Extending Target Stop-Hooks

Stop hooks fire whenever the process stops just before control is returned to the user. Stop hooks can either be a set of lldb command-line commands, or can be implemented by a suitably defined Python class. The Python-based stop-hooks can also be passed as a set of -key -value pairs when they are added, and those will get packaged up into a SBStructuredData Dictionary and passed to the constructor of the Python object managing the stop hook. This allows for parameterization of the stop hooks.

To add a Python-based stop hook, first define a class with the following methods:

Name	Arguments	Description
__init__	target: lldb.SBTarget extra_args: lldb.SBStructuredData	This is the constructor for the new stop-hook. target is the SBTarget to which the stop hook is added. extra_args is an SBStructuredData object that the user can pass in when creating instances of this breakpoint. It is not required, but allows for reuse of stop-hook classes.
handle_stop	exe_ctx: lldb.SBExecutionContext stream: lldb.SBStream	This is the called when the target stops. exe_ctx argument will be filled with the current stop point for which the stop hook is being evaluated. stream an lldb.SBStream, anything written to this stream will be written to the debugger console. The return value is a “Should Stop” vote from this thread. If the method returns either True or no return this thread votes to stop. If it returns False, then the thread votes to continue after all the stop-hooks are evaluated. Note, the –auto-continue flag to ‘target stop-hook add’ overrides a True return value from the method.

To use this class in lldb, run the command:

(lldb) command script import MyModule.py
(lldb) target stop-hook add -P MyModule.MyStopHook -k first -v 1 -k second -v 2

where MyModule.py is the file containing the class definition MyStopHook.