The container control requires that the application use the CM_ALLOCRECORD message to allocate memory for container records.

When a record is allocated, the cb field of the record will be initialized with the size of the record structure type currently in use, either RECORDCORE or MINIRECORDCORE. If the CCS_MINIRECORDCORE style bit is not specified, the record is allocated according to the size of the RECORDCORE data structure. However, if the CCS_MINIRECORDCORE style bit is specified, the record is allocated according to the size of the MINIRECORDCORE data structure. This size should not be modified by the application.