BugReporterVisitors.cpp revision 0cd59482abd8aec9ed1eaad11f5fe9c1e42639f6 
1// BugReporterVisitors.cpp - Helpers for reporting bugs -----------*- C++ -*--//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10//  This file defines a set of BugReporter "visitors" which can be used to
11//  enhance the diagnostics reported for a bug.
12//
13//===----------------------------------------------------------------------===//
14#include "clang/StaticAnalyzer/Core/BugReporter/BugReporterVisitor.h"
15
16#include "clang/AST/Expr.h"
17#include "clang/AST/ExprObjC.h"
18#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
19#include "clang/StaticAnalyzer/Core/BugReporter/PathDiagnostic.h"
20#include "clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h"
21#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
22#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
23
24using namespace clang;
25using namespace ento;
26
27//===----------------------------------------------------------------------===//
28// Utility functions.
29//===----------------------------------------------------------------------===//
30
31const Stmt *bugreporter::GetDerefExpr(const ExplodedNode *N) {
32  // Pattern match for a few useful cases (do something smarter later):
33  //   a[0], p->f, *p
34  const Stmt *S = N->getLocationAs<PostStmt>()->getStmt();
35
36  if (const UnaryOperator *U = dyn_cast<UnaryOperator>(S)) {
37    if (U->getOpcode() == UO_Deref)
38      return U->getSubExpr()->IgnoreParenCasts();
39  }
40  else if (const MemberExpr *ME = dyn_cast<MemberExpr>(S)) {
41    return ME->getBase()->IgnoreParenCasts();
42  }
43  else if (const ArraySubscriptExpr *AE = dyn_cast<ArraySubscriptExpr>(S)) {
44    return AE->getBase();
45  }
46
47  return NULL;
48}
49
50const Stmt *bugreporter::GetDenomExpr(const ExplodedNode *N) {
51  const Stmt *S = N->getLocationAs<PreStmt>()->getStmt();
52  if (const BinaryOperator *BE = dyn_cast<BinaryOperator>(S))
53    return BE->getRHS();
54  return NULL;
55}
56
57const Stmt *bugreporter::GetCalleeExpr(const ExplodedNode *N) {
58  // Callee is checked as a PreVisit to the CallExpr.
59  const Stmt *S = N->getLocationAs<PreStmt>()->getStmt();
60  if (const CallExpr *CE = dyn_cast<CallExpr>(S))
61    return CE->getCallee();
62  return NULL;
63}
64
65const Stmt *bugreporter::GetRetValExpr(const ExplodedNode *N) {
66  const Stmt *S = N->getLocationAs<PostStmt>()->getStmt();
67  if (const ReturnStmt *RS = dyn_cast<ReturnStmt>(S))
68    return RS->getRetValue();
69  return NULL;
70}
71
72//===----------------------------------------------------------------------===//
73// Definitions for bug reporter visitors.
74//===----------------------------------------------------------------------===//
75
76PathDiagnosticPiece*
77BugReporterVisitor::getEndPath(BugReporterContext &BRC,
78                               const ExplodedNode *EndPathNode,
79                               BugReport &BR) {
80  return 0;
81}
82
83PathDiagnosticPiece*
84BugReporterVisitor::getDefaultEndPath(BugReporterContext &BRC,
85                                      const ExplodedNode *EndPathNode,
86                                      BugReport &BR) {
87  const ProgramPoint &PP = EndPathNode->getLocation();
88  PathDiagnosticLocation L;
89
90  if (const BlockEntrance *BE = dyn_cast<BlockEntrance>(&PP)) {
91    const CFGBlock *block = BE->getBlock();
92    if (block->getBlockID() == 0) {
93      L = PathDiagnosticLocation::createDeclEnd(PP.getLocationContext(),
94                                                BRC.getSourceManager());
95    }
96  }
97
98  if (!L.isValid()) {
99    const Stmt *S = BR.getStmt();
100
101    if (!S)
102      return NULL;
103
104    L = PathDiagnosticLocation(S, BRC.getSourceManager(),
105                                  PP.getLocationContext());
106  }
107
108  BugReport::ranges_iterator Beg, End;
109  llvm::tie(Beg, End) = BR.getRanges();
110
111  // Only add the statement itself as a range if we didn't specify any
112  // special ranges for this report.
113  PathDiagnosticPiece *P = new PathDiagnosticEventPiece(L,
114      BR.getDescription(),
115      Beg == End);
116  for (; Beg != End; ++Beg)
117    P->addRange(*Beg);
118
119  return P;
120}
121
122
123void FindLastStoreBRVisitor ::Profile(llvm::FoldingSetNodeID &ID) const {
124  static int tag = 0;
125  ID.AddPointer(&tag);
126  ID.AddPointer(R);
127  ID.Add(V);
128}
129
130PathDiagnosticPiece *FindLastStoreBRVisitor::VisitNode(const ExplodedNode *N,
131                                                     const ExplodedNode *PrevN,
132                                                     BugReporterContext &BRC,
133                                                     BugReport &BR) {
134
135  if (satisfied)
136    return NULL;
137
138  if (!StoreSite) {
139    const ExplodedNode *Node = N, *Last = NULL;
140
141    for ( ; Node ; Last = Node, Node = Node->getFirstPred()) {
142
143      if (const VarRegion *VR = dyn_cast<VarRegion>(R)) {
144        if (const PostStmt *P = Node->getLocationAs<PostStmt>())
145          if (const DeclStmt *DS = P->getStmtAs<DeclStmt>())
146            if (DS->getSingleDecl() == VR->getDecl()) {
147              Last = Node;
148              break;
149            }
150      }
151
152      if (Node->getState()->getSVal(R) != V)
153        break;
154    }
155
156    if (!Node || !Last) {
157      satisfied = true;
158      return NULL;
159    }
160
161    StoreSite = Last;
162  }
163
164  if (StoreSite != N)
165    return NULL;
166
167  satisfied = true;
168  llvm::SmallString<256> sbuf;
169  llvm::raw_svector_ostream os(sbuf);
170
171  if (const PostStmt *PS = N->getLocationAs<PostStmt>()) {
172    if (const DeclStmt *DS = PS->getStmtAs<DeclStmt>()) {
173
174      if (const VarRegion *VR = dyn_cast<VarRegion>(R)) {
175        os << "Variable '" << VR->getDecl() << "' ";
176      }
177      else
178        return NULL;
179
180      if (isa<loc::ConcreteInt>(V)) {
181        bool b = false;
182        if (R->isBoundable()) {
183          if (const TypedValueRegion *TR = dyn_cast<TypedValueRegion>(R)) {
184            if (TR->getValueType()->isObjCObjectPointerType()) {
185              os << "initialized to nil";
186              b = true;
187            }
188          }
189        }
190
191        if (!b)
192          os << "initialized to a null pointer value";
193      }
194      else if (isa<nonloc::ConcreteInt>(V)) {
195        os << "initialized to " << cast<nonloc::ConcreteInt>(V).getValue();
196      }
197      else if (V.isUndef()) {
198        if (isa<VarRegion>(R)) {
199          const VarDecl *VD = cast<VarDecl>(DS->getSingleDecl());
200          if (VD->getInit())
201            os << "initialized to a garbage value";
202          else
203            os << "declared without an initial value";
204        }
205      }
206    }
207  }
208
209  if (os.str().empty()) {
210    if (isa<loc::ConcreteInt>(V)) {
211      bool b = false;
212      if (R->isBoundable()) {
213        if (const TypedValueRegion *TR = dyn_cast<TypedValueRegion>(R)) {
214          if (TR->getValueType()->isObjCObjectPointerType()) {
215            os << "nil object reference stored to ";
216            b = true;
217          }
218        }
219      }
220
221      if (!b)
222        os << "Null pointer value stored to ";
223    }
224    else if (V.isUndef()) {
225      os << "Uninitialized value stored to ";
226    }
227    else if (isa<nonloc::ConcreteInt>(V)) {
228      os << "The value " << cast<nonloc::ConcreteInt>(V).getValue()
229               << " is assigned to ";
230    }
231    else
232      return NULL;
233
234    if (const VarRegion *VR = dyn_cast<VarRegion>(R)) {
235      os << '\'' << VR->getDecl() << '\'';
236    }
237    else
238      return NULL;
239  }
240
241  // Construct a new PathDiagnosticPiece.
242  ProgramPoint P = N->getLocation();
243  PathDiagnosticLocation L = PathDiagnosticLocation(P,BRC.getSourceManager());
244  if (!L.isValid())
245    return NULL;
246  return new PathDiagnosticEventPiece(L, os.str());
247}
248
249void TrackConstraintBRVisitor::Profile(llvm::FoldingSetNodeID &ID) const {
250  static int tag = 0;
251  ID.AddPointer(&tag);
252  ID.AddBoolean(Assumption);
253  ID.Add(Constraint);
254}
255
256PathDiagnosticPiece *
257TrackConstraintBRVisitor::VisitNode(const ExplodedNode *N,
258                                    const ExplodedNode *PrevN,
259                                    BugReporterContext &BRC,
260                                    BugReport &BR) {
261  if (isSatisfied)
262    return NULL;
263
264  // Check if in the previous state it was feasible for this constraint
265  // to *not* be true.
266  if (PrevN->getState()->assume(Constraint, !Assumption)) {
267
268    isSatisfied = true;
269
270    // As a sanity check, make sure that the negation of the constraint
271    // was infeasible in the current state.  If it is feasible, we somehow
272    // missed the transition point.
273    if (N->getState()->assume(Constraint, !Assumption))
274      return NULL;
275
276    // We found the transition point for the constraint.  We now need to
277    // pretty-print the constraint. (work-in-progress)
278    std::string sbuf;
279    llvm::raw_string_ostream os(sbuf);
280
281    if (isa<Loc>(Constraint)) {
282      os << "Assuming pointer value is ";
283      os << (Assumption ? "non-null" : "null");
284    }
285
286    if (os.str().empty())
287      return NULL;
288
289    // Construct a new PathDiagnosticPiece.
290    ProgramPoint P = N->getLocation();
291    PathDiagnosticLocation L = PathDiagnosticLocation(P,BRC.getSourceManager());
292    if (!L.isValid())
293      return NULL;
294    return new PathDiagnosticEventPiece(L, os.str());
295  }
296
297  return NULL;
298}
299
300BugReporterVisitor *
301bugreporter::getTrackNullOrUndefValueVisitor(const ExplodedNode *N,
302                                             const Stmt *S) {
303  if (!S || !N)
304    return 0;
305
306  ProgramStateManager &StateMgr = N->getState()->getStateManager();
307
308  // Walk through nodes until we get one that matches the statement
309  // exactly.
310  while (N) {
311    const ProgramPoint &pp = N->getLocation();
312    if (const PostStmt *ps = dyn_cast<PostStmt>(&pp)) {
313      if (ps->getStmt() == S)
314        break;
315    }
316    N = *N->pred_begin();
317  }
318
319  if (!N)
320    return 0;
321
322  const ProgramState *state = N->getState();
323
324  // Walk through lvalue-to-rvalue conversions.
325  if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(S)) {
326    if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) {
327      const VarRegion *R =
328        StateMgr.getRegionManager().getVarRegion(VD, N->getLocationContext());
329
330      // What did we load?
331      SVal V = state->getSVal(loc::MemRegionVal(R));
332
333      if (isa<loc::ConcreteInt>(V) || isa<nonloc::ConcreteInt>(V)
334          || V.isUndef()) {
335        return new FindLastStoreBRVisitor(V, R);
336      }
337    }
338  }
339
340  SVal V = state->getSValAsScalarOrLoc(S);
341
342  // Uncomment this to find cases where we aren't properly getting the
343  // base value that was dereferenced.
344  // assert(!V.isUnknownOrUndef());
345
346  // Is it a symbolic value?
347  if (loc::MemRegionVal *L = dyn_cast<loc::MemRegionVal>(&V)) {
348    const SubRegion *R = cast<SubRegion>(L->getRegion());
349    while (R && !isa<SymbolicRegion>(R)) {
350      R = dyn_cast<SubRegion>(R->getSuperRegion());
351    }
352
353    if (R) {
354      assert(isa<SymbolicRegion>(R));
355      return new TrackConstraintBRVisitor(loc::MemRegionVal(R), false);
356    }
357  }
358
359  return 0;
360}
361
362BugReporterVisitor *
363FindLastStoreBRVisitor::createVisitorObject(const ExplodedNode *N,
364                                            const MemRegion *R) {
365  assert(R && "The memory region is null.");
366
367  const ProgramState *state = N->getState();
368  SVal V = state->getSVal(R);
369  if (V.isUnknown())
370    return 0;
371
372  return new FindLastStoreBRVisitor(V, R);
373}
374
375
376PathDiagnosticPiece *NilReceiverBRVisitor::VisitNode(const ExplodedNode *N,
377                                                     const ExplodedNode *PrevN,
378                                                     BugReporterContext &BRC,
379                                                     BugReport &BR) {
380  const PostStmt *P = N->getLocationAs<PostStmt>();
381  if (!P)
382    return 0;
383  const ObjCMessageExpr *ME = P->getStmtAs<ObjCMessageExpr>();
384  if (!ME)
385    return 0;
386  const Expr *Receiver = ME->getInstanceReceiver();
387  if (!Receiver)
388    return 0;
389  const ProgramState *state = N->getState();
390  const SVal &V = state->getSVal(Receiver);
391  const DefinedOrUnknownSVal *DV = dyn_cast<DefinedOrUnknownSVal>(&V);
392  if (!DV)
393    return 0;
394  state = state->assume(*DV, true);
395  if (state)
396    return 0;
397
398  // The receiver was nil, and hence the method was skipped.
399  // Register a BugReporterVisitor to issue a message telling us how
400  // the receiver was null.
401  BR.addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, Receiver));
402  // Issue a message saying that the method was skipped.
403  PathDiagnosticLocation L(Receiver, BRC.getSourceManager(),
404                                     N->getLocationContext());
405  return new PathDiagnosticEventPiece(L, "No method actually called "
406      "because the receiver is nil");
407}
408
409// Registers every VarDecl inside a Stmt with a last store visitor.
410void FindLastStoreBRVisitor::registerStatementVarDecls(BugReport &BR,
411                                                       const Stmt *S) {
412  const ExplodedNode *N = BR.getErrorNode();
413  std::deque<const Stmt *> WorkList;
414  WorkList.push_back(S);
415
416  while (!WorkList.empty()) {
417    const Stmt *Head = WorkList.front();
418    WorkList.pop_front();
419
420    const ProgramState *state = N->getState();
421    ProgramStateManager &StateMgr = state->getStateManager();
422
423    if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Head)) {
424      if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) {
425        const VarRegion *R =
426        StateMgr.getRegionManager().getVarRegion(VD, N->getLocationContext());
427
428        // What did we load?
429        SVal V = state->getSVal(S);
430
431        if (isa<loc::ConcreteInt>(V) || isa<nonloc::ConcreteInt>(V)) {
432          // Register a new visitor with the BugReport.
433          BR.addVisitor(new FindLastStoreBRVisitor(V, R));
434        }
435      }
436    }
437
438    for (Stmt::const_child_iterator I = Head->child_begin();
439        I != Head->child_end(); ++I)
440      WorkList.push_back(*I);
441  }
442}
443
444//===----------------------------------------------------------------------===//
445// Visitor that tries to report interesting diagnostics from conditions.
446//===----------------------------------------------------------------------===//
447PathDiagnosticPiece *ConditionBRVisitor::VisitNode(const ExplodedNode *N,
448                                                   const ExplodedNode *Prev,
449                                                   BugReporterContext &BRC,
450                                                   BugReport &BR) {
451
452  const ProgramPoint &progPoint = N->getLocation();
453
454  const ProgramState *CurrentState = N->getState();
455  const ProgramState *PrevState = Prev->getState();
456
457  // Compare the GDMs of the state, because that is where constraints
458  // are managed.  Note that ensure that we only look at nodes that
459  // were generated by the analyzer engine proper, not checkers.
460  if (CurrentState->getGDM().getRoot() ==
461      PrevState->getGDM().getRoot())
462    return 0;
463
464  // If an assumption was made on a branch, it should be caught
465  // here by looking at the state transition.
466  if (const BlockEdge *BE = dyn_cast<BlockEdge>(&progPoint)) {
467    const CFGBlock *srcBlk = BE->getSrc();
468    if (const Stmt *term = srcBlk->getTerminator())
469      return VisitTerminator(term, N, srcBlk, BE->getDst(), BRC);
470    return 0;
471  }
472
473  if (const PostStmt *PS = dyn_cast<PostStmt>(&progPoint)) {
474    // FIXME: Assuming that BugReporter is a GRBugReporter is a layering
475    // violation.
476    const std::pair<const ProgramPointTag *, const ProgramPointTag *> &tags =
477      cast<GRBugReporter>(BRC.getBugReporter()).
478        getEngine().getEagerlyAssumeTags();
479
480    const ProgramPointTag *tag = PS->getTag();
481    if (tag == tags.first)
482      return VisitTrueTest(cast<Expr>(PS->getStmt()), true,
483                           BRC, N->getLocationContext());
484    if (tag == tags.second)
485      return VisitTrueTest(cast<Expr>(PS->getStmt()), false,
486                           BRC, N->getLocationContext());
487
488    return 0;
489  }
490
491  return 0;
492}
493
494PathDiagnosticPiece *
495ConditionBRVisitor::VisitTerminator(const Stmt *Term,
496                                    const ExplodedNode *N,
497                                    const CFGBlock *srcBlk,
498                                    const CFGBlock *dstBlk,
499                                    BugReporterContext &BRC) {
500  const Expr *Cond = 0;
501
502  switch (Term->getStmtClass()) {
503  default:
504    return 0;
505  case Stmt::IfStmtClass:
506    Cond = cast<IfStmt>(Term)->getCond();
507    break;
508  case Stmt::ConditionalOperatorClass:
509    Cond = cast<ConditionalOperator>(Term)->getCond();
510    break;
511  }
512
513  assert(Cond);
514  assert(srcBlk->succ_size() == 2);
515  const bool tookTrue = *(srcBlk->succ_begin()) == dstBlk;
516  return VisitTrueTest(Cond->IgnoreParenNoopCasts(BRC.getASTContext()),
517                       tookTrue, BRC, N->getLocationContext());
518}
519
520PathDiagnosticPiece *
521ConditionBRVisitor::VisitTrueTest(const Expr *Cond,
522                                  bool tookTrue,
523                                  BugReporterContext &BRC,
524                                  const LocationContext *LC) {
525
526  const Expr *Ex = Cond;
527
528  while (true) {
529    Ex = Ex->IgnoreParens();
530    switch (Ex->getStmtClass()) {
531      default:
532        return 0;
533      case Stmt::BinaryOperatorClass:
534        return VisitTrueTest(Cond, cast<BinaryOperator>(Ex), tookTrue, BRC, LC);
535      case Stmt::DeclRefExprClass:
536        return VisitTrueTest(Cond, cast<DeclRefExpr>(Ex), tookTrue, BRC, LC);
537      case Stmt::UnaryOperatorClass: {
538        const UnaryOperator *UO = cast<UnaryOperator>(Ex);
539        if (UO->getOpcode() == UO_LNot) {
540          tookTrue = !tookTrue;
541          Ex = UO->getSubExpr()->IgnoreParenNoopCasts(BRC.getASTContext());
542          continue;
543        }
544        return 0;
545      }
546    }
547  }
548}
549
550bool ConditionBRVisitor::patternMatch(const Expr *Ex, llvm::raw_ostream &Out,
551                                      BugReporterContext &BRC) {
552  const Expr *OriginalExpr = Ex;
553  Ex = Ex->IgnoreParenCasts();
554
555  if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Ex)) {
556    const bool quotes = isa<VarDecl>(DR->getDecl());
557    if (quotes)
558      Out << '\'';
559    Out << DR->getDecl()->getDeclName().getAsString();
560    if (quotes)
561      Out << '\'';
562    return quotes;
563  }
564
565  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(Ex)) {
566    QualType OriginalTy = OriginalExpr->getType();
567    if (OriginalTy->isPointerType()) {
568      if (IL->getValue() == 0) {
569        Out << "null";
570        return false;
571      }
572    }
573    else if (OriginalTy->isObjCObjectPointerType()) {
574      if (IL->getValue() == 0) {
575        Out << "nil";
576        return false;
577      }
578    }
579
580    Out << IL->getValue();
581    return false;
582  }
583
584  return false;
585}
586
587PathDiagnosticPiece *
588ConditionBRVisitor::VisitTrueTest(const Expr *Cond,
589                                  const BinaryOperator *BExpr,
590                                  const bool tookTrue,
591                                  BugReporterContext &BRC,
592                                  const LocationContext *LC) {
593
594  bool shouldInvert = false;
595
596  llvm::SmallString<128> LhsString, RhsString;
597  {
598    llvm::raw_svector_ostream OutLHS(LhsString), OutRHS(RhsString);
599    const bool isVarLHS = patternMatch(BExpr->getLHS(), OutLHS, BRC);
600    const bool isVarRHS = patternMatch(BExpr->getRHS(), OutRHS, BRC);
601
602    shouldInvert = !isVarLHS && isVarRHS;
603  }
604
605  if (LhsString.empty() || RhsString.empty())
606    return 0;
607
608  // Should we invert the strings if the LHS is not a variable name?
609
610  llvm::SmallString<256> buf;
611  llvm::raw_svector_ostream Out(buf);
612  Out << "Assuming " << (shouldInvert ? RhsString : LhsString) << " is ";
613
614  // Do we need to invert the opcode?
615  BinaryOperator::Opcode Op = BExpr->getOpcode();
616
617  if (shouldInvert)
618    switch (Op) {
619      default: break;
620      case BO_LT: Op = BO_GT; break;
621      case BO_GT: Op = BO_LT; break;
622      case BO_LE: Op = BO_GE; break;
623      case BO_GE: Op = BO_LE; break;
624    }
625
626  if (!tookTrue)
627    switch (Op) {
628      case BO_EQ: Op = BO_NE; break;
629      case BO_NE: Op = BO_EQ; break;
630      case BO_LT: Op = BO_GE; break;
631      case BO_GT: Op = BO_LE; break;
632      case BO_LE: Op = BO_GT; break;
633      case BO_GE: Op = BO_LT; break;
634      default:
635        return 0;
636    }
637
638  switch (BExpr->getOpcode()) {
639    case BO_EQ:
640      Out << "equal to ";
641      break;
642    case BO_NE:
643      Out << "not equal to ";
644      break;
645    default:
646      Out << BinaryOperator::getOpcodeStr(Op) << ' ';
647      break;
648  }
649
650  Out << (shouldInvert ? LhsString : RhsString);
651
652  PathDiagnosticLocation Loc(Cond, BRC.getSourceManager(), LC);
653  return new PathDiagnosticEventPiece(Loc, Out.str());
654}
655
656PathDiagnosticPiece *
657ConditionBRVisitor::VisitTrueTest(const Expr *Cond,
658                                  const DeclRefExpr *DR,
659                                  const bool tookTrue,
660                                  BugReporterContext &BRC,
661                                  const LocationContext *LC) {
662
663  const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl());
664  if (!VD)
665    return 0;
666
667  llvm::SmallString<256> Buf;
668  llvm::raw_svector_ostream Out(Buf);
669
670  Out << "Assuming '";
671  VD->getDeclName().printName(Out);
672  Out << "' is ";
673
674  QualType VDTy = VD->getType();
675
676  if (VDTy->isPointerType())
677    Out << (tookTrue ? "non-null" : "null");
678  else if (VDTy->isObjCObjectPointerType())
679    Out << (tookTrue ? "non-nil" : "nil");
680  else if (VDTy->isScalarType())
681    Out << (tookTrue ? "not equal to 0" : "0");
682  else
683    return 0;
684
685  PathDiagnosticLocation Loc(Cond, BRC.getSourceManager(), LC);
686  return new PathDiagnosticEventPiece(Loc, Out.str());
687}
688