diff -up v8-6.2.91/build/config/compiler/BUILD.gn.oldclang v8-6.2.91/build/config/compiler/BUILD.gn
--- v8-6.2.91/build/config/compiler/BUILD.gn.oldclang	2017-08-31 21:05:13.342875120 -0400
+++ v8-6.2.91/build/config/compiler/BUILD.gn	2017-08-31 21:05:40.092124090 -0400
@@ -1168,13 +1168,13 @@ config("default_warnings") {
         "-Wno-nonportable-include-path",
 
         # TODO(hans): https://crbug.com/637306
-        "-Wno-address-of-packed-member",
+        # "-Wno-address-of-packed-member",
 
         # TODO(hans): https://crbug.com/681136
         # "-Wno-unused-lambda-capture",
 
         # TODO(thakis ): https://crbug.com/683349
-        "-Wno-user-defined-warnings",
+        # "-Wno-user-defined-warnings",
       ]
     } else if (use_xcode_clang && xcode_version_int >= 830) {
       # This is necessary to allow a progressive transition from using xcode 8.0