CallAndMessageChecker.cpp revision 37926da411d5a0047240b3ffd4dad0c4838aac57 
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>, 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;
43  mutable OwningPtr<BugType> BT_call_few_args;
44public:
45
46  void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
47  void checkPreObjCMessage(const ObjCMethodCall &msg, CheckerContext &C) const;
48  void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
49
50private:
51  static bool PreVisitProcessArg(CheckerContext &C, SVal V,
52                                 SourceRange argRange, const Expr *argEx,
53                                 bool IsFirstArgument, bool checkUninitFields,
54                                 const CallEvent &Call, OwningPtr<BugType> &BT);
55
56  static void emitBadCall(BugType *BT, CheckerContext &C, const Expr *BadE);
57  void emitNilReceiverBug(CheckerContext &C, const ObjCMethodCall &msg,
58                          ExplodedNode *N) const;
59
60  void HandleNilReceiver(CheckerContext &C,
61                         ProgramStateRef state,
62                         const ObjCMethodCall &msg) const;
63
64  static void LazyInit_BT(const char *desc, OwningPtr<BugType> &BT) {
65    if (!BT)
66      BT.reset(new BuiltinBug(desc));
67  }
68};
69} // end anonymous namespace
70
71void CallAndMessageChecker::emitBadCall(BugType *BT, CheckerContext &C,
72                                        const Expr *BadE) {
73  ExplodedNode *N = C.generateSink();
74  if (!N)
75    return;
76
77  BugReport *R = new BugReport(*BT, BT->getName(), N);
78  if (BadE) {
79    R->addRange(BadE->getSourceRange());
80    if (BadE->isGLValue())
81      BadE = bugreporter::getDerefExpr(BadE);
82    bugreporter::trackNullOrUndefValue(N, BadE, *R);
83  }
84  C.emitReport(R);
85}
86
87static StringRef describeUninitializedArgumentInCall(const CallEvent &Call,
88                                                     bool IsFirstArgument) {
89  switch (Call.getKind()) {
90  case CE_ObjCMessage: {
91    const ObjCMethodCall &Msg = cast<ObjCMethodCall>(Call);
92    switch (Msg.getMessageKind()) {
93    case OCM_Message:
94      return "Argument in message expression is an uninitialized value";
95    case OCM_PropertyAccess:
96      assert(Msg.isSetter() && "Getters have no args");
97      return "Argument for property setter is an uninitialized value";
98    case OCM_Subscript:
99      if (Msg.isSetter() && IsFirstArgument)
100        return "Argument for subscript setter is an uninitialized value";
101      return "Subscript index is an uninitialized value";
102    }
103    llvm_unreachable("Unknown message kind.");
104  }
105  case CE_Block:
106    return "Block call argument is an uninitialized value";
107  default:
108    return "Function call argument is an uninitialized value";
109  }
110}
111
112bool CallAndMessageChecker::PreVisitProcessArg(CheckerContext &C,
113                                               SVal V, SourceRange argRange,
114                                               const Expr *argEx,
115                                               bool IsFirstArgument,
116                                               bool checkUninitFields,
117                                               const CallEvent &Call,
118                                               OwningPtr<BugType> &BT) {
119  if (V.isUndef()) {
120    if (ExplodedNode *N = C.generateSink()) {
121      LazyInit_BT("Uninitialized argument value", BT);
122
123      // Generate a report for this bug.
124      StringRef Desc = describeUninitializedArgumentInCall(Call,
125                                                           IsFirstArgument);
126      BugReport *R = new BugReport(*BT, Desc, N);
127      R->addRange(argRange);
128      if (argEx)
129        bugreporter::trackNullOrUndefValue(N, argEx, *R);
130      C.emitReport(R);
131    }
132    return true;
133  }
134
135  if (!checkUninitFields)
136    return false;
137
138  if (Optional<nonloc::LazyCompoundVal> LV =
139          V.getAs<nonloc::LazyCompoundVal>()) {
140
141    class FindUninitializedField {
142    public:
143      SmallVector<const FieldDecl *, 10> FieldChain;
144    private:
145      StoreManager &StoreMgr;
146      MemRegionManager &MrMgr;
147      Store store;
148    public:
149      FindUninitializedField(StoreManager &storeMgr,
150                             MemRegionManager &mrMgr, Store s)
151      : StoreMgr(storeMgr), MrMgr(mrMgr), store(s) {}
152
153      bool Find(const TypedValueRegion *R) {
154        QualType T = R->getValueType();
155        if (const RecordType *RT = T->getAsStructureType()) {
156          const RecordDecl *RD = RT->getDecl()->getDefinition();
157          assert(RD && "Referred record has no definition");
158          for (RecordDecl::field_iterator I =
159               RD->field_begin(), E = RD->field_end(); I!=E; ++I) {
160            const FieldRegion *FR = MrMgr.getFieldRegion(*I, R);
161            FieldChain.push_back(*I);
162            T = I->getType();
163            if (T->getAsStructureType()) {
164              if (Find(FR))
165                return true;
166            }
167            else {
168              const SVal &V = StoreMgr.getBinding(store, loc::MemRegionVal(FR));
169              if (V.isUndef())
170                return true;
171            }
172            FieldChain.pop_back();
173          }
174        }
175
176        return false;
177      }
178    };
179
180    const LazyCompoundValData *D = LV->getCVData();
181    FindUninitializedField F(C.getState()->getStateManager().getStoreManager(),
182                             C.getSValBuilder().getRegionManager(),
183                             D->getStore());
184
185    if (F.Find(D->getRegion())) {
186      if (ExplodedNode *N = C.generateSink()) {
187        LazyInit_BT("Uninitialized argument value", BT);
188        SmallString<512> Str;
189        llvm::raw_svector_ostream os(Str);
190        os << "Passed-by-value struct argument contains uninitialized data";
191
192        if (F.FieldChain.size() == 1)
193          os << " (e.g., field: '" << *F.FieldChain[0] << "')";
194        else {
195          os << " (e.g., via the field chain: '";
196          bool first = true;
197          for (SmallVectorImpl<const FieldDecl *>::iterator
198               DI = F.FieldChain.begin(), DE = F.FieldChain.end(); DI!=DE;++DI){
199            if (first)
200              first = false;
201            else
202              os << '.';
203            os << **DI;
204          }
205          os << "')";
206        }
207
208        // Generate a report for this bug.
209        BugReport *R = new BugReport(*BT, os.str(), N);
210        R->addRange(argRange);
211
212        // FIXME: enhance track back for uninitialized value for arbitrary
213        // memregions
214        C.emitReport(R);
215      }
216      return true;
217    }
218  }
219
220  return false;
221}
222
223void CallAndMessageChecker::checkPreStmt(const CallExpr *CE,
224                                         CheckerContext &C) const{
225
226  const Expr *Callee = CE->getCallee()->IgnoreParens();
227  ProgramStateRef State = C.getState();
228  const LocationContext *LCtx = C.getLocationContext();
229  SVal L = State->getSVal(Callee, LCtx);
230
231  if (L.isUndef()) {
232    if (!BT_call_undef)
233      BT_call_undef.reset(new BuiltinBug("Called function pointer is an "
234                                         "uninitalized pointer value"));
235    emitBadCall(BT_call_undef.get(), C, Callee);
236    return;
237  }
238
239  ProgramStateRef StNonNull, StNull;
240  llvm::tie(StNonNull, StNull) =
241      State->assume(L.castAs<DefinedOrUnknownSVal>());
242
243  if (StNull && !StNonNull) {
244    if (!BT_call_null)
245      BT_call_null.reset(
246        new BuiltinBug("Called function pointer is null (null dereference)"));
247    emitBadCall(BT_call_null.get(), C, Callee);
248  }
249
250  C.addTransition(StNonNull);
251}
252
253void CallAndMessageChecker::checkPreCall(const CallEvent &Call,
254                                         CheckerContext &C) const {
255  ProgramStateRef State = C.getState();
256
257  // If this is a call to a C++ method, check if the callee is null or
258  // undefined.
259  if (const CXXInstanceCall *CC = dyn_cast<CXXInstanceCall>(&Call)) {
260    SVal V = CC->getCXXThisVal();
261    if (V.isUndef()) {
262      if (!BT_cxx_call_undef)
263        BT_cxx_call_undef.reset(new BuiltinBug("Called C++ object pointer is "
264                                               "uninitialized"));
265      emitBadCall(BT_cxx_call_undef.get(), C, CC->getCXXThisExpr());
266      return;
267    }
268
269    ProgramStateRef StNonNull, StNull;
270    llvm::tie(StNonNull, StNull) =
271        State->assume(V.castAs<DefinedOrUnknownSVal>());
272
273    if (StNull && !StNonNull) {
274      if (!BT_cxx_call_null)
275        BT_cxx_call_null.reset(new BuiltinBug("Called C++ object pointer "
276                                              "is null"));
277      emitBadCall(BT_cxx_call_null.get(), C, CC->getCXXThisExpr());
278      return;
279    }
280
281    State = StNonNull;
282  }
283
284  const Decl *D = Call.getDecl();
285  if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D)) {
286    // If we have a declaration, we can make sure we pass enough parameters to
287    // the function.
288    unsigned Params = FD->getNumParams();
289    if (Call.getNumArgs() < Params) {
290      ExplodedNode *N = C.generateSink();
291      if (!N)
292        return;
293
294      LazyInit_BT("Function call with too few arguments", BT_call_few_args);
295
296      SmallString<512> Str;
297      llvm::raw_svector_ostream os(Str);
298      os << "Function taking " << Params << " argument"
299         << (Params == 1 ? "" : "s") << " is called with less ("
300         << Call.getNumArgs() << ")";
301
302      BugReport *R = new BugReport(*BT_call_few_args, os.str(), N);
303      C.emitReport(R);
304    }
305  }
306
307  // Don't check for uninitialized field values in arguments if the
308  // caller has a body that is available and we have the chance to inline it.
309  // This is a hack, but is a reasonable compromise betweens sometimes warning
310  // and sometimes not depending on if we decide to inline a function.
311  const bool checkUninitFields =
312    !(C.getAnalysisManager().shouldInlineCall() && (D && D->getBody()));
313
314  OwningPtr<BugType> *BT;
315  if (isa<ObjCMethodCall>(Call))
316    BT = &BT_msg_arg;
317  else
318    BT = &BT_call_arg;
319
320  for (unsigned i = 0, e = Call.getNumArgs(); i != e; ++i)
321    if (PreVisitProcessArg(C, Call.getArgSVal(i), Call.getArgSourceRange(i),
322                           Call.getArgExpr(i), /*IsFirstArgument=*/i == 0,
323                           checkUninitFields, Call, *BT))
324      return;
325
326  // If we make it here, record our assumptions about the callee.
327  C.addTransition(State);
328}
329
330void CallAndMessageChecker::checkPreObjCMessage(const ObjCMethodCall &msg,
331                                                CheckerContext &C) const {
332  SVal recVal = msg.getReceiverSVal();
333  if (recVal.isUndef()) {
334    if (ExplodedNode *N = C.generateSink()) {
335      BugType *BT = 0;
336      switch (msg.getMessageKind()) {
337      case OCM_Message:
338        if (!BT_msg_undef)
339          BT_msg_undef.reset(new BuiltinBug("Receiver in message expression "
340                                            "is an uninitialized value"));
341        BT = BT_msg_undef.get();
342        break;
343      case OCM_PropertyAccess:
344        if (!BT_objc_prop_undef)
345          BT_objc_prop_undef.reset(new BuiltinBug("Property access on an "
346                                                  "uninitialized object "
347                                                  "pointer"));
348        BT = BT_objc_prop_undef.get();
349        break;
350      case OCM_Subscript:
351        if (!BT_objc_subscript_undef)
352          BT_objc_subscript_undef.reset(new BuiltinBug("Subscript access on an "
353                                                       "uninitialized object "
354                                                       "pointer"));
355        BT = BT_objc_subscript_undef.get();
356        break;
357      }
358      assert(BT && "Unknown message kind.");
359
360      BugReport *R = new BugReport(*BT, BT->getName(), N);
361      const ObjCMessageExpr *ME = msg.getOriginExpr();
362      R->addRange(ME->getReceiverRange());
363
364      // FIXME: getTrackNullOrUndefValueVisitor can't handle "super" yet.
365      if (const Expr *ReceiverE = ME->getInstanceReceiver())
366        bugreporter::trackNullOrUndefValue(N, ReceiverE, *R);
367      C.emitReport(R);
368    }
369    return;
370  } else {
371    // Bifurcate the state into nil and non-nil ones.
372    DefinedOrUnknownSVal receiverVal = recVal.castAs<DefinedOrUnknownSVal>();
373
374    ProgramStateRef state = C.getState();
375    ProgramStateRef notNilState, nilState;
376    llvm::tie(notNilState, nilState) = state->assume(receiverVal);
377
378    // Handle receiver must be nil.
379    if (nilState && !notNilState) {
380      HandleNilReceiver(C, state, msg);
381      return;
382    }
383  }
384}
385
386void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C,
387                                               const ObjCMethodCall &msg,
388                                               ExplodedNode *N) const {
389
390  if (!BT_msg_ret)
391    BT_msg_ret.reset(
392      new BuiltinBug("Receiver in message expression is 'nil'"));
393
394  const ObjCMessageExpr *ME = msg.getOriginExpr();
395
396  QualType ResTy = msg.getResultType();
397
398  SmallString<200> buf;
399  llvm::raw_svector_ostream os(buf);
400  os << "The receiver of message '" << ME->getSelector().getAsString()
401     << "' is nil";
402  if (ResTy->isReferenceType()) {
403    os << ", which results in forming a null reference";
404  } else {
405    os << " and returns a value of type '";
406    msg.getResultType().print(os, C.getLangOpts());
407    os << "' that will be garbage";
408  }
409
410  BugReport *report = new BugReport(*BT_msg_ret, os.str(), N);
411  report->addRange(ME->getReceiverRange());
412  // FIXME: This won't track "self" in messages to super.
413  if (const Expr *receiver = ME->getInstanceReceiver()) {
414    bugreporter::trackNullOrUndefValue(N, receiver, *report);
415  }
416  C.emitReport(report);
417}
418
419static bool supportsNilWithFloatRet(const llvm::Triple &triple) {
420  return (triple.getVendor() == llvm::Triple::Apple &&
421          (triple.getOS() == llvm::Triple::IOS ||
422           !triple.isMacOSXVersionLT(10,5)));
423}
424
425void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C,
426                                              ProgramStateRef state,
427                                              const ObjCMethodCall &Msg) const {
428  ASTContext &Ctx = C.getASTContext();
429  static SimpleProgramPointTag Tag("CallAndMessageChecker : NilReceiver");
430
431  // Check the return type of the message expression.  A message to nil will
432  // return different values depending on the return type and the architecture.
433  QualType RetTy = Msg.getResultType();
434  CanQualType CanRetTy = Ctx.getCanonicalType(RetTy);
435  const LocationContext *LCtx = C.getLocationContext();
436
437  if (CanRetTy->isStructureOrClassType()) {
438    // Structure returns are safe since the compiler zeroes them out.
439    SVal V = C.getSValBuilder().makeZeroVal(RetTy);
440    C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag);
441    return;
442  }
443
444  // Other cases: check if sizeof(return type) > sizeof(void*)
445  if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap()
446                                  .isConsumedExpr(Msg.getOriginExpr())) {
447    // Compute: sizeof(void *) and sizeof(return type)
448    const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy);
449    const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy);
450
451    if (CanRetTy.getTypePtr()->isReferenceType()||
452        (voidPtrSize < returnTypeSize &&
453         !(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) &&
454           (Ctx.FloatTy == CanRetTy ||
455            Ctx.DoubleTy == CanRetTy ||
456            Ctx.LongDoubleTy == CanRetTy ||
457            Ctx.LongLongTy == CanRetTy ||
458            Ctx.UnsignedLongLongTy == CanRetTy)))) {
459      if (ExplodedNode *N = C.generateSink(state, 0 , &Tag))
460        emitNilReceiverBug(C, Msg, N);
461      return;
462    }
463
464    // Handle the safe cases where the return value is 0 if the
465    // receiver is nil.
466    //
467    // FIXME: For now take the conservative approach that we only
468    // return null values if we *know* that the receiver is nil.
469    // This is because we can have surprises like:
470    //
471    //   ... = [[NSScreens screens] objectAtIndex:0];
472    //
473    // What can happen is that [... screens] could return nil, but
474    // it most likely isn't nil.  We should assume the semantics
475    // of this case unless we have *a lot* more knowledge.
476    //
477    SVal V = C.getSValBuilder().makeZeroVal(RetTy);
478    C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag);
479    return;
480  }
481
482  C.addTransition(state);
483}
484
485void ento::registerCallAndMessageChecker(CheckerManager &mgr) {
486  mgr.registerChecker<CallAndMessageChecker>();
487}
488