Mac Build Instructions

Prerequisites

  • A Mac running 10.9+.
  • https://developer.apple.com/xcode, 5+
  • Install gclient, part of the depot_tools package (download). gclient is a wrapper around svn that we use to manage our working copies.
  • Install Xcode's “Command Line Tools” via Xcode menu -> Preferences -> Downloads
  • The OSX 10.10 SDK. Run
    ls `xcode-select -p`/Platforms/MacOSX.platform/Developer/SDKs
    
    to check whether you have it. If you don't have it, you need to get one from an install of Xcode 6, and place it in the above directory.

Getting the code

Check out the source code using Git. If you're new to the project, you can skip all the information about git-svn, since you will not be committing directly to the repository.

Before checking out, go to the waterfall and check that the source tree is open (to avoid pulling a broken tree).

The path to the build directory should not contain spaces (e.g. not ~/Mac OS X/chromium), as this will cause the build to fail. This includes your drive name, the default “Macintosh HD2” for a second drive has a space.

Building

Chromium on OS X can only be built using the Ninja tool and the Clang compiler. See both of those pages for further details on how to tune the build.

Before you build, you may want to install API keys so that Chrome-integrated Google services work. This step is optional if you aren't testing those features.

Raising system-wide and per-user process limits

If you see errors like the following:

clang: error: unable to execute command: posix_spawn failed: Resource temporarily unavailable
clang: error: clang frontend command failed due to signal (use -v to see invocation)

you may be running into too-low limits on the number of concurrent processes allowed on the machine. Check:

sysctl kern.maxproc
sysctl kern.maxprocperuid

You can increase them with e.g.:

sudo sysctl -w kern.maxproc=2500
sudo sysctl -w kern.maxprocperuid=2500

But normally this shouldn‘t be necessary if you’re building on 10.7 or higher. If you see this, check if some rogue program spawned hundreds of processes and kill them first.

Faster builds

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

Run

GYP_DEFINES=fastbuild=1 build/gyp_chromium

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

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

Running

All build output is located in the out directory (in the example above, ~/chromium/src/out). You can find the applications at {Debug|Release}/ContentShell.app and {Debug|Release}/Chromium.app, depending on the selected configuration.

Unit Tests

We have several unit test targets that build, and tests that run and pass. A small subset of these is:

  • unit_tests from chrome/chrome.gyp
  • base_unittests from base/base.gyp
  • net_unittests from net/net.gyp
  • url_unittests from url/url.gyp

When these tests are built, you will find them in the out/{Debug|Release} directory. You can run them from the command line:

~/chromium/src/out/Release/unit_tests

Coding

According to the Chromium style guide code is not allowed to have whitespace on the ends of lines. If you edit in Xcode, know that it loves adding whitespace to the ends of lines which can make editing in Xcode more painful than it should be. The GTM Xcode Plugin adds a preference panel to Xcode that allows you to strip whitespace off of the ends of lines on save. Documentation on how to install it is here.

Debugging

Good debugging tips can be found here. 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 for information on how.

Contributing

Once you’re comfortable with building Chromium, check out Contributing Code for information about writing code for Chromium and contributing it.

Using Xcode-Ninja Hybrid

While using Xcode is unsupported, GYP supports a hybrid approach of using ninja for building, but Xcode for editing and driving compliation. Xcode can still be slow, but it runs fairly well even with indexing enabled.

With hybrid builds, compilation is still handled by ninja, and can be run by the command line (e.g. ninja -C out/Debug chrome) or by choosing the chrome target in the hybrid workspace and choosing build.

To use Xcode-Ninja Hybrid, set GYP_GENERATORS=ninja,xcode-ninja.

Due to the way Xcode parses ninja output paths, it's also necessary to change the main gyp location to anything two directories deep. Otherwise Xcode build output will not be clickable. Adding xcode_ninja_main_gyp=src/build/ninja/all.ninja.gyp to your GYP_GENERATOR_FLAGS will fix this.

After generating the project files with gclient runhooks, open src/build/ninja/all.ninja.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 want to limit the number of targets visible, which is known to improve Xcode performance, add xcode_ninja_executable_target_pattern=%target% where %target% is a regular expression matching executable targets you'd like to include.

To include non-executable targets, use xcode_ninja_target_pattern=All_iOS.

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

Using Emacs as EDITOR for git commit

Using the Cocoa version of Emacs as the EDITOR environment variable on Mac OS will cause git commit to open the message in a window underneath all the others. To fix this, create a shell script somewhere (call it $HOME/bin/EmacsEditor in this example) containing the following:

#!/bin/sh

# All of these hacks are needed to get "git commit" to launch a new
# instance of Emacs on top of everything else, properly pointing to
# the COMMIT_EDITMSG.

realpath() {
    [[ $1 = /* ]] && echo "$1" || echo "$PWD/${1#./}"
}

i=0
full_paths=()
for arg in "$@"
do
  full_paths[$i]=$(realpath $arg)
  ((++i))
done

open -nWa /Applications/Emacs.app/Contents/MacOS/Emacs --args --no-desktop \
    "${full_paths[@]}"

and in your .bashrc or similar,

export EDITOR=$HOME/bin/EmacsEditor

Improving performance of git status

git status is used frequently to determine the status of your checkout. Due to the 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, the startup setting can be set in /etc/sysctl.conf:

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

Or edit the file directly.

If your git --version reports 2.6 or higher, the following may also improve performance of git status:

git update-index --untracked-cache