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 =
38         new (Context, alignof(NestedNameSpecifier)) 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, alignof(NestedNameSpecifier)) NestedNameSpecifier();
117   return Context.GlobalNestedNameSpecifier;
118 }
119 
120 NestedNameSpecifier *
121 NestedNameSpecifier::SuperSpecifier(const ASTContext &Context,
122                                     CXXRecordDecl *RD) {
123   NestedNameSpecifier Mockup;
124   Mockup.Prefix.setPointer(nullptr);
125   Mockup.Prefix.setInt(StoredDecl);
126   Mockup.Specifier = RD;
127   return FindOrInsert(Context, Mockup);
128 }
129 
130 NestedNameSpecifier::SpecifierKind NestedNameSpecifier::getKind() const {
131   if (!Specifier)
132     return Global;
133 
134   switch (Prefix.getInt()) {
135   case StoredIdentifier:
136     return Identifier;
137 
138   case StoredDecl: {
139     NamedDecl *ND = static_cast<NamedDecl *>(Specifier);
140     if (isa<CXXRecordDecl>(ND))
141       return Super;
142     return isa<NamespaceDecl>(ND) ? Namespace : NamespaceAlias;
143   }
144 
145   case StoredTypeSpec:
146     return TypeSpec;
147 
148   case StoredTypeSpecWithTemplate:
149     return TypeSpecWithTemplate;
150   }
151 
152   llvm_unreachable("Invalid NNS Kind!");
153 }
154 
155 /// \brief Retrieve the namespace stored in this nested name specifier.
156 NamespaceDecl *NestedNameSpecifier::getAsNamespace() const {
157   if (Prefix.getInt() == StoredDecl)
158     return dyn_cast<NamespaceDecl>(static_cast<NamedDecl *>(Specifier));
159 
160   return nullptr;
161 }
162 
163 /// \brief Retrieve the namespace alias stored in this nested name specifier.
164 NamespaceAliasDecl *NestedNameSpecifier::getAsNamespaceAlias() const {
165   if (Prefix.getInt() == StoredDecl)
166     return dyn_cast<NamespaceAliasDecl>(static_cast<NamedDecl *>(Specifier));
167 
168   return nullptr;
169 }
170 
171 /// \brief Retrieve the record declaration stored in this nested name specifier.
172 CXXRecordDecl *NestedNameSpecifier::getAsRecordDecl() const {
173   switch (Prefix.getInt()) {
174   case StoredIdentifier:
175     return nullptr;
176 
177   case StoredDecl:
178     return dyn_cast<CXXRecordDecl>(static_cast<NamedDecl *>(Specifier));
179 
180   case StoredTypeSpec:
181   case StoredTypeSpecWithTemplate:
182     return getAsType()->getAsCXXRecordDecl();
183   }
184 
185   llvm_unreachable("Invalid NNS Kind!");
186 }
187 
188 /// \brief Whether this nested name specifier refers to a dependent
189 /// type or not.
190 bool NestedNameSpecifier::isDependent() const {
191   switch (getKind()) {
192   case Identifier:
193     // Identifier specifiers always represent dependent types
194     return true;
195 
196   case Namespace:
197   case NamespaceAlias:
198   case Global:
199     return false;
200 
201   case Super: {
202     CXXRecordDecl *RD = static_cast<CXXRecordDecl *>(Specifier);
203     for (const auto &Base : RD->bases())
204       if (Base.getType()->isDependentType())
205         return true;
206 
207     return false;
208   }
209 
210   case TypeSpec:
211   case TypeSpecWithTemplate:
212     return getAsType()->isDependentType();
213   }
214 
215   llvm_unreachable("Invalid NNS Kind!");
216 }
217 
218 /// \brief Whether this nested name specifier refers to a dependent
219 /// type or not.
220 bool NestedNameSpecifier::isInstantiationDependent() const {
221   switch (getKind()) {
222   case Identifier:
223     // Identifier specifiers always represent dependent types
224     return true;
225 
226   case Namespace:
227   case NamespaceAlias:
228   case Global:
229   case Super:
230     return false;
231 
232   case TypeSpec:
233   case TypeSpecWithTemplate:
234     return getAsType()->isInstantiationDependentType();
235   }
236 
237   llvm_unreachable("Invalid NNS Kind!");
238 }
239 
240 bool NestedNameSpecifier::containsUnexpandedParameterPack() const {
241   switch (getKind()) {
242   case Identifier:
243     return getPrefix() && getPrefix()->containsUnexpandedParameterPack();
244 
245   case Namespace:
246   case NamespaceAlias:
247   case Global:
248   case Super:
249     return false;
250 
251   case TypeSpec:
252   case TypeSpecWithTemplate:
253     return getAsType()->containsUnexpandedParameterPack();
254   }
255 
256   llvm_unreachable("Invalid NNS Kind!");
257 }
258 
259 /// \brief Print this nested name specifier to the given output
260 /// stream.
261 void
262 NestedNameSpecifier::print(raw_ostream &OS,
263                            const PrintingPolicy &Policy) const {
264   if (getPrefix())
265     getPrefix()->print(OS, Policy);
266 
267   switch (getKind()) {
268   case Identifier:
269     OS << getAsIdentifier()->getName();
270     break;
271 
272   case Namespace:
273     if (getAsNamespace()->isAnonymousNamespace())
274       return;
275 
276     OS << getAsNamespace()->getName();
277     break;
278 
279   case NamespaceAlias:
280     OS << getAsNamespaceAlias()->getName();
281     break;
282 
283   case Global:
284     break;
285 
286   case Super:
287     OS << "__super";
288     break;
289 
290   case TypeSpecWithTemplate:
291     OS << "template ";
292     // Fall through to print the type.
293 
294   case TypeSpec: {
295     const Type *T = getAsType();
296 
297     PrintingPolicy InnerPolicy(Policy);
298     InnerPolicy.SuppressScope = true;
299 
300     // Nested-name-specifiers are intended to contain minimally-qualified
301     // types. An actual ElaboratedType will not occur, since we'll store
302     // just the type that is referred to in the nested-name-specifier (e.g.,
303     // a TypedefType, TagType, etc.). However, when we are dealing with
304     // dependent template-id types (e.g., Outer<T>::template Inner<U>),
305     // the type requires its own nested-name-specifier for uniqueness, so we
306     // suppress that nested-name-specifier during printing.
307     assert(!isa<ElaboratedType>(T) &&
308            "Elaborated type in nested-name-specifier");
309     if (const TemplateSpecializationType *SpecType
310           = dyn_cast<TemplateSpecializationType>(T)) {
311       // Print the template name without its corresponding
312       // nested-name-specifier.
313       SpecType->getTemplateName().print(OS, InnerPolicy, true);
314 
315       // Print the template argument list.
316       TemplateSpecializationType::PrintTemplateArgumentList(
317           OS, SpecType->template_arguments(), InnerPolicy);
318     } else {
319       // Print the type normally
320       QualType(T, 0).print(OS, InnerPolicy);
321     }
322     break;
323   }
324   }
325 
326   OS << "::";
327 }
328 
329 void NestedNameSpecifier::dump(const LangOptions &LO) const {
330   print(llvm::errs(), PrintingPolicy(LO));
331 }
332 
333 LLVM_DUMP_METHOD void NestedNameSpecifier::dump() const {
334   LangOptions LO;
335   print(llvm::errs(), PrintingPolicy(LO));
336 }
337 
338 unsigned
339 NestedNameSpecifierLoc::getLocalDataLength(NestedNameSpecifier *Qualifier) {
340   assert(Qualifier && "Expected a non-NULL qualifier");
341 
342   // Location of the trailing '::'.
343   unsigned Length = sizeof(unsigned);
344 
345   switch (Qualifier->getKind()) {
346   case NestedNameSpecifier::Global:
347     // Nothing more to add.
348     break;
349 
350   case NestedNameSpecifier::Identifier:
351   case NestedNameSpecifier::Namespace:
352   case NestedNameSpecifier::NamespaceAlias:
353   case NestedNameSpecifier::Super:
354     // The location of the identifier or namespace name.
355     Length += sizeof(unsigned);
356     break;
357 
358   case NestedNameSpecifier::TypeSpecWithTemplate:
359   case NestedNameSpecifier::TypeSpec:
360     // The "void*" that points at the TypeLoc data.
361     // Note: the 'template' keyword is part of the TypeLoc.
362     Length += sizeof(void *);
363     break;
364   }
365 
366   return Length;
367 }
368 
369 unsigned
370 NestedNameSpecifierLoc::getDataLength(NestedNameSpecifier *Qualifier) {
371   unsigned Length = 0;
372   for (; Qualifier; Qualifier = Qualifier->getPrefix())
373     Length += getLocalDataLength(Qualifier);
374   return Length;
375 }
376 
377 namespace {
378   /// \brief Load a (possibly unaligned) source location from a given address
379   /// and offset.
380   SourceLocation LoadSourceLocation(void *Data, unsigned Offset) {
381     unsigned Raw;
382     memcpy(&Raw, static_cast<char *>(Data) + Offset, sizeof(unsigned));
383     return SourceLocation::getFromRawEncoding(Raw);
384   }
385 
386   /// \brief Load a (possibly unaligned) pointer from a given address and
387   /// offset.
388   void *LoadPointer(void *Data, unsigned Offset) {
389     void *Result;
390     memcpy(&Result, static_cast<char *>(Data) + Offset, sizeof(void*));
391     return Result;
392   }
393 }
394 
395 SourceRange NestedNameSpecifierLoc::getSourceRange() const {
396   if (!Qualifier)
397     return SourceRange();
398 
399   NestedNameSpecifierLoc First = *this;
400   while (NestedNameSpecifierLoc Prefix = First.getPrefix())
401     First = Prefix;
402 
403   return SourceRange(First.getLocalSourceRange().getBegin(),
404                      getLocalSourceRange().getEnd());
405 }
406 
407 SourceRange NestedNameSpecifierLoc::getLocalSourceRange() const {
408   if (!Qualifier)
409     return SourceRange();
410 
411   unsigned Offset = getDataLength(Qualifier->getPrefix());
412   switch (Qualifier->getKind()) {
413   case NestedNameSpecifier::Global:
414     return LoadSourceLocation(Data, Offset);
415 
416   case NestedNameSpecifier::Identifier:
417   case NestedNameSpecifier::Namespace:
418   case NestedNameSpecifier::NamespaceAlias:
419   case NestedNameSpecifier::Super:
420     return SourceRange(LoadSourceLocation(Data, Offset),
421                        LoadSourceLocation(Data, Offset + sizeof(unsigned)));
422 
423   case NestedNameSpecifier::TypeSpecWithTemplate:
424   case NestedNameSpecifier::TypeSpec: {
425     // The "void*" that points at the TypeLoc data.
426     // Note: the 'template' keyword is part of the TypeLoc.
427     void *TypeData = LoadPointer(Data, Offset);
428     TypeLoc TL(Qualifier->getAsType(), TypeData);
429     return SourceRange(TL.getBeginLoc(),
430                        LoadSourceLocation(Data, Offset + sizeof(void*)));
431   }
432   }
433 
434   llvm_unreachable("Invalid NNS Kind!");
435 }
436 
437 TypeLoc NestedNameSpecifierLoc::getTypeLoc() const {
438   assert((Qualifier->getKind() == NestedNameSpecifier::TypeSpec ||
439           Qualifier->getKind() == NestedNameSpecifier::TypeSpecWithTemplate) &&
440          "Nested-name-specifier location is not a type");
441 
442   // The "void*" that points at the TypeLoc data.
443   unsigned Offset = getDataLength(Qualifier->getPrefix());
444   void *TypeData = LoadPointer(Data, Offset);
445   return TypeLoc(Qualifier->getAsType(), TypeData);
446 }
447 
448 namespace {
449   void Append(char *Start, char *End, char *&Buffer, unsigned &BufferSize,
450               unsigned &BufferCapacity) {
451     if (Start == End)
452       return;
453 
454     if (BufferSize + (End - Start) > BufferCapacity) {
455       // Reallocate the buffer.
456       unsigned NewCapacity = std::max(
457           (unsigned)(BufferCapacity ? BufferCapacity * 2 : sizeof(void *) * 2),
458           (unsigned)(BufferSize + (End - Start)));
459       char *NewBuffer = static_cast<char *>(malloc(NewCapacity));
460       if (BufferCapacity) {
461         memcpy(NewBuffer, Buffer, BufferSize);
462         free(Buffer);
463       }
464       Buffer = NewBuffer;
465       BufferCapacity = NewCapacity;
466     }
467 
468     memcpy(Buffer + BufferSize, Start, End - Start);
469     BufferSize += End-Start;
470   }
471 
472   /// \brief Save a source location to the given buffer.
473   void SaveSourceLocation(SourceLocation Loc, char *&Buffer,
474                           unsigned &BufferSize, unsigned &BufferCapacity) {
475     unsigned Raw = Loc.getRawEncoding();
476     Append(reinterpret_cast<char *>(&Raw),
477            reinterpret_cast<char *>(&Raw) + sizeof(unsigned),
478            Buffer, BufferSize, BufferCapacity);
479   }
480 
481   /// \brief Save a pointer to the given buffer.
482   void SavePointer(void *Ptr, char *&Buffer, unsigned &BufferSize,
483                    unsigned &BufferCapacity) {
484     Append(reinterpret_cast<char *>(&Ptr),
485            reinterpret_cast<char *>(&Ptr) + sizeof(void *),
486            Buffer, BufferSize, BufferCapacity);
487   }
488 }
489 
490 NestedNameSpecifierLocBuilder::
491 NestedNameSpecifierLocBuilder(const NestedNameSpecifierLocBuilder &Other)
492   : Representation(Other.Representation), Buffer(nullptr),
493     BufferSize(0), BufferCapacity(0)
494 {
495   if (!Other.Buffer)
496     return;
497 
498   if (Other.BufferCapacity == 0) {
499     // Shallow copy is okay.
500     Buffer = Other.Buffer;
501     BufferSize = Other.BufferSize;
502     return;
503   }
504 
505   // Deep copy
506   Append(Other.Buffer, Other.Buffer + Other.BufferSize, Buffer, BufferSize,
507          BufferCapacity);
508 }
509 
510 NestedNameSpecifierLocBuilder &
511 NestedNameSpecifierLocBuilder::
512 operator=(const NestedNameSpecifierLocBuilder &Other) {
513   Representation = Other.Representation;
514 
515   if (Buffer && Other.Buffer && BufferCapacity >= Other.BufferSize) {
516     // Re-use our storage.
517     BufferSize = Other.BufferSize;
518     memcpy(Buffer, Other.Buffer, BufferSize);
519     return *this;
520   }
521 
522   // Free our storage, if we have any.
523   if (BufferCapacity) {
524     free(Buffer);
525     BufferCapacity = 0;
526   }
527 
528   if (!Other.Buffer) {
529     // Empty.
530     Buffer = nullptr;
531     BufferSize = 0;
532     return *this;
533   }
534 
535   if (Other.BufferCapacity == 0) {
536     // Shallow copy is okay.
537     Buffer = Other.Buffer;
538     BufferSize = Other.BufferSize;
539     return *this;
540   }
541 
542   // Deep copy.
543   Append(Other.Buffer, Other.Buffer + Other.BufferSize, Buffer, BufferSize,
544          BufferCapacity);
545   return *this;
546 }
547 
548 void NestedNameSpecifierLocBuilder::Extend(ASTContext &Context,
549                                            SourceLocation TemplateKWLoc,
550                                            TypeLoc TL,
551                                            SourceLocation ColonColonLoc) {
552   Representation = NestedNameSpecifier::Create(Context, Representation,
553                                                TemplateKWLoc.isValid(),
554                                                TL.getTypePtr());
555 
556   // Push source-location info into the buffer.
557   SavePointer(TL.getOpaqueData(), Buffer, BufferSize, BufferCapacity);
558   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
559 }
560 
561 void NestedNameSpecifierLocBuilder::Extend(ASTContext &Context,
562                                            IdentifierInfo *Identifier,
563                                            SourceLocation IdentifierLoc,
564                                            SourceLocation ColonColonLoc) {
565   Representation = NestedNameSpecifier::Create(Context, Representation,
566                                                Identifier);
567 
568   // Push source-location info into the buffer.
569   SaveSourceLocation(IdentifierLoc, Buffer, BufferSize, BufferCapacity);
570   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
571 }
572 
573 void NestedNameSpecifierLocBuilder::Extend(ASTContext &Context,
574                                            NamespaceDecl *Namespace,
575                                            SourceLocation NamespaceLoc,
576                                            SourceLocation ColonColonLoc) {
577   Representation = NestedNameSpecifier::Create(Context, Representation,
578                                                Namespace);
579 
580   // Push source-location info into the buffer.
581   SaveSourceLocation(NamespaceLoc, Buffer, BufferSize, BufferCapacity);
582   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
583 }
584 
585 void NestedNameSpecifierLocBuilder::Extend(ASTContext &Context,
586                                            NamespaceAliasDecl *Alias,
587                                            SourceLocation AliasLoc,
588                                            SourceLocation ColonColonLoc) {
589   Representation = NestedNameSpecifier::Create(Context, Representation, Alias);
590 
591   // Push source-location info into the buffer.
592   SaveSourceLocation(AliasLoc, Buffer, BufferSize, BufferCapacity);
593   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
594 }
595 
596 void NestedNameSpecifierLocBuilder::MakeGlobal(ASTContext &Context,
597                                                SourceLocation ColonColonLoc) {
598   assert(!Representation && "Already have a nested-name-specifier!?");
599   Representation = NestedNameSpecifier::GlobalSpecifier(Context);
600 
601   // Push source-location info into the buffer.
602   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
603 }
604 
605 void NestedNameSpecifierLocBuilder::MakeSuper(ASTContext &Context,
606                                               CXXRecordDecl *RD,
607                                               SourceLocation SuperLoc,
608                                               SourceLocation ColonColonLoc) {
609   Representation = NestedNameSpecifier::SuperSpecifier(Context, RD);
610 
611   // Push source-location info into the buffer.
612   SaveSourceLocation(SuperLoc, Buffer, BufferSize, BufferCapacity);
613   SaveSourceLocation(ColonColonLoc, Buffer, BufferSize, BufferCapacity);
614 }
615 
616 void NestedNameSpecifierLocBuilder::MakeTrivial(ASTContext &Context,
617                                                 NestedNameSpecifier *Qualifier,
618                                                 SourceRange R) {
619   Representation = Qualifier;
620 
621   // Construct bogus (but well-formed) source information for the
622   // nested-name-specifier.
623   BufferSize = 0;
624   SmallVector<NestedNameSpecifier *, 4> Stack;
625   for (NestedNameSpecifier *NNS = Qualifier; NNS; NNS = NNS->getPrefix())
626     Stack.push_back(NNS);
627   while (!Stack.empty()) {
628     NestedNameSpecifier *NNS = Stack.pop_back_val();
629     switch (NNS->getKind()) {
630       case NestedNameSpecifier::Identifier:
631       case NestedNameSpecifier::Namespace:
632       case NestedNameSpecifier::NamespaceAlias:
633         SaveSourceLocation(R.getBegin(), Buffer, BufferSize, BufferCapacity);
634         break;
635 
636       case NestedNameSpecifier::TypeSpec:
637       case NestedNameSpecifier::TypeSpecWithTemplate: {
638         TypeSourceInfo *TSInfo
639         = Context.getTrivialTypeSourceInfo(QualType(NNS->getAsType(), 0),
640                                            R.getBegin());
641         SavePointer(TSInfo->getTypeLoc().getOpaqueData(), Buffer, BufferSize,
642                     BufferCapacity);
643         break;
644       }
645 
646       case NestedNameSpecifier::Global:
647       case NestedNameSpecifier::Super:
648         break;
649     }
650 
651     // Save the location of the '::'.
652     SaveSourceLocation(Stack.empty()? R.getEnd() : R.getBegin(),
653                        Buffer, BufferSize, BufferCapacity);
654   }
655 }
656 
657 void NestedNameSpecifierLocBuilder::Adopt(NestedNameSpecifierLoc Other) {
658   if (BufferCapacity)
659     free(Buffer);
660 
661   if (!Other) {
662     Representation = nullptr;
663     BufferSize = 0;
664     return;
665   }
666 
667   // Rather than copying the data (which is wasteful), "adopt" the
668   // pointer (which points into the ASTContext) but set the capacity to zero to
669   // indicate that we don't own it.
670   Representation = Other.getNestedNameSpecifier();
671   Buffer = static_cast<char *>(Other.getOpaqueData());
672   BufferSize = Other.getDataLength();
673   BufferCapacity = 0;
674 }
675 
676 NestedNameSpecifierLoc
677 NestedNameSpecifierLocBuilder::getWithLocInContext(ASTContext &Context) const {
678   if (!Representation)
679     return NestedNameSpecifierLoc();
680 
681   // If we adopted our data pointer from elsewhere in the AST context, there's
682   // no need to copy the memory.
683   if (BufferCapacity == 0)
684     return NestedNameSpecifierLoc(Representation, Buffer);
685 
686   // FIXME: After copying the source-location information, should we free
687   // our (temporary) buffer and adopt the ASTContext-allocated memory?
688   // Doing so would optimize repeated calls to getWithLocInContext().
689   void *Mem = Context.Allocate(BufferSize, alignof(void *));
690   memcpy(Mem, Buffer, BufferSize);
691   return NestedNameSpecifierLoc(Representation, Mem);
692 }
693