Issue 220724.1: Remove .debug_aranges and require unit-level ranges/high/low
| Author: | David Blaikie |
|---|---|
| Champion: | David Blaikie |
| Date submitted: | 2022-07-24 |
| Date revised: | 2023-04-18 |
| Date closed: | |
| Type: | Improvement |
| Status: | Accepted pending revised wording |
| DWARF Version: | 6 |
Section 6.1.2, pg 147
Given a discussion on dwarf-discuss (mailing lists down at the moment, so I
can't include a link) and Clang's experience with debug_aranges being disabled
by default for the better part of a decade at this point, I'd propose removing
them from the DWARF standard in favor of adding a guarantee that CU DIEs must
(rather than may) include a comprehensive address range (DW_AT_high/low_pc) or
list of ranges (DW_AT_ranges). This reduces redundancy in DWARF — reducing
debug info size and implementation complexity (having to support reading data
from multiple/varied locations — aranges or CU DIE ranges).
Proposed solution
Remove section 6.1.2 and 7.21 and all other references to .debug_aranges.
The index lists the following references to .debug_aranges: 147, 184, 186,
187, 197, 235, 274, 275, 278, 279, 366, 371, 393, 394, 399–401, 416 - these
seem to generally be easy to remove/an editorial matter of removing a
reference from a list of examples/descriptions. (I can enumerate them all
explicitly if desired.)
Edit 3.1.1, p61 from:
A full or partial compilation unit entry may have the following attributes:
1. Either a
DW_AT_low_pcandDW_AT_high_pcpair of attributes or aDW_AT_rangesattribute whose values encode the contiguous or non-contiguous address ranges, respectively, of the machine instructions generated for the compilation unit (see Section 2.17 on page 51).A
DW_AT_low_pcattribute may also be specified in ...
to:
A full or partial compilation unit entry must have either a
DW_AT_low_pcandDW_AT_high_pcpair of attributes or aDW_AT_rangesattribute whose values encode the contiguous or non-contiguous address ranges, respectively, of the machine instructions generated from the compilation unit (see Section 2.17 on page 61).A full or partial compilation unit entry may have the following attributes:
1. A
DW_AT_low_pcattribute may be specified in ...
On p67, bullet 2 should be moved above the immediately preceding non-bullet text, before line 13 (thereby making it required), and revised as follows:
2. Either a
DW_AT_low_pcandDW_AT_high_pcpair of attributes or aDW_AT_rangesattribute whose values encode the contiguous or non-contiguous address ranges, respectively, of the machine instructions and static data generated for the compilation unit (see Section 2.17 and page 61).
2023-04-18: Revised.
2023-05-15: Accepted pending revised wording.
