[lldb][DWARFASTParserClang] Added a check for the specialization existence

lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp

@@ -1899,6 +1899,17 @@ DWARFASTParserClang::ParseStructureLikeDIE(const SymbolContext &sc,
         m_ast.CreateClassTemplateSpecializationDecl(
             containing_decl_ctx, GetOwningClangModule(die), class_template_decl,
             tag_decl_kind, template_param_infos);
+    if (!class_specialization_decl) {
+      if (log) {
+        dwarf->GetObjectFile()->GetModule()->LogMessage(
+            log,
+            "SymbolFileDWARF({0:p}) - Failed to create specialization for "
+            "clang::ClassTemplateDecl({1}, {2:p}).",
+            this, llvm::StringRef(attrs.name), class_template_decl);
+      }
+      return TypeSP();
+    }
+
     clang_type =
         m_ast.CreateClassTemplateSpecializationType(class_specialization_decl);
 

lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp

@@ -1674,6 +1674,11 @@ TypeSystemClang::CreateClassTemplateSpecializationDecl(
   class_template_specialization_decl->setInstantiationOf(class_template_decl);
   class_template_specialization_decl->setTemplateArgs(
       TemplateArgumentList::CreateCopy(ast, args));
+  void *insert_pos = nullptr;
+  if (class_template_decl->findSpecialization(args, insert_pos))
+    return nullptr;
+  class_template_decl->AddSpecialization(class_template_specialization_decl,
+                                         insert_pos);
   class_template_specialization_decl->setDeclName(
       class_template_decl->getDeclName());
 

lldb/unittests/SymbolFile/DWARF/CMakeLists.txt

@@ -27,6 +27,7 @@ add_lldb_unittest(SymbolFileDWARFTests
 
 set(test_inputs
    test-dwarf.exe
-   DW_AT_default_value-test.yaml)
+   DW_AT_default_value-test.yaml
+   DW_AT_spec_decl_exists-test.yaml)
 
 add_unittest_inputs(SymbolFileDWARFTests "${test_inputs}")

lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp

@@ -599,6 +599,40 @@ TEST_F(DWARFASTParserClangTests, TestDefaultTemplateParamParsing) {
   }
 }
 
+TEST_F(DWARFASTParserClangTests, TestSpecDeclExistsError) {
+  // Tests that parsing a ClassTemplateSpecializationDecl that already exists
+  // is handled gracefully.
+  auto BufferOrError = llvm::MemoryBuffer::getFile(
+      GetInputFilePath("DW_AT_spec_decl_exists-test.yaml"), /*IsText=*/true);
+  ASSERT_TRUE(BufferOrError);
+  YAMLModuleTester t(BufferOrError.get()->getBuffer());
+
+  DWARFUnit *unit = t.GetDwarfUnit();
+  ASSERT_NE(unit, nullptr);
+  const DWARFDebugInfoEntry *cu_entry = unit->DIE().GetDIE();
+  ASSERT_EQ(cu_entry->Tag(), DW_TAG_compile_unit);
+  DWARFDIE cu_die(unit, cu_entry);
+
+  auto holder = std::make_unique<clang_utils::TypeSystemClangHolder>("ast");
+  auto &ast_ctx = *holder->GetAST();
+  DWARFASTParserClangStub ast_parser(ast_ctx);
+
+  llvm::SmallVector<lldb::TypeSP, 2> specializations;
+  for (DWARFDIE die : cu_die.children()) {
+    SymbolContext sc;
+    bool new_type = false;
+    auto type = ast_parser.ParseTypeFromDWARF(sc, die, &new_type);
+    llvm::StringRef die_name = llvm::StringRef(die.GetName());
+    if (die_name.starts_with("_Optional_payload")) {
+      specializations.push_back(std::move(type));
+    }
+  }
+
+  ASSERT_EQ(specializations.size(), 2U);
+  ASSERT_NE(specializations[0], nullptr);
+  ASSERT_EQ(specializations[1], nullptr);
+}
+
 TEST_F(DWARFASTParserClangTests, TestUniqueDWARFASTTypeMap_CppInsertMapFind) {
   // This tests the behaviour of UniqueDWARFASTTypeMap under
   // following scenario: