1// BugReporterVisitors.cpp - Helpers for reporting bugs -----------*- C++ -*--//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10//  This file defines a set of BugReporter "visitors" which can be used to
11//  enhance the diagnostics reported for a bug.
12//
13//===----------------------------------------------------------------------===//
14#include "clang/StaticAnalyzer/Core/BugReporter/BugReporterVisitor.h"
15#include "clang/AST/Expr.h"
16#include "clang/AST/ExprObjC.h"
17#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
18#include "clang/StaticAnalyzer/Core/BugReporter/PathDiagnostic.h"
19#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
20#include "clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h"
21#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
22#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
23#include "llvm/ADT/SmallString.h"
24#include "llvm/ADT/StringExtras.h"
25#include "llvm/Support/raw_ostream.h"
26
27using namespace clang;
28using namespace ento;
29
30using llvm::FoldingSetNodeID;
31
32//===----------------------------------------------------------------------===//
33// Utility functions.
34//===----------------------------------------------------------------------===//
35
36bool bugreporter::isDeclRefExprToReference(const Expr *E) {
37  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
38    return DRE->getDecl()->getType()->isReferenceType();
39  }
40  return false;
41}
42
43const Expr *bugreporter::getDerefExpr(const Stmt *S) {
44  // Pattern match for a few useful cases:
45  //   a[0], p->f, *p
46  const Expr *E = dyn_cast<Expr>(S);
47  if (!E)
48    return nullptr;
49  E = E->IgnoreParenCasts();
50
51  while (true) {
52    if (const BinaryOperator *B = dyn_cast<BinaryOperator>(E)) {
53      assert(B->isAssignmentOp());
54      E = B->getLHS()->IgnoreParenCasts();
55      continue;
56    }
57    else if (const UnaryOperator *U = dyn_cast<UnaryOperator>(E)) {
58      if (U->getOpcode() == UO_Deref)
59        return U->getSubExpr()->IgnoreParenCasts();
60    }
61    else if (const MemberExpr *ME = dyn_cast<MemberExpr>(E)) {
62      if (ME->isArrow() || isDeclRefExprToReference(ME->getBase())) {
63        return ME->getBase()->IgnoreParenCasts();
64      } else {
65        // If we have a member expr with a dot, the base must have been
66        // dereferenced.
67        return getDerefExpr(ME->getBase());
68      }
69    }
70    else if (const ObjCIvarRefExpr *IvarRef = dyn_cast<ObjCIvarRefExpr>(E)) {
71      return IvarRef->getBase()->IgnoreParenCasts();
72    }
73    else if (const ArraySubscriptExpr *AE = dyn_cast<ArraySubscriptExpr>(E)) {
74      return AE->getBase();
75    }
76    else if (isDeclRefExprToReference(E)) {
77      return E;
78    }
79    break;
80  }
81
82  return nullptr;
83}
84
85const Stmt *bugreporter::GetDenomExpr(const ExplodedNode *N) {
86  const Stmt *S = N->getLocationAs<PreStmt>()->getStmt();
87  if (const BinaryOperator *BE = dyn_cast<BinaryOperator>(S))
88    return BE->getRHS();
89  return nullptr;
90}
91
92const Stmt *bugreporter::GetRetValExpr(const ExplodedNode *N) {
93  const Stmt *S = N->getLocationAs<PostStmt>()->getStmt();
94  if (const ReturnStmt *RS = dyn_cast<ReturnStmt>(S))
95    return RS->getRetValue();
96  return nullptr;
97}
98
99//===----------------------------------------------------------------------===//
100// Definitions for bug reporter visitors.
101//===----------------------------------------------------------------------===//
102
103std::unique_ptr<PathDiagnosticPiece>
104BugReporterVisitor::getEndPath(BugReporterContext &BRC,
105                               const ExplodedNode *EndPathNode, BugReport &BR) {
106  return nullptr;
107}
108
109std::unique_ptr<PathDiagnosticPiece> BugReporterVisitor::getDefaultEndPath(
110    BugReporterContext &BRC, const ExplodedNode *EndPathNode, BugReport &BR) {
111  PathDiagnosticLocation L =
112    PathDiagnosticLocation::createEndOfPath(EndPathNode,BRC.getSourceManager());
113
114  const auto &Ranges = BR.getRanges();
115
116  // Only add the statement itself as a range if we didn't specify any
117  // special ranges for this report.
118  auto P = llvm::make_unique<PathDiagnosticEventPiece>(
119      L, BR.getDescription(), Ranges.begin() == Ranges.end());
120  for (SourceRange Range : Ranges)
121    P->addRange(Range);
122
123  return std::move(P);
124}
125
126
127namespace {
128/// Emits an extra note at the return statement of an interesting stack frame.
129///
130/// The returned value is marked as an interesting value, and if it's null,
131/// adds a visitor to track where it became null.
132///
133/// This visitor is intended to be used when another visitor discovers that an
134/// interesting value comes from an inlined function call.
135class ReturnVisitor : public BugReporterVisitorImpl<ReturnVisitor> {
136  const StackFrameContext *StackFrame;
137  enum {
138    Initial,
139    MaybeUnsuppress,
140    Satisfied
141  } Mode;
142
143  bool EnableNullFPSuppression;
144
145public:
146  ReturnVisitor(const StackFrameContext *Frame, bool Suppressed)
147    : StackFrame(Frame), Mode(Initial), EnableNullFPSuppression(Suppressed) {}
148
149  static void *getTag() {
150    static int Tag = 0;
151    return static_cast<void *>(&Tag);
152  }
153
154  void Profile(llvm::FoldingSetNodeID &ID) const override {
155    ID.AddPointer(ReturnVisitor::getTag());
156    ID.AddPointer(StackFrame);
157    ID.AddBoolean(EnableNullFPSuppression);
158  }
159
160  /// Adds a ReturnVisitor if the given statement represents a call that was
161  /// inlined.
162  ///
163  /// This will search back through the ExplodedGraph, starting from the given
164  /// node, looking for when the given statement was processed. If it turns out
165  /// the statement is a call that was inlined, we add the visitor to the
166  /// bug report, so it can print a note later.
167  static void addVisitorIfNecessary(const ExplodedNode *Node, const Stmt *S,
168                                    BugReport &BR,
169                                    bool InEnableNullFPSuppression) {
170    if (!CallEvent::isCallStmt(S))
171      return;
172
173    // First, find when we processed the statement.
174    do {
175      if (Optional<CallExitEnd> CEE = Node->getLocationAs<CallExitEnd>())
176        if (CEE->getCalleeContext()->getCallSite() == S)
177          break;
178      if (Optional<StmtPoint> SP = Node->getLocationAs<StmtPoint>())
179        if (SP->getStmt() == S)
180          break;
181
182      Node = Node->getFirstPred();
183    } while (Node);
184
185    // Next, step over any post-statement checks.
186    while (Node && Node->getLocation().getAs<PostStmt>())
187      Node = Node->getFirstPred();
188    if (!Node)
189      return;
190
191    // Finally, see if we inlined the call.
192    Optional<CallExitEnd> CEE = Node->getLocationAs<CallExitEnd>();
193    if (!CEE)
194      return;
195
196    const StackFrameContext *CalleeContext = CEE->getCalleeContext();
197    if (CalleeContext->getCallSite() != S)
198      return;
199
200    // Check the return value.
201    ProgramStateRef State = Node->getState();
202    SVal RetVal = State->getSVal(S, Node->getLocationContext());
203
204    // Handle cases where a reference is returned and then immediately used.
205    if (cast<Expr>(S)->isGLValue())
206      if (Optional<Loc> LValue = RetVal.getAs<Loc>())
207        RetVal = State->getSVal(*LValue);
208
209    // See if the return value is NULL. If so, suppress the report.
210    SubEngine *Eng = State->getStateManager().getOwningEngine();
211    assert(Eng && "Cannot file a bug report without an owning engine");
212    AnalyzerOptions &Options = Eng->getAnalysisManager().options;
213
214    bool EnableNullFPSuppression = false;
215    if (InEnableNullFPSuppression && Options.shouldSuppressNullReturnPaths())
216      if (Optional<Loc> RetLoc = RetVal.getAs<Loc>())
217        EnableNullFPSuppression = State->isNull(*RetLoc).isConstrainedTrue();
218
219    BR.markInteresting(CalleeContext);
220    BR.addVisitor(llvm::make_unique<ReturnVisitor>(CalleeContext,
221                                                   EnableNullFPSuppression));
222  }
223
224  /// Returns true if any counter-suppression heuristics are enabled for
225  /// ReturnVisitor.
226  static bool hasCounterSuppression(AnalyzerOptions &Options) {
227    return Options.shouldAvoidSuppressingNullArgumentPaths();
228  }
229
230  PathDiagnosticPiece *visitNodeInitial(const ExplodedNode *N,
231                                        const ExplodedNode *PrevN,
232                                        BugReporterContext &BRC,
233                                        BugReport &BR) {
234    // Only print a message at the interesting return statement.
235    if (N->getLocationContext() != StackFrame)
236      return nullptr;
237
238    Optional<StmtPoint> SP = N->getLocationAs<StmtPoint>();
239    if (!SP)
240      return nullptr;
241
242    const ReturnStmt *Ret = dyn_cast<ReturnStmt>(SP->getStmt());
243    if (!Ret)
244      return nullptr;
245
246    // Okay, we're at the right return statement, but do we have the return
247    // value available?
248    ProgramStateRef State = N->getState();
249    SVal V = State->getSVal(Ret, StackFrame);
250    if (V.isUnknownOrUndef())
251      return nullptr;
252
253    // Don't print any more notes after this one.
254    Mode = Satisfied;
255
256    const Expr *RetE = Ret->getRetValue();
257    assert(RetE && "Tracking a return value for a void function");
258
259    // Handle cases where a reference is returned and then immediately used.
260    Optional<Loc> LValue;
261    if (RetE->isGLValue()) {
262      if ((LValue = V.getAs<Loc>())) {
263        SVal RValue = State->getRawSVal(*LValue, RetE->getType());
264        if (RValue.getAs<DefinedSVal>())
265          V = RValue;
266      }
267    }
268
269    // Ignore aggregate rvalues.
270    if (V.getAs<nonloc::LazyCompoundVal>() ||
271        V.getAs<nonloc::CompoundVal>())
272      return nullptr;
273
274    RetE = RetE->IgnoreParenCasts();
275
276    // If we can't prove the return value is 0, just mark it interesting, and
277    // make sure to track it into any further inner functions.
278    if (!State->isNull(V).isConstrainedTrue()) {
279      BR.markInteresting(V);
280      ReturnVisitor::addVisitorIfNecessary(N, RetE, BR,
281                                           EnableNullFPSuppression);
282      return nullptr;
283    }
284
285    // If we're returning 0, we should track where that 0 came from.
286    bugreporter::trackNullOrUndefValue(N, RetE, BR, /*IsArg*/ false,
287                                       EnableNullFPSuppression);
288
289    // Build an appropriate message based on the return value.
290    SmallString<64> Msg;
291    llvm::raw_svector_ostream Out(Msg);
292
293    if (V.getAs<Loc>()) {
294      // If we have counter-suppression enabled, make sure we keep visiting
295      // future nodes. We want to emit a path note as well, in case
296      // the report is resurrected as valid later on.
297      ExprEngine &Eng = BRC.getBugReporter().getEngine();
298      AnalyzerOptions &Options = Eng.getAnalysisManager().options;
299      if (EnableNullFPSuppression && hasCounterSuppression(Options))
300        Mode = MaybeUnsuppress;
301
302      if (RetE->getType()->isObjCObjectPointerType())
303        Out << "Returning nil";
304      else
305        Out << "Returning null pointer";
306    } else {
307      Out << "Returning zero";
308    }
309
310    if (LValue) {
311      if (const MemRegion *MR = LValue->getAsRegion()) {
312        if (MR->canPrintPretty()) {
313          Out << " (reference to ";
314          MR->printPretty(Out);
315          Out << ")";
316        }
317      }
318    } else {
319      // FIXME: We should have a more generalized location printing mechanism.
320      if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(RetE))
321        if (const DeclaratorDecl *DD = dyn_cast<DeclaratorDecl>(DR->getDecl()))
322          Out << " (loaded from '" << *DD << "')";
323    }
324
325    PathDiagnosticLocation L(Ret, BRC.getSourceManager(), StackFrame);
326    return new PathDiagnosticEventPiece(L, Out.str());
327  }
328
329  PathDiagnosticPiece *visitNodeMaybeUnsuppress(const ExplodedNode *N,
330                                                const ExplodedNode *PrevN,
331                                                BugReporterContext &BRC,
332                                                BugReport &BR) {
333#ifndef NDEBUG
334    ExprEngine &Eng = BRC.getBugReporter().getEngine();
335    AnalyzerOptions &Options = Eng.getAnalysisManager().options;
336    assert(hasCounterSuppression(Options));
337#endif
338
339    // Are we at the entry node for this call?
340    Optional<CallEnter> CE = N->getLocationAs<CallEnter>();
341    if (!CE)
342      return nullptr;
343
344    if (CE->getCalleeContext() != StackFrame)
345      return nullptr;
346
347    Mode = Satisfied;
348
349    // Don't automatically suppress a report if one of the arguments is
350    // known to be a null pointer. Instead, start tracking /that/ null
351    // value back to its origin.
352    ProgramStateManager &StateMgr = BRC.getStateManager();
353    CallEventManager &CallMgr = StateMgr.getCallEventManager();
354
355    ProgramStateRef State = N->getState();
356    CallEventRef<> Call = CallMgr.getCaller(StackFrame, State);
357    for (unsigned I = 0, E = Call->getNumArgs(); I != E; ++I) {
358      Optional<Loc> ArgV = Call->getArgSVal(I).getAs<Loc>();
359      if (!ArgV)
360        continue;
361
362      const Expr *ArgE = Call->getArgExpr(I);
363      if (!ArgE)
364        continue;
365
366      // Is it possible for this argument to be non-null?
367      if (!State->isNull(*ArgV).isConstrainedTrue())
368        continue;
369
370      if (bugreporter::trackNullOrUndefValue(N, ArgE, BR, /*IsArg=*/true,
371                                             EnableNullFPSuppression))
372        BR.removeInvalidation(ReturnVisitor::getTag(), StackFrame);
373
374      // If we /can't/ track the null pointer, we should err on the side of
375      // false negatives, and continue towards marking this report invalid.
376      // (We will still look at the other arguments, though.)
377    }
378
379    return nullptr;
380  }
381
382  PathDiagnosticPiece *VisitNode(const ExplodedNode *N,
383                                 const ExplodedNode *PrevN,
384                                 BugReporterContext &BRC,
385                                 BugReport &BR) override {
386    switch (Mode) {
387    case Initial:
388      return visitNodeInitial(N, PrevN, BRC, BR);
389    case MaybeUnsuppress:
390      return visitNodeMaybeUnsuppress(N, PrevN, BRC, BR);
391    case Satisfied:
392      return nullptr;
393    }
394
395    llvm_unreachable("Invalid visit mode!");
396  }
397
398  std::unique_ptr<PathDiagnosticPiece> getEndPath(BugReporterContext &BRC,
399                                                  const ExplodedNode *N,
400                                                  BugReport &BR) override {
401    if (EnableNullFPSuppression)
402      BR.markInvalid(ReturnVisitor::getTag(), StackFrame);
403    return nullptr;
404  }
405};
406} // end anonymous namespace
407
408
409void FindLastStoreBRVisitor ::Profile(llvm::FoldingSetNodeID &ID) const {
410  static int tag = 0;
411  ID.AddPointer(&tag);
412  ID.AddPointer(R);
413  ID.Add(V);
414  ID.AddBoolean(EnableNullFPSuppression);
415}
416
417/// Returns true if \p N represents the DeclStmt declaring and initializing
418/// \p VR.
419static bool isInitializationOfVar(const ExplodedNode *N, const VarRegion *VR) {
420  Optional<PostStmt> P = N->getLocationAs<PostStmt>();
421  if (!P)
422    return false;
423
424  const DeclStmt *DS = P->getStmtAs<DeclStmt>();
425  if (!DS)
426    return false;
427
428  if (DS->getSingleDecl() != VR->getDecl())
429    return false;
430
431  const MemSpaceRegion *VarSpace = VR->getMemorySpace();
432  const StackSpaceRegion *FrameSpace = dyn_cast<StackSpaceRegion>(VarSpace);
433  if (!FrameSpace) {
434    // If we ever directly evaluate global DeclStmts, this assertion will be
435    // invalid, but this still seems preferable to silently accepting an
436    // initialization that may be for a path-sensitive variable.
437    assert(VR->getDecl()->isStaticLocal() && "non-static stackless VarRegion");
438    return true;
439  }
440
441  assert(VR->getDecl()->hasLocalStorage());
442  const LocationContext *LCtx = N->getLocationContext();
443  return FrameSpace->getStackFrame() == LCtx->getCurrentStackFrame();
444}
445
446PathDiagnosticPiece *FindLastStoreBRVisitor::VisitNode(const ExplodedNode *Succ,
447                                                       const ExplodedNode *Pred,
448                                                       BugReporterContext &BRC,
449                                                       BugReport &BR) {
450
451  if (Satisfied)
452    return nullptr;
453
454  const ExplodedNode *StoreSite = nullptr;
455  const Expr *InitE = nullptr;
456  bool IsParam = false;
457
458  // First see if we reached the declaration of the region.
459  if (const VarRegion *VR = dyn_cast<VarRegion>(R)) {
460    if (isInitializationOfVar(Pred, VR)) {
461      StoreSite = Pred;
462      InitE = VR->getDecl()->getInit();
463    }
464  }
465
466  // If this is a post initializer expression, initializing the region, we
467  // should track the initializer expression.
468  if (Optional<PostInitializer> PIP = Pred->getLocationAs<PostInitializer>()) {
469    const MemRegion *FieldReg = (const MemRegion *)PIP->getLocationValue();
470    if (FieldReg && FieldReg == R) {
471      StoreSite = Pred;
472      InitE = PIP->getInitializer()->getInit();
473    }
474  }
475
476  // Otherwise, see if this is the store site:
477  // (1) Succ has this binding and Pred does not, i.e. this is
478  //     where the binding first occurred.
479  // (2) Succ has this binding and is a PostStore node for this region, i.e.
480  //     the same binding was re-assigned here.
481  if (!StoreSite) {
482    if (Succ->getState()->getSVal(R) != V)
483      return nullptr;
484
485    if (Pred->getState()->getSVal(R) == V) {
486      Optional<PostStore> PS = Succ->getLocationAs<PostStore>();
487      if (!PS || PS->getLocationValue() != R)
488        return nullptr;
489    }
490
491    StoreSite = Succ;
492
493    // If this is an assignment expression, we can track the value
494    // being assigned.
495    if (Optional<PostStmt> P = Succ->getLocationAs<PostStmt>())
496      if (const BinaryOperator *BO = P->getStmtAs<BinaryOperator>())
497        if (BO->isAssignmentOp())
498          InitE = BO->getRHS();
499
500    // If this is a call entry, the variable should be a parameter.
501    // FIXME: Handle CXXThisRegion as well. (This is not a priority because
502    // 'this' should never be NULL, but this visitor isn't just for NULL and
503    // UndefinedVal.)
504    if (Optional<CallEnter> CE = Succ->getLocationAs<CallEnter>()) {
505      if (const VarRegion *VR = dyn_cast<VarRegion>(R)) {
506        const ParmVarDecl *Param = cast<ParmVarDecl>(VR->getDecl());
507
508        ProgramStateManager &StateMgr = BRC.getStateManager();
509        CallEventManager &CallMgr = StateMgr.getCallEventManager();
510
511        CallEventRef<> Call = CallMgr.getCaller(CE->getCalleeContext(),
512                                                Succ->getState());
513        InitE = Call->getArgExpr(Param->getFunctionScopeIndex());
514        IsParam = true;
515      }
516    }
517
518    // If this is a CXXTempObjectRegion, the Expr responsible for its creation
519    // is wrapped inside of it.
520    if (const CXXTempObjectRegion *TmpR = dyn_cast<CXXTempObjectRegion>(R))
521      InitE = TmpR->getExpr();
522  }
523
524  if (!StoreSite)
525    return nullptr;
526  Satisfied = true;
527
528  // If we have an expression that provided the value, try to track where it
529  // came from.
530  if (InitE) {
531    if (V.isUndef() ||
532        V.getAs<loc::ConcreteInt>() || V.getAs<nonloc::ConcreteInt>()) {
533      if (!IsParam)
534        InitE = InitE->IgnoreParenCasts();
535      bugreporter::trackNullOrUndefValue(StoreSite, InitE, BR, IsParam,
536                                         EnableNullFPSuppression);
537    } else {
538      ReturnVisitor::addVisitorIfNecessary(StoreSite, InitE->IgnoreParenCasts(),
539                                           BR, EnableNullFPSuppression);
540    }
541  }
542
543  // Okay, we've found the binding. Emit an appropriate message.
544  SmallString<256> sbuf;
545  llvm::raw_svector_ostream os(sbuf);
546
547  if (Optional<PostStmt> PS = StoreSite->getLocationAs<PostStmt>()) {
548    const Stmt *S = PS->getStmt();
549    const char *action = nullptr;
550    const DeclStmt *DS = dyn_cast<DeclStmt>(S);
551    const VarRegion *VR = dyn_cast<VarRegion>(R);
552
553    if (DS) {
554      action = R->canPrintPretty() ? "initialized to " :
555                                     "Initializing to ";
556    } else if (isa<BlockExpr>(S)) {
557      action = R->canPrintPretty() ? "captured by block as " :
558                                     "Captured by block as ";
559      if (VR) {
560        // See if we can get the BlockVarRegion.
561        ProgramStateRef State = StoreSite->getState();
562        SVal V = State->getSVal(S, PS->getLocationContext());
563        if (const BlockDataRegion *BDR =
564              dyn_cast_or_null<BlockDataRegion>(V.getAsRegion())) {
565          if (const VarRegion *OriginalR = BDR->getOriginalRegion(VR)) {
566            if (Optional<KnownSVal> KV =
567                State->getSVal(OriginalR).getAs<KnownSVal>())
568              BR.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
569                  *KV, OriginalR, EnableNullFPSuppression));
570          }
571        }
572      }
573    }
574
575    if (action) {
576      if (R->canPrintPretty()) {
577        R->printPretty(os);
578        os << " ";
579      }
580
581      if (V.getAs<loc::ConcreteInt>()) {
582        bool b = false;
583        if (R->isBoundable()) {
584          if (const TypedValueRegion *TR = dyn_cast<TypedValueRegion>(R)) {
585            if (TR->getValueType()->isObjCObjectPointerType()) {
586              os << action << "nil";
587              b = true;
588            }
589          }
590        }
591
592        if (!b)
593          os << action << "a null pointer value";
594      } else if (Optional<nonloc::ConcreteInt> CVal =
595                     V.getAs<nonloc::ConcreteInt>()) {
596        os << action << CVal->getValue();
597      }
598      else if (DS) {
599        if (V.isUndef()) {
600          if (isa<VarRegion>(R)) {
601            const VarDecl *VD = cast<VarDecl>(DS->getSingleDecl());
602            if (VD->getInit()) {
603              os << (R->canPrintPretty() ? "initialized" : "Initializing")
604                 << " to a garbage value";
605            } else {
606              os << (R->canPrintPretty() ? "declared" : "Declaring")
607                 << " without an initial value";
608            }
609          }
610        }
611        else {
612          os << (R->canPrintPretty() ? "initialized" : "Initialized")
613             << " here";
614        }
615      }
616    }
617  } else if (StoreSite->getLocation().getAs<CallEnter>()) {
618    if (const VarRegion *VR = dyn_cast<VarRegion>(R)) {
619      const ParmVarDecl *Param = cast<ParmVarDecl>(VR->getDecl());
620
621      os << "Passing ";
622
623      if (V.getAs<loc::ConcreteInt>()) {
624        if (Param->getType()->isObjCObjectPointerType())
625          os << "nil object reference";
626        else
627          os << "null pointer value";
628      } else if (V.isUndef()) {
629        os << "uninitialized value";
630      } else if (Optional<nonloc::ConcreteInt> CI =
631                     V.getAs<nonloc::ConcreteInt>()) {
632        os << "the value " << CI->getValue();
633      } else {
634        os << "value";
635      }
636
637      // Printed parameter indexes are 1-based, not 0-based.
638      unsigned Idx = Param->getFunctionScopeIndex() + 1;
639      os << " via " << Idx << llvm::getOrdinalSuffix(Idx) << " parameter";
640      if (R->canPrintPretty()) {
641        os << " ";
642        R->printPretty(os);
643      }
644    }
645  }
646
647  if (os.str().empty()) {
648    if (V.getAs<loc::ConcreteInt>()) {
649      bool b = false;
650      if (R->isBoundable()) {
651        if (const TypedValueRegion *TR = dyn_cast<TypedValueRegion>(R)) {
652          if (TR->getValueType()->isObjCObjectPointerType()) {
653            os << "nil object reference stored";
654            b = true;
655          }
656        }
657      }
658      if (!b) {
659        if (R->canPrintPretty())
660          os << "Null pointer value stored";
661        else
662          os << "Storing null pointer value";
663      }
664
665    } else if (V.isUndef()) {
666      if (R->canPrintPretty())
667        os << "Uninitialized value stored";
668      else
669        os << "Storing uninitialized value";
670
671    } else if (Optional<nonloc::ConcreteInt> CV =
672                   V.getAs<nonloc::ConcreteInt>()) {
673      if (R->canPrintPretty())
674        os << "The value " << CV->getValue() << " is assigned";
675      else
676        os << "Assigning " << CV->getValue();
677
678    } else {
679      if (R->canPrintPretty())
680        os << "Value assigned";
681      else
682        os << "Assigning value";
683    }
684
685    if (R->canPrintPretty()) {
686      os << " to ";
687      R->printPretty(os);
688    }
689  }
690
691  // Construct a new PathDiagnosticPiece.
692  ProgramPoint P = StoreSite->getLocation();
693  PathDiagnosticLocation L;
694  if (P.getAs<CallEnter>() && InitE)
695    L = PathDiagnosticLocation(InitE, BRC.getSourceManager(),
696                               P.getLocationContext());
697
698  if (!L.isValid() || !L.asLocation().isValid())
699    L = PathDiagnosticLocation::create(P, BRC.getSourceManager());
700
701  if (!L.isValid() || !L.asLocation().isValid())
702    return nullptr;
703
704  return new PathDiagnosticEventPiece(L, os.str());
705}
706
707void TrackConstraintBRVisitor::Profile(llvm::FoldingSetNodeID &ID) const {
708  static int tag = 0;
709  ID.AddPointer(&tag);
710  ID.AddBoolean(Assumption);
711  ID.Add(Constraint);
712}
713
714/// Return the tag associated with this visitor.  This tag will be used
715/// to make all PathDiagnosticPieces created by this visitor.
716const char *TrackConstraintBRVisitor::getTag() {
717  return "TrackConstraintBRVisitor";
718}
719
720bool TrackConstraintBRVisitor::isUnderconstrained(const ExplodedNode *N) const {
721  if (IsZeroCheck)
722    return N->getState()->isNull(Constraint).isUnderconstrained();
723  return (bool)N->getState()->assume(Constraint, !Assumption);
724}
725
726PathDiagnosticPiece *
727TrackConstraintBRVisitor::VisitNode(const ExplodedNode *N,
728                                    const ExplodedNode *PrevN,
729                                    BugReporterContext &BRC,
730                                    BugReport &BR) {
731  if (IsSatisfied)
732    return nullptr;
733
734  // Start tracking after we see the first state in which the value is
735  // constrained.
736  if (!IsTrackingTurnedOn)
737    if (!isUnderconstrained(N))
738      IsTrackingTurnedOn = true;
739  if (!IsTrackingTurnedOn)
740    return nullptr;
741
742  // Check if in the previous state it was feasible for this constraint
743  // to *not* be true.
744  if (isUnderconstrained(PrevN)) {
745
746    IsSatisfied = true;
747
748    // As a sanity check, make sure that the negation of the constraint
749    // was infeasible in the current state.  If it is feasible, we somehow
750    // missed the transition point.
751    assert(!isUnderconstrained(N));
752
753    // We found the transition point for the constraint.  We now need to
754    // pretty-print the constraint. (work-in-progress)
755    SmallString<64> sbuf;
756    llvm::raw_svector_ostream os(sbuf);
757
758    if (Constraint.getAs<Loc>()) {
759      os << "Assuming pointer value is ";
760      os << (Assumption ? "non-null" : "null");
761    }
762
763    if (os.str().empty())
764      return nullptr;
765
766    // Construct a new PathDiagnosticPiece.
767    ProgramPoint P = N->getLocation();
768    PathDiagnosticLocation L =
769      PathDiagnosticLocation::create(P, BRC.getSourceManager());
770    if (!L.isValid())
771      return nullptr;
772
773    PathDiagnosticEventPiece *X = new PathDiagnosticEventPiece(L, os.str());
774    X->setTag(getTag());
775    return X;
776  }
777
778  return nullptr;
779}
780
781SuppressInlineDefensiveChecksVisitor::
782SuppressInlineDefensiveChecksVisitor(DefinedSVal Value, const ExplodedNode *N)
783  : V(Value), IsSatisfied(false), IsTrackingTurnedOn(false) {
784
785    // Check if the visitor is disabled.
786    SubEngine *Eng = N->getState()->getStateManager().getOwningEngine();
787    assert(Eng && "Cannot file a bug report without an owning engine");
788    AnalyzerOptions &Options = Eng->getAnalysisManager().options;
789    if (!Options.shouldSuppressInlinedDefensiveChecks())
790      IsSatisfied = true;
791
792    assert(N->getState()->isNull(V).isConstrainedTrue() &&
793           "The visitor only tracks the cases where V is constrained to 0");
794}
795
796void SuppressInlineDefensiveChecksVisitor::Profile(FoldingSetNodeID &ID) const {
797  static int id = 0;
798  ID.AddPointer(&id);
799  ID.Add(V);
800}
801
802const char *SuppressInlineDefensiveChecksVisitor::getTag() {
803  return "IDCVisitor";
804}
805
806PathDiagnosticPiece *
807SuppressInlineDefensiveChecksVisitor::VisitNode(const ExplodedNode *Succ,
808                                                const ExplodedNode *Pred,
809                                                BugReporterContext &BRC,
810                                                BugReport &BR) {
811  if (IsSatisfied)
812    return nullptr;
813
814  // Start tracking after we see the first state in which the value is null.
815  if (!IsTrackingTurnedOn)
816    if (Succ->getState()->isNull(V).isConstrainedTrue())
817      IsTrackingTurnedOn = true;
818  if (!IsTrackingTurnedOn)
819    return nullptr;
820
821  // Check if in the previous state it was feasible for this value
822  // to *not* be null.
823  if (!Pred->getState()->isNull(V).isConstrainedTrue()) {
824    IsSatisfied = true;
825
826    assert(Succ->getState()->isNull(V).isConstrainedTrue());
827
828    // Check if this is inlined defensive checks.
829    const LocationContext *CurLC =Succ->getLocationContext();
830    const LocationContext *ReportLC = BR.getErrorNode()->getLocationContext();
831    if (CurLC != ReportLC && !CurLC->isParentOf(ReportLC))
832      BR.markInvalid("Suppress IDC", CurLC);
833  }
834  return nullptr;
835}
836
837static const MemRegion *getLocationRegionIfReference(const Expr *E,
838                                                     const ExplodedNode *N) {
839  if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(E)) {
840    if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) {
841      if (!VD->getType()->isReferenceType())
842        return nullptr;
843      ProgramStateManager &StateMgr = N->getState()->getStateManager();
844      MemRegionManager &MRMgr = StateMgr.getRegionManager();
845      return MRMgr.getVarRegion(VD, N->getLocationContext());
846    }
847  }
848
849  // FIXME: This does not handle other kinds of null references,
850  // for example, references from FieldRegions:
851  //   struct Wrapper { int &ref; };
852  //   Wrapper w = { *(int *)0 };
853  //   w.ref = 1;
854
855  return nullptr;
856}
857
858static const Expr *peelOffOuterExpr(const Expr *Ex,
859                                    const ExplodedNode *N) {
860  Ex = Ex->IgnoreParenCasts();
861  if (const ExprWithCleanups *EWC = dyn_cast<ExprWithCleanups>(Ex))
862    return peelOffOuterExpr(EWC->getSubExpr(), N);
863  if (const OpaqueValueExpr *OVE = dyn_cast<OpaqueValueExpr>(Ex))
864    return peelOffOuterExpr(OVE->getSourceExpr(), N);
865
866  // Peel off the ternary operator.
867  if (const ConditionalOperator *CO = dyn_cast<ConditionalOperator>(Ex)) {
868    // Find a node where the branching occurred and find out which branch
869    // we took (true/false) by looking at the ExplodedGraph.
870    const ExplodedNode *NI = N;
871    do {
872      ProgramPoint ProgPoint = NI->getLocation();
873      if (Optional<BlockEdge> BE = ProgPoint.getAs<BlockEdge>()) {
874        const CFGBlock *srcBlk = BE->getSrc();
875        if (const Stmt *term = srcBlk->getTerminator()) {
876          if (term == CO) {
877            bool TookTrueBranch = (*(srcBlk->succ_begin()) == BE->getDst());
878            if (TookTrueBranch)
879              return peelOffOuterExpr(CO->getTrueExpr(), N);
880            else
881              return peelOffOuterExpr(CO->getFalseExpr(), N);
882          }
883        }
884      }
885      NI = NI->getFirstPred();
886    } while (NI);
887  }
888  return Ex;
889}
890
891bool bugreporter::trackNullOrUndefValue(const ExplodedNode *N,
892                                        const Stmt *S,
893                                        BugReport &report, bool IsArg,
894                                        bool EnableNullFPSuppression) {
895  if (!S || !N)
896    return false;
897
898  if (const Expr *Ex = dyn_cast<Expr>(S)) {
899    Ex = Ex->IgnoreParenCasts();
900    const Expr *PeeledEx = peelOffOuterExpr(Ex, N);
901    if (Ex != PeeledEx)
902      S = PeeledEx;
903  }
904
905  const Expr *Inner = nullptr;
906  if (const Expr *Ex = dyn_cast<Expr>(S)) {
907    Ex = Ex->IgnoreParenCasts();
908    if (ExplodedGraph::isInterestingLValueExpr(Ex) || CallEvent::isCallStmt(Ex))
909      Inner = Ex;
910  }
911
912  if (IsArg && !Inner) {
913    assert(N->getLocation().getAs<CallEnter>() && "Tracking arg but not at call");
914  } else {
915    // Walk through nodes until we get one that matches the statement exactly.
916    // Alternately, if we hit a known lvalue for the statement, we know we've
917    // gone too far (though we can likely track the lvalue better anyway).
918    do {
919      const ProgramPoint &pp = N->getLocation();
920      if (Optional<StmtPoint> ps = pp.getAs<StmtPoint>()) {
921        if (ps->getStmt() == S || ps->getStmt() == Inner)
922          break;
923      } else if (Optional<CallExitEnd> CEE = pp.getAs<CallExitEnd>()) {
924        if (CEE->getCalleeContext()->getCallSite() == S ||
925            CEE->getCalleeContext()->getCallSite() == Inner)
926          break;
927      }
928      N = N->getFirstPred();
929    } while (N);
930
931    if (!N)
932      return false;
933  }
934
935  ProgramStateRef state = N->getState();
936
937  // The message send could be nil due to the receiver being nil.
938  // At this point in the path, the receiver should be live since we are at the
939  // message send expr. If it is nil, start tracking it.
940  if (const Expr *Receiver = NilReceiverBRVisitor::getNilReceiver(S, N))
941    trackNullOrUndefValue(N, Receiver, report, false, EnableNullFPSuppression);
942
943
944  // See if the expression we're interested refers to a variable.
945  // If so, we can track both its contents and constraints on its value.
946  if (Inner && ExplodedGraph::isInterestingLValueExpr(Inner)) {
947    const MemRegion *R = nullptr;
948
949    // Find the ExplodedNode where the lvalue (the value of 'Ex')
950    // was computed.  We need this for getting the location value.
951    const ExplodedNode *LVNode = N;
952    while (LVNode) {
953      if (Optional<PostStmt> P = LVNode->getLocation().getAs<PostStmt>()) {
954        if (P->getStmt() == Inner)
955          break;
956      }
957      LVNode = LVNode->getFirstPred();
958    }
959    assert(LVNode && "Unable to find the lvalue node.");
960    ProgramStateRef LVState = LVNode->getState();
961    SVal LVal = LVState->getSVal(Inner, LVNode->getLocationContext());
962
963    if (LVState->isNull(LVal).isConstrainedTrue()) {
964      // In case of C++ references, we want to differentiate between a null
965      // reference and reference to null pointer.
966      // If the LVal is null, check if we are dealing with null reference.
967      // For those, we want to track the location of the reference.
968      if (const MemRegion *RR = getLocationRegionIfReference(Inner, N))
969        R = RR;
970    } else {
971      R = LVState->getSVal(Inner, LVNode->getLocationContext()).getAsRegion();
972
973      // If this is a C++ reference to a null pointer, we are tracking the
974      // pointer. In additon, we should find the store at which the reference
975      // got initialized.
976      if (const MemRegion *RR = getLocationRegionIfReference(Inner, N)) {
977        if (Optional<KnownSVal> KV = LVal.getAs<KnownSVal>())
978          report.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
979              *KV, RR, EnableNullFPSuppression));
980      }
981    }
982
983    if (R) {
984      // Mark both the variable region and its contents as interesting.
985      SVal V = LVState->getRawSVal(loc::MemRegionVal(R));
986
987      report.markInteresting(R);
988      report.markInteresting(V);
989      report.addVisitor(llvm::make_unique<UndefOrNullArgVisitor>(R));
990
991      // If the contents are symbolic, find out when they became null.
992      if (V.getAsLocSymbol(/*IncludeBaseRegions*/ true))
993        report.addVisitor(llvm::make_unique<TrackConstraintBRVisitor>(
994            V.castAs<DefinedSVal>(), false));
995
996      // Add visitor, which will suppress inline defensive checks.
997      if (Optional<DefinedSVal> DV = V.getAs<DefinedSVal>()) {
998        if (!DV->isZeroConstant() && LVState->isNull(*DV).isConstrainedTrue() &&
999            EnableNullFPSuppression) {
1000          report.addVisitor(
1001              llvm::make_unique<SuppressInlineDefensiveChecksVisitor>(*DV,
1002                                                                      LVNode));
1003        }
1004      }
1005
1006      if (Optional<KnownSVal> KV = V.getAs<KnownSVal>())
1007        report.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
1008            *KV, R, EnableNullFPSuppression));
1009      return true;
1010    }
1011  }
1012
1013  // If the expression is not an "lvalue expression", we can still
1014  // track the constraints on its contents.
1015  SVal V = state->getSValAsScalarOrLoc(S, N->getLocationContext());
1016
1017  // If the value came from an inlined function call, we should at least make
1018  // sure that function isn't pruned in our output.
1019  if (const Expr *E = dyn_cast<Expr>(S))
1020    S = E->IgnoreParenCasts();
1021
1022  ReturnVisitor::addVisitorIfNecessary(N, S, report, EnableNullFPSuppression);
1023
1024  // Uncomment this to find cases where we aren't properly getting the
1025  // base value that was dereferenced.
1026  // assert(!V.isUnknownOrUndef());
1027  // Is it a symbolic value?
1028  if (Optional<loc::MemRegionVal> L = V.getAs<loc::MemRegionVal>()) {
1029    // At this point we are dealing with the region's LValue.
1030    // However, if the rvalue is a symbolic region, we should track it as well.
1031    // Try to use the correct type when looking up the value.
1032    SVal RVal;
1033    if (const Expr *E = dyn_cast<Expr>(S))
1034      RVal = state->getRawSVal(L.getValue(), E->getType());
1035    else
1036      RVal = state->getSVal(L->getRegion());
1037
1038    const MemRegion *RegionRVal = RVal.getAsRegion();
1039    report.addVisitor(llvm::make_unique<UndefOrNullArgVisitor>(L->getRegion()));
1040
1041    if (RegionRVal && isa<SymbolicRegion>(RegionRVal)) {
1042      report.markInteresting(RegionRVal);
1043      report.addVisitor(llvm::make_unique<TrackConstraintBRVisitor>(
1044          loc::MemRegionVal(RegionRVal), false));
1045    }
1046  }
1047
1048  return true;
1049}
1050
1051const Expr *NilReceiverBRVisitor::getNilReceiver(const Stmt *S,
1052                                                 const ExplodedNode *N) {
1053  const ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(S);
1054  if (!ME)
1055    return nullptr;
1056  if (const Expr *Receiver = ME->getInstanceReceiver()) {
1057    ProgramStateRef state = N->getState();
1058    SVal V = state->getSVal(Receiver, N->getLocationContext());
1059    if (state->isNull(V).isConstrainedTrue())
1060      return Receiver;
1061  }
1062  return nullptr;
1063}
1064
1065PathDiagnosticPiece *NilReceiverBRVisitor::VisitNode(const ExplodedNode *N,
1066                                                     const ExplodedNode *PrevN,
1067                                                     BugReporterContext &BRC,
1068                                                     BugReport &BR) {
1069  Optional<PreStmt> P = N->getLocationAs<PreStmt>();
1070  if (!P)
1071    return nullptr;
1072
1073  const Stmt *S = P->getStmt();
1074  const Expr *Receiver = getNilReceiver(S, N);
1075  if (!Receiver)
1076    return nullptr;
1077
1078  llvm::SmallString<256> Buf;
1079  llvm::raw_svector_ostream OS(Buf);
1080
1081  if (const ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(S)) {
1082    OS << "'";
1083    ME->getSelector().print(OS);
1084    OS << "' not called";
1085  }
1086  else {
1087    OS << "No method is called";
1088  }
1089  OS << " because the receiver is nil";
1090
1091  // The receiver was nil, and hence the method was skipped.
1092  // Register a BugReporterVisitor to issue a message telling us how
1093  // the receiver was null.
1094  bugreporter::trackNullOrUndefValue(N, Receiver, BR, /*IsArg*/ false,
1095                                     /*EnableNullFPSuppression*/ false);
1096  // Issue a message saying that the method was skipped.
1097  PathDiagnosticLocation L(Receiver, BRC.getSourceManager(),
1098                                     N->getLocationContext());
1099  return new PathDiagnosticEventPiece(L, OS.str());
1100}
1101
1102// Registers every VarDecl inside a Stmt with a last store visitor.
1103void FindLastStoreBRVisitor::registerStatementVarDecls(BugReport &BR,
1104                                                const Stmt *S,
1105                                                bool EnableNullFPSuppression) {
1106  const ExplodedNode *N = BR.getErrorNode();
1107  std::deque<const Stmt *> WorkList;
1108  WorkList.push_back(S);
1109
1110  while (!WorkList.empty()) {
1111    const Stmt *Head = WorkList.front();
1112    WorkList.pop_front();
1113
1114    ProgramStateRef state = N->getState();
1115    ProgramStateManager &StateMgr = state->getStateManager();
1116
1117    if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Head)) {
1118      if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) {
1119        const VarRegion *R =
1120        StateMgr.getRegionManager().getVarRegion(VD, N->getLocationContext());
1121
1122        // What did we load?
1123        SVal V = state->getSVal(S, N->getLocationContext());
1124
1125        if (V.getAs<loc::ConcreteInt>() || V.getAs<nonloc::ConcreteInt>()) {
1126          // Register a new visitor with the BugReport.
1127          BR.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
1128              V.castAs<KnownSVal>(), R, EnableNullFPSuppression));
1129        }
1130      }
1131    }
1132
1133    for (const Stmt *SubStmt : Head->children())
1134      WorkList.push_back(SubStmt);
1135  }
1136}
1137
1138//===----------------------------------------------------------------------===//
1139// Visitor that tries to report interesting diagnostics from conditions.
1140//===----------------------------------------------------------------------===//
1141
1142/// Return the tag associated with this visitor.  This tag will be used
1143/// to make all PathDiagnosticPieces created by this visitor.
1144const char *ConditionBRVisitor::getTag() {
1145  return "ConditionBRVisitor";
1146}
1147
1148PathDiagnosticPiece *ConditionBRVisitor::VisitNode(const ExplodedNode *N,
1149                                                   const ExplodedNode *Prev,
1150                                                   BugReporterContext &BRC,
1151                                                   BugReport &BR) {
1152  PathDiagnosticPiece *piece = VisitNodeImpl(N, Prev, BRC, BR);
1153  if (piece) {
1154    piece->setTag(getTag());
1155    if (PathDiagnosticEventPiece *ev=dyn_cast<PathDiagnosticEventPiece>(piece))
1156      ev->setPrunable(true, /* override */ false);
1157  }
1158  return piece;
1159}
1160
1161PathDiagnosticPiece *ConditionBRVisitor::VisitNodeImpl(const ExplodedNode *N,
1162                                                       const ExplodedNode *Prev,
1163                                                       BugReporterContext &BRC,
1164                                                       BugReport &BR) {
1165
1166  ProgramPoint progPoint = N->getLocation();
1167  ProgramStateRef CurrentState = N->getState();
1168  ProgramStateRef PrevState = Prev->getState();
1169
1170  // Compare the GDMs of the state, because that is where constraints
1171  // are managed.  Note that ensure that we only look at nodes that
1172  // were generated by the analyzer engine proper, not checkers.
1173  if (CurrentState->getGDM().getRoot() ==
1174      PrevState->getGDM().getRoot())
1175    return nullptr;
1176
1177  // If an assumption was made on a branch, it should be caught
1178  // here by looking at the state transition.
1179  if (Optional<BlockEdge> BE = progPoint.getAs<BlockEdge>()) {
1180    const CFGBlock *srcBlk = BE->getSrc();
1181    if (const Stmt *term = srcBlk->getTerminator())
1182      return VisitTerminator(term, N, srcBlk, BE->getDst(), BR, BRC);
1183    return nullptr;
1184  }
1185
1186  if (Optional<PostStmt> PS = progPoint.getAs<PostStmt>()) {
1187    // FIXME: Assuming that BugReporter is a GRBugReporter is a layering
1188    // violation.
1189    const std::pair<const ProgramPointTag *, const ProgramPointTag *> &tags =
1190      cast<GRBugReporter>(BRC.getBugReporter()).
1191        getEngine().geteagerlyAssumeBinOpBifurcationTags();
1192
1193    const ProgramPointTag *tag = PS->getTag();
1194    if (tag == tags.first)
1195      return VisitTrueTest(cast<Expr>(PS->getStmt()), true,
1196                           BRC, BR, N);
1197    if (tag == tags.second)
1198      return VisitTrueTest(cast<Expr>(PS->getStmt()), false,
1199                           BRC, BR, N);
1200
1201    return nullptr;
1202  }
1203
1204  return nullptr;
1205}
1206
1207PathDiagnosticPiece *
1208ConditionBRVisitor::VisitTerminator(const Stmt *Term,
1209                                    const ExplodedNode *N,
1210                                    const CFGBlock *srcBlk,
1211                                    const CFGBlock *dstBlk,
1212                                    BugReport &R,
1213                                    BugReporterContext &BRC) {
1214  const Expr *Cond = nullptr;
1215
1216  switch (Term->getStmtClass()) {
1217  default:
1218    return nullptr;
1219  case Stmt::IfStmtClass:
1220    Cond = cast<IfStmt>(Term)->getCond();
1221    break;
1222  case Stmt::ConditionalOperatorClass:
1223    Cond = cast<ConditionalOperator>(Term)->getCond();
1224    break;
1225  }
1226
1227  assert(Cond);
1228  assert(srcBlk->succ_size() == 2);
1229  const bool tookTrue = *(srcBlk->succ_begin()) == dstBlk;
1230  return VisitTrueTest(Cond, tookTrue, BRC, R, N);
1231}
1232
1233PathDiagnosticPiece *
1234ConditionBRVisitor::VisitTrueTest(const Expr *Cond,
1235                                  bool tookTrue,
1236                                  BugReporterContext &BRC,
1237                                  BugReport &R,
1238                                  const ExplodedNode *N) {
1239
1240  const Expr *Ex = Cond;
1241
1242  while (true) {
1243    Ex = Ex->IgnoreParenCasts();
1244    switch (Ex->getStmtClass()) {
1245      default:
1246        return nullptr;
1247      case Stmt::BinaryOperatorClass:
1248        return VisitTrueTest(Cond, cast<BinaryOperator>(Ex), tookTrue, BRC,
1249                             R, N);
1250      case Stmt::DeclRefExprClass:
1251        return VisitTrueTest(Cond, cast<DeclRefExpr>(Ex), tookTrue, BRC,
1252                             R, N);
1253      case Stmt::UnaryOperatorClass: {
1254        const UnaryOperator *UO = cast<UnaryOperator>(Ex);
1255        if (UO->getOpcode() == UO_LNot) {
1256          tookTrue = !tookTrue;
1257          Ex = UO->getSubExpr();
1258          continue;
1259        }
1260        return nullptr;
1261      }
1262    }
1263  }
1264}
1265
1266bool ConditionBRVisitor::patternMatch(const Expr *Ex, raw_ostream &Out,
1267                                      BugReporterContext &BRC,
1268                                      BugReport &report,
1269                                      const ExplodedNode *N,
1270                                      Optional<bool> &prunable) {
1271  const Expr *OriginalExpr = Ex;
1272  Ex = Ex->IgnoreParenCasts();
1273
1274  if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Ex)) {
1275    const bool quotes = isa<VarDecl>(DR->getDecl());
1276    if (quotes) {
1277      Out << '\'';
1278      const LocationContext *LCtx = N->getLocationContext();
1279      const ProgramState *state = N->getState().get();
1280      if (const MemRegion *R = state->getLValue(cast<VarDecl>(DR->getDecl()),
1281                                                LCtx).getAsRegion()) {
1282        if (report.isInteresting(R))
1283          prunable = false;
1284        else {
1285          const ProgramState *state = N->getState().get();
1286          SVal V = state->getSVal(R);
1287          if (report.isInteresting(V))
1288            prunable = false;
1289        }
1290      }
1291    }
1292    Out << DR->getDecl()->getDeclName().getAsString();
1293    if (quotes)
1294      Out << '\'';
1295    return quotes;
1296  }
1297
1298  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(Ex)) {
1299    QualType OriginalTy = OriginalExpr->getType();
1300    if (OriginalTy->isPointerType()) {
1301      if (IL->getValue() == 0) {
1302        Out << "null";
1303        return false;
1304      }
1305    }
1306    else if (OriginalTy->isObjCObjectPointerType()) {
1307      if (IL->getValue() == 0) {
1308        Out << "nil";
1309        return false;
1310      }
1311    }
1312
1313    Out << IL->getValue();
1314    return false;
1315  }
1316
1317  return false;
1318}
1319
1320PathDiagnosticPiece *
1321ConditionBRVisitor::VisitTrueTest(const Expr *Cond,
1322                                  const BinaryOperator *BExpr,
1323                                  const bool tookTrue,
1324                                  BugReporterContext &BRC,
1325                                  BugReport &R,
1326                                  const ExplodedNode *N) {
1327
1328  bool shouldInvert = false;
1329  Optional<bool> shouldPrune;
1330
1331  SmallString<128> LhsString, RhsString;
1332  {
1333    llvm::raw_svector_ostream OutLHS(LhsString), OutRHS(RhsString);
1334    const bool isVarLHS = patternMatch(BExpr->getLHS(), OutLHS, BRC, R, N,
1335                                       shouldPrune);
1336    const bool isVarRHS = patternMatch(BExpr->getRHS(), OutRHS, BRC, R, N,
1337                                       shouldPrune);
1338
1339    shouldInvert = !isVarLHS && isVarRHS;
1340  }
1341
1342  BinaryOperator::Opcode Op = BExpr->getOpcode();
1343
1344  if (BinaryOperator::isAssignmentOp(Op)) {
1345    // For assignment operators, all that we care about is that the LHS
1346    // evaluates to "true" or "false".
1347    return VisitConditionVariable(LhsString, BExpr->getLHS(), tookTrue,
1348                                  BRC, R, N);
1349  }
1350
1351  // For non-assignment operations, we require that we can understand
1352  // both the LHS and RHS.
1353  if (LhsString.empty() || RhsString.empty() ||
1354      !BinaryOperator::isComparisonOp(Op))
1355    return nullptr;
1356
1357  // Should we invert the strings if the LHS is not a variable name?
1358  SmallString<256> buf;
1359  llvm::raw_svector_ostream Out(buf);
1360  Out << "Assuming " << (shouldInvert ? RhsString : LhsString) << " is ";
1361
1362  // Do we need to invert the opcode?
1363  if (shouldInvert)
1364    switch (Op) {
1365      default: break;
1366      case BO_LT: Op = BO_GT; break;
1367      case BO_GT: Op = BO_LT; break;
1368      case BO_LE: Op = BO_GE; break;
1369      case BO_GE: Op = BO_LE; break;
1370    }
1371
1372  if (!tookTrue)
1373    switch (Op) {
1374      case BO_EQ: Op = BO_NE; break;
1375      case BO_NE: Op = BO_EQ; break;
1376      case BO_LT: Op = BO_GE; break;
1377      case BO_GT: Op = BO_LE; break;
1378      case BO_LE: Op = BO_GT; break;
1379      case BO_GE: Op = BO_LT; break;
1380      default:
1381        return nullptr;
1382    }
1383
1384  switch (Op) {
1385    case BO_EQ:
1386      Out << "equal to ";
1387      break;
1388    case BO_NE:
1389      Out << "not equal to ";
1390      break;
1391    default:
1392      Out << BinaryOperator::getOpcodeStr(Op) << ' ';
1393      break;
1394  }
1395
1396  Out << (shouldInvert ? LhsString : RhsString);
1397  const LocationContext *LCtx = N->getLocationContext();
1398  PathDiagnosticLocation Loc(Cond, BRC.getSourceManager(), LCtx);
1399  PathDiagnosticEventPiece *event =
1400    new PathDiagnosticEventPiece(Loc, Out.str());
1401  if (shouldPrune.hasValue())
1402    event->setPrunable(shouldPrune.getValue());
1403  return event;
1404}
1405
1406PathDiagnosticPiece *
1407ConditionBRVisitor::VisitConditionVariable(StringRef LhsString,
1408                                           const Expr *CondVarExpr,
1409                                           const bool tookTrue,
1410                                           BugReporterContext &BRC,
1411                                           BugReport &report,
1412                                           const ExplodedNode *N) {
1413  // FIXME: If there's already a constraint tracker for this variable,
1414  // we shouldn't emit anything here (c.f. the double note in
1415  // test/Analysis/inlining/path-notes.c)
1416  SmallString<256> buf;
1417  llvm::raw_svector_ostream Out(buf);
1418  Out << "Assuming " << LhsString << " is ";
1419
1420  QualType Ty = CondVarExpr->getType();
1421
1422  if (Ty->isPointerType())
1423    Out << (tookTrue ? "not null" : "null");
1424  else if (Ty->isObjCObjectPointerType())
1425    Out << (tookTrue ? "not nil" : "nil");
1426  else if (Ty->isBooleanType())
1427    Out << (tookTrue ? "true" : "false");
1428  else if (Ty->isIntegralOrEnumerationType())
1429    Out << (tookTrue ? "non-zero" : "zero");
1430  else
1431    return nullptr;
1432
1433  const LocationContext *LCtx = N->getLocationContext();
1434  PathDiagnosticLocation Loc(CondVarExpr, BRC.getSourceManager(), LCtx);
1435  PathDiagnosticEventPiece *event =
1436    new PathDiagnosticEventPiece(Loc, Out.str());
1437
1438  if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(CondVarExpr)) {
1439    if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) {
1440      const ProgramState *state = N->getState().get();
1441      if (const MemRegion *R = state->getLValue(VD, LCtx).getAsRegion()) {
1442        if (report.isInteresting(R))
1443          event->setPrunable(false);
1444      }
1445    }
1446  }
1447
1448  return event;
1449}
1450
1451PathDiagnosticPiece *
1452ConditionBRVisitor::VisitTrueTest(const Expr *Cond,
1453                                  const DeclRefExpr *DR,
1454                                  const bool tookTrue,
1455                                  BugReporterContext &BRC,
1456                                  BugReport &report,
1457                                  const ExplodedNode *N) {
1458
1459  const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl());
1460  if (!VD)
1461    return nullptr;
1462
1463  SmallString<256> Buf;
1464  llvm::raw_svector_ostream Out(Buf);
1465
1466  Out << "Assuming '" << VD->getDeclName() << "' is ";
1467
1468  QualType VDTy = VD->getType();
1469
1470  if (VDTy->isPointerType())
1471    Out << (tookTrue ? "non-null" : "null");
1472  else if (VDTy->isObjCObjectPointerType())
1473    Out << (tookTrue ? "non-nil" : "nil");
1474  else if (VDTy->isScalarType())
1475    Out << (tookTrue ? "not equal to 0" : "0");
1476  else
1477    return nullptr;
1478
1479  const LocationContext *LCtx = N->getLocationContext();
1480  PathDiagnosticLocation Loc(Cond, BRC.getSourceManager(), LCtx);
1481  PathDiagnosticEventPiece *event =
1482    new PathDiagnosticEventPiece(Loc, Out.str());
1483
1484  const ProgramState *state = N->getState().get();
1485  if (const MemRegion *R = state->getLValue(VD, LCtx).getAsRegion()) {
1486    if (report.isInteresting(R))
1487      event->setPrunable(false);
1488    else {
1489      SVal V = state->getSVal(R);
1490      if (report.isInteresting(V))
1491        event->setPrunable(false);
1492    }
1493  }
1494  return event;
1495}
1496
1497
1498// FIXME: Copied from ExprEngineCallAndReturn.cpp.
1499static bool isInStdNamespace(const Decl *D) {
1500  const DeclContext *DC = D->getDeclContext()->getEnclosingNamespaceContext();
1501  const NamespaceDecl *ND = dyn_cast<NamespaceDecl>(DC);
1502  if (!ND)
1503    return false;
1504
1505  while (const NamespaceDecl *Parent = dyn_cast<NamespaceDecl>(ND->getParent()))
1506    ND = Parent;
1507
1508  return ND->isStdNamespace();
1509}
1510
1511std::unique_ptr<PathDiagnosticPiece>
1512LikelyFalsePositiveSuppressionBRVisitor::getEndPath(BugReporterContext &BRC,
1513                                                    const ExplodedNode *N,
1514                                                    BugReport &BR) {
1515  // Here we suppress false positives coming from system headers. This list is
1516  // based on known issues.
1517  ExprEngine &Eng = BRC.getBugReporter().getEngine();
1518  AnalyzerOptions &Options = Eng.getAnalysisManager().options;
1519  const Decl *D = N->getLocationContext()->getDecl();
1520
1521  if (isInStdNamespace(D)) {
1522    // Skip reports within the 'std' namespace. Although these can sometimes be
1523    // the user's fault, we currently don't report them very well, and
1524    // Note that this will not help for any other data structure libraries, like
1525    // TR1, Boost, or llvm/ADT.
1526    if (Options.shouldSuppressFromCXXStandardLibrary()) {
1527      BR.markInvalid(getTag(), nullptr);
1528      return nullptr;
1529
1530    } else {
1531      // If the complete 'std' suppression is not enabled, suppress reports
1532      // from the 'std' namespace that are known to produce false positives.
1533
1534      // The analyzer issues a false use-after-free when std::list::pop_front
1535      // or std::list::pop_back are called multiple times because we cannot
1536      // reason about the internal invariants of the datastructure.
1537      if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(D)) {
1538        const CXXRecordDecl *CD = MD->getParent();
1539        if (CD->getName() == "list") {
1540          BR.markInvalid(getTag(), nullptr);
1541          return nullptr;
1542        }
1543      }
1544
1545      // The analyzer issues a false positive on
1546      //   std::basic_string<uint8_t> v; v.push_back(1);
1547      // and
1548      //   std::u16string s; s += u'a';
1549      // because we cannot reason about the internal invariants of the
1550      // datastructure.
1551      for (const LocationContext *LCtx = N->getLocationContext(); LCtx;
1552           LCtx = LCtx->getParent()) {
1553        const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(LCtx->getDecl());
1554        if (!MD)
1555          continue;
1556
1557        const CXXRecordDecl *CD = MD->getParent();
1558        if (CD->getName() == "basic_string") {
1559          BR.markInvalid(getTag(), nullptr);
1560          return nullptr;
1561        }
1562      }
1563    }
1564  }
1565
1566  // Skip reports within the sys/queue.h macros as we do not have the ability to
1567  // reason about data structure shapes.
1568  SourceManager &SM = BRC.getSourceManager();
1569  FullSourceLoc Loc = BR.getLocation(SM).asLocation();
1570  while (Loc.isMacroID()) {
1571    Loc = Loc.getSpellingLoc();
1572    if (SM.getFilename(Loc).endswith("sys/queue.h")) {
1573      BR.markInvalid(getTag(), nullptr);
1574      return nullptr;
1575    }
1576  }
1577
1578  return nullptr;
1579}
1580
1581PathDiagnosticPiece *
1582UndefOrNullArgVisitor::VisitNode(const ExplodedNode *N,
1583                                  const ExplodedNode *PrevN,
1584                                  BugReporterContext &BRC,
1585                                  BugReport &BR) {
1586
1587  ProgramStateRef State = N->getState();
1588  ProgramPoint ProgLoc = N->getLocation();
1589
1590  // We are only interested in visiting CallEnter nodes.
1591  Optional<CallEnter> CEnter = ProgLoc.getAs<CallEnter>();
1592  if (!CEnter)
1593    return nullptr;
1594
1595  // Check if one of the arguments is the region the visitor is tracking.
1596  CallEventManager &CEMgr = BRC.getStateManager().getCallEventManager();
1597  CallEventRef<> Call = CEMgr.getCaller(CEnter->getCalleeContext(), State);
1598  unsigned Idx = 0;
1599  ArrayRef<ParmVarDecl*> parms = Call->parameters();
1600
1601  for (ArrayRef<ParmVarDecl*>::iterator I = parms.begin(), E = parms.end();
1602                              I != E; ++I, ++Idx) {
1603    const MemRegion *ArgReg = Call->getArgSVal(Idx).getAsRegion();
1604
1605    // Are we tracking the argument or its subregion?
1606    if ( !ArgReg || (ArgReg != R && !R->isSubRegionOf(ArgReg->StripCasts())))
1607      continue;
1608
1609    // Check the function parameter type.
1610    const ParmVarDecl *ParamDecl = *I;
1611    assert(ParamDecl && "Formal parameter has no decl?");
1612    QualType T = ParamDecl->getType();
1613
1614    if (!(T->isAnyPointerType() || T->isReferenceType())) {
1615      // Function can only change the value passed in by address.
1616      continue;
1617    }
1618
1619    // If it is a const pointer value, the function does not intend to
1620    // change the value.
1621    if (T->getPointeeType().isConstQualified())
1622      continue;
1623
1624    // Mark the call site (LocationContext) as interesting if the value of the
1625    // argument is undefined or '0'/'NULL'.
1626    SVal BoundVal = State->getSVal(R);
1627    if (BoundVal.isUndef() || BoundVal.isZeroConstant()) {
1628      BR.markInteresting(CEnter->getCalleeContext());
1629      return nullptr;
1630    }
1631  }
1632  return nullptr;
1633}
1634