Nix Flake for Reproducible Development

This guide explains how to use the Nix flake to set up a reproducible development environment for NuttX. The Nix flake ensures that all required build tools and dependencies are consistently available, simplifying onboarding and reducing “works on my machine” issues.

Prerequisites

  • Nix installed on your system.

  • Nix flakes enabled (add experimental-features = nix-command flakes to your nix.conf).

Setting up the Development Environment

To enter the NuttX development shell, navigate to the root of the NuttX directory and run:

nix develop

This command will:

  • Download and set up all necessary build tools and dependencies, including: * CMake, Ninja, GNU Make * Clang tools * ARM toolchain (gcc-arm-embedded) * Automake, Bison, Flex, Genromfs, Gettext, Gperf * Kconfig-frontends, libelf, expat, gmp, isl, libmpc, mpfr, ncurses, zlib * Python with kconfiglib

  • Set the CMAKE_EXPORT_COMPILE_COMMANDS environment variable to ON.

  • Display a welcome message.

Once inside the development shell, you can proceed with building NuttX as usual.

Benefits

  • Reproducibility: Ensures a consistent build environment across all developers and machines.

  • Simplified Onboarding: New contributors can quickly set up their development environment with a single command.

  • Dependency Management: All dependencies are managed by Nix, avoiding conflicts with system-wide packages.

Contents of the Nix Flake

The flake.nix file defines a devShell that includes the following build inputs:

buildInputs = [
  # Build tools
  pkgs.cmake
  pkgs.ninja
  pkgs.gnumake
  pkgs.clang-tools

  # ARM toolchain
  pkgs.gcc-arm-embedded

  # NuttX dependencies
  pkgs.automake
  pkgs.bison
  pkgs.flex
  pkgs.genromfs
  pkgs.gettext
  pkgs.gperf
  pkgs.kconfig-frontends
  pkgs.libelf
  pkgs.expat.dev
  pkgs.gmp.dev
  pkgs.isl
  pkgs.libmpc
  pkgs.mpfr.dev
  pkgs.ncurses.dev
  pkgs.zlib
  pkgs.python313Packages.kconfiglib
];

The shellHook sets up the CMAKE_EXPORT_COMPILE_COMMANDS and provides a welcome message:

shellHook = ''
  export CMAKE_EXPORT_COMPILE_COMMANDS=ON
  echo "Welcome to NuttX devShell"
'';

This setup ensures that the development environment is fully configured for NuttX development.