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Installing an Apple Silicon Native GNAT Compiler


As most people who follow technology developments (and others too perhaps) know, Apple are in the process of moving from Intel amd64 CPU based computers, to new Apple Silicon M1 arm64 based computers. While the benefits are many (such as more power efficient performance), there are also downside.

One of these is the initial lack of native programs compiled to run and get the best use out of the new arm64 M1 technology. Over the past 18 months the situation has been improving rapidly.

One area that also obtained native arm64 support was a pre-release build of GCC GNAT 12.0.1 (arm64) compiler and tools, built and shared by Simon Wright. Simon announced the pre-release on his GitHub page (see below) and on the Ada Reddit forum.

This was great news to me, as I have been waiting to run GNAT on my M1 machines to be able to do native Ada language development for well over a year, so was very keen to try it out!

Installing GCC GNAT 12.0.1 (arm64)

The download from Simon Wright’s release page comes as a .pkg file, and when run, installs the GNAT compiler and supporting Ada language development tools to the folder: /opt/gcc-12.0.1-aarch64.

I tried this out and it all works very well - thank you Simon!

Installation Personal Preferences

In the install notes, Simon does point out that the default install directory can be changed post install if needed - for example just move the install directory to a slightly shorter path if needed:

sudo mv /opt/gcc-12.0.1-aarch64 /opt/gcc-12.0.1

Apart from this, my other personal preferences for the install would be:

Please do not think there is anything wrong with the default installer - these are just personal preference.

The Fix To Make Me Even Happier!

Below I describe my workaround and approach to using the great work Simon has done, and using it to satisfy my own requirements. I am only sharing them in case others have a similar desire, or the information is useful for a similar exercise perhaps…

The steps I followed are document below, should you wish to read on!

First, download the installer package ‘Asset’ file from Simon Wright’s GitHub ‘Release’ page.

Make sure the correct pre-release version is downloaded as the names are similar, but only the one tagged as b9b013b is the native Apple Silicon version compiled for native arm64 use. The direct URL is below, but check the tag, and also for any new ‘pre-released / released’ versions:

Once downloaded the file will probably have the macOS quarantine flag enabled: com.apple.quarantine. This can be checked in a Terminal window by listing the file with the command: ls -l@, as the ‘@’ also shows the macOS extended attributes for any file. Alternatively the xattr command can do the same.

The package file I downloaded is named: gcc-12.0.1-aarch64-apple-darwin21.pkg.

% ls -l@

total 477312
drwxr-xr-x  3 simon  staff    96B  3 Apr 09:59 ./
drwxr-xr-x  8 simon  staff   256B  3 Apr 09:59 ../
-rw-r--r--@ 1 simon  staff   233M  3 Apr 09:58 gcc-12.0.1-aarch64-apple-darwin21.pkg
	com.apple.metadata:kMDItemDownloadedDate	  53B 
	com.apple.metadata:kMDItemWhereFroms	 689B 
	com.apple.quarantine	  57B

To remove the com.apple.quarantine attribute the on the downloaded file: gcc-12.0.1-aarch64-apple-darwin21.pkg use the command:

xattr -r -d com.apple.quarantine gcc-12.0.1-aarch64-apple-darwin21.pkg

or just clear all the extended attribute information from the file with the command:

xattr -c gcc-12.0.1-aarch64-apple-darwin21.pkg

If you are not bothered (or already have) Rosetta 2 installed for macOS, and you just want to install with package installer defaults, then you can now go ahead and install the package file by double clicking it in the macOS Finder, or via a Terminal with the command:

installer -pkg gcc-12.0.1-aarch64-apple-darwin21.pkg -target /

If you wish to continue to bypass the package installer choices, and manually install yourself instead, then read on…

The actual files contained in the package installer can be installed manually to a location of your choice. By default the package installer will install with administrator privileges on you computer, and will also install all the files with root:wheel permissions, into the directory: /opt/gcc-12.0.1-aarch64/

My preference is to run the Ada GNAT compiler and tools with user privileges only, so also locating them within my own home directory too.

This can be done by first extracting the files from the installer package, and then by moving the GNAT Ada compiler and tools to a new directory in $HOME.

First unpack the files from the package installer (ie the file gcc-12.0.1-aarch64-apple-darwin21.pkg) into a new directory (called gcc-unpack in the example), and then change into the new directory, and then extract the package files into it.

NB: Don’t try to copy the installer package into the new unpacking directory and then extract them, as you will see lots of messages starting with: error while extracting archive:....

Make sure you are in the same folder (ie perhaps Downloads) as the downloaded file gcc-12.0.1-aarch64-apple-darwin21.pkg. Then enter the command below into the Terminal:

mkdir gcc-unpack
cd gcc-unpack
xar -xf ../gcc-12.0.1-aarch64-apple-darwin21.pkg

Once the above commands have been completed the files and directories in the gcc-unpack directory should be:

% ls

Distribution                           Resources/                             gcc-12.0.1-aarch64-apple-darwin21.pkg/

The actual file we want is the Payload file located here: pkg-unpack/gcc-12.0.1-aarch64-apple-darwin21.pkg/Payload

Move into that sub-directory with the command:

cd gcc-12.0.1-aarch64-apple-darwin21.pkg/

and then extract the contents of the Payload file into a new gnat directory (or another name of your choosing!) using the commands:

mkdir gnat
cd gnat
cat ../Payload | gunzip -dc | cpio -i

That is the last extract step completed, and if the contents of the new gnat directory are listed as below, then the copies of the binaries for gcc, g++ and gnat etc are all available in the bin sub-directory. The outputs should be:

% ls

bin/     include/ lib/     libexec/ ocaml/   python/  share/

% ls bin/

aarch64-apple-darwin21-c++*        gcc*                               gnatchop*                          gnatpp*                            gprslave*
aarch64-apple-darwin21-g++*        gcc-ar*                            gnatclean*                         gnatprep*                          lal_parse*
aarch64-apple-darwin21-gcc*        gcc-nm*                            gnatcoll_sqlite2ada*               gnatstub*                          lal_playground*
aarch64-apple-darwin21-gcc-12.0.1* gcc-ranlib*                        gnatinspect*                       gnattest*                          lto-dump*
aarch64-apple-darwin21-gcc-ar*     gcov*                              gnatkr*                            gprbuild*                          nameres*
aarch64-apple-darwin21-gcc-nm*     gcov-dump*                         gnatlink*                          gprclean*                          navigate*
aarch64-apple-darwin21-gcc-ranlib* gcov-tool*                         gnatls*                            gprconfig*
c++*                               gnat*                              gnatmake*                          gprinstall*
cpp*                               gnat_compare*                      gnatmetric*                        gprls*
g++*                               gnatbind*                          gnatname*                          gprname*

The final steps are to move the extracted files and directories to a location we want to run them from, which will be under my home directory, and then add the bin sub-directory to my shells path, so the tools can be found and run from the Terminal. Commands used to move the files to my home directory (ie ~) are:

cd ..
mv gnat ~/
cd ~
ls gnat/bin/

The files should all now be in place where you want to use them from…

To ensure the tools are available in the Terminals $PATH add the following to the file: ~/.zshrc (ie assuming the default macOS zsh is being used!):

#    SETUP Path for local Ada GCC 12.0.1 (macOS arm64 version) installation
# add path update if Ada GCC is installed in '~/gnat`
if [[ -d $HOME/gnat/bin ]] && [[ ":$PATH:" != *":$HOME/gnat/bin:"* ]]; then
    export PATH=$HOME/gnat/bin:"${PATH}"

If you used a different directory in your $HOME other than ~/gnat to store the GNAT compiler and tools, then change the above to that directory instead.

Once you re-start the Terminal it should pick up the installed GNAT compiler and tools in your PATH, and you can now use them.

The download files and other extracted files left overs from the package installer can now be deleted as well if you wish.

Next - enjoy, and do some Ada development natively on your Mac.

Future Wishes

Hopefully, in the near future the GCC GNAT compiler and tools (or even the GNAT LLVM equivalent!) will be installable via Homebrew or using the Alire and its great supporting tool alr.

Learning More About Ada

There are plenty of good resources for more background on the Ada language such as:

One great free resource to learn the Ada language from AdaCore, so you can write your own programs, is available here:

You can also download a very nice PDF book copy of the above learning Ada resource, that was recently updated (ie Release 2022-03):

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