json_object_private: Use unsigned 32-bit integer type for refcount

json_object.c

@@ -169,6 +169,9 @@ extern struct json_object* json_object_get(struct json_object *jso)
 {
 	if (!jso) return jso;
 
+	// Don't overflow the refcounter.
+	assert(jso->_ref_count < UINT_FAST32_MAX);
+
 #if defined(HAVE_ATOMIC_BUILTINS) && defined(ENABLE_THREADING)
 	__sync_add_and_fetch(&jso->_ref_count, 1);
 #else

json_object_private.h

@@ -29,7 +29,7 @@ struct json_object
   enum json_type o_type;
   json_object_private_delete_fn *_delete;
   json_object_to_json_string_fn *_to_json_string;
-  int _ref_count;
+  uint_fast32_t _ref_count;
   struct printbuf *_pb;
   union data {
     json_bool c_boolean;