bug#6490: 24.0.50; src/lread.c: old style backquote bug?

[Tetsurou Okazaki]

At Wed, 23 Jun 2010 00:23:15 +0200,
Stefan Monnier wrote:
> 
> > Attached patch for Emacs fixes this error.
> 
> I'm glad the patch fixes things for you, since this patch indeed looks
> perfectly harmless, but I'm a bit puzzled because it doesn't just look
> harmless: it looks to me like the patch does change anything to the way
> the code works.  So could you explain to me how&why the patch fixes
> the problem?  I'm probably just overlooking some "obvious" detail,

The changes committed in rev:100605 reassigns the next character to the 
variable `c'.
When the next character is SPC (32, #o40, #x20), old style backquote is 
detected.

  if (first_in_list && (c = READCHAR, UNREAD (c), c == ' '))
    {
      Vold_style_backquotes = Qt;
      goto default_label;
    }

But backquote handling is skipped because `c' is SPC.

    default_label:
      if (c <= 040) goto retry;

      ... old style backquote handling ...

My patch avoids reassignment of `c' not to skip old style backquote handling.

To keep more compatibility with released Emacs, it is preferable to
allow a character such as \r or \n after the old style backquote.

src-lread-old-backquote2.diff
Description: Text document