Add the clang library to the repo (with some of my changes, too).

1 files changed, 932 insertions, 0 deletions

diff --git a/clang/tools/libclang/CIndexUSRs.cpp b/clang/tools/libclang/CIndexUSRs.cpp
new file mode 100644
index 0000000..7c79b69
--- /dev/null
+++ b/clang/tools/libclang/CIndexUSRs.cpp
@@ -0,0 +1,932 @@
+//===- CIndexUSR.cpp - Clang-C Source Indexing Library --------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the generation and use of USRs from CXEntities.
+//
+//===----------------------------------------------------------------------===//
+
+#include "CIndexer.h"
+#include "CXCursor.h"
+#include "CXString.h"
+#include "clang/AST/DeclTemplate.h"
+#include "clang/AST/DeclVisitor.h"
+#include "clang/Frontend/ASTUnit.h"
+#include "clang/Lex/PreprocessingRecord.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace clang;
+using namespace clang::cxstring;
+
+//===----------------------------------------------------------------------===//
+// USR generation.
+//===----------------------------------------------------------------------===//
+
+namespace {
+class USRGenerator : public DeclVisitor<USRGenerator> {
+  OwningPtr<SmallString<128> > OwnedBuf;
+  SmallVectorImpl<char> &Buf;
+  llvm::raw_svector_ostream Out;
+  bool IgnoreResults;
+  ASTContext *Context;
+  bool generatedLoc;
+  
+  llvm::DenseMap<const Type *, unsigned> TypeSubstitutions;
+  
+public:
+  explicit USRGenerator(ASTContext *Ctx = 0, SmallVectorImpl<char> *extBuf = 0)
+  : OwnedBuf(extBuf ? 0 : new SmallString<128>()),
+    Buf(extBuf ? *extBuf : *OwnedBuf.get()),
+    Out(Buf),
+    IgnoreResults(false),
+    Context(Ctx),
+    generatedLoc(false)
+  {
+    // Add the USR space prefix.
+    Out << "c:";
+  }
+
+  StringRef str() {
+    return Out.str();
+  }
+
+  USRGenerator* operator->() { return this; }
+
+  template <typename T>
+  llvm::raw_svector_ostream &operator<<(const T &x) {
+    Out << x;
+    return Out;
+  }
+
+  bool ignoreResults() const { return IgnoreResults; }
+
+  // Visitation methods from generating USRs from AST elements.
+  void VisitDeclContext(DeclContext *D);
+  void VisitFieldDecl(FieldDecl *D);
+  void VisitFunctionDecl(FunctionDecl *D);
+  void VisitNamedDecl(NamedDecl *D);
+  void VisitNamespaceDecl(NamespaceDecl *D);
+  void VisitNamespaceAliasDecl(NamespaceAliasDecl *D);
+  void VisitFunctionTemplateDecl(FunctionTemplateDecl *D);
+  void VisitClassTemplateDecl(ClassTemplateDecl *D);
+  void VisitObjCContainerDecl(ObjCContainerDecl *CD);
+  void VisitObjCMethodDecl(ObjCMethodDecl *MD);
+  void VisitObjCPropertyDecl(ObjCPropertyDecl *D);
+  void VisitObjCPropertyImplDecl(ObjCPropertyImplDecl *D);
+  void VisitTagDecl(TagDecl *D);
+  void VisitTypedefDecl(TypedefDecl *D);
+  void VisitTemplateTypeParmDecl(TemplateTypeParmDecl *D);
+  void VisitVarDecl(VarDecl *D);
+  void VisitNonTypeTemplateParmDecl(NonTypeTemplateParmDecl *D);
+  void VisitTemplateTemplateParmDecl(TemplateTemplateParmDecl *D);
+  void VisitLinkageSpecDecl(LinkageSpecDecl *D) {
+    IgnoreResults = true;
+  }
+  void VisitUsingDirectiveDecl(UsingDirectiveDecl *D) {
+    IgnoreResults = true;
+  }
+  void VisitUsingDecl(UsingDecl *D) { 
+    IgnoreResults = true;
+  }
+  void VisitUnresolvedUsingValueDecl(UnresolvedUsingValueDecl *D) { 
+    IgnoreResults = true;
+  }
+  void VisitUnresolvedUsingTypenameDecl(UnresolvedUsingTypenameDecl *D) { 
+    IgnoreResults = true;
+  }
+  
+  /// Generate the string component containing the location of the
+  ///  declaration.
+  bool GenLoc(const Decl *D);
+
+  /// String generation methods used both by the visitation methods
+  /// and from other clients that want to directly generate USRs.  These
+  /// methods do not construct complete USRs (which incorporate the parents
+  /// of an AST element), but only the fragments concerning the AST element
+  /// itself.
+
+  /// Generate a USR for an Objective-C class.
+  void GenObjCClass(StringRef cls);
+  /// Generate a USR for an Objective-C class category.
+  void GenObjCCategory(StringRef cls, StringRef cat);
+  /// Generate a USR fragment for an Objective-C instance variable.  The
+  /// complete USR can be created by concatenating the USR for the
+  /// encompassing class with this USR fragment.
+  void GenObjCIvar(StringRef ivar);
+  /// Generate a USR fragment for an Objective-C method.
+  void GenObjCMethod(StringRef sel, bool isInstanceMethod);
+  /// Generate a USR fragment for an Objective-C property.
+  void GenObjCProperty(StringRef prop);
+  /// Generate a USR for an Objective-C protocol.
+  void GenObjCProtocol(StringRef prot);
+
+  void VisitType(QualType T);
+  void VisitTemplateParameterList(const TemplateParameterList *Params);
+  void VisitTemplateName(TemplateName Name);
+  void VisitTemplateArgument(const TemplateArgument &Arg);
+  
+  /// Emit a Decl's name using NamedDecl::printName() and return true if
+  ///  the decl had no name.
+  bool EmitDeclName(const NamedDecl *D);
+};
+
+} // end anonymous namespace
+
+//===----------------------------------------------------------------------===//
+// Generating USRs from ASTS.
+//===----------------------------------------------------------------------===//
+
+bool USRGenerator::EmitDeclName(const NamedDecl *D) {
+  Out.flush();
+  const unsigned startSize = Buf.size();
+  D->printName(Out);
+  Out.flush();
+  const unsigned endSize = Buf.size();
+  return startSize == endSize;
+}
+
+static bool InAnonymousNamespace(const Decl *D) {
+  if (const NamespaceDecl *ND = dyn_cast<NamespaceDecl>(D->getDeclContext()))
+    return ND->isAnonymousNamespace();
+  return false;
+}
+
+static inline bool ShouldGenerateLocation(const NamedDecl *D) {
+  return D->getLinkage() != ExternalLinkage && !InAnonymousNamespace(D);
+}
+
+void USRGenerator::VisitDeclContext(DeclContext *DC) {
+  if (NamedDecl *D = dyn_cast<NamedDecl>(DC))
+    Visit(D);
+}
+
+void USRGenerator::VisitFieldDecl(FieldDecl *D) {
+  // The USR for an ivar declared in a class extension is based on the
+  // ObjCInterfaceDecl, not the ObjCCategoryDecl.
+  if (ObjCInterfaceDecl *ID = Context->getObjContainingInterface(D))
+    Visit(ID);
+  else
+    VisitDeclContext(D->getDeclContext());
+  Out << (isa<ObjCIvarDecl>(D) ? "@" : "@FI@");
+  if (EmitDeclName(D)) {
+    // Bit fields can be anonymous.
+    IgnoreResults = true;
+    return;
+  }
+}
+
+void USRGenerator::VisitFunctionDecl(FunctionDecl *D) {
+  if (ShouldGenerateLocation(D) && GenLoc(D))
+    return;
+
+  VisitDeclContext(D->getDeclContext());
+  if (FunctionTemplateDecl *FunTmpl = D->getDescribedFunctionTemplate()) {
+    Out << "@FT@";
+    VisitTemplateParameterList(FunTmpl->getTemplateParameters());
+  } else
+    Out << "@F@";
+  D->printName(Out);
+
+  ASTContext &Ctx = *Context;
+  if (!Ctx.getLangOpts().CPlusPlus || D->isExternC())
+    return;
+
+  if (const TemplateArgumentList *
+        SpecArgs = D->getTemplateSpecializationArgs()) {
+    Out << '<';
+    for (unsigned I = 0, N = SpecArgs->size(); I != N; ++I) {
+      Out << '#';
+      VisitTemplateArgument(SpecArgs->get(I));
+    }
+    Out << '>';
+  }
+
+  // Mangle in type information for the arguments.
+  for (FunctionDecl::param_iterator I = D->param_begin(), E = D->param_end();
+       I != E; ++I) {
+    Out << '#';
+    if (ParmVarDecl *PD = *I)
+      VisitType(PD->getType());
+  }
+  if (D->isVariadic())
+    Out << '.';
+  Out << '#';
+  if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(D)) {
+    if (MD->isStatic())
+      Out << 'S';
+    if (unsigned quals = MD->getTypeQualifiers())
+      Out << (char)('0' + quals);
+  }
+}
+
+void USRGenerator::VisitNamedDecl(NamedDecl *D) {
+  VisitDeclContext(D->getDeclContext());
+  Out << "@";
+
+  if (EmitDeclName(D)) {
+    // The string can be empty if the declaration has no name; e.g., it is
+    // the ParmDecl with no name for declaration of a function pointer type,
+    // e.g.: void  (*f)(void *);
+    // In this case, don't generate a USR.
+    IgnoreResults = true;
+  }
+}
+
+void USRGenerator::VisitVarDecl(VarDecl *D) {
+  // VarDecls can be declared 'extern' within a function or method body,
+  // but their enclosing DeclContext is the function, not the TU.  We need
+  // to check the storage class to correctly generate the USR.
+  if (ShouldGenerateLocation(D) && GenLoc(D))
+    return;
+
+  VisitDeclContext(D->getDeclContext());
+
+  // Variables always have simple names.
+  StringRef s = D->getName();
+
+  // The string can be empty if the declaration has no name; e.g., it is
+  // the ParmDecl with no name for declaration of a function pointer type, e.g.:
+  //    void  (*f)(void *);
+  // In this case, don't generate a USR.
+  if (s.empty())
+    IgnoreResults = true;
+  else
+    Out << '@' << s;
+}
+
+void USRGenerator::VisitNonTypeTemplateParmDecl(NonTypeTemplateParmDecl *D) {
+  GenLoc(D);
+  return;
+}
+
+void USRGenerator::VisitTemplateTemplateParmDecl(TemplateTemplateParmDecl *D) {
+  GenLoc(D);
+  return;
+}
+
+void USRGenerator::VisitNamespaceDecl(NamespaceDecl *D) {
+  if (D->isAnonymousNamespace()) {
+    Out << "@aN";
+    return;
+  }
+
+  VisitDeclContext(D->getDeclContext());
+  if (!IgnoreResults)
+    Out << "@N@" << D->getName();
+}
+
+void USRGenerator::VisitFunctionTemplateDecl(FunctionTemplateDecl *D) {
+  VisitFunctionDecl(D->getTemplatedDecl());
+}
+
+void USRGenerator::VisitClassTemplateDecl(ClassTemplateDecl *D) {
+  VisitTagDecl(D->getTemplatedDecl());
+}
+
+void USRGenerator::VisitNamespaceAliasDecl(NamespaceAliasDecl *D) {
+  VisitDeclContext(D->getDeclContext());
+  if (!IgnoreResults)
+    Out << "@NA@" << D->getName();  
+}
+
+void USRGenerator::VisitObjCMethodDecl(ObjCMethodDecl *D) {
+  DeclContext *container = D->getDeclContext();
+  if (ObjCProtocolDecl *pd = dyn_cast<ObjCProtocolDecl>(container)) {
+    Visit(pd);
+  }
+  else {
+    // The USR for a method declared in a class extension or category is based on
+    // the ObjCInterfaceDecl, not the ObjCCategoryDecl.
+    ObjCInterfaceDecl *ID = D->getClassInterface();
+    if (!ID) {
+      IgnoreResults = true;
+      return;
+    }
+    Visit(ID);
+  }
+  // Ideally we would use 'GenObjCMethod', but this is such a hot path
+  // for Objective-C code that we don't want to use
+  // DeclarationName::getAsString().
+  Out << (D->isInstanceMethod() ? "(im)" : "(cm)");
+  DeclarationName N(D->getSelector());
+  N.printName(Out);
+}
+
+void USRGenerator::VisitObjCContainerDecl(ObjCContainerDecl *D) {
+  switch (D->getKind()) {
+    default:
+      llvm_unreachable("Invalid ObjC container.");
+    case Decl::ObjCInterface:
+    case Decl::ObjCImplementation:
+      GenObjCClass(D->getName());
+      break;
+    case Decl::ObjCCategory: {
+      ObjCCategoryDecl *CD = cast<ObjCCategoryDecl>(D);
+      ObjCInterfaceDecl *ID = CD->getClassInterface();
+      if (!ID) {
+        // Handle invalid code where the @interface might not
+        // have been specified.
+        // FIXME: We should be able to generate this USR even if the
+        // @interface isn't available.
+        IgnoreResults = true;
+        return;
+      }
+      // Specially handle class extensions, which are anonymous categories.
+      // We want to mangle in the location to uniquely distinguish them.
+      if (CD->IsClassExtension()) {
+        Out << "objc(ext)" << ID->getName() << '@';
+        GenLoc(CD);
+      }
+      else
+        GenObjCCategory(ID->getName(), CD->getName());
+
+      break;
+    }
+    case Decl::ObjCCategoryImpl: {
+      ObjCCategoryImplDecl *CD = cast<ObjCCategoryImplDecl>(D);
+      ObjCInterfaceDecl *ID = CD->getClassInterface();
+      if (!ID) {
+        // Handle invalid code where the @interface might not
+        // have been specified.
+        // FIXME: We should be able to generate this USR even if the
+        // @interface isn't available.
+        IgnoreResults = true;
+        return;
+      }
+      GenObjCCategory(ID->getName(), CD->getName());
+      break;
+    }
+    case Decl::ObjCProtocol:
+      GenObjCProtocol(cast<ObjCProtocolDecl>(D)->getName());
+      break;
+  }
+}
+
+void USRGenerator::VisitObjCPropertyDecl(ObjCPropertyDecl *D) {
+  // The USR for a property declared in a class extension or category is based
+  // on the ObjCInterfaceDecl, not the ObjCCategoryDecl.
+  if (ObjCInterfaceDecl *ID = Context->getObjContainingInterface(D))
+    Visit(ID);
+  else
+    Visit(cast<Decl>(D->getDeclContext()));
+  GenObjCProperty(D->getName());
+}
+
+void USRGenerator::VisitObjCPropertyImplDecl(ObjCPropertyImplDecl *D) {
+  if (ObjCPropertyDecl *PD = D->getPropertyDecl()) {
+    VisitObjCPropertyDecl(PD);
+    return;
+  }
+
+  IgnoreResults = true;
+}
+
+void USRGenerator::VisitTagDecl(TagDecl *D) {
+  // Add the location of the tag decl to handle resolution across
+  // translation units.
+  if (ShouldGenerateLocation(D) && GenLoc(D))
+    return;
+
+  D = D->getCanonicalDecl();
+  VisitDeclContext(D->getDeclContext());
+
+  bool AlreadyStarted = false;
+  if (CXXRecordDecl *CXXRecord = dyn_cast<CXXRecordDecl>(D)) {
+    if (ClassTemplateDecl *ClassTmpl = CXXRecord->getDescribedClassTemplate()) {
+      AlreadyStarted = true;
+      
+      switch (D->getTagKind()) {
+      case TTK_Struct: Out << "@ST"; break;
+      case TTK_Class:  Out << "@CT"; break;
+      case TTK_Union:  Out << "@UT"; break;
+      case TTK_Enum: llvm_unreachable("enum template");
+      }
+      VisitTemplateParameterList(ClassTmpl->getTemplateParameters());
+    } else if (ClassTemplatePartialSpecializationDecl *PartialSpec
+                = dyn_cast<ClassTemplatePartialSpecializationDecl>(CXXRecord)) {
+      AlreadyStarted = true;
+      
+      switch (D->getTagKind()) {
+      case TTK_Struct: Out << "@SP"; break;
+      case TTK_Class:  Out << "@CP"; break;
+      case TTK_Union:  Out << "@UP"; break;
+      case TTK_Enum: llvm_unreachable("enum partial specialization");
+      }      
+      VisitTemplateParameterList(PartialSpec->getTemplateParameters());
+    }
+  }
+  
+  if (!AlreadyStarted) {
+    switch (D->getTagKind()) {
+      case TTK_Struct: Out << "@S"; break;
+      case TTK_Class:  Out << "@C"; break;
+      case TTK_Union:  Out << "@U"; break;
+      case TTK_Enum:   Out << "@E"; break;
+    }
+  }
+  
+  Out << '@';
+  Out.flush();
+  assert(Buf.size() > 0);
+  const unsigned off = Buf.size() - 1;
+
+  if (EmitDeclName(D)) {
+    if (const TypedefNameDecl *TD = D->getTypedefNameForAnonDecl()) {
+      Buf[off] = 'A';
+      Out << '@' << *TD;
+    }
+    else
+      Buf[off] = 'a';
+  }
+  
+  // For a class template specialization, mangle the template arguments.
+  if (ClassTemplateSpecializationDecl *Spec
+                              = dyn_cast<ClassTemplateSpecializationDecl>(D)) {
+    const TemplateArgumentList &Args = Spec->getTemplateInstantiationArgs();
+    Out << '>';
+    for (unsigned I = 0, N = Args.size(); I != N; ++I) {
+      Out << '#';
+      VisitTemplateArgument(Args.get(I));
+    }
+  }
+}
+
+void USRGenerator::VisitTypedefDecl(TypedefDecl *D) {
+  if (ShouldGenerateLocation(D) && GenLoc(D))
+    return;
+  DeclContext *DC = D->getDeclContext();
+  if (NamedDecl *DCN = dyn_cast<NamedDecl>(DC))
+    Visit(DCN);
+  Out << "@T@";
+  Out << D->getName();
+}
+
+void USRGenerator::VisitTemplateTypeParmDecl(TemplateTypeParmDecl *D) {
+  GenLoc(D);
+  return;
+}
+
+bool USRGenerator::GenLoc(const Decl *D) {
+  if (generatedLoc)
+    return IgnoreResults;
+  generatedLoc = true;
+  
+  // Guard against null declarations in invalid code.
+  if (!D) {
+    IgnoreResults = true;
+    return true;
+  }
+
+  // Use the location of canonical decl.
+  D = D->getCanonicalDecl();
+
+  const SourceManager &SM = Context->getSourceManager();
+  SourceLocation L = D->getLocStart();
+  if (L.isInvalid()) {
+    IgnoreResults = true;
+    return true;
+  }
+  L = SM.getExpansionLoc(L);
+  const std::pair<FileID, unsigned> &Decomposed = SM.getDecomposedLoc(L);
+  const FileEntry *FE = SM.getFileEntryForID(Decomposed.first);
+  if (FE) {
+    Out << llvm::sys::path::filename(FE->getName());
+  }
+  else {
+    // This case really isn't interesting.
+    IgnoreResults = true;
+    return true;
+  }
+  // Use the offest into the FileID to represent the location.  Using
+  // a line/column can cause us to look back at the original source file,
+  // which is expensive.
+  Out << '@' << Decomposed.second;
+  return IgnoreResults;
+}
+
+void USRGenerator::VisitType(QualType T) {
+  // This method mangles in USR information for types.  It can possibly
+  // just reuse the naming-mangling logic used by codegen, although the
+  // requirements for USRs might not be the same.
+  ASTContext &Ctx = *Context;
+
+  do {
+    T = Ctx.getCanonicalType(T);
+    Qualifiers Q = T.getQualifiers();
+    unsigned qVal = 0;
+    if (Q.hasConst())
+      qVal |= 0x1;
+    if (Q.hasVolatile())
+      qVal |= 0x2;
+    if (Q.hasRestrict())
+      qVal |= 0x4;
+    if(qVal)
+      Out << ((char) ('0' + qVal));
+
+    // Mangle in ObjC GC qualifiers?
+
+    if (const PackExpansionType *Expansion = T->getAs<PackExpansionType>()) {
+      Out << 'P';
+      T = Expansion->getPattern();
+    }
+    
+    if (const BuiltinType *BT = T->getAs<BuiltinType>()) {
+      unsigned char c = '\0';
+      switch (BT->getKind()) {
+        case BuiltinType::Void:
+          c = 'v'; break;
+        case BuiltinType::Bool:
+          c = 'b'; break;
+        case BuiltinType::Char_U:
+        case BuiltinType::UChar:
+          c = 'c'; break;
+        case BuiltinType::Char16:
+          c = 'q'; break;
+        case BuiltinType::Char32:
+          c = 'w'; break;
+        case BuiltinType::UShort:
+          c = 's'; break;
+        case BuiltinType::UInt:
+          c = 'i'; break;
+        case BuiltinType::ULong:
+          c = 'l'; break;
+        case BuiltinType::ULongLong:
+          c = 'k'; break;
+        case BuiltinType::UInt128:
+          c = 'j'; break;
+        case BuiltinType::Char_S:
+        case BuiltinType::SChar:
+          c = 'C'; break;
+        case BuiltinType::WChar_S:
+        case BuiltinType::WChar_U:
+          c = 'W'; break;
+        case BuiltinType::Short:
+          c = 'S'; break;
+        case BuiltinType::Int:
+          c = 'I'; break;
+        case BuiltinType::Long:
+          c = 'L'; break;
+        case BuiltinType::LongLong:
+          c = 'K'; break;
+        case BuiltinType::Int128:
+          c = 'J'; break;
+        case BuiltinType::Half:
+          c = 'h'; break;
+        case BuiltinType::Float:
+          c = 'f'; break;
+        case BuiltinType::Double:
+          c = 'd'; break;
+        case BuiltinType::LongDouble:
+          c = 'D'; break;
+        case BuiltinType::NullPtr:
+          c = 'n'; break;
+#define BUILTIN_TYPE(Id, SingletonId)
+#define PLACEHOLDER_TYPE(Id, SingletonId) case BuiltinType::Id:
+#include "clang/AST/BuiltinTypes.def"
+        case BuiltinType::Dependent:
+          IgnoreResults = true;
+          return;
+        case BuiltinType::ObjCId:
+          c = 'o'; break;
+        case BuiltinType::ObjCClass:
+          c = 'O'; break;
+        case BuiltinType::ObjCSel:
+          c = 'e'; break;
+      }
+      Out << c;
+      return;
+    }
+
+    // If we have already seen this (non-built-in) type, use a substitution
+    // encoding.
+    llvm::DenseMap<const Type *, unsigned>::iterator Substitution
+      = TypeSubstitutions.find(T.getTypePtr());
+    if (Substitution != TypeSubstitutions.end()) {
+      Out << 'S' << Substitution->second << '_';
+      return;
+    } else {
+      // Record this as a substitution.
+      unsigned Number = TypeSubstitutions.size();
+      TypeSubstitutions[T.getTypePtr()] = Number;
+    }
+    
+    if (const PointerType *PT = T->getAs<PointerType>()) {
+      Out << '*';
+      T = PT->getPointeeType();
+      continue;
+    }
+    if (const ReferenceType *RT = T->getAs<ReferenceType>()) {
+      Out << '&';
+      T = RT->getPointeeType();
+      continue;
+    }
+    if (const FunctionProtoType *FT = T->getAs<FunctionProtoType>()) {
+      Out << 'F';
+      VisitType(FT->getResultType());
+      for (FunctionProtoType::arg_type_iterator
+            I = FT->arg_type_begin(), E = FT->arg_type_end(); I!=E; ++I) {
+        VisitType(*I);
+      }
+      if (FT->isVariadic())
+        Out << '.';
+      return;
+    }
+    if (const BlockPointerType *BT = T->getAs<BlockPointerType>()) {
+      Out << 'B';
+      T = BT->getPointeeType();
+      continue;
+    }
+    if (const ComplexType *CT = T->getAs<ComplexType>()) {
+      Out << '<';
+      T = CT->getElementType();
+      continue;
+    }
+    if (const TagType *TT = T->getAs<TagType>()) {
+      Out << '$';
+      VisitTagDecl(TT->getDecl());
+      return;
+    }
+    if (const TemplateTypeParmType *TTP = T->getAs<TemplateTypeParmType>()) {
+      Out << 't' << TTP->getDepth() << '.' << TTP->getIndex();
+      return;
+    }
+    if (const TemplateSpecializationType *Spec
+                                    = T->getAs<TemplateSpecializationType>()) {
+      Out << '>';
+      VisitTemplateName(Spec->getTemplateName());
+      Out << Spec->getNumArgs();
+      for (unsigned I = 0, N = Spec->getNumArgs(); I != N; ++I)
+        VisitTemplateArgument(Spec->getArg(I));
+      return;
+    }
+    
+    // Unhandled type.
+    Out << ' ';
+    break;
+  } while (true);
+}
+
+void USRGenerator::VisitTemplateParameterList(
+                                         const TemplateParameterList *Params) {
+  if (!Params)
+    return;
+  Out << '>' << Params->size();
+  for (TemplateParameterList::const_iterator P = Params->begin(),
+                                          PEnd = Params->end();
+       P != PEnd; ++P) {
+    Out << '#';
+    if (isa<TemplateTypeParmDecl>(*P)) {
+      if (cast<TemplateTypeParmDecl>(*P)->isParameterPack())
+        Out<< 'p';
+      Out << 'T';
+      continue;
+    }
+    
+    if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(*P)) {
+      if (NTTP->isParameterPack())
+        Out << 'p';
+      Out << 'N';
+      VisitType(NTTP->getType());
+      continue;
+    }
+    
+    TemplateTemplateParmDecl *TTP = cast<TemplateTemplateParmDecl>(*P);
+    if (TTP->isParameterPack())
+      Out << 'p';
+    Out << 't';
+    VisitTemplateParameterList(TTP->getTemplateParameters());
+  }
+}
+
+void USRGenerator::VisitTemplateName(TemplateName Name) {
+  if (TemplateDecl *Template = Name.getAsTemplateDecl()) {
+    if (TemplateTemplateParmDecl *TTP
+                              = dyn_cast<TemplateTemplateParmDecl>(Template)) {
+      Out << 't' << TTP->getDepth() << '.' << TTP->getIndex();
+      return;
+    }
+    
+    Visit(Template);
+    return;
+  }
+  
+  // FIXME: Visit dependent template names.
+}
+
+void USRGenerator::VisitTemplateArgument(const TemplateArgument &Arg) {
+  switch (Arg.getKind()) {
+  case TemplateArgument::Null:
+    break;
+
+  case TemplateArgument::Declaration:
+    if (Decl *D = Arg.getAsDecl())
+      Visit(D);
+    break;
+      
+  case TemplateArgument::TemplateExpansion:
+    Out << 'P'; // pack expansion of...
+    // Fall through
+  case TemplateArgument::Template:
+    VisitTemplateName(Arg.getAsTemplateOrTemplatePattern());
+    break;
+      
+  case TemplateArgument::Expression:
+    // FIXME: Visit expressions.
+    break;
+      
+  case TemplateArgument::Pack:
+    Out << 'p' << Arg.pack_size();
+    for (TemplateArgument::pack_iterator P = Arg.pack_begin(), PEnd = Arg.pack_end();
+         P != PEnd; ++P)
+      VisitTemplateArgument(*P);
+    break;
+      
+  case TemplateArgument::Type:
+    VisitType(Arg.getAsType());
+    break;
+      
+  case TemplateArgument::Integral:
+    Out << 'V';
+    VisitType(Arg.getIntegralType());
+    Out << *Arg.getAsIntegral();
+    break;
+  }
+}
+
+//===----------------------------------------------------------------------===//
+// General purpose USR generation methods.
+//===----------------------------------------------------------------------===//
+
+void USRGenerator::GenObjCClass(StringRef cls) {
+  Out << "objc(cs)" << cls;
+}
+
+void USRGenerator::GenObjCCategory(StringRef cls, StringRef cat) {
+  Out << "objc(cy)" << cls << '@' << cat;
+}
+
+void USRGenerator::GenObjCIvar(StringRef ivar) {
+  Out << '@' << ivar;
+}
+
+void USRGenerator::GenObjCMethod(StringRef meth, bool isInstanceMethod) {
+  Out << (isInstanceMethod ? "(im)" : "(cm)") << meth;
+}
+
+void USRGenerator::GenObjCProperty(StringRef prop) {
+  Out << "(py)" << prop;
+}
+
+void USRGenerator::GenObjCProtocol(StringRef prot) {
+  Out << "objc(pl)" << prot;
+}
+
+//===----------------------------------------------------------------------===//
+// API hooks.
+//===----------------------------------------------------------------------===//
+
+static inline StringRef extractUSRSuffix(StringRef s) {
+  return s.startswith("c:") ? s.substr(2) : "";
+}
+
+bool cxcursor::getDeclCursorUSR(const Decl *D, SmallVectorImpl<char> &Buf) {
+  // Don't generate USRs for things with invalid locations.
+  if (!D || D->getLocStart().isInvalid())
+    return true;
+
+  // Check if the cursor has 'NoLinkage'.
+  if (const NamedDecl *ND = dyn_cast<NamedDecl>(D))
+    switch (ND->getLinkage()) {
+      case ExternalLinkage:
+        // Generate USRs for all entities with external linkage.
+        break;
+      case NoLinkage:
+      case UniqueExternalLinkage:
+        // We allow enums, typedefs, and structs that have no linkage to
+        // have USRs that are anchored to the file they were defined in
+        // (e.g., the header).  This is a little gross, but in principal
+        // enums/anonymous structs/etc. defined in a common header file
+        // are referred to across multiple translation units.
+        if (isa<TagDecl>(ND) || isa<TypedefDecl>(ND) ||
+            isa<EnumConstantDecl>(ND) || isa<FieldDecl>(ND) ||
+            isa<VarDecl>(ND) || isa<NamespaceDecl>(ND))
+          break;
+        // Fall-through.
+      case InternalLinkage:
+        if (isa<FunctionDecl>(ND))
+          break;
+    }
+
+  {
+    USRGenerator UG(&D->getASTContext(), &Buf);
+    UG->Visit(const_cast<Decl*>(D));
+
+    if (UG->ignoreResults())
+      return true;
+  }
+
+  return false;
+}
+
+extern "C" {
+
+CXString clang_getCursorUSR(CXCursor C) {
+  const CXCursorKind &K = clang_getCursorKind(C);
+
+  if (clang_isDeclaration(K)) {
+    Decl *D = cxcursor::getCursorDecl(C);
+    if (!D)
+      return createCXString("");
+
+    CXTranslationUnit TU = cxcursor::getCursorTU(C);
+    if (!TU)
+      return createCXString("");
+
+    CXStringBuf *buf = cxstring::getCXStringBuf(TU);
+    if (!buf)
+      return createCXString("");
+
+    bool Ignore = cxcursor::getDeclCursorUSR(D, buf->Data);
+    if (Ignore) {
+      disposeCXStringBuf(buf);
+      return createCXString("");
+    }
+
+    // Return the C-string, but don't make a copy since it is already in
+    // the string buffer.
+    buf->Data.push_back('\0');
+    return createCXString(buf);
+  }
+
+  if (K == CXCursor_MacroDefinition) {
+    CXTranslationUnit TU = cxcursor::getCursorTU(C);
+    if (!TU)
+      return createCXString("");
+
+    CXStringBuf *buf = cxstring::getCXStringBuf(TU);
+    if (!buf)
+      return createCXString("");
+
+    {
+      USRGenerator UG(&cxcursor::getCursorASTUnit(C)->getASTContext(),
+                      &buf->Data);
+      UG << "macro@"
+        << cxcursor::getCursorMacroDefinition(C)->getName()->getNameStart();
+    }
+    buf->Data.push_back('\0');
+    return createCXString(buf);
+  }
+
+  return createCXString("");
+}
+
+CXString clang_constructUSR_ObjCIvar(const char *name, CXString classUSR) {
+  USRGenerator UG;
+  UG << extractUSRSuffix(clang_getCString(classUSR));
+  UG->GenObjCIvar(name);
+  return createCXString(UG.str(), true);
+}
+
+CXString clang_constructUSR_ObjCMethod(const char *name,
+                                       unsigned isInstanceMethod,
+                                       CXString classUSR) {
+  USRGenerator UG;
+  UG << extractUSRSuffix(clang_getCString(classUSR));
+  UG->GenObjCMethod(name, isInstanceMethod);
+  return createCXString(UG.str(), true);
+}
+
+CXString clang_constructUSR_ObjCClass(const char *name) {
+  USRGenerator UG;
+  UG->GenObjCClass(name);
+  return createCXString(UG.str(), true);
+}
+
+CXString clang_constructUSR_ObjCProtocol(const char *name) {
+  USRGenerator UG;
+  UG->GenObjCProtocol(name);
+  return createCXString(UG.str(), true);
+}
+
+CXString clang_constructUSR_ObjCCategory(const char *class_name,
+                                         const char *category_name) {
+  USRGenerator UG;
+  UG->GenObjCCategory(class_name, category_name);
+  return createCXString(UG.str(), true);
+}
+
+CXString clang_constructUSR_ObjCProperty(const char *property,
+                                         CXString classUSR) {
+  USRGenerator UG;
+  UG << extractUSRSuffix(clang_getCString(classUSR));
+  UG->GenObjCProperty(property);
+  return createCXString(UG.str(), true);
+}
+
+} // end extern "C"