[lldb-dev] Call python script on stop?

[Greg Clayton]

> On Sep 10, 2014, at 1:00 PM, Ted Woodward <ted.woodward at codeaurora.org> wrote:
> 
> Let me back up a little - I'm running this from lldb, not python.

Ah, gotcha.

> Ultimately I want to have lldb run from eclipse, connected to a gdb server, but use python to pop up TK windows so we can enhance the gui without having to write  eclipse java code.

Got it.

> I've got my script creating the TK window, and I can populate the window by reading registers. Then I moved the window code to another thread, but now I can't read registers.

Many windowing frameworks require UI updates happen on a specific thread. I am not sure if you are running into such a problem here. There should be nothing stopping you from being able to read registers from another thread. You will need to make sure your target is stopped (otherwise the register read will fail saying the process is running).

> I'm connected to the gdb server, and can read registers from the command line. I pass the debugger in to my handler code in the other thread, and lldb crashes when I try to access it.

That shouldn't happen if you have a valid debugger handle.

> If I create a new debugger instead, I get "error: invalid frame".

Each debugger has a target list:

debugger
   target = 0x11110000
   target = 0x22220000

Each target may or may not have a process

debugger
   target = 0x11110000
       process = 0x12340000
   target = 0x22220000
       process = 0x00000000

Then each process, if valid might have one or more threads and one or more frames within each thread:

debugger
   target = 0x11110000
       process = 0x12340000
            thread 1 = 0x12310000
            thread 2 = 0x12310000
                frame[0] = 0x123092302
                frame[1] = 0x223092302
   target = 0x22220000
       process = 0x00000000


So there is no reason to create a new debugger, it won't contain anything. You need to access the current debugger. If you are running through the embedded python interpreter, you can just use "lldb.debugger". That will always be correct for your current session.

> 
> How do I start up a new thread, but access the debugger on the main thread, which is attached to the remote gdb server?

All LLDB code is multi-theaded so you should be able to read registers on any thread. You need to make sure you have good instances:

(lldb) script print lldb.debugger
Debugger (instance: "debugger_1", id: 1)


When you print the debugger, you get valid text. You should also validate that you have valid target, process, thread, and frame objects before you use them.

Maybe you can post the code that is using the debugger to get the current target, and how you are getting the thread and frame that you are getting registers from?

Greg
> 
> -----Original Message-----
> From: Greg Clayton [mailto:gclayton at apple.com] 
> Sent: Tuesday, September 09, 2014 7:08 PM
> To: Ted Woodward
> Cc: Jim Ingham; lldb-dev at cs.uiuc.edu
> Subject: Re: [lldb-dev] Call python script on stop?
> 
> You would use two python threads.
> 
> Info on python threads:
> 
> http://www.tutorialspoint.com/python/python_multithreading.htm
> 
> You would make one thread run your command prompt code, and one thread just consuming events. You would make a function in python:
> 
> 
> def lldb_event_thread():
>    ....
> 
> 
> And the code inside lldb_event_thread would be consuming the events (copy code from process_events.py). 
> 
> You actually might want 3 thread:
> 1 - main thread that waits for anything from the two other threads
> 2 - command prompt thread
> 3 - event thread
> 
> 
> 
>> On Sep 9, 2014, at 4:43 PM, Ted Woodward <ted.woodward at codeaurora.org> wrote:
>> 
>> Can I do that from inside lldb, or are we talking another python process? If inside lldb, how do I do that?
>> 
>> -----Original Message-----
>> From: Greg Clayton [mailto:gclayton at apple.com] 
>> Sent: Tuesday, September 09, 2014 6:35 PM
>> To: Ted Woodward
>> Cc: Jim Ingham; lldb-dev at cs.uiuc.edu
>> Subject: Re: [lldb-dev] Call python script on stop?
>> 
>> You will need to launch another python thread, and in that thread, handle all events just like the process_events.py script.
>> 
>> 
>>> On Sep 9, 2014, at 4:31 PM, Ted Woodward <ted.woodward at codeaurora.org> wrote:
>>> 
>>> Is there a way to launch another lldb thread, so I have the command prompt and a python script running at the same time?
>>> 
>>> -----Original Message-----
>>> From: jingham at apple.com [mailto:jingham at apple.com] 
>>> Sent: Tuesday, September 09, 2014 5:38 PM
>>> To: Greg Clayton
>>> Cc: Ted Woodward; lldb-dev at cs.uiuc.edu
>>> Subject: Re: [lldb-dev] Call python script on stop?
>>> 
>>> Yes, you definitely want to handle events yourself.  The target stop hooks are fine for printing some variables and threads, etc, but I wouldn't try to update your GUI, etc, from there.
>>> 
>>> Jim
>>> 
>>>> On Sep 9, 2014, at 3:22 PM, Greg Clayton <gclayton at apple.com> wrote:
>>>> 
>>>> 
>>>>> On Sep 9, 2014, at 1:36 PM, Ted Woodward <ted.woodward at codeaurora.org> wrote:
>>>>> 
>>>>> I’m working on a simple python gui proof-of-concept. I’m going to use the Tkinter module to open a Tk window that displays registers. I’d like to have it auto-update when the target stops.
>>>>> 
>>>>> Is there a way to automatically call a python script when a target stops, and to call another (to clean up) when the target is killed?
>>>> 
>>>> Why not just consume the events yourself?
>>>> 
>>>> See the following sample python code:
>>>> 
>>>> svn cat http://llvm.org/svn/llvm-project/lldb/trunk/examples/python/process_events.py
>>>> 
>>>> There is a "target stop-hook" command you could use:
>>>> 
>>>> (lldb) help target stop-hook 
>>>> 
>>>> But I would suggest consuming the events on another thread from python, or just making a polling loop where you want for events for a specified amount of time.
>>>> 
>>>> Greg
>>>> 
>>>> 
>>>> _______________________________________________
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>>>> lldb-dev at cs.uiuc.edu
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>>> 
>>> 
>> 
>> 
> 
>