Contents of /xml/htdocs/proj/en/glep/glep-0022.txt

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1 g2boojum 1.1 GLEP: 22
2     Title: New "keyword" system to incorporate various userlands/kernels/archs
3 g2boojum 1.5 Version: $Revision: 1.4 $
4     Last-Modified: $Date: 2004/06/06 00:41:40 $
5 g2boojum 1.1 Author: Grant Goodyear <g2boojum@gentoo.org>
6 g2boojum 1.3 Status: Draft
7 g2boojum 1.1 Type: Standards Track
8     Content-Type: text/x-rst
9     Created: 6-Mar-2004
10 g2boojum 1.5 Post-History: 6-Mar-2004, 5-Jun-2004, 20-Jul-2004
11 g2boojum 1.1
12 g2boojum 1.2 Status
13     ======
15 g2boojum 1.3 After withdrawing this GLEP temporarily, a rewritten version has
16     now been resubmitted. This version no longer tries to prevent a
17     keyword explosion, but merely tries to make it manageable.
18 g2boojum 1.2
19 g2boojum 1.5 This version was approved on 14-Jun-2004, with the amendment that cascading
20     profiles should be used.
22 g2boojum 1.1 Credits
23     =======
25 g2boojum 1.3 This GLEP originated from the concerns that Daniel Robbins had with the
26     *x86obsd* keyword, and his desire to make the KEYWORDS variable more
27     "feature-rich". Drobbins' original idea was that we should allow compound
28 g2boojum 1.1 keywords such as gnu/x86, gnu/ppc, and macos/ppc (which would be explicit
29     versions of the more familiar x86, ppc, and macos keywords). Method noted
30 g2boojum 1.3 that userland/arch failed to capture the full range of possibilities (what
31     about a GNU userland on a BSD kernel+libc?), and the issue has languished due
32     to a lack of reasonable solutions. The original version of this GLEP
33     generated quite useful comments which hopefully have been addressed here to
34     make the GLEP much more reasonable.
35 g2boojum 1.1
36     Abstract
37     ========
39 g2boojum 1.3 As Gentoo branches out to support non-Linux and non-GNU systems (such as Hurd,
40     the \*BSDs, or even the soon-to-be-open-sourced Solaris), the potential for an
41     "explosion" of possible keywords becomes rather large, since each new
42     userland/kernel/arch/whatever combination will require a new keyword. This
43     GLEP proposes a simple extension to the current KEYWORDS variable that
44     encompasses the four parameters ARCH, USERLAND, KERNEL, and LIBC, but uses
45     sensible defaults to keep the new system manageable.
46 g2boojum 1.1
47     Motivation
48     ==========
50     Since the beginning, Gentoo Linux has been conceived as a "metadistribution"
51     that combines remarkable flexibility with sensible defaults and exceptional
52     maintainablilty. The goal of the Gentoo-Alt_ project has been to extend that
53     flexibility to include systems other than GNU/Linux. For example, the author
54 g2boojum 1.3 of this GLEP has been working to create a version_ of Gentoo that uses
55     OpenBSD_ as the underlying kernel, userland, and libc. OpenBSD_ supports a
56     variety of different architectures, so, in principle, we would need a new
57     *openbsd-arch* keyword for each supported architecture. In fact, the
58     situation is even more complicated, because the Gentoo-Alt_ project would
59     eventually like to support the option of "mixing-and-matching"
60     GNU/\*BSD/whatever userlands and libcs irrespective of the underlying kernel.
61     (Debian_, for example has a similar BSD project_, except that they have
62     replaced the BSD userland with a GNU userland.) The net result is that we
63     need keywords that can specify all possible permutations of arch,
64     userland, kernel and libc. A systematic nomenclature is needed.
65     Fortunately, the author is a Chemist. *Grin*
66 g2boojum 1.1
67     .. _Gentoo-Alt: http://www.gentoo.org/proj/en/gentoo-alt/index.xml
68     .. _OpenBSD: http://www.openbsd.com
69     .. _version: http://www.gentoo.org/proj/en/gentoo-alt/bsd/index.xml
70     .. _Debian: http://www.debian.org
71     .. _project: http://www.debian.org/ports/netbsd/
73     Specification
74     =============
76 g2boojum 1.3 Keyword Fragments
77     -----------------
78 g2boojum 1.1
79 g2boojum 1.3 Each keyword needs to specify, either explicitly or
80     implicitly, the following parameters: ARCH, USERLAND, LIBC, and KERNEL.
81 g2boojum 1.1
82     ARCH:
83     x86, amd64, cobalt, mips64, arm, hppa, ia64, ppc64, sparc
84     USERLAND:
85     gnu, bsd
86     LIBC:
87     glibc, openbsd, freebsd, netbsd, macosx
88     KERNEL:
89     linux, selinux, openbsd, freebsd, netbsd, macosx
91     (The above examples are not meant to be complete. Hurd, for example
92     is not included because I know very little about Hurd.)
93 g2boojum 1.3
94     A fully-specified keyword would look like
95     "ARCH-KERNEL-USERLAND-LIBC", so, for example,
96     "ppc-fbsd-gnu-glibc" would indicate a Gentoo system corresponding to
97     a ppc architecture running the FreeBSD kernel with a GNU userland and glibc
98     as the system C library.
99 g2boojum 1.1
100     Reasonable Defaults
101     -------------------
103 g2boojum 1.3 To keep this system manageable (and both to reduce typing and maintain
104     backwards compatibility), we need sensible defaults. For backwards
105     compatibility, the Gentoo default is a Linux kernel with a GNU userland
106     and glibc C library. Thus, the current crop of ARCH-based keywords
107     (x86, ppc, etcetera) require no change whatsoever. For the \*BSD-based
108     systems the default USERLAND and LIBC would be those normally associated
109     with the corresponding KERNEL, so "x86-obsd" describes an x86 system
110     with an OpenBSD kernel, a BSD userland, and the OpenBSD C library. If
111     either USERLAND or LIBC is specified, and thus not the default, then the
112     entire four-parameter string must be used.
115     Ebuild Keyword Database?
116     ------------------------
118     One issue that has been raised is that adding a large number of keywords
119     to ebuilds is likely to become cumbersome over the long run. (One could
120     imagine that for a simple `econf && emake && einstall` ebuild that the
121     list of keywords could grow to be the lengthiest part of the ebuild.)
122     Instead, perhaps it would make more sense to move each ebuild's keywords
123     out of the ebuild proper into a separate, perhaps online, database.
124     Nothing in this GLEP would be incompatible with such an approach, so
125     any further discussion will be deferred to a possible future GLEP on
126     that topic.
128 g2boojum 1.1
129     Profiles
130     --------
132 g2boojum 1.3 Along with an explosion of keywords comes a concomitant explosion of potential
133     profiles. Just as in the current system, the profile name would be
134 g2boojum 1.4 "FLAVOR-KEYWORD-VERSION" (such as "default-s390-2004.1"). One drawback
135 g2boojum 1.3 to having a large number of profiles is that maintainance becomes a
136     significant problem. In fact, one could reasonably argue that the current
137     number of profiles is already too many to be easily maintained. One proposal
138     that has been raised to simplify matters is the idea of stackable, or
139     cascading, profiles, so that only differences between profiles would have to
140     be maintained.
142 g2boojum 1.1
143     Rationale
144     =========
146     The proposed new "keywording" system is far from elegant, which is
147     a substantial drawback. On the other hand, it is simple, it requires
148 g2boojum 1.3 relatively minor changes, and the changes can be implemented
149 g2boojum 1.1 gradually over time.
151 g2boojum 1.3
152 g2boojum 1.1 Implementation
153     ==============
155 g2boojum 1.3 Since the new keyword system is backwards-compatible with the current
156     system, "implementation" just means adding new keywords to ebuilds
157     as new systems are supported.
158 g2boojum 1.1
160     Backwards Compatibility
161     =======================
163     Backwards compatibility has already been addressed in some detail,
164     with the stated goal being a system that would leave all current
165 g2boojum 1.3 ebuilds working exactly as they are now.
166 g2boojum 1.1
168     Copyright
169     =========
171 g2boojum 1.3 This document has been placed in the public domain.

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