funny-looking eval thingie on stack

[DAVE.TOURETZKY at CMU-10A]

I am trying to make FIXIT, my MacLisp debugger, invisible to the
user.  This means it has to know what parts of itself will appear on
the stack so it can edit them out.  I found a rather strange thing
on the stack today, that apparently only gets built when a uuo call
to EVAL, made inside of the function DEBUG, is snapped.  The stack item
looks like  (APPLY -nnn (EVAL (#24016 -1)) -mmm).  Where do those weird
arguments come from?

The file AI:SEF;FIXIT LOG is a log of a brief terminal session demonstrating
this bug.  The source code for FIXIT is on AI:SEF;FIXIT 1, and the FASL file
was created by :QC at AI.  The utility function ERUN is used in the bug demo
to print out the stack.  Its definition is in AI:SEF;FIXUTL 1.

Please let me know if this oddity is due to a bug, or if I must take it
into account in FIXIT's stack editing routine.  Thanks,  -- Dave Touretzky