CallAndMessageChecker.cpp revision 261991 
1//===--- CallAndMessageChecker.cpp ------------------------------*- C++ -*--==//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This defines CallAndMessageChecker, a builtin checker that checks for various
11// errors of call and objc message expressions.
12//
13//===----------------------------------------------------------------------===//
14
15#include "ClangSACheckers.h"
16#include "clang/AST/ParentMap.h"
17#include "clang/Basic/TargetInfo.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/Support/raw_ostream.h"
25
26using namespace clang;
27using namespace ento;
28
29namespace {
30class CallAndMessageChecker
31  : public Checker< check::PreStmt<CallExpr>,
32                    check::PreStmt<CXXDeleteExpr>,
33                    check::PreObjCMessage,
34                    check::PreCall > {
35  mutable OwningPtr<BugType> BT_call_null;
36  mutable OwningPtr<BugType> BT_call_undef;
37  mutable OwningPtr<BugType> BT_cxx_call_null;
38  mutable OwningPtr<BugType> BT_cxx_call_undef;
39  mutable OwningPtr<BugType> BT_call_arg;
40  mutable OwningPtr<BugType> BT_cxx_delete_undef;
41  mutable OwningPtr<BugType> BT_msg_undef;
42  mutable OwningPtr<BugType> BT_objc_prop_undef;
43  mutable OwningPtr<BugType> BT_objc_subscript_undef;
44  mutable OwningPtr<BugType> BT_msg_arg;
45  mutable OwningPtr<BugType> BT_msg_ret;
46  mutable OwningPtr<BugType> BT_call_few_args;
47public:
48
49  void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
50  void checkPreStmt(const CXXDeleteExpr *DE, CheckerContext &C) const;
51  void checkPreObjCMessage(const ObjCMethodCall &msg, CheckerContext &C) const;
52  void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
53
54private:
55  static bool PreVisitProcessArg(CheckerContext &C, SVal V,
56                                 SourceRange argRange, const Expr *argEx,
57                                 bool IsFirstArgument, bool checkUninitFields,
58                                 const CallEvent &Call, OwningPtr<BugType> &BT);
59
60  static void emitBadCall(BugType *BT, CheckerContext &C, const Expr *BadE);
61  void emitNilReceiverBug(CheckerContext &C, const ObjCMethodCall &msg,
62                          ExplodedNode *N) const;
63
64  void HandleNilReceiver(CheckerContext &C,
65                         ProgramStateRef state,
66                         const ObjCMethodCall &msg) const;
67
68  static void LazyInit_BT(const char *desc, OwningPtr<BugType> &BT) {
69    if (!BT)
70      BT.reset(new BuiltinBug(desc));
71  }
72};
73} // end anonymous namespace
74
75void CallAndMessageChecker::emitBadCall(BugType *BT, CheckerContext &C,
76                                        const Expr *BadE) {
77  ExplodedNode *N = C.generateSink();
78  if (!N)
79    return;
80
81  BugReport *R = new BugReport(*BT, BT->getName(), N);
82  if (BadE) {
83    R->addRange(BadE->getSourceRange());
84    if (BadE->isGLValue())
85      BadE = bugreporter::getDerefExpr(BadE);
86    bugreporter::trackNullOrUndefValue(N, BadE, *R);
87  }
88  C.emitReport(R);
89}
90
91static StringRef describeUninitializedArgumentInCall(const CallEvent &Call,
92                                                     bool IsFirstArgument) {
93  switch (Call.getKind()) {
94  case CE_ObjCMessage: {
95    const ObjCMethodCall &Msg = cast<ObjCMethodCall>(Call);
96    switch (Msg.getMessageKind()) {
97    case OCM_Message:
98      return "Argument in message expression is an uninitialized value";
99    case OCM_PropertyAccess:
100      assert(Msg.isSetter() && "Getters have no args");
101      return "Argument for property setter is an uninitialized value";
102    case OCM_Subscript:
103      if (Msg.isSetter() && IsFirstArgument)
104        return "Argument for subscript setter is an uninitialized value";
105      return "Subscript index is an uninitialized value";
106    }
107    llvm_unreachable("Unknown message kind.");
108  }
109  case CE_Block:
110    return "Block call argument is an uninitialized value";
111  default:
112    return "Function call argument is an uninitialized value";
113  }
114}
115
116bool CallAndMessageChecker::PreVisitProcessArg(CheckerContext &C,
117                                               SVal V, SourceRange argRange,
118                                               const Expr *argEx,
119                                               bool IsFirstArgument,
120                                               bool checkUninitFields,
121                                               const CallEvent &Call,
122                                               OwningPtr<BugType> &BT) {
123  if (V.isUndef()) {
124    if (ExplodedNode *N = C.generateSink()) {
125      LazyInit_BT("Uninitialized argument value", BT);
126
127      // Generate a report for this bug.
128      StringRef Desc = describeUninitializedArgumentInCall(Call,
129                                                           IsFirstArgument);
130      BugReport *R = new BugReport(*BT, Desc, N);
131      R->addRange(argRange);
132      if (argEx)
133        bugreporter::trackNullOrUndefValue(N, argEx, *R);
134      C.emitReport(R);
135    }
136    return true;
137  }
138
139  if (!checkUninitFields)
140    return false;
141
142  if (Optional<nonloc::LazyCompoundVal> LV =
143          V.getAs<nonloc::LazyCompoundVal>()) {
144
145    class FindUninitializedField {
146    public:
147      SmallVector<const FieldDecl *, 10> FieldChain;
148    private:
149      StoreManager &StoreMgr;
150      MemRegionManager &MrMgr;
151      Store store;
152    public:
153      FindUninitializedField(StoreManager &storeMgr,
154                             MemRegionManager &mrMgr, Store s)
155      : StoreMgr(storeMgr), MrMgr(mrMgr), store(s) {}
156
157      bool Find(const TypedValueRegion *R) {
158        QualType T = R->getValueType();
159        if (const RecordType *RT = T->getAsStructureType()) {
160          const RecordDecl *RD = RT->getDecl()->getDefinition();
161          assert(RD && "Referred record has no definition");
162          for (RecordDecl::field_iterator I =
163               RD->field_begin(), E = RD->field_end(); I!=E; ++I) {
164            const FieldRegion *FR = MrMgr.getFieldRegion(*I, R);
165            FieldChain.push_back(*I);
166            T = I->getType();
167            if (T->getAsStructureType()) {
168              if (Find(FR))
169                return true;
170            }
171            else {
172              const SVal &V = StoreMgr.getBinding(store, loc::MemRegionVal(FR));
173              if (V.isUndef())
174                return true;
175            }
176            FieldChain.pop_back();
177          }
178        }
179
180        return false;
181      }
182    };
183
184    const LazyCompoundValData *D = LV->getCVData();
185    FindUninitializedField F(C.getState()->getStateManager().getStoreManager(),
186                             C.getSValBuilder().getRegionManager(),
187                             D->getStore());
188
189    if (F.Find(D->getRegion())) {
190      if (ExplodedNode *N = C.generateSink()) {
191        LazyInit_BT("Uninitialized argument value", BT);
192        SmallString<512> Str;
193        llvm::raw_svector_ostream os(Str);
194        os << "Passed-by-value struct argument contains uninitialized data";
195
196        if (F.FieldChain.size() == 1)
197          os << " (e.g., field: '" << *F.FieldChain[0] << "')";
198        else {
199          os << " (e.g., via the field chain: '";
200          bool first = true;
201          for (SmallVectorImpl<const FieldDecl *>::iterator
202               DI = F.FieldChain.begin(), DE = F.FieldChain.end(); DI!=DE;++DI){
203            if (first)
204              first = false;
205            else
206              os << '.';
207            os << **DI;
208          }
209          os << "')";
210        }
211
212        // Generate a report for this bug.
213        BugReport *R = new BugReport(*BT, os.str(), N);
214        R->addRange(argRange);
215
216        // FIXME: enhance track back for uninitialized value for arbitrary
217        // memregions
218        C.emitReport(R);
219      }
220      return true;
221    }
222  }
223
224  return false;
225}
226
227void CallAndMessageChecker::checkPreStmt(const CallExpr *CE,
228                                         CheckerContext &C) const{
229
230  const Expr *Callee = CE->getCallee()->IgnoreParens();
231  ProgramStateRef State = C.getState();
232  const LocationContext *LCtx = C.getLocationContext();
233  SVal L = State->getSVal(Callee, LCtx);
234
235  if (L.isUndef()) {
236    if (!BT_call_undef)
237      BT_call_undef.reset(new BuiltinBug("Called function pointer is an "
238                                         "uninitalized pointer value"));
239    emitBadCall(BT_call_undef.get(), C, Callee);
240    return;
241  }
242
243  ProgramStateRef StNonNull, StNull;
244  llvm::tie(StNonNull, StNull) =
245      State->assume(L.castAs<DefinedOrUnknownSVal>());
246
247  if (StNull && !StNonNull) {
248    if (!BT_call_null)
249      BT_call_null.reset(
250        new BuiltinBug("Called function pointer is null (null dereference)"));
251    emitBadCall(BT_call_null.get(), C, Callee);
252    return;
253  }
254
255  C.addTransition(StNonNull);
256}
257
258void CallAndMessageChecker::checkPreStmt(const CXXDeleteExpr *DE,
259                                         CheckerContext &C) const {
260
261  SVal Arg = C.getSVal(DE->getArgument());
262  if (Arg.isUndef()) {
263    StringRef Desc;
264    ExplodedNode *N = C.generateSink();
265    if (!N)
266      return;
267    if (!BT_cxx_delete_undef)
268      BT_cxx_delete_undef.reset(new BuiltinBug("Uninitialized argument value"));
269    if (DE->isArrayFormAsWritten())
270      Desc = "Argument to 'delete[]' is uninitialized";
271    else
272      Desc = "Argument to 'delete' is uninitialized";
273    BugType *BT = BT_cxx_delete_undef.get();
274    BugReport *R = new BugReport(*BT, Desc, N);
275    bugreporter::trackNullOrUndefValue(N, DE, *R);
276    C.emitReport(R);
277    return;
278  }
279}
280
281
282void CallAndMessageChecker::checkPreCall(const CallEvent &Call,
283                                         CheckerContext &C) const {
284  ProgramStateRef State = C.getState();
285
286  // If this is a call to a C++ method, check if the callee is null or
287  // undefined.
288  if (const CXXInstanceCall *CC = dyn_cast<CXXInstanceCall>(&Call)) {
289    SVal V = CC->getCXXThisVal();
290    if (V.isUndef()) {
291      if (!BT_cxx_call_undef)
292        BT_cxx_call_undef.reset(new BuiltinBug("Called C++ object pointer is "
293                                               "uninitialized"));
294      emitBadCall(BT_cxx_call_undef.get(), C, CC->getCXXThisExpr());
295      return;
296    }
297
298    ProgramStateRef StNonNull, StNull;
299    llvm::tie(StNonNull, StNull) =
300        State->assume(V.castAs<DefinedOrUnknownSVal>());
301
302    if (StNull && !StNonNull) {
303      if (!BT_cxx_call_null)
304        BT_cxx_call_null.reset(new BuiltinBug("Called C++ object pointer "
305                                              "is null"));
306      emitBadCall(BT_cxx_call_null.get(), C, CC->getCXXThisExpr());
307      return;
308    }
309
310    State = StNonNull;
311  }
312
313  const Decl *D = Call.getDecl();
314  if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D)) {
315    // If we have a declaration, we can make sure we pass enough parameters to
316    // the function.
317    unsigned Params = FD->getNumParams();
318    if (Call.getNumArgs() < Params) {
319      ExplodedNode *N = C.generateSink();
320      if (!N)
321        return;
322
323      LazyInit_BT("Function call with too few arguments", BT_call_few_args);
324
325      SmallString<512> Str;
326      llvm::raw_svector_ostream os(Str);
327      os << "Function taking " << Params << " argument"
328         << (Params == 1 ? "" : "s") << " is called with less ("
329         << Call.getNumArgs() << ")";
330
331      BugReport *R = new BugReport(*BT_call_few_args, os.str(), N);
332      C.emitReport(R);
333    }
334  }
335
336  // Don't check for uninitialized field values in arguments if the
337  // caller has a body that is available and we have the chance to inline it.
338  // This is a hack, but is a reasonable compromise betweens sometimes warning
339  // and sometimes not depending on if we decide to inline a function.
340  const bool checkUninitFields =
341    !(C.getAnalysisManager().shouldInlineCall() && (D && D->getBody()));
342
343  OwningPtr<BugType> *BT;
344  if (isa<ObjCMethodCall>(Call))
345    BT = &BT_msg_arg;
346  else
347    BT = &BT_call_arg;
348
349  for (unsigned i = 0, e = Call.getNumArgs(); i != e; ++i)
350    if (PreVisitProcessArg(C, Call.getArgSVal(i), Call.getArgSourceRange(i),
351                           Call.getArgExpr(i), /*IsFirstArgument=*/i == 0,
352                           checkUninitFields, Call, *BT))
353      return;
354
355  // If we make it here, record our assumptions about the callee.
356  C.addTransition(State);
357}
358
359void CallAndMessageChecker::checkPreObjCMessage(const ObjCMethodCall &msg,
360                                                CheckerContext &C) const {
361  SVal recVal = msg.getReceiverSVal();
362  if (recVal.isUndef()) {
363    if (ExplodedNode *N = C.generateSink()) {
364      BugType *BT = 0;
365      switch (msg.getMessageKind()) {
366      case OCM_Message:
367        if (!BT_msg_undef)
368          BT_msg_undef.reset(new BuiltinBug("Receiver in message expression "
369                                            "is an uninitialized value"));
370        BT = BT_msg_undef.get();
371        break;
372      case OCM_PropertyAccess:
373        if (!BT_objc_prop_undef)
374          BT_objc_prop_undef.reset(new BuiltinBug("Property access on an "
375                                                  "uninitialized object "
376                                                  "pointer"));
377        BT = BT_objc_prop_undef.get();
378        break;
379      case OCM_Subscript:
380        if (!BT_objc_subscript_undef)
381          BT_objc_subscript_undef.reset(new BuiltinBug("Subscript access on an "
382                                                       "uninitialized object "
383                                                       "pointer"));
384        BT = BT_objc_subscript_undef.get();
385        break;
386      }
387      assert(BT && "Unknown message kind.");
388
389      BugReport *R = new BugReport(*BT, BT->getName(), N);
390      const ObjCMessageExpr *ME = msg.getOriginExpr();
391      R->addRange(ME->getReceiverRange());
392
393      // FIXME: getTrackNullOrUndefValueVisitor can't handle "super" yet.
394      if (const Expr *ReceiverE = ME->getInstanceReceiver())
395        bugreporter::trackNullOrUndefValue(N, ReceiverE, *R);
396      C.emitReport(R);
397    }
398    return;
399  } else {
400    // Bifurcate the state into nil and non-nil ones.
401    DefinedOrUnknownSVal receiverVal = recVal.castAs<DefinedOrUnknownSVal>();
402
403    ProgramStateRef state = C.getState();
404    ProgramStateRef notNilState, nilState;
405    llvm::tie(notNilState, nilState) = state->assume(receiverVal);
406
407    // Handle receiver must be nil.
408    if (nilState && !notNilState) {
409      HandleNilReceiver(C, state, msg);
410      return;
411    }
412  }
413}
414
415void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C,
416                                               const ObjCMethodCall &msg,
417                                               ExplodedNode *N) const {
418
419  if (!BT_msg_ret)
420    BT_msg_ret.reset(
421      new BuiltinBug("Receiver in message expression is 'nil'"));
422
423  const ObjCMessageExpr *ME = msg.getOriginExpr();
424
425  QualType ResTy = msg.getResultType();
426
427  SmallString<200> buf;
428  llvm::raw_svector_ostream os(buf);
429  os << "The receiver of message '" << ME->getSelector().getAsString()
430     << "' is nil";
431  if (ResTy->isReferenceType()) {
432    os << ", which results in forming a null reference";
433  } else {
434    os << " and returns a value of type '";
435    msg.getResultType().print(os, C.getLangOpts());
436    os << "' that will be garbage";
437  }
438
439  BugReport *report = new BugReport(*BT_msg_ret, os.str(), N);
440  report->addRange(ME->getReceiverRange());
441  // FIXME: This won't track "self" in messages to super.
442  if (const Expr *receiver = ME->getInstanceReceiver()) {
443    bugreporter::trackNullOrUndefValue(N, receiver, *report);
444  }
445  C.emitReport(report);
446}
447
448static bool supportsNilWithFloatRet(const llvm::Triple &triple) {
449  return (triple.getVendor() == llvm::Triple::Apple &&
450          (triple.isiOS() || !triple.isMacOSXVersionLT(10,5)));
451}
452
453void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C,
454                                              ProgramStateRef state,
455                                              const ObjCMethodCall &Msg) const {
456  ASTContext &Ctx = C.getASTContext();
457  static SimpleProgramPointTag Tag("CallAndMessageChecker : NilReceiver");
458
459  // Check the return type of the message expression.  A message to nil will
460  // return different values depending on the return type and the architecture.
461  QualType RetTy = Msg.getResultType();
462  CanQualType CanRetTy = Ctx.getCanonicalType(RetTy);
463  const LocationContext *LCtx = C.getLocationContext();
464
465  if (CanRetTy->isStructureOrClassType()) {
466    // Structure returns are safe since the compiler zeroes them out.
467    SVal V = C.getSValBuilder().makeZeroVal(RetTy);
468    C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag);
469    return;
470  }
471
472  // Other cases: check if sizeof(return type) > sizeof(void*)
473  if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap()
474                                  .isConsumedExpr(Msg.getOriginExpr())) {
475    // Compute: sizeof(void *) and sizeof(return type)
476    const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy);
477    const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy);
478
479    if (CanRetTy.getTypePtr()->isReferenceType()||
480        (voidPtrSize < returnTypeSize &&
481         !(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) &&
482           (Ctx.FloatTy == CanRetTy ||
483            Ctx.DoubleTy == CanRetTy ||
484            Ctx.LongDoubleTy == CanRetTy ||
485            Ctx.LongLongTy == CanRetTy ||
486            Ctx.UnsignedLongLongTy == CanRetTy)))) {
487      if (ExplodedNode *N = C.generateSink(state, 0 , &Tag))
488        emitNilReceiverBug(C, Msg, N);
489      return;
490    }
491
492    // Handle the safe cases where the return value is 0 if the
493    // receiver is nil.
494    //
495    // FIXME: For now take the conservative approach that we only
496    // return null values if we *know* that the receiver is nil.
497    // This is because we can have surprises like:
498    //
499    //   ... = [[NSScreens screens] objectAtIndex:0];
500    //
501    // What can happen is that [... screens] could return nil, but
502    // it most likely isn't nil.  We should assume the semantics
503    // of this case unless we have *a lot* more knowledge.
504    //
505    SVal V = C.getSValBuilder().makeZeroVal(RetTy);
506    C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag);
507    return;
508  }
509
510  C.addTransition(state);
511}
512
513void ento::registerCallAndMessageChecker(CheckerManager &mgr) {
514  mgr.registerChecker<CallAndMessageChecker>();
515}
516