Re: RFC: "set" command with 2 arguments instead of one?

[Doug Evans <xdje42 at gmail dot com>]

On Tue, Apr 14, 2015 at 5:49 AM, Joel Brobecker <brobecker@adacore.com> wrote:
>> Sorry for the long delay here. Now I could come back to the patches again.
>>
>> Was there any outcome on that discussion. How do you think I could use
>> the multiple arguments?
>
> I don't remember any reply to the message you quote above, which
> summarizes my current thinking and position. As you indicate, it is
> a question of making a decision.
>
> Global Maintainers: What do you think? Let's make a decision so that
> Walfred can resume his work on this.
>
> Thanks!

Hi.

As a data point, regarding this comment:

"Commas also have a meaning in C, so arguably they could be used in
expressions as well."

note that parse_to_comma_and_eval handles parenthesized expressions,
so one *can* use commas in expressions.  If they pose a problem to parsing
of the command then one can wrap that expression in parens.

E.g.,

(gdb) p $pc
$1 = (void (*)(void)) 0x400764 <main()+4>
(gdb) disas (($pc+42),($pc+0)),+16
Dump of assembler code from 0x400764 to 0x400774:
=> 0x0000000000400764 <main()+4>:       mov    $0x400860,%esi
   0x0000000000400769 <main()+9>:       mov    $0x401c80,%edi
   0x000000000040076e <main()+14>:      callq  0x400630
<_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc@plt>
   0x0000000000400773 <main()+19>:      mov    $0x0,%eax

So I'm not worried about commas in expressions.

gdb is never going to be at a point where all commands can use buildargv.
I think choosing either buildargv or commas (using parse_to_comma_and_eval
or whatever) should consider what the arguments to the command are.
And since this command takes things that are more like expressions
than like strings, I'm leaning towards commas.


>> -----Original Message-----
>> From: gdb-patches-owner@sourceware.org [mailto:gdb-patches-owner@sourceware.org] On Behalf Of Joel Brobecker
>> Sent: Monday, November 24, 2014 8:13 AM
>> To: Doug Evans
>> Cc: Andreas Schwab; gdb-patches@sourceware.org
>> Subject: Re: RFC: "set" command with 2 arguments instead of one?
>>
>> > This feels like a case where we need to at least think about some
>> > future-proofing.
>> > One way some commands separate expressions is with commas.
>> > I'm not fond of optional commas (setting aside the thread on info
>> > macro -at LOCATION,).
>> > IOW, if it turns out that we want to use commas down the road to
>> > separate expressions here, then I'd prefer the commas be required
>> > today.
>> > E.g., set mpx bound ADDR, LBOUND, UBOUND
>>
>> > As for how to process multiple arguments to a "set" command, one way
>> > would be to stage the value in a string parameter, and then have a set
>> > handler post-process the result.
>>
>> I think using commas systematically is making it worse for ourselves, since it prevents us from using gdb_buildargv to parse the command arguments for us. Commas also have a meaning in C, so arguably they could be used in expressions as well. But, if that's the way people prefer, then having a standard gdb_buildargv-like API that everyone consistently uses will make it easier for me to accept that decision.
>>
>> --
>> Joel
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>
> --
> Joel