On Friday 2011-12-30 12:48, Pablo Neira Ayuso wrote:
>On Fri, Dec 30, 2011 at 02:46:33AM +0100, Jan Engelhardt wrote:
>> This is mostly cosmetic, as using a libxtables.so with a too old
>> libiptc should now say something about "version symbol LIBIP4TC_1.4.13
>> required" (or so) instead of just "unknown symbol: iptc_ops".
>
>I think this can be done much simpler. You can with the current symbol
>list by the iptables version that includes the first symbol map.
>[...]
>Old iptables binaries will not benefit for such fine definition that
>you're proposing.
I know, though it seemed like having it differentiated out is an
interesting piece of documentation of history :)
>Moreover, I remember to have read that once you start using symbol
>maps, you only bump the revision field of the c:r:a library version
>numbers.
>I looked into this time ago (and I'm telling you by heart), so please
>correct me if I'm wrong.
This is a two-part consideration.
1.
I do not see a big practical value in the R field and therefore do
not care to change it for my projects. It perhaps tells you that
something changed, but distro tools will of course clean up
.so.12.3.4 if you install a new libfoo when it ships .so.12.3.5,
and all the symlinks point to .so.12.3.5 then as well.
Consider so.12.3.5 misbehaving. Changing the .so.12/.so.12.3 symlink
has no effect, since ldconfig will usually pick the newest version,
which is still so.12.3.5. Therefore, people will do a distro-assisted
downgrade or just remove 12.3.5 from their libdir rather than trying
to fiddle export LD_PRELOAD=libfoo.so.12.3.4 into their environment.
So I find R rather useless. libc.so also does not care about it
either :)
>Moreover, I remember to have read that once you start using symbol
>maps, you only bump the revision field of the c:r:a library version
>numbers.
2.
Symbol maps are a means to have more than one {function
implementation with the same name} to coexist, thereby making it
possible to avoid having to delete an ABI revision that would
otherwise be necessary, provided that you can keep the ABI for all
existing symbols.
But one still needs to do C::A housekeeping, because deletion of old
ABIs - if you do get around to do it someday - still demands
adjusting C,A.
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