ada-mode ada-initialize-properties has an error with read-only files

[Philippe Waroquiers]

We have encountered a small problem with the ada-mode and emacs 22.
When an Ada file is visited in emacs (in this case, I find this file
with M-x find-tag) and this Ada file is a read-only file,
we see an error message appearing in the mini-buffer/*Messages*:
File mode specification error: (buffer-read-only #<buffer flight.adb>)

After investigation, we see that this error message is produced 
by ada-initialize-properties.

To see what is going wrong, I have added various calls to (message) inside
ada-initialize-properties (see modified code below).

We get the messages "1", "2", "2.1" but not "3" .. "6"
=> so this looks to be the indication of a real problem 
as ada-initialize-properties does not finish its work.
(NB: I tested with emacs 21 the same "message" modifications. With emacs 21,
ada-initialize-properties properly does the loops. E.g. it gives
multiple messages "2.1", and then gives the messages "3" .. "6".

The consequences of this problem are not clear to me. I suspect I see
not much consequences because font-lock-mode is also enabled, and
this may "repair" the properties. 
I however highly suspect that in case font-lock-mode is not active,
that ada-mode has a bug.

I suspect that one way or another, in emacs 21, ada-initialize-properties
was called in a context where the buffer could be temporarily modified,
while with emacs 22, this is not the case anymore.
I see that ada-initialize-properties is doing things similar to font-lock.
font-lock has defined a macro save-buffer-state to save/set/restore buffer 
state when
setting properties. A.o., it sets and then restores inhibit-read-only
and other things. Maybe ada-mode should use this macro or a similar logic ?


(defun ada-initialize-properties ()
  "Initialize some special text properties in the whole buffer.
In particular, character constants are said to be strings, #...# are treated
as numbers instead of gnatprep comments."
  (message "1")
  (save-excursion
    (save-restriction
      (widen)
      (goto-char (point-min))
      (message "2")
      (while (re-search-forward "'.'" nil t)
        (progn
          (message "2.1")
          (add-text-properties (match-beginning 0) (match-end 0)
                               '(syntax-table ("'" . ?\")))))
      (goto-char (point-min))
      (message "3")
      (while (re-search-forward "^[ \t]*#" nil t)
        (add-text-properties (match-beginning 0) (match-end 0)
                             '(syntax-table (11 . 10))))
      (message "4")
      (set-buffer-modified-p nil)
      (message "5")

      ;;  Setting this only if font-lock is not set won't work
      ;;  if the user activates or deactivates font-lock-mode,
      ;;  but will make things faster most of the time
      (add-hook 'after-change-functions 'ada-after-change-function nil t)
      (message "6")
      )))


In GNU Emacs 22.1.1 (hppa1.1-hp-hpux11.11, Motif Version 2.1.0)
 of 2007-08-04 on bobcat
Windowing system distributor `Hewlett-Packard Company', version 11.0.600000
configured using `configure  'hppa1.1-hp-hpux11.11' 
'--prefix=/cm/ot/TOOL/GNU!12.43/build_G!67.IP.11/generated' 
'--exec-prefix=/cm/ot/TOOL/GNU!12.43/build_G!67.IP.11/generated/libexec/emacs-22.1'
 '--mandir=/cm/ot/TOOL/GNU!12.43/build_G!67.IP.11/generated/man' 
'--with-gcc=no' '--with-xpm' '--with-x11r6' '--with-x-toolkit=motif' 
'--x-libraries=/usr/lib/X11R6:/usr/contrib/X11R6/lib' 
'build_alias=hppa1.1-hp-hpux11.11' 'host_alias=hppa1.1-hp-hpux11.11' 
'target_alias=hppa1.1-hp-hpux11.11' 'CFLAGS=-g -Ae +O0 +DA1.1' 'LDFLAGS= 
-L/cm/ot/TOOL/GNU!12.43/build_G!67.IP.11/generated/work/emacs-22.1/xpm-3.4k/lib'
 
'CPPFLAGS=-I/cm/ot/TOOL/GNU!12.43/build_G!67.IP.11/generated/work/emacs-22.1/xpm-3.4k
 ''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: C
  locale-coding-system: nil
  default-enable-multibyte-characters: nil


-- 
Philippe WAROQUIERS                  Eurocontrol - Central Flow Management Unit
philippe.waroquiers@eurocontrol.int  Rue de la fusee, 96
Tel: +32 2 729 97 35                 1130 Brussels
Fax: +32 2 729 90 22                 Belgium
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