This post is a guide to build a GCC toolchain. The GCC toolchain is portable and self-contained (the only dependency is the Linux kernel).

I use docker to set the environment up.

TL;DR: Just download the all-in-one script in the release page and use it.

Prerequisite

Preparation

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# Use ubuntu:22.04 image
docker run -it ubuntu:22.04 bash

cd /root

apt update && apt upgrade --yes

# Install dependencies
DEBIAN_FRONTEND=noninteractive apt install --yes \
    build-essential texinfo bison git curl rsync gawk \
    python-is-python3 help2man file

# Download sources
mkdir packages
curl -L 'https://ftpmirror.gnu.org/binutils/binutils-2.42.tar.xz' \
    -o packages/binutils-2.42.tar.xz

curl -L 'https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.6.30.tar.xz' \
    -o packages/linux-6.6.30.tar.xz

curl -L 'https://ftpmirror.gnu.org/glibc/glibc-2.39.tar.xz' \
    -o packages/glibc-2.39.tar.xz

curl -L 'https://ftpmirror.gnu.org/gcc/gcc-14.1.0/gcc-14.1.0.tar.xz' \
    -o packages/gcc-14.1.0.tar.xz

curl -L 'https://github.com/besser82/libxcrypt/releases/download/v4.4.36/libxcrypt-4.4.36.tar.xz' \
    -o packages/libxcrypt-4.4.36.tar.xz

The layout in the disk:

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packages/
|-- binutils-2.42.tar.xz
|-- gcc-14.1.0.tar.xz
|-- glibc-2.39.tar.xz
|-- libxcrypt-4.4.36.tar.xz
`-- linux-6.6.30.tar.xz

Extract all sources.

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find packages/ -mindepth 1 -exec tar -Jxf {} \;

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# Layout
.
|-- binutils-2.42
|-- gcc-14.1.0
|-- glibc-2.39
|-- libxcrypt-4.4.36
|-- linux-6.6.30
`-- packages

Overview

Build and install cross GCC toolchain (NOTE: the corss here is not accurate, because the target architecture is the same as the build one).
- Build and install cross Binutils.
- Install Linux Kernel headers.
- Build stage1 cross GCC
  - Build and install gcc
- Build stage1 glibc
  - Build and install headers stubs.h and libraries crt1.o crti.o crtn.o libc.so …
- Build stage2 cross GCC
  - Build and install libgcc
- Build and install final glibc
- Build and install final cross GCC
Build final GCC toolchain by the cross GCC toolchain.
Build and install libxcrypt by the final GCC toolchain.

Environment

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export PREFIX='/opt/toolchain'
export TARGET='x86_64-linux-gnu'
export CROSS_PREFIX="${PREFIX}/cross"
export TARGET_PREFIX="${CROSS_PREFIX}/${TARGET}"
export ARCH='x86'
export PATH="/opt/toolchain/bin:/opt/toolchain/cross/bin:${PATH}"

NOTE: The path /opt/toolchain/cross is temporary and will be removed after setting all up. The final path is /opt/toolchain.

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mkdir -p "${CROSS_PREFIX}"
ln -snf .. "${CROSS_PREFIX}/${TARGET}"

mkdir -p "${TARGET_PREFIX}/lib"
ln -snf "lib" "${TARGET_PREFIX}/lib64"

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# Layout
/opt/
`-- toolchain
    |-- cross
    |   `-- x86_64-linux-gnu -> ..
    |-- lib
    `-- lib64 -> lib

Build and install cross GCC toolchain

Build and install cross Binutils.

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pushd binutils-2.42

./configure --prefix="${CROSS_PREFIX}" \
    --target="${TARGET}" \
    --disable-multilib
make -j "$(nproc)"
make install

popd

We specified x86_64-linux-gnu as the target system type.
--disable-multilib means that we only want our Binutils installation to work with programs and libraries using the 64-bits instruction set.

Install Linux Kernel headers.

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pushd linux-6.6.30

make ARCH="${ARCH}" INSTALL_HDR_PATH="${TARGET_PREFIX}" headers_install

popd

We installed the headers to /opt/toolchain/include.

Build stage1 cross GCC

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pushd gcc-14.1.0

# Download prerequisites
contrib/download_prerequisites

mkdir build
cd build

../configure --prefix="${CROSS_PREFIX}" \
    --target="${TARGET}" \
    --libdir="${TARGET_PREFIX}/lib" \
    --libexecdir="${TARGET_PREFIX}/libexec" \
    --with-local-prefix="${TARGET_PREFIX}" \
    --with-gxx-include-dir="${TARGET_PREFIX}/include/c++" \
    --enable-languages=c,c++ \
    --enable-default-pie \
    --disable-multilib \
    --disable-libssp \
    --disable-threads \
    --disable-libatomic \
    --disable-libffi \
    --disable-libgomp \
    --disable-libitm \
    --disable-libquadmath \
    --disable-libquadmath-support \
    --disable-libsanitizer \
    --disable-bootstrap
make -j "$(nproc)" all-gcc
make install-gcc

popd

We specified x86_64-linux-gnu as the target system type.
We installed the executables to /opt/toolchain/cross/bin and installed headers and libraries to /opt/toolchain/include and /opt/toolchain/lib respectively.
We enabled C and C++ and disabled many libraries to accelerate the build time.

Build stage1 glibc

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pushd glibc-2.39

mkdir build
cd build

../configure --prefix="${TARGET_PREFIX}" \
    --build="${MACHTYPE}" \
    --host="${TARGET}" \
    --target="${TARGET}" \
    --with-headers="${TARGET_PREFIX}"/include \
    --disable-multilib \
    libc_cv_forced_unwind=yes
make install-bootstrap-headers=yes install-headers
make -j "$(nproc)" csu/subdir_lib

install csu/crt1.o csu/crti.o csu/crtn.o "${TARGET_PREFIX}"/lib
"${TARGET}-gcc" -nostdlib -nostartfiles -shared -x c /dev/null -o "${TARGET_PREFIX}"/lib/libc.so
touch "${TARGET_PREFIX}"/include/gnu/stubs.h

popd

We installed the libraries to /opt/toolchain/lib.
We installed the C library’s startup files, crt1.o, crti.o and crtn.o to the installation directory manually. There’s doesn’t seem to a make rule that does this without having other side effects.
We created a couple of dummy files, libc.so and stubs.h, which are expected in step #5, but which will be replaced by step #6.

Build stage2 cross GCC

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pushd gcc-14.1.0

cd build

make -j "$(nproc)" all-target-libgcc
make install-target-libgcc

popd

Build and install final glibc

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pushd glibc-2.39

cd build

make -j "$(nproc)"
make install

popd

Build and install final cross GCC

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pushd gcc-14.1.0

cd build

make -j "$(nproc)"
make install

popd

Validation

Now, we have a corss GCC toolchain, we can test the toolchain whether it works as expect.

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#include <iostream>

auto main() -> int {
    std::cout << "Hello, world!" << std::endl;
    return 0;
}

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$ x86_64-linux-gnu-g++ -Wl,-rpath,/opt/toolchain/lib \
    -Wl,-dynamic-linker,/opt/toolchain/lib/ld-linux-x86-64.so.2 \
    hello.cc -o hello
$ ./hello
Hello, world!

It works!

Build final GCC toolchain by the cross GCC toolchain.

Build and install final Binutils.

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rm -rf binutils-2.42
tar -Jxf packages/binutils-2.42.tar.xz

pushd binutils-2.42

LDFLAGS="-L${PREFIX}/lib -Wl,-rpath,${PREFIX}/lib \
    -Wl,-dynamic-linker,$(find "${PREFIX}/lib" -name 'ld-linux-*')" \
    ./configure --prefix="${PREFIX}" \
    --host="${TARGET}" \
    --enable-gold \
    --enable-plugins \
    --disable-multilib
make -j "$(nproc)"
make install-strip

# Remove the old files
rm -rf "${PREFIX}/lib/ldscripts"

popd

Build and install final GCC

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rm -rf gcc-14.1.0
tar -Jxf packages/gcc-14.1.0.tar.xz

# Download prerequisites
pushd gcc-14.1.0

contrib/download_prerequisites

mkdir build
cd build

ldflags="-L${PREFIX}/lib -Wl,-rpath,${PREFIX}/lib \
    -Wl,-dynamic-linker,$(find "${PREFIX}/lib" -name 'ld-linux-*')"

LDFLAGS="${ldflags}" LDFLAGS_FOR_TARGET="${ldflags}" \
    ../configure --prefix="${PREFIX}" \
    --host="${TARGET}" \
    --with-local-prefix="${PREFIX}" \
    --enable-languages=c,c++ \
    --enable-default-pie \
    --disable-multilib

make BOOT_LDFLAGS="${ldflags}" -j "$(nproc)"

# Remove the old files
rm -rf "${PREFIX}/include/c++"

make install-strip

popd

Build and install final glibc

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rm -rf glibc-2.39
tar -Jxf packages/glibc-2.39.tar.xz

pushd glibc-2.39

mkdir build
cd build

../configure --prefix="${PREFIX}" \
    --with-headers="${PREFIX}"/include \
    --disable-multilib
make -j "$(nproc)"
make install

popd

Build and install libxcrypt

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pushd libxcrypt-4.4.36

./configure --prefix="${PREFIX}"
make -j "$(nproc)"
make install

rm -rf "${PREFIX}/lib/pkgconfig"

popd

Use the GCC toolchain seamlessly

We can use the GCC toolchain like this.

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$ g++ -Wl,-rpath,/opt/toolchain/lib \
    -Wl,-dynamic-linker,/opt/toolchain/lib/ld-linux-x86-64.so.2 \
    hello.cc -o hello
$ ./hello
Hello, world!

However, it is verbose. We can use GCC specs file to simplify the usage.

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toolchain_home='/opt/toolchain'
interpreter="$(find "${toolchain_home}" -name "ld-linux-*")"
filename="$(basename "${interpreter}")"
dirname="$(dirname "${interpreter}")"

"${toolchain_home}/bin/gcc" -dumpspecs | sed "{
    s/:\([^;}:]*\)\/\(${filename/.so*/}\)/:${dirname//\//\\/}\/\2/g
    s/collect2/collect2 -rpath ${dirname//\//\\/}/
}" >"${toolchain_home}/lib/gcc/$(uname -m)-linux-gnu/specs"

Validation

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$ gcc -v
Using built-in specs.
Reading specs from /opt/toolchain/lib/gcc/x86_64-linux-gnu/specs
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/opt/toolchain/libexec/gcc/x86_64-linux-gnu/14.1.0/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../configure --prefix=/opt/toolchain --host=x86_64-linux-gnu --with-local-prefix=/opt/toolchain --enable-languages=c,c++ --enable-default-pie --disable-multilib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 14.1.0 (GCC)

Now, GCC uses the specs file /opt/toolchain/lib/gcc/x86_64-linux-gnu/specs which was created by us.

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$ g++ hello.cc -o hello
$ ./hello
Hello, world!

It works!

Make GCC toolchain portable by patchelf

So far, we have built our GCC toolchain. In this section, we use patchelf to make the toolchain portable.

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mkdir -p /opt/patchelf

curl -L "https://github.com/NixOS/patchelf/releases/download/0.16.1/patchelf-0.16.1-$(uname -m).tar.gz" \
    -o - | tar -zxv -C /opt/patchelf

export PATH="/opt/patchelf/bin:${PATH}"

We move the GCC toolchain to a different location to pretend that we extracted the toolchain to a new machine.

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mv /opt/toolchain /root/

We will find the executable GCC can’t be executed.

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$ cd /root/toolchain/bin
$ ./gcc --version
bash: ./gcc: No such file or directory

We can use the tool patchelf to fix this issue.

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$ patchelf --set-rpath /root/toolchain/lib gcc
$ patchelf --set-interpreter /root/toolchain/lib/ld-linux-x86-64.so.2 gcc
$ ./gcc --version
gcc (GCC) 14.1.0
Copyright (C) 2024 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.

For the sake of convenience, we can use the following function.

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function relocate() {
	local opts
	local overwrite=false
	if ! opts="$(getopt -o '' -l 'overwrite' -- "${@}")"; then
		return 1
	fi
	eval "set -- ${opts}"

	while true; do
		case "${1}" in
		--overwrite)
			overwrite=true
			shift
			;;
		--)
			shift
			break
			;;
		*)
			echo 'Invalid arguments'
			return 1
			;;
		esac
	done

	local search_path="${1}"
	local base_path="${2}"
	local libc_so
	local library_path
	local interpreter
	libc_so="$(find "${search_path}" -name 'libc.so.6')"
	library_path="$(dirname "${libc_so}")"
	interpreter="$(find "${search_path}" -name 'ld-linux-*.so.*')"

	local old_rpath
	local new_rpath
	while read -r file; do
		if old_rpath="$(patchelf --print-rpath "${file}" 2>/dev/null)"; then
			if ${overwrite}; then
				old_rpath="\$ORIGIN:\$ORIGIN/lib:\$ORIGIN/lib64:\$ORIGIN/../lib:\$ORIGIN/../lib64"
			fi
			new_rpath="${old_rpath:+${old_rpath}:}${library_path}"
			patchelf --set-rpath "${new_rpath}" "${file}"
			if readelf -S "${file}" | grep '.interp' >/dev/null; then
				patchelf --set-interpreter "${interpreter}" "${file}"
			fi
		fi
	done < <(find "$(readlink -f "${base_path}")" -type f)
}

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$ ./g++ --version
bash: ./g++: No such file or directory

$ relocate --overwrite /root/toolchain g++

$ patchelf --print-rpath g++
$ORIGIN:$ORIGIN/lib:$ORIGIN/lib64:$ORIGIN/../lib:$ORIGIN/../lib64:/root/toolchain/lib

$ patchelf --print-interpreter g++
/root/toolchain/lib/ld-linux-x86-64.so.2

$ ./g++ --version
g++ (GCC) 14.1.0
Copyright (C) 2024 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.

Next, we fix the whole GCC toolchain by apply the following function.

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function configure_toolchain() {
	local PATCHELF='patchelf'
	local LIBC_SO='libc.so.6'
	local INTERPRETER='ld-linux-*'
	local READELF='readelf'

	local prefix="${1}"
	echo -e 'Configuring the toolchain...'
	if ! cd "${prefix}"; then
		echo -e "Failed to change the current directory to \033[34;1m${prefix}/${TOOLCHAIN_DIRNAME}\033[0m ."
	fi

	local patchelf
	patchelf="$(command -v "${PATCHELF}")"
	if [[ ! -f "${patchelf}" ]]; then
		echo -e "Failed to find the tool \033[34;1m${patchelf}\033[0m ."
	fi
	echo -e "Program ${PATCHELF} was found: \033[34;1m${patchelf}\033[0m"

	local readelf="/usr/bin/readelf"
	if [[ ! -f "${readelf}" ]]; then
		echo -e "Failed to find the tool \033[34;1m${readelf}\033[0m ."
	fi
	echo -e "Program ${READELF} was found: \033[34;1m${readelf}\033[0m"

	local interpreter
	if ! interpreter="$(find "$(pwd)" -name "${INTERPRETER}")" || [[ -z "${interpreter}" ]]; then
		echo -e "Failed to find the interpreter \033[34;1m${INTERPRETER}\033[0m"
	fi
	echo -e "Interpreter was found: \033[34;1m${interpreter}\033[0m"

	local libc_so
	if ! libc_so="$(find "$(pwd)" -name "${LIBC_SO}")" || [[ -z "${libc_so}" ]]; then
		echo -e "Failed to find the library \033[34;1m${LIBC_SO}\033[0m"
	fi
	echo -e "Library was found: \033[34;1m${libc_so}\033[0m"

	# Remove useless files
	rm -rf "$(pwd)/$(uname -m)-linux-gnu"/*
	find "$(pwd)" -name '*.la' -delete

	mkdir "$(pwd)/$(uname -m)-linux-gnu/include"
	mkdir "$(pwd)/$(uname -m)-linux-gnu/lib"
	ln -snf lib "$(pwd)/$(uname -m)-linux-gnu/lib64"

	# Link headers
	local include_path
	include_path="$(pwd)/include"
	pushd "$(uname -m)-linux-gnu/include" >/dev/null || exit
	while read -r path; do
		local absolute_path="${include_path}/${path}"
		if [[ -d "${absolute_path}" ]]; then
			mkdir -p "${path}"
		else
			ln -snf "${absolute_path}" "${path}"
		fi
	done < <(find "${include_path}" -mindepth 1 -printf '%P\n')
	popd >/dev/null || exit

	local rpaths=(
		"\$ORIGIN"
		"\$ORIGIN/lib"
		"\$ORIGIN/lib64"
		"\$ORIGIN/../lib"
		"\$ORIGIN/../lib64"
		"$(pwd)/$(uname -m)-linux-gnu/lib"
		"$(dirname "${libc_so}")"
	)
	local rpaths_in_line
	rpaths_in_line="$(
		IFS=':'
		echo "${rpaths[*]}"
	)"

	while read -r file; do
		if ! file "${file}" | grep ELF >/dev/null; then
			continue
		fi
		"${patchelf}" --set-rpath "${rpaths_in_line}" "${file}"
		if "${readelf}" -S "${file}" | grep '.interp' >/dev/null; then
			"${patchelf}" --set-interpreter "${interpreter}" "${file}"
		fi
	done < <(
		find "$(pwd)" -type f ! -name '*.o' ! -name '*.a' \
			! -name "${PATCHELF}" ! -name "${INTERPRETER}" ! -name "${LIBC_SO}"
	)
	"${patchelf}" --set-interpreter "${interpreter}" "${libc_so}"

	pushd bin >/dev/null || exit
	ln -snf gcc cc
	popd >/dev/null || exit

	# Modify files
	local current_path
	current_path="$(pwd)"
	while read -r file; do
		sed -i "s/\/opt\/toolchain/${current_path//\//\\/}/g" "${file}"
	done < <(
		find . -type f -exec grep -E -I -l $'[=\'" ]/opt/toolchain' {} \;
	)

	# Modify ldd
	sed -i "/RTLDLIST=/s/${current_path//\//\\/}//g" bin/ldd

	# Configure gcc specs
	local filename
	filename="$(basename "${interpreter}")"
	local dirname
	dirname="$(dirname "${interpreter}")"
	"$(pwd)/bin/gcc" -dumpspecs | sed "{
		s/:\([^;}:]*\)\/\(${filename/.so*/}\)/:${dirname//\//\\/}\/\2/g
		s/collect2/collect2 -rpath ${rpaths_in_line//\//\\/}/
	}" >"$(pwd)/lib/gcc/specs"
}

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$ configure_toolchain /root/toolchain

Validation

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$ export PATH="/root/toolchain/bin:${PATH}"
$ cd /root/
$ g++ hello.cc -o hello
$ ./hello
Hello, world!

It works!

Use the all-in-one script

I made an all-in-one script to install a portable GCC toolchain. See the release page.

Example

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curl -LO 'https://github.com/adonis0147/devel-env/releases/download/v2024.05/install_toolchain_x86_64.sh'

bash install_toolchain_x86_64.sh /root

export PATH="/root/compiler/bin:${PATH}"

References

How to Build a GCC Cross-Compiler

Build a Portable GCC Toolchain

Contents

Prerequisite

Preparation

Overview

Environment

Build and install cross GCC toolchain

Validation

Build final GCC toolchain by the cross GCC toolchain.

Use the GCC toolchain seamlessly

Validation

Make GCC toolchain portable by patchelf

Validation

Use the all-in-one script

Example

References