Upgraded to MacOS 27, and then Emacs and biber failed on me.

I use Emacs installed through Homebrew, also use MacTeX, have the Apple developer command line tools installed, and recently upgraded to MacOS 27. A few days after that I upgraded my Homebrew packages (I do this every once in a while), and this included an upgrade of emacs-app. And then the problems started. (Dumping this here in case others are also bitten by this and are looking for a fix…)

Emacs issues

Starting up Emacs after that suddenly gave me lots of errors.

clang: error: invalid version number in '-mmacosx-version-min=18.0'
libgccjit.so: error: error invoking gcc driver

Apparently something was wrong with byte compiling the lisp files. At first it seemed the problem was that I still had a pre-MacOS 27 version of the developer command line tools installed. The System Settings -> General -> Software Update didn’t show them. The solution was to first run

sudo rm -rf /Library/Developer/CommandLineTools

to uninstall the old version, and then run

sudo xcode-select --install

to install the new version (27.0).

This didn’t fix my Emacs problem yet. Poking around on the web I discovered there are two homebrew versions of Emacs: emacs-app (the one I had installed) and emacs-plus-app (see here for more information on it). I decided to give it a go and ran

brew uninstall emacs-app
brew trust d12frosted/emacs-plus
brew tap d12frosted/emacs-plus
brew install emacs-plus-app

Now Emacs started up without errors. Great, problem solved.

MacTeX issues

A few days later, another problem surfaced. With biber, part of MacTeX. Running it printed an error message starting with:

usage: lipo <input_file> <command> [<options> ...]   command is one of:

Apparently this was caused by my recent upgrade of the developer command line tools. I didn’t like the fix proposed in the stack exchange post, so decided to use the TeX Live utility to upgrade MacTeX (and in particular biber) to the latest version. It asked whether I wanted to install a critical upgrade. I agreed, but this failed with the following error:

2026-09-24 08:01:43 +0000 Warning tlu_ipctask[51211]    ./runme.sh: Cannot find TeX Live root using kpsewhich --var-value=SELFAUTOPARENT.

As the GUI version failed, I turned to the shell. First to upgrade the upgrade tool itself with

sudo tlmgr update --self

and then to upgrade all packages with

sudo tlmgr update --all

This worked.