def-gdb-auto-update-trigger is a Lisp macro in `gdb-mi.el'.

(def-gdb-auto-update-trigger TRIGGER-NAME GDB-COMMAND HANDLER-NAME &optional SIGNAL-LIST)

Define a trigger TRIGGER-NAME which sends GDB-COMMAND and sets
HANDLER-NAME as its handler. HANDLER-NAME is bound to current
buffer with `gdb-bind-function-to-buffer'.

If SIGNAL-LIST is non-nil, GDB-COMMAND is sent only when the
defined trigger is called with an argument from SIGNAL-LIST. It's
not recommended to define triggers with empty SIGNAL-LIST.
Normally triggers should respond at least to 'update signal.

Normally the trigger defined by this command must be called from
the buffer where HANDLER-NAME must work. This should be done so
that buffer-local thread number may be used in GDB-COMMAND (by
calling `gdb-current-context-command').
`gdb-bind-function-to-buffer' is used to achieve this, see

Triggers defined by this command are meant to be used as a
trigger argument when describing buffer types with