Hi Fabian, Is m_cData a static member? If not, then I don't think you can do a sizeof(SINOSEventLogBuffer::m_cData) on that. Try this instead: m_uMaxEntrySize = sizeof(((SINOSEventLogBuffer*)NULL)->m_cData); Or use this: m_uMaxEntrySize = LOGGER_BUF_SIZE-LOGGER_HEADER_SIZE; HTH, --Eljay