Re: [gentoo-dev] Council meeting 19 April 2010

[Ciaran McCreesh <ciaran.mccreesh@googlemail.com>]

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On Thu, 08 Apr 2010 16:08:57 +0200
Patrick Lauer <patrick@gentoo.org> wrote:
> > Please detail your cycle breaking algorithm that works in such a way
> > that it's guaranteed not to toggle flags that will break a system,
> > but that does not require any changes to be made to ebuilds etc
> > telling the package manager what those flags are.
> > 
> That would violate the Entscheidungsproblem.
> 
> But why would you make the cycle breaking depend on an oracle? Once we
> have the method in place we can find the two special cases and think
> of ways to fix them.

The problem is, the special cases where it goes horribly wrong aren't
rare. As soon as you start looking for cycles, you find flags like
'build', 'bootstrap' and 'acl'.

> Abandoning the idea as a whole just because there may be a corner
> case that isn't as easy appears quite silly to me.

I'm not after abandoning the idea. I'm after doing it properly, and
doing it properly starts by handling the problematic cases rather than
pretending they don't exist.

We've already seen repeatedly what goes wrong when you start with the
assumption "it'll probably work" and then pile on special exceptions
every time someone gets screwed over by something you didn't think of.
Why don't we go with "we'll only do it for things where we know it'll
work" instead this time?

-- 
Ciaran McCreesh

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