bug#716: Bug in buffer-swap-text

[jasonr@f2s.com]

Quoting Stefan Monnier <monnier@iro.umontreal.ca>:

> Your analysis sounds right, thank you.  I'd suggest to use another
> r_alloc primitve, something like r_alloc_reset_variable, so you could do

I've adapted your suggestion so it does not remove the consistency check in
find_bloc (instead it does a non-checking find inline):

*** buffer.c.~1.575.~	2008-12-10 21:52:40.562500000 +0800
--- buffer.c	2008-12-24 09:12:15.536522600 +0800
***************
*** 2182,2187 ****
--- 2182,2191 ----
    return byte_pos;
  }

+ #ifdef REL_ALLOC
+ extern void r_alloc_reset_variable P_ ((PTR *));
+ #endif
+
  DEFUN ("buffer-swap-text", Fbuffer_swap_text, Sbuffer_swap_text,
         1, 1, 0,
         doc: /* Swap the text between current buffer and BUFFER.  */)
***************
*** 2223,2228 ****
--- 2227,2237 ----
    swapfield (own_text, struct buffer_text);
    eassert (current_buffer->text == &current_buffer->own_text);
    eassert (other_buffer->text == &other_buffer->own_text);
+ #ifdef REL_ALLOC
+   r_alloc_reset_variable ((PTR *) &current_buffer->own_text.beg);
+   r_alloc_reset_variable ((PTR *) &other_buffer->own_text.beg);
+ #endif
+
    swapfield (pt, EMACS_INT);
    swapfield (pt_byte, EMACS_INT);
    swapfield (begv, EMACS_INT);
*** ralloc.c.~1.69.~	2008-11-23 22:34:01.250000000 +0800
--- ralloc.c	2008-12-24 09:12:35.643967100 +0800
***************
*** 1223,1228 ****
--- 1223,1254 ----

  #endif /* DEBUG */

+ /* Update the internal record of which variable points to some data.
+    Used by buffer-swap-text in Emacs to restore consistency after it
+    swaps the buffer text between two buffer objects.  */
+ void
+ r_alloc_reset_variable (ptr)
+      POINTER *ptr;
+ {
+   bloc_ptr bloc = first_bloc;
+
+   /* Find the bloc that corresponds to the data pointed to by pointer.
+      find_bloc cannot be used, as it has internal consistency checks
+      which fail when the variable needs reseting.  */
+   while (bloc != NIL_BLOC)
+     {
+       if (bloc->data == *ptr)
+ 	break;
+
+       bloc = bloc->next;
+     }
+
+   if (bloc == NIL_BLOC)
+     abort ();
+
+   /* Update variable to point to the new location.  */
+   bloc->variable = ptr;
+ }

  \f
  /***********************************************************************