1 files changed, 9 insertions, 7 deletions

diff --git a/src/buffer.h b/src/buffer.h
index dc1d62beb00..4643e0d9d0e 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -309,8 +309,10 @@ while (0)
 
 /* Maximum number of bytes in a buffer.
    A buffer cannot contain more bytes than a 1-origin fixnum can represent,
-   nor can it be so large that C pointer arithmetic stops working.  */
-#define BUF_BYTES_MAX min (MOST_POSITIVE_FIXNUM - 1, min (SIZE_MAX, PTRDIFF_MAX))
+   nor can it be so large that C pointer arithmetic stops working.
+   The ptrdiff_t cast ensures that this is signed, not unsigned.  */
+#define BUF_BYTES_MAX \
+  (ptrdiff_t) min (MOST_POSITIVE_FIXNUM - 1, min (SIZE_MAX, PTRDIFF_MAX))
 
 /* Return the address of byte position N in current buffer.  */
 
@@ -885,10 +887,10 @@ extern struct buffer buffer_local_symbols;
 extern void delete_all_overlays (struct buffer *);
 extern void reset_buffer (struct buffer *);
 extern void evaporate_overlays (EMACS_INT);
-extern int overlays_at (EMACS_INT pos, int extend, Lisp_Object **vec_ptr,
-                        int *len_ptr, EMACS_INT *next_ptr,
-                        EMACS_INT *prev_ptr, int change_req);
-extern int sort_overlays (Lisp_Object *, int, struct window *);
+extern ptrdiff_t overlays_at (EMACS_INT pos, int extend, Lisp_Object **vec_ptr,
+                              ptrdiff_t *len_ptr, EMACS_INT *next_ptr,
+                              EMACS_INT *prev_ptr, int change_req);
+extern ptrdiff_t sort_overlays (Lisp_Object *, ptrdiff_t, struct window *);
 extern void recenter_overlay_lists (struct buffer *, EMACS_INT);
 extern EMACS_INT overlay_strings (EMACS_INT, struct window *, unsigned char **);
 extern void validate_region (Lisp_Object *, Lisp_Object *);
@@ -906,7 +908,7 @@ extern void mmap_set_vars (int);
 
 #define GET_OVERLAYS_AT(posn, overlays, noverlays, nextp, chrq)         \
   do {                                                                  \
-    int maxlen = 40;                                                    \
+    ptrdiff_t maxlen = 40;                                                      \
     overlays = (Lisp_Object *) alloca (maxlen * sizeof (Lisp_Object));  \
     noverlays = overlays_at (posn, 0, &overlays, &maxlen,               \
                              nextp, NULL, chrq);                                \