Re: [PATCH v3 08/11] [PR gdb/14441] gdb: python: support rvalue references in the gdb module

[Keith Seitz <keiths@redhat.com>]

On 03/04/2016 07:19 PM, Artemiy Volkov wrote:
> This patch adds the ability to inspect rvalue reference types and values using
> the gdb python module. This is achieved by simply using the ReferenceExplorer
> class to handle the objects of rvalue reference types and placing necessary
> checks for a TYPE_CODE_RVALUE_REF type code next to the checks for a
> TYPE_CODE_REF type code.
> 
> gdb/ChangeLog:
> 
> 2016-03-04  Artemiy Volkov  <artemiyv@acm.org>
> 
>         * python/lib/gdb/command/explore.py: Support exploring values
>         of rvalue reference types.
>         * python/lib/gdb/types.py: Implement get_basic_type() for
>         rvalue reference types.
>         * python/py-type.c (pyty_codes) <TYPE_CODE_RVALUE_REF>: New
>         constant.
>         * python/py-value.c (valpy_getitem): Add an rvalue reference
>         check.
>         * python/py-xmethods.c (gdbpy_get_xmethod_result_type)
>         (gdbpy_invoke_xmethod): Likewise.
> ---
>  gdb/python/lib/gdb/command/explore.py |  2 +-
>  gdb/python/lib/gdb/types.py           |  4 +++-
>  gdb/python/py-type.c                  |  1 +
>  gdb/python/py-value.c                 |  3 +++
>  gdb/python/py-xmethods.c              | 14 ++++++++------
>  5 files changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/gdb/python/py-xmethods.c b/gdb/python/py-xmethods.c
> index d70cdd1..859e346 100644
> --- a/gdb/python/py-xmethods.c
> +++ b/gdb/python/py-xmethods.c
> @@ -548,10 +548,11 @@ gdbpy_get_xmethod_result_type (const struct extension_language_defn *extlang,
>        if (!types_equal (obj_type, this_ptr))
>  	obj = value_cast (this_ptr, obj);
>      }
> -  else if (TYPE_CODE (obj_type) == TYPE_CODE_REF)
> +  else if (TYPE_IS_REFERENCE (obj_type))
>      {
> -      struct type *this_ref = lookup_lvalue_reference_type (this_type);
> -
> +      struct type *this_ref = TYPE_CODE (obj_type) == TYPE_CODE_REF
> +                                ? lookup_lvalue_reference_type (this_type)
> +                                : lookup_rvalue_reference_type (this_type);
>        if (!types_equal (obj_type, this_ref))
>  	obj = value_cast (this_ref, obj);
>      }

I see this same paradigm repeated in a handful of places...  In other
places, I've seen

  struct type *this_ref
    = lookup_reference_type (this_type, TYPE_CODE (obj_type);

Those are equivalent, right? If so, let's use the above. It's a lot
easier/quicker to read than the ternary conditional.

> @@ -634,10 +635,11 @@ gdbpy_invoke_xmethod (const struct extension_language_defn *extlang,
>        if (!types_equal (obj_type, this_ptr))
>  	obj = value_cast (this_ptr, obj);
>      }
> -  else if (TYPE_CODE (obj_type) == TYPE_CODE_REF)
> +  else if (TYPE_IS_REFERENCE (obj_type))
>      {
> -      struct type *this_ref = lookup_lvalue_reference_type (this_type);
> -
> +      struct type *this_ref = TYPE_CODE (obj_type) == TYPE_CODE_REF 
> +                                ? lookup_lvalue_reference_type (this_type)
> +                                : lookup_rvalue_reference_type (this_type);
>        if (!types_equal (obj_type, this_ref))
>  	obj = value_cast (this_ref, obj);
>      }
> 

Likewise?

Keith