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commit: a7e1e6accfd537734321ddcefcc0515fe64a25e5 |
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Author: Michał Górny <mgorny <AT> gentoo <DOT> org> |
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AuthorDate: Sun Dec 29 08:47:41 2019 +0000 |
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Commit: Ulrich Müller <ulm <AT> gentoo <DOT> org> |
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CommitDate: Wed Jan 29 07:58:27 2020 +0000 |
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URL: https://gitweb.gentoo.org/proj/devmanual.git/commit/?id=a7e1e6ac |
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|
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general-concepts/dependencies: Describe circular deps in detail |
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|
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Signed-off-by: Michał Górny <mgorny <AT> gentoo.org> |
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Signed-off-by: Ulrich Müller <ulm <AT> gentoo.org> |
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|
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general-concepts/dependencies/text.xml | 49 ++++++++++++++++++++++++++++++++++ |
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1 file changed, 49 insertions(+) |
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|
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diff --git a/general-concepts/dependencies/text.xml b/general-concepts/dependencies/text.xml |
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index dde6cda..2aca289 100644 |
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--- a/general-concepts/dependencies/text.xml |
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+++ b/general-concepts/dependencies/text.xml |
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@@ -620,6 +620,55 @@ RESTRICT="!test? ( test )" |
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DEPEND="test? ( dev-util/foo )" |
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</codesample> |
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|
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+</body> |
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+</section> |
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+ |
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+<section> |
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+<title>Circular Dependencies</title> |
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+<body> |
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+ |
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+<p> |
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+Circular dependencies occur if one or more of package's (possibly indirect) |
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+dependencies depend on the package itself. This creates a dependency cycle where |
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+each of the packages must technically be installed before the other. |
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+For example, if package A depends on B, B depends on C and C depends on A, then |
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+the package manager cannot install A before C, and C before A. |
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+</p> |
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+ |
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+<p> |
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+There are three kinds of circular dependencies: |
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+</p> |
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+ |
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+<ol> |
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+ <li> |
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+ Circular dependencies that occur if only one of the packages strictly needs |
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+ to be installed before the other. For example, <c>dev-python/certifi</c> |
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+ strictly requires <c>dev-python/setuptools</c> to build but the latter |
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+ package requires the former for some runtime functionality. As a result, |
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+ <c>dev-python/certifi</c> can be installed later than the other package. |
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+ <c>PDEPEND</c> is used to express this and automatically resolve |
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+ the circular dependency. |
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+ </li> |
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+ |
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+ <li> |
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+ Circular dependencies that occur if the cycle applies only to some |
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+ combination of USE flags on one of the packages. For example, running tests |
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+ in <c>dev-python/setuptools</c> requires a number of packages which require |
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+ <c>dev-python/setuptools</c> to be installed first. This kind of circular |
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+ dependency can be resolved by the user by adjusting USE flags on one |
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+ of the packages, e.g. by disabling tests on <c>dev-python/setuptools</c>, |
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+ and reenabling them once the dependency is initially installed. |
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+ </li> |
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+ |
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+ <li> |
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+ Circular dependencies that cannot be resolved using the regular means. |
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+ For example, <c>dev-util/cmake</c> used to depend |
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+ on <c>dev-libs/jsoncpp</c>, while the latter package used the former |
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+ to build. Resolving this kind of dependency usually requires bundling one |
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+ of the dependencies conditionally, or providing an alternate bootstrap path. |
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+ </li> |
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+</ol> |
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+ |
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</body> |
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</section> |
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</chapter> |
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