[lldb-dev] JIT debugging and Windows

Keno Fischer kfischer at college.harvard.edu
Wed Jan 1 06:39:00 PST 2014

I'm currently in holiday mode as well. A couple of things that I didn't get
to that need to be resolved (these are pretty general questions on lldb
itself, so I'd appreciate input from anybody on this list):

- I'm using a regular rather than an internal breakpoint, because the
latter does not get updated when shared libraries are loaded (Is this
intended? Is there a recommended workaround?)

- I'm not seeing the function in backtraces even though I can set
breakpoints. Is there anything else that needs to be done/ Do the
backtraces use different information that is perhaps not relocated
properly? If so, how can I check?

- I'm also not seeing line numbers, etc. Probably related to the second

- Keno

On Tue, Dec 31, 2013 at 10:16 AM, Andrew MacPherson
<andrew.macp at gmail.com>wrote:

> This looks great. I'm still in holiday mode but will tackle any
> outstanding ELF-related work when I'm back on Thursday, feel free to ping
> me or the list again if you get any further. Thanks for pushing on this!
> Cheers,
> Andrew
> On Sun, Dec 29, 2013 at 6:29 PM, Keno Fischer <
> kfischer at college.harvard.edu> wrote:
>> I've gotten pretty far,
>> Code is here: https://github.com/loladiro/lldb
>> It's interacting correctly with the debug interface and I've got it
>> loading the object file from memory correctly for
>> MachO/DWARF (working on ELF right now). Currently not much use as it
>> doesn't seem to be looking at the
>> debug information that were just added (I can see them via `image dump
>> sections` and I can set breakpoints
>> correctly though, so that's a plus). For DWARF, there's a few changes for
>> upstream LLVM needed. I'll put them
>> up if anybody's interested, otherwise, I'll just keep chugging along and
>> wait until I have more complete patch.
>> - Keno
>> On Sat, Dec 28, 2013 at 1:07 PM, Andrew MacPherson <andrew.macp at gmail.com
>> > wrote:
>>> Hi Keno,
>>> I noticed the same thing and agree that the JIT loader doesn't perfectly
>>> fit as a DynamicLoader, the suggestion from a couple of years back on the
>>> list was to make the Process -> DynamicLoader relationship 1:n but I prefer
>>> your suggestion of adding a new plugin type (JITLoader). Right now there
>>> would only be one JITLoader type for the GDB interface.
>>> The patch could probably be fixed up as-is as a first step (leaving the
>>> JIT loading bits as a growth on the DynamicLoaderPOSIXDYLD) and we could
>>> move it out into its own plugin type once that's working. I should have
>>> time this coming week to get this working but if you'll also have time then
>>> I'm happy to leave it with you.
>>> Cheers,
>>> Andrew
>>> On Sat, Dec 28, 2013 at 9:37 AM, Keno Fischer <
>>> kfischer at college.harvard.edu> wrote:
>>>> I've started looking into this and it's actually not that difficult to
>>>> do (the JIT part at least). I think the most difficult thing is
>>>> figuring out where to put the functionality. The way I see it, the JIT
>>>> interface is almost a DynamicLoader, with the difference
>>>> that asking it about things like whether or not loading a dynamic
>>>> library is safe doesn't make much sense. Another problem
>>>> is that currently there's a 1:1 relationship between Processes and
>>>> DynamicLoaders. Perhaps a new class of Plugins
>>>> (JITLoader?) could be added with a 1:n relationship to processes. Some
>>>> of the interface (I'm thinking
>>>>  DidLaunch,DidAttach,Get/SetStopWhenImagesChange) could be pulled out
>>>> into an abstract base class. Does that make
>>>> sense. I'd be happy to implement this once we decide on the design.
>>>> Keno
>>>> On Wed, Dec 25, 2013 at 10:30 AM, Andrew MacPherson <
>>>> andrew.macp at gmail.com> wrote:
>>>>> Looks great, thanks Keno. I'll look into this next week and keep you
>>>>> posted.
>>>>> Cheers,
>>>>> Andrew
>>>>> On Tue, Dec 24, 2013 at 1:19 PM, Keno Fischer <
>>>>> kfischer at college.harvard.edu> wrote:
>>>>>> I have this (as I said, I haven't tried it). It seems to be a
>>>>>> different patch.
>>>>>> On Tue, Dec 24, 2013 at 11:17 AM, Andrew MacPherson <
>>>>>> andrew.macp at gmail.com> wrote:
>>>>>>> Hi Keno,
>>>>>>> I found this old patch that hooks into the GDB JIT registration
>>>>>>> mechanism which we were planning to use as a starting point:
>>>>>>> http://lists.cs.uiuc.edu/pipermail/lldb-dev/2010-December/000314.html
>>>>>>> If you have anything else we'd love to take a look!
>>>>>>> Cheers,
>>>>>>> Andrew
>>>>>>> On Tue, Dec 24, 2013 at 8:34 AM, Keno Fischer <
>>>>>>> kfischer at college.harvard.edu> wrote:
>>>>>>>> Hi Andrew,
>>>>>>>> I'm also one of the Julia core developers and the guy currently
>>>>>>>> working on
>>>>>>>> debugging support. I was given a patch to add MCJIT debugging
>>>>>>>> support
>>>>>>>> to LLDB with the disclaimer that it probably doesn't work. I
>>>>>>>> haven't tried it
>>>>>>>> yet, so I can't say how close it is, but it's probably at least a
>>>>>>>> starting point.
>>>>>>>> I'd be happy to coordinate any efforts.
>>>>>>>> - Keno
>>>>>>>> _______________________________________________
>>>>>>>> lldb-dev mailing list
>>>>>>>> lldb-dev at cs.uiuc.edu
>>>>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/lldb-dev
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