Some issues arose with macOS's Xcode/Command Line Tools version 15. The obvious one was that programs wouldn't link! A less obvious one was that Ada exception handling was unreliable (some exceptions would be caught, others not).
Apple provided a "classic" linker in the version 15 SDKs, ld-classic, which has the old ld's behaviour. You can invoke this by giving ld the switch -ld_classic (this switch isn't available in the ld in the pre-15 SDKs, which interpret it as requesting a library libd_classic.a). The version 15.1 beta releases will link even without the -ld_classic switch.
Unfortunately, this didn't resolve the exception handling problem.
It turns out that linking with ld-classic also resolves the exception handling issue, though this can hardly have been Apple's intention.
It's easy to forget to invoke ld-classic, so we've provided a shim to invoke it instead of ld if it's available.
We want to install our ld shim where the compiler will look for it. The first place it looks (see --with-as=pathname in the GCC Configuration documentation) is libexec/gcc/target/version. This is the place where gcc keeps the actual compiler executables (gcc itself is a driver), such as cc1, gnat1; our task is to place an executable object (e.g. a script) named ld there, whose task is to check whether ld-classic is present; if so, invoke it, if not, invoke ld.
To install: in a shell where your gcc is first on the PATH,
sh install-ld-shim.sh
or, if you're running Alire,
alr exec -- sh install-ld-shim.sh
Note, depending on how your compiler was installed you may need to use sudo.
To uninstall,
sh uninstall-ld-shim.sh
or, if you're running Alire,
alr exec -- sh uninstall-ld-shim.sh
There's a demonstrator in the xcode_issue/ directory.