1 //===--- ExprClassification.cpp - Expression AST Node Implementation ------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file implements Expr::classify. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/Support/ErrorHandling.h" 15 #include "clang/AST/Expr.h" 16 #include "clang/AST/ExprCXX.h" 17 #include "clang/AST/ExprObjC.h" 18 #include "clang/AST/ASTContext.h" 19 #include "clang/AST/DeclObjC.h" 20 #include "clang/AST/DeclCXX.h" 21 #include "clang/AST/DeclTemplate.h" 22 using namespace clang; 23 24 typedef Expr::Classification Cl; 25 26 static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E); 27 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D); 28 static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T); 29 static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E); 30 static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E); 31 static Cl::Kinds ClassifyConditional(ASTContext &Ctx, 32 const Expr *trueExpr, 33 const Expr *falseExpr); 34 static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, 35 Cl::Kinds Kind, SourceLocation &Loc); 36 37 static Cl::Kinds ClassifyExprValueKind(const LangOptions &Lang, 38 const Expr *E, 39 ExprValueKind Kind) { 40 switch (Kind) { 41 case VK_RValue: 42 return Lang.CPlusPlus && E->getType()->isRecordType() ? 43 Cl::CL_ClassTemporary : Cl::CL_PRValue; 44 case VK_LValue: 45 return Cl::CL_LValue; 46 case VK_XValue: 47 return Cl::CL_XValue; 48 } 49 llvm_unreachable("Invalid value category of implicit cast."); 50 } 51 52 Cl Expr::ClassifyImpl(ASTContext &Ctx, SourceLocation *Loc) const { 53 assert(!TR->isReferenceType() && "Expressions can't have reference type."); 54 55 Cl::Kinds kind = ClassifyInternal(Ctx, this); 56 // C99 6.3.2.1: An lvalue is an expression with an object type or an 57 // incomplete type other than void. 58 if (!Ctx.getLangOpts().CPlusPlus) { 59 // Thus, no functions. 60 if (TR->isFunctionType() || TR == Ctx.OverloadTy) 61 kind = Cl::CL_Function; 62 // No void either, but qualified void is OK because it is "other than void". 63 // Void "lvalues" are classified as addressable void values, which are void 64 // expressions whose address can be taken. 65 else if (TR->isVoidType() && !TR.hasQualifiers()) 66 kind = (kind == Cl::CL_LValue ? Cl::CL_AddressableVoid : Cl::CL_Void); 67 } 68 69 // Enable this assertion for testing. 70 switch (kind) { 71 case Cl::CL_LValue: assert(getValueKind() == VK_LValue); break; 72 case Cl::CL_XValue: assert(getValueKind() == VK_XValue); break; 73 case Cl::CL_Function: 74 case Cl::CL_Void: 75 case Cl::CL_AddressableVoid: 76 case Cl::CL_DuplicateVectorComponents: 77 case Cl::CL_MemberFunction: 78 case Cl::CL_SubObjCPropertySetting: 79 case Cl::CL_ClassTemporary: 80 case Cl::CL_ObjCMessageRValue: 81 case Cl::CL_PRValue: assert(getValueKind() == VK_RValue); break; 82 } 83 84 Cl::ModifiableType modifiable = Cl::CM_Untested; 85 if (Loc) 86 modifiable = IsModifiable(Ctx, this, kind, *Loc); 87 return Classification(kind, modifiable); 88 } 89 90 static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) { 91 // This function takes the first stab at classifying expressions. 92 const LangOptions &Lang = Ctx.getLangOpts(); 93 94 switch (E->getStmtClass()) { 95 case Stmt::NoStmtClass: 96 #define ABSTRACT_STMT(Kind) 97 #define STMT(Kind, Base) case Expr::Kind##Class: 98 #define EXPR(Kind, Base) 99 #include "clang/AST/StmtNodes.inc" 100 llvm_unreachable("cannot classify a statement"); 101 102 // First come the expressions that are always lvalues, unconditionally. 103 case Expr::ObjCIsaExprClass: 104 // C++ [expr.prim.general]p1: A string literal is an lvalue. 105 case Expr::StringLiteralClass: 106 // @encode is equivalent to its string 107 case Expr::ObjCEncodeExprClass: 108 // __func__ and friends are too. 109 case Expr::PredefinedExprClass: 110 // Property references are lvalues 111 case Expr::ObjCSubscriptRefExprClass: 112 case Expr::ObjCPropertyRefExprClass: 113 // C++ [expr.typeid]p1: The result of a typeid expression is an lvalue of... 114 case Expr::CXXTypeidExprClass: 115 // Unresolved lookups get classified as lvalues. 116 // FIXME: Is this wise? Should they get their own kind? 117 case Expr::UnresolvedLookupExprClass: 118 case Expr::UnresolvedMemberExprClass: 119 case Expr::CXXDependentScopeMemberExprClass: 120 case Expr::DependentScopeDeclRefExprClass: 121 // ObjC instance variables are lvalues 122 // FIXME: ObjC++0x might have different rules 123 case Expr::ObjCIvarRefExprClass: 124 return Cl::CL_LValue; 125 126 // C99 6.5.2.5p5 says that compound literals are lvalues. 127 // In C++, they're class temporaries. 128 case Expr::CompoundLiteralExprClass: 129 return Ctx.getLangOpts().CPlusPlus? Cl::CL_ClassTemporary 130 : Cl::CL_LValue; 131 132 // Expressions that are prvalues. 133 case Expr::CXXBoolLiteralExprClass: 134 case Expr::CXXPseudoDestructorExprClass: 135 case Expr::UnaryExprOrTypeTraitExprClass: 136 case Expr::CXXNewExprClass: 137 case Expr::CXXThisExprClass: 138 case Expr::CXXNullPtrLiteralExprClass: 139 case Expr::ImaginaryLiteralClass: 140 case Expr::GNUNullExprClass: 141 case Expr::OffsetOfExprClass: 142 case Expr::CXXThrowExprClass: 143 case Expr::ShuffleVectorExprClass: 144 case Expr::IntegerLiteralClass: 145 case Expr::CharacterLiteralClass: 146 case Expr::AddrLabelExprClass: 147 case Expr::CXXDeleteExprClass: 148 case Expr::ImplicitValueInitExprClass: 149 case Expr::BlockExprClass: 150 case Expr::FloatingLiteralClass: 151 case Expr::CXXNoexceptExprClass: 152 case Expr::CXXScalarValueInitExprClass: 153 case Expr::UnaryTypeTraitExprClass: 154 case Expr::BinaryTypeTraitExprClass: 155 case Expr::TypeTraitExprClass: 156 case Expr::ArrayTypeTraitExprClass: 157 case Expr::ExpressionTraitExprClass: 158 case Expr::ObjCSelectorExprClass: 159 case Expr::ObjCProtocolExprClass: 160 case Expr::ObjCStringLiteralClass: 161 case Expr::ObjCBoxedExprClass: 162 case Expr::ObjCArrayLiteralClass: 163 case Expr::ObjCDictionaryLiteralClass: 164 case Expr::ObjCBoolLiteralExprClass: 165 case Expr::ParenListExprClass: 166 case Expr::SizeOfPackExprClass: 167 case Expr::SubstNonTypeTemplateParmPackExprClass: 168 case Expr::AsTypeExprClass: 169 case Expr::ObjCIndirectCopyRestoreExprClass: 170 case Expr::AtomicExprClass: 171 return Cl::CL_PRValue; 172 173 // Next come the complicated cases. 174 case Expr::SubstNonTypeTemplateParmExprClass: 175 return ClassifyInternal(Ctx, 176 cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement()); 177 178 // C++ [expr.sub]p1: The result is an lvalue of type "T". 179 // However, subscripting vector types is more like member access. 180 case Expr::ArraySubscriptExprClass: 181 if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType()) 182 return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase()); 183 return Cl::CL_LValue; 184 185 // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a 186 // function or variable and a prvalue otherwise. 187 case Expr::DeclRefExprClass: 188 if (E->getType() == Ctx.UnknownAnyTy) 189 return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl()) 190 ? Cl::CL_PRValue : Cl::CL_LValue; 191 return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl()); 192 193 // Member access is complex. 194 case Expr::MemberExprClass: 195 return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E)); 196 197 case Expr::UnaryOperatorClass: 198 switch (cast<UnaryOperator>(E)->getOpcode()) { 199 // C++ [expr.unary.op]p1: The unary * operator performs indirection: 200 // [...] the result is an lvalue referring to the object or function 201 // to which the expression points. 202 case UO_Deref: 203 return Cl::CL_LValue; 204 205 // GNU extensions, simply look through them. 206 case UO_Extension: 207 return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr()); 208 209 // Treat _Real and _Imag basically as if they were member 210 // expressions: l-value only if the operand is a true l-value. 211 case UO_Real: 212 case UO_Imag: { 213 const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens(); 214 Cl::Kinds K = ClassifyInternal(Ctx, Op); 215 if (K != Cl::CL_LValue) return K; 216 217 if (isa<ObjCPropertyRefExpr>(Op)) 218 return Cl::CL_SubObjCPropertySetting; 219 return Cl::CL_LValue; 220 } 221 222 // C++ [expr.pre.incr]p1: The result is the updated operand; it is an 223 // lvalue, [...] 224 // Not so in C. 225 case UO_PreInc: 226 case UO_PreDec: 227 return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue; 228 229 default: 230 return Cl::CL_PRValue; 231 } 232 233 case Expr::OpaqueValueExprClass: 234 return ClassifyExprValueKind(Lang, E, E->getValueKind()); 235 236 // Pseudo-object expressions can produce l-values with reference magic. 237 case Expr::PseudoObjectExprClass: 238 return ClassifyExprValueKind(Lang, E, 239 cast<PseudoObjectExpr>(E)->getValueKind()); 240 241 // Implicit casts are lvalues if they're lvalue casts. Other than that, we 242 // only specifically record class temporaries. 243 case Expr::ImplicitCastExprClass: 244 return ClassifyExprValueKind(Lang, E, E->getValueKind()); 245 246 // C++ [expr.prim.general]p4: The presence of parentheses does not affect 247 // whether the expression is an lvalue. 248 case Expr::ParenExprClass: 249 return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr()); 250 251 // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator, 252 // or a void expression if its result expression is, respectively, an 253 // lvalue, a function designator, or a void expression. 254 case Expr::GenericSelectionExprClass: 255 if (cast<GenericSelectionExpr>(E)->isResultDependent()) 256 return Cl::CL_PRValue; 257 return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr()); 258 259 case Expr::BinaryOperatorClass: 260 case Expr::CompoundAssignOperatorClass: 261 // C doesn't have any binary expressions that are lvalues. 262 if (Lang.CPlusPlus) 263 return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E)); 264 return Cl::CL_PRValue; 265 266 case Expr::CallExprClass: 267 case Expr::CXXOperatorCallExprClass: 268 case Expr::CXXMemberCallExprClass: 269 case Expr::UserDefinedLiteralClass: 270 case Expr::CUDAKernelCallExprClass: 271 return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType()); 272 273 // __builtin_choose_expr is equivalent to the chosen expression. 274 case Expr::ChooseExprClass: 275 return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr(Ctx)); 276 277 // Extended vector element access is an lvalue unless there are duplicates 278 // in the shuffle expression. 279 case Expr::ExtVectorElementExprClass: 280 return cast<ExtVectorElementExpr>(E)->containsDuplicateElements() ? 281 Cl::CL_DuplicateVectorComponents : Cl::CL_LValue; 282 283 // Simply look at the actual default argument. 284 case Expr::CXXDefaultArgExprClass: 285 return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr()); 286 287 // Same idea for temporary binding. 288 case Expr::CXXBindTemporaryExprClass: 289 return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr()); 290 291 // And the cleanups guard. 292 case Expr::ExprWithCleanupsClass: 293 return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr()); 294 295 // Casts depend completely on the target type. All casts work the same. 296 case Expr::CStyleCastExprClass: 297 case Expr::CXXFunctionalCastExprClass: 298 case Expr::CXXStaticCastExprClass: 299 case Expr::CXXDynamicCastExprClass: 300 case Expr::CXXReinterpretCastExprClass: 301 case Expr::CXXConstCastExprClass: 302 case Expr::ObjCBridgedCastExprClass: 303 // Only in C++ can casts be interesting at all. 304 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 305 return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten()); 306 307 case Expr::CXXUnresolvedConstructExprClass: 308 return ClassifyUnnamed(Ctx, 309 cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten()); 310 311 case Expr::BinaryConditionalOperatorClass: { 312 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 313 const BinaryConditionalOperator *co = cast<BinaryConditionalOperator>(E); 314 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); 315 } 316 317 case Expr::ConditionalOperatorClass: { 318 // Once again, only C++ is interesting. 319 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 320 const ConditionalOperator *co = cast<ConditionalOperator>(E); 321 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); 322 } 323 324 // ObjC message sends are effectively function calls, if the target function 325 // is known. 326 case Expr::ObjCMessageExprClass: 327 if (const ObjCMethodDecl *Method = 328 cast<ObjCMessageExpr>(E)->getMethodDecl()) { 329 Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getResultType()); 330 return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind; 331 } 332 return Cl::CL_PRValue; 333 334 // Some C++ expressions are always class temporaries. 335 case Expr::CXXConstructExprClass: 336 case Expr::CXXTemporaryObjectExprClass: 337 case Expr::LambdaExprClass: 338 return Cl::CL_ClassTemporary; 339 340 case Expr::VAArgExprClass: 341 return ClassifyUnnamed(Ctx, E->getType()); 342 343 case Expr::DesignatedInitExprClass: 344 return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit()); 345 346 case Expr::StmtExprClass: { 347 const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt(); 348 if (const Expr *LastExpr = dyn_cast_or_null<Expr>(S->body_back())) 349 return ClassifyUnnamed(Ctx, LastExpr->getType()); 350 return Cl::CL_PRValue; 351 } 352 353 case Expr::CXXUuidofExprClass: 354 return Cl::CL_LValue; 355 356 case Expr::PackExpansionExprClass: 357 return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern()); 358 359 case Expr::MaterializeTemporaryExprClass: 360 return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference() 361 ? Cl::CL_LValue 362 : Cl::CL_XValue; 363 364 case Expr::InitListExprClass: 365 // An init list can be an lvalue if it is bound to a reference and 366 // contains only one element. In that case, we look at that element 367 // for an exact classification. Init list creation takes care of the 368 // value kind for us, so we only need to fine-tune. 369 if (E->isRValue()) 370 return ClassifyExprValueKind(Lang, E, E->getValueKind()); 371 assert(cast<InitListExpr>(E)->getNumInits() == 1 && 372 "Only 1-element init lists can be glvalues."); 373 return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0)); 374 } 375 376 llvm_unreachable("unhandled expression kind in classification"); 377 } 378 379 /// ClassifyDecl - Return the classification of an expression referencing the 380 /// given declaration. 381 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) { 382 // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a 383 // function, variable, or data member and a prvalue otherwise. 384 // In C, functions are not lvalues. 385 // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an 386 // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to 387 // special-case this. 388 389 if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance()) 390 return Cl::CL_MemberFunction; 391 392 bool islvalue; 393 if (const NonTypeTemplateParmDecl *NTTParm = 394 dyn_cast<NonTypeTemplateParmDecl>(D)) 395 islvalue = NTTParm->getType()->isReferenceType(); 396 else 397 islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) || 398 isa<IndirectFieldDecl>(D) || 399 (Ctx.getLangOpts().CPlusPlus && 400 (isa<FunctionDecl>(D) || isa<FunctionTemplateDecl>(D))); 401 402 return islvalue ? Cl::CL_LValue : Cl::CL_PRValue; 403 } 404 405 /// ClassifyUnnamed - Return the classification of an expression yielding an 406 /// unnamed value of the given type. This applies in particular to function 407 /// calls and casts. 408 static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) { 409 // In C, function calls are always rvalues. 410 if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue; 411 412 // C++ [expr.call]p10: A function call is an lvalue if the result type is an 413 // lvalue reference type or an rvalue reference to function type, an xvalue 414 // if the result type is an rvalue reference to object type, and a prvalue 415 // otherwise. 416 if (T->isLValueReferenceType()) 417 return Cl::CL_LValue; 418 const RValueReferenceType *RV = T->getAs<RValueReferenceType>(); 419 if (!RV) // Could still be a class temporary, though. 420 return T->isRecordType() ? Cl::CL_ClassTemporary : Cl::CL_PRValue; 421 422 return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue; 423 } 424 425 static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) { 426 if (E->getType() == Ctx.UnknownAnyTy) 427 return (isa<FunctionDecl>(E->getMemberDecl()) 428 ? Cl::CL_PRValue : Cl::CL_LValue); 429 430 // Handle C first, it's easier. 431 if (!Ctx.getLangOpts().CPlusPlus) { 432 // C99 6.5.2.3p3 433 // For dot access, the expression is an lvalue if the first part is. For 434 // arrow access, it always is an lvalue. 435 if (E->isArrow()) 436 return Cl::CL_LValue; 437 // ObjC property accesses are not lvalues, but get special treatment. 438 Expr *Base = E->getBase()->IgnoreParens(); 439 if (isa<ObjCPropertyRefExpr>(Base)) 440 return Cl::CL_SubObjCPropertySetting; 441 return ClassifyInternal(Ctx, Base); 442 } 443 444 NamedDecl *Member = E->getMemberDecl(); 445 // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2. 446 // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then 447 // E1.E2 is an lvalue. 448 if (ValueDecl *Value = dyn_cast<ValueDecl>(Member)) 449 if (Value->getType()->isReferenceType()) 450 return Cl::CL_LValue; 451 452 // Otherwise, one of the following rules applies. 453 // -- If E2 is a static member [...] then E1.E2 is an lvalue. 454 if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord()) 455 return Cl::CL_LValue; 456 457 // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then 458 // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue; 459 // otherwise, it is a prvalue. 460 if (isa<FieldDecl>(Member)) { 461 // *E1 is an lvalue 462 if (E->isArrow()) 463 return Cl::CL_LValue; 464 Expr *Base = E->getBase()->IgnoreParenImpCasts(); 465 if (isa<ObjCPropertyRefExpr>(Base)) 466 return Cl::CL_SubObjCPropertySetting; 467 return ClassifyInternal(Ctx, E->getBase()); 468 } 469 470 // -- If E2 is a [...] member function, [...] 471 // -- If it refers to a static member function [...], then E1.E2 is an 472 // lvalue; [...] 473 // -- Otherwise [...] E1.E2 is a prvalue. 474 if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member)) 475 return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction; 476 477 // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue. 478 // So is everything else we haven't handled yet. 479 return Cl::CL_PRValue; 480 } 481 482 static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) { 483 assert(Ctx.getLangOpts().CPlusPlus && 484 "This is only relevant for C++."); 485 // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand. 486 // Except we override this for writes to ObjC properties. 487 if (E->isAssignmentOp()) 488 return (E->getLHS()->getObjectKind() == OK_ObjCProperty 489 ? Cl::CL_PRValue : Cl::CL_LValue); 490 491 // C++ [expr.comma]p1: the result is of the same value category as its right 492 // operand, [...]. 493 if (E->getOpcode() == BO_Comma) 494 return ClassifyInternal(Ctx, E->getRHS()); 495 496 // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand 497 // is a pointer to a data member is of the same value category as its first 498 // operand. 499 if (E->getOpcode() == BO_PtrMemD) 500 return (E->getType()->isFunctionType() || 501 E->hasPlaceholderType(BuiltinType::BoundMember)) 502 ? Cl::CL_MemberFunction 503 : ClassifyInternal(Ctx, E->getLHS()); 504 505 // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its 506 // second operand is a pointer to data member and a prvalue otherwise. 507 if (E->getOpcode() == BO_PtrMemI) 508 return (E->getType()->isFunctionType() || 509 E->hasPlaceholderType(BuiltinType::BoundMember)) 510 ? Cl::CL_MemberFunction 511 : Cl::CL_LValue; 512 513 // All other binary operations are prvalues. 514 return Cl::CL_PRValue; 515 } 516 517 static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True, 518 const Expr *False) { 519 assert(Ctx.getLangOpts().CPlusPlus && 520 "This is only relevant for C++."); 521 522 // C++ [expr.cond]p2 523 // If either the second or the third operand has type (cv) void, [...] 524 // the result [...] is a prvalue. 525 if (True->getType()->isVoidType() || False->getType()->isVoidType()) 526 return Cl::CL_PRValue; 527 528 // Note that at this point, we have already performed all conversions 529 // according to [expr.cond]p3. 530 // C++ [expr.cond]p4: If the second and third operands are glvalues of the 531 // same value category [...], the result is of that [...] value category. 532 // C++ [expr.cond]p5: Otherwise, the result is a prvalue. 533 Cl::Kinds LCl = ClassifyInternal(Ctx, True), 534 RCl = ClassifyInternal(Ctx, False); 535 return LCl == RCl ? LCl : Cl::CL_PRValue; 536 } 537 538 static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, 539 Cl::Kinds Kind, SourceLocation &Loc) { 540 // As a general rule, we only care about lvalues. But there are some rvalues 541 // for which we want to generate special results. 542 if (Kind == Cl::CL_PRValue) { 543 // For the sake of better diagnostics, we want to specifically recognize 544 // use of the GCC cast-as-lvalue extension. 545 if (const ExplicitCastExpr *CE = 546 dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) { 547 if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) { 548 Loc = CE->getExprLoc(); 549 return Cl::CM_LValueCast; 550 } 551 } 552 } 553 if (Kind != Cl::CL_LValue) 554 return Cl::CM_RValue; 555 556 // This is the lvalue case. 557 // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6) 558 if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType()) 559 return Cl::CM_Function; 560 561 // Assignment to a property in ObjC is an implicit setter access. But a 562 // setter might not exist. 563 if (const ObjCPropertyRefExpr *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) { 564 if (Expr->isImplicitProperty() && Expr->getImplicitPropertySetter() == 0) 565 return Cl::CM_NoSetterProperty; 566 } 567 568 CanQualType CT = Ctx.getCanonicalType(E->getType()); 569 // Const stuff is obviously not modifiable. 570 if (CT.isConstQualified()) 571 return Cl::CM_ConstQualified; 572 573 // Arrays are not modifiable, only their elements are. 574 if (CT->isArrayType()) 575 return Cl::CM_ArrayType; 576 // Incomplete types are not modifiable. 577 if (CT->isIncompleteType()) 578 return Cl::CM_IncompleteType; 579 580 // Records with any const fields (recursively) are not modifiable. 581 if (const RecordType *R = CT->getAs<RecordType>()) { 582 assert((E->getObjectKind() == OK_ObjCProperty || 583 !Ctx.getLangOpts().CPlusPlus) && 584 "C++ struct assignment should be resolved by the " 585 "copy assignment operator."); 586 if (R->hasConstFields()) 587 return Cl::CM_ConstQualified; 588 } 589 590 return Cl::CM_Modifiable; 591 } 592 593 Expr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const { 594 Classification VC = Classify(Ctx); 595 switch (VC.getKind()) { 596 case Cl::CL_LValue: return LV_Valid; 597 case Cl::CL_XValue: return LV_InvalidExpression; 598 case Cl::CL_Function: return LV_NotObjectType; 599 case Cl::CL_Void: return LV_InvalidExpression; 600 case Cl::CL_AddressableVoid: return LV_IncompleteVoidType; 601 case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents; 602 case Cl::CL_MemberFunction: return LV_MemberFunction; 603 case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting; 604 case Cl::CL_ClassTemporary: return LV_ClassTemporary; 605 case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression; 606 case Cl::CL_PRValue: return LV_InvalidExpression; 607 } 608 llvm_unreachable("Unhandled kind"); 609 } 610 611 Expr::isModifiableLvalueResult 612 Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const { 613 SourceLocation dummy; 614 Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy); 615 switch (VC.getKind()) { 616 case Cl::CL_LValue: break; 617 case Cl::CL_XValue: return MLV_InvalidExpression; 618 case Cl::CL_Function: return MLV_NotObjectType; 619 case Cl::CL_Void: return MLV_InvalidExpression; 620 case Cl::CL_AddressableVoid: return MLV_IncompleteVoidType; 621 case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents; 622 case Cl::CL_MemberFunction: return MLV_MemberFunction; 623 case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting; 624 case Cl::CL_ClassTemporary: return MLV_ClassTemporary; 625 case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression; 626 case Cl::CL_PRValue: 627 return VC.getModifiable() == Cl::CM_LValueCast ? 628 MLV_LValueCast : MLV_InvalidExpression; 629 } 630 assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind"); 631 switch (VC.getModifiable()) { 632 case Cl::CM_Untested: llvm_unreachable("Did not test modifiability"); 633 case Cl::CM_Modifiable: return MLV_Valid; 634 case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match"); 635 case Cl::CM_Function: return MLV_NotObjectType; 636 case Cl::CM_LValueCast: 637 llvm_unreachable("CM_LValueCast and CL_LValue don't match"); 638 case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty; 639 case Cl::CM_ConstQualified: return MLV_ConstQualified; 640 case Cl::CM_ArrayType: return MLV_ArrayType; 641 case Cl::CM_IncompleteType: return MLV_IncompleteType; 642 } 643 llvm_unreachable("Unhandled modifiable type"); 644 } 645