# Add an example for DWARF6 vtable

## Introduction

How vtables are handled in DWARF was significantly changed
without an example in [250506.1][250506.1], Improve Support for Finding
vtables; [250506.2][250506.2], Improve Support for Downcasting Objects; and
[250506.3][250506.3], Replace `DW_AT_vtable_elem_location` Attribute with
`DW_AT_vtable_elem_index`. One of the reasons for this change was
that current compilers had not iomplemented DWARF5 correctly. To
prevent future confusion during the DWARF6 implementation phase,
we propose adding an example.

[250506.1]: https://dwarfstd.org/issues/250506.1.html
[250506.2]: https://dwarfstd.org/issues/250506.2.html
[250506.3]: https://dwarfstd.org/issues/250506.3.html

## Proposal

Add a new example to Appendix D.

> D.n Virtual Table Example
> 
> Consider the C++ class with a virtual table in Figure D.x
> 
>     class MyClass {
>     public:
>         virtual void doSomething();
>         int myData; // 4 bytes
>     };
> 
> A DWARF representation for this example, with many details elided, is
> shown in Figure D.y
> 
>     DW_TAG_class_type
>         DW_AT_name        : "MyClass"
>         DW_AT_byte_size   : 16
>         DW_AT_vtable_location: (DW_OP_deref)
>  
>         DW_TAG_member
>             DW_AT_name        : "myData"
>             DW_AT_type        : <Reference to 'int' type>
>             DW_AT_data_member_location: 8
>  
>         DW_TAG_subprogram
>             DW_AT_name        : "doSomething"
>             DW_AT_virtuality  : DW_VIRTUALITY_virtual
>             DW_AT_vtable_elem_index: 0
>             DW_AT_declaration : 1
>  
>     DW_TAG_vtable
>         DW_AT_artificial     : 1
>         DW_AT_location       : <Address of the vtable>
>         DW_AT_vtable_for_type: <reference to MyClass class>