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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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<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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<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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<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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</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). |
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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="as-is" |
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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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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> |
