Re: [PATCH v3 4/7] gdb/python: allow ref_ptr<T, Policy>::new_reference to accept subclasses of T

[Tom Tromey <tom@tromey.com>]

>>>>> Matthieu Longo <matthieu.longo@arm.com> writes:

> When ref_ptr<T,Policy>::new_reference() is specialized for 'PyObject'
> (i.e. gdbpy_ref<>), it currently requires the argument type to be exactly
> 'PyObject *'. As a result, pointers to subclasses of 'PyObject' must be
> explicitly cast before being passed, making call sites unnecessarily
> verbose.

> This patch makes ref_ptr<T,Policy>::new_reference() a template method
> that accepts both T and subclasses of T, performing the cast to 'T *'
> internally when needed. This removes redundant casts at call sites
> without changing behavior.

This seems fine but I noticed something weird.

Approved-By: Tom Tromey <tom@tromey.com>

>    block_object *result = (block_object *) htab_find_with_hash (table, block,
>  							       hash);
>    if (result != nullptr)
> -    return gdbpy_ref<>::new_reference ((PyObject *) result);
> +    return gdbpy_ref<>::new_reference (result);
 
... this part makes sense to me.

>    for (const thread_map_t::value_type &entry : *inf_obj->threads)
>      {
> -      auto thr = gdbpy_ref<>::new_reference ((PyObject *) entry.second.get ());
> +      auto thr = gdbpy_ref<>::new_reference (entry.second.get ());

I guess it isn't super important but new_reference isn't really needed
for a gdbpy_ref<> since we already have a copy constructor.  So just

    gdbpy_ref<> thr = entry.second;

... should do it?

Perhaps an explicit new_reference is more clear.

Tom