diff --git a/libcxx/docs/Contributing.rst b/libcxx/docs/Contributing.rst
--- a/libcxx/docs/Contributing.rst
+++ b/libcxx/docs/Contributing.rst
@@ -23,18 +23,19 @@
 2. Update the ``include/__libcpp_version`` file
 3. Update the version number in ``docs/conf.py``
 
+Modifying feature test macros
+=============================
+
+When adding or updating feature test macros, you should update the corresponding tests.
+To do that, modify ``feature_test_macros`` table in the script ``utils/generate_feature_test_macro_components.py``, run it, and commit updated files.
+
 Adding a new header TODO
 ========================
 
 When adding a new header to libc++:
 
 1. Add a test under ``test/libcxx`` that the new header defines ``_LIBCPP_VERSION``. See ``test/libcxx/algorithms/version.pass.cpp`` for an example.
-2. Update the following test files to include the new header:
-
-  * ``test/libcxx/double_include.sh.cpp``
-  * ``test/libcxx/min_max_macros.compile.pass.cpp``
-  * ``test/libcxx/no_assert_include.compile.pass.cpp``
-
+2. Run ``python utils/generate_header_tests.py``, verify and commit the modifications.
 3. Create a submodule in ``include/module.modulemap`` for the new header.
 4. Update the ``include/CMakeLists.txt`` file to include the new header.
 
diff --git a/libcxx/test/libcxx/double_include.sh.cpp b/libcxx/test/libcxx/double_include.sh.cpp
--- a/libcxx/test/libcxx/double_include.sh.cpp
+++ b/libcxx/test/libcxx/double_include.sh.cpp
@@ -19,20 +19,29 @@
 // when included.
 // UNSUPPORTED: gcc-5 && c++17
 
+// clang-format off
+
 // Prevent <ext/hash_map> from generating deprecated warnings for this test.
 #if defined(__DEPRECATED)
-#undef __DEPRECATED
+#    undef __DEPRECATED
 #endif
 
+////////////////////////////////////////////////////////////////////////////////
+// BEGIN-GENERATED-HEADERS
+////////////////////////////////////////////////////////////////////////////////
+
+// WARNING: This test was generated by generate_header_tests.py
+// and should not be edited manually.
+
 // Top level headers
 #include <algorithm>
 #include <any>
 #include <array>
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <atomic>
+#    include <atomic>
 #endif
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <barrier>
+#    include <barrier>
 #endif
 #include <bit>
 #include <bitset>
@@ -47,7 +56,13 @@
 #include <cinttypes>
 #include <ciso646>
 #include <climits>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <clocale>
+#endif
 #include <cmath>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <codecvt>
+#endif
 #include <compare>
 #include <complex>
 #include <complex.h>
@@ -75,43 +90,73 @@
 #include <filesystem>
 #include <float.h>
 #include <forward_list>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <fstream>
+#endif
 #include <functional>
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <future>
+#    include <future>
 #endif
 #include <initializer_list>
 #include <inttypes.h>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <iomanip>
+#endif
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <ios>
+#endif
 #include <iosfwd>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <iostream>
+#endif
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <istream>
+#endif
 #include <iterator>
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <latch>
+#    include <latch>
 #endif
 #include <limits>
 #include <limits.h>
 #include <list>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <locale>
+#endif
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <locale.h>
+#endif
 #include <map>
 #include <math.h>
 #include <memory>
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <mutex>
+#    include <mutex>
 #endif
 #include <new>
 #include <numbers>
 #include <numeric>
 #include <optional>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <ostream>
+#endif
 #include <queue>
 #include <random>
 #include <ratio>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <regex>
+#endif
 #include <scoped_allocator>
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <semaphore>
+#    include <semaphore>
 #endif
 #include <set>
 #include <setjmp.h>
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <shared_mutex>
+#    include <shared_mutex>
 #endif
 #include <span>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <sstream>
+#endif
 #include <stack>
 #include <stdbool.h>
 #include <stddef.h>
@@ -119,13 +164,19 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <streambuf>
+#endif
 #include <string>
 #include <string.h>
 #include <string_view>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <strstream>
+#endif
 #include <system_error>
 #include <tgmath.h>
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <thread>
+#    include <thread>
 #endif
 #include <tuple>
 #include <typeindex>
@@ -141,55 +192,42 @@
 #include <wchar.h>
 #include <wctype.h>
 
-#ifndef _LIBCPP_HAS_NO_LOCALIZATION
-#   include <clocale>
-#   include <codecvt>
-#   include <fstream>
-#   include <iomanip>
-#   include <ios>
-#   include <iostream>
-#   include <istream>
-#   include <locale.h>
-#   include <locale>
-#   include <ostream>
-#   include <regex>
-#   include <sstream>
-#   include <streambuf>
-#   include <strstream>
-#   if __cplusplus >= 201103L
-#       include <experimental/regex>
-#   endif
-#endif
-
 // experimental headers
 #if __cplusplus >= 201103L
-#include <experimental/algorithm>
-#if defined(__cpp_coroutines)
-#include <experimental/coroutine>
-#endif
-#include <experimental/deque>
-#include <experimental/filesystem>
-#include <experimental/forward_list>
-#include <experimental/functional>
-#include <experimental/iterator>
-#include <experimental/list>
-#include <experimental/map>
-#include <experimental/memory_resource>
-#include <experimental/propagate_const>
-#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 <experimental/algorithm>
+#    if defined(__cpp_coroutines)
+#        include <experimental/coroutine>
+#    endif
+#    include <experimental/deque>
+#    include <experimental/filesystem>
+#    include <experimental/forward_list>
+#    include <experimental/functional>
+#    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 // __cplusplus >= 201103L
 
 // extended headers
 #include <ext/hash_map>
 #include <ext/hash_set>
 
+////////////////////////////////////////////////////////////////////////////////
+// END-GENERATED-HEADERS
+////////////////////////////////////////////////////////////////////////////////
+
 #if defined(WITH_MAIN)
 int main(int, char**) { return 0; }
 #endif
diff --git a/libcxx/test/libcxx/min_max_macros.compile.pass.cpp b/libcxx/test/libcxx/min_max_macros.compile.pass.cpp
--- a/libcxx/test/libcxx/min_max_macros.compile.pass.cpp
+++ b/libcxx/test/libcxx/min_max_macros.compile.pass.cpp
@@ -13,15 +13,24 @@
 // GCC 5 has incomplete support for C++17, so some headers fail when included.
 // UNSUPPORTED: gcc-5 && c++17
 
+// clang-format off
+
 // Prevent <ext/hash_map> from generating deprecated warnings for this test.
 #if defined(__DEPRECATED)
-#undef __DEPRECATED
+#    undef __DEPRECATED
 #endif
 
 #define TEST_MACROS() static_assert(min() == true && max() == true, "")
 #define min() true
 #define max() true
 
+////////////////////////////////////////////////////////////////////////////////
+// BEGIN-GENERATED-HEADERS
+////////////////////////////////////////////////////////////////////////////////
+
+// WARNING: This test was generated by generate_header_tests.py
+// and should not be edited manually.
+
 // Top level headers
 #include <algorithm>
 TEST_MACROS();
@@ -30,11 +39,11 @@
 #include <array>
 TEST_MACROS();
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <atomic>
+#    include <atomic>
 TEST_MACROS();
 #endif
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <barrier>
+#    include <barrier>
 TEST_MACROS();
 #endif
 #include <bit>
@@ -63,8 +72,16 @@
 TEST_MACROS();
 #include <climits>
 TEST_MACROS();
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <clocale>
+TEST_MACROS();
+#endif
 #include <cmath>
 TEST_MACROS();
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <codecvt>
+TEST_MACROS();
+#endif
 #include <compare>
 TEST_MACROS();
 #include <complex>
@@ -119,22 +136,42 @@
 TEST_MACROS();
 #include <forward_list>
 TEST_MACROS();
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <fstream>
+TEST_MACROS();
+#endif
 #include <functional>
 TEST_MACROS();
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <future>
+#    include <future>
 TEST_MACROS();
 #endif
 #include <initializer_list>
 TEST_MACROS();
 #include <inttypes.h>
 TEST_MACROS();
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <iomanip>
+TEST_MACROS();
+#endif
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <ios>
+TEST_MACROS();
+#endif
 #include <iosfwd>
 TEST_MACROS();
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <iostream>
+TEST_MACROS();
+#endif
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <istream>
+TEST_MACROS();
+#endif
 #include <iterator>
 TEST_MACROS();
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <latch>
+#    include <latch>
 TEST_MACROS();
 #endif
 #include <limits>
@@ -143,6 +180,14 @@
 TEST_MACROS();
 #include <list>
 TEST_MACROS();
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <locale>
+TEST_MACROS();
+#endif
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <locale.h>
+TEST_MACROS();
+#endif
 #include <map>
 TEST_MACROS();
 #include <math.h>
@@ -150,7 +195,7 @@
 #include <memory>
 TEST_MACROS();
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <mutex>
+#    include <mutex>
 TEST_MACROS();
 #endif
 #include <new>
@@ -161,16 +206,24 @@
 TEST_MACROS();
 #include <optional>
 TEST_MACROS();
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <ostream>
+TEST_MACROS();
+#endif
 #include <queue>
 TEST_MACROS();
 #include <random>
 TEST_MACROS();
 #include <ratio>
 TEST_MACROS();
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <regex>
+TEST_MACROS();
+#endif
 #include <scoped_allocator>
 TEST_MACROS();
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <semaphore>
+#    include <semaphore>
 TEST_MACROS();
 #endif
 #include <set>
@@ -178,11 +231,15 @@
 #include <setjmp.h>
 TEST_MACROS();
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <shared_mutex>
+#    include <shared_mutex>
 TEST_MACROS();
 #endif
 #include <span>
 TEST_MACROS();
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <sstream>
+TEST_MACROS();
+#endif
 #include <stack>
 TEST_MACROS();
 #include <stdbool.h>
@@ -197,18 +254,26 @@
 TEST_MACROS();
 #include <stdlib.h>
 TEST_MACROS();
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <streambuf>
+TEST_MACROS();
+#endif
 #include <string>
 TEST_MACROS();
 #include <string.h>
 TEST_MACROS();
 #include <string_view>
 TEST_MACROS();
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <strstream>
+TEST_MACROS();
+#endif
 #include <system_error>
 TEST_MACROS();
 #include <tgmath.h>
 TEST_MACROS();
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <thread>
+#    include <thread>
 TEST_MACROS();
 #endif
 #include <tuple>
@@ -238,82 +303,51 @@
 #include <wctype.h>
 TEST_MACROS();
 
-#ifndef _LIBCPP_HAS_NO_LOCALIZATION
-#   include <clocale>
-    TEST_MACROS();
-#   include <codecvt>
-    TEST_MACROS();
-#   include <fstream>
-    TEST_MACROS();
-#   include <iomanip>
-    TEST_MACROS();
-#   include <ios>
-    TEST_MACROS();
-#   include <iostream>
-    TEST_MACROS();
-#   include <istream>
-    TEST_MACROS();
-#   include <locale>
-    TEST_MACROS();
-#   include <locale.h>
-    TEST_MACROS();
-#   include <ostream>
-    TEST_MACROS();
-#   include <regex>
-    TEST_MACROS();
-#   include <sstream>
-    TEST_MACROS();
-#   include <streambuf>
-    TEST_MACROS();
-#   include <strstream>
-    TEST_MACROS();
-#   if __cplusplus >= 201103L
-#       include <experimental/regex>
-        TEST_MACROS();
-#   endif
-#endif
-
 // experimental headers
 #if __cplusplus >= 201103L
-#include <experimental/algorithm>
+#    include <experimental/algorithm>
 TEST_MACROS();
-#if defined(__cpp_coroutines)
-#include <experimental/coroutine>
+#    if defined(__cpp_coroutines)
+#        include <experimental/coroutine>
 TEST_MACROS();
-#endif
-#include <experimental/deque>
+#    endif
+#    include <experimental/deque>
+TEST_MACROS();
+#    include <experimental/filesystem>
 TEST_MACROS();
-#include <experimental/filesystem>
+#    include <experimental/forward_list>
 TEST_MACROS();
-#include <experimental/forward_list>
+#    include <experimental/functional>
 TEST_MACROS();
-#include <experimental/functional>
+#    include <experimental/iterator>
 TEST_MACROS();
-#include <experimental/iterator>
+#    include <experimental/list>
 TEST_MACROS();
-#include <experimental/list>
+#    include <experimental/map>
 TEST_MACROS();
-#include <experimental/map>
+#    include <experimental/memory_resource>
 TEST_MACROS();
-#include <experimental/memory_resource>
+#    include <experimental/propagate_const>
 TEST_MACROS();
-#include <experimental/propagate_const>
+#    ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#        include <experimental/regex>
 TEST_MACROS();
-#include <experimental/set>
+#    endif
+#    include <experimental/set>
 TEST_MACROS();
-#include <experimental/simd>
+#    include <experimental/simd>
 TEST_MACROS();
-#include <experimental/string>
+#    include <experimental/string>
 TEST_MACROS();
-#include <experimental/type_traits>
+#    include <experimental/type_traits>
 TEST_MACROS();
-#include <experimental/unordered_map>
+#    include <experimental/unordered_map>
 TEST_MACROS();
-#include <experimental/unordered_set>
+#    include <experimental/unordered_set>
 TEST_MACROS();
-#include <experimental/utility>
+#    include <experimental/utility>
 TEST_MACROS();
-#include <experimental/vector>
+#    include <experimental/vector>
 TEST_MACROS();
 #endif // __cplusplus >= 201103L
 
@@ -322,3 +356,7 @@
 TEST_MACROS();
 #include <ext/hash_set>
 TEST_MACROS();
+
+////////////////////////////////////////////////////////////////////////////////
+// END-GENERATED-HEADERS
+////////////////////////////////////////////////////////////////////////////////
diff --git a/libcxx/test/libcxx/no_assert_include.compile.pass.cpp b/libcxx/test/libcxx/no_assert_include.compile.pass.cpp
--- a/libcxx/test/libcxx/no_assert_include.compile.pass.cpp
+++ b/libcxx/test/libcxx/no_assert_include.compile.pass.cpp
@@ -13,20 +13,29 @@
 // GCC 5 has incomplete support for C++17, so some headers fail when included.
 // UNSUPPORTED: gcc-5 && c++17
 
+// clang-format off
+
 // Prevent <ext/hash_map> from generating deprecated warnings for this test.
 #if defined(__DEPRECATED)
-#undef __DEPRECATED
+#    undef __DEPRECATED
 #endif
 
+////////////////////////////////////////////////////////////////////////////////
+// BEGIN-GENERATED-HEADERS
+////////////////////////////////////////////////////////////////////////////////
+
+// WARNING: This test was generated by generate_header_tests.py
+// and should not be edited manually.
+
 // Top level headers
 #include <algorithm>
 #include <any>
 #include <array>
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <atomic>
+#    include <atomic>
 #endif
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <barrier>
+#    include <barrier>
 #endif
 #include <bit>
 #include <bitset>
@@ -40,7 +49,13 @@
 #include <cinttypes>
 #include <ciso646>
 #include <climits>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <clocale>
+#endif
 #include <cmath>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <codecvt>
+#endif
 #include <compare>
 #include <complex>
 #include <complex.h>
@@ -68,43 +83,73 @@
 #include <filesystem>
 #include <float.h>
 #include <forward_list>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <fstream>
+#endif
 #include <functional>
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <future>
+#    include <future>
 #endif
 #include <initializer_list>
 #include <inttypes.h>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <iomanip>
+#endif
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <ios>
+#endif
 #include <iosfwd>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <iostream>
+#endif
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <istream>
+#endif
 #include <iterator>
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <latch>
+#    include <latch>
 #endif
 #include <limits>
 #include <limits.h>
 #include <list>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <locale>
+#endif
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <locale.h>
+#endif
 #include <map>
 #include <math.h>
 #include <memory>
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <mutex>
+#    include <mutex>
 #endif
 #include <new>
 #include <numbers>
 #include <numeric>
 #include <optional>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <ostream>
+#endif
 #include <queue>
 #include <random>
 #include <ratio>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <regex>
+#endif
 #include <scoped_allocator>
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <semaphore>
+#    include <semaphore>
 #endif
 #include <set>
 #include <setjmp.h>
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <shared_mutex>
+#    include <shared_mutex>
 #endif
 #include <span>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <sstream>
+#endif
 #include <stack>
 #include <stdbool.h>
 #include <stddef.h>
@@ -112,13 +157,19 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <streambuf>
+#endif
 #include <string>
 #include <string.h>
 #include <string_view>
+#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#    include <strstream>
+#endif
 #include <system_error>
 #include <tgmath.h>
 #ifndef _LIBCPP_HAS_NO_THREADS
-#include <thread>
+#    include <thread>
 #endif
 #include <tuple>
 #include <typeindex>
@@ -134,55 +185,42 @@
 #include <wchar.h>
 #include <wctype.h>
 
-#ifndef _LIBCPP_HAS_NO_LOCALIZATION
-#   include <clocale>
-#   include <codecvt>
-#   include <fstream>
-#   include <iomanip>
-#   include <ios>
-#   include <iostream>
-#   include <istream>
-#   include <locale>
-#   include <locale.h>
-#   include <ostream>
-#   include <regex>
-#   include <sstream>
-#   include <streambuf>
-#   include <strstream>
-#   if __cplusplus >= 201103L
-#       include <experimental/regex>
-#   endif
-#endif
-
 // experimental headers
 #if __cplusplus >= 201103L
-#include <experimental/algorithm>
-#if defined(__cpp_coroutines)
-#include <experimental/coroutine>
-#endif
-#include <experimental/deque>
-#include <experimental/filesystem>
-#include <experimental/forward_list>
-#include <experimental/functional>
-#include <experimental/iterator>
-#include <experimental/list>
-#include <experimental/map>
-#include <experimental/memory_resource>
-#include <experimental/propagate_const>
-#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 <experimental/algorithm>
+#    if defined(__cpp_coroutines)
+#        include <experimental/coroutine>
+#    endif
+#    include <experimental/deque>
+#    include <experimental/filesystem>
+#    include <experimental/forward_list>
+#    include <experimental/functional>
+#    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 // __cplusplus >= 201103L
 
 // extended headers
 #include <ext/hash_map>
 #include <ext/hash_set>
 
+////////////////////////////////////////////////////////////////////////////////
+// END-GENERATED-HEADERS
+////////////////////////////////////////////////////////////////////////////////
+
 #ifdef assert
 #error "Do not include cassert or assert.h in standard header files"
 #endif
diff --git a/libcxx/utils/generate_header_tests.py b/libcxx/utils/generate_header_tests.py
new file mode 100644
--- /dev/null
+++ b/libcxx/utils/generate_header_tests.py
@@ -0,0 +1,201 @@
+#!/usr/bin/env python
+
+import glob
+import os
+import posixpath
+import re
+
+
+def get_libcxx_paths():
+    utils_path = os.path.dirname(os.path.abspath(__file__))
+    script_name = os.path.basename(__file__)
+    assert os.path.exists(utils_path)
+    src_root = os.path.dirname(utils_path)
+    include_path = os.path.join(src_root, 'include')
+    assert os.path.exists(include_path)
+    libcxx_test_path = os.path.join(src_root, 'test', 'libcxx')
+    assert os.path.exists(libcxx_test_path)
+    return script_name, src_root, include_path, libcxx_test_path
+
+
+script_name, source_root, include_path, libcxx_test_path = get_libcxx_paths()
+
+header_markup = {
+    "atomic": ["ifndef _LIBCPP_HAS_NO_THREADS"],
+    "barrier": ["ifndef _LIBCPP_HAS_NO_THREADS"],
+    "future": ["ifndef _LIBCPP_HAS_NO_THREADS"],
+    "latch": ["ifndef _LIBCPP_HAS_NO_THREADS"],
+    "mutex": ["ifndef _LIBCPP_HAS_NO_THREADS"],
+    "shared_mutex": ["ifndef _LIBCPP_HAS_NO_THREADS"],
+    "semaphore": ["ifndef _LIBCPP_HAS_NO_THREADS"],
+    "thread": ["ifndef _LIBCPP_HAS_NO_THREADS"],
+
+    "clocale": ["ifndef _LIBCPP_HAS_NO_LOCALIZATION"],
+    "codecvt": ["ifndef _LIBCPP_HAS_NO_LOCALIZATION"],
+    "fstream": ["ifndef _LIBCPP_HAS_NO_LOCALIZATION"],
+    "iomanip": ["ifndef _LIBCPP_HAS_NO_LOCALIZATION"],
+    "ios": ["ifndef _LIBCPP_HAS_NO_LOCALIZATION"],
+    "iostream": ["ifndef _LIBCPP_HAS_NO_LOCALIZATION"],
+    "istream": ["ifndef _LIBCPP_HAS_NO_LOCALIZATION"],
+    "locale": ["ifndef _LIBCPP_HAS_NO_LOCALIZATION"],
+    "locale.h": ["ifndef _LIBCPP_HAS_NO_LOCALIZATION"],
+    "ostream": ["ifndef _LIBCPP_HAS_NO_LOCALIZATION"],
+    "regex": ["ifndef _LIBCPP_HAS_NO_LOCALIZATION"],
+    "sstream": ["ifndef _LIBCPP_HAS_NO_LOCALIZATION"],
+    "streambuf": ["ifndef _LIBCPP_HAS_NO_LOCALIZATION"],
+    "strstream": ["ifndef _LIBCPP_HAS_NO_LOCALIZATION"],
+
+    "experimental/coroutine": ["if defined(__cpp_coroutines)"],
+    "experimental/regex": ["ifndef _LIBCPP_HAS_NO_LOCALIZATION"],
+}
+
+allowed_extensions = ['', '.h']
+indent_width = 4
+
+
+begin_pattern = """\
+////////////////////////////////////////////////////////////////////////////////
+// BEGIN-GENERATED-HEADERS
+////////////////////////////////////////////////////////////////////////////////
+"""
+
+warning_note = """\
+// WARNING: This test was generated by {script_name}
+// and should not be edited manually.
+
+""".format(script_name=script_name)
+
+end_pattern = """\
+////////////////////////////////////////////////////////////////////////////////
+// END-GENERATED-HEADERS
+////////////////////////////////////////////////////////////////////////////////
+"""
+
+generated_part_pattern = re.compile(re.escape(begin_pattern) + ".*" + re.escape(end_pattern),
+                                    re.MULTILINE | re.DOTALL)
+
+headers_template = """\
+// Top level headers
+{top_level_headers}
+
+// experimental headers
+#if __cplusplus >= 201103L
+{experimental_headers}
+#endif // __cplusplus >= 201103L
+
+// extended headers
+{extended_headers}
+"""
+
+
+def should_keep_header(p, exclusions=None):
+    if os.path.isdir(p):
+        return False
+
+    if exclusions:
+        relpath = os.path.relpath(p, include_path)
+        relpath = posixpath.join(*os.path.split(relpath))
+        if relpath in exclusions:
+            print('Excluded file:', relpath)
+            return False
+
+    return os.path.splitext(p)[1] in allowed_extensions
+
+
+def produce_include(relpath, indent_level, post_include=None):
+    relpath = posixpath.join(*os.path.split(relpath))
+    template = "{preambule}#{indentation}include <{include}>{post_include}{postambule}"
+
+    base_indentation = ' '*(indent_width * indent_level)
+    next_indentation = base_indentation + ' '*(indent_width)
+    post_include = "\n{}".format(post_include) if post_include else ''
+
+    markup = header_markup.get(relpath, None)
+    if markup:
+        preambule = '#{indentation}{directive}\n'.format(
+            directive=markup[0],
+            indentation=base_indentation,
+        )
+        postambule = '\n#{indentation}endif'.format(
+            indentation=base_indentation,
+        )
+        indentation = next_indentation
+    else:
+        preambule = ''
+        postambule = ''
+        indentation = base_indentation
+
+    return template.format(
+        include=relpath,
+        post_include=post_include,
+        preambule=preambule,
+        postambule=postambule,
+        indentation=indentation,
+    )
+
+
+def produce_headers(path_parts, indent_level, post_include=None, exclusions=None):
+    pattern = os.path.join(*path_parts, '[a-z]*')
+
+    include_headers = glob.glob(pattern, recursive=False)
+
+    include_headers = [
+        produce_include(os.path.relpath(p, include_path),
+                        indent_level, post_include=post_include)
+        for p in include_headers
+        if should_keep_header(p, exclusions)]
+
+    return '\n'.join(include_headers)
+
+
+def produce_top_level_headers(post_include=None, exclusions=None):
+    return produce_headers([include_path], 0, post_include=post_include, exclusions=exclusions)
+
+
+def produce_experimental_headers(post_include=None, exclusions=None):
+    return produce_headers([include_path, 'experimental'], 1, post_include=post_include, exclusions=exclusions)
+
+
+def produce_extended_headers(post_include=None, exclusions=None):
+    return produce_headers([include_path, 'ext'], 0, post_include=post_include, exclusions=exclusions)
+
+
+def replace_generated_headers(test_path, test_str):
+    with open(test_path, 'r') as f:
+        content = f.read()
+
+    content = generated_part_pattern.sub(begin_pattern + '\n' + warning_note + test_str +
+                                         '\n' + end_pattern, content)
+
+    with open(test_path, 'w') as f:
+        f.write(content)
+
+
+def produce_test(test_filename, exclusions=None, post_include=None):
+    test_str = headers_template.format(
+        top_level_headers=produce_top_level_headers(
+            post_include=post_include,
+            exclusions=exclusions,
+        ),
+        experimental_headers=produce_experimental_headers(
+            post_include=post_include,
+        ),
+        extended_headers=produce_extended_headers(
+            post_include=post_include,
+        ),
+    )
+
+    replace_generated_headers(os.path.join(
+        libcxx_test_path, test_filename), test_str)
+
+
+def main():
+    produce_test('double_include.sh.cpp')
+    produce_test('min_max_macros.compile.pass.cpp',
+                 post_include='TEST_MACROS();')
+    produce_test('no_assert_include.compile.pass.cpp',
+                 exclusions=['cassert'])
+
+
+if __name__ == '__main__':
+    main()