Issue 240618.2: DW_AT_rnglists_base missing

David Anderson

## BACKGROUND

References are to DWARF5 unless otherwise indicated.

If a split-full CU uses `DW_FORM_rnglistx`,
is a `DW_AT_rnglists_base` required?

Apparently not, since in cases I have seen in object files
with a single rnglist in `.debug_rnglists.dwo`
there is no `DW_AT_rnglists_base`.

The operative assumption seems to be that consumers will simply

assume size-of-rnglists-header
of the initial `.debug_rnglists.dwo` contribution

assume zero as the (missing) `DW_AT_rnglists_base`.

as the (missing) `DW_AT_rnglists_base`.

Seen in llvm and gcc.

Similarly for `.debug_loclists[.dwo]` and `DW_AT_loclists_base`.

The intent of this proposal is to get clarity.

The intent of this proposal is to allow this common
practice as correct dwarf.

An alternative version could state:

> If a Split Full Compilation Unit
> refers to `.debug_rnglists.dwo`
> with `DW_FORM_rnglistx`
> the CU DIE must have a `DW_AT_rnglists_base`
> attribute.

## PROPOSAL

At the end Sec F.1 Overview just before
Table F.1:

Section 7.28 Range List Table Following the last paragraph
before Section 7.29:

> If a Split Full Compilation Unit

 > If a Split Full Compilation Unit

> refers to `.debug_rnglists.dwo`

 > refers to `.debug_rnglists.dwo`

> with `DW_FORM_rnglistx`

 > with `DW_FORM_rnglistx`

> and the correct `DW_AT_rnglists_base`

 > and the correct `DW_AT_rnglists_base`
 > would be size-of-rnglists-header
 > of the initial contribution to
 > `.debug_rnglists.dwo`,

> would be zero, the `DW_AT_rnglists_base`

 > the `DW_AT_rnglists_base`

> may be omitted.

 > may be omitted.
 > In a dwp package file (See F.3 Package File Example)
 > a `.debug_cu_index` or `.debug_tu_index`
 > entry `DW_SECT_RNGLISTS` makes rnglists base unnecessary
 > by providing the offset of the contribution to
 >`.debug_rnglists.dwo`.

Section 7.29 Location List Table Following the last paragraph
before Section 7.30:

 > If a Split Full Compilation Unit
 > refers to `.debug_loclists.dwo`
 > with `DW_FORM_loclistx`
 > and the correct `DW_AT_loclists_base`
 > would be size-of-loclists-header
 > of the initial contribution to
 > `.debug_loclists.dwo`,
 > the `DW_AT_loclists_base`
 > may be omitted.
 > In a dwp package file (See F.3 Package File Example)
 > a `.debug_cu_index` or `.debug_tu_index`
 > entry `DW_SECT_LOCLISTS` makes loclists base unnecessary
 > by providing the offset of the contribution to
 >`.debug_loclists.dwo`.

---

2024-06-18: [Original proposal][orig].

2024-09-24: [Revised][diff1].

2025-01-11: [Revised][diff2].

2025-03-13: Withdrawn in favor of [250311.1][250311.1].

[250311.1]: https://dwarfstd.org/issues/250311.1.html

Author:	David Anderson
Champion:
Date submitted:	2024-06-18
Date revised:	2025-01-28
Date closed:	2025-03-13
Type:	Clarification
Status:	Withdrawn
DWARF version:	6