[InstallAPI] Add support for C++ headers

This includes capturing symbols for global variables, functions, classes, and templated defintions.
As pre-determing what symbols are generated from C++ declarations can be
non-trivial, InstallAPI only parses select declarations for symbol
generation when parsing c++.

For example, installapi only looks at explicit template instantiations
or full template specializations, instead of general function or class templates, for
symbol emittion.

Author: cyndyishida

clang/include/clang/InstallAPI/Visitor.h

@@ -13,6 +13,7 @@
 #ifndef LLVM_CLANG_INSTALLAPI_VISITOR_H
 #define LLVM_CLANG_INSTALLAPI_VISITOR_H
 
+#include "clang/AST/Availability.h"
 #include "clang/AST/Mangle.h"
 #include "clang/AST/RecursiveASTVisitor.h"
 #include "clang/Basic/TargetInfo.h"
@@ -33,6 +34,7 @@ class InstallAPIVisitor final : public ASTConsumer,
         MC(ItaniumMangleContext::create(ASTCtx, ASTCtx.getDiagnostics())),
         Layout(ASTCtx.getTargetInfo().getDataLayoutString()) {}
   void HandleTranslationUnit(ASTContext &ASTCtx) override;
+  bool shouldVisitTemplateInstantiations() const { return true; }
 
   /// Collect global variables.
   bool VisitVarDecl(const VarDecl *D);
@@ -51,16 +53,28 @@ class InstallAPIVisitor final : public ASTConsumer,
   /// is therefore itself not collected.
   bool VisitObjCCategoryDecl(const ObjCCategoryDecl *D);
 
+  /// Collect global c++ declarations.
+  bool VisitCXXRecordDecl(const CXXRecordDecl *D);
+
 private:
   std::string getMangledName(const NamedDecl *D) const;
   std::string getBackendMangledName(llvm::Twine Name) const;
+  std::string getMangledCXXVTableName(const CXXRecordDecl *D) const;
+  std::string getMangledCXXThunk(const GlobalDecl &D,
+                                 const ThunkInfo &Thunk) const;
+  std::string getMangledCXXRTTI(const CXXRecordDecl *D) const;
+  std::string getMangledCXXRTTIName(const CXXRecordDecl *D) const;
+  std::string getMangledCtorDtor(const CXXMethodDecl *D, int Type) const;
+
   std::optional<HeaderType> getAccessForDecl(const NamedDecl *D) const;
   void recordObjCInstanceVariables(
       const ASTContext &ASTCtx, llvm::MachO::ObjCContainerRecord *Record,
       StringRef SuperClass,
       const llvm::iterator_range<
           DeclContext::specific_decl_iterator<ObjCIvarDecl>>
           Ivars);
+  void emitVTableSymbols(const CXXRecordDecl *D, const AvailabilityInfo &Avail,
+                         const HeaderType Access, bool EmittedVTable = false);
 
   InstallAPIContext &Ctx;
   SourceManager &SrcMgr;

clang/lib/InstallAPI/Frontend.cpp

@@ -136,9 +136,9 @@ std::unique_ptr<MemoryBuffer> createInputBuffer(InstallAPIContext &Ctx) {
     else
       OS << "#import ";
     if (H.useIncludeName())
-      OS << "<" << H.getIncludeName() << ">";
+      OS << "<" << H.getIncludeName() << ">\n";
     else
-      OS << "\"" << H.getPath() << "\"";
+      OS << "\"" << H.getPath() << "\"\n";
 
     Ctx.addKnownHeader(H);
   }