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. With support for native-compilation.

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.

Binary Builds

Nightly and stable binary builds produced with this build script are available from jimeh/emacs-builds.

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 automatically, but the CLI tool used to sign the nightly builds is available. Run go run ./cmd/emacs-builder package --help for details. More detailed instructions will come soon.

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
  

Status

As of writing (2021-11-27) it works for me on my machine and for the nightly builds in jimeh/emacs-builds. Your luck may vary.

I have successfully built:

• emacs-28 release branch
• master branch (Emacs 29.x)

For reference, my machine is:

• 13-inch MacBook Pro (2020), 10th-gen 2.3 GHz Quad-Core Intel Core i7 (4c/8t)
• macOS Monterey 12.0.1 (21A559)
• Xcode 13.1 (13A1030d)

Nightly builds are built with GitHub Actions on GitHub-hosted runners, using macos-10.15.

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 if supported (default: enabled)
        --[no-]native-comp           Enable/disable native-comp (default: enabled if supported)
        --[no-]native-march          Enable/disable -march=native CFLAG(default: disabled)
        --[no-]native-full-aot       Enable/disable NATIVE_FULL_AOT / Ahead of Time compilation (default: disabled)
        --[no-]relink-eln-files      Enable/disable re-linking shared libraries in bundled *.eln files (default: enabled)
        --[no-]rsvg                  Enable/disable SVG image support via librsvg (default: enabled)
        --no-titlebar                Apply no-titlebar patch (default: disabled)
        --posix-spawn                Apply posix-spawn patch (default: disabled)
        --no-frame-refocus           Apply no-frame-refocus patch (default: disabled)
        --[no-]github-auth           Make authenticated GitHub API requests if GITHUB_TOKEN environment variable is set.(default: enabled)
        --work-dir DIR               Specify a working directory where tarballs, sources, and builds will be stored and worked with
    -o, --output DIR                 Output directory for finished builds (default: <work-dir>/builds)
        --build-name NAME            Override generated build name
        --dist-include x,y,z         List of extra files to copy from Emacs source into build folder/archive (default: COPYING)
        --[no-]archive               Enable/disable creating *.tbz archive (default: enabled)
        --[no-]archive-keep-build-dir
                                     Enable/disable keeping source folder for archive (default: disabled)
        --plan FILE                  Follow given plan file, instead of using given git ref/sha

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 with native-compilation 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 Emacs.app as emacs CLI Tool

Builds come with a custom emacs shell script launcher for use from the command line, located next to emacsclient in Emacs.app/Contents/MacOS/bin.

The custom emacs script makes sure to use the main Emacs.app/Contents/MacOS/Emacs executable from the correct path, ensuring it finds all the relevant dependencies within the Emacs.app bundle, regardless of it it's exposed via PATH or symlinked to from elsewhere.

To use it, simply add Emacs.app/Contents/MacOS/bin to your PATH. For example, if you place Emacs.app in /Applications:

if [ -d "/Applications/Emacs.app/Contents/MacOS/bin" ]; then
  export PATH="/Applications/Emacs.app/Contents/MacOS/bin:$PATH"
  alias emacs="emacs -nw" # Always launch "emacs" in terminal mode.
fi

If you want emacs in your terminal to launch a GUI instance of Emacs, don't use the alias from the above example.

Native-Comp

Note: On 2021-04-25 the feature/native-comp branch was merged into master.

The build script will automatically detect if the source tree being built supports native-compilation, and enable it if available. You can override the auto-detection logic to force enable or force disable native-compilation by passing --native-comp or --no-native-comp respectfully.

By default NATIVE_FULL_AOT is disabled which ensures a fast build by native compiling as few elisp source files as possible to build Emacs itself. Any remaining elisp files will be dynamically compiled in the background the first time they are used.

To enable native full Ahead-of-Time compilation, pass in the --native-full-aot option, which will native-compile all of Emacs' elisp at built-time. On my machine it takes around 10 minutes to build Emacs.app with NATIVE_FULL_AOT disabled, and around 20-25 minutes with it enabled.

Configuration

Native-Lisp Cache Directory

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

Compilation Warnings

By default any warnings encountered during async native compilation will pop up a warnings buffer. As this tends to happen rather frequently with a lot of packages, it can get annoying. You can disable showing these warnings by setting native-comp-async-report-warnings-errors to nil:

(setq native-comp-async-report-warnings-errors nil)

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 for native-comp

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:
  • https://gist.github.com/mikroskeem/0a5c909c1880408adf732ceba6d3f9ab#1-gcc-with-libgccjit-enabled
  • https://github.com/shshkn/emacs.d/blob/master/docs/nativecomp.md
  • https://gist.github.com/AllenDang/f019593e65572a8e0aefc96058a2d23e

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