I don't have a solution neither. Such flag could help, but I still
have to check if this is really the cause of my MATLAB crash
(it only occurs under Linux, not Windows).
Due to a message of yours having bounced from one of the list receivers, I got to know about your last post, but it does not appear in the mailing list.
You suggested rewriting QUIT so that it throws to an enclosing catch. I do not like the idea, because it forces the enclosing code to use SI:TOPLEVEL. I would rather signal a condition, EXT:EXIT-PROGRAM, and set as default handler a function that invokes EXIT. This allows you to override the handler with your own routine and in case that the user provides no handler it will have the expected behavior.
However, that will have to wait. I am now packing ECL for a new release before I travel away next week.