Cross compiling toolchains in Docker images.

• Pre-built and configured toolchains for cross compiling.
• Most images also contain an emulator for the target system.
• Clean separation of build tools, source code, and build artifacts.
• Commands in the container are run as the calling user, so that any created files have the expected ownership, (i.e. not root).
• Make variables (CC, CXX, LD, AS etc) are set to point to the appropriate tools in the container.
• Recent CMake and ninja are precompiled.
• Meson is pre-installed.
• Conan.io can be used as a package manager.
• Toolchain files configured for CMake.
• Current directory is mounted as the container's workdir, /work.
• Works with the Docker for Mac and Docker for Windows.
• Support using alternative container executor by setting OCI_EXE environment variable. By default, it searches for docker and podman executable.
• crosstool-ng and buildroot configuration files.

1. dockcross make: Build the Makefile in the current directory.
2. dockcross cmake -Bbuild -S. -GNinja: Run CMake with a build directory ./build for a CMakeLists.txt file in the current directory and generate ninja build configuration files.
3. dockcross ninja -Cbuild: Run ninja in the ./build directory.
4. dockcross bash -c '$CC test/C/hello.c -o hello': Build the hello.c file with the compiler identified with the CC environmental variable in the build environment.
5. dockcross bash: Run an interactive shell in the build environment.

Note that commands are executed verbatim. If any shell processing for environment variable expansion or redirection is required, please use

bash -c "<command args>"

See CONTRIBUTING.md.

This image does not need to be run manually. Instead, there is a helper script to execute build commands on source code existing on the local host filesystem. This script is bundled with the image.

To install the helper script, run one of the images with no arguments, and redirect the output to a file:

docker run --rm CROSS_COMPILER_IMAGE_NAME > ./dockcross
chmod +x ./dockcross
mv ./dockcross ~/bin/

Where CROSS_COMPILER_IMAGE_NAME is the name of the cross-compiler toolchain Docker instance, e.g: dockcross/linux-armv7.

Only 64-bit x86_64 images are provided, a 64-bit x86_64 host system is required.

For the impatient, here's how to compile a hello world for armv7:

git clone https://github.com/dockcross/dockcross.git
cd dockcross
docker run --rm dockcross/linux-armv7 > ./dockcross-linux-armv7
chmod +x ./dockcross-linux-armv7
./dockcross-linux-armv7 bash -c '$CC test/C/hello.c -o hello_arm'

Note how invoking any toolchain command (make, gcc, etc.) is just a matter of prepending the dockcross script on the commandline:

./dockcross-linux-armv7 [command] [args...]

The dockcross script will execute the given command-line inside the container, along with all arguments passed after the command. Commands that evaluate environmental variables in the image, like $CC or $CXX above, should be executed in [bash -c]. The present working directory is mounted within the image, which can be used to make source code available in the Docker container.

The list of docker images that are no longer maintained.

Base image for other toolchain images. From Debian Bookworm with GCC, make, autotools, CMake, Ninja, Git, and Python.

The Android NDK standalone toolchain for the arm architecture.

The Android NDK standalone toolchain for the arm64 architecture.

The Android NDK standalone toolchain for the x86 architecture.

The Android NDK standalone toolchain for the x86_64 architecture.

Cross compiler for the 64-bit ARM platform on Linux, also known as AArch64.

Cross compiler for the 64-bit ARM platform on Linux, also known as AArch64, with Long-term support (For Ubuntu 18.04 or Debian Buster). With GCC 8.5.0 and GLibc 2.27.

Cross compiler for the 64-bit ARM platform on Linux, with cross-libs: SDL2, OpenSSL, Boost, OpenCV and Qt5 (minimal).

Cross compiler for the 64-bit ARM platform on Linux (also known as AArch64), using musl as base "libc".

Linux armv5 cross compiler toolchain for legacy devices like the Parrot AR Drone.

Linux armv5 cross compiler toolchain using musl as base "libc".

Linux armv5 cross compiler toolchain for legacy devices like wrt routers Linux kernel 2.6 uclibc as base "libc".

Linux ARMv6 cross compiler toolchain for the Raspberry Pi

Linux ARMv6 cross compiler toolchain for the Raspberry Pi (Debian buster...)

Linux ARMv6 cross compiler toolchain for the Raspberry Pi, etc, using musl as base "libc".

Generic Linux armv7 cross compiler toolchain.

Linux ARMv7 cross compiler toolchain for the Raspberry Pi (Debian buster...)

Toolchain configured for ARMv7-A used in Beaglebone Black single board PC with TI SoC AM3358 on board, Cortex-A8.

Toolchain configured for ARMv7-L, using musl as base "libc".

Linux mips cross compiler toolchain for big endian 32-bit hard float MIPS GNU systems.

Linux mips cross compiler toolchain for big endian 32-bit hard float MIPS GNU systems, with GCC 8.5.0, Glibc 2.28 ....

Linux mips cross compiler toolchain for little endian 32-bit soft float MIPS GNU systems.

Linux s390x cross compiler toolchain for S390X GNU systems.

Linux risc-v 64bit cross compiler toolchain for risc-v 64bit GNU systems.

Linux risc-v 32bit cross compiler toolchain for risc-v 32bit GNU systems.

Linux m68k cross compiler toolchain for m68k GNU systems (http://www.mac.linux-m68k.org/ and http://www.linux-m68k.org/).

Linux PowerPC cross compiler toolchain for CPUs like the G3, G4, etc.

Linux PowerPC 64 little endian cross compiler toolchain for the POWER8, etc.

Linux PowerPC 64 little endian cross compiler toolchain for the POWER8, with GCC 8.5.0, Glibc 2.28 ....

Linux x86_64/amd64 compiler. Since the Docker image is natively x86_64, this is not actually a cross compiler.

Linux x86_64/amd64 compiler with libs: SDL2, OpenSSL, Boost, OpenCV and Qt5 (minimal).

Linux clang x86_64/amd64 compiler. Since the Docker image is natively x86_64, this is not actually a cross compiler.

Linux x86_64 32bit (i686) toolchain using gcc/g++ multilib. Multilib is a mechanism to support building and running code for different ABIs for the same CPU family on the host system. Most commonly it is used to support 32-bit code on 64-bit systems and 64-bit code on 32-bit systems with a 64-bit kernel. Since the Docker image is natively x86_64, this is not actually a cross compiler, it just adds capability to the existing host toolchain.

Linux tcc compiler for C compiler, and GCC for C++ compiler, for linux x86_64/amd64 arch.

Standalone Linux i686 cross compiler.

Docker manylinux_2_28 image for building Linux x86_64 / amd64 Python wheel packages. It includes Python 3.6, 3.7, 3.8, 3.9, 3.10 and 3.11. Also has support for the dockcross script, and it has installations of CMake, Ninja, and scikit-build. For CMake, it sets MANYLINUX_2_28 to "TRUE" in the toolchain.

Docker manylinux2014 image for building Linux x86_64 / amd64 Python wheel packages. It includes Python 3.5, 3.6, 3.7, 3.8, and 3.9. Also has support for the dockcross script, and it has installations of CMake, Ninja, and scikit-build. For CMake, it sets MANYLINUX2014 to "TRUE" in the toolchain.

Docker manylinux2014 image for building Linux i686 Python wheel packages. It includes Python 3.5, 3.6, 3.7, 3.8, and 3.9. Also has support for the dockcross script, and it has installations of CMake, Ninja, and scikit-build. For CMake, it sets MANYLINUX2014 to "TRUE" in the toolchain.

Docker manylinux2014 image for building Linux aarch64 / arm64 Python wheel packages. It includes Python 3.5, 3.6, 3.7, 3.8, and 3.9. Also has support for the dockcross script, and it has installations of CMake, Ninja, and scikit-build. For CMake, it sets MANYLINUX2014 to "TRUE" in the toolchain.

The Emscripten WebAssembly/JavaScript cross compiler.

The WebAssembly System Interface (WASI) SDK LLVM/Clang/WASI Sysroot cross compiler.

The WebAssembly System Interface (WASI) SDK LLVM/Clang/WASI Sysroot cross compiler with the toolchain configured to enable the wasm threading proposal.

64-bit Windows cross-compiler based on MXE/MinGW-w64 with win32 threads and static linking.

64-bit Windows cross-compiler based on MXE/MinGW-w64 with posix threads and static linking.

32-bit Windows cross-compiler based on MXE/MinGW-w64 with win32 threads and static linking.

64-bit Windows cross-compiler based on MXE/MinGW-w64 with win32 threads and dynamic linking.

64-bit Windows cross-compiler based on MXE/MinGW-w64 with posix threads and dynamic linking.

32-bit Windows cross-compiler based on MXE/MinGW-w64 with win32 threads and dynamic linking.

ARMv7 32-bit Windows cross-compiler based on LLVM/MinGW-w64

ARMv8 64-bit Windows cross-compiler based on llvm-mingw

• dockcross: C++ Write Once, Run Anywhere
• Cross-compiling binaries for multiple architectures with Docker

A special update command can be executed that will update the source cross-compiler Docker image or the dockcross script itself.

• dockcross [--] command [args...]: Forces a command to run inside the container (in case of a name clash with a built-in command), use -- before the command.
• dockcross update-image: Fetch the latest version of the docker image.
• dockcross update-script: Update the installed dockcross script with the one bundled in the image.
• dockcross update: Update both the docker image, and the dockcross script.

To easily download all images, the convenience target display_images could be used:

curl https://raw.githubusercontent.com/dockcross/dockcross/master/Makefile -o dockcross-Makefile
for image in $(make -f dockcross-Makefile display_images); do
  echo "Pulling dockcross/$image"
  docker pull dockcross/$image
done

To automatically install in ~/bin the dockcross scripts for each images already downloaded, the convenience target display_images could be used:

curl https://raw.githubusercontent.com/dockcross/dockcross/master/Makefile -o dockcross-Makefile
for image in $(make -f dockcross-Makefile display_images); do
  if [[ $(docker images -q dockcross/$image) == "" ]]; then
    echo "~/bin/dockcross-$image skipping: image not found locally"
    continue
  fi
  echo "~/bin/dockcross-$image ok"
  docker run dockcross/$image > ~/bin/dockcross-$image && \
  chmod u+x  ~/bin/dockcross-$image
done

The following environmental variables and command-line options are used. In all cases, the command-line option overrides the environment variable.

This file is sourced, if it exists, before executing the rest of the dockcross script.

Default: ~/.dockcross

The Docker cross-compiler image to run.

Default: Image with which the script was created.

Extra arguments to pass to the docker run command. Quote the entire set of args if they contain spaces.

If a shell script named .dockcross is found in the current directory where the dockcross script is started, it is executed before the dockcross script command argument. The shell script is expected to have a shebang like #!/usr/bin/env bash.

For example, commands like git config --global advice.detachedHead false can be added to this script.

In order to extend Dockcross images with your own commands, one must:

1. Use FROM dockcross/<name_of_image>.
2. Set DEFAULT_DOCKCROSS_IMAGE to a name of the tag you're planning to use for the image. This tag must then be used during the build phase, unless you mean to pass the resulting helper script the DOCKCROSS_IMAGE argument.

An example Dockerfile would be:

FROM dockcross/linux-armv7

ENV DEFAULT_DOCKCROSS_IMAGE my_cool_image
RUN apt-get install -y nano

And then in the shell:

docker build -t my_cool_image .                   ## Builds the dockcross image.
docker run my_cool_image > linux-armv7                ## Creates a helper script named linux-armv7.
chmod +x linux-armv7                          ## Gives the script execution permission.
./linux-armv7 bash                            ## Runs the helper script with the argument "bash", which starts an interactive container using your extended image.

The key difference is that dockbuild images do NOT provide a toolchain file but they use the same method to conveniently isolate the build environment as dockcross.

dockbuild is used to build binaries for Linux x86_64/amd64 that will work across most Linux distributions. dockbuild performs a native Linux build where the host build system is a Linux x86_64 / amd64 Docker image (so that it can be used for building binaries on any system which can run Docker images) and the target runtime system is Linux x86_x64/ amd64.

dockcross is used to build binaries for many different platforms. dockcross performs a cross compilation where the host build system is a Linux x86_64 / amd64 Docker image (so that it can be used for building binaries on any system which can run Docker images) and the target runtime system varies.

Prebuilt images available on Docker hub are single architecture amd64 images. Those images work even on different architectures: for example, if you run a dockcross image on Docker running on an Apple M1, the image will run in emulation mode, meaning that it will still work as expected, although it will be slower than running on native hardware (you can expect a factor or 10 or more).

To overcome this limitation, you can build your own images on non-amd64 architectures. To do so, you can use the Makefile provided in this repository. For example, to build the linux-armv7 image, and provided that your Docker hub organization name is ACME, you can run:

$ make ORG=ACME base
$ make ORG=ACME linux-armv7

This will create the Docker images ACME/base and ACME/linux-armv7, so that you can later launch a container using the ACME/linux-armv7 image:

$ docker run --rm ACME/linux-armv7 uname -a
Linux 89b164ee8d90 5.15.49-linuxkit #1 SMP PREEMPT Tue Sep 13 07:51:32 UTC 2022 aarch64 GNU/Linux

Note that the architecture is now aarch64 instead of amd64, so it runs natively on the Apple M1.

---

Credits:

• sdt/docker-raspberry-pi-cross-compiler, who invented the base of the dockcross script.
• https://github.com/steeve/cross-compiler,