What to do when GT hangs?

This typically happens if you run some code that has an infinite recursion.

To interrupt the GT Processor, just type Cmd+. (MacOS) or Ctrl+. (Windows).

This should interrupt the currently running process and open a debugger.

NB: You may have to do this multiple times to get the attention of the Processor.

If all fails, you may have to force-quit GT.