6.6 Debugging

The SVM simulator supports low-level debugging. Its debug mode is entered whenever the user inputs the ``debug'' special event. If the simulation makes use of a model-specific interface, the debug mode may be entered in a different way. For example, the CDPlayer example in the SVM distribution provides a ``Debug'' button that switches to the debug mode.

When the debug mode is entered, the simulation is suspended. The user is allowed to execute arbitrary Python code. If the default curses interface or the default graphical interface is used, the Python code entered by the user is highlighted according to a combined syntax of Python and SVM model description.

The Python code executed in the debug mode may inspect the status of the simulation and the model running in it, as well as modify their variables. eventhandler is an important object that contains most information concerning the simulation. Its following attributes are useful for debugging:

• eventhandler.state contains the current leaf states (a Python list of strings). Modifying this list changes the state of the model.

• eventhandler.trans contains the definition of all the transitions. It is a Python dictionary.

• eventhandler.stateH is another Python dictionary that contains the definition of the state hierarchy.

• eventhandler.enter and eventhandler.exit are the two Python dictionaries that contain the enter actions and the exit actions, respectively.

• eventhandler.ports is a Python dictionary that contains all the ports and their properties.

• eventhandler.connections is a Python dictionary that contains all the required connections between this model and other components.