Issue 200505.4: Augmentation string
Section 6.1.1.4.1, pg 144
The very unusual augmentation string needs some
elaboration for clarity.
Here is the full original DWARF5 wording on page 144, Sec 6.1.1.4.1
As a whole it clearly presents a non-null-terminated
string with the odd aspect of possible null-bytes.
So neither a standard length-known string nor a null-terminated
string.
Because a non-null terminated string whose length field
may cover null-bytes after the non-null bytes is so unusual in
the DWARF context a few words should be added (see below).
Problem: the original text is not precise (what does it mean
by 'character', given it implies ASCII but does not say so?)
and calling it 'string' leads to confusion because it does not
quite fit the dwarf standard definition of a 'string'. The
original allowance of multi-byte (UTF-8) characters in the
vendor id initial four characters seems unnecessary.
Originally the two section header fields numbered 10 and 11
referred to 'string' Ron B. and David A. considered 'block'
but settled on 'sequence'.
We propose this as an appropriate replacement for the DWARF5
text. All instances of 'string' in the original text of 10.
and 11. have been removed or replaced (depending on context).
ASCII DWARF5 content remains valid with this wording and we
believe this is sufficiently precise. For example, LLVM's
DWARF5 interpretation remains valid with the wording proposed below.
================original text
page 144:
10. augmentation_string_size (uword)
The size in bytes of the augmentation string. This value must be
a multiple of four, possibly zero.
.
11. Augmentation...
A vendor-specific sequence of bytes, which
provides additional information about the
contents of this index. If provided, the sequence
begins with four bytes which serve
as a vendor ID. The remainder of the sequence is
meant to be read by a cooperating consumer,
and its contents and interpretation are not
specified here. The augmentation is a multiple
of four bytes in length.
*The presence of an unrecognized augmentation
does not make it impossible for a consumer to
process data in the .debug_names section. The
augmentation only provides hints to the
consumer regarding the completeness of the
set of names in the index.*
--
2021-03-14: Updated.
2021-10-18: Accepted.
2022-03-20: Reopened.
2022-03-26: Revised.
Previous version: http://dwarfstd.org/issues/200505.4-1.html
2022-05-16: Revised to replace 'character' with 'string of bytes'.
2022-05-16: Accepted.
