//=-- ExprEngineC.cpp - ExprEngine support for C expressions ----*- C++ -*-===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file defines ExprEngine's support for C expressions. // //===----------------------------------------------------------------------===// #include "clang/StaticAnalyzer/Core/CheckerManager.h" #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" #include "clang/Analysis/Support/SaveAndRestore.h" using namespace clang; using namespace ento; using llvm::APSInt; 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) { const ProgramState *state = (*it)->getState(); SVal LeftV = state->getSVal(LHS); SVal RightV = state->getSVal(RHS); BinaryOperator::Opcode Op = B->getOpcode(); if (Op == BO_Assign) { // EXPERIMENTAL: "Conjured" symbols. // FIXME: Handle structs. if (RightV.isUnknown() || !getConstraintManager().canReasonAbout(RightV)) { unsigned Count = Builder->getCurrentBlockCount(); RightV = svalBuilder.getConjuredSymbolVal(NULL, B->getRHS(), Count); } // Simulate the effects of a "store": bind the value of the RHS // to the L-Value represented by the LHS. SVal ExprVal = B->isLValue() ? LeftV : RightV; evalStore(Tmp2, B, LHS, *it, state->BindExpr(B, ExprVal), LeftV, RightV); continue; } if (!B->isAssignmentOp()) { // 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()) { MakeNode(Tmp2, B, *it, state); continue; } state = state->BindExpr(B, Result); MakeNode(Tmp2, 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, LHS, *it, state, location); for (ExplodedNodeSet::iterator I = Tmp.begin(), E = Tmp.end(); I != E; ++I) { state = (*I)->getState(); SVal V = state->getSVal(LHS); // 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() || !getConstraintManager().canReasonAbout(Result)) { unsigned Count = Builder->getCurrentBlockCount(); // 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.getConjuredSymbolVal(NULL, B->getRHS(), LTy, Count); // 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->isLValue()) state = state->BindExpr(B, location); else state = state->BindExpr(B, 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()); SVal V = svalBuilder.getBlockPointer(BE->getBlockDecl(), T, Pred->getLocationContext()); ExplodedNodeSet Tmp; MakeNode(Tmp, BE, Pred, Pred->getState()->BindExpr(BE, V), ProgramPoint::PostLValueKind); // FIXME: Move all post/pre visits to ::Visit(). getCheckerManager().runCheckersForPostStmt(Dst, Tmp, BE, *this); } 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_GetObjCProperty) { for (ExplodedNodeSet::iterator I = dstPreStmt.begin(), E = dstPreStmt.end(); I!=E; ++I) { ExplodedNode *subExprNode = *I; const ProgramState *state = subExprNode->getState(); evalLoad(Dst, CastE, subExprNode, state, state->getSVal(Ex)); } return; } // All other casts. QualType T = CastE->getType(); QualType ExTy = Ex->getType(); if (const ExplicitCastExpr *ExCast=dyn_cast_or_null(CastE)) T = ExCast->getTypeAsWritten(); for (ExplodedNodeSet::iterator I = dstPreStmt.begin(), E = dstPreStmt.end(); I != E; ++I) { Pred = *I; switch (CastE->getCastKind()) { case CK_LValueToRValue: llvm_unreachable("LValueToRValue casts handled earlier."); case CK_GetObjCProperty: llvm_unreachable("GetObjCProperty casts handled earlier."); case CK_ToVoid: Dst.Add(Pred); 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. // True no-ops. case CK_NoOp: case CK_FunctionToPointerDecay: { // Copy the SVal of Ex to CastE. const ProgramState *state = Pred->getState(); SVal V = state->getSVal(Ex); state = state->BindExpr(CastE, V); MakeNode(Dst, CastE, Pred, state); continue; } case CK_Dependent: case CK_ArrayToPointerDecay: case CK_BitCast: case CK_LValueBitCast: case CK_IntegralCast: case CK_NullToPointer: case CK_IntegralToPointer: case CK_PointerToIntegral: case CK_PointerToBoolean: 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: { // Delegate to SValBuilder to process. const ProgramState *state = Pred->getState(); SVal V = state->getSVal(Ex); V = svalBuilder.evalCast(V, T, ExTy); state = state->BindExpr(CastE, V); MakeNode(Dst, CastE, Pred, state); continue; } case CK_DerivedToBase: case CK_UncheckedDerivedToBase: { // For DerivedToBase cast, delegate to the store manager. const ProgramState *state = Pred->getState(); SVal val = state->getSVal(Ex); val = getStoreManager().evalDerivedToBase(val, T); state = state->BindExpr(CastE, val); MakeNode(Dst, CastE, Pred, state); continue; } // Various C++ casts that are not handled yet. case CK_Dynamic: case CK_ToUnion: case CK_BaseToDerived: case CK_NullToMemberPointer: case CK_BaseToDerivedMemberPointer: case CK_DerivedToBaseMemberPointer: case CK_UserDefinedConversion: case CK_ConstructorConversion: case CK_VectorSplat: case CK_MemberPointerToBoolean: { // Recover some path-sensitivty by conjuring a new value. QualType resultType = CastE->getType(); if (CastE->isLValue()) resultType = getContext().getPointerType(resultType); SVal result = svalBuilder.getConjuredSymbolVal(NULL, CastE, resultType, Builder->getCurrentBlockCount()); const ProgramState *state = Pred->getState()->BindExpr(CastE, result); MakeNode(Dst, CastE, Pred, state); continue; } } } } void ExprEngine::VisitCompoundLiteralExpr(const CompoundLiteralExpr *CL, ExplodedNode *Pred, ExplodedNodeSet &Dst) { const InitListExpr *ILE = cast(CL->getInitializer()->IgnoreParens()); const ProgramState *state = Pred->getState(); SVal ILV = state->getSVal(ILE); const LocationContext *LC = Pred->getLocationContext(); state = state->bindCompoundLiteral(CL, LC, ILV); if (CL->isLValue()) MakeNode(Dst, CL, Pred, state->BindExpr(CL, state->getLValue(CL, LC))); else MakeNode(Dst, CL, Pred, state->BindExpr(CL, ILV)); } void ExprEngine::VisitDeclStmt(const DeclStmt *DS, ExplodedNode *Pred, ExplodedNodeSet &Dst) { // FIXME: static variables may have an initializer, but the second // time a function is called those values may not be current. // This may need to be reflected in the CFG. // Assumption: The CFG has one DeclStmt per Decl. const Decl *D = *DS->decl_begin(); if (!D || !isa(D)) return; // FIXME: all pre/post visits should eventually be handled by ::Visit(). ExplodedNodeSet dstPreVisit; getCheckerManager().runCheckersForPreStmt(dstPreVisit, Pred, DS, *this); const VarDecl *VD = dyn_cast(D); for (ExplodedNodeSet::iterator I = dstPreVisit.begin(), E = dstPreVisit.end(); I!=E; ++I) { ExplodedNode *N = *I; const ProgramState *state = N->getState(); // Decls without InitExpr are not initialized explicitly. const LocationContext *LC = N->getLocationContext(); if (const Expr *InitEx = VD->getInit()) { SVal InitVal = state->getSVal(InitEx); // We bound the temp obj region to the CXXConstructExpr. Now recover // the lazy compound value when the variable is not a reference. if (AMgr.getLangOptions().CPlusPlus && VD->getType()->isRecordType() && !VD->getType()->isReferenceType() && isa(InitVal)){ InitVal = state->getSVal(cast(InitVal).getRegion()); assert(isa(InitVal)); } // Recover some path-sensitivity if a scalar value evaluated to // UnknownVal. if ((InitVal.isUnknown() || !getConstraintManager().canReasonAbout(InitVal)) && !VD->getType()->isReferenceType()) { InitVal = svalBuilder.getConjuredSymbolVal(NULL, InitEx, Builder->getCurrentBlockCount()); } evalBind(Dst, DS, N, state->getLValue(VD, LC), InitVal, true); } else { MakeNode(Dst, DS, N, state->bindDeclWithNoInit(state->getRegion(VD, LC))); } } } void ExprEngine::VisitLogicalExpr(const BinaryOperator* B, ExplodedNode *Pred, ExplodedNodeSet &Dst) { assert(B->getOpcode() == BO_LAnd || B->getOpcode() == BO_LOr); const ProgramState *state = Pred->getState(); SVal X = state->getSVal(B); assert(X.isUndef()); const Expr *Ex = (const Expr*) cast(X).getData(); assert(Ex); if (Ex == B->getRHS()) { X = state->getSVal(Ex); // Handle undefined values. if (X.isUndef()) { MakeNode(Dst, B, Pred, state->BindExpr(B, X)); return; } DefinedOrUnknownSVal XD = cast(X); // We took the RHS. Because the value of the '&&' or '||' expression must // evaluate to 0 or 1, we must assume the value of the RHS evaluates to 0 // or 1. Alternatively, we could take a lazy approach, and calculate this // value later when necessary. We don't have the machinery in place for // this right now, and since most logical expressions are used for branches, // the payoff is not likely to be large. Instead, we do eager evaluation. if (const ProgramState *newState = state->assume(XD, true)) MakeNode(Dst, B, Pred, newState->BindExpr(B, svalBuilder.makeIntVal(1U, B->getType()))); if (const ProgramState *newState = state->assume(XD, false)) MakeNode(Dst, B, Pred, newState->BindExpr(B, svalBuilder.makeIntVal(0U, B->getType()))); } else { // We took the LHS expression. Depending on whether we are '&&' or // '||' we know what the value of the expression is via properties of // the short-circuiting. X = svalBuilder.makeIntVal(B->getOpcode() == BO_LAnd ? 0U : 1U, B->getType()); MakeNode(Dst, B, Pred, state->BindExpr(B, X)); } } void ExprEngine::VisitInitListExpr(const InitListExpr *IE, ExplodedNode *Pred, ExplodedNodeSet &Dst) { const ProgramState *state = Pred->getState(); QualType T = getContext().getCanonicalType(IE->getType()); unsigned NumInitElements = IE->getNumInits(); if (T->isArrayType() || T->isRecordType() || T->isVectorType()) { 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); MakeNode(Dst, IE, Pred, state->BindExpr(IE, V)); return; } for (InitListExpr::const_reverse_iterator it = IE->rbegin(), ei = IE->rend(); it != ei; ++it) { vals = getBasicVals().consVals(state->getSVal(cast(*it)), vals); } MakeNode(Dst, IE, Pred, state->BindExpr(IE, svalBuilder.makeCompoundVal(T, vals))); return; } if (Loc::isLocType(T) || T->isIntegerType()) { assert(IE->getNumInits() == 1); const Expr *initEx = IE->getInit(0); MakeNode(Dst, IE, Pred, state->BindExpr(IE, state->getSVal(initEx))); return; } llvm_unreachable("unprocessed InitListExpr type"); } void ExprEngine::VisitGuardedExpr(const Expr *Ex, const Expr *L, const Expr *R, ExplodedNode *Pred, ExplodedNodeSet &Dst) { const ProgramState *state = Pred->getState(); SVal X = state->getSVal(Ex); assert (X.isUndef()); const Expr *SE = (Expr*) cast(X).getData(); assert(SE); X = state->getSVal(SE); // Make sure that we invalidate the previous binding. MakeNode(Dst, Ex, Pred, state->BindExpr(Ex, X, true)); } void ExprEngine:: VisitOffsetOfExpr(const OffsetOfExpr *OOE, ExplodedNode *Pred, ExplodedNodeSet &Dst) { Expr::EvalResult Res; if (OOE->Evaluate(Res, getContext()) && Res.Val.isInt()) { const APSInt &IV = Res.Val.getInt(); assert(IV.getBitWidth() == getContext().getTypeSize(OOE->getType())); assert(OOE->getType()->isIntegerType()); assert(IV.isSigned() == OOE->getType()->isSignedIntegerOrEnumerationType()); SVal X = svalBuilder.makeIntVal(IV); MakeNode(Dst, OOE, Pred, Pred->getState()->BindExpr(OOE, X)); return; } // FIXME: Handle the case where __builtin_offsetof is not a constant. Dst.Add(Pred); } void ExprEngine:: VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *Ex, ExplodedNode *Pred, ExplodedNodeSet &Dst) { QualType T = Ex->getTypeOfArgument(); 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. Dst.Add(Pred); return; } 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. Dst.Add(Pred); return; } } Expr::EvalResult Result; Ex->Evaluate(Result, getContext()); CharUnits amt = CharUnits::fromQuantity(Result.Val.getInt().getZExtValue()); const ProgramState *state = Pred->getState(); state = state->BindExpr(Ex, svalBuilder.makeIntVal(amt.getQuantity(), Ex->getType())); MakeNode(Dst, Ex, Pred, state); } void ExprEngine::VisitUnaryOperator(const UnaryOperator* U, ExplodedNode *Pred, ExplodedNodeSet &Dst) { switch (U->getOpcode()) { default: break; case UO_Real: { const Expr *Ex = U->getSubExpr()->IgnoreParens(); ExplodedNodeSet Tmp; Visit(Ex, Pred, Tmp); for (ExplodedNodeSet::iterator I=Tmp.begin(), E=Tmp.end(); I!=E; ++I) { // FIXME: We don't have complex SValues yet. if (Ex->getType()->isAnyComplexType()) { // Just report "Unknown." Dst.Add(*I); continue; } // For all other types, UO_Real is an identity operation. assert (U->getType() == Ex->getType()); const ProgramState *state = (*I)->getState(); MakeNode(Dst, U, *I, state->BindExpr(U, state->getSVal(Ex))); } return; } case UO_Imag: { const Expr *Ex = U->getSubExpr()->IgnoreParens(); ExplodedNodeSet Tmp; Visit(Ex, Pred, Tmp); for (ExplodedNodeSet::iterator I=Tmp.begin(), E=Tmp.end(); I!=E; ++I) { // FIXME: We don't have complex SValues yet. if (Ex->getType()->isAnyComplexType()) { // Just report "Unknown." Dst.Add(*I); continue; } // For all other types, UO_Imag returns 0. const ProgramState *state = (*I)->getState(); SVal X = svalBuilder.makeZeroVal(Ex->getType()); MakeNode(Dst, U, *I, state->BindExpr(U, X)); } return; } case UO_Plus: assert(!U->isLValue()); // FALL-THROUGH. case UO_Deref: case UO_AddrOf: case UO_Extension: { // 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(); ExplodedNodeSet Tmp; Visit(Ex, Pred, Tmp); for (ExplodedNodeSet::iterator I=Tmp.begin(), E=Tmp.end(); I!=E; ++I) { const ProgramState *state = (*I)->getState(); MakeNode(Dst, U, *I, state->BindExpr(U, state->getSVal(Ex))); } return; } case UO_LNot: case UO_Minus: case UO_Not: { assert (!U->isLValue()); const Expr *Ex = U->getSubExpr()->IgnoreParens(); ExplodedNodeSet Tmp; Visit(Ex, Pred, Tmp); for (ExplodedNodeSet::iterator I=Tmp.begin(), E=Tmp.end(); I!=E; ++I) { const ProgramState *state = (*I)->getState(); // Get the value of the subexpression. SVal V = state->getSVal(Ex); if (V.isUnknownOrUndef()) { MakeNode(Dst, U, *I, state->BindExpr(U, V)); continue; } switch (U->getOpcode()) { default: llvm_unreachable("Invalid Opcode."); case UO_Not: // FIXME: Do we need to handle promotions? state = state->BindExpr(U, evalComplement(cast(V))); break; case UO_Minus: // FIXME: Do we need to handle promotions? state = state->BindExpr(U, evalMinus(cast(V))); 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 (isa(V)) { Loc X = svalBuilder.makeNull(); Result = evalBinOp(state, BO_EQ, cast(V), X, U->getType()); } else { nonloc::ConcreteInt X(getBasicVals().getValue(0, Ex->getType())); Result = evalBinOp(state, BO_EQ, cast(V), X, U->getType()); } state = state->BindExpr(U, Result); break; } MakeNode(Dst, U, *I, state); } return; } } // Handle ++ and -- (both pre- and post-increment). assert (U->isIncrementDecrementOp()); ExplodedNodeSet Tmp; const Expr *Ex = U->getSubExpr()->IgnoreParens(); Visit(Ex, Pred, Tmp); for (ExplodedNodeSet::iterator I = Tmp.begin(), E = Tmp.end(); I!=E; ++I) { const ProgramState *state = (*I)->getState(); SVal loc = state->getSVal(Ex); // Perform a load. ExplodedNodeSet Tmp2; evalLoad(Tmp2, Ex, *I, state, loc); for (ExplodedNodeSet::iterator I2=Tmp2.begin(), E2=Tmp2.end();I2!=E2;++I2) { state = (*I2)->getState(); SVal V2_untested = state->getSVal(Ex); // Propagate unknown and undefined values. if (V2_untested.isUnknownOrUndef()) { MakeNode(Dst, U, *I2, state->BindExpr(U, V2_untested)); continue; } DefinedSVal V2 = cast(V2_untested); // 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; if (U->getType()->isAnyPointerType()) RHS = svalBuilder.makeArrayIndex(1); else RHS = svalBuilder.makeIntVal(1, U->getType()); SVal Result = evalBinOp(state, Op, V2, RHS, U->getType()); // Conjure a new symbol if necessary to recover precision. if (Result.isUnknown() || !getConstraintManager().canReasonAbout(Result)){ DefinedOrUnknownSVal SymVal = svalBuilder.getConjuredSymbolVal(NULL, Ex, Builder->getCurrentBlockCount()); 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->isLValue()) state = state->BindExpr(U, loc); else state = state->BindExpr(U, U->isPostfix() ? V2 : Result); // Perform the store. evalStore(Dst, NULL, U, *I2, state, loc, Result); } } }