Re: [gentoo-user] downgrading gcc

[Alan McKinnon <alan.mckinnon@gmail.com>]

On Monday 20 April 2009 09:30:56 Dale wrote:
> That said, it has worked well for me.  Everything on my rig is working
> again.  If he has to do this downgrade of gcc, then a emerge -e world
> and everything works again, I'm going to really wonder what the deal is
> with gcc.  Just me running into problems is one thing but to have
> someone else have issues as well, that's makes me wonder.  Is there
> something funny going on that only affects certain hardware or something
> like that?  How would one test it to see what is wrong when it is only a
> couple or a few people?

It's more likely a compatibility issue between very specific modules or bits 
of code that affect lots of systems. Take for example this elog from the 
nvidia drivers:

===
This ebuild installs a kernel module and X driver. Both must
match explicitly in their version. This means, if you restart
X, you most modprobe -r nvidia before starting it back up
===

The interfaces that these things use have never been guaranteed to be stable, 
and gcc itself is free (within reason) to lay things out in memory anyway it 
sees fit. You get the same thing with X and it's drivers too. It makes sense - 
a server and it's drivers should all be part of the same release series and be 
built together with the same toolchain for best results.

You DON'T get this problem with normal packages. You can upgrade and downgrade 
cairo all day long if you want and firefox won't care - the API it uses is 
stable and doesn't change.

In your case and Mark's, you tried to downgrade something critical but have no 
information about what you should be downgrading to. When you synced portage, 
you lost the information about what was the latest arch and ~arch versions. 
Upgrade is easy - "emerge latest <arch> for everything, we know it works", but 
portage doesn't offer a rollback function so downgrade is much harder. Once 
someone has figured out $LIST, you can "emerge $LIST" and life is good, but 
you don't have $LIST yet.

Logic tells me you had two problems, and gcc is neither of them. Your box does 
not like latest X for whatever reason (problem 1) but you can't rollback to 
the last working version of everything involved as you don't know what it is 
(problem 2).

So when all other efforts have failed, downgrade gcc and rebuild everything is 
very likely to fix those problems.

-- 
alan dot mckinnon at gmail dot com