Re: MI and backwards compatibility

[Bob Rossi <bob@brasko.net>]

Ping.

I guess the main questions is, is the goal of GDB to support old
versions of MI? For instance, if GDB is currently at MI3, will it
support a front end that only knows MI2? If so, then I need the
documentation for the MI2 interface if I want to make my front end work
with that version of the protocol.

This is a general issue and quit frankly a very simple question. Could I
get a response to at least what GDB does now. Then, maybe we can talk
about what it should do, and if it is doing what it should do.

Thanks,
Bob Rossi

On Fri, Oct 01, 2004 at 10:25:17AM -0400, Bob Rossi wrote:
> Hi,
> 
> Taking Eli's suggestion, I am starting a simple discussion here only on
> how front end developers should expect there front end to work with
> different versions of GDB.
> 
> >From Eli Zaretskii <eliz@gnu.org>
> > All the MI versions except the latest are kept for one reason only:
> > backward compatibility.  So an already existing front end should use
> > the version it was written to support, while a new front end should
> > use the latest version, the one invoked by "-interpreter=mi".  Doesn't
> > this solve the problem?  If not, why not, and what solutions you can
> > suggest to solve that?
> 
> I guess the *real* problem is how we expect a front end and multiple
> versions of GDB work together. I think there needs to be a section in the
> documentation that describes backwards compatibility. For instance, I
> think that a front end programmed to understand mi1 should always work
> with a GDB that is capable of outputting mi1. For instance, here are
> some example GDB's and MI versions for demonstration,
> 
> GDB version with MI versions
> 
>    GDB 1.0 -> mi1
>    GDB 2.0 -> mi1,mi2
>    GDB 3.0 -> mi1,mi2
>    GDB 4.0 -> mi1,mi2,mi3
>    GDB 5.0 -> mi1,mi2,mi3,mi4
> 
> Front end version which understands MI version
>    FE  1.0 -> mi2
>    FE  2.0 -> mi2,mi3
>    FE  3.0 -> mi2,mi3,mi4
> 
> So, here is an example that I don't see to far fetched within the next
> few years. The question is, what does backwards compatibility mean?
> This is what I expect,
> 
> FE 1.0 or after to never work with GDB 1.0
> FE 1.0 to work with GDB 2.0 on using mi2.
> FE 2.0 to work with GDB 2.0 and 3.0 using mi2
>            and with GDB 4.0 on with mi3
> FE 3.0 to work with GDB 2.0 and 3.0 using mi2
>            and with GDB 4.0 with mi3
>            and with GDB 5.0 with mi4
> 
> Is this what everyone else expects?
> 
> Thanks,
> Bob Rossi