diff --git a/libcxx/include/__config b/libcxx/include/__config
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -667,10 +667,45 @@
 // Just so we can migrate to the new macros gradually.
 #  define _LIBCPP_INLINE_VISIBILITY _LIBCPP_HIDE_FROM_ABI
 
+#  ifdef _LIBCPP_COMPILER_CLANG_BASED
+#    define _LIBCPP_DIAGNOSTIC_PUSH _Pragma("clang diagnostic push")
+#    define _LIBCPP_DIAGNOSTIC_POP _Pragma("clang diagnostic pop")
+#    define _LIBCPP_CLANG_DIAGNOSTIC_IGNORED(str) _Pragma(_LIBCPP_TOSTRING(clang diagnostic ignored str))
+#    define _LIBCPP_GCC_DIAGNOSTIC_IGNORED(str)
+#  elif defined(_LIBCPP_COMPILER_GCC)
+#    define _LIBCPP_DIAGNOSTIC_PUSH _Pragma("GCC diagnostic push")
+#    define _LIBCPP_DIAGNOSTIC_POP _Pragma("GCC diagnostic pop")
+#    define _LIBCPP_CLANG_DIAGNOSTIC_IGNORED(str)
+#    define _LIBCPP_GCC_DIAGNOSTIC_IGNORED(str) _Pragma(_LIBCPP_TOSTRING(GCC diagnostic ignored str))
+#  else
+#    define _LIBCPP_DIAGNOSTIC_PUSH
+#    define _LIBCPP_DIAGNOSTIC_POP
+#    define _LIBCPP_CLANG_DIAGNOSTIC_IGNORED(str)
+#    define _LIBCPP_GCC_DIAGNOSTIC_IGNORED(str)
+#  endif
+
+#  if defined(_AIX) && !defined(_LIBCPP_COMPILER_GCC)
+#    define _LIBCPP_PACKED_BYTE_FOR_AIX _Pragma("pack(1)")
+#    define _LIBCPP_PACKED_BYTE_FOR_AIX_END _Pragma("pack(pop)")
+#  else
+#    define _LIBCPP_PACKED_BYTE_FOR_AIX     /* empty */
+#    define _LIBCPP_PACKED_BYTE_FOR_AIX_END /* empty */
+#  endif
+
 // Inline namespaces are available in Clang/GCC/MSVC regardless of C++ dialect.
 // clang-format off
-#  define _LIBCPP_BEGIN_NAMESPACE_STD namespace std { inline namespace _LIBCPP_ABI_NAMESPACE {
-#  define _LIBCPP_END_NAMESPACE_STD }}
+#  define _LIBCPP_BEGIN_NAMESPACE_STD _LIBCPP_DIAGNOSTIC_PUSH                                                          \
+                                      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++14-extensions")                           \
+                                      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++17-extensions")                           \
+                                      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++20-extensions")                           \
+                                      _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wc++2b-extensions")                           \
+                                      _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++14-extensions")                             \
+                                      _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++17-extensions")                             \
+                                      _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++20-extensions")                             \
+                                      _LIBCPP_GCC_DIAGNOSTIC_IGNORED("-Wc++2b-extensions")                             \
+                                      namespace std { inline namespace _LIBCPP_ABI_NAMESPACE {
+
+#  define _LIBCPP_END_NAMESPACE_STD }} _LIBCPP_DIAGNOSTIC_POP
 #  define _VSTD std
 
 _LIBCPP_BEGIN_NAMESPACE_STD _LIBCPP_END_NAMESPACE_STD
@@ -1209,31 +1244,6 @@
 // the ABI inconsistent.
 #  endif
 
-#  ifdef _LIBCPP_COMPILER_CLANG_BASED
-#    define _LIBCPP_DIAGNOSTIC_PUSH _Pragma("clang diagnostic push")
-#    define _LIBCPP_DIAGNOSTIC_POP _Pragma("clang diagnostic pop")
-#    define _LIBCPP_CLANG_DIAGNOSTIC_IGNORED(str) _Pragma(_LIBCPP_TOSTRING(clang diagnostic ignored str))
-#    define _LIBCPP_GCC_DIAGNOSTIC_IGNORED(str)
-#  elif defined(_LIBCPP_COMPILER_GCC)
-#    define _LIBCPP_DIAGNOSTIC_PUSH _Pragma("GCC diagnostic push")
-#    define _LIBCPP_DIAGNOSTIC_POP _Pragma("GCC diagnostic pop")
-#    define _LIBCPP_CLANG_DIAGNOSTIC_IGNORED(str)
-#    define _LIBCPP_GCC_DIAGNOSTIC_IGNORED(str) _Pragma(_LIBCPP_TOSTRING(GCC diagnostic ignored str))
-#  else
-#    define _LIBCPP_DIAGNOSTIC_PUSH
-#    define _LIBCPP_DIAGNOSTIC_POP
-#    define _LIBCPP_CLANG_DIAGNOSTIC_IGNORED(str)
-#    define _LIBCPP_GCC_DIAGNOSTIC_IGNORED(str)
-#  endif
-
-#  if defined(_AIX) && !defined(_LIBCPP_COMPILER_GCC)
-#    define _LIBCPP_PACKED_BYTE_FOR_AIX _Pragma("pack(1)")
-#    define _LIBCPP_PACKED_BYTE_FOR_AIX_END _Pragma("pack(pop)")
-#  else
-#    define _LIBCPP_PACKED_BYTE_FOR_AIX     /* empty */
-#    define _LIBCPP_PACKED_BYTE_FOR_AIX_END /* empty */
-#  endif
-
 #  if __has_attribute(__packed__)
 #    define _LIBCPP_PACKED __attribute__((__packed__))
 #  else