[Lldb-commits] [lldb] [lldb/DWARF] Don't start class definitions in ParseStructureLikeDIE (PR #96755)

[Michael Buch via lldb-commits]

================
@@ -1893,72 +1849,21 @@ DWARFASTParserClang::ParseStructureLikeDIE(const SymbolContext &sc,
   dwarf->GetUniqueDWARFASTTypeMap().Insert(unique_typename,
                                            *unique_ast_entry_up);
 
-  if (!attrs.is_forward_declaration) {
-    // Always start the definition for a class type so that if the class
-    // has child classes or types that require the class to be created
-    // for use as their decl contexts the class will be ready to accept
-    // these child definitions.
-    if (!def_die.HasChildren()) {
-      // No children for this struct/union/class, lets finish it
-      if (TypeSystemClang::StartTagDeclarationDefinition(clang_type)) {
-        TypeSystemClang::CompleteTagDeclarationDefinition(clang_type);
-      } else {
-        dwarf->GetObjectFile()->GetModule()->ReportError(
-
-            "DWARF DIE {0:x16} named \"{1}\" was not able to start its "
-            "definition.\nPlease file a bug and attach the file at the "
-            "start of this error message",
-            def_die.GetID(), attrs.name.GetCString());
-      }
-
-      // Setting authority byte size and alignment for empty structures.
-      //
-      // If the byte size or alignmenet of the record is specified then
-      // overwrite the ones that would be computed by Clang.
-      // This is only needed as LLDB's TypeSystemClang is always in C++ mode,
-      // but some compilers such as GCC and Clang give empty structs a size of 0
-      // in C mode (in contrast to the size of 1 for empty structs that would be
-      // computed in C++ mode).
-      if (attrs.byte_size || attrs.alignment) {
-        clang::RecordDecl *record_decl =
-            TypeSystemClang::GetAsRecordDecl(clang_type);
-        if (record_decl) {
-          ClangASTImporter::LayoutInfo layout;
-          layout.bit_size = attrs.byte_size.value_or(0) * 8;
-          layout.alignment = attrs.alignment.value_or(0) * 8;
-          GetClangASTImporter().SetRecordLayout(record_decl, layout);
-        }
-      }
-    } else if (clang_type_was_created) {
-      // Start the definition if the class is not objective C since the
-      // underlying decls respond to isCompleteDefinition(). Objective
-      // C decls don't respond to isCompleteDefinition() so we can't
-      // start the declaration definition right away. For C++
-      // class/union/structs we want to start the definition in case the
-      // class is needed as the declaration context for a contained class
-      // or type without the need to complete that type..
-
-      if (attrs.class_language != eLanguageTypeObjC &&
-          attrs.class_language != eLanguageTypeObjC_plus_plus)
-        TypeSystemClang::StartTagDeclarationDefinition(clang_type);
-
-      // Leave this as a forward declaration until we need to know the
-      // details of the type. lldb_private::Type will automatically call
-      // the SymbolFile virtual function
-      // "SymbolFileDWARF::CompleteType(Type *)" When the definition
-      // needs to be defined.
-      assert(!dwarf->GetForwardDeclCompilerTypeToDIE().count(
-                 ClangUtil::RemoveFastQualifiers(clang_type)
-                     .GetOpaqueQualType()) &&
-             "Type already in the forward declaration map!");
-      // Can't assume m_ast.GetSymbolFile() is actually a
-      // SymbolFileDWARF, it can be a SymbolFileDWARFDebugMap for Apple
-      // binaries.
-      dwarf->GetForwardDeclCompilerTypeToDIE().try_emplace(
-          ClangUtil::RemoveFastQualifiers(clang_type).GetOpaqueQualType(),
-          *def_die.GetDIERef());
-      m_ast.SetHasExternalStorage(clang_type.GetOpaqueQualType(), true);
-    }
+  if (clang_type_was_created) {
----------------
Michael137 wrote:

Could there be any consequence of doing this for empty types now? We might end up with some lookups into empty types? Since we're going to turn off the external storage bit in `CompleteRecordTypeFromDWARF` this is probably fine though?

https://github.com/llvm/llvm-project/pull/96755