Cygwin: Can’t quit Emacs using C-x C-c

On some installations of Cygwin on Windows, it is impossible to exit Emacs using C-x C-c. After digging around in the message lists, I discovered that the C-x key Control-C is trapped by the OS.

UPDATE: Specifically, Control-C handling on Windows is tied to a console. Only a process that is attached to a proper Windows console can receive Control-C or Control-Break events.

The fix for this is to set a Windows environment variable:

CYGWIN=tty

Then quit all of the Cygwin windows and start them up again. Works like a charm.

UPDATE: Also works for any other situation where Windows is making Control-C kill your process instead of handing it over to the application.