| //===- ExprClassification.cpp - Expression AST Node Implementation --------===// |
| // |
| // 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 implements Expr::classify. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "clang/AST/Expr.h" |
| #include "clang/AST/ASTContext.h" |
| #include "clang/AST/DeclCXX.h" |
| #include "clang/AST/DeclObjC.h" |
| #include "clang/AST/DeclTemplate.h" |
| #include "clang/AST/ExprCXX.h" |
| #include "clang/AST/ExprObjC.h" |
| #include "llvm/Support/ErrorHandling.h" |
| |
| using namespace clang; |
| |
| using Cl = Expr::Classification; |
| |
| static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E); |
| static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D); |
| static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T); |
| static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E); |
| static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E); |
| static Cl::Kinds ClassifyConditional(ASTContext &Ctx, |
| const Expr *trueExpr, |
| const Expr *falseExpr); |
| static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, |
| Cl::Kinds Kind, SourceLocation &Loc); |
| |
| Cl Expr::ClassifyImpl(ASTContext &Ctx, SourceLocation *Loc) const { |
| assert(!TR->isReferenceType() && "Expressions can't have reference type."); |
| |
| Cl::Kinds kind = ClassifyInternal(Ctx, this); |
| // C99 6.3.2.1: An lvalue is an expression with an object type or an |
| // incomplete type other than void. |
| if (!Ctx.getLangOpts().CPlusPlus) { |
| // Thus, no functions. |
| if (TR->isFunctionType() || TR == Ctx.OverloadTy) |
| kind = Cl::CL_Function; |
| // No void either, but qualified void is OK because it is "other than void". |
| // Void "lvalues" are classified as addressable void values, which are void |
| // expressions whose address can be taken. |
| else if (TR->isVoidType() && !TR.hasQualifiers()) |
| kind = (kind == Cl::CL_LValue ? Cl::CL_AddressableVoid : Cl::CL_Void); |
| } |
| |
| // Enable this assertion for testing. |
| switch (kind) { |
| case Cl::CL_LValue: assert(getValueKind() == VK_LValue); break; |
| case Cl::CL_XValue: assert(getValueKind() == VK_XValue); break; |
| case Cl::CL_Function: |
| case Cl::CL_Void: |
| case Cl::CL_AddressableVoid: |
| case Cl::CL_DuplicateVectorComponents: |
| case Cl::CL_MemberFunction: |
| case Cl::CL_SubObjCPropertySetting: |
| case Cl::CL_ClassTemporary: |
| case Cl::CL_ArrayTemporary: |
| case Cl::CL_ObjCMessageRValue: |
| case Cl::CL_PRValue: assert(getValueKind() == VK_RValue); break; |
| } |
| |
| Cl::ModifiableType modifiable = Cl::CM_Untested; |
| if (Loc) |
| modifiable = IsModifiable(Ctx, this, kind, *Loc); |
| return Classification(kind, modifiable); |
| } |
| |
| /// Classify an expression which creates a temporary, based on its type. |
| static Cl::Kinds ClassifyTemporary(QualType T) { |
| if (T->isRecordType()) |
| return Cl::CL_ClassTemporary; |
| if (T->isArrayType()) |
| return Cl::CL_ArrayTemporary; |
| |
| // No special classification: these don't behave differently from normal |
| // prvalues. |
| return Cl::CL_PRValue; |
| } |
| |
| static Cl::Kinds ClassifyExprValueKind(const LangOptions &Lang, |
| const Expr *E, |
| ExprValueKind Kind) { |
| switch (Kind) { |
| case VK_RValue: |
| return Lang.CPlusPlus ? ClassifyTemporary(E->getType()) : Cl::CL_PRValue; |
| case VK_LValue: |
| return Cl::CL_LValue; |
| case VK_XValue: |
| return Cl::CL_XValue; |
| } |
| llvm_unreachable("Invalid value category of implicit cast."); |
| } |
| |
| static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) { |
| // This function takes the first stab at classifying expressions. |
| const LangOptions &Lang = Ctx.getLangOpts(); |
| |
| switch (E->getStmtClass()) { |
| case Stmt::NoStmtClass: |
| #define ABSTRACT_STMT(Kind) |
| #define STMT(Kind, Base) case Expr::Kind##Class: |
| #define EXPR(Kind, Base) |
| #include "clang/AST/StmtNodes.inc" |
| llvm_unreachable("cannot classify a statement"); |
| |
| // First come the expressions that are always lvalues, unconditionally. |
| case Expr::ObjCIsaExprClass: |
| // C++ [expr.prim.general]p1: A string literal is an lvalue. |
| case Expr::StringLiteralClass: |
| // @encode is equivalent to its string |
| case Expr::ObjCEncodeExprClass: |
| // __func__ and friends are too. |
| case Expr::PredefinedExprClass: |
| // Property references are lvalues |
| case Expr::ObjCSubscriptRefExprClass: |
| case Expr::ObjCPropertyRefExprClass: |
| // C++ [expr.typeid]p1: The result of a typeid expression is an lvalue of... |
| case Expr::CXXTypeidExprClass: |
| // Unresolved lookups and uncorrected typos get classified as lvalues. |
| // FIXME: Is this wise? Should they get their own kind? |
| case Expr::UnresolvedLookupExprClass: |
| case Expr::UnresolvedMemberExprClass: |
| case Expr::TypoExprClass: |
| case Expr::DependentCoawaitExprClass: |
| case Expr::CXXDependentScopeMemberExprClass: |
| case Expr::DependentScopeDeclRefExprClass: |
| // ObjC instance variables are lvalues |
| // FIXME: ObjC++0x might have different rules |
| case Expr::ObjCIvarRefExprClass: |
| case Expr::FunctionParmPackExprClass: |
| case Expr::MSPropertyRefExprClass: |
| case Expr::MSPropertySubscriptExprClass: |
| case Expr::OMPArraySectionExprClass: |
| return Cl::CL_LValue; |
| |
| // C99 6.5.2.5p5 says that compound literals are lvalues. |
| // In C++, they're prvalue temporaries, except for file-scope arrays. |
| case Expr::CompoundLiteralExprClass: |
| return !E->isLValue() ? ClassifyTemporary(E->getType()) : Cl::CL_LValue; |
| |
| // Expressions that are prvalues. |
| case Expr::CXXBoolLiteralExprClass: |
| case Expr::CXXPseudoDestructorExprClass: |
| case Expr::UnaryExprOrTypeTraitExprClass: |
| case Expr::CXXNewExprClass: |
| case Expr::CXXThisExprClass: |
| case Expr::CXXNullPtrLiteralExprClass: |
| case Expr::ImaginaryLiteralClass: |
| case Expr::GNUNullExprClass: |
| case Expr::OffsetOfExprClass: |
| case Expr::CXXThrowExprClass: |
| case Expr::ShuffleVectorExprClass: |
| case Expr::ConvertVectorExprClass: |
| case Expr::IntegerLiteralClass: |
| case Expr::FixedPointLiteralClass: |
| case Expr::CharacterLiteralClass: |
| case Expr::AddrLabelExprClass: |
| case Expr::CXXDeleteExprClass: |
| case Expr::ImplicitValueInitExprClass: |
| case Expr::BlockExprClass: |
| case Expr::FloatingLiteralClass: |
| case Expr::CXXNoexceptExprClass: |
| case Expr::CXXScalarValueInitExprClass: |
| case Expr::TypeTraitExprClass: |
| case Expr::ArrayTypeTraitExprClass: |
| case Expr::ExpressionTraitExprClass: |
| case Expr::ObjCSelectorExprClass: |
| case Expr::ObjCProtocolExprClass: |
| case Expr::ObjCStringLiteralClass: |
| case Expr::ObjCBoxedExprClass: |
| case Expr::ObjCArrayLiteralClass: |
| case Expr::ObjCDictionaryLiteralClass: |
| case Expr::ObjCBoolLiteralExprClass: |
| case Expr::ObjCAvailabilityCheckExprClass: |
| case Expr::ParenListExprClass: |
| case Expr::SizeOfPackExprClass: |
| case Expr::SubstNonTypeTemplateParmPackExprClass: |
| case Expr::AsTypeExprClass: |
| case Expr::ObjCIndirectCopyRestoreExprClass: |
| case Expr::AtomicExprClass: |
| case Expr::CXXFoldExprClass: |
| case Expr::ArrayInitLoopExprClass: |
| case Expr::ArrayInitIndexExprClass: |
| case Expr::NoInitExprClass: |
| case Expr::DesignatedInitUpdateExprClass: |
| case Expr::SourceLocExprClass: |
| case Expr::ConceptSpecializationExprClass: |
| return Cl::CL_PRValue; |
| |
| case Expr::ConstantExprClass: |
| return ClassifyInternal(Ctx, cast<ConstantExpr>(E)->getSubExpr()); |
| |
| // Next come the complicated cases. |
| case Expr::SubstNonTypeTemplateParmExprClass: |
| return ClassifyInternal(Ctx, |
| cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement()); |
| |
| // C, C++98 [expr.sub]p1: The result is an lvalue of type "T". |
| // C++11 (DR1213): in the case of an array operand, the result is an lvalue |
| // if that operand is an lvalue and an xvalue otherwise. |
| // Subscripting vector types is more like member access. |
| case Expr::ArraySubscriptExprClass: |
| if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType()) |
| return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase()); |
| if (Lang.CPlusPlus11) { |
| // Step over the array-to-pointer decay if present, but not over the |
| // temporary materialization. |
| auto *Base = cast<ArraySubscriptExpr>(E)->getBase()->IgnoreImpCasts(); |
| if (Base->getType()->isArrayType()) |
| return ClassifyInternal(Ctx, Base); |
| } |
| return Cl::CL_LValue; |
| |
| // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a |
| // function or variable and a prvalue otherwise. |
| case Expr::DeclRefExprClass: |
| if (E->getType() == Ctx.UnknownAnyTy) |
| return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl()) |
| ? Cl::CL_PRValue : Cl::CL_LValue; |
| return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl()); |
| |
| // Member access is complex. |
| case Expr::MemberExprClass: |
| return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E)); |
| |
| case Expr::UnaryOperatorClass: |
| switch (cast<UnaryOperator>(E)->getOpcode()) { |
| // C++ [expr.unary.op]p1: The unary * operator performs indirection: |
| // [...] the result is an lvalue referring to the object or function |
| // to which the expression points. |
| case UO_Deref: |
| return Cl::CL_LValue; |
| |
| // GNU extensions, simply look through them. |
| case UO_Extension: |
| return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr()); |
| |
| // Treat _Real and _Imag basically as if they were member |
| // expressions: l-value only if the operand is a true l-value. |
| case UO_Real: |
| case UO_Imag: { |
| const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens(); |
| Cl::Kinds K = ClassifyInternal(Ctx, Op); |
| if (K != Cl::CL_LValue) return K; |
| |
| if (isa<ObjCPropertyRefExpr>(Op)) |
| return Cl::CL_SubObjCPropertySetting; |
| return Cl::CL_LValue; |
| } |
| |
| // C++ [expr.pre.incr]p1: The result is the updated operand; it is an |
| // lvalue, [...] |
| // Not so in C. |
| case UO_PreInc: |
| case UO_PreDec: |
| return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue; |
| |
| default: |
| return Cl::CL_PRValue; |
| } |
| |
| case Expr::OpaqueValueExprClass: |
| return ClassifyExprValueKind(Lang, E, E->getValueKind()); |
| |
| // Pseudo-object expressions can produce l-values with reference magic. |
| case Expr::PseudoObjectExprClass: |
| return ClassifyExprValueKind(Lang, E, |
| cast<PseudoObjectExpr>(E)->getValueKind()); |
| |
| // Implicit casts are lvalues if they're lvalue casts. Other than that, we |
| // only specifically record class temporaries. |
| case Expr::ImplicitCastExprClass: |
| return ClassifyExprValueKind(Lang, E, E->getValueKind()); |
| |
| // C++ [expr.prim.general]p4: The presence of parentheses does not affect |
| // whether the expression is an lvalue. |
| case Expr::ParenExprClass: |
| return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr()); |
| |
| // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator, |
| // or a void expression if its result expression is, respectively, an |
| // lvalue, a function designator, or a void expression. |
| case Expr::GenericSelectionExprClass: |
| if (cast<GenericSelectionExpr>(E)->isResultDependent()) |
| return Cl::CL_PRValue; |
| return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr()); |
| |
| case Expr::BinaryOperatorClass: |
| case Expr::CompoundAssignOperatorClass: |
| // C doesn't have any binary expressions that are lvalues. |
| if (Lang.CPlusPlus) |
| return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E)); |
| return Cl::CL_PRValue; |
| |
| case Expr::CallExprClass: |
| case Expr::CXXOperatorCallExprClass: |
| case Expr::CXXMemberCallExprClass: |
| case Expr::UserDefinedLiteralClass: |
| case Expr::CUDAKernelCallExprClass: |
| return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType(Ctx)); |
| |
| // __builtin_choose_expr is equivalent to the chosen expression. |
| case Expr::ChooseExprClass: |
| return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr()); |
| |
| // Extended vector element access is an lvalue unless there are duplicates |
| // in the shuffle expression. |
| case Expr::ExtVectorElementExprClass: |
| if (cast<ExtVectorElementExpr>(E)->containsDuplicateElements()) |
| return Cl::CL_DuplicateVectorComponents; |
| if (cast<ExtVectorElementExpr>(E)->isArrow()) |
| return Cl::CL_LValue; |
| return ClassifyInternal(Ctx, cast<ExtVectorElementExpr>(E)->getBase()); |
| |
| // Simply look at the actual default argument. |
| case Expr::CXXDefaultArgExprClass: |
| return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr()); |
| |
| // Same idea for default initializers. |
| case Expr::CXXDefaultInitExprClass: |
| return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr()); |
| |
| // Same idea for temporary binding. |
| case Expr::CXXBindTemporaryExprClass: |
| return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr()); |
| |
| // And the cleanups guard. |
| case Expr::ExprWithCleanupsClass: |
| return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr()); |
| |
| // Casts depend completely on the target type. All casts work the same. |
| case Expr::CStyleCastExprClass: |
| case Expr::CXXFunctionalCastExprClass: |
| case Expr::CXXStaticCastExprClass: |
| case Expr::CXXDynamicCastExprClass: |
| case Expr::CXXReinterpretCastExprClass: |
| case Expr::CXXConstCastExprClass: |
| case Expr::ObjCBridgedCastExprClass: |
| case Expr::BuiltinBitCastExprClass: |
| // Only in C++ can casts be interesting at all. |
| if (!Lang.CPlusPlus) return Cl::CL_PRValue; |
| return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten()); |
| |
| case Expr::CXXUnresolvedConstructExprClass: |
| return ClassifyUnnamed(Ctx, |
| cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten()); |
| |
| case Expr::BinaryConditionalOperatorClass: { |
| if (!Lang.CPlusPlus) return Cl::CL_PRValue; |
| const auto *co = cast<BinaryConditionalOperator>(E); |
| return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); |
| } |
| |
| case Expr::ConditionalOperatorClass: { |
| // Once again, only C++ is interesting. |
| if (!Lang.CPlusPlus) return Cl::CL_PRValue; |
| const auto *co = cast<ConditionalOperator>(E); |
| return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); |
| } |
| |
| // ObjC message sends are effectively function calls, if the target function |
| // is known. |
| case Expr::ObjCMessageExprClass: |
| if (const ObjCMethodDecl *Method = |
| cast<ObjCMessageExpr>(E)->getMethodDecl()) { |
| Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getReturnType()); |
| return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind; |
| } |
| return Cl::CL_PRValue; |
| |
| // Some C++ expressions are always class temporaries. |
| case Expr::CXXConstructExprClass: |
| case Expr::CXXInheritedCtorInitExprClass: |
| case Expr::CXXTemporaryObjectExprClass: |
| case Expr::LambdaExprClass: |
| case Expr::CXXStdInitializerListExprClass: |
| return Cl::CL_ClassTemporary; |
| |
| case Expr::VAArgExprClass: |
| return ClassifyUnnamed(Ctx, E->getType()); |
| |
| case Expr::DesignatedInitExprClass: |
| return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit()); |
| |
| case Expr::StmtExprClass: { |
| const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt(); |
| if (const auto *LastExpr = dyn_cast_or_null<Expr>(S->body_back())) |
| return ClassifyUnnamed(Ctx, LastExpr->getType()); |
| return Cl::CL_PRValue; |
| } |
| |
| case Expr::CXXUuidofExprClass: |
| return Cl::CL_LValue; |
| |
| case Expr::PackExpansionExprClass: |
| return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern()); |
| |
| case Expr::MaterializeTemporaryExprClass: |
| return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference() |
| ? Cl::CL_LValue |
| : Cl::CL_XValue; |
| |
| case Expr::InitListExprClass: |
| // An init list can be an lvalue if it is bound to a reference and |
| // contains only one element. In that case, we look at that element |
| // for an exact classification. Init list creation takes care of the |
| // value kind for us, so we only need to fine-tune. |
| if (E->isRValue()) |
| return ClassifyExprValueKind(Lang, E, E->getValueKind()); |
| assert(cast<InitListExpr>(E)->getNumInits() == 1 && |
| "Only 1-element init lists can be glvalues."); |
| return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0)); |
| |
| case Expr::CoawaitExprClass: |
| case Expr::CoyieldExprClass: |
| return ClassifyInternal(Ctx, cast<CoroutineSuspendExpr>(E)->getResumeExpr()); |
| } |
| |
| llvm_unreachable("unhandled expression kind in classification"); |
| } |
| |
| /// ClassifyDecl - Return the classification of an expression referencing the |
| /// given declaration. |
| static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) { |
| // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a |
| // function, variable, or data member and a prvalue otherwise. |
| // In C, functions are not lvalues. |
| // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an |
| // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to |
| // special-case this. |
| |
| if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance()) |
| return Cl::CL_MemberFunction; |
| |
| bool islvalue; |
| if (const auto *NTTParm = dyn_cast<NonTypeTemplateParmDecl>(D)) |
| islvalue = NTTParm->getType()->isReferenceType(); |
| else |
| islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) || |
| isa<IndirectFieldDecl>(D) || |
| isa<BindingDecl>(D) || |
| (Ctx.getLangOpts().CPlusPlus && |
| (isa<FunctionDecl>(D) || isa<MSPropertyDecl>(D) || |
| isa<FunctionTemplateDecl>(D))); |
| |
| return islvalue ? Cl::CL_LValue : Cl::CL_PRValue; |
| } |
| |
| /// ClassifyUnnamed - Return the classification of an expression yielding an |
| /// unnamed value of the given type. This applies in particular to function |
| /// calls and casts. |
| static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) { |
| // In C, function calls are always rvalues. |
| if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue; |
| |
| // C++ [expr.call]p10: A function call is an lvalue if the result type is an |
| // lvalue reference type or an rvalue reference to function type, an xvalue |
| // if the result type is an rvalue reference to object type, and a prvalue |
| // otherwise. |
| if (T->isLValueReferenceType()) |
| return Cl::CL_LValue; |
| const auto *RV = T->getAs<RValueReferenceType>(); |
| if (!RV) // Could still be a class temporary, though. |
| return ClassifyTemporary(T); |
| |
| return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue; |
| } |
| |
| static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) { |
| if (E->getType() == Ctx.UnknownAnyTy) |
| return (isa<FunctionDecl>(E->getMemberDecl()) |
| ? Cl::CL_PRValue : Cl::CL_LValue); |
| |
| // Handle C first, it's easier. |
| if (!Ctx.getLangOpts().CPlusPlus) { |
| // C99 6.5.2.3p3 |
| // For dot access, the expression is an lvalue if the first part is. For |
| // arrow access, it always is an lvalue. |
| if (E->isArrow()) |
| return Cl::CL_LValue; |
| // ObjC property accesses are not lvalues, but get special treatment. |
| Expr *Base = E->getBase()->IgnoreParens(); |
| if (isa<ObjCPropertyRefExpr>(Base)) |
| return Cl::CL_SubObjCPropertySetting; |
| return ClassifyInternal(Ctx, Base); |
| } |
| |
| NamedDecl *Member = E->getMemberDecl(); |
| // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2. |
| // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then |
| // E1.E2 is an lvalue. |
| if (const auto *Value = dyn_cast<ValueDecl>(Member)) |
| if (Value->getType()->isReferenceType()) |
| return Cl::CL_LValue; |
| |
| // Otherwise, one of the following rules applies. |
| // -- If E2 is a static member [...] then E1.E2 is an lvalue. |
| if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord()) |
| return Cl::CL_LValue; |
| |
| // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then |
| // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue; |
| // otherwise, it is a prvalue. |
| if (isa<FieldDecl>(Member)) { |
| // *E1 is an lvalue |
| if (E->isArrow()) |
| return Cl::CL_LValue; |
| Expr *Base = E->getBase()->IgnoreParenImpCasts(); |
| if (isa<ObjCPropertyRefExpr>(Base)) |
| return Cl::CL_SubObjCPropertySetting; |
| return ClassifyInternal(Ctx, E->getBase()); |
| } |
| |
| // -- If E2 is a [...] member function, [...] |
| // -- If it refers to a static member function [...], then E1.E2 is an |
| // lvalue; [...] |
| // -- Otherwise [...] E1.E2 is a prvalue. |
| if (const auto *Method = dyn_cast<CXXMethodDecl>(Member)) |
| return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction; |
| |
| // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue. |
| // So is everything else we haven't handled yet. |
| return Cl::CL_PRValue; |
| } |
| |
| static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) { |
| assert(Ctx.getLangOpts().CPlusPlus && |
| "This is only relevant for C++."); |
| // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand. |
| // Except we override this for writes to ObjC properties. |
| if (E->isAssignmentOp()) |
| return (E->getLHS()->getObjectKind() == OK_ObjCProperty |
| ? Cl::CL_PRValue : Cl::CL_LValue); |
| |
| // C++ [expr.comma]p1: the result is of the same value category as its right |
| // operand, [...]. |
| if (E->getOpcode() == BO_Comma) |
| return ClassifyInternal(Ctx, E->getRHS()); |
| |
| // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand |
| // is a pointer to a data member is of the same value category as its first |
| // operand. |
| if (E->getOpcode() == BO_PtrMemD) |
| return (E->getType()->isFunctionType() || |
| E->hasPlaceholderType(BuiltinType::BoundMember)) |
| ? Cl::CL_MemberFunction |
| : ClassifyInternal(Ctx, E->getLHS()); |
| |
| // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its |
| // second operand is a pointer to data member and a prvalue otherwise. |
| if (E->getOpcode() == BO_PtrMemI) |
| return (E->getType()->isFunctionType() || |
| E->hasPlaceholderType(BuiltinType::BoundMember)) |
| ? Cl::CL_MemberFunction |
| : Cl::CL_LValue; |
| |
| // All other binary operations are prvalues. |
| return Cl::CL_PRValue; |
| } |
| |
| static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True, |
| const Expr *False) { |
| assert(Ctx.getLangOpts().CPlusPlus && |
| "This is only relevant for C++."); |
| |
| // C++ [expr.cond]p2 |
| // If either the second or the third operand has type (cv) void, |
| // one of the following shall hold: |
| if (True->getType()->isVoidType() || False->getType()->isVoidType()) { |
| // The second or the third operand (but not both) is a (possibly |
| // parenthesized) throw-expression; the result is of the [...] value |
| // category of the other. |
| bool TrueIsThrow = isa<CXXThrowExpr>(True->IgnoreParenImpCasts()); |
| bool FalseIsThrow = isa<CXXThrowExpr>(False->IgnoreParenImpCasts()); |
| if (const Expr *NonThrow = TrueIsThrow ? (FalseIsThrow ? nullptr : False) |
| : (FalseIsThrow ? True : nullptr)) |
| return ClassifyInternal(Ctx, NonThrow); |
| |
| // [Otherwise] the result [...] is a prvalue. |
| return Cl::CL_PRValue; |
| } |
| |
| // Note that at this point, we have already performed all conversions |
| // according to [expr.cond]p3. |
| // C++ [expr.cond]p4: If the second and third operands are glvalues of the |
| // same value category [...], the result is of that [...] value category. |
| // C++ [expr.cond]p5: Otherwise, the result is a prvalue. |
| Cl::Kinds LCl = ClassifyInternal(Ctx, True), |
| RCl = ClassifyInternal(Ctx, False); |
| return LCl == RCl ? LCl : Cl::CL_PRValue; |
| } |
| |
| static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, |
| Cl::Kinds Kind, SourceLocation &Loc) { |
| // As a general rule, we only care about lvalues. But there are some rvalues |
| // for which we want to generate special results. |
| if (Kind == Cl::CL_PRValue) { |
| // For the sake of better diagnostics, we want to specifically recognize |
| // use of the GCC cast-as-lvalue extension. |
| if (const auto *CE = dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) { |
| if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) { |
| Loc = CE->getExprLoc(); |
| return Cl::CM_LValueCast; |
| } |
| } |
| } |
| if (Kind != Cl::CL_LValue) |
| return Cl::CM_RValue; |
| |
| // This is the lvalue case. |
| // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6) |
| if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType()) |
| return Cl::CM_Function; |
| |
| // Assignment to a property in ObjC is an implicit setter access. But a |
| // setter might not exist. |
| if (const auto *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) { |
| if (Expr->isImplicitProperty() && |
| Expr->getImplicitPropertySetter() == nullptr) |
| return Cl::CM_NoSetterProperty; |
| } |
| |
| CanQualType CT = Ctx.getCanonicalType(E->getType()); |
| // Const stuff is obviously not modifiable. |
| if (CT.isConstQualified()) |
| return Cl::CM_ConstQualified; |
| if (Ctx.getLangOpts().OpenCL && |
| CT.getQualifiers().getAddressSpace() == LangAS::opencl_constant) |
| return Cl::CM_ConstAddrSpace; |
| |
| // Arrays are not modifiable, only their elements are. |
| if (CT->isArrayType()) |
| return Cl::CM_ArrayType; |
| // Incomplete types are not modifiable. |
| if (CT->isIncompleteType()) |
| return Cl::CM_IncompleteType; |
| |
| // Records with any const fields (recursively) are not modifiable. |
| if (const RecordType *R = CT->getAs<RecordType>()) |
| if (R->hasConstFields()) |
| return Cl::CM_ConstQualifiedField; |
| |
| return Cl::CM_Modifiable; |
| } |
| |
| Expr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const { |
| Classification VC = Classify(Ctx); |
| switch (VC.getKind()) { |
| case Cl::CL_LValue: return LV_Valid; |
| case Cl::CL_XValue: return LV_InvalidExpression; |
| case Cl::CL_Function: return LV_NotObjectType; |
| case Cl::CL_Void: return LV_InvalidExpression; |
| case Cl::CL_AddressableVoid: return LV_IncompleteVoidType; |
| case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents; |
| case Cl::CL_MemberFunction: return LV_MemberFunction; |
| case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting; |
| case Cl::CL_ClassTemporary: return LV_ClassTemporary; |
| case Cl::CL_ArrayTemporary: return LV_ArrayTemporary; |
| case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression; |
| case Cl::CL_PRValue: return LV_InvalidExpression; |
| } |
| llvm_unreachable("Unhandled kind"); |
| } |
| |
| Expr::isModifiableLvalueResult |
| Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const { |
| SourceLocation dummy; |
| Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy); |
| switch (VC.getKind()) { |
| case Cl::CL_LValue: break; |
| case Cl::CL_XValue: return MLV_InvalidExpression; |
| case Cl::CL_Function: return MLV_NotObjectType; |
| case Cl::CL_Void: return MLV_InvalidExpression; |
| case Cl::CL_AddressableVoid: return MLV_IncompleteVoidType; |
| case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents; |
| case Cl::CL_MemberFunction: return MLV_MemberFunction; |
| case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting; |
| case Cl::CL_ClassTemporary: return MLV_ClassTemporary; |
| case Cl::CL_ArrayTemporary: return MLV_ArrayTemporary; |
| case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression; |
| case Cl::CL_PRValue: |
| return VC.getModifiable() == Cl::CM_LValueCast ? |
| MLV_LValueCast : MLV_InvalidExpression; |
| } |
| assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind"); |
| switch (VC.getModifiable()) { |
| case Cl::CM_Untested: llvm_unreachable("Did not test modifiability"); |
| case Cl::CM_Modifiable: return MLV_Valid; |
| case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match"); |
| case Cl::CM_Function: return MLV_NotObjectType; |
| case Cl::CM_LValueCast: |
| llvm_unreachable("CM_LValueCast and CL_LValue don't match"); |
| case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty; |
| case Cl::CM_ConstQualified: return MLV_ConstQualified; |
| case Cl::CM_ConstQualifiedField: return MLV_ConstQualifiedField; |
| case Cl::CM_ConstAddrSpace: return MLV_ConstAddrSpace; |
| case Cl::CM_ArrayType: return MLV_ArrayType; |
| case Cl::CM_IncompleteType: return MLV_IncompleteType; |
| } |
| llvm_unreachable("Unhandled modifiable type"); |
| } |