lfs-book/chapter05/adjusting.xml

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<sect1 id="ch-tools-adjusting">
<title>Adjusting the toolchain</title>
<?dbhtml filename="adjusting.html"?>

<para>Now that the temporary C libraries have been installed, we want all
the tools compiled in the rest of this chapter to be linked against these
libraries. To accomplish this, we need to adjust the linker and the compiler's
specs file. Some people would say that it is <emphasis><quote>black magic juju
below this line</quote></emphasis>, but it is really very simple.</para>

<para>First install the adjusted linker (adjusted at the end of the first pass
of Binutils) by running the following command from within
the <filename class="directory">binutils-build</filename> directory:</para>

<screen><userinput>make -C ld install</userinput></screen>

<para>From this point onwards everything will link <emphasis>only</emphasis>
against the libraries in <filename>/tools/lib</filename>.</para>

<note><para>If you somehow missed the earlier warning to retain the Binutils
source and build directories from the first pass or otherwise accidentally
deleted them or just don't have access to them, don't worry, all is not lost.
Just ignore the above command. The result is a small chance of the subsequent
testing programs linking against libraries on the host. This is not ideal, but
it's not a major problem. The situation is corrected when we install the
second pass of Binutils a bit further on.</para></note>

<para>Now that the adjusted linker is installed, you have to
<emphasis>remove</emphasis> the Binutils build and source directories.</para>

<para>The next thing to do is to amend our GCC specs file so that it points
to the new dynamic linker. A simple sed will accomplish this:</para>

<!-- Ampersands are needed to allow cut and paste -->

<screen><userinput>SPECFILE=/tools/lib/gcc-lib/*/*/specs &amp;&amp;
sed -e 's@ /lib/ld-linux.so.2@ /tools/lib/ld-linux.so.2@g' \
    $SPECFILE &gt; tempspecfile &amp;&amp;
mv -f tempspecfile $SPECFILE &amp;&amp;
unset SPECFILE</userinput></screen>

<para>We recommend that you cut-and-paste the above rather than try and type it
all in. Or you can edit the specs file by hand if you want to: just replace the
occurrence of <quote>/lib/ld-linux.so.2</quote> with
<quote>/tools/lib/ld-linux.so.2</quote>. Be sure to visually inspect the specs
file to verify the intended change was actually made.</para>

<important><para>If you are working on a platform where the name of the dynamic
linker is something other than <filename>ld-linux.so.2</filename>, you
<emphasis>must</emphasis> replace <filename>ld-linux.so.2</filename> with the
name of your platform's dynamic linker in the above commands. Refer back to
<xref linkend="ch-tools-toolchaintechnotes"/> if necessary.</para></important>

<para>Lastly, there is a possibility that some include files from the host
system have found their way into GCC's private include dir. This can happen
because of GCC's <quote>fixincludes</quote> process which runs as part of the
GCC build.  We'll explain more about this further on in this chapter. For now,
run the following commands to eliminate this possibility:</para>

<screen><userinput>rm -f /tools/lib/gcc-lib/*/*/include/{pthread.h,bits/sigthread.h}</userinput></screen>


<caution><para>It is imperative at this point to stop and ensure that the basic
functions (compiling and linking) of the new toolchain are working as expected.
For this we are going to perform a simple sanity check:</para>

<screen><userinput>echo 'main(){}' &gt; dummy.c
cc 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 (allowing for platform specific differences
in dynamic linker name):</para>

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

<para>Note especially that <filename class="directory">/tools/lib</filename>
appears as the prefix of our dynamic linker.</para>

<para>If you did not receive the output
as shown above, or received no output at all, then something is seriously wrong.
You will need to investigate and retrace your steps to find out where the
problem is and correct it. There is no point in continuing until this is done.
First, redo the sanity check using <command>gcc</command> instead of
<command>cc</command>. If this works it means the
<filename class="symlink">/tools/bin/cc</filename> symlink is missing. Revisit
<xref linkend="ch-tools-gcc-pass1"/> and fix the symlink. Second, ensure your PATH
is correct. You can check this by running <userinput>echo $PATH</userinput> and
verifying that <filename class="directory">/tools/bin</filename> is at the head
of the list. If the PATH is wrong it could mean you're not logged in as user
<emphasis>lfs</emphasis> or something went wrong back in
<xref linkend="ch-tools-settingenviron"/>. Third, something may have gone wrong with
the specs file amendment above. In this case redo the specs file amendment
ensuring to cut-and-paste the commands as was recommended.</para>

<para>Once you are satisfied that all is well, clean up the test files:</para>

<screen><userinput>rm dummy.c a.out</userinput></screen>
</caution>


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