electron/docs/development/build-instructions-gn.md

Build Instructions (experimental GN build)

Follow the guidelines below for building Electron with the experimental GN build.

NOTE: The GN build system is in experimental status.

Platform prerequisites

Check the build prerequisites for your platform before proceeding

• macOS
• Linux
• Windows

GN prerequisites

You'll need to install depot_tools, the toolset used for fetching Chromium and its dependencies.

Also, on Windows, you'll need to set the environment variable DEPOT_TOOLS_WIN_TOOLCHAIN=0. To do so, open Control Panel → System and Security → System → Advanced system settings and add a system variable DEPOT_TOOLS_WIN_TOOLCHAIN with value 0. This tells depot_tools to use your locally installed version of Visual Studio (by default, depot_tools will try to download a Google-internal version that only Googlers have access to).

Cached builds (optional step)

GIT_CACHE_PATH

If you plan on building Electron more than once, adding a git cache will speed up subsequent calls to gclient. To do this, set a GIT_CACHE_PATH environment variable:

$ export GIT_CACHE_PATH="${HOME}/.git_cache"
$ mkdir -p "${GIT_CACHE_PATH}"
# This will use about 16G.

sccache

Thousands of files must be compiled to build Chromium and Electron. You can avoid much of the wait by reusing Electron CI's build output via sccache. This requires some optional steps (listed below) and these two environment variables:

export SCCACHE_BUCKET="electronjs-sccache"
export SCCACHE_TWO_TIER=true

Getting the code

$ mkdir electron-gn && cd electron-gn
$ gclient config \
    --name "src/electron" \
    --unmanaged \
    https://github.com/electron/electron
$ gclient sync --with_branch_heads --with_tags
# This will take a while, go get a coffee.

Building

$ cd src
$ export CHROMIUM_BUILDTOOLS_PATH=`pwd`/buildtools
# this next line is needed only if building with sccache
$ export GN_EXTRA_ARGS="${GN_EXTRA_ARGS} cc_wrapper=\"${PWD}/electron/external_binaries/sccache\""
$ gn gen out/Default --args="import(\"//electron/build/args/debug.gn\") $GN_EXTRA_ARGS"

This will generate a build directory out/Default under src/ with debug build configuration. You can replace Default with another name, but it should be a subdirectory of out. Also you shouldn't have to run gn gen again—if you want to change the build arguments, you can run gn args out/Default to bring up an editor.

To see the list of available build configuration options, run gn args out/Default --list.

For generating Debug (aka "component" or "shared") build config of Electron:

$ gn gen out/Default --args="import(\"//electron/build/args/debug.gn\") $GN_EXTRA_ARGS"

For generating Release (aka "non-component" or "static") build config of Electron:

$ gn gen out/Default --args="import(\"//electron/build/args/release.gn\") $GN_EXTRA_ARGS"

To build, run ninja with the electron:electron_app target:

$ ninja -C out/Default electron:electron_app
# This will also take a while and probably heat up your lap.

This will build all of what was previously 'libchromiumcontent' (i.e. the content/ directory of chromium and its dependencies, incl. WebKit and V8), so it will take a while.

To speed up subsequent builds, you can use sccache. Add the GN arg cc_wrapper = "sccache" by running gn args out/Default to bring up an editor and adding a line to the end of the file.

The built executable will be under ./out/Default:

$ ./out/Default/Electron.app/Contents/MacOS/Electron
# or, on Windows
$ ./out/Default/electron.exe
# or, on Linux
$ ./out/Default/electron

Cross-compiling

To compile for a platform that isn't the same as the one you're building on, set the target_cpu and target_os GN arguments. For example, to compile an x86 target from an x64 host, specify target_cpu = "x86" in gn args.

$ gn gen out/Default-x86 --args='... target_cpu = "x86"'

Not all combinations of source and target CPU/OS are supported by Chromium. Only cross-compiling Windows 32-bit from Windows 64-bit and Linux 32-bit from Linux 64-bit have been tested in Electron. If you test other combinations and find them to work, please update this document :)

See the GN reference for allowable values of target_os and target_cpu

Tests

To run the tests, you'll first need to build the test modules against the same version of Node.js that was built as part of the build process. To generate build headers for the modules to compile against, run the following under src/ directory.

$ ninja -C out/Default third_party/electron_node:headers
# Install the test modules with the generated headers
$ (cd electron/spec && npm i --nodedir=../../out/Default/gen/node_headers)

Then, run Electron with electron/spec as the argument:

# on Mac:
$ ./out/Default/Electron.app/Contents/MacOS/Electron electron/spec
# on Windows:
$ ./out/Default/electron.exe electron/spec
# on Linux:
$ ./out/Default/electron electron/spec

If you're debugging something, it can be helpful to pass some extra flags to the Electron binary:

$ ./out/Default/Electron.app/Contents/MacOS/Electron electron/spec \
  --ci --enable-logging -g 'BrowserWindow module'