CFRefCount.cpp

public:
  
  static RefBindings GetRefBindings(ValueState& StImpl) {
    return RefBindings((RefBindings::TreeTy*) StImpl.CheckerState);
  }

private:
  
  static void SetRefBindings(ValueState& StImpl, RefBindings B) {
    StImpl.CheckerState = B.getRoot();
  }

  RefBindings Remove(RefBindings B, SymbolID sym) {
    return RefBFactory.Remove(B, sym);
  }
  
  RefBindings Update(RefBindings B, SymbolID sym, RefVal V, ArgEffect E,
                     RefVal::Kind& hasErr);
  
  void ProcessNonLeakError(ExplodedNodeSet<ValueState>& Dst,
                           GRStmtNodeBuilder<ValueState>& Builder,
                           Expr* NodeExpr, Expr* ErrorExpr,                        
                           ExplodedNode<ValueState>* Pred,
                           ValueState* St,
                           RefVal::Kind hasErr, SymbolID Sym);
  
  ValueState* HandleSymbolDeath(ValueStateManager& VMgr, ValueState* St,
                                SymbolID sid, RefVal V, bool& hasLeak);
  
  ValueState* NukeBinding(ValueStateManager& VMgr, ValueState* St,
                          SymbolID sid);
  
public:
  
  CFRefCount(ASTContext& Ctx, bool gcenabled, bool StandardWarnings,
             const LangOptions& lopts)
    : Summaries(Ctx, gcenabled),
      EmitStandardWarnings(StandardWarnings),
      LOpts(lopts),
      RetainSelector(GetNullarySelector("retain", Ctx)),
      ReleaseSelector(GetNullarySelector("release", Ctx)),
      AutoreleaseSelector(GetNullarySelector("autorelease", Ctx)) {}
  
  virtual ~CFRefCount() {
    for (LeaksTy::iterator I = Leaks.begin(), E = Leaks.end(); I!=E; ++I)
      delete I->second;
  }
  
  virtual void RegisterChecks(GRExprEngine& Eng);
 
  virtual ValueState::CheckerStatePrinter* getCheckerStatePrinter() {
    return &Printer;
  }
  
  bool isGCEnabled() const { return Summaries.isGCEnabled(); }
  const LangOptions& getLangOptions() const { return LOpts; }
  
  // Calls.

  void EvalSummary(ExplodedNodeSet<ValueState>& Dst,
                   GRExprEngine& Eng,
                   GRStmtNodeBuilder<ValueState>& Builder,
                   Expr* Ex,
                   Expr* Receiver,
                   RetainSummary* Summ,
                   ExprIterator arg_beg, ExprIterator arg_end,                             
                   ExplodedNode<ValueState>* Pred);
    
  virtual void EvalCall(ExplodedNodeSet<ValueState>& Dst,
                        GRExprEngine& Eng,
                        GRStmtNodeBuilder<ValueState>& Builder,
                        CallExpr* CE, RVal L,
                        ExplodedNode<ValueState>* Pred);  
  
  
  virtual void EvalObjCMessageExpr(ExplodedNodeSet<ValueState>& Dst,
                                   GRExprEngine& Engine,
                                   GRStmtNodeBuilder<ValueState>& Builder,
                                   ObjCMessageExpr* ME,
                                   ExplodedNode<ValueState>* Pred);
  
  bool EvalObjCMessageExprAux(ExplodedNodeSet<ValueState>& Dst,
                              GRExprEngine& Engine,
                              GRStmtNodeBuilder<ValueState>& Builder,
                              ObjCMessageExpr* ME,
                              ExplodedNode<ValueState>* Pred);

  // Stores.
  
  virtual void EvalStore(ExplodedNodeSet<ValueState>& Dst,
                         GRExprEngine& Engine,
                         GRStmtNodeBuilder<ValueState>& Builder,
                         Expr* E, ExplodedNode<ValueState>* Pred,
                         ValueState* St, RVal TargetLV, RVal Val);
  // End-of-path.
  
  virtual void EvalEndPath(GRExprEngine& Engine,
                           GREndPathNodeBuilder<ValueState>& Builder);
  
  virtual void EvalDeadSymbols(ExplodedNodeSet<ValueState>& Dst,
                               GRExprEngine& Engine,
                               GRStmtNodeBuilder<ValueState>& Builder,
                               ExplodedNode<ValueState>* Pred,
                               Stmt* S,
                               ValueState* St,
                               const ValueStateManager::DeadSymbolsTy& Dead);
  // Return statements.
  
  virtual void EvalReturn(ExplodedNodeSet<ValueState>& Dst,
                          GRExprEngine& Engine,
                          GRStmtNodeBuilder<ValueState>& Builder,
                          ReturnStmt* S,
                          ExplodedNode<ValueState>* Pred);

  // Assumptions.

  virtual ValueState* EvalAssume(GRExprEngine& Engine, ValueState* St,
                                 RVal Cond, bool Assumption, bool& isFeasible);

  // Error iterators.

  typedef UseAfterReleasesTy::iterator use_after_iterator;  
  typedef ReleasesNotOwnedTy::iterator bad_release_iterator;
  typedef LeaksTy::iterator            leaks_iterator;
  
  use_after_iterator use_after_begin() { return UseAfterReleases.begin(); }
  use_after_iterator use_after_end() { return UseAfterReleases.end(); }
  
  bad_release_iterator bad_release_begin() { return ReleasesNotOwned.begin(); }
  bad_release_iterator bad_release_end() { return ReleasesNotOwned.end(); }
  
  leaks_iterator leaks_begin() { return Leaks.begin(); }
  leaks_iterator leaks_end() { return Leaks.end(); }
};

} // end anonymous namespace




void CFRefCount::BindingsPrinter::PrintCheckerState(std::ostream& Out,
                                                    void* State, const char* nl,
                                                    const char* sep) {
  RefBindings B((RefBindings::TreeTy*) State);
  
  if (State)
    Out << sep << nl;
  
  for (RefBindings::iterator I=B.begin(), E=B.end(); I!=E; ++I) {
    Out << (*I).first << " : ";
    (*I).second.print(Out);
    Out << nl;
  }
}

static inline ArgEffect GetArgE(RetainSummary* Summ, unsigned idx) {
  return Summ ? Summ->getArg(idx) : MayEscape;
}

static inline RetEffect GetRetEffect(RetainSummary* Summ) {
  return Summ ? Summ->getRetEffect() : RetEffect::MakeNoRet();
}

static inline ArgEffect GetReceiverE(RetainSummary* Summ) {
  return Summ ? Summ->getReceiverEffect() : DoNothing;
}

void CFRefCount::ProcessNonLeakError(ExplodedNodeSet<ValueState>& Dst,
                                     GRStmtNodeBuilder<ValueState>& Builder,
                                     Expr* NodeExpr, Expr* ErrorExpr,                        
                                     ExplodedNode<ValueState>* Pred,
                                     ValueState* St,
                                     RefVal::Kind hasErr, SymbolID Sym) {
  Builder.BuildSinks = true;
  GRExprEngine::NodeTy* N  = Builder.MakeNode(Dst, NodeExpr, Pred, St);

  if (!N) return;
    
  switch (hasErr) {
    default: assert(false);
    case RefVal::ErrorUseAfterRelease:
      UseAfterReleases[N] = std::make_pair(ErrorExpr, Sym);
      break;
      
    case RefVal::ErrorReleaseNotOwned:
      ReleasesNotOwned[N] = std::make_pair(ErrorExpr, Sym);
      break;
  }
}

void CFRefCount::EvalSummary(ExplodedNodeSet<ValueState>& Dst,
                             GRExprEngine& Eng,
                             GRStmtNodeBuilder<ValueState>& Builder,
                             Expr* Ex,
                             Expr* Receiver,
                             RetainSummary* Summ,
                             ExprIterator arg_beg, ExprIterator arg_end,                             
                             ExplodedNode<ValueState>* Pred) {
  
  
  // Get the state.
  ValueStateManager& StateMgr = Eng.getStateManager();  
  ValueState* St = Builder.GetState(Pred);
  

  // Evaluate the effect of the arguments.
  
  ValueState StVals = *St;
  RefVal::Kind hasErr = (RefVal::Kind) 0;
  unsigned idx = 0;
  Expr* ErrorExpr = NULL;
  SymbolID ErrorSym = 0;                                        
  
  for (ExprIterator I = arg_beg; I != arg_end; ++I, ++idx) {
    
    RVal V = StateMgr.GetRVal(St, *I);
    
    if (isa<lval::SymbolVal>(V)) {
      SymbolID Sym = cast<lval::SymbolVal>(V).getSymbol();
      RefBindings B = GetRefBindings(StVals);      
      
      if (RefBindings::TreeTy* T = B.SlimFind(Sym)) {
        B = Update(B, Sym, T->getValue().second, GetArgE(Summ, idx), hasErr);
        SetRefBindings(StVals, B);
        
        if (hasErr) {
          ErrorExpr = *I;
          ErrorSym = T->getValue().first;
          break;
        }
      }
    }  
    else if (isa<LVal>(V)) {
      // Nuke all arguments passed by reference.
      StateMgr.Unbind(StVals, cast<LVal>(V));
    }
    else if (isa<nonlval::LValAsInteger>(V))
      StateMgr.Unbind(StVals, cast<nonlval::LValAsInteger>(V).getLVal());
  } 
  
  // Evaluate the effect on the message receiver.
  
  if (!ErrorExpr && Receiver) {
    RVal V = StateMgr.GetRVal(St, Receiver);

    if (isa<lval::SymbolVal>(V)) {
      SymbolID Sym = cast<lval::SymbolVal>(V).getSymbol();
      RefBindings B = GetRefBindings(StVals);      
      
      if (RefBindings::TreeTy* T = B.SlimFind(Sym)) {
        B = Update(B, Sym, T->getValue().second, GetReceiverE(Summ), hasErr);
        SetRefBindings(StVals, B);
        
        if (hasErr) {
          ErrorExpr = Receiver;
          ErrorSym = T->getValue().first;
        }
      }
    }
  }

  // Get the persistent state.
  
  St = StateMgr.getPersistentState(StVals);
  
  // Process any errors.
  
  if (hasErr) {
    ProcessNonLeakError(Dst, Builder, Ex, ErrorExpr, Pred, St,
                        hasErr, ErrorSym);
    return;
  }
  
  // Finally, consult the summary for the return value.
  
  RetEffect RE = GetRetEffect(Summ);
  
  switch (RE.getKind()) {
    default:
      assert (false && "Unhandled RetEffect."); break;
      
    case RetEffect::NoRet:
      
      // Make up a symbol for the return value (not reference counted).
      // FIXME: This is basically copy-and-paste from GRSimpleVals.  We 
      //  should compose behavior, not copy it.
      
      if (Ex->getType() != Eng.getContext().VoidTy) {    
        unsigned Count = Builder.getCurrentBlockCount();
        SymbolID Sym = Eng.getSymbolManager().getConjuredSymbol(Ex, Count);
        
        RVal X = LVal::IsLValType(Ex->getType())
               ? cast<RVal>(lval::SymbolVal(Sym)) 
               : cast<RVal>(nonlval::SymbolVal(Sym));
        
        St = StateMgr.SetRVal(St, Ex, X, Eng.getCFG().isBlkExpr(Ex), false);
      }      
      
      break;
      
    case RetEffect::Alias: {
      unsigned idx = RE.getValue();
      assert (arg_end >= arg_beg);
      assert (idx < (unsigned) (arg_end - arg_beg));
      RVal V = StateMgr.GetRVal(St, *(arg_beg+idx));
      St = StateMgr.SetRVal(St, Ex, V, Eng.getCFG().isBlkExpr(Ex), false);
      break;
    }
      
    case RetEffect::ReceiverAlias: {
      assert (Receiver);
      RVal V = StateMgr.GetRVal(St, Receiver);
      St = StateMgr.SetRVal(St, Ex, V, Eng.getCFG().isBlkExpr(Ex), false);
      break;
    }
      
    case RetEffect::OwnedAllocatedSymbol:
    case RetEffect::OwnedSymbol: {
      unsigned Count = Builder.getCurrentBlockCount();
      SymbolID Sym = Eng.getSymbolManager().getConjuredSymbol(Ex, Count);
      
      ValueState StImpl = *St;
      RefBindings B = GetRefBindings(StImpl);
      SetRefBindings(StImpl, RefBFactory.Add(B, Sym, RefVal::makeOwned()));
      
      St = StateMgr.SetRVal(StateMgr.getPersistentState(StImpl),
                            Ex, lval::SymbolVal(Sym),
                            Eng.getCFG().isBlkExpr(Ex), false);
      
      // FIXME: Add a flag to the checker where allocations are allowed to fail.      
      if (RE.getKind() == RetEffect::OwnedAllocatedSymbol)
        St = StateMgr.AddNE(St, Sym, Eng.getBasicVals().getZeroWithPtrWidth());
      
      break;
    }
      
    case RetEffect::NotOwnedSymbol: {
      unsigned Count = Builder.getCurrentBlockCount();
      SymbolID Sym = Eng.getSymbolManager().getConjuredSymbol(Ex, Count);
      
      ValueState StImpl = *St;
      RefBindings B = GetRefBindings(StImpl);
      SetRefBindings(StImpl, RefBFactory.Add(B, Sym, RefVal::makeNotOwned()));
      
      St = StateMgr.SetRVal(StateMgr.getPersistentState(StImpl),
                            Ex, lval::SymbolVal(Sym),
                            Eng.getCFG().isBlkExpr(Ex), false);
      
      break;
    }
  }
  
  Builder.MakeNode(Dst, Ex, Pred, St);
}


void CFRefCount::EvalCall(ExplodedNodeSet<ValueState>& Dst,
                          GRExprEngine& Eng,
                          GRStmtNodeBuilder<ValueState>& Builder,
                          CallExpr* CE, RVal L,
                          ExplodedNode<ValueState>* Pred) {
  
  
  RetainSummary* Summ = NULL;
  
  // Get the summary.

  if (isa<lval::FuncVal>(L)) {  
    lval::FuncVal FV = cast<lval::FuncVal>(L);
    FunctionDecl* FD = FV.getDecl();
    Summ = Summaries.getSummary(FD);
  }
  
  EvalSummary(Dst, Eng, Builder, CE, 0, Summ,
              CE->arg_begin(), CE->arg_end(), Pred);
}


void CFRefCount::EvalObjCMessageExpr(ExplodedNodeSet<ValueState>& Dst,
                                     GRExprEngine& Eng,
                                     GRStmtNodeBuilder<ValueState>& Builder,
                                     ObjCMessageExpr* ME,
                                     ExplodedNode<ValueState>* Pred) {
  
  RetainSummary* Summ;
  
  if (ME->getReceiver())
    Summ = Summaries.getMethodSummary(ME);
  else
    Summ = Summaries.getClassMethodSummary(ME->getClassName(),
                                           ME->getSelector());

  EvalSummary(Dst, Eng, Builder, ME, ME->getReceiver(), Summ,
              ME->arg_begin(), ME->arg_end(), Pred);
}
  
// Stores.

void CFRefCount::EvalStore(ExplodedNodeSet<ValueState>& Dst,
                           GRExprEngine& Eng,
                           GRStmtNodeBuilder<ValueState>& Builder,
                           Expr* E, ExplodedNode<ValueState>* Pred,
                           ValueState* St, RVal TargetLV, RVal Val) {
  
  // Check if we have a binding for "Val" and if we are storing it to something
  // we don't understand or otherwise the value "escapes" the function.
  
  if (!isa<lval::SymbolVal>(Val))
    return;
  
  // Are we storing to something that causes the value to "escape"?
  
  bool escapes = false;
  
  if (!isa<lval::DeclVal>(TargetLV))
    escapes = true;
  else
    escapes = cast<lval::DeclVal>(TargetLV).getDecl()->hasGlobalStorage();
  
  if (!escapes)
    return;
  
  SymbolID Sym = cast<lval::SymbolVal>(Val).getSymbol();
  RefBindings B = GetRefBindings(*St);
  RefBindings::TreeTy* T = B.SlimFind(Sym);
  
  if (!T)
    return;
  
  // Nuke the binding.  
  St = NukeBinding(Eng.getStateManager(), St, Sym);
  
  // Hand of the remaining logic to the parent implementation.
  GRSimpleVals::EvalStore(Dst, Eng, Builder, E, Pred, St, TargetLV, Val);
}


ValueState* CFRefCount::NukeBinding(ValueStateManager& VMgr, ValueState* St,
                                    SymbolID sid) {
  ValueState StImpl = *St;
  RefBindings B = GetRefBindings(StImpl);
  StImpl.CheckerState = RefBFactory.Remove(B, sid).getRoot();
  return VMgr.getPersistentState(StImpl);
}

// End-of-path.

ValueState* CFRefCount::HandleSymbolDeath(ValueStateManager& VMgr,
                                          ValueState* St, SymbolID sid,
                                          RefVal V, bool& hasLeak) {
    
  hasLeak = V.isOwned() || 
            ((V.isNotOwned() || V.isReturnedOwned()) && V.getCount() > 0);

  if (!hasLeak)
    return NukeBinding(VMgr, St, sid);
  
  RefBindings B = GetRefBindings(*St);
  ValueState StImpl = *St;  

  StImpl.CheckerState =
    RefBFactory.Add(B, sid, RefVal::makeLeak(V.getCount())).getRoot();
  
  return VMgr.getPersistentState(StImpl);
}

void CFRefCount::EvalEndPath(GRExprEngine& Eng,
                             GREndPathNodeBuilder<ValueState>& Builder) {
  
  ValueState* St = Builder.getState();
  RefBindings B = GetRefBindings(*St);
  
  llvm::SmallVector<SymbolID, 10> Leaked;
  
  for (RefBindings::iterator I = B.begin(), E = B.end(); I != E; ++I) {
    bool hasLeak = false;
    
    St = HandleSymbolDeath(Eng.getStateManager(), St,
                           (*I).first, (*I).second, hasLeak);
    
    if (hasLeak) Leaked.push_back((*I).first);
  }

  if (Leaked.empty())
    return;
  
  ExplodedNode<ValueState>* N = Builder.MakeNode(St);  
  
  if (!N)
    return;
    
  std::vector<SymbolID>*& LeaksAtNode = Leaks[N];
  assert (!LeaksAtNode);
  LeaksAtNode = new std::vector<SymbolID>();
  
  for (llvm::SmallVector<SymbolID, 10>::iterator I=Leaked.begin(),
       E = Leaked.end(); I != E; ++I)
    (*LeaksAtNode).push_back(*I);
}

// Dead symbols.

void CFRefCount::EvalDeadSymbols(ExplodedNodeSet<ValueState>& Dst,
                                 GRExprEngine& Eng,
                                 GRStmtNodeBuilder<ValueState>& Builder,
                                 ExplodedNode<ValueState>* Pred,
                                 Stmt* S,
                                 ValueState* St,
                                 const ValueStateManager::DeadSymbolsTy& Dead) {
    
  // FIXME: a lot of copy-and-paste from EvalEndPath.  Refactor.
  
  RefBindings B = GetRefBindings(*St);
  llvm::SmallVector<SymbolID, 10> Leaked;
  
  for (ValueStateManager::DeadSymbolsTy::const_iterator
       I=Dead.begin(), E=Dead.end(); I!=E; ++I) {
    
    RefBindings::TreeTy* T = B.SlimFind(*I);

    if (!T)
      continue;
    
    bool hasLeak = false;
    
    St = HandleSymbolDeath(Eng.getStateManager(), St,
                           *I, T->getValue().second, hasLeak);
    
    if (hasLeak) Leaked.push_back(*I);    
  }
  
  if (Leaked.empty())
    return;    
  
  ExplodedNode<ValueState>* N = Builder.MakeNode(Dst, S, Pred, St);  
  
  if (!N)
    return;
  
  std::vector<SymbolID>*& LeaksAtNode = Leaks[N];
  assert (!LeaksAtNode);
  LeaksAtNode = new std::vector<SymbolID>();
  
  for (llvm::SmallVector<SymbolID, 10>::iterator I=Leaked.begin(),
       E = Leaked.end(); I != E; ++I)
    (*LeaksAtNode).push_back(*I);    
}

 // Return statements.

void CFRefCount::EvalReturn(ExplodedNodeSet<ValueState>& Dst,
                            GRExprEngine& Eng,
                            GRStmtNodeBuilder<ValueState>& Builder,
                            ReturnStmt* S,
                            ExplodedNode<ValueState>* Pred) {
  
  Expr* RetE = S->getRetValue();
  if (!RetE) return;
  
  ValueStateManager& StateMgr = Eng.getStateManager();
  ValueState* St = Builder.GetState(Pred);
  RVal V = StateMgr.GetRVal(St, RetE);
  
  if (!isa<lval::SymbolVal>(V))
    return;
  
  // Get the reference count binding (if any).
  SymbolID Sym = cast<lval::SymbolVal>(V).getSymbol();
  RefBindings B = GetRefBindings(*St);
  RefBindings::TreeTy* T = B.SlimFind(Sym);
  
  if (!T)
    return;
  
  // Change the reference count.
  
  RefVal X = T->getValue().second;  
  
  switch (X.getKind()) {
      
    case RefVal::Owned: { 
      unsigned cnt = X.getCount();
      assert (cnt > 0);
      X = RefVal::makeReturnedOwned(cnt - 1);
      break;
    }
      
    case RefVal::NotOwned: {
      unsigned cnt = X.getCount();
      X = cnt ? RefVal::makeReturnedOwned(cnt - 1)
              : RefVal::makeReturnedNotOwned();
      break;
    }
      
    default: 
      return;
  }
  
  // Update the binding.

  ValueState StImpl = *St;
  StImpl.CheckerState = RefBFactory.Add(B, Sym, X).getRoot();        
  Builder.MakeNode(Dst, S, Pred, StateMgr.getPersistentState(StImpl));
}

// Assumptions.

ValueState* CFRefCount::EvalAssume(GRExprEngine& Eng, ValueState* St,
                                   RVal Cond, bool Assumption,
                                   bool& isFeasible) {

  // FIXME: We may add to the interface of EvalAssume the list of symbols
  //  whose assumptions have changed.  For now we just iterate through the
  //  bindings and check if any of the tracked symbols are NULL.  This isn't
  //  too bad since the number of symbols we will track in practice are 
  //  probably small and EvalAssume is only called at branches and a few
  //  other places.
    
  RefBindings B = GetRefBindings(*St);
  
  if (B.isEmpty())
    return St;
  
  bool changed = false;

  for (RefBindings::iterator I=B.begin(), E=B.end(); I!=E; ++I) {    

    // Check if the symbol is null (or equal to any constant).
    // If this is the case, stop tracking the symbol.
  
    if (St->getSymVal(I.getKey())) {
      changed = true;
      B = RefBFactory.Remove(B, I.getKey());
    }
  }
  
  if (!changed)
    return St;
  
  ValueState StImpl = *St;
  StImpl.CheckerState = B.getRoot();
  return Eng.getStateManager().getPersistentState(StImpl);
}

CFRefCount::RefBindings CFRefCount::Update(RefBindings B, SymbolID sym,
                                           RefVal V, ArgEffect E,
                                           RefVal::Kind& hasErr) {
  
  // FIXME: This dispatch can potentially be sped up by unifiying it into
  //  a single switch statement.  Opt for simplicity for now.
  
  switch (E) {
    default:
      assert (false && "Unhandled CFRef transition.");

    case MayEscape:
      if (V.getKind() == RefVal::Owned) {
        V = RefVal::makeNotOwned(V.getCount());
        break;
      }

      // Fall-through.
      
    case DoNothing:
      if (!isGCEnabled() && V.getKind() == RefVal::Released) {
        V = RefVal::makeUseAfterRelease();        
        hasErr = V.getKind();
        break;
      }
      
      return B;
      
    case StopTracking:
      return RefBFactory.Remove(B, sym);
      
    case IncRef:      
      switch (V.getKind()) {
        default:
          assert(false);

        case RefVal::Owned:
          V = RefVal::makeOwned(V.getCount()+1);
          break;
                    
        case RefVal::NotOwned:
          V = RefVal::makeNotOwned(V.getCount()+1);
          break;
          
        case RefVal::Released:
          if (isGCEnabled())
            V = RefVal::makeOwned();
          else {          
            V = RefVal::makeUseAfterRelease();
            hasErr = V.getKind();
          }
          
          break;
      }
      
      break;
      
    case DecRef:
      switch (V.getKind()) {
        default:
          assert (false);
          
        case RefVal::Owned: {
          unsigned Count = V.getCount();
          V = Count > 1 ? RefVal::makeOwned(Count - 1) : RefVal::makeReleased();
          break;
        }
          
        case RefVal::NotOwned: {
          unsigned Count = V.getCount();
          
          if (Count > 0)
            V = RefVal::makeNotOwned(Count - 1);
          else {
            V = RefVal::makeReleaseNotOwned();
            hasErr = V.getKind();
          }
          
          break;
        }

        case RefVal::Released:
          V = RefVal::makeUseAfterRelease();
          hasErr = V.getKind();
          break;          
      }
      
      break;
  }

  return RefBFactory.Add(B, sym, V);
}


//===----------------------------------------------------------------------===//
// Error reporting.
//===----------------------------------------------------------------------===//

namespace {
  
  //===-------------===//
  // Bug Descriptions. //
  //===-------------===//  
  
  class VISIBILITY_HIDDEN CFRefBug : public BugTypeCacheLocation {
  protected:
    CFRefCount& TF;
    
  public:
    CFRefBug(CFRefCount& tf) : TF(tf) {}
    
    CFRefCount& getTF() { return TF; }
    const CFRefCount& getTF() const { return TF; }

    virtual bool isLeak() const { return false; }
  };
  
  class VISIBILITY_HIDDEN UseAfterRelease : public CFRefBug {
  public:
    UseAfterRelease(CFRefCount& tf) : CFRefBug(tf) {}
    
    virtual const char* getName() const {
      return "Use-After-Release";
    }
    virtual const char* getDescription() const {
      return "Reference-counted object is used"
             " after it is released.";
    }
    
    virtual void EmitWarnings(BugReporter& BR);
  };
  
  class VISIBILITY_HIDDEN BadRelease : public CFRefBug {
  public:
    BadRelease(CFRefCount& tf) : CFRefBug(tf) {}
    
    virtual const char* getName() const {
      return "Bad Release";
    }
    virtual const char* getDescription() const {
      return "Incorrect decrement of the reference count of a "
      "CoreFoundation object: "
      "The object is not owned at this point by the caller.";
    }
    
    virtual void EmitWarnings(BugReporter& BR);
  };
  
  class VISIBILITY_HIDDEN Leak : public CFRefBug {
  public:
    Leak(CFRefCount& tf) : CFRefBug(tf) {}
    
    virtual const char* getName() const {
      
      if (getTF().isGCEnabled())
        return "Memory Leak (GC)";
      
      if (getTF().getLangOptions().getGCMode() == LangOptions::HybridGC)
        return "Memory Leak (Hybrid MM, non-GC)";
      
      assert (getTF().getLangOptions().getGCMode() == LangOptions::NonGC);
      return "Memory Leak";
    }
    
    virtual const char* getDescription() const {
      return "Object leaked.";
    }
    
    virtual void EmitWarnings(BugReporter& BR);
    virtual void GetErrorNodes(std::vector<ExplodedNode<ValueState>*>& Nodes);
    virtual bool isLeak() const { return true; }
    virtual bool isCached(BugReport& R);
  };
  
  //===---------===//
  // Bug Reports.  //
  //===---------===//
  
  class VISIBILITY_HIDDEN CFRefReport : public RangedBugReport {
    SymbolID Sym;
  public:
    CFRefReport(CFRefBug& D, ExplodedNode<ValueState> *n, SymbolID sym)
      : RangedBugReport(D, n), Sym(sym) {}
        
    virtual ~CFRefReport() {}
    
    CFRefBug& getBugType() {
      return (CFRefBug&) RangedBugReport::getBugType();
    }
    const CFRefBug& getBugType() const {
      return (const CFRefBug&) RangedBugReport::getBugType();
    }
    
    virtual void getRanges(BugReporter& BR, const SourceRange*& beg,           
                           const SourceRange*& end) {
      
      if (!getBugType().isLeak())
        RangedBugReport::getRanges(BR, beg, end);
      else {
        beg = 0;
        end = 0;
      }
    }
    
    SymbolID getSymbol() const { return Sym; }
    
    virtual PathDiagnosticPiece* getEndPath(BugReporter& BR,
                                            ExplodedNode<ValueState>* N);
    
    virtual std::pair<const char**,const char**> getExtraDescriptiveText();
    
    virtual PathDiagnosticPiece* VisitNode(ExplodedNode<ValueState>* N,
                                           ExplodedNode<ValueState>* PrevN,
                                           ExplodedGraph<ValueState>& G,
                                           BugReporter& BR);
  };
  
  
} // end anonymous namespace

void CFRefCount::RegisterChecks(GRExprEngine& Eng) {
  if (EmitStandardWarnings) GRSimpleVals::RegisterChecks(Eng);
  Eng.Register(new UseAfterRelease(*this));
  Eng.Register(new BadRelease(*this));
  Eng.Register(new Leak(*this));
}


static const char* Msgs[] = {
  "Code is compiled in garbage collection only mode"  // GC only
  "  (the bug occurs with garbage collection enabled).",
  
  "Code is compiled without garbage collection.", // No GC.
  
  "Code is compiled for use with and without garbage collection (GC)."
  "  The bug occurs with GC enabled.", // Hybrid, with GC.
  
  "Code is compiled for use with and without garbage collection (GC)."
  "  The bug occurs in non-GC mode."  // Hyrbird, without GC/
};

std::pair<const char**,const char**> CFRefReport::getExtraDescriptiveText() {
  CFRefCount& TF = static_cast<CFRefBug&>(getBugType()).getTF();

  switch (TF.getLangOptions().getGCMode()) {
    default:
      assert(false);
          
    case LangOptions::GCOnly:
      assert (TF.isGCEnabled());
      return std::make_pair(&Msgs[0], &Msgs[0]+1);
      
    case LangOptions::NonGC:
      assert (!TF.isGCEnabled());
      return std::make_pair(&Msgs[1], &Msgs[1]+1);
    
    case LangOptions::HybridGC:
      if (TF.isGCEnabled())
        return std::make_pair(&Msgs[2], &Msgs[2]+1);
      else
        return std::make_pair(&Msgs[3], &Msgs[3]+1);
  }
}

PathDiagnosticPiece* CFRefReport::VisitNode(ExplodedNode<ValueState>* N,
                                            ExplodedNode<ValueState>* PrevN,
                                            ExplodedGraph<ValueState>& G,
                                            BugReporter& BR) {

  // Check if the type state has changed.
  
  ValueState* PrevSt = PrevN->getState();
  ValueState* CurrSt = N->getState();
  
  CFRefCount::RefBindings PrevB = CFRefCount::GetRefBindings(*PrevSt);
  CFRefCount::RefBindings CurrB = CFRefCount::GetRefBindings(*CurrSt);
  
  CFRefCount::RefBindings::TreeTy* PrevT = PrevB.SlimFind(Sym);
  CFRefCount::RefBindings::TreeTy* CurrT = CurrB.SlimFind(Sym);
  
  if (!CurrT)
    return NULL;  
  
  const char* Msg = NULL;  
  RefVal CurrV = CurrB.SlimFind(Sym)->getValue().second;

  if (!PrevT) {
    
    Stmt* S = cast<PostStmt>(N->getLocation()).getStmt();

    if (CurrV.isOwned()) {

      if (isa<CallExpr>(S))
        Msg = "Function call returns an object with a +1 retain count"
              " (owning reference).";
      else {
        assert (isa<ObjCMessageExpr>(S));
        Msg = "Method returns an object with a +1 retain count"
              " (owning reference).";
      }
    }
    else {
      assert (CurrV.isNotOwned());
      
      if (isa<CallExpr>(S))
        Msg = "Function call returns an object with a +0 retain count"
              " (non-owning reference).";
      else {
        assert (isa<ObjCMessageExpr>(S));
        Msg = "Method returns an object with a +0 retain count"
              " (non-owning reference).";
      }      
    }
    
    FullSourceLoc Pos(S->getLocStart(), BR.getContext().getSourceManager());
    PathDiagnosticPiece* P = new PathDiagnosticPiece(Pos, Msg);
    
    if (Expr* Exp = dyn_cast<Expr>(S))
      P->addRange(Exp->getSourceRange());
    
    return P;    
  }
  
  // Determine if the typestate has changed.
  
  RefVal PrevV = PrevB.SlimFind(Sym)->getValue().second;
  
  if (PrevV == CurrV)
    return NULL;
  
  // The typestate has changed.
  
  std::ostringstream os;
  
  switch (CurrV.getKind()) {
    case RefVal::Owned:
    case RefVal::NotOwned:

      if (PrevV.getCount() == CurrV.getCount())
        return 0;
      
      if (PrevV.getCount() > CurrV.getCount())
        os << "Reference count decremented.";
      else
        os << "Reference count incremented.";
      
      if (unsigned Count = CurrV.getCount()) {

        os << " Object has +" << Count;
        
        if (Count > 1)
          os << " retain counts.";
        else
          os << " retain count.";
      }