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From: "Ulrich Müller" <ulm@gentoo.org>
To: gentoo-commits@lists.gentoo.org
Subject: [gentoo-commits] proj/devmanual:master commit in: general-concepts/dependencies/
Date: Wed, 29 Jan 2020 07:59:56 +0000 (UTC)	[thread overview]
Message-ID: <1580284707.a7e1e6accfd537734321ddcefcc0515fe64a25e5.ulm@gentoo> (raw)

commit:     a7e1e6accfd537734321ddcefcc0515fe64a25e5
Author:     Michał Górny <mgorny <AT> gentoo <DOT> org>
AuthorDate: Sun Dec 29 08:47:41 2019 +0000
Commit:     Ulrich Müller <ulm <AT> gentoo <DOT> org>
CommitDate: Wed Jan 29 07:58:27 2020 +0000
URL:        https://gitweb.gentoo.org/proj/devmanual.git/commit/?id=a7e1e6ac

general-concepts/dependencies: Describe circular deps in detail

Signed-off-by: Michał Górny <mgorny <AT> gentoo.org>
Signed-off-by: Ulrich Müller <ulm <AT> gentoo.org>

 general-concepts/dependencies/text.xml | 49 ++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

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
@@ -620,6 +620,55 @@ RESTRICT="!test? ( test )"
 DEPEND="test? ( dev-util/foo )"
 </codesample>
 
+</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>


             reply	other threads:[~2020-01-29  8:00 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-29  7:59 Ulrich Müller [this message]
  -- strict thread matches above, loose matches on Subject: below --
2024-09-28 19:36 [gentoo-commits] proj/devmanual:master commit in: general-concepts/dependencies/ Ulrich Müller
2023-09-27  8:30 Ulrich Müller
2022-06-24  9:14 Ulrich Müller
2022-05-27  9:00 Ulrich Müller
2022-05-22  6:37 Joonas Niilola
2022-05-22  6:37 Joonas Niilola
2022-02-21  5:22 Sam James
2022-02-21  5:22 Sam James
2021-10-19  9:27 Mike Frysinger
2021-10-13 13:42 Ulrich Müller
2021-03-29 20:44 Ulrich Müller
2021-03-29 20:44 Ulrich Müller
2021-03-29 20:44 Ulrich Müller
2021-03-11 12:44 Ulrich Müller
2021-03-11 12:44 Ulrich Müller
2021-03-11 12:44 Ulrich Müller
2020-05-25 15:43 Ulrich Müller
2020-05-25 15:43 Ulrich Müller
2020-01-29  7:59 Ulrich Müller
2020-01-29  7:59 Ulrich Müller
2020-01-23  7:47 Ulrich Müller
2019-12-21  5:19 Ulrich Müller
2019-10-16 18:49 Göktürk Yüksek
2018-09-10 15:20 Mike Gilbert
2017-09-25  4:31 Göktürk Yüksek
2017-09-25  4:31 Göktürk Yüksek
2017-09-25  4:31 Göktürk Yüksek
2014-10-18 17:40 Markos Chandras
2013-07-29 21:53 Julian Ospald
2013-07-29 21:53 Julian Ospald
2011-02-17 21:08 Jeremy Olexa

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