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GN build configuration

This page provides some common build setups for the GN build. It assumes you already got a Chromium checkout.

See also

Understanding GN build flags

Recall that in GN, you pick your own build directory. These should generally go in a subdirectory of src/out. You set build arguments on a build directory by typing:

$ gn args out/mybuild

This will bring up an editor. The format of the stuff in the args file is just GN code, so set variables according to normal GN syntax (true/false for booleans, double-quotes for string values, # for comments). When you close the editor, a build will be made in that directory. To change the arguments for an existing build, just re-run this command on the existing directory.

You can get a list of all available build arguments for a given build directory, with documentation, by typing

$ gn args out/mybuild --list

To get documentation for a single flag (in this example, is_component_build):

$ gn args out/mybuild --list=is_component_build

You have to list your build directory as the first argument because the available arguments and their default values are build-specific. For example, setting Android as your target OS might expose new Android-specific build arguments or use different default values.

"GN args" as used on this page are not the command line arguments passed to GN. They refer to the individual variables that are passed as part of the --args command line flag and/or written to the args.gn file.

Common build variants

Release build

The default GN build is debug. To do a release build:

is_debug = false

On Android, you can toggle ProGuard on/off with:

is_java_debug = false # Defaults to is_debug.

Trybots that run release builds have DCHECKs enabled, to catch potential bugs.

dcheck_always_on = true

Component build

The component build links many parts of Chrome into separate shared libraries to avoid the long link step at the end. It is the default when compiling debug non-iOS builds and most developers use this mode for everyday builds and debugging. Startup is slower and some linker optimizations won't work, so don't do benchmarks in this mode. Some people like to turn it on for release builds to get both faster links and reasonable runtime performance.

is_component_build = true

Faster builds with no or minimal symbols

The symbol_level setting varies from 0 (no symbols or minimal symbols) to 2 (full symbols). Lower levels make debugging almost impossible, but the build will be much faster. It can be useful in some cases where you just want a build ASAP (many build bots do this).

symbol_level = 0

Alternately you can set symbol_level=1 which will build almost as fast as symbol_level=0 but will give you additional information in call stacks.

Disable Native Client

Most developers don't normally need to test Native Client capabilities and can speed up the build by disabling it.

enable_nacl = false

Remove WebCore symbols

WebCore has lots of templates that account for a large portion of the debugging symbols. If you're not debugging WebCore, you can set the blink symbol level to 0 or 1:

blink_symbol_level=0

Remove v8 symbols

v8 is often the second-largest source of debugging symbols. If you're not debugging v8, you can set the v8 symbol level to 0 or 1:

v8_symbol_level=0

Overriding the CPU architecture

By default, the GN build will match that of the host OS and CPU architecture. To override:

target_cpu = "x86"

Possible values for the target_cpu:

Official Chrome build

This build requires that you are a Googler with src-internal checked out.

Use these args for official builds:

is_official_build = true
is_chrome_branded = true

For 32-bit official builds, append this arg to the above set:

target_cpu = "x86"

On Windows and Mac you also need to add the following entry to your .gclient file to automatically fetch the PGO profiles required to do an official build:

solutions = [
  {
    "name": "src",
    # ...
    "custom_vars": {
      "checkout_pgo_profiles": True,
    },
  },
],

Chrome Branding and Experimental Flags: In unbranded builds, testing/variations/fieldtrial_testing_config.json is used for default field trial settings. You may also disable field trial experimental flags by building with disable_fieldtrial_testing_config=true.

You can also set the following GN argument to disable PGO if needed:

chrome_pgo_phase = 0

Windows

There is a gn gen argument (--ide) for producing Visual Studio project and solution files:

$ gn gen out\mybuild --ide=vs

Projects are configured for VS 2019 by default.

See this page for more information on configuring Chromium builds for Windows.

Android build (from Linux)

This assumes you've already followed the Android build instructions to check out.

It is easy to use the same checkout on Linux to build both Android and desktop Linux versions of Chrome. Your .gclient file must list Android, however, to get the proper SDKs downloaded. This will happen automatically if you follow the Android checkout instructions. To add this to an existing Linux checkout, add target_os to your .gclient file (in the directory above src), and run gclient runhooks.

solutions = [
  ...existing stuff in here...
]
target_os = [ 'android' ]  # Add this to get Android stuff checked out.

Chrome OS build (from Linux)

This will build the Chrome OS variant of the browser that is distributed with the operating system. You can run it on your Linux desktop for feature development.

target_os = "chromeos"

Checkouts which are used to build Chrome OS builds must also have 'chromeos' added to the target_os list in the .gclient file. After making this change, you will need to run gclient sync once.

solutions = [
   ...existing stuff in here...
]
target_os = ['chromeos']
# Or if you also build e.g. android, this might be
# target_os = ['android', 'chromeos']