+/*
+ * IMPORTANT: this structure is part of the ABI between the probe and
+ * UST. Fields need to be only added at the end, never reordered, never
+ * removed.
+ *
+ * struct lttng_ust_event_common is the common ancestor of the various
+ * public event actions. Inheritance is done by composition: The parent
+ * has a pointer to its child, and the child has a pointer to its
+ * parent. Inheritance of those public structures is done by composition
+ * to ensure both parent and child structures can be extended.
+ *
+ * The field @struct_size should be used to determine the size of the
+ * structure. It should be queried before using additional fields added
+ * at the end of the structure.
+ */