build-emacs-for-macos

My personal hacked together script for building a completely self-contained Emacs.app application on macOS, from any git branch, tag, or ref.

Use this script at your own risk.

Why?

To use new features available from master or branches, which have not made it into a official stable release yet.
Homebrew builds of Emacs are not self-contained applications, making it very difficult when doing HEAD builds and you need to rollback to a earlier version.
Both Homebrew HEAD builds, and nightly builds from emacsformacosx.com are built from the master branch. This script allows you to choose any branch, tag, or git ref you want.

Status

As of writing (2021-01-15) it works for me on my machine. Your luck may vary.

I have successfully built:

emacs-27.1 release git tag
master branch (Emacs 28.x)
feature/native-comp branch (Emacs 28.x)

For reference, my machine is:

13-inch MacBook Pro (2020), 10th-gen 2.3 GHz Quad-Core Intel Core i7 (4c/8t)
macOS Big Sur 11.1 (20C69)
Xcode 12.3 (12C33)

Limitations

The build produced does have some limitations:

It is not a universal application. The CPU architecture of the built application will be that of the machine it was built on.
The minimum required macOS version of the built application will be the same as that of the machine it was built on.
The application is not signed, so running it on machines other than the one that built the application will yield warnings. If you want to make a signed Emacs.app, google is you friend for finding signing instructions.

Requirements

Xcode
Homebrew
All Homebrew formula listed in the Brewfile, which can all easily be installed by running:
```
brew bundle
```
Ruby 2.3.0 or later is needed to execute the build script itself. macOS comes with Ruby, check your version with ruby --version. If it's too old, you can install a newer version with:
```
brew install ruby
```

Usage

Usage: ./build-emacs-for-macos [options] <branch/tag/sha>

Branch, tag, and SHA are from the emacs-mirror/emacs/emacs Github repo,
available here: https://github.com/emacs-mirror/emacs

Options:
    -j, --parallel COUNT             Compile using COUNT parallel processes (detected: 8)
        --git-sha SHA                Override detected git SHA of specified branch allowing builds of old commits
        --[no-]xwidgets              Enable/disable XWidgets (default: enabled if supported)
        --[no-]native-comp           Enable/disable native-comp (default: enabled if supported)
        --[no-]native-full-aot       Enable/disable NATIVE_FULL_AOT / Ahead of Time compilation (default: disabled)
        --rsvg                       Enable SVG image support via librsvg, can yield a unstable build (default: disabled)
        --no-titlebar                Apply no-titlebar patch (default: disabled)
        --no-frame-refocus           Apply no-frame-refocus patch (default: disabled)
        --[no-]native-fast-boot      DEPRECATED: use --[no-]native-full-aot instead
        --[no-]launcher              DEPRECATED: Launcher script is no longer used.

Resulting applications are saved to the builds directory in a bzip2 compressed tarball.

If you don't want the build process to eat all your CPU cores, pass in a -j value of how many CPU cores you want it to use.

Re-building the same Git SHA again can yield weird results unless you first trash the corresponding directory from the sources directory.

Examples

To download a tarball of the master branch (Emacs 28.x as of writing) and build Emacs.app from it:

./build-emacs-for-macos

To build the stable emacs-27.1 release git tag run:

./build-emacs-for-macos emacs-27.1

All sources as downloaded as tarballs from the emacs-mirror GitHub repository. Hence to get a list of tags/branches available to install, simply check said repository.

Use Self-Contained Emacs.app as `emacs` CLI Tool

As the application bundle is self-contained, the main executable needs to be run from within the application bundle. This means a simple symlink to Emacs.app/Contents/MacOS/Emacs will not work. Instead the best approach is to create a shell alias called emacs pointing to the right place.

Personally I use something similar to this:

if [ -f "/Applications/Emacs.app/Contents/MacOS/Emacs" ]; then
  export EMACS="/Applications/Emacs.app/Contents/MacOS/Emacs"
  alias emacs="$EMACS -nw"
fi

if [ -f "/Applications/Emacs.app/Contents/MacOS/bin/emacsclient" ]; then
  alias emacsclient="/Applications/Emacs.app/Contents/MacOS/bin/emacsclient"
fi

Setting the EMACS variable to the binary path seems to be a good idea, as some tools seems to use it to figure out the path to Emacs' executable, including doom-emacs' doom CLI tool.

Native-Comp

Building a Emacs.app with native-comp support (gccemacs) from the feature/native-comp branch is now supported without much hassle thanks to the newly released libgccjit Homebrew formula.

To build a Emacs.app with native compilation enabled, simply run:

./build-emacs-for-macos feature/native-comp

By default NATIVE_FULL_AOT is disabled which ensures a fast build by native compiling as few lisp source files as possible to build the app. Any remaining lisp files will be dynamically compiled in the background the first time you use them. To enable native full AoT, pass in the --native-full-aot option.

On my machine it takes around 10 minutes to build Emacs.app with NATIVE_FULL_AOT disabled. With it enabled it takes around 20-25 minutes.

Configuration

Add the following near the top of your early-init.el or init.el:

(setq comp-speed 2)

By default natively compiled *.eln files will be cached in ~/.emacs.d/eln-cache/. If you want to customize that, simply set a new path as the first element of the comp-eln-load-path variable. The path string must end with a /.

Below is an example which stores all compiled *.eln files in cache/eln-cache within your Emacs configuration directory:

(when (boundp 'comp-eln-load-path)
  (setcar comp-eln-load-path
          (expand-file-name "cache/eln-cache/" user-emacs-directory)))

Issues

Please see all issues with the native-comp label. It's a good idea if you read through them so you're familiar with the types of issues and or behavior you can expect.

Known Good Commits/Builds

A list of known "good" commits which produce working builds is tracked in: #6 Known good commits of feature/native-comp branch

Credits

I've borrowed some ideas from David Caldwell's excellent build-emacs project, which produces all builds for emacsformacosx.com.
Patches applied are pulled from emacs-plus, which is an excellent Homebrew formula with lots of options not available elsewhere.
The following sources were extremely useful in figuring out how get get the feature/native-comp branch building on macOS:

Internals

The script downloads the source code as a gzipped tar archive from the GitHub mirror repository, as it makes it very easy to get a tarball of any given git reference.

It then runs ./configure with a various options, including copying various dynamic libraries into the application itself. So the built application should in theory run on a macOS install that does not have Homebrew, or does not have the relevant Homebrew formulas installed.

Code quality of the script itself, is well, non-existent. The build script started life a super-quick hack back in 2013, and now it's even more of a dirty hack. I might clean it up and add unit tests if I end up relying on this script for a prolonged period of time. For now I plan to use it at least until native-comp lands in a stable Emacs release for macOS.

License

CC0 1.0 Universal

tjsousa/build-emacs-for-macos