Re: [RFC] Fix for gdb.parameter('architecture') returning empty string

[Siva Chandra <sivachandra at google dot com>]

On Thu, Nov 1, 2012 at 1:18 PM, Tom Tromey <tromey@redhat.com> wrote:

> I'm not certain that this patch is correct.  Also I tend to think (but
> of course I am willing to be convinced otherwise) that a different
> direction would be preferable.
>
> Siva> +static void
> Siva> +on_architecture_change (struct gdbarch *arch)
> Siva> +{
> Siva> +  architecture_string = gdbarch_bfd_arch_info (arch)->printable_name;
> Siva> +  set_endian_string (arch);
> Siva> +}
>
> Siva> +    observer_attach_architecture_changed (on_architecture_change);
>
> I suspect this means that gdb.parameter('architecture') will not always
> show the same result as "show architecture".

I do not understand this completely. In my patch, show_architecture
only prints 'architecture_string'. Hence,
gdb.parameter('architecture') and "show architecture" should always
show the same result. Did I miss something?

> Right now, in the auto case show_architecture will call
> get_current_arch:
>
>     struct gdbarch *
>     get_current_arch (void)
>     {
>       if (has_stack_frames ())
>         return get_frame_arch (get_selected_frame (NULL));
>       else
>         return target_gdbarch;
>     }
>
> But from what I can tell, the architecture-change observer is not
> notified in every situation that might cause that function to return a
> different result.

Pardon my ignorance here, does target arch change between frames?

> I think a better approach might be to address the problem of "auto" gdb
> parameters more globally.  For example, we could add a method to the
> appropriate CLI object so that the Python could call this to get the
> correct current value.

Do you mean that the CLI object should have a method (which can
evaluate the property value on the go), rather than a property like
'architecture_string' and 'endian_string'? If yes, do you envision
that Python make use of the method if it exists, otherwise use the
property?

Thanks,
Siva Chandra