ExprClassification.cpp revision 3026348bd4c13a0f83b59839f64065e0fcbea253
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.getLangOptions().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 90static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) { 91 // This function takes the first stab at classifying expressions. 92 const LangOptions &Lang = Ctx.getLangOptions(); 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::ObjCPropertyRefExprClass: 112 // C++ [expr.typeid]p1: The result of a typeid expression is an lvalue of... 113 case Expr::CXXTypeidExprClass: 114 // Unresolved lookups get classified as lvalues. 115 // FIXME: Is this wise? Should they get their own kind? 116 case Expr::UnresolvedLookupExprClass: 117 case Expr::UnresolvedMemberExprClass: 118 case Expr::CXXDependentScopeMemberExprClass: 119 case Expr::DependentScopeDeclRefExprClass: 120 // ObjC instance variables are lvalues 121 // FIXME: ObjC++0x might have different rules 122 case Expr::ObjCIvarRefExprClass: 123 return Cl::CL_LValue; 124 125 // C99 6.5.2.5p5 says that compound literals are lvalues. 126 // In C++, they're class temporaries. 127 case Expr::CompoundLiteralExprClass: 128 return Ctx.getLangOptions().CPlusPlus? Cl::CL_ClassTemporary 129 : Cl::CL_LValue; 130 131 // Expressions that are prvalues. 132 case Expr::CXXBoolLiteralExprClass: 133 case Expr::CXXPseudoDestructorExprClass: 134 case Expr::UnaryExprOrTypeTraitExprClass: 135 case Expr::CXXNewExprClass: 136 case Expr::CXXThisExprClass: 137 case Expr::CXXNullPtrLiteralExprClass: 138 case Expr::ImaginaryLiteralClass: 139 case Expr::GNUNullExprClass: 140 case Expr::OffsetOfExprClass: 141 case Expr::CXXThrowExprClass: 142 case Expr::ShuffleVectorExprClass: 143 case Expr::IntegerLiteralClass: 144 case Expr::CharacterLiteralClass: 145 case Expr::AddrLabelExprClass: 146 case Expr::CXXDeleteExprClass: 147 case Expr::ImplicitValueInitExprClass: 148 case Expr::BlockExprClass: 149 case Expr::FloatingLiteralClass: 150 case Expr::CXXNoexceptExprClass: 151 case Expr::CXXScalarValueInitExprClass: 152 case Expr::UnaryTypeTraitExprClass: 153 case Expr::BinaryTypeTraitExprClass: 154 case Expr::ArrayTypeTraitExprClass: 155 case Expr::ExpressionTraitExprClass: 156 case Expr::ObjCSelectorExprClass: 157 case Expr::ObjCProtocolExprClass: 158 case Expr::ObjCStringLiteralClass: 159 case Expr::ParenListExprClass: 160 case Expr::SizeOfPackExprClass: 161 case Expr::SubstNonTypeTemplateParmPackExprClass: 162 case Expr::AsTypeExprClass: 163 case Expr::ObjCIndirectCopyRestoreExprClass: 164 case Expr::AtomicExprClass: 165 return Cl::CL_PRValue; 166 167 // Next come the complicated cases. 168 case Expr::SubstNonTypeTemplateParmExprClass: 169 return ClassifyInternal(Ctx, 170 cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement()); 171 172 // C++ [expr.sub]p1: The result is an lvalue of type "T". 173 // However, subscripting vector types is more like member access. 174 case Expr::ArraySubscriptExprClass: 175 if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType()) 176 return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase()); 177 return Cl::CL_LValue; 178 179 // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a 180 // function or variable and a prvalue otherwise. 181 case Expr::DeclRefExprClass: 182 if (E->getType() == Ctx.UnknownAnyTy) 183 return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl()) 184 ? Cl::CL_PRValue : Cl::CL_LValue; 185 return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl()); 186 // We deal with names referenced from blocks the same way. 187 case Expr::BlockDeclRefExprClass: 188 return ClassifyDecl(Ctx, cast<BlockDeclRefExpr>(E)->getDecl()); 189 190 // Member access is complex. 191 case Expr::MemberExprClass: 192 return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E)); 193 194 case Expr::UnaryOperatorClass: 195 switch (cast<UnaryOperator>(E)->getOpcode()) { 196 // C++ [expr.unary.op]p1: The unary * operator performs indirection: 197 // [...] the result is an lvalue referring to the object or function 198 // to which the expression points. 199 case UO_Deref: 200 return Cl::CL_LValue; 201 202 // GNU extensions, simply look through them. 203 case UO_Extension: 204 return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr()); 205 206 // Treat _Real and _Imag basically as if they were member 207 // expressions: l-value only if the operand is a true l-value. 208 case UO_Real: 209 case UO_Imag: { 210 const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens(); 211 Cl::Kinds K = ClassifyInternal(Ctx, Op); 212 if (K != Cl::CL_LValue) return K; 213 214 if (isa<ObjCPropertyRefExpr>(Op)) 215 return Cl::CL_SubObjCPropertySetting; 216 return Cl::CL_LValue; 217 } 218 219 // C++ [expr.pre.incr]p1: The result is the updated operand; it is an 220 // lvalue, [...] 221 // Not so in C. 222 case UO_PreInc: 223 case UO_PreDec: 224 return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue; 225 226 default: 227 return Cl::CL_PRValue; 228 } 229 230 case Expr::OpaqueValueExprClass: 231 return ClassifyExprValueKind(Lang, E, E->getValueKind()); 232 233 // Pseudo-object expressions can produce l-values with reference magic. 234 case Expr::PseudoObjectExprClass: 235 return ClassifyExprValueKind(Lang, E, 236 cast<PseudoObjectExpr>(E)->getValueKind()); 237 238 // Implicit casts are lvalues if they're lvalue casts. Other than that, we 239 // only specifically record class temporaries. 240 case Expr::ImplicitCastExprClass: 241 return ClassifyExprValueKind(Lang, E, E->getValueKind()); 242 243 // C++ [expr.prim.general]p4: The presence of parentheses does not affect 244 // whether the expression is an lvalue. 245 case Expr::ParenExprClass: 246 return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr()); 247 248 // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator, 249 // or a void expression if its result expression is, respectively, an 250 // lvalue, a function designator, or a void expression. 251 case Expr::GenericSelectionExprClass: 252 if (cast<GenericSelectionExpr>(E)->isResultDependent()) 253 return Cl::CL_PRValue; 254 return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr()); 255 256 case Expr::BinaryOperatorClass: 257 case Expr::CompoundAssignOperatorClass: 258 // C doesn't have any binary expressions that are lvalues. 259 if (Lang.CPlusPlus) 260 return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E)); 261 return Cl::CL_PRValue; 262 263 case Expr::CallExprClass: 264 case Expr::CXXOperatorCallExprClass: 265 case Expr::CXXMemberCallExprClass: 266 case Expr::CUDAKernelCallExprClass: 267 return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType()); 268 269 // __builtin_choose_expr is equivalent to the chosen expression. 270 case Expr::ChooseExprClass: 271 return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr(Ctx)); 272 273 // Extended vector element access is an lvalue unless there are duplicates 274 // in the shuffle expression. 275 case Expr::ExtVectorElementExprClass: 276 return cast<ExtVectorElementExpr>(E)->containsDuplicateElements() ? 277 Cl::CL_DuplicateVectorComponents : Cl::CL_LValue; 278 279 // Simply look at the actual default argument. 280 case Expr::CXXDefaultArgExprClass: 281 return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr()); 282 283 // Same idea for temporary binding. 284 case Expr::CXXBindTemporaryExprClass: 285 return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr()); 286 287 // And the cleanups guard. 288 case Expr::ExprWithCleanupsClass: 289 return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr()); 290 291 // Casts depend completely on the target type. All casts work the same. 292 case Expr::CStyleCastExprClass: 293 case Expr::CXXFunctionalCastExprClass: 294 case Expr::CXXStaticCastExprClass: 295 case Expr::CXXDynamicCastExprClass: 296 case Expr::CXXReinterpretCastExprClass: 297 case Expr::CXXConstCastExprClass: 298 case Expr::ObjCBridgedCastExprClass: 299 // Only in C++ can casts be interesting at all. 300 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 301 return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten()); 302 303 case Expr::CXXUnresolvedConstructExprClass: 304 return ClassifyUnnamed(Ctx, 305 cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten()); 306 307 case Expr::BinaryConditionalOperatorClass: { 308 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 309 const BinaryConditionalOperator *co = cast<BinaryConditionalOperator>(E); 310 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); 311 } 312 313 case Expr::ConditionalOperatorClass: { 314 // Once again, only C++ is interesting. 315 if (!Lang.CPlusPlus) return Cl::CL_PRValue; 316 const ConditionalOperator *co = cast<ConditionalOperator>(E); 317 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); 318 } 319 320 // ObjC message sends are effectively function calls, if the target function 321 // is known. 322 case Expr::ObjCMessageExprClass: 323 if (const ObjCMethodDecl *Method = 324 cast<ObjCMessageExpr>(E)->getMethodDecl()) { 325 Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getResultType()); 326 return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind; 327 } 328 return Cl::CL_PRValue; 329 330 // Some C++ expressions are always class temporaries. 331 case Expr::CXXConstructExprClass: 332 case Expr::CXXTemporaryObjectExprClass: 333 return Cl::CL_ClassTemporary; 334 335 case Expr::VAArgExprClass: 336 return ClassifyUnnamed(Ctx, E->getType()); 337 338 case Expr::DesignatedInitExprClass: 339 return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit()); 340 341 case Expr::StmtExprClass: { 342 const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt(); 343 if (const Expr *LastExpr = dyn_cast_or_null<Expr>(S->body_back())) 344 return ClassifyUnnamed(Ctx, LastExpr->getType()); 345 return Cl::CL_PRValue; 346 } 347 348 case Expr::CXXUuidofExprClass: 349 return Cl::CL_LValue; 350 351 case Expr::PackExpansionExprClass: 352 return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern()); 353 354 case Expr::MaterializeTemporaryExprClass: 355 return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference() 356 ? Cl::CL_LValue 357 : Cl::CL_XValue; 358 359 case Expr::InitListExprClass: 360 // An init list can be an lvalue if it is bound to a reference and 361 // contains only one element. In that case, we look at that element 362 // for an exact classification. Init list creation takes care of the 363 // value kind for us, so we only need to fine-tune. 364 if (E->isRValue()) 365 return ClassifyExprValueKind(Lang, E, E->getValueKind()); 366 assert(cast<InitListExpr>(E)->getNumInits() == 1 && 367 "Only 1-element init lists can be glvalues."); 368 return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0)); 369 } 370 371 llvm_unreachable("unhandled expression kind in classification"); 372} 373 374/// ClassifyDecl - Return the classification of an expression referencing the 375/// given declaration. 376static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) { 377 // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a 378 // function, variable, or data member and a prvalue otherwise. 379 // In C, functions are not lvalues. 380 // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an 381 // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to 382 // special-case this. 383 384 if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance()) 385 return Cl::CL_MemberFunction; 386 387 bool islvalue; 388 if (const NonTypeTemplateParmDecl *NTTParm = 389 dyn_cast<NonTypeTemplateParmDecl>(D)) 390 islvalue = NTTParm->getType()->isReferenceType(); 391 else 392 islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) || 393 isa<IndirectFieldDecl>(D) || 394 (Ctx.getLangOptions().CPlusPlus && 395 (isa<FunctionDecl>(D) || isa<FunctionTemplateDecl>(D))); 396 397 return islvalue ? Cl::CL_LValue : Cl::CL_PRValue; 398} 399 400/// ClassifyUnnamed - Return the classification of an expression yielding an 401/// unnamed value of the given type. This applies in particular to function 402/// calls and casts. 403static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) { 404 // In C, function calls are always rvalues. 405 if (!Ctx.getLangOptions().CPlusPlus) return Cl::CL_PRValue; 406 407 // C++ [expr.call]p10: A function call is an lvalue if the result type is an 408 // lvalue reference type or an rvalue reference to function type, an xvalue 409 // if the result type is an rvalue reference to object type, and a prvalue 410 // otherwise. 411 if (T->isLValueReferenceType()) 412 return Cl::CL_LValue; 413 const RValueReferenceType *RV = T->getAs<RValueReferenceType>(); 414 if (!RV) // Could still be a class temporary, though. 415 return T->isRecordType() ? Cl::CL_ClassTemporary : Cl::CL_PRValue; 416 417 return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue; 418} 419 420static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) { 421 if (E->getType() == Ctx.UnknownAnyTy) 422 return (isa<FunctionDecl>(E->getMemberDecl()) 423 ? Cl::CL_PRValue : Cl::CL_LValue); 424 425 // Handle C first, it's easier. 426 if (!Ctx.getLangOptions().CPlusPlus) { 427 // C99 6.5.2.3p3 428 // For dot access, the expression is an lvalue if the first part is. For 429 // arrow access, it always is an lvalue. 430 if (E->isArrow()) 431 return Cl::CL_LValue; 432 // ObjC property accesses are not lvalues, but get special treatment. 433 Expr *Base = E->getBase()->IgnoreParens(); 434 if (isa<ObjCPropertyRefExpr>(Base)) 435 return Cl::CL_SubObjCPropertySetting; 436 return ClassifyInternal(Ctx, Base); 437 } 438 439 NamedDecl *Member = E->getMemberDecl(); 440 // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2. 441 // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then 442 // E1.E2 is an lvalue. 443 if (ValueDecl *Value = dyn_cast<ValueDecl>(Member)) 444 if (Value->getType()->isReferenceType()) 445 return Cl::CL_LValue; 446 447 // Otherwise, one of the following rules applies. 448 // -- If E2 is a static member [...] then E1.E2 is an lvalue. 449 if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord()) 450 return Cl::CL_LValue; 451 452 // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then 453 // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue; 454 // otherwise, it is a prvalue. 455 if (isa<FieldDecl>(Member)) { 456 // *E1 is an lvalue 457 if (E->isArrow()) 458 return Cl::CL_LValue; 459 Expr *Base = E->getBase()->IgnoreParenImpCasts(); 460 if (isa<ObjCPropertyRefExpr>(Base)) 461 return Cl::CL_SubObjCPropertySetting; 462 return ClassifyInternal(Ctx, E->getBase()); 463 } 464 465 // -- If E2 is a [...] member function, [...] 466 // -- If it refers to a static member function [...], then E1.E2 is an 467 // lvalue; [...] 468 // -- Otherwise [...] E1.E2 is a prvalue. 469 if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member)) 470 return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction; 471 472 // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue. 473 // So is everything else we haven't handled yet. 474 return Cl::CL_PRValue; 475} 476 477static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) { 478 assert(Ctx.getLangOptions().CPlusPlus && 479 "This is only relevant for C++."); 480 // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand. 481 // Except we override this for writes to ObjC properties. 482 if (E->isAssignmentOp()) 483 return (E->getLHS()->getObjectKind() == OK_ObjCProperty 484 ? Cl::CL_PRValue : Cl::CL_LValue); 485 486 // C++ [expr.comma]p1: the result is of the same value category as its right 487 // operand, [...]. 488 if (E->getOpcode() == BO_Comma) 489 return ClassifyInternal(Ctx, E->getRHS()); 490 491 // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand 492 // is a pointer to a data member is of the same value category as its first 493 // operand. 494 if (E->getOpcode() == BO_PtrMemD) 495 return (E->getType()->isFunctionType() || 496 E->hasPlaceholderType(BuiltinType::BoundMember)) 497 ? Cl::CL_MemberFunction 498 : ClassifyInternal(Ctx, E->getLHS()); 499 500 // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its 501 // second operand is a pointer to data member and a prvalue otherwise. 502 if (E->getOpcode() == BO_PtrMemI) 503 return (E->getType()->isFunctionType() || 504 E->hasPlaceholderType(BuiltinType::BoundMember)) 505 ? Cl::CL_MemberFunction 506 : Cl::CL_LValue; 507 508 // All other binary operations are prvalues. 509 return Cl::CL_PRValue; 510} 511 512static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True, 513 const Expr *False) { 514 assert(Ctx.getLangOptions().CPlusPlus && 515 "This is only relevant for C++."); 516 517 // C++ [expr.cond]p2 518 // If either the second or the third operand has type (cv) void, [...] 519 // the result [...] is a prvalue. 520 if (True->getType()->isVoidType() || False->getType()->isVoidType()) 521 return Cl::CL_PRValue; 522 523 // Note that at this point, we have already performed all conversions 524 // according to [expr.cond]p3. 525 // C++ [expr.cond]p4: If the second and third operands are glvalues of the 526 // same value category [...], the result is of that [...] value category. 527 // C++ [expr.cond]p5: Otherwise, the result is a prvalue. 528 Cl::Kinds LCl = ClassifyInternal(Ctx, True), 529 RCl = ClassifyInternal(Ctx, False); 530 return LCl == RCl ? LCl : Cl::CL_PRValue; 531} 532 533static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, 534 Cl::Kinds Kind, SourceLocation &Loc) { 535 // As a general rule, we only care about lvalues. But there are some rvalues 536 // for which we want to generate special results. 537 if (Kind == Cl::CL_PRValue) { 538 // For the sake of better diagnostics, we want to specifically recognize 539 // use of the GCC cast-as-lvalue extension. 540 if (const ExplicitCastExpr *CE = 541 dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) { 542 if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) { 543 Loc = CE->getExprLoc(); 544 return Cl::CM_LValueCast; 545 } 546 } 547 } 548 if (Kind != Cl::CL_LValue) 549 return Cl::CM_RValue; 550 551 // This is the lvalue case. 552 // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6) 553 if (Ctx.getLangOptions().CPlusPlus && E->getType()->isFunctionType()) 554 return Cl::CM_Function; 555 556 // You cannot assign to a variable outside a block from within the block if 557 // it is not marked __block, e.g. 558 // void takeclosure(void (^C)(void)); 559 // void func() { int x = 1; takeclosure(^{ x = 7; }); } 560 if (const BlockDeclRefExpr *BDR = dyn_cast<BlockDeclRefExpr>(E)) { 561 if (!BDR->isByRef() && isa<VarDecl>(BDR->getDecl())) 562 return Cl::CM_NotBlockQualified; 563 } 564 565 // Assignment to a property in ObjC is an implicit setter access. But a 566 // setter might not exist. 567 if (const ObjCPropertyRefExpr *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) { 568 if (Expr->isImplicitProperty() && Expr->getImplicitPropertySetter() == 0) 569 return Cl::CM_NoSetterProperty; 570 } 571 572 CanQualType CT = Ctx.getCanonicalType(E->getType()); 573 // Const stuff is obviously not modifiable. 574 if (CT.isConstQualified()) 575 return Cl::CM_ConstQualified; 576 // Arrays are not modifiable, only their elements are. 577 if (CT->isArrayType()) 578 return Cl::CM_ArrayType; 579 // Incomplete types are not modifiable. 580 if (CT->isIncompleteType()) 581 return Cl::CM_IncompleteType; 582 583 // Records with any const fields (recursively) are not modifiable. 584 if (const RecordType *R = CT->getAs<RecordType>()) { 585 assert((E->getObjectKind() == OK_ObjCProperty || 586 !Ctx.getLangOptions().CPlusPlus) && 587 "C++ struct assignment should be resolved by the " 588 "copy assignment operator."); 589 if (R->hasConstFields()) 590 return Cl::CM_ConstQualified; 591 } 592 593 return Cl::CM_Modifiable; 594} 595 596Expr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const { 597 Classification VC = Classify(Ctx); 598 switch (VC.getKind()) { 599 case Cl::CL_LValue: return LV_Valid; 600 case Cl::CL_XValue: return LV_InvalidExpression; 601 case Cl::CL_Function: return LV_NotObjectType; 602 case Cl::CL_Void: return LV_InvalidExpression; 603 case Cl::CL_AddressableVoid: return LV_IncompleteVoidType; 604 case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents; 605 case Cl::CL_MemberFunction: return LV_MemberFunction; 606 case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting; 607 case Cl::CL_ClassTemporary: return LV_ClassTemporary; 608 case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression; 609 case Cl::CL_PRValue: return LV_InvalidExpression; 610 } 611 llvm_unreachable("Unhandled kind"); 612} 613 614Expr::isModifiableLvalueResult 615Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const { 616 SourceLocation dummy; 617 Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy); 618 switch (VC.getKind()) { 619 case Cl::CL_LValue: break; 620 case Cl::CL_XValue: return MLV_InvalidExpression; 621 case Cl::CL_Function: return MLV_NotObjectType; 622 case Cl::CL_Void: return MLV_InvalidExpression; 623 case Cl::CL_AddressableVoid: return MLV_IncompleteVoidType; 624 case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents; 625 case Cl::CL_MemberFunction: return MLV_MemberFunction; 626 case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting; 627 case Cl::CL_ClassTemporary: return MLV_ClassTemporary; 628 case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression; 629 case Cl::CL_PRValue: 630 return VC.getModifiable() == Cl::CM_LValueCast ? 631 MLV_LValueCast : MLV_InvalidExpression; 632 } 633 assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind"); 634 switch (VC.getModifiable()) { 635 case Cl::CM_Untested: llvm_unreachable("Did not test modifiability"); 636 case Cl::CM_Modifiable: return MLV_Valid; 637 case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match"); 638 case Cl::CM_Function: return MLV_NotObjectType; 639 case Cl::CM_LValueCast: 640 llvm_unreachable("CM_LValueCast and CL_LValue don't match"); 641 case Cl::CM_NotBlockQualified: return MLV_NotBlockQualified; 642 case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty; 643 case Cl::CM_ConstQualified: return MLV_ConstQualified; 644 case Cl::CM_ArrayType: return MLV_ArrayType; 645 case Cl::CM_IncompleteType: return MLV_IncompleteType; 646 } 647 llvm_unreachable("Unhandled modifiable type"); 648} 649