5.5. Glibc-2.38

#### Linux From Scratch - Version 12.0-systemd

### Chapter 5. Compiling a Cross-Toolchain

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# 5.5. Glibc-2.38

The Glibc package contains the main C library. This library provides the basic routines for allocating memory, searching directories, opening and closing files, reading and writing files, string handling, pattern matching, arithmetic, and so on.

Approximate build time: 1.6 SBU
Required disk space: 858 MB

## 5.5.1. Installation of Glibc

First, create a symbolic link for LSB compliance. Additionally, for x86_64, create a compatibility symbolic link required for proper operation of the dynamic library loader:

    case $(uname -m) in
        i?86)   ln -sfv ld-linux.so.2 $LFS/lib/ld-lsb.so.3
        ;;
        x86_64) ln -sfv ../lib/ld-linux-x86-64.so.2 $LFS/lib64
                ln -sfv ../lib/ld-linux-x86-64.so.2 $LFS/lib64/ld-lsb-x86-64.so.3
        ;;
    esac

### Note

The above command is correct. The ln command has several syntactic versions, so be sure to check info coreutils ln and `ln(1)` before reporting what may appear to be an error.

Some of the Glibc programs use the non-FHS-compliant `/var/db` directory to store their runtime data. Apply the following patch to make such programs store their runtime data in the FHS-compliant locations:

    patch -Np1 -i ../glibc-2.38-fhs-1.patch

The Glibc documentation recommends building Glibc in a dedicated build directory:

    mkdir -v build
    cd       build

Ensure that the ldconfig and sln utilities are installed into `/usr/sbin`:

    echo "rootsbindir=/usr/sbin" > configparms

Next, prepare Glibc for compilation:

    ../configure                             \
          --prefix=/usr                      \
          --host=$LFS_TGT                    \
          --build=$(../scripts/config.guess) \
          --enable-kernel=4.14               \
          --with-headers=$LFS/usr/include    \
          libc_cv_slibdir=/usr/lib

The meaning of the configure options:

`--host=$LFS_TGT, --build=$(../scripts/config.guess)`

  The combined effect of these switches is that Glibc's build system configures itself to be cross-compiled, using the cross-linker and cross-compiler in `$LFS/tools`.

`--enable-kernel=4.14`

  This tells Glibc to compile the library with support for 4.14 and later Linux kernels. Workarounds for older kernels are not enabled.

`--with-headers=$LFS/usr/include`

  This tells Glibc to compile itself against the headers recently installed to the $LFS/usr/include directory, so that it knows exactly what features the kernel has and can optimize itself accordingly.

`libc_cv_slibdir=/usr/lib`

  This ensures that the library is installed in /usr/lib instead of the default /lib64 on 64-bit machines.

During this stage the following warning might appear:

>     configure: WARNING:
>     *** These auxiliary programs are missing or
>     *** incompatible versions: msgfmt
>     *** some features will be disabled.
>     *** Check the INSTALL file for required versions.

The missing or incompatible msgfmt program is generally harmless. This msgfmt program is part of the Gettext package, which the host distribution should provide.

### Note

There have been reports that this package may fail when building as a "parallel make". If that occurs, rerun the make command with the "-j1" option.

Compile the package:

    make

Install the package:

### Warning

If `LFS` is not properly set, and despite the recommendations, you are building as `root`, the next command will install the newly built Glibc to your host system, which will almost certainly render it unusable. So double-check that the environment is correctly set, and that you are not `root`, before running the following command.

    make DESTDIR=$LFS install

The meaning of the make install option:

`DESTDIR=$LFS`

  The `DESTDIR` make variable is used by almost all packages to define the location where the package should be installed. If it is not set, it defaults to the root (`/`) directory. Here we specify that the package is installed in `$LFS` , which will become the root directory in Section 7.4, “Entering the Chroot Environment”.

Fix a hard coded path to the executable loader in the ldd script:

    sed '/RTLDLIST=/s@/usr@@g' -i $LFS/usr/bin/ldd

### Caution

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:

    echo 'int main(){}' | $LFS_TGT-gcc -xc -
    readelf -l a.out | grep ld-linux

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

    [Requesting program interpreter: /lib64/ld-linux-x86-64.so.2]

Note that for 32-bit machines, the interpreter name will be `/lib/ld-linux.so.2`.

If the output is not as shown above, or there is 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.

Once all is well, clean up the test file:

    rm -v a.out

### Note

Building the packages in the next chapter will serve as an additional check that the toolchain has been built properly. If some package, especially Binutils-pass2 or GCC-pass2, fails to build, it is an indication that something has gone wrong with the preceding Binutils, GCC, or Glibc installations.

Details on this package are located in Section 8.5.3, “Contents of Glibc.”

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