[lldb-dev] Emacs LLDB support & the GDB/MI Interface

Sat Jul 29 23:12:33 PDT 2017

On July 30, 2017 7:15:29 AM GMT+03:00, Eli Zaretskii via lldb-dev <lldb-dev at lists.llvm.org> wrote:
> On July 30, 2017 7:05:52 AM GMT+03:00, Eli Zaretskii via lldb-dev
> <lldb-dev at lists.llvm.org> wrote:
> > On July 30, 2017 6:30:04 AM GMT+03:00, Zachary Turner
> > <zturner at google.com> wrote:
> > > Are we talking about some kind of mi support other than lldb's
> > > existing MI
> > > interface? Afaik it works reasonably well (for some definition of
> > > reasonably well), and is even used for example in msvc on windows
> to
> > > support remote debugging of non windows targets.
> > > 
> > > That said, most lldb developers are paid by their company to work
> on
> > > specific things that are important to their company's users, and
> > emacs
> > > support is probably not going to be that high up on the list.
> > > 
> > > So if you can figure out where the deficiencies are in the
> existing
> > mi
> > > implementation, patches are always welcome
> > > On Sat, Jul 29, 2017 at 7:39 PM Eli Zaretskii via lldb-dev <
> > > lldb-dev at lists.llvm.org> wrote:
> > > 
> > > > > Date: Sat, 29 Jul 2017 22:43:59 +0200
> > > > > Cc: lldb-dev at lists.llvm.org
> > > > > From: Jan Kratochvil via lldb-dev <lldb-dev at lists.llvm.org>
> > > > >
> > > > > MI protocol was designed to minimize the amount of data
> > > transferred
> > > > between
> > > > > gdb/lldb and a front end.  But this communication isn't
> anything
> > > > expensive as
> > > > > the debugger always runs on the same host as the frontend
> anyway
> > > > > (gdb/lldb<->gdbserver link is for remote debugging). 
> > > Unfortunately
> > > > complexity
> > > > > of the GDB/MI protocol from this misoptimization leads to many
> > > bugs on
> > > > both
> > > > > sides of the implementation, for GDB:
> > > > >
> > > >
> > >
> >
> https://sourceware.org/bugzilla/buglist.cgi?bug_status=UNCONFIRMED&bug_status=NEW&bug_status=ASSIGNED&bug_status=SUSPENDED&bug_status=WAITING&bug_status=REOPENED&component=mi&list_id=37310&product=gdb&query_format=advanced
> > > > >       101 bugs found.
> > > > >
> > > > > The MI protocol in use does not conform to its spec as there
> is
> > a
> > > > bug-to-bug
> > > > > compatibility instead such as:
> > > > >      
> > https://sourceware.org/ml/gdb-patches/2008-11/msg00275.html
> > > > >
> > > > > There still also isn't any reasonable MI library to be used by
> a
> > > front
> > > > end.
> > > >
> > > > Correct or not, buggy or not, the Emacs support for GDB is based
> > on
> > > > MI, and it works reasonably well for the last few years.  So
> much
> > so
> > > > that Emacs developers have deprecated the previous GUD interface
> > > based
> > > > on annotations (which are also deprecated by the GDB team).
> > > >
> > > > > I find the LLDB API to be a better choice to be used by the
> > > > frontend/emacs
> > > > > (I have only little but great experience with the LLDB API).
> > > >
> > > > Good luck with that attitude having LLDB support in Emacs any
> time
> > > > soon.  Even supporting it via the ancient GUD, which required a
> > > couple
> > > > of minor changes, was met with some resistance.  (Some think
> that
> > > this
> > > > resistance was overcome, but IMO the jury is still out on that
> > one,
> > > > and we won't know the truth until an attempt to add that support
> > is
> > > > made in earnest.)
> > > >
> > > > Having LLDB support MI would solve this problem cleanly and
> > > > seamlessly.  It's your call to decide whether Emacs support is
> > > > important enough to you to do that.
> > > > _______________________________________________
> > > > lldb-dev mailing list
> > > > lldb-dev at lists.llvm.org
> > > > http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
> > > >
> > 
> > Last time I tried, it wasn't "reasonable" enough to start debugging
> a
> > program under Emacs.  See this discussion for details:
> > 
> > http://lists.llvm.org/pipermail/llvm-dev/2016-December/108512.html
> > 
> > The failed commands it shows are the initial ones issued by Emacs
> > when a debugging session starts.  Without support of these commands
> in
> > lldb-mi there's no hope for any
> > practical debugging using lldb.
> > If llvm developers could implement those minimal commands, maybe the
> > rest would be easier.
> > _______________________________________________
> > lldb-dev mailing list
> > lldb-dev at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
> 
> Sorry, I meant
> http://lists.llvm.org/pipermail/lldb-dev/2016-December/108511.html
> _______________________________________________
> lldb-dev mailing list
> lldb-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev

It's embarrassing...  The correct URL is http://lists.llvm.org/pipermail/llvm-dev/2016-December/108511.html