Building Matter

Matter supports configuring the build with GN, a fast and scalable meta-build system that generates inputs to ninja.

Tested on:

  • macOS 10.15

  • Debian 11

  • Ubuntu 20.04 LTS

Build system features:

  • Very fast and small footprint

  • Cross-platform handling: (Linux, Darwin, embedded arm, etc.)

  • Multiple toolchains & cross toolchain dependencies

  • Integrates automated testing framework: ninja check

  • Introspection: gn desc

  • Automatic formatting: gn format

Checking out the Matter code

To check out the Matter repository:

git clone --recurse-submodules git@github.com:project-chip/connectedhomeip.git

If you already have a checkout, run the following command to sync submodules:

git submodule update --init

Prerequisites

Before building, you’ll need to install a few OS specific dependencies.

Installing prerequisites on Linux

On Debian-based Linux distributions such as Ubuntu, these dependencies can be satisfied with the following:

sudo apt-get install git gcc g++ python pkg-config libssl-dev libdbus-1-dev \
     libglib2.0-dev libavahi-client-dev ninja-build python3-venv python3-dev \
     python3-pip unzip libgirepository1.0-dev libcairo2-dev libreadline-dev

Installing prerequisites on macOS

On macOS, first install Xcode from the Mac App Store. The remaining dependencies can be installed and satisfied using Brew:

brew install openssl pkg-config

However, that does not expose the package to pkg-config. To fix that, one needs to run something like the following:

Intel:

cd /usr/local/lib/pkgconfig
ln -s ../../Cellar/openssl@1.1/1.1.1g/lib/pkgconfig/* .

where openssl@1.1/1.1.1g may need to be replaced with the actual version of OpenSSL installed by Brew.

Apple Silicon:

export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:"/opt/homebrew/opt/openssl@3/lib/pkgconfig"

Note: If using MacPorts, port install openssl is sufficient to satisfy this dependency.

Installing prerequisites on Raspberry Pi 4

Using rpi-imager, install the Ubuntu 21.04 64-bit server OS for arm64 architectures on a micro SD card. This release will have bluez 5.55 or newer which is required for BLE functionality.

Boot the SD card, login with the default user account “ubuntu” and password “ubuntu”, then proceed with “How to install prerequisites on Linux”.

Finally, install some Raspberry Pi specific dependencies:

sudo apt-get install pi-bluetooth avahi-utils

You need to reboot your RPi after install pi-bluetooth.

By default, wpa_supplicant is not allowed to update (overwrite) configuration, if you want the Matter app to be able to store the configuration changes permanently, we need to make the following changes.

  1. Edit the dbus-fi.w1.wpa_supplicant1.service file to use configuration file instead.

sudo nano /etc/systemd/system/dbus-fi.w1.wpa_supplicant1.service

Change the wpa_supplicant start parameters to:

ExecStart=/sbin/wpa_supplicant -u -s -i wlan0 -c /etc/wpa_supplicant/wpa_supplicant.conf
  1. Add the wpa-supplicant configuration file

sudo nano /etc/wpa_supplicant/wpa_supplicant.conf

And add the following content to the file:

ctrl_interface=DIR=/run/wpa_supplicant
update_config=1

Finally, reboot your RPi.

Prepare for building

Before running any other build command, the scripts/activate.sh environment setup script should be sourced at the top level. This script takes care of downloading GN, ninja, and setting up a Python environment with libraries used to build and test.

source scripts/activate.sh

If this script says the environment is out of date, it can be updated by running:

source scripts/bootstrap.sh

The scripts/bootstrap.sh script re-creates the environment from scratch, which is expensive, so avoid running it unless the environment is out of date.

Build for the host OS (Linux or macOS)

This will build all sources, libraries, and tests for the host platform:

source scripts/activate.sh

gn gen out/host

ninja -C out/host

This generates a configuration suitable for debugging. To configure an optimized build, specify is_debug=false:

gn gen out/host --args='is_debug=false'

ninja -C out/host

The directory name out/host can be any directory, although it’s conventional to build within the out directory. This example uses host to emphasize that we’re building for the host system. Different build directories can be used for different configurations, or a single directory can be used and reconfigured as necessary via gn args.

To run all tests, run:

ninja -C out/host check

To run only the tests in src/inet/tests, you can run:

ninja -C out/host src/inet/tests:tests_run

Note that the build system caches passing tests, so if you see

ninja: no work to do

that means that the tests passed in a previous build.

Build custom configuration

The build is configured by setting build arguments. These are set by passing the --args option to gn gen, by running gn args on the output directory, or by hand editing args.gn in the output directory. To configure a new build or edit the arguments to existing build, run:

source scripts/activate.sh

gn args out/custom

ninja -C out/custom

Two key builtin build arguments are target_os and target_cpu, which control the OS & CPU of the build.

To see help for all available build arguments:

gn gen out/custom
gn args --list out/custom

Build examples

Examples can be built in two ways, as separate projects that add Matter in the third_party directory, or in the top level Matter project.

To build the chip-shell example as a separate project:

cd examples/shell
gn gen out/debug
ninja -C out/debug

To build it at the top level, see below under “Unified Builds”.

Unified builds

To build a unified configuration that approximates the set of continuous builds:

source scripts/activate.sh

gn gen out/unified --args='is_debug=true target_os="all"'

ninja -C out/unified all

This can be used prior to change submission to configure, build, and test the gcc, clang, mbedtls, & examples configurations all together in one parallel build. Each configuration has a separate subdirectory in the output dir.

This unified build can be used for day to day development, although it’s more expensive to build everything for every edit. To save time, you can name the configuration to build:

ninja -C out/unified host_gcc
ninja -C out/unified check_host_gcc

Replace host_gcc with the name of the configuration, which is found in the root BUILD.gn.

You can also fine tune the configurations generated via arguments such as:

gn gen out/unified --args='is_debug=true target_os="all" enable_host_clang_build=false'

For a full list, see the root BUILD.gn.

Note that in the unified build, targets have multiple instances and need to be disambiguated by adding a (toolchain) suffix. Use gn ls out/debug to list all of the target instances. For example:

gn desc out/unified '//src/controller(//build/toolchain/host:linux_x64_clang)'

Note: Some platforms that can be built as part of the unified build require downloading additional tools. To add these to the build, the location must be provided as a build argument. For example, to add the Simplelink cc13x2_26x2 examples to the unified build, install SysConfig and add the following build arguments:

gn gen out/unified --args="target_os=\"all\" enable_ti_simplelink_builds=true ti_sysconfig_root=\"/path/to/sysconfig\""

Getting help

GN has builtin help via

gn help

Recommended topics:

gn help execution
gn help grammar
gn help toolchain

Also see the quick start guide.

Introspection

GN has various introspection tools to help examine the build configuration.

To show all of the targets in an output directory:

gn ls out/host

To show all of the files that will be built:

gn outputs out/host '*'

To show the GN representation of a configured target:

gn desc out/host //src/inet --all

To dump the GN representation of the entire build as JSON:

gn desc out/host/ '*' --all --format=json

To show the dependency tree:

gn desc out/host //:all deps --tree --all

To find dependency paths:

gn path out/host //src/transport/tests:tests //src/system

To list useful information for linking against libCHIP:

gn desc out/host //src/lib include_dirs
gn desc out/host //src/lib defines
gn desc out/host //src/lib outputs

# everything as JSON
gn desc out/host //src/lib --format=json

Maintaining Matter

If you make any change to the GN build system, the next build will regenerate the ninja files automatically. No need to do anything.