-const struct lttng_ust_lib_ring_buffer_client_cb *lttng_client_callbacks_metadata;
-const struct lttng_ust_lib_ring_buffer_client_cb *lttng_client_callbacks_discard;
-const struct lttng_ust_lib_ring_buffer_client_cb *lttng_client_callbacks_overwrite;
+extern const struct lttng_ust_lib_ring_buffer_client_cb *lttng_client_callbacks_metadata;
+extern const struct lttng_ust_lib_ring_buffer_client_cb *lttng_client_callbacks_discard;
+extern const struct lttng_ust_lib_ring_buffer_client_cb *lttng_client_callbacks_overwrite;