Package: emacs;
Reported by: Eli Zaretskii <eliz <at> gnu.org>
Date: Tue, 14 Jul 2015 14:59:02 UTC
Severity: normal
Done: Eli Zaretskii <eliz <at> gnu.org>
Bug is archived. No further changes may be made.
Message #11 received at submit <at> debbugs.gnu.org (full text, mbox):
From: Eli Zaretskii <eliz <at> gnu.org> To: Juri Linkov <juri <at> jurta.org> Cc: ludo <at> gnu.org, bug-gnu-emacs <at> gnu.org Subject: Re: Info reader fails to follow xrefs to anchors Date: Wed, 15 Jul 2015 18:09:56 +0300
> From: Juri Linkov <juri <at> jurta.org>
> Cc: ludo <at> gnu.org (Ludovic Courtès),
> bug-gnu-emacs <at> gnu.org
> Date: Wed, 15 Jul 2015 02:16:32 +0300
>
> I'm attaching here all the files that I used to fix bug#14125,
> so you could compare the output of different makeinfo versions
> and see the problem. The command line used to translate
> Texinfo files was: makeinfo --split-size=2000 test.texi
Thanks.
I see the problem now. It only happened in makeinfo 5.0 and 5.1, and
is fixed since 5.2. Furthermore, it only rears its ugly head if the
Texinfo source has an @ifnottex block before the Top node; any other
blurbs usually put there, like @copying, @direntry, etc. -- don't
trigger the problem even in those 2 versions of makeinfo. Moreover,
when this problem happens, it only affects the 1st subfile; the rest
have their offsets set correctly. So it's a pretty rare combination
of conditions.
Therefore, I think we should fix the anchor use case by making the
value returned from Info-read-subfile as accurate as possible, and
then cater to the problematic output of makeinfo 5.0 and 5.1 by
attempting another search for a node with a larger slop value.
So any objections to the patch below? It introduces a new
infrastructure, and then uses it to get the file byte offset
corresponding to the first node on a subfile.
--- lisp/international/mule-util.el~0 2015-06-21 06:45:33.000000000 +0300
+++ lisp/international/mule-util.el 2015-07-15 18:00:57.053036400 +0300
@@ -412,6 +412,79 @@
(decode-coding-region (point-min)
(min (point-max) (+ pm byte))
coding-system t))))))))))))
+;;;###autoload
+(defun bufferpos-to-filepos (position &optional quality coding-system)
+ "Try to return the file byte corresponding to a particular buffer POSITION.
+Value is the file position given as a (0-based) byte count.
+The function presumes the file is encoded with CODING-SYSTEM, which defaults
+to `buffer-file-coding-system'.
+QUALITY can be:
+ `approximate', in which case we may cut some corners to avoid
+ excessive work.
+ `exact', in which case we may end up re-(en/de)coding a large
+ part of the file/buffer.
+ nil, in which case we may return nil rather than an approximation."
+ (unless coding-system (setq coding-system buffer-file-coding-system))
+ (let* ((eol (coding-system-eol-type coding-system))
+ (lineno (if (= eol 1) (1- (line-number-at-pos position)) 0))
+ (type (coding-system-type coding-system))
+ (base (coding-system-base coding-system))
+ byte)
+ (and (eq type 'utf-8)
+ ;; Any post-read/pre-write conversions mean it's not really UTF-8.
+ (not (null (coding-system-get coding-system :post-read-conversion)))
+ (setq type 'not-utf-8))
+ (and (memq type '(charset raw-text undecided))
+ ;; The following are all of type 'charset', but they are
+ ;; actually variable-width encodings.
+ (not (memq base '(chinese-gbk chinese-gb18030 euc-tw euc-jis-2004
+ korean-iso-8bit chinese-iso-8bit
+ japanese-iso-8bit chinese-big5-hkscs
+ japanese-cp932 korean-cp949)))
+ (setq type 'single-byte))
+ (pcase type
+ (`utf-8
+ (setq byte (position-bytes position))
+ (when (null byte)
+ (if (<= position 0)
+ (setq byte 1)
+ (setq byte (position-bytes (point-max)))))
+ (setq byte (1- byte))
+ (+ byte
+ ;; Account for BOM, if any.
+ (if (coding-system-get coding-system :bom) 3 0)
+ ;; Account for CR in CRLF pairs.
+ lineno))
+ (`single-byte
+ (+ position -1 lineno))
+ ((and `utf-16
+ ;; FIXME: For utf-16, we could use the same approach as used for
+ ;; dos EOLs (counting the number of non-BMP chars instead of the
+ ;; number of lines).
+ (guard (not (eq quality 'exact))))
+ ;; In approximate mode, assume all characters are within the
+ ;; BMP, i.e. each one takes up 2 bytes.
+ (+ (* (1- position) 2)
+ ;; Account for BOM, if any.
+ (if (coding-system-get coding-system :bom) 2 0)
+ ;; Account for CR in CRLF pairs.
+ lineno))
+ (_
+ (pcase quality
+ (`approximate (+ (position-bytes position) -1 lineno))
+ (`exact
+ ;; Rather than assume that the file exists and still holds the right
+ ;; data, we reconstruct its relevant portion.
+ (let ((buf (current-buffer)))
+ (with-temp-buffer
+ (set-buffer-multibyte nil)
+ (let ((tmp-buf (current-buffer)))
+ (with-current-buffer buf
+ (save-restriction
+ (widen)
+ (encode-coding-region (point-min) (min (point-max) position)
+ coding-system tmp-buf)))
+ (1- (point-max)))))))))))
(provide 'mule-util)
--- lisp/info.el~0 2015-06-16 10:34:22.000000000 +0300
+++ lisp/info.el 2015-07-15 18:08:58.585385400 +0300
@@ -1217,6 +1217,18 @@
(goto-char pos)
(throw 'foo t)))
+ ;; If the Texinfo source had an @ifnottex block of text
+ ;; before the Top node, makeinfo 5.0 and 5.1 mistakenly
+ ;; omitted that block's size from the starting position
+ ;; of the 1st subfile, which makes GUESSPOS overshoot
+ ;; the correct position by the length of that text. So
+ ;; we try again with a larger slop.
+ (goto-char (max (point-min) (- guesspos 10000)))
+ (let ((pos (Info-find-node-in-buffer regexp strict-case)))
+ (when pos
+ (goto-char pos)
+ (throw 'foo t)))
+
(when (string-match "\\([^.]+\\)\\." nodename)
(let (Info-point-loc)
(Info-find-node-2
@@ -1553,10 +1565,13 @@
(if (looking-at "\^_")
(forward-char 1)
(search-forward "\n\^_"))
- ;; Don't add the length of the skipped summary segment to
- ;; the value returned to `Info-find-node-2'. (Bug#14125)
(if (numberp nodepos)
- (- nodepos lastfilepos))))
+ ;; Our caller ('Info-find-node-2') wants the (zero-based) byte
+ ;; offset corresponding to NODEPOS, from the beginning of the
+ ;; subfile. This is especially important if NODEPOS is for an
+ ;; anchor reference, because for those the position is all we
+ ;; have.
+ (+ (- nodepos lastfilepos) (bufferpos-to-filepos (point) 'exact)))))
(defun Info-unescape-quotes (value)
"Unescape double quotes and backslashes in VALUE."
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