rxvt -sl 32767 -fg white -bg black -fn fixed
then, run "find /" on a drive with a large number of files
and rxvt will core dump with this message:
rxvt: screen.c:889: scr_add_lines: Assertion `screen.cur.row
>= -TermWin.nscrolled' failed.
Aborted (core dumped)
Fails on 6.0 also.
Seems to be fixed in the latest rxvt in 6.1.