Re: [RFAv3 0/3] Convenience functions $_gdb_setting/$_gdb_int_setting

Pedro Alves
2019-07-08T16:34:55Z

Hi Philippe,

Some overall design comments below.

On 7/6/19 11:49 AM, Philippe Waroquiers wrote:
> As part of the discussion of 'show | set may-call-functions [on|off]',
> Eli suggested to have a way to access the GDB settings from
> user defined commands.
>

As I had mentioned back then:

https://sourceware.org/ml/gdb-patches/2019-04/msg00562.html

we can already access the settings via Python. E.g. see it
done here from a gdbinit script:

https://gcc.gnu.org/ml/gcc-patches/2019-01/msg00135.html

Copied here for convenience:

python __gcc_prev_pagination=gdb.parameter("pagination")
set pagination off
...
python if __gcc_prev_pagination: gdb.execute("set pagination on")

Given that, and the existence of the "with" command now for the
common case, I'd like to at least see some mention/rationale/argument
in the commit logs about why this is worth having/maintaining
over just using gdb.parameter.

BTW, did you look into how gdb.parameter is implemented, see if
anything could be shared?

BTWÂ², kind of unfortunate that Python used a different naming
here (settings vs parameters).

> So, this patch series implements this.
>
> 2 functions are provided:
> * $_gdb_setting that gives access to all settings, giving back a string value.
> * $_gdb_int_setting, giving access to boolean, auto-boolean and integers.
> This is easier to use for such types than the string version.

The naming of the functions kind of seems a bit reversed to me. Off hand, I'd
expect $_gdb_setting to give me the setting in its native type, and then
something like $_gdb_setting_str to give me a string version/representation.

Also, it seems like a design issue that settings that are unsigned
internally get their values exposed as signed.

I guess it could be even better if the setting's types were some new built-in
types specific for the settings, and then if you wanted to get a string
representation, you'd use '$_as_string($_gdb_setting(...))'. (*)

(*) this made me wonder about a special $_python convenience function,
which would take some python code as argument, and return a value, so you
could write:

if $_python(gdb.parameter ("pagination"))
...
end

etc.

> This is v3.
> Compared to v1, it rebases to a recent master, and handles the comments
> of Eli about the documentation.
>
> (there was in fact no changes between v2 and v1, because I forgot to
> commit the changes before sending the RFAv2 mail).
Thanks,
Pedro Alves