RtlIsZeroLuid - NtDoc

Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers
#ifndef _NTRTL_H

FORCEINLINE BOOLEAN RtlIsZeroLuid(
    _In_ PLUID L1
    )
{
    return (L1->LowPart | L1->HighPart) == 0;
}

#endif

View code on GitHub

This macro is documented in Windows Driver Kit.