poky/documentation/sdk-manual/sdk-working-projects.xml

<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >

<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 cross-toolchain installed, it is very easy
            to develop a project outside of the OpenEmbedded build system.
            This section presents a simple "Helloworld" example that shows how
            to set up, compile, and run the project.
        </para>

        <section id='creating-and-running-a-project-based-on-gnu-autotools'>
            <title>Creating and Running a Project Based on GNU Autotools</title>

            <para>
                Follow these steps to create a simple Autotools-based project:
                <orderedlist>
                    <listitem><para>
                        <emphasis>Create your directory:</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>
                        </para></listitem>
                    <listitem><para>
                        <emphasis>Populate the directory:</emphasis>
                        Create <filename>hello.c</filename>,
                        <filename>Makefile.am</filename>,
                        and <filename>configure.ac</filename> files as follows:
                        <itemizedlist>
                            <listitem><para>
                                For <filename>hello.c</filename>, include
                                these lines:
                                <literallayout class='monospaced'>
     #include &lt;stdio.h&gt;

     main()
        {
           printf("Hello World!\n");
        }
                                </literallayout>
                                </para></listitem>
                            <listitem><para>
                                For <filename>Makefile.am</filename>,
                                include these lines:
                                <literallayout class='monospaced'>
     bin_PROGRAMS = hello
     hello_SOURCES = hello.c
                                </literallayout>
                                </para></listitem>
                            <listitem><para>
                                For <filename>configure.in</filename>,
                                include these lines:
                                <literallayout class='monospaced'>
     AC_INIT(hello,0.1)
     AM_INIT_AUTOMAKE([foreign])
     AC_PROG_CC
     AC_PROG_INSTALL
     AC_OUTPUT(Makefile)
                                </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".
                        Here is an example that 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 aclocal.m4
                        files and create the configure script:</emphasis>
                        The following GNU Autotools generate the local
                        <filename>aclocal.m4</filename> files and create the
                        configure script:
                        <literallayout class='monospaced'>
     $ aclocal
     $ 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 configure file:</emphasis>
                        This command generates the
                        <filename>configure</filename>:
                        <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>
                        </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>
                        </para></listitem>
                    <listitem><para>
                        <emphasis>Verify the installation:</emphasis>
                        This 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='passing-host-options'>
            <title>Passing Host Options</title>

            <para>
                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>
        </section>
    </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 the list of variables set up by the cross-toolchain
                environment setup script, see the
                "<link linkend='sdk-running-the-sdk-environment-setup-script'>Running the SDK Environment Setup Script</link>"
                section.
            </note>
        </para>
    </section>
</chapter>
<!--
vim: expandtab tw=80 ts=4
-->