MallocChecker.cpp revision 56a938ff85a444eb3d30d2634d92ce5b1f6fae56 
1//=== MallocChecker.cpp - A malloc/free checker -------------------*- C++ -*--//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file defines malloc/free checker, which checks for potential memory
11// leaks, double free, and use-after-free problems.
12//
13//===----------------------------------------------------------------------===//
14
15#include "ClangSACheckers.h"
16#include "InterCheckerAPI.h"
17#include "clang/StaticAnalyzer/Core/Checker.h"
18#include "clang/StaticAnalyzer/Core/CheckerManager.h"
19#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
20#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
21#include "clang/StaticAnalyzer/Core/PathSensitive/ObjCMessage.h"
22#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
23#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
24#include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
25#include "clang/Basic/SourceManager.h"
26#include "llvm/ADT/ImmutableMap.h"
27#include "llvm/ADT/SmallString.h"
28#include "llvm/ADT/STLExtras.h"
29#include <climits>
30
31using namespace clang;
32using namespace ento;
33
34namespace {
35
36class RefState {
37  enum Kind { AllocateUnchecked, AllocateFailed, Released, Escaped,
38              Relinquished } K;
39  const Stmt *S;
40
41public:
42  RefState(Kind k, const Stmt *s) : K(k), S(s) {}
43
44  bool isAllocated() const { return K == AllocateUnchecked; }
45  bool isReleased() const { return K == Released; }
46
47  const Stmt *getStmt() const { return S; }
48
49  bool operator==(const RefState &X) const {
50    return K == X.K && S == X.S;
51  }
52
53  static RefState getAllocateUnchecked(const Stmt *s) {
54    return RefState(AllocateUnchecked, s);
55  }
56  static RefState getAllocateFailed() {
57    return RefState(AllocateFailed, 0);
58  }
59  static RefState getReleased(const Stmt *s) { return RefState(Released, s); }
60  static RefState getEscaped(const Stmt *s) { return RefState(Escaped, s); }
61  static RefState getRelinquished(const Stmt *s) {
62    return RefState(Relinquished, s);
63  }
64
65  void Profile(llvm::FoldingSetNodeID &ID) const {
66    ID.AddInteger(K);
67    ID.AddPointer(S);
68  }
69};
70
71struct ReallocPair {
72  SymbolRef ReallocatedSym;
73  bool IsFreeOnFailure;
74  ReallocPair(SymbolRef S, bool F) : ReallocatedSym(S), IsFreeOnFailure(F) {}
75  void Profile(llvm::FoldingSetNodeID &ID) const {
76    ID.AddInteger(IsFreeOnFailure);
77    ID.AddPointer(ReallocatedSym);
78  }
79  bool operator==(const ReallocPair &X) const {
80    return ReallocatedSym == X.ReallocatedSym &&
81           IsFreeOnFailure == X.IsFreeOnFailure;
82  }
83};
84
85class MallocChecker : public Checker<check::DeadSymbols,
86                                     check::EndPath,
87                                     check::PreStmt<ReturnStmt>,
88                                     check::PreStmt<CallExpr>,
89                                     check::PostStmt<CallExpr>,
90                                     check::Location,
91                                     check::Bind,
92                                     eval::Assume,
93                                     check::RegionChanges>
94{
95  mutable OwningPtr<BugType> BT_DoubleFree;
96  mutable OwningPtr<BugType> BT_Leak;
97  mutable OwningPtr<BugType> BT_UseFree;
98  mutable OwningPtr<BugType> BT_BadFree;
99  mutable IdentifierInfo *II_malloc, *II_free, *II_realloc, *II_calloc,
100                         *II_valloc, *II_reallocf, *II_strndup, *II_strdup;
101
102public:
103  MallocChecker() : II_malloc(0), II_free(0), II_realloc(0), II_calloc(0),
104                    II_valloc(0), II_reallocf(0), II_strndup(0), II_strdup(0) {}
105
106  /// In pessimistic mode, the checker assumes that it does not know which
107  /// functions might free the memory.
108  struct ChecksFilter {
109    DefaultBool CMallocPessimistic;
110    DefaultBool CMallocOptimistic;
111  };
112
113  ChecksFilter Filter;
114
115  void checkPreStmt(const CallExpr *S, CheckerContext &C) const;
116  void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
117  void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;
118  void checkEndPath(CheckerContext &C) const;
119  void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const;
120  ProgramStateRef evalAssume(ProgramStateRef state, SVal Cond,
121                            bool Assumption) const;
122  void checkLocation(SVal l, bool isLoad, const Stmt *S,
123                     CheckerContext &C) const;
124  void checkBind(SVal location, SVal val, const Stmt*S,
125                 CheckerContext &C) const;
126  ProgramStateRef
127  checkRegionChanges(ProgramStateRef state,
128                     const StoreManager::InvalidatedSymbols *invalidated,
129                     ArrayRef<const MemRegion *> ExplicitRegions,
130                     ArrayRef<const MemRegion *> Regions,
131                     const CallOrObjCMessage *Call) const;
132  bool wantsRegionChangeUpdate(ProgramStateRef state) const {
133    return true;
134  }
135
136private:
137  void initIdentifierInfo(ASTContext &C) const;
138
139  /// Check if this is one of the functions which can allocate/reallocate memory
140  /// pointed to by one of its arguments.
141  bool isMemFunction(const FunctionDecl *FD, ASTContext &C) const;
142
143  static ProgramStateRef MallocMemReturnsAttr(CheckerContext &C,
144                                              const CallExpr *CE,
145                                              const OwnershipAttr* Att);
146  static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
147                                     const Expr *SizeEx, SVal Init,
148                                     ProgramStateRef state) {
149    return MallocMemAux(C, CE,
150                        state->getSVal(SizeEx, C.getLocationContext()),
151                        Init, state);
152  }
153
154  static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
155                                     SVal SizeEx, SVal Init,
156                                     ProgramStateRef state);
157
158  /// Update the RefState to reflect the new memory allocation.
159  static ProgramStateRef MallocUpdateRefState(CheckerContext &C,
160                                              const CallExpr *CE,
161                                              ProgramStateRef state);
162
163  ProgramStateRef FreeMemAttr(CheckerContext &C, const CallExpr *CE,
164                              const OwnershipAttr* Att) const;
165  ProgramStateRef FreeMemAux(CheckerContext &C, const CallExpr *CE,
166                                 ProgramStateRef state, unsigned Num,
167                                 bool Hold) const;
168
169  ProgramStateRef ReallocMem(CheckerContext &C, const CallExpr *CE,
170                             bool FreesMemOnFailure) const;
171  static ProgramStateRef CallocMem(CheckerContext &C, const CallExpr *CE);
172
173  bool checkEscape(SymbolRef Sym, const Stmt *S, CheckerContext &C) const;
174  bool checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
175                         const Stmt *S = 0) const;
176
177  /// Check if the function is not known to us. So, for example, we could
178  /// conservatively assume it can free/reallocate it's pointer arguments.
179  bool doesNotFreeMemory(const CallOrObjCMessage *Call,
180                         ProgramStateRef State) const;
181
182  static bool SummarizeValue(raw_ostream &os, SVal V);
183  static bool SummarizeRegion(raw_ostream &os, const MemRegion *MR);
184  void ReportBadFree(CheckerContext &C, SVal ArgVal, SourceRange range) const;
185
186  /// Find the location of the allocation for Sym on the path leading to the
187  /// exploded node N.
188  const Stmt *getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
189                                CheckerContext &C) const;
190
191  void reportLeak(SymbolRef Sym, ExplodedNode *N, CheckerContext &C) const;
192
193  /// The bug visitor which allows us to print extra diagnostics along the
194  /// BugReport path. For example, showing the allocation site of the leaked
195  /// region.
196  class MallocBugVisitor : public BugReporterVisitor {
197  protected:
198    enum NotificationMode {
199      Normal,
200      Complete,
201      ReallocationFailed
202    };
203
204    // The allocated region symbol tracked by the main analysis.
205    SymbolRef Sym;
206    NotificationMode Mode;
207
208  public:
209    MallocBugVisitor(SymbolRef S) : Sym(S), Mode(Normal) {}
210    virtual ~MallocBugVisitor() {}
211
212    void Profile(llvm::FoldingSetNodeID &ID) const {
213      static int X = 0;
214      ID.AddPointer(&X);
215      ID.AddPointer(Sym);
216    }
217
218    inline bool isAllocated(const RefState *S, const RefState *SPrev,
219                            const Stmt *Stmt) {
220      // Did not track -> allocated. Other state (released) -> allocated.
221      return (Stmt && isa<CallExpr>(Stmt) &&
222              (S && S->isAllocated()) && (!SPrev || !SPrev->isAllocated()));
223    }
224
225    inline bool isReleased(const RefState *S, const RefState *SPrev,
226                           const Stmt *Stmt) {
227      // Did not track -> released. Other state (allocated) -> released.
228      return (Stmt && isa<CallExpr>(Stmt) &&
229              (S && S->isReleased()) && (!SPrev || !SPrev->isReleased()));
230    }
231
232    inline bool isReallocFailedCheck(const RefState *S, const RefState *SPrev,
233                                     const Stmt *Stmt) {
234      // If the expression is not a call, and the state change is
235      // released -> allocated, it must be the realloc return value
236      // check. If we have to handle more cases here, it might be cleaner just
237      // to track this extra bit in the state itself.
238      return ((!Stmt || !isa<CallExpr>(Stmt)) &&
239              (S && S->isAllocated()) && (SPrev && !SPrev->isAllocated()));
240    }
241
242    PathDiagnosticPiece *VisitNode(const ExplodedNode *N,
243                                   const ExplodedNode *PrevN,
244                                   BugReporterContext &BRC,
245                                   BugReport &BR);
246  private:
247    class StackHintGeneratorForReallocationFailed
248        : public StackHintGeneratorForSymbol {
249    public:
250      StackHintGeneratorForReallocationFailed(SymbolRef S, StringRef M)
251        : StackHintGeneratorForSymbol(S, M) {}
252
253      virtual std::string getMessageForArg(const Expr *ArgE, unsigned ArgIndex) {
254        SmallString<200> buf;
255        llvm::raw_svector_ostream os(buf);
256
257        os << "; reallocation of ";
258        // Printed parameters start at 1, not 0.
259        printOrdinal(++ArgIndex, os);
260        os << " parameter failed";
261
262        return os.str();
263      }
264
265      virtual std::string getMessageForReturn(const CallExpr *CallExpr) {
266        return "; reallocation of returned value failed";
267      }
268    };
269  };
270};
271} // end anonymous namespace
272
273typedef llvm::ImmutableMap<SymbolRef, RefState> RegionStateTy;
274typedef llvm::ImmutableMap<SymbolRef, ReallocPair > ReallocMap;
275class RegionState {};
276class ReallocPairs {};
277namespace clang {
278namespace ento {
279  template <>
280  struct ProgramStateTrait<RegionState>
281    : public ProgramStatePartialTrait<RegionStateTy> {
282    static void *GDMIndex() { static int x; return &x; }
283  };
284
285  template <>
286  struct ProgramStateTrait<ReallocPairs>
287    : public ProgramStatePartialTrait<ReallocMap> {
288    static void *GDMIndex() { static int x; return &x; }
289  };
290}
291}
292
293namespace {
294class StopTrackingCallback : public SymbolVisitor {
295  ProgramStateRef state;
296public:
297  StopTrackingCallback(ProgramStateRef st) : state(st) {}
298  ProgramStateRef getState() const { return state; }
299
300  bool VisitSymbol(SymbolRef sym) {
301    state = state->remove<RegionState>(sym);
302    return true;
303  }
304};
305} // end anonymous namespace
306
307void MallocChecker::initIdentifierInfo(ASTContext &Ctx) const {
308  if (!II_malloc)
309    II_malloc = &Ctx.Idents.get("malloc");
310  if (!II_free)
311    II_free = &Ctx.Idents.get("free");
312  if (!II_realloc)
313    II_realloc = &Ctx.Idents.get("realloc");
314  if (!II_reallocf)
315    II_reallocf = &Ctx.Idents.get("reallocf");
316  if (!II_calloc)
317    II_calloc = &Ctx.Idents.get("calloc");
318  if (!II_valloc)
319    II_valloc = &Ctx.Idents.get("valloc");
320  if (!II_strdup)
321    II_strdup = &Ctx.Idents.get("strdup");
322  if (!II_strndup)
323    II_strndup = &Ctx.Idents.get("strndup");
324}
325
326bool MallocChecker::isMemFunction(const FunctionDecl *FD, ASTContext &C) const {
327  if (!FD)
328    return false;
329  IdentifierInfo *FunI = FD->getIdentifier();
330  if (!FunI)
331    return false;
332
333  initIdentifierInfo(C);
334
335  if (FunI == II_malloc || FunI == II_free || FunI == II_realloc ||
336      FunI == II_reallocf || FunI == II_calloc || FunI == II_valloc ||
337      FunI == II_strdup || FunI == II_strndup)
338    return true;
339
340  if (Filter.CMallocOptimistic && FD->hasAttrs() &&
341      FD->specific_attr_begin<OwnershipAttr>() !=
342          FD->specific_attr_end<OwnershipAttr>())
343    return true;
344
345
346  return false;
347}
348
349void MallocChecker::checkPostStmt(const CallExpr *CE, CheckerContext &C) const {
350  const FunctionDecl *FD = C.getCalleeDecl(CE);
351  if (!FD)
352    return;
353
354  initIdentifierInfo(C.getASTContext());
355  IdentifierInfo *FunI = FD->getIdentifier();
356  if (!FunI)
357    return;
358
359  ProgramStateRef State = C.getState();
360  if (FunI == II_malloc || FunI == II_valloc) {
361    State = MallocMemAux(C, CE, CE->getArg(0), UndefinedVal(), State);
362  } else if (FunI == II_realloc) {
363    State = ReallocMem(C, CE, false);
364  } else if (FunI == II_reallocf) {
365    State = ReallocMem(C, CE, true);
366  } else if (FunI == II_calloc) {
367    State = CallocMem(C, CE);
368  } else if (FunI == II_free) {
369    State = FreeMemAux(C, CE, C.getState(), 0, false);
370  } else if (FunI == II_strdup) {
371    State = MallocUpdateRefState(C, CE, State);
372  } else if (FunI == II_strndup) {
373    State = MallocUpdateRefState(C, CE, State);
374  } else if (Filter.CMallocOptimistic) {
375    // Check all the attributes, if there are any.
376    // There can be multiple of these attributes.
377    if (FD->hasAttrs())
378      for (specific_attr_iterator<OwnershipAttr>
379          i = FD->specific_attr_begin<OwnershipAttr>(),
380          e = FD->specific_attr_end<OwnershipAttr>();
381          i != e; ++i) {
382        switch ((*i)->getOwnKind()) {
383        case OwnershipAttr::Returns:
384          State = MallocMemReturnsAttr(C, CE, *i);
385          break;
386        case OwnershipAttr::Takes:
387        case OwnershipAttr::Holds:
388          State = FreeMemAttr(C, CE, *i);
389          break;
390        }
391      }
392  }
393  C.addTransition(State);
394}
395
396ProgramStateRef MallocChecker::MallocMemReturnsAttr(CheckerContext &C,
397                                                    const CallExpr *CE,
398                                                    const OwnershipAttr* Att) {
399  if (Att->getModule() != "malloc")
400    return 0;
401
402  OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
403  if (I != E) {
404    return MallocMemAux(C, CE, CE->getArg(*I), UndefinedVal(), C.getState());
405  }
406  return MallocMemAux(C, CE, UnknownVal(), UndefinedVal(), C.getState());
407}
408
409ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C,
410                                           const CallExpr *CE,
411                                           SVal Size, SVal Init,
412                                           ProgramStateRef state) {
413  // Get the return value.
414  SVal retVal = state->getSVal(CE, C.getLocationContext());
415
416  // We expect the malloc functions to return a pointer.
417  if (!isa<Loc>(retVal))
418    return 0;
419
420  // Fill the region with the initialization value.
421  state = state->bindDefault(retVal, Init);
422
423  // Set the region's extent equal to the Size parameter.
424  const SymbolicRegion *R =
425      dyn_cast_or_null<SymbolicRegion>(retVal.getAsRegion());
426  if (!R)
427    return 0;
428  if (isa<DefinedOrUnknownSVal>(Size)) {
429    SValBuilder &svalBuilder = C.getSValBuilder();
430    DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder);
431    DefinedOrUnknownSVal DefinedSize = cast<DefinedOrUnknownSVal>(Size);
432    DefinedOrUnknownSVal extentMatchesSize =
433        svalBuilder.evalEQ(state, Extent, DefinedSize);
434
435    state = state->assume(extentMatchesSize, true);
436    assert(state);
437  }
438
439  return MallocUpdateRefState(C, CE, state);
440}
441
442ProgramStateRef MallocChecker::MallocUpdateRefState(CheckerContext &C,
443                                                    const CallExpr *CE,
444                                                    ProgramStateRef state) {
445  // Get the return value.
446  SVal retVal = state->getSVal(CE, C.getLocationContext());
447
448  // We expect the malloc functions to return a pointer.
449  if (!isa<Loc>(retVal))
450    return 0;
451
452  SymbolRef Sym = retVal.getAsLocSymbol();
453  assert(Sym);
454
455  // Set the symbol's state to Allocated.
456  return state->set<RegionState>(Sym, RefState::getAllocateUnchecked(CE));
457
458}
459
460ProgramStateRef MallocChecker::FreeMemAttr(CheckerContext &C,
461                                           const CallExpr *CE,
462                                           const OwnershipAttr* Att) const {
463  if (Att->getModule() != "malloc")
464    return 0;
465
466  ProgramStateRef State = C.getState();
467
468  for (OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
469       I != E; ++I) {
470    ProgramStateRef StateI = FreeMemAux(C, CE, State, *I,
471                               Att->getOwnKind() == OwnershipAttr::Holds);
472    if (StateI)
473      State = StateI;
474  }
475  return State;
476}
477
478ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
479                                          const CallExpr *CE,
480                                          ProgramStateRef state,
481                                          unsigned Num,
482                                          bool Hold) const {
483  const Expr *ArgExpr = CE->getArg(Num);
484  SVal ArgVal = state->getSVal(ArgExpr, C.getLocationContext());
485  if (!isa<DefinedOrUnknownSVal>(ArgVal))
486    return 0;
487  DefinedOrUnknownSVal location = cast<DefinedOrUnknownSVal>(ArgVal);
488
489  // Check for null dereferences.
490  if (!isa<Loc>(location))
491    return 0;
492
493  // The explicit NULL case, no operation is performed.
494  ProgramStateRef notNullState, nullState;
495  llvm::tie(notNullState, nullState) = state->assume(location);
496  if (nullState && !notNullState)
497    return 0;
498
499  // Unknown values could easily be okay
500  // Undefined values are handled elsewhere
501  if (ArgVal.isUnknownOrUndef())
502    return 0;
503
504  const MemRegion *R = ArgVal.getAsRegion();
505
506  // Nonlocs can't be freed, of course.
507  // Non-region locations (labels and fixed addresses) also shouldn't be freed.
508  if (!R) {
509    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
510    return 0;
511  }
512
513  R = R->StripCasts();
514
515  // Blocks might show up as heap data, but should not be free()d
516  if (isa<BlockDataRegion>(R)) {
517    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
518    return 0;
519  }
520
521  const MemSpaceRegion *MS = R->getMemorySpace();
522
523  // Parameters, locals, statics, and globals shouldn't be freed.
524  if (!(isa<UnknownSpaceRegion>(MS) || isa<HeapSpaceRegion>(MS))) {
525    // FIXME: at the time this code was written, malloc() regions were
526    // represented by conjured symbols, which are all in UnknownSpaceRegion.
527    // This means that there isn't actually anything from HeapSpaceRegion
528    // that should be freed, even though we allow it here.
529    // Of course, free() can work on memory allocated outside the current
530    // function, so UnknownSpaceRegion is always a possibility.
531    // False negatives are better than false positives.
532
533    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
534    return 0;
535  }
536
537  const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R);
538  // Various cases could lead to non-symbol values here.
539  // For now, ignore them.
540  if (!SR)
541    return 0;
542
543  SymbolRef Sym = SR->getSymbol();
544  const RefState *RS = state->get<RegionState>(Sym);
545
546  // If the symbol has not been tracked, return. This is possible when free() is
547  // called on a pointer that does not get its pointee directly from malloc().
548  // Full support of this requires inter-procedural analysis.
549  if (!RS)
550    return 0;
551
552  // Check double free.
553  if (RS->isReleased()) {
554    if (ExplodedNode *N = C.generateSink()) {
555      if (!BT_DoubleFree)
556        BT_DoubleFree.reset(
557          new BugType("Double free", "Memory Error"));
558      BugReport *R = new BugReport(*BT_DoubleFree,
559                        "Attempt to free released memory", N);
560      R->addRange(ArgExpr->getSourceRange());
561      R->markInteresting(Sym);
562      R->addVisitor(new MallocBugVisitor(Sym));
563      C.EmitReport(R);
564    }
565    return 0;
566  }
567
568  // Normal free.
569  if (Hold)
570    return state->set<RegionState>(Sym, RefState::getRelinquished(CE));
571  return state->set<RegionState>(Sym, RefState::getReleased(CE));
572}
573
574bool MallocChecker::SummarizeValue(raw_ostream &os, SVal V) {
575  if (nonloc::ConcreteInt *IntVal = dyn_cast<nonloc::ConcreteInt>(&V))
576    os << "an integer (" << IntVal->getValue() << ")";
577  else if (loc::ConcreteInt *ConstAddr = dyn_cast<loc::ConcreteInt>(&V))
578    os << "a constant address (" << ConstAddr->getValue() << ")";
579  else if (loc::GotoLabel *Label = dyn_cast<loc::GotoLabel>(&V))
580    os << "the address of the label '" << Label->getLabel()->getName() << "'";
581  else
582    return false;
583
584  return true;
585}
586
587bool MallocChecker::SummarizeRegion(raw_ostream &os,
588                                    const MemRegion *MR) {
589  switch (MR->getKind()) {
590  case MemRegion::FunctionTextRegionKind: {
591    const FunctionDecl *FD = cast<FunctionTextRegion>(MR)->getDecl();
592    if (FD)
593      os << "the address of the function '" << *FD << '\'';
594    else
595      os << "the address of a function";
596    return true;
597  }
598  case MemRegion::BlockTextRegionKind:
599    os << "block text";
600    return true;
601  case MemRegion::BlockDataRegionKind:
602    // FIXME: where the block came from?
603    os << "a block";
604    return true;
605  default: {
606    const MemSpaceRegion *MS = MR->getMemorySpace();
607
608    if (isa<StackLocalsSpaceRegion>(MS)) {
609      const VarRegion *VR = dyn_cast<VarRegion>(MR);
610      const VarDecl *VD;
611      if (VR)
612        VD = VR->getDecl();
613      else
614        VD = NULL;
615
616      if (VD)
617        os << "the address of the local variable '" << VD->getName() << "'";
618      else
619        os << "the address of a local stack variable";
620      return true;
621    }
622
623    if (isa<StackArgumentsSpaceRegion>(MS)) {
624      const VarRegion *VR = dyn_cast<VarRegion>(MR);
625      const VarDecl *VD;
626      if (VR)
627        VD = VR->getDecl();
628      else
629        VD = NULL;
630
631      if (VD)
632        os << "the address of the parameter '" << VD->getName() << "'";
633      else
634        os << "the address of a parameter";
635      return true;
636    }
637
638    if (isa<GlobalsSpaceRegion>(MS)) {
639      const VarRegion *VR = dyn_cast<VarRegion>(MR);
640      const VarDecl *VD;
641      if (VR)
642        VD = VR->getDecl();
643      else
644        VD = NULL;
645
646      if (VD) {
647        if (VD->isStaticLocal())
648          os << "the address of the static variable '" << VD->getName() << "'";
649        else
650          os << "the address of the global variable '" << VD->getName() << "'";
651      } else
652        os << "the address of a global variable";
653      return true;
654    }
655
656    return false;
657  }
658  }
659}
660
661void MallocChecker::ReportBadFree(CheckerContext &C, SVal ArgVal,
662                                  SourceRange range) const {
663  if (ExplodedNode *N = C.generateSink()) {
664    if (!BT_BadFree)
665      BT_BadFree.reset(new BugType("Bad free", "Memory Error"));
666
667    SmallString<100> buf;
668    llvm::raw_svector_ostream os(buf);
669
670    const MemRegion *MR = ArgVal.getAsRegion();
671    if (MR) {
672      while (const ElementRegion *ER = dyn_cast<ElementRegion>(MR))
673        MR = ER->getSuperRegion();
674
675      // Special case for alloca()
676      if (isa<AllocaRegion>(MR))
677        os << "Argument to free() was allocated by alloca(), not malloc()";
678      else {
679        os << "Argument to free() is ";
680        if (SummarizeRegion(os, MR))
681          os << ", which is not memory allocated by malloc()";
682        else
683          os << "not memory allocated by malloc()";
684      }
685    } else {
686      os << "Argument to free() is ";
687      if (SummarizeValue(os, ArgVal))
688        os << ", which is not memory allocated by malloc()";
689      else
690        os << "not memory allocated by malloc()";
691    }
692
693    BugReport *R = new BugReport(*BT_BadFree, os.str(), N);
694    R->markInteresting(MR);
695    R->addRange(range);
696    C.EmitReport(R);
697  }
698}
699
700ProgramStateRef MallocChecker::ReallocMem(CheckerContext &C,
701                                          const CallExpr *CE,
702                                          bool FreesOnFail) const {
703  ProgramStateRef state = C.getState();
704  const Expr *arg0Expr = CE->getArg(0);
705  const LocationContext *LCtx = C.getLocationContext();
706  SVal Arg0Val = state->getSVal(arg0Expr, LCtx);
707  if (!isa<DefinedOrUnknownSVal>(Arg0Val))
708    return 0;
709  DefinedOrUnknownSVal arg0Val = cast<DefinedOrUnknownSVal>(Arg0Val);
710
711  SValBuilder &svalBuilder = C.getSValBuilder();
712
713  DefinedOrUnknownSVal PtrEQ =
714    svalBuilder.evalEQ(state, arg0Val, svalBuilder.makeNull());
715
716  // Get the size argument. If there is no size arg then give up.
717  const Expr *Arg1 = CE->getArg(1);
718  if (!Arg1)
719    return 0;
720
721  // Get the value of the size argument.
722  SVal Arg1ValG = state->getSVal(Arg1, LCtx);
723  if (!isa<DefinedOrUnknownSVal>(Arg1ValG))
724    return 0;
725  DefinedOrUnknownSVal Arg1Val = cast<DefinedOrUnknownSVal>(Arg1ValG);
726
727  // Compare the size argument to 0.
728  DefinedOrUnknownSVal SizeZero =
729    svalBuilder.evalEQ(state, Arg1Val,
730                       svalBuilder.makeIntValWithPtrWidth(0, false));
731
732  ProgramStateRef StatePtrIsNull, StatePtrNotNull;
733  llvm::tie(StatePtrIsNull, StatePtrNotNull) = state->assume(PtrEQ);
734  ProgramStateRef StateSizeIsZero, StateSizeNotZero;
735  llvm::tie(StateSizeIsZero, StateSizeNotZero) = state->assume(SizeZero);
736  // We only assume exceptional states if they are definitely true; if the
737  // state is under-constrained, assume regular realloc behavior.
738  bool PrtIsNull = StatePtrIsNull && !StatePtrNotNull;
739  bool SizeIsZero = StateSizeIsZero && !StateSizeNotZero;
740
741  // If the ptr is NULL and the size is not 0, the call is equivalent to
742  // malloc(size).
743  if ( PrtIsNull && !SizeIsZero) {
744    ProgramStateRef stateMalloc = MallocMemAux(C, CE, CE->getArg(1),
745                                               UndefinedVal(), StatePtrIsNull);
746    return stateMalloc;
747  }
748
749  if (PrtIsNull && SizeIsZero)
750    return 0;
751
752  // Get the from and to pointer symbols as in toPtr = realloc(fromPtr, size).
753  assert(!PrtIsNull);
754  SymbolRef FromPtr = arg0Val.getAsSymbol();
755  SVal RetVal = state->getSVal(CE, LCtx);
756  SymbolRef ToPtr = RetVal.getAsSymbol();
757  if (!FromPtr || !ToPtr)
758    return 0;
759
760  // If the size is 0, free the memory.
761  if (SizeIsZero)
762    if (ProgramStateRef stateFree = FreeMemAux(C, CE, StateSizeIsZero,0,false)){
763      // The semantics of the return value are:
764      // If size was equal to 0, either NULL or a pointer suitable to be passed
765      // to free() is returned.
766      stateFree = stateFree->set<ReallocPairs>(ToPtr,
767                                            ReallocPair(FromPtr, FreesOnFail));
768      C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr);
769      return stateFree;
770    }
771
772  // Default behavior.
773  if (ProgramStateRef stateFree = FreeMemAux(C, CE, state, 0, false)) {
774    // FIXME: We should copy the content of the original buffer.
775    ProgramStateRef stateRealloc = MallocMemAux(C, CE, CE->getArg(1),
776                                                UnknownVal(), stateFree);
777    if (!stateRealloc)
778      return 0;
779    stateRealloc = stateRealloc->set<ReallocPairs>(ToPtr,
780                                            ReallocPair(FromPtr, FreesOnFail));
781    C.getSymbolManager().addSymbolDependency(ToPtr, FromPtr);
782    return stateRealloc;
783  }
784  return 0;
785}
786
787ProgramStateRef MallocChecker::CallocMem(CheckerContext &C, const CallExpr *CE){
788  ProgramStateRef state = C.getState();
789  SValBuilder &svalBuilder = C.getSValBuilder();
790  const LocationContext *LCtx = C.getLocationContext();
791  SVal count = state->getSVal(CE->getArg(0), LCtx);
792  SVal elementSize = state->getSVal(CE->getArg(1), LCtx);
793  SVal TotalSize = svalBuilder.evalBinOp(state, BO_Mul, count, elementSize,
794                                        svalBuilder.getContext().getSizeType());
795  SVal zeroVal = svalBuilder.makeZeroVal(svalBuilder.getContext().CharTy);
796
797  return MallocMemAux(C, CE, TotalSize, zeroVal, state);
798}
799
800const Stmt *
801MallocChecker::getAllocationSite(const ExplodedNode *N, SymbolRef Sym,
802                                 CheckerContext &C) const {
803  const LocationContext *LeakContext = N->getLocationContext();
804  // Walk the ExplodedGraph backwards and find the first node that referred to
805  // the tracked symbol.
806  const ExplodedNode *AllocNode = N;
807
808  while (N) {
809    if (!N->getState()->get<RegionState>(Sym))
810      break;
811    // Allocation node, is the last node in the current context in which the
812    // symbol was tracked.
813    if (N->getLocationContext() == LeakContext)
814      AllocNode = N;
815    N = N->pred_empty() ? NULL : *(N->pred_begin());
816  }
817
818  ProgramPoint P = AllocNode->getLocation();
819  if (!isa<StmtPoint>(P))
820    return 0;
821
822  return cast<StmtPoint>(P).getStmt();
823}
824
825void MallocChecker::reportLeak(SymbolRef Sym, ExplodedNode *N,
826                               CheckerContext &C) const {
827  assert(N);
828  if (!BT_Leak) {
829    BT_Leak.reset(new BugType("Memory leak", "Memory Error"));
830    // Leaks should not be reported if they are post-dominated by a sink:
831    // (1) Sinks are higher importance bugs.
832    // (2) NoReturnFunctionChecker uses sink nodes to represent paths ending
833    //     with __noreturn functions such as assert() or exit(). We choose not
834    //     to report leaks on such paths.
835    BT_Leak->setSuppressOnSink(true);
836  }
837
838  // Most bug reports are cached at the location where they occurred.
839  // With leaks, we want to unique them by the location where they were
840  // allocated, and only report a single path.
841  PathDiagnosticLocation LocUsedForUniqueing;
842  if (const Stmt *AllocStmt = getAllocationSite(N, Sym, C))
843    LocUsedForUniqueing = PathDiagnosticLocation::createBegin(AllocStmt,
844                            C.getSourceManager(), N->getLocationContext());
845
846  BugReport *R = new BugReport(*BT_Leak,
847    "Memory is never released; potential memory leak", N, LocUsedForUniqueing);
848  R->markInteresting(Sym);
849  R->addVisitor(new MallocBugVisitor(Sym));
850  C.EmitReport(R);
851}
852
853void MallocChecker::checkDeadSymbols(SymbolReaper &SymReaper,
854                                     CheckerContext &C) const
855{
856  if (!SymReaper.hasDeadSymbols())
857    return;
858
859  ProgramStateRef state = C.getState();
860  RegionStateTy RS = state->get<RegionState>();
861  RegionStateTy::Factory &F = state->get_context<RegionState>();
862
863  bool generateReport = false;
864  llvm::SmallVector<SymbolRef, 2> Errors;
865  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
866    if (SymReaper.isDead(I->first)) {
867      if (I->second.isAllocated()) {
868        generateReport = true;
869        Errors.push_back(I->first);
870      }
871      // Remove the dead symbol from the map.
872      RS = F.remove(RS, I->first);
873
874    }
875  }
876
877  // Cleanup the Realloc Pairs Map.
878  ReallocMap RP = state->get<ReallocPairs>();
879  for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
880    if (SymReaper.isDead(I->first) ||
881        SymReaper.isDead(I->second.ReallocatedSym)) {
882      state = state->remove<ReallocPairs>(I->first);
883    }
884  }
885
886  // Generate leak node.
887  static SimpleProgramPointTag Tag("MallocChecker : DeadSymbolsLeak");
888  ExplodedNode *N = C.addTransition(C.getState(), C.getPredecessor(), &Tag);
889
890  if (generateReport) {
891    for (llvm::SmallVector<SymbolRef, 2>::iterator
892         I = Errors.begin(), E = Errors.end(); I != E; ++I) {
893      reportLeak(*I, N, C);
894    }
895  }
896  C.addTransition(state->set<RegionState>(RS), N);
897}
898
899void MallocChecker::checkEndPath(CheckerContext &C) const {
900  ProgramStateRef state = C.getState();
901  RegionStateTy M = state->get<RegionState>();
902
903  // If inside inlined call, skip it.
904  if (C.getLocationContext()->getParent() != 0)
905    return;
906
907  for (RegionStateTy::iterator I = M.begin(), E = M.end(); I != E; ++I) {
908    RefState RS = I->second;
909    if (RS.isAllocated()) {
910      ExplodedNode *N = C.addTransition(state);
911      if (N)
912        reportLeak(I->first, N, C);
913    }
914  }
915}
916
917bool MallocChecker::checkEscape(SymbolRef Sym, const Stmt *S,
918                                CheckerContext &C) const {
919  ProgramStateRef state = C.getState();
920  const RefState *RS = state->get<RegionState>(Sym);
921  if (!RS)
922    return false;
923
924  if (RS->isAllocated()) {
925    state = state->set<RegionState>(Sym, RefState::getEscaped(S));
926    C.addTransition(state);
927    return true;
928  }
929  return false;
930}
931
932void MallocChecker::checkPreStmt(const CallExpr *CE, CheckerContext &C) const {
933  if (isMemFunction(C.getCalleeDecl(CE), C.getASTContext()))
934    return;
935
936  // Check use after free, when a freed pointer is passed to a call.
937  ProgramStateRef State = C.getState();
938  for (CallExpr::const_arg_iterator I = CE->arg_begin(),
939                                    E = CE->arg_end(); I != E; ++I) {
940    const Expr *A = *I;
941    if (A->getType().getTypePtr()->isAnyPointerType()) {
942      SymbolRef Sym = State->getSVal(A, C.getLocationContext()).getAsSymbol();
943      if (!Sym)
944        continue;
945      if (checkUseAfterFree(Sym, C, A))
946        return;
947    }
948  }
949}
950
951void MallocChecker::checkPreStmt(const ReturnStmt *S, CheckerContext &C) const {
952  const Expr *E = S->getRetValue();
953  if (!E)
954    return;
955
956  // Check if we are returning a symbol.
957  SVal RetVal = C.getState()->getSVal(E, C.getLocationContext());
958  SymbolRef Sym = RetVal.getAsSymbol();
959  if (!Sym)
960    // If we are returning a field of the allocated struct or an array element,
961    // the callee could still free the memory.
962    // TODO: This logic should be a part of generic symbol escape callback.
963    if (const MemRegion *MR = RetVal.getAsRegion())
964      if (isa<FieldRegion>(MR) || isa<ElementRegion>(MR))
965        if (const SymbolicRegion *BMR =
966              dyn_cast<SymbolicRegion>(MR->getBaseRegion()))
967          Sym = BMR->getSymbol();
968  if (!Sym)
969    return;
970
971  // Check if we are returning freed memory.
972  if (checkUseAfterFree(Sym, C, E))
973    return;
974
975  // If this function body is not inlined, check if the symbol is escaping.
976  if (C.getLocationContext()->getParent() == 0)
977    checkEscape(Sym, E, C);
978}
979
980bool MallocChecker::checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
981                                      const Stmt *S) const {
982  assert(Sym);
983  const RefState *RS = C.getState()->get<RegionState>(Sym);
984  if (RS && RS->isReleased()) {
985    if (ExplodedNode *N = C.generateSink()) {
986      if (!BT_UseFree)
987        BT_UseFree.reset(new BugType("Use-after-free", "Memory Error"));
988
989      BugReport *R = new BugReport(*BT_UseFree,
990                                   "Use of memory after it is freed",N);
991      if (S)
992        R->addRange(S->getSourceRange());
993      R->markInteresting(Sym);
994      R->addVisitor(new MallocBugVisitor(Sym));
995      C.EmitReport(R);
996      return true;
997    }
998  }
999  return false;
1000}
1001
1002// Check if the location is a freed symbolic region.
1003void MallocChecker::checkLocation(SVal l, bool isLoad, const Stmt *S,
1004                                  CheckerContext &C) const {
1005  SymbolRef Sym = l.getLocSymbolInBase();
1006  if (Sym)
1007    checkUseAfterFree(Sym, C);
1008}
1009
1010//===----------------------------------------------------------------------===//
1011// Check various ways a symbol can be invalidated.
1012// TODO: This logic (the next 3 functions) is copied/similar to the
1013// RetainRelease checker. We might want to factor this out.
1014//===----------------------------------------------------------------------===//
1015
1016// Stop tracking symbols when a value escapes as a result of checkBind.
1017// A value escapes in three possible cases:
1018// (1) we are binding to something that is not a memory region.
1019// (2) we are binding to a memregion that does not have stack storage
1020// (3) we are binding to a memregion with stack storage that the store
1021//     does not understand.
1022void MallocChecker::checkBind(SVal loc, SVal val, const Stmt *S,
1023                              CheckerContext &C) const {
1024  // Are we storing to something that causes the value to "escape"?
1025  bool escapes = true;
1026  ProgramStateRef state = C.getState();
1027
1028  if (loc::MemRegionVal *regionLoc = dyn_cast<loc::MemRegionVal>(&loc)) {
1029    escapes = !regionLoc->getRegion()->hasStackStorage();
1030
1031    if (!escapes) {
1032      // To test (3), generate a new state with the binding added.  If it is
1033      // the same state, then it escapes (since the store cannot represent
1034      // the binding).
1035      escapes = (state == (state->bindLoc(*regionLoc, val)));
1036    }
1037    if (!escapes) {
1038      // Case 4: We do not currently model what happens when a symbol is
1039      // assigned to a struct field, so be conservative here and let the symbol
1040      // go. TODO: This could definitely be improved upon.
1041      escapes = !isa<VarRegion>(regionLoc->getRegion());
1042    }
1043  }
1044
1045  // If our store can represent the binding and we aren't storing to something
1046  // that doesn't have local storage then just return and have the simulation
1047  // state continue as is.
1048  if (!escapes)
1049      return;
1050
1051  // Otherwise, find all symbols referenced by 'val' that we are tracking
1052  // and stop tracking them.
1053  state = state->scanReachableSymbols<StopTrackingCallback>(val).getState();
1054  C.addTransition(state);
1055}
1056
1057// If a symbolic region is assumed to NULL (or another constant), stop tracking
1058// it - assuming that allocation failed on this path.
1059ProgramStateRef MallocChecker::evalAssume(ProgramStateRef state,
1060                                              SVal Cond,
1061                                              bool Assumption) const {
1062  RegionStateTy RS = state->get<RegionState>();
1063  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
1064    // If the symbol is assumed to NULL or another constant, this will
1065    // return an APSInt*.
1066    if (state->getSymVal(I.getKey()))
1067      state = state->remove<RegionState>(I.getKey());
1068  }
1069
1070  // Realloc returns 0 when reallocation fails, which means that we should
1071  // restore the state of the pointer being reallocated.
1072  ReallocMap RP = state->get<ReallocPairs>();
1073  for (ReallocMap::iterator I = RP.begin(), E = RP.end(); I != E; ++I) {
1074    // If the symbol is assumed to NULL or another constant, this will
1075    // return an APSInt*.
1076    if (state->getSymVal(I.getKey())) {
1077      SymbolRef ReallocSym = I.getData().ReallocatedSym;
1078      const RefState *RS = state->get<RegionState>(ReallocSym);
1079      if (RS) {
1080        if (RS->isReleased() && ! I.getData().IsFreeOnFailure)
1081          state = state->set<RegionState>(ReallocSym,
1082                             RefState::getAllocateUnchecked(RS->getStmt()));
1083      }
1084      state = state->remove<ReallocPairs>(I.getKey());
1085    }
1086  }
1087
1088  return state;
1089}
1090
1091// Check if the function is known to us. So, for example, we could
1092// conservatively assume it can free/reallocate it's pointer arguments.
1093// (We assume that the pointers cannot escape through calls to system
1094// functions not handled by this checker.)
1095bool MallocChecker::doesNotFreeMemory(const CallOrObjCMessage *Call,
1096                                      ProgramStateRef State) const {
1097  if (!Call)
1098    return false;
1099
1100  // For now, assume that any C++ call can free memory.
1101  // TODO: If we want to be more optimistic here, we'll need to make sure that
1102  // regions escape to C++ containers. They seem to do that even now, but for
1103  // mysterious reasons.
1104  if (Call->isCXXCall())
1105    return false;
1106
1107  const Decl *D = Call->getDecl();
1108  if (!D)
1109    return false;
1110
1111  ASTContext &ASTC = State->getStateManager().getContext();
1112
1113  // If it's one of the allocation functions we can reason about, we model
1114  // its behavior explicitly.
1115  if (isa<FunctionDecl>(D) && isMemFunction(cast<FunctionDecl>(D), ASTC)) {
1116    return true;
1117  }
1118
1119  // If it's not a system call, assume it frees memory.
1120  SourceManager &SM = ASTC.getSourceManager();
1121  if (!SM.isInSystemHeader(D->getLocation()))
1122    return false;
1123
1124  // Process C/ObjC functions.
1125  if (const FunctionDecl *FD  = dyn_cast<FunctionDecl>(D)) {
1126    // White list the system functions whose arguments escape.
1127    const IdentifierInfo *II = FD->getIdentifier();
1128    if (!II)
1129      return true;
1130    StringRef FName = II->getName();
1131
1132    // White list thread local storage.
1133    if (FName.equals("pthread_setspecific"))
1134      return false;
1135
1136    // White list the 'XXXNoCopy' ObjC functions.
1137    if (FName.endswith("NoCopy")) {
1138      // Look for the deallocator argument. We know that the memory ownership
1139      // is not transfered only if the deallocator argument is
1140      // 'kCFAllocatorNull'.
1141      for (unsigned i = 1; i < Call->getNumArgs(); ++i) {
1142        const Expr *ArgE = Call->getArg(i)->IgnoreParenCasts();
1143        if (const DeclRefExpr *DE = dyn_cast<DeclRefExpr>(ArgE)) {
1144          StringRef DeallocatorName = DE->getFoundDecl()->getName();
1145          if (DeallocatorName == "kCFAllocatorNull")
1146            return true;
1147        }
1148      }
1149      return false;
1150    }
1151
1152    // PR12101
1153    // Many CoreFoundation and CoreGraphics might allow a tracked object
1154    // to escape.
1155    if (Call->isCFCGAllowingEscape(FName))
1156      return false;
1157
1158    // Associating streams with malloced buffers. The pointer can escape if
1159    // 'closefn' is specified (and if that function does free memory).
1160    // Currently, we do not inspect the 'closefn' function (PR12101).
1161    if (FName == "funopen")
1162      if (Call->getNumArgs() >= 4 && !Call->getArgSVal(4).isConstant(0))
1163        return false;
1164
1165    // Do not warn on pointers passed to 'setbuf' when used with std streams,
1166    // these leaks might be intentional when setting the buffer for stdio.
1167    // http://stackoverflow.com/questions/2671151/who-frees-setvbuf-buffer
1168    if (FName == "setbuf" || FName =="setbuffer" ||
1169        FName == "setlinebuf" || FName == "setvbuf") {
1170      if (Call->getNumArgs() >= 1)
1171        if (const DeclRefExpr *Arg =
1172              dyn_cast<DeclRefExpr>(Call->getArg(0)->IgnoreParenCasts()))
1173          if (const VarDecl *D = dyn_cast<VarDecl>(Arg->getDecl()))
1174              if (D->getCanonicalDecl()->getName().find("std")
1175                                                   != StringRef::npos)
1176                return false;
1177    }
1178
1179    // A bunch of other functions, which take ownership of a pointer (See retain
1180    // release checker). Not all the parameters here are invalidated, but the
1181    // Malloc checker cannot differentiate between them. The right way of doing
1182    // this would be to implement a pointer escapes callback.
1183    if (FName == "CVPixelBufferCreateWithBytes" ||
1184        FName == "CGBitmapContextCreateWithData" ||
1185        FName == "CVPixelBufferCreateWithPlanarBytes") {
1186      return false;
1187    }
1188
1189    // Otherwise, assume that the function does not free memory.
1190    // Most system calls, do not free the memory.
1191    return true;
1192
1193  // Process ObjC functions.
1194  } else if (const ObjCMethodDecl * ObjCD = dyn_cast<ObjCMethodDecl>(D)) {
1195    Selector S = ObjCD->getSelector();
1196
1197    // White list the ObjC functions which do free memory.
1198    // - Anything containing 'freeWhenDone' param set to 1.
1199    //   Ex: dataWithBytesNoCopy:length:freeWhenDone.
1200    for (unsigned i = 1; i < S.getNumArgs(); ++i) {
1201      if (S.getNameForSlot(i).equals("freeWhenDone")) {
1202        if (Call->getArgSVal(i).isConstant(1))
1203          return false;
1204        else
1205          return true;
1206      }
1207    }
1208
1209    // If the first selector ends with NoCopy, assume that the ownership is
1210    // transfered as well.
1211    // Ex:  [NSData dataWithBytesNoCopy:bytes length:10];
1212    if (S.getNameForSlot(0).endswith("NoCopy")) {
1213      return false;
1214    }
1215
1216    // Otherwise, assume that the function does not free memory.
1217    // Most system calls, do not free the memory.
1218    return true;
1219  }
1220
1221  // Otherwise, assume that the function can free memory.
1222  return false;
1223
1224}
1225
1226// If the symbol we are tracking is invalidated, but not explicitly (ex: the &p
1227// escapes, when we are tracking p), do not track the symbol as we cannot reason
1228// about it anymore.
1229ProgramStateRef
1230MallocChecker::checkRegionChanges(ProgramStateRef State,
1231                            const StoreManager::InvalidatedSymbols *invalidated,
1232                                    ArrayRef<const MemRegion *> ExplicitRegions,
1233                                    ArrayRef<const MemRegion *> Regions,
1234                                    const CallOrObjCMessage *Call) const {
1235  if (!invalidated || invalidated->empty())
1236    return State;
1237  llvm::SmallPtrSet<SymbolRef, 8> WhitelistedSymbols;
1238
1239  // If it's a call which might free or reallocate memory, we assume that all
1240  // regions (explicit and implicit) escaped.
1241
1242  // Otherwise, whitelist explicit pointers; we still can track them.
1243  if (!Call || doesNotFreeMemory(Call, State)) {
1244    for (ArrayRef<const MemRegion *>::iterator I = ExplicitRegions.begin(),
1245        E = ExplicitRegions.end(); I != E; ++I) {
1246      if (const SymbolicRegion *R = (*I)->StripCasts()->getAs<SymbolicRegion>())
1247        WhitelistedSymbols.insert(R->getSymbol());
1248    }
1249  }
1250
1251  for (StoreManager::InvalidatedSymbols::const_iterator I=invalidated->begin(),
1252       E = invalidated->end(); I!=E; ++I) {
1253    SymbolRef sym = *I;
1254    if (WhitelistedSymbols.count(sym))
1255      continue;
1256    // The symbol escaped.
1257    if (const RefState *RS = State->get<RegionState>(sym))
1258      State = State->set<RegionState>(sym, RefState::getEscaped(RS->getStmt()));
1259  }
1260  return State;
1261}
1262
1263PathDiagnosticPiece *
1264MallocChecker::MallocBugVisitor::VisitNode(const ExplodedNode *N,
1265                                           const ExplodedNode *PrevN,
1266                                           BugReporterContext &BRC,
1267                                           BugReport &BR) {
1268  const RefState *RS = N->getState()->get<RegionState>(Sym);
1269  const RefState *RSPrev = PrevN->getState()->get<RegionState>(Sym);
1270  if (!RS && !RSPrev)
1271    return 0;
1272
1273  const Stmt *S = 0;
1274  const char *Msg = 0;
1275  StackHintGeneratorForSymbol *StackHint = 0;
1276
1277  // Retrieve the associated statement.
1278  ProgramPoint ProgLoc = N->getLocation();
1279  if (isa<StmtPoint>(ProgLoc))
1280    S = cast<StmtPoint>(ProgLoc).getStmt();
1281  // If an assumption was made on a branch, it should be caught
1282  // here by looking at the state transition.
1283  if (isa<BlockEdge>(ProgLoc)) {
1284    const CFGBlock *srcBlk = cast<BlockEdge>(ProgLoc).getSrc();
1285    S = srcBlk->getTerminator();
1286  }
1287  if (!S)
1288    return 0;
1289
1290  // Find out if this is an interesting point and what is the kind.
1291  // TODO: Replace 'callee' by the function name.
1292  if (Mode == Normal) {
1293    if (isAllocated(RS, RSPrev, S)) {
1294      Msg = "Memory is allocated";
1295      StackHint = new StackHintGeneratorForSymbol(Sym, "; allocated memory");
1296    } else if (isReleased(RS, RSPrev, S)) {
1297      Msg = "Memory is released";
1298      StackHint = new StackHintGeneratorForSymbol(Sym, "; released memory");
1299    } else if (isReallocFailedCheck(RS, RSPrev, S)) {
1300      Mode = ReallocationFailed;
1301      Msg = "Reallocation failed";
1302      StackHint = new StackHintGeneratorForReallocationFailed(Sym,
1303                                                   "; reallocation failed");
1304    }
1305
1306  // We are in a special mode if a reallocation failed later in the path.
1307  } else if (Mode == ReallocationFailed) {
1308    // Generate a special diagnostic for the first realloc we find.
1309    if (!isAllocated(RS, RSPrev, S) && !isReleased(RS, RSPrev, S))
1310      return 0;
1311
1312    // Check that the name of the function is realloc.
1313    const CallExpr *CE = dyn_cast<CallExpr>(S);
1314    if (!CE)
1315      return 0;
1316    const FunctionDecl *funDecl = CE->getDirectCallee();
1317    if (!funDecl)
1318      return 0;
1319    StringRef FunName = funDecl->getName();
1320    if (!(FunName.equals("realloc") || FunName.equals("reallocf")))
1321      return 0;
1322    Msg = "Attempt to reallocate memory";
1323    StackHint = new StackHintGeneratorForSymbol(Sym, "; reallocated memory");
1324    Mode = Normal;
1325  }
1326
1327  if (!Msg)
1328    return 0;
1329  assert(StackHint);
1330
1331  // Generate the extra diagnostic.
1332  PathDiagnosticLocation Pos(S, BRC.getSourceManager(),
1333                             N->getLocationContext());
1334  return new PathDiagnosticEventPiece(Pos, Msg, true, StackHint);
1335}
1336
1337
1338#define REGISTER_CHECKER(name) \
1339void ento::register##name(CheckerManager &mgr) {\
1340  registerCStringCheckerBasic(mgr); \
1341  mgr.registerChecker<MallocChecker>()->Filter.C##name = true;\
1342}
1343
1344REGISTER_CHECKER(MallocPessimistic)
1345REGISTER_CHECKER(MallocOptimistic)
1346