bug#30735: 25.3; slow comment c++-mode

[Noam Postavsky <npostavs@gmail.com>]

On Sun, Mar 11, 2018 at 4:15 PM, Nil Geisweiller
<ngeiswei@googlemail.com> wrote:

> Unfortunately, I couldn't apply the patch completely because I couldn't get
> my hand on the source code of 25.3.1, only 25.3.

25.3 is the same as 25.3.1, the ".1" just refers to the build number
(i.e., how many times you've built that version of Emacs).

That said, it seems that the patch is against emacs-26 or master, not
25.3. In particular, the first hunk:

@@ -4677,10 +4677,10 @@
           (t 'c)))            ; Assuming the range is valid.
     range))

-(defsubst c-determine-limit-get-base (start try-size)
+(defsubst c-determine-limit-get-base (start try-size &optional abs-limit)
   ;; Get a "safe place" approximately TRY-SIZE characters before START.
-  ;; This doesn't preserve point.
-  (let* ((pos (max (- start try-size) (point-min)))
+  ;; This defsubst doesn't preserve point.
+  (let* ((pos (max (- start try-size) (point-min) (or abs-limit 0)))
      (base (c-state-semi-safe-place pos))
      (s (save-restriction
           (widen)

In 25.3, the end context would look like this:

     (base (c-state-semi-safe-place pos))
     (s (parse-partial-sexp base pos)))
    (if (or (nth 4 s) (nth 3 s))    ; comment or string