aliBuild prerequisites for macOS

ALICE software on macOS is supported on a best effort basis. Even though we systematically check macOS builds there is no guarantee that software builds or runs correctly. Support requests might have low priority. That said, we were able to successfully build on:

Ventura (13.0) on x86, M1 and M2

Get Xcode

Xcode bundles the necessary tools to build software in the apple ecosystem including compilers, build systems and version control.

Download it from the App Store
Open once installed. It will ask to install additional components - approve the action.
Open a terminal (Applicaions>Utilities>Terminal) and install the command line tools using:
```
sudo xcode-select --install
```
approve the license conditions by
```
sudo xcodebuild -license
```

Get Homebrew

Homebrew is a command-line package manager for macOS used to install software packages similar to yum on CentOS or apt on Ubuntu.

Install Homebrew using the instructions on their webpage.
Once installed detect any problems regarding Homebrew and your system using
```
brew doctor
```

Install the required packages

Note that Homebrew does not run as root. Do not prepend sudo to any of the following commands.

Install the prerequisites and aliBuild via:

brew install alisw/system-deps/o2-full-deps alisw/system-deps/alibuild

Set up Homebrew in your shell by running the following command:

echo 'eval "$(/opt/homebrew/bin/brew shellenv)"' >> ~/.zprofile

Close Terminal and reopen it to apply changes.

Check installed package versions

Homebrew might sometimes install multiple versions of some packages, such as llvm or python. This can happen after you have used brew for a while.

Make sure you have only the currently-supported versions of packages installed, as listed in the dependencies of alisw/system-deps/o2-full-deps, paying particular attention to llvm and python.

You may have to run brew uninstall for package versions that are unsupported by ALICE, if they have ended up installed on your system.

(Recommended) Exclude your work directory from Spotlight

The mac search engine (Spotlight) will be indexing the build directory which can have severe effects on your system performance. To avoid that, you can exclude your working directory (we are assuming ~/alice - create if not yet existing). Go to (Apple) menu>System preferences>Spotlight. In the Privacy tab, hit the + button. Now select the ~/alice directory and confirm.

You are now ready for installing aliBuild and start building ALICE software

Troubleshooting:

Some users have reported that homebrew commands might terminate with an error. The solution oddly enough seems to be to execute the above command multiple times until brew does not complain anymore.

If you have just upgraded your Xcode or macOS, you should run brew reinstall instead, in order to force the reinstallation of already installed packages. You also might want to run brew cleanup at the end to free up some space.

Prerequisites for macOS