15821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)//===--- ExprClassification.cpp - Expression AST Node Implementation ------===// 25821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 35821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// The LLVM Compiler Infrastructure 45821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 55821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// This file is distributed under the University of Illinois Open Source 65821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// License. See LICENSE.TXT for details. 75821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 85821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)//===----------------------------------------------------------------------===// 95821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// This file implements Expr::classify. 112a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)// 12c2e0dbddbe15c98d52c4786dac06cb8952a8ae6dTorne (Richard Coles)//===----------------------------------------------------------------------===// 135821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 145821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "clang/AST/Expr.h" 155821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "clang/AST/ASTContext.h" 165821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "clang/AST/DeclCXX.h" 175821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "clang/AST/DeclObjC.h" 185821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "clang/AST/DeclTemplate.h" 195821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "clang/AST/ExprCXX.h" 205821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "clang/AST/ExprObjC.h" 215821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/Support/ErrorHandling.h" 225821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)using namespace clang; 235821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 245821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)typedef Expr::Classification Cl; 255821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 265821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E); 275821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D); 285821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T); 295821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E); 302a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles)static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E); 315821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)static Cl::Kinds ClassifyConditional(ASTContext &Ctx, 325821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) const Expr *trueExpr, 335821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) const Expr *falseExpr); 345821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, 355821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Cl::Kinds Kind, SourceLocation &Loc); 365821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 375821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)Cl Expr::ClassifyImpl(ASTContext &Ctx, SourceLocation *Loc) const { 385821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) assert(!TR->isReferenceType() && "Expressions can't have reference type."); 395821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 405821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Cl::Kinds kind = ClassifyInternal(Ctx, this); 415821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // C99 6.3.2.1: An lvalue is an expression with an object type or an 425821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // incomplete type other than void. 435821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (!Ctx.getLangOpts().CPlusPlus) { 445821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Thus, no functions. 455821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (TR->isFunctionType() || TR == Ctx.OverloadTy) 465821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) kind = Cl::CL_Function; 475821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // No void either, but qualified void is OK because it is "other than void". 485821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Void "lvalues" are classified as addressable void values, which are void 495821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // expressions whose address can be taken. 505821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) else if (TR->isVoidType() && !TR.hasQualifiers()) 515821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) kind = (kind == Cl::CL_LValue ? Cl::CL_AddressableVoid : Cl::CL_Void); 525821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) } 535821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 545821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // Enable this assertion for testing. 555821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) switch (kind) { 565821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) case Cl::CL_LValue: assert(getValueKind() == VK_LValue); break; 575821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) case Cl::CL_XValue: assert(getValueKind() == VK_XValue); break; 587d4cd473f85ac64c3747c96c277f9e506a0d2246Torne (Richard Coles) case Cl::CL_Function: 595821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) case Cl::CL_Void: 605821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) case Cl::CL_AddressableVoid: 615821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) case Cl::CL_DuplicateVectorComponents: 625821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) case Cl::CL_MemberFunction: 637d4cd473f85ac64c3747c96c277f9e506a0d2246Torne (Richard Coles) case Cl::CL_SubObjCPropertySetting: 645821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) case Cl::CL_ClassTemporary: 655821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) case Cl::CL_ArrayTemporary: 665821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) case Cl::CL_ObjCMessageRValue: 675821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) case Cl::CL_PRValue: assert(getValueKind() == VK_RValue); break; 687d4cd473f85ac64c3747c96c277f9e506a0d2246Torne (Richard Coles) } 695821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 705821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) Cl::ModifiableType modifiable = Cl::CM_Untested; 715821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (Loc) 725821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) modifiable = IsModifiable(Ctx, this, kind, *Loc); 735821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return Classification(kind, modifiable); 745821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 755821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 765821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)/// Classify an expression which creates a temporary, based on its type. 775821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)static Cl::Kinds ClassifyTemporary(QualType T) { 785821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (T->isRecordType()) 795821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return Cl::CL_ClassTemporary; 805821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) if (T->isArrayType()) 81868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles) return Cl::CL_ArrayTemporary; 825821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 835821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) // No special classification: these don't behave differently from normal 842a99a7e74a7f215066514fe81d2bfa6639d9edddTorne (Richard Coles) // prvalues. 855821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) return Cl::CL_PRValue; 865821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)} 875821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 88static Cl::Kinds ClassifyExprValueKind(const LangOptions &Lang, 89 const Expr *E, 90 ExprValueKind Kind) { 91 switch (Kind) { 92 case VK_RValue: 93 return Lang.CPlusPlus ? ClassifyTemporary(E->getType()) : Cl::CL_PRValue; 94 case VK_LValue: 95 return Cl::CL_LValue; 96 case VK_XValue: 97 return Cl::CL_XValue; 98 } 99 llvm_unreachable("Invalid value category of implicit cast."); 100} 101 102static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) { 103 // This function takes the first stab at classifying expressions. 104 const LangOptions &Lang = Ctx.getLangOpts(); 105 106 switch (E->getStmtClass()) { 107 case Stmt::NoStmtClass: 108#define ABSTRACT_STMT(Kind) 109#define STMT(Kind, Base) case Expr::Kind##Class: 110#define EXPR(Kind, Base) 111#include "clang/AST/StmtNodes.inc" 112 llvm_unreachable("cannot classify a statement"); 113 114 // First come the expressions that are always lvalues, unconditionally. 115 case Expr::ObjCIsaExprClass: 116 // C++ [expr.prim.general]p1: A string literal is an lvalue. 117 case Expr::StringLiteralClass: 118 // @encode is equivalent to its string 119 case Expr::ObjCEncodeExprClass: 120 // __func__ and friends are too. 121 case Expr::PredefinedExprClass: 122 // Property references are lvalues 123 case Expr::ObjCSubscriptRefExprClass: 124 case Expr::ObjCPropertyRefExprClass: 125 // C++ [expr.typeid]p1: The result of a typeid expression is an lvalue of... 126 case Expr::CXXTypeidExprClass: 127 // Unresolved lookups get classified as lvalues. 128 // FIXME: Is this wise? Should they get their own kind? 129 case Expr::UnresolvedLookupExprClass: 130 case Expr::UnresolvedMemberExprClass: 131 case Expr::CXXDependentScopeMemberExprClass: 132 case Expr::DependentScopeDeclRefExprClass: 133 // ObjC instance variables are lvalues 134 // FIXME: ObjC++0x might have different rules 135 case Expr::ObjCIvarRefExprClass: 136 case Expr::FunctionParmPackExprClass: 137 case Expr::MSPropertyRefExprClass: 138 return Cl::CL_LValue; 139 140 // C99 6.5.2.5p5 says that compound literals are lvalues. 141 // In C++, they're prvalue temporaries. 142 case Expr::CompoundLiteralExprClass: 143 return Ctx.getLangOpts().CPlusPlus ? ClassifyTemporary(E->getType()) 144 : Cl::CL_LValue; 145 146 // Expressions that are prvalues. 147 case Expr::CXXBoolLiteralExprClass: 148 case Expr::CXXPseudoDestructorExprClass: 149 case Expr::UnaryExprOrTypeTraitExprClass: 150 case Expr::CXXNewExprClass: 151 case Expr::CXXThisExprClass: 152 case Expr::CXXNullPtrLiteralExprClass: 153 case Expr::ImaginaryLiteralClass: 154 case Expr::GNUNullExprClass: 155 case Expr::OffsetOfExprClass: 156 case Expr::CXXThrowExprClass: 157 case Expr::ShuffleVectorExprClass: 158 case Expr::ConvertVectorExprClass: 159 case Expr::IntegerLiteralClass: 160 case Expr::CharacterLiteralClass: 161 case Expr::AddrLabelExprClass: 162 case Expr::CXXDeleteExprClass: 163 case Expr::ImplicitValueInitExprClass: 164 case Expr::BlockExprClass: 165 case Expr::FloatingLiteralClass: 166 case Expr::CXXNoexceptExprClass: 167 case Expr::CXXScalarValueInitExprClass: 168 case Expr::TypeTraitExprClass: 169 case Expr::ArrayTypeTraitExprClass: 170 case Expr::ExpressionTraitExprClass: 171 case Expr::ObjCSelectorExprClass: 172 case Expr::ObjCProtocolExprClass: 173 case Expr::ObjCStringLiteralClass: 174 case Expr::ObjCBoxedExprClass: 175 case Expr::ObjCArrayLiteralClass: 176 case Expr::ObjCDictionaryLiteralClass: 177 case Expr::ObjCBoolLiteralExprClass: 178 case Expr::ParenListExprClass: 179 case Expr::SizeOfPackExprClass: 180 case Expr::SubstNonTypeTemplateParmPackExprClass: 181 case Expr::AsTypeExprClass: 182 case Expr::ObjCIndirectCopyRestoreExprClass: 183 case Expr::AtomicExprClass: 184 return Cl::CL_PRValue; 185 186 // Next come the complicated cases. 187 case Expr::SubstNonTypeTemplateParmExprClass: 188 return ClassifyInternal(Ctx, 189 cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement()); 190 191 // C++ [expr.sub]p1: The result is an lvalue of type "T". 192 // However, subscripting vector types is more like member access. 193 case Expr::ArraySubscriptExprClass: 194 if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType()) 195 return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase()); 196 return Cl::CL_LValue; 197 198 // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a 199 // function or variable and a prvalue otherwise. 200 case Expr::DeclRefExprClass: 201 if (E->getType() == Ctx.UnknownAnyTy) 202 return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl()) 203 ? Cl::CL_PRValue : Cl::CL_LValue; 204 return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl()); 205 206 // Member access is complex. 207 case Expr::MemberExprClass: 208 return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E)); 209 210 case Expr::UnaryOperatorClass: 211 switch (cast<UnaryOperator>(E)->getOpcode()) { 212 // C++ [expr.unary.op]p1: The unary * operator performs indirection: 213 // [...] the result is an lvalue referring to the object or function 214 // to which the expression points. 215 case UO_Deref: 216 return Cl::CL_LValue; 217 218 // GNU extensions, simply look through them. 219 case UO_Extension: 220 return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr()); 221 222 // Treat _Real and _Imag basically as if they were member 223 // expressions: l-value only if the operand is a true l-value. 224 case UO_Real: 225 case UO_Imag: { 226 const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens(); 227 Cl::Kinds K = ClassifyInternal(Ctx, Op); 228 if (K != Cl::CL_LValue) return K; 229 230 if (isa<ObjCPropertyRefExpr>(Op)) 231 return Cl::CL_SubObjCPropertySetting; 232 return Cl::CL_LValue; 233 } 234 235 // C++ [expr.pre.incr]p1: The result is the updated operand; it is an 236 // lvalue, [...] 237 // Not so in C. 238 case UO_PreInc: 239 case UO_PreDec: 240 return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue; 241 242 default: 243 return Cl::CL_PRValue; 244 } 245 246 case Expr::OpaqueValueExprClass: 247 return ClassifyExprValueKind(Lang, E, E->getValueKind()); 248 249 // Pseudo-object expressions can produce l-values with reference magic. 250 case Expr::PseudoObjectExprClass: 251 return ClassifyExprValueKind(Lang, E, 252 cast<PseudoObjectExpr>(E)->getValueKind()); 253 254 // Implicit casts are lvalues if they're lvalue casts. Other than that, we 255 // only specifically record class temporaries. 256 case Expr::ImplicitCastExprClass: 257 return ClassifyExprValueKind(Lang, E, E->getValueKind()); 258 259 // C++ [expr.prim.general]p4: The presence of parentheses does not affect 260 // whether the expression is an lvalue. 261 case Expr::ParenExprClass: 262 return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr()); 263 264 // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator, 265 // or a void expression if its result expression is, respectively, an 266 // lvalue, a function designator, or a void expression. 267 case Expr::GenericSelectionExprClass: 268 if (cast<GenericSelectionExpr>(E)->isResultDependent()) 269 return Cl::CL_PRValue; 270 return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr()); 271 272 case Expr::BinaryOperatorClass: 273 case Expr::CompoundAssignOperatorClass: 274 // C doesn't have any binary expressions that are lvalues. 275 if (Lang.CPlusPlus) 276 return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E)); 277 return Cl::CL_PRValue; 278 279 case Expr::CallExprClass: 280 case Expr::CXXOperatorCallExprClass: 281 case Expr::CXXMemberCallExprClass: 282 case Expr::UserDefinedLiteralClass: 283 case Expr::CUDAKernelCallExprClass: 284 return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType()); 285 286 // __builtin_choose_expr is equivalent to the chosen expression. 287 case Expr::ChooseExprClass: 288 return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr()); 289 290 // Extended vector element access is an lvalue unless there are duplicates 291 // in the shuffle expression. 292 case Expr::ExtVectorElementExprClass: 293 if (cast<ExtVectorElementExpr>(E)->containsDuplicateElements()) 294 return Cl::CL_DuplicateVectorComponents; 295 if (cast<ExtVectorElementExpr>(E)->isArrow()) 296 return Cl::CL_LValue; 297 return ClassifyInternal(Ctx, cast<ExtVectorElementExpr>(E)->getBase()); 298 299 // Simply look at the actual default argument. 300 case Expr::CXXDefaultArgExprClass: 301 return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr()); 302 303 // Same idea for default initializers. 304 case Expr::CXXDefaultInitExprClass: 305 return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr()); 306 307 // Same idea for temporary binding. 308 case Expr::CXXBindTemporaryExprClass: 309 return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr()); 310 311 // And the cleanups guard. 312 case Expr::ExprWithCleanupsClass: 313 return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr()); 314 315 // Casts depend completely on the target type. All casts work the same. 316 case Expr::CStyleCastExprClass: 317 case Expr::CXXFunctionalCastExprClass: 318 case Expr::CXXStaticCastExprClass: 319 case Expr::CXXDynamicCastExprClass: 320 case Expr::CXXReinterpretCastExprClass: 321 case Expr::CXXConstCastExprClass: 322 case Expr::ObjCBridgedCastExprClass: 323 // Only in C++ can casts be interesting at all. 324 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 325 return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten()); 326 327 case Expr::CXXUnresolvedConstructExprClass: 328 return ClassifyUnnamed(Ctx, 329 cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten()); 330 331 case Expr::BinaryConditionalOperatorClass: { 332 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 333 const BinaryConditionalOperator *co = cast<BinaryConditionalOperator>(E); 334 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); 335 } 336 337 case Expr::ConditionalOperatorClass: { 338 // Once again, only C++ is interesting. 339 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 340 const ConditionalOperator *co = cast<ConditionalOperator>(E); 341 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); 342 } 343 344 // ObjC message sends are effectively function calls, if the target function 345 // is known. 346 case Expr::ObjCMessageExprClass: 347 if (const ObjCMethodDecl *Method = 348 cast<ObjCMessageExpr>(E)->getMethodDecl()) { 349 Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getReturnType()); 350 return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind; 351 } 352 return Cl::CL_PRValue; 353 354 // Some C++ expressions are always class temporaries. 355 case Expr::CXXConstructExprClass: 356 case Expr::CXXTemporaryObjectExprClass: 357 case Expr::LambdaExprClass: 358 case Expr::CXXStdInitializerListExprClass: 359 return Cl::CL_ClassTemporary; 360 361 case Expr::VAArgExprClass: 362 return ClassifyUnnamed(Ctx, E->getType()); 363 364 case Expr::DesignatedInitExprClass: 365 return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit()); 366 367 case Expr::StmtExprClass: { 368 const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt(); 369 if (const Expr *LastExpr = dyn_cast_or_null<Expr>(S->body_back())) 370 return ClassifyUnnamed(Ctx, LastExpr->getType()); 371 return Cl::CL_PRValue; 372 } 373 374 case Expr::CXXUuidofExprClass: 375 return Cl::CL_LValue; 376 377 case Expr::PackExpansionExprClass: 378 return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern()); 379 380 case Expr::MaterializeTemporaryExprClass: 381 return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference() 382 ? Cl::CL_LValue 383 : Cl::CL_XValue; 384 385 case Expr::InitListExprClass: 386 // An init list can be an lvalue if it is bound to a reference and 387 // contains only one element. In that case, we look at that element 388 // for an exact classification. Init list creation takes care of the 389 // value kind for us, so we only need to fine-tune. 390 if (E->isRValue()) 391 return ClassifyExprValueKind(Lang, E, E->getValueKind()); 392 assert(cast<InitListExpr>(E)->getNumInits() == 1 && 393 "Only 1-element init lists can be glvalues."); 394 return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0)); 395 } 396 397 llvm_unreachable("unhandled expression kind in classification"); 398} 399 400/// ClassifyDecl - Return the classification of an expression referencing the 401/// given declaration. 402static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) { 403 // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a 404 // function, variable, or data member and a prvalue otherwise. 405 // In C, functions are not lvalues. 406 // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an 407 // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to 408 // special-case this. 409 410 if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance()) 411 return Cl::CL_MemberFunction; 412 413 bool islvalue; 414 if (const NonTypeTemplateParmDecl *NTTParm = 415 dyn_cast<NonTypeTemplateParmDecl>(D)) 416 islvalue = NTTParm->getType()->isReferenceType(); 417 else 418 islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) || 419 isa<IndirectFieldDecl>(D) || 420 (Ctx.getLangOpts().CPlusPlus && 421 (isa<FunctionDecl>(D) || isa<FunctionTemplateDecl>(D))); 422 423 return islvalue ? Cl::CL_LValue : Cl::CL_PRValue; 424} 425 426/// ClassifyUnnamed - Return the classification of an expression yielding an 427/// unnamed value of the given type. This applies in particular to function 428/// calls and casts. 429static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) { 430 // In C, function calls are always rvalues. 431 if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue; 432 433 // C++ [expr.call]p10: A function call is an lvalue if the result type is an 434 // lvalue reference type or an rvalue reference to function type, an xvalue 435 // if the result type is an rvalue reference to object type, and a prvalue 436 // otherwise. 437 if (T->isLValueReferenceType()) 438 return Cl::CL_LValue; 439 const RValueReferenceType *RV = T->getAs<RValueReferenceType>(); 440 if (!RV) // Could still be a class temporary, though. 441 return ClassifyTemporary(T); 442 443 return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue; 444} 445 446static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) { 447 if (E->getType() == Ctx.UnknownAnyTy) 448 return (isa<FunctionDecl>(E->getMemberDecl()) 449 ? Cl::CL_PRValue : Cl::CL_LValue); 450 451 // Handle C first, it's easier. 452 if (!Ctx.getLangOpts().CPlusPlus) { 453 // C99 6.5.2.3p3 454 // For dot access, the expression is an lvalue if the first part is. For 455 // arrow access, it always is an lvalue. 456 if (E->isArrow()) 457 return Cl::CL_LValue; 458 // ObjC property accesses are not lvalues, but get special treatment. 459 Expr *Base = E->getBase()->IgnoreParens(); 460 if (isa<ObjCPropertyRefExpr>(Base)) 461 return Cl::CL_SubObjCPropertySetting; 462 return ClassifyInternal(Ctx, Base); 463 } 464 465 NamedDecl *Member = E->getMemberDecl(); 466 // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2. 467 // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then 468 // E1.E2 is an lvalue. 469 if (ValueDecl *Value = dyn_cast<ValueDecl>(Member)) 470 if (Value->getType()->isReferenceType()) 471 return Cl::CL_LValue; 472 473 // Otherwise, one of the following rules applies. 474 // -- If E2 is a static member [...] then E1.E2 is an lvalue. 475 if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord()) 476 return Cl::CL_LValue; 477 478 // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then 479 // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue; 480 // otherwise, it is a prvalue. 481 if (isa<FieldDecl>(Member)) { 482 // *E1 is an lvalue 483 if (E->isArrow()) 484 return Cl::CL_LValue; 485 Expr *Base = E->getBase()->IgnoreParenImpCasts(); 486 if (isa<ObjCPropertyRefExpr>(Base)) 487 return Cl::CL_SubObjCPropertySetting; 488 return ClassifyInternal(Ctx, E->getBase()); 489 } 490 491 // -- If E2 is a [...] member function, [...] 492 // -- If it refers to a static member function [...], then E1.E2 is an 493 // lvalue; [...] 494 // -- Otherwise [...] E1.E2 is a prvalue. 495 if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member)) 496 return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction; 497 498 // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue. 499 // So is everything else we haven't handled yet. 500 return Cl::CL_PRValue; 501} 502 503static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) { 504 assert(Ctx.getLangOpts().CPlusPlus && 505 "This is only relevant for C++."); 506 // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand. 507 // Except we override this for writes to ObjC properties. 508 if (E->isAssignmentOp()) 509 return (E->getLHS()->getObjectKind() == OK_ObjCProperty 510 ? Cl::CL_PRValue : Cl::CL_LValue); 511 512 // C++ [expr.comma]p1: the result is of the same value category as its right 513 // operand, [...]. 514 if (E->getOpcode() == BO_Comma) 515 return ClassifyInternal(Ctx, E->getRHS()); 516 517 // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand 518 // is a pointer to a data member is of the same value category as its first 519 // operand. 520 if (E->getOpcode() == BO_PtrMemD) 521 return (E->getType()->isFunctionType() || 522 E->hasPlaceholderType(BuiltinType::BoundMember)) 523 ? Cl::CL_MemberFunction 524 : ClassifyInternal(Ctx, E->getLHS()); 525 526 // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its 527 // second operand is a pointer to data member and a prvalue otherwise. 528 if (E->getOpcode() == BO_PtrMemI) 529 return (E->getType()->isFunctionType() || 530 E->hasPlaceholderType(BuiltinType::BoundMember)) 531 ? Cl::CL_MemberFunction 532 : Cl::CL_LValue; 533 534 // All other binary operations are prvalues. 535 return Cl::CL_PRValue; 536} 537 538static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True, 539 const Expr *False) { 540 assert(Ctx.getLangOpts().CPlusPlus && 541 "This is only relevant for C++."); 542 543 // C++ [expr.cond]p2 544 // If either the second or the third operand has type (cv) void, 545 // one of the following shall hold: 546 if (True->getType()->isVoidType() || False->getType()->isVoidType()) { 547 // The second or the third operand (but not both) is a (possibly 548 // parenthesized) throw-expression; the result is of the [...] value 549 // category of the other. 550 bool TrueIsThrow = isa<CXXThrowExpr>(True->IgnoreParenImpCasts()); 551 bool FalseIsThrow = isa<CXXThrowExpr>(False->IgnoreParenImpCasts()); 552 if (const Expr *NonThrow = TrueIsThrow ? (FalseIsThrow ? nullptr : False) 553 : (FalseIsThrow ? True : nullptr)) 554 return ClassifyInternal(Ctx, NonThrow); 555 556 // [Otherwise] the result [...] is a prvalue. 557 return Cl::CL_PRValue; 558 } 559 560 // Note that at this point, we have already performed all conversions 561 // according to [expr.cond]p3. 562 // C++ [expr.cond]p4: If the second and third operands are glvalues of the 563 // same value category [...], the result is of that [...] value category. 564 // C++ [expr.cond]p5: Otherwise, the result is a prvalue. 565 Cl::Kinds LCl = ClassifyInternal(Ctx, True), 566 RCl = ClassifyInternal(Ctx, False); 567 return LCl == RCl ? LCl : Cl::CL_PRValue; 568} 569 570static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, 571 Cl::Kinds Kind, SourceLocation &Loc) { 572 // As a general rule, we only care about lvalues. But there are some rvalues 573 // for which we want to generate special results. 574 if (Kind == Cl::CL_PRValue) { 575 // For the sake of better diagnostics, we want to specifically recognize 576 // use of the GCC cast-as-lvalue extension. 577 if (const ExplicitCastExpr *CE = 578 dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) { 579 if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) { 580 Loc = CE->getExprLoc(); 581 return Cl::CM_LValueCast; 582 } 583 } 584 } 585 if (Kind != Cl::CL_LValue) 586 return Cl::CM_RValue; 587 588 // This is the lvalue case. 589 // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6) 590 if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType()) 591 return Cl::CM_Function; 592 593 // Assignment to a property in ObjC is an implicit setter access. But a 594 // setter might not exist. 595 if (const ObjCPropertyRefExpr *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) { 596 if (Expr->isImplicitProperty() && 597 Expr->getImplicitPropertySetter() == nullptr) 598 return Cl::CM_NoSetterProperty; 599 } 600 601 CanQualType CT = Ctx.getCanonicalType(E->getType()); 602 // Const stuff is obviously not modifiable. 603 if (CT.isConstQualified()) 604 return Cl::CM_ConstQualified; 605 if (CT.getQualifiers().getAddressSpace() == LangAS::opencl_constant) 606 return Cl::CM_ConstQualified; 607 608 // Arrays are not modifiable, only their elements are. 609 if (CT->isArrayType()) 610 return Cl::CM_ArrayType; 611 // Incomplete types are not modifiable. 612 if (CT->isIncompleteType()) 613 return Cl::CM_IncompleteType; 614 615 // Records with any const fields (recursively) are not modifiable. 616 if (const RecordType *R = CT->getAs<RecordType>()) { 617 assert((E->getObjectKind() == OK_ObjCProperty || 618 !Ctx.getLangOpts().CPlusPlus) && 619 "C++ struct assignment should be resolved by the " 620 "copy assignment operator."); 621 if (R->hasConstFields()) 622 return Cl::CM_ConstQualified; 623 } 624 625 return Cl::CM_Modifiable; 626} 627 628Expr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const { 629 Classification VC = Classify(Ctx); 630 switch (VC.getKind()) { 631 case Cl::CL_LValue: return LV_Valid; 632 case Cl::CL_XValue: return LV_InvalidExpression; 633 case Cl::CL_Function: return LV_NotObjectType; 634 case Cl::CL_Void: return LV_InvalidExpression; 635 case Cl::CL_AddressableVoid: return LV_IncompleteVoidType; 636 case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents; 637 case Cl::CL_MemberFunction: return LV_MemberFunction; 638 case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting; 639 case Cl::CL_ClassTemporary: return LV_ClassTemporary; 640 case Cl::CL_ArrayTemporary: return LV_ArrayTemporary; 641 case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression; 642 case Cl::CL_PRValue: return LV_InvalidExpression; 643 } 644 llvm_unreachable("Unhandled kind"); 645} 646 647Expr::isModifiableLvalueResult 648Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const { 649 SourceLocation dummy; 650 Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy); 651 switch (VC.getKind()) { 652 case Cl::CL_LValue: break; 653 case Cl::CL_XValue: return MLV_InvalidExpression; 654 case Cl::CL_Function: return MLV_NotObjectType; 655 case Cl::CL_Void: return MLV_InvalidExpression; 656 case Cl::CL_AddressableVoid: return MLV_IncompleteVoidType; 657 case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents; 658 case Cl::CL_MemberFunction: return MLV_MemberFunction; 659 case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting; 660 case Cl::CL_ClassTemporary: return MLV_ClassTemporary; 661 case Cl::CL_ArrayTemporary: return MLV_ArrayTemporary; 662 case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression; 663 case Cl::CL_PRValue: 664 return VC.getModifiable() == Cl::CM_LValueCast ? 665 MLV_LValueCast : MLV_InvalidExpression; 666 } 667 assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind"); 668 switch (VC.getModifiable()) { 669 case Cl::CM_Untested: llvm_unreachable("Did not test modifiability"); 670 case Cl::CM_Modifiable: return MLV_Valid; 671 case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match"); 672 case Cl::CM_Function: return MLV_NotObjectType; 673 case Cl::CM_LValueCast: 674 llvm_unreachable("CM_LValueCast and CL_LValue don't match"); 675 case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty; 676 case Cl::CM_ConstQualified: return MLV_ConstQualified; 677 case Cl::CM_ArrayType: return MLV_ArrayType; 678 case Cl::CM_IncompleteType: return MLV_IncompleteType; 679 } 680 llvm_unreachable("Unhandled modifiable type"); 681} 682