//=-- ExprEngineC.cpp - ExprEngine support for C expressions ----*- C++ -*-===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// // // This file defines ExprEngine's support for C expressions. // //===----------------------------------------------------------------------===// #include "clang/AST/ExprCXX.h" #include "clang/AST/DeclCXX.h" #include "clang/StaticAnalyzer/Core/CheckerManager.h" #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" using namespace clang; using namespace ento; using llvm::APSInt; /// Optionally conjure and return a symbol for offset when processing /// an expression \p Expression. /// If \p Other is a location, conjure a symbol for \p Symbol /// (offset) if it is unknown so that memory arithmetic always /// results in an ElementRegion. /// \p Count The number of times the current basic block was visited. static SVal conjureOffsetSymbolOnLocation( SVal Symbol, SVal Other, Expr* Expression, SValBuilder &svalBuilder, unsigned Count, const LocationContext *LCtx) { QualType Ty = Expression->getType(); if (Other.getAs() && Ty->isIntegralOrEnumerationType() && Symbol.isUnknown()) { return svalBuilder.conjureSymbolVal(Expression, LCtx, Ty, Count); } return Symbol; } void ExprEngine::VisitBinaryOperator(const BinaryOperator* B, ExplodedNode *Pred, ExplodedNodeSet &Dst) { Expr *LHS = B->getLHS()->IgnoreParens(); Expr *RHS = B->getRHS()->IgnoreParens(); // FIXME: Prechecks eventually go in ::Visit(). ExplodedNodeSet CheckedSet; ExplodedNodeSet Tmp2; getCheckerManager().runCheckersForPreStmt(CheckedSet, Pred, B, *this); // With both the LHS and RHS evaluated, process the operation itself. for (ExplodedNodeSet::iterator it=CheckedSet.begin(), ei=CheckedSet.end(); it != ei; ++it) { ProgramStateRef state = (*it)->getState(); const LocationContext *LCtx = (*it)->getLocationContext(); SVal LeftV = state->getSVal(LHS, LCtx); SVal RightV = state->getSVal(RHS, LCtx); BinaryOperator::Opcode Op = B->getOpcode(); if (Op == BO_Assign) { // EXPERIMENTAL: "Conjured" symbols. // FIXME: Handle structs. if (RightV.isUnknown()) { unsigned Count = currBldrCtx->blockCount(); RightV = svalBuilder.conjureSymbolVal(nullptr, B->getRHS(), LCtx, Count); } // Simulate the effects of a "store": bind the value of the RHS // to the L-Value represented by the LHS. SVal ExprVal = B->isGLValue() ? LeftV : RightV; evalStore(Tmp2, B, LHS, *it, state->BindExpr(B, LCtx, ExprVal), LeftV, RightV); continue; } if (!B->isAssignmentOp()) { StmtNodeBuilder Bldr(*it, Tmp2, *currBldrCtx); if (B->isAdditiveOp()) { // TODO: This can be removed after we enable history tracking with // SymSymExpr. unsigned Count = currBldrCtx->blockCount(); RightV = conjureOffsetSymbolOnLocation( RightV, LeftV, RHS, svalBuilder, Count, LCtx); LeftV = conjureOffsetSymbolOnLocation( LeftV, RightV, LHS, svalBuilder, Count, LCtx); } // Although we don't yet model pointers-to-members, we do need to make // sure that the members of temporaries have a valid 'this' pointer for // other checks. if (B->getOpcode() == BO_PtrMemD) state = createTemporaryRegionIfNeeded(state, LCtx, LHS); // Process non-assignments except commas or short-circuited // logical expressions (LAnd and LOr). SVal Result = evalBinOp(state, Op, LeftV, RightV, B->getType()); if (!Result.isUnknown()) { state = state->BindExpr(B, LCtx, Result); } else { // If we cannot evaluate the operation escape the operands. state = escapeValues(state, LeftV, PSK_EscapeOther); state = escapeValues(state, RightV, PSK_EscapeOther); } Bldr.generateNode(B, *it, state); continue; } assert (B->isCompoundAssignmentOp()); switch (Op) { default: llvm_unreachable("Invalid opcode for compound assignment."); case BO_MulAssign: Op = BO_Mul; break; case BO_DivAssign: Op = BO_Div; break; case BO_RemAssign: Op = BO_Rem; break; case BO_AddAssign: Op = BO_Add; break; case BO_SubAssign: Op = BO_Sub; break; case BO_ShlAssign: Op = BO_Shl; break; case BO_ShrAssign: Op = BO_Shr; break; case BO_AndAssign: Op = BO_And; break; case BO_XorAssign: Op = BO_Xor; break; case BO_OrAssign: Op = BO_Or; break; } // Perform a load (the LHS). This performs the checks for // null dereferences, and so on. ExplodedNodeSet Tmp; SVal location = LeftV; evalLoad(Tmp, B, LHS, *it, state, location); for (ExplodedNodeSet::iterator I = Tmp.begin(), E = Tmp.end(); I != E; ++I) { state = (*I)->getState(); const LocationContext *LCtx = (*I)->getLocationContext(); SVal V = state->getSVal(LHS, LCtx); // Get the computation type. QualType CTy = cast(B)->getComputationResultType(); CTy = getContext().getCanonicalType(CTy); QualType CLHSTy = cast(B)->getComputationLHSType(); CLHSTy = getContext().getCanonicalType(CLHSTy); QualType LTy = getContext().getCanonicalType(LHS->getType()); // Promote LHS. V = svalBuilder.evalCast(V, CLHSTy, LTy); // Compute the result of the operation. SVal Result = svalBuilder.evalCast(evalBinOp(state, Op, V, RightV, CTy), B->getType(), CTy); // EXPERIMENTAL: "Conjured" symbols. // FIXME: Handle structs. SVal LHSVal; if (Result.isUnknown()) { // The symbolic value is actually for the type of the left-hand side // expression, not the computation type, as this is the value the // LValue on the LHS will bind to. LHSVal = svalBuilder.conjureSymbolVal(nullptr, B->getRHS(), LCtx, LTy, currBldrCtx->blockCount()); // However, we need to convert the symbol to the computation type. Result = svalBuilder.evalCast(LHSVal, CTy, LTy); } else { // The left-hand side may bind to a different value then the // computation type. LHSVal = svalBuilder.evalCast(Result, LTy, CTy); } // In C++, assignment and compound assignment operators return an // lvalue. if (B->isGLValue()) state = state->BindExpr(B, LCtx, location); else state = state->BindExpr(B, LCtx, Result); evalStore(Tmp2, B, LHS, *I, state, location, LHSVal); } } // FIXME: postvisits eventually go in ::Visit() getCheckerManager().runCheckersForPostStmt(Dst, Tmp2, B, *this); } void ExprEngine::VisitBlockExpr(const BlockExpr *BE, ExplodedNode *Pred, ExplodedNodeSet &Dst) { CanQualType T = getContext().getCanonicalType(BE->getType()); const BlockDecl *BD = BE->getBlockDecl(); // Get the value of the block itself. SVal V = svalBuilder.getBlockPointer(BD, T, Pred->getLocationContext(), currBldrCtx->blockCount()); ProgramStateRef State = Pred->getState(); // If we created a new MemRegion for the block, we should explicitly bind // the captured variables. if (const BlockDataRegion *BDR = dyn_cast_or_null(V.getAsRegion())) { BlockDataRegion::referenced_vars_iterator I = BDR->referenced_vars_begin(), E = BDR->referenced_vars_end(); auto CI = BD->capture_begin(); auto CE = BD->capture_end(); for (; I != E; ++I) { const VarRegion *capturedR = I.getCapturedRegion(); const TypedValueRegion *originalR = I.getOriginalRegion(); // If the capture had a copy expression, use the result of evaluating // that expression, otherwise use the original value. // We rely on the invariant that the block declaration's capture variables // are a prefix of the BlockDataRegion's referenced vars (which may include // referenced globals, etc.) to enable fast lookup of the capture for a // given referenced var. const Expr *copyExpr = nullptr; if (CI != CE) { assert(CI->getVariable() == capturedR->getDecl()); copyExpr = CI->getCopyExpr(); CI++; } if (capturedR != originalR) { SVal originalV; const LocationContext *LCtx = Pred->getLocationContext(); if (copyExpr) { originalV = State->getSVal(copyExpr, LCtx); } else { originalV = State->getSVal(loc::MemRegionVal(originalR)); } State = State->bindLoc(loc::MemRegionVal(capturedR), originalV, LCtx); } } } ExplodedNodeSet Tmp; StmtNodeBuilder Bldr(Pred, Tmp, *currBldrCtx); Bldr.generateNode(BE, Pred, State->BindExpr(BE, Pred->getLocationContext(), V), nullptr, ProgramPoint::PostLValueKind); // FIXME: Move all post/pre visits to ::Visit(). getCheckerManager().runCheckersForPostStmt(Dst, Tmp, BE, *this); } ProgramStateRef ExprEngine::handleLValueBitCast( ProgramStateRef state, const Expr* Ex, const LocationContext* LCtx, QualType T, QualType ExTy, const CastExpr* CastE, StmtNodeBuilder& Bldr, ExplodedNode* Pred) { if (T->isLValueReferenceType()) { assert(!CastE->getType()->isLValueReferenceType()); ExTy = getContext().getLValueReferenceType(ExTy); } else if (T->isRValueReferenceType()) { assert(!CastE->getType()->isRValueReferenceType()); ExTy = getContext().getRValueReferenceType(ExTy); } // Delegate to SValBuilder to process. SVal OrigV = state->getSVal(Ex, LCtx); SVal V = svalBuilder.evalCast(OrigV, T, ExTy); // Negate the result if we're treating the boolean as a signed i1 if (CastE->getCastKind() == CK_BooleanToSignedIntegral) V = evalMinus(V); state = state->BindExpr(CastE, LCtx, V); if (V.isUnknown() && !OrigV.isUnknown()) { state = escapeValues(state, OrigV, PSK_EscapeOther); } Bldr.generateNode(CastE, Pred, state); return state; } void ExprEngine::VisitCast(const CastExpr *CastE, const Expr *Ex, ExplodedNode *Pred, ExplodedNodeSet &Dst) { ExplodedNodeSet dstPreStmt; getCheckerManager().runCheckersForPreStmt(dstPreStmt, Pred, CastE, *this); if (CastE->getCastKind() == CK_LValueToRValue || CastE->getCastKind() == CK_LValueToRValueBitCast) { for (ExplodedNodeSet::iterator I = dstPreStmt.begin(), E = dstPreStmt.end(); I!=E; ++I) { ExplodedNode *subExprNode = *I; ProgramStateRef state = subExprNode->getState(); const LocationContext *LCtx = subExprNode->getLocationContext(); evalLoad(Dst, CastE, CastE, subExprNode, state, state->getSVal(Ex, LCtx)); } return; } // All other casts. QualType T = CastE->getType(); QualType ExTy = Ex->getType(); if (const ExplicitCastExpr *ExCast=dyn_cast_or_null(CastE)) T = ExCast->getTypeAsWritten(); StmtNodeBuilder Bldr(dstPreStmt, Dst, *currBldrCtx); for (ExplodedNodeSet::iterator I = dstPreStmt.begin(), E = dstPreStmt.end(); I != E; ++I) { Pred = *I; ProgramStateRef state = Pred->getState(); const LocationContext *LCtx = Pred->getLocationContext(); switch (CastE->getCastKind()) { case CK_LValueToRValue: case CK_LValueToRValueBitCast: llvm_unreachable("LValueToRValue casts handled earlier."); case CK_ToVoid: continue; // The analyzer doesn't do anything special with these casts, // since it understands retain/release semantics already. case CK_ARCProduceObject: case CK_ARCConsumeObject: case CK_ARCReclaimReturnedObject: case CK_ARCExtendBlockObject: // Fall-through. case CK_CopyAndAutoreleaseBlockObject: // The analyser can ignore atomic casts for now, although some future // checkers may want to make certain that you're not modifying the same // value through atomic and nonatomic pointers. case CK_AtomicToNonAtomic: case CK_NonAtomicToAtomic: // True no-ops. case CK_NoOp: case CK_ConstructorConversion: case CK_UserDefinedConversion: case CK_FunctionToPointerDecay: case CK_BuiltinFnToFnPtr: { // Copy the SVal of Ex to CastE. ProgramStateRef state = Pred->getState(); const LocationContext *LCtx = Pred->getLocationContext(); SVal V = state->getSVal(Ex, LCtx); state = state->BindExpr(CastE, LCtx, V); Bldr.generateNode(CastE, Pred, state); continue; } case CK_MemberPointerToBoolean: case CK_PointerToBoolean: { SVal V = state->getSVal(Ex, LCtx); auto PTMSV = V.getAs(); if (PTMSV) V = svalBuilder.makeTruthVal(!PTMSV->isNullMemberPointer(), ExTy); if (V.isUndef() || PTMSV) { state = state->BindExpr(CastE, LCtx, V); Bldr.generateNode(CastE, Pred, state); continue; } // Explicitly proceed with default handler for this case cascade. state = handleLValueBitCast(state, Ex, LCtx, T, ExTy, CastE, Bldr, Pred); continue; } case CK_Dependent: case CK_ArrayToPointerDecay: case CK_BitCast: case CK_AddressSpaceConversion: case CK_BooleanToSignedIntegral: case CK_IntegralToPointer: case CK_PointerToIntegral: { SVal V = state->getSVal(Ex, LCtx); if (V.getAs()) { state = state->BindExpr(CastE, LCtx, UnknownVal()); Bldr.generateNode(CastE, Pred, state); continue; } // Explicitly proceed with default handler for this case cascade. state = handleLValueBitCast(state, Ex, LCtx, T, ExTy, CastE, Bldr, Pred); continue; } case CK_IntegralToBoolean: case CK_IntegralToFloating: case CK_FloatingToIntegral: case CK_FloatingToBoolean: case CK_FloatingCast: case CK_FloatingRealToComplex: case CK_FloatingComplexToReal: case CK_FloatingComplexToBoolean: case CK_FloatingComplexCast: case CK_FloatingComplexToIntegralComplex: case CK_IntegralRealToComplex: case CK_IntegralComplexToReal: case CK_IntegralComplexToBoolean: case CK_IntegralComplexCast: case CK_IntegralComplexToFloatingComplex: case CK_CPointerToObjCPointerCast: case CK_BlockPointerToObjCPointerCast: case CK_AnyPointerToBlockPointerCast: case CK_ObjCObjectLValueCast: case CK_ZeroToOCLOpaqueType: case CK_IntToOCLSampler: case CK_LValueBitCast: case CK_FloatingToFixedPoint: case CK_FixedPointToFloating: case CK_FixedPointCast: case CK_FixedPointToBoolean: case CK_FixedPointToIntegral: case CK_IntegralToFixedPoint: { state = handleLValueBitCast(state, Ex, LCtx, T, ExTy, CastE, Bldr, Pred); continue; } case CK_IntegralCast: { // Delegate to SValBuilder to process. SVal V = state->getSVal(Ex, LCtx); if (AMgr.options.ShouldSupportSymbolicIntegerCasts) V = svalBuilder.evalCast(V, T, ExTy); else V = svalBuilder.evalIntegralCast(state, V, T, ExTy); state = state->BindExpr(CastE, LCtx, V); Bldr.generateNode(CastE, Pred, state); continue; } case CK_DerivedToBase: case CK_UncheckedDerivedToBase: { // For DerivedToBase cast, delegate to the store manager. SVal val = state->getSVal(Ex, LCtx); val = getStoreManager().evalDerivedToBase(val, CastE); state = state->BindExpr(CastE, LCtx, val); Bldr.generateNode(CastE, Pred, state); continue; } // Handle C++ dyn_cast. case CK_Dynamic: { SVal val = state->getSVal(Ex, LCtx); // Compute the type of the result. QualType resultType = CastE->getType(); if (CastE->isGLValue()) resultType = getContext().getPointerType(resultType); bool Failed = true; // Check if the value being cast does not evaluates to 0. if (!val.isZeroConstant()) if (Optional V = StateMgr.getStoreManager().evalBaseToDerived(val, T)) { val = *V; Failed = false; } if (Failed) { if (T->isReferenceType()) { // A bad_cast exception is thrown if input value is a reference. // Currently, we model this, by generating a sink. Bldr.generateSink(CastE, Pred, state); continue; } else { // If the cast fails on a pointer, bind to 0. state = state->BindExpr(CastE, LCtx, svalBuilder.makeNull()); } } else { // If we don't know if the cast succeeded, conjure a new symbol. if (val.isUnknown()) { DefinedOrUnknownSVal NewSym = svalBuilder.conjureSymbolVal(nullptr, CastE, LCtx, resultType, currBldrCtx->blockCount()); state = state->BindExpr(CastE, LCtx, NewSym); } else // Else, bind to the derived region value. state = state->BindExpr(CastE, LCtx, val); } Bldr.generateNode(CastE, Pred, state); continue; } case CK_BaseToDerived: { SVal val = state->getSVal(Ex, LCtx); QualType resultType = CastE->getType(); if (CastE->isGLValue()) resultType = getContext().getPointerType(resultType); if (!val.isConstant()) { Optional V = getStoreManager().evalBaseToDerived(val, T); val = V ? *V : UnknownVal(); } // Failed to cast or the result is unknown, fall back to conservative. if (val.isUnknown()) { val = svalBuilder.conjureSymbolVal(nullptr, CastE, LCtx, resultType, currBldrCtx->blockCount()); } state = state->BindExpr(CastE, LCtx, val); Bldr.generateNode(CastE, Pred, state); continue; } case CK_NullToPointer: { SVal V = svalBuilder.makeNull(); state = state->BindExpr(CastE, LCtx, V); Bldr.generateNode(CastE, Pred, state); continue; } case CK_NullToMemberPointer: { SVal V = svalBuilder.getMemberPointer(nullptr); state = state->BindExpr(CastE, LCtx, V); Bldr.generateNode(CastE, Pred, state); continue; } case CK_DerivedToBaseMemberPointer: case CK_BaseToDerivedMemberPointer: case CK_ReinterpretMemberPointer: { SVal V = state->getSVal(Ex, LCtx); if (auto PTMSV = V.getAs()) { SVal CastedPTMSV = svalBuilder.makePointerToMember(getBasicVals().accumCXXBase( CastE->path(), *PTMSV, CastE->getCastKind())); state = state->BindExpr(CastE, LCtx, CastedPTMSV); Bldr.generateNode(CastE, Pred, state); continue; } // Explicitly proceed with default handler for this case cascade. } LLVM_FALLTHROUGH; // Various C++ casts that are not handled yet. case CK_ToUnion: case CK_MatrixCast: case CK_VectorSplat: { QualType resultType = CastE->getType(); if (CastE->isGLValue()) resultType = getContext().getPointerType(resultType); SVal result = svalBuilder.conjureSymbolVal( /*symbolTag=*/nullptr, CastE, LCtx, resultType, currBldrCtx->blockCount()); state = state->BindExpr(CastE, LCtx, result); Bldr.generateNode(CastE, Pred, state); continue; } } } } void ExprEngine::VisitCompoundLiteralExpr(const CompoundLiteralExpr *CL, ExplodedNode *Pred, ExplodedNodeSet &Dst) { StmtNodeBuilder B(Pred, Dst, *currBldrCtx); ProgramStateRef State = Pred->getState(); const LocationContext *LCtx = Pred->getLocationContext(); const Expr *Init = CL->getInitializer(); SVal V = State->getSVal(CL->getInitializer(), LCtx); if (isa(Init)) { // No work needed. Just pass the value up to this expression. } else { assert(isa(Init)); Loc CLLoc = State->getLValue(CL, LCtx); State = State->bindLoc(CLLoc, V, LCtx); if (CL->isGLValue()) V = CLLoc; } B.generateNode(CL, Pred, State->BindExpr(CL, LCtx, V)); } void ExprEngine::VisitDeclStmt(const DeclStmt *DS, ExplodedNode *Pred, ExplodedNodeSet &Dst) { if (isa(*DS->decl_begin())) { // C99 6.7.7 "Any array size expressions associated with variable length // array declarators are evaluated each time the declaration of the typedef // name is reached in the order of execution." // The checkers should know about typedef to be able to handle VLA size // expressions. ExplodedNodeSet DstPre; getCheckerManager().runCheckersForPreStmt(DstPre, Pred, DS, *this); getCheckerManager().runCheckersForPostStmt(Dst, DstPre, DS, *this); return; } // Assumption: The CFG has one DeclStmt per Decl. const VarDecl *VD = dyn_cast_or_null(*DS->decl_begin()); if (!VD) { //TODO:AZ: remove explicit insertion after refactoring is done. Dst.insert(Pred); return; } // FIXME: all pre/post visits should eventually be handled by ::Visit(). ExplodedNodeSet dstPreVisit; getCheckerManager().runCheckersForPreStmt(dstPreVisit, Pred, DS, *this); ExplodedNodeSet dstEvaluated; StmtNodeBuilder B(dstPreVisit, dstEvaluated, *currBldrCtx); for (ExplodedNodeSet::iterator I = dstPreVisit.begin(), E = dstPreVisit.end(); I!=E; ++I) { ExplodedNode *N = *I; ProgramStateRef state = N->getState(); const LocationContext *LC = N->getLocationContext(); // Decls without InitExpr are not initialized explicitly. if (const Expr *InitEx = VD->getInit()) { // Note in the state that the initialization has occurred. ExplodedNode *UpdatedN = N; SVal InitVal = state->getSVal(InitEx, LC); assert(DS->isSingleDecl()); if (getObjectUnderConstruction(state, DS, LC)) { state = finishObjectConstruction(state, DS, LC); // We constructed the object directly in the variable. // No need to bind anything. B.generateNode(DS, UpdatedN, state); } else { // Recover some path-sensitivity if a scalar value evaluated to // UnknownVal. if (InitVal.isUnknown()) { QualType Ty = InitEx->getType(); if (InitEx->isGLValue()) { Ty = getContext().getPointerType(Ty); } InitVal = svalBuilder.conjureSymbolVal(nullptr, InitEx, LC, Ty, currBldrCtx->blockCount()); } B.takeNodes(UpdatedN); ExplodedNodeSet Dst2; evalBind(Dst2, DS, UpdatedN, state->getLValue(VD, LC), InitVal, true); B.addNodes(Dst2); } } else { B.generateNode(DS, N, state); } } getCheckerManager().runCheckersForPostStmt(Dst, B.getResults(), DS, *this); } void ExprEngine::VisitLogicalExpr(const BinaryOperator* B, ExplodedNode *Pred, ExplodedNodeSet &Dst) { // This method acts upon CFG elements for logical operators && and || // and attaches the value (true or false) to them as expressions. // It doesn't produce any state splits. // If we made it that far, we're past the point when we modeled the short // circuit. It means that we should have precise knowledge about whether // we've short-circuited. If we did, we already know the value we need to // bind. If we didn't, the value of the RHS (casted to the boolean type) // is the answer. // Currently this method tries to figure out whether we've short-circuited // by looking at the ExplodedGraph. This method is imperfect because there // could inevitably have been merges that would have resulted in multiple // potential path traversal histories. We bail out when we fail. // Due to this ambiguity, a more reliable solution would have been to // track the short circuit operation history path-sensitively until // we evaluate the respective logical operator. assert(B->getOpcode() == BO_LAnd || B->getOpcode() == BO_LOr); StmtNodeBuilder Bldr(Pred, Dst, *currBldrCtx); ProgramStateRef state = Pred->getState(); if (B->getType()->isVectorType()) { // FIXME: We do not model vector arithmetic yet. When adding support for // that, note that the CFG-based reasoning below does not apply, because // logical operators on vectors are not short-circuit. Currently they are // modeled as short-circuit in Clang CFG but this is incorrect. // Do not set the value for the expression. It'd be UnknownVal by default. Bldr.generateNode(B, Pred, state); return; } ExplodedNode *N = Pred; while (!N->getLocation().getAs()) { ProgramPoint P = N->getLocation(); assert(P.getAs()|| P.getAs()); (void) P; if (N->pred_size() != 1) { // We failed to track back where we came from. Bldr.generateNode(B, Pred, state); return; } N = *N->pred_begin(); } if (N->pred_size() != 1) { // We failed to track back where we came from. Bldr.generateNode(B, Pred, state); return; } N = *N->pred_begin(); BlockEdge BE = N->getLocation().castAs(); SVal X; // Determine the value of the expression by introspecting how we // got this location in the CFG. This requires looking at the previous // block we were in and what kind of control-flow transfer was involved. const CFGBlock *SrcBlock = BE.getSrc(); // The only terminator (if there is one) that makes sense is a logical op. CFGTerminator T = SrcBlock->getTerminator(); if (const BinaryOperator *Term = cast_or_null(T.getStmt())) { (void) Term; assert(Term->isLogicalOp()); assert(SrcBlock->succ_size() == 2); // Did we take the true or false branch? unsigned constant = (*SrcBlock->succ_begin() == BE.getDst()) ? 1 : 0; X = svalBuilder.makeIntVal(constant, B->getType()); } else { // If there is no terminator, by construction the last statement // in SrcBlock is the value of the enclosing expression. // However, we still need to constrain that value to be 0 or 1. assert(!SrcBlock->empty()); CFGStmt Elem = SrcBlock->rbegin()->castAs(); const Expr *RHS = cast(Elem.getStmt()); SVal RHSVal = N->getState()->getSVal(RHS, Pred->getLocationContext()); if (RHSVal.isUndef()) { X = RHSVal; } else { // We evaluate "RHSVal != 0" expression which result in 0 if the value is // known to be false, 1 if the value is known to be true and a new symbol // when the assumption is unknown. nonloc::ConcreteInt Zero(getBasicVals().getValue(0, B->getType())); X = evalBinOp(N->getState(), BO_NE, svalBuilder.evalCast(RHSVal, B->getType(), RHS->getType()), Zero, B->getType()); } } Bldr.generateNode(B, Pred, state->BindExpr(B, Pred->getLocationContext(), X)); } void ExprEngine::VisitInitListExpr(const InitListExpr *IE, ExplodedNode *Pred, ExplodedNodeSet &Dst) { StmtNodeBuilder B(Pred, Dst, *currBldrCtx); ProgramStateRef state = Pred->getState(); const LocationContext *LCtx = Pred->getLocationContext(); QualType T = getContext().getCanonicalType(IE->getType()); unsigned NumInitElements = IE->getNumInits(); if (!IE->isGLValue() && !IE->isTransparent() && (T->isArrayType() || T->isRecordType() || T->isVectorType() || T->isAnyComplexType())) { llvm::ImmutableList vals = getBasicVals().getEmptySValList(); // Handle base case where the initializer has no elements. // e.g: static int* myArray[] = {}; if (NumInitElements == 0) { SVal V = svalBuilder.makeCompoundVal(T, vals); B.generateNode(IE, Pred, state->BindExpr(IE, LCtx, V)); return; } for (const Stmt *S : llvm::reverse(*IE)) { SVal V = state->getSVal(cast(S), LCtx); vals = getBasicVals().prependSVal(V, vals); } B.generateNode(IE, Pred, state->BindExpr(IE, LCtx, svalBuilder.makeCompoundVal(T, vals))); return; } // Handle scalars: int{5} and int{} and GLvalues. // Note, if the InitListExpr is a GLvalue, it means that there is an address // representing it, so it must have a single init element. assert(NumInitElements <= 1); SVal V; if (NumInitElements == 0) V = getSValBuilder().makeZeroVal(T); else V = state->getSVal(IE->getInit(0), LCtx); B.generateNode(IE, Pred, state->BindExpr(IE, LCtx, V)); } void ExprEngine::VisitGuardedExpr(const Expr *Ex, const Expr *L, const Expr *R, ExplodedNode *Pred, ExplodedNodeSet &Dst) { assert(L && R); StmtNodeBuilder B(Pred, Dst, *currBldrCtx); ProgramStateRef state = Pred->getState(); const LocationContext *LCtx = Pred->getLocationContext(); const CFGBlock *SrcBlock = nullptr; // Find the predecessor block. ProgramStateRef SrcState = state; for (const ExplodedNode *N = Pred ; N ; N = *N->pred_begin()) { ProgramPoint PP = N->getLocation(); if (PP.getAs() || PP.getAs()) { // If the state N has multiple predecessors P, it means that successors // of P are all equivalent. // In turn, that means that all nodes at P are equivalent in terms // of observable behavior at N, and we can follow any of them. // FIXME: a more robust solution which does not walk up the tree. continue; } SrcBlock = PP.castAs().getSrc(); SrcState = N->getState(); break; } assert(SrcBlock && "missing function entry"); // Find the last expression in the predecessor block. That is the // expression that is used for the value of the ternary expression. bool hasValue = false; SVal V; for (CFGElement CE : llvm::reverse(*SrcBlock)) { if (Optional CS = CE.getAs()) { const Expr *ValEx = cast(CS->getStmt()); ValEx = ValEx->IgnoreParens(); // For GNU extension '?:' operator, the left hand side will be an // OpaqueValueExpr, so get the underlying expression. if (const OpaqueValueExpr *OpaqueEx = dyn_cast(L)) L = OpaqueEx->getSourceExpr(); // If the last expression in the predecessor block matches true or false // subexpression, get its the value. if (ValEx == L->IgnoreParens() || ValEx == R->IgnoreParens()) { hasValue = true; V = SrcState->getSVal(ValEx, LCtx); } break; } } if (!hasValue) V = svalBuilder.conjureSymbolVal(nullptr, Ex, LCtx, currBldrCtx->blockCount()); // Generate a new node with the binding from the appropriate path. B.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, V, true)); } void ExprEngine:: VisitOffsetOfExpr(const OffsetOfExpr *OOE, ExplodedNode *Pred, ExplodedNodeSet &Dst) { StmtNodeBuilder B(Pred, Dst, *currBldrCtx); Expr::EvalResult Result; if (OOE->EvaluateAsInt(Result, getContext())) { APSInt IV = Result.Val.getInt(); assert(IV.getBitWidth() == getContext().getTypeSize(OOE->getType())); assert(OOE->getType()->castAs()->isInteger()); assert(IV.isSigned() == OOE->getType()->isSignedIntegerType()); SVal X = svalBuilder.makeIntVal(IV); B.generateNode(OOE, Pred, Pred->getState()->BindExpr(OOE, Pred->getLocationContext(), X)); } // FIXME: Handle the case where __builtin_offsetof is not a constant. } void ExprEngine:: VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *Ex, ExplodedNode *Pred, ExplodedNodeSet &Dst) { // FIXME: Prechecks eventually go in ::Visit(). ExplodedNodeSet CheckedSet; getCheckerManager().runCheckersForPreStmt(CheckedSet, Pred, Ex, *this); ExplodedNodeSet EvalSet; StmtNodeBuilder Bldr(CheckedSet, EvalSet, *currBldrCtx); QualType T = Ex->getTypeOfArgument(); for (ExplodedNodeSet::iterator I = CheckedSet.begin(), E = CheckedSet.end(); I != E; ++I) { if (Ex->getKind() == UETT_SizeOf) { if (!T->isIncompleteType() && !T->isConstantSizeType()) { assert(T->isVariableArrayType() && "Unknown non-constant-sized type."); // FIXME: Add support for VLA type arguments and VLA expressions. // When that happens, we should probably refactor VLASizeChecker's code. continue; } else if (T->getAs()) { // Some code tries to take the sizeof an ObjCObjectType, relying that // the compiler has laid out its representation. Just report Unknown // for these. continue; } } APSInt Value = Ex->EvaluateKnownConstInt(getContext()); CharUnits amt = CharUnits::fromQuantity(Value.getZExtValue()); ProgramStateRef state = (*I)->getState(); state = state->BindExpr(Ex, (*I)->getLocationContext(), svalBuilder.makeIntVal(amt.getQuantity(), Ex->getType())); Bldr.generateNode(Ex, *I, state); } getCheckerManager().runCheckersForPostStmt(Dst, EvalSet, Ex, *this); } void ExprEngine::handleUOExtension(ExplodedNodeSet::iterator I, const UnaryOperator *U, StmtNodeBuilder &Bldr) { // FIXME: We can probably just have some magic in Environment::getSVal() // that propagates values, instead of creating a new node here. // // Unary "+" is a no-op, similar to a parentheses. We still have places // where it may be a block-level expression, so we need to // generate an extra node that just propagates the value of the // subexpression. const Expr *Ex = U->getSubExpr()->IgnoreParens(); ProgramStateRef state = (*I)->getState(); const LocationContext *LCtx = (*I)->getLocationContext(); Bldr.generateNode(U, *I, state->BindExpr(U, LCtx, state->getSVal(Ex, LCtx))); } void ExprEngine::VisitUnaryOperator(const UnaryOperator* U, ExplodedNode *Pred, ExplodedNodeSet &Dst) { // FIXME: Prechecks eventually go in ::Visit(). ExplodedNodeSet CheckedSet; getCheckerManager().runCheckersForPreStmt(CheckedSet, Pred, U, *this); ExplodedNodeSet EvalSet; StmtNodeBuilder Bldr(CheckedSet, EvalSet, *currBldrCtx); for (ExplodedNodeSet::iterator I = CheckedSet.begin(), E = CheckedSet.end(); I != E; ++I) { switch (U->getOpcode()) { default: { Bldr.takeNodes(*I); ExplodedNodeSet Tmp; VisitIncrementDecrementOperator(U, *I, Tmp); Bldr.addNodes(Tmp); break; } case UO_Real: { const Expr *Ex = U->getSubExpr()->IgnoreParens(); // FIXME: We don't have complex SValues yet. if (Ex->getType()->isAnyComplexType()) { // Just report "Unknown." break; } // For all other types, UO_Real is an identity operation. assert (U->getType() == Ex->getType()); ProgramStateRef state = (*I)->getState(); const LocationContext *LCtx = (*I)->getLocationContext(); Bldr.generateNode(U, *I, state->BindExpr(U, LCtx, state->getSVal(Ex, LCtx))); break; } case UO_Imag: { const Expr *Ex = U->getSubExpr()->IgnoreParens(); // FIXME: We don't have complex SValues yet. if (Ex->getType()->isAnyComplexType()) { // Just report "Unknown." break; } // For all other types, UO_Imag returns 0. ProgramStateRef state = (*I)->getState(); const LocationContext *LCtx = (*I)->getLocationContext(); SVal X = svalBuilder.makeZeroVal(Ex->getType()); Bldr.generateNode(U, *I, state->BindExpr(U, LCtx, X)); break; } case UO_AddrOf: { // Process pointer-to-member address operation. const Expr *Ex = U->getSubExpr()->IgnoreParens(); if (const DeclRefExpr *DRE = dyn_cast(Ex)) { const ValueDecl *VD = DRE->getDecl(); if (isa(VD)) { ProgramStateRef State = (*I)->getState(); const LocationContext *LCtx = (*I)->getLocationContext(); SVal SV = svalBuilder.getMemberPointer(cast(VD)); Bldr.generateNode(U, *I, State->BindExpr(U, LCtx, SV)); break; } } // Explicitly proceed with default handler for this case cascade. handleUOExtension(I, U, Bldr); break; } case UO_Plus: assert(!U->isGLValue()); LLVM_FALLTHROUGH; case UO_Deref: case UO_Extension: { handleUOExtension(I, U, Bldr); break; } case UO_LNot: case UO_Minus: case UO_Not: { assert (!U->isGLValue()); const Expr *Ex = U->getSubExpr()->IgnoreParens(); ProgramStateRef state = (*I)->getState(); const LocationContext *LCtx = (*I)->getLocationContext(); // Get the value of the subexpression. SVal V = state->getSVal(Ex, LCtx); if (V.isUnknownOrUndef()) { Bldr.generateNode(U, *I, state->BindExpr(U, LCtx, V)); break; } switch (U->getOpcode()) { default: llvm_unreachable("Invalid Opcode."); case UO_Not: // FIXME: Do we need to handle promotions? state = state->BindExpr(U, LCtx, evalComplement(V.castAs())); break; case UO_Minus: // FIXME: Do we need to handle promotions? state = state->BindExpr(U, LCtx, evalMinus(V.castAs())); break; case UO_LNot: // C99 6.5.3.3: "The expression !E is equivalent to (0==E)." // // Note: technically we do "E == 0", but this is the same in the // transfer functions as "0 == E". SVal Result; if (Optional LV = V.getAs()) { Loc X = svalBuilder.makeNullWithType(Ex->getType()); Result = evalBinOp(state, BO_EQ, *LV, X, U->getType()); } else if (Ex->getType()->isFloatingType()) { // FIXME: handle floating point types. Result = UnknownVal(); } else { nonloc::ConcreteInt X(getBasicVals().getValue(0, Ex->getType())); Result = evalBinOp(state, BO_EQ, V.castAs(), X, U->getType()); } state = state->BindExpr(U, LCtx, Result); break; } Bldr.generateNode(U, *I, state); break; } } } getCheckerManager().runCheckersForPostStmt(Dst, EvalSet, U, *this); } void ExprEngine::VisitIncrementDecrementOperator(const UnaryOperator* U, ExplodedNode *Pred, ExplodedNodeSet &Dst) { // Handle ++ and -- (both pre- and post-increment). assert (U->isIncrementDecrementOp()); const Expr *Ex = U->getSubExpr()->IgnoreParens(); const LocationContext *LCtx = Pred->getLocationContext(); ProgramStateRef state = Pred->getState(); SVal loc = state->getSVal(Ex, LCtx); // Perform a load. ExplodedNodeSet Tmp; evalLoad(Tmp, U, Ex, Pred, state, loc); ExplodedNodeSet Dst2; StmtNodeBuilder Bldr(Tmp, Dst2, *currBldrCtx); for (ExplodedNodeSet::iterator I=Tmp.begin(), E=Tmp.end();I!=E;++I) { state = (*I)->getState(); assert(LCtx == (*I)->getLocationContext()); SVal V2_untested = state->getSVal(Ex, LCtx); // Propagate unknown and undefined values. if (V2_untested.isUnknownOrUndef()) { state = state->BindExpr(U, LCtx, V2_untested); // Perform the store, so that the uninitialized value detection happens. Bldr.takeNodes(*I); ExplodedNodeSet Dst3; evalStore(Dst3, U, Ex, *I, state, loc, V2_untested); Bldr.addNodes(Dst3); continue; } DefinedSVal V2 = V2_untested.castAs(); // Handle all other values. BinaryOperator::Opcode Op = U->isIncrementOp() ? BO_Add : BO_Sub; // If the UnaryOperator has non-location type, use its type to create the // constant value. If the UnaryOperator has location type, create the // constant with int type and pointer width. SVal RHS; SVal Result; if (U->getType()->isAnyPointerType()) RHS = svalBuilder.makeArrayIndex(1); else if (U->getType()->isIntegralOrEnumerationType()) RHS = svalBuilder.makeIntVal(1, U->getType()); else RHS = UnknownVal(); // The use of an operand of type bool with the ++ operators is deprecated // but valid until C++17. And if the operand of the ++ operator is of type // bool, it is set to true until C++17. Note that for '_Bool', it is also // set to true when it encounters ++ operator. if (U->getType()->isBooleanType() && U->isIncrementOp()) Result = svalBuilder.makeTruthVal(true, U->getType()); else Result = evalBinOp(state, Op, V2, RHS, U->getType()); // Conjure a new symbol if necessary to recover precision. if (Result.isUnknown()){ DefinedOrUnknownSVal SymVal = svalBuilder.conjureSymbolVal(nullptr, U, LCtx, currBldrCtx->blockCount()); Result = SymVal; // If the value is a location, ++/-- should always preserve // non-nullness. Check if the original value was non-null, and if so // propagate that constraint. if (Loc::isLocType(U->getType())) { DefinedOrUnknownSVal Constraint = svalBuilder.evalEQ(state, V2,svalBuilder.makeZeroVal(U->getType())); if (!state->assume(Constraint, true)) { // It isn't feasible for the original value to be null. // Propagate this constraint. Constraint = svalBuilder.evalEQ(state, SymVal, svalBuilder.makeZeroVal(U->getType())); state = state->assume(Constraint, false); assert(state); } } } // Since the lvalue-to-rvalue conversion is explicit in the AST, // we bind an l-value if the operator is prefix and an lvalue (in C++). if (U->isGLValue()) state = state->BindExpr(U, LCtx, loc); else state = state->BindExpr(U, LCtx, U->isPostfix() ? V2 : Result); // Perform the store. Bldr.takeNodes(*I); ExplodedNodeSet Dst3; evalStore(Dst3, U, Ex, *I, state, loc, Result); Bldr.addNodes(Dst3); } Dst.insert(Dst2); }