path: root/documentation/sdk-manual/sdk-working-projects.xml

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<chapter id='sdk-working-projects'>

    <title>Using the SDK Toolchain Directly</title>

    <para>
        You can use the SDK toolchain directly with Makefile,
        Autotools, and <trademark class='trade'>Eclipse</trademark>-based
        projects.
        This chapter covers the first two, while the
        "<link linkend='sdk-eclipse-project'>Developing Applications Using <trademark class='trade'>Eclipse</trademark></link>"
        Chapter covers the latter.
    </para>

    <section id='autotools-based-projects'>
        <title>Autotools-Based Projects</title>

        <para>
            Once you have a suitable
            <ulink url='&YOCTO_DOCS_REF_URL;#cross-development-toolchain'>cross-development toolchain</ulink>
            installed, it is very easy to develop a project using the
            <ulink url='https://en.wikipedia.org/wiki/GNU_Build_System'>GNU Autotools-based</ulink>
            workflow, which is outside of the
            <ulink url='&YOCTO_DOCS_REF_URL;#build-system-term'>OpenEmbedded build system</ulink>.
        </para>

        <para>
            The following figure presents a simple Autotools workflow.
            <imagedata fileref="figures/sdk-autotools-flow.png" width="7in" height="8in" align="center" />
        </para>

        <para>
            Follow these steps to create a simple Autotools-based
            "Hello World" project:
            <note>
                For more information on the GNU Autotools workflow,
                see the same example on the
                <ulink url='https://developer.gnome.org/anjuta-build-tutorial/stable/create-autotools.html.en'>GNOME Developer</ulink>
                site.
            </note>
            <orderedlist>
                <listitem><para>
                    <emphasis>Create a Working Directory and Populate It:</emphasis>
                    Create a clean directory for your project and then make
                    that directory your working location.
                    <literallayout class='monospaced'>
     $ mkdir $HOME/helloworld
     $ cd $HOME/helloworld
                    </literallayout>
                    After setting up the directory, populate it with three
                    simple files needed for the flow.
                    You need a project source file, a file to help with
                    configuration, and a file to help create the Makefile:
                    <filename>hello.c</filename>,
                    <filename>configure.ac</filename>, and
                    <filename>Makefile.am</filename>, respectively:
                    <itemizedlist>
                        <listitem><para>
                            <emphasis><filename>hello.c</filename>:</emphasis>
                            <literallayout class='monospaced'>
     #include &lt;stdio.h&gt;

     main()
        {
           printf("Hello World!\n");
        }
                            </literallayout>
                            </para></listitem>
                        <listitem><para>
                            <emphasis><filename>configure.ac</filename>:</emphasis>
                            <literallayout class='monospaced'>
     AC_INIT(hello,0.1)
     AM_INIT_AUTOMAKE([foreign])
     AC_PROG_CC
     AC_CONFIG_FILES(Makefile)
     AC_OUTPUT
                            </literallayout>
                            </para></listitem>
                        <listitem><para>
                            <emphasis><filename>Makefile.am</filename>:</emphasis>
                            <literallayout class='monospaced'>
     bin_PROGRAMS = hello
     hello_SOURCES = hello.c
                            </literallayout>
                            </para></listitem>
                    </itemizedlist>
                    </para></listitem>
                <listitem><para>
                    <emphasis>Source the Cross-Toolchain
                    Environment Setup File:</emphasis>
                    As described earlier in the manual, installing the
                    cross-toolchain creates a cross-toolchain
                    environment setup script in the directory that the SDK
                    was installed.
                    Before you can use the tools to develop your project,
                    you must source this setup script.
                    The script begins with the string "environment-setup"
                    and contains the machine architecture, which is
                    followed by the string "poky-linux".
                    For this example, the command sources a script from the
                    default SDK installation directory that uses the
                    32-bit Intel x86 Architecture and the
                    &DISTRO_NAME; Yocto Project release:
                    <literallayout class='monospaced'>
     $ source /opt/poky/&DISTRO;/environment-setup-i586-poky-linux
                    </literallayout>
                    </para></listitem>
                <listitem><para>
                    <emphasis>Generate the Local <filename>aclocal.m4</filename> Files:</emphasis>
                    The following command generates the local
                    <filename>aclocal.m4</filename> files, which are used
                    later with the <filename>autoconf</filename> command:
                    <literallayout class='monospaced'>
     $ aclocal
                    </literallayout>
                    </para></listitem>
                <listitem><para>
                    <emphasis>Create the <filename>configure</filename> Script:</emphasis>
                    The following command creates the
                    <filename>configure</filename> script:
                    <literallayout class='monospaced'>
     $ autoconf
                    </literallayout>
                    </para></listitem>
                <listitem><para>
                    <emphasis>Generate Files Needed by GNU Coding
                    Standards:</emphasis>
                    GNU coding standards require certain files in order
                    for the project to be compliant.
                    This command creates those files:
                    <literallayout class='monospaced'>
     $ touch NEWS README AUTHORS ChangeLog
                    </literallayout>
                    </para></listitem>
                <listitem><para>
                    <emphasis>Generate the <filename>Makefile.in</filename> File:</emphasis>
                    This command generates the
                    <filename>Makefile.in</filename>, which is used later
                    during cross-compilation:
                    <literallayout class='monospaced'>
     $ automake -a
                    </literallayout>
                    </para></listitem>
                <listitem><para>
                    <emphasis>Cross-Compile the Project:</emphasis>
                    This command compiles the project using the
                    cross-compiler.
                    The
                    <ulink url='&YOCTO_DOCS_REF_URL;#var-CONFIGURE_FLAGS'><filename>CONFIGURE_FLAGS</filename></ulink>
                    environment variable provides the minimal arguments for
                    GNU configure:
                    <literallayout class='monospaced'>
     $ ./configure ${CONFIGURE_FLAGS}
                    </literallayout>
                    For an Autotools-based project, you can use the
                    cross-toolchain by just passing the appropriate host
                    option to <filename>configure.sh</filename>.
                    The host option you use is derived from the name of the
                    environment setup script found in the directory in which you
                    installed the cross-toolchain.
                    For example, the host option for an ARM-based target that uses
                    the GNU EABI is
                    <filename>armv5te-poky-linux-gnueabi</filename>.
                    You will notice that the name of the script is
                    <filename>environment-setup-armv5te-poky-linux-gnueabi</filename>.
                    Thus, the following command works to update your project
                    and rebuild it using the appropriate cross-toolchain tools:
                    <literallayout class='monospaced'>
     $ ./configure --host=armv5te-poky-linux-gnueabi \
        --with-libtool-sysroot=<replaceable>sysroot_dir</replaceable>
                    </literallayout>
                    <note>
                        If the <filename>configure</filename> script results in
                        problems recognizing the
                        <filename>--with-libtool-sysroot=</filename><replaceable>sysroot-dir</replaceable>
                        option, regenerate the script to enable the support by
                        doing the following and then run the script again:
                        <literallayout class='monospaced'>
     $ libtoolize --automake
     $ aclocal -I ${OECORE_TARGET_SYSROOT}/usr/share/aclocal [-I <replaceable>dir_containing_your_project-specific_m4_macros</replaceable>]
     $ autoconf
     $ autoheader
     $ automake -a
                        </literallayout>
                    </note>
                    </para></listitem>
                <listitem><para>
                    <emphasis>Make and Install the Project:</emphasis>
                    These two commands generate and install the project
                    into the destination directory:
                    <literallayout class='monospaced'>
     $ make
     $ make install DESTDIR=./tmp
                    </literallayout>
                    This next command is a simple way to verify the
                    installation of your project.
                    Running the command prints the architecture on which
                    the binary file can run.
                    This architecture should be the same architecture that
                    the installed cross-toolchain supports.
                    <literallayout class='monospaced'>
     $ file ./tmp/usr/local/bin/hello
                    </literallayout>
                    </para></listitem>
                <listitem><para>
                    <emphasis>Execute Your Project:</emphasis>
                    To execute the project in the shell, simply enter
                    the name.
                    You could also copy the binary to the actual target
                    hardware and run the project there as well:
                    <literallayout class='monospaced'>
     $ ./hello
                    </literallayout>
                    As expected, the project displays the "Hello World!"
                    message.
                    </para></listitem>
            </orderedlist>
        </para>
    </section>

    <section id='makefile-based-projects'>
        <title>Makefile-Based Projects</title>

        <para>
            For Makefile-based projects, the cross-toolchain environment
            variables established by running the cross-toolchain environment
            setup script are subject to general <filename>make</filename>
            rules.
        </para>

        <para>
            To illustrate this, consider the following four cross-toolchain
            environment variables:
            <literallayout class='monospaced'>
     <ulink url='&YOCTO_DOCS_REF_URL;#var-CC'>CC</ulink>=i586-poky-linux-gcc -m32 -march=i586 --sysroot=/opt/poky/&DISTRO;/sysroots/i586-poky-linux
     <ulink url='&YOCTO_DOCS_REF_URL;#var-LD'>LD</ulink>=i586-poky-linux-ld --sysroot=/opt/poky/&DISTRO;/sysroots/i586-poky-linux
     <ulink url='&YOCTO_DOCS_REF_URL;#var-CFLAGS'>CFLAGS</ulink>=-O2 -pipe -g -feliminate-unused-debug-types
     <ulink url='&YOCTO_DOCS_REF_URL;#var-CXXFLAGS'>CXXFLAGS</ulink>=-O2 -pipe -g -feliminate-unused-debug-types
            </literallayout>
            Now, consider the following three cases:
            <itemizedlist>
                <listitem><para>
                    <emphasis>Case 1 - No Variables Set in the
                    <filename>Makefile</filename>:</emphasis>
                    Because these variables are not specifically set in the
                    <filename>Makefile</filename>, the variables retain their
                    values based on the environment.
                    </para></listitem>
                <listitem><para>
                    <emphasis>Case 2 - Variables Set in the
                    <filename>Makefile</filename>:</emphasis>
                    Specifically setting variables in the
                    <filename>Makefile</filename> during the build results in
                    the environment settings of the variables being
                    overwritten.
                    </para></listitem>
                <listitem><para>
                    <emphasis>Case 3 - Variables Set when the
                    <filename>Makefile</filename> is Executed from the
                    Command Line:</emphasis>
                    Executing the <filename>Makefile</filename> from the
                    command-line results in the variables being overwritten
                    with command-line content regardless of what is being set
                    in the <filename>Makefile</filename>.
                    In this case, environment variables are not considered
                    unless you use the "-e" flag during the build:
                    <literallayout class='monospaced'>
     $ make -e <replaceable>file</replaceable>
                    </literallayout>
                    If you use this flag, then the environment values of the
                    variables override any variables specifically set in the
                    <filename>Makefile</filename>.
                    </para></listitem>
            </itemizedlist>
            <note>
                For information on the variables set up by the cross-toolchain
                environment setup script, see the
                "<link linkend='sdk-running-the-extensible-sdk-environment-setup-script'>Running the Extensible SDK Environment Setup Script</link>"
                section.
            </note>
        </para>
    </section>
</chapter>
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