/[gentoo]/xml/htdocs/proj/en/glep/glep-0055.txt

Diff of /xml/htdocs/proj/en/glep/glep-0055.txt

Parent Directory | Revision Log | View Patch Patch

Revision 1.3		Revision 1.5
1	GLEP: 55	1	GLEP: 55
2	Title: Use EAPI-suffixed ebuilds (.ebuild-EAPI)	2	Title: Use EAPI-suffixed ebuilds (.ebuild-EAPI)
3	Version: $Revision: 1.3 $	3	Version: $Revision: 1.5 $
4	Last-Modified: $Date: 2009/05/17 15:50:27 $	4	Last-Modified: $Date: 2009/05/17 20:56:53 $
5	Author: Piotr Jaroszyński <peper@gentoo.org>	5	Author: Piotr Jaroszyński <peper@gentoo.org>
6	Status: Draft	6	Status: Draft
7	Type: Standards Track	7	Type: Standards Track
8	Content-Type: text/x-rst	8	Content-Type: text/x-rst
9	Created: 17-Dec-2007	9	Created: 17-Dec-2007
…		…
36	* Add new global scope functions in any sane way.	36	* Add new global scope functions in any sane way.
37		37
38	* Extend versioning rules in an EAPI - for example, addition of the scm	38	* Extend versioning rules in an EAPI - for example, addition of the scm
39	suffix - GLEP54 [#GLEP54]_ or allowing more sensible version formats like	39	suffix - GLEP54 [#GLEP54]_ or allowing more sensible version formats like
40	``1-rc1``, ``1-alpha`` etc. to match upstream more closely.	40	``1-rc1``, ``1-alpha`` etc. to match upstream more closely.
		41
		42	* Use newer bash features.
41		43
42		44
43	Current behaviour	45	Current behaviour
44	=================	46	=================
45		47
…		…
120		122
121	emerge: there are no ebuilds to satisfy "sys-apps/foo"	123	emerge: there are no ebuilds to satisfy "sys-apps/foo"
122		124
123	Not the best error message, especially if there are lots of them.	125	Not the best error message, especially if there are lots of them.
124		126
		127	Use newer bash features
		128	-----------------------
		129
		130	``\|&`` is a new type of redirection added in bash-4. It cannot be used even in
		131	local scope as bash still parses the whole ebuild.
		132
		133	``sys-apps/foo-1.ebuild``::
		134
		135	EAPI="5"
		136
		137	foo() {
		138	echo "foo" \|& cat
		139	}
		140
		141	Result::
		142
		143	/var/lib/gentoo/repositories/peper/sys-apps/foo/foo-1.ebuild: line 8: syntax error near unexpected token `&'
		144	/var/lib/gentoo/repositories/peper/sys-apps/foo/foo-1.ebuild: line 8: ` echo "foo" \|& cat'
		145	*
		146	* ERROR: sys-apps/foo-1 failed.
		147	* Call stack:
		148	* ebuild.sh, line 1879: Called _source_ebuild
		149	* ebuild.sh, line 1818: Called die
		150	* The specific snippet of code:
		151	* source "${EBUILD}" \|\| die "error sourcing ebuild"
		152	* The die message:
		153	* error sourcing ebuild
		154	*
		155	* If you need support, post the topmost build error, and the call stack if relevant.
		156	* This ebuild is from an overlay: '/var/lib/gentoo/repositories/peper/'
		157	* ... done!
		158
		159	!!! All ebuilds that could satisfy "sys-apps/foo" have been masked.
		160	!!! One of the following masked packages is required to complete your request:
		161	- sys-apps/foo-1 (masked by: corruption)
		162
		163	Again, not the best error.
		164
125	Abstract solution	165	Abstract solution
126	=================	166	=================
127		167
128	A solution to this problem has to lift those limitations and the only way to do	168	A solution to this problem has to lift those limitations and the only way to do
129	it is to make the EAPI of an ebuild available to the package managers in a way	169	it is to make the EAPI of an ebuild available to the package managers in a way
…		…
175	problems too. The first is the requirement to have strict EAPI ordering, the	215	problems too. The first is the requirement to have strict EAPI ordering, the
176	second is ensuring that all the ebuilds for a single category/package-version	216	second is ensuring that all the ebuilds for a single category/package-version
177	are equivalent, i.e. installing any of them has exactly the same effect on a	217	are equivalent, i.e. installing any of them has exactly the same effect on a
178	given system.	218	given system.
179		219
		220	Also note that it is not a new restriction. It is already possible to illegally
		221	have multiple versions with different EAPIs as e.g. ``1.0 == 1.00 == 1.00-r0``
		222	and hence you could have ``foo-1.0.ebuild`` with EAPI X and ``foo-1.00.ebuild``
		223	with EAPI Y.
		224
180	Summary of ideas	225	Summary of ideas
181	================	226	================
182		227
183	EAPI-suffixed ebuilds (proposed solution)	228	EAPI-suffixed ebuilds (proposed solution)
184	-----------------------------------------	229	-----------------------------------------
…		…
216	Performance decrease comes from the fact that with version format changes in the	261	Performance decrease comes from the fact that with version format changes in the
217	picture package managers need EAPI to parse the ebuild's version. That means that merely	262	picture package managers need EAPI to parse the ebuild's version. That means that merely
218	picking the best version of a package requires loading EAPI (from cache or the	263	picking the best version of a package requires loading EAPI (from cache or the
219	ebuild) for each available ebuild.	264	ebuild) for each available ebuild.
220		265
		266	Here is more or less how the package manager figures out the best available
		267	version for a package with N versions available.
		268
		269	* EAPI in the filename
		270
		271	* Read the directory containing the package - readdir()
		272	* For each ebuild, read its EAPI and using that parse its version - no I/O
		273	* Sort the versions - no I/O
		274	* Going down from the highest to the lowest version
		275
		276	* Get the metadata from cache - 2 x stat() + read()
		277	* break if the version is visible
		278
		279	* EAPI in the ebuild
		280
		281	* Read the directory containing the package - readdir()
		282	* For each ebuild load its metadata from cache to get its EAPI - N x (2 x stat() + read())
		283	* Sort the versions - no I/O
		284	* Going down from the highest to the lowest version
		285
		286	* (metadata is already loaded) - no I/O
		287	* break if the version is visible - no I/O
		288
		289	The difference is in for how many versions the package manager needs to hit
		290	cache. With EAPI in the ebuild it needs to do that for all versions, with EAPI
		291	in the filename it depends on versions visibility.
		292	For example, package foo has versions 1, 2, 3, 4, 5 and 6. 6 is masked, 5 is
		293	~arch and 1,2,3 and 4 are arch. Say, the user accepts only arch for this
		294	package. With EAPI in the filename it will read metadata only for versions
		295	6, 5 and 4. With EAPI in the ebuild it needs to load metadata for all versions.
		296
		297	It's hard to say what's the avarage case, but surely the worst case scenario
		298	(when only the lowest version is visible) is uncommon.
221		299
222	Easily fetchable EAPI inside the ebuild and one-time extension change	300	Easily fetchable EAPI inside the ebuild and one-time extension change
223	---------------------------------------------------------------------	301	---------------------------------------------------------------------
224		302
225	Properties:	303	Properties:

 Legend:



Removed from v.1.3
 


changed lines


 
Added in v.1.5
 Legend:



Removed from v.1.3
 


changed lines


 
Added in v.1.5
-Removed from v.1.3
+Added in v.1.5

	ViewVC Help
Powered by ViewVC 1.1.13