CallAndMessageChecker.cpp revision 6f42b62b6194f53bcbc349f5d17388e1936535d7 
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_msg_arg;
36  mutable OwningPtr<BugType> BT_msg_ret;
37public:
38
39  void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
40  void checkPreObjCMessage(ObjCMessage msg, CheckerContext &C) const;
41
42private:
43  static void PreVisitProcessArgs(CheckerContext &C,CallOrObjCMessage callOrMsg,
44                             const char *BT_desc, OwningPtr<BugType> &BT);
45  static bool PreVisitProcessArg(CheckerContext &C, SVal V,SourceRange argRange,
46          const Expr *argEx, const char *BT_desc, OwningPtr<BugType> &BT);
47
48  static void EmitBadCall(BugType *BT, CheckerContext &C, const CallExpr *CE);
49  void emitNilReceiverBug(CheckerContext &C, const ObjCMessage &msg,
50                          ExplodedNode *N) const;
51
52  void HandleNilReceiver(CheckerContext &C,
53                         ProgramStateRef state,
54                         ObjCMessage msg) const;
55
56  static void LazyInit_BT(const char *desc, OwningPtr<BugType> &BT) {
57    if (!BT)
58      BT.reset(new BuiltinBug(desc));
59  }
60};
61} // end anonymous namespace
62
63void CallAndMessageChecker::EmitBadCall(BugType *BT, CheckerContext &C,
64                                        const CallExpr *CE) {
65  ExplodedNode *N = C.generateSink();
66  if (!N)
67    return;
68
69  BugReport *R = new BugReport(*BT, BT->getName(), N);
70  R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N,
71                               bugreporter::GetCalleeExpr(N)));
72  C.EmitReport(R);
73}
74
75void CallAndMessageChecker::PreVisitProcessArgs(CheckerContext &C,
76                                                CallOrObjCMessage callOrMsg,
77                                                const char *BT_desc,
78                                                OwningPtr<BugType> &BT) {
79  for (unsigned i = 0, e = callOrMsg.getNumArgs(); i != e; ++i)
80    if (PreVisitProcessArg(C, callOrMsg.getArgSVal(i),
81                           callOrMsg.getArgSourceRange(i), callOrMsg.getArg(i),
82                           BT_desc, BT))
83      return;
84}
85
86bool CallAndMessageChecker::PreVisitProcessArg(CheckerContext &C,
87                                               SVal V, SourceRange argRange,
88                                               const Expr *argEx,
89                                               const char *BT_desc,
90                                               OwningPtr<BugType> &BT) {
91
92  if (V.isUndef()) {
93    if (ExplodedNode *N = C.generateSink()) {
94      LazyInit_BT(BT_desc, BT);
95
96      // Generate a report for this bug.
97      BugReport *R = new BugReport(*BT, BT->getName(), N);
98      R->addRange(argRange);
99      if (argEx)
100        R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, argEx));
101      C.EmitReport(R);
102    }
103    return true;
104  }
105
106  if (const nonloc::LazyCompoundVal *LV =
107        dyn_cast<nonloc::LazyCompoundVal>(&V)) {
108
109    class FindUninitializedField {
110    public:
111      SmallVector<const FieldDecl *, 10> FieldChain;
112    private:
113      ASTContext &C;
114      StoreManager &StoreMgr;
115      MemRegionManager &MrMgr;
116      Store store;
117    public:
118      FindUninitializedField(ASTContext &c, StoreManager &storeMgr,
119                             MemRegionManager &mrMgr, Store s)
120      : C(c), StoreMgr(storeMgr), MrMgr(mrMgr), store(s) {}
121
122      bool Find(const TypedValueRegion *R) {
123        QualType T = R->getValueType();
124        if (const RecordType *RT = T->getAsStructureType()) {
125          const RecordDecl *RD = RT->getDecl()->getDefinition();
126          assert(RD && "Referred record has no definition");
127          for (RecordDecl::field_iterator I =
128               RD->field_begin(), E = RD->field_end(); I!=E; ++I) {
129            const FieldRegion *FR = MrMgr.getFieldRegion(*I, R);
130            FieldChain.push_back(*I);
131            T = (*I)->getType();
132            if (T->getAsStructureType()) {
133              if (Find(FR))
134                return true;
135            }
136            else {
137              const SVal &V = StoreMgr.getBinding(store, loc::MemRegionVal(FR));
138              if (V.isUndef())
139                return true;
140            }
141            FieldChain.pop_back();
142          }
143        }
144
145        return false;
146      }
147    };
148
149    const LazyCompoundValData *D = LV->getCVData();
150    FindUninitializedField F(C.getASTContext(),
151                             C.getState()->getStateManager().getStoreManager(),
152                             C.getSValBuilder().getRegionManager(),
153                             D->getStore());
154
155    if (F.Find(D->getRegion())) {
156      if (ExplodedNode *N = C.generateSink()) {
157        LazyInit_BT(BT_desc, BT);
158        llvm::SmallString<512> Str;
159        llvm::raw_svector_ostream os(Str);
160        os << "Passed-by-value struct argument contains uninitialized data";
161
162        if (F.FieldChain.size() == 1)
163          os << " (e.g., field: '" << *F.FieldChain[0] << "')";
164        else {
165          os << " (e.g., via the field chain: '";
166          bool first = true;
167          for (SmallVectorImpl<const FieldDecl *>::iterator
168               DI = F.FieldChain.begin(), DE = F.FieldChain.end(); DI!=DE;++DI){
169            if (first)
170              first = false;
171            else
172              os << '.';
173            os << **DI;
174          }
175          os << "')";
176        }
177
178        // Generate a report for this bug.
179        BugReport *R = new BugReport(*BT, os.str(), N);
180        R->addRange(argRange);
181
182        // FIXME: enhance track back for uninitialized value for arbitrary
183        // memregions
184        C.EmitReport(R);
185      }
186      return true;
187    }
188  }
189
190  return false;
191}
192
193void CallAndMessageChecker::checkPreStmt(const CallExpr *CE,
194                                         CheckerContext &C) const{
195
196  const Expr *Callee = CE->getCallee()->IgnoreParens();
197  const LocationContext *LCtx = C.getLocationContext();
198  SVal L = C.getState()->getSVal(Callee, LCtx);
199
200  if (L.isUndef()) {
201    if (!BT_call_undef)
202      BT_call_undef.reset(new BuiltinBug("Called function pointer is an "
203                                         "uninitalized pointer value"));
204    EmitBadCall(BT_call_undef.get(), C, CE);
205    return;
206  }
207
208  if (isa<loc::ConcreteInt>(L)) {
209    if (!BT_call_null)
210      BT_call_null.reset(
211        new BuiltinBug("Called function pointer is null (null dereference)"));
212    EmitBadCall(BT_call_null.get(), C, CE);
213  }
214
215  PreVisitProcessArgs(C, CallOrObjCMessage(CE, C.getState(), LCtx),
216                      "Function call argument is an uninitialized value",
217                      BT_call_arg);
218}
219
220void CallAndMessageChecker::checkPreObjCMessage(ObjCMessage msg,
221                                                CheckerContext &C) const {
222
223  ProgramStateRef state = C.getState();
224  const LocationContext *LCtx = C.getLocationContext();
225
226  // FIXME: Handle 'super'?
227  if (const Expr *receiver = msg.getInstanceReceiver()) {
228    SVal recVal = state->getSVal(receiver, LCtx);
229    if (recVal.isUndef()) {
230      if (ExplodedNode *N = C.generateSink()) {
231        if (!BT_msg_undef)
232          BT_msg_undef.reset(new BuiltinBug("Receiver in message expression is "
233                                            "an uninitialized value"));
234        BugReport *R =
235          new BugReport(*BT_msg_undef, BT_msg_undef->getName(), N);
236        R->addRange(receiver->getSourceRange());
237        R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N,
238                                                                   receiver));
239        C.EmitReport(R);
240      }
241      return;
242    } else {
243      // Bifurcate the state into nil and non-nil ones.
244      DefinedOrUnknownSVal receiverVal = cast<DefinedOrUnknownSVal>(recVal);
245
246      ProgramStateRef notNilState, nilState;
247      llvm::tie(notNilState, nilState) = state->assume(receiverVal);
248
249      // Handle receiver must be nil.
250      if (nilState && !notNilState) {
251        HandleNilReceiver(C, state, msg);
252        return;
253      }
254    }
255  }
256
257  const char *bugDesc = msg.isPropertySetter() ?
258                     "Argument for property setter is an uninitialized value"
259                   : "Argument in message expression is an uninitialized value";
260  // Check for any arguments that are uninitialized/undefined.
261  PreVisitProcessArgs(C, CallOrObjCMessage(msg, state, LCtx),
262                      bugDesc, BT_msg_arg);
263}
264
265void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C,
266                                               const ObjCMessage &msg,
267                                               ExplodedNode *N) const {
268
269  if (!BT_msg_ret)
270    BT_msg_ret.reset(
271      new BuiltinBug("Receiver in message expression is "
272                     "'nil' and returns a garbage value"));
273
274  llvm::SmallString<200> buf;
275  llvm::raw_svector_ostream os(buf);
276  os << "The receiver of message '" << msg.getSelector().getAsString()
277     << "' is nil and returns a value of type '"
278     << msg.getType(C.getASTContext()).getAsString() << "' that will be garbage";
279
280  BugReport *report = new BugReport(*BT_msg_ret, os.str(), N);
281  if (const Expr *receiver = msg.getInstanceReceiver()) {
282    report->addRange(receiver->getSourceRange());
283    report->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N,
284                                                                    receiver));
285  }
286  C.EmitReport(report);
287}
288
289static bool supportsNilWithFloatRet(const llvm::Triple &triple) {
290  return (triple.getVendor() == llvm::Triple::Apple &&
291          (triple.getOS() == llvm::Triple::IOS ||
292           !triple.isMacOSXVersionLT(10,5)));
293}
294
295void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C,
296                                              ProgramStateRef state,
297                                              ObjCMessage msg) const {
298  ASTContext &Ctx = C.getASTContext();
299
300  // Check the return type of the message expression.  A message to nil will
301  // return different values depending on the return type and the architecture.
302  QualType RetTy = msg.getType(Ctx);
303  CanQualType CanRetTy = Ctx.getCanonicalType(RetTy);
304  const LocationContext *LCtx = C.getLocationContext();
305
306  if (CanRetTy->isStructureOrClassType()) {
307    // Structure returns are safe since the compiler zeroes them out.
308    SVal V = C.getSValBuilder().makeZeroVal(msg.getType(Ctx));
309    C.addTransition(state->BindExpr(msg.getOriginExpr(), LCtx, V));
310    return;
311  }
312
313  // Other cases: check if sizeof(return type) > sizeof(void*)
314  if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap()
315                                  .isConsumedExpr(msg.getOriginExpr())) {
316    // Compute: sizeof(void *) and sizeof(return type)
317    const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy);
318    const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy);
319
320    if (voidPtrSize < returnTypeSize &&
321        !(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) &&
322          (Ctx.FloatTy == CanRetTy ||
323           Ctx.DoubleTy == CanRetTy ||
324           Ctx.LongDoubleTy == CanRetTy ||
325           Ctx.LongLongTy == CanRetTy ||
326           Ctx.UnsignedLongLongTy == CanRetTy))) {
327      if (ExplodedNode *N = C.generateSink(state))
328        emitNilReceiverBug(C, msg, N);
329      return;
330    }
331
332    // Handle the safe cases where the return value is 0 if the
333    // receiver is nil.
334    //
335    // FIXME: For now take the conservative approach that we only
336    // return null values if we *know* that the receiver is nil.
337    // This is because we can have surprises like:
338    //
339    //   ... = [[NSScreens screens] objectAtIndex:0];
340    //
341    // What can happen is that [... screens] could return nil, but
342    // it most likely isn't nil.  We should assume the semantics
343    // of this case unless we have *a lot* more knowledge.
344    //
345    SVal V = C.getSValBuilder().makeZeroVal(msg.getType(Ctx));
346    C.addTransition(state->BindExpr(msg.getOriginExpr(), LCtx, V));
347    return;
348  }
349
350  C.addTransition(state);
351}
352
353void ento::registerCallAndMessageChecker(CheckerManager &mgr) {
354  mgr.registerChecker<CallAndMessageChecker>();
355}
356