* lisp.h (XCONS, XSTRING, XSYMBOL, XFLOAT, XPROCESS, XWINDOW, XSUBR, XBUFFER):

Verify correct object type before returning pointer, using eassert.
* frame.h (XFRAME): Likewise.

* buffer.c (Frename_buffer, Fset_buffer_multibyte,
swap_out_buffer_local_variables, Fmove_overlay): Don't apply XSYMBOL, XBUFFER,
etc, to values that may be nil or of the wrong type.
* data.c (set_internal): Likewise.
* dispextern.h (WINDOW_WANTS_MODELINE_P, WINDOW_WANTS_HEADER_LINE_P): Likewise.
* fileio.c (auto_save_1): Likewise.
* insdel.c (check_markers): Likewise.
* marker.c (buf_charpos_to_bytepos, unchain_marker): Likewise.
* undo.c (record_insert): Likewise.
* vmsproc.c (child_sig): Likewise.
* window.c (unshow_buffer, window_loop): Likewise.
* xterm.c (x_erase_phys_cursor): Likewise.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/data.c b/src/data.c
index f736f7f6c81..c267c5540f0 100644
--- a/src/data.c
+++ b/src/data.c
@@ -1012,7 +1012,8 @@ set_internal (symbol, newval, buf, bindflag)
          isn't the right one, or if it's a Lisp_Buffer_Local_Value and
          the default binding is loaded, the loaded binding may be the
          wrong one.  */
-      if (buf != XBUFFER (XBUFFER_LOCAL_VALUE (valcontents)->buffer)
+      if (!BUFFERP (XBUFFER_LOCAL_VALUE (valcontents)->buffer)
+          || buf != XBUFFER (XBUFFER_LOCAL_VALUE (valcontents)->buffer)
           || (XBUFFER_LOCAL_VALUE (valcontents)->check_frame
               && !EQ (selected_frame, XBUFFER_LOCAL_VALUE (valcontents)->frame))
           || (BUFFER_LOCAL_VALUEP (valcontents)