MIDL2141
The documentation lists this name without a value.
Documented in Win32
use of a parameter deriving from a type containing type-modifiers/type-qualifiers needs /c_ext The use of keywords such as far , near , const , and volatile in the IDL file is a Microsoft extension to DCE RPC. These keywords are not available when you compile with the /osf switch, which turns off the default /c_ext extension switch.