Remove unportable assumption about struct layout (Bug#8884).

* buffer.c (clone_per_buffer_values): Don't assume that
sizeof (struct buffer) is a multiple of sizeof (Lisp_Object).
This isn't true in general, and it's particularly not true
if Emacs is configured with --with-wide-int.
* buffer.h (FIRST_FIELD_PER_BUFFER, LAST_FIELD_PER_BUFFER):
New macros, used in the buffer.c change.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/buffer.c b/src/buffer.c
index 2339416eb36..6c7c2ec0d86 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -471,8 +471,8 @@ clone_per_buffer_values (struct buffer *from, struct buffer *to)
 
   /* buffer-local Lisp variables start at `undo_list',
      tho only the ones from `name' on are GC'd normally.  */
-  for (offset = PER_BUFFER_VAR_OFFSET (undo_list);
-       offset < sizeof *to;
+  for (offset = PER_BUFFER_VAR_OFFSET (FIRST_FIELD_PER_BUFFER);
+       offset <= PER_BUFFER_VAR_OFFSET (LAST_FIELD_PER_BUFFER);
        offset += sizeof (Lisp_Object))
     {
       Lisp_Object obj;