1.8 Vendor-Extensible Fields
The DCOM Remote Protocol uses HRESULTs, which are vendor-extensible. Vendors are free to choose their own values for this field, as long as the C bit (0x20000000) is set, indicating that it is a customer code, as specified in [MS-ERREF] section 2.1.
The error_status_t return values used by this protocol are Win32 error codes as specified in [MS-ERREF] section 2.2. Vendors SHOULD reuse those values with their indicated meanings. If vendors choose any other value, they run the risk of a future collision.<1>