Re: Gdb in emacs 24

[Lluís]

Stefan Monnier writes:

>>>> Pretty much any MI command will do that, e.g., "-list-features".
>>> Then could someone patch gdb-mi.el to use this as a test and send
>>> a clear error message to the user about the need for "-i=mi"?
>>> I think it's too late to use "interpreter exec" for 24.1, but such
>>> a test would at least address some of the bug reports I've seen where
>>> users had used "--annotate=3".
>> As I said, if the use of annotate is the only problem, it can be disabled 
>> with a
>> simple gdb command just after gdb-mi.el starts gdb:

>> set annotate 0

>> This trivial change should address all the bugs you referred to.

> I don't think so: those users had "--annotate=3" *instead* of "-i=mi",
> so setting annotation to 0 would probably not help much, since M-x gdb
> would still hang, waiting for the MI-style answers which gdb wouldn't give.

>> Then the check you say is just to cover the case of the user starting gdb 
>> with
>> "-i=tui", which will probably never happen.

> No it's also to cover the case where "-i=mi" is missing.

Right, both were assuming the use of the "interpreter-exec" command.

I've been looking into it, and just starting gdb should be enough to know if
we're under GDB/MI. The possible cases I've looked into are:

* console
* console + annotate
* mi
* tui

GDB/MI gives us a unique greeting format:

    =thread-group-added,id="i1"
    ~"GNU gdb (GDB) 7.3-debian\n"
    ....
    (gdb)

What I've done is use a new gud marker filter during initialization
(gud-common-init) to establish whether the correct interpreter is being
used. After that check, the original filter (gud-gdbmi-marker-filter) is used.

The problem is that my poor elisp knowledge isn't enough to find a way to
communicate the result back into the main emacs process (as the filter seems to
be running on a separate process, I'm unable to simply set a variable to tell
whether the test is ok).

Any hints on how to communicate the result back to the 'gdb' function?


Lluis

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