Alire vs Apple silicon

Alire releases available from the Alire website are all built for Intel silicon. For pure Ada work, this has no effect, whether or not you're working on Apple silicon.

One area where there's a considerable impact is when your work involves "external releases". These are external libraries which Alire manages as required using your system's "package manager". An example is the crate sdlada, which depends on libsdl2 amongst others. On a Debian system, Alire will load the package libsdl2-dev; on macOS with Homebrew, sdl2.

For macOS, the package managers supported are Homebrew and MacPorts - if you have both installed (not really recommended) Alire will choose Homebrew. Homebrew is the one that this page concentrates on.

If yours is an x86_64 Mac, Homebrew will load x86_64 binaries under /usr/local/. If it's an aarch64 Mac, Homebrew will load aarch64 binaries under /opt/homebrew/ (this is by default; trying to mix architectures is likely to be at best confusing).

So, if you're on an aarch64 Mac with an x86_64 GNAT compiler, you won't be able to use external libraries, because the linker will refuse to link your x86_64 binaries with Homebrew's aarch64 ones.