Add a warning to the announcement.
@@ -27,7 +27,9 @@ Highlights of this release include:
- Significant improvements to ARC, including
* The runtime no longer acquires a global lock on every object deallocation (a
- global lock is still used for objects that have weak references).
+ global lock is still used for objects that have weak references). *NOTE:*
+ This is incompatible with other code directly inspecting the reference
+ count and will break with older versions of GNUstep Base!
* Weak references use a scheme closer to C++ `std::weak_pointer` and are
lazily zeroed on access. This reduces the space overheads for weak
