clang/lib/StaticAnalyzer/Core/ExprEngineC.cpp

   1 //=-- ExprEngineC.cpp - ExprEngine support for C expressions ----*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 //  This file defines ExprEngine's support for C expressions.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "clang/AST/DeclCXX.h"
  14 #include "clang/AST/ExprCXX.h"
  15 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
  16 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
  17 #include <optional>
  18
  19 using namespace clang;
  20 using namespace ento;
  21 using llvm::APSInt;
  22
  23 /// Optionally conjure and return a symbol for offset when processing
  24 /// an expression \p Expression.
  25 /// If \p Other is a location, conjure a symbol for \p Symbol
  26 /// (offset) if it is unknown so that memory arithmetic always
  27 /// results in an ElementRegion.
  28 /// \p Count The number of times the current basic block was visited.
  29 static SVal conjureOffsetSymbolOnLocation(
  30     SVal Symbol, SVal Other, Expr* Expression, SValBuilder &svalBuilder,
  31     unsigned Count, const LocationContext *LCtx) {
  32   QualType Ty = Expression->getType();
  33   if (isa<Loc>(Other) && Ty->isIntegralOrEnumerationType() &&
  34       Symbol.isUnknown()) {
  35     return svalBuilder.conjureSymbolVal(Expression, LCtx, Ty, Count);
  36   }
  37   return Symbol;
  38 }
  39
  40 void ExprEngine::VisitBinaryOperator(const BinaryOperator* B,
  41                                      ExplodedNode *Pred,
  42                                      ExplodedNodeSet &Dst) {
  43
  44   Expr *LHS = B->getLHS()->IgnoreParens();
  45   Expr *RHS = B->getRHS()->IgnoreParens();
  46
  47   // FIXME: Prechecks eventually go in ::Visit().
  48   ExplodedNodeSet CheckedSet;
  49   ExplodedNodeSet Tmp2;
  50   getCheckerManager().runCheckersForPreStmt(CheckedSet, Pred, B, *this);
  51
  52   // With both the LHS and RHS evaluated, process the operation itself.
  53   for (ExplodedNodeSet::iterator it=CheckedSet.begin(), ei=CheckedSet.end();
  54          it != ei; ++it) {
  55
  56     ProgramStateRef state = (*it)->getState();
  57     const LocationContext *LCtx = (*it)->getLocationContext();
  58     SVal LeftV = state->getSVal(LHS, LCtx);
  59     SVal RightV = state->getSVal(RHS, LCtx);
  60
  61     BinaryOperator::Opcode Op = B->getOpcode();
  62
  63     if (Op == BO_Assign) {
  64       // EXPERIMENTAL: "Conjured" symbols.
  65       // FIXME: Handle structs.
  66       if (RightV.isUnknown()) {
  67         unsigned Count = currBldrCtx->blockCount();
  68         RightV = svalBuilder.conjureSymbolVal(nullptr, B->getRHS(), LCtx,
  69                                               Count);
  70       }
  71       // Simulate the effects of a "store":  bind the value of the RHS
  72       // to the L-Value represented by the LHS.
  73       SVal ExprVal = B->isGLValue() ? LeftV : RightV;
  74       evalStore(Tmp2, B, LHS, *it, state->BindExpr(B, LCtx, ExprVal),
  75                 LeftV, RightV);
  76       continue;
  77     }
  78
  79     if (!B->isAssignmentOp()) {
  80       StmtNodeBuilder Bldr(*it, Tmp2, *currBldrCtx);
  81
  82       if (B->isAdditiveOp()) {
  83         // TODO: This can be removed after we enable history tracking with
  84         // SymSymExpr.
  85         unsigned Count = currBldrCtx->blockCount();
  86         RightV = conjureOffsetSymbolOnLocation(
  87             RightV, LeftV, RHS, svalBuilder, Count, LCtx);
  88         LeftV = conjureOffsetSymbolOnLocation(
  89             LeftV, RightV, LHS, svalBuilder, Count, LCtx);
  90       }
  91
  92       // Although we don't yet model pointers-to-members, we do need to make
  93       // sure that the members of temporaries have a valid 'this' pointer for
  94       // other checks.
  95       if (B->getOpcode() == BO_PtrMemD)
  96         state = createTemporaryRegionIfNeeded(state, LCtx, LHS);
  97
  98       // Process non-assignments except commas or short-circuited
  99       // logical expressions (LAnd and LOr).
 100       SVal Result = evalBinOp(state, Op, LeftV, RightV, B->getType());
 101       if (!Result.isUnknown()) {
 102         state = state->BindExpr(B, LCtx, Result);
 103       } else {
 104         // If we cannot evaluate the operation escape the operands.
 105         state = escapeValues(state, LeftV, PSK_EscapeOther);
 106         state = escapeValues(state, RightV, PSK_EscapeOther);
 107       }
 108
 109       Bldr.generateNode(B, *it, state);
 110       continue;
 111     }
 112
 113     assert (B->isCompoundAssignmentOp());
 114
 115     switch (Op) {
 116       default:
 117         llvm_unreachable("Invalid opcode for compound assignment.");
 118       case BO_MulAssign: Op = BO_Mul; break;
 119       case BO_DivAssign: Op = BO_Div; break;
 120       case BO_RemAssign: Op = BO_Rem; break;
 121       case BO_AddAssign: Op = BO_Add; break;
 122       case BO_SubAssign: Op = BO_Sub; break;
 123       case BO_ShlAssign: Op = BO_Shl; break;
 124       case BO_ShrAssign: Op = BO_Shr; break;
 125       case BO_AndAssign: Op = BO_And; break;
 126       case BO_XorAssign: Op = BO_Xor; break;
 127       case BO_OrAssign:  Op = BO_Or;  break;
 128     }
 129
 130     // Perform a load (the LHS).  This performs the checks for
 131     // null dereferences, and so on.
 132     ExplodedNodeSet Tmp;
 133     SVal location = LeftV;
 134     evalLoad(Tmp, B, LHS, *it, state, location);
 135
 136     for (ExplodedNode *N : Tmp) {
 137       state = N->getState();
 138       const LocationContext *LCtx = N->getLocationContext();
 139       SVal V = state->getSVal(LHS, LCtx);
 140
 141       // Get the computation type.
 142       QualType CTy =
 143         cast<CompoundAssignOperator>(B)->getComputationResultType();
 144       CTy = getContext().getCanonicalType(CTy);
 145
 146       QualType CLHSTy =
 147         cast<CompoundAssignOperator>(B)->getComputationLHSType();
 148       CLHSTy = getContext().getCanonicalType(CLHSTy);
 149
 150       QualType LTy = getContext().getCanonicalType(LHS->getType());
 151
 152       // Promote LHS.
 153       V = svalBuilder.evalCast(V, CLHSTy, LTy);
 154
 155       // Compute the result of the operation.
 156       SVal Result = svalBuilder.evalCast(evalBinOp(state, Op, V, RightV, CTy),
 157                                          B->getType(), CTy);
 158
 159       // EXPERIMENTAL: "Conjured" symbols.
 160       // FIXME: Handle structs.
 161
 162       SVal LHSVal;
 163
 164       if (Result.isUnknown()) {
 165         // The symbolic value is actually for the type of the left-hand side
 166         // expression, not the computation type, as this is the value the
 167         // LValue on the LHS will bind to.
 168         LHSVal = svalBuilder.conjureSymbolVal(nullptr, B->getRHS(), LCtx, LTy,
 169                                               currBldrCtx->blockCount());
 170         // However, we need to convert the symbol to the computation type.
 171         Result = svalBuilder.evalCast(LHSVal, CTy, LTy);
 172       } else {
 173         // The left-hand side may bind to a different value then the
 174         // computation type.
 175         LHSVal = svalBuilder.evalCast(Result, LTy, CTy);
 176       }
 177
 178       // In C++, assignment and compound assignment operators return an
 179       // lvalue.
 180       if (B->isGLValue())
 181         state = state->BindExpr(B, LCtx, location);
 182       else
 183         state = state->BindExpr(B, LCtx, Result);
 184
 185       evalStore(Tmp2, B, LHS, N, state, location, LHSVal);
 186     }
 187   }
 188
 189   // FIXME: postvisits eventually go in ::Visit()
 190   getCheckerManager().runCheckersForPostStmt(Dst, Tmp2, B, *this);
 191 }
 192
 193 void ExprEngine::VisitBlockExpr(const BlockExpr *BE, ExplodedNode *Pred,
 194                                 ExplodedNodeSet &Dst) {
 195
 196   CanQualType T = getContext().getCanonicalType(BE->getType());
 197
 198   const BlockDecl *BD = BE->getBlockDecl();
 199   // Get the value of the block itself.
 200   SVal V = svalBuilder.getBlockPointer(BD, T,
 201                                        Pred->getLocationContext(),
 202                                        currBldrCtx->blockCount());
 203
 204   ProgramStateRef State = Pred->getState();
 205
 206   // If we created a new MemRegion for the block, we should explicitly bind
 207   // the captured variables.
 208   if (const BlockDataRegion *BDR =
 209       dyn_cast_or_null<BlockDataRegion>(V.getAsRegion())) {
 210
 211     auto ReferencedVars = BDR->referenced_vars();
 212     auto CI = BD->capture_begin();
 213     auto CE = BD->capture_end();
 214     for (auto Var : ReferencedVars) {
 215       const VarRegion *capturedR = Var.getCapturedRegion();
 216       const TypedValueRegion *originalR = Var.getOriginalRegion();
 217
 218       // If the capture had a copy expression, use the result of evaluating
 219       // that expression, otherwise use the original value.
 220       // We rely on the invariant that the block declaration's capture variables
 221       // are a prefix of the BlockDataRegion's referenced vars (which may include
 222       // referenced globals, etc.) to enable fast lookup of the capture for a
 223       // given referenced var.
 224       const Expr *copyExpr = nullptr;
 225       if (CI != CE) {
 226         assert(CI->getVariable() == capturedR->getDecl());
 227         copyExpr = CI->getCopyExpr();
 228         CI++;
 229       }
 230
 231       if (capturedR != originalR) {
 232         SVal originalV;
 233         const LocationContext *LCtx = Pred->getLocationContext();
 234         if (copyExpr) {
 235           originalV = State->getSVal(copyExpr, LCtx);
 236         } else {
 237           originalV = State->getSVal(loc::MemRegionVal(originalR));
 238         }
 239         State = State->bindLoc(loc::MemRegionVal(capturedR), originalV, LCtx);
 240       }
 241     }
 242   }
 243
 244   ExplodedNodeSet Tmp;
 245   StmtNodeBuilder Bldr(Pred, Tmp, *currBldrCtx);
 246   Bldr.generateNode(BE, Pred,
 247                     State->BindExpr(BE, Pred->getLocationContext(), V),
 248                     nullptr, ProgramPoint::PostLValueKind);
 249
 250   // FIXME: Move all post/pre visits to ::Visit().
 251   getCheckerManager().runCheckersForPostStmt(Dst, Tmp, BE, *this);
 252 }
 253
 254 ProgramStateRef ExprEngine::handleLValueBitCast(
 255     ProgramStateRef state, const Expr* Ex, const LocationContext* LCtx,
 256     QualType T, QualType ExTy, const CastExpr* CastE, StmtNodeBuilder& Bldr,
 257     ExplodedNode* Pred) {
 258   if (T->isLValueReferenceType()) {
 259     assert(!CastE->getType()->isLValueReferenceType());
 260     ExTy = getContext().getLValueReferenceType(ExTy);
 261   } else if (T->isRValueReferenceType()) {
 262     assert(!CastE->getType()->isRValueReferenceType());
 263     ExTy = getContext().getRValueReferenceType(ExTy);
 264   }
 265   // Delegate to SValBuilder to process.
 266   SVal OrigV = state->getSVal(Ex, LCtx);
 267   SVal SimplifiedOrigV = svalBuilder.simplifySVal(state, OrigV);
 268   SVal V = svalBuilder.evalCast(SimplifiedOrigV, T, ExTy);
 269   // Negate the result if we're treating the boolean as a signed i1
 270   if (CastE->getCastKind() == CK_BooleanToSignedIntegral && V.isValid())
 271     V = svalBuilder.evalMinus(V.castAs<NonLoc>());
 272
 273   state = state->BindExpr(CastE, LCtx, V);
 274   if (V.isUnknown() && !OrigV.isUnknown()) {
 275     state = escapeValues(state, OrigV, PSK_EscapeOther);
 276   }
 277   Bldr.generateNode(CastE, Pred, state);
 278
 279   return state;
 280 }
 281
 282 void ExprEngine::VisitCast(const CastExpr *CastE, const Expr *Ex,
 283                            ExplodedNode *Pred, ExplodedNodeSet &Dst) {
 284
 285   ExplodedNodeSet dstPreStmt;
 286   getCheckerManager().runCheckersForPreStmt(dstPreStmt, Pred, CastE, *this);
 287
 288   if (CastE->getCastKind() == CK_LValueToRValue ||
 289       CastE->getCastKind() == CK_LValueToRValueBitCast) {
 290     for (ExplodedNode *subExprNode : dstPreStmt) {
 291       ProgramStateRef state = subExprNode->getState();
 292       const LocationContext *LCtx = subExprNode->getLocationContext();
 293       evalLoad(Dst, CastE, CastE, subExprNode, state, state->getSVal(Ex, LCtx));
 294     }
 295     return;
 296   }
 297
 298   // All other casts.
 299   QualType T = CastE->getType();
 300   QualType ExTy = Ex->getType();
 301
 302   if (const ExplicitCastExpr *ExCast=dyn_cast_or_null<ExplicitCastExpr>(CastE))
 303     T = ExCast->getTypeAsWritten();
 304
 305   StmtNodeBuilder Bldr(dstPreStmt, Dst, *currBldrCtx);
 306   for (ExplodedNode *Pred : dstPreStmt) {
 307     ProgramStateRef state = Pred->getState();
 308     const LocationContext *LCtx = Pred->getLocationContext();
 309
 310     switch (CastE->getCastKind()) {
 311       case CK_LValueToRValue:
 312       case CK_LValueToRValueBitCast:
 313         llvm_unreachable("LValueToRValue casts handled earlier.");
 314       case CK_ToVoid:
 315         continue;
 316         // The analyzer doesn't do anything special with these casts,
 317         // since it understands retain/release semantics already.
 318       case CK_ARCProduceObject:
 319       case CK_ARCConsumeObject:
 320       case CK_ARCReclaimReturnedObject:
 321       case CK_ARCExtendBlockObject: // Fall-through.
 322       case CK_CopyAndAutoreleaseBlockObject:
 323         // The analyser can ignore atomic casts for now, although some future
 324         // checkers may want to make certain that you're not modifying the same
 325         // value through atomic and nonatomic pointers.
 326       case CK_AtomicToNonAtomic:
 327       case CK_NonAtomicToAtomic:
 328         // True no-ops.
 329       case CK_NoOp:
 330       case CK_ConstructorConversion:
 331       case CK_UserDefinedConversion:
 332       case CK_FunctionToPointerDecay:
 333       case CK_BuiltinFnToFnPtr: {
 334         // Copy the SVal of Ex to CastE.
 335         ProgramStateRef state = Pred->getState();
 336         const LocationContext *LCtx = Pred->getLocationContext();
 337         SVal V = state->getSVal(Ex, LCtx);
 338         state = state->BindExpr(CastE, LCtx, V);
 339         Bldr.generateNode(CastE, Pred, state);
 340         continue;
 341       }
 342       case CK_MemberPointerToBoolean:
 343       case CK_PointerToBoolean: {
 344         SVal V = state->getSVal(Ex, LCtx);
 345         auto PTMSV = V.getAs<nonloc::PointerToMember>();
 346         if (PTMSV)
 347           V = svalBuilder.makeTruthVal(!PTMSV->isNullMemberPointer(), ExTy);
 348         if (V.isUndef() || PTMSV) {
 349           state = state->BindExpr(CastE, LCtx, V);
 350           Bldr.generateNode(CastE, Pred, state);
 351           continue;
 352         }
 353         // Explicitly proceed with default handler for this case cascade.
 354         state =
 355             handleLValueBitCast(state, Ex, LCtx, T, ExTy, CastE, Bldr, Pred);
 356         continue;
 357       }
 358       case CK_Dependent:
 359       case CK_ArrayToPointerDecay:
 360       case CK_BitCast:
 361       case CK_AddressSpaceConversion:
 362       case CK_BooleanToSignedIntegral:
 363       case CK_IntegralToPointer:
 364       case CK_PointerToIntegral: {
 365         SVal V = state->getSVal(Ex, LCtx);
 366         if (isa<nonloc::PointerToMember>(V)) {
 367           state = state->BindExpr(CastE, LCtx, UnknownVal());
 368           Bldr.generateNode(CastE, Pred, state);
 369           continue;
 370         }
 371         // Explicitly proceed with default handler for this case cascade.
 372         state =
 373             handleLValueBitCast(state, Ex, LCtx, T, ExTy, CastE, Bldr, Pred);
 374         continue;
 375       }
 376       case CK_IntegralToBoolean:
 377       case CK_IntegralToFloating:
 378       case CK_FloatingToIntegral:
 379       case CK_FloatingToBoolean:
 380       case CK_FloatingCast:
 381       case CK_FloatingRealToComplex:
 382       case CK_FloatingComplexToReal:
 383       case CK_FloatingComplexToBoolean:
 384       case CK_FloatingComplexCast:
 385       case CK_FloatingComplexToIntegralComplex:
 386       case CK_IntegralRealToComplex:
 387       case CK_IntegralComplexToReal:
 388       case CK_IntegralComplexToBoolean:
 389       case CK_IntegralComplexCast:
 390       case CK_IntegralComplexToFloatingComplex:
 391       case CK_CPointerToObjCPointerCast:
 392       case CK_BlockPointerToObjCPointerCast:
 393       case CK_AnyPointerToBlockPointerCast:
 394       case CK_ObjCObjectLValueCast:
 395       case CK_ZeroToOCLOpaqueType:
 396       case CK_IntToOCLSampler:
 397       case CK_LValueBitCast:
 398       case CK_FloatingToFixedPoint:
 399       case CK_FixedPointToFloating:
 400       case CK_FixedPointCast:
 401       case CK_FixedPointToBoolean:
 402       case CK_FixedPointToIntegral:
 403       case CK_IntegralToFixedPoint: {
 404         state =
 405             handleLValueBitCast(state, Ex, LCtx, T, ExTy, CastE, Bldr, Pred);
 406         continue;
 407       }
 408       case CK_IntegralCast: {
 409         // Delegate to SValBuilder to process.
 410         SVal V = state->getSVal(Ex, LCtx);
 411         if (AMgr.options.ShouldSupportSymbolicIntegerCasts)
 412           V = svalBuilder.evalCast(V, T, ExTy);
 413         else
 414           V = svalBuilder.evalIntegralCast(state, V, T, ExTy);
 415         state = state->BindExpr(CastE, LCtx, V);
 416         Bldr.generateNode(CastE, Pred, state);
 417         continue;
 418       }
 419       case CK_DerivedToBase:
 420       case CK_UncheckedDerivedToBase: {
 421         // For DerivedToBase cast, delegate to the store manager.
 422         SVal val = state->getSVal(Ex, LCtx);
 423         val = getStoreManager().evalDerivedToBase(val, CastE);
 424         state = state->BindExpr(CastE, LCtx, val);
 425         Bldr.generateNode(CastE, Pred, state);
 426         continue;
 427       }
 428       // Handle C++ dyn_cast.
 429       case CK_Dynamic: {
 430         SVal val = state->getSVal(Ex, LCtx);
 431
 432         // Compute the type of the result.
 433         QualType resultType = CastE->getType();
 434         if (CastE->isGLValue())
 435           resultType = getContext().getPointerType(resultType);
 436
 437         bool Failed = true;
 438
 439         // Check if the value being cast does not evaluates to 0.
 440         if (!val.isZeroConstant())
 441           if (std::optional<SVal> V =
 442                   StateMgr.getStoreManager().evalBaseToDerived(val, T)) {
 443           val = *V;
 444           Failed = false;
 445           }
 446
 447         if (Failed) {
 448           if (T->isReferenceType()) {
 449             // A bad_cast exception is thrown if input value is a reference.
 450             // Currently, we model this, by generating a sink.
 451             Bldr.generateSink(CastE, Pred, state);
 452             continue;
 453           } else {
 454             // If the cast fails on a pointer, bind to 0.
 455             state = state->BindExpr(CastE, LCtx,
 456                                     svalBuilder.makeNullWithType(resultType));
 457           }
 458         } else {
 459           // If we don't know if the cast succeeded, conjure a new symbol.
 460           if (val.isUnknown()) {
 461             DefinedOrUnknownSVal NewSym =
 462               svalBuilder.conjureSymbolVal(nullptr, CastE, LCtx, resultType,
 463                                            currBldrCtx->blockCount());
 464             state = state->BindExpr(CastE, LCtx, NewSym);
 465           } else
 466             // Else, bind to the derived region value.
 467             state = state->BindExpr(CastE, LCtx, val);
 468         }
 469         Bldr.generateNode(CastE, Pred, state);
 470         continue;
 471       }
 472       case CK_BaseToDerived: {
 473         SVal val = state->getSVal(Ex, LCtx);
 474         QualType resultType = CastE->getType();
 475         if (CastE->isGLValue())
 476           resultType = getContext().getPointerType(resultType);
 477
 478         if (!val.isConstant()) {
 479           std::optional<SVal> V = getStoreManager().evalBaseToDerived(val, T);
 480           val = V ? *V : UnknownVal();
 481         }
 482
 483         // Failed to cast or the result is unknown, fall back to conservative.
 484         if (val.isUnknown()) {
 485           val =
 486             svalBuilder.conjureSymbolVal(nullptr, CastE, LCtx, resultType,
 487                                          currBldrCtx->blockCount());
 488         }
 489         state = state->BindExpr(CastE, LCtx, val);
 490         Bldr.generateNode(CastE, Pred, state);
 491         continue;
 492       }
 493       case CK_NullToPointer: {
 494         SVal V = svalBuilder.makeNullWithType(CastE->getType());
 495         state = state->BindExpr(CastE, LCtx, V);
 496         Bldr.generateNode(CastE, Pred, state);
 497         continue;
 498       }
 499       case CK_NullToMemberPointer: {
 500         SVal V = svalBuilder.getMemberPointer(nullptr);
 501         state = state->BindExpr(CastE, LCtx, V);
 502         Bldr.generateNode(CastE, Pred, state);
 503         continue;
 504       }
 505       case CK_DerivedToBaseMemberPointer:
 506       case CK_BaseToDerivedMemberPointer:
 507       case CK_ReinterpretMemberPointer: {
 508         SVal V = state->getSVal(Ex, LCtx);
 509         if (auto PTMSV = V.getAs<nonloc::PointerToMember>()) {
 510           SVal CastedPTMSV =
 511               svalBuilder.makePointerToMember(getBasicVals().accumCXXBase(
 512                   CastE->path(), *PTMSV, CastE->getCastKind()));
 513           state = state->BindExpr(CastE, LCtx, CastedPTMSV);
 514           Bldr.generateNode(CastE, Pred, state);
 515           continue;
 516         }
 517         // Explicitly proceed with default handler for this case cascade.
 518       }
 519         [[fallthrough]];
 520       // Various C++ casts that are not handled yet.
 521       case CK_ToUnion:
 522       case CK_MatrixCast:
 523       case CK_VectorSplat: {
 524         QualType resultType = CastE->getType();
 525         if (CastE->isGLValue())
 526           resultType = getContext().getPointerType(resultType);
 527         SVal result = svalBuilder.conjureSymbolVal(
 528             /*symbolTag=*/nullptr, CastE, LCtx, resultType,
 529             currBldrCtx->blockCount());
 530         state = state->BindExpr(CastE, LCtx, result);
 531         Bldr.generateNode(CastE, Pred, state);
 532         continue;
 533       }
 534     }
 535   }
 536 }
 537
 538 void ExprEngine::VisitCompoundLiteralExpr(const CompoundLiteralExpr *CL,
 539                                           ExplodedNode *Pred,
 540                                           ExplodedNodeSet &Dst) {
 541   StmtNodeBuilder B(Pred, Dst, *currBldrCtx);
 542
 543   ProgramStateRef State = Pred->getState();
 544   const LocationContext *LCtx = Pred->getLocationContext();
 545
 546   const Expr *Init = CL->getInitializer();
 547   SVal V = State->getSVal(CL->getInitializer(), LCtx);
 548
 549   if (isa<CXXConstructExpr, CXXStdInitializerListExpr>(Init)) {
 550     // No work needed. Just pass the value up to this expression.
 551   } else {
 552     assert(isa<InitListExpr>(Init));
 553     Loc CLLoc = State->getLValue(CL, LCtx);
 554     State = State->bindLoc(CLLoc, V, LCtx);
 555
 556     if (CL->isGLValue())
 557       V = CLLoc;
 558   }
 559
 560   B.generateNode(CL, Pred, State->BindExpr(CL, LCtx, V));
 561 }
 562
 563 void ExprEngine::VisitDeclStmt(const DeclStmt *DS, ExplodedNode *Pred,
 564                                ExplodedNodeSet &Dst) {
 565   if (isa<TypedefNameDecl>(*DS->decl_begin())) {
 566     // C99 6.7.7 "Any array size expressions associated with variable length
 567     // array declarators are evaluated each time the declaration of the typedef
 568     // name is reached in the order of execution."
 569     // The checkers should know about typedef to be able to handle VLA size
 570     // expressions.
 571     ExplodedNodeSet DstPre;
 572     getCheckerManager().runCheckersForPreStmt(DstPre, Pred, DS, *this);
 573     getCheckerManager().runCheckersForPostStmt(Dst, DstPre, DS, *this);
 574     return;
 575   }
 576
 577   // Assumption: The CFG has one DeclStmt per Decl.
 578   const VarDecl *VD = dyn_cast_or_null<VarDecl>(*DS->decl_begin());
 579
 580   if (!VD) {
 581     //TODO:AZ: remove explicit insertion after refactoring is done.
 582     Dst.insert(Pred);
 583     return;
 584   }
 585
 586   // FIXME: all pre/post visits should eventually be handled by ::Visit().
 587   ExplodedNodeSet dstPreVisit;
 588   getCheckerManager().runCheckersForPreStmt(dstPreVisit, Pred, DS, *this);
 589
 590   ExplodedNodeSet dstEvaluated;
 591   StmtNodeBuilder B(dstPreVisit, dstEvaluated, *currBldrCtx);
 592   for (ExplodedNodeSet::iterator I = dstPreVisit.begin(), E = dstPreVisit.end();
 593        I!=E; ++I) {
 594     ExplodedNode *N = *I;
 595     ProgramStateRef state = N->getState();
 596     const LocationContext *LC = N->getLocationContext();
 597
 598     // Decls without InitExpr are not initialized explicitly.
 599     if (const Expr *InitEx = VD->getInit()) {
 600
 601       // Note in the state that the initialization has occurred.
 602       ExplodedNode *UpdatedN = N;
 603       SVal InitVal = state->getSVal(InitEx, LC);
 604
 605       assert(DS->isSingleDecl());
 606       if (getObjectUnderConstruction(state, DS, LC)) {
 607         state = finishObjectConstruction(state, DS, LC);
 608         // We constructed the object directly in the variable.
 609         // No need to bind anything.
 610         B.generateNode(DS, UpdatedN, state);
 611       } else {
 612         // Recover some path-sensitivity if a scalar value evaluated to
 613         // UnknownVal.
 614         if (InitVal.isUnknown()) {
 615           QualType Ty = InitEx->getType();
 616           if (InitEx->isGLValue()) {
 617             Ty = getContext().getPointerType(Ty);
 618           }
 619
 620           InitVal = svalBuilder.conjureSymbolVal(nullptr, InitEx, LC, Ty,
 621                                                  currBldrCtx->blockCount());
 622         }
 623
 624
 625         B.takeNodes(UpdatedN);
 626         ExplodedNodeSet Dst2;
 627         evalBind(Dst2, DS, UpdatedN, state->getLValue(VD, LC), InitVal, true);
 628         B.addNodes(Dst2);
 629       }
 630     }
 631     else {
 632       B.generateNode(DS, N, state);
 633     }
 634   }
 635
 636   getCheckerManager().runCheckersForPostStmt(Dst, B.getResults(), DS, *this);
 637 }
 638
 639 void ExprEngine::VisitLogicalExpr(const BinaryOperator* B, ExplodedNode *Pred,
 640                                   ExplodedNodeSet &Dst) {
 641   // This method acts upon CFG elements for logical operators && and ||
 642   // and attaches the value (true or false) to them as expressions.
 643   // It doesn't produce any state splits.
 644   // If we made it that far, we're past the point when we modeled the short
 645   // circuit. It means that we should have precise knowledge about whether
 646   // we've short-circuited. If we did, we already know the value we need to
 647   // bind. If we didn't, the value of the RHS (casted to the boolean type)
 648   // is the answer.
 649   // Currently this method tries to figure out whether we've short-circuited
 650   // by looking at the ExplodedGraph. This method is imperfect because there
 651   // could inevitably have been merges that would have resulted in multiple
 652   // potential path traversal histories. We bail out when we fail.
 653   // Due to this ambiguity, a more reliable solution would have been to
 654   // track the short circuit operation history path-sensitively until
 655   // we evaluate the respective logical operator.
 656   assert(B->getOpcode() == BO_LAnd ||
 657          B->getOpcode() == BO_LOr);
 658
 659   StmtNodeBuilder Bldr(Pred, Dst, *currBldrCtx);
 660   ProgramStateRef state = Pred->getState();
 661
 662   if (B->getType()->isVectorType()) {
 663     // FIXME: We do not model vector arithmetic yet. When adding support for
 664     // that, note that the CFG-based reasoning below does not apply, because
 665     // logical operators on vectors are not short-circuit. Currently they are
 666     // modeled as short-circuit in Clang CFG but this is incorrect.
 667     // Do not set the value for the expression. It'd be UnknownVal by default.
 668     Bldr.generateNode(B, Pred, state);
 669     return;
 670   }
 671
 672   ExplodedNode *N = Pred;
 673   while (!N->getLocation().getAs<BlockEntrance>()) {
 674     ProgramPoint P = N->getLocation();
 675     assert(P.getAs<PreStmt>()|| P.getAs<PreStmtPurgeDeadSymbols>());
 676     (void) P;
 677     if (N->pred_size() != 1) {
 678       // We failed to track back where we came from.
 679       Bldr.generateNode(B, Pred, state);
 680       return;
 681     }
 682     N = *N->pred_begin();
 683   }
 684
 685   if (N->pred_size() != 1) {
 686     // We failed to track back where we came from.
 687     Bldr.generateNode(B, Pred, state);
 688     return;
 689   }
 690
 691   N = *N->pred_begin();
 692   BlockEdge BE = N->getLocation().castAs<BlockEdge>();
 693   SVal X;
 694
 695   // Determine the value of the expression by introspecting how we
 696   // got this location in the CFG.  This requires looking at the previous
 697   // block we were in and what kind of control-flow transfer was involved.
 698   const CFGBlock *SrcBlock = BE.getSrc();
 699   // The only terminator (if there is one) that makes sense is a logical op.
 700   CFGTerminator T = SrcBlock->getTerminator();
 701   if (const BinaryOperator *Term = cast_or_null<BinaryOperator>(T.getStmt())) {
 702     (void) Term;
 703     assert(Term->isLogicalOp());
 704     assert(SrcBlock->succ_size() == 2);
 705     // Did we take the true or false branch?
 706     unsigned constant = (*SrcBlock->succ_begin() == BE.getDst()) ? 1 : 0;
 707     X = svalBuilder.makeIntVal(constant, B->getType());
 708   }
 709   else {
 710     // If there is no terminator, by construction the last statement
 711     // in SrcBlock is the value of the enclosing expression.
 712     // However, we still need to constrain that value to be 0 or 1.
 713     assert(!SrcBlock->empty());
 714     CFGStmt Elem = SrcBlock->rbegin()->castAs<CFGStmt>();
 715     const Expr *RHS = cast<Expr>(Elem.getStmt());
 716     SVal RHSVal = N->getState()->getSVal(RHS, Pred->getLocationContext());
 717
 718     if (RHSVal.isUndef()) {
 719       X = RHSVal;
 720     } else {
 721       // We evaluate "RHSVal != 0" expression which result in 0 if the value is
 722       // known to be false, 1 if the value is known to be true and a new symbol
 723       // when the assumption is unknown.
 724       nonloc::ConcreteInt Zero(getBasicVals().getValue(0, B->getType()));
 725       X = evalBinOp(N->getState(), BO_NE,
 726                     svalBuilder.evalCast(RHSVal, B->getType(), RHS->getType()),
 727                     Zero, B->getType());
 728     }
 729   }
 730   Bldr.generateNode(B, Pred, state->BindExpr(B, Pred->getLocationContext(), X));
 731 }
 732
 733 void ExprEngine::VisitInitListExpr(const InitListExpr *IE,
 734                                    ExplodedNode *Pred,
 735                                    ExplodedNodeSet &Dst) {
 736   StmtNodeBuilder B(Pred, Dst, *currBldrCtx);
 737
 738   ProgramStateRef state = Pred->getState();
 739   const LocationContext *LCtx = Pred->getLocationContext();
 740   QualType T = getContext().getCanonicalType(IE->getType());
 741   unsigned NumInitElements = IE->getNumInits();
 742
 743   if (!IE->isGLValue() && !IE->isTransparent() &&
 744       (T->isArrayType() || T->isRecordType() || T->isVectorType() ||
 745        T->isAnyComplexType())) {
 746     llvm::ImmutableList<SVal> vals = getBasicVals().getEmptySValList();
 747
 748     // Handle base case where the initializer has no elements.
 749     // e.g: static int* myArray[] = {};
 750     if (NumInitElements == 0) {
 751       SVal V = svalBuilder.makeCompoundVal(T, vals);
 752       B.generateNode(IE, Pred, state->BindExpr(IE, LCtx, V));
 753       return;
 754     }
 755
 756     for (const Stmt *S : llvm::reverse(*IE)) {
 757       SVal V = state->getSVal(cast<Expr>(S), LCtx);
 758       vals = getBasicVals().prependSVal(V, vals);
 759     }
 760
 761     B.generateNode(IE, Pred,
 762                    state->BindExpr(IE, LCtx,
 763                                    svalBuilder.makeCompoundVal(T, vals)));
 764     return;
 765   }
 766
 767   // Handle scalars: int{5} and int{} and GLvalues.
 768   // Note, if the InitListExpr is a GLvalue, it means that there is an address
 769   // representing it, so it must have a single init element.
 770   assert(NumInitElements <= 1);
 771
 772   SVal V;
 773   if (NumInitElements == 0)
 774     V = getSValBuilder().makeZeroVal(T);
 775   else
 776     V = state->getSVal(IE->getInit(0), LCtx);
 777
 778   B.generateNode(IE, Pred, state->BindExpr(IE, LCtx, V));
 779 }
 780
 781 void ExprEngine::VisitGuardedExpr(const Expr *Ex,
 782                                   const Expr *L,
 783                                   const Expr *R,
 784                                   ExplodedNode *Pred,
 785                                   ExplodedNodeSet &Dst) {
 786   assert(L && R);
 787
 788   StmtNodeBuilder B(Pred, Dst, *currBldrCtx);
 789   ProgramStateRef state = Pred->getState();
 790   const LocationContext *LCtx = Pred->getLocationContext();
 791   const CFGBlock *SrcBlock = nullptr;
 792
 793   // Find the predecessor block.
 794   ProgramStateRef SrcState = state;
 795   for (const ExplodedNode *N = Pred ; N ; N = *N->pred_begin()) {
 796     ProgramPoint PP = N->getLocation();
 797     if (PP.getAs<PreStmtPurgeDeadSymbols>() || PP.getAs<BlockEntrance>()) {
 798       // If the state N has multiple predecessors P, it means that successors
 799       // of P are all equivalent.
 800       // In turn, that means that all nodes at P are equivalent in terms
 801       // of observable behavior at N, and we can follow any of them.
 802       // FIXME: a more robust solution which does not walk up the tree.
 803       continue;
 804     }
 805     SrcBlock = PP.castAs<BlockEdge>().getSrc();
 806     SrcState = N->getState();
 807     break;
 808   }
 809
 810   assert(SrcBlock && "missing function entry");
 811
 812   // Find the last expression in the predecessor block.  That is the
 813   // expression that is used for the value of the ternary expression.
 814   bool hasValue = false;
 815   SVal V;
 816
 817   for (CFGElement CE : llvm::reverse(*SrcBlock)) {
 818     if (std::optional<CFGStmt> CS = CE.getAs<CFGStmt>()) {
 819       const Expr *ValEx = cast<Expr>(CS->getStmt());
 820       ValEx = ValEx->IgnoreParens();
 821
 822       // For GNU extension '?:' operator, the left hand side will be an
 823       // OpaqueValueExpr, so get the underlying expression.
 824       if (const OpaqueValueExpr *OpaqueEx = dyn_cast<OpaqueValueExpr>(L))
 825         L = OpaqueEx->getSourceExpr();
 826
 827       // If the last expression in the predecessor block matches true or false
 828       // subexpression, get its the value.
 829       if (ValEx == L->IgnoreParens() || ValEx == R->IgnoreParens()) {
 830         hasValue = true;
 831         V = SrcState->getSVal(ValEx, LCtx);
 832       }
 833       break;
 834     }
 835   }
 836
 837   if (!hasValue)
 838     V = svalBuilder.conjureSymbolVal(nullptr, Ex, LCtx,
 839                                      currBldrCtx->blockCount());
 840
 841   // Generate a new node with the binding from the appropriate path.
 842   B.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, V, true));
 843 }
 844
 845 void ExprEngine::
 846 VisitOffsetOfExpr(const OffsetOfExpr *OOE,
 847                   ExplodedNode *Pred, ExplodedNodeSet &Dst) {
 848   StmtNodeBuilder B(Pred, Dst, *currBldrCtx);
 849   Expr::EvalResult Result;
 850   if (OOE->EvaluateAsInt(Result, getContext())) {
 851     APSInt IV = Result.Val.getInt();
 852     assert(IV.getBitWidth() == getContext().getTypeSize(OOE->getType()));
 853     assert(OOE->getType()->castAs<BuiltinType>()->isInteger());
 854     assert(IV.isSigned() == OOE->getType()->isSignedIntegerType());
 855     SVal X = svalBuilder.makeIntVal(IV);
 856     B.generateNode(OOE, Pred,
 857                    Pred->getState()->BindExpr(OOE, Pred->getLocationContext(),
 858                                               X));
 859   }
 860   // FIXME: Handle the case where __builtin_offsetof is not a constant.
 861 }
 862
 863
 864 void ExprEngine::
 865 VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *Ex,
 866                               ExplodedNode *Pred,
 867                               ExplodedNodeSet &Dst) {
 868   // FIXME: Prechecks eventually go in ::Visit().
 869   ExplodedNodeSet CheckedSet;
 870   getCheckerManager().runCheckersForPreStmt(CheckedSet, Pred, Ex, *this);
 871
 872   ExplodedNodeSet EvalSet;
 873   StmtNodeBuilder Bldr(CheckedSet, EvalSet, *currBldrCtx);
 874
 875   QualType T = Ex->getTypeOfArgument();
 876
 877   for (ExplodedNode *N : CheckedSet) {
 878     if (Ex->getKind() == UETT_SizeOf) {
 879       if (!T->isIncompleteType() && !T->isConstantSizeType()) {
 880         assert(T->isVariableArrayType() && "Unknown non-constant-sized type.");
 881
 882         // FIXME: Add support for VLA type arguments and VLA expressions.
 883         // When that happens, we should probably refactor VLASizeChecker's code.
 884         continue;
 885       } else if (T->getAs<ObjCObjectType>()) {
 886         // Some code tries to take the sizeof an ObjCObjectType, relying that
 887         // the compiler has laid out its representation.  Just report Unknown
 888         // for these.
 889         continue;
 890       }
 891     }
 892
 893     APSInt Value = Ex->EvaluateKnownConstInt(getContext());
 894     CharUnits amt = CharUnits::fromQuantity(Value.getZExtValue());
 895
 896     ProgramStateRef state = N->getState();
 897     state = state->BindExpr(
 898         Ex, N->getLocationContext(),
 899         svalBuilder.makeIntVal(amt.getQuantity(), Ex->getType()));
 900     Bldr.generateNode(Ex, N, state);
 901   }
 902
 903   getCheckerManager().runCheckersForPostStmt(Dst, EvalSet, Ex, *this);
 904 }
 905
 906 void ExprEngine::handleUOExtension(ExplodedNode *N, const UnaryOperator *U,
 907                                    StmtNodeBuilder &Bldr) {
 908   // FIXME: We can probably just have some magic in Environment::getSVal()
 909   // that propagates values, instead of creating a new node here.
 910   //
 911   // Unary "+" is a no-op, similar to a parentheses.  We still have places
 912   // where it may be a block-level expression, so we need to
 913   // generate an extra node that just propagates the value of the
 914   // subexpression.
 915   const Expr *Ex = U->getSubExpr()->IgnoreParens();
 916   ProgramStateRef state = N->getState();
 917   const LocationContext *LCtx = N->getLocationContext();
 918   Bldr.generateNode(U, N, state->BindExpr(U, LCtx, state->getSVal(Ex, LCtx)));
 919 }
 920
 921 void ExprEngine::VisitUnaryOperator(const UnaryOperator* U, ExplodedNode *Pred,
 922                                     ExplodedNodeSet &Dst) {
 923   // FIXME: Prechecks eventually go in ::Visit().
 924   ExplodedNodeSet CheckedSet;
 925   getCheckerManager().runCheckersForPreStmt(CheckedSet, Pred, U, *this);
 926
 927   ExplodedNodeSet EvalSet;
 928   StmtNodeBuilder Bldr(CheckedSet, EvalSet, *currBldrCtx);
 929
 930   for (ExplodedNode *N : CheckedSet) {
 931     switch (U->getOpcode()) {
 932     default: {
 933       Bldr.takeNodes(N);
 934       ExplodedNodeSet Tmp;
 935       VisitIncrementDecrementOperator(U, N, Tmp);
 936       Bldr.addNodes(Tmp);
 937       break;
 938     }
 939     case UO_Real: {
 940       const Expr *Ex = U->getSubExpr()->IgnoreParens();
 941
 942       // FIXME: We don't have complex SValues yet.
 943       if (Ex->getType()->isAnyComplexType()) {
 944         // Just report "Unknown."
 945         break;
 946       }
 947
 948       // For all other types, UO_Real is an identity operation.
 949       assert (U->getType() == Ex->getType());
 950       ProgramStateRef state = N->getState();
 951       const LocationContext *LCtx = N->getLocationContext();
 952       Bldr.generateNode(U, N,
 953                         state->BindExpr(U, LCtx, state->getSVal(Ex, LCtx)));
 954       break;
 955     }
 956
 957     case UO_Imag: {
 958       const Expr *Ex = U->getSubExpr()->IgnoreParens();
 959       // FIXME: We don't have complex SValues yet.
 960       if (Ex->getType()->isAnyComplexType()) {
 961         // Just report "Unknown."
 962         break;
 963       }
 964       // For all other types, UO_Imag returns 0.
 965       ProgramStateRef state = N->getState();
 966       const LocationContext *LCtx = N->getLocationContext();
 967       SVal X = svalBuilder.makeZeroVal(Ex->getType());
 968       Bldr.generateNode(U, N, state->BindExpr(U, LCtx, X));
 969       break;
 970     }
 971
 972     case UO_AddrOf: {
 973       // Process pointer-to-member address operation.
 974       const Expr *Ex = U->getSubExpr()->IgnoreParens();
 975       if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Ex)) {
 976         const ValueDecl *VD = DRE->getDecl();
 977
 978         if (isa<CXXMethodDecl, FieldDecl, IndirectFieldDecl>(VD)) {
 979           ProgramStateRef State = N->getState();
 980           const LocationContext *LCtx = N->getLocationContext();
 981           SVal SV = svalBuilder.getMemberPointer(cast<NamedDecl>(VD));
 982           Bldr.generateNode(U, N, State->BindExpr(U, LCtx, SV));
 983           break;
 984         }
 985       }
 986       // Explicitly proceed with default handler for this case cascade.
 987       handleUOExtension(N, U, Bldr);
 988       break;
 989     }
 990     case UO_Plus:
 991       assert(!U->isGLValue());
 992       [[fallthrough]];
 993     case UO_Deref:
 994     case UO_Extension: {
 995       handleUOExtension(N, U, Bldr);
 996       break;
 997     }
 998
 999     case UO_LNot:
1000     case UO_Minus:
1001     case UO_Not: {
1002       assert (!U->isGLValue());
1003       const Expr *Ex = U->getSubExpr()->IgnoreParens();
1004       ProgramStateRef state = N->getState();
1005       const LocationContext *LCtx = N->getLocationContext();
1006
1007       // Get the value of the subexpression.
1008       SVal V = state->getSVal(Ex, LCtx);
1009
1010       if (V.isUnknownOrUndef()) {
1011         Bldr.generateNode(U, N, state->BindExpr(U, LCtx, V));
1012         break;
1013       }
1014
1015       switch (U->getOpcode()) {
1016         default:
1017           llvm_unreachable("Invalid Opcode.");
1018         case UO_Not:
1019           // FIXME: Do we need to handle promotions?
1020           state = state->BindExpr(
1021               U, LCtx, svalBuilder.evalComplement(V.castAs<NonLoc>()));
1022           break;
1023         case UO_Minus:
1024           // FIXME: Do we need to handle promotions?
1025           state = state->BindExpr(U, LCtx,
1026                                   svalBuilder.evalMinus(V.castAs<NonLoc>()));
1027           break;
1028         case UO_LNot:
1029           // C99 6.5.3.3: "The expression !E is equivalent to (0==E)."
1030           //
1031           //  Note: technically we do "E == 0", but this is the same in the
1032           //    transfer functions as "0 == E".
1033           SVal Result;
1034           if (std::optional<Loc> LV = V.getAs<Loc>()) {
1035           Loc X = svalBuilder.makeNullWithType(Ex->getType());
1036           Result = evalBinOp(state, BO_EQ, *LV, X, U->getType());
1037           } else if (Ex->getType()->isFloatingType()) {
1038           // FIXME: handle floating point types.
1039           Result = UnknownVal();
1040           } else {
1041           nonloc::ConcreteInt X(getBasicVals().getValue(0, Ex->getType()));
1042           Result = evalBinOp(state, BO_EQ, V.castAs<NonLoc>(), X, U->getType());
1043           }
1044
1045           state = state->BindExpr(U, LCtx, Result);
1046           break;
1047       }
1048       Bldr.generateNode(U, N, state);
1049       break;
1050     }
1051     }
1052   }
1053
1054   getCheckerManager().runCheckersForPostStmt(Dst, EvalSet, U, *this);
1055 }
1056
1057 void ExprEngine::VisitIncrementDecrementOperator(const UnaryOperator* U,
1058                                                  ExplodedNode *Pred,
1059                                                  ExplodedNodeSet &Dst) {
1060   // Handle ++ and -- (both pre- and post-increment).
1061   assert (U->isIncrementDecrementOp());
1062   const Expr *Ex = U->getSubExpr()->IgnoreParens();
1063
1064   const LocationContext *LCtx = Pred->getLocationContext();
1065   ProgramStateRef state = Pred->getState();
1066   SVal loc = state->getSVal(Ex, LCtx);
1067
1068   // Perform a load.
1069   ExplodedNodeSet Tmp;
1070   evalLoad(Tmp, U, Ex, Pred, state, loc);
1071
1072   ExplodedNodeSet Dst2;
1073   StmtNodeBuilder Bldr(Tmp, Dst2, *currBldrCtx);
1074   for (ExplodedNode *N : Tmp) {
1075     state = N->getState();
1076     assert(LCtx == N->getLocationContext());
1077     SVal V2_untested = state->getSVal(Ex, LCtx);
1078
1079     // Propagate unknown and undefined values.
1080     if (V2_untested.isUnknownOrUndef()) {
1081       state = state->BindExpr(U, LCtx, V2_untested);
1082
1083       // Perform the store, so that the uninitialized value detection happens.
1084       Bldr.takeNodes(N);
1085       ExplodedNodeSet Dst3;
1086       evalStore(Dst3, U, Ex, N, state, loc, V2_untested);
1087       Bldr.addNodes(Dst3);
1088
1089       continue;
1090     }
1091     DefinedSVal V2 = V2_untested.castAs<DefinedSVal>();
1092
1093     // Handle all other values.
1094     BinaryOperator::Opcode Op = U->isIncrementOp() ? BO_Add : BO_Sub;
1095
1096     // If the UnaryOperator has non-location type, use its type to create the
1097     // constant value. If the UnaryOperator has location type, create the
1098     // constant with int type and pointer width.
1099     SVal RHS;
1100     SVal Result;
1101
1102     if (U->getType()->isAnyPointerType())
1103       RHS = svalBuilder.makeArrayIndex(1);
1104     else if (U->getType()->isIntegralOrEnumerationType())
1105       RHS = svalBuilder.makeIntVal(1, U->getType());
1106     else
1107       RHS = UnknownVal();
1108
1109     // The use of an operand of type bool with the ++ operators is deprecated
1110     // but valid until C++17. And if the operand of the ++ operator is of type
1111     // bool, it is set to true until C++17. Note that for '_Bool', it is also
1112     // set to true when it encounters ++ operator.
1113     if (U->getType()->isBooleanType() && U->isIncrementOp())
1114       Result = svalBuilder.makeTruthVal(true, U->getType());
1115     else
1116       Result = evalBinOp(state, Op, V2, RHS, U->getType());
1117
1118     // Conjure a new symbol if necessary to recover precision.
1119     if (Result.isUnknown()){
1120       DefinedOrUnknownSVal SymVal =
1121         svalBuilder.conjureSymbolVal(nullptr, U, LCtx,
1122                                      currBldrCtx->blockCount());
1123       Result = SymVal;
1124
1125       // If the value is a location, ++/-- should always preserve
1126       // non-nullness.  Check if the original value was non-null, and if so
1127       // propagate that constraint.
1128       if (Loc::isLocType(U->getType())) {
1129         DefinedOrUnknownSVal Constraint =
1130         svalBuilder.evalEQ(state, V2,svalBuilder.makeZeroVal(U->getType()));
1131
1132         if (!state->assume(Constraint, true)) {
1133           // It isn't feasible for the original value to be null.
1134           // Propagate this constraint.
1135           Constraint = svalBuilder.evalEQ(state, SymVal,
1136                                        svalBuilder.makeZeroVal(U->getType()));
1137
1138           state = state->assume(Constraint, false);
1139           assert(state);
1140         }
1141       }
1142     }
1143
1144     // Since the lvalue-to-rvalue conversion is explicit in the AST,
1145     // we bind an l-value if the operator is prefix and an lvalue (in C++).
1146     if (U->isGLValue())
1147       state = state->BindExpr(U, LCtx, loc);
1148     else
1149       state = state->BindExpr(U, LCtx, U->isPostfix() ? V2 : Result);
1150
1151     // Perform the store.
1152     Bldr.takeNodes(N);
1153     ExplodedNodeSet Dst3;
1154     evalStore(Dst3, U, Ex, N, state, loc, Result);
1155     Bldr.addNodes(Dst3);
1156   }
1157   Dst.insert(Dst2);
1158 }