Re: libGDB and gdbserver questions

[Vladimir Prus <ghost@cs.msu.su>]

Donny Kurniawan wrote:

>> > "master UI controller" (that controls GDBs).
>>
>> I'm not sure what you mean about "master UI controller". The biggest
> 
> What I mean is the UI that is presented to the user, which manages
> breakpoints, execution, stepping etc. for multiple processes.

Well, UI has to deal with 1000 threads of executions anyway, be it
processes, threads, or anything. It's not trivial, but independent of the
number of gdb instances, IMO.

>> However, it's not likely that you have 1000 different programs. If you
>> have
> 
> It is only one single program being run for 1000 times (1000 processes).

Not MPI, per chance? 
Actually, I always though it's a good idea to add multi-process debugging
(including MPI) to KDevelop (http://kdevelop.org). Maybe, we can team up
for that?

>> two programs, and each one is run on 500 machines, you can start two
>> copies of gdb.
>>
>> Then each copy of gdb would connect to a "redirector" you can write, that
>> will basically forward all packets to invididual instances of gdbserver.
>> But it will present those 500 instances as 500 threads, and gdb can work
>> with threads more or less fine.
> 
> Hmmm.... I'm curious with this approach. I did write a "proxy"
> redirector between gdbserver and gdb. But it only connects one
> gdbserver to one gdb.
> 
> So basically with this approach (many gdbservers to one gdb), we
> present processes as threads to gdb? How about debugging multi-thread
> (!) program with many processes then? How do we present threads to
> gdb?

Heh, that's problem of your "master UI controller". I'd extend the remote
protocol to allow UI to query which real process and real thread each
gdb-visible thread corresponds to.

> It seems to me, this approach is a clean hack, but not the way it's
> supposed to be.

Unfortunately, I don't know better way. Refactoring gdb to support several
connections to remote targets and to add an explicit notion of "process"
might be very hard.

- Volodya