Gentoo Archives: gentoo-dev

From: Tom Wijsman <TomWij@g.o>
To: axs@g.o
Cc: gentoo-dev@l.g.o
Subject: Re: [gentoo-dev] Dependencies default to accept any slot value acceptable (:*), can we default to :0 instead?
Date: Tue, 10 Dec 2013 23:36:51
Message-Id: 20131211003500.652e58c9@TOMWIJ-GENTOO
In Reply to: Re: [gentoo-dev] Dependencies default to accept any slot value acceptable (:*), can we default to :0 instead? by Ian Stakenvicius
2 Hash: SHA1
4 On Tue, 10 Dec 2013 16:06:51 -0500
5 Ian Stakenvicius <axs@g.o> wrote:
7 > SLOT allows multiple versions of a package to be installed
8 > concurrently. In the case of libraries or dependencies, this supports
9 > the specific case where certain ebuilds only support a particular
10 > SLOT. However, that doesn't mean that all packages need to be tied to
11 > one slot or another.
13 This discussion results in no change for the above paragraph; it will
14 still allow multiple versions to be installed, packages can still be
15 tied to multiple slots by specifying :*.
17 We're kind of discussion a problem here we don't know the answer to;
18 because in order to obtain numbers, we have to enumerate everything to
19 see how slots are being used. And only then we can determine that X%
20 would depend on a specific :${SLOT} and that (100-X)% would depend
21 on :*; the comparison here is what would suggest the default.
23 In another part in this thread we went looking for packages that
24 have multiple slots to judge; but, it comes to mind now that we might
25 want to look at the opposite which might be easier to study:
27 "What if we create multiple slots for libraries that have none?"
29 In order to do so, it again depends on how slots are being used:
31 "Why is a new slot made?"
33 One argument is "side-by-side install", another argument is "API
34 breakage" (eg. dev-java); some might only pick one argument or the
35 other, though what jumps to mind is that having the need for a
36 side-by-side install is the consequence of API breakage. Leading to:
38 "Do we create a new package or a new slot?"
40 It looks cleaner to me to have slots; because if you look at what a
41 "package" means, API breakages or major versions do not necessarily
42 mean it is a new package (depending on the way you look at it).
44 > It should be noted here that this discussion is revolving entirely
45 > around multi-SLOT libraries.
47 Anything that fits a dependency relationship, thus almost entirely; as
48 shown in the other thread with those numbers there are some applications
49 that are also used as a dependency, that don't have to be a library.
51 > Firstly, there are packages like
52 > dev-db/postgresql that use SLOTs not just for library provision.
54 True, but I think we should look at the Portage tree at a wider scale
55 than bring up single examples; I think we have an example for multiple
56 variations, but how do we reflect the majority in the Portage tree?
58 > Secondly, SLOT= on the libraries being discussed may not actually be
59 > the correct method to deal with this at all, and rather, these libs
60 > should be using a subslot and the rdeps be using an upper-bound
61 > version on dependency atoms to limit which dependency it can be used
62 > with--it all depends on whether the library maintainer intends to
63 > support both major versions in the long term or not.
65 There are some varying thoughts wrt SLOT= here and there; looking at
66 what the devmanual says [1], it mentions: "Packages can support having
67 multiple versions installed simultaneously. This is useful for
68 libraries which may have changed interfaces between versions."
70 It almost seems as if it the combination of those both is the only
71 reason for the usage of SLOT= in the context of dependencies and/or
72 libraries. In this context, are there others one can think of?
74 That same page of the devmanual covers sub slots, it says [1]:
75 "Sometimes a package installs a library that changes interfaces between
76 versions, but it's undesirable or inconvenient to allow some of these
77 versions to be installed simultaneously. "
79 What is written here is different than our context; because we're
80 trying to have multiple slots here, and sub slots do the opposite.
82 [1]:
84 - --
85 With kind regards,
87 Tom Wijsman (TomWij)
88 Gentoo Developer
90 E-mail address : TomWij@g.o
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