Re: [gentoo-user] revdep-rebuild vs. @preserved-rebuild [was: Kmplayer, video and audio not syncing.]

["Jesús Guerrero" <i92guboj@terra.es>]

On Mon, 2 Nov 2009 16:12:49 +0200, Alan McKinnon <alan.mckinnon@gmail.com>
wrote:
> On Monday 02 November 2009 15:58:57 Jesús Guerrero wrote:
>> On Mon, 2 Nov 2009 13:25:08 +0000, Neil Bothwick <neil@digimed.co.uk>
>> 
>> wrote:
>> > On Mon, 02 Nov 2009 13:58:03 +0100, Jesús Guerrero wrote:
>> >> @preserved-rebuild never worked for me, maybe it's just that it
>> >> doesn't
>> >> like ~arch. I am just too lazy to work on how to fix a thing when
>> >> there's an alternative that always worked reliably, revdep-rebuild.
>> >
>> > If it didn't work on ~arch, how would it ever make it into arch?
>> 
>> I am not the one to answer that, all I can say is that the few times
I've
>> tried it, it kept rebuilding the same  packages again, and again, and
>> again
>> ad infinitum, as said, I didn't even bother to find what the problem
was,
>> because I have a working alternative. Sure it could be better, but that
>> hasn't been the case for me with @preserved-rebuild.
>> 
>> I've seen people reporting the same problems in the forums, so I am
>> fairly
>> sure that's a common problem and not just exclusive to my
installations.
>> 
>> > The trouble with revdep-rebuild is that you have to break your system
>> 
>> and
>> 
>> > then fix it. Most of the time this is trivial, but updates like
>> 
>> expat-2.0
>> 
>> > showed the usefulness of being able to recompile the packages before
>> 
>> they
>> 
>> > were broken.
>> 
>> I can't understand that. You CAN'T recompile your packages against the
>> new
>> ABI's until the new ABI is in your system, and hence your system is
>> already
>> broken. There's no preemptive measure against this. Both methods fix
the
>> system *after* it's broken.
> 
> Unless the old and the new ABI version are installed side by side. When 
> @preserved-rebuild is run, it deletes the old libs only after everything
> left 
> that used it is now linked against the new one.
 
Thanks for the feedback. However there's one thing I can't understand:
whether the libraries are kept of removed is decided at the merge time,
isn't it? So, whatever breaks, breaks when using "emerge" to update the
offending library, the one that will break the ABI. So, how can using a
tool *after that* have any impact over what's broken? It can fix the
problem, but so can revdep-rebuild.

I mean: if the old libs with the old abi's are kept, how it is relevant if
you are using @preserved-rebuild, revdep-rebuild or another method, or none
at all? Your programs will continue to work ok without needing to rebuild
anything, won't them? And after rebuilding the package it's irrelevant
*how* did you rebuild them... I must obviously be missing something here,
if you have the time please, direct me to an adequate source of information
or explain a bit, I am curious.


> There's only one case where this can't work - the developer changes the
> ABI 
> and does not change the .so version number. That ain't gentoo's fault -
> shoot 
> the developer.

Of course, I can understand that.

However and even if @preserved-rebuild has some reason to exist, it still
doesn't fix the weird behavior that it exhibited for me in the past. But to
tell the truth, I haven't tested lately. It just came to mi mind because of
the Dale's problem, which seems to be the same one. Please, understand that
I'm not complaining, merely describing my experience, I'd rather be filling
bugs than complain uselessly, it's just that -as I said- I really didn't
see a need to because the old way just works.

-- 
Jesús Guerrero