lfs-book/chapter05/adjusting.xml

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  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../general.ent">
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<sect1 id="ch-tools-adjusting">
  <?dbhtml filename="adjusting.html"?>

  <title>Adjusting the Toolchain</title>

  <para>Now that the temporary C libraries have been installed, all
  tools compiled in the rest of this chapter should be linked against
  these libraries. In order to accomplish this, the cross-compiler's
  specs file needs to be adjusted to point to the new dynamic linker
  in <filename class="directory">/tools</filename>.</para>

  <para>This is done by dumping the compiler's <quote>specs</quote> file to a
  location where it will look for it by default.
  A simple <command>sed</command> substitution then alters the
  dynamic linker that GCC will use. The principle here is to find all references
  to the dynamic linker file in <filename class="directory">/lib</filename>
  or possibly <filename class="directory">/lib64</filename> if the host system
  is 64-bit capable, and adjust them to point to the new location in
  <filename class="directory">/tools</filename>.</para>

  <para>For the sake of accuracy, it is recommended to use a copy-and-paste
  method when issuing the following command. Be sure to visually inspect the
  specs file to verify that it has properly adjusted all references to the
  dynamic linker location. Refer to <xref
    linkend="ch-tools-toolchaintechnotes" role=","/> for the default name
  of the dynamic linker, if necessary.</para>

<!-- Ampersands are needed to allow copy and paste -->
<screen><userinput>SPECS=`dirname $($LFS_TGT-gcc -print-libgcc-file-name)`/specs
$LFS_TGT-gcc -dumpspecs | sed \
  -e 's@/lib\(64\)\?/ld@/tools&amp;@g' \
  -e "/^\*cpp:$/{n;s,$, -isystem /tools/include,}" &gt; $SPECS 
echo "New specs file is: $SPECS"
unset SPECS</userinput></screen>

  <caution>
    <para>At this point, it is imperative to stop and ensure that the basic
    functions (compiling and linking) of the new toolchain are working as
    expected. To perform a sanity check, run the following commands:</para>

<screen><userinput>echo 'main(){}' &gt; dummy.c
$LFS_TGT-gcc -B/tools/lib dummy.c
readelf -l a.out | grep ': /tools'</userinput></screen>

    <para>If everything is working correctly, there should be no errors,
    and the output of the last command will be of the form:</para>

<screen><computeroutput>[Requesting program interpreter: /tools/lib/ld-linux.so.2]</computeroutput></screen>

    <para>Note that <filename class="directory">/tools/lib</filename>, or
    <filename class="directory">/tools/lib64</filename> for 64-bit machines
    appears as the prefix of the dynamic linker.</para>

    <para>If the output is not shown as above or there was no output at all,
    then something is wrong. Investigate and retrace the steps to find out
    where the problem is and correct it. This issue must be resolved before
    continuing on. Something may have gone wrong with the
    specs file amendment above. In this case, redo the specs file amendment,
    being careful to copy-and-paste the commands.</para>

    <para>Once all is well, clean up the test files:</para>

<screen><userinput>rm -v dummy.c a.out</userinput></screen>

  </caution>

  <note><para>Building Binutils in the next section will serve as an additional check that
  the toolchain has been built properly. If Binutils fails to build, it is an
  indication that something has gone wrong with the previous Binutils, GCC, or Glibc
  installations.</para></note>

</sect1>