MallocChecker.cpp revision 368a0d565f078666ca5bfb7fe08d04648688e4bc 
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
31using namespace clang;
32using namespace ento;
33
34namespace {
35
36class RefState {
37  enum Kind { AllocateUnchecked, AllocateFailed, Released, Escaped,
38              Relinquished } K;
39  const Stmt *S;
40
41public:
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
71struct 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
85class 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
102public:
103  MallocChecker() : II_malloc(0), II_free(0), II_realloc(0), II_calloc(0),
104                    II_valloc(0), II_reallocf(0), II_strndup(0), II_strdup(0) {}
105
106  /// In pessimistic mode, the checker assumes that it does not know which
107  /// functions might free the memory.
108  struct ChecksFilter {
109    DefaultBool CMallocPessimistic;
110    DefaultBool CMallocOptimistic;
111  };
112
113  ChecksFilter Filter;
114
115  void checkPreStmt(const CallExpr *S, CheckerContext &C) const;
116  void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
117  void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;
118  void checkEndPath(CheckerContext &C) const;
119  void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const;
120  ProgramStateRef evalAssume(ProgramStateRef state, SVal Cond,
121                            bool Assumption) const;
122  void checkLocation(SVal l, bool isLoad, const Stmt *S,
123                     CheckerContext &C) const;
124  void checkBind(SVal location, SVal val, const Stmt*S,
125                 CheckerContext &C) const;
126  ProgramStateRef
127  checkRegionChanges(ProgramStateRef state,
128                     const StoreManager::InvalidatedSymbols *invalidated,
129                     ArrayRef<const MemRegion *> ExplicitRegions,
130                     ArrayRef<const MemRegion *> Regions,
131                     const CallOrObjCMessage *Call) const;
132  bool wantsRegionChangeUpdate(ProgramStateRef state) const {
133    return true;
134  }
135
136private:
137  void initIdentifierInfo(ASTContext &C) const;
138
139  /// Check if this is one of the functions which can allocate/reallocate memory
140  /// pointed to by one of its arguments.
141  bool isMemFunction(const FunctionDecl *FD, ASTContext &C) const;
142
143  static ProgramStateRef MallocMemReturnsAttr(CheckerContext &C,
144                                              const CallExpr *CE,
145                                              const OwnershipAttr* Att);
146  static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
147                                     const Expr *SizeEx, SVal Init,
148                                     ProgramStateRef state) {
149    return MallocMemAux(C, CE,
150                        state->getSVal(SizeEx, C.getLocationContext()),
151                        Init, state);
152  }
153
154  static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
155                                     SVal SizeEx, SVal Init,
156                                     ProgramStateRef state);
157
158  /// Update the RefState to reflect the new memory allocation.
159  static ProgramStateRef MallocUpdateRefState(CheckerContext &C,
160                                              const CallExpr *CE,
161                                              ProgramStateRef state);
162
163  ProgramStateRef FreeMemAttr(CheckerContext &C, const CallExpr *CE,
164                              const OwnershipAttr* Att) const;
165  ProgramStateRef FreeMemAux(CheckerContext &C, const CallExpr *CE,
166                                 ProgramStateRef state, unsigned Num,
167                                 bool Hold) const;
168
169  ProgramStateRef ReallocMem(CheckerContext &C, const CallExpr *CE,
170                             bool FreesMemOnFailure) const;
171  static ProgramStateRef CallocMem(CheckerContext &C, const CallExpr *CE);
172
173  bool checkEscape(SymbolRef Sym, const Stmt *S, CheckerContext &C) const;
174  bool checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
175                         const Stmt *S = 0) const;
176
177  /// Check if the function is not known to us. So, for example, we could
178  /// conservatively assume it can free/reallocate it's pointer arguments.
179  bool doesNotFreeMemory(const CallOrObjCMessage *Call,
180                         ProgramStateRef State) const;
181
182  static bool SummarizeValue(raw_ostream &os, SVal V);
183  static bool SummarizeRegion(raw_ostream &os, const MemRegion *MR);
184  void ReportBadFree(CheckerContext &C, SVal ArgVal, SourceRange range) const;
185
186  /// Find the location of the allocation for Sym on the path leading to the
187  /// exploded node N.
188  const Stmt *getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
189                                CheckerContext &C) const;
190
191  void reportLeak(SymbolRef Sym, ExplodedNode *N, CheckerContext &C) const;
192
193  /// The bug visitor which allows us to print extra diagnostics along the
194  /// BugReport path. For example, showing the allocation site of the leaked
195  /// region.
196  class MallocBugVisitor : public BugReporterVisitor {
197  protected:
198    enum NotificationMode {
199      Normal,
200      Complete,
201      ReallocationFailed
202    };
203
204    // The allocated region symbol tracked by the main analysis.
205    SymbolRef Sym;
206    NotificationMode Mode;
207
208  public:
209    MallocBugVisitor(SymbolRef S) : Sym(S), Mode(Normal) {}
210    virtual ~MallocBugVisitor() {}
211
212    void Profile(llvm::FoldingSetNodeID &ID) const {
213      static int X = 0;
214      ID.AddPointer(&X);
215      ID.AddPointer(Sym);
216    }
217
218    inline bool isAllocated(const RefState *S, const RefState *SPrev,
219                            const Stmt *Stmt) {
220      // Did not track -> allocated. Other state (released) -> allocated.
221      return (Stmt && isa<CallExpr>(Stmt) &&
222              (S && S->isAllocated()) && (!SPrev || !SPrev->isAllocated()));
223    }
224
225    inline bool isReleased(const RefState *S, const RefState *SPrev,
226                           const Stmt *Stmt) {
227      // Did not track -> released. Other state (allocated) -> released.
228      return (Stmt && isa<CallExpr>(Stmt) &&
229              (S && S->isReleased()) && (!SPrev || !SPrev->isReleased()));
230    }
231
232    inline bool isReallocFailedCheck(const RefState *S, const RefState *SPrev,
233                                     const Stmt *Stmt) {
234      // If the expression is not a call, and the state change is
235      // released -> allocated, it must be the realloc return value
236      // check. If we have to handle more cases here, it might be cleaner just
237      // to track this extra bit in the state itself.
238      return ((!Stmt || !isa<CallExpr>(Stmt)) &&
239              (S && S->isAllocated()) && (SPrev && !SPrev->isAllocated()));
240    }
241
242    PathDiagnosticPiece *VisitNode(const ExplodedNode *N,
243                                   const ExplodedNode *PrevN,
244                                   BugReporterContext &BRC,
245                                   BugReport &BR);
246  };
247};
248} // end anonymous namespace
249
250typedef llvm::ImmutableMap<SymbolRef, RefState> RegionStateTy;
251typedef llvm::ImmutableMap<SymbolRef, ReallocPair > ReallocMap;
252class RegionState {};
253class ReallocPairs {};
254namespace clang {
255namespace ento {
256  template <>
257  struct ProgramStateTrait<RegionState>
258    : public ProgramStatePartialTrait<RegionStateTy> {
259    static void *GDMIndex() { static int x; return &x; }
260  };
261
262  template <>
263  struct ProgramStateTrait<ReallocPairs>
264    : public ProgramStatePartialTrait<ReallocMap> {
265    static void *GDMIndex() { static int x; return &x; }
266  };
267}
268}
269
270namespace {
271class StopTrackingCallback : public SymbolVisitor {
272  ProgramStateRef state;
273public:
274  StopTrackingCallback(ProgramStateRef st) : state(st) {}
275  ProgramStateRef getState() const { return state; }
276
277  bool VisitSymbol(SymbolRef sym) {
278    state = state->remove<RegionState>(sym);
279    return true;
280  }
281};
282} // end anonymous namespace
283
284void MallocChecker::initIdentifierInfo(ASTContext &Ctx) const {
285  if (!II_malloc)
286    II_malloc = &Ctx.Idents.get("malloc");
287  if (!II_free)
288    II_free = &Ctx.Idents.get("free");
289  if (!II_realloc)
290    II_realloc = &Ctx.Idents.get("realloc");
291  if (!II_reallocf)
292    II_reallocf = &Ctx.Idents.get("reallocf");
293  if (!II_calloc)
294    II_calloc = &Ctx.Idents.get("calloc");
295  if (!II_valloc)
296    II_valloc = &Ctx.Idents.get("valloc");
297  if (!II_strdup)
298    II_strdup = &Ctx.Idents.get("strdup");
299  if (!II_strndup)
300    II_strndup = &Ctx.Idents.get("strndup");
301}
302
303bool MallocChecker::isMemFunction(const FunctionDecl *FD, ASTContext &C) const {
304  if (!FD)
305    return false;
306  IdentifierInfo *FunI = FD->getIdentifier();
307  if (!FunI)
308    return false;
309
310  initIdentifierInfo(C);
311
312  if (FunI == II_malloc || FunI == II_free || FunI == II_realloc ||
313      FunI == II_reallocf || FunI == II_calloc || FunI == II_valloc ||
314      FunI == II_strdup || FunI == II_strndup)
315    return true;
316
317  if (Filter.CMallocOptimistic && FD->hasAttrs() &&
318      FD->specific_attr_begin<OwnershipAttr>() !=
319          FD->specific_attr_end<OwnershipAttr>())
320    return true;
321
322
323  return false;
324}
325
326void MallocChecker::checkPostStmt(const CallExpr *CE, CheckerContext &C) const {
327  const FunctionDecl *FD = C.getCalleeDecl(CE);
328  if (!FD)
329    return;
330
331  initIdentifierInfo(C.getASTContext());
332  IdentifierInfo *FunI = FD->getIdentifier();
333  if (!FunI)
334    return;
335
336  ProgramStateRef State = C.getState();
337  if (FunI == II_malloc || FunI == II_valloc) {
338    State = MallocMemAux(C, CE, CE->getArg(0), UndefinedVal(), State);
339  } else if (FunI == II_realloc) {
340    State = ReallocMem(C, CE, false);
341  } else if (FunI == II_reallocf) {
342    State = ReallocMem(C, CE, true);
343  } else if (FunI == II_calloc) {
344    State = CallocMem(C, CE);
345  } else if (FunI == II_free) {
346    State = FreeMemAux(C, CE, C.getState(), 0, false);
347  } else if (FunI == II_strdup) {
348    State = MallocUpdateRefState(C, CE, State);
349  } else if (FunI == II_strndup) {
350    State = MallocUpdateRefState(C, CE, State);
351  } else if (Filter.CMallocOptimistic) {
352    // Check all the attributes, if there are any.
353    // There can be multiple of these attributes.
354    if (FD->hasAttrs())
355      for (specific_attr_iterator<OwnershipAttr>
356          i = FD->specific_attr_begin<OwnershipAttr>(),
357          e = FD->specific_attr_end<OwnershipAttr>();
358          i != e; ++i) {
359        switch ((*i)->getOwnKind()) {
360        case OwnershipAttr::Returns:
361          State = MallocMemReturnsAttr(C, CE, *i);
362          break;
363        case OwnershipAttr::Takes:
364        case OwnershipAttr::Holds:
365          State = FreeMemAttr(C, CE, *i);
366          break;
367        }
368      }
369  }
370  C.addTransition(State);
371}
372
373ProgramStateRef MallocChecker::MallocMemReturnsAttr(CheckerContext &C,
374                                                    const CallExpr *CE,
375                                                    const OwnershipAttr* Att) {
376  if (Att->getModule() != "malloc")
377    return 0;
378
379  OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
380  if (I != E) {
381    return MallocMemAux(C, CE, CE->getArg(*I), UndefinedVal(), C.getState());
382  }
383  return MallocMemAux(C, CE, UnknownVal(), UndefinedVal(), C.getState());
384}
385
386ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C,
387                                           const CallExpr *CE,
388                                           SVal Size, SVal Init,
389                                           ProgramStateRef state) {
390  // Get the return value.
391  SVal retVal = state->getSVal(CE, C.getLocationContext());
392
393  // We expect the malloc functions to return a pointer.
394  if (!isa<Loc>(retVal))
395    return 0;
396
397  // Fill the region with the initialization value.
398  state = state->bindDefault(retVal, Init);
399
400  // Set the region's extent equal to the Size parameter.
401  const SymbolicRegion *R =
402      dyn_cast_or_null<SymbolicRegion>(retVal.getAsRegion());
403  if (!R)
404    return 0;
405  if (isa<DefinedOrUnknownSVal>(Size)) {
406    SValBuilder &svalBuilder = C.getSValBuilder();
407    DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder);
408    DefinedOrUnknownSVal DefinedSize = cast<DefinedOrUnknownSVal>(Size);
409    DefinedOrUnknownSVal extentMatchesSize =
410        svalBuilder.evalEQ(state, Extent, DefinedSize);
411
412    state = state->assume(extentMatchesSize, true);
413    assert(state);
414  }
415
416  return MallocUpdateRefState(C, CE, state);
417}
418
419ProgramStateRef MallocChecker::MallocUpdateRefState(CheckerContext &C,
420                                                    const CallExpr *CE,
421                                                    ProgramStateRef state) {
422  // Get the return value.
423  SVal retVal = state->getSVal(CE, C.getLocationContext());
424
425  // We expect the malloc functions to return a pointer.
426  if (!isa<Loc>(retVal))
427    return 0;
428
429  SymbolRef Sym = retVal.getAsLocSymbol();
430  assert(Sym);
431
432  // Set the symbol's state to Allocated.
433  return state->set<RegionState>(Sym, RefState::getAllocateUnchecked(CE));
434
435}
436
437ProgramStateRef MallocChecker::FreeMemAttr(CheckerContext &C,
438                                           const CallExpr *CE,
439                                           const OwnershipAttr* Att) const {
440  if (Att->getModule() != "malloc")
441    return 0;
442
443  ProgramStateRef State = C.getState();
444
445  for (OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
446       I != E; ++I) {
447    ProgramStateRef StateI = FreeMemAux(C, CE, State, *I,
448                               Att->getOwnKind() == OwnershipAttr::Holds);
449    if (StateI)
450      State = StateI;
451  }
452  return State;
453}
454
455ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
456                                          const CallExpr *CE,
457                                          ProgramStateRef state,
458                                          unsigned Num,
459                                          bool Hold) const {
460  const Expr *ArgExpr = CE->getArg(Num);
461  SVal ArgVal = state->getSVal(ArgExpr, C.getLocationContext());
462  if (!isa<DefinedOrUnknownSVal>(ArgVal))
463    return 0;
464  DefinedOrUnknownSVal location = cast<DefinedOrUnknownSVal>(ArgVal);
465
466  // Check for null dereferences.
467  if (!isa<Loc>(location))
468    return 0;
469
470  // The explicit NULL case, no operation is performed.
471  ProgramStateRef notNullState, nullState;
472  llvm::tie(notNullState, nullState) = state->assume(location);
473  if (nullState && !notNullState)
474    return 0;
475
476  // Unknown values could easily be okay
477  // Undefined values are handled elsewhere
478  if (ArgVal.isUnknownOrUndef())
479    return 0;
480
481  const MemRegion *R = ArgVal.getAsRegion();
482
483  // Nonlocs can't be freed, of course.
484  // Non-region locations (labels and fixed addresses) also shouldn't be freed.
485  if (!R) {
486    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
487    return 0;
488  }
489
490  R = R->StripCasts();
491
492  // Blocks might show up as heap data, but should not be free()d
493  if (isa<BlockDataRegion>(R)) {
494    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
495    return 0;
496  }
497
498  const MemSpaceRegion *MS = R->getMemorySpace();
499
500  // Parameters, locals, statics, and globals shouldn't be freed.
501  if (!(isa<UnknownSpaceRegion>(MS) || isa<HeapSpaceRegion>(MS))) {
502    // FIXME: at the time this code was written, malloc() regions were
503    // represented by conjured symbols, which are all in UnknownSpaceRegion.
504    // This means that there isn't actually anything from HeapSpaceRegion
505    // that should be freed, even though we allow it here.
506    // Of course, free() can work on memory allocated outside the current
507    // function, so UnknownSpaceRegion is always a possibility.
508    // False negatives are better than false positives.
509
510    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
511    return 0;
512  }
513
514  const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R);
515  // Various cases could lead to non-symbol values here.
516  // For now, ignore them.
517  if (!SR)
518    return 0;
519
520  SymbolRef Sym = SR->getSymbol();
521  const RefState *RS = state->get<RegionState>(Sym);
522
523  // If the symbol has not been tracked, return. This is possible when free() is
524  // called on a pointer that does not get its pointee directly from malloc().
525  // Full support of this requires inter-procedural analysis.
526  if (!RS)
527    return 0;
528
529  // Check double free.
530  if (RS->isReleased()) {
531    if (ExplodedNode *N = C.generateSink()) {
532      if (!BT_DoubleFree)
533        BT_DoubleFree.reset(
534          new BugType("Double free", "Memory Error"));
535      BugReport *R = new BugReport(*BT_DoubleFree,
536                        "Attempt to free released memory", N);
537      R->addRange(ArgExpr->getSourceRange());
538      R->markInteresting(Sym);
539      R->addVisitor(new MallocBugVisitor(Sym));
540      C.EmitReport(R);
541    }
542    return 0;
543  }
544
545  // Normal free.
546  if (Hold)
547    return state->set<RegionState>(Sym, RefState::getRelinquished(CE));
548  return state->set<RegionState>(Sym, RefState::getReleased(CE));
549}
550
551bool MallocChecker::SummarizeValue(raw_ostream &os, SVal V) {
552  if (nonloc::ConcreteInt *IntVal = dyn_cast<nonloc::ConcreteInt>(&V))
553    os << "an integer (" << IntVal->getValue() << ")";
554  else if (loc::ConcreteInt *ConstAddr = dyn_cast<loc::ConcreteInt>(&V))
555    os << "a constant address (" << ConstAddr->getValue() << ")";
556  else if (loc::GotoLabel *Label = dyn_cast<loc::GotoLabel>(&V))
557    os << "the address of the label '" << Label->getLabel()->getName() << "'";
558  else
559    return false;
560
561  return true;
562}
563
564bool MallocChecker::SummarizeRegion(raw_ostream &os,
565                                    const MemRegion *MR) {
566  switch (MR->getKind()) {
567  case MemRegion::FunctionTextRegionKind: {
568    const FunctionDecl *FD = cast<FunctionTextRegion>(MR)->getDecl();
569    if (FD)
570      os << "the address of the function '" << *FD << '\'';
571    else
572      os << "the address of a function";
573    return true;
574  }
575  case MemRegion::BlockTextRegionKind:
576    os << "block text";
577    return true;
578  case MemRegion::BlockDataRegionKind:
579    // FIXME: where the block came from?
580    os << "a block";
581    return true;
582  default: {
583    const MemSpaceRegion *MS = MR->getMemorySpace();
584
585    if (isa<StackLocalsSpaceRegion>(MS)) {
586      const VarRegion *VR = dyn_cast<VarRegion>(MR);
587      const VarDecl *VD;
588      if (VR)
589        VD = VR->getDecl();
590      else
591        VD = NULL;
592
593      if (VD)
594        os << "the address of the local variable '" << VD->getName() << "'";
595      else
596        os << "the address of a local stack variable";
597      return true;
598    }
599
600    if (isa<StackArgumentsSpaceRegion>(MS)) {
601      const VarRegion *VR = dyn_cast<VarRegion>(MR);
602      const VarDecl *VD;
603      if (VR)
604        VD = VR->getDecl();
605      else
606        VD = NULL;
607
608      if (VD)
609        os << "the address of the parameter '" << VD->getName() << "'";
610      else
611        os << "the address of a parameter";
612      return true;
613    }
614
615    if (isa<GlobalsSpaceRegion>(MS)) {
616      const VarRegion *VR = dyn_cast<VarRegion>(MR);
617      const VarDecl *VD;
618      if (VR)
619        VD = VR->getDecl();
620      else
621        VD = NULL;
622
623      if (VD) {
624        if (VD->isStaticLocal())
625          os << "the address of the static variable '" << VD->getName() << "'";
626        else
627          os << "the address of the global variable '" << VD->getName() << "'";
628      } else
629        os << "the address of a global variable";
630      return true;
631    }
632
633    return false;
634  }
635  }
636}
637
638void MallocChecker::ReportBadFree(CheckerContext &C, SVal ArgVal,
639                                  SourceRange range) const {
640  if (ExplodedNode *N = C.generateSink()) {
641    if (!BT_BadFree)
642      BT_BadFree.reset(new BugType("Bad free", "Memory Error"));
643
644    SmallString<100> buf;
645    llvm::raw_svector_ostream os(buf);
646
647    const MemRegion *MR = ArgVal.getAsRegion();
648    if (MR) {
649      while (const ElementRegion *ER = dyn_cast<ElementRegion>(MR))
650        MR = ER->getSuperRegion();
651
652      // Special case for alloca()
653      if (isa<AllocaRegion>(MR))
654        os << "Argument to free() was allocated by alloca(), not malloc()";
655      else {
656        os << "Argument to free() is ";
657        if (SummarizeRegion(os, MR))
658          os << ", which is not memory allocated by malloc()";
659        else
660          os << "not memory allocated by malloc()";
661      }
662    } else {
663      os << "Argument to free() is ";
664      if (SummarizeValue(os, ArgVal))
665        os << ", which is not memory allocated by malloc()";
666      else
667        os << "not memory allocated by malloc()";
668    }
669
670    BugReport *R = new BugReport(*BT_BadFree, os.str(), N);
671    R->markInteresting(MR);
672    R->addRange(range);
673    C.EmitReport(R);
674  }
675}
676
677ProgramStateRef 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
764ProgramStateRef 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
777const Stmt *
778MallocChecker::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
802void 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->markInteresting(Sym);
826  R->addVisitor(new MallocBugVisitor(Sym));
827  C.EmitReport(R);
828}
829
830void MallocChecker::checkDeadSymbols(SymbolReaper &SymReaper,
831                                     CheckerContext &C) const
832{
833  if (!SymReaper.hasDeadSymbols())
834    return;
835
836  ProgramStateRef state = C.getState();
837  RegionStateTy RS = state->get<RegionState>();
838  RegionStateTy::Factory &F = state->get_context<RegionState>();
839
840  bool generateReport = false;
841  llvm::SmallVector<SymbolRef, 2> Errors;
842  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
843    if (SymReaper.isDead(I->first)) {
844      if (I->second.isAllocated()) {
845        generateReport = true;
846        Errors.push_back(I->first);
847      }
848      // Remove the dead symbol from the map.
849      RS = F.remove(RS, I->first);
850
851    }
852  }
853
854  // Cleanup the Realloc Pairs Map.
855  ReallocMap RP = state->get<ReallocPairs>();
856  for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
857    if (SymReaper.isDead(I->first) ||
858        SymReaper.isDead(I->second.ReallocatedSym)) {
859      state = state->remove<ReallocPairs>(I->first);
860    }
861  }
862
863  // Generate leak node.
864  static SimpleProgramPointTag Tag("MallocChecker : DeadSymbolsLeak");
865  ExplodedNode *N = C.addTransition(C.getState(), C.getPredecessor(), &Tag);
866
867  if (generateReport) {
868    for (llvm::SmallVector<SymbolRef, 2>::iterator
869         I = Errors.begin(), E = Errors.end(); I != E; ++I) {
870      reportLeak(*I, N, C);
871    }
872  }
873  C.addTransition(state->set<RegionState>(RS), N);
874}
875
876void MallocChecker::checkEndPath(CheckerContext &C) const {
877  ProgramStateRef state = C.getState();
878  RegionStateTy M = state->get<RegionState>();
879
880  // If inside inlined call, skip it.
881  if (C.getLocationContext()->getParent() != 0)
882    return;
883
884  for (RegionStateTy::iterator I = M.begin(), E = M.end(); I != E; ++I) {
885    RefState RS = I->second;
886    if (RS.isAllocated()) {
887      ExplodedNode *N = C.addTransition(state);
888      if (N)
889        reportLeak(I->first, N, C);
890    }
891  }
892}
893
894bool MallocChecker::checkEscape(SymbolRef Sym, const Stmt *S,
895                                CheckerContext &C) const {
896  ProgramStateRef state = C.getState();
897  const RefState *RS = state->get<RegionState>(Sym);
898  if (!RS)
899    return false;
900
901  if (RS->isAllocated()) {
902    state = state->set<RegionState>(Sym, RefState::getEscaped(S));
903    C.addTransition(state);
904    return true;
905  }
906  return false;
907}
908
909void MallocChecker::checkPreStmt(const CallExpr *CE, CheckerContext &C) const {
910  if (isMemFunction(C.getCalleeDecl(CE), C.getASTContext()))
911    return;
912
913  // Check use after free, when a freed pointer is passed to a call.
914  ProgramStateRef State = C.getState();
915  for (CallExpr::const_arg_iterator I = CE->arg_begin(),
916                                    E = CE->arg_end(); I != E; ++I) {
917    const Expr *A = *I;
918    if (A->getType().getTypePtr()->isAnyPointerType()) {
919      SymbolRef Sym = State->getSVal(A, C.getLocationContext()).getAsSymbol();
920      if (!Sym)
921        continue;
922      if (checkUseAfterFree(Sym, C, A))
923        return;
924    }
925  }
926}
927
928void MallocChecker::checkPreStmt(const ReturnStmt *S, CheckerContext &C) const {
929  const Expr *E = S->getRetValue();
930  if (!E)
931    return;
932
933  // Check if we are returning a symbol.
934  SVal RetVal = C.getState()->getSVal(E, C.getLocationContext());
935  SymbolRef Sym = RetVal.getAsSymbol();
936  if (!Sym)
937    // If we are returning a field of the allocated struct or an array element,
938    // the callee could still free the memory.
939    // TODO: This logic should be a part of generic symbol escape callback.
940    if (const MemRegion *MR = RetVal.getAsRegion())
941      if (isa<FieldRegion>(MR) || isa<ElementRegion>(MR))
942        if (const SymbolicRegion *BMR =
943              dyn_cast<SymbolicRegion>(MR->getBaseRegion()))
944          Sym = BMR->getSymbol();
945  if (!Sym)
946    return;
947
948  // Check if we are returning freed memory.
949  if (checkUseAfterFree(Sym, C, E))
950    return;
951
952  // If this function body is not inlined, check if the symbol is escaping.
953  if (C.getLocationContext()->getParent() == 0)
954    checkEscape(Sym, E, C);
955}
956
957bool MallocChecker::checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
958                                      const Stmt *S) const {
959  assert(Sym);
960  const RefState *RS = C.getState()->get<RegionState>(Sym);
961  if (RS && RS->isReleased()) {
962    if (ExplodedNode *N = C.generateSink()) {
963      if (!BT_UseFree)
964        BT_UseFree.reset(new BugType("Use-after-free", "Memory Error"));
965
966      BugReport *R = new BugReport(*BT_UseFree,
967                                   "Use of memory after it is freed",N);
968      if (S)
969        R->addRange(S->getSourceRange());
970      R->markInteresting(Sym);
971      R->addVisitor(new MallocBugVisitor(Sym));
972      C.EmitReport(R);
973      return true;
974    }
975  }
976  return false;
977}
978
979// Check if the location is a freed symbolic region.
980void MallocChecker::checkLocation(SVal l, bool isLoad, const Stmt *S,
981                                  CheckerContext &C) const {
982  SymbolRef Sym = l.getLocSymbolInBase();
983  if (Sym)
984    checkUseAfterFree(Sym, C);
985}
986
987//===----------------------------------------------------------------------===//
988// Check various ways a symbol can be invalidated.
989// TODO: This logic (the next 3 functions) is copied/similar to the
990// RetainRelease checker. We might want to factor this out.
991//===----------------------------------------------------------------------===//
992
993// Stop tracking symbols when a value escapes as a result of checkBind.
994// A value escapes in three possible cases:
995// (1) we are binding to something that is not a memory region.
996// (2) we are binding to a memregion that does not have stack storage
997// (3) we are binding to a memregion with stack storage that the store
998//     does not understand.
999void MallocChecker::checkBind(SVal loc, SVal val, const Stmt *S,
1000                              CheckerContext &C) const {
1001  // Are we storing to something that causes the value to "escape"?
1002  bool escapes = true;
1003  ProgramStateRef state = C.getState();
1004
1005  if (loc::MemRegionVal *regionLoc = dyn_cast<loc::MemRegionVal>(&loc)) {
1006    escapes = !regionLoc->getRegion()->hasStackStorage();
1007
1008    if (!escapes) {
1009      // To test (3), generate a new state with the binding added.  If it is
1010      // the same state, then it escapes (since the store cannot represent
1011      // the binding).
1012      escapes = (state == (state->bindLoc(*regionLoc, val)));
1013    }
1014    if (!escapes) {
1015      // Case 4: We do not currently model what happens when a symbol is
1016      // assigned to a struct field, so be conservative here and let the symbol
1017      // go. TODO: This could definitely be improved upon.
1018      escapes = !isa<VarRegion>(regionLoc->getRegion());
1019    }
1020  }
1021
1022  // If our store can represent the binding and we aren't storing to something
1023  // that doesn't have local storage then just return and have the simulation
1024  // state continue as is.
1025  if (!escapes)
1026      return;
1027
1028  // Otherwise, find all symbols referenced by 'val' that we are tracking
1029  // and stop tracking them.
1030  state = state->scanReachableSymbols<StopTrackingCallback>(val).getState();
1031  C.addTransition(state);
1032}
1033
1034// If a symbolic region is assumed to NULL (or another constant), stop tracking
1035// it - assuming that allocation failed on this path.
1036ProgramStateRef MallocChecker::evalAssume(ProgramStateRef state,
1037                                              SVal Cond,
1038                                              bool Assumption) const {
1039  RegionStateTy RS = state->get<RegionState>();
1040  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
1041    // If the symbol is assumed to NULL or another constant, this will
1042    // return an APSInt*.
1043    if (state->getSymVal(I.getKey()))
1044      state = state->remove<RegionState>(I.getKey());
1045  }
1046
1047  // Realloc returns 0 when reallocation fails, which means that we should
1048  // restore the state of the pointer being reallocated.
1049  ReallocMap RP = state->get<ReallocPairs>();
1050  for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
1051    // If the symbol is assumed to NULL or another constant, this will
1052    // return an APSInt*.
1053    if (state->getSymVal(I.getKey())) {
1054      SymbolRef ReallocSym = I.getData().ReallocatedSym;
1055      const RefState *RS = state->get<RegionState>(ReallocSym);
1056      if (RS) {
1057        if (RS->isReleased() && ! I.getData().IsFreeOnFailure)
1058          state = state->set<RegionState>(ReallocSym,
1059                             RefState::getAllocateUnchecked(RS->getStmt()));
1060      }
1061      state = state->remove<ReallocPairs>(I.getKey());
1062    }
1063  }
1064
1065  return state;
1066}
1067
1068// Check if the function is known to us. So, for example, we could
1069// conservatively assume it can free/reallocate it's pointer arguments.
1070// (We assume that the pointers cannot escape through calls to system
1071// functions not handled by this checker.)
1072bool MallocChecker::doesNotFreeMemory(const CallOrObjCMessage *Call,
1073                                      ProgramStateRef State) const {
1074  if (!Call)
1075    return false;
1076
1077  // For now, assume that any C++ call can free memory.
1078  // TODO: If we want to be more optimistic here, we'll need to make sure that
1079  // regions escape to C++ containers. They seem to do that even now, but for
1080  // mysterious reasons.
1081  if (Call->isCXXCall())
1082    return false;
1083
1084  const Decl *D = Call->getDecl();
1085  if (!D)
1086    return false;
1087
1088  ASTContext &ASTC = State->getStateManager().getContext();
1089
1090  // If it's one of the allocation functions we can reason about, we model
1091  // its behavior explicitly.
1092  if (isa<FunctionDecl>(D) && isMemFunction(cast<FunctionDecl>(D), ASTC)) {
1093    return true;
1094  }
1095
1096  // If it's not a system call, assume it frees memory.
1097  SourceManager &SM = ASTC.getSourceManager();
1098  if (!SM.isInSystemHeader(D->getLocation()))
1099    return false;
1100
1101  // Process C/ObjC functions.
1102  if (const FunctionDecl *FD  = dyn_cast<FunctionDecl>(D)) {
1103    // White list the system functions whose arguments escape.
1104    const IdentifierInfo *II = FD->getIdentifier();
1105    if (!II)
1106      return true;
1107    StringRef FName = II->getName();
1108
1109    // White list thread local storage.
1110    if (FName.equals("pthread_setspecific"))
1111      return false;
1112
1113    // White list the 'XXXNoCopy' ObjC functions.
1114    if (FName.endswith("NoCopy")) {
1115      // Look for the deallocator argument. We know that the memory ownership
1116      // is not transfered only if the deallocator argument is
1117      // 'kCFAllocatorNull'.
1118      for (unsigned i = 1; i < Call->getNumArgs(); ++i) {
1119        const Expr *ArgE = Call->getArg(i)->IgnoreParenCasts();
1120        if (const DeclRefExpr *DE = dyn_cast<DeclRefExpr>(ArgE)) {
1121          StringRef DeallocatorName = DE->getFoundDecl()->getName();
1122          if (DeallocatorName == "kCFAllocatorNull")
1123            return true;
1124        }
1125      }
1126      return false;
1127    }
1128
1129    // PR12101
1130    // Many CoreFoundation and CoreGraphics might allow a tracked object
1131    // to escape.
1132    if (Call->isCFCGAllowingEscape(FName))
1133      return false;
1134
1135    // Associating streams with malloced buffers. The pointer can escape if
1136    // 'closefn' is specified (and if that function does free memory).
1137    // Currently, we do not inspect the 'closefn' function (PR12101).
1138    if (FName == "funopen")
1139      if (Call->getNumArgs() >= 4 && !Call->getArgSVal(4).isConstant(0))
1140        return false;
1141
1142    // Do not warn on pointers passed to 'setbuf' when used with std streams,
1143    // these leaks might be intentional when setting the buffer for stdio.
1144    // http://stackoverflow.com/questions/2671151/who-frees-setvbuf-buffer
1145    if (FName == "setbuf" || FName =="setbuffer" ||
1146        FName == "setlinebuf" || FName == "setvbuf") {
1147      if (Call->getNumArgs() >= 1)
1148        if (const DeclRefExpr *Arg =
1149              dyn_cast<DeclRefExpr>(Call->getArg(0)->IgnoreParenCasts()))
1150          if (const VarDecl *D = dyn_cast<VarDecl>(Arg->getDecl()))
1151              if (D->getCanonicalDecl()->getName().find("std")
1152                                                   != StringRef::npos)
1153                return false;
1154    }
1155
1156    // A bunch of other functions, which take ownership of a pointer (See retain
1157    // release checker). Not all the parameters here are invalidated, but the
1158    // Malloc checker cannot differentiate between them. The right way of doing
1159    // this would be to implement a pointer escapes callback.
1160    if (FName == "CVPixelBufferCreateWithBytes" ||
1161        FName == "CGBitmapContextCreateWithData" ||
1162        FName == "CVPixelBufferCreateWithPlanarBytes") {
1163      return false;
1164    }
1165
1166    // Otherwise, assume that the function does not free memory.
1167    // Most system calls, do not free the memory.
1168    return true;
1169
1170  // Process ObjC functions.
1171  } else if (const ObjCMethodDecl * ObjCD = dyn_cast<ObjCMethodDecl>(D)) {
1172    Selector S = ObjCD->getSelector();
1173
1174    // White list the ObjC functions which do free memory.
1175    // - Anything containing 'freeWhenDone' param set to 1.
1176    //   Ex: dataWithBytesNoCopy:length:freeWhenDone.
1177    for (unsigned i = 1; i < S.getNumArgs(); ++i) {
1178      if (S.getNameForSlot(i).equals("freeWhenDone")) {
1179        if (Call->getArgSVal(i).isConstant(1))
1180          return false;
1181        else
1182          return true;
1183      }
1184    }
1185
1186    // If the first selector ends with NoCopy, assume that the ownership is
1187    // transfered as well.
1188    // Ex:  [NSData dataWithBytesNoCopy:bytes length:10];
1189    if (S.getNameForSlot(0).endswith("NoCopy")) {
1190      return false;
1191    }
1192
1193    // Otherwise, assume that the function does not free memory.
1194    // Most system calls, do not free the memory.
1195    return true;
1196  }
1197
1198  // Otherwise, assume that the function can free memory.
1199  return false;
1200
1201}
1202
1203// If the symbol we are tracking is invalidated, but not explicitly (ex: the &p
1204// escapes, when we are tracking p), do not track the symbol as we cannot reason
1205// about it anymore.
1206ProgramStateRef
1207MallocChecker::checkRegionChanges(ProgramStateRef State,
1208                            const StoreManager::InvalidatedSymbols *invalidated,
1209                                    ArrayRef<const MemRegion *> ExplicitRegions,
1210                                    ArrayRef<const MemRegion *> Regions,
1211                                    const CallOrObjCMessage *Call) const {
1212  if (!invalidated || invalidated->empty())
1213    return State;
1214  llvm::SmallPtrSet<SymbolRef, 8> WhitelistedSymbols;
1215
1216  // If it's a call which might free or reallocate memory, we assume that all
1217  // regions (explicit and implicit) escaped.
1218
1219  // Otherwise, whitelist explicit pointers; we still can track them.
1220  if (!Call || doesNotFreeMemory(Call, State)) {
1221    for (ArrayRef<const MemRegion *>::iterator I = ExplicitRegions.begin(),
1222        E = ExplicitRegions.end(); I != E; ++I) {
1223      if (const SymbolicRegion *R = (*I)->StripCasts()->getAs<SymbolicRegion>())
1224        WhitelistedSymbols.insert(R->getSymbol());
1225    }
1226  }
1227
1228  for (StoreManager::InvalidatedSymbols::const_iterator I=invalidated->begin(),
1229       E = invalidated->end(); I!=E; ++I) {
1230    SymbolRef sym = *I;
1231    if (WhitelistedSymbols.count(sym))
1232      continue;
1233    // The symbol escaped.
1234    if (const RefState *RS = State->get<RegionState>(sym))
1235      State = State->set<RegionState>(sym, RefState::getEscaped(RS->getStmt()));
1236  }
1237  return State;
1238}
1239
1240PathDiagnosticPiece *
1241MallocChecker::MallocBugVisitor::VisitNode(const ExplodedNode *N,
1242                                           const ExplodedNode *PrevN,
1243                                           BugReporterContext &BRC,
1244                                           BugReport &BR) {
1245  const RefState *RS = N->getState()->get<RegionState>(Sym);
1246  const RefState *RSPrev = PrevN->getState()->get<RegionState>(Sym);
1247  if (!RS && !RSPrev)
1248    return 0;
1249
1250  const Stmt *S = 0;
1251  const char *Msg = 0;
1252  const char *StackMsg = 0;
1253
1254  // Retrieve the associated statement.
1255  ProgramPoint ProgLoc = N->getLocation();
1256  if (isa<StmtPoint>(ProgLoc))
1257    S = cast<StmtPoint>(ProgLoc).getStmt();
1258  // If an assumption was made on a branch, it should be caught
1259  // here by looking at the state transition.
1260  if (isa<BlockEdge>(ProgLoc)) {
1261    const CFGBlock *srcBlk = cast<BlockEdge>(ProgLoc).getSrc();
1262    S = srcBlk->getTerminator();
1263  }
1264  if (!S)
1265    return 0;
1266
1267  // Find out if this is an interesting point and what is the kind.
1268  // TODO: Replace 'callee' by the function name.
1269  if (Mode == Normal) {
1270    if (isAllocated(RS, RSPrev, S)) {
1271      Msg = "Memory is allocated";
1272      StackMsg = ", which allocated memory";
1273    } else if (isReleased(RS, RSPrev, S)) {
1274      Msg = "Memory is released";
1275      StackMsg = ", which released memory";
1276    } else if (isReallocFailedCheck(RS, RSPrev, S)) {
1277      Mode = ReallocationFailed;
1278      Msg = "Reallocation failed";
1279      StackMsg = ", where reallocation failed";
1280    }
1281
1282  // We are in a special mode if a reallocation failed later in the path.
1283  } else if (Mode == ReallocationFailed) {
1284    // Generate a special diagnostic for the first realloc we find.
1285    if (!isAllocated(RS, RSPrev, S) && !isReleased(RS, RSPrev, S))
1286      return 0;
1287
1288    // Check that the name of the function is realloc.
1289    const CallExpr *CE = dyn_cast<CallExpr>(S);
1290    if (!CE)
1291      return 0;
1292    const FunctionDecl *funDecl = CE->getDirectCallee();
1293    if (!funDecl)
1294      return 0;
1295    StringRef FunName = funDecl->getName();
1296    if (!(FunName.equals("realloc") || FunName.equals("reallocf")))
1297      return 0;
1298    Msg = "Attempt to reallocate memory";
1299    StackMsg = ", which attempted to reallocate memory";
1300    Mode = Normal;
1301  }
1302
1303  if (!Msg)
1304    return 0;
1305  assert(StackMsg);
1306
1307  // Generate the extra diagnostic.
1308  PathDiagnosticLocation Pos(S, BRC.getSourceManager(),
1309                             N->getLocationContext());
1310  return new PathDiagnosticEventPiece(Pos, Msg, true, StackMsg);
1311}
1312
1313
1314#define REGISTER_CHECKER(name) \
1315void ento::register##name(CheckerManager &mgr) {\
1316  registerCStringCheckerBasic(mgr); \
1317  mgr.registerChecker<MallocChecker>()->Filter.C##name = true;\
1318}
1319
1320REGISTER_CHECKER(MallocPessimistic)
1321REGISTER_CHECKER(MallocOptimistic)
1322