Re: [AUCTeX-devel] Re: Changes in font locking

Tuesday, 13 March 2007

        On 3/13/07, David Kastrup <dak(a)gnu.org&gt; wrote:
...

 "Robert Pluim" <rpluim(a)gmail.com&gt; writes:

 > Patch to paper over this problem follows.  I suspect that
 'copy-syntax-table'
 > is actually at fault, but with this at least the test in
 http://mid.gmane.org/
 > cp7323$qm7$1%40sea.gmane.org works.
 >

 The idea of the copy probably was to have things like
 `modify-syntax-entry' in `body' not have a lasting effect.  I doubt
 that this is actually the intent of the macro according to its doc
 string: actually, it is quite likely that people would set up a syntax
 table with

 (with-syntax-table some-table
   (modify-syntax-entry ?x ?y)
   ...
 ) 

I agree that people would use it like that, although the test case doesn't
seem to be modifying the syntax-table that I can see.

The corresponding macro in Emacs, if I am not mistaken, is the
...
 following:

 (defmacro with-syntax-table (table &rest body)
   "Evaluate BODY with syntax table of current buffer set to TABLE.
 The syntax table of the current buffer is saved, BODY is evaluated, and
 the
 saved table is restored, even in case of an abnormal exit.
 Value is what BODY returns."
   (declare (debug t))
   (let ((old-table (make-symbol "table"))
         (old-buffer (make-symbol "buffer")))
     `(let ((,old-table (syntax-table))
            (,old-buffer (current-buffer)))
        (unwind-protect
            (progn
              (set-syntax-table ,table)
              ,＠body)
          (save-current-buffer
            (set-buffer ,old-buffer)
            (set-syntax-table ,old-table)))))) 

This is identical to the 21.5 version, modulo the 'copy-syntax-table'.

I think it likely that copying the syntax table is a mistake, given
...
 what people would expect from the doc string of the macro and given
 that there is a non-trivial amount of code around which relies on the
 non-copying behavior. 

Perhaps, although I don't see how the copy-syntax-table could cause a
problem when not modifying the syntax-table, unless it was not copying
correctly.

So I don't think your patch is "papering over the problem", but rather
...
 fixing it.  I think it likely that `copy-syntax-table' works as
 intended, and that it is just misused here. 

Well, to answer that properly I need to understand the xemacs implementation
of syntax-tables, and I don't yet ;-)

Robert

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