clang  9.0.0svn
BugReporterVisitors.cpp
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1 //===- BugReporterVisitors.cpp - Helpers for reporting bugs ---------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file defines a set of BugReporter "visitors" which can be used to
10 // enhance the diagnostics reported for a bug.
11 //
12 //===----------------------------------------------------------------------===//
13 
15 #include "clang/AST/ASTContext.h"
16 #include "clang/AST/Decl.h"
17 #include "clang/AST/DeclBase.h"
18 #include "clang/AST/DeclCXX.h"
19 #include "clang/AST/Expr.h"
20 #include "clang/AST/ExprCXX.h"
21 #include "clang/AST/ExprObjC.h"
22 #include "clang/AST/Stmt.h"
23 #include "clang/AST/Type.h"
26 #include "clang/Analysis/CFG.h"
30 #include "clang/Basic/LLVM.h"
33 #include "clang/Lex/Lexer.h"
48 #include "llvm/ADT/ArrayRef.h"
49 #include "llvm/ADT/None.h"
50 #include "llvm/ADT/Optional.h"
51 #include "llvm/ADT/STLExtras.h"
52 #include "llvm/ADT/SmallPtrSet.h"
53 #include "llvm/ADT/SmallString.h"
54 #include "llvm/ADT/SmallVector.h"
55 #include "llvm/ADT/StringExtras.h"
56 #include "llvm/ADT/StringRef.h"
57 #include "llvm/Support/Casting.h"
58 #include "llvm/Support/ErrorHandling.h"
59 #include "llvm/Support/raw_ostream.h"
60 #include <cassert>
61 #include <deque>
62 #include <memory>
63 #include <string>
64 #include <utility>
65 
66 using namespace clang;
67 using namespace ento;
68 
69 //===----------------------------------------------------------------------===//
70 // Utility functions.
71 //===----------------------------------------------------------------------===//
72 
73 static const Expr *peelOffPointerArithmetic(const BinaryOperator *B) {
74  if (B->isAdditiveOp() && B->getType()->isPointerType()) {
75  if (B->getLHS()->getType()->isPointerType()) {
76  return B->getLHS();
77  } else if (B->getRHS()->getType()->isPointerType()) {
78  return B->getRHS();
79  }
80  }
81  return nullptr;
82 }
83 
84 /// Given that expression S represents a pointer that would be dereferenced,
85 /// try to find a sub-expression from which the pointer came from.
86 /// This is used for tracking down origins of a null or undefined value:
87 /// "this is null because that is null because that is null" etc.
88 /// We wipe away field and element offsets because they merely add offsets.
89 /// We also wipe away all casts except lvalue-to-rvalue casts, because the
90 /// latter represent an actual pointer dereference; however, we remove
91 /// the final lvalue-to-rvalue cast before returning from this function
92 /// because it demonstrates more clearly from where the pointer rvalue was
93 /// loaded. Examples:
94 /// x->y.z ==> x (lvalue)
95 /// foo()->y.z ==> foo() (rvalue)
96 const Expr *bugreporter::getDerefExpr(const Stmt *S) {
97  const auto *E = dyn_cast<Expr>(S);
98  if (!E)
99  return nullptr;
100 
101  while (true) {
102  if (const auto *CE = dyn_cast<CastExpr>(E)) {
103  if (CE->getCastKind() == CK_LValueToRValue) {
104  // This cast represents the load we're looking for.
105  break;
106  }
107  E = CE->getSubExpr();
108  } else if (const auto *B = dyn_cast<BinaryOperator>(E)) {
109  // Pointer arithmetic: '*(x + 2)' -> 'x') etc.
110  if (const Expr *Inner = peelOffPointerArithmetic(B)) {
111  E = Inner;
112  } else {
113  // Probably more arithmetic can be pattern-matched here,
114  // but for now give up.
115  break;
116  }
117  } else if (const auto *U = dyn_cast<UnaryOperator>(E)) {
118  if (U->getOpcode() == UO_Deref || U->getOpcode() == UO_AddrOf ||
119  (U->isIncrementDecrementOp() && U->getType()->isPointerType())) {
120  // Operators '*' and '&' don't actually mean anything.
121  // We look at casts instead.
122  E = U->getSubExpr();
123  } else {
124  // Probably more arithmetic can be pattern-matched here,
125  // but for now give up.
126  break;
127  }
128  }
129  // Pattern match for a few useful cases: a[0], p->f, *p etc.
130  else if (const auto *ME = dyn_cast<MemberExpr>(E)) {
131  E = ME->getBase();
132  } else if (const auto *IvarRef = dyn_cast<ObjCIvarRefExpr>(E)) {
133  E = IvarRef->getBase();
134  } else if (const auto *AE = dyn_cast<ArraySubscriptExpr>(E)) {
135  E = AE->getBase();
136  } else if (const auto *PE = dyn_cast<ParenExpr>(E)) {
137  E = PE->getSubExpr();
138  } else if (const auto *FE = dyn_cast<FullExpr>(E)) {
139  E = FE->getSubExpr();
140  } else {
141  // Other arbitrary stuff.
142  break;
143  }
144  }
145 
146  // Special case: remove the final lvalue-to-rvalue cast, but do not recurse
147  // deeper into the sub-expression. This way we return the lvalue from which
148  // our pointer rvalue was loaded.
149  if (const auto *CE = dyn_cast<ImplicitCastExpr>(E))
150  if (CE->getCastKind() == CK_LValueToRValue)
151  E = CE->getSubExpr();
152 
153  return E;
154 }
155 
156 /// Comparing internal representations of symbolic values (via
157 /// SVal::operator==()) is a valid way to check if the value was updated,
158 /// unless it's a LazyCompoundVal that may have a different internal
159 /// representation every time it is loaded from the state. In this function we
160 /// do an approximate comparison for lazy compound values, checking that they
161 /// are the immediate snapshots of the tracked region's bindings within the
162 /// node's respective states but not really checking that these snapshots
163 /// actually contain the same set of bindings.
164 static bool hasVisibleUpdate(const ExplodedNode *LeftNode, SVal LeftVal,
165  const ExplodedNode *RightNode, SVal RightVal) {
166  if (LeftVal == RightVal)
167  return true;
168 
169  const auto LLCV = LeftVal.getAs<nonloc::LazyCompoundVal>();
170  if (!LLCV)
171  return false;
172 
173  const auto RLCV = RightVal.getAs<nonloc::LazyCompoundVal>();
174  if (!RLCV)
175  return false;
176 
177  return LLCV->getRegion() == RLCV->getRegion() &&
178  LLCV->getStore() == LeftNode->getState()->getStore() &&
179  RLCV->getStore() == RightNode->getState()->getStore();
180 }
181 
182 //===----------------------------------------------------------------------===//
183 // Definitions for bug reporter visitors.
184 //===----------------------------------------------------------------------===//
185 
186 std::shared_ptr<PathDiagnosticPiece>
187 BugReporterVisitor::getEndPath(BugReporterContext &,
188  const ExplodedNode *, BugReport &) {
189  return nullptr;
190 }
191 
192 void
193 BugReporterVisitor::finalizeVisitor(BugReporterContext &,
194  const ExplodedNode *, BugReport &) {}
195 
196 std::shared_ptr<PathDiagnosticPiece> BugReporterVisitor::getDefaultEndPath(
197  BugReporterContext &BRC, const ExplodedNode *EndPathNode, BugReport &BR) {
198  PathDiagnosticLocation L =
199  PathDiagnosticLocation::createEndOfPath(EndPathNode,BRC.getSourceManager());
200 
201  const auto &Ranges = BR.getRanges();
202 
203  // Only add the statement itself as a range if we didn't specify any
204  // special ranges for this report.
205  auto P = std::make_shared<PathDiagnosticEventPiece>(
206  L, BR.getDescription(), Ranges.begin() == Ranges.end());
207  for (SourceRange Range : Ranges)
208  P->addRange(Range);
209 
210  return P;
211 }
212 
213 /// \return name of the macro inside the location \p Loc.
214 static StringRef getMacroName(SourceLocation Loc,
215  BugReporterContext &BRC) {
217  Loc,
218  BRC.getSourceManager(),
219  BRC.getASTContext().getLangOpts());
220 }
221 
222 /// \return Whether given spelling location corresponds to an expansion
223 /// of a function-like macro.
225  const SourceManager &SM) {
226  if (!Loc.isMacroID())
227  return false;
228  while (SM.isMacroArgExpansion(Loc))
229  Loc = SM.getImmediateExpansionRange(Loc).getBegin();
230  std::pair<FileID, unsigned> TLInfo = SM.getDecomposedLoc(Loc);
231  SrcMgr::SLocEntry SE = SM.getSLocEntry(TLInfo.first);
232  const SrcMgr::ExpansionInfo &EInfo = SE.getExpansion();
233  return EInfo.isFunctionMacroExpansion();
234 }
235 
236 /// \return Whether \c RegionOfInterest was modified at \p N,
237 /// where \p ReturnState is a state associated with the return
238 /// from the current frame.
240  const SubRegion *RegionOfInterest,
241  const ExplodedNode *N,
242  SVal ValueAfter) {
243  ProgramStateRef State = N->getState();
244  ProgramStateManager &Mgr = N->getState()->getStateManager();
245 
246  if (!N->getLocationAs<PostStore>()
247  && !N->getLocationAs<PostInitializer>()
248  && !N->getLocationAs<PostStmt>())
249  return false;
250 
251  // Writing into region of interest.
252  if (auto PS = N->getLocationAs<PostStmt>())
253  if (auto *BO = PS->getStmtAs<BinaryOperator>())
254  if (BO->isAssignmentOp() && RegionOfInterest->isSubRegionOf(
255  N->getSVal(BO->getLHS()).getAsRegion()))
256  return true;
257 
258  // SVal after the state is possibly different.
259  SVal ValueAtN = N->getState()->getSVal(RegionOfInterest);
260  if (!Mgr.getSValBuilder().areEqual(State, ValueAtN, ValueAfter).isConstrainedTrue() &&
261  (!ValueAtN.isUndef() || !ValueAfter.isUndef()))
262  return true;
263 
264  return false;
265 }
266 
267 
268 namespace {
269 
270 /// Put a diagnostic on return statement of all inlined functions
271 /// for which the region of interest \p RegionOfInterest was passed into,
272 /// but not written inside, and it has caused an undefined read or a null
273 /// pointer dereference outside.
274 class NoStoreFuncVisitor final : public BugReporterVisitor {
275  const SubRegion *RegionOfInterest;
276  MemRegionManager &MmrMgr;
277  const SourceManager &SM;
278  const PrintingPolicy &PP;
279 
280  /// Recursion limit for dereferencing fields when looking for the
281  /// region of interest.
282  /// The limit of two indicates that we will dereference fields only once.
283  static const unsigned DEREFERENCE_LIMIT = 2;
284 
285  /// Frames writing into \c RegionOfInterest.
286  /// This visitor generates a note only if a function does not write into
287  /// a region of interest. This information is not immediately available
288  /// by looking at the node associated with the exit from the function
289  /// (usually the return statement). To avoid recomputing the same information
290  /// many times (going up the path for each node and checking whether the
291  /// region was written into) we instead lazily compute the
292  /// stack frames along the path which write into the region of interest.
293  llvm::SmallPtrSet<const StackFrameContext *, 32> FramesModifyingRegion;
294  llvm::SmallPtrSet<const StackFrameContext *, 32> FramesModifyingCalculated;
295 
296  using RegionVector = SmallVector<const MemRegion *, 5>;
297 public:
298  NoStoreFuncVisitor(const SubRegion *R)
299  : RegionOfInterest(R), MmrMgr(*R->getMemRegionManager()),
300  SM(MmrMgr.getContext().getSourceManager()),
301  PP(MmrMgr.getContext().getPrintingPolicy()) {}
302 
303  void Profile(llvm::FoldingSetNodeID &ID) const override {
304  static int Tag = 0;
305  ID.AddPointer(&Tag);
306  ID.AddPointer(RegionOfInterest);
307  }
308 
309  void *getTag() const {
310  static int Tag = 0;
311  return static_cast<void *>(&Tag);
312  }
313 
314  std::shared_ptr<PathDiagnosticPiece> VisitNode(const ExplodedNode *N,
315  BugReporterContext &BR,
316  BugReport &R) override {
317 
318  const LocationContext *Ctx = N->getLocationContext();
319  const StackFrameContext *SCtx = Ctx->getStackFrame();
320  ProgramStateRef State = N->getState();
321  auto CallExitLoc = N->getLocationAs<CallExitBegin>();
322 
323  // No diagnostic if region was modified inside the frame.
324  if (!CallExitLoc || isRegionOfInterestModifiedInFrame(N))
325  return nullptr;
326 
327  CallEventRef<> Call =
328  BR.getStateManager().getCallEventManager().getCaller(SCtx, State);
329 
330  // Region of interest corresponds to an IVar, exiting a method
331  // which could have written into that IVar, but did not.
332  if (const auto *MC = dyn_cast<ObjCMethodCall>(Call)) {
333  if (const auto *IvarR = dyn_cast<ObjCIvarRegion>(RegionOfInterest)) {
334  const MemRegion *SelfRegion = MC->getReceiverSVal().getAsRegion();
335  if (RegionOfInterest->isSubRegionOf(SelfRegion) &&
336  potentiallyWritesIntoIvar(Call->getRuntimeDefinition().getDecl(),
337  IvarR->getDecl()))
338  return maybeEmitNote(R, *Call, N, {}, SelfRegion, "self",
339  /*FirstIsReferenceType=*/false, 1);
340  }
341  }
342 
343  if (const auto *CCall = dyn_cast<CXXConstructorCall>(Call)) {
344  const MemRegion *ThisR = CCall->getCXXThisVal().getAsRegion();
345  if (RegionOfInterest->isSubRegionOf(ThisR)
346  && !CCall->getDecl()->isImplicit())
347  return maybeEmitNote(R, *Call, N, {}, ThisR, "this",
348  /*FirstIsReferenceType=*/false, 1);
349 
350  // Do not generate diagnostics for not modified parameters in
351  // constructors.
352  return nullptr;
353  }
354 
355  ArrayRef<ParmVarDecl *> parameters = getCallParameters(Call);
356  for (unsigned I = 0; I < Call->getNumArgs() && I < parameters.size(); ++I) {
357  const ParmVarDecl *PVD = parameters[I];
358  SVal V = Call->getArgSVal(I);
359  bool ParamIsReferenceType = PVD->getType()->isReferenceType();
360  std::string ParamName = PVD->getNameAsString();
361 
362  int IndirectionLevel = 1;
363  QualType T = PVD->getType();
364  while (const MemRegion *MR = V.getAsRegion()) {
365  if (RegionOfInterest->isSubRegionOf(MR) && !isPointerToConst(T))
366  return maybeEmitNote(R, *Call, N, {}, MR, ParamName,
367  ParamIsReferenceType, IndirectionLevel);
368 
369  QualType PT = T->getPointeeType();
370  if (PT.isNull() || PT->isVoidType()) break;
371 
372  if (const RecordDecl *RD = PT->getAsRecordDecl())
373  if (auto P = findRegionOfInterestInRecord(RD, State, MR))
374  return maybeEmitNote(R, *Call, N, *P, RegionOfInterest, ParamName,
375  ParamIsReferenceType, IndirectionLevel);
376 
377  V = State->getSVal(MR, PT);
378  T = PT;
379  IndirectionLevel++;
380  }
381  }
382 
383  return nullptr;
384  }
385 
386 private:
387  /// Attempts to find the region of interest in a given CXX decl,
388  /// by either following the base classes or fields.
389  /// Dereferences fields up to a given recursion limit.
390  /// Note that \p Vec is passed by value, leading to quadratic copying cost,
391  /// but it's OK in practice since its length is limited to DEREFERENCE_LIMIT.
392  /// \return A chain fields leading to the region of interest or None.
394  findRegionOfInterestInRecord(const RecordDecl *RD, ProgramStateRef State,
395  const MemRegion *R,
396  const RegionVector &Vec = {},
397  int depth = 0) {
398 
399  if (depth == DEREFERENCE_LIMIT) // Limit the recursion depth.
400  return None;
401 
402  if (const auto *RDX = dyn_cast<CXXRecordDecl>(RD))
403  if (!RDX->hasDefinition())
404  return None;
405 
406  // Recursively examine the base classes.
407  // Note that following base classes does not increase the recursion depth.
408  if (const auto *RDX = dyn_cast<CXXRecordDecl>(RD))
409  for (const auto II : RDX->bases())
410  if (const RecordDecl *RRD = II.getType()->getAsRecordDecl())
411  if (auto Out = findRegionOfInterestInRecord(RRD, State, R, Vec, depth))
412  return Out;
413 
414  for (const FieldDecl *I : RD->fields()) {
415  QualType FT = I->getType();
416  const FieldRegion *FR = MmrMgr.getFieldRegion(I, cast<SubRegion>(R));
417  const SVal V = State->getSVal(FR);
418  const MemRegion *VR = V.getAsRegion();
419 
420  RegionVector VecF = Vec;
421  VecF.push_back(FR);
422 
423  if (RegionOfInterest == VR)
424  return VecF;
425 
426  if (const RecordDecl *RRD = FT->getAsRecordDecl())
427  if (auto Out =
428  findRegionOfInterestInRecord(RRD, State, FR, VecF, depth + 1))
429  return Out;
430 
431  QualType PT = FT->getPointeeType();
432  if (PT.isNull() || PT->isVoidType() || !VR) continue;
433 
434  if (const RecordDecl *RRD = PT->getAsRecordDecl())
435  if (auto Out =
436  findRegionOfInterestInRecord(RRD, State, VR, VecF, depth + 1))
437  return Out;
438 
439  }
440 
441  return None;
442  }
443 
444  /// \return Whether the method declaration \p Parent
445  /// syntactically has a binary operation writing into the ivar \p Ivar.
446  bool potentiallyWritesIntoIvar(const Decl *Parent,
447  const ObjCIvarDecl *Ivar) {
448  using namespace ast_matchers;
449  const char * IvarBind = "Ivar";
450  if (!Parent || !Parent->hasBody())
451  return false;
452  StatementMatcher WriteIntoIvarM = binaryOperator(
453  hasOperatorName("="),
454  hasLHS(ignoringParenImpCasts(
455  objcIvarRefExpr(hasDeclaration(equalsNode(Ivar))).bind(IvarBind))));
456  StatementMatcher ParentM = stmt(hasDescendant(WriteIntoIvarM));
457  auto Matches = match(ParentM, *Parent->getBody(), Parent->getASTContext());
458  for (BoundNodes &Match : Matches) {
459  auto IvarRef = Match.getNodeAs<ObjCIvarRefExpr>(IvarBind);
460  if (IvarRef->isFreeIvar())
461  return true;
462 
463  const Expr *Base = IvarRef->getBase();
464  if (const auto *ICE = dyn_cast<ImplicitCastExpr>(Base))
465  Base = ICE->getSubExpr();
466 
467  if (const auto *DRE = dyn_cast<DeclRefExpr>(Base))
468  if (const auto *ID = dyn_cast<ImplicitParamDecl>(DRE->getDecl()))
469  if (ID->getParameterKind() == ImplicitParamDecl::ObjCSelf)
470  return true;
471 
472  return false;
473  }
474  return false;
475  }
476 
477  /// Check and lazily calculate whether the region of interest is
478  /// modified in the stack frame to which \p N belongs.
479  /// The calculation is cached in FramesModifyingRegion.
480  bool isRegionOfInterestModifiedInFrame(const ExplodedNode *N) {
481  const LocationContext *Ctx = N->getLocationContext();
482  const StackFrameContext *SCtx = Ctx->getStackFrame();
483  if (!FramesModifyingCalculated.count(SCtx))
484  findModifyingFrames(N);
485  return FramesModifyingRegion.count(SCtx);
486  }
487 
488 
489  /// Write to \c FramesModifyingRegion all stack frames along
490  /// the path in the current stack frame which modify \c RegionOfInterest.
491  void findModifyingFrames(const ExplodedNode *N) {
492  assert(N->getLocationAs<CallExitBegin>());
493  ProgramStateRef LastReturnState = N->getState();
494  SVal ValueAtReturn = LastReturnState->getSVal(RegionOfInterest);
495  const LocationContext *Ctx = N->getLocationContext();
496  const StackFrameContext *OriginalSCtx = Ctx->getStackFrame();
497 
498  do {
499  ProgramStateRef State = N->getState();
500  auto CallExitLoc = N->getLocationAs<CallExitBegin>();
501  if (CallExitLoc) {
502  LastReturnState = State;
503  ValueAtReturn = LastReturnState->getSVal(RegionOfInterest);
504  }
505 
506  FramesModifyingCalculated.insert(
507  N->getLocationContext()->getStackFrame());
508 
509  if (wasRegionOfInterestModifiedAt(RegionOfInterest, N, ValueAtReturn)) {
510  const StackFrameContext *SCtx = N->getStackFrame();
511  while (!SCtx->inTopFrame()) {
512  auto p = FramesModifyingRegion.insert(SCtx);
513  if (!p.second)
514  break; // Frame and all its parents already inserted.
515  SCtx = SCtx->getParent()->getStackFrame();
516  }
517  }
518 
519  // Stop calculation at the call to the current function.
520  if (auto CE = N->getLocationAs<CallEnter>())
521  if (CE->getCalleeContext() == OriginalSCtx)
522  break;
523 
524  N = N->getFirstPred();
525  } while (N);
526  }
527 
528  /// Get parameters associated with runtime definition in order
529  /// to get the correct parameter name.
530  ArrayRef<ParmVarDecl *> getCallParameters(CallEventRef<> Call) {
531  // Use runtime definition, if available.
532  RuntimeDefinition RD = Call->getRuntimeDefinition();
533  if (const auto *FD = dyn_cast_or_null<FunctionDecl>(RD.getDecl()))
534  return FD->parameters();
535  if (const auto *MD = dyn_cast_or_null<ObjCMethodDecl>(RD.getDecl()))
536  return MD->parameters();
537 
538  return Call->parameters();
539  }
540 
541  /// \return whether \p Ty points to a const type, or is a const reference.
542  bool isPointerToConst(QualType Ty) {
543  return !Ty->getPointeeType().isNull() &&
545  }
546 
547  /// Consume the information on the no-store stack frame in order to
548  /// either emit a note or suppress the report enirely.
549  /// \return Diagnostics piece for region not modified in the current function,
550  /// if it decides to emit one.
551  std::shared_ptr<PathDiagnosticPiece>
552  maybeEmitNote(BugReport &R, const CallEvent &Call, const ExplodedNode *N,
553  const RegionVector &FieldChain, const MemRegion *MatchedRegion,
554  StringRef FirstElement, bool FirstIsReferenceType,
555  unsigned IndirectionLevel) {
556  // Optimistically suppress uninitialized value bugs that result
557  // from system headers having a chance to initialize the value
558  // but failing to do so. It's too unlikely a system header's fault.
559  // It's much more likely a situation in which the function has a failure
560  // mode that the user decided not to check. If we want to hunt such
561  // omitted checks, we should provide an explicit function-specific note
562  // describing the precondition under which the function isn't supposed to
563  // initialize its out-parameter, and additionally check that such
564  // precondition can actually be fulfilled on the current path.
565  if (Call.isInSystemHeader()) {
566  // We make an exception for system header functions that have no branches.
567  // Such functions unconditionally fail to initialize the variable.
568  // If they call other functions that have more paths within them,
569  // this suppression would still apply when we visit these inner functions.
570  // One common example of a standard function that doesn't ever initialize
571  // its out parameter is operator placement new; it's up to the follow-up
572  // constructor (if any) to initialize the memory.
573  if (!N->getStackFrame()->getCFG()->isLinear())
574  R.markInvalid(getTag(), nullptr);
575  return nullptr;
576  }
577 
578  PathDiagnosticLocation L =
579  PathDiagnosticLocation::create(N->getLocation(), SM);
580 
581  // For now this shouldn't trigger, but once it does (as we add more
582  // functions to the body farm), we'll need to decide if these reports
583  // are worth suppressing as well.
584  if (!L.hasValidLocation())
585  return nullptr;
586 
587  SmallString<256> sbuf;
588  llvm::raw_svector_ostream os(sbuf);
589  os << "Returning without writing to '";
590 
591  // Do not generate the note if failed to pretty-print.
592  if (!prettyPrintRegionName(FirstElement, FirstIsReferenceType,
593  MatchedRegion, FieldChain, IndirectionLevel, os))
594  return nullptr;
595 
596  os << "'";
597  return std::make_shared<PathDiagnosticEventPiece>(L, os.str());
598  }
599 
600  /// Pretty-print region \p MatchedRegion to \p os.
601  /// \return Whether printing succeeded.
602  bool prettyPrintRegionName(StringRef FirstElement, bool FirstIsReferenceType,
603  const MemRegion *MatchedRegion,
604  const RegionVector &FieldChain,
605  int IndirectionLevel,
606  llvm::raw_svector_ostream &os) {
607 
608  if (FirstIsReferenceType)
609  IndirectionLevel--;
610 
611  RegionVector RegionSequence;
612 
613  // Add the regions in the reverse order, then reverse the resulting array.
614  assert(RegionOfInterest->isSubRegionOf(MatchedRegion));
615  const MemRegion *R = RegionOfInterest;
616  while (R != MatchedRegion) {
617  RegionSequence.push_back(R);
618  R = cast<SubRegion>(R)->getSuperRegion();
619  }
620  std::reverse(RegionSequence.begin(), RegionSequence.end());
621  RegionSequence.append(FieldChain.begin(), FieldChain.end());
622 
623  StringRef Sep;
624  for (const MemRegion *R : RegionSequence) {
625 
626  // Just keep going up to the base region.
627  // Element regions may appear due to casts.
628  if (isa<CXXBaseObjectRegion>(R) || isa<CXXTempObjectRegion>(R))
629  continue;
630 
631  if (Sep.empty())
632  Sep = prettyPrintFirstElement(FirstElement,
633  /*MoreItemsExpected=*/true,
634  IndirectionLevel, os);
635 
636  os << Sep;
637 
638  // Can only reasonably pretty-print DeclRegions.
639  if (!isa<DeclRegion>(R))
640  return false;
641 
642  const auto *DR = cast<DeclRegion>(R);
643  Sep = DR->getValueType()->isAnyPointerType() ? "->" : ".";
644  DR->getDecl()->getDeclName().print(os, PP);
645  }
646 
647  if (Sep.empty())
648  prettyPrintFirstElement(FirstElement,
649  /*MoreItemsExpected=*/false, IndirectionLevel,
650  os);
651  return true;
652  }
653 
654  /// Print first item in the chain, return new separator.
655  StringRef prettyPrintFirstElement(StringRef FirstElement,
656  bool MoreItemsExpected,
657  int IndirectionLevel,
658  llvm::raw_svector_ostream &os) {
659  StringRef Out = ".";
660 
661  if (IndirectionLevel > 0 && MoreItemsExpected) {
662  IndirectionLevel--;
663  Out = "->";
664  }
665 
666  if (IndirectionLevel > 0 && MoreItemsExpected)
667  os << "(";
668 
669  for (int i=0; i<IndirectionLevel; i++)
670  os << "*";
671  os << FirstElement;
672 
673  if (IndirectionLevel > 0 && MoreItemsExpected)
674  os << ")";
675 
676  return Out;
677  }
678 };
679 
680 /// Suppress null-pointer-dereference bugs where dereferenced null was returned
681 /// the macro.
682 class MacroNullReturnSuppressionVisitor final : public BugReporterVisitor {
683  const SubRegion *RegionOfInterest;
684  const SVal ValueAtDereference;
685 
686  // Do not invalidate the reports where the value was modified
687  // after it got assigned to from the macro.
688  bool WasModified = false;
689 
690 public:
691  MacroNullReturnSuppressionVisitor(const SubRegion *R,
692  const SVal V) : RegionOfInterest(R),
693  ValueAtDereference(V) {}
694 
695  std::shared_ptr<PathDiagnosticPiece> VisitNode(const ExplodedNode *N,
696  BugReporterContext &BRC,
697  BugReport &BR) override {
698  if (WasModified)
699  return nullptr;
700 
701  auto BugPoint = BR.getErrorNode()->getLocation().getAs<StmtPoint>();
702  if (!BugPoint)
703  return nullptr;
704 
705  const SourceManager &SMgr = BRC.getSourceManager();
706  if (auto Loc = matchAssignment(N)) {
707  if (isFunctionMacroExpansion(*Loc, SMgr)) {
708  std::string MacroName = getMacroName(*Loc, BRC);
709  SourceLocation BugLoc = BugPoint->getStmt()->getBeginLoc();
710  if (!BugLoc.isMacroID() || getMacroName(BugLoc, BRC) != MacroName)
711  BR.markInvalid(getTag(), MacroName.c_str());
712  }
713  }
714 
715  if (wasRegionOfInterestModifiedAt(RegionOfInterest, N, ValueAtDereference))
716  WasModified = true;
717 
718  return nullptr;
719  }
720 
721  static void addMacroVisitorIfNecessary(
722  const ExplodedNode *N, const MemRegion *R,
723  bool EnableNullFPSuppression, BugReport &BR,
724  const SVal V) {
725  AnalyzerOptions &Options = N->getState()->getAnalysisManager().options;
726  if (EnableNullFPSuppression &&
727  Options.ShouldSuppressNullReturnPaths && V.getAs<Loc>())
728  BR.addVisitor(llvm::make_unique<MacroNullReturnSuppressionVisitor>(
729  R->getAs<SubRegion>(), V));
730  }
731 
732  void* getTag() const {
733  static int Tag = 0;
734  return static_cast<void *>(&Tag);
735  }
736 
737  void Profile(llvm::FoldingSetNodeID &ID) const override {
738  ID.AddPointer(getTag());
739  }
740 
741 private:
742  /// \return Source location of right hand side of an assignment
743  /// into \c RegionOfInterest, empty optional if none found.
744  Optional<SourceLocation> matchAssignment(const ExplodedNode *N) {
746  ProgramStateRef State = N->getState();
747  auto *LCtx = N->getLocationContext();
748  if (!S)
749  return None;
750 
751  if (const auto *DS = dyn_cast<DeclStmt>(S)) {
752  if (const auto *VD = dyn_cast<VarDecl>(DS->getSingleDecl()))
753  if (const Expr *RHS = VD->getInit())
754  if (RegionOfInterest->isSubRegionOf(
755  State->getLValue(VD, LCtx).getAsRegion()))
756  return RHS->getBeginLoc();
757  } else if (const auto *BO = dyn_cast<BinaryOperator>(S)) {
758  const MemRegion *R = N->getSVal(BO->getLHS()).getAsRegion();
759  const Expr *RHS = BO->getRHS();
760  if (BO->isAssignmentOp() && RegionOfInterest->isSubRegionOf(R)) {
761  return RHS->getBeginLoc();
762  }
763  }
764  return None;
765  }
766 };
767 
768 /// Emits an extra note at the return statement of an interesting stack frame.
769 ///
770 /// The returned value is marked as an interesting value, and if it's null,
771 /// adds a visitor to track where it became null.
772 ///
773 /// This visitor is intended to be used when another visitor discovers that an
774 /// interesting value comes from an inlined function call.
775 class ReturnVisitor : public BugReporterVisitor {
776  const StackFrameContext *StackFrame;
777  enum {
778  Initial,
779  MaybeUnsuppress,
780  Satisfied
781  } Mode = Initial;
782 
783  bool EnableNullFPSuppression;
784  bool ShouldInvalidate = true;
785  AnalyzerOptions& Options;
786 
787 public:
788  ReturnVisitor(const StackFrameContext *Frame,
789  bool Suppressed,
790  AnalyzerOptions &Options)
791  : StackFrame(Frame), EnableNullFPSuppression(Suppressed),
792  Options(Options) {}
793 
794  static void *getTag() {
795  static int Tag = 0;
796  return static_cast<void *>(&Tag);
797  }
798 
799  void Profile(llvm::FoldingSetNodeID &ID) const override {
800  ID.AddPointer(ReturnVisitor::getTag());
801  ID.AddPointer(StackFrame);
802  ID.AddBoolean(EnableNullFPSuppression);
803  }
804 
805  /// Adds a ReturnVisitor if the given statement represents a call that was
806  /// inlined.
807  ///
808  /// This will search back through the ExplodedGraph, starting from the given
809  /// node, looking for when the given statement was processed. If it turns out
810  /// the statement is a call that was inlined, we add the visitor to the
811  /// bug report, so it can print a note later.
812  static void addVisitorIfNecessary(const ExplodedNode *Node, const Stmt *S,
813  BugReport &BR,
814  bool InEnableNullFPSuppression) {
815  if (!CallEvent::isCallStmt(S))
816  return;
817 
818  // First, find when we processed the statement.
819  do {
820  if (auto CEE = Node->getLocationAs<CallExitEnd>())
821  if (CEE->getCalleeContext()->getCallSite() == S)
822  break;
823  if (auto SP = Node->getLocationAs<StmtPoint>())
824  if (SP->getStmt() == S)
825  break;
826 
827  Node = Node->getFirstPred();
828  } while (Node);
829 
830  // Next, step over any post-statement checks.
831  while (Node && Node->getLocation().getAs<PostStmt>())
832  Node = Node->getFirstPred();
833  if (!Node)
834  return;
835 
836  // Finally, see if we inlined the call.
837  Optional<CallExitEnd> CEE = Node->getLocationAs<CallExitEnd>();
838  if (!CEE)
839  return;
840 
841  const StackFrameContext *CalleeContext = CEE->getCalleeContext();
842  if (CalleeContext->getCallSite() != S)
843  return;
844 
845  // Check the return value.
846  ProgramStateRef State = Node->getState();
847  SVal RetVal = Node->getSVal(S);
848 
849  // Handle cases where a reference is returned and then immediately used.
850  if (cast<Expr>(S)->isGLValue())
851  if (Optional<Loc> LValue = RetVal.getAs<Loc>())
852  RetVal = State->getSVal(*LValue);
853 
854  // See if the return value is NULL. If so, suppress the report.
855  AnalyzerOptions &Options = State->getAnalysisManager().options;
856 
857  bool EnableNullFPSuppression = false;
858  if (InEnableNullFPSuppression &&
859  Options.ShouldSuppressNullReturnPaths)
860  if (Optional<Loc> RetLoc = RetVal.getAs<Loc>())
861  EnableNullFPSuppression = State->isNull(*RetLoc).isConstrainedTrue();
862 
863  BR.markInteresting(CalleeContext);
864  BR.addVisitor(llvm::make_unique<ReturnVisitor>(CalleeContext,
865  EnableNullFPSuppression,
866  Options));
867  }
868 
869  std::shared_ptr<PathDiagnosticPiece>
870  visitNodeInitial(const ExplodedNode *N,
871  BugReporterContext &BRC, BugReport &BR) {
872  // Only print a message at the interesting return statement.
873  if (N->getLocationContext() != StackFrame)
874  return nullptr;
875 
876  Optional<StmtPoint> SP = N->getLocationAs<StmtPoint>();
877  if (!SP)
878  return nullptr;
879 
880  const auto *Ret = dyn_cast<ReturnStmt>(SP->getStmt());
881  if (!Ret)
882  return nullptr;
883 
884  // Okay, we're at the right return statement, but do we have the return
885  // value available?
886  ProgramStateRef State = N->getState();
887  SVal V = State->getSVal(Ret, StackFrame);
888  if (V.isUnknownOrUndef())
889  return nullptr;
890 
891  // Don't print any more notes after this one.
892  Mode = Satisfied;
893 
894  const Expr *RetE = Ret->getRetValue();
895  assert(RetE && "Tracking a return value for a void function");
896 
897  // Handle cases where a reference is returned and then immediately used.
898  Optional<Loc> LValue;
899  if (RetE->isGLValue()) {
900  if ((LValue = V.getAs<Loc>())) {
901  SVal RValue = State->getRawSVal(*LValue, RetE->getType());
902  if (RValue.getAs<DefinedSVal>())
903  V = RValue;
904  }
905  }
906 
907  // Ignore aggregate rvalues.
908  if (V.getAs<nonloc::LazyCompoundVal>() ||
909  V.getAs<nonloc::CompoundVal>())
910  return nullptr;
911 
912  RetE = RetE->IgnoreParenCasts();
913 
914  // If we're returning 0, we should track where that 0 came from.
915  bugreporter::trackExpressionValue(N, RetE, BR, EnableNullFPSuppression);
916 
917  // Build an appropriate message based on the return value.
918  SmallString<64> Msg;
919  llvm::raw_svector_ostream Out(Msg);
920 
921  if (State->isNull(V).isConstrainedTrue()) {
922  if (V.getAs<Loc>()) {
923 
924  // If we have counter-suppression enabled, make sure we keep visiting
925  // future nodes. We want to emit a path note as well, in case
926  // the report is resurrected as valid later on.
927  if (EnableNullFPSuppression &&
928  Options.ShouldAvoidSuppressingNullArgumentPaths)
929  Mode = MaybeUnsuppress;
930 
931  if (RetE->getType()->isObjCObjectPointerType()) {
932  Out << "Returning nil";
933  } else {
934  Out << "Returning null pointer";
935  }
936  } else {
937  Out << "Returning zero";
938  }
939 
940  } else {
941  if (auto CI = V.getAs<nonloc::ConcreteInt>()) {
942  Out << "Returning the value " << CI->getValue();
943  } else if (V.getAs<Loc>()) {
944  Out << "Returning pointer";
945  } else {
946  Out << "Returning value";
947  }
948  }
949 
950  if (LValue) {
951  if (const MemRegion *MR = LValue->getAsRegion()) {
952  if (MR->canPrintPretty()) {
953  Out << " (reference to ";
954  MR->printPretty(Out);
955  Out << ")";
956  }
957  }
958  } else {
959  // FIXME: We should have a more generalized location printing mechanism.
960  if (const auto *DR = dyn_cast<DeclRefExpr>(RetE))
961  if (const auto *DD = dyn_cast<DeclaratorDecl>(DR->getDecl()))
962  Out << " (loaded from '" << *DD << "')";
963  }
964 
965  PathDiagnosticLocation L(Ret, BRC.getSourceManager(), StackFrame);
966  if (!L.isValid() || !L.asLocation().isValid())
967  return nullptr;
968 
969  return std::make_shared<PathDiagnosticEventPiece>(L, Out.str());
970  }
971 
972  std::shared_ptr<PathDiagnosticPiece>
973  visitNodeMaybeUnsuppress(const ExplodedNode *N,
974  BugReporterContext &BRC, BugReport &BR) {
975 #ifndef NDEBUG
976  assert(Options.ShouldAvoidSuppressingNullArgumentPaths);
977 #endif
978 
979  // Are we at the entry node for this call?
980  Optional<CallEnter> CE = N->getLocationAs<CallEnter>();
981  if (!CE)
982  return nullptr;
983 
984  if (CE->getCalleeContext() != StackFrame)
985  return nullptr;
986 
987  Mode = Satisfied;
988 
989  // Don't automatically suppress a report if one of the arguments is
990  // known to be a null pointer. Instead, start tracking /that/ null
991  // value back to its origin.
992  ProgramStateManager &StateMgr = BRC.getStateManager();
993  CallEventManager &CallMgr = StateMgr.getCallEventManager();
994 
995  ProgramStateRef State = N->getState();
996  CallEventRef<> Call = CallMgr.getCaller(StackFrame, State);
997  for (unsigned I = 0, E = Call->getNumArgs(); I != E; ++I) {
998  Optional<Loc> ArgV = Call->getArgSVal(I).getAs<Loc>();
999  if (!ArgV)
1000  continue;
1001 
1002  const Expr *ArgE = Call->getArgExpr(I);
1003  if (!ArgE)
1004  continue;
1005 
1006  // Is it possible for this argument to be non-null?
1007  if (!State->isNull(*ArgV).isConstrainedTrue())
1008  continue;
1009 
1010  if (bugreporter::trackExpressionValue(N, ArgE, BR, EnableNullFPSuppression))
1011  ShouldInvalidate = false;
1012 
1013  // If we /can't/ track the null pointer, we should err on the side of
1014  // false negatives, and continue towards marking this report invalid.
1015  // (We will still look at the other arguments, though.)
1016  }
1017 
1018  return nullptr;
1019  }
1020 
1021  std::shared_ptr<PathDiagnosticPiece> VisitNode(const ExplodedNode *N,
1022  BugReporterContext &BRC,
1023  BugReport &BR) override {
1024  switch (Mode) {
1025  case Initial:
1026  return visitNodeInitial(N, BRC, BR);
1027  case MaybeUnsuppress:
1028  return visitNodeMaybeUnsuppress(N, BRC, BR);
1029  case Satisfied:
1030  return nullptr;
1031  }
1032 
1033  llvm_unreachable("Invalid visit mode!");
1034  }
1035 
1036  void finalizeVisitor(BugReporterContext &, const ExplodedNode *,
1037  BugReport &BR) override {
1038  if (EnableNullFPSuppression && ShouldInvalidate)
1039  BR.markInvalid(ReturnVisitor::getTag(), StackFrame);
1040  }
1041 };
1042 
1043 } // namespace
1044 
1045 void FindLastStoreBRVisitor::Profile(llvm::FoldingSetNodeID &ID) const {
1046  static int tag = 0;
1047  ID.AddPointer(&tag);
1048  ID.AddPointer(R);
1049  ID.Add(V);
1050  ID.AddBoolean(EnableNullFPSuppression);
1051 }
1052 
1053 /// Returns true if \p N represents the DeclStmt declaring and initializing
1054 /// \p VR.
1055 static bool isInitializationOfVar(const ExplodedNode *N, const VarRegion *VR) {
1056  Optional<PostStmt> P = N->getLocationAs<PostStmt>();
1057  if (!P)
1058  return false;
1059 
1060  const DeclStmt *DS = P->getStmtAs<DeclStmt>();
1061  if (!DS)
1062  return false;
1063 
1064  if (DS->getSingleDecl() != VR->getDecl())
1065  return false;
1066 
1067  const MemSpaceRegion *VarSpace = VR->getMemorySpace();
1068  const auto *FrameSpace = dyn_cast<StackSpaceRegion>(VarSpace);
1069  if (!FrameSpace) {
1070  // If we ever directly evaluate global DeclStmts, this assertion will be
1071  // invalid, but this still seems preferable to silently accepting an
1072  // initialization that may be for a path-sensitive variable.
1073  assert(VR->getDecl()->isStaticLocal() && "non-static stackless VarRegion");
1074  return true;
1075  }
1076 
1077  assert(VR->getDecl()->hasLocalStorage());
1078  const LocationContext *LCtx = N->getLocationContext();
1079  return FrameSpace->getStackFrame() == LCtx->getStackFrame();
1080 }
1081 
1082 /// Show diagnostics for initializing or declaring a region \p R with a bad value.
1083 static void showBRDiagnostics(const char *action, llvm::raw_svector_ostream &os,
1084  const MemRegion *R, SVal V, const DeclStmt *DS) {
1085  if (R->canPrintPretty()) {
1086  R->printPretty(os);
1087  os << " ";
1088  }
1089 
1090  if (V.getAs<loc::ConcreteInt>()) {
1091  bool b = false;
1092  if (R->isBoundable()) {
1093  if (const auto *TR = dyn_cast<TypedValueRegion>(R)) {
1094  if (TR->getValueType()->isObjCObjectPointerType()) {
1095  os << action << "nil";
1096  b = true;
1097  }
1098  }
1099  }
1100  if (!b)
1101  os << action << "a null pointer value";
1102 
1103  } else if (auto CVal = V.getAs<nonloc::ConcreteInt>()) {
1104  os << action << CVal->getValue();
1105  } else if (DS) {
1106  if (V.isUndef()) {
1107  if (isa<VarRegion>(R)) {
1108  const auto *VD = cast<VarDecl>(DS->getSingleDecl());
1109  if (VD->getInit()) {
1110  os << (R->canPrintPretty() ? "initialized" : "Initializing")
1111  << " to a garbage value";
1112  } else {
1113  os << (R->canPrintPretty() ? "declared" : "Declaring")
1114  << " without an initial value";
1115  }
1116  }
1117  } else {
1118  os << (R->canPrintPretty() ? "initialized" : "Initialized")
1119  << " here";
1120  }
1121  }
1122 }
1123 
1124 /// Display diagnostics for passing bad region as a parameter.
1125 static void showBRParamDiagnostics(llvm::raw_svector_ostream& os,
1126  const VarRegion *VR,
1127  SVal V) {
1128  const auto *Param = cast<ParmVarDecl>(VR->getDecl());
1129 
1130  os << "Passing ";
1131 
1132  if (V.getAs<loc::ConcreteInt>()) {
1133  if (Param->getType()->isObjCObjectPointerType())
1134  os << "nil object reference";
1135  else
1136  os << "null pointer value";
1137  } else if (V.isUndef()) {
1138  os << "uninitialized value";
1139  } else if (auto CI = V.getAs<nonloc::ConcreteInt>()) {
1140  os << "the value " << CI->getValue();
1141  } else {
1142  os << "value";
1143  }
1144 
1145  // Printed parameter indexes are 1-based, not 0-based.
1146  unsigned Idx = Param->getFunctionScopeIndex() + 1;
1147  os << " via " << Idx << llvm::getOrdinalSuffix(Idx) << " parameter";
1148  if (VR->canPrintPretty()) {
1149  os << " ";
1150  VR->printPretty(os);
1151  }
1152 }
1153 
1154 /// Show default diagnostics for storing bad region.
1155 static void showBRDefaultDiagnostics(llvm::raw_svector_ostream& os,
1156  const MemRegion *R,
1157  SVal V) {
1158  if (V.getAs<loc::ConcreteInt>()) {
1159  bool b = false;
1160  if (R->isBoundable()) {
1161  if (const auto *TR = dyn_cast<TypedValueRegion>(R)) {
1162  if (TR->getValueType()->isObjCObjectPointerType()) {
1163  os << "nil object reference stored";
1164  b = true;
1165  }
1166  }
1167  }
1168  if (!b) {
1169  if (R->canPrintPretty())
1170  os << "Null pointer value stored";
1171  else
1172  os << "Storing null pointer value";
1173  }
1174 
1175  } else if (V.isUndef()) {
1176  if (R->canPrintPretty())
1177  os << "Uninitialized value stored";
1178  else
1179  os << "Storing uninitialized value";
1180 
1181  } else if (auto CV = V.getAs<nonloc::ConcreteInt>()) {
1182  if (R->canPrintPretty())
1183  os << "The value " << CV->getValue() << " is assigned";
1184  else
1185  os << "Assigning " << CV->getValue();
1186 
1187  } else {
1188  if (R->canPrintPretty())
1189  os << "Value assigned";
1190  else
1191  os << "Assigning value";
1192  }
1193 
1194  if (R->canPrintPretty()) {
1195  os << " to ";
1196  R->printPretty(os);
1197  }
1198 }
1199 
1200 std::shared_ptr<PathDiagnosticPiece>
1201 FindLastStoreBRVisitor::VisitNode(const ExplodedNode *Succ,
1202  BugReporterContext &BRC, BugReport &BR) {
1203  if (Satisfied)
1204  return nullptr;
1205 
1206  const ExplodedNode *StoreSite = nullptr;
1207  const ExplodedNode *Pred = Succ->getFirstPred();
1208  const Expr *InitE = nullptr;
1209  bool IsParam = false;
1210 
1211  // First see if we reached the declaration of the region.
1212  if (const auto *VR = dyn_cast<VarRegion>(R)) {
1213  if (isInitializationOfVar(Pred, VR)) {
1214  StoreSite = Pred;
1215  InitE = VR->getDecl()->getInit();
1216  }
1217  }
1218 
1219  // If this is a post initializer expression, initializing the region, we
1220  // should track the initializer expression.
1221  if (Optional<PostInitializer> PIP = Pred->getLocationAs<PostInitializer>()) {
1222  const MemRegion *FieldReg = (const MemRegion *)PIP->getLocationValue();
1223  if (FieldReg && FieldReg == R) {
1224  StoreSite = Pred;
1225  InitE = PIP->getInitializer()->getInit();
1226  }
1227  }
1228 
1229  // Otherwise, see if this is the store site:
1230  // (1) Succ has this binding and Pred does not, i.e. this is
1231  // where the binding first occurred.
1232  // (2) Succ has this binding and is a PostStore node for this region, i.e.
1233  // the same binding was re-assigned here.
1234  if (!StoreSite) {
1235  if (Succ->getState()->getSVal(R) != V)
1236  return nullptr;
1237 
1238  if (hasVisibleUpdate(Pred, Pred->getState()->getSVal(R), Succ, V)) {
1239  Optional<PostStore> PS = Succ->getLocationAs<PostStore>();
1240  if (!PS || PS->getLocationValue() != R)
1241  return nullptr;
1242  }
1243 
1244  StoreSite = Succ;
1245 
1246  // If this is an assignment expression, we can track the value
1247  // being assigned.
1248  if (Optional<PostStmt> P = Succ->getLocationAs<PostStmt>())
1249  if (const BinaryOperator *BO = P->getStmtAs<BinaryOperator>())
1250  if (BO->isAssignmentOp())
1251  InitE = BO->getRHS();
1252 
1253  // If this is a call entry, the variable should be a parameter.
1254  // FIXME: Handle CXXThisRegion as well. (This is not a priority because
1255  // 'this' should never be NULL, but this visitor isn't just for NULL and
1256  // UndefinedVal.)
1257  if (Optional<CallEnter> CE = Succ->getLocationAs<CallEnter>()) {
1258  if (const auto *VR = dyn_cast<VarRegion>(R)) {
1259 
1260  const auto *Param = cast<ParmVarDecl>(VR->getDecl());
1261 
1262  ProgramStateManager &StateMgr = BRC.getStateManager();
1263  CallEventManager &CallMgr = StateMgr.getCallEventManager();
1264 
1265  CallEventRef<> Call = CallMgr.getCaller(CE->getCalleeContext(),
1266  Succ->getState());
1267  InitE = Call->getArgExpr(Param->getFunctionScopeIndex());
1268  IsParam = true;
1269  }
1270  }
1271 
1272  // If this is a CXXTempObjectRegion, the Expr responsible for its creation
1273  // is wrapped inside of it.
1274  if (const auto *TmpR = dyn_cast<CXXTempObjectRegion>(R))
1275  InitE = TmpR->getExpr();
1276  }
1277 
1278  if (!StoreSite)
1279  return nullptr;
1280  Satisfied = true;
1281 
1282  // If we have an expression that provided the value, try to track where it
1283  // came from.
1284  if (InitE) {
1285  if (V.isUndef() ||
1286  V.getAs<loc::ConcreteInt>() || V.getAs<nonloc::ConcreteInt>()) {
1287  if (!IsParam)
1288  InitE = InitE->IgnoreParenCasts();
1289  bugreporter::trackExpressionValue(StoreSite, InitE, BR,
1290  EnableNullFPSuppression);
1291  }
1292  ReturnVisitor::addVisitorIfNecessary(StoreSite, InitE->IgnoreParenCasts(),
1293  BR, EnableNullFPSuppression);
1294  }
1295 
1296  // Okay, we've found the binding. Emit an appropriate message.
1297  SmallString<256> sbuf;
1298  llvm::raw_svector_ostream os(sbuf);
1299 
1300  if (Optional<PostStmt> PS = StoreSite->getLocationAs<PostStmt>()) {
1301  const Stmt *S = PS->getStmt();
1302  const char *action = nullptr;
1303  const auto *DS = dyn_cast<DeclStmt>(S);
1304  const auto *VR = dyn_cast<VarRegion>(R);
1305 
1306  if (DS) {
1307  action = R->canPrintPretty() ? "initialized to " :
1308  "Initializing to ";
1309  } else if (isa<BlockExpr>(S)) {
1310  action = R->canPrintPretty() ? "captured by block as " :
1311  "Captured by block as ";
1312  if (VR) {
1313  // See if we can get the BlockVarRegion.
1314  ProgramStateRef State = StoreSite->getState();
1315  SVal V = StoreSite->getSVal(S);
1316  if (const auto *BDR =
1317  dyn_cast_or_null<BlockDataRegion>(V.getAsRegion())) {
1318  if (const VarRegion *OriginalR = BDR->getOriginalRegion(VR)) {
1319  if (auto KV = State->getSVal(OriginalR).getAs<KnownSVal>())
1320  BR.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
1321  *KV, OriginalR, EnableNullFPSuppression));
1322  }
1323  }
1324  }
1325  }
1326  if (action)
1327  showBRDiagnostics(action, os, R, V, DS);
1328 
1329  } else if (StoreSite->getLocation().getAs<CallEnter>()) {
1330  if (const auto *VR = dyn_cast<VarRegion>(R))
1331  showBRParamDiagnostics(os, VR, V);
1332  }
1333 
1334  if (os.str().empty())
1335  showBRDefaultDiagnostics(os, R, V);
1336 
1337  // Construct a new PathDiagnosticPiece.
1338  ProgramPoint P = StoreSite->getLocation();
1339  PathDiagnosticLocation L;
1340  if (P.getAs<CallEnter>() && InitE)
1341  L = PathDiagnosticLocation(InitE, BRC.getSourceManager(),
1342  P.getLocationContext());
1343 
1344  if (!L.isValid() || !L.asLocation().isValid())
1345  L = PathDiagnosticLocation::create(P, BRC.getSourceManager());
1346 
1347  if (!L.isValid() || !L.asLocation().isValid())
1348  return nullptr;
1349 
1350  return std::make_shared<PathDiagnosticEventPiece>(L, os.str());
1351 }
1352 
1353 void TrackConstraintBRVisitor::Profile(llvm::FoldingSetNodeID &ID) const {
1354  static int tag = 0;
1355  ID.AddPointer(&tag);
1356  ID.AddBoolean(Assumption);
1357  ID.Add(Constraint);
1358 }
1359 
1360 /// Return the tag associated with this visitor. This tag will be used
1361 /// to make all PathDiagnosticPieces created by this visitor.
1362 const char *TrackConstraintBRVisitor::getTag() {
1363  return "TrackConstraintBRVisitor";
1364 }
1365 
1366 bool TrackConstraintBRVisitor::isUnderconstrained(const ExplodedNode *N) const {
1367  if (IsZeroCheck)
1368  return N->getState()->isNull(Constraint).isUnderconstrained();
1369  return (bool)N->getState()->assume(Constraint, !Assumption);
1370 }
1371 
1372 std::shared_ptr<PathDiagnosticPiece>
1373 TrackConstraintBRVisitor::VisitNode(const ExplodedNode *N,
1374  BugReporterContext &BRC, BugReport &) {
1375  const ExplodedNode *PrevN = N->getFirstPred();
1376  if (IsSatisfied)
1377  return nullptr;
1378 
1379  // Start tracking after we see the first state in which the value is
1380  // constrained.
1381  if (!IsTrackingTurnedOn)
1382  if (!isUnderconstrained(N))
1383  IsTrackingTurnedOn = true;
1384  if (!IsTrackingTurnedOn)
1385  return nullptr;
1386 
1387  // Check if in the previous state it was feasible for this constraint
1388  // to *not* be true.
1389  if (isUnderconstrained(PrevN)) {
1390  IsSatisfied = true;
1391 
1392  // As a sanity check, make sure that the negation of the constraint
1393  // was infeasible in the current state. If it is feasible, we somehow
1394  // missed the transition point.
1395  assert(!isUnderconstrained(N));
1396 
1397  // We found the transition point for the constraint. We now need to
1398  // pretty-print the constraint. (work-in-progress)
1399  SmallString<64> sbuf;
1400  llvm::raw_svector_ostream os(sbuf);
1401 
1402  if (Constraint.getAs<Loc>()) {
1403  os << "Assuming pointer value is ";
1404  os << (Assumption ? "non-null" : "null");
1405  }
1406 
1407  if (os.str().empty())
1408  return nullptr;
1409 
1410  // Construct a new PathDiagnosticPiece.
1411  ProgramPoint P = N->getLocation();
1412  PathDiagnosticLocation L =
1413  PathDiagnosticLocation::create(P, BRC.getSourceManager());
1414  if (!L.isValid())
1415  return nullptr;
1416 
1417  auto X = std::make_shared<PathDiagnosticEventPiece>(L, os.str());
1418  X->setTag(getTag());
1419  return std::move(X);
1420  }
1421 
1422  return nullptr;
1423 }
1424 
1425 SuppressInlineDefensiveChecksVisitor::
1426 SuppressInlineDefensiveChecksVisitor(DefinedSVal Value, const ExplodedNode *N)
1427  : V(Value) {
1428  // Check if the visitor is disabled.
1429  AnalyzerOptions &Options = N->getState()->getAnalysisManager().options;
1430  if (!Options.ShouldSuppressInlinedDefensiveChecks)
1431  IsSatisfied = true;
1432 
1433  assert(N->getState()->isNull(V).isConstrainedTrue() &&
1434  "The visitor only tracks the cases where V is constrained to 0");
1435 }
1436 
1437 void SuppressInlineDefensiveChecksVisitor::Profile(
1438  llvm::FoldingSetNodeID &ID) const {
1439  static int id = 0;
1440  ID.AddPointer(&id);
1441  ID.Add(V);
1442 }
1443 
1444 const char *SuppressInlineDefensiveChecksVisitor::getTag() {
1445  return "IDCVisitor";
1446 }
1447 
1448 std::shared_ptr<PathDiagnosticPiece>
1449 SuppressInlineDefensiveChecksVisitor::VisitNode(const ExplodedNode *Succ,
1450  BugReporterContext &BRC,
1451  BugReport &BR) {
1452  const ExplodedNode *Pred = Succ->getFirstPred();
1453  if (IsSatisfied)
1454  return nullptr;
1455 
1456  // Start tracking after we see the first state in which the value is null.
1457  if (!IsTrackingTurnedOn)
1458  if (Succ->getState()->isNull(V).isConstrainedTrue())
1459  IsTrackingTurnedOn = true;
1460  if (!IsTrackingTurnedOn)
1461  return nullptr;
1462 
1463  // Check if in the previous state it was feasible for this value
1464  // to *not* be null.
1465  if (!Pred->getState()->isNull(V).isConstrainedTrue()) {
1466  IsSatisfied = true;
1467 
1468  assert(Succ->getState()->isNull(V).isConstrainedTrue());
1469 
1470  // Check if this is inlined defensive checks.
1471  const LocationContext *CurLC =Succ->getLocationContext();
1472  const LocationContext *ReportLC = BR.getErrorNode()->getLocationContext();
1473  if (CurLC != ReportLC && !CurLC->isParentOf(ReportLC)) {
1474  BR.markInvalid("Suppress IDC", CurLC);
1475  return nullptr;
1476  }
1477 
1478  // Treat defensive checks in function-like macros as if they were an inlined
1479  // defensive check. If the bug location is not in a macro and the
1480  // terminator for the current location is in a macro then suppress the
1481  // warning.
1482  auto BugPoint = BR.getErrorNode()->getLocation().getAs<StmtPoint>();
1483 
1484  if (!BugPoint)
1485  return nullptr;
1486 
1487  ProgramPoint CurPoint = Succ->getLocation();
1488  const Stmt *CurTerminatorStmt = nullptr;
1489  if (auto BE = CurPoint.getAs<BlockEdge>()) {
1490  CurTerminatorStmt = BE->getSrc()->getTerminator().getStmt();
1491  } else if (auto SP = CurPoint.getAs<StmtPoint>()) {
1492  const Stmt *CurStmt = SP->getStmt();
1493  if (!CurStmt->getBeginLoc().isMacroID())
1494  return nullptr;
1495 
1496  CFGStmtMap *Map = CurLC->getAnalysisDeclContext()->getCFGStmtMap();
1497  CurTerminatorStmt = Map->getBlock(CurStmt)->getTerminator();
1498  } else {
1499  return nullptr;
1500  }
1501 
1502  if (!CurTerminatorStmt)
1503  return nullptr;
1504 
1505  SourceLocation TerminatorLoc = CurTerminatorStmt->getBeginLoc();
1506  if (TerminatorLoc.isMacroID()) {
1507  SourceLocation BugLoc = BugPoint->getStmt()->getBeginLoc();
1508 
1509  // Suppress reports unless we are in that same macro.
1510  if (!BugLoc.isMacroID() ||
1511  getMacroName(BugLoc, BRC) != getMacroName(TerminatorLoc, BRC)) {
1512  BR.markInvalid("Suppress Macro IDC", CurLC);
1513  }
1514  return nullptr;
1515  }
1516  }
1517  return nullptr;
1518 }
1519 
1520 static const MemRegion *getLocationRegionIfReference(const Expr *E,
1521  const ExplodedNode *N) {
1522  if (const auto *DR = dyn_cast<DeclRefExpr>(E)) {
1523  if (const auto *VD = dyn_cast<VarDecl>(DR->getDecl())) {
1524  if (!VD->getType()->isReferenceType())
1525  return nullptr;
1526  ProgramStateManager &StateMgr = N->getState()->getStateManager();
1527  MemRegionManager &MRMgr = StateMgr.getRegionManager();
1528  return MRMgr.getVarRegion(VD, N->getLocationContext());
1529  }
1530  }
1531 
1532  // FIXME: This does not handle other kinds of null references,
1533  // for example, references from FieldRegions:
1534  // struct Wrapper { int &ref; };
1535  // Wrapper w = { *(int *)0 };
1536  // w.ref = 1;
1537 
1538  return nullptr;
1539 }
1540 
1541 /// \return A subexpression of {@code Ex} which represents the
1542 /// expression-of-interest.
1543 static const Expr *peelOffOuterExpr(const Expr *Ex,
1544  const ExplodedNode *N) {
1545  Ex = Ex->IgnoreParenCasts();
1546  if (const auto *FE = dyn_cast<FullExpr>(Ex))
1547  return peelOffOuterExpr(FE->getSubExpr(), N);
1548  if (const auto *OVE = dyn_cast<OpaqueValueExpr>(Ex))
1549  return peelOffOuterExpr(OVE->getSourceExpr(), N);
1550  if (const auto *POE = dyn_cast<PseudoObjectExpr>(Ex)) {
1551  const auto *PropRef = dyn_cast<ObjCPropertyRefExpr>(POE->getSyntacticForm());
1552  if (PropRef && PropRef->isMessagingGetter()) {
1553  const Expr *GetterMessageSend =
1554  POE->getSemanticExpr(POE->getNumSemanticExprs() - 1);
1555  assert(isa<ObjCMessageExpr>(GetterMessageSend->IgnoreParenCasts()));
1556  return peelOffOuterExpr(GetterMessageSend, N);
1557  }
1558  }
1559 
1560  // Peel off the ternary operator.
1561  if (const auto *CO = dyn_cast<ConditionalOperator>(Ex)) {
1562  // Find a node where the branching occurred and find out which branch
1563  // we took (true/false) by looking at the ExplodedGraph.
1564  const ExplodedNode *NI = N;
1565  do {
1566  ProgramPoint ProgPoint = NI->getLocation();
1567  if (Optional<BlockEdge> BE = ProgPoint.getAs<BlockEdge>()) {
1568  const CFGBlock *srcBlk = BE->getSrc();
1569  if (const Stmt *term = srcBlk->getTerminator()) {
1570  if (term == CO) {
1571  bool TookTrueBranch = (*(srcBlk->succ_begin()) == BE->getDst());
1572  if (TookTrueBranch)
1573  return peelOffOuterExpr(CO->getTrueExpr(), N);
1574  else
1575  return peelOffOuterExpr(CO->getFalseExpr(), N);
1576  }
1577  }
1578  }
1579  NI = NI->getFirstPred();
1580  } while (NI);
1581  }
1582 
1583  if (auto *BO = dyn_cast<BinaryOperator>(Ex))
1584  if (const Expr *SubEx = peelOffPointerArithmetic(BO))
1585  return peelOffOuterExpr(SubEx, N);
1586 
1587  if (auto *UO = dyn_cast<UnaryOperator>(Ex)) {
1588  if (UO->getOpcode() == UO_LNot)
1589  return peelOffOuterExpr(UO->getSubExpr(), N);
1590 
1591  // FIXME: There's a hack in our Store implementation that always computes
1592  // field offsets around null pointers as if they are always equal to 0.
1593  // The idea here is to report accesses to fields as null dereferences
1594  // even though the pointer value that's being dereferenced is actually
1595  // the offset of the field rather than exactly 0.
1596  // See the FIXME in StoreManager's getLValueFieldOrIvar() method.
1597  // This code interacts heavily with this hack; otherwise the value
1598  // would not be null at all for most fields, so we'd be unable to track it.
1599  if (UO->getOpcode() == UO_AddrOf && UO->getSubExpr()->isLValue())
1600  if (const Expr *DerefEx = bugreporter::getDerefExpr(UO->getSubExpr()))
1601  return peelOffOuterExpr(DerefEx, N);
1602  }
1603 
1604  return Ex;
1605 }
1606 
1607 /// Find the ExplodedNode where the lvalue (the value of 'Ex')
1608 /// was computed.
1609 static const ExplodedNode* findNodeForExpression(const ExplodedNode *N,
1610  const Expr *Inner) {
1611  while (N) {
1612  if (PathDiagnosticLocation::getStmt(N) == Inner)
1613  return N;
1614  N = N->getFirstPred();
1615  }
1616  return N;
1617 }
1618 
1619 bool bugreporter::trackExpressionValue(const ExplodedNode *InputNode,
1620  const Expr *E, BugReport &report,
1621  bool EnableNullFPSuppression) {
1622  if (!E || !InputNode)
1623  return false;
1624 
1625  const Expr *Inner = peelOffOuterExpr(E, InputNode);
1626  const ExplodedNode *LVNode = findNodeForExpression(InputNode, Inner);
1627  if (!LVNode)
1628  return false;
1629 
1630  ProgramStateRef LVState = LVNode->getState();
1631 
1632  // The message send could be nil due to the receiver being nil.
1633  // At this point in the path, the receiver should be live since we are at the
1634  // message send expr. If it is nil, start tracking it.
1635  if (const Expr *Receiver = NilReceiverBRVisitor::getNilReceiver(Inner, LVNode))
1636  trackExpressionValue(LVNode, Receiver, report, EnableNullFPSuppression);
1637 
1638  // See if the expression we're interested refers to a variable.
1639  // If so, we can track both its contents and constraints on its value.
1641  SVal LVal = LVNode->getSVal(Inner);
1642 
1643  const MemRegion *RR = getLocationRegionIfReference(Inner, LVNode);
1644  bool LVIsNull = LVState->isNull(LVal).isConstrainedTrue();
1645 
1646  // If this is a C++ reference to a null pointer, we are tracking the
1647  // pointer. In addition, we should find the store at which the reference
1648  // got initialized.
1649  if (RR && !LVIsNull)
1650  if (auto KV = LVal.getAs<KnownSVal>())
1651  report.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
1652  *KV, RR, EnableNullFPSuppression));
1653 
1654  // In case of C++ references, we want to differentiate between a null
1655  // reference and reference to null pointer.
1656  // If the LVal is null, check if we are dealing with null reference.
1657  // For those, we want to track the location of the reference.
1658  const MemRegion *R = (RR && LVIsNull) ? RR :
1659  LVNode->getSVal(Inner).getAsRegion();
1660 
1661  if (R) {
1662 
1663  // Mark both the variable region and its contents as interesting.
1664  SVal V = LVState->getRawSVal(loc::MemRegionVal(R));
1665  report.addVisitor(
1666  llvm::make_unique<NoStoreFuncVisitor>(cast<SubRegion>(R)));
1667 
1668  MacroNullReturnSuppressionVisitor::addMacroVisitorIfNecessary(
1669  LVNode, R, EnableNullFPSuppression, report, V);
1670 
1671  report.markInteresting(V);
1672  report.addVisitor(llvm::make_unique<UndefOrNullArgVisitor>(R));
1673 
1674  // If the contents are symbolic, find out when they became null.
1675  if (V.getAsLocSymbol(/*IncludeBaseRegions*/ true))
1676  report.addVisitor(llvm::make_unique<TrackConstraintBRVisitor>(
1677  V.castAs<DefinedSVal>(), false));
1678 
1679  // Add visitor, which will suppress inline defensive checks.
1680  if (auto DV = V.getAs<DefinedSVal>())
1681  if (!DV->isZeroConstant() && LVState->isNull(*DV).isConstrainedTrue() &&
1682  EnableNullFPSuppression)
1683  report.addVisitor(
1684  llvm::make_unique<SuppressInlineDefensiveChecksVisitor>(*DV,
1685  LVNode));
1686 
1687  if (auto KV = V.getAs<KnownSVal>())
1688  report.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
1689  *KV, R, EnableNullFPSuppression));
1690  return true;
1691  }
1692  }
1693 
1694  // If the expression is not an "lvalue expression", we can still
1695  // track the constraints on its contents.
1696  SVal V = LVState->getSValAsScalarOrLoc(Inner, LVNode->getLocationContext());
1697 
1698  ReturnVisitor::addVisitorIfNecessary(
1699  LVNode, Inner, report, EnableNullFPSuppression);
1700 
1701  // Is it a symbolic value?
1702  if (auto L = V.getAs<loc::MemRegionVal>()) {
1703  report.addVisitor(llvm::make_unique<UndefOrNullArgVisitor>(L->getRegion()));
1704 
1705  // FIXME: this is a hack for fixing a later crash when attempting to
1706  // dereference a void* pointer.
1707  // We should not try to dereference pointers at all when we don't care
1708  // what is written inside the pointer.
1709  bool CanDereference = true;
1710  if (const auto *SR = dyn_cast<SymbolicRegion>(L->getRegion()))
1711  if (SR->getSymbol()->getType()->getPointeeType()->isVoidType())
1712  CanDereference = false;
1713 
1714  // At this point we are dealing with the region's LValue.
1715  // However, if the rvalue is a symbolic region, we should track it as well.
1716  // Try to use the correct type when looking up the value.
1717  SVal RVal;
1719  RVal = LVState->getRawSVal(L.getValue(), Inner->getType());
1720  } else if (CanDereference) {
1721  RVal = LVState->getSVal(L->getRegion());
1722  }
1723 
1724  if (CanDereference)
1725  if (auto KV = RVal.getAs<KnownSVal>())
1726  report.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
1727  *KV, L->getRegion(), EnableNullFPSuppression));
1728 
1729  const MemRegion *RegionRVal = RVal.getAsRegion();
1730  if (RegionRVal && isa<SymbolicRegion>(RegionRVal)) {
1731  report.markInteresting(RegionRVal);
1732  report.addVisitor(llvm::make_unique<TrackConstraintBRVisitor>(
1733  loc::MemRegionVal(RegionRVal), /*assumption=*/false));
1734  }
1735  }
1736  return true;
1737 }
1738 
1739 const Expr *NilReceiverBRVisitor::getNilReceiver(const Stmt *S,
1740  const ExplodedNode *N) {
1741  const auto *ME = dyn_cast<ObjCMessageExpr>(S);
1742  if (!ME)
1743  return nullptr;
1744  if (const Expr *Receiver = ME->getInstanceReceiver()) {
1745  ProgramStateRef state = N->getState();
1746  SVal V = N->getSVal(Receiver);
1747  if (state->isNull(V).isConstrainedTrue())
1748  return Receiver;
1749  }
1750  return nullptr;
1751 }
1752 
1753 std::shared_ptr<PathDiagnosticPiece>
1754 NilReceiverBRVisitor::VisitNode(const ExplodedNode *N,
1755  BugReporterContext &BRC, BugReport &BR) {
1756  Optional<PreStmt> P = N->getLocationAs<PreStmt>();
1757  if (!P)
1758  return nullptr;
1759 
1760  const Stmt *S = P->getStmt();
1761  const Expr *Receiver = getNilReceiver(S, N);
1762  if (!Receiver)
1763  return nullptr;
1764 
1766  llvm::raw_svector_ostream OS(Buf);
1767 
1768  if (const auto *ME = dyn_cast<ObjCMessageExpr>(S)) {
1769  OS << "'";
1770  ME->getSelector().print(OS);
1771  OS << "' not called";
1772  }
1773  else {
1774  OS << "No method is called";
1775  }
1776  OS << " because the receiver is nil";
1777 
1778  // The receiver was nil, and hence the method was skipped.
1779  // Register a BugReporterVisitor to issue a message telling us how
1780  // the receiver was null.
1781  bugreporter::trackExpressionValue(N, Receiver, BR,
1782  /*EnableNullFPSuppression*/ false);
1783  // Issue a message saying that the method was skipped.
1784  PathDiagnosticLocation L(Receiver, BRC.getSourceManager(),
1785  N->getLocationContext());
1786  return std::make_shared<PathDiagnosticEventPiece>(L, OS.str());
1787 }
1788 
1789 // Registers every VarDecl inside a Stmt with a last store visitor.
1790 void FindLastStoreBRVisitor::registerStatementVarDecls(BugReport &BR,
1791  const Stmt *S,
1792  bool EnableNullFPSuppression) {
1793  const ExplodedNode *N = BR.getErrorNode();
1794  std::deque<const Stmt *> WorkList;
1795  WorkList.push_back(S);
1796 
1797  while (!WorkList.empty()) {
1798  const Stmt *Head = WorkList.front();
1799  WorkList.pop_front();
1800 
1801  ProgramStateManager &StateMgr = N->getState()->getStateManager();
1802 
1803  if (const auto *DR = dyn_cast<DeclRefExpr>(Head)) {
1804  if (const auto *VD = dyn_cast<VarDecl>(DR->getDecl())) {
1805  const VarRegion *R =
1806  StateMgr.getRegionManager().getVarRegion(VD, N->getLocationContext());
1807 
1808  // What did we load?
1809  SVal V = N->getSVal(S);
1810 
1811  if (V.getAs<loc::ConcreteInt>() || V.getAs<nonloc::ConcreteInt>()) {
1812  // Register a new visitor with the BugReport.
1813  BR.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
1814  V.castAs<KnownSVal>(), R, EnableNullFPSuppression));
1815  }
1816  }
1817  }
1818 
1819  for (const Stmt *SubStmt : Head->children())
1820  WorkList.push_back(SubStmt);
1821  }
1822 }
1823 
1824 //===----------------------------------------------------------------------===//
1825 // Visitor that tries to report interesting diagnostics from conditions.
1826 //===----------------------------------------------------------------------===//
1827 
1828 /// Return the tag associated with this visitor. This tag will be used
1829 /// to make all PathDiagnosticPieces created by this visitor.
1830 const char *ConditionBRVisitor::getTag() {
1831  return "ConditionBRVisitor";
1832 }
1833 
1834 std::shared_ptr<PathDiagnosticPiece>
1835 ConditionBRVisitor::VisitNode(const ExplodedNode *N,
1836  BugReporterContext &BRC, BugReport &BR) {
1837  auto piece = VisitNodeImpl(N, BRC, BR);
1838  if (piece) {
1839  piece->setTag(getTag());
1840  if (auto *ev = dyn_cast<PathDiagnosticEventPiece>(piece.get()))
1841  ev->setPrunable(true, /* override */ false);
1842  }
1843  return piece;
1844 }
1845 
1846 std::shared_ptr<PathDiagnosticPiece>
1847 ConditionBRVisitor::VisitNodeImpl(const ExplodedNode *N,
1848  BugReporterContext &BRC, BugReport &BR) {
1849  ProgramPoint progPoint = N->getLocation();
1850 
1851  // If an assumption was made on a branch, it should be caught
1852  // here by looking at the state transition.
1853  if (Optional<BlockEdge> BE = progPoint.getAs<BlockEdge>()) {
1854  const CFGBlock *srcBlk = BE->getSrc();
1855  if (const Stmt *term = srcBlk->getTerminator())
1856  return VisitTerminator(term, N, srcBlk, BE->getDst(), BR, BRC);
1857  return nullptr;
1858  }
1859 
1860  if (Optional<PostStmt> PS = progPoint.getAs<PostStmt>()) {
1861  const std::pair<const ProgramPointTag *, const ProgramPointTag *> &tags =
1863 
1864  const ProgramPointTag *tag = PS->getTag();
1865  if (tag == tags.first)
1866  return VisitTrueTest(cast<Expr>(PS->getStmt()), true,
1867  BRC, BR, N);
1868  if (tag == tags.second)
1869  return VisitTrueTest(cast<Expr>(PS->getStmt()), false,
1870  BRC, BR, N);
1871 
1872  return nullptr;
1873  }
1874 
1875  return nullptr;
1876 }
1877 
1878 std::shared_ptr<PathDiagnosticPiece> ConditionBRVisitor::VisitTerminator(
1879  const Stmt *Term, const ExplodedNode *N, const CFGBlock *srcBlk,
1880  const CFGBlock *dstBlk, BugReport &R, BugReporterContext &BRC) {
1881  const Expr *Cond = nullptr;
1882 
1883  // In the code below, Term is a CFG terminator and Cond is a branch condition
1884  // expression upon which the decision is made on this terminator.
1885  //
1886  // For example, in "if (x == 0)", the "if (x == 0)" statement is a terminator,
1887  // and "x == 0" is the respective condition.
1888  //
1889  // Another example: in "if (x && y)", we've got two terminators and two
1890  // conditions due to short-circuit nature of operator "&&":
1891  // 1. The "if (x && y)" statement is a terminator,
1892  // and "y" is the respective condition.
1893  // 2. Also "x && ..." is another terminator,
1894  // and "x" is its condition.
1895 
1896  switch (Term->getStmtClass()) {
1897  // FIXME: Stmt::SwitchStmtClass is worth handling, however it is a bit
1898  // more tricky because there are more than two branches to account for.
1899  default:
1900  return nullptr;
1901  case Stmt::IfStmtClass:
1902  Cond = cast<IfStmt>(Term)->getCond();
1903  break;
1904  case Stmt::ConditionalOperatorClass:
1905  Cond = cast<ConditionalOperator>(Term)->getCond();
1906  break;
1907  case Stmt::BinaryOperatorClass:
1908  // When we encounter a logical operator (&& or ||) as a CFG terminator,
1909  // then the condition is actually its LHS; otherwise, we'd encounter
1910  // the parent, such as if-statement, as a terminator.
1911  const auto *BO = cast<BinaryOperator>(Term);
1912  assert(BO->isLogicalOp() &&
1913  "CFG terminator is not a short-circuit operator!");
1914  Cond = BO->getLHS();
1915  break;
1916  }
1917 
1918  Cond = Cond->IgnoreParens();
1919 
1920  // However, when we encounter a logical operator as a branch condition,
1921  // then the condition is actually its RHS, because LHS would be
1922  // the condition for the logical operator terminator.
1923  while (const auto *InnerBO = dyn_cast<BinaryOperator>(Cond)) {
1924  if (!InnerBO->isLogicalOp())
1925  break;
1926  Cond = InnerBO->getRHS()->IgnoreParens();
1927  }
1928 
1929  assert(Cond);
1930  assert(srcBlk->succ_size() == 2);
1931  const bool tookTrue = *(srcBlk->succ_begin()) == dstBlk;
1932  return VisitTrueTest(Cond, tookTrue, BRC, R, N);
1933 }
1934 
1935 std::shared_ptr<PathDiagnosticPiece>
1936 ConditionBRVisitor::VisitTrueTest(const Expr *Cond, bool tookTrue,
1937  BugReporterContext &BRC, BugReport &R,
1938  const ExplodedNode *N) {
1939  ProgramStateRef CurrentState = N->getState();
1940  ProgramStateRef PreviousState = N->getFirstPred()->getState();
1941  const LocationContext *LCtx = N->getLocationContext();
1942 
1943  // If the constraint information is changed between the current and the
1944  // previous program state we assuming the newly seen constraint information.
1945  // If we cannot evaluate the condition (and the constraints are the same)
1946  // the analyzer has no information about the value and just assuming it.
1947  if (BRC.getStateManager().haveEqualConstraints(CurrentState, PreviousState) &&
1948  CurrentState->getSVal(Cond, LCtx).isValid())
1949  return nullptr;
1950 
1951  // These will be modified in code below, but we need to preserve the original
1952  // values in case we want to throw the generic message.
1953  const Expr *CondTmp = Cond;
1954  bool tookTrueTmp = tookTrue;
1955 
1956  while (true) {
1957  CondTmp = CondTmp->IgnoreParenCasts();
1958  switch (CondTmp->getStmtClass()) {
1959  default:
1960  break;
1961  case Stmt::BinaryOperatorClass:
1962  if (auto P = VisitTrueTest(Cond, cast<BinaryOperator>(CondTmp),
1963  tookTrueTmp, BRC, R, N))
1964  return P;
1965  break;
1966  case Stmt::DeclRefExprClass:
1967  if (auto P = VisitTrueTest(Cond, cast<DeclRefExpr>(CondTmp),
1968  tookTrueTmp, BRC, R, N))
1969  return P;
1970  break;
1971  case Stmt::UnaryOperatorClass: {
1972  const auto *UO = cast<UnaryOperator>(CondTmp);
1973  if (UO->getOpcode() == UO_LNot) {
1974  tookTrueTmp = !tookTrueTmp;
1975  CondTmp = UO->getSubExpr();
1976  continue;
1977  }
1978  break;
1979  }
1980  }
1981  break;
1982  }
1983 
1984  // Condition too complex to explain? Just say something so that the user
1985  // knew we've made some path decision at this point.
1986  PathDiagnosticLocation Loc(Cond, BRC.getSourceManager(), LCtx);
1987  if (!Loc.isValid() || !Loc.asLocation().isValid())
1988  return nullptr;
1989 
1990  return std::make_shared<PathDiagnosticEventPiece>(
1991  Loc, tookTrue ? GenericTrueMessage : GenericFalseMessage);
1992 }
1993 
1994 bool ConditionBRVisitor::patternMatch(const Expr *Ex,
1995  const Expr *ParentEx,
1996  raw_ostream &Out,
1997  BugReporterContext &BRC,
1998  BugReport &report,
1999  const ExplodedNode *N,
2000  Optional<bool> &prunable) {
2001  const Expr *OriginalExpr = Ex;
2002  Ex = Ex->IgnoreParenCasts();
2003 
2004  if (isa<GNUNullExpr>(Ex) || isa<ObjCBoolLiteralExpr>(Ex) ||
2005  isa<CXXBoolLiteralExpr>(Ex) || isa<IntegerLiteral>(Ex) ||
2006  isa<FloatingLiteral>(Ex)) {
2007  // Use heuristics to determine if the expression is a macro
2008  // expanding to a literal and if so, use the macro's name.
2009  SourceLocation BeginLoc = OriginalExpr->getBeginLoc();
2010  SourceLocation EndLoc = OriginalExpr->getEndLoc();
2011  if (BeginLoc.isMacroID() && EndLoc.isMacroID()) {
2012  SourceManager &SM = BRC.getSourceManager();
2013  const LangOptions &LO = BRC.getASTContext().getLangOpts();
2014  if (Lexer::isAtStartOfMacroExpansion(BeginLoc, SM, LO) &&
2015  Lexer::isAtEndOfMacroExpansion(EndLoc, SM, LO)) {
2016  CharSourceRange R = Lexer::getAsCharRange({BeginLoc, EndLoc}, SM, LO);
2017  Out << Lexer::getSourceText(R, SM, LO);
2018  return false;
2019  }
2020  }
2021  }
2022 
2023  if (const auto *DR = dyn_cast<DeclRefExpr>(Ex)) {
2024  const bool quotes = isa<VarDecl>(DR->getDecl());
2025  if (quotes) {
2026  Out << '\'';
2027  const LocationContext *LCtx = N->getLocationContext();
2028  const ProgramState *state = N->getState().get();
2029  if (const MemRegion *R = state->getLValue(cast<VarDecl>(DR->getDecl()),
2030  LCtx).getAsRegion()) {
2031  if (report.isInteresting(R))
2032  prunable = false;
2033  else {
2034  const ProgramState *state = N->getState().get();
2035  SVal V = state->getSVal(R);
2036  if (report.isInteresting(V))
2037  prunable = false;
2038  }
2039  }
2040  }
2041  Out << DR->getDecl()->getDeclName().getAsString();
2042  if (quotes)
2043  Out << '\'';
2044  return quotes;
2045  }
2046 
2047  if (const auto *IL = dyn_cast<IntegerLiteral>(Ex)) {
2048  QualType OriginalTy = OriginalExpr->getType();
2049  if (OriginalTy->isPointerType()) {
2050  if (IL->getValue() == 0) {
2051  Out << "null";
2052  return false;
2053  }
2054  }
2055  else if (OriginalTy->isObjCObjectPointerType()) {
2056  if (IL->getValue() == 0) {
2057  Out << "nil";
2058  return false;
2059  }
2060  }
2061 
2062  Out << IL->getValue();
2063  return false;
2064  }
2065 
2066  return false;
2067 }
2068 
2069 std::shared_ptr<PathDiagnosticPiece>
2070 ConditionBRVisitor::VisitTrueTest(const Expr *Cond, const BinaryOperator *BExpr,
2071  const bool tookTrue, BugReporterContext &BRC,
2072  BugReport &R, const ExplodedNode *N) {
2073  bool shouldInvert = false;
2074  Optional<bool> shouldPrune;
2075 
2076  SmallString<128> LhsString, RhsString;
2077  {
2078  llvm::raw_svector_ostream OutLHS(LhsString), OutRHS(RhsString);
2079  const bool isVarLHS = patternMatch(BExpr->getLHS(), BExpr, OutLHS,
2080  BRC, R, N, shouldPrune);
2081  const bool isVarRHS = patternMatch(BExpr->getRHS(), BExpr, OutRHS,
2082  BRC, R, N, shouldPrune);
2083 
2084  shouldInvert = !isVarLHS && isVarRHS;
2085  }
2086 
2087  BinaryOperator::Opcode Op = BExpr->getOpcode();
2088 
2090  // For assignment operators, all that we care about is that the LHS
2091  // evaluates to "true" or "false".
2092  return VisitConditionVariable(LhsString, BExpr->getLHS(), tookTrue,
2093  BRC, R, N);
2094  }
2095 
2096  // For non-assignment operations, we require that we can understand
2097  // both the LHS and RHS.
2098  if (LhsString.empty() || RhsString.empty() ||
2099  !BinaryOperator::isComparisonOp(Op) || Op == BO_Cmp)
2100  return nullptr;
2101 
2102  // Should we invert the strings if the LHS is not a variable name?
2103  SmallString<256> buf;
2104  llvm::raw_svector_ostream Out(buf);
2105  Out << "Assuming " << (shouldInvert ? RhsString : LhsString) << " is ";
2106 
2107  // Do we need to invert the opcode?
2108  if (shouldInvert)
2109  switch (Op) {
2110  default: break;
2111  case BO_LT: Op = BO_GT; break;
2112  case BO_GT: Op = BO_LT; break;
2113  case BO_LE: Op = BO_GE; break;
2114  case BO_GE: Op = BO_LE; break;
2115  }
2116 
2117  if (!tookTrue)
2118  switch (Op) {
2119  case BO_EQ: Op = BO_NE; break;
2120  case BO_NE: Op = BO_EQ; break;
2121  case BO_LT: Op = BO_GE; break;
2122  case BO_GT: Op = BO_LE; break;
2123  case BO_LE: Op = BO_GT; break;
2124  case BO_GE: Op = BO_LT; break;
2125  default:
2126  return nullptr;
2127  }
2128 
2129  switch (Op) {
2130  case BO_EQ:
2131  Out << "equal to ";
2132  break;
2133  case BO_NE:
2134  Out << "not equal to ";
2135  break;
2136  default:
2137  Out << BinaryOperator::getOpcodeStr(Op) << ' ';
2138  break;
2139  }
2140 
2141  Out << (shouldInvert ? LhsString : RhsString);
2142  const LocationContext *LCtx = N->getLocationContext();
2143  PathDiagnosticLocation Loc(Cond, BRC.getSourceManager(), LCtx);
2144  auto event = std::make_shared<PathDiagnosticEventPiece>(Loc, Out.str());
2145  if (shouldPrune.hasValue())
2146  event->setPrunable(shouldPrune.getValue());
2147  return event;
2148 }
2149 
2150 std::shared_ptr<PathDiagnosticPiece> ConditionBRVisitor::VisitConditionVariable(
2151  StringRef LhsString, const Expr *CondVarExpr, const bool tookTrue,
2152  BugReporterContext &BRC, BugReport &report, const ExplodedNode *N) {
2153  // FIXME: If there's already a constraint tracker for this variable,
2154  // we shouldn't emit anything here (c.f. the double note in
2155  // test/Analysis/inlining/path-notes.c)
2156  SmallString<256> buf;
2157  llvm::raw_svector_ostream Out(buf);
2158  Out << "Assuming " << LhsString << " is ";
2159 
2160  QualType Ty = CondVarExpr->getType();
2161 
2162  if (Ty->isPointerType())
2163  Out << (tookTrue ? "not null" : "null");
2164  else if (Ty->isObjCObjectPointerType())
2165  Out << (tookTrue ? "not nil" : "nil");
2166  else if (Ty->isBooleanType())
2167  Out << (tookTrue ? "true" : "false");
2168  else if (Ty->isIntegralOrEnumerationType())
2169  Out << (tookTrue ? "non-zero" : "zero");
2170  else
2171  return nullptr;
2172 
2173  const LocationContext *LCtx = N->getLocationContext();
2174  PathDiagnosticLocation Loc(CondVarExpr, BRC.getSourceManager(), LCtx);
2175  auto event = std::make_shared<PathDiagnosticEventPiece>(Loc, Out.str());
2176 
2177  if (const auto *DR = dyn_cast<DeclRefExpr>(CondVarExpr)) {
2178  if (const auto *VD = dyn_cast<VarDecl>(DR->getDecl())) {
2179  const ProgramState *state = N->getState().get();
2180  if (const MemRegion *R = state->getLValue(VD, LCtx).getAsRegion()) {
2181  if (report.isInteresting(R))
2182  event->setPrunable(false);
2183  }
2184  }
2185  }
2186 
2187  return event;
2188 }
2189 
2190 std::shared_ptr<PathDiagnosticPiece>
2191 ConditionBRVisitor::VisitTrueTest(const Expr *Cond, const DeclRefExpr *DR,
2192  const bool tookTrue, BugReporterContext &BRC,
2193  BugReport &report, const ExplodedNode *N) {
2194  const auto *VD = dyn_cast<VarDecl>(DR->getDecl());
2195  if (!VD)
2196  return nullptr;
2197 
2198  SmallString<256> Buf;
2199  llvm::raw_svector_ostream Out(Buf);
2200 
2201  Out << "Assuming '" << VD->getDeclName() << "' is ";
2202 
2203  QualType VDTy = VD->getType();
2204 
2205  if (VDTy->isPointerType())
2206  Out << (tookTrue ? "non-null" : "null");
2207  else if (VDTy->isObjCObjectPointerType())
2208  Out << (tookTrue ? "non-nil" : "nil");
2209  else if (VDTy->isScalarType())
2210  Out << (tookTrue ? "not equal to 0" : "0");
2211  else
2212  return nullptr;
2213 
2214  const LocationContext *LCtx = N->getLocationContext();
2215  PathDiagnosticLocation Loc(Cond, BRC.getSourceManager(), LCtx);
2216  auto event = std::make_shared<PathDiagnosticEventPiece>(Loc, Out.str());
2217 
2218  const ProgramState *state = N->getState().get();
2219  if (const MemRegion *R = state->getLValue(VD, LCtx).getAsRegion()) {
2220  if (report.isInteresting(R))
2221  event->setPrunable(false);
2222  else {
2223  SVal V = state->getSVal(R);
2224  if (report.isInteresting(V))
2225  event->setPrunable(false);
2226  }
2227  }
2228  return std::move(event);
2229 }
2230 
2231 const char *const ConditionBRVisitor::GenericTrueMessage =
2232  "Assuming the condition is true";
2233 const char *const ConditionBRVisitor::GenericFalseMessage =
2234  "Assuming the condition is false";
2235 
2236 bool ConditionBRVisitor::isPieceMessageGeneric(
2237  const PathDiagnosticPiece *Piece) {
2238  return Piece->getString() == GenericTrueMessage ||
2239  Piece->getString() == GenericFalseMessage;
2240 }
2241 
2242 void LikelyFalsePositiveSuppressionBRVisitor::finalizeVisitor(
2243  BugReporterContext &BRC, const ExplodedNode *N, BugReport &BR) {
2244  // Here we suppress false positives coming from system headers. This list is
2245  // based on known issues.
2246  AnalyzerOptions &Options = BRC.getAnalyzerOptions();
2247  const Decl *D = N->getLocationContext()->getDecl();
2248 
2250  // Skip reports within the 'std' namespace. Although these can sometimes be
2251  // the user's fault, we currently don't report them very well, and
2252  // Note that this will not help for any other data structure libraries, like
2253  // TR1, Boost, or llvm/ADT.
2254  if (Options.ShouldSuppressFromCXXStandardLibrary) {
2255  BR.markInvalid(getTag(), nullptr);
2256  return;
2257  } else {
2258  // If the complete 'std' suppression is not enabled, suppress reports
2259  // from the 'std' namespace that are known to produce false positives.
2260 
2261  // The analyzer issues a false use-after-free when std::list::pop_front
2262  // or std::list::pop_back are called multiple times because we cannot
2263  // reason about the internal invariants of the data structure.
2264  if (const auto *MD = dyn_cast<CXXMethodDecl>(D)) {
2265  const CXXRecordDecl *CD = MD->getParent();
2266  if (CD->getName() == "list") {
2267  BR.markInvalid(getTag(), nullptr);
2268  return;
2269  }
2270  }
2271 
2272  // The analyzer issues a false positive when the constructor of
2273  // std::__independent_bits_engine from algorithms is used.
2274  if (const auto *MD = dyn_cast<CXXConstructorDecl>(D)) {
2275  const CXXRecordDecl *CD = MD->getParent();
2276  if (CD->getName() == "__independent_bits_engine") {
2277  BR.markInvalid(getTag(), nullptr);
2278  return;
2279  }
2280  }
2281 
2282  for (const LocationContext *LCtx = N->getLocationContext(); LCtx;
2283  LCtx = LCtx->getParent()) {
2284  const auto *MD = dyn_cast<CXXMethodDecl>(LCtx->getDecl());
2285  if (!MD)
2286  continue;
2287 
2288  const CXXRecordDecl *CD = MD->getParent();
2289  // The analyzer issues a false positive on
2290  // std::basic_string<uint8_t> v; v.push_back(1);
2291  // and
2292  // std::u16string s; s += u'a';
2293  // because we cannot reason about the internal invariants of the
2294  // data structure.
2295  if (CD->getName() == "basic_string") {
2296  BR.markInvalid(getTag(), nullptr);
2297  return;
2298  }
2299 
2300  // The analyzer issues a false positive on
2301  // std::shared_ptr<int> p(new int(1)); p = nullptr;
2302  // because it does not reason properly about temporary destructors.
2303  if (CD->getName() == "shared_ptr") {
2304  BR.markInvalid(getTag(), nullptr);
2305  return;
2306  }
2307  }
2308  }
2309  }
2310 
2311  // Skip reports within the sys/queue.h macros as we do not have the ability to
2312  // reason about data structure shapes.
2313  SourceManager &SM = BRC.getSourceManager();
2314  FullSourceLoc Loc = BR.getLocation(SM).asLocation();
2315  while (Loc.isMacroID()) {
2316  Loc = Loc.getSpellingLoc();
2317  if (SM.getFilename(Loc).endswith("sys/queue.h")) {
2318  BR.markInvalid(getTag(), nullptr);
2319  return;
2320  }
2321  }
2322 }
2323 
2324 std::shared_ptr<PathDiagnosticPiece>
2325 UndefOrNullArgVisitor::VisitNode(const ExplodedNode *N,
2326  BugReporterContext &BRC, BugReport &BR) {
2327  ProgramStateRef State = N->getState();
2328  ProgramPoint ProgLoc = N->getLocation();
2329 
2330  // We are only interested in visiting CallEnter nodes.
2331  Optional<CallEnter> CEnter = ProgLoc.getAs<CallEnter>();
2332  if (!CEnter)
2333  return nullptr;
2334 
2335  // Check if one of the arguments is the region the visitor is tracking.
2336  CallEventManager &CEMgr = BRC.getStateManager().getCallEventManager();
2337  CallEventRef<> Call = CEMgr.getCaller(CEnter->getCalleeContext(), State);
2338  unsigned Idx = 0;
2339  ArrayRef<ParmVarDecl *> parms = Call->parameters();
2340 
2341  for (const auto ParamDecl : parms) {
2342  const MemRegion *ArgReg = Call->getArgSVal(Idx).getAsRegion();
2343  ++Idx;
2344 
2345  // Are we tracking the argument or its subregion?
2346  if ( !ArgReg || !R->isSubRegionOf(ArgReg->StripCasts()))
2347  continue;
2348 
2349  // Check the function parameter type.
2350  assert(ParamDecl && "Formal parameter has no decl?");
2351  QualType T = ParamDecl->getType();
2352 
2353  if (!(T->isAnyPointerType() || T->isReferenceType())) {
2354  // Function can only change the value passed in by address.
2355  continue;
2356  }
2357 
2358  // If it is a const pointer value, the function does not intend to
2359  // change the value.
2360  if (T->getPointeeType().isConstQualified())
2361  continue;
2362 
2363  // Mark the call site (LocationContext) as interesting if the value of the
2364  // argument is undefined or '0'/'NULL'.
2365  SVal BoundVal = State->getSVal(R);
2366  if (BoundVal.isUndef() || BoundVal.isZeroConstant()) {
2367  BR.markInteresting(CEnter->getCalleeContext());
2368  return nullptr;
2369  }
2370  }
2371  return nullptr;
2372 }
2373 
2374 std::shared_ptr<PathDiagnosticPiece>
2375 CXXSelfAssignmentBRVisitor::VisitNode(const ExplodedNode *Succ,
2376  BugReporterContext &BRC, BugReport &) {
2377  if (Satisfied)
2378  return nullptr;
2379 
2380  const auto Edge = Succ->getLocation().getAs<BlockEdge>();
2381  if (!Edge.hasValue())
2382  return nullptr;
2383 
2384  auto Tag = Edge->getTag();
2385  if (!Tag)
2386  return nullptr;
2387 
2388  if (Tag->getTagDescription() != "cplusplus.SelfAssignment")
2389  return nullptr;
2390 
2391  Satisfied = true;
2392 
2393  const auto *Met =
2394  dyn_cast<CXXMethodDecl>(Succ->getCodeDecl().getAsFunction());
2395  assert(Met && "Not a C++ method.");
2396  assert((Met->isCopyAssignmentOperator() || Met->isMoveAssignmentOperator()) &&
2397  "Not a copy/move assignment operator.");
2398 
2399  const auto *LCtx = Edge->getLocationContext();
2400 
2401  const auto &State = Succ->getState();
2402  auto &SVB = State->getStateManager().getSValBuilder();
2403 
2404  const auto Param =
2405  State->getSVal(State->getRegion(Met->getParamDecl(0), LCtx));
2406  const auto This =
2407  State->getSVal(SVB.getCXXThis(Met, LCtx->getStackFrame()));
2408 
2409  auto L = PathDiagnosticLocation::create(Met, BRC.getSourceManager());
2410 
2411  if (!L.isValid() || !L.asLocation().isValid())
2412  return nullptr;
2413 
2414  SmallString<256> Buf;
2415  llvm::raw_svector_ostream Out(Buf);
2416 
2417  Out << "Assuming " << Met->getParamDecl(0)->getName() <<
2418  ((Param == This) ? " == " : " != ") << "*this";
2419 
2420  auto Piece = std::make_shared<PathDiagnosticEventPiece>(L, Out.str());
2421  Piece->addRange(Met->getSourceRange());
2422 
2423  return std::move(Piece);
2424 }
2425 
2426 
2427 FalsePositiveRefutationBRVisitor::FalsePositiveRefutationBRVisitor()
2428  : Constraints(ConstraintRangeTy::Factory().getEmptyMap()) {}
2429 
2430 void FalsePositiveRefutationBRVisitor::finalizeVisitor(
2431  BugReporterContext &BRC, const ExplodedNode *EndPathNode, BugReport &BR) {
2432  // Collect new constraints
2433  VisitNode(EndPathNode, BRC, BR);
2434 
2435  // Create a refutation manager
2436  llvm::SMTSolverRef RefutationSolver = llvm::CreateZ3Solver();
2437  ASTContext &Ctx = BRC.getASTContext();
2438 
2439  // Add constraints to the solver
2440  for (const auto &I : Constraints) {
2441  const SymbolRef Sym = I.first;
2442  auto RangeIt = I.second.begin();
2443 
2444  llvm::SMTExprRef Constraints = SMTConv::getRangeExpr(
2445  RefutationSolver, Ctx, Sym, RangeIt->From(), RangeIt->To(),
2446  /*InRange=*/true);
2447  while ((++RangeIt) != I.second.end()) {
2448  Constraints = RefutationSolver->mkOr(
2449  Constraints, SMTConv::getRangeExpr(RefutationSolver, Ctx, Sym,
2450  RangeIt->From(), RangeIt->To(),
2451  /*InRange=*/true));
2452  }
2453 
2454  RefutationSolver->addConstraint(Constraints);
2455  }
2456 
2457  // And check for satisfiability
2458  Optional<bool> isSat = RefutationSolver->check();
2459  if (!isSat.hasValue())
2460  return;
2461 
2462  if (!isSat.getValue())
2463  BR.markInvalid("Infeasible constraints", EndPathNode->getLocationContext());
2464 }
2465 
2466 std::shared_ptr<PathDiagnosticPiece>
2467 FalsePositiveRefutationBRVisitor::VisitNode(const ExplodedNode *N,
2468  BugReporterContext &,
2469  BugReport &) {
2470  // Collect new constraints
2471  const ConstraintRangeTy &NewCs = N->getState()->get<ConstraintRange>();
2472  ConstraintRangeTy::Factory &CF =
2473  N->getState()->get_context<ConstraintRange>();
2474 
2475  // Add constraints if we don't have them yet
2476  for (auto const &C : NewCs) {
2477  const SymbolRef &Sym = C.first;
2478  if (!Constraints.contains(Sym)) {
2479  Constraints = CF.add(Constraints, Sym, C.second);
2480  }
2481  }
2482 
2483  return nullptr;
2484 }
2485 
2486 int NoteTag::Kind = 0;
2487 
2488 void TagVisitor::Profile(llvm::FoldingSetNodeID &ID) const {
2489  static int Tag = 0;
2490  ID.AddPointer(&Tag);
2491 }
2492 
2493 std::shared_ptr<PathDiagnosticPiece>
2494 TagVisitor::VisitNode(const ExplodedNode *N, BugReporterContext &BRC,
2495  BugReport &R) {
2496  ProgramPoint PP = N->getLocation();
2497  const NoteTag *T = dyn_cast_or_null<NoteTag>(PP.getTag());
2498  if (!T)
2499  return nullptr;
2500 
2501  if (Optional<std::string> Msg = T->generateMessage(BRC, R)) {
2502  PathDiagnosticLocation Loc =
2503  PathDiagnosticLocation::create(PP, BRC.getSourceManager());
2504  return std::make_shared<PathDiagnosticEventPiece>(Loc, *Msg);
2505  }
2506 
2507  return nullptr;
2508 }
2509 
2510 void FalsePositiveRefutationBRVisitor::Profile(
2511  llvm::FoldingSetNodeID &ID) const {
2512  static int Tag = 0;
2513  ID.AddPointer(&Tag);
2514 }
ObjCPropertyRefExpr - A dot-syntax expression to access an ObjC property.
Definition: ExprObjC.h:614
Indicates that the tracked object is a CF object.
Defines the clang::ASTContext interface.
This is a discriminated union of FileInfo and ExpansionInfo.
A (possibly-)qualified type.
Definition: Type.h:639
static StringRef getMacroName(SourceLocation Loc, BugReporterContext &BRC)
const internal::VariadicAllOfMatcher< Stmt > stmt
Matches statements.
succ_iterator succ_begin()
Definition: CFG.h:750
virtual Stmt * getBody() const
getBody - If this Decl represents a declaration for a body of code, such as a function or method defi...
Definition: DeclBase.h:979
const SymExpr * SymbolRef
Stmt - This represents one statement.
Definition: Stmt.h:65
internal::Matcher< Stmt > StatementMatcher
Definition: ASTMatchers.h:147
QualType getPointeeType() const
If this is a pointer, ObjC object pointer, or block pointer, this returns the respective pointee...
Definition: Type.cpp:505
internal::PolymorphicMatcherWithParam1< internal::HasDeclarationMatcher, internal::Matcher< Decl >, void(internal::HasDeclarationSupportedTypes)> hasDeclaration(const internal::Matcher< Decl > &InnerMatcher)
Matches a node if the declaration associated with that node matches the given matcher.
Definition: ASTMatchers.h:2873
C Language Family Type Representation.
Defines the SourceManager interface.
static bool isPointerToConst(const QualType &QT)
Decl - This represents one declaration (or definition), e.g.
Definition: DeclBase.h:88
Represents a point when we begin processing an inlined call.
Definition: ProgramPoint.h:630
Manages the lifetime of CallEvent objects.
Definition: CallEvent.h:1086
IntrusiveRefCntPtr< const ProgramState > ProgramStateRef
Opcode getOpcode() const
Definition: Expr.h:3360
StringRef P
const internal::ArgumentAdaptingMatcherFunc< internal::HasDescendantMatcher > hasDescendant
Matches AST nodes that have descendant AST nodes that match the provided matcher. ...
Each ExpansionInfo encodes the expansion location - where the token was ultimately expanded...
llvm::ImmutableMap< SymbolRef, RangeSet > ConstraintRangeTy
unsigned succ_size() const
Definition: CFG.h:768
static bool isAtStartOfMacroExpansion(SourceLocation loc, const SourceManager &SM, const LangOptions &LangOpts, SourceLocation *MacroBegin=nullptr)
Returns true if the given MacroID location points at the first token of the macro expansion...
Definition: Lexer.cpp:792
Represents a variable declaration or definition.
Definition: Decl.h:812
const T * getAs() const
Member-template getAs<specific type>&#39;.
Definition: Type.h:6805
const internal::VariadicDynCastAllOfMatcher< Stmt, BinaryOperator > binaryOperator
Matches binary operator expressions.
const internal::VariadicDynCastAllOfMatcher< Stmt, ObjCIvarRefExpr > objcIvarRefExpr
Matches a reference to an ObjCIvar.
Describes how types, statements, expressions, and declarations should be printed. ...
Definition: PrettyPrinter.h:37
Represents a parameter to a function.
Definition: Decl.h:1559
Defines the clang::Expr interface and subclasses for C++ expressions.
bool isParentOf(const LocationContext *LC) const
Represents a struct/union/class.
Definition: Decl.h:3598
SourceLocation getBegin() const
Holds long-lived AST nodes (such as types and decls) that can be referred to throughout the semantic ...
Definition: ASTContext.h:154
LineState State
field_range fields() const
Definition: Decl.h:3789
SourceLocation getBeginLoc() const LLVM_READONLY
Definition: Stmt.cpp:263
Represents a member of a struct/union/class.
Definition: Decl.h:2584
Represents a program point after a store evaluation.
Definition: ProgramPoint.h:431
bool isReferenceType() const
Definition: Type.h:6357
Keeps track of the various options that can be enabled, which controls the dialect of C or C++ that i...
Definition: LangOptions.h:49
i32 captured_struct **param SharedsTy A type which contains references the shared variables *param Shareds Context with the list of shared variables from the p *TaskFunction *param Data Additional data for task generation like final * state
bool isAssignmentOp() const
Definition: Expr.h:3454
bool isIntegralOrEnumerationType() const
Determine whether this type is an integral or enumeration type.
Definition: Type.h:6701
Represents a point when we start the call exit sequence (for inlined call).
Definition: ProgramPoint.h:668
StringRef getOpcodeStr() const
Definition: Expr.h:3381
bool isGLValue() const
Definition: Expr.h:254
BinaryOperatorKind
static bool isInStdNamespace(const Decl *D)
Returns true if the root namespace of the given declaration is the &#39;std&#39; C++ namespace.
Forward-declares and imports various common LLVM datatypes that clang wants to use unqualified...
child_range children()
Definition: Stmt.cpp:212
const LocationContext * getParent() const
A builtin binary operation expression such as "x + y" or "x <= y".
Definition: Expr.h:3325
static bool wasRegionOfInterestModifiedAt(const SubRegion *RegionOfInterest, const ExplodedNode *N, SVal ValueAfter)
Expr * IgnoreParenCasts() LLVM_READONLY
Skip past any parentheses and casts which might surround this expression until reaching a fixed point...
Definition: Expr.cpp:2814
static const Expr * peelOffPointerArithmetic(const BinaryOperator *B)
static PathDiagnosticLocation create(const Decl *D, const SourceManager &SM)
Create a location corresponding to the given declaration.
static const MemRegion * getLocationRegionIfReference(const Expr *E, const ExplodedNode *N)
bool isScalarType() const
Definition: Type.h:6686
SmallVector< BoundNodes, 1 > match(MatcherT Matcher, const NodeT &Node, ASTContext &Context)
Returns the results of matching Matcher on Node.
static bool hasVisibleUpdate(const ExplodedNode *LeftNode, SVal LeftVal, const ExplodedNode *RightNode, SVal RightVal)
Comparing internal representations of symbolic values (via SVal::operator==()) is a valid way to chec...
NodeId Parent
Definition: ASTDiff.cpp:191
RecordDecl * getAsRecordDecl() const
Retrieves the RecordDecl this type refers to.
Definition: Type.cpp:1640
const Stmt * getCallSite() const
Represents a single basic block in a source-level CFG.
Definition: CFG.h:551
Represents a point when we finish the call exit sequence (for inlined call).
Definition: ProgramPoint.h:688
static StringRef getSourceText(CharSourceRange Range, const SourceManager &SM, const LangOptions &LangOpts, bool *Invalid=nullptr)
Returns a string for the source that the range encompasses.
Definition: Lexer.cpp:931
static bool isAtEndOfMacroExpansion(SourceLocation loc, const SourceManager &SM, const LangOptions &LangOpts, SourceLocation *MacroEnd=nullptr)
Returns true if the given MacroID location points at the last token of the macro expansion.
Definition: Lexer.cpp:814
This represents one expression.
Definition: Expr.h:108
Represents a character-granular source range.
CFGBlock * getBlock(Stmt *S)
Returns the CFGBlock the specified Stmt* appears in.
Definition: CFGStmtMap.cpp:26
CallEventRef getCaller(const StackFrameContext *CalleeCtx, ProgramStateRef State)
Gets an outside caller given a callee context.
Definition: CallEvent.cpp:1362
#define V(N, I)
Definition: ASTContext.h:2905
bool inTopFrame() const override
Return true if the current LocationContext has no caller context.
Defines the clang::IdentifierInfo, clang::IdentifierTable, and clang::Selector interfaces.
static std::pair< const ProgramPointTag *, const ProgramPointTag * > geteagerlyAssumeBinOpBifurcationTags()
QualType getType() const
Definition: Expr.h:130
CharSourceRange getImmediateExpansionRange(SourceLocation Loc) const
Return the start/end of the expansion information for an expansion location.
DeclContext * getParent()
getParent - Returns the containing DeclContext.
Definition: DeclBase.h:1763
ReturnStmt - This represents a return, optionally of an expression: return; return 4;...
Definition: Stmt.h:2562
An expression that sends a message to the given Objective-C object or class.
Definition: ExprObjC.h:950
ValueDecl * getDecl()
Definition: Expr.h:1147
bool isNull() const
Return true if this QualType doesn&#39;t point to a type yet.
Definition: Type.h:704
const SourceManager & SM
Definition: Format.cpp:1568
const ExpansionInfo & getExpansion() const
SourceLocation getEndLoc() const LLVM_READONLY
Definition: Stmt.cpp:276
virtual bool hasBody() const
Returns true if this Decl represents a declaration for a body of code, such as a function or method d...
Definition: DeclBase.h:985
bool isConstQualified() const
Determine whether this type is const-qualified.
Definition: Type.h:6180
bool isComparisonOp() const
Definition: Expr.h:3416
static const Stmt * getStmt(const ExplodedNode *N)
Given an exploded node, retrieve the statement that should be used for the diagnostic location...
Maps string IDs to AST nodes matched by parts of a matcher.
Definition: ASTMatchers.h:103
StringRef getFilename(SourceLocation SpellingLoc) const
Return the filename of the file containing a SourceLocation.
CFGTerminator getTerminator()
Definition: CFG.h:839
QualType getCanonicalType() const
Definition: Type.h:6160
Encodes a location in the source.
static bool isCallStmt(const Stmt *S)
Returns true if this is a statement is a function or method call of some kind.
Definition: CallEvent.cpp:441
ProgramPoints can be "tagged" as representing points specific to a given analysis entity...
Definition: ProgramPoint.h:39
std::string getNameAsString() const
Get a human-readable name for the declaration, even if it is one of the special kinds of names (C++ c...
Definition: Decl.h:291
ASTContext & getASTContext() const LLVM_READONLY
Definition: DeclBase.cpp:376
DeclStmt - Adaptor class for mixing declarations with statements and expressions. ...
Definition: Stmt.h:1170
Represents a static or instance method of a struct/union/class.
Definition: DeclCXX.h:2108
bool isAnyPointerType() const
Definition: Type.h:6349
bool isObjCObjectPointerType() const
Definition: Type.h:6442
static void showBRDiagnostics(const char *action, llvm::raw_svector_ostream &os, const MemRegion *R, SVal V, const DeclStmt *DS)
Show diagnostics for initializing or declaring a region R with a bad value.
static StringRef getImmediateMacroName(SourceLocation Loc, const SourceManager &SM, const LangOptions &LangOpts)
Retrieve the name of the immediate macro expansion.
Definition: Lexer.cpp:967
static bool isFunctionMacroExpansion(SourceLocation Loc, const SourceManager &SM)
Expr * getLHS() const
Definition: Expr.h:3365
ast_type_traits::DynTypedNode Node
Dataflow Directional Tag Classes.
static void showBRDefaultDiagnostics(llvm::raw_svector_ostream &os, const MemRegion *R, SVal V)
Show default diagnostics for storing bad region.
Parameter for Objective-C &#39;self&#39; argument.
Definition: Decl.h:1504
StmtClass getStmtClass() const
Definition: Stmt.h:1053
bool isBooleanType() const
Definition: Type.h:6714
const Decl * getSingleDecl() const
Definition: Stmt.h:1185
const ProgramPointTag * getTag() const
Definition: ProgramPoint.h:177
static void showBRParamDiagnostics(llvm::raw_svector_ostream &os, const VarRegion *VR, SVal V)
Display diagnostics for passing bad region as a parameter.
bool isMacroID() const
static CharSourceRange getAsCharRange(SourceRange Range, const SourceManager &SM, const LangOptions &LangOpts)
Given a token range, produce a corresponding CharSourceRange that is not a token range.
Definition: Lexer.h:379
bool isMacroArgExpansion(SourceLocation Loc, SourceLocation *StartLoc=nullptr) const
Tests whether the given source location represents a macro argument&#39;s expansion into the function-lik...
Indicates that the tracking object is a descendant of a referenced-counted OSObject, used in the Darwin kernel.
const LocationContext * getLocationContext() const
Definition: ProgramPoint.h:179
static bool isAdditiveOp(Opcode Opc)
Definition: Expr.h:3401
const StackFrameContext * getStackFrame() const
Stores options for the analyzer from the command line.
const SrcMgr::SLocEntry & getSLocEntry(FileID FID, bool *Invalid=nullptr) const
ObjCIvarRefExpr - A reference to an ObjC instance variable.
Definition: ExprObjC.h:546
X
Add a minimal nested name specifier fixit hint to allow lookup of a tag name from an outer enclosing ...
Definition: SemaDecl.cpp:14095
Defines the C++ Decl subclasses, other than those for templates (found in DeclTemplate.h) and friends (in DeclFriend.h).
Defines the clang::SourceLocation class and associated facilities.
Represents a C++ struct/union/class.
Definition: DeclCXX.h:299
bool isVoidType() const
Definition: Type.h:6597
ObjCIvarDecl - Represents an ObjC instance variable.
Definition: DeclObjC.h:1944
static PathDiagnosticLocation createEndOfPath(const ExplodedNode *N, const SourceManager &SM)
Create a location corresponding to the next valid ExplodedNode as end of path location.
static bool isInitializationOfVar(const ExplodedNode *N, const VarRegion *VR)
Returns true if N represents the DeclStmt declaring and initializing VR.
FullSourceLoc getSpellingLoc() const
A SourceLocation and its associated SourceManager.
StringRef getName() const
Get the name of identifier for this declaration as a StringRef.
Definition: Decl.h:275
A reference to a declared variable, function, enum, etc.
Definition: Expr.h:1074
Expr * getRHS() const
Definition: Expr.h:3367
bool isFunctionMacroExpansion() const
bool isPointerType() const
Definition: Type.h:6345
QualType getType() const
Definition: Decl.h:647
A trivial tuple used to represent a source range.
Optional< T > getAs() const
Convert to the specified ProgramPoint type, returning None if this ProgramPoint is not of the desired...
Definition: ProgramPoint.h:151
static bool isInterestingLValueExpr(const Expr *Ex)
Returns true if nodes for the given expression kind are always kept around.
This class handles loading and caching of source files into memory.
std::pair< FileID, unsigned > getDecomposedLoc(SourceLocation Loc) const
Decompose the specified location into a raw FileID + Offset pair.
Expr * IgnoreParens() LLVM_READONLY
Skip past any parentheses which might surround this expression until reaching a fixed point...
Definition: Expr.cpp:2805
static llvm::SMTExprRef getRangeExpr(llvm::SMTSolverRef &Solver, ASTContext &Ctx, SymbolRef Sym, const llvm::APSInt &From, const llvm::APSInt &To, bool InRange)
Definition: SMTConv.h:504