bug#6808: 24.0.50; Incomplete match highlighting with `query-replace-regexp'

[Tassilo Horn <tassilo@member.fsf.org>]

On Friday 06 August 2010 15:13:55 Stefan Monnier wrote:
> > The matches to be replaced by `query-replace-regexp' aren't highlighted
> > completely, although the replacement is correct.
> 
> > Here's a recipe:
> 
> > 1. emacs -Q
> > 2. Create a buffer with contents:
> 
> >  #1 153030 120 = 423988
> >  #2 152845 181 = 1500234
> >  #3 155160 247 = 767821
> >  #4 155160 310 = 11131347
> >  #5 155160 319 = 13979167
> 
> > 3. M-x query-replace-regexp RET [0-9]+ = RET RET
> 
> > Result:
> 
> > - The first match "120 =" is highlighted completely.
> > - All further matches have only the last number highlighted, e.g. "1 =",
> >   "7 =", ...
> > - Performing the replacement replaces the correct, complete match,
> >   e.g. "120 =", "181 =", "247 ="
> 
> I'd guess that those incorrect matches are search with
> re-search-backward rather than re-search-forward.

To check your guess, I adviced that subr:

(defadvice re-search-backward (before rsb-called activate)
  (message "re-search-backward was called"))

Indeed, with that example above, for the 5 replacements that subr is
called 25 times.

I tried the same in an emacs without -Q, and although I had that
incorrect highlighting at first, after typing the advice and evaling it,
out of sudden it highlighted correctly...

Another thing that is a bit strange (but it doesn't qualify as a bug) is
that if you have point in the middle of the example, also matches before
point are highlighted, although you won't reach them.

Bye,
Tassilo