Re: [PATCH 2/2] gdb: Allow parenthesis to group arguments to user-defined commands

Philippe Waroquiers
2018-08-28T20:29:04Z

On Tue, 2018-08-28 at 19:43 +0100, Andrew Burgess wrote:
> * Tom Tromey <tom@tromey.com> [2018-08-28 09:53:52 -0600]:
>
> > > > > > > "Andrew" == Andrew Burgess <andrew.burgess@embecosm.com> writes:
> >
> > Andrew> So, my suggestion deliberately avoids using quotes or backslashes as
> > Andrew> these are bogged down in the existing code. And using (...) is fairly
> > Andrew> intuitive given GDBs C like expression handling, personally I'd rather
> > Andrew> write:
> > Andrew> my_command ({unsigned long long} &global_var)
> > Andrew> than:
> > Andrew> my_command {unsigned\ long\ long}\ &global_var
> >
> > FWIW I tend to agree with your logic here.
> >
> > User-defined argument parsing is broken (and I think there's at least
> > one bug in bugzilla about this), but at the same time, making breaking
> > changes seems unfriendly. Your approach doesn't seem to be breaking
> > anything that is likely to be actually used.

I do not think a \ followed by a space will create a lot of incompatibilities.
i
.e. that someone would type
some_user_defined_command a\ b
to give 2
different args to the command.

For single quotes: it is unlikely that someone types something like
some_user_defined_command 'abc def'
and was expecting the user defined command to receive two args.
What is however a lot more likely is
some_user_defined_command 'a'
and this command expects to receive a character value.
So, yes, single quotes has more potential to create incompatibilities.

On the downside, quoting with parenthesis is something very peculiar
(is there some other tool/shell/... using this convention ?).

And from a previous discussion with Pedro, he indicated that
some commands in gdb already are using single quotes.
The 'Not sure' below is a quote of Pedro :), replying to a suggestion
I gave to let the user tell explicitly if an arg was quoted or not.
>Â Â Â * have a way to (explicitely) quote an argument e.g.
>Â Â Â Â Â Â Â info varÂ Â -Qt 'long int'Â Â regexpofsomevars
>Â Â Â Â Â where -Q indicates that the next "value argument" is
>Â Â Â Â Â explicitely quoted.

Not sure we need that -Q.Â Â We can support optional quotes, and
tell users to add quotes if necessary?Â Â That's what we've done
since forever in linespecs and expressions, for example.

It is based on this that I used single quotes in theÂ
info var/func/arg/local -t TYPEREGEXP NAMEREGEXP
patch.

> Given that the argument passing for user-defined functions is pretty
> self contained we could, conceivably, implement a whole new system and
> have a switch to select between them... the existing code does seem
> rather odd.
>
> But ideally, I'd like that to be a project for another day.
And we also have the 'generalised arg parser' prototype that Pedro has
in a corner.

IMO, clearly, what to do is unclear :).

Philippe