CallAndMessageChecker.cpp revision 57b1da1588a3f5785ad8bd5d9f2d795d685e1058 
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  }
253
254  C.addTransition(StNonNull);
255}
256
257void CallAndMessageChecker::checkPreStmt(const CXXDeleteExpr *DE,
258                                         CheckerContext &C) const {
259
260  SVal Arg = C.getSVal(DE->getArgument());
261  if (Arg.isUndef()) {
262    StringRef Desc;
263    ExplodedNode *N = C.generateSink();
264    if (!N)
265      return;
266    if (!BT_cxx_delete_undef)
267      BT_cxx_delete_undef.reset(new BuiltinBug("Uninitialized argument value"));
268    if (DE->isArrayFormAsWritten())
269      Desc = "Argument to 'delete[]' is uninitialized";
270    else
271      Desc = "Argument to 'delete' is uninitialized";
272    BugType *BT = BT_cxx_delete_undef.get();
273    BugReport *R = new BugReport(*BT, Desc, N);
274    bugreporter::trackNullOrUndefValue(N, DE, *R);
275    C.emitReport(R);
276    return;
277  }
278}
279
280
281void CallAndMessageChecker::checkPreCall(const CallEvent &Call,
282                                         CheckerContext &C) const {
283  ProgramStateRef State = C.getState();
284
285  // If this is a call to a C++ method, check if the callee is null or
286  // undefined.
287  if (const CXXInstanceCall *CC = dyn_cast<CXXInstanceCall>(&Call)) {
288    SVal V = CC->getCXXThisVal();
289    if (V.isUndef()) {
290      if (!BT_cxx_call_undef)
291        BT_cxx_call_undef.reset(new BuiltinBug("Called C++ object pointer is "
292                                               "uninitialized"));
293      emitBadCall(BT_cxx_call_undef.get(), C, CC->getCXXThisExpr());
294      return;
295    }
296
297    ProgramStateRef StNonNull, StNull;
298    llvm::tie(StNonNull, StNull) =
299        State->assume(V.castAs<DefinedOrUnknownSVal>());
300
301    if (StNull && !StNonNull) {
302      if (!BT_cxx_call_null)
303        BT_cxx_call_null.reset(new BuiltinBug("Called C++ object pointer "
304                                              "is null"));
305      emitBadCall(BT_cxx_call_null.get(), C, CC->getCXXThisExpr());
306      return;
307    }
308
309    State = StNonNull;
310  }
311
312  const Decl *D = Call.getDecl();
313  if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D)) {
314    // If we have a declaration, we can make sure we pass enough parameters to
315    // the function.
316    unsigned Params = FD->getNumParams();
317    if (Call.getNumArgs() < Params) {
318      ExplodedNode *N = C.generateSink();
319      if (!N)
320        return;
321
322      LazyInit_BT("Function call with too few arguments", BT_call_few_args);
323
324      SmallString<512> Str;
325      llvm::raw_svector_ostream os(Str);
326      os << "Function taking " << Params << " argument"
327         << (Params == 1 ? "" : "s") << " is called with less ("
328         << Call.getNumArgs() << ")";
329
330      BugReport *R = new BugReport(*BT_call_few_args, os.str(), N);
331      C.emitReport(R);
332    }
333  }
334
335  // Don't check for uninitialized field values in arguments if the
336  // caller has a body that is available and we have the chance to inline it.
337  // This is a hack, but is a reasonable compromise betweens sometimes warning
338  // and sometimes not depending on if we decide to inline a function.
339  const bool checkUninitFields =
340    !(C.getAnalysisManager().shouldInlineCall() && (D && D->getBody()));
341
342  OwningPtr<BugType> *BT;
343  if (isa<ObjCMethodCall>(Call))
344    BT = &BT_msg_arg;
345  else
346    BT = &BT_call_arg;
347
348  for (unsigned i = 0, e = Call.getNumArgs(); i != e; ++i)
349    if (PreVisitProcessArg(C, Call.getArgSVal(i), Call.getArgSourceRange(i),
350                           Call.getArgExpr(i), /*IsFirstArgument=*/i == 0,
351                           checkUninitFields, Call, *BT))
352      return;
353
354  // If we make it here, record our assumptions about the callee.
355  C.addTransition(State);
356}
357
358void CallAndMessageChecker::checkPreObjCMessage(const ObjCMethodCall &msg,
359                                                CheckerContext &C) const {
360  SVal recVal = msg.getReceiverSVal();
361  if (recVal.isUndef()) {
362    if (ExplodedNode *N = C.generateSink()) {
363      BugType *BT = 0;
364      switch (msg.getMessageKind()) {
365      case OCM_Message:
366        if (!BT_msg_undef)
367          BT_msg_undef.reset(new BuiltinBug("Receiver in message expression "
368                                            "is an uninitialized value"));
369        BT = BT_msg_undef.get();
370        break;
371      case OCM_PropertyAccess:
372        if (!BT_objc_prop_undef)
373          BT_objc_prop_undef.reset(new BuiltinBug("Property access on an "
374                                                  "uninitialized object "
375                                                  "pointer"));
376        BT = BT_objc_prop_undef.get();
377        break;
378      case OCM_Subscript:
379        if (!BT_objc_subscript_undef)
380          BT_objc_subscript_undef.reset(new BuiltinBug("Subscript access on an "
381                                                       "uninitialized object "
382                                                       "pointer"));
383        BT = BT_objc_subscript_undef.get();
384        break;
385      }
386      assert(BT && "Unknown message kind.");
387
388      BugReport *R = new BugReport(*BT, BT->getName(), N);
389      const ObjCMessageExpr *ME = msg.getOriginExpr();
390      R->addRange(ME->getReceiverRange());
391
392      // FIXME: getTrackNullOrUndefValueVisitor can't handle "super" yet.
393      if (const Expr *ReceiverE = ME->getInstanceReceiver())
394        bugreporter::trackNullOrUndefValue(N, ReceiverE, *R);
395      C.emitReport(R);
396    }
397    return;
398  } else {
399    // Bifurcate the state into nil and non-nil ones.
400    DefinedOrUnknownSVal receiverVal = recVal.castAs<DefinedOrUnknownSVal>();
401
402    ProgramStateRef state = C.getState();
403    ProgramStateRef notNilState, nilState;
404    llvm::tie(notNilState, nilState) = state->assume(receiverVal);
405
406    // Handle receiver must be nil.
407    if (nilState && !notNilState) {
408      HandleNilReceiver(C, state, msg);
409      return;
410    }
411  }
412}
413
414void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C,
415                                               const ObjCMethodCall &msg,
416                                               ExplodedNode *N) const {
417
418  if (!BT_msg_ret)
419    BT_msg_ret.reset(
420      new BuiltinBug("Receiver in message expression is 'nil'"));
421
422  const ObjCMessageExpr *ME = msg.getOriginExpr();
423
424  QualType ResTy = msg.getResultType();
425
426  SmallString<200> buf;
427  llvm::raw_svector_ostream os(buf);
428  os << "The receiver of message '" << ME->getSelector().getAsString()
429     << "' is nil";
430  if (ResTy->isReferenceType()) {
431    os << ", which results in forming a null reference";
432  } else {
433    os << " and returns a value of type '";
434    msg.getResultType().print(os, C.getLangOpts());
435    os << "' that will be garbage";
436  }
437
438  BugReport *report = new BugReport(*BT_msg_ret, os.str(), N);
439  report->addRange(ME->getReceiverRange());
440  // FIXME: This won't track "self" in messages to super.
441  if (const Expr *receiver = ME->getInstanceReceiver()) {
442    bugreporter::trackNullOrUndefValue(N, receiver, *report);
443  }
444  C.emitReport(report);
445}
446
447static bool supportsNilWithFloatRet(const llvm::Triple &triple) {
448  return (triple.getVendor() == llvm::Triple::Apple &&
449          (triple.isiOS() || !triple.isMacOSXVersionLT(10,5)));
450}
451
452void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C,
453                                              ProgramStateRef state,
454                                              const ObjCMethodCall &Msg) const {
455  ASTContext &Ctx = C.getASTContext();
456  static SimpleProgramPointTag Tag("CallAndMessageChecker : NilReceiver");
457
458  // Check the return type of the message expression.  A message to nil will
459  // return different values depending on the return type and the architecture.
460  QualType RetTy = Msg.getResultType();
461  CanQualType CanRetTy = Ctx.getCanonicalType(RetTy);
462  const LocationContext *LCtx = C.getLocationContext();
463
464  if (CanRetTy->isStructureOrClassType()) {
465    // Structure returns are safe since the compiler zeroes them out.
466    SVal V = C.getSValBuilder().makeZeroVal(RetTy);
467    C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag);
468    return;
469  }
470
471  // Other cases: check if sizeof(return type) > sizeof(void*)
472  if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap()
473                                  .isConsumedExpr(Msg.getOriginExpr())) {
474    // Compute: sizeof(void *) and sizeof(return type)
475    const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy);
476    const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy);
477
478    if (CanRetTy.getTypePtr()->isReferenceType()||
479        (voidPtrSize < returnTypeSize &&
480         !(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) &&
481           (Ctx.FloatTy == CanRetTy ||
482            Ctx.DoubleTy == CanRetTy ||
483            Ctx.LongDoubleTy == CanRetTy ||
484            Ctx.LongLongTy == CanRetTy ||
485            Ctx.UnsignedLongLongTy == CanRetTy)))) {
486      if (ExplodedNode *N = C.generateSink(state, 0 , &Tag))
487        emitNilReceiverBug(C, Msg, N);
488      return;
489    }
490
491    // Handle the safe cases where the return value is 0 if the
492    // receiver is nil.
493    //
494    // FIXME: For now take the conservative approach that we only
495    // return null values if we *know* that the receiver is nil.
496    // This is because we can have surprises like:
497    //
498    //   ... = [[NSScreens screens] objectAtIndex:0];
499    //
500    // What can happen is that [... screens] could return nil, but
501    // it most likely isn't nil.  We should assume the semantics
502    // of this case unless we have *a lot* more knowledge.
503    //
504    SVal V = C.getSValBuilder().makeZeroVal(RetTy);
505    C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag);
506    return;
507  }
508
509  C.addTransition(state);
510}
511
512void ento::registerCallAndMessageChecker(CheckerManager &mgr) {
513  mgr.registerChecker<CallAndMessageChecker>();
514}
515