Re: Bug #8901: (C-u C-<space> fails in Isearch) - proposed fix.

[Alan Mackenzie]

Hi, Juri.

On Tue, Aug 30, 2011 at 12:33:28AM +0300, Juri Linkov wrote:
> > Bug #8901 again, for reference:
> > 1.   emacs -Q
> > 2.   M-: (setq isearch-allow-scroll t)
> > 3.   C-x C-f <any file>
> > 4.   C-s <a few characters>
> > 5.   C-u C-<space>

> > This last command ought to terminate the isearch and move point to where
> > the search began.  Instead, it pushes a mark, as though the C-u were not
> > there.

> Please note that it works correctly on X, but fails on a tty.
> So this is a tty-specific bug.

I hadn't actually tried it on X.  ;-(

I have now, though.  The difference seems to be (with C-h l):

tty:   C-u C-@
X:     C-u C-SPC

C-@ has an entry in local-function-key-map, which transforms it into the
vector [67108896] i.e. [2^26 + 32].  Because of this l-f-k-map entry, it
gets caught by the first arm of the cond in `isearch-other-meta-char',
where there's no handling for prefix-arg.

In the X case, C-SPC drops through to some arm where the prefix-arg does
get set.  Probably.

It's too late for me to concentrate fully on this.

-- 
Alan Mackenzie (Nuremberg, Germany).