CallAndMessageChecker.cpp revision 9da59a67a27a4d3fc9d59552f07808a32f85e9d3
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 R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(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 R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, argEx, 126 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 if (L.isZeroConstant()) { 237 if (!BT_call_null) 238 BT_call_null.reset( 239 new BuiltinBug("Called function pointer is null (null dereference)")); 240 emitBadCall(BT_call_null.get(), C, Callee); 241 } 242} 243 244void CallAndMessageChecker::checkPreCall(const CallEvent &Call, 245 CheckerContext &C) const { 246 // If this is a call to a C++ method, check if the callee is null or 247 // undefined. 248 if (const CXXInstanceCall *CC = dyn_cast<CXXInstanceCall>(&Call)) { 249 SVal V = CC->getCXXThisVal(); 250 if (V.isUndef()) { 251 if (!BT_cxx_call_undef) 252 BT_cxx_call_undef.reset(new BuiltinBug("Called C++ object pointer is " 253 "uninitialized")); 254 emitBadCall(BT_cxx_call_undef.get(), C, CC->getCXXThisExpr()); 255 return; 256 } 257 if (V.isZeroConstant()) { 258 if (!BT_cxx_call_null) 259 BT_cxx_call_null.reset(new BuiltinBug("Called C++ object pointer " 260 "is null")); 261 emitBadCall(BT_cxx_call_null.get(), C, CC->getCXXThisExpr()); 262 return; 263 } 264 } 265 266 // Don't check for uninitialized field values in arguments if the 267 // caller has a body that is available and we have the chance to inline it. 268 // This is a hack, but is a reasonable compromise betweens sometimes warning 269 // and sometimes not depending on if we decide to inline a function. 270 const Decl *D = Call.getDecl(); 271 const bool checkUninitFields = 272 !(C.getAnalysisManager().shouldInlineCall() && (D && D->getBody())); 273 274 OwningPtr<BugType> *BT; 275 if (isa<ObjCMethodCall>(Call)) 276 BT = &BT_msg_arg; 277 else 278 BT = &BT_call_arg; 279 280 for (unsigned i = 0, e = Call.getNumArgs(); i != e; ++i) 281 if (PreVisitProcessArg(C, Call.getArgSVal(i), Call.getArgSourceRange(i), 282 Call.getArgExpr(i), /*IsFirstArgument=*/i == 0, 283 checkUninitFields, Call, *BT)) 284 return; 285} 286 287void CallAndMessageChecker::checkPreObjCMessage(const ObjCMethodCall &msg, 288 CheckerContext &C) const { 289 SVal recVal = msg.getReceiverSVal(); 290 if (recVal.isUndef()) { 291 if (ExplodedNode *N = C.generateSink()) { 292 BugType *BT = 0; 293 switch (msg.getMessageKind()) { 294 case OCM_Message: 295 if (!BT_msg_undef) 296 BT_msg_undef.reset(new BuiltinBug("Receiver in message expression " 297 "is an uninitialized value")); 298 BT = BT_msg_undef.get(); 299 break; 300 case OCM_PropertyAccess: 301 if (!BT_objc_prop_undef) 302 BT_objc_prop_undef.reset(new BuiltinBug("Property access on an " 303 "uninitialized object " 304 "pointer")); 305 BT = BT_objc_prop_undef.get(); 306 break; 307 case OCM_Subscript: 308 if (!BT_objc_subscript_undef) 309 BT_objc_subscript_undef.reset(new BuiltinBug("Subscript access on an " 310 "uninitialized object " 311 "pointer")); 312 BT = BT_objc_subscript_undef.get(); 313 break; 314 } 315 assert(BT && "Unknown message kind."); 316 317 BugReport *R = new BugReport(*BT, BT->getName(), N); 318 const ObjCMessageExpr *ME = msg.getOriginExpr(); 319 R->addRange(ME->getReceiverRange()); 320 321 // FIXME: getTrackNullOrUndefValueVisitor can't handle "super" yet. 322 if (const Expr *ReceiverE = ME->getInstanceReceiver()) 323 R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, 324 ReceiverE, 325 R)); 326 C.EmitReport(R); 327 } 328 return; 329 } else { 330 // Bifurcate the state into nil and non-nil ones. 331 DefinedOrUnknownSVal receiverVal = cast<DefinedOrUnknownSVal>(recVal); 332 333 ProgramStateRef state = C.getState(); 334 ProgramStateRef notNilState, nilState; 335 llvm::tie(notNilState, nilState) = state->assume(receiverVal); 336 337 // Handle receiver must be nil. 338 if (nilState && !notNilState) { 339 HandleNilReceiver(C, state, msg); 340 return; 341 } 342 } 343} 344 345void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C, 346 const ObjCMethodCall &msg, 347 ExplodedNode *N) const { 348 349 if (!BT_msg_ret) 350 BT_msg_ret.reset( 351 new BuiltinBug("Receiver in message expression is " 352 "'nil' and returns a garbage value")); 353 354 const ObjCMessageExpr *ME = msg.getOriginExpr(); 355 356 SmallString<200> buf; 357 llvm::raw_svector_ostream os(buf); 358 os << "The receiver of message '" << ME->getSelector().getAsString() 359 << "' is nil and returns a value of type '"; 360 msg.getResultType().print(os, C.getLangOpts()); 361 os << "' that will be garbage"; 362 363 BugReport *report = new BugReport(*BT_msg_ret, os.str(), N); 364 report->addRange(ME->getReceiverRange()); 365 // FIXME: This won't track "self" in messages to super. 366 if (const Expr *receiver = ME->getInstanceReceiver()) { 367 report->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, 368 receiver, 369 report)); 370 } 371 C.EmitReport(report); 372} 373 374static bool supportsNilWithFloatRet(const llvm::Triple &triple) { 375 return (triple.getVendor() == llvm::Triple::Apple && 376 (triple.getOS() == llvm::Triple::IOS || 377 !triple.isMacOSXVersionLT(10,5))); 378} 379 380void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C, 381 ProgramStateRef state, 382 const ObjCMethodCall &Msg) const { 383 ASTContext &Ctx = C.getASTContext(); 384 385 // Check the return type of the message expression. A message to nil will 386 // return different values depending on the return type and the architecture. 387 QualType RetTy = Msg.getResultType(); 388 CanQualType CanRetTy = Ctx.getCanonicalType(RetTy); 389 const LocationContext *LCtx = C.getLocationContext(); 390 391 if (CanRetTy->isStructureOrClassType()) { 392 // Structure returns are safe since the compiler zeroes them out. 393 SVal V = C.getSValBuilder().makeZeroVal(RetTy); 394 C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V)); 395 return; 396 } 397 398 // Other cases: check if sizeof(return type) > sizeof(void*) 399 if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap() 400 .isConsumedExpr(Msg.getOriginExpr())) { 401 // Compute: sizeof(void *) and sizeof(return type) 402 const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy); 403 const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy); 404 405 if (voidPtrSize < returnTypeSize && 406 !(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) && 407 (Ctx.FloatTy == CanRetTy || 408 Ctx.DoubleTy == CanRetTy || 409 Ctx.LongDoubleTy == CanRetTy || 410 Ctx.LongLongTy == CanRetTy || 411 Ctx.UnsignedLongLongTy == CanRetTy))) { 412 if (ExplodedNode *N = C.generateSink(state)) 413 emitNilReceiverBug(C, Msg, N); 414 return; 415 } 416 417 // Handle the safe cases where the return value is 0 if the 418 // receiver is nil. 419 // 420 // FIXME: For now take the conservative approach that we only 421 // return null values if we *know* that the receiver is nil. 422 // This is because we can have surprises like: 423 // 424 // ... = [[NSScreens screens] objectAtIndex:0]; 425 // 426 // What can happen is that [... screens] could return nil, but 427 // it most likely isn't nil. We should assume the semantics 428 // of this case unless we have *a lot* more knowledge. 429 // 430 SVal V = C.getSValBuilder().makeZeroVal(RetTy); 431 C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V)); 432 return; 433 } 434 435 C.addTransition(state); 436} 437 438void ento::registerCallAndMessageChecker(CheckerManager &mgr) { 439 mgr.registerChecker<CallAndMessageChecker>(); 440} 441