This is Emacs 25.1 installed via MacPorts on macOS 10.12.

This happens randomly but very frequently. I'm told that a reliable way to reproduce it is to resize the window while mashing C-g.

On Wed, Oct 12, 2016 at 12:44 PM Jean de Largentaye <jlargentaye@gmail.com> wrote:

crashing in org.gnu.Emacs in deliver_fatal_thread_signal • Uncaught Exception 'NSInternalInconsistencyException': nextEventMatchingMask should only be called from the Main Thread!terminating with uncaught exception of type NSException : at com.apple.AppKit in -[NSApplication(NSEvent) shouldBeTreatedAsInkEvent:] + 0

Apparently, calling nextEventMatchingMask from a background thread is risky, and this has been made an assert as on 10.12, hence the crash.