MallocChecker.cpp revision 7fb4900f83832432dd4cdb84eb6e2ed132e6daf1 
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 "clang/StaticAnalyzer/Core/Checker.h"
17#include "clang/StaticAnalyzer/Core/CheckerManager.h"
18#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
19#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
20#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
21#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
22#include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
23#include "llvm/ADT/ImmutableMap.h"
24#include "llvm/ADT/SmallString.h"
25#include "llvm/ADT/STLExtras.h"
26using namespace clang;
27using namespace ento;
28
29namespace {
30
31class RefState {
32  enum Kind { AllocateUnchecked, AllocateFailed, Released, Escaped,
33              Relinquished } K;
34  const Stmt *S;
35
36public:
37  RefState(Kind k, const Stmt *s) : K(k), S(s) {}
38
39  bool isAllocated() const { return K == AllocateUnchecked; }
40  //bool isFailed() const { return K == AllocateFailed; }
41  bool isReleased() const { return K == Released; }
42  //bool isEscaped() const { return K == Escaped; }
43  //bool isRelinquished() const { return K == Relinquished; }
44
45  bool operator==(const RefState &X) const {
46    return K == X.K && S == X.S;
47  }
48
49  static RefState getAllocateUnchecked(const Stmt *s) {
50    return RefState(AllocateUnchecked, s);
51  }
52  static RefState getAllocateFailed() {
53    return RefState(AllocateFailed, 0);
54  }
55  static RefState getReleased(const Stmt *s) { return RefState(Released, s); }
56  static RefState getEscaped(const Stmt *s) { return RefState(Escaped, s); }
57  static RefState getRelinquished(const Stmt *s) {
58    return RefState(Relinquished, s);
59  }
60
61  void Profile(llvm::FoldingSetNodeID &ID) const {
62    ID.AddInteger(K);
63    ID.AddPointer(S);
64  }
65};
66
67class RegionState {};
68
69class MallocChecker : public Checker<check::DeadSymbols,
70                                     check::EndPath,
71                                     check::PreStmt<ReturnStmt>,
72                                     check::PostStmt<CallExpr>,
73                                     check::Location,
74                                     check::Bind,
75                                     eval::Assume>
76{
77  mutable OwningPtr<BuiltinBug> BT_DoubleFree;
78  mutable OwningPtr<BuiltinBug> BT_Leak;
79  mutable OwningPtr<BuiltinBug> BT_UseFree;
80  mutable OwningPtr<BuiltinBug> BT_UseRelinquished;
81  mutable OwningPtr<BuiltinBug> BT_BadFree;
82  mutable IdentifierInfo *II_malloc, *II_free, *II_realloc, *II_calloc;
83
84public:
85  MallocChecker() : II_malloc(0), II_free(0), II_realloc(0), II_calloc(0) {}
86
87  /// In pessimistic mode, the checker assumes that it does not know which
88  /// functions might free the memory.
89  struct ChecksFilter {
90    DefaultBool CMallocPessimistic;
91    DefaultBool CMallocOptimistic;
92  };
93
94  ChecksFilter Filter;
95
96  void initIdentifierInfo(CheckerContext &C) const;
97
98  void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
99  void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;
100  void checkEndPath(CheckerContext &C) const;
101  void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const;
102  ProgramStateRef evalAssume(ProgramStateRef state, SVal Cond,
103                            bool Assumption) const;
104  void checkLocation(SVal l, bool isLoad, const Stmt *S,
105                     CheckerContext &C) const;
106  void checkBind(SVal location, SVal val, const Stmt*S,
107                 CheckerContext &C) const;
108
109private:
110  static void MallocMem(CheckerContext &C, const CallExpr *CE);
111  static void MallocMemReturnsAttr(CheckerContext &C, const CallExpr *CE,
112                                   const OwnershipAttr* Att);
113  static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
114                                     const Expr *SizeEx, SVal Init,
115                                     ProgramStateRef state) {
116    return MallocMemAux(C, CE,
117                        state->getSVal(SizeEx, C.getLocationContext()),
118                        Init, state);
119  }
120  static ProgramStateRef MallocMemAux(CheckerContext &C, const CallExpr *CE,
121                                     SVal SizeEx, SVal Init,
122                                     ProgramStateRef state);
123
124  void FreeMem(CheckerContext &C, const CallExpr *CE) const;
125  void FreeMemAttr(CheckerContext &C, const CallExpr *CE,
126                   const OwnershipAttr* Att) const;
127  ProgramStateRef FreeMemAux(CheckerContext &C, const CallExpr *CE,
128                                 ProgramStateRef state, unsigned Num,
129                                 bool Hold) const;
130
131  void ReallocMem(CheckerContext &C, const CallExpr *CE) const;
132  static void CallocMem(CheckerContext &C, const CallExpr *CE);
133
134  bool checkEscape(SymbolRef Sym, const Stmt *S, CheckerContext &C) const;
135  bool checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
136                         const Stmt *S = 0) const;
137
138  static bool SummarizeValue(raw_ostream &os, SVal V);
139  static bool SummarizeRegion(raw_ostream &os, const MemRegion *MR);
140  void ReportBadFree(CheckerContext &C, SVal ArgVal, SourceRange range) const;
141
142  /// The bug visitor which allows us to print extra diagnostics along the
143  /// BugReport path. For example, showing the allocation site of the leaked
144  /// region.
145  class MallocBugVisitor : public BugReporterVisitor {
146  protected:
147    // The allocated region symbol tracked by the main analysis.
148    SymbolRef Sym;
149
150  public:
151    MallocBugVisitor(SymbolRef S) : Sym(S) {}
152    virtual ~MallocBugVisitor() {}
153
154    void Profile(llvm::FoldingSetNodeID &ID) const {
155      static int X = 0;
156      ID.AddPointer(&X);
157      ID.AddPointer(Sym);
158    }
159
160    inline bool isAllocated(const RefState *S, const RefState *SPrev) {
161      // Did not track -> allocated. Other state (released) -> allocated.
162      return ((S && S->isAllocated()) && (!SPrev || !SPrev->isAllocated()));
163    }
164
165    inline bool isReleased(const RefState *S, const RefState *SPrev) {
166      // Did not track -> released. Other state (allocated) -> released.
167      return ((S && S->isReleased()) && (!SPrev || !SPrev->isReleased()));
168    }
169
170    PathDiagnosticPiece *VisitNode(const ExplodedNode *N,
171                                   const ExplodedNode *PrevN,
172                                   BugReporterContext &BRC,
173                                   BugReport &BR);
174  };
175};
176} // end anonymous namespace
177
178typedef llvm::ImmutableMap<SymbolRef, RefState> RegionStateTy;
179
180namespace clang {
181namespace ento {
182  template <>
183  struct ProgramStateTrait<RegionState>
184    : public ProgramStatePartialTrait<RegionStateTy> {
185    static void *GDMIndex() { static int x; return &x; }
186  };
187}
188}
189
190void MallocChecker::initIdentifierInfo(CheckerContext &C) const {
191  ASTContext &Ctx = C.getASTContext();
192  if (!II_malloc)
193    II_malloc = &Ctx.Idents.get("malloc");
194  if (!II_free)
195    II_free = &Ctx.Idents.get("free");
196  if (!II_realloc)
197    II_realloc = &Ctx.Idents.get("realloc");
198  if (!II_calloc)
199    II_calloc = &Ctx.Idents.get("calloc");
200}
201
202void MallocChecker::checkPostStmt(const CallExpr *CE, CheckerContext &C) const {
203  const FunctionDecl *FD = C.getCalleeDecl(CE);
204  if (!FD)
205    return;
206  initIdentifierInfo(C);
207
208  if (FD->getIdentifier() == II_malloc) {
209    MallocMem(C, CE);
210    return;
211  }
212  if (FD->getIdentifier() == II_realloc) {
213    ReallocMem(C, CE);
214    return;
215  }
216
217  if (FD->getIdentifier() == II_calloc) {
218    CallocMem(C, CE);
219    return;
220  }
221
222  if (FD->getIdentifier() == II_free) {
223    FreeMem(C, CE);
224    return;
225  }
226
227  if (Filter.CMallocOptimistic)
228  // Check all the attributes, if there are any.
229  // There can be multiple of these attributes.
230  if (FD->hasAttrs()) {
231    for (specific_attr_iterator<OwnershipAttr>
232                  i = FD->specific_attr_begin<OwnershipAttr>(),
233                  e = FD->specific_attr_end<OwnershipAttr>();
234         i != e; ++i) {
235      switch ((*i)->getOwnKind()) {
236      case OwnershipAttr::Returns: {
237        MallocMemReturnsAttr(C, CE, *i);
238        break;
239      }
240      case OwnershipAttr::Takes:
241      case OwnershipAttr::Holds: {
242        FreeMemAttr(C, CE, *i);
243        break;
244      }
245      }
246    }
247  }
248
249  if (Filter.CMallocPessimistic) {
250    ProgramStateRef State = C.getState();
251    // The pointer might escape through a function call.
252    for (CallExpr::const_arg_iterator I = CE->arg_begin(),
253                                      E = CE->arg_end(); I != E; ++I) {
254      const Expr *A = *I;
255      if (A->getType().getTypePtr()->isAnyPointerType()) {
256        SymbolRef Sym = State->getSVal(A, C.getLocationContext()).getAsSymbol();
257        if (!Sym)
258          return;
259        checkEscape(Sym, A, C);
260        checkUseAfterFree(Sym, C, A);
261      }
262    }
263  }
264}
265
266void MallocChecker::MallocMem(CheckerContext &C, const CallExpr *CE) {
267  ProgramStateRef state = MallocMemAux(C, CE, CE->getArg(0), UndefinedVal(),
268                                      C.getState());
269  C.addTransition(state);
270}
271
272void MallocChecker::MallocMemReturnsAttr(CheckerContext &C, const CallExpr *CE,
273                                         const OwnershipAttr* Att) {
274  if (Att->getModule() != "malloc")
275    return;
276
277  OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
278  if (I != E) {
279    ProgramStateRef state =
280        MallocMemAux(C, CE, CE->getArg(*I), UndefinedVal(), C.getState());
281    C.addTransition(state);
282    return;
283  }
284  ProgramStateRef state = MallocMemAux(C, CE, UnknownVal(), UndefinedVal(),
285                                        C.getState());
286  C.addTransition(state);
287}
288
289ProgramStateRef MallocChecker::MallocMemAux(CheckerContext &C,
290                                           const CallExpr *CE,
291                                           SVal Size, SVal Init,
292                                           ProgramStateRef state) {
293  SValBuilder &svalBuilder = C.getSValBuilder();
294
295  // Get the return value.
296  SVal retVal = state->getSVal(CE, C.getLocationContext());
297
298  // Fill the region with the initialization value.
299  state = state->bindDefault(retVal, Init);
300
301  // Set the region's extent equal to the Size parameter.
302  const SymbolicRegion *R = cast<SymbolicRegion>(retVal.getAsRegion());
303  DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder);
304  DefinedOrUnknownSVal DefinedSize = cast<DefinedOrUnknownSVal>(Size);
305  DefinedOrUnknownSVal extentMatchesSize =
306    svalBuilder.evalEQ(state, Extent, DefinedSize);
307
308  state = state->assume(extentMatchesSize, true);
309  assert(state);
310
311  SymbolRef Sym = retVal.getAsLocSymbol();
312  assert(Sym);
313
314  // Set the symbol's state to Allocated.
315  return state->set<RegionState>(Sym, RefState::getAllocateUnchecked(CE));
316}
317
318void MallocChecker::FreeMem(CheckerContext &C, const CallExpr *CE) const {
319  ProgramStateRef state = FreeMemAux(C, CE, C.getState(), 0, false);
320
321  if (state)
322    C.addTransition(state);
323}
324
325void MallocChecker::FreeMemAttr(CheckerContext &C, const CallExpr *CE,
326                                const OwnershipAttr* Att) const {
327  if (Att->getModule() != "malloc")
328    return;
329
330  for (OwnershipAttr::args_iterator I = Att->args_begin(), E = Att->args_end();
331       I != E; ++I) {
332    ProgramStateRef state =
333      FreeMemAux(C, CE, C.getState(), *I,
334                 Att->getOwnKind() == OwnershipAttr::Holds);
335    if (state)
336      C.addTransition(state);
337  }
338}
339
340ProgramStateRef MallocChecker::FreeMemAux(CheckerContext &C,
341                                              const CallExpr *CE,
342                                              ProgramStateRef state,
343                                              unsigned Num,
344                                              bool Hold) const {
345  const Expr *ArgExpr = CE->getArg(Num);
346  SVal ArgVal = state->getSVal(ArgExpr, C.getLocationContext());
347
348  DefinedOrUnknownSVal location = cast<DefinedOrUnknownSVal>(ArgVal);
349
350  // Check for null dereferences.
351  if (!isa<Loc>(location))
352    return 0;
353
354  // FIXME: Technically using 'Assume' here can result in a path
355  //  bifurcation.  In such cases we need to return two states, not just one.
356  ProgramStateRef notNullState, nullState;
357  llvm::tie(notNullState, nullState) = state->assume(location);
358
359  // The explicit NULL case, no operation is performed.
360  if (nullState && !notNullState)
361    return 0;
362
363  assert(notNullState);
364
365  // Unknown values could easily be okay
366  // Undefined values are handled elsewhere
367  if (ArgVal.isUnknownOrUndef())
368    return 0;
369
370  const MemRegion *R = ArgVal.getAsRegion();
371
372  // Nonlocs can't be freed, of course.
373  // Non-region locations (labels and fixed addresses) also shouldn't be freed.
374  if (!R) {
375    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
376    return 0;
377  }
378
379  R = R->StripCasts();
380
381  // Blocks might show up as heap data, but should not be free()d
382  if (isa<BlockDataRegion>(R)) {
383    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
384    return 0;
385  }
386
387  const MemSpaceRegion *MS = R->getMemorySpace();
388
389  // Parameters, locals, statics, and globals shouldn't be freed.
390  if (!(isa<UnknownSpaceRegion>(MS) || isa<HeapSpaceRegion>(MS))) {
391    // FIXME: at the time this code was written, malloc() regions were
392    // represented by conjured symbols, which are all in UnknownSpaceRegion.
393    // This means that there isn't actually anything from HeapSpaceRegion
394    // that should be freed, even though we allow it here.
395    // Of course, free() can work on memory allocated outside the current
396    // function, so UnknownSpaceRegion is always a possibility.
397    // False negatives are better than false positives.
398
399    ReportBadFree(C, ArgVal, ArgExpr->getSourceRange());
400    return 0;
401  }
402
403  const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R);
404  // Various cases could lead to non-symbol values here.
405  // For now, ignore them.
406  if (!SR)
407    return 0;
408
409  SymbolRef Sym = SR->getSymbol();
410  const RefState *RS = state->get<RegionState>(Sym);
411
412  // If the symbol has not been tracked, return. This is possible when free() is
413  // called on a pointer that does not get its pointee directly from malloc().
414  // Full support of this requires inter-procedural analysis.
415  if (!RS)
416    return 0;
417
418  // Check double free.
419  if (RS->isReleased()) {
420    if (ExplodedNode *N = C.generateSink()) {
421      if (!BT_DoubleFree)
422        BT_DoubleFree.reset(
423          new BuiltinBug("Double free",
424                         "Try to free a memory block that has been released"));
425      BugReport *R = new BugReport(*BT_DoubleFree,
426                                   BT_DoubleFree->getDescription(), N);
427      R->addVisitor(new MallocBugVisitor(Sym));
428      C.EmitReport(R);
429    }
430    return 0;
431  }
432
433  // Normal free.
434  if (Hold)
435    return notNullState->set<RegionState>(Sym, RefState::getRelinquished(CE));
436  return notNullState->set<RegionState>(Sym, RefState::getReleased(CE));
437}
438
439bool MallocChecker::SummarizeValue(raw_ostream &os, SVal V) {
440  if (nonloc::ConcreteInt *IntVal = dyn_cast<nonloc::ConcreteInt>(&V))
441    os << "an integer (" << IntVal->getValue() << ")";
442  else if (loc::ConcreteInt *ConstAddr = dyn_cast<loc::ConcreteInt>(&V))
443    os << "a constant address (" << ConstAddr->getValue() << ")";
444  else if (loc::GotoLabel *Label = dyn_cast<loc::GotoLabel>(&V))
445    os << "the address of the label '" << Label->getLabel()->getName() << "'";
446  else
447    return false;
448
449  return true;
450}
451
452bool MallocChecker::SummarizeRegion(raw_ostream &os,
453                                    const MemRegion *MR) {
454  switch (MR->getKind()) {
455  case MemRegion::FunctionTextRegionKind: {
456    const FunctionDecl *FD = cast<FunctionTextRegion>(MR)->getDecl();
457    if (FD)
458      os << "the address of the function '" << *FD << '\'';
459    else
460      os << "the address of a function";
461    return true;
462  }
463  case MemRegion::BlockTextRegionKind:
464    os << "block text";
465    return true;
466  case MemRegion::BlockDataRegionKind:
467    // FIXME: where the block came from?
468    os << "a block";
469    return true;
470  default: {
471    const MemSpaceRegion *MS = MR->getMemorySpace();
472
473    if (isa<StackLocalsSpaceRegion>(MS)) {
474      const VarRegion *VR = dyn_cast<VarRegion>(MR);
475      const VarDecl *VD;
476      if (VR)
477        VD = VR->getDecl();
478      else
479        VD = NULL;
480
481      if (VD)
482        os << "the address of the local variable '" << VD->getName() << "'";
483      else
484        os << "the address of a local stack variable";
485      return true;
486    }
487
488    if (isa<StackArgumentsSpaceRegion>(MS)) {
489      const VarRegion *VR = dyn_cast<VarRegion>(MR);
490      const VarDecl *VD;
491      if (VR)
492        VD = VR->getDecl();
493      else
494        VD = NULL;
495
496      if (VD)
497        os << "the address of the parameter '" << VD->getName() << "'";
498      else
499        os << "the address of a parameter";
500      return true;
501    }
502
503    if (isa<GlobalsSpaceRegion>(MS)) {
504      const VarRegion *VR = dyn_cast<VarRegion>(MR);
505      const VarDecl *VD;
506      if (VR)
507        VD = VR->getDecl();
508      else
509        VD = NULL;
510
511      if (VD) {
512        if (VD->isStaticLocal())
513          os << "the address of the static variable '" << VD->getName() << "'";
514        else
515          os << "the address of the global variable '" << VD->getName() << "'";
516      } else
517        os << "the address of a global variable";
518      return true;
519    }
520
521    return false;
522  }
523  }
524}
525
526void MallocChecker::ReportBadFree(CheckerContext &C, SVal ArgVal,
527                                  SourceRange range) const {
528  if (ExplodedNode *N = C.generateSink()) {
529    if (!BT_BadFree)
530      BT_BadFree.reset(new BuiltinBug("Bad free"));
531
532    SmallString<100> buf;
533    llvm::raw_svector_ostream os(buf);
534
535    const MemRegion *MR = ArgVal.getAsRegion();
536    if (MR) {
537      while (const ElementRegion *ER = dyn_cast<ElementRegion>(MR))
538        MR = ER->getSuperRegion();
539
540      // Special case for alloca()
541      if (isa<AllocaRegion>(MR))
542        os << "Argument to free() was allocated by alloca(), not malloc()";
543      else {
544        os << "Argument to free() is ";
545        if (SummarizeRegion(os, MR))
546          os << ", which is not memory allocated by malloc()";
547        else
548          os << "not memory allocated by malloc()";
549      }
550    } else {
551      os << "Argument to free() is ";
552      if (SummarizeValue(os, ArgVal))
553        os << ", which is not memory allocated by malloc()";
554      else
555        os << "not memory allocated by malloc()";
556    }
557
558    BugReport *R = new BugReport(*BT_BadFree, os.str(), N);
559    R->addRange(range);
560    C.EmitReport(R);
561  }
562}
563
564void MallocChecker::ReallocMem(CheckerContext &C, const CallExpr *CE) const {
565  ProgramStateRef state = C.getState();
566  const Expr *arg0Expr = CE->getArg(0);
567  const LocationContext *LCtx = C.getLocationContext();
568  DefinedOrUnknownSVal arg0Val
569    = cast<DefinedOrUnknownSVal>(state->getSVal(arg0Expr, LCtx));
570
571  SValBuilder &svalBuilder = C.getSValBuilder();
572
573  DefinedOrUnknownSVal PtrEQ =
574    svalBuilder.evalEQ(state, arg0Val, svalBuilder.makeNull());
575
576  // Get the size argument. If there is no size arg then give up.
577  const Expr *Arg1 = CE->getArg(1);
578  if (!Arg1)
579    return;
580
581  // Get the value of the size argument.
582  DefinedOrUnknownSVal Arg1Val =
583    cast<DefinedOrUnknownSVal>(state->getSVal(Arg1, LCtx));
584
585  // Compare the size argument to 0.
586  DefinedOrUnknownSVal SizeZero =
587    svalBuilder.evalEQ(state, Arg1Val,
588                       svalBuilder.makeIntValWithPtrWidth(0, false));
589
590  // If the ptr is NULL and the size is not 0, the call is equivalent to
591  // malloc(size).
592  ProgramStateRef stateEqual = state->assume(PtrEQ, true);
593  if (stateEqual && state->assume(SizeZero, false)) {
594    // Hack: set the NULL symbolic region to released to suppress false warning.
595    // In the future we should add more states for allocated regions, e.g.,
596    // CheckedNull, CheckedNonNull.
597
598    SymbolRef Sym = arg0Val.getAsLocSymbol();
599    if (Sym)
600      stateEqual = stateEqual->set<RegionState>(Sym, RefState::getReleased(CE));
601
602    ProgramStateRef stateMalloc = MallocMemAux(C, CE, CE->getArg(1),
603                                              UndefinedVal(), stateEqual);
604    C.addTransition(stateMalloc);
605  }
606
607  if (ProgramStateRef stateNotEqual = state->assume(PtrEQ, false)) {
608    // If the size is 0, free the memory.
609    if (ProgramStateRef stateSizeZero =
610          stateNotEqual->assume(SizeZero, true))
611      if (ProgramStateRef stateFree =
612          FreeMemAux(C, CE, stateSizeZero, 0, false)) {
613
614        // Bind the return value to NULL because it is now free.
615        C.addTransition(stateFree->BindExpr(CE, LCtx,
616                                            svalBuilder.makeNull(), true));
617      }
618    if (ProgramStateRef stateSizeNotZero =
619          stateNotEqual->assume(SizeZero,false))
620      if (ProgramStateRef stateFree = FreeMemAux(C, CE, stateSizeNotZero,
621                                                0, false)) {
622        // FIXME: We should copy the content of the original buffer.
623        ProgramStateRef stateRealloc = MallocMemAux(C, CE, CE->getArg(1),
624                                                   UnknownVal(), stateFree);
625        C.addTransition(stateRealloc);
626      }
627  }
628}
629
630void MallocChecker::CallocMem(CheckerContext &C, const CallExpr *CE) {
631  ProgramStateRef state = C.getState();
632  SValBuilder &svalBuilder = C.getSValBuilder();
633  const LocationContext *LCtx = C.getLocationContext();
634  SVal count = state->getSVal(CE->getArg(0), LCtx);
635  SVal elementSize = state->getSVal(CE->getArg(1), LCtx);
636  SVal TotalSize = svalBuilder.evalBinOp(state, BO_Mul, count, elementSize,
637                                        svalBuilder.getContext().getSizeType());
638  SVal zeroVal = svalBuilder.makeZeroVal(svalBuilder.getContext().CharTy);
639
640  C.addTransition(MallocMemAux(C, CE, TotalSize, zeroVal, state));
641}
642
643void MallocChecker::checkDeadSymbols(SymbolReaper &SymReaper,
644                                     CheckerContext &C) const
645{
646  if (!SymReaper.hasDeadSymbols())
647    return;
648
649  ProgramStateRef state = C.getState();
650  RegionStateTy RS = state->get<RegionState>();
651  RegionStateTy::Factory &F = state->get_context<RegionState>();
652
653  bool generateReport = false;
654  llvm::SmallVector<SymbolRef, 2> Errors;
655  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
656    if (SymReaper.isDead(I->first)) {
657      if (I->second.isAllocated()) {
658        generateReport = true;
659        Errors.push_back(I->first);
660      }
661      // Remove the dead symbol from the map.
662      RS = F.remove(RS, I->first);
663
664    }
665  }
666
667  ExplodedNode *N = C.addTransition(state->set<RegionState>(RS));
668
669  if (N && generateReport) {
670    if (!BT_Leak)
671      BT_Leak.reset(new BuiltinBug("Memory leak",
672          "Allocated memory never released. Potential memory leak."));
673    for (llvm::SmallVector<SymbolRef, 2>::iterator
674          I = Errors.begin(), E = Errors.end(); I != E; ++I) {
675      BugReport *R = new BugReport(*BT_Leak, BT_Leak->getDescription(), N);
676      R->addVisitor(new MallocBugVisitor(*I));
677      C.EmitReport(R);
678    }
679  }
680}
681
682void MallocChecker::checkEndPath(CheckerContext &Ctx) const {
683  ProgramStateRef state = Ctx.getState();
684  RegionStateTy M = state->get<RegionState>();
685
686  for (RegionStateTy::iterator I = M.begin(), E = M.end(); I != E; ++I) {
687    RefState RS = I->second;
688    if (RS.isAllocated()) {
689      ExplodedNode *N = Ctx.addTransition(state);
690      if (N) {
691        if (!BT_Leak)
692          BT_Leak.reset(new BuiltinBug("Memory leak",
693                    "Allocated memory never released. Potential memory leak."));
694        BugReport *R = new BugReport(*BT_Leak, BT_Leak->getDescription(), N);
695        R->addVisitor(new MallocBugVisitor(I->first));
696        Ctx.EmitReport(R);
697      }
698    }
699  }
700}
701
702bool MallocChecker::checkEscape(SymbolRef Sym, const Stmt *S,
703                                CheckerContext &C) const {
704  ProgramStateRef state = C.getState();
705  const RefState *RS = state->get<RegionState>(Sym);
706  if (!RS)
707    return false;
708
709  if (RS->isAllocated()) {
710    state = state->set<RegionState>(Sym, RefState::getEscaped(S));
711    C.addTransition(state);
712    return true;
713  }
714  return false;
715}
716
717void MallocChecker::checkPreStmt(const ReturnStmt *S, CheckerContext &C) const {
718  const Expr *E = S->getRetValue();
719  if (!E)
720    return;
721  SymbolRef Sym = C.getState()->getSVal(E, C.getLocationContext()).getAsSymbol();
722  if (!Sym)
723    return;
724
725  checkEscape(Sym, S, C);
726}
727
728ProgramStateRef MallocChecker::evalAssume(ProgramStateRef state,
729                                              SVal Cond,
730                                              bool Assumption) const {
731  // If a symbolic region is assumed to NULL, set its state to AllocateFailed.
732  // FIXME: should also check symbols assumed to non-null.
733
734  RegionStateTy RS = state->get<RegionState>();
735
736  for (RegionStateTy::iterator I = RS.begin(), E = RS.end(); I != E; ++I) {
737    // If the symbol is assumed to NULL, this will return an APSInt*.
738    if (state->getSymVal(I.getKey()))
739      state = state->set<RegionState>(I.getKey(),RefState::getAllocateFailed());
740  }
741
742  return state;
743}
744
745bool MallocChecker::checkUseAfterFree(SymbolRef Sym, CheckerContext &C,
746                                      const Stmt *S) const {
747  assert(Sym);
748  const RefState *RS = C.getState()->get<RegionState>(Sym);
749  if (RS && RS->isReleased()) {
750    if (ExplodedNode *N = C.addTransition()) {
751      if (!BT_UseFree)
752        BT_UseFree.reset(new BuiltinBug("Use dynamically allocated memory "
753            "after it is freed."));
754
755      BugReport *R = new BugReport(*BT_UseFree, BT_UseFree->getDescription(),N);
756      if (S)
757        R->addRange(S->getSourceRange());
758      R->addVisitor(new MallocBugVisitor(Sym));
759      C.EmitReport(R);
760      return true;
761    }
762  }
763  return false;
764}
765
766// Check if the location is a freed symbolic region.
767void MallocChecker::checkLocation(SVal l, bool isLoad, const Stmt *S,
768                                  CheckerContext &C) const {
769  SymbolRef Sym = l.getLocSymbolInBase();
770  if (Sym)
771    checkUseAfterFree(Sym, C);
772}
773
774void MallocChecker::checkBind(SVal location, SVal val,
775                              const Stmt *BindS, CheckerContext &C) const {
776  // The PreVisitBind implements the same algorithm as already used by the
777  // Objective C ownership checker: if the pointer escaped from this scope by
778  // assignment, let it go.  However, assigning to fields of a stack-storage
779  // structure does not transfer ownership.
780
781  ProgramStateRef state = C.getState();
782  DefinedOrUnknownSVal l = cast<DefinedOrUnknownSVal>(location);
783
784  // Check for null dereferences.
785  if (!isa<Loc>(l))
786    return;
787
788  // Before checking if the state is null, check if 'val' has a RefState.
789  // Only then should we check for null and bifurcate the state.
790  SymbolRef Sym = val.getLocSymbolInBase();
791  if (Sym) {
792    if (const RefState *RS = state->get<RegionState>(Sym)) {
793      // If ptr is NULL, no operation is performed.
794      ProgramStateRef notNullState, nullState;
795      llvm::tie(notNullState, nullState) = state->assume(l);
796
797      // Generate a transition for 'nullState' to record the assumption
798      // that the state was null.
799      if (nullState)
800        C.addTransition(nullState);
801
802      if (!notNullState)
803        return;
804
805      if (RS->isAllocated()) {
806        // Something we presently own is being assigned somewhere.
807        const MemRegion *AR = location.getAsRegion();
808        if (!AR)
809          return;
810        AR = AR->StripCasts()->getBaseRegion();
811        do {
812          // If it is on the stack, we still own it.
813          if (AR->hasStackNonParametersStorage())
814            break;
815
816          // If the state can't represent this binding, we still own it.
817          if (notNullState == (notNullState->bindLoc(cast<Loc>(location),
818                                                     UnknownVal())))
819            break;
820
821          // We no longer own this pointer.
822          notNullState =
823            notNullState->set<RegionState>(Sym,
824                                        RefState::getRelinquished(BindS));
825        }
826        while (false);
827      }
828      C.addTransition(notNullState);
829    }
830  }
831}
832
833PathDiagnosticPiece *
834MallocChecker::MallocBugVisitor::VisitNode(const ExplodedNode *N,
835                                           const ExplodedNode *PrevN,
836                                           BugReporterContext &BRC,
837                                           BugReport &BR) {
838  const RefState *RS = N->getState()->get<RegionState>(Sym);
839  const RefState *RSPrev = PrevN->getState()->get<RegionState>(Sym);
840  if (!RS && !RSPrev)
841    return 0;
842
843  // We expect the interesting locations be StmtPoints corresponding to call
844  // expressions. We do not support indirect function calls as of now.
845  const CallExpr *CE = 0;
846  if (isa<StmtPoint>(N->getLocation()))
847    CE = dyn_cast<CallExpr>(cast<StmtPoint>(N->getLocation()).getStmt());
848  if (!CE)
849    return 0;
850  const FunctionDecl *funDecl = CE->getDirectCallee();
851  if (!funDecl)
852    return 0;
853
854  // Find out if this is an interesting point and what is the kind.
855  const char *Msg = 0;
856  if (isAllocated(RS, RSPrev))
857    Msg = "Memory is allocated here";
858  else if (isReleased(RS, RSPrev))
859    Msg = "Memory is released here";
860  if (!Msg)
861    return 0;
862
863  // Generate the extra diagnostic.
864  PathDiagnosticLocation Pos(CE, BRC.getSourceManager(),
865                             N->getLocationContext());
866  return new PathDiagnosticEventPiece(Pos, Msg);
867}
868
869
870#define REGISTER_CHECKER(name) \
871void ento::register##name(CheckerManager &mgr) {\
872  mgr.registerChecker<MallocChecker>()->Filter.C##name = true;\
873}
874
875REGISTER_CHECKER(MallocPessimistic)
876REGISTER_CHECKER(MallocOptimistic)
877