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

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

Differential Revision: https://reviews.llvm.org/D94983

(cherry picked from commit 76fc357)

Author: ldionne

libcxx/include/__availability

@@ -43,6 +43,14 @@
 // 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
@@ -76,6 +84,8 @@
     // 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
@@ -114,6 +124,7 @@
 #   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
@@ -122,6 +133,10 @@
     // 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__)
 
@@ -130,6 +145,14 @@
         __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)))               \
@@ -139,27 +162,34 @@
         _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)))               \
@@ -175,10 +205,23 @@
         _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
 

libcxx/include/version

@@ -184,7 +184,7 @@ __cpp_lib_void_t                                        201411L <type_traits>
 # 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
@@ -213,7 +213,9 @@ __cpp_lib_void_t                                        201411L <type_traits>
 # 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)
@@ -241,7 +243,7 @@ __cpp_lib_void_t                                        201411L <type_traits>
 # 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
@@ -279,10 +281,10 @@ __cpp_lib_void_t                                        201411L <type_traits>
 # 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
@@ -326,7 +328,7 @@ __cpp_lib_void_t                                        201411L <type_traits>
 # 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
@@ -336,7 +338,7 @@ __cpp_lib_void_t                                        201411L <type_traits>
 // # 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

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

@@ -248,7 +248,7 @@
 #   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
@@ -257,7 +257,7 @@
 #   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
 
@@ -367,7 +367,7 @@
 #   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
@@ -376,7 +376,7 @@
 #   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
 

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

@@ -44,7 +44,7 @@
 
 #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
@@ -53,13 +53,13 @@
 #   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
@@ -68,7 +68,7 @@
 #   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
 

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

@@ -51,11 +51,17 @@
 #   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"
+# 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
@@ -73,11 +79,17 @@
 #   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"
+# 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
@@ -95,11 +107,17 @@
 #   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"
+# 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

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

@@ -44,7 +44,7 @@
 
 #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
@@ -53,13 +53,13 @@
 #   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
@@ -68,7 +68,7 @@
 #   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