🚀 go-pugleaf

There's a well known bug (to VM users at least) in emacs 18.5[5-7] and 19,
which goes something like this: you are in a mail buffer, and reply to the
current message.  You are now in a sendmail buffer; if you switch back to the
mail buffer, it is narrowed to the wrong place, beginning somewhere near the
beginning of the buffer (often in the middle of a line).

This is due to a subtle bug in save_restriction_restore() in editfns.c:
This function does this as its last action:

  /* If point is outside the new visible range, move it inside. */
  SET_BUF_PT (buf, in_accessible_range (BUF_PT (buf)));

But the problem is, the function in_accessible_range() looks at the narrowing
region of current_buffer instead of the buffer whose restriction is being
restored!  This means that if the current buffer is not the same on exit from
save-restriction as on the way in, all bets are off.

I believe the correct fix is for in_accessible_range() to take an additional
argument, the buffer in question.  There are only two calls to it.

static int
in_accessible_range (buf, loc)
     struct buffer *buf;
     int loc;
{
  if (loc < BUF_BEGV (buf))
    return BUF_BEGV (buf);

  if (loc > BUF_ZV (buf))
    return BUF_ZV (buf);

  return loc;
}

Note that this bug could cause emacs to crash, because it can allow point to
exceed point-max.

	-- Jamie