Com 使用ATL和IUnknownPtr时，正确的施法方式是什么？

在修改现有ATL COM对象的过程中，我看到了一篇来自“新旧事物”博客的文章，名为“人们搞乱IUnknown:：QueryInterface的方式”，在评论部分有一个讨论，开始于一位受访者（诺曼·戴蒙德）指出在文章的一个例子中，强制作废**是不正确的

然而，当我试图纠正我的代码以正确地进行转换时，我最终导致了内存泄漏

示例如下：

IShellFolder *psf = some object;
IUnknown *punk = NULL;
psf->QueryInterface(IID_IUnknown, (void**)&punk);

#include <comdef.h>

...

HRESULT FinalConstruct()
{ 
    if (m_dwROTCookie != 0)
        return E_FAIL;

    //Check whether there already is an instance of the Object
    IUnknownPtr pUnk = NULL;
    if (GetActiveObject(CLSID_Object, NULL, &pUnk) == S_OK)
    {
        TRACE_WARNING("An instance of Object already exists in the current context");
        return S_OK;
    }
    HRESULT hr = QueryInterface(IID_IUnknown, reinterpret_cast<void **>(&pUnk));

    hr = RegisterActiveObject(pUnk, CLSID_Object, ACTIVEOBJECT_WEAK, m_dwROTCookie);        
    if (FAILED(hr))
        return hr;

    hr = CoLockObjectExternal(pUnk, TRUE, TRUE);
    pUnk = NULL;
    ATLASSERT(m_dwRef == 2);
    return hr;
}

HRESULT FinalConstruct()
{ 
    if (m_dwROTCookie != 0)
        return E_FAIL;

    //Check whether there already is an instance of the Object
    IUnknownPtr pUnk = NULL;
    if (GetActiveObject(CLSID_Object, NULL, &pUnk) == S_OK)
    {
        TRACE_WARNING("An instance of Object already exists in the current context");
        return S_OK;
    }
    void* pUnkVoid = NULL;
    HRESULT hr = QueryInterface(IID_IUnknown, &pUnkVoid);

    if (SUCCEEDED(hr)
    {
        pUnk = reinterpret_cast<IUnknown*>(pUnkVoid);
        hr = RegisterActiveObject(pUnk, CLSID_Object, ACTIVEOBJECT_WEAK, m_dwROTCookie);        
        if (FAILED(hr))
            return hr;

        hr = CoLockObjectExternal(pUnk, TRUE, TRUE);
        pUnk = NULL;
    }
    ATLASSERT(m_dwRef == 2);

    return hr;

诺曼说

朋克不是一片空白*。朋克是个不为人知的人

void**不是通用指针类型。void*是一种通用的指针类型，char*和其亲属可以通过这种方式等效，但void**不是

如果你想遵守召唤规则，避免可怕的死亡，你必须做到： IUnknown*朋克； void*punkvoid； psf->查询接口（IID_IUnknown和punkvoid）； 朋克=（IUnknown*）朋克球形

许多其他MSDN贡献者犯了同样的错误。。。。有些人可能会说，到目前为止，它在所有VC++实现中都有效，但这并不意味着它的代码是正确的，而且它仍然违反了调用约定

有鉴于此，我改变了我的旧代码-如下所示：

IShellFolder *psf = some object;
IUnknown *punk = NULL;
psf->QueryInterface(IID_IUnknown, (void**)&punk);

#include <comdef.h>

...

HRESULT FinalConstruct()
{ 
    if (m_dwROTCookie != 0)
        return E_FAIL;

    //Check whether there already is an instance of the Object
    IUnknownPtr pUnk = NULL;
    if (GetActiveObject(CLSID_Object, NULL, &pUnk) == S_OK)
    {
        TRACE_WARNING("An instance of Object already exists in the current context");
        return S_OK;
    }
    HRESULT hr = QueryInterface(IID_IUnknown, reinterpret_cast<void **>(&pUnk));

    hr = RegisterActiveObject(pUnk, CLSID_Object, ACTIVEOBJECT_WEAK, m_dwROTCookie);        
    if (FAILED(hr))
        return hr;

    hr = CoLockObjectExternal(pUnk, TRUE, TRUE);
    pUnk = NULL;
    ATLASSERT(m_dwRef == 2);
    return hr;
}

HRESULT FinalConstruct()
{ 
    if (m_dwROTCookie != 0)
        return E_FAIL;

    //Check whether there already is an instance of the Object
    IUnknownPtr pUnk = NULL;
    if (GetActiveObject(CLSID_Object, NULL, &pUnk) == S_OK)
    {
        TRACE_WARNING("An instance of Object already exists in the current context");
        return S_OK;
    }
    void* pUnkVoid = NULL;
    HRESULT hr = QueryInterface(IID_IUnknown, &pUnkVoid);

    if (SUCCEEDED(hr)
    {
        pUnk = reinterpret_cast<IUnknown*>(pUnkVoid);
        hr = RegisterActiveObject(pUnk, CLSID_Object, ACTIVEOBJECT_WEAK, m_dwROTCookie);        
        if (FAILED(hr))
            return hr;

        hr = CoLockObjectExternal(pUnk, TRUE, TRUE);
        pUnk = NULL;
    }
    ATLASSERT(m_dwRef == 2);

    return hr;

#包括
...
HRESULT FinalConstruct（）
{ 
如果（m_dwROTCookie！=0）
返回E_失败；
//检查是否已经存在该对象的实例
IUnknownPtr pUnk=NULL；
if（GetActiveObject（CLSID_Object、NULL和pUnk）==S_OK）
{
TRACE_警告（“当前上下文中已存在对象的实例”）；
返回S_OK；
}
HRESULT hr=查询界面（IID_IUnknown，重新解释演员和朋克））；
hr=RegisterActiveObject（朋克、CLSID_对象、ACTIVEOBJECT_弱、m_dwROTCookie）；
如果（失败（小时））
返回人力资源；
hr=CoLockObjectExternal（朋克，真，真）；
朋克=零；
ATLASSERT（m_dwRef==2）；
返回人力资源；
}

然后我将其更改如下：

IShellFolder *psf = some object;
IUnknown *punk = NULL;
psf->QueryInterface(IID_IUnknown, (void**)&punk);

#include <comdef.h>

...

HRESULT FinalConstruct()
{ 
    if (m_dwROTCookie != 0)
        return E_FAIL;

    //Check whether there already is an instance of the Object
    IUnknownPtr pUnk = NULL;
    if (GetActiveObject(CLSID_Object, NULL, &pUnk) == S_OK)
    {
        TRACE_WARNING("An instance of Object already exists in the current context");
        return S_OK;
    }
    HRESULT hr = QueryInterface(IID_IUnknown, reinterpret_cast<void **>(&pUnk));

    hr = RegisterActiveObject(pUnk, CLSID_Object, ACTIVEOBJECT_WEAK, m_dwROTCookie);        
    if (FAILED(hr))
        return hr;

    hr = CoLockObjectExternal(pUnk, TRUE, TRUE);
    pUnk = NULL;
    ATLASSERT(m_dwRef == 2);
    return hr;
}

HRESULT FinalConstruct()
{ 
    if (m_dwROTCookie != 0)
        return E_FAIL;

    //Check whether there already is an instance of the Object
    IUnknownPtr pUnk = NULL;
    if (GetActiveObject(CLSID_Object, NULL, &pUnk) == S_OK)
    {
        TRACE_WARNING("An instance of Object already exists in the current context");
        return S_OK;
    }
    void* pUnkVoid = NULL;
    HRESULT hr = QueryInterface(IID_IUnknown, &pUnkVoid);

    if (SUCCEEDED(hr)
    {
        pUnk = reinterpret_cast<IUnknown*>(pUnkVoid);
        hr = RegisterActiveObject(pUnk, CLSID_Object, ACTIVEOBJECT_WEAK, m_dwROTCookie);        
        if (FAILED(hr))
            return hr;

        hr = CoLockObjectExternal(pUnk, TRUE, TRUE);
        pUnk = NULL;
    }
    ATLASSERT(m_dwRef == 2);

    return hr;

HRESULT FinalConstruct（）
{ 
如果（m_dwROTCookie！=0）
返回E_失败；
//检查是否已经存在该对象的实例
IUnknownPtr pUnk=NULL；
if（GetActiveObject（CLSID_Object、NULL和pUnk）==S_OK）
{
TRACE_警告（“当前上下文中已存在对象的实例”）；
返回S_OK；
}
void*pUnkVoid=NULL；
HRESULT hr=查询接口（IID_IUnknown和pUnkVoid）；
如果成功（hr）
{
朋克=重新解释铸造（朋克球形）；
hr=RegisterActiveObject（朋克、CLSID_对象、ACTIVEOBJECT_弱、m_dwROTCookie）；
如果（失败（小时））
返回人力资源；
hr=CoLockObjectExternal（朋克，真，真）；
朋克=零；
}
ATLASSERT（m_dwRef==2）；
返回人力资源；

---

但是现在我的应用程序有一个来自COM对象的内存泄漏，我认为与其将void*分配给pUnk，不如使用：

pUnk.Attach(reinterpret_cast<IUnknown*>(pUnkVoid));

pUnk.Attach（重新解释（pUnkVoid））；

您可能有内存泄漏，因为您调用了

GetActiveObject（）

和

QueryInterface（）

，成功后会增加对象上的引用计数，但以后不要调用

Release（）

来减少引用计数