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 "clang/AST/Expr.h"
15 #include "clang/AST/ASTContext.h"
16 #include "clang/AST/DeclCXX.h"
17 #include "clang/AST/DeclObjC.h"
18 #include "clang/AST/DeclTemplate.h"
19 #include "clang/AST/ExprCXX.h"
20 #include "clang/AST/ExprObjC.h"
21 #include "llvm/Support/ErrorHandling.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
ClassifyImpl(ASTContext & Ctx,SourceLocation * Loc) const37 Cl Expr::ClassifyImpl(ASTContext &Ctx, SourceLocation *Loc) const {
38 assert(!TR->isReferenceType() && "Expressions can't have reference type.");
39
40 Cl::Kinds kind = ClassifyInternal(Ctx, this);
41 // C99 6.3.2.1: An lvalue is an expression with an object type or an
42 // incomplete type other than void.
43 if (!Ctx.getLangOpts().CPlusPlus) {
44 // Thus, no functions.
45 if (TR->isFunctionType() || TR == Ctx.OverloadTy)
46 kind = Cl::CL_Function;
47 // No void either, but qualified void is OK because it is "other than void".
48 // Void "lvalues" are classified as addressable void values, which are void
49 // expressions whose address can be taken.
50 else if (TR->isVoidType() && !TR.hasQualifiers())
51 kind = (kind == Cl::CL_LValue ? Cl::CL_AddressableVoid : Cl::CL_Void);
52 }
53
54 // Enable this assertion for testing.
55 switch (kind) {
56 case Cl::CL_LValue: assert(getValueKind() == VK_LValue); break;
57 case Cl::CL_XValue: assert(getValueKind() == VK_XValue); break;
58 case Cl::CL_Function:
59 case Cl::CL_Void:
60 case Cl::CL_AddressableVoid:
61 case Cl::CL_DuplicateVectorComponents:
62 case Cl::CL_MemberFunction:
63 case Cl::CL_SubObjCPropertySetting:
64 case Cl::CL_ClassTemporary:
65 case Cl::CL_ArrayTemporary:
66 case Cl::CL_ObjCMessageRValue:
67 case Cl::CL_PRValue: assert(getValueKind() == VK_RValue); break;
68 }
69
70 Cl::ModifiableType modifiable = Cl::CM_Untested;
71 if (Loc)
72 modifiable = IsModifiable(Ctx, this, kind, *Loc);
73 return Classification(kind, modifiable);
74 }
75
76 /// Classify an expression which creates a temporary, based on its type.
ClassifyTemporary(QualType T)77 static Cl::Kinds ClassifyTemporary(QualType T) {
78 if (T->isRecordType())
79 return Cl::CL_ClassTemporary;
80 if (T->isArrayType())
81 return Cl::CL_ArrayTemporary;
82
83 // No special classification: these don't behave differently from normal
84 // prvalues.
85 return Cl::CL_PRValue;
86 }
87
ClassifyExprValueKind(const LangOptions & Lang,const Expr * E,ExprValueKind Kind)88 static Cl::Kinds ClassifyExprValueKind(const LangOptions &Lang,
89 const Expr *E,
90 ExprValueKind Kind) {
91 switch (Kind) {
92 case VK_RValue:
93 return Lang.CPlusPlus ? ClassifyTemporary(E->getType()) : Cl::CL_PRValue;
94 case VK_LValue:
95 return Cl::CL_LValue;
96 case VK_XValue:
97 return Cl::CL_XValue;
98 }
99 llvm_unreachable("Invalid value category of implicit cast.");
100 }
101
ClassifyInternal(ASTContext & Ctx,const Expr * E)102 static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) {
103 // This function takes the first stab at classifying expressions.
104 const LangOptions &Lang = Ctx.getLangOpts();
105
106 switch (E->getStmtClass()) {
107 case Stmt::NoStmtClass:
108 #define ABSTRACT_STMT(Kind)
109 #define STMT(Kind, Base) case Expr::Kind##Class:
110 #define EXPR(Kind, Base)
111 #include "clang/AST/StmtNodes.inc"
112 llvm_unreachable("cannot classify a statement");
113
114 // First come the expressions that are always lvalues, unconditionally.
115 case Expr::ObjCIsaExprClass:
116 // C++ [expr.prim.general]p1: A string literal is an lvalue.
117 case Expr::StringLiteralClass:
118 // @encode is equivalent to its string
119 case Expr::ObjCEncodeExprClass:
120 // __func__ and friends are too.
121 case Expr::PredefinedExprClass:
122 // Property references are lvalues
123 case Expr::ObjCSubscriptRefExprClass:
124 case Expr::ObjCPropertyRefExprClass:
125 // C++ [expr.typeid]p1: The result of a typeid expression is an lvalue of...
126 case Expr::CXXTypeidExprClass:
127 // Unresolved lookups and uncorrected typos get classified as lvalues.
128 // FIXME: Is this wise? Should they get their own kind?
129 case Expr::UnresolvedLookupExprClass:
130 case Expr::UnresolvedMemberExprClass:
131 case Expr::TypoExprClass:
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 case Expr::FunctionParmPackExprClass:
138 case Expr::MSPropertyRefExprClass:
139 case Expr::MSPropertySubscriptExprClass:
140 case Expr::OMPArraySectionExprClass:
141 return Cl::CL_LValue;
142
143 // C99 6.5.2.5p5 says that compound literals are lvalues.
144 // In C++, they're prvalue temporaries.
145 case Expr::CompoundLiteralExprClass:
146 return Ctx.getLangOpts().CPlusPlus ? ClassifyTemporary(E->getType())
147 : Cl::CL_LValue;
148
149 // Expressions that are prvalues.
150 case Expr::CXXBoolLiteralExprClass:
151 case Expr::CXXPseudoDestructorExprClass:
152 case Expr::UnaryExprOrTypeTraitExprClass:
153 case Expr::CXXNewExprClass:
154 case Expr::CXXThisExprClass:
155 case Expr::CXXNullPtrLiteralExprClass:
156 case Expr::ImaginaryLiteralClass:
157 case Expr::GNUNullExprClass:
158 case Expr::OffsetOfExprClass:
159 case Expr::CXXThrowExprClass:
160 case Expr::ShuffleVectorExprClass:
161 case Expr::ConvertVectorExprClass:
162 case Expr::IntegerLiteralClass:
163 case Expr::CharacterLiteralClass:
164 case Expr::AddrLabelExprClass:
165 case Expr::CXXDeleteExprClass:
166 case Expr::ImplicitValueInitExprClass:
167 case Expr::BlockExprClass:
168 case Expr::FloatingLiteralClass:
169 case Expr::CXXNoexceptExprClass:
170 case Expr::CXXScalarValueInitExprClass:
171 case Expr::TypeTraitExprClass:
172 case Expr::ArrayTypeTraitExprClass:
173 case Expr::ExpressionTraitExprClass:
174 case Expr::ObjCSelectorExprClass:
175 case Expr::ObjCProtocolExprClass:
176 case Expr::ObjCStringLiteralClass:
177 case Expr::ObjCBoxedExprClass:
178 case Expr::ObjCArrayLiteralClass:
179 case Expr::ObjCDictionaryLiteralClass:
180 case Expr::ObjCBoolLiteralExprClass:
181 case Expr::ParenListExprClass:
182 case Expr::SizeOfPackExprClass:
183 case Expr::SubstNonTypeTemplateParmPackExprClass:
184 case Expr::AsTypeExprClass:
185 case Expr::ObjCIndirectCopyRestoreExprClass:
186 case Expr::AtomicExprClass:
187 case Expr::CXXFoldExprClass:
188 case Expr::NoInitExprClass:
189 case Expr::DesignatedInitUpdateExprClass:
190 case Expr::CoyieldExprClass:
191 return Cl::CL_PRValue;
192
193 // Next come the complicated cases.
194 case Expr::SubstNonTypeTemplateParmExprClass:
195 return ClassifyInternal(Ctx,
196 cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement());
197
198 // C++ [expr.sub]p1: The result is an lvalue of type "T".
199 // However, subscripting vector types is more like member access.
200 case Expr::ArraySubscriptExprClass:
201 if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType())
202 return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase());
203 return Cl::CL_LValue;
204
205 // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a
206 // function or variable and a prvalue otherwise.
207 case Expr::DeclRefExprClass:
208 if (E->getType() == Ctx.UnknownAnyTy)
209 return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl())
210 ? Cl::CL_PRValue : Cl::CL_LValue;
211 return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl());
212
213 // Member access is complex.
214 case Expr::MemberExprClass:
215 return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E));
216
217 case Expr::UnaryOperatorClass:
218 switch (cast<UnaryOperator>(E)->getOpcode()) {
219 // C++ [expr.unary.op]p1: The unary * operator performs indirection:
220 // [...] the result is an lvalue referring to the object or function
221 // to which the expression points.
222 case UO_Deref:
223 return Cl::CL_LValue;
224
225 // GNU extensions, simply look through them.
226 case UO_Extension:
227 return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr());
228
229 // Treat _Real and _Imag basically as if they were member
230 // expressions: l-value only if the operand is a true l-value.
231 case UO_Real:
232 case UO_Imag: {
233 const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens();
234 Cl::Kinds K = ClassifyInternal(Ctx, Op);
235 if (K != Cl::CL_LValue) return K;
236
237 if (isa<ObjCPropertyRefExpr>(Op))
238 return Cl::CL_SubObjCPropertySetting;
239 return Cl::CL_LValue;
240 }
241
242 // C++ [expr.pre.incr]p1: The result is the updated operand; it is an
243 // lvalue, [...]
244 // Not so in C.
245 case UO_PreInc:
246 case UO_PreDec:
247 return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue;
248
249 default:
250 return Cl::CL_PRValue;
251 }
252
253 case Expr::OpaqueValueExprClass:
254 return ClassifyExprValueKind(Lang, E, E->getValueKind());
255
256 // Pseudo-object expressions can produce l-values with reference magic.
257 case Expr::PseudoObjectExprClass:
258 return ClassifyExprValueKind(Lang, E,
259 cast<PseudoObjectExpr>(E)->getValueKind());
260
261 // Implicit casts are lvalues if they're lvalue casts. Other than that, we
262 // only specifically record class temporaries.
263 case Expr::ImplicitCastExprClass:
264 return ClassifyExprValueKind(Lang, E, E->getValueKind());
265
266 // C++ [expr.prim.general]p4: The presence of parentheses does not affect
267 // whether the expression is an lvalue.
268 case Expr::ParenExprClass:
269 return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr());
270
271 // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator,
272 // or a void expression if its result expression is, respectively, an
273 // lvalue, a function designator, or a void expression.
274 case Expr::GenericSelectionExprClass:
275 if (cast<GenericSelectionExpr>(E)->isResultDependent())
276 return Cl::CL_PRValue;
277 return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr());
278
279 case Expr::BinaryOperatorClass:
280 case Expr::CompoundAssignOperatorClass:
281 // C doesn't have any binary expressions that are lvalues.
282 if (Lang.CPlusPlus)
283 return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E));
284 return Cl::CL_PRValue;
285
286 case Expr::CallExprClass:
287 case Expr::CXXOperatorCallExprClass:
288 case Expr::CXXMemberCallExprClass:
289 case Expr::UserDefinedLiteralClass:
290 case Expr::CUDAKernelCallExprClass:
291 return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType(Ctx));
292
293 // __builtin_choose_expr is equivalent to the chosen expression.
294 case Expr::ChooseExprClass:
295 return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr());
296
297 // Extended vector element access is an lvalue unless there are duplicates
298 // in the shuffle expression.
299 case Expr::ExtVectorElementExprClass:
300 if (cast<ExtVectorElementExpr>(E)->containsDuplicateElements())
301 return Cl::CL_DuplicateVectorComponents;
302 if (cast<ExtVectorElementExpr>(E)->isArrow())
303 return Cl::CL_LValue;
304 return ClassifyInternal(Ctx, cast<ExtVectorElementExpr>(E)->getBase());
305
306 // Simply look at the actual default argument.
307 case Expr::CXXDefaultArgExprClass:
308 return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr());
309
310 // Same idea for default initializers.
311 case Expr::CXXDefaultInitExprClass:
312 return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr());
313
314 // Same idea for temporary binding.
315 case Expr::CXXBindTemporaryExprClass:
316 return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr());
317
318 // And the cleanups guard.
319 case Expr::ExprWithCleanupsClass:
320 return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr());
321
322 // Casts depend completely on the target type. All casts work the same.
323 case Expr::CStyleCastExprClass:
324 case Expr::CXXFunctionalCastExprClass:
325 case Expr::CXXStaticCastExprClass:
326 case Expr::CXXDynamicCastExprClass:
327 case Expr::CXXReinterpretCastExprClass:
328 case Expr::CXXConstCastExprClass:
329 case Expr::ObjCBridgedCastExprClass:
330 // Only in C++ can casts be interesting at all.
331 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
332 return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten());
333
334 case Expr::CXXUnresolvedConstructExprClass:
335 return ClassifyUnnamed(Ctx,
336 cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten());
337
338 case Expr::BinaryConditionalOperatorClass: {
339 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
340 const BinaryConditionalOperator *co = cast<BinaryConditionalOperator>(E);
341 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
342 }
343
344 case Expr::ConditionalOperatorClass: {
345 // Once again, only C++ is interesting.
346 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
347 const ConditionalOperator *co = cast<ConditionalOperator>(E);
348 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
349 }
350
351 // ObjC message sends are effectively function calls, if the target function
352 // is known.
353 case Expr::ObjCMessageExprClass:
354 if (const ObjCMethodDecl *Method =
355 cast<ObjCMessageExpr>(E)->getMethodDecl()) {
356 Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getReturnType());
357 return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind;
358 }
359 return Cl::CL_PRValue;
360
361 // Some C++ expressions are always class temporaries.
362 case Expr::CXXConstructExprClass:
363 case Expr::CXXInheritedCtorInitExprClass:
364 case Expr::CXXTemporaryObjectExprClass:
365 case Expr::LambdaExprClass:
366 case Expr::CXXStdInitializerListExprClass:
367 return Cl::CL_ClassTemporary;
368
369 case Expr::VAArgExprClass:
370 return ClassifyUnnamed(Ctx, E->getType());
371
372 case Expr::DesignatedInitExprClass:
373 return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit());
374
375 case Expr::StmtExprClass: {
376 const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt();
377 if (const Expr *LastExpr = dyn_cast_or_null<Expr>(S->body_back()))
378 return ClassifyUnnamed(Ctx, LastExpr->getType());
379 return Cl::CL_PRValue;
380 }
381
382 case Expr::CXXUuidofExprClass:
383 return Cl::CL_LValue;
384
385 case Expr::PackExpansionExprClass:
386 return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern());
387
388 case Expr::MaterializeTemporaryExprClass:
389 return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference()
390 ? Cl::CL_LValue
391 : Cl::CL_XValue;
392
393 case Expr::InitListExprClass:
394 // An init list can be an lvalue if it is bound to a reference and
395 // contains only one element. In that case, we look at that element
396 // for an exact classification. Init list creation takes care of the
397 // value kind for us, so we only need to fine-tune.
398 if (E->isRValue())
399 return ClassifyExprValueKind(Lang, E, E->getValueKind());
400 assert(cast<InitListExpr>(E)->getNumInits() == 1 &&
401 "Only 1-element init lists can be glvalues.");
402 return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0));
403
404 case Expr::CoawaitExprClass:
405 return ClassifyInternal(Ctx, cast<CoawaitExpr>(E)->getResumeExpr());
406 }
407
408 llvm_unreachable("unhandled expression kind in classification");
409 }
410
411 /// ClassifyDecl - Return the classification of an expression referencing the
412 /// given declaration.
ClassifyDecl(ASTContext & Ctx,const Decl * D)413 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) {
414 // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a
415 // function, variable, or data member and a prvalue otherwise.
416 // In C, functions are not lvalues.
417 // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an
418 // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to
419 // special-case this.
420
421 if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance())
422 return Cl::CL_MemberFunction;
423
424 bool islvalue;
425 if (const NonTypeTemplateParmDecl *NTTParm =
426 dyn_cast<NonTypeTemplateParmDecl>(D))
427 islvalue = NTTParm->getType()->isReferenceType();
428 else
429 islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) ||
430 isa<IndirectFieldDecl>(D) ||
431 (Ctx.getLangOpts().CPlusPlus &&
432 (isa<FunctionDecl>(D) || isa<MSPropertyDecl>(D) ||
433 isa<FunctionTemplateDecl>(D)));
434
435 return islvalue ? Cl::CL_LValue : Cl::CL_PRValue;
436 }
437
438 /// ClassifyUnnamed - Return the classification of an expression yielding an
439 /// unnamed value of the given type. This applies in particular to function
440 /// calls and casts.
ClassifyUnnamed(ASTContext & Ctx,QualType T)441 static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) {
442 // In C, function calls are always rvalues.
443 if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue;
444
445 // C++ [expr.call]p10: A function call is an lvalue if the result type is an
446 // lvalue reference type or an rvalue reference to function type, an xvalue
447 // if the result type is an rvalue reference to object type, and a prvalue
448 // otherwise.
449 if (T->isLValueReferenceType())
450 return Cl::CL_LValue;
451 const RValueReferenceType *RV = T->getAs<RValueReferenceType>();
452 if (!RV) // Could still be a class temporary, though.
453 return ClassifyTemporary(T);
454
455 return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue;
456 }
457
ClassifyMemberExpr(ASTContext & Ctx,const MemberExpr * E)458 static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) {
459 if (E->getType() == Ctx.UnknownAnyTy)
460 return (isa<FunctionDecl>(E->getMemberDecl())
461 ? Cl::CL_PRValue : Cl::CL_LValue);
462
463 // Handle C first, it's easier.
464 if (!Ctx.getLangOpts().CPlusPlus) {
465 // C99 6.5.2.3p3
466 // For dot access, the expression is an lvalue if the first part is. For
467 // arrow access, it always is an lvalue.
468 if (E->isArrow())
469 return Cl::CL_LValue;
470 // ObjC property accesses are not lvalues, but get special treatment.
471 Expr *Base = E->getBase()->IgnoreParens();
472 if (isa<ObjCPropertyRefExpr>(Base))
473 return Cl::CL_SubObjCPropertySetting;
474 return ClassifyInternal(Ctx, Base);
475 }
476
477 NamedDecl *Member = E->getMemberDecl();
478 // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2.
479 // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then
480 // E1.E2 is an lvalue.
481 if (ValueDecl *Value = dyn_cast<ValueDecl>(Member))
482 if (Value->getType()->isReferenceType())
483 return Cl::CL_LValue;
484
485 // Otherwise, one of the following rules applies.
486 // -- If E2 is a static member [...] then E1.E2 is an lvalue.
487 if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord())
488 return Cl::CL_LValue;
489
490 // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then
491 // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue;
492 // otherwise, it is a prvalue.
493 if (isa<FieldDecl>(Member)) {
494 // *E1 is an lvalue
495 if (E->isArrow())
496 return Cl::CL_LValue;
497 Expr *Base = E->getBase()->IgnoreParenImpCasts();
498 if (isa<ObjCPropertyRefExpr>(Base))
499 return Cl::CL_SubObjCPropertySetting;
500 return ClassifyInternal(Ctx, E->getBase());
501 }
502
503 // -- If E2 is a [...] member function, [...]
504 // -- If it refers to a static member function [...], then E1.E2 is an
505 // lvalue; [...]
506 // -- Otherwise [...] E1.E2 is a prvalue.
507 if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member))
508 return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction;
509
510 // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue.
511 // So is everything else we haven't handled yet.
512 return Cl::CL_PRValue;
513 }
514
ClassifyBinaryOp(ASTContext & Ctx,const BinaryOperator * E)515 static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) {
516 assert(Ctx.getLangOpts().CPlusPlus &&
517 "This is only relevant for C++.");
518 // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand.
519 // Except we override this for writes to ObjC properties.
520 if (E->isAssignmentOp())
521 return (E->getLHS()->getObjectKind() == OK_ObjCProperty
522 ? Cl::CL_PRValue : Cl::CL_LValue);
523
524 // C++ [expr.comma]p1: the result is of the same value category as its right
525 // operand, [...].
526 if (E->getOpcode() == BO_Comma)
527 return ClassifyInternal(Ctx, E->getRHS());
528
529 // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand
530 // is a pointer to a data member is of the same value category as its first
531 // operand.
532 if (E->getOpcode() == BO_PtrMemD)
533 return (E->getType()->isFunctionType() ||
534 E->hasPlaceholderType(BuiltinType::BoundMember))
535 ? Cl::CL_MemberFunction
536 : ClassifyInternal(Ctx, E->getLHS());
537
538 // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its
539 // second operand is a pointer to data member and a prvalue otherwise.
540 if (E->getOpcode() == BO_PtrMemI)
541 return (E->getType()->isFunctionType() ||
542 E->hasPlaceholderType(BuiltinType::BoundMember))
543 ? Cl::CL_MemberFunction
544 : Cl::CL_LValue;
545
546 // All other binary operations are prvalues.
547 return Cl::CL_PRValue;
548 }
549
ClassifyConditional(ASTContext & Ctx,const Expr * True,const Expr * False)550 static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True,
551 const Expr *False) {
552 assert(Ctx.getLangOpts().CPlusPlus &&
553 "This is only relevant for C++.");
554
555 // C++ [expr.cond]p2
556 // If either the second or the third operand has type (cv) void,
557 // one of the following shall hold:
558 if (True->getType()->isVoidType() || False->getType()->isVoidType()) {
559 // The second or the third operand (but not both) is a (possibly
560 // parenthesized) throw-expression; the result is of the [...] value
561 // category of the other.
562 bool TrueIsThrow = isa<CXXThrowExpr>(True->IgnoreParenImpCasts());
563 bool FalseIsThrow = isa<CXXThrowExpr>(False->IgnoreParenImpCasts());
564 if (const Expr *NonThrow = TrueIsThrow ? (FalseIsThrow ? nullptr : False)
565 : (FalseIsThrow ? True : nullptr))
566 return ClassifyInternal(Ctx, NonThrow);
567
568 // [Otherwise] the result [...] is a prvalue.
569 return Cl::CL_PRValue;
570 }
571
572 // Note that at this point, we have already performed all conversions
573 // according to [expr.cond]p3.
574 // C++ [expr.cond]p4: If the second and third operands are glvalues of the
575 // same value category [...], the result is of that [...] value category.
576 // C++ [expr.cond]p5: Otherwise, the result is a prvalue.
577 Cl::Kinds LCl = ClassifyInternal(Ctx, True),
578 RCl = ClassifyInternal(Ctx, False);
579 return LCl == RCl ? LCl : Cl::CL_PRValue;
580 }
581
IsModifiable(ASTContext & Ctx,const Expr * E,Cl::Kinds Kind,SourceLocation & Loc)582 static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E,
583 Cl::Kinds Kind, SourceLocation &Loc) {
584 // As a general rule, we only care about lvalues. But there are some rvalues
585 // for which we want to generate special results.
586 if (Kind == Cl::CL_PRValue) {
587 // For the sake of better diagnostics, we want to specifically recognize
588 // use of the GCC cast-as-lvalue extension.
589 if (const ExplicitCastExpr *CE =
590 dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) {
591 if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) {
592 Loc = CE->getExprLoc();
593 return Cl::CM_LValueCast;
594 }
595 }
596 }
597 if (Kind != Cl::CL_LValue)
598 return Cl::CM_RValue;
599
600 // This is the lvalue case.
601 // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6)
602 if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType())
603 return Cl::CM_Function;
604
605 // Assignment to a property in ObjC is an implicit setter access. But a
606 // setter might not exist.
607 if (const ObjCPropertyRefExpr *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) {
608 if (Expr->isImplicitProperty() &&
609 Expr->getImplicitPropertySetter() == nullptr)
610 return Cl::CM_NoSetterProperty;
611 }
612
613 CanQualType CT = Ctx.getCanonicalType(E->getType());
614 // Const stuff is obviously not modifiable.
615 if (CT.isConstQualified())
616 return Cl::CM_ConstQualified;
617 if (CT.getQualifiers().getAddressSpace() == LangAS::opencl_constant)
618 return Cl::CM_ConstAddrSpace;
619
620 // Arrays are not modifiable, only their elements are.
621 if (CT->isArrayType())
622 return Cl::CM_ArrayType;
623 // Incomplete types are not modifiable.
624 if (CT->isIncompleteType())
625 return Cl::CM_IncompleteType;
626
627 // Records with any const fields (recursively) are not modifiable.
628 if (const RecordType *R = CT->getAs<RecordType>())
629 if (R->hasConstFields())
630 return Cl::CM_ConstQualified;
631
632 return Cl::CM_Modifiable;
633 }
634
ClassifyLValue(ASTContext & Ctx) const635 Expr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const {
636 Classification VC = Classify(Ctx);
637 switch (VC.getKind()) {
638 case Cl::CL_LValue: return LV_Valid;
639 case Cl::CL_XValue: return LV_InvalidExpression;
640 case Cl::CL_Function: return LV_NotObjectType;
641 case Cl::CL_Void: return LV_InvalidExpression;
642 case Cl::CL_AddressableVoid: return LV_IncompleteVoidType;
643 case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents;
644 case Cl::CL_MemberFunction: return LV_MemberFunction;
645 case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting;
646 case Cl::CL_ClassTemporary: return LV_ClassTemporary;
647 case Cl::CL_ArrayTemporary: return LV_ArrayTemporary;
648 case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression;
649 case Cl::CL_PRValue: return LV_InvalidExpression;
650 }
651 llvm_unreachable("Unhandled kind");
652 }
653
654 Expr::isModifiableLvalueResult
isModifiableLvalue(ASTContext & Ctx,SourceLocation * Loc) const655 Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const {
656 SourceLocation dummy;
657 Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy);
658 switch (VC.getKind()) {
659 case Cl::CL_LValue: break;
660 case Cl::CL_XValue: return MLV_InvalidExpression;
661 case Cl::CL_Function: return MLV_NotObjectType;
662 case Cl::CL_Void: return MLV_InvalidExpression;
663 case Cl::CL_AddressableVoid: return MLV_IncompleteVoidType;
664 case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents;
665 case Cl::CL_MemberFunction: return MLV_MemberFunction;
666 case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting;
667 case Cl::CL_ClassTemporary: return MLV_ClassTemporary;
668 case Cl::CL_ArrayTemporary: return MLV_ArrayTemporary;
669 case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression;
670 case Cl::CL_PRValue:
671 return VC.getModifiable() == Cl::CM_LValueCast ?
672 MLV_LValueCast : MLV_InvalidExpression;
673 }
674 assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind");
675 switch (VC.getModifiable()) {
676 case Cl::CM_Untested: llvm_unreachable("Did not test modifiability");
677 case Cl::CM_Modifiable: return MLV_Valid;
678 case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match");
679 case Cl::CM_Function: return MLV_NotObjectType;
680 case Cl::CM_LValueCast:
681 llvm_unreachable("CM_LValueCast and CL_LValue don't match");
682 case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty;
683 case Cl::CM_ConstQualified: return MLV_ConstQualified;
684 case Cl::CM_ConstAddrSpace: return MLV_ConstAddrSpace;
685 case Cl::CM_ArrayType: return MLV_ArrayType;
686 case Cl::CM_IncompleteType: return MLV_IncompleteType;
687 }
688 llvm_unreachable("Unhandled modifiable type");
689 }
690