Issue 260716.1: Add an example for DWARF6 vtable

Author:	Ben Woodard
Champion:
Date submitted:	2026-07-16
Date revised:
Date closed:
Type:	Clarification
Status:	Open
DWARF version:	6

Introduction

How vtables are handled in DWARF was significantly changed without an example in 250506.1, Improve Support for Finding vtables; 250506.2, Improve Support for Downcasting Objects; and 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.

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>