#ifndef _NTINTSAFE_H_INCLUDED_
#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP | WINAPI_PARTITION_SYSTEM | WINAPI_PARTITION_GAMES)
//
// DWORD_PTR subtraction
//
#ifdef _WIN64

#define RtlDWordPtrSub    RtlULongLongSub

#endif
#endif
#endif
View code on GitHub

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

_Must_inspect_result_
__inline
NTSTATUS
RtlDWordPtrSub(
    _In_ DWORD_PTR dwMinuend,
    _In_ DWORD_PTR dwSubtrahend,
    _Out_ _Deref_out_range_(==, dwMinuend - dwSubtrahend) DWORD_PTR* pdwResult)
{
    NTSTATUS status;

    if (dwMinuend >= dwSubtrahend)
    {
        *pdwResult = (dwMinuend - dwSubtrahend);
        status = STATUS_SUCCESS;
    }
    else
    {
        *pdwResult = DWORD_PTR_ERROR;
        status = STATUS_INTEGER_OVERFLOW;
    }

    return status;
}

#endif
#endif
#endif
View code on GitHub

// ntintsafe.h

NTSTATUS RtlDWordPtrSub(
  [in]  DWORD_PTR dwMinuend,
  [in]  DWORD_PTR dwSubtrahend,
  [out] DWORD_PTR *pdwResult
);
View the official Windows Driver Kit DDI reference

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Windows Driver Kit DDI reference (nf-ntintsafe-rtldwordptrsub)

RtlDWordPtrSub function

Description

Subtracts one value of type DWORD_PTR from another.

Parameters

`dwMinuend` [in]

The value from which dwSubtrahend is subtracted.

`dwSubtrahend` [in]

The value to subtract from dwMinuend.

`pdwResult` [out]

A pointer to the result. If the operation results in a value that overflows or underflows the capacity of the type, the function returns STATUS_INTEGER_OVERFLOW and this parameter is not valid.

Return value

Returns STATUS_SUCCESS if the operation is successful.

See the implementation of this helper function in ntintsafe.h in the WDK for possible error return values.

Remarks

This is one of a set of inline functions designed to provide arithmetic operations and perform validity checks with minimal impact on performance.

View the official Windows Driver Kit DDI reference