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BugReporter.cpp
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00001 // BugReporter.cpp - Generate PathDiagnostics for Bugs ------------*- C++ -*--//
00002 //
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file is distributed under the University of Illinois Open Source
00006 // License. See LICENSE.TXT for details.
00007 //
00008 //===----------------------------------------------------------------------===//
00009 //
00010 //  This file defines BugReporter, a utility class for generating
00011 //  PathDiagnostics.
00012 //
00013 //===----------------------------------------------------------------------===//
00014 
00015 #include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
00016 #include "clang/AST/ASTContext.h"
00017 #include "clang/AST/DeclObjC.h"
00018 #include "clang/AST/Expr.h"
00019 #include "clang/AST/ExprCXX.h"
00020 #include "clang/AST/ParentMap.h"
00021 #include "clang/AST/StmtCXX.h"
00022 #include "clang/AST/StmtObjC.h"
00023 #include "clang/Analysis/CFG.h"
00024 #include "clang/Analysis/ProgramPoint.h"
00025 #include "clang/Basic/SourceManager.h"
00026 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
00027 #include "clang/StaticAnalyzer/Core/BugReporter/PathDiagnostic.h"
00028 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
00029 #include "llvm/ADT/DenseMap.h"
00030 #include "llvm/ADT/IntrusiveRefCntPtr.h"
00031 #include "llvm/ADT/STLExtras.h"
00032 #include "llvm/ADT/SmallString.h"
00033 #include "llvm/ADT/Statistic.h"
00034 #include "llvm/Support/raw_ostream.h"
00035 #include <memory>
00036 #include <queue>
00037 
00038 using namespace clang;
00039 using namespace ento;
00040 
00041 #define DEBUG_TYPE "BugReporter"
00042 
00043 STATISTIC(MaxBugClassSize,
00044           "The maximum number of bug reports in the same equivalence class");
00045 STATISTIC(MaxValidBugClassSize,
00046           "The maximum number of bug reports in the same equivalence class "
00047           "where at least one report is valid (not suppressed)");
00048 
00049 BugReporterVisitor::~BugReporterVisitor() {}
00050 
00051 void BugReporterContext::anchor() {}
00052 
00053 //===----------------------------------------------------------------------===//
00054 // Helper routines for walking the ExplodedGraph and fetching statements.
00055 //===----------------------------------------------------------------------===//
00056 
00057 static const Stmt *GetPreviousStmt(const ExplodedNode *N) {
00058   for (N = N->getFirstPred(); N; N = N->getFirstPred())
00059     if (const Stmt *S = PathDiagnosticLocation::getStmt(N))
00060       return S;
00061 
00062   return nullptr;
00063 }
00064 
00065 static inline const Stmt*
00066 GetCurrentOrPreviousStmt(const ExplodedNode *N) {
00067   if (const Stmt *S = PathDiagnosticLocation::getStmt(N))
00068     return S;
00069 
00070   return GetPreviousStmt(N);
00071 }
00072 
00073 //===----------------------------------------------------------------------===//
00074 // Diagnostic cleanup.
00075 //===----------------------------------------------------------------------===//
00076 
00077 static PathDiagnosticEventPiece *
00078 eventsDescribeSameCondition(PathDiagnosticEventPiece *X,
00079                             PathDiagnosticEventPiece *Y) {
00080   // Prefer diagnostics that come from ConditionBRVisitor over
00081   // those that came from TrackConstraintBRVisitor.
00082   const void *tagPreferred = ConditionBRVisitor::getTag();
00083   const void *tagLesser = TrackConstraintBRVisitor::getTag();
00084   
00085   if (X->getLocation() != Y->getLocation())
00086     return nullptr;
00087 
00088   if (X->getTag() == tagPreferred && Y->getTag() == tagLesser)
00089     return X;
00090   
00091   if (Y->getTag() == tagPreferred && X->getTag() == tagLesser)
00092     return Y;
00093 
00094   return nullptr;
00095 }
00096 
00097 /// An optimization pass over PathPieces that removes redundant diagnostics
00098 /// generated by both ConditionBRVisitor and TrackConstraintBRVisitor.  Both
00099 /// BugReporterVisitors use different methods to generate diagnostics, with
00100 /// one capable of emitting diagnostics in some cases but not in others.  This
00101 /// can lead to redundant diagnostic pieces at the same point in a path.
00102 static void removeRedundantMsgs(PathPieces &path) {
00103   unsigned N = path.size();
00104   if (N < 2)
00105     return;
00106   // NOTE: this loop intentionally is not using an iterator.  Instead, we
00107   // are streaming the path and modifying it in place.  This is done by
00108   // grabbing the front, processing it, and if we decide to keep it append
00109   // it to the end of the path.  The entire path is processed in this way.
00110   for (unsigned i = 0; i < N; ++i) {
00111     IntrusiveRefCntPtr<PathDiagnosticPiece> piece(path.front());
00112     path.pop_front();
00113     
00114     switch (piece->getKind()) {
00115       case clang::ento::PathDiagnosticPiece::Call:
00116         removeRedundantMsgs(cast<PathDiagnosticCallPiece>(piece)->path);
00117         break;
00118       case clang::ento::PathDiagnosticPiece::Macro:
00119         removeRedundantMsgs(cast<PathDiagnosticMacroPiece>(piece)->subPieces);
00120         break;
00121       case clang::ento::PathDiagnosticPiece::ControlFlow:
00122         break;
00123       case clang::ento::PathDiagnosticPiece::Event: {
00124         if (i == N-1)
00125           break;
00126         
00127         if (PathDiagnosticEventPiece *nextEvent =
00128             dyn_cast<PathDiagnosticEventPiece>(path.front().get())) {
00129           PathDiagnosticEventPiece *event =
00130             cast<PathDiagnosticEventPiece>(piece);
00131           // Check to see if we should keep one of the two pieces.  If we
00132           // come up with a preference, record which piece to keep, and consume
00133           // another piece from the path.
00134           if (PathDiagnosticEventPiece *pieceToKeep =
00135               eventsDescribeSameCondition(event, nextEvent)) {
00136             piece = pieceToKeep;
00137             path.pop_front();
00138             ++i;
00139           }
00140         }
00141         break;
00142       }
00143     }
00144     path.push_back(piece);
00145   }
00146 }
00147 
00148 /// A map from PathDiagnosticPiece to the LocationContext of the inlined
00149 /// function call it represents.
00150 typedef llvm::DenseMap<const PathPieces *, const LocationContext *>
00151         LocationContextMap;
00152 
00153 /// Recursively scan through a path and prune out calls and macros pieces
00154 /// that aren't needed.  Return true if afterwards the path contains
00155 /// "interesting stuff" which means it shouldn't be pruned from the parent path.
00156 static bool removeUnneededCalls(PathPieces &pieces, BugReport *R,
00157                                 LocationContextMap &LCM) {
00158   bool containsSomethingInteresting = false;
00159   const unsigned N = pieces.size();
00160   
00161   for (unsigned i = 0 ; i < N ; ++i) {
00162     // Remove the front piece from the path.  If it is still something we
00163     // want to keep once we are done, we will push it back on the end.
00164     IntrusiveRefCntPtr<PathDiagnosticPiece> piece(pieces.front());
00165     pieces.pop_front();
00166     
00167     switch (piece->getKind()) {
00168       case PathDiagnosticPiece::Call: {
00169         PathDiagnosticCallPiece *call = cast<PathDiagnosticCallPiece>(piece);
00170         // Check if the location context is interesting.
00171         assert(LCM.count(&call->path));
00172         if (R->isInteresting(LCM[&call->path])) {
00173           containsSomethingInteresting = true;
00174           break;
00175         }
00176 
00177         if (!removeUnneededCalls(call->path, R, LCM))
00178           continue;
00179         
00180         containsSomethingInteresting = true;
00181         break;
00182       }
00183       case PathDiagnosticPiece::Macro: {
00184         PathDiagnosticMacroPiece *macro = cast<PathDiagnosticMacroPiece>(piece);
00185         if (!removeUnneededCalls(macro->subPieces, R, LCM))
00186           continue;
00187         containsSomethingInteresting = true;
00188         break;
00189       }
00190       case PathDiagnosticPiece::Event: {
00191         PathDiagnosticEventPiece *event = cast<PathDiagnosticEventPiece>(piece);
00192         
00193         // We never throw away an event, but we do throw it away wholesale
00194         // as part of a path if we throw the entire path away.
00195         containsSomethingInteresting |= !event->isPrunable();
00196         break;
00197       }
00198       case PathDiagnosticPiece::ControlFlow:
00199         break;
00200     }
00201     
00202     pieces.push_back(piece);
00203   }
00204   
00205   return containsSomethingInteresting;
00206 }
00207 
00208 /// Returns true if the given decl has been implicitly given a body, either by
00209 /// the analyzer or by the compiler proper.
00210 static bool hasImplicitBody(const Decl *D) {
00211   assert(D);
00212   return D->isImplicit() || !D->hasBody();
00213 }
00214 
00215 /// Recursively scan through a path and make sure that all call pieces have
00216 /// valid locations. 
00217 static void
00218 adjustCallLocations(PathPieces &Pieces,
00219                     PathDiagnosticLocation *LastCallLocation = nullptr) {
00220   for (PathPieces::iterator I = Pieces.begin(), E = Pieces.end(); I != E; ++I) {
00221     PathDiagnosticCallPiece *Call = dyn_cast<PathDiagnosticCallPiece>(*I);
00222 
00223     if (!Call) {
00224       assert((*I)->getLocation().asLocation().isValid());
00225       continue;
00226     }
00227 
00228     if (LastCallLocation) {
00229       bool CallerIsImplicit = hasImplicitBody(Call->getCaller());
00230       if (CallerIsImplicit || !Call->callEnter.asLocation().isValid())
00231         Call->callEnter = *LastCallLocation;
00232       if (CallerIsImplicit || !Call->callReturn.asLocation().isValid())
00233         Call->callReturn = *LastCallLocation;
00234     }
00235 
00236     // Recursively clean out the subclass.  Keep this call around if
00237     // it contains any informative diagnostics.
00238     PathDiagnosticLocation *ThisCallLocation;
00239     if (Call->callEnterWithin.asLocation().isValid() &&
00240         !hasImplicitBody(Call->getCallee()))
00241       ThisCallLocation = &Call->callEnterWithin;
00242     else
00243       ThisCallLocation = &Call->callEnter;
00244 
00245     assert(ThisCallLocation && "Outermost call has an invalid location");
00246     adjustCallLocations(Call->path, ThisCallLocation);
00247   }
00248 }
00249 
00250 /// Remove edges in and out of C++ default initializer expressions. These are
00251 /// for fields that have in-class initializers, as opposed to being initialized
00252 /// explicitly in a constructor or braced list.
00253 static void removeEdgesToDefaultInitializers(PathPieces &Pieces) {
00254   for (PathPieces::iterator I = Pieces.begin(), E = Pieces.end(); I != E;) {
00255     if (PathDiagnosticCallPiece *C = dyn_cast<PathDiagnosticCallPiece>(*I))
00256       removeEdgesToDefaultInitializers(C->path);
00257 
00258     if (PathDiagnosticMacroPiece *M = dyn_cast<PathDiagnosticMacroPiece>(*I))
00259       removeEdgesToDefaultInitializers(M->subPieces);
00260 
00261     if (PathDiagnosticControlFlowPiece *CF =
00262           dyn_cast<PathDiagnosticControlFlowPiece>(*I)) {
00263       const Stmt *Start = CF->getStartLocation().asStmt();
00264       const Stmt *End = CF->getEndLocation().asStmt();
00265       if (Start && isa<CXXDefaultInitExpr>(Start)) {
00266         I = Pieces.erase(I);
00267         continue;
00268       } else if (End && isa<CXXDefaultInitExpr>(End)) {
00269         PathPieces::iterator Next = std::next(I);
00270         if (Next != E) {
00271           if (PathDiagnosticControlFlowPiece *NextCF =
00272                 dyn_cast<PathDiagnosticControlFlowPiece>(*Next)) {
00273             NextCF->setStartLocation(CF->getStartLocation());
00274           }
00275         }
00276         I = Pieces.erase(I);
00277         continue;
00278       }
00279     }
00280 
00281     I++;
00282   }
00283 }
00284 
00285 /// Remove all pieces with invalid locations as these cannot be serialized.
00286 /// We might have pieces with invalid locations as a result of inlining Body
00287 /// Farm generated functions.
00288 static void removePiecesWithInvalidLocations(PathPieces &Pieces) {
00289   for (PathPieces::iterator I = Pieces.begin(), E = Pieces.end(); I != E;) {
00290     if (PathDiagnosticCallPiece *C = dyn_cast<PathDiagnosticCallPiece>(*I))
00291       removePiecesWithInvalidLocations(C->path);
00292 
00293     if (PathDiagnosticMacroPiece *M = dyn_cast<PathDiagnosticMacroPiece>(*I))
00294       removePiecesWithInvalidLocations(M->subPieces);
00295 
00296     if (!(*I)->getLocation().isValid() ||
00297         !(*I)->getLocation().asLocation().isValid()) {
00298       I = Pieces.erase(I);
00299       continue;
00300     }
00301     I++;
00302   }
00303 }
00304 
00305 //===----------------------------------------------------------------------===//
00306 // PathDiagnosticBuilder and its associated routines and helper objects.
00307 //===----------------------------------------------------------------------===//
00308 
00309 namespace {
00310 class NodeMapClosure : public BugReport::NodeResolver {
00311   InterExplodedGraphMap &M;
00312 public:
00313   NodeMapClosure(InterExplodedGraphMap &m) : M(m) {}
00314 
00315   const ExplodedNode *getOriginalNode(const ExplodedNode *N) override {
00316     return M.lookup(N);
00317   }
00318 };
00319 
00320 class PathDiagnosticBuilder : public BugReporterContext {
00321   BugReport *R;
00322   PathDiagnosticConsumer *PDC;
00323   NodeMapClosure NMC;
00324 public:
00325   const LocationContext *LC;
00326   
00327   PathDiagnosticBuilder(GRBugReporter &br,
00328                         BugReport *r, InterExplodedGraphMap &Backmap,
00329                         PathDiagnosticConsumer *pdc)
00330     : BugReporterContext(br),
00331       R(r), PDC(pdc), NMC(Backmap), LC(r->getErrorNode()->getLocationContext())
00332   {}
00333 
00334   PathDiagnosticLocation ExecutionContinues(const ExplodedNode *N);
00335 
00336   PathDiagnosticLocation ExecutionContinues(llvm::raw_string_ostream &os,
00337                                             const ExplodedNode *N);
00338 
00339   BugReport *getBugReport() { return R; }
00340 
00341   Decl const &getCodeDecl() { return R->getErrorNode()->getCodeDecl(); }
00342   
00343   ParentMap& getParentMap() { return LC->getParentMap(); }
00344 
00345   const Stmt *getParent(const Stmt *S) {
00346     return getParentMap().getParent(S);
00347   }
00348 
00349   NodeMapClosure& getNodeResolver() override { return NMC; }
00350 
00351   PathDiagnosticLocation getEnclosingStmtLocation(const Stmt *S);
00352 
00353   PathDiagnosticConsumer::PathGenerationScheme getGenerationScheme() const {
00354     return PDC ? PDC->getGenerationScheme() : PathDiagnosticConsumer::Extensive;
00355   }
00356 
00357   bool supportsLogicalOpControlFlow() const {
00358     return PDC ? PDC->supportsLogicalOpControlFlow() : true;
00359   }
00360 };
00361 } // end anonymous namespace
00362 
00363 PathDiagnosticLocation
00364 PathDiagnosticBuilder::ExecutionContinues(const ExplodedNode *N) {
00365   if (const Stmt *S = PathDiagnosticLocation::getNextStmt(N))
00366     return PathDiagnosticLocation(S, getSourceManager(), LC);
00367 
00368   return PathDiagnosticLocation::createDeclEnd(N->getLocationContext(),
00369                                                getSourceManager());
00370 }
00371 
00372 PathDiagnosticLocation
00373 PathDiagnosticBuilder::ExecutionContinues(llvm::raw_string_ostream &os,
00374                                           const ExplodedNode *N) {
00375 
00376   // Slow, but probably doesn't matter.
00377   if (os.str().empty())
00378     os << ' ';
00379 
00380   const PathDiagnosticLocation &Loc = ExecutionContinues(N);
00381 
00382   if (Loc.asStmt())
00383     os << "Execution continues on line "
00384        << getSourceManager().getExpansionLineNumber(Loc.asLocation())
00385        << '.';
00386   else {
00387     os << "Execution jumps to the end of the ";
00388     const Decl *D = N->getLocationContext()->getDecl();
00389     if (isa<ObjCMethodDecl>(D))
00390       os << "method";
00391     else if (isa<FunctionDecl>(D))
00392       os << "function";
00393     else {
00394       assert(isa<BlockDecl>(D));
00395       os << "anonymous block";
00396     }
00397     os << '.';
00398   }
00399 
00400   return Loc;
00401 }
00402 
00403 static const Stmt *getEnclosingParent(const Stmt *S, const ParentMap &PM) {
00404   if (isa<Expr>(S) && PM.isConsumedExpr(cast<Expr>(S)))
00405     return PM.getParentIgnoreParens(S);
00406 
00407   const Stmt *Parent = PM.getParentIgnoreParens(S);
00408   if (!Parent)
00409     return nullptr;
00410 
00411   switch (Parent->getStmtClass()) {
00412   case Stmt::ForStmtClass:
00413   case Stmt::DoStmtClass:
00414   case Stmt::WhileStmtClass:
00415   case Stmt::ObjCForCollectionStmtClass:
00416   case Stmt::CXXForRangeStmtClass:
00417     return Parent;
00418   default:
00419     break;
00420   }
00421 
00422   return nullptr;
00423 }
00424 
00425 static PathDiagnosticLocation
00426 getEnclosingStmtLocation(const Stmt *S, SourceManager &SMgr, const ParentMap &P,
00427                          const LocationContext *LC, bool allowNestedContexts) {
00428   if (!S)
00429     return PathDiagnosticLocation();
00430 
00431   while (const Stmt *Parent = getEnclosingParent(S, P)) {
00432     switch (Parent->getStmtClass()) {
00433       case Stmt::BinaryOperatorClass: {
00434         const BinaryOperator *B = cast<BinaryOperator>(Parent);
00435         if (B->isLogicalOp())
00436           return PathDiagnosticLocation(allowNestedContexts ? B : S, SMgr, LC);
00437         break;
00438       }
00439       case Stmt::CompoundStmtClass:
00440       case Stmt::StmtExprClass:
00441         return PathDiagnosticLocation(S, SMgr, LC);
00442       case Stmt::ChooseExprClass:
00443         // Similar to '?' if we are referring to condition, just have the edge
00444         // point to the entire choose expression.
00445         if (allowNestedContexts || cast<ChooseExpr>(Parent)->getCond() == S)
00446           return PathDiagnosticLocation(Parent, SMgr, LC);
00447         else
00448           return PathDiagnosticLocation(S, SMgr, LC);
00449       case Stmt::BinaryConditionalOperatorClass:
00450       case Stmt::ConditionalOperatorClass:
00451         // For '?', if we are referring to condition, just have the edge point
00452         // to the entire '?' expression.
00453         if (allowNestedContexts ||
00454             cast<AbstractConditionalOperator>(Parent)->getCond() == S)
00455           return PathDiagnosticLocation(Parent, SMgr, LC);
00456         else
00457           return PathDiagnosticLocation(S, SMgr, LC);
00458       case Stmt::CXXForRangeStmtClass:
00459         if (cast<CXXForRangeStmt>(Parent)->getBody() == S)
00460           return PathDiagnosticLocation(S, SMgr, LC);
00461         break;
00462       case Stmt::DoStmtClass:
00463           return PathDiagnosticLocation(S, SMgr, LC);
00464       case Stmt::ForStmtClass:
00465         if (cast<ForStmt>(Parent)->getBody() == S)
00466           return PathDiagnosticLocation(S, SMgr, LC);
00467         break;
00468       case Stmt::IfStmtClass:
00469         if (cast<IfStmt>(Parent)->getCond() != S)
00470           return PathDiagnosticLocation(S, SMgr, LC);
00471         break;
00472       case Stmt::ObjCForCollectionStmtClass:
00473         if (cast<ObjCForCollectionStmt>(Parent)->getBody() == S)
00474           return PathDiagnosticLocation(S, SMgr, LC);
00475         break;
00476       case Stmt::WhileStmtClass:
00477         if (cast<WhileStmt>(Parent)->getCond() != S)
00478           return PathDiagnosticLocation(S, SMgr, LC);
00479         break;
00480       default:
00481         break;
00482     }
00483 
00484     S = Parent;
00485   }
00486 
00487   assert(S && "Cannot have null Stmt for PathDiagnosticLocation");
00488 
00489   return PathDiagnosticLocation(S, SMgr, LC);
00490 }
00491 
00492 PathDiagnosticLocation
00493 PathDiagnosticBuilder::getEnclosingStmtLocation(const Stmt *S) {
00494   assert(S && "Null Stmt passed to getEnclosingStmtLocation");
00495   return ::getEnclosingStmtLocation(S, getSourceManager(), getParentMap(), LC,
00496                                     /*allowNestedContexts=*/false);
00497 }
00498 
00499 //===----------------------------------------------------------------------===//
00500 // "Visitors only" path diagnostic generation algorithm.
00501 //===----------------------------------------------------------------------===//
00502 static bool GenerateVisitorsOnlyPathDiagnostic(
00503     PathDiagnostic &PD, PathDiagnosticBuilder &PDB, const ExplodedNode *N,
00504     ArrayRef<std::unique_ptr<BugReporterVisitor>> visitors) {
00505   // All path generation skips the very first node (the error node).
00506   // This is because there is special handling for the end-of-path note.
00507   N = N->getFirstPred();
00508   if (!N)
00509     return true;
00510 
00511   BugReport *R = PDB.getBugReport();
00512   while (const ExplodedNode *Pred = N->getFirstPred()) {
00513     for (auto &V : visitors) {
00514       // Visit all the node pairs, but throw the path pieces away.
00515       PathDiagnosticPiece *Piece = V->VisitNode(N, Pred, PDB, *R);
00516       delete Piece;
00517     }
00518 
00519     N = Pred;
00520   }
00521 
00522   return R->isValid();
00523 }
00524 
00525 //===----------------------------------------------------------------------===//
00526 // "Minimal" path diagnostic generation algorithm.
00527 //===----------------------------------------------------------------------===//
00528 typedef std::pair<PathDiagnosticCallPiece*, const ExplodedNode*> StackDiagPair;
00529 typedef SmallVector<StackDiagPair, 6> StackDiagVector;
00530 
00531 static void updateStackPiecesWithMessage(PathDiagnosticPiece *P,
00532                                          StackDiagVector &CallStack) {
00533   // If the piece contains a special message, add it to all the call
00534   // pieces on the active stack.
00535   if (PathDiagnosticEventPiece *ep =
00536         dyn_cast<PathDiagnosticEventPiece>(P)) {
00537 
00538     if (ep->hasCallStackHint())
00539       for (StackDiagVector::iterator I = CallStack.begin(),
00540                                      E = CallStack.end(); I != E; ++I) {
00541         PathDiagnosticCallPiece *CP = I->first;
00542         const ExplodedNode *N = I->second;
00543         std::string stackMsg = ep->getCallStackMessage(N);
00544 
00545         // The last message on the path to final bug is the most important
00546         // one. Since we traverse the path backwards, do not add the message
00547         // if one has been previously added.
00548         if  (!CP->hasCallStackMessage())
00549           CP->setCallStackMessage(stackMsg);
00550       }
00551   }
00552 }
00553 
00554 static void CompactPathDiagnostic(PathPieces &path, const SourceManager& SM);
00555 
00556 static bool GenerateMinimalPathDiagnostic(
00557     PathDiagnostic &PD, PathDiagnosticBuilder &PDB, const ExplodedNode *N,
00558     LocationContextMap &LCM,
00559     ArrayRef<std::unique_ptr<BugReporterVisitor>> visitors) {
00560 
00561   SourceManager& SMgr = PDB.getSourceManager();
00562   const LocationContext *LC = PDB.LC;
00563   const ExplodedNode *NextNode = N->pred_empty()
00564                                         ? nullptr : *(N->pred_begin());
00565 
00566   StackDiagVector CallStack;
00567 
00568   while (NextNode) {
00569     N = NextNode;
00570     PDB.LC = N->getLocationContext();
00571     NextNode = N->getFirstPred();
00572 
00573     ProgramPoint P = N->getLocation();
00574 
00575     do {
00576       if (Optional<CallExitEnd> CE = P.getAs<CallExitEnd>()) {
00577         PathDiagnosticCallPiece *C =
00578             PathDiagnosticCallPiece::construct(N, *CE, SMgr);
00579         // Record the mapping from call piece to LocationContext.
00580         LCM[&C->path] = CE->getCalleeContext();
00581         PD.getActivePath().push_front(C);
00582         PD.pushActivePath(&C->path);
00583         CallStack.push_back(StackDiagPair(C, N));
00584         break;
00585       }
00586 
00587       if (Optional<CallEnter> CE = P.getAs<CallEnter>()) {
00588         // Flush all locations, and pop the active path.
00589         bool VisitedEntireCall = PD.isWithinCall();
00590         PD.popActivePath();
00591 
00592         // Either we just added a bunch of stuff to the top-level path, or
00593         // we have a previous CallExitEnd.  If the former, it means that the
00594         // path terminated within a function call.  We must then take the
00595         // current contents of the active path and place it within
00596         // a new PathDiagnosticCallPiece.
00597         PathDiagnosticCallPiece *C;
00598         if (VisitedEntireCall) {
00599           C = cast<PathDiagnosticCallPiece>(PD.getActivePath().front());
00600         } else {
00601           const Decl *Caller = CE->getLocationContext()->getDecl();
00602           C = PathDiagnosticCallPiece::construct(PD.getActivePath(), Caller);
00603           // Record the mapping from call piece to LocationContext.
00604           LCM[&C->path] = CE->getCalleeContext();
00605         }
00606 
00607         C->setCallee(*CE, SMgr);
00608         if (!CallStack.empty()) {
00609           assert(CallStack.back().first == C);
00610           CallStack.pop_back();
00611         }
00612         break;
00613       }
00614 
00615       if (Optional<BlockEdge> BE = P.getAs<BlockEdge>()) {
00616         const CFGBlock *Src = BE->getSrc();
00617         const CFGBlock *Dst = BE->getDst();
00618         const Stmt *T = Src->getTerminator();
00619 
00620         if (!T)
00621           break;
00622 
00623         PathDiagnosticLocation Start =
00624             PathDiagnosticLocation::createBegin(T, SMgr,
00625                 N->getLocationContext());
00626 
00627         switch (T->getStmtClass()) {
00628         default:
00629           break;
00630 
00631         case Stmt::GotoStmtClass:
00632         case Stmt::IndirectGotoStmtClass: {
00633           const Stmt *S = PathDiagnosticLocation::getNextStmt(N);
00634 
00635           if (!S)
00636             break;
00637 
00638           std::string sbuf;
00639           llvm::raw_string_ostream os(sbuf);
00640           const PathDiagnosticLocation &End = PDB.getEnclosingStmtLocation(S);
00641 
00642           os << "Control jumps to line "
00643               << End.asLocation().getExpansionLineNumber();
00644           PD.getActivePath().push_front(new PathDiagnosticControlFlowPiece(
00645               Start, End, os.str()));
00646           break;
00647         }
00648 
00649         case Stmt::SwitchStmtClass: {
00650           // Figure out what case arm we took.
00651           std::string sbuf;
00652           llvm::raw_string_ostream os(sbuf);
00653 
00654           if (const Stmt *S = Dst->getLabel()) {
00655             PathDiagnosticLocation End(S, SMgr, LC);
00656 
00657             switch (S->getStmtClass()) {
00658             default:
00659               os << "No cases match in the switch statement. "
00660               "Control jumps to line "
00661               << End.asLocation().getExpansionLineNumber();
00662               break;
00663             case Stmt::DefaultStmtClass:
00664               os << "Control jumps to the 'default' case at line "
00665               << End.asLocation().getExpansionLineNumber();
00666               break;
00667 
00668             case Stmt::CaseStmtClass: {
00669               os << "Control jumps to 'case ";
00670               const CaseStmt *Case = cast<CaseStmt>(S);
00671               const Expr *LHS = Case->getLHS()->IgnoreParenCasts();
00672 
00673               // Determine if it is an enum.
00674               bool GetRawInt = true;
00675 
00676               if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(LHS)) {
00677                 // FIXME: Maybe this should be an assertion.  Are there cases
00678                 // were it is not an EnumConstantDecl?
00679                 const EnumConstantDecl *D =
00680                     dyn_cast<EnumConstantDecl>(DR->getDecl());
00681 
00682                 if (D) {
00683                   GetRawInt = false;
00684                   os << *D;
00685                 }
00686               }
00687 
00688               if (GetRawInt)
00689                 os << LHS->EvaluateKnownConstInt(PDB.getASTContext());
00690 
00691               os << ":'  at line "
00692                   << End.asLocation().getExpansionLineNumber();
00693               break;
00694             }
00695             }
00696             PD.getActivePath().push_front(new PathDiagnosticControlFlowPiece(
00697                 Start, End, os.str()));
00698           }
00699           else {
00700             os << "'Default' branch taken. ";
00701             const PathDiagnosticLocation &End = PDB.ExecutionContinues(os, N);
00702             PD.getActivePath().push_front(new PathDiagnosticControlFlowPiece(
00703                 Start, End, os.str()));
00704           }
00705 
00706           break;
00707         }
00708 
00709         case Stmt::BreakStmtClass:
00710         case Stmt::ContinueStmtClass: {
00711           std::string sbuf;
00712           llvm::raw_string_ostream os(sbuf);
00713           PathDiagnosticLocation End = PDB.ExecutionContinues(os, N);
00714           PD.getActivePath().push_front(new PathDiagnosticControlFlowPiece(
00715               Start, End, os.str()));
00716           break;
00717         }
00718 
00719         // Determine control-flow for ternary '?'.
00720         case Stmt::BinaryConditionalOperatorClass:
00721         case Stmt::ConditionalOperatorClass: {
00722           std::string sbuf;
00723           llvm::raw_string_ostream os(sbuf);
00724           os << "'?' condition is ";
00725 
00726           if (*(Src->succ_begin()+1) == Dst)
00727             os << "false";
00728           else
00729             os << "true";
00730 
00731           PathDiagnosticLocation End = PDB.ExecutionContinues(N);
00732 
00733           if (const Stmt *S = End.asStmt())
00734             End = PDB.getEnclosingStmtLocation(S);
00735 
00736           PD.getActivePath().push_front(new PathDiagnosticControlFlowPiece(
00737               Start, End, os.str()));
00738           break;
00739         }
00740 
00741         // Determine control-flow for short-circuited '&&' and '||'.
00742         case Stmt::BinaryOperatorClass: {
00743           if (!PDB.supportsLogicalOpControlFlow())
00744             break;
00745 
00746           const BinaryOperator *B = cast<BinaryOperator>(T);
00747           std::string sbuf;
00748           llvm::raw_string_ostream os(sbuf);
00749           os << "Left side of '";
00750 
00751           if (B->getOpcode() == BO_LAnd) {
00752             os << "&&" << "' is ";
00753 
00754             if (*(Src->succ_begin()+1) == Dst) {
00755               os << "false";
00756               PathDiagnosticLocation End(B->getLHS(), SMgr, LC);
00757               PathDiagnosticLocation Start =
00758                   PathDiagnosticLocation::createOperatorLoc(B, SMgr);
00759               PD.getActivePath().push_front(new PathDiagnosticControlFlowPiece(
00760                   Start, End, os.str()));
00761             }
00762             else {
00763               os << "true";
00764               PathDiagnosticLocation Start(B->getLHS(), SMgr, LC);
00765               PathDiagnosticLocation End = PDB.ExecutionContinues(N);
00766               PD.getActivePath().push_front(new PathDiagnosticControlFlowPiece(
00767                   Start, End, os.str()));
00768             }
00769           }
00770           else {
00771             assert(B->getOpcode() == BO_LOr);
00772             os << "||" << "' is ";
00773 
00774             if (*(Src->succ_begin()+1) == Dst) {
00775               os << "false";
00776               PathDiagnosticLocation Start(B->getLHS(), SMgr, LC);
00777               PathDiagnosticLocation End = PDB.ExecutionContinues(N);
00778               PD.getActivePath().push_front(new PathDiagnosticControlFlowPiece(
00779                   Start, End, os.str()));
00780             }
00781             else {
00782               os << "true";
00783               PathDiagnosticLocation End(B->getLHS(), SMgr, LC);
00784               PathDiagnosticLocation Start =
00785                   PathDiagnosticLocation::createOperatorLoc(B, SMgr);
00786               PD.getActivePath().push_front(new PathDiagnosticControlFlowPiece(
00787                   Start, End, os.str()));
00788             }
00789           }
00790 
00791           break;
00792         }
00793 
00794         case Stmt::DoStmtClass:  {
00795           if (*(Src->succ_begin()) == Dst) {
00796             std::string sbuf;
00797             llvm::raw_string_ostream os(sbuf);
00798 
00799             os << "Loop condition is true. ";
00800             PathDiagnosticLocation End = PDB.ExecutionContinues(os, N);
00801 
00802             if (const Stmt *S = End.asStmt())
00803               End = PDB.getEnclosingStmtLocation(S);
00804 
00805             PD.getActivePath().push_front(new PathDiagnosticControlFlowPiece(
00806                 Start, End, os.str()));
00807           }
00808           else {
00809             PathDiagnosticLocation End = PDB.ExecutionContinues(N);
00810 
00811             if (const Stmt *S = End.asStmt())
00812               End = PDB.getEnclosingStmtLocation(S);
00813 
00814             PD.getActivePath().push_front(new PathDiagnosticControlFlowPiece(
00815                 Start, End, "Loop condition is false.  Exiting loop"));
00816           }
00817 
00818           break;
00819         }
00820 
00821         case Stmt::WhileStmtClass:
00822         case Stmt::ForStmtClass: {
00823           if (*(Src->succ_begin()+1) == Dst) {
00824             std::string sbuf;
00825             llvm::raw_string_ostream os(sbuf);
00826 
00827             os << "Loop condition is false. ";
00828             PathDiagnosticLocation End = PDB.ExecutionContinues(os, N);
00829             if (const Stmt *S = End.asStmt())
00830               End = PDB.getEnclosingStmtLocation(S);
00831 
00832             PD.getActivePath().push_front(new PathDiagnosticControlFlowPiece(
00833                 Start, End, os.str()));
00834           }
00835           else {
00836             PathDiagnosticLocation End = PDB.ExecutionContinues(N);
00837             if (const Stmt *S = End.asStmt())
00838               End = PDB.getEnclosingStmtLocation(S);
00839 
00840             PD.getActivePath().push_front(new PathDiagnosticControlFlowPiece(
00841                 Start, End, "Loop condition is true.  Entering loop body"));
00842           }
00843 
00844           break;
00845         }
00846 
00847         case Stmt::IfStmtClass: {
00848           PathDiagnosticLocation End = PDB.ExecutionContinues(N);
00849 
00850           if (const Stmt *S = End.asStmt())
00851             End = PDB.getEnclosingStmtLocation(S);
00852 
00853           if (*(Src->succ_begin()+1) == Dst)
00854             PD.getActivePath().push_front(new PathDiagnosticControlFlowPiece(
00855                 Start, End, "Taking false branch"));
00856           else
00857             PD.getActivePath().push_front(new PathDiagnosticControlFlowPiece(
00858                 Start, End, "Taking true branch"));
00859 
00860           break;
00861         }
00862         }
00863       }
00864     } while(0);
00865 
00866     if (NextNode) {
00867       // Add diagnostic pieces from custom visitors.
00868       BugReport *R = PDB.getBugReport();
00869       for (auto &V : visitors) {
00870         if (PathDiagnosticPiece *p = V->VisitNode(N, NextNode, PDB, *R)) {
00871           PD.getActivePath().push_front(p);
00872           updateStackPiecesWithMessage(p, CallStack);
00873         }
00874       }
00875     }
00876   }
00877 
00878   if (!PDB.getBugReport()->isValid())
00879     return false;
00880 
00881   // After constructing the full PathDiagnostic, do a pass over it to compact
00882   // PathDiagnosticPieces that occur within a macro.
00883   CompactPathDiagnostic(PD.getMutablePieces(), PDB.getSourceManager());
00884   return true;
00885 }
00886 
00887 //===----------------------------------------------------------------------===//
00888 // "Extensive" PathDiagnostic generation.
00889 //===----------------------------------------------------------------------===//
00890 
00891 static bool IsControlFlowExpr(const Stmt *S) {
00892   const Expr *E = dyn_cast<Expr>(S);
00893 
00894   if (!E)
00895     return false;
00896 
00897   E = E->IgnoreParenCasts();
00898 
00899   if (isa<AbstractConditionalOperator>(E))
00900     return true;
00901 
00902   if (const BinaryOperator *B = dyn_cast<BinaryOperator>(E))
00903     if (B->isLogicalOp())
00904       return true;
00905 
00906   return false;
00907 }
00908 
00909 namespace {
00910 class ContextLocation : public PathDiagnosticLocation {
00911   bool IsDead;
00912 public:
00913   ContextLocation(const PathDiagnosticLocation &L, bool isdead = false)
00914     : PathDiagnosticLocation(L), IsDead(isdead) {}
00915 
00916   void markDead() { IsDead = true; }
00917   bool isDead() const { return IsDead; }
00918 };
00919 
00920 static PathDiagnosticLocation cleanUpLocation(PathDiagnosticLocation L,
00921                                               const LocationContext *LC,
00922                                               bool firstCharOnly = false) {
00923   if (const Stmt *S = L.asStmt()) {
00924     const Stmt *Original = S;
00925     while (1) {
00926       // Adjust the location for some expressions that are best referenced
00927       // by one of their subexpressions.
00928       switch (S->getStmtClass()) {
00929         default:
00930           break;
00931         case Stmt::ParenExprClass:
00932         case Stmt::GenericSelectionExprClass:
00933           S = cast<Expr>(S)->IgnoreParens();
00934           firstCharOnly = true;
00935           continue;
00936         case Stmt::BinaryConditionalOperatorClass:
00937         case Stmt::ConditionalOperatorClass:
00938           S = cast<AbstractConditionalOperator>(S)->getCond();
00939           firstCharOnly = true;
00940           continue;
00941         case Stmt::ChooseExprClass:
00942           S = cast<ChooseExpr>(S)->getCond();
00943           firstCharOnly = true;
00944           continue;
00945         case Stmt::BinaryOperatorClass:
00946           S = cast<BinaryOperator>(S)->getLHS();
00947           firstCharOnly = true;
00948           continue;
00949       }
00950 
00951       break;
00952     }
00953 
00954     if (S != Original)
00955       L = PathDiagnosticLocation(S, L.getManager(), LC);
00956   }
00957 
00958   if (firstCharOnly)
00959     L  = PathDiagnosticLocation::createSingleLocation(L);
00960   
00961   return L;
00962 }
00963 
00964 class EdgeBuilder {
00965   std::vector<ContextLocation> CLocs;
00966   typedef std::vector<ContextLocation>::iterator iterator;
00967   PathDiagnostic &PD;
00968   PathDiagnosticBuilder &PDB;
00969   PathDiagnosticLocation PrevLoc;
00970 
00971   bool IsConsumedExpr(const PathDiagnosticLocation &L);
00972 
00973   bool containsLocation(const PathDiagnosticLocation &Container,
00974                         const PathDiagnosticLocation &Containee);
00975 
00976   PathDiagnosticLocation getContextLocation(const PathDiagnosticLocation &L);
00977 
00978 
00979 
00980   void popLocation() {
00981     if (!CLocs.back().isDead() && CLocs.back().asLocation().isFileID()) {
00982       // For contexts, we only one the first character as the range.
00983       rawAddEdge(cleanUpLocation(CLocs.back(), PDB.LC, true));
00984     }
00985     CLocs.pop_back();
00986   }
00987 
00988 public:
00989   EdgeBuilder(PathDiagnostic &pd, PathDiagnosticBuilder &pdb)
00990     : PD(pd), PDB(pdb) {
00991 
00992       // If the PathDiagnostic already has pieces, add the enclosing statement
00993       // of the first piece as a context as well.
00994       if (!PD.path.empty()) {
00995         PrevLoc = (*PD.path.begin())->getLocation();
00996 
00997         if (const Stmt *S = PrevLoc.asStmt())
00998           addExtendedContext(PDB.getEnclosingStmtLocation(S).asStmt());
00999       }
01000   }
01001 
01002   ~EdgeBuilder() {
01003     while (!CLocs.empty()) popLocation();
01004     
01005     // Finally, add an initial edge from the start location of the first
01006     // statement (if it doesn't already exist).
01007     PathDiagnosticLocation L = PathDiagnosticLocation::createDeclBegin(
01008                                                        PDB.LC,
01009                                                        PDB.getSourceManager());
01010     if (L.isValid())
01011       rawAddEdge(L);
01012   }
01013 
01014   void flushLocations() {
01015     while (!CLocs.empty())
01016       popLocation();
01017     PrevLoc = PathDiagnosticLocation();
01018   }
01019   
01020   void addEdge(PathDiagnosticLocation NewLoc, bool alwaysAdd = false,
01021                bool IsPostJump = false);
01022 
01023   void rawAddEdge(PathDiagnosticLocation NewLoc);
01024 
01025   void addContext(const Stmt *S);
01026   void addContext(const PathDiagnosticLocation &L);
01027   void addExtendedContext(const Stmt *S);
01028 };
01029 } // end anonymous namespace
01030 
01031 
01032 PathDiagnosticLocation
01033 EdgeBuilder::getContextLocation(const PathDiagnosticLocation &L) {
01034   if (const Stmt *S = L.asStmt()) {
01035     if (IsControlFlowExpr(S))
01036       return L;
01037 
01038     return PDB.getEnclosingStmtLocation(S);
01039   }
01040 
01041   return L;
01042 }
01043 
01044 bool EdgeBuilder::containsLocation(const PathDiagnosticLocation &Container,
01045                                    const PathDiagnosticLocation &Containee) {
01046 
01047   if (Container == Containee)
01048     return true;
01049 
01050   if (Container.asDecl())
01051     return true;
01052 
01053   if (const Stmt *S = Containee.asStmt())
01054     if (const Stmt *ContainerS = Container.asStmt()) {
01055       while (S) {
01056         if (S == ContainerS)
01057           return true;
01058         S = PDB.getParent(S);
01059       }
01060       return false;
01061     }
01062 
01063   // Less accurate: compare using source ranges.
01064   SourceRange ContainerR = Container.asRange();
01065   SourceRange ContaineeR = Containee.asRange();
01066 
01067   SourceManager &SM = PDB.getSourceManager();
01068   SourceLocation ContainerRBeg = SM.getExpansionLoc(ContainerR.getBegin());
01069   SourceLocation ContainerREnd = SM.getExpansionLoc(ContainerR.getEnd());
01070   SourceLocation ContaineeRBeg = SM.getExpansionLoc(ContaineeR.getBegin());
01071   SourceLocation ContaineeREnd = SM.getExpansionLoc(ContaineeR.getEnd());
01072 
01073   unsigned ContainerBegLine = SM.getExpansionLineNumber(ContainerRBeg);
01074   unsigned ContainerEndLine = SM.getExpansionLineNumber(ContainerREnd);
01075   unsigned ContaineeBegLine = SM.getExpansionLineNumber(ContaineeRBeg);
01076   unsigned ContaineeEndLine = SM.getExpansionLineNumber(ContaineeREnd);
01077 
01078   assert(ContainerBegLine <= ContainerEndLine);
01079   assert(ContaineeBegLine <= ContaineeEndLine);
01080 
01081   return (ContainerBegLine <= ContaineeBegLine &&
01082           ContainerEndLine >= ContaineeEndLine &&
01083           (ContainerBegLine != ContaineeBegLine ||
01084            SM.getExpansionColumnNumber(ContainerRBeg) <=
01085            SM.getExpansionColumnNumber(ContaineeRBeg)) &&
01086           (ContainerEndLine != ContaineeEndLine ||
01087            SM.getExpansionColumnNumber(ContainerREnd) >=
01088            SM.getExpansionColumnNumber(ContaineeREnd)));
01089 }
01090 
01091 void EdgeBuilder::rawAddEdge(PathDiagnosticLocation NewLoc) {
01092   if (!PrevLoc.isValid()) {
01093     PrevLoc = NewLoc;
01094     return;
01095   }
01096 
01097   const PathDiagnosticLocation &NewLocClean = cleanUpLocation(NewLoc, PDB.LC);
01098   const PathDiagnosticLocation &PrevLocClean = cleanUpLocation(PrevLoc, PDB.LC);
01099 
01100   if (PrevLocClean.asLocation().isInvalid()) {
01101     PrevLoc = NewLoc;
01102     return;
01103   }
01104   
01105   if (NewLocClean.asLocation() == PrevLocClean.asLocation())
01106     return;
01107 
01108   // FIXME: Ignore intra-macro edges for now.
01109   if (NewLocClean.asLocation().getExpansionLoc() ==
01110       PrevLocClean.asLocation().getExpansionLoc())
01111     return;
01112 
01113   PD.getActivePath().push_front(new PathDiagnosticControlFlowPiece(NewLocClean, PrevLocClean));
01114   PrevLoc = NewLoc;
01115 }
01116 
01117 void EdgeBuilder::addEdge(PathDiagnosticLocation NewLoc, bool alwaysAdd,
01118                           bool IsPostJump) {
01119 
01120   if (!alwaysAdd && NewLoc.asLocation().isMacroID())
01121     return;
01122 
01123   const PathDiagnosticLocation &CLoc = getContextLocation(NewLoc);
01124 
01125   while (!CLocs.empty()) {
01126     ContextLocation &TopContextLoc = CLocs.back();
01127 
01128     // Is the top location context the same as the one for the new location?
01129     if (TopContextLoc == CLoc) {
01130       if (alwaysAdd) {
01131         if (IsConsumedExpr(TopContextLoc))
01132           TopContextLoc.markDead();
01133 
01134         rawAddEdge(NewLoc);
01135       }
01136 
01137       if (IsPostJump)
01138         TopContextLoc.markDead();
01139       return;
01140     }
01141 
01142     if (containsLocation(TopContextLoc, CLoc)) {
01143       if (alwaysAdd) {
01144         rawAddEdge(NewLoc);
01145 
01146         if (IsConsumedExpr(CLoc)) {
01147           CLocs.push_back(ContextLocation(CLoc, /*IsDead=*/true));
01148           return;
01149         }
01150       }
01151 
01152       CLocs.push_back(ContextLocation(CLoc, /*IsDead=*/IsPostJump));
01153       return;
01154     }
01155 
01156     // Context does not contain the location.  Flush it.
01157     popLocation();
01158   }
01159 
01160   // If we reach here, there is no enclosing context.  Just add the edge.
01161   rawAddEdge(NewLoc);
01162 }
01163 
01164 bool EdgeBuilder::IsConsumedExpr(const PathDiagnosticLocation &L) {
01165   if (const Expr *X = dyn_cast_or_null<Expr>(L.asStmt()))
01166     return PDB.getParentMap().isConsumedExpr(X) && !IsControlFlowExpr(X);
01167 
01168   return false;
01169 }
01170 
01171 void EdgeBuilder::addExtendedContext(const Stmt *S) {
01172   if (!S)
01173     return;
01174 
01175   const Stmt *Parent = PDB.getParent(S);
01176   while (Parent) {
01177     if (isa<CompoundStmt>(Parent))
01178       Parent = PDB.getParent(Parent);
01179     else
01180       break;
01181   }
01182 
01183   if (Parent) {
01184     switch (Parent->getStmtClass()) {
01185       case Stmt::DoStmtClass:
01186       case Stmt::ObjCAtSynchronizedStmtClass:
01187         addContext(Parent);
01188       default:
01189         break;
01190     }
01191   }
01192 
01193   addContext(S);
01194 }
01195 
01196 void EdgeBuilder::addContext(const Stmt *S) {
01197   if (!S)
01198     return;
01199 
01200   PathDiagnosticLocation L(S, PDB.getSourceManager(), PDB.LC);
01201   addContext(L);
01202 }
01203 
01204 void EdgeBuilder::addContext(const PathDiagnosticLocation &L) {
01205   while (!CLocs.empty()) {
01206     const PathDiagnosticLocation &TopContextLoc = CLocs.back();
01207 
01208     // Is the top location context the same as the one for the new location?
01209     if (TopContextLoc == L)
01210       return;
01211 
01212     if (containsLocation(TopContextLoc, L)) {
01213       CLocs.push_back(L);
01214       return;
01215     }
01216 
01217     // Context does not contain the location.  Flush it.
01218     popLocation();
01219   }
01220 
01221   CLocs.push_back(L);
01222 }
01223 
01224 // Cone-of-influence: support the reverse propagation of "interesting" symbols
01225 // and values by tracing interesting calculations backwards through evaluated
01226 // expressions along a path.  This is probably overly complicated, but the idea
01227 // is that if an expression computed an "interesting" value, the child
01228 // expressions are are also likely to be "interesting" as well (which then
01229 // propagates to the values they in turn compute).  This reverse propagation
01230 // is needed to track interesting correlations across function call boundaries,
01231 // where formal arguments bind to actual arguments, etc.  This is also needed
01232 // because the constraint solver sometimes simplifies certain symbolic values
01233 // into constants when appropriate, and this complicates reasoning about
01234 // interesting values.
01235 typedef llvm::DenseSet<const Expr *> InterestingExprs;
01236 
01237 static void reversePropagateIntererstingSymbols(BugReport &R,
01238                                                 InterestingExprs &IE,
01239                                                 const ProgramState *State,
01240                                                 const Expr *Ex,
01241                                                 const LocationContext *LCtx) {
01242   SVal V = State->getSVal(Ex, LCtx);
01243   if (!(R.isInteresting(V) || IE.count(Ex)))
01244     return;
01245   
01246   switch (Ex->getStmtClass()) {
01247     default:
01248       if (!isa<CastExpr>(Ex))
01249         break;
01250       // Fall through.
01251     case Stmt::BinaryOperatorClass:
01252     case Stmt::UnaryOperatorClass: {
01253       for (Stmt::const_child_iterator CI = Ex->child_begin(),
01254             CE = Ex->child_end();
01255             CI != CE; ++CI) {
01256         if (const Expr *child = dyn_cast_or_null<Expr>(*CI)) {
01257           IE.insert(child);
01258           SVal ChildV = State->getSVal(child, LCtx);
01259           R.markInteresting(ChildV);
01260         }
01261       }
01262       break;
01263     }
01264   }
01265   
01266   R.markInteresting(V);
01267 }
01268 
01269 static void reversePropagateInterestingSymbols(BugReport &R,
01270                                                InterestingExprs &IE,
01271                                                const ProgramState *State,
01272                                                const LocationContext *CalleeCtx,
01273                                                const LocationContext *CallerCtx)
01274 {
01275   // FIXME: Handle non-CallExpr-based CallEvents.
01276   const StackFrameContext *Callee = CalleeCtx->getCurrentStackFrame();
01277   const Stmt *CallSite = Callee->getCallSite();
01278   if (const CallExpr *CE = dyn_cast_or_null<CallExpr>(CallSite)) {
01279     if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(CalleeCtx->getDecl())) {
01280       FunctionDecl::param_const_iterator PI = FD->param_begin(), 
01281                                          PE = FD->param_end();
01282       CallExpr::const_arg_iterator AI = CE->arg_begin(), AE = CE->arg_end();
01283       for (; AI != AE && PI != PE; ++AI, ++PI) {
01284         if (const Expr *ArgE = *AI) {
01285           if (const ParmVarDecl *PD = *PI) {
01286             Loc LV = State->getLValue(PD, CalleeCtx);
01287             if (R.isInteresting(LV) || R.isInteresting(State->getRawSVal(LV)))
01288               IE.insert(ArgE);
01289           }
01290         }
01291       }
01292     }
01293   }
01294 }
01295 
01296 //===----------------------------------------------------------------------===//
01297 // Functions for determining if a loop was executed 0 times.
01298 //===----------------------------------------------------------------------===//
01299 
01300 static bool isLoop(const Stmt *Term) {
01301   switch (Term->getStmtClass()) {
01302     case Stmt::ForStmtClass:
01303     case Stmt::WhileStmtClass:
01304     case Stmt::ObjCForCollectionStmtClass:
01305     case Stmt::CXXForRangeStmtClass:
01306       return true;
01307     default:
01308       // Note that we intentionally do not include do..while here.
01309       return false;
01310   }
01311 }
01312 
01313 static bool isJumpToFalseBranch(const BlockEdge *BE) {
01314   const CFGBlock *Src = BE->getSrc();
01315   assert(Src->succ_size() == 2);
01316   return (*(Src->succ_begin()+1) == BE->getDst());
01317 }
01318 
01319 /// Return true if the terminator is a loop and the destination is the
01320 /// false branch.
01321 static bool isLoopJumpPastBody(const Stmt *Term, const BlockEdge *BE) {
01322   if (!isLoop(Term))
01323     return false;
01324 
01325   // Did we take the false branch?
01326   return isJumpToFalseBranch(BE);
01327 }
01328 
01329 static bool isContainedByStmt(ParentMap &PM, const Stmt *S, const Stmt *SubS) {
01330   while (SubS) {
01331     if (SubS == S)
01332       return true;
01333     SubS = PM.getParent(SubS);
01334   }
01335   return false;
01336 }
01337 
01338 static const Stmt *getStmtBeforeCond(ParentMap &PM, const Stmt *Term,
01339                                      const ExplodedNode *N) {
01340   while (N) {
01341     Optional<StmtPoint> SP = N->getLocation().getAs<StmtPoint>();
01342     if (SP) {
01343       const Stmt *S = SP->getStmt();
01344       if (!isContainedByStmt(PM, Term, S))
01345         return S;
01346     }
01347     N = N->getFirstPred();
01348   }
01349   return nullptr;
01350 }
01351 
01352 static bool isInLoopBody(ParentMap &PM, const Stmt *S, const Stmt *Term) {
01353   const Stmt *LoopBody = nullptr;
01354   switch (Term->getStmtClass()) {
01355     case Stmt::CXXForRangeStmtClass: {
01356       const CXXForRangeStmt *FR = cast<CXXForRangeStmt>(Term);
01357       if (isContainedByStmt(PM, FR->getInc(), S))
01358         return true;
01359       if (isContainedByStmt(PM, FR->getLoopVarStmt(), S))
01360         return true;
01361       LoopBody = FR->getBody();
01362       break;
01363     }
01364     case Stmt::ForStmtClass: {
01365       const ForStmt *FS = cast<ForStmt>(Term);
01366       if (isContainedByStmt(PM, FS->getInc(), S))
01367         return true;
01368       LoopBody = FS->getBody();
01369       break;
01370     }
01371     case Stmt::ObjCForCollectionStmtClass: {
01372       const ObjCForCollectionStmt *FC = cast<ObjCForCollectionStmt>(Term);
01373       LoopBody = FC->getBody();
01374       break;
01375     }
01376     case Stmt::WhileStmtClass:
01377       LoopBody = cast<WhileStmt>(Term)->getBody();
01378       break;
01379     default:
01380       return false;
01381   }
01382   return isContainedByStmt(PM, LoopBody, S);
01383 }
01384 
01385 //===----------------------------------------------------------------------===//
01386 // Top-level logic for generating extensive path diagnostics.
01387 //===----------------------------------------------------------------------===//
01388 
01389 static bool GenerateExtensivePathDiagnostic(
01390     PathDiagnostic &PD, PathDiagnosticBuilder &PDB, const ExplodedNode *N,
01391     LocationContextMap &LCM,
01392     ArrayRef<std::unique_ptr<BugReporterVisitor>> visitors) {
01393   EdgeBuilder EB(PD, PDB);
01394   const SourceManager& SM = PDB.getSourceManager();
01395   StackDiagVector CallStack;
01396   InterestingExprs IE;
01397 
01398   const ExplodedNode *NextNode = N->pred_empty() ? nullptr : *(N->pred_begin());
01399   while (NextNode) {
01400     N = NextNode;
01401     NextNode = N->getFirstPred();
01402     ProgramPoint P = N->getLocation();
01403 
01404     do {
01405       if (Optional<PostStmt> PS = P.getAs<PostStmt>()) {
01406         if (const Expr *Ex = PS->getStmtAs<Expr>())
01407           reversePropagateIntererstingSymbols(*PDB.getBugReport(), IE,
01408                                               N->getState().get(), Ex,
01409                                               N->getLocationContext());
01410       }
01411       
01412       if (Optional<CallExitEnd> CE = P.getAs<CallExitEnd>()) {
01413         const Stmt *S = CE->getCalleeContext()->getCallSite();
01414         if (const Expr *Ex = dyn_cast_or_null<Expr>(S)) {
01415             reversePropagateIntererstingSymbols(*PDB.getBugReport(), IE,
01416                                                 N->getState().get(), Ex,
01417                                                 N->getLocationContext());
01418         }
01419         
01420         PathDiagnosticCallPiece *C =
01421           PathDiagnosticCallPiece::construct(N, *CE, SM);
01422         LCM[&C->path] = CE->getCalleeContext();
01423 
01424         EB.addEdge(C->callReturn, /*AlwaysAdd=*/true, /*IsPostJump=*/true);
01425         EB.flushLocations();
01426 
01427         PD.getActivePath().push_front(C);
01428         PD.pushActivePath(&C->path);
01429         CallStack.push_back(StackDiagPair(C, N));
01430         break;
01431       }
01432       
01433       // Pop the call hierarchy if we are done walking the contents
01434       // of a function call.
01435       if (Optional<CallEnter> CE = P.getAs<CallEnter>()) {
01436         // Add an edge to the start of the function.
01437         const Decl *D = CE->getCalleeContext()->getDecl();
01438         PathDiagnosticLocation pos =
01439           PathDiagnosticLocation::createBegin(D, SM);
01440         EB.addEdge(pos);
01441         
01442         // Flush all locations, and pop the active path.
01443         bool VisitedEntireCall = PD.isWithinCall();
01444         EB.flushLocations();
01445         PD.popActivePath();
01446         PDB.LC = N->getLocationContext();
01447 
01448         // Either we just added a bunch of stuff to the top-level path, or
01449         // we have a previous CallExitEnd.  If the former, it means that the
01450         // path terminated within a function call.  We must then take the
01451         // current contents of the active path and place it within
01452         // a new PathDiagnosticCallPiece.
01453         PathDiagnosticCallPiece *C;
01454         if (VisitedEntireCall) {
01455           C = cast<PathDiagnosticCallPiece>(PD.getActivePath().front());
01456         } else {
01457           const Decl *Caller = CE->getLocationContext()->getDecl();
01458           C = PathDiagnosticCallPiece::construct(PD.getActivePath(), Caller);
01459           LCM[&C->path] = CE->getCalleeContext();
01460         }
01461 
01462         C->setCallee(*CE, SM);
01463         EB.addContext(C->getLocation());
01464 
01465         if (!CallStack.empty()) {
01466           assert(CallStack.back().first == C);
01467           CallStack.pop_back();
01468         }
01469         break;
01470       }
01471       
01472       // Note that is important that we update the LocationContext
01473       // after looking at CallExits.  CallExit basically adds an
01474       // edge in the *caller*, so we don't want to update the LocationContext
01475       // too soon.
01476       PDB.LC = N->getLocationContext();
01477 
01478       // Block edges.
01479       if (Optional<BlockEdge> BE = P.getAs<BlockEdge>()) {
01480         // Does this represent entering a call?  If so, look at propagating
01481         // interesting symbols across call boundaries.
01482         if (NextNode) {
01483           const LocationContext *CallerCtx = NextNode->getLocationContext();
01484           const LocationContext *CalleeCtx = PDB.LC;
01485           if (CallerCtx != CalleeCtx) {
01486             reversePropagateInterestingSymbols(*PDB.getBugReport(), IE,
01487                                                N->getState().get(),
01488                                                CalleeCtx, CallerCtx);
01489           }
01490         }
01491        
01492         // Are we jumping to the head of a loop?  Add a special diagnostic.
01493         if (const Stmt *Loop = BE->getSrc()->getLoopTarget()) {
01494           PathDiagnosticLocation L(Loop, SM, PDB.LC);
01495           const CompoundStmt *CS = nullptr;
01496 
01497           if (const ForStmt *FS = dyn_cast<ForStmt>(Loop))
01498             CS = dyn_cast<CompoundStmt>(FS->getBody());
01499           else if (const WhileStmt *WS = dyn_cast<WhileStmt>(Loop))
01500             CS = dyn_cast<CompoundStmt>(WS->getBody());
01501 
01502           PathDiagnosticEventPiece *p =
01503             new PathDiagnosticEventPiece(L,
01504                                         "Looping back to the head of the loop");
01505           p->setPrunable(true);
01506 
01507           EB.addEdge(p->getLocation(), true);
01508           PD.getActivePath().push_front(p);
01509 
01510           if (CS) {
01511             PathDiagnosticLocation BL =
01512               PathDiagnosticLocation::createEndBrace(CS, SM);
01513             EB.addEdge(BL);
01514           }
01515         }
01516 
01517         const CFGBlock *BSrc = BE->getSrc();
01518         ParentMap &PM = PDB.getParentMap();
01519 
01520         if (const Stmt *Term = BSrc->getTerminator()) {
01521           // Are we jumping past the loop body without ever executing the
01522           // loop (because the condition was false)?
01523           if (isLoopJumpPastBody(Term, &*BE) &&
01524               !isInLoopBody(PM,
01525                             getStmtBeforeCond(PM,
01526                                               BSrc->getTerminatorCondition(),
01527                                               N),
01528                             Term)) {
01529             PathDiagnosticLocation L(Term, SM, PDB.LC);
01530             PathDiagnosticEventPiece *PE =
01531                 new PathDiagnosticEventPiece(L, "Loop body executed 0 times");
01532             PE->setPrunable(true);
01533 
01534             EB.addEdge(PE->getLocation(), true);
01535             PD.getActivePath().push_front(PE);
01536           }
01537 
01538           // In any case, add the terminator as the current statement
01539           // context for control edges.
01540           EB.addContext(Term);
01541         }
01542 
01543         break;
01544       }
01545 
01546       if (Optional<BlockEntrance> BE = P.getAs<BlockEntrance>()) {
01547         Optional<CFGElement> First = BE->getFirstElement();
01548         if (Optional<CFGStmt> S = First ? First->getAs<CFGStmt>() : None) {
01549           const Stmt *stmt = S->getStmt();
01550           if (IsControlFlowExpr(stmt)) {
01551             // Add the proper context for '&&', '||', and '?'.
01552             EB.addContext(stmt);
01553           }
01554           else
01555             EB.addExtendedContext(PDB.getEnclosingStmtLocation(stmt).asStmt());
01556         }
01557         
01558         break;
01559       }
01560       
01561       
01562     } while (0);
01563 
01564     if (!NextNode)
01565       continue;
01566 
01567     // Add pieces from custom visitors.
01568     BugReport *R = PDB.getBugReport();
01569     for (auto &V : visitors) {
01570       if (PathDiagnosticPiece *p = V->VisitNode(N, NextNode, PDB, *R)) {
01571         const PathDiagnosticLocation &Loc = p->getLocation();
01572         EB.addEdge(Loc, true);
01573         PD.getActivePath().push_front(p);
01574         updateStackPiecesWithMessage(p, CallStack);
01575 
01576         if (const Stmt *S = Loc.asStmt())
01577           EB.addExtendedContext(PDB.getEnclosingStmtLocation(S).asStmt());
01578       }
01579     }
01580   }
01581 
01582   return PDB.getBugReport()->isValid();
01583 }
01584 
01585 /// \brief Adds a sanitized control-flow diagnostic edge to a path.
01586 static void addEdgeToPath(PathPieces &path,
01587                           PathDiagnosticLocation &PrevLoc,
01588                           PathDiagnosticLocation NewLoc,
01589                           const LocationContext *LC) {
01590   if (!NewLoc.isValid())
01591     return;
01592 
01593   SourceLocation NewLocL = NewLoc.asLocation();
01594   if (NewLocL.isInvalid())
01595     return;
01596 
01597   if (!PrevLoc.isValid() || !PrevLoc.asLocation().isValid()) {
01598     PrevLoc = NewLoc;
01599     return;
01600   }
01601 
01602   // Ignore self-edges, which occur when there are multiple nodes at the same
01603   // statement.
01604   if (NewLoc.asStmt() && NewLoc.asStmt() == PrevLoc.asStmt())
01605     return;
01606 
01607   path.push_front(new PathDiagnosticControlFlowPiece(NewLoc,
01608                                                      PrevLoc));
01609   PrevLoc = NewLoc;
01610 }
01611 
01612 /// A customized wrapper for CFGBlock::getTerminatorCondition()
01613 /// which returns the element for ObjCForCollectionStmts.
01614 static const Stmt *getTerminatorCondition(const CFGBlock *B) {
01615   const Stmt *S = B->getTerminatorCondition();
01616   if (const ObjCForCollectionStmt *FS =
01617       dyn_cast_or_null<ObjCForCollectionStmt>(S))
01618     return FS->getElement();
01619   return S;
01620 }
01621 
01622 static const char StrEnteringLoop[] = "Entering loop body";
01623 static const char StrLoopBodyZero[] = "Loop body executed 0 times";
01624 static const char StrLoopRangeEmpty[] =
01625   "Loop body skipped when range is empty";
01626 static const char StrLoopCollectionEmpty[] =
01627   "Loop body skipped when collection is empty";
01628 
01629 static bool GenerateAlternateExtensivePathDiagnostic(
01630     PathDiagnostic &PD, PathDiagnosticBuilder &PDB, const ExplodedNode *N,
01631     LocationContextMap &LCM,
01632     ArrayRef<std::unique_ptr<BugReporterVisitor>> visitors) {
01633 
01634   BugReport *report = PDB.getBugReport();
01635   const SourceManager& SM = PDB.getSourceManager();
01636   StackDiagVector CallStack;
01637   InterestingExprs IE;
01638 
01639   PathDiagnosticLocation PrevLoc = PD.getLocation();
01640 
01641   const ExplodedNode *NextNode = N->getFirstPred();
01642   while (NextNode) {
01643     N = NextNode;
01644     NextNode = N->getFirstPred();
01645     ProgramPoint P = N->getLocation();
01646 
01647     do {
01648       // Have we encountered an entrance to a call?  It may be
01649       // the case that we have not encountered a matching
01650       // call exit before this point.  This means that the path
01651       // terminated within the call itself.
01652       if (Optional<CallEnter> CE = P.getAs<CallEnter>()) {
01653         // Add an edge to the start of the function.
01654         const StackFrameContext *CalleeLC = CE->getCalleeContext();
01655         const Decl *D = CalleeLC->getDecl();
01656         addEdgeToPath(PD.getActivePath(), PrevLoc,
01657                       PathDiagnosticLocation::createBegin(D, SM),
01658                       CalleeLC);
01659 
01660         // Did we visit an entire call?
01661         bool VisitedEntireCall = PD.isWithinCall();
01662         PD.popActivePath();
01663 
01664         PathDiagnosticCallPiece *C;
01665         if (VisitedEntireCall) {
01666           PathDiagnosticPiece *P = PD.getActivePath().front().get();
01667           C = cast<PathDiagnosticCallPiece>(P);
01668         } else {
01669           const Decl *Caller = CE->getLocationContext()->getDecl();
01670           C = PathDiagnosticCallPiece::construct(PD.getActivePath(), Caller);
01671 
01672           // Since we just transferred the path over to the call piece,
01673           // reset the mapping from active to location context.
01674           assert(PD.getActivePath().size() == 1 &&
01675                  PD.getActivePath().front() == C);
01676           LCM[&PD.getActivePath()] = nullptr;
01677 
01678           // Record the location context mapping for the path within
01679           // the call.
01680           assert(LCM[&C->path] == nullptr ||
01681                  LCM[&C->path] == CE->getCalleeContext());
01682           LCM[&C->path] = CE->getCalleeContext();
01683 
01684           // If this is the first item in the active path, record
01685           // the new mapping from active path to location context.
01686           const LocationContext *&NewLC = LCM[&PD.getActivePath()];
01687           if (!NewLC)
01688             NewLC = N->getLocationContext();
01689 
01690           PDB.LC = NewLC;
01691         }
01692         C->setCallee(*CE, SM);
01693 
01694         // Update the previous location in the active path.
01695         PrevLoc = C->getLocation();
01696 
01697         if (!CallStack.empty()) {
01698           assert(CallStack.back().first == C);
01699           CallStack.pop_back();
01700         }
01701         break;
01702       }
01703 
01704       // Query the location context here and the previous location
01705       // as processing CallEnter may change the active path.
01706       PDB.LC = N->getLocationContext();
01707 
01708       // Record the mapping from the active path to the location
01709       // context.
01710       assert(!LCM[&PD.getActivePath()] ||
01711              LCM[&PD.getActivePath()] == PDB.LC);
01712       LCM[&PD.getActivePath()] = PDB.LC;
01713 
01714       // Have we encountered an exit from a function call?
01715       if (Optional<CallExitEnd> CE = P.getAs<CallExitEnd>()) {
01716         const Stmt *S = CE->getCalleeContext()->getCallSite();
01717         // Propagate the interesting symbols accordingly.
01718         if (const Expr *Ex = dyn_cast_or_null<Expr>(S)) {
01719           reversePropagateIntererstingSymbols(*PDB.getBugReport(), IE,
01720                                               N->getState().get(), Ex,
01721                                               N->getLocationContext());
01722         }
01723 
01724         // We are descending into a call (backwards).  Construct
01725         // a new call piece to contain the path pieces for that call.
01726         PathDiagnosticCallPiece *C =
01727           PathDiagnosticCallPiece::construct(N, *CE, SM);
01728 
01729         // Record the location context for this call piece.
01730         LCM[&C->path] = CE->getCalleeContext();
01731 
01732         // Add the edge to the return site.
01733         addEdgeToPath(PD.getActivePath(), PrevLoc, C->callReturn, PDB.LC);
01734         PD.getActivePath().push_front(C);
01735         PrevLoc.invalidate();
01736 
01737         // Make the contents of the call the active path for now.
01738         PD.pushActivePath(&C->path);
01739         CallStack.push_back(StackDiagPair(C, N));
01740         break;
01741       }
01742 
01743       if (Optional<PostStmt> PS = P.getAs<PostStmt>()) {
01744         // For expressions, make sure we propagate the
01745         // interesting symbols correctly.
01746         if (const Expr *Ex = PS->getStmtAs<Expr>())
01747           reversePropagateIntererstingSymbols(*PDB.getBugReport(), IE,
01748                                               N->getState().get(), Ex,
01749                                               N->getLocationContext());
01750 
01751         // Add an edge.  If this is an ObjCForCollectionStmt do
01752         // not add an edge here as it appears in the CFG both
01753         // as a terminator and as a terminator condition.
01754         if (!isa<ObjCForCollectionStmt>(PS->getStmt())) {
01755           PathDiagnosticLocation L =
01756             PathDiagnosticLocation(PS->getStmt(), SM, PDB.LC);
01757           addEdgeToPath(PD.getActivePath(), PrevLoc, L, PDB.LC);
01758         }
01759         break;
01760       }
01761 
01762       // Block edges.
01763       if (Optional<BlockEdge> BE = P.getAs<BlockEdge>()) {
01764         // Does this represent entering a call?  If so, look at propagating
01765         // interesting symbols across call boundaries.
01766         if (NextNode) {
01767           const LocationContext *CallerCtx = NextNode->getLocationContext();
01768           const LocationContext *CalleeCtx = PDB.LC;
01769           if (CallerCtx != CalleeCtx) {
01770             reversePropagateInterestingSymbols(*PDB.getBugReport(), IE,
01771                                                N->getState().get(),
01772                                                CalleeCtx, CallerCtx);
01773           }
01774         }
01775 
01776         // Are we jumping to the head of a loop?  Add a special diagnostic.
01777         if (const Stmt *Loop = BE->getSrc()->getLoopTarget()) {
01778           PathDiagnosticLocation L(Loop, SM, PDB.LC);
01779           const Stmt *Body = nullptr;
01780 
01781           if (const ForStmt *FS = dyn_cast<ForStmt>(Loop))
01782             Body = FS->getBody();
01783           else if (const WhileStmt *WS = dyn_cast<WhileStmt>(Loop))
01784             Body = WS->getBody();
01785           else if (const ObjCForCollectionStmt *OFS =
01786                      dyn_cast<ObjCForCollectionStmt>(Loop)) {
01787             Body = OFS->getBody();
01788           } else if (const CXXForRangeStmt *FRS =
01789                        dyn_cast<CXXForRangeStmt>(Loop)) {
01790             Body = FRS->getBody();
01791           }
01792           // do-while statements are explicitly excluded here
01793 
01794           PathDiagnosticEventPiece *p =
01795             new PathDiagnosticEventPiece(L, "Looping back to the head "
01796                                             "of the loop");
01797           p->setPrunable(true);
01798 
01799           addEdgeToPath(PD.getActivePath(), PrevLoc, p->getLocation(), PDB.LC);
01800           PD.getActivePath().push_front(p);
01801 
01802           if (const CompoundStmt *CS = dyn_cast_or_null<CompoundStmt>(Body)) {
01803             addEdgeToPath(PD.getActivePath(), PrevLoc,
01804                           PathDiagnosticLocation::createEndBrace(CS, SM),
01805                           PDB.LC);
01806           }
01807         }
01808 
01809         const CFGBlock *BSrc = BE->getSrc();
01810         ParentMap &PM = PDB.getParentMap();
01811 
01812         if (const Stmt *Term = BSrc->getTerminator()) {
01813           // Are we jumping past the loop body without ever executing the
01814           // loop (because the condition was false)?
01815           if (isLoop(Term)) {
01816             const Stmt *TermCond = getTerminatorCondition(BSrc);
01817             bool IsInLoopBody =
01818               isInLoopBody(PM, getStmtBeforeCond(PM, TermCond, N), Term);
01819 
01820             const char *str = nullptr;
01821 
01822             if (isJumpToFalseBranch(&*BE)) {
01823               if (!IsInLoopBody) {
01824                 if (isa<ObjCForCollectionStmt>(Term)) {
01825                   str = StrLoopCollectionEmpty;
01826                 } else if (isa<CXXForRangeStmt>(Term)) {
01827                   str = StrLoopRangeEmpty;
01828                 } else {
01829                   str = StrLoopBodyZero;
01830                 }
01831               }
01832             } else {
01833               str = StrEnteringLoop;
01834             }
01835 
01836             if (str) {
01837               PathDiagnosticLocation L(TermCond ? TermCond : Term, SM, PDB.LC);
01838               PathDiagnosticEventPiece *PE =
01839                 new PathDiagnosticEventPiece(L, str);
01840               PE->setPrunable(true);
01841               addEdgeToPath(PD.getActivePath(), PrevLoc,
01842                             PE->getLocation(), PDB.LC);
01843               PD.getActivePath().push_front(PE);
01844             }
01845           } else if (isa<BreakStmt>(Term) || isa<ContinueStmt>(Term) ||
01846                      isa<GotoStmt>(Term)) {
01847             PathDiagnosticLocation L(Term, SM, PDB.LC);
01848             addEdgeToPath(PD.getActivePath(), PrevLoc, L, PDB.LC);
01849           }
01850         }
01851         break;
01852       }
01853     } while (0);
01854 
01855     if (!NextNode)
01856       continue;
01857 
01858     // Add pieces from custom visitors.
01859     for (auto &V : visitors) {
01860       if (PathDiagnosticPiece *p = V->VisitNode(N, NextNode, PDB, *report)) {
01861         addEdgeToPath(PD.getActivePath(), PrevLoc, p->getLocation(), PDB.LC);
01862         PD.getActivePath().push_front(p);
01863         updateStackPiecesWithMessage(p, CallStack);
01864       }
01865     }
01866   }
01867 
01868   // Add an edge to the start of the function.
01869   // We'll prune it out later, but it helps make diagnostics more uniform.
01870   const StackFrameContext *CalleeLC = PDB.LC->getCurrentStackFrame();
01871   const Decl *D = CalleeLC->getDecl();
01872   addEdgeToPath(PD.getActivePath(), PrevLoc,
01873                 PathDiagnosticLocation::createBegin(D, SM),
01874                 CalleeLC);
01875 
01876   return report->isValid();
01877 }
01878 
01879 static const Stmt *getLocStmt(PathDiagnosticLocation L) {
01880   if (!L.isValid())
01881     return nullptr;
01882   return L.asStmt();
01883 }
01884 
01885 static const Stmt *getStmtParent(const Stmt *S, const ParentMap &PM) {
01886   if (!S)
01887     return nullptr;
01888 
01889   while (true) {
01890     S = PM.getParentIgnoreParens(S);
01891 
01892     if (!S)
01893       break;
01894 
01895     if (isa<ExprWithCleanups>(S) ||
01896         isa<CXXBindTemporaryExpr>(S) ||
01897         isa<SubstNonTypeTemplateParmExpr>(S))
01898       continue;
01899 
01900     break;
01901   }
01902 
01903   return S;
01904 }
01905 
01906 static bool isConditionForTerminator(const Stmt *S, const Stmt *Cond) {
01907   switch (S->getStmtClass()) {
01908     case Stmt::BinaryOperatorClass: {
01909       const BinaryOperator *BO = cast<BinaryOperator>(S);
01910       if (!BO->isLogicalOp())
01911         return false;
01912       return BO->getLHS() == Cond || BO->getRHS() == Cond;
01913     }
01914     case Stmt::IfStmtClass:
01915       return cast<IfStmt>(S)->getCond() == Cond;
01916     case Stmt::ForStmtClass:
01917       return cast<ForStmt>(S)->getCond() == Cond;
01918     case Stmt::WhileStmtClass:
01919       return cast<WhileStmt>(S)->getCond() == Cond;
01920     case Stmt::DoStmtClass:
01921       return cast<DoStmt>(S)->getCond() == Cond;
01922     case Stmt::ChooseExprClass:
01923       return cast<ChooseExpr>(S)->getCond() == Cond;
01924     case Stmt::IndirectGotoStmtClass:
01925       return cast<IndirectGotoStmt>(S)->getTarget() == Cond;
01926     case Stmt::SwitchStmtClass:
01927       return cast<SwitchStmt>(S)->getCond() == Cond;
01928     case Stmt::BinaryConditionalOperatorClass:
01929       return cast<BinaryConditionalOperator>(S)->getCond() == Cond;
01930     case Stmt::ConditionalOperatorClass: {
01931       const ConditionalOperator *CO = cast<ConditionalOperator>(S);
01932       return CO->getCond() == Cond ||
01933              CO->getLHS() == Cond ||
01934              CO->getRHS() == Cond;
01935     }
01936     case Stmt::ObjCForCollectionStmtClass:
01937       return cast<ObjCForCollectionStmt>(S)->getElement() == Cond;
01938     case Stmt::CXXForRangeStmtClass: {
01939       const CXXForRangeStmt *FRS = cast<CXXForRangeStmt>(S);
01940       return FRS->getCond() == Cond || FRS->getRangeInit() == Cond;
01941     }
01942     default:
01943       return false;
01944   }
01945 }
01946 
01947 static bool isIncrementOrInitInForLoop(const Stmt *S, const Stmt *FL) {
01948   if (const ForStmt *FS = dyn_cast<ForStmt>(FL))
01949     return FS->getInc() == S || FS->getInit() == S;
01950   if (const CXXForRangeStmt *FRS = dyn_cast<CXXForRangeStmt>(FL))
01951     return FRS->getInc() == S || FRS->getRangeStmt() == S ||
01952            FRS->getLoopVarStmt() || FRS->getRangeInit() == S;
01953   return false;
01954 }
01955 
01956 typedef llvm::DenseSet<const PathDiagnosticCallPiece *>
01957         OptimizedCallsSet;
01958 
01959 /// Adds synthetic edges from top-level statements to their subexpressions.
01960 ///
01961 /// This avoids a "swoosh" effect, where an edge from a top-level statement A
01962 /// points to a sub-expression B.1 that's not at the start of B. In these cases,
01963 /// we'd like to see an edge from A to B, then another one from B to B.1.
01964 static void addContextEdges(PathPieces &pieces, SourceManager &SM,
01965                             const ParentMap &PM, const LocationContext *LCtx) {
01966   PathPieces::iterator Prev = pieces.end();
01967   for (PathPieces::iterator I = pieces.begin(), E = Prev; I != E;
01968        Prev = I, ++I) {
01969     PathDiagnosticControlFlowPiece *Piece =
01970       dyn_cast<PathDiagnosticControlFlowPiece>(*I);
01971 
01972     if (!Piece)
01973       continue;
01974 
01975     PathDiagnosticLocation SrcLoc = Piece->getStartLocation();
01976     SmallVector<PathDiagnosticLocation, 4> SrcContexts;
01977 
01978     PathDiagnosticLocation NextSrcContext = SrcLoc;
01979     const Stmt *InnerStmt = nullptr;
01980     while (NextSrcContext.isValid() && NextSrcContext.asStmt() != InnerStmt) {
01981       SrcContexts.push_back(NextSrcContext);
01982       InnerStmt = NextSrcContext.asStmt();
01983       NextSrcContext = getEnclosingStmtLocation(InnerStmt, SM, PM, LCtx,
01984                                                 /*allowNested=*/true);
01985     }
01986 
01987     // Repeatedly split the edge as necessary.
01988     // This is important for nested logical expressions (||, &&, ?:) where we
01989     // want to show all the levels of context.
01990     while (true) {
01991       const Stmt *Dst = getLocStmt(Piece->getEndLocation());
01992 
01993       // We are looking at an edge. Is the destination within a larger
01994       // expression?
01995       PathDiagnosticLocation DstContext =
01996         getEnclosingStmtLocation(Dst, SM, PM, LCtx, /*allowNested=*/true);
01997       if (!DstContext.isValid() || DstContext.asStmt() == Dst)
01998         break;
01999 
02000       // If the source is in the same context, we're already good.
02001       if (std::find(SrcContexts.begin(), SrcContexts.end(), DstContext) !=
02002           SrcContexts.end())
02003         break;
02004 
02005       // Update the subexpression node to point to the context edge.
02006       Piece->setStartLocation(DstContext);
02007 
02008       // Try to extend the previous edge if it's at the same level as the source
02009       // context.
02010       if (Prev != E) {
02011         PathDiagnosticControlFlowPiece *PrevPiece =
02012           dyn_cast<PathDiagnosticControlFlowPiece>(*Prev);
02013 
02014         if (PrevPiece) {
02015           if (const Stmt *PrevSrc = getLocStmt(PrevPiece->getStartLocation())) {
02016             const Stmt *PrevSrcParent = getStmtParent(PrevSrc, PM);
02017             if (PrevSrcParent == getStmtParent(getLocStmt(DstContext), PM)) {
02018               PrevPiece->setEndLocation(DstContext);
02019               break;
02020             }
02021           }
02022         }
02023       }
02024 
02025       // Otherwise, split the current edge into a context edge and a
02026       // subexpression edge. Note that the context statement may itself have
02027       // context.
02028       Piece = new PathDiagnosticControlFlowPiece(SrcLoc, DstContext);
02029       I = pieces.insert(I, Piece);
02030     }
02031   }
02032 }
02033 
02034 /// \brief Move edges from a branch condition to a branch target
02035 ///        when the condition is simple.
02036 ///
02037 /// This restructures some of the work of addContextEdges.  That function
02038 /// creates edges this may destroy, but they work together to create a more
02039 /// aesthetically set of edges around branches.  After the call to
02040 /// addContextEdges, we may have (1) an edge to the branch, (2) an edge from
02041 /// the branch to the branch condition, and (3) an edge from the branch
02042 /// condition to the branch target.  We keep (1), but may wish to remove (2)
02043 /// and move the source of (3) to the branch if the branch condition is simple.
02044 ///
02045 static void simplifySimpleBranches(PathPieces &pieces) {
02046   for (PathPieces::iterator I = pieces.begin(), E = pieces.end(); I != E; ++I) {
02047 
02048     PathDiagnosticControlFlowPiece *PieceI =
02049       dyn_cast<PathDiagnosticControlFlowPiece>(*I);
02050 
02051     if (!PieceI)
02052       continue;
02053 
02054     const Stmt *s1Start = getLocStmt(PieceI->getStartLocation());
02055     const Stmt *s1End   = getLocStmt(PieceI->getEndLocation());
02056 
02057     if (!s1Start || !s1End)
02058       continue;
02059 
02060     PathPieces::iterator NextI = I; ++NextI;
02061     if (NextI == E)
02062       break;
02063 
02064     PathDiagnosticControlFlowPiece *PieceNextI = nullptr;
02065 
02066     while (true) {
02067       if (NextI == E)
02068         break;
02069 
02070       PathDiagnosticEventPiece *EV = dyn_cast<PathDiagnosticEventPiece>(*NextI);
02071       if (EV) {
02072         StringRef S = EV->getString();
02073         if (S == StrEnteringLoop || S == StrLoopBodyZero ||
02074             S == StrLoopCollectionEmpty || S == StrLoopRangeEmpty) {
02075           ++NextI;
02076           continue;
02077         }
02078         break;
02079       }
02080 
02081       PieceNextI = dyn_cast<PathDiagnosticControlFlowPiece>(*NextI);
02082       break;
02083     }
02084 
02085     if (!PieceNextI)
02086       continue;
02087 
02088     const Stmt *s2Start = getLocStmt(PieceNextI->getStartLocation());
02089     const Stmt *s2End   = getLocStmt(PieceNextI->getEndLocation());
02090 
02091     if (!s2Start || !s2End || s1End != s2Start)
02092       continue;
02093 
02094     // We only perform this transformation for specific branch kinds.
02095     // We don't want to do this for do..while, for example.
02096     if (!(isa<ForStmt>(s1Start) || isa<WhileStmt>(s1Start) ||
02097           isa<IfStmt>(s1Start) || isa<ObjCForCollectionStmt>(s1Start) ||
02098           isa<CXXForRangeStmt>(s1Start)))
02099       continue;
02100 
02101     // Is s1End the branch condition?
02102     if (!isConditionForTerminator(s1Start, s1End))
02103       continue;
02104 
02105     // Perform the hoisting by eliminating (2) and changing the start
02106     // location of (3).
02107     PieceNextI->setStartLocation(PieceI->getStartLocation());
02108     I = pieces.erase(I);
02109   }
02110 }
02111 
02112 /// Returns the number of bytes in the given (character-based) SourceRange.
02113 ///
02114 /// If the locations in the range are not on the same line, returns None.
02115 ///
02116 /// Note that this does not do a precise user-visible character or column count.
02117 static Optional<size_t> getLengthOnSingleLine(SourceManager &SM,
02118                                               SourceRange Range) {
02119   SourceRange ExpansionRange(SM.getExpansionLoc(Range.getBegin()),
02120                              SM.getExpansionRange(Range.getEnd()).second);
02121 
02122   FileID FID = SM.getFileID(ExpansionRange.getBegin());
02123   if (FID != SM.getFileID(ExpansionRange.getEnd()))
02124     return None;
02125 
02126   bool Invalid;
02127   const llvm::MemoryBuffer *Buffer = SM.getBuffer(FID, &Invalid);
02128   if (Invalid)
02129     return None;
02130 
02131   unsigned BeginOffset = SM.getFileOffset(ExpansionRange.getBegin());
02132   unsigned EndOffset = SM.getFileOffset(ExpansionRange.getEnd());
02133   StringRef Snippet = Buffer->getBuffer().slice(BeginOffset, EndOffset);
02134 
02135   // We're searching the raw bytes of the buffer here, which might include
02136   // escaped newlines and such. That's okay; we're trying to decide whether the
02137   // SourceRange is covering a large or small amount of space in the user's
02138   // editor.
02139   if (Snippet.find_first_of("\r\n") != StringRef::npos)
02140     return None;
02141 
02142   // This isn't Unicode-aware, but it doesn't need to be.
02143   return Snippet.size();
02144 }
02145 
02146 /// \sa getLengthOnSingleLine(SourceManager, SourceRange)
02147 static Optional<size_t> getLengthOnSingleLine(SourceManager &SM,
02148                                               const Stmt *S) {
02149   return getLengthOnSingleLine(SM, S->getSourceRange());
02150 }
02151 
02152 /// Eliminate two-edge cycles created by addContextEdges().
02153 ///
02154 /// Once all the context edges are in place, there are plenty of cases where
02155 /// there's a single edge from a top-level statement to a subexpression,
02156 /// followed by a single path note, and then a reverse edge to get back out to
02157 /// the top level. If the statement is simple enough, the subexpression edges
02158 /// just add noise and make it harder to understand what's going on.
02159 ///
02160 /// This function only removes edges in pairs, because removing only one edge
02161 /// might leave other edges dangling.
02162 ///
02163 /// This will not remove edges in more complicated situations:
02164 /// - if there is more than one "hop" leading to or from a subexpression.
02165 /// - if there is an inlined call between the edges instead of a single event.
02166 /// - if the whole statement is large enough that having subexpression arrows
02167 ///   might be helpful.
02168 static void removeContextCycles(PathPieces &Path, SourceManager &SM,
02169                                 ParentMap &PM) {
02170   for (PathPieces::iterator I = Path.begin(), E = Path.end(); I != E; ) {
02171     // Pattern match the current piece and its successor.
02172     PathDiagnosticControlFlowPiece *PieceI =
02173       dyn_cast<PathDiagnosticControlFlowPiece>(*I);
02174 
02175     if (!PieceI) {
02176       ++I;
02177       continue;
02178     }
02179 
02180     const Stmt *s1Start = getLocStmt(PieceI->getStartLocation());
02181     const Stmt *s1End   = getLocStmt(PieceI->getEndLocation());
02182 
02183     PathPieces::iterator NextI = I; ++NextI;
02184     if (NextI == E)
02185       break;
02186 
02187     PathDiagnosticControlFlowPiece *PieceNextI =
02188       dyn_cast<PathDiagnosticControlFlowPiece>(*NextI);
02189 
02190     if (!PieceNextI) {
02191       if (isa<PathDiagnosticEventPiece>(*NextI)) {
02192         ++NextI;
02193         if (NextI == E)
02194           break;
02195         PieceNextI = dyn_cast<PathDiagnosticControlFlowPiece>(*NextI);
02196       }
02197 
02198       if (!PieceNextI) {
02199         ++I;
02200         continue;
02201       }
02202     }
02203 
02204     const Stmt *s2Start = getLocStmt(PieceNextI->getStartLocation());
02205     const Stmt *s2End   = getLocStmt(PieceNextI->getEndLocation());
02206 
02207     if (s1Start && s2Start && s1Start == s2End && s2Start == s1End) {
02208       const size_t MAX_SHORT_LINE_LENGTH = 80;
02209       Optional<size_t> s1Length = getLengthOnSingleLine(SM, s1Start);
02210       if (s1Length && *s1Length <= MAX_SHORT_LINE_LENGTH) {
02211         Optional<size_t> s2Length = getLengthOnSingleLine(SM, s2Start);
02212         if (s2Length && *s2Length <= MAX_SHORT_LINE_LENGTH) {
02213           Path.erase(I);
02214           I = Path.erase(NextI);
02215           continue;
02216         }
02217       }
02218     }
02219 
02220     ++I;
02221   }
02222 }
02223 
02224 /// \brief Return true if X is contained by Y.
02225 static bool lexicalContains(ParentMap &PM,
02226                             const Stmt *X,
02227                             const Stmt *Y) {
02228   while (X) {
02229     if (X == Y)
02230       return true;
02231     X = PM.getParent(X);
02232   }
02233   return false;
02234 }
02235 
02236 // Remove short edges on the same line less than 3 columns in difference.
02237 static void removePunyEdges(PathPieces &path,
02238                             SourceManager &SM,
02239                             ParentMap &PM) {
02240 
02241   bool erased = false;
02242 
02243   for (PathPieces::iterator I = path.begin(), E = path.end(); I != E;
02244        erased ? I : ++I) {
02245 
02246     erased = false;
02247 
02248     PathDiagnosticControlFlowPiece *PieceI =
02249       dyn_cast<PathDiagnosticControlFlowPiece>(*I);
02250 
02251     if (!PieceI)
02252       continue;
02253 
02254     const Stmt *start = getLocStmt(PieceI->getStartLocation());
02255     const Stmt *end   = getLocStmt(PieceI->getEndLocation());
02256 
02257     if (!start || !end)
02258       continue;
02259 
02260     const Stmt *endParent = PM.getParent(end);
02261     if (!endParent)
02262       continue;
02263 
02264     if (isConditionForTerminator(end, endParent))
02265       continue;
02266 
02267     SourceLocation FirstLoc = start->getLocStart();
02268     SourceLocation SecondLoc = end->getLocStart();
02269 
02270     if (!SM.isWrittenInSameFile(FirstLoc, SecondLoc))
02271       continue;
02272     if (SM.isBeforeInTranslationUnit(SecondLoc, FirstLoc))
02273       std::swap(SecondLoc, FirstLoc);
02274 
02275     SourceRange EdgeRange(FirstLoc, SecondLoc);
02276     Optional<size_t> ByteWidth = getLengthOnSingleLine(SM, EdgeRange);
02277 
02278     // If the statements are on different lines, continue.
02279     if (!ByteWidth)
02280       continue;
02281 
02282     const size_t MAX_PUNY_EDGE_LENGTH = 2;
02283     if (*ByteWidth <= MAX_PUNY_EDGE_LENGTH) {
02284       // FIXME: There are enough /bytes/ between the endpoints of the edge, but
02285       // there might not be enough /columns/. A proper user-visible column count
02286       // is probably too expensive, though.
02287       I = path.erase(I);
02288       erased = true;
02289       continue;
02290     }
02291   }
02292 }
02293 
02294 static void removeIdenticalEvents(PathPieces &path) {
02295   for (PathPieces::iterator I = path.begin(), E = path.end(); I != E; ++I) {
02296     PathDiagnosticEventPiece *PieceI =
02297       dyn_cast<PathDiagnosticEventPiece>(*I);
02298 
02299     if (!PieceI)
02300       continue;
02301 
02302     PathPieces::iterator NextI = I; ++NextI;
02303     if (NextI == E)
02304       return;
02305 
02306     PathDiagnosticEventPiece *PieceNextI =
02307       dyn_cast<PathDiagnosticEventPiece>(*NextI);
02308 
02309     if (!PieceNextI)
02310       continue;
02311 
02312     // Erase the second piece if it has the same exact message text.
02313     if (PieceI->getString() == PieceNextI->getString()) {
02314       path.erase(NextI);
02315     }
02316   }
02317 }
02318 
02319 static bool optimizeEdges(PathPieces &path, SourceManager &SM,
02320                           OptimizedCallsSet &OCS,
02321                           LocationContextMap &LCM) {
02322   bool hasChanges = false;
02323   const LocationContext *LC = LCM[&path];
02324   assert(LC);
02325   ParentMap &PM = LC->getParentMap();
02326 
02327   for (PathPieces::iterator I = path.begin(), E = path.end(); I != E; ) {
02328     // Optimize subpaths.
02329     if (PathDiagnosticCallPiece *CallI = dyn_cast<PathDiagnosticCallPiece>(*I)){
02330       // Record the fact that a call has been optimized so we only do the
02331       // effort once.
02332       if (!OCS.count(CallI)) {
02333         while (optimizeEdges(CallI->path, SM, OCS, LCM)) {}
02334         OCS.insert(CallI);
02335       }
02336       ++I;
02337       continue;
02338     }
02339 
02340     // Pattern match the current piece and its successor.
02341     PathDiagnosticControlFlowPiece *PieceI =
02342       dyn_cast<PathDiagnosticControlFlowPiece>(*I);
02343 
02344     if (!PieceI) {
02345       ++I;
02346       continue;
02347     }
02348 
02349     const Stmt *s1Start = getLocStmt(PieceI->getStartLocation());
02350     const Stmt *s1End   = getLocStmt(PieceI->getEndLocation());
02351     const Stmt *level1 = getStmtParent(s1Start, PM);
02352     const Stmt *level2 = getStmtParent(s1End, PM);
02353 
02354     PathPieces::iterator NextI = I; ++NextI;
02355     if (NextI == E)
02356       break;
02357 
02358     PathDiagnosticControlFlowPiece *PieceNextI =
02359       dyn_cast<PathDiagnosticControlFlowPiece>(*NextI);
02360 
02361     if (!PieceNextI) {
02362       ++I;
02363       continue;
02364     }
02365 
02366     const Stmt *s2Start = getLocStmt(PieceNextI->getStartLocation());
02367     const Stmt *s2End   = getLocStmt(PieceNextI->getEndLocation());
02368     const Stmt *level3 = getStmtParent(s2Start, PM);
02369     const Stmt *level4 = getStmtParent(s2End, PM);
02370 
02371     // Rule I.
02372     //
02373     // If we have two consecutive control edges whose end/begin locations
02374     // are at the same level (e.g. statements or top-level expressions within
02375     // a compound statement, or siblings share a single ancestor expression),
02376     // then merge them if they have no interesting intermediate event.
02377     //
02378     // For example:
02379     //
02380     // (1.1 -> 1.2) -> (1.2 -> 1.3) becomes (1.1 -> 1.3) because the common
02381     // parent is '1'.  Here 'x.y.z' represents the hierarchy of statements.
02382     //
02383     // NOTE: this will be limited later in cases where we add barriers
02384     // to prevent this optimization.
02385     //
02386     if (level1 && level1 == level2 && level1 == level3 && level1 == level4) {
02387       PieceI->setEndLocation(PieceNextI->getEndLocation());
02388       path.erase(NextI);
02389       hasChanges = true;
02390       continue;
02391     }
02392 
02393     // Rule II.
02394     //
02395     // Eliminate edges between subexpressions and parent expressions
02396     // when the subexpression is consumed.
02397     //
02398     // NOTE: this will be limited later in cases where we add barriers
02399     // to prevent this optimization.
02400     //
02401     if (s1End && s1End == s2Start && level2) {
02402       bool removeEdge = false;
02403       // Remove edges into the increment or initialization of a
02404       // loop that have no interleaving event.  This means that
02405       // they aren't interesting.
02406       if (isIncrementOrInitInForLoop(s1End, level2))
02407         removeEdge = true;
02408       // Next only consider edges that are not anchored on
02409       // the condition of a terminator.  This are intermediate edges
02410       // that we might want to trim.
02411       else if (!isConditionForTerminator(level2, s1End)) {
02412         // Trim edges on expressions that are consumed by
02413         // the parent expression.
02414         if (isa<Expr>(s1End) && PM.isConsumedExpr(cast<Expr>(s1End))) {
02415           removeEdge = true;          
02416         }
02417         // Trim edges where a lexical containment doesn't exist.
02418         // For example:
02419         //
02420         //  X -> Y -> Z
02421         //
02422         // If 'Z' lexically contains Y (it is an ancestor) and
02423         // 'X' does not lexically contain Y (it is a descendant OR
02424         // it has no lexical relationship at all) then trim.
02425         //
02426         // This can eliminate edges where we dive into a subexpression
02427         // and then pop back out, etc.
02428         else if (s1Start && s2End &&
02429                  lexicalContains(PM, s2Start, s2End) &&
02430                  !lexicalContains(PM, s1End, s1Start)) {
02431           removeEdge = true;
02432         }
02433         // Trim edges from a subexpression back to the top level if the
02434         // subexpression is on a different line.
02435         //
02436         // A.1 -> A -> B
02437         // becomes
02438         // A.1 -> B
02439         //
02440         // These edges just look ugly and don't usually add anything.
02441         else if (s1Start && s2End &&
02442                  lexicalContains(PM, s1Start, s1End)) {
02443           SourceRange EdgeRange(PieceI->getEndLocation().asLocation(),
02444                                 PieceI->getStartLocation().asLocation());
02445           if (!getLengthOnSingleLine(SM, EdgeRange).hasValue())
02446             removeEdge = true;
02447         }
02448       }
02449 
02450       if (removeEdge) {
02451         PieceI->setEndLocation(PieceNextI->getEndLocation());
02452         path.erase(NextI);
02453         hasChanges = true;
02454         continue;
02455       }
02456     }
02457 
02458     // Optimize edges for ObjC fast-enumeration loops.
02459     //
02460     // (X -> collection) -> (collection -> element)
02461     //
02462     // becomes:
02463     //
02464     // (X -> element)
02465     if (s1End == s2Start) {
02466       const ObjCForCollectionStmt *FS =
02467         dyn_cast_or_null<ObjCForCollectionStmt>(level3);
02468       if (FS && FS->getCollection()->IgnoreParens() == s2Start &&
02469           s2End == FS->getElement()) {
02470         PieceI->setEndLocation(PieceNextI->getEndLocation());
02471         path.erase(NextI);
02472         hasChanges = true;
02473         continue;
02474       }
02475     }
02476 
02477     // No changes at this index?  Move to the next one.
02478     ++I;
02479   }
02480 
02481   if (!hasChanges) {
02482     // Adjust edges into subexpressions to make them more uniform
02483     // and aesthetically pleasing.
02484     addContextEdges(path, SM, PM, LC);
02485     // Remove "cyclical" edges that include one or more context edges.
02486     removeContextCycles(path, SM, PM);
02487     // Hoist edges originating from branch conditions to branches
02488     // for simple branches.
02489     simplifySimpleBranches(path);
02490     // Remove any puny edges left over after primary optimization pass.
02491     removePunyEdges(path, SM, PM);
02492     // Remove identical events.
02493     removeIdenticalEvents(path);
02494   }
02495 
02496   return hasChanges;
02497 }
02498 
02499 /// Drop the very first edge in a path, which should be a function entry edge.
02500 ///
02501 /// If the first edge is not a function entry edge (say, because the first
02502 /// statement had an invalid source location), this function does nothing.
02503 // FIXME: We should just generate invalid edges anyway and have the optimizer
02504 // deal with them.
02505 static void dropFunctionEntryEdge(PathPieces &Path,
02506                                   LocationContextMap &LCM,
02507                                   SourceManager &SM) {
02508   const PathDiagnosticControlFlowPiece *FirstEdge =
02509     dyn_cast<PathDiagnosticControlFlowPiece>(Path.front());
02510   if (!FirstEdge)
02511     return;
02512 
02513   const Decl *D = LCM[&Path]->getDecl();
02514   PathDiagnosticLocation EntryLoc = PathDiagnosticLocation::createBegin(D, SM);
02515   if (FirstEdge->getStartLocation() != EntryLoc)
02516     return;
02517 
02518   Path.pop_front();
02519 }
02520 
02521 
02522 //===----------------------------------------------------------------------===//
02523 // Methods for BugType and subclasses.
02524 //===----------------------------------------------------------------------===//
02525 void BugType::anchor() { }
02526 
02527 void BugType::FlushReports(BugReporter &BR) {}
02528 
02529 void BuiltinBug::anchor() {}
02530 
02531 //===----------------------------------------------------------------------===//
02532 // Methods for BugReport and subclasses.
02533 //===----------------------------------------------------------------------===//
02534 
02535 void BugReport::NodeResolver::anchor() {}
02536 
02537 void BugReport::addVisitor(std::unique_ptr<BugReporterVisitor> visitor) {
02538   if (!visitor)
02539     return;
02540 
02541   llvm::FoldingSetNodeID ID;
02542   visitor->Profile(ID);
02543   void *InsertPos;
02544 
02545   if (CallbacksSet.FindNodeOrInsertPos(ID, InsertPos))
02546     return;
02547 
02548   CallbacksSet.InsertNode(visitor.get(), InsertPos);
02549   Callbacks.push_back(std::move(visitor));
02550   ++ConfigurationChangeToken;
02551 }
02552 
02553 BugReport::~BugReport() {
02554   while (!interestingSymbols.empty()) {
02555     popInterestingSymbolsAndRegions();
02556   }
02557 }
02558 
02559 const Decl *BugReport::getDeclWithIssue() const {
02560   if (DeclWithIssue)
02561     return DeclWithIssue;
02562   
02563   const ExplodedNode *N = getErrorNode();
02564   if (!N)
02565     return nullptr;
02566 
02567   const LocationContext *LC = N->getLocationContext();
02568   return LC->getCurrentStackFrame()->getDecl();
02569 }
02570 
02571 void BugReport::Profile(llvm::FoldingSetNodeID& hash) const {
02572   hash.AddPointer(&BT);
02573   hash.AddString(Description);
02574   PathDiagnosticLocation UL = getUniqueingLocation();
02575   if (UL.isValid()) {
02576     UL.Profile(hash);
02577   } else if (Location.isValid()) {
02578     Location.Profile(hash);
02579   } else {
02580     assert(ErrorNode);
02581     hash.AddPointer(GetCurrentOrPreviousStmt(ErrorNode));
02582   }
02583 
02584   for (SmallVectorImpl<SourceRange>::const_iterator I =
02585       Ranges.begin(), E = Ranges.end(); I != E; ++I) {
02586     const SourceRange range = *I;
02587     if (!range.isValid())
02588       continue;
02589     hash.AddInteger(range.getBegin().getRawEncoding());
02590     hash.AddInteger(range.getEnd().getRawEncoding());
02591   }
02592 }
02593 
02594 void BugReport::markInteresting(SymbolRef sym) {
02595   if (!sym)
02596     return;
02597 
02598   // If the symbol wasn't already in our set, note a configuration change.
02599   if (getInterestingSymbols().insert(sym).second)
02600     ++ConfigurationChangeToken;
02601 
02602   if (const SymbolMetadata *meta = dyn_cast<SymbolMetadata>(sym))
02603     getInterestingRegions().insert(meta->getRegion());
02604 }
02605 
02606 void BugReport::markInteresting(const MemRegion *R) {
02607   if (!R)
02608     return;
02609 
02610   // If the base region wasn't already in our set, note a configuration change.
02611   R = R->getBaseRegion();
02612   if (getInterestingRegions().insert(R).second)
02613     ++ConfigurationChangeToken;
02614 
02615   if (const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R))
02616     getInterestingSymbols().insert(SR->getSymbol());
02617 }
02618 
02619 void BugReport::markInteresting(SVal V) {
02620   markInteresting(V.getAsRegion());
02621   markInteresting(V.getAsSymbol());
02622 }
02623 
02624 void BugReport::markInteresting(const LocationContext *LC) {
02625   if (!LC)
02626     return;
02627   InterestingLocationContexts.insert(LC);
02628 }
02629 
02630 bool BugReport::isInteresting(SVal V) {
02631   return isInteresting(V.getAsRegion()) || isInteresting(V.getAsSymbol());
02632 }
02633 
02634 bool BugReport::isInteresting(SymbolRef sym) {
02635   if (!sym)
02636     return false;
02637   // We don't currently consider metadata symbols to be interesting
02638   // even if we know their region is interesting. Is that correct behavior?
02639   return getInterestingSymbols().count(sym);
02640 }
02641 
02642 bool BugReport::isInteresting(const MemRegion *R) {
02643   if (!R)
02644     return false;
02645   R = R->getBaseRegion();
02646   bool b = getInterestingRegions().count(R);
02647   if (b)
02648     return true;
02649   if (const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R))
02650     return getInterestingSymbols().count(SR->getSymbol());
02651   return false;
02652 }
02653 
02654 bool BugReport::isInteresting(const LocationContext *LC) {
02655   if (!LC)
02656     return false;
02657   return InterestingLocationContexts.count(LC);
02658 }
02659 
02660 void BugReport::lazyInitializeInterestingSets() {
02661   if (interestingSymbols.empty()) {
02662     interestingSymbols.push_back(new Symbols());
02663     interestingRegions.push_back(new Regions());
02664   }
02665 }
02666 
02667 BugReport::Symbols &BugReport::getInterestingSymbols() {
02668   lazyInitializeInterestingSets();
02669   return *interestingSymbols.back();
02670 }
02671 
02672 BugReport::Regions &BugReport::getInterestingRegions() {
02673   lazyInitializeInterestingSets();
02674   return *interestingRegions.back();
02675 }
02676 
02677 void BugReport::pushInterestingSymbolsAndRegions() {
02678   interestingSymbols.push_back(new Symbols(getInterestingSymbols()));
02679   interestingRegions.push_back(new Regions(getInterestingRegions()));
02680 }
02681 
02682 void BugReport::popInterestingSymbolsAndRegions() {
02683   delete interestingSymbols.pop_back_val();
02684   delete interestingRegions.pop_back_val();
02685 }
02686 
02687 const Stmt *BugReport::getStmt() const {
02688   if (!ErrorNode)
02689     return nullptr;
02690 
02691   ProgramPoint ProgP = ErrorNode->getLocation();
02692   const Stmt *S = nullptr;
02693 
02694   if (Optional<BlockEntrance> BE = ProgP.getAs<BlockEntrance>()) {
02695     CFGBlock &Exit = ProgP.getLocationContext()->getCFG()->getExit();
02696     if (BE->getBlock() == &Exit)
02697       S = GetPreviousStmt(ErrorNode);
02698   }
02699   if (!S)
02700     S = PathDiagnosticLocation::getStmt(ErrorNode);
02701 
02702   return S;
02703 }
02704 
02705 std::pair<BugReport::ranges_iterator, BugReport::ranges_iterator>
02706 BugReport::getRanges() {
02707     // If no custom ranges, add the range of the statement corresponding to
02708     // the error node.
02709     if (Ranges.empty()) {
02710       if (const Expr *E = dyn_cast_or_null<Expr>(getStmt()))
02711         addRange(E->getSourceRange());
02712       else
02713         return std::make_pair(ranges_iterator(), ranges_iterator());
02714     }
02715 
02716     // User-specified absence of range info.
02717     if (Ranges.size() == 1 && !Ranges.begin()->isValid())
02718       return std::make_pair(ranges_iterator(), ranges_iterator());
02719 
02720     return std::make_pair(Ranges.begin(), Ranges.end());
02721 }
02722 
02723 PathDiagnosticLocation BugReport::getLocation(const SourceManager &SM) const {
02724   if (ErrorNode) {
02725     assert(!Location.isValid() &&
02726      "Either Location or ErrorNode should be specified but not both.");
02727     return PathDiagnosticLocation::createEndOfPath(ErrorNode, SM);
02728   }
02729 
02730   assert(Location.isValid());
02731   return Location;
02732 }
02733 
02734 //===----------------------------------------------------------------------===//
02735 // Methods for BugReporter and subclasses.
02736 //===----------------------------------------------------------------------===//
02737 
02738 BugReportEquivClass::~BugReportEquivClass() { }
02739 GRBugReporter::~GRBugReporter() { }
02740 BugReporterData::~BugReporterData() {}
02741 
02742 ExplodedGraph &GRBugReporter::getGraph() { return Eng.getGraph(); }
02743 
02744 ProgramStateManager&
02745 GRBugReporter::getStateManager() { return Eng.getStateManager(); }
02746 
02747 BugReporter::~BugReporter() {
02748   FlushReports();
02749 
02750   // Free the bug reports we are tracking.
02751   typedef std::vector<BugReportEquivClass *> ContTy;
02752   for (ContTy::iterator I = EQClassesVector.begin(), E = EQClassesVector.end();
02753        I != E; ++I) {
02754     delete *I;
02755   }
02756 }
02757 
02758 void BugReporter::FlushReports() {
02759   if (BugTypes.isEmpty())
02760     return;
02761 
02762   // First flush the warnings for each BugType.  This may end up creating new
02763   // warnings and new BugTypes.
02764   // FIXME: Only NSErrorChecker needs BugType's FlushReports.
02765   // Turn NSErrorChecker into a proper checker and remove this.
02766   SmallVector<const BugType*, 16> bugTypes;
02767   for (BugTypesTy::iterator I=BugTypes.begin(), E=BugTypes.end(); I!=E; ++I)
02768     bugTypes.push_back(*I);
02769   for (SmallVectorImpl<const BugType *>::iterator
02770          I = bugTypes.begin(), E = bugTypes.end(); I != E; ++I)
02771     const_cast<BugType*>(*I)->FlushReports(*this);
02772 
02773   // We need to flush reports in deterministic order to ensure the order
02774   // of the reports is consistent between runs.
02775   typedef std::vector<BugReportEquivClass *> ContVecTy;
02776   for (ContVecTy::iterator EI=EQClassesVector.begin(), EE=EQClassesVector.end();
02777        EI != EE; ++EI){
02778     BugReportEquivClass& EQ = **EI;
02779     FlushReport(EQ);
02780   }
02781 
02782   // BugReporter owns and deletes only BugTypes created implicitly through
02783   // EmitBasicReport.
02784   // FIXME: There are leaks from checkers that assume that the BugTypes they
02785   // create will be destroyed by the BugReporter.
02786   llvm::DeleteContainerSeconds(StrBugTypes);
02787 
02788   // Remove all references to the BugType objects.
02789   BugTypes = F.getEmptySet();
02790 }
02791 
02792 //===----------------------------------------------------------------------===//
02793 // PathDiagnostics generation.
02794 //===----------------------------------------------------------------------===//
02795 
02796 namespace {
02797 /// A wrapper around a report graph, which contains only a single path, and its
02798 /// node maps.
02799 class ReportGraph {
02800 public:
02801   InterExplodedGraphMap BackMap;
02802   std::unique_ptr<ExplodedGraph> Graph;
02803   const ExplodedNode *ErrorNode;
02804   size_t Index;
02805 };
02806 
02807 /// A wrapper around a trimmed graph and its node maps.
02808 class TrimmedGraph {
02809   InterExplodedGraphMap InverseMap;
02810 
02811   typedef llvm::DenseMap<const ExplodedNode *, unsigned> PriorityMapTy;
02812   PriorityMapTy PriorityMap;
02813 
02814   typedef std::pair<const ExplodedNode *, size_t> NodeIndexPair;
02815   SmallVector<NodeIndexPair, 32> ReportNodes;
02816 
02817   std::unique_ptr<ExplodedGraph> G;
02818 
02819   /// A helper class for sorting ExplodedNodes by priority.
02820   template <bool Descending>
02821   class PriorityCompare {
02822     const PriorityMapTy &PriorityMap;
02823 
02824   public:
02825     PriorityCompare(const PriorityMapTy &M) : PriorityMap(M) {}
02826 
02827     bool operator()(const ExplodedNode *LHS, const ExplodedNode *RHS) const {
02828       PriorityMapTy::const_iterator LI = PriorityMap.find(LHS);
02829       PriorityMapTy::const_iterator RI = PriorityMap.find(RHS);
02830       PriorityMapTy::const_iterator E = PriorityMap.end();
02831 
02832       if (LI == E)
02833         return Descending;
02834       if (RI == E)
02835         return !Descending;
02836 
02837       return Descending ? LI->second > RI->second
02838                         : LI->second < RI->second;
02839     }
02840 
02841     bool operator()(const NodeIndexPair &LHS, const NodeIndexPair &RHS) const {
02842       return (*this)(LHS.first, RHS.first);
02843     }
02844   };
02845 
02846 public:
02847   TrimmedGraph(const ExplodedGraph *OriginalGraph,
02848                ArrayRef<const ExplodedNode *> Nodes);
02849 
02850   bool popNextReportGraph(ReportGraph &GraphWrapper);
02851 };
02852 }
02853 
02854 TrimmedGraph::TrimmedGraph(const ExplodedGraph *OriginalGraph,
02855                            ArrayRef<const ExplodedNode *> Nodes) {
02856   // The trimmed graph is created in the body of the constructor to ensure
02857   // that the DenseMaps have been initialized already.
02858   InterExplodedGraphMap ForwardMap;
02859   G = OriginalGraph->trim(Nodes, &ForwardMap, &InverseMap);
02860 
02861   // Find the (first) error node in the trimmed graph.  We just need to consult
02862   // the node map which maps from nodes in the original graph to nodes
02863   // in the new graph.
02864   llvm::SmallPtrSet<const ExplodedNode *, 32> RemainingNodes;
02865 
02866   for (unsigned i = 0, count = Nodes.size(); i < count; ++i) {
02867     if (const ExplodedNode *NewNode = ForwardMap.lookup(Nodes[i])) {
02868       ReportNodes.push_back(std::make_pair(NewNode, i));
02869       RemainingNodes.insert(NewNode);
02870     }
02871   }
02872 
02873   assert(!RemainingNodes.empty() && "No error node found in the trimmed graph");
02874 
02875   // Perform a forward BFS to find all the shortest paths.
02876   std::queue<const ExplodedNode *> WS;
02877 
02878   assert(G->num_roots() == 1);
02879   WS.push(*G->roots_begin());
02880   unsigned Priority = 0;
02881 
02882   while (!WS.empty()) {
02883     const ExplodedNode *Node = WS.front();
02884     WS.pop();
02885 
02886     PriorityMapTy::iterator PriorityEntry;
02887     bool IsNew;
02888     std::tie(PriorityEntry, IsNew) =
02889       PriorityMap.insert(std::make_pair(Node, Priority));
02890     ++Priority;
02891 
02892     if (!IsNew) {
02893       assert(PriorityEntry->second <= Priority);
02894       continue;
02895     }
02896 
02897     if (RemainingNodes.erase(Node))
02898       if (RemainingNodes.empty())
02899         break;
02900 
02901     for (ExplodedNode::const_pred_iterator I = Node->succ_begin(),
02902                                            E = Node->succ_end();
02903          I != E; ++I)
02904       WS.push(*I);
02905   }
02906 
02907   // Sort the error paths from longest to shortest.
02908   std::sort(ReportNodes.begin(), ReportNodes.end(),
02909             PriorityCompare<true>(PriorityMap));
02910 }
02911 
02912 bool TrimmedGraph::popNextReportGraph(ReportGraph &GraphWrapper) {
02913   if (ReportNodes.empty())
02914     return false;
02915 
02916   const ExplodedNode *OrigN;
02917   std::tie(OrigN, GraphWrapper.Index) = ReportNodes.pop_back_val();
02918   assert(PriorityMap.find(OrigN) != PriorityMap.end() &&
02919          "error node not accessible from root");
02920 
02921   // Create a new graph with a single path.  This is the graph
02922   // that will be returned to the caller.
02923   auto GNew = llvm::make_unique<ExplodedGraph>();
02924   GraphWrapper.BackMap.clear();
02925 
02926   // Now walk from the error node up the BFS path, always taking the
02927   // predeccessor with the lowest number.
02928   ExplodedNode *Succ = nullptr;
02929   while (true) {
02930     // Create the equivalent node in the new graph with the same state
02931     // and location.
02932     ExplodedNode *NewN = GNew->getNode(OrigN->getLocation(), OrigN->getState(),
02933                                        OrigN->isSink());
02934 
02935     // Store the mapping to the original node.
02936     InterExplodedGraphMap::const_iterator IMitr = InverseMap.find(OrigN);
02937     assert(IMitr != InverseMap.end() && "No mapping to original node.");
02938     GraphWrapper.BackMap[NewN] = IMitr->second;
02939 
02940     // Link up the new node with the previous node.
02941     if (Succ)
02942       Succ->addPredecessor(NewN, *GNew);
02943     else
02944       GraphWrapper.ErrorNode = NewN;
02945 
02946     Succ = NewN;
02947 
02948     // Are we at the final node?
02949     if (OrigN->pred_empty()) {
02950       GNew->addRoot(NewN);
02951       break;
02952     }
02953 
02954     // Find the next predeccessor node.  We choose the node that is marked
02955     // with the lowest BFS number.
02956     OrigN = *std::min_element(OrigN->pred_begin(), OrigN->pred_end(),
02957                           PriorityCompare<false>(PriorityMap));
02958   }
02959 
02960   GraphWrapper.Graph = std::move(GNew);
02961 
02962   return true;
02963 }
02964 
02965 
02966 /// CompactPathDiagnostic - This function postprocesses a PathDiagnostic object
02967 ///  and collapses PathDiagosticPieces that are expanded by macros.
02968 static void CompactPathDiagnostic(PathPieces &path, const SourceManager& SM) {
02969   typedef std::vector<std::pair<IntrusiveRefCntPtr<PathDiagnosticMacroPiece>,
02970                                 SourceLocation> > MacroStackTy;
02971 
02972   typedef std::vector<IntrusiveRefCntPtr<PathDiagnosticPiece> >
02973           PiecesTy;
02974 
02975   MacroStackTy MacroStack;
02976   PiecesTy Pieces;
02977 
02978   for (PathPieces::const_iterator I = path.begin(), E = path.end();
02979        I!=E; ++I) {
02980     
02981     PathDiagnosticPiece *piece = I->get();
02982 
02983     // Recursively compact calls.
02984     if (PathDiagnosticCallPiece *call=dyn_cast<PathDiagnosticCallPiece>(piece)){
02985       CompactPathDiagnostic(call->path, SM);
02986     }
02987     
02988     // Get the location of the PathDiagnosticPiece.
02989     const FullSourceLoc Loc = piece->getLocation().asLocation();
02990 
02991     // Determine the instantiation location, which is the location we group
02992     // related PathDiagnosticPieces.
02993     SourceLocation InstantiationLoc = Loc.isMacroID() ?
02994                                       SM.getExpansionLoc(Loc) :
02995                                       SourceLocation();
02996 
02997     if (Loc.isFileID()) {
02998       MacroStack.clear();
02999       Pieces.push_back(piece);
03000       continue;
03001     }
03002 
03003     assert(Loc.isMacroID());
03004 
03005     // Is the PathDiagnosticPiece within the same macro group?
03006     if (!MacroStack.empty() && InstantiationLoc == MacroStack.back().second) {
03007       MacroStack.back().first->subPieces.push_back(piece);
03008       continue;
03009     }
03010 
03011     // We aren't in the same group.  Are we descending into a new macro
03012     // or are part of an old one?
03013     IntrusiveRefCntPtr<PathDiagnosticMacroPiece> MacroGroup;
03014 
03015     SourceLocation ParentInstantiationLoc = InstantiationLoc.isMacroID() ?
03016                                           SM.getExpansionLoc(Loc) :
03017                                           SourceLocation();
03018 
03019     // Walk the entire macro stack.
03020     while (!MacroStack.empty()) {
03021       if (InstantiationLoc == MacroStack.back().second) {
03022         MacroGroup = MacroStack.back().first;
03023         break;
03024       }
03025 
03026       if (ParentInstantiationLoc == MacroStack.back().second) {
03027         MacroGroup = MacroStack.back().first;
03028         break;
03029       }
03030 
03031       MacroStack.pop_back();
03032     }
03033 
03034     if (!MacroGroup || ParentInstantiationLoc == MacroStack.back().second) {
03035       // Create a new macro group and add it to the stack.
03036       PathDiagnosticMacroPiece *NewGroup =
03037         new PathDiagnosticMacroPiece(
03038           PathDiagnosticLocation::createSingleLocation(piece->getLocation()));
03039 
03040       if (MacroGroup)
03041         MacroGroup->subPieces.push_back(NewGroup);
03042       else {
03043         assert(InstantiationLoc.isFileID());
03044         Pieces.push_back(NewGroup);
03045       }
03046 
03047       MacroGroup = NewGroup;
03048       MacroStack.push_back(std::make_pair(MacroGroup, InstantiationLoc));
03049     }
03050 
03051     // Finally, add the PathDiagnosticPiece to the group.
03052     MacroGroup->subPieces.push_back(piece);
03053   }
03054 
03055   // Now take the pieces and construct a new PathDiagnostic.
03056   path.clear();
03057 
03058   for (PiecesTy::iterator I=Pieces.begin(), E=Pieces.end(); I!=E; ++I)
03059     path.push_back(*I);
03060 }
03061 
03062 bool GRBugReporter::generatePathDiagnostic(PathDiagnostic& PD,
03063                                            PathDiagnosticConsumer &PC,
03064                                            ArrayRef<BugReport *> &bugReports) {
03065   assert(!bugReports.empty());
03066 
03067   bool HasValid = false;
03068   bool HasInvalid = false;
03069   SmallVector<const ExplodedNode *, 32> errorNodes;
03070   for (ArrayRef<BugReport*>::iterator I = bugReports.begin(),
03071                                       E = bugReports.end(); I != E; ++I) {
03072     if ((*I)->isValid()) {
03073       HasValid = true;
03074       errorNodes.push_back((*I)->getErrorNode());
03075     } else {
03076       // Keep the errorNodes list in sync with the bugReports list.
03077       HasInvalid = true;
03078       errorNodes.push_back(nullptr);
03079     }
03080   }
03081 
03082   // If all the reports have been marked invalid by a previous path generation,
03083   // we're done.
03084   if (!HasValid)
03085     return false;
03086 
03087   typedef PathDiagnosticConsumer::PathGenerationScheme PathGenerationScheme;
03088   PathGenerationScheme ActiveScheme = PC.getGenerationScheme();
03089 
03090   if (ActiveScheme == PathDiagnosticConsumer::Extensive) {
03091     AnalyzerOptions &options = getAnalyzerOptions();
03092     if (options.getBooleanOption("path-diagnostics-alternate", true)) {
03093       ActiveScheme = PathDiagnosticConsumer::AlternateExtensive;
03094     }
03095   }
03096 
03097   TrimmedGraph TrimG(&getGraph(), errorNodes);
03098   ReportGraph ErrorGraph;
03099 
03100   while (TrimG.popNextReportGraph(ErrorGraph)) {
03101     // Find the BugReport with the original location.
03102     assert(ErrorGraph.Index < bugReports.size());
03103     BugReport *R = bugReports[ErrorGraph.Index];
03104     assert(R && "No original report found for sliced graph.");
03105     assert(R->isValid() && "Report selected by trimmed graph marked invalid.");
03106 
03107     // Start building the path diagnostic...
03108     PathDiagnosticBuilder PDB(*this, R, ErrorGraph.BackMap, &PC);
03109     const ExplodedNode *N = ErrorGraph.ErrorNode;
03110 
03111     // Register additional node visitors.
03112     R->addVisitor(llvm::make_unique<NilReceiverBRVisitor>());
03113     R->addVisitor(llvm::make_unique<ConditionBRVisitor>());
03114     R->addVisitor(llvm::make_unique<LikelyFalsePositiveSuppressionBRVisitor>());
03115 
03116     BugReport::VisitorList visitors;
03117     unsigned origReportConfigToken, finalReportConfigToken;
03118     LocationContextMap LCM;
03119 
03120     // While generating diagnostics, it's possible the visitors will decide
03121     // new symbols and regions are interesting, or add other visitors based on
03122     // the information they find. If they do, we need to regenerate the path
03123     // based on our new report configuration.
03124     do {
03125       // Get a clean copy of all the visitors.
03126       for (BugReport::visitor_iterator I = R->visitor_begin(),
03127                                        E = R->visitor_end(); I != E; ++I)
03128         visitors.push_back((*I)->clone());
03129 
03130       // Clear out the active path from any previous work.
03131       PD.resetPath();
03132       origReportConfigToken = R->getConfigurationChangeToken();
03133 
03134       // Generate the very last diagnostic piece - the piece is visible before 
03135       // the trace is expanded.
03136       std::unique_ptr<PathDiagnosticPiece> LastPiece;
03137       for (BugReport::visitor_iterator I = visitors.begin(), E = visitors.end();
03138           I != E; ++I) {
03139         if (std::unique_ptr<PathDiagnosticPiece> Piece =
03140                 (*I)->getEndPath(PDB, N, *R)) {
03141           assert (!LastPiece &&
03142               "There can only be one final piece in a diagnostic.");
03143           LastPiece = std::move(Piece);
03144         }
03145       }
03146 
03147       if (ActiveScheme != PathDiagnosticConsumer::None) {
03148         if (!LastPiece)
03149           LastPiece = BugReporterVisitor::getDefaultEndPath(PDB, N, *R);
03150         assert(LastPiece);
03151         PD.setEndOfPath(std::move(LastPiece));
03152       }
03153 
03154       // Make sure we get a clean location context map so we don't
03155       // hold onto old mappings.
03156       LCM.clear();
03157 
03158       switch (ActiveScheme) {
03159       case PathDiagnosticConsumer::AlternateExtensive:
03160         GenerateAlternateExtensivePathDiagnostic(PD, PDB, N, LCM, visitors);
03161         break;
03162       case PathDiagnosticConsumer::Extensive:
03163         GenerateExtensivePathDiagnostic(PD, PDB, N, LCM, visitors);
03164         break;
03165       case PathDiagnosticConsumer::Minimal:
03166         GenerateMinimalPathDiagnostic(PD, PDB, N, LCM, visitors);
03167         break;
03168       case PathDiagnosticConsumer::None:
03169         GenerateVisitorsOnlyPathDiagnostic(PD, PDB, N, visitors);
03170         break;
03171       }
03172 
03173       // Clean up the visitors we used.
03174       visitors.clear();
03175 
03176       // Did anything change while generating this path?
03177       finalReportConfigToken = R->getConfigurationChangeToken();
03178     } while (finalReportConfigToken != origReportConfigToken);
03179 
03180     if (!R->isValid())
03181       continue;
03182 
03183     // Finally, prune the diagnostic path of uninteresting stuff.
03184     if (!PD.path.empty()) {
03185       if (R->shouldPrunePath() && getAnalyzerOptions().shouldPrunePaths()) {
03186         bool stillHasNotes = removeUnneededCalls(PD.getMutablePieces(), R, LCM);
03187         assert(stillHasNotes);
03188         (void)stillHasNotes;
03189       }
03190 
03191       // Redirect all call pieces to have valid locations.
03192       adjustCallLocations(PD.getMutablePieces());
03193       removePiecesWithInvalidLocations(PD.getMutablePieces());
03194 
03195       if (ActiveScheme == PathDiagnosticConsumer::AlternateExtensive) {
03196         SourceManager &SM = getSourceManager();
03197 
03198         // Reduce the number of edges from a very conservative set
03199         // to an aesthetically pleasing subset that conveys the
03200         // necessary information.
03201         OptimizedCallsSet OCS;
03202         while (optimizeEdges(PD.getMutablePieces(), SM, OCS, LCM)) {}
03203 
03204         // Drop the very first function-entry edge. It's not really necessary
03205         // for top-level functions.
03206         dropFunctionEntryEdge(PD.getMutablePieces(), LCM, SM);
03207       }
03208 
03209       // Remove messages that are basically the same, and edges that may not
03210       // make sense.
03211       // We have to do this after edge optimization in the Extensive mode.
03212       removeRedundantMsgs(PD.getMutablePieces());
03213       removeEdgesToDefaultInitializers(PD.getMutablePieces());
03214     }
03215 
03216     // We found a report and didn't suppress it.
03217     return true;
03218   }
03219 
03220   // We suppressed all the reports in this equivalence class.
03221   assert(!HasInvalid && "Inconsistent suppression");
03222   (void)HasInvalid;
03223   return false;
03224 }
03225 
03226 void BugReporter::Register(BugType *BT) {
03227   BugTypes = F.add(BugTypes, BT);
03228 }
03229 
03230 void BugReporter::emitReport(BugReport* R) {
03231   // To guarantee memory release.
03232   std::unique_ptr<BugReport> UniqueR(R);
03233 
03234   if (const ExplodedNode *E = R->getErrorNode()) {
03235     const AnalysisDeclContext *DeclCtx =
03236         E->getLocationContext()->getAnalysisDeclContext();
03237     // The source of autosynthesized body can be handcrafted AST or a model
03238     // file. The locations from handcrafted ASTs have no valid source locations
03239     // and have to be discarded. Locations from model files should be preserved
03240     // for processing and reporting.
03241     if (DeclCtx->isBodyAutosynthesized() &&
03242         !DeclCtx->isBodyAutosynthesizedFromModelFile())
03243       return;
03244   }
03245   
03246   bool ValidSourceLoc = R->getLocation(getSourceManager()).isValid();
03247   assert(ValidSourceLoc);
03248   // If we mess up in a release build, we'd still prefer to just drop the bug
03249   // instead of trying to go on.
03250   if (!ValidSourceLoc)
03251     return;
03252 
03253   // Compute the bug report's hash to determine its equivalence class.
03254   llvm::FoldingSetNodeID ID;
03255   R->Profile(ID);
03256 
03257   // Lookup the equivance class.  If there isn't one, create it.
03258   BugType& BT = R->getBugType();
03259   Register(&BT);
03260   void *InsertPos;
03261   BugReportEquivClass* EQ = EQClasses.FindNodeOrInsertPos(ID, InsertPos);
03262 
03263   if (!EQ) {
03264     EQ = new BugReportEquivClass(std::move(UniqueR));
03265     EQClasses.InsertNode(EQ, InsertPos);
03266     EQClassesVector.push_back(EQ);
03267   } else
03268     EQ->AddReport(std::move(UniqueR));
03269 }
03270 
03271 
03272 //===----------------------------------------------------------------------===//
03273 // Emitting reports in equivalence classes.
03274 //===----------------------------------------------------------------------===//
03275 
03276 namespace {
03277 struct FRIEC_WLItem {
03278   const ExplodedNode *N;
03279   ExplodedNode::const_succ_iterator I, E;
03280   
03281   FRIEC_WLItem(const ExplodedNode *n)
03282   : N(n), I(N->succ_begin()), E(N->succ_end()) {}
03283 };  
03284 }
03285 
03286 static BugReport *
03287 FindReportInEquivalenceClass(BugReportEquivClass& EQ,
03288                              SmallVectorImpl<BugReport*> &bugReports) {
03289 
03290   BugReportEquivClass::iterator I = EQ.begin(), E = EQ.end();
03291   assert(I != E);
03292   BugType& BT = I->getBugType();
03293 
03294   // If we don't need to suppress any of the nodes because they are
03295   // post-dominated by a sink, simply add all the nodes in the equivalence class
03296   // to 'Nodes'.  Any of the reports will serve as a "representative" report.
03297   if (!BT.isSuppressOnSink()) {
03298     BugReport *R = I;
03299     for (BugReportEquivClass::iterator I=EQ.begin(), E=EQ.end(); I!=E; ++I) {
03300       const ExplodedNode *N = I->getErrorNode();
03301       if (N) {
03302         R = I;
03303         bugReports.push_back(R);
03304       }
03305     }
03306     return R;
03307   }
03308 
03309   // For bug reports that should be suppressed when all paths are post-dominated
03310   // by a sink node, iterate through the reports in the equivalence class
03311   // until we find one that isn't post-dominated (if one exists).  We use a
03312   // DFS traversal of the ExplodedGraph to find a non-sink node.  We could write
03313   // this as a recursive function, but we don't want to risk blowing out the
03314   // stack for very long paths.
03315   BugReport *exampleReport = nullptr;
03316 
03317   for (; I != E; ++I) {
03318     const ExplodedNode *errorNode = I->getErrorNode();
03319 
03320     if (!errorNode)
03321       continue;
03322     if (errorNode->isSink()) {
03323       llvm_unreachable(
03324            "BugType::isSuppressSink() should not be 'true' for sink end nodes");
03325     }
03326     // No successors?  By definition this nodes isn't post-dominated by a sink.
03327     if (errorNode->succ_empty()) {
03328       bugReports.push_back(I);
03329       if (!exampleReport)
03330         exampleReport = I;
03331       continue;
03332     }
03333 
03334     // At this point we know that 'N' is not a sink and it has at least one
03335     // successor.  Use a DFS worklist to find a non-sink end-of-path node.    
03336     typedef FRIEC_WLItem WLItem;
03337     typedef SmallVector<WLItem, 10> DFSWorkList;
03338     llvm::DenseMap<const ExplodedNode *, unsigned> Visited;
03339     
03340     DFSWorkList WL;
03341     WL.push_back(errorNode);
03342     Visited[errorNode] = 1;
03343     
03344     while (!WL.empty()) {
03345       WLItem &WI = WL.back();
03346       assert(!WI.N->succ_empty());
03347             
03348       for (; WI.I != WI.E; ++WI.I) {
03349         const ExplodedNode *Succ = *WI.I;        
03350         // End-of-path node?
03351         if (Succ->succ_empty()) {
03352           // If we found an end-of-path node that is not a sink.
03353           if (!Succ->isSink()) {
03354             bugReports.push_back(I);
03355             if (!exampleReport)
03356               exampleReport = I;
03357             WL.clear();
03358             break;
03359           }
03360           // Found a sink?  Continue on to the next successor.
03361           continue;
03362         }
03363         // Mark the successor as visited.  If it hasn't been explored,
03364         // enqueue it to the DFS worklist.
03365         unsigned &mark = Visited[Succ];
03366         if (!mark) {
03367           mark = 1;
03368           WL.push_back(Succ);
03369           break;
03370         }
03371       }
03372 
03373       // The worklist may have been cleared at this point.  First
03374       // check if it is empty before checking the last item.
03375       if (!WL.empty() && &WL.back() == &WI)
03376         WL.pop_back();
03377     }
03378   }
03379 
03380   // ExampleReport will be NULL if all the nodes in the equivalence class
03381   // were post-dominated by sinks.
03382   return exampleReport;
03383 }
03384 
03385 void BugReporter::FlushReport(BugReportEquivClass& EQ) {
03386   SmallVector<BugReport*, 10> bugReports;
03387   BugReport *exampleReport = FindReportInEquivalenceClass(EQ, bugReports);
03388   if (exampleReport) {
03389     for (PathDiagnosticConsumer *PDC : getPathDiagnosticConsumers()) {
03390       FlushReport(exampleReport, *PDC, bugReports);
03391     }
03392   }
03393 }
03394 
03395 void BugReporter::FlushReport(BugReport *exampleReport,
03396                               PathDiagnosticConsumer &PD,
03397                               ArrayRef<BugReport*> bugReports) {
03398 
03399   // FIXME: Make sure we use the 'R' for the path that was actually used.
03400   // Probably doesn't make a difference in practice.
03401   BugType& BT = exampleReport->getBugType();
03402 
03403   std::unique_ptr<PathDiagnostic> D(new PathDiagnostic(
03404       exampleReport->getBugType().getCheckName(),
03405       exampleReport->getDeclWithIssue(), exampleReport->getBugType().getName(),
03406       exampleReport->getDescription(),
03407       exampleReport->getShortDescription(/*Fallback=*/false), BT.getCategory(),
03408       exampleReport->getUniqueingLocation(),
03409       exampleReport->getUniqueingDecl()));
03410 
03411   MaxBugClassSize = std::max(bugReports.size(),
03412                              static_cast<size_t>(MaxBugClassSize));
03413 
03414   // Generate the full path diagnostic, using the generation scheme
03415   // specified by the PathDiagnosticConsumer. Note that we have to generate
03416   // path diagnostics even for consumers which do not support paths, because
03417   // the BugReporterVisitors may mark this bug as a false positive.
03418   if (!bugReports.empty())
03419     if (!generatePathDiagnostic(*D.get(), PD, bugReports))
03420       return;
03421 
03422   MaxValidBugClassSize = std::max(bugReports.size(),
03423                                   static_cast<size_t>(MaxValidBugClassSize));
03424 
03425   // Examine the report and see if the last piece is in a header. Reset the
03426   // report location to the last piece in the main source file.
03427   AnalyzerOptions& Opts = getAnalyzerOptions();
03428   if (Opts.shouldReportIssuesInMainSourceFile() && !Opts.AnalyzeAll)
03429     D->resetDiagnosticLocationToMainFile();
03430 
03431   // If the path is empty, generate a single step path with the location
03432   // of the issue.
03433   if (D->path.empty()) {
03434     PathDiagnosticLocation L = exampleReport->getLocation(getSourceManager());
03435     auto piece = llvm::make_unique<PathDiagnosticEventPiece>(
03436         L, exampleReport->getDescription());
03437     BugReport::ranges_iterator Beg, End;
03438     std::tie(Beg, End) = exampleReport->getRanges();
03439     for ( ; Beg != End; ++Beg)
03440       piece->addRange(*Beg);
03441     D->setEndOfPath(std::move(piece));
03442   }
03443 
03444   // Get the meta data.
03445   const BugReport::ExtraTextList &Meta = exampleReport->getExtraText();
03446   for (BugReport::ExtraTextList::const_iterator i = Meta.begin(),
03447                                                 e = Meta.end(); i != e; ++i) {
03448     D->addMeta(*i);
03449   }
03450 
03451   PD.HandlePathDiagnostic(std::move(D));
03452 }
03453 
03454 void BugReporter::EmitBasicReport(const Decl *DeclWithIssue,
03455                                   const CheckerBase *Checker,
03456                                   StringRef Name, StringRef Category,
03457                                   StringRef Str, PathDiagnosticLocation Loc,
03458                                   ArrayRef<SourceRange> Ranges) {
03459   EmitBasicReport(DeclWithIssue, Checker->getCheckName(), Name, Category, Str,
03460                   Loc, Ranges);
03461 }
03462 void BugReporter::EmitBasicReport(const Decl *DeclWithIssue,
03463                                   CheckName CheckName,
03464                                   StringRef name, StringRef category,
03465                                   StringRef str, PathDiagnosticLocation Loc,
03466                                   ArrayRef<SourceRange> Ranges) {
03467 
03468   // 'BT' is owned by BugReporter.
03469   BugType *BT = getBugTypeForName(CheckName, name, category);
03470   BugReport *R = new BugReport(*BT, str, Loc);
03471   R->setDeclWithIssue(DeclWithIssue);
03472   for (ArrayRef<SourceRange>::iterator I = Ranges.begin(), E = Ranges.end();
03473        I != E; ++I)
03474     R->addRange(*I);
03475   emitReport(R);
03476 }
03477 
03478 BugType *BugReporter::getBugTypeForName(CheckName CheckName, StringRef name,
03479                                         StringRef category) {
03480   SmallString<136> fullDesc;
03481   llvm::raw_svector_ostream(fullDesc) << CheckName.getName() << ":" << name
03482                                       << ":" << category;
03483   BugType *&BT = StrBugTypes[fullDesc];
03484   if (!BT)
03485     BT = new BugType(CheckName, name, category);
03486   return BT;
03487 }
03488 
03489 LLVM_DUMP_METHOD void PathPieces::dump() const {
03490   unsigned index = 0;
03491   for (PathPieces::const_iterator I = begin(), E = end(); I != E; ++I) {
03492     llvm::errs() << "[" << index++ << "]  ";
03493     (*I)->dump();
03494     llvm::errs() << "\n";
03495   }
03496 }
03497 
03498 void PathDiagnosticCallPiece::dump() const {
03499   llvm::errs() << "CALL\n--------------\n";
03500 
03501   if (const Stmt *SLoc = getLocStmt(getLocation()))
03502     SLoc->dump();
03503   else if (const NamedDecl *ND = dyn_cast<NamedDecl>(getCallee()))
03504     llvm::errs() << *ND << "\n";
03505   else
03506     getLocation().dump();
03507 }
03508 
03509 void PathDiagnosticEventPiece::dump() const {
03510   llvm::errs() << "EVENT\n--------------\n";
03511   llvm::errs() << getString() << "\n";
03512   llvm::errs() << " ---- at ----\n";
03513   getLocation().dump();
03514 }
03515 
03516 void PathDiagnosticControlFlowPiece::dump() const {
03517   llvm::errs() << "CONTROL\n--------------\n";
03518   getStartLocation().dump();
03519   llvm::errs() << " ---- to ----\n";
03520   getEndLocation().dump();
03521 }
03522 
03523 void PathDiagnosticMacroPiece::dump() const {
03524   llvm::errs() << "MACRO\n--------------\n";
03525   // FIXME: Print which macro is being invoked.
03526 }
03527 
03528 void PathDiagnosticLocation::dump() const {
03529   if (!isValid()) {
03530     llvm::errs() << "<INVALID>\n";
03531     return;
03532   }
03533 
03534   switch (K) {
03535   case RangeK:
03536     // FIXME: actually print the range.
03537     llvm::errs() << "<range>\n";
03538     break;
03539   case SingleLocK:
03540     asLocation().dump();
03541     llvm::errs() << "\n";
03542     break;
03543   case StmtK:
03544     if (S)
03545       S->dump();
03546     else
03547       llvm::errs() << "<NULL STMT>\n";
03548     break;
03549   case DeclK:
03550     if (const NamedDecl *ND = dyn_cast_or_null<NamedDecl>(D))
03551       llvm::errs() << *ND << "\n";
03552     else if (isa<BlockDecl>(D))
03553       // FIXME: Make this nicer.
03554       llvm::errs() << "<block>\n";
03555     else if (D)
03556       llvm::errs() << "<unknown decl>\n";
03557     else
03558       llvm::errs() << "<NULL DECL>\n";
03559     break;
03560   }
03561 }