VM-BUG: "Unrecognized property" alias-coding-systems

[Aidan Kehoe]

 Ar an triú lá de mí Bealtaine, scríobh Stephen J. Turnbull: 

 > XEmacs package version 8.03
 > upstream version 8.0.10-devo
 > 
 > I was getting mail, when I got the following traceback.  I've done
 > this many times on this folder; I wonder if this might be due to an
 > error in some asynchronous task VM is running (ie, on an itimer), at a
 > time when I had debug-on-signal enabled to debug something else?

I think that’s the most likely explanation, given the implementation of
coding-system-get: 

(defun coding-system-get (coding-system prop)
  "Extract a value from CODING-SYSTEM's property list for property PROP."
  (or (plist-get
       (get (coding-system-name coding-system) 'coding-system-property)
       prop)
      (condition-case nil
	  (coding-system-property coding-system prop)
	(error nil))))

And the docstring of debug-on-signal:

  DEFVAR_LISP ("debug-on-signal", &Vdebug_on_signal /*
*Non-nil means enter debugger if an error is signalled.
The debugger will be entered whether or not the error is handled by
a `condition-case'.
[...]

It seems to me that one way around this particular problem would be a
NOERROR argument to #'coding-system-property. 

 > Debugger entered--Lisp error: (invalid-constant "Unrecognized property" alias-coding-systems)
 >   coding-system-property(#<coding-system utf-8 unicode(utf-8)> alias-coding-systems)
 >   coding-system-get(#<coding-system utf-8 unicode(utf-8)> alias-coding-systems)

-- 
¿Dónde estará ahora mi sobrino Yoghurtu Nghé, que tuvo que huir
precipitadamente de la aldea por culpa de la escasez de rinocerontes?