[RFA] Fix frame argument printing when using auto language mode

[Yao Qi]

On Tue, Feb 20, 2018 at 4:28 PM, Xavier Roirand <roirand@adacore.com> wrote:
>
> It was my first idea, but it would imply a consequent amount of work because
> when ada_val_print_1 is called, the stack is the following one:
>
> #0  ada_val_print_1
> #1  ada_val_print
> #2  val_print (got the language of the frame arg)
>
> So if we want to pass the per-frame language down to ada_val_print_1 then in
> the generic val_print function, we have to change:
>
>       language->la_val_print (type, embedded_offset, address,
>                               stream, recurse, val,
>                               &local_opts);
> to something like:
>
>       language->la_val_print (type, embedded_offset, address,
>                               stream, recurse, val,
>                               &local_opts, language);
>                                            ^^^^^^^^
>

We don't have to do that.  ada_val_print_1 is called in ada_val_print,

      ada_val_print_1 (type, embedded_offset, address,
       stream, recurse, val, options,
       current_language);

and ada_val_print is language->la_val_print in effect, so "language"
is ada_language_defn, and we can rewrite the code above like this,

      ada_val_print_1 (type, embedded_offset, address,
       stream, recurse, val, options,
       &ada_language_defn);

This change may break existing behaviour.  Printing for ada (or other
languages) shouldn't depend on current_language, IMO.

> Fix me if I'm wrong but it means that <language>_val_print functions for all
> the supported GDB languages have to be modified in order to support the
> language parameter.
>

-- 
Yao (齐尧)