CallAndMessageChecker.cpp revision e4d653b5a4cba281502177f6ef03d43e3ebb2b6a 
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/CheckerContext.h"
19#include "clang/StaticAnalyzer/Core/PathSensitive/ObjCMessage.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  mutable OwningPtr<BugType> BT_call_null;
32  mutable OwningPtr<BugType> BT_call_undef;
33  mutable OwningPtr<BugType> BT_call_arg;
34  mutable OwningPtr<BugType> BT_msg_undef;
35  mutable OwningPtr<BugType> BT_objc_prop_undef;
36  mutable OwningPtr<BugType> BT_msg_arg;
37  mutable OwningPtr<BugType> BT_msg_ret;
38public:
39
40  void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
41  void checkPreObjCMessage(ObjCMessage msg, CheckerContext &C) const;
42
43private:
44  static void PreVisitProcessArgs(CheckerContext &C,CallOrObjCMessage callOrMsg,
45                             const char *BT_desc, OwningPtr<BugType> &BT);
46  static bool PreVisitProcessArg(CheckerContext &C, SVal V,SourceRange argRange,
47                                 const Expr *argEx,
48                                 const bool checkUninitFields,
49                                 const char *BT_desc,
50                                 OwningPtr<BugType> &BT);
51
52  static void EmitBadCall(BugType *BT, CheckerContext &C, const CallExpr *CE);
53  void emitNilReceiverBug(CheckerContext &C, const ObjCMessage &msg,
54                          ExplodedNode *N) const;
55
56  void HandleNilReceiver(CheckerContext &C,
57                         ProgramStateRef state,
58                         ObjCMessage msg) const;
59
60  static void LazyInit_BT(const char *desc, OwningPtr<BugType> &BT) {
61    if (!BT)
62      BT.reset(new BuiltinBug(desc));
63  }
64};
65} // end anonymous namespace
66
67void CallAndMessageChecker::EmitBadCall(BugType *BT, CheckerContext &C,
68                                        const CallExpr *CE) {
69  ExplodedNode *N = C.generateSink();
70  if (!N)
71    return;
72
73  BugReport *R = new BugReport(*BT, BT->getName(), N);
74  R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N,
75                               bugreporter::GetCalleeExpr(N)));
76  C.EmitReport(R);
77}
78
79void CallAndMessageChecker::PreVisitProcessArgs(CheckerContext &C,
80                                                CallOrObjCMessage callOrMsg,
81                                                const char *BT_desc,
82                                                OwningPtr<BugType> &BT) {
83  // Don't check for uninitialized field values in arguments if the
84  // caller has a body that is available and we have the chance to inline it.
85  // This is a hack, but is a reasonable compromise betweens sometimes warning
86  // and sometimes not depending on if we decide to inline a function.
87  const Decl *D = callOrMsg.getDecl();
88  const bool checkUninitFields =
89    !(C.getAnalysisManager().shouldInlineCall() &&
90      (D && D->getBody()));
91
92  for (unsigned i = 0, e = callOrMsg.getNumArgs(); i != e; ++i)
93    if (PreVisitProcessArg(C, callOrMsg.getArgSVal(i),
94                           callOrMsg.getArgSourceRange(i), callOrMsg.getArg(i),
95                           checkUninitFields,
96                           BT_desc, BT))
97      return;
98}
99
100bool CallAndMessageChecker::PreVisitProcessArg(CheckerContext &C,
101                                               SVal V, SourceRange argRange,
102                                               const Expr *argEx,
103                                               const bool checkUninitFields,
104                                               const char *BT_desc,
105                                               OwningPtr<BugType> &BT) {
106  if (V.isUndef()) {
107    if (ExplodedNode *N = C.generateSink()) {
108      LazyInit_BT(BT_desc, BT);
109
110      // Generate a report for this bug.
111      BugReport *R = new BugReport(*BT, BT->getName(), N);
112      R->addRange(argRange);
113      if (argEx)
114        R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, argEx));
115      C.EmitReport(R);
116    }
117    return true;
118  }
119
120  if (!checkUninitFields)
121    return false;
122
123  if (const nonloc::LazyCompoundVal *LV =
124        dyn_cast<nonloc::LazyCompoundVal>(&V)) {
125
126    class FindUninitializedField {
127    public:
128      SmallVector<const FieldDecl *, 10> FieldChain;
129    private:
130      ASTContext &C;
131      StoreManager &StoreMgr;
132      MemRegionManager &MrMgr;
133      Store store;
134    public:
135      FindUninitializedField(ASTContext &c, StoreManager &storeMgr,
136                             MemRegionManager &mrMgr, Store s)
137      : C(c), StoreMgr(storeMgr), MrMgr(mrMgr), store(s) {}
138
139      bool Find(const TypedValueRegion *R) {
140        QualType T = R->getValueType();
141        if (const RecordType *RT = T->getAsStructureType()) {
142          const RecordDecl *RD = RT->getDecl()->getDefinition();
143          assert(RD && "Referred record has no definition");
144          for (RecordDecl::field_iterator I =
145               RD->field_begin(), E = RD->field_end(); I!=E; ++I) {
146            const FieldRegion *FR = MrMgr.getFieldRegion(*I, R);
147            FieldChain.push_back(*I);
148            T = (*I)->getType();
149            if (T->getAsStructureType()) {
150              if (Find(FR))
151                return true;
152            }
153            else {
154              const SVal &V = StoreMgr.getBinding(store, loc::MemRegionVal(FR));
155              if (V.isUndef())
156                return true;
157            }
158            FieldChain.pop_back();
159          }
160        }
161
162        return false;
163      }
164    };
165
166    const LazyCompoundValData *D = LV->getCVData();
167    FindUninitializedField F(C.getASTContext(),
168                             C.getState()->getStateManager().getStoreManager(),
169                             C.getSValBuilder().getRegionManager(),
170                             D->getStore());
171
172    if (F.Find(D->getRegion())) {
173      if (ExplodedNode *N = C.generateSink()) {
174        LazyInit_BT(BT_desc, BT);
175        SmallString<512> Str;
176        llvm::raw_svector_ostream os(Str);
177        os << "Passed-by-value struct argument contains uninitialized data";
178
179        if (F.FieldChain.size() == 1)
180          os << " (e.g., field: '" << *F.FieldChain[0] << "')";
181        else {
182          os << " (e.g., via the field chain: '";
183          bool first = true;
184          for (SmallVectorImpl<const FieldDecl *>::iterator
185               DI = F.FieldChain.begin(), DE = F.FieldChain.end(); DI!=DE;++DI){
186            if (first)
187              first = false;
188            else
189              os << '.';
190            os << **DI;
191          }
192          os << "')";
193        }
194
195        // Generate a report for this bug.
196        BugReport *R = new BugReport(*BT, os.str(), N);
197        R->addRange(argRange);
198
199        // FIXME: enhance track back for uninitialized value for arbitrary
200        // memregions
201        C.EmitReport(R);
202      }
203      return true;
204    }
205  }
206
207  return false;
208}
209
210void CallAndMessageChecker::checkPreStmt(const CallExpr *CE,
211                                         CheckerContext &C) const{
212
213  const Expr *Callee = CE->getCallee()->IgnoreParens();
214  const LocationContext *LCtx = C.getLocationContext();
215  SVal L = C.getState()->getSVal(Callee, LCtx);
216
217  if (L.isUndef()) {
218    if (!BT_call_undef)
219      BT_call_undef.reset(new BuiltinBug("Called function pointer is an "
220                                         "uninitalized pointer value"));
221    EmitBadCall(BT_call_undef.get(), C, CE);
222    return;
223  }
224
225  if (isa<loc::ConcreteInt>(L)) {
226    if (!BT_call_null)
227      BT_call_null.reset(
228        new BuiltinBug("Called function pointer is null (null dereference)"));
229    EmitBadCall(BT_call_null.get(), C, CE);
230  }
231
232  PreVisitProcessArgs(C, CallOrObjCMessage(CE, C.getState(), LCtx),
233                      "Function call argument is an uninitialized value",
234                      BT_call_arg);
235}
236
237void CallAndMessageChecker::checkPreObjCMessage(ObjCMessage msg,
238                                                CheckerContext &C) const {
239
240  ProgramStateRef state = C.getState();
241  const LocationContext *LCtx = C.getLocationContext();
242
243  // FIXME: Handle 'super'?
244  if (const Expr *receiver = msg.getInstanceReceiver()) {
245    SVal recVal = state->getSVal(receiver, LCtx);
246    if (recVal.isUndef()) {
247      if (ExplodedNode *N = C.generateSink()) {
248        BugType *BT = 0;
249        if (msg.isPureMessageExpr()) {
250          if (!BT_msg_undef)
251            BT_msg_undef.reset(new BuiltinBug("Receiver in message expression "
252                                              "is an uninitialized value"));
253          BT = BT_msg_undef.get();
254        }
255        else {
256          if (!BT_objc_prop_undef)
257            BT_objc_prop_undef.reset(new BuiltinBug("Property access on an "
258                                              "uninitialized object pointer"));
259          BT = BT_objc_prop_undef.get();
260        }
261        BugReport *R =
262          new BugReport(*BT, BT->getName(), N);
263        R->addRange(receiver->getSourceRange());
264        R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N,
265                                                                   receiver));
266        C.EmitReport(R);
267      }
268      return;
269    } else {
270      // Bifurcate the state into nil and non-nil ones.
271      DefinedOrUnknownSVal receiverVal = cast<DefinedOrUnknownSVal>(recVal);
272
273      ProgramStateRef notNilState, nilState;
274      llvm::tie(notNilState, nilState) = state->assume(receiverVal);
275
276      // Handle receiver must be nil.
277      if (nilState && !notNilState) {
278        HandleNilReceiver(C, state, msg);
279        return;
280      }
281    }
282  }
283
284  const char *bugDesc = msg.isPropertySetter() ?
285                     "Argument for property setter is an uninitialized value"
286                   : "Argument in message expression is an uninitialized value";
287  // Check for any arguments that are uninitialized/undefined.
288  PreVisitProcessArgs(C, CallOrObjCMessage(msg, state, LCtx),
289                      bugDesc, BT_msg_arg);
290}
291
292void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C,
293                                               const ObjCMessage &msg,
294                                               ExplodedNode *N) const {
295
296  if (!BT_msg_ret)
297    BT_msg_ret.reset(
298      new BuiltinBug("Receiver in message expression is "
299                     "'nil' and returns a garbage value"));
300
301  SmallString<200> buf;
302  llvm::raw_svector_ostream os(buf);
303  os << "The receiver of message '" << msg.getSelector().getAsString()
304     << "' is nil and returns a value of type '"
305     << msg.getType(C.getASTContext()).getAsString() << "' that will be garbage";
306
307  BugReport *report = new BugReport(*BT_msg_ret, os.str(), N);
308  if (const Expr *receiver = msg.getInstanceReceiver()) {
309    report->addRange(receiver->getSourceRange());
310    report->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N,
311                                                                    receiver));
312  }
313  C.EmitReport(report);
314}
315
316static bool supportsNilWithFloatRet(const llvm::Triple &triple) {
317  return (triple.getVendor() == llvm::Triple::Apple &&
318          (triple.getOS() == llvm::Triple::IOS ||
319           !triple.isMacOSXVersionLT(10,5)));
320}
321
322void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C,
323                                              ProgramStateRef state,
324                                              ObjCMessage msg) const {
325  ASTContext &Ctx = C.getASTContext();
326
327  // Check the return type of the message expression.  A message to nil will
328  // return different values depending on the return type and the architecture.
329  QualType RetTy = msg.getType(Ctx);
330  CanQualType CanRetTy = Ctx.getCanonicalType(RetTy);
331  const LocationContext *LCtx = C.getLocationContext();
332
333  if (CanRetTy->isStructureOrClassType()) {
334    // Structure returns are safe since the compiler zeroes them out.
335    SVal V = C.getSValBuilder().makeZeroVal(msg.getType(Ctx));
336    C.addTransition(state->BindExpr(msg.getMessageExpr(), LCtx, V));
337    return;
338  }
339
340  // Other cases: check if sizeof(return type) > sizeof(void*)
341  if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap()
342                                  .isConsumedExpr(msg.getMessageExpr())) {
343    // Compute: sizeof(void *) and sizeof(return type)
344    const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy);
345    const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy);
346
347    if (voidPtrSize < returnTypeSize &&
348        !(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) &&
349          (Ctx.FloatTy == CanRetTy ||
350           Ctx.DoubleTy == CanRetTy ||
351           Ctx.LongDoubleTy == CanRetTy ||
352           Ctx.LongLongTy == CanRetTy ||
353           Ctx.UnsignedLongLongTy == CanRetTy))) {
354      if (ExplodedNode *N = C.generateSink(state))
355        emitNilReceiverBug(C, msg, N);
356      return;
357    }
358
359    // Handle the safe cases where the return value is 0 if the
360    // receiver is nil.
361    //
362    // FIXME: For now take the conservative approach that we only
363    // return null values if we *know* that the receiver is nil.
364    // This is because we can have surprises like:
365    //
366    //   ... = [[NSScreens screens] objectAtIndex:0];
367    //
368    // What can happen is that [... screens] could return nil, but
369    // it most likely isn't nil.  We should assume the semantics
370    // of this case unless we have *a lot* more knowledge.
371    //
372    SVal V = C.getSValBuilder().makeZeroVal(msg.getType(Ctx));
373    C.addTransition(state->BindExpr(msg.getMessageExpr(), LCtx, V));
374    return;
375  }
376
377  C.addTransition(state);
378}
379
380void ento::registerCallAndMessageChecker(CheckerManager &mgr) {
381  mgr.registerChecker<CallAndMessageChecker>();
382}
383