Reland [clang][ASTImport] Add support for import of empty records

Patch represents the clang part of changes in D143347

Reviewed By: balazske

Differential Revision: https://reviews.llvm.org/D145057

~~

Huawei RRI, OS Lab

Author: kpdev

clang/include/clang/AST/ASTImporter.h

@@ -258,6 +258,7 @@ class TypeSourceInfo;
     FoundDeclsTy findDeclsInToCtx(DeclContext *DC, DeclarationName Name);
 
     void AddToLookupTable(Decl *ToD);
+    llvm::Error ImportAttrs(Decl *ToD, Decl *FromD);
 
   protected:
     /// Can be overwritten by subclasses to implement their own import logic.

clang/include/clang/AST/DeclCXX.h

@@ -1165,6 +1165,10 @@ class CXXRecordDecl : public RecordDecl {
   ///
   /// \note This does NOT include a check for union-ness.
   bool isEmpty() const { return data().Empty; }
+  /// Marks this record as empty. This is used by DWARFASTParserClang
+  /// when parsing records with empty fields having [[no_unique_address]]
+  /// attribute
+  void markEmpty() { data().Empty = true; }
 
   void setInitMethod(bool Val) { data().HasInitMethod = Val; }
   bool hasInitMethod() const { return data().HasInitMethod; }

clang/lib/AST/ASTImporter.cpp

@@ -3895,6 +3895,12 @@ ExpectedDecl ASTNodeImporter::VisitFieldDecl(FieldDecl *D) {
                               D->getInClassInitStyle()))
     return ToField;
 
+  // We need [[no_unqiue_address]] attributes to be added to FieldDecl, before
+  // we add fields in CXXRecordDecl::addedMember, otherwise record will be
+  // marked as having non-zero size.
+  Err = Importer.ImportAttrs(ToField, D);
+  if (Err)
+    return std::move(Err);
   ToField->setAccess(D->getAccess());
   ToField->setLexicalDeclContext(LexicalDC);
   if (ToInitializer)
@@ -8981,6 +8987,19 @@ TranslationUnitDecl *ASTImporter::GetFromTU(Decl *ToD) {
   return FromDPos->second->getTranslationUnitDecl();
 }
 
+Error ASTImporter::ImportAttrs(Decl *ToD, Decl *FromD) {
+  if (!FromD->hasAttrs() || ToD->hasAttrs())
+    return Error::success();
+  for (const Attr *FromAttr : FromD->getAttrs()) {
+    auto ToAttrOrErr = Import(FromAttr);
+    if (ToAttrOrErr)
+      ToD->addAttr(*ToAttrOrErr);
+    else
+      return ToAttrOrErr.takeError();
+  }
+  return Error::success();
+}
+
 Expected<Decl *> ASTImporter::Import(Decl *FromD) {
   if (!FromD)
     return nullptr;
@@ -9115,15 +9134,8 @@ Expected<Decl *> ASTImporter::Import(Decl *FromD) {
 
   // Make sure that ImportImpl registered the imported decl.
   assert(ImportedDecls.count(FromD) != 0 && "Missing call to MapImported?");
-
-  if (FromD->hasAttrs())
-    for (const Attr *FromAttr : FromD->getAttrs()) {
-      auto ToAttrOrErr = Import(FromAttr);
-      if (ToAttrOrErr)
-        ToD->addAttr(*ToAttrOrErr);
-      else
-        return ToAttrOrErr.takeError();
-    }
+  if (auto Error = ImportAttrs(ToD, FromD))
+    return std::move(Error);
 
   // Notify subclasses.
   Imported(FromD, ToD);

clang/unittests/AST/ASTImporterTest.cpp

@@ -8478,6 +8478,29 @@ TEST_P(ASTImporterOptionSpecificTestBase, VaListCpp) {
       ToVaList->getUnderlyingType(), ToBuiltinVaList->getUnderlyingType()));
 }
 
+TEST_P(ASTImporterOptionSpecificTestBase,
+       ImportDefinitionOfEmptyClassWithNoUniqueAddressField) {
+  Decl *FromTU = getTuDecl(
+      R"(
+      struct B {};
+      struct A { B b; };
+      )",
+      Lang_CXX20);
+
+  CXXRecordDecl *FromD = FirstDeclMatcher<CXXRecordDecl>().match(
+      FromTU, cxxRecordDecl(hasName("A")));
+
+  for (auto *FD : FromD->fields())
+    FD->addAttr(clang::NoUniqueAddressAttr::Create(FromD->getASTContext(),
+                                                   clang::SourceRange()));
+  FromD->markEmpty();
+
+  CXXRecordDecl *ToD = Import(FromD, Lang_CXX20);
+  EXPECT_TRUE(ToD->isEmpty());
+  for (auto *FD : ToD->fields())
+    EXPECT_EQ(true, FD->hasAttr<NoUniqueAddressAttr>());
+}
+
 INSTANTIATE_TEST_SUITE_P(ParameterizedTests, ASTImporterLookupTableTest,
                          DefaultTestValuesForRunOptions);