The ordering is the reason we add annex. As you said, events
with the same basic notification are handled in a FIFO manner. Events
with Point:created, Point:modified, and Point:deleted should be
processed in a FIFO order, while Trace:status and Trace:foo should be
processed in FIFO too. When this series was written, 2013 Jan, hui was
proposing "target-defined breakpoint", which requires some asnyc
notifications on breakpoints, so we added annex in V3.
[PATCH 1/5] Add annex in a async remote notification.
https://sourceware.org/ml/gdb-patches/2013-01/msg00506.html
Nowadays, we have few notifications (Stop and Trace) and each of them
are not related. As more notification added, we'll need annex in the
infrastructure, IMO.