arm-cmake-toolchains

CMake toolchain files for bare-metal ARM Cortex development — Cortex-M, Cortex-R, and Cortex-A targets are all in scope. Drop a toolchain file into your project, point CMake at it, and cross-compilation for ARM works out of the box: the file locates the compiler and its ancillary tools, detects the sysroot, and configures CMake's root-path search. Architecture flags, linker scripts, and optimisation levels stay in your project — see Scope below for the boundary between what the toolchain configures and what belongs downstream.

Scope

Toolchain files in this repo configure compilers, ancillary tools, sysroot detection, and CMake root-path search behaviour. Things that belong in the consumer's CMakeLists.txt, not here:

• -mcpu=..., -mthumb, -mfloat-abi=... and other architecture-specific flags
• Linker scripts (-T)
• Newlib / nano / nosys spec selection
• Optimisation flags (-O...)
• Project-level warnings (-Wall, -Werror, …)

If you find yourself wanting to add any of those to the toolchain file, that's a strong sign the change belongs downstream.

Available Toolchains

File	Toolchain
arm_none_eabi_gcc.cmake	Arm GNU Toolchain (arm-none-eabi-gcc)
arm_none_eabi_llvm.cmake	LLVM Embedded Toolchain for Arm (clang with arm-none-eabi target)

Both toolchains configure all standard CMake tools (compiler, linker, objcopy, size, etc.) and set up automatic sysroot detection via the compiler's -print-sysroot.

Important — for the LLVM toolchain file. Sysroot detection runs clang --target=arm-none-eabi -print-sysroot and expects a real path back. This works with the LLVM Embedded Toolchain for Arm (which bundles picolibc, multilibs, startup files, and linker scripts), but not with stock upstream LLVM — stock clang can target ARM Cortex but ships no sysroot for arm-none-eabi, and -print-sysroot returns an empty string. If you must use stock LLVM, set CMAKE_SYSROOT and CMAKE_FIND_ROOT_PATH manually on the CMake command line and the toolchain will respect your overrides.

Want another toolchain, default, or target supported? Open a feature request — see CONTRIBUTING.md for how suggestions are scoped.

Usage

Copy the toolchain file you need into your project, then pass it to CMake:

cmake -B build -DCMAKE_TOOLCHAIN_FILE=arm_none_eabi_gcc.cmake
cmake --build build

Or with a preset:

{
    "configurePresets": [
        {
            "name": "arm-gcc",
            "toolchainFile": "${sourceDir}/arm_none_eabi_gcc.cmake"
        }
    ]
}

Customisation

All tool paths can be overridden before including the toolchain file. For example, to use a specific GCC version:

cmake -B build \
    -DCMAKE_C_COMPILER=/opt/arm-gnu-toolchain-13/bin/arm-none-eabi-gcc \
    -DCMAKE_CXX_COMPILER=/opt/arm-gnu-toolchain-13/bin/arm-none-eabi-g++ \
    -DCMAKE_TOOLCHAIN_FILE=arm_none_eabi_gcc.cmake

Licence

This project is licensed under the Apache License Version 2.0.
Copyright (C) 2026 The Embedded Society https://github.com/embedded-society/arm-cmake-toolchains.
See the attached LICENCE file for more info.