https://sourceware.org/bugzilla/show_bug.cgi?id=33577
--- Comment #5 from Ali Bahrami <ali_swbugzilla at emvision dot com> ---
I don't think this is specifically a Solaris issue, but rather,
just one that was noticed on Solaris by virtue of comparing objects
from the two link-editors.
My understanding of versioning:
- Versioned symbols defined by the object (definitions) are associated
with a VERDEF record.
- Versioned symbols that are defined externally by some other object
(references) are associated with a VERNEED record.
- Symbols that are not versioned are given version index 0. These can
be either definitions, or external references.
- The BASE version, which has index 1, is the version that holds the
symbols defined by the object itself, that have not otherwise been
assigned to a different version, possibly with a linker script.
By convention, the version is given the SONAME of the object. This
is a VERDEF, so external references don't belong here.
- Named versions, first VERDEF, and then VERNEED, are given indexes
starting at 2.
So in this example, we have the following versions:
% elfdump -v a.out
Version Definition Section: .gnu.version_d
index version dependency
[1] a.out [ BASE ]
[2] VERS_1
Version Needed Section: .gnu.version_r
index file version
[3] libc.so.1 SUNW_0.7
Or summarizing:
[0] Not versioned
[1] BASE definitions
[2] Definitions assigned to version VERS_1 by the linker script
[3] External Symbols identified as coming from version SUNW_0.7 in libc
The problem then, is that show_undef_weak is an external reference,
not a definition, so it should not be assigned to any VERDEF (BASE,
or otherwise). The valid options would be version index 0 (not versioned),
or the index of a VERNEED record.
As you pointed out earlier, we have no information that would identify
such a VERNEED. The source of this symbol, if it even exists, is
completely unknown to the link-edit, so it has no version, and version
index 0 is the appropriate assignment for it.
I believe that these details are the same on Solaris as on GNU. I also
don't think it's causing any known problems today, as the example is
artificial, and the approach using a weak symbol is poor. It's just
something that was noticed while testing.
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