bug#73018: 31.0.50; wdired + replace-regexp only modifies the visible portion of the buffer

[Eli Zaretskii <eliz@gnu.org>]

> Cc: Michael Heerdegen <michael_heerdegen@web.de>, Madhu <enometh@meer.net>,
>  73018@debbugs.gnu.org
> Date: Tue, 10 Sep 2024 09:27:31 -0400
> From:  Stefan Monnier via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> > We should probably use something like
> >
> >     ptrdiff_t
> >     search_regs_last_reg (void)
> >     {
> >       ptrdiff_t i = search_regs.num_regs - 1;
> >       while (i >= 0 && search_regs.start[i] < 0)
> >         i--;
> >       return i;
> >     }
> >
> > instead of `search_regs.num_regs`.
> 
> And maybe we should consider changing `struct re_search` to keep track
> of the last non-nil subgroup.  Currently, things like `match-data` loop
> through all the elements of `search_regs` whose size depends on the
> size (in number of subgroups) of the largest regexp we have ever matched
> so far, rather than the actual number of subgroups currently in use, so
> there's some wasted work there.  Maybe the cost of maintaining the "last
> reg" would pay off.

Since this is a regression in Emacs 30, I'd like to solve it on the
release branch.  Can you suggest the safest fix you can come up with
for that purpose?

TIA