clang  8.0.0svn
ExprClassification.cpp
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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 
23 using namespace clang;
24 
26 
27 static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E);
28 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D);
30 static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E);
33  const Expr *trueExpr,
34  const Expr *falseExpr);
35 static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E,
37 
38 Cl Expr::ClassifyImpl(ASTContext &Ctx, SourceLocation *Loc) const {
39  assert(!TR->isReferenceType() && "Expressions can't have reference type.");
40 
41  Cl::Kinds kind = ClassifyInternal(Ctx, this);
42  // C99 6.3.2.1: An lvalue is an expression with an object type or an
43  // incomplete type other than void.
44  if (!Ctx.getLangOpts().CPlusPlus) {
45  // Thus, no functions.
46  if (TR->isFunctionType() || TR == Ctx.OverloadTy)
47  kind = Cl::CL_Function;
48  // No void either, but qualified void is OK because it is "other than void".
49  // Void "lvalues" are classified as addressable void values, which are void
50  // expressions whose address can be taken.
51  else if (TR->isVoidType() && !TR.hasQualifiers())
53  }
54 
55  // Enable this assertion for testing.
56  switch (kind) {
57  case Cl::CL_LValue: assert(getValueKind() == VK_LValue); break;
58  case Cl::CL_XValue: assert(getValueKind() == VK_XValue); break;
59  case Cl::CL_Function:
60  case Cl::CL_Void:
68  case Cl::CL_PRValue: assert(getValueKind() == VK_RValue); break;
69  }
70 
72  if (Loc)
73  modifiable = IsModifiable(Ctx, this, kind, *Loc);
74  return Classification(kind, modifiable);
75 }
76 
77 /// Classify an expression which creates a temporary, based on its type.
79  if (T->isRecordType())
80  return Cl::CL_ClassTemporary;
81  if (T->isArrayType())
82  return Cl::CL_ArrayTemporary;
83 
84  // No special classification: these don't behave differently from normal
85  // prvalues.
86  return Cl::CL_PRValue;
87 }
88 
90  const Expr *E,
92  switch (Kind) {
93  case VK_RValue:
94  return Lang.CPlusPlus ? ClassifyTemporary(E->getType()) : Cl::CL_PRValue;
95  case VK_LValue:
96  return Cl::CL_LValue;
97  case VK_XValue:
98  return Cl::CL_XValue;
99  }
100  llvm_unreachable("Invalid value category of implicit cast.");
101 }
102 
103 static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) {
104  // This function takes the first stab at classifying expressions.
105  const LangOptions &Lang = Ctx.getLangOpts();
106 
107  switch (E->getStmtClass()) {
108  case Stmt::NoStmtClass:
109 #define ABSTRACT_STMT(Kind)
110 #define STMT(Kind, Base) case Expr::Kind##Class:
111 #define EXPR(Kind, Base)
112 #include "clang/AST/StmtNodes.inc"
113  llvm_unreachable("cannot classify a statement");
114 
115  // First come the expressions that are always lvalues, unconditionally.
116  case Expr::ObjCIsaExprClass:
117  // C++ [expr.prim.general]p1: A string literal is an lvalue.
118  case Expr::StringLiteralClass:
119  // @encode is equivalent to its string
120  case Expr::ObjCEncodeExprClass:
121  // __func__ and friends are too.
122  case Expr::PredefinedExprClass:
123  // Property references are lvalues
124  case Expr::ObjCSubscriptRefExprClass:
125  case Expr::ObjCPropertyRefExprClass:
126  // C++ [expr.typeid]p1: The result of a typeid expression is an lvalue of...
127  case Expr::CXXTypeidExprClass:
128  // Unresolved lookups and uncorrected typos get classified as lvalues.
129  // FIXME: Is this wise? Should they get their own kind?
130  case Expr::UnresolvedLookupExprClass:
131  case Expr::UnresolvedMemberExprClass:
132  case Expr::TypoExprClass:
133  case Expr::DependentCoawaitExprClass:
134  case Expr::CXXDependentScopeMemberExprClass:
135  case Expr::DependentScopeDeclRefExprClass:
136  // ObjC instance variables are lvalues
137  // FIXME: ObjC++0x might have different rules
138  case Expr::ObjCIvarRefExprClass:
139  case Expr::FunctionParmPackExprClass:
140  case Expr::MSPropertyRefExprClass:
141  case Expr::MSPropertySubscriptExprClass:
142  case Expr::OMPArraySectionExprClass:
143  return Cl::CL_LValue;
144 
145  // C99 6.5.2.5p5 says that compound literals are lvalues.
146  // In C++, they're prvalue temporaries, except for file-scope arrays.
147  case Expr::CompoundLiteralExprClass:
148  return !E->isLValue() ? ClassifyTemporary(E->getType()) : Cl::CL_LValue;
149 
150  // Expressions that are prvalues.
151  case Expr::CXXBoolLiteralExprClass:
152  case Expr::CXXPseudoDestructorExprClass:
153  case Expr::UnaryExprOrTypeTraitExprClass:
154  case Expr::CXXNewExprClass:
155  case Expr::CXXThisExprClass:
156  case Expr::CXXNullPtrLiteralExprClass:
157  case Expr::ImaginaryLiteralClass:
158  case Expr::GNUNullExprClass:
159  case Expr::OffsetOfExprClass:
160  case Expr::CXXThrowExprClass:
161  case Expr::ShuffleVectorExprClass:
162  case Expr::ConvertVectorExprClass:
163  case Expr::IntegerLiteralClass:
164  case Expr::FixedPointLiteralClass:
165  case Expr::CharacterLiteralClass:
166  case Expr::AddrLabelExprClass:
167  case Expr::CXXDeleteExprClass:
168  case Expr::ImplicitValueInitExprClass:
169  case Expr::BlockExprClass:
170  case Expr::FloatingLiteralClass:
171  case Expr::CXXNoexceptExprClass:
172  case Expr::CXXScalarValueInitExprClass:
173  case Expr::TypeTraitExprClass:
174  case Expr::ArrayTypeTraitExprClass:
175  case Expr::ExpressionTraitExprClass:
176  case Expr::ObjCSelectorExprClass:
177  case Expr::ObjCProtocolExprClass:
178  case Expr::ObjCStringLiteralClass:
179  case Expr::ObjCBoxedExprClass:
180  case Expr::ObjCArrayLiteralClass:
181  case Expr::ObjCDictionaryLiteralClass:
182  case Expr::ObjCBoolLiteralExprClass:
183  case Expr::ObjCAvailabilityCheckExprClass:
184  case Expr::ParenListExprClass:
185  case Expr::SizeOfPackExprClass:
186  case Expr::SubstNonTypeTemplateParmPackExprClass:
187  case Expr::AsTypeExprClass:
188  case Expr::ObjCIndirectCopyRestoreExprClass:
189  case Expr::AtomicExprClass:
190  case Expr::CXXFoldExprClass:
191  case Expr::ArrayInitLoopExprClass:
192  case Expr::ArrayInitIndexExprClass:
193  case Expr::NoInitExprClass:
194  case Expr::DesignatedInitUpdateExprClass:
195  return Cl::CL_PRValue;
196 
197  case Expr::ConstantExprClass:
198  return ClassifyInternal(Ctx, cast<ConstantExpr>(E)->getSubExpr());
199 
200  // Next come the complicated cases.
201  case Expr::SubstNonTypeTemplateParmExprClass:
202  return ClassifyInternal(Ctx,
203  cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement());
204 
205  // C, C++98 [expr.sub]p1: The result is an lvalue of type "T".
206  // C++11 (DR1213): in the case of an array operand, the result is an lvalue
207  // if that operand is an lvalue and an xvalue otherwise.
208  // Subscripting vector types is more like member access.
209  case Expr::ArraySubscriptExprClass:
210  if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType())
211  return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase());
212  if (Lang.CPlusPlus11) {
213  // Step over the array-to-pointer decay if present, but not over the
214  // temporary materialization.
215  auto *Base = cast<ArraySubscriptExpr>(E)->getBase()->IgnoreImpCasts();
216  if (Base->getType()->isArrayType())
217  return ClassifyInternal(Ctx, Base);
218  }
219  return Cl::CL_LValue;
220 
221  // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a
222  // function or variable and a prvalue otherwise.
223  case Expr::DeclRefExprClass:
224  if (E->getType() == Ctx.UnknownAnyTy)
225  return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl())
227  return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl());
228 
229  // Member access is complex.
230  case Expr::MemberExprClass:
231  return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E));
232 
233  case Expr::UnaryOperatorClass:
234  switch (cast<UnaryOperator>(E)->getOpcode()) {
235  // C++ [expr.unary.op]p1: The unary * operator performs indirection:
236  // [...] the result is an lvalue referring to the object or function
237  // to which the expression points.
238  case UO_Deref:
239  return Cl::CL_LValue;
240 
241  // GNU extensions, simply look through them.
242  case UO_Extension:
243  return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr());
244 
245  // Treat _Real and _Imag basically as if they were member
246  // expressions: l-value only if the operand is a true l-value.
247  case UO_Real:
248  case UO_Imag: {
249  const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens();
250  Cl::Kinds K = ClassifyInternal(Ctx, Op);
251  if (K != Cl::CL_LValue) return K;
252 
253  if (isa<ObjCPropertyRefExpr>(Op))
255  return Cl::CL_LValue;
256  }
257 
258  // C++ [expr.pre.incr]p1: The result is the updated operand; it is an
259  // lvalue, [...]
260  // Not so in C.
261  case UO_PreInc:
262  case UO_PreDec:
263  return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue;
264 
265  default:
266  return Cl::CL_PRValue;
267  }
268 
269  case Expr::OpaqueValueExprClass:
270  return ClassifyExprValueKind(Lang, E, E->getValueKind());
271 
272  // Pseudo-object expressions can produce l-values with reference magic.
273  case Expr::PseudoObjectExprClass:
274  return ClassifyExprValueKind(Lang, E,
275  cast<PseudoObjectExpr>(E)->getValueKind());
276 
277  // Implicit casts are lvalues if they're lvalue casts. Other than that, we
278  // only specifically record class temporaries.
279  case Expr::ImplicitCastExprClass:
280  return ClassifyExprValueKind(Lang, E, E->getValueKind());
281 
282  // C++ [expr.prim.general]p4: The presence of parentheses does not affect
283  // whether the expression is an lvalue.
284  case Expr::ParenExprClass:
285  return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr());
286 
287  // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator,
288  // or a void expression if its result expression is, respectively, an
289  // lvalue, a function designator, or a void expression.
290  case Expr::GenericSelectionExprClass:
291  if (cast<GenericSelectionExpr>(E)->isResultDependent())
292  return Cl::CL_PRValue;
293  return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr());
294 
295  case Expr::BinaryOperatorClass:
296  case Expr::CompoundAssignOperatorClass:
297  // C doesn't have any binary expressions that are lvalues.
298  if (Lang.CPlusPlus)
299  return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E));
300  return Cl::CL_PRValue;
301 
302  case Expr::CallExprClass:
303  case Expr::CXXOperatorCallExprClass:
304  case Expr::CXXMemberCallExprClass:
305  case Expr::UserDefinedLiteralClass:
306  case Expr::CUDAKernelCallExprClass:
307  return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType(Ctx));
308 
309  // __builtin_choose_expr is equivalent to the chosen expression.
310  case Expr::ChooseExprClass:
311  return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr());
312 
313  // Extended vector element access is an lvalue unless there are duplicates
314  // in the shuffle expression.
315  case Expr::ExtVectorElementExprClass:
316  if (cast<ExtVectorElementExpr>(E)->containsDuplicateElements())
318  if (cast<ExtVectorElementExpr>(E)->isArrow())
319  return Cl::CL_LValue;
320  return ClassifyInternal(Ctx, cast<ExtVectorElementExpr>(E)->getBase());
321 
322  // Simply look at the actual default argument.
323  case Expr::CXXDefaultArgExprClass:
324  return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr());
325 
326  // Same idea for default initializers.
327  case Expr::CXXDefaultInitExprClass:
328  return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr());
329 
330  // Same idea for temporary binding.
331  case Expr::CXXBindTemporaryExprClass:
332  return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr());
333 
334  // And the cleanups guard.
335  case Expr::ExprWithCleanupsClass:
336  return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr());
337 
338  // Casts depend completely on the target type. All casts work the same.
339  case Expr::CStyleCastExprClass:
340  case Expr::CXXFunctionalCastExprClass:
341  case Expr::CXXStaticCastExprClass:
342  case Expr::CXXDynamicCastExprClass:
343  case Expr::CXXReinterpretCastExprClass:
344  case Expr::CXXConstCastExprClass:
345  case Expr::ObjCBridgedCastExprClass:
346  // Only in C++ can casts be interesting at all.
347  if (!Lang.CPlusPlus) return Cl::CL_PRValue;
348  return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten());
349 
350  case Expr::CXXUnresolvedConstructExprClass:
351  return ClassifyUnnamed(Ctx,
352  cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten());
353 
354  case Expr::BinaryConditionalOperatorClass: {
355  if (!Lang.CPlusPlus) return Cl::CL_PRValue;
356  const auto *co = cast<BinaryConditionalOperator>(E);
357  return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
358  }
359 
360  case Expr::ConditionalOperatorClass: {
361  // Once again, only C++ is interesting.
362  if (!Lang.CPlusPlus) return Cl::CL_PRValue;
363  const auto *co = cast<ConditionalOperator>(E);
364  return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());
365  }
366 
367  // ObjC message sends are effectively function calls, if the target function
368  // is known.
369  case Expr::ObjCMessageExprClass:
370  if (const ObjCMethodDecl *Method =
371  cast<ObjCMessageExpr>(E)->getMethodDecl()) {
372  Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getReturnType());
373  return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind;
374  }
375  return Cl::CL_PRValue;
376 
377  // Some C++ expressions are always class temporaries.
378  case Expr::CXXConstructExprClass:
379  case Expr::CXXInheritedCtorInitExprClass:
380  case Expr::CXXTemporaryObjectExprClass:
381  case Expr::LambdaExprClass:
382  case Expr::CXXStdInitializerListExprClass:
383  return Cl::CL_ClassTemporary;
384 
385  case Expr::VAArgExprClass:
386  return ClassifyUnnamed(Ctx, E->getType());
387 
388  case Expr::DesignatedInitExprClass:
389  return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit());
390 
391  case Expr::StmtExprClass: {
392  const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt();
393  if (const auto *LastExpr = dyn_cast_or_null<Expr>(S->body_back()))
394  return ClassifyUnnamed(Ctx, LastExpr->getType());
395  return Cl::CL_PRValue;
396  }
397 
398  case Expr::CXXUuidofExprClass:
399  return Cl::CL_LValue;
400 
401  case Expr::PackExpansionExprClass:
402  return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern());
403 
404  case Expr::MaterializeTemporaryExprClass:
405  return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference()
406  ? Cl::CL_LValue
407  : Cl::CL_XValue;
408 
409  case Expr::InitListExprClass:
410  // An init list can be an lvalue if it is bound to a reference and
411  // contains only one element. In that case, we look at that element
412  // for an exact classification. Init list creation takes care of the
413  // value kind for us, so we only need to fine-tune.
414  if (E->isRValue())
415  return ClassifyExprValueKind(Lang, E, E->getValueKind());
416  assert(cast<InitListExpr>(E)->getNumInits() == 1 &&
417  "Only 1-element init lists can be glvalues.");
418  return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0));
419 
420  case Expr::CoawaitExprClass:
421  case Expr::CoyieldExprClass:
422  return ClassifyInternal(Ctx, cast<CoroutineSuspendExpr>(E)->getResumeExpr());
423  }
424 
425  llvm_unreachable("unhandled expression kind in classification");
426 }
427 
428 /// ClassifyDecl - Return the classification of an expression referencing the
429 /// given declaration.
430 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) {
431  // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a
432  // function, variable, or data member and a prvalue otherwise.
433  // In C, functions are not lvalues.
434  // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an
435  // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to
436  // special-case this.
437 
438  if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance())
439  return Cl::CL_MemberFunction;
440 
441  bool islvalue;
442  if (const auto *NTTParm = dyn_cast<NonTypeTemplateParmDecl>(D))
443  islvalue = NTTParm->getType()->isReferenceType();
444  else
445  islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) ||
446  isa<IndirectFieldDecl>(D) ||
447  isa<BindingDecl>(D) ||
448  (Ctx.getLangOpts().CPlusPlus &&
449  (isa<FunctionDecl>(D) || isa<MSPropertyDecl>(D) ||
450  isa<FunctionTemplateDecl>(D)));
451 
452  return islvalue ? Cl::CL_LValue : Cl::CL_PRValue;
453 }
454 
455 /// ClassifyUnnamed - Return the classification of an expression yielding an
456 /// unnamed value of the given type. This applies in particular to function
457 /// calls and casts.
459  // In C, function calls are always rvalues.
460  if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue;
461 
462  // C++ [expr.call]p10: A function call is an lvalue if the result type is an
463  // lvalue reference type or an rvalue reference to function type, an xvalue
464  // if the result type is an rvalue reference to object type, and a prvalue
465  // otherwise.
466  if (T->isLValueReferenceType())
467  return Cl::CL_LValue;
468  const auto *RV = T->getAs<RValueReferenceType>();
469  if (!RV) // Could still be a class temporary, though.
470  return ClassifyTemporary(T);
471 
472  return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue;
473 }
474 
476  if (E->getType() == Ctx.UnknownAnyTy)
477  return (isa<FunctionDecl>(E->getMemberDecl())
479 
480  // Handle C first, it's easier.
481  if (!Ctx.getLangOpts().CPlusPlus) {
482  // C99 6.5.2.3p3
483  // For dot access, the expression is an lvalue if the first part is. For
484  // arrow access, it always is an lvalue.
485  if (E->isArrow())
486  return Cl::CL_LValue;
487  // ObjC property accesses are not lvalues, but get special treatment.
488  Expr *Base = E->getBase()->IgnoreParens();
489  if (isa<ObjCPropertyRefExpr>(Base))
491  return ClassifyInternal(Ctx, Base);
492  }
493 
494  NamedDecl *Member = E->getMemberDecl();
495  // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2.
496  // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then
497  // E1.E2 is an lvalue.
498  if (const auto *Value = dyn_cast<ValueDecl>(Member))
499  if (Value->getType()->isReferenceType())
500  return Cl::CL_LValue;
501 
502  // Otherwise, one of the following rules applies.
503  // -- If E2 is a static member [...] then E1.E2 is an lvalue.
504  if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord())
505  return Cl::CL_LValue;
506 
507  // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then
508  // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue;
509  // otherwise, it is a prvalue.
510  if (isa<FieldDecl>(Member)) {
511  // *E1 is an lvalue
512  if (E->isArrow())
513  return Cl::CL_LValue;
515  if (isa<ObjCPropertyRefExpr>(Base))
517  return ClassifyInternal(Ctx, E->getBase());
518  }
519 
520  // -- If E2 is a [...] member function, [...]
521  // -- If it refers to a static member function [...], then E1.E2 is an
522  // lvalue; [...]
523  // -- Otherwise [...] E1.E2 is a prvalue.
524  if (const auto *Method = dyn_cast<CXXMethodDecl>(Member))
525  return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction;
526 
527  // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue.
528  // So is everything else we haven't handled yet.
529  return Cl::CL_PRValue;
530 }
531 
533  assert(Ctx.getLangOpts().CPlusPlus &&
534  "This is only relevant for C++.");
535  // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand.
536  // Except we override this for writes to ObjC properties.
537  if (E->isAssignmentOp())
538  return (E->getLHS()->getObjectKind() == OK_ObjCProperty
540 
541  // C++ [expr.comma]p1: the result is of the same value category as its right
542  // operand, [...].
543  if (E->getOpcode() == BO_Comma)
544  return ClassifyInternal(Ctx, E->getRHS());
545 
546  // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand
547  // is a pointer to a data member is of the same value category as its first
548  // operand.
549  if (E->getOpcode() == BO_PtrMemD)
550  return (E->getType()->isFunctionType() ||
551  E->hasPlaceholderType(BuiltinType::BoundMember))
553  : ClassifyInternal(Ctx, E->getLHS());
554 
555  // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its
556  // second operand is a pointer to data member and a prvalue otherwise.
557  if (E->getOpcode() == BO_PtrMemI)
558  return (E->getType()->isFunctionType() ||
559  E->hasPlaceholderType(BuiltinType::BoundMember))
561  : Cl::CL_LValue;
562 
563  // All other binary operations are prvalues.
564  return Cl::CL_PRValue;
565 }
566 
567 static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True,
568  const Expr *False) {
569  assert(Ctx.getLangOpts().CPlusPlus &&
570  "This is only relevant for C++.");
571 
572  // C++ [expr.cond]p2
573  // If either the second or the third operand has type (cv) void,
574  // one of the following shall hold:
575  if (True->getType()->isVoidType() || False->getType()->isVoidType()) {
576  // The second or the third operand (but not both) is a (possibly
577  // parenthesized) throw-expression; the result is of the [...] value
578  // category of the other.
579  bool TrueIsThrow = isa<CXXThrowExpr>(True->IgnoreParenImpCasts());
580  bool FalseIsThrow = isa<CXXThrowExpr>(False->IgnoreParenImpCasts());
581  if (const Expr *NonThrow = TrueIsThrow ? (FalseIsThrow ? nullptr : False)
582  : (FalseIsThrow ? True : nullptr))
583  return ClassifyInternal(Ctx, NonThrow);
584 
585  // [Otherwise] the result [...] is a prvalue.
586  return Cl::CL_PRValue;
587  }
588 
589  // Note that at this point, we have already performed all conversions
590  // according to [expr.cond]p3.
591  // C++ [expr.cond]p4: If the second and third operands are glvalues of the
592  // same value category [...], the result is of that [...] value category.
593  // C++ [expr.cond]p5: Otherwise, the result is a prvalue.
594  Cl::Kinds LCl = ClassifyInternal(Ctx, True),
595  RCl = ClassifyInternal(Ctx, False);
596  return LCl == RCl ? LCl : Cl::CL_PRValue;
597 }
598 
600  Cl::Kinds Kind, SourceLocation &Loc) {
601  // As a general rule, we only care about lvalues. But there are some rvalues
602  // for which we want to generate special results.
603  if (Kind == Cl::CL_PRValue) {
604  // For the sake of better diagnostics, we want to specifically recognize
605  // use of the GCC cast-as-lvalue extension.
606  if (const auto *CE = dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) {
607  if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) {
608  Loc = CE->getExprLoc();
609  return Cl::CM_LValueCast;
610  }
611  }
612  }
613  if (Kind != Cl::CL_LValue)
614  return Cl::CM_RValue;
615 
616  // This is the lvalue case.
617  // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6)
618  if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType())
619  return Cl::CM_Function;
620 
621  // Assignment to a property in ObjC is an implicit setter access. But a
622  // setter might not exist.
623  if (const auto *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) {
624  if (Expr->isImplicitProperty() &&
625  Expr->getImplicitPropertySetter() == nullptr)
627  }
628 
629  CanQualType CT = Ctx.getCanonicalType(E->getType());
630  // Const stuff is obviously not modifiable.
631  if (CT.isConstQualified())
632  return Cl::CM_ConstQualified;
633  if (Ctx.getLangOpts().OpenCL &&
635  return Cl::CM_ConstAddrSpace;
636 
637  // Arrays are not modifiable, only their elements are.
638  if (CT->isArrayType())
639  return Cl::CM_ArrayType;
640  // Incomplete types are not modifiable.
641  if (CT->isIncompleteType())
642  return Cl::CM_IncompleteType;
643 
644  // Records with any const fields (recursively) are not modifiable.
645  if (const RecordType *R = CT->getAs<RecordType>())
646  if (R->hasConstFields())
648 
649  return Cl::CM_Modifiable;
650 }
651 
653  Classification VC = Classify(Ctx);
654  switch (VC.getKind()) {
655  case Cl::CL_LValue: return LV_Valid;
656  case Cl::CL_XValue: return LV_InvalidExpression;
657  case Cl::CL_Function: return LV_NotObjectType;
658  case Cl::CL_Void: return LV_InvalidExpression;
667  }
668  llvm_unreachable("Unhandled kind");
669 }
670 
673  SourceLocation dummy;
674  Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy);
675  switch (VC.getKind()) {
676  case Cl::CL_LValue: break;
678  case Cl::CL_Function: return MLV_NotObjectType;
679  case Cl::CL_Void: return MLV_InvalidExpression;
687  case Cl::CL_PRValue:
688  return VC.getModifiable() == Cl::CM_LValueCast ?
690  }
691  assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind");
692  switch (VC.getModifiable()) {
693  case Cl::CM_Untested: llvm_unreachable("Did not test modifiability");
694  case Cl::CM_Modifiable: return MLV_Valid;
695  case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match");
696  case Cl::CM_Function: return MLV_NotObjectType;
697  case Cl::CM_LValueCast:
698  llvm_unreachable("CM_LValueCast and CL_LValue don't match");
703  case Cl::CM_ArrayType: return MLV_ArrayType;
705  }
706  llvm_unreachable("Unhandled modifiable type");
707 }
Defines the clang::ASTContext interface.
Stmt * body_back()
Definition: Stmt.h:861
A (possibly-)qualified type.
Definition: Type.h:642
bool isArrayType() const
Definition: Type.h:6331
ValueDecl * getMemberDecl() const
Retrieve the member declaration to which this expression refers.
Definition: Expr.h:2650
bool isConstQualified() const
bool hasPlaceholderType() const
Returns whether this expression has a placeholder type.
Definition: Expr.h:472
bool isRecordType() const
Definition: Type.h:6355
Expr * getBase() const
Definition: Expr.h:2644
Decl - This represents one declaration (or definition), e.g.
Definition: DeclBase.h:87
Defines the C++ template declaration subclasses.
Opcode getOpcode() const
Definition: Expr.h:3234
Classification Classify(ASTContext &Ctx) const
Classify - Classify this expression according to the C++11 expression taxonomy.
Definition: Expr.h:377
isModifiableLvalueResult
Definition: Expr.h:269
static Cl::Kinds ClassifyExprValueKind(const LangOptions &Lang, const Expr *E, ExprValueKind Kind)
const T * getAs() const
Member-template getAs<specific type>&#39;.
Definition: Type.h:6716
ObjCMethodDecl - Represents an instance or class method declaration.
Definition: DeclObjC.h:139
static bool isAssignmentOp(Opcode Opc)
Definition: Expr.h:3316
Defines the clang::Expr interface and subclasses for C++ expressions.
Qualifiers getQualifiers() const
Retrieve all qualifiers.
Holds long-lived AST nodes (such as types and decls) that can be referred to throughout the semantic ...
Definition: ASTContext.h:154
LValueClassification ClassifyLValue(ASTContext &Ctx) const
Reasons why an expression might not be an l-value.
static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, Cl::Kinds Kind, SourceLocation &Loc)
bool isReferenceType() const
Definition: Type.h:6294
Classification ClassifyModifiable(ASTContext &Ctx, SourceLocation &Loc) const
ClassifyModifiable - Classify this expression according to the C++11 expression taxonomy, and see if it is valid on the left side of an assignment.
Definition: Expr.h:389
Keeps track of the various options that can be enabled, which controls the dialect of C or C++ that i...
Definition: LangOptions.h:50
An r-value expression (a pr-value in the C++11 taxonomy) produces a temporary value.
Definition: Specifiers.h:110
An rvalue reference type, per C++11 [dcl.ref].
Definition: Type.h:2744
An x-value expression is a reference to an object with independent storage but which can be "moved"...
Definition: Specifiers.h:119
ExprValueKind getValueKind() const
getValueKind - The value kind that this expression produces.
Definition: Expr.h:405
A builtin binary operation expression such as "x + y" or "x <= y".
Definition: Expr.h:3193
LangAS getAddressSpace() const
Definition: Type.h:356
bool isArrow() const
Definition: Expr.h:2749
CompoundStmt - This represents a group of statements like { stmt stmt }.
Definition: Stmt.h:823
The return type of classify().
Definition: Expr.h:302
bool hasQualifiers() const
Determine whether this type has any qualifiers.
Definition: Type.h:6133
Kinds
The various classification results. Most of these mean prvalue.
Definition: Expr.h:305
An Objective-C property is a logical field of an Objective-C object which is read and written via Obj...
Definition: Specifiers.h:136
This represents one expression.
Definition: Expr.h:106
ExprValueKind
The categorization of expression values, currently following the C++11 scheme.
Definition: Specifiers.h:107
DeclContext * getDeclContext()
Definition: DeclBase.h:427
QualType getType() const
Definition: Expr.h:128
ModifiableType
The results of modification testing.
Definition: Expr.h:320
ExprObjectKind getObjectKind() const
getObjectKind - The object kind that this expression produces.
Definition: Expr.h:412
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 ClassifyInternal(ASTContext &Ctx, const Expr *E)
CanQualType OverloadTy
Definition: ASTContext.h:1044
Kind
Encodes a location in the source.
bool isLValue() const
isLValue - True if this expression is an "l-value" according to the rules of the current language...
Definition: Expr.h:249
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...
static Cl::Kinds ClassifyTemporary(QualType T)
Classify an expression which creates a temporary, based on its type.
CanProxy< U > getAs() const
Retrieve a canonical type pointer with a different static type, upcasting or downcasting as needed...
Expr * getLHS() const
Definition: Expr.h:3237
static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E)
Dataflow Directional Tag Classes.
ModifiableType getModifiable() const
Definition: Expr.h:348
bool isRecord() const
Definition: DeclBase.h:1826
BinaryOperator::Opcode getOpcode(const SymExpr *SE)
static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D)
ClassifyDecl - Return the classification of an expression referencing the given declaration.
StmtClass getStmtClass() const
Definition: Stmt.h:611
Kinds getKind() const
Definition: Expr.h:347
static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *trueExpr, const Expr *falseExpr)
Expr * IgnoreParenImpCasts() LLVM_READONLY
IgnoreParenImpCasts - Ignore parentheses and implicit casts.
Definition: Expr.cpp:2669
A helper class that allows the use of isa/cast/dyncast to detect TagType objects of structs/unions/cl...
Definition: Type.h:4356
CanQualType UnknownAnyTy
Definition: ASTContext.h:1044
bool isFunctionType() const
Definition: Type.h:6278
LValueClassification
Definition: Expr.h:254
CanQualType getCanonicalType(QualType T) const
Return the canonical (structural) type corresponding to the specified potentially non-canonical type ...
Definition: ASTContext.h:2252
bool isLValueReferenceType() const
Definition: Type.h:6298
Defines the C++ Decl subclasses, other than those for templates (found in DeclTemplate.h) and friends (in DeclFriend.h).
MemberExpr - [C99 6.5.2.3] Structure and Union Members.
Definition: Expr.h:2554
bool isVoidType() const
Definition: Type.h:6530
bool isRValue() const
Definition: Expr.h:250
unsigned kind
All of the diagnostics that can be emitted by the frontend.
Definition: DiagnosticIDs.h:61
static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E)
Expr * getRHS() const
Definition: Expr.h:3239
An l-value expression is a reference to an object with independent storage.
Definition: Specifiers.h:114
This represents a decl that may have a name.
Definition: Decl.h:248
const LangOptions & getLangOpts() const
Definition: ASTContext.h:706
Expr * IgnoreParens() LLVM_READONLY
IgnoreParens - Ignore parentheses.
Definition: Expr.cpp:2540