Visual Studio, Ada Language Server, macOS

If you’re using VSCode on a Mac with Apple silicon (an M-series chip) you will probably have noticed that Ada code formatting doesn’t work.

This is thought to be because of an issue with the aarch64-apple-darwin compiler. It’s stated that the problem doesn’t occur if the Ada Language Server is compiled for the Intel (x86_64) architecture.

Can we run the Intel version?

Macs with Apple silicon (arm64 or aarch64) can use Rosetta to run x86_64 programs.

VSCode installs the Ada Language Server of the architecture matching the CPU, in the directory darwin/ in (for ALS release 26.0.202412191)

~/.vscode/extensions/adacore.ada-26.0.202412191-darwin-arm64/arm64/

The contents of darwin/ are

-rwxr-xr-x  1 simon  staff  108059392 23 Jan 11:10 ada_language_server
drwxr-xr-x  3 simon  staff         96 23 Jan 11:10 ada_language_server.dSYM
-r--r--r--  1 simon  staff     452816 23 Jan 11:10 libgmp.10.dylib

where

$ darwin/ada_language_server --version
ALS version: 26.0.202412191 ()
$ file darwin/ada_language_server
darwin/ada_language_server: Mach-O 64-bit executable arm64

Yes, we can!

Since this ada_language_server is an executable, we can trick VSCode into running the x86_64 version by replacing the contents of darwin/.

Going to AdaCore’s Releases directory, download als-26.0.202412191-darwin-x64.tar.gz.

Remove the quarantine attribute:

$ xattr -d com.apple.quarantine` als-26.0.202412191-darwin-x64.tar.gz

and unpack it into a convenient directory, e.g. ~/als-downloads, where the darwin/ directory will be at integration-202412191/vscode/ada/x64/darwin/.

Make this be the one that VSCode finds. I’ve used symbolic links to avoid accidents as far as possible.

$ cd ~/.vscode/extensions/adacore.ada-26.0.202412191-darwin-arm64/arm64/
$ mv darwin darwin-arm64
$ cp -pR ~/als-downloads/integration-202412191/vscode/ada/x64/darwin darwin-x86_64
$ ln -s darwin-x86_64 darwin

Should you want to reverse this, you can swap the symlink over, but be aware that whatever man ln may say, ln -sf darwin-arm64 darwin will not work; you need to delete the original symlink first, rm darwin.

What next?

It turns out that if you build ada_language_server with GCC 15, this issue isn’t present. GCC 15 is still in the pre-release stage (15.0.1 20250126), and it’ll be a while before it’s released and then makes it onto one of the standard download sites.