Linux From Scratch - Version cross-r12.0-499

Chapter 5. Compiling a Cross-Toolchain

5.5. Glibc-2.40

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: 1.3 SBU
Required disk space: 828 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. It's needed to adjust the command if you are building LFS for a target other than 32-bit or 64-bit x86. 

case $LFS_TGT 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]

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-2.40-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=6.10                \
      --with-headers=$LFS/usr/include    \
      --disable-nscd                     \
      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=6.10

This option tells the build system that this glibc may be used with kernels as old as 6.10. This means generating workarounds in case a system call introduced in a later version cannot be used.

--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.

--disable-nscd

Do not build the name service cache daemon which is no longer used.

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]

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]

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 7.3, “Setting up the 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]

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]

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.”