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

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Build Instructions

Follow the guidelines below for building Electron.

Platform prerequisites

Check the build prerequisites for your platform before proceeding

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.

NOTE: the git cache will set the origin of the src/electron repository to point to the local cache, instead of the upstream git repository. This is undesirable when running git push—you probably want to push to github, not your local cache. To fix this, from the src/electron directory, run:

$ git remote set-url origin https://github.com/electron/electron

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.

Instead of https://github.com/electron/electron, you can use your own fork here (something like https://github.com/<username>/electron).

A note on pulling/pushing

If you intend to git pull or git push from the official electron repository in the future, you now need to update the respective folder's origin URLs.

$ cd src/electron
$ git remote remove origin
$ git remote add origin https://github.com/electron/electron
$ git branch --set-upstream-to=origin/master
$ cd -

📝 gclient works by checking a file called DEPS inside the src/electron folder for dependencies (like Chromium or Node.js). Running gclient sync -f ensures that all dependencies required to build Electron match that file.

So, in order to pull, you'd run the following commands:

$ cd src/electron
$ git pull
$ gclient sync -f

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

Or on Windows (without the optional argument):

$ cd src
$ set CHROMIUM_BUILDTOOLS_PATH=%cd%\buildtools
$ gn gen out/Debug --args="import(\"//electron/build/args/debug.gn\")"

This will generate a build directory out/Debug under src/ with debug build configuration. You can replace Debug 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/Debug to bring up an editor.

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

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

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

To build, run ninja with the electron target: Nota Bene: This will also take a while and probably heat up your lap.

For the debug configuration:

$ ninja -C out/Debug electron

For the release configuration:

$ ninja -C out/Release electron

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/Debug to bring up an editor and adding a line to the end of the file.

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

$ ./out/Debug/Electron.app/Contents/MacOS/Electron
# or, on Windows
$ ./out/Debug/electron.exe
# or, on Linux
$ ./out/Debug/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/Debug-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/Debug third_party/electron_node:headers
# Install the test modules with the generated headers
$ (cd electron/spec && npm i --nodedir=../../out/Debug/gen/node_headers)

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

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

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

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

Sharing the git cache between multiple machines

It is possible to share the gclient git cache with other machines by exporting it as SMB share on linux, but only one process/machine can be using the cache at a time. The locks created by git-cache script will try to prevent this, but it may not work perfectly in a network.

On Windows, SMBv2 has a directory cache that will cause problems with the git cache script, so it is necessary to disable it by setting the registry key

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Lanmanworkstation\Parameters\DirectoryCacheLifetime

to 0. More information: https://stackoverflow.com/a/9935126

Troubleshooting

Stale locks in the git cache

If gclient sync is interrupted while using the git cache, it will leave the cache locked. To remove the lock, pass the --break_repo_locks argument to gclient sync.

I'm being asked for a username/password for chromium-internal.googlesource.com

If you see a prompt for Username for 'https://chrome-internal.googlesource.com': when running gclient sync on Windows, it's probably because the DEPOT_TOOLS_WIN_TOOLCHAIN environment variable is not set to 0. 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).