source: BOOK/final-system/multilib/multiarch_wrapper.xml@ 3a86839

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
  "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../../general.ent">
  %general-entities;
]>

<sect1 id="ch-system-multiarch-wrapper" role="wrap">
  <?dbhtml filename="multiarch_wrapper.html"?>

  <title>Creating a Multiarch Wrapper</title>

  <indexterm zone="ch-system-multiarch-wrapper">
    <primary sortas="a-File">Multiarch Wrapper</primary>
  </indexterm>

  <sect2 role="package">
    <title/>

    <para>The Multiarch Wrapper is used to wrap certain binaries that have
    hardcoded paths to libraries or are architecture specific.</para>

  </sect2>

  <sect2 role="installation">
    <title>Installation of The Multiarch Wrapper</title>

    <para os="a">Create the source file:</para>

<screen os="b"><userinput>cat &gt; multiarch_wrapper.c &lt;&lt; "EOF"
#include &lt;stdio.h&gt;
#include &lt;stdlib.h&gt;
#include &lt;string.h&gt;
#include &lt;errno.h&gt;

#ifndef DEFAULT_ARCH
# define DEFAULT_ARCH "64"
#endif

int main (int argc, char *argv[])
{
  char *use_arch;
  if ((use_arch = getenv("USE_ARCH")) == NULL)
    use_arch = DEFAULT_ARCH;

  char *filename = malloc(strlen(argv[0]) + strlen(use_arch) + 2);
  strcpy(filename, argv[0]);
  strcat(filename, "-");
  strcat(filename, use_arch);

  int ret = execvp(filename, argv);
  if ((ret != 0)&amp;&amp;(errno != 0))
  {
    char *errmsg = malloc(strlen(filename) + 19);
    strcpy(errmsg, "Unable to execute ");
    strcat(errmsg, filename);
    perror(errmsg);
    free(errmsg);
  }

  free(filename);

  return ret;
}
EOF</userinput></screen>

    <para os="c">Compile and Install the Multiarch Wrapper:</para>

<screen os="d"><userinput>gcc ${BUILD64} multiarch_wrapper.c -o /usr/bin/multiarch_wrapper</userinput></screen>

    <para os="e">This multiarch wrapper is going to be used later on in the book
    with perl. It will also be very useful outside of the base CLFS system.</para>

    <para os="f">Creating the testcase:</para>

<screen os="g"><userinput>echo 'echo "32bit Version"' &gt; test-32
echo 'echo "64bit Version"' &gt; test-64
chmod 755 test-32 test-64
ln -sv /usr/bin/multiarch_wrapper test</userinput></screen>

    <para os="h">Testing the wrapper:</para>

<screen os="i"><userinput>USE_ARCH=32 ./test
USE_ARCH=64 ./test</userinput></screen>

    <para os="j">The output of the above command should be:</para>

<screen os="k"><userinput>32bit Version
64bit Version</userinput></screen>

  </sect2>

  <sect2 id="contents-multiarch-wrapper" role="content">
    <title>Contents of The Multiarch Wrapper</title>

    <segmentedlist>
      <segtitle>Installed programs</segtitle>

      <seglistitem>
        <seg>multiarch_wrapper</seg>
      </seglistitem>
    </segmentedlist>

    <variablelist>
      <bridgehead renderas="sect3">Short Descriptions</bridgehead>
      <?dbfo list-presentation="list"?>
      <?dbhtml list-presentation="table"?>

      <varlistentry id="multiarch_wrapper">
        <term><command>multiarch_wrapper</command></term>
        <listitem>
          <para>Will execute a different program based on the
          <envar>USE_ARCH</envar> variable. The <envar>USE_ARCH</envar>
          variable will be the suffix of the executed program.</para>
          <indexterm zone="ch-system-multiarch-wrapper multiarch_wrapper">
            <primary sortas="b-multiarch_wrapper">multiarch_wrapper</primary>
          </indexterm>
        </listitem>
      </varlistentry>

    </variablelist>

  </sect2>

</sect1>