1 files changed, 7 insertions, 1 deletions

diff --git a/src/buffer.c b/src/buffer.c
index 62a3d66c8b7..77e8b6bb779 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -105,7 +105,7 @@ static char buffer_permanent_local_flags[MAX_PER_BUFFER_VARS];
 
 /* Number of per-buffer variables used.  */
 
-int last_per_buffer_idx;
+static int last_per_buffer_idx;
 
 static void call_overlay_mod_hooks (Lisp_Object list, Lisp_Object overlay,
                                     bool after, Lisp_Object arg1,
@@ -655,6 +655,12 @@ set_buffer_overlays_after (struct buffer *b, struct Lisp_Overlay *o)
   b->overlays_after = o;
 }
 
+bool
+valid_per_buffer_idx (int idx)
+{
+  return 0 <= idx && idx < last_per_buffer_idx;
+}
+
 /* Clone per-buffer values of buffer FROM.
 
    Buffer TO gets the same per-buffer values as FROM, with the