diff --git a/libcxx/docs/Contributing.rst b/libcxx/docs/Contributing.rst
--- a/libcxx/docs/Contributing.rst
+++ b/libcxx/docs/Contributing.rst
@@ -49,7 +49,7 @@
 
   - Did you add it to ``include/module.modulemap.in``?
   - Did you add it to ``include/CMakeLists.txt``?
-  - If it's a public header, did you update ``utils/libcxx/test/header_information.py``?
+  - If it's a public header, did you update ``utils/libcxx/header_information.py``?
 
 - Did you add the relevant feature test macro(s) for your feature? Did you update the ``generate_feature_test_macro_components.py`` script with it?
 - Did you run the ``libcxx-generate-files`` target and verify its output?
diff --git a/libcxx/include/__std_clang_module b/libcxx/include/__std_clang_module
--- a/libcxx/include/__std_clang_module
+++ b/libcxx/include/__std_clang_module
@@ -7,6 +7,10 @@
 //
 //===----------------------------------------------------------------------===//
 
+// WARNING, this entire header is generated by
+// utils/generate_std_clang_module_header.py
+// DO NOT MODIFY!
+
 // This header should not be directly included, it's exclusively to import all
 // of the libc++ public clang modules for the `std` clang module to export. In
 // other words, it's to facilitate `@import std;` in Objective-C++ and `import std`
@@ -17,7 +21,6 @@
 #  error "Do not include this header directly, include individual headers instead"
 #endif
 
-#include <__availability>
 #include <__config>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -27,52 +30,187 @@
 #include <algorithm>
 #include <any>
 #include <array>
-#include <atomic>
+#if !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
+#  include <atomic>
+#endif
+#if !defined(_LIBCPP_HAS_NO_THREADS)
+#  include <barrier>
+#endif
 #include <bit>
 #include <bitset>
+#include <cassert>
+#include <ccomplex>
+#include <cctype>
+#include <cerrno>
+#include <cfenv>
+#include <cfloat>
 #include <charconv>
 #include <chrono>
+#include <cinttypes>
+#include <ciso646>
+#include <climits>
+#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+#  include <clocale>
+#endif
+#include <cmath>
+#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+#  include <codecvt>
+#endif
 #include <compare>
+#include <complex.h>
 #include <complex>
 #include <concepts>
 #include <condition_variable>
+#include <coroutine>
+#include <csetjmp>
+#include <csignal>
+#include <cstdarg>
+#include <cstdbool>
+#include <cstddef>
+#include <cstdint>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <ctgmath>
+#include <ctime>
+#include <ctype.h>
+#include <cuchar>
+#if !defined(_LIBCPP_HAS_NO_WIDE_CHARACTERS)
+#  include <cwchar>
+#endif
+#if !defined(_LIBCPP_HAS_NO_WIDE_CHARACTERS)
+#  include <cwctype>
+#endif
 #include <deque>
+#include <errno.h>
 #include <exception>
 #include <execution>
 #include <expected>
+#include <experimental/deque>
+#include <experimental/forward_list>
+#include <experimental/iterator>
+#include <experimental/list>
+#include <experimental/map>
+#include <experimental/memory_resource>
+#include <experimental/propagate_const>
+#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+#  include <experimental/regex>
+#endif
+#include <experimental/set>
+#include <experimental/simd>
+#include <experimental/string>
+#include <experimental/type_traits>
+#include <experimental/unordered_map>
+#include <experimental/unordered_set>
+#include <experimental/utility>
+#include <experimental/vector>
+#include <fenv.h>
+#include <filesystem>
+#include <float.h>
 #include <format>
 #include <forward_list>
+#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+#  include <fstream>
+#endif
 #include <functional>
+#if !defined(_LIBCPP_HAS_NO_THREADS)
+#  include <future>
+#endif
 #include <initializer_list>
+#include <inttypes.h>
+#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+#  include <iomanip>
+#endif
+#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+#  include <ios>
+#endif
 #include <iosfwd>
+#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+#  include <iostream>
+#endif
+#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+#  include <istream>
+#endif
 #include <iterator>
+#if !defined(_LIBCPP_HAS_NO_THREADS)
+#  include <latch>
+#endif
+#include <limits.h>
 #include <limits>
 #include <list>
+#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+#  include <locale.h>
+#endif
+#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+#  include <locale>
+#endif
 #include <map>
+#include <math.h>
 #include <mdspan>
 #include <memory>
 #include <memory_resource>
+#include <mutex>
 #include <new>
 #include <numbers>
 #include <numeric>
 #include <optional>
+#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+#  include <ostream>
+#endif
+#include <print>
 #include <queue>
 #include <random>
 #include <ranges>
 #include <ratio>
+#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+#  include <regex>
+#endif
 #include <scoped_allocator>
+#if !defined(_LIBCPP_HAS_NO_THREADS)
+#  include <semaphore>
+#endif
 #include <set>
+#include <setjmp.h>
+#if !defined(_LIBCPP_HAS_NO_THREADS)
+#  include <shared_mutex>
+#endif
 #include <source_location>
 #include <span>
+#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+#  include <sstream>
+#endif
 #include <stack>
+#if !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
+#  include <stdatomic.h>
+#endif
+#include <stdbool.h>
+#include <stddef.h>
 #include <stdexcept>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#if !defined(_LIBCPP_HAS_NO_THREADS)
+#  include <stop_token>
+#endif
+#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+#  include <streambuf>
+#endif
+#include <string.h>
 #include <string>
 #include <string_view>
+#if !defined(_LIBCPP_HAS_NO_LOCALIZATION)
+#  include <strstream>
+#endif
 #include <system_error>
+#include <tgmath.h>
+#if !defined(_LIBCPP_HAS_NO_THREADS)
+#  include <thread>
+#endif
 #include <tuple>
 #include <type_traits>
 #include <typeindex>
 #include <typeinfo>
+#include <uchar.h>
 #include <unordered_map>
 #include <unordered_set>
 #include <utility>
@@ -80,133 +218,9 @@
 #include <variant>
 #include <vector>
 #include <version>
-
-#include <cassert>
-#include <ccomplex>
-#include <cctype>
-#include <cerrno>
-#include <cfenv>
-#include <cfloat>
-#include <cinttypes>
-#include <ciso646>
-#include <climits>
-#include <cmath>
-#include <csetjmp>
-#include <csignal>
-#include <cstdarg>
-#include <cstdbool>
-#include <cstddef>
-#include <cstdint>
-#include <cstdio>
-#include <cstdlib>
-#include <cstring>
-#include <ctgmath>
-#include <ctime>
-#include <cuchar>
-
-#include <complex.h>
-#include <ctype.h>
-#include <errno.h>
-#include <fenv.h>
-#include <float.h>
-#include <inttypes.h>
-#include <limits.h>
-#include <math.h>
-#include <setjmp.h>
-#include <stdbool.h>
-#include <stddef.h>
-#include <stdint.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <tgmath.h>
-#include <uchar.h>
-
-#ifndef _LIBCPP_HAS_NO_LOCALIZATION
-#  include <codecvt>
-#  ifndef _LIBCPP_HAS_NO_FILESYSTEM
-#    include <fstream>
-#  endif
-#  include <iomanip>
-#  include <ios>
-#  include <iostream>
-#  include <istream>
-#  include <locale>
-#  include <ostream>
-#  include <regex>
-#  include <sstream>
-#  include <streambuf>
-#  include <strstream>
-
-#  include <clocale>
-
-#  include <locale.h>
-#endif
-
-#ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
-#  include <cwchar>
-#  include <cwctype>
-
+#if !defined(_LIBCPP_HAS_NO_WIDE_CHARACTERS)
 #  include <wchar.h>
-#  include <wctype.h>
-#endif
-
-#ifdef _LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT
-#  include <print>
-#endif
-
-#ifndef _LIBCPP_CXX03_LANG
-#  ifndef _LIBCPP_HAS_NO_THREADS
-#    include <future>
-#    include <mutex>
-#    include <thread>
-#  endif
-
-#  include <experimental/deque>
-#  include <experimental/forward_list>
-#  include <experimental/iterator>
-#  include <experimental/list>
-#  include <experimental/map>
-#  include <experimental/memory_resource>
-#  include <experimental/propagate_const>
-#  ifndef _LIBCPP_HAS_NO_LOCALIZATION
-#    include <experimental/regex>
-#  endif
-#  include <experimental/set>
-#  include <experimental/simd>
-#  include <experimental/string>
-#  include <experimental/type_traits>
-#  include <experimental/unordered_map>
-#  include <experimental/unordered_set>
-#  include <experimental/utility>
-#  include <experimental/vector>
 #endif
-
-#if _LIBCPP_STD_VER >= 14
-#  ifndef _LIBCPP_HAS_NO_THREADS
-#    include <shared_mutex>
-#  endif
-#endif
-
-#if _LIBCPP_STD_VER >= 17
-#  ifndef _LIBCPP_HAS_NO_FILESYSTEM
-#    include <filesystem>
-#  endif
-#endif
-
-#if _LIBCPP_STD_VER >= 20
-#  include <coroutine>
-
-#  ifndef _LIBCPP_HAS_NO_THREADS
-#    include <barrier>
-#    include <latch>
-#    include <semaphore>
-#    include <stop_token>
-#  endif
-#endif
-
-#if _LIBCPP_STD_VER >= 23
-#  ifndef _LIBCPP_HAS_NO_THREADS
-#    include <stdatomic.h>
-#  endif
+#if !defined(_LIBCPP_HAS_NO_WIDE_CHARACTERS)
+#  include <wctype.h>
 #endif
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -16,7 +16,6 @@
   export *
 }
 module std_barrier [system] {
-  @requires_LIBCXX_ENABLE_THREADS@
   header "barrier"
   export *
 }
@@ -37,7 +36,6 @@
   export *
 }
 module std_codecvt [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "codecvt"
   export *
 }
@@ -78,7 +76,6 @@
   export *
 }
 module std_filesystem [system] {
-  @requires_LIBCXX_ENABLE_FILESYSTEM@
   header "filesystem"
   export *
 }
@@ -91,8 +88,6 @@
   export *
 }
 module std_fstream [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
-  @requires_LIBCXX_ENABLE_FILESYSTEM@
   header "fstream"
   export *
 }
@@ -101,7 +96,6 @@
   export *
 }
 module std_future [system] {
-  @requires_LIBCXX_ENABLE_THREADS@
   header "future"
   export *
 }
@@ -110,12 +104,10 @@
   export *
 }
 module std_iomanip [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "iomanip"
   export *
 }
 module std_ios [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "ios"
   export *
 }
@@ -124,12 +116,10 @@
   export *
 }
 module std_iostream [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "iostream"
   export *
 }
 module std_istream [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "istream"
   export *
 }
@@ -138,7 +128,6 @@
   export *
 }
 module std_latch [system] {
-  @requires_LIBCXX_ENABLE_THREADS@
   header "latch"
   export *
 }
@@ -151,7 +140,6 @@
   export *
 }
 module std_locale [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "locale"
   export *
 }
@@ -192,7 +180,6 @@
   export *
 }
 module std_ostream [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "ostream"
   export *
 }
@@ -217,7 +204,6 @@
   export *
 }
 module std_regex [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "regex"
   export *
 }
@@ -226,7 +212,6 @@
   export *
 }
 module std_semaphore [system] {
-  @requires_LIBCXX_ENABLE_THREADS@
   header "semaphore"
   export *
 }
@@ -235,7 +220,6 @@
   export *
 }
 module std_shared_mutex [system] {
-  @requires_LIBCXX_ENABLE_THREADS@
   header "shared_mutex"
   export std_version
 }
@@ -250,7 +234,6 @@
   export std_private_span_span_fwd
 }
 module std_sstream [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "sstream"
   export *
 }
@@ -263,12 +246,10 @@
   export *
 }
 module std_stop_token {
-  @requires_LIBCXX_ENABLE_THREADS@
   header "stop_token"
   export *
 }
 module std_streambuf [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "streambuf"
   export *
 }
@@ -281,7 +262,6 @@
   export *
 }
 module std_strstream [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "strstream"
   export *
 }
@@ -290,7 +270,6 @@
   export *
 }
 module std_thread [system] {
-  @requires_LIBCXX_ENABLE_THREADS@
   header "thread"
   export *
 }
@@ -377,7 +356,6 @@
   export *
 }
 module std_clocale [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "clocale"
   export *
 }
@@ -435,12 +413,10 @@
   export *
 }
 module std_cwchar [system] {
-  @requires_LIBCXX_ENABLE_WIDE_CHARACTERS@
   header "cwchar"
   export *
 }
 module std_cwctype [system] {
-  @requires_LIBCXX_ENABLE_WIDE_CHARACTERS@
   header "cwctype"
   export *
 }
@@ -477,7 +453,6 @@
   export *
 }
 module std_locale_h [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "locale.h"
   export *
 }
@@ -493,8 +468,6 @@
 // FIXME: <stdalign.h> is missing.
 // <stdarg.h> provided by compiler.
 module std_stdatomic_h [system] {
-  @requires_LIBCXX_ENABLE_THREADS@
-  requires cplusplus23
   header "stdatomic.h"
   export *
 }
@@ -536,21 +509,17 @@
 }
 // <time.h> provided by C library.
 module std_wchar_h [system] {
-  @requires_LIBCXX_ENABLE_WIDE_CHARACTERS@
   // <wchar.h>'s __need_* macros require textual inclusion.
   textual header "wchar.h"
   export *
 }
 module std_wctype_h [system] {
-  @requires_LIBCXX_ENABLE_WIDE_CHARACTERS@
   header "wctype.h"
   export *
 }
 
 // Experimental C++ standard library interfaces
 module std_experimental [system] {
-  requires cplusplus11
-
   module deque {
     header "experimental/deque"
     export *
@@ -657,7 +626,6 @@
   export *
 }
 module std_private_locale            [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "__locale"
   export *
 }
@@ -1196,7 +1164,6 @@
 }
 module std_private_chrono_file_clock             [system] { header "__chrono/file_clock.h" }
 module std_private_chrono_formatter              [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "__chrono/formatter.h"
 }
 module std_private_chrono_hh_mm_ss               [system] { header "__chrono/hh_mm_ss.h" }
@@ -1210,11 +1177,9 @@
 module std_private_chrono_month_weekday          [system] { header "__chrono/month_weekday.h" }
 module std_private_chrono_monthday               [system] { header "__chrono/monthday.h" }
 module std_private_chrono_ostream                [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "__chrono/ostream.h"
 }
 module std_private_chrono_parser_std_format_spec [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "__chrono/parser_std_format_spec.h"
 }
 module std_private_chrono_statically_widen       [system] { header "__chrono/statically_widen.h" }
@@ -1699,7 +1664,6 @@
 module std_private_ranges_from_range                 [system] { header "__ranges/from_range.h" }
 module std_private_ranges_iota_view                  [system] { header "__ranges/iota_view.h" }
 module std_private_ranges_istream_view               [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "__ranges/istream_view.h"
 }
 module std_private_ranges_join_view                  [system] {
diff --git a/libcxx/test/libcxx/assertions/headers_declare_verbose_abort.gen.py b/libcxx/test/libcxx/assertions/headers_declare_verbose_abort.gen.py
--- a/libcxx/test/libcxx/assertions/headers_declare_verbose_abort.gen.py
+++ b/libcxx/test/libcxx/assertions/headers_declare_verbose_abort.gen.py
@@ -14,7 +14,7 @@
 
 import sys
 sys.path.append(sys.argv[1])
-from libcxx.test.header_information import lit_header_restrictions, public_headers
+from libcxx.header_information import lit_header_restrictions, public_headers
 
 for header in public_headers:
     # Skip C compatibility headers.
diff --git a/libcxx/test/libcxx/clang_tidy.gen.py b/libcxx/test/libcxx/clang_tidy.gen.py
--- a/libcxx/test/libcxx/clang_tidy.gen.py
+++ b/libcxx/test/libcxx/clang_tidy.gen.py
@@ -12,7 +12,7 @@
 
 import sys
 sys.path.append(sys.argv[1])
-from libcxx.test.header_information import lit_header_restrictions, public_headers
+from libcxx.header_information import lit_header_restrictions, public_headers
 
 for header in public_headers:
   BLOCKLIT = '' # block Lit from interpreting a RUN/XFAIL/etc inside the generation script
diff --git a/libcxx/test/libcxx/double_include.gen.py b/libcxx/test/libcxx/double_include.gen.py
--- a/libcxx/test/libcxx/double_include.gen.py
+++ b/libcxx/test/libcxx/double_include.gen.py
@@ -12,7 +12,7 @@
 
 import sys
 sys.path.append(sys.argv[1])
-from libcxx.test.header_information import lit_header_restrictions, public_headers
+from libcxx.header_information import lit_header_restrictions, public_headers
 
 for header in public_headers:
   BLOCKLIT = '' # block Lit from interpreting a RUN/XFAIL/etc inside the generation script
diff --git a/libcxx/test/libcxx/header_inclusions.gen.py b/libcxx/test/libcxx/header_inclusions.gen.py
--- a/libcxx/test/libcxx/header_inclusions.gen.py
+++ b/libcxx/test/libcxx/header_inclusions.gen.py
@@ -13,7 +13,7 @@
 
 import sys
 sys.path.append(sys.argv[1])
-from libcxx.test.header_information import lit_header_restrictions, public_headers, mandatory_inclusions
+from libcxx.header_information import lit_header_restrictions, public_headers, mandatory_inclusions
 
 for header in public_headers:
   header_guard = lambda h: f"_LIBCPP_{h.upper().replace('.', '_').replace('/', '_')}"
diff --git a/libcxx/test/libcxx/libcpp_version.gen.py b/libcxx/test/libcxx/libcpp_version.gen.py
--- a/libcxx/test/libcxx/libcpp_version.gen.py
+++ b/libcxx/test/libcxx/libcpp_version.gen.py
@@ -12,7 +12,7 @@
 
 import sys
 sys.path.append(sys.argv[1])
-from libcxx.test.header_information import lit_header_restrictions, public_headers
+from libcxx.header_information import lit_header_restrictions, public_headers
 
 for header in public_headers:
   print(f"""\
diff --git a/libcxx/test/libcxx/module_std.gen.py b/libcxx/test/libcxx/module_std.gen.py
--- a/libcxx/test/libcxx/module_std.gen.py
+++ b/libcxx/test/libcxx/module_std.gen.py
@@ -21,7 +21,7 @@
 import sys
 
 sys.path.append(sys.argv[1])
-from libcxx.test.header_information import toplevel_headers
+from libcxx.header_information import toplevel_headers
 
 BLOCKLIT = (
     ""  # block Lit from interpreting a RUN/XFAIL/etc inside the generation script
diff --git a/libcxx/test/libcxx/modules_include.gen.py b/libcxx/test/libcxx/modules_include.gen.py
--- a/libcxx/test/libcxx/modules_include.gen.py
+++ b/libcxx/test/libcxx/modules_include.gen.py
@@ -14,10 +14,11 @@
 
 import sys
 sys.path.append(sys.argv[1])
-from libcxx.test.header_information import lit_header_restrictions, public_headers
+from libcxx.header_information import lit_header_restrictions, public_headers
+
+BLOCKLIT = '' # block Lit from interpreting a RUN/XFAIL/etc inside the generation script
 
 for header in public_headers:
-  BLOCKLIT = '' # block Lit from interpreting a RUN/XFAIL/etc inside the generation script
   print(f"""\
 //--- {header}.compile.pass.cpp
 // RUN{BLOCKLIT}: %{{cxx}} %s %{{flags}} %{{compile_flags}} -fmodules -fcxx-modules -fmodules-cache-path=%t -fsyntax-only
@@ -45,7 +46,7 @@
 #include <{header}>
 """)
 
-print(f"""
+print(f"""\
 //--- __std_clang_module.compile.pass.mm
 // RUN{BLOCKLIT}: %{{cxx}} %s %{{flags}} %{{compile_flags}} -fmodules -fcxx-modules -fmodules-cache-path=%t -fsyntax-only
 
@@ -68,10 +69,6 @@
 // TODO: Investigate this failure
 // UNSUPPORTED{BLOCKLIT}: LIBCXX-FREEBSD-FIXME
 
-// Lit seems to compile this twice: once with the default flags and once with with
-// the flags specified in the RUN directive. Guard the first compile from failing.
-#if __has_feature(modules)
 @import std;
-#endif
 
 """)
diff --git a/libcxx/test/libcxx/nasty_macros.gen.py b/libcxx/test/libcxx/nasty_macros.gen.py
--- a/libcxx/test/libcxx/nasty_macros.gen.py
+++ b/libcxx/test/libcxx/nasty_macros.gen.py
@@ -13,7 +13,7 @@
 
 import sys
 sys.path.append(sys.argv[1])
-from libcxx.test.header_information import lit_header_restrictions, public_headers
+from libcxx.header_information import lit_header_restrictions, public_headers
 
 for header in public_headers:
   print(f"""\
diff --git a/libcxx/test/libcxx/no_assert_include.gen.py b/libcxx/test/libcxx/no_assert_include.gen.py
--- a/libcxx/test/libcxx/no_assert_include.gen.py
+++ b/libcxx/test/libcxx/no_assert_include.gen.py
@@ -13,7 +13,7 @@
 
 import sys
 sys.path.append(sys.argv[1])
-from libcxx.test.header_information import lit_header_restrictions, public_headers
+from libcxx.header_information import lit_header_restrictions, public_headers
 
 for header in public_headers:
   if header == 'cassert':
diff --git a/libcxx/test/libcxx/transitive_includes.gen.py b/libcxx/test/libcxx/transitive_includes.gen.py
--- a/libcxx/test/libcxx/transitive_includes.gen.py
+++ b/libcxx/test/libcxx/transitive_includes.gen.py
@@ -20,7 +20,7 @@
 
 import sys
 sys.path.append(sys.argv[1])
-from libcxx.test.header_information import lit_header_restrictions, public_headers
+from libcxx.header_information import lit_header_restrictions, public_headers
 
 import re
 
diff --git a/libcxx/utils/CMakeLists.txt b/libcxx/utils/CMakeLists.txt
--- a/libcxx/utils/CMakeLists.txt
+++ b/libcxx/utils/CMakeLists.txt
@@ -2,6 +2,10 @@
     COMMAND "${Python3_EXECUTABLE}" "${LIBCXX_SOURCE_DIR}/utils/generate_feature_test_macro_components.py"
     COMMENT "Generate the <version> header and tests for feature test macros.")
 
+add_custom_target(libcxx-generate-std-clang-module-header
+  COMMAND "${Python3_EXECUTABLE}" "${CMAKE_CURRENT_SOURCE_DIR}/generate_std_clang_module_header.py"
+  COMMENT "Generate the <__std_clang_module> header")
+
 add_custom_target(libcxx-generate-extended-grapheme-cluster-tables
     COMMAND
         "${Python3_EXECUTABLE}"
@@ -38,6 +42,7 @@
 
 add_custom_target(libcxx-generate-files
     DEPENDS libcxx-generate-feature-test-macros
+            libcxx-generate-std-clang-module-header
             libcxx-generate-extended-grapheme-cluster-tables
             libcxx-generate-extended-grapheme-cluster-tests
             libcxx-generate-escaped-output-table
diff --git a/libcxx/utils/generate_std_clang_module_header.py b/libcxx/utils/generate_std_clang_module_header.py
new file mode 100644
--- /dev/null
+++ b/libcxx/utils/generate_std_clang_module_header.py
@@ -0,0 +1,64 @@
+# ===----------------------------------------------------------------------===##
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+# ===----------------------------------------------------------------------===##
+
+import operator
+import os.path
+
+import libcxx.header_information
+
+header_restrictions = libcxx.header_information.header_restrictions
+
+libcxx_include_directory = os.path.join(
+    os.path.dirname(os.path.dirname(os.path.realpath(__file__))), "include"
+)
+with open(
+    os.path.join(libcxx_include_directory, "__std_clang_module"), "w"
+) as std_clang_module_header:
+    std_clang_module_header.write(
+        """\
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// WARNING, this entire header is generated by
+// utils/generate_std_clang_module_header.py
+// DO NOT MODIFY!
+
+// This header should not be directly included, it's exclusively to import all
+// of the libc++ public clang modules for the `std` clang module to export. In
+// other words, it's to facilitate `@import std;` in Objective-C++ and `import std`
+// in Swift to expose all of the libc++ interfaces. This is generally not
+// recommended, however there are some clients that need to import all of libc++
+// without knowing what "all" is.
+#if !__building_module(std)
+#  error "Do not include this header directly, include individual headers instead"
+#endif
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+"""
+    )
+    # Include the angle brackets in sorting so that <a.h> sorts before <a>
+    # like check-format wants.
+    for include, header in sorted([(f"<{header}>", header) for header in libcxx.header_information.public_headers]):
+        header_restriction = header_restrictions.get(header)
+        if header_restriction:
+            std_clang_module_header.write(f"#if {header_restriction}\n")
+            std_clang_module_header.write(f"#  include {include}\n")
+            std_clang_module_header.write(f"#endif\n")
+        else:
+            std_clang_module_header.write(f"#include {include}\n")
diff --git a/libcxx/utils/libcxx/test/header_information.py b/libcxx/utils/libcxx/header_information.py
rename from libcxx/utils/libcxx/test/header_information.py
rename to libcxx/utils/libcxx/header_information.py
--- a/libcxx/utils/libcxx/test/header_information.py
+++ b/libcxx/utils/libcxx/header_information.py
@@ -8,6 +8,46 @@
 
 import os, pathlib
 
+header_restrictions = {
+    # headers with #error directives
+    "atomic": "!defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)",
+    "stdatomic.h": "!defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)",
+
+    # headers with #error directives
+    "ios": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
+    "locale.h": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
+    # transitive includers of the above headers
+    "clocale": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
+    "codecvt": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
+    "experimental/regex": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
+    "fstream": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
+    "iomanip": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
+    "iostream": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
+    "istream": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
+    "locale": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
+    "ostream": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
+    "regex": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
+    "sstream": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
+    "streambuf": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
+    "strstream": "!defined(_LIBCPP_HAS_NO_LOCALIZATION)",
+
+    # headers with #error directives
+    "barrier": "!defined(_LIBCPP_HAS_NO_THREADS)",
+    "future": "!defined(_LIBCPP_HAS_NO_THREADS)",
+    "latch": "!defined(_LIBCPP_HAS_NO_THREADS)",
+    "semaphore": "!defined(_LIBCPP_HAS_NO_THREADS)",
+    "shared_mutex": "!defined(_LIBCPP_HAS_NO_THREADS)",
+    "stop_token": "!defined(_LIBCPP_HAS_NO_THREADS)",
+    "thread": "!defined(_LIBCPP_HAS_NO_THREADS)",
+
+    # headers with #error directives
+    "wchar.h": "!defined(_LIBCPP_HAS_NO_WIDE_CHARACTERS)",
+    "wctype.h": "!defined(_LIBCPP_HAS_NO_WIDE_CHARACTERS)",
+    # transitive includers of the above headers
+    "cwchar": "!defined(_LIBCPP_HAS_NO_WIDE_CHARACTERS)",
+    "cwctype": "!defined(_LIBCPP_HAS_NO_WIDE_CHARACTERS)",
+}
+
 lit_header_restrictions = {
     "barrier": "// UNSUPPORTED: no-threads, c++03, c++11, c++14, c++17",
     "clocale": "// UNSUPPORTED: no-localization",
@@ -136,7 +176,7 @@
         and file.name != "libcxx.imp"
     )
 
-libcxx_root = pathlib.Path(os.path.dirname(os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))))
+libcxx_root = pathlib.Path(os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__)))))
 include = pathlib.Path(os.path.join(libcxx_root, "include"))
 test = pathlib.Path(os.path.join(libcxx_root, "test"))
 assert libcxx_root.exists()