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