On Sat, Feb 26, 2011 at 10:39:51AM -0800, Steve Langasek wrote: > On Wed, Feb 23, 2011 at 05:52:27PM +0100, Cyril Brulebois wrote: > > > Tiny question: you say it eases backports. But then backports get > > autobuilt on debian buildds, so will likely use the same set of > > packages as say unstable, if build-depends aren't changed specifically > > for the backports. So I'm not exactly sure it actually eases anything. > > The one aspect of the current buildd behavior not addressed here is that the > autobuilders will only *consider* the first alternative build-dep for > *installation*; but if at the end of b-d installation the full build-dep > relationship is satisfied because a different package was pulled in (or > previously installed) that satisfies one of the other alternatives, the > build dependencies of the package as a whole are considered satisfied. > > This was touched on briefly in <20110223115755.GM31726@codelibre.net> on > debian-devel. Yes, this is a very good point. None of the resolvers do a good job at enforcing things post-installation (historically). And dpkg-buildpackage will also consider all alternatives when checking they are satisfied as well. I think that one recent change does enforce this, however. Previously, the internal resolver would just pick the first alternative, and then do the necessary package installation/removal to satisfy things, but would not subsequently enforce things. The new dependency package support in the apt and aptitude resolvers /will/ enforce the first-only alternatives installation. This is because the arch-reduced, first-only alternatives are in the Depends: of the dependency package. The other alternatives are not present in the Depends: at all (unless you enable it). Thus, the other alternatives aren't considered, and because the dependency package is installed for the duration of the build, we are enforcing installation of the first-only alternatives under all circumstances, even when the build-deps could be satisfied through other alternatives. Note this isn't yet in use on the buildds, but it is present in the unstable sbuild. Regards, Roger -- .''`. Roger Leigh : :' : Debian GNU/Linux http://people.debian.org/~rleigh/ `. `' Printing on GNU/Linux? http://gutenprint.sourceforge.net/ `- GPG Public Key: 0x25BFB848 Please GPG sign your mail.
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