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170427.2 Alexandre Oliva Extending loclists Enhancement Open


Section 6.2, pg. 149-160.  

This proposal introduces an extension mechanism to loclists, that can
be used to share location list fragments among multiple location
lists, and to experiment with extensions to location list standards in
a way that does not break backward compatibility and that enables the
experimental extensions to be welcomed into the standard without
encoding changes.


In Section 2.6.2:

  * List extension.  This kind of entry extends a location list with
    entries from another loclist.  It can be used to share list
    entries among multiple lists, and also to extend location lists
    with nonstandard entry kinds, in a way that will be disregarded by
    debug information consumers that do not support the extensions.

In Section 2.6.2, page 44, add to 1. DW_LLE_end_of_list:

  Any non-standard entry kind may be interpreted as a
  DW_LLE_end_of_list entry.

  2. DW_LLE_extend_loclistx

  This is a form of list extension, that has one unsigned LEB128
  operand.  The value is an index into the .debug_loclists section,
  like the operand of a DW_FORM_loclistx loclist.  The contents of the
  location identified by the index are added to the base to determine
  the address of the first entry of a loclist whose entries are to be
  regarded as part of the loclist containing the list extension entry.

In Section 2.6.2, page 45, add after 9. DW_LLE_start_length:

  10. DW_LLE_extend_loclist

  This is a form of list extension, that has one offset operand.  The
  value is an offset into the .debug_loclists section, like the
  operand of a DW_FORM_sec_offset loclist.  The offset identifies the
  first entry of a loclist whose entries are to be regarded as part of
  the loclist containing the list extension entry.

In Section 7.7.3, add to Table 7.10:

  DW_LLE_extend_loclist  | 0x0A
  DW_LLE_extend_loclistx | 0x0B


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