CallAndMessageChecker.cpp revision a93d0f280693b8418bc88cf7a8c93325f7fcf4c6 
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/StaticAnalyzer/Core/Checker.h"
17#include "clang/StaticAnalyzer/Core/CheckerManager.h"
18#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
19#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
20#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
21#include "clang/AST/ParentMap.h"
22#include "clang/Basic/TargetInfo.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>, check::PreObjCMessage,
32                    check::PreCall > {
33  mutable OwningPtr<BugType> BT_call_null;
34  mutable OwningPtr<BugType> BT_call_undef;
35  mutable OwningPtr<BugType> BT_cxx_call_null;
36  mutable OwningPtr<BugType> BT_cxx_call_undef;
37  mutable OwningPtr<BugType> BT_call_arg;
38  mutable OwningPtr<BugType> BT_msg_undef;
39  mutable OwningPtr<BugType> BT_objc_prop_undef;
40  mutable OwningPtr<BugType> BT_objc_subscript_undef;
41  mutable OwningPtr<BugType> BT_msg_arg;
42  mutable OwningPtr<BugType> BT_msg_ret;
43public:
44
45  void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
46  void checkPreObjCMessage(const ObjCMethodCall &msg, CheckerContext &C) const;
47  void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
48
49private:
50  static bool PreVisitProcessArg(CheckerContext &C, SVal V,
51                                 SourceRange argRange, const Expr *argEx,
52                                 bool IsFirstArgument, bool checkUninitFields,
53                                 const CallEvent &Call, OwningPtr<BugType> &BT);
54
55  static void emitBadCall(BugType *BT, CheckerContext &C, const Expr *BadE);
56  void emitNilReceiverBug(CheckerContext &C, const ObjCMethodCall &msg,
57                          ExplodedNode *N) const;
58
59  void HandleNilReceiver(CheckerContext &C,
60                         ProgramStateRef state,
61                         const ObjCMethodCall &msg) const;
62
63  static void LazyInit_BT(const char *desc, OwningPtr<BugType> &BT) {
64    if (!BT)
65      BT.reset(new BuiltinBug(desc));
66  }
67};
68} // end anonymous namespace
69
70void CallAndMessageChecker::emitBadCall(BugType *BT, CheckerContext &C,
71                                        const Expr *BadE) {
72  ExplodedNode *N = C.generateSink();
73  if (!N)
74    return;
75
76  BugReport *R = new BugReport(*BT, BT->getName(), N);
77  if (BadE) {
78    R->addRange(BadE->getSourceRange());
79    bugreporter::trackNullOrUndefValue(N, BadE, *R);
80  }
81  C.emitReport(R);
82}
83
84static StringRef describeUninitializedArgumentInCall(const CallEvent &Call,
85                                                     bool IsFirstArgument) {
86  switch (Call.getKind()) {
87  case CE_ObjCMessage: {
88    const ObjCMethodCall &Msg = cast<ObjCMethodCall>(Call);
89    switch (Msg.getMessageKind()) {
90    case OCM_Message:
91      return "Argument in message expression is an uninitialized value";
92    case OCM_PropertyAccess:
93      assert(Msg.isSetter() && "Getters have no args");
94      return "Argument for property setter is an uninitialized value";
95    case OCM_Subscript:
96      if (Msg.isSetter() && IsFirstArgument)
97        return "Argument for subscript setter is an uninitialized value";
98      return "Subscript index is an uninitialized value";
99    }
100    llvm_unreachable("Unknown message kind.");
101  }
102  case CE_Block:
103    return "Block call argument is an uninitialized value";
104  default:
105    return "Function call argument is an uninitialized value";
106  }
107}
108
109bool CallAndMessageChecker::PreVisitProcessArg(CheckerContext &C,
110                                               SVal V, SourceRange argRange,
111                                               const Expr *argEx,
112                                               bool IsFirstArgument,
113                                               bool checkUninitFields,
114                                               const CallEvent &Call,
115                                               OwningPtr<BugType> &BT) {
116  if (V.isUndef()) {
117    if (ExplodedNode *N = C.generateSink()) {
118      LazyInit_BT("Uninitialized argument value", BT);
119
120      // Generate a report for this bug.
121      StringRef Desc = describeUninitializedArgumentInCall(Call,
122                                                           IsFirstArgument);
123      BugReport *R = new BugReport(*BT, Desc, N);
124      R->addRange(argRange);
125      if (argEx)
126        bugreporter::trackNullOrUndefValue(N, argEx, *R);
127      C.emitReport(R);
128    }
129    return true;
130  }
131
132  if (!checkUninitFields)
133    return false;
134
135  if (const nonloc::LazyCompoundVal *LV =
136        dyn_cast<nonloc::LazyCompoundVal>(&V)) {
137
138    class FindUninitializedField {
139    public:
140      SmallVector<const FieldDecl *, 10> FieldChain;
141    private:
142      StoreManager &StoreMgr;
143      MemRegionManager &MrMgr;
144      Store store;
145    public:
146      FindUninitializedField(StoreManager &storeMgr,
147                             MemRegionManager &mrMgr, Store s)
148      : StoreMgr(storeMgr), MrMgr(mrMgr), store(s) {}
149
150      bool Find(const TypedValueRegion *R) {
151        QualType T = R->getValueType();
152        if (const RecordType *RT = T->getAsStructureType()) {
153          const RecordDecl *RD = RT->getDecl()->getDefinition();
154          assert(RD && "Referred record has no definition");
155          for (RecordDecl::field_iterator I =
156               RD->field_begin(), E = RD->field_end(); I!=E; ++I) {
157            const FieldRegion *FR = MrMgr.getFieldRegion(*I, R);
158            FieldChain.push_back(*I);
159            T = I->getType();
160            if (T->getAsStructureType()) {
161              if (Find(FR))
162                return true;
163            }
164            else {
165              const SVal &V = StoreMgr.getBinding(store, loc::MemRegionVal(FR));
166              if (V.isUndef())
167                return true;
168            }
169            FieldChain.pop_back();
170          }
171        }
172
173        return false;
174      }
175    };
176
177    const LazyCompoundValData *D = LV->getCVData();
178    FindUninitializedField F(C.getState()->getStateManager().getStoreManager(),
179                             C.getSValBuilder().getRegionManager(),
180                             D->getStore());
181
182    if (F.Find(D->getRegion())) {
183      if (ExplodedNode *N = C.generateSink()) {
184        LazyInit_BT("Uninitialized argument value", BT);
185        SmallString<512> Str;
186        llvm::raw_svector_ostream os(Str);
187        os << "Passed-by-value struct argument contains uninitialized data";
188
189        if (F.FieldChain.size() == 1)
190          os << " (e.g., field: '" << *F.FieldChain[0] << "')";
191        else {
192          os << " (e.g., via the field chain: '";
193          bool first = true;
194          for (SmallVectorImpl<const FieldDecl *>::iterator
195               DI = F.FieldChain.begin(), DE = F.FieldChain.end(); DI!=DE;++DI){
196            if (first)
197              first = false;
198            else
199              os << '.';
200            os << **DI;
201          }
202          os << "')";
203        }
204
205        // Generate a report for this bug.
206        BugReport *R = new BugReport(*BT, os.str(), N);
207        R->addRange(argRange);
208
209        // FIXME: enhance track back for uninitialized value for arbitrary
210        // memregions
211        C.emitReport(R);
212      }
213      return true;
214    }
215  }
216
217  return false;
218}
219
220void CallAndMessageChecker::checkPreStmt(const CallExpr *CE,
221                                         CheckerContext &C) const{
222
223  const Expr *Callee = CE->getCallee()->IgnoreParens();
224  ProgramStateRef State = C.getState();
225  const LocationContext *LCtx = C.getLocationContext();
226  SVal L = State->getSVal(Callee, LCtx);
227
228  if (L.isUndef()) {
229    if (!BT_call_undef)
230      BT_call_undef.reset(new BuiltinBug("Called function pointer is an "
231                                         "uninitalized pointer value"));
232    emitBadCall(BT_call_undef.get(), C, Callee);
233    return;
234  }
235
236  ProgramStateRef StNonNull, StNull;
237  llvm::tie(StNonNull, StNull) = State->assume(cast<DefinedOrUnknownSVal>(L));
238
239  if (StNull && !StNonNull) {
240    if (!BT_call_null)
241      BT_call_null.reset(
242        new BuiltinBug("Called function pointer is null (null dereference)"));
243    emitBadCall(BT_call_null.get(), C, Callee);
244  }
245
246  C.addTransition(StNonNull);
247}
248
249void CallAndMessageChecker::checkPreCall(const CallEvent &Call,
250                                         CheckerContext &C) const {
251  ProgramStateRef State = C.getState();
252
253  // If this is a call to a C++ method, check if the callee is null or
254  // undefined.
255  if (const CXXInstanceCall *CC = dyn_cast<CXXInstanceCall>(&Call)) {
256    SVal V = CC->getCXXThisVal();
257    if (V.isUndef()) {
258      if (!BT_cxx_call_undef)
259        BT_cxx_call_undef.reset(new BuiltinBug("Called C++ object pointer is "
260                                               "uninitialized"));
261      emitBadCall(BT_cxx_call_undef.get(), C, CC->getCXXThisExpr());
262      return;
263    }
264
265    ProgramStateRef StNonNull, StNull;
266    llvm::tie(StNonNull, StNull) = State->assume(cast<DefinedOrUnknownSVal>(V));
267
268    if (StNull && !StNonNull) {
269      if (!BT_cxx_call_null)
270        BT_cxx_call_null.reset(new BuiltinBug("Called C++ object pointer "
271                                              "is null"));
272      emitBadCall(BT_cxx_call_null.get(), C, CC->getCXXThisExpr());
273      return;
274    }
275
276    State = StNonNull;
277  }
278
279  // Don't check for uninitialized field values in arguments if the
280  // caller has a body that is available and we have the chance to inline it.
281  // This is a hack, but is a reasonable compromise betweens sometimes warning
282  // and sometimes not depending on if we decide to inline a function.
283  const Decl *D = Call.getDecl();
284  const bool checkUninitFields =
285    !(C.getAnalysisManager().shouldInlineCall() && (D && D->getBody()));
286
287  OwningPtr<BugType> *BT;
288  if (isa<ObjCMethodCall>(Call))
289    BT = &BT_msg_arg;
290  else
291    BT = &BT_call_arg;
292
293  for (unsigned i = 0, e = Call.getNumArgs(); i != e; ++i)
294    if (PreVisitProcessArg(C, Call.getArgSVal(i), Call.getArgSourceRange(i),
295                           Call.getArgExpr(i), /*IsFirstArgument=*/i == 0,
296                           checkUninitFields, Call, *BT))
297      return;
298
299  // If we make it here, record our assumptions about the callee.
300  C.addTransition(State);
301}
302
303void CallAndMessageChecker::checkPreObjCMessage(const ObjCMethodCall &msg,
304                                                CheckerContext &C) const {
305  SVal recVal = msg.getReceiverSVal();
306  if (recVal.isUndef()) {
307    if (ExplodedNode *N = C.generateSink()) {
308      BugType *BT = 0;
309      switch (msg.getMessageKind()) {
310      case OCM_Message:
311        if (!BT_msg_undef)
312          BT_msg_undef.reset(new BuiltinBug("Receiver in message expression "
313                                            "is an uninitialized value"));
314        BT = BT_msg_undef.get();
315        break;
316      case OCM_PropertyAccess:
317        if (!BT_objc_prop_undef)
318          BT_objc_prop_undef.reset(new BuiltinBug("Property access on an "
319                                                  "uninitialized object "
320                                                  "pointer"));
321        BT = BT_objc_prop_undef.get();
322        break;
323      case OCM_Subscript:
324        if (!BT_objc_subscript_undef)
325          BT_objc_subscript_undef.reset(new BuiltinBug("Subscript access on an "
326                                                       "uninitialized object "
327                                                       "pointer"));
328        BT = BT_objc_subscript_undef.get();
329        break;
330      }
331      assert(BT && "Unknown message kind.");
332
333      BugReport *R = new BugReport(*BT, BT->getName(), N);
334      const ObjCMessageExpr *ME = msg.getOriginExpr();
335      R->addRange(ME->getReceiverRange());
336
337      // FIXME: getTrackNullOrUndefValueVisitor can't handle "super" yet.
338      if (const Expr *ReceiverE = ME->getInstanceReceiver())
339        bugreporter::trackNullOrUndefValue(N, ReceiverE, *R);
340      C.emitReport(R);
341    }
342    return;
343  } else {
344    // Bifurcate the state into nil and non-nil ones.
345    DefinedOrUnknownSVal receiverVal = cast<DefinedOrUnknownSVal>(recVal);
346
347    ProgramStateRef state = C.getState();
348    ProgramStateRef notNilState, nilState;
349    llvm::tie(notNilState, nilState) = state->assume(receiverVal);
350
351    // Handle receiver must be nil.
352    if (nilState && !notNilState) {
353      HandleNilReceiver(C, state, msg);
354      return;
355    }
356  }
357}
358
359void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C,
360                                               const ObjCMethodCall &msg,
361                                               ExplodedNode *N) const {
362
363  if (!BT_msg_ret)
364    BT_msg_ret.reset(
365      new BuiltinBug("Receiver in message expression is "
366                     "'nil' and returns a garbage value"));
367
368  const ObjCMessageExpr *ME = msg.getOriginExpr();
369
370  SmallString<200> buf;
371  llvm::raw_svector_ostream os(buf);
372  os << "The receiver of message '" << ME->getSelector().getAsString()
373     << "' is nil and returns a value of type '";
374  msg.getResultType().print(os, C.getLangOpts());
375  os << "' that will be garbage";
376
377  BugReport *report = new BugReport(*BT_msg_ret, os.str(), N);
378  report->addRange(ME->getReceiverRange());
379  // FIXME: This won't track "self" in messages to super.
380  if (const Expr *receiver = ME->getInstanceReceiver()) {
381    bugreporter::trackNullOrUndefValue(N, receiver, *report);
382  }
383  C.emitReport(report);
384}
385
386static bool supportsNilWithFloatRet(const llvm::Triple &triple) {
387  return (triple.getVendor() == llvm::Triple::Apple &&
388          (triple.getOS() == llvm::Triple::IOS ||
389           !triple.isMacOSXVersionLT(10,5)));
390}
391
392void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C,
393                                              ProgramStateRef state,
394                                              const ObjCMethodCall &Msg) const {
395  ASTContext &Ctx = C.getASTContext();
396
397  // Check the return type of the message expression.  A message to nil will
398  // return different values depending on the return type and the architecture.
399  QualType RetTy = Msg.getResultType();
400  CanQualType CanRetTy = Ctx.getCanonicalType(RetTy);
401  const LocationContext *LCtx = C.getLocationContext();
402
403  if (CanRetTy->isStructureOrClassType()) {
404    // Structure returns are safe since the compiler zeroes them out.
405    SVal V = C.getSValBuilder().makeZeroVal(RetTy);
406    C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V));
407    return;
408  }
409
410  // Other cases: check if sizeof(return type) > sizeof(void*)
411  if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap()
412                                  .isConsumedExpr(Msg.getOriginExpr())) {
413    // Compute: sizeof(void *) and sizeof(return type)
414    const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy);
415    const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy);
416
417    if (voidPtrSize < returnTypeSize &&
418        !(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) &&
419          (Ctx.FloatTy == CanRetTy ||
420           Ctx.DoubleTy == CanRetTy ||
421           Ctx.LongDoubleTy == CanRetTy ||
422           Ctx.LongLongTy == CanRetTy ||
423           Ctx.UnsignedLongLongTy == CanRetTy))) {
424      if (ExplodedNode *N = C.generateSink(state))
425        emitNilReceiverBug(C, Msg, N);
426      return;
427    }
428
429    // Handle the safe cases where the return value is 0 if the
430    // receiver is nil.
431    //
432    // FIXME: For now take the conservative approach that we only
433    // return null values if we *know* that the receiver is nil.
434    // This is because we can have surprises like:
435    //
436    //   ... = [[NSScreens screens] objectAtIndex:0];
437    //
438    // What can happen is that [... screens] could return nil, but
439    // it most likely isn't nil.  We should assume the semantics
440    // of this case unless we have *a lot* more knowledge.
441    //
442    SVal V = C.getSValBuilder().makeZeroVal(RetTy);
443    C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V));
444    return;
445  }
446
447  C.addTransition(state);
448}
449
450void ento::registerCallAndMessageChecker(CheckerManager &mgr) {
451  mgr.registerChecker<CallAndMessageChecker>();
452}
453