status and session_tracik callback function:

This feature allows client applications to register a callback function,
which is called as soon as the server status changes or session_track
information was sent by the server.

Registration is handled via mysql_optionsv() API function:

mysql_optionsv(mysql, MARIADB_OPT_STATUS_CALLBACK, function, data)

The callback function must be defined as follws:

void status_callback(void *data, enum enum_mariadb_status_info type, ..)

  Parameters:
    - data  Pointer passed with registration of callback function
            (usually a connection handle)
    - type  Information type  STATUS_TYPE or SESSION_TRACK_TYPE

  Variadic Parameters:

  if (type == STATUS_TYPE):
    - server status (unsigned int)

  if (type == SESSION_TRACK_TYPE)
    - enum enum_session_state_type track_type - session track type

    if (track_type == SESSION_TRACK_SYSTEM_VARIABLES)
      - MARIADB_CONST_STRING *key
      - MARIADB_CONST_STRING *value

    else
      - MARIADB_CONST_STRING *value

An example can be found in connection.c (test_status_callback)

include/mysql.h

@@ -249,7 +249,8 @@ extern const char *SQLSTATE_UNKNOWN;
     MARIADB_OPT_IO_WAIT,
     MARIADB_OPT_SKIP_READ_RESPONSE,
     MARIADB_OPT_RESTRICTED_AUTH,
-    MARIADB_OPT_RPL_REGISTER_REPLICA
+    MARIADB_OPT_RPL_REGISTER_REPLICA,
+    MARIADB_OPT_STATUS_CALLBACK
   };
 
   enum mariadb_value {