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" 22using namespace clang; 23 24typedef Expr::Classification Cl; 25 26static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E); 27static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D); 28static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T); 29static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E); 30static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E); 31static Cl::Kinds ClassifyConditional(ASTContext &Ctx, 32 const Expr *trueExpr, 33 const Expr *falseExpr); 34static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, 35 Cl::Kinds Kind, SourceLocation &Loc); 36 37static 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 52Cl 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_ArrayTemporary: 81 case Cl::CL_ObjCMessageRValue: 82 case Cl::CL_PRValue: assert(getValueKind() == VK_RValue); break; 83 } 84 85 Cl::ModifiableType modifiable = Cl::CM_Untested; 86 if (Loc) 87 modifiable = IsModifiable(Ctx, this, kind, *Loc); 88 return Classification(kind, modifiable); 89} 90 91/// Classify an expression which creates a temporary, based on its type. 92static Cl::Kinds ClassifyTemporary(QualType T) { 93 if (T->isRecordType()) 94 return Cl::CL_ClassTemporary; 95 if (T->isArrayType()) 96 return Cl::CL_ArrayTemporary; 97 98 // No special classification: these don't behave differently from normal 99 // prvalues. 100 return Cl::CL_PRValue; 101} 102 103static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) { 104 // This function takes the first stab at classifying expressions. 105 const LangOptions &Lang = Ctx.getLangOpts(); 106 107 switch (E->getStmtClass()) { 108 case Stmt::NoStmtClass: 109#define ABSTRACT_STMT(Kind) 110#define STMT(Kind, Base) case Expr::Kind##Class: 111#define EXPR(Kind, Base) 112#include "clang/AST/StmtNodes.inc" 113 llvm_unreachable("cannot classify a statement"); 114 115 // First come the expressions that are always lvalues, unconditionally. 116 case Expr::ObjCIsaExprClass: 117 // C++ [expr.prim.general]p1: A string literal is an lvalue. 118 case Expr::StringLiteralClass: 119 // @encode is equivalent to its string 120 case Expr::ObjCEncodeExprClass: 121 // __func__ and friends are too. 122 case Expr::PredefinedExprClass: 123 // Property references are lvalues 124 case Expr::ObjCSubscriptRefExprClass: 125 case Expr::ObjCPropertyRefExprClass: 126 // C++ [expr.typeid]p1: The result of a typeid expression is an lvalue of... 127 case Expr::CXXTypeidExprClass: 128 // Unresolved lookups get classified as lvalues. 129 // FIXME: Is this wise? Should they get their own kind? 130 case Expr::UnresolvedLookupExprClass: 131 case Expr::UnresolvedMemberExprClass: 132 case Expr::CXXDependentScopeMemberExprClass: 133 case Expr::DependentScopeDeclRefExprClass: 134 // ObjC instance variables are lvalues 135 // FIXME: ObjC++0x might have different rules 136 case Expr::ObjCIvarRefExprClass: 137 return Cl::CL_LValue; 138 139 // C99 6.5.2.5p5 says that compound literals are lvalues. 140 // In C++, they're prvalue temporaries. 141 case Expr::CompoundLiteralExprClass: 142 return Ctx.getLangOpts().CPlusPlus ? ClassifyTemporary(E->getType()) 143 : Cl::CL_LValue; 144 145 // Expressions that are prvalues. 146 case Expr::CXXBoolLiteralExprClass: 147 case Expr::CXXPseudoDestructorExprClass: 148 case Expr::UnaryExprOrTypeTraitExprClass: 149 case Expr::CXXNewExprClass: 150 case Expr::CXXThisExprClass: 151 case Expr::CXXNullPtrLiteralExprClass: 152 case Expr::ImaginaryLiteralClass: 153 case Expr::GNUNullExprClass: 154 case Expr::OffsetOfExprClass: 155 case Expr::CXXThrowExprClass: 156 case Expr::ShuffleVectorExprClass: 157 case Expr::IntegerLiteralClass: 158 case Expr::CharacterLiteralClass: 159 case Expr::AddrLabelExprClass: 160 case Expr::CXXDeleteExprClass: 161 case Expr::ImplicitValueInitExprClass: 162 case Expr::BlockExprClass: 163 case Expr::FloatingLiteralClass: 164 case Expr::CXXNoexceptExprClass: 165 case Expr::CXXScalarValueInitExprClass: 166 case Expr::UnaryTypeTraitExprClass: 167 case Expr::BinaryTypeTraitExprClass: 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(Ctx)); 289 290 // Extended vector element access is an lvalue unless there are duplicates 291 // in the shuffle expression. 292 case Expr::ExtVectorElementExprClass: 293 return cast<ExtVectorElementExpr>(E)->containsDuplicateElements() ? 294 Cl::CL_DuplicateVectorComponents : Cl::CL_LValue; 295 296 // Simply look at the actual default argument. 297 case Expr::CXXDefaultArgExprClass: 298 return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr()); 299 300 // Same idea for temporary binding. 301 case Expr::CXXBindTemporaryExprClass: 302 return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr()); 303 304 // And the cleanups guard. 305 case Expr::ExprWithCleanupsClass: 306 return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr()); 307 308 // Casts depend completely on the target type. All casts work the same. 309 case Expr::CStyleCastExprClass: 310 case Expr::CXXFunctionalCastExprClass: 311 case Expr::CXXStaticCastExprClass: 312 case Expr::CXXDynamicCastExprClass: 313 case Expr::CXXReinterpretCastExprClass: 314 case Expr::CXXConstCastExprClass: 315 case Expr::ObjCBridgedCastExprClass: 316 // Only in C++ can casts be interesting at all. 317 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 318 return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten()); 319 320 case Expr::CXXUnresolvedConstructExprClass: 321 return ClassifyUnnamed(Ctx, 322 cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten()); 323 324 case Expr::BinaryConditionalOperatorClass: { 325 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 326 const BinaryConditionalOperator *co = cast<BinaryConditionalOperator>(E); 327 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); 328 } 329 330 case Expr::ConditionalOperatorClass: { 331 // Once again, only C++ is interesting. 332 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 333 const ConditionalOperator *co = cast<ConditionalOperator>(E); 334 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); 335 } 336 337 // ObjC message sends are effectively function calls, if the target function 338 // is known. 339 case Expr::ObjCMessageExprClass: 340 if (const ObjCMethodDecl *Method = 341 cast<ObjCMessageExpr>(E)->getMethodDecl()) { 342 Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getResultType()); 343 return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind; 344 } 345 return Cl::CL_PRValue; 346 347 // Some C++ expressions are always class temporaries. 348 case Expr::CXXConstructExprClass: 349 case Expr::CXXTemporaryObjectExprClass: 350 case Expr::LambdaExprClass: 351 return Cl::CL_ClassTemporary; 352 353 case Expr::VAArgExprClass: 354 return ClassifyUnnamed(Ctx, E->getType()); 355 356 case Expr::DesignatedInitExprClass: 357 return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit()); 358 359 case Expr::StmtExprClass: { 360 const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt(); 361 if (const Expr *LastExpr = dyn_cast_or_null<Expr>(S->body_back())) 362 return ClassifyUnnamed(Ctx, LastExpr->getType()); 363 return Cl::CL_PRValue; 364 } 365 366 case Expr::CXXUuidofExprClass: 367 return Cl::CL_LValue; 368 369 case Expr::PackExpansionExprClass: 370 return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern()); 371 372 case Expr::MaterializeTemporaryExprClass: 373 return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference() 374 ? Cl::CL_LValue 375 : Cl::CL_XValue; 376 377 case Expr::InitListExprClass: 378 // An init list can be an lvalue if it is bound to a reference and 379 // contains only one element. In that case, we look at that element 380 // for an exact classification. Init list creation takes care of the 381 // value kind for us, so we only need to fine-tune. 382 if (E->isRValue()) 383 return ClassifyExprValueKind(Lang, E, E->getValueKind()); 384 assert(cast<InitListExpr>(E)->getNumInits() == 1 && 385 "Only 1-element init lists can be glvalues."); 386 return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0)); 387 } 388 389 llvm_unreachable("unhandled expression kind in classification"); 390} 391 392/// ClassifyDecl - Return the classification of an expression referencing the 393/// given declaration. 394static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) { 395 // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a 396 // function, variable, or data member and a prvalue otherwise. 397 // In C, functions are not lvalues. 398 // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an 399 // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to 400 // special-case this. 401 402 if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance()) 403 return Cl::CL_MemberFunction; 404 405 bool islvalue; 406 if (const NonTypeTemplateParmDecl *NTTParm = 407 dyn_cast<NonTypeTemplateParmDecl>(D)) 408 islvalue = NTTParm->getType()->isReferenceType(); 409 else 410 islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) || 411 isa<IndirectFieldDecl>(D) || 412 (Ctx.getLangOpts().CPlusPlus && 413 (isa<FunctionDecl>(D) || isa<FunctionTemplateDecl>(D))); 414 415 return islvalue ? Cl::CL_LValue : Cl::CL_PRValue; 416} 417 418/// ClassifyUnnamed - Return the classification of an expression yielding an 419/// unnamed value of the given type. This applies in particular to function 420/// calls and casts. 421static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) { 422 // In C, function calls are always rvalues. 423 if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue; 424 425 // C++ [expr.call]p10: A function call is an lvalue if the result type is an 426 // lvalue reference type or an rvalue reference to function type, an xvalue 427 // if the result type is an rvalue reference to object type, and a prvalue 428 // otherwise. 429 if (T->isLValueReferenceType()) 430 return Cl::CL_LValue; 431 const RValueReferenceType *RV = T->getAs<RValueReferenceType>(); 432 if (!RV) // Could still be a class temporary, though. 433 return ClassifyTemporary(T); 434 435 return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue; 436} 437 438static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) { 439 if (E->getType() == Ctx.UnknownAnyTy) 440 return (isa<FunctionDecl>(E->getMemberDecl()) 441 ? Cl::CL_PRValue : Cl::CL_LValue); 442 443 // Handle C first, it's easier. 444 if (!Ctx.getLangOpts().CPlusPlus) { 445 // C99 6.5.2.3p3 446 // For dot access, the expression is an lvalue if the first part is. For 447 // arrow access, it always is an lvalue. 448 if (E->isArrow()) 449 return Cl::CL_LValue; 450 // ObjC property accesses are not lvalues, but get special treatment. 451 Expr *Base = E->getBase()->IgnoreParens(); 452 if (isa<ObjCPropertyRefExpr>(Base)) 453 return Cl::CL_SubObjCPropertySetting; 454 return ClassifyInternal(Ctx, Base); 455 } 456 457 NamedDecl *Member = E->getMemberDecl(); 458 // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2. 459 // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then 460 // E1.E2 is an lvalue. 461 if (ValueDecl *Value = dyn_cast<ValueDecl>(Member)) 462 if (Value->getType()->isReferenceType()) 463 return Cl::CL_LValue; 464 465 // Otherwise, one of the following rules applies. 466 // -- If E2 is a static member [...] then E1.E2 is an lvalue. 467 if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord()) 468 return Cl::CL_LValue; 469 470 // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then 471 // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue; 472 // otherwise, it is a prvalue. 473 if (isa<FieldDecl>(Member)) { 474 // *E1 is an lvalue 475 if (E->isArrow()) 476 return Cl::CL_LValue; 477 Expr *Base = E->getBase()->IgnoreParenImpCasts(); 478 if (isa<ObjCPropertyRefExpr>(Base)) 479 return Cl::CL_SubObjCPropertySetting; 480 return ClassifyInternal(Ctx, E->getBase()); 481 } 482 483 // -- If E2 is a [...] member function, [...] 484 // -- If it refers to a static member function [...], then E1.E2 is an 485 // lvalue; [...] 486 // -- Otherwise [...] E1.E2 is a prvalue. 487 if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member)) 488 return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction; 489 490 // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue. 491 // So is everything else we haven't handled yet. 492 return Cl::CL_PRValue; 493} 494 495static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) { 496 assert(Ctx.getLangOpts().CPlusPlus && 497 "This is only relevant for C++."); 498 // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand. 499 // Except we override this for writes to ObjC properties. 500 if (E->isAssignmentOp()) 501 return (E->getLHS()->getObjectKind() == OK_ObjCProperty 502 ? Cl::CL_PRValue : Cl::CL_LValue); 503 504 // C++ [expr.comma]p1: the result is of the same value category as its right 505 // operand, [...]. 506 if (E->getOpcode() == BO_Comma) 507 return ClassifyInternal(Ctx, E->getRHS()); 508 509 // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand 510 // is a pointer to a data member is of the same value category as its first 511 // operand. 512 if (E->getOpcode() == BO_PtrMemD) 513 return (E->getType()->isFunctionType() || 514 E->hasPlaceholderType(BuiltinType::BoundMember)) 515 ? Cl::CL_MemberFunction 516 : ClassifyInternal(Ctx, E->getLHS()); 517 518 // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its 519 // second operand is a pointer to data member and a prvalue otherwise. 520 if (E->getOpcode() == BO_PtrMemI) 521 return (E->getType()->isFunctionType() || 522 E->hasPlaceholderType(BuiltinType::BoundMember)) 523 ? Cl::CL_MemberFunction 524 : Cl::CL_LValue; 525 526 // All other binary operations are prvalues. 527 return Cl::CL_PRValue; 528} 529 530static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True, 531 const Expr *False) { 532 assert(Ctx.getLangOpts().CPlusPlus && 533 "This is only relevant for C++."); 534 535 // C++ [expr.cond]p2 536 // If either the second or the third operand has type (cv) void, [...] 537 // the result [...] is a prvalue. 538 if (True->getType()->isVoidType() || False->getType()->isVoidType()) 539 return Cl::CL_PRValue; 540 541 // Note that at this point, we have already performed all conversions 542 // according to [expr.cond]p3. 543 // C++ [expr.cond]p4: If the second and third operands are glvalues of the 544 // same value category [...], the result is of that [...] value category. 545 // C++ [expr.cond]p5: Otherwise, the result is a prvalue. 546 Cl::Kinds LCl = ClassifyInternal(Ctx, True), 547 RCl = ClassifyInternal(Ctx, False); 548 return LCl == RCl ? LCl : Cl::CL_PRValue; 549} 550 551static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, 552 Cl::Kinds Kind, SourceLocation &Loc) { 553 // As a general rule, we only care about lvalues. But there are some rvalues 554 // for which we want to generate special results. 555 if (Kind == Cl::CL_PRValue) { 556 // For the sake of better diagnostics, we want to specifically recognize 557 // use of the GCC cast-as-lvalue extension. 558 if (const ExplicitCastExpr *CE = 559 dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) { 560 if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) { 561 Loc = CE->getExprLoc(); 562 return Cl::CM_LValueCast; 563 } 564 } 565 } 566 if (Kind != Cl::CL_LValue) 567 return Cl::CM_RValue; 568 569 // This is the lvalue case. 570 // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6) 571 if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType()) 572 return Cl::CM_Function; 573 574 // Assignment to a property in ObjC is an implicit setter access. But a 575 // setter might not exist. 576 if (const ObjCPropertyRefExpr *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) { 577 if (Expr->isImplicitProperty() && Expr->getImplicitPropertySetter() == 0) 578 return Cl::CM_NoSetterProperty; 579 } 580 581 CanQualType CT = Ctx.getCanonicalType(E->getType()); 582 // Const stuff is obviously not modifiable. 583 if (CT.isConstQualified()) 584 return Cl::CM_ConstQualified; 585 586 // Arrays are not modifiable, only their elements are. 587 if (CT->isArrayType()) 588 return Cl::CM_ArrayType; 589 // Incomplete types are not modifiable. 590 if (CT->isIncompleteType()) 591 return Cl::CM_IncompleteType; 592 593 // Records with any const fields (recursively) are not modifiable. 594 if (const RecordType *R = CT->getAs<RecordType>()) { 595 assert((E->getObjectKind() == OK_ObjCProperty || 596 !Ctx.getLangOpts().CPlusPlus) && 597 "C++ struct assignment should be resolved by the " 598 "copy assignment operator."); 599 if (R->hasConstFields()) 600 return Cl::CM_ConstQualified; 601 } 602 603 return Cl::CM_Modifiable; 604} 605 606Expr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const { 607 Classification VC = Classify(Ctx); 608 switch (VC.getKind()) { 609 case Cl::CL_LValue: return LV_Valid; 610 case Cl::CL_XValue: return LV_InvalidExpression; 611 case Cl::CL_Function: return LV_NotObjectType; 612 case Cl::CL_Void: return LV_InvalidExpression; 613 case Cl::CL_AddressableVoid: return LV_IncompleteVoidType; 614 case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents; 615 case Cl::CL_MemberFunction: return LV_MemberFunction; 616 case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting; 617 case Cl::CL_ClassTemporary: return LV_ClassTemporary; 618 case Cl::CL_ArrayTemporary: return LV_ArrayTemporary; 619 case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression; 620 case Cl::CL_PRValue: return LV_InvalidExpression; 621 } 622 llvm_unreachable("Unhandled kind"); 623} 624 625Expr::isModifiableLvalueResult 626Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const { 627 SourceLocation dummy; 628 Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy); 629 switch (VC.getKind()) { 630 case Cl::CL_LValue: break; 631 case Cl::CL_XValue: return MLV_InvalidExpression; 632 case Cl::CL_Function: return MLV_NotObjectType; 633 case Cl::CL_Void: return MLV_InvalidExpression; 634 case Cl::CL_AddressableVoid: return MLV_IncompleteVoidType; 635 case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents; 636 case Cl::CL_MemberFunction: return MLV_MemberFunction; 637 case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting; 638 case Cl::CL_ClassTemporary: return MLV_ClassTemporary; 639 case Cl::CL_ArrayTemporary: return MLV_ArrayTemporary; 640 case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression; 641 case Cl::CL_PRValue: 642 return VC.getModifiable() == Cl::CM_LValueCast ? 643 MLV_LValueCast : MLV_InvalidExpression; 644 } 645 assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind"); 646 switch (VC.getModifiable()) { 647 case Cl::CM_Untested: llvm_unreachable("Did not test modifiability"); 648 case Cl::CM_Modifiable: return MLV_Valid; 649 case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match"); 650 case Cl::CM_Function: return MLV_NotObjectType; 651 case Cl::CM_LValueCast: 652 llvm_unreachable("CM_LValueCast and CL_LValue don't match"); 653 case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty; 654 case Cl::CM_ConstQualified: return MLV_ConstQualified; 655 case Cl::CM_ArrayType: return MLV_ArrayType; 656 case Cl::CM_IncompleteType: return MLV_IncompleteType; 657 } 658 llvm_unreachable("Unhandled modifiable type"); 659} 660