--- /dev/null
+#include <ccan/typesafe_cb/typesafe_cb.h>
+#include <stdlib.h>
+
+/* NULL args for callback function should be OK for _exact and _def. */
+
+static void _register_callback(void (*cb)(void *arg), void *arg)
+{
+}
+
+#define register_callback_def(cb, arg) \
+ _register_callback(typesafe_cb_def(void, (cb), (arg)), (arg))
+
+#define register_callback_exact(cb, arg) \
+ _register_callback(typesafe_cb_exact(void, (cb), (arg)), (arg))
+
+int main(int argc, char *argv[])
+{
+ register_callback_def(NULL, "hello world");
+ register_callback_exact(NULL, "hello world");
+ return 0;
+}