We find that when using emacs regular expressions and running them over large sets of files, that the following sort of error can occur periodically: Stack overflow in regexp matcher XEmacs exiting. Debugging such problems would be much simpler if emacs wrote out the regexp in use and the filename or current buffer being scanned along with the error. Since the user that encountered the error can't typically send hundreds or thousands of files for us to test against, without this information, debugging is often nearly impossible. With this information, the file that generated the error could be sent to the developers to test against. A second suggestion that we have long been following with good results in our own software is to embed the name of the function that signals an error within the error message, since often users will get errors like the one above but will not have a stack trace available. This allows them to report the error and pinpoint the location of its generation for quicker debugging. We use errors of the following form: (error "(function-name): error message") Cheers, Bob