[libcxx-commits] [libcxx] [libc++] Deprecate removed features macros. (PR #77879)

[Louis Dionne via libcxx-commits]

================
@@ -123,6 +123,12 @@ Deprecations and Removals
   overload of ``allocate``. However, this led to the library being non-conforming due to incorrect
   constexpr-ness.
 
+- The macros ``_LIBCPP_ENABLE_CXX17_REMOVED_FEATURES`` and
+  ``_LIBCPP_ENABLE_CXX20_REMOVED_FEATURES`` have been deprecated and
+  will be removed in LLVM 19. These macros used to enable all features
+  removed in C++17 and C++20. Instead of using these macros, use the
+  macros to enable the individual features.
----------------
ldionne wrote:

```suggestion
- The macros ``_LIBCPP_ENABLE_CXX17_REMOVED_FEATURES`` and
  ``_LIBCPP_ENABLE_CXX20_REMOVED_FEATURES`` have been deprecated and
  will be removed in LLVM 19. These macros used to re-enable all features
  that were removed in the C++17 and C++20 standards. Instead of using these
  macros, please use the macros to re-enable individual features.
```

https://github.com/llvm/llvm-project/pull/77879