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      1 //===- CIndexUSR.cpp - Clang-C Source Indexing Library --------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file implements the generation and use of USRs from CXEntities.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "CIndexer.h"
     15 #include "CXCursor.h"
     16 #include "CXString.h"
     17 #include "clang/AST/DeclTemplate.h"
     18 #include "clang/AST/DeclVisitor.h"
     19 #include "clang/Frontend/ASTUnit.h"
     20 #include "clang/Lex/PreprocessingRecord.h"
     21 #include "llvm/ADT/SmallString.h"
     22 #include "llvm/Support/raw_ostream.h"
     23 
     24 using namespace clang;
     25 
     26 //===----------------------------------------------------------------------===//
     27 // USR generation.
     28 //===----------------------------------------------------------------------===//
     29 
     30 namespace {
     31 class USRGenerator : public ConstDeclVisitor<USRGenerator> {
     32   OwningPtr<SmallString<128> > OwnedBuf;
     33   SmallVectorImpl<char> &Buf;
     34   llvm::raw_svector_ostream Out;
     35   bool IgnoreResults;
     36   ASTContext *Context;
     37   bool generatedLoc;
     38 
     39   llvm::DenseMap<const Type *, unsigned> TypeSubstitutions;
     40 
     41 public:
     42   explicit USRGenerator(ASTContext *Ctx = 0, SmallVectorImpl<char> *extBuf = 0)
     43   : OwnedBuf(extBuf ? 0 : new SmallString<128>()),
     44     Buf(extBuf ? *extBuf : *OwnedBuf.get()),
     45     Out(Buf),
     46     IgnoreResults(false),
     47     Context(Ctx),
     48     generatedLoc(false)
     49   {
     50     // Add the USR space prefix.
     51     Out << "c:";
     52   }
     53 
     54   StringRef str() {
     55     return Out.str();
     56   }
     57 
     58   USRGenerator* operator->() { return this; }
     59 
     60   template <typename T>
     61   llvm::raw_svector_ostream &operator<<(const T &x) {
     62     Out << x;
     63     return Out;
     64   }
     65 
     66   bool ignoreResults() const { return IgnoreResults; }
     67 
     68   // Visitation methods from generating USRs from AST elements.
     69   void VisitDeclContext(const DeclContext *D);
     70   void VisitFieldDecl(const FieldDecl *D);
     71   void VisitFunctionDecl(const FunctionDecl *D);
     72   void VisitNamedDecl(const NamedDecl *D);
     73   void VisitNamespaceDecl(const NamespaceDecl *D);
     74   void VisitNamespaceAliasDecl(const NamespaceAliasDecl *D);
     75   void VisitFunctionTemplateDecl(const FunctionTemplateDecl *D);
     76   void VisitClassTemplateDecl(const ClassTemplateDecl *D);
     77   void VisitObjCContainerDecl(const ObjCContainerDecl *CD);
     78   void VisitObjCMethodDecl(const ObjCMethodDecl *MD);
     79   void VisitObjCPropertyDecl(const ObjCPropertyDecl *D);
     80   void VisitObjCPropertyImplDecl(const ObjCPropertyImplDecl *D);
     81   void VisitTagDecl(const TagDecl *D);
     82   void VisitTypedefDecl(const TypedefDecl *D);
     83   void VisitTemplateTypeParmDecl(const TemplateTypeParmDecl *D);
     84   void VisitVarDecl(const VarDecl *D);
     85   void VisitNonTypeTemplateParmDecl(const NonTypeTemplateParmDecl *D);
     86   void VisitTemplateTemplateParmDecl(const TemplateTemplateParmDecl *D);
     87   void VisitLinkageSpecDecl(const LinkageSpecDecl *D) {
     88     IgnoreResults = true;
     89   }
     90   void VisitUsingDirectiveDecl(const UsingDirectiveDecl *D) {
     91     IgnoreResults = true;
     92   }
     93   void VisitUsingDecl(const UsingDecl *D) {
     94     IgnoreResults = true;
     95   }
     96   void VisitUnresolvedUsingValueDecl(const UnresolvedUsingValueDecl *D) {
     97     IgnoreResults = true;
     98   }
     99   void VisitUnresolvedUsingTypenameDecl(const UnresolvedUsingTypenameDecl *D) {
    100     IgnoreResults = true;
    101   }
    102 
    103   /// Generate the string component containing the location of the
    104   ///  declaration.
    105   bool GenLoc(const Decl *D);
    106 
    107   /// String generation methods used both by the visitation methods
    108   /// and from other clients that want to directly generate USRs.  These
    109   /// methods do not construct complete USRs (which incorporate the parents
    110   /// of an AST element), but only the fragments concerning the AST element
    111   /// itself.
    112 
    113   /// Generate a USR for an Objective-C class.
    114   void GenObjCClass(StringRef cls);
    115   /// Generate a USR for an Objective-C class category.
    116   void GenObjCCategory(StringRef cls, StringRef cat);
    117   /// Generate a USR fragment for an Objective-C instance variable.  The
    118   /// complete USR can be created by concatenating the USR for the
    119   /// encompassing class with this USR fragment.
    120   void GenObjCIvar(StringRef ivar);
    121   /// Generate a USR fragment for an Objective-C method.
    122   void GenObjCMethod(StringRef sel, bool isInstanceMethod);
    123   /// Generate a USR fragment for an Objective-C property.
    124   void GenObjCProperty(StringRef prop);
    125   /// Generate a USR for an Objective-C protocol.
    126   void GenObjCProtocol(StringRef prot);
    127 
    128   void VisitType(QualType T);
    129   void VisitTemplateParameterList(const TemplateParameterList *Params);
    130   void VisitTemplateName(TemplateName Name);
    131   void VisitTemplateArgument(const TemplateArgument &Arg);
    132 
    133   /// Emit a Decl's name using NamedDecl::printName() and return true if
    134   ///  the decl had no name.
    135   bool EmitDeclName(const NamedDecl *D);
    136 };
    137 
    138 } // end anonymous namespace
    139 
    140 //===----------------------------------------------------------------------===//
    141 // Generating USRs from ASTS.
    142 //===----------------------------------------------------------------------===//
    143 
    144 bool USRGenerator::EmitDeclName(const NamedDecl *D) {
    145   Out.flush();
    146   const unsigned startSize = Buf.size();
    147   D->printName(Out);
    148   Out.flush();
    149   const unsigned endSize = Buf.size();
    150   return startSize == endSize;
    151 }
    152 
    153 static inline bool ShouldGenerateLocation(const NamedDecl *D) {
    154   return D->getLinkage() != ExternalLinkage;
    155 }
    156 
    157 void USRGenerator::VisitDeclContext(const DeclContext *DC) {
    158   if (const NamedDecl *D = dyn_cast<NamedDecl>(DC))
    159     Visit(D);
    160 }
    161 
    162 void USRGenerator::VisitFieldDecl(const FieldDecl *D) {
    163   // The USR for an ivar declared in a class extension is based on the
    164   // ObjCInterfaceDecl, not the ObjCCategoryDecl.
    165   if (const ObjCInterfaceDecl *ID = Context->getObjContainingInterface(D))
    166     Visit(ID);
    167   else
    168     VisitDeclContext(D->getDeclContext());
    169   Out << (isa<ObjCIvarDecl>(D) ? "@" : "@FI@");
    170   if (EmitDeclName(D)) {
    171     // Bit fields can be anonymous.
    172     IgnoreResults = true;
    173     return;
    174   }
    175 }
    176 
    177 void USRGenerator::VisitFunctionDecl(const FunctionDecl *D) {
    178   if (ShouldGenerateLocation(D) && GenLoc(D))
    179     return;
    180 
    181   VisitDeclContext(D->getDeclContext());
    182   if (FunctionTemplateDecl *FunTmpl = D->getDescribedFunctionTemplate()) {
    183     Out << "@FT@";
    184     VisitTemplateParameterList(FunTmpl->getTemplateParameters());
    185   } else
    186     Out << "@F@";
    187   D->printName(Out);
    188 
    189   ASTContext &Ctx = *Context;
    190   if (!Ctx.getLangOpts().CPlusPlus || D->isExternC())
    191     return;
    192 
    193   if (const TemplateArgumentList *
    194         SpecArgs = D->getTemplateSpecializationArgs()) {
    195     Out << '<';
    196     for (unsigned I = 0, N = SpecArgs->size(); I != N; ++I) {
    197       Out << '#';
    198       VisitTemplateArgument(SpecArgs->get(I));
    199     }
    200     Out << '>';
    201   }
    202 
    203   // Mangle in type information for the arguments.
    204   for (FunctionDecl::param_const_iterator I = D->param_begin(),
    205                                           E = D->param_end();
    206        I != E; ++I) {
    207     Out << '#';
    208     if (ParmVarDecl *PD = *I)
    209       VisitType(PD->getType());
    210   }
    211   if (D->isVariadic())
    212     Out << '.';
    213   Out << '#';
    214   if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(D)) {
    215     if (MD->isStatic())
    216       Out << 'S';
    217     if (unsigned quals = MD->getTypeQualifiers())
    218       Out << (char)('0' + quals);
    219   }
    220 }
    221 
    222 void USRGenerator::VisitNamedDecl(const NamedDecl *D) {
    223   VisitDeclContext(D->getDeclContext());
    224   Out << "@";
    225 
    226   if (EmitDeclName(D)) {
    227     // The string can be empty if the declaration has no name; e.g., it is
    228     // the ParmDecl with no name for declaration of a function pointer type,
    229     // e.g.: void  (*f)(void *);
    230     // In this case, don't generate a USR.
    231     IgnoreResults = true;
    232   }
    233 }
    234 
    235 void USRGenerator::VisitVarDecl(const VarDecl *D) {
    236   // VarDecls can be declared 'extern' within a function or method body,
    237   // but their enclosing DeclContext is the function, not the TU.  We need
    238   // to check the storage class to correctly generate the USR.
    239   if (ShouldGenerateLocation(D) && GenLoc(D))
    240     return;
    241 
    242   VisitDeclContext(D->getDeclContext());
    243 
    244   // Variables always have simple names.
    245   StringRef s = D->getName();
    246 
    247   // The string can be empty if the declaration has no name; e.g., it is
    248   // the ParmDecl with no name for declaration of a function pointer type, e.g.:
    249   //    void  (*f)(void *);
    250   // In this case, don't generate a USR.
    251   if (s.empty())
    252     IgnoreResults = true;
    253   else
    254     Out << '@' << s;
    255 }
    256 
    257 void USRGenerator::VisitNonTypeTemplateParmDecl(
    258                                         const NonTypeTemplateParmDecl *D) {
    259   GenLoc(D);
    260   return;
    261 }
    262 
    263 void USRGenerator::VisitTemplateTemplateParmDecl(
    264                                         const TemplateTemplateParmDecl *D) {
    265   GenLoc(D);
    266   return;
    267 }
    268 
    269 void USRGenerator::VisitNamespaceDecl(const NamespaceDecl *D) {
    270   if (D->isAnonymousNamespace()) {
    271     Out << "@aN";
    272     return;
    273   }
    274 
    275   VisitDeclContext(D->getDeclContext());
    276   if (!IgnoreResults)
    277     Out << "@N@" << D->getName();
    278 }
    279 
    280 void USRGenerator::VisitFunctionTemplateDecl(const FunctionTemplateDecl *D) {
    281   VisitFunctionDecl(D->getTemplatedDecl());
    282 }
    283 
    284 void USRGenerator::VisitClassTemplateDecl(const ClassTemplateDecl *D) {
    285   VisitTagDecl(D->getTemplatedDecl());
    286 }
    287 
    288 void USRGenerator::VisitNamespaceAliasDecl(const NamespaceAliasDecl *D) {
    289   VisitDeclContext(D->getDeclContext());
    290   if (!IgnoreResults)
    291     Out << "@NA@" << D->getName();
    292 }
    293 
    294 void USRGenerator::VisitObjCMethodDecl(const ObjCMethodDecl *D) {
    295   const DeclContext *container = D->getDeclContext();
    296   if (const ObjCProtocolDecl *pd = dyn_cast<ObjCProtocolDecl>(container)) {
    297     Visit(pd);
    298   }
    299   else {
    300     // The USR for a method declared in a class extension or category is based on
    301     // the ObjCInterfaceDecl, not the ObjCCategoryDecl.
    302     const ObjCInterfaceDecl *ID = D->getClassInterface();
    303     if (!ID) {
    304       IgnoreResults = true;
    305       return;
    306     }
    307     Visit(ID);
    308   }
    309   // Ideally we would use 'GenObjCMethod', but this is such a hot path
    310   // for Objective-C code that we don't want to use
    311   // DeclarationName::getAsString().
    312   Out << (D->isInstanceMethod() ? "(im)" : "(cm)");
    313   DeclarationName N(D->getSelector());
    314   N.printName(Out);
    315 }
    316 
    317 void USRGenerator::VisitObjCContainerDecl(const ObjCContainerDecl *D) {
    318   switch (D->getKind()) {
    319     default:
    320       llvm_unreachable("Invalid ObjC container.");
    321     case Decl::ObjCInterface:
    322     case Decl::ObjCImplementation:
    323       GenObjCClass(D->getName());
    324       break;
    325     case Decl::ObjCCategory: {
    326       const ObjCCategoryDecl *CD = cast<ObjCCategoryDecl>(D);
    327       const ObjCInterfaceDecl *ID = CD->getClassInterface();
    328       if (!ID) {
    329         // Handle invalid code where the @interface might not
    330         // have been specified.
    331         // FIXME: We should be able to generate this USR even if the
    332         // @interface isn't available.
    333         IgnoreResults = true;
    334         return;
    335       }
    336       // Specially handle class extensions, which are anonymous categories.
    337       // We want to mangle in the location to uniquely distinguish them.
    338       if (CD->IsClassExtension()) {
    339         Out << "objc(ext)" << ID->getName() << '@';
    340         GenLoc(CD);
    341       }
    342       else
    343         GenObjCCategory(ID->getName(), CD->getName());
    344 
    345       break;
    346     }
    347     case Decl::ObjCCategoryImpl: {
    348       const ObjCCategoryImplDecl *CD = cast<ObjCCategoryImplDecl>(D);
    349       const ObjCInterfaceDecl *ID = CD->getClassInterface();
    350       if (!ID) {
    351         // Handle invalid code where the @interface might not
    352         // have been specified.
    353         // FIXME: We should be able to generate this USR even if the
    354         // @interface isn't available.
    355         IgnoreResults = true;
    356         return;
    357       }
    358       GenObjCCategory(ID->getName(), CD->getName());
    359       break;
    360     }
    361     case Decl::ObjCProtocol:
    362       GenObjCProtocol(cast<ObjCProtocolDecl>(D)->getName());
    363       break;
    364   }
    365 }
    366 
    367 void USRGenerator::VisitObjCPropertyDecl(const ObjCPropertyDecl *D) {
    368   // The USR for a property declared in a class extension or category is based
    369   // on the ObjCInterfaceDecl, not the ObjCCategoryDecl.
    370   if (const ObjCInterfaceDecl *ID = Context->getObjContainingInterface(D))
    371     Visit(ID);
    372   else
    373     Visit(cast<Decl>(D->getDeclContext()));
    374   GenObjCProperty(D->getName());
    375 }
    376 
    377 void USRGenerator::VisitObjCPropertyImplDecl(const ObjCPropertyImplDecl *D) {
    378   if (ObjCPropertyDecl *PD = D->getPropertyDecl()) {
    379     VisitObjCPropertyDecl(PD);
    380     return;
    381   }
    382 
    383   IgnoreResults = true;
    384 }
    385 
    386 void USRGenerator::VisitTagDecl(const TagDecl *D) {
    387   // Add the location of the tag decl to handle resolution across
    388   // translation units.
    389   if (ShouldGenerateLocation(D) && GenLoc(D))
    390     return;
    391 
    392   D = D->getCanonicalDecl();
    393   VisitDeclContext(D->getDeclContext());
    394 
    395   bool AlreadyStarted = false;
    396   if (const CXXRecordDecl *CXXRecord = dyn_cast<CXXRecordDecl>(D)) {
    397     if (ClassTemplateDecl *ClassTmpl = CXXRecord->getDescribedClassTemplate()) {
    398       AlreadyStarted = true;
    399 
    400       switch (D->getTagKind()) {
    401       case TTK_Interface:
    402       case TTK_Struct: Out << "@ST"; break;
    403       case TTK_Class:  Out << "@CT"; break;
    404       case TTK_Union:  Out << "@UT"; break;
    405       case TTK_Enum: llvm_unreachable("enum template");
    406       }
    407       VisitTemplateParameterList(ClassTmpl->getTemplateParameters());
    408     } else if (const ClassTemplatePartialSpecializationDecl *PartialSpec
    409                 = dyn_cast<ClassTemplatePartialSpecializationDecl>(CXXRecord)) {
    410       AlreadyStarted = true;
    411 
    412       switch (D->getTagKind()) {
    413       case TTK_Interface:
    414       case TTK_Struct: Out << "@SP"; break;
    415       case TTK_Class:  Out << "@CP"; break;
    416       case TTK_Union:  Out << "@UP"; break;
    417       case TTK_Enum: llvm_unreachable("enum partial specialization");
    418       }
    419       VisitTemplateParameterList(PartialSpec->getTemplateParameters());
    420     }
    421   }
    422 
    423   if (!AlreadyStarted) {
    424     switch (D->getTagKind()) {
    425       case TTK_Interface:
    426       case TTK_Struct: Out << "@S"; break;
    427       case TTK_Class:  Out << "@C"; break;
    428       case TTK_Union:  Out << "@U"; break;
    429       case TTK_Enum:   Out << "@E"; break;
    430     }
    431   }
    432 
    433   Out << '@';
    434   Out.flush();
    435   assert(Buf.size() > 0);
    436   const unsigned off = Buf.size() - 1;
    437 
    438   if (EmitDeclName(D)) {
    439     if (const TypedefNameDecl *TD = D->getTypedefNameForAnonDecl()) {
    440       Buf[off] = 'A';
    441       Out << '@' << *TD;
    442     }
    443     else
    444       Buf[off] = 'a';
    445   }
    446 
    447   // For a class template specialization, mangle the template arguments.
    448   if (const ClassTemplateSpecializationDecl *Spec
    449                               = dyn_cast<ClassTemplateSpecializationDecl>(D)) {
    450     const TemplateArgumentList &Args = Spec->getTemplateInstantiationArgs();
    451     Out << '>';
    452     for (unsigned I = 0, N = Args.size(); I != N; ++I) {
    453       Out << '#';
    454       VisitTemplateArgument(Args.get(I));
    455     }
    456   }
    457 }
    458 
    459 void USRGenerator::VisitTypedefDecl(const TypedefDecl *D) {
    460   if (ShouldGenerateLocation(D) && GenLoc(D))
    461     return;
    462   const DeclContext *DC = D->getDeclContext();
    463   if (const NamedDecl *DCN = dyn_cast<NamedDecl>(DC))
    464     Visit(DCN);
    465   Out << "@T@";
    466   Out << D->getName();
    467 }
    468 
    469 void USRGenerator::VisitTemplateTypeParmDecl(const TemplateTypeParmDecl *D) {
    470   GenLoc(D);
    471   return;
    472 }
    473 
    474 bool USRGenerator::GenLoc(const Decl *D) {
    475   if (generatedLoc)
    476     return IgnoreResults;
    477   generatedLoc = true;
    478 
    479   // Guard against null declarations in invalid code.
    480   if (!D) {
    481     IgnoreResults = true;
    482     return true;
    483   }
    484 
    485   // Use the location of canonical decl.
    486   D = D->getCanonicalDecl();
    487 
    488   const SourceManager &SM = Context->getSourceManager();
    489   SourceLocation L = D->getLocStart();
    490   if (L.isInvalid()) {
    491     IgnoreResults = true;
    492     return true;
    493   }
    494   L = SM.getExpansionLoc(L);
    495   const std::pair<FileID, unsigned> &Decomposed = SM.getDecomposedLoc(L);
    496   const FileEntry *FE = SM.getFileEntryForID(Decomposed.first);
    497   if (FE) {
    498     Out << llvm::sys::path::filename(FE->getName());
    499   }
    500   else {
    501     // This case really isn't interesting.
    502     IgnoreResults = true;
    503     return true;
    504   }
    505   // Use the offest into the FileID to represent the location.  Using
    506   // a line/column can cause us to look back at the original source file,
    507   // which is expensive.
    508   Out << '@' << Decomposed.second;
    509   return IgnoreResults;
    510 }
    511 
    512 void USRGenerator::VisitType(QualType T) {
    513   // This method mangles in USR information for types.  It can possibly
    514   // just reuse the naming-mangling logic used by codegen, although the
    515   // requirements for USRs might not be the same.
    516   ASTContext &Ctx = *Context;
    517 
    518   do {
    519     T = Ctx.getCanonicalType(T);
    520     Qualifiers Q = T.getQualifiers();
    521     unsigned qVal = 0;
    522     if (Q.hasConst())
    523       qVal |= 0x1;
    524     if (Q.hasVolatile())
    525       qVal |= 0x2;
    526     if (Q.hasRestrict())
    527       qVal |= 0x4;
    528     if(qVal)
    529       Out << ((char) ('0' + qVal));
    530 
    531     // Mangle in ObjC GC qualifiers?
    532 
    533     if (const PackExpansionType *Expansion = T->getAs<PackExpansionType>()) {
    534       Out << 'P';
    535       T = Expansion->getPattern();
    536     }
    537 
    538     if (const BuiltinType *BT = T->getAs<BuiltinType>()) {
    539       unsigned char c = '\0';
    540       switch (BT->getKind()) {
    541         case BuiltinType::Void:
    542           c = 'v'; break;
    543         case BuiltinType::Bool:
    544           c = 'b'; break;
    545         case BuiltinType::Char_U:
    546         case BuiltinType::UChar:
    547           c = 'c'; break;
    548         case BuiltinType::Char16:
    549           c = 'q'; break;
    550         case BuiltinType::Char32:
    551           c = 'w'; break;
    552         case BuiltinType::UShort:
    553           c = 's'; break;
    554         case BuiltinType::UInt:
    555           c = 'i'; break;
    556         case BuiltinType::ULong:
    557           c = 'l'; break;
    558         case BuiltinType::ULongLong:
    559           c = 'k'; break;
    560         case BuiltinType::UInt128:
    561           c = 'j'; break;
    562         case BuiltinType::Char_S:
    563         case BuiltinType::SChar:
    564           c = 'C'; break;
    565         case BuiltinType::WChar_S:
    566         case BuiltinType::WChar_U:
    567           c = 'W'; break;
    568         case BuiltinType::Short:
    569           c = 'S'; break;
    570         case BuiltinType::Int:
    571           c = 'I'; break;
    572         case BuiltinType::Long:
    573           c = 'L'; break;
    574         case BuiltinType::LongLong:
    575           c = 'K'; break;
    576         case BuiltinType::Int128:
    577           c = 'J'; break;
    578         case BuiltinType::Half:
    579           c = 'h'; break;
    580         case BuiltinType::Float:
    581           c = 'f'; break;
    582         case BuiltinType::Double:
    583           c = 'd'; break;
    584         case BuiltinType::LongDouble:
    585           c = 'D'; break;
    586         case BuiltinType::NullPtr:
    587           c = 'n'; break;
    588 #define BUILTIN_TYPE(Id, SingletonId)
    589 #define PLACEHOLDER_TYPE(Id, SingletonId) case BuiltinType::Id:
    590 #include "clang/AST/BuiltinTypes.def"
    591         case BuiltinType::Dependent:
    592         case BuiltinType::OCLImage1d:
    593         case BuiltinType::OCLImage1dArray:
    594         case BuiltinType::OCLImage1dBuffer:
    595         case BuiltinType::OCLImage2d:
    596         case BuiltinType::OCLImage2dArray:
    597         case BuiltinType::OCLImage3d:
    598         case BuiltinType::OCLEvent:
    599         case BuiltinType::OCLSampler:
    600           IgnoreResults = true;
    601           return;
    602         case BuiltinType::ObjCId:
    603           c = 'o'; break;
    604         case BuiltinType::ObjCClass:
    605           c = 'O'; break;
    606         case BuiltinType::ObjCSel:
    607           c = 'e'; break;
    608       }
    609       Out << c;
    610       return;
    611     }
    612 
    613     // If we have already seen this (non-built-in) type, use a substitution
    614     // encoding.
    615     llvm::DenseMap<const Type *, unsigned>::iterator Substitution
    616       = TypeSubstitutions.find(T.getTypePtr());
    617     if (Substitution != TypeSubstitutions.end()) {
    618       Out << 'S' << Substitution->second << '_';
    619       return;
    620     } else {
    621       // Record this as a substitution.
    622       unsigned Number = TypeSubstitutions.size();
    623       TypeSubstitutions[T.getTypePtr()] = Number;
    624     }
    625 
    626     if (const PointerType *PT = T->getAs<PointerType>()) {
    627       Out << '*';
    628       T = PT->getPointeeType();
    629       continue;
    630     }
    631     if (const ReferenceType *RT = T->getAs<ReferenceType>()) {
    632       Out << '&';
    633       T = RT->getPointeeType();
    634       continue;
    635     }
    636     if (const FunctionProtoType *FT = T->getAs<FunctionProtoType>()) {
    637       Out << 'F';
    638       VisitType(FT->getResultType());
    639       for (FunctionProtoType::arg_type_iterator
    640             I = FT->arg_type_begin(), E = FT->arg_type_end(); I!=E; ++I) {
    641         VisitType(*I);
    642       }
    643       if (FT->isVariadic())
    644         Out << '.';
    645       return;
    646     }
    647     if (const BlockPointerType *BT = T->getAs<BlockPointerType>()) {
    648       Out << 'B';
    649       T = BT->getPointeeType();
    650       continue;
    651     }
    652     if (const ComplexType *CT = T->getAs<ComplexType>()) {
    653       Out << '<';
    654       T = CT->getElementType();
    655       continue;
    656     }
    657     if (const TagType *TT = T->getAs<TagType>()) {
    658       Out << '$';
    659       VisitTagDecl(TT->getDecl());
    660       return;
    661     }
    662     if (const TemplateTypeParmType *TTP = T->getAs<TemplateTypeParmType>()) {
    663       Out << 't' << TTP->getDepth() << '.' << TTP->getIndex();
    664       return;
    665     }
    666     if (const TemplateSpecializationType *Spec
    667                                     = T->getAs<TemplateSpecializationType>()) {
    668       Out << '>';
    669       VisitTemplateName(Spec->getTemplateName());
    670       Out << Spec->getNumArgs();
    671       for (unsigned I = 0, N = Spec->getNumArgs(); I != N; ++I)
    672         VisitTemplateArgument(Spec->getArg(I));
    673       return;
    674     }
    675 
    676     // Unhandled type.
    677     Out << ' ';
    678     break;
    679   } while (true);
    680 }
    681 
    682 void USRGenerator::VisitTemplateParameterList(
    683                                          const TemplateParameterList *Params) {
    684   if (!Params)
    685     return;
    686   Out << '>' << Params->size();
    687   for (TemplateParameterList::const_iterator P = Params->begin(),
    688                                           PEnd = Params->end();
    689        P != PEnd; ++P) {
    690     Out << '#';
    691     if (isa<TemplateTypeParmDecl>(*P)) {
    692       if (cast<TemplateTypeParmDecl>(*P)->isParameterPack())
    693         Out<< 'p';
    694       Out << 'T';
    695       continue;
    696     }
    697 
    698     if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(*P)) {
    699       if (NTTP->isParameterPack())
    700         Out << 'p';
    701       Out << 'N';
    702       VisitType(NTTP->getType());
    703       continue;
    704     }
    705 
    706     TemplateTemplateParmDecl *TTP = cast<TemplateTemplateParmDecl>(*P);
    707     if (TTP->isParameterPack())
    708       Out << 'p';
    709     Out << 't';
    710     VisitTemplateParameterList(TTP->getTemplateParameters());
    711   }
    712 }
    713 
    714 void USRGenerator::VisitTemplateName(TemplateName Name) {
    715   if (TemplateDecl *Template = Name.getAsTemplateDecl()) {
    716     if (TemplateTemplateParmDecl *TTP
    717                               = dyn_cast<TemplateTemplateParmDecl>(Template)) {
    718       Out << 't' << TTP->getDepth() << '.' << TTP->getIndex();
    719       return;
    720     }
    721 
    722     Visit(Template);
    723     return;
    724   }
    725 
    726   // FIXME: Visit dependent template names.
    727 }
    728 
    729 void USRGenerator::VisitTemplateArgument(const TemplateArgument &Arg) {
    730   switch (Arg.getKind()) {
    731   case TemplateArgument::Null:
    732     break;
    733 
    734   case TemplateArgument::Declaration:
    735     Visit(Arg.getAsDecl());
    736     break;
    737 
    738   case TemplateArgument::NullPtr:
    739     break;
    740 
    741   case TemplateArgument::TemplateExpansion:
    742     Out << 'P'; // pack expansion of...
    743     // Fall through
    744   case TemplateArgument::Template:
    745     VisitTemplateName(Arg.getAsTemplateOrTemplatePattern());
    746     break;
    747 
    748   case TemplateArgument::Expression:
    749     // FIXME: Visit expressions.
    750     break;
    751 
    752   case TemplateArgument::Pack:
    753     Out << 'p' << Arg.pack_size();
    754     for (TemplateArgument::pack_iterator P = Arg.pack_begin(), PEnd = Arg.pack_end();
    755          P != PEnd; ++P)
    756       VisitTemplateArgument(*P);
    757     break;
    758 
    759   case TemplateArgument::Type:
    760     VisitType(Arg.getAsType());
    761     break;
    762 
    763   case TemplateArgument::Integral:
    764     Out << 'V';
    765     VisitType(Arg.getIntegralType());
    766     Out << Arg.getAsIntegral();
    767     break;
    768   }
    769 }
    770 
    771 //===----------------------------------------------------------------------===//
    772 // General purpose USR generation methods.
    773 //===----------------------------------------------------------------------===//
    774 
    775 void USRGenerator::GenObjCClass(StringRef cls) {
    776   Out << "objc(cs)" << cls;
    777 }
    778 
    779 void USRGenerator::GenObjCCategory(StringRef cls, StringRef cat) {
    780   Out << "objc(cy)" << cls << '@' << cat;
    781 }
    782 
    783 void USRGenerator::GenObjCIvar(StringRef ivar) {
    784   Out << '@' << ivar;
    785 }
    786 
    787 void USRGenerator::GenObjCMethod(StringRef meth, bool isInstanceMethod) {
    788   Out << (isInstanceMethod ? "(im)" : "(cm)") << meth;
    789 }
    790 
    791 void USRGenerator::GenObjCProperty(StringRef prop) {
    792   Out << "(py)" << prop;
    793 }
    794 
    795 void USRGenerator::GenObjCProtocol(StringRef prot) {
    796   Out << "objc(pl)" << prot;
    797 }
    798 
    799 //===----------------------------------------------------------------------===//
    800 // API hooks.
    801 //===----------------------------------------------------------------------===//
    802 
    803 static inline StringRef extractUSRSuffix(StringRef s) {
    804   return s.startswith("c:") ? s.substr(2) : "";
    805 }
    806 
    807 bool cxcursor::getDeclCursorUSR(const Decl *D, SmallVectorImpl<char> &Buf) {
    808   // Don't generate USRs for things with invalid locations.
    809   if (!D || D->getLocStart().isInvalid())
    810     return true;
    811 
    812   USRGenerator UG(&D->getASTContext(), &Buf);
    813   UG->Visit(D);
    814 
    815   if (UG->ignoreResults())
    816     return true;
    817 
    818   return false;
    819 }
    820 
    821 extern "C" {
    822 
    823 CXString clang_getCursorUSR(CXCursor C) {
    824   const CXCursorKind &K = clang_getCursorKind(C);
    825 
    826   if (clang_isDeclaration(K)) {
    827     const Decl *D = cxcursor::getCursorDecl(C);
    828     if (!D)
    829       return cxstring::createEmpty();
    830 
    831     CXTranslationUnit TU = cxcursor::getCursorTU(C);
    832     if (!TU)
    833       return cxstring::createEmpty();
    834 
    835     cxstring::CXStringBuf *buf = cxstring::getCXStringBuf(TU);
    836     if (!buf)
    837       return cxstring::createEmpty();
    838 
    839     bool Ignore = cxcursor::getDeclCursorUSR(D, buf->Data);
    840     if (Ignore) {
    841       buf->dispose();
    842       return cxstring::createEmpty();
    843     }
    844 
    845     // Return the C-string, but don't make a copy since it is already in
    846     // the string buffer.
    847     buf->Data.push_back('\0');
    848     return createCXString(buf);
    849   }
    850 
    851   if (K == CXCursor_MacroDefinition) {
    852     CXTranslationUnit TU = cxcursor::getCursorTU(C);
    853     if (!TU)
    854       return cxstring::createEmpty();
    855 
    856     cxstring::CXStringBuf *buf = cxstring::getCXStringBuf(TU);
    857     if (!buf)
    858       return cxstring::createEmpty();
    859 
    860     {
    861       USRGenerator UG(&cxcursor::getCursorASTUnit(C)->getASTContext(),
    862                       &buf->Data);
    863       UG << "macro@"
    864         << cxcursor::getCursorMacroDefinition(C)->getName()->getNameStart();
    865     }
    866     buf->Data.push_back('\0');
    867     return createCXString(buf);
    868   }
    869 
    870   return cxstring::createEmpty();
    871 }
    872 
    873 CXString clang_constructUSR_ObjCIvar(const char *name, CXString classUSR) {
    874   USRGenerator UG;
    875   UG << extractUSRSuffix(clang_getCString(classUSR));
    876   UG->GenObjCIvar(name);
    877   return cxstring::createDup(UG.str());
    878 }
    879 
    880 CXString clang_constructUSR_ObjCMethod(const char *name,
    881                                        unsigned isInstanceMethod,
    882                                        CXString classUSR) {
    883   USRGenerator UG;
    884   UG << extractUSRSuffix(clang_getCString(classUSR));
    885   UG->GenObjCMethod(name, isInstanceMethod);
    886   return cxstring::createDup(UG.str());
    887 }
    888 
    889 CXString clang_constructUSR_ObjCClass(const char *name) {
    890   USRGenerator UG;
    891   UG->GenObjCClass(name);
    892   return cxstring::createDup(UG.str());
    893 }
    894 
    895 CXString clang_constructUSR_ObjCProtocol(const char *name) {
    896   USRGenerator UG;
    897   UG->GenObjCProtocol(name);
    898   return cxstring::createDup(UG.str());
    899 }
    900 
    901 CXString clang_constructUSR_ObjCCategory(const char *class_name,
    902                                          const char *category_name) {
    903   USRGenerator UG;
    904   UG->GenObjCCategory(class_name, category_name);
    905   return cxstring::createDup(UG.str());
    906 }
    907 
    908 CXString clang_constructUSR_ObjCProperty(const char *property,
    909                                          CXString classUSR) {
    910   USRGenerator UG;
    911   UG << extractUSRSuffix(clang_getCString(classUSR));
    912   UG->GenObjCProperty(property);
    913   return cxstring::createDup(UG.str());
    914 }
    915 
    916 } // end extern "C"
    917