# DW_AT_object_pointer: clarify wording around implicit versus explicit object parameters
## Background With C++23 we got the ability to explicitly spell out in source the object parameter of a class method [1]. The object parameter for such methods is not compiler-generated and is explicitly named by the user. The wording of the current DWARF spec assumes object parameters are implicit and specifies that those parameters be marked DW_AT_artificial, despite them not falling into the category for "artificial" parameters. Other examples of languages with explicit object parameters are Python and Rust. Recently Clang started emitting DW_AT_object_pointer for explicit object parameters but decided not to mark them artificial [2][3]. ## Overview This proposal adjusts the wording in the DWARF spec to clarify that explicit DW_AT_object_parameter's might not be marked DW_AT_artificial. ## Proposed Changes In chapter "5.7.8 Member Function Entries", change the mention of `DW_AT_artificial` in the last sentence as follows: [ORIGINAL TEXT] >>>>>>>>>>>>>>> If the member function entry describes a non-static member function, then that entry has a DW_AT_object_pointer attribute whose value is a reference to the formal parameter entry that corresponds to the object for which the function is called. The name attribute of that formal parameter is defined by the current language (for example, this for C++ or self for Objective C and some other languages). That parameter also has a DW_AT_artificial attribute whose value is true. [NEW TEXT] ========== If the member function entry describes a non-static member function, then that entry has a DW_AT_object_pointer attribute whose value is a reference to the formal parameter entry that corresponds to the object for which the function is called. The name attribute of that formal parameter is defined by the current language (for example, this for C++ or self for Objective C and some other languages). Many languages make the object pointer an implicit parameter with no syntax. In that case the parameter should have a DW_AT_artificial attribute whose value is true. <<<<<<<<<<<<<<< Alternatively we could just omit any mention of DW_AT_artificial. And we might want to add some informative text about C++23's explicit object parameters. ## References * [1]: https://en.cppreference.com/w/cpp/language/member_functions#Explicit_object_member_functions * [2]: https://github.com/llvm/llvm-project/pull/122897 * [3]: https://github.com/llvm/llvm-project/pull/122928 -- Dwarf-discuss mailing list Dwarf-discuss@lists.dwarfstd.org https://lists.dwarfstd.org/mailman/listinfo/dwarf-discuss
