Re: enable-local-variables

[Eric Twietmeyer]

Eric Twietmeyer wrote:
> Ralf Angeli wrote:
> > * Eric Twietmeyer (2007-01-01) writes:
> >
> > > Ralf Angeli wrote:
> > >>
> > >> I'd also be interested in knowing which package or code uses the
> > >> variable before giving you a means to shoot yourself in the foot.
> > >
> > > Here is what the text looks like at the bottom of a typical C++ file I
> > > edit:
> > >
> > > /*
> > > Local Variables:
> > > typedefs:("boost" "noncopyable" "shared_ptr" "size_t" "std" "string"
> > > "tCursorIPtr" "tDestroyI" "tEndian" "tStreamI" "tStreamIPtr" "wchar_t"
> > > "wstring")
> > > End:
> > > */
> > >
> > > So the value of "typedefs" is just a list of quoted symbols.
> >
> > Then
> > (put 'typedefs 'safe-local-variable 'listp)
> > should work.
> >
> > > This list
> > > changes from file to file.  It is used by the syntax highlighting code
> > > in C/C++ mode.
> >
> > I couldn't find anything regarding "typedefs" in Emacs' sources.
> > Which mode is this and who is maintaining it?  Could you inform those
> > people that they should mark the variable as safe (in case it really
> > is) in their mode?
> >
> > > The question therefore remains, what can I do so that all such values
> > > of typedefs are always considered "safe".  I'm not certain why this is
> > > being flagged in the first place, as the documentation I saw about
> > > ricky variables indicates that their name should end in some special
> > > characters, and my typedefs do not end in such characters.  So I have
> > > been confused from the start why this is marked as risky in the first
> > > place and therefore why I am being queried about it each time I open
> > > the file.
> >
> > All unknown variables are considered risky in CVS Emacs.
> >
> > --
> > Ralf
>
> Ok, now I understand the confusion.  I didn't realize that my extended
> .emacs had code I took long ago from someone that added this "feature",
> I thought it was part of the standard font-lock stuff.  Here is the
> relevant code:
>
> -------------------------------------------------------------------------------------------------------
>
> ;; Need to have a new variable to hold the typedefs for this buffer.
> (defvar typedefs nil "Typedefs in this buffer.")
> (make-variable-buffer-local 'typedefs)
>
> ;; Add the word at the current point to the list of typedefs.  Insert
> stuff
> ;; at bottom of file to save the information.
> (defun make-word-into-typedef ()
>   "Take the word at the current point and make font-lock realize it's a
> type.
> The word will be added to the local variable list at the end of the
> file."
>   (interactive)
>   (let ((this-type (current-word)))
>     (if (member this-type typedefs)
>         (message "%s is already a type" this-type)
>       ;; Sort for niceness
>       (setq typedefs (sort (cons this-type typedefs) 'string<))
>       ;; Find the typedefs line if we have one, and replace it
>       (save-excursion
>         (goto-char (point-min))
>         (if (re-search-forward "^typedefs:" nil 1)
>             (progn
>               (beginning-of-line)
>               (push-mark nil t t)
>               (end-of-line)
>               (delete-region (mark) (point)))
>           (progn
>             ;; Break up the string so Emacs doesn't get confused when
>             ;; reading this file
>             (insert "/*\nLocal ")
>             (insert "Variables:\n\nEnd:\n*/\n")
>             (forward-line -3)))
>         (insert "typedefs:")
>         (insert (prin1-to-string typedefs)))
>
>       (hack-local-variables)
>       (add-extra-type (make-regexp typedefs))
>
>       ;; Reset font-lock
>       (font-lock-mode 0)
>       (font-lock-mode 1))))
>
> ;; Called to add the types when the hook executes.
> (defun add-extra-type (new_type)
>   (setq c-font-lock-extra-types
>         (cons new_type c++-font-lock-extra-types))
>   (setq c++-font-lock-extra-types c-font-lock-extra-types)
>   )
>
> Part of my c-mode-hook:
>
>   (if typedefs (add-extra-type (make-regexp typedefs)))
>
> ----------------------------------------------------------------------------------
>
> So what do I need to do to make this typedef variable always safe?  Or
> where do I look in the docs to learn how to do this?
>
> Thanks again for your help!
>
> -Eric Twietmeyer

Well, looking through files.el where all of this stuff is used, it
looks like perhaps this is what I needed to do:

(defvar typedefs nil "Typedefs in this buffer.")
(make-variable-buffer-local 'typedefs)
(put 'typedefs 'safe-local-variable '(lambda (x) t))

It looked like the safe-local-variable property is what controls
things.

Please let me know if this is the correct way, thanks!

-Eric Twietmeyer