Subject: Re: bug#19892: 25.0.50; hideshow: hs-hide-all-non-comment-function example infloop

From: Lars Ingebrigtsen <[email-masked]>
Date: Fri, 02 Aug 2019 21:17:00 +0200

This was introduced (by me applying the following patch) seven years
ago.

Hm...  Oh, I see what the brittle logic here really is.  The code (by
default) calls this function:

(defun hs-hide-block-at-point (&optional end comment-reg)
[...]
    (when (hs-looking-at-block-start-p)

And:

(defun hs-looking-at-block-start-p ()
  "Return non-nil if the point is at the block start."
  (and (looking-at hs-block-start-regexp)
       (save-match-data (not (nth 8 (syntax-ppss))))))

So if the match is successful, but whatever (nth 8 (syntax-ppss)) means
doesn't, then we go to the end of that match data.

So it kinda works...  But not if `hs-hide-all-non-comment-function' is
set.  I'll try to rework this in a more logical fashion.

commit 43956923c00921499e0582f5da4cd739bc005240
Author: Sébastien Gross <[email-masked]>
Date:   Wed Apr 11 01:34:25 2012 +0200

    (hs-hide-all): Don't infloop on comments that start in the middle of the line.
    
    Fixes: debbugs:10496

diff --git a/lisp/progmodes/hideshow.el b/lisp/progmodes/hideshow.el
--- a/lisp/progmodes/hideshow.el
+++ b/lisp/progmodes/hideshow.el
@@ -804,7 +804,10 @@
          (if (match-beginning 1)
-             ;; we have found a block beginning
+             ;; We have found a block beginning.
              (progn
                (goto-char (match-beginning 1))
-               (if hs-hide-all-non-comment-function
-                   (funcall hs-hide-all-non-comment-function)
-                 (hs-hide-block-at-point t)))
+	       (unless (if hs-hide-all-non-comment-function
+			   (funcall hs-hide-all-non-comment-function)
+			 (hs-hide-block-at-point t))
+		 ;; Go to end of matched data to prevent from getting stuck
+		 ;; with an endless loop.
+		 (goto-char (match-end 0))))

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no