RtlUIntPtrAdd - NtDoc

#ifndef _NTINTSAFE_H_INCLUDED_
#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP | WINAPI_PARTITION_SYSTEM | WINAPI_PARTITION_GAMES)
//
// UINT_PTR addition
//
#ifdef _WIN64

#define RtlUIntPtrAdd      RtlULongLongAdd

#endif
#endif
#endif
View code on GitHub

#ifndef _NTINTSAFE_H_INCLUDED_
#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP | WINAPI_PARTITION_SYSTEM | WINAPI_PARTITION_GAMES)
//
// UINT_PTR addition
//
#ifdef _WIN64
// ...
#else

_Must_inspect_result_
__inline
NTSTATUS
RtlUIntPtrAdd(
    _In_ UINT_PTR uAugend,
    _In_ UINT_PTR uAddend,
    _Out_ _Deref_out_range_(==, uAugend + uAddend) UINT_PTR* puResult)
{
    NTSTATUS status;

    if ((uAugend + uAddend) >= uAugend)
    {
        *puResult = (uAugend + uAddend);
        status = STATUS_SUCCESS;
    }
    else
    {
        *puResult = UINT_PTR_ERROR;
        status = STATUS_INTEGER_OVERFLOW;
    }
    
    return status;
}

#endif
#endif
#endif
View code on GitHub