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<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
<chapter id='ref-classes'>
<title>Classes</title>
<para>
Class files are used to abstract common functionality and share it amongst
multiple recipe (<filename>.bb</filename>) files.
To use a class file, you simply make sure the recipe inherits the class.
In most cases, when a recipe inherits a class it is enough to enable its
features.
There are cases, however, where in the recipe you might need to set
variables or override some default behavior.
</para>
<para>
Any <ulink url='&YOCTO_DOCS_DEV_URL;#metadata'>Metadata</ulink> usually
found in a recipe can also be placed in a class file.
Class files are identified by the extension <filename>.bbclass</filename>
and are usually placed in a <filename>classes/</filename> directory beneath
the <filename>meta*/</filename> directory found in the
<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>.
Class files can also be pointed to by
<link linkend='var-BUILDDIR'><filename>BUILDDIR</filename></link>
(e.g. <filename>build/</filename>) in the same way as
<filename>.conf</filename> files in the <filename>conf</filename> directory.
Class files are searched for in
<link linkend='var-BBPATH'><filename>BBPATH</filename></link>
using the same method by which <filename>.conf</filename> files are
searched.
</para>
<para>
This chapter discusses only the most useful and important classes.
Other classes do exist within the <filename>meta/classes</filename>
directory in the
<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>.
You can reference the <filename>.bbclass</filename> files directly
for more information.
</para>
<section id='ref-classes-allarch'>
<title><filename>allarch.bbclass</filename></title>
<para>
The <filename>allarch</filename> class is inherited
by recipes that do not produce architecture-specific output.
The class disables functionality that is normally needed for recipes
that produce executable binaries (such as building the cross-compiler
and a C library as pre-requisites, and splitting out of debug symbols
during packaging).
<note>
<para>Unlike some distro recipes (e.g. Debian), OpenEmbedded recipes
that produce packages that depend on tunings through use of the
<link linkend='var-RDEPENDS'><filename>RDEPENDS</filename></link>
and
<link linkend='var-TUNE_PKGARCH'><filename>TUNE_PKGARCH</filename></link>
variables, should never be configured for all architectures
using <filename>allarch</filename>.
This is the case even if the recipes do not produce
architecture-specific output.</para>
<para>Configuring such recipes for all architectures causes the
<link linkend='ref-tasks-package_write_deb'><filename>do_package_write_*</filename></link>
tasks to have different signatures for the machines with different
tunings.
Additionally, unnecessary rebuilds occur every time an
image for a different <filename>MACHINE</filename> is built
even when the recipe never changes.</para>
</note>
</para>
<para>
By default, all recipes inherit the
<link linkend='ref-classes-base'><filename>base</filename></link> and
<link linkend='ref-classes-package'><filename>package</filename></link>
classes, which enable functionality
needed for recipes that produce executable output.
If your recipe, for example, only produces packages that contain
configuration files, media files, or scripts (e.g. Python and Perl),
then it should inherit the <filename>allarch</filename> class.
</para>
</section>
<section id='ref-classes-archiver'>
<title><filename>archiver.bbclass</filename></title>
<para>
The <filename>archiver</filename> class supports releasing
source code and other materials with the binaries.
</para>
<para>
For more details on the source archiver, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#maintaining-open-source-license-compliance-during-your-products-lifecycle'>Maintaining Open Source License Compliance During Your Product's Lifecycle</ulink>"
section in the Yocto Project Development Manual.
You can also see the
<link linkend='var-ARCHIVER_MODE'><filename>ARCHIVER_MODE</filename></link>
variable for information about the variable flags (varflags)
that help control archive creation.
</para>
</section>
<section id='ref-classes-autotools'>
<title><filename>autotools*.bbclass</filename></title>
<para>
The <filename>autotools*</filename> classes support Autotooled
packages.
</para>
<para>
The <filename>autoconf</filename>, <filename>automake</filename>,
and <filename>libtool</filename> packages bring standardization.
This class defines a set of tasks (e.g.
<filename>configure</filename>, <filename>compile</filename> and
so forth) that
work for all Autotooled packages.
It should usually be enough to define a few standard variables
and then simply <filename>inherit autotools</filename>.
These classes can also work with software that emulates Autotools.
For more information, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#new-recipe-autotooled-package'>Autotooled Package</ulink>"
section in the Yocto Project Development Manual.
</para>
<para>
By default, the <filename>autotools*</filename> classes
use out-of-tree builds (i.e.
<filename>autotools.bbclass</filename>).
(<link linkend='var-B'><filename>B</filename></link> <filename>!=</filename>
<link linkend='var-S'><filename>S</filename></link>).
</para>
<para>
If the software being built by a recipe does not support
using out-of-tree builds, you should have the recipe inherit the
<filename>autotools-brokensep</filename> class.
The <filename>autotools-brokensep</filename> class behaves the same
as the <filename>autotools</filename> class but builds with
<link linkend='var-B'><filename>B</filename></link> ==
<link linkend='var-S'><filename>S</filename></link>.
This method is useful when out-of-tree build support is either not
present or is broken.
<note>
It is recommended that out-of-tree support be fixed and used
if at all possible.
</note>
</para>
<para>
It's useful to have some idea of how the tasks defined by
the <filename>autotools*</filename> classes work and what they do
behind the scenes.
<itemizedlist>
<listitem><para><link linkend='ref-tasks-configure'><filename>do_configure</filename></link> -
Regenerates the
configure script (using <filename>autoreconf</filename>) and
then launches it with a standard set of arguments used during
cross-compilation.
You can pass additional parameters to
<filename>configure</filename> through the
<filename><link linkend='var-EXTRA_OECONF'>EXTRA_OECONF</link></filename> variable.
</para></listitem>
<listitem><para><link linkend='ref-tasks-compile'><filename>do_compile</filename></link> -
Runs <filename>make</filename> with arguments that specify the
compiler and linker.
You can pass additional arguments through
the <filename><link linkend='var-EXTRA_OEMAKE'>EXTRA_OEMAKE</link></filename> variable.
</para></listitem>
<listitem><para><link linkend='ref-tasks-install'><filename>do_install</filename></link> -
Runs <filename>make install</filename> and passes in
<filename>${</filename><link linkend='var-D'><filename>D</filename></link><filename>}</filename>
as <filename>DESTDIR</filename>.
</para></listitem>
</itemizedlist>
</para>
</section>
<section id='ref-classes-base'>
<title><filename>base.bbclass</filename></title>
<para>
The <filename>base</filename> class is special in that every
<filename>.bb</filename> file implicitly inherits the class.
This class contains definitions for standard basic
tasks such as fetching, unpacking, configuring (empty by default),
compiling (runs any <filename>Makefile</filename> present), installing
(empty by default) and packaging (empty by default).
These classes are often overridden or extended by other classes
such as the
<link linkend='ref-classes-autotools'><filename>autotools</filename></link>
class or the
<link linkend='ref-classes-package'><filename>package</filename></link>
class.
The class also contains some commonly used functions such as
<filename>oe_runmake</filename>.
</para>
</section>
<section id='ref-classes-bash-completion'>
<title><filename>bash-completion.bbclass</filename></title>
<para>
Sets up packaging and dependencies appropriate for recipes that
build software that includes bash-completion data.
</para>
</section>
<section id='ref-classes-bin-package'>
<title><filename>bin_package.bbclass</filename></title>
<para>
The <filename>bin_package</filename> class is a
helper class for recipes that extract the contents of a binary package
(e.g. an RPM) and install those contents rather than building the
binary from source.
The binary package is extracted and new packages in the configured
output package format are created.
Extraction and installation of proprietary binaries is a good example
use for this class.
<note>
For RPMs and other packages that do not contain a subdirectory,
you should specify an appropriate fetcher parameter to point to
the subdirectory.
For example, if BitBake is using the Git fetcher
(<filename>git://</filename>), the "subpath" parameter limits
the checkout to a specific subpath of the tree.
Here is an example where <filename>${BP}</filename> is used so that
the files are extracted into the subdirectory expected by the
default value of
<link linkend='var-S'><filename>S</filename></link>:
<literallayout class='monospaced'>
SRC_URI = "git://example.com/downloads/somepackage.rpm;subpath=${BP}"
</literallayout>
See the
"<ulink url='&YOCTO_DOCS_BB_URL;#bb-fetchers'>Fetchers</ulink>"
section in the BitBake User Manual for more information on
supported BitBake Fetchers.
</note>
</para>
</section>
<section id='ref-classes-binconfig'>
<title><filename>binconfig.bbclass</filename></title>
<para>
The <filename>binconfig</filename> class helps to correct paths in
shell scripts.
</para>
<para>
Before <filename>pkg-config</filename> had become widespread, libraries
shipped shell scripts to give information about the libraries and
include paths needed to build software (usually named
<filename>LIBNAME-config</filename>).
This class assists any recipe using such scripts.
</para>
<para>
During staging, the OpenEmbedded build system installs such scripts
into the <filename>sysroots/</filename> directory.
Inheriting this class results in all paths in these scripts being
changed to point into the <filename>sysroots/</filename> directory so
that all builds that use the script use the correct directories
for the cross compiling layout.
See the
<link linkend='var-BINCONFIG_GLOB'><filename>BINCONFIG_GLOB</filename></link>
variable for more information.
</para>
</section>
<section id='ref-classes-binconfig-disabled'>
<title><filename>binconfig-disabled.bbclass</filename></title>
<para>
An alternative version of the
<link linkend='ref-classes-binconfig'><filename>binconfig</filename></link>
class, which disables binary configuration scripts by making them
return an error in favor of using <filename>pkg-config</filename>
to query the information.
The scripts to be disabled should be specified using the
<link linkend='var-BINCONFIG'><filename>BINCONFIG</filename></link>
variable within the recipe inheriting the class.
</para>
</section>
<section id='ref-classes-blacklist'>
<title><filename>blacklist.bbclass</filename></title>
<para>
The <filename>blacklist</filename> class prevents
the OpenEmbedded build system from building specific recipes
(blacklists them).
To use this class, inherit the class globally and set
<link linkend='var-PNBLACKLIST'><filename>PNBLACKLIST</filename></link>
for each recipe you wish to blacklist.
Specify the <link linkend='var-PN'><filename>PN</filename></link>
value as a variable flag (varflag) and provide a reason, which is
reported, if the package is requested to be built as the value.
For example, if you want to blacklist a recipe called "exoticware",
you add the following to your <filename>local.conf</filename>
or distribution configuration:
<literallayout class='monospaced'>
INHERIT += "blacklist"
PNBLACKLIST[exoticware] = "Not supported by our organization."
</literallayout>
</para>
</section>
<section id='ref-classes-bluetooth'>
<title><filename>bluetooth.bbclass</filename></title>
<para>
The <filename>bluetooth</filename> class defines a variable that
expands to the recipe (package) providing core
bluetooth support on the platform.
</para>
<para>
For details on how the class works, see the
<filename>meta/classes/bluetooth.bbclass</filename> file in the Yocto
Project
<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>.
</para>
</section>
<section id='ref-classes-bugzilla'>
<title><filename>bugzilla.bbclass</filename></title>
<para>
The <filename>bugzilla</filename> class supports setting up an
instance of Bugzilla in which you can automatically files bug reports
in response to build failures.
For this class to work, you need to enable the XML-RPC interface in
the instance of Bugzilla.
</para>
</section>
<section id='ref-classes-buildhistory'>
<title><filename>buildhistory.bbclass</filename></title>
<para>
The <filename>buildhistory</filename> class records a
history of build output metadata, which can be used to detect possible
regressions as well as used for analysis of the build output.
For more information on using Build History, see the
"<link linkend='maintaining-build-output-quality'>Maintaining Build Output Quality</link>"
section.
</para>
</section>
<section id='ref-classes-buildstats'>
<title><filename>buildstats.bbclass</filename></title>
<para>
The <filename>buildstats</filename> class records
performance statistics about each task executed during the build
(e.g. elapsed time, CPU usage, and I/O usage).
</para>
<para>
When you use this class, the output goes into the
<link linkend='var-BUILDSTATS_BASE'><filename>BUILDSTATS_BASE</filename></link>
directory, which defaults to <filename>${TMPDIR}/buildstats/</filename>.
You can analyze the elapsed time using
<filename>scripts/pybootchartgui/pybootchartgui.py</filename>, which
produces a cascading chart of the entire build process and can be
useful for highlighting bottlenecks.
</para>
<para>
Collecting build statistics is enabled by default through the
<link linkend='var-USER_CLASSES'><filename>USER_CLASSES</filename></link>
variable from your <filename>local.conf</filename> file.
Consequently, you do not have to do anything to enable the class.
However, if you want to disable the class, simply remove "buildstats"
from the <filename>USER_CLASSES</filename> list.
</para>
</section>
<section id='ref-classes-buildstats-summary'>
<title><filename>buildstats-summary.bbclass</filename></title>
<para>
When inherited globally, prints statistics at the end of the build
on sstate re-use.
In order to function, this class requires the
<link linkend='ref-classes-buildstats'><filename>buildstats</filename></link>
class be enabled.
</para>
</section>
<section id='ref-classes-ccache'>
<title><filename>ccache.bbclass</filename></title>
<para>
The <filename>ccache</filename> class enables the
<ulink url='http://ccache.samba.org/'>C/C++ Compiler Cache</ulink>
for the build.
This class is used to give a minor performance boost during the build.
However, using the class can lead to unexpected side-effects.
Thus, it is recommended that you do not use this class.
See <ulink url='http://ccache.samba.org/'></ulink> for information on
the C/C++ Compiler Cache.
</para>
</section>
<section id='ref-classes-chrpath'>
<title><filename>chrpath.bbclass</filename></title>
<para>
The <filename>chrpath</filename> class
is a wrapper around the "chrpath" utility, which is used during the
build process for <filename>nativesdk</filename>,
<filename>cross</filename>, and
<filename>cross-canadian</filename> recipes to change
<filename>RPATH</filename> records within binaries in order to make
them relocatable.
</para>
</section>
<section id='ref-classes-clutter'>
<title><filename>clutter.bbclass</filename></title>
<para>
The <filename>clutter</filename> class consolidates the
major and minor version naming and other common items used by Clutter
and related recipes.
<note>
Unlike some other classes related to specific libraries, recipes
building other software that uses Clutter do not need to
inherit this class unless they use the same recipe versioning
scheme that the Clutter and related recipes do.
</note>
</para>
</section>
<section id='ref-classes-cmake'>
<title><filename>cmake.bbclass</filename></title>
<para>
The <filename>cmake</filename> class allows for
recipes that need to build software using the CMake build system.
You can use the
<link linkend='var-EXTRA_OECMAKE'><filename>EXTRA_OECMAKE</filename></link>
variable to specify additional configuration options to be passed on
the <filename>cmake</filename> command line.
</para>
</section>
<section id='ref-classes-cml1'>
<title><filename>cml1.bbclass</filename></title>
<para>
The <filename>cml1</filename> class provides basic support for the
Linux kernel style build configuration system.
</para>
</section>
<section id='ref-classes-compress_doc'>
<title><filename>compress_doc.bbclass</filename></title>
<para>
Enables compression for man pages and info pages.
This class is intended to be inherited globally.
The default compression mechanism is gz (gzip) but you can
select an alternative mechanism by setting the
<link linkend='var-DOC_COMPRESS'><filename>DOC_COMPRESS</filename></link>
variable.
</para>
</section>
<section id='ref-classes-copyleft_compliance'>
<title><filename>copyleft_compliance.bbclass</filename></title>
<para>
The <filename>copyleft_compliance</filename> class
preserves source code for the purposes of license compliance.
This class is an alternative to the <filename>archiver</filename>
class and is still used by some users even though it has been
deprecated in favor of the
<link linkend='ref-classes-archiver'><filename>archiver</filename></link>
class.
</para>
</section>
<section id='ref-classes-copyleft_filter'>
<title><filename>copyleft_filter.bbclass</filename></title>
<para>
A class used by the
<link linkend='ref-classes-archiver'><filename>archiver</filename></link>
and
<link linkend='ref-classes-copyleft_compliance'><filename>copyleft_compliance</filename></link>
classes for filtering licenses.
The <filename>copyleft_filter</filename> class is an internal class
and is not intended to be used directly.
</para>
</section>
<section id='ref-classes-core-image'>
<title><filename>core-image.bbclass</filename></title>
<para>
The <filename>core-image</filename> class
provides common definitions for the
<filename>core-image-*</filename> image recipes, such as support for
additional
<link linkend='var-IMAGE_FEATURES'><filename>IMAGE_FEATURES</filename></link>.
</para>
</section>
<section id='ref-classes-cpan'>
<title><filename>cpan*.bbclass</filename></title>
<para>
The <filename>cpan*</filename> classes support Perl modules.
</para>
<para>
Recipes for Perl modules are simple.
These recipes usually only need to point to the source's archive and
then inherit the proper class file.
Building is split into two methods depending on which method the module
authors used.
<itemizedlist>
<listitem><para>Modules that use old
<filename>Makefile.PL</filename>-based build system require
<filename>cpan.bbclass</filename> in their recipes.
</para></listitem>
<listitem><para>Modules that use
<filename>Build.PL</filename>-based build system require
using <filename>cpan_build.bbclass</filename> in their recipes.
</para></listitem>
</itemizedlist>
Both build methods inherit the <filename>cpan-base</filename> class
for basic Perl support.
</para>
</section>
<section id='ref-classes-cross'>
<title><filename>cross.bbclass</filename></title>
<para>
The <filename>cross</filename> class provides support for the recipes
that build the cross-compilation tools.
</para>
</section>
<section id='ref-classes-cross-canadian'>
<title><filename>cross-canadian.bbclass</filename></title>
<para>
The <filename>cross-canadian</filename> class
provides support for the recipes that build the Canadian
Cross-compilation tools for SDKs.
See the
"<link linkend='cross-development-toolchain-generation'>Cross-Development Toolchain Generation</link>"
section for more discussion on these cross-compilation tools.
</para>
</section>
<section id='ref-classes-crosssdk'>
<title><filename>crosssdk.bbclass</filename></title>
<para>
The <filename>crosssdk</filename> class
provides support for the recipes that build the cross-compilation
tools used for building SDKs.
See the
"<link linkend='cross-development-toolchain-generation'>Cross-Development Toolchain Generation</link>"
section for more discussion on these cross-compilation tools.
</para>
</section>
<section id='ref-classes-debian'>
<title><filename>debian.bbclass</filename></title>
<para>
The <filename>debian</filename> class renames output packages so that
they follow the Debian naming policy (i.e. <filename>glibc</filename>
becomes <filename>libc6</filename> and <filename>glibc-devel</filename>
becomes <filename>libc6-dev</filename>.)
Renaming includes the library name and version as part of the package
name.
</para>
<para>
If a recipe creates packages for multiple libraries
(shared object files of <filename>.so</filename> type), use the
<link linkend='var-LEAD_SONAME'><filename>LEAD_SONAME</filename></link>
variable in the recipe to specify the library on which to apply the
naming scheme.
</para>
</section>
<section id='ref-classes-deploy'>
<title><filename>deploy.bbclass</filename></title>
<para>
The <filename>deploy</filename> class handles deploying files
to the
<link linkend='var-DEPLOY_DIR_IMAGE'><filename>DEPLOY_DIR_IMAGE</filename></link>
directory.
The main function of this class is to allow the deploy step to be
accelerated by shared state.
Recipes that inherit this class should define their own
<link linkend='ref-tasks-deploy'><filename>do_deploy</filename></link>
function to copy the files to be deployed to
<link linkend='var-DEPLOYDIR'><filename>DEPLOYDIR</filename></link>,
and use <filename>addtask</filename> to add the task at the appropriate
place, which is usually after
<link linkend='ref-tasks-compile'><filename>do_compile</filename></link>
or
<link linkend='ref-tasks-install'><filename>do_install</filename></link>.
The class then takes care of staging the files from
<filename>DEPLOYDIR</filename> to
<filename>DEPLOY_DIR_IMAGE</filename>.
</para>
</section>
<section id='ref-classes-devshell'>
<title><filename>devshell.bbclass</filename></title>
<para>
The <filename>devshell</filename> class adds the
<filename>do_devshell</filename> task.
Distribution policy dictates whether to include this class.
See the
"<ulink url='&YOCTO_DOCS_DEV_URL;#platdev-appdev-devshell'>Using a Development Shell</ulink>" section
in the Yocto Project Development Manual for more information about
using <filename>devshell</filename>.
</para>
</section>
<section id='ref-classes-distro_features_check'>
<title><filename>distro_features_check.bbclass</filename></title>
<para>
The <filename>distro_features_check</filename> class
allows individual recipes to check for required and conflicting
<link linkend='var-DISTRO_FEATURES'><filename>DISTRO_FEATURES</filename></link>.
</para>
<para>
This class provides support for the
<link linkend='var-REQUIRED_DISTRO_FEATURES'><filename>REQUIRED_DISTRO_FEATURES</filename></link>
and
<link linkend='var-CONFLICT_DISTRO_FEATURES'><filename>CONFLICT_DISTRO_FEATURES</filename></link>
variables.
If any conditions specified in the recipe using the above variables are
not met, the recipe will be skipped.
</para>
</section>
<section id='ref-classes-distrodata'>
<title><filename>distrodata.bbclass</filename></title>
<para>
The <filename>distrodata</filename> class
provides for automatic checking for upstream recipe updates.
The class creates a comma-separated value (CSV) spreadsheet that
contains information about the recipes.
The information provides the
<link linkend='ref-tasks-distrodata'><filename>do_distrodata</filename></link>
and
<filename>do_distro_check</filename> tasks, which do upstream checking
and also verify if a package is used in multiple major distributions.
</para>
<para>
The class is not included by default.
To use it, you must set the
<link linkend='var-INHERIT'><filename>INHERIT</filename></link>
variable:
<literallayout class='monospaced'>
INHERIT+= "distrodata"
</literallayout>
</para>
<para>
The <filename>distrodata</filename> class also provides the
<link linkend='ref-tasks-checkpkg'><filename>do_checkpkg</filename></link>
task, which can be used against a simple recipe or against an
image to get all its recipe information.
</para>
</section>
<section id='ref-classes-distutils'>
<title><filename>distutils*.bbclass</filename></title>
<para>
The <filename>distutils*</filename> classes support recipes for Python
version 2.x extensions, which are simple.
These recipes usually only need to point to the source's archive and
then inherit the proper class.
Building is split into two methods depending on which method the
module authors used.
<itemizedlist>
<listitem><para>Extensions that use an Autotools-based build system
require Autotools and the classes based on
<filename>distutils</filename> in their recipes.
</para></listitem>
<listitem><para>Extensions that use build systems based on
<filename>distutils</filename> require
the <filename>distutils</filename> class in their recipes.
</para></listitem>
<listitem><para>Extensions that use build systems based on
<filename>setuptools</filename> require the
<link linkend='ref-classes-setuptools'><filename>setuptools</filename></link>
class in their recipes.
</para></listitem>
</itemizedlist>
The <filename>distutils-common-base</filename> class is required by
some of the <filename>distutils*</filename> classes to provide common
Python2 support.
</para>
<para>
The <filename>distutils-tools</filename> class supports recipes for
additional "distutils" tools.
</para>
</section>
<section id='ref-classes-distutils3'>
<title><filename>distutils3*.bbclass</filename></title>
<para>
The <filename>distutils3*</filename> classes support recipes for Python
version 3.x extensions, which are simple.
These recipes usually only need to point to the source's archive and
then inherit the proper class.
Building is split into three methods depending on which method the
module authors used.
<itemizedlist>
<listitem><para>Extensions that use an Autotools-based build system
require Autotools and
<filename>distutils</filename>-based classes in their recipes.
</para></listitem>
<listitem><para>Extensions that use
<filename>distutils</filename>-based build systems require
the <filename>distutils</filename> class in their recipes.
</para></listitem>
<listitem><para>Extensions that use build systems based on
<filename>setuptools3</filename> require the
<link linkend='ref-classes-setuptools'><filename>setuptools3</filename></link>
class in their recipes.
</para></listitem>
</itemizedlist>
The <filename>distutils3*</filename> classes either inherit their
corresponding <filename>distutils*</filename> class or replicate them
using a Python3 version instead (e.g.
<filename>distutils3-base</filename> inherits
<filename>distutils-common-base</filename>, which is the same as
<filename>distutils-base</filename> but inherits
<filename>python3native</filename> instead of
<filename>pythonnative</filename>).
</para>
</section>
<section id='ref-classes-externalsrc'>
<title><filename>externalsrc.bbclass</filename></title>
<para>
The <filename>externalsrc</filename> class supports building software
from source code that is external to the OpenEmbedded build system.
Building software from an external source tree means that the build
system's normal fetch, unpack, and patch process is not used.
</para>
<para>
By default, the OpenEmbedded build system uses the
<link linkend='var-S'><filename>S</filename></link> and
<link linkend='var-B'><filename>B</filename></link> variables to
locate unpacked recipe source code and to build it, respectively.
When your recipe inherits the <filename>externalsrc</filename> class,
you use the
<link linkend='var-EXTERNALSRC'><filename>EXTERNALSRC</filename></link>
and
<link linkend='var-EXTERNALSRC_BUILD'><filename>EXTERNALSRC_BUILD</filename></link>
variables to ultimately define <filename>S</filename> and
<filename>B</filename>.
</para>
<para>
By default, this class expects the source code to support recipe builds
that use the <link linkend='var-B'><filename>B</filename></link>
variable to point to the directory in which the OpenEmbedded build
system places the generated objects built from the recipes.
By default, the <filename>B</filename> directory is set to the
following, which is separate from the source directory
(<filename>S</filename>):
<literallayout class='monospaced'>
${WORKDIR}/${BPN}/{PV}/
</literallayout>
See these variables for more information:
<link linkend='var-WORKDIR'><filename>WORKDIR</filename></link>,
<link linkend='var-BPN'><filename>BPN</filename></link>, and
<link linkend='var-PV'><filename>PV</filename></link>,
</para>
<para>
For more information on the
<filename>externalsrc</filename> class, see the comments in
<filename>meta/classes/externalsrc.bbclass</filename> in the
<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>.
For information on how to use the <filename>externalsrc</filename>
class, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#building-software-from-an-external-source'>Building Software from an External Source</ulink>"
section in the Yocto Project Development Manual.
</para>
</section>
<section id='ref-classes-extrausers'>
<title><filename>extrausers.bbclass</filename></title>
<para>
The <filename>extrausers</filename> class allows
additional user and group configuration to be applied at the image
level.
Inheriting this class either globally or from an image recipe allows
additional user and group operations to be performed using the
<link linkend='var-EXTRA_USERS_PARAMS'><filename>EXTRA_USERS_PARAMS</filename></link>
variable.
<note>
The user and group operations added using the
<filename>extrausers</filename> class are not tied to a specific
recipe outside of the recipe for the image.
Thus, the operations can be performed across the image as a whole.
Use the
<link linkend='ref-classes-useradd'><filename>useradd</filename></link>
class to add user and group configuration to a specific recipe.
</note>
Here is an example that uses this class in an image recipe:
<literallayout class='monospaced'>
inherit extrausers
EXTRA_USERS_PARAMS = "\
useradd -p '' tester; \
groupadd developers; \
userdel nobody; \
groupdel -g video; \
groupmod -g 1020 developers; \
usermod -s /bin/sh tester; \
"
</literallayout>
Here is an example that adds two users named "tester-jim" and
"tester-sue" and assigns passwords:
<literallayout class='monospaced'>
inherit extrausers
EXTRA_USERS_PARAMS = "\
useradd -P tester01 tester-jim; \
useradd -P tester01 tester-sue; \
"
</literallayout>
Finally, here is an example that sets the root password to
"1876*18":
<literallayout class='monospaced'>
inherit extrausers
EXTRA_USERS_PARAMS = "\
usermod -P 1876*18 root; \
"
</literallayout>
</para>
</section>
<section id='ref-classes-fontcache'>
<title><filename>fontcache.bbclass</filename></title>
<para>
The <filename>fontcache</filename> class generates the
proper post-install and post-remove (postinst and postrm)
scriptlets for font packages.
These scriptlets call <filename>fc-cache</filename> (part of
<filename>Fontconfig</filename>) to add the fonts to the font
information cache.
Since the cache files are architecture-specific,
<filename>fc-cache</filename> runs using QEMU if the postinst
scriptlets need to be run on the build host during image creation.
</para>
<para>
If the fonts being installed are in packages other than the main
package, set
<link linkend='var-FONT_PACKAGES'><filename>FONT_PACKAGES</filename></link>
to specify the packages containing the fonts.
</para>
</section>
<section id='ref-classes-fs-uuid'>
<title><filename>fs-uuid.bbclass</filename></title>
<para>
The <filename>fs-uuid</filename> class extracts UUID from
<filename>${</filename><link linkend='var-ROOTFS'><filename>ROOTFS</filename></link><filename>}</filename>,
which must have been built by the time that this function gets called.
The <filename>fs-uuid</filename> class only works on
<filename>ext</filename> file systems and depends on
<filename>tune2fs</filename>.
</para>
</section>
<section id='ref-classes-gconf'>
<title><filename>gconf.bbclass</filename></title>
<para>
The <filename>gconf</filename> class provides common
functionality for recipes that need to install GConf schemas.
The schemas will be put into a separate package
(<filename>${</filename><link linkend='var-PN'><filename>PN</filename></link><filename>}-gconf</filename>)
that is created automatically when this class is inherited.
This package uses the appropriate post-install and post-remove
(postinst/postrm) scriptlets to register and unregister the schemas
in the target image.
</para>
</section>
<section id='ref-classes-gettext'>
<title><filename>gettext.bbclass</filename></title>
<para>
The <filename>gettext</filename> class provides support for
building software that uses the GNU <filename>gettext</filename>
internationalization and localization system.
All recipes building software that use
<filename>gettext</filename> should inherit this class.
</para>
</section>
<section id='ref-classes-gnome'>
<title><filename>gnome.bbclass</filename></title>
<para>
The <filename>gnome</filename> class supports recipes that
build software from the GNOME stack.
This class inherits the
<link linkend='ref-classes-gnomebase'><filename>gnomebase</filename></link>,
<link linkend='ref-classes-gtk-icon-cache'><filename>gtk-icon-cache</filename></link>,
<link linkend='ref-classes-gconf'><filename>gconf</filename></link> and
<link linkend='ref-classes-mime'><filename>mime</filename></link> classes.
The class also disables GObject introspection where applicable.
</para>
</section>
<section id='ref-classes-gnomebase'>
<title><filename>gnomebase.bbclass</filename></title>
<para>
The <filename>gnomebase</filename> class is the base
class for recipes that build software from the GNOME stack.
This class sets
<link linkend='var-SRC_URI'><filename>SRC_URI</filename></link> to
download the source from the GNOME mirrors as well as extending
<link linkend='var-FILES'><filename>FILES</filename></link>
with the typical GNOME installation paths.
</para>
</section>
<section id='ref-classes-gobject-introspection'>
<title><filename>gobject-introspection.bbclass</filename></title>
<para>
Provides support for recipes building software that
supports GObject introspection.
This functionality is only enabled if the
"gobject-introspection-data" feature is in
<link linkend='var-DISTRO_FEATURES'><filename>DISTRO_FEATURES</filename></link>
as well as "qemu-usermode" being in
<link linkend='var-MACHINE_FEATURES'><filename>MACHINE_FEATURES</filename></link>.
<note>
This functionality is backfilled by default and,
if not applicable, should be disabled through
<link linkend='var-DISTRO_FEATURES_BACKFILL_CONSIDERED'><filename>DISTRO_FEATURES_BACKFILL_CONSIDERED</filename></link>
or
<link linkend='var-MACHINE_FEATURES_BACKFILL_CONSIDERED'><filename>MACHINE_FEATURES_BACKFILL_CONSIDERED</filename></link>,
respectively.
</note>
</para>
</section>
<section id='ref-classes-grub-efi'>
<title><filename>grub-efi.bbclass</filename></title>
<para>
The <filename>grub-efi</filename>
class provides <filename>grub-efi</filename>-specific functions for
building bootable images.
</para>
<para>
This class supports several variables:
<itemizedlist>
<listitem><para>
<link linkend='var-INITRD'><filename>INITRD</filename></link>:
Indicates list of filesystem images to concatenate and use
as an initial RAM disk (initrd) (optional).
</para></listitem>
<listitem><para>
<link linkend='var-ROOTFS'><filename>ROOTFS</filename></link>:
Indicates a filesystem image to include as the root filesystem
(optional).</para></listitem>
<listitem><para>
<link linkend='var-GRUB_GFXSERIAL'><filename>GRUB_GFXSERIAL</filename></link>:
Set this to "1" to have graphics and serial in the boot menu.
</para></listitem>
<listitem><para>
<link linkend='var-LABELS'><filename>LABELS</filename></link>:
A list of targets for the automatic configuration.
</para></listitem>
<listitem><para>
<link linkend='var-APPEND'><filename>APPEND</filename></link>:
An override list of append strings for each
<filename>LABEL</filename>.
</para></listitem>
<listitem><para>
<link linkend='var-GRUB_OPTS'><filename>GRUB_OPTS</filename></link>:
Additional options to add to the configuration (optional).
Options are delimited using semi-colon characters
(<filename>;</filename>).</para></listitem>
<listitem><para>
<link linkend='var-GRUB_TIMEOUT'><filename>GRUB_TIMEOUT</filename></link>:
Timeout before executing the default <filename>LABEL</filename>
(optional).
</para></listitem>
</itemizedlist>
</para>
</section>
<section id='ref-classes-gsettings'>
<title><filename>gsettings.bbclass</filename></title>
<para>
The <filename>gsettings</filename> class
provides common functionality for recipes that need to install
GSettings (glib) schemas.
The schemas are assumed to be part of the main package.
Appropriate post-install and post-remove (postinst/postrm)
scriptlets are added to register and unregister the schemas in the
target image.
</para>
</section>
<section id='ref-classes-gtk-doc'>
<title><filename>gtk-doc.bbclass</filename></title>
<para>
The <filename>gtk-doc</filename> class
is a helper class to pull in the appropriate
<filename>gtk-doc</filename> dependencies and disable
<filename>gtk-doc</filename>.
</para>
</section>
<section id='ref-classes-gtk-icon-cache'>
<title><filename>gtk-icon-cache.bbclass</filename></title>
<para>
The <filename>gtk-icon-cache</filename> class
generates the proper post-install and post-remove (postinst/postrm)
scriptlets for packages that use GTK+ and install icons.
These scriptlets call <filename>gtk-update-icon-cache</filename> to add
the fonts to GTK+'s icon cache.
Since the cache files are architecture-specific,
<filename>gtk-update-icon-cache</filename> is run using QEMU if the
postinst scriptlets need to be run on the build host during image
creation.
</para>
</section>
<section id='ref-classes-gtk-immodules-cache'>
<title><filename>gtk-immodules-cache.bbclass</filename></title>
<para>
The <filename>gtk-immodules-cache</filename> class
generates the proper post-install and post-remove (postinst/postrm)
scriptlets for packages that install GTK+ input method modules for
virtual keyboards.
These scriptlets call <filename>gtk-update-icon-cache</filename> to add
the input method modules to the cache.
Since the cache files are architecture-specific,
<filename>gtk-update-icon-cache</filename> is run using QEMU if the
postinst scriptlets need to be run on the build host during image
creation.
</para>
<para>
If the input method modules being installed are in packages other than
the main package, set
<link linkend='var-GTKIMMODULES_PACKAGES'><filename>GTKIMMODULES_PACKAGES</filename></link>
to specify the packages containing the modules.
</para>
</section>
<section id='ref-classes-gummiboot'>
<title><filename>gummiboot.bbclass</filename></title>
<para>
The <filename>gummiboot</filename> class provides functions specific
to the gummiboot bootloader for building bootable images.
This is an internal class and is not intended to be
used directly.
Set the
<link linkend='var-EFI_PROVIDER'><filename>EFI_PROVIDER</filename></link>
variable to "gummiboot" to use this class.
</para>
<para>
For information on more variables used and supported in this class,
see the
<link linkend='var-GUMMIBOOT_CFG'><filename>GUMMIBOOT_CFG</filename></link>,
<link linkend='var-GUMMIBOOT_ENTRIES'><filename>GUMMIBOOT_ENTRIES</filename></link>,
and
<link linkend='var-GUMMIBOOT_TIMEOUT'><filename>GUMMIBOOT_TIMEOUT</filename></link>
variables.
</para>
<para>
You can also see the
<ulink url='http://freedesktop.org/wiki/Software/gummiboot/'>Gummiboot documentation</ulink>
for more information.
</para>
</section>
<section id='ref-classes-gzipnative'>
<title><filename>gzipnative.bbclass</filename></title>
<para>
The <filename>gzipnative</filename> class enables the use of
different native versions of <filename>gzip</filename>
and <filename>pigz</filename> rather than the versions of these tools
from the build host.
</para>
</section>
<section id='ref-classes-icecc'>
<title><filename>icecc.bbclass</filename></title>
<para>
The <filename>icecc</filename> class supports
<ulink url='https://github.com/icecc/icecream'>Icecream</ulink>, which
facilitates taking compile jobs and distributing them among remote
machines.
</para>
<para>
The class stages directories with symlinks from <filename>gcc</filename>
and <filename>g++</filename> to <filename>icecc</filename>, for both
native and cross compilers.
Depending on each configure or compile, the OpenEmbedded build system
adds the directories at the head of the <filename>PATH</filename> list
and then sets the <filename>ICECC_CXX</filename> and
<filename>ICEC_CC</filename> variables, which are the paths to the
<filename>g++</filename> and <filename>gcc</filename> compilers,
respectively.
</para>
<para>
For the cross compiler, the class creates a <filename>tar.gz</filename>
file that contains the Yocto Project toolchain and sets
<filename>ICECC_VERSION</filename>, which is the version of the
cross-compiler used in the cross-development toolchain, accordingly.
</para>
<para>
The class handles all three different compile stages
(i.e native ,cross-kernel and target) and creates the necessary
environment <filename>tar.gz</filename> file to be used by the remote
machines.
The class also supports SDK generation.
</para>
<para>
If <link linkend='var-ICECC_PATH'><filename>ICECC_PATH</filename></link>
is not set in your <filename>local.conf</filename> file, then the
class tries to locate the <filename>icecc</filename> binary
using <filename>which</filename>.
If
<link linkend='var-ICECC_ENV_EXEC'><filename>ICECC_ENV_EXEC</filename></link>
is set in your <filename>local.conf</filename> file, the variable should
point to the <filename>icecc-create-env</filename> script
provided by the user.
If you do not point to a user-provided script, the build system
uses the default script provided by the recipe
<filename>icecc-create-env-native.bb</filename>.
<note>
This script is a modified version and not the one that comes with
<filename>icecc</filename>.
</note>
</para>
<para>
If you do not want the Icecream distributed compile support to apply
to specific recipes or classes, you can effectively "blacklist" them
by listing the recipes and classes using the
<link linkend='var-ICECC_USER_PACKAGE_BL'><filename>ICECC_USER_PACKAGE_BL</filename></link>
and
<link linkend='var-ICECC_USER_CLASS_BL'><filename>ICECC_USER_CLASS_BL</filename></link>,
variables, respectively, in your <filename>local.conf</filename> file.
Doing so causes the OpenEmbedded build system to handle these
compilations locally.
</para>
<para>
Additionally, you can list recipes using the
<link linkend='var-ICECC_USER_PACKAGE_WL'><filename>ICECC_USER_PACKAGE_WL</filename></link>
variable in your <filename>local.conf</filename> file to force
<filename>icecc</filename> to be enabled for recipes using an empty
<link linkend='var-PARALLEL_MAKE'><filename>PARALLEL_MAKE</filename></link>
variable.
</para>
<para>
Inheriting the <filename>icecc</filename> class changes all sstate
signatures.
Consequently, if a development team has a dedicated build system
that populates
<link linkend='var-SSTATE_MIRRORS'><filename>STATE_MIRRORS</filename></link>
and they want to reuse sstate from
<filename>STATE_MIRRORS</filename>, then all developers and the
build system need to either inherit the <filename>icecc</filename>
class or nobody should.
</para>
<para>
At the distribution level, you can inherit the
<filename>icecc</filename> class to be sure that all builders start
with the same sstate signatures.
After inheriting the class, you can then disable the feature by setting
the
<link linkend='var-ICECC_DISABLED'><filename>ICECC_DISABLED</filename></link>
variable to "1" as follows:
<literallayout class='monospaced'>
INHERIT_DISTRO_append = " icecc"
ICECC_DISABLED ??= "1"
</literallayout>
This practice makes sure everyone is using the same signatures but also
requires individuals that do want to use Icecream to enable the feature
individually as follows in your <filename>local.conf</filename> file:
<literallayout class='monospaced'>
ICECC_DISABLED = ""
</literallayout>
</para>
</section>
<section id='ref-classes-image'>
<title><filename>image.bbclass</filename></title>
<para>
The <filename>image</filename> class helps support creating images
in different formats.
First, the root filesystem is created from packages using
one of the <filename>rootfs*.bbclass</filename>
files (depending on the package format used) and then one or more image
files are created.
<itemizedlist>
<listitem><para>The
<filename><link linkend='var-IMAGE_FSTYPES'>IMAGE_FSTYPES</link></filename>
variable controls the types of images to generate.
</para></listitem>
<listitem><para>The
<filename><link linkend='var-IMAGE_INSTALL'>IMAGE_INSTALL</link></filename>
variable controls the list of packages to install into the
image.</para></listitem>
</itemizedlist>
For information on customizing images, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#usingpoky-extend-customimage'>Customizing Images</ulink>"
section in the Yocto Project Development Manual.
For information on how images are created, see the
"<link linkend='images-dev-environment'>Images</link>" section elsewhere
in this manual.
</para>
</section>
<section id='ref-classes-image-buildinfo'>
<title><filename>image-buildinfo.bbclass</filename></title>
<para>
The <filename>image-buildinfo</filename> class writes information
to the target filesystem on <filename>/etc/build</filename>.
</para>
</section>
<section id='ref-classes-image_types'>
<title><filename>image_types.bbclass</filename></title>
<para>
The <filename>image_types</filename> class defines all of
the standard image output types that you can enable through the
<link linkend='var-IMAGE_FSTYPES'><filename>IMAGE_FSTYPES</filename></link>
variable.
You can use this class as a reference on how to add support for custom
image output types.
</para>
<para>
By default, this class is enabled through the
<link linkend='var-IMAGE_CLASSES'><filename>IMAGE_CLASSES</filename></link>
variable in
<link linkend='ref-classes-image'><filename>image.bbclass</filename></link>.
If you define your own image types using a custom BitBake class and
then use <filename>IMAGE_CLASSES</filename> to enable it, the custom
class must either inherit <filename>image_types</filename> or
<filename>image_types</filename> must also appear in
<filename>IMAGE_CLASSES</filename>.
</para>
</section>
<section id='ref-classes-image_types_uboot'>
<title><filename>image_types_uboot.bbclass</filename></title>
<para>
The <filename>image_types_uboot</filename> class
defines additional image types specifically for the U-Boot bootloader.
</para>
</section>
<section id='ref-classes-image-live'>
<title><filename>image-live.bbclass</filename></title>
<para>
The <filename>image-live</filename> class supports building "live"
images.
</para>
<para>
Normally, you do not use this class directly.
Instead, you add "live" to
<link linkend='var-IMAGE_FSTYPES'><filename>IMAGE_FSTYPES</filename></link>.
For example, if you were building an ISO image, you would add "live"
to <filename>IMAGE_FSTYPES</filename>, set the
<link linkend='var-NOISO'><filename>NOISO</filename></link> variable to
"0" and the build system would use the <filename>image-live</filename>
class to build the ISO image.
</para>
</section>
<section id='ref-classes-image-mklibs'>
<title><filename>image-mklibs.bbclass</filename></title>
<para>
The <filename>image-mklibs</filename> class
enables the use of the <filename>mklibs</filename> utility during the
<link linkend='ref-tasks-rootfs'><filename>do_rootfs</filename></link>
task, which optimizes the size of
libraries contained in the image.
</para>
<para>
By default, the class is enabled in the
<filename>local.conf.template</filename> using the
<link linkend='var-USER_CLASSES'><filename>USER_CLASSES</filename></link>
variable as follows:
<literallayout class='monospaced'>
USER_CLASSES ?= "buildstats image-mklibs image-prelink"
</literallayout>
</para>
</section>
<section id='ref-classes-image-prelink'>
<title><filename>image-prelink.bbclass</filename></title>
<para>
The <filename>image-prelink</filename> class
enables the use of the <filename>prelink</filename> utility during
the
<link linkend='ref-tasks-rootfs'><filename>do_rootfs</filename></link>
task, which optimizes the dynamic
linking of shared libraries to reduce executable startup time.
</para>
<para>
By default, the class is enabled in the
<filename>local.conf.template</filename> using the
<link linkend='var-USER_CLASSES'><filename>USER_CLASSES</filename></link>
variable as follows:
<literallayout class='monospaced'>
USER_CLASSES ?= "buildstats image-mklibs image-prelink"
</literallayout>
</para>
</section>
<section id='ref-classes-image-swab'>
<title><filename>image-swab.bbclass</filename></title>
<para>
The <filename>image-swab</filename> class enables the
<ulink url='&YOCTO_HOME_URL;/tools-resources/projects/swabber'>Swabber</ulink>
tool in order to detect and log accesses to the host system during
the OpenEmbedded build process.
<note>
This class is currently unmaintained.
The <filename>strace</filename> package needs to be installed
in the build host as a dependency for this tool.
</note>
</para>
</section>
<section id='ref-classes-image-vm'>
<title><filename>image-vm.bbclass</filename></title>
<para>
The <filename>image-vm</filename> class supports building VM
images.
</para>
</section>
<section id='ref-classes-image-vmdk'>
<title><filename>image-vmdk.bbclass</filename></title>
<para>
The <filename>image-vmdk</filename> class supports building VMware
VMDK images.
Normally, you do not use this class directly.
Instead, you add "vmdk" to
<link linkend='var-IMAGE_FSTYPES'><filename>IMAGE_FSTYPES</filename></link>.
</para>
</section>
<section id='ref-classes-insane'>
<title><filename>insane.bbclass</filename></title>
<para>
The <filename>insane</filename> class adds a step to the package
generation process so that output quality assurance checks are
generated by the OpenEmbedded build system.
A range of checks are performed that check the build's output
for common problems that show up during runtime.
Distribution policy usually dictates whether to include this class.
</para>
<para>
You can configure the sanity checks so that specific test failures
either raise a warning or an error message.
Typically, failures for new tests generate a warning.
Subsequent failures for the same test would then generate an error
message once the metadata is in a known and good condition.
See the
"<link linkend='ref-qa-checks'>QA Error and Warning Messages</link>"
Chapter for a list of all the warning and error messages
you might encounter using a default configuration.
</para>
<para>
Use the
<link linkend='var-WARN_QA'><filename>WARN_QA</filename></link> and
<link linkend='var-ERROR_QA'><filename>ERROR_QA</filename></link>
variables to control the behavior of
these checks at the global level (i.e. in your custom distro
configuration).
However, to skip one or more checks in recipes, you should use
<link linkend='var-INSANE_SKIP'><filename>INSANE_SKIP</filename></link>.
For example, to skip the check for symbolic link
<filename>.so</filename> files in the main package of a recipe,
add the following to the recipe.
You need to realize that the package name override, in this example
<filename>${PN}</filename>, must be used:
<literallayout class='monospaced'>
INSANE_SKIP_${PN} += "dev-so"
</literallayout>
Please keep in mind that the QA checks exist in order to detect real
or potential problems in the packaged output.
So exercise caution when disabling these checks.
</para>
<para>
The following list shows the tests you can list with the
<filename>WARN_QA</filename> and <filename>ERROR_QA</filename>
variables:
<itemizedlist>
<listitem><para><emphasis><filename>already-stripped:</filename></emphasis>
Checks that produced binaries have not already been
stripped prior to the build system extracting debug symbols.
It is common for upstream software projects to default to
stripping debug symbols for output binaries.
In order for debugging to work on the target using
<filename>-dbg</filename> packages, this stripping must be
disabled.
</para></listitem>
<listitem><para><emphasis><filename>arch:</filename></emphasis>
Checks the Executable and Linkable Format (ELF) type, bit size,
and endianness of any binaries to ensure they match the target
architecture.
This test fails if any binaries do not match the type since
there would be an incompatibility.
The test could indicate that the
wrong compiler or compiler options have been used.
Sometimes software, like bootloaders, might need to bypass
this check.
</para></listitem>
<listitem><para><emphasis><filename>buildpaths:</filename></emphasis>
Checks for paths to locations on the build host inside the
output files.
Currently, this test triggers too many false positives and
thus is not normally enabled.
</para></listitem>
<listitem><para><emphasis><filename>build-deps:</filename></emphasis>
Determines if a build-time dependency that is specified through
<link linkend='var-DEPENDS'><filename>DEPENDS</filename></link>,
explicit
<link linkend='var-RDEPENDS'><filename>RDEPENDS</filename></link>,
or task-level dependencies exists to match any runtime
dependency.
This determination is particularly useful to discover where
runtime dependencies are detected and added during packaging.
If no explicit dependency has been specified within the
metadata, at the packaging stage it is too late to ensure that
the dependency is built, and thus you can end up with an
error when the package is installed into the image during the
<link linkend='ref-tasks-rootfs'><filename>do_rootfs</filename></link>
task because the auto-detected dependency was not satisfied.
An example of this would be where the
<link linkend='ref-classes-update-rc.d'><filename>update-rc.d</filename></link>
class automatically adds a dependency on the
<filename>initscripts-functions</filename> package to packages
that install an initscript that refers to
<filename>/etc/init.d/functions</filename>.
The recipe should really have an explicit
<filename>RDEPENDS</filename> for the package in question on
<filename>initscripts-functions</filename> so that the
OpenEmbedded build system is able to ensure that the
<filename>initscripts</filename> recipe is actually built and
thus the <filename>initscripts-functions</filename> package is
made available.
</para></listitem>
<listitem><para><emphasis><filename>compile-host-path:</filename></emphasis>
Checks the
<link linkend='ref-tasks-compile'><filename>do_compile</filename></link>
log for indications
that paths to locations on the build host were used.
Using such paths might result in host contamination of the
build output.
</para></listitem>
<listitem><para><emphasis><filename>debug-deps:</filename></emphasis>
Checks that all packages except <filename>-dbg</filename>
packages do not depend on <filename>-dbg</filename>
packages, which would cause a packaging bug.
</para></listitem>
<listitem><para><emphasis><filename>debug-files:</filename></emphasis>
Checks for <filename>.debug</filename> directories in anything but the
<filename>-dbg</filename> package.
The debug files should all be in the <filename>-dbg</filename> package.
Thus, anything packaged elsewhere is incorrect packaging.</para></listitem>
<listitem><para><emphasis><filename>dep-cmp:</filename></emphasis>
Checks for invalid version comparison statements in runtime
dependency relationships between packages (i.e. in
<link linkend='var-RDEPENDS'><filename>RDEPENDS</filename></link>,
<link linkend='var-RRECOMMENDS'><filename>RRECOMMENDS</filename></link>,
<link linkend='var-RSUGGESTS'><filename>RSUGGESTS</filename></link>,
<link linkend='var-RPROVIDES'><filename>RPROVIDES</filename></link>,
<link linkend='var-RREPLACES'><filename>RREPLACES</filename></link>,
and
<link linkend='var-RCONFLICTS'><filename>RCONFLICTS</filename></link>
variable values).
Any invalid comparisons might trigger failures or undesirable
behavior when passed to the package manager.
</para></listitem>
<listitem><para><emphasis><filename>desktop:</filename></emphasis>
Runs the <filename>desktop-file-validate</filename> program
against any <filename>.desktop</filename> files to validate
their contents against the specification for
<filename>.desktop</filename> files.</para></listitem>
<listitem><para><emphasis><filename>dev-deps:</filename></emphasis>
Checks that all packages except <filename>-dev</filename>
or <filename>-staticdev</filename> packages do not depend on
<filename>-dev</filename> packages, which would be a
packaging bug.</para></listitem>
<listitem><para><emphasis><filename>dev-so:</filename></emphasis>
Checks that the <filename>.so</filename> symbolic links are in the
<filename>-dev</filename> package and not in any of the other packages.
In general, these symlinks are only useful for development purposes.
Thus, the <filename>-dev</filename> package is the correct location for
them.
Some very rare cases do exist for dynamically loaded modules where
these symlinks are needed instead in the main package.
</para></listitem>
<listitem><para><emphasis><filename>file-rdeps:</filename></emphasis>
Checks that file-level dependencies identified by the
OpenEmbedded build system at packaging time are satisfied.
For example, a shell script might start with the line
<filename>#!/bin/bash</filename>.
This line would translate to a file dependency on
<filename>/bin/bash</filename>.
Of the three package managers that the OpenEmbedded build
system supports, only RPM directly handles file-level
dependencies, resolving them automatically to packages
providing the files.
However, the lack of that functionality in the other two
package managers does not mean the dependencies do not still
need resolving.
This QA check attempts to ensure that explicitly declared
<link linkend='var-RDEPENDS'><filename>RDEPENDS</filename></link>
exist to handle any file-level dependency detected in
packaged files.
</para></listitem>
<listitem><para><emphasis><filename>files-invalid:</filename></emphasis>
Checks for
<link linkend='var-FILES'><filename>FILES</filename></link>
variable values that contain "//", which is invalid.
</para></listitem>
<listitem><para><emphasis><filename>incompatible-license:</filename></emphasis>
Report when packages are excluded from being created due to
being marked with a license that is in
<link linkend='var-INCOMPATIBLE_LICENSE'><filename>INCOMPATIBLE_LICENSE</filename></link>.
</para></listitem>
<listitem><para><emphasis><filename>install-host-path:</filename></emphasis>
Checks the
<link linkend='ref-tasks-install'><filename>do_install</filename></link>
log for indications
that paths to locations on the build host were used.
Using such paths might result in host contamination of the
build output.
</para></listitem>
<listitem><para><emphasis><filename>installed-vs-shipped:</filename></emphasis>
Reports when files have been installed within
<filename>do_install</filename> but have not been included in
any package by way of the
<link linkend='var-FILES'><filename>FILES</filename></link>
variable.
Files that do not appear in any package cannot be present in
an image later on in the build process.
Ideally, all installed files should be packaged or not
installed at all.
These files can be deleted at the end of
<filename>do_install</filename> if the files are not
needed in any package.
</para></listitem>
<listitem><para><emphasis><filename>la:</filename></emphasis>
Checks <filename>.la</filename> files for any <filename>TMPDIR</filename>
paths.
Any <filename>.la</filename> file containing these paths is incorrect since
<filename>libtool</filename> adds the correct sysroot prefix when using the
files automatically itself.</para></listitem>
<listitem><para><emphasis><filename>ldflags:</filename></emphasis>
Ensures that the binaries were linked with the
<link linkend='var-LDFLAGS'><filename>LDFLAGS</filename></link>
options provided by the build system.
If this test fails, check that the <filename>LDFLAGS</filename> variable
is being passed to the linker command.</para></listitem>
<listitem><para><emphasis><filename>libdir:</filename></emphasis>
Checks for libraries being installed into incorrect
(possibly hardcoded) installation paths.
For example, this test will catch recipes that install
<filename>/lib/bar.so</filename> when
<filename>${base_libdir}</filename> is "lib32".
Another example is when recipes install
<filename>/usr/lib64/foo.so</filename> when
<filename>${libdir}</filename> is "/usr/lib".
</para></listitem>
<listitem><para><emphasis><filename>libexec:</filename></emphasis>
Checks if a package contains files in
<filename>/usr/libexec</filename>.
This check is not performed if the
<filename>libexecdir</filename> variable has been set
explicitly to <filename>/usr/libexec</filename>.
</para></listitem>
<listitem><para><emphasis><filename>packages-list:</filename></emphasis>
Checks for the same package being listed multiple times through
the <link linkend='var-PACKAGES'><filename>PACKAGES</filename></link>
variable value.
Installing the package in this manner can cause errors during
packaging.
</para></listitem>
<listitem><para><emphasis><filename>perm-config:</filename></emphasis>
Reports lines in <filename>fs-perms.txt</filename> that have
an invalid format.
</para></listitem>
<listitem><para><emphasis><filename>perm-line:</filename></emphasis>
Reports lines in <filename>fs-perms.txt</filename> that have
an invalid format.
</para></listitem>
<listitem><para><emphasis><filename>perm-link:</filename></emphasis>
Reports lines in <filename>fs-perms.txt</filename> that
specify 'link' where the specified target already exists.
</para></listitem>
<listitem><para><emphasis><filename>perms:</filename></emphasis>
Currently, this check is unused but reserved.
</para></listitem>
<listitem><para><emphasis><filename>pkgconfig:</filename></emphasis>
Checks <filename>.pc</filename> files for any
<link linkend='var-TMPDIR'><filename>TMPDIR</filename></link>/<link linkend='var-WORKDIR'><filename>WORKDIR</filename></link>
paths.
Any <filename>.pc</filename> file containing these paths is incorrect
since <filename>pkg-config</filename> itself adds the correct sysroot prefix
when the files are accessed.</para></listitem>
<listitem><para><emphasis><filename>pkgname:</filename></emphasis>
Checks that all packages in
<link linkend='var-PACKAGES'><filename>PACKAGES</filename></link>
have names that do not contain invalid characters (i.e.
characters other than 0-9, a-z, ., +, and -).
</para></listitem>
<listitem><para><emphasis><filename>pkgv-undefined:</filename></emphasis>
Checks to see if the <filename>PKGV</filename> variable
is undefined during
<link linkend='ref-tasks-package'><filename>do_package</filename></link>.
</para></listitem>
<listitem><para><emphasis><filename>pkgvarcheck:</filename></emphasis>
Checks through the variables
<link linkend='var-RDEPENDS'><filename>RDEPENDS</filename></link>,
<link linkend='var-RRECOMMENDS'><filename>RRECOMMENDS</filename></link>,
<link linkend='var-RSUGGESTS'><filename>RSUGGESTS</filename></link>,
<link linkend='var-RCONFLICTS'><filename>RCONFLICTS</filename></link>,
<link linkend='var-RPROVIDES'><filename>RPROVIDES</filename></link>,
<link linkend='var-RREPLACES'><filename>RREPLACES</filename></link>,
<link linkend='var-FILES'><filename>FILES</filename></link>,
<link linkend='var-ALLOW_EMPTY'><filename>ALLOW_EMPTY</filename></link>,
<filename>pkg_preinst</filename>,
<filename>pkg_postinst</filename>,
<filename>pkg_prerm</filename>
and <filename>pkg_postrm</filename>, and reports if there are
variable sets that are not package-specific.
Using these variables without a package suffix is bad practice,
and might unnecessarily complicate dependencies of other packages
within the same recipe or have other unintended consequences.
</para></listitem>
<listitem><para><emphasis><filename>pn-overrides:</filename></emphasis>
Checks that a recipe does not have a name
(<link linkend='var-PN'><filename>PN</filename></link>) value
that appears in
<link linkend='var-OVERRIDES'><filename>OVERRIDES</filename></link>.
If a recipe is named such that its <filename>PN</filename>
value matches something already in
<filename>OVERRIDES</filename> (e.g. <filename>PN</filename>
happens to be the same as
<link linkend='var-MACHINE'><filename>MACHINE</filename></link>
or
<link linkend='var-DISTRO'><filename>DISTRO</filename></link>),
it can have unexpected consequences.
For example, assignments such as
<filename>FILES_${PN} = "xyz"</filename> effectively turn into
<filename>FILES = "xyz"</filename>.
</para></listitem>
<listitem><para><emphasis><filename>rpaths:</filename></emphasis>
Checks for rpaths in the binaries that contain build system paths such
as <filename>TMPDIR</filename>.
If this test fails, bad <filename>-rpath</filename> options are being
passed to the linker commands and your binaries have potential security
issues.</para></listitem>
<listitem><para><emphasis><filename>split-strip:</filename></emphasis>
Reports that splitting or stripping debug symbols from binaries
has failed.
</para></listitem>
<listitem><para><emphasis><filename>staticdev:</filename></emphasis>
Checks for static library files (<filename>*.a</filename>) in
non-<filename>staticdev</filename> packages.
</para></listitem>
<listitem><para><emphasis><filename>symlink-to-sysroot:</filename></emphasis>
Checks for symlinks in packages that point into
<link linkend='var-TMPDIR'><filename>TMPDIR</filename></link>
on the host.
Such symlinks will work on the host, but are clearly invalid
when running on the target.
</para></listitem>
<listitem><para><emphasis><filename>textrel:</filename></emphasis>
Checks for ELF binaries that contain relocations in their
<filename>.text</filename> sections, which can result in a
performance impact at runtime.
See the explanation for the
<link linkend='qa-issue-textrel'><filename>ELF binary</filename></link>
message for more information regarding runtime performance issues.
</para></listitem>
<listitem><para><emphasis><filename>unsafe-references-in-binaries:</filename></emphasis>
Reports when a binary installed in
<filename>${base_libdir}</filename>,
<filename>${base_bindir}</filename>, or
<filename>${base_sbindir}</filename>, depends on another
binary installed under <filename>${exec_prefix}</filename>.
This dependency is a concern if you want the system to remain
basically operable if <filename>/usr</filename> is mounted
separately and is not mounted.
<note>
Defaults for binaries installed in
<filename>${base_libdir}</filename>,
<filename>${base_bindir}</filename>, and
<filename>${base_sbindir}</filename> are
<filename>/lib</filename>, <filename>/bin</filename>, and
<filename>/sbin</filename>, respectively.
The default for a binary installed
under <filename>${exec_prefix}</filename> is
<filename>/usr</filename>.
</note>
</para></listitem>
<listitem><para><emphasis><filename>unsafe-references-in-scripts:</filename></emphasis>
Reports when a script file installed in
<filename>${base_libdir}</filename>,
<filename>${base_bindir}</filename>, or
<filename>${base_sbindir}</filename>, depends on files
installed under <filename>${exec_prefix}</filename>.
This dependency is a concern if you want the system to remain
basically operable if <filename>/usr</filename> is mounted
separately and is not mounted.
<note>
Defaults for binaries installed in
<filename>${base_libdir}</filename>,
<filename>${base_bindir}</filename>, and
<filename>${base_sbindir}</filename> are
<filename>/lib</filename>, <filename>/bin</filename>, and
<filename>/sbin</filename>, respectively.
The default for a binary installed
under <filename>${exec_prefix}</filename> is
<filename>/usr</filename>.
</note>
</para></listitem>
<listitem><para><emphasis><filename>useless-rpaths:</filename></emphasis>
Checks for dynamic library load paths (rpaths) in the binaries that
by default on a standard system are searched by the linker (e.g.
<filename>/lib</filename> and <filename>/usr/lib</filename>).
While these paths will not cause any breakage, they do waste space and
are unnecessary.</para></listitem>
<listitem><para><emphasis><filename>var-undefined:</filename></emphasis>
Reports when variables fundamental to packaging (i.e.
<link linkend='var-WORKDIR'><filename>WORKDIR</filename></link>,
<link linkend='var-DEPLOY_DIR'><filename>DEPLOY_DIR</filename></link>,
<link linkend='var-D'><filename>D</filename></link>,
<link linkend='var-PN'><filename>PN</filename></link>, and
<link linkend='var-PKGD'><filename>PKGD</filename></link>) are
undefined during
<link linkend='ref-tasks-package'><filename>do_package</filename></link>.
</para></listitem>
<listitem><para><emphasis><filename>version-going-backwards:</filename></emphasis>
If Build History is enabled, reports when a package
being written out has a lower version than the previously
written package under the same name.
If you are placing output packages into a feed and
upgrading packages on a target system using that feed, the
version of a package going backwards can result in the target
system not correctly upgrading to the "new" version of the
package.
<note>
If you are not using runtime package management on your
target system, then you do not need to worry about
this situation.
</note>
</para></listitem>
<listitem><para><emphasis><filename>xorg-driver-abi:</filename></emphasis>
Checks that all packages containing Xorg drivers have ABI
dependencies.
The <filename>xserver-xorg</filename> recipe provides driver
ABI names.
All drivers should depend on the ABI versions that they have
been built against.
Driver recipes that include
<filename>xorg-driver-input.inc</filename>
or <filename>xorg-driver-video.inc</filename> will
automatically get these versions.
Consequently, you should only need to explicitly add
dependencies to binary driver recipes.
</para></listitem>
</itemizedlist>
</para>
</section>
<section id='ref-classes-insserv'>
<title><filename>insserv.bbclass</filename></title>
<para>
The <filename>insserv</filename> class
uses the <filename>insserv</filename> utility to update the order of
symbolic links in <filename>/etc/rc?.d/</filename> within an image
based on dependencies specified by LSB headers in the
<filename>init.d</filename> scripts themselves.
</para>
</section>
<section id='ref-classes-kernel'>
<title><filename>kernel.bbclass</filename></title>
<para>
The <filename>kernel</filename> class handles building Linux kernels.
The class contains code to build all kernel trees.
All needed headers are staged into the
<filename><link linkend='var-STAGING_KERNEL_DIR'>STAGING_KERNEL_DIR</link></filename>
directory to allow out-of-tree module builds using
the
<link linkend='ref-classes-module'><filename>module</filename></link>
class.
</para>
<para>
This means that each built kernel module is packaged separately and inter-module
dependencies are created by parsing the <filename>modinfo</filename> output.
If all modules are required, then installing the <filename>kernel-modules</filename>
package installs all packages with modules and various other kernel packages
such as <filename>kernel-vmlinux</filename>.
</para>
<para>
Various other classes are used by the <filename>kernel</filename>
and <filename>module</filename> classes internally including the
<link linkend='ref-classes-kernel-arch'><filename>kernel-arch</filename></link>,
<link linkend='ref-classes-module-base'><filename>module-base</filename></link>,
and
<link linkend='ref-classes-linux-kernel-base'><filename>linux-kernel-base</filename></link>
classes.
</para>
</section>
<section id='ref-classes-kernel-arch'>
<title><filename>kernel-arch.bbclass</filename></title>
<para>
The <filename>kernel-arch</filename> class
sets the <filename>ARCH</filename> environment variable for Linux
kernel compilation (including modules).
</para>
</section>
<section id='ref-classes-kernel-fitimage'>
<title><filename>kernel-fitimage.bbclass</filename></title>
<para>
The <filename>kernel-fitimage</filename> class provides support to
pack zImages.
</para>
</section>
<section id='ref-classes-kernel-grub'>
<title><filename>kernel-grub.bbclass</filename></title>
<para>
The <filename>kernel-grub</filename> class updates the boot area and
the boot menu with the kernel as the priority boot mechanism while
installing a RPM to update the kernel on a deployed target.
</para>
</section>
<section id='ref-classes-kernel-module-split'>
<title><filename>kernel-module-split.bbclass</filename></title>
<para>
The <filename>kernel-module-split</filename> class
provides common functionality for splitting Linux kernel modules into
separate packages.
</para>
</section>
<section id='ref-classes-kernel-uboot'>
<title><filename>kernel-uboot.bbclass</filename></title>
<para>
The <filename>kernel-uboot</filename> class provides support for
building from vmlinux-style kernel sources.
</para>
</section>
<section id='ref-classes-kernel-uimage'>
<title><filename>kernel-uimage.bbclass</filename></title>
<para>
The <filename>kernel-uimage</filename> class provides support to
pack uImage.
</para>
</section>
<section id='ref-classes-kernel-yocto'>
<title><filename>kernel-yocto.bbclass</filename></title>
<para>
The <filename>kernel-yocto</filename> class
provides common functionality for building from linux-yocto style
kernel source repositories.
</para>
</section>
<section id='ref-classes-kernelsrc'>
<title><filename>kernelsrc.bbclass</filename></title>
<para>
The <filename>kernelsrc</filename> class sets the Linux kernel
source and version.
</para>
</section>
<section id='ref-classes-lib_package'>
<title><filename>lib_package.bbclass</filename></title>
<para>
The <filename>lib_package</filename> class
supports recipes that build libraries and produce executable
binaries, where those binaries should not be installed by default
along with the library.
Instead, the binaries are added to a separate
<filename>${</filename><link linkend='var-PN'><filename>PN</filename></link><filename>}-bin</filename>
package to make their installation optional.
</para>
</section>
<section id='ref-classes-libc*'>
<title><filename>libc*.bbclass</filename></title>
<para>
The <filename>libc*</filename> classes support recipes that build
packages with <filename>libc</filename>:
<itemizedlist>
<listitem><para>The <filename>libc-common</filename> class
provides common support for building with
<filename>libc</filename>.
</para></listitem>
<listitem><para>The <filename>libc-package</filename> class
supports packaging up <filename>glibc</filename> and
<filename>eglibc</filename>.
</para></listitem>
</itemizedlist>
</para>
</section>
<section id='ref-classes-license'>
<title><filename>license.bbclass</filename></title>
<para>
The <filename>license</filename> class provides license
manifest creation and license exclusion.
This class is enabled by default using the default value for the
<link linkend='var-INHERIT_DISTRO'><filename>INHERIT_DISTRO</filename></link>
variable.
</para>
</section>
<section id='ref-classes-linux-kernel-base'>
<title><filename>linux-kernel-base.bbclass</filename></title>
<para>
The <filename>linux-kernel-base</filename> class
provides common functionality for recipes that build out of the Linux
kernel source tree.
These builds goes beyond the kernel itself.
For example, the Perf recipe also inherits this class.
</para>
</section>
<section id='ref-classes-linuxloader'>
<title><filename>linuxloader.bbclass</filename></title>
<para>
Provides the function <filename>linuxloader()</filename>, which gives
the value of the dynamic loader/linker provided on the platform.
This value is used by a number of other classes.
</para>
</section>
<section id='ref-classes-logging'>
<title><filename>logging.bbclass</filename></title>
<para>
The <filename>logging</filename> class provides the standard
shell functions used to log messages for various BitBake severity levels
(i.e. <filename>bbplain</filename>, <filename>bbnote</filename>,
<filename>bbwarn</filename>, <filename>bberror</filename>,
<filename>bbfatal</filename>, and <filename>bbdebug</filename>).
</para>
<para>
This class is enabled by default since it is inherited by
the <filename>base</filename> class.
</para>
</section>
<section id='ref-classes-meta'>
<title><filename>meta.bbclass</filename></title>
<para>
The <filename>meta</filename> class is inherited by recipes
that do not build any output packages themselves, but act as a "meta"
target for building other recipes.
</para>
</section>
<section id='ref-classes-metadata_scm'>
<title><filename>metadata_scm.bbclass</filename></title>
<para>
The <filename>metadata_scm</filename> class provides functionality for
querying the branch and revision of a Source Code Manager (SCM)
repository.
</para>
<para>
The <link linkend='ref-classes-base'><filename>base</filename></link>
class uses this class to print the revisions of each layer before
starting every build.
The <filename>metadata_scm</filename> class is enabled by default
because it is inherited by the <filename>base</filename> class.
</para>
</section>
<section id='ref-classes-migrate_localcount'>
<title><filename>migrate_localcount.bbclass</filename></title>
<para>
The <filename>migrate_localcount</filename> class verifies a recipe's
localcount data and increments it appropriately.
</para>
</section>
<section id='ref-classes-mime'>
<title><filename>mime.bbclass</filename></title>
<para>
The <filename>mime</filename> class generates the proper
post-install and post-remove (postinst/postrm) scriptlets for packages
that install MIME type files.
These scriptlets call <filename>update-mime-database</filename> to add
the MIME types to the shared database.
</para>
</section>
<section id='ref-classes-mirrors'>
<title><filename>mirrors.bbclass</filename></title>
<para>
The <filename>mirrors</filename> class sets up some standard
<link linkend='var-MIRRORS'><filename>MIRRORS</filename></link> entries
for source code mirrors.
These mirrors provide a fall-back path in case the upstream source
specified in
<link linkend='var-SRC_URI'><filename>SRC_URI</filename></link>
within recipes is unavailable.
</para>
<para>
This class is enabled by default since it is inherited by the
<link linkend='ref-classes-base'><filename>base</filename></link> class.
</para>
</section>
<section id='ref-classes-module'>
<title><filename>module.bbclass</filename></title>
<para>
The <filename>module</filename> class provides support for building
out-of-tree Linux kernel modules.
The class inherits the
<link linkend='ref-classes-module-base'><filename>module-base</filename></link>
and
<link linkend='ref-classes-kernel-module-split'><filename>kernel-module-split</filename></link>
classes, and implements the
<link linkend='ref-tasks-compile'><filename>do_compile</filename></link>
and
<link linkend='ref-tasks-install'><filename>do_install</filename></link>
tasks.
The class provides everything needed to build and package a kernel
module.
</para>
<para>
For general information on out-of-tree Linux kernel modules, see the
"<ulink url='&YOCTO_DOCS_KERNEL_URL;#incorporating-out-of-tree-modules'>Incorporating Out-of-Tree Modules</ulink>"
section in the Yocto Project Linux Kernel Development Manual.
</para>
</section>
<section id='ref-classes-module-base'>
<title><filename>module-base.bbclass</filename></title>
<para>
The <filename>module-base</filename> class provides the base
functionality for building Linux kernel modules.
Typically, a recipe that builds software that includes one or
more kernel modules and has its own means of building
the module inherits this class as opposed to inheriting the
<link linkend='ref-classes-module'><filename>module</filename></link>
class.
</para>
</section>
<section id='ref-classes-multilib*'>
<title><filename>multilib*.bbclass</filename></title>
<para>
The <filename>multilib*</filename> classes provide support
for building libraries with different target optimizations or target
architectures and installing them side-by-side in the same image.
</para>
<para>
For more information on using the Multilib feature, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#combining-multiple-versions-library-files-into-one-image'>Combining Multiple Versions of Library Files into One Image</ulink>"
section in the Yocto Project Development Manual.
</para>
</section>
<section id='ref-classes-native'>
<title><filename>native.bbclass</filename></title>
<para>
The <filename>native</filename> class provides common
functionality for recipes that wish to build tools to run on the build
host (i.e. tools that use the compiler or other tools from the
build host).
</para>
<para>
You can create a recipe that builds tools that run natively on the
host a couple different ways:
<itemizedlist>
<listitem><para>Create a <replaceable>myrecipe</replaceable><filename>-native.bb</filename>
that inherits the <filename>native</filename> class.
If you use this method, you must order the inherit statement
in the recipe after all other inherit statements so that the
<filename>native</filename> class is inherited last.
</para></listitem>
<listitem><para>Create or modify a target recipe that contains
the following:
<literallayout class='monospaced'>
<link linkend='var-BBCLASSEXTEND'><filename>BBCLASSEXTEND</filename></link> = "native"
</literallayout>
Inside the recipe, use <filename>_class-native</filename> and
<filename>_class-target</filename> overrides to specify any
functionality specific to the respective native or target
case.</para></listitem>
</itemizedlist>
</para>
<para>
Although applied differently, the <filename>native</filename> class is
used with both methods.
The advantage of the second method is that you do not need to have two
separate recipes (assuming you need both) for native and target.
All common parts of the recipe are automatically shared.
</para>
</section>
<section id='ref-classes-nativesdk'>
<title><filename>nativesdk.bbclass</filename></title>
<para>
The <filename>nativesdk</filename> class provides common
functionality for recipes that wish to build tools to run as part of
an SDK (i.e. tools that run on
<link linkend='var-SDKMACHINE'><filename>SDKMACHINE</filename></link>).
</para>
<para>
You can create a recipe that builds tools that run on the SDK machine
a couple different ways:
<itemizedlist>
<listitem><para>Create a
<filename>nativesdk-</filename><replaceable>myrecipe</replaceable><filename>.bb</filename>
recipe that inherits the <filename>nativesdk</filename> class.
If you use this method, you must order the inherit statement
in the recipe after all other inherit statements so that the
<filename>nativesdk</filename> class is inherited last.
</para></listitem>
<listitem><para>Create a <filename>nativesdk</filename> variant
of any recipe by adding the following:
<literallayout class='monospaced'>
<link linkend='var-BBCLASSEXTEND'><filename>BBCLASSEXTEND</filename></link> = "nativesdk"
</literallayout>
Inside the recipe, use <filename>_class-nativesdk</filename> and
<filename>_class-target</filename> overrides to specify any
functionality specific to the respective SDK machine or target
case.</para></listitem>
</itemizedlist>
</para>
<para>
Although applied differently, the <filename>nativesdk</filename> class
is used with both methods.
The advantage of the second method is that you do not need to have two
separate recipes (assuming you need both) for the SDK machine and the
target.
All common parts of the recipe are automatically shared.
</para>
</section>
<section id='ref-classes-nopackages'>
<title><filename>nopackages.bbclass</filename></title>
<para>
Disables packaging tasks for those recipes and classes where
packaging is not needed.
</para>
</section>
<section id='ref-classes-npm'>
<title><filename>npm.bbclass</filename></title>
<para>
Provides support for building Node.js software fetched using the npm
package manager.
<note>
Currently, recipes inheriting this class must use the
<filename>npm://</filename> fetcher to have dependencies fetched
and packaged automatically.
</note>
</para>
</section>
<section id='ref-classes-oelint'>
<title><filename>oelint.bbclass</filename></title>
<para>
The <filename>oelint</filename> class is an
obsolete lint checking tool that exists in
<filename>meta/classes</filename> in the
<ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>.
</para>
<para>
A number of classes exist that could be generally useful in
OE-Core but are never actually used within OE-Core itself.
The <filename>oelint</filename> class is one such example.
However, being aware of this class can reduce the proliferation of
different versions of similar classes across multiple layers.
</para>
</section>
<section id='ref-classes-own-mirrors'>
<title><filename>own-mirrors.bbclass</filename></title>
<para>
The <filename>own-mirrors</filename> class makes it
easier to set up your own
<link linkend='var-PREMIRRORS'><filename>PREMIRRORS</filename></link>
from which to first fetch source before attempting to fetch it from the
upstream specified in
<link linkend='var-SRC_URI'><filename>SRC_URI</filename></link>
within each recipe.
</para>
<para>
To use this class, inherit it globally and specify
<link linkend='var-SOURCE_MIRROR_URL'><filename>SOURCE_MIRROR_URL</filename></link>.
Here is an example:
<literallayout class='monospaced'>
INHERIT += "own-mirrors"
SOURCE_MIRROR_URL = "http://example.com/my-source-mirror"
</literallayout>
You can specify only a single URL in
<filename>SOURCE_MIRROR_URL</filename>.
</para>
</section>
<section id='ref-classes-package'>
<title><filename>package.bbclass</filename></title>
<para>
The <filename>package</filename> class supports generating
packages from a build's output.
The core generic functionality is in
<filename>package.bbclass</filename>.
The code specific to particular package types resides in these
package-specific classes:
<link linkend='ref-classes-package_deb'><filename>package_deb</filename></link>,
<link linkend='ref-classes-package_rpm'><filename>package_rpm</filename></link>,
<link linkend='ref-classes-package_ipk'><filename>package_ipk</filename></link>,
and
<link linkend='ref-classes-package_tar'><filename>package_tar</filename></link>.
<note><title>Warning</title>
The <filename>package_tar</filename> class is broken and not
supported.
It is recommended that you do not use this class.
</note>
</para>
<para>
You can control the list of resulting package formats by using the
<filename><link linkend='var-PACKAGE_CLASSES'>PACKAGE_CLASSES</link></filename>
variable defined in your <filename>conf/local.conf</filename>
configuration file, which is located in the
<ulink url='&YOCTO_DOCS_DEV_URL;#build-directory'>Build Directory</ulink>.
When defining the variable, you can specify one or more package types.
Since images are generated from packages, a packaging class is
needed to enable image generation.
The first class listed in this variable is used for image generation.
</para>
<para>
If you take the optional step to set up a repository (package feed)
on the development host that can be used by Smart, you can
install packages from the feed while you are running the image
on the target (i.e. runtime installation of packages).
For more information, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#using-runtime-package-management'>Using Runtime Package Management</ulink>"
section in the Yocto Project Development Manual.
</para>
<para>
The package-specific class you choose can affect build-time performance
and has space ramifications.
In general, building a package with IPK takes about thirty percent less
time as compared to using RPM to build the same or similar package.
This comparison takes into account a complete build of the package with
all dependencies previously built.
The reason for this discrepancy is because the RPM package manager
creates and processes more
<ulink url='&YOCTO_DOCS_DEV_URL;#metadata'>Metadata</ulink> than the
IPK package manager.
Consequently, you might consider setting
<filename>PACKAGE_CLASSES</filename> to "package_ipk" if you are
building smaller systems.
</para>
<para>
Before making your package manager decision, however, you should
consider some further things about using RPM:
<itemizedlist>
<listitem><para>
RPM starts to provide more abilities than IPK due to
the fact that it processes more Metadata.
For example, this information includes individual file types,
file checksum generation and evaluation on install, sparse file
support, conflict detection and resolution for Multilib systems,
ACID style upgrade, and repackaging abilities for rollbacks.
</para></listitem>
<listitem><para>
For smaller systems, the extra space used for the Berkeley
Database and the amount of metadata when using RPM can affect
your ability to perform on-device upgrades.
</para></listitem>
</itemizedlist>
</para>
<para>
You can find additional information on the effects of the package
class at these two Yocto Project mailing list links:
<itemizedlist>
<listitem><para><ulink url='&YOCTO_LISTS_URL;/pipermail/poky/2011-May/006362.html'>
https://lists.yoctoproject.org/pipermail/poky/2011-May/006362.html</ulink></para></listitem>
<listitem><para><ulink url='&YOCTO_LISTS_URL;/pipermail/poky/2011-May/006363.html'>
https://lists.yoctoproject.org/pipermail/poky/2011-May/006363.html</ulink></para></listitem>
</itemizedlist>
</para>
</section>
<section id='ref-classes-package_deb'>
<title><filename>package_deb.bbclass</filename></title>
<para>
The <filename>package_deb</filename> class
provides support for creating packages that use the Debian
(i.e. <filename>.deb</filename>) file format.
The class ensures the packages are written out in a
<filename>.deb</filename> file format to the
<filename>${</filename><link linkend='var-DEPLOY_DIR_DEB'><filename>DEPLOY_DIR_DEB</filename></link><filename>}</filename>
directory.
</para>
<para>
This class inherits the
<link linkend='ref-classes-package'><filename>package</filename></link>
class and is enabled through the
<link linkend='var-PACKAGE_CLASSES'><filename>PACKAGE_CLASSES</filename></link>
variable in the <filename>local.conf</filename> file.
</para>
</section>
<section id='ref-classes-package_ipk'>
<title><filename>package_ipk.bbclass</filename></title>
<para>
The <filename>package_ipk</filename> class
provides support for creating packages that use the IPK
(i.e. <filename>.ipk</filename>) file format.
The class ensures the packages are written out in a
<filename>.ipk</filename> file format to the
<filename>${</filename><link linkend='var-DEPLOY_DIR_IPK'><filename>DEPLOY_DIR_IPK</filename></link><filename>}</filename>
directory.
</para>
<para>
This class inherits the
<link linkend='ref-classes-package'><filename>package</filename></link>
class and is enabled through the
<link linkend='var-PACKAGE_CLASSES'><filename>PACKAGE_CLASSES</filename></link>
variable in the <filename>local.conf</filename> file.
</para>
</section>
<section id='ref-classes-package_rpm'>
<title><filename>package_rpm.bbclass</filename></title>
<para>
The <filename>package_rpm</filename> class
provides support for creating packages that use the RPM
(i.e. <filename>.rpm</filename>) file format.
The class ensures the packages are written out in a
<filename>.rpm</filename> file format to the
<filename>${</filename><link linkend='var-DEPLOY_DIR_RPM'><filename>DEPLOY_DIR_RPM</filename></link><filename>}</filename>
directory.
</para>
<para>
This class inherits the
<link linkend='ref-classes-package'><filename>package</filename></link>
class and is enabled through the
<link linkend='var-PACKAGE_CLASSES'><filename>PACKAGE_CLASSES</filename></link>
variable in the <filename>local.conf</filename> file.
</para>
</section>
<section id='ref-classes-package_tar'>
<title><filename>package_tar.bbclass</filename></title>
<para>
The <filename>package_tar</filename> class
provides support for creating tarballs.
The class ensures the packages are written out in a
tarball format to the
<filename>${</filename><link linkend='var-DEPLOY_DIR_TAR'><filename>DEPLOY_DIR_TAR</filename></link><filename>}</filename>
directory.
</para>
<para>
This class inherits the
<link linkend='ref-classes-package'><filename>package</filename></link>
class and is enabled through the
<link linkend='var-PACKAGE_CLASSES'><filename>PACKAGE_CLASSES</filename></link>
variable in the <filename>local.conf</filename> file.
<note>
You cannot specify the <filename>package_tar</filename> class
first using the <filename>PACKAGE_CLASSES</filename> variable.
You must use <filename>.deb</filename>,
<filename>.ipk</filename>, or <filename>.rpm</filename> file
formats for your image or SDK.
</note>
</para>
</section>
<section id='ref-classes-packagedata'>
<title><filename>packagedata.bbclass</filename></title>
<para>
The <filename>packagedata</filename> class provides
common functionality for reading <filename>pkgdata</filename> files
found in
<link linkend='var-PKGDATA_DIR'><filename>PKGDATA_DIR</filename></link>.
These files contain information about each output package produced by
the OpenEmbedded build system.
</para>
<para>
This class is enabled by default because it is inherited by the
<link linkend='ref-classes-package'><filename>package</filename></link>
class.
</para>
</section>
<section id='ref-classes-packagegroup'>
<title><filename>packagegroup.bbclass</filename></title>
<para>
The <filename>packagegroup</filename> class sets default values
appropriate for package group recipes (e.g.
<filename><link linkend='var-PACKAGES'>PACKAGES</link></filename>,
<filename><link linkend='var-PACKAGE_ARCH'>PACKAGE_ARCH</link></filename>,
<filename><link linkend='var-ALLOW_EMPTY'>ALLOW_EMPTY</link></filename>,
and so forth).
It is highly recommended that all package group recipes inherit this class.
</para>
<para>
For information on how to use this class, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#usingpoky-extend-customimage-customtasks'>Customizing Images Using Custom Package Groups</ulink>"
section in the Yocto Project Development Manual.
</para>
<para>
Previously, this class was called the <filename>task</filename> class.
</para>
</section>
<section id='ref-classes-patch'>
<title><filename>patch.bbclass</filename></title>
<para>
The <filename>patch</filename> class provides all functionality for
applying patches during the
<link linkend='ref-tasks-patch'><filename>do_patch</filename></link>
task.
</para>
<para>
This class is enabled by default because it is inherited by the
<link linkend='ref-classes-base'><filename>base</filename></link>
class.
</para>
</section>
<section id='ref-classes-perlnative'>
<title><filename>perlnative.bbclass</filename></title>
<para>
When inherited by a recipe, the <filename>perlnative</filename> class
supports using the native version of Perl built by the build system
rather than using the version provided by the build host.
</para>
</section>
<section id='ref-classes-pixbufcache'>
<title><filename>pixbufcache.bbclass</filename></title>
<para>
The <filename>pixbufcache</filename> class generates the proper
post-install and post-remove (postinst/postrm) scriptlets for packages
that install pixbuf loaders, which are used with
<filename>gdk-pixbuf</filename>.
These scriptlets call <filename>update_pixbuf_cache</filename>
to add the pixbuf loaders to the cache.
Since the cache files are architecture-specific,
<filename>update_pixbuf_cache</filename> is run using QEMU if the
postinst scriptlets need to be run on the build host during image
creation.
</para>
<para>
If the pixbuf loaders being installed are in packages other
than the recipe's main package, set
<link linkend='var-PIXBUF_PACKAGES'><filename>PIXBUF_PACKAGES</filename></link>
to specify the packages containing the loaders.
</para>
</section>
<section id='ref-classes-pkgconfig'>
<title><filename>pkgconfig.bbclass</filename></title>
<para>
The <filename>pkgconfig</filename> class provides a standard way to get
header and library information by using <filename>pkg-config</filename>.
This class aims to smooth integration of
<filename>pkg-config</filename> into libraries that use it.
</para>
<para>
During staging, BitBake installs <filename>pkg-config</filename>
data into the <filename>sysroots/</filename> directory.
By making use of sysroot functionality within
<filename>pkg-config</filename>, the <filename>pkgconfig</filename>
class no longer has to manipulate the files.
</para>
</section>
<section id='ref-classes-populate-sdk'>
<title><filename>populate_sdk.bbclass</filename></title>
<para>
The <filename>populate_sdk</filename> class provides support for
SDK-only recipes.
For information on advantages gained when building a cross-development
toolchain using the
<link linkend='ref-tasks-populate_sdk'><filename>do_populate_sdk</filename></link>
task, see the
"<ulink url='&YOCTO_DOCS_SDK_URL;#sdk-building-an-sdk-installer'>Building an SDK Installer</ulink>"
section in the Yocto Project Software Development Kit (SDK) Developer's Guide.
</para>
</section>
<section id='ref-classes-populate-sdk-*'>
<title><filename>populate_sdk_*.bbclass</filename></title>
<para>
The <filename>populate_sdk_*</filename> classes support SDK creation
and consist of the following classes:
<itemizedlist>
<listitem><para><emphasis><filename>populate_sdk_base</filename>:</emphasis>
The base class supporting SDK creation under all package
managers (i.e. DEB, RPM, and opkg).</para></listitem>
<listitem><para><emphasis><filename>populate_sdk_deb</filename>:</emphasis>
Supports creation of the SDK given the Debian package manager.
</para></listitem>
<listitem><para><emphasis><filename>populate_sdk_rpm</filename>:</emphasis>
Supports creation of the SDK given the RPM package manager.
</para></listitem>
<listitem><para><emphasis><filename>populate_sdk_ipk</filename>:</emphasis>
Supports creation of the SDK given the opkg (IPK format)
package manager.
</para></listitem>
<listitem><para><emphasis><filename>populate_sdk_ext</filename>:</emphasis>
Supports extensible SDK creation under all package managers.
</para></listitem>
</itemizedlist>
</para>
<para>
The <filename>populate_sdk_base</filename> class inherits the
appropriate <filename>populate_sdk_*</filename> (i.e.
<filename>deb</filename>, <filename>rpm</filename>, and
<filename>ipk</filename>) based on
<link linkend='var-IMAGE_PKGTYPE'><filename>IMAGE_PKGTYPE</filename></link>.
</para>
<para>
The base class ensures all source and destination directories are
established and then populates the SDK.
After populating the SDK, the <filename>populate_sdk_base</filename>
class constructs two sysroots:
<filename>${</filename><link linkend='var-SDK_ARCH'><filename>SDK_ARCH</filename></link><filename>}-nativesdk</filename>,
which contains the cross-compiler and associated tooling, and the
target, which contains a target root filesystem that is configured for
the SDK usage.
These two images reside in
<link linkend='var-SDK_OUTPUT'><filename>SDK_OUTPUT</filename></link>,
which consists of the following:
<literallayout class='monospaced'>
${SDK_OUTPUT}/${SDK_ARCH}<replaceable>-nativesdk-pkgs</replaceable>
${SDK_OUTPUT}/${SDKTARGETSYSROOT}/<replaceable>target-pkgs</replaceable>
</literallayout>
</para>
<para>
Finally, the base populate SDK class creates the toolchain
environment setup script, the tarball of the SDK, and the installer.
</para>
<para>
The respective <filename>populate_sdk_deb</filename>,
<filename>populate_sdk_rpm</filename>, and
<filename>populate_sdk_ipk</filename> classes each support the
specific type of SDK.
These classes are inherited by and used with the
<filename>populate_sdk_base</filename> class.
</para>
<para>
For more information on the cross-development toolchain
generation, see the
"<link linkend='cross-development-toolchain-generation'>Cross-Development Toolchain Generation</link>"
section.
For information on advantages gained when building a
cross-development toolchain using the
<link linkend='ref-tasks-populate_sdk'><filename>do_populate_sdk</filename></link>
task, see the
"<ulink url='&YOCTO_DOCS_SDK_URL;#sdk-building-an-sdk-installer'>Building an SDK Installer</ulink>"
section in the Yocto Project Software Development Kit (SDK) Developer's
Guide.
</para>
</section>
<section id='ref-classes-prexport'>
<title><filename>prexport.bbclass</filename></title>
<para>
The <filename>prexport</filename> class provides functionality for
exporting
<link linkend='var-PR'><filename>PR</filename></link> values.
<note>
This class is not intended to be used directly.
Rather, it is enabled when using
"<filename>bitbake-prserv-tool export</filename>".
</note>
</para>
</section>
<section id='ref-classes-primport'>
<title><filename>primport.bbclass</filename></title>
<para>
The <filename>primport</filename> class provides functionality for
importing
<link linkend='var-PR'><filename>PR</filename></link> values.
<note>
This class is not intended to be used directly.
Rather, it is enabled when using
"<filename>bitbake-prserv-tool import</filename>".
</note>
</para>
</section>
<section id='ref-classes-prserv'>
<title><filename>prserv.bbclass</filename></title>
<para>
The <filename>prserv</filename> class provides functionality for
using a
<ulink url='&YOCTO_DOCS_DEV_URL;#working-with-a-pr-service'>PR service</ulink>
in order to automatically manage the incrementing of the
<link linkend='var-PR'><filename>PR</filename></link> variable for
each recipe.
</para>
<para>
This class is enabled by default because it is inherited by the
<link linkend='ref-classes-package'><filename>package</filename></link>
class.
However, the OpenEmbedded build system will not enable the
functionality of this class unless
<link linkend='var-PRSERV_HOST'><filename>PRSERV_HOST</filename></link>
has been set.
</para>
</section>
<section id='ref-classes-ptest'>
<title><filename>ptest.bbclass</filename></title>
<para>
The <filename>ptest</filename> class provides functionality for
packaging and installing runtime tests for recipes that build software
that provides these tests.
</para>
<para>
This class is intended to be inherited by individual recipes.
However, the class' functionality is largely disabled unless "ptest"
appears in
<link linkend='var-DISTRO_FEATURES'><filename>DISTRO_FEATURES</filename></link>.
See the
"<ulink url='&YOCTO_DOCS_DEV_URL;#testing-packages-with-ptest'>Testing Packages With ptest</ulink>"
section in the Yocto Project Development Manual for more information
on ptest.
</para>
</section>
<section id='ref-classes-ptest-gnome'>
<title><filename>ptest-gnome.bbclass</filename></title>
<para>
Enables package tests (ptests) specifically for GNOME packages,
which have tests intended to be executed with
<filename>gnome-desktop-testing</filename>.
</para>
<para>
For information on setting up and running ptests, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#testing-packages-with-ptest'>Testing Packages With ptest</ulink>"
section in the Yocto Project Development Manual.
</para>
</section>
<section id='ref-classes-python-dir'>
<title><filename>python-dir.bbclass</filename></title>
<para>
The <filename>python-dir</filename> class provides the base version,
location, and site package location for Python.
</para>
</section>
<section id='ref-classes-python3native'>
<title><filename>python3native.bbclass</filename></title>
<para>
The <filename>python3native</filename> class supports using the
native version of Python 3 built by the build system rather than
support of the version provided by the build host.
</para>
</section>
<section id='ref-classes-pythonnative'>
<title><filename>pythonnative.bbclass</filename></title>
<para>
When inherited by a recipe, the <filename>pythonnative</filename> class
supports using the native version of Python built by the build system
rather than using the version provided by the build host.
</para>
</section>
<section id='ref-classes-qemu'>
<title><filename>qemu.bbclass</filename></title>
<para>
The <filename>qemu</filename> class provides functionality for recipes
that either need QEMU or test for the existence of QEMU.
Typically, this class is used to run programs for a target system on
the build host using QEMU's application emulation mode.
</para>
</section>
<section id='ref-classes-recipe_sanity'>
<title><filename>recipe_sanity.bbclass</filename></title>
<para>
The <filename>recipe_sanity</filename> class checks for the presence
of any host system recipe prerequisites that might affect the
build (e.g. variables that are set or software that is present).
</para>
</section>
<section id='ref-classes-relocatable'>
<title><filename>relocatable.bbclass</filename></title>
<para>
The <filename>relocatable</filename> class enables relocation of
binaries when they are installed into the sysroot.
</para>
<para>
This class makes use of the
<link linkend='ref-classes-chrpath'><filename>chrpath</filename></link>
class and is used by both the
<link linkend='ref-classes-cross'><filename>cross</filename></link>
and
<link linkend='ref-classes-native'><filename>native</filename></link>
classes.
</para>
</section>
<section id='ref-classes-remove-libtool'>
<title><filename>remove-libtool.bbclass</filename></title>
<para>
The <filename>remove-libtool</filename> class adds a post function
to the
<link linkend='ref-tasks-install'><filename>do_install</filename></link>
task to remove all <filename>.la</filename> files installed by
<filename>libtool</filename>.
Removing these files results in them being absent from both the
sysroot and target packages.
</para>
<para>
If a recipe needs the <filename>.la</filename> files to be installed,
then the recipe can override the removal by setting
<filename>REMOVE_LIBTOOL_LA</filename> to "0" as follows:
<literallayout class='monospaced'>
REMOVE_LIBTOOL_LA = "0"
</literallayout>
<note>
The <filename>remove-libtool</filename> class is not enabled by
default.
</note>
</para>
</section>
<section id='ref-classes-report-error'>
<title><filename>report-error.bbclass</filename></title>
<para>
The <filename>report-error</filename> class supports enabling the
<ulink url='&YOCTO_DOCS_DEV_URL;#using-the-error-reporting-tool'>error reporting tool</ulink>,
which allows you to submit build error information to a central
database.
</para>
<para>
The class collects debug information for recipe, recipe version, task,
machine, distro, build system, target system, host distro, branch,
commit, and log.
From the information, report files using a JSON format are created and
stored in
<filename>${</filename><link linkend='var-LOG_DIR'><filename>LOG_DIR</filename></link><filename>}/error-report</filename>.
</para>
</section>
<section id='ref-classes-rm-work'>
<title><filename>rm_work.bbclass</filename></title>
<para>
The <filename>rm_work</filename> class supports deletion of temporary
workspace, which can ease your hard drive demands during builds.
</para>
<para>
The OpenEmbedded build system can use a substantial amount of disk
space during the build process.
A portion of this space is the work files under the
<filename>${TMPDIR}/work</filename> directory for each recipe.
Once the build system generates the packages for a recipe, the work
files for that recipe are no longer needed.
However, by default, the build system preserves these files
for inspection and possible debugging purposes.
If you would rather have these files deleted to save disk space
as the build progresses, you can enable <filename>rm_work</filename>
by adding the following to your <filename>local.conf</filename> file,
which is found in the
<ulink url='&YOCTO_DOCS_DEV_URL;#build-directory'>Build Directory</ulink>.
<literallayout class='monospaced'>
INHERIT += "rm_work"
</literallayout>
If you are modifying and building source code out of the work directory
for a recipe, enabling <filename>rm_work</filename> will potentially
result in your changes to the source being lost.
To exclude some recipes from having their work directories deleted by
<filename>rm_work</filename>, you can add the names of the recipe or
recipes you are working on to the <filename>RM_WORK_EXCLUDE</filename>
variable, which can also be set in your <filename>local.conf</filename>
file.
Here is an example:
<literallayout class='monospaced'>
RM_WORK_EXCLUDE += "busybox glibc"
</literallayout>
</para>
</section>
<section id='ref-classes-rootfs*'>
<title><filename>rootfs*.bbclass</filename></title>
<para>
The <filename>rootfs*</filename> classes support creating
the root filesystem for an image and consist of the following classes:
<itemizedlist>
<listitem><para>
The <filename>rootfs-postcommands</filename> class, which
defines filesystem post-processing functions for image recipes.
</para></listitem>
<listitem><para>
The <filename>rootfs_deb</filename> class, which supports
creation of root filesystems for images built using
<filename>.deb</filename> packages.</para></listitem>
<listitem><para>
The <filename>rootfs_rpm</filename> class, which supports
creation of root filesystems for images built using
<filename>.rpm</filename> packages.</para></listitem>
<listitem><para>
The <filename>rootfs_ipk</filename> class, which supports
creation of root filesystems for images built using
<filename>.ipk</filename> packages.</para></listitem>
<listitem><para>
The <filename>rootfsdebugfiles</filename> class, which installs
additional files found on the build host directly into the
root filesystem.
</para></listitem>
</itemizedlist>
</para>
<para>
The root filesystem is created from packages using one of the
<filename>rootfs*.bbclass</filename> files as determined by the
<link linkend='var-PACKAGE_CLASSES'><filename>PACKAGE_CLASSES</filename></link>
variable.
</para>
<para>
For information on how root filesystem images are created, see the
"<link linkend='image-generation-dev-environment'>Image Generation</link>"
section.
</para>
</section>
<section id='ref-classes-sanity'>
<title><filename>sanity.bbclass</filename></title>
<para>
The <filename>sanity</filename> class checks to see if prerequisite
software is present on the host system so that users can be notified
of potential problems that might affect their build.
The class also performs basic user configuration checks from
the <filename>local.conf</filename> configuration file to
prevent common mistakes that cause build failures.
Distribution policy usually determines whether to include this class.
</para>
</section>
<section id='ref-classes-scons'>
<title><filename>scons.bbclass</filename></title>
<para>
The <filename>scons</filename> class supports recipes that need to
build software that uses the SCons build system.
You can use the
<link linkend='var-EXTRA_OESCONS'><filename>EXTRA_OESCONS</filename></link>
variable to specify additional configuration options you want to pass
SCons command line.
</para>
</section>
<section id='ref-classes-sdl'>
<title><filename>sdl.bbclass</filename></title>
<para>
The <filename>sdl</filename> class supports recipes that need to build
software that uses the Simple DirectMedia Layer (SDL) library.
</para>
</section>
<section id='ref-classes-setuptools'>
<title><filename>setuptools.bbclass</filename></title>
<para>
The <filename>setuptools</filename> class supports Python
version 2.x extensions that use build systems based on
<filename>setuptools</filename>.
If your recipe uses these build systems, the recipe needs to
inherit the <filename>setuptools</filename> class.
</para>
</section>
<section id='ref-classes-setuptools3'>
<title><filename>setuptools3.bbclass</filename></title>
<para>
The <filename>setuptools3</filename> class supports Python
version 3.x extensions that use build systems based on
<filename>setuptools3</filename>.
If your recipe uses these build systems, the recipe needs to
inherit the <filename>setuptools3</filename> class.
</para>
</section>
<section id='ref-classes-sign_rpm'>
<title><filename>sign_rpm.bbclass</filename></title>
<para>
The <filename>sign_rpm</filename> class supports generating signed
RPM packages.
</para>
</section>
<section id='ref-classes-sip'>
<title><filename>sip.bbclass</filename></title>
<para>
The <filename>sip</filename> class
supports recipes that build or package SIP-based Python bindings.
</para>
</section>
<section id='ref-classes-siteconfig'>
<title><filename>siteconfig.bbclass</filename></title>
<para>
The <filename>siteconfig</filename> class
provides functionality for handling site configuration.
The class is used by the
<link linkend='ref-classes-autotools'><filename>autotools</filename></link>
class to accelerate the
<link linkend='ref-tasks-configure'><filename>do_configure</filename></link>
task.
</para>
</section>
<section id='ref-classes-siteinfo'>
<title><filename>siteinfo.bbclass</filename></title>
<para>
The <filename>siteinfo</filename> class provides information about
the targets that might be needed by other classes or recipes.
</para>
<para>
As an example, consider Autotools, which can require tests that must
execute on the target hardware.
Since this is not possible in general when cross compiling, site
information is used to provide cached test results so these tests can
be skipped over but still make the correct values available.
The
<filename><link linkend='structure-meta-site'>meta/site directory</link></filename>
contains test results sorted into different categories such as
architecture, endianness, and the <filename>libc</filename> used.
Site information provides a list of files containing data relevant to
the current build in the
<filename><link linkend='var-CONFIG_SITE'>CONFIG_SITE</link></filename> variable
that Autotools automatically picks up.
</para>
<para>
The class also provides variables like
<filename><link linkend='var-SITEINFO_ENDIANNESS'>SITEINFO_ENDIANNESS</link></filename>
and <filename><link linkend='var-SITEINFO_BITS'>SITEINFO_BITS</link></filename>
that can be used elsewhere in the metadata.
</para>
<para>
Because the
<link linkend='ref-classes-base'><filename>base</filename></link> class
includes the <filename>siteinfo</filename> class, it is always active.
</para>
</section>
<section id='ref-classes-spdx'>
<title><filename>spdx.bbclass</filename></title>
<para>
The <filename>spdx</filename> class integrates real-time license
scanning, generation of SPDX standard output, and verification
of license information during the build.
<note>
This class is currently at the prototype stage in the 1.6
release.
</note>
</para>
</section>
<section id='ref-classes-sstate'>
<title><filename>sstate.bbclass</filename></title>
<para>
The <filename>sstate</filename> class provides support for Shared
State (sstate).
By default, the class is enabled through the
<link linkend='var-INHERIT_DISTRO'><filename>INHERIT_DISTRO</filename></link>
variable's default value.
</para>
<para>
For more information on sstate, see the
"<link linkend='shared-state-cache'>Shared State Cache</link>"
section.
</para>
</section>
<section id='ref-classes-staging'>
<title><filename>staging.bbclass</filename></title>
<para>
The <filename>staging</filename> class provides the
<link linkend='ref-tasks-populate_sysroot'><filename>do_populate_sysroot</filename></link>
task, which stages files into the sysroot to make them available to
other recipes at build time.
The class is enabled by default because it is inherited by the
<link linkend='ref-classes-base'><filename>base</filename></link>
class.
</para>
</section>
<section id='ref-classes-syslinux'>
<title><filename>syslinux.bbclass</filename></title>
<para>
The <filename>syslinux</filename> class provides syslinux-specific
functions for building bootable images.
</para>
<para>
The class supports the following variables:
<itemizedlist>
<listitem><para><link linkend='var-INITRD'><filename>INITRD</filename></link>:
Indicates list of filesystem images to concatenate and use as
an initial RAM disk (initrd).
This variable is optional.</para></listitem>
<listitem><para><link linkend='var-ROOTFS'><filename>ROOTFS</filename></link>:
Indicates a filesystem image to include as the root filesystem.
This variable is optional.</para></listitem>
<listitem><para><link linkend='var-AUTO_SYSLINUXMENU'><filename>AUTO_SYSLINUXMENU</filename></link>:
Enables creating an automatic menu when set to "1".
</para></listitem>
<listitem><para><link linkend='var-LABELS'><filename>LABELS</filename></link>:
Lists targets for automatic configuration.
</para></listitem>
<listitem><para><link linkend='var-APPEND'><filename>APPEND</filename></link>:
Lists append string overrides for each label.
</para></listitem>
<listitem><para><link linkend='var-SYSLINUX_OPTS'><filename>SYSLINUX_OPTS</filename></link>:
Lists additional options to add to the syslinux file.
Semicolon characters separate multiple options.
</para></listitem>
<listitem><para><link linkend='var-SYSLINUX_SPLASH'><filename>SYSLINUX_SPLASH</filename></link>:
Lists a background for the VGA boot menu when you are using the
boot menu.</para></listitem>
<listitem><para><link linkend='var-SYSLINUX_DEFAULT_CONSOLE'><filename>SYSLINUX_DEFAULT_CONSOLE</filename></link>:
Set to "console=ttyX" to change kernel boot default console.
</para></listitem>
<listitem><para><link linkend='var-SYSLINUX_SERIAL'><filename>SYSLINUX_SERIAL</filename></link>:
Sets an alternate serial port.
Or, turns off serial when the variable is set with an
empty string.</para></listitem>
<listitem><para><link linkend='var-SYSLINUX_SERIAL_TTY'><filename>SYSLINUX_SERIAL_TTY</filename></link>:
Sets an alternate "console=tty..." kernel boot argument.
</para></listitem>
</itemizedlist>
</para>
</section>
<section id='ref-classes-systemd'>
<title><filename>systemd.bbclass</filename></title>
<para>
The <filename>systemd</filename> class provides support for recipes
that install systemd unit files.
</para>
<para>
The functionality for this class is disabled unless you have "systemd"
in
<link linkend='var-DISTRO_FEATURES'><filename>DISTRO_FEATURES</filename></link>.
</para>
<para>
Under this class, the recipe or Makefile (i.e. whatever the recipe is
calling during the
<link linkend='ref-tasks-install'><filename>do_install</filename></link>
task) installs unit files into
<filename>${</filename><link linkend='var-D'><filename>D</filename></link><filename>}${systemd_unitdir}/system</filename>.
If the unit files being installed go into packages other than the
main package, you need to set
<link linkend='var-SYSTEMD_PACKAGES'><filename>SYSTEMD_PACKAGES</filename></link>
in your recipe to identify the packages in which the files will be
installed.
</para>
<para>
You should set
<link linkend='var-SYSTEMD_SERVICE'><filename>SYSTEMD_SERVICE</filename></link>
to the name of the service file.
You should also use a package name override to indicate the package
to which the value applies.
If the value applies to the recipe's main package, use
<filename>${</filename><link linkend='var-PN'><filename>PN</filename></link><filename>}</filename>.
Here is an example from the connman recipe:
<literallayout class='monospaced'>
SYSTEMD_SERVICE_${PN} = "connman.service"
</literallayout>
Services are set up to start on boot automatically unless
you have set
<link linkend='var-SYSTEMD_AUTO_ENABLE'><filename>SYSTEMD_AUTO_ENABLE</filename></link>
to "disable".
</para>
<para>
For more information on <filename>systemd</filename>, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#selecting-an-initialization-manager'>Selecting an Initialization Manager</ulink>"
section in the Yocto Project Development Manual.
</para>
</section>
<section id='ref-classes-terminal'>
<title><filename>terminal.bbclass</filename></title>
<para>
The <filename>terminal</filename> class provides support for starting
a terminal session.
The
<link linkend='var-OE_TERMINAL'><filename>OE_TERMINAL</filename></link>
variable controls which terminal emulator is used for the session.
</para>
<para>
Other classes use the <filename>terminal</filename> class anywhere a
separate terminal session needs to be started.
For example, the
<link linkend='ref-classes-patch'><filename>patch</filename></link>
class assuming
<link linkend='var-PATCHRESOLVE'><filename>PATCHRESOLVE</filename></link>
is set to "user", the
<link linkend='ref-classes-cml1'><filename>cml1</filename></link>
class, and the
<link linkend='ref-classes-devshell'><filename>devshell</filename></link>
class all use the <filename>terminal</filename> class.
</para>
</section>
<section id='ref-classes-testimage*'>
<title><filename>testimage*.bbclass</filename></title>
<para>
The <filename>testimage*</filename> classes support running
automated tests against images using QEMU and on actual hardware.
The classes handle loading the tests and starting the image.
To use the classes, you need to perform steps to set up the
environment.
</para>
<para>
The tests are commands that run on the target system over
<filename>ssh</filename>.
Each test is written in Python and makes use of the
<filename>unittest</filename> module.
</para>
<para>
The <filename>testimage.bbclass</filename> runs tests on an image
when called using the following:
<literallayout class='monospaced'>
$ bitbake -c testimage <replaceable>image</replaceable>
</literallayout>
The <filename>testimage-auto</filename> class runs tests on an image
after the image is constructed (i.e.
<link linkend='var-TEST_IMAGE'><filename>TEST_IMAGE</filename></link>
must be set to "1").
</para>
<para>
For information on how to enable, run, and create new tests, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#performing-automated-runtime-testing'>Performing Automated Runtime Testing</ulink>"
section in the Yocto Project Development Manual.
</para>
</section>
<section id='ref-classes-testsdk'>
<title><filename>testsdk.bbclass</filename></title>
<para>
This class supports running automated tests against
software development kits (SDKs).
The <filename>testsdk</filename> class runs tests on an SDK when
called using the following:
<literallayout class='monospaced'>
$ bitbake -c testsdk image
</literallayout>
</para>
</section>
<section id='ref-classes-texinfo'>
<title><filename>texinfo.bbclass</filename></title>
<para>
This class should be inherited by recipes whose upstream packages
invoke the <filename>texinfo</filename> utilities at build-time.
Native and cross recipes are made to use the dummy scripts provided
by <filename>texinfo-dummy-native</filename>, for improved performance.
Target architecture recipes use the genuine
Texinfo utilities.
By default, they use the Texinfo utilities on the host system.
<note>
If you want to use the Texinfo recipe shipped with the build
system, you can remove "texinfo-native" from
<link linkend='var-ASSUME_PROVIDED'><filename>ASSUME_PROVIDED</filename></link>
and makeinfo from
<link linkend='var-SANITY_REQUIRED_UTILITIES'><filename>SANITY_REQUIRED_UTILITIES</filename></link>.
</note>
</para>
</section>
<section id='ref-classes-tinderclient'>
<title><filename>tinderclient.bbclass</filename></title>
<para>
The <filename>tinderclient</filename> class submits build results to
an external Tinderbox instance.
<note>
This class is currently unmaintained.
</note>
</para>
</section>
<section id='ref-classes-toaster'>
<title><filename>toaster.bbclass</filename></title>
<para>
The <filename>toaster</filename> class collects information about
packages and images and sends them as events that the BitBake
user interface can receive.
The class is enabled when the Toaster user interface is running.
</para>
<para>
This class is not intended to be used directly.
</para>
</section>
<section id='ref-classes-toolchain-scripts'>
<title><filename>toolchain-scripts.bbclass</filename></title>
<para>
The <filename>toolchain-scripts</filename> class provides the scripts
used for setting up the environment for installed SDKs.
</para>
</section>
<section id='ref-classes-typecheck'>
<title><filename>typecheck.bbclass</filename></title>
<para>
The <filename>typecheck</filename> class provides support for
validating the values of variables set at the configuration level
against their defined types.
The OpenEmbedded build system allows you to define the type of a
variable using the "type" varflag.
Here is an example:
<literallayout class='monospaced'>
IMAGE_FEATURES[type] = "list"
</literallayout>
</para>
</section>
<section id='ref-classes-uboot-config'>
<title><filename>uboot-config.bbclass</filename></title>
<para>
The <filename>uboot-config</filename> class provides support for
U-Boot configuration for a machine.
Specify the machine in your recipe as follows:
<literallayout class='monospaced'>
UBOOT_CONFIG ??= &lt;default&gt;
UBOOT_CONFIG[foo] = "config,images"
</literallayout>
You can also specify the machine using this method:
<literallayout class='monospaced'>
UBOOT_MACHINE = "config"
</literallayout>
See the
<link linkend='var-UBOOT_CONFIG'><filename>UBOOT_CONFIG</filename></link>
and
<link linkend='var-UBOOT_MACHINE'><filename>UBOOT_MACHINE</filename></link>
variables for additional information.
</para>
</section>
<section id='ref-classes-uninative'>
<title><filename>uninative.bbclass</filename></title>
<para>
Attempts to isolate the build system from the host
distribution's C library in order to make re-use of native shared state
artifacts across different host distributions practical.
With this class enabled, a tarball containing a pre-built C library
is downloaded at the start of the build.
In the Poky reference distribution this is enabled by default
through
<filename>meta/conf/distro/include/yocto-uninative.inc</filename>.
Other distributions that do not derive from poky can also
"<filename>require conf/distro/include/yocto-uninative.inc</filename>"
to use this.
Alternatively if you prefer, you can build the uninative-tarball recipe
yourself, publish the resulting tarball (e.g. via HTTP) and set
<filename>UNINATIVE_URL</filename> and
<filename>UNINATIVE_CHECKSUM</filename> appropriately.
For an example, see the
<filename>meta/conf/distro/include/yocto-uninative.inc</filename>.
</para>
</section>
<section id='ref-classes-update-alternatives'>
<title><filename>update-alternatives.bbclass</filename></title>
<para>
The <filename>update-alternatives</filename> class helps the
alternatives system when multiple sources provide the same command.
This situation occurs when several programs that have the same or
similar function are installed with the same name.
For example, the <filename>ar</filename> command is available from the
<filename>busybox</filename>, <filename>binutils</filename> and
<filename>elfutils</filename> packages.
The <filename>update-alternatives</filename> class handles
renaming the binaries so that multiple packages can be installed
without conflicts.
The <filename>ar</filename> command still works regardless of which
packages are installed or subsequently removed.
The class renames the conflicting binary in each package and symlinks
the highest priority binary during installation or removal of packages.
</para>
<para>
To use this class, you need to define a number of variables:
<itemizedlist>
<listitem><para><link linkend='var-ALTERNATIVE'><filename>ALTERNATIVE</filename></link>
</para></listitem>
<listitem><para><link linkend='var-ALTERNATIVE_LINK_NAME'><filename>ALTERNATIVE_LINK_NAME</filename></link>
</para></listitem>
<listitem><para><link linkend='var-ALTERNATIVE_TARGET'><filename>ALTERNATIVE_TARGET</filename></link>
</para></listitem>
<listitem><para><link linkend='var-ALTERNATIVE_PRIORITY'><filename>ALTERNATIVE_PRIORITY</filename></link>
</para></listitem>
</itemizedlist>
These variables list alternative commands needed by a package,
provide pathnames for links, default links for targets, and
so forth.
For details on how to use this class, see the comments in the
<ulink url='&YOCTO_GIT_URL;/cgit/cgit.cgi/poky/tree/meta/classes/update-alternatives.bbclass'><filename>update-alternatives.bbclass</filename></ulink>.
</para>
<note>
You can use the <filename>update-alternatives</filename> command
directly in your recipes.
However, this class simplifies things in most cases.
</note>
</section>
<section id='ref-classes-update-rc.d'>
<title><filename>update-rc.d.bbclass</filename></title>
<para>
The <filename>update-rc.d</filename> class uses
<filename>update-rc.d</filename> to safely install an
initialization script on behalf of the package.
The OpenEmbedded build system takes care of details such as making
sure the script is stopped before a package is removed and started when
the package is installed.
</para>
<para>
Three variables control this class:
<filename><link linkend='var-INITSCRIPT_PACKAGES'>INITSCRIPT_PACKAGES</link></filename>,
<filename><link linkend='var-INITSCRIPT_NAME'>INITSCRIPT_NAME</link></filename> and
<filename><link linkend='var-INITSCRIPT_PARAMS'>INITSCRIPT_PARAMS</link></filename>.
See the variable links for details.
</para>
</section>
<section id='ref-classes-useradd'>
<title><filename>useradd*.bbclass</filename></title>
<para>
The <filename>useradd*</filename> classes support the addition of users
or groups for usage by the package on the target.
For example, if you have packages that contain system services that
should be run under their own user or group, you can use these classes
to enable creation of the user or group.
The <filename>meta-skeleton/recipes-skeleton/useradd/useradd-example.bb</filename>
recipe in the <ulink url='&YOCTO_DOCS_DEV_URL;#source-directory'>Source Directory</ulink>
provides a simple example that shows how to add three
users and groups to two packages.
See the <filename>useradd-example.bb</filename> recipe for more
information on how to use these classes.
</para>
<para>
The <filename>useradd_base</filename> class provides basic
functionality for user or groups settings.
</para>
<para>
The <filename>useradd*</filename> classes support the
<link linkend='var-USERADD_PACKAGES'><filename>USERADD_PACKAGES</filename></link>,
<link linkend='var-USERADD_PARAM'><filename>USERADD_PARAM</filename></link>,
<link linkend='var-GROUPADD_PARAM'><filename>GROUPADD_PARAM</filename></link>,
and
<link linkend='var-GROUPMEMS_PARAM'><filename>GROUPMEMS_PARAM</filename></link>
variables.
</para>
<para>
The <filename>useradd-staticids</filename> class supports the addition
of users or groups that have static user identification
(<filename>uid</filename>) and group identification
(<filename>gid</filename>) values.
</para>
<para>
The default behavior of the OpenEmbedded build system for assigning
<filename>uid</filename> and <filename>gid</filename> values when
packages add users and groups during package install time is to
add them dynamically.
This works fine for programs that do not care what the values of the
resulting users and groups become.
In these cases, the order of the installation determines the final
<filename>uid</filename> and <filename>gid</filename> values.
However, if non-deterministic
<filename>uid</filename> and <filename>gid</filename> values are a
problem, you can override the default, dynamic application of these
values by setting static values.
When you set static values, the OpenEmbedded build system looks in
<link linkend='var-BBPATH'><filename>BBPATH</filename></link> for
<filename>files/passwd</filename> and <filename>files/group</filename>
files for the values.
</para>
<para>
To use static <filename>uid</filename> and <filename>gid</filename>
values, you need to set some variables.
See the
<link linkend='var-USERADDEXTENSION'><filename>USERADDEXTENSION</filename></link>,
<link linkend='var-USERADD_UID_TABLES'><filename>USERADD_UID_TABLES</filename></link>,
<link linkend='var-USERADD_GID_TABLES'><filename>USERADD_GID_TABLES</filename></link>,
and
<link linkend='var-USERADD_ERROR_DYNAMIC'><filename>USERADD_ERROR_DYNAMIC</filename></link>
variables.
You can also see the
<link linkend='ref-classes-useradd'><filename>useradd</filename></link>
class for additional information.
</para>
<note><title>Notes</title>
You do not use the <filename>useradd-staticids</filename>
class directly.
You either enable or disable the class by setting the
<filename>USERADDEXTENSION</filename> variable.
If you enable or disable the class in a configured system,
<link linkend='var-TMPDIR'><filename>TMPDIR</filename></link>
might contain incorrect <filename>uid</filename> and
<filename>gid</filename> values.
Deleting the <filename>TMPDIR</filename> directory
will correct this condition.
</note>
</section>
<section id='ref-classes-utility-tasks'>
<title><filename>utility-tasks.bbclass</filename></title>
<para>
The <filename>utility-tasks</filename> class provides support for
various "utility" type tasks that are applicable to all recipes,
such as
<link linkend='ref-tasks-clean'><filename>do_clean</filename></link> and
<link linkend='ref-tasks-listtasks'><filename>do_listtasks</filename></link>.
</para>
<para>
This class is enabled by default because it is inherited by
the
<link linkend='ref-classes-base'><filename>base</filename></link>
class.
</para>
</section>
<section id='ref-classes-utils'>
<title><filename>utils.bbclass</filename></title>
<para>
The <filename>utils</filename> class provides some useful Python
functions that are typically used in inline Python expressions
(e.g. <filename>${@...}</filename>).
One example use is for <filename>bb.utils.contains()</filename>.
</para>
<para>
This class is enabled by default because it is inherited by the
<link linkend='ref-classes-base'><filename>base</filename></link>
class.
</para>
</section>
<section id='ref-classes-vala'>
<title><filename>vala.bbclass</filename></title>
<para>
The <filename>vala</filename> class supports recipes that need to
build software written using the Vala programming language.
</para>
</section>
<section id='ref-classes-waf'>
<title><filename>waf.bbclass</filename></title>
<para>
The <filename>waf</filename> class supports recipes that need to build
software that uses the Waf build system.
You can use the
<link linkend='var-EXTRA_OECONF'><filename>EXTRA_OECONF</filename></link>
variable to specify additional configuration options to be passed on
the Waf command line.
</para>
</section>
<!-- Undocumented classes are:
image-empty.bbclass (possibly being dropped)
migrate_localcount.bbclass (still need a description)
-->
</chapter>
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vim: expandtab tw=80 ts=4
-->