MallocChecker.cpp revision 93c5a24b517e65eb61481ed866b503f1e37cff20 
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
85typedef std::pair<const Stmt*, const MemRegion*> LeakInfo;
86
87class MallocChecker : public Checker<check::DeadSymbols,
88                                     check::EndPath,
89                                     check::PreStmt<ReturnStmt>,
90                                     check::PreStmt<CallExpr>,
91                                     check::PostStmt<CallExpr>,
92                                     check::PostStmt<BlockExpr>,
93                                     check::Location,
94                                     check::Bind,
95                                     eval::Assume,
96                                     check::RegionChanges>
97{
98  mutable OwningPtr<BugType> BT_DoubleFree;
99  mutable OwningPtr<BugType> BT_Leak;
100  mutable OwningPtr<BugType> BT_UseFree;
101  mutable OwningPtr<BugType> BT_BadFree;
102  mutable IdentifierInfo *II_malloc, *II_free, *II_realloc, *II_calloc,
103                         *II_valloc, *II_reallocf, *II_strndup, *II_strdup;
104
105public:
106  MallocChecker() : II_malloc(0), II_free(0), II_realloc(0), II_calloc(0),
107                    II_valloc(0), II_reallocf(0), II_strndup(0), II_strdup(0) {}
108
109  /// In pessimistic mode, the checker assumes that it does not know which
110  /// functions might free the memory.
111  struct ChecksFilter {
112    DefaultBool CMallocPessimistic;
113    DefaultBool CMallocOptimistic;
114  };
115
116  ChecksFilter Filter;
117
118  void checkPreStmt(const CallExpr *S, CheckerContext &C) const;
119  void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
120  void checkPostStmt(const BlockExpr *BE, CheckerContext &C) const;
121  void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;
122  void checkEndPath(CheckerContext &C) const;
123  void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const;
124  ProgramStateRef evalAssume(ProgramStateRef state, SVal Cond,
125                            bool Assumption) const;
126  void checkLocation(SVal l, bool isLoad, const Stmt *S,
127                     CheckerContext &C) const;
128  void checkBind(SVal location, SVal val, const Stmt*S,
129                 CheckerContext &C) const;
130  ProgramStateRef
131  checkRegionChanges(ProgramStateRef state,
132                     const StoreManager::InvalidatedSymbols *invalidated,
133                     ArrayRef<const MemRegion *> ExplicitRegions,
134                     ArrayRef<const MemRegion *> Regions,
135                     const CallOrObjCMessage *Call) const;
136  bool wantsRegionChangeUpdate(ProgramStateRef state) const {
137    return true;
138  }
139
140  void printState(raw_ostream &Out, ProgramStateRef State,
141                  const char *NL, const char *Sep) const;
142
143private:
144  void initIdentifierInfo(ASTContext &C) const;
145
146  /// Check if this is one of the functions which can allocate/reallocate memory
147  /// pointed to by one of its arguments.
148  bool isMemFunction(const FunctionDecl *FD, ASTContext &C) const;
149
150  static ProgramStateRef MallocMemReturnsAttr(CheckerContext &C,
151                                              const CallExpr *CE,
152                                              const OwnershipAttr* Att);
153  static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
154                                     const Expr *SizeEx, SVal Init,
155                                     ProgramStateRef state) {
156    return MallocMemAux(C, CE,
157                        state->getSVal(SizeEx, C.getLocationContext()),
158                        Init, state);
159  }
160
161  static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
162                                     SVal SizeEx, SVal Init,
163                                     ProgramStateRef state);
164
165  /// Update the RefState to reflect the new memory allocation.
166  static ProgramStateRef MallocUpdateRefState(CheckerContext &C,
167                                              const CallExpr *CE,
168                                              ProgramStateRef state);
169
170  ProgramStateRef FreeMemAttr(CheckerContext &C, const CallExpr *CE,
171                              const OwnershipAttr* Att) const;
172  ProgramStateRef FreeMemAux(CheckerContext &C, const CallExpr *CE,
173                                 ProgramStateRef state, unsigned Num,
174                                 bool Hold) const;
175
176  ProgramStateRef ReallocMem(CheckerContext &C, const CallExpr *CE,
177                             bool FreesMemOnFailure) const;
178  static ProgramStateRef CallocMem(CheckerContext &C, const CallExpr *CE);
179
180  bool checkEscape(SymbolRef Sym, const Stmt *S, CheckerContext &C) const;
181  bool checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
182                         const Stmt *S = 0) const;
183
184  /// Check if the function is not known to us. So, for example, we could
185  /// conservatively assume it can free/reallocate it's pointer arguments.
186  bool doesNotFreeMemory(const CallOrObjCMessage *Call,
187                         ProgramStateRef State) const;
188
189  static bool SummarizeValue(raw_ostream &os, SVal V);
190  static bool SummarizeRegion(raw_ostream &os, const MemRegion *MR);
191  void ReportBadFree(CheckerContext &C, SVal ArgVal, SourceRange range) const;
192
193  /// Find the location of the allocation for Sym on the path leading to the
194  /// exploded node N.
195  LeakInfo getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
196                             CheckerContext &C) const;
197
198  void reportLeak(SymbolRef Sym, ExplodedNode *N, CheckerContext &C) const;
199
200  /// The bug visitor which allows us to print extra diagnostics along the
201  /// BugReport path. For example, showing the allocation site of the leaked
202  /// region.
203  class MallocBugVisitor : public BugReporterVisitorImpl<MallocBugVisitor> {
204  protected:
205    enum NotificationMode {
206      Normal,
207      ReallocationFailed
208    };
209
210    // The allocated region symbol tracked by the main analysis.
211    SymbolRef Sym;
212
213     // The mode we are in, i.e. what kind of diagnostics will be emitted.
214     NotificationMode Mode;
215
216     // A symbol from when the primary region should have been reallocated.
217     SymbolRef FailedReallocSymbol;
218
219   public:
220     MallocBugVisitor(SymbolRef S)
221       : Sym(S), Mode(Normal), FailedReallocSymbol(0) {}
222
223    virtual ~MallocBugVisitor() {}
224
225    void Profile(llvm::FoldingSetNodeID &ID) const {
226      static int X = 0;
227      ID.AddPointer(&X);
228      ID.AddPointer(Sym);
229    }
230
231    inline bool isAllocated(const RefState *S, const RefState *SPrev,
232                            const Stmt *Stmt) {
233      // Did not track -> allocated. Other state (released) -> allocated.
234      return (Stmt && isa<CallExpr>(Stmt) &&
235              (S && S->isAllocated()) && (!SPrev || !SPrev->isAllocated()));
236    }
237
238    inline bool isReleased(const RefState *S, const RefState *SPrev,
239                           const Stmt *Stmt) {
240      // Did not track -> released. Other state (allocated) -> released.
241      return (Stmt && isa<CallExpr>(Stmt) &&
242              (S && S->isReleased()) && (!SPrev || !SPrev->isReleased()));
243    }
244
245    inline bool isReallocFailedCheck(const RefState *S, const RefState *SPrev,
246                                     const Stmt *Stmt) {
247      // If the expression is not a call, and the state change is
248      // released -> allocated, it must be the realloc return value
249      // check. If we have to handle more cases here, it might be cleaner just
250      // to track this extra bit in the state itself.
251      return ((!Stmt || !isa<CallExpr>(Stmt)) &&
252              (S && S->isAllocated()) && (SPrev && !SPrev->isAllocated()));
253    }
254
255    PathDiagnosticPiece *VisitNode(const ExplodedNode *N,
256                                   const ExplodedNode *PrevN,
257                                   BugReporterContext &BRC,
258                                   BugReport &BR);
259  private:
260    class StackHintGeneratorForReallocationFailed
261        : public StackHintGeneratorForSymbol {
262    public:
263      StackHintGeneratorForReallocationFailed(SymbolRef S, StringRef M)
264        : StackHintGeneratorForSymbol(S, M) {}
265
266      virtual std::string getMessageForArg(const Expr *ArgE, unsigned ArgIndex) {
267        SmallString<200> buf;
268        llvm::raw_svector_ostream os(buf);
269
270        os << "Reallocation of ";
271        // Printed parameters start at 1, not 0.
272        printOrdinal(++ArgIndex, os);
273        os << " parameter failed";
274
275        return os.str();
276      }
277
278      virtual std::string getMessageForReturn(const CallExpr *CallExpr) {
279        return "Reallocation of returned value failed";
280      }
281    };
282  };
283};
284} // end anonymous namespace
285
286typedef llvm::ImmutableMap<SymbolRef, RefState> RegionStateTy;
287typedef llvm::ImmutableMap<SymbolRef, ReallocPair > ReallocMap;
288class RegionState {};
289class ReallocPairs {};
290namespace clang {
291namespace ento {
292  template <>
293  struct ProgramStateTrait<RegionState>
294    : public ProgramStatePartialTrait<RegionStateTy> {
295    static void *GDMIndex() { static int x; return &x; }
296  };
297
298  template <>
299  struct ProgramStateTrait<ReallocPairs>
300    : public ProgramStatePartialTrait<ReallocMap> {
301    static void *GDMIndex() { static int x; return &x; }
302  };
303}
304}
305
306namespace {
307class StopTrackingCallback : public SymbolVisitor {
308  ProgramStateRef state;
309public:
310  StopTrackingCallback(ProgramStateRef st) : state(st) {}
311  ProgramStateRef getState() const { return state; }
312
313  bool VisitSymbol(SymbolRef sym) {
314    state = state->remove<RegionState>(sym);
315    return true;
316  }
317};
318} // end anonymous namespace
319
320void MallocChecker::initIdentifierInfo(ASTContext &Ctx) const {
321  if (!II_malloc)
322    II_malloc = &Ctx.Idents.get("malloc");
323  if (!II_free)
324    II_free = &Ctx.Idents.get("free");
325  if (!II_realloc)
326    II_realloc = &Ctx.Idents.get("realloc");
327  if (!II_reallocf)
328    II_reallocf = &Ctx.Idents.get("reallocf");
329  if (!II_calloc)
330    II_calloc = &Ctx.Idents.get("calloc");
331  if (!II_valloc)
332    II_valloc = &Ctx.Idents.get("valloc");
333  if (!II_strdup)
334    II_strdup = &Ctx.Idents.get("strdup");
335  if (!II_strndup)
336    II_strndup = &Ctx.Idents.get("strndup");
337}
338
339bool MallocChecker::isMemFunction(const FunctionDecl *FD, ASTContext &C) const {
340  if (!FD)
341    return false;
342  IdentifierInfo *FunI = FD->getIdentifier();
343  if (!FunI)
344    return false;
345
346  initIdentifierInfo(C);
347
348  if (FunI == II_malloc || FunI == II_free || FunI == II_realloc ||
349      FunI == II_reallocf || FunI == II_calloc || FunI == II_valloc ||
350      FunI == II_strdup || FunI == II_strndup)
351    return true;
352
353  if (Filter.CMallocOptimistic && FD->hasAttrs() &&
354      FD->specific_attr_begin<OwnershipAttr>() !=
355          FD->specific_attr_end<OwnershipAttr>())
356    return true;
357
358
359  return false;
360}
361
362void MallocChecker::checkPostStmt(const CallExpr *CE, CheckerContext &C) const {
363  const FunctionDecl *FD = C.getCalleeDecl(CE);
364  if (!FD)
365    return;
366
367  initIdentifierInfo(C.getASTContext());
368  IdentifierInfo *FunI = FD->getIdentifier();
369  if (!FunI)
370    return;
371
372  ProgramStateRef State = C.getState();
373  if (FunI == II_malloc || FunI == II_valloc) {
374    if (CE->getNumArgs() < 1)
375      return;
376    State = MallocMemAux(C, CE, CE->getArg(0), UndefinedVal(), State);
377  } else if (FunI == II_realloc) {
378    State = ReallocMem(C, CE, false);
379  } else if (FunI == II_reallocf) {
380    State = ReallocMem(C, CE, true);
381  } else if (FunI == II_calloc) {
382    State = CallocMem(C, CE);
383  } else if (FunI == II_free) {
384    State = FreeMemAux(C, CE, C.getState(), 0, false);
385  } else if (FunI == II_strdup) {
386    State = MallocUpdateRefState(C, CE, State);
387  } else if (FunI == II_strndup) {
388    State = MallocUpdateRefState(C, CE, State);
389  } else if (Filter.CMallocOptimistic) {
390    // Check all the attributes, if there are any.
391    // There can be multiple of these attributes.
392    if (FD->hasAttrs())
393      for (specific_attr_iterator<OwnershipAttr>
394          i = FD->specific_attr_begin<OwnershipAttr>(),
395          e = FD->specific_attr_end<OwnershipAttr>();
396          i != e; ++i) {
397        switch ((*i)->getOwnKind()) {
398        case OwnershipAttr::Returns:
399          State = MallocMemReturnsAttr(C, CE, *i);
400          break;
401        case OwnershipAttr::Takes:
402        case OwnershipAttr::Holds:
403          State = FreeMemAttr(C, CE, *i);
404          break;
405        }
406      }
407  }
408  C.addTransition(State);
409}
410
411ProgramStateRef MallocChecker::MallocMemReturnsAttr(CheckerContext &C,
412                                                    const CallExpr *CE,
413                                                    const OwnershipAttr* Att) {
414  if (Att->getModule() != "malloc")
415    return 0;
416
417  OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
418  if (I != E) {
419    return MallocMemAux(C, CE, CE->getArg(*I), UndefinedVal(), C.getState());
420  }
421  return MallocMemAux(C, CE, UnknownVal(), UndefinedVal(), C.getState());
422}
423
424ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C,
425                                           const CallExpr *CE,
426                                           SVal Size, SVal Init,
427                                           ProgramStateRef state) {
428  // Get the return value.
429  SVal retVal = state->getSVal(CE, C.getLocationContext());
430
431  // We expect the malloc functions to return a pointer.
432  if (!isa<Loc>(retVal))
433    return 0;
434
435  // Fill the region with the initialization value.
436  state = state->bindDefault(retVal, Init);
437
438  // Set the region's extent equal to the Size parameter.
439  const SymbolicRegion *R =
440      dyn_cast_or_null<SymbolicRegion>(retVal.getAsRegion());
441  if (!R)
442    return 0;
443  if (isa<DefinedOrUnknownSVal>(Size)) {
444    SValBuilder &svalBuilder = C.getSValBuilder();
445    DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder);
446    DefinedOrUnknownSVal DefinedSize = cast<DefinedOrUnknownSVal>(Size);
447    DefinedOrUnknownSVal extentMatchesSize =
448        svalBuilder.evalEQ(state, Extent, DefinedSize);
449
450    state = state->assume(extentMatchesSize, true);
451    assert(state);
452  }
453
454  return MallocUpdateRefState(C, CE, state);
455}
456
457ProgramStateRef MallocChecker::MallocUpdateRefState(CheckerContext &C,
458                                                    const CallExpr *CE,
459                                                    ProgramStateRef state) {
460  // Get the return value.
461  SVal retVal = state->getSVal(CE, C.getLocationContext());
462
463  // We expect the malloc functions to return a pointer.
464  if (!isa<Loc>(retVal))
465    return 0;
466
467  SymbolRef Sym = retVal.getAsLocSymbol();
468  assert(Sym);
469
470  // Set the symbol's state to Allocated.
471  return state->set<RegionState>(Sym, RefState::getAllocateUnchecked(CE));
472
473}
474
475ProgramStateRef MallocChecker::FreeMemAttr(CheckerContext &C,
476                                           const CallExpr *CE,
477                                           const OwnershipAttr* Att) const {
478  if (Att->getModule() != "malloc")
479    return 0;
480
481  ProgramStateRef State = C.getState();
482
483  for (OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
484       I != E; ++I) {
485    ProgramStateRef StateI = FreeMemAux(C, CE, State, *I,
486                               Att->getOwnKind() == OwnershipAttr::Holds);
487    if (StateI)
488      State = StateI;
489  }
490  return State;
491}
492
493ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
494                                          const CallExpr *CE,
495                                          ProgramStateRef state,
496                                          unsigned Num,
497                                          bool Hold) const {
498  if (CE->getNumArgs() < (Num + 1))
499    return 0;
500
501  const Expr *ArgExpr = CE->getArg(Num);
502  SVal ArgVal = state->getSVal(ArgExpr, C.getLocationContext());
503  if (!isa<DefinedOrUnknownSVal>(ArgVal))
504    return 0;
505  DefinedOrUnknownSVal location = cast<DefinedOrUnknownSVal>(ArgVal);
506
507  // Check for null dereferences.
508  if (!isa<Loc>(location))
509    return 0;
510
511  // The explicit NULL case, no operation is performed.
512  ProgramStateRef notNullState, nullState;
513  llvm::tie(notNullState, nullState) = state->assume(location);
514  if (nullState && !notNullState)
515    return 0;
516
517  // Unknown values could easily be okay
518  // Undefined values are handled elsewhere
519  if (ArgVal.isUnknownOrUndef())
520    return 0;
521
522  const MemRegion *R = ArgVal.getAsRegion();
523
524  // Nonlocs can't be freed, of course.
525  // Non-region locations (labels and fixed addresses) also shouldn't be freed.
526  if (!R) {
527    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
528    return 0;
529  }
530
531  R = R->StripCasts();
532
533  // Blocks might show up as heap data, but should not be free()d
534  if (isa<BlockDataRegion>(R)) {
535    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
536    return 0;
537  }
538
539  const MemSpaceRegion *MS = R->getMemorySpace();
540
541  // Parameters, locals, statics, and globals shouldn't be freed.
542  if (!(isa<UnknownSpaceRegion>(MS) || isa<HeapSpaceRegion>(MS))) {
543    // FIXME: at the time this code was written, malloc() regions were
544    // represented by conjured symbols, which are all in UnknownSpaceRegion.
545    // This means that there isn't actually anything from HeapSpaceRegion
546    // that should be freed, even though we allow it here.
547    // Of course, free() can work on memory allocated outside the current
548    // function, so UnknownSpaceRegion is always a possibility.
549    // False negatives are better than false positives.
550
551    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
552    return 0;
553  }
554
555  const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R);
556  // Various cases could lead to non-symbol values here.
557  // For now, ignore them.
558  if (!SR)
559    return 0;
560
561  SymbolRef Sym = SR->getSymbol();
562  const RefState *RS = state->get<RegionState>(Sym);
563
564  // If the symbol has not been tracked, return. This is possible when free() is
565  // called on a pointer that does not get its pointee directly from malloc().
566  // Full support of this requires inter-procedural analysis.
567  if (!RS)
568    return 0;
569
570  // Check double free.
571  if (RS->isReleased()) {
572    if (ExplodedNode *N = C.generateSink()) {
573      if (!BT_DoubleFree)
574        BT_DoubleFree.reset(
575          new BugType("Double free", "Memory Error"));
576      BugReport *R = new BugReport(*BT_DoubleFree,
577                        "Attempt to free released memory", N);
578      R->addRange(ArgExpr->getSourceRange());
579      R->markInteresting(Sym);
580      R->addVisitor(new MallocBugVisitor(Sym));
581      C.EmitReport(R);
582    }
583    return 0;
584  }
585
586  // Normal free.
587  if (Hold)
588    return state->set<RegionState>(Sym, RefState::getRelinquished(CE));
589  return state->set<RegionState>(Sym, RefState::getReleased(CE));
590}
591
592bool MallocChecker::SummarizeValue(raw_ostream &os, SVal V) {
593  if (nonloc::ConcreteInt *IntVal = dyn_cast<nonloc::ConcreteInt>(&V))
594    os << "an integer (" << IntVal->getValue() << ")";
595  else if (loc::ConcreteInt *ConstAddr = dyn_cast<loc::ConcreteInt>(&V))
596    os << "a constant address (" << ConstAddr->getValue() << ")";
597  else if (loc::GotoLabel *Label = dyn_cast<loc::GotoLabel>(&V))
598    os << "the address of the label '" << Label->getLabel()->getName() << "'";
599  else
600    return false;
601
602  return true;
603}
604
605bool MallocChecker::SummarizeRegion(raw_ostream &os,
606                                    const MemRegion *MR) {
607  switch (MR->getKind()) {
608  case MemRegion::FunctionTextRegionKind: {
609    const FunctionDecl *FD = cast<FunctionTextRegion>(MR)->getDecl();
610    if (FD)
611      os << "the address of the function '" << *FD << '\'';
612    else
613      os << "the address of a function";
614    return true;
615  }
616  case MemRegion::BlockTextRegionKind:
617    os << "block text";
618    return true;
619  case MemRegion::BlockDataRegionKind:
620    // FIXME: where the block came from?
621    os << "a block";
622    return true;
623  default: {
624    const MemSpaceRegion *MS = MR->getMemorySpace();
625
626    if (isa<StackLocalsSpaceRegion>(MS)) {
627      const VarRegion *VR = dyn_cast<VarRegion>(MR);
628      const VarDecl *VD;
629      if (VR)
630        VD = VR->getDecl();
631      else
632        VD = NULL;
633
634      if (VD)
635        os << "the address of the local variable '" << VD->getName() << "'";
636      else
637        os << "the address of a local stack variable";
638      return true;
639    }
640
641    if (isa<StackArgumentsSpaceRegion>(MS)) {
642      const VarRegion *VR = dyn_cast<VarRegion>(MR);
643      const VarDecl *VD;
644      if (VR)
645        VD = VR->getDecl();
646      else
647        VD = NULL;
648
649      if (VD)
650        os << "the address of the parameter '" << VD->getName() << "'";
651      else
652        os << "the address of a parameter";
653      return true;
654    }
655
656    if (isa<GlobalsSpaceRegion>(MS)) {
657      const VarRegion *VR = dyn_cast<VarRegion>(MR);
658      const VarDecl *VD;
659      if (VR)
660        VD = VR->getDecl();
661      else
662        VD = NULL;
663
664      if (VD) {
665        if (VD->isStaticLocal())
666          os << "the address of the static variable '" << VD->getName() << "'";
667        else
668          os << "the address of the global variable '" << VD->getName() << "'";
669      } else
670        os << "the address of a global variable";
671      return true;
672    }
673
674    return false;
675  }
676  }
677}
678
679void MallocChecker::ReportBadFree(CheckerContext &C, SVal ArgVal,
680                                  SourceRange range) const {
681  if (ExplodedNode *N = C.generateSink()) {
682    if (!BT_BadFree)
683      BT_BadFree.reset(new BugType("Bad free", "Memory Error"));
684
685    SmallString<100> buf;
686    llvm::raw_svector_ostream os(buf);
687
688    const MemRegion *MR = ArgVal.getAsRegion();
689    if (MR) {
690      while (const ElementRegion *ER = dyn_cast<ElementRegion>(MR))
691        MR = ER->getSuperRegion();
692
693      // Special case for alloca()
694      if (isa<AllocaRegion>(MR))
695        os << "Argument to free() was allocated by alloca(), not malloc()";
696      else {
697        os << "Argument to free() is ";
698        if (SummarizeRegion(os, MR))
699          os << ", which is not memory allocated by malloc()";
700        else
701          os << "not memory allocated by malloc()";
702      }
703    } else {
704      os << "Argument to free() is ";
705      if (SummarizeValue(os, ArgVal))
706        os << ", which is not memory allocated by malloc()";
707      else
708        os << "not memory allocated by malloc()";
709    }
710
711    BugReport *R = new BugReport(*BT_BadFree, os.str(), N);
712    R->markInteresting(MR);
713    R->addRange(range);
714    C.EmitReport(R);
715  }
716}
717
718ProgramStateRef MallocChecker::ReallocMem(CheckerContext &C,
719                                          const CallExpr *CE,
720                                          bool FreesOnFail) const {
721  if (CE->getNumArgs() < 2)
722    return 0;
723
724  ProgramStateRef state = C.getState();
725  const Expr *arg0Expr = CE->getArg(0);
726  const LocationContext *LCtx = C.getLocationContext();
727  SVal Arg0Val = state->getSVal(arg0Expr, LCtx);
728  if (!isa<DefinedOrUnknownSVal>(Arg0Val))
729    return 0;
730  DefinedOrUnknownSVal arg0Val = cast<DefinedOrUnknownSVal>(Arg0Val);
731
732  SValBuilder &svalBuilder = C.getSValBuilder();
733
734  DefinedOrUnknownSVal PtrEQ =
735    svalBuilder.evalEQ(state, arg0Val, svalBuilder.makeNull());
736
737  // Get the size argument. If there is no size arg then give up.
738  const Expr *Arg1 = CE->getArg(1);
739  if (!Arg1)
740    return 0;
741
742  // Get the value of the size argument.
743  SVal Arg1ValG = state->getSVal(Arg1, LCtx);
744  if (!isa<DefinedOrUnknownSVal>(Arg1ValG))
745    return 0;
746  DefinedOrUnknownSVal Arg1Val = cast<DefinedOrUnknownSVal>(Arg1ValG);
747
748  // Compare the size argument to 0.
749  DefinedOrUnknownSVal SizeZero =
750    svalBuilder.evalEQ(state, Arg1Val,
751                       svalBuilder.makeIntValWithPtrWidth(0, false));
752
753  ProgramStateRef StatePtrIsNull, StatePtrNotNull;
754  llvm::tie(StatePtrIsNull, StatePtrNotNull) = state->assume(PtrEQ);
755  ProgramStateRef StateSizeIsZero, StateSizeNotZero;
756  llvm::tie(StateSizeIsZero, StateSizeNotZero) = state->assume(SizeZero);
757  // We only assume exceptional states if they are definitely true; if the
758  // state is under-constrained, assume regular realloc behavior.
759  bool PrtIsNull = StatePtrIsNull && !StatePtrNotNull;
760  bool SizeIsZero = StateSizeIsZero && !StateSizeNotZero;
761
762  // If the ptr is NULL and the size is not 0, the call is equivalent to
763  // malloc(size).
764  if ( PrtIsNull && !SizeIsZero) {
765    ProgramStateRef stateMalloc = MallocMemAux(C, CE, CE->getArg(1),
766                                               UndefinedVal(), StatePtrIsNull);
767    return stateMalloc;
768  }
769
770  if (PrtIsNull && SizeIsZero)
771    return 0;
772
773  // Get the from and to pointer symbols as in toPtr = realloc(fromPtr, size).
774  assert(!PrtIsNull);
775  SymbolRef FromPtr = arg0Val.getAsSymbol();
776  SVal RetVal = state->getSVal(CE, LCtx);
777  SymbolRef ToPtr = RetVal.getAsSymbol();
778  if (!FromPtr || !ToPtr)
779    return 0;
780
781  // If the size is 0, free the memory.
782  if (SizeIsZero)
783    if (ProgramStateRef stateFree = FreeMemAux(C, CE, StateSizeIsZero,0,false)){
784      // The semantics of the return value are:
785      // If size was equal to 0, either NULL or a pointer suitable to be passed
786      // to free() is returned.
787      stateFree = stateFree->set<ReallocPairs>(ToPtr,
788                                            ReallocPair(FromPtr, FreesOnFail));
789      C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr);
790      return stateFree;
791    }
792
793  // Default behavior.
794  if (ProgramStateRef stateFree = FreeMemAux(C, CE, state, 0, false)) {
795    // FIXME: We should copy the content of the original buffer.
796    ProgramStateRef stateRealloc = MallocMemAux(C, CE, CE->getArg(1),
797                                                UnknownVal(), stateFree);
798    if (!stateRealloc)
799      return 0;
800    stateRealloc = stateRealloc->set<ReallocPairs>(ToPtr,
801                                            ReallocPair(FromPtr, FreesOnFail));
802    C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr);
803    return stateRealloc;
804  }
805  return 0;
806}
807
808ProgramStateRef MallocChecker::CallocMem(CheckerContext &C, const CallExpr *CE){
809  if (CE->getNumArgs() < 2)
810    return 0;
811
812  ProgramStateRef state = C.getState();
813  SValBuilder &svalBuilder = C.getSValBuilder();
814  const LocationContext *LCtx = C.getLocationContext();
815  SVal count = state->getSVal(CE->getArg(0), LCtx);
816  SVal elementSize = state->getSVal(CE->getArg(1), LCtx);
817  SVal TotalSize = svalBuilder.evalBinOp(state, BO_Mul, count, elementSize,
818                                        svalBuilder.getContext().getSizeType());
819  SVal zeroVal = svalBuilder.makeZeroVal(svalBuilder.getContext().CharTy);
820
821  return MallocMemAux(C, CE, TotalSize, zeroVal, state);
822}
823
824LeakInfo
825MallocChecker::getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
826                                 CheckerContext &C) const {
827  const LocationContext *LeakContext = N->getLocationContext();
828  // Walk the ExplodedGraph backwards and find the first node that referred to
829  // the tracked symbol.
830  const ExplodedNode *AllocNode = N;
831  const MemRegion *ReferenceRegion = 0;
832
833  while (N) {
834    ProgramStateRef State = N->getState();
835    if (!State->get<RegionState>(Sym))
836      break;
837
838    // Find the most recent expression bound to the symbol in the current
839    // context.
840    if (!ReferenceRegion) {
841      if (const MemRegion *MR = C.getLocationRegionIfPostStore(N)) {
842        SVal Val = State->getSVal(MR);
843        if (Val.getAsLocSymbol() == Sym)
844          ReferenceRegion = MR;
845      }
846    }
847
848    // Allocation node, is the last node in the current context in which the
849    // symbol was tracked.
850    if (N->getLocationContext() == LeakContext)
851      AllocNode = N;
852    N = N->pred_empty() ? NULL : *(N->pred_begin());
853  }
854
855  ProgramPoint P = AllocNode->getLocation();
856  const Stmt *AllocationStmt = 0;
857  if (isa<StmtPoint>(P))
858    AllocationStmt = cast<StmtPoint>(P).getStmt();
859
860  return LeakInfo(AllocationStmt, ReferenceRegion);
861}
862
863void MallocChecker::reportLeak(SymbolRef Sym, ExplodedNode *N,
864                               CheckerContext &C) const {
865  assert(N);
866  if (!BT_Leak) {
867    BT_Leak.reset(new BugType("Memory leak", "Memory Error"));
868    // Leaks should not be reported if they are post-dominated by a sink:
869    // (1) Sinks are higher importance bugs.
870    // (2) NoReturnFunctionChecker uses sink nodes to represent paths ending
871    //     with __noreturn functions such as assert() or exit(). We choose not
872    //     to report leaks on such paths.
873    BT_Leak->setSuppressOnSink(true);
874  }
875
876  // Most bug reports are cached at the location where they occurred.
877  // With leaks, we want to unique them by the location where they were
878  // allocated, and only report a single path.
879  PathDiagnosticLocation LocUsedForUniqueing;
880  const Stmt *AllocStmt = 0;
881  const MemRegion *Region = 0;
882  llvm::tie(AllocStmt, Region) = getAllocationSite(N, Sym, C);
883  if (AllocStmt)
884    LocUsedForUniqueing = PathDiagnosticLocation::createBegin(AllocStmt,
885                            C.getSourceManager(), N->getLocationContext());
886
887  SmallString<200> buf;
888  llvm::raw_svector_ostream os(buf);
889  os << "Memory is never released; potential leak";
890  if (Region) {
891    os << " of memory pointed to by '";
892    Region->dumpPretty(os);
893    os <<'\'';
894  }
895
896  BugReport *R = new BugReport(*BT_Leak, os.str(), N, LocUsedForUniqueing);
897  R->markInteresting(Sym);
898  R->addVisitor(new MallocBugVisitor(Sym));
899  C.EmitReport(R);
900}
901
902void MallocChecker::checkDeadSymbols(SymbolReaper &SymReaper,
903                                     CheckerContext &C) const
904{
905  if (!SymReaper.hasDeadSymbols())
906    return;
907
908  ProgramStateRef state = C.getState();
909  RegionStateTy RS = state->get<RegionState>();
910  RegionStateTy::Factory &F = state->get_context<RegionState>();
911
912  bool generateReport = false;
913  llvm::SmallVector<SymbolRef, 2> Errors;
914  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
915    if (SymReaper.isDead(I->first)) {
916      if (I->second.isAllocated()) {
917        generateReport = true;
918        Errors.push_back(I->first);
919      }
920      // Remove the dead symbol from the map.
921      RS = F.remove(RS, I->first);
922
923    }
924  }
925
926  // Cleanup the Realloc Pairs Map.
927  ReallocMap RP = state->get<ReallocPairs>();
928  for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
929    if (SymReaper.isDead(I->first) ||
930        SymReaper.isDead(I->second.ReallocatedSym)) {
931      state = state->remove<ReallocPairs>(I->first);
932    }
933  }
934
935  // Generate leak node.
936  static SimpleProgramPointTag Tag("MallocChecker : DeadSymbolsLeak");
937  ExplodedNode *N = C.addTransition(C.getState(), C.getPredecessor(), &Tag);
938
939  if (generateReport) {
940    for (llvm::SmallVector<SymbolRef, 2>::iterator
941         I = Errors.begin(), E = Errors.end(); I != E; ++I) {
942      reportLeak(*I, N, C);
943    }
944  }
945  C.addTransition(state->set<RegionState>(RS), N);
946}
947
948void MallocChecker::checkEndPath(CheckerContext &C) const {
949  ProgramStateRef state = C.getState();
950  RegionStateTy M = state->get<RegionState>();
951
952  // If inside inlined call, skip it.
953  if (C.getLocationContext()->getParent() != 0)
954    return;
955
956  for (RegionStateTy::iterator I = M.begin(), E = M.end(); I != E; ++I) {
957    RefState RS = I->second;
958    if (RS.isAllocated()) {
959      ExplodedNode *N = C.addTransition(state);
960      if (N)
961        reportLeak(I->first, N, C);
962    }
963  }
964}
965
966bool MallocChecker::checkEscape(SymbolRef Sym, const Stmt *S,
967                                CheckerContext &C) const {
968  ProgramStateRef state = C.getState();
969  const RefState *RS = state->get<RegionState>(Sym);
970  if (!RS)
971    return false;
972
973  if (RS->isAllocated()) {
974    state = state->set<RegionState>(Sym, RefState::getEscaped(S));
975    C.addTransition(state);
976    return true;
977  }
978  return false;
979}
980
981void MallocChecker::checkPreStmt(const CallExpr *CE, CheckerContext &C) const {
982  if (isMemFunction(C.getCalleeDecl(CE), C.getASTContext()))
983    return;
984
985  // Check use after free, when a freed pointer is passed to a call.
986  ProgramStateRef State = C.getState();
987  for (CallExpr::const_arg_iterator I = CE->arg_begin(),
988                                    E = CE->arg_end(); I != E; ++I) {
989    const Expr *A = *I;
990    if (A->getType().getTypePtr()->isAnyPointerType()) {
991      SymbolRef Sym = State->getSVal(A, C.getLocationContext()).getAsSymbol();
992      if (!Sym)
993        continue;
994      if (checkUseAfterFree(Sym, C, A))
995        return;
996    }
997  }
998}
999
1000void MallocChecker::checkPreStmt(const ReturnStmt *S, CheckerContext &C) const {
1001  const Expr *E = S->getRetValue();
1002  if (!E)
1003    return;
1004
1005  // Check if we are returning a symbol.
1006  SVal RetVal = C.getState()->getSVal(E, C.getLocationContext());
1007  SymbolRef Sym = RetVal.getAsSymbol();
1008  if (!Sym)
1009    // If we are returning a field of the allocated struct or an array element,
1010    // the callee could still free the memory.
1011    // TODO: This logic should be a part of generic symbol escape callback.
1012    if (const MemRegion *MR = RetVal.getAsRegion())
1013      if (isa<FieldRegion>(MR) || isa<ElementRegion>(MR))
1014        if (const SymbolicRegion *BMR =
1015              dyn_cast<SymbolicRegion>(MR->getBaseRegion()))
1016          Sym = BMR->getSymbol();
1017  if (!Sym)
1018    return;
1019
1020  // Check if we are returning freed memory.
1021  if (checkUseAfterFree(Sym, C, E))
1022    return;
1023
1024  // If this function body is not inlined, check if the symbol is escaping.
1025  if (C.getLocationContext()->getParent() == 0)
1026    checkEscape(Sym, E, C);
1027}
1028
1029// TODO: Blocks should be either inlined or should call invalidate regions
1030// upon invocation. After that's in place, special casing here will not be
1031// needed.
1032void MallocChecker::checkPostStmt(const BlockExpr *BE,
1033                                  CheckerContext &C) const {
1034
1035  // Scan the BlockDecRefExprs for any object the retain count checker
1036  // may be tracking.
1037  if (!BE->getBlockDecl()->hasCaptures())
1038    return;
1039
1040  ProgramStateRef state = C.getState();
1041  const BlockDataRegion *R =
1042    cast<BlockDataRegion>(state->getSVal(BE,
1043                                         C.getLocationContext()).getAsRegion());
1044
1045  BlockDataRegion::referenced_vars_iterator I = R->referenced_vars_begin(),
1046                                            E = R->referenced_vars_end();
1047
1048  if (I == E)
1049    return;
1050
1051  SmallVector<const MemRegion*, 10> Regions;
1052  const LocationContext *LC = C.getLocationContext();
1053  MemRegionManager &MemMgr = C.getSValBuilder().getRegionManager();
1054
1055  for ( ; I != E; ++I) {
1056    const VarRegion *VR = *I;
1057    if (VR->getSuperRegion() == R) {
1058      VR = MemMgr.getVarRegion(VR->getDecl(), LC);
1059    }
1060    Regions.push_back(VR);
1061  }
1062
1063  state =
1064    state->scanReachableSymbols<StopTrackingCallback>(Regions.data(),
1065                                    Regions.data() + Regions.size()).getState();
1066  C.addTransition(state);
1067}
1068
1069bool MallocChecker::checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
1070                                      const Stmt *S) const {
1071  assert(Sym);
1072  const RefState *RS = C.getState()->get<RegionState>(Sym);
1073  if (RS && RS->isReleased()) {
1074    if (ExplodedNode *N = C.generateSink()) {
1075      if (!BT_UseFree)
1076        BT_UseFree.reset(new BugType("Use-after-free", "Memory Error"));
1077
1078      BugReport *R = new BugReport(*BT_UseFree,
1079                                   "Use of memory after it is freed",N);
1080      if (S)
1081        R->addRange(S->getSourceRange());
1082      R->markInteresting(Sym);
1083      R->addVisitor(new MallocBugVisitor(Sym));
1084      C.EmitReport(R);
1085      return true;
1086    }
1087  }
1088  return false;
1089}
1090
1091// Check if the location is a freed symbolic region.
1092void MallocChecker::checkLocation(SVal l, bool isLoad, const Stmt *S,
1093                                  CheckerContext &C) const {
1094  SymbolRef Sym = l.getLocSymbolInBase();
1095  if (Sym)
1096    checkUseAfterFree(Sym, C);
1097}
1098
1099//===----------------------------------------------------------------------===//
1100// Check various ways a symbol can be invalidated.
1101// TODO: This logic (the next 3 functions) is copied/similar to the
1102// RetainRelease checker. We might want to factor this out.
1103//===----------------------------------------------------------------------===//
1104
1105// Stop tracking symbols when a value escapes as a result of checkBind.
1106// A value escapes in three possible cases:
1107// (1) we are binding to something that is not a memory region.
1108// (2) we are binding to a memregion that does not have stack storage
1109// (3) we are binding to a memregion with stack storage that the store
1110//     does not understand.
1111void MallocChecker::checkBind(SVal loc, SVal val, const Stmt *S,
1112                              CheckerContext &C) const {
1113  // Are we storing to something that causes the value to "escape"?
1114  bool escapes = true;
1115  ProgramStateRef state = C.getState();
1116
1117  if (loc::MemRegionVal *regionLoc = dyn_cast<loc::MemRegionVal>(&loc)) {
1118    escapes = !regionLoc->getRegion()->hasStackStorage();
1119
1120    if (!escapes) {
1121      // To test (3), generate a new state with the binding added.  If it is
1122      // the same state, then it escapes (since the store cannot represent
1123      // the binding).
1124      // Do this only if we know that the store is not supposed to generate the
1125      // same state.
1126      SVal StoredVal = state->getSVal(regionLoc->getRegion());
1127      if (StoredVal != val)
1128        escapes = (state == (state->bindLoc(*regionLoc, val)));
1129    }
1130    if (!escapes) {
1131      // Case 4: We do not currently model what happens when a symbol is
1132      // assigned to a struct field, so be conservative here and let the symbol
1133      // go. TODO: This could definitely be improved upon.
1134      escapes = !isa<VarRegion>(regionLoc->getRegion());
1135    }
1136  }
1137
1138  // If our store can represent the binding and we aren't storing to something
1139  // that doesn't have local storage then just return and have the simulation
1140  // state continue as is.
1141  if (!escapes)
1142      return;
1143
1144  // Otherwise, find all symbols referenced by 'val' that we are tracking
1145  // and stop tracking them.
1146  state = state->scanReachableSymbols<StopTrackingCallback>(val).getState();
1147  C.addTransition(state);
1148}
1149
1150// If a symbolic region is assumed to NULL (or another constant), stop tracking
1151// it - assuming that allocation failed on this path.
1152ProgramStateRef MallocChecker::evalAssume(ProgramStateRef state,
1153                                              SVal Cond,
1154                                              bool Assumption) const {
1155  RegionStateTy RS = state->get<RegionState>();
1156  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
1157    // If the symbol is assumed to NULL or another constant, this will
1158    // return an APSInt*.
1159    if (state->getSymVal(I.getKey()))
1160      state = state->remove<RegionState>(I.getKey());
1161  }
1162
1163  // Realloc returns 0 when reallocation fails, which means that we should
1164  // restore the state of the pointer being reallocated.
1165  ReallocMap RP = state->get<ReallocPairs>();
1166  for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
1167    // If the symbol is assumed to NULL or another constant, this will
1168    // return an APSInt*.
1169    if (state->getSymVal(I.getKey())) {
1170      SymbolRef ReallocSym = I.getData().ReallocatedSym;
1171      const RefState *RS = state->get<RegionState>(ReallocSym);
1172      if (RS) {
1173        if (RS->isReleased() && ! I.getData().IsFreeOnFailure)
1174          state = state->set<RegionState>(ReallocSym,
1175                             RefState::getAllocateUnchecked(RS->getStmt()));
1176      }
1177      state = state->remove<ReallocPairs>(I.getKey());
1178    }
1179  }
1180
1181  return state;
1182}
1183
1184// Check if the function is known to us. So, for example, we could
1185// conservatively assume it can free/reallocate it's pointer arguments.
1186// (We assume that the pointers cannot escape through calls to system
1187// functions not handled by this checker.)
1188bool MallocChecker::doesNotFreeMemory(const CallOrObjCMessage *Call,
1189                                      ProgramStateRef State) const {
1190  if (!Call)
1191    return false;
1192
1193  // For now, assume that any C++ call can free memory.
1194  // TODO: If we want to be more optimistic here, we'll need to make sure that
1195  // regions escape to C++ containers. They seem to do that even now, but for
1196  // mysterious reasons.
1197  if (Call->isCXXCall())
1198    return false;
1199
1200  const Decl *D = Call->getDecl();
1201  if (!D)
1202    return false;
1203
1204  ASTContext &ASTC = State->getStateManager().getContext();
1205
1206  // If it's one of the allocation functions we can reason about, we model
1207  // its behavior explicitly.
1208  if (isa<FunctionDecl>(D) && isMemFunction(cast<FunctionDecl>(D), ASTC)) {
1209    return true;
1210  }
1211
1212  // If it's not a system call, assume it frees memory.
1213  SourceManager &SM = ASTC.getSourceManager();
1214  if (!SM.isInSystemHeader(D->getLocation()))
1215    return false;
1216
1217  // Process C/ObjC functions.
1218  if (const FunctionDecl *FD  = dyn_cast<FunctionDecl>(D)) {
1219    // White list the system functions whose arguments escape.
1220    const IdentifierInfo *II = FD->getIdentifier();
1221    if (!II)
1222      return true;
1223    StringRef FName = II->getName();
1224
1225    // White list thread local storage.
1226    if (FName.equals("pthread_setspecific"))
1227      return false;
1228
1229    // White list the 'XXXNoCopy' ObjC functions.
1230    if (FName.endswith("NoCopy")) {
1231      // Look for the deallocator argument. We know that the memory ownership
1232      // is not transfered only if the deallocator argument is
1233      // 'kCFAllocatorNull'.
1234      for (unsigned i = 1; i < Call->getNumArgs(); ++i) {
1235        const Expr *ArgE = Call->getArg(i)->IgnoreParenCasts();
1236        if (const DeclRefExpr *DE = dyn_cast<DeclRefExpr>(ArgE)) {
1237          StringRef DeallocatorName = DE->getFoundDecl()->getName();
1238          if (DeallocatorName == "kCFAllocatorNull")
1239            return true;
1240        }
1241      }
1242      return false;
1243    }
1244
1245    // PR12101
1246    // Many CoreFoundation and CoreGraphics might allow a tracked object
1247    // to escape.
1248    if (Call->isCFCGAllowingEscape(FName))
1249      return false;
1250
1251    // Associating streams with malloced buffers. The pointer can escape if
1252    // 'closefn' is specified (and if that function does free memory).
1253    // Currently, we do not inspect the 'closefn' function (PR12101).
1254    if (FName == "funopen")
1255      if (Call->getNumArgs() >= 4 && !Call->getArgSVal(4).isConstant(0))
1256        return false;
1257
1258    // Do not warn on pointers passed to 'setbuf' when used with std streams,
1259    // these leaks might be intentional when setting the buffer for stdio.
1260    // http://stackoverflow.com/questions/2671151/who-frees-setvbuf-buffer
1261    if (FName == "setbuf" || FName =="setbuffer" ||
1262        FName == "setlinebuf" || FName == "setvbuf") {
1263      if (Call->getNumArgs() >= 1)
1264        if (const DeclRefExpr *Arg =
1265              dyn_cast<DeclRefExpr>(Call->getArg(0)->IgnoreParenCasts()))
1266          if (const VarDecl *D = dyn_cast<VarDecl>(Arg->getDecl()))
1267              if (D->getCanonicalDecl()->getName().find("std")
1268                                                   != StringRef::npos)
1269                return false;
1270    }
1271
1272    // A bunch of other functions, which take ownership of a pointer (See retain
1273    // release checker). Not all the parameters here are invalidated, but the
1274    // Malloc checker cannot differentiate between them. The right way of doing
1275    // this would be to implement a pointer escapes callback.
1276    if (FName == "CVPixelBufferCreateWithBytes" ||
1277        FName == "CGBitmapContextCreateWithData" ||
1278        FName == "CVPixelBufferCreateWithPlanarBytes" ||
1279        FName == "OSAtomicEnqueue") {
1280      return false;
1281    }
1282
1283    // Whitelist NSXXInsertXX, for example NSMapInsertIfAbsent, since they can
1284    // be deallocated by NSMapRemove.
1285    if (FName.startswith("NS") && (FName.find("Insert") != StringRef::npos))
1286      return false;
1287
1288    // Otherwise, assume that the function does not free memory.
1289    // Most system calls, do not free the memory.
1290    return true;
1291
1292  // Process ObjC functions.
1293  } else if (const ObjCMethodDecl * ObjCD = dyn_cast<ObjCMethodDecl>(D)) {
1294    Selector S = ObjCD->getSelector();
1295
1296    // White list the ObjC functions which do free memory.
1297    // - Anything containing 'freeWhenDone' param set to 1.
1298    //   Ex: dataWithBytesNoCopy:length:freeWhenDone.
1299    for (unsigned i = 1; i < S.getNumArgs(); ++i) {
1300      if (S.getNameForSlot(i).equals("freeWhenDone")) {
1301        if (Call->getArgSVal(i).isConstant(1))
1302          return false;
1303        else
1304          return true;
1305      }
1306    }
1307
1308    // If the first selector ends with NoCopy, assume that the ownership is
1309    // transfered as well.
1310    // Ex:  [NSData dataWithBytesNoCopy:bytes length:10];
1311    if (S.getNameForSlot(0).endswith("NoCopy")) {
1312      return false;
1313    }
1314
1315    // Otherwise, assume that the function does not free memory.
1316    // Most system calls, do not free the memory.
1317    return true;
1318  }
1319
1320  // Otherwise, assume that the function can free memory.
1321  return false;
1322
1323}
1324
1325// If the symbol we are tracking is invalidated, but not explicitly (ex: the &p
1326// escapes, when we are tracking p), do not track the symbol as we cannot reason
1327// about it anymore.
1328ProgramStateRef
1329MallocChecker::checkRegionChanges(ProgramStateRef State,
1330                            const StoreManager::InvalidatedSymbols *invalidated,
1331                                    ArrayRef<const MemRegion *> ExplicitRegions,
1332                                    ArrayRef<const MemRegion *> Regions,
1333                                    const CallOrObjCMessage *Call) const {
1334  if (!invalidated || invalidated->empty())
1335    return State;
1336  llvm::SmallPtrSet<SymbolRef, 8> WhitelistedSymbols;
1337
1338  // If it's a call which might free or reallocate memory, we assume that all
1339  // regions (explicit and implicit) escaped.
1340
1341  // Otherwise, whitelist explicit pointers; we still can track them.
1342  if (!Call || doesNotFreeMemory(Call, State)) {
1343    for (ArrayRef<const MemRegion *>::iterator I = ExplicitRegions.begin(),
1344        E = ExplicitRegions.end(); I != E; ++I) {
1345      if (const SymbolicRegion *R = (*I)->StripCasts()->getAs<SymbolicRegion>())
1346        WhitelistedSymbols.insert(R->getSymbol());
1347    }
1348  }
1349
1350  for (StoreManager::InvalidatedSymbols::const_iterator I=invalidated->begin(),
1351       E = invalidated->end(); I!=E; ++I) {
1352    SymbolRef sym = *I;
1353    if (WhitelistedSymbols.count(sym))
1354      continue;
1355    // The symbol escaped.
1356    if (const RefState *RS = State->get<RegionState>(sym))
1357      State = State->set<RegionState>(sym, RefState::getEscaped(RS->getStmt()));
1358  }
1359  return State;
1360}
1361
1362static SymbolRef findFailedReallocSymbol(ProgramStateRef currState,
1363                                         ProgramStateRef prevState) {
1364  ReallocMap currMap = currState->get<ReallocPairs>();
1365  ReallocMap prevMap = prevState->get<ReallocPairs>();
1366
1367  for (ReallocMap::iterator I = prevMap.begin(), E = prevMap.end();
1368       I != E; ++I) {
1369    SymbolRef sym = I.getKey();
1370    if (!currMap.lookup(sym))
1371      return sym;
1372  }
1373
1374  return NULL;
1375}
1376
1377PathDiagnosticPiece *
1378MallocChecker::MallocBugVisitor::VisitNode(const ExplodedNode *N,
1379                                           const ExplodedNode *PrevN,
1380                                           BugReporterContext &BRC,
1381                                           BugReport &BR) {
1382  ProgramStateRef state = N->getState();
1383  ProgramStateRef statePrev = PrevN->getState();
1384
1385  const RefState *RS = state->get<RegionState>(Sym);
1386  const RefState *RSPrev = statePrev->get<RegionState>(Sym);
1387  if (!RS && !RSPrev)
1388    return 0;
1389
1390  const Stmt *S = 0;
1391  const char *Msg = 0;
1392  StackHintGeneratorForSymbol *StackHint = 0;
1393
1394  // Retrieve the associated statement.
1395  ProgramPoint ProgLoc = N->getLocation();
1396  if (isa<StmtPoint>(ProgLoc))
1397    S = cast<StmtPoint>(ProgLoc).getStmt();
1398  // If an assumption was made on a branch, it should be caught
1399  // here by looking at the state transition.
1400  if (isa<BlockEdge>(ProgLoc)) {
1401    const CFGBlock *srcBlk = cast<BlockEdge>(ProgLoc).getSrc();
1402    S = srcBlk->getTerminator();
1403  }
1404  if (!S)
1405    return 0;
1406
1407  // Find out if this is an interesting point and what is the kind.
1408  if (Mode == Normal) {
1409    if (isAllocated(RS, RSPrev, S)) {
1410      Msg = "Memory is allocated";
1411      StackHint = new StackHintGeneratorForSymbol(Sym,
1412                                                  "Returned allocated memory");
1413    } else if (isReleased(RS, RSPrev, S)) {
1414      Msg = "Memory is released";
1415      StackHint = new StackHintGeneratorForSymbol(Sym,
1416                                                  "Returned released memory");
1417    } else if (isReallocFailedCheck(RS, RSPrev, S)) {
1418      Mode = ReallocationFailed;
1419      Msg = "Reallocation failed";
1420      StackHint = new StackHintGeneratorForReallocationFailed(Sym,
1421                                                       "Reallocation failed");
1422
1423      if (SymbolRef sym = findFailedReallocSymbol(state, statePrev)) {
1424        // Is it possible to fail two reallocs WITHOUT testing in between?
1425        assert((!FailedReallocSymbol || FailedReallocSymbol == sym) &&
1426          "We only support one failed realloc at a time.");
1427        BR.markInteresting(sym);
1428        FailedReallocSymbol = sym;
1429      }
1430    }
1431
1432  // We are in a special mode if a reallocation failed later in the path.
1433  } else if (Mode == ReallocationFailed) {
1434    assert(FailedReallocSymbol && "No symbol to look for.");
1435
1436    // Is this is the first appearance of the reallocated symbol?
1437    if (!statePrev->get<RegionState>(FailedReallocSymbol)) {
1438      // If we ever hit this assert, that means BugReporter has decided to skip
1439      // node pairs or visit them out of order.
1440      assert(state->get<RegionState>(FailedReallocSymbol) &&
1441        "Missed the reallocation point");
1442
1443      // We're at the reallocation point.
1444      Msg = "Attempt to reallocate memory";
1445      StackHint = new StackHintGeneratorForSymbol(Sym,
1446                                                 "Returned reallocated memory");
1447      FailedReallocSymbol = NULL;
1448      Mode = Normal;
1449    }
1450  }
1451
1452  if (!Msg)
1453    return 0;
1454  assert(StackHint);
1455
1456  // Generate the extra diagnostic.
1457  PathDiagnosticLocation Pos(S, BRC.getSourceManager(),
1458                             N->getLocationContext());
1459  return new PathDiagnosticEventPiece(Pos, Msg, true, StackHint);
1460}
1461
1462void MallocChecker::printState(raw_ostream &Out, ProgramStateRef State,
1463                               const char *NL, const char *Sep) const {
1464
1465  RegionStateTy RS = State->get<RegionState>();
1466
1467  if (!RS.isEmpty())
1468    Out << "Has Malloc data" << NL;
1469}
1470
1471#define REGISTER_CHECKER(name) \
1472void ento::register##name(CheckerManager &mgr) {\
1473  registerCStringCheckerBasic(mgr); \
1474  mgr.registerChecker<MallocChecker>()->Filter.C##name = true;\
1475}
1476
1477REGISTER_CHECKER(MallocPessimistic)
1478REGISTER_CHECKER(MallocOptimistic)
1479