gdb provides a general event facility so that Python code can be notified of various state changes, particularly changes that occur in the inferior.
An event is just an object that describes some state change. The type of the object and its attributes will vary depending on the details of the change. All the existing events are described below.
In order to be notified of an event, you must register an event handler
with an event registry. An event registry is an object in the
gdb.events
module which dispatches particular events. A registry
provides methods to register and unregister event handlers:
Here is an example:
def exit_handler (event): print "event type: exit" print "exit code: %d" % (event.exit_code) gdb.events.exited.connect (exit_handler)
In the above example we connect our handler exit_handler
to the
registry events.exited
. Once connected, exit_handler
gets
called when the inferior exits. The argument event in this example is
of type gdb.ExitedEvent
. As you can see in the example the
ExitedEvent
object has an attribute which indicates the exit code of
the inferior.
The following is a listing of the event registries that are available and details of the events they emit:
events.cont
gdb.ThreadEvent
.
Some events can be thread specific when gdb is running in non-stop
mode. When represented in Python, these events all extend
gdb.ThreadEvent
. Note, this event is not emitted directly; instead,
events which are emitted by this or other modules might extend this event.
Examples of these events are gdb.BreakpointEvent
and
gdb.ContinueEvent
.
Emits gdb.ContinueEvent
which extends gdb.ThreadEvent
.
This event indicates that the inferior has been continued after a stop. For
inherited attribute refer to gdb.ThreadEvent
above.
events.exited
events.ExitedEvent
which indicates that the inferior has exited.
events.ExitedEvent
has one optional attribute. This attribute
will exist only in the case that the inferior exited with some
status.
events.stop
gdb.StopEvent
which extends gdb.ThreadEvent
.
Indicates that the inferior has stopped. All events emitted by this registry
extend StopEvent. As a child of gdb.ThreadEvent
, gdb.StopEvent
will indicate the stopped thread when gdb is running in non-stop
mode. Refer to gdb.ThreadEvent
above for more details.
Emits gdb.SignalEvent
which extends gdb.StopEvent
.
This event indicates that the inferior or one of its threads has received as
signal. gdb.SignalEvent
has the following attributes:
Also emits gdb.BreakpointEvent
which extends gdb.StopEvent
.
gdb.BreakpointEvent
event indicates that a breakpoint has been hit, and
has the following attributes:
A reference to the breakpoint that was hit of type
gdb.Breakpoint
. See Breakpoints In Python, for details of thegdb.Breakpoint
object.