[Emacs-ada-mode] FW: ada-mode ada-initialize-properties has an error with read-only files

[WAROQUIERS Philippe]

Forward of a feedback received on bug-gnu-emacs.


>-----Original Message-----
>From: martin rudalics [mailto:rudalics at gmx.at] 
>Sent: Sunday 12 August 2007 11:20
>To: WAROQUIERS Philippe
>Cc: bug-gnu-emacs at gnu.org
>Subject: Re: ada-mode ada-initialize-properties has an error 
>with read-only files
>
>
> > 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 ?
>
>Thanks for finding and investigating this.  Indeed ada-mode should use
>such a macro here.  Also because `ada-initialize-properties' and
>`ada-after-change-function' may create undo entries which are 
>completely
>useless.  However, I'd strongly favour a canonical macro in subr.el
>which could be used by other programming modes as well: antlr-mode,
>Delphi, cperl-mode, or c-mode which has theses lines in cc-defs.el
>
>;; The following is essentially `save-buffer-state' from lazy-lock.el.
>;; It ought to be a standard macro.
>(defmacro c-save-buffer-state (varlist &rest body)
>   ....
>
>Something like the following:
>
>(eval-when-compile
>   (require 'cl)
>   (defmacro with-buffer-state-unmodified (varlist &rest body)
>     "Bind variables according to VARLIST and eval BODY 
>restoring buffer state.
>Evaluating BODY does not alter the current buffer's modified
>state and undo list.  In addition this macro permits BODY to
>modify read-only text and inhibits running any hooks related to
>buffer changes or character properties.
>
>Avoid leaving the current buffer in BODY since this may lead to
>unpredictable results."
>     (declare (indent 1) (debug let))
>     (let ((modified (make-symbol "modified")))
>       `(let* ,(append varlist
>		      `((,modified (buffer-modified-p))
>			(buffer-undo-list t)
>			(inhibit-read-only t)
>			(inhibit-point-motion-hooks t)
>			(inhibit-modification-hooks t)
>			deactivate-mark
>			buffer-file-name
>			buffer-file-truename))
>	 (progn
>	   , at body)
>	 (unless ,modified
>	   (restore-buffer-modified-p nil)))))
>
>
____

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