[libc++] Make feature-test macros consistent with availability macros

[ldionne]

Summary

Before this patch, feature-test macros didn't take special availability
markup into account, which means that feature-test macros can sometimes
appear to "lie". For example, if you compile in C++20 mode and target
macOS 10.13, the __cpp_lib_filesystem feature-test macro will be provided
even though the <filesystem> declarations are marked as unavailable.
This patch fixes that.

rdar://68142369

(cherry picked from commit 76fc35752d19ac605c1c1fd757af9c7c3bb4a906)

[ldionne]

Associated release blocker bug: http://llvm.org/PR50758

[ldionne]

This has been merged to release/12.x

libcxx/include/__availability

 // program references something that isn't available on the deployment target.
 //
 // This mechanism is general in nature, and any vendor can add their markup to
 // the library (see below). Whenever a new feature is added that requires support
 // in the shared library, a macro should be added below to mark this feature
 // as unavailable. When vendors decide to ship the feature as part of their
 // shared library, they can update the markup appropriately.
 //
+// Furthermore, many features in the standard library have corresponding
+// feature-test macros. When a feature is made unavailable on some deployment
+// target, a macro should be defined to signal that it is unavailable. That
+// macro can then be picked up when feature-test macros are generated (see
+// generate_feature_test_macro_components.py) to make sure that feature-test
+// macros don't announce a feature as being implemented if it has been marked
+// as unavailable.
+//
 // Note that this mechanism is disabled by default in the "upstream" libc++.
 // Availability annotations are only meaningful when shipping libc++ inside
 // a platform (i.e. as a system library), and so vendors that want them should
 // turn those annotations on at CMake configuration time.
 //
 // [1]: https://clang.llvm.org/docs/AttributeReference.html#availability
 
 

 #   endif
 #endif
 
 #if defined(_LIBCPP_HAS_NO_VENDOR_AVAILABILITY_ANNOTATIONS)
 
     // This controls the availability of std::shared_mutex and std::shared_timed_mutex,
     // which were added to the dylib later.
 #   define _LIBCPP_AVAILABILITY_SHARED_MUTEX
+// #   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_mutex
+// #   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex
 
     // These macros control the availability of std::bad_optional_access and
     // other exception types. These were put in the shared library to prevent
     // code bloat from every user program defining the vtable for these exception
     // types.
 #   define _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS
 #   define _LIBCPP_AVAILABILITY_BAD_VARIANT_ACCESS
 #   define _LIBCPP_AVAILABILITY_BAD_ANY_CAST
#   define _LIBCPP_AVAILABILITY_LOCALE_CATEGORY
     // lock table located in the dylib.
 #   define _LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
 
     // These macros control the availability of all parts of <filesystem> that
     // depend on something in the dylib.
 #   define _LIBCPP_AVAILABILITY_FILESYSTEM
 #   define _LIBCPP_AVAILABILITY_FILESYSTEM_PUSH
 #   define _LIBCPP_AVAILABILITY_FILESYSTEM_POP
+// #   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem
 
     // This controls the availability of std::to_chars.
 #   define _LIBCPP_AVAILABILITY_TO_CHARS
 
     // This controls the availability of the C++20 synchronization library,
     // which requires shared library support for various operations
     // (see libcxx/src/atomic.cpp).
 #   define _LIBCPP_AVAILABILITY_SYNC
+// #   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_atomic_wait
+// #   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_barrier
+// #   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_latch
+// #   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_semaphore
 
 #elif defined(__APPLE__)
 
 #   define _LIBCPP_AVAILABILITY_SHARED_MUTEX                                    \
         __attribute__((availability(macosx,strict,introduced=10.12)))           \
         __attribute__((availability(ios,strict,introduced=10.0)))               \
         __attribute__((availability(tvos,strict,introduced=10.0)))              \
         __attribute__((availability(watchos,strict,introduced=3.0)))
+#   if (defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 101200) ||    \
+        (defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ < 100000) || \
+        (defined(__ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__ < 100000) ||         \
+        (defined(__ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__ < 30000)
+#       define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_mutex
+#       define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex
+#   endif
+
 #   define _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS                             \
         __attribute__((availability(macosx,strict,introduced=10.13)))           \
         __attribute__((availability(ios,strict,introduced=11.0)))               \
         __attribute__((availability(tvos,strict,introduced=11.0)))              \
         __attribute__((availability(watchos,strict,introduced=4.0)))
 #   define _LIBCPP_AVAILABILITY_BAD_VARIANT_ACCESS                              \
         _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS
 #   define _LIBCPP_AVAILABILITY_BAD_ANY_CAST                                    \
         _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS
+
 #   define _LIBCPP_AVAILABILITY_UNCAUGHT_EXCEPTIONS                             \
         __attribute__((availability(macosx,strict,introduced=10.12)))           \
         __attribute__((availability(ios,strict,introduced=10.0)))               \
         __attribute__((availability(tvos,strict,introduced=10.0)))              \
         __attribute__((availability(watchos,strict,introduced=3.0)))
+
 #   define _LIBCPP_AVAILABILITY_SIZED_NEW_DELETE                                \
         __attribute__((availability(macosx,strict,introduced=10.12)))           \
         __attribute__((availability(ios,strict,introduced=10.0)))               \
         __attribute__((availability(tvos,strict,introduced=10.0)))              \
         __attribute__((availability(watchos,strict,introduced=3.0)))
+
 #   define _LIBCPP_AVAILABILITY_FUTURE_ERROR                                    \
         __attribute__((availability(ios,strict,introduced=6.0)))
+
 #   define _LIBCPP_AVAILABILITY_TYPEINFO_VTABLE                                 \
         __attribute__((availability(macosx,strict,introduced=10.9)))            \
         __attribute__((availability(ios,strict,introduced=7.0)))
+
 #   define _LIBCPP_AVAILABILITY_LOCALE_CATEGORY                                 \
         __attribute__((availability(macosx,strict,introduced=10.9)))            \
         __attribute__((availability(ios,strict,introduced=7.0)))
+
 #   define _LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR                               \
         __attribute__((availability(macosx,strict,introduced=10.9)))            \
         __attribute__((availability(ios,strict,introduced=7.0)))
+
 #   define _LIBCPP_AVAILABILITY_FILESYSTEM                                      \
         __attribute__((availability(macosx,strict,introduced=10.15)))           \
         __attribute__((availability(ios,strict,introduced=13.0)))               \
         __attribute__((availability(tvos,strict,introduced=13.0)))              \
         __attribute__((availability(watchos,strict,introduced=6.0)))
 #   define _LIBCPP_AVAILABILITY_FILESYSTEM_PUSH                                 \
         _Pragma("clang attribute push(__attribute__((availability(macosx,strict,introduced=10.15))), apply_to=any(function,record))") \
         _Pragma("clang attribute push(__attribute__((availability(ios,strict,introduced=13.0))), apply_to=any(function,record))")     \
         _Pragma("clang attribute push(__attribute__((availability(tvos,strict,introduced=13.0))), apply_to=any(function,record))")    \
         _Pragma("clang attribute push(__attribute__((availability(watchos,strict,introduced=6.0))), apply_to=any(function,record))")
 #   define _LIBCPP_AVAILABILITY_FILESYSTEM_POP                                  \
         _Pragma("clang attribute pop")                                          \
         _Pragma("clang attribute pop")                                          \
         _Pragma("clang attribute pop")                                          \
         _Pragma("clang attribute pop")
+#   if (defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 101500) ||    \
+        (defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ < 130000) || \
+        (defined(__ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__ < 130000) ||         \
+        (defined(__ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__ < 60000)
+#       define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem
+#   endif
+
 #   define _LIBCPP_AVAILABILITY_TO_CHARS                                        \
         _LIBCPP_AVAILABILITY_FILESYSTEM
+
+    // Note: Those are not ABI-stable yet, so we can't ship them.
 #   define _LIBCPP_AVAILABILITY_SYNC                                            \
         __attribute__((unavailable))
+#   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_atomic_wait
+#   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_barrier
+#   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_latch
+#   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_semaphore
 
 #else
 
 // ...New vendors can add availability markup here...
 
 #   error "It looks like you're trying to enable vendor availability markup, but you haven't defined the corresponding macros yet!"
 
 #endif

libcxx/include/version

 # define __cpp_lib_is_final                             201402L
 # define __cpp_lib_is_null_pointer                      201309L
 # define __cpp_lib_make_reverse_iterator                201402L
 # define __cpp_lib_make_unique                          201304L
 # define __cpp_lib_null_iterators                       201304L
 # define __cpp_lib_quoted_string_io                     201304L
 # define __cpp_lib_result_of_sfinae                     201210L
 # define __cpp_lib_robust_nonmodifying_seq_ops          201304L
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex)
 #   define __cpp_lib_shared_timed_mutex                 201402L
 # endif
 # define __cpp_lib_string_udls                          201304L
 # define __cpp_lib_transformation_trait_aliases         201304L
 # define __cpp_lib_transparent_operators                201210L
 # define __cpp_lib_tuple_element_t                      201402L
 # define __cpp_lib_tuples_by_type                       201304L
 #endif

 # endif
 # define __cpp_lib_bool_constant                        201505L
 // # define __cpp_lib_boyer_moore_searcher                 201603L
 # define __cpp_lib_byte                                 201603L
 # define __cpp_lib_chrono                               201611L
 # define __cpp_lib_clamp                                201603L
 # define __cpp_lib_enable_shared_from_this              201603L
 // # define __cpp_lib_execution                            201603L
-# define __cpp_lib_filesystem                           201703L
+# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem)
+#   define __cpp_lib_filesystem                         201703L
+# endif
 # define __cpp_lib_gcd_lcm                              201606L
 // # define __cpp_lib_hardware_interference_size           201703L
 # if defined(_LIBCPP_HAS_UNIQUE_OBJECT_REPRESENTATIONS)
 #   define __cpp_lib_has_unique_object_representations  201606L
 # endif
 # define __cpp_lib_hypot                                201603L
 # define __cpp_lib_incomplete_container_elements        201505L
 # define __cpp_lib_invoke                               201411L

 # define __cpp_lib_node_extract                         201606L
 # define __cpp_lib_nonmember_container_access           201411L
 # define __cpp_lib_not_fn                               201603L
 # define __cpp_lib_optional                             201606L
 // # define __cpp_lib_parallel_algorithm                   201603L
 # define __cpp_lib_raw_memory_algorithms                201606L
 # define __cpp_lib_sample                               201603L
 # define __cpp_lib_scoped_lock                          201703L
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_mutex)
 #   define __cpp_lib_shared_mutex                       201505L
 # endif
 # define __cpp_lib_shared_ptr_arrays                    201611L
 # define __cpp_lib_shared_ptr_weak_type                 201606L
 # define __cpp_lib_string_view                          201606L
 // # define __cpp_lib_to_chars                             201611L
 # undef  __cpp_lib_transparent_operators
 # define __cpp_lib_transparent_operators                201510L

 // #   define __cpp_lib_atomic_ref                         201806L
 # endif
 # if !defined(_LIBCPP_HAS_NO_THREADS)
 // #   define __cpp_lib_atomic_shared_ptr                  201711L
 # endif
 # if !defined(_LIBCPP_HAS_NO_THREADS)
 // #   define __cpp_lib_atomic_value_initialization        201911L
 # endif
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_atomic_wait)
 #   define __cpp_lib_atomic_wait                        201907L
 # endif
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_barrier)
 #   define __cpp_lib_barrier                            201907L
 # endif
 // # define __cpp_lib_bind_front                           201907L
 // # define __cpp_lib_bit_cast                             201806L
 // # define __cpp_lib_bitops                               201907L
 # define __cpp_lib_bounded_array_traits                 201902L
 # if !defined(_LIBCPP_NO_HAS_CHAR8_T)
 #   define __cpp_lib_char8_t                            201811L

 #   define __cpp_lib_is_constant_evaluated              201811L
 # endif
 // # define __cpp_lib_is_layout_compatible                 201907L
 # define __cpp_lib_is_nothrow_convertible               201806L
 // # define __cpp_lib_is_pointer_interconvertible          201907L
 # if !defined(_LIBCPP_HAS_NO_THREADS)
 // #   define __cpp_lib_jthread                            201911L
 # endif
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_latch)
 #   define __cpp_lib_latch                              201907L
 # endif
 # define __cpp_lib_list_remove_return_type              201806L
 # if defined(__cpp_concepts) && __cpp_concepts >= 201811L
 #   define __cpp_lib_math_constants                     201907L
 # endif
 // # define __cpp_lib_polymorphic_allocator                201902L
 // # define __cpp_lib_ranges                               201811L
 # define __cpp_lib_remove_cvref                         201711L
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_semaphore)
 #   define __cpp_lib_semaphore                          201907L
 # endif
 # define __cpp_lib_shift                                201806L
 // # define __cpp_lib_smart_ptr_for_overwrite              202002L
 // # define __cpp_lib_source_location                      201907L
 # define __cpp_lib_span                                 202002L
 # define __cpp_lib_ssize                                201902L
 # define __cpp_lib_starts_ends_with                     201711L

libcxx/test/std/input.output/filesystems/fs.req.macros/feature_macro.pass.cpp

-//===----------------------------------------------------------------------===//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-
-// <filesystem>
-
-// #define __cpp_lib_filesystem 201703L
-
-#include <filesystem>
-#include "test_macros.h"
-
-#if TEST_STD_VER >= 17
-#ifndef __cpp_lib_filesystem
-#error Filesystem feature test macro is not defined  (__cpp_lib_filesystem)
-#elif __cpp_lib_filesystem != 201703L
-#error Filesystem feature test macro has an incorrect value (__cpp_lib_filesystem)
-#endif
-#else // TEST_STD_VER < 17
-#ifdef __cpp_lib_filesystem
-#error Filesystem feature test macro should not be defined before C++17
-#endif
-#endif
-
-int main(int, char**) {
-  return 0;
-}

libcxx/test/std/language.support/support.limits/support.limits.general/atomic.version.pass.cpp

 #     error "__cpp_lib_atomic_value_initialization should have the value 201911L in c++20"
 #   endif
 # else // _LIBCPP_VERSION
 #   ifdef __cpp_lib_atomic_value_initialization
 #     error "__cpp_lib_atomic_value_initialization should not be defined because it is unimplemented in libc++!"
 #   endif
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_atomic_wait)
 #   ifndef __cpp_lib_atomic_wait
 #     error "__cpp_lib_atomic_wait should be defined in c++20"
 #   endif
 #   if __cpp_lib_atomic_wait != 201907L
 #     error "__cpp_lib_atomic_wait should have the value 201907L in c++20"
 #   endif
 # else
 #   ifdef __cpp_lib_atomic_wait
-#     error "__cpp_lib_atomic_wait should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_atomic_wait should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_atomic_wait) is not defined!"
 #   endif
 # endif
 
 # if defined(__cpp_char8_t)
 #   ifndef __cpp_lib_char8_t
 #     error "__cpp_lib_char8_t should be defined in c++20"
 #   endif
 #   if __cpp_lib_char8_t != 201811L

 #     error "__cpp_lib_atomic_value_initialization should have the value 201911L in c++2b"
 #   endif
 # else // _LIBCPP_VERSION
 #   ifdef __cpp_lib_atomic_value_initialization
 #     error "__cpp_lib_atomic_value_initialization should not be defined because it is unimplemented in libc++!"
 #   endif
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_atomic_wait)
 #   ifndef __cpp_lib_atomic_wait
 #     error "__cpp_lib_atomic_wait should be defined in c++2b"
 #   endif
 #   if __cpp_lib_atomic_wait != 201907L
 #     error "__cpp_lib_atomic_wait should have the value 201907L in c++2b"
 #   endif
 # else
 #   ifdef __cpp_lib_atomic_wait
-#     error "__cpp_lib_atomic_wait should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_atomic_wait should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_atomic_wait) is not defined!"
 #   endif
 # endif
 
 # if defined(__cpp_char8_t)
 #   ifndef __cpp_lib_char8_t
 #     error "__cpp_lib_char8_t should be defined in c++2b"
 #   endif
 #   if __cpp_lib_char8_t != 201811L

libcxx/test/std/language.support/support.limits/support.limits.general/barrier.version.pass.cpp

 #elif TEST_STD_VER == 17
 
 # ifdef __cpp_lib_barrier
 #   error "__cpp_lib_barrier should not be defined before c++20"
 # endif
 
 #elif TEST_STD_VER == 20
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_barrier)
 #   ifndef __cpp_lib_barrier
 #     error "__cpp_lib_barrier should be defined in c++20"
 #   endif
 #   if __cpp_lib_barrier != 201907L
 #     error "__cpp_lib_barrier should have the value 201907L in c++20"
 #   endif
 # else
 #   ifdef __cpp_lib_barrier
-#     error "__cpp_lib_barrier should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_barrier should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_barrier) is not defined!"
 #   endif
 # endif
 
 #elif TEST_STD_VER > 20
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_barrier)
 #   ifndef __cpp_lib_barrier
 #     error "__cpp_lib_barrier should be defined in c++2b"
 #   endif
 #   if __cpp_lib_barrier != 201907L
 #     error "__cpp_lib_barrier should have the value 201907L in c++2b"
 #   endif
 # else
 #   ifdef __cpp_lib_barrier
-#     error "__cpp_lib_barrier should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_barrier should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_barrier) is not defined!"
 #   endif
 # endif
 
 #endif // TEST_STD_VER > 20
 
 int main(int, char**) { return 0; }

libcxx/test/std/language.support/support.limits/support.limits.general/filesystem.version.pass.cpp

 # endif
 
 #elif TEST_STD_VER == 17
 
 # ifdef __cpp_lib_char8_t
 #   error "__cpp_lib_char8_t should not be defined before c++20"
 # endif
 
-# ifndef __cpp_lib_filesystem
-#   error "__cpp_lib_filesystem should be defined in c++17"
-# endif
-# if __cpp_lib_filesystem != 201703L
-#   error "__cpp_lib_filesystem should have the value 201703L in c++17"
-# endif
+# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem)
+#   ifndef __cpp_lib_filesystem
+#     error "__cpp_lib_filesystem should be defined in c++17"
+#   endif
+#   if __cpp_lib_filesystem != 201703L
+#     error "__cpp_lib_filesystem should have the value 201703L in c++17"
+#   endif
+# else
+#   ifdef __cpp_lib_filesystem
+#     error "__cpp_lib_filesystem should not be defined when !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem) is not defined!"
+#   endif
+# endif
 
 #elif TEST_STD_VER == 20
 
 # if defined(__cpp_char8_t)
 #   ifndef __cpp_lib_char8_t
 #     error "__cpp_lib_char8_t should be defined in c++20"
 #   endif
 #   if __cpp_lib_char8_t != 201811L
 #     error "__cpp_lib_char8_t should have the value 201811L in c++20"
 #   endif
 # else
 #   ifdef __cpp_lib_char8_t
 #     error "__cpp_lib_char8_t should not be defined when defined(__cpp_char8_t) is not defined!"
 #   endif
 # endif
 
-# ifndef __cpp_lib_filesystem
-#   error "__cpp_lib_filesystem should be defined in c++20"
-# endif
-# if __cpp_lib_filesystem != 201703L
-#   error "__cpp_lib_filesystem should have the value 201703L in c++20"
-# endif
+# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem)
+#   ifndef __cpp_lib_filesystem
+#     error "__cpp_lib_filesystem should be defined in c++20"
+#   endif
+#   if __cpp_lib_filesystem != 201703L
+#     error "__cpp_lib_filesystem should have the value 201703L in c++20"
+#   endif
+# else
+#   ifdef __cpp_lib_filesystem
+#     error "__cpp_lib_filesystem should not be defined when !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem) is not defined!"
+#   endif
+# endif
 
 #elif TEST_STD_VER > 20
 
 # if defined(__cpp_char8_t)
 #   ifndef __cpp_lib_char8_t
 #     error "__cpp_lib_char8_t should be defined in c++2b"
 #   endif
 #   if __cpp_lib_char8_t != 201811L
 #     error "__cpp_lib_char8_t should have the value 201811L in c++2b"
 #   endif
 # else
 #   ifdef __cpp_lib_char8_t
 #     error "__cpp_lib_char8_t should not be defined when defined(__cpp_char8_t) is not defined!"
 #   endif
 # endif
 
-# ifndef __cpp_lib_filesystem
-#   error "__cpp_lib_filesystem should be defined in c++2b"
-# endif
-# if __cpp_lib_filesystem != 201703L
-#   error "__cpp_lib_filesystem should have the value 201703L in c++2b"
-# endif
+# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem)
+#   ifndef __cpp_lib_filesystem
+#     error "__cpp_lib_filesystem should be defined in c++2b"
+#   endif
+#   if __cpp_lib_filesystem != 201703L
+#     error "__cpp_lib_filesystem should have the value 201703L in c++2b"
+#   endif
+# else
+#   ifdef __cpp_lib_filesystem
+#     error "__cpp_lib_filesystem should not be defined when !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem) is not defined!"
+#   endif
+# endif
 
 #endif // TEST_STD_VER > 20
 
 int main(int, char**) { return 0; }

libcxx/test/std/language.support/support.limits/support.limits.general/latch.version.pass.cpp

 #elif TEST_STD_VER == 17
 
 # ifdef __cpp_lib_latch
 #   error "__cpp_lib_latch should not be defined before c++20"
 # endif
 
 #elif TEST_STD_VER == 20
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_latch)
 #   ifndef __cpp_lib_latch
 #     error "__cpp_lib_latch should be defined in c++20"
 #   endif
 #   if __cpp_lib_latch != 201907L
 #     error "__cpp_lib_latch should have the value 201907L in c++20"
 #   endif
 # else
 #   ifdef __cpp_lib_latch
-#     error "__cpp_lib_latch should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_latch should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_latch) is not defined!"
 #   endif
 # endif
 
 #elif TEST_STD_VER > 20
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_latch)
 #   ifndef __cpp_lib_latch
 #     error "__cpp_lib_latch should be defined in c++2b"
 #   endif
 #   if __cpp_lib_latch != 201907L
 #     error "__cpp_lib_latch should have the value 201907L in c++2b"
 #   endif
 # else
 #   ifdef __cpp_lib_latch
-#     error "__cpp_lib_latch should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_latch should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_latch) is not defined!"
 #   endif
 # endif
 
 #endif // TEST_STD_VER > 20
 
 int main(int, char**) { return 0; }

libcxx/test/std/language.support/support.limits/support.limits.general/semaphore.version.pass.cpp

 #elif TEST_STD_VER == 17
 
 # ifdef __cpp_lib_semaphore
 #   error "__cpp_lib_semaphore should not be defined before c++20"
 # endif
 
 #elif TEST_STD_VER == 20
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_semaphore)
 #   ifndef __cpp_lib_semaphore
 #     error "__cpp_lib_semaphore should be defined in c++20"
 #   endif
 #   if __cpp_lib_semaphore != 201907L
 #     error "__cpp_lib_semaphore should have the value 201907L in c++20"
 #   endif
 # else
 #   ifdef __cpp_lib_semaphore
-#     error "__cpp_lib_semaphore should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_semaphore should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_semaphore) is not defined!"
 #   endif
 # endif
 
 #elif TEST_STD_VER > 20
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_semaphore)
 #   ifndef __cpp_lib_semaphore
 #     error "__cpp_lib_semaphore should be defined in c++2b"
 #   endif
 #   if __cpp_lib_semaphore != 201907L
 #     error "__cpp_lib_semaphore should have the value 201907L in c++2b"
 #   endif
 # else
 #   ifdef __cpp_lib_semaphore
-#     error "__cpp_lib_semaphore should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_semaphore should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_semaphore) is not defined!"
 #   endif
 # endif
 
 #endif // TEST_STD_VER > 20
 
 int main(int, char**) { return 0; }

libcxx/test/std/language.support/support.limits/support.limits.general/shared_mutex.version.pass.cpp

 # endif
 
 #elif TEST_STD_VER == 14
 
 # ifdef __cpp_lib_shared_mutex
 #   error "__cpp_lib_shared_mutex should not be defined before c++17"
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex)
 #   ifndef __cpp_lib_shared_timed_mutex
 #     error "__cpp_lib_shared_timed_mutex should be defined in c++14"
 #   endif
 #   if __cpp_lib_shared_timed_mutex != 201402L
 #     error "__cpp_lib_shared_timed_mutex should have the value 201402L in c++14"
 #   endif
 # else
 #   ifdef __cpp_lib_shared_timed_mutex
-#     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex) is not defined!"
 #   endif
 # endif
 
 #elif TEST_STD_VER == 17
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_mutex)
 #   ifndef __cpp_lib_shared_mutex
 #     error "__cpp_lib_shared_mutex should be defined in c++17"
 #   endif
 #   if __cpp_lib_shared_mutex != 201505L
 #     error "__cpp_lib_shared_mutex should have the value 201505L in c++17"
 #   endif
 # else
 #   ifdef __cpp_lib_shared_mutex
-#     error "__cpp_lib_shared_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_shared_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_mutex) is not defined!"
 #   endif
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex)
 #   ifndef __cpp_lib_shared_timed_mutex
 #     error "__cpp_lib_shared_timed_mutex should be defined in c++17"
 #   endif
 #   if __cpp_lib_shared_timed_mutex != 201402L
 #     error "__cpp_lib_shared_timed_mutex should have the value 201402L in c++17"
 #   endif
 # else
 #   ifdef __cpp_lib_shared_timed_mutex
-#     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex) is not defined!"
 #   endif
 # endif
 
 #elif TEST_STD_VER == 20
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_mutex)
 #   ifndef __cpp_lib_shared_mutex
 #     error "__cpp_lib_shared_mutex should be defined in c++20"
 #   endif
 #   if __cpp_lib_shared_mutex != 201505L
 #     error "__cpp_lib_shared_mutex should have the value 201505L in c++20"
 #   endif
 # else
 #   ifdef __cpp_lib_shared_mutex
-#     error "__cpp_lib_shared_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_shared_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_mutex) is not defined!"
 #   endif
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex)
 #   ifndef __cpp_lib_shared_timed_mutex
 #     error "__cpp_lib_shared_timed_mutex should be defined in c++20"
 #   endif
 #   if __cpp_lib_shared_timed_mutex != 201402L
 #     error "__cpp_lib_shared_timed_mutex should have the value 201402L in c++20"
 #   endif
 # else
 #   ifdef __cpp_lib_shared_timed_mutex
-#     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex) is not defined!"
 #   endif
 # endif
 
 #elif TEST_STD_VER > 20
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_mutex)
 #   ifndef __cpp_lib_shared_mutex
 #     error "__cpp_lib_shared_mutex should be defined in c++2b"
 #   endif
 #   if __cpp_lib_shared_mutex != 201505L
 #     error "__cpp_lib_shared_mutex should have the value 201505L in c++2b"
 #   endif
 # else
 #   ifdef __cpp_lib_shared_mutex
-#     error "__cpp_lib_shared_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_shared_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_mutex) is not defined!"
 #   endif
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex)
 #   ifndef __cpp_lib_shared_timed_mutex
 #     error "__cpp_lib_shared_timed_mutex should be defined in c++2b"
 #   endif
 #   if __cpp_lib_shared_timed_mutex != 201402L
 #     error "__cpp_lib_shared_timed_mutex should have the value 201402L in c++2b"
 #   endif
 # else
 #   ifdef __cpp_lib_shared_timed_mutex
-#     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex) is not defined!"
 #   endif
 # endif
 
 #endif // TEST_STD_VER > 20
 
 int main(int, char**) { return 0; }

libcxx/test/std/language.support/support.limits/support.limits.general/version.version.pass.cpp

 # ifdef __cpp_lib_shared_ptr_arrays
 #   error "__cpp_lib_shared_ptr_arrays should not be defined before c++17"
 # endif
 
 # ifdef __cpp_lib_shared_ptr_weak_type
 #   error "__cpp_lib_shared_ptr_weak_type should not be defined before c++17"
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex)
 #   ifndef __cpp_lib_shared_timed_mutex
 #     error "__cpp_lib_shared_timed_mutex should be defined in c++14"
 #   endif
 #   if __cpp_lib_shared_timed_mutex != 201402L
 #     error "__cpp_lib_shared_timed_mutex should have the value 201402L in c++14"
 #   endif
 # else
 #   ifdef __cpp_lib_shared_timed_mutex
-#     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex) is not defined!"
 #   endif
 # endif
 
 # ifdef __cpp_lib_shift
 #   error "__cpp_lib_shift should not be defined before c++20"
 # endif
 
 # ifdef __cpp_lib_smart_ptr_for_overwrite

 #     error "__cpp_lib_execution should have the value 201603L in c++17"
 #   endif
 # else // _LIBCPP_VERSION
 #   ifdef __cpp_lib_execution
 #     error "__cpp_lib_execution should not be defined because it is unimplemented in libc++!"
 #   endif
 # endif
 
-# ifndef __cpp_lib_filesystem
-#   error "__cpp_lib_filesystem should be defined in c++17"
-# endif
-# if __cpp_lib_filesystem != 201703L
-#   error "__cpp_lib_filesystem should have the value 201703L in c++17"
-# endif
+# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem)
+#   ifndef __cpp_lib_filesystem
+#     error "__cpp_lib_filesystem should be defined in c++17"
+#   endif
+#   if __cpp_lib_filesystem != 201703L
+#     error "__cpp_lib_filesystem should have the value 201703L in c++17"
+#   endif
+# else
+#   ifdef __cpp_lib_filesystem
+#     error "__cpp_lib_filesystem should not be defined when !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem) is not defined!"
+#   endif
+# endif
 
 # ifndef __cpp_lib_gcd_lcm
 #   error "__cpp_lib_gcd_lcm should be defined in c++17"
 # endif
 # if __cpp_lib_gcd_lcm != 201606L
 #   error "__cpp_lib_gcd_lcm should have the value 201606L in c++17"
 # endif
 

 # if __cpp_lib_scoped_lock != 201703L
 #   error "__cpp_lib_scoped_lock should have the value 201703L in c++17"
 # endif
 
 # ifdef __cpp_lib_semaphore
 #   error "__cpp_lib_semaphore should not be defined before c++20"
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_mutex)
 #   ifndef __cpp_lib_shared_mutex
 #     error "__cpp_lib_shared_mutex should be defined in c++17"
 #   endif
 #   if __cpp_lib_shared_mutex != 201505L
 #     error "__cpp_lib_shared_mutex should have the value 201505L in c++17"
 #   endif
 # else
 #   ifdef __cpp_lib_shared_mutex
-#     error "__cpp_lib_shared_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_shared_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_mutex) is not defined!"
 #   endif
 # endif
 
 # ifndef __cpp_lib_shared_ptr_arrays
 #   error "__cpp_lib_shared_ptr_arrays should be defined in c++17"
 # endif
 # if __cpp_lib_shared_ptr_arrays != 201611L
 #   error "__cpp_lib_shared_ptr_arrays should have the value 201611L in c++17"
 # endif
 
 # ifndef __cpp_lib_shared_ptr_weak_type
 #   error "__cpp_lib_shared_ptr_weak_type should be defined in c++17"
 # endif
 # if __cpp_lib_shared_ptr_weak_type != 201606L
 #   error "__cpp_lib_shared_ptr_weak_type should have the value 201606L in c++17"
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex)
 #   ifndef __cpp_lib_shared_timed_mutex
 #     error "__cpp_lib_shared_timed_mutex should be defined in c++17"
 #   endif
 #   if __cpp_lib_shared_timed_mutex != 201402L
 #     error "__cpp_lib_shared_timed_mutex should have the value 201402L in c++17"
 #   endif
 # else
 #   ifdef __cpp_lib_shared_timed_mutex
-#     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex) is not defined!"
 #   endif
 # endif
 
 # ifdef __cpp_lib_shift
 #   error "__cpp_lib_shift should not be defined before c++20"
 # endif
 
 # ifdef __cpp_lib_smart_ptr_for_overwrite

 #     error "__cpp_lib_atomic_value_initialization should have the value 201911L in c++20"
 #   endif
 # else // _LIBCPP_VERSION
 #   ifdef __cpp_lib_atomic_value_initialization
 #     error "__cpp_lib_atomic_value_initialization should not be defined because it is unimplemented in libc++!"
 #   endif
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_atomic_wait)
 #   ifndef __cpp_lib_atomic_wait
 #     error "__cpp_lib_atomic_wait should be defined in c++20"
 #   endif
 #   if __cpp_lib_atomic_wait != 201907L
 #     error "__cpp_lib_atomic_wait should have the value 201907L in c++20"
 #   endif
 # else
 #   ifdef __cpp_lib_atomic_wait
-#     error "__cpp_lib_atomic_wait should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_atomic_wait should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_atomic_wait) is not defined!"
 #   endif
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_barrier)
 #   ifndef __cpp_lib_barrier
 #     error "__cpp_lib_barrier should be defined in c++20"
 #   endif
 #   if __cpp_lib_barrier != 201907L
 #     error "__cpp_lib_barrier should have the value 201907L in c++20"
 #   endif
 # else
 #   ifdef __cpp_lib_barrier
-#     error "__cpp_lib_barrier should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_barrier should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_barrier) is not defined!"
 #   endif
 # endif
 
 # if !defined(_LIBCPP_VERSION)
 #   ifndef __cpp_lib_bind_front
 #     error "__cpp_lib_bind_front should be defined in c++20"
 #   endif
 #   if __cpp_lib_bind_front != 201907L

 #     error "__cpp_lib_execution should have the value 201902L in c++20"
 #   endif
 # else // _LIBCPP_VERSION
 #   ifdef __cpp_lib_execution
 #     error "__cpp_lib_execution should not be defined because it is unimplemented in libc++!"
 #   endif
 # endif
 
-# ifndef __cpp_lib_filesystem
-#   error "__cpp_lib_filesystem should be defined in c++20"
-# endif
-# if __cpp_lib_filesystem != 201703L
-#   error "__cpp_lib_filesystem should have the value 201703L in c++20"
-# endif
+# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem)
+#   ifndef __cpp_lib_filesystem
+#     error "__cpp_lib_filesystem should be defined in c++20"
+#   endif
+#   if __cpp_lib_filesystem != 201703L
+#     error "__cpp_lib_filesystem should have the value 201703L in c++20"
+#   endif
+# else
+#   ifdef __cpp_lib_filesystem
+#     error "__cpp_lib_filesystem should not be defined when !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem) is not defined!"
+#   endif
+# endif
 
 # ifndef __cpp_lib_gcd_lcm
 #   error "__cpp_lib_gcd_lcm should be defined in c++20"
 # endif
 # if __cpp_lib_gcd_lcm != 201606L
 #   error "__cpp_lib_gcd_lcm should have the value 201606L in c++20"
 # endif
 

 #     error "__cpp_lib_jthread should have the value 201911L in c++20"
 #   endif
 # else // _LIBCPP_VERSION
 #   ifdef __cpp_lib_jthread
 #     error "__cpp_lib_jthread should not be defined because it is unimplemented in libc++!"
 #   endif
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_latch)
 #   ifndef __cpp_lib_latch
 #     error "__cpp_lib_latch should be defined in c++20"
 #   endif
 #   if __cpp_lib_latch != 201907L
 #     error "__cpp_lib_latch should have the value 201907L in c++20"
 #   endif
 # else
 #   ifdef __cpp_lib_latch
-#     error "__cpp_lib_latch should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_latch should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_latch) is not defined!"
 #   endif
 # endif
 
 # ifndef __cpp_lib_launder
 #   error "__cpp_lib_launder should be defined in c++20"
 # endif
 # if __cpp_lib_launder != 201606L
 #   error "__cpp_lib_launder should have the value 201606L in c++20"

 
 # ifndef __cpp_lib_scoped_lock
 #   error "__cpp_lib_scoped_lock should be defined in c++20"
 # endif
 # if __cpp_lib_scoped_lock != 201703L
 #   error "__cpp_lib_scoped_lock should have the value 201703L in c++20"
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_semaphore)
 #   ifndef __cpp_lib_semaphore
 #     error "__cpp_lib_semaphore should be defined in c++20"
 #   endif
 #   if __cpp_lib_semaphore != 201907L
 #     error "__cpp_lib_semaphore should have the value 201907L in c++20"
 #   endif
 # else
 #   ifdef __cpp_lib_semaphore
-#     error "__cpp_lib_semaphore should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_semaphore should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_semaphore) is not defined!"
 #   endif
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_mutex)
 #   ifndef __cpp_lib_shared_mutex
 #     error "__cpp_lib_shared_mutex should be defined in c++20"
 #   endif
 #   if __cpp_lib_shared_mutex != 201505L
 #     error "__cpp_lib_shared_mutex should have the value 201505L in c++20"
 #   endif
 # else
 #   ifdef __cpp_lib_shared_mutex
-#     error "__cpp_lib_shared_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_shared_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_mutex) is not defined!"
 #   endif
 # endif
 
 # ifndef __cpp_lib_shared_ptr_arrays
 #   error "__cpp_lib_shared_ptr_arrays should be defined in c++20"
 # endif
 # if __cpp_lib_shared_ptr_arrays != 201611L
 #   error "__cpp_lib_shared_ptr_arrays should have the value 201611L in c++20"
 # endif
 
 # ifndef __cpp_lib_shared_ptr_weak_type
 #   error "__cpp_lib_shared_ptr_weak_type should be defined in c++20"
 # endif
 # if __cpp_lib_shared_ptr_weak_type != 201606L
 #   error "__cpp_lib_shared_ptr_weak_type should have the value 201606L in c++20"
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex)
 #   ifndef __cpp_lib_shared_timed_mutex
 #     error "__cpp_lib_shared_timed_mutex should be defined in c++20"
 #   endif
 #   if __cpp_lib_shared_timed_mutex != 201402L
 #     error "__cpp_lib_shared_timed_mutex should have the value 201402L in c++20"
 #   endif
 # else
 #   ifdef __cpp_lib_shared_timed_mutex
-#     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex) is not defined!"
 #   endif
 # endif
 
 # ifndef __cpp_lib_shift
 #   error "__cpp_lib_shift should be defined in c++20"
 # endif
 # if __cpp_lib_shift != 201806L
 #   error "__cpp_lib_shift should have the value 201806L in c++20"

 #     error "__cpp_lib_atomic_value_initialization should have the value 201911L in c++2b"
 #   endif
 # else // _LIBCPP_VERSION
 #   ifdef __cpp_lib_atomic_value_initialization
 #     error "__cpp_lib_atomic_value_initialization should not be defined because it is unimplemented in libc++!"
 #   endif
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_atomic_wait)
 #   ifndef __cpp_lib_atomic_wait
 #     error "__cpp_lib_atomic_wait should be defined in c++2b"
 #   endif
 #   if __cpp_lib_atomic_wait != 201907L
 #     error "__cpp_lib_atomic_wait should have the value 201907L in c++2b"
 #   endif
 # else
 #   ifdef __cpp_lib_atomic_wait
-#     error "__cpp_lib_atomic_wait should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_atomic_wait should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_atomic_wait) is not defined!"
 #   endif
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_barrier)
 #   ifndef __cpp_lib_barrier
 #     error "__cpp_lib_barrier should be defined in c++2b"
 #   endif
 #   if __cpp_lib_barrier != 201907L
 #     error "__cpp_lib_barrier should have the value 201907L in c++2b"
 #   endif
 # else
 #   ifdef __cpp_lib_barrier
-#     error "__cpp_lib_barrier should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_barrier should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_barrier) is not defined!"
 #   endif
 # endif
 
 # if !defined(_LIBCPP_VERSION)
 #   ifndef __cpp_lib_bind_front
 #     error "__cpp_lib_bind_front should be defined in c++2b"
 #   endif
 #   if __cpp_lib_bind_front != 201907L

 #     error "__cpp_lib_execution should have the value 201902L in c++2b"
 #   endif
 # else // _LIBCPP_VERSION
 #   ifdef __cpp_lib_execution
 #     error "__cpp_lib_execution should not be defined because it is unimplemented in libc++!"
 #   endif
 # endif
 
-# ifndef __cpp_lib_filesystem
-#   error "__cpp_lib_filesystem should be defined in c++2b"
-# endif
-# if __cpp_lib_filesystem != 201703L
-#   error "__cpp_lib_filesystem should have the value 201703L in c++2b"
-# endif
+# if !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem)
+#   ifndef __cpp_lib_filesystem
+#     error "__cpp_lib_filesystem should be defined in c++2b"
+#   endif
+#   if __cpp_lib_filesystem != 201703L
+#     error "__cpp_lib_filesystem should have the value 201703L in c++2b"
+#   endif
+# else
+#   ifdef __cpp_lib_filesystem
+#     error "__cpp_lib_filesystem should not be defined when !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem) is not defined!"
+#   endif
+# endif
 
 # ifndef __cpp_lib_gcd_lcm
 #   error "__cpp_lib_gcd_lcm should be defined in c++2b"
 # endif
 # if __cpp_lib_gcd_lcm != 201606L
 #   error "__cpp_lib_gcd_lcm should have the value 201606L in c++2b"
 # endif
 

 #     error "__cpp_lib_jthread should have the value 201911L in c++2b"
 #   endif
 # else // _LIBCPP_VERSION
 #   ifdef __cpp_lib_jthread
 #     error "__cpp_lib_jthread should not be defined because it is unimplemented in libc++!"
 #   endif
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_latch)
 #   ifndef __cpp_lib_latch
 #     error "__cpp_lib_latch should be defined in c++2b"
 #   endif
 #   if __cpp_lib_latch != 201907L
 #     error "__cpp_lib_latch should have the value 201907L in c++2b"
 #   endif
 # else
 #   ifdef __cpp_lib_latch
-#     error "__cpp_lib_latch should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_latch should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_latch) is not defined!"
 #   endif
 # endif
 
 # ifndef __cpp_lib_launder
 #   error "__cpp_lib_launder should be defined in c++2b"
 # endif
 # if __cpp_lib_launder != 201606L
 #   error "__cpp_lib_launder should have the value 201606L in c++2b"

 
 # ifndef __cpp_lib_scoped_lock
 #   error "__cpp_lib_scoped_lock should be defined in c++2b"
 # endif
 # if __cpp_lib_scoped_lock != 201703L
 #   error "__cpp_lib_scoped_lock should have the value 201703L in c++2b"
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_semaphore)
 #   ifndef __cpp_lib_semaphore
 #     error "__cpp_lib_semaphore should be defined in c++2b"
 #   endif
 #   if __cpp_lib_semaphore != 201907L
 #     error "__cpp_lib_semaphore should have the value 201907L in c++2b"
 #   endif
 # else
 #   ifdef __cpp_lib_semaphore
-#     error "__cpp_lib_semaphore should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_semaphore should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_semaphore) is not defined!"
 #   endif
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_mutex)
 #   ifndef __cpp_lib_shared_mutex
 #     error "__cpp_lib_shared_mutex should be defined in c++2b"
 #   endif
 #   if __cpp_lib_shared_mutex != 201505L
 #     error "__cpp_lib_shared_mutex should have the value 201505L in c++2b"
 #   endif
 # else
 #   ifdef __cpp_lib_shared_mutex
-#     error "__cpp_lib_shared_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_shared_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_mutex) is not defined!"
 #   endif
 # endif
 
 # ifndef __cpp_lib_shared_ptr_arrays
 #   error "__cpp_lib_shared_ptr_arrays should be defined in c++2b"
 # endif
 # if __cpp_lib_shared_ptr_arrays != 201611L
 #   error "__cpp_lib_shared_ptr_arrays should have the value 201611L in c++2b"
 # endif
 
 # ifndef __cpp_lib_shared_ptr_weak_type
 #   error "__cpp_lib_shared_ptr_weak_type should be defined in c++2b"
 # endif
 # if __cpp_lib_shared_ptr_weak_type != 201606L
 #   error "__cpp_lib_shared_ptr_weak_type should have the value 201606L in c++2b"
 # endif
 
-# if !defined(_LIBCPP_HAS_NO_THREADS)
+# if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex)
 #   ifndef __cpp_lib_shared_timed_mutex
 #     error "__cpp_lib_shared_timed_mutex should be defined in c++2b"
 #   endif
 #   if __cpp_lib_shared_timed_mutex != 201402L
 #     error "__cpp_lib_shared_timed_mutex should have the value 201402L in c++2b"
 #   endif
 # else
 #   ifdef __cpp_lib_shared_timed_mutex
-#     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
+#     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex) is not defined!"
 #   endif
 # endif
 
 # ifndef __cpp_lib_shift
 #   error "__cpp_lib_shift should be defined in c++2b"
 # endif
 # if __cpp_lib_shift != 201806L
 #   error "__cpp_lib_shift should have the value 201806L in c++2b"

libcxx/utils/generate_feature_test_macro_components.py

feature_test_macros = [ add_version_header(x) for x in [
     "headers": ["atomic", "memory"],
     "depends": "!defined(_LIBCPP_HAS_NO_THREADS)",
     "internal_depends": "!defined(_LIBCPP_HAS_NO_THREADS)",
     "unimplemented": True,
   }, {
     "name": "__cpp_lib_atomic_wait",
     "values": { "c++20": 201907 },
     "headers": ["atomic"],
-    "depends": "!defined(_LIBCPP_HAS_NO_THREADS)",
-    "internal_depends": "!defined(_LIBCPP_HAS_NO_THREADS)",
+    "depends": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_atomic_wait)",
+    "internal_depends": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_atomic_wait)",
   }, {
     "name": "__cpp_lib_barrier",
     "values": { "c++20": 201907 },
     "headers": ["barrier"],
-    "depends": "!defined(_LIBCPP_HAS_NO_THREADS)",
-    "internal_depends": "!defined(_LIBCPP_HAS_NO_THREADS)",
+    "depends": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_barrier)",
+    "internal_depends": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_barrier)",
   }, {
     "name": "__cpp_lib_bind_front",
     "values": { "c++20": 201907 },
     "headers": ["functional"],
     "unimplemented": True,
   }, {
     "name": "__cpp_lib_bit_cast",
     "values": { "c++20": 201806 },
feature_test_macros = [ add_version_header(x) for x in [
     "name": "__cpp_lib_execution",
     "values": { "c++17": 201603, "c++20": 201902 },
     "headers": ["execution"],
     "unimplemented": True,
   }, {
     "name": "__cpp_lib_filesystem",
     "values": { "c++17": 201703 },
     "headers": ["filesystem"],
+    "depends": "!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem)",
+    "internal_depends": "!defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem)"
   }, {
     "name": "__cpp_lib_gcd_lcm",
     "values": { "c++17": 201606 },
     "headers": ["numeric"],
   }, {
     "name": "__cpp_lib_generic_associative_lookup",
     "values": { "c++14": 201304 },
     "headers": ["map", "set"],
feature_test_macros = [ add_version_header(x) for x in [
     "headers": ["stop_token", "thread"],
     "depends": "!defined(_LIBCPP_HAS_NO_THREADS)",
     "internal_depends": "!defined(_LIBCPP_HAS_NO_THREADS)",
     "unimplemented": True,
   }, {
     "name": "__cpp_lib_latch",
     "values": { "c++20": 201907 },
     "headers": ["latch"],
-    "depends": "!defined(_LIBCPP_HAS_NO_THREADS)",
-    "internal_depends": "!defined(_LIBCPP_HAS_NO_THREADS)",
+    "depends": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_latch)",
+    "internal_depends": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_latch)",
   }, {
     "name": "__cpp_lib_launder",
     "values": { "c++17": 201606 },
     "headers": ["new"],
   }, {
     "name": "__cpp_lib_list_remove_return_type",
     "values": { "c++20": 201806 },
     "headers": ["forward_list", "list"],
feature_test_macros = [ add_version_header(x) for x in [
   }, {
     "name": "__cpp_lib_scoped_lock",
     "values": { "c++17": 201703 },
     "headers": ["mutex"],
   }, {
     "name": "__cpp_lib_semaphore",
     "values": { "c++20": 201907 },
     "headers": ["semaphore"],
-    "depends": "!defined(_LIBCPP_HAS_NO_THREADS)",
-    "internal_depends": "!defined(_LIBCPP_HAS_NO_THREADS)",
+    "depends": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_semaphore)",
+    "internal_depends": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_semaphore)",
   }, {
     "name": "__cpp_lib_shared_mutex",
     "values": { "c++17": 201505 },
     "headers": ["shared_mutex"],
-    "depends": "!defined(_LIBCPP_HAS_NO_THREADS)",
-    "internal_depends": "!defined(_LIBCPP_HAS_NO_THREADS)",
+    "depends": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_mutex)",
+    "internal_depends": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_mutex)",
   }, {
     "name": "__cpp_lib_shared_ptr_arrays",
     "values": { "c++17": 201611 },
     "headers": ["memory"],
   }, {
     "name": "__cpp_lib_shared_ptr_weak_type",
     "values": { "c++17": 201606 },
     "headers": ["memory"],
   }, {
     "name": "__cpp_lib_shared_timed_mutex",
     "values": { "c++14": 201402 },
     "headers": ["shared_mutex"],
-    "depends": "!defined(_LIBCPP_HAS_NO_THREADS)",
-    "internal_depends": "!defined(_LIBCPP_HAS_NO_THREADS)",
+    "depends": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex)",
+    "internal_depends": "!defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_shared_timed_mutex)",
   }, {
     "name": "__cpp_lib_shift",
     "values": { "c++20": 201806 },
     "headers": ["algorithm"],
   }, {
     "name": "__cpp_lib_smart_ptr_for_overwrite",
     "values": { "c++20": 202002 },
     "headers": ["memory"],