[Nix-dev] Questions about the all-packages fixpoint

[Benno Fünfstück]

Ok, thanks again!

>  - 0 hop: means that you are linking statically.  Any change of such
dependency would cause your package to be rebuilt.

Does this mean that when I link statically, I cannot go through self? so
the following would be wrong:

    foo = import foo.nix { bar = self.bar; }

if `foo` links statically against `bar`?

Nicolas Pierron <nicolas.b.pierron at nbp.name> schrieb am Sa., 18. März 2017
um 17:59 Uhr:

> On Sat, Mar 18, 2017 at 3:27 PM, Benno Fünfstück
> <benno.fuenfstueck at gmail.com> wrote:
> > Nicolas Pierron <nicolas.b.pierron at nbp.name> schrieb am Fr., 17. März
> 2017
> > um 22:36 Uhr:
> >>
> >> On Fri, Mar 17, 2017 at 9:38 PM, Benno Fünfstück
> >> <benno.fuenfstueck at gmail.com> wrote:
> >> > One thing that is nicer about `self.callPackage` though is that you
> can
> >> > follow the rule "whenever taking something from self does not lead
> >> > infinite
> >> > recursion, take it from self" when writing overrides.
> >>
> >> And we should not advertise that, because this would lead to packages
> >> which are not patched, under the rules of the future security-update
> >> work.
> >> So whatever you think this is simpler or not, this is incorrect, I
> >> guess we could nullify these functions in the latest layer, preventing
> >> callPackage to ever be used through `self`.
> >
> >
> > Oh, why would that lead to not applying security updates? I'm not very
> > familar with "future security-update work", but that sounds unexpected to
> > me. What's so deeply magical about security updates?
>
> The security-update branch needs to peel off the fix-point of Nixpkgs.
> Then the patching behaviour is added in-between every package by doing
> one more step of the Nixpkgs function.
> This has the consequences of giving the following semantic to the
> numbers of hops that you use to fetch the dependencies:
>  - 0 hop: means that you are linking statically.  Any change of such
> dependency would cause your package to be rebuilt.
>  - 1 hop: means that you are linking dynamically. Any change of such
> dependency would cause your package to be patched.
>  - >1 hops: means nothing. Any change of such dependency would leave
> your package to be unchanged.
>
> Going through `self` is adding hops.  If you were to call
> `self.callPackage` instead of `super.callPackage`, you would have 2
> hops instead of 1 hop, because callPackage generate attribute set out
> of `self`.
>
> --
> Nicolas Pierron
> http://www.linkedin.com/in/nicolasbpierron - http://nbp.name/
>
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