lib/Analysis/CFRefCount.cpp

// CFRefCount.cpp - Transfer functions for tracking simple values -*- C++ -*--//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//  This file defines the methods for CFRefCount, which implements
//  a reference count checker for Core Foundation (Mac OS X).
//
//===----------------------------------------------------------------------===//

#include "GRSimpleVals.h"
#include "clang/Basic/LangOptions.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Analysis/PathSensitive/GRExprEngineBuilders.h"
#include "clang/Analysis/PathSensitive/GRStateTrait.h"
#include "clang/Analysis/PathDiagnostic.h"
#include "clang/Analysis/LocalCheckers.h"
#include "clang/Analysis/PathDiagnostic.h"
#include "clang/Analysis/PathSensitive/BugReporter.h"
#include "clang/Analysis/PathSensitive/SymbolManager.h"
#include "clang/AST/DeclObjC.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/ImmutableMap.h"
#include "llvm/ADT/ImmutableList.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/Compiler.h"
#include "llvm/ADT/STLExtras.h"
#include <ostream>
#include <stdarg.h>

using namespace clang;

//===----------------------------------------------------------------------===//
// Utility functions.
//===----------------------------------------------------------------------===//

// The "fundamental rule" for naming conventions of methods:
//  (url broken into two lines)
//  http://developer.apple.com/documentation/Cocoa/Conceptual/
//     MemoryMgmt/Tasks/MemoryManagementRules.html
//
// "You take ownership of an object if you create it using a method whose name
//  begins with “alloc” or “new” or contains “copy” (for example, alloc, 
//  newObject, or mutableCopy), or if you send it a retain message. You are
//  responsible for relinquishing ownership of objects you own using release
//  or autorelease. Any other time you receive an object, you must
//  not release it."
//

using llvm::CStrInCStrNoCase;
using llvm::StringsEqualNoCase;

enum NamingConvention { NoConvention, CreateRule, InitRule };

static inline bool isWordEnd(char ch, char prev, char next) {
  return ch == '\0'
      || (islower(prev) && isupper(ch)) // xxxC
      || (isupper(prev) && isupper(ch) && islower(next)) // XXCreate
      || !isalpha(ch);
}
  
static inline const char* parseWord(const char* s) {  
  char ch = *s, prev = '\0';
  assert(ch != '\0');
  char next = *(s+1);
  while (!isWordEnd(ch, prev, next)) {
    prev = ch;
    ch = next;
    next = *((++s)+1);
  }
  return s;
}

static NamingConvention deriveNamingConvention(const char* s) {
  // A method/function name may contain a prefix.  We don't know it is there,
  // however, until we encounter the first '_'.
  bool InPossiblePrefix = true;
  bool AtBeginning = true;
  NamingConvention C = NoConvention;
  
  while (*s != '\0') {
    // Skip '_'.
    if (*s == '_') {
      if (InPossiblePrefix) {
        InPossiblePrefix = false;
        AtBeginning = true;
        // Discard whatever 'convention' we
        // had already derived since it occurs
        // in the prefix.
        C = NoConvention;
      }
      ++s;
      continue;
    }
    
    // Skip numbers, ':', etc.
    if (!isalpha(*s)) {
      ++s;
      continue;
    }
    
    const char *wordEnd = parseWord(s);
    assert(wordEnd > s);
    unsigned len = wordEnd - s;
    
    switch (len) {
    default:
      break;
    case 3:
      // Methods starting with 'new' follow the create rule.
      if (AtBeginning && StringsEqualNoCase("new", s, len))
        C = CreateRule;      
      break;
    case 4:
      // Methods starting with 'alloc' or contain 'copy' follow the
      // create rule
      if (C == NoConvention && StringsEqualNoCase("copy", s, len))
        C = CreateRule;
      else // Methods starting with 'init' follow the init rule.
        if (AtBeginning && StringsEqualNoCase("init", s, len))
          C = InitRule;
      break;
    case 5:
      if (AtBeginning && StringsEqualNoCase("alloc", s, len))
        C = CreateRule;
      break;
    }
    
    // If we aren't in the prefix and have a derived convention then just
    // return it now.
    if (!InPossiblePrefix && C != NoConvention)
      return C;

    AtBeginning = false;
    s = wordEnd;
  }

  // We will get here if there wasn't more than one word
  // after the prefix.
  return C;
}

static bool followsFundamentalRule(const char* s) {
  return deriveNamingConvention(s) == CreateRule;
}

static bool followsReturnRule(const char* s) {
  NamingConvention C = deriveNamingConvention(s);
  return C == CreateRule || C == InitRule;
}

//===----------------------------------------------------------------------===//
// Selector creation functions.
//===----------------------------------------------------------------------===//

static inline Selector GetNullarySelector(const char* name, ASTContext& Ctx) {
  IdentifierInfo* II = &Ctx.Idents.get(name);
  return Ctx.Selectors.getSelector(0, &II);
}

static inline Selector GetUnarySelector(const char* name, ASTContext& Ctx) {
  IdentifierInfo* II = &Ctx.Idents.get(name);
  return Ctx.Selectors.getSelector(1, &II);
}

//===----------------------------------------------------------------------===//
// Type querying functions.
//===----------------------------------------------------------------------===//

static bool hasPrefix(const char* s, const char* prefix) {
  if (!prefix)
    return true;
  
  char c = *s;
  char cP = *prefix;
  
  while (c != '\0' && cP != '\0') {
    if (c != cP) break;
    c = *(++s);
    cP = *(++prefix);
  }
  
  return cP == '\0';
}

static bool hasSuffix(const char* s, const char* suffix) {
  const char* loc = strstr(s, suffix);
  return loc && strcmp(suffix, loc) == 0;
}

static bool isRefType(QualType RetTy, const char* prefix,
                      ASTContext* Ctx = 0, const char* name = 0) {
  
  if (TypedefType* TD = dyn_cast<TypedefType>(RetTy.getTypePtr())) {
    const char* TDName = TD->getDecl()->getIdentifier()->getName();
    return hasPrefix(TDName, prefix) && hasSuffix(TDName, "Ref");
  }

  if (!Ctx || !name)
    return false;

  // Is the type void*?
  const PointerType* PT = RetTy->getAsPointerType();
  if (!(PT->getPointeeType().getUnqualifiedType() == Ctx->VoidTy))
    return false;

  // Does the name start with the prefix?
  return hasPrefix(name, prefix);
}

//===----------------------------------------------------------------------===//
// Primitives used for constructing summaries for function/method calls.
//===----------------------------------------------------------------------===//

namespace {
/// ArgEffect is used to summarize a function/method call's effect on a
/// particular argument.
enum ArgEffect { Autorelease, Dealloc, DecRef, DecRefMsg, DoNothing,
                 DoNothingByRef, IncRefMsg, IncRef, MakeCollectable, MayEscape,
                 NewAutoreleasePool, SelfOwn, StopTracking };

/// ArgEffects summarizes the effects of a function/method call on all of
/// its arguments.
typedef std::vector<std::pair<unsigned,ArgEffect> > ArgEffects;
}

namespace llvm {
template <> struct FoldingSetTrait<ArgEffects> {
  static void Profile(const ArgEffects& X, FoldingSetNodeID& ID) {
    for (ArgEffects::const_iterator I = X.begin(), E = X.end(); I!= E; ++I) {
      ID.AddInteger(I->first);
      ID.AddInteger((unsigned) I->second);
    }
  }    
};
} // end llvm namespace

namespace {

///  RetEffect is used to summarize a function/method call's behavior with
///  respect to its return value.  
class VISIBILITY_HIDDEN RetEffect {
public:
  enum Kind { NoRet, Alias, OwnedSymbol, OwnedAllocatedSymbol,
              NotOwnedSymbol, ReceiverAlias };
    
  enum ObjKind { CF, ObjC, AnyObj };  

private:
  Kind K;
  ObjKind O;
  unsigned index;

  RetEffect(Kind k, unsigned idx = 0) : K(k), O(AnyObj), index(idx) {}
  RetEffect(Kind k, ObjKind o) : K(k), O(o), index(0) {}
  
public:
  Kind getKind() const { return K; }

  ObjKind getObjKind() const { return O; }
  
  unsigned getIndex() const { 
    assert(getKind() == Alias);
    return index;
  }
  
  static RetEffect MakeAlias(unsigned Idx) {
    return RetEffect(Alias, Idx);
  }
  static RetEffect MakeReceiverAlias() {
    return RetEffect(ReceiverAlias);
  }  
  static RetEffect MakeOwned(ObjKind o, bool isAllocated = false) {
    return RetEffect(isAllocated ? OwnedAllocatedSymbol : OwnedSymbol, o);
  }  
  static RetEffect MakeNotOwned(ObjKind o) {
    return RetEffect(NotOwnedSymbol, o);
  }  
  static RetEffect MakeNoRet() {
    return RetEffect(NoRet);
  }
  
  void Profile(llvm::FoldingSetNodeID& ID) const {
    ID.AddInteger((unsigned)K);
    ID.AddInteger((unsigned)O);
    ID.AddInteger(index);
  }
};
  
  
class VISIBILITY_HIDDEN RetainSummary : public llvm::FoldingSetNode {
  /// Args - an ordered vector of (index, ArgEffect) pairs, where index
  ///  specifies the argument (starting from 0).  This can be sparsely
  ///  populated; arguments with no entry in Args use 'DefaultArgEffect'.
  ArgEffects* Args;
  
  /// DefaultArgEffect - The default ArgEffect to apply to arguments that
  ///  do not have an entry in Args.
  ArgEffect   DefaultArgEffect;
  
  /// Receiver - If this summary applies to an Objective-C message expression,
  ///  this is the effect applied to the state of the receiver.
  ArgEffect   Receiver;
  
  /// Ret - The effect on the return value.  Used to indicate if the
  ///  function/method call returns a new tracked symbol, returns an
  ///  alias of one of the arguments in the call, and so on.
  RetEffect   Ret;
  
  /// EndPath - Indicates that execution of this method/function should
  ///  terminate the simulation of a path.
  bool EndPath;
  
public:
  
  RetainSummary(ArgEffects* A, RetEffect R, ArgEffect defaultEff,
                ArgEffect ReceiverEff, bool endpath = false)
    : Args(A), DefaultArgEffect(defaultEff), Receiver(ReceiverEff), Ret(R),
      EndPath(endpath) {}  
  
  /// getArg - Return the argument effect on the argument specified by
  ///  idx (starting from 0).
  ArgEffect getArg(unsigned idx) const {

    if (!Args)
      return DefaultArgEffect;
    
    // If Args is present, it is likely to contain only 1 element.
    // Just do a linear search.  Do it from the back because functions with
    // large numbers of arguments will be tail heavy with respect to which
    // argument they actually modify with respect to the reference count.    
    for (ArgEffects::reverse_iterator I=Args->rbegin(), E=Args->rend();
           I!=E; ++I) {
      
      if (idx > I->first)
        return DefaultArgEffect;
      
      if (idx == I->first)
        return I->second;
    }
    
    return DefaultArgEffect;
  }
  
  /// getRetEffect - Returns the effect on the return value of the call.
  RetEffect getRetEffect() const {
    return Ret;
  }
  
  /// isEndPath - Returns true if executing the given method/function should
  ///  terminate the path.
  bool isEndPath() const { return EndPath; }
  
  /// getReceiverEffect - Returns the effect on the receiver of the call.
  ///  This is only meaningful if the summary applies to an ObjCMessageExpr*.
  ArgEffect getReceiverEffect() const {
    return Receiver;
  }
  
  typedef ArgEffects::const_iterator ExprIterator;
  
  ExprIterator begin_args() const { return Args->begin(); }
  ExprIterator end_args()   const { return Args->end(); }
  
  static void Profile(llvm::FoldingSetNodeID& ID, ArgEffects* A,
                      RetEffect RetEff, ArgEffect DefaultEff,
                      ArgEffect ReceiverEff, bool EndPath) {
    ID.AddPointer(A);
    ID.Add(RetEff);
    ID.AddInteger((unsigned) DefaultEff);
    ID.AddInteger((unsigned) ReceiverEff);
    ID.AddInteger((unsigned) EndPath);
  }
      
  void Profile(llvm::FoldingSetNodeID& ID) const {
    Profile(ID, Args, Ret, DefaultArgEffect, Receiver, EndPath);
  }
};
} // end anonymous namespace

//===----------------------------------------------------------------------===//
// Data structures for constructing summaries.
//===----------------------------------------------------------------------===//

namespace {
class VISIBILITY_HIDDEN ObjCSummaryKey {
  IdentifierInfo* II;
  Selector S;
public:    
  ObjCSummaryKey(IdentifierInfo* ii, Selector s)
    : II(ii), S(s) {}

  ObjCSummaryKey(ObjCInterfaceDecl* d, Selector s)
    : II(d ? d->getIdentifier() : 0), S(s) {}
  
  ObjCSummaryKey(Selector s)
    : II(0), S(s) {}
  
  IdentifierInfo* getIdentifier() const { return II; }
  Selector getSelector() const { return S; }
};
}

namespace llvm {
template <> struct DenseMapInfo<ObjCSummaryKey> {
  static inline ObjCSummaryKey getEmptyKey() {
    return ObjCSummaryKey(DenseMapInfo<IdentifierInfo*>::getEmptyKey(),
                          DenseMapInfo<Selector>::getEmptyKey());
  }
    
  static inline ObjCSummaryKey getTombstoneKey() {
    return ObjCSummaryKey(DenseMapInfo<IdentifierInfo*>::getTombstoneKey(),
                          DenseMapInfo<Selector>::getTombstoneKey());      
  }
  
  static unsigned getHashValue(const ObjCSummaryKey &V) {
    return (DenseMapInfo<IdentifierInfo*>::getHashValue(V.getIdentifier())
            & 0x88888888) 
        | (DenseMapInfo<Selector>::getHashValue(V.getSelector())
            & 0x55555555);
  }
  
  static bool isEqual(const ObjCSummaryKey& LHS, const ObjCSummaryKey& RHS) {
    return DenseMapInfo<IdentifierInfo*>::isEqual(LHS.getIdentifier(),
                                                  RHS.getIdentifier()) &&
           DenseMapInfo<Selector>::isEqual(LHS.getSelector(),
                                           RHS.getSelector());
  }
  
  static bool isPod() {
    return DenseMapInfo<ObjCInterfaceDecl*>::isPod() &&
           DenseMapInfo<Selector>::isPod();
  }
};
} // end llvm namespace
  
namespace {
class VISIBILITY_HIDDEN ObjCSummaryCache {
  typedef llvm::DenseMap<ObjCSummaryKey, RetainSummary*> MapTy;
  MapTy M;
public:
  ObjCSummaryCache() {}
  
  typedef MapTy::iterator iterator;
  
  iterator find(ObjCInterfaceDecl* D, Selector S) {
    
    // Do a lookup with the (D,S) pair.  If we find a match return
    // the iterator.
    ObjCSummaryKey K(D, S);
    MapTy::iterator I = M.find(K);
    
    if (I != M.end() || !D)
      return I;
    
    // Walk the super chain.  If we find a hit with a parent, we'll end
    // up returning that summary.  We actually allow that key (null,S), as
    // we cache summaries for the null ObjCInterfaceDecl* to allow us to
    // generate initial summaries without having to worry about NSObject
    // being declared.
    // FIXME: We may change this at some point.
    for (ObjCInterfaceDecl* C=D->getSuperClass() ;; C=C->getSuperClass()) {
      if ((I = M.find(ObjCSummaryKey(C, S))) != M.end())
        break;
      
      if (!C)
        return I;
    }
    
    // Cache the summary with original key to make the next lookup faster 
    // and return the iterator.
    M[K] = I->second;
    return I;
  }
  

  iterator find(Expr* Receiver, Selector S) {
    return find(getReceiverDecl(Receiver), S);
  }
  
  iterator find(IdentifierInfo* II, Selector S) {
    // FIXME: Class method lookup.  Right now we dont' have a good way
    // of going between IdentifierInfo* and the class hierarchy.
    iterator I = M.find(ObjCSummaryKey(II, S));
    return I == M.end() ? M.find(ObjCSummaryKey(S)) : I;
  }
  
  ObjCInterfaceDecl* getReceiverDecl(Expr* E) {
    
    const PointerType* PT = E->getType()->getAsPointerType();
    if (!PT) return 0;
    
    ObjCInterfaceType* OI = dyn_cast<ObjCInterfaceType>(PT->getPointeeType());
    if (!OI) return 0;
    
    return OI ? OI->getDecl() : 0;
  }
  
  iterator end() { return M.end(); }
  
  RetainSummary*& operator[](ObjCMessageExpr* ME) {
    
    Selector S = ME->getSelector();
    
    if (Expr* Receiver = ME->getReceiver()) {
      ObjCInterfaceDecl* OD = getReceiverDecl(Receiver);
      return OD ? M[ObjCSummaryKey(OD->getIdentifier(), S)] : M[S];
    }
    
    return M[ObjCSummaryKey(ME->getClassName(), S)];
  }
  
  RetainSummary*& operator[](ObjCSummaryKey K) {
    return M[K];
  }
  
  RetainSummary*& operator[](Selector S) {
    return M[ ObjCSummaryKey(S) ];
  }
};   
} // end anonymous namespace

//===----------------------------------------------------------------------===//
// Data structures for managing collections of summaries.
//===----------------------------------------------------------------------===//

namespace {
class VISIBILITY_HIDDEN RetainSummaryManager {

  //==-----------------------------------------------------------------==//
  //  Typedefs.
  //==-----------------------------------------------------------------==//
  
  typedef llvm::FoldingSet<llvm::FoldingSetNodeWrapper<ArgEffects> >
          ArgEffectsSetTy;
  
  typedef llvm::FoldingSet<RetainSummary>
          SummarySetTy;
  
  typedef llvm::DenseMap<FunctionDecl*, RetainSummary*>
          FuncSummariesTy;
  
  typedef ObjCSummaryCache ObjCMethodSummariesTy;
    
  //==-----------------------------------------------------------------==//
  //  Data.
  //==-----------------------------------------------------------------==//
  
  /// Ctx - The ASTContext object for the analyzed ASTs.
  ASTContext& Ctx;

  /// CFDictionaryCreateII - An IdentifierInfo* representing the indentifier
  ///  "CFDictionaryCreate".
  IdentifierInfo* CFDictionaryCreateII;
  
  /// GCEnabled - Records whether or not the analyzed code runs in GC mode.
  const bool GCEnabled;
  
  /// SummarySet - A FoldingSet of uniqued summaries.
  SummarySetTy SummarySet;
  
  /// FuncSummaries - A map from FunctionDecls to summaries.
  FuncSummariesTy FuncSummaries; 
  
  /// ObjCClassMethodSummaries - A map from selectors (for instance methods)
  ///  to summaries.
  ObjCMethodSummariesTy ObjCClassMethodSummaries;

  /// ObjCMethodSummaries - A map from selectors to summaries.
  ObjCMethodSummariesTy ObjCMethodSummaries;

  /// ArgEffectsSet - A FoldingSet of uniqued ArgEffects.
  ArgEffectsSetTy ArgEffectsSet;
  
  /// BPAlloc - A BumpPtrAllocator used for allocating summaries, ArgEffects,
  ///  and all other data used by the checker.
  llvm::BumpPtrAllocator BPAlloc;
  
  /// ScratchArgs - A holding buffer for construct ArgEffects.
  ArgEffects ScratchArgs;
  
  RetainSummary* StopSummary;
  
  //==-----------------------------------------------------------------==//
  //  Methods.
  //==-----------------------------------------------------------------==//
  
  /// getArgEffects - Returns a persistent ArgEffects object based on the
  ///  data in ScratchArgs.
  ArgEffects*   getArgEffects();

  enum UnaryFuncKind { cfretain, cfrelease, cfmakecollectable };  
  
public:
  RetainSummary* getUnarySummary(const FunctionType* FT, UnaryFuncKind func);
  
  RetainSummary* getCFSummaryCreateRule(FunctionDecl* FD);
  RetainSummary* getCFSummaryGetRule(FunctionDecl* FD);  
  RetainSummary* getCFCreateGetRuleSummary(FunctionDecl* FD, const char* FName);
  
  RetainSummary* getPersistentSummary(ArgEffects* AE, RetEffect RetEff,
                                      ArgEffect ReceiverEff = DoNothing,
                                      ArgEffect DefaultEff = MayEscape,
                                      bool isEndPath = false);

  RetainSummary* getPersistentSummary(RetEffect RE,
                                      ArgEffect ReceiverEff = DoNothing,
                                      ArgEffect DefaultEff = MayEscape) {
    return getPersistentSummary(getArgEffects(), RE, ReceiverEff, DefaultEff);
  }
  
  RetainSummary* getPersistentStopSummary() {
    if (StopSummary)
      return StopSummary;
    
    StopSummary = getPersistentSummary(RetEffect::MakeNoRet(),
                                       StopTracking, StopTracking);

    return StopSummary;
  }  

  RetainSummary* getInitMethodSummary(ObjCMessageExpr* ME);

  void InitializeClassMethodSummaries();
  void InitializeMethodSummaries();
  
  bool isTrackedObjectType(QualType T);
  
private:
  
  void addClsMethSummary(IdentifierInfo* ClsII, Selector S,
                         RetainSummary* Summ) {
    ObjCClassMethodSummaries[ObjCSummaryKey(ClsII, S)] = Summ;
  }
  
  void addNSObjectClsMethSummary(Selector S, RetainSummary *Summ) {
    ObjCClassMethodSummaries[S] = Summ;
  }
    
  void addNSObjectMethSummary(Selector S, RetainSummary *Summ) {
    ObjCMethodSummaries[S] = Summ;
  }

  void addClassMethSummary(const char* Cls, const char* nullaryName,
                           RetainSummary *Summ) {
    IdentifierInfo* ClsII = &Ctx.Idents.get(Cls);
    Selector S = GetNullarySelector(nullaryName, Ctx);
    ObjCClassMethodSummaries[ObjCSummaryKey(ClsII, S)]  = Summ;
  }
  
  void addInstMethSummary(const char* Cls, const char* nullaryName,
                          RetainSummary *Summ) {
    IdentifierInfo* ClsII = &Ctx.Idents.get(Cls);
    Selector S = GetNullarySelector(nullaryName, Ctx);
    ObjCMethodSummaries[ObjCSummaryKey(ClsII, S)]  = Summ;
  }
  
  Selector generateSelector(va_list argp) {
    llvm::SmallVector<IdentifierInfo*, 10> II;

    while (const char* s = va_arg(argp, const char*))
      II.push_back(&Ctx.Idents.get(s));

    return Ctx.Selectors.getSelector(II.size(), &II[0]);    
  }
  
  void addMethodSummary(IdentifierInfo *ClsII, ObjCMethodSummariesTy& Summaries,
                        RetainSummary* Summ, va_list argp) {
    Selector S = generateSelector(argp);
    Summaries[ObjCSummaryKey(ClsII, S)] = Summ;
  }
  
  void addInstMethSummary(const char* Cls, RetainSummary* Summ, ...) {
    va_list argp;
    va_start(argp, Summ);
    addMethodSummary(&Ctx.Idents.get(Cls), ObjCMethodSummaries, Summ, argp);
    va_end(argp);    
  }
  
  void addClsMethSummary(const char* Cls, RetainSummary* Summ, ...) {
    va_list argp;
    va_start(argp, Summ);
    addMethodSummary(&Ctx.Idents.get(Cls),ObjCClassMethodSummaries, Summ, argp);
    va_end(argp);
  }
  
  void addClsMethSummary(IdentifierInfo *II, RetainSummary* Summ, ...) {
    va_list argp;
    va_start(argp, Summ);
    addMethodSummary(II, ObjCClassMethodSummaries, Summ, argp);
    va_end(argp);
  }

  void addPanicSummary(const char* Cls, ...) {
    RetainSummary* Summ = getPersistentSummary(0, RetEffect::MakeNoRet(),
                                               DoNothing,  DoNothing, true);
    va_list argp;
    va_start (argp, Cls);
    addMethodSummary(&Ctx.Idents.get(Cls), ObjCMethodSummaries, Summ, argp);
    va_end(argp);
  }
  
public:
  
  RetainSummaryManager(ASTContext& ctx, bool gcenabled)
   : Ctx(ctx),
     CFDictionaryCreateII(&ctx.Idents.get("CFDictionaryCreate")),
     GCEnabled(gcenabled), StopSummary(0) {

    InitializeClassMethodSummaries();
    InitializeMethodSummaries();
  }
  
  ~RetainSummaryManager();
  
  RetainSummary* getSummary(FunctionDecl* FD);  
  RetainSummary* getMethodSummary(ObjCMessageExpr* ME, ObjCInterfaceDecl* ID);
  RetainSummary* getClassMethodSummary(ObjCMessageExpr *ME);
  RetainSummary* getCommonMethodSummary(ObjCMessageExpr *ME, const char *s);
  
  bool isGCEnabled() const { return GCEnabled; }
};
  
} // end anonymous namespace

//===----------------------------------------------------------------------===//
// Implementation of checker data structures.
//===----------------------------------------------------------------------===//

RetainSummaryManager::~RetainSummaryManager() {
  
  // FIXME: The ArgEffects could eventually be allocated from BPAlloc, 
  //   mitigating the need to do explicit cleanup of the
  //   Argument-Effect summaries.
  
  for (ArgEffectsSetTy::iterator I = ArgEffectsSet.begin(), 
                                 E = ArgEffectsSet.end(); I!=E; ++I)
    I->getValue().~ArgEffects();
}

ArgEffects* RetainSummaryManager::getArgEffects() {

  if (ScratchArgs.empty())
    return NULL;
  
  // Compute a profile for a non-empty ScratchArgs.
  llvm::FoldingSetNodeID profile;
  profile.Add(ScratchArgs);
  void* InsertPos;
  
  // Look up the uniqued copy, or create a new one.
  llvm::FoldingSetNodeWrapper<ArgEffects>* E =
    ArgEffectsSet.FindNodeOrInsertPos(profile, InsertPos);
  
  if (E) {
    ScratchArgs.clear();
    return &E->getValue();
  }
  
  E = (llvm::FoldingSetNodeWrapper<ArgEffects>*)
        BPAlloc.Allocate<llvm::FoldingSetNodeWrapper<ArgEffects> >();
                       
  new (E) llvm::FoldingSetNodeWrapper<ArgEffects>(ScratchArgs);
  ArgEffectsSet.InsertNode(E, InsertPos);

  ScratchArgs.clear();
  return &E->getValue();
}

RetainSummary*
RetainSummaryManager::getPersistentSummary(ArgEffects* AE, RetEffect RetEff,
                                           ArgEffect ReceiverEff,
                                           ArgEffect DefaultEff,
                                           bool isEndPath) {
  
  // Generate a profile for the summary.
  llvm::FoldingSetNodeID profile;
  RetainSummary::Profile(profile, AE, RetEff, DefaultEff, ReceiverEff,
                         isEndPath);
  
  // Look up the uniqued summary, or create one if it doesn't exist.
  void* InsertPos;  
  RetainSummary* Summ = SummarySet.FindNodeOrInsertPos(profile, InsertPos);
  
  if (Summ)
    return Summ;
  
  // Create the summary and return it.
  Summ = (RetainSummary*) BPAlloc.Allocate<RetainSummary>();
  new (Summ) RetainSummary(AE, RetEff, DefaultEff, ReceiverEff, isEndPath);
  SummarySet.InsertNode(Summ, InsertPos);
  
  return Summ;
}

//===----------------------------------------------------------------------===//
// Predicates.
//===----------------------------------------------------------------------===//

bool RetainSummaryManager::isTrackedObjectType(QualType Ty) {
  if (!Ctx.isObjCObjectPointerType(Ty))
    return false;

  // We assume that id<..>, id, and "Class" all represent tracked objects.
  const PointerType *PT = Ty->getAsPointerType();
  if (PT == 0)
    return true;
    
  const ObjCInterfaceType *OT = PT->getPointeeType()->getAsObjCInterfaceType();

  // We assume that id<..>, id, and "Class" all represent tracked objects.
  if (!OT)
    return true;
    
  // Does the interface subclass NSObject?
  // FIXME: We can memoize here if this gets too expensive.  
  IdentifierInfo* NSObjectII = &Ctx.Idents.get("NSObject");
  ObjCInterfaceDecl* ID = OT->getDecl();  

  for ( ; ID ; ID = ID->getSuperClass())
    if (ID->getIdentifier() == NSObjectII)
      return true;
  
  return false;
}

//===----------------------------------------------------------------------===//
// Summary creation for functions (largely uses of Core Foundation).
//===----------------------------------------------------------------------===//

static bool isRetain(FunctionDecl* FD, const char* FName) {
  const char* loc = strstr(FName, "Retain");
  return loc && loc[sizeof("Retain")-1] == '\0';
}

static bool isRelease(FunctionDecl* FD, const char* FName) {
  const char* loc = strstr(FName, "Release");
  return loc && loc[sizeof("Release")-1] == '\0';
}

RetainSummary* RetainSummaryManager::getSummary(FunctionDecl* FD) {

  SourceLocation Loc = FD->getLocation();
  
  if (!Loc.isFileID())
    return NULL;
  
  // Look up a summary in our cache of FunctionDecls -> Summaries.
  FuncSummariesTy::iterator I = FuncSummaries.find(FD);

  if (I != FuncSummaries.end())
    return I->second;

  // No summary.  Generate one.
  RetainSummary *S = 0;
  
  do {
    // We generate "stop" summaries for implicitly defined functions.
    if (FD->isImplicit()) {
      S = getPersistentStopSummary();
      break;
    }
    
    // [PR 3337] Use 'getAsFunctionType' to strip away any typedefs on the
    // function's type.
    const FunctionType* FT = FD->getType()->getAsFunctionType();
    const char* FName = FD->getIdentifier()->getName();
    
    // Strip away preceding '_'.  Doing this here will effect all the checks
    // down below.
    while (*FName == '_') ++FName;
    
    // Inspect the result type.
    QualType RetTy = FT->getResultType();
    
    // FIXME: This should all be refactored into a chain of "summary lookup"
    //  filters.
    if (strcmp(FName, "IOServiceGetMatchingServices") == 0) {
      // FIXES: <rdar://problem/6326900>
      // This should be addressed using a API table.  This strcmp is also
      // a little gross, but there is no need to super optimize here.
      assert (ScratchArgs.empty());
      ScratchArgs.push_back(std::make_pair(1, DecRef));
      S = getPersistentSummary(RetEffect::MakeNoRet(), DoNothing, DoNothing);
      break;
    }

    // Enable this code once the semantics of NSDeallocateObject are resolved
    // for GC.  <rdar://problem/6619988>
#if 0
    // Handle: NSDeallocateObject(id anObject);
    // This method does allow 'nil' (although we don't check it now).
    if (strcmp(FName, "NSDeallocateObject") == 0) {      
      return RetTy == Ctx.VoidTy
        ? getPersistentSummary(RetEffect::MakeNoRet(), DoNothing, Dealloc)
        : getPersistentStopSummary();
    }
#endif
    
    // Handle: id NSMakeCollectable(CFTypeRef)
    if (strcmp(FName, "NSMakeCollectable") == 0) {
      S = (RetTy == Ctx.getObjCIdType())
          ? getUnarySummary(FT, cfmakecollectable)
          : getPersistentStopSummary();
        
      break;
    }

    if (RetTy->isPointerType()) {
      // For CoreFoundation ('CF') types.
      if (isRefType(RetTy, "CF", &Ctx, FName)) {
        if (isRetain(FD, FName))
          S = getUnarySummary(FT, cfretain);
        else if (strstr(FName, "MakeCollectable"))
          S = getUnarySummary(FT, cfmakecollectable);
        else 
          S = getCFCreateGetRuleSummary(FD, FName);

        break;
      }

      // For CoreGraphics ('CG') types.
      if (isRefType(RetTy, "CG", &Ctx, FName)) {
        if (isRetain(FD, FName))
          S = getUnarySummary(FT, cfretain);
        else
          S = getCFCreateGetRuleSummary(FD, FName);

        break;
      }

      // For the Disk Arbitration API (DiskArbitration/DADisk.h)
      if (isRefType(RetTy, "DADisk") ||
          isRefType(RetTy, "DADissenter") ||
          isRefType(RetTy, "DASessionRef")) {
        S = getCFCreateGetRuleSummary(FD, FName);
        break;
      }
      
      break;
    }

    // Check for release functions, the only kind of functions that we care
    // about that don't return a pointer type.
    if (FName[0] == 'C' && (FName[1] == 'F' || FName[1] == 'G')) {
      // Test for 'CGCF'.
      if (FName[1] == 'G' && FName[2] == 'C' && FName[3] == 'F')
        FName += 4;
      else
        FName += 2;
      
      if (isRelease(FD, FName))
        S = getUnarySummary(FT, cfrelease);
      else {
        assert (ScratchArgs.empty());
        // Remaining CoreFoundation and CoreGraphics functions.
        // We use to assume that they all strictly followed the ownership idiom
        // and that ownership cannot be transferred.  While this is technically
        // correct, many methods allow a tracked object to escape.  For example:
        //
        //   CFMutableDictionaryRef x = CFDictionaryCreateMutable(...);        
        //   CFDictionaryAddValue(y, key, x);
        //   CFRelease(x); 
        //   ... it is okay to use 'x' since 'y' has a reference to it
        //
        // We handle this and similar cases with the follow heuristic.  If the
        // function name contains "InsertValue", "SetValue" or "AddValue" then
        // we assume that arguments may "escape."
        //
        ArgEffect E = (CStrInCStrNoCase(FName, "InsertValue") ||
                       CStrInCStrNoCase(FName, "AddValue") ||
                       CStrInCStrNoCase(FName, "SetValue") ||
                       CStrInCStrNoCase(FName, "AppendValue"))
                      ? MayEscape : DoNothing;
        
        S = getPersistentSummary(RetEffect::MakeNoRet(), DoNothing, E);
      }
    }
  }
  while (0);

  FuncSummaries[FD] = S;
  return S;  
}

RetainSummary*
RetainSummaryManager::getCFCreateGetRuleSummary(FunctionDecl* FD,
                                                const char* FName) {
  
  if (strstr(FName, "Create") || strstr(FName, "Copy"))
    return getCFSummaryCreateRule(FD);
  
  if (strstr(FName, "Get"))
    return getCFSummaryGetRule(FD);
  
  return 0;
}

RetainSummary*
RetainSummaryManager::getUnarySummary(const FunctionType* FT,
                                      UnaryFuncKind func) {

  // Sanity check that this is *really* a unary function.  This can
  // happen if people do weird things.
  const FunctionProtoType* FTP = dyn_cast<FunctionProtoType>(FT);
  if (!FTP || FTP->getNumArgs() != 1)
    return getPersistentStopSummary();
  
  assert (ScratchArgs.empty());
  
  switch (func) {
    case cfretain: {      
      ScratchArgs.push_back(std::make_pair(0, IncRef));
      return getPersistentSummary(RetEffect::MakeAlias(0),
                                  DoNothing, DoNothing);
    }
      
    case cfrelease: {
      ScratchArgs.push_back(std::make_pair(0, DecRef));
      return getPersistentSummary(RetEffect::MakeNoRet(),
                                  DoNothing, DoNothing);
    }
      
    case cfmakecollectable: {
      ScratchArgs.push_back(std::make_pair(0, MakeCollectable));
      return getPersistentSummary(RetEffect::MakeAlias(0),DoNothing, DoNothing);    
    }
      
    default:
      assert (false && "Not a supported unary function.");
      return 0;
  }
}

RetainSummary* RetainSummaryManager::getCFSummaryCreateRule(FunctionDecl* FD) {
  assert (ScratchArgs.empty());
  
  if (FD->getIdentifier() == CFDictionaryCreateII) {
    ScratchArgs.push_back(std::make_pair(1, DoNothingByRef));
    ScratchArgs.push_back(std::make_pair(2, DoNothingByRef));
  }
  
  return getPersistentSummary(RetEffect::MakeOwned(RetEffect::CF, true));
}

RetainSummary* RetainSummaryManager::getCFSummaryGetRule(FunctionDecl* FD) {
  assert (ScratchArgs.empty());  
  return getPersistentSummary(RetEffect::MakeNotOwned(RetEffect::CF),
                              DoNothing, DoNothing);
}

//===----------------------------------------------------------------------===//
// Summary creation for Selectors.
//===----------------------------------------------------------------------===//

RetainSummary*
RetainSummaryManager::getInitMethodSummary(ObjCMessageExpr* ME) {
  assert(ScratchArgs.empty());
    
  // 'init' methods only return an alias if the return type is a location type.
  QualType T = ME->getType();
  RetainSummary* Summ =
    getPersistentSummary(Loc::IsLocType(T) ? RetEffect::MakeReceiverAlias()
                                           : RetEffect::MakeNoRet());
  
  ObjCMethodSummaries[ME] = Summ;
  return Summ;
}


RetainSummary*
RetainSummaryManager::getCommonMethodSummary(ObjCMessageExpr* ME, const char *s)
{
  if (ObjCMethodDecl *MD = ME->getMethodDecl()) {
    // Scan the method decl for 'void*' arguments.  These should be treated
    // as 'StopTracking' because they are often used with delegates.
    // Delegates are a frequent form of false positives with the retain
    // count checker.
    unsigned i = 0;
    for (ObjCMethodDecl::param_iterator I = MD->param_begin(),
         E = MD->param_end(); I != E; ++I, ++i)
      if (ParmVarDecl *PD = *I) {
        QualType Ty = Ctx.getCanonicalType(PD->getType());
        if (Ty.getUnqualifiedType() == Ctx.VoidPtrTy)
          ScratchArgs.push_back(std::make_pair(i, StopTracking));
      }
  }
  
  // Look for methods that return an owned object.
  if (!isTrackedObjectType(ME->getType())) {
    if (ScratchArgs.empty())    
      return 0;
    
    return getPersistentSummary(RetEffect::MakeNoRet());
  }
  
  // EXPERIMENTAL: Assume the Cocoa conventions for all objects returned
  //  by instance methods.
  
  RetEffect E =
    followsFundamentalRule(s)
    ? (isGCEnabled() ? RetEffect::MakeNotOwned(RetEffect::ObjC)
                     : RetEffect::MakeOwned(RetEffect::ObjC, true))
      : RetEffect::MakeNotOwned(RetEffect::ObjC);
  
  return getPersistentSummary(E);
}

RetainSummary*
RetainSummaryManager::getMethodSummary(ObjCMessageExpr* ME,
                                       ObjCInterfaceDecl* ID) {

  Selector S = ME->getSelector();
  
  // Look up a summary in our summary cache.  
  ObjCMethodSummariesTy::iterator I = ObjCMethodSummaries.find(ID, S);
  
  if (I != ObjCMethodSummaries.end())
    return I->second;

  // "initXXX": pass-through for receiver.
  const char* s = S.getIdentifierInfoForSlot(0)->getName();
  assert(ScratchArgs.empty());
  
  if (deriveNamingConvention(s) == InitRule)
    return getInitMethodSummary(ME);
  
  RetainSummary *Summ = getCommonMethodSummary(ME, s);
  ObjCMethodSummaries[ME] = Summ;
  return Summ;
}

RetainSummary*
RetainSummaryManager::getClassMethodSummary(ObjCMessageExpr *ME) {

  Selector S = ME->getSelector();
  ObjCMethodSummariesTy::iterator I;
  
  if (ObjCInterfaceDecl *ID = ME->getClassInfo().first) {
    // Lookup the method using the decl for the class @interface.
    I = ObjCClassMethodSummaries.find(ID, S); 
  }
  else {
    // Fallback to using the class name.
    IdentifierInfo *ClsName = ME->getClassName();
  
    // Look up a summary in our cache of Selectors -> Summaries.
    I = ObjCClassMethodSummaries.find(ClsName, S);
  }
  
  if (I != ObjCClassMethodSummaries.end())
    return I->second;
  
  RetainSummary* Summ =
    getCommonMethodSummary(ME, S.getIdentifierInfoForSlot(0)->getName());

  ObjCClassMethodSummaries[ObjCSummaryKey(ME->getClassName(), S)] = Summ;
  return Summ;
}

void RetainSummaryManager::InitializeClassMethodSummaries() {
  
  assert (ScratchArgs.empty());
  
  RetEffect E = isGCEnabled() ? RetEffect::MakeNoRet()
                              : RetEffect::MakeOwned(RetEffect::ObjC, true);  
  
  RetainSummary* Summ = getPersistentSummary(E);
  
  // Create the summaries for "alloc", "new", and "allocWithZone:" for
  // NSObject and its derivatives.
  addNSObjectClsMethSummary(GetNullarySelector("alloc", Ctx), Summ);
  addNSObjectClsMethSummary(GetNullarySelector("new", Ctx), Summ);
  addNSObjectClsMethSummary(GetUnarySelector("allocWithZone", Ctx), Summ);
  
  // Create the [NSAssertionHandler currentHander] summary.  
  addClsMethSummary(&Ctx.Idents.get("NSAssertionHandler"),
                GetNullarySelector("currentHandler", Ctx),
                getPersistentSummary(RetEffect::MakeNotOwned(RetEffect::ObjC)));
  
  // Create the [NSAutoreleasePool addObject:] summary.
  ScratchArgs.push_back(std::make_pair(0, Autorelease));
  addClsMethSummary(&Ctx.Idents.get("NSAutoreleasePool"),
                    GetUnarySelector("addObject", Ctx),
                    getPersistentSummary(RetEffect::MakeNoRet(),
                                         DoNothing, Autorelease));
  
  // Create the summaries for [NSObject performSelector...].  We treat
  // these as 'stop tracking' for the arguments because they are often
  // used for delegates that can release the object.  When we have better
  // inter-procedural analysis we can potentially do something better.  This
  // workaround is to remove false positives.
  Summ = getPersistentSummary(RetEffect::MakeNoRet(), DoNothing, StopTracking);
  IdentifierInfo *NSObjectII = &Ctx.Idents.get("NSObject");
  addClsMethSummary(NSObjectII, Summ, "performSelector", "withObject",
                    "afterDelay", NULL);
  addClsMethSummary(NSObjectII, Summ, "performSelector", "withObject",
                    "afterDelay", "inModes", NULL);
  addClsMethSummary(NSObjectII, Summ, "performSelectorOnMainThread",
                    "withObject", "waitUntilDone", NULL);
  addClsMethSummary(NSObjectII, Summ, "performSelectorOnMainThread",
                    "withObject", "waitUntilDone", "modes", NULL);
  addClsMethSummary(NSObjectII, Summ, "performSelector", "onThread",
                    "withObject", "waitUntilDone", NULL);
  addClsMethSummary(NSObjectII, Summ, "performSelector", "onThread",
                    "withObject", "waitUntilDone", "modes", NULL);
  addClsMethSummary(NSObjectII, Summ, "performSelectorInBackground",
                    "withObject", NULL);
}

void RetainSummaryManager::InitializeMethodSummaries() {
  
  assert (ScratchArgs.empty());  
  
  // Create the "init" selector.  It just acts as a pass-through for the
  // receiver.
  RetainSummary* InitSumm =
    getPersistentSummary(RetEffect::MakeReceiverAlias());
  addNSObjectMethSummary(GetNullarySelector("init", Ctx), InitSumm);
  
  // The next methods are allocators.
  RetEffect E = isGCEnabled() ? RetEffect::MakeNoRet()
                              : RetEffect::MakeOwned(RetEffect::ObjC, true);
  
  RetainSummary* Summ = getPersistentSummary(E);  
  
  // Create the "copy" selector.  
  addNSObjectMethSummary(GetNullarySelector("copy", Ctx), Summ);  

  // Create the "mutableCopy" selector.
  addNSObjectMethSummary(GetNullarySelector("mutableCopy", Ctx), Summ);
  
  // Create the "retain" selector.
  E = RetEffect::MakeReceiverAlias();
  Summ = getPersistentSummary(E, IncRefMsg);
  addNSObjectMethSummary(GetNullarySelector("retain", Ctx), Summ);
  
  // Create the "release" selector.
  Summ = getPersistentSummary(E, DecRefMsg);
  addNSObjectMethSummary(GetNullarySelector("release", Ctx), Summ);
  
  // Create the "drain" selector.
  Summ = getPersistentSummary(E, isGCEnabled() ? DoNothing : DecRef);
  addNSObjectMethSummary(GetNullarySelector("drain", Ctx), Summ);
  
  // Create the -dealloc summary.
  Summ = getPersistentSummary(RetEffect::MakeNoRet(), Dealloc);
  addNSObjectMethSummary(GetNullarySelector("dealloc", Ctx), Summ);

  // Create the "autorelease" selector.
  Summ = getPersistentSummary(E, Autorelease);
  addNSObjectMethSummary(GetNullarySelector("autorelease", Ctx), Summ);
  
  // Specially handle NSAutoreleasePool.
  addInstMethSummary("NSAutoreleasePool", "init",
                     getPersistentSummary(RetEffect::MakeReceiverAlias(),
                                          NewAutoreleasePool));
  
  // For NSWindow, allocated objects are (initially) self-owned.  
  // FIXME: For now we opt for false negatives with NSWindow, as these objects
  //  self-own themselves.  However, they only do this once they are displayed.
  //  Thus, we need to track an NSWindow's display status.
  //  This is tracked in <rdar://problem/6062711>.
  //  See also http://llvm.org/bugs/show_bug.cgi?id=3714.
  RetainSummary *NoTrackYet = getPersistentSummary(RetEffect::MakeNoRet());
  
  addClassMethSummary("NSWindow", "alloc", NoTrackYet);


#if 0
  RetainSummary *NSWindowSumm =
    getPersistentSummary(RetEffect::MakeReceiverAlias(), StopTracking);
  
  addInstMethSummary("NSWindow", NSWindowSumm, "initWithContentRect",
                     "styleMask", "backing", "defer", NULL);
  
  addInstMethSummary("NSWindow", NSWindowSumm, "initWithContentRect",
                     "styleMask", "backing", "defer", "screen", NULL);
#endif
    
  // For NSPanel (which subclasses NSWindow), allocated objects are not
  //  self-owned.
  // FIXME: For now we don't track NSPanels. object for the same reason
  //   as for NSWindow objects.
  addClassMethSummary("NSPanel", "alloc", NoTrackYet);
  
  addInstMethSummary("NSPanel", InitSumm, "initWithContentRect",
                     "styleMask", "backing", "defer", NULL);
  
  addInstMethSummary("NSPanel", InitSumm, "initWithContentRect",
                     "styleMask", "backing", "defer", "screen", NULL);

  // Create NSAssertionHandler summaries.
  addPanicSummary("NSAssertionHandler", "handleFailureInFunction", "file",
                  "lineNumber", "description", NULL); 
  
  addPanicSummary("NSAssertionHandler", "handleFailureInMethod", "object",
                  "file", "lineNumber", "description", NULL);
}

//===----------------------------------------------------------------------===//
// Reference-counting logic (typestate + counts).
//===----------------------------------------------------------------------===//

namespace {
  
class VISIBILITY_HIDDEN RefVal {
public:  
  enum Kind {
    Owned = 0, // Owning reference.    
    NotOwned,  // Reference is not owned by still valid (not freed).    
    Released,  // Object has been released.
    ReturnedOwned, // Returned object passes ownership to caller.
    ReturnedNotOwned, // Return object does not pass ownership to caller.
    ERROR_START,
    ErrorDeallocNotOwned, // -dealloc called on non-owned object.
    ErrorDeallocGC, // Calling -dealloc with GC enabled.
    ErrorUseAfterRelease, // Object used after released.    
    ErrorReleaseNotOwned, // Release of an object that was not owned.
    ERROR_LEAK_START,
    ErrorLeak,  // A memory leak due to excessive reference counts.
    ErrorLeakReturned // A memory leak due to the returning method not having
                      // the correct naming conventions.            
  };

private:  
  Kind kind;
  RetEffect::ObjKind okind;
  unsigned Cnt;
  QualType T;

  RefVal(Kind k, RetEffect::ObjKind o, unsigned cnt, QualType t)
    : kind(k), okind(o), Cnt(cnt), T(t) {}

  RefVal(Kind k, unsigned cnt = 0)
    : kind(k), okind(RetEffect::AnyObj), Cnt(cnt) {}

public:    
  Kind getKind() const { return kind; }
  
  RetEffect::ObjKind getObjKind() const { return okind; }

  unsigned getCount() const { return Cnt; }    
  void clearCounts() { Cnt = 0; }
  
  QualType getType() const { return T; }
  
  // Useful predicates.
  
  static bool isError(Kind k) { return k >= ERROR_START; }
  
  static bool isLeak(Kind k) { return k >= ERROR_LEAK_START; }
  
  bool isOwned() const {
    return getKind() == Owned;
  }
  
  bool isNotOwned() const {
    return getKind() == NotOwned;
  }
  
  bool isReturnedOwned() const {
    return getKind() == ReturnedOwned;
  }
  
  bool isReturnedNotOwned() const {
    return getKind() == ReturnedNotOwned;
  }
  
  bool isNonLeakError() const {
    Kind k = getKind();
    return isError(k) && !isLeak(k);
  }
  
  static RefVal makeOwned(RetEffect::ObjKind o, QualType t,
                          unsigned Count = 1) {
    return RefVal(Owned, o, Count, t);
  }
  
  static RefVal makeNotOwned(RetEffect::ObjKind o, QualType t,
                             unsigned Count = 0) {
    return RefVal(NotOwned, o, Count, t);
  }

  static RefVal makeReturnedOwned(unsigned Count) {
    return RefVal(ReturnedOwned, Count);
  }
  
  static RefVal makeReturnedNotOwned() {
    return RefVal(ReturnedNotOwned);
  }
  
  // Comparison, profiling, and pretty-printing.
  
  bool operator==(const RefVal& X) const {
    return kind == X.kind && Cnt == X.Cnt && T == X.T;
  }
  
  RefVal operator-(size_t i) const {
    return RefVal(getKind(), getObjKind(), getCount() - i, getType());
  }
  
  RefVal operator+(size_t i) const {
    return RefVal(getKind(), getObjKind(), getCount() + i, getType());
  }
  
  RefVal operator^(Kind k) const {
    return RefVal(k, getObjKind(), getCount(), getType());
  }
    
  void Profile(llvm::FoldingSetNodeID& ID) const {
    ID.AddInteger((unsigned) kind);
    ID.AddInteger(Cnt);
    ID.Add(T);
  }

  void print(std::ostream& Out) const;
};
  
void RefVal::print(std::ostream& Out) const {
  if (!T.isNull())
    Out << "Tracked Type:" << T.getAsString() << '\n';
    
  switch (getKind()) {
    default: assert(false);
    case Owned: { 
      Out << "Owned";
      unsigned cnt = getCount();
      if (cnt) Out << " (+ " << cnt << ")";
      break;
    }
      
    case NotOwned: {
      Out << "NotOwned";
      unsigned cnt = getCount();
      if (cnt) Out << " (+ " << cnt << ")";
      break;
    }
      
    case ReturnedOwned: { 
      Out << "ReturnedOwned";
      unsigned cnt = getCount();
      if (cnt) Out << " (+ " << cnt << ")";
      break;
    }
      
    case ReturnedNotOwned: {
      Out << "ReturnedNotOwned";
      unsigned cnt = getCount();
      if (cnt) Out << " (+ " << cnt << ")";
      break;
    }
            
    case Released:
      Out << "Released";
      break;

    case ErrorDeallocGC:
      Out << "-dealloc (GC)";
      break;
    
    case ErrorDeallocNotOwned:
      Out << "-dealloc (not-owned)";
      break;
      
    case ErrorLeak:
      Out << "Leaked";
      break;            
      
    case ErrorLeakReturned:
      Out << "Leaked (Bad naming)";
      break;
      
    case ErrorUseAfterRelease:
      Out << "Use-After-Release [ERROR]";
      break;
      
    case ErrorReleaseNotOwned:
      Out << "Release of Not-Owned [ERROR]";
      break;
  }
}
  
} // end anonymous namespace

//===----------------------------------------------------------------------===//
// RefBindings - State used to track object reference counts.
//===----------------------------------------------------------------------===//
  
typedef llvm::ImmutableMap<SymbolRef, RefVal> RefBindings;
static int RefBIndex = 0;
static std::pair<const void*, const void*> LeakProgramPointTag(&RefBIndex, 0);

namespace clang {
  template<>
  struct GRStateTrait<RefBindings> : public GRStatePartialTrait<RefBindings> {
    static inline void* GDMIndex() { return &RefBIndex; }  
  };
}

//===----------------------------------------------------------------------===//
// AutoreleaseBindings - State used to track objects in autorelease pools.
//===----------------------------------------------------------------------===//

typedef llvm::ImmutableMap<SymbolRef, unsigned> ARCounts;
typedef llvm::ImmutableMap<SymbolRef, ARCounts> ARPoolContents;
typedef llvm::ImmutableList<SymbolRef> ARStack;

static int AutoRCIndex = 0;
static int AutoRBIndex = 0;

namespace { class VISIBILITY_HIDDEN AutoreleasePoolContents {}; }
namespace { class VISIBILITY_HIDDEN AutoreleaseStack {}; }

namespace clang {
template<> struct GRStateTrait<AutoreleaseStack>
  : public GRStatePartialTrait<ARStack> {
  static inline void* GDMIndex() { return &AutoRBIndex; }  
};

template<> struct GRStateTrait<AutoreleasePoolContents>
  : public GRStatePartialTrait<ARPoolContents> {
  static inline void* GDMIndex() { return &AutoRCIndex; }  
};
} // end clang namespace

static SymbolRef GetCurrentAutoreleasePool(const GRState* state) {
  ARStack stack = state->get<AutoreleaseStack>();
  return stack.isEmpty() ? SymbolRef() : stack.getHead();
}

static GRStateRef SendAutorelease(GRStateRef state, ARCounts::Factory &F,
                                  SymbolRef sym) {

  SymbolRef pool = GetCurrentAutoreleasePool(state);
  const ARCounts *cnts = state.get<AutoreleasePoolContents>(pool);
  ARCounts newCnts(0);
  
  if (cnts) {
    const unsigned *cnt = (*cnts).lookup(sym);
    newCnts = F.Add(*cnts, sym, cnt ? *cnt  + 1 : 1);
  }
  else
    newCnts = F.Add(F.GetEmptyMap(), sym, 1);
  
  return state.set<AutoreleasePoolContents>(pool, newCnts);
}

//===----------------------------------------------------------------------===//
// Transfer functions.
//===----------------------------------------------------------------------===//

namespace {
  
class VISIBILITY_HIDDEN CFRefCount : public GRSimpleVals {
public:
  class BindingsPrinter : public GRState::Printer {
  public:
    virtual void Print(std::ostream& Out, const GRState* state,
                       const char* nl, const char* sep);
  };

private:
  typedef llvm::DenseMap<const GRExprEngine::NodeTy*, const RetainSummary*>
          SummaryLogTy;  

  RetainSummaryManager Summaries;  
  SummaryLogTy SummaryLog;
  const LangOptions&   LOpts;
  ARCounts::Factory    ARCountFactory;

  BugType *useAfterRelease, *releaseNotOwned;
  BugType *deallocGC, *deallocNotOwned;
  BugType *leakWithinFunction, *leakAtReturn;
  BugReporter *BR;
  
  GRStateRef Update(GRStateRef state, SymbolRef sym, RefVal V, ArgEffect E,
                    RefVal::Kind& hasErr);

  void ProcessNonLeakError(ExplodedNodeSet<GRState>& Dst,
                           GRStmtNodeBuilder<GRState>& Builder,
                           Expr* NodeExpr, Expr* ErrorExpr,                        
                           ExplodedNode<GRState>* Pred,
                           const GRState* St,
                           RefVal::Kind hasErr, SymbolRef Sym);
  
  std::pair<GRStateRef, bool>
  HandleSymbolDeath(GRStateManager& VMgr, const GRState* St,
                    const Decl* CD, SymbolRef sid, RefVal V, bool& hasLeak);
  
public:  
  CFRefCount(ASTContext& Ctx, bool gcenabled, const LangOptions& lopts)
    : Summaries(Ctx, gcenabled),
      LOpts(lopts), useAfterRelease(0), releaseNotOwned(0),
      deallocGC(0), deallocNotOwned(0),
      leakWithinFunction(0), leakAtReturn(0), BR(0) {}
  
  virtual ~CFRefCount() {}
  
  void RegisterChecks(BugReporter &BR);
 
  virtual void RegisterPrinters(std::vector<GRState::Printer*>& Printers) {
    Printers.push_back(new BindingsPrinter());
  }
  
  bool isGCEnabled() const { return Summaries.isGCEnabled(); }
  const LangOptions& getLangOptions() const { return LOpts; }
  
  const RetainSummary *getSummaryOfNode(const ExplodedNode<GRState> *N) const {
    SummaryLogTy::const_iterator I = SummaryLog.find(N);
    return I == SummaryLog.end() ? 0 : I->second;
  }
  
  // Calls.

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

  // Stores.  
  virtual void EvalBind(GRStmtNodeBuilderRef& B, SVal location, SVal val);

  // End-of-path.
  
  virtual void EvalEndPath(GRExprEngine& Engine,
                           GREndPathNodeBuilder<GRState>& Builder);
  
  virtual void EvalDeadSymbols(ExplodedNodeSet<GRState>& Dst,
                               GRExprEngine& Engine,
                               GRStmtNodeBuilder<GRState>& Builder,
                               ExplodedNode<GRState>* Pred,
                               Stmt* S, const GRState* state,
                               SymbolReaper& SymReaper);

  // Return statements.
  
  virtual void EvalReturn(ExplodedNodeSet<GRState>& Dst,
                          GRExprEngine& Engine,
                          GRStmtNodeBuilder<GRState>& Builder,
                          ReturnStmt* S,
                          ExplodedNode<GRState>* Pred);

  // Assumptions.

  virtual const GRState* EvalAssume(GRStateManager& VMgr,
                                       const GRState* St, SVal Cond,
                                       bool Assumption, bool& isFeasible);
};

} // end anonymous namespace

static void PrintPool(std::ostream &Out, SymbolRef Sym, const GRState *state) {
  Out << ' ';
  if (Sym)
    Out << Sym->getSymbolID();
  else
    Out << "<pool>";
  Out << ":{";
    
  // Get the contents of the pool.
  if (const ARCounts *cnts = state->get<AutoreleasePoolContents>(Sym))
    for (ARCounts::iterator J=cnts->begin(), EJ=cnts->end(); J != EJ; ++J)
      Out << '(' << J.getKey() << ',' << J.getData() << ')';

  Out << '}';  
}

void CFRefCount::BindingsPrinter::Print(std::ostream& Out, const GRState* state,
                                        const char* nl, const char* sep) {
  
  
    
  RefBindings B = state->get<RefBindings>();
  
  if (!B.isEmpty())
    Out << sep << nl;
  
  for (RefBindings::iterator I=B.begin(), E=B.end(); I!=E; ++I) {
    Out << (*I).first << " : ";
    (*I).second.print(Out);
    Out << nl;
  }
  
  // Print the autorelease stack.
  Out << sep << nl << "AR pool stack:";
  ARStack stack = state->get<AutoreleaseStack>();
  
  PrintPool(Out, SymbolRef(), state);  // Print the caller's pool.
  for (ARStack::iterator I=stack.begin(), E=stack.end(); I!=E; ++I)
    PrintPool(Out, *I, state);

  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;
}

static inline bool IsEndPath(RetainSummary* Summ) {
  return Summ ? Summ->isEndPath() : false;
}


/// GetReturnType - Used to get the return type of a message expression or
///  function call with the intention of affixing that type to a tracked symbol.
///  While the the return type can be queried directly from RetEx, when
///  invoking class methods we augment to the return type to be that of
///  a pointer to the class (as opposed it just being id).
static QualType GetReturnType(Expr* RetE, ASTContext& Ctx) {

  QualType RetTy = RetE->getType();

  // FIXME: We aren't handling id<...>.
  const PointerType* PT = RetTy->getAsPointerType();
  if (!PT)
    return RetTy;
    
  // If RetEx is not a message expression just return its type.
  // If RetEx is a message expression, return its types if it is something
  /// more specific than id.
  
  ObjCMessageExpr* ME = dyn_cast<ObjCMessageExpr>(RetE);
  
  if (!ME || !Ctx.isObjCIdStructType(PT->getPointeeType()))
    return RetTy;
  
  ObjCInterfaceDecl* D = ME->getClassInfo().first;  

  // At this point we know the return type of the message expression is id.
  // If we have an ObjCInterceDecl, we know this is a call to a class method
  // whose type we can resolve.  In such cases, promote the return type to
  // Class*.  
  return !D ? RetTy : Ctx.getPointerType(Ctx.getObjCInterfaceType(D));
}


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

  // Evaluate the effect of the arguments.
  RefVal::Kind hasErr = (RefVal::Kind) 0;
  unsigned idx = 0;
  Expr* ErrorExpr = NULL;
  SymbolRef ErrorSym = 0;                                        
  
  for (ExprIterator I = arg_beg; I != arg_end; ++I, ++idx) {    
    SVal V = state.GetSValAsScalarOrLoc(*I);    
    SymbolRef Sym = V.getAsLocSymbol();

    if (Sym)
      if (RefBindings::data_type* T = state.get<RefBindings>(Sym)) {
        state = Update(state, Sym, *T, GetArgE(Summ, idx), hasErr);
        if (hasErr) {
          ErrorExpr = *I;
          ErrorSym = Sym;
          break;
        }        
        continue;
      }

    if (isa<Loc>(V)) {
      if (loc::MemRegionVal* MR = dyn_cast<loc::MemRegionVal>(&V)) {
        if (GetArgE(Summ, idx) == DoNothingByRef)
          continue;
        
        // Invalidate the value of the variable passed by reference.
        
        // FIXME: Either this logic should also be replicated in GRSimpleVals
        //  or should be pulled into a separate "constraint engine."
        
        // FIXME: We can have collisions on the conjured symbol if the
        //  expression *I also creates conjured symbols.  We probably want
        //  to identify conjured symbols by an expression pair: the enclosing
        //  expression (the context) and the expression itself.  This should
        //  disambiguate conjured symbols. 
        
        const TypedRegion* R = dyn_cast<TypedRegion>(MR->getRegion());
        
        // Blast through TypedViewRegions to get the original region type.
        while (R) {
          const TypedViewRegion* ATR = dyn_cast<TypedViewRegion>(R);
          if (!ATR) break;
          R = dyn_cast<TypedRegion>(ATR->getSuperRegion());
        }
        
        if (R) {          
          // Is the invalidated variable something that we were tracking?
          SymbolRef Sym = state.GetSValAsScalarOrLoc(R).getAsLocSymbol();
          
          // Remove any existing reference-count binding.
          if (Sym) state = state.remove<RefBindings>(Sym);
          
          if (R->isBoundable(Ctx)) {
            // Set the value of the variable to be a conjured symbol.
            unsigned Count = Builder.getCurrentBlockCount();
            QualType T = R->getRValueType(Ctx);
          
            if (Loc::IsLocType(T) || (T->isIntegerType() && T->isScalarType())){
              ValueManager &ValMgr = Eng.getValueManager();
              SVal V = ValMgr.getConjuredSymbolVal(*I, T, Count);
              state = state.BindLoc(Loc::MakeVal(R), V);
            }
            else if (const RecordType *RT = T->getAsStructureType()) {
              // Handle structs in a not so awesome way.  Here we just
              // eagerly bind new symbols to the fields.  In reality we
              // should have the store manager handle this.  The idea is just
              // to prototype some basic functionality here.  All of this logic
              // should one day soon just go away.
              const RecordDecl *RD = RT->getDecl()->getDefinition(Ctx);
              
              // No record definition.  There is nothing we can do.
              if (!RD)
                continue;
              
              MemRegionManager &MRMgr = state.getManager().getRegionManager();
              
              // Iterate through the fields and construct new symbols.
              for (RecordDecl::field_iterator FI=RD->field_begin(Ctx),
                   FE=RD->field_end(Ctx); FI!=FE; ++FI) {
                
                // For now just handle scalar fields.
                FieldDecl *FD = *FI;
                QualType FT = FD->getType();
                
                if (Loc::IsLocType(FT) || 
                    (FT->isIntegerType() && FT->isScalarType())) {                  
                  const FieldRegion* FR = MRMgr.getFieldRegion(FD, R);
                  ValueManager &ValMgr = Eng.getValueManager();
                  SVal V = ValMgr.getConjuredSymbolVal(*I, FT, Count);
                  state = state.BindLoc(Loc::MakeVal(FR), V);
                }                
              }
            }
            else {
              // Just blast away other values.
              state = state.BindLoc(*MR, UnknownVal());
            }
          }
        }
        else
          state = state.BindLoc(*MR, UnknownVal());
      }
      else {
        // Nuke all other arguments passed by reference.
        state = state.Unbind(cast<Loc>(V));
      }
    }
    else if (isa<nonloc::LocAsInteger>(V))
      state = state.Unbind(cast<nonloc::LocAsInteger>(V).getLoc());
  } 
  
  // Evaluate the effect on the message receiver.  
  if (!ErrorExpr && Receiver) {
    SymbolRef Sym = state.GetSValAsScalarOrLoc(Receiver).getAsLocSymbol();
    if (Sym) {
      if (const RefVal* T = state.get<RefBindings>(Sym)) {
        state = Update(state, Sym, *T, GetReceiverE(Summ), hasErr);
        if (hasErr) {
          ErrorExpr = Receiver;
          ErrorSym = Sym;
        }
      }
    }
  }
  
  // Process any errors.  
  if (hasErr) {
    ProcessNonLeakError(Dst, Builder, Ex, ErrorExpr, Pred, state,
                        hasErr, ErrorSym);
    return;
  }
  
  // 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.
      
      // FIXME: We eventually should handle structs and other compound types
      // that are returned by value.
      
      QualType T = Ex->getType();
      
      if (Loc::IsLocType(T) || (T->isIntegerType() && T->isScalarType())) {
        unsigned Count = Builder.getCurrentBlockCount();
        ValueManager &ValMgr = Eng.getValueManager();
        SVal X = ValMgr.getConjuredSymbolVal(Ex, T, Count);
        state = state.BindExpr(Ex, X, false);
      }      
      
      break;
    }
      
    case RetEffect::Alias: {
      unsigned idx = RE.getIndex();
      assert (arg_end >= arg_beg);
      assert (idx < (unsigned) (arg_end - arg_beg));
      SVal V = state.GetSValAsScalarOrLoc(*(arg_beg+idx));
      state = state.BindExpr(Ex, V, false);
      break;
    }
      
    case RetEffect::ReceiverAlias: {
      assert (Receiver);
      SVal V = state.GetSValAsScalarOrLoc(Receiver);
      state = state.BindExpr(Ex, V, false);
      break;
    }
      
    case RetEffect::OwnedAllocatedSymbol:
    case RetEffect::OwnedSymbol: {
      unsigned Count = Builder.getCurrentBlockCount();
      ValueManager &ValMgr = Eng.getValueManager();      
      SymbolRef Sym = ValMgr.getConjuredSymbol(Ex, Count);
      QualType RetT = GetReturnType(Ex, ValMgr.getContext());      
      state = state.set<RefBindings>(Sym, RefVal::makeOwned(RE.getObjKind(),
                                                            RetT));
      state = state.BindExpr(Ex, ValMgr.makeRegionVal(Sym), false);

      // FIXME: Add a flag to the checker where allocations are assumed to
      // *not fail.
#if 0
      if (RE.getKind() == RetEffect::OwnedAllocatedSymbol) {
        bool isFeasible;
        state = state.Assume(loc::SymbolVal(Sym), true, isFeasible);
        assert(isFeasible && "Cannot assume fresh symbol is non-null.");        
      }
#endif
      
      break;
    }
      
    case RetEffect::NotOwnedSymbol: {
      unsigned Count = Builder.getCurrentBlockCount();
      ValueManager &ValMgr = Eng.getValueManager();
      SymbolRef Sym = ValMgr.getConjuredSymbol(Ex, Count);
      QualType RetT = GetReturnType(Ex, ValMgr.getContext());      
      state = state.set<RefBindings>(Sym, RefVal::makeNotOwned(RE.getObjKind(),
                                                               RetT));
      state = state.BindExpr(Ex, ValMgr.makeRegionVal(Sym), false);
      break;
    }
  }
  
  // Generate a sink node if we are at the end of a path.
  GRExprEngine::NodeTy *NewNode =
    IsEndPath(Summ) ? Builder.MakeSinkNode(Dst, Ex, Pred, state)
                    : Builder.MakeNode(Dst, Ex, Pred, state);
  
  // Annotate the edge with summary we used.
  // FIXME: This assumes that we always use the same summary when generating
  //  this node.
  if (NewNode) SummaryLog[NewNode] = Summ;
}


void CFRefCount::EvalCall(ExplodedNodeSet<GRState>& Dst,
                          GRExprEngine& Eng,
                          GRStmtNodeBuilder<GRState>& Builder,
                          CallExpr* CE, SVal L,
                          ExplodedNode<GRState>* Pred) {
  const FunctionDecl* FD = L.getAsFunctionDecl();
  RetainSummary* Summ = !FD ? 0 
                        : Summaries.getSummary(const_cast<FunctionDecl*>(FD));
  
  EvalSummary(Dst, Eng, Builder, CE, 0, Summ,
              CE->arg_begin(), CE->arg_end(), Pred);
}

void CFRefCount::EvalObjCMessageExpr(ExplodedNodeSet<GRState>& Dst,
                                     GRExprEngine& Eng,
                                     GRStmtNodeBuilder<GRState>& Builder,
                                     ObjCMessageExpr* ME,
                                     ExplodedNode<GRState>* Pred) {  
  RetainSummary* Summ;
  
  if (Expr* Receiver = ME->getReceiver()) {
    // We need the type-information of the tracked receiver object
    // Retrieve it from the state.
    ObjCInterfaceDecl* ID = 0;

    // FIXME: Wouldn't it be great if this code could be reduced?  It's just
    // a chain of lookups.
    const GRState* St = Builder.GetState(Pred);
    SVal V = Eng.getStateManager().GetSValAsScalarOrLoc(St, Receiver);

    SymbolRef Sym = V.getAsLocSymbol();
    if (Sym) {
      if (const RefVal* T  = St->get<RefBindings>(Sym)) {
        QualType Ty = T->getType();
        
        if (const PointerType* PT = Ty->getAsPointerType()) {
          QualType PointeeTy = PT->getPointeeType();
          
          if (ObjCInterfaceType* IT = dyn_cast<ObjCInterfaceType>(PointeeTy))
            ID = IT->getDecl();
        }
      }
    }
    
    Summ = Summaries.getMethodSummary(ME, ID);

    // Special-case: are we sending a mesage to "self"?
    //  This is a hack.  When we have full-IP this should be removed.
    if (!Summ) {
      ObjCMethodDecl* MD = 
        dyn_cast<ObjCMethodDecl>(&Eng.getGraph().getCodeDecl());
      
      if (MD) {
        if (Expr* Receiver = ME->getReceiver()) {
          SVal X = Eng.getStateManager().GetSValAsScalarOrLoc(St, Receiver);
          if (loc::MemRegionVal* L = dyn_cast<loc::MemRegionVal>(&X))
            if (L->getRegion() == Eng.getStateManager().getSelfRegion(St)) {
              // Create a summmary where all of the arguments "StopTracking".
              Summ = Summaries.getPersistentSummary(RetEffect::MakeNoRet(),
                                                    DoNothing,
                                                    StopTracking);
            }
        }
      }
    }
  }
  else
    Summ = Summaries.getClassMethodSummary(ME);


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

namespace {
class VISIBILITY_HIDDEN StopTrackingCallback : public SymbolVisitor {
  GRStateRef state;
public:
  StopTrackingCallback(GRStateRef st) : state(st) {}
  GRStateRef getState() { return state; }

  bool VisitSymbol(SymbolRef sym) {
    state = state.remove<RefBindings>(sym);
    return true;
  }
  
  const GRState* getState() const { return state.getState(); }
};
} // end anonymous namespace
  

void CFRefCount::EvalBind(GRStmtNodeBuilderRef& B, SVal location, SVal val) {  
  // Are we storing to something that causes the value to "escape"?  
  bool escapes = false;
  
  // A value escapes in three possible cases (this may change):
  //
  // (1) we are binding to something that is not a memory region.
  // (2) we are binding to a memregion that does not have stack storage
  // (3) we are binding to a memregion with stack storage that the store
  //     does not understand.  
  GRStateRef state = B.getState();

  if (!isa<loc::MemRegionVal>(location))
    escapes = true;
  else {
    const MemRegion* R = cast<loc::MemRegionVal>(location).getRegion();
    escapes = !B.getStateManager().hasStackStorage(R);
    
    if (!escapes) {
      // To test (3), generate a new state with the binding removed.  If it is
      // the same state, then it escapes (since the store cannot represent
      // the binding).
      escapes = (state == (state.BindLoc(cast<Loc>(location), UnknownVal())));
    }
  }

  // If our store can represent the binding and we aren't storing to something
  // that doesn't have local storage then just return and have the simulation
  // state continue as is.
  if (!escapes)
      return;

  // Otherwise, find all symbols referenced by 'val' that we are tracking
  // and stop tracking them.
  B.MakeNode(state.scanReachableSymbols<StopTrackingCallback>(val).getState());
}

std::pair<GRStateRef,bool>
CFRefCount::HandleSymbolDeath(GRStateManager& VMgr,
                              const GRState* St, const Decl* CD,
                              SymbolRef sid,
                              RefVal V, bool& hasLeak) {

  GRStateRef state(St, VMgr);
  assert ((!V.isReturnedOwned() || CD) &&
          "CodeDecl must be available for reporting ReturnOwned errors.");

  if (V.isReturnedOwned() && V.getCount() == 0)
    if (const ObjCMethodDecl* MD = dyn_cast<ObjCMethodDecl>(CD)) {
      std::string s = MD->getSelector().getAsString();
      if (!followsReturnRule(s.c_str())) {
        hasLeak = true;
        state = state.set<RefBindings>(sid, V ^ RefVal::ErrorLeakReturned);
        return std::make_pair(state, true);
      }
    }
  
  // All other cases.
  
  hasLeak = V.isOwned() || 
            ((V.isNotOwned() || V.isReturnedOwned()) && V.getCount() > 0);

  if (!hasLeak)
    return std::make_pair(state.remove<RefBindings>(sid), false);
  
  return std::make_pair(state.set<RefBindings>(sid, V ^ RefVal::ErrorLeak),
                        false);
}



// Dead symbols.



 // Return statements.

void CFRefCount::EvalReturn(ExplodedNodeSet<GRState>& Dst,
                            GRExprEngine& Eng,
                            GRStmtNodeBuilder<GRState>& Builder,
                            ReturnStmt* S,
                            ExplodedNode<GRState>* Pred) {
  
  Expr* RetE = S->getRetValue();
  if (!RetE)
    return;
  
  GRStateRef state(Builder.GetState(Pred), Eng.getStateManager());
  SymbolRef Sym = state.GetSValAsScalarOrLoc(RetE).getAsLocSymbol();
  
  if (!Sym)
    return;

  // Get the reference count binding (if any).
  const RefVal* T = state.get<RefBindings>(Sym);
  
  if (!T)
    return;
  
  // Change the reference count.  
  RefVal X = *T;  
  
  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.
  state = state.set<RefBindings>(Sym, X);
  Builder.MakeNode(Dst, S, Pred, state);
}

// Assumptions.

const GRState* CFRefCount::EvalAssume(GRStateManager& VMgr,
                                         const GRState* St,
                                         SVal 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 = St->get<RefBindings>();
  
  if (B.isEmpty())
    return St;
  
  bool changed = false;
  
  GRStateRef state(St, VMgr);
  RefBindings::Factory& RefBFactory = state.get_context<RefBindings>();

  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 (VMgr.getSymVal(St, I.getKey())) {
      changed = true;
      B = RefBFactory.Remove(B, I.getKey());
    }
  }
  
  if (changed)
    state = state.set<RefBindings>(B);
  
  return state;
}

GRStateRef CFRefCount::Update(GRStateRef state, SymbolRef sym,
                              RefVal V, ArgEffect E,
                              RefVal::Kind& hasErr) {

  // In GC mode [... release] and [... retain] do nothing.
  switch (E) {
    default: break;
    case IncRefMsg: E = isGCEnabled() ? DoNothing : IncRef; break;
    case DecRefMsg: E = isGCEnabled() ? DoNothing : DecRef; break;
    case MakeCollectable: E = isGCEnabled() ? DecRef : DoNothing; break;
    case NewAutoreleasePool: E = isGCEnabled() ? DoNothing : 
                                                 NewAutoreleasePool; break;
  }
  
  // Handle all use-after-releases.
  if (!isGCEnabled() && V.getKind() == RefVal::Released) {
    V = V ^ RefVal::ErrorUseAfterRelease;
    hasErr = V.getKind();
    return state.set<RefBindings>(sym, V);
  }      
  
  switch (E) {
    default:
      assert (false && "Unhandled CFRef transition.");
      
    case Dealloc:
      // Any use of -dealloc in GC is *bad*.
      if (isGCEnabled()) {
        V = V ^ RefVal::ErrorDeallocGC;
        hasErr = V.getKind();
        break;
      }
      
      switch (V.getKind()) {
        default:
          assert(false && "Invalid case.");
        case RefVal::Owned:
          // The object immediately transitions to the released state.
          V = V ^ RefVal::Released;
          V.clearCounts();
          return state.set<RefBindings>(sym, V);
        case RefVal::NotOwned:
          V = V ^ RefVal::ErrorDeallocNotOwned;
          hasErr = V.getKind();
          break;
      }      
      break;

    case NewAutoreleasePool:
      assert(!isGCEnabled());
      return state.add<AutoreleaseStack>(sym);
      
    case MayEscape:
      if (V.getKind() == RefVal::Owned) {
        V = V ^ RefVal::NotOwned;
        break;
      }

      // Fall-through.
      
    case DoNothingByRef:
    case DoNothing:
      return state;

    case Autorelease:
      if (isGCEnabled())
        return state;
      
      // Update the autorelease counts.
      state = SendAutorelease(state, ARCountFactory, sym);

      // Fall-through.
      
    case StopTracking:
      return state.remove<RefBindings>(sym);

    case IncRef:      
      switch (V.getKind()) {
        default:
          assert(false);

        case RefVal::Owned:
        case RefVal::NotOwned:
          V = V + 1;
          break;          
        case RefVal::Released:
          // Non-GC cases are handled above.
          assert(isGCEnabled());
          V = (V ^ RefVal::Owned) + 1;
          break;
      }      
      break;
      
    case SelfOwn:
      V = V ^ RefVal::NotOwned;
      // Fall-through.
    case DecRef:
      switch (V.getKind()) {
        default:
          // case 'RefVal::Released' handled above.
          assert (false);

        case RefVal::Owned:
          assert(V.getCount() > 0);
          if (V.getCount() == 1) V = V ^ RefVal::Released;
          V = V - 1;
          break;
          
        case RefVal::NotOwned:
          if (V.getCount() > 0)
            V = V - 1;
          else {
            V = V ^ RefVal::ErrorReleaseNotOwned;
            hasErr = V.getKind();
          }          
          break;
          
        case RefVal::Released:
          // Non-GC cases are handled above.
          assert(isGCEnabled());
          V = V ^ RefVal::ErrorUseAfterRelease;
          hasErr = V.getKind();
          break;  
      }      
      break;
  }
  return state.set<RefBindings>(sym, V);
}

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

namespace {
  
  //===-------------===//
  // Bug Descriptions. //
  //===-------------===//  
  
  class VISIBILITY_HIDDEN CFRefBug : public BugType {
  protected:
    CFRefCount& TF;

    CFRefBug(CFRefCount* tf, const char* name) 
      : BugType(name, "Memory (Core Foundation/Objective-C)"), TF(*tf) {}    
  public:
    
    CFRefCount& getTF() { return TF; }
    const CFRefCount& getTF() const { return TF; }

    // FIXME: Eventually remove.
    virtual const char* getDescription() const = 0;
    
    virtual bool isLeak() const { return false; }
  };
  
  class VISIBILITY_HIDDEN UseAfterRelease : public CFRefBug {
  public:
    UseAfterRelease(CFRefCount* tf)
      : CFRefBug(tf, "Use-after-release") {}
    
    const char* getDescription() const {
      return "Reference-counted object is used after it is released";
    }    
  };
  
  class VISIBILITY_HIDDEN BadRelease : public CFRefBug {
  public:
    BadRelease(CFRefCount* tf) : CFRefBug(tf, "Bad release") {}

    const char* getDescription() const {
      return "Incorrect decrement of the reference count of an "
             "object is not owned at this point by the caller";
    }
  };
  
  class VISIBILITY_HIDDEN DeallocGC : public CFRefBug {
  public:
    DeallocGC(CFRefCount *tf) : CFRefBug(tf,
                                         "-dealloc called while using GC") {}
    
    const char *getDescription() const {
      return "-dealloc called while using GC";
    }
  };
  
  class VISIBILITY_HIDDEN DeallocNotOwned : public CFRefBug {
  public:
    DeallocNotOwned(CFRefCount *tf) : CFRefBug(tf,
                            "-dealloc sent to non-exclusively owned object") {}
    
    const char *getDescription() const {
      return "-dealloc sent to object that may be referenced elsewhere";
    }
  };  
  
  class VISIBILITY_HIDDEN Leak : public CFRefBug {
    const bool isReturn;
  protected:
    Leak(CFRefCount* tf, const char* name, bool isRet)
      : CFRefBug(tf, name), isReturn(isRet) {}
  public:
    
    const char* getDescription() const { return ""; }

    bool isLeak() const { return true; }
  };
    
  class VISIBILITY_HIDDEN LeakAtReturn : public Leak {
  public:
    LeakAtReturn(CFRefCount* tf, const char* name)
      : Leak(tf, name, true) {}
  };
  
  class VISIBILITY_HIDDEN LeakWithinFunction : public Leak {
  public:
    LeakWithinFunction(CFRefCount* tf, const char* name)
      : Leak(tf, name, false) {}
  };  
  
  //===---------===//
  // Bug Reports.  //
  //===---------===//
  
  class VISIBILITY_HIDDEN CFRefReport : public RangedBugReport {
  protected:
    SymbolRef Sym;
    const CFRefCount &TF;
  public:
    CFRefReport(CFRefBug& D, const CFRefCount &tf,
                ExplodedNode<GRState> *n, SymbolRef sym)
      : RangedBugReport(D, D.getDescription(), n), Sym(sym), TF(tf) {}
        
    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 = end = 0;
    }
    
    SymbolRef getSymbol() const { return Sym; }
    
    PathDiagnosticPiece* getEndPath(BugReporter& BR,
                                    const ExplodedNode<GRState>* N);
    
    std::pair<const char**,const char**> getExtraDescriptiveText();
    
    PathDiagnosticPiece* VisitNode(const ExplodedNode<GRState>* N,
                                   const ExplodedNode<GRState>* PrevN,
                                   const ExplodedGraph<GRState>& G,
                                   BugReporter& BR,
                                   NodeResolver& NR);
  };
  
  class VISIBILITY_HIDDEN CFRefLeakReport : public CFRefReport {
    SourceLocation AllocSite;
    const MemRegion* AllocBinding;
  public:
    CFRefLeakReport(CFRefBug& D, const CFRefCount &tf,
                    ExplodedNode<GRState> *n, SymbolRef sym,
                    GRExprEngine& Eng);

    PathDiagnosticPiece* getEndPath(BugReporter& BR,
                                    const ExplodedNode<GRState>* N);

    SourceLocation getLocation() const { return AllocSite; }
  };  
} // end anonymous namespace

void CFRefCount::RegisterChecks(BugReporter& BR) {
  useAfterRelease = new UseAfterRelease(this);
  BR.Register(useAfterRelease);
  
  releaseNotOwned = new BadRelease(this);
  BR.Register(releaseNotOwned);
  
  deallocGC = new DeallocGC(this);
  BR.Register(deallocGC);
  
  deallocNotOwned = new DeallocNotOwned(this);
  BR.Register(deallocNotOwned);
  
  // First register "return" leaks.
  const char* name = 0;
  
  if (isGCEnabled())
    name = "Leak of returned object when using garbage collection";
  else if (getLangOptions().getGCMode() == LangOptions::HybridGC)
    name = "Leak of returned object when not using garbage collection (GC) in "
           "dual GC/non-GC code";
  else {
    assert(getLangOptions().getGCMode() == LangOptions::NonGC);
    name = "Leak of returned object";
  }
  
  leakAtReturn = new LeakAtReturn(this, name);
  BR.Register(leakAtReturn);

  // Second, register leaks within a function/method.
  if (isGCEnabled())
    name = "Leak of object when using garbage collection";  
  else if (getLangOptions().getGCMode() == LangOptions::HybridGC)
    name = "Leak of object when not using garbage collection (GC) in "
           "dual GC/non-GC code";
  else {
    assert(getLangOptions().getGCMode() == LangOptions::NonGC);
    name = "Leak";
  }
  
  leakWithinFunction = new LeakWithinFunction(this, name);
  BR.Register(leakWithinFunction);
  
  // Save the reference to the BugReporter.
  this->BR = &BR;
}

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

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);
  }
}

static inline bool contains(const llvm::SmallVectorImpl<ArgEffect>& V,
                              ArgEffect X) {
  for (llvm::SmallVectorImpl<ArgEffect>::const_iterator I=V.begin(), E=V.end();
        I!=E; ++I)
    if (*I == X) return true;
  
  return false;
}

PathDiagnosticPiece* CFRefReport::VisitNode(const ExplodedNode<GRState>* N,
                                            const ExplodedNode<GRState>* PrevN,
                                            const ExplodedGraph<GRState>& G,
                                            BugReporter& BR,
                                            NodeResolver& NR) {

  // Check if the type state has changed.  
  GRStateManager &StMgr = cast<GRBugReporter>(BR).getStateManager();
  GRStateRef PrevSt(PrevN->getState(), StMgr);
  GRStateRef CurrSt(N->getState(), StMgr);

  const RefVal* CurrT = CurrSt.get<RefBindings>(Sym);  
  if (!CurrT) return NULL;

  const RefVal& CurrV = *CurrT;
  const RefVal* PrevT = PrevSt.get<RefBindings>(Sym);

  // Create a string buffer to constain all the useful things we want
  // to tell the user.
  std::string sbuf;
  llvm::raw_string_ostream os(sbuf);

  // This is the allocation site since the previous node had no bindings
  // for this symbol.
  if (!PrevT) {
    Stmt* S = cast<PostStmt>(N->getLocation()).getStmt();

    if (CallExpr *CE = dyn_cast<CallExpr>(S)) {
      // Get the name of the callee (if it is available).
      SVal X = CurrSt.GetSValAsScalarOrLoc(CE->getCallee());
      if (const FunctionDecl* FD = X.getAsFunctionDecl())
        os << "Call to function '" << FD->getNameAsString() <<'\'';
      else
        os << "function call";      
    }          
    else {
      assert (isa<ObjCMessageExpr>(S));
      os << "Method";
    }
    
    if (CurrV.getObjKind() == RetEffect::CF) {
      os << " returns a Core Foundation object with a ";
    }
    else {
      assert (CurrV.getObjKind() == RetEffect::ObjC);
      os << " returns an Objective-C object with a ";
    }
    
    if (CurrV.isOwned()) {
      os << "+1 retain count (owning reference).";
      
      if (static_cast<CFRefBug&>(getBugType()).getTF().isGCEnabled()) {
        assert(CurrV.getObjKind() == RetEffect::CF);
        os << "  "
          "Core Foundation objects are not automatically garbage collected.";
      }
    }
    else {
      assert (CurrV.isNotOwned());
      os << "+0 retain count (non-owning reference).";
    }
    
    PathDiagnosticLocation Pos(S, BR.getContext().getSourceManager());
    return new PathDiagnosticEventPiece(Pos, os.str());
  }
  
  // Gather up the effects that were performed on the object at this
  // program point
  llvm::SmallVector<ArgEffect, 2> AEffects;

  if (const RetainSummary *Summ = TF.getSummaryOfNode(NR.getOriginalNode(N))) {
    // We only have summaries attached to nodes after evaluating CallExpr and
    // ObjCMessageExprs.
    Stmt* S = cast<PostStmt>(N->getLocation()).getStmt();
    
    if (CallExpr *CE = dyn_cast<CallExpr>(S)) {
      // Iterate through the parameter expressions and see if the symbol
      // was ever passed as an argument.
      unsigned i = 0;
      
      for (CallExpr::arg_iterator AI=CE->arg_begin(), AE=CE->arg_end();
           AI!=AE; ++AI, ++i) {
        
        // Retrieve the value of the argument.  Is it the symbol
        // we are interested in?
        if (CurrSt.GetSValAsScalarOrLoc(*AI).getAsLocSymbol() != Sym)
          continue;

        // We have an argument.  Get the effect!
        AEffects.push_back(Summ->getArg(i));
      }
    }
    else if (ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(S)) {      
      if (Expr *receiver = ME->getReceiver())
        if (CurrSt.GetSValAsScalarOrLoc(receiver).getAsLocSymbol() == Sym) {
          // The symbol we are tracking is the receiver.
          AEffects.push_back(Summ->getReceiverEffect());
        }
    }
  }
  
  do {
    // Get the previous type state.
    RefVal PrevV = *PrevT;
    
    // Specially handle -dealloc.
    if (!TF.isGCEnabled() && contains(AEffects, Dealloc)) {
      // Determine if the object's reference count was pushed to zero.
      assert(!(PrevV == CurrV) && "The typestate *must* have changed.");
      // We may not have transitioned to 'release' if we hit an error.
      // This case is handled elsewhere.
      if (CurrV.getKind() == RefVal::Released) {
        assert(CurrV.getCount() == 0);
        os << "Object released by directly sending the '-dealloc' message";
        break;
      }
    }

    // Specially handle CFMakeCollectable and friends.
    if (contains(AEffects, MakeCollectable)) {
      // Get the name of the function.
      Stmt* S = cast<PostStmt>(N->getLocation()).getStmt();
      SVal X = CurrSt.GetSValAsScalarOrLoc(cast<CallExpr>(S)->getCallee());
      const FunctionDecl* FD = X.getAsFunctionDecl();
      const std::string& FName = FD->getNameAsString();
      
      if (TF.isGCEnabled()) {
        // Determine if the object's reference count was pushed to zero.
        assert(!(PrevV == CurrV) && "The typestate *must* have changed.");
        
        os << "In GC mode a call to '" << FName
           <<  "' decrements an object's retain count and registers the "
               "object with the garbage collector. ";

        if (CurrV.getKind() == RefVal::Released) {
          assert(CurrV.getCount() == 0);
          os << "Since it now has a 0 retain count the object can be "
                "automatically collected by the garbage collector.";
        }
        else
          os << "An object must have a 0 retain count to be garbage collected. "
                "After this call its retain count is +" << CurrV.getCount()
             << '.';
      }
      else 
        os << "When GC is not enabled a call to '" << FName
           << "' has no effect on its argument.";

      // Nothing more to say.
      break;
    }

    // Determine if the typestate has changed.  
    if (!(PrevV == CurrV))
      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 << " The object now has a +" << Count << " retain count.";
          
        if (PrevV.getKind() == RefVal::Released) {
          assert(TF.isGCEnabled() && CurrV.getCount() > 0);
          os << " The object is not eligible for garbage collection until the "
                "retain count reaches 0 again.";
        }
          
        break;
        
      case RefVal::Released:
        os << "Object released.";
        break;
        
      case RefVal::ReturnedOwned:
        os << "Object returned to caller as an owning reference (single retain "
              "count transferred to caller).";
        break;
        
      case RefVal::ReturnedNotOwned:
        os << "Object returned to caller with a +0 (non-owning) retain count.";
        break;

      default:
        return NULL;
      }
    
    // Emit any remaining diagnostics for the argument effects (if any).
    for (llvm::SmallVectorImpl<ArgEffect>::iterator I=AEffects.begin(),
         E=AEffects.end(); I != E; ++I) {
      
      // A bunch of things have alternate behavior under GC.
      if (TF.isGCEnabled())
        switch (*I) {
          default: break;
          case Autorelease:
            os << "In GC mode an 'autorelease' has no effect.";
            continue;
          case IncRefMsg:
            os << "In GC mode the 'retain' message has no effect.";
            continue;
          case DecRefMsg:
            os << "In GC mode the 'release' message has no effect.";
            continue;
        }
    }
  } while(0);

  if (os.str().empty())
    return 0; // We have nothing to say!
  
  Stmt* S = cast<PostStmt>(N->getLocation()).getStmt();    
  PathDiagnosticLocation Pos(S, BR.getContext().getSourceManager());
  PathDiagnosticPiece* P = new PathDiagnosticEventPiece(Pos, os.str());
  
  // Add the range by scanning the children of the statement for any bindings
  // to Sym.
  for (Stmt::child_iterator I = S->child_begin(), E = S->child_end(); I!=E; ++I)
    if (Expr* Exp = dyn_cast_or_null<Expr>(*I))
      if (CurrSt.GetSValAsScalarOrLoc(Exp).getAsLocSymbol() == Sym) {
        P->addRange(Exp->getSourceRange());
        break;
      }
  
  return P;
}

namespace {
class VISIBILITY_HIDDEN FindUniqueBinding :
  public StoreManager::BindingsHandler {
    SymbolRef Sym;
    const MemRegion* Binding;
    bool First;
    
  public:
    FindUniqueBinding(SymbolRef sym) : Sym(sym), Binding(0), First(true) {}
    
  bool HandleBinding(StoreManager& SMgr, Store store, const MemRegion* R,
                     SVal val) {

    SymbolRef SymV = val.getAsSymbol();    
    if (!SymV || SymV != Sym)
      return true;
    
    if (Binding) {
      First = false;
      return false;
    }
    else
      Binding = R;
    
    return true;    
  }
    
  operator bool() { return First && Binding; }
  const MemRegion* getRegion() { return Binding; }
};  
}

static std::pair<const ExplodedNode<GRState>*,const MemRegion*>
GetAllocationSite(GRStateManager& StateMgr, const ExplodedNode<GRState>* N,
                  SymbolRef Sym) {

  // Find both first node that referred to the tracked symbol and the
  // memory location that value was store to.
  const ExplodedNode<GRState>* Last = N;
  const MemRegion* FirstBinding = 0;  
  
  while (N) {
    const GRState* St = N->getState();
    RefBindings B = St->get<RefBindings>();
    
    if (!B.lookup(Sym))
      break;

    FindUniqueBinding FB(Sym);
    StateMgr.iterBindings(St, FB);      
    if (FB) FirstBinding = FB.getRegion();      
    
    Last = N;
    N = N->pred_empty() ? NULL : *(N->pred_begin());    
  }
  
  return std::make_pair(Last, FirstBinding);
}

PathDiagnosticPiece*
CFRefReport::getEndPath(BugReporter& br, const ExplodedNode<GRState>* EndN) {
  // Tell the BugReporter to report cases when the tracked symbol is
  // assigned to different variables, etc.
  GRBugReporter& BR = cast<GRBugReporter>(br);
  cast<GRBugReporter>(BR).addNotableSymbol(Sym);
  return RangedBugReport::getEndPath(BR, EndN);
}

PathDiagnosticPiece*
CFRefLeakReport::getEndPath(BugReporter& br, const ExplodedNode<GRState>* EndN){

  GRBugReporter& BR = cast<GRBugReporter>(br);
  // Tell the BugReporter to report cases when the tracked symbol is
  // assigned to different variables, etc.
  cast<GRBugReporter>(BR).addNotableSymbol(Sym);
    
  // We are reporting a leak.  Walk up the graph to get to the first node where
  // the symbol appeared, and also get the first VarDecl that tracked object
  // is stored to.
  const ExplodedNode<GRState>* AllocNode = 0;
  const MemRegion* FirstBinding = 0;

  llvm::tie(AllocNode, FirstBinding) =
    GetAllocationSite(BR.getStateManager(), EndN, Sym);
  
  // Get the allocate site.  
  assert(AllocNode);
  Stmt* FirstStmt = cast<PostStmt>(AllocNode->getLocation()).getStmt();

  SourceManager& SMgr = BR.getContext().getSourceManager();
  unsigned AllocLine =SMgr.getInstantiationLineNumber(FirstStmt->getLocStart());

  // Compute an actual location for the leak.  Sometimes a leak doesn't
  // occur at an actual statement (e.g., transition between blocks; end
  // of function) so we need to walk the graph and compute a real location.
  const ExplodedNode<GRState>* LeakN = EndN;
  PathDiagnosticLocation L;
  
  while (LeakN) {
    ProgramPoint P = LeakN->getLocation();
    
    if (const PostStmt *PS = dyn_cast<PostStmt>(&P)) {
      L = PathDiagnosticLocation(PS->getStmt()->getLocStart(), SMgr);
      break;
    }
    else if (const BlockEdge *BE = dyn_cast<BlockEdge>(&P)) {
      if (const Stmt* Term = BE->getSrc()->getTerminator()) {
        L = PathDiagnosticLocation(Term->getLocStart(), SMgr);
        break;
      }
    }

    LeakN = LeakN->succ_empty() ? 0 : *(LeakN->succ_begin());
  }
  
  if (!L.isValid()) {
    CompoundStmt *CS 
      = BR.getStateManager().getCodeDecl().getBody(BR.getContext());
    L = PathDiagnosticLocation(CS->getRBracLoc(), SMgr);
  }

  std::string sbuf;
  llvm::raw_string_ostream os(sbuf);
  
  os << "Object allocated on line " << AllocLine;
  
  if (FirstBinding)
    os << " and stored into '" << FirstBinding->getString() << '\'';  
  
  // Get the retain count.
  const RefVal* RV = EndN->getState()->get<RefBindings>(Sym);
  
  if (RV->getKind() == RefVal::ErrorLeakReturned) {
    // FIXME: Per comments in rdar://6320065, "create" only applies to CF
    // ojbects.  Only "copy", "alloc", "retain" and "new" transfer ownership
    // to the caller for NS objects.
    ObjCMethodDecl& MD = cast<ObjCMethodDecl>(BR.getGraph().getCodeDecl());
    os << " is returned from a method whose name ('"
       << MD.getSelector().getAsString()
       << "') does not contain 'copy' or otherwise starts with"
          " 'new' or 'alloc'.  This violates the naming convention rules given"
          " in the Memory Management Guide for Cocoa (object leaked).";
  }
  else
    os << " is no longer referenced after this point and has a retain count of"
          " +"
       << RV->getCount() << " (object leaked).";
  
  return new PathDiagnosticEventPiece(L, os.str());
}


CFRefLeakReport::CFRefLeakReport(CFRefBug& D, const CFRefCount &tf,
                                 ExplodedNode<GRState> *n,
                                 SymbolRef sym, GRExprEngine& Eng)
  : CFRefReport(D, tf, n, sym)
{
  
  // Most bug reports are cached at the location where they occured.
  // With leaks, we want to unique them by the location where they were
  // allocated, and only report a single path.  To do this, we need to find
  // the allocation site of a piece of tracked memory, which we do via a
  // call to GetAllocationSite.  This will walk the ExplodedGraph backwards.
  // Note that this is *not* the trimmed graph; we are guaranteed, however,
  // that all ancestor nodes that represent the allocation site have the
  // same SourceLocation.
  const ExplodedNode<GRState>* AllocNode = 0;
  
  llvm::tie(AllocNode, AllocBinding) =  // Set AllocBinding.
    GetAllocationSite(Eng.getStateManager(), getEndNode(), getSymbol());

  // Get the SourceLocation for the allocation site.
  ProgramPoint P = AllocNode->getLocation();
  AllocSite = cast<PostStmt>(P).getStmt()->getLocStart();
    
  // Fill in the description of the bug.
  Description.clear();
  llvm::raw_string_ostream os(Description);
  SourceManager& SMgr = Eng.getContext().getSourceManager();
  unsigned AllocLine = SMgr.getInstantiationLineNumber(AllocSite);
  os << "Potential leak of object allocated on line " << AllocLine;
  
  // FIXME: AllocBinding doesn't get populated for RegionStore yet.
  if (AllocBinding)
    os << " and stored into '" << AllocBinding->getString() << '\'';
}

//===----------------------------------------------------------------------===//
// Handle dead symbols and end-of-path.
//===----------------------------------------------------------------------===//

void CFRefCount::EvalEndPath(GRExprEngine& Eng,
                             GREndPathNodeBuilder<GRState>& Builder) {
  
  const GRState* St = Builder.getState();
  RefBindings B = St->get<RefBindings>();
  
  llvm::SmallVector<std::pair<SymbolRef, bool>, 10> Leaked;
  const Decl* CodeDecl = &Eng.getGraph().getCodeDecl();
  
  for (RefBindings::iterator I = B.begin(), E = B.end(); I != E; ++I) {
    bool hasLeak = false;
    
    std::pair<GRStateRef, bool> X =
      HandleSymbolDeath(Eng.getStateManager(), St, CodeDecl,
                        (*I).first, (*I).second, hasLeak);
    
    St = X.first;
    if (hasLeak) Leaked.push_back(std::make_pair((*I).first, X.second));
  }
  
  if (Leaked.empty())
    return;
  
  ExplodedNode<GRState>* N = Builder.MakeNode(St);  
  
  if (!N)
    return;
  
  for (llvm::SmallVector<std::pair<SymbolRef,bool>, 10>::iterator
       I = Leaked.begin(), E = Leaked.end(); I != E; ++I) {
    
    CFRefBug *BT = static_cast<CFRefBug*>(I->second ? leakAtReturn 
                                                    : leakWithinFunction);
    assert(BT && "BugType not initialized.");
    CFRefLeakReport* report = new CFRefLeakReport(*BT, *this, N, I->first, Eng);
    BR->EmitReport(report);
  }
}

void CFRefCount::EvalDeadSymbols(ExplodedNodeSet<GRState>& Dst,
                                 GRExprEngine& Eng,
                                 GRStmtNodeBuilder<GRState>& Builder,
                                 ExplodedNode<GRState>* Pred,
                                 Stmt* S,
                                 const GRState* St,
                                 SymbolReaper& SymReaper) {
  
  // FIXME: a lot of copy-and-paste from EvalEndPath.  Refactor.  
  RefBindings B = St->get<RefBindings>();
  llvm::SmallVector<std::pair<SymbolRef,bool>, 10> Leaked;
  
  for (SymbolReaper::dead_iterator I = SymReaper.dead_begin(),
       E = SymReaper.dead_end(); I != E; ++I) {
    
    const RefVal* T = B.lookup(*I);
    if (!T) continue;
    
    bool hasLeak = false;
    
    std::pair<GRStateRef, bool> X
      = HandleSymbolDeath(Eng.getStateManager(), St, 0, *I, *T, hasLeak);
    
    St = X.first;
    
    if (hasLeak)
      Leaked.push_back(std::make_pair(*I,X.second));    
  }
  
  if (!Leaked.empty()) {
    // Create a new intermediate node representing the leak point.  We
    // use a special program point that represents this checker-specific
    // transition.  We use the address of RefBIndex as a unique tag for this
    // checker.  We will create another node (if we don't cache out) that
    // removes the retain-count bindings from the state.
    // NOTE: We use 'generateNode' so that it does interplay with the
    // auto-transition logic.
    ExplodedNode<GRState>* N =
      Builder.generateNode(PostStmtCustom(S, &LeakProgramPointTag), St, Pred);
  
    if (!N)
      return;

    // Generate the bug reports.
    for (llvm::SmallVectorImpl<std::pair<SymbolRef,bool> >::iterator
         I = Leaked.begin(), E = Leaked.end(); I != E; ++I) {
      
      CFRefBug *BT = static_cast<CFRefBug*>(I->second ? leakAtReturn 
                                            : leakWithinFunction);
      assert(BT && "BugType not initialized.");
      CFRefLeakReport* report = new CFRefLeakReport(*BT, *this, N,
                                                    I->first, Eng);
      BR->EmitReport(report);
    }
    
    Pred = N;
  }
  
  // Now generate a new node that nukes the old bindings.
  GRStateRef state(St, Eng.getStateManager());
  RefBindings::Factory& F = state.get_context<RefBindings>();

  for (SymbolReaper::dead_iterator I = SymReaper.dead_begin(),
        E = SymReaper.dead_end(); I!=E; ++I)
       B = F.Remove(B, *I);

  state = state.set<RefBindings>(B);
  Builder.MakeNode(Dst, S, Pred, state);
}

void CFRefCount::ProcessNonLeakError(ExplodedNodeSet<GRState>& Dst,
                                     GRStmtNodeBuilder<GRState>& Builder,
                                     Expr* NodeExpr, Expr* ErrorExpr,                        
                                     ExplodedNode<GRState>* Pred,
                                     const GRState* St,
                                     RefVal::Kind hasErr, SymbolRef Sym) {
  Builder.BuildSinks = true;
  GRExprEngine::NodeTy* N  = Builder.MakeNode(Dst, NodeExpr, Pred, St);
  
  if (!N) return;
  
  CFRefBug *BT = 0;
  
  switch (hasErr) {
    default:
      assert(false && "Unhandled error.");
      return;
    case RefVal::ErrorUseAfterRelease:
      BT = static_cast<CFRefBug*>(useAfterRelease);
      break;      
    case RefVal::ErrorReleaseNotOwned:
      BT = static_cast<CFRefBug*>(releaseNotOwned);
      break;
    case RefVal::ErrorDeallocGC:
      BT = static_cast<CFRefBug*>(deallocGC);
      break;
    case RefVal::ErrorDeallocNotOwned:
      BT = static_cast<CFRefBug*>(deallocNotOwned);
      break;
  }
    
  CFRefReport *report = new CFRefReport(*BT, *this, N, Sym);
  report->addRange(ErrorExpr->getSourceRange());
  BR->EmitReport(report);
}

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

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