Add support for LLDB

[gnzlbg]

I mostly use lldb on mac and gdb on linux. Could this be made to work with lldb as well?

The mapping in commands from gdb to lldb is 1:1, the commands are often just named slightly differently. I'd like to use something that gives me a smooth experience with both.

[cs01]

Absolutely, I'll take a look at lldb and see how hard it would accommodate it.

[cs01]

gdbgui relies on gdb's machine interface (mi) output. lldb does not have this as a built in option, but it looks like someone wrote an intermediate application to provide mi-like output: https://www.codeplay.com/portal/lldb-mi-driver---part-1-introduction. Looks like it won't be as easy as I was hoping, but still seems possible to do.

[gnzlbg]

I think you just need to call lldb-mi instead of lldb. The lldb-mi driver is part of LLVM and is built by default when you build lldb.

[cs01]

Thanks, lldb-mi is what I was looking for. Documentation and implementation are a little sparse for lldb-mi. I did make a lot of progress, but there are some commands that don't seem to have a gdb-mi equivalent.

You can try it out now with, for example, gdbgui/backend.py -g lldb-mi-3.8.

Where gdbgui works with lldb:

• Loading and running files
• Viewing Locals
• Viewing Expressions
• Console
• Registers
• Memory

Where gdbgui has issues or partial functionality with lldb:

• Breakpoints
• Threads/Stack rendering
• Disassembly

I marked all areas of the source code that have such issues with TODOLLDB.

Any help in these areas would be appreciated.

[gnzlbg]

@cs01 IIUC lldb-mi should be 1:1 exactly compatible with gdb-mi, but the project is not that old, so maybe the features that you mention are just not implemented yet. I think that you could show your work on the llvm mailing list, and ask for help about the remaining lldb-mi commands that right now do not work. I see that you are using llvm 3.8, so maybe those issues are already fixed in 3.9 or 4.0. I'm sure the LLDB guys will be keen to help!

[cs01]

@gnzlbg I updated and tried with

>> lldb-mi-4.0 --version
Version: GNU gdb (GDB) 7.4 
(This is a MI stub on top of LLDB and not GDB)
All rights reserved.

It seemed a little improved but certainly still not 1:1. The earliest version of gdb that gdbgui was tested with was 7.7.1, and it looks like this lldb-mi api is compatible with gdb 7.4. I'll try sending an email to the mailing list, thanks.

[gnzlbg]

@cs01 thanks!

[cs01]

@gnzlbg I sent two emails to the mailing list and haven't heard anything back.

lldb-mi compatibility with gdb 7.12 mi2 interpreter

lldb-mi functionality

[gnzlbg]

pinging: @codeplaysoftware , @zjturner , @abidh , they might be able to help.

[cs01]

Thanks @gnzlbg, @zjturner tried to get something going for me on the lldb-dev mailing list, but still no responses.

It looks like another path forward would be to use the LLDB Python Reference: http://lldb.llvm.org/python-reference.html.

Rather than extending lldb-mi to fully implement gdb-mi, the lldb Python interface may be useful. I would like to try to use some existing code that does this. Perhaps from the voltron project. Other recommendations for lldb/python script api's are welcome.

Once that's implemented, gdbgui can choose which controller to use depending on if the user wants to use gdb or lldb.