MallocChecker.cpp revision 393f98b5b7f7c950d2b0a7d84501b5dfd00ad780 
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  private:
247    class StackHintGeneratorForReallocationFailed
248        : public StackHintGeneratorForSymbol {
249    public:
250      StackHintGeneratorForReallocationFailed(SymbolRef S, StringRef M)
251        : StackHintGeneratorForSymbol(S, M) {}
252
253      virtual std::string getMessageForArg(const Expr *ArgE, unsigned ArgIndex) {
254        SmallString<200> buf;
255        llvm::raw_svector_ostream os(buf);
256
257        os << "Reallocation of ";
258        // Printed parameters start at 1, not 0.
259        printOrdinal(++ArgIndex, os);
260        os << " parameter failed";
261
262        return os.str();
263      }
264
265      virtual std::string getMessageForReturn(const CallExpr *CallExpr) {
266        return "Reallocation of returned value failed";
267      }
268    };
269  };
270};
271} // end anonymous namespace
272
273typedef llvm::ImmutableMap<SymbolRef, RefState> RegionStateTy;
274typedef llvm::ImmutableMap<SymbolRef, ReallocPair > ReallocMap;
275class RegionState {};
276class ReallocPairs {};
277namespace clang {
278namespace ento {
279  template <>
280  struct ProgramStateTrait<RegionState>
281    : public ProgramStatePartialTrait<RegionStateTy> {
282    static void *GDMIndex() { static int x; return &x; }
283  };
284
285  template <>
286  struct ProgramStateTrait<ReallocPairs>
287    : public ProgramStatePartialTrait<ReallocMap> {
288    static void *GDMIndex() { static int x; return &x; }
289  };
290}
291}
292
293namespace {
294class StopTrackingCallback : public SymbolVisitor {
295  ProgramStateRef state;
296public:
297  StopTrackingCallback(ProgramStateRef st) : state(st) {}
298  ProgramStateRef getState() const { return state; }
299
300  bool VisitSymbol(SymbolRef sym) {
301    state = state->remove<RegionState>(sym);
302    return true;
303  }
304};
305} // end anonymous namespace
306
307void MallocChecker::initIdentifierInfo(ASTContext &Ctx) const {
308  if (!II_malloc)
309    II_malloc = &Ctx.Idents.get("malloc");
310  if (!II_free)
311    II_free = &Ctx.Idents.get("free");
312  if (!II_realloc)
313    II_realloc = &Ctx.Idents.get("realloc");
314  if (!II_reallocf)
315    II_reallocf = &Ctx.Idents.get("reallocf");
316  if (!II_calloc)
317    II_calloc = &Ctx.Idents.get("calloc");
318  if (!II_valloc)
319    II_valloc = &Ctx.Idents.get("valloc");
320  if (!II_strdup)
321    II_strdup = &Ctx.Idents.get("strdup");
322  if (!II_strndup)
323    II_strndup = &Ctx.Idents.get("strndup");
324}
325
326bool MallocChecker::isMemFunction(const FunctionDecl *FD, ASTContext &C) const {
327  if (!FD)
328    return false;
329  IdentifierInfo *FunI = FD->getIdentifier();
330  if (!FunI)
331    return false;
332
333  initIdentifierInfo(C);
334
335  if (FunI == II_malloc || FunI == II_free || FunI == II_realloc ||
336      FunI == II_reallocf || FunI == II_calloc || FunI == II_valloc ||
337      FunI == II_strdup || FunI == II_strndup)
338    return true;
339
340  if (Filter.CMallocOptimistic && FD->hasAttrs() &&
341      FD->specific_attr_begin<OwnershipAttr>() !=
342          FD->specific_attr_end<OwnershipAttr>())
343    return true;
344
345
346  return false;
347}
348
349void MallocChecker::checkPostStmt(const CallExpr *CE, CheckerContext &C) const {
350  const FunctionDecl *FD = C.getCalleeDecl(CE);
351  if (!FD)
352    return;
353
354  initIdentifierInfo(C.getASTContext());
355  IdentifierInfo *FunI = FD->getIdentifier();
356  if (!FunI)
357    return;
358
359  ProgramStateRef State = C.getState();
360  if (FunI == II_malloc || FunI == II_valloc) {
361    State = MallocMemAux(C, CE, CE->getArg(0), UndefinedVal(), State);
362  } else if (FunI == II_realloc) {
363    State = ReallocMem(C, CE, false);
364  } else if (FunI == II_reallocf) {
365    State = ReallocMem(C, CE, true);
366  } else if (FunI == II_calloc) {
367    State = CallocMem(C, CE);
368  } else if (FunI == II_free) {
369    State = FreeMemAux(C, CE, C.getState(), 0, false);
370  } else if (FunI == II_strdup) {
371    State = MallocUpdateRefState(C, CE, State);
372  } else if (FunI == II_strndup) {
373    State = MallocUpdateRefState(C, CE, State);
374  } else if (Filter.CMallocOptimistic) {
375    // Check all the attributes, if there are any.
376    // There can be multiple of these attributes.
377    if (FD->hasAttrs())
378      for (specific_attr_iterator<OwnershipAttr>
379          i = FD->specific_attr_begin<OwnershipAttr>(),
380          e = FD->specific_attr_end<OwnershipAttr>();
381          i != e; ++i) {
382        switch ((*i)->getOwnKind()) {
383        case OwnershipAttr::Returns:
384          State = MallocMemReturnsAttr(C, CE, *i);
385          break;
386        case OwnershipAttr::Takes:
387        case OwnershipAttr::Holds:
388          State = FreeMemAttr(C, CE, *i);
389          break;
390        }
391      }
392  }
393  C.addTransition(State);
394}
395
396ProgramStateRef MallocChecker::MallocMemReturnsAttr(CheckerContext &C,
397                                                    const CallExpr *CE,
398                                                    const OwnershipAttr* Att) {
399  if (Att->getModule() != "malloc")
400    return 0;
401
402  OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
403  if (I != E) {
404    return MallocMemAux(C, CE, CE->getArg(*I), UndefinedVal(), C.getState());
405  }
406  return MallocMemAux(C, CE, UnknownVal(), UndefinedVal(), C.getState());
407}
408
409ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C,
410                                           const CallExpr *CE,
411                                           SVal Size, SVal Init,
412                                           ProgramStateRef state) {
413  // Get the return value.
414  SVal retVal = state->getSVal(CE, C.getLocationContext());
415
416  // We expect the malloc functions to return a pointer.
417  if (!isa<Loc>(retVal))
418    return 0;
419
420  // Fill the region with the initialization value.
421  state = state->bindDefault(retVal, Init);
422
423  // Set the region's extent equal to the Size parameter.
424  const SymbolicRegion *R =
425      dyn_cast_or_null<SymbolicRegion>(retVal.getAsRegion());
426  if (!R)
427    return 0;
428  if (isa<DefinedOrUnknownSVal>(Size)) {
429    SValBuilder &svalBuilder = C.getSValBuilder();
430    DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder);
431    DefinedOrUnknownSVal DefinedSize = cast<DefinedOrUnknownSVal>(Size);
432    DefinedOrUnknownSVal extentMatchesSize =
433        svalBuilder.evalEQ(state, Extent, DefinedSize);
434
435    state = state->assume(extentMatchesSize, true);
436    assert(state);
437  }
438
439  return MallocUpdateRefState(C, CE, state);
440}
441
442ProgramStateRef MallocChecker::MallocUpdateRefState(CheckerContext &C,
443                                                    const CallExpr *CE,
444                                                    ProgramStateRef state) {
445  // Get the return value.
446  SVal retVal = state->getSVal(CE, C.getLocationContext());
447
448  // We expect the malloc functions to return a pointer.
449  if (!isa<Loc>(retVal))
450    return 0;
451
452  SymbolRef Sym = retVal.getAsLocSymbol();
453  assert(Sym);
454
455  // Set the symbol's state to Allocated.
456  return state->set<RegionState>(Sym, RefState::getAllocateUnchecked(CE));
457
458}
459
460ProgramStateRef MallocChecker::FreeMemAttr(CheckerContext &C,
461                                           const CallExpr *CE,
462                                           const OwnershipAttr* Att) const {
463  if (Att->getModule() != "malloc")
464    return 0;
465
466  ProgramStateRef State = C.getState();
467
468  for (OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
469       I != E; ++I) {
470    ProgramStateRef StateI = FreeMemAux(C, CE, State, *I,
471                               Att->getOwnKind() == OwnershipAttr::Holds);
472    if (StateI)
473      State = StateI;
474  }
475  return State;
476}
477
478ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
479                                          const CallExpr *CE,
480                                          ProgramStateRef state,
481                                          unsigned Num,
482                                          bool Hold) const {
483  const Expr *ArgExpr = CE->getArg(Num);
484  SVal ArgVal = state->getSVal(ArgExpr, C.getLocationContext());
485  if (!isa<DefinedOrUnknownSVal>(ArgVal))
486    return 0;
487  DefinedOrUnknownSVal location = cast<DefinedOrUnknownSVal>(ArgVal);
488
489  // Check for null dereferences.
490  if (!isa<Loc>(location))
491    return 0;
492
493  // The explicit NULL case, no operation is performed.
494  ProgramStateRef notNullState, nullState;
495  llvm::tie(notNullState, nullState) = state->assume(location);
496  if (nullState && !notNullState)
497    return 0;
498
499  // Unknown values could easily be okay
500  // Undefined values are handled elsewhere
501  if (ArgVal.isUnknownOrUndef())
502    return 0;
503
504  const MemRegion *R = ArgVal.getAsRegion();
505
506  // Nonlocs can't be freed, of course.
507  // Non-region locations (labels and fixed addresses) also shouldn't be freed.
508  if (!R) {
509    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
510    return 0;
511  }
512
513  R = R->StripCasts();
514
515  // Blocks might show up as heap data, but should not be free()d
516  if (isa<BlockDataRegion>(R)) {
517    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
518    return 0;
519  }
520
521  const MemSpaceRegion *MS = R->getMemorySpace();
522
523  // Parameters, locals, statics, and globals shouldn't be freed.
524  if (!(isa<UnknownSpaceRegion>(MS) || isa<HeapSpaceRegion>(MS))) {
525    // FIXME: at the time this code was written, malloc() regions were
526    // represented by conjured symbols, which are all in UnknownSpaceRegion.
527    // This means that there isn't actually anything from HeapSpaceRegion
528    // that should be freed, even though we allow it here.
529    // Of course, free() can work on memory allocated outside the current
530    // function, so UnknownSpaceRegion is always a possibility.
531    // False negatives are better than false positives.
532
533    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
534    return 0;
535  }
536
537  const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R);
538  // Various cases could lead to non-symbol values here.
539  // For now, ignore them.
540  if (!SR)
541    return 0;
542
543  SymbolRef Sym = SR->getSymbol();
544  const RefState *RS = state->get<RegionState>(Sym);
545
546  // If the symbol has not been tracked, return. This is possible when free() is
547  // called on a pointer that does not get its pointee directly from malloc().
548  // Full support of this requires inter-procedural analysis.
549  if (!RS)
550    return 0;
551
552  // Check double free.
553  if (RS->isReleased()) {
554    if (ExplodedNode *N = C.generateSink()) {
555      if (!BT_DoubleFree)
556        BT_DoubleFree.reset(
557          new BugType("Double free", "Memory Error"));
558      BugReport *R = new BugReport(*BT_DoubleFree,
559                        "Attempt to free released memory", N);
560      R->addRange(ArgExpr->getSourceRange());
561      R->markInteresting(Sym);
562      R->addVisitor(new MallocBugVisitor(Sym));
563      C.EmitReport(R);
564    }
565    return 0;
566  }
567
568  // Normal free.
569  if (Hold)
570    return state->set<RegionState>(Sym, RefState::getRelinquished(CE));
571  return state->set<RegionState>(Sym, RefState::getReleased(CE));
572}
573
574bool MallocChecker::SummarizeValue(raw_ostream &os, SVal V) {
575  if (nonloc::ConcreteInt *IntVal = dyn_cast<nonloc::ConcreteInt>(&V))
576    os << "an integer (" << IntVal->getValue() << ")";
577  else if (loc::ConcreteInt *ConstAddr = dyn_cast<loc::ConcreteInt>(&V))
578    os << "a constant address (" << ConstAddr->getValue() << ")";
579  else if (loc::GotoLabel *Label = dyn_cast<loc::GotoLabel>(&V))
580    os << "the address of the label '" << Label->getLabel()->getName() << "'";
581  else
582    return false;
583
584  return true;
585}
586
587bool MallocChecker::SummarizeRegion(raw_ostream &os,
588                                    const MemRegion *MR) {
589  switch (MR->getKind()) {
590  case MemRegion::FunctionTextRegionKind: {
591    const FunctionDecl *FD = cast<FunctionTextRegion>(MR)->getDecl();
592    if (FD)
593      os << "the address of the function '" << *FD << '\'';
594    else
595      os << "the address of a function";
596    return true;
597  }
598  case MemRegion::BlockTextRegionKind:
599    os << "block text";
600    return true;
601  case MemRegion::BlockDataRegionKind:
602    // FIXME: where the block came from?
603    os << "a block";
604    return true;
605  default: {
606    const MemSpaceRegion *MS = MR->getMemorySpace();
607
608    if (isa<StackLocalsSpaceRegion>(MS)) {
609      const VarRegion *VR = dyn_cast<VarRegion>(MR);
610      const VarDecl *VD;
611      if (VR)
612        VD = VR->getDecl();
613      else
614        VD = NULL;
615
616      if (VD)
617        os << "the address of the local variable '" << VD->getName() << "'";
618      else
619        os << "the address of a local stack variable";
620      return true;
621    }
622
623    if (isa<StackArgumentsSpaceRegion>(MS)) {
624      const VarRegion *VR = dyn_cast<VarRegion>(MR);
625      const VarDecl *VD;
626      if (VR)
627        VD = VR->getDecl();
628      else
629        VD = NULL;
630
631      if (VD)
632        os << "the address of the parameter '" << VD->getName() << "'";
633      else
634        os << "the address of a parameter";
635      return true;
636    }
637
638    if (isa<GlobalsSpaceRegion>(MS)) {
639      const VarRegion *VR = dyn_cast<VarRegion>(MR);
640      const VarDecl *VD;
641      if (VR)
642        VD = VR->getDecl();
643      else
644        VD = NULL;
645
646      if (VD) {
647        if (VD->isStaticLocal())
648          os << "the address of the static variable '" << VD->getName() << "'";
649        else
650          os << "the address of the global variable '" << VD->getName() << "'";
651      } else
652        os << "the address of a global variable";
653      return true;
654    }
655
656    return false;
657  }
658  }
659}
660
661void MallocChecker::ReportBadFree(CheckerContext &C, SVal ArgVal,
662                                  SourceRange range) const {
663  if (ExplodedNode *N = C.generateSink()) {
664    if (!BT_BadFree)
665      BT_BadFree.reset(new BugType("Bad free", "Memory Error"));
666
667    SmallString<100> buf;
668    llvm::raw_svector_ostream os(buf);
669
670    const MemRegion *MR = ArgVal.getAsRegion();
671    if (MR) {
672      while (const ElementRegion *ER = dyn_cast<ElementRegion>(MR))
673        MR = ER->getSuperRegion();
674
675      // Special case for alloca()
676      if (isa<AllocaRegion>(MR))
677        os << "Argument to free() was allocated by alloca(), not malloc()";
678      else {
679        os << "Argument to free() is ";
680        if (SummarizeRegion(os, MR))
681          os << ", which is not memory allocated by malloc()";
682        else
683          os << "not memory allocated by malloc()";
684      }
685    } else {
686      os << "Argument to free() is ";
687      if (SummarizeValue(os, ArgVal))
688        os << ", which is not memory allocated by malloc()";
689      else
690        os << "not memory allocated by malloc()";
691    }
692
693    BugReport *R = new BugReport(*BT_BadFree, os.str(), N);
694    R->markInteresting(MR);
695    R->addRange(range);
696    C.EmitReport(R);
697  }
698}
699
700ProgramStateRef MallocChecker::ReallocMem(CheckerContext &C,
701                                          const CallExpr *CE,
702                                          bool FreesOnFail) const {
703  ProgramStateRef state = C.getState();
704  const Expr *arg0Expr = CE->getArg(0);
705  const LocationContext *LCtx = C.getLocationContext();
706  SVal Arg0Val = state->getSVal(arg0Expr, LCtx);
707  if (!isa<DefinedOrUnknownSVal>(Arg0Val))
708    return 0;
709  DefinedOrUnknownSVal arg0Val = cast<DefinedOrUnknownSVal>(Arg0Val);
710
711  SValBuilder &svalBuilder = C.getSValBuilder();
712
713  DefinedOrUnknownSVal PtrEQ =
714    svalBuilder.evalEQ(state, arg0Val, svalBuilder.makeNull());
715
716  // Get the size argument. If there is no size arg then give up.
717  const Expr *Arg1 = CE->getArg(1);
718  if (!Arg1)
719    return 0;
720
721  // Get the value of the size argument.
722  SVal Arg1ValG = state->getSVal(Arg1, LCtx);
723  if (!isa<DefinedOrUnknownSVal>(Arg1ValG))
724    return 0;
725  DefinedOrUnknownSVal Arg1Val = cast<DefinedOrUnknownSVal>(Arg1ValG);
726
727  // Compare the size argument to 0.
728  DefinedOrUnknownSVal SizeZero =
729    svalBuilder.evalEQ(state, Arg1Val,
730                       svalBuilder.makeIntValWithPtrWidth(0, false));
731
732  ProgramStateRef StatePtrIsNull, StatePtrNotNull;
733  llvm::tie(StatePtrIsNull, StatePtrNotNull) = state->assume(PtrEQ);
734  ProgramStateRef StateSizeIsZero, StateSizeNotZero;
735  llvm::tie(StateSizeIsZero, StateSizeNotZero) = state->assume(SizeZero);
736  // We only assume exceptional states if they are definitely true; if the
737  // state is under-constrained, assume regular realloc behavior.
738  bool PrtIsNull = StatePtrIsNull && !StatePtrNotNull;
739  bool SizeIsZero = StateSizeIsZero && !StateSizeNotZero;
740
741  // If the ptr is NULL and the size is not 0, the call is equivalent to
742  // malloc(size).
743  if ( PrtIsNull && !SizeIsZero) {
744    ProgramStateRef stateMalloc = MallocMemAux(C, CE, CE->getArg(1),
745                                               UndefinedVal(), StatePtrIsNull);
746    return stateMalloc;
747  }
748
749  if (PrtIsNull && SizeIsZero)
750    return 0;
751
752  // Get the from and to pointer symbols as in toPtr = realloc(fromPtr, size).
753  assert(!PrtIsNull);
754  SymbolRef FromPtr = arg0Val.getAsSymbol();
755  SVal RetVal = state->getSVal(CE, LCtx);
756  SymbolRef ToPtr = RetVal.getAsSymbol();
757  if (!FromPtr || !ToPtr)
758    return 0;
759
760  // If the size is 0, free the memory.
761  if (SizeIsZero)
762    if (ProgramStateRef stateFree = FreeMemAux(C, CE, StateSizeIsZero,0,false)){
763      // The semantics of the return value are:
764      // If size was equal to 0, either NULL or a pointer suitable to be passed
765      // to free() is returned.
766      stateFree = stateFree->set<ReallocPairs>(ToPtr,
767                                            ReallocPair(FromPtr, FreesOnFail));
768      C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr);
769      return stateFree;
770    }
771
772  // Default behavior.
773  if (ProgramStateRef stateFree = FreeMemAux(C, CE, state, 0, false)) {
774    // FIXME: We should copy the content of the original buffer.
775    ProgramStateRef stateRealloc = MallocMemAux(C, CE, CE->getArg(1),
776                                                UnknownVal(), stateFree);
777    if (!stateRealloc)
778      return 0;
779    stateRealloc = stateRealloc->set<ReallocPairs>(ToPtr,
780                                            ReallocPair(FromPtr, FreesOnFail));
781    C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr);
782    return stateRealloc;
783  }
784  return 0;
785}
786
787ProgramStateRef MallocChecker::CallocMem(CheckerContext &C, const CallExpr *CE){
788  ProgramStateRef state = C.getState();
789  SValBuilder &svalBuilder = C.getSValBuilder();
790  const LocationContext *LCtx = C.getLocationContext();
791  SVal count = state->getSVal(CE->getArg(0), LCtx);
792  SVal elementSize = state->getSVal(CE->getArg(1), LCtx);
793  SVal TotalSize = svalBuilder.evalBinOp(state, BO_Mul, count, elementSize,
794                                        svalBuilder.getContext().getSizeType());
795  SVal zeroVal = svalBuilder.makeZeroVal(svalBuilder.getContext().CharTy);
796
797  return MallocMemAux(C, CE, TotalSize, zeroVal, state);
798}
799
800const Stmt *
801MallocChecker::getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
802                                 CheckerContext &C) const {
803  const LocationContext *LeakContext = N->getLocationContext();
804  // Walk the ExplodedGraph backwards and find the first node that referred to
805  // the tracked symbol.
806  const ExplodedNode *AllocNode = N;
807
808  while (N) {
809    if (!N->getState()->get<RegionState>(Sym))
810      break;
811    // Allocation node, is the last node in the current context in which the
812    // symbol was tracked.
813    if (N->getLocationContext() == LeakContext)
814      AllocNode = N;
815    N = N->pred_empty() ? NULL : *(N->pred_begin());
816  }
817
818  ProgramPoint P = AllocNode->getLocation();
819  if (!isa<StmtPoint>(P))
820    return 0;
821
822  return cast<StmtPoint>(P).getStmt();
823}
824
825void MallocChecker::reportLeak(SymbolRef Sym, ExplodedNode *N,
826                               CheckerContext &C) const {
827  assert(N);
828  if (!BT_Leak) {
829    BT_Leak.reset(new BugType("Memory leak", "Memory Error"));
830    // Leaks should not be reported if they are post-dominated by a sink:
831    // (1) Sinks are higher importance bugs.
832    // (2) NoReturnFunctionChecker uses sink nodes to represent paths ending
833    //     with __noreturn functions such as assert() or exit(). We choose not
834    //     to report leaks on such paths.
835    BT_Leak->setSuppressOnSink(true);
836  }
837
838  // Most bug reports are cached at the location where they occurred.
839  // With leaks, we want to unique them by the location where they were
840  // allocated, and only report a single path.
841  PathDiagnosticLocation LocUsedForUniqueing;
842  if (const Stmt *AllocStmt = getAllocationSite(N, Sym, C))
843    LocUsedForUniqueing = PathDiagnosticLocation::createBegin(AllocStmt,
844                            C.getSourceManager(), N->getLocationContext());
845
846  BugReport *R = new BugReport(*BT_Leak,
847    "Memory is never released; potential memory leak", N, LocUsedForUniqueing);
848  R->markInteresting(Sym);
849  // FIXME: This is a hack to make sure the MallocBugVisitor gets to look at
850  // the ExplodedNode chain first, in order to mark any failed realloc symbols
851  // as interesting for ConditionBRVisitor.
852  R->addVisitor(new ConditionBRVisitor());
853  R->addVisitor(new MallocBugVisitor(Sym));
854  C.EmitReport(R);
855}
856
857void MallocChecker::checkDeadSymbols(SymbolReaper &SymReaper,
858                                     CheckerContext &C) const
859{
860  if (!SymReaper.hasDeadSymbols())
861    return;
862
863  ProgramStateRef state = C.getState();
864  RegionStateTy RS = state->get<RegionState>();
865  RegionStateTy::Factory &F = state->get_context<RegionState>();
866
867  bool generateReport = false;
868  llvm::SmallVector<SymbolRef, 2> Errors;
869  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
870    if (SymReaper.isDead(I->first)) {
871      if (I->second.isAllocated()) {
872        generateReport = true;
873        Errors.push_back(I->first);
874      }
875      // Remove the dead symbol from the map.
876      RS = F.remove(RS, I->first);
877
878    }
879  }
880
881  // Cleanup the Realloc Pairs Map.
882  ReallocMap RP = state->get<ReallocPairs>();
883  for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
884    if (SymReaper.isDead(I->first) ||
885        SymReaper.isDead(I->second.ReallocatedSym)) {
886      state = state->remove<ReallocPairs>(I->first);
887    }
888  }
889
890  // Generate leak node.
891  static SimpleProgramPointTag Tag("MallocChecker : DeadSymbolsLeak");
892  ExplodedNode *N = C.addTransition(C.getState(), C.getPredecessor(), &Tag);
893
894  if (generateReport) {
895    for (llvm::SmallVector<SymbolRef, 2>::iterator
896         I = Errors.begin(), E = Errors.end(); I != E; ++I) {
897      reportLeak(*I, N, C);
898    }
899  }
900  C.addTransition(state->set<RegionState>(RS), N);
901}
902
903void MallocChecker::checkEndPath(CheckerContext &C) const {
904  ProgramStateRef state = C.getState();
905  RegionStateTy M = state->get<RegionState>();
906
907  // If inside inlined call, skip it.
908  if (C.getLocationContext()->getParent() != 0)
909    return;
910
911  for (RegionStateTy::iterator I = M.begin(), E = M.end(); I != E; ++I) {
912    RefState RS = I->second;
913    if (RS.isAllocated()) {
914      ExplodedNode *N = C.addTransition(state);
915      if (N)
916        reportLeak(I->first, N, C);
917    }
918  }
919}
920
921bool MallocChecker::checkEscape(SymbolRef Sym, const Stmt *S,
922                                CheckerContext &C) const {
923  ProgramStateRef state = C.getState();
924  const RefState *RS = state->get<RegionState>(Sym);
925  if (!RS)
926    return false;
927
928  if (RS->isAllocated()) {
929    state = state->set<RegionState>(Sym, RefState::getEscaped(S));
930    C.addTransition(state);
931    return true;
932  }
933  return false;
934}
935
936void MallocChecker::checkPreStmt(const CallExpr *CE, CheckerContext &C) const {
937  if (isMemFunction(C.getCalleeDecl(CE), C.getASTContext()))
938    return;
939
940  // Check use after free, when a freed pointer is passed to a call.
941  ProgramStateRef State = C.getState();
942  for (CallExpr::const_arg_iterator I = CE->arg_begin(),
943                                    E = CE->arg_end(); I != E; ++I) {
944    const Expr *A = *I;
945    if (A->getType().getTypePtr()->isAnyPointerType()) {
946      SymbolRef Sym = State->getSVal(A, C.getLocationContext()).getAsSymbol();
947      if (!Sym)
948        continue;
949      if (checkUseAfterFree(Sym, C, A))
950        return;
951    }
952  }
953}
954
955void MallocChecker::checkPreStmt(const ReturnStmt *S, CheckerContext &C) const {
956  const Expr *E = S->getRetValue();
957  if (!E)
958    return;
959
960  // Check if we are returning a symbol.
961  SVal RetVal = C.getState()->getSVal(E, C.getLocationContext());
962  SymbolRef Sym = RetVal.getAsSymbol();
963  if (!Sym)
964    // If we are returning a field of the allocated struct or an array element,
965    // the callee could still free the memory.
966    // TODO: This logic should be a part of generic symbol escape callback.
967    if (const MemRegion *MR = RetVal.getAsRegion())
968      if (isa<FieldRegion>(MR) || isa<ElementRegion>(MR))
969        if (const SymbolicRegion *BMR =
970              dyn_cast<SymbolicRegion>(MR->getBaseRegion()))
971          Sym = BMR->getSymbol();
972  if (!Sym)
973    return;
974
975  // Check if we are returning freed memory.
976  if (checkUseAfterFree(Sym, C, E))
977    return;
978
979  // If this function body is not inlined, check if the symbol is escaping.
980  if (C.getLocationContext()->getParent() == 0)
981    checkEscape(Sym, E, C);
982}
983
984bool MallocChecker::checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
985                                      const Stmt *S) const {
986  assert(Sym);
987  const RefState *RS = C.getState()->get<RegionState>(Sym);
988  if (RS && RS->isReleased()) {
989    if (ExplodedNode *N = C.generateSink()) {
990      if (!BT_UseFree)
991        BT_UseFree.reset(new BugType("Use-after-free", "Memory Error"));
992
993      BugReport *R = new BugReport(*BT_UseFree,
994                                   "Use of memory after it is freed",N);
995      if (S)
996        R->addRange(S->getSourceRange());
997      R->markInteresting(Sym);
998      R->addVisitor(new MallocBugVisitor(Sym));
999      C.EmitReport(R);
1000      return true;
1001    }
1002  }
1003  return false;
1004}
1005
1006// Check if the location is a freed symbolic region.
1007void MallocChecker::checkLocation(SVal l, bool isLoad, const Stmt *S,
1008                                  CheckerContext &C) const {
1009  SymbolRef Sym = l.getLocSymbolInBase();
1010  if (Sym)
1011    checkUseAfterFree(Sym, C);
1012}
1013
1014//===----------------------------------------------------------------------===//
1015// Check various ways a symbol can be invalidated.
1016// TODO: This logic (the next 3 functions) is copied/similar to the
1017// RetainRelease checker. We might want to factor this out.
1018//===----------------------------------------------------------------------===//
1019
1020// Stop tracking symbols when a value escapes as a result of checkBind.
1021// A value escapes in three possible cases:
1022// (1) we are binding to something that is not a memory region.
1023// (2) we are binding to a memregion that does not have stack storage
1024// (3) we are binding to a memregion with stack storage that the store
1025//     does not understand.
1026void MallocChecker::checkBind(SVal loc, SVal val, const Stmt *S,
1027                              CheckerContext &C) const {
1028  // Are we storing to something that causes the value to "escape"?
1029  bool escapes = true;
1030  ProgramStateRef state = C.getState();
1031
1032  if (loc::MemRegionVal *regionLoc = dyn_cast<loc::MemRegionVal>(&loc)) {
1033    escapes = !regionLoc->getRegion()->hasStackStorage();
1034
1035    if (!escapes) {
1036      // To test (3), generate a new state with the binding added.  If it is
1037      // the same state, then it escapes (since the store cannot represent
1038      // the binding).
1039      escapes = (state == (state->bindLoc(*regionLoc, val)));
1040    }
1041    if (!escapes) {
1042      // Case 4: We do not currently model what happens when a symbol is
1043      // assigned to a struct field, so be conservative here and let the symbol
1044      // go. TODO: This could definitely be improved upon.
1045      escapes = !isa<VarRegion>(regionLoc->getRegion());
1046    }
1047  }
1048
1049  // If our store can represent the binding and we aren't storing to something
1050  // that doesn't have local storage then just return and have the simulation
1051  // state continue as is.
1052  if (!escapes)
1053      return;
1054
1055  // Otherwise, find all symbols referenced by 'val' that we are tracking
1056  // and stop tracking them.
1057  state = state->scanReachableSymbols<StopTrackingCallback>(val).getState();
1058  C.addTransition(state);
1059}
1060
1061// If a symbolic region is assumed to NULL (or another constant), stop tracking
1062// it - assuming that allocation failed on this path.
1063ProgramStateRef MallocChecker::evalAssume(ProgramStateRef state,
1064                                              SVal Cond,
1065                                              bool Assumption) const {
1066  RegionStateTy RS = state->get<RegionState>();
1067  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
1068    // If the symbol is assumed to NULL or another constant, this will
1069    // return an APSInt*.
1070    if (state->getSymVal(I.getKey()))
1071      state = state->remove<RegionState>(I.getKey());
1072  }
1073
1074  // Realloc returns 0 when reallocation fails, which means that we should
1075  // restore the state of the pointer being reallocated.
1076  ReallocMap RP = state->get<ReallocPairs>();
1077  for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
1078    // If the symbol is assumed to NULL or another constant, this will
1079    // return an APSInt*.
1080    if (state->getSymVal(I.getKey())) {
1081      SymbolRef ReallocSym = I.getData().ReallocatedSym;
1082      const RefState *RS = state->get<RegionState>(ReallocSym);
1083      if (RS) {
1084        if (RS->isReleased() && ! I.getData().IsFreeOnFailure)
1085          state = state->set<RegionState>(ReallocSym,
1086                             RefState::getAllocateUnchecked(RS->getStmt()));
1087      }
1088      state = state->remove<ReallocPairs>(I.getKey());
1089    }
1090  }
1091
1092  return state;
1093}
1094
1095// Check if the function is known to us. So, for example, we could
1096// conservatively assume it can free/reallocate it's pointer arguments.
1097// (We assume that the pointers cannot escape through calls to system
1098// functions not handled by this checker.)
1099bool MallocChecker::doesNotFreeMemory(const CallOrObjCMessage *Call,
1100                                      ProgramStateRef State) const {
1101  if (!Call)
1102    return false;
1103
1104  // For now, assume that any C++ call can free memory.
1105  // TODO: If we want to be more optimistic here, we'll need to make sure that
1106  // regions escape to C++ containers. They seem to do that even now, but for
1107  // mysterious reasons.
1108  if (Call->isCXXCall())
1109    return false;
1110
1111  const Decl *D = Call->getDecl();
1112  if (!D)
1113    return false;
1114
1115  ASTContext &ASTC = State->getStateManager().getContext();
1116
1117  // If it's one of the allocation functions we can reason about, we model
1118  // its behavior explicitly.
1119  if (isa<FunctionDecl>(D) && isMemFunction(cast<FunctionDecl>(D), ASTC)) {
1120    return true;
1121  }
1122
1123  // If it's not a system call, assume it frees memory.
1124  SourceManager &SM = ASTC.getSourceManager();
1125  if (!SM.isInSystemHeader(D->getLocation()))
1126    return false;
1127
1128  // Process C/ObjC functions.
1129  if (const FunctionDecl *FD  = dyn_cast<FunctionDecl>(D)) {
1130    // White list the system functions whose arguments escape.
1131    const IdentifierInfo *II = FD->getIdentifier();
1132    if (!II)
1133      return true;
1134    StringRef FName = II->getName();
1135
1136    // White list thread local storage.
1137    if (FName.equals("pthread_setspecific"))
1138      return false;
1139
1140    // White list the 'XXXNoCopy' ObjC functions.
1141    if (FName.endswith("NoCopy")) {
1142      // Look for the deallocator argument. We know that the memory ownership
1143      // is not transfered only if the deallocator argument is
1144      // 'kCFAllocatorNull'.
1145      for (unsigned i = 1; i < Call->getNumArgs(); ++i) {
1146        const Expr *ArgE = Call->getArg(i)->IgnoreParenCasts();
1147        if (const DeclRefExpr *DE = dyn_cast<DeclRefExpr>(ArgE)) {
1148          StringRef DeallocatorName = DE->getFoundDecl()->getName();
1149          if (DeallocatorName == "kCFAllocatorNull")
1150            return true;
1151        }
1152      }
1153      return false;
1154    }
1155
1156    // PR12101
1157    // Many CoreFoundation and CoreGraphics might allow a tracked object
1158    // to escape.
1159    if (Call->isCFCGAllowingEscape(FName))
1160      return false;
1161
1162    // Associating streams with malloced buffers. The pointer can escape if
1163    // 'closefn' is specified (and if that function does free memory).
1164    // Currently, we do not inspect the 'closefn' function (PR12101).
1165    if (FName == "funopen")
1166      if (Call->getNumArgs() >= 4 && !Call->getArgSVal(4).isConstant(0))
1167        return false;
1168
1169    // Do not warn on pointers passed to 'setbuf' when used with std streams,
1170    // these leaks might be intentional when setting the buffer for stdio.
1171    // http://stackoverflow.com/questions/2671151/who-frees-setvbuf-buffer
1172    if (FName == "setbuf" || FName =="setbuffer" ||
1173        FName == "setlinebuf" || FName == "setvbuf") {
1174      if (Call->getNumArgs() >= 1)
1175        if (const DeclRefExpr *Arg =
1176              dyn_cast<DeclRefExpr>(Call->getArg(0)->IgnoreParenCasts()))
1177          if (const VarDecl *D = dyn_cast<VarDecl>(Arg->getDecl()))
1178              if (D->getCanonicalDecl()->getName().find("std")
1179                                                   != StringRef::npos)
1180                return false;
1181    }
1182
1183    // A bunch of other functions, which take ownership of a pointer (See retain
1184    // release checker). Not all the parameters here are invalidated, but the
1185    // Malloc checker cannot differentiate between them. The right way of doing
1186    // this would be to implement a pointer escapes callback.
1187    if (FName == "CVPixelBufferCreateWithBytes" ||
1188        FName == "CGBitmapContextCreateWithData" ||
1189        FName == "CVPixelBufferCreateWithPlanarBytes") {
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  // Process ObjC functions.
1198  } else if (const ObjCMethodDecl * ObjCD = dyn_cast<ObjCMethodDecl>(D)) {
1199    Selector S = ObjCD->getSelector();
1200
1201    // White list the ObjC functions which do free memory.
1202    // - Anything containing 'freeWhenDone' param set to 1.
1203    //   Ex: dataWithBytesNoCopy:length:freeWhenDone.
1204    for (unsigned i = 1; i < S.getNumArgs(); ++i) {
1205      if (S.getNameForSlot(i).equals("freeWhenDone")) {
1206        if (Call->getArgSVal(i).isConstant(1))
1207          return false;
1208        else
1209          return true;
1210      }
1211    }
1212
1213    // If the first selector ends with NoCopy, assume that the ownership is
1214    // transfered as well.
1215    // Ex:  [NSData dataWithBytesNoCopy:bytes length:10];
1216    if (S.getNameForSlot(0).endswith("NoCopy")) {
1217      return false;
1218    }
1219
1220    // Otherwise, assume that the function does not free memory.
1221    // Most system calls, do not free the memory.
1222    return true;
1223  }
1224
1225  // Otherwise, assume that the function can free memory.
1226  return false;
1227
1228}
1229
1230// If the symbol we are tracking is invalidated, but not explicitly (ex: the &p
1231// escapes, when we are tracking p), do not track the symbol as we cannot reason
1232// about it anymore.
1233ProgramStateRef
1234MallocChecker::checkRegionChanges(ProgramStateRef State,
1235                            const StoreManager::InvalidatedSymbols *invalidated,
1236                                    ArrayRef<const MemRegion *> ExplicitRegions,
1237                                    ArrayRef<const MemRegion *> Regions,
1238                                    const CallOrObjCMessage *Call) const {
1239  if (!invalidated || invalidated->empty())
1240    return State;
1241  llvm::SmallPtrSet<SymbolRef, 8> WhitelistedSymbols;
1242
1243  // If it's a call which might free or reallocate memory, we assume that all
1244  // regions (explicit and implicit) escaped.
1245
1246  // Otherwise, whitelist explicit pointers; we still can track them.
1247  if (!Call || doesNotFreeMemory(Call, State)) {
1248    for (ArrayRef<const MemRegion *>::iterator I = ExplicitRegions.begin(),
1249        E = ExplicitRegions.end(); I != E; ++I) {
1250      if (const SymbolicRegion *R = (*I)->StripCasts()->getAs<SymbolicRegion>())
1251        WhitelistedSymbols.insert(R->getSymbol());
1252    }
1253  }
1254
1255  for (StoreManager::InvalidatedSymbols::const_iterator I=invalidated->begin(),
1256       E = invalidated->end(); I!=E; ++I) {
1257    SymbolRef sym = *I;
1258    if (WhitelistedSymbols.count(sym))
1259      continue;
1260    // The symbol escaped.
1261    if (const RefState *RS = State->get<RegionState>(sym))
1262      State = State->set<RegionState>(sym, RefState::getEscaped(RS->getStmt()));
1263  }
1264  return State;
1265}
1266
1267static SymbolRef findFailedReallocSymbol(ProgramStateRef currState,
1268                                         ProgramStateRef prevState) {
1269  ReallocMap currMap = currState->get<ReallocPairs>();
1270  ReallocMap prevMap = prevState->get<ReallocPairs>();
1271
1272  for (ReallocMap::iterator I = prevMap.begin(), E = prevMap.end();
1273       I != E; ++I) {
1274    SymbolRef sym = I.getKey();
1275    if (!currMap.lookup(sym))
1276      return sym;
1277  }
1278
1279  return NULL;
1280}
1281
1282PathDiagnosticPiece *
1283MallocChecker::MallocBugVisitor::VisitNode(const ExplodedNode *N,
1284                                           const ExplodedNode *PrevN,
1285                                           BugReporterContext &BRC,
1286                                           BugReport &BR) {
1287  ProgramStateRef state = N->getState();
1288  ProgramStateRef statePrev = PrevN->getState();
1289
1290  const RefState *RS = state->get<RegionState>(Sym);
1291  const RefState *RSPrev = statePrev->get<RegionState>(Sym);
1292  if (!RS && !RSPrev)
1293    return 0;
1294
1295  const Stmt *S = 0;
1296  const char *Msg = 0;
1297  StackHintGeneratorForSymbol *StackHint = 0;
1298
1299  // Retrieve the associated statement.
1300  ProgramPoint ProgLoc = N->getLocation();
1301  if (isa<StmtPoint>(ProgLoc))
1302    S = cast<StmtPoint>(ProgLoc).getStmt();
1303  // If an assumption was made on a branch, it should be caught
1304  // here by looking at the state transition.
1305  if (isa<BlockEdge>(ProgLoc)) {
1306    const CFGBlock *srcBlk = cast<BlockEdge>(ProgLoc).getSrc();
1307    S = srcBlk->getTerminator();
1308  }
1309  if (!S)
1310    return 0;
1311
1312  // Find out if this is an interesting point and what is the kind.
1313  if (Mode == Normal) {
1314    if (isAllocated(RS, RSPrev, S)) {
1315      Msg = "Memory is allocated";
1316      StackHint = new StackHintGeneratorForSymbol(Sym,
1317                                                  "Returned allocated memory");
1318    } else if (isReleased(RS, RSPrev, S)) {
1319      Msg = "Memory is released";
1320      StackHint = new StackHintGeneratorForSymbol(Sym,
1321                                                  "Returned released memory");
1322    } else if (isReallocFailedCheck(RS, RSPrev, S)) {
1323      Mode = ReallocationFailed;
1324      Msg = "Reallocation failed";
1325      StackHint = new StackHintGeneratorForReallocationFailed(Sym,
1326                                                       "Reallocation failed");
1327
1328      if (SymbolRef sym = findFailedReallocSymbol(state, statePrev))
1329        BR.markInteresting(sym);
1330    }
1331
1332  // We are in a special mode if a reallocation failed later in the path.
1333  } else if (Mode == ReallocationFailed) {
1334    // Generate a special diagnostic for the first realloc we find.
1335    if (!isAllocated(RS, RSPrev, S) && !isReleased(RS, RSPrev, S))
1336      return 0;
1337
1338    // Check that the name of the function is realloc.
1339    const CallExpr *CE = dyn_cast<CallExpr>(S);
1340    if (!CE)
1341      return 0;
1342    const FunctionDecl *funDecl = CE->getDirectCallee();
1343    if (!funDecl)
1344      return 0;
1345    StringRef FunName = funDecl->getName();
1346    if (!(FunName.equals("realloc") || FunName.equals("reallocf")))
1347      return 0;
1348    Msg = "Attempt to reallocate memory";
1349    StackHint = new StackHintGeneratorForSymbol(Sym,
1350                                                "Returned reallocated memory");
1351    Mode = Normal;
1352  }
1353
1354  if (!Msg)
1355    return 0;
1356  assert(StackHint);
1357
1358  // Generate the extra diagnostic.
1359  PathDiagnosticLocation Pos(S, BRC.getSourceManager(),
1360                             N->getLocationContext());
1361  return new PathDiagnosticEventPiece(Pos, Msg, true, StackHint);
1362}
1363
1364
1365#define REGISTER_CHECKER(name) \
1366void ento::register##name(CheckerManager &mgr) {\
1367  registerCStringCheckerBasic(mgr); \
1368  mgr.registerChecker<MallocChecker>()->Filter.C##name = true;\
1369}
1370
1371REGISTER_CHECKER(MallocPessimistic)
1372REGISTER_CHECKER(MallocOptimistic)
1373