一个臭虫???在C ++中实现IUnknown [英] A Bug ??? Implementing IUnknown in C++

问题描述

您好，全部：

请参阅：  < a href ="http://msdn.microsoft.com/en-us/library/office/cc839627.aspx"style ="font-size：0.75em; line-height：1.5"> http://msdn.microsoft .com / zh-CN / library / office / cc839627.aspx

我想有一个错误：

 InterlockedIncrement（m_cRef）; 

应该是

 InterlockedIncrement（& m_cRef）; 

和

< pre class ="prettyprint"> ULONG ulRefCount = InterlockedDecrement（m_cRef）;

应该是

 ULONG ulRefCount = InterlockedDecrement（& m_cRef）; 

请确认......

干杯

Pei

解决方案

Ye s，这是一个错字。

虽然技术上很有趣，因为没有显示m_cRef的声明，这个特殊的例子仍然可能是通过假设m_cRef是使用支持隐式
的运算符来实现运行符号 volatile unsigned long * 和 ULONG 之类的这个：

 #include< windows.h> 
 
 class MyRefCount 
 {
 public：
 MyRefCount（）：n（1）{} 
 
 operator volatile unsigned long *（） 
 {
 return& n; 
} 
运营商ULONG（）
 {
 return n; 
} 
 
私人：
 volatile ULONG n; 
}; 
 
 class CMyMAPIObject 
 {
 public：
 ULONG Release（）; 
 
 private：
 MyRefCount m_cRef; 
}; 
 
 ULONG CMyMAPIObject :: Release（）
 {
 //减少对象的内部计数器。 
 ULONG ulRefCount = InterlockedDecrement（m_cRef）; 
 if（0 == m_cRef）
 {
删除此; 
} 
返回ulRefCount; 
} 
 
 int WINAPI WinMain（HINSTANCE hInstance，HINSTANCE hPrevInstance，LPSTR sCmdLine，int nCmdShow）
 {
 CMyMAPIObject * m = new CMyMAPIObject; 
 m-> Release（）; 
 
返回0; 
} 

但这只是一个C ++特技。   ;; - ）

我认为你最有意义的是它是一个错字。

Hi, all:

Please refer to :  http://msdn.microsoft.com/en-us/library/office/cc839627.aspx

I guess there is a bug:

InterlockedIncrement(m_cRef);

should be

InterlockedIncrement(&m_cRef);

and

ULONG ulRefCount = InterlockedDecrement(m_cRef);

should be

ULONG ulRefCount = InterlockedDecrement(&m_cRef);

Please confirm...

Cheers

Pei

解决方案

Yes, it is a typo.

Although it's amusing that technically, because the declaration of m_cRef is not shown, this particular example could still be correct (with a little tricky thinking alone) by assuming that m_cRef is implemented with a class that supports implicit cast operators to both volatile unsigned long* and ULONG like this:

#include <windows.h>

class MyRefCount
{
public:
	MyRefCount() : n(1) {}

	operator volatile unsigned long*()
	{
		return &n;
	}
	operator ULONG()
	{
		return n;
	}

private:
	volatile ULONG n;
};

class CMyMAPIObject
{
public:
	ULONG Release();

private:
	MyRefCount m_cRef;
};

ULONG CMyMAPIObject::Release()
{
    // Decrement the object's internal counter.
    ULONG ulRefCount = InterlockedDecrement(m_cRef);
    if (0 == m_cRef)
    {
        delete this;
    }
    return ulRefCount;
}

int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR sCmdLine, int nCmdShow )
{
	CMyMAPIObject* m = new CMyMAPIObject;
	m->Release();

	return 0;
}

But that's just a C++ stunt.  ;-)

I think that it makes the most sense that you're right about it being a typo.

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