GN toolchains function both as a set of tools for compilation and as a workspace for evaluating build files. The same compilations and actions can be executed by different toolchains. Each toolchain maintains its own set of build args, and build steps from all toolchains can be executed in parallel.


pw_toolchain provides GN toolchains that may be used to build Pigweed. The following toolchains are defined:

  • arm_gcc_cortex_m4_og

  • arm_gcc_cortex_m4_o1

  • arm_gcc_cortex_m4_o2

  • arm_gcc_cortex_m4_os

  • arm_gcc_cortex_m4f_og

  • arm_gcc_cortex_m4f_o1

  • arm_gcc_cortex_m4f_o2

  • arm_gcc_cortex_m4f_os

  • host_clang_og

  • host_clang_o2

  • host_clang_os

  • host_gcc_og

  • host_gcc_o2

  • host_gcc_os


The documentation for this module is currently incomplete.

Non-C/C++ toolchains

pw_toolchain/non_c_toolchain.gni provides the pw_non_c_toolchain template. This template creates toolchains that cannot compile C/C++ source code. These toolchains may only be used to execute GN actions or declare groups of targets in other toolchains. Attempting to compile C/C++ code with either of these toolchains results in errors.

Non-C/C++ toolchains can be used to consolidate actions that should only occur once in a multi-toolchain build. Build targets from all toolchains can refer to these actions in a non-C/C++ toolchain so they only execute once instead of once per toolchain.

For example, Pigweed runs protobuf compilation and Python package actions like installation and Pylint in toolchains created with pw_non_c_toolchain. This allows all toolchains to cleanly share the same protobuf and Python declarations without any duplicated work.

Testing other compiler versions

The clang-based toolchain provided by Pigweed can be substituted with another version by modifying the pw_toolchain_CLANG_PREFIX GN build argument to point to the directory that contains the desired clang, clang++, and llvm-ar binaries. This should only be used for debugging purposes. Pigweed does not officially support any compilers other than those provided by Pigweed.