[InstallAPI] Collect C++ Decls (#84403)

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.

clang/include/clang/InstallAPI/Visitor.h

@@ -21,6 +21,7 @@
 #include "llvm/ADT/Twine.h"
 
 namespace clang {
+struct AvailabilityInfo;
 namespace installapi {
 
 /// ASTVisitor for collecting declarations that represent global symbols.
@@ -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

@@ -137,9 +137,9 @@ 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);
   }