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commit: 7266aee16fa73086a1d9553ab9129013d83a4761 |
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Author: Michał Górny <mgorny <AT> gentoo <DOT> org> |
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AuthorDate: Fri Jan 12 23:23:30 2018 +0000 |
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Commit: Göktürk Yüksek <gokturk <AT> gentoo <DOT> org> |
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CommitDate: Tue Feb 13 16:43:32 2018 +0000 |
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URL: https://gitweb.gentoo.org/proj/devmanual.git/commit/?id=7266aee1 |
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|
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general-concepts/virtuals: Tips on virtual and subslots |
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|
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general-concepts/virtuals/text.xml | 80 ++++++++++++++++++++++++++++++++++++++ |
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1 file changed, 80 insertions(+) |
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|
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diff --git a/general-concepts/virtuals/text.xml b/general-concepts/virtuals/text.xml |
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index 4809394..ff4995a 100644 |
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--- a/general-concepts/virtuals/text.xml |
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+++ b/general-concepts/virtuals/text.xml |
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@@ -70,5 +70,85 @@ RDEPEND="|| ( dev-libs/liblinux dev-libs/libbsd )" |
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|
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</section> |
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|
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+<section> |
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+<title>Virtuals and subslots</title> |
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+ |
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+<body> |
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+<warning> |
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+This section is only applicable if virtual providers include versions that |
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+are ABI-compatible with one another (and use matching SONAMEs) and/or |
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+the incompatible providers are being obsoleted. |
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+</warning> |
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+ |
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+<p> |
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+Like regular packages, virtuals can define subslots that can be used |
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+to trigger rebuilds of their reverse dependencies. For this to work, a new |
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+version of the virtual is created for each subslot of the providers, |
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+where each version contains dependencies on a specific subslot. |
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+</p> |
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+ |
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+<p> |
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+For example, a virtual for different packages providing ABI-compatible |
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+<c>libfoo.so.1</c> libraries could look like the following: |
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+</p> |
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+ |
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+<codesample lang="ebuild"> |
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+EAPI=6 |
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+ |
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+DESCRIPTION="Virtual for libfoo.so.1" |
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+SLOT="0/1" |
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+ |
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+RDEPEND=" |
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+ || ( |
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+ dev-libs/libfoo:0/1 |
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+ dev-libs/libfoo-alternate:0/1 |
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+ dev-libs/bigpack:0/libfoo-1+libbar-0 |
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+ dev-libs/bigpack:0/libfoo-1+libbar-1 |
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+ ) |
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+" |
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+</codesample> |
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+ |
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+<p> |
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+Virtuals can also be used when one of the providers is being obsoleted in favor |
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+of another that breaks ABI compatibility while remaining API-compatible. In this |
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+case, multiple versions of the virtual are created, each specifying a single |
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+provider and a unique subslot. |
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+</p> |
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+ |
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+<p> |
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+For example, if <c>dev-libs/libfoo</c> (<c>libfoo.so.0</c>) is being replaced |
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+by <c>dev-libs/newfoo</c> (<c>libfoo.so.1</c>), <c>virtual/libfoo-0.ebuild</c> |
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+would contain: |
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+</p> |
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+ |
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+<codesample lang="ebuild"> |
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+EAPI=6 |
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+ |
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+DESCRIPTION="Virtual for libfoo.so.0" |
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+SLOT="0/0" |
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+RDEPEND="dev-libs/libfoo:0/0" |
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+</codesample> |
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+ |
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+<p> |
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+while <c>virtual/libfoo-1.ebuild</c> would contain: |
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+</p> |
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+ |
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+<codesample lang="ebuild"> |
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+EAPI=6 |
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+ |
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+DESCRIPTION="Virtual for libfoo.so.1" |
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+SLOT="0/1" |
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+RDEPEND="dev-libs/newfoo:0/1" |
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+</codesample> |
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+ |
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+<note> |
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+In this case, the package manager will naturally want to upgrade |
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+to <c>dev-libs/newfoo</c> whenever possible. Therefore, this solution |
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+is not viable if clean choice between the two providers is desired. |
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+</note> |
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+ |
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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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