[lldb-dev] Debugging Python scripts (backtraces, variables) with LLDB

Tue Nov 20 10:07:23 PST 2018

Thanks. That's useful info that covers the "squishing" of C frames into Python frames.

The link to the slides at the end also mentions two other useful projects for walking the stack, py-spy and pyflame.

Having said that, I'm more interested on the "lldb" side of things.

On 20. Nov 2018, at 18:45, Leonard Mosescu <mosescu at google.com<mailto:mosescu at google.com>> wrote:

Not strictly related to LLDB but you might find this interesting: https://blogs.dropbox.com/tech/2018/11/crash-reporting-in-desktop-python-applications

On Tue, Nov 20, 2018 at 8:51 AM Alexandru Croitor via lldb-dev <lldb-dev at lists.llvm.org<mailto:lldb-dev at lists.llvm.org>> wrote:
Hello,

It's been a while since I asked this question on the mailing list ( 2~ years ago).

I am interested in what would be the current best way for implementing interleaved / mixed-mode Python backtraces when debugging the CPython interpreter.

So if I run lldb -- python /path/to/my/script, set a breakpoint somewhere in the C code, and then do "bt", I would see a list of both C stack frames and Python stack frames, and if I do "frame select x" for a python frame, I could inspect the Python locals for instance.

Last time I asked, Jim mentioned using a custom "thread provider". Would this still be the way to go?

I also saw mentions of Java / Go support in the VCS log, but the support was removed due to no maintainers, so I don't know if that would also be the best way of doing it for Python.

I would appreciate, if someone could point me to some relevant code that does something similar to what I'm asking, so I could use it as a base point for exploration.

Many thanks.

> On 8. Jul 2016, at 12:24, Alexandru Croitor <alexandru.croitor at qt.io<mailto:alexandru.croitor at qt.io>> wrote:
>
> Thanks for replying, it's good to know what the status is at least, as well as how it's done in GDB.
>
>> On 06 Jul 2016, at 20:56, Jim Ingham <jingham at apple.com<mailto:jingham at apple.com>> wrote:
>>
>> Nothing of this sort has been done to my knowledge, and I haven't heard of any plans to do so either.
>>
>> It should certainly be possible, you just need to grub the C stack and recognize the pattern of a Python stack frame in it and where said frame stashes away the arguments & locals, and then re-present it as a Python frame.  The SB API's should make that fairly straight forward.
>>
>> It looks like the Python work in gdb is based on a generic "frame filter" concept in the gdb Python API's.  That's something Greg and I talked about when working on gdb way back, and has been a future goal for lldb from the start, but it hasn't ever gotten beyond discussion to date.  We already have the notion of a "thread provider" which allows the Mach Kernel plugin to present its activations as threads in lldb.  You could do much the same thing in lldb, where a thread would have the native unwind based stack frame and then pluggable StackFrame provider that would show different representations of the stack.
>>
>> If anybody is interested in taking on such a project, that would be very cool.
>>
>> Jim
>>
>>> On Jul 6, 2016, at 8:48 AM, Alexandru Croitor via lldb-dev <lldb-dev at lists.llvm.org<mailto:lldb-dev at lists.llvm.org>> wrote:
>>>
>>> Hello,
>>>
>>> I've searched for information wether it is possible to debug a python script using LLDB, and haven't found anything so far.
>>>
>>> Specifically I'm interested in an LLDB counterpart to what GDB provides (the two main pages being https://wiki.python.org/moin/DebuggingWithGdb and http://fedoraproject.org/wiki/Features/EasierPythonDebugging ).
>>>
>>> So python stack traces, python values, etc.
>>>
>>> I assume this is not implemented, but are there any plans, or is it even feasible to implement?
>>>
>>> Regards, Alex.
>>> _______________________________________________
>>> lldb-dev mailing list
>>> lldb-dev at lists.llvm.org<mailto:lldb-dev at lists.llvm.org>
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
>>
>

_______________________________________________
lldb-dev mailing list
lldb-dev at lists.llvm.org<mailto:lldb-dev at lists.llvm.org>
http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/lldb-dev/attachments/20181120/f0bde07d/attachment-0001.html>