Linking against your own glibc

The glibc is what defines the base C libraries needed by a program.

# Quentin Ducasse, March 2022
#   taken from Claas Heuer, August 2015, https://gist.github.com/cheuerde/7229f304856e59ce183a
#
# urls:
# http://stackoverflow.com/questions/847179/multiple-glibc-libraries-on-a-single-host
# http://www.gnu.org/software/libc/download.html

# Arguments handling
if [ "$#" -ne 1 ]; then
  echo "Usage: $0 <glibc_version>" >&2
  exit 1
fi
libc_version=$1

# create a temp folder to build glibc
cd $HOME
mkdir glibc_update
cd glibc_update

# get glibc version
wget https://ftp.gnu.org/gnu/glibc/glibc-${libc_version}.tar.gz
tar -xf glibc-${libc_version}.tar.gz

# configure and set the installation path
cd glibc-${libc_version}
mkdir build
cd build
../configure --prefix=/opt/glibc-${libc_version} --enable-cet

# compile
make -j6
sudo make install

You can then link with this version with flags:

$ export GLIBC_VERSION="2.30"
$ gcc main.o -o myapp ... \
	-Wl,--rpath=/opt/glibc-${GLIBC_VERSION} \
	-Wl,--dynamic-linker=/opt/glibc-${GLIBC_VERSION}/lib/ld-${GLIBC_VERSION}.so

Cross-compiling

Before any action on the toolchain, check which version of glibc you will need on the target architecture. This is available through ldd --version.

In my case, working on RISC-V, I will look at (1) the QEMU image (Fedora-Rawhide-Minimal-20200108.n.0) (2) Actual hardware (Beagle-V with Fedora-riscv64-jh7100-developer-xfce-Rawhide-20211226-214100.n.0)

$ ldd --version # qemu
	ldd (GNU libc) 2.30.9000
	Copyright (C) 2020 Free Software Foundation, Inc.
	This is free software; see the source for copying conditions.  There is NO
	warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
	Written by Roland McGrath and Ulrich Drepper.

$ ldd --version # beagle-v
	ldd (GNU libc) 2.32
	Copyright (C) 2020 Free Software Foundation, Inc.
	This is free software; see the source for copying conditions.  There is NO
	warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
	Written by Roland McGrath and Ulrich Drepper.

Now that we have these information, we need to compile the toolchain using the correct glibc version. We will go with glibc-2.30.9000 here.

$ git clone https://github.com/riscv/riscv-gnu-toolchain
$ cd riscv-gnu-toolchain
$ git submodule update --init --recursive

We need to change the glibc version:

$ cd riscv-glibc
$ git checkout glibc-2.30.9000

Now compile the toolchain as usual:

$ ./configure --prefix=/opt/riscv-glibc-2.30.9000
$ sudo make linux

Note: The option --enable-multilib that allows cross-compiler support for both 32-bit and 64-bit is not available as glibc-2.30 does not support rv32 yet