StaticAnalyzer/Core/BugReporter.cpp

// BugReporter.cpp - Generate PathDiagnostics for Bugs ------------*- 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 BugReporter, a utility class for generating
//  PathDiagnostics.
//
//===----------------------------------------------------------------------===//

#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
#include "clang/AST/ASTContext.h"
#include "clang/Analysis/CFG.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ParentMap.h"
#include "clang/AST/StmtObjC.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Analysis/ProgramPoint.h"
#include "clang/StaticAnalyzer/Core/BugReporter/PathDiagnostic.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/OwningPtr.h"
#include <queue>

using namespace clang;
using namespace ento;

BugReporterVisitor::~BugReporterVisitor() {}

//===----------------------------------------------------------------------===//
// Helper routines for walking the ExplodedGraph and fetching statements.
//===----------------------------------------------------------------------===//

static inline const Stmt *GetStmt(const ProgramPoint &P) {
  if (const StmtPoint* SP = dyn_cast<StmtPoint>(&P))
    return SP->getStmt();
  else if (const BlockEdge *BE = dyn_cast<BlockEdge>(&P))
    return BE->getSrc()->getTerminator();

  return 0;
}

static inline const ExplodedNode*
GetPredecessorNode(const ExplodedNode *N) {
  return N->pred_empty() ? NULL : *(N->pred_begin());
}

static inline const ExplodedNode*
GetSuccessorNode(const ExplodedNode *N) {
  return N->succ_empty() ? NULL : *(N->succ_begin());
}

static const Stmt *GetPreviousStmt(const ExplodedNode *N) {
  for (N = GetPredecessorNode(N); N; N = GetPredecessorNode(N))
    if (const Stmt *S = GetStmt(N->getLocation()))
      return S;

  return 0;
}

static const Stmt *GetNextStmt(const ExplodedNode *N) {
  for (N = GetSuccessorNode(N); N; N = GetSuccessorNode(N))
    if (const Stmt *S = GetStmt(N->getLocation())) {
      // Check if the statement is '?' or '&&'/'||'.  These are "merges",
      // not actual statement points.
      switch (S->getStmtClass()) {
        case Stmt::ChooseExprClass:
        case Stmt::BinaryConditionalOperatorClass: continue;
        case Stmt::ConditionalOperatorClass: continue;
        case Stmt::BinaryOperatorClass: {
          BinaryOperatorKind Op = cast<BinaryOperator>(S)->getOpcode();
          if (Op == BO_LAnd || Op == BO_LOr)
            continue;
          break;
        }
        default:
          break;
      }
      return S;
    }

  return 0;
}

static inline const Stmt*
GetCurrentOrPreviousStmt(const ExplodedNode *N) {
  if (const Stmt *S = GetStmt(N->getLocation()))
    return S;

  return GetPreviousStmt(N);
}

static inline const Stmt*
GetCurrentOrNextStmt(const ExplodedNode *N) {
  if (const Stmt *S = GetStmt(N->getLocation()))
    return S;

  return GetNextStmt(N);
}

//===----------------------------------------------------------------------===//
// PathDiagnosticBuilder and its associated routines and helper objects.
//===----------------------------------------------------------------------===//

typedef llvm::DenseMap<const ExplodedNode*,
const ExplodedNode*> NodeBackMap;

namespace {
class NodeMapClosure : public BugReport::NodeResolver {
  NodeBackMap& M;
public:
  NodeMapClosure(NodeBackMap *m) : M(*m) {}
  ~NodeMapClosure() {}

  const ExplodedNode *getOriginalNode(const ExplodedNode *N) {
    NodeBackMap::iterator I = M.find(N);
    return I == M.end() ? 0 : I->second;
  }
};

class PathDiagnosticBuilder : public BugReporterContext {
  BugReport *R;
  PathDiagnosticClient *PDC;
  llvm::OwningPtr<ParentMap> PM;
  NodeMapClosure NMC;
public:
  PathDiagnosticBuilder(GRBugReporter &br,
                        BugReport *r, NodeBackMap *Backmap,
                        PathDiagnosticClient *pdc)
    : BugReporterContext(br),
      R(r), PDC(pdc), NMC(Backmap) {}

  PathDiagnosticLocation ExecutionContinues(const ExplodedNode *N);

  PathDiagnosticLocation ExecutionContinues(llvm::raw_string_ostream &os,
                                            const ExplodedNode *N);

  BugReport *getBugReport() { return R; }

  Decl const &getCodeDecl() { return R->getErrorNode()->getCodeDecl(); }

  const LocationContext* getLocationContext() {
    return R->getErrorNode()->getLocationContext();
  }

  ParentMap& getParentMap() { return R->getErrorNode()->getParentMap(); }

  const Stmt *getParent(const Stmt *S) {
    return getParentMap().getParent(S);
  }

  virtual NodeMapClosure& getNodeResolver() { return NMC; }

  PathDiagnosticLocation getEnclosingStmtLocation(const Stmt *S);

  PathDiagnosticClient::PathGenerationScheme getGenerationScheme() const {
    return PDC ? PDC->getGenerationScheme() : PathDiagnosticClient::Extensive;
  }

  bool supportsLogicalOpControlFlow() const {
    return PDC ? PDC->supportsLogicalOpControlFlow() : true;
  }
};
} // end anonymous namespace

PathDiagnosticLocation
PathDiagnosticBuilder::ExecutionContinues(const ExplodedNode *N) {
  if (const Stmt *S = GetNextStmt(N))
    return PathDiagnosticLocation(S, getSourceManager(), getLocationContext());

  return FullSourceLoc(N->getLocationContext()->getDecl()->getBodyRBrace(),
                       getSourceManager());
}

PathDiagnosticLocation
PathDiagnosticBuilder::ExecutionContinues(llvm::raw_string_ostream &os,
                                          const ExplodedNode *N) {

  // Slow, but probably doesn't matter.
  if (os.str().empty())
    os << ' ';

  const PathDiagnosticLocation &Loc = ExecutionContinues(N);

  if (Loc.asStmt())
    os << "Execution continues on line "
       << getSourceManager().getExpansionLineNumber(Loc.asLocation())
       << '.';
  else {
    os << "Execution jumps to the end of the ";
    const Decl *D = N->getLocationContext()->getDecl();
    if (isa<ObjCMethodDecl>(D))
      os << "method";
    else if (isa<FunctionDecl>(D))
      os << "function";
    else {
      assert(isa<BlockDecl>(D));
      os << "anonymous block";
    }
    os << '.';
  }

  return Loc;
}

static bool IsNested(const Stmt *S, ParentMap &PM) {
  if (isa<Expr>(S) && PM.isConsumedExpr(cast<Expr>(S)))
    return true;

  const Stmt *Parent = PM.getParentIgnoreParens(S);

  if (Parent)
    switch (Parent->getStmtClass()) {
      case Stmt::ForStmtClass:
      case Stmt::DoStmtClass:
      case Stmt::WhileStmtClass:
        return true;
      default:
        break;
    }

  return false;
}

PathDiagnosticLocation
PathDiagnosticBuilder::getEnclosingStmtLocation(const Stmt *S) {
  assert(S && "Null Stmt *passed to getEnclosingStmtLocation");
  ParentMap &P = getParentMap();
  SourceManager &SMgr = getSourceManager();
  const LocationContext *LC = getLocationContext();

  while (IsNested(S, P)) {
    const Stmt *Parent = P.getParentIgnoreParens(S);

    if (!Parent)
      break;

    switch (Parent->getStmtClass()) {
      case Stmt::BinaryOperatorClass: {
        const BinaryOperator *B = cast<BinaryOperator>(Parent);
        if (B->isLogicalOp())
          return PathDiagnosticLocation(S, SMgr, LC);
        break;
      }
      case Stmt::CompoundStmtClass:
      case Stmt::StmtExprClass:
        return PathDiagnosticLocation(S, SMgr, LC);
      case Stmt::ChooseExprClass:
        // Similar to '?' if we are referring to condition, just have the edge
        // point to the entire choose expression.
        if (cast<ChooseExpr>(Parent)->getCond() == S)
          return PathDiagnosticLocation(Parent, SMgr, LC);
        else
          return PathDiagnosticLocation(S, SMgr, LC);
      case Stmt::BinaryConditionalOperatorClass:
      case Stmt::ConditionalOperatorClass:
        // For '?', if we are referring to condition, just have the edge point
        // to the entire '?' expression.
        if (cast<AbstractConditionalOperator>(Parent)->getCond() == S)
          return PathDiagnosticLocation(Parent, SMgr, LC);
        else
          return PathDiagnosticLocation(S, SMgr, LC);
      case Stmt::DoStmtClass:
          return PathDiagnosticLocation(S, SMgr, LC);
      case Stmt::ForStmtClass:
        if (cast<ForStmt>(Parent)->getBody() == S)
          return PathDiagnosticLocation(S, SMgr, LC);
        break;
      case Stmt::IfStmtClass:
        if (cast<IfStmt>(Parent)->getCond() != S)
          return PathDiagnosticLocation(S, SMgr, LC);
        break;
      case Stmt::ObjCForCollectionStmtClass:
        if (cast<ObjCForCollectionStmt>(Parent)->getBody() == S)
          return PathDiagnosticLocation(S, SMgr, LC);
        break;
      case Stmt::WhileStmtClass:
        if (cast<WhileStmt>(Parent)->getCond() != S)
          return PathDiagnosticLocation(S, SMgr, LC);
        break;
      default:
        break;
    }

    S = Parent;
  }

  assert(S && "Cannot have null Stmt for PathDiagnosticLocation");

  // Special case: DeclStmts can appear in for statement declarations, in which
  //  case the ForStmt is the context.
  if (isa<DeclStmt>(S)) {
    if (const Stmt *Parent = P.getParent(S)) {
      switch (Parent->getStmtClass()) {
        case Stmt::ForStmtClass:
        case Stmt::ObjCForCollectionStmtClass:
          return PathDiagnosticLocation(Parent, SMgr, LC);
        default:
          break;
      }
    }
  }
  else if (isa<BinaryOperator>(S)) {
    // Special case: the binary operator represents the initialization
    // code in a for statement (this can happen when the variable being
    // initialized is an old variable.
    if (const ForStmt *FS =
          dyn_cast_or_null<ForStmt>(P.getParentIgnoreParens(S))) {
      if (FS->getInit() == S)
        return PathDiagnosticLocation(FS, SMgr, LC);
    }
  }

  return PathDiagnosticLocation(S, SMgr, LC);
}

//===----------------------------------------------------------------------===//
// ScanNotableSymbols: closure-like callback for scanning Store bindings.
//===----------------------------------------------------------------------===//

static const VarDecl* GetMostRecentVarDeclBinding(const ExplodedNode *N,
                                                  ProgramStateManager& VMgr,
                                                  SVal X) {

  for ( ; N ; N = N->pred_empty() ? 0 : *N->pred_begin()) {

    ProgramPoint P = N->getLocation();

    if (!isa<PostStmt>(P))
      continue;

    const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(cast<PostStmt>(P).getStmt());

    if (!DR)
      continue;

    SVal Y = N->getState()->getSVal(DR);

    if (X != Y)
      continue;

    const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl());

    if (!VD)
      continue;

    return VD;
  }

  return 0;
}

namespace {
class NotableSymbolHandler
: public StoreManager::BindingsHandler {

  SymbolRef Sym;
  const ProgramState *PrevSt;
  const Stmt *S;
  ProgramStateManager& VMgr;
  const ExplodedNode *Pred;
  PathDiagnostic& PD;
  BugReporter& BR;

public:

  NotableSymbolHandler(SymbolRef sym,
                       const ProgramState *prevst,
                       const Stmt *s,
                       ProgramStateManager& vmgr,
                       const ExplodedNode *pred,
                       PathDiagnostic& pd,
                       BugReporter& br)
  : Sym(sym),
    PrevSt(prevst),
    S(s),
    VMgr(vmgr),
    Pred(pred),
    PD(pd),
    BR(br) {}

  bool HandleBinding(StoreManager& SMgr, Store store, const MemRegion* R,
                     SVal V) {

    SymbolRef ScanSym = V.getAsSymbol();

    if (ScanSym != Sym)
      return true;

    // Check if the previous state has this binding.
    SVal X = PrevSt->getSVal(loc::MemRegionVal(R));

    if (X == V) // Same binding?
      return true;

    // Different binding.  Only handle assignments for now.  We don't pull
    // this check out of the loop because we will eventually handle other
    // cases.

    VarDecl *VD = 0;

    if (const BinaryOperator* B = dyn_cast<BinaryOperator>(S)) {
      if (!B->isAssignmentOp())
        return true;

      // What variable did we assign to?
      DeclRefExpr *DR = dyn_cast<DeclRefExpr>(B->getLHS()->IgnoreParenCasts());

      if (!DR)
        return true;

      VD = dyn_cast<VarDecl>(DR->getDecl());
    }
    else if (const DeclStmt *DS = dyn_cast<DeclStmt>(S)) {
      // FIXME: Eventually CFGs won't have DeclStmts.  Right now we
      //  assume that each DeclStmt has a single Decl.  This invariant
      //  holds by construction in the CFG.
      VD = dyn_cast<VarDecl>(*DS->decl_begin());
    }

    if (!VD)
      return true;

    // What is the most recently referenced variable with this binding?
    const VarDecl *MostRecent = GetMostRecentVarDeclBinding(Pred, VMgr, V);

    if (!MostRecent)
      return true;

    // Create the diagnostic.
    FullSourceLoc L(S->getLocStart(), BR.getSourceManager());

    if (Loc::isLocType(VD->getType())) {
      llvm::SmallString<64> buf;
      llvm::raw_svector_ostream os(buf);
      os << '\'' << VD << "' now aliases '" << MostRecent << '\'';

      PD.push_front(new PathDiagnosticEventPiece(L, os.str()));
    }

    return true;
  }
};
}

static void HandleNotableSymbol(const ExplodedNode *N,
                                const Stmt *S,
                                SymbolRef Sym, BugReporter& BR,
                                PathDiagnostic& PD) {

  const ExplodedNode *Pred = N->pred_empty() ? 0 : *N->pred_begin();
  const ProgramState *PrevSt = Pred ? Pred->getState() : 0;

  if (!PrevSt)
    return;

  // Look at the region bindings of the current state that map to the
  // specified symbol.  Are any of them not in the previous state?
  ProgramStateManager& VMgr = cast<GRBugReporter>(BR).getStateManager();
  NotableSymbolHandler H(Sym, PrevSt, S, VMgr, Pred, PD, BR);
  cast<GRBugReporter>(BR).getStateManager().iterBindings(N->getState(), H);
}

namespace {
class ScanNotableSymbols
: public StoreManager::BindingsHandler {

  llvm::SmallSet<SymbolRef, 10> AlreadyProcessed;
  const ExplodedNode *N;
  const Stmt *S;
  GRBugReporter& BR;
  PathDiagnostic& PD;

public:
  ScanNotableSymbols(const ExplodedNode *n, const Stmt *s,
                     GRBugReporter& br, PathDiagnostic& pd)
  : N(n), S(s), BR(br), PD(pd) {}

  bool HandleBinding(StoreManager& SMgr, Store store,
                     const MemRegion* R, SVal V) {

    SymbolRef ScanSym = V.getAsSymbol();

    if (!ScanSym)
      return true;

    if (!BR.isNotable(ScanSym))
      return true;

    if (AlreadyProcessed.count(ScanSym))
      return true;

    AlreadyProcessed.insert(ScanSym);

    HandleNotableSymbol(N, S, ScanSym, BR, PD);
    return true;
  }
};
} // end anonymous namespace

//===----------------------------------------------------------------------===//
// "Minimal" path diagnostic generation algorithm.
//===----------------------------------------------------------------------===//

static void CompactPathDiagnostic(PathDiagnostic &PD, const SourceManager& SM);

static void GenerateMinimalPathDiagnostic(PathDiagnostic& PD,
                                          PathDiagnosticBuilder &PDB,
                                          const ExplodedNode *N) {

  SourceManager& SMgr = PDB.getSourceManager();
  const LocationContext *LC = PDB.getLocationContext();
  const ExplodedNode *NextNode = N->pred_empty()
                                        ? NULL : *(N->pred_begin());
  while (NextNode) {
    N = NextNode;
    NextNode = GetPredecessorNode(N);

    ProgramPoint P = N->getLocation();

    if (const BlockEdge *BE = dyn_cast<BlockEdge>(&P)) {
      const CFGBlock *Src = BE->getSrc();
      const CFGBlock *Dst = BE->getDst();
      const Stmt *T = Src->getTerminator();

      if (!T)
        continue;

      FullSourceLoc Start(T->getLocStart(), SMgr);

      switch (T->getStmtClass()) {
        default:
          break;

        case Stmt::GotoStmtClass:
        case Stmt::IndirectGotoStmtClass: {
          const Stmt *S = GetNextStmt(N);

          if (!S)
            continue;

          std::string sbuf;
          llvm::raw_string_ostream os(sbuf);
          const PathDiagnosticLocation &End = PDB.getEnclosingStmtLocation(S);

          os << "Control jumps to line "
          << End.asLocation().getExpansionLineNumber();
          PD.push_front(new PathDiagnosticControlFlowPiece(Start, End,
                                                           os.str()));
          break;
        }

        case Stmt::SwitchStmtClass: {
          // Figure out what case arm we took.
          std::string sbuf;
          llvm::raw_string_ostream os(sbuf);

          if (const Stmt *S = Dst->getLabel()) {
            PathDiagnosticLocation End(S, SMgr, LC);

            switch (S->getStmtClass()) {
              default:
                os << "No cases match in the switch statement. "
                "Control jumps to line "
                << End.asLocation().getExpansionLineNumber();
                break;
              case Stmt::DefaultStmtClass:
                os << "Control jumps to the 'default' case at line "
                << End.asLocation().getExpansionLineNumber();
                break;

              case Stmt::CaseStmtClass: {
                os << "Control jumps to 'case ";
                const CaseStmt *Case = cast<CaseStmt>(S);
                const Expr *LHS = Case->getLHS()->IgnoreParenCasts();

                // Determine if it is an enum.
                bool GetRawInt = true;

                if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(LHS)) {
                  // FIXME: Maybe this should be an assertion.  Are there cases
                  // were it is not an EnumConstantDecl?
                  const EnumConstantDecl *D =
                    dyn_cast<EnumConstantDecl>(DR->getDecl());

                  if (D) {
                    GetRawInt = false;
                    os << D;
                  }
                }

                if (GetRawInt)
                  os << LHS->EvaluateAsInt(PDB.getASTContext());

                os << ":'  at line "
                << End.asLocation().getExpansionLineNumber();
                break;
              }
            }
            PD.push_front(new PathDiagnosticControlFlowPiece(Start, End,
                                                             os.str()));
          }
          else {
            os << "'Default' branch taken. ";
            const PathDiagnosticLocation &End = PDB.ExecutionContinues(os, N);
            PD.push_front(new PathDiagnosticControlFlowPiece(Start, End,
                                                             os.str()));
          }

          break;
        }

        case Stmt::BreakStmtClass:
        case Stmt::ContinueStmtClass: {
          std::string sbuf;
          llvm::raw_string_ostream os(sbuf);
          PathDiagnosticLocation End = PDB.ExecutionContinues(os, N);
          PD.push_front(new PathDiagnosticControlFlowPiece(Start, End,
                                                           os.str()));
          break;
        }

          // Determine control-flow for ternary '?'.
        case Stmt::BinaryConditionalOperatorClass:
        case Stmt::ConditionalOperatorClass: {
          std::string sbuf;
          llvm::raw_string_ostream os(sbuf);
          os << "'?' condition is ";

          if (*(Src->succ_begin()+1) == Dst)
            os << "false";
          else
            os << "true";

          PathDiagnosticLocation End = PDB.ExecutionContinues(N);

          if (const Stmt *S = End.asStmt())
            End = PDB.getEnclosingStmtLocation(S);

          PD.push_front(new PathDiagnosticControlFlowPiece(Start, End,
                                                           os.str()));
          break;
        }

          // Determine control-flow for short-circuited '&&' and '||'.
        case Stmt::BinaryOperatorClass: {
          if (!PDB.supportsLogicalOpControlFlow())
            break;

          const BinaryOperator *B = cast<BinaryOperator>(T);
          std::string sbuf;
          llvm::raw_string_ostream os(sbuf);
          os << "Left side of '";

          if (B->getOpcode() == BO_LAnd) {
            os << "&&" << "' is ";

            if (*(Src->succ_begin()+1) == Dst) {
              os << "false";
              PathDiagnosticLocation End(B->getLHS(), SMgr, LC);
              PathDiagnosticLocation Start(B->getOperatorLoc(), SMgr);
              PD.push_front(new PathDiagnosticControlFlowPiece(Start, End,
                                                               os.str()));
            }
            else {
              os << "true";
              PathDiagnosticLocation Start(B->getLHS(), SMgr, LC);
              PathDiagnosticLocation End = PDB.ExecutionContinues(N);
              PD.push_front(new PathDiagnosticControlFlowPiece(Start, End,
                                                               os.str()));
            }
          }
          else {
            assert(B->getOpcode() == BO_LOr);
            os << "||" << "' is ";

            if (*(Src->succ_begin()+1) == Dst) {
              os << "false";
              PathDiagnosticLocation Start(B->getLHS(), SMgr, LC);
              PathDiagnosticLocation End = PDB.ExecutionContinues(N);
              PD.push_front(new PathDiagnosticControlFlowPiece(Start, End,
                                                               os.str()));
            }
            else {
              os << "true";
              PathDiagnosticLocation End(B->getLHS(), SMgr, LC);
              PathDiagnosticLocation Start(B->getOperatorLoc(), SMgr);
              PD.push_front(new PathDiagnosticControlFlowPiece(Start, End,
                                                               os.str()));
            }
          }

          break;
        }

        case Stmt::DoStmtClass:  {
          if (*(Src->succ_begin()) == Dst) {
            std::string sbuf;
            llvm::raw_string_ostream os(sbuf);

            os << "Loop condition is true. ";
            PathDiagnosticLocation End = PDB.ExecutionContinues(os, N);

            if (const Stmt *S = End.asStmt())
              End = PDB.getEnclosingStmtLocation(S);

            PD.push_front(new PathDiagnosticControlFlowPiece(Start, End,
                                                             os.str()));
          }
          else {
            PathDiagnosticLocation End = PDB.ExecutionContinues(N);

            if (const Stmt *S = End.asStmt())
              End = PDB.getEnclosingStmtLocation(S);

            PD.push_front(new PathDiagnosticControlFlowPiece(Start, End,
                              "Loop condition is false.  Exiting loop"));
          }

          break;
        }

        case Stmt::WhileStmtClass:
        case Stmt::ForStmtClass: {
          if (*(Src->succ_begin()+1) == Dst) {
            std::string sbuf;
            llvm::raw_string_ostream os(sbuf);

            os << "Loop condition is false. ";
            PathDiagnosticLocation End = PDB.ExecutionContinues(os, N);
            if (const Stmt *S = End.asStmt())
              End = PDB.getEnclosingStmtLocation(S);

            PD.push_front(new PathDiagnosticControlFlowPiece(Start, End,
                                                             os.str()));
          }
          else {
            PathDiagnosticLocation End = PDB.ExecutionContinues(N);
            if (const Stmt *S = End.asStmt())
              End = PDB.getEnclosingStmtLocation(S);

            PD.push_front(new PathDiagnosticControlFlowPiece(Start, End,
                            "Loop condition is true.  Entering loop body"));
          }

          break;
        }

        case Stmt::IfStmtClass: {
          PathDiagnosticLocation End = PDB.ExecutionContinues(N);

          if (const Stmt *S = End.asStmt())
            End = PDB.getEnclosingStmtLocation(S);

          if (*(Src->succ_begin()+1) == Dst)
            PD.push_front(new PathDiagnosticControlFlowPiece(Start, End,
                                                        "Taking false branch"));
          else
            PD.push_front(new PathDiagnosticControlFlowPiece(Start, End,
                                                         "Taking true branch"));

          break;
        }
      }
    }

    if (NextNode) {
      // Add diagnostic pieces from custom visitors.
      BugReport *R = PDB.getBugReport();
      for (BugReport::visitor_iterator I = R->visitor_begin(),
           E = R->visitor_end(); I!=E; ++I) {
        if (PathDiagnosticPiece *p = (*I)->VisitNode(N, NextNode, PDB, *R))
          PD.push_front(p);
      }
    }

    if (const PostStmt *PS = dyn_cast<PostStmt>(&P)) {
      // Scan the region bindings, and see if a "notable" symbol has a new
      // lval binding.
      ScanNotableSymbols SNS(N, PS->getStmt(), PDB.getBugReporter(), PD);
      PDB.getStateManager().iterBindings(N->getState(), SNS);
    }
  }

  // After constructing the full PathDiagnostic, do a pass over it to compact
  // PathDiagnosticPieces that occur within a macro.
  CompactPathDiagnostic(PD, PDB.getSourceManager());
}

//===----------------------------------------------------------------------===//
// "Extensive" PathDiagnostic generation.
//===----------------------------------------------------------------------===//

static bool IsControlFlowExpr(const Stmt *S) {
  const Expr *E = dyn_cast<Expr>(S);

  if (!E)
    return false;

  E = E->IgnoreParenCasts();

  if (isa<AbstractConditionalOperator>(E))
    return true;

  if (const BinaryOperator *B = dyn_cast<BinaryOperator>(E))
    if (B->isLogicalOp())
      return true;

  return false;
}

namespace {
class ContextLocation : public PathDiagnosticLocation {
  bool IsDead;
public:
  ContextLocation(const PathDiagnosticLocation &L, bool isdead = false)
    : PathDiagnosticLocation(L), IsDead(isdead) {}

  void markDead() { IsDead = true; }
  bool isDead() const { return IsDead; }
};

class EdgeBuilder {
  std::vector<ContextLocation> CLocs;
  typedef std::vector<ContextLocation>::iterator iterator;
  PathDiagnostic &PD;
  PathDiagnosticBuilder &PDB;
  PathDiagnosticLocation PrevLoc;

  bool IsConsumedExpr(const PathDiagnosticLocation &L);

  bool containsLocation(const PathDiagnosticLocation &Container,
                        const PathDiagnosticLocation &Containee);

  PathDiagnosticLocation getContextLocation(const PathDiagnosticLocation &L);

  PathDiagnosticLocation cleanUpLocation(PathDiagnosticLocation L,
                                         bool firstCharOnly = false) {
    if (const Stmt *S = L.asStmt()) {
      const Stmt *Original = S;
      while (1) {
        // Adjust the location for some expressions that are best referenced
        // by one of their subexpressions.
        switch (S->getStmtClass()) {
          default:
            break;
          case Stmt::ParenExprClass:
          case Stmt::GenericSelectionExprClass:
            S = cast<Expr>(S)->IgnoreParens();
            firstCharOnly = true;
            continue;
          case Stmt::BinaryConditionalOperatorClass:
          case Stmt::ConditionalOperatorClass:
            S = cast<AbstractConditionalOperator>(S)->getCond();
            firstCharOnly = true;
            continue;
          case Stmt::ChooseExprClass:
            S = cast<ChooseExpr>(S)->getCond();
            firstCharOnly = true;
            continue;
          case Stmt::BinaryOperatorClass:
            S = cast<BinaryOperator>(S)->getLHS();
            firstCharOnly = true;
            continue;
        }

        break;
      }

      if (S != Original)
        L = PathDiagnosticLocation(S, L.getManager(), L.getLocationContext());
    }

    if (firstCharOnly)
      L = PathDiagnosticLocation(L.asLocation());

    return L;
  }

  void popLocation() {
    if (!CLocs.back().isDead() && CLocs.back().asLocation().isFileID()) {
      // For contexts, we only one the first character as the range.
      rawAddEdge(cleanUpLocation(CLocs.back(), true));
    }
    CLocs.pop_back();
  }

public:
  EdgeBuilder(PathDiagnostic &pd, PathDiagnosticBuilder &pdb)
    : PD(pd), PDB(pdb) {

      // If the PathDiagnostic already has pieces, add the enclosing statement
      // of the first piece as a context as well.
      if (!PD.empty()) {
        PrevLoc = PD.begin()->getLocation();

        if (const Stmt *S = PrevLoc.asStmt())
          addExtendedContext(PDB.getEnclosingStmtLocation(S).asStmt());
      }
  }

  ~EdgeBuilder() {
    while (!CLocs.empty()) popLocation();

    // Finally, add an initial edge from the start location of the first
    // statement (if it doesn't already exist).
    // FIXME: Should handle CXXTryStmt if analyser starts supporting C++.
    if (const CompoundStmt *CS =
          dyn_cast_or_null<CompoundStmt>(PDB.getCodeDecl().getBody()))
      if (!CS->body_empty()) {
        SourceLocation Loc = (*CS->body_begin())->getLocStart();
        rawAddEdge(PathDiagnosticLocation(Loc, PDB.getSourceManager()));
      }

  }

  void addEdge(PathDiagnosticLocation NewLoc, bool alwaysAdd = false);

  void rawAddEdge(PathDiagnosticLocation NewLoc);

  void addContext(const Stmt *S);
  void addExtendedContext(const Stmt *S);
};
} // end anonymous namespace


PathDiagnosticLocation
EdgeBuilder::getContextLocation(const PathDiagnosticLocation &L) {
  if (const Stmt *S = L.asStmt()) {
    if (IsControlFlowExpr(S))
      return L;

    return PDB.getEnclosingStmtLocation(S);
  }

  return L;
}

bool EdgeBuilder::containsLocation(const PathDiagnosticLocation &Container,
                                   const PathDiagnosticLocation &Containee) {

  if (Container == Containee)
    return true;

  if (Container.asDecl())
    return true;

  if (const Stmt *S = Containee.asStmt())
    if (const Stmt *ContainerS = Container.asStmt()) {
      while (S) {
        if (S == ContainerS)
          return true;
        S = PDB.getParent(S);
      }
      return false;
    }

  // Less accurate: compare using source ranges.
  SourceRange ContainerR = Container.asRange();
  SourceRange ContaineeR = Containee.asRange();

  SourceManager &SM = PDB.getSourceManager();
  SourceLocation ContainerRBeg = SM.getExpansionLoc(ContainerR.getBegin());
  SourceLocation ContainerREnd = SM.getExpansionLoc(ContainerR.getEnd());
  SourceLocation ContaineeRBeg = SM.getExpansionLoc(ContaineeR.getBegin());
  SourceLocation ContaineeREnd = SM.getExpansionLoc(ContaineeR.getEnd());

  unsigned ContainerBegLine = SM.getExpansionLineNumber(ContainerRBeg);
  unsigned ContainerEndLine = SM.getExpansionLineNumber(ContainerREnd);
  unsigned ContaineeBegLine = SM.getExpansionLineNumber(ContaineeRBeg);
  unsigned ContaineeEndLine = SM.getExpansionLineNumber(ContaineeREnd);

  assert(ContainerBegLine <= ContainerEndLine);
  assert(ContaineeBegLine <= ContaineeEndLine);

  return (ContainerBegLine <= ContaineeBegLine &&
          ContainerEndLine >= ContaineeEndLine &&
          (ContainerBegLine != ContaineeBegLine ||
           SM.getExpansionColumnNumber(ContainerRBeg) <=
           SM.getExpansionColumnNumber(ContaineeRBeg)) &&
          (ContainerEndLine != ContaineeEndLine ||
           SM.getExpansionColumnNumber(ContainerREnd) >=
           SM.getExpansionColumnNumber(ContainerREnd)));
}

void EdgeBuilder::rawAddEdge(PathDiagnosticLocation NewLoc) {
  if (!PrevLoc.isValid()) {
    PrevLoc = NewLoc;
    return;
  }

  const PathDiagnosticLocation &NewLocClean = cleanUpLocation(NewLoc);
  const PathDiagnosticLocation &PrevLocClean = cleanUpLocation(PrevLoc);

  if (NewLocClean.asLocation() == PrevLocClean.asLocation())
    return;

  // FIXME: Ignore intra-macro edges for now.
  if (NewLocClean.asLocation().getExpansionLoc() ==
      PrevLocClean.asLocation().getExpansionLoc())
    return;

  PD.push_front(new PathDiagnosticControlFlowPiece(NewLocClean, PrevLocClean));
  PrevLoc = NewLoc;
}

void EdgeBuilder::addEdge(PathDiagnosticLocation NewLoc, bool alwaysAdd) {

  if (!alwaysAdd && NewLoc.asLocation().isMacroID())
    return;

  const PathDiagnosticLocation &CLoc = getContextLocation(NewLoc);

  while (!CLocs.empty()) {
    ContextLocation &TopContextLoc = CLocs.back();

    // Is the top location context the same as the one for the new location?
    if (TopContextLoc == CLoc) {
      if (alwaysAdd) {
        if (IsConsumedExpr(TopContextLoc) &&
            !IsControlFlowExpr(TopContextLoc.asStmt()))
            TopContextLoc.markDead();

        rawAddEdge(NewLoc);
      }

      return;
    }

    if (containsLocation(TopContextLoc, CLoc)) {
      if (alwaysAdd) {
        rawAddEdge(NewLoc);

        if (IsConsumedExpr(CLoc) && !IsControlFlowExpr(CLoc.asStmt())) {
          CLocs.push_back(ContextLocation(CLoc, true));
          return;
        }
      }

      CLocs.push_back(CLoc);
      return;
    }

    // Context does not contain the location.  Flush it.
    popLocation();
  }

  // If we reach here, there is no enclosing context.  Just add the edge.
  rawAddEdge(NewLoc);
}

bool EdgeBuilder::IsConsumedExpr(const PathDiagnosticLocation &L) {
  if (const Expr *X = dyn_cast_or_null<Expr>(L.asStmt()))
    return PDB.getParentMap().isConsumedExpr(X) && !IsControlFlowExpr(X);

  return false;
}

void EdgeBuilder::addExtendedContext(const Stmt *S) {
  if (!S)
    return;

  const Stmt *Parent = PDB.getParent(S);
  while (Parent) {
    if (isa<CompoundStmt>(Parent))
      Parent = PDB.getParent(Parent);
    else
      break;
  }

  if (Parent) {
    switch (Parent->getStmtClass()) {
      case Stmt::DoStmtClass:
      case Stmt::ObjCAtSynchronizedStmtClass:
        addContext(Parent);
      default:
        break;
    }
  }

  addContext(S);
}

void EdgeBuilder::addContext(const Stmt *S) {
  if (!S)
    return;

  PathDiagnosticLocation L(S, PDB.getSourceManager(), PDB.getLocationContext());

  while (!CLocs.empty()) {
    const PathDiagnosticLocation &TopContextLoc = CLocs.back();

    // Is the top location context the same as the one for the new location?
    if (TopContextLoc == L)
      return;

    if (containsLocation(TopContextLoc, L)) {
      CLocs.push_back(L);
      return;
    }

    // Context does not contain the location.  Flush it.
    popLocation();
  }

  CLocs.push_back(L);
}

static void GenerateExtensivePathDiagnostic(PathDiagnostic& PD,
                                            PathDiagnosticBuilder &PDB,
                                            const ExplodedNode *N) {
  EdgeBuilder EB(PD, PDB);

  const ExplodedNode *NextNode = N->pred_empty() ? NULL : *(N->pred_begin());
  while (NextNode) {
    N = NextNode;
    NextNode = GetPredecessorNode(N);
    ProgramPoint P = N->getLocation();

    do {
      // Block edges.
      if (const BlockEdge *BE = dyn_cast<BlockEdge>(&P)) {
        const CFGBlock &Blk = *BE->getSrc();
        const Stmt *Term = Blk.getTerminator();

        // Are we jumping to the head of a loop?  Add a special diagnostic.
        if (const Stmt *Loop = BE->getDst()->getLoopTarget()) {
          PathDiagnosticLocation L(Loop, PDB.getSourceManager(),
                                         PDB.getLocationContext());
          const CompoundStmt *CS = NULL;

          if (!Term) {
            if (const ForStmt *FS = dyn_cast<ForStmt>(Loop))
              CS = dyn_cast<CompoundStmt>(FS->getBody());
            else if (const WhileStmt *WS = dyn_cast<WhileStmt>(Loop))
              CS = dyn_cast<CompoundStmt>(WS->getBody());
          }

          PathDiagnosticEventPiece *p =
            new PathDiagnosticEventPiece(L,
                                        "Looping back to the head of the loop");

          EB.addEdge(p->getLocation(), true);
          PD.push_front(p);

          if (CS) {
            PathDiagnosticLocation BL(CS->getRBracLoc(),
                                      PDB.getSourceManager());
            BL = PathDiagnosticLocation(BL.asLocation());
            EB.addEdge(BL);
          }
        }

        if (Term)
          EB.addContext(Term);

        break;
      }

      if (const BlockEntrance *BE = dyn_cast<BlockEntrance>(&P)) {
        if (const CFGStmt *S = BE->getFirstElement().getAs<CFGStmt>()) {
          const Stmt *stmt = S->getStmt();
          if (IsControlFlowExpr(stmt)) {
            // Add the proper context for '&&', '||', and '?'.
            EB.addContext(stmt);
          }
          else
            EB.addExtendedContext(PDB.getEnclosingStmtLocation(stmt).asStmt());
        }

        break;
      }
    } while (0);

    if (!NextNode)
      continue;

    // Add pieces from custom visitors.
    BugReport *R = PDB.getBugReport();
    for (BugReport::visitor_iterator I = R->visitor_begin(),
                                     E = R->visitor_end(); I!=E; ++I) {
      if (PathDiagnosticPiece *p = (*I)->VisitNode(N, NextNode, PDB, *R)) {
        const PathDiagnosticLocation &Loc = p->getLocation();
        EB.addEdge(Loc, true);
        PD.push_front(p);
        if (const Stmt *S = Loc.asStmt())
          EB.addExtendedContext(PDB.getEnclosingStmtLocation(S).asStmt());
      }
    }
  }
}

//===----------------------------------------------------------------------===//
// Methods for BugType and subclasses.
//===----------------------------------------------------------------------===//
BugType::~BugType() { }

void BugType::FlushReports(BugReporter &BR) {}

//===----------------------------------------------------------------------===//
// Methods for BugReport and subclasses.
//===----------------------------------------------------------------------===//

void BugReport::addVisitor(BugReporterVisitor* visitor) {
  if (!visitor)
    return;

  llvm::FoldingSetNodeID ID;
  visitor->Profile(ID);
  void *InsertPos;

  if (CallbacksSet.FindNodeOrInsertPos(ID, InsertPos)) {
    delete visitor;
    return;
  }

  CallbacksSet.InsertNode(visitor, InsertPos);
  Callbacks = F.add(visitor, Callbacks);
}

BugReport::~BugReport() {
  for (visitor_iterator I = visitor_begin(), E = visitor_end(); I != E; ++I) {
    delete *I;
  }
}

void BugReport::Profile(llvm::FoldingSetNodeID& hash) const {
  hash.AddPointer(&BT);
  hash.AddInteger(getLocation().getRawEncoding());
  hash.AddString(Description);

  for (SmallVectorImpl<SourceRange>::const_iterator I =
      Ranges.begin(), E = Ranges.end(); I != E; ++I) {
    const SourceRange range = *I;
    if (!range.isValid())
      continue;
    hash.AddInteger(range.getBegin().getRawEncoding());
    hash.AddInteger(range.getEnd().getRawEncoding());
  }
}

const Stmt *BugReport::getStmt() const {
  if (!ErrorNode)
    return 0;

  ProgramPoint ProgP = ErrorNode->getLocation();
  const Stmt *S = NULL;

  if (BlockEntrance *BE = dyn_cast<BlockEntrance>(&ProgP)) {
    CFGBlock &Exit = ProgP.getLocationContext()->getCFG()->getExit();
    if (BE->getBlock() == &Exit)
      S = GetPreviousStmt(ErrorNode);
  }
  if (!S)
    S = GetStmt(ProgP);

  return S;
}

std::pair<BugReport::ranges_iterator, BugReport::ranges_iterator>
BugReport::getRanges() {
    // If no custom ranges, add the range of the statement corresponding to
    // the error node.
    if (Ranges.empty()) {
      if (const Expr *E = dyn_cast_or_null<Expr>(getStmt()))
        addRange(E->getSourceRange());
      else
        return std::make_pair(ranges_iterator(), ranges_iterator());
    }

    // User-specified absence of range info.
    if (Ranges.size() == 1 && !Ranges.begin()->isValid())
      return std::make_pair(ranges_iterator(), ranges_iterator());

    return std::make_pair(Ranges.begin(), Ranges.end());
}

SourceLocation BugReport::getLocation() const {
  if (ErrorNode) {
    (Location.isInvalid() &&
     "Either Location or ErrorNode should be specified but not both.");

    if (const Stmt *S = GetCurrentOrPreviousStmt(ErrorNode)) {
      // For member expressions, return the location of the '.' or '->'.
      if (const MemberExpr *ME = dyn_cast<MemberExpr>(S))
        return ME->getMemberLoc();
      // For binary operators, return the location of the operator.
      if (const BinaryOperator *B = dyn_cast<BinaryOperator>(S))
        return B->getOperatorLoc();

      return S->getLocStart();
    }

  } else {
    assert(Location.isValid());
    return Location;
  }

  return FullSourceLoc();
}

//===----------------------------------------------------------------------===//
// Methods for BugReporter and subclasses.
//===----------------------------------------------------------------------===//

BugReportEquivClass::~BugReportEquivClass() {
  for (iterator I=begin(), E=end(); I!=E; ++I) delete *I;
}

GRBugReporter::~GRBugReporter() { }
BugReporterData::~BugReporterData() {}

ExplodedGraph &GRBugReporter::getGraph() { return Eng.getGraph(); }

ProgramStateManager&
GRBugReporter::getStateManager() { return Eng.getStateManager(); }

BugReporter::~BugReporter() {
  FlushReports();

  // Free the bug reports we are tracking.
  typedef std::vector<BugReportEquivClass *> ContTy;
  for (ContTy::iterator I = EQClassesVector.begin(), E = EQClassesVector.end();
       I != E; ++I) {
    delete *I;
  }
}

void BugReporter::FlushReports() {
  if (BugTypes.isEmpty())
    return;

  // First flush the warnings for each BugType.  This may end up creating new
  // warnings and new BugTypes.
  // FIXME: Only NSErrorChecker needs BugType's FlushReports.
  // Turn NSErrorChecker into a proper checker and remove this.
  SmallVector<const BugType*, 16> bugTypes;
  for (BugTypesTy::iterator I=BugTypes.begin(), E=BugTypes.end(); I!=E; ++I)
    bugTypes.push_back(*I);
  for (SmallVector<const BugType*, 16>::iterator
         I = bugTypes.begin(), E = bugTypes.end(); I != E; ++I)
    const_cast<BugType*>(*I)->FlushReports(*this);

  typedef llvm::FoldingSet<BugReportEquivClass> SetTy;
  for (SetTy::iterator EI=EQClasses.begin(), EE=EQClasses.end(); EI!=EE;++EI){
    BugReportEquivClass& EQ = *EI;
    FlushReport(EQ);
  }

  // BugReporter owns and deletes only BugTypes created implicitly through
  // EmitBasicReport.
  // FIXME: There are leaks from checkers that assume that the BugTypes they
  // create will be destroyed by the BugReporter.
  for (llvm::StringMap<BugType*>::iterator
         I = StrBugTypes.begin(), E = StrBugTypes.end(); I != E; ++I)
    delete I->second;

  // Remove all references to the BugType objects.
  BugTypes = F.getEmptySet();
}

//===----------------------------------------------------------------------===//
// PathDiagnostics generation.
//===----------------------------------------------------------------------===//

static std::pair<std::pair<ExplodedGraph*, NodeBackMap*>,
                 std::pair<ExplodedNode*, unsigned> >
MakeReportGraph(const ExplodedGraph* G,
                SmallVectorImpl<const ExplodedNode*> &nodes) {

  // Create the trimmed graph.  It will contain the shortest paths from the
  // error nodes to the root.  In the new graph we should only have one
  // error node unless there are two or more error nodes with the same minimum
  // path length.
  ExplodedGraph* GTrim;
  InterExplodedGraphMap* NMap;

  llvm::DenseMap<const void*, const void*> InverseMap;
  llvm::tie(GTrim, NMap) = G->Trim(nodes.data(), nodes.data() + nodes.size(),
                                   &InverseMap);

  // Create owning pointers for GTrim and NMap just to ensure that they are
  // released when this function exists.
  llvm::OwningPtr<ExplodedGraph> AutoReleaseGTrim(GTrim);
  llvm::OwningPtr<InterExplodedGraphMap> AutoReleaseNMap(NMap);

  // Find the (first) error node in the trimmed graph.  We just need to consult
  // the node map (NMap) which maps from nodes in the original graph to nodes
  // in the new graph.

  std::queue<const ExplodedNode*> WS;
  typedef llvm::DenseMap<const ExplodedNode*, unsigned> IndexMapTy;
  IndexMapTy IndexMap;

  for (unsigned nodeIndex = 0 ; nodeIndex < nodes.size(); ++nodeIndex) {
    const ExplodedNode *originalNode = nodes[nodeIndex];
    if (const ExplodedNode *N = NMap->getMappedNode(originalNode)) {
      WS.push(N);
      IndexMap[originalNode] = nodeIndex;
    }
  }

  assert(!WS.empty() && "No error node found in the trimmed graph.");

  // Create a new (third!) graph with a single path.  This is the graph
  // that will be returned to the caller.
  ExplodedGraph *GNew = new ExplodedGraph();

  // Sometimes the trimmed graph can contain a cycle.  Perform a reverse BFS
  // to the root node, and then construct a new graph that contains only
  // a single path.
  llvm::DenseMap<const void*,unsigned> Visited;

  unsigned cnt = 0;
  const ExplodedNode *Root = 0;

  while (!WS.empty()) {
    const ExplodedNode *Node = WS.front();
    WS.pop();

    if (Visited.find(Node) != Visited.end())
      continue;

    Visited[Node] = cnt++;

    if (Node->pred_empty()) {
      Root = Node;
      break;
    }

    for (ExplodedNode::const_pred_iterator I=Node->pred_begin(),
         E=Node->pred_end(); I!=E; ++I)
      WS.push(*I);
  }

  assert(Root);

  // Now walk from the root down the BFS path, always taking the successor
  // with the lowest number.
  ExplodedNode *Last = 0, *First = 0;
  NodeBackMap *BM = new NodeBackMap();
  unsigned NodeIndex = 0;

  for ( const ExplodedNode *N = Root ;;) {
    // Lookup the number associated with the current node.
    llvm::DenseMap<const void*,unsigned>::iterator I = Visited.find(N);
    assert(I != Visited.end());

    // Create the equivalent node in the new graph with the same state
    // and location.
    ExplodedNode *NewN = GNew->getNode(N->getLocation(), N->getState());

    // Store the mapping to the original node.
    llvm::DenseMap<const void*, const void*>::iterator IMitr=InverseMap.find(N);
    assert(IMitr != InverseMap.end() && "No mapping to original node.");
    (*BM)[NewN] = (const ExplodedNode*) IMitr->second;

    // Link up the new node with the previous node.
    if (Last)
      NewN->addPredecessor(Last, *GNew);

    Last = NewN;

    // Are we at the final node?
    IndexMapTy::iterator IMI =
      IndexMap.find((const ExplodedNode*)(IMitr->second));
    if (IMI != IndexMap.end()) {
      First = NewN;
      NodeIndex = IMI->second;
      break;
    }

    // Find the next successor node.  We choose the node that is marked
    // with the lowest DFS number.
    ExplodedNode::const_succ_iterator SI = N->succ_begin();
    ExplodedNode::const_succ_iterator SE = N->succ_end();
    N = 0;

    for (unsigned MinVal = 0; SI != SE; ++SI) {

      I = Visited.find(*SI);

      if (I == Visited.end())
        continue;

      if (!N || I->second < MinVal) {
        N = *SI;
        MinVal = I->second;
      }
    }

    assert(N);
  }

  assert(First);

  return std::make_pair(std::make_pair(GNew, BM),
                        std::make_pair(First, NodeIndex));
}

/// CompactPathDiagnostic - This function postprocesses a PathDiagnostic object
///  and collapses PathDiagosticPieces that are expanded by macros.
static void CompactPathDiagnostic(PathDiagnostic &PD, const SourceManager& SM) {
  typedef std::vector<std::pair<PathDiagnosticMacroPiece*, SourceLocation> >
          MacroStackTy;

  typedef std::vector<PathDiagnosticPiece*>
          PiecesTy;

  MacroStackTy MacroStack;
  PiecesTy Pieces;

  for (PathDiagnostic::iterator I = PD.begin(), E = PD.end(); I!=E; ++I) {
    // Get the location of the PathDiagnosticPiece.
    const FullSourceLoc Loc = I->getLocation().asLocation();

    // Determine the instantiation location, which is the location we group
    // related PathDiagnosticPieces.
    SourceLocation InstantiationLoc = Loc.isMacroID() ?
                                      SM.getExpansionLoc(Loc) :
                                      SourceLocation();

    if (Loc.isFileID()) {
      MacroStack.clear();
      Pieces.push_back(&*I);
      continue;
    }

    assert(Loc.isMacroID());

    // Is the PathDiagnosticPiece within the same macro group?
    if (!MacroStack.empty() && InstantiationLoc == MacroStack.back().second) {
      MacroStack.back().first->push_back(&*I);
      continue;
    }

    // We aren't in the same group.  Are we descending into a new macro
    // or are part of an old one?
    PathDiagnosticMacroPiece *MacroGroup = 0;

    SourceLocation ParentInstantiationLoc = InstantiationLoc.isMacroID() ?
                                          SM.getExpansionLoc(Loc) :
                                          SourceLocation();

    // Walk the entire macro stack.
    while (!MacroStack.empty()) {
      if (InstantiationLoc == MacroStack.back().second) {
        MacroGroup = MacroStack.back().first;
        break;
      }

      if (ParentInstantiationLoc == MacroStack.back().second) {
        MacroGroup = MacroStack.back().first;
        break;
      }

      MacroStack.pop_back();
    }

    if (!MacroGroup || ParentInstantiationLoc == MacroStack.back().second) {
      // Create a new macro group and add it to the stack.
      PathDiagnosticMacroPiece *NewGroup = new PathDiagnosticMacroPiece(Loc);

      if (MacroGroup)
        MacroGroup->push_back(NewGroup);
      else {
        assert(InstantiationLoc.isFileID());
        Pieces.push_back(NewGroup);
      }

      MacroGroup = NewGroup;
      MacroStack.push_back(std::make_pair(MacroGroup, InstantiationLoc));
    }

    // Finally, add the PathDiagnosticPiece to the group.
    MacroGroup->push_back(&*I);
  }

  // Now take the pieces and construct a new PathDiagnostic.
  PD.resetPath(false);

  for (PiecesTy::iterator I=Pieces.begin(), E=Pieces.end(); I!=E; ++I) {
    if (PathDiagnosticMacroPiece *MP=dyn_cast<PathDiagnosticMacroPiece>(*I))
      if (!MP->containsEvent()) {
        delete MP;
        continue;
      }

    PD.push_back(*I);
  }
}

void GRBugReporter::GeneratePathDiagnostic(PathDiagnostic& PD,
                        SmallVectorImpl<BugReport *> &bugReports) {

  assert(!bugReports.empty());
  SmallVector<const ExplodedNode *, 10> errorNodes;
  for (SmallVectorImpl<BugReport*>::iterator I = bugReports.begin(),
    E = bugReports.end(); I != E; ++I) {
      errorNodes.push_back((*I)->getErrorNode());
  }

  // Construct a new graph that contains only a single path from the error
  // node to a root.
  const std::pair<std::pair<ExplodedGraph*, NodeBackMap*>,
  std::pair<ExplodedNode*, unsigned> >&
    GPair = MakeReportGraph(&getGraph(), errorNodes);

  // Find the BugReport with the original location.
  assert(GPair.second.second < bugReports.size());
  BugReport *R = bugReports[GPair.second.second];
  assert(R && "No original report found for sliced graph.");

  llvm::OwningPtr<ExplodedGraph> ReportGraph(GPair.first.first);
  llvm::OwningPtr<NodeBackMap> BackMap(GPair.first.second);
  const ExplodedNode *N = GPair.second.first;

  // Start building the path diagnostic...
  PathDiagnosticBuilder PDB(*this, R, BackMap.get(), getPathDiagnosticClient());

  // Register additional node visitors.
  R->addVisitor(new NilReceiverBRVisitor());
  R->addVisitor(new ConditionBRVisitor());

  // Generate the very last diagnostic piece - the piece is visible before
  // the trace is expanded.
  PathDiagnosticPiece *LastPiece = 0;
  for (BugReport::visitor_iterator I = R->visitor_begin(),
                                   E = R->visitor_end(); I!=E; ++I) {
    if (PathDiagnosticPiece *Piece = (*I)->getEndPath(PDB, N, *R)) {
      assert (!LastPiece &&
              "There can only be one final piece in a diagnostic.");
      LastPiece = Piece;
    }
  }
  if (!LastPiece)
    LastPiece = BugReporterVisitor::getDefaultEndPath(PDB, N, *R);
  if (LastPiece)
    PD.push_back(LastPiece);
  else
    return;

  switch (PDB.getGenerationScheme()) {
    case PathDiagnosticClient::Extensive:
      GenerateExtensivePathDiagnostic(PD, PDB, N);
      break;
    case PathDiagnosticClient::Minimal:
      GenerateMinimalPathDiagnostic(PD, PDB, N);
      break;
  }
}

void BugReporter::Register(BugType *BT) {
  BugTypes = F.add(BugTypes, BT);
}

void BugReporter::EmitReport(BugReport* R) {
  // Compute the bug report's hash to determine its equivalence class.
  llvm::FoldingSetNodeID ID;
  R->Profile(ID);

  // Lookup the equivance class.  If there isn't one, create it.
  BugType& BT = R->getBugType();
  Register(&BT);
  void *InsertPos;
  BugReportEquivClass* EQ = EQClasses.FindNodeOrInsertPos(ID, InsertPos);

  if (!EQ) {
    EQ = new BugReportEquivClass(R);
    EQClasses.InsertNode(EQ, InsertPos);
    EQClassesVector.push_back(EQ);
  }
  else
    EQ->AddReport(R);
}


//===----------------------------------------------------------------------===//
// Emitting reports in equivalence classes.
//===----------------------------------------------------------------------===//

namespace {
struct FRIEC_WLItem {
  const ExplodedNode *N;
  ExplodedNode::const_succ_iterator I, E;

  FRIEC_WLItem(const ExplodedNode *n)
  : N(n), I(N->succ_begin()), E(N->succ_end()) {}
};
}

static BugReport *
FindReportInEquivalenceClass(BugReportEquivClass& EQ,
                             SmallVectorImpl<BugReport*> &bugReports) {

  BugReportEquivClass::iterator I = EQ.begin(), E = EQ.end();
  assert(I != E);
  BugReport *R = *I;
  BugType& BT = R->getBugType();

  // If we don't need to suppress any of the nodes because they are
  // post-dominated by a sink, simply add all the nodes in the equivalence class
  // to 'Nodes'.  Any of the reports will serve as a "representative" report.
  if (!BT.isSuppressOnSink()) {
    for (BugReportEquivClass::iterator I=EQ.begin(), E=EQ.end(); I!=E; ++I) {
      const ExplodedNode *N = I->getErrorNode();
      if (N) {
        R = *I;
        bugReports.push_back(R);
      }
    }
    return R;
  }

  // For bug reports that should be suppressed when all paths are post-dominated
  // by a sink node, iterate through the reports in the equivalence class
  // until we find one that isn't post-dominated (if one exists).  We use a
  // DFS traversal of the ExplodedGraph to find a non-sink node.  We could write
  // this as a recursive function, but we don't want to risk blowing out the
  // stack for very long paths.
  BugReport *exampleReport = 0;

  for (; I != E; ++I) {
    R = *I;
    const ExplodedNode *errorNode = R->getErrorNode();

    if (!errorNode)
      continue;
    if (errorNode->isSink()) {
      assert(false &&
           "BugType::isSuppressSink() should not be 'true' for sink end nodes");
      return 0;
    }
    // No successors?  By definition this nodes isn't post-dominated by a sink.
    if (errorNode->succ_empty()) {
      bugReports.push_back(R);
      if (!exampleReport)
        exampleReport = R;
      continue;
    }

    // At this point we know that 'N' is not a sink and it has at least one
    // successor.  Use a DFS worklist to find a non-sink end-of-path node.
    typedef FRIEC_WLItem WLItem;
    typedef SmallVector<WLItem, 10> DFSWorkList;
    llvm::DenseMap<const ExplodedNode *, unsigned> Visited;

    DFSWorkList WL;
    WL.push_back(errorNode);
    Visited[errorNode] = 1;

    while (!WL.empty()) {
      WLItem &WI = WL.back();
      assert(!WI.N->succ_empty());

      for (; WI.I != WI.E; ++WI.I) {
        const ExplodedNode *Succ = *WI.I;
        // End-of-path node?
        if (Succ->succ_empty()) {
          // If we found an end-of-path node that is not a sink.
          if (!Succ->isSink()) {
            bugReports.push_back(R);
            if (!exampleReport)
              exampleReport = R;
            WL.clear();
            break;
          }
          // Found a sink?  Continue on to the next successor.
          continue;
        }
        // Mark the successor as visited.  If it hasn't been explored,
        // enqueue it to the DFS worklist.
        unsigned &mark = Visited[Succ];
        if (!mark) {
          mark = 1;
          WL.push_back(Succ);
          break;
        }
      }

      // The worklist may have been cleared at this point.  First
      // check if it is empty before checking the last item.
      if (!WL.empty() && &WL.back() == &WI)
        WL.pop_back();
    }
  }

  // ExampleReport will be NULL if all the nodes in the equivalence class
  // were post-dominated by sinks.
  return exampleReport;
}

//===----------------------------------------------------------------------===//
// DiagnosticCache.  This is a hack to cache analyzer diagnostics.  It
// uses global state, which eventually should go elsewhere.
//===----------------------------------------------------------------------===//
namespace {
class DiagCacheItem : public llvm::FoldingSetNode {
  llvm::FoldingSetNodeID ID;
public:
  DiagCacheItem(BugReport *R, PathDiagnostic *PD) {
    ID.AddString(R->getBugType().getName());
    ID.AddString(R->getBugType().getCategory());
    ID.AddString(R->getDescription());
    ID.AddInteger(R->getLocation().getRawEncoding());
    PD->Profile(ID);
  }

  void Profile(llvm::FoldingSetNodeID &id) {
    id = ID;
  }

  llvm::FoldingSetNodeID &getID() { return ID; }
};
}

static bool IsCachedDiagnostic(BugReport *R, PathDiagnostic *PD) {
  // FIXME: Eventually this diagnostic cache should reside in something
  // like AnalysisManager instead of being a static variable.  This is
  // really unsafe in the long term.
  typedef llvm::FoldingSet<DiagCacheItem> DiagnosticCache;
  static DiagnosticCache DC;

  void *InsertPos;
  DiagCacheItem *Item = new DiagCacheItem(R, PD);

  if (DC.FindNodeOrInsertPos(Item->getID(), InsertPos)) {
    delete Item;
    return true;
  }

  DC.InsertNode(Item, InsertPos);
  return false;
}

void BugReporter::FlushReport(BugReportEquivClass& EQ) {
  SmallVector<BugReport*, 10> bugReports;
  BugReport *exampleReport = FindReportInEquivalenceClass(EQ, bugReports);
  if (!exampleReport)
    return;

  PathDiagnosticClient* PD = getPathDiagnosticClient();

  // FIXME: Make sure we use the 'R' for the path that was actually used.
  // Probably doesn't make a difference in practice.
  BugType& BT = exampleReport->getBugType();

  llvm::OwningPtr<PathDiagnostic>
    D(new PathDiagnostic(exampleReport->getBugType().getName(),
                         !PD || PD->useVerboseDescription()
                         ? exampleReport->getDescription()
                         : exampleReport->getShortDescription(),
                         BT.getCategory()));

  if (!bugReports.empty())
    GeneratePathDiagnostic(*D.get(), bugReports);

  if (IsCachedDiagnostic(exampleReport, D.get()))
    return;

  // Get the meta data.
  const BugReport::ExtraTextList &Meta =
                                  exampleReport->getExtraText();
  for (BugReport::ExtraTextList::const_iterator i = Meta.begin(),
                                                e = Meta.end(); i != e; ++i) {
    D->addMeta(*i);
  }

  // Emit a summary diagnostic to the regular Diagnostics engine.
  BugReport::ranges_iterator Beg, End;
  llvm::tie(Beg, End) = exampleReport->getRanges();
  Diagnostic &Diag = getDiagnostic();
  FullSourceLoc L(exampleReport->getLocation(), getSourceManager());

  // Search the description for '%', as that will be interpretted as a
  // format character by FormatDiagnostics.
  StringRef desc = exampleReport->getShortDescription();
  unsigned ErrorDiag;
  {
    llvm::SmallString<512> TmpStr;
    llvm::raw_svector_ostream Out(TmpStr);
    for (StringRef::iterator I=desc.begin(), E=desc.end(); I!=E; ++I)
      if (*I == '%')
        Out << "%%";
      else
        Out << *I;

    Out.flush();
    ErrorDiag = Diag.getCustomDiagID(Diagnostic::Warning, TmpStr);
  }

  {
    DiagnosticBuilder diagBuilder = Diag.Report(L, ErrorDiag);
    for (BugReport::ranges_iterator I = Beg; I != End; ++I)
      diagBuilder << *I;
  }

  // Emit a full diagnostic for the path if we have a PathDiagnosticClient.
  if (!PD)
    return;

  if (D->empty()) {
    PathDiagnosticPiece *piece =
      new PathDiagnosticEventPiece(L, exampleReport->getDescription());

    for ( ; Beg != End; ++Beg) piece->addRange(*Beg);
    D->push_back(piece);
  }

  PD->HandlePathDiagnostic(D.take());
}

void BugReporter::EmitBasicReport(StringRef name, StringRef str,
                                  SourceLocation Loc,
                                  SourceRange* RBeg, unsigned NumRanges) {
  EmitBasicReport(name, "", str, Loc, RBeg, NumRanges);
}

void BugReporter::EmitBasicReport(StringRef name,
                                  StringRef category,
                                  StringRef str, SourceLocation Loc,
                                  SourceRange* RBeg, unsigned NumRanges) {

  // 'BT' is owned by BugReporter.
  BugType *BT = getBugTypeForName(name, category);
  FullSourceLoc L = getContext().getFullLoc(Loc);
  BugReport *R = new BugReport(*BT, str, L);
  for ( ; NumRanges > 0 ; --NumRanges, ++RBeg) R->addRange(*RBeg);
  EmitReport(R);
}

BugType *BugReporter::getBugTypeForName(StringRef name,
                                        StringRef category) {
  llvm::SmallString<136> fullDesc;
  llvm::raw_svector_ostream(fullDesc) << name << ":" << category;
  llvm::StringMapEntry<BugType *> &
      entry = StrBugTypes.GetOrCreateValue(fullDesc);
  BugType *BT = entry.getValue();
  if (!BT) {
    BT = new BugType(name, category);
    entry.setValue(BT);
  }
  return BT;
}