On Thu, 11 Aug 2011 08:54:54 +0200 Fabio Erculiani <lx...@gentoo.org> wrote: > >> I've intermittently spent my last two days trying to figure out a > >> weird bug on Entropy dependency resolution algorithm (which is > >> actually just a simple topological sorting out of a digraph) > > > > You can't use a naive topological sort to do dependency resolution. > > RDEPEND-RDEPEND cycles are legal and common. > > Yes, they're legal and common but they can likely generate build > failures.
They're also necessary to support if you want to handle 'system' correctly. Something I made a while back (and being careful to keep X out of system, since usually it's in there): http://dev.exherbo.org/~ciaranm/resolution-neato.png All the orange packages depend upon all the other orange packages. > Given your definition of PDEPEND, jdom stuff should get fixed. No > matter what Portage/Paludis quirks do. Yup. > > Purely as a quality of implementation issue, scheduling a PDEPEND > > reasonably soon after (or even before) the package requiring it may > > be a good idea, simply because users may get confused if when they > > try to install a bunch of things and one of those things gets > > installed long before related packages. But you can't rely upon > > that happening. > > But since this can lead to failures, the correct behaviour must get > defined by PMS. Otherwise everybody will go implementing schedulers as > they like most. There is no single correct behaviour. Any ordering that meets the rules specified in PMS is correct. > > (Incidentally, one could also argue that package manglers should > > always try to come up with the most perverse legal ordering > > possible for any situation. That way bugs will be identified much > > more quickly. Part of the problem with Portage is that it has so > > many tricks and so little error checking that broken things quite > > often appear to work.) > > Bad design is bad design. And there is no excuse. > My feeling is that since Portage is actually able to figure out the > correct order by just using tricks like the "ASAP", and even though > PMS doesn't say anything about that, the issue is considered minor. > I would rather see PMS clarify the correct behaviour of schedulers > with respect to PDEPEND. Forced ASAP is logically inconsistent. ASAP only *sometimes* works, and it can't be relied upon. If a package only works with ASAP, it's broken, both by the spec and by Portage under certain circumstances. -- Ciaran McCreesh
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