From: Alan Mackenzie <acm@muc.de>
To: npostavs@users.sourceforge.net
Cc: 24870@debbugs.gnu.org, Matt Armstrong <marmstrong@google.com>
Subject: bug#24870: 26.0.50; parse-partial-sexp ignores comment-end
Date: Wed, 14 Dec 2016 21:58:34 +0000 [thread overview]
Message-ID: <20161214215834.GB3881@acm.fritz.box> (raw)
In-Reply-To: <87eg1bcg0y.fsf@users.sourceforge.net>
Hello again, Noam.
On Tue, Dec 13, 2016 at 11:04:45PM -0500, npostavs@users.sourceforge.net wrote:
> npostavs@users.sourceforge.net writes:
> > I have tracked the issue down to scan_sexps_forward in syntax.c
> Applying this change which reverts part of [1] seems to fix the issue:
> --- i/src/syntax.c
> +++ w/src/syntax.c
> @@ -3192,7 +3192,11 @@ scan_sexps_forward (struct lisp_parse_state *state,
> while (from < end)
> {
> - if (SYNTAX_FLAGS_COMSTART_FIRST (prev_from_syntax)
> + INC_FROM;
> + code = prev_from_syntax & 0xff;
> +
> + if (from < end
> + && SYNTAX_FLAGS_COMSTART_FIRST (prev_from_syntax)
> && (c1 = FETCH_CHAR (from_byte),
> syntax = SYNTAX_WITH_FLAGS (c1),
> SYNTAX_FLAGS_COMSTART_SECOND (syntax)))
> @@ -3213,8 +3217,6 @@ scan_sexps_forward (struct lisp_parse_state *state,
> }
> else
> {
> - INC_FROM;
> - code = prev_from_syntax & 0xff;
> if (code == Scomment_fence)
> {
> /* Record the comment style we have entered so that only
Alas, that patch won't do. The very first thing that must be done in the
loop is to check for a two-character comment delimiter, of which the
first character might have been recorded in OLDSTATE element 9 rather
than having been scanned by scan_sexps_forward on the previous loop
iteration.
My analysis of what's happening in the bug recipe you posted one or two
posts previously, here in scan_sexps_forward is as follows. (In that
recipe, "{-C-}\nX" was parse-partial-sexp'd over, and the syntax table
had been set to recognise "{-" and "-}" as matching comment delimiters.)
(i) On the first iteration of the main loop, the "{" is read. It is
recognised as an opening paren, and causes the "current paren depth" to
be incremented.
(ii) On the second iteration of the loop, the "-" is read. The function
now recognises the two-character comment opener, and proceeds to read
the innards of the comment together with its closing delimiter (the
"-}").
(iii) On the third and fourth iterations, the function reads "\n" and
"X". It then terminates, having reached point-max.
(iv) The paren depth counter remains at 1.
What is new here is characters with paren syntax also being components of
2-char comment delimiters. I recently fixed a similar problem when
characters with word syntax were also flagged as 2-char comment delimiter
parts. I think a similar patch at case label Sopen: (Line ~3322), which
would peek ahead at the next character to check for "{-" before
recognising the "{" as an open paren would be the best fix.
Do you want to make this fix, or should I do it? If you want to do it,
I'm willing (indeed, eager) to review it for you.
[ .... ]
--
Alan Mackenzie (Nuremberg, Germany).
next prev parent reply other threads:[~2016-12-14 21:58 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-03 19:38 bug#24870: 26.0.50; parse-partial-sexp ignores comment-end Andreas Röhler
2016-11-30 9:10 ` Matt Armstrong
2016-11-30 12:37 ` Andreas Röhler
2016-11-30 23:02 ` Matt Armstrong
2016-12-01 1:17 ` npostavs
2016-12-01 8:24 ` Andreas Röhler
2016-12-14 3:00 ` npostavs
2016-12-14 4:04 ` npostavs
2016-12-14 6:45 ` Andreas Röhler
2016-12-14 19:56 ` Alan Mackenzie
2016-12-15 8:18 ` Andreas Röhler
2016-12-15 16:01 ` Eli Zaretskii
2016-12-15 16:50 ` Alan Mackenzie
2016-12-15 17:59 ` Andreas Röhler
2016-12-14 21:58 ` Alan Mackenzie [this message]
2016-12-15 16:33 ` Noam Postavsky
2016-12-15 16:44 ` Alan Mackenzie
2016-12-18 5:39 ` npostavs
2016-12-29 11:14 ` Alan Mackenzie
2016-12-30 1:55 ` npostavs
2017-01-13 2:07 ` npostavs
2017-01-23 20:12 ` Alan Mackenzie
2017-01-24 0:30 ` npostavs
2016-12-01 8:33 ` Andreas Röhler
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20161214215834.GB3881@acm.fritz.box \
--to=acm@muc.de \
--cc=24870@debbugs.gnu.org \
--cc=marmstrong@google.com \
--cc=npostavs@users.sourceforge.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this external index
https://git.savannah.gnu.org/cgit/emacs.git
https://git.savannah.gnu.org/cgit/emacs/org-mode.git
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.