Index: /trunk/include/iprt/cdefs.h
===================================================================
--- /trunk/include/iprt/cdefs.h	(revision 66088)
+++ /trunk/include/iprt/cdefs.h	(revision 66089)
@@ -2291,4 +2291,5 @@
  * @note    Never to a sizeof() on the structure or member!
  * @note    The member must be the last one.
+ * @note    GCC does not permit using this in a union.
  * @note    GCC does not permit using this in nested structures, where as MSC
  *          does.  So, use RT_FLEXIBLE_ARRAY_NESTED for that.
@@ -2318,4 +2319,7 @@
  * GCC only allow the use of flexible array member in the top structure, whereas
  * MSC is less strict and let you do struct { struct { char szName[]; } s; };
+ *
+ * @note    GCC does not permit using this in a union.
+ *
  * @sa      RT_FLEXIBLE_ARRAY
  */