On Thu, Mar 20, 2008 at 02:07:46AM +0100, Daniel Hahler wrote:
> Package: apt
> Version: 0.7.11
> Severity: wishlist
> Tags: patch
>
> When installing a package A, which depends on a virtual package V, apt
> uses the first package, which provides "V".
>
> Imagine that "V" gets provided by M and N, where M depends on M1 and N
> on N1. N1 is already installed, but M1 isn't.
>
> Now, installing A will also install M and M1, while it would be better
> to install N only.
>
> At least that was what I was expecting and this seems to be the reason
> for a bug in Ubuntu, where installing virtualbox-ose on a system with
> "generic" kernel pulls in the 386 kernel.
> See https://launchpad.net/bugs/188579 for more details.
>
> I've looked at the source and started hacking around (without much C++
> knowledge at hand).
>
> What I came up with, was the following:
> In pkgDepCache::MarkInstall, instead of using the first candidate (in
> case of provides), run MarkInstall on all of them (recursively) and use
> the version where iInstCount changes the least.
> The missing part in my patch is to really revert the pkgCache; I have no
> idea how to do this properly and since this whole approach might be
> wrong, I'd like to only propose this.
Trying this with the python module for apt, using markDelete has not removed every package again.
>
> Please consider adding this feature/functionality/idea.
>
>
> btw: do you have any suggestion about fixing the particular
> virtualbox-ose issue mentioned above?
> Apart from moving the modules into the general "kernel modules" package, I
> only see the fallback of making the "Depends" and "Recommends" again.
>
>
> I hope that the feature suggestion makes any sense and that you can help
> me to work around/fix it for apt currents behavior.
>
> Thank you.
I think that this is a bit too heavy and would take to long to finish. Instead, I would suggest to use the behavior I suggested in
Bug#473247: When trying to satisfy a dependency on a virtual package, prefer the providing package with the higher priority
(http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=473247)
and let apt handle kernel modules in a special way, i.e. installing the module for the current kernel.
Your way should also be added, but disabled by default and given an option like Apt::ResolutionStrategy 0 for the current behavior, 1 for my
suggestion (and set 1 as default) and 2 for your suggestion.
And if one uses 2, we should still compare first with my mode, than your mode, and then classical mode.
1. Install with higher priority
2. Install package with less dependencies (if priorities are equal)
3. Install first package (if number of dependencies is equal)
This should give use the fastest mode. and remember, the package with the higher priority is much more likely to pull in less dependencies than the
other package. My mode is also used in debimg's (http://wiki.debian.org/DebImg | http://jak-linux.org/projects/debimg/) dependency resolver.
> diff -Nur apt-0.7.11.orig/apt-pkg/depcache.cc apt-0.7.11/apt-pkg/depcache.cc
> --- apt-0.7.11.orig/apt-pkg/depcache.cc 2007-07-28 17:24:10.000000000 +0200
> +++ apt-0.7.11/apt-pkg/depcache.cc 2008-03-20 02:06:04.976191209 +0100
> @@ -958,18 +958,34 @@
> if (InstPkg.end() == true)
> {
> pkgPrioSortList(*Cache,Cur);
> + std::clog << "Searching for best resolution of " << Pkg.Name() << "..." << std::endl;
> + int iBestInstCount = -1;
> +
> for (; *Cur != 0; Cur++)
> {
> PkgIterator Pkg(*Cache,Cache->PkgP + (*Cur)->ParentPkg);
> if (PkgState[Pkg->ID].CandidateVer != *Cur)
> continue;
> +
> + std::clog << "DEBUG: Temp install of " << Pkg.Name() << ", depth " << Depth << std::endl;
> +
> + int iInstCountBefore = iInstCount;
> + MarkInstall(Pkg,true,0,false);
> + int iInstCountNew = iInstCount - iInstCountBefore;
> +
> + std::clog << "DEBUG: Number of new packages for " << Pkg.Name() << ": " << iInstCountNew << std::endl;
> + if (iInstCountNew > iBestInstCount)
> + {
> InstPkg = Pkg;
> - break;
> + iBestInstCount = iInstCountNew;
> + }
> + MarkDelete(Pkg); // FIXME: does not remove "depends of depend"!
> }
> }
>
> if (InstPkg.end() == false)
> {
> + std::clog << "InstPkg: " << InstPkg.Name() << std::endl;
> if(_config->FindB("Debug::pkgDepCache::AutoInstall",false) == true)
> std::clog << "Installing " << InstPkg.Name()
> << " as dep of " << Pkg.Name()
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