[debbugs-tracker] bug#31551: closed (27.0.50; emacs hangs in hexl-mode on modula2 files)

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Your message dated Thu, 21 Jun 2018 23:31:55 -0400
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and subject line Re: bug#31551: 27.0.50; emacs hangs in hexl-mode on modula2 
files
has caused the debbugs.gnu.org bug report #31551,
regarding 27.0.50; emacs hangs in hexl-mode on modula2 files
to be marked as done.

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31551: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=31551
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--- Begin Message --- Subject: 27.0.50; emacs hangs in hexl-mode on modula2 files Date: Tue, 22 May 2018 15:24:09 +0200

Hi,

I run into an issue lately while trying to use the hexl-mode with
a modula2 file that I found and emacs starts to hang after the
hexl-mode starts. I tested it on emacs 24.5, 25.2 and master.

To reproduce the issue you can use :
echo "abcd" > test.MOD
emacs -Q --eval '(show-paren-mode 1)' test.MOD
M-x hexl-mode

--> emacs hangs and use 100% cpu. It only happen on the first character so
we can run out the hang with multiple C-g + an arrow key.

I dig into the issue and it appears that the was because of the
show-paren-mode and the fact that the ":" character have meaning in
modula-2-mode. Emacs is stuck in the loop of the
m2-smie-refine-colon function because after the "00000000" that start
the hexl buffer there is no more sexp to parse so the tok variable is
empty but the (forward-sexp -1) call does not fail.

I fixed that myself by stopping the loop if the point is at the beginning
of the buffer. Not sure if it correct but here is the diff :

diff --git a/lisp/progmodes/modula2.el b/lisp/progmodes/modula2.el
index 582e495..30c8c46 100644
--- a/lisp/progmodes/modula2.el
+++ b/lisp/progmodes/modula2.el
@@ -203,6 +203,7 @@ m2-smie-refine-colon
     (while (not res)
       (let ((tok (smie-default-backward-token)))
         (cond
+         ((= (point) (point-min)) (setq res ":"))
          ((zerop (length tok))
           (let ((forward-sexp-function nil))

             (condition-case nil

I am not really into modula2 files but this bug was quite surprising.

best regards,

Alexandre

--- End Message ---

> --- Begin Message ---
>
>
>
> Subject: 
>
> Re: bug#31551: 27.0.50; emacs hangs in hexl-mode on modula2 files
>
>
>
>
> Date: 
>
> Thu, 21 Jun 2018 23:31:55 -0400
>
>
>
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> User-agent: 
>
> Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux)
>
>
>
>
> > idea.  So I plan on cleaning it up (and adding an entry in NEWS, not
> > sure if it deserves an entry in the lispref) and installing it
> > into master.
>
> Installed,
>
>
>         Stefan
>
>
> --- End Message ---