Update document for objc_arc_weak_unavailable attribute
on class declarations. Documentation for // rdar://9693477
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@134558 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/AutomaticReferenceCounting.html b/docs/AutomaticReferenceCounting.html
index 2804624..11bd020 100644
--- a/docs/AutomaticReferenceCounting.html
+++ b/docs/AutomaticReferenceCounting.html
@@ -728,7 +728,10 @@
in which case it the lvalue is updated to a null pointer. This must
execute atomically with respect to other assignments to the object, to
reads from the object, and to the final release of the new pointed-to
-value.</li>
+value. If class is not compatible with weak references,
+<tt>objc_arc_weak_unavailable</tt>
+attribute must be specified on class declaration to disallow weak
+references to their objects.</li>
<li>For <tt>__unsafe_unretained</tt> objects, the new pointee is
stored into the lvalue using primitive semantics.</li>
<li>For <tt>__autoreleasing</tt> objects, the new pointee is retained,