[libcxx-commits] [libcxx] [libc++] Reformulate availability in terms of LLVM releases (PR #87563)

[Louis Dionne via libcxx-commits]

================
@@ -121,175 +121,287 @@
 // TODO: Enable additional explicit instantiations on GCC once it supports exclude_from_explicit_instantiation,
 //       or once libc++ doesn't use the attribute anymore.
 // TODO: Enable them on Windows once https://llvm.org/PR41018 has been fixed.
-#  if !defined(_LIBCPP_COMPILER_GCC) && !defined(_WIN32)
-#    define _LIBCPP_AVAILABILITY_HAS_ADDITIONAL_IOSTREAM_EXPLICIT_INSTANTIATIONS_1 1
-#  else
-#    define _LIBCPP_AVAILABILITY_HAS_ADDITIONAL_IOSTREAM_EXPLICIT_INSTANTIATIONS_1 0
-#  endif
+#if !defined(_LIBCPP_COMPILER_GCC) && !defined(_WIN32)
+#  define _LIBCPP_AVAILABILITY_HAS_ADDITIONAL_IOSTREAM_EXPLICIT_INSTANTIATIONS_1 _LIBCPP_INTRODUCED_IN_LLVM_12
+#else
+#  define _LIBCPP_AVAILABILITY_HAS_ADDITIONAL_IOSTREAM_EXPLICIT_INSTANTIATIONS_1 0
+#endif
 
 // This controls the availability of floating-point std::to_chars functions.
 // These overloads were added later than the integer overloads.
-#  define _LIBCPP_AVAILABILITY_HAS_TO_CHARS_FLOATING_POINT 1
-#  define _LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT
+#define _LIBCPP_AVAILABILITY_HAS_TO_CHARS_FLOATING_POINT _LIBCPP_INTRODUCED_IN_LLVM_14
+#define _LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_INTRODUCED_IN_LLVM_14_MARKUP
 
 // This controls whether the library claims to provide a default verbose
 // termination function, and consequently whether the headers will try
 // to use it when the mechanism isn't overriden at compile-time.
-#  define _LIBCPP_AVAILABILITY_HAS_VERBOSE_ABORT 1
-#  define _LIBCPP_AVAILABILITY_VERBOSE_ABORT
+#define _LIBCPP_AVAILABILITY_HAS_VERBOSE_ABORT _LIBCPP_INTRODUCED_IN_LLVM_15
+#define _LIBCPP_AVAILABILITY_VERBOSE_ABORT _LIBCPP_INTRODUCED_IN_LLVM_15_MARKUP
 
 // This controls the availability of the C++17 std::pmr library,
 // which is implemented in large part in the built library.
-#  define _LIBCPP_AVAILABILITY_HAS_PMR 1
-#  define _LIBCPP_AVAILABILITY_PMR
+//
+// TODO: Enable std::pmr markup once https://github.com/llvm/llvm-project/issues/40340 has been fixed
+//       Until then, it is possible for folks to try to use `std::pmr` when back-deploying to targets that don't support
+//       it and it'll be a load-time error, but we don't have a good alternative because the library won't compile if we
+//       use availability annotations until that bug has been fixed.
+#define _LIBCPP_AVAILABILITY_HAS_PMR _LIBCPP_INTRODUCED_IN_LLVM_16
+#define _LIBCPP_AVAILABILITY_PMR
 
 // These macros controls the availability of __cxa_init_primary_exception
 // in the built library, which std::make_exception_ptr might use
 // (see libcxx/include/__exception/exception_ptr.h).
-#  define _LIBCPP_AVAILABILITY_HAS_INIT_PRIMARY_EXCEPTION 1
-#  define _LIBCPP_AVAILABILITY_INIT_PRIMARY_EXCEPTION
+#define _LIBCPP_AVAILABILITY_HAS_INIT_PRIMARY_EXCEPTION _LIBCPP_INTRODUCED_IN_LLVM_18
+#define _LIBCPP_AVAILABILITY_INIT_PRIMARY_EXCEPTION _LIBCPP_INTRODUCED_IN_LLVM_18_MARKUP
 
 // This controls the availability of C++23 <print>, which
 // has a dependency on the built library (it needs access to
 // the underlying buffer types of std::cout, std::cerr, and std::clog.
-#  define _LIBCPP_AVAILABILITY_HAS_PRINT 1
-#  define _LIBCPP_AVAILABILITY_PRINT
+#define _LIBCPP_AVAILABILITY_HAS_PRINT _LIBCPP_INTRODUCED_IN_LLVM_18
+#define _LIBCPP_AVAILABILITY_PRINT _LIBCPP_INTRODUCED_IN_LLVM_18_MARKUP
 
 // This controls the availability of the C++20 time zone database.
 // The parser code is built in the library.
-#  define _LIBCPP_AVAILABILITY_HAS_TZDB 1
-#  define _LIBCPP_AVAILABILITY_TZDB
+#define _LIBCPP_AVAILABILITY_HAS_TZDB _LIBCPP_INTRODUCED_IN_LLVM_19
+#define _LIBCPP_AVAILABILITY_TZDB _LIBCPP_INTRODUCED_IN_LLVM_19_MARKUP
 
-#elif defined(__APPLE__)
+// When availability annotations are disabled, we take for granted that features introduced
+// in all versions of the library are available.
+#if defined(_LIBCPP_HAS_NO_VENDOR_AVAILABILITY_ANNOTATIONS)
 
-#  define _LIBCPP_AVAILABILITY_HAS_BAD_OPTIONAL_ACCESS                                                                 \
-    (!defined(__ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__) || __ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__ >= 50000)
+#  define _LIBCPP_INTRODUCED_IN_LLVM_4 1
+#  define _LIBCPP_INTRODUCED_IN_LLVM_4_MARKUP /* nothing */
 
-#  define _LIBCPP_AVAILABILITY_HAS_BAD_VARIANT_ACCESS _LIBCPP_AVAILABILITY_HAS_BAD_OPTIONAL_ACCESS
-#  define _LIBCPP_AVAILABILITY_HAS_BAD_ANY_CAST _LIBCPP_AVAILABILITY_HAS_BAD_OPTIONAL_ACCESS
+#  define _LIBCPP_INTRODUCED_IN_LLVM_5 1
+#  define _LIBCPP_INTRODUCED_IN_LLVM_5_MARKUP /* nothing */
 
-#  define _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS __attribute__((availability(watchos, strict, introduced = 5.0)))
-#  define _LIBCPP_AVAILABILITY_BAD_VARIANT_ACCESS _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS
-#  define _LIBCPP_AVAILABILITY_BAD_ANY_CAST _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS
+#  define _LIBCPP_INTRODUCED_IN_LLVM_6 1
+#  define _LIBCPP_INTRODUCED_IN_LLVM_6_MARKUP /* nothing */
 
-// TODO: Update once this is released
-#  define _LIBCPP_AVAILABILITY_HAS_INIT_PRIMARY_EXCEPTION 0
-#  define _LIBCPP_AVAILABILITY_INIT_PRIMARY_EXCEPTION __attribute__((unavailable))
+#  define _LIBCPP_INTRODUCED_IN_LLVM_7 1
+#  define _LIBCPP_INTRODUCED_IN_LLVM_7_MARKUP /* nothing */
----------------
ldionne wrote:

Ok, I reordered them. I think I agree it's more readable that way.

https://github.com/llvm/llvm-project/pull/87563