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ref-manual: New section and updates for runtime dep work

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fixes [YOCTO #10248]

The bulk of this change is a new section called "Automatically
Added Runtime Dependencies".  Additionally, changes were made
to the RDEPENDS and DEPENDS variables. Some cross-referencing
to the new material was also added in the do_package task entry,
the do_packagedata task entry, the PKGDATA_DIR glossary entry,
and the PRIVATE_LIBS glossary entry.

(From yocto-docs rev: 16504cd0eb23e102322c6c6096c5b52500a04640)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Scott Rifenbark
2016-09-13 11:15:02 -07:00
committed by Richard Purdie
parent 899ea9cb48
commit 8bc6c1c2c8
3 changed files with 196 additions and 70 deletions
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documentation/ref-manual/technical-details.xml
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@@ -979,6 +979,113 @@
</section>
</section>
<section id='automatically-added-runtime-dependencies'>
<title>Automatically Added Runtime Dependencies</title>
<para>
The OpenEmbedded build system automatically adds common types of
runtime dependencies between packages, which means you do not need to
explicitly declare the packages using
<link linkend='var-RDEPENDS'><filename>RDEPENDS</filename></link>.
Two automatic mechanisms exist (<filename>shlibdeps</filename> and
<filename>pcdeps</filename>) that handle shared libraries and
package configuration (pkg-config) modules, respectively.
For other types of runtime dependencies, you must manually declare
the dependencies.
<itemizedlist>
<listitem><para>
<filename>shlibdeps</filename>:
During the
<link linkend='ref-tasks-package'><filename>do_package</filename></link>
task of each recipe, all shared libraries installed by the
recipe are located.
For each shared library, the package that contains the shared
library is registered as providing the shared library.
More specifically, the package is registered as providing the
<ulink url='https://en.wikipedia.org/wiki/Soname'>soname</ulink>
of the library.
The resulting shared-library-to-package mapping
is saved globally in
<link linkend='var-PKGDATA_DIR'><filename>PKGDATA_DIR</filename></link>
by the
<link linkend='ref-tasks-packagedata'><filename>do_packagedata</filename></link>
task.</para>
<para>Simultaneously, all executables and shared libraries
installed by the recipe are inspected to see what shared
libraries they link against.
For each shared library dependency that is found,
<filename>PKGDATA_DIR</filename> is queried to
see if some package (likely from a different recipe) contains
the shared library.
If such a package is found, a runtime dependency is added from
the package that depends on the shared library to the package
that contains the library.</para>
<para>If the library being linked against is versioned
(i.e. includes a version number), then the automatically added
runtime dependency will specify at least that version, as if
"<replaceable>package</replaceable> (>= <replaceable>version</replaceable>)"
had been added to
<link linkend='var-RDEPENDS'><filename>RDEPENDS</filename></link>.
This dependency forces an upgrade of the package that provides
the shared library when installing the package that depends on
the library, if needed.</para>
<para>If you want to avoid a package being registered as
providing a particular shared library (e.g. because the library
is for internal use only), then add the library to
<link linkend='var-PRIVATE_LIBS'><filename>PRIVATE_LIBS</filename></link>
inside the package's recipe.
</para></listitem>
<listitem><para>
<filename>pcdeps</filename>:
During the
<link linkend='ref-tasks-package'><filename>do_package</filename></link>
task of each recipe, all pkg-config modules
(<filename>*.pc</filename> files) installed by the recipe are
located.
For each module, the package that contains the module is
registered as providing the module.
The resulting module-to-package mapping is saved globally in
<link linkend='var-PKGDATA_DIR'><filename>PKGDATA_DIR</filename></link>
by the
<link linkend='ref-tasks-packagedata'><filename>do_packagedata</filename></link>
task.</para>
<para>Simultaneously, all pkg-config modules installed by the
recipe are inspected to see what other modules on which the
pkg-config modules depend.
A module is seen as depending on another module if it contains
a "Requires:" line that specifies the other module.
For each module dependency,
<filename>PKGDATA_DIR</filename> is queried to see if some
package contains the module.
If such a package is found, a runtime dependency is added from
the package that depends on the module to the package that
contains the module.
<note>
The <filename>pcdeps</filename> mechanism most often infers
dependencies between <filename>-dev</filename> packages.
</note>
</para></listitem>
</itemizedlist>
</para>
<para>
The <filename>do_package</filename> task depends on the
<link linkend='ref-tasks-packagedata'><filename>do_packagedata</filename></link>
task of each recipe in
<link linkend='var-DEPENDS'><filename>DEPENDS</filename></link>
through use of a
<ulink url='&YOCTO_DOCS_BB_URL;#variable-flags'><filename>[vardeps]</filename></ulink>
declaration, which guarantees that the required
shared-library/module-to-package mapping information will be available
when needed as long as <filename>DEPENDS</filename> has been
correctly set.
</para>
</section>
<section id='fakeroot-and-pseudo'>
<title>Fakeroot and Pseudo</title>