[Bug: 21.5-b27] font-lock-fontify-* / infinite loop

[Aidan Kehoe]

 Ar an naoiú lá de mí Eanair, scríobh Wulf C. Krueger: 

 > Hallo Stephen!
 > 
 > "SJT" == Stephen J Turnbull <stephen at xemacs.org> writes:
 > 
 >  >> font locking runs into an infinite loop while "Fontifying *wide
 >  >> reply to <recipient>*... (regexps).." is shown in the status bar.
 >  SJT> Does this happen with all replies, or just for a particular
 >  SJT> message?
 > 
 > It always happens. I just found out it doesn't even happen with replies
 > only but even for new messages. The following backtrace is being
 > generated (this time *without* the inf. loop and without aborting):
 > 
 > (40) (general/warning) Error in unknown: Invalid function: (macro . #<compiled-function (&rest cdr) "...(6)" [cdr function lambda] 3 737017>)
 > 
 > Backtrace follows:
 > 
 >   lambda(284)
 >   # bind (highlights matcher keyword nkeywords iter old-progress progress bufname keywords case-fold-search loudly loudvar end start)
 >   font-lock-fontify-keywords-region(1 284 nil)

In a buffer where this happens, what does M-: font-lock-keywords RET give?
The error seems to be provoked by the line

   (funcall matcher end)))

in font-lock.el:1870, and if so, we can probably work out where
font-lock-keywords is being set to something not sensible. 

-- 
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