--- /dev/null
+/* These are in a separate C file so we can test undefined structures. */
+struct opaque;
+typedef struct opaque opaque_t;
+
+opaque_t *create_opaque_blob(void);
+bool if_blobs_know_the_secret(opaque_t *blob);
+void destroy_opaque_blob(opaque_t *blob);
+
+