| 1 | <sect1 id="ch06-adjustingtoolchain">
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| 2 | <title>Re-adjusting the toolchain</title>
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| 3 | <?dbhtml filename="adjustingtoolchain.html" dir="chapter06"?>
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| 4 |
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| 5 | <para>Now that the new C libraries have been installed, it's time to re-adjust
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| 6 | our toolchain. We'll adjust it so that it will link any newly compiled program
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| 7 | against the new C libraries. Basically, this is the reverse of what we did
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| 8 | in the "Locking in" stage in the beginning of the previous chapter.</para>
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| 9 |
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| 10 | <para>The first thing to do is to adjust the linker. For this we retained the
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| 11 | source and build directories from the second pass over Binutils. Install the
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| 12 | adjusted linker by running the following from within the
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| 13 | <filename class="directory">binutils-build</filename> directory:</para>
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| 14 |
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| 15 | <para><screen><userinput>make -C ld install</userinput></screen></para>
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| 16 |
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| 17 | <para>From now on every compiled program will link <emphasis>only</emphasis>
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| 18 | against the libraries in <filename>/usr/lib</filename> and <filename>/lib
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| 19 | </filename>.</para>
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| 20 |
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| 21 | <para>You can now remove the Binutils source and build directories.</para>
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| 22 |
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| 23 | <para>The next thing to do is to amend our GCC specs file so that it points
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| 24 | to the new dynamic linker. Just like earlier on, we use a sed to accomplish
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| 25 | this:</para>
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| 26 |
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| 27 | <para><screen><userinput>SPECFILE=/tools/lib/gcc-lib/*/*/specs
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| 28 | sed -e 's@/tools/lib/ld.so.1@/lib/ld.so.1@g' \
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| 29 | -e 's@/tools/lib/ld-linux.so.2@/lib/ld-linux.so.2@g' \
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| 30 | $SPECFILE > newspecfile
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| 31 | mv newspecfile $SPECFILE
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| 32 | unset SPECFILE</userinput></screen></para>
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| 33 |
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| 34 | <para>Again, cutting and pasting the above is recommended. And just like
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| 35 | before, it is a good idea to check the specs file to ensure the intended
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| 36 | changes were actually made.</para>
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| 37 |
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| 38 | <caution><para>It is imperative at this point to stop and ensure that the
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| 39 | basic functions (compiling and linking) of the adjusted toolchain are working
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| 40 | as expected. For this we are going to perform a simple sanity check:</para>
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| 41 |
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| 42 | <para><screen><userinput>echo 'main(){}' > dummy.c
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| 43 | gcc dummy.c
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| 44 | readelf -l a.out | grep ': /lib'</userinput></screen></para>
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| 45 |
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| 46 | <para>If everything is working correctly, there should be no errors, and the
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| 47 | output of the last command will be:</para>
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| 48 |
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| 49 | <para><screen>[Requesting program interpreter: /lib/ld-linux.so.2]
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| 50 | </screen></para>
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| 51 |
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| 52 | <para>If you did not receive the output as shown above, then something is
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| 53 | seriously wrong. You will need to investigate and retrace your steps to find
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| 54 | out where the problem is and correct it. There is no point in continuing
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| 55 | until this is done. Most likely something went wrong with the specs file
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| 56 | amendment above. Note especially that <filename>/lib</filename> now appears as
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| 57 | the prefix of our dynamic linker. Of course, if you are working on a platform
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| 58 | where the name of the dynamic linker is something other than
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| 59 | <filename>ld-linux.so.2</filename>, then the output will be slightly
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| 60 | different.</para>
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| 61 |
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| 62 | <para>Once you are satisfied that all is well, clean up the test files:</para>
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| 63 |
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| 64 | <para><screen><userinput>rm dummy.c a.out</userinput></screen></para>
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| 65 | </caution>
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| 66 |
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| 67 | </sect1>
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| 68 |
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