->getModule() != "malloc")
443     return 0;
444 
445   ProgramStateRef State = C.getState();
446 
447   for (OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
448        I != E; ++I) {
449     ProgramStateRef StateI = FreeMemAux(C, CE, State, *I,
450                                Att->getOwnKind() == OwnershipAttr::Holds);
451     if (StateI)
452       State = StateI;
453   }
454   return State;
455 }
456 
457 ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
458                                           const CallExpr *CE,
459                                           ProgramStateRef state,
460                                           unsigned Num,
461                                           bool Hold) const {
462   const Expr *ArgExpr = CE->getArg(Num);
463   SVal ArgVal = state->getSVal(ArgExpr, C.getLocationContext());
464   if (!isa<DefinedOrUnknownSVal>(ArgVal))
465     return 0;
466   DefinedOrUnknownSVal location = cast<DefinedOrUnknownSVal>(ArgVal);
467 
468   // Check for null dereferences.
469   if (!isa<Loc>(location))
470     return 0;
471 
472   // The explicit NULL case, no operation is performed.
473   ProgramStateRef notNullState, nullState;
474   llvm::tie(notNullState, nullState) = state->assume(location);
475   if (nullState && !notNullState)
476     return 0;
477 
478   // Unknown values could easily be okay
479   // Undefined values are handled elsewhere
480   if (ArgVal.isUnknownOrUndef())
481     return 0;
482 
483   const MemRegion *R = ArgVal.getAsRegion();
484 
485   // Nonlocs can't be freed, of course.
486   // Non-region locations (labels and fixed addresses) also shouldn't be freed.
487   if (!R) {
488     ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
489     return 0;
490   }
491 
492   R = R->StripCasts();
493 
494   // Blocks might show up as heap data, but should not be free()d
495   if (isa<BlockDataRegion>(R)) {
496     ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
497     return 0;
498   }
499 
500   const MemSpaceRegion *MS = R->getMemorySpace();
501 
502   // Parameters, locals, statics, and globals shouldn't be freed.
503   if (!(isa<UnknownSpaceRegion>(MS) || isa<HeapSpaceRegion>(MS))) {
504     // FIXME: at the time this code was written, malloc() regions were
505     // represented by conjured symbols, which are all in UnknownSpaceRegion.
506     // This means that there isn't actually anything from HeapSpaceRegion
507     // that should be freed, even though we allow it here.
508     // Of course, free() can work on memory allocated outside the current
509     // function, so UnknownSpaceRegion is always a possibility.
510     // False negatives are better than false positives.
511 
512     ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
513     return 0;
514   }
515 
516   const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R);
517   // Various cases could lead to non-symbol values here.
518   // For now, ignore them.
519   if (!SR)
520     return 0;
521 
522   SymbolRef Sym = SR->getSymbol();
523   const RefState *RS = state->get<RegionState>(Sym);
524 
525   // If the symbol has not been tracked, return. This is possible when free() is
526   // called on a pointer that does not get its pointee directly from malloc().
527   // Full support of this requires inter-procedural analysis.
528   if (!RS)
529     return 0;
530 
531   // Check double free.
532   if (RS->isReleased()) {
533     if (ExplodedNode *N = C.generateSink()) {
534       if (!BT_DoubleFree)
535         BT_DoubleFree.reset(
536           new BugType("Double free", "Memory Error"));
537       BugReport *R = new BugReport(*BT_DoubleFree,
538                         "Attempt to free released memory", N);
539       R->addRange(ArgExpr->getSourceRange());
540       R->addVisitor(new MallocBugVisitor(Sym));
541       C.EmitReport(R);
542     }
543     return 0;
544   }
545 
546   // Normal free.
547   if (Hold)
548     return state->set<RegionState>(Sym, RefState::getRelinquished(CE));
549   return state->set<RegionState>(Sym, RefState::getReleased(CE));
550 }
551 
552 bool MallocChecker::SummarizeValue(raw_ostream &os, SVal V) {
553   if (nonloc::ConcreteInt *IntVal = dyn_cast<nonloc::ConcreteInt>(&V))
554     os << "an integer (" << IntVal->getValue() << ")";
555   else if (loc::ConcreteInt *ConstAddr = dyn_cast<loc::ConcreteInt>(&V))
556     os << "a constant address (" << ConstAddr->getValue() << ")";
557   else if (loc::GotoLabel *Label = dyn_cast<loc::GotoLabel>(&V))
558     os << "the address of the label '" << Label->getLabel()->getName() << "'";
559   else
560     return false;
561 
562   return true;
563 }
564 
565 bool MallocChecker::SummarizeRegion(raw_ostream &os,
566                                     const MemRegion *MR) {
567   switch (MR->getKind()) {
568   case MemRegion::FunctionTextRegionKind: {
569     const FunctionDecl *FD = cast<FunctionTextRegion>(MR)->getDecl();
570     if (FD)
571       os << "the address of the function '" << *FD << '\'';
572     else
573       os << "the address of a function";
574     return true;
575   }
576   case MemRegion::BlockTextRegionKind:
577     os << "block text";
578     return true;
579   case MemRegion::BlockDataRegionKind:
580     // FIXME: where the block came from?
581     os << "a block";
582     return true;
583   default: {
584     const MemSpaceRegion *MS = MR->getMemorySpace();
585 
586     if (isa<StackLocalsSpaceRegion>(MS)) {
587       const VarRegion *VR = dyn_cast<VarRegion>(MR);
588       const VarDecl *VD;
589       if (VR)
590         VD = VR->getDecl();
591       else
592         VD = NULL;
593 
594       if (VD)
595         os << "the address of the local variable '" << VD->getName() << "'";
596       else
597         os << "the address of a local stack variable";
598       return true;
599     }
600 
601     if (isa<StackArgumentsSpaceRegion>(MS)) {
602       const VarRegion *VR = dyn_cast<VarRegion>(MR);
603       const VarDecl *VD;
604       if (VR)
605         VD = VR->getDecl();
606       else
607         VD = NULL;
608 
609       if (VD)
610         os << "the address of the parameter '" << VD->getName() << "'";
611       else
612         os << "the address of a parameter";
613       return true;
614     }
615 
616     if (isa<GlobalsSpaceRegion>(MS)) {
617       const VarRegion *VR = dyn_cast<VarRegion>(MR);
618       const VarDecl *VD;
619       if (VR)
620         VD = VR->getDecl();
621       else
622         VD = NULL;
623 
624       if (VD) {
625         if (VD->isStaticLocal())
626           os << "the address of the static variable '" << VD->getName() << "'";
627         else
628           os << "the address of the global variable '" << VD->getName() << "'";
629       } else
630         os << "the address of a global variable";
631       return true;
632     }
633 
634     return false;
635   }
636   }
637 }
638 
639 void MallocChecker::ReportBadFree(CheckerContext &C, SVal ArgVal,
640                                   SourceRange range) const {
641   if (ExplodedNode *N = C.generateSink()) {
642     if (!BT_BadFree)
643       BT_BadFree.reset(new BugType("Bad free", "Memory Error"));
644 
645     SmallString<100> buf;
646     llvm::raw_svector_ostream os(buf);
647 
648     const MemRegion *MR = ArgVal.getAsRegion();
649     if (MR) {
650       while (const ElementRegion *ER = dyn_cast<ElementRegion>(MR))
651         MR = ER->getSuperRegion();
652 
653       // Special case for alloca()
654       if (isa<AllocaRegion>(MR))
655         os << "Argument to free() was allocated by alloca(), not malloc()";
656       else {
657         os << "Argument to free() is ";
658         if (SummarizeRegion(os, MR))
659           os << ", which is not memory allocated by malloc()";
660         else
661           os << "not memory allocated by malloc()";
662       }
663     } else {
664       os << "Argument to free() is ";
665       if (SummarizeValue(os, ArgVal))
666         os << ", which is not memory allocated by malloc()";
667       else
668         os << "not memory allocated by malloc()";
669     }
670 
671     BugReport *R = new BugReport(*BT_BadFree, os.str(), N);
672     R->addRange(range);
673     C.EmitReport(R);
674   }
675 }
676 
677 ProgramStateRef MallocChecker::ReallocMem(CheckerContext &C,
678                                           const CallExpr *CE,
679                                           bool FreesOnFail) const {
680   ProgramStateRef state = C.getState();
681   const Expr *arg0Expr = CE->getArg(0);
682   const LocationContext *LCtx = C.getLocationContext();
683   SVal Arg0Val = state->getSVal(arg0Expr, LCtx);
684   if (!isa<DefinedOrUnknownSVal>(Arg0Val))
685     return 0;
686   DefinedOrUnknownSVal arg0Val = cast<DefinedOrUnknownSVal>(Arg0Val);
687 
688   SValBuilder &svalBuilder = C.getSValBuilder();
689 
690   DefinedOrUnknownSVal PtrEQ =
691     svalBuilder.evalEQ(state, arg0Val, svalBuilder.makeNull());
692 
693   // Get the size argument. If there is no size arg then give up.
694   const Expr *Arg1 = CE->getArg(1);
695   if (!Arg1)
696     return 0;
697 
698   // Get the value of the size argument.
699   SVal Arg1ValG = state->getSVal(Arg1, LCtx);
700   if (!isa<DefinedOrUnknownSVal>(Arg1ValG))
701     return 0;
702   DefinedOrUnknownSVal Arg1Val = cast<DefinedOrUnknownSVal>(Arg1ValG);
703 
704   // Compare the size argument to 0.
705   DefinedOrUnknownSVal SizeZero =
706     svalBuilder.evalEQ(state, Arg1Val,
707                        svalBuilder.makeIntValWithPtrWidth(0, false));
708 
709   ProgramStateRef StatePtrIsNull, StatePtrNotNull;
710   llvm::tie(StatePtrIsNull, StatePtrNotNull) = state->assume(PtrEQ);
711   ProgramStateRef StateSizeIsZero, StateSizeNotZero;
712   llvm::tie(StateSizeIsZero, StateSizeNotZero) = state->assume(SizeZero);
713   // We only assume exceptional states if they are definitely true; if the
714   // state is under-constrained, assume regular realloc behavior.
715   bool PrtIsNull = StatePtrIsNull && !StatePtrNotNull;
716   bool SizeIsZero = StateSizeIsZero && !StateSizeNotZero;
717 
718   // If the ptr is NULL and the size is not 0, the call is equivalent to
719   // malloc(size).
720   if ( PrtIsNull && !SizeIsZero) {
721     ProgramStateRef stateMalloc = MallocMemAux(C, CE, CE->getArg(1),
722                                                UndefinedVal(), StatePtrIsNull);
723     return stateMalloc;
724   }
725 
726   if (PrtIsNull && SizeIsZero)
727     return 0;
728 
729   // Get the from and to pointer symbols as in toPtr = realloc(fromPtr, size).
730   assert(!PrtIsNull);
731   SymbolRef FromPtr = arg0Val.getAsSymbol();
732   SVal RetVal = state->getSVal(CE, LCtx);
733   SymbolRef ToPtr = RetVal.getAsSymbol();
734   if (!FromPtr || !ToPtr)
735     return 0;
736 
737   // If the size is 0, free the memory.
738   if (SizeIsZero)
739     if (ProgramStateRef stateFree = FreeMemAux(C, CE, StateSizeIsZero,0,false)){
740       // The semantics of the return value are:
741       // If size was equal to 0, either NULL or a pointer suitable to be passed
742       // to free() is returned.
743       stateFree = stateFree->set<ReallocPairs>(ToPtr,
744                                             ReallocPair(FromPtr, FreesOnFail));
745       C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr);
746       return stateFree;
747     }
748 
749   // Default behavior.
750   if (ProgramStateRef stateFree = FreeMemAux(C, CE, state, 0, false)) {
751     // FIXME: We should copy the content of the original buffer.
752     ProgramStateRef stateRealloc = MallocMemAux(C, CE, CE->getArg(1),
753                                                 UnknownVal(), stateFree);
754     if (!stateRealloc)
755       return 0;
756     stateRealloc = stateRealloc->set<ReallocPairs>(ToPtr,
757                                             ReallocPair(FromPtr, FreesOnFail));
758     C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr);
759     return stateRealloc;
760   }
761   return 0;
762 }
763 
764 ProgramStateRef MallocChecker::CallocMem(CheckerContext &C, const CallExpr *CE){
765   ProgramStateRef state = C.getState();
766   SValBuilder &svalBuilder = C.getSValBuilder();
767   const LocationContext *LCtx = C.getLocationContext();
768   SVal count = state->getSVal(CE->getArg(0), LCtx);
769   SVal elementSize = state->getSVal(CE->getArg(1), LCtx);
770   SVal TotalSize = svalBuilder.evalBinOp(state, BO_Mul, count, elementSize,
771                                         svalBuilder.getContext().getSizeType());
772   SVal zeroVal = svalBuilder.makeZeroVal(svalBuilder.getContext().CharTy);
773 
774   return MallocMemAux(C, CE, TotalSize, zeroVal, state);
775 }
776 
777 const Stmt *
778 MallocChecker::getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
779                                  CheckerContext &C) const {
780   const LocationContext *LeakContext = N->getLocationContext();
781   // Walk the ExplodedGraph backwards and find the first node that referred to
782   // the tracked symbol.
783   const ExplodedNode *AllocNode = N;
784 
785   while (N) {
786     if (!N->getState()->get<RegionState>(Sym))
787       break;
788     // Allocation node, is the last node in the current context in which the
789     // symbol was tracked.
790     if (N->getLocationContext() == LeakContext)
791       AllocNode = N;
792     N = N->pred_empty() ? NULL : *(N->pred_begin());
793   }
794 
795   ProgramPoint P = AllocNode->getLocation();
796   if (!isa<StmtPoint>(P))
797     return 0;
798 
799   return cast<StmtPoint>(P).getStmt();
800 }
801 
802 void MallocChecker::reportLeak(SymbolRef Sym, ExplodedNode *N,
803                                CheckerContext &C) const {
804   assert(N);
805   if (!BT_Leak) {
806     BT_Leak.reset(new BugType("Memory leak", "Memory Error"));
807     // Leaks should not be reported if they are post-dominated by a sink:
808     // (1) Sinks are higher importance bugs.
809     // (2) NoReturnFunctionChecker uses sink nodes to represent paths ending
810     //     with __noreturn functions such as assert() or exit(). We choose not
811     //     to report leaks on such paths.
812     BT_Leak->setSuppressOnSink(true);
813   }
814 
815   // Most bug reports are cached at the location where they occurred.
816   // With leaks, we want to unique them by the location where they were
817   // allocated, and only report a single path.
818   PathDiagnosticLocation LocUsedForUniqueing;
819   if (const Stmt *AllocStmt = getAllocationSite(N, Sym, C))
820     LocUsedForUniqueing = PathDiagnosticLocation::createBegin(AllocStmt,
821                             C.getSourceManager(), N->getLocationContext());
822 
823   BugReport *R = new BugReport(*BT_Leak,
824     "Memory is never released; potential memory leak", N, LocUsedForUniqueing);
825   R->addVisitor(new MallocBugVisitor(Sym));
826   C.EmitReport(R);
827 }
828 
829 void MallocChecker::checkDeadSymbols(SymbolReaper &SymReaper,
830                                      CheckerContext &C) const
831 {
832   if (!SymReaper.hasDeadSymbols())
833     return;
834 
835   ProgramStateRef state = C.getState();
836   RegionStateTy RS = state->get<RegionState>();
837   RegionStateTy::Factory &F = state->get_context<RegionState>();
838 
839   bool generateReport = false;
840   llvm::SmallVector<SymbolRef, 2> Errors;
841   for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
842     if (SymReaper.isDead(I->first)) {
843       if (I->second.isAllocated()) {
844         generateReport = true;
845         Errors.push_back(I->first);
846       }
847       // Remove the dead symbol from the map.
848       RS = F.remove(RS, I->first);
849 
850     }
851   }
852 
853   // Cleanup the Realloc Pairs Map.
854   ReallocMap RP = state->get<ReallocPairs>();
855   for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
856     if (SymReaper.isDead(I->first) ||
857         SymReaper.isDead(I->second.ReallocatedSym)) {
858       state = state->remove<ReallocPairs>(I->first);
859     }
860   }
861 
862   // Generate leak node.
863   static SimpleProgramPointTag Tag("MallocChecker : DeadSymbolsLeak");
864   ExplodedNode *N = C.addTransition(C.getState(), C.getPredecessor(), &Tag);
865 
866   if (generateReport) {
867     for (llvm::SmallVector<SymbolRef, 2>::iterator
868          I = Errors.begin(), E = Errors.end(); I != E; ++I) {
869       reportLeak(*I, N, C);
870     }
871   }
872   C.addTransition(state->set<RegionState>(RS), N);
873 }
874 
875 void MallocChecker::checkEndPath(CheckerContext &C) const {
876   ProgramStateRef state = C.getState();
877   RegionStateTy M = state->get<RegionState>();
878 
879   // If inside inlined call, skip it.
880   if (C.getLocationContext()->getParent() != 0)
881     return;
882 
883   for (RegionStateTy::iterator I = M.begin(), E = M.end(); I != E; ++I) {
884     RefState RS = I->second;
885     if (RS.isAllocated()) {
886       ExplodedNode *N = C.addTransition(state);
887       if (N)
888         reportLeak(I->first, N, C);
889     }
890   }
891 }
892 
893 bool MallocChecker::checkEscape(SymbolRef Sym, const Stmt *S,
894                                 CheckerContext &C) const {
895   ProgramStateRef state = C.getState();
896   const RefState *RS = state->get<RegionState>(Sym);
897   if (!RS)
898     return false;
899 
900   if (RS->isAllocated()) {
901     state = state->set<RegionState>(Sym, RefState::getEscaped(S));
902     C.addTransition(state);
903     return true;
904   }
905   return false;
906 }
907 
908 void MallocChecker::checkPreStmt(const CallExpr *CE, CheckerContext &C) const {
909   if (isMemFunction(C.getCalleeDecl(CE), C.getASTContext()))
910     return;
911 
912   // Check use after free, when a freed pointer is passed to a call.
913   ProgramStateRef State = C.getState();
914   for (CallExpr::const_arg_iterator I = CE->arg_begin(),
915                                     E = CE->arg_end(); I != E; ++I) {
916     const Expr *A = *I;
917     if (A->getType().getTypePtr()->isAnyPointerType()) {
918       SymbolRef Sym = State->getSVal(A, C.getLocationContext()).getAsSymbol();
919       if (!Sym)
920         continue;
921       if (checkUseAfterFree(Sym, C, A))
922         return;
923     }
924   }
925 }
926 
927 void MallocChecker::checkPreStmt(const ReturnStmt *S, CheckerContext &C) const {
928   const Expr *E = S->getRetValue();
929   if (!E)
930     return;
931 
932   // Check if we are returning a symbol.
933   SVal RetVal = C.getState()->getSVal(E, C.getLocationContext());
934   SymbolRef Sym = RetVal.getAsSymbol();
935   if (!Sym)
936     // If we are returning a field of the allocated struct or an array element,
937     // the callee could still free the memory.
938     // TODO: This logic should be a part of generic symbol escape callback.
939     if (const MemRegion *MR = RetVal.getAsRegion())
940       if (isa<FieldRegion>(MR) || isa<ElementRegion>(MR))
941         if (const SymbolicRegion *BMR =
942               dyn_cast<SymbolicRegion>(MR->getBaseRegion()))
943           Sym = BMR->getSymbol();
944   if (!Sym)
945     return;
946 
947   // Check if we are returning freed memory.
948   if (checkUseAfterFree(Sym, C, E))
949     return;
950 
951   // If this function body is not inlined, check if the symbol is escaping.
952   if (C.getLocationContext()->getParent() == 0)
953     checkEscape(Sym, E, C);
954 }
955 
956 bool MallocChecker::checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
957                                       const Stmt *S) const {
958   assert(Sym);
959   const RefState *RS = C.getState()->get<RegionState>(Sym);
960   if (RS && RS->isReleased()) {
961     if (ExplodedNode *N = C.generateSink()) {
962       if (!BT_UseFree)
963         BT_UseFree.reset(new BugType("Use-after-free", "Memory Error"));
964 
965       BugReport *R = new BugReport(*BT_UseFree,
966                                    "Use of memory after it is freed",N);
967       if (S)
968         R->addRange(S->getSourceRange());
969       R->addVisitor(new MallocBugVisitor(Sym));
970       C.EmitReport(R);
971       return true;
972     }
973   }
974   return false;
975 }
976 
977 // Check if the location is a freed symbolic region.
978 void MallocChecker::checkLocation(SVal l, bool isLoad, const Stmt *S,
979                                   CheckerContext &C) const {
980   SymbolRef Sym = l.getLocSymbolInBase();
981   if (Sym)
982     checkUseAfterFree(Sym, C);
983 }
984 
985 //===----------------------------------------------------------------------===//
986 // Check various ways a symbol can be invalidated.
987 // TODO: This logic (the next 3 functions) is copied/similar to the
988 // RetainRelease checker. We might want to factor this out.
989 //===----------------------------------------------------------------------===//
990 
991 // Stop tracking symbols when a value escapes as a result of checkBind.
992 // A value escapes in three possible cases:
993 // (1) we are binding to something that is not a memory region.
994 // (2) we are binding to a memregion that does not have stack storage
995 // (3) we are binding to a memregion with stack storage that the store
996 //     does not understand.
997 void MallocChecker::checkBind(SVal loc, SVal val, const Stmt *S,
998                               CheckerContext &C) const {
999   // Are we storing to something that causes the value to "escape"?
1000   bool escapes = true;
1001   ProgramStateRef state = C.getState();
1002 
1003   if (loc::MemRegionVal *regionLoc = dyn_cast<loc::MemRegionVal>(&loc)) {
1004     escapes = !regionLoc->getRegion()->hasStackStorage();
1005 
1006     if (!escapes) {
1007       // To test (3), generate a new state with the binding added.  If it is
1008       // the same state, then it escapes (since the store cannot represent
1009       // the binding).
1010       escapes = (state == (state->bindLoc(*regionLoc, val)));
1011     }
1012     if (!escapes) {
1013       // Case 4: We do not currently model what happens when a symbol is
1014       // assigned to a struct field, so be conservative here and let the symbol
1015       // go. TODO: This could definitely be improved upon.
1016       escapes = !isa<VarRegion>(regionLoc->getRegion());
1017     }
1018   }
1019 
1020   // If our store can represent the binding and we aren't storing to something
1021   // that doesn't have local storage then just return and have the simulation
1022   // state continue as is.
1023   if (!escapes)
1024       return;
1025 
1026   // Otherwise, find all symbols referenced by 'val' that we are tracking
1027   // and stop tracking them.
1028   state = state->scanReachableSymbols<StopTrackingCallback>(val).getState();
1029   C.addTransition(state);
1030 }
1031 
1032 // If a symbolic region is assumed to NULL (or another constant), stop tracking
1033 // it - assuming that allocation failed on this path.
1034 ProgramStateRef MallocChecker::evalAssume(ProgramStateRef state,
1035                                               SVal Cond,
1036                                               bool Assumption) const {
1037   RegionStateTy RS = state->get<RegionState>();
1038   for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
1039     // If the symbol is assumed to NULL or another constant, this will
1040     // return an APSInt*.
1041     if (state->getSymVal(I.getKey()))
1042       state = state->remove<RegionState>(I.getKey());
1043   }
1044 
1045   // Realloc returns 0 when reallocation fails, which means that we should
1046   // restore the state of the pointer being reallocated.
1047   ReallocMap RP = state->get<ReallocPairs>();
1048   for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
1049     // If the symbol is assumed to NULL or another constant, this will
1050     // return an APSInt*.
1051     if (state->getSymVal(I.getKey())) {
1052       SymbolRef ReallocSym = I.getData().ReallocatedSym;
1053       const RefState *RS = state->get<RegionState>(ReallocSym);
1054       if (RS) {
1055         if (RS->isReleased() && ! I.getData().IsFreeOnFailure)
1056           state = state->set<RegionState>(ReallocSym,
1057                              RefState::getAllocateUnchecked(RS->getStmt()));
1058       }
1059       state = state->remove<ReallocPairs>(I.getKey());
1060     }
1061   }
1062 
1063   return state;
1064 }
1065 
1066 // Check if the function is known to us. So, for example, we could
1067 // conservatively assume it can free/reallocate it's pointer arguments.
1068 // (We assume that the pointers cannot escape through calls to system
1069 // functions not handled by this checker.)
1070 bool MallocChecker::doesNotFreeMemory(const CallOrObjCMessage *Call,
1071                                       ProgramStateRef State) const {
1072   if (!Call)
1073     return false;
1074 
1075   // For now, assume that any C++ call can free memory.
1076   // TODO: If we want to be more optimistic here, we'll need to make sure that
1077   // regions escape to C++ containers. They seem to do that even now, but for
1078   // mysterious reasons.
1079   if (Call->isCXXCall())
1080     return false;
1081 
1082   const Decl *D = Call->getDecl();
1083   if (!D)
1084     return false;
1085 
1086   ASTContext &ASTC = State->getStateManager().getContext();
1087 
1088   // If it's one of the allocation functions we can reason about, we model
1089   // it's behavior explicitly.
1090   if (isa<FunctionDecl>(D) && isMemFunction(cast<FunctionDecl>(D), ASTC)) {
1091     return true;
1092   }
1093 
1094   // If it's not a system call, assume it frees memory.
1095   SourceManager &SM = ASTC.getSourceManager();
1096   if (!SM.isInSystemHeader(D->getLocation()))
1097     return false;
1098 
1099   // Process C/ObjC functions.
1100   if (const FunctionDecl *FD  = dyn_cast_or_null<FunctionDecl>(D)) {
1101     // White list the system functions whose arguments escape.
1102     const IdentifierInfo *II = FD->getIdentifier();
1103     if (!II)
1104       return true;
1105     StringRef FName = II->getName();
1106 
1107     // White list thread local storage.
1108     if (FName.equals("pthread_setspecific"))
1109       return false;
1110 
1111     // White list the 'XXXNoCopy' ObjC Methods.
1112     if (FName.endswith("NoCopy")) {
1113       // Look for the deallocator argument. We know that the memory ownership
1114       // is not transfered only if the deallocator argument is
1115       // 'kCFAllocatorNull'.
1116       for (unsigned i = 1; i < Call->getNumArgs(); ++i) {
1117         const Expr *ArgE = Call->getArg(i)->IgnoreParenCasts();
1118         if (const DeclRefExpr *DE = dyn_cast<DeclRefExpr>(ArgE)) {
1119           StringRef DeallocatorName = DE->getFoundDecl()->getName();
1120           if (DeallocatorName == "kCFAllocatorNull")
1121             return true;
1122         }
1123       }
1124       return false;
1125     }
1126 
1127     // PR12101
1128     // Many CoreFoundation and CoreGraphics might allow a tracked object
1129     // to escape.
1130     if (Call->isCFCGAllowingEscape(FName))
1131       return false;
1132 
1133     // Associating streams with malloced buffers. The pointer can escape if
1134     // 'closefn' is specified (and if that function does free memory).
1135     // Currently, we do not inspect the 'closefn' function (PR12101).
1136     if (FName == "funopen")
1137       if (Call->getNumArgs() >= 4 && !Call->getArgSVal(4).isConstant(0))
1138         return false;
1139 
1140     // Do not warn on pointers passed to 'setbuf' when used with std streams,
1141     // these leaks might be intentional when setting the buffer for stdio.
1142     // http://stackoverflow.com/questions/2671151/who-frees-setvbuf-buffer
1143     if (FName == "setbuf" || FName =="setbuffer" ||
1144         FName == "setlinebuf" || FName == "setvbuf") {
1145       if (Call->getNumArgs() >= 1)
1146         if (const DeclRefExpr *Arg =
1147               dyn_cast<DeclRefExpr>(Call->getArg(0)->IgnoreParenCasts()))
1148           if (const VarDecl *D = dyn_cast<VarDecl>(Arg->getDecl()))
1149               if (D->getCanonicalDecl()->getName().find("std")
1150                                                    != StringRef::npos)
1151                 return false;
1152     }
1153 
1154     // A bunch of other functions, which take ownership of a pointer (See retain
1155     // release checker). Not all the parameters here are invalidated, but the
1156     // Malloc checker cannot differentiate between them. The right way of doing
1157     // this would be to implement a pointer escapes callback.
1158     if (FName == "CVPixelBufferCreateWithBytes" ||
1159         FName == "CGBitmapContextCreateWithData" ||
1160         FName == "CVPixelBufferCreateWithPlanarBytes") {
1161       return false;
1162     }
1163 
1164     // Otherwise, assume that the function does not free memory.
1165     // Most system calls, do not free the memory.
1166     return true;
1167 
1168   // Process ObjC functions.
1169   } else if (const ObjCMethodDecl * ObjCD = dyn_cast<ObjCMethodDecl>(D)) {
1170     Selector S = ObjCD->getSelector();
1171 
1172     // White list the ObjC functions which do free memory.
1173     // - Anything containing 'freeWhenDone' param set to 1.
1174     //   Ex: dataWithBytesNoCopy:length:freeWhenDone.
1175     for (unsigned i = 1; i < S.getNumArgs(); ++i) {
1176       if (S.getNameForSlot(i).equals("freeWhenDone")) {
1177         if (Call->getArgSVal(i).isConstant(1))
1178           return false;
1179       }
1180     }
1181 
1182     // Otherwise, assume that the function does not free memory.
1183     // Most system calls, do not free the memory.
1184     return true;
1185   }
1186 
1187   // Otherwise, assume that the function can free memory.
1188   return false;
1189 
1190 }
1191 
1192 // If the symbol we are tracking is invalidated, but not explicitly (ex: the &p
1193 // escapes, when we are tracking p), do not track the symbol as we cannot reason
1194 // about it anymore.
1195 ProgramStateRef
1196 MallocChecker::checkRegionChanges(ProgramStateRef State,
1197                             const StoreManager::InvalidatedSymbols *invalidated,
1198                                     ArrayRef<const MemRegion *> ExplicitRegions,
1199                                     ArrayRef<const MemRegion *> Regions,
1200                                     const CallOrObjCMessage *Call) const {
1201   if (!invalidated || invalidated->empty())
1202     return State;
1203   llvm::SmallPtrSet<SymbolRef, 8> WhitelistedSymbols;
1204 
1205   // If it's a call which might free or reallocate memory, we assume that all
1206   // regions (explicit and implicit) escaped.
1207 
1208   // Otherwise, whitelist explicit pointers; we still can track them.
1209   if (!Call || doesNotFreeMemory(Call, State)) {
1210     for (ArrayRef<const MemRegion *>::iterator I = ExplicitRegions.begin(),
1211         E = ExplicitRegions.end(); I != E; ++I) {
1212       if (const SymbolicRegion *R = (*I)->StripCasts()->getAs<SymbolicRegion>())
1213         WhitelistedSymbols.insert(R->getSymbol());
1214     }
1215   }
1216 
1217   for (StoreManager::InvalidatedSymbols::const_iterator I=invalidated->begin(),
1218        E = invalidated->end(); I!=E; ++I) {
1219     SymbolRef sym = *I;
1220     if (WhitelistedSymbols.count(sym))
1221       continue;
1222     // The symbol escaped.
1223     if (const RefState *RS = State->get<RegionState>(sym))
1224       State = State->set<RegionState>(sym, RefState::getEscaped(RS->getStmt()));
1225   }
1226   return State;
1227 }
1228 
1229 PathDiagnosticPiece *
1230 MallocChecker::MallocBugVisitor::VisitNode(const ExplodedNode *N,
1231                                            const ExplodedNode *PrevN,
1232                                            BugReporterContext &BRC,
1233                                            BugReport &BR) {
1234   const RefState *RS = N->getState()->get<RegionState>(Sym);
1235   const RefState *RSPrev = PrevN->getState()->get<RegionState>(Sym);
1236   if (!RS && !RSPrev)
1237     return 0;
1238 
1239   const Stmt *S = 0;
1240   const char *Msg = 0;
1241 
1242   // Retrieve the associated statement.
1243   ProgramPoint ProgLoc = N->getLocation();
1244   if (isa<StmtPoint>(ProgLoc))
1245     S = cast<StmtPoint>(ProgLoc).getStmt();
1246   // If an assumption was made on a branch, it should be caught
1247   // here by looking at the state transition.
1248   if (isa<BlockEdge>(ProgLoc)) {
1249     const CFGBlock *srcBlk = cast<BlockEdge>(ProgLoc).getSrc();
1250     S = srcBlk->getTerminator();
1251   }
1252   if (!S)
1253     return 0;
1254 
1255   // Find out if this is an interesting point and what is the kind.
1256   if (Mode == Normal) {
1257     if (isAllocated(RS, RSPrev, S))
1258       Msg = "Memory is allocated";
1259     else if (isReleased(RS, RSPrev, S))
1260       Msg = "Memory is released";
1261     else if (isReallocFailedCheck(RS, RSPrev, S)) {
1262       Mode = ReallocationFailed;
1263       Msg = "Reallocation failed";
1264     }
1265 
1266   // We are in a special mode if a reallocation failed later in the path.
1267   } else if (Mode == ReallocationFailed) {
1268     // Generate a special diagnostic for the first realloc we find.
1269     if (!isAllocated(RS, RSPrev, S) && !isReleased(RS, RSPrev, S))
1270       return 0;
1271 
1272     // Check that the name of the function is realloc.
1273     const CallExpr *CE = dyn_cast<CallExpr>(S);
1274     if (!CE)
1275       return 0;
1276     const FunctionDecl *funDecl = CE->getDirectCallee();
1277     if (!funDecl)
1278       return 0;
1279     StringRef FunName = funDecl->getName();
1280     if (!(FunName.equals("realloc") || FunName.equals("reallocf")))
1281       return 0;
1282     Msg = "Attempt to reallocate memory";
1283     Mode = Normal;
1284   }
1285 
1286   if (!Msg)
1287     return 0;
1288 
1289   // Generate the extra diagnostic.
1290   PathDiagnosticLocation Pos(S, BRC.getSourceManager(),
1291                              N->getLocationContext());
1292   return new PathDiagnosticEventPiece(Pos, Msg);
1293 }
1294 
1295 
1296 #define REGISTER_CHECKER(name) \
1297 void ento::register##name(CheckerManager &mgr) {\
1298   registerCStringCheckerBasic(mgr); \
1299   mgr.registerChecker<MallocChecker>()->Filter.C##name = true;\
1300 }
1301 
1302 REGISTER_CHECKER(MallocPessimistic)
1303 REGISTER_CHECKER(MallocOptimistic)
1304