5.10. "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.

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 subsequent programs linking against libraries on the host. This is not ideal, however, it's not a major problem. The situation is corrected when we install the second pass of Binutils later 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 any occurrence of "/lib/ld-linux.so.2" with "/tools/lib/ld-linux.so.2".

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 Section 5.2 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}

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 gcc 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] 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. Most likely something went wrong with the specs file amendment above. Note especially that /tools/lib appears as the prefix of our dynamic linker. Of course, if you are working on a platform where the name of the dynamic linker is something other than ld-linux.so.2, then the output will be slightly different. 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.