Re: [PATCH v2 9/9] gdb/python: add accessor helpers for __dict__ in Python extension objects

[Matthieu Longo <matthieu.longo@arm.com>]

On 03/03/2026 19:02, Tom Tromey wrote:
>>>>>> Matthieu Longo <matthieu.longo@arm.com> writes:
> 
>> A previous patch centralized the creation logic; this patch focuses
>> on centralizing the access to the dictionary. It introduces two new
>> macros:
> 
> Thanks.
> 
>   
>> +  #define gdbpy_dict_wrapper_PyGetSetDef(object_name)		\
>> +    {								\
>> +      "__dict__", /* name */					\
>> +      (getter) gdb_py_generic_dict_getter,			\
>> +      (setter) nullptr,						\
>> +      "The __dict__ for this " object_name ".", /* doc */	\
>> +      nullptr, /* closure */					\
>> +    }
>> +
>> +  #define gdbpy_dict_wrapper_PyTypeObject_tps				\
>> +    /*tp_getattro*/							\
>> +    gdb_py_generic_getattro,						\
>> +    /*tp_setattro*/							\
>> +    gdb_py_generic_setattro
> 
> I wouldn't indent the '#define'.  But I tend to think it would be better
> to just use constexpr functions here.
> 

For gdbpy_dict_wrapper_PyGetSetDef, I tried to use a constexpr function at first, but there is an issue.
I am not aware of an easy way to concatenate strings with a constexpr in C++17.

This code requires C++20.

   static constexpr PyGetSetDef
   configure_dict_getter (std::string_view object_name)
   {
     return {
       "__dict__", /* name */
       (getter) gdb_py_generic_dict_getter,
       (setter) nullptr,
       std::views::join (std::array {
         "The __dict__ for this "sv, object_name, "."sv
       }).data (), /* doc */
       nullptr, /* closure */
     }
   }

Please let me know if you know a way of making it compatible with C++17.

Regarding gdbpy_dict_wrapper_PyTypeObject_tps, I am not sure how to expand the array in the calling code using a constexpr function.
Please let me know if you know a solution for it.

> I'd also suggest changing the name, the "PyGetSetDef" suffix is kind of
> un-gdb-ish and anyway not really needed for a function, since this will
> be clear from the return type.
> 

If the code is convertible to C++17, configure_dict_getter seems a good name.
Otherwise, gdbpy_dict_wrapper_configure_dict_getter ?

Regarding gdbpy_dict_wrapper_PyTypeObject_tps, what about gdbpy_dict_wrapper_getsetattro ?

> You can see an example of doing this in a similar-ish context here
> 
> https://sourceware.org/pipermail/gdb-patches/2026-February/225253.html
> 
> Tom

Matthieu