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Author: halcy0n |
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Date: 2008-05-29 02:31:48 +0000 (Thu, 29 May 2008) |
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New Revision: 128 |
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|
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Added: |
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trunk/general-concepts/virtuals/ |
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trunk/general-concepts/virtuals/text.xml |
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Modified: |
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trunk/general-concepts/text.xml |
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Log: |
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Add in documentation about virtuals; bug #140180 |
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|
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|
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Modified: trunk/general-concepts/text.xml |
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=================================================================== |
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--- trunk/general-concepts/text.xml 2008-05-23 02:20:21 UTC (rev 127) |
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+++ trunk/general-concepts/text.xml 2008-05-29 02:31:48 UTC (rev 128) |
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@@ -43,4 +43,5 @@ |
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<include href="tree/"/> |
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<include href="use-flags/"/> |
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<include href="user-environment/"/> |
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+<include href="virtuals/"/> |
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</guide> |
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|
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Added: trunk/general-concepts/virtuals/text.xml |
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=================================================================== |
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--- trunk/general-concepts/virtuals/text.xml (rev 0) |
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+++ trunk/general-concepts/virtuals/text.xml 2008-05-29 02:31:48 UTC (rev 128) |
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@@ -0,0 +1,91 @@ |
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+<?xml version="1.0"?> |
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+<guide self="general-concepts/viruals/"> |
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+<chapter> |
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+<title>Virtuals</title> |
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+ |
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+<body> |
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+<p> |
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+Currently there exist two different forms of virtuals, our regular |
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+<c>PROVIDE</c> type virtuals, and so called <e>new-style</e> virtuals. |
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+</p> |
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+</body> |
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+ |
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+<section> |
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+<title><e>Old-style</e> Virtuals</title> |
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+<body> |
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+<p> |
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+<e>Old-style</e> virtuals are not really packages, but are something you can depend |
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+upon and install. All <e>old-style</e> virtuals must have a category of |
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+"virtual". In order to use an <e>old-style</e> virtual there are a few things |
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+that need to be present in the tree: |
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+ |
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+<ul> |
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+ <li> |
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+ Atleast one ebuild must <c>PROVIDE</c> the virtual <d/> see |
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+ <uri link="::ebuild-writing/variables#Optional Variables" /> |
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+ </li> |
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+ <li> |
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+ An entry in the virtuals file for each profile to list the default provider |
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+ </li> |
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+</ul> |
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+ |
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+<e>Old-style</e> virtuals are not as flexible as <e>new-style</e> virtuals |
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+because there is no concept of a version. You can only depend upon a virtual, |
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+but not a particular version of that virtual. |
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+</p> |
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+<p> |
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+There are some things that are still only possible with old-style virtuals, |
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+which is why they are still useful: |
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+ |
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+<ul> |
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+ <li> |
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+ Packages providing the virtual can block the virtual, so you can ensure |
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+ nothing else is installed that also provides that virtual. |
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+ </li> |
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+ <li> |
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+ The ability to set a default in the profile for what the virtual should |
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+ pull in (without the need of pulling the package into the system set). |
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+ </li> |
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+</ul> |
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+</p> |
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+</body> |
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+</section> |
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+ |
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+<section> |
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+<title><e>New-style</e> Virtuals</title> |
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+<body> |
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+<p> |
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+<e>New-style</e> virtuals are merely packages that are in the category of |
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+<c>virtual</c>. They use their dependency string to specify the providers for |
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+the virtual and should not install any files. Since they are regular ebuilds, |
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+there can be several versions of a virtual (which can be helpful when a package |
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+may be provided by another in some versions, and not others <d/> see the perl |
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+virtuals for an example of this). One other difference (besides not installing |
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+any files) is that a <e>new-style</e> virtual has an empty string for the value |
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+of the <c>LICENSE</c> and <c>HOMEPAGE</c> variables. Since it installs no files, |
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+it really does not have a license. |
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+</p> |
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+ |
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+<p> |
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+An example of a <e>new-style</e> virtual: |
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+ |
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+<codesample lang="ebuild"> |
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+DESCRIPTION="Virtual for C++ tr1 <type_traits>" |
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+HOMEPAGE="http://www.gentoo.org/proj/en/base/" |
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+SRC_URI="" |
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+LICENSE="" |
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+SLOT="0" |
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+KEYWORDS="alpha amd64 arm hppa ia64 mips ppc ppc64 s390 sparc x86 ~x86-fbsd" |
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+IUSE="" |
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+RDEPEND="|| ( >=sys-devel/gcc-4.1 dev-libs/boost )" |
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+DEPEND="" |
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+</codesample> |
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+ |
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+Looks familar...right? It should since its going to look just like a regular |
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+ebuild. |
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+</p> |
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+</body> |
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+</section> |
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+ |
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+</chapter> |
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+</guide> |
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|
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-- |
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