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ref-manual, overview-manual, Makefile: Moved toolchain concepts
Fixes [YOCTO #12370] Moved the "Cross-Development Toolchain Generation" section from the ref-manual to the overview-manual into the concepts chapter. This information is conceptual and now needs to live in the concepts chapter of the new overview-manual. Moving the section caused a few links to have to be fixed in the ref-manual. There was also a figure in the section. So, I had to move the figure from the ref-manual to the overview-manual "figures" folder and update the Makefile for the TARFILE generation. (From yocto-docs rev: 1f3ee5ab308cbe6bd7194086026db397b67ca7c4) Signed-off-by: Scott Rifenbark <srifenbark@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
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</section>
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</section>
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<section id="cross-development-toolchain-generation">
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<title>Cross-Development Toolchain Generation</title>
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<para>
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The Yocto Project does most of the work for you when it comes to
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creating
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<ulink url='&YOCTO_DOCS_REF_URL;#cross-development-toolchain'>cross-development toolchains</ulink>.
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This section provides some technical background on how
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cross-development toolchains are created and used.
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For more information on toolchains, you can also see the
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<ulink url='&YOCTO_DOCS_SDK_URL;'>Yocto Project Application Development and the Extensible Software Development Kit (eSDK)</ulink>
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manual.
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</para>
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<para>
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In the Yocto Project development environment, cross-development
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toolchains are used to build the image and applications that run
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on the target hardware.
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With just a few commands, the OpenEmbedded build system creates
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these necessary toolchains for you.
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</para>
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<para>
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The following figure shows a high-level build environment regarding
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toolchain construction and use.
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</para>
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<para>
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<imagedata fileref="figures/cross-development-toolchains.png" width="8in" depth="6in" align="center" />
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</para>
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<para>
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Most of the work occurs on the Build Host.
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This is the machine used to build images and generally work within the
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the Yocto Project environment.
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When you run BitBake to create an image, the OpenEmbedded build system
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uses the host <filename>gcc</filename> compiler to bootstrap a
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cross-compiler named <filename>gcc-cross</filename>.
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The <filename>gcc-cross</filename> compiler is what BitBake uses to
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compile source files when creating the target image.
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You can think of <filename>gcc-cross</filename> simply as an
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automatically generated cross-compiler that is used internally within
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BitBake only.
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<note>
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The extensible SDK does not use
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<filename>gcc-cross-canadian</filename> since this SDK
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ships a copy of the OpenEmbedded build system and the sysroot
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within it contains <filename>gcc-cross</filename>.
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</note>
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</para>
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<para>
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The chain of events that occurs when <filename>gcc-cross</filename> is
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bootstrapped is as follows:
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<literallayout class='monospaced'>
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gcc -> binutils-cross -> gcc-cross-initial -> linux-libc-headers -> glibc-initial -> glibc -> gcc-cross -> gcc-runtime
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</literallayout>
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<itemizedlist>
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<listitem><para>
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<filename>gcc</filename>:
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The build host's GNU Compiler Collection (GCC).
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</para></listitem>
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<listitem><para>
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<filename>binutils-cross</filename>:
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The bare minimum binary utilities needed in order to run
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the <filename>gcc-cross-initial</filename> phase of the
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bootstrap operation.
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</para></listitem>
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<listitem><para>
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<filename>gcc-cross-initial</filename>:
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An early stage of the bootstrap process for creating
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the cross-compiler.
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This stage builds enough of the <filename>gcc-cross</filename>,
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the C library, and other pieces needed to finish building the
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final cross-compiler in later stages.
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This tool is a "native" package (i.e. it is designed to run on
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the build host).
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</para></listitem>
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<listitem><para>
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<filename>linux-libc-headers</filename>:
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Headers needed for the cross-compiler.
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</para></listitem>
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<listitem><para>
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<filename>glibc-initial</filename>:
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An initial version of the Embedded GLIBC needed to bootstrap
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<filename>glibc</filename>.
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</para></listitem>
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<listitem><para>
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<filename>gcc-cross</filename>:
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The final stage of the bootstrap process for the
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cross-compiler.
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This stage results in the actual cross-compiler that
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BitBake uses when it builds an image for a targeted
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device.
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<note>
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If you are replacing this cross compiler toolchain
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with a custom version, you must replace
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<filename>gcc-cross</filename>.
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</note>
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This tool is also a "native" package (i.e. it is
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designed to run on the build host).
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</para></listitem>
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<listitem><para>
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<filename>gcc-runtime</filename>:
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Runtime libraries resulting from the toolchain bootstrapping
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process.
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This tool produces a binary that consists of the
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runtime libraries need for the targeted device.
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</para></listitem>
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</itemizedlist>
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</para>
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<para>
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You can use the OpenEmbedded build system to build an installer for
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the relocatable SDK used to develop applications.
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When you run the installer, it installs the toolchain, which contains
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the development tools (e.g., the
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<filename>gcc-cross-canadian</filename>),
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<filename>binutils-cross-canadian</filename>, and other
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<filename>nativesdk-*</filename> tools,
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which are tools native to the SDK (i.e. native to
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<ulink url='&YOCTO_DOCS_REF_URL;#var-SDK_ARCH'><filename>SDK_ARCH</filename></ulink>),
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you need to cross-compile and test your software.
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The figure shows the commands you use to easily build out this
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toolchain.
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This cross-development toolchain is built to execute on the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-SDKMACHINE'><filename>SDKMACHINE</filename></ulink>,
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which might or might not be the same
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machine as the Build Host.
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<note>
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If your target architecture is supported by the Yocto Project,
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you can take advantage of pre-built images that ship with the
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Yocto Project and already contain cross-development toolchain
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installers.
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</note>
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</para>
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<para>
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Here is the bootstrap process for the relocatable toolchain:
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<literallayout class='monospaced'>
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gcc -> binutils-crosssdk -> gcc-crosssdk-initial -> linux-libc-headers ->
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glibc-initial -> nativesdk-glibc -> gcc-crosssdk -> gcc-cross-canadian
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</literallayout>
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<itemizedlist>
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<listitem><para>
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<filename>gcc</filename>:
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The build host's GNU Compiler Collection (GCC).
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</para></listitem>
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<listitem><para>
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<filename>binutils-crosssdk</filename>:
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The bare minimum binary utilities needed in order to run
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the <filename>gcc-crosssdk-initial</filename> phase of the
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bootstrap operation.
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</para></listitem>
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<listitem><para>
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<filename>gcc-crosssdk-initial</filename>:
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An early stage of the bootstrap process for creating
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the cross-compiler.
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This stage builds enough of the
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<filename>gcc-crosssdk</filename> and supporting pieces so that
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the final stage of the bootstrap process can produce the
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finished cross-compiler.
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This tool is a "native" binary that runs on the build host.
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</para></listitem>
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<listitem><para>
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<filename>linux-libc-headers</filename>:
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Headers needed for the cross-compiler.
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</para></listitem>
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<listitem><para>
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<filename>glibc-initial</filename>:
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An initial version of the Embedded GLIBC needed to bootstrap
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<filename>nativesdk-glibc</filename>.
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</para></listitem>
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<listitem><para>
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<filename>nativesdk-glibc</filename>:
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The Embedded GLIBC needed to bootstrap the
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<filename>gcc-crosssdk</filename>.
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</para></listitem>
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<listitem><para>
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<filename>gcc-crosssdk</filename>:
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The final stage of the bootstrap process for the
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relocatable cross-compiler.
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The <filename>gcc-crosssdk</filename> is a transitory compiler
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and never leaves the build host.
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Its purpose is to help in the bootstrap process to create the
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eventual relocatable <filename>gcc-cross-canadian</filename>
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compiler, which is relocatable.
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This tool is also a "native" package (i.e. it is
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designed to run on the build host).
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</para></listitem>
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<listitem><para>
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<filename>gcc-cross-canadian</filename>:
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The final relocatable cross-compiler.
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When run on the
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<ulink url='&YOCTO_DOCS_REF_URL;#var-SDKMACHINE'><filename>SDKMACHINE</filename></ulink>,
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this tool
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produces executable code that runs on the target device.
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Only one cross-canadian compiler is produced per architecture
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since they can be targeted at different processor optimizations
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using configurations passed to the compiler through the
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compile commands.
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This circumvents the need for multiple compilers and thus
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reduces the size of the toolchains.
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</para></listitem>
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</itemizedlist>
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</para>
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<note>
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For information on advantages gained when building a
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cross-development toolchain installer, see the
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"<ulink url='&YOCTO_DOCS_SDK_URL;#sdk-building-an-sdk-installer'>Building an SDK Installer</ulink>"
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section in the Yocto Project Application Development and the
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Extensible Software Development Kit (eSDK) manual.
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</note>
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</section>
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<section id='x32'>
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<title>x32 psABI</title>
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@@ -2426,8 +2426,8 @@
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<note>
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For more information on the cross-development toolchain
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generation, see the
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"<ulink url='&YOCTO_DOCS_REF_URL;#cross-development-toolchain-generation'>Cross-Development Toolchain Generation</ulink>"
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section in the Yocto Project Reference Manual.
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"<link linkend='cross-development-toolchain-generation'>Cross-Development Toolchain Generation</link>"
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section.
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For information on advantages gained when building a
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cross-development toolchain using the
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<ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-populate_sdk'><filename>do_populate_sdk</filename></ulink>
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@@ -2792,8 +2792,8 @@
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<listitem><para>
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For background information on cross-development toolchains
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in the Yocto Project development environment, see the
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"<ulink url='&YOCTO_DOCS_REF_URL;#cross-development-toolchain-generation'>Cross-Development Toolchain Generation</ulink>"
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section in the Yocto Project Reference Manual.
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"<link linkend='cross-development-toolchain-generation'>Cross-Development Toolchain Generation</link>"
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section.
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</para></listitem>
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<listitem><para>
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For information on setting up a cross-development
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