clang 19.0.0git
ExprClassification.cpp
Go to the documentation of this file.
1//===- ExprClassification.cpp - Expression AST Node Implementation --------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements Expr::classify.
10//
11//===----------------------------------------------------------------------===//
12
13#include "clang/AST/Expr.h"
15#include "clang/AST/DeclCXX.h"
16#include "clang/AST/DeclObjC.h"
18#include "clang/AST/ExprCXX.h"
19#include "clang/AST/ExprObjC.h"
20#include "llvm/Support/ErrorHandling.h"
21
22using namespace clang;
23
25
26static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E);
27static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D);
32 const Expr *trueExpr,
33 const Expr *falseExpr);
36
37Cl 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())
52 }
53
54 // Enable this assertion for testing.
55 switch (kind) {
56 case Cl::CL_LValue:
57 assert(isLValue());
58 break;
59 case Cl::CL_XValue:
60 assert(isXValue());
61 break;
62 case Cl::CL_Function:
63 case Cl::CL_Void:
71 case Cl::CL_PRValue:
72 assert(isPRValue());
73 break;
74 }
75
77 if (Loc)
78 modifiable = IsModifiable(Ctx, this, kind, *Loc);
79 return Classification(kind, modifiable);
80}
81
82/// Classify an expression which creates a temporary, based on its type.
84 if (T->isRecordType())
86 if (T->isArrayType())
88
89 // No special classification: these don't behave differently from normal
90 // prvalues.
91 return Cl::CL_PRValue;
92}
93
95 const Expr *E,
96 ExprValueKind Kind) {
97 switch (Kind) {
98 case VK_PRValue:
99 return Lang.CPlusPlus ? ClassifyTemporary(E->getType()) : Cl::CL_PRValue;
100 case VK_LValue:
101 return Cl::CL_LValue;
102 case VK_XValue:
103 return Cl::CL_XValue;
104 }
105 llvm_unreachable("Invalid value category of implicit cast.");
106}
107
109 // This function takes the first stab at classifying expressions.
110 const LangOptions &Lang = Ctx.getLangOpts();
111
112 switch (E->getStmtClass()) {
114#define ABSTRACT_STMT(Kind)
115#define STMT(Kind, Base) case Expr::Kind##Class:
116#define EXPR(Kind, Base)
117#include "clang/AST/StmtNodes.inc"
118 llvm_unreachable("cannot classify a statement");
119
120 // First come the expressions that are always lvalues, unconditionally.
121 case Expr::ObjCIsaExprClass:
122 // C++ [expr.prim.general]p1: A string literal is an lvalue.
123 case Expr::StringLiteralClass:
124 // @encode is equivalent to its string
125 case Expr::ObjCEncodeExprClass:
126 // __func__ and friends are too.
127 case Expr::PredefinedExprClass:
128 // Property references are lvalues
129 case Expr::ObjCSubscriptRefExprClass:
130 case Expr::ObjCPropertyRefExprClass:
131 // C++ [expr.typeid]p1: The result of a typeid expression is an lvalue of...
132 case Expr::CXXTypeidExprClass:
133 case Expr::CXXUuidofExprClass:
134 // Unresolved lookups and uncorrected typos get classified as lvalues.
135 // FIXME: Is this wise? Should they get their own kind?
136 case Expr::UnresolvedLookupExprClass:
137 case Expr::UnresolvedMemberExprClass:
138 case Expr::TypoExprClass:
139 case Expr::DependentCoawaitExprClass:
140 case Expr::CXXDependentScopeMemberExprClass:
141 case Expr::DependentScopeDeclRefExprClass:
142 // ObjC instance variables are lvalues
143 // FIXME: ObjC++0x might have different rules
144 case Expr::ObjCIvarRefExprClass:
145 case Expr::FunctionParmPackExprClass:
146 case Expr::MSPropertyRefExprClass:
147 case Expr::MSPropertySubscriptExprClass:
148 case Expr::ArraySectionExprClass:
149 case Expr::OMPArrayShapingExprClass:
150 case Expr::OMPIteratorExprClass:
151 return Cl::CL_LValue;
152
153 // C99 6.5.2.5p5 says that compound literals are lvalues.
154 // In C++, they're prvalue temporaries, except for file-scope arrays.
155 case Expr::CompoundLiteralExprClass:
157
158 // Expressions that are prvalues.
159 case Expr::CXXBoolLiteralExprClass:
160 case Expr::CXXPseudoDestructorExprClass:
161 case Expr::UnaryExprOrTypeTraitExprClass:
162 case Expr::CXXNewExprClass:
163 case Expr::CXXNullPtrLiteralExprClass:
164 case Expr::ImaginaryLiteralClass:
165 case Expr::GNUNullExprClass:
166 case Expr::OffsetOfExprClass:
167 case Expr::CXXThrowExprClass:
168 case Expr::ShuffleVectorExprClass:
169 case Expr::ConvertVectorExprClass:
170 case Expr::IntegerLiteralClass:
171 case Expr::FixedPointLiteralClass:
172 case Expr::CharacterLiteralClass:
173 case Expr::AddrLabelExprClass:
174 case Expr::CXXDeleteExprClass:
175 case Expr::ImplicitValueInitExprClass:
176 case Expr::BlockExprClass:
177 case Expr::FloatingLiteralClass:
178 case Expr::CXXNoexceptExprClass:
179 case Expr::CXXScalarValueInitExprClass:
180 case Expr::TypeTraitExprClass:
181 case Expr::ArrayTypeTraitExprClass:
182 case Expr::ExpressionTraitExprClass:
183 case Expr::ObjCSelectorExprClass:
184 case Expr::ObjCProtocolExprClass:
185 case Expr::ObjCStringLiteralClass:
186 case Expr::ObjCBoxedExprClass:
187 case Expr::ObjCArrayLiteralClass:
188 case Expr::ObjCDictionaryLiteralClass:
189 case Expr::ObjCBoolLiteralExprClass:
190 case Expr::ObjCAvailabilityCheckExprClass:
191 case Expr::ParenListExprClass:
192 case Expr::SizeOfPackExprClass:
193 case Expr::SubstNonTypeTemplateParmPackExprClass:
194 case Expr::AsTypeExprClass:
195 case Expr::ObjCIndirectCopyRestoreExprClass:
196 case Expr::AtomicExprClass:
197 case Expr::CXXFoldExprClass:
198 case Expr::ArrayInitLoopExprClass:
199 case Expr::ArrayInitIndexExprClass:
200 case Expr::NoInitExprClass:
201 case Expr::DesignatedInitUpdateExprClass:
202 case Expr::SourceLocExprClass:
203 case Expr::ConceptSpecializationExprClass:
204 case Expr::RequiresExprClass:
205 return Cl::CL_PRValue;
206
207 case Expr::EmbedExprClass:
208 // Nominally, this just goes through as a PRValue until we actually expand
209 // it and check it.
210 return Cl::CL_PRValue;
211
212 // Make HLSL this reference-like
213 case Expr::CXXThisExprClass:
214 return Lang.HLSL ? Cl::CL_LValue : Cl::CL_PRValue;
215
216 case Expr::ConstantExprClass:
217 return ClassifyInternal(Ctx, cast<ConstantExpr>(E)->getSubExpr());
218
219 // Next come the complicated cases.
220 case Expr::SubstNonTypeTemplateParmExprClass:
221 return ClassifyInternal(Ctx,
222 cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement());
223
224 case Expr::PackIndexingExprClass: {
225 // A pack-index-expression always expands to an id-expression.
226 // Consider it as an LValue expression.
227 if (cast<PackIndexingExpr>(E)->isInstantiationDependent())
228 return Cl::CL_LValue;
229 return ClassifyInternal(Ctx, cast<PackIndexingExpr>(E)->getSelectedExpr());
230 }
231
232 // C, C++98 [expr.sub]p1: The result is an lvalue of type "T".
233 // C++11 (DR1213): in the case of an array operand, the result is an lvalue
234 // if that operand is an lvalue and an xvalue otherwise.
235 // Subscripting vector types is more like member access.
236 case Expr::ArraySubscriptExprClass:
237 if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType())
238 return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase());
239 if (Lang.CPlusPlus11) {
240 // Step over the array-to-pointer decay if present, but not over the
241 // temporary materialization.
242 auto *Base = cast<ArraySubscriptExpr>(E)->getBase()->IgnoreImpCasts();
243 if (Base->getType()->isArrayType())
244 return ClassifyInternal(Ctx, Base);
245 }
246 return Cl::CL_LValue;
247
248 // Subscripting matrix types behaves like member accesses.
249 case Expr::MatrixSubscriptExprClass:
250 return ClassifyInternal(Ctx, cast<MatrixSubscriptExpr>(E)->getBase());
251
252 // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a
253 // function or variable and a prvalue otherwise.
254 case Expr::DeclRefExprClass:
255 if (E->getType() == Ctx.UnknownAnyTy)
256 return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl())
258 return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl());
259
260 // Member access is complex.
261 case Expr::MemberExprClass:
262 return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E));
263
264 case Expr::UnaryOperatorClass:
265 switch (cast<UnaryOperator>(E)->getOpcode()) {
266 // C++ [expr.unary.op]p1: The unary * operator performs indirection:
267 // [...] the result is an lvalue referring to the object or function
268 // to which the expression points.
269 case UO_Deref:
270 return Cl::CL_LValue;
271
272 // GNU extensions, simply look through them.
273 case UO_Extension:
274 return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr());
275
276 // Treat _Real and _Imag basically as if they were member
277 // expressions: l-value only if the operand is a true l-value.
278 case UO_Real:
279 case UO_Imag: {
280 const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens();
281 Cl::Kinds K = ClassifyInternal(Ctx, Op);
282 if (K != Cl::CL_LValue) return K;
283
284 if (isa<ObjCPropertyRefExpr>(Op))
286 return Cl::CL_LValue;
287 }
288
289 // C++ [expr.pre.incr]p1: The result is the updated operand; it is an
290 // lvalue, [...]
291 // Not so in C.
292 case UO_PreInc:
293 case UO_PreDec:
294 return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue;
295
296 default:
297 return Cl::CL_PRValue;
298 }
299
300 case Expr::RecoveryExprClass:
301 case Expr::OpaqueValueExprClass:
302 return ClassifyExprValueKind(Lang, E, E->getValueKind());
303
304 // Pseudo-object expressions can produce l-values with reference magic.
305 case Expr::PseudoObjectExprClass:
306 return ClassifyExprValueKind(Lang, E,
307 cast<PseudoObjectExpr>(E)->getValueKind());
308
309 // Implicit casts are lvalues if they're lvalue casts. Other than that, we
310 // only specifically record class temporaries.
311 case Expr::ImplicitCastExprClass:
312 return ClassifyExprValueKind(Lang, E, E->getValueKind());
313
314 // C++ [expr.prim.general]p4: The presence of parentheses does not affect
315 // whether the expression is an lvalue.
316 case Expr::ParenExprClass:
317 return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr());
318
319 // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator,
320 // or a void expression if its result expression is, respectively, an
321 // lvalue, a function designator, or a void expression.
322 case Expr::GenericSelectionExprClass:
323 if (cast<GenericSelectionExpr>(E)->isResultDependent())
324 return Cl::CL_PRValue;
325 return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr());
326
327 case Expr::BinaryOperatorClass:
328 case Expr::CompoundAssignOperatorClass:
329 // C doesn't have any binary expressions that are lvalues.
330 if (Lang.CPlusPlus)
331 return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E));
332 return Cl::CL_PRValue;
333
334 case Expr::CallExprClass:
335 case Expr::CXXOperatorCallExprClass:
336 case Expr::CXXMemberCallExprClass:
337 case Expr::UserDefinedLiteralClass:
338 case Expr::CUDAKernelCallExprClass:
339 return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType(Ctx));
340
341 case Expr::CXXRewrittenBinaryOperatorClass:
342 return ClassifyInternal(
343 Ctx, cast<CXXRewrittenBinaryOperator>(E)->getSemanticForm());
344
345 // __builtin_choose_expr is equivalent to the chosen expression.
346 case Expr::ChooseExprClass:
347 return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr());
348
349 // Extended vector element access is an lvalue unless there are duplicates
350 // in the shuffle expression.
351 case Expr::ExtVectorElementExprClass:
352 if (cast<ExtVectorElementExpr>(E)->containsDuplicateElements())
354 if (cast<ExtVectorElementExpr>(E)->isArrow())
355 return Cl::CL_LValue;
356 return ClassifyInternal(Ctx, cast<ExtVectorElementExpr>(E)->getBase());
357
358 // Simply look at the actual default argument.
359 case Expr::CXXDefaultArgExprClass:
360 return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr());
361
362 // Same idea for default initializers.
363 case Expr::CXXDefaultInitExprClass:
364 return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr());
365
366 // Same idea for temporary binding.
367 case Expr::CXXBindTemporaryExprClass:
368 return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr());
369
370 // And the cleanups guard.
371 case Expr::ExprWithCleanupsClass:
372 return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr());
373
374 // Casts depend completely on the target type. All casts work the same.
375 case Expr::CStyleCastExprClass:
376 case Expr::CXXFunctionalCastExprClass:
377 case Expr::CXXStaticCastExprClass:
378 case Expr::CXXDynamicCastExprClass:
379 case Expr::CXXReinterpretCastExprClass:
380 case Expr::CXXConstCastExprClass:
381 case Expr::CXXAddrspaceCastExprClass:
382 case Expr::ObjCBridgedCastExprClass:
383 case Expr::BuiltinBitCastExprClass:
384 // Only in C++ can casts be interesting at all.
385 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
386 return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten());
387
388 case Expr::CXXUnresolvedConstructExprClass:
389 return ClassifyUnnamed(Ctx,
390 cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten());
391
392 case Expr::BinaryConditionalOperatorClass: {
393 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
394 const auto *co = cast<BinaryConditionalOperator>(E);
395 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
396 }
397
398 case Expr::ConditionalOperatorClass: {
399 // Once again, only C++ is interesting.
400 if (!Lang.CPlusPlus) return Cl::CL_PRValue;
401 const auto *co = cast<ConditionalOperator>(E);
402 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
403 }
404
405 // ObjC message sends are effectively function calls, if the target function
406 // is known.
407 case Expr::ObjCMessageExprClass:
408 if (const ObjCMethodDecl *Method =
409 cast<ObjCMessageExpr>(E)->getMethodDecl()) {
410 Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getReturnType());
411 return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind;
412 }
413 return Cl::CL_PRValue;
414
415 // Some C++ expressions are always class temporaries.
416 case Expr::CXXConstructExprClass:
417 case Expr::CXXInheritedCtorInitExprClass:
418 case Expr::CXXTemporaryObjectExprClass:
419 case Expr::LambdaExprClass:
420 case Expr::CXXStdInitializerListExprClass:
422
423 case Expr::VAArgExprClass:
424 return ClassifyUnnamed(Ctx, E->getType());
425
426 case Expr::DesignatedInitExprClass:
427 return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit());
428
429 case Expr::StmtExprClass: {
430 const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt();
431 if (const auto *LastExpr = dyn_cast_or_null<Expr>(S->body_back()))
432 return ClassifyUnnamed(Ctx, LastExpr->getType());
433 return Cl::CL_PRValue;
434 }
435
436 case Expr::PackExpansionExprClass:
437 return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern());
438
439 case Expr::MaterializeTemporaryExprClass:
440 return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference()
443
444 case Expr::InitListExprClass:
445 // An init list can be an lvalue if it is bound to a reference and
446 // contains only one element. In that case, we look at that element
447 // for an exact classification. Init list creation takes care of the
448 // value kind for us, so we only need to fine-tune.
449 if (E->isPRValue())
450 return ClassifyExprValueKind(Lang, E, E->getValueKind());
451 assert(cast<InitListExpr>(E)->getNumInits() == 1 &&
452 "Only 1-element init lists can be glvalues.");
453 return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0));
454
455 case Expr::CoawaitExprClass:
456 case Expr::CoyieldExprClass:
457 return ClassifyInternal(Ctx, cast<CoroutineSuspendExpr>(E)->getResumeExpr());
458 case Expr::SYCLUniqueStableNameExprClass:
459 return Cl::CL_PRValue;
460 break;
461
462 case Expr::CXXParenListInitExprClass:
463 if (isa<ArrayType>(E->getType()))
466 }
467
468 llvm_unreachable("unhandled expression kind in classification");
469}
470
471/// ClassifyDecl - Return the classification of an expression referencing the
472/// given declaration.
473static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) {
474 // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a
475 // function, variable, or data member and a prvalue otherwise.
476 // In C, functions are not lvalues.
477 // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an
478 // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to
479 // special-case this.
480
481 if (const auto *M = dyn_cast<CXXMethodDecl>(D)) {
482 if (M->isImplicitObjectMemberFunction())
484 if (M->isStatic())
485 return Cl::CL_LValue;
486 return Cl::CL_PRValue;
487 }
488
489 bool islvalue;
490 if (const auto *NTTParm = dyn_cast<NonTypeTemplateParmDecl>(D))
491 islvalue = NTTParm->getType()->isReferenceType() ||
492 NTTParm->getType()->isRecordType();
493 else
494 islvalue =
497 (Ctx.getLangOpts().CPlusPlus &&
498 (isa<FunctionDecl, MSPropertyDecl, FunctionTemplateDecl>(D)));
499
500 return islvalue ? Cl::CL_LValue : Cl::CL_PRValue;
501}
502
503/// ClassifyUnnamed - Return the classification of an expression yielding an
504/// unnamed value of the given type. This applies in particular to function
505/// calls and casts.
507 // In C, function calls are always rvalues.
508 if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue;
509
510 // C++ [expr.call]p10: A function call is an lvalue if the result type is an
511 // lvalue reference type or an rvalue reference to function type, an xvalue
512 // if the result type is an rvalue reference to object type, and a prvalue
513 // otherwise.
515 return Cl::CL_LValue;
516 const auto *RV = T->getAs<RValueReferenceType>();
517 if (!RV) // Could still be a class temporary, though.
518 return ClassifyTemporary(T);
519
520 return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue;
521}
522
524 if (E->getType() == Ctx.UnknownAnyTy)
525 return (isa<FunctionDecl>(E->getMemberDecl())
527
528 // Handle C first, it's easier.
529 if (!Ctx.getLangOpts().CPlusPlus) {
530 // C99 6.5.2.3p3
531 // For dot access, the expression is an lvalue if the first part is. For
532 // arrow access, it always is an lvalue.
533 if (E->isArrow())
534 return Cl::CL_LValue;
535 // ObjC property accesses are not lvalues, but get special treatment.
536 Expr *Base = E->getBase()->IgnoreParens();
537 if (isa<ObjCPropertyRefExpr>(Base))
539 return ClassifyInternal(Ctx, Base);
540 }
541
542 NamedDecl *Member = E->getMemberDecl();
543 // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2.
544 // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then
545 // E1.E2 is an lvalue.
546 if (const auto *Value = dyn_cast<ValueDecl>(Member))
547 if (Value->getType()->isReferenceType())
548 return Cl::CL_LValue;
549
550 // Otherwise, one of the following rules applies.
551 // -- If E2 is a static member [...] then E1.E2 is an lvalue.
552 if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord())
553 return Cl::CL_LValue;
554
555 // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then
556 // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue;
557 // otherwise, it is a prvalue.
558 if (isa<FieldDecl>(Member)) {
559 // *E1 is an lvalue
560 if (E->isArrow())
561 return Cl::CL_LValue;
562 Expr *Base = E->getBase()->IgnoreParenImpCasts();
563 if (isa<ObjCPropertyRefExpr>(Base))
565 return ClassifyInternal(Ctx, E->getBase());
566 }
567
568 // -- If E2 is a [...] member function, [...]
569 // -- If it refers to a static member function [...], then E1.E2 is an
570 // lvalue; [...]
571 // -- Otherwise [...] E1.E2 is a prvalue.
572 if (const auto *Method = dyn_cast<CXXMethodDecl>(Member)) {
573 if (Method->isStatic())
574 return Cl::CL_LValue;
575 if (Method->isImplicitObjectMemberFunction())
577 return Cl::CL_PRValue;
578 }
579
580 // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue.
581 // So is everything else we haven't handled yet.
582 return Cl::CL_PRValue;
583}
584
586 assert(Ctx.getLangOpts().CPlusPlus &&
587 "This is only relevant for C++.");
588 // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand.
589 // Except we override this for writes to ObjC properties.
590 if (E->isAssignmentOp())
591 return (E->getLHS()->getObjectKind() == OK_ObjCProperty
593
594 // C++ [expr.comma]p1: the result is of the same value category as its right
595 // operand, [...].
596 if (E->getOpcode() == BO_Comma)
597 return ClassifyInternal(Ctx, E->getRHS());
598
599 // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand
600 // is a pointer to a data member is of the same value category as its first
601 // operand.
602 if (E->getOpcode() == BO_PtrMemD)
603 return (E->getType()->isFunctionType() ||
604 E->hasPlaceholderType(BuiltinType::BoundMember))
606 : ClassifyInternal(Ctx, E->getLHS());
607
608 // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its
609 // second operand is a pointer to data member and a prvalue otherwise.
610 if (E->getOpcode() == BO_PtrMemI)
611 return (E->getType()->isFunctionType() ||
612 E->hasPlaceholderType(BuiltinType::BoundMember))
615
616 // All other binary operations are prvalues.
617 return Cl::CL_PRValue;
618}
619
621 const Expr *False) {
622 assert(Ctx.getLangOpts().CPlusPlus &&
623 "This is only relevant for C++.");
624
625 // C++ [expr.cond]p2
626 // If either the second or the third operand has type (cv) void,
627 // one of the following shall hold:
628 if (True->getType()->isVoidType() || False->getType()->isVoidType()) {
629 // The second or the third operand (but not both) is a (possibly
630 // parenthesized) throw-expression; the result is of the [...] value
631 // category of the other.
632 bool TrueIsThrow = isa<CXXThrowExpr>(True->IgnoreParenImpCasts());
633 bool FalseIsThrow = isa<CXXThrowExpr>(False->IgnoreParenImpCasts());
634 if (const Expr *NonThrow = TrueIsThrow ? (FalseIsThrow ? nullptr : False)
635 : (FalseIsThrow ? True : nullptr))
636 return ClassifyInternal(Ctx, NonThrow);
637
638 // [Otherwise] the result [...] is a prvalue.
639 return Cl::CL_PRValue;
640 }
641
642 // Note that at this point, we have already performed all conversions
643 // according to [expr.cond]p3.
644 // C++ [expr.cond]p4: If the second and third operands are glvalues of the
645 // same value category [...], the result is of that [...] value category.
646 // C++ [expr.cond]p5: Otherwise, the result is a prvalue.
647 Cl::Kinds LCl = ClassifyInternal(Ctx, True),
648 RCl = ClassifyInternal(Ctx, False);
649 return LCl == RCl ? LCl : Cl::CL_PRValue;
650}
651
654 // As a general rule, we only care about lvalues. But there are some rvalues
655 // for which we want to generate special results.
656 if (Kind == Cl::CL_PRValue) {
657 // For the sake of better diagnostics, we want to specifically recognize
658 // use of the GCC cast-as-lvalue extension.
659 if (const auto *CE = dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) {
660 if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) {
661 Loc = CE->getExprLoc();
662 return Cl::CM_LValueCast;
663 }
664 }
665 }
666 if (Kind != Cl::CL_LValue)
667 return Cl::CM_RValue;
668
669 // This is the lvalue case.
670 // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6)
671 if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType())
672 return Cl::CM_Function;
673
674 // Assignment to a property in ObjC is an implicit setter access. But a
675 // setter might not exist.
676 if (const auto *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) {
677 if (Expr->isImplicitProperty() &&
678 Expr->getImplicitPropertySetter() == nullptr)
680 }
681
683 // Const stuff is obviously not modifiable.
684 if (CT.isConstQualified())
686 if (Ctx.getLangOpts().OpenCL &&
689
690 // Arrays are not modifiable, only their elements are.
691 if (CT->isArrayType())
692 return Cl::CM_ArrayType;
693 // Incomplete types are not modifiable.
694 if (CT->isIncompleteType())
696
697 // Records with any const fields (recursively) are not modifiable.
698 if (const RecordType *R = CT->getAs<RecordType>())
699 if (R->hasConstFields())
701
702 return Cl::CM_Modifiable;
703}
704
706 Classification VC = Classify(Ctx);
707 switch (VC.getKind()) {
708 case Cl::CL_LValue: return LV_Valid;
720 }
721 llvm_unreachable("Unhandled kind");
722}
723
726 SourceLocation dummy;
727 Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy);
728 switch (VC.getKind()) {
729 case Cl::CL_LValue: break;
740 case Cl::CL_PRValue:
741 return VC.getModifiable() == Cl::CM_LValueCast ?
743 }
744 assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind");
745 switch (VC.getModifiable()) {
746 case Cl::CM_Untested: llvm_unreachable("Did not test modifiability");
747 case Cl::CM_Modifiable: return MLV_Valid;
748 case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match");
751 llvm_unreachable("CM_LValueCast and CL_LValue don't match");
756 case Cl::CM_ArrayType: return MLV_ArrayType;
758 }
759 llvm_unreachable("Unhandled modifiable type");
760}
Defines the clang::ASTContext interface.
const Decl * D
Expr * E
Defines the C++ Decl subclasses, other than those for templates (found in DeclTemplate....
Defines the C++ template declaration subclasses.
Defines the clang::Expr interface and subclasses for C++ expressions.
static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T)
ClassifyUnnamed - Return the classification of an expression yielding an unnamed value of the given t...
static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *trueExpr, const Expr *falseExpr)
static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D)
ClassifyDecl - Return the classification of an expression referencing the given declaration.
static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E)
static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E)
static Cl::Kinds ClassifyExprValueKind(const LangOptions &Lang, const Expr *E, ExprValueKind Kind)
static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, Cl::Kinds Kind, SourceLocation &Loc)
static Cl::Kinds ClassifyTemporary(QualType T)
Classify an expression which creates a temporary, based on its type.
static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E)
SourceLocation Loc
Definition: SemaObjC.cpp:758
Holds long-lived AST nodes (such as types and decls) that can be referred to throughout the semantic ...
Definition: ASTContext.h:186
CanQualType getCanonicalType(QualType T) const
Return the canonical (structural) type corresponding to the specified potentially non-canonical type ...
Definition: ASTContext.h:2616
const LangOptions & getLangOpts() const
Definition: ASTContext.h:787
CanQualType OverloadTy
Definition: ASTContext.h:1137
CanQualType UnknownAnyTy
Definition: ASTContext.h:1138
A builtin binary operation expression such as "x + y" or "x <= y".
Definition: Expr.h:3845
A binding in a decomposition declaration.
Definition: DeclCXX.h:4107
bool isConstQualified() const
Qualifiers getQualifiers() const
Retrieve all qualifiers.
CanProxy< U > getAs() const
Retrieve a canonical type pointer with a different static type, upcasting or downcasting as needed.
CompoundStmt - This represents a group of statements like { stmt stmt }.
Definition: Stmt.h:1607
Decl - This represents one declaration (or definition), e.g.
Definition: DeclBase.h:86
The return type of classify().
Definition: Expr.h:330
ModifiableType
The results of modification testing.
Definition: Expr.h:348
ModifiableType getModifiable() const
Definition: Expr.h:376
Kinds getKind() const
Definition: Expr.h:375
Kinds
The various classification results. Most of these mean prvalue.
Definition: Expr.h:333
This represents one expression.
Definition: Expr.h:110
LValueClassification
Definition: Expr.h:282
@ LV_ArrayTemporary
Definition: Expr.h:292
@ LV_DuplicateVectorComponents
Definition: Expr.h:286
@ LV_ClassTemporary
Definition: Expr.h:291
@ LV_InvalidMessageExpression
Definition: Expr.h:288
@ LV_NotObjectType
Definition: Expr.h:284
@ LV_MemberFunction
Definition: Expr.h:289
@ LV_InvalidExpression
Definition: Expr.h:287
@ LV_IncompleteVoidType
Definition: Expr.h:285
@ LV_Valid
Definition: Expr.h:283
@ LV_SubObjCPropertySetting
Definition: Expr.h:290
Classification ClassifyModifiable(ASTContext &Ctx, SourceLocation &Loc) const
ClassifyModifiable - Classify this expression according to the C++11 expression taxonomy,...
Definition: Expr.h:417
bool isXValue() const
Definition: Expr.h:279
isModifiableLvalueResult isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc=nullptr) const
isModifiableLvalue - C99 6.3.2.1: an lvalue that does not have array type, does not have an incomplet...
LValueClassification ClassifyLValue(ASTContext &Ctx) const
Reasons why an expression might not be an l-value.
ExprValueKind getValueKind() const
getValueKind - The value kind that this expression produces.
Definition: Expr.h:437
Expr * IgnoreParenImpCasts() LLVM_READONLY
Skip past any parentheses and implicit casts which might surround this expression until reaching a fi...
Definition: Expr.cpp:3070
Expr * IgnoreParens() LLVM_READONLY
Skip past any parentheses which might surround this expression until reaching a fixed point.
Definition: Expr.cpp:3066
bool isPRValue() const
Definition: Expr.h:278
bool isLValue() const
isLValue - True if this expression is an "l-value" according to the rules of the current language.
Definition: Expr.h:277
ExprObjectKind getObjectKind() const
getObjectKind - The object kind that this expression produces.
Definition: Expr.h:444
isModifiableLvalueResult
Definition: Expr.h:297
@ MLV_DuplicateVectorComponents
Definition: Expr.h:301
@ MLV_LValueCast
Definition: Expr.h:303
@ MLV_InvalidMessageExpression
Definition: Expr.h:312
@ MLV_ConstQualifiedField
Definition: Expr.h:306
@ MLV_InvalidExpression
Definition: Expr.h:302
@ MLV_IncompleteType
Definition: Expr.h:304
@ MLV_Valid
Definition: Expr.h:298
@ MLV_ConstQualified
Definition: Expr.h:305
@ MLV_NoSetterProperty
Definition: Expr.h:309
@ MLV_ArrayTemporary
Definition: Expr.h:314
@ MLV_SubObjCPropertySetting
Definition: Expr.h:311
@ MLV_ConstAddrSpace
Definition: Expr.h:307
@ MLV_MemberFunction
Definition: Expr.h:310
@ MLV_NotObjectType
Definition: Expr.h:299
@ MLV_ArrayType
Definition: Expr.h:308
@ MLV_ClassTemporary
Definition: Expr.h:313
@ MLV_IncompleteVoidType
Definition: Expr.h:300
Classification Classify(ASTContext &Ctx) const
Classify - Classify this expression according to the C++11 expression taxonomy.
Definition: Expr.h:405
QualType getType() const
Definition: Expr.h:142
bool hasPlaceholderType() const
Returns whether this expression has a placeholder type.
Definition: Expr.h:516
Represents a member of a struct/union/class.
Definition: Decl.h:3069
Represents a field injected from an anonymous union/struct into the parent scope.
Definition: Decl.h:3353
Keeps track of the various options that can be enabled, which controls the dialect of C or C++ that i...
Definition: LangOptions.h:461
A global _GUID constant.
Definition: DeclCXX.h:4289
MemberExpr - [C99 6.5.2.3] Structure and Union Members.
Definition: Expr.h:3177
This represents a decl that may have a name.
Definition: Decl.h:249
ObjCMethodDecl - Represents an instance or class method declaration.
Definition: DeclObjC.h:140
A (possibly-)qualified type.
Definition: Type.h:942
bool hasQualifiers() const
Determine whether this type has any qualifiers.
Definition: Type.h:7833
LangAS getAddressSpace() const
Definition: Type.h:559
An rvalue reference type, per C++11 [dcl.ref].
Definition: Type.h:3461
A helper class that allows the use of isa/cast/dyncast to detect TagType objects of structs/unions/cl...
Definition: Type.h:5937
Encodes a location in the source.
@ NoStmtClass
Definition: Stmt.h:87
StmtClass getStmtClass() const
Definition: Stmt.h:1359
A template parameter object.
bool isVoidType() const
Definition: Type.h:8296
bool isArrayType() const
Definition: Type.h:8065
bool isReferenceType() const
Definition: Type.h:8011
bool isLValueReferenceType() const
Definition: Type.h:8015
bool isFunctionType() const
Definition: Type.h:7993
const T * getAs() const
Member-template getAs<specific type>'.
Definition: Type.h:8517
bool isRecordType() const
Definition: Type.h:8093
An artificial decl, representing a global anonymous constant value which is uniquified by value withi...
Definition: DeclCXX.h:4346
QualType getType() const
Definition: Value.cpp:234
Represents a variable declaration or definition.
Definition: Decl.h:918
The JSON file list parser is used to communicate input to InstallAPI.
bool isa(CodeGen::Address addr)
Definition: Address.h:294
@ OK_ObjCProperty
An Objective-C property is a logical field of an Objective-C object which is read and written via Obj...
Definition: Specifiers.h:158
ExprValueKind
The categorization of expression values, currently following the C++11 scheme.
Definition: Specifiers.h:129
@ VK_PRValue
A pr-value expression (in the C++11 taxonomy) produces a temporary value.
Definition: Specifiers.h:132
@ VK_XValue
An x-value expression is a reference to an object with independent storage but which can be "moved",...
Definition: Specifiers.h:141
@ VK_LValue
An l-value expression is a reference to an object with independent storage.
Definition: Specifiers.h:136
const FunctionProtoType * T