Similar question was asked before, but i haven't found some answers there.
As i understand, for making custom HRESULT codes i create an .mc file where i describe the codes, then compile it and get an .h file. But i can't get it how to prevent possible overlapping with the system ones.
Example:
LanguageNames=(English=0x409:MSG00409)
MessageId = 0x0
Severity = Success
Facility = Application
SymbolicName = CUSTOME_CODE
Language=English
Cusome message
.
produces
#define CUSTOME_CODE 0x00000000L
which is actually the same with S_OK.
If i return CUSTOME_CODE from my method, a caller can't distinguish it from S_OK;
Wiki says HRESULT contains a bit for distinguishing Microsoft / User defined code properties, but i don't understand how to set it. Also MSDN says that the bit is just "reserved".
How do i make code which can't overlap the system ones?
A HRESULT, which describes an interface-specific return code, should contain the FACILTY_ITF facility code. Note however that return values between 0x0000 and 0x01FF are reserved for COM-defined FACILITY_ITF codes.
See this link for further details.