clang  3.8.0
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 using namespace clang;
23 
25 
26 static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E);
27 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D);
32  const Expr *trueExpr,
33  const Expr *falseExpr);
34 static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E,
36 
37 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())
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:
67  case Cl::CL_PRValue: assert(getValueKind() == VK_RValue); break;
68  }
69 
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.
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 
89  const Expr *E,
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 
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())
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))
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())
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::CXXTemporaryObjectExprClass:
364  case Expr::LambdaExprClass:
365  case Expr::CXXStdInitializerListExprClass:
366  return Cl::CL_ClassTemporary;
367 
368  case Expr::VAArgExprClass:
369  return ClassifyUnnamed(Ctx, E->getType());
370 
371  case Expr::DesignatedInitExprClass:
372  return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit());
373 
374  case Expr::StmtExprClass: {
375  const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt();
376  if (const Expr *LastExpr = dyn_cast_or_null<Expr>(S->body_back()))
377  return ClassifyUnnamed(Ctx, LastExpr->getType());
378  return Cl::CL_PRValue;
379  }
380 
381  case Expr::CXXUuidofExprClass:
382  return Cl::CL_LValue;
383 
384  case Expr::PackExpansionExprClass:
385  return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern());
386 
387  case Expr::MaterializeTemporaryExprClass:
388  return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference()
389  ? Cl::CL_LValue
390  : Cl::CL_XValue;
391 
392  case Expr::InitListExprClass:
393  // An init list can be an lvalue if it is bound to a reference and
394  // contains only one element. In that case, we look at that element
395  // for an exact classification. Init list creation takes care of the
396  // value kind for us, so we only need to fine-tune.
397  if (E->isRValue())
398  return ClassifyExprValueKind(Lang, E, E->getValueKind());
399  assert(cast<InitListExpr>(E)->getNumInits() == 1 &&
400  "Only 1-element init lists can be glvalues.");
401  return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0));
402 
403  case Expr::CoawaitExprClass:
404  return ClassifyInternal(Ctx, cast<CoawaitExpr>(E)->getResumeExpr());
405  }
406 
407  llvm_unreachable("unhandled expression kind in classification");
408 }
409 
410 /// ClassifyDecl - Return the classification of an expression referencing the
411 /// given declaration.
412 static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) {
413  // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a
414  // function, variable, or data member and a prvalue otherwise.
415  // In C, functions are not lvalues.
416  // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an
417  // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to
418  // special-case this.
419 
420  if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance())
421  return Cl::CL_MemberFunction;
422 
423  bool islvalue;
424  if (const NonTypeTemplateParmDecl *NTTParm =
425  dyn_cast<NonTypeTemplateParmDecl>(D))
426  islvalue = NTTParm->getType()->isReferenceType();
427  else
428  islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) ||
429  isa<IndirectFieldDecl>(D) ||
430  (Ctx.getLangOpts().CPlusPlus &&
431  (isa<FunctionDecl>(D) || isa<MSPropertyDecl>(D) ||
432  isa<FunctionTemplateDecl>(D)));
433 
434  return islvalue ? Cl::CL_LValue : Cl::CL_PRValue;
435 }
436 
437 /// ClassifyUnnamed - Return the classification of an expression yielding an
438 /// unnamed value of the given type. This applies in particular to function
439 /// calls and casts.
441  // In C, function calls are always rvalues.
442  if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue;
443 
444  // C++ [expr.call]p10: A function call is an lvalue if the result type is an
445  // lvalue reference type or an rvalue reference to function type, an xvalue
446  // if the result type is an rvalue reference to object type, and a prvalue
447  // otherwise.
448  if (T->isLValueReferenceType())
449  return Cl::CL_LValue;
451  if (!RV) // Could still be a class temporary, though.
452  return ClassifyTemporary(T);
453 
455 }
456 
458  if (E->getType() == Ctx.UnknownAnyTy)
459  return (isa<FunctionDecl>(E->getMemberDecl())
461 
462  // Handle C first, it's easier.
463  if (!Ctx.getLangOpts().CPlusPlus) {
464  // C99 6.5.2.3p3
465  // For dot access, the expression is an lvalue if the first part is. For
466  // arrow access, it always is an lvalue.
467  if (E->isArrow())
468  return Cl::CL_LValue;
469  // ObjC property accesses are not lvalues, but get special treatment.
470  Expr *Base = E->getBase()->IgnoreParens();
471  if (isa<ObjCPropertyRefExpr>(Base))
473  return ClassifyInternal(Ctx, Base);
474  }
475 
476  NamedDecl *Member = E->getMemberDecl();
477  // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2.
478  // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then
479  // E1.E2 is an lvalue.
480  if (ValueDecl *Value = dyn_cast<ValueDecl>(Member))
481  if (Value->getType()->isReferenceType())
482  return Cl::CL_LValue;
483 
484  // Otherwise, one of the following rules applies.
485  // -- If E2 is a static member [...] then E1.E2 is an lvalue.
486  if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord())
487  return Cl::CL_LValue;
488 
489  // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then
490  // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue;
491  // otherwise, it is a prvalue.
492  if (isa<FieldDecl>(Member)) {
493  // *E1 is an lvalue
494  if (E->isArrow())
495  return Cl::CL_LValue;
497  if (isa<ObjCPropertyRefExpr>(Base))
499  return ClassifyInternal(Ctx, E->getBase());
500  }
501 
502  // -- If E2 is a [...] member function, [...]
503  // -- If it refers to a static member function [...], then E1.E2 is an
504  // lvalue; [...]
505  // -- Otherwise [...] E1.E2 is a prvalue.
506  if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member))
507  return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction;
508 
509  // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue.
510  // So is everything else we haven't handled yet.
511  return Cl::CL_PRValue;
512 }
513 
515  assert(Ctx.getLangOpts().CPlusPlus &&
516  "This is only relevant for C++.");
517  // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand.
518  // Except we override this for writes to ObjC properties.
519  if (E->isAssignmentOp())
520  return (E->getLHS()->getObjectKind() == OK_ObjCProperty
522 
523  // C++ [expr.comma]p1: the result is of the same value category as its right
524  // operand, [...].
525  if (E->getOpcode() == BO_Comma)
526  return ClassifyInternal(Ctx, E->getRHS());
527 
528  // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand
529  // is a pointer to a data member is of the same value category as its first
530  // operand.
531  if (E->getOpcode() == BO_PtrMemD)
532  return (E->getType()->isFunctionType() ||
533  E->hasPlaceholderType(BuiltinType::BoundMember))
535  : ClassifyInternal(Ctx, E->getLHS());
536 
537  // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its
538  // second operand is a pointer to data member and a prvalue otherwise.
539  if (E->getOpcode() == BO_PtrMemI)
540  return (E->getType()->isFunctionType() ||
541  E->hasPlaceholderType(BuiltinType::BoundMember))
543  : Cl::CL_LValue;
544 
545  // All other binary operations are prvalues.
546  return Cl::CL_PRValue;
547 }
548 
549 static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True,
550  const Expr *False) {
551  assert(Ctx.getLangOpts().CPlusPlus &&
552  "This is only relevant for C++.");
553 
554  // C++ [expr.cond]p2
555  // If either the second or the third operand has type (cv) void,
556  // one of the following shall hold:
557  if (True->getType()->isVoidType() || False->getType()->isVoidType()) {
558  // The second or the third operand (but not both) is a (possibly
559  // parenthesized) throw-expression; the result is of the [...] value
560  // category of the other.
561  bool TrueIsThrow = isa<CXXThrowExpr>(True->IgnoreParenImpCasts());
562  bool FalseIsThrow = isa<CXXThrowExpr>(False->IgnoreParenImpCasts());
563  if (const Expr *NonThrow = TrueIsThrow ? (FalseIsThrow ? nullptr : False)
564  : (FalseIsThrow ? True : nullptr))
565  return ClassifyInternal(Ctx, NonThrow);
566 
567  // [Otherwise] the result [...] is a prvalue.
568  return Cl::CL_PRValue;
569  }
570 
571  // Note that at this point, we have already performed all conversions
572  // according to [expr.cond]p3.
573  // C++ [expr.cond]p4: If the second and third operands are glvalues of the
574  // same value category [...], the result is of that [...] value category.
575  // C++ [expr.cond]p5: Otherwise, the result is a prvalue.
576  Cl::Kinds LCl = ClassifyInternal(Ctx, True),
577  RCl = ClassifyInternal(Ctx, False);
578  return LCl == RCl ? LCl : Cl::CL_PRValue;
579 }
580 
582  Cl::Kinds Kind, SourceLocation &Loc) {
583  // As a general rule, we only care about lvalues. But there are some rvalues
584  // for which we want to generate special results.
585  if (Kind == Cl::CL_PRValue) {
586  // For the sake of better diagnostics, we want to specifically recognize
587  // use of the GCC cast-as-lvalue extension.
588  if (const ExplicitCastExpr *CE =
589  dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) {
590  if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) {
591  Loc = CE->getExprLoc();
592  return Cl::CM_LValueCast;
593  }
594  }
595  }
596  if (Kind != Cl::CL_LValue)
597  return Cl::CM_RValue;
598 
599  // This is the lvalue case.
600  // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6)
601  if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType())
602  return Cl::CM_Function;
603 
604  // Assignment to a property in ObjC is an implicit setter access. But a
605  // setter might not exist.
606  if (const ObjCPropertyRefExpr *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) {
607  if (Expr->isImplicitProperty() &&
608  Expr->getImplicitPropertySetter() == nullptr)
610  }
611 
612  CanQualType CT = Ctx.getCanonicalType(E->getType());
613  // Const stuff is obviously not modifiable.
614  if (CT.isConstQualified())
615  return Cl::CM_ConstQualified;
617  return Cl::CM_ConstAddrSpace;
618 
619  // Arrays are not modifiable, only their elements are.
620  if (CT->isArrayType())
621  return Cl::CM_ArrayType;
622  // Incomplete types are not modifiable.
623  if (CT->isIncompleteType())
624  return Cl::CM_IncompleteType;
625 
626  // Records with any const fields (recursively) are not modifiable.
627  if (const RecordType *R = CT->getAs<RecordType>())
628  if (R->hasConstFields())
629  return Cl::CM_ConstQualified;
630 
631  return Cl::CM_Modifiable;
632 }
633 
635  Classification VC = Classify(Ctx);
636  switch (VC.getKind()) {
637  case Cl::CL_LValue: return LV_Valid;
638  case Cl::CL_XValue: return LV_InvalidExpression;
639  case Cl::CL_Function: return LV_NotObjectType;
640  case Cl::CL_Void: return LV_InvalidExpression;
649  }
650  llvm_unreachable("Unhandled kind");
651 }
652 
655  SourceLocation dummy;
656  Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy);
657  switch (VC.getKind()) {
658  case Cl::CL_LValue: break;
660  case Cl::CL_Function: return MLV_NotObjectType;
661  case Cl::CL_Void: return MLV_InvalidExpression;
669  case Cl::CL_PRValue:
670  return VC.getModifiable() == Cl::CM_LValueCast ?
672  }
673  assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind");
674  switch (VC.getModifiable()) {
675  case Cl::CM_Untested: llvm_unreachable("Did not test modifiability");
676  case Cl::CM_Modifiable: return MLV_Valid;
677  case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match");
678  case Cl::CM_Function: return MLV_NotObjectType;
679  case Cl::CM_LValueCast:
680  llvm_unreachable("CM_LValueCast and CL_LValue don't match");
684  case Cl::CM_ArrayType: return MLV_ArrayType;
686  }
687  llvm_unreachable("Unhandled modifiable type");
688 }
ObjCPropertyRefExpr - A dot-syntax expression to access an ObjC property.
Definition: ExprObjC.h:539
LValueClassification ClassifyLValue(ASTContext &Ctx) const
Reasons why an expression might not be an l-value.
ValueDecl * getMemberDecl() const
Retrieve the member declaration to which this expression refers.
Definition: Expr.h:2393
Defines the clang::ASTContext interface.
ExprObjectKind getObjectKind() const
getObjectKind - The object kind that this expression produces.
Definition: Expr.h:407
Stmt * body_back()
Definition: Stmt.h:573
A (possibly-)qualified type.
Definition: Type.h:575
bool hasPlaceholderType() const
Returns whether this expression has a placeholder type.
Definition: Expr.h:462
bool isRecordType() const
Definition: Type.h:5362
Decl - This represents one declaration (or definition), e.g.
Definition: DeclBase.h:77
Defines the C++ template declaration subclasses.
bool isConstQualified() const
isModifiableLvalueResult
Definition: Expr.h:266
static Cl::Kinds ClassifyExprValueKind(const LangOptions &Lang, const Expr *E, ExprValueKind Kind)
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:384
ObjCMethodDecl - Represents an instance or class method declaration.
Definition: DeclObjC.h:113
static bool isAssignmentOp(Opcode Opc)
Definition: Expr.h:3000
Defines the clang::Expr interface and subclasses for C++ expressions.
bool isVoidType() const
Definition: Type.h:5546
Holds long-lived AST nodes (such as types and decls) that can be referred to throughout the semantic ...
Definition: ASTContext.h:91
bool isReferenceType() const
Definition: Type.h:5314
static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, Cl::Kinds Kind, SourceLocation &Loc)
Keeps track of the various options that can be enabled, which controls the dialect of C or C++ that i...
Definition: LangOptions.h:48
Expr::Classification Cl
An r-value expression (a pr-value in the C++11 taxonomy) produces a temporary value.
Definition: Specifiers.h:102
Expr * getLHS() const
Definition: Expr.h:2921
An rvalue reference type, per C++11 [dcl.ref].
Definition: Type.h:2351
const LangOptions & getLangOpts() const
Definition: ASTContext.h:596
CanProxy< U > getAs() const
Retrieve a canonical type pointer with a different static type, upcasting or downcasting as needed...
An x-value expression is a reference to an object with independent storage but which can be "moved"...
Definition: Specifiers.h:111
A builtin binary operation expression such as "x + y" or "x <= y".
Definition: Expr.h:2875
ConditionalOperator - The ?: ternary operator.
Definition: Expr.h:3148
Expr * getFalseExpr() const
Definition: Expr.h:3191
CompoundStmt - This represents a group of statements like { stmt stmt }.
Definition: Stmt.h:539
The return type of classify().
Definition: Expr.h:298
Kinds
The various classification results. Most of these mean prvalue.
Definition: Expr.h:301
An Objective-C property is a logical field of an Objective-C object which is read and written via Obj...
Definition: Specifiers.h:128
ValueDecl - Represent the declaration of a variable (in which case it is an lvalue) a function (in wh...
Definition: Decl.h:521
Expr - This represents one expression.
Definition: Expr.h:104
ExprValueKind
The categorization of expression values, currently following the C++11 scheme.
Definition: Specifiers.h:99
Qualifiers getQualifiers() const
Retrieve all qualifiers.
Kinds getKind() const
Definition: Expr.h:342
DeclContext * getDeclContext()
Definition: DeclBase.h:393
NonTypeTemplateParmDecl - Declares a non-type template parameter, e.g., "Size" in.
Classification Classify(ASTContext &Ctx) const
Classify - Classify this expression according to the C++11 expression taxonomy.
Definition: Expr.h:372
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...
ModifiableType
The results of modification testing.
Definition: Expr.h:316
Expr * getTrueExpr() const
Definition: Expr.h:3186
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:896
Kind
Encodes a location in the source.
Represents a static or instance method of a struct/union/class.
Definition: DeclCXX.h:1701
bool isRValue() const
Definition: Expr.h:247
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)
bool isArrow() const
Definition: Expr.h:2488
QualType getType() const
Definition: Expr.h:125
static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D)
ClassifyDecl - Return the classification of an expression referencing the given declaration.
ModifiableType getModifiable() const
Definition: Expr.h:343
detail::InMemoryDirectory::const_iterator E
CanQualType getCanonicalType(QualType T) const
Return the canonical (structural) type corresponding to the specified potentially non-canonical type ...
Definition: ASTContext.h:1946
bool isLValueReferenceType() const
Definition: Type.h:5317
ExplicitCastExpr - An explicit cast written in the source code.
Definition: Expr.h:2778
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:2551
A helper class that allows the use of isa/cast/dyncast to detect TagType objects of structs/unions/cl...
Definition: Type.h:3544
CanQualType UnknownAnyTy
Definition: ASTContext.h:896
const T * getAs() const
Member-template getAs<specific type>'.
Definition: Type.h:5675
bool isFunctionType() const
Definition: Type.h:5302
LValueClassification
Definition: Expr.h:251
unsigned getAddressSpace() const
Definition: Type.h:316
QualType getPointeeType() const
Definition: Type.h:2308
Expr * getFalseExpr() const
getFalseExpr - Return the subexpression which will be evaluated if the condnition evaluates to false;...
Definition: Expr.h:3277
Expr * getBase() const
Definition: Expr.h:2387
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:2297
Opcode getOpcode() const
Definition: Expr.h:2918
BinaryConditionalOperator - The GNU extension to the conditional operator which allows the middle ope...
Definition: Expr.h:3218
unsigned kind
All of the diagnostics that can be emitted by the frontend.
Definition: DiagnosticIDs.h:43
bool isArrayType() const
Definition: Type.h:5344
Expr * getRHS() const
Definition: Expr.h:2923
bool isRecord() const
Definition: DeclBase.h:1273
static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E)
ExprValueKind getValueKind() const
getValueKind - The value kind that this expression produces.
Definition: Expr.h:400
bool hasQualifiers() const
Determine whether this type has any qualifiers.
Definition: Type.h:5164
Expr * getTrueExpr() const
getTrueExpr - Return the subexpression which will be evaluated if the condition evaluates to true; th...
Definition: Expr.h:3270
An l-value expression is a reference to an object with independent storage.
Definition: Specifiers.h:106
NamedDecl - This represents a decl with a name.
Definition: Decl.h:145
Expr * IgnoreParens() LLVM_READONLY
IgnoreParens - Ignore parentheses.
Definition: Expr.cpp:2433