See Also: NativeConvert Members
Different operating systems give different values to the same identifier. For example, SIGBUS is 10 under FreeBSD, while it's 7 for x86 Linux. Meanwhile, Signum.SIGBUS will have the same value everywhere. Since it is undesirable to require recompilation for every target platform, the Mono.Unix.Native namespace instead exports a stable ABI, and provides conversion functions to convert between the managed and appropriate OS-specific values.
Normally this conversion is handled transparently by the wrapper functions, so members of this class shouldn't need to be used.
You cannot blindly cast a value to an enumeration without sacrificing portability, as the platform may not support the value you want.