ExprClassification.cpp revision f111d935722ed488144600cea5ed03a6b5069e8f
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 return Cl::CL_PRValue; 51} 52 53Cl Expr::ClassifyImpl(ASTContext &Ctx, SourceLocation *Loc) const { 54 assert(!TR->isReferenceType() && "Expressions can't have reference type."); 55 56 Cl::Kinds kind = ClassifyInternal(Ctx, this); 57 // C99 6.3.2.1: An lvalue is an expression with an object type or an 58 // incomplete type other than void. 59 if (!Ctx.getLangOptions().CPlusPlus) { 60 // Thus, no functions. 61 if (TR->isFunctionType() || TR == Ctx.OverloadTy) 62 kind = Cl::CL_Function; 63 // No void either, but qualified void is OK because it is "other than void". 64 else if (TR->isVoidType() && !Ctx.getCanonicalType(TR).hasQualifiers()) 65 kind = Cl::CL_Void; 66 } 67 68 // Enable this assertion for testing. 69 switch (kind) { 70 case Cl::CL_LValue: assert(getValueKind() == VK_LValue); break; 71 case Cl::CL_XValue: assert(getValueKind() == VK_XValue); break; 72 case Cl::CL_Function: 73 case Cl::CL_Void: 74 case Cl::CL_DuplicateVectorComponents: 75 case Cl::CL_MemberFunction: 76 case Cl::CL_SubObjCPropertySetting: 77 case Cl::CL_ClassTemporary: 78 case Cl::CL_ObjCMessageRValue: 79 case Cl::CL_PRValue: assert(getValueKind() == VK_RValue); break; 80 } 81 82 Cl::ModifiableType modifiable = Cl::CM_Untested; 83 if (Loc) 84 modifiable = IsModifiable(Ctx, this, kind, *Loc); 85 return Classification(kind, modifiable); 86} 87 88static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) { 89 // This function takes the first stab at classifying expressions. 90 const LangOptions &Lang = Ctx.getLangOptions(); 91 92 switch (E->getStmtClass()) { 93 // First come the expressions that are always lvalues, unconditionally. 94 case Stmt::NoStmtClass: 95#define ABSTRACT_STMT(Kind) 96#define STMT(Kind, Base) case Expr::Kind##Class: 97#define EXPR(Kind, Base) 98#include "clang/AST/StmtNodes.inc" 99 llvm_unreachable("cannot classify a statement"); 100 break; 101 case Expr::ObjCIsaExprClass: 102 // C++ [expr.prim.general]p1: A string literal is an lvalue. 103 case Expr::StringLiteralClass: 104 // @encode is equivalent to its string 105 case Expr::ObjCEncodeExprClass: 106 // __func__ and friends are too. 107 case Expr::PredefinedExprClass: 108 // Property references are lvalues 109 case Expr::ObjCPropertyRefExprClass: 110 // C++ [expr.typeid]p1: The result of a typeid expression is an lvalue of... 111 case Expr::CXXTypeidExprClass: 112 // Unresolved lookups get classified as lvalues. 113 // FIXME: Is this wise? Should they get their own kind? 114 case Expr::UnresolvedLookupExprClass: 115 case Expr::UnresolvedMemberExprClass: 116 case Expr::CXXDependentScopeMemberExprClass: 117 case Expr::CXXUnresolvedConstructExprClass: 118 case Expr::DependentScopeDeclRefExprClass: 119 // ObjC instance variables are lvalues 120 // FIXME: ObjC++0x might have different rules 121 case Expr::ObjCIvarRefExprClass: 122 return Cl::CL_LValue; 123 // C99 6.5.2.5p5 says that compound literals are lvalues. 124 // In C++, they're class temporaries. 125 case Expr::CompoundLiteralExprClass: 126 return Ctx.getLangOptions().CPlusPlus? Cl::CL_ClassTemporary 127 : Cl::CL_LValue; 128 129 // Expressions that are prvalues. 130 case Expr::CXXBoolLiteralExprClass: 131 case Expr::CXXPseudoDestructorExprClass: 132 case Expr::UnaryExprOrTypeTraitExprClass: 133 case Expr::CXXNewExprClass: 134 case Expr::CXXThisExprClass: 135 case Expr::CXXNullPtrLiteralExprClass: 136 case Expr::ImaginaryLiteralClass: 137 case Expr::GNUNullExprClass: 138 case Expr::OffsetOfExprClass: 139 case Expr::CXXThrowExprClass: 140 case Expr::ShuffleVectorExprClass: 141 case Expr::IntegerLiteralClass: 142 case Expr::CharacterLiteralClass: 143 case Expr::AddrLabelExprClass: 144 case Expr::CXXDeleteExprClass: 145 case Expr::ImplicitValueInitExprClass: 146 case Expr::BlockExprClass: 147 case Expr::FloatingLiteralClass: 148 case Expr::CXXNoexceptExprClass: 149 case Expr::CXXScalarValueInitExprClass: 150 case Expr::UnaryTypeTraitExprClass: 151 case Expr::BinaryTypeTraitExprClass: 152 case Expr::ObjCSelectorExprClass: 153 case Expr::ObjCProtocolExprClass: 154 case Expr::ObjCStringLiteralClass: 155 case Expr::ParenListExprClass: 156 case Expr::InitListExprClass: 157 case Expr::SizeOfPackExprClass: 158 case Expr::SubstNonTypeTemplateParmPackExprClass: 159 return Cl::CL_PRValue; 160 161 // Next come the complicated cases. 162 163 // C++ [expr.sub]p1: The result is an lvalue of type "T". 164 // However, subscripting vector types is more like member access. 165 case Expr::ArraySubscriptExprClass: 166 if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType()) 167 return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase()); 168 return Cl::CL_LValue; 169 170 // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a 171 // function or variable and a prvalue otherwise. 172 case Expr::DeclRefExprClass: 173 if (E->getType() == Ctx.UnknownAnyTy) 174 return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl()) 175 ? Cl::CL_PRValue : Cl::CL_LValue; 176 return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl()); 177 // We deal with names referenced from blocks the same way. 178 case Expr::BlockDeclRefExprClass: 179 return ClassifyDecl(Ctx, cast<BlockDeclRefExpr>(E)->getDecl()); 180 181 // Member access is complex. 182 case Expr::MemberExprClass: 183 return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E)); 184 185 case Expr::UnaryOperatorClass: 186 switch (cast<UnaryOperator>(E)->getOpcode()) { 187 // C++ [expr.unary.op]p1: The unary * operator performs indirection: 188 // [...] the result is an lvalue referring to the object or function 189 // to which the expression points. 190 case UO_Deref: 191 return Cl::CL_LValue; 192 193 // GNU extensions, simply look through them. 194 case UO_Extension: 195 return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr()); 196 197 // Treat _Real and _Imag basically as if they were member 198 // expressions: l-value only if the operand is a true l-value. 199 case UO_Real: 200 case UO_Imag: { 201 const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens(); 202 Cl::Kinds K = ClassifyInternal(Ctx, Op); 203 if (K != Cl::CL_LValue) return K; 204 205 if (isa<ObjCPropertyRefExpr>(Op)) 206 return Cl::CL_SubObjCPropertySetting; 207 return Cl::CL_LValue; 208 } 209 210 // C++ [expr.pre.incr]p1: The result is the updated operand; it is an 211 // lvalue, [...] 212 // Not so in C. 213 case UO_PreInc: 214 case UO_PreDec: 215 return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue; 216 217 default: 218 return Cl::CL_PRValue; 219 } 220 221 case Expr::OpaqueValueExprClass: 222 return ClassifyExprValueKind(Lang, E, 223 cast<OpaqueValueExpr>(E)->getValueKind()); 224 225 // Implicit casts are lvalues if they're lvalue casts. Other than that, we 226 // only specifically record class temporaries. 227 case Expr::ImplicitCastExprClass: 228 return ClassifyExprValueKind(Lang, E, 229 cast<ImplicitCastExpr>(E)->getValueKind()); 230 231 // C++ [expr.prim.general]p4: The presence of parentheses does not affect 232 // whether the expression is an lvalue. 233 case Expr::ParenExprClass: 234 return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr()); 235 236 // C1X 6.5.1.1p4: [A generic selection] is an lvalue, a function designator, 237 // or a void expression if its result expression is, respectively, an 238 // lvalue, a function designator, or a void expression. 239 case Expr::GenericSelectionExprClass: 240 if (cast<GenericSelectionExpr>(E)->isResultDependent()) 241 return Cl::CL_PRValue; 242 return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr()); 243 244 case Expr::BinaryOperatorClass: 245 case Expr::CompoundAssignOperatorClass: 246 // C doesn't have any binary expressions that are lvalues. 247 if (Lang.CPlusPlus) 248 return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E)); 249 return Cl::CL_PRValue; 250 251 case Expr::CallExprClass: 252 case Expr::CXXOperatorCallExprClass: 253 case Expr::CXXMemberCallExprClass: 254 case Expr::CUDAKernelCallExprClass: 255 return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType()); 256 257 // __builtin_choose_expr is equivalent to the chosen expression. 258 case Expr::ChooseExprClass: 259 return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr(Ctx)); 260 261 // Extended vector element access is an lvalue unless there are duplicates 262 // in the shuffle expression. 263 case Expr::ExtVectorElementExprClass: 264 return cast<ExtVectorElementExpr>(E)->containsDuplicateElements() ? 265 Cl::CL_DuplicateVectorComponents : Cl::CL_LValue; 266 267 // Simply look at the actual default argument. 268 case Expr::CXXDefaultArgExprClass: 269 return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr()); 270 271 // Same idea for temporary binding. 272 case Expr::CXXBindTemporaryExprClass: 273 return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr()); 274 275 // And the cleanups guard. 276 case Expr::ExprWithCleanupsClass: 277 return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr()); 278 279 // Casts depend completely on the target type. All casts work the same. 280 case Expr::CStyleCastExprClass: 281 case Expr::CXXFunctionalCastExprClass: 282 case Expr::CXXStaticCastExprClass: 283 case Expr::CXXDynamicCastExprClass: 284 case Expr::CXXReinterpretCastExprClass: 285 case Expr::CXXConstCastExprClass: 286 // Only in C++ can casts be interesting at all. 287 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 288 return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten()); 289 290 case Expr::BinaryConditionalOperatorClass: { 291 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 292 const BinaryConditionalOperator *co = cast<BinaryConditionalOperator>(E); 293 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); 294 } 295 296 case Expr::ConditionalOperatorClass: { 297 // Once again, only C++ is interesting. 298 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 299 const ConditionalOperator *co = cast<ConditionalOperator>(E); 300 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); 301 } 302 303 // ObjC message sends are effectively function calls, if the target function 304 // is known. 305 case Expr::ObjCMessageExprClass: 306 if (const ObjCMethodDecl *Method = 307 cast<ObjCMessageExpr>(E)->getMethodDecl()) { 308 Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getResultType()); 309 return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind; 310 } 311 return Cl::CL_PRValue; 312 313 // Some C++ expressions are always class temporaries. 314 case Expr::CXXConstructExprClass: 315 case Expr::CXXTemporaryObjectExprClass: 316 return Cl::CL_ClassTemporary; 317 318 case Expr::VAArgExprClass: 319 return ClassifyUnnamed(Ctx, E->getType()); 320 321 case Expr::DesignatedInitExprClass: 322 return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit()); 323 324 case Expr::StmtExprClass: { 325 const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt(); 326 if (const Expr *LastExpr = dyn_cast_or_null<Expr>(S->body_back())) 327 return ClassifyUnnamed(Ctx, LastExpr->getType()); 328 return Cl::CL_PRValue; 329 } 330 331 case Expr::CXXUuidofExprClass: 332 return Cl::CL_LValue; 333 334 case Expr::PackExpansionExprClass: 335 return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern()); 336 } 337 338 llvm_unreachable("unhandled expression kind in classification"); 339 return Cl::CL_LValue; 340} 341 342/// ClassifyDecl - Return the classification of an expression referencing the 343/// given declaration. 344static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) { 345 // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a 346 // function, variable, or data member and a prvalue otherwise. 347 // In C, functions are not lvalues. 348 // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an 349 // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to 350 // special-case this. 351 352 if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance()) 353 return Cl::CL_MemberFunction; 354 355 bool islvalue; 356 if (const NonTypeTemplateParmDecl *NTTParm = 357 dyn_cast<NonTypeTemplateParmDecl>(D)) 358 islvalue = NTTParm->getType()->isReferenceType(); 359 else 360 islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) || 361 isa<IndirectFieldDecl>(D) || 362 (Ctx.getLangOptions().CPlusPlus && 363 (isa<FunctionDecl>(D) || isa<FunctionTemplateDecl>(D))); 364 365 return islvalue ? Cl::CL_LValue : Cl::CL_PRValue; 366} 367 368/// ClassifyUnnamed - Return the classification of an expression yielding an 369/// unnamed value of the given type. This applies in particular to function 370/// calls and casts. 371static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) { 372 // In C, function calls are always rvalues. 373 if (!Ctx.getLangOptions().CPlusPlus) return Cl::CL_PRValue; 374 375 // C++ [expr.call]p10: A function call is an lvalue if the result type is an 376 // lvalue reference type or an rvalue reference to function type, an xvalue 377 // if the result type is an rvalue refernence to object type, and a prvalue 378 // otherwise. 379 if (T->isLValueReferenceType()) 380 return Cl::CL_LValue; 381 const RValueReferenceType *RV = T->getAs<RValueReferenceType>(); 382 if (!RV) // Could still be a class temporary, though. 383 return T->isRecordType() ? Cl::CL_ClassTemporary : Cl::CL_PRValue; 384 385 return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue; 386} 387 388static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) { 389 if (E->getType() == Ctx.UnknownAnyTy) 390 return (isa<FunctionDecl>(E->getMemberDecl()) 391 ? Cl::CL_PRValue : Cl::CL_LValue); 392 393 // Handle C first, it's easier. 394 if (!Ctx.getLangOptions().CPlusPlus) { 395 // C99 6.5.2.3p3 396 // For dot access, the expression is an lvalue if the first part is. For 397 // arrow access, it always is an lvalue. 398 if (E->isArrow()) 399 return Cl::CL_LValue; 400 // ObjC property accesses are not lvalues, but get special treatment. 401 Expr *Base = E->getBase()->IgnoreParens(); 402 if (isa<ObjCPropertyRefExpr>(Base)) 403 return Cl::CL_SubObjCPropertySetting; 404 return ClassifyInternal(Ctx, Base); 405 } 406 407 NamedDecl *Member = E->getMemberDecl(); 408 // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2. 409 // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then 410 // E1.E2 is an lvalue. 411 if (ValueDecl *Value = dyn_cast<ValueDecl>(Member)) 412 if (Value->getType()->isReferenceType()) 413 return Cl::CL_LValue; 414 415 // Otherwise, one of the following rules applies. 416 // -- If E2 is a static member [...] then E1.E2 is an lvalue. 417 if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord()) 418 return Cl::CL_LValue; 419 420 // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then 421 // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue; 422 // otherwise, it is a prvalue. 423 if (isa<FieldDecl>(Member)) { 424 // *E1 is an lvalue 425 if (E->isArrow()) 426 return Cl::CL_LValue; 427 Expr *Base = E->getBase()->IgnoreParenImpCasts(); 428 if (isa<ObjCPropertyRefExpr>(Base)) 429 return Cl::CL_SubObjCPropertySetting; 430 return ClassifyInternal(Ctx, E->getBase()); 431 } 432 433 // -- If E2 is a [...] member function, [...] 434 // -- If it refers to a static member function [...], then E1.E2 is an 435 // lvalue; [...] 436 // -- Otherwise [...] E1.E2 is a prvalue. 437 if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member)) 438 return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction; 439 440 // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue. 441 // So is everything else we haven't handled yet. 442 return Cl::CL_PRValue; 443} 444 445static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) { 446 assert(Ctx.getLangOptions().CPlusPlus && 447 "This is only relevant for C++."); 448 // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand. 449 // Except we override this for writes to ObjC properties. 450 if (E->isAssignmentOp()) 451 return (E->getLHS()->getObjectKind() == OK_ObjCProperty 452 ? Cl::CL_PRValue : Cl::CL_LValue); 453 454 // C++ [expr.comma]p1: the result is of the same value category as its right 455 // operand, [...]. 456 if (E->getOpcode() == BO_Comma) 457 return ClassifyInternal(Ctx, E->getRHS()); 458 459 // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand 460 // is a pointer to a data member is of the same value category as its first 461 // operand. 462 if (E->getOpcode() == BO_PtrMemD) 463 return E->getType()->isFunctionType() ? Cl::CL_MemberFunction : 464 ClassifyInternal(Ctx, E->getLHS()); 465 466 // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its 467 // second operand is a pointer to data member and a prvalue otherwise. 468 if (E->getOpcode() == BO_PtrMemI) 469 return E->getType()->isFunctionType() ? 470 Cl::CL_MemberFunction : Cl::CL_LValue; 471 472 // All other binary operations are prvalues. 473 return Cl::CL_PRValue; 474} 475 476static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True, 477 const Expr *False) { 478 assert(Ctx.getLangOptions().CPlusPlus && 479 "This is only relevant for C++."); 480 481 // C++ [expr.cond]p2 482 // If either the second or the third operand has type (cv) void, [...] 483 // the result [...] is a prvalue. 484 if (True->getType()->isVoidType() || False->getType()->isVoidType()) 485 return Cl::CL_PRValue; 486 487 // Note that at this point, we have already performed all conversions 488 // according to [expr.cond]p3. 489 // C++ [expr.cond]p4: If the second and third operands are glvalues of the 490 // same value category [...], the result is of that [...] value category. 491 // C++ [expr.cond]p5: Otherwise, the result is a prvalue. 492 Cl::Kinds LCl = ClassifyInternal(Ctx, True), 493 RCl = ClassifyInternal(Ctx, False); 494 return LCl == RCl ? LCl : Cl::CL_PRValue; 495} 496 497static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, 498 Cl::Kinds Kind, SourceLocation &Loc) { 499 // As a general rule, we only care about lvalues. But there are some rvalues 500 // for which we want to generate special results. 501 if (Kind == Cl::CL_PRValue) { 502 // For the sake of better diagnostics, we want to specifically recognize 503 // use of the GCC cast-as-lvalue extension. 504 if (const ExplicitCastExpr *CE = 505 dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) { 506 if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) { 507 Loc = CE->getExprLoc(); 508 return Cl::CM_LValueCast; 509 } 510 } 511 } 512 if (Kind != Cl::CL_LValue) 513 return Cl::CM_RValue; 514 515 // This is the lvalue case. 516 // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6) 517 if (Ctx.getLangOptions().CPlusPlus && E->getType()->isFunctionType()) 518 return Cl::CM_Function; 519 520 // You cannot assign to a variable outside a block from within the block if 521 // it is not marked __block, e.g. 522 // void takeclosure(void (^C)(void)); 523 // void func() { int x = 1; takeclosure(^{ x = 7; }); } 524 if (const BlockDeclRefExpr *BDR = dyn_cast<BlockDeclRefExpr>(E)) { 525 if (!BDR->isByRef() && isa<VarDecl>(BDR->getDecl())) 526 return Cl::CM_NotBlockQualified; 527 } 528 529 // Assignment to a property in ObjC is an implicit setter access. But a 530 // setter might not exist. 531 if (const ObjCPropertyRefExpr *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) { 532 if (Expr->isImplicitProperty() && Expr->getImplicitPropertySetter() == 0) 533 return Cl::CM_NoSetterProperty; 534 } 535 536 CanQualType CT = Ctx.getCanonicalType(E->getType()); 537 // Const stuff is obviously not modifiable. 538 if (CT.isConstQualified()) 539 return Cl::CM_ConstQualified; 540 // Arrays are not modifiable, only their elements are. 541 if (CT->isArrayType()) 542 return Cl::CM_ArrayType; 543 // Incomplete types are not modifiable. 544 if (CT->isIncompleteType()) 545 return Cl::CM_IncompleteType; 546 547 // Records with any const fields (recursively) are not modifiable. 548 if (const RecordType *R = CT->getAs<RecordType>()) { 549 assert((E->getObjectKind() == OK_ObjCProperty || 550 !Ctx.getLangOptions().CPlusPlus) && 551 "C++ struct assignment should be resolved by the " 552 "copy assignment operator."); 553 if (R->hasConstFields()) 554 return Cl::CM_ConstQualified; 555 } 556 557 return Cl::CM_Modifiable; 558} 559 560Expr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const { 561 Classification VC = Classify(Ctx); 562 switch (VC.getKind()) { 563 case Cl::CL_LValue: return LV_Valid; 564 case Cl::CL_XValue: return LV_InvalidExpression; 565 case Cl::CL_Function: return LV_NotObjectType; 566 case Cl::CL_Void: return LV_IncompleteVoidType; 567 case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents; 568 case Cl::CL_MemberFunction: return LV_MemberFunction; 569 case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting; 570 case Cl::CL_ClassTemporary: return LV_ClassTemporary; 571 case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression; 572 case Cl::CL_PRValue: return LV_InvalidExpression; 573 } 574 llvm_unreachable("Unhandled kind"); 575} 576 577Expr::isModifiableLvalueResult 578Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const { 579 SourceLocation dummy; 580 Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy); 581 switch (VC.getKind()) { 582 case Cl::CL_LValue: break; 583 case Cl::CL_XValue: return MLV_InvalidExpression; 584 case Cl::CL_Function: return MLV_NotObjectType; 585 case Cl::CL_Void: return MLV_IncompleteVoidType; 586 case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents; 587 case Cl::CL_MemberFunction: return MLV_MemberFunction; 588 case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting; 589 case Cl::CL_ClassTemporary: return MLV_ClassTemporary; 590 case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression; 591 case Cl::CL_PRValue: 592 return VC.getModifiable() == Cl::CM_LValueCast ? 593 MLV_LValueCast : MLV_InvalidExpression; 594 } 595 assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind"); 596 switch (VC.getModifiable()) { 597 case Cl::CM_Untested: llvm_unreachable("Did not test modifiability"); 598 case Cl::CM_Modifiable: return MLV_Valid; 599 case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match"); 600 case Cl::CM_Function: return MLV_NotObjectType; 601 case Cl::CM_LValueCast: 602 llvm_unreachable("CM_LValueCast and CL_LValue don't match"); 603 case Cl::CM_NotBlockQualified: return MLV_NotBlockQualified; 604 case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty; 605 case Cl::CM_ConstQualified: return MLV_ConstQualified; 606 case Cl::CM_ArrayType: return MLV_ArrayType; 607 case Cl::CM_IncompleteType: return MLV_IncompleteType; 608 } 609 llvm_unreachable("Unhandled modifiable type"); 610} 611