GDB/MI interactive capability?

[Joel Brobecker <brobecker@adacore.com>]

Vladimir, All,

A question that I was asked by the IDE Team at AdaCore, who is trying
to transition to using GDB/MI instead of CLI + annotations.

Consider a program where we have multiple functions having the same
name (In our case "foo"). In CLI mode, evaluating an expression
referencing one of those functions results in a multiple-choice menu
being printed, asking for the user to select the one he meant us
to call. Eg:

    (gdb) p foo(null)
    Multiple matches for foo
    [0] cancel
    [1] foo.foo at foo.adb:9
    [2] foo.foo at foo.adb:19

Ideally, we'd like to have the same behavior when using the GDB/MI
protocol, and be able to query the user. Do you think we could enhance
the protocol that way?

For instance ("->" means we send to GDB, and "<-" means we receive
from GDB):

-> -data-evaluate-expression foo(null)

<- ^user-input-needed,id=NNN,choices=[
        {number=0, description='cancel'},
        {number=1, description='foo.foo at foo.adb:9'},
        {number=2, description='foo.foo at foo.adb:19}]

The id=NNN would just be a way to identify each user query, and
would be used to identify which query the user's answer is for.
We'd answer the query as follow:

-> -user-input NNNN  ANSWER
<- ^done,[as usual]

This is just thinking out loud. I'm not even sure whether it'll be
all that easy to implement this idea, especially if we want GDB to
remain responsive (Eg, to perform other operations and therefore
send other GDB/MI commands) while waiting for the user's answer.

Another idea, which might be easier to implement, would be to use
a two-step approach where the first step is to return an error
that shows the various choices the user can choose, have the IDE
use that to query the user, and then have the IDE resubmit the
expression evaluation, this time with the choice given by the user.

WDYT?

-- 
Joel