Other Cross Compilers

This toolchain variant is borrowed from the Linux kernel build system’s mechanism of using a CROSS_COMPILE environment variable to set up a GNU-based cross toolchain.

Examples of such “other cross compilers” are cross toolchains that your Linux distribution packaged, that you compiled on your own, or that you downloaded from the net. Unlike toolchains specifically listed in 3rd Party Toolchains, the Zephyr build system may not have been tested with them, and doesn’t officially support them. (Nonetheless, the toolchain set-up mechanism itself is supported.)

Follow these steps to use one of these toolchains.

  1. Install a cross compiler suitable for your host and target systems.

    For example, you might install the gcc-arm-none-eabi package on Debian-based Linux systems, or arm-none-eabi-newlib on Fedora or Red Hat:

    # On Debian or Ubuntu
    sudo apt-get install gcc-arm-none-eabi
    # On Fedora or Red Hat
    sudo dnf install arm-none-eabi-newlib
    
  2. Configure the environment variables needed to inform the Zephyr build system to use this toolchain:

    • Set ZEPHYR_TOOLCHAIN_VARIANT to cross-compile.
    • Set CROSS_COMPILE to the common path prefix which your toolchain’s binaries have, e.g. the path to the directory containing the compiler binaries plus the target triplet and trailing dash.

    Continuing the above Debian or Ubuntu example:

    export ZEPHYR_TOOLCHAIN_VARIANT=cross-compile
    export CROSS_COMPILE=/usr/bin/arm-none-eabi-
    

    You can also set CROSS_COMPILE as a CMake variable, or using the Kconfig symbol CONFIG_CROSS_COMPILE.

When using this option, all of your toolchain binaries must reside in the same directory and have a common file name prefix. The CROSS_COMPILE variable is set to the directory concatenated with the file name prefix. In the Debian example above, the gcc-arm-none-eabi package installs binaries such as arm-none-eabi-gcc and arm-none-eabi-ld in directory /usr/bin/, so the common prefix is /usr/bin/arm-none-eabi- (including the trailing dash, -). If your toolchain is installed in /opt/mytoolchain/bin with binary names based on target triplet myarch-none-elf, CROSS_COMPILE would be set to /opt/mytoolchain/bin/myarch-none-elf-.