bug#17983: 24.4.50; digit keys in *Messages* unhelpful, hang Emacs, etc.

[Drew Adams <drew.adams@oracle.com>]

> > C-q 7 C-q 7 C-q 7.  You see ^G inserted each time (except the first)
> > that you hit C-q (not when you hit 7), because 7 acts as a prefix arg
> > for the following ^Q.  Wunderbar.  A feature, no doubt.
> 
> As Glenn points out, this is normal (and very old) behavior of C-q,
> which is well documented.

Yes, for inserting a char via an octal sequence.  And yes, any number
of octal digits can be used.  I had forgotten that this single 7 fell
into that use case.

So the behavior is normal: each C-q after the first ends the octal
sequence, so it is just 7, which is the code for ^G.  Thanks for the
reminder that this is what I was seeing here.

It would be good, IMO, if there were some echo-area feedback when
you hit an octal digit after C-q.  Please consider that enhancement
request.

> > C-q 7 7 7.  Now Emacs is hosed - in Neverneverland.  ESC ESC ESC no
> > good; C-g no good.  No mouse, no keys, nada.  And no CPU use.  Just
> > hosed.
> 
> Not here, it isn't.  After "C-q 7 7 7", any key gets something
> inserted, and there's no hang.  None.

As I said before, sometimes it happens and sometimes it does not.
I was not able to determine just when or why.  Each time, I started
with emacs -Q, and the result was sometimes a hang and sometimes not.
I reproduced the hang several times, including several times in a
row (always from emacs -Q), but the same recipe sometimes did not
result in a hang.

> > Regardless of whether it freezes each time, if you hit C-q and then
> > 7 one or more times there is no feedback - already a no-no (bug).
> 
> That's indeed a bug, worthy of a separate bug report.

See above.  There should be no need for a separate report.  This was
part of this report, from the beginning.  If you want to create a
separate report for it or rename the subject to better reflect this,
feel free to do so.

I feel that I've reported the problem and asked that it be fixed.
If you find that part of what I reported is not a bug, and because
of that you want to ignore other parts and not fix them, that's
your prerogative.

> But everything else you describe isn't, or is not reproducible here.

See above.

> > C-q should simply quote the 7, as it should quote other characters you
> > type (including ^U, BTW).
> 
> No, numeric characters after C-q behave specially.

(Only octal digits, to be specific - or whatever is specified by
`read-quoted-char-radix'.)

Yes, thanks for that reminder.  I did not realize that that's what
I was seeing here (even though I have long used C-q to input an octal
sequence.)