bug#74666: 31.0.50; Regression in replace-match with empty-adjacent groups

[Eli Zaretskii]

Ping!

> Cc: 74666@debbugs.gnu.org
> Date: Tue, 03 Dec 2024 16:05:40 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> 
> > Date: Tue, 3 Dec 2024 21:56:02 +1100
> > From: Campbell Barton <ideasman42@gmail.com>
> > 
> > 
> > Run the following file as an executable script:
> > 
> > emacs -Q --batch -l ./emacs-test.el
> > 
> > ;; BEGIN SCRIPT:
> > #!/usr/bin/env -S emacs --batch -l
> > ;;; emacs-git-log --- Batch check emacs-lisp. -*- lexical-binding: t -*-
> > 
> > (defun printf (&rest args)
> >    (princ (apply #'format args) #'external-debugging-output))
> > 
> > (defun test-me (is-forward)
> >    (let ((result ""))
> >      (with-temp-buffer
> >        (insert "__B_\n")
> >        (save-match-data
> >          (set-match-data (list 2 4 2 2 2 4))
> >          (cond
> >           (is-forward
> >            (replace-match "HELLO" t t nil 1)
> >            (replace-match "WORLD" t t nil 2))
> >           (t
> >            (replace-match "WORLD" t t nil 2)
> >            (replace-match "HELLO" t t nil 1))))
> >        (setq result (buffer-substring-no-properties (point-min) 
> > (point-max))))
> >      result))
> > 
> > (printf "A: %s" (test-me t))
> > (printf "B: %s" (test-me nil))
> > ;; END SCRIPT:
> > 
> > In emacs 29.4 this prints:
> > 
> > A: _HELLOWORLD_
> > B: _HELLOWORLD_
> > 
> > In emacs 31.0.50 this prints:
> > 
> > A: _WORLD_
> > B: _HELLOWORLD_
> > 
> > This is a regression in 47b497b4dac91e5ea56102018223bdeb5e21a93b.
> 
> Stefan, could you please take a look?
> 
> 
> 
>