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Checking out and building Chromium for Mac

There are instructions for other platforms linked from the get the code page.

Instructions for Google Employees

Are you a Google employee? See go/building-chrome instead.

[TOC]

System requirements

  • A Mac, Intel or Arm. (More details about Arm Macs.)

  • Xcode. Xcode comes with...

  • The macOS SDK. Run

    $ ls `xcode-select -p`/Platforms/MacOSX.platform/Developer/SDKs

    to check whether you have it, and what version you have. mac_sdk_official_version in mac_sdk.gni is the SDK version used on all the bots and for official builds, so that version is guaranteed to work. Building with a newer SDK usually works too (please fix or file a bug if it doesn't).

    Building with an older SDK might also work, but if it doesn't then we won't accept changes for making it work.

    The easiest way to get the newest SDK is to use the newest version of Xcode, which often requires using the newest version of macOS. We don't use Xcode itself much, so if you're know what you're doing, you can likely get the build working with an older version of macOS as long as you get a new version of the macOS SDK on it.

  • An APFS-formatted volume (this is the default format for macOS volumes).

Install depot_tools

Clone the depot_tools repository:

$ git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git

Add depot_tools to the end of your PATH (you will probably want to put this in your ~/.bash_profile or ~/.zshrc). Assuming you cloned depot_tools to /path/to/depot_tools (note: you must use the absolute path or Python will not be able to find infra tools):

$ export PATH="$PATH:/path/to/depot_tools"

Get the code

Create a chromium directory for the checkout and change to it (you can call this whatever you like and put it wherever you like, as long as the full path has no spaces):

$ mkdir chromium && cd chromium

Run the fetch tool from depot_tools to check out the code and its dependencies.

$ caffeinate fetch chromium

Running the fetch with caffeinate is optional, but it will prevent the system from sleeping for the duration of the fetch command, which may run for a considerable amount of time.

If you don't need the full repo history, you can save time by using fetch --no-history chromium. You can call git fetch --unshallow to retrieve the full history later.

Expect the command to take 30 minutes on even a fast connection, and many hours on slower ones.

When fetch completes, it will have created a hidden .gclient file and a directory called src in the working directory. The remaining instructions assume you have switched to the src directory:

$ cd src

Optional: You can also install API keys if you want your build to talk to some Google services, but this is not necessary for most development and testing purposes.

Setting up the build

Chromium uses Ninja as its main build tool along with a tool called GN to generate .ninja files. You can create any number of build directories with different configurations. To create a build directory:

$ gn gen out/Default
  • You only have to run this once for each new build directory, Ninja will update the build files as needed.
  • You can replace Default with another name, but it should be a subdirectory of out.
  • For other build arguments, including release settings, see GN build configuration. The default will be a debug component build matching the current host operating system and CPU.
  • For more info on GN, run gn help on the command line or read the quick start guide.
  • Building Chromium for arm Macs requires additional setup.

Faster builds

Full rebuilds are about the same speed in Debug and Release, but linking is a lot faster in Release builds.

Put

is_debug = false

in your args.gn to do a release build.

Put

is_component_build = true

in your args.gn to build many small dylibs instead of a single large executable. This makes incremental builds much faster, at the cost of producing a binary that opens less quickly. Component builds work in both debug and release.

Put

symbol_level = 0

in your args.gn to disable debug symbols altogether. This makes both full rebuilds and linking faster (at the cost of not getting symbolized backtraces in gdb).

Use Reclient

In addition, Google employees should use Reclient, a distributed compilation system. Detailed information is available internally but the relevant gn arg is:

  • use_remoteexec = true

Google employees can visit go/building-chrome-mac#using-remote-execution for more information. For external contributors, Reclient does not support Mac builds.

CCache

You might also want to install ccache to speed up the build.

Build Chromium

Build Chromium (the "chrome" target) with Ninja using the command:

$ autoninja -C out/Default chrome

(autoninja is a wrapper that automatically provides optimal values for the arguments passed to ninja.)

You can get a list of all of the other build targets from GN by running gn ls out/Default from the command line. To compile one, pass the GN label to Ninja with no preceding "//" (so, for //chrome/test:unit_tests use autoninja -C out/Default chrome/test:unit_tests).

Run Chromium

Once it is built, you can simply run the browser:

$ out/Default/Chromium.app/Contents/MacOS/Chromium

Avoiding system permissions dialogs after each build

Every time you start a new developer build, you may get two system dialogs: Chromium wants to use your confidential information stored in "Chromium Safe Storage" in your keychain., and Do you want the application "Chromium.app" to accept incoming network connections?.

To avoid them, you can run Chromium with these command-line flags (but of course beware that they will change the behavior of certain subsystems):

--use-mock-keychain --disable-features=DialMediaRouteProvider

Build and run test targets

Tests are split into multiple test targets based on their type and where they exist in the directory structure. To see what target a given unit test or browser test file corresponds to, the following command can be used:

$ gn refs out/Default --testonly=true --type=executable --all chrome/browser/ui/browser_list_unittest.cc
//chrome/test:unit_tests

In the example above, the target is unit_tests. The unit_tests binary can be built by running the following command:

$ autoninja -C out/Default unit_tests

You can run the tests by running the unit_tests binary. You can also limit which tests are run using the --gtest_filter arg, e.g.:

$ out/Default/unit_tests --gtest_filter="BrowserListUnitTest.*"

You can find out more about GoogleTest at its GitHub page.

Debugging

Good debugging tips can be found here.

Update your checkout

To update an existing checkout, you can run

$ git rebase-update
$ gclient sync

The first command updates the primary Chromium source repository and rebases any of your local branches on top of tip-of-tree (aka the Git branch origin/main). If you don't want to use this script, you can also just use git pull or other common Git commands to update the repo.

The second command syncs dependencies to the appropriate versions and re-runs hooks as needed.

Tips, tricks, and troubleshooting

Using Xcode-Ninja Hybrid

While using Xcode is unsupported, GN supports a hybrid approach of using Ninja for building, but Xcode for editing and driving compilation. Xcode is still slow, but it runs fairly well even with indexing enabled. Most people build in the Terminal and write code with a text editor, though.

With hybrid builds, compilation is still handled by Ninja, and can be run from the command line (e.g. autoninja -C out/gn chrome) or by choosing the chrome target in the hybrid project and choosing Build.

To use Xcode-Ninja Hybrid pass --ide=xcode to gn gen:

$ gn gen out/gn --ide=xcode

Open it:

$ open out/gn/all.xcodeproj

You may run into a problem where http://YES is opened as a new tab every time you launch Chrome. To fix this, open the scheme editor for the Run scheme, choose the Options tab, and uncheck "Allow debugging when using document Versions Browser". When this option is checked, Xcode adds --NSDocumentRevisionsDebugMode YES to the launch arguments, and the YES gets interpreted as a URL to open.

If you have problems building, join us in #chromium on irc.freenode.net and ask there. Be sure that the waterfall is green and the tree is open before checking out. This will increase your chances of success.

Improving performance of git commands

Increase the vnode cache size

git status is used frequently to determine the status of your checkout. Due to the large number of files in Chromium's checkout, git status performance can be quite variable. Increasing the system's vnode cache appears to help. By default, this command:

$ sysctl -a | egrep 'kern\..*vnodes'

Outputs kern.maxvnodes: 263168 (263168 is 257 * 1024). To increase this setting:

$ sudo sysctl kern.maxvnodes=$((512*1024))

Higher values may be appropriate if you routinely move between different Chromium checkouts. This setting will reset on reboot. To apply it at startup:

$ sudo tee /Library/LaunchDaemons/kern.maxvnodes.plist > /dev/null <<EOF
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
  <dict>
    <key>Label</key>
      <string>kern.maxvnodes</string>
    <key>ProgramArguments</key>
      <array>
        <string>sysctl</string>
        <string>kern.maxvnodes=524288</string>
      </array>
    <key>RunAtLoad</key>
      <true/>
  </dict>
</plist>
EOF

Or edit the file directly.

Configure git to use an untracked cache

Try running

$ git update-index --test-untracked-cache

If the output ends with OK, then the following may also improve performance of git status:

$ git config core.untrackedCache true

Configure git to use fsmonitor

You can significantly speed up git by using fsmonitor. You should enable fsmonitor in large repos, such as Chromium and v8. Enabling it globally will launch many processes and probably isn't worthwhile. Be sure you have at least version 2.43 (fsmonitor on the Mac is broken before then). The command to enable fsmonitor in the current repo is:

$ git config core.fsmonitor true

Xcode license agreement

If you're getting the error

Agreeing to the Xcode/iOS license requires admin privileges, please re-run as root via sudo.

the Xcode license hasn't been accepted yet which (contrary to the message) any user can do by running:

$ xcodebuild -license

Only accepting for all users of the machine requires root:

$ sudo xcodebuild -license

Exclude checkout from Spotlight indexing

Chromium's checkout contains a lot of files, and building generates many more. Spotlight will try to index all of those files, and uses a lot of CPU time doing so, especially during a build, which can slow things down.

To prevent the Chromium checkout from being indexed by Spotlight, open System Preferences, go to "Spotlight" -> "Privacy" and add your Chromium checkout directory to the list of excluded locations.