Building a full embedded ARM toolchain on Windows using Cygwin

Overview

This tool can be used to build a full ARM toolchain under Cygwin. The tool initially had patch files specific to build on Cygwin, but these bugs were fixed in recent version of the GNU tools so this program is actually not specific to Cygwin in its current state. So it can maybe be used on other platforms. But these other platforms usually have pre-packaged version of the toolchain that will be more conveniant to use (and this tool is tested only under Cygwin).

The toolchain built by this tool have been used to build programs for the Raspberry Pi RP2040 using the Pico SDK and for various Atmel SAMD devices using the Atmel Start framework.

Why Cygwin

For peoples that have or prefer to use Windows, there are these days many options (full virtualization, Windows Subsystem for Linux, native toolchains, etc.). However, I find that Cygwin has the best balance between a Linux look-and-feel and a good and fast integration with the standard Windows system.

Within Cygwin, it would be possible to use a Windows toolchain. However a Cygwin native one is much simpler to use (no complex file path conversion) and usually compatible with more open source projects and tools.

Installing

To build the toolchain, you will need the following package from the Cygwin installer:

gcc-core
gcc-g++
make
bison
flex
perl
patch
git
libgmp-devel
libmpfr-devel
zlib-devel
libmpc-devel
libisl-devel
libexpat-devel

You can then clone the repository as well as the submodules containing the required sources. This might take a couple of minutes as the dependencies are quite large:

git clone https://github.com/mkende/cygwin-arm-toolchain.git
cd cygwin-arm-toolchain
git submodule update --init

Building the toolchain

Just run the ./build-toolchain command. This will build and install a complete ARM toolchain in your Cygwin environment. By default the toolchain is installed under /usr/local/bin which should already be in your $PATH variable.

The build operation is organized in projects that you can individually activate or deactivate, although you should generally just build everything with the default options. The projects, all targetted to the ARM architecture, are the following:

binutils: a standard set of GNU tools (the most important ones are the linker ld and the debugger gdb). These tools are running on your computer so they are built with your default GCC.
gcc-bootstrap: a bootstrap version of the GCC compiler with only the support for C. This is skipped if there is already an ARM GCC available on the system (typically from a previous run).
newlib: a small standard library, meant for embedded systems.
gcc: the full version, with support for C and C++. It requires newlib to be built.
newlib-nano: an even smaller version of newlib.
newlib-final: just the same as newlib but built again with our full gcc. This is skipped if gcc-bootstrap was built too (as newlib was built with the same version of GCC in that case).

You can execute ./build-toolchain -h to see a list of options affecting the program.

Cleanup

Just delete the build directory within the project to remove all build artifacts. If you use the --build-here argument then, obviously, you should remove any directories you used to build.

Bugs

The various projects that are built are not always tested with Cygwin so they may fail to build. By using the versions specified in this repository you should be using known-good versions (you are getting them by default when this repository is cloned). If needed patches will be provided with this tool to allow a successful compilation under Cygwin.

Updating

TODO