CallAndMessageChecker.cpp revision a1f81bb0e55749a1414b1b5124bb83b9052ff2ac 
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
25using namespace clang;
26using namespace ento;
27
28namespace {
29class CallAndMessageChecker
30  : public Checker< check::PreStmt<CallExpr>, check::PreObjCMessage,
31                    check::PreCall > {
32  mutable OwningPtr<BugType> BT_call_null;
33  mutable OwningPtr<BugType> BT_call_undef;
34  mutable OwningPtr<BugType> BT_cxx_call_null;
35  mutable OwningPtr<BugType> BT_cxx_call_undef;
36  mutable OwningPtr<BugType> BT_call_arg;
37  mutable OwningPtr<BugType> BT_msg_undef;
38  mutable OwningPtr<BugType> BT_objc_prop_undef;
39  mutable OwningPtr<BugType> BT_objc_subscript_undef;
40  mutable OwningPtr<BugType> BT_msg_arg;
41  mutable OwningPtr<BugType> BT_msg_ret;
42public:
43
44  void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
45  void checkPreObjCMessage(const ObjCMethodCall &msg, CheckerContext &C) const;
46  void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
47
48private:
49  static bool PreVisitProcessArg(CheckerContext &C, SVal V,
50                                 SourceRange argRange, const Expr *argEx,
51                                 bool IsFirstArgument, bool checkUninitFields,
52                                 const CallEvent &Call, OwningPtr<BugType> &BT);
53
54  static void emitBadCall(BugType *BT, CheckerContext &C, const Expr *BadE);
55  void emitNilReceiverBug(CheckerContext &C, const ObjCMethodCall &msg,
56                          ExplodedNode *N) const;
57
58  void HandleNilReceiver(CheckerContext &C,
59                         ProgramStateRef state,
60                         const ObjCMethodCall &msg) const;
61
62  static void LazyInit_BT(const char *desc, OwningPtr<BugType> &BT) {
63    if (!BT)
64      BT.reset(new BuiltinBug(desc));
65  }
66};
67} // end anonymous namespace
68
69void CallAndMessageChecker::emitBadCall(BugType *BT, CheckerContext &C,
70                                        const Expr *BadE) {
71  ExplodedNode *N = C.generateSink();
72  if (!N)
73    return;
74
75  BugReport *R = new BugReport(*BT, BT->getName(), N);
76  if (BadE) {
77    R->addRange(BadE->getSourceRange());
78    bugreporter::trackNullOrUndefValue(N, BadE, *R);
79  }
80  C.EmitReport(R);
81}
82
83StringRef describeUninitializedArgumentInCall(const CallEvent &Call,
84                                              bool IsFirstArgument) {
85  switch (Call.getKind()) {
86  case CE_ObjCMessage: {
87    const ObjCMethodCall &Msg = cast<ObjCMethodCall>(Call);
88    switch (Msg.getMessageKind()) {
89    case OCM_Message:
90      return "Argument in message expression is an uninitialized value";
91    case OCM_PropertyAccess:
92      assert(Msg.isSetter() && "Getters have no args");
93      return "Argument for property setter is an uninitialized value";
94    case OCM_Subscript:
95      if (Msg.isSetter() && IsFirstArgument)
96        return "Argument for subscript setter is an uninitialized value";
97      return "Subscript index is an uninitialized value";
98    }
99    llvm_unreachable("Unknown message kind.");
100  }
101  case CE_Block:
102    return "Block call argument is an uninitialized value";
103  default:
104    return "Function call argument is an uninitialized value";
105  }
106}
107
108bool CallAndMessageChecker::PreVisitProcessArg(CheckerContext &C,
109                                               SVal V, SourceRange argRange,
110                                               const Expr *argEx,
111                                               bool IsFirstArgument,
112                                               bool checkUninitFields,
113                                               const CallEvent &Call,
114                                               OwningPtr<BugType> &BT) {
115  if (V.isUndef()) {
116    if (ExplodedNode *N = C.generateSink()) {
117      LazyInit_BT("Uninitialized argument value", BT);
118
119      // Generate a report for this bug.
120      StringRef Desc = describeUninitializedArgumentInCall(Call,
121                                                           IsFirstArgument);
122      BugReport *R = new BugReport(*BT, Desc, N);
123      R->addRange(argRange);
124      if (argEx)
125        bugreporter::trackNullOrUndefValue(N, argEx, *R);
126      C.EmitReport(R);
127    }
128    return true;
129  }
130
131  if (!checkUninitFields)
132    return false;
133
134  if (const nonloc::LazyCompoundVal *LV =
135        dyn_cast<nonloc::LazyCompoundVal>(&V)) {
136
137    class FindUninitializedField {
138    public:
139      SmallVector<const FieldDecl *, 10> FieldChain;
140    private:
141      StoreManager &StoreMgr;
142      MemRegionManager &MrMgr;
143      Store store;
144    public:
145      FindUninitializedField(StoreManager &storeMgr,
146                             MemRegionManager &mrMgr, Store s)
147      : StoreMgr(storeMgr), MrMgr(mrMgr), store(s) {}
148
149      bool Find(const TypedValueRegion *R) {
150        QualType T = R->getValueType();
151        if (const RecordType *RT = T->getAsStructureType()) {
152          const RecordDecl *RD = RT->getDecl()->getDefinition();
153          assert(RD && "Referred record has no definition");
154          for (RecordDecl::field_iterator I =
155               RD->field_begin(), E = RD->field_end(); I!=E; ++I) {
156            const FieldRegion *FR = MrMgr.getFieldRegion(*I, R);
157            FieldChain.push_back(*I);
158            T = I->getType();
159            if (T->getAsStructureType()) {
160              if (Find(FR))
161                return true;
162            }
163            else {
164              const SVal &V = StoreMgr.getBinding(store, loc::MemRegionVal(FR));
165              if (V.isUndef())
166                return true;
167            }
168            FieldChain.pop_back();
169          }
170        }
171
172        return false;
173      }
174    };
175
176    const LazyCompoundValData *D = LV->getCVData();
177    FindUninitializedField F(C.getState()->getStateManager().getStoreManager(),
178                             C.getSValBuilder().getRegionManager(),
179                             D->getStore());
180
181    if (F.Find(D->getRegion())) {
182      if (ExplodedNode *N = C.generateSink()) {
183        LazyInit_BT("Uninitialized argument value", BT);
184        SmallString<512> Str;
185        llvm::raw_svector_ostream os(Str);
186        os << "Passed-by-value struct argument contains uninitialized data";
187
188        if (F.FieldChain.size() == 1)
189          os << " (e.g., field: '" << *F.FieldChain[0] << "')";
190        else {
191          os << " (e.g., via the field chain: '";
192          bool first = true;
193          for (SmallVectorImpl<const FieldDecl *>::iterator
194               DI = F.FieldChain.begin(), DE = F.FieldChain.end(); DI!=DE;++DI){
195            if (first)
196              first = false;
197            else
198              os << '.';
199            os << **DI;
200          }
201          os << "')";
202        }
203
204        // Generate a report for this bug.
205        BugReport *R = new BugReport(*BT, os.str(), N);
206        R->addRange(argRange);
207
208        // FIXME: enhance track back for uninitialized value for arbitrary
209        // memregions
210        C.EmitReport(R);
211      }
212      return true;
213    }
214  }
215
216  return false;
217}
218
219void CallAndMessageChecker::checkPreStmt(const CallExpr *CE,
220                                         CheckerContext &C) const{
221
222  const Expr *Callee = CE->getCallee()->IgnoreParens();
223  ProgramStateRef State = C.getState();
224  const LocationContext *LCtx = C.getLocationContext();
225  SVal L = State->getSVal(Callee, LCtx);
226
227  if (L.isUndef()) {
228    if (!BT_call_undef)
229      BT_call_undef.reset(new BuiltinBug("Called function pointer is an "
230                                         "uninitalized pointer value"));
231    emitBadCall(BT_call_undef.get(), C, Callee);
232    return;
233  }
234
235  ProgramStateRef StNonNull, StNull;
236  llvm::tie(StNonNull, StNull) = State->assume(cast<DefinedOrUnknownSVal>(L));
237
238  if (StNull && !StNonNull) {
239    if (!BT_call_null)
240      BT_call_null.reset(
241        new BuiltinBug("Called function pointer is null (null dereference)"));
242    emitBadCall(BT_call_null.get(), C, Callee);
243  }
244
245  C.addTransition(StNonNull);
246}
247
248void CallAndMessageChecker::checkPreCall(const CallEvent &Call,
249                                         CheckerContext &C) const {
250  ProgramStateRef State = C.getState();
251
252  // If this is a call to a C++ method, check if the callee is null or
253  // undefined.
254  if (const CXXInstanceCall *CC = dyn_cast<CXXInstanceCall>(&Call)) {
255    SVal V = CC->getCXXThisVal();
256    if (V.isUndef()) {
257      if (!BT_cxx_call_undef)
258        BT_cxx_call_undef.reset(new BuiltinBug("Called C++ object pointer is "
259                                               "uninitialized"));
260      emitBadCall(BT_cxx_call_undef.get(), C, CC->getCXXThisExpr());
261      return;
262    }
263
264    ProgramStateRef StNonNull, StNull;
265    llvm::tie(StNonNull, StNull) = State->assume(cast<DefinedOrUnknownSVal>(V));
266
267    if (StNull && !StNonNull) {
268      if (!BT_cxx_call_null)
269        BT_cxx_call_null.reset(new BuiltinBug("Called C++ object pointer "
270                                              "is null"));
271      emitBadCall(BT_cxx_call_null.get(), C, CC->getCXXThisExpr());
272      return;
273    }
274
275    State = StNonNull;
276  }
277
278  // Don't check for uninitialized field values in arguments if the
279  // caller has a body that is available and we have the chance to inline it.
280  // This is a hack, but is a reasonable compromise betweens sometimes warning
281  // and sometimes not depending on if we decide to inline a function.
282  const Decl *D = Call.getDecl();
283  const bool checkUninitFields =
284    !(C.getAnalysisManager().shouldInlineCall() && (D && D->getBody()));
285
286  OwningPtr<BugType> *BT;
287  if (isa<ObjCMethodCall>(Call))
288    BT = &BT_msg_arg;
289  else
290    BT = &BT_call_arg;
291
292  for (unsigned i = 0, e = Call.getNumArgs(); i != e; ++i)
293    if (PreVisitProcessArg(C, Call.getArgSVal(i), Call.getArgSourceRange(i),
294                           Call.getArgExpr(i), /*IsFirstArgument=*/i == 0,
295                           checkUninitFields, Call, *BT))
296      return;
297
298  // If we make it here, record our assumptions about the callee.
299  C.addTransition(State);
300}
301
302void CallAndMessageChecker::checkPreObjCMessage(const ObjCMethodCall &msg,
303                                                CheckerContext &C) const {
304  SVal recVal = msg.getReceiverSVal();
305  if (recVal.isUndef()) {
306    if (ExplodedNode *N = C.generateSink()) {
307      BugType *BT = 0;
308      switch (msg.getMessageKind()) {
309      case OCM_Message:
310        if (!BT_msg_undef)
311          BT_msg_undef.reset(new BuiltinBug("Receiver in message expression "
312                                            "is an uninitialized value"));
313        BT = BT_msg_undef.get();
314        break;
315      case OCM_PropertyAccess:
316        if (!BT_objc_prop_undef)
317          BT_objc_prop_undef.reset(new BuiltinBug("Property access on an "
318                                                  "uninitialized object "
319                                                  "pointer"));
320        BT = BT_objc_prop_undef.get();
321        break;
322      case OCM_Subscript:
323        if (!BT_objc_subscript_undef)
324          BT_objc_subscript_undef.reset(new BuiltinBug("Subscript access on an "
325                                                       "uninitialized object "
326                                                       "pointer"));
327        BT = BT_objc_subscript_undef.get();
328        break;
329      }
330      assert(BT && "Unknown message kind.");
331
332      BugReport *R = new BugReport(*BT, BT->getName(), N);
333      const ObjCMessageExpr *ME = msg.getOriginExpr();
334      R->addRange(ME->getReceiverRange());
335
336      // FIXME: getTrackNullOrUndefValueVisitor can't handle "super" yet.
337      if (const Expr *ReceiverE = ME->getInstanceReceiver())
338        bugreporter::trackNullOrUndefValue(N, ReceiverE, *R);
339      C.EmitReport(R);
340    }
341    return;
342  } else {
343    // Bifurcate the state into nil and non-nil ones.
344    DefinedOrUnknownSVal receiverVal = cast<DefinedOrUnknownSVal>(recVal);
345
346    ProgramStateRef state = C.getState();
347    ProgramStateRef notNilState, nilState;
348    llvm::tie(notNilState, nilState) = state->assume(receiverVal);
349
350    // Handle receiver must be nil.
351    if (nilState && !notNilState) {
352      HandleNilReceiver(C, state, msg);
353      return;
354    }
355  }
356}
357
358void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C,
359                                               const ObjCMethodCall &msg,
360                                               ExplodedNode *N) const {
361
362  if (!BT_msg_ret)
363    BT_msg_ret.reset(
364      new BuiltinBug("Receiver in message expression is "
365                     "'nil' and returns a garbage value"));
366
367  const ObjCMessageExpr *ME = msg.getOriginExpr();
368
369  SmallString<200> buf;
370  llvm::raw_svector_ostream os(buf);
371  os << "The receiver of message '" << ME->getSelector().getAsString()
372     << "' is nil and returns a value of type '";
373  msg.getResultType().print(os, C.getLangOpts());
374  os << "' that will be garbage";
375
376  BugReport *report = new BugReport(*BT_msg_ret, os.str(), N);
377  report->addRange(ME->getReceiverRange());
378  // FIXME: This won't track "self" in messages to super.
379  if (const Expr *receiver = ME->getInstanceReceiver()) {
380    bugreporter::trackNullOrUndefValue(N, receiver, *report);
381  }
382  C.EmitReport(report);
383}
384
385static bool supportsNilWithFloatRet(const llvm::Triple &triple) {
386  return (triple.getVendor() == llvm::Triple::Apple &&
387          (triple.getOS() == llvm::Triple::IOS ||
388           !triple.isMacOSXVersionLT(10,5)));
389}
390
391void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C,
392                                              ProgramStateRef state,
393                                              const ObjCMethodCall &Msg) const {
394  ASTContext &Ctx = C.getASTContext();
395
396  // Check the return type of the message expression.  A message to nil will
397  // return different values depending on the return type and the architecture.
398  QualType RetTy = Msg.getResultType();
399  CanQualType CanRetTy = Ctx.getCanonicalType(RetTy);
400  const LocationContext *LCtx = C.getLocationContext();
401
402  if (CanRetTy->isStructureOrClassType()) {
403    // Structure returns are safe since the compiler zeroes them out.
404    SVal V = C.getSValBuilder().makeZeroVal(RetTy);
405    C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V));
406    return;
407  }
408
409  // Other cases: check if sizeof(return type) > sizeof(void*)
410  if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap()
411                                  .isConsumedExpr(Msg.getOriginExpr())) {
412    // Compute: sizeof(void *) and sizeof(return type)
413    const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy);
414    const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy);
415
416    if (voidPtrSize < returnTypeSize &&
417        !(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) &&
418          (Ctx.FloatTy == CanRetTy ||
419           Ctx.DoubleTy == CanRetTy ||
420           Ctx.LongDoubleTy == CanRetTy ||
421           Ctx.LongLongTy == CanRetTy ||
422           Ctx.UnsignedLongLongTy == CanRetTy))) {
423      if (ExplodedNode *N = C.generateSink(state))
424        emitNilReceiverBug(C, Msg, N);
425      return;
426    }
427
428    // Handle the safe cases where the return value is 0 if the
429    // receiver is nil.
430    //
431    // FIXME: For now take the conservative approach that we only
432    // return null values if we *know* that the receiver is nil.
433    // This is because we can have surprises like:
434    //
435    //   ... = [[NSScreens screens] objectAtIndex:0];
436    //
437    // What can happen is that [... screens] could return nil, but
438    // it most likely isn't nil.  We should assume the semantics
439    // of this case unless we have *a lot* more knowledge.
440    //
441    SVal V = C.getSValBuilder().makeZeroVal(RetTy);
442    C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V));
443    return;
444  }
445
446  C.addTransition(state);
447}
448
449void ento::registerCallAndMessageChecker(CheckerManager &mgr) {
450  mgr.registerChecker<CallAndMessageChecker>();
451}
452