build-emacs-for-macos/README.md

# 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](https://github.com/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

Required with both Nix and Homebrew approaches:

- [Xcode](https://apps.apple.com/gb/app/xcode/id497799835?mt=12)

### Nix

The [Nix](https://nixos.org/) package manager is the preferred and most reliable
way to install all dependencies required to build Emacs, by way of a Nix flake
included in the project root.

To install all required dependencies within the nix shell, run:

```
nix develop --command make bootstrap
```

### Homebrew

If you do not have Nix installed, then the alternative way to manage and install
build-time dependencies is via [Homebrew](https://brew.sh/).

Ruby 3.3.x or later is also needed to execute the build script. Earlier versions
may work, but are untested. Simplest way to install a recent Ruby version is via
Homebrew:

```
brew install ruby
```

And finally, to install all built-time dependencies, run:

```
make bootstrap
```

## Status

As of writing (2023-11-20) it works for me on my machine and for the nightly
builds in [jimeh/emacs-builds](https://github.com/jimeh/emacs-builds). Your luck
may vary.

I have successfully built:

- `emacs-29.1` release tag.
- `master` branch (Emacs 30.x).

For reference, my machine is:

- 14-inch MacBook Pro (2023), Apple M3 Pro (11-cores)
- macOS Sonoma 14.1.1 (23B2082)
- Xcode 15.0.1 (15A507)

Nightly builds are built with GitHub Actions on GitHub-hosted runners, using
`macos-12` for Intel builds, and `macos-13-xlarge` for Apple Silicon builds.

## Usage

### Nix

Ensure [Flakes](https://nixos.wiki/wiki/Flakes) are enabled, and enter the flake
development environment with `nix develop`. Within this environment, you can
execute the `./build-emacs-for-macos --help` to get started.

Or you can run the build script via `nix develop`:

```
nix develop --command ./build-emacs-for-macos --help
```

### Homebrew

Run `make boostrap` to ensure all Ruby and Homebrew dependencies are installed.

### Build Script

```
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:
        --info                       Print environment info and detected library paths, then exit
        --preview                    Print preview details about build and exit.
    -j, --parallel COUNT             Compile using COUNT parallel processes (detected: 16)
        --git-sha SHA                Override detected git SHA of specified branch allowing builds of old commits
        --[no-]use-nix               Use Nix instead of Homebrew to find dependencies (default: enabled if IN_NIX_SHELL is set)
        --[no-]xwidgets              Enable/disable XWidgets if supported (default: enabled)
        --[no-]tree-sitter           Enable/disable tree-sitter 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-]dbus                  Enable/disable dbus support (default: enabled)
        --no-titlebar                Apply no-titlebar patch (default: disabled)
        --posix-spawn                Apply posix-spawn patch (deprecated)
        --no-frame-refocus           Apply no-frame-refocus patch (default: disabled)
        --[no-]poll                  Apply poll patch (deprecated)
        --[no-]fd-setsize SIZE       Set an file descriptor (max open files) limit (default: 10000)
        --github-src-repo REPO       Specify a GitHub repo to download source tarballs from (default: emacs-mirror/emacs)
        --[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-]self-sign             Enable/disable self-signing of Emacs.app (default: enabled)
        --[no-]archive               Enable/disable creating *.tbz archive (default: enabled)
        --[no-]archive-keep-build-dir
                                     Enable/disable keeping source folder for archive (default: disabled)
        --log-level LEVEL            Build script log level (default: info)
        --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-29.1` release git tag run:

```
./build-emacs-for-macos emacs-29.1
```

All sources as downloaded as tarballs from the
[emacs-mirror](https://github.com/emacs-mirror/emacs) 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`:

```bash
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

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` respectively.

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:

```elisp
(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`:

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

### Issues

Please see all issues with the
[`native-comp`](https://github.com/jimeh/build-emacs-for-macos/issues?q=is%3Aissue+is%3Aopen+label%3Anative-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](https://github.com/jimeh/build-emacs-for-macos/issues/6)

## Credits

- I've borrowed some ideas from [David Caldwell](https://github.com/caldwell)'s
  excellent [build-emacs](https://github.com/caldwell/build-emacs) project,
  which produces all builds for
  [emacsformacosx.com](https://emacsformacosx.com).
- Patches applied are pulled from
  [emacs-plus](https://github.com/d12frosted/homebrew-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](https://github.com/emacs-mirror/emacs) 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](http://creativecommons.org/publicdomain/zero/1.0/)