ExprEngineC.cpp revision 9852f58f50b4fc20914fbce5b4454135a42343f4
1//=-- ExprEngineC.cpp - ExprEngine support for C expressions ----*- 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 file defines ExprEngine's support for C expressions. 11// 12//===----------------------------------------------------------------------===// 13 14#include "clang/AST/ExprCXX.h" 15#include "clang/StaticAnalyzer/Core/CheckerManager.h" 16#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" 17 18using namespace clang; 19using namespace ento; 20using llvm::APSInt; 21 22void ExprEngine::VisitBinaryOperator(const BinaryOperator* B, 23 ExplodedNode *Pred, 24 ExplodedNodeSet &Dst) { 25 26 Expr *LHS = B->getLHS()->IgnoreParens(); 27 Expr *RHS = B->getRHS()->IgnoreParens(); 28 29 // FIXME: Prechecks eventually go in ::Visit(). 30 ExplodedNodeSet CheckedSet; 31 ExplodedNodeSet Tmp2; 32 getCheckerManager().runCheckersForPreStmt(CheckedSet, Pred, B, *this); 33 34 // With both the LHS and RHS evaluated, process the operation itself. 35 for (ExplodedNodeSet::iterator it=CheckedSet.begin(), ei=CheckedSet.end(); 36 it != ei; ++it) { 37 38 ProgramStateRef state = (*it)->getState(); 39 const LocationContext *LCtx = (*it)->getLocationContext(); 40 SVal LeftV = state->getSVal(LHS, LCtx); 41 SVal RightV = state->getSVal(RHS, LCtx); 42 43 BinaryOperator::Opcode Op = B->getOpcode(); 44 45 if (Op == BO_Assign) { 46 // EXPERIMENTAL: "Conjured" symbols. 47 // FIXME: Handle structs. 48 if (RightV.isUnknown()) { 49 unsigned Count = currBldrCtx->blockCount(); 50 RightV = svalBuilder.conjureSymbolVal(0, B->getRHS(), LCtx, Count); 51 } 52 // Simulate the effects of a "store": bind the value of the RHS 53 // to the L-Value represented by the LHS. 54 SVal ExprVal = B->isGLValue() ? LeftV : RightV; 55 evalStore(Tmp2, B, LHS, *it, state->BindExpr(B, LCtx, ExprVal), 56 LeftV, RightV); 57 continue; 58 } 59 60 if (!B->isAssignmentOp()) { 61 StmtNodeBuilder Bldr(*it, Tmp2, *currBldrCtx); 62 63 if (B->isAdditiveOp()) { 64 // If one of the operands is a location, conjure a symbol for the other 65 // one (offset) if it's unknown so that memory arithmetic always 66 // results in an ElementRegion. 67 // TODO: This can be removed after we enable history tracking with 68 // SymSymExpr. 69 unsigned Count = currBldrCtx->blockCount(); 70 if (isa<Loc>(LeftV) && 71 RHS->getType()->isIntegerType() && RightV.isUnknown()) { 72 RightV = svalBuilder.conjureSymbolVal(RHS, LCtx, RHS->getType(), 73 Count); 74 } 75 if (isa<Loc>(RightV) && 76 LHS->getType()->isIntegerType() && LeftV.isUnknown()) { 77 LeftV = svalBuilder.conjureSymbolVal(LHS, LCtx, LHS->getType(), 78 Count); 79 } 80 } 81 82 // Process non-assignments except commas or short-circuited 83 // logical expressions (LAnd and LOr). 84 SVal Result = evalBinOp(state, Op, LeftV, RightV, B->getType()); 85 if (Result.isUnknown()) { 86 Bldr.generateNode(B, *it, state); 87 continue; 88 } 89 90 state = state->BindExpr(B, LCtx, Result); 91 Bldr.generateNode(B, *it, state); 92 continue; 93 } 94 95 assert (B->isCompoundAssignmentOp()); 96 97 switch (Op) { 98 default: 99 llvm_unreachable("Invalid opcode for compound assignment."); 100 case BO_MulAssign: Op = BO_Mul; break; 101 case BO_DivAssign: Op = BO_Div; break; 102 case BO_RemAssign: Op = BO_Rem; break; 103 case BO_AddAssign: Op = BO_Add; break; 104 case BO_SubAssign: Op = BO_Sub; break; 105 case BO_ShlAssign: Op = BO_Shl; break; 106 case BO_ShrAssign: Op = BO_Shr; break; 107 case BO_AndAssign: Op = BO_And; break; 108 case BO_XorAssign: Op = BO_Xor; break; 109 case BO_OrAssign: Op = BO_Or; break; 110 } 111 112 // Perform a load (the LHS). This performs the checks for 113 // null dereferences, and so on. 114 ExplodedNodeSet Tmp; 115 SVal location = LeftV; 116 evalLoad(Tmp, B, LHS, *it, state, location); 117 118 for (ExplodedNodeSet::iterator I = Tmp.begin(), E = Tmp.end(); I != E; 119 ++I) { 120 121 state = (*I)->getState(); 122 const LocationContext *LCtx = (*I)->getLocationContext(); 123 SVal V = state->getSVal(LHS, LCtx); 124 125 // Get the computation type. 126 QualType CTy = 127 cast<CompoundAssignOperator>(B)->getComputationResultType(); 128 CTy = getContext().getCanonicalType(CTy); 129 130 QualType CLHSTy = 131 cast<CompoundAssignOperator>(B)->getComputationLHSType(); 132 CLHSTy = getContext().getCanonicalType(CLHSTy); 133 134 QualType LTy = getContext().getCanonicalType(LHS->getType()); 135 136 // Promote LHS. 137 V = svalBuilder.evalCast(V, CLHSTy, LTy); 138 139 // Compute the result of the operation. 140 SVal Result = svalBuilder.evalCast(evalBinOp(state, Op, V, RightV, CTy), 141 B->getType(), CTy); 142 143 // EXPERIMENTAL: "Conjured" symbols. 144 // FIXME: Handle structs. 145 146 SVal LHSVal; 147 148 if (Result.isUnknown()) { 149 // The symbolic value is actually for the type of the left-hand side 150 // expression, not the computation type, as this is the value the 151 // LValue on the LHS will bind to. 152 LHSVal = svalBuilder.conjureSymbolVal(0, B->getRHS(), LCtx, LTy, 153 currBldrCtx->blockCount()); 154 // However, we need to convert the symbol to the computation type. 155 Result = svalBuilder.evalCast(LHSVal, CTy, LTy); 156 } 157 else { 158 // The left-hand side may bind to a different value then the 159 // computation type. 160 LHSVal = svalBuilder.evalCast(Result, LTy, CTy); 161 } 162 163 // In C++, assignment and compound assignment operators return an 164 // lvalue. 165 if (B->isGLValue()) 166 state = state->BindExpr(B, LCtx, location); 167 else 168 state = state->BindExpr(B, LCtx, Result); 169 170 evalStore(Tmp2, B, LHS, *I, state, location, LHSVal); 171 } 172 } 173 174 // FIXME: postvisits eventually go in ::Visit() 175 getCheckerManager().runCheckersForPostStmt(Dst, Tmp2, B, *this); 176} 177 178void ExprEngine::VisitBlockExpr(const BlockExpr *BE, ExplodedNode *Pred, 179 ExplodedNodeSet &Dst) { 180 181 CanQualType T = getContext().getCanonicalType(BE->getType()); 182 183 // Get the value of the block itself. 184 SVal V = svalBuilder.getBlockPointer(BE->getBlockDecl(), T, 185 Pred->getLocationContext()); 186 187 ProgramStateRef State = Pred->getState(); 188 189 // If we created a new MemRegion for the block, we should explicitly bind 190 // the captured variables. 191 if (const BlockDataRegion *BDR = 192 dyn_cast_or_null<BlockDataRegion>(V.getAsRegion())) { 193 194 BlockDataRegion::referenced_vars_iterator I = BDR->referenced_vars_begin(), 195 E = BDR->referenced_vars_end(); 196 197 for (; I != E; ++I) { 198 const MemRegion *capturedR = I.getCapturedRegion(); 199 const MemRegion *originalR = I.getOriginalRegion(); 200 if (capturedR != originalR) { 201 SVal originalV = State->getSVal(loc::MemRegionVal(originalR)); 202 State = State->bindLoc(loc::MemRegionVal(capturedR), originalV); 203 } 204 } 205 } 206 207 ExplodedNodeSet Tmp; 208 StmtNodeBuilder Bldr(Pred, Tmp, *currBldrCtx); 209 Bldr.generateNode(BE, Pred, 210 State->BindExpr(BE, Pred->getLocationContext(), V), 211 0, ProgramPoint::PostLValueKind); 212 213 // FIXME: Move all post/pre visits to ::Visit(). 214 getCheckerManager().runCheckersForPostStmt(Dst, Tmp, BE, *this); 215} 216 217void ExprEngine::VisitCast(const CastExpr *CastE, const Expr *Ex, 218 ExplodedNode *Pred, ExplodedNodeSet &Dst) { 219 220 ExplodedNodeSet dstPreStmt; 221 getCheckerManager().runCheckersForPreStmt(dstPreStmt, Pred, CastE, *this); 222 223 if (CastE->getCastKind() == CK_LValueToRValue) { 224 for (ExplodedNodeSet::iterator I = dstPreStmt.begin(), E = dstPreStmt.end(); 225 I!=E; ++I) { 226 ExplodedNode *subExprNode = *I; 227 ProgramStateRef state = subExprNode->getState(); 228 const LocationContext *LCtx = subExprNode->getLocationContext(); 229 evalLoad(Dst, CastE, CastE, subExprNode, state, state->getSVal(Ex, LCtx)); 230 } 231 return; 232 } 233 234 // All other casts. 235 QualType T = CastE->getType(); 236 QualType ExTy = Ex->getType(); 237 238 if (const ExplicitCastExpr *ExCast=dyn_cast_or_null<ExplicitCastExpr>(CastE)) 239 T = ExCast->getTypeAsWritten(); 240 241 StmtNodeBuilder Bldr(dstPreStmt, Dst, *currBldrCtx); 242 for (ExplodedNodeSet::iterator I = dstPreStmt.begin(), E = dstPreStmt.end(); 243 I != E; ++I) { 244 245 Pred = *I; 246 ProgramStateRef state = Pred->getState(); 247 const LocationContext *LCtx = Pred->getLocationContext(); 248 249 switch (CastE->getCastKind()) { 250 case CK_LValueToRValue: 251 llvm_unreachable("LValueToRValue casts handled earlier."); 252 case CK_ToVoid: 253 continue; 254 // The analyzer doesn't do anything special with these casts, 255 // since it understands retain/release semantics already. 256 case CK_ARCProduceObject: 257 case CK_ARCConsumeObject: 258 case CK_ARCReclaimReturnedObject: 259 case CK_ARCExtendBlockObject: // Fall-through. 260 case CK_CopyAndAutoreleaseBlockObject: 261 // The analyser can ignore atomic casts for now, although some future 262 // checkers may want to make certain that you're not modifying the same 263 // value through atomic and nonatomic pointers. 264 case CK_AtomicToNonAtomic: 265 case CK_NonAtomicToAtomic: 266 // True no-ops. 267 case CK_NoOp: 268 case CK_ConstructorConversion: 269 case CK_UserDefinedConversion: 270 case CK_FunctionToPointerDecay: 271 case CK_BuiltinFnToFnPtr: { 272 // Copy the SVal of Ex to CastE. 273 ProgramStateRef state = Pred->getState(); 274 const LocationContext *LCtx = Pred->getLocationContext(); 275 SVal V = state->getSVal(Ex, LCtx); 276 state = state->BindExpr(CastE, LCtx, V); 277 Bldr.generateNode(CastE, Pred, state); 278 continue; 279 } 280 case CK_MemberPointerToBoolean: 281 // FIXME: For now, member pointers are represented by void *. 282 // FALLTHROUGH 283 case CK_Dependent: 284 case CK_ArrayToPointerDecay: 285 case CK_BitCast: 286 case CK_IntegralCast: 287 case CK_NullToPointer: 288 case CK_IntegralToPointer: 289 case CK_PointerToIntegral: 290 case CK_PointerToBoolean: 291 case CK_IntegralToBoolean: 292 case CK_IntegralToFloating: 293 case CK_FloatingToIntegral: 294 case CK_FloatingToBoolean: 295 case CK_FloatingCast: 296 case CK_FloatingRealToComplex: 297 case CK_FloatingComplexToReal: 298 case CK_FloatingComplexToBoolean: 299 case CK_FloatingComplexCast: 300 case CK_FloatingComplexToIntegralComplex: 301 case CK_IntegralRealToComplex: 302 case CK_IntegralComplexToReal: 303 case CK_IntegralComplexToBoolean: 304 case CK_IntegralComplexCast: 305 case CK_IntegralComplexToFloatingComplex: 306 case CK_CPointerToObjCPointerCast: 307 case CK_BlockPointerToObjCPointerCast: 308 case CK_AnyPointerToBlockPointerCast: 309 case CK_ObjCObjectLValueCast: { 310 // Delegate to SValBuilder to process. 311 SVal V = state->getSVal(Ex, LCtx); 312 V = svalBuilder.evalCast(V, T, ExTy); 313 state = state->BindExpr(CastE, LCtx, V); 314 Bldr.generateNode(CastE, Pred, state); 315 continue; 316 } 317 case CK_DerivedToBase: 318 case CK_UncheckedDerivedToBase: { 319 // For DerivedToBase cast, delegate to the store manager. 320 SVal val = state->getSVal(Ex, LCtx); 321 val = getStoreManager().evalDerivedToBase(val, CastE); 322 state = state->BindExpr(CastE, LCtx, val); 323 Bldr.generateNode(CastE, Pred, state); 324 continue; 325 } 326 // Handle C++ dyn_cast. 327 case CK_Dynamic: { 328 SVal val = state->getSVal(Ex, LCtx); 329 330 // Compute the type of the result. 331 QualType resultType = CastE->getType(); 332 if (CastE->isGLValue()) 333 resultType = getContext().getPointerType(resultType); 334 335 bool Failed = false; 336 337 // Check if the value being cast evaluates to 0. 338 if (val.isZeroConstant()) 339 Failed = true; 340 // Else, evaluate the cast. 341 else 342 val = getStoreManager().evalDynamicCast(val, T, Failed); 343 344 if (Failed) { 345 if (T->isReferenceType()) { 346 // A bad_cast exception is thrown if input value is a reference. 347 // Currently, we model this, by generating a sink. 348 Bldr.generateSink(CastE, Pred, state); 349 continue; 350 } else { 351 // If the cast fails on a pointer, bind to 0. 352 state = state->BindExpr(CastE, LCtx, svalBuilder.makeNull()); 353 } 354 } else { 355 // If we don't know if the cast succeeded, conjure a new symbol. 356 if (val.isUnknown()) { 357 DefinedOrUnknownSVal NewSym = 358 svalBuilder.conjureSymbolVal(0, CastE, LCtx, resultType, 359 currBldrCtx->blockCount()); 360 state = state->BindExpr(CastE, LCtx, NewSym); 361 } else 362 // Else, bind to the derived region value. 363 state = state->BindExpr(CastE, LCtx, val); 364 } 365 Bldr.generateNode(CastE, Pred, state); 366 continue; 367 } 368 case CK_NullToMemberPointer: { 369 // FIXME: For now, member pointers are represented by void *. 370 SVal V = svalBuilder.makeIntValWithPtrWidth(0, true); 371 state = state->BindExpr(CastE, LCtx, V); 372 Bldr.generateNode(CastE, Pred, state); 373 continue; 374 } 375 // Various C++ casts that are not handled yet. 376 case CK_ToUnion: 377 case CK_BaseToDerived: 378 case CK_BaseToDerivedMemberPointer: 379 case CK_DerivedToBaseMemberPointer: 380 case CK_ReinterpretMemberPointer: 381 case CK_VectorSplat: 382 case CK_LValueBitCast: { 383 // Recover some path-sensitivty by conjuring a new value. 384 QualType resultType = CastE->getType(); 385 if (CastE->isGLValue()) 386 resultType = getContext().getPointerType(resultType); 387 SVal result = svalBuilder.conjureSymbolVal(0, CastE, LCtx, 388 resultType, 389 currBldrCtx->blockCount()); 390 state = state->BindExpr(CastE, LCtx, result); 391 Bldr.generateNode(CastE, Pred, state); 392 continue; 393 } 394 } 395 } 396} 397 398void ExprEngine::VisitCompoundLiteralExpr(const CompoundLiteralExpr *CL, 399 ExplodedNode *Pred, 400 ExplodedNodeSet &Dst) { 401 StmtNodeBuilder B(Pred, Dst, *currBldrCtx); 402 403 const InitListExpr *ILE 404 = cast<InitListExpr>(CL->getInitializer()->IgnoreParens()); 405 406 ProgramStateRef state = Pred->getState(); 407 SVal ILV = state->getSVal(ILE, Pred->getLocationContext()); 408 const LocationContext *LC = Pred->getLocationContext(); 409 state = state->bindCompoundLiteral(CL, LC, ILV); 410 411 // Compound literal expressions are a GNU extension in C++. 412 // Unlike in C, where CLs are lvalues, in C++ CLs are prvalues, 413 // and like temporary objects created by the functional notation T() 414 // CLs are destroyed at the end of the containing full-expression. 415 // HOWEVER, an rvalue of array type is not something the analyzer can 416 // reason about, since we expect all regions to be wrapped in Locs. 417 // So we treat array CLs as lvalues as well, knowing that they will decay 418 // to pointers as soon as they are used. 419 if (CL->isGLValue() || CL->getType()->isArrayType()) 420 B.generateNode(CL, Pred, state->BindExpr(CL, LC, state->getLValue(CL, LC))); 421 else 422 B.generateNode(CL, Pred, state->BindExpr(CL, LC, ILV)); 423} 424 425void ExprEngine::VisitDeclStmt(const DeclStmt *DS, ExplodedNode *Pred, 426 ExplodedNodeSet &Dst) { 427 428 // FIXME: static variables may have an initializer, but the second 429 // time a function is called those values may not be current. 430 // This may need to be reflected in the CFG. 431 432 // Assumption: The CFG has one DeclStmt per Decl. 433 const Decl *D = *DS->decl_begin(); 434 435 if (!D || !isa<VarDecl>(D)) { 436 //TODO:AZ: remove explicit insertion after refactoring is done. 437 Dst.insert(Pred); 438 return; 439 } 440 441 // FIXME: all pre/post visits should eventually be handled by ::Visit(). 442 ExplodedNodeSet dstPreVisit; 443 getCheckerManager().runCheckersForPreStmt(dstPreVisit, Pred, DS, *this); 444 445 StmtNodeBuilder B(dstPreVisit, Dst, *currBldrCtx); 446 const VarDecl *VD = dyn_cast<VarDecl>(D); 447 for (ExplodedNodeSet::iterator I = dstPreVisit.begin(), E = dstPreVisit.end(); 448 I!=E; ++I) { 449 ExplodedNode *N = *I; 450 ProgramStateRef state = N->getState(); 451 452 // Decls without InitExpr are not initialized explicitly. 453 const LocationContext *LC = N->getLocationContext(); 454 455 if (const Expr *InitEx = VD->getInit()) { 456 SVal InitVal = state->getSVal(InitEx, LC); 457 458 if (InitVal == state->getLValue(VD, LC) || 459 (VD->getType()->isArrayType() && 460 isa<CXXConstructExpr>(InitEx->IgnoreImplicit()))) { 461 // We constructed the object directly in the variable. 462 // No need to bind anything. 463 B.generateNode(DS, N, state); 464 } else { 465 // We bound the temp obj region to the CXXConstructExpr. Now recover 466 // the lazy compound value when the variable is not a reference. 467 if (AMgr.getLangOpts().CPlusPlus && VD->getType()->isRecordType() && 468 !VD->getType()->isReferenceType() && isa<loc::MemRegionVal>(InitVal)){ 469 InitVal = state->getSVal(cast<loc::MemRegionVal>(InitVal).getRegion()); 470 assert(isa<nonloc::LazyCompoundVal>(InitVal)); 471 } 472 473 // Recover some path-sensitivity if a scalar value evaluated to 474 // UnknownVal. 475 if (InitVal.isUnknown()) { 476 QualType Ty = InitEx->getType(); 477 if (InitEx->isGLValue()) { 478 Ty = getContext().getPointerType(Ty); 479 } 480 481 InitVal = svalBuilder.conjureSymbolVal(0, InitEx, LC, Ty, 482 currBldrCtx->blockCount()); 483 } 484 B.takeNodes(N); 485 ExplodedNodeSet Dst2; 486 evalBind(Dst2, DS, N, state->getLValue(VD, LC), InitVal, true); 487 B.addNodes(Dst2); 488 } 489 } 490 else { 491 B.generateNode(DS, N, state); 492 } 493 } 494} 495 496void ExprEngine::VisitLogicalExpr(const BinaryOperator* B, ExplodedNode *Pred, 497 ExplodedNodeSet &Dst) { 498 assert(B->getOpcode() == BO_LAnd || 499 B->getOpcode() == BO_LOr); 500 501 StmtNodeBuilder Bldr(Pred, Dst, *currBldrCtx); 502 ProgramStateRef state = Pred->getState(); 503 504 ExplodedNode *N = Pred; 505 while (!isa<BlockEntrance>(N->getLocation())) { 506 ProgramPoint P = N->getLocation(); 507 assert(isa<PreStmt>(P)|| isa<PreStmtPurgeDeadSymbols>(P)); 508 (void) P; 509 assert(N->pred_size() == 1); 510 N = *N->pred_begin(); 511 } 512 assert(N->pred_size() == 1); 513 N = *N->pred_begin(); 514 BlockEdge BE = cast<BlockEdge>(N->getLocation()); 515 SVal X; 516 517 // Determine the value of the expression by introspecting how we 518 // got this location in the CFG. This requires looking at the previous 519 // block we were in and what kind of control-flow transfer was involved. 520 const CFGBlock *SrcBlock = BE.getSrc(); 521 // The only terminator (if there is one) that makes sense is a logical op. 522 CFGTerminator T = SrcBlock->getTerminator(); 523 if (const BinaryOperator *Term = cast_or_null<BinaryOperator>(T.getStmt())) { 524 (void) Term; 525 assert(Term->isLogicalOp()); 526 assert(SrcBlock->succ_size() == 2); 527 // Did we take the true or false branch? 528 unsigned constant = (*SrcBlock->succ_begin() == BE.getDst()) ? 1 : 0; 529 X = svalBuilder.makeIntVal(constant, B->getType()); 530 } 531 else { 532 // If there is no terminator, by construction the last statement 533 // in SrcBlock is the value of the enclosing expression. 534 // However, we still need to constrain that value to be 0 or 1. 535 assert(!SrcBlock->empty()); 536 CFGStmt Elem = cast<CFGStmt>(*SrcBlock->rbegin()); 537 const Expr *RHS = cast<Expr>(Elem.getStmt()); 538 SVal RHSVal = N->getState()->getSVal(RHS, Pred->getLocationContext()); 539 540 DefinedOrUnknownSVal DefinedRHS = cast<DefinedOrUnknownSVal>(RHSVal); 541 ProgramStateRef StTrue, StFalse; 542 llvm::tie(StTrue, StFalse) = N->getState()->assume(DefinedRHS); 543 if (StTrue) { 544 if (StFalse) { 545 // We can't constrain the value to 0 or 1; the best we can do is a cast. 546 X = getSValBuilder().evalCast(RHSVal, B->getType(), RHS->getType()); 547 } else { 548 // The value is known to be true. 549 X = getSValBuilder().makeIntVal(1, B->getType()); 550 } 551 } else { 552 // The value is known to be false. 553 assert(StFalse && "Infeasible path!"); 554 X = getSValBuilder().makeIntVal(0, B->getType()); 555 } 556 } 557 558 Bldr.generateNode(B, Pred, state->BindExpr(B, Pred->getLocationContext(), X)); 559} 560 561void ExprEngine::VisitInitListExpr(const InitListExpr *IE, 562 ExplodedNode *Pred, 563 ExplodedNodeSet &Dst) { 564 StmtNodeBuilder B(Pred, Dst, *currBldrCtx); 565 566 ProgramStateRef state = Pred->getState(); 567 const LocationContext *LCtx = Pred->getLocationContext(); 568 QualType T = getContext().getCanonicalType(IE->getType()); 569 unsigned NumInitElements = IE->getNumInits(); 570 571 if (T->isArrayType() || T->isRecordType() || T->isVectorType() || 572 T->isAnyComplexType()) { 573 llvm::ImmutableList<SVal> vals = getBasicVals().getEmptySValList(); 574 575 // Handle base case where the initializer has no elements. 576 // e.g: static int* myArray[] = {}; 577 if (NumInitElements == 0) { 578 SVal V = svalBuilder.makeCompoundVal(T, vals); 579 B.generateNode(IE, Pred, state->BindExpr(IE, LCtx, V)); 580 return; 581 } 582 583 for (InitListExpr::const_reverse_iterator it = IE->rbegin(), 584 ei = IE->rend(); it != ei; ++it) { 585 SVal V = state->getSVal(cast<Expr>(*it), LCtx); 586 if (dyn_cast_or_null<CXXTempObjectRegion>(V.getAsRegion())) 587 V = UnknownVal(); 588 vals = getBasicVals().consVals(V, vals); 589 } 590 591 B.generateNode(IE, Pred, 592 state->BindExpr(IE, LCtx, 593 svalBuilder.makeCompoundVal(T, vals))); 594 return; 595 } 596 597 // Handle scalars: int{5} and int{}. 598 assert(NumInitElements <= 1); 599 600 SVal V; 601 if (NumInitElements == 0) 602 V = getSValBuilder().makeZeroVal(T); 603 else 604 V = state->getSVal(IE->getInit(0), LCtx); 605 606 B.generateNode(IE, Pred, state->BindExpr(IE, LCtx, V)); 607} 608 609void ExprEngine::VisitGuardedExpr(const Expr *Ex, 610 const Expr *L, 611 const Expr *R, 612 ExplodedNode *Pred, 613 ExplodedNodeSet &Dst) { 614 StmtNodeBuilder B(Pred, Dst, *currBldrCtx); 615 ProgramStateRef state = Pred->getState(); 616 const LocationContext *LCtx = Pred->getLocationContext(); 617 const CFGBlock *SrcBlock = 0; 618 619 for (const ExplodedNode *N = Pred ; N ; N = *N->pred_begin()) { 620 ProgramPoint PP = N->getLocation(); 621 if (isa<PreStmtPurgeDeadSymbols>(PP) || isa<BlockEntrance>(PP)) { 622 assert(N->pred_size() == 1); 623 continue; 624 } 625 SrcBlock = cast<BlockEdge>(&PP)->getSrc(); 626 break; 627 } 628 629 // Find the last expression in the predecessor block. That is the 630 // expression that is used for the value of the ternary expression. 631 bool hasValue = false; 632 SVal V; 633 634 for (CFGBlock::const_reverse_iterator I = SrcBlock->rbegin(), 635 E = SrcBlock->rend(); I != E; ++I) { 636 CFGElement CE = *I; 637 if (CFGStmt *CS = dyn_cast<CFGStmt>(&CE)) { 638 const Expr *ValEx = cast<Expr>(CS->getStmt()); 639 hasValue = true; 640 V = state->getSVal(ValEx, LCtx); 641 break; 642 } 643 } 644 645 assert(hasValue); 646 (void) hasValue; 647 648 // Generate a new node with the binding from the appropriate path. 649 B.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, V, true)); 650} 651 652void ExprEngine:: 653VisitOffsetOfExpr(const OffsetOfExpr *OOE, 654 ExplodedNode *Pred, ExplodedNodeSet &Dst) { 655 StmtNodeBuilder B(Pred, Dst, *currBldrCtx); 656 APSInt IV; 657 if (OOE->EvaluateAsInt(IV, getContext())) { 658 assert(IV.getBitWidth() == getContext().getTypeSize(OOE->getType())); 659 assert(OOE->getType()->isIntegerType()); 660 assert(IV.isSigned() == OOE->getType()->isSignedIntegerOrEnumerationType()); 661 SVal X = svalBuilder.makeIntVal(IV); 662 B.generateNode(OOE, Pred, 663 Pred->getState()->BindExpr(OOE, Pred->getLocationContext(), 664 X)); 665 } 666 // FIXME: Handle the case where __builtin_offsetof is not a constant. 667} 668 669 670void ExprEngine:: 671VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *Ex, 672 ExplodedNode *Pred, 673 ExplodedNodeSet &Dst) { 674 StmtNodeBuilder Bldr(Pred, Dst, *currBldrCtx); 675 676 QualType T = Ex->getTypeOfArgument(); 677 678 if (Ex->getKind() == UETT_SizeOf) { 679 if (!T->isIncompleteType() && !T->isConstantSizeType()) { 680 assert(T->isVariableArrayType() && "Unknown non-constant-sized type."); 681 682 // FIXME: Add support for VLA type arguments and VLA expressions. 683 // When that happens, we should probably refactor VLASizeChecker's code. 684 return; 685 } 686 else if (T->getAs<ObjCObjectType>()) { 687 // Some code tries to take the sizeof an ObjCObjectType, relying that 688 // the compiler has laid out its representation. Just report Unknown 689 // for these. 690 return; 691 } 692 } 693 694 APSInt Value = Ex->EvaluateKnownConstInt(getContext()); 695 CharUnits amt = CharUnits::fromQuantity(Value.getZExtValue()); 696 697 ProgramStateRef state = Pred->getState(); 698 state = state->BindExpr(Ex, Pred->getLocationContext(), 699 svalBuilder.makeIntVal(amt.getQuantity(), 700 Ex->getType())); 701 Bldr.generateNode(Ex, Pred, state); 702} 703 704void ExprEngine::VisitUnaryOperator(const UnaryOperator* U, 705 ExplodedNode *Pred, 706 ExplodedNodeSet &Dst) { 707 StmtNodeBuilder Bldr(Pred, Dst, *currBldrCtx); 708 switch (U->getOpcode()) { 709 default: { 710 Bldr.takeNodes(Pred); 711 ExplodedNodeSet Tmp; 712 VisitIncrementDecrementOperator(U, Pred, Tmp); 713 Bldr.addNodes(Tmp); 714 } 715 break; 716 case UO_Real: { 717 const Expr *Ex = U->getSubExpr()->IgnoreParens(); 718 719 // FIXME: We don't have complex SValues yet. 720 if (Ex->getType()->isAnyComplexType()) { 721 // Just report "Unknown." 722 break; 723 } 724 725 // For all other types, UO_Real is an identity operation. 726 assert (U->getType() == Ex->getType()); 727 ProgramStateRef state = Pred->getState(); 728 const LocationContext *LCtx = Pred->getLocationContext(); 729 Bldr.generateNode(U, Pred, state->BindExpr(U, LCtx, 730 state->getSVal(Ex, LCtx))); 731 break; 732 } 733 734 case UO_Imag: { 735 const Expr *Ex = U->getSubExpr()->IgnoreParens(); 736 // FIXME: We don't have complex SValues yet. 737 if (Ex->getType()->isAnyComplexType()) { 738 // Just report "Unknown." 739 break; 740 } 741 // For all other types, UO_Imag returns 0. 742 ProgramStateRef state = Pred->getState(); 743 const LocationContext *LCtx = Pred->getLocationContext(); 744 SVal X = svalBuilder.makeZeroVal(Ex->getType()); 745 Bldr.generateNode(U, Pred, state->BindExpr(U, LCtx, X)); 746 break; 747 } 748 749 case UO_Plus: 750 assert(!U->isGLValue()); 751 // FALL-THROUGH. 752 case UO_Deref: 753 case UO_AddrOf: 754 case UO_Extension: { 755 // FIXME: We can probably just have some magic in Environment::getSVal() 756 // that propagates values, instead of creating a new node here. 757 // 758 // Unary "+" is a no-op, similar to a parentheses. We still have places 759 // where it may be a block-level expression, so we need to 760 // generate an extra node that just propagates the value of the 761 // subexpression. 762 const Expr *Ex = U->getSubExpr()->IgnoreParens(); 763 ProgramStateRef state = Pred->getState(); 764 const LocationContext *LCtx = Pred->getLocationContext(); 765 Bldr.generateNode(U, Pred, state->BindExpr(U, LCtx, 766 state->getSVal(Ex, LCtx))); 767 break; 768 } 769 770 case UO_LNot: 771 case UO_Minus: 772 case UO_Not: { 773 assert (!U->isGLValue()); 774 const Expr *Ex = U->getSubExpr()->IgnoreParens(); 775 ProgramStateRef state = Pred->getState(); 776 const LocationContext *LCtx = Pred->getLocationContext(); 777 778 // Get the value of the subexpression. 779 SVal V = state->getSVal(Ex, LCtx); 780 781 if (V.isUnknownOrUndef()) { 782 Bldr.generateNode(U, Pred, state->BindExpr(U, LCtx, V)); 783 break; 784 } 785 786 switch (U->getOpcode()) { 787 default: 788 llvm_unreachable("Invalid Opcode."); 789 case UO_Not: 790 // FIXME: Do we need to handle promotions? 791 state = state->BindExpr(U, LCtx, evalComplement(cast<NonLoc>(V))); 792 break; 793 case UO_Minus: 794 // FIXME: Do we need to handle promotions? 795 state = state->BindExpr(U, LCtx, evalMinus(cast<NonLoc>(V))); 796 break; 797 case UO_LNot: 798 // C99 6.5.3.3: "The expression !E is equivalent to (0==E)." 799 // 800 // Note: technically we do "E == 0", but this is the same in the 801 // transfer functions as "0 == E". 802 SVal Result; 803 if (isa<Loc>(V)) { 804 Loc X = svalBuilder.makeNull(); 805 Result = evalBinOp(state, BO_EQ, cast<Loc>(V), X, 806 U->getType()); 807 } 808 else { 809 nonloc::ConcreteInt X(getBasicVals().getValue(0, Ex->getType())); 810 Result = evalBinOp(state, BO_EQ, cast<NonLoc>(V), X, 811 U->getType()); 812 } 813 814 state = state->BindExpr(U, LCtx, Result); 815 break; 816 } 817 Bldr.generateNode(U, Pred, state); 818 break; 819 } 820 } 821 822} 823 824void ExprEngine::VisitIncrementDecrementOperator(const UnaryOperator* U, 825 ExplodedNode *Pred, 826 ExplodedNodeSet &Dst) { 827 // Handle ++ and -- (both pre- and post-increment). 828 assert (U->isIncrementDecrementOp()); 829 const Expr *Ex = U->getSubExpr()->IgnoreParens(); 830 831 const LocationContext *LCtx = Pred->getLocationContext(); 832 ProgramStateRef state = Pred->getState(); 833 SVal loc = state->getSVal(Ex, LCtx); 834 835 // Perform a load. 836 ExplodedNodeSet Tmp; 837 evalLoad(Tmp, U, Ex, Pred, state, loc); 838 839 ExplodedNodeSet Dst2; 840 StmtNodeBuilder Bldr(Tmp, Dst2, *currBldrCtx); 841 for (ExplodedNodeSet::iterator I=Tmp.begin(), E=Tmp.end();I!=E;++I) { 842 843 state = (*I)->getState(); 844 assert(LCtx == (*I)->getLocationContext()); 845 SVal V2_untested = state->getSVal(Ex, LCtx); 846 847 // Propagate unknown and undefined values. 848 if (V2_untested.isUnknownOrUndef()) { 849 Bldr.generateNode(U, *I, state->BindExpr(U, LCtx, V2_untested)); 850 continue; 851 } 852 DefinedSVal V2 = cast<DefinedSVal>(V2_untested); 853 854 // Handle all other values. 855 BinaryOperator::Opcode Op = U->isIncrementOp() ? BO_Add : BO_Sub; 856 857 // If the UnaryOperator has non-location type, use its type to create the 858 // constant value. If the UnaryOperator has location type, create the 859 // constant with int type and pointer width. 860 SVal RHS; 861 862 if (U->getType()->isAnyPointerType()) 863 RHS = svalBuilder.makeArrayIndex(1); 864 else if (U->getType()->isIntegralOrEnumerationType()) 865 RHS = svalBuilder.makeIntVal(1, U->getType()); 866 else 867 RHS = UnknownVal(); 868 869 SVal Result = evalBinOp(state, Op, V2, RHS, U->getType()); 870 871 // Conjure a new symbol if necessary to recover precision. 872 if (Result.isUnknown()){ 873 DefinedOrUnknownSVal SymVal = 874 svalBuilder.conjureSymbolVal(0, Ex, LCtx, currBldrCtx->blockCount()); 875 Result = SymVal; 876 877 // If the value is a location, ++/-- should always preserve 878 // non-nullness. Check if the original value was non-null, and if so 879 // propagate that constraint. 880 if (Loc::isLocType(U->getType())) { 881 DefinedOrUnknownSVal Constraint = 882 svalBuilder.evalEQ(state, V2,svalBuilder.makeZeroVal(U->getType())); 883 884 if (!state->assume(Constraint, true)) { 885 // It isn't feasible for the original value to be null. 886 // Propagate this constraint. 887 Constraint = svalBuilder.evalEQ(state, SymVal, 888 svalBuilder.makeZeroVal(U->getType())); 889 890 891 state = state->assume(Constraint, false); 892 assert(state); 893 } 894 } 895 } 896 897 // Since the lvalue-to-rvalue conversion is explicit in the AST, 898 // we bind an l-value if the operator is prefix and an lvalue (in C++). 899 if (U->isGLValue()) 900 state = state->BindExpr(U, LCtx, loc); 901 else 902 state = state->BindExpr(U, LCtx, U->isPostfix() ? V2 : Result); 903 904 // Perform the store. 905 Bldr.takeNodes(*I); 906 ExplodedNodeSet Dst3; 907 evalStore(Dst3, U, U, *I, state, loc, Result); 908 Bldr.addNodes(Dst3); 909 } 910 Dst.insert(Dst2); 911} 912