Re: MI documentation

[Bob Rossi <bob@brasko.net>]

On Thu, Sep 30, 2004 at 03:57:31PM +0200, Eli Zaretskii wrote:
> > Date: Thu, 30 Sep 2004 07:49:17 -0400
> > From: Bob Rossi <bob@brasko.net>
> > Cc: gdb@sources.redhat.com
> > 
> > It still doesn't tell you the asyncronous commands like you mentioned or
> > the fields that are available for input commands or anything else that I
> > would need to know for certain versions.
> > 
> > I feel that knowing these things are a minimum requirement for having a
> > protocol between 2 processes.
> 
> Upon thinking about this issue, I came to a conclusion that, as
> surprising as it might sound, I don't understand the problem that bugs
> you.
> 
> 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