MSXML内存泄漏

Question

我必须处理一个遗留应用程序，它使用MSXML将度量数据写入一个简单的XML文件。简单地说，这就是正在发生的事情：

MSXML2::IXMLDOMDocument2Ptr pXmlDocument;
HRESULT comResult = CXMLUtil::createXMLDocument(pXmlDocument);
// ... check HRESULT ...
MSXML2::IXMLDOMNodePtr pXmlMainNode = pXmlDocument.GetInterfacePtr();
MSXML2::IXMLDOMNodePtr pXmlSubNode = CXMLUtil::AppendNewElement(pXmlDocument, pXmlMainNode, RootTag, "");
// ... create further nodes ...
MSXML2::IXMLDOMNodePtr pXmlTmpNode = CXMLUtil::AppendNewElement(
pXmlDocument,
pXmlDataSetNode,
measDataTag,
measdata,
numberOfDataItems );
// ... append further items ...

在每个项目之后，调用pXmlTmpNode.Release()。最后，所有其他节点以及pXmlDocument都是Released。

createXMLDocument的定义如下：

HRESULT CXMLUtil::createXMLDocument(MSXML2::IXMLDOMDocument2Ptr &pXmlDocument) {
    MSXML2::IXMLDOMDocument2 *xmlDocument = 0;
    HRESULT comError = CoCreateInstance(__uuidof(MSXML2::DOMDocument),NULL,CLSCTX_INPROC_SERVER,IID_PPV_ARGS(&xmlDocument));
    if (comError) return comError;
    xmlDocument->put_async(VARIANT_FALSE);
    xmlDocument->put_validateOnParse(VARIANT_FALSE);
    xmlDocument->put_resolveExternals(VARIANT_FALSE);
    xmlDocument->put_preserveWhiteSpace(VARIANT_TRUE);
    MSXML2::IXMLDOMDocument2Ptr ptr(xmlDocument);
    pXmlDocument = ptr;
    return comError;
}

对于附加新元素(即unsiged char数组)，应用此函数：

MSXML2::IXMLDOMNodePtr CXMLUtil::AppendNewElement(MSXML2::IXMLDOMDocument2Ptr pXMLDom, MSXML2::IXMLDOMNodePtr pParent, CComBSTR strElementName, unsigned char* pData, long nData) {
    MSXML2::IXMLDOMNodePtr pData1 = pXMLDom->createElement(BSTR(strElementName));
    pData1->put_dataType(CComBSTR(_T("bin.base64")));
    SAFEARRAY* psa = SafeArrayCreateVector( VT_UI1, 0L, nData);
    psa->pvData = pData;
    VARIANT var;
    VariantInit(&var);
    var.parray = psa;
    var.vt = (VT_ARRAY | VT_UI1 );
    pData1->nodeTypedValue = var;
    pParent->appendChild(pData1);
    SafeArrayDestroy(psa);
    return pData1;
}

不管使用的是#import <msxml4.dll>还是#import <msxml6.dll>，内存似乎都有漏洞。由于measdata等可能是巨大的，这是一个相当大的问题。我能做些什么来使代码正常工作吗？谢谢，马修

Answer 1

MSXML2::IXMLDOMDocument2 *xmlDocument = 0;
HRESULT comError = CoCreateInstance(__uuidof(MSXML2::DOMDocument),
    NULL,CLSCTX_INPROC_SERVER,IID_PPV_ARGS(&xmlDocument));
...
MSXML2::IXMLDOMDocument2Ptr ptr(xmlDocument);
pXmlDocument = ptr;

此代码泄漏xmlDocument。ptr(xmlDocument)做了一个额外的AddRef，但是xmlDocument没有超出范围的Release。你在任何地方都使用智能ptrs，没有理由不在这里也使用ptrs，也许是这样的：

MSXML2::IXMLDOMDocument2Ptr xmlDocument;
HRESULT comError = CoCreateInstance(__uuidof(MSXML2::DOMDocument),
    NULL,CLSCTX_INPROC_SERVER,IID_PPV_ARGS(&xmlDocument));
...
pXmlDocument = xmlDocument;