1//===--- CallAndMessageChecker.cpp ------------------------------*- C++ -*--==//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This defines CallAndMessageChecker, a builtin checker that checks for various
10// errors of call and objc message expressions.
11//
12//===----------------------------------------------------------------------===//
13
14#include "clang/AST/ExprCXX.h"
15#include "clang/AST/ParentMap.h"
16#include "clang/Basic/TargetInfo.h"
17#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
18#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
19#include "clang/StaticAnalyzer/Core/Checker.h"
20#include "clang/StaticAnalyzer/Core/CheckerManager.h"
21#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
22#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
23#include "llvm/ADT/SmallString.h"
24#include "llvm/ADT/StringExtras.h"
25#include "llvm/Support/Casting.h"
26#include "llvm/Support/raw_ostream.h"
27
28using namespace clang;
29using namespace ento;
30
31namespace {
32
33class CallAndMessageChecker
34    : public Checker<check::PreObjCMessage, check::ObjCMessageNil,
35                     check::PreCall> {
36  mutable std::unique_ptr<BugType> BT_call_null;
37  mutable std::unique_ptr<BugType> BT_call_undef;
38  mutable std::unique_ptr<BugType> BT_cxx_call_null;
39  mutable std::unique_ptr<BugType> BT_cxx_call_undef;
40  mutable std::unique_ptr<BugType> BT_call_arg;
41  mutable std::unique_ptr<BugType> BT_cxx_delete_undef;
42  mutable std::unique_ptr<BugType> BT_msg_undef;
43  mutable std::unique_ptr<BugType> BT_objc_prop_undef;
44  mutable std::unique_ptr<BugType> BT_objc_subscript_undef;
45  mutable std::unique_ptr<BugType> BT_msg_arg;
46  mutable std::unique_ptr<BugType> BT_msg_ret;
47  mutable std::unique_ptr<BugType> BT_call_few_args;
48
49public:
50  // These correspond with the checker options. Looking at other checkers such
51  // as MallocChecker and CStringChecker, this is similar as to how they pull
52  // off having a modeling class, but emitting diagnostics under a smaller
53  // checker's name that can be safely disabled without disturbing the
54  // underlaying modeling engine.
55  // The reason behind having *checker options* rather then actual *checkers*
56  // here is that CallAndMessage is among the oldest checkers out there, and can
57  // be responsible for the majority of the reports on any given project. This
58  // is obviously not ideal, but changing checker name has the consequence of
59  // changing the issue hashes associated with the reports, and databases
60  // relying on this (CodeChecker, for instance) would suffer greatly.
61  // If we ever end up making changes to the issue hash generation algorithm, or
62  // the warning messages here, we should totally jump on the opportunity to
63  // convert these to actual checkers.
64  enum CheckKind {
65    CK_FunctionPointer,
66    CK_ParameterCount,
67    CK_CXXThisMethodCall,
68    CK_CXXDeallocationArg,
69    CK_ArgInitializedness,
70    CK_ArgPointeeInitializedness,
71    CK_NilReceiver,
72    CK_UndefReceiver,
73    CK_NumCheckKinds
74  };
75
76  bool ChecksEnabled[CK_NumCheckKinds] = {false};
77  // The original core.CallAndMessage checker name. This should rather be an
78  // array, as seen in MallocChecker and CStringChecker.
79  CheckerNameRef OriginalName;
80
81  void checkPreObjCMessage(const ObjCMethodCall &msg, CheckerContext &C) const;
82
83  /// Fill in the return value that results from messaging nil based on the
84  /// return type and architecture and diagnose if the return value will be
85  /// garbage.
86  void checkObjCMessageNil(const ObjCMethodCall &msg, CheckerContext &C) const;
87
88  void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
89
90  ProgramStateRef checkFunctionPointerCall(const CallExpr *CE,
91                                           CheckerContext &C,
92                                           ProgramStateRef State) const;
93
94  ProgramStateRef checkCXXMethodCall(const CXXInstanceCall *CC,
95                                     CheckerContext &C,
96                                     ProgramStateRef State) const;
97
98  ProgramStateRef checkParameterCount(const CallEvent &Call, CheckerContext &C,
99                                      ProgramStateRef State) const;
100
101  ProgramStateRef checkCXXDeallocation(const CXXDeallocatorCall *DC,
102                                       CheckerContext &C,
103                                       ProgramStateRef State) const;
104
105  ProgramStateRef checkArgInitializedness(const CallEvent &Call,
106                                          CheckerContext &C,
107                                          ProgramStateRef State) const;
108
109private:
110  bool PreVisitProcessArg(CheckerContext &C, SVal V, SourceRange ArgRange,
111                          const Expr *ArgEx, int ArgumentNumber,
112                          bool CheckUninitFields, const CallEvent &Call,
113                          std::unique_ptr<BugType> &BT,
114                          const ParmVarDecl *ParamDecl) const;
115
116  static void emitBadCall(BugType *BT, CheckerContext &C, const Expr *BadE);
117  void emitNilReceiverBug(CheckerContext &C, const ObjCMethodCall &msg,
118                          ExplodedNode *N) const;
119
120  void HandleNilReceiver(CheckerContext &C,
121                         ProgramStateRef state,
122                         const ObjCMethodCall &msg) const;
123
124  void LazyInit_BT(const char *desc, std::unique_ptr<BugType> &BT) const {
125    if (!BT)
126      BT.reset(new BuiltinBug(OriginalName, desc));
127  }
128  bool uninitRefOrPointer(CheckerContext &C, const SVal &V,
129                          SourceRange ArgRange, const Expr *ArgEx,
130                          std::unique_ptr<BugType> &BT,
131                          const ParmVarDecl *ParamDecl, const char *BD,
132                          int ArgumentNumber) const;
133};
134} // end anonymous namespace
135
136void CallAndMessageChecker::emitBadCall(BugType *BT, CheckerContext &C,
137                                        const Expr *BadE) {
138  ExplodedNode *N = C.generateErrorNode();
139  if (!N)
140    return;
141
142  auto R = std::make_unique<PathSensitiveBugReport>(*BT, BT->getDescription(), N);
143  if (BadE) {
144    R->addRange(BadE->getSourceRange());
145    if (BadE->isGLValue())
146      BadE = bugreporter::getDerefExpr(BadE);
147    bugreporter::trackExpressionValue(N, BadE, *R);
148  }
149  C.emitReport(std::move(R));
150}
151
152static void describeUninitializedArgumentInCall(const CallEvent &Call,
153                                                int ArgumentNumber,
154                                                llvm::raw_svector_ostream &Os) {
155  switch (Call.getKind()) {
156  case CE_ObjCMessage: {
157    const ObjCMethodCall &Msg = cast<ObjCMethodCall>(Call);
158    switch (Msg.getMessageKind()) {
159    case OCM_Message:
160      Os << (ArgumentNumber + 1) << llvm::getOrdinalSuffix(ArgumentNumber + 1)
161         << " argument in message expression is an uninitialized value";
162      return;
163    case OCM_PropertyAccess:
164      assert(Msg.isSetter() && "Getters have no args");
165      Os << "Argument for property setter is an uninitialized value";
166      return;
167    case OCM_Subscript:
168      if (Msg.isSetter() && (ArgumentNumber == 0))
169        Os << "Argument for subscript setter is an uninitialized value";
170      else
171        Os << "Subscript index is an uninitialized value";
172      return;
173    }
174    llvm_unreachable("Unknown message kind.");
175  }
176  case CE_Block:
177    Os << (ArgumentNumber + 1) << llvm::getOrdinalSuffix(ArgumentNumber + 1)
178       << " block call argument is an uninitialized value";
179    return;
180  default:
181    Os << (ArgumentNumber + 1) << llvm::getOrdinalSuffix(ArgumentNumber + 1)
182       << " function call argument is an uninitialized value";
183    return;
184  }
185}
186
187bool CallAndMessageChecker::uninitRefOrPointer(
188    CheckerContext &C, const SVal &V, SourceRange ArgRange, const Expr *ArgEx,
189    std::unique_ptr<BugType> &BT, const ParmVarDecl *ParamDecl, const char *BD,
190    int ArgumentNumber) const {
191
192  // The pointee being uninitialized is a sign of code smell, not a bug, no need
193  // to sink here.
194  if (!ChecksEnabled[CK_ArgPointeeInitializedness])
195    return false;
196
197  // No parameter declaration available, i.e. variadic function argument.
198  if(!ParamDecl)
199    return false;
200
201  // If parameter is declared as pointer to const in function declaration,
202  // then check if corresponding argument in function call is
203  // pointing to undefined symbol value (uninitialized memory).
204  SmallString<200> Buf;
205  llvm::raw_svector_ostream Os(Buf);
206
207  if (ParamDecl->getType()->isPointerType()) {
208    Os << (ArgumentNumber + 1) << llvm::getOrdinalSuffix(ArgumentNumber + 1)
209       << " function call argument is a pointer to uninitialized value";
210  } else if (ParamDecl->getType()->isReferenceType()) {
211    Os << (ArgumentNumber + 1) << llvm::getOrdinalSuffix(ArgumentNumber + 1)
212       << " function call argument is an uninitialized value";
213  } else
214    return false;
215
216  if(!ParamDecl->getType()->getPointeeType().isConstQualified())
217    return false;
218
219  if (const MemRegion *SValMemRegion = V.getAsRegion()) {
220    const ProgramStateRef State = C.getState();
221    const SVal PSV = State->getSVal(SValMemRegion, C.getASTContext().CharTy);
222    if (PSV.isUndef()) {
223      if (ExplodedNode *N = C.generateErrorNode()) {
224        LazyInit_BT(BD, BT);
225        auto R = std::make_unique<PathSensitiveBugReport>(*BT, Os.str(), N);
226        R->addRange(ArgRange);
227        if (ArgEx)
228          bugreporter::trackExpressionValue(N, ArgEx, *R);
229
230        C.emitReport(std::move(R));
231      }
232      return true;
233    }
234  }
235  return false;
236}
237
238namespace {
239class FindUninitializedField {
240public:
241  SmallVector<const FieldDecl *, 10> FieldChain;
242
243private:
244  StoreManager &StoreMgr;
245  MemRegionManager &MrMgr;
246  Store store;
247
248public:
249  FindUninitializedField(StoreManager &storeMgr, MemRegionManager &mrMgr,
250                         Store s)
251      : StoreMgr(storeMgr), MrMgr(mrMgr), store(s) {}
252
253  bool Find(const TypedValueRegion *R) {
254    QualType T = R->getValueType();
255    if (const RecordType *RT = T->getAsStructureType()) {
256      const RecordDecl *RD = RT->getDecl()->getDefinition();
257      assert(RD && "Referred record has no definition");
258      for (const auto *I : RD->fields()) {
259        const FieldRegion *FR = MrMgr.getFieldRegion(I, R);
260        FieldChain.push_back(I);
261        T = I->getType();
262        if (T->getAsStructureType()) {
263          if (Find(FR))
264            return true;
265        } else {
266          const SVal &V = StoreMgr.getBinding(store, loc::MemRegionVal(FR));
267          if (V.isUndef())
268            return true;
269        }
270        FieldChain.pop_back();
271      }
272    }
273
274    return false;
275  }
276};
277} // namespace
278
279bool CallAndMessageChecker::PreVisitProcessArg(CheckerContext &C,
280                                               SVal V,
281                                               SourceRange ArgRange,
282                                               const Expr *ArgEx,
283                                               int ArgumentNumber,
284                                               bool CheckUninitFields,
285                                               const CallEvent &Call,
286                                               std::unique_ptr<BugType> &BT,
287                                               const ParmVarDecl *ParamDecl
288                                               ) const {
289  const char *BD = "Uninitialized argument value";
290
291  if (uninitRefOrPointer(C, V, ArgRange, ArgEx, BT, ParamDecl, BD,
292                         ArgumentNumber))
293    return true;
294
295  if (V.isUndef()) {
296    if (!ChecksEnabled[CK_ArgInitializedness]) {
297      C.addSink();
298      return true;
299    }
300    if (ExplodedNode *N = C.generateErrorNode()) {
301      LazyInit_BT(BD, BT);
302      // Generate a report for this bug.
303      SmallString<200> Buf;
304      llvm::raw_svector_ostream Os(Buf);
305      describeUninitializedArgumentInCall(Call, ArgumentNumber, Os);
306      auto R = std::make_unique<PathSensitiveBugReport>(*BT, Os.str(), N);
307
308      R->addRange(ArgRange);
309      if (ArgEx)
310        bugreporter::trackExpressionValue(N, ArgEx, *R);
311      C.emitReport(std::move(R));
312    }
313    return true;
314  }
315
316  if (!CheckUninitFields)
317    return false;
318
319  if (auto LV = V.getAs<nonloc::LazyCompoundVal>()) {
320    const LazyCompoundValData *D = LV->getCVData();
321    FindUninitializedField F(C.getState()->getStateManager().getStoreManager(),
322                             C.getSValBuilder().getRegionManager(),
323                             D->getStore());
324
325    if (F.Find(D->getRegion())) {
326      if (!ChecksEnabled[CK_ArgInitializedness]) {
327        C.addSink();
328        return true;
329      }
330      if (ExplodedNode *N = C.generateErrorNode()) {
331        LazyInit_BT(BD, BT);
332        SmallString<512> Str;
333        llvm::raw_svector_ostream os(Str);
334        os << "Passed-by-value struct argument contains uninitialized data";
335
336        if (F.FieldChain.size() == 1)
337          os << " (e.g., field: '" << *F.FieldChain[0] << "')";
338        else {
339          os << " (e.g., via the field chain: '";
340          bool first = true;
341          for (SmallVectorImpl<const FieldDecl *>::iterator
342               DI = F.FieldChain.begin(), DE = F.FieldChain.end(); DI!=DE;++DI){
343            if (first)
344              first = false;
345            else
346              os << '.';
347            os << **DI;
348          }
349          os << "')";
350        }
351
352        // Generate a report for this bug.
353        auto R = std::make_unique<PathSensitiveBugReport>(*BT, os.str(), N);
354        R->addRange(ArgRange);
355
356        if (ArgEx)
357          bugreporter::trackExpressionValue(N, ArgEx, *R);
358        // FIXME: enhance track back for uninitialized value for arbitrary
359        // memregions
360        C.emitReport(std::move(R));
361      }
362      return true;
363    }
364  }
365
366  return false;
367}
368
369ProgramStateRef CallAndMessageChecker::checkFunctionPointerCall(
370    const CallExpr *CE, CheckerContext &C, ProgramStateRef State) const {
371
372  const Expr *Callee = CE->getCallee()->IgnoreParens();
373  const LocationContext *LCtx = C.getLocationContext();
374  SVal L = State->getSVal(Callee, LCtx);
375
376  if (L.isUndef()) {
377    if (!ChecksEnabled[CK_FunctionPointer]) {
378      C.addSink(State);
379      return nullptr;
380    }
381    if (!BT_call_undef)
382      BT_call_undef.reset(new BuiltinBug(
383          OriginalName,
384          "Called function pointer is an uninitialized pointer value"));
385    emitBadCall(BT_call_undef.get(), C, Callee);
386    return nullptr;
387  }
388
389  ProgramStateRef StNonNull, StNull;
390  std::tie(StNonNull, StNull) = State->assume(L.castAs<DefinedOrUnknownSVal>());
391
392  if (StNull && !StNonNull) {
393    if (!ChecksEnabled[CK_FunctionPointer]) {
394      C.addSink(StNull);
395      return nullptr;
396    }
397    if (!BT_call_null)
398      BT_call_null.reset(new BuiltinBug(
399          OriginalName, "Called function pointer is null (null dereference)"));
400    emitBadCall(BT_call_null.get(), C, Callee);
401    return nullptr;
402  }
403
404  return StNonNull;
405}
406
407ProgramStateRef CallAndMessageChecker::checkParameterCount(
408    const CallEvent &Call, CheckerContext &C, ProgramStateRef State) const {
409
410  // If we have a function or block declaration, we can make sure we pass
411  // enough parameters.
412  unsigned Params = Call.parameters().size();
413  if (Call.getNumArgs() >= Params)
414    return State;
415
416  if (!ChecksEnabled[CK_ParameterCount]) {
417    C.addSink(State);
418    return nullptr;
419  }
420
421  ExplodedNode *N = C.generateErrorNode();
422  if (!N)
423    return nullptr;
424
425  LazyInit_BT("Function call with too few arguments", BT_call_few_args);
426
427  SmallString<512> Str;
428  llvm::raw_svector_ostream os(Str);
429  if (isa<AnyFunctionCall>(Call)) {
430    os << "Function ";
431  } else {
432    assert(isa<BlockCall>(Call));
433    os << "Block ";
434  }
435  os << "taking " << Params << " argument" << (Params == 1 ? "" : "s")
436     << " is called with fewer (" << Call.getNumArgs() << ")";
437
438  C.emitReport(
439      std::make_unique<PathSensitiveBugReport>(*BT_call_few_args, os.str(), N));
440  return nullptr;
441}
442
443ProgramStateRef CallAndMessageChecker::checkCXXMethodCall(
444    const CXXInstanceCall *CC, CheckerContext &C, ProgramStateRef State) const {
445
446  SVal V = CC->getCXXThisVal();
447  if (V.isUndef()) {
448    if (!ChecksEnabled[CK_CXXThisMethodCall]) {
449      C.addSink(State);
450      return nullptr;
451    }
452    if (!BT_cxx_call_undef)
453      BT_cxx_call_undef.reset(new BuiltinBug(
454          OriginalName, "Called C++ object pointer is uninitialized"));
455    emitBadCall(BT_cxx_call_undef.get(), C, CC->getCXXThisExpr());
456    return nullptr;
457  }
458
459  ProgramStateRef StNonNull, StNull;
460  std::tie(StNonNull, StNull) = State->assume(V.castAs<DefinedOrUnknownSVal>());
461
462  if (StNull && !StNonNull) {
463    if (!ChecksEnabled[CK_CXXThisMethodCall]) {
464      C.addSink(StNull);
465      return nullptr;
466    }
467    if (!BT_cxx_call_null)
468      BT_cxx_call_null.reset(
469          new BuiltinBug(OriginalName, "Called C++ object pointer is null"));
470    emitBadCall(BT_cxx_call_null.get(), C, CC->getCXXThisExpr());
471    return nullptr;
472  }
473
474  return StNonNull;
475}
476
477ProgramStateRef
478CallAndMessageChecker::checkCXXDeallocation(const CXXDeallocatorCall *DC,
479                                            CheckerContext &C,
480                                            ProgramStateRef State) const {
481  const CXXDeleteExpr *DE = DC->getOriginExpr();
482  assert(DE);
483  SVal Arg = C.getSVal(DE->getArgument());
484  if (!Arg.isUndef())
485    return State;
486
487  if (!ChecksEnabled[CK_CXXDeallocationArg]) {
488    C.addSink(State);
489    return nullptr;
490  }
491
492  StringRef Desc;
493  ExplodedNode *N = C.generateErrorNode();
494  if (!N)
495    return nullptr;
496  if (!BT_cxx_delete_undef)
497    BT_cxx_delete_undef.reset(
498        new BuiltinBug(OriginalName, "Uninitialized argument value"));
499  if (DE->isArrayFormAsWritten())
500    Desc = "Argument to 'delete[]' is uninitialized";
501  else
502    Desc = "Argument to 'delete' is uninitialized";
503  BugType *BT = BT_cxx_delete_undef.get();
504  auto R = std::make_unique<PathSensitiveBugReport>(*BT, Desc, N);
505  bugreporter::trackExpressionValue(N, DE, *R);
506  C.emitReport(std::move(R));
507  return nullptr;
508}
509
510ProgramStateRef CallAndMessageChecker::checkArgInitializedness(
511    const CallEvent &Call, CheckerContext &C, ProgramStateRef State) const {
512
513  const Decl *D = Call.getDecl();
514
515  // Don't check for uninitialized field values in arguments if the
516  // caller has a body that is available and we have the chance to inline it.
517  // This is a hack, but is a reasonable compromise betweens sometimes warning
518  // and sometimes not depending on if we decide to inline a function.
519  const bool checkUninitFields =
520      !(C.getAnalysisManager().shouldInlineCall() && (D && D->getBody()));
521
522  std::unique_ptr<BugType> *BT;
523  if (isa<ObjCMethodCall>(Call))
524    BT = &BT_msg_arg;
525  else
526    BT = &BT_call_arg;
527
528  const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D);
529  for (unsigned i = 0, e = Call.getNumArgs(); i != e; ++i) {
530    const ParmVarDecl *ParamDecl = nullptr;
531    if (FD && i < FD->getNumParams())
532      ParamDecl = FD->getParamDecl(i);
533    if (PreVisitProcessArg(C, Call.getArgSVal(i), Call.getArgSourceRange(i),
534                           Call.getArgExpr(i), i, checkUninitFields, Call, *BT,
535                           ParamDecl))
536      return nullptr;
537  }
538  return State;
539}
540
541void CallAndMessageChecker::checkPreCall(const CallEvent &Call,
542                                         CheckerContext &C) const {
543  ProgramStateRef State = C.getState();
544
545  if (const CallExpr *CE = dyn_cast_or_null<CallExpr>(Call.getOriginExpr()))
546    State = checkFunctionPointerCall(CE, C, State);
547
548  if (!State)
549    return;
550
551  if (Call.getDecl())
552    State = checkParameterCount(Call, C, State);
553
554  if (!State)
555    return;
556
557  if (const auto *CC = dyn_cast<CXXInstanceCall>(&Call))
558    State = checkCXXMethodCall(CC, C, State);
559
560  if (!State)
561    return;
562
563  if (const auto *DC = dyn_cast<CXXDeallocatorCall>(&Call))
564    State = checkCXXDeallocation(DC, C, State);
565
566  if (!State)
567    return;
568
569  State = checkArgInitializedness(Call, C, State);
570
571  // If we make it here, record our assumptions about the callee.
572  C.addTransition(State);
573}
574
575void CallAndMessageChecker::checkPreObjCMessage(const ObjCMethodCall &msg,
576                                                CheckerContext &C) const {
577  SVal recVal = msg.getReceiverSVal();
578  if (recVal.isUndef()) {
579    if (!ChecksEnabled[CK_UndefReceiver]) {
580      C.addSink();
581      return;
582    }
583    if (ExplodedNode *N = C.generateErrorNode()) {
584      BugType *BT = nullptr;
585      switch (msg.getMessageKind()) {
586      case OCM_Message:
587        if (!BT_msg_undef)
588          BT_msg_undef.reset(new BuiltinBug(OriginalName,
589                                            "Receiver in message expression "
590                                            "is an uninitialized value"));
591        BT = BT_msg_undef.get();
592        break;
593      case OCM_PropertyAccess:
594        if (!BT_objc_prop_undef)
595          BT_objc_prop_undef.reset(new BuiltinBug(
596              OriginalName,
597              "Property access on an uninitialized object pointer"));
598        BT = BT_objc_prop_undef.get();
599        break;
600      case OCM_Subscript:
601        if (!BT_objc_subscript_undef)
602          BT_objc_subscript_undef.reset(new BuiltinBug(
603              OriginalName,
604              "Subscript access on an uninitialized object pointer"));
605        BT = BT_objc_subscript_undef.get();
606        break;
607      }
608      assert(BT && "Unknown message kind.");
609
610      auto R = std::make_unique<PathSensitiveBugReport>(*BT, BT->getDescription(), N);
611      const ObjCMessageExpr *ME = msg.getOriginExpr();
612      R->addRange(ME->getReceiverRange());
613
614      // FIXME: getTrackNullOrUndefValueVisitor can't handle "super" yet.
615      if (const Expr *ReceiverE = ME->getInstanceReceiver())
616        bugreporter::trackExpressionValue(N, ReceiverE, *R);
617      C.emitReport(std::move(R));
618    }
619    return;
620  }
621}
622
623void CallAndMessageChecker::checkObjCMessageNil(const ObjCMethodCall &msg,
624                                                CheckerContext &C) const {
625  HandleNilReceiver(C, C.getState(), msg);
626}
627
628void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C,
629                                               const ObjCMethodCall &msg,
630                                               ExplodedNode *N) const {
631  if (!ChecksEnabled[CK_NilReceiver]) {
632    C.addSink();
633    return;
634  }
635
636  if (!BT_msg_ret)
637    BT_msg_ret.reset(new BuiltinBug(OriginalName,
638                                    "Receiver in message expression is 'nil'"));
639
640  const ObjCMessageExpr *ME = msg.getOriginExpr();
641
642  QualType ResTy = msg.getResultType();
643
644  SmallString<200> buf;
645  llvm::raw_svector_ostream os(buf);
646  os << "The receiver of message '";
647  ME->getSelector().print(os);
648  os << "' is nil";
649  if (ResTy->isReferenceType()) {
650    os << ", which results in forming a null reference";
651  } else {
652    os << " and returns a value of type '";
653    msg.getResultType().print(os, C.getLangOpts());
654    os << "' that will be garbage";
655  }
656
657  auto report =
658      std::make_unique<PathSensitiveBugReport>(*BT_msg_ret, os.str(), N);
659  report->addRange(ME->getReceiverRange());
660  // FIXME: This won't track "self" in messages to super.
661  if (const Expr *receiver = ME->getInstanceReceiver()) {
662    bugreporter::trackExpressionValue(N, receiver, *report);
663  }
664  C.emitReport(std::move(report));
665}
666
667static bool supportsNilWithFloatRet(const llvm::Triple &triple) {
668  return (triple.getVendor() == llvm::Triple::Apple &&
669          (triple.isiOS() || triple.isWatchOS() ||
670           !triple.isMacOSXVersionLT(10,5)));
671}
672
673void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C,
674                                              ProgramStateRef state,
675                                              const ObjCMethodCall &Msg) const {
676  ASTContext &Ctx = C.getASTContext();
677  static CheckerProgramPointTag Tag(this, "NilReceiver");
678
679  // Check the return type of the message expression.  A message to nil will
680  // return different values depending on the return type and the architecture.
681  QualType RetTy = Msg.getResultType();
682  CanQualType CanRetTy = Ctx.getCanonicalType(RetTy);
683  const LocationContext *LCtx = C.getLocationContext();
684
685  if (CanRetTy->isStructureOrClassType()) {
686    // Structure returns are safe since the compiler zeroes them out.
687    SVal V = C.getSValBuilder().makeZeroVal(RetTy);
688    C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag);
689    return;
690  }
691
692  // Other cases: check if sizeof(return type) > sizeof(void*)
693  if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap()
694                                  .isConsumedExpr(Msg.getOriginExpr())) {
695    // Compute: sizeof(void *) and sizeof(return type)
696    const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy);
697    const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy);
698
699    if (CanRetTy.getTypePtr()->isReferenceType()||
700        (voidPtrSize < returnTypeSize &&
701         !(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) &&
702           (Ctx.FloatTy == CanRetTy ||
703            Ctx.DoubleTy == CanRetTy ||
704            Ctx.LongDoubleTy == CanRetTy ||
705            Ctx.LongLongTy == CanRetTy ||
706            Ctx.UnsignedLongLongTy == CanRetTy)))) {
707      if (ExplodedNode *N = C.generateErrorNode(state, &Tag))
708        emitNilReceiverBug(C, Msg, N);
709      return;
710    }
711
712    // Handle the safe cases where the return value is 0 if the
713    // receiver is nil.
714    //
715    // FIXME: For now take the conservative approach that we only
716    // return null values if we *know* that the receiver is nil.
717    // This is because we can have surprises like:
718    //
719    //   ... = [[NSScreens screens] objectAtIndex:0];
720    //
721    // What can happen is that [... screens] could return nil, but
722    // it most likely isn't nil.  We should assume the semantics
723    // of this case unless we have *a lot* more knowledge.
724    //
725    SVal V = C.getSValBuilder().makeZeroVal(RetTy);
726    C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag);
727    return;
728  }
729
730  C.addTransition(state);
731}
732
733void ento::registerCallAndMessageModeling(CheckerManager &mgr) {
734  mgr.registerChecker<CallAndMessageChecker>();
735}
736
737bool ento::shouldRegisterCallAndMessageModeling(const CheckerManager &mgr) {
738  return true;
739}
740
741void ento::registerCallAndMessageChecker(CheckerManager &mgr) {
742  CallAndMessageChecker *checker = mgr.getChecker<CallAndMessageChecker>();
743
744  checker->OriginalName = mgr.getCurrentCheckerName();
745
746#define QUERY_CHECKER_OPTION(OPTION)                                           \
747  checker->ChecksEnabled[CallAndMessageChecker::CK_##OPTION] =                 \
748      mgr.getAnalyzerOptions().getCheckerBooleanOption(                        \
749          mgr.getCurrentCheckerName(), #OPTION);
750
751  QUERY_CHECKER_OPTION(FunctionPointer)
752  QUERY_CHECKER_OPTION(ParameterCount)
753  QUERY_CHECKER_OPTION(CXXThisMethodCall)
754  QUERY_CHECKER_OPTION(CXXDeallocationArg)
755  QUERY_CHECKER_OPTION(ArgInitializedness)
756  QUERY_CHECKER_OPTION(ArgPointeeInitializedness)
757  QUERY_CHECKER_OPTION(NilReceiver)
758  QUERY_CHECKER_OPTION(UndefReceiver)
759}
760
761bool ento::shouldRegisterCallAndMessageChecker(const CheckerManager &mgr) {
762  return true;
763}
764