--- /dev/null
+#include <ccan/typesafe_cb/typesafe_cb.h>
+
+void _set_some_value(void *val);
+
+void _set_some_value(void *val)
+{
+}
+
+#define set_some_value(expr) \
+ _set_some_value(typesafe_cb_cast(void *, unsigned long, (expr)))
+
+int main(int argc, char *argv[])
+{
+#ifdef FAIL
+ int x = 0;
+ set_some_value(x);
+#if !HAVE_TYPEOF||!HAVE_CAST_TO_UNION
+#error "Unfortunately we don't fail if typesafe_cb_cast is a noop."
+#endif
+#else
+ void *p = 0;
+ set_some_value(p);
+#endif
+ return 0;
+}