BUG-OF-THE-YEAR-AWARD

[JONL at MIT-MC (Jon L White)]

I hereby award to myself and Dave Touretzky the BOTYA
distinction, for having snaked out that told sneaky
loser, the disappearing cold-water FRETURN blues.
It seems that the various UserInterruptBReaK service
routines were correctly saving and restoring the PROG
pdl level variable, so that the sequence
  PROG-a==>Good-Frame==>UIBRK==>PROG-b==>FRETURN-to-GoodFrame
would indeed unwind thru PROG-b and UIBRK back to
the pdl level of Good-Frame, with the PROG-pdl-level 
restored to PROG-a;  *** but the PROG-pc-counter (label "PA3")
was left at the point in PROG-b ***.  This bug may even
account for other reproducible but unilluminated and
mysterious phenomena;  a correction has been applied
and is available on the ITS machines as SYS:TS NLISP
and at CMU as [c380ml5p]NEWLSP.  Try it and send
comments to bug-lisp.