CFRefCount.cpp

                           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()).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();
      X = RefVal::makeReturnedOwned(cnt);
      break;
    }
      
    case RefVal::NotOwned: {
      unsigned cnt = X.getCount();
      X = cnt ? RefVal::makeReturnedOwned(cnt - 1)
              : RefVal::makeReturnedNotOwned();
      break;
    }
      
    default: 
      // None of the error states should be possible at this point.
      // A symbol could not have been leaked (yet) if we are returning it
      // (and thus it is still live), and the other errors are hard errors.
      assert(false);
      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 DoNothing:
      if (V.getKind() == RefVal::Released) {
        V = RefVal::makeUseAfterRelease();        
        hasErr = V.getKind();
        break;
      }
      
      return B;
      
    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:
          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 > 0 ? 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) {}
  };
  
  class VISIBILITY_HIDDEN UseAfterRelease : public CFRefBug {
  public:
    UseAfterRelease(CFRefCount& tf) : CFRefBug(tf) {}
    
    virtual const char* getName() const {
      return "Core Foundation: 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 "Core Foundation: Release of non-owned object";
    }
    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 {
      return "Core Foundation: Memory Leak";
    }
    
    virtual const char* getDescription() const {
      return "Object leaked.";
    }
    
    virtual void EmitWarnings(BugReporter& BR);
    virtual void GetErrorNodes(std::vector<ExplodedNode<ValueState>*>& Nodes);    
  };
  
  //===---------===//
  // Bug Reports.  //
  //===---------===//
  
  class VISIBILITY_HIDDEN CFRefReport : public RangedBugReport {
    SymbolID Sym;
  public:
    CFRefReport(BugType& D, ExplodedNode<ValueState> *n, SymbolID sym)
      : RangedBugReport(D, n), Sym(sym) {}
        
    virtual ~CFRefReport() {}
    
    
    virtual PathDiagnosticPiece* VisitNode(ExplodedNode<ValueState>* N,
                                           ExplodedNode<ValueState>* PrevN,
                                           ExplodedGraph<ValueState>& G,
                                           BugReporter& BR);
  };
  
  
} // end anonymous namespace

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

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) {
    
    // Check for the point where we start tracking the value.
    
    if (CurrV.isOwned())
      Msg = "Function call returns 'Owned' Core Foundation object.";
    else {
      assert (CurrV.isNotOwned());
      Msg = "Function call returns 'Non-Owned' Core Foundation object.";
    }

    Stmt* S = cast<PostStmt>(N->getLocation()).getStmt();    
    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:
      assert (PrevV.getKind() == CurrV.getKind());
      
      if (PrevV.getCount() > CurrV.getCount())
        os << "Reference count decremented.";
      else
        os << "Reference count incremented.";
      
      if (CurrV.getCount()) {
        os << " Object has +" << CurrV.getCount();
        
        if (CurrV.getCount() > 1)
          os << " reference counts.";
        else
          os << " reference count.";
      }
      
      Msg = os.str().c_str();
      
      break;
      
    case RefVal::Released:
      Msg = "Object released.";
      break;
      
    case RefVal::ReturnedOwned:
      Msg = "Object returned to caller.  "
            "Caller gets ownership of object.";
      break;
      
    case RefVal::ReturnedNotOwned:
      Msg = "Object returned to caller.  "
            "Caller does not get ownership of object.";
      break;

    default:
      return NULL;
  }
  
  Stmt* S = cast<PostStmt>(N->getLocation()).getStmt();    
  FullSourceLoc Pos(S->getLocStart(), BR.getContext().getSourceManager());
  PathDiagnosticPiece* P = new PathDiagnosticPiece(Pos, Msg);
  
  // Add the range by scanning the children of the statement for any bindings
  // to Sym.
  
  ValueStateManager& VSM = BR.getEngine().getStateManager();
  
  for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I)
    if (Expr* Exp = dyn_cast_or_null<Expr>(*I)) {
      RVal X = VSM.GetRVal(CurrSt, Exp);
      
      if (lval::SymbolVal* SV = dyn_cast<lval::SymbolVal>(&X))
        if (SV->getSymbol() == Sym) {
          P->addRange(Exp->getSourceRange()); break;
        }
    }
  
  return P;
}

void UseAfterRelease::EmitWarnings(BugReporter& BR) {

  for (CFRefCount::use_after_iterator I = TF.use_after_begin(),
        E = TF.use_after_end(); I != E; ++I) {
    
    CFRefReport report(*this, I->first, I->second.second);
    report.addRange(I->second.first->getSourceRange());    
    BR.EmitWarning(report);    
  }
}

void BadRelease::EmitWarnings(BugReporter& BR) {
  
  for (CFRefCount::bad_release_iterator I = TF.bad_release_begin(),
       E = TF.bad_release_end(); I != E; ++I) {
    
    CFRefReport report(*this, I->first, I->second.second);
    report.addRange(I->second.first->getSourceRange());    
    BR.EmitWarning(report);    
  }  
}

void Leak::EmitWarnings(BugReporter& BR) {
  
  for (CFRefCount::leaks_iterator I = TF.leaks_begin(),
       E = TF.leaks_end(); I != E; ++I) {
    
    std::vector<SymbolID>& SymV = *(I->second);
    unsigned n = SymV.size();
    
    for (unsigned i = 0; i < n; ++i) {
      CFRefReport report(*this, I->first, SymV[i]);
      BR.EmitWarning(report);
    }
  }  
}

void Leak::GetErrorNodes(std::vector<ExplodedNode<ValueState>*>& Nodes) {
  for (CFRefCount::leaks_iterator I=TF.leaks_begin(), E=TF.leaks_end();
       I!=E; ++I)
    Nodes.push_back(I->first);
}

//===----------------------------------------------------------------------===//
// Transfer function creation for external clients.
//===----------------------------------------------------------------------===//

GRTransferFuncs* clang::MakeCFRefCountTF(ASTContext& Ctx, bool GCEnabled) {
  return new CFRefCount(Ctx, GCEnabled);
}