# Checking out and building Chromium for Mac

There are instructions for other platforms linked from the
[get the code](get_the_code.md) page.

## Instructions for Google Employees

Are you a Google employee? See
[go/building-chrome](https://goto.google.com/building-chrome) instead.

[TOC]

## System requirements

*   A 64-bit Mac running 10.12+.
*   [Xcode](https://developer.apple.com/xcode) 8+
*   The OS X 10.12 SDK. Run

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

    to check whether you have it.  Building with a newer SDK works too, but
    the releases currently use the 10.12 SDK.

## Install `depot_tools`

Clone the `depot_tools` repository:

```shell
$ 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):

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

## Get the code

Ensure that unicode filenames aren't mangled by HFS:

```shell
$ git config --global core.precomposeUnicode true
```

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):

```shell
$ mkdir chromium && cd chromium
```

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

```shell
$ fetch chromium
```

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:

```shell
$ cd src
```

*Optional*: You can also [install API
keys](https://www.chromium.org/developers/how-tos/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](https://ninja-build.org) as its main build tool along with
a tool called [GN](https://gn.googlesource.com/gn/+/master/docs/quick_start.md)
to generate `.ninja` files. You can create any number of *build directories*
with different configurations. To create a build directory:

```shell
$ 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](https://www.chromium.org/developers/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](../tools/gn/docs/quick_start.md).


### 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).

#### Jumbo/Unity builds

Jumbo builds merge many translation units ("source files") and compile them
together. Since a large portion of Chromium's code is in shared header files,
this dramatically reduces the total amount of work needed. Check out the
[Jumbo / Unity builds](jumbo.md) for more information.

Enable jumbo builds by setting the GN arg `use_jumbo_build=true`.

#### CCache

You might also want to [install ccache](ccache_mac.md) to speed up the build.

## Build Chromium

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

```shell
$ 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:

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

## Running test targets

You can run the tests in the same way. You can also limit which tests are
run using the `--gtest_filter` arg, e.g.:

```
$ out/Default/unit_tests --gtest_filter="PushClientTest.*"
```

You can find out more about GoogleTest at its
[GitHub page](https://github.com/google/googletest).

## Debugging

Good debugging tips can be found
[here](https://dev.chromium.org/developers/how-tos/debugging-on-os-x). If you
would like to debug in a graphical environment, rather than using `lldb` at the
command line, that is possible without building in Xcode (see
[Debugging in Xcode](https://www.chromium.org/developers/how-tos/debugging-on-os-x/building-with-ninja-debugging-with-xcode)).

Tips for printing variables from `lldb` prompt (both in Xcode or in terminal):
* If `uptr` is a `std::unique_ptr`, the address it wraps is accessible as
  `uptr.__ptr_.__value_`.
* To pretty-print `base::string16`, ensure you have a `~/.lldbinit` file and
  add the following line into it (substitute {SRC} for your actual path to the
  root of Chromium's sources):
```
command script import {SRC}/tools/lldb/lldb_chrome.py
```

## Update your checkout

To update an existing checkout, you can run

```shell
$ 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/master`). 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 workspace and choosing Build.

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

```shell
$ gn gen out/gn --ide=xcode
```

Open it:

```shell
$ open out/gn/ninja/all.xcworkspace
```

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](https://build.chromium.org/buildbot/waterfall/) is green and the
tree is open before checking out. This will increase your chances of success.

### Improving performance of `git status`

#### 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:

```shell
$ sysctl -a | egrep kern\..*vnodes
```

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

```shell
$ 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, the startup setting can
be set in `/etc/sysctl.conf`:

```shell
$ echo kern.maxvnodes=$((512*1024)) | sudo tee -a /etc/sysctl.conf
```

Or edit the file directly.

#### Configure git to use an untracked cache

If `git --version` reports 2.8 or higher, try running

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

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

```shell
$ git config core.untrackedCache true
```

If `git --version` reports 2.6 or higher, but below 2.8, you can instead run

```shell
$ git update-index --untracked-cache
```

### 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:

```shell
$ xcodebuild -license
```

Only accepting for all users of the machine requires root:

```shell
$ sudo xcodebuild -license
```