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| author |   Michał Górny <mgorny@gentoo.org> | 2019-12-29 09:47:41 +0100 |
|---|---|---|
| committer |   Ulrich Müller <ulm@gentoo.org> | 2020-01-29 08:58:27 +0100 |
| commit | a7e1e6accfd537734321ddcefcc0515fe64a25e5 (patch) | |
| tree | 8f8eb2d1d949247760a1d13c4b304c65a91556d7 /general-concepts/dependencies/text.xml | |
| parent | general-concepts/dependencies: Improve PDEPEND (diff) | |
| download | devmanual-a7e1e6accfd537734321ddcefcc0515fe64a25e5.tar.gz devmanual-a7e1e6accfd537734321ddcefcc0515fe64a25e5.tar.bz2 devmanual-a7e1e6accfd537734321ddcefcc0515fe64a25e5.zip | |
general-concepts/dependencies: Describe circular deps in detail
Signed-off-by: Michał Górny <mgorny@gentoo.org>
Signed-off-by: Ulrich Müller <ulm@gentoo.org>
Diffstat (limited to 'general-concepts/dependencies/text.xml')
| -rw-r--r-- | general-concepts/dependencies/text.xml | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/general-concepts/dependencies/text.xml b/general-concepts/dependencies/text.xml index dde6cda..2aca289 100644 --- a/general-concepts/dependencies/text.xml +++ b/general-concepts/dependencies/text.xml @@ -622,5 +622,54 @@ DEPEND="test? ( dev-util/foo )" </body> </section> + +<section> +<title>Circular Dependencies</title> +<body> + +<p> +Circular dependencies occur if one or more of package's (possibly indirect) +dependencies depend on the package itself. This creates a dependency cycle where +each of the packages must technically be installed before the other. +For example, if package A depends on B, B depends on C and C depends on A, then +the package manager cannot install A before C, and C before A. +</p> + +<p> +There are three kinds of circular dependencies: +</p> + +<ol> + <li> + Circular dependencies that occur if only one of the packages strictly needs + to be installed before the other. For example, <c>dev-python/certifi</c> + strictly requires <c>dev-python/setuptools</c> to build but the latter + package requires the former for some runtime functionality. As a result, + <c>dev-python/certifi</c> can be installed later than the other package. + <c>PDEPEND</c> is used to express this and automatically resolve + the circular dependency. + </li> + + <li> + Circular dependencies that occur if the cycle applies only to some + combination of USE flags on one of the packages. For example, running tests + in <c>dev-python/setuptools</c> requires a number of packages which require + <c>dev-python/setuptools</c> to be installed first. This kind of circular + dependency can be resolved by the user by adjusting USE flags on one + of the packages, e.g. by disabling tests on <c>dev-python/setuptools</c>, + and reenabling them once the dependency is initially installed. + </li> + + <li> + Circular dependencies that cannot be resolved using the regular means. + For example, <c>dev-util/cmake</c> used to depend + on <c>dev-libs/jsoncpp</c>, while the latter package used the former + to build. Resolving this kind of dependency usually requires bundling one + of the dependencies conditionally, or providing an alternate bootstrap path. + </li> +</ol> + +</body> +</section> </chapter> </guide> |