Re: attach u/i oddity

[Doug Evans <dje@google.com>]

On Tue, Oct 11, 2011 at 10:20 AM, Pedro Alves <pedro@codesourcery.com> wrote:
>> We don't need to make this case simple though.
>> I'd be surprised if it was the more frequent case (or even close).
>
> Err.  It's close.  The "different executable" is usually the one
> with debug info, while the one deployed in the target/system is the
> one without debug info.
>
>> Even if that case required several commands, as long as it was
>> robustly scriptable that would be fine.
>
> I don't take it so lightly.  This is quite old behavior.  We
> should not break things unless there's very good reason.

No disagreement here.
I'm curious what motivated inferring I was taking it lightly.
[I hate needing to be verbose just to avoid such things, it implies a
community in need of some, umm, love. :-)
But maybe better word choices would help.]

>> We should be optimizing for the common case.
>
> Yadayada...  :-)
>
>> > and "file FOO; attach PID" is the idiom GDB uses since forever for that.
>>
>> In this case the user explicitly specified the file.
>> One way to go (though I'm not entirely happy with it) would be to
>> continue to be clever as long as we didn't override what the user
>> explicitly specified.
>
> What I don't like about that, is that is adds state, that is likely
> to confuse users one way or another anyway.

Yep.
OTOH, I claim the current behaviour is already confusing. :-)

> Sometimes we can't
> avoid it, but stateless things are easier to grok.

Yadayada ...?  1/2 :-)

> Maybe GDB could
> print a note when it loaded the executable automatically?
>
> "Note: Hello, hello!  This is GDB speaking.  How are you?
> I've detected the file the process you're attaching to is running
> is /path/to/FOO, and that you hadn't told me which executable goes
> with that process.  So I've hopefully helpfully asked the target
> backend which it was, and loaded it automatically for you.  How
> cool is that, huh?!?  Beware that I won't do this again until
> you unload the executable.  Happy debugging!
>
> Yours,
> --
> G.D.B."
>
> Might need copy editing too.  :-)
>
>> The "file" command needs to do more to make this completely work btw.
>> E.g., it needs to effect a reloading of thread_db (which would fix
>> "gdb -c core, file foo" for the dynamic case).
>
> It's a bit unrelated, wouldn't you say?

Eh?  I don't understand.

>> We could add an option to attach (attach -f PID, or whatever) that
>> explicitly set the file, overriding what's currently in effect.
>
> That would work for me.  But then again, if you know to do this,
> you can also do "file; attach" (or define myattach...).
>
>> > ( certainly needs copy/editing :-) )
>> >
>> > Note this would be tricky to get right for remote targets.  Also,
>> > not all targets can fetch the running executable on attach.
>>
>> Sure, but that didn't stop making attach be clever in the first place. :-)
>
> I can't imagine _not_ wanting it to be clever when I don't
> have a file loaded yet.

I can't imagine not wanting the simple case of attach,detach,attach to
Just Work.
"But seriously ..."
There was some cleverness that was wanted, was "tricky to get right
right for remote targets. Also not all targets can fetch the running
executable on attach", and yet was added anyway.  Awesome.