MallocChecker.cpp revision f5aa3f5e58356d0bea823fe75dd7bf6aea6f47f4 
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
140private:
141  void initIdentifierInfo(ASTContext &C) const;
142
143  /// Check if this is one of the functions which can allocate/reallocate memory
144  /// pointed to by one of its arguments.
145  bool isMemFunction(const FunctionDecl *FD, ASTContext &C) const;
146
147  static ProgramStateRef MallocMemReturnsAttr(CheckerContext &C,
148                                              const CallExpr *CE,
149                                              const OwnershipAttr* Att);
150  static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
151                                     const Expr *SizeEx, SVal Init,
152                                     ProgramStateRef state) {
153    return MallocMemAux(C, CE,
154                        state->getSVal(SizeEx, C.getLocationContext()),
155                        Init, state);
156  }
157
158  static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
159                                     SVal SizeEx, SVal Init,
160                                     ProgramStateRef state);
161
162  /// Update the RefState to reflect the new memory allocation.
163  static ProgramStateRef MallocUpdateRefState(CheckerContext &C,
164                                              const CallExpr *CE,
165                                              ProgramStateRef state);
166
167  ProgramStateRef FreeMemAttr(CheckerContext &C, const CallExpr *CE,
168                              const OwnershipAttr* Att) const;
169  ProgramStateRef FreeMemAux(CheckerContext &C, const CallExpr *CE,
170                                 ProgramStateRef state, unsigned Num,
171                                 bool Hold) const;
172
173  ProgramStateRef ReallocMem(CheckerContext &C, const CallExpr *CE,
174                             bool FreesMemOnFailure) const;
175  static ProgramStateRef CallocMem(CheckerContext &C, const CallExpr *CE);
176
177  bool checkEscape(SymbolRef Sym, const Stmt *S, CheckerContext &C) const;
178  bool checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
179                         const Stmt *S = 0) const;
180
181  /// Check if the function is not known to us. So, for example, we could
182  /// conservatively assume it can free/reallocate it's pointer arguments.
183  bool doesNotFreeMemory(const CallOrObjCMessage *Call,
184                         ProgramStateRef State) const;
185
186  static bool SummarizeValue(raw_ostream &os, SVal V);
187  static bool SummarizeRegion(raw_ostream &os, const MemRegion *MR);
188  void ReportBadFree(CheckerContext &C, SVal ArgVal, SourceRange range) const;
189
190  /// Find the location of the allocation for Sym on the path leading to the
191  /// exploded node N.
192  LeakInfo getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
193                             CheckerContext &C) const;
194
195  void reportLeak(SymbolRef Sym, ExplodedNode *N, CheckerContext &C) const;
196
197  /// The bug visitor which allows us to print extra diagnostics along the
198  /// BugReport path. For example, showing the allocation site of the leaked
199  /// region.
200  class MallocBugVisitor : public BugReporterVisitor {
201  protected:
202    enum NotificationMode {
203      Normal,
204      Complete,
205      ReallocationFailed
206    };
207
208    // The allocated region symbol tracked by the main analysis.
209    SymbolRef Sym;
210    NotificationMode Mode;
211
212  public:
213    MallocBugVisitor(SymbolRef S) : Sym(S), Mode(Normal) {}
214    virtual ~MallocBugVisitor() {}
215
216    void Profile(llvm::FoldingSetNodeID &ID) const {
217      static int X = 0;
218      ID.AddPointer(&X);
219      ID.AddPointer(Sym);
220    }
221
222    inline bool isAllocated(const RefState *S, const RefState *SPrev,
223                            const Stmt *Stmt) {
224      // Did not track -> allocated. Other state (released) -> allocated.
225      return (Stmt && isa<CallExpr>(Stmt) &&
226              (S && S->isAllocated()) && (!SPrev || !SPrev->isAllocated()));
227    }
228
229    inline bool isReleased(const RefState *S, const RefState *SPrev,
230                           const Stmt *Stmt) {
231      // Did not track -> released. Other state (allocated) -> released.
232      return (Stmt && isa<CallExpr>(Stmt) &&
233              (S && S->isReleased()) && (!SPrev || !SPrev->isReleased()));
234    }
235
236    inline bool isReallocFailedCheck(const RefState *S, const RefState *SPrev,
237                                     const Stmt *Stmt) {
238      // If the expression is not a call, and the state change is
239      // released -> allocated, it must be the realloc return value
240      // check. If we have to handle more cases here, it might be cleaner just
241      // to track this extra bit in the state itself.
242      return ((!Stmt || !isa<CallExpr>(Stmt)) &&
243              (S && S->isAllocated()) && (SPrev && !SPrev->isAllocated()));
244    }
245
246    PathDiagnosticPiece *VisitNode(const ExplodedNode *N,
247                                   const ExplodedNode *PrevN,
248                                   BugReporterContext &BRC,
249                                   BugReport &BR);
250  private:
251    class StackHintGeneratorForReallocationFailed
252        : public StackHintGeneratorForSymbol {
253    public:
254      StackHintGeneratorForReallocationFailed(SymbolRef S, StringRef M)
255        : StackHintGeneratorForSymbol(S, M) {}
256
257      virtual std::string getMessageForArg(const Expr *ArgE, unsigned ArgIndex) {
258        SmallString<200> buf;
259        llvm::raw_svector_ostream os(buf);
260
261        os << "Reallocation of ";
262        // Printed parameters start at 1, not 0.
263        printOrdinal(++ArgIndex, os);
264        os << " parameter failed";
265
266        return os.str();
267      }
268
269      virtual std::string getMessageForReturn(const CallExpr *CallExpr) {
270        return "Reallocation of returned value failed";
271      }
272    };
273  };
274};
275} // end anonymous namespace
276
277typedef llvm::ImmutableMap<SymbolRef, RefState> RegionStateTy;
278typedef llvm::ImmutableMap<SymbolRef, ReallocPair > ReallocMap;
279class RegionState {};
280class ReallocPairs {};
281namespace clang {
282namespace ento {
283  template <>
284  struct ProgramStateTrait<RegionState>
285    : public ProgramStatePartialTrait<RegionStateTy> {
286    static void *GDMIndex() { static int x; return &x; }
287  };
288
289  template <>
290  struct ProgramStateTrait<ReallocPairs>
291    : public ProgramStatePartialTrait<ReallocMap> {
292    static void *GDMIndex() { static int x; return &x; }
293  };
294}
295}
296
297namespace {
298class StopTrackingCallback : public SymbolVisitor {
299  ProgramStateRef state;
300public:
301  StopTrackingCallback(ProgramStateRef st) : state(st) {}
302  ProgramStateRef getState() const { return state; }
303
304  bool VisitSymbol(SymbolRef sym) {
305    state = state->remove<RegionState>(sym);
306    return true;
307  }
308};
309} // end anonymous namespace
310
311void MallocChecker::initIdentifierInfo(ASTContext &Ctx) const {
312  if (!II_malloc)
313    II_malloc = &Ctx.Idents.get("malloc");
314  if (!II_free)
315    II_free = &Ctx.Idents.get("free");
316  if (!II_realloc)
317    II_realloc = &Ctx.Idents.get("realloc");
318  if (!II_reallocf)
319    II_reallocf = &Ctx.Idents.get("reallocf");
320  if (!II_calloc)
321    II_calloc = &Ctx.Idents.get("calloc");
322  if (!II_valloc)
323    II_valloc = &Ctx.Idents.get("valloc");
324  if (!II_strdup)
325    II_strdup = &Ctx.Idents.get("strdup");
326  if (!II_strndup)
327    II_strndup = &Ctx.Idents.get("strndup");
328}
329
330bool MallocChecker::isMemFunction(const FunctionDecl *FD, ASTContext &C) const {
331  if (!FD)
332    return false;
333  IdentifierInfo *FunI = FD->getIdentifier();
334  if (!FunI)
335    return false;
336
337  initIdentifierInfo(C);
338
339  if (FunI == II_malloc || FunI == II_free || FunI == II_realloc ||
340      FunI == II_reallocf || FunI == II_calloc || FunI == II_valloc ||
341      FunI == II_strdup || FunI == II_strndup)
342    return true;
343
344  if (Filter.CMallocOptimistic && FD->hasAttrs() &&
345      FD->specific_attr_begin<OwnershipAttr>() !=
346          FD->specific_attr_end<OwnershipAttr>())
347    return true;
348
349
350  return false;
351}
352
353void MallocChecker::checkPostStmt(const CallExpr *CE, CheckerContext &C) const {
354  const FunctionDecl *FD = C.getCalleeDecl(CE);
355  if (!FD)
356    return;
357
358  initIdentifierInfo(C.getASTContext());
359  IdentifierInfo *FunI = FD->getIdentifier();
360  if (!FunI)
361    return;
362
363  ProgramStateRef State = C.getState();
364  if (FunI == II_malloc || FunI == II_valloc) {
365    State = MallocMemAux(C, CE, CE->getArg(0), UndefinedVal(), State);
366  } else if (FunI == II_realloc) {
367    State = ReallocMem(C, CE, false);
368  } else if (FunI == II_reallocf) {
369    State = ReallocMem(C, CE, true);
370  } else if (FunI == II_calloc) {
371    State = CallocMem(C, CE);
372  } else if (FunI == II_free) {
373    State = FreeMemAux(C, CE, C.getState(), 0, false);
374  } else if (FunI == II_strdup) {
375    State = MallocUpdateRefState(C, CE, State);
376  } else if (FunI == II_strndup) {
377    State = MallocUpdateRefState(C, CE, State);
378  } else if (Filter.CMallocOptimistic) {
379    // Check all the attributes, if there are any.
380    // There can be multiple of these attributes.
381    if (FD->hasAttrs())
382      for (specific_attr_iterator<OwnershipAttr>
383          i = FD->specific_attr_begin<OwnershipAttr>(),
384          e = FD->specific_attr_end<OwnershipAttr>();
385          i != e; ++i) {
386        switch ((*i)->getOwnKind()) {
387        case OwnershipAttr::Returns:
388          State = MallocMemReturnsAttr(C, CE, *i);
389          break;
390        case OwnershipAttr::Takes:
391        case OwnershipAttr::Holds:
392          State = FreeMemAttr(C, CE, *i);
393          break;
394        }
395      }
396  }
397  C.addTransition(State);
398}
399
400ProgramStateRef MallocChecker::MallocMemReturnsAttr(CheckerContext &C,
401                                                    const CallExpr *CE,
402                                                    const OwnershipAttr* Att) {
403  if (Att->getModule() != "malloc")
404    return 0;
405
406  OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
407  if (I != E) {
408    return MallocMemAux(C, CE, CE->getArg(*I), UndefinedVal(), C.getState());
409  }
410  return MallocMemAux(C, CE, UnknownVal(), UndefinedVal(), C.getState());
411}
412
413ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C,
414                                           const CallExpr *CE,
415                                           SVal Size, SVal Init,
416                                           ProgramStateRef state) {
417  // Get the return value.
418  SVal retVal = state->getSVal(CE, C.getLocationContext());
419
420  // We expect the malloc functions to return a pointer.
421  if (!isa<Loc>(retVal))
422    return 0;
423
424  // Fill the region with the initialization value.
425  state = state->bindDefault(retVal, Init);
426
427  // Set the region's extent equal to the Size parameter.
428  const SymbolicRegion *R =
429      dyn_cast_or_null<SymbolicRegion>(retVal.getAsRegion());
430  if (!R)
431    return 0;
432  if (isa<DefinedOrUnknownSVal>(Size)) {
433    SValBuilder &svalBuilder = C.getSValBuilder();
434    DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder);
435    DefinedOrUnknownSVal DefinedSize = cast<DefinedOrUnknownSVal>(Size);
436    DefinedOrUnknownSVal extentMatchesSize =
437        svalBuilder.evalEQ(state, Extent, DefinedSize);
438
439    state = state->assume(extentMatchesSize, true);
440    assert(state);
441  }
442
443  return MallocUpdateRefState(C, CE, state);
444}
445
446ProgramStateRef MallocChecker::MallocUpdateRefState(CheckerContext &C,
447                                                    const CallExpr *CE,
448                                                    ProgramStateRef state) {
449  // Get the return value.
450  SVal retVal = state->getSVal(CE, C.getLocationContext());
451
452  // We expect the malloc functions to return a pointer.
453  if (!isa<Loc>(retVal))
454    return 0;
455
456  SymbolRef Sym = retVal.getAsLocSymbol();
457  assert(Sym);
458
459  // Set the symbol's state to Allocated.
460  return state->set<RegionState>(Sym, RefState::getAllocateUnchecked(CE));
461
462}
463
464ProgramStateRef MallocChecker::FreeMemAttr(CheckerContext &C,
465                                           const CallExpr *CE,
466                                           const OwnershipAttr* Att) const {
467  if (Att->getModule() != "malloc")
468    return 0;
469
470  ProgramStateRef State = C.getState();
471
472  for (OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
473       I != E; ++I) {
474    ProgramStateRef StateI = FreeMemAux(C, CE, State, *I,
475                               Att->getOwnKind() == OwnershipAttr::Holds);
476    if (StateI)
477      State = StateI;
478  }
479  return State;
480}
481
482ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
483                                          const CallExpr *CE,
484                                          ProgramStateRef state,
485                                          unsigned Num,
486                                          bool Hold) const {
487  const Expr *ArgExpr = CE->getArg(Num);
488  SVal ArgVal = state->getSVal(ArgExpr, C.getLocationContext());
489  if (!isa<DefinedOrUnknownSVal>(ArgVal))
490    return 0;
491  DefinedOrUnknownSVal location = cast<DefinedOrUnknownSVal>(ArgVal);
492
493  // Check for null dereferences.
494  if (!isa<Loc>(location))
495    return 0;
496
497  // The explicit NULL case, no operation is performed.
498  ProgramStateRef notNullState, nullState;
499  llvm::tie(notNullState, nullState) = state->assume(location);
500  if (nullState && !notNullState)
501    return 0;
502
503  // Unknown values could easily be okay
504  // Undefined values are handled elsewhere
505  if (ArgVal.isUnknownOrUndef())
506    return 0;
507
508  const MemRegion *R = ArgVal.getAsRegion();
509
510  // Nonlocs can't be freed, of course.
511  // Non-region locations (labels and fixed addresses) also shouldn't be freed.
512  if (!R) {
513    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
514    return 0;
515  }
516
517  R = R->StripCasts();
518
519  // Blocks might show up as heap data, but should not be free()d
520  if (isa<BlockDataRegion>(R)) {
521    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
522    return 0;
523  }
524
525  const MemSpaceRegion *MS = R->getMemorySpace();
526
527  // Parameters, locals, statics, and globals shouldn't be freed.
528  if (!(isa<UnknownSpaceRegion>(MS) || isa<HeapSpaceRegion>(MS))) {
529    // FIXME: at the time this code was written, malloc() regions were
530    // represented by conjured symbols, which are all in UnknownSpaceRegion.
531    // This means that there isn't actually anything from HeapSpaceRegion
532    // that should be freed, even though we allow it here.
533    // Of course, free() can work on memory allocated outside the current
534    // function, so UnknownSpaceRegion is always a possibility.
535    // False negatives are better than false positives.
536
537    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
538    return 0;
539  }
540
541  const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R);
542  // Various cases could lead to non-symbol values here.
543  // For now, ignore them.
544  if (!SR)
545    return 0;
546
547  SymbolRef Sym = SR->getSymbol();
548  const RefState *RS = state->get<RegionState>(Sym);
549
550  // If the symbol has not been tracked, return. This is possible when free() is
551  // called on a pointer that does not get its pointee directly from malloc().
552  // Full support of this requires inter-procedural analysis.
553  if (!RS)
554    return 0;
555
556  // Check double free.
557  if (RS->isReleased()) {
558    if (ExplodedNode *N = C.generateSink()) {
559      if (!BT_DoubleFree)
560        BT_DoubleFree.reset(
561          new BugType("Double free", "Memory Error"));
562      BugReport *R = new BugReport(*BT_DoubleFree,
563                        "Attempt to free released memory", N);
564      R->addRange(ArgExpr->getSourceRange());
565      R->markInteresting(Sym);
566      R->addVisitor(new MallocBugVisitor(Sym));
567      C.EmitReport(R);
568    }
569    return 0;
570  }
571
572  // Normal free.
573  if (Hold)
574    return state->set<RegionState>(Sym, RefState::getRelinquished(CE));
575  return state->set<RegionState>(Sym, RefState::getReleased(CE));
576}
577
578bool MallocChecker::SummarizeValue(raw_ostream &os, SVal V) {
579  if (nonloc::ConcreteInt *IntVal = dyn_cast<nonloc::ConcreteInt>(&V))
580    os << "an integer (" << IntVal->getValue() << ")";
581  else if (loc::ConcreteInt *ConstAddr = dyn_cast<loc::ConcreteInt>(&V))
582    os << "a constant address (" << ConstAddr->getValue() << ")";
583  else if (loc::GotoLabel *Label = dyn_cast<loc::GotoLabel>(&V))
584    os << "the address of the label '" << Label->getLabel()->getName() << "'";
585  else
586    return false;
587
588  return true;
589}
590
591bool MallocChecker::SummarizeRegion(raw_ostream &os,
592                                    const MemRegion *MR) {
593  switch (MR->getKind()) {
594  case MemRegion::FunctionTextRegionKind: {
595    const FunctionDecl *FD = cast<FunctionTextRegion>(MR)->getDecl();
596    if (FD)
597      os << "the address of the function '" << *FD << '\'';
598    else
599      os << "the address of a function";
600    return true;
601  }
602  case MemRegion::BlockTextRegionKind:
603    os << "block text";
604    return true;
605  case MemRegion::BlockDataRegionKind:
606    // FIXME: where the block came from?
607    os << "a block";
608    return true;
609  default: {
610    const MemSpaceRegion *MS = MR->getMemorySpace();
611
612    if (isa<StackLocalsSpaceRegion>(MS)) {
613      const VarRegion *VR = dyn_cast<VarRegion>(MR);
614      const VarDecl *VD;
615      if (VR)
616        VD = VR->getDecl();
617      else
618        VD = NULL;
619
620      if (VD)
621        os << "the address of the local variable '" << VD->getName() << "'";
622      else
623        os << "the address of a local stack variable";
624      return true;
625    }
626
627    if (isa<StackArgumentsSpaceRegion>(MS)) {
628      const VarRegion *VR = dyn_cast<VarRegion>(MR);
629      const VarDecl *VD;
630      if (VR)
631        VD = VR->getDecl();
632      else
633        VD = NULL;
634
635      if (VD)
636        os << "the address of the parameter '" << VD->getName() << "'";
637      else
638        os << "the address of a parameter";
639      return true;
640    }
641
642    if (isa<GlobalsSpaceRegion>(MS)) {
643      const VarRegion *VR = dyn_cast<VarRegion>(MR);
644      const VarDecl *VD;
645      if (VR)
646        VD = VR->getDecl();
647      else
648        VD = NULL;
649
650      if (VD) {
651        if (VD->isStaticLocal())
652          os << "the address of the static variable '" << VD->getName() << "'";
653        else
654          os << "the address of the global variable '" << VD->getName() << "'";
655      } else
656        os << "the address of a global variable";
657      return true;
658    }
659
660    return false;
661  }
662  }
663}
664
665void MallocChecker::ReportBadFree(CheckerContext &C, SVal ArgVal,
666                                  SourceRange range) const {
667  if (ExplodedNode *N = C.generateSink()) {
668    if (!BT_BadFree)
669      BT_BadFree.reset(new BugType("Bad free", "Memory Error"));
670
671    SmallString<100> buf;
672    llvm::raw_svector_ostream os(buf);
673
674    const MemRegion *MR = ArgVal.getAsRegion();
675    if (MR) {
676      while (const ElementRegion *ER = dyn_cast<ElementRegion>(MR))
677        MR = ER->getSuperRegion();
678
679      // Special case for alloca()
680      if (isa<AllocaRegion>(MR))
681        os << "Argument to free() was allocated by alloca(), not malloc()";
682      else {
683        os << "Argument to free() is ";
684        if (SummarizeRegion(os, MR))
685          os << ", which is not memory allocated by malloc()";
686        else
687          os << "not memory allocated by malloc()";
688      }
689    } else {
690      os << "Argument to free() is ";
691      if (SummarizeValue(os, ArgVal))
692        os << ", which is not memory allocated by malloc()";
693      else
694        os << "not memory allocated by malloc()";
695    }
696
697    BugReport *R = new BugReport(*BT_BadFree, os.str(), N);
698    R->markInteresting(MR);
699    R->addRange(range);
700    C.EmitReport(R);
701  }
702}
703
704ProgramStateRef MallocChecker::ReallocMem(CheckerContext &C,
705                                          const CallExpr *CE,
706                                          bool FreesOnFail) const {
707  ProgramStateRef state = C.getState();
708  const Expr *arg0Expr = CE->getArg(0);
709  const LocationContext *LCtx = C.getLocationContext();
710  SVal Arg0Val = state->getSVal(arg0Expr, LCtx);
711  if (!isa<DefinedOrUnknownSVal>(Arg0Val))
712    return 0;
713  DefinedOrUnknownSVal arg0Val = cast<DefinedOrUnknownSVal>(Arg0Val);
714
715  SValBuilder &svalBuilder = C.getSValBuilder();
716
717  DefinedOrUnknownSVal PtrEQ =
718    svalBuilder.evalEQ(state, arg0Val, svalBuilder.makeNull());
719
720  // Get the size argument. If there is no size arg then give up.
721  const Expr *Arg1 = CE->getArg(1);
722  if (!Arg1)
723    return 0;
724
725  // Get the value of the size argument.
726  SVal Arg1ValG = state->getSVal(Arg1, LCtx);
727  if (!isa<DefinedOrUnknownSVal>(Arg1ValG))
728    return 0;
729  DefinedOrUnknownSVal Arg1Val = cast<DefinedOrUnknownSVal>(Arg1ValG);
730
731  // Compare the size argument to 0.
732  DefinedOrUnknownSVal SizeZero =
733    svalBuilder.evalEQ(state, Arg1Val,
734                       svalBuilder.makeIntValWithPtrWidth(0, false));
735
736  ProgramStateRef StatePtrIsNull, StatePtrNotNull;
737  llvm::tie(StatePtrIsNull, StatePtrNotNull) = state->assume(PtrEQ);
738  ProgramStateRef StateSizeIsZero, StateSizeNotZero;
739  llvm::tie(StateSizeIsZero, StateSizeNotZero) = state->assume(SizeZero);
740  // We only assume exceptional states if they are definitely true; if the
741  // state is under-constrained, assume regular realloc behavior.
742  bool PrtIsNull = StatePtrIsNull && !StatePtrNotNull;
743  bool SizeIsZero = StateSizeIsZero && !StateSizeNotZero;
744
745  // If the ptr is NULL and the size is not 0, the call is equivalent to
746  // malloc(size).
747  if ( PrtIsNull && !SizeIsZero) {
748    ProgramStateRef stateMalloc = MallocMemAux(C, CE, CE->getArg(1),
749                                               UndefinedVal(), StatePtrIsNull);
750    return stateMalloc;
751  }
752
753  if (PrtIsNull && SizeIsZero)
754    return 0;
755
756  // Get the from and to pointer symbols as in toPtr = realloc(fromPtr, size).
757  assert(!PrtIsNull);
758  SymbolRef FromPtr = arg0Val.getAsSymbol();
759  SVal RetVal = state->getSVal(CE, LCtx);
760  SymbolRef ToPtr = RetVal.getAsSymbol();
761  if (!FromPtr || !ToPtr)
762    return 0;
763
764  // If the size is 0, free the memory.
765  if (SizeIsZero)
766    if (ProgramStateRef stateFree = FreeMemAux(C, CE, StateSizeIsZero,0,false)){
767      // The semantics of the return value are:
768      // If size was equal to 0, either NULL or a pointer suitable to be passed
769      // to free() is returned.
770      stateFree = stateFree->set<ReallocPairs>(ToPtr,
771                                            ReallocPair(FromPtr, FreesOnFail));
772      C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr);
773      return stateFree;
774    }
775
776  // Default behavior.
777  if (ProgramStateRef stateFree = FreeMemAux(C, CE, state, 0, false)) {
778    // FIXME: We should copy the content of the original buffer.
779    ProgramStateRef stateRealloc = MallocMemAux(C, CE, CE->getArg(1),
780                                                UnknownVal(), stateFree);
781    if (!stateRealloc)
782      return 0;
783    stateRealloc = stateRealloc->set<ReallocPairs>(ToPtr,
784                                            ReallocPair(FromPtr, FreesOnFail));
785    C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr);
786    return stateRealloc;
787  }
788  return 0;
789}
790
791ProgramStateRef MallocChecker::CallocMem(CheckerContext &C, const CallExpr *CE){
792  ProgramStateRef state = C.getState();
793  SValBuilder &svalBuilder = C.getSValBuilder();
794  const LocationContext *LCtx = C.getLocationContext();
795  SVal count = state->getSVal(CE->getArg(0), LCtx);
796  SVal elementSize = state->getSVal(CE->getArg(1), LCtx);
797  SVal TotalSize = svalBuilder.evalBinOp(state, BO_Mul, count, elementSize,
798                                        svalBuilder.getContext().getSizeType());
799  SVal zeroVal = svalBuilder.makeZeroVal(svalBuilder.getContext().CharTy);
800
801  return MallocMemAux(C, CE, TotalSize, zeroVal, state);
802}
803
804LeakInfo
805MallocChecker::getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
806                                 CheckerContext &C) const {
807  const LocationContext *LeakContext = N->getLocationContext();
808  // Walk the ExplodedGraph backwards and find the first node that referred to
809  // the tracked symbol.
810  const ExplodedNode *AllocNode = N;
811  const MemRegion *ReferenceRegion = 0;
812
813  while (N) {
814    ProgramStateRef State = N->getState();
815    if (!State->get<RegionState>(Sym))
816      break;
817
818    // Find the most recent expression bound to the symbol in the current
819    // context.
820    if (!ReferenceRegion) {
821      if (const MemRegion *MR = C.getLocationRegionIfPostStore(N)) {
822        SVal Val = State->getSVal(MR);
823        if (Val.getAsLocSymbol() == Sym)
824          ReferenceRegion = MR;
825      }
826    }
827
828    // Allocation node, is the last node in the current context in which the
829    // symbol was tracked.
830    if (N->getLocationContext() == LeakContext)
831      AllocNode = N;
832    N = N->pred_empty() ? NULL : *(N->pred_begin());
833  }
834
835  ProgramPoint P = AllocNode->getLocation();
836  const Stmt *AllocationStmt = 0;
837  if (isa<StmtPoint>(P))
838    AllocationStmt = cast<StmtPoint>(P).getStmt();
839
840  return LeakInfo(AllocationStmt, ReferenceRegion);
841}
842
843void MallocChecker::reportLeak(SymbolRef Sym, ExplodedNode *N,
844                               CheckerContext &C) const {
845  assert(N);
846  if (!BT_Leak) {
847    BT_Leak.reset(new BugType("Memory leak", "Memory Error"));
848    // Leaks should not be reported if they are post-dominated by a sink:
849    // (1) Sinks are higher importance bugs.
850    // (2) NoReturnFunctionChecker uses sink nodes to represent paths ending
851    //     with __noreturn functions such as assert() or exit(). We choose not
852    //     to report leaks on such paths.
853    BT_Leak->setSuppressOnSink(true);
854  }
855
856  // Most bug reports are cached at the location where they occurred.
857  // With leaks, we want to unique them by the location where they were
858  // allocated, and only report a single path.
859  PathDiagnosticLocation LocUsedForUniqueing;
860  const Stmt *AllocStmt = 0;
861  const MemRegion *Region = 0;
862  llvm::tie(AllocStmt, Region) = getAllocationSite(N, Sym, C);
863  if (AllocStmt)
864    LocUsedForUniqueing = PathDiagnosticLocation::createBegin(AllocStmt,
865                            C.getSourceManager(), N->getLocationContext());
866
867  SmallString<200> buf;
868  llvm::raw_svector_ostream os(buf);
869  os << "Memory is never released; potential leak";
870  if (Region) {
871    os << " of memory pointed to by '";
872    Region->dumpPretty(os);
873    os <<'\'';
874  }
875
876  BugReport *R = new BugReport(*BT_Leak, os.str(), N, LocUsedForUniqueing);
877  R->markInteresting(Sym);
878  // FIXME: This is a hack to make sure the MallocBugVisitor gets to look at
879  // the ExplodedNode chain first, in order to mark any failed realloc symbols
880  // as interesting for ConditionBRVisitor.
881  R->addVisitor(new ConditionBRVisitor());
882  R->addVisitor(new MallocBugVisitor(Sym));
883  C.EmitReport(R);
884}
885
886void MallocChecker::checkDeadSymbols(SymbolReaper &SymReaper,
887                                     CheckerContext &C) const
888{
889  if (!SymReaper.hasDeadSymbols())
890    return;
891
892  ProgramStateRef state = C.getState();
893  RegionStateTy RS = state->get<RegionState>();
894  RegionStateTy::Factory &F = state->get_context<RegionState>();
895
896  bool generateReport = false;
897  llvm::SmallVector<SymbolRef, 2> Errors;
898  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
899    if (SymReaper.isDead(I->first)) {
900      if (I->second.isAllocated()) {
901        generateReport = true;
902        Errors.push_back(I->first);
903      }
904      // Remove the dead symbol from the map.
905      RS = F.remove(RS, I->first);
906
907    }
908  }
909
910  // Cleanup the Realloc Pairs Map.
911  ReallocMap RP = state->get<ReallocPairs>();
912  for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
913    if (SymReaper.isDead(I->first) ||
914        SymReaper.isDead(I->second.ReallocatedSym)) {
915      state = state->remove<ReallocPairs>(I->first);
916    }
917  }
918
919  // Generate leak node.
920  static SimpleProgramPointTag Tag("MallocChecker : DeadSymbolsLeak");
921  ExplodedNode *N = C.addTransition(C.getState(), C.getPredecessor(), &Tag);
922
923  if (generateReport) {
924    for (llvm::SmallVector<SymbolRef, 2>::iterator
925         I = Errors.begin(), E = Errors.end(); I != E; ++I) {
926      reportLeak(*I, N, C);
927    }
928  }
929  C.addTransition(state->set<RegionState>(RS), N);
930}
931
932void MallocChecker::checkEndPath(CheckerContext &C) const {
933  ProgramStateRef state = C.getState();
934  RegionStateTy M = state->get<RegionState>();
935
936  // If inside inlined call, skip it.
937  if (C.getLocationContext()->getParent() != 0)
938    return;
939
940  for (RegionStateTy::iterator I = M.begin(), E = M.end(); I != E; ++I) {
941    RefState RS = I->second;
942    if (RS.isAllocated()) {
943      ExplodedNode *N = C.addTransition(state);
944      if (N)
945        reportLeak(I->first, N, C);
946    }
947  }
948}
949
950bool MallocChecker::checkEscape(SymbolRef Sym, const Stmt *S,
951                                CheckerContext &C) const {
952  ProgramStateRef state = C.getState();
953  const RefState *RS = state->get<RegionState>(Sym);
954  if (!RS)
955    return false;
956
957  if (RS->isAllocated()) {
958    state = state->set<RegionState>(Sym, RefState::getEscaped(S));
959    C.addTransition(state);
960    return true;
961  }
962  return false;
963}
964
965void MallocChecker::checkPreStmt(const CallExpr *CE, CheckerContext &C) const {
966  if (isMemFunction(C.getCalleeDecl(CE), C.getASTContext()))
967    return;
968
969  // Check use after free, when a freed pointer is passed to a call.
970  ProgramStateRef State = C.getState();
971  for (CallExpr::const_arg_iterator I = CE->arg_begin(),
972                                    E = CE->arg_end(); I != E; ++I) {
973    const Expr *A = *I;
974    if (A->getType().getTypePtr()->isAnyPointerType()) {
975      SymbolRef Sym = State->getSVal(A, C.getLocationContext()).getAsSymbol();
976      if (!Sym)
977        continue;
978      if (checkUseAfterFree(Sym, C, A))
979        return;
980    }
981  }
982}
983
984void MallocChecker::checkPreStmt(const ReturnStmt *S, CheckerContext &C) const {
985  const Expr *E = S->getRetValue();
986  if (!E)
987    return;
988
989  // Check if we are returning a symbol.
990  SVal RetVal = C.getState()->getSVal(E, C.getLocationContext());
991  SymbolRef Sym = RetVal.getAsSymbol();
992  if (!Sym)
993    // If we are returning a field of the allocated struct or an array element,
994    // the callee could still free the memory.
995    // TODO: This logic should be a part of generic symbol escape callback.
996    if (const MemRegion *MR = RetVal.getAsRegion())
997      if (isa<FieldRegion>(MR) || isa<ElementRegion>(MR))
998        if (const SymbolicRegion *BMR =
999              dyn_cast<SymbolicRegion>(MR->getBaseRegion()))
1000          Sym = BMR->getSymbol();
1001  if (!Sym)
1002    return;
1003
1004  // Check if we are returning freed memory.
1005  if (checkUseAfterFree(Sym, C, E))
1006    return;
1007
1008  // If this function body is not inlined, check if the symbol is escaping.
1009  if (C.getLocationContext()->getParent() == 0)
1010    checkEscape(Sym, E, C);
1011}
1012
1013// TODO: Blocks should be either inlined or should call invalidate regions
1014// upon invocation. After that's in place, special casing here will not be
1015// needed.
1016void MallocChecker::checkPostStmt(const BlockExpr *BE,
1017                                  CheckerContext &C) const {
1018
1019  // Scan the BlockDecRefExprs for any object the retain count checker
1020  // may be tracking.
1021  if (!BE->getBlockDecl()->hasCaptures())
1022    return;
1023
1024  ProgramStateRef state = C.getState();
1025  const BlockDataRegion *R =
1026    cast<BlockDataRegion>(state->getSVal(BE,
1027                                         C.getLocationContext()).getAsRegion());
1028
1029  BlockDataRegion::referenced_vars_iterator I = R->referenced_vars_begin(),
1030                                            E = R->referenced_vars_end();
1031
1032  if (I == E)
1033    return;
1034
1035  SmallVector<const MemRegion*, 10> Regions;
1036  const LocationContext *LC = C.getLocationContext();
1037  MemRegionManager &MemMgr = C.getSValBuilder().getRegionManager();
1038
1039  for ( ; I != E; ++I) {
1040    const VarRegion *VR = *I;
1041    if (VR->getSuperRegion() == R) {
1042      VR = MemMgr.getVarRegion(VR->getDecl(), LC);
1043    }
1044    Regions.push_back(VR);
1045  }
1046
1047  state =
1048    state->scanReachableSymbols<StopTrackingCallback>(Regions.data(),
1049                                    Regions.data() + Regions.size()).getState();
1050  C.addTransition(state);
1051}
1052
1053bool MallocChecker::checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
1054                                      const Stmt *S) const {
1055  assert(Sym);
1056  const RefState *RS = C.getState()->get<RegionState>(Sym);
1057  if (RS && RS->isReleased()) {
1058    if (ExplodedNode *N = C.generateSink()) {
1059      if (!BT_UseFree)
1060        BT_UseFree.reset(new BugType("Use-after-free", "Memory Error"));
1061
1062      BugReport *R = new BugReport(*BT_UseFree,
1063                                   "Use of memory after it is freed",N);
1064      if (S)
1065        R->addRange(S->getSourceRange());
1066      R->markInteresting(Sym);
1067      R->addVisitor(new MallocBugVisitor(Sym));
1068      C.EmitReport(R);
1069      return true;
1070    }
1071  }
1072  return false;
1073}
1074
1075// Check if the location is a freed symbolic region.
1076void MallocChecker::checkLocation(SVal l, bool isLoad, const Stmt *S,
1077                                  CheckerContext &C) const {
1078  SymbolRef Sym = l.getLocSymbolInBase();
1079  if (Sym)
1080    checkUseAfterFree(Sym, C);
1081}
1082
1083//===----------------------------------------------------------------------===//
1084// Check various ways a symbol can be invalidated.
1085// TODO: This logic (the next 3 functions) is copied/similar to the
1086// RetainRelease checker. We might want to factor this out.
1087//===----------------------------------------------------------------------===//
1088
1089// Stop tracking symbols when a value escapes as a result of checkBind.
1090// A value escapes in three possible cases:
1091// (1) we are binding to something that is not a memory region.
1092// (2) we are binding to a memregion that does not have stack storage
1093// (3) we are binding to a memregion with stack storage that the store
1094//     does not understand.
1095void MallocChecker::checkBind(SVal loc, SVal val, const Stmt *S,
1096                              CheckerContext &C) const {
1097  // Are we storing to something that causes the value to "escape"?
1098  bool escapes = true;
1099  ProgramStateRef state = C.getState();
1100
1101  if (loc::MemRegionVal *regionLoc = dyn_cast<loc::MemRegionVal>(&loc)) {
1102    escapes = !regionLoc->getRegion()->hasStackStorage();
1103
1104    if (!escapes) {
1105      // To test (3), generate a new state with the binding added.  If it is
1106      // the same state, then it escapes (since the store cannot represent
1107      // the binding).
1108      escapes = (state == (state->bindLoc(*regionLoc, val)));
1109    }
1110    if (!escapes) {
1111      // Case 4: We do not currently model what happens when a symbol is
1112      // assigned to a struct field, so be conservative here and let the symbol
1113      // go. TODO: This could definitely be improved upon.
1114      escapes = !isa<VarRegion>(regionLoc->getRegion());
1115    }
1116  }
1117
1118  // If our store can represent the binding and we aren't storing to something
1119  // that doesn't have local storage then just return and have the simulation
1120  // state continue as is.
1121  if (!escapes)
1122      return;
1123
1124  // Otherwise, find all symbols referenced by 'val' that we are tracking
1125  // and stop tracking them.
1126  state = state->scanReachableSymbols<StopTrackingCallback>(val).getState();
1127  C.addTransition(state);
1128}
1129
1130// If a symbolic region is assumed to NULL (or another constant), stop tracking
1131// it - assuming that allocation failed on this path.
1132ProgramStateRef MallocChecker::evalAssume(ProgramStateRef state,
1133                                              SVal Cond,
1134                                              bool Assumption) const {
1135  RegionStateTy RS = state->get<RegionState>();
1136  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
1137    // If the symbol is assumed to NULL or another constant, this will
1138    // return an APSInt*.
1139    if (state->getSymVal(I.getKey()))
1140      state = state->remove<RegionState>(I.getKey());
1141  }
1142
1143  // Realloc returns 0 when reallocation fails, which means that we should
1144  // restore the state of the pointer being reallocated.
1145  ReallocMap RP = state->get<ReallocPairs>();
1146  for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
1147    // If the symbol is assumed to NULL or another constant, this will
1148    // return an APSInt*.
1149    if (state->getSymVal(I.getKey())) {
1150      SymbolRef ReallocSym = I.getData().ReallocatedSym;
1151      const RefState *RS = state->get<RegionState>(ReallocSym);
1152      if (RS) {
1153        if (RS->isReleased() && ! I.getData().IsFreeOnFailure)
1154          state = state->set<RegionState>(ReallocSym,
1155                             RefState::getAllocateUnchecked(RS->getStmt()));
1156      }
1157      state = state->remove<ReallocPairs>(I.getKey());
1158    }
1159  }
1160
1161  return state;
1162}
1163
1164// Check if the function is known to us. So, for example, we could
1165// conservatively assume it can free/reallocate it's pointer arguments.
1166// (We assume that the pointers cannot escape through calls to system
1167// functions not handled by this checker.)
1168bool MallocChecker::doesNotFreeMemory(const CallOrObjCMessage *Call,
1169                                      ProgramStateRef State) const {
1170  if (!Call)
1171    return false;
1172
1173  // For now, assume that any C++ call can free memory.
1174  // TODO: If we want to be more optimistic here, we'll need to make sure that
1175  // regions escape to C++ containers. They seem to do that even now, but for
1176  // mysterious reasons.
1177  if (Call->isCXXCall())
1178    return false;
1179
1180  const Decl *D = Call->getDecl();
1181  if (!D)
1182    return false;
1183
1184  ASTContext &ASTC = State->getStateManager().getContext();
1185
1186  // If it's one of the allocation functions we can reason about, we model
1187  // its behavior explicitly.
1188  if (isa<FunctionDecl>(D) && isMemFunction(cast<FunctionDecl>(D), ASTC)) {
1189    return true;
1190  }
1191
1192  // If it's not a system call, assume it frees memory.
1193  SourceManager &SM = ASTC.getSourceManager();
1194  if (!SM.isInSystemHeader(D->getLocation()))
1195    return false;
1196
1197  // Process C/ObjC functions.
1198  if (const FunctionDecl *FD  = dyn_cast<FunctionDecl>(D)) {
1199    // White list the system functions whose arguments escape.
1200    const IdentifierInfo *II = FD->getIdentifier();
1201    if (!II)
1202      return true;
1203    StringRef FName = II->getName();
1204
1205    // White list thread local storage.
1206    if (FName.equals("pthread_setspecific"))
1207      return false;
1208
1209    // White list the 'XXXNoCopy' ObjC functions.
1210    if (FName.endswith("NoCopy")) {
1211      // Look for the deallocator argument. We know that the memory ownership
1212      // is not transfered only if the deallocator argument is
1213      // 'kCFAllocatorNull'.
1214      for (unsigned i = 1; i < Call->getNumArgs(); ++i) {
1215        const Expr *ArgE = Call->getArg(i)->IgnoreParenCasts();
1216        if (const DeclRefExpr *DE = dyn_cast<DeclRefExpr>(ArgE)) {
1217          StringRef DeallocatorName = DE->getFoundDecl()->getName();
1218          if (DeallocatorName == "kCFAllocatorNull")
1219            return true;
1220        }
1221      }
1222      return false;
1223    }
1224
1225    // PR12101
1226    // Many CoreFoundation and CoreGraphics might allow a tracked object
1227    // to escape.
1228    if (Call->isCFCGAllowingEscape(FName))
1229      return false;
1230
1231    // Associating streams with malloced buffers. The pointer can escape if
1232    // 'closefn' is specified (and if that function does free memory).
1233    // Currently, we do not inspect the 'closefn' function (PR12101).
1234    if (FName == "funopen")
1235      if (Call->getNumArgs() >= 4 && !Call->getArgSVal(4).isConstant(0))
1236        return false;
1237
1238    // Do not warn on pointers passed to 'setbuf' when used with std streams,
1239    // these leaks might be intentional when setting the buffer for stdio.
1240    // http://stackoverflow.com/questions/2671151/who-frees-setvbuf-buffer
1241    if (FName == "setbuf" || FName =="setbuffer" ||
1242        FName == "setlinebuf" || FName == "setvbuf") {
1243      if (Call->getNumArgs() >= 1)
1244        if (const DeclRefExpr *Arg =
1245              dyn_cast<DeclRefExpr>(Call->getArg(0)->IgnoreParenCasts()))
1246          if (const VarDecl *D = dyn_cast<VarDecl>(Arg->getDecl()))
1247              if (D->getCanonicalDecl()->getName().find("std")
1248                                                   != StringRef::npos)
1249                return false;
1250    }
1251
1252    // A bunch of other functions, which take ownership of a pointer (See retain
1253    // release checker). Not all the parameters here are invalidated, but the
1254    // Malloc checker cannot differentiate between them. The right way of doing
1255    // this would be to implement a pointer escapes callback.
1256    if (FName == "CVPixelBufferCreateWithBytes" ||
1257        FName == "CGBitmapContextCreateWithData" ||
1258        FName == "CVPixelBufferCreateWithPlanarBytes") {
1259      return false;
1260    }
1261
1262    // Otherwise, assume that the function does not free memory.
1263    // Most system calls, do not free the memory.
1264    return true;
1265
1266  // Process ObjC functions.
1267  } else if (const ObjCMethodDecl * ObjCD = dyn_cast<ObjCMethodDecl>(D)) {
1268    Selector S = ObjCD->getSelector();
1269
1270    // White list the ObjC functions which do free memory.
1271    // - Anything containing 'freeWhenDone' param set to 1.
1272    //   Ex: dataWithBytesNoCopy:length:freeWhenDone.
1273    for (unsigned i = 1; i < S.getNumArgs(); ++i) {
1274      if (S.getNameForSlot(i).equals("freeWhenDone")) {
1275        if (Call->getArgSVal(i).isConstant(1))
1276          return false;
1277        else
1278          return true;
1279      }
1280    }
1281
1282    // If the first selector ends with NoCopy, assume that the ownership is
1283    // transfered as well.
1284    // Ex:  [NSData dataWithBytesNoCopy:bytes length:10];
1285    if (S.getNameForSlot(0).endswith("NoCopy")) {
1286      return false;
1287    }
1288
1289    // Otherwise, assume that the function does not free memory.
1290    // Most system calls, do not free the memory.
1291    return true;
1292  }
1293
1294  // Otherwise, assume that the function can free memory.
1295  return false;
1296
1297}
1298
1299// If the symbol we are tracking is invalidated, but not explicitly (ex: the &p
1300// escapes, when we are tracking p), do not track the symbol as we cannot reason
1301// about it anymore.
1302ProgramStateRef
1303MallocChecker::checkRegionChanges(ProgramStateRef State,
1304                            const StoreManager::InvalidatedSymbols *invalidated,
1305                                    ArrayRef<const MemRegion *> ExplicitRegions,
1306                                    ArrayRef<const MemRegion *> Regions,
1307                                    const CallOrObjCMessage *Call) const {
1308  if (!invalidated || invalidated->empty())
1309    return State;
1310  llvm::SmallPtrSet<SymbolRef, 8> WhitelistedSymbols;
1311
1312  // If it's a call which might free or reallocate memory, we assume that all
1313  // regions (explicit and implicit) escaped.
1314
1315  // Otherwise, whitelist explicit pointers; we still can track them.
1316  if (!Call || doesNotFreeMemory(Call, State)) {
1317    for (ArrayRef<const MemRegion *>::iterator I = ExplicitRegions.begin(),
1318        E = ExplicitRegions.end(); I != E; ++I) {
1319      if (const SymbolicRegion *R = (*I)->StripCasts()->getAs<SymbolicRegion>())
1320        WhitelistedSymbols.insert(R->getSymbol());
1321    }
1322  }
1323
1324  for (StoreManager::InvalidatedSymbols::const_iterator I=invalidated->begin(),
1325       E = invalidated->end(); I!=E; ++I) {
1326    SymbolRef sym = *I;
1327    if (WhitelistedSymbols.count(sym))
1328      continue;
1329    // The symbol escaped.
1330    if (const RefState *RS = State->get<RegionState>(sym))
1331      State = State->set<RegionState>(sym, RefState::getEscaped(RS->getStmt()));
1332  }
1333  return State;
1334}
1335
1336static SymbolRef findFailedReallocSymbol(ProgramStateRef currState,
1337                                         ProgramStateRef prevState) {
1338  ReallocMap currMap = currState->get<ReallocPairs>();
1339  ReallocMap prevMap = prevState->get<ReallocPairs>();
1340
1341  for (ReallocMap::iterator I = prevMap.begin(), E = prevMap.end();
1342       I != E; ++I) {
1343    SymbolRef sym = I.getKey();
1344    if (!currMap.lookup(sym))
1345      return sym;
1346  }
1347
1348  return NULL;
1349}
1350
1351PathDiagnosticPiece *
1352MallocChecker::MallocBugVisitor::VisitNode(const ExplodedNode *N,
1353                                           const ExplodedNode *PrevN,
1354                                           BugReporterContext &BRC,
1355                                           BugReport &BR) {
1356  ProgramStateRef state = N->getState();
1357  ProgramStateRef statePrev = PrevN->getState();
1358
1359  const RefState *RS = state->get<RegionState>(Sym);
1360  const RefState *RSPrev = statePrev->get<RegionState>(Sym);
1361  if (!RS && !RSPrev)
1362    return 0;
1363
1364  const Stmt *S = 0;
1365  const char *Msg = 0;
1366  StackHintGeneratorForSymbol *StackHint = 0;
1367
1368  // Retrieve the associated statement.
1369  ProgramPoint ProgLoc = N->getLocation();
1370  if (isa<StmtPoint>(ProgLoc))
1371    S = cast<StmtPoint>(ProgLoc).getStmt();
1372  // If an assumption was made on a branch, it should be caught
1373  // here by looking at the state transition.
1374  if (isa<BlockEdge>(ProgLoc)) {
1375    const CFGBlock *srcBlk = cast<BlockEdge>(ProgLoc).getSrc();
1376    S = srcBlk->getTerminator();
1377  }
1378  if (!S)
1379    return 0;
1380
1381  // Find out if this is an interesting point and what is the kind.
1382  if (Mode == Normal) {
1383    if (isAllocated(RS, RSPrev, S)) {
1384      Msg = "Memory is allocated";
1385      StackHint = new StackHintGeneratorForSymbol(Sym,
1386                                                  "Returned allocated memory");
1387    } else if (isReleased(RS, RSPrev, S)) {
1388      Msg = "Memory is released";
1389      StackHint = new StackHintGeneratorForSymbol(Sym,
1390                                                  "Returned released memory");
1391    } else if (isReallocFailedCheck(RS, RSPrev, S)) {
1392      Mode = ReallocationFailed;
1393      Msg = "Reallocation failed";
1394      StackHint = new StackHintGeneratorForReallocationFailed(Sym,
1395                                                       "Reallocation failed");
1396
1397      if (SymbolRef sym = findFailedReallocSymbol(state, statePrev))
1398        BR.markInteresting(sym);
1399    }
1400
1401  // We are in a special mode if a reallocation failed later in the path.
1402  } else if (Mode == ReallocationFailed) {
1403    // Generate a special diagnostic for the first realloc we find.
1404    if (!isAllocated(RS, RSPrev, S) && !isReleased(RS, RSPrev, S))
1405      return 0;
1406
1407    // Check that the name of the function is realloc.
1408    const CallExpr *CE = dyn_cast<CallExpr>(S);
1409    if (!CE)
1410      return 0;
1411    const FunctionDecl *funDecl = CE->getDirectCallee();
1412    if (!funDecl)
1413      return 0;
1414    StringRef FunName = funDecl->getName();
1415    if (!(FunName.equals("realloc") || FunName.equals("reallocf")))
1416      return 0;
1417    Msg = "Attempt to reallocate memory";
1418    StackHint = new StackHintGeneratorForSymbol(Sym,
1419                                                "Returned reallocated memory");
1420    Mode = Normal;
1421  }
1422
1423  if (!Msg)
1424    return 0;
1425  assert(StackHint);
1426
1427  // Generate the extra diagnostic.
1428  PathDiagnosticLocation Pos(S, BRC.getSourceManager(),
1429                             N->getLocationContext());
1430  return new PathDiagnosticEventPiece(Pos, Msg, true, StackHint);
1431}
1432
1433
1434#define REGISTER_CHECKER(name) \
1435void ento::register##name(CheckerManager &mgr) {\
1436  registerCStringCheckerBasic(mgr); \
1437  mgr.registerChecker<MallocChecker>()->Filter.C##name = true;\
1438}
1439
1440REGISTER_CHECKER(MallocPessimistic)
1441REGISTER_CHECKER(MallocOptimistic)
1442