clang  8.0.0svn
BugReporterVisitors.cpp
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1 //===- BugReporterVisitors.cpp - Helpers for reporting bugs ---------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file defines a set of BugReporter "visitors" which can be used to
11 // enhance the diagnostics reported for a bug.
12 //
13 //===----------------------------------------------------------------------===//
14 
16 #include "clang/AST/ASTContext.h"
17 #include "clang/AST/Decl.h"
18 #include "clang/AST/DeclBase.h"
19 #include "clang/AST/DeclCXX.h"
20 #include "clang/AST/Expr.h"
21 #include "clang/AST/ExprCXX.h"
22 #include "clang/AST/ExprObjC.h"
23 #include "clang/AST/Stmt.h"
24 #include "clang/AST/Type.h"
27 #include "clang/Analysis/CFG.h"
31 #include "clang/Basic/LLVM.h"
34 #include "clang/Lex/Lexer.h"
49 #include "llvm/ADT/ArrayRef.h"
50 #include "llvm/ADT/None.h"
51 #include "llvm/ADT/Optional.h"
52 #include "llvm/ADT/STLExtras.h"
53 #include "llvm/ADT/SmallPtrSet.h"
54 #include "llvm/ADT/SmallString.h"
55 #include "llvm/ADT/SmallVector.h"
56 #include "llvm/ADT/StringExtras.h"
57 #include "llvm/ADT/StringRef.h"
58 #include "llvm/Support/Casting.h"
59 #include "llvm/Support/ErrorHandling.h"
60 #include "llvm/Support/raw_ostream.h"
61 #include <cassert>
62 #include <deque>
63 #include <memory>
64 #include <string>
65 #include <utility>
66 
67 using namespace clang;
68 using namespace ento;
69 
70 //===----------------------------------------------------------------------===//
71 // Utility functions.
72 //===----------------------------------------------------------------------===//
73 
74 bool bugreporter::isDeclRefExprToReference(const Expr *E) {
75  if (const auto *DRE = dyn_cast<DeclRefExpr>(E))
76  return DRE->getDecl()->getType()->isReferenceType();
77  return false;
78 }
79 
80 static const Expr *peelOffPointerArithmetic(const BinaryOperator *B) {
81  if (B->isAdditiveOp() && B->getType()->isPointerType()) {
82  if (B->getLHS()->getType()->isPointerType()) {
83  return B->getLHS();
84  } else if (B->getRHS()->getType()->isPointerType()) {
85  return B->getRHS();
86  }
87  }
88  return nullptr;
89 }
90 
91 /// Given that expression S represents a pointer that would be dereferenced,
92 /// try to find a sub-expression from which the pointer came from.
93 /// This is used for tracking down origins of a null or undefined value:
94 /// "this is null because that is null because that is null" etc.
95 /// We wipe away field and element offsets because they merely add offsets.
96 /// We also wipe away all casts except lvalue-to-rvalue casts, because the
97 /// latter represent an actual pointer dereference; however, we remove
98 /// the final lvalue-to-rvalue cast before returning from this function
99 /// because it demonstrates more clearly from where the pointer rvalue was
100 /// loaded. Examples:
101 /// x->y.z ==> x (lvalue)
102 /// foo()->y.z ==> foo() (rvalue)
103 const Expr *bugreporter::getDerefExpr(const Stmt *S) {
104  const auto *E = dyn_cast<Expr>(S);
105  if (!E)
106  return nullptr;
107 
108  while (true) {
109  if (const auto *CE = dyn_cast<CastExpr>(E)) {
110  if (CE->getCastKind() == CK_LValueToRValue) {
111  // This cast represents the load we're looking for.
112  break;
113  }
114  E = CE->getSubExpr();
115  } else if (const auto *B = dyn_cast<BinaryOperator>(E)) {
116  // Pointer arithmetic: '*(x + 2)' -> 'x') etc.
117  if (const Expr *Inner = peelOffPointerArithmetic(B)) {
118  E = Inner;
119  } else {
120  // Probably more arithmetic can be pattern-matched here,
121  // but for now give up.
122  break;
123  }
124  } else if (const auto *U = dyn_cast<UnaryOperator>(E)) {
125  if (U->getOpcode() == UO_Deref || U->getOpcode() == UO_AddrOf ||
126  (U->isIncrementDecrementOp() && U->getType()->isPointerType())) {
127  // Operators '*' and '&' don't actually mean anything.
128  // We look at casts instead.
129  E = U->getSubExpr();
130  } else {
131  // Probably more arithmetic can be pattern-matched here,
132  // but for now give up.
133  break;
134  }
135  }
136  // Pattern match for a few useful cases: a[0], p->f, *p etc.
137  else if (const auto *ME = dyn_cast<MemberExpr>(E)) {
138  E = ME->getBase();
139  } else if (const auto *IvarRef = dyn_cast<ObjCIvarRefExpr>(E)) {
140  E = IvarRef->getBase();
141  } else if (const auto *AE = dyn_cast<ArraySubscriptExpr>(E)) {
142  E = AE->getBase();
143  } else if (const auto *PE = dyn_cast<ParenExpr>(E)) {
144  E = PE->getSubExpr();
145  } else if (const auto *EWC = dyn_cast<ExprWithCleanups>(E)) {
146  E = EWC->getSubExpr();
147  } else {
148  // Other arbitrary stuff.
149  break;
150  }
151  }
152 
153  // Special case: remove the final lvalue-to-rvalue cast, but do not recurse
154  // deeper into the sub-expression. This way we return the lvalue from which
155  // our pointer rvalue was loaded.
156  if (const auto *CE = dyn_cast<ImplicitCastExpr>(E))
157  if (CE->getCastKind() == CK_LValueToRValue)
158  E = CE->getSubExpr();
159 
160  return E;
161 }
162 
163 const Stmt *bugreporter::GetDenomExpr(const ExplodedNode *N) {
164  const Stmt *S = N->getLocationAs<PreStmt>()->getStmt();
165  if (const auto *BE = dyn_cast<BinaryOperator>(S))
166  return BE->getRHS();
167  return nullptr;
168 }
169 
170 const Stmt *bugreporter::GetRetValExpr(const ExplodedNode *N) {
171  const Stmt *S = N->getLocationAs<PostStmt>()->getStmt();
172  if (const auto *RS = dyn_cast<ReturnStmt>(S))
173  return RS->getRetValue();
174  return nullptr;
175 }
176 
177 //===----------------------------------------------------------------------===//
178 // Definitions for bug reporter visitors.
179 //===----------------------------------------------------------------------===//
180 
181 std::shared_ptr<PathDiagnosticPiece>
182 BugReporterVisitor::getEndPath(BugReporterContext &BRC,
183  const ExplodedNode *EndPathNode, BugReport &BR) {
184  return nullptr;
185 }
186 
187 void
188 BugReporterVisitor::finalizeVisitor(BugReporterContext &BRC,
189  const ExplodedNode *EndPathNode,
190  BugReport &BR) {}
191 
192 std::shared_ptr<PathDiagnosticPiece> BugReporterVisitor::getDefaultEndPath(
193  BugReporterContext &BRC, const ExplodedNode *EndPathNode, BugReport &BR) {
194  PathDiagnosticLocation L =
195  PathDiagnosticLocation::createEndOfPath(EndPathNode,BRC.getSourceManager());
196 
197  const auto &Ranges = BR.getRanges();
198 
199  // Only add the statement itself as a range if we didn't specify any
200  // special ranges for this report.
201  auto P = std::make_shared<PathDiagnosticEventPiece>(
202  L, BR.getDescription(), Ranges.begin() == Ranges.end());
203  for (SourceRange Range : Ranges)
204  P->addRange(Range);
205 
206  return P;
207 }
208 
209 /// \return name of the macro inside the location \p Loc.
210 static StringRef getMacroName(SourceLocation Loc,
211  BugReporterContext &BRC) {
213  Loc,
214  BRC.getSourceManager(),
215  BRC.getASTContext().getLangOpts());
216 }
217 
218 /// \return Whether given spelling location corresponds to an expansion
219 /// of a function-like macro.
221  const SourceManager &SM) {
222  if (!Loc.isMacroID())
223  return false;
224  while (SM.isMacroArgExpansion(Loc))
225  Loc = SM.getImmediateExpansionRange(Loc).getBegin();
226  std::pair<FileID, unsigned> TLInfo = SM.getDecomposedLoc(Loc);
227  SrcMgr::SLocEntry SE = SM.getSLocEntry(TLInfo.first);
228  const SrcMgr::ExpansionInfo &EInfo = SE.getExpansion();
229  return EInfo.isFunctionMacroExpansion();
230 }
231 
232 /// \return Whether \c RegionOfInterest was modified at \p N,
233 /// where \p ReturnState is a state associated with the return
234 /// from the current frame.
236  const SubRegion *RegionOfInterest,
237  const ExplodedNode *N,
238  SVal ValueAfter) {
239  ProgramStateRef State = N->getState();
240  ProgramStateManager &Mgr = N->getState()->getStateManager();
241 
242  if (!N->getLocationAs<PostStore>()
243  && !N->getLocationAs<PostInitializer>()
244  && !N->getLocationAs<PostStmt>())
245  return false;
246 
247  // Writing into region of interest.
248  if (auto PS = N->getLocationAs<PostStmt>())
249  if (auto *BO = PS->getStmtAs<BinaryOperator>())
250  if (BO->isAssignmentOp() && RegionOfInterest->isSubRegionOf(
251  N->getSVal(BO->getLHS()).getAsRegion()))
252  return true;
253 
254  // SVal after the state is possibly different.
255  SVal ValueAtN = N->getState()->getSVal(RegionOfInterest);
256  if (!Mgr.getSValBuilder().areEqual(State, ValueAtN, ValueAfter).isConstrainedTrue() &&
257  (!ValueAtN.isUndef() || !ValueAfter.isUndef()))
258  return true;
259 
260  return false;
261 }
262 
263 
264 namespace {
265 
266 /// Put a diagnostic on return statement of all inlined functions
267 /// for which the region of interest \p RegionOfInterest was passed into,
268 /// but not written inside, and it has caused an undefined read or a null
269 /// pointer dereference outside.
270 class NoStoreFuncVisitor final : public BugReporterVisitor {
271  const SubRegion *RegionOfInterest;
272  MemRegionManager &MmrMgr;
273  const SourceManager &SM;
274  const PrintingPolicy &PP;
275 
276  /// Recursion limit for dereferencing fields when looking for the
277  /// region of interest.
278  /// The limit of two indicates that we will dereference fields only once.
279  static const unsigned DEREFERENCE_LIMIT = 2;
280 
281  /// Frames writing into \c RegionOfInterest.
282  /// This visitor generates a note only if a function does not write into
283  /// a region of interest. This information is not immediately available
284  /// by looking at the node associated with the exit from the function
285  /// (usually the return statement). To avoid recomputing the same information
286  /// many times (going up the path for each node and checking whether the
287  /// region was written into) we instead lazily compute the
288  /// stack frames along the path which write into the region of interest.
289  llvm::SmallPtrSet<const StackFrameContext *, 32> FramesModifyingRegion;
290  llvm::SmallPtrSet<const StackFrameContext *, 32> FramesModifyingCalculated;
291 
292  using RegionVector = SmallVector<const MemRegion *, 5>;
293 public:
294  NoStoreFuncVisitor(const SubRegion *R)
295  : RegionOfInterest(R), MmrMgr(*R->getMemRegionManager()),
296  SM(MmrMgr.getContext().getSourceManager()),
297  PP(MmrMgr.getContext().getPrintingPolicy()) {}
298 
299  void Profile(llvm::FoldingSetNodeID &ID) const override {
300  static int Tag = 0;
301  ID.AddPointer(&Tag);
302  ID.AddPointer(RegionOfInterest);
303  }
304 
305  std::shared_ptr<PathDiagnosticPiece> VisitNode(const ExplodedNode *N,
306  const ExplodedNode *PrevN,
307  BugReporterContext &BRC,
308  BugReport &BR) override {
309 
310  const LocationContext *Ctx = N->getLocationContext();
311  const StackFrameContext *SCtx = Ctx->getStackFrame();
312  ProgramStateRef State = N->getState();
313  auto CallExitLoc = N->getLocationAs<CallExitBegin>();
314 
315  // No diagnostic if region was modified inside the frame.
316  if (!CallExitLoc || isRegionOfInterestModifiedInFrame(N))
317  return nullptr;
318 
319  CallEventRef<> Call =
320  BRC.getStateManager().getCallEventManager().getCaller(SCtx, State);
321 
322  if (SM.isInSystemHeader(Call->getDecl()->getSourceRange().getBegin()))
323  return nullptr;
324 
325  // Region of interest corresponds to an IVar, exiting a method
326  // which could have written into that IVar, but did not.
327  if (const auto *MC = dyn_cast<ObjCMethodCall>(Call)) {
328  if (const auto *IvarR = dyn_cast<ObjCIvarRegion>(RegionOfInterest)) {
329  const MemRegion *SelfRegion = MC->getReceiverSVal().getAsRegion();
330  if (RegionOfInterest->isSubRegionOf(SelfRegion) &&
331  potentiallyWritesIntoIvar(Call->getRuntimeDefinition().getDecl(),
332  IvarR->getDecl()))
333  return notModifiedDiagnostics(Ctx, *CallExitLoc, Call, {}, SelfRegion,
334  "self", /*FirstIsReferenceType=*/false,
335  1);
336  }
337  }
338 
339  if (const auto *CCall = dyn_cast<CXXConstructorCall>(Call)) {
340  const MemRegion *ThisR = CCall->getCXXThisVal().getAsRegion();
341  if (RegionOfInterest->isSubRegionOf(ThisR)
342  && !CCall->getDecl()->isImplicit())
343  return notModifiedDiagnostics(Ctx, *CallExitLoc, Call, {}, ThisR,
344  "this",
345  /*FirstIsReferenceType=*/false, 1);
346 
347  // Do not generate diagnostics for not modified parameters in
348  // constructors.
349  return nullptr;
350  }
351 
352  ArrayRef<ParmVarDecl *> parameters = getCallParameters(Call);
353  for (unsigned I = 0; I < Call->getNumArgs() && I < parameters.size(); ++I) {
354  const ParmVarDecl *PVD = parameters[I];
355  SVal S = Call->getArgSVal(I);
356  bool ParamIsReferenceType = PVD->getType()->isReferenceType();
357  std::string ParamName = PVD->getNameAsString();
358 
359  int IndirectionLevel = 1;
360  QualType T = PVD->getType();
361  while (const MemRegion *R = S.getAsRegion()) {
362  if (RegionOfInterest->isSubRegionOf(R) && !isPointerToConst(T))
363  return notModifiedDiagnostics(Ctx, *CallExitLoc, Call, {}, R,
364  ParamName, ParamIsReferenceType,
365  IndirectionLevel);
366 
367  QualType PT = T->getPointeeType();
368  if (PT.isNull() || PT->isVoidType()) break;
369 
370  if (const RecordDecl *RD = PT->getAsRecordDecl())
371  if (auto P = findRegionOfInterestInRecord(RD, State, R))
372  return notModifiedDiagnostics(
373  Ctx, *CallExitLoc, Call, *P, RegionOfInterest, ParamName,
374  ParamIsReferenceType, IndirectionLevel);
375 
376  S = State->getSVal(R, PT);
377  T = PT;
378  IndirectionLevel++;
379  }
380  }
381 
382  return nullptr;
383  }
384 
385 private:
386  /// Attempts to find the region of interest in a given CXX decl,
387  /// by either following the base classes or fields.
388  /// Dereferences fields up to a given recursion limit.
389  /// Note that \p Vec is passed by value, leading to quadratic copying cost,
390  /// but it's OK in practice since its length is limited to DEREFERENCE_LIMIT.
391  /// \return A chain fields leading to the region of interest or None.
393  findRegionOfInterestInRecord(const RecordDecl *RD, ProgramStateRef State,
394  const MemRegion *R,
395  const RegionVector &Vec = {},
396  int depth = 0) {
397 
398  if (depth == DEREFERENCE_LIMIT) // Limit the recursion depth.
399  return None;
400 
401  if (const auto *RDX = dyn_cast<CXXRecordDecl>(RD))
402  if (!RDX->hasDefinition())
403  return None;
404 
405  // Recursively examine the base classes.
406  // Note that following base classes does not increase the recursion depth.
407  if (const auto *RDX = dyn_cast<CXXRecordDecl>(RD))
408  for (const auto II : RDX->bases())
409  if (const RecordDecl *RRD = II.getType()->getAsRecordDecl())
410  if (auto Out = findRegionOfInterestInRecord(RRD, State, R, Vec, depth))
411  return Out;
412 
413  for (const FieldDecl *I : RD->fields()) {
414  QualType FT = I->getType();
415  const FieldRegion *FR = MmrMgr.getFieldRegion(I, cast<SubRegion>(R));
416  const SVal V = State->getSVal(FR);
417  const MemRegion *VR = V.getAsRegion();
418 
419  RegionVector VecF = Vec;
420  VecF.push_back(FR);
421 
422  if (RegionOfInterest == VR)
423  return VecF;
424 
425  if (const RecordDecl *RRD = FT->getAsRecordDecl())
426  if (auto Out =
427  findRegionOfInterestInRecord(RRD, State, FR, VecF, depth + 1))
428  return Out;
429 
430  QualType PT = FT->getPointeeType();
431  if (PT.isNull() || PT->isVoidType() || !VR) continue;
432 
433  if (const RecordDecl *RRD = PT->getAsRecordDecl())
434  if (auto Out =
435  findRegionOfInterestInRecord(RRD, State, VR, VecF, depth + 1))
436  return Out;
437 
438  }
439 
440  return None;
441  }
442 
443  /// \return Whether the method declaration \p Parent
444  /// syntactically has a binary operation writing into the ivar \p Ivar.
445  bool potentiallyWritesIntoIvar(const Decl *Parent,
446  const ObjCIvarDecl *Ivar) {
447  using namespace ast_matchers;
448  const char * IvarBind = "Ivar";
449  if (!Parent || !Parent->hasBody())
450  return false;
451  StatementMatcher WriteIntoIvarM = binaryOperator(
452  hasOperatorName("="),
453  hasLHS(ignoringParenImpCasts(
454  objcIvarRefExpr(hasDeclaration(equalsNode(Ivar))).bind(IvarBind))));
455  StatementMatcher ParentM = stmt(hasDescendant(WriteIntoIvarM));
456  auto Matches = match(ParentM, *Parent->getBody(), Parent->getASTContext());
457  for (BoundNodes &Match : Matches) {
458  auto IvarRef = Match.getNodeAs<ObjCIvarRefExpr>(IvarBind);
459  if (IvarRef->isFreeIvar())
460  return true;
461 
462  const Expr *Base = IvarRef->getBase();
463  if (const auto *ICE = dyn_cast<ImplicitCastExpr>(Base))
464  Base = ICE->getSubExpr();
465 
466  if (const auto *DRE = dyn_cast<DeclRefExpr>(Base))
467  if (const auto *ID = dyn_cast<ImplicitParamDecl>(DRE->getDecl()))
468  if (ID->getParameterKind() == ImplicitParamDecl::ObjCSelf)
469  return true;
470 
471  return false;
472  }
473  return false;
474  }
475 
476  /// Check and lazily calculate whether the region of interest is
477  /// modified in the stack frame to which \p N belongs.
478  /// The calculation is cached in FramesModifyingRegion.
479  bool isRegionOfInterestModifiedInFrame(const ExplodedNode *N) {
480  const LocationContext *Ctx = N->getLocationContext();
481  const StackFrameContext *SCtx = Ctx->getStackFrame();
482  if (!FramesModifyingCalculated.count(SCtx))
483  findModifyingFrames(N);
484  return FramesModifyingRegion.count(SCtx);
485  }
486 
487 
488  /// Write to \c FramesModifyingRegion all stack frames along
489  /// the path in the current stack frame which modify \c RegionOfInterest.
490  void findModifyingFrames(const ExplodedNode *N) {
491  assert(N->getLocationAs<CallExitBegin>());
492  ProgramStateRef LastReturnState = N->getState();
493  SVal ValueAtReturn = LastReturnState->getSVal(RegionOfInterest);
494  const LocationContext *Ctx = N->getLocationContext();
495  const StackFrameContext *OriginalSCtx = Ctx->getStackFrame();
496 
497  do {
498  ProgramStateRef State = N->getState();
499  auto CallExitLoc = N->getLocationAs<CallExitBegin>();
500  if (CallExitLoc) {
501  LastReturnState = State;
502  ValueAtReturn = LastReturnState->getSVal(RegionOfInterest);
503  }
504 
505  FramesModifyingCalculated.insert(
506  N->getLocationContext()->getStackFrame());
507 
508  if (wasRegionOfInterestModifiedAt(RegionOfInterest, N, ValueAtReturn)) {
509  const StackFrameContext *SCtx = N->getStackFrame();
510  while (!SCtx->inTopFrame()) {
511  auto p = FramesModifyingRegion.insert(SCtx);
512  if (!p.second)
513  break; // Frame and all its parents already inserted.
514  SCtx = SCtx->getParent()->getStackFrame();
515  }
516  }
517 
518  // Stop calculation at the call to the current function.
519  if (auto CE = N->getLocationAs<CallEnter>())
520  if (CE->getCalleeContext() == OriginalSCtx)
521  break;
522 
523  N = N->getFirstPred();
524  } while (N);
525  }
526 
527  /// Get parameters associated with runtime definition in order
528  /// to get the correct parameter name.
529  ArrayRef<ParmVarDecl *> getCallParameters(CallEventRef<> Call) {
530  // Use runtime definition, if available.
531  RuntimeDefinition RD = Call->getRuntimeDefinition();
532  if (const auto *FD = dyn_cast_or_null<FunctionDecl>(RD.getDecl()))
533  return FD->parameters();
534  if (const auto *MD = dyn_cast_or_null<ObjCMethodDecl>(RD.getDecl()))
535  return MD->parameters();
536 
537  return Call->parameters();
538  }
539 
540  /// \return whether \p Ty points to a const type, or is a const reference.
541  bool isPointerToConst(QualType Ty) {
542  return !Ty->getPointeeType().isNull() &&
544  }
545 
546  /// \return Diagnostics piece for region not modified in the current function.
547  std::shared_ptr<PathDiagnosticPiece>
548  notModifiedDiagnostics(const LocationContext *Ctx, CallExitBegin &CallExitLoc,
549  CallEventRef<> Call, const RegionVector &FieldChain,
550  const MemRegion *MatchedRegion, StringRef FirstElement,
551  bool FirstIsReferenceType, unsigned IndirectionLevel) {
552 
553  PathDiagnosticLocation L;
554  if (const ReturnStmt *RS = CallExitLoc.getReturnStmt()) {
555  L = PathDiagnosticLocation::createBegin(RS, SM, Ctx);
556  } else {
557  L = PathDiagnosticLocation(
558  Call->getRuntimeDefinition().getDecl()->getSourceRange().getEnd(),
559  SM);
560  }
561 
562  SmallString<256> sbuf;
563  llvm::raw_svector_ostream os(sbuf);
564  os << "Returning without writing to '";
565 
566  // Do not generate the note if failed to pretty-print.
567  if (!prettyPrintRegionName(FirstElement, FirstIsReferenceType,
568  MatchedRegion, FieldChain, IndirectionLevel, os))
569  return nullptr;
570 
571  os << "'";
572  return std::make_shared<PathDiagnosticEventPiece>(L, os.str());
573  }
574 
575  /// Pretty-print region \p MatchedRegion to \p os.
576  /// \return Whether printing succeeded.
577  bool prettyPrintRegionName(StringRef FirstElement, bool FirstIsReferenceType,
578  const MemRegion *MatchedRegion,
579  const RegionVector &FieldChain,
580  int IndirectionLevel,
581  llvm::raw_svector_ostream &os) {
582 
583  if (FirstIsReferenceType)
584  IndirectionLevel--;
585 
586  RegionVector RegionSequence;
587 
588  // Add the regions in the reverse order, then reverse the resulting array.
589  assert(RegionOfInterest->isSubRegionOf(MatchedRegion));
590  const MemRegion *R = RegionOfInterest;
591  while (R != MatchedRegion) {
592  RegionSequence.push_back(R);
593  R = cast<SubRegion>(R)->getSuperRegion();
594  }
595  std::reverse(RegionSequence.begin(), RegionSequence.end());
596  RegionSequence.append(FieldChain.begin(), FieldChain.end());
597 
598  StringRef Sep;
599  for (const MemRegion *R : RegionSequence) {
600 
601  // Just keep going up to the base region.
602  // Element regions may appear due to casts.
603  if (isa<CXXBaseObjectRegion>(R) || isa<CXXTempObjectRegion>(R))
604  continue;
605 
606  if (Sep.empty())
607  Sep = prettyPrintFirstElement(FirstElement,
608  /*MoreItemsExpected=*/true,
609  IndirectionLevel, os);
610 
611  os << Sep;
612 
613  // Can only reasonably pretty-print DeclRegions.
614  if (!isa<DeclRegion>(R))
615  return false;
616 
617  const auto *DR = cast<DeclRegion>(R);
618  Sep = DR->getValueType()->isAnyPointerType() ? "->" : ".";
619  DR->getDecl()->getDeclName().print(os, PP);
620  }
621 
622  if (Sep.empty())
623  prettyPrintFirstElement(FirstElement,
624  /*MoreItemsExpected=*/false, IndirectionLevel,
625  os);
626  return true;
627  }
628 
629  /// Print first item in the chain, return new separator.
630  StringRef prettyPrintFirstElement(StringRef FirstElement,
631  bool MoreItemsExpected,
632  int IndirectionLevel,
633  llvm::raw_svector_ostream &os) {
634  StringRef Out = ".";
635 
636  if (IndirectionLevel > 0 && MoreItemsExpected) {
637  IndirectionLevel--;
638  Out = "->";
639  }
640 
641  if (IndirectionLevel > 0 && MoreItemsExpected)
642  os << "(";
643 
644  for (int i=0; i<IndirectionLevel; i++)
645  os << "*";
646  os << FirstElement;
647 
648  if (IndirectionLevel > 0 && MoreItemsExpected)
649  os << ")";
650 
651  return Out;
652  }
653 };
654 
655 /// Suppress null-pointer-dereference bugs where dereferenced null was returned
656 /// the macro.
657 class MacroNullReturnSuppressionVisitor final : public BugReporterVisitor {
658  const SubRegion *RegionOfInterest;
659  const SVal ValueAtDereference;
660 
661  // Do not invalidate the reports where the value was modified
662  // after it got assigned to from the macro.
663  bool WasModified = false;
664 
665 public:
666  MacroNullReturnSuppressionVisitor(const SubRegion *R,
667  const SVal V) : RegionOfInterest(R),
668  ValueAtDereference(V) {}
669 
670  std::shared_ptr<PathDiagnosticPiece> VisitNode(const ExplodedNode *N,
671  const ExplodedNode *PrevN,
672  BugReporterContext &BRC,
673  BugReport &BR) override {
674  if (WasModified)
675  return nullptr;
676 
677  auto BugPoint = BR.getErrorNode()->getLocation().getAs<StmtPoint>();
678  if (!BugPoint)
679  return nullptr;
680 
681  const SourceManager &SMgr = BRC.getSourceManager();
682  if (auto Loc = matchAssignment(N, BRC)) {
683  if (isFunctionMacroExpansion(*Loc, SMgr)) {
684  std::string MacroName = getMacroName(*Loc, BRC);
685  SourceLocation BugLoc = BugPoint->getStmt()->getBeginLoc();
686  if (!BugLoc.isMacroID() || getMacroName(BugLoc, BRC) != MacroName)
687  BR.markInvalid(getTag(), MacroName.c_str());
688  }
689  }
690 
691  if (wasRegionOfInterestModifiedAt(RegionOfInterest, N, ValueAtDereference))
692  WasModified = true;
693 
694  return nullptr;
695  }
696 
697  static void addMacroVisitorIfNecessary(
698  const ExplodedNode *N, const MemRegion *R,
699  bool EnableNullFPSuppression, BugReport &BR,
700  const SVal V) {
701  AnalyzerOptions &Options = N->getState()->getAnalysisManager().options;
702  if (EnableNullFPSuppression && Options.shouldSuppressNullReturnPaths()
703  && V.getAs<Loc>())
704  BR.addVisitor(llvm::make_unique<MacroNullReturnSuppressionVisitor>(
705  R->getAs<SubRegion>(), V));
706  }
707 
708  void* getTag() const {
709  static int Tag = 0;
710  return static_cast<void *>(&Tag);
711  }
712 
713  void Profile(llvm::FoldingSetNodeID &ID) const override {
714  ID.AddPointer(getTag());
715  }
716 
717 private:
718  /// \return Source location of right hand side of an assignment
719  /// into \c RegionOfInterest, empty optional if none found.
720  Optional<SourceLocation> matchAssignment(const ExplodedNode *N,
721  BugReporterContext &BRC) {
723  ProgramStateRef State = N->getState();
724  auto *LCtx = N->getLocationContext();
725  if (!S)
726  return None;
727 
728  if (const auto *DS = dyn_cast<DeclStmt>(S)) {
729  if (const auto *VD = dyn_cast<VarDecl>(DS->getSingleDecl()))
730  if (const Expr *RHS = VD->getInit())
731  if (RegionOfInterest->isSubRegionOf(
732  State->getLValue(VD, LCtx).getAsRegion()))
733  return RHS->getBeginLoc();
734  } else if (const auto *BO = dyn_cast<BinaryOperator>(S)) {
735  const MemRegion *R = N->getSVal(BO->getLHS()).getAsRegion();
736  const Expr *RHS = BO->getRHS();
737  if (BO->isAssignmentOp() && RegionOfInterest->isSubRegionOf(R)) {
738  return RHS->getBeginLoc();
739  }
740  }
741  return None;
742  }
743 };
744 
745 /// Emits an extra note at the return statement of an interesting stack frame.
746 ///
747 /// The returned value is marked as an interesting value, and if it's null,
748 /// adds a visitor to track where it became null.
749 ///
750 /// This visitor is intended to be used when another visitor discovers that an
751 /// interesting value comes from an inlined function call.
752 class ReturnVisitor : public BugReporterVisitor {
753  const StackFrameContext *StackFrame;
754  enum {
755  Initial,
756  MaybeUnsuppress,
757  Satisfied
758  } Mode = Initial;
759 
760  bool EnableNullFPSuppression;
761  bool ShouldInvalidate = true;
762  AnalyzerOptions& Options;
763 
764 public:
765  ReturnVisitor(const StackFrameContext *Frame,
766  bool Suppressed,
767  AnalyzerOptions &Options)
768  : StackFrame(Frame), EnableNullFPSuppression(Suppressed),
769  Options(Options) {}
770 
771  static void *getTag() {
772  static int Tag = 0;
773  return static_cast<void *>(&Tag);
774  }
775 
776  void Profile(llvm::FoldingSetNodeID &ID) const override {
777  ID.AddPointer(ReturnVisitor::getTag());
778  ID.AddPointer(StackFrame);
779  ID.AddBoolean(EnableNullFPSuppression);
780  }
781 
782  /// Adds a ReturnVisitor if the given statement represents a call that was
783  /// inlined.
784  ///
785  /// This will search back through the ExplodedGraph, starting from the given
786  /// node, looking for when the given statement was processed. If it turns out
787  /// the statement is a call that was inlined, we add the visitor to the
788  /// bug report, so it can print a note later.
789  static void addVisitorIfNecessary(const ExplodedNode *Node, const Stmt *S,
790  BugReport &BR,
791  bool InEnableNullFPSuppression) {
792  if (!CallEvent::isCallStmt(S))
793  return;
794 
795  // First, find when we processed the statement.
796  do {
797  if (auto CEE = Node->getLocationAs<CallExitEnd>())
798  if (CEE->getCalleeContext()->getCallSite() == S)
799  break;
800  if (auto SP = Node->getLocationAs<StmtPoint>())
801  if (SP->getStmt() == S)
802  break;
803 
804  Node = Node->getFirstPred();
805  } while (Node);
806 
807  // Next, step over any post-statement checks.
808  while (Node && Node->getLocation().getAs<PostStmt>())
809  Node = Node->getFirstPred();
810  if (!Node)
811  return;
812 
813  // Finally, see if we inlined the call.
814  Optional<CallExitEnd> CEE = Node->getLocationAs<CallExitEnd>();
815  if (!CEE)
816  return;
817 
818  const StackFrameContext *CalleeContext = CEE->getCalleeContext();
819  if (CalleeContext->getCallSite() != S)
820  return;
821 
822  // Check the return value.
823  ProgramStateRef State = Node->getState();
824  SVal RetVal = Node->getSVal(S);
825 
826  // Handle cases where a reference is returned and then immediately used.
827  if (cast<Expr>(S)->isGLValue())
828  if (Optional<Loc> LValue = RetVal.getAs<Loc>())
829  RetVal = State->getSVal(*LValue);
830 
831  // See if the return value is NULL. If so, suppress the report.
832  AnalyzerOptions &Options = State->getAnalysisManager().options;
833 
834  bool EnableNullFPSuppression = false;
835  if (InEnableNullFPSuppression && Options.shouldSuppressNullReturnPaths())
836  if (Optional<Loc> RetLoc = RetVal.getAs<Loc>())
837  EnableNullFPSuppression = State->isNull(*RetLoc).isConstrainedTrue();
838 
839  BR.markInteresting(CalleeContext);
840  BR.addVisitor(llvm::make_unique<ReturnVisitor>(CalleeContext,
841  EnableNullFPSuppression,
842  Options));
843  }
844 
845  std::shared_ptr<PathDiagnosticPiece>
846  visitNodeInitial(const ExplodedNode *N, const ExplodedNode *PrevN,
847  BugReporterContext &BRC, BugReport &BR) {
848  // Only print a message at the interesting return statement.
849  if (N->getLocationContext() != StackFrame)
850  return nullptr;
851 
852  Optional<StmtPoint> SP = N->getLocationAs<StmtPoint>();
853  if (!SP)
854  return nullptr;
855 
856  const auto *Ret = dyn_cast<ReturnStmt>(SP->getStmt());
857  if (!Ret)
858  return nullptr;
859 
860  // Okay, we're at the right return statement, but do we have the return
861  // value available?
862  ProgramStateRef State = N->getState();
863  SVal V = State->getSVal(Ret, StackFrame);
864  if (V.isUnknownOrUndef())
865  return nullptr;
866 
867  // Don't print any more notes after this one.
868  Mode = Satisfied;
869 
870  const Expr *RetE = Ret->getRetValue();
871  assert(RetE && "Tracking a return value for a void function");
872 
873  // Handle cases where a reference is returned and then immediately used.
874  Optional<Loc> LValue;
875  if (RetE->isGLValue()) {
876  if ((LValue = V.getAs<Loc>())) {
877  SVal RValue = State->getRawSVal(*LValue, RetE->getType());
878  if (RValue.getAs<DefinedSVal>())
879  V = RValue;
880  }
881  }
882 
883  // Ignore aggregate rvalues.
884  if (V.getAs<nonloc::LazyCompoundVal>() ||
885  V.getAs<nonloc::CompoundVal>())
886  return nullptr;
887 
888  RetE = RetE->IgnoreParenCasts();
889 
890  // If we're returning 0, we should track where that 0 came from.
891  bugreporter::trackNullOrUndefValue(N, RetE, BR, /*IsArg*/ false,
892  EnableNullFPSuppression);
893 
894  // Build an appropriate message based on the return value.
895  SmallString<64> Msg;
896  llvm::raw_svector_ostream Out(Msg);
897 
898  if (State->isNull(V).isConstrainedTrue()) {
899  if (V.getAs<Loc>()) {
900 
901  // If we have counter-suppression enabled, make sure we keep visiting
902  // future nodes. We want to emit a path note as well, in case
903  // the report is resurrected as valid later on.
904  if (EnableNullFPSuppression &&
906  Mode = MaybeUnsuppress;
907 
908  if (RetE->getType()->isObjCObjectPointerType()) {
909  Out << "Returning nil";
910  } else {
911  Out << "Returning null pointer";
912  }
913  } else {
914  Out << "Returning zero";
915  }
916 
917  } else {
918  if (auto CI = V.getAs<nonloc::ConcreteInt>()) {
919  Out << "Returning the value " << CI->getValue();
920  } else if (V.getAs<Loc>()) {
921  Out << "Returning pointer";
922  } else {
923  Out << "Returning value";
924  }
925  }
926 
927  if (LValue) {
928  if (const MemRegion *MR = LValue->getAsRegion()) {
929  if (MR->canPrintPretty()) {
930  Out << " (reference to ";
931  MR->printPretty(Out);
932  Out << ")";
933  }
934  }
935  } else {
936  // FIXME: We should have a more generalized location printing mechanism.
937  if (const auto *DR = dyn_cast<DeclRefExpr>(RetE))
938  if (const auto *DD = dyn_cast<DeclaratorDecl>(DR->getDecl()))
939  Out << " (loaded from '" << *DD << "')";
940  }
941 
942  PathDiagnosticLocation L(Ret, BRC.getSourceManager(), StackFrame);
943  if (!L.isValid() || !L.asLocation().isValid())
944  return nullptr;
945 
946  return std::make_shared<PathDiagnosticEventPiece>(L, Out.str());
947  }
948 
949  std::shared_ptr<PathDiagnosticPiece>
950  visitNodeMaybeUnsuppress(const ExplodedNode *N, const ExplodedNode *PrevN,
951  BugReporterContext &BRC, BugReport &BR) {
952 #ifndef NDEBUG
953  assert(Options.shouldAvoidSuppressingNullArgumentPaths());
954 #endif
955 
956  // Are we at the entry node for this call?
957  Optional<CallEnter> CE = N->getLocationAs<CallEnter>();
958  if (!CE)
959  return nullptr;
960 
961  if (CE->getCalleeContext() != StackFrame)
962  return nullptr;
963 
964  Mode = Satisfied;
965 
966  // Don't automatically suppress a report if one of the arguments is
967  // known to be a null pointer. Instead, start tracking /that/ null
968  // value back to its origin.
969  ProgramStateManager &StateMgr = BRC.getStateManager();
970  CallEventManager &CallMgr = StateMgr.getCallEventManager();
971 
972  ProgramStateRef State = N->getState();
973  CallEventRef<> Call = CallMgr.getCaller(StackFrame, State);
974  for (unsigned I = 0, E = Call->getNumArgs(); I != E; ++I) {
975  Optional<Loc> ArgV = Call->getArgSVal(I).getAs<Loc>();
976  if (!ArgV)
977  continue;
978 
979  const Expr *ArgE = Call->getArgExpr(I);
980  if (!ArgE)
981  continue;
982 
983  // Is it possible for this argument to be non-null?
984  if (!State->isNull(*ArgV).isConstrainedTrue())
985  continue;
986 
987  if (bugreporter::trackNullOrUndefValue(N, ArgE, BR, /*IsArg=*/true,
988  EnableNullFPSuppression))
989  ShouldInvalidate = false;
990 
991  // If we /can't/ track the null pointer, we should err on the side of
992  // false negatives, and continue towards marking this report invalid.
993  // (We will still look at the other arguments, though.)
994  }
995 
996  return nullptr;
997  }
998 
999  std::shared_ptr<PathDiagnosticPiece> VisitNode(const ExplodedNode *N,
1000  const ExplodedNode *PrevN,
1001  BugReporterContext &BRC,
1002  BugReport &BR) override {
1003  switch (Mode) {
1004  case Initial:
1005  return visitNodeInitial(N, PrevN, BRC, BR);
1006  case MaybeUnsuppress:
1007  return visitNodeMaybeUnsuppress(N, PrevN, BRC, BR);
1008  case Satisfied:
1009  return nullptr;
1010  }
1011 
1012  llvm_unreachable("Invalid visit mode!");
1013  }
1014 
1015  void finalizeVisitor(BugReporterContext &BRC, const ExplodedNode *N,
1016  BugReport &BR) override {
1017  if (EnableNullFPSuppression && ShouldInvalidate)
1018  BR.markInvalid(ReturnVisitor::getTag(), StackFrame);
1019  }
1020 };
1021 
1022 } // namespace
1023 
1024 void FindLastStoreBRVisitor::Profile(llvm::FoldingSetNodeID &ID) const {
1025  static int tag = 0;
1026  ID.AddPointer(&tag);
1027  ID.AddPointer(R);
1028  ID.Add(V);
1029  ID.AddBoolean(EnableNullFPSuppression);
1030 }
1031 
1032 /// Returns true if \p N represents the DeclStmt declaring and initializing
1033 /// \p VR.
1034 static bool isInitializationOfVar(const ExplodedNode *N, const VarRegion *VR) {
1035  Optional<PostStmt> P = N->getLocationAs<PostStmt>();
1036  if (!P)
1037  return false;
1038 
1039  const DeclStmt *DS = P->getStmtAs<DeclStmt>();
1040  if (!DS)
1041  return false;
1042 
1043  if (DS->getSingleDecl() != VR->getDecl())
1044  return false;
1045 
1046  const MemSpaceRegion *VarSpace = VR->getMemorySpace();
1047  const auto *FrameSpace = dyn_cast<StackSpaceRegion>(VarSpace);
1048  if (!FrameSpace) {
1049  // If we ever directly evaluate global DeclStmts, this assertion will be
1050  // invalid, but this still seems preferable to silently accepting an
1051  // initialization that may be for a path-sensitive variable.
1052  assert(VR->getDecl()->isStaticLocal() && "non-static stackless VarRegion");
1053  return true;
1054  }
1055 
1056  assert(VR->getDecl()->hasLocalStorage());
1057  const LocationContext *LCtx = N->getLocationContext();
1058  return FrameSpace->getStackFrame() == LCtx->getStackFrame();
1059 }
1060 
1061 /// Show diagnostics for initializing or declaring a region \p R with a bad value.
1062 static void showBRDiagnostics(const char *action, llvm::raw_svector_ostream &os,
1063  const MemRegion *R, SVal V, const DeclStmt *DS) {
1064  if (R->canPrintPretty()) {
1065  R->printPretty(os);
1066  os << " ";
1067  }
1068 
1069  if (V.getAs<loc::ConcreteInt>()) {
1070  bool b = false;
1071  if (R->isBoundable()) {
1072  if (const auto *TR = dyn_cast<TypedValueRegion>(R)) {
1073  if (TR->getValueType()->isObjCObjectPointerType()) {
1074  os << action << "nil";
1075  b = true;
1076  }
1077  }
1078  }
1079  if (!b)
1080  os << action << "a null pointer value";
1081 
1082  } else if (auto CVal = V.getAs<nonloc::ConcreteInt>()) {
1083  os << action << CVal->getValue();
1084  } else if (DS) {
1085  if (V.isUndef()) {
1086  if (isa<VarRegion>(R)) {
1087  const auto *VD = cast<VarDecl>(DS->getSingleDecl());
1088  if (VD->getInit()) {
1089  os << (R->canPrintPretty() ? "initialized" : "Initializing")
1090  << " to a garbage value";
1091  } else {
1092  os << (R->canPrintPretty() ? "declared" : "Declaring")
1093  << " without an initial value";
1094  }
1095  }
1096  } else {
1097  os << (R->canPrintPretty() ? "initialized" : "Initialized")
1098  << " here";
1099  }
1100  }
1101 }
1102 
1103 /// Display diagnostics for passing bad region as a parameter.
1104 static void showBRParamDiagnostics(llvm::raw_svector_ostream& os,
1105  const VarRegion *VR,
1106  SVal V) {
1107  const auto *Param = cast<ParmVarDecl>(VR->getDecl());
1108 
1109  os << "Passing ";
1110 
1111  if (V.getAs<loc::ConcreteInt>()) {
1112  if (Param->getType()->isObjCObjectPointerType())
1113  os << "nil object reference";
1114  else
1115  os << "null pointer value";
1116  } else if (V.isUndef()) {
1117  os << "uninitialized value";
1118  } else if (auto CI = V.getAs<nonloc::ConcreteInt>()) {
1119  os << "the value " << CI->getValue();
1120  } else {
1121  os << "value";
1122  }
1123 
1124  // Printed parameter indexes are 1-based, not 0-based.
1125  unsigned Idx = Param->getFunctionScopeIndex() + 1;
1126  os << " via " << Idx << llvm::getOrdinalSuffix(Idx) << " parameter";
1127  if (VR->canPrintPretty()) {
1128  os << " ";
1129  VR->printPretty(os);
1130  }
1131 }
1132 
1133 /// Show default diagnostics for storing bad region.
1134 static void showBRDefaultDiagnostics(llvm::raw_svector_ostream& os,
1135  const MemRegion *R,
1136  SVal V) {
1137  if (V.getAs<loc::ConcreteInt>()) {
1138  bool b = false;
1139  if (R->isBoundable()) {
1140  if (const auto *TR = dyn_cast<TypedValueRegion>(R)) {
1141  if (TR->getValueType()->isObjCObjectPointerType()) {
1142  os << "nil object reference stored";
1143  b = true;
1144  }
1145  }
1146  }
1147  if (!b) {
1148  if (R->canPrintPretty())
1149  os << "Null pointer value stored";
1150  else
1151  os << "Storing null pointer value";
1152  }
1153 
1154  } else if (V.isUndef()) {
1155  if (R->canPrintPretty())
1156  os << "Uninitialized value stored";
1157  else
1158  os << "Storing uninitialized value";
1159 
1160  } else if (auto CV = V.getAs<nonloc::ConcreteInt>()) {
1161  if (R->canPrintPretty())
1162  os << "The value " << CV->getValue() << " is assigned";
1163  else
1164  os << "Assigning " << CV->getValue();
1165 
1166  } else {
1167  if (R->canPrintPretty())
1168  os << "Value assigned";
1169  else
1170  os << "Assigning value";
1171  }
1172 
1173  if (R->canPrintPretty()) {
1174  os << " to ";
1175  R->printPretty(os);
1176  }
1177 }
1178 
1179 std::shared_ptr<PathDiagnosticPiece>
1180 FindLastStoreBRVisitor::VisitNode(const ExplodedNode *Succ,
1181  const ExplodedNode *Pred,
1182  BugReporterContext &BRC, BugReport &BR) {
1183  if (Satisfied)
1184  return nullptr;
1185 
1186  const ExplodedNode *StoreSite = nullptr;
1187  const Expr *InitE = nullptr;
1188  bool IsParam = false;
1189 
1190  // First see if we reached the declaration of the region.
1191  if (const auto *VR = dyn_cast<VarRegion>(R)) {
1192  if (isInitializationOfVar(Pred, VR)) {
1193  StoreSite = Pred;
1194  InitE = VR->getDecl()->getInit();
1195  }
1196  }
1197 
1198  // If this is a post initializer expression, initializing the region, we
1199  // should track the initializer expression.
1200  if (Optional<PostInitializer> PIP = Pred->getLocationAs<PostInitializer>()) {
1201  const MemRegion *FieldReg = (const MemRegion *)PIP->getLocationValue();
1202  if (FieldReg && FieldReg == R) {
1203  StoreSite = Pred;
1204  InitE = PIP->getInitializer()->getInit();
1205  }
1206  }
1207 
1208  // Otherwise, see if this is the store site:
1209  // (1) Succ has this binding and Pred does not, i.e. this is
1210  // where the binding first occurred.
1211  // (2) Succ has this binding and is a PostStore node for this region, i.e.
1212  // the same binding was re-assigned here.
1213  if (!StoreSite) {
1214  if (Succ->getState()->getSVal(R) != V)
1215  return nullptr;
1216 
1217  if (Pred->getState()->getSVal(R) == V) {
1218  Optional<PostStore> PS = Succ->getLocationAs<PostStore>();
1219  if (!PS || PS->getLocationValue() != R)
1220  return nullptr;
1221  }
1222 
1223  StoreSite = Succ;
1224 
1225  // If this is an assignment expression, we can track the value
1226  // being assigned.
1227  if (Optional<PostStmt> P = Succ->getLocationAs<PostStmt>())
1228  if (const BinaryOperator *BO = P->getStmtAs<BinaryOperator>())
1229  if (BO->isAssignmentOp())
1230  InitE = BO->getRHS();
1231 
1232  // If this is a call entry, the variable should be a parameter.
1233  // FIXME: Handle CXXThisRegion as well. (This is not a priority because
1234  // 'this' should never be NULL, but this visitor isn't just for NULL and
1235  // UndefinedVal.)
1236  if (Optional<CallEnter> CE = Succ->getLocationAs<CallEnter>()) {
1237  if (const auto *VR = dyn_cast<VarRegion>(R)) {
1238  const auto *Param = cast<ParmVarDecl>(VR->getDecl());
1239 
1240  ProgramStateManager &StateMgr = BRC.getStateManager();
1241  CallEventManager &CallMgr = StateMgr.getCallEventManager();
1242 
1243  CallEventRef<> Call = CallMgr.getCaller(CE->getCalleeContext(),
1244  Succ->getState());
1245  InitE = Call->getArgExpr(Param->getFunctionScopeIndex());
1246  IsParam = true;
1247  }
1248  }
1249 
1250  // If this is a CXXTempObjectRegion, the Expr responsible for its creation
1251  // is wrapped inside of it.
1252  if (const auto *TmpR = dyn_cast<CXXTempObjectRegion>(R))
1253  InitE = TmpR->getExpr();
1254  }
1255 
1256  if (!StoreSite)
1257  return nullptr;
1258  Satisfied = true;
1259 
1260  // If we have an expression that provided the value, try to track where it
1261  // came from.
1262  if (InitE) {
1263  if (V.isUndef() ||
1264  V.getAs<loc::ConcreteInt>() || V.getAs<nonloc::ConcreteInt>()) {
1265  if (!IsParam)
1266  InitE = InitE->IgnoreParenCasts();
1267  bugreporter::trackNullOrUndefValue(StoreSite, InitE, BR, IsParam,
1268  EnableNullFPSuppression);
1269  }
1270  ReturnVisitor::addVisitorIfNecessary(StoreSite, InitE->IgnoreParenCasts(),
1271  BR, EnableNullFPSuppression);
1272  }
1273 
1274  // Okay, we've found the binding. Emit an appropriate message.
1275  SmallString<256> sbuf;
1276  llvm::raw_svector_ostream os(sbuf);
1277 
1278  if (Optional<PostStmt> PS = StoreSite->getLocationAs<PostStmt>()) {
1279  const Stmt *S = PS->getStmt();
1280  const char *action = nullptr;
1281  const auto *DS = dyn_cast<DeclStmt>(S);
1282  const auto *VR = dyn_cast<VarRegion>(R);
1283 
1284  if (DS) {
1285  action = R->canPrintPretty() ? "initialized to " :
1286  "Initializing to ";
1287  } else if (isa<BlockExpr>(S)) {
1288  action = R->canPrintPretty() ? "captured by block as " :
1289  "Captured by block as ";
1290  if (VR) {
1291  // See if we can get the BlockVarRegion.
1292  ProgramStateRef State = StoreSite->getState();
1293  SVal V = StoreSite->getSVal(S);
1294  if (const auto *BDR =
1295  dyn_cast_or_null<BlockDataRegion>(V.getAsRegion())) {
1296  if (const VarRegion *OriginalR = BDR->getOriginalRegion(VR)) {
1297  if (Optional<KnownSVal> KV =
1298  State->getSVal(OriginalR).getAs<KnownSVal>())
1299  BR.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
1300  *KV, OriginalR, EnableNullFPSuppression));
1301  }
1302  }
1303  }
1304  }
1305  if (action)
1306  showBRDiagnostics(action, os, R, V, DS);
1307 
1308  } else if (StoreSite->getLocation().getAs<CallEnter>()) {
1309  if (const auto *VR = dyn_cast<VarRegion>(R))
1310  showBRParamDiagnostics(os, VR, V);
1311  }
1312 
1313  if (os.str().empty())
1314  showBRDefaultDiagnostics(os, R, V);
1315 
1316  // Construct a new PathDiagnosticPiece.
1317  ProgramPoint P = StoreSite->getLocation();
1318  PathDiagnosticLocation L;
1319  if (P.getAs<CallEnter>() && InitE)
1320  L = PathDiagnosticLocation(InitE, BRC.getSourceManager(),
1321  P.getLocationContext());
1322 
1323  if (!L.isValid() || !L.asLocation().isValid())
1324  L = PathDiagnosticLocation::create(P, BRC.getSourceManager());
1325 
1326  if (!L.isValid() || !L.asLocation().isValid())
1327  return nullptr;
1328 
1329  return std::make_shared<PathDiagnosticEventPiece>(L, os.str());
1330 }
1331 
1332 void TrackConstraintBRVisitor::Profile(llvm::FoldingSetNodeID &ID) const {
1333  static int tag = 0;
1334  ID.AddPointer(&tag);
1335  ID.AddBoolean(Assumption);
1336  ID.Add(Constraint);
1337 }
1338 
1339 /// Return the tag associated with this visitor. This tag will be used
1340 /// to make all PathDiagnosticPieces created by this visitor.
1341 const char *TrackConstraintBRVisitor::getTag() {
1342  return "TrackConstraintBRVisitor";
1343 }
1344 
1345 bool TrackConstraintBRVisitor::isUnderconstrained(const ExplodedNode *N) const {
1346  if (IsZeroCheck)
1347  return N->getState()->isNull(Constraint).isUnderconstrained();
1348  return (bool)N->getState()->assume(Constraint, !Assumption);
1349 }
1350 
1351 std::shared_ptr<PathDiagnosticPiece>
1352 TrackConstraintBRVisitor::VisitNode(const ExplodedNode *N,
1353  const ExplodedNode *PrevN,
1354  BugReporterContext &BRC, BugReport &BR) {
1355  if (IsSatisfied)
1356  return nullptr;
1357 
1358  // Start tracking after we see the first state in which the value is
1359  // constrained.
1360  if (!IsTrackingTurnedOn)
1361  if (!isUnderconstrained(N))
1362  IsTrackingTurnedOn = true;
1363  if (!IsTrackingTurnedOn)
1364  return nullptr;
1365 
1366  // Check if in the previous state it was feasible for this constraint
1367  // to *not* be true.
1368  if (isUnderconstrained(PrevN)) {
1369  IsSatisfied = true;
1370 
1371  // As a sanity check, make sure that the negation of the constraint
1372  // was infeasible in the current state. If it is feasible, we somehow
1373  // missed the transition point.
1374  assert(!isUnderconstrained(N));
1375 
1376  // We found the transition point for the constraint. We now need to
1377  // pretty-print the constraint. (work-in-progress)
1378  SmallString<64> sbuf;
1379  llvm::raw_svector_ostream os(sbuf);
1380 
1381  if (Constraint.getAs<Loc>()) {
1382  os << "Assuming pointer value is ";
1383  os << (Assumption ? "non-null" : "null");
1384  }
1385 
1386  if (os.str().empty())
1387  return nullptr;
1388 
1389  // Construct a new PathDiagnosticPiece.
1390  ProgramPoint P = N->getLocation();
1391  PathDiagnosticLocation L =
1392  PathDiagnosticLocation::create(P, BRC.getSourceManager());
1393  if (!L.isValid())
1394  return nullptr;
1395 
1396  auto X = std::make_shared<PathDiagnosticEventPiece>(L, os.str());
1397  X->setTag(getTag());
1398  return std::move(X);
1399  }
1400 
1401  return nullptr;
1402 }
1403 
1404 SuppressInlineDefensiveChecksVisitor::
1405 SuppressInlineDefensiveChecksVisitor(DefinedSVal Value, const ExplodedNode *N)
1406  : V(Value) {
1407  // Check if the visitor is disabled.
1408  AnalyzerOptions &Options = N->getState()->getAnalysisManager().options;
1409  if (!Options.shouldSuppressInlinedDefensiveChecks())
1410  IsSatisfied = true;
1411 
1412  assert(N->getState()->isNull(V).isConstrainedTrue() &&
1413  "The visitor only tracks the cases where V is constrained to 0");
1414 }
1415 
1416 void SuppressInlineDefensiveChecksVisitor::Profile(
1417  llvm::FoldingSetNodeID &ID) const {
1418  static int id = 0;
1419  ID.AddPointer(&id);
1420  ID.Add(V);
1421 }
1422 
1423 const char *SuppressInlineDefensiveChecksVisitor::getTag() {
1424  return "IDCVisitor";
1425 }
1426 
1427 std::shared_ptr<PathDiagnosticPiece>
1428 SuppressInlineDefensiveChecksVisitor::VisitNode(const ExplodedNode *Succ,
1429  const ExplodedNode *Pred,
1430  BugReporterContext &BRC,
1431  BugReport &BR) {
1432  if (IsSatisfied)
1433  return nullptr;
1434 
1435  // Start tracking after we see the first state in which the value is null.
1436  if (!IsTrackingTurnedOn)
1437  if (Succ->getState()->isNull(V).isConstrainedTrue())
1438  IsTrackingTurnedOn = true;
1439  if (!IsTrackingTurnedOn)
1440  return nullptr;
1441 
1442  // Check if in the previous state it was feasible for this value
1443  // to *not* be null.
1444  if (!Pred->getState()->isNull(V).isConstrainedTrue()) {
1445  IsSatisfied = true;
1446 
1447  assert(Succ->getState()->isNull(V).isConstrainedTrue());
1448 
1449  // Check if this is inlined defensive checks.
1450  const LocationContext *CurLC =Succ->getLocationContext();
1451  const LocationContext *ReportLC = BR.getErrorNode()->getLocationContext();
1452  if (CurLC != ReportLC && !CurLC->isParentOf(ReportLC)) {
1453  BR.markInvalid("Suppress IDC", CurLC);
1454  return nullptr;
1455  }
1456 
1457  // Treat defensive checks in function-like macros as if they were an inlined
1458  // defensive check. If the bug location is not in a macro and the
1459  // terminator for the current location is in a macro then suppress the
1460  // warning.
1461  auto BugPoint = BR.getErrorNode()->getLocation().getAs<StmtPoint>();
1462 
1463  if (!BugPoint)
1464  return nullptr;
1465 
1466  ProgramPoint CurPoint = Succ->getLocation();
1467  const Stmt *CurTerminatorStmt = nullptr;
1468  if (auto BE = CurPoint.getAs<BlockEdge>()) {
1469  CurTerminatorStmt = BE->getSrc()->getTerminator().getStmt();
1470  } else if (auto SP = CurPoint.getAs<StmtPoint>()) {
1471  const Stmt *CurStmt = SP->getStmt();
1472  if (!CurStmt->getBeginLoc().isMacroID())
1473  return nullptr;
1474 
1475  CFGStmtMap *Map = CurLC->getAnalysisDeclContext()->getCFGStmtMap();
1476  CurTerminatorStmt = Map->getBlock(CurStmt)->getTerminator();
1477  } else {
1478  return nullptr;
1479  }
1480 
1481  if (!CurTerminatorStmt)
1482  return nullptr;
1483 
1484  SourceLocation TerminatorLoc = CurTerminatorStmt->getBeginLoc();
1485  if (TerminatorLoc.isMacroID()) {
1486  SourceLocation BugLoc = BugPoint->getStmt()->getBeginLoc();
1487 
1488  // Suppress reports unless we are in that same macro.
1489  if (!BugLoc.isMacroID() ||
1490  getMacroName(BugLoc, BRC) != getMacroName(TerminatorLoc, BRC)) {
1491  BR.markInvalid("Suppress Macro IDC", CurLC);
1492  }
1493  return nullptr;
1494  }
1495  }
1496  return nullptr;
1497 }
1498 
1499 static const MemRegion *getLocationRegionIfReference(const Expr *E,
1500  const ExplodedNode *N) {
1501  if (const auto *DR = dyn_cast<DeclRefExpr>(E)) {
1502  if (const auto *VD = dyn_cast<VarDecl>(DR->getDecl())) {
1503  if (!VD->getType()->isReferenceType())
1504  return nullptr;
1505  ProgramStateManager &StateMgr = N->getState()->getStateManager();
1506  MemRegionManager &MRMgr = StateMgr.getRegionManager();
1507  return MRMgr.getVarRegion(VD, N->getLocationContext());
1508  }
1509  }
1510 
1511  // FIXME: This does not handle other kinds of null references,
1512  // for example, references from FieldRegions:
1513  // struct Wrapper { int &ref; };
1514  // Wrapper w = { *(int *)0 };
1515  // w.ref = 1;
1516 
1517  return nullptr;
1518 }
1519 
1520 static const Expr *peelOffOuterExpr(const Expr *Ex,
1521  const ExplodedNode *N) {
1522  Ex = Ex->IgnoreParenCasts();
1523  if (const auto *EWC = dyn_cast<ExprWithCleanups>(Ex))
1524  return peelOffOuterExpr(EWC->getSubExpr(), N);
1525  if (const auto *OVE = dyn_cast<OpaqueValueExpr>(Ex))
1526  return peelOffOuterExpr(OVE->getSourceExpr(), N);
1527  if (const auto *POE = dyn_cast<PseudoObjectExpr>(Ex)) {
1528  const auto *PropRef = dyn_cast<ObjCPropertyRefExpr>(POE->getSyntacticForm());
1529  if (PropRef && PropRef->isMessagingGetter()) {
1530  const Expr *GetterMessageSend =
1531  POE->getSemanticExpr(POE->getNumSemanticExprs() - 1);
1532  assert(isa<ObjCMessageExpr>(GetterMessageSend->IgnoreParenCasts()));
1533  return peelOffOuterExpr(GetterMessageSend, N);
1534  }
1535  }
1536 
1537  // Peel off the ternary operator.
1538  if (const auto *CO = dyn_cast<ConditionalOperator>(Ex)) {
1539  // Find a node where the branching occurred and find out which branch
1540  // we took (true/false) by looking at the ExplodedGraph.
1541  const ExplodedNode *NI = N;
1542  do {
1543  ProgramPoint ProgPoint = NI->getLocation();
1544  if (Optional<BlockEdge> BE = ProgPoint.getAs<BlockEdge>()) {
1545  const CFGBlock *srcBlk = BE->getSrc();
1546  if (const Stmt *term = srcBlk->getTerminator()) {
1547  if (term == CO) {
1548  bool TookTrueBranch = (*(srcBlk->succ_begin()) == BE->getDst());
1549  if (TookTrueBranch)
1550  return peelOffOuterExpr(CO->getTrueExpr(), N);
1551  else
1552  return peelOffOuterExpr(CO->getFalseExpr(), N);
1553  }
1554  }
1555  }
1556  NI = NI->getFirstPred();
1557  } while (NI);
1558  }
1559 
1560  if (auto *BO = dyn_cast<BinaryOperator>(Ex))
1561  if (const Expr *SubEx = peelOffPointerArithmetic(BO))
1562  return peelOffOuterExpr(SubEx, N);
1563 
1564  if (auto *UO = dyn_cast<UnaryOperator>(Ex))
1565  if (UO->getOpcode() == UO_LNot)
1566  return peelOffOuterExpr(UO->getSubExpr(), N);
1567 
1568  return Ex;
1569 }
1570 
1571 /// Walk through nodes until we get one that matches the statement exactly.
1572 /// Alternately, if we hit a known lvalue for the statement, we know we've
1573 /// gone too far (though we can likely track the lvalue better anyway).
1574 static const ExplodedNode* findNodeForStatement(const ExplodedNode *N,
1575  const Stmt *S,
1576  const Expr *Inner) {
1577  do {
1578  const ProgramPoint &pp = N->getLocation();
1579  if (auto ps = pp.getAs<StmtPoint>()) {
1580  if (ps->getStmt() == S || ps->getStmt() == Inner)
1581  break;
1582  } else if (auto CEE = pp.getAs<CallExitEnd>()) {
1583  if (CEE->getCalleeContext()->getCallSite() == S ||
1584  CEE->getCalleeContext()->getCallSite() == Inner)
1585  break;
1586  }
1587  N = N->getFirstPred();
1588  } while (N);
1589  return N;
1590 }
1591 
1592 /// Find the ExplodedNode where the lvalue (the value of 'Ex')
1593 /// was computed.
1594 static const ExplodedNode* findNodeForExpression(const ExplodedNode *N,
1595  const Expr *Inner) {
1596  while (N) {
1597  if (auto P = N->getLocation().getAs<PostStmt>()) {
1598  if (P->getStmt() == Inner)
1599  break;
1600  }
1601  N = N->getFirstPred();
1602  }
1603  assert(N && "Unable to find the lvalue node.");
1604  return N;
1605 }
1606 
1607 /// Performing operator `&' on an lvalue expression is essentially a no-op.
1608 /// Then, if we are taking addresses of fields or elements, these are also
1609 /// unlikely to matter.
1610 static const Expr* peelOfOuterAddrOf(const Expr* Ex) {
1611  Ex = Ex->IgnoreParenCasts();
1612 
1613  // FIXME: There's a hack in our Store implementation that always computes
1614  // field offsets around null pointers as if they are always equal to 0.
1615  // The idea here is to report accesses to fields as null dereferences
1616  // even though the pointer value that's being dereferenced is actually
1617  // the offset of the field rather than exactly 0.
1618  // See the FIXME in StoreManager's getLValueFieldOrIvar() method.
1619  // This code interacts heavily with this hack; otherwise the value
1620  // would not be null at all for most fields, so we'd be unable to track it.
1621  if (const auto *Op = dyn_cast<UnaryOperator>(Ex))
1622  if (Op->getOpcode() == UO_AddrOf && Op->getSubExpr()->isLValue())
1623  if (const Expr *DerefEx = bugreporter::getDerefExpr(Op->getSubExpr()))
1624  return DerefEx;
1625  return Ex;
1626 }
1627 
1628 bool bugreporter::trackNullOrUndefValue(const ExplodedNode *N,
1629  const Stmt *S,
1630  BugReport &report, bool IsArg,
1631  bool EnableNullFPSuppression) {
1632  if (!S || !N)
1633  return false;
1634 
1635  if (const auto *Ex = dyn_cast<Expr>(S))
1636  S = peelOffOuterExpr(Ex, N);
1637 
1638  const Expr *Inner = nullptr;
1639  if (const auto *Ex = dyn_cast<Expr>(S)) {
1640  Ex = peelOfOuterAddrOf(Ex);
1641  Ex = Ex->IgnoreParenCasts();
1642 
1644  || CallEvent::isCallStmt(Ex)))
1645  Inner = Ex;
1646  }
1647 
1648  if (IsArg && !Inner) {
1649  assert(N->getLocation().getAs<CallEnter>() && "Tracking arg but not at call");
1650  } else {
1651  N = findNodeForStatement(N, S, Inner);
1652  if (!N)
1653  return false;
1654  }
1655 
1656  ProgramStateRef state = N->getState();
1657 
1658  // The message send could be nil due to the receiver being nil.
1659  // At this point in the path, the receiver should be live since we are at the
1660  // message send expr. If it is nil, start tracking it.
1661  if (const Expr *Receiver = NilReceiverBRVisitor::getNilReceiver(S, N))
1662  trackNullOrUndefValue(N, Receiver, report, /* IsArg=*/ false,
1663  EnableNullFPSuppression);
1664 
1665  // See if the expression we're interested refers to a variable.
1666  // If so, we can track both its contents and constraints on its value.
1667  if (Inner && ExplodedGraph::isInterestingLValueExpr(Inner)) {
1668  const ExplodedNode *LVNode = findNodeForExpression(N, Inner);
1669  ProgramStateRef LVState = LVNode->getState();
1670  SVal LVal = LVNode->getSVal(Inner);
1671 
1672  const MemRegion *RR = getLocationRegionIfReference(Inner, N);
1673  bool LVIsNull = LVState->isNull(LVal).isConstrainedTrue();
1674 
1675  // If this is a C++ reference to a null pointer, we are tracking the
1676  // pointer. In addition, we should find the store at which the reference
1677  // got initialized.
1678  if (RR && !LVIsNull) {
1679  if (auto KV = LVal.getAs<KnownSVal>())
1680  report.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
1681  *KV, RR, EnableNullFPSuppression));
1682  }
1683 
1684  // In case of C++ references, we want to differentiate between a null
1685  // reference and reference to null pointer.
1686  // If the LVal is null, check if we are dealing with null reference.
1687  // For those, we want to track the location of the reference.
1688  const MemRegion *R = (RR && LVIsNull) ? RR :
1689  LVNode->getSVal(Inner).getAsRegion();
1690 
1691  if (R) {
1692  ProgramStateRef S = N->getState();
1693 
1694  // Mark both the variable region and its contents as interesting.
1695  SVal V = LVState->getRawSVal(loc::MemRegionVal(R));
1696  report.addVisitor(
1697  llvm::make_unique<NoStoreFuncVisitor>(cast<SubRegion>(R)));
1698 
1699  MacroNullReturnSuppressionVisitor::addMacroVisitorIfNecessary(
1700  N, R, EnableNullFPSuppression, report, V);
1701 
1702  report.markInteresting(R);
1703  report.markInteresting(V);
1704  report.addVisitor(llvm::make_unique<UndefOrNullArgVisitor>(R));
1705 
1706  // If the contents are symbolic, find out when they became null.
1707  if (V.getAsLocSymbol(/*IncludeBaseRegions*/ true))
1708  report.addVisitor(llvm::make_unique<TrackConstraintBRVisitor>(
1709  V.castAs<DefinedSVal>(), false));
1710 
1711  // Add visitor, which will suppress inline defensive checks.
1712  if (auto DV = V.getAs<DefinedSVal>()) {
1713  if (!DV->isZeroConstant() && LVState->isNull(*DV).isConstrainedTrue() &&
1714  EnableNullFPSuppression) {
1715  report.addVisitor(
1716  llvm::make_unique<SuppressInlineDefensiveChecksVisitor>(*DV,
1717  LVNode));
1718  }
1719  }
1720 
1721  if (auto KV = V.getAs<KnownSVal>())
1722  report.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
1723  *KV, R, EnableNullFPSuppression));
1724  return true;
1725  }
1726  }
1727 
1728  // If the expression is not an "lvalue expression", we can still
1729  // track the constraints on its contents.
1730  SVal V = state->getSValAsScalarOrLoc(S, N->getLocationContext());
1731 
1732  // If the value came from an inlined function call, we should at least make
1733  // sure that function isn't pruned in our output.
1734  if (const auto *E = dyn_cast<Expr>(S))
1735  S = E->IgnoreParenCasts();
1736 
1737  ReturnVisitor::addVisitorIfNecessary(N, S, report, EnableNullFPSuppression);
1738 
1739  // Uncomment this to find cases where we aren't properly getting the
1740  // base value that was dereferenced.
1741  // assert(!V.isUnknownOrUndef());
1742  // Is it a symbolic value?
1743  if (auto L = V.getAs<loc::MemRegionVal>()) {
1744  report.addVisitor(llvm::make_unique<UndefOrNullArgVisitor>(L->getRegion()));
1745 
1746  // At this point we are dealing with the region's LValue.
1747  // However, if the rvalue is a symbolic region, we should track it as well.
1748  // Try to use the correct type when looking up the value.
1749  SVal RVal;
1750  if (const auto *E = dyn_cast<Expr>(S))
1751  RVal = state->getRawSVal(L.getValue(), E->getType());
1752  else
1753  RVal = state->getSVal(L->getRegion());
1754 
1755  if (auto KV = RVal.getAs<KnownSVal>())
1756  report.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
1757  *KV, L->getRegion(), EnableNullFPSuppression));
1758 
1759  const MemRegion *RegionRVal = RVal.getAsRegion();
1760  if (RegionRVal && isa<SymbolicRegion>(RegionRVal)) {
1761  report.markInteresting(RegionRVal);
1762  report.addVisitor(llvm::make_unique<TrackConstraintBRVisitor>(
1763  loc::MemRegionVal(RegionRVal), false));
1764  }
1765  }
1766  return true;
1767 }
1768 
1769 const Expr *NilReceiverBRVisitor::getNilReceiver(const Stmt *S,
1770  const ExplodedNode *N) {
1771  const auto *ME = dyn_cast<ObjCMessageExpr>(S);
1772  if (!ME)
1773  return nullptr;
1774  if (const Expr *Receiver = ME->getInstanceReceiver()) {
1775  ProgramStateRef state = N->getState();
1776  SVal V = N->getSVal(Receiver);
1777  if (state->isNull(V).isConstrainedTrue())
1778  return Receiver;
1779  }
1780  return nullptr;
1781 }
1782 
1783 std::shared_ptr<PathDiagnosticPiece>
1784 NilReceiverBRVisitor::VisitNode(const ExplodedNode *N,
1785  const ExplodedNode *PrevN,
1786  BugReporterContext &BRC, BugReport &BR) {
1787  Optional<PreStmt> P = N->getLocationAs<PreStmt>();
1788  if (!P)
1789  return nullptr;
1790 
1791  const Stmt *S = P->getStmt();
1792  const Expr *Receiver = getNilReceiver(S, N);
1793  if (!Receiver)
1794  return nullptr;
1795 
1797  llvm::raw_svector_ostream OS(Buf);
1798 
1799  if (const auto *ME = dyn_cast<ObjCMessageExpr>(S)) {
1800  OS << "'";
1801  ME->getSelector().print(OS);
1802  OS << "' not called";
1803  }
1804  else {
1805  OS << "No method is called";
1806  }
1807  OS << " because the receiver is nil";
1808 
1809  // The receiver was nil, and hence the method was skipped.
1810  // Register a BugReporterVisitor to issue a message telling us how
1811  // the receiver was null.
1812  bugreporter::trackNullOrUndefValue(N, Receiver, BR, /*IsArg*/ false,
1813  /*EnableNullFPSuppression*/ false);
1814  // Issue a message saying that the method was skipped.
1815  PathDiagnosticLocation L(Receiver, BRC.getSourceManager(),
1816  N->getLocationContext());
1817  return std::make_shared<PathDiagnosticEventPiece>(L, OS.str());
1818 }
1819 
1820 // Registers every VarDecl inside a Stmt with a last store visitor.
1821 void FindLastStoreBRVisitor::registerStatementVarDecls(BugReport &BR,
1822  const Stmt *S,
1823  bool EnableNullFPSuppression) {
1824  const ExplodedNode *N = BR.getErrorNode();
1825  std::deque<const Stmt *> WorkList;
1826  WorkList.push_back(S);
1827 
1828  while (!WorkList.empty()) {
1829  const Stmt *Head = WorkList.front();
1830  WorkList.pop_front();
1831 
1832  ProgramStateManager &StateMgr = N->getState()->getStateManager();
1833 
1834  if (const auto *DR = dyn_cast<DeclRefExpr>(Head)) {
1835  if (const auto *VD = dyn_cast<VarDecl>(DR->getDecl())) {
1836  const VarRegion *R =
1837  StateMgr.getRegionManager().getVarRegion(VD, N->getLocationContext());
1838 
1839  // What did we load?
1840  SVal V = N->getSVal(S);
1841 
1842  if (V.getAs<loc::ConcreteInt>() || V.getAs<nonloc::ConcreteInt>()) {
1843  // Register a new visitor with the BugReport.
1844  BR.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
1845  V.castAs<KnownSVal>(), R, EnableNullFPSuppression));
1846  }
1847  }
1848  }
1849 
1850  for (const Stmt *SubStmt : Head->children())
1851  WorkList.push_back(SubStmt);
1852  }
1853 }
1854 
1855 //===----------------------------------------------------------------------===//
1856 // Visitor that tries to report interesting diagnostics from conditions.
1857 //===----------------------------------------------------------------------===//
1858 
1859 /// Return the tag associated with this visitor. This tag will be used
1860 /// to make all PathDiagnosticPieces created by this visitor.
1861 const char *ConditionBRVisitor::getTag() {
1862  return "ConditionBRVisitor";
1863 }
1864 
1865 std::shared_ptr<PathDiagnosticPiece>
1866 ConditionBRVisitor::VisitNode(const ExplodedNode *N, const ExplodedNode *Prev,
1867  BugReporterContext &BRC, BugReport &BR) {
1868  auto piece = VisitNodeImpl(N, Prev, BRC, BR);
1869  if (piece) {
1870  piece->setTag(getTag());
1871  if (auto *ev = dyn_cast<PathDiagnosticEventPiece>(piece.get()))
1872  ev->setPrunable(true, /* override */ false);
1873  }
1874  return piece;
1875 }
1876 
1877 std::shared_ptr<PathDiagnosticPiece>
1878 ConditionBRVisitor::VisitNodeImpl(const ExplodedNode *N,
1879  const ExplodedNode *Prev,
1880  BugReporterContext &BRC, BugReport &BR) {
1881  ProgramPoint progPoint = N->getLocation();
1882  ProgramStateRef CurrentState = N->getState();
1883  ProgramStateRef PrevState = Prev->getState();
1884 
1885  // Compare the GDMs of the state, because that is where constraints
1886  // are managed. Note that ensure that we only look at nodes that
1887  // were generated by the analyzer engine proper, not checkers.
1888  if (CurrentState->getGDM().getRoot() ==
1889  PrevState->getGDM().getRoot())
1890  return nullptr;
1891 
1892  // If an assumption was made on a branch, it should be caught
1893  // here by looking at the state transition.
1894  if (Optional<BlockEdge> BE = progPoint.getAs<BlockEdge>()) {
1895  const CFGBlock *srcBlk = BE->getSrc();
1896  if (const Stmt *term = srcBlk->getTerminator())
1897  return VisitTerminator(term, N, srcBlk, BE->getDst(), BR, BRC);
1898  return nullptr;
1899  }
1900 
1901  if (Optional<PostStmt> PS = progPoint.getAs<PostStmt>()) {
1902  const std::pair<const ProgramPointTag *, const ProgramPointTag *> &tags =
1904 
1905  const ProgramPointTag *tag = PS->getTag();
1906  if (tag == tags.first)
1907  return VisitTrueTest(cast<Expr>(PS->getStmt()), true,
1908  BRC, BR, N);
1909  if (tag == tags.second)
1910  return VisitTrueTest(cast<Expr>(PS->getStmt()), false,
1911  BRC, BR, N);
1912 
1913  return nullptr;
1914  }
1915 
1916  return nullptr;
1917 }
1918 
1919 std::shared_ptr<PathDiagnosticPiece> ConditionBRVisitor::VisitTerminator(
1920  const Stmt *Term, const ExplodedNode *N, const CFGBlock *srcBlk,
1921  const CFGBlock *dstBlk, BugReport &R, BugReporterContext &BRC) {
1922  const Expr *Cond = nullptr;
1923 
1924  // In the code below, Term is a CFG terminator and Cond is a branch condition
1925  // expression upon which the decision is made on this terminator.
1926  //
1927  // For example, in "if (x == 0)", the "if (x == 0)" statement is a terminator,
1928  // and "x == 0" is the respective condition.
1929  //
1930  // Another example: in "if (x && y)", we've got two terminators and two
1931  // conditions due to short-circuit nature of operator "&&":
1932  // 1. The "if (x && y)" statement is a terminator,
1933  // and "y" is the respective condition.
1934  // 2. Also "x && ..." is another terminator,
1935  // and "x" is its condition.
1936 
1937  switch (Term->getStmtClass()) {
1938  // FIXME: Stmt::SwitchStmtClass is worth handling, however it is a bit
1939  // more tricky because there are more than two branches to account for.
1940  default:
1941  return nullptr;
1942  case Stmt::IfStmtClass:
1943  Cond = cast<IfStmt>(Term)->getCond();
1944  break;
1945  case Stmt::ConditionalOperatorClass:
1946  Cond = cast<ConditionalOperator>(Term)->getCond();
1947  break;
1948  case Stmt::BinaryOperatorClass:
1949  // When we encounter a logical operator (&& or ||) as a CFG terminator,
1950  // then the condition is actually its LHS; otherwise, we'd encounter
1951  // the parent, such as if-statement, as a terminator.
1952  const auto *BO = cast<BinaryOperator>(Term);
1953  assert(BO->isLogicalOp() &&
1954  "CFG terminator is not a short-circuit operator!");
1955  Cond = BO->getLHS();
1956  break;
1957  }
1958 
1959  // However, when we encounter a logical operator as a branch condition,
1960  // then the condition is actually its RHS, because LHS would be
1961  // the condition for the logical operator terminator.
1962  while (const auto *InnerBO = dyn_cast<BinaryOperator>(Cond)) {
1963  if (!InnerBO->isLogicalOp())
1964  break;
1965  Cond = InnerBO->getRHS()->IgnoreParens();
1966  }
1967 
1968  assert(Cond);
1969  assert(srcBlk->succ_size() == 2);
1970  const bool tookTrue = *(srcBlk->succ_begin()) == dstBlk;
1971  return VisitTrueTest(Cond, tookTrue, BRC, R, N);
1972 }
1973 
1974 std::shared_ptr<PathDiagnosticPiece>
1975 ConditionBRVisitor::VisitTrueTest(const Expr *Cond, bool tookTrue,
1976  BugReporterContext &BRC, BugReport &R,
1977  const ExplodedNode *N) {
1978  // These will be modified in code below, but we need to preserve the original
1979  // values in case we want to throw the generic message.
1980  const Expr *CondTmp = Cond;
1981  bool tookTrueTmp = tookTrue;
1982 
1983  while (true) {
1984  CondTmp = CondTmp->IgnoreParenCasts();
1985  switch (CondTmp->getStmtClass()) {
1986  default:
1987  break;
1988  case Stmt::BinaryOperatorClass:
1989  if (auto P = VisitTrueTest(Cond, cast<BinaryOperator>(CondTmp),
1990  tookTrueTmp, BRC, R, N))
1991  return P;
1992  break;
1993  case Stmt::DeclRefExprClass:
1994  if (auto P = VisitTrueTest(Cond, cast<DeclRefExpr>(CondTmp),
1995  tookTrueTmp, BRC, R, N))
1996  return P;
1997  break;
1998  case Stmt::UnaryOperatorClass: {
1999  const auto *UO = cast<UnaryOperator>(CondTmp);
2000  if (UO->getOpcode() == UO_LNot) {
2001  tookTrueTmp = !tookTrueTmp;
2002  CondTmp = UO->getSubExpr();
2003  continue;
2004  }
2005  break;
2006  }
2007  }
2008  break;
2009  }
2010 
2011  // Condition too complex to explain? Just say something so that the user
2012  // knew we've made some path decision at this point.
2013  const LocationContext *LCtx = N->getLocationContext();
2014  PathDiagnosticLocation Loc(Cond, BRC.getSourceManager(), LCtx);
2015  if (!Loc.isValid() || !Loc.asLocation().isValid())
2016  return nullptr;
2017 
2018  return std::make_shared<PathDiagnosticEventPiece>(
2019  Loc, tookTrue ? GenericTrueMessage : GenericFalseMessage);
2020 }
2021 
2022 bool ConditionBRVisitor::patternMatch(const Expr *Ex,
2023  const Expr *ParentEx,
2024  raw_ostream &Out,
2025  BugReporterContext &BRC,
2026  BugReport &report,
2027  const ExplodedNode *N,
2028  Optional<bool> &prunable) {
2029  const Expr *OriginalExpr = Ex;
2030  Ex = Ex->IgnoreParenCasts();
2031 
2032  // Use heuristics to determine if Ex is a macro expending to a literal and
2033  // if so, use the macro's name.
2034  SourceLocation LocStart = Ex->getBeginLoc();
2035  SourceLocation LocEnd = Ex->getEndLoc();
2036  if (LocStart.isMacroID() && LocEnd.isMacroID() &&
2037  (isa<GNUNullExpr>(Ex) ||
2038  isa<ObjCBoolLiteralExpr>(Ex) ||
2039  isa<CXXBoolLiteralExpr>(Ex) ||
2040  isa<IntegerLiteral>(Ex) ||
2041  isa<FloatingLiteral>(Ex))) {
2042  StringRef StartName = Lexer::getImmediateMacroNameForDiagnostics(LocStart,
2043  BRC.getSourceManager(), BRC.getASTContext().getLangOpts());
2044  StringRef EndName = Lexer::getImmediateMacroNameForDiagnostics(LocEnd,
2045  BRC.getSourceManager(), BRC.getASTContext().getLangOpts());
2046  bool beginAndEndAreTheSameMacro = StartName.equals(EndName);
2047 
2048  bool partOfParentMacro = false;
2049  if (ParentEx->getBeginLoc().isMacroID()) {
2051  ParentEx->getBeginLoc(), BRC.getSourceManager(),
2052  BRC.getASTContext().getLangOpts());
2053  partOfParentMacro = PName.equals(StartName);
2054  }
2055 
2056  if (beginAndEndAreTheSameMacro && !partOfParentMacro ) {
2057  // Get the location of the macro name as written by the caller.
2058  SourceLocation Loc = LocStart;
2059  while (LocStart.isMacroID()) {
2060  Loc = LocStart;
2061  LocStart = BRC.getSourceManager().getImmediateMacroCallerLoc(LocStart);
2062  }
2063  StringRef MacroName = Lexer::getImmediateMacroNameForDiagnostics(
2064  Loc, BRC.getSourceManager(), BRC.getASTContext().getLangOpts());
2065 
2066  // Return the macro name.
2067  Out << MacroName;
2068  return false;
2069  }
2070  }
2071 
2072  if (const auto *DR = dyn_cast<DeclRefExpr>(Ex)) {
2073  const bool quotes = isa<VarDecl>(DR->getDecl());
2074  if (quotes) {
2075  Out << '\'';
2076  const LocationContext *LCtx = N->getLocationContext();
2077  const ProgramState *state = N->getState().get();
2078  if (const MemRegion *R = state->getLValue(cast<VarDecl>(DR->getDecl()),
2079  LCtx).getAsRegion()) {
2080  if (report.isInteresting(R))
2081  prunable = false;
2082  else {
2083  const ProgramState *state = N->getState().get();
2084  SVal V = state->getSVal(R);
2085  if (report.isInteresting(V))
2086  prunable = false;
2087  }
2088  }
2089  }
2090  Out << DR->getDecl()->getDeclName().getAsString();
2091  if (quotes)
2092  Out << '\'';
2093  return quotes;
2094  }
2095 
2096  if (const auto *IL = dyn_cast<IntegerLiteral>(Ex)) {
2097  QualType OriginalTy = OriginalExpr->getType();
2098  if (OriginalTy->isPointerType()) {
2099  if (IL->getValue() == 0) {
2100  Out << "null";
2101  return false;
2102  }
2103  }
2104  else if (OriginalTy->isObjCObjectPointerType()) {
2105  if (IL->getValue() == 0) {
2106  Out << "nil";
2107  return false;
2108  }
2109  }
2110 
2111  Out << IL->getValue();
2112  return false;
2113  }
2114 
2115  return false;
2116 }
2117 
2118 std::shared_ptr<PathDiagnosticPiece>
2119 ConditionBRVisitor::VisitTrueTest(const Expr *Cond, const BinaryOperator *BExpr,
2120  const bool tookTrue, BugReporterContext &BRC,
2121  BugReport &R, const ExplodedNode *N) {
2122  bool shouldInvert = false;
2123  Optional<bool> shouldPrune;
2124 
2125  SmallString<128> LhsString, RhsString;
2126  {
2127  llvm::raw_svector_ostream OutLHS(LhsString), OutRHS(RhsString);
2128  const bool isVarLHS = patternMatch(BExpr->getLHS(), BExpr, OutLHS,
2129  BRC, R, N, shouldPrune);
2130  const bool isVarRHS = patternMatch(BExpr->getRHS(), BExpr, OutRHS,
2131  BRC, R, N, shouldPrune);
2132 
2133  shouldInvert = !isVarLHS && isVarRHS;
2134  }
2135 
2136  BinaryOperator::Opcode Op = BExpr->getOpcode();
2137 
2139  // For assignment operators, all that we care about is that the LHS
2140  // evaluates to "true" or "false".
2141  return VisitConditionVariable(LhsString, BExpr->getLHS(), tookTrue,
2142  BRC, R, N);
2143  }
2144 
2145  // For non-assignment operations, we require that we can understand
2146  // both the LHS and RHS.
2147  if (LhsString.empty() || RhsString.empty() ||
2148  !BinaryOperator::isComparisonOp(Op) || Op == BO_Cmp)
2149  return nullptr;
2150 
2151  // Should we invert the strings if the LHS is not a variable name?
2152  SmallString<256> buf;
2153  llvm::raw_svector_ostream Out(buf);
2154  Out << "Assuming " << (shouldInvert ? RhsString : LhsString) << " is ";
2155 
2156  // Do we need to invert the opcode?
2157  if (shouldInvert)
2158  switch (Op) {
2159  default: break;
2160  case BO_LT: Op = BO_GT; break;
2161  case BO_GT: Op = BO_LT; break;
2162  case BO_LE: Op = BO_GE; break;
2163  case BO_GE: Op = BO_LE; break;
2164  }
2165 
2166  if (!tookTrue)
2167  switch (Op) {
2168  case BO_EQ: Op = BO_NE; break;
2169  case BO_NE: Op = BO_EQ; break;
2170  case BO_LT: Op = BO_GE; break;
2171  case BO_GT: Op = BO_LE; break;
2172  case BO_LE: Op = BO_GT; break;
2173  case BO_GE: Op = BO_LT; break;
2174  default:
2175  return nullptr;
2176  }
2177 
2178  switch (Op) {
2179  case BO_EQ:
2180  Out << "equal to ";
2181  break;
2182  case BO_NE:
2183  Out << "not equal to ";
2184  break;
2185  default:
2186  Out << BinaryOperator::getOpcodeStr(Op) << ' ';
2187  break;
2188  }
2189 
2190  Out << (shouldInvert ? LhsString : RhsString);
2191  const LocationContext *LCtx = N->getLocationContext();
2192  PathDiagnosticLocation Loc(Cond, BRC.getSourceManager(), LCtx);
2193  auto event = std::make_shared<PathDiagnosticEventPiece>(Loc, Out.str());
2194  if (shouldPrune.hasValue())
2195  event->setPrunable(shouldPrune.getValue());
2196  return event;
2197 }
2198 
2199 std::shared_ptr<PathDiagnosticPiece> ConditionBRVisitor::VisitConditionVariable(
2200  StringRef LhsString, const Expr *CondVarExpr, const bool tookTrue,
2201  BugReporterContext &BRC, BugReport &report, const ExplodedNode *N) {
2202  // FIXME: If there's already a constraint tracker for this variable,
2203  // we shouldn't emit anything here (c.f. the double note in
2204  // test/Analysis/inlining/path-notes.c)
2205  SmallString<256> buf;
2206  llvm::raw_svector_ostream Out(buf);
2207  Out << "Assuming " << LhsString << " is ";
2208 
2209  QualType Ty = CondVarExpr->getType();
2210 
2211  if (Ty->isPointerType())
2212  Out << (tookTrue ? "not null" : "null");
2213  else if (Ty->isObjCObjectPointerType())
2214  Out << (tookTrue ? "not nil" : "nil");
2215  else if (Ty->isBooleanType())
2216  Out << (tookTrue ? "true" : "false");
2217  else if (Ty->isIntegralOrEnumerationType())
2218  Out << (tookTrue ? "non-zero" : "zero");
2219  else
2220  return nullptr;
2221 
2222  const LocationContext *LCtx = N->getLocationContext();
2223  PathDiagnosticLocation Loc(CondVarExpr, BRC.getSourceManager(), LCtx);
2224  auto event = std::make_shared<PathDiagnosticEventPiece>(Loc, Out.str());
2225 
2226  if (const auto *DR = dyn_cast<DeclRefExpr>(CondVarExpr)) {
2227  if (const auto *VD = dyn_cast<VarDecl>(DR->getDecl())) {
2228  const ProgramState *state = N->getState().get();
2229  if (const MemRegion *R = state->getLValue(VD, LCtx).getAsRegion()) {
2230  if (report.isInteresting(R))
2231  event->setPrunable(false);
2232  }
2233  }
2234  }
2235 
2236  return event;
2237 }
2238 
2239 std::shared_ptr<PathDiagnosticPiece>
2240 ConditionBRVisitor::VisitTrueTest(const Expr *Cond, const DeclRefExpr *DR,
2241  const bool tookTrue, BugReporterContext &BRC,
2242  BugReport &report, const ExplodedNode *N) {
2243  const auto *VD = dyn_cast<VarDecl>(DR->getDecl());
2244  if (!VD)
2245  return nullptr;
2246 
2247  SmallString<256> Buf;
2248  llvm::raw_svector_ostream Out(Buf);
2249 
2250  Out << "Assuming '" << VD->getDeclName() << "' is ";
2251 
2252  QualType VDTy = VD->getType();
2253 
2254  if (VDTy->isPointerType())
2255  Out << (tookTrue ? "non-null" : "null");
2256  else if (VDTy->isObjCObjectPointerType())
2257  Out << (tookTrue ? "non-nil" : "nil");
2258  else if (VDTy->isScalarType())
2259  Out << (tookTrue ? "not equal to 0" : "0");
2260  else
2261  return nullptr;
2262 
2263  const LocationContext *LCtx = N->getLocationContext();
2264  PathDiagnosticLocation Loc(Cond, BRC.getSourceManager(), LCtx);
2265  auto event = std::make_shared<PathDiagnosticEventPiece>(Loc, Out.str());
2266 
2267  const ProgramState *state = N->getState().get();
2268  if (const MemRegion *R = state->getLValue(VD, LCtx).getAsRegion()) {
2269  if (report.isInteresting(R))
2270  event->setPrunable(false);
2271  else {
2272  SVal V = state->getSVal(R);
2273  if (report.isInteresting(V))
2274  event->setPrunable(false);
2275  }
2276  }
2277  return std::move(event);
2278 }
2279 
2280 const char *const ConditionBRVisitor::GenericTrueMessage =
2281  "Assuming the condition is true";
2282 const char *const ConditionBRVisitor::GenericFalseMessage =
2283  "Assuming the condition is false";
2284 
2285 bool ConditionBRVisitor::isPieceMessageGeneric(
2286  const PathDiagnosticPiece *Piece) {
2287  return Piece->getString() == GenericTrueMessage ||
2288  Piece->getString() == GenericFalseMessage;
2289 }
2290 
2291 void LikelyFalsePositiveSuppressionBRVisitor::finalizeVisitor(
2292  BugReporterContext &BRC, const ExplodedNode *N, BugReport &BR) {
2293  // Here we suppress false positives coming from system headers. This list is
2294  // based on known issues.
2295  AnalyzerOptions &Options = BRC.getAnalyzerOptions();
2296  const Decl *D = N->getLocationContext()->getDecl();
2297 
2299  // Skip reports within the 'std' namespace. Although these can sometimes be
2300  // the user's fault, we currently don't report them very well, and
2301  // Note that this will not help for any other data structure libraries, like
2302  // TR1, Boost, or llvm/ADT.
2303  if (Options.shouldSuppressFromCXXStandardLibrary()) {
2304  BR.markInvalid(getTag(), nullptr);
2305  return;
2306  } else {
2307  // If the complete 'std' suppression is not enabled, suppress reports
2308  // from the 'std' namespace that are known to produce false positives.
2309 
2310  // The analyzer issues a false use-after-free when std::list::pop_front
2311  // or std::list::pop_back are called multiple times because we cannot
2312  // reason about the internal invariants of the data structure.
2313  if (const auto *MD = dyn_cast<CXXMethodDecl>(D)) {
2314  const CXXRecordDecl *CD = MD->getParent();
2315  if (CD->getName() == "list") {
2316  BR.markInvalid(getTag(), nullptr);
2317  return;
2318  }
2319  }
2320 
2321  // The analyzer issues a false positive when the constructor of
2322  // std::__independent_bits_engine from algorithms is used.
2323  if (const auto *MD = dyn_cast<CXXConstructorDecl>(D)) {
2324  const CXXRecordDecl *CD = MD->getParent();
2325  if (CD->getName() == "__independent_bits_engine") {
2326  BR.markInvalid(getTag(), nullptr);
2327  return;
2328  }
2329  }
2330 
2331  for (const LocationContext *LCtx = N->getLocationContext(); LCtx;
2332  LCtx = LCtx->getParent()) {
2333  const auto *MD = dyn_cast<CXXMethodDecl>(LCtx->getDecl());
2334  if (!MD)
2335  continue;
2336 
2337  const CXXRecordDecl *CD = MD->getParent();
2338  // The analyzer issues a false positive on
2339  // std::basic_string<uint8_t> v; v.push_back(1);
2340  // and
2341  // std::u16string s; s += u'a';
2342  // because we cannot reason about the internal invariants of the
2343  // data structure.
2344  if (CD->getName() == "basic_string") {
2345  BR.markInvalid(getTag(), nullptr);
2346  return;
2347  }
2348 
2349  // The analyzer issues a false positive on
2350  // std::shared_ptr<int> p(new int(1)); p = nullptr;
2351  // because it does not reason properly about temporary destructors.
2352  if (CD->getName() == "shared_ptr") {
2353  BR.markInvalid(getTag(), nullptr);
2354  return;
2355  }
2356  }
2357  }
2358  }
2359 
2360  // Skip reports within the sys/queue.h macros as we do not have the ability to
2361  // reason about data structure shapes.
2362  SourceManager &SM = BRC.getSourceManager();
2363  FullSourceLoc Loc = BR.getLocation(SM).asLocation();
2364  while (Loc.isMacroID()) {
2365  Loc = Loc.getSpellingLoc();
2366  if (SM.getFilename(Loc).endswith("sys/queue.h")) {
2367  BR.markInvalid(getTag(), nullptr);
2368  return;
2369  }
2370  }
2371 }
2372 
2373 std::shared_ptr<PathDiagnosticPiece>
2374 UndefOrNullArgVisitor::VisitNode(const ExplodedNode *N,
2375  const ExplodedNode *PrevN,
2376  BugReporterContext &BRC, BugReport &BR) {
2377  ProgramStateRef State = N->getState();
2378  ProgramPoint ProgLoc = N->getLocation();
2379 
2380  // We are only interested in visiting CallEnter nodes.
2381  Optional<CallEnter> CEnter = ProgLoc.getAs<CallEnter>();
2382  if (!CEnter)
2383  return nullptr;
2384 
2385  // Check if one of the arguments is the region the visitor is tracking.
2386  CallEventManager &CEMgr = BRC.getStateManager().getCallEventManager();
2387  CallEventRef<> Call = CEMgr.getCaller(CEnter->getCalleeContext(), State);
2388  unsigned Idx = 0;
2389  ArrayRef<ParmVarDecl *> parms = Call->parameters();
2390 
2391  for (const auto ParamDecl : parms) {
2392  const MemRegion *ArgReg = Call->getArgSVal(Idx).getAsRegion();
2393  ++Idx;
2394 
2395  // Are we tracking the argument or its subregion?
2396  if ( !ArgReg || !R->isSubRegionOf(ArgReg->StripCasts()))
2397  continue;
2398 
2399  // Check the function parameter type.
2400  assert(ParamDecl && "Formal parameter has no decl?");
2401  QualType T = ParamDecl->getType();
2402 
2403  if (!(T->isAnyPointerType() || T->isReferenceType())) {
2404  // Function can only change the value passed in by address.
2405  continue;
2406  }
2407 
2408  // If it is a const pointer value, the function does not intend to
2409  // change the value.
2410  if (T->getPointeeType().isConstQualified())
2411  continue;
2412 
2413  // Mark the call site (LocationContext) as interesting if the value of the
2414  // argument is undefined or '0'/'NULL'.
2415  SVal BoundVal = State->getSVal(R);
2416  if (BoundVal.isUndef() || BoundVal.isZeroConstant()) {
2417  BR.markInteresting(CEnter->getCalleeContext());
2418  return nullptr;
2419  }
2420  }
2421  return nullptr;
2422 }
2423 
2424 std::shared_ptr<PathDiagnosticPiece>
2425 CXXSelfAssignmentBRVisitor::VisitNode(const ExplodedNode *Succ,
2426  const ExplodedNode *Pred,
2427  BugReporterContext &BRC, BugReport &BR) {
2428  if (Satisfied)
2429  return nullptr;
2430 
2431  const auto Edge = Succ->getLocation().getAs<BlockEdge>();
2432  if (!Edge.hasValue())
2433  return nullptr;
2434 
2435  auto Tag = Edge->getTag();
2436  if (!Tag)
2437  return nullptr;
2438 
2439  if (Tag->getTagDescription() != "cplusplus.SelfAssignment")
2440  return nullptr;
2441 
2442  Satisfied = true;
2443 
2444  const auto *Met =
2445  dyn_cast<CXXMethodDecl>(Succ->getCodeDecl().getAsFunction());
2446  assert(Met && "Not a C++ method.");
2447  assert((Met->isCopyAssignmentOperator() || Met->isMoveAssignmentOperator()) &&
2448  "Not a copy/move assignment operator.");
2449 
2450  const auto *LCtx = Edge->getLocationContext();
2451 
2452  const auto &State = Succ->getState();
2453  auto &SVB = State->getStateManager().getSValBuilder();
2454 
2455  const auto Param =
2456  State->getSVal(State->getRegion(Met->getParamDecl(0), LCtx));
2457  const auto This =
2458  State->getSVal(SVB.getCXXThis(Met, LCtx->getStackFrame()));
2459 
2460  auto L = PathDiagnosticLocation::create(Met, BRC.getSourceManager());
2461 
2462  if (!L.isValid() || !L.asLocation().isValid())
2463  return nullptr;
2464 
2465  SmallString<256> Buf;
2466  llvm::raw_svector_ostream Out(Buf);
2467 
2468  Out << "Assuming " << Met->getParamDecl(0)->getName() <<
2469  ((Param == This) ? " == " : " != ") << "*this";
2470 
2471  auto Piece = std::make_shared<PathDiagnosticEventPiece>(L, Out.str());
2472  Piece->addRange(Met->getSourceRange());
2473 
2474  return std::move(Piece);
2475 }
2476 
2477 std::shared_ptr<PathDiagnosticPiece>
2478 TaintBugVisitor::VisitNode(const ExplodedNode *N, const ExplodedNode *PrevN,
2479  BugReporterContext &BRC, BugReport &BR) {
2480 
2481  // Find the ExplodedNode where the taint was first introduced
2482  if (!N->getState()->isTainted(V) || PrevN->getState()->isTainted(V))
2483  return nullptr;
2484 
2485  const Stmt *S = PathDiagnosticLocation::getStmt(N);
2486  if (!S)
2487  return nullptr;
2488 
2489  const LocationContext *NCtx = N->getLocationContext();
2490  PathDiagnosticLocation L =
2491  PathDiagnosticLocation::createBegin(S, BRC.getSourceManager(), NCtx);
2492  if (!L.isValid() || !L.asLocation().isValid())
2493  return nullptr;
2494 
2495  return std::make_shared<PathDiagnosticEventPiece>(L, "Taint originated here");
2496 }
2497 
2498 FalsePositiveRefutationBRVisitor::FalsePositiveRefutationBRVisitor()
2499  : Constraints(ConstraintRangeTy::Factory().getEmptyMap()) {}
2500 
2501 void FalsePositiveRefutationBRVisitor::finalizeVisitor(
2502  BugReporterContext &BRC, const ExplodedNode *EndPathNode, BugReport &BR) {
2503  // Collect new constraints
2504  VisitNode(EndPathNode, nullptr, BRC, BR);
2505 
2506  // Create a refutation manager
2507  SMTSolverRef RefutationSolver = CreateZ3Solver();
2508  ASTContext &Ctx = BRC.getASTContext();
2509 
2510  // Add constraints to the solver
2511  for (const auto &I : Constraints) {
2512  SymbolRef Sym = I.first;
2513 
2514  SMTExprRef Constraints = RefutationSolver->fromBoolean(false);
2515  for (const auto &Range : I.second) {
2516  Constraints = RefutationSolver->mkOr(
2517  Constraints, SMTConv::getRangeExpr(RefutationSolver, Ctx, Sym,
2518  Range.From(), Range.To(),
2519  /*InRange=*/true));
2520  }
2521  RefutationSolver->addConstraint(Constraints);
2522  }
2523 
2524  // And check for satisfiability
2525  Optional<bool> isSat = RefutationSolver->check();
2526  if (!isSat.hasValue())
2527  return;
2528 
2529  if (!isSat.getValue())
2530  BR.markInvalid("Infeasible constraints", EndPathNode->getLocationContext());
2531 }
2532 
2533 std::shared_ptr<PathDiagnosticPiece>
2534 FalsePositiveRefutationBRVisitor::VisitNode(const ExplodedNode *N,
2535  const ExplodedNode *PrevN,
2536  BugReporterContext &BRC,
2537  BugReport &BR) {
2538  // Collect new constraints
2539  const ConstraintRangeTy &NewCs = N->getState()->get<ConstraintRange>();
2540  ConstraintRangeTy::Factory &CF =
2541  N->getState()->get_context<ConstraintRange>();
2542 
2543  // Add constraints if we don't have them yet
2544  for (auto const &C : NewCs) {
2545  const SymbolRef &Sym = C.first;
2546  if (!Constraints.contains(Sym)) {
2547  Constraints = CF.add(Constraints, Sym, C.second);
2548  }
2549  }
2550 
2551  return nullptr;
2552 }
2553 
2554 void FalsePositiveRefutationBRVisitor::Profile(
2555  llvm::FoldingSetNodeID &ID) const {
2556  static int Tag = 0;
2557  ID.AddPointer(&Tag);
2558 }
ObjCPropertyRefExpr - A dot-syntax expression to access an ObjC property.
Definition: ExprObjC.h:577
Defines the clang::ASTContext interface.
This is a discriminated union of FileInfo and ExpansionInfo.
A (possibly-)qualified type.
Definition: Type.h:642
static StringRef getMacroName(SourceLocation Loc, BugReporterContext &BRC)
const internal::VariadicAllOfMatcher< Stmt > stmt
Matches statements.
static SMTExprRef getRangeExpr(SMTSolverRef &Solver, ASTContext &Ctx, SymbolRef Sym, const llvm::APSInt &From, const llvm::APSInt &To, bool InRange)
Definition: SMTConv.h:489
succ_iterator succ_begin()
Definition: CFG.h:751
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:985
const SymExpr * SymbolRef
Stmt - This represents one statement.
Definition: Stmt.h:66
internal::Matcher< Stmt > StatementMatcher
Definition: ASTMatchers.h:146
QualType getPointeeType() const
If this is a pointer, ObjC object pointer, or block pointer, this returns the respective pointee...
Definition: Type.cpp:497
bool shouldSuppressNullReturnPaths()
Returns whether or not paths that go through null returns should be suppressed.
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:2794
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:87
Represents a point when we begin processing an inlined call.
Definition: ProgramPoint.h:628
Manages the lifetime of CallEvent objects.
Definition: CallEvent.h:1083
IntrusiveRefCntPtr< const ProgramState > ProgramStateRef
Opcode getOpcode() const
Definition: Expr.h:3143
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
bool shouldAvoidSuppressingNullArgumentPaths()
Returns whether a bug report should not be suppressed if its path includes a call with a null argumen...
unsigned succ_size() const
Definition: CFG.h:769
Represents a variable declaration or definition.
Definition: Decl.h:812
const T * getAs() const
Member-template getAs<specific type>&#39;.
Definition: Type.h:6590
const internal::VariadicDynCastAllOfMatcher< Stmt, BinaryOperator > binaryOperator
Matches binary operator expressions.
static const Expr * peelOffOuterExpr(const Expr *Ex, const ExplodedNode *N)
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:38
Represents a parameter to a function.
Definition: Decl.h:1536
Defines the clang::Expr interface and subclasses for C++ expressions.
bool isParentOf(const LocationContext *LC) const
Represents a struct/union/class.
Definition: Decl.h:3570
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:3761
SourceLocation getBeginLoc() const LLVM_READONLY
Definition: Stmt.cpp:280
Represents a member of a struct/union/class.
Definition: Decl.h:2556
Represents a program point after a store evaluation.
Definition: ProgramPoint.h:429
bool isReferenceType() const
Definition: Type.h:6189
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:3228
bool isIntegralOrEnumerationType() const
Determine whether this type is an integral or enumeration type.
Definition: Type.h:6504
Represents a point when we start the call exit sequence (for inlined call).
Definition: ProgramPoint.h:666
StringRef getOpcodeStr() const
Definition: Expr.h:3162
bool isGLValue() const
Definition: Expr.h:251
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:229
static const Expr * peelOfOuterAddrOf(const Expr *Ex)
Performing operator `&&#39; on an lvalue expression is essentially a no-op.
const LocationContext * getParent() const
A builtin binary operation expression such as "x + y" or "x <= y".
Definition: Expr.h:3102
static bool wasRegionOfInterestModifiedAt(const SubRegion *RegionOfInterest, const ExplodedNode *N, SVal ValueAfter)
Expr * IgnoreParenCasts() LLVM_READONLY
IgnoreParenCasts - Ignore parentheses and casts.
Definition: Expr.cpp:2544
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:6489
SmallVector< BoundNodes, 1 > match(MatcherT Matcher, const NodeT &Node, ASTContext &Context)
Returns the results of matching Matcher on Node.
NodeId Parent
Definition: ASTDiff.cpp:192
RecordDecl * getAsRecordDecl() const
Retrieves the RecordDecl this type refers to.
Definition: Type.cpp:1609
bool shouldSuppressInlinedDefensiveChecks()
Returns whether or not diagnostics containing inlined defensive NULL checks should be suppressed...
const Stmt * getCallSite() const
Represents a single basic block in a source-level CFG.
Definition: CFG.h:552
Represents a point when we finish the call exit sequence (for inlined call).
Definition: ProgramPoint.h:686
This represents one expression.
Definition: Expr.h:105
bool isInSystemHeader(SourceLocation Loc) const
Returns if a SourceLocation is in a system header.
CFGBlock * getBlock(Stmt *S)
Returns the CFGBlock the specified Stmt* appears in.
Definition: CFGStmtMap.cpp:27
CallEventRef getCaller(const StackFrameContext *CalleeCtx, ProgramStateRef State)
Definition: CallEvent.cpp:1355
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:127
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:1758
ReturnStmt - This represents a return, optionally of an expression: return; return 4;...
Definition: Stmt.h:1444
An expression that sends a message to the given Objective-C object or class.
Definition: ExprObjC.h:904
ValueDecl * getDecl()
Definition: Expr.h:1056
bool isNull() const
Return true if this QualType doesn&#39;t point to a type yet.
Definition: Type.h:707
const SourceManager & SM
Definition: Format.cpp:1472
const ExpansionInfo & getExpansion() const
SourceLocation getEndLoc() const LLVM_READONLY
Definition: Stmt.cpp:293
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:991
bool isConstQualified() const
Determine whether this type is const-qualified.
Definition: Type.h:6012
bool isComparisonOp() const
Definition: Expr.h:3193
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:102
StringRef getFilename(SourceLocation SpellingLoc) const
Return the filename of the file containing a SourceLocation.
CFGTerminator getTerminator()
Definition: CFG.h:840
static PathDiagnosticLocation createBegin(const Decl *D, const SourceManager &SM)
Create a location for the beginning of the declaration.
QualType getCanonicalType() const
Definition: Type.h:5992
static const ExplodedNode * findNodeForStatement(const ExplodedNode *N, const Stmt *S, const Expr *Inner)
Walk through nodes until we get one that matches the statement exactly.
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:439
ProgramPoints can be "tagged" as representing points specific to a given analysis entity...
Definition: ProgramPoint.h:40
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:505
Represents a static or instance method of a struct/union/class.
Definition: DeclCXX.h:2043
bool isAnyPointerType() const
Definition: Type.h:6181
bool isObjCObjectPointerType() const
Definition: Type.h:6274
SMTSolverRef CreateZ3Solver()
Convenience method to create and Z3Solver object.
const ReturnStmt * getReturnStmt() const
Definition: ProgramPoint.h:672
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:968
static StringRef getImmediateMacroNameForDiagnostics(SourceLocation Loc, const SourceManager &SM, const LangOptions &LangOpts)
Retrieve the name of the immediate macro expansion.
Definition: Lexer.cpp:1015
static bool isFunctionMacroExpansion(SourceLocation Loc, const SourceManager &SM)
Expr * getLHS() const
Definition: Expr.h:3146
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:1481
StmtClass getStmtClass() const
Definition: Stmt.h:391
bool isBooleanType() const
Definition: Type.h:6517
const Decl * getSingleDecl() const
Definition: Stmt.h:522
const ProgramPointTag * getTag() const
Definition: ProgramPoint.h:179
static void showBRParamDiagnostics(llvm::raw_svector_ostream &os, const VarRegion *VR, SVal V)
Display diagnostics for passing bad region as a parameter.
std::shared_ptr< SMTSolver > SMTSolverRef
Shared pointer for SMTSolvers.
Definition: SMTSolver.h:304
static const ExplodedNode * findNodeForExpression(const ExplodedNode *N, const Expr *Inner)
Find the ExplodedNode where the lvalue (the value of &#39;Ex&#39;) was computed.
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...
const LocationContext * getLocationContext() const
Definition: ProgramPoint.h:181
bool shouldSuppressFromCXXStandardLibrary()
Returns whether or not diagnostics reported within the C++ standard library should be suppressed...
static bool isAdditiveOp(Opcode Opc)
Definition: Expr.h:3178
const StackFrameContext * getStackFrame() const
const SrcMgr::SLocEntry & getSLocEntry(FileID FID, bool *Invalid=nullptr) const
ObjCIvarRefExpr - A reference to an ObjC instance variable.
Definition: ExprObjC.h:513
X
Add a minimal nested name specifier fixit hint to allow lookup of a tag name from an outer enclosing ...
Definition: SemaDecl.cpp:13824
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:300
bool isVoidType() const
Definition: Type.h:6404
ObjCIvarDecl - Represents an ObjC instance variable.
Definition: DeclObjC.h:1937
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.
std::shared_ptr< SMTExpr > SMTExprRef
Shared pointer for SMTExprs, used by SMTSolver API.
Definition: SMTExpr.h:57
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:971
Expr * getRHS() const
Definition: Expr.h:3148
bool isFunctionMacroExpansion() const
bool isPointerType() const
Definition: Type.h:6177
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:153
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
IgnoreParens - Ignore parentheses.
Definition: Expr.cpp:2513