Linux From Scratch: Version 5.1-pre1
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# "Locking in" Glibc

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.

First install the adjusted linker by running the following from within the `binutils-build` directory:

    make -C ld install

The linker was adjusted a little while back, at the end of the first pass of Binutils. From this point onwards everything will link only against the libraries in `/tools/lib`.

> Note: 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.

Now that the adjusted linker is installed, you have to remove the Binutils build and source directories.

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:

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

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 "/lib/ld-linux.so.2" with "/tools/lib/ld-linux.so.2". Be sure to visually inspect the specs file to verify the intended change was actually made.

> Important: If you are working on a platform where the name of the dynamic linker is something other than `ld-linux.so.2`, you must substitute `ld-linux.so.2` with the name of your platform's dynamic linker in the above commands. Refer back to the Section called Toolchain technical notes if necessary.

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 "fixincludes" 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:

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

Caution
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:
    echo 'main(){}' > dummy.c
    cc dummy.c
    readelf -l a.out | grep ': /tools'
> If everything is working correctly, there should be no errors, and the output of the last command will be:
>     [Requesting program interpreter: /tools/lib/ld-linux.so.2]
(Of course allowing for platform specific differences in dynamic linker name). Note especially that `/tools/lib` appears as the prefix of our dynamic linker. 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 gcc instead of cc. If this works it means the `/tools/bin/cc` symlink is missing. Revisit the Section called Installing GCC-3.3.2 - Pass 1 and fix the symlink. Second, ensure your $PATH is correct. You can check this by running `echo $PATH` and verifying that `/tools/bin` is at the head of the list. If the $PATH is wrong it could mean you're not logged in as user lfs or something went wrong back in the Section called Setting up the environment. 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. Once you are satisfied that all is well, clean up the test files:
    rm dummy.c a.out

This completes the installation of the self-contained toolchain, and it can now be used to build the rest of the temporary tools.

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