1 //===--- NestedNameSpecifier.cpp - C++ nested name specifiers -----*- C++ -*-=//
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 defines the NestedNameSpecifier class, which represents
11 //  a C++ nested-name-specifier.
12 //
13 //===----------------------------------------------------------------------===//
14 #include "clang/AST/NestedNameSpecifier.h"
15 #include "clang/AST/ASTContext.h"
16 #include "clang/AST/Decl.h"
17 #include "clang/AST/DeclCXX.h"
18 #include "clang/AST/PrettyPrinter.h"
19 #include "clang/AST/Type.h"
20 #include "clang/AST/TypeLoc.h"
21 #include "llvm/Support/AlignOf.h"
22 #include "llvm/Support/raw_ostream.h"
23 #include <cassert>
24 
25 using namespace clang;
26 
27 NestedNameSpecifier *
28 NestedNameSpecifier::FindOrInsert(const ASTContext &Context,
29                                   const NestedNameSpecifier &Mockup) {
30   llvm::FoldingSetNodeID ID;
31   Mockup.Profile(ID);
32 
33   void *InsertPos = nullptr;
34   NestedNameSpecifier *NNS
35     = Context.NestedNameSpecifiers.FindNodeOrInsertPos(ID, InsertPos);
36   if (!NNS) {
37     NNS = new (Context, llvm::alignOf<NestedNameSpecifier>())
38         NestedNameSpecifier(Mockup);
39     Context.NestedNameSpecifiers.InsertNode(NNS, InsertPos);
40   }
41 
42   return NNS;
43 }
44 
45 NestedNameSpecifier *
46 NestedNameSpecifier::Create(const ASTContext &Context,
47                             NestedNameSpecifier *Prefix, IdentifierInfo *II) {
48   assert(II && "Identifier cannot be NULL");
49   assert((!Prefix || Prefix->isDependent()) && "Prefix must be dependent");
50 
51   NestedNameSpecifier Mockup;
52   Mockup.Prefix.setPointer(Prefix);
53   Mockup.Prefix.setInt(StoredIdentifier);
54   Mockup.Specifier = II;
55   return FindOrInsert(Context, Mockup);
56 }
57 
58 NestedNameSpecifier *
59 NestedNameSpecifier::Create(const ASTContext &Context,
60                             NestedNameSpecifier *Prefix,
61                             const NamespaceDecl *NS) {
62   assert(NS && "Namespace cannot be NULL");
63   assert((!Prefix ||
64           (Prefix->getAsType() == nullptr &&
65            Prefix->getAsIdentifier() == nullptr)) &&
66          "Broken nested name specifier");
67   NestedNameSpecifier Mockup;
68   Mockup.Prefix.setPointer(Prefix);
69   Mockup.Prefix.setInt(StoredDecl);
70   Mockup.Specifier = const_cast<NamespaceDecl *>(NS);
71   return FindOrInsert(Context, Mockup);
72 }
73 
74 NestedNameSpecifier *
75 NestedNameSpecifier::Create(const ASTContext &Context,
76                             NestedNameSpecifier *Prefix,
77                             NamespaceAliasDecl *Alias) {
78   assert(Alias && "Namespace alias cannot be NULL");
79   assert((!Prefix ||
80           (Prefix->getAsType() == nullptr &&
81            Prefix->getAsIdentifier() == nullptr)) &&
82          "Broken nested name specifier");
83   NestedNameSpecifier Mockup;
84   Mockup.Prefix.setPointer(Prefix);
85   Mockup.Prefix.setInt(StoredDecl);
86   Mockup.Specifier = Alias;
87   return FindOrInsert(Context, Mockup);
88 }
89 
90 NestedNameSpecifier *
91 NestedNameSpecifier::Create(const ASTContext &Context,
92                             NestedNameSpecifier *Prefix,
93                             bool Template, const Type *T) {
94   assert(T && "Type cannot be NULL");
95   NestedNameSpecifier Mockup;
96   Mockup.Prefix.setPointer(Prefix);
97   Mockup.Prefix.setInt(Template? StoredTypeSpecWithTemplate : StoredTypeSpec);
98   Mockup.Specifier = const_cast<Type*>(T);
99   return FindOrInsert(Context, Mockup);
100 }
101 
102 NestedNameSpecifier *
103 NestedNameSpecifier::Create(const ASTContext &Context, IdentifierInfo *II) {
104   assert(II && "Identifier cannot be NULL");
105   NestedNameSpecifier Mockup;
106   Mockup.Prefix.setPointer(nullptr);
107   Mockup.Prefix.setInt(StoredIdentifier);
108   Mockup.Specifier = II;
109   return FindOrInsert(Context, Mockup);
110 }
111 
112 NestedNameSpecifier *
113 NestedNameSpecifier::GlobalSpecifier(const ASTContext &Context) {
114   if (!Context.GlobalNestedNameSpecifier)
115     Context.GlobalNestedNameSpecifier =
116         new (Context, llvm::alignOf<NestedNameSpecifier>())
117             NestedNameSpecifier();
118   return Context.GlobalNestedNameSpecifier;
119 }
120 
121 NestedNameSpecifier *
122 NestedNameSpecifier::SuperSpecifier(const ASTContext &Context,
123                                     CXXRecordDecl *RD) {
124   NestedNameSpecifier Mockup;
125   Mockup.Prefix.setPointer(nullptr);
126   Mockup.Prefix.setInt(StoredDecl);
127   Mockup.Specifier = RD;
128   return FindOrInsert(Context, Mockup);
129 }
130 
131 NestedNameSpecifier::SpecifierKind NestedNameSpecifier::getKind() const {
132   if (!Specifier)
133     return Global;
134 
135   switch (Prefix.getInt()) {
136   case StoredIdentifier:
137     return Identifier;
138 
139   case StoredDecl: {
140     NamedDecl *ND = static_cast<NamedDecl *>(Specifier);
141     if (isa<CXXRecordDecl>(ND))
142       return Super;
143     return isa<NamespaceDecl>(ND) ? Namespace : NamespaceAlias;
144   }
145 
146   case StoredTypeSpec:
147     return TypeSpec;
148 
149   case StoredTypeSpecWithTemplate:
150     return TypeSpecWithTemplate;
151   }
152 
153   llvm_unreachable("Invalid NNS Kind!");
154 }
155 
156 /// \brief Retrieve the namespace stored in this nested name specifier.
157 NamespaceDecl *NestedNameSpecifier::getAsNamespace() const {
158 	if (Prefix.getInt() == StoredDecl)
159     return dyn_cast<NamespaceDecl>(static_cast<NamedDecl *>(Specifier));
160 
161   return nullptr;
162 }
163 
164 /// \brief Retrieve the namespace alias stored in this nested name specifier.
165 NamespaceAliasDecl *NestedNameSpecifier::getAsNamespaceAlias() const {
166 	if (Prefix.getInt() == StoredDecl)
167     return dyn_cast<NamespaceAliasDecl>(static_cast<NamedDecl *>(Specifier));
168 
169   return nullptr;
170 }
171 
172 /// \brief Retrieve the record declaration stored in this nested name specifier.
173 CXXRecordDecl *NestedNameSpecifier::getAsRecordDecl() const {
174   if (Prefix.getInt() == StoredDecl)
175     return dyn_cast<CXXRecordDecl>(static_cast<NamedDecl *>(Specifier));
176 
177   return nullptr;
178 }
179 
180 /// \brief Whether this nested name specifier refers to a dependent
181 /// type or not.
182 bool NestedNameSpecifier::isDependent() const {
183   switch (getKind()) {
184   case Identifier:
185     // Identifier specifiers always represent dependent types
186     return true;
187 
188   case Namespace:
189   case NamespaceAlias:
190   case Global:
191     return false;
192 
193   case Super: {
194     CXXRecordDecl *RD = static_cast<CXXRecordDecl *>(Specifier);
195     for (const auto &Base : RD->bases())
196       if (Base.getType()->isDependentType())
197         return true;
198 
199     return false;
200   }
201 
202   case TypeSpec:
203   case TypeSpecWithTemplate:
204     return getAsType()->isDependentType();
205   }
206 
207   llvm_unreachable("Invalid NNS Kind!");
208 }
209 
210 /// \brief Whether this nested name specifier refers to a dependent
211 /// type or not.
212 bool NestedNameSpecifier::isInstantiationDependent() const {
213   switch (getKind()) {
214   case Identifier:
215     // Identifier specifiers always represent dependent types
216     return true;
217 
218   case Namespace:
219   case NamespaceAlias:
220   case Global:
221   case Super:
222     return false;
223 
224   case TypeSpec:
225   case TypeSpecWithTemplate:
226     return getAsType()->isInstantiationDependentType();
227   }
228 
229   llvm_unreachable("Invalid NNS Kind!");
230 }
231 
232 bool NestedNameSpecifier::containsUnexpandedParameterPack() const {
233   switch (getKind()) {
234   case Identifier:
235     return getPrefix() && getPrefix()->containsUnexpandedParameterPack();
236 
237   case Namespace:
238   case NamespaceAlias:
239   case Global:
240   case Super:
241     return false;
242 
243   case TypeSpec:
244   case TypeSpecWithTemplate:
245     return getAsType()->containsUnexpandedParameterPack();
246   }
247 
248   llvm_unreachable("Invalid NNS Kind!");
249 }
250 
251 /// \brief Print this nested name specifier to the given output
252 /// stream.
253 void
254 NestedNameSpecifier::print(raw_ostream &OS,
255                            const PrintingPolicy &Policy) const {
256   if (getPrefix())
257     getPrefix()->print(OS, Policy);
258 
259   switch (getKind()) {
260   case Identifier:
261     OS << getAsIdentifier()->getName();
262     break;
263 
264   case Namespace:
265     if (getAsNamespace()->isAnonymousNamespace())
266       return;
267 
268     OS << getAsNamespace()->getName();
269     break;
270 
271   case NamespaceAlias:
272     OS << getAsNamespaceAlias()->getName();
273     break;
274 
275   case Global:
276     break;
277 
278   case Super:
279     OS << "__super";
280     break;
281 
282   case TypeSpecWithTemplate:
283     OS << "template ";
284     // Fall through to print the type.
285 
286   case TypeSpec: {
287     const Type *T = getAsType();
288 
289     PrintingPolicy InnerPolicy(Policy);
290     InnerPolicy.SuppressScope = true;
291 
292     // Nested-name-specifiers are intended to contain minimally-qualified
293     // types. An actual ElaboratedType will not occur, since we'll store
294     // just the type that is referred to in the nested-name-specifier (e.g.,
295     // a TypedefType, TagType, etc.). However, when we are dealing with
296     // dependent template-id types (e.g., Outer<T>::template Inner<U>),
297     // the type requires its own nested-name-specifier for uniqueness, so we
298     // suppress that nested-name-specifier during printing.
299     assert(!isa<ElaboratedType>(T) &&
300            "Elaborated type in nested-name-specifier");
301     if (const TemplateSpecializationType *SpecType
302           = dyn_cast<TemplateSpecializationType>(T)) {
303       // Print the template name without its corresponding
304       // nested-name-specifier.
305       SpecType->getTemplateName().print(OS, InnerPolicy, true);
306 
307       // Print the template argument list.
308       TemplateSpecializationType::PrintTemplateArgumentList(
309           OS, SpecType->getArgs(), SpecType->getNumArgs(), InnerPolicy);
310     } else {
311       // Print the type normally
312       QualType(T, 0).print(OS, InnerPolicy);
313     }
314     break;
315   }
316   }
317 
318   OS << "::";
319 }
320 
321 void NestedNameSpecifier::dump(const LangOptions &LO) const {
322   print(llvm::errs(), PrintingPolicy(LO));
323 }
324 
325 LLVM_DUMP_METHOD void NestedNameSpecifier::dump() const {
326   LangOptions LO;
327   print(llvm::errs(), PrintingPolicy(LO));
328 }
329 
330 unsigned
331 NestedNameSpecifierLoc::getLocalDataLength(NestedNameSpecifier *Qualifier) {
332   assert(Qualifier && "Expected a non-NULL qualifier");
333 
334   // Location of the trailing '::'.
335   unsigned Length = sizeof(unsigned);
336 
337   switch (Qualifier->getKind()) {
338   case NestedNameSpecifier::Global:
339     // Nothing more to add.
340     break;
341 
342   case NestedNameSpecifier::Identifier:
343   case NestedNameSpecifier::Namespace:
344   case NestedNameSpecifier::NamespaceAlias:
345   case NestedNameSpecifier::Super:
346     // The location of the identifier or namespace name.
347     Length += sizeof(unsigned);
348     break;
349 
350   case NestedNameSpecifier::TypeSpecWithTemplate:
351   case NestedNameSpecifier::TypeSpec:
352     // The "void*" that points at the TypeLoc data.
353     // Note: the 'template' keyword is part of the TypeLoc.
354     Length += sizeof(void *);
355     break;
356   }
357 
358   return Length;
359 }
360 
361 unsigned
362 NestedNameSpecifierLoc::getDataLength(NestedNameSpecifier *Qualifier) {
363   unsigned Length = 0;
364   for (; Qualifier; Qualifier = Qualifier->getPrefix())
365     Length += getLocalDataLength(Qualifier);
366   return Length;
367 }
368 
369 namespace {
370   /// \brief Load a (possibly unaligned) source location from a given address
371   /// and offset.
372   SourceLocation LoadSourceLocation(void *Data, unsigned Offset) {
373     unsigned Raw;
374     memcpy(&Raw, static_cast<char *>(Data) + Offset, sizeof(unsigned));
375     return SourceLocation::getFromRawEncoding(Raw);
376   }
377 
378   /// \brief Load a (possibly unaligned) pointer from a given address and
379   /// offset.
380   void *LoadPointer(void *Data, unsigned Offset) {
381     void *Result;
382     memcpy(&Result, static_cast<char *>(Data) + Offset, sizeof(void*));
383     return Result;
384   }
385 }
386 
387 SourceRange NestedNameSpecifierLoc::getSourceRange() const {
388   if (!Qualifier)
389     return SourceRange();
390 
391   NestedNameSpecifierLoc First = *this;
392   while (NestedNameSpecifierLoc Prefix = First.getPrefix())
393     First = Prefix;
394 
395   return SourceRange(First.getLocalSourceRange().getBegin(),
396                      getLocalSourceRange().getEnd());
397 }
398 
399 SourceRange NestedNameSpecifierLoc::getLocalSourceRange() const {
400   if (!Qualifier)
401     return SourceRange();
402 
403   unsigned Offset = getDataLength(Qualifier->getPrefix());
404   switch (Qualifier->getKind()) {
405   case NestedNameSpecifier::Global:
406     return LoadSourceLocation(Data, Offset);
407 
408   case NestedNameSpecifier::Identifier:
409   case NestedNameSpecifier::Namespace:
410   case NestedNameSpecifier::NamespaceAlias:
411   case NestedNameSpecifier::Super:
412     return SourceRange(LoadSourceLocation(Data, Offset),
413                        LoadSourceLocation(Data, Offset + sizeof(unsigned)));
414 
415   case NestedNameSpecifier::TypeSpecWithTemplate:
416   case NestedNameSpecifier::TypeSpec: {
417     // The "void*" that points at the TypeLoc data.
418     // Note: the 'template' keyword is part of the TypeLoc.
419     void *TypeData = LoadPointer(Data, Offset);
420     TypeLoc TL(Qualifier->getAsType(), TypeData);
421     return SourceRange(TL.getBeginLoc(),
422                        LoadSourceLocation(Data, Offset + sizeof(void*)));
423   }
424   }
425 
426   llvm_unreachable("Invalid NNS Kind!");
427 }
428 
429 TypeLoc NestedNameSpecifierLoc::getTypeLoc() const {
430   assert((Qualifier->getKind() == NestedNameSpecifier::TypeSpec ||
431           Qualifier->getKind() == NestedNameSpecifier::TypeSpecWithTemplate) &&
432          "Nested-name-specifier location is not a type");
433 
434   // The "void*" that points at the TypeLoc data.
435   unsigned Offset = getDataLength(Qualifier->getPrefix());
436   void *TypeData = LoadPointer(Data, Offset);
437   return TypeLoc(Qualifier->getAsType(), TypeData);
438 }
439 
440 namespace {
441   void Append(char *Start, char *End, char *&Buffer, unsigned &BufferSize,
442               unsigned &BufferCapacity) {
443     if (Start == End)
444       return;
445 
446     if (BufferSize + (End - Start) > BufferCapacity) {
447       // Reallocate the buffer.
448       unsigned NewCapacity = std::max(
449           (unsigned)(BufferCapacity ? BufferCapacity * 2 : sizeof(void *) * 2),
450           (unsigned)(BufferSize + (End - Start)));
451       char *NewBuffer = static_cast<char *>(malloc(NewCapacity));
452       if (BufferCapacity) {
453         memcpy(NewBuffer, Buffer, BufferSize);
454         free(Buffer);
455       }
456       Buffer = NewBuffer;
457       BufferCapacity = NewCapacity;
458     }
459 
460     memcpy(Buffer + BufferSize, Start, End - Start);
461     BufferSize += End-Start;
462   }
463 
464   /// \brief Save a source location to the given buffer.
465   void SaveSourceLocation(SourceLocation Loc, char *&Buffer,
466                           unsigned &BufferSize, unsigned &BufferCapacity) {
467     unsigned Raw = Loc.getRawEncoding();
468     Append(reinterpret_cast<char *>(&Raw),
469            reinterpret_cast<char *>(&Raw) + sizeof(unsigned),
470            Buffer, BufferSize, BufferCapacity);
471   }
472 
473   /// \brief Save a pointer to the given buffer.
474   void SavePointer(void *Ptr, char *&Buffer, unsigned &BufferSize,
475                    unsigned &BufferCapacity) {
476     Append(reinterpret_cast<char *>(&Ptr),
477            reinterpret_cast<char *>(&Ptr) + sizeof(void *),
478            Buffer, BufferSize, BufferCapacity);
479   }
480 }
481 
482 NestedNameSpecifierLocBuilder::
483 NestedNameSpecifierLocBuilder(const NestedNameSpecifierLocBuilder &Other)
484   : Representation(Other.Representation), Buffer(nullptr),
485     BufferSize(0), BufferCapacity(0)
486 {
487   if (!Other.Buffer)
488     return;
489 
490   if (Other.BufferCapacity == 0) {
491     // Shallow copy is okay.
492     Buffer = Other.Buffer;
493     BufferSize = Other.BufferSize;
494     return;
495   }
496 
497   // Deep copy
498   Append(Other.Buffer, Other.Buffer + Other.BufferSize, Buffer, BufferSize,
499          BufferCapacity);
500 }
501 
502 NestedNameSpecifierLocBuilder &
503 NestedNameSpecifierLocBuilder::
504 operator=(const NestedNameSpecifierLocBuilder &Other) {
505   Representation = Other.Representation;
506 
507   if (Buffer && Other.Buffer && BufferCapacity >= Other.BufferSize) {
508     // Re-use our storage.
509     BufferSize = Other.BufferSize;
510     memcpy(Buffer, Other.Buffer, BufferSize);
511     return *this;
512   }
513 
514   // Free our storage, if we have any.
515   if (BufferCapacity) {
516     free(Buffer);
517     BufferCapacity = 0;
518   }
519 
520   if (!Other.Buffer) {
521     // Empty.
522     Buffer = nullptr;
523     BufferSize = 0;
524     return *this;
525   }
526 
527   if (Other.BufferCapacity == 0) {
528     // Shallow copy is okay.
529     Buffer = Other.Buffer;
530     BufferSize = Other.BufferSize;
531     return *this;
532   }
533 
534   // Deep copy.
535   Append(Other.Buffer, Other.Buffer + Other.BufferSize, Buffer, BufferSize,
536          BufferCapacity);
537   return *this;
538 }
539 
540 void NestedNameSpecifierLocBuilder::Extend(ASTContext &Context,
541                                            SourceLocation TemplateKWLoc,
542                                            TypeLoc TL,
543                                            SourceLocation ColonColonLoc) {
544   Representation = NestedNameSpecifier::Create(Context, Representation,
545                                                TemplateKWLoc.isValid(),
546                                                TL.getTypePtr());
547 
548   // Push source-location info into the buffer.
549   SavePointer(TL.getOpaqueData(), Buffer, BufferSize, BufferCapacity);
550   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
551 }
552 
553 void NestedNameSpecifierLocBuilder::Extend(ASTContext &Context,
554                                            IdentifierInfo *Identifier,
555                                            SourceLocation IdentifierLoc,
556                                            SourceLocation ColonColonLoc) {
557   Representation = NestedNameSpecifier::Create(Context, Representation,
558                                                Identifier);
559 
560   // Push source-location info into the buffer.
561   SaveSourceLocation(IdentifierLoc, Buffer, BufferSize, BufferCapacity);
562   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
563 }
564 
565 void NestedNameSpecifierLocBuilder::Extend(ASTContext &Context,
566                                            NamespaceDecl *Namespace,
567                                            SourceLocation NamespaceLoc,
568                                            SourceLocation ColonColonLoc) {
569   Representation = NestedNameSpecifier::Create(Context, Representation,
570                                                Namespace);
571 
572   // Push source-location info into the buffer.
573   SaveSourceLocation(NamespaceLoc, Buffer, BufferSize, BufferCapacity);
574   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
575 }
576 
577 void NestedNameSpecifierLocBuilder::Extend(ASTContext &Context,
578                                            NamespaceAliasDecl *Alias,
579                                            SourceLocation AliasLoc,
580                                            SourceLocation ColonColonLoc) {
581   Representation = NestedNameSpecifier::Create(Context, Representation, Alias);
582 
583   // Push source-location info into the buffer.
584   SaveSourceLocation(AliasLoc, Buffer, BufferSize, BufferCapacity);
585   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
586 }
587 
588 void NestedNameSpecifierLocBuilder::MakeGlobal(ASTContext &Context,
589                                                SourceLocation ColonColonLoc) {
590   assert(!Representation && "Already have a nested-name-specifier!?");
591   Representation = NestedNameSpecifier::GlobalSpecifier(Context);
592 
593   // Push source-location info into the buffer.
594   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
595 }
596 
597 void NestedNameSpecifierLocBuilder::MakeSuper(ASTContext &Context,
598                                               CXXRecordDecl *RD,
599                                               SourceLocation SuperLoc,
600                                               SourceLocation ColonColonLoc) {
601   Representation = NestedNameSpecifier::SuperSpecifier(Context, RD);
602 
603   // Push source-location info into the buffer.
604   SaveSourceLocation(SuperLoc, Buffer, BufferSize, BufferCapacity);
605   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
606 }
607 
608 void NestedNameSpecifierLocBuilder::MakeTrivial(ASTContext &Context,
609                                                 NestedNameSpecifier *Qualifier,
610                                                 SourceRange R) {
611   Representation = Qualifier;
612 
613   // Construct bogus (but well-formed) source information for the
614   // nested-name-specifier.
615   BufferSize = 0;
616   SmallVector<NestedNameSpecifier *, 4> Stack;
617   for (NestedNameSpecifier *NNS = Qualifier; NNS; NNS = NNS->getPrefix())
618     Stack.push_back(NNS);
619   while (!Stack.empty()) {
620     NestedNameSpecifier *NNS = Stack.pop_back_val();
621     switch (NNS->getKind()) {
622       case NestedNameSpecifier::Identifier:
623       case NestedNameSpecifier::Namespace:
624       case NestedNameSpecifier::NamespaceAlias:
625         SaveSourceLocation(R.getBegin(), Buffer, BufferSize, BufferCapacity);
626         break;
627 
628       case NestedNameSpecifier::TypeSpec:
629       case NestedNameSpecifier::TypeSpecWithTemplate: {
630         TypeSourceInfo *TSInfo
631         = Context.getTrivialTypeSourceInfo(QualType(NNS->getAsType(), 0),
632                                            R.getBegin());
633         SavePointer(TSInfo->getTypeLoc().getOpaqueData(), Buffer, BufferSize,
634                     BufferCapacity);
635         break;
636       }
637 
638       case NestedNameSpecifier::Global:
639       case NestedNameSpecifier::Super:
640         break;
641     }
642 
643     // Save the location of the '::'.
644     SaveSourceLocation(Stack.empty()? R.getEnd() : R.getBegin(),
645                        Buffer, BufferSize, BufferCapacity);
646   }
647 }
648 
649 void NestedNameSpecifierLocBuilder::Adopt(NestedNameSpecifierLoc Other) {
650   if (BufferCapacity)
651     free(Buffer);
652 
653   if (!Other) {
654     Representation = nullptr;
655     BufferSize = 0;
656     return;
657   }
658 
659   // Rather than copying the data (which is wasteful), "adopt" the
660   // pointer (which points into the ASTContext) but set the capacity to zero to
661   // indicate that we don't own it.
662   Representation = Other.getNestedNameSpecifier();
663   Buffer = static_cast<char *>(Other.getOpaqueData());
664   BufferSize = Other.getDataLength();
665   BufferCapacity = 0;
666 }
667 
668 NestedNameSpecifierLoc
669 NestedNameSpecifierLocBuilder::getWithLocInContext(ASTContext &Context) const {
670   if (!Representation)
671     return NestedNameSpecifierLoc();
672 
673   // If we adopted our data pointer from elsewhere in the AST context, there's
674   // no need to copy the memory.
675   if (BufferCapacity == 0)
676     return NestedNameSpecifierLoc(Representation, Buffer);
677 
678   // FIXME: After copying the source-location information, should we free
679   // our (temporary) buffer and adopt the ASTContext-allocated memory?
680   // Doing so would optimize repeated calls to getWithLocInContext().
681   void *Mem = Context.Allocate(BufferSize, llvm::alignOf<void *>());
682   memcpy(Mem, Buffer, BufferSize);
683   return NestedNameSpecifierLoc(Representation, Mem);
684 }
685