Index: docs/UsersManual.rst
===================================================================
--- docs/UsersManual.rst	(revision 173822)
+++ docs/UsersManual.rst	(working copy)
@@ -1195,7 +1195,15 @@
 Objective-C++ Language Features
 ===============================
 
+.. _implementation_defined_behavior:
 
+Implementation-defined behavior
+===============================
+
+clang generally matches `gcc's implementation-defined
+behavior <http://gcc.gnu.org/onlinedocs/gcc-4.2.1/gcc/C-Implementation.html#C-Implementation>`.
+
+
 .. _target_features:
 
 Target-Specific Features and Limitations